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+Project Gutenberg's Oxy-Acetylene Welding and Cutting, by Harold P. Manly
+
+This eBook is for the use of anyone anywhere at no cost and with
+almost no restrictions whatsoever.  You may copy it, give it away or
+re-use it under the terms of the Project Gutenberg License included
+with this eBook or online at www.gutenberg.org
+
+
+Title: Oxy-Acetylene Welding and Cutting
+       Electric, Forge and Thermit Welding together with related
+       methods and materials used in metal working and the oxygen
+       process for removal of carbon
+
+Author: Harold P. Manly
+
+Posting Date: April 12, 2014 [EBook #7969]
+Release Date: April, 2005
+First Posted: June 7, 2003
+
+Language: English
+
+Character set encoding: ISO-8859-1
+
+*** START OF THIS PROJECT GUTENBERG EBOOK OXY-ACETYLENE WELDING AND CUTTING ***
+
+
+
+
+Produced by Juliet Sutherland, John Argus, Tonya Allen,
+Charles Franks and the Online Distributed Proofreading Team.
+
+
+
+
+
+
+
+
+
+
+Oxy-Acetylene Welding and Cutting
+
+Electric, Forge and Thermit Welding
+
+Together with Related Methods and Materials Used in Metal Working
+And
+The Oxygen Process for Removal of Carbon
+
+By
+HAROLD P. MANLY
+
+
+
+
+PREFACE
+
+In the preparation of this work, the object has been to cover not only the
+several processes of welding, but also those other processes which are so
+closely allied in method and results as to make them a part of the whole
+subject of joining metal to metal with the aid of heat.
+
+The workman who wishes to handle his trade from start to finish finds that
+it is necessary to become familiar with certain other operations which
+precede or follow the actual joining of the metal parts, the purpose of
+these operations being to add or retain certain desirable qualities in the
+materials being handled. For this reason the following subjects have been
+included: Annealing, tempering, hardening, heat treatment and the
+restoration of steel.
+
+In order that the user may understand the underlying principles and the
+materials employed in this work, much practical information is given on the
+uses and characteristics of the various metals; on the production, handling
+and use of the gases and other materials which are a part of the equipment;
+and on the tools and accessories for the production and handling of these
+materials.
+
+An examination will show that the greatest usefulness of this book lies in
+the fact that all necessary information and data has been included in one
+volume, making it possible for the workman to use one source for securing a
+knowledge of both principle and practice, preparation and finishing of the
+work, and both large and small repair work as well as manufacturing methods
+used in metal working.
+
+An effort has been made to eliminate all matter which is not of direct
+usefulness in practical work, while including all that those engaged in
+this trade find necessary. To this end, the descriptions have been limited
+to those methods and accessories which are found in actual use today. For
+the same reason, the work includes the application of the rules laid down
+by the insurance underwriters which govern this work as well as
+instructions for the proper care and handling of the generators, torches
+and materials found in the shop.
+
+Special attention has been given to definite directions for handling the
+different metals and alloys which must be handled. The instructions have
+been arranged to form rules which are placed in the order of their use
+during the work described and the work has been subdivided in such a way
+that it will be found possible to secure information on any one point
+desired without the necessity of spending time in other fields.
+
+The facts which the expert welder and metalworker finds it most necessary
+to have readily available have been secured, and prepared especially for
+this work, and those of most general use have been combined with the
+chapter on welding practice to which they apply.
+
+The size of this volume has been kept as small as possible, but an
+examination of the alphabetical index will show that the range of subjects
+and details covered is complete in all respects. This has been accomplished
+through careful classification of the contents and the elimination of all
+repetition and all theoretical, historical and similar matter that is not
+absolutely necessary.
+
+Free use has been made of the information given by those manufacturers who
+are recognized as the leaders in their respective fields, thus insuring
+that the work is thoroughly practical and that it represents present day
+methods and practice.
+
+THE AUTHOR.
+
+
+
+
+CONTENTS
+
+   CHAPTER I
+
+METALS AND ALLOYS--HEAT TREATMENT:--The Use and Characteristics of the
+Industrial Alloys and Metal Elements--Annealing, Hardening, Tempering and
+Case Hardening of Steel
+
+   CHAPTER II
+
+WELDING MATERIALS:--Production, Handling and Use of the Gases, Oxygen and
+Acetylene--Welding Rods--Fluxes--Supplies and Fixtures
+
+   CHAPTER III
+
+ACETYLENE GENERATORS:--Generator Requirements and Types--Construction--Care
+and Operation of Generators.
+
+   CHAPTER IV
+
+WELDING INSTRUMENTS:--Tank and Regulating Valves and Gauges--High, Low and
+Medium Pressure Torches--Cutting Torches--Acetylene-Air Torches
+
+   CHAPTER V
+
+OXY-ACETYLENE WELDING PRACTICE:--Preparation of Work--Torch Practice--
+Control of the Flame--Welding Various Metals and Alloys--Tables of
+Information Required in Welding Operations
+
+   CHAPTER VI
+
+ELECTRIC WELDING:--Resistance Method--Butt, Spot and Lap Welding--Troubles
+and Remedies--Electric Arc Welding
+
+   CHAPTER VII
+
+HAND FORGING AND WELDING:--Blacksmithing, Forging and Bending--Forge
+Welding Methods
+
+   CHAPTER VIII
+
+SOLDERING, BRAZING AND THERMIT WELDING:--Soldering Materials and Practice--
+Brazing--Thermit Welding
+
+   CHAPTER IX
+
+OXYGEN PROCESS FOR REMOVAL OF CARBON
+
+INDEX
+
+
+
+
+
+OXY-ACETYLENE WELDING AND CUTTING, ELECTRIC AND THERMIT WELDING
+
+
+
+
+CHAPTER I
+
+METALS AND THEIR ALLOYS--HEAT TREATMENT
+
+
+THE METALS
+
+_Iron._--Iron, in its pure state, is a soft, white, easily worked
+metal. It is the most important of all the metallic elements, and is, next
+to aluminum, the commonest metal found in the earth.
+
+Mechanically speaking, we have three kinds of iron: wrought iron, cast iron
+and steel. Wrought iron is very nearly pure iron; cast iron contains carbon
+and silicon, also chemical impurities; and steel contains a definite
+proportion of carbon, but in smaller quantities than cast iron.
+
+Pure iron is never obtained commercially, the metal always being mixed with
+various proportions of carbon, silicon, sulphur, phosphorus, and other
+elements, making it more or less suitable for different purposes. Iron is
+magnetic to the extent that it is attracted by magnets, but it does not
+retain magnetism itself, as does steel. Iron forms, with other elements,
+many important combinations, such as its alloys, oxides, and sulphates.
+
+[Illustration: Figure 1.--Section Through a Blast Furnace]
+
+_Cast Iron._--Metallic iron is separated from iron ore in the blast
+furnace (Figure 1), and when allowed to run into moulds is called cast
+iron. This form is used for engine cylinders and pistons, for brackets,
+covers, housings and at any point where its brittleness is not
+objectionable. Good cast iron breaks with a gray fracture, is free from
+blowholes or roughness, and is easily machined, drilled, etc. Cast iron is
+slightly lighter than steel, melts at about 2,400 degrees in practice, is
+about one-eighth as good an electrical conductor as copper and has a
+tensile strength of 13,000 to 30,000 pounds per square inch. Its
+compressive strength, or resistance to crushing, is very great. It has
+excellent wearing qualities and is not easily warped and deformed by heat.
+Chilled iron is cast into a metal mould so that the outside is cooled
+quickly, making the surface very hard and difficult to cut and giving great
+resistance to wear. It is used for making cheap gear wheels and parts that
+must withstand surface friction.
+
+_Malleable Cast Iron._--This is often called simply malleable iron. It
+is a form of cast iron obtained by removing much of the carbon from cast
+iron, making it softer and less brittle. It has a tensile strength of
+25,000 to 45,000 pounds per square inch, is easily machined, will stand a
+small amount of bending at a low red heat and is used chiefly in making
+brackets, fittings and supports where low cost is of considerable
+importance. It is often used in cheap constructions in place of steel
+forgings. The greatest strength of a malleable casting, like a steel
+forging, is in the surface, therefore but little machining should be done.
+
+_Wrought Iron._--This grade is made by treating the cast iron to
+remove almost all of the carbon, silicon, phosphorus, sulphur, manganese
+and other impurities. This process leaves a small amount of the slag from
+the ore mixed with the wrought iron.
+
+Wrought iron is used for making bars to be machined into various parts. If
+drawn through the rolls at the mill once, while being made, it is called
+"muck bar;" if rolled twice, it is called "merchant bar" (the commonest
+kind), and a still better grade is made by rolling a third time. Wrought
+iron is being gradually replaced in use by mild rolled steels.
+
+Wrought iron is slightly heavier than cast iron, is a much better
+electrical conductor than either cast iron or steel, has a tensile strength
+of 40,000 to 60,000 pounds per square inch and costs slightly more than
+steel. Unlike either steel or cast iron, wrought iron does not harden when
+cooled suddenly from a red heat.
+
+_Grades of Irons._--The mechanical properties of cast iron differ
+greatly according to the amount of other materials it contains. The most
+important of these contained elements is carbon, which is present to a
+degree varying from 2 to 5-1/2 per cent. When iron containing much carbon
+is quickly cooled and then broken, the fracture is nearly white in color
+and the metal is found to be hard and brittle. When the iron is slowly
+cooled and then broken the fracture is gray and the iron is more malleable
+and less brittle. If cast iron contains sulphur or phosphorus, it will show
+a white fracture regardless of the rapidity of cooling, being brittle and
+less desirable for general work.
+
+_Steel._--Steel is composed of extremely minute particles of iron and
+carbon, forming a network of layers and bands. This carbon is a smaller
+proportion of the metal than found in cast iron, the percentage being from
+3/10 to 2-1/2 per cent.
+
+Carbon steel is specified according to the number of "points" of carbon, a
+point being one one-hundredth of one per cent of the weight of the steel.
+Steel may contain anywhere from 30 to 250 points, which is equivalent to
+saying, anywhere from 3/10 to 2-1/2 per cent, as above. A 70-point steel
+would contain 70/100 of one per cent or 7/10 of one per cent of carbon by
+weight. The percentage of carbon determines the hardness of the steel, also
+many other qualities, and its suitability for various kinds of work. The
+more carbon contained in the steel, the harder the metal will be, and, of
+course, its brittleness increases with the hardness. The smaller the grains
+or particles of iron which are separated by the carbon, the stronger the
+steel will be, and the control of the size of these particles is the object
+of the science of heat treatment.
+
+In addition to the carbon, steel may contain the following:
+
+Silicon, which increases the hardness, brittleness, strength and difficulty
+  of working if from 2 to 3 per cent is present.
+
+Phosphorus, which hardens and weakens the metal but makes it easier to
+  cast. Three-tenths per cent of phosphorus serves as a hardening agent and
+  may be present in good steel if the percentage of carbon is low. More
+  than this weakens the metal.
+
+Sulphur, which tends to make the metal hard and filled with small holes.
+
+Manganese, which makes the steel so hard and tough that it can with
+  difficulty be cut with steel tools. Its hardness is not lessened by
+  annealing, and it has great tensile strength.
+
+Alloy steel has a varying but small percentage of other elements mixed with
+it to give certain desired qualities. Silicon steel and manganese steel are
+sometimes classed as alloy steels. This subject is taken up in the latter
+part of this chapter under _Alloys_, where the various combinations
+and their characteristics are given consideration.
+
+Steel has a tensile strength varying from 50,000 to 300,000 pounds per
+square inch, depending on the carbon percentage and the other alloys
+present, as well as upon the texture of the grain. Steel is heavier than
+cast iron and weighs about the same as wrought iron. It is about one-ninth
+as good a conductor of electricity as copper.
+
+Steel is made from cast iron by three principal processes: the crucible,
+Bessemer and open hearth.
+
+_Crucible steel_ is made by placing pieces of iron in a clay or
+graphite crucible, mixed with charcoal and a small amount of any desired
+alloy. The crucible is then heated with coal, oil or gas fires until the
+iron melts, and, by absorbing the desired elements and giving up or
+changing its percentage of carbon, becomes steel. The molten steel is then
+poured from the crucible into moulds or bars for use. Crucible steel may
+also be made by placing crude steel in the crucibles in place of the iron.
+This last method gives the finest grade of metal and the crucible process
+in general gives the best grades of steel for mechanical use.
+
+[Illustration: Figure 2.--A Bessemer Converter]
+
+_Bessemer steel_ is made by heating iron until all the undesirable
+elements are burned out by air blasts which furnish the necessary oxygen.
+The iron is placed in a large retort called a converter, being poured,
+while at a melting heat, directly from the blast furnace into the
+converter. While the iron in the converter is molten, blasts of air are
+forced through the liquid, making it still hotter and burning out the
+impurities together with the carbon and manganese. These two elements are
+then restored to the iron by adding spiegeleisen (an alloy of iron, carbon
+and manganese). A converter holds from 5 to 25 tons of metal and requires
+about 20 minutes to finish a charge. This makes the cheapest steel.
+
+[Illustration: Figure 3.--An Open Hearth Furnace]
+
+_Open hearth steel_ is made by placing the molten iron in a receptacle
+while currents of air pass over it, this air having itself been highly
+heated by just passing over white hot brick (Figure. 3). Open hearth steel
+is considered more uniform and reliable than Bessemer, and is used for
+springs, bar steel, tool steel, steel plates, etc.
+
+_Aluminum_ is one of the commonest industrial metals. It is used for
+gear cases, engine crank cases, covers, fittings, and wherever lightness
+and moderate strength are desirable.
+
+Aluminum is about one-third the weight of iron and about the same weight as
+glass and porcelain; it is a good electrical conductor (about one-half as
+good as copper); is fairly strong itself and gives great strength to other
+metals when alloyed with them. One of the greatest advantages of aluminum
+is that it will not rust or corrode under ordinary conditions. The granular
+formation of aluminum makes its strength very unreliable and it is too soft
+to resist wear.
+
+_Copper_ is one of the most important metals used in the trades, and
+the best commercial conductor of electricity, being exceeded in this
+respect only by silver, which is but slightly better. Copper is very
+malleable and ductile when cold, and in this state may be easily worked
+under the hammer. Working in this way makes the copper stronger and harder,
+but less ductile. Copper is not affected by air, but acids cause the
+formation of a green deposit called verdigris.
+
+Copper is one of the best conductors of heat, as well as electricity, being
+used for kettles, boilers, stills and wherever this quality is desirable.
+Copper is also used in alloys with other metals, forming an important part
+of brass, bronze, german silver, bell metal and gun metal. It is about
+one-eighth heavier than steel and has a tensile strength of about 25,000 to
+50,000 pounds per square inch.
+
+_Lead._--The peculiar properties of lead, and especially its quality
+of showing but little action or chemical change in the presence of other
+elements, makes it valuable under certain conditions of use. Its principal
+use is in pipes for water and gas, coverings for roofs and linings for vats
+and tanks. It is also used to coat sheet iron for similar uses and as an
+important part of ordinary solder.
+
+Lead is the softest and weakest of all the commercial metals, being very
+pliable and inelastic. It should be remembered that lead and all its
+compounds are poisonous when received into the system. Lead is more than
+one-third heavier than steel, has a tensile strength of only about 2,000
+pounds per square inch, and is only about one-tenth as good a conductor of
+electricity as copper.
+
+_Zinc._--This is a bluish-white metal of crystalline form. It is
+brittle at ordinary temperatures and becomes malleable at about 250 to 300
+degrees Fahrenheit, but beyond this point becomes even more brittle than at
+ordinary temperatures. Zinc is practically unaffected by air or moisture
+through becoming covered with one of its own compounds which immediately
+resists further action. Zinc melts at low temperatures, and when heated
+beyond the melting point gives off very poisonous fumes.
+
+The principal use of zinc is as an alloy with other metals to form brass,
+bronze, german silver and bearing metals. It is also used to cover the
+surface of steel and iron plates, the plates being then called galvanized.
+
+Zinc weighs slightly less than steel, has a tensile strength of 5,000
+pounds per square inch, and is not quite half as good as copper in
+conducting electricity.
+
+_Tin_ resembles silver in color and luster. Tin is ductile and
+malleable and slightly crystalline in form, almost as heavy as steel, and
+has a tensile strength of 4,500 pounds per square inch.
+
+The principal use of tin is for protective platings on household utensils
+and in wrappings of tin-foil. Tin forms an important part of many alloys
+such as babbitt, Britannia metal, bronze, gun metal and bearing metals.
+
+_Nickel_ is important in mechanics because of its combinations with
+other metals as alloys. Pure nickel is grayish-white, malleable, ductile
+and tenacious. It weighs almost as much as steel and, next to manganese, is
+the hardest of metals. Nickel is one of the three magnetic metals, the
+others being iron and cobalt. The commonest alloy containing nickel is
+german silver, although one of its most important alloys is found in nickel
+steel. Nickel is about ten per cent heavier than steel, and has a tensile
+strength of 90,000 pounds per square inch.
+
+_Platinum._--This metal is valuable for two reasons: it is not
+affected by the air or moisture or any ordinary acid or salt, and in
+addition to this property it melts only at the highest temperatures. It is
+a fairly good electrical conductor, being better than iron or steel. It is
+nearly three times as heavy as steel and its tensile strength is 25,000
+pounds per square inch.
+
+
+ALLOYS
+
+An alloy is formed by the union of a metal with some other material, either
+metal or non-metallic, this union being composed of two or more elements
+and usually brought about by heating the substances together until they
+melt and unite. Metals are alloyed with materials which have been found to
+give to the metal certain characteristics which are desired according to
+the use the metal will be put to.
+
+The alloys of metals are, almost without exception, more important from an
+industrial standpoint than the metals themselves. There are innumerable
+possible combinations, the most useful of which are here classed under the
+head of the principal metal entering into their composition.
+
+_Steel._--Steel may be alloyed with almost any of the metals or
+elements, the combinations that have proven valuable numbering more than a
+score. The principal ones are given in alphabetical order, as follows:
+
+Aluminum is added to steel in very small amounts for the purpose of
+preventing blow holes in castings.
+
+Boron increases the density and toughness of the metal.
+
+Bronze, added by alloying copper, tin and iron, is used for gun metal.
+
+Carbon has already been considered under the head of steel in the section
+devoted to the metals. Carbon, while increasing the strength and hardness,
+decreases the ease of forging and bending and decreases the magnetism and
+electrical conductivity. High carbon steel can be welded only with
+difficulty. When the percentage of carbon is low, the steel is called "low
+carbon" or "mild" steel. This is used for rods and shafts, and called
+"machine" steel. When the carbon percentage is high, the steel is called
+"high carbon" steel, and it is used in the shop as tool steel. One-tenth
+per cent of carbon gives steel a tensile strength of 50,000 to 65,000
+pounds per square inch; two-tenths per cent gives from 60,000 to 80,000;
+four-tenths per cent gives 70,000 to 100,000, and six-tenths per cent
+gives 90,000 to 120,000.
+
+Chromium forms chrome steel, and with the further addition of nickel is
+called chrome nickel steel. This increases the hardness to a high degree
+and adds strength without much decrease in ductility. Chrome steels are
+used for high-speed cutting tools, armor plate, files, springs, safes,
+dies, etc.
+
+Manganese has been mentioned under _Steel_. Its alloy is much used for
+high-speed cutting tools, the steel hardening when cooled in the air and
+being called self-hardening.
+
+Molybdenum is used to increase the hardness to a high degree and makes the
+steel suitable for high-speed cutting and gives it self-hardening
+properties.
+
+Nickel, with which is often combined chromium, increases the strength,
+springiness and toughness and helps to prevent corrosion.
+
+Silicon has already been described. It suits the metal for use in
+high-speed tools.
+
+Silver added to steel has many of the properties of nickel.
+
+Tungsten increases the hardness without making the steel brittle. This
+makes the steel well suited for gas engine valves as it resists corrosion
+and pitting. Chromium and manganese are often used in combination with
+tungsten when high-speed cutting tools are made.
+
+Vanadium as an alloy increases the elastic limit, making the steel
+stronger, tougher and harder. It also makes the steel able to stand much
+bending and vibration.
+
+_Copper._--The principal copper alloys include brass, bronze, german
+silver and gun metal.
+
+Brass is composed of approximately one-third zinc and two-thirds copper. It
+is used for bearings and bushings where the speeds are slow and the loads
+rather heavy for the bearing size. It also finds use in washers, collars
+and forms of brackets where the metal should be non-magnetic, also for many
+highly finished parts.
+
+Brass is about one-third as good an electrical conductor as copper, is
+slightly heavier than steel and has a tensile strength of 15,000 pounds
+when cast and about 75,000 to 100,000 pounds when drawn into wire.
+
+Bronze is composed of copper and tin in various proportions, according to
+the use to which it is to be put. There will always be from six-tenths to
+nine-tenths of copper in the mixture. Bronze is used for bearings,
+bushings, thrust washers, brackets and gear wheels. It is heavier than
+steel, about 1/15 as good an electrical conductor as pure copper and has a
+tensile strength of 30,000 to 60,000 pounds.
+
+Aluminum bronze, composed of copper, zinc and aluminum has high tensile
+strength combined with ductility and is used for parts requiring this
+combination.
+
+Bearing bronze is a variable material, its composition and proportion
+depending on the maker and the use for which it is designed. It usually
+contains from 75 to 85 per cent of copper combined with one or more
+elements, such as tin, zinc, antimony and lead.
+
+White metal is one form of bearing bronze containing over 80 per cent of
+zinc together with copper, tin, antimony and lead. Another form is made
+with nearly 90 per cent of tin combined with copper and antimony.
+
+Gun metal bronze is made from 90 per cent copper with 10 per cent of tin
+and is used for heavy bearings, brackets and highly finished parts.
+
+Phosphor bronze is used for very strong castings and bearings. It is
+similar to gun metal bronze, except that about 1-1/2 per cent of phosphorus
+has been added.
+
+Manganese bronze contains about 1 per cent of manganese and is used for
+parts requiring great strength while being free from corrosion.
+
+German silver is made from 60 per cent of copper with 20 per cent each of
+zinc and nickel. Its high electrical resistance makes it valuable for
+regulating devices and rheostats.
+
+_Tin_ is the principal part of _babbitt_ and _solder_. A
+commonly used babbitt is composed of 89 per cent tin, 8 per cent antimony
+and 3 per cent of copper. A grade suitable for repairing is made from
+80 per cent of lead and 20 per cent antimony. This last formula should not
+be used for particular work or heavy loads, being more suitable for
+spacers. Innumerable proportions of metals are marketed under the name of
+babbitt.
+
+Solder is made from 50 per cent tin and 50 per cent lead, this grade being
+called "half-and-half." Hard solder is made from two-thirds tin and
+one-third lead.
+
+Aluminum forms many different alloys, giving increased strength to whatever
+metal it unites with.
+
+Aluminum brass is composed of approximately 65 per cent copper, 30 per cent
+zinc and 5 per cent aluminum. It forms a metal with high tensile strength
+while being ductile and malleable.
+
+Aluminum zinc is suitable for castings which must be stiff and hard.
+
+Nickel aluminum has a tensile strength of 40,000 pounds per square inch.
+
+Magnalium is a silver-white alloy of aluminum with from 5 to 20 per cent of
+magnesium, forming a metal even lighter than aluminum and strong enough to
+be used in making high-speed gasoline engines.
+
+
+HEAT TREATMENT OF STEEL
+
+The processes of heat treatment are designed to suit the steel for various
+purposes by changing the size of the grain in the metal, therefore the
+strength; and by altering the chemical composition of the alloys in the
+metal to give it different physical properties. Heat treatment, as applied
+in ordinary shop work, includes the three processes of annealing, hardening
+and tempering, each designed to accomplish a certain definite result.
+
+All of these processes require that the metal treated be gradually brought
+to a certain predetermined degree of heat which shall be uniform throughout
+the piece being handled and, from this point, cooled according to certain
+rules, the selection of which forms the difference in the three methods.
+
+_Annealing._--This is the process which relieves all internal strains
+and distortion in the metal and softens it so that it may more easily be
+cut, machined or bent to the required form. In some cases annealing is used
+only to relieve the strains, this being the case after forging or welding
+operations have been performed. In other cases it is only desired to soften
+the metal sufficiently that it may be handled easily. In some cases both of
+these things must be accomplished, as after a piece has been forged and
+must be machined. No matter what the object, the procedure is the same.
+
+The steel to be annealed must first be heated to a dull red. This heating
+should be done slowly so that all parts of the piece have time to reach the
+same temperature at very nearly the same time. The piece may be heated in
+the forge, but a much better way is to heat in an oven or furnace of some
+type where the work is protected against air currents, either hot or cold,
+and is also protected against the direct action of the fire.
+
+[Illustration: Figure 4.--A Gaspipe Annealing Oven]
+
+Probably the simplest of all ovens for small tools is made by placing a
+piece of ordinary gas pipe in the fire (Figure 4), and heating until the
+inside of the pipe is bright red. Parts placed in this pipe, after one end
+has been closed, may be brought to the desired heat without danger of
+cooling draughts or chemical change from the action of the fire. More
+elaborate ovens may be bought which use gas, fuel oils or coal to produce
+the heat and in which the work may be placed on trays so that the fire will
+not strike directly on the steel being treated.
+
+If the work is not very important, it may be withdrawn from the fire or
+oven, after heating to the desired point, and allowed to cool in the air
+until all traces of red have disappeared when held in a dark place. The
+work should be held where it is reasonably free from cold air currents. If,
+upon touching a pine stick to the piece being annealed, the wood does not
+smoke, the work may then be cooled in water.
+
+Better annealing is secured and harder metal may be annealed if the cooling
+is extended over a number of hours by placing the work in a bed of
+non-heat-conducting material, such as ashes, charred bone, asbestos fibre,
+lime, sand or fire clay. It should be well covered with the heat retaining
+material and allowed to remain until cool. Cooling may be accomplished by
+allowing the fire in an oven or furnace to die down and go out, leaving the
+work inside the oven with all openings closed. The greater the time taken
+for gradual cooling from the red heat, the more perfect will be the results
+of the annealing.
+
+While steel is annealed by slow cooling, copper or brass is annealed by
+bringing to a low red heat and quickly plunging into cold water.
+
+_Hardening._--Steel is hardened by bringing to a proper temperature,
+slowly and evenly as for annealing, and then cooling more or less quickly,
+according to the grade of steel being handled. The degree of hardening is
+determined by the kind of steel, the temperature from which the metal is
+cooled and the temperature and nature of the bath into which it is plunged
+for cooling.
+
+Steel to be hardened is often heated in the fire until at some heat around
+600 to 700 degrees is reached, then placed in a heating bath of molten
+lead, heated mercury, fused cyanate of potassium, etc., the heating bath
+itself being kept at the proper temperature by fires acting on it. While
+these baths have the advantage of heating the metal evenly and to exactly
+the temperature desired throughout without any part becoming over or under
+heated, their disadvantages consist of the fact that their materials and
+the fumes are poisonous in most all cases, and if not poisonous, are
+extremely disagreeable.
+
+The degree of heat that a piece of steel must be brought to in order that
+it may be hardened depends on the percentage of carbon in the steel. The
+greater the percentage of carbon, the lower the heat necessary to harden.
+
+[Illustration: Figure 5.--Cooling the Test Bar for Hardening]
+
+To find the proper heat from which any steel must be cooled, a simple test
+may be carried out provided a sample of the steel, about six inches long
+can be secured. One end of this test bar should be heated almost to its
+melting point, and held at this heat until the other end just turns red.
+Now cool the piece in water by plunging it so that both ends enter at the
+same time (Figure 5), that is, hold it parallel with the surface of the
+water when plunged in. This serves the purpose of cooling each point along
+the bar from a different heat. When it has cooled in the water remove the
+piece and break it at short intervals, about 1/2 inch, along its length.
+The point along the test bar which was cooled from the best possible
+temperature will show a very fine smooth grain and the piece cannot be cut
+by a file at this point. It will be necessary to remember the exact color
+of that point when taken from the fire, making another test if necessary,
+and heat all pieces of this same steel to this heat. It will be necessary
+to have the cooling bath always at the same temperature, or the results
+cannot be alike.
+
+While steel to be hardened is usually cooled in water, many other liquids
+may be used. If cooled in strong brine, the heat will be extracted much
+quicker, and the degree of hardness will be greater. A still greater degree
+of hardness is secured by cooling in a bath of mercury. Care should be used
+with the mercury bath, as the fumes that arise are poisonous.
+
+Should toughness be desired, without extreme hardness, the steel may be
+cooled in a bath of lard oil, neatsfoot oil or fish oil. To secure a result
+between water and oil, it is customary to place a thick layer of oil on top
+of water. In cooling, the piece will pass through the oil first, thus
+avoiding the sudden shock of the cold water, yet producing a degree of
+hardness almost as great as if the oil were not used.
+
+It will, of course, be necessary to make a separate test for each cooling
+medium used. If the fracture of the test piece shows a coarse grain, the
+steel was too hot at that point; if the fracture can be cut with a file,
+the metal was not hot enough at that point.
+
+When hardening carbon tool steel its heat should be brought to a cherry
+red, the exact degree of heat depending on the amount of carbon and the
+test made, then plunged into water and held there until all hissing sound
+and vibration ceases. Brine may be used for this purpose; it is even better
+than plain water. As soon as the hissing stops, remove the work from the
+water or brine and plunge in oil for complete cooling.
+
+[Illustration: Figure 6.--Cooling the Tool for Tempering]
+
+In hardening high-speed tool steel, or air hardening steels, the tool
+should be handled as for carbon steel, except that after the body reaches
+a cherry red, the cutting point must be quickly brought to a white heat,
+almost melting, so that it seems ready for welding. Then cool in an oil
+bath or in a current of cool air.
+
+Hardening of copper, brass and bronze is accomplished by hammering or
+working them while cold.
+
+_Tempering_ is the process of making steel tough after it has been
+hardened, so that it will hold a cutting edge and resist cracking.
+Tempering makes the grain finer and the metal stronger. It does not affect
+the hardness, but increases the elastic limit and reduces the brittleness
+of the steel. In that tempering is usually performed immediately after
+hardening, it might be considered as a continuation of the former process.
+
+The work or tool to be tempered is slowly heated to a cherry red and the
+cutting end is then dipped into water to a depth of 1/2 to 3/4 inch above
+the point (Figure 6). As soon as the point cools, still leaving the tool
+red above the part in water, remove the work from the bath and quickly rub
+the end with a fine emery cloth.
+
+As the heat from the uncooled part gradually heats the point again, the
+color of the polished portion changes rapidly. When a certain color is
+reached, the tool should be completely immersed in the water until cold.
+
+For lathe, planer, shaper and slotter tools, this color should be a light
+straw.
+
+Reamers and taps should be cooled from an ordinary straw color.
+
+Drills, punches and wood working tools should have a brown color.
+
+Blue or light purple is right for cold chisels and screwdrivers.
+
+Dark blue should be reached for springs and wood saws.
+
+Darker colors than this, ranging through green and gray, denote that the
+piece has reached its ordinary temper, that is, it is partially annealed.
+
+After properly hardening a spring by dipping in lard or fish oil, it should
+be held over a fire while still wet with the oil. The oil takes fire and
+burns off, properly tempering the spring.
+
+Remember that self-hardening steels must never be dipped in water, and
+always remember for all work requiring degrees of heat, that the more
+carbon, the less heat.
+
+_Case Hardening._--This is a process for adding more carbon to the
+surface of a piece of steel, so that it will have good wear-resisting
+qualities, while being tough and strong on the inside. It has the effect of
+forming a very hard and durable skin on the surface of soft steel, leaving
+the inside unaffected.
+
+The simplest way, although not the most efficient, is to heat the piece to
+be case hardened to a red heat and then sprinkle or rub the part of the
+surface to be hardened with potassium ferrocyanide. This material is a
+deadly poison and should be handled with care. Allow the cyanide to fuse on
+the surface of the metal and then plunge into water, brine or mercury.
+Repeating the process makes the surface harder and the hard skin deeper
+each time.
+
+Another method consists of placing the piece to be hardened in a bed of
+powdered bone (bone which has been burned and then powdered) and cover with
+more powdered bone, holding the whole in an iron tray. Now heat the tray
+and bone with the work in an oven to a bright red heat for 30 minutes to an
+hour and then plunge the work into water or brine.
+
+
+
+
+CHAPTER II
+
+OXY-ACETYLENE WELDING AND CUTTING MATERIALS
+
+
+_Welding._--Oxy-acetylene welding is an autogenous welding process, in
+which two parts of the same or different metals are joined by causing the
+edges to melt and unite while molten without the aid of hammering or
+compression. When cool, the parts form one piece of metal.
+
+The oxy-acetylene flame is made by mixing oxygen and acetylene gases in a
+special welding torch or blowpipe, producing, when burned, a heat of 6,300
+degrees, which is more than twice the melting temperature of the common
+metals. This flame, while being of intense heat, is of very small size.
+
+_Cutting._--The process of cutting metals with the flame produced from
+oxygen and acetylene depends on the fact that a jet of oxygen directed upon
+hot metal causes the metal itself to burn away with great rapidity,
+resulting in a narrow slot through the section cut. The action is so fast
+that metal is not injured on either side of the cut.
+
+_Carbon Removal._--This process depends on the fact that carbon will
+burn and almost completely vanish if the action is assisted with a supply
+of pure oxygen gas. After the combustion is started with any convenient
+flame, it continues as long as carbon remains in the path of the jet of
+oxygen.
+
+_Materials._--For the performance of the above operations we require
+the two gases, oxygen and acetylene, to produce the flames; rods of metal
+which may be added to the joints while molten in order to give the weld
+sufficient strength and proper form, and various chemical powders, called
+fluxes, which assist in the flow of metal and in doing away with many of
+the impurities and other objectionable features.
+
+_Instruments._--To control the combustion of the gases and add to the
+convenience of the operator a number of accessories are required.
+
+The pressure of the gases in their usual containers is much too high for
+their proper use in the torch and we therefore need suitable valves which
+allow the gas to escape from the containers when wanted, and other
+specially designed valves which reduce the pressure. Hose, composed of
+rubber and fabric, together with suitable connections, is used to carry the
+gas to the torch.
+
+The torches for welding and cutting form a class of highly developed
+instruments of the greatest accuracy in manufacture, and must be thoroughly
+understood by the welder. Tables, stands and special supports are provided
+for holding the work while being welded, and in order to handle the various
+metals and allow for their peculiarities while heated use is made of ovens
+and torches for preheating. The operator requires the protection of
+goggles, masks, gloves and appliances which prevent undue radiation of the
+heat.
+
+_Torch Practice._--The actual work of welding and cutting requires
+preliminary preparation in the form of heat treatment for the metals,
+including preheating, annealing and tempering. The surfaces to be joined
+must be properly prepared for the flame, and the operation of the torches
+for best results requires careful and correct regulation of the gases and
+the flame produced.
+
+Finally, the different metals that are to be welded require special
+treatment for each one, depending on the physical and chemical
+characteristics of the material.
+
+It will thus be seen that the apparently simple operations of welding and
+cutting require special materials, instruments and preparation on the part
+of the operator and it is a proved fact that failures, which have been
+attributed to the method, are really due to lack of these necessary
+qualifications.
+
+
+OXYGEN
+
+Oxygen, the gas which supports the rapid combustion of the acetylene in the
+torch flame, is one of the elements of the air. It is the cause and the
+active agent of all combustion that takes place in the atmosphere. Oxygen
+was first discovered as a separate gas in 1774, when it was produced by
+heating red oxide of mercury and was given its present name by the famous
+chemist, Lavoisier.
+
+Oxygen is prepared in the laboratory by various methods, these including
+the heating of chloride of lime and peroxide of cobalt mixed in a retort,
+the heating of chlorate of potash, and the separation of water into its
+elements, hydrogen and oxygen, by the passage of an electric current. While
+the last process is used on a large scale in commercial work, the others
+are not practical for work other than that of an experimental or temporary
+nature.
+
+This gas is a colorless, odorless, tasteless element. It is sixteen times
+as heavy as the gas hydrogen when measured by volume under the same
+temperature and pressure. Under all ordinary conditions oxygen remains in
+a gaseous form, although it turns to a liquid when compressed to 4,400
+pounds to the square inch and at a temperature of 220° below zero.
+
+Oxygen unites with almost every other element, this union often taking
+place with great heat and much light, producing flame. Steel and iron will
+burn rapidly when placed in this gas if the combustion is started with a
+flame of high heat playing on the metal. If the end of a wire is heated
+bright red and quickly plunged into a jar containing this gas, the wire
+will burn away with a dazzling light and be entirely consumed except for
+the molten drops that separate themselves. This property of oxygen is used
+in oxy-acetylene cutting of steel.
+
+The combination of oxygen with other substances does not necessarily cause
+great heat, in fact the combination may be so slow and gradual that the
+change of temperature can not be noticed. An example of this slow
+combustion, or oxidation, is found in the conversion of iron into rust as
+the metal combines with the active gas. The respiration of human beings
+and animals is a form of slow combustion and is the source of animal heat.
+It is a general rule that the process of oxidation takes place with
+increasing rapidity as the temperature of the body being acted upon rises.
+Iron and steel at a red heat oxidize rapidly with the formation of a scale
+and possible damage to the metal.
+
+_Air._--Atmospheric air is a mixture of oxygen and nitrogen with
+traces of carbonic acid gas and water vapor. Twenty-one per cent of the
+air, by volume, is oxygen and the remaining seventy-nine per cent is the
+inactive gas, nitrogen. But for the presence of the nitrogen, which deadens
+the action of the other gas, combustion would take place at a destructive
+rate and be beyond human control in almost all cases. These two gases exist
+simply as a mixture to form the air and are not chemically combined. It is
+therefore a comparatively simple matter to separate them with the processes
+now available.
+
+_Water._--Water is a combination of oxygen and hydrogen, being
+composed of exactly two volumes of hydrogen to one volume of oxygen. If
+these two gases be separated from each other and then allowed to mix in
+these proportions they unite with explosive violence and form water. Water
+itself may be separated into the gases by any one of several means, one
+making use of a temperature of 2,200° to bring about this separation.
+
+[Illustration: Figure 7.--Obtaining Oxygen by Electrolysis]
+
+The easiest way to separate water into its two parts is by the process
+called electrolysis (Figure 7). Water, with which has been mixed a small
+quantity of acid, is placed in a vat through the walls of which enter the
+platinum tipped ends of two electrical conductors, one positive and the
+other negative.
+
+Tubes are placed directly above these wire terminals in the vat, one tube
+being over each electrode and separated from each other by some distance.
+With the passage of an electric current from one wire terminal to the
+other, bubbles of gas rise from each and pass into the tubes. The gas that
+comes from the negative terminal is hydrogen and that from the positive
+pole is oxygen, both gases being almost pure if the work is properly
+conducted. This method produces electrolytic oxygen and electrolytic
+hydrogen.
+
+_The Liquid Air Process._--While several of the foregoing methods of
+securing oxygen are successful as far as this result is concerned, they are
+not profitable from a financial standpoint. A process for separating oxygen
+from the nitrogen in the air has been brought to a high state of perfection
+and is now supplying a major part of this gas for oxy-acetylene welding. It
+is known as the Linde process and the gas is distributed by the Linde Air
+Products Company from its plants and warehouses located in the large cities
+of the country.
+
+The air is first liquefied by compression, after which the gases are
+separated and the oxygen collected. The air is purified and then compressed
+by successive stages in powerful machines designed for this purpose until
+it reaches a pressure of about 3,000 pounds to the square inch. The large
+amount of heat produced is absorbed by special coolers during the process
+of compression. The highly compressed air is then dried and the
+temperature further reduced by other coolers.
+
+The next point in the separation is that at which the air is introduced
+into an apparatus called an interchanger and is allowed to escape through a
+valve, causing it to turn to a liquid. This liquid air is sprayed onto
+plates and as it falls, the nitrogen return to its gaseous state and leaves
+ the oxygen to run to the bottom of the container. This liquid oxygen is
+then allowed to return to a gas and is stored in large gasometers or tanks.
+
+The oxygen gas is taken from the storage tanks and compressed to
+approximately 1,800 pounds to the square inch, under which pressure it is
+passed into steel cylinders and made ready for delivery to the customer.
+This oxygen is guaranteed to be ninety-seven per cent pure.
+
+Another process, known as the Hildebrandt process, is coming into use in
+this country. It is a later process and is used in Germany to a much
+greater extent than the Linde process. The Superior Oxygen Co. has secured
+the American rights and has established several plants.
+
+_Oxygen Cylinders_.--Two sizes of cylinders are in use, one containing
+100 cubic feet of gas when it is at atmospheric pressure and the other
+containing 250 cubic feet under similar conditions. The cylinders are made
+from one piece of steel and are without seams. These containers are tested
+at double the pressure of the gas contained to insure safety while
+handling.
+
+One hundred cubic feet of oxygen weighs nearly nine pounds (8.921), and
+therefore the cylinders will weigh practically nine pounds more when full
+than after emptying, if of the 100 cubic feet size. The large cylinders
+weigh about eighteen and one-quarter pounds more when full than when empty,
+making approximately 212 pounds empty and 230 pounds full.
+
+The following table gives the number of cubic feet of oxygen remaining in
+the cylinders according to various gauge pressures from an initial pressure
+of 1,800 pounds. The amounts given are not exactly correct as this would
+necessitate lengthy calculations which would not make great enough
+difference to affect the practical usefulness of the table:
+
+Cylinder of 100 Cu. Ft. Capacity at 68° Fahr.
+
+ Gauge     Volume     Gauge     Volume
+Pressure  Remaining  Pressure  Remaining
+
+ 1800        100       700        39
+ 1620         90       500        28
+ 1440         80       300        17
+ 1260         70       100         6
+ 1080         60        18         1
+  900         50         9          1/2
+
+Cylinder of 250 Cu. Ft. Capacity at 68° Fahr.
+
+ Gauge     Volume     Gauge     Volume
+Pressure  Remaining  Pressure  Remaining
+
+ 1800        250       700        97
+ 1620        225       500        70
+ 1440        200       300        42
+ 1260        175       100        15
+ 1080        150        18         8
+  900        125         9         1-1/4
+
+The temperature of the cylinder affects the pressure in a large degree, the
+pressure increasing with a rise in temperature and falling with a fall in
+temperature. The variation for a 100 cubic foot cylinder at various
+temperatures is given in the following tabulation:
+
+At 150° Fahr........................ 2090 pounds.
+At 100° Fahr........................ 1912 pounds.
+At  80° Fahr........................ 1844 pounds.
+At  68° Fahr........................ 1800 pounds.
+At  50° Fahr........................ 1736 pounds.
+At  32° Fahr........................ 1672 pounds.
+At   0  Fahr........................ 1558 pounds.
+At -10° Fahr........................ 1522 pounds.
+
+_Chlorate of Potash Method._--In spite of its higher cost and the
+inferior gas produced, the chlorate of potash method of producing oxygen is
+used to a limited extent when it is impossible to secure the gas in
+cylinders.
+
+[Illustration: Figure 8.--Oxygen from Chlorate of Potash]
+
+An iron retort (Figure 8) is arranged to receive about fifteen pounds of
+chlorate of potash mixed with three pounds of manganese dioxide, after
+which the cylinder is closed with a tight cap, clamped on. This retort is
+carried above a burner using fuel gas or other means of generating heat and
+this burner is lighted after the chemical charge is mixed and compressed in
+the tube.
+
+The generation of gas commences and the oxygen is led through water baths
+which wash and cool it before storing in a tank connected with the plant.
+From this tank the gas is compressed into portable cylinders at a pressure
+of about 300 pounds to the square inch for use as required in welding
+operations.
+
+Each pound of chlorate of potash liberates about three cubic feet of
+oxygen, and taking everything into consideration, the cost of gas produced
+in this way is several times that of the purer product secured by the
+liquid air process.
+
+These chemical generators are oftentimes a source of great danger,
+especially when used with or near the acetylene gas generator, as is
+sometimes the case with cheap portable outfits. Their use should not be
+tolerated when any other method is available, as the danger from accident
+alone should prohibit the practice except when properly installed and
+cared for away from other sources of combustible gases.
+
+
+ACETYLENE
+
+In 1862 a chemist, Woehler, announced the discovery of the preparation of
+acetylene gas from calcium carbide, which he had made by heating to a high
+temperature a mixture of charcoal with an alloy of zinc and calcium. His
+product would decompose water and yield the gas. For nearly thirty years
+these substances were neglected, with the result that acetylene was
+practically unknown, and up to 1892 an acetylene flame was seen by very few
+persons and its possibilities were not dreamed of. With the development of
+the modern electric furnace the possibility of calcium carbide as a
+commercial product became known.
+
+In the above year, Thomas L. Willson, an electrical engineer of Spray,
+North Carolina, was experimenting in an attempt to prepare metallic
+calcium, for which purpose he employed an electric furnace operating on a
+mixture of lime and coal tar with about ninety-five horse power. The result
+was a molten mass which became hard and brittle when cool. This apparently
+useless product was discarded and thrown in a nearby stream, when, to the
+astonishment of onlookers, a large volume of gas was immediately
+liberated, which, when ignited, burned with a bright and smoky flame and
+gave off quantities of soot. The solid material proved to be calcium
+carbide and the gas acetylene.
+
+Thus, through the incidental study of a by-product, and as the result of an
+accident, the possibilities in carbide were made known, and in the spring
+of 1895 the first factory in the world for the production of this substance
+was established by the Willson Aluminum Company.
+
+When water and calcium carbide are brought together an action takes place
+which results in the formation of acetylene gas and slaked lime.
+
+
+CARBIDE
+
+Calcium carbide is a chemical combination of the elements carbon and
+calcium, being dark brown, black or gray with sometimes a blue or red
+tinge. It looks like stone and will only burn when heated with oxygen.
+
+Calcium carbide may be preserved for any length of time if protected from
+the air, but the ordinary moisture in the atmosphere gradually affects it
+until nothing remains but slaked lime. It always possesses a penetrating
+odor, which is not due to the carbide itself but to the fact that it is
+being constantly affected by moisture and producing small quantities of
+acetylene gas.
+
+This material is not readily dissolved by liquids, but if allowed to come
+in contact with water, a decomposition takes place with the evolution of
+large quantities of gas. Carbide is not affected by shock, jarring or age.
+
+A pound of absolutely pure carbide will yield five and one-half cubic feet
+of acetylene. Absolute purity cannot be attained commercially, and in
+practice good carbide will produce from four and one-half to five cubic
+feet for each pound used.
+
+Carbide is prepared by fusing lime and carbon in the electric furnace under
+a heat in excess of 6,000 degrees Fahrenheit. These materials are among the
+most difficult to melt that are known. Lime is so infusible that it is
+frequently employed for the materials of crucibles in which the highest
+melting metals are fused, and for the pencils in the calcium light because
+it will stand extremely high temperatures.
+
+Carbon is the material employed in the manufacture of arc light electrodes
+and other electrical appliances that must stand extreme heat. Yet these two
+substances are forced into combination in the manufacture of calcium
+carbide. It is the excessively high temperature attainable in the electric
+furnace that causes this combination and not any effect of the electricity
+other than the heat produced.
+
+A mixture of ground coke and lime is introduced into the furnace through
+which an electric arc has been drawn. The materials unite and form an ingot
+of very pure carbide surrounded by a crust of less purity. The poorer crust
+is rejected in breaking up the mass into lumps which are graded according
+to their size. The largest size is 2 by 3-1/2 inches and is called "lump,"
+a medium size is 1/2 by 2 inches and is called "egg," an intermediate size
+for certain types of generators is 3/8 by 1-1/4 inches and called "nut,"
+and the finely crushed pieces for use in still other types of generators
+are 1/12 by 1/4 inch in size and are called "quarter." Instructions as to
+the size best suited to different generators are furnished by the makers
+of those instruments.
+
+These sizes are packed in air-tight sheet steel drums containing 100 pounds
+each. The Union Carbide Company of Chicago and New York, operating under
+patents, manufactures and distributes the supply of calcium carbide for the
+entire United States. Plants for this manufacture are established at
+Niagara Falls, New York, and Sault Ste. Marie, Michigan. This company
+maintains a system of warehouses in more than one hundred and ten cities,
+where large stocks of all sizes are carried.
+
+The National Board of Fire Underwriters gives the following rules for the
+storage of carbide:
+
+Calcium carbide in quantities not to exceed six hundred pounds may be
+stored, when contained in approved metal packages not to exceed one hundred
+pounds each, inside insured property, provided that the place of storage be
+dry, waterproof and well ventilated and also provided that all but one of
+the packages in any one building shall be sealed and that seals shall not
+be broken so long as there is carbide in excess of one pound in any other
+unsealed package in the building.
+
+Calcium carbide in quantities in excess of six hundred pounds must be
+stored above ground in detached buildings, used exclusively for the storage
+of calcium carbide, in approved metal packages, and such buildings shall be
+constructed to be dry, waterproof and well ventilated.
+
+_Properties of Acetylene._--This gas is composed of twenty-four parts
+of carbon and two parts of hydrogen by weight and is classed with natural
+gas, petroleum, etc., as one of the hydrocarbons. This gas contains the
+highest percentage of carbon known to exist in any combination of this form
+and it may therefore be considered as gaseous carbon. Carbon is the fuel
+that is used in all forms of combustion and is present in all fuels from
+whatever source or in whatever form. Acetylene is therefore the most
+powerful of all fuel gases and is able to give to the torch flame in
+welding the highest temperature of any flame.
+
+Acetylene is a colorless and tasteless gas, possessed of a peculiar and
+penetrating odor. The least trace in the air of a room is easily noticed,
+and if this odor is detected about an apparatus in operation, it is certain
+to indicate a leakage of gas through faulty piping, open valves, broken
+hose or otherwise. This leakage must be prevented before proceeding with
+the work to be done.
+
+All gases which burn in air will, when mixed with air previous to ignition,
+produce more or less violent explosions, if fired. To this rule acetylene
+is no exception. One measure of acetylene and twelve and one-half of air
+are required for complete combustion; this is therefore the proportion for
+the most perfect explosion. This is not the only possible mixture that will
+explode, for all proportions from three to thirty per cent of acetylene in
+air will explode with more or less force if ignited.
+
+The igniting point of acetylene is lower than that of coal gas, being about
+900 degrees Fahrenheit as against eleven hundred degrees for coal gas. The
+gas issuing from a torch will ignite if allowed to play on the tip of a
+lighted cigar.
+
+It is still further true that acetylene, at some pressures, greater than
+normal, has under most favorable conditions for the effect, been found to
+explode; yet it may be stated with perfect confidence that under no
+circumstances has anyone ever secured an explosion in it when subjected to
+pressures not exceeding fifteen pounds to the square inch.
+
+Although not exploded by the application of high heat, acetylene is injured
+by such treatment. It is partly converted, by high heat, into other
+compounds, thus lessening the actual quantity of the gas, wasting it and
+polluting the rest by the introduction of substances which do not belong
+there. These compounds remain in part with the gas, causing it to burn with
+a persistent smoky flame and with the deposit of objectionable tarry
+substances. Where the gas is generated without undue rise of temperature
+these difficulties are avoided.
+
+_Purification of Acetylene._--Impurities in this gas are caused by
+impurities in the calcium carbide from which it is made or by improper
+methods and lack of care in generation. Impurities from the material will
+be considered first.
+
+Impurities in the carbide may be further divided into two classes: those
+which exert no action on water and those which act with the water to throw
+off other gaseous products which remain in the acetylene. Those impurities
+which exert no action on the water consist of coke that has not been
+changed in the furnace and sand and some other substances which are
+harmless except that they increase the ash left after the acetylene has
+been generated.
+
+An analysis of the gas coming from a typical generator is as follows:
+
+                                          Per cent
+  Acetylene ................................ 99.36
+  Oxygen ...................................   .08
+  Nitrogen .................................   .11
+  Hydrogen .................................   .06
+  Sulphuretted Hydrogen ....................   .17
+  Phosphoretted Hydrogen ...................   .04
+  Ammonia ..................................   .10
+  Silicon Hydride ..........................   .03
+  Carbon Monoxide ..........................   .01
+  Methane ..................................   .04
+
+The oxygen, nitrogen, hydrogen, methane and carbon monoxide are either
+harmless or are present in such small quantities as to be neglected. The
+phosphoretted hydrogen and silicon hydride are self-inflammable gases when
+exposed to the air, but their quantity is so very small that this
+possibility may be dismissed. The ammonia and sulphuretted hydrogen are
+almost entirely dissolved by the water used in the gas generator. The
+surest way to avoid impure gas is to use high-grade calcium carbide in the
+generator and the carbide of American manufacture is now so pure that it
+never causes trouble.
+
+The first and most important purification to which the gas is subjected is
+its passage through the body of water in the generator as it bubbles to the
+top. It is then filtered through felt to remove the solid particles of lime
+dust and other impurities which float in the gas.
+
+Further purification to remove the remaining ammonia, sulphuretted hydrogen
+and phosphorus containing compounds is accomplished by chemical means. If
+this is considered necessary it can be easily accomplished by readily
+available purifying apparatus which can be attached to any generator or
+inserted between the generator and torch outlets. The following mixtures
+have been used.
+
+"_Heratol,_" a solution of chromic acid or sulphuric acid absorbed in
+porous earth.
+
+"_Acagine,_" a mixture of bleaching powder with fifteen per cent of
+lead chromate.
+
+"_Puratylene,_" a mixture of bleaching powder and hydroxide of lime,
+made very porous, and containing from eighteen to twenty per cent of active
+chlorine.
+
+"_Frankoline,_" a mixture of cuprous and ferric chlorides dissolved in
+strong hydrochloric acid absorbed in infusorial earth.
+
+A test for impure acetylene gas is made by placing a drop of ten per cent
+solution of silver nitrate on a white blotter and holding the paper in a
+stream of gas coming from the torch tip. Blackening of the paper in a short
+length of time indicates impurities.
+
+_Acetylene in Tanks._--Acetylene is soluble in water to a very limited
+extent, too limited to be of practical use. There is only one liquid that
+possesses sufficient power of containing acetylene in solution to be of
+commercial value, this being the liquid acetone. Acetone is produced in
+various ways, oftentimes from the distillation of wood. It is a
+transparent, colorless liquid that flows with ease. It boils at 133°
+Fahrenheit, is inflammable and burns with a luminous flame. It has a
+peculiar but rather agreeable odor.
+
+Acetone dissolves twenty-four times its own bulk of acetylene at ordinary
+atmospheric pressure. If this pressure is increased to two atmospheres,
+14.7 pounds above ordinary pressure, it will dissolve just twice as much of
+the gas and for each atmosphere that the pressure is increased it will
+dissolve as much more.
+
+If acetylene be compressed above fifteen pounds per square inch at ordinary
+temperature without first being dissolved in acetone a danger is present of
+self-ignition. This danger, while practically nothing at fifteen pounds,
+increases with the pressure until at forty atmospheres it is very
+explosive. Mixed with acetone, the gas loses this dangerous property and is
+safe for handling and transportation. As acetylene is dissolved in the
+liquid the acetone increases its volume slightly so that when the gas has
+been drawn out of a closed tank a space is left full of free acetylene.
+
+This last difficulty is removed by first filling the cylinder or tank with
+some porous material, such as asbestos, wood charcoal, infusorial earth,
+etc. Asbestos is used in practice and by a system of packing and supporting
+the absorbent material no space is left for the free gas, even when the
+acetylene has been completely withdrawn.
+
+The acetylene is generated in the usual way and is washed, purified and
+dried. Great care is used to make the gas as free as possible from all
+impurities and from air. The gas is forced into containers filled with
+acetone as described and is compressed to one hundred and fifty pounds to
+the square inch. From these tanks it is transferred to the smaller portable
+cylinders for consumers' use.
+
+The exact volume of gas remaining in a cylinder at atmospheric temperature
+may be calculated if the weight of the cylinder empty is known. One pound
+of the gas occupies 13.6 cubic feet, so that if the difference in weight
+between the empty cylinder and the one considered be multiplied by 13.6.
+the result will be the number of cubic feet of gas contained.
+
+The cylinders contain from 100 to 500 cubic feet of acetylene under
+pressure. They cannot be filled with the ordinary type of generator as they
+require special purifying and compressing apparatus, which should never be
+installed in any building where other work is being carried on, or near
+other buildings which are occupied, because of the danger of explosion.
+
+Dissolved acetylene is manufactured by the Prest-O-Lite Company, the
+Commercial Acetylene Company and the Searchlight Gas Company and is
+distributed from warehouses in various cities.
+
+These tanks should not be discharged at a rate per hour greater than
+one-seventh of their total capacity, that is, from a tank of 100 cubic feet
+capacity, the discharge should not be more than fourteen cubic feet per
+hour. If discharge is carried on at an excessive rate the acetone is drawn
+out with the gas and reduces the heat of the welding flame.
+
+For this reason welding should not be attempted with cylinders designed for
+automobile and boat lighting. When the work demands a greater delivery than
+one of the larger tanks will give, two or more tanks may be connected with
+a special coupler such as may be secured from the makers and distributers
+of the gas. These couplers may be arranged for two, three, four or five
+tanks in one battery by removing the plugs on the body of the coupler and
+attaching additional connecting pipes. The coupler body carries a pressure
+gauge and the valve for controlling the pressure of the gas as it flows to
+the welding torches. The following capacities should be provided for:
+
+Acetylene Consumption         Combined Capacity of
+ of Torches per Hour           Cylinders in Use
+Up to 15 feet.......................100 cubic feet
+16 to 30 feet.......................200 cubic feet
+31 to 45 feet.......................300 cubic feet
+46 to 60 feet.......................400 cubic feet
+61 to 75 feet.......................500 cubic feet
+
+
+WELDING RODS
+
+The best welding cannot be done without using the best grade of materials,
+and the added cost of these materials over less desirable forms is so
+slight when compared to the quality of work performed and the waste of
+gases with inferior supplies, that it is very unprofitable to take any
+chances in this respect. The makers of welding equipment carry an
+assortment of supplies that have been standardized and that may be relied
+upon to produce the desired result when properly used. The safest plan is
+to secure this class of material from the makers.
+
+Welding rods, or welding sticks, are used to supply the additional metal
+required in the body of the weld to replace that broken or cut away and
+also to add to the joint whenever possible so that the work may have the
+same or greater strength than that found in the original piece. A rod of
+the same material as that being welded is used when both parts of the work
+are the same. When dissimilar metals are to be joined rods of a composition
+suited to the work are employed.
+
+These filling rods are required in all work except steel of less than 16
+gauge. Alloy iron rods are used for cast iron. These rods have a high
+silicon content, the silicon reacting with the carbon in the iron to
+produce a softer and more easily machined weld than would otherwise be the
+case. These rods are often made so that they melt at a slightly lower point
+than cast iron. This is done for the reason that when the part being welded
+has been brought to the fusing heat by the torch, the filling material can
+be instantly melted in without allowing the parts to cool. The metal can be
+added faster and more easily controlled.
+
+Rods or wires of Norway iron are used for steel welding in almost all
+cases. The purity of this grade of iron gives a homogeneous, soft weld of
+even texture, great ductility and exceptionally good machining qualities.
+For welding heavy steel castings, a rod of rolled carbon steel is employed.
+For working on high carbon steel, a rod of the steel being welded must be
+employed and for alloy steels, such as nickel, manganese, vanadium, etc.,
+special rods of suitable alloy composition are preferable.
+
+Aluminum welding rods are made from this metal alloyed to give the even
+flowing that is essential. Aluminum is one of the most difficult of all the
+metals to handle in this work and the selection of the proper rod is of
+great importance.
+
+Brass is filled with brass wire when in small castings and sheets. For
+general work with brass castings, manganese bronze or Tobin bronze may be
+used.
+
+Bronze is welded with manganese bronze or Tobin bronze, while copper is
+filled with copper wire.
+
+These welding rods should always be used to fill the weld when the
+thickness of material makes their employment necessary, and additional
+metal should always be added at the weld when possible as the joint cannot
+have the same strength as the original piece if made or dressed off flush
+with the surfaces around the weld. This is true because the metal welded
+into the joint is a casting and will never have more strength than a
+casting of the material used for filling.
+
+Great care should be exercised when adding metal from welding rods to make
+sure that no metal is added at a point that is not itself melted and molten
+when the addition is made. When molten metal is placed upon cooler surfaces
+the result is not a weld but merely a sticking together of the two parts
+without any strength in the joint.
+
+
+FLUXES
+
+Difficulty would be experienced in welding with only the metal and rod to
+work with because of the scale that forms on many materials under heat, the
+oxides of other metals and the impurities found in almost all metals. These
+things tend to prevent a perfect joining of the metals and some means are
+necessary to prevent their action.
+
+Various chemicals, usually in powder form, are used to accomplish the
+result of cleaning the weld and making the work of the operator less
+difficult. They are called fluxes.
+
+A flux is used to float off physical impurities from the molten metal; to
+furnish a protecting coating around the weld; to assist in the removal of
+any objectionable oxide of the metals being handled; to lower the
+temperature at which the materials flow; to make a cleaner weld and to
+produce a better quality of metal in the finished work.
+
+The flux must be of such composition that it will accomplish the desired
+result without introducing new difficulties. They may be prepared by the
+operator in many cases or may be secured from the makers of welding
+apparatus, the same remarks applying to their quality as were made
+regarding the welding rods, that is, only the best should be considered.
+
+The flux used for cast iron should have a softening effect and should
+prevent burning of the metal. In many cases it is possible and even
+preferable to weld cast iron without the use of a flux, and in any event
+the smaller the quantity used the better the result should be. Flux should
+not be added just before the completion of the work because the heat will
+not have time to drive the added elements out of the metal or to
+incorporate them with the metal properly.
+
+Aluminum should never be welded without using a flux because of the oxide
+formed. This oxide, called alumina, does not melt until a heat of 5,000°
+Fahrenheit is reached, four times the heat needed to melt the aluminum
+itself. It is necessary that this oxide be broken down or dissolved so that
+the aluminum may have a chance to flow together. Copper is another metal
+that requires a flux because of its rapid oxidation under heat.
+
+While the flux is often thrown or sprinkled along the break while welding,
+much better results will be obtained by dipping the hot end of the welding
+rod into the flux whenever the work needs it. Sufficient powder will stick
+on the end of the rod for all purposes, and with some fluxes too much will
+adhere. Care should always be used to avoid the application of excessive
+flux, as this is usually worse than using too little.
+
+
+SUPPLIES AND FIXTURES
+
+_Goggles._--The oxy-acetylene torch should not be used without the
+protection to the eyes afforded by goggles. These not only relieve
+unnecessary strain, but make it much easier to watch the exact progress of
+the work with the molten metal. The difficulty of protecting the sight
+while welding is even greater than when cutting metal with the torch.
+
+Acetylene gives a light which is nearest to sunlight of any artificial
+illuminant. But for the fact that this gas light gives a little more green
+and less blue in its composition, it would be the same in quality and
+practically the same in intensity. This light from the gas is almost absent
+during welding, being lost with the addition of the extra oxygen needed to
+produce the welding heat. The light that is dangerous comes from the molten
+metal which flows under the torch at a bright white heat.
+
+Goggles for protection against this light and the heat that goes with it
+may be secured in various tints, the darker glass being for welding and
+the lighter for cutting. Those having frames in which the metal parts do
+not touch the flesh directly are most desirable because of the high
+temperature reached by these parts.
+
+_Gloves._--While not as necessary as are the goggles, gloves are a
+convenience in many cases. Those in which leather touches the hands
+directly are really of little value as the heat that protection is desired
+against makes the leather so hot that nothing is gained in comfort. Gloves
+are made with asbestos cloth, which are not open to this objection in so
+great a degree.
+
+[Illustration: Figure 9.--Frame for Welding Stand]
+
+_Tables and Stands._--Tables for holding work while being welded
+(Figure 9) are usually made from lengths of angle steel welded together.
+The top should be rectangular, about two feet wide and two and one-half
+feet long. The legs should support the working surface at a height of
+thirty-two to thirty-six inches from the floor. Metal lattice work may be
+fastened or laid in the top framework and used to support a layer of
+firebrick bound together with a mixture of one-third cement and two-thirds
+fireclay. The piece being welded is braced and supported on this table with
+pieces of firebrick so that it will remain stationary during the operation.
+
+Holders for supporting the tanks of gas may be
+made or purchased in forms that rest directly on the floor or that are
+mounted on wheels. These holders are quite useful where the floor or ground
+is very uneven.
+
+_Hose._--All permanent lines from tanks and generators to the torches
+are made with piping rigidly supported, but the short distance from the end
+of the pipe line to the torch itself is completed with a flexible hose so
+that the operator may be free in his movements while welding. An accident
+through which the gases mix in the hose and are ignited will burst this
+part of the equipment, with more or less painful results to the person
+handling it. For that reason it is well to use hose with great enough
+strength to withstand excessive pressure.
+
+A poor grade of hose will also break down inside and clog the flow of gas,
+both through itself and through the parts of the torch. To avoid outside
+damage and cuts this hose is sometimes encased with coiled sheet metal.
+Hose may be secured with a bursting strength of more than 1,000 pounds to
+the square inch. Many operators prefer to distinguish between the oxygen
+and acetylene lines by their color and to allow this, red is used for the
+oxygen and black for acetylene.
+
+_Other Materials._--Sheet asbestos and asbestos fibre in flakes are
+used to cover parts of the work while preparing them for welding and during
+the operation itself. The flakes and small pieces that become detached from
+the large sheets are thrown into a bin where the completed small work is
+placed to allow slow and even cooling while protected by the asbestos.
+
+Asbestos fibre and also ordinary fireclay are often used to make a backing
+or mould into a form that may be placed behind aluminum and some other
+metals that flow at a low heat and which are accordingly difficult to
+handle under ordinary methods. This forms a solid mould into which the
+metal is practically cast as melted by the torch so that the desired shape
+is secured without danger of the walls of metal breaking through and
+flowing away.
+
+Carbon blocks and rods are made in various shapes and sizes so that they
+may be used to fill threaded holes and other places that it is desired to
+protect during welding. These may be secured in rods of various diameters
+up to one inch and in blocks of several different dimensions.
+
+
+
+
+CHAPTER III
+
+ACETYLENE GENERATORS
+
+
+Acetylene generators used for producing the gas from the action of water on
+calcium carbide are divided into three principal classes according to the
+pressure under which they operate.
+
+Low pressure generators are designed to operate at one pound or less per
+square inch. Medium pressure systems deliver the gas at not to exceed
+fifteen pounds to the square inch while high pressure types furnish gas
+above fifteen pounds per square inch. High pressure systems are almost
+unknown in this country, the medium pressure type being often referred to
+as "high pressure."
+
+Another important distinction is formed by the method of bringing the
+carbide and water together. The majority of those now in use operate by
+dropping small quantities of carbide into a large volume of water, allowing
+the generated gas to bubble up through the water before being collected
+above the surface. This type is known as the "carbide to water" generator.
+
+A less used type brings a measured and small quantity of water to a
+comparatively large body of the carbide, the gas being formed and collected
+from the chamber in which the action takes place. This is called the "water
+to carbide" type. Another way of expressing the difference in feed is that
+of designating the two types as "carbide feed" for the former and "water
+feed" for the latter.
+
+A further division of the carbide to water machines is made by mentioning
+the exact method of feeding the carbide. One type, called "gravity feed"
+operates by allowing the carbide to escape and fall by the action of its
+own weight, or gravity; the other type, called "forced feed," includes a
+separate mechanism driven by power. This mechanism feeds definite amounts
+of the carbide to the water as required by the demands on the generator.
+The action of either feed is controlled by the withdrawal of gas from the
+generator, the aim being to supply sufficient carbide to maintain a nearly
+constant supply.
+
+_Generator Requirements._--The qualities of a good generator are
+outlined as follows: [Footnote: See Pond's "Calcium Carbide and
+Acetylene."]
+
+It must allow no possibility of the existence of an explosive mixture in
+any of its parts at any time. It is not enough to argue that a mixture,
+even if it exists, cannot be exploded unless kindled. It is necessary to
+demand that a dangerous mixture can at no time be formed, even if the
+machine is tampered with by an ignorant person. The perfect machine must be
+so constructed that it shall be impossible at any time, under any
+circumstances, to blow it up.
+
+It must insure cool generation. Since this is a relative term, all machines
+being heated somewhat during the generation of gas, this amounts to saying
+that a machine must heat but little. A pound of carbide decomposed by water
+develops the same amount of heat under all circumstances, but that heat
+can be allowed to increase locally to a high point, or it can be equalized
+by water so that no part of the material becomes heated enough to do
+damage.
+
+It must be well constructed. A good generator does not need, perhaps, to be
+"built like a watch," but it should be solid, substantial and of good
+material. It should be built for service, to last and not simply to sell;
+anything short of this is to be avoided as unsafe and unreliable.
+
+It must be simple. The more complicated the machine the sooner it will get
+out of order. Understand your generator. Know what is inside of it and
+beware of an apparatus, however attractive its exterior, whose interior is
+filled with pipes and tubes, valves and diaphragms whose functions you do
+not perfectly understand.
+
+It should be capable of being cleaned and recharged and of receiving all
+other necessary attention without loss of gas, both for economy's sake, and
+more particularly to avoid danger of fire.
+
+It should require little attention. All machines have to be emptied and
+recharged periodically; but the more this process is simplified and the
+more quickly this can be accomplished, the better.
+
+It should be provided with a suitable indicator to designate how low the
+charge is in order that the refilling may be done in good season.
+
+It should completely use up the carbide, generating the maximum amount of
+gas.
+
+_Overheating._--A large amount of heat is liberated when acetylene gas
+is formed from the union of calcium carbide and water. Overheating during
+this process, that is to say, an intense local heat rather than a large
+amount of heat well distributed, brings about the phenomenon of
+polymerization, converting the gas, or part of it, into oily matters, which
+can do nothing but harm. This tarry mass coming through the small openings
+in the torches causes them to become partly closed and alters the
+proportions of the gases to the detriment of the welding flame. The only
+remedy for this trouble is to avoid its cause and secure cool generation.
+
+Overheating can be detected by the appearance of the sludge remaining after
+the gas has been made. Discoloration, yellow or brown, shows that there has
+been trouble in this direction and the resultant effects at the torches may
+be looked for. The abundance of water in the carbide to water machines
+effects this cooling naturally and is a characteristic of well designed
+machines of this class. It has been found best and has practically become a
+fundamental rule of generation that a gallon of water must be provided for
+each pound of carbide placed in the generator. With this ratio and a
+generator large enough for the number of torches to be supplied, little
+trouble need be looked for with overheating.
+
+_Water to Carbide Generators._--It is, of course, much easier to
+obtain a measured and regular flow of water than to obtain such a flow of
+any solid substance, especially when the solid substance is in the form of
+lumps, as is carbide This fact led to the use of a great many water-feed
+generators for all classes of work, and this type is still in common use
+for the small portable machines, such, for instance, as those used on motor
+cars for the lamps. The water-feed machine is not, however, favored for
+welding plants, as is the carbide feed, in spite of the greater
+difficulties attending the handling of the solid material.
+
+A water-feed generator is made up of the gas producing part and a holder
+for the acetylene after it is made. The carbide is held in a tray formed of
+a number of small compartments so that the charge in each compartment is
+nearly equal to that in each of the others. The water is allowed to flow
+into one of these compartments in a volume sufficient to produce the
+desired amount of gas and the carbide is completely used from this one
+division. The water then floods the first compartment and finally overflows
+into the next one, where the same process is repeated. After using the
+carbide in this division, it is flooded in turn and the water passing on to
+those next in order, uses the entire charge of the whole tray.
+
+These generators are charged with the larger sizes of carbide and are
+easily taken care of. The residue is removed in the tray and emptied,
+making the generator ready for a fresh supply of carbide.
+
+_Carbide to Water Generators._--This type also is made up of two
+principal parts, the generating chamber and a gas holder, the holder being
+part of the generating chamber or a separate device. The generator (Figure
+10) contains a hopper to receive the charge of carbide and is fitted with
+the feeding mechanism to drop the proper amount of carbide into the water
+as required by the demands of the torches. The charge of carbide is of one
+of the smaller sizes, usually "nut" or "quarter."
+
+_Feed Mechanisms._--The device for dropping the carbide into the water
+is the only part of the machine that is at all complicated. This
+complication is brought about by the necessity of controlling the mass of
+carbide so that it can never be discharged into the water at an excessive
+rate, feeding it at a regular rate and in definite amounts, feeding it
+positively whenever required and shutting off the feed just as positively
+when the supply of gas in the holder is enough for the immediate needs.
+
+[Illustration: Figure 10.--Carbide to Water Generator. A. Feed motor weight;
+B. Carbide feed motor; C. Carbide hopper; D. Water for gas generation;
+E. Agitator for loosening residuum; F. Water seal in gas bell; G. Filter;
+H. Hydraulic Valve; J. Motor control levers.]
+
+The charge of carbide is unavoidably acted upon by the water vapor in the
+generator and will in time become more or less pasty and sticky. This is
+more noticeable if the generator stands idle for a considerable length of
+time This condition imposes another duty on the feeding mechanism; that is,
+the necessity of self-cleaning so that the carbide, no matter in what
+condition, cannot prevent the positive action of this part of the device,
+especially so that it cannot prevent the supply from being stopped at the
+proper time.
+
+The gas holder is usually made in the bell form so that the upper portion
+rises and falls with the addition to or withdrawal from the supply of gas
+in the holder. The rise and fall of this bell is often used to control the
+feed mechanism because this movement indicates positively whether enough
+gas has been made or that more is required. As the bell lowers it sets the
+feed mechanism in motion, and when the gas passing into the holder has
+raised the bell a sufficient distance, the movement causes the feed
+mechanism to stop the fall of carbide into the water. In practice, the
+movement of this part of the holder is held within very narrow limits.
+
+_Gas Holders._--No matter how close the adjustment of the feeding
+device, there will always be a slight amount of gas made after the fall of
+carbide is stopped, this being caused by the evolution of gas from the
+carbide with which water is already in contact. This action is called
+"after generation" and the gas holder in any type of generator must
+provide sufficient capacity to accommodate this excess gas. As a general
+rule the water to carbide generator requires a larger gas holder than the
+carbide to water type because of the greater amount of carbide being acted
+upon by the water at any one time, also because the surface of carbide
+presented to the moist air within the generating chamber is greater with
+this type.
+
+_Freezing._--Because of the rather large body of water contained in
+any type of generator, there is always danger of its freezing and
+rendering the device inoperative unless placed in a temperature above the
+freezing point of the water. It is, of course, dangerous and against the
+insurance rules to place a generator in the same room with a fire of any
+kind, but the room may be heated by steam or hot water coils from a furnace
+in another building or in another part of the same building.
+
+When the generator is housed in a separate structure the walls should be
+made of materials or construction that prevents the passage of heat or
+cold through them to any great extent. This may be accomplished by the use
+of hollow tile or concrete blocks or by any other form of double wall
+providing air spaces between the outer and inner facings. The space between
+the parts of the wall may be filled with materials that further retard the
+loss of heat if this is necessary under the conditions prevailing.
+
+_Residue From Generators._--The sludge remaining in the carbide to
+water generator may be drawn off into the sewer if the piping is run at a
+slant great enough to give a fall that carries the whole quantity, both
+water and ash, away without allowing settling and consequent clogging.
+Generators are provided with agitators which are operated to stir the ash
+up with the water so that the whole mass is carried off when the drain cock
+is opened.
+
+If sewer connections cannot be made in such a way that the ash is entirely
+carried away, it is best to run the liquid mass into a settling basin
+outside of the building. This should be in the form of a shallow pit which
+will allow the water to pass off by soaking into the ground and by
+evaporation, leaving the comparatively dry ash in the pit. This ash which
+remains is essentially slaked lime and can often be disposed of to more or
+less advantage to be used in mortar, whitewash, marking paths and any other
+use for which slaked lime is suited. The disposition of the ash depends
+entirely on local conditions. An average analysis of this ash is as
+follows:
+
+Sand.......................  1.10 per cent.
+Carbon.....................  2.72    "
+Oxide of iron and alumina..  2.77    "
+Lime....................... 64.06    "
+Water and carbonic acid.... 29.35    "
+                           ------
+                           100.00
+
+
+GENERATOR CONSTRUCTION
+
+The water for generating purposes is carried in the large tank-like
+compartment directly below the carbide chamber. See Figure 11. This water
+compartment is filled through a pipe of such a height that the water level
+cannot be brought above the proper point or else the water compartment is
+provided with a drain connection which accomplishes this same result by
+allowing an excess to flow away.
+
+The quantity of water depends on the capacity of the generator inasmuch as
+there must be one gallon for each pound of carbide required. The generator
+should be of sufficient capacity to furnish gas under working conditions
+from one charge of carbide to all torches installed for at least five hours
+continuous use.
+
+After calculating the withdrawal of the whole number of torches according
+to the work they are to do for this period of five hours the proper
+generator capacity may be found on the basis of one cubic foot of gas per
+hour for each pound of carbide. Thus if the torches were to use sixty cubic
+feet of gas per hour, five hours would call for three hundred cubic feet
+and a three hundred pound generator should be installed. Generators are
+rated according to their carbide capacity in pounds.
+
+_Charging._--The carbide capacity of the generator should be great
+enough to furnish a continuous supply of gas for the maximum operating
+time, basing the quantity of gas generated on four and one-half cubic feet
+from each pound of lump carbide and on four cubic feet from each pound of
+quarter, intermediate sizes being in proportion.
+
+Generators are built in such a way that it is impossible for the acetylene
+to escape from the gas holding compartment during the recharging process.
+This is accomplished (1) by connecting the water inlet pipe opening with a
+shut off valve in such a way that the inlet cannot be uncovered or opened
+without first closing the shut off valve with the same movement of the
+operator; (2) by incorporating an automatic or hydraulic one-way valve so
+that this valve closes and acts as a check when the gas attempts to flow
+from the holder back to the generating chamber, or by any other means that
+will positively accomplish this result.
+
+In generators having no separate gas holding chamber but carrying the
+supply in the same compartment in which it is generated, the gas contained
+under pressure is allowed to escape through vent pipes into the outside
+air before recharging with carbide. As in the former case, the parts are
+so interlocked that it is impossible to introduce carbide or water without
+first allowing the escape of the gas in the generator.
+
+It is required by the insurance rules that the entire change of carbide
+while in the generator be held in such a way that it may be entirely
+removed without difficulty in case the necessity should arise.
+
+Generators should be cleaned and recharged at regular stated intervals.
+This work should be done during daylight hours only and likewise all
+repairs should be made at such a time that artificial light is not needed.
+Where it is absolutely necessary to use artificial light it should be
+provided only by incandescent electric lamps enclosed in gas tight globes.
+
+In charging generating chambers the old ash and all residue must first be
+cleaned out and the operator should be sure that no drain or other pipe has
+become clogged. The generator should then be filled with the required
+amount of water. In charging carbide feed machines be careful not to place
+less than a gallon of water in the water compartment for each pound of
+carbide to be used and the water must be brought to, but not above, the
+proper level as indicated by the mark or the maker's instructions. The
+generating chamber must be filled with the proper amount of water before
+any attempt is made to place the carbide in its holder. This rule must
+always be followed. It is also necessary that all automatic water seals
+and valves, as well as any other water tanks, be filled with clean water
+at this time.
+
+Never recharge with carbide without first cleaning the generating chamber
+and completely refilling with clean water. Never test the generator or
+piping for leaks with any flame, and never apply flame to any open pipe or
+at any point other than the torch, and only to the torch after it has a
+welding or cutting nozzle attached. Never use a lighted match, lamp,
+candle, lantern, cigar or any open flame near a generator. Failure to
+observe these precautions is liable to endanger life and property.
+
+_Operation and Care of Generators._--The following instructions apply
+especially to the Davis Bournonville pressure generator, illustrated in
+Figure 11. The motor feed mechanism is illustrated in Figure 12.
+
+Before filling the machine, the cover should be removed and the hopper
+taken out and examined to see that the feeding disc revolves freely; that
+no chains have been displaced or broken, and that the carbide displacer
+itself hangs barely free of the feeding disc when it is revolved. After
+replacing the cover, replace the bolts and tighten them equally, a little
+at a time all around the circumference of the cover--not screwing tight in
+one place only. Do not screw the cover down any more than is necessary to
+make a tight fit.
+
+To charge the generator, proceed as follows: Open the vent valve by turning
+the handle which extends over the filling tube until it stands at a right
+angle with the generator. Open the valve in the water filling pipe, and
+through this fill with water until it runs out of the overflow pipe of the
+drainage chamber, then close the valve in the water filling pipe and vent
+valve. Remove the carbide filling plugs and fill the hopper with
+1-1/4"x3/8" carbide ("nut" size). Then replace the plugs and the
+safety-locking lever chains. Now rewind the motor weight. Run the pressure
+up to about five pounds by raising the controlling diaphragm valve lever
+by hand (Figure 12, lever marked _E_). Then raise the blow-off lever,
+allowing the gas to blow off until the gauge shows about two pounds; this
+to clear the generator of air mixture. Then run the pressure up to about
+eight pounds by raising the controlling valve lever _E_, or until
+this controlling lever rests against the upper wing of the fan governor,
+and prevents operation of the feed motor. After this is done, the motor
+will operate automatically as the gas is consumed.
+
+[Illustration: Figure 11.--Pressure Generator (Davis Bournonville).
+_A_, Feed motor weight;
+_B_, Carbide feed motor;
+_C_, Motor Control diaphragm;
+_D_, Carbide hopper;
+_E_, Carbide feed disc;
+_F_, Overflow pipe;
+_G_, Overflow pipe seal;
+_H_, Overflow pipe valve;
+_J_, Filling funnel;
+_K_, Hydraulic valve;
+_L_, Expansion chamber;
+_M_, Escape pipe;
+_N_, Feed pipe;
+_O_, Agitator for residuum;
+_P_, Residuum valve;
+_Q_, Water level]
+
+[Illustration: Figure 12.--Feed Mechanism of Pressure Generator]
+
+Should the pressure rise much above the blow-off point, the safety
+controlling diaphragm valve will operate and throw the safety clutch in
+interference and thus stop the motor. This interference clutch will then
+have to be returned to its former position before the motor will operate,
+but cannot be replaced before the pressure has been reduced below the
+blow-off point.
+
+The parts of the feed mechanism illustrated in Figure 12 are as follows:
+_A_, motor drum for weight cable. _B_, carbide filling plugs.
+_C_, chains for connecting safety locking lever of motor to pins on
+the top of the carbide plugs. _D_, interference clutch of motor.
+_E_, lever on feed controlling diaphragm valve. _F_, lever of
+interference controlling diaphragm valve that operates interference clutch.
+_G_, feed controlling diaphragm valve. _H_, diaphragm valve
+controlling operation of interference clutch. _I_, interference pin
+to engage emergency clutch. _J_, main shaft driving carbide feeding
+disc. _Y_, safety locking lever.
+
+_Recharging Generator._--Turn the agitator handle rapidly for several
+revolutions, and then open the residuum valve, having five or six pounds
+gas pressure on the machine. If the carbide charge has been exhausted and
+the motor has stopped, there is generally enough carbide remaining in the
+feeding disc that can be shaken off, and fed by running the motor to
+obtain some pressure in the generator. The desirability of discharging
+the residuum with some gas pressure is because the pressure facilitates
+the discharge and at the same time keeps the generator full of gas,
+preventing air mixture to a great extent. As soon as the pressure is
+relieved by the withdrawal of the residuum, the vent valve should be
+opened, as if the pressure is maintained until all of the residuum is
+discharged gas would escape through the discharge valve.
+
+Having opened the vent pipe valve and relieved the pressure, open the
+valve in the water filling tube. Close the residuum valve, then run in
+several gallons of water and revolve the agitator, after which draw out the
+remaining residuum; then again close the residuum valve and pour in water
+until it discharges from the overflow pipe of the drainage chamber. It is
+desirable in filling the generator to pour the water in rapidly enough to
+keep the filling pipe full of water, so that air will not pass in at the
+same time.
+
+After the generator is cleaned and filled with water, fill with carbide and
+proceed in the same manner as when first charging.
+
+_Carbide Feed Mechanism._--Any form of carbide to water machine should
+be so designed that the carbide never falls directly from its holder into
+the water, but so that it must take a more or less circuitous path. This
+should be true, no matter what position the mechanism is in. One of the
+commonest types of forced feed machine carries the carbide in a hopper with
+slanting sides, this hopper having a large opening in the bottom through
+which the carbide passes to a revolving circular plate. As the pieces of
+carbide work out toward the edge of the plate under the influence of the
+mass behind them, they are thrown off into the water by small stationary
+fins or plows which are in such a position that they catch the pieces
+nearest the edges and force them off as the plate revolves. This
+arrangement, while allowing a free passage for the carbide, prevents an
+excess from falling should the machine stop in any position.
+
+When, as is usually the case, the feed mechanism is actuated by the rise
+or fall of pressure in the generator or of the level of some part of the
+gas holder, it must be built in such a way that the feeding remains
+inoperative as long as the filling opening on the carbide holder remains
+open.
+
+The feed of carbide should always be shut off and controlled so that under
+no condition can more gas be generated than could be cared for by the
+relief valve provided. It is necessary also to have the feed mechanism at
+least ten inches above the surface of the water so that the parts will
+never become clogged with damp lime dust.
+
+_Motor Feed._--The feed mechanism itself is usually operated by power
+secured from a slowly falling weight which, through a cable, revolves a
+drum. To this drum is attached suitable gearing for moving the feed parts
+with sufficient power and in the way desired. This part, called the motor,
+is controlled by two levers, one releasing a brake and allowing the motor
+to operate the feed, the other locking the gearing so that no more carbide
+will be dropped into the water. These levers are moved either by the
+quantity of gas in the holder or by the pressure of the gas, depending on
+the type of machine.
+
+With a separate gas holder, such as used with low pressure systems, the
+levers are operated by the rise and fall of the bell of the holder or
+gasometer, alternately starting and stopping the motor as the bell falls
+and rises again. Medium pressure generators are provided with a diaphragm
+to control the feed motor.
+
+This diaphragm is carried so that the pressure within the generator acts
+on one side while a spring, whose tension is under the control of the
+operator, acts on the other side. The diaphragm is connected to the brake
+and locking device on the motor in such a way that increasing the tension
+on the spring presses the diaphragm and moves a rod that releases the brake
+and starts the feed. The gas pressure, increasing with the continuation of
+carbide feed, acts on the other side and finally overcomes the pressure of
+the spring tension, moving the control rod the other way and stopping the
+motor and carbide feed. This spring tension is adjusted and checked with
+the help of a pressure gauge attached to the generating chamber.
+
+_Gravity Feed._--This type of feed differs from the foregoing in that
+the carbide is simply released and is allowed to fall into the water
+without being forced to do so. Any form of valve that is sufficiently
+powerful in action to close with the carbide passing through is used and is
+operated by the power secured from the rise and fall of the gas holder
+bell. When this valve is first opened the carbide runs into the water until
+sufficient pressure and volume of gas is generated to raise the bell. This
+movement operates the arm attached to the carbide shut off valve and slowly
+closes it. A fall of the bell occasioned by gas being withdrawn again opens
+the valve and more gas is generated.
+
+_Mechanical Feed._--The previously described methods of feeding
+carbide to the water have all been automatic in action and do not depend
+on the operator for their proper action.
+
+Some types of large generating plants have a power-driven feed, the power
+usually being from some kind of motor other than one operated by a weight,
+such as a water motor, for instance. This motor is started and stopped by
+the operator when, in his judgment, more gas is wanted or enough has been
+generated. This type of machine, often called a "non-automatic generator,"
+is suitable for large installations and is attached to a gas holder of
+sufficient size to hold a day's supply of acetylene. The generator can then
+be operated until a quantity of gas has been made that will fill the large
+holder, or gasometer, and then allowed to remain idle for some time.
+
+_Gas Holders._--The commonest type of gas container is that known as a
+gasometer. This consists of a circular tank partly filled with water, into
+which is lowered another circular tank, inverted, which is made enough
+smaller in diameter than the first one so that three-quarters of an inch is
+left between them. This upper and inverted portion, called the bell,
+receives the gas from the generator and rises or falls in the bath of water
+provided in the lower tank as a greater or less amount of gas is contained
+in it.
+
+These holders are made large enough so that they will provide a means of
+caring for any after generation and so that they maintain a steady and even
+flow. The generator, however, must be of a capacity great enough so that
+the gas holder will not be drawn on for part of the supply with all torches
+in operation. That is, the holder must not be depended on for a reserve
+supply.
+
+The bell of the holder is made so that when full of gas its lower edge is
+still under a depth of at least nine inches of water in the lower tank. Any
+further rise beyond this point should always release the gas, or at least
+part of it, to the escape pipe so that the gas will under no circumstances
+be forced into the room from, between the bell and tank. The bell is guided
+in its rise and fall by vertical rods so that it will not wedge at any
+point in its travel.
+
+A condensing chamber to receive the water which condenses from the
+acetylene gas in the holder is usually placed under this part and is
+provided with a drain so that this water of condensation may be easily
+removed.
+
+_Filtering._--A small chamber containing some closely packed but
+porous material such as felt is placed in the pipe leading to the torch
+lines. As the acetylene gas passes through this filter the particles of
+lime dust and other impurities are extracted from it so that danger of
+clogging the torch openings is avoided as much as possible.
+
+The gas is also filtered to a large extent by its passage through the water
+in the generating chamber, this filtering or "scrubbing" often being
+facilitated by the form of piping through which the gas must pass from the
+generating chamber into the holder. If the gas passes out of a number of
+small openings when going into the holder the small bubbles give a better
+washing than large ones would.
+
+_Piping._--Connections from generators to service pipes should
+preferably be made with right and left couplings or long thread nipples
+with lock nuts. If unions are used, they should be of a type that does not
+require gaskets. The piping should be carried and supported so that any
+moisture condensing in the lines will drain back toward the generator and
+where low points occur they should be drained through tees leading into
+drip cups which are permanently closed with screw caps or plugs. No pet
+cocks should be used for this purpose.
+
+For the feed pipes to the torch lines the following pipe sizes are
+recommended.
+
+    3/8 inch pipe.  26 feet long.   2 cubic feet per hour.
+    1/2 inch pipe.  30 feet long.   4 cubic feet per hour.
+    3/4 inch pipe.  50 feet long.  15 cubic feet per hour.
+  1     inch pipe.  70 feet long.  27 cubic feet per hour.
+  1-1/4 inch pipe. 100 feet long.  50 cubic feet per hour.
+  1-1/2 inch pipe. 150 feet long.  65 cubic feet per hour.
+  2     inch pipe. 200 feet long. 125 cubic feet per hour.
+  2-1/2 inch pipe. 300 feet long. 190 cubic feet per hour.
+  3     inch pipe. 450 feet long. 335 cubic feet per hour.
+
+When drainage is possible into a sewer, the generator should not be
+connected directly into the sewer but should first discharge into an open
+receptacle, which may in turn be connected to the sewer.
+
+No valves or pet cocks should open into the generator room or any other
+room when it would be possible, by opening them for draining purposes, to
+allow any escape of gas. Any condensation must be removed without the use
+of valves or other working parts, being drained into closed receptacles. It
+should be needless to say that all the piping for gas must be perfectly
+tight at every point in its length.
+
+_Safety Devices._--Good generators are built in such a way that the
+operator must follow the proper order of operation in charging and cleaning
+as well as in all other necessary care. It has been mentioned that the gas
+pressure is released or shut off before it is possible to fill the water
+compartment, and this same idea is carried further in making the generator
+inoperative and free from gas pressure before opening the residue drain of
+the carbide filling opening on top of the hopper. Some machines are made so
+that they automatically cease to generate should there be a sudden and
+abnormal withdrawal of gas such as would be caused by a bad leak. This
+method of adding safety by automatic means and interlocking parts may be
+carried to any extent that seems desirable or necessary to the maker.
+
+All generators should be provided with escape or relief pipes of large size
+which lead to the open air. These pipes are carried so that condensation
+will drain back toward the generator and after being led out of the
+building to a point at least twelve feet above ground, they end in a
+protecting hood so that no rain or solid matter can find its way into them.
+Any escape of gas which might ordinarily pass into the generator room is
+led into these escape pipes, all parts of the system being connected with
+the pipe so that the gas will find this way out.
+
+Safety blow off valves are provided so that any excess gas which cannot be
+contained by the gas holder may be allowed to escape without causing an
+undue rise in pressure. This valve also allows the escape of pressure above
+that for which the generator was designed. Gas released in this way passes
+into the escape pipe just described.
+
+Inasmuch as the pressure of the oxygen is much greater than that of the
+acetylene when used in the torch, it will be seen that anything that caused
+the torch outlet to become closed would allow the oxygen to force the
+acetylene back into the generator and the oxygen would follow it, making a
+very explosive mixture. This return of the gas is prevented by a hydraulic
+safety valve or back pressure valve, as it is often called.
+
+Mechanical check valves have been found unsuitable for this use and those
+which employ water as a seal are now required by the insurance rules. The
+valve itself (Figure 13) consists of a large cylinder containing water to a
+certain depth, which is indicated on the valve body. Two pipes come into
+the upper end of this cylinder and lead down into the water, one being
+longer than the other. The shorter pipe leads to the escape pipe mentioned
+above, while the longer one comes from the generator. The upper end of the
+cylinder has an opening to which is attached the pipe leading to the
+torches.
+
+[Illustration: Figure 13.--Hydraulic Back-Pressure Valve.
+_A_, Acetylene supply line;
+_B_, Vent pipe;
+_C_, Water filling plug;
+_D_, Acetylene service cock;
+_E_, Plug to gauge height of water;
+_F_, Gas openings under water;
+_G_, Return pipe for sealing water;
+_H_, Tube to carry gas below water line;
+_I_, Tube to carry gas to escape pipe;
+_J_, Gas chamber;
+_K_, Plug in upper gas chamber;
+_L_, High water level;
+_M_, Opening through which water returns;
+_O_, Bottom clean out casting]
+
+The gas coming from the generator through the longer pipe passes out of the
+lower end of the pipe which is under water and bubbles up through the water
+to the space in the top of the cylinder. From there the gas goes to the
+pipe leading to the torches. The shorter pipe is closed by the depth of
+water so that the gas does not escape to the relief pipe. As long as the
+gas flows in the normal direction as described there will be no escape to
+the air. Should the gas in the torch line return into the hydraulic valve
+its pressure will lower the level of water in the cylinder by forcing some
+of the liquid up into the two pipes. As the level of the water lowers, the
+shorter pipe will be uncovered first, and as this is the pipe leading to
+the open air the gas will be allowed to escape, while the pipe leading back
+to the generator is still closed by the water seal. As soon as this reverse
+flow ceases, the water will again resume its level and the action will
+continue. Because of the small amount of water blown out of the escape pipe
+each time the valve is called upon to perform this duty, it is necessary to
+see that the correct water level is always maintained.
+
+While there are modifications of this construction, the same principle is
+used in all types. The pressure escape valve is often attached to this
+hydraulic valve body.
+
+_Construction Details._--Flexible tubing (except at torches), swing
+pipe joints, springs, mechanical check valves, chains, pulleys and lead or
+fusible piping should never be used on acetylene apparatus except where the
+failure of those parts will not affect the safety of the machine or permit,
+either directly or indirectly, the escape of gas into a room. Floats should
+not be used except where failure will only render the machine inoperative.
+
+It should be said that the National Board of Fire Underwriters have
+established an inspection service for acetylene generators and any
+apparatus which bears their label, stating that that particular model and
+type has been passed, is safe to use. This service is for the best
+interests of all concerned and looks toward the prevention of accidents.
+Such inspection is a very important and desirable feature of any outfit and
+should be insisted upon.
+
+_Location of Generators._--Generators should preferably be placed
+outside of insured buildings and in properly constructed generator houses.
+The operating mechanism should have ample room to work in and there should
+be room enough for the attendant to reach the various parts and perform the
+required duties without hindrance or the need of artificial light. They
+should also be protected from tampering by unauthorized persons.
+
+Generator houses should not be within five feet of any opening into, nor
+have any opening toward, any adjacent building, and should be kept under
+lock and key. The size of the house should be no greater than called for by
+the requirements mentioned above and it should be well ventilated.
+
+The foundation for the generator itself should be of brick, stone, concrete
+or iron, if possible. If of wood, they should be extra heavy, located in a
+dry place and open to circulation of air. A board platform is not
+satisfactory, but the foundation should be of heavy planking or timber to
+make a firm base and so that the air can circulate around the wood.
+
+The generator should stand level and no strain should be placed on any of
+the pipes or connections or any parts of the generator proper.
+
+
+
+
+CHAPTER IV
+
+WELDING INSTRUMENTS
+
+
+VALVES
+
+_Tank Valves._--The acetylene tank valve is of the needle type, fitted
+with suitable stuffing box nuts and ending in an exposed square shank to
+which the special wrench may be fitted when the valve is to be opened or
+closed.
+
+The valve used on Linde oxygen cylinders is also a needle type, but of
+slightly more complex construction. The body of the valve, which screws
+into the top of the cylinder, has an opening below through which the gas
+comes from the cylinder, and another opening on the side through which it
+issues to the torch line. A needle screws down from above to close this
+lower opening. The needle which closes the valve is not connected directly
+to the threaded member, but fits loosely into it. The threaded part is
+turned by a small hand wheel attached to the upper end. When this hand
+wheel is turned to the left, or up, as far as it will go, opening the
+valve, a rubber disc is compressed inside of the valve body and this disc
+serves to prevent leakage of the gas around the spindle.
+
+The oxygen valve also includes a safety nut having a small hole through it
+closed by a fusible metal which melts at 250° Fahrenheit. Melting of this
+plug allows the gas to exert its pressure against a thin copper diaphragm,
+this diaphragm bursting under the gas pressure and allowing the oxygen to
+escape into the air.
+
+The hand wheel and upper end of the valve mechanism are protected during
+shipment by a large steel cap which covers them when screwed on to the end
+of the cylinder. This cap should always be in place when tanks are received
+from the makers or returned to them.
+
+[Illustration: Figure 14.--Regulating Valve]
+
+_Regulating Valves._--While the pressure in the gas containers may be
+anything from zero to 1,800 pounds, and will vary as the gas is withdrawn,
+the pressure of the gas admitted to the torch must be held steady and at a
+definite point. This is accomplished by various forms of automatic
+regulating valves, which, while they differ somewhat in details of
+construction, all operate on the same principle.
+
+The regulator body (Figure 14) carries a union which attaches to the side
+outlet on the oxygen tank valve. The gas passes through this union,
+following an opening which leads to a large gauge which registers the
+pressure on the oxygen remaining in the tank and also to a very small
+opening in the end of a tube. The gas passes through this opening and into
+the interior of the regulator body. Inside of the body is a metal or rubber
+diaphragm placed so that the pressure of the incoming gas causes it to
+bulge slightly. Attached to the diaphragm is a sleeve or an arm tipped
+with a small piece of fibre, the fibre being placed so that it is directly
+opposite the small hole through which the gas entered the diaphragm
+chamber. The slight movement of the diaphragm draws the fibre tightly over
+the small opening through which the gas is entering, with the result that
+further flow is prevented.
+
+Against the opposite side of the diaphragm is the end of a plunger. This
+plunger is pressed against the diaphragm by a coiled spring. The tension on
+the coiled spring is controlled by the operator through a threaded spindle
+ending in a wing or milled nut on the outside of the regulator body.
+Screwing in on the nut causes the tension on the spring to increase, with a
+consequent increase of pressure on the side of the diaphragm opposite to
+that on which the gas acts. Inasmuch as the gas pressure acted to close the
+small gas opening and the spring pressure acts in the opposite direction
+from the gas, it will be seen that the spring pressure tends to keep the
+valve open.
+
+When the nut is turned way out there is of course, no pressure on the
+spring side of the diaphragm and the first gas coming through automatically
+closes the opening through which it entered. If now the tension on the
+spring be slightly increased, the valve will again open and admit gas until
+the pressure of gas within the regulator is just sufficient to overcome the
+spring pressure and again close the opening. There will then be a pressure
+of gas within the regulator that corresponds to the pressure placed on the
+spring by the operator. An opening leads from the regulator interior to the
+torch lines so that all gas going to the torches is drawn from the
+diaphragm chamber.
+
+Any withdrawal of gas will, of course, lower the pressure of that remaining
+inside the regulator. The spring tension, remaining at the point determined
+by the operator, will overcome this lessened pressure of the gas, and the
+valve will again open and admit enough more gas to bring the pressure back
+to the starting point. This action continues as long as the spring tension
+remains at this point and as long as any gas is taken from the regulator.
+Increasing the spring tension will require a greater gas pressure to close
+the valve and the pressure of that in the regulator will be correspondingly
+higher.
+
+When the regulator is not being used, the hand nut should be unscrewed
+until no tension remains on the spring, thus closing the valve. After the
+oxygen tank valve is open, the regulator hand nut is slowly screwed in
+until the spring tension is sufficient to give the required pressure in the
+torch lines. Another gauge is attached to the regulator so that it
+communicates with the interior of the diaphragm chamber, this gauge showing
+the gas pressure going to the torch. It is customary to incorporate a
+safety valve in the regulator which will blow off at a dangerous pressure.
+
+In regulating valves and tank valves, as well as all other parts with which
+the oxygen comes in contact, it is not permissible to use any form of oil
+or grease because of danger of ignition and explosion. The mechanism of a
+regulator is too delicate to be handled in the ordinary shop and should any
+trouble or leakage develop in this part of the equipment it should be sent
+to a company familiar with this class of work for the necessary repairs.
+Gas must never be admitted to a regulator until the hand nut is all the way
+out, because of danger to the regulator itself and to the operator as well.
+A regulator can only be properly adjusted when the tank valve and torch
+valves are fully opened.
+
+[Illustration: Figure 15.--High and Low Pressure Gauges with Regulator]
+
+Acetylene regulators are used in connection with tanks of compressed gas.
+They are built on exactly the same lines as the oxygen regulating valve and
+operate in a similar way. One gauge only, the low pressure indicator, is
+used for acetylene regulators, although both high and low pressure may be
+used if desired. (See Figure 15.)
+
+
+TORCHES
+
+Flame is always produced by the combustion of a gas with oxygen and in no
+other way. When we burn oil or candles or anything else, the material of
+the fuel is first turned to a gas by the heat and is then burned by
+combining with the oxygen of the air. If more than a normal supply of air
+is forced into the flame, a greater heat and more active burning follows.
+If the amount of air, and consequently oxygen, is reduced, the flame
+becomes smaller and weaker and the combustion is less rapid. A flame may be
+easily extinguished by shutting off all of its air supply.
+
+The oxygen of the combustion only forms one-fifth of the total volume of
+air; therefore, if we were to supply pure oxygen in place of air, and in
+equal volume, the action would be several times as intense. If the oxygen
+is mixed with the fuel gas in the proportion that burns to the very best
+advantage, the flame is still further strengthened and still more heat is
+developed because of the perfect combustion. The greater the amount of fuel
+gas that can be burned in a certain space and within a certain time, the
+more heat will be developed from that fuel.
+
+The great amount of heat contained in acetylene gas, greater than that
+found in any other gaseous fuel, is used by leading this gas to the
+oxy-acetylene torch and there combining it with just the right amount of
+oxygen to make a flame of the greatest power and heat than can possibly be
+produced by any form of combustion of fuels of this kind. The heat
+developed by the flame is about 6300° Fahrenheit and easily melts all the
+metals, as well as other solids.
+
+Other gases have been and are now being used in the torch. None of them,
+however, produce the heat that acetylene does, and therefore the
+oxy-acetylene process has proved the most useful of all. Hydrogen was used
+for many years before acetylene was introduced in this field. The
+oxy-hydrogen flame develops a heat far below that of oxy-acetylene, namely
+4500° Fahrenheit. Coal gas, benzine gas, blaugas and others have also been
+used in successful applications, but for the present we will deal
+exclusively with the acetylene fuel.
+
+It was only with great difficulty that the obstacles in the way of
+successfully using acetylene were overcome by the development of
+practicable controlling devices and torches, as well as generators. At
+present the oxy-acetylene process is the most universally adaptable, and
+probably finds the most widely extended field of usefulness of any welding
+process.
+
+The theoretical proportion of the gases for perfect combustion is two and
+one-half volumes of oxygen to one of acetylene. In practice this proportion
+is one and one-eighth or one and one-quarter volumes of oxygen to one
+volume of acetylene, so that the cost is considerably reduced below what it
+would be if the theoretical quantity were really necessary, as oxygen costs
+much more than acetylene in all cases.
+
+While the heat is so intense as to fuse anything brought into the path of
+the flame, it is localized in the small "welding cone" at the torch tip so
+that the torch is not at all difficult to handle without special protection
+except for the eyes, as already noted. The art of successful welding may be
+acquired by any operator of average intelligence within a reasonable time
+and with some practice. One trouble met with in the adoption of this
+process has been that the operation looks so simple and so easy of
+performance that unskilled and unprepared persons have been tempted to try
+welding, with results that often caused condemnation of the process, when
+the real fault lay entirely with the operator.
+
+The form of torch usually employed is from twelve to twenty-four inches
+long and is composed of a handle at one end with tubes leading from this
+handle to the "welding head" or torch proper. At or near one end of the
+handle are adjustable cocks or valves for allowing the gases to flow into
+the torch or to prevent them from doing so. These cocks are often used for
+regulating the pressure and amount of gas flowing to the welding head, but
+are not always constructed for this purpose and should not be so used when
+it is possible to secure pressure adjustment at the regulators (Figure 16).
+
+Figure 16 shows three different sizes of torches. The number 5 torch is
+designed especially for jewelers' work and thin sheet steel welding. It is
+eleven inches in length and weighs nineteen ounces. The tips for the number
+10 torch are interchangeable with the number 5. The number 10 torch is
+adapted for general use on light and medium heavy work. It has six tips and
+its length is sixteen inches, with a weight of twenty-three ounces.
+
+The number 15 torch is designed for heavy work, being twenty-five inches in
+length, permitting the operator to stand away from the heat of the metal
+being worked. These heavy tips are in two parts, the oxygen check being
+renewable.
+
+[Illustration: Figure 16.--Three Sizes of Torches, with Tips]
+
+Figures 17 and 18 show two sizes of another welding torch. Still another
+type is shown in Figure 19 with four interchangeable tips, the function of
+each being as follows:
+
+  No. 1. For heavy castings.
+  No. 2. Light castings and heavy sheet metal.
+  No. 3. Light sheet metal.
+  No. 4. Very light sheet metal and wire.
+
+[Illustration: Figure 17.--Cox Welding Torch (No. 1)]
+
+[Illustration: Figure 18.--Cox Welding Torch (No. 2)]
+
+[Illustration: Figure 19.--Monarch Welding Torch]
+
+At the side of the shut off cock away from the torch handle the gas tubes
+end in standard forms of hose nozzles, to which the rubber hose from the
+gas supply tanks or generators can be attached. The tubes from the handle
+to the head may be entirely separate from each other, or one may be
+contained within the other. As a general rule the upper one of two
+separate tubes carries the oxygen, while this gas is carried in the inside
+tube when they are concentric with each other.
+
+In the welding head is the mixing chamber designed to produce an intimate
+mixture of the two gases before they issue from the nozzle to the flame.
+The nozzle, or welding tip, of a suitable size are design for the work to
+be handled and the pressure of gases being used, is attached to the welding
+head and consists essentially of the passage at the outer end of which the
+flame appears.
+
+The torch body and tubes are usually made of brass, although copper is
+sometimes used. The joint must be very strong, and are usually threaded and
+soldered with silver solder. The nozzle proper is made from copper, because
+it withstands the heat of the flame better than other less suitable metals.
+The torch must be built in such a way that it is not at all liable to come
+apart under the influence of high temperatures.
+
+All torches are constructed in such a way that it is impossible for the
+gases to mix by any possible chance before they reach the head, and the
+amount of gas contained in the head and tip after being mixed is made as
+small as possible. In order to prevent the return of the flame through the
+acetylene tube under the influence of the high pressure oxygen some form of
+back flash preventer is usually incorporated in the torch at or near the
+point at which the acetylene enters. This preventer takes the form of some
+porous and heat absorbing material, such as aluminum shavings, contained in
+a small cavity through which the gas passes on its way to the head.
+
+_High Pressure Torches._--Torches are divided into the same classes as
+are the generators; that is, high pressure, medium pressure and low
+pressure. As mentioned before, the medium pressure is usually called the
+high pressure, because there are very few true high pressure systems in
+use, and comparatively speaking the medium pressure type is one of high
+pressure.
+
+[Illustration: Figure 20.--High Pressure Torch Head]
+
+With a true high pressure torch (Figure 20) the gases are used at very
+nearly equal heads so that the mixing before ignition is a simple matter.
+This type admits the oxygen at the inner end of a straight passage leading
+to the tip of the nozzle. The acetylene comes into this same passage from
+openings at one side and near the inner end. The difference in direction of
+the two gases as they enter the passage assists in making a homogeneous
+mixture. The construction of this nozzle is perfectly simple and is easily
+understood. The true high pressure torch nozzle is only suited for use with
+compressed and dissolved acetylene, no other gas being at a sufficient
+pressure to make the action necessary in mixing the gases.
+
+_Medium Pressure Torches._--The medium pressure (usually called high
+pressure) torch (Figure 21) uses acetylene from a medium pressure generator
+or from tanks of compressed gas, but will not take the acetylene from low
+pressure generators.
+
+[Illustration: Figure 21.--Medium Pressure Torch Head]
+
+The construction of the mixing chamber and nozzle is very similar to that
+of the high pressure torch, the gases entering in the same way and from the
+same positions of openings. The pressure of the acetylene is but little
+lower than that of the oxygen, and the two gases, meeting at right angles,
+form a very intimate mixture at this point of juncture. The mixture in its
+proportions of gases depends entirely on the sizes of the oxygen and
+acetylene openings into the mixing chamber and on the pressures at which
+the gases are admitted. There is a very slight injector action as the fast
+moving stream of oxygen tends to draw the acetylene from the side openings
+into the chamber, but the operation of the torch does not depend on this
+action to any extent.
+
+_Low Pressure Torches._--The low pressure torch (Figure 22) will use
+gas from low pressure generators from medium pressure machines or from
+tanks in which it has been compressed and dissolved. This type depends for
+a perfect mixture of gas upon the principle of the injector just as it is
+applied in steam boiler practice.
+
+[Illustration: Figure 22.--Low Pressure Torch with Separate Injector
+Nozzle]
+
+The oxygen enters the head at considerable pressure and passes through its
+tube to a small jet within the head. The opening of this jet is directly
+opposite the end of the opening through the nozzle which forms the mixing
+chamber and the path of the gases to the flame. A small distance remains
+between the opening from which the oxygen issues and the inner opening into
+the mixing passage. The stream of oxygen rushes across this space and
+enters the mixing chamber, being driven by its own pressure.
+
+The acetylene enters the head in an annular space surrounding the oxygen
+tube. The space between oxygen jet and mixing chamber opening is at one end
+of this acetylene space and the stream of oxygen seizes the acetylene and
+under the injector action draws it into the mixing chamber, it being
+necessary only to have a sufficient supply of acetylene flowing into the
+head to allow the oxygen to draw the required proportion for a proper
+mixture.
+
+The volume of gas drawn into the mixing chamber depends on the size of the
+injector openings and the pressure of the oxygen. In practice the oxygen
+pressure is not altered to produce different sized flames, but a new nozzle
+is substituted which is designed to give the required flame. Each nozzle
+carries its own injector, so that the design is always suited to the
+conditions. While torches are made having the injector as a permanent part
+of the torch body, the replaceable nozzle is more commonly used because it
+makes the one torch suitable for a large range of work and a large number
+of different sized flames. With the replaceable head a definite pressure of
+oxygen is required for the size being used, this pressure being the one for
+which the injector and corresponding mixing chamber were designed in
+producing the correct mixture.
+
+_Adjustable Injectors._-Another form of low pressure torch operates on
+the injector principle, but the injector itself is a permanent part of the
+torch, the nozzle only being changed for different sizes of work and flame.
+The injector is placed in or near the handle and its opening is the largest
+required by any work that can be handled by this particular torch. The
+opening through the tip of the injector through which the oxygen issues on
+its way to the mixing chamber may be wholly or partly closed by a needle
+valve which may be screwed into the opening or withdrawn from it, according
+to the operator's judgment. The needle valve ends in a milled nut outside
+the torch handle, this being the adjustment provided for the different
+nozzles.
+
+_Torch Construction._--A well designed torch is so designed that the
+weight distribution is best for holding it in the proper position for
+welding. When a torch is grasped by its handle with the gas hose attached,
+it should balance so that it does not feel appreciably heavier on one end
+than on the other.
+
+The head and nozzle may be placed so that the flame issues in a line at
+right angles with the torch body, or they may be attached at an angle
+convenient for the work to be done. The head set at an angle of from 120 to
+170 degrees with the body is usually preferred for general work in welding,
+while the cutting torch usually has its head at right angles to the body.
+
+Removable nozzles have various size openings through them and the different
+sizes are designated by numbers from 1 up. The same number does not always
+indicate the same size opening in torches of different makes, nor does it
+indicate a nozzle of the same capacity.
+
+The design of the nozzle, the mixing chamber, the injector, when one is
+used, and the size of the gas openings must be such that all these things
+are suited to each other if a proper mixture of gas is to be secured. Parts
+that are not made to work together are unsafe if used because of the danger
+of a flash back of the flame into the mixing chamber and gas tubes. It is
+well known that flame travels through any inflammable gas at a certain
+definite rate of speed, depending on the degree of inflammability of the
+gas. The easier and quicker the gas burns, the faster will the flame travel
+through it.
+
+If the gas in the nozzle and mixing chamber stood still, the flame would
+immediately travel back into these parts and produce an explosion of more
+or less violence. The speed with which the gases issue from the nozzle
+prevent this from happening because the flame travels back through the gas
+at the same speed at which the gas issues from the torch tip. Should the
+velocity of the gas be greater than the speed of flame propagation through
+it, it will be impossible to keep the flame at the tip, the tendency being
+for a space of unburned gas to appear between tip and flame. On the other
+hand, should the speed of the flame exceed the velocity with which the gas
+comes from the torch there will result a flash back and explosion.
+
+_Care of Torches._--An oxy-acetylene torch is a very delicate and
+sensitive device, much more so that appears on the surface. It must be
+given equally as good care and attention as any other high-priced piece of
+machinery if it is to be maintained in good condition for use.
+
+It requires cleaning of the nozzles at regular intervals if used regularly.
+This cleaning is accomplished with a piece of copper or brass wire run
+through the opening, and never with any metal such as steel or iron that is
+harder than the nozzle itself, because of the danger of changing the size
+of the openings. The torch head and nozzle can often be cleaned by allowing
+the oxygen to blow through at high pressure without the use of any tools.
+
+In using a torch a deposit of carbon will gradually form inside of the
+head, and this deposit will be more rapid if the operator lights the stream
+of acetylene before turning any oxygen into the torch. This deposit may be
+removed by running kerosene through the nozzle while it is removed from the
+torch, setting fire to the kerosene and allowing oxygen to flow through
+while the oil is burning.
+
+Should a torch become clogged in the head or tubes, it may usually be
+cleaned by removing the oxygen hose from the handle end, closing the
+acetylene cock on the torch, placing the end of the oxygen hose over the
+opening in the nozzle and turning on the oxygen under pressure to blow the
+obstruction back through the passage that it has entered. By opening the
+acetylene cock and closing the oxygen cock at the handle, the acetylene
+passages may then be cleaned in the same way. Under no conditions should a
+torch be taken apart any more than to remove the changeable nozzle, except
+in the hands of those experienced in this work.
+
+_Nozzle Sizes._--The size of opening through the nozzle is determined
+according to the thickness and kind of metal being handled. The following
+sizes are recommended for steel:
+
+                      Davis-Bournonville.   Oxweld Low
+  Thickness of Metal  (Medium Pressure.)      Pressure
+  1/32                     Tip No. 1        Head No. 2
+  1/16                             2
+  5/64                                               3
+  3/32                             3                 4
+  3/8                              4                 5
+  3/16                             5                 6
+  1/4                              6                 7
+  5/16                             7
+  3/8                              8                 8
+  1/2                              9                10
+  5/8                             10                12
+  3/4                             11                15
+  Very heavy                      12                15
+
+_Cutting Torches._--Steel may be cut with a jet of oxygen at a rate of
+speed greater than in any other practicable way under usual conditions. The
+action consists of burning away a thin section of the metal by allowing a
+stream of oxygen to flow onto it while the gas is at high pressure and the
+metal at a white heat.
+
+[Illustration: Figure 23.--Cutting Torch]
+
+The cutting torch (Figure 23) has the same characteristics as the welding
+torch, but has an additional nozzle or means for temporarily using the
+welding opening for the high pressure oxygen. The oxygen issues from the
+opening while cutting at a pressure of from ten to 100 pounds to the square
+inch.
+
+The work is first heated to a white heat by adjusting the torch for a
+welding flame. As soon as the metal reaches this temperature, the high
+pressure oxygen is turned on to the white-hot portion of the steel. When
+the jet of gas strikes the metal it cuts straight through, leaving a very
+narrow slot and removing but little metal. Thicknesses of steel up to ten
+inches can be economically handled in this way.
+
+The oxygen nozzle is usually arranged so that it is surrounded by a number
+of small jets for the heating flame. It will be seen that this arrangement
+makes the heating flame always precede the oxygen jet, no matter in which
+direction the torch is moved.
+
+The torch is held firmly, either by hand or with the help of special
+mechanism for guiding it in the desired path, and is steadily advanced in
+the direction it is desired to extend the cut, the rate of advance being
+from three inches to two feet per minute through metal from nine inches
+down to one-quarter of an inch in thickness.
+
+The following data on cutting is given by the Davis-Bournonville Company:
+
+                            Cubic
+                            Feet                          Cost of
+Thickness                   of Gas               Inches   Gases
+of        Cutting  Heating  per Foot  Oxygen     Cut per  per Foot
+Steel     Oxygen   Oxygen   of Cut    Acetylene  Min.     of Cut
+  1/4     10 lbs.  4 lbs.     .40      .086      24        $ .013
+  1/2     20       4          .91      .150      15          .029
+  3/4     30       4         1.16      .150      15          .036
+1         30       4         1.45      .172      12          .045
+1 1/2     30       5         2.40      .380      12          .076
+2         40       5         2.96      .380      12          .093
+4         50       5         9.70      .800       7          .299
+6         70       6        21.09     1.50        4          .648
+9        100       6        43.20     2.00        3         1.311
+
+_Acetylene-Air Torch._--A form of torch which burns the acetylene after
+mixing it with atmospheric air at normal pressure rather than with the
+oxygen under higher pressures has been found useful in certain pre-heating,
+brazing and similar operations. This torch (Figure 24) is attached by a
+rubber gas hose to any compressed acetylene tank and is regulated as to
+flame size and temperature by opening or closing the tank valve more or
+less.
+
+After attaching the torch to the tank, the gas is turned on very slowly and
+is lighted at the torch tip. The adjustment should cause the presence of a
+greenish-white cone of flame surrounded by a larger body of burning gas,
+the cone starting at the mouth of the torch.
+
+[Illustration: Figure 24.--Acetylene-Air Torch]
+
+By opening the tank valve more, a longer and hotter flame is produced, the
+length being regulated by the tank valve also. This torch will give
+sufficient heat to melt steel, although not under conditions suited to
+welding. Because of the excess of acetylene always present there is no
+danger of oxidizing the metal being heated.
+
+The only care required by this torch is to keep the small air passages at
+the nozzle clean and free from carbon deposits. The flame should be
+extinguished when not in use rather than turned low, because this low flame
+rapidly deposits large quantities of soot in the burner.
+
+
+
+
+CHAPTER V
+
+OXY-ACETYLENE WELDING PRACTICE
+
+
+PREPARATION OF WORK
+
+_Preheating._--The practice of heating the metal around the weld
+before applying the torch flame is a desirable one for two reasons. First,
+it makes the whole process more economical; second, it avoids the danger of
+breakage through expansion and contraction of the work as it is heated and
+as it cools.
+
+When it is desired to join two surfaces by welding them, it is, of course,
+necessary to raise the metal from the temperature of the surrounding air to
+its melting point, involving an increase in temperature of from one
+thousand to nearly three thousand degrees. To obtain this entire increase
+of temperature with the torch flame is very wasteful of fuel and of the
+operator's time. The total amount of heat necessary to put into metal is
+increased by the conductivity of that metal because the heat applied at the
+weld is carried to other parts of the piece being handled until the whole
+mass is considerably raised in temperature. To secure this widely
+distributed increase the various methods of preheating are adopted.
+
+As to the second reason for preliminary heating. It is understood that the
+metal added to the joint is molten at the time it flows into place. All the
+metals used in welding contract as they cool and occupy a much smaller
+space than when molten. If additional metal is run between two adjoining
+surfaces which are parts of a surrounding body of cool metal, this added
+metal will cool while the surfaces themselves are held stationary in the
+position they originally occupied. The inevitable result is that the metal
+added will crack under the strain, or, if the weld is exceptionally strong,
+the main body of the work will be broken by the force of contraction. To
+overcome these difficulties is the second and most important reason for
+preheating and also for slow cooling following the completion of the weld.
+
+There are many ways of securing this preheating. The work may be brought to
+a red heat in the forge if it is cast iron or steel; it may be heated in
+special ovens built for the purpose; it may be placed in a bed of charcoal
+while suitably supported; it may be heated by gas or gasoline preheating
+torches, and with very small work the outer flame of the welding torch
+automatically provides means to this end.
+
+The temperature of the parts heated should be gradually raised in all
+cases, giving the entire mass of metal a chance to expand equally and to
+adjust itself to the strains imposed by the preheating. After the region
+around the weld has been brought to a proper temperature the opening to be
+filled is exposed so that the torch flame can reach it, while the remaining
+surfaces are still protected from cold air currents and from cooling
+through natural radiation.
+
+One of the commonest methods and one of the best for handling work of
+rather large size is to place the piece to be welded on a bed of fire brick
+and build a loose wall around it with other fire brick placed in rows, one
+on top of the other, with air spaces left between adjacent bricks in each
+row. The space between the brick retaining wall and the work is filled with
+charcoal, which is lighted from below. The top opening of the temporary
+oven is then covered with asbestos and the fire kept up until the work has
+been uniformly raised in temperature to the desired point.
+
+When much work of the same general character and size is to be handled, a
+permanent oven may be constructed of fire brick, leaving a large opening
+through the top and also through one side. Charcoal may be used in this
+form of oven as with the temporary arrangement, or the heat may be secured
+from any form of burner or torch giving a large volume of flame. In any
+method employing flame to do the heating, the work itself must be protected
+from the direct blast of the fire. Baffles of brick or metal should be
+placed between the mouth of the torch and the nearest surface of the work
+so that the flame will be deflected to either side and around the piece
+being heated.
+
+The heat should be applied to bring the point of welding to the highest
+temperature desired and, except in the smallest work, the heat should
+gradually shade off from this point to the other parts of the piece. In the
+case of cast iron and steel the temperature at the point to be welded
+should be great enough to produce a dull red heat. This will make the whole
+operation much easier, because there will be no surrounding cool metal to
+reduce the temperature of the molten material from the welding rod below
+the point at which it will join the work. From this red heat the mass of
+metal should grow cooler as the distance from the weld becomes greater, so
+that no great strain is placed upon any one part. With work of a very
+irregular shape it is always best to heat the entire piece so that the
+strains will be so evenly distributed that they can cause no distortion or
+breakage under any conditions.
+
+The melting point of the work which is being preheated should be kept in
+mind and care exercised not to approach it too closely. Special care is
+necessary with aluminum in this respect, because of its low melting
+temperature and the sudden weakening and flowing without warning. Workmen
+have carelessly overheated aluminum castings and, upon uncovering the piece
+to make the weld, have been astonished to find that it had disappeared.
+Six hundred degrees is about the safe limit for this metal. It is possible
+to gauge the exact temperature of the work with a pyrometer, but when this
+instrument cannot be procured, it might be well to secure a number of
+"temperature cones" from a chemical or laboratory supply house. These cones
+are made from material that will soften at a certain heat and in form they
+are long and pointed. Placed in position on the part being heated, the
+point may be watched, and when it bends over it is sure that the metal
+itself has reached a temperature considerably in excess of the temperature
+at which that particular cone was designed to soften.
+
+The object in preheating the metal around the weld is to cause it to expand
+sufficiently to open the crack a distance equal to the contraction when
+cooling from the melting point. In the case of a crack running from the
+edge of a piece into the body or of a crack wholly within the body, it is
+usually satisfactory to heat the metal at each end of the opening. This
+will cause the whole length of the crack to open sufficiently to receive
+the molten material from the rod.
+
+The judgment of the operator will be called upon to decide just where a
+piece of metal should be heated to open the weld properly. It is often
+possible to apply the preheating flame to a point some distance from the
+point of work if the parts are so connected that the expansion of the
+heated part will serve to draw the edges of the weld apart. Whatever part
+of the work is heated to cause expansion and separation, this part must
+remain hot during the entire time of welding and must then cool slowly at
+the same time as the metal in the weld cools.
+
+[Illustration: Figure 25.--Preheating at _A_ While Welding at
+_B_. _C_ also May Be Heated.]
+
+An example of heating points away from the crack might be found in welding
+a lattice work with one of the bars cracked through (Figure 25). If the
+strips parallel and near to the broken bar are heated gradually, the work
+will be so expanded that the edges of the break are drawn apart and the
+weld can be successfully made. In this case, the parallel bars next to the
+broken one would be heated highest, the next row not quite so hot and so on
+for some distance away. If only the one row were heated, the strains set up
+in the next ones would be sufficient to cause a new break to appear.
+
+[Illustration: Figure 26.--Cutting Through the Rim of a Wheel (Cut Shown
+at A)]
+
+If welding is to be done near the central portion of a large piece, the
+strains will be brought to bear on the parts farthest away from the center.
+Should a fly wheel spoke be broken and made ready to weld, the greatest
+strain will come on the rim of the wheel. In cases like this it is often
+desirable to cut through at the point of greatest strain with a saw or
+cutting torch, allowing free movement while the weld is made at the
+original break (Figure 26). After the inside weld is completed, the cut may
+be welded without danger, for the reason that it will always be at some
+point at which severe strains cannot be set up by the contraction of the
+cooling metal.
+
+[Illustration: Figure 27.--Using a Wedge While Welding]
+
+In materials that will spring to some extent without breakage, that is, in
+parts that are not brittle, it may be possible to force the work out of
+shape with jacks or wedges (Figure 27) in the same way that it would be
+distorted by heating and expanding some portion of it as described. A
+careful examination will show whether this method can be followed in such a
+way as to force the edges of the break to separate. If the plan seems
+feasible, the wedges may be put in place and allowed to remain while the
+weld is completed. As soon as the work is finished the wedges should be
+removed so that the natural contraction can take place without damage.
+
+It should always be remembered that it is not so much the expansion of the
+work when heated as it is the contraction caused by cooling that will do
+the damage. A weld may be made that, to all appearances, is perfect and it
+may be perfect when completed; but if provision has not been made to allow
+for the contraction that is certain to follow, there will be a breakage at
+some point. It is not possible to weld the simplest shapes, other than
+straight bars, without considering this difficulty and making provision to
+take care of it.
+
+The exact method to employ in preheating will always call for good judgment
+on the part of the workman, and he should remember that the success or
+failure of his work will depend fully as much on proper preparation as on
+correct handling of the weld itself. It should be remembered that the outer
+flame of the oxy-acetylene torch may be depended on for a certain amount of
+preheating, as this flame gives a very large volume of heat, but a heat
+that is not so intense nor so localized as the welding flame itself. The
+heat of this part of the flame should be fully utilized during the
+operation of melting the metal and it should be so directed, when possible,
+that it will bring the parts next to be joined to as high a temperature as
+possible.
+
+When the work has been brought to the desired temperature, all parts except
+the break and the surface immediately surrounding it on both sides should
+be covered with heavy sheet asbestos. This protecting cover should remain
+in place throughout the operation and should only be moved a distance
+sufficient to allow the torch flame to travel in the path of the weld. The
+use of asbestos in this way serves a twofold purpose. It retains the heat
+in the work and prevents the breakage that would follow if a draught of air
+were to strike the heated metal, and it also prevents such a radiation of
+heat through the surrounding air as would make it almost impossible for the
+operator to perform his work, especially in the case of large and heavy
+castings when the amount of heat utilized is large.
+
+_Cleaning and Champfering._--A perfect weld can never be made unless
+the surfaces to be joined have been properly prepared to receive the new
+metal.
+
+All spoiled, burned, corroded and rough particles must positively be
+removed with chisel and hammer and with a free application of emery cloth
+and wire brush. The metal exposed to the welding flame should be perfectly
+clean and bright all over, or else the additional material will not unite,
+but will only stick at best.
+
+[Illustration: Figure 28.--Tapering the Opening Formed by a Break]
+
+Following the cleaning it is always necessary to bevel, or champfer, the
+edges except in the thinnest sheet metal. To make a weld that will hold,
+the metal must be made into one piece, without holes or unfilled portions
+at any point, and must be solid from inside to outside. This can only be
+accomplished by starting the addition of metal at one point and gradually
+building it up until the outside, or top, is reached. With comparatively
+thin plates the molten metal may be started from the side farthest from the
+operator and brought through, but with thicker sections the addition is
+started in the middle and brought flush with one side and then with the
+other.
+
+It will readily be seen that the molten material cannot be depended upon to
+flow between the tightly closed surfaces of a crack in a way that can be at
+all sure to make a true weld. It will be necessary for the operator to
+reach to the farthest side with the flame and welding rod, and to start the
+new surfaces there. To allow this, the edges that are to be joined are
+beveled from one side to the other (Figure 28), so that when placed
+together in approximately the position they are to occupy they will leave a
+grooved channel between them with its sides at an angle with each other
+sufficient in size to allow access to every point of each surface.
+
+[Illustration: Figure 29.--Beveling for Thin Work]
+
+[Illustration: Figure 30.--Beveling for Thick Work]
+
+With work less than one-fourth inch thick, this angle should be forty-five
+degrees on each piece (Figure 29), so that when they are placed together
+the extreme edges will meet at the bottom of a groove whose sides are
+square, or at right angles, to each other. This beveling should be done so
+that only a thin edge is left where the two parts come together, just
+enough points in contact to make the alignment easy to hold. With work of a
+thickness greater than a quarter of an inch, the angle of bevel on each
+piece may be sixty degrees (Figure 30), so that when placed together the
+angle included between the sloping sides will also be sixty degrees. If the
+plate is less than one-eighth of an inch thick the beveling is not
+necessary, as the edges may be melted all the way through without danger of
+leaving blowholes at any point.
+
+[Illustration: Figure 31.--Beveling Both Sides of a Thick Piece]
+
+[Illustration: Figure 32.--Beveling the End of a Pipe]
+
+This beveling may be done in any convenient way. A chisel is usually most
+satisfactory and also quickest. Small sections may be handled by filing,
+while metal that is too hard to cut in either of these ways may be shaped
+on the emery wheel. It is not necessary that the edges be perfectly
+finished and absolutely smooth, but they should be of regular outline and
+should always taper off to a thin edge so that when the flame is first
+applied it can be seen issuing from the far side of the crack. If the work
+is quite thick and is of a shape that will allow it to be turned over, the
+bevel may be brought from both sides (Figure 31), so that there will be two
+grooves, one on each surface of the work. After completing the weld on one
+side, the piece is reversed and finished on the other side. Figure 32 shows
+the proper beveling for welding pipe. Figure 33 shows how sheet metal may
+be flanged for welding.
+
+Welding should not be attempted with the edges separated in place of
+beveled, because it will be found impossible to build up a solid web of new
+metal from one side clear through to the other by this method. The flame
+cannot reach the surfaces to make them molten while receiving new material
+from the rod, and if the flame does not reach them it will only serve to
+cause a few drops of the metal to join and will surely cause a weak and
+defective weld.
+
+[Illustration: Figure 33.--Flanging Sheet Metal for Welding]
+
+_Supporting Work._--During the operation of welding it is necessary
+that the work be well supported in the position it should occupy. This may
+be done with fire brick placed under the pieces in the correct position,
+or, better still, with some form of clamp. The edges of the crack should
+touch each other at the point where welding is to start and from there
+should gradually separate at the rate of about one-fourth inch to the foot.
+This is done so that the cooling of the molten metal as it is added will
+draw the edges together by its contraction.
+
+Care must be used to see that the work is supported so that it will
+maintain the same relative position between the parts as must be present
+when the work is finished. In this connection it must be remembered that
+the expansion of the metal when heated may be great enough to cause serious
+distortion and to provide against this is one of the difficulties to be
+overcome.
+
+Perfect alignment should be secured between the separate parts that are to
+be joined and the two edges must be held up so that they will be in the
+same plane while welding is carried out. If, by any chance, one drops
+below the other while molten metal is being added, the whole job may have
+to be undone and done over again. One precaution that is necessary is that
+of making sure that the clamping or supporting does not in itself pull the
+work out of shape while melted.
+
+
+TORCH PRACTICE
+
+[Illustration: Figure 34.--Rotary Movement of Torch in Welding]
+
+The weld is made by bringing the tip of the welding flame to the edges of
+the metals to be joined. The torch should be held in the right hand and
+moved slowly along the crack with a rotating motion, traveling in small
+circles (Figure 34), so that the Welding flame touches first on one side of
+the crack and then on the other. On large work the motion may be simply
+back and forth across the crack, advancing regularly as the metal unites.
+It is usually best to weld toward the operator rather than from him,
+although this rule is governed by circumstances. The head of the torch
+should be inclined at an angle of about 60 degrees to the surface of the
+work. The torch handle should extend in the same line with the break
+(Figure 35) and not across it, except when welding very light plates.
+
+[Illustration: Figure 35.--Torch Held in Line with the Break]
+
+If the metal is 1/16 inch or less in thickness it is only necessary to
+circle along the crack, the metal itself furnishing enough material to
+complete the weld without additions. Heat both sides evenly until they flow
+together.
+
+Material thicker than the above requires the addition of more metal of the
+same or different kind from the welding rod, this rod being held by the
+left hand. The proper size rod for cast iron is one having a diameter equal
+to the thickness of metal being welded up to a one-half inch rod, which is
+the largest used. For steel the rod should be one-half the thickness of the
+metal being joined up to one-fourth inch rod. As a general rule, better
+results will be obtained by the use of smaller rods, the very small sizes
+being twisted together to furnish enough material while retaining the free
+melting qualities.
+
+[Illustration: Figure 36.--The Welding Rod Should Be Held in the Molten
+Metal]
+
+The tip of the rod must at all times be held in contact with the pieces
+being welded and the flame must be so directed that the two sides of the
+crack and the end of the rod are melted at the same time (Figure 36).
+Before anything is added from the rod, the sides of the crack are melted
+down sufficiently to fill the bottom of the groove and join the two sides.
+Afterward, as metal comes from the rod in filling the crack, the flame is
+circled along the joint being made, the rod always following the flame.
+
+[Illustration: Figure 37.--Welding Pieces of Unequal Thickness]
+
+Figure 37 illustrates the welding of pieces of unequal thickness.
+
+Figure 38 illustrates welding at an angle.
+
+The molten metal may be directed as to where it should go by the tip of the
+welding flame, which has considerable force, but care must be taken not to
+blow melted metal on to cooler surfaces which it cannot join. If, while
+welding, a spot appears which does not unite with the weld, it may be
+handled by heating all around it to a white heat and then immediately
+welding the bad place.
+
+[Illustration: Figure 38.--Welding at an Angle]
+
+Never stop in the middle of a weld, as it is extremely difficult to
+continue smoothly when resuming work.
+
+_The Flame._--The welding flame must have exactly the right
+proportions of each gas. If there is too much oxygen, the metal will be
+burned or oxidized; the presence of too much acetylene carbonizes the
+metal; that is to say, it adds carbon and makes the work harder. Just the
+right mixture will neither burn nor carbonize and is said to be a "neutral"
+flame. The neutral flame, if of the correct size for the work, reduces the
+metal to a melted condition, not too fluid, and for a width about the same
+as the thickness of the metal being welded.
+
+When ready to light the torch, after attaching the right tip or head as
+directed in accordance with the thickness of metal to be handled, it will
+be necessary to regulate the pressure of gases to secure the neutral flame.
+
+The oxygen will have a pressure of from 2 to 20 pounds, according to the
+nozzle used. The acetylene will have much less. Even with the compressed
+gas, the pressure should never exceed 10 pounds for the largest work, and
+it will usually be from 4 to 6. In low pressure systems, the acetylene will
+be received at generator pressure. It should first be seen that the
+hand-screws on the regulators are turned way out so that the springs are
+free from any tension. It will do no harm if these screws are turned back
+until they come out of the threads. This must be done with both oxygen and
+acetylene regulators.
+
+Next, open the valve from the generator, or on the acetylene tank, and
+carefully note whether there is any odor of escaping gas. Any leakage of
+this gas must be stopped before going on with the work.
+
+The hand wheel controlling the oxygen cylinder valve should now be turned
+very slowly to the left as far as it will go, which opens the valve, and
+it should be borne in mind the pressure that is being released. Turn in the
+hand screw on the oxygen regulator until the small pressure gauge shows a
+reading according to the requirements of the nozzle being used. This oxygen
+regulator adjustment should be made with the cock on the torch open, and
+after the regulator is thus adjusted the torch cock may be closed.
+
+Open the acetylene cock on the torch and screw in on the acetylene
+regulator hand-screw until gas commences to come through the torch. Light
+this flow of acetylene and adjust the regulator screw to the pressure
+desired, or, if there is no gauge, so that there is a good full flame. With
+the pressure of acetylene controlled by the type of generator it will only
+be necessary to open the torch cock.
+
+With the acetylene burning, slowly open the oxygen cock on the torch and
+allow this gas to join the flame. The flame will turn intensely bright and
+then blue white. There will be an outer flame from four to eight inches
+long and from one to three inches thick. Inside of this flame will be two
+more rather distinctly defined flames. The inner one at the torch tip is
+very small, and the intermediate one is long and pointed. The oxygen should
+be turned on until the two inner flames unite into one blue-white cone from
+one-fourth to one-half inch long and one-eighth to one-fourth inch in
+diameter. If this single, clearly defined cone does not appear when the
+oxygen torch cock has been fully opened, turn off some of the acetylene
+until it does appear.
+
+If too much oxygen is added to the flame, there will still be the central
+blue-white cone, but it will be smaller and more or less ragged around the
+edges (Figure 39). When there is just enough oxygen to make the single
+cone, and when, by turning on more acetylene or by turning off oxygen, two
+cones are caused to appear, the flame is neutral (Figure 40), and the small
+blue-white cone is called the welding flame.
+
+[Illustration: Figure 39.--Oxidizing Flame--Too Much Oxygen]
+
+[Illustration: Figure 40.--Neutral Flame]
+
+[Illustration: Figure 41.--Reducing Flame--Showing an Excess of Acetylene]
+
+While welding, test the correctness of the flame adjustment occasionally by
+turning on more acetylene or by turning off some oxygen until two flames or
+cones appear. Then regulate as before to secure the single distinct cone.
+Too much oxygen is not usually so harmful as too much acetylene, except
+with aluminum. (See Figure 41.) An excessive amount of sparks coming from
+the weld denotes that there is too much oxygen in the flame. Should the
+opening in the tip become partly clogged, it will be difficult to secure a
+neutral flame and the tip should be cleaned with a brass or copper
+wire--never with iron or steel tools or wire of any kind. While the torch
+is doing its work, the tip may become excessively hot due to the heat
+radiated from the molten metal. The tip may be cooled by turning off the
+acetylene and dipping in water with a slight flow of oxygen through the
+nozzle to prevent water finding its way into the mixing chamber.
+
+The regulators for cutting are similar to those for welding, except that
+higher pressures may be handled, and they are fitted with gauges reading up
+to 200 or 250 pounds pressure.
+
+In welding metals which conduct the heat very rapidly it is necessary to
+use a much larger nozzle and flame than for metals which have not this
+property. This peculiarity is found to the greatest extent in copper,
+aluminum and brass.
+
+Should a hole be blown through the work, it may be closed by withdrawing
+the flame for a few seconds and then commencing to build additional metal
+around the edges, working all the way around and finally closing the small
+opening left at the center with a drop or two from the welding rod.
+
+
+WELDING VARIOUS METALS
+
+Because of the varying melting points, rates of expansion and contraction,
+and other peculiarities of different metals, it is necessary to give
+detailed consideration to the most important ones.
+
+_Characteristics of Metals._--The welder should thoroughly understand
+the peculiarities of the various metals with which he has to deal. The
+metals and their alloys are described under this heading in the first
+chapter of this book and a tabulated list of the most important points
+relating to each metal will be found at the end of the present chapter.
+All this information should be noted by the operator of a welding
+installation before commencing actual work.
+
+Because of the nature of welding, the melting point of a metal is of great
+importance. A metal melting at a low temperature should have more careful
+treatment to avoid undesired flow than one which melts at a temperature
+which is relatively high. When two dissimilar metals are to be joined, the
+one which melts at the higher temperature must be acted upon by the flame
+first and when it is in a molten condition the heat contained in it will in
+many cases be sufficient to cause fusion of the lower melting metal and
+allow them to unite without playing the flame on the lower metal to any
+great extent.
+
+The heat conductivity bears a very important relation to welding, inasmuch
+as a metal with a high rate of conductance requires more protection from
+cooling air currents and heat radiation than one not having this quality to
+such a marked extent. A metal which conducts heat rapidly will require a
+larger volume of flame, a larger nozzle, than otherwise, this being
+necessary to supply the additional heat taken away from the welding point
+by this conductance.
+
+The relative rates of expansion of the various metals under heat should be
+understood in order that parts made from such material may have proper
+preparation to compensate for this expansion and contraction. Parts made
+from metals having widely varying rates of expansion must have special
+treatment to allow for this quality, otherwise breakage is sure to occur.
+
+_Cast Iron._--All spoiled metal should be cut away and if the work is
+more than one-eighth inch in thickness the sides of the crack should be
+beveled to a 45 degree angle, leaving a number of points touching at the
+bottom of the bevel so that the work may be joined in its original
+relation.
+
+The entire piece should be preheated in a bricked-up oven or with charcoal
+placed on the forge, when size does not warrant building a temporary oven.
+The entire piece should be slowly heated and the portion immediately
+surrounding the weld should be brought to a dull red. Care should be used
+that the heat does not warp the metal through application to one part more
+than the others. After welding, the work should be slowly cooled by
+covering with ashes, slaked lime, asbestos fibre or some other
+non-conductor of heat. These precautions are absolutely essential in the
+case of cast iron.
+
+A neutral flame, from a nozzle proportioned to the thickness of the work,
+should be held with the point of the blue-white cone about one-eighth inch
+from the surface of the iron.
+
+A cast iron rod of correct diameter, usually made with an excess of
+silicon, is used by keeping its end in contact with the molten metal and
+flowing it into the puddle formed at the point of fusion. Metal should be
+added so that the weld stands about one-eighth inch above the surrounding
+surface of the work.
+
+Various forms of flux may be used and they are applied by dipping the end
+of the welding rod into the powder at intervals. These powders may contain
+borax or salt, and to prevent a hard, brittle weld, graphite or
+ferro-silicon may be added. Flux should be added only after the iron is
+molten and as little as possible should be used. No flux should be used
+just before completion of the work.
+
+The welding flame should be played on the work around the crack and
+gradually brought to bear on the work. The bottom of the bevel should be
+joined first and it will be noted that the cast iron tends to run toward
+the flame, but does not stick together easily. A hard and porous weld
+should be carefully guarded against, as described above, and upon
+completion of the work the welded surface should be scraped with a file,
+while still red hot, in order to remove the surface scale.
+
+_Malleable Iron._--This material should be beveled in the same way
+that cast iron is handled, and preheating and slow cooling are equally
+desirable. The flame used is the same as for cast iron and so is the flux.
+The welding rod may be of cast iron, although better results are secured
+with Norway iron wire or else a mild steel wire wrapped with a coil of
+copper wire.
+
+It will be understood that malleable iron turns to ordinary cast iron when
+melted and cooled. Welds in malleable iron are usually far from
+satisfactory and a better joint is secured by brazing the edges together
+with bronze. The edges to be joined are brought to a heat just a little
+below the point at which they will flow and the opening is then
+quickly-filled from a rod of Tobin bronze or manganese bronze, a brass or
+bronze flux being used in this work.
+
+_Wrought Iron or Semi-Steel._--This metal should be beveled and heated
+in the same way as described for cast iron. The flame should be neutral, of
+the same size as for steel, and used with the tip of the blue-white cone
+just touching the work. The welding rod should be of mild steel, or, if
+wrought iron is to be welded to steel, a cast iron rod may be used. A cast
+iron flux is well suited for this work. It should be noted that wrought
+iron turns to ordinary cast iron if kept heated for any length of time.
+
+_Steel._--Steel should be beveled if more than one-eighth inch in
+thickness. It requires only a local preheating around the point to be
+welded. The welding flame should be absolutely neutral, without excess of
+either gas. If the metal is one-sixteenth inch or less in thickness, the
+tip of the blue-white cone must be held a short distance from the surface
+of the work; in all other cases the tip of this cone is touched to the
+metal being welded.
+
+The welding rod may be of mild, low carbon steel or of Norway iron. Nickel
+steel rods may be used for parts requiring great strength, but vanadium
+alloys are very difficult to handle. A very satisfactory rod is made by
+twisting together two wires of the required material. The rod must be kept
+constantly in contact with the work and should not be added until the edges
+are thoroughly melted. The flux may or may not be used. If one is wanted,
+it may be made from three parts iron filings, six parts borax and one part
+sal ammoniac.
+
+It will be noticed that the steel runs from the flame, but tends to hold
+together. Should foaming commence in the molten metal, it shows an excess
+of oxygen and that the metal is being burned.
+
+High carbon steels are very difficult to handle. It is claimed that a drop
+or two of copper added to the weld will assist the flow, but will also
+harden the work. An excess of oxygen reduces the amount of carbon and
+softens the steel, while an excess of acetylene increases the proportion of
+carbon and hardens the metal. High speed steels may sometimes be welded if
+first coated with semi-steel before welding.
+
+_Aluminum._--This is the most difficult of the commonly found metals
+to weld. This is caused by its high rate of expansion and contraction and
+its liability to melt and fall away from under the flame. The aluminum
+seems to melt on the inside first, and, without previous warning, a portion
+of the work will simply vanish from in front of the operator's eyes. The
+metal tends to run from the flame and separate at the same time. To keep
+the metal in shape and free from oxide, it is worked or puddled while in a
+plastic condition by an iron rod which has been flattened at one end.
+Several of these rods should be at hand and may be kept in a jar of salt
+water while not being used. These rods must not become coated with aluminum
+and they must not get red hot while in the weld.
+
+The surfaces to be joined, together with the adjacent parts, should be
+cleaned thoroughly and then washed with a 25 per cent solution of nitric
+acid in hot water, used on a swab. The parts should then be rinsed in clean
+water and dried with sawdust. It is also well to make temporary fire clay
+moulds back of the parts to be heated, so that the metal may be flowed into
+place and allowed to cool without danger of breakage.
+
+Aluminum must invariably be preheated to about 600 degrees, and the whole
+piece being handled should be well covered with sheet asbestos to prevent
+excessive heat radiation.
+
+The flame is formed with an excess of acetylene such that the second cone
+extends about an inch, or slightly more, beyond the small blue-white point.
+The torch should be held so that the end of this second cone is in contact
+with the work, the small cone ordinarily used being kept an inch or an inch
+and a half from the surface of the work.
+
+Welding rods of special aluminum are used and must be handled with their
+end submerged in the molten metal of the weld at all times.
+
+When aluminum is melted it forms alumina, an oxide of the metal. This
+alumina surrounds small masses of the metal, and as it does not melt at
+temperatures below 5000 degrees (while aluminum melts at about 1200), it
+prevents a weld from being made. The formation of this oxide is retarded
+and the oxide itself is dissolved by a suitable flux, which usually
+contains phosphorus to break down the alumina.
+
+_Copper._--The whole piece should be preheated and kept well covered
+while welding. The flame must be much larger than for the same thickness of
+steel and neutral in character. A slight excess of acetylene would be
+preferable to an excess of oxygen, and in all cases the molten metal should
+be kept enveloped with the flame. The welding rod is of copper which
+contains phosphorus; and a flux, also containing phosphorus, should be
+spread for about an inch each side of the joint. These assist in preventing
+oxidation, which is sure to occur with heated copper.
+
+Copper breaks very easily at a heat slightly under the welding temperature
+and after cooling it is simply cast copper in all cases.
+
+_Brass and Bronze._--It is necessary to preheat these metals, although
+not to a very high temperature. They must be kept well covered at all times
+to prevent undue radiation. The flame should be produced with a nozzle one
+size larger than for the same thickness of steel and the small blue-white
+cone should be held from one-fourth to one-half inch above the surface of
+the work. The flame should be neutral in character.
+
+A rod or wire of soft brass containing a large percentage of zinc is
+suitable for adding to brass, while copper requires the use of copper or
+manganese bronze rods. Special flux or borax may be used to assist the
+flow.
+
+The emission of white smoke indicates that the zinc contained in these
+alloys is being burned away and the heat should immediately be turned away
+or reduced. The fumes from brass and bronze welding are very poisonous and
+should not be breathed.
+
+
+RESTORATION OF STEEL
+
+The result of the high heat to which the steel has been subjected is that
+it is weakened and of a different character than before welding. The
+operator may avoid this as much as possible by first playing the outer
+flame of the torch all over the surfaces of the work just completed until
+these faces are all of uniform color, after which the metal should be well
+covered with asbestos and allowed to cool without being disturbed. If a
+temporary heating oven has been employed, the work and oven should be
+allowed to cool together while protected with the sheet asbestos. If the
+outside air strikes the freshly welded work, even for a moment, the result
+will be breakage.
+
+A weld in steel will always leave the metal with a coarse grain and with
+all the characteristics of rather low grade cast steel. As previously
+mentioned in another chapter, the larger the grain size in steel the weaker
+the metal will be, and it is the purpose of the good workman to avoid, as
+far as possible, this weakening.
+
+The structure of the metal in one piece of steel will differ according to
+the heat that it has under gone. The parts of the work that have been at
+the melting point will, therefore, have the largest grain size and the
+least strength. Those parts that have not suffered any great rise in
+temperature will be practically unaffected, and all the parts between these
+two extremes will be weaker or stronger according to their distance from
+the weld itself. To restore the steel so that it will have the best grain
+size, the operator may resort to either of two methods: (1) The grain may
+be improved by forging. That means that the metal added to the weld and the
+surfaces that have been at the welding heat are hammered much as a
+blacksmith would hammer his finished work to give it greater strength. The
+hammering should continue from the time the metal first starts to cool
+until it has reached the temperature at which the grain size is best for
+strength. This temperature will vary somewhat with the composition of the
+metal being handled, but in a general way, it may be stated that the
+hammering should continue without intermission from the time the flame is
+removed from the weld until the steel just begins to show attraction for a
+magnet presented to it. This temperature of magnetic attraction will always
+be low enough and the hammering should be immediately discontinued at this
+point. (2) A method that is more satisfactory, although harder to apply, is
+that of reheating the steel to a certain temperature throughout its whole
+mass where the heat has had any effect, and then allowing slow and even
+cooling from this temperature. The grain size is affected by the
+temperature at which the reheating is stopped, and not by the cooling, yet
+the cooling should be slow enough to avoid strains caused by uneven
+contraction.
+
+After the weld has been completed the steel must be allowed to cool until
+below 1200° Fahrenheit. The next step is to heat the work slowly until all
+those parts to be restored have reached a temperature at which the magnet
+just ceases to be attracted. While the very best temperature will vary
+according to the nature and hardness of the steel being handled, it will be
+safe to carry the heating to the point indicated by the magnet in the
+absence of suitable means of measuring accurately these high temperatures.
+In using a magnet for testing, it will be most satisfactory if it is an
+electromagnet and not of the permanent type. The electric current may be
+secured from any small battery and will be the means of making sure of the
+test. The permanent magnet will quickly lose its power of attraction under
+the combined action of the heat and the jarring to which it will be
+subjected.
+
+In reheating the work it is necessary to make sure that no part reaches a
+temperature above that desired for best grain size and also to see that all
+parts are brought to this temperature. Here enters the greatest difficulty
+in restoring the metal. The heating may be done so slowly that no part of
+the work on the outside reaches too high a temperature and then keeps the
+outside at this heat until the entire mass is at the same temperature. A
+less desirable way is to heat the outside higher than this temperature and
+allow the conductivity of the metal to distribute the excess to the inside.
+
+The most satisfactory method, where it can be employed, is to make use of a
+bath of some molten metal or some chemical mixture that can be kept at the
+exact heat necessary by means of gas fires that admit of close regulation.
+The temperature of these baths may be maintained at a constant point by
+watching a pyrometer, and the finished work may be allowed to remain in the
+bath until all parts have reached the desired temperature.
+
+
+WELDING INFORMATION
+
+The following tables include much of the information that the operator must
+use continually to handle the various metals successfully. The temperature
+scales are given for convenience only. The composition of various alloys
+will give an idea of the difficulties to be contended with by consulting
+the information on welding various metals. The remaining tables are of
+self-evident value in this work.
+
+TEMPERATURE SCALES
+Centigrade  Fahrenheit      Centigrade  Fahrenheit
+   200°        392°            1000°      1832°
+   225°        437°            1050°      1922°
+   250°        482°            1100°      2012°
+   275°        527°            1150°      2102°
+   300°        572°            1200°      2192°
+   325°        617°            1250°      2282°
+   350°        662°            1300°      2372°
+   375°        707°            1350°      2462°
+   400°        752°            1400°      2552°
+   425°        797°            1450°      2642°
+   450°        842°            1500°      2732°
+   475°        887°            1550°      2822°
+   500°        932°            1600°      2912°
+   525°        977°            1650°      3002°
+   550°       1022°            1700°      3092°
+   575°       1067°            1750°      3182°
+   600°       1112°            1800°      3272°
+   625°       1157°            1850°      3362°
+   650°       1202°            1900°      3452°
+   675°       1247°            2000°      3632°
+   700°       1292°            2050°      3722°
+   725°       1337°            2100°      3812°
+   750°       1382°            2150°      3902°
+   775°       1427°            2200°      3992°
+   800°       1472°            2250°      4082°
+   825°       1517°            2300°      4172°
+   850°       1562°            2350°      4262°
+   875°       1607°            2400°      4352°
+   900°       1652°            2450°      4442°
+   925°       1697°            2500°      4532°
+   950°       1742°            2550°      4622°
+   975°       1787°            2600°      4712°
+
+METAL ALLOYS
+(Society of Automobile Engineers)
+
+Babbitt--
+  Tin...........................           84.00%
+  Antimony......................            9.00%
+  Copper........................            7.00%
+
+Brass, White--
+  Copper........................  3.00% to  6.00%
+  Tin (minimum) ................           65.00%
+  Zinc.......................... 28.00% to 30.00%
+
+Brass, Red Cast--
+  Copper........................           85.00%
+  Tin...........................            5.00%
+  Lead..........................            5.00%
+  Zinc..........................            5.00%
+
+Brass, Yellow--
+  Copper........................ 62.00% to 65.00%
+  Lead..........................  2.00% to  4.00%
+  Zinc.......................... 36.00% to 31.00%
+
+Bronze, Hard--
+  Copper........................ 87.00% to 88.00%
+  Tin...........................  9.50% to 10.50%
+  Zinc..........................  1.50% to  2.50%
+
+Bronze, Phosphor--
+  Copper........................           80.00%
+  Tin...........................           10.00%
+  Lead..........................           10.00%
+  Phosphorus....................   .50% to   .25%
+
+Bronze, Manganese--
+  Copper (approximate) .........           60.00%
+  Zinc (approximate) ...........           40.00%
+  Manganese (variable) .........            small
+
+Bronze, Gear--
+  Copper........................ 88.00% to 89.00%
+  Tin........................... 11.00% to 12.00%
+
+Aluminum Alloys--
+          Aluminum   Copper   Zinc   Manganese
+  No. 1.. 90.00%    8.5-7.0%
+  No. 2.. 80.00%    2.0-3.0%  15%  Not over 0.40%
+  No. 3.. 65.00%              35.0%
+
+Cast Iron--
+                      Gray Iron      Malleable
+  Total carbon........3.0 to 3.5%
+  Combined carbon.....0.4 to 0.7%
+  Manganese...........0.4 to 0.7%    0.3 to 0.7%
+  Phosphorus..........0.6 to 1.0%  Not over 0.2%
+  Sulphur...........Not over 0.1%  Not over 0.6%
+  Silicon............1.75 to 2.25% Not over 1.0%
+
+Carbon Steel (10 Point)--
+  Carbon........................     .05% to .15%
+  Manganese.....................     .30% to .60%
+  Phosphorus (maximum)..........             .045%
+  Sulphur (maximum).............             .05%
+(20 Point)--
+  Carbon........................     .15% to .25%
+  Manganese.....................     .30% to .60%
+  Phosphorus (maximum)..........             .045%
+  Sulphur (maximum).............             .05%
+(35 Point)--
+  Manganese.....................     .50% to .80%
+  Carbon........................     .30% to .40%
+  Phosphorus (maximum)..........             .05%
+  Sulphur (maximum).............             .05%
+(95 Point)--
+  Carbon........................    .90% to 1.05%
+  Manganese.....................    .25% to  .50%
+  Phosphorus (maximum)..........             .04%
+  Sulphur (maximum).............             .05%
+
+HEATING POWER OF FUEL GASES
+
+(In B.T.U. per Cubic Foot.)
+  Acetylene....... 1498.99   Ethylene....... 1562.9
+  Hydrogen........  291.96   Methane........  953.6
+  Alcohol......... 1501.76
+
+MELTING POINTS OF METALS
+  Platinum....................3200°
+  Iron, wrought...............2900°
+    malleable.................2500°
+    cast......................2400°
+    pure......................2760°
+  Steel, mild.................2700°
+    Medium....................2600°
+    Hard......................2500°
+  Copper......................1950°
+  Brass.......................1800°
+  Silver......................1750°
+  Bronze......................1700°
+  Aluminum....................1175°
+  Antimony....................1150°
+  Zinc........................ 800°
+  Lead........................ 620°
+  Babbitt..................500-700°
+  Solder...................500-575°
+  Tin......................... 450°
+
+_NOTE.--These melting points are for average compositions and conditions.
+The exact proportion of elements entering into the metals affects their
+melting points one way or the other in practice._
+
+TENSILE STRENGTH OF METALS
+
+Alloy steels can be made with tensile strengths as high as 300,000 pounds
+per square inch. Some carbon steels are given below according to "points":
+
+                           Pounds per Square Inch
+Steel, 10 point................ 50,000 to  65,000
+  20 point..................... 60,000 to  80,000
+  40 point..................... 70,000 to 100,000
+  60 point..................... 90,000 to 120,000
+Iron, Cast..................... 13,000 to  30,000
+  Wrought...................... 40,000 to  60,000
+  Malleable.................... 25,000 to  45,000
+Copper......................... 24,000 to  50,000
+Bronze......................... 30,000 to  60,000
+Brass, Cast.................... 12,000 to  18,000
+  Rolled....................... 30,000 to  40,000
+  Wire......................... 60,000 to  75,000
+Aluminum....................... 12,000 to  23,000
+Zinc...........................  5,000 to  15,000
+Tin............................  3,000 to   5,000
+Lead...........................  1,500 to   2,500
+
+CONDUCTIVITY OF METALS
+
+(Based on the Value of Silver as 100)
+
+                          Heat  Electricity
+Silver....................100     100
+Copper.................... 74      99
+Aluminum.................. 38      63
+Brass..................... 23      22
+Zinc...................... 19      29
+Tin....................... 14      15
+Wrought Iron.............. 12      16
+Steel..................... 11.5    12
+Cast Iron................. 11      12
+Bronze....................  9       7
+Lead......................  8       9
+
+WEIGHT OF METALS
+
+(Per Cubic Inch)
+                 Pounds                  Pounds
+Lead............  .410  Wrought Iron.....  .278
+Copper..........  .320  Tin..............  .263
+Bronze..........  .313  Cast Iron........  .260
+Brass...........  .300  Zinc.............  .258
+Steel...........  .283  Aluminum.........  .093
+
+EXPANSION OF METALS
+
+(Measured in Thousandths of an Inch per Foot of
+Length When Raised 1000 Degrees in Temperature)
+                  Inch                     Inch
+Lead............  .188  Brass............  .115
+Zinc............  .168  Copper...........  .106
+Aluminum........  .148  Steel............  .083
+Silver..........  .129  Wrought Iron.....  .078
+Bronze..........  .118  Cast Iron........  .068
+
+
+
+
+CHAPTER VI
+
+ELECTRIC WELDING
+
+
+RESISTANCE METHOD
+
+Two distinct forms of electric welding apparatus are in use, one producing
+heat by the resistance of the metal being treated to the passage of
+electric current, the other using the heat of the electric arc.
+
+The resistance process is of the greatest use in manufacturing lines where
+there is a large quantity of one kind of work to do, many thousand pieces
+of one kind, for instance. The arc method may be applied in practically any
+case where any other form of weld may be made. The resistance process will
+be described first.
+
+It is a well known fact that a poor conductor of electricity will offer so
+much resistance to the flow of electricity that it will heat. Copper is a
+good conductor, and a bar of iron, a comparatively poor conductor, when
+placed between heavy copper conductors of a welder, becomes heated in
+attempting to carry the large volume of current. The degree of heat depends
+on the amount of current and the resistance of the conductor.
+
+In an electric circuit the ends of two pieces of metal brought together
+form the point of greatest resistance in the electric circuit, and the
+abutting ends instantly begin to heat. The hotter this metal becomes, the
+greater the resistance to the flow of current; consequently, as the edges
+of the abutting ends heat, the current is forced into the adjacent cooler
+parts, until there is a uniform heat throughout the entire mass. The heat
+is first developed in the interior of the metal so that it is welded there
+as perfectly as at the surface.
+
+[Illustration: Figure 42.--Spot Welding Machine]
+
+The electric welder (Figure 42) is built to hold the parts to be joined
+between two heavy copper dies or contacts. A current of three to five
+volts, but of very great volume (amperage), is allowed to pass across
+these dies, and in going through the metal to be welded, heats the edges
+to a welding temperature. It may be explained that the voltage of an
+electric current measures the pressure or force with which it is being sent
+through the circuit and has nothing to do with the quantity or volume
+passing. Amperes measure the rate at which the current is passing through
+the circuit and consequently give a measure of the quantity which passes in
+any given time. Volts correspond to water pressure measured by pounds to
+the square inch; amperes represent the flow in gallons per minute. The low
+voltage used avoids all danger to the operator, this pressure not being
+sufficient to be felt even with the hands resting on the copper contacts.
+
+Current is supplied to the welding machine at a higher voltage and lower
+amperage than is actually used between the dies, the low voltage and high
+amperage being produced by a transformer incorporated in the machine
+itself. By means of windings of suitable size wire, the outside current may
+be received at voltages ranging from 110 to 550 and converted to the low
+pressure needed.
+
+The source of current for the resistance welder must be alternating, that
+is, the current must first be negative in value and then positive, passing
+from one extreme to the other at rates varying from 25 to 133 times a
+second. This form is known as alternating current, as opposed to direct
+current, in which there is no changing of positive and negative.
+
+The current must also be what is known as single phase, that is, a current
+which rises from zero in value to the highest point as a positive current
+and then recedes to zero before rising to the highest point of negative
+value. Two-phase of three-phase currents would give two or three positive
+impulses during this time.
+
+As long as the current is single phase alternating, the voltage and cycles
+(number of alternations per second) may be anything convenient. Various
+voltages and cycles are taken care of by specifying all these points when
+designing the transformer which is to handle the current.
+
+Direct current is not used because there is no way of reducing the voltage
+conveniently without placing resistance wires in the circuit and this uses
+power without producing useful work. Direct current may be changed to
+alternating by having a direct current motor running an alternating current
+dynamo, or the change may be made by a rotary converter, although this last
+method is not so satisfactory as the first.
+
+The voltage used in welding being so low to start with, it is absolutely
+necessary that it be maintained at the correct point. If the source of
+current supply is not of ample capacity for the welder being used, it will
+be very hard to avoid a fall of voltage when the current is forced to pass
+through the high resistance of the weld. The current voltage for various
+work is calculated accurately, and the efficiency of the outfit depends to
+a great extent on the voltage being constant.
+
+A simple test for fall of voltage is made by connecting an incandescent
+electric lamp across the supply lines at some point near the welder. The
+lamp should burn with the same brilliancy when the weld is being made as at
+any other time. If the lamp burns dim at any time, it indicates a drop in
+voltage, and this condition should be corrected.
+
+The dynamo furnishing the alternating current may be in the same building
+with the welder and operated from a direct current motor, as mentioned
+above, or operated from any convenient shafting or source of power. When
+the dynamo is a part of the welding plant it should be placed as close to
+the welding machine as possible, because the length of the wire used
+affects the voltage appreciably.
+
+In order to hold the voltage constant, the Toledo Electric Welder Company
+has devised connections which include a rheostat to insert a variable
+resistance in the field windings of the dynamo so that the voltage may be
+increased by cutting this resistance out at the proper time. An auxiliary
+switch is connected to the welder switch so that both switches act
+together. When the welder switch is closed in making a weld, that portion
+of the rheostat resistance between two arms determining the voltage is
+short circuited. This lowers the resistance and the field magnets of the
+dynamo are made stronger so that additional voltage is provided to care for
+the resistance in the metal being heated.
+
+A typical machine is shown in the accompanying cut (Figure 43). On top of
+the welder are two jaws for holding the ends of the pieces to be welded.
+The lower part of the jaws is rigid while the top is brought down on top of
+the work, acting as a clamp. These jaws carry the copper dies through which
+the current enters the work being handled. After the work is clamped
+between the jaws, the upper set is forced closer to the lower set by a long
+compression lever. The current being turned on with the surfaces of the
+work in contact, they immediately heat to the welding point when added
+pressure on the lever forces them together and completes the weld.
+
+[Illustration: Figure 43--Operating Parts of a Toledo Spot Welder]
+
+[Illustration: Figure 43a.--Method of Testing Electric Welder]
+[Illustration: Figure 44.--Detail of Water-Cooled Spot Welding Head]
+
+The transformer is carried in the base of the machine and on the left-hand
+side is a regulator for controlling the voltage for various kinds of work.
+The clamps are applied by treadles convenient to the foot of the operator.
+A treadle is provided which instantly releases both jaws upon the
+completion of the weld. One or both of the copper dies may be cooled by a
+stream of water circulating through it from the city water mains
+(Figure 44). The regulator and switch give the operator control of the
+heat, anything from a dull red to the melting point being easily obtained
+by movement of the lever (figure 45).
+
+[Illustration: Figure 45.--Welding Head of a Water-Cooled Welder]
+
+_Welding._--It is not necessary to give the metal to be welded any
+special preparation, although when very rusty or covered with scale, the
+rust and scale should be removed sufficiently to allow good contact of
+clean metal on the copper dies. The cleaner and better the stock, the less
+current it takes, and there is less wear on the dies. The dies should be
+kept firm and tight in their holders to make a good contact. All bolts and
+nuts fastening the electrical contacts should be clean and tight at all
+times.
+
+The scale may be removed from forgings by immersing them in a pickling
+solution in a wood, stone or lead-lined tank.
+
+The solution is made with five gallons of commercial sulphuric acid in
+150 gallons of water. To get the quickest and best results from this
+method, the solution should be kept as near the boiling point as possible
+by having a coil of extra heavy lead pipe running inside the tank and
+carrying live steam. A very few minutes in this bath will remove the scale
+and the parts should then be washed in running water. After this washing
+they should be dipped into a bath of 50 pounds of unslaked lime in 150
+gallons of water to neutralize any trace of acid.
+
+Cast iron cannot be commercially welded, as it is high in carbon and
+silicon, and passes suddenly from a crystalline to a fluid state when
+brought to the welding temperature. With steel or wrought iron the
+temperature must be kept below the melting point to avoid injury to the
+metal. The metal must be heated quickly and pressed together with
+sufficient force to push all burnt metal out of the joint.
+
+High carbon steel can be welded, but must be annealed after welding to
+overcome the strains set up by the heat being applied at one place. Good
+results are hard to obtain when the carbon runs as high as 75 points, and
+steel of this class can only be handled by an experienced operator. If the
+steel is below 25 points in carbon content, good welds will always be the
+result. To weld high carbon to low carbon steel, the stock should be
+clamped in the dies with the low carbon stock sticking considerably further
+out from the die than the high carbon stock. Nickel steel welds readily,
+the nickel increasing the strength of the weld.
+
+Iron and copper may be welded together by reducing the size of the copper
+end where it comes in contact with the iron. When welding copper and brass
+the pressure must be less than when welding iron. The metal is allowed to
+actually fuse or melt at the juncture and the pressure must be sufficient
+to force the burned metal out. The current is cut off the instant the metal
+ends begin to soften, this being done by means of an automatic switch which
+opens when the softening of the metal allows the ends to come together. The
+pressure is applied to the weld by having the sliding jaw moved by a weight
+on the end of an arm.
+
+Copper and brass require a larger volume of current at a lower voltage than
+for steel and iron. The die faces are set apart three times the diameter of
+the stock for brass and four times the diameter for copper.
+
+Light gauges of sheet steel can be welded to heavy gauges or to solid bars
+of steel by "spot" welding, which will be described later. Galvanized iron
+can be welded, but the zinc coating will be burned off. Sheet steel can be
+welded to cast iron, but will pull apart, tearing out particles of the
+iron.
+
+Sheet copper and sheet brass may be welded, although this work requires
+more experience than with iron and steel. Some grades of sheet aluminum can
+be spot-welded if the slight roughness left on the surface under the die
+is not objectionable.
+
+_Butt Welding._--This is the process which joins the ends of two
+pieces of metal as described in the foregoing part of this chapter. The
+ends are in plain sight of the operator at all times and it can easily be
+seen when the metal reaches the welding heat and begins to soften (Figure
+46). It is at this point that the pressure must be applied with the lever
+and the ends forced together in the weld.
+
+[Illustration: Figure 46.--Butt Welder]
+
+The parts are placed in the clamping jaws (Figure 47) with 1/8 to 1/2 inch
+of metal extending beyond the jaw. The ends of the metal touch each other
+and the current is turned on by means of a switch. To raise the ends to the
+proper heat requires from 3 seconds for 1/4-inch rods to 35 seconds for a
+1-1/2-inch bar.
+
+This method is applicable to metals having practically the same area of
+metal to be brought into contact on each end. When such parts are forced
+together a slight projection will be left in the form of a fin or an
+enlarged portion called an upset. The degree of heat required for any work
+is found by moving the handle of the regulator one way or the other while
+testing several parts. When this setting is right the work can continue as
+long as the same sizes are being handled.
+
+[Illustration: Figure 47.--Clamping Dies of a Butt Welder]
+
+Copper, brass, tool steel and all other metals that are harmed by high
+temperatures must be heated quickly and pressed together with sufficient
+force to force all burned metal from the weld.
+
+In case it is desired to make a weld in the form of a capital letter T, it
+is necessary to heat the part corresponding to the top bar of the T to a
+bright red, then bring the lower bar to the pre-heated one and again turn
+on the current, when a weld can be quickly made.
+
+_Spot Welding._--This is a method of joining metal sheets together at
+any desired point by a welded spot about the size of a rivet. It is done on
+a spot welder by fusing the metal at the point desired and at the same
+instant applying sufficient pressure to force the particles of molten metal
+together. The dies are usually placed one above the other so that the work
+may rest on the lower one while the upper one is brought down on top of the
+upper sheet to be welded.
+
+One of the dies is usually pointed slightly, the opposing one being left
+flat. The pointed die leaves a slight indentation on one side of the metal,
+while the other side is left smooth. The dies may be reversed so that the
+outside surface of any work may be left smooth. The current is allowed to
+flow through the dies by a switch which is closed after pressure is applied
+to the work.
+
+There is a limit to the thickness of sheet metal that can be welded by this
+process because of the fact that the copper rods can only carry a certain
+quantity of current without becoming unduly heated themselves. Another
+reason is that it is difficult to make heavy sections of metal touch at the
+welding point without excessive pressure.
+
+_Lap welding_ is the process used when two pieces of metal are caused
+to overlap and when brought to a welding heat are forced together by
+passing through rollers, or under a press, thus leaving the welded joint
+practically the same thickness as the balance of the work.
+
+Where it is desirable to make a continuous seam, a special machine is
+required, or an attachment for one of the other types. In this form of work
+the stock must be thoroughly cleaned and is then passed between copper
+rollers which act in the same capacity as the copper dies.
+
+_Other Applications._--Hardening and tempering can be done by clamping
+the work in the welding dies and setting the control and time to bring the
+metal to the proper color, when it is cooled in the usual manner.
+
+Brazing is done by clamping the work in the jaws and heating until the
+flux, then the spelter has melted and run into the joint. Riveting and
+heading of rivets can be done by bringing the dies down on opposite ends of
+the rivet after it has been inserted in the hole, the dies being shaped to
+form the heads properly.
+
+Hardened steel may be softened and annealed so that it can be machined by
+connecting the dies of the welder to each side of the point to be softened.
+The current is then applied until the work has reached a point at which it
+will soften when cooled.
+
+_Troubles and Remedies._--The following methods have been furnished by
+the Toledo Electric Welder Company and are recommended for this class of
+work whenever necessary.
+
+To locate grounds in the primary or high voltage side of the circuit,
+connect incandescent lamps in series by means of a long piece of lamp cord,
+as shown, in Figure 43a. For 110 volts use one lamp, for 220 volts use two
+lamps and for 440 volts use four lamps. Attach one end of the lamp cord to
+one side of the switch, and close the switch. Take the other end of the
+cord in the hand and press it against some part of the welder frame where
+the metal is clean and bright. Paint, grease and dirt act as insulators and
+prevent electrical contact. If the lamp lights, the circuit is in
+electrical contact with the frame; in other words, grounded. If the lamps
+do not light, connect the wire to a terminal block, die or slide. If the
+lamps then light, the circuit, coils or leads are in electrical contact
+with the large coil in the transformer or its connections.
+
+If, however, the lamps do not light in either case, the lamp cord should be
+disconnected from the switch and connected to the other side, and the
+operations of connecting to welder frame, dies, terminal blocks, etc., as
+explained above, should be repeated. If the lamps light at any of these
+connections, a "ground" is indicated. "Grounds" can usually be found by
+carefully tracing the primary circuit until a place is found where the
+insulation is defective. Reinsulate and make the above tests again to make
+sure everything is clear. If the ground can not be located by observation,
+the various parts of the primary circuit should be disconnected, and the
+transformer, switch, regulator, etc., tested separately.
+
+To locate a ground in the regulator or other part, disconnect the lines
+running to the welder from the switch. The test lamps used in the previous
+tests are connected, one end of lamp cord to the switch, the other end to a
+binding post of the regulator. Connect the other side of the switch to some
+part of the regulator housing. (This must be a clean connection to a bolt
+head or the paint should be scraped off.) Close the switch. If the lamps
+light, the regulator winding or some part of the switch is "grounded" to
+the iron base or core of the regulator. If the lamps do not light, this
+part of the apparatus is clear.
+
+This test can be easily applied to any part of the welder outfit by
+connecting to the current carrying part of the apparatus, and to the iron
+base or frame that should not carry current. If the lamps light, it
+indicates that the insulation is broken down or is defective.
+
+An A.C. voltmeter can, of course, be substituted for the lamps, or a D.C.
+voltmeter with D.C. current can be used in making the tests.
+
+A short circuit in the primary is caused by the insulation of the coils
+becoming defective and allowing the bare copper wires to touch each other.
+This may result in a "burn out" of one or more of the transformer coils, if
+the trouble is in the transformer, or in the continued blowing of fuses in
+the line. Feel of each coil separately. If a short circuit exists in a coil
+it will heat excessively. Examine all the wires; the insulation may have
+worn through and two of them may cross, or be in contact with the frame or
+other part of the welder. A short circuit in the regulator winding is
+indicated by failure of the apparatus to regulate properly, and sometimes,
+though not always, by the heating of the regulator coils.
+
+The remedy for a short circuit is to reinsulate the defective parts. It is
+a good plan to prevent trouble by examining the wiring occasionally and see
+that the insulation is perfect.
+
+_To Locate Grounds and Short Circuits in the Secondary, or Low Voltage
+Side._--Trouble of this kind is indicated by the machine acting sluggish
+or, perhaps, refusing to operate. To make a test, it will be necessary to
+first ascertain the exciting current of your particular transformer. This
+is the current the transformer draws on "open circuit," or when supplied
+with current from the line with no stock in the welder dies. The following
+table will give this information close enough for all practical purposes:
+
+K.W.      ----------------- Amperes at ----------------
+Rating    110 Volts   220 Volts   440 Volts   550 Volts
+3         1.5         .75         .38         .3
+5         2.5         1.25        .63         .5
+8         3.6         1.8         .9          .72
+10        4.25        2.13        1.07        .85
+15        6.          3.          1.5         1.2
+20        7.          3.5         1.75        1.4
+30        9.          4.5         2.25        1.8
+35        9.6         4.8         2.4         1.92
+50        10.         5.          2.5         2
+
+Remove the fuses from the wall switch and substitute fuses just large
+enough to carry the "exciting" current. If no suitable fuses are at hand,
+fine strands of copper from an ordinary lamp cord may be used. These
+strands are usually No. 30 gauge wire and will fuse at about 10 amperes.
+One or more strands should be used, depending on the amount of exciting
+current, and are connected across the fuse clips in place of fuse wire.
+Place a piece of wood or fibre between the welding dies in the welder as
+though you were going to weld them. See that the regulator is on the
+highest point and close the welder switch. If the secondary circuit is
+badly grounded, current will flow through the ground, and the small fuses
+or small strands of wire will burn out. This is an indication that both
+sides of the secondary circuit are grounded or that a short circuit exists
+in a primary coil. In either case the welder should not be operated until
+the trouble is found and removed. If, however, the small fuses do not
+"blow," remove same and replace the large fuses, then disconnect wires
+running from the wall switch to the welder and substitute two pieces of
+No. 8 or No. 6 insulated copper wire, after scraping off the insulation for
+an inch or two at each end. Connect one wire from the switch to the frame
+of welder; this will leave one loose end. Hold this a foot or so away from
+the place where the insulation is cut off; then turn on the current and
+strike the free end of this wire lightly against one of the copper dies,
+drawing it away quickly. If no sparking is produced, the secondary circuit
+is free from ground, and you will then look for a broken connection in the
+circuit. Some caution must be used in making the above test, as in case one
+terminal is heavily grounded the testing wire may be fused if allowed to
+stay in contact with the die.
+
+_The Remedy._--Clean the slides, dies and terminal blocks thoroughly
+and dry out the fibre insulation if it is damp. See that no scale or metal
+has worked under the sliding parts, and that the secondary leads do not
+touch the frame. If the ground is very heavy it may be necessary to remove
+the slides in order to facilitate the examination and removal of the
+ground. Insulation, where torn or worn through, must be carefully replaced
+or taped. If the transformer coils are grounded to the iron core of the
+transformer or to the secondary, it may be necessary to remove the coils
+and reinsulate them at the points of contact. A short circuited coil will
+heat excessively and eventually burn out. This may mean a new coil if you
+are unable to repair the old one. In all cases the transformer windings
+should be protected from mechanical injury or dampness. Unless excessively
+overloaded, transformers will last for years without giving a moment's
+trouble, if they are not exposed to moisture or are not injured
+mechanically.
+
+The most common trouble arises from poor electrical contacts, and they are
+the cause of endless trouble and annoyance. See that all connections are
+clean and bright. Take out the dies every day or two and see that there is
+no scale, grease or dirt between them and the holders. Clean them
+thoroughly before replacing. Tighten the bolts running from the transformer
+leads to the work jaws.
+
+
+ELECTRIC ARC WELDING
+
+This method bears no relation to the one just considered, except that the
+source of heat is the same in both cases. Arc welding makes use of the
+flame produced by the voltaic arc in practically the same way that
+oxy-acetylene welding uses the flame from the gases.
+
+If the ends of two pieces of carbon through which a current of electricity
+is flowing while they are in contact are separated from each other quite
+slowly, a brilliant arc of flame is formed between them which consists
+mainly of carbon vapor. The carbons are consumed by combination with the
+oxygen in the air and through being turned to a gas under the intense heat.
+
+The most intense action takes place at the center of the carbon which
+carries the positive current and this is the point of greatest heat. The
+temperature at this point in the arc is greater than can be produced by any
+other means under human control.
+
+An arc may be formed between pieces of metal, called electrodes, in the
+same way as between carbon. The metallic arc is called a flaming arc and as
+the metal of the electrode burns with the heat, it gives the flame a color
+characteristic of the material being used. The metallic arc may be drawn
+out to a much greater length than one formed between carbon electrodes.
+
+Arc Welding is carried out by drawing a piece of carbon which is of
+negative polarity away from the pieces of metal to be welded while the
+metal is made positive in polarity. The negative wire is fastened to the
+carbon electrode and the work is laid on a table made of cast or wrought
+iron to which the positive wire is made fast. The direction of the flame is
+then from the metal being welded to the carbon and the work is thus
+prevented from being saturated with carbon, which would prove very
+detrimental to its strength. A secondary advantage is found in the fact
+that the greatest heat is at the metal being welded because of its being
+the positive electrode.
+
+The carbon electrode is usually made from one quarter to one and a half
+inches in diameter and from six to twelve inches in length. The length of
+the arc may be anywhere from one inch to four inches, depending on the size
+of the work being handled.
+
+While the parts are carefully insulated to avoid danger of shock, it is
+necessary for the operator to wear rubber gloves as a further protection,
+and to wear some form of hood over the head to shield him against the
+extreme heat liberated. This hood may be made from metal, although some
+material that does not conduct electricity is to be preferred. The work is
+watched through pieces of glass formed with one sheet, which is either blue
+or green, placed over another which is red. Screens of glass are sometimes
+used without the head protector. Some protection for the eyes is absolutely
+necessary because of the intense white light.
+
+It is seldom necessary to preheat the work as with the gas processes,
+because the heat is localized at the point of welding and the action is so
+rapid that the expansion is not so great. The necessity of preheating,
+however, depends entirely on the material, form and size of the work being
+handled. The same advice applies to arc welding as to the gas flame method
+but in a lesser degree. Filling rods are used in the same way as with any
+other flame process.
+
+It is the purpose of this explanation to state the fundamental principles
+of the application of the electric arc to welding metals, and by applying
+the principles the following questions will be answered:
+
+What metals can be welded by the electric arc?
+
+What difficulties are to be encountered in applying the electric arc to
+welding?
+
+What is the strength of the weld in comparison with the original piece?
+
+What is the function of the arc welding machine itself?
+
+What is the comparative application of the electric arc and the
+oxy-acetylene method and others of a similar nature?
+
+The answers to these questions will make it possible to understand the
+application of this process to any work. In a great many places the use of
+the arc is cutting the cost of welding to a very small fraction of what it
+would be by any other method, so that the importance of this method may be
+well understood.
+
+Any two metals which are brought to the melting temperature and applied to
+each other will adhere so that they are no more apt to break at the weld
+than at any other point outside of the weld. It is the property of all
+metals to stick together under these conditions. The electric arc is used
+in this connection merely as a heating agent. This is its only function in
+the process.
+
+It has advantages in its ease of application and the cheapness with which
+heat can be liberated at any given point by its use. There is nothing in
+connection with arc welding that the above principles will not answer; that
+is, that metals at the melting point will weld and that the electric arc
+will furnish the heat to bring them to this point. As to the first
+question, what metals can be welded, all metals can be welded.
+
+The difficulties which are encountered are as follows:
+
+In the case of brass or zinc, the metals will be covered with a coat of
+zinc oxide before they reach a welding heat. This zinc oxide makes it
+impossible for two clean surfaces to come together and some method has to
+be used for eliminating this possibility and allowing the two surfaces to
+join without the possibility of the oxide intervening. The same is true of
+aluminum, in which the oxide, alumina, will be formed, and with several
+other alloys comprising elements of different melting points.
+
+In order to eliminate these oxides, it is necessary in practical work, to
+puddle the weld; this is, to have a sufficient quantity of molten metal at
+the weld so that the oxide is floated away. When this is done, the two
+surfaces which are to be joined are covered with a coat of melted metal on
+which floats the oxide and other impurities. The two pieces are thus
+allowed to join while their surfaces are protected. This precaution is not
+necessary in working with steel except in extreme cases.
+
+Another difficulty which is met with in the welding of a great many metals
+is their expansion under heat, which results in so great a contraction when
+the weld cools that the metal is left with a considerable strain on it. In
+extreme cases this will result in cracking at the weld or near it. To
+eliminate this danger it is necessary to apply heat either all over the
+piece to be welded or at certain points. In the case of cast iron and
+sometimes with copper it is necessary to anneal after welding, since
+otherwise the welded pieces will be very brittle on account of the
+chilling. This is also true of malleable iron.
+
+Very thin metals which are welded together and are not backed up by
+something to carry away the excess heat, are very apt to burn through,
+leaving a hole where the weld should be. This difficulty can be eliminated
+by backing up the weld with a metal face or by decreasing the intensity of
+the arc so that this melting through will not occur. However, the practical
+limit for arc welding without backing up the work with a metal face or
+decreasing the intensity of the arc is approximately 22 gauge, although
+thinner metal can be welded by a very skillful and careful operator.
+
+One difficulty with arc welding is the lack of skillful operators. This
+method is often looked upon as being something out of the ordinary and
+governed by laws entirely different from other welding. As a matter of
+fact, it does not take as much skill to make a good arc weld as it does to
+make a good weld in a forge fire as the blacksmith does it. There are few
+jobs which cannot be handled successfully by an operator of average
+intelligence with one week's instructions, although his work will become
+better and better in quality as he continues to use the arc.
+
+Now comes the question of the strength of the weld after it has been made.
+This strength is equally as great as that of the metal that is used to make
+the weld. It should be remembered, however, that the metal which goes into
+the weld is put in there as a casting and has not been rolled. This would
+make the strength of the weld as great as the same metal that is used for
+filling if in the cast form.
+
+Two pieces of steel could be welded together having a tensile strength at
+the weld of 50,000 pounds. Higher strengths than this can be obtained by
+the use of special alloys for the filling material or by rolling. Welds
+with a tensile strength as great as mentioned will give a result which is
+perfectly satisfactory in almost all cases.
+
+There are a great many jobs where it is possible to fill up the weld, that
+is, make the section at the point of the weld a little larger than the
+section through the rest of the piece. By doing this, the disadvantages
+of the weld being in the form of a casting in comparison with the rest of
+the piece being in the form of rolled steel can be overcome, and make the
+weld itself even stronger than the original piece.
+
+The next question is the adaptability of the electric arc in comparison
+with forge fire, oxy-acetylene or other method. The answer is somewhat
+difficult if made general. There are no doubt some cases where the use of a
+drop hammer and forge fire or the use of the oxy-acetylene torch will make,
+all things being considered, a better job than the use of the electric arc,
+although a case where this is absolutely proved is rare.
+
+The electric arc will melt metal in a weld for less than the same metal can
+be melted by the use of the oxy-acetylene torch, and, on account of the
+fact that the heat can be applied exactly where it is required and in the
+amount required, the arc can in almost all cases supply welding heat for
+less cost than a forge fire or heating furnace.
+
+The one great advantage of the oxy-acetylene method in comparison with
+other methods of welding is the fact that in some cases of very thin sheet,
+the weld can be made somewhat sooner than is possible otherwise. With metal
+of 18 gauge or thicker, this advantage is eliminated. In cutting steel, the
+oxy-acetylene torch is superior to almost any other possible method.
+
+_Arc Welding Machines._--A consideration of the function and purpose
+of the various types of arc welding machines shows that the only reason for
+the use of any machine is either for conversion of the current from
+alternating to direct, or, if the current is already direct, then the
+saving in the application of this current in the arc.
+
+It is practically out of the question to apply an alternating current arc
+to welding for the reason that in any arc practically all the heat is
+liberated at the positive electrode, which means that, in alternating
+current, half the heat is liberated at each electrode as the current
+changes its direction of flow or alternates. Another disadvantage of the
+alternating arc is that it is difficult of control and application.
+
+In all arc welding by the use of the carbon arc, the positive electrode is
+made the piece to be welded, while in welding with metallic electrodes this
+may be either the piece to be welded of the rod that is used as a filler.
+The voltage across the arc is a variable quantity, depending on the length
+of the flame, its temperature and the gases liberated in the arc. With a
+carbon electrode the voltage will vary from zero to forty-five volts. With
+the metallic electrode the voltage will vary from zero to thirty volts. It
+is, therefore, necessary for the welding machine to be able to furnish to
+the arc the requisite amount of current, this amount being varied, and
+furnish it at all times at the voltage required.
+
+The simplest welding apparatus is a resistance in series with the arc. This
+is entirely satisfactory in every way except in cost of current. By the use
+of resistance in series with the arc and using 220 volts as the supply,
+from eighty to ninety per cent of the current is lost in heat at the
+resistance. Another disadvantage is the fact that most materials change
+their resistance as their temperature changes, thus making the amount of
+current for the arc a variable quantity, depending on the temperature of
+the resistance.
+
+There have been various methods originated for saving the power mentioned
+and a good many machines have been put on the market for this purpose. All
+of them save some power over what a plain resistance would use. Practically
+all arc welding machines at the present time are motor generator sets, the
+motor of which is arranged for the supply voltage and current, this motor
+being direct connected to a compound wound generator delivering
+approximately seventy-five volts direct current. Then by the use of a
+resistance, this seventy-five volt supply is applied to the arc. Since the
+voltage across the arc will vary from zero to fifty volts, this machine
+will save from zero up to seventy per cent of the power that the machine
+delivers. The rest of the power, of course, has to be dissipated in the
+resistance used in series with the arc.
+
+A motor generator set which can be purchased from any electrical company,
+with a long piece of fence wire wound around a piece of asbestos, gives
+results equally as good and at a very small part of the first cost.
+
+It is possible to construct a machine which will eliminate all losses in
+the resistance; in other words, eliminate all resistance in series with the
+arc. A machine of this kind will save its cost within a very short time,
+providing the welder is used to any extent.
+
+Putting it in figures, the results are as follows for average conditions.
+Current at 2c per kilowatt hour, metallic electrode arc of 150 amperes,
+carbon arc 500 amperes; voltage across the metallic electrode arc 20,
+voltage across the carbon arc 35. Supply current 220 volts, direct. In the
+case of the metallic electrode, if resistance is used, the cost of running
+this arc is sixty-six cents per hour. With the carbon electrode, $2.20 per
+hour. If a motor generator set with a seventy volt constant potential
+machine is used for a welder, the cost will be as follows:
+
+Metallic electrode 25.2c. Carbon electrode 84c per hour. With a machine
+which will deliver the required voltage at the arc and eliminate all the
+resistance in series with the arc, the cost will be as follows: Metallic
+electrode 7.2c per hour; carbon electrode 42c per hour. This is with the
+understanding that the arc is held constant and continuously at its full
+value. This, however, is practically impossible and the actual load factor
+is approximately fifty per cent, which would mean that operating a welder
+as it is usually operated, this result will be reduced to one-half of that
+stated in all cases.
+
+
+
+
+CHAPTER VII
+
+HAND FORGING AND WELDING
+
+
+Smithing, or blacksmithing, is the process of working heated iron, steel or
+other metals by forging, bending or welding them.
+
+_The Forge._--The metal is heated in a forge consisting of a shallow
+pan for holding the fire, in the center of which is an opening from below
+through which air is forced to make a hot fire.
+
+[Illustration: Figure 48.--Tuyere Construction on a Forge]
+
+Air is forced through this hole, called a "tuyere" (Figure 48) by means of
+a hand bellows, a rotary fan operated with crank or lever, or with a fan
+driven from an electric motor. The harder the air is driven into the fire
+above the tuyere the more oxygen is furnished and the hotter the fire
+becomes.
+
+Directly below the tuyere is an opening through which the ashes that drop
+from the fire may be cleaned out.
+
+_The Fire._--The fire is made by placing a small piece of waste soaked
+in oil, kerosene or gasoline, over the tuyere, lighting the waste, then
+starting the fan or blower slowly. Gradually cover the waste, while it is
+burning brightly, with a layer of soft coal. The coal will catch fire and
+burn after the waste has been consumed. A piece of waste half the size of a
+person's hand is ample for this purpose.
+
+The fuel should be "smithing coal." A lump of smithing coal breaks easily,
+shows clean and even on all sides and should not break into layers. The
+coal is broken into fine pieces and wet before being used on the fire.
+
+The fire should be kept deep enough so that there is always three or four
+inches of fire below the piece of metal to be heated and there should be
+enough fire above the work so that no part of the metal being heated comes
+in contact with the air. The fire should be kept as small as possible while
+following these rules as to depth.
+
+To make the fire larger, loosen the coal around the edges. To make the fire
+smaller, pack wet coal around the edges in a compact mass and loosen the
+fire in the center. Add fresh coal only around the edges of the fire. It
+will turn to coke and can then be raked onto the fire. Blow only enough air
+into the fire to keep it burning brightly, not so much that the fire is
+blown up through the top of the coal pack. To prevent the fire from going
+out between jobs, stick a piece of soft wood into it and cover with fresh
+wet coal.
+
+_Tools._--The _hammer_ is a ball pene, or blacksmith's hammer,
+weighing about a pound and a half.
+
+The _sledge_ is a heavy hammer, weighing from 5 to 20 pounds and
+having a handle 30 to 36 inches long.
+
+The _anvil_ is a heavy piece of wrought iron (Figure 49), faced with
+steel and having four legs. It has a pointed horn on one end, an
+overhanging tail on the other end and a flat top. In the tail there is a
+square hole called the "hardie" hole and a round one called the "spud"
+hole.
+
+[Illustration: Figure 49.--Anvil, Showing Horn, Tail, Hardie Hole and Spud
+Hole]
+
+_Tongs_, with handles about one foot long and jaws suitable for
+holding the work, are used. To secure a firm grip on the work, the jaws may
+be heated red hot and hammered into shape over the piece to be held, thus
+giving a properly formed jaw. Jaws should touch the work along their entire
+length.
+
+The _set hammer_ is a hammer, one end of whose head is square and
+flat, and from this face the head tapers evenly to the other face. The
+large face is about 1-1/4 inches square.
+
+The _flatter_ is a hammer having one face of its head flat and about
+2-1/2 inches square.
+
+_Swages_ are hammers having specially formed faces for finishing
+rounds, squares, hexagons, ovals, tapers, etc.
+
+_Fullers_ are hammers having a rounded face, long in one direction.
+They are used for spreading metal in one direction only.
+
+The _hardy_ is a form of chisel with a short, square shank which may
+be set into the hardie hole for cutting off hot bars.
+
+_Operations._--Blacksmithing consists of bending, drawing or upsetting
+with the various hammers, or in punching holes.
+
+Bending is done over the square corners of the anvil if square cornered
+bends are desired, or over the horn of the anvil if rounding bends, eyes,
+hooks, etc., are wanted.
+
+To bend a ring or eye in the end of a bar, first figure the length of stock
+needed by multiplying the diameter of the hole by 31/7, then heat the piece
+to a good full red at a point this distance back from the end. Next bend
+the iron over at a 90 degree angle (square) at this point. Next, heat the
+iron from the bend just made clear to the point and make the eye by laying
+the part that was bent square over the horn of the anvil and bending the
+extreme tip into part of a circle. Keep pushing the piece farther and
+farther over the horn of the anvil, bending it as you go. Do not hammer
+directly over the horn of the anvil, but on the side where you are doing
+the bending.
+
+To make the outside of a bend square, sharp and full, rather than slightly
+rounding, the bent piece must be laid edgewise on the face of the anvil.
+That is, after making the bend over the corner of the anvil, lay the piece
+on top of the anvil so that its edge and not the flat side rests on the
+anvil top. With the work in this position, strike directly against the
+corner with the hammer so that the blows come in line, first with one leg
+of the work, then the other, and always directly on the corner of the
+piece. This operation cannot be performed by laying the work so that one
+leg hangs over the anvil's corner.
+
+To make a shoulder on a rod or bar, heat the work and lay flat across the
+top of the anvil with the point at which the shoulder is desired at the
+edge of the anvil. Then place the set hammer on top of the piece, with the
+outside edge of the set hammer directly over the edge of the anvil. While
+hammering in this position keep the work turning continually.
+
+To draw stock means to make it longer and thinner by hammering. A piece to
+be drawn out is usually laid across the horn of the anvil while being
+struck with the hammer. The metal is then spread in only one direction in
+place of being spread in every direction, as it would be if laid on the
+anvil face. To draw the work, heat it to as high a temperature as it will
+stand without throwing sparks and burning. The fuller may be used for
+drawing metal in place of laying the work over the horn of the anvil.
+
+When drawing round stock, it should be first drawn out square, and when
+almost down to size it may be rounded. When pointing stock, the same rule
+of first drawing out square applies.
+
+Upsetting means to make a piece shorter in length and greater in thickness
+or width, or both shorter and thicker. To upset short pieces, heat to a
+bright red at the place to be upset, then stand on end on the anvil face
+and hammer directly down on top until of the right form. Longer pieces may
+be swung against the anvil or placed upright on a heavy piece of metal
+lying on the floor or that is sunk into the floor. While standing on this
+heavy piece the metal may be upset by striking down on the end with a heavy
+hammer or the sledge. If a bend appears while upsetting, it should be
+straightened by hammering back into shape on the anvil face.
+
+Light blows affect the metal for only a short distance from the point of
+striking, but heavy blows tend to swell the metal more equally through its
+entire length. In driving rivets that should fill the holes, heavy blows
+should be struck, but to shape the end of a rivet or to make a head on a
+rod, light blows should be used.
+
+The part of the piece that is heated most will upset the most.
+
+To punch a hole through metal, use a tool steel punch with its end slightly
+tapering to a size a little smaller than the hole to be punched. The end of
+the punch must be square across and never pointed or rounded.
+
+First drive the punch part way through from one side and then turn the work
+over. When you turn it over, notice where the bulge appears and in that way
+locate the hole and drive the punch through from the second side. This
+makes a cleaner and more even hole than to drive completely through from
+one side. When the punch is driven in from the second side, the place to be
+punched through should be laid over the spud hole in the tail of the anvil
+and the piece driven out of the work.
+
+Work when hot is larger than it will be after cooling. This must be
+remembered when fitting parts or trouble will result. A two-foot bar of
+steel will be 1/4 inch longer when red hot than when cold.
+
+The temperatures of iron correspond to the following colors:
+
+  Dullest red seen in the dark...  878°
+  Dullest red seen in daylight...  887°
+  Dull red....................... 1100°
+  Full red....................... 1370°
+  Light red...................... 1550°
+  Orange......................... 1650°
+  Light orange................... 1725°
+  Yellow......................... 1825°
+  Light yellow................... 1950°
+
+_Bending Pipes and Tubes._--It is difficult to make bends or curves in
+pipes and tubing without leaving a noticeable bulge at some point of the
+work. Seamless steel tubing may be handled without very great danger of
+this trouble if care is used, but iron pipe, having a seam running
+lengthwise, must be given special attention to avoid opening the seam.
+
+Bends may be made without kinking if the tube or pipe is brought to a full
+red heat all the way around its circumference and at the place where the
+bend is desired. Hold the cool portion solidly in a vise and, by taking
+hold of the free end, bend very slowly and with a steady pull. The pipe
+must be kept at full red heat with the flames from one or more torches and
+must not be hammered to produce the bend. If a sufficient purchase cannot
+be secured on the free end by the hand, insert a piece of rod or a smaller
+pipe into the opening.
+
+While making the bend, should small bulges appear, they may be hammered
+back into shape before proceeding with the work.
+
+Tubing or pipes may be bent while being held between two flat metal
+surfaces while at a bright red heat. The metal plates at each side of the
+work prevent bulging.
+
+Another method by which tubing may be bent consists of filling completely
+with tightly packed sand and fitting a solid cap or plug at each end.
+
+Thin brass tubing may be filled with melted resin and may be bent after the
+resin cools. To remove the resin it is necessary to heat the tube, allowing
+it to run out.
+
+Large jobs of bending should be handled in special pipe bending machines in
+which the work is forced through formed rolls which prevent its bulging.
+
+
+WELDING
+
+Welding with the heat of a blacksmith forge fire, or a coal or illuminating
+gas fire, can only be performed with iron and steel because of the low heat
+which is not localized as with the oxy-acetylene and electric processes.
+Iron to be welded in this manner is heated until it reaches the temperature
+indicated by an orange color, not white, as is often stated, this orange
+color being slightly above 3600 degrees Fahrenheit. Steel is usually welded
+at a bright red heat because of the danger of oxidizing or burning the
+metal if the temperature is carried above this point.
+
+_The Fire._--If made in a forge, the fire should be built from good
+smithing coal or, better still, from coke. Gas fires are, of course,
+produced by suitable burners and require no special preparation except
+adjustment of the heat to the proper degree for the size and thickness of
+the metal being welded so that it will not be burned.
+
+A coal fire used for ordinary forging operations should not be used for
+welding because of the impurities it contains. A fresh fire should be built
+with a rather deep bed of coal, four to eight inches being about right for
+work ordinarily met with. The fire should be kept burning until the coal
+around the edges has been thoroughly coked and a sufficient quantity of
+fuel should be on and around the fire so that no fresh coal will have to
+be added while working.
+
+After the coking process has progressed sufficiently, the edges should be
+packed down and the fire made as small as possible while still surrounding
+the ends to be joined. The fire should not be altered by poking it while
+the metal is being heated. The best form of fire to use is one having
+rather high banks of coked coal on each side of the mass, leaving an
+opening or channel from end to end. This will allow the added fuel to be
+brought down on top of the fire with a small amount of disturbance.
+
+_Preparing to Weld._--If the operator is not familiar with the metal
+to be handled, it is best to secure a test piece if at all possible and try
+heating it and joining the ends. Various grades of iron and steel call for
+different methods of handling and for different degrees of heat, the proper
+method and temperature being determined best by actual test under the
+hammer.
+
+The form of the pieces also has a great deal to do with their handling,
+especially in the case of a more or less inexperienced workman. If the
+pieces are at all irregular in shape, the motions should be gone through
+with before the metal is heated and the best positions on the anvil as well
+as in the fire determined with regard to the convenience of the workman and
+speed of handling the work after being brought to a welding temperature.
+Unnatural positions at the anvil should be avoided as good work is most
+difficult of performance under these conditions.
+
+_Scarfing._--While there are many forms of welds, depending on the
+relative shape of the pieces to be joined, the portions that are to meet
+and form one piece are always shaped in the same general way, this shape
+being called a "scarf." The end of a piece of work, when scarfed, is
+tapered off on one side so that the extremity comes to a rather sharp edge.
+The other side of the piece is left flat and a continuation in the same
+straight plane with its side of the whole piece of work. The end is then in
+the form of a bevel or mitre joint (Figure 50).
+
+[Illustration: Figure 50.--Scarfing Ends of Work Ready for Welding]
+
+Scarfing may be produced in any one of several ways. The usual method is to
+bring the ends to a forging heat, at which time they are upset to give a
+larger body of metal at the ends to be joined. This body of metal is then
+hammered down to the taper on one side, the length of the tapered portion
+being about one and a half times the thickness of the whole piece being
+handled. Each piece should be given this shape before proceeding farther.
+
+The scarf may be produced by filing, sawing or chiseling the ends, although
+this is not good practice because it is then impossible to give the desired
+upset and additional metal for the weld. This added thickness is called for
+by the fact that the metal burns away to a certain extent or turns to
+scale, which is removed before welding.
+
+When the two ends have been given this shape they should not fit as closely
+together as might be expected, but should touch only at the center of the
+area to be joined (Figure 51). That is to say, the surface of the beveled
+portion should bulge in the middle or should be convex in shape so that the
+edges are separated by a little distance when the pieces are laid together
+with the bevels toward each other. This is done so that the scale which is
+formed on the metal by the heat of the fire can have a chance to escape
+from the interior of the weld as the two parts are forced together.
+
+[Illustration: Figure 51.--Proper Shape of Scarfed Ends]
+
+If the scarf were to be formed with one or more of the edges touching each
+other at the same time or before the centers did so, the scale would be
+imprisoned within the body of the weld and would cause the finished work to
+be weak, while possibly giving a satisfactory appearance from the outside.
+
+_Fluxes._--In order to assist in removing the scale and other
+impurities and to make the welding surfaces as clean as possible while
+being joined, various fluxing materials are used as in other methods of
+welding.
+
+For welding iron, a flux of white sand is usually used, this material being
+placed on the metal after it has been brought to a red heat in the fire.
+Steel is welded with dry borax powder, this flux being applied at the same
+time as the iron flux just mentioned. Borax may also be used for iron
+welding and a mixture of borax with steel borings may also be used for
+either class of work. Mixtures of sal ammoniac with borax have been
+successfully used, the proportions being about four parts of borax to one
+of sal ammoniac. Various prepared fluxing powders are on the market for
+this work, practically all of them producing satisfactory results.
+
+After the metal has been in the fire long enough to reach a red heat, it is
+removed temporarily and, if small enough in size, the ends are dipped into
+a box of flux. If the pieces are large, they may simply be pulled to the
+edge of the fire and the flux then sprinkled on the portions to be joined.
+A greater quantity of flux is required in forge welding than in electric or
+oxy-acetylene processes because of the losses in the fire. After the powder
+has been applied to the surfaces, the work is returned to the fire and
+heated to the welding temperature.
+
+_Heating the Work._--After being scarfed, the two pieces to be welded
+are placed in the fire and brought to the correct temperature. This
+temperature can only be recognized by experiment and experience. The metal
+must be just below that point at which small sparks begin to be thrown out
+of the fire and naturally this is a hard point to distinguish. At the
+welding heat the metal is almost ready to flow and is about the consistency
+of putty. Against the background of the fire and coal the color appears to
+be a cream or very light yellow and the work feels soft as it is handled.
+
+It is absolutely necessary that both parts be heated uniformly and so that
+they reach the welding temperature at the same time. For this reason they
+should be as close together in the fire as possible and side by side. When
+removed to be hammered together, time is saved if they are picked up in
+such a way that when laid together naturally the beveled surfaces come
+together. This makes it necessary that the workman remember whether the
+scarfed side is up or down, and to assist in this it is a good thing to
+mark the scarfed side with chalk or in some other noticeable manner, so
+that no mistake will be made in the hurry of placing the work on the anvil.
+
+The common practice in heating allows the temperature to rise until the
+small white sparks are seen to come from the fire. Any heating above this
+point will surely result in burning that will ruin the iron or steel being
+handled. The best welding heat can be discerned by the appearance of the
+metal and its color after experience has been gained with this particular
+material. Test welds can be made and then broken, if possible, so that the
+strength gained through different degrees of heat can be known before
+attempting more important work.
+
+_Welding._--When the work has reached the welding temperature after
+having been replaced in the fire with the flux applied, the two parts are
+quickly tapped to remove the loose scale from their surfaces. They are then
+immediately laid across the top of the anvil, being placed in a diagonal
+position if both pieces are straight. The lower piece is rested on the
+anvil first with the scarf turned up and ready to receive the top piece in
+the position desired. The second piece must be laid in exactly the position
+it is to finally occupy because the two parts will stick together as soon
+as they touch and they cannot well be moved after having once been allowed
+to come in contact with each other. This part of the work must be done
+without any unnecessary loss of time because the comparatively low heat at
+which the parts weld allows them to cool below the working temperature in
+a few seconds.
+
+The greatest difficulty will be experienced in withdrawing the metal from
+the fire before it becomes burned and in getting it joined before it cools
+below this critical point. The beveled edges of the scarf are, of course,
+the first parts to cool and the weld must be made before they reach a point
+at which they will not join, or else the work will be defective in
+appearance and in fact.
+
+If the parts being handled are of such a shape that there is danger of
+bending a portion back of the weld, this part may be cooled by quickly
+dipping it into water before laying the work on the anvil to be joined.
+
+The workman uses a heavy hand hammer in making the joint, and his helper,
+if one is employed, uses a sledge. With the two parts of the work in place
+on the anvil, the workman strikes several light blows, the first ones being
+at a point directly over the center of the weld, so that the joint will
+start from this point and be worked toward the edges. After the pieces have
+united the helper strikes alternate blows with his sledge, always striking
+in exactly the same place as the last stroke of the workman. The hammer
+blows are carried nearer and nearer to the edges of the weld and are made
+steadily heavier as the work progresses.
+
+The aim during the first part of the operation should be to make a perfect
+joint, with every part of the surfaces united, and too much attention
+should not be paid to appearance, at least not enough to take any chance
+with the strength of the work.
+
+It will be found, after completion of the weld, that there has been a loss
+in length equal to one-half the thickness of the metal being welded. This
+loss is occasioned by the burned metal and the scale which has been formed.
+
+_Finishing the Weld._--If it is possible to do so, the material should
+be hammered into the shape that it should remain with the same heat that
+was used for welding. It will usually be found, however, that the metal has
+cooled below the point at which it can be worked to advantage. It should
+then be replaced in the fire and brought back to a forging heat.
+
+[Illustration: Figure 52.--Upsetting and Scarfing the End of a Rod]
+
+While shaping the work at this forging heat every part that has been at a
+red heat should be hammered with uniformly light and even blows as it
+cools. This restores the grain and strength of the iron or steel to a great
+extent and makes the unavoidable weakness as small as possible.
+
+_Forms of Welds._--The simplest of all welds is that called a "lap
+weld." This is made between the ends of two pieces of equal size and
+similar form by scarfing them as described and then laying one on top of
+the other while they are hammered together.
+
+A butt weld (Figure 52) is made between the ends of two pieces of shaft or
+other bar shapes by upsetting the ends so that they have a considerable
+flare and shaping the face of the end so that it is slightly higher in the
+center than around the edges, this being done to make the centers come
+together first. The pieces are heated and pushed into contact, after which
+the hammering is done as with any other weld.
+
+[Illustration: Figure 53.--Scarfing for a T Weld]
+
+A form similar to the butt weld in some ways is used for joining the end of
+a bar to a flat surface and is called a jump weld. The bar is shaped in the
+same way as for a butt weld. The flat plate may be left as it is, but if
+possible a depression should be made at the point where the shaft is to be
+placed. With the two parts heated as usual, the bar is dropped into
+position and hammered from above. As soon as the center of the weld has
+been made perfect, the joint may be finished with a fuller driven all the
+way around the edge of the joint.
+
+When it is required to join a bar to another bar or to the edge of any
+piece at right angles the work is called a "T" weld from its shape when
+complete (Figure 53). The end of the bar is scarfed as described and the
+point of the other bar or piece where the weld is to be made is hammered so
+that it tapers to a thin edge like one-half of a circular depression. The
+pieces are then laid together and hammered as for a lap weld.
+
+The ends of heavy bar shapes are often joined with a "V," or cleft, weld.
+One bar end is shaped so that it is tapering on both sides and comes to a
+broad edge like the end of a chisel. The other bar is heated to a forging
+temperature and then slit open in a lengthwise direction so that the
+V-shaped opening which is formed will just receive the pointed edge of the
+first piece. With the work at welding heat, the two parts are driven
+together by hammering on the rear ends and the hammering then continues as
+with a lap weld, except that the work is turned over to complete both sides
+of the joint.
+
+[Illustration: Figure 54.-Splitting Ends to Be Welded in Thin Work]
+
+The forms so far described all require that the pieces be laid together in
+the proper position after removal from the fire, and this always causes a
+slight loss of time and a consequent lowering of the temperature. With very
+light stock, this fall of temperature would be so rapid that the weld would
+be unsuccessful, and in this case the "lock" weld is resorted to. The ends
+of the two pieces to be joined are split for some distance back, and
+one-half of each end is bent up and the other half down (Figure 54). The
+two are then pushed together and placed in the fire in this position. When
+the welding heat is reached, it is only necessary to take the work out of
+the fire and hammer the parts together, inasmuch as they are already in the
+correct position.
+
+Other forms of welds in which the parts are too small to retain their heat,
+can be made by first riveting them together or cutting them so that they
+can be temporarily fastened in any convenient way when first placed in the
+fire.
+
+
+
+
+CHAPTER VIII
+
+SOLDERING, BRAZING AND THERMIT WELDING
+
+
+SOLDERING
+
+Common solder is an alloy of one-half lead with one-half tin, and is called
+"half and half." Hard solder is made with two-thirds tin and one-third
+lead. These alloys, when heated, are used to join surfaces of the same or
+dissimilar metals such as copper, brass, lead, galvanized iron, zinc,
+tinned plate, etc. These metals are easily joined, but the action of solder
+with iron, steel and aluminum is not so satisfactory and requires greater
+care and skill.
+
+The solder is caused to make a perfect union with the surfaces treated with
+the help of heat from a soldering iron. The soldering iron is made from a
+piece of copper, pointed at one end and with the other end attached to an
+iron rod and wooden handle. A flux is used to remove impurities from the
+joint and allow the solder to secure a firm union with the metal surface.
+The iron, and in many cases the work, is heated with a gasoline blow torch,
+a small gas furnace, an electric heater or an acetylene and air torch.
+
+The gasoline torch which is most commonly used should be filled two-thirds
+full of gasoline through the hole in the bottom, which is closed by a screw
+plug. After working the small hand pump for 10 to 20 strokes, hold the palm
+of your hand over the end of the large iron tube on top of the torch and
+open the gasoline needle valve about a half turn. Hold the torch so that
+the liquid runs down into the cup below the tube and fills it. Shut the
+gasoline needle valve, wipe the hands dry, and set fire to the fuel in the
+cup. Just as the gasoline fire goes out, open the gasoline needle valve
+about a half turn and hold a lighted match at the end of the iron tube to
+ignite the mixture of vaporized gasoline and air. Open or close the needle
+valve to secure a flame about 4 inches long.
+
+On top of the iron tube from which the flame issues there is a rest for
+supporting the soldering iron with the copper part in the flame. Place the
+iron in the flame and allow it to remain until the copper becomes very hot,
+not quite red, but almost so.
+
+A new soldering iron or one that has been misused will have to be "tinned"
+before using. To do this, take the iron from the fire while very hot and
+rub the tip on some flux or dip it into soldering acid. Then rub the tip of
+the iron on a stick of solder or rub the solder on the iron. If the solder
+melts off the stick without coating the end of the iron, allow a few drops
+to fall on a piece of tin plate, then nil the end of the iron on the tin
+plate with considerable force. Alternately rub the iron on the solder and
+dip into flux until the tip has a coating of bright solder for about half
+an inch from the end. If the iron is in very bad shape, it may be necessary
+to scrape or file the end before dipping in the flux for the first time.
+After the end of the iron is tinned in this way, replace it on the rest of
+the torch so that the tinned point is not directly in the flame, turning
+the flame down to accomplish this.
+
+_Flux._--The commonest flux, which is called "soldering acid," is made
+by placing pieces of zinc in muriatic (hydrochloric) acid contained in a
+heavy glass or porcelain dish. There will be bubbles and considerable heat
+evolved and zinc should be added until this action ceases and the zinc
+remains in the liquid, which is now chloride of zinc.
+
+This soldering acid may be used on any metal to be soldered by applying
+with a brush or swab. For electrical work, this acid should be made neutral
+by the addition of one part ammonia and one part water to each three parts
+of the acid. This neutralized flux will not corrode metal as will the
+ordinary acid.
+
+Powdered resin makes a good flux for lead, tin plate, galvanized iron and
+aluminum. Tallow, olive oil, beeswax and vaseline are also used for this
+purpose. Muriatic acid may be used for zinc or galvanized iron without the
+addition of the zinc, as described in making zinc chloride. The addition of
+two heaping teaspoonfuls of sal ammoniac to each pint of the chloride of
+zinc is sometimes found to improve its action.
+
+_Soldering Metal Parts._--All surfaces to be joined should be fitted
+to each other as accurately as possible and then thoroughly cleaned with a
+file, emery cloth, scratch bush or by dipping in lye. Work may be cleaned
+by dipping it into nitric acid which has been diluted with an equal volume
+of water. The work should be heated as hot as possible without danger of
+melting, as this causes the solder to flow better and secure a much better
+hold on the surfaces. Hard solder gives better results than half and half,
+but is more difficult to work. It is very important that the soldering iron
+be kept at a high heat during all work, otherwise the solder will only
+stick to the surfaces and will not join with them.
+
+Sweating is a form of soldering in which the surfaces of the work are first
+covered with a thin layer of solder by rubbing them with the hot iron after
+it has been dipped in or touched to the soldering stick. These surfaces are
+then placed in contact and heated to a point at which the solder melts and
+unites. Sweating is much to be preferred to ordinary soldering where the
+form of the work permits it. This is the only method which should ever be
+used when a fitting is to be placed over the end of a length of tube.
+
+_Soldering Holes._--Clean the surfaces for some distance around the
+hole until they are bright, and apply flux while holding the hot iron near
+the hole. Touch the tip of the iron to some solder until the solder is
+picked up on the iron, and then place this solder, which was just picked
+up, around the edge of the hole. It will leave the soldering iron and stick
+to the metal. Keep adding solder in this way until the hole has been closed
+up by working from the edges and building toward the center. After the hole
+is closed, apply more flux to the job and smooth over with the hot iron
+until there are no rough spots. Should the solder refuse to flow smoothly,
+the iron is not hot enough.
+
+_Soldering Seams._--Clean back from the seam or split for at least
+half an inch all around and then build up the solder in the same way as was
+done with the hole. After closing the opening, apply more flux to the work
+and run the hot iron lengthwise to smooth the job.
+
+_Soldering Wires._--Clean all insulation from the ends to be soldered
+and scrape the ends bright. Lay the ends parallel to each other and,
+starting at the middle of the cleaned portion, wrap the ends around each
+other, one being wrapped to the right, the other to the left. Hold the hot
+iron under the twisted joint and apply flux to the wire. Then dip the iron
+in the solder and apply to the twisted portion until the spaces between the
+wires are filled with solder. Finish by smoothing the joint and cleaning
+away all excess metal by rubbing the hot iron lengthwise. The joint should
+now be covered with a layer of rubber tape and this covered with a layer of
+ordinary friction tape.
+
+_Steel and Iron._--Steel surfaces should be cleaned, then covered with
+clear muriatic acid. While the acid is on the metal, rub with a stick of
+zinc and then tin the surfaces with the hot iron as directed. Cast iron
+should be cleaned and dipped in strong lye to remove grease. Wash the lye
+away with clean water and cover with muriatic acid as with steel. Then rub
+with a piece of zinc and tin the surfaces by using resin as a flux.
+
+It is very difficult to solder aluminum with ordinary solder. A special
+aluminum solder should be secured, which is easily applied and makes a
+strong joint. Zinc or phosphor tin may be used in place of ordinary solder
+to tin the surfaces or to fill small holes or cracks. The aluminum must be
+thoroughly heated before attempting to solder and the flux may be either
+resin or soldering acid. The aluminum must be thoroughly cleaned with
+dilute nitric acid and kept hot while the solder is applied by forcible
+rubbing with the hot iron.
+
+
+BRAZING
+
+This is a process for joining metal parts, very similar to soldering,
+except that brass is used to make the joint in place of the lead and zinc
+alloys which form solder. Brazing must not be attempted on metals whose
+melting point is less than that of sheet brass.
+
+Two pieces of brass to be brazed together are heated to a temperature at
+which the brass used in the process will melt and flow between the
+surfaces. The brass amalgamates with the surfaces and makes a very strong
+and perfect joint, which is far superior to any form of soldering where the
+work allows this process to be used, and in many cases is the equal of
+welding for the particular field in which it applies.
+
+_Brazing Heat and Tools._--The metal commonly used for brazing will
+melt at heats between 1350° and 1650° Fahrenheit. To bring the parts to
+this temperature, various methods are in use, using solid, liquid or
+gaseous fuels. While brazing may be accomplished with the fire of the
+blacksmith forge, this method is seldom satisfactory because of the
+difficulty of making a sufficiently clean fire with smithing coal, and it
+should not be used when anything else is available. Large jobs of brazing
+may be handled with a charcoal fire built in the forge, as this fuel
+produces a very satisfactory and clean fire. The only objection is in the
+difficulty of confining the heat to the desired parts of the work.
+
+The most satisfactory fire is that from a fuel gas torch built for this
+work. These torches are simply forms of Bunsen burners, mixing the proper
+quantity of air with the gas to bring about a perfect combustion. Hose
+lines lead to the mixing tube of the gas torch, one line carrying the gas
+and the other air under a moderate pressure. The air line is often
+dispensed with, allowing the gas to draw air into the burner on the
+injector principle, much the same as with illuminating gas burners for use
+with incandescent mantles. Valves are provided with which the operator may
+regulate the amount of both gas and air, and ordinarily the quality and
+intensity of the flame.
+
+When gas is not available, recourse may be had to the gasoline torch made
+for brazing. This torch is built in the same way as the small portable
+gasoline torches for soldering operations, with the exception that two
+regulating needle valves are incorporated in place of only one.
+
+The torches are carried on a framework, which also supports the work being
+handled. Fuel is forced to the torch from a large tank of gasoline into
+which air pressure is pumped by hand. The torches are regulated to give
+the desired flame by means of the needle valves in much the same way as
+with any other form of pressure torch using liquid fuel.
+
+Another very satisfactory form of torch for brazing is the acetylene-air
+combination described in the chapter on welding instruments. This torch
+gives the correct degree of heat and may be regulated to give a clean and
+easily controlled flame.
+
+Regardless of the source of heat, the fire or flame must be adjusted so
+that no soot is deposited on the metal surfaces of the work. This can only
+be accomplished by supplying the exact amounts of gas and air that will
+produce a complete burning of the fuel. With the brazing torches in common
+use two heads are furnished, being supplied from the same source of fuel,
+but with separate regulating devices. The torches are adjustably mounted in
+such a way that the flames may be directed toward each other, heating two
+sides of the work at the same time and allowing the pieces to be completely
+surrounded with the flame.
+
+Except for the source of heat, but one tool is required for ordinary
+brazing operations, this being a spatula formed by flattening one end of a
+quarter-inch steel rod. The spatula is used for placing the brazing metal
+on the work and for handling the flux that is required in this work as in
+all other similar operations.
+
+_Spelter._--The metal that is melted into the joint is called spelter.
+While this name originally applied to but one particular grade or
+composition of metal, common use has extended the meaning until it is
+generally applied to all grades.
+
+Spelter is variously composed of alloys containing copper, zinc, tin and
+antimony, the mixture employed depending on the work to be done. The
+different grades are of varying hardness, the harder kinds melting at
+higher temperatures than the soft ones and producing a stronger joint when
+used. The reason for not using hard spelter in all cases is the increased
+difficulty of working it and the fact that its melting point is so near to
+some of the metals brazed that there is great danger of melting the work as
+well as the spelter.
+
+The hardest grade of spelter is made from three-fourths copper with
+one-fourth zinc and is used for working on malleable and cast iron and for
+steel.
+
+This hard spelter melts at about 1650° and is correspondingly difficult to
+handle.
+
+A spelter suitable for working with copper is made from equal parts of
+copper and zinc, melting at about 1400° Fahrenheit, 500° below the melting
+point of the copper itself. A still softer brazing metal is composed of
+half copper, three-eighths zinc and one-eighth tin. This grade is used for
+fastening brass to iron and copper and for working with large pieces of
+brass to brass. For brazing thin sheet brass and light brass castings, a
+metal is used which contains two-thirds tin and one-third antimony. The
+low melting point of this last composition makes it very easy to work with
+and the danger of melting the work is very slight. However, as might be
+expected, a comparatively weak joint is secured, which will not stand any
+great strain.
+
+All of the above brazing metals are used in powder form so that they may be
+applied with the spatula where the joint is exposed on the outside of the
+work. In case it is necessary to braze on the inside of a tube or any deep
+recess, the spelter may be placed on a flat rod long enough to reach to
+the farthest point. By distributing the spelter at the proper points along
+the rod it may be placed at the right points by turning the rod over after
+inserting into the recess.
+
+_Flux._--In order to remove the oxides produced under brazing heat and
+to allow the brazing metal to flow freely into place, a flux of some kind
+must be used. The commonest flux is simply a pure calcined borax powder,
+that is, a borax powder that has been heated until practically all the
+water has been driven off.
+
+Calcined borax may also be mixed with about 15 per cent of sal ammoniac to
+make a satisfactory fluxing powder. It is absolutely necessary to use flux
+of some kind and a part of whatever is used should be made into a paste
+with water so that it can be applied to the joint to be brazed before
+heating. The remainder of the powder should be kept dry for use during the
+operation and after the heat has been applied.
+
+_Preparing the Work._--The surfaces to be brazed are first thoroughly
+cleaned with files, emery cloth or sand paper. If the work is greasy, it
+should be dipped into a bath of lye or hot soda water so that all trace of
+oil is removed. The parts are then placed in the relation to each other
+that they are to occupy when the work has been completed. The edges to be
+joined should make a secure and tight fit, and should match each other at
+all points so that the smallest possible space is left between them. This
+fit should not be so tight that it is necessary to force the work into
+place, neither should it be loose enough to allow any considerable space
+between the surfaces. The molten spelter will penetrate between surfaces
+that water will flow between when the work and spelter have both been
+brought to the proper heat. It is, of course, necessary that the two parts
+have a sufficient number of points of contact so that they will remain in
+the proper relative position.
+
+The work is placed on the surface of the brazing table in such a position
+that the flame from the torches will strike the parts to be heated, and
+with the joint in such a position that the melted spelter will flow down
+through it and fill every possible part of the space between the surfaces
+under the action of gravity. That means that the edge of the joint must be
+uppermost and the crack to be filled must not lie horizontal, but at the
+greatest slant possible. Better than any degree of slant would be to have
+the line of the joint vertical.
+
+The work is braced up or clamped in the proper position before commencing
+to braze, and it is best to place fire brick in such positions that it will
+be impossible for cooling draughts of air to reach the heated metal should
+the flame be removed temporarily during the process. In case there is a
+large body of iron, steel or copper to be handled, it is often advisable to
+place charcoal around the work, igniting this with the flame of the torch
+before starting to braze so that the metal will be maintained at the
+correct heat without depending entirely on the torch.
+
+When handling brass pieces having thin sections there is danger of melting
+the brass and causing it to flow away from under the flame, with the result
+that the work is ruined. If, in the judgment of the workman, this may
+happen with the particular job in hand, it is well to build up a mould of
+fire clay back of the thin parts or preferably back of the whole piece, so
+that the metal will have the necessary support. This mould may be made by
+mixing the fire clay into a stiff paste with water and then packing it
+against the piece to be supported tightly enough so that the form will be
+retained even if the metal softens.
+
+_Brazing._--With the work in place, it should be well covered with the
+paste of flux and water, then heated until this flux boils up and runs over
+the surfaces. Spelter is then placed in such a position that it will run
+into the joint and the heat is continued or increased until the spelter
+melts and flows in between the two surfaces. The flame should surround the
+work during the heating so that outside air is excluded as far as is
+possible to prevent excessive oxidization.
+
+When handling brass or copper, the flame should not be directed so that its
+center strikes the metal squarely, but so that it glances from one side or
+the other. Directing the flame straight against the work is often the cause
+of melting the pieces before the operation is completed. When brazing two
+different metals, the flame should play only on the one that melts at the
+higher temperature, the lower melting part receiving its heat from the
+other. This avoids the danger of melting one before the other reaches the
+brazing point.
+
+The heat should be continued only long enough to cause the spelter to flow
+into place and no longer. Prolonged heating of any metal can do nothing but
+oxidize and weaken it, and this practice should be avoided as much as
+possible. If the spelter melts into small globules in place of flowing, it
+may be caused to spread and run into the joint by lightly tapping the work.
+More dry flux may be added with the spatula if the tapping does not produce
+the desired result.
+
+Excessive use of flux, especially toward the end of the work, will result
+in a very hard surface on all the work, a surface which will be extremely
+difficult to finish properly. This trouble will be present to a certain
+extent anyway, but it may be lessened by a vigorous scraping with a wire
+brush just as soon as the work is removed from the fire. If allowed to cool
+before cleaning, the final appearance will not be as good as with the
+surplus metal and scale removed immediately upon completing the job.
+
+After the work has been cleaned with the brush it may be allowed to cool
+and finished to the desired shape, size and surface by filing and
+polishing. When filed, a very thin line of brass should appear where the
+crack was at the beginning of the work. If it is desired to avoid a square
+shoulder and fill in an angle joint to make it rounding, the filling is
+best accomplished by winding a coil of very thin brass wire around the part
+of the work that projects and then causing this to flow itself or else
+allow the spelter to fill the spaces between the layers of wire. Copper
+wire may also be used for this purpose, the spaces being filled with
+melted spelter.
+
+
+THERMIT WELDING
+
+The process of welding which makes use of the great heat produced by oxygen
+combining with aluminum is known as the Thermit process and was perfected
+by Dr. Hans Goldschmidt. The process, which is controlled by the
+Goldschmidt Thermit Company, makes use of a mixture of finely powdered
+aluminum with an oxide of iron called by the trade name, Thermit.
+
+The reaction is started with a special ignition powder, such as barium
+superoxide and aluminum, and the oxygen from the iron oxide combining with
+the aluminum, producing a mass of superheated steel at about 5000 degrees
+Fahrenheit. After the reaction, which takes from. 30 seconds to a minute,
+the molten metal is drawn from the crucible on to the surfaces to be
+joined. Its extreme heat fuses the metal and a perfect joint is the result.
+This process is suited for welding iron or steel parts of comparatively
+large size.
+
+_Preparation._--The parts to be joined are thoroughly cleaned on the
+surfaces and for several inches back from the joint, after which they are
+supported in place. The surfaces between which the metal will flow are
+separated from 1/4 to 1 inch, depending on the size of the parts, but
+cutting or drilling part of the metal away. After this separation is made
+for allowing the entrance of new metal, the effects of contraction of the
+molten steel are cared for by preheating adjacent parts or by forcing the
+ends apart with wedges and jacks. The amount of this last separation must
+be determined by the shape and proportions of the parts in the same way as
+would be done for any other class of welding which heats the parts to a
+melting point.
+
+Yellow wax, which has been warmed until plastic, is then placed around the
+joint to form a collar, the wax completely filling the space between the
+ends and being provided with vent holes by imbedding a piece of stout cord,
+which is pulled out after the wax cools.
+
+A retaining mould (Figure 55) made from sheet steel or fire brick is then
+placed around the parts. This mould is then filled with a mixture of one
+part fire clay, one part ground fire brick and one part fire sand. These
+materials are well mixed and moistened with enough water so that they will
+pack. This mixture is then placed in the mould, filling the space between
+the walls and the wax, and is packed hard with a rammer so that the
+material forms a wall several inches thick between any point of the mould
+and the wax. The mixture must be placed in the mould in small quantities
+and packed tight as the filling progresses.
+
+[Illustration: Figure 55.--Thermit Mould Construction]
+
+Three or more openings are provided through this moulding material by the
+insertion of wood or pipe forms. One of these openings will lead from the
+lowest point of the wax pattern and is used for the introduction of the
+preheating flame. Another opening leads from the top of the mould into this
+preheating gate, opening into the preheating gate at a point about one inch
+from the wax pattern. Openings, called risers, are then provided from each
+of the high points of the wax pattern to the top of the mould, these risers
+ending at the top in a shallow basin. The molten metal comes up into these
+risers and cares for contraction of the casting, as well as avoiding
+defects in the collar of the weld. After the moulding material is well
+packed, these gate patterns are tapped lightly and withdrawn, except in the
+case of the metal pipes which are placed at points at which it would be
+impossible to withdraw a pattern.
+
+_Preheating._--The ends to be welded are brought to a bright red heat
+by introducing the flame from a torch through the preheating gate. The
+torch must use either gasoline or kerosene, and not crude oil, as the crude
+oil deposits too much carbon on the parts. Preheating of other adjacent
+parts to care for contraction is done at this time by an additional torch
+burner.
+
+The heating flame is started gently at first and gradually increased. The
+wax will melt and may be allowed to run out of the preheating gate by
+removing the flame at intervals for a few seconds. The heat is continued
+until the mould is thoroughly dried and the parts to be joined are brought
+to the red heat required. This leaves a mould just the shape of the wax
+pattern.
+
+The heating gate should then be plugged with a sand core, iron plug or
+piece of fitted fire brick, and backed up with several shovels full of the
+moulding mixture, well packed.
+
+[Illustration: Figure 56.--Thermit Crucible Plug.
+_A_, Hard burn magnesia stone;
+_B_, Magnesia thimble;
+_C_, Refractory sand;
+_D_, Metal disc;
+_E_, Asbestos washer;
+_F_, Tapping pin]
+
+_Thermit Metal._--The reaction takes place in a special crucible lined
+with magnesia tar, which is baked at a red heat until the tar is driven off
+and the magnesia left. This lining should last from twelve to fifteen
+reactions. This magnesia lining ends at the bottom of the crucible in a
+ring of magnesia stone and this ring carries a magnesia thimble through
+which the molten steel passes on its way to the mould. It will usually be
+necessary to renew this thimble after each reaction. This lower opening is
+closed before filling the crucible with thermit by means of a small disc or
+iron carrying a stem, which is called a tapping pin (Figure 56). This pin,
+_F_, is placed in the thimble with the stem extending down through the
+opening and exposing about two inches. The top of this pin is covered with
+an asbestos, washer, _E_, then with another iron disc. _D_, and
+finally with a layer of refractory sand. The crucible is tapped by knocking
+the stem of the pin upwards with a spade or piece of flat iron about four
+feet long.
+
+The charge of thermit is added by placing a few handfuls over the
+refractory sand and then pouring in the balance required. The amount of
+thermit required is calculated from the wax used. The wax is weighed before
+and after filling _the entire space that the thermit will occupy_.
+This does not mean only the wax collar, but the space of the mould with all
+gates filled with wax. The number of pounds of wax required for this
+filling multiplied by 25 will give the number of pounds of thermit to be
+used. To this quantity of thermit should be added I per cent of pure
+manganese, 1 per cent nickel thermit and 15 per cent of steel punchings.
+
+It is necessary, when more than 10 pounds of thermit will be used, to mix
+steel punchings not exceeding 3/8 inch diameter by 1/8 inch thick with the
+powder in order to sufficiently retard the intensity of the reaction.
+
+Half a teaspoonful of ignition powder is placed on top of the thermit
+charge and ignited with a storm match or piece of red hot iron. The cover
+should be immediately closed on the top of the crucible and the operator
+should get away to a safe distance because of the metal that may be thrown
+out of the crucible.
+
+After allowing about 30 seconds to a minute for the reaction to take place
+and the slag to rise to the top of the crucible, the tapping pin is struck
+from below and the molten metal allowed to run into the mould. The mould
+should be allowed to remain in place as long as possible, preferably over
+night, so as to anneal the steel in the weld, but in no case should it be
+disturbed for several hours after pouring. After removing the mould, drill
+through the metal left in the riser and gates and knock these sections off.
+No part of the collar should be removed unless absolutely necessary.
+
+
+
+
+CHAPTER IX
+
+OXYGEN PROCESS FOR REMOVAL OF CARBON
+
+
+Until recently the methods used for removing carbon deposits from gas
+engine cylinders were very impractical and unsatisfactory. The job meant
+dismantling the motor, tearing out all parts, and scraping the pistons and
+cylinder walls by hand.
+
+The work was never done thoroughly. It required hours of time to do it, and
+then there was always the danger of injuring the inside of the cylinders.
+
+These methods have been to a large extent superseded by the use of oxygen
+under pressure. The various devices that are being manufactured are known
+as carbon removers, decarbonizers, etc., and large numbers of them are in
+use in the automobile and gasoline traction motor industry.
+
+_Outfit._--The oxygen carbon cleaner consists of a high pressure
+oxygen cylinder with automatic reducing valve, usually constructed on the
+diaphragm principle, thus assuring positive regulation of pressure. This
+valve is fitted with a pressure gauge, rubber hose, decarbonizing torch
+with shut off and flexible tube for insertion into the chamber from which
+the carbon is to be removed.
+
+There should also be an asbestos swab for swabbing out the inside of the
+cylinder or other chamber with kerosene previous to starting the operation.
+The action consists in simply burning the carbon to a fine dust in the
+presence of the stream of oxygen, this dust being then blown out.
+
+_Operation._--The following are instructions for operating the
+cleaner:--
+
+(1) Close valve in gasoline supply line and start the motor, letting it run
+until the gasoline is exhausted.
+
+(2) If the cylinders be T or L head, remove either the inlet or the exhaust
+valve cap, or a spark plug if the cap is tight. If the cylinders have
+overhead valves, remove a spark plug. If any spark plug is then remaining
+in the cylinder it should be removed and an old one or an iron pipe plug
+substituted.
+
+(3) Raise the piston of the cylinder first to be cleaned to the top of the
+compression stroke and continue this from cylinder to cylinder as the work
+progresses.
+
+(4) In motors where carbon has been burned hard, the cylinder interior
+should then be swabbed with kerosene before proceeding. Work the swab,
+saturated with kerosene, around the inside of the cylinder until all the
+carbon has been moistened with the oil. This same swab may be used to
+ignite the gas in the cylinder in place of using a match or taper.
+
+(5) Make all connections to the oxygen cylinder.
+
+(6) Insert the torch nozzle in the cylinder, open the torch valve gradually
+and regulate to about two lbs. pressure. Manipulate the nozzle inside the
+cylinder and light a match or other flame at the opening so that the carbon
+starts to burn. Cover the various points within the cylinder and when there
+is no further burning the carbon has been removed. The regulating and
+oxygen tank valves are operated in exactly the same way as for welding as
+previously explained.
+
+
+It should be carefully noted that when the piston is up, ready to start the
+operation, both valves must be closed. There will be a considerable display
+of sparks while this operation is taking place, but they will not set fire
+to the grease and oil. Care should be used to see that no gasoline is
+about.
+
+
+
+
+INDEX
+
+
+Acetylene
+  filtering
+  generators
+  in tanks
+  piping
+  properties of
+  purification of
+Acetylene-air torches
+Air
+  oxygen from
+Alloys
+  table of
+Alloy steel
+Aluminum
+  alloys
+  welding
+Annealing
+Anvil
+Arc welding, electric
+  machines
+Asbestos, use of, in welding
+
+Babbitt
+Bending pipes and tubes
+Bessemer steel
+Beveling
+Brass
+  welding
+Brazing
+  electric
+  heat and tools
+  spelter
+Bronze
+  welding
+Butt welding
+
+Calcium carbide
+Carbide
+  storage of, Fire Underwriters' Rules
+  to water generator
+Carbon removal
+  by oxygen process
+Case hardening steel
+Cast iron
+  welding
+Champfering
+Charging generator
+Chlorate of potash oxygen
+Conductivity of metals
+Copper
+  alloys
+  welding
+Crucible steel
+Cutting, oxy-acetylene
+  torches
+
+Dissolved acetylene
+
+Electric arc welding
+Electric welding
+  troubles and remedies
+Expansion of metals
+
+Flame, welding
+Fluxes
+  for brazing
+  for soldering
+Forge
+  fire
+  practice
+  tools
+  tuvere construction of
+  welding
+  welding preparation
+  welds, forms of
+Forging
+
+Gas holders
+Gases, heating power of
+Generator, acetylene
+  carbide to water
+  construction
+Generator
+  location of
+  operation and care of
+  overheating
+  requirements
+  water to carbide
+German silver
+Gloves
+Goggles
+
+Hand forging
+Hardening steel
+Heat treatment of steel
+Hildebrandt process
+Hose
+
+Injectors, adjuster
+Iron
+  cast
+  grades of
+  malleable cast
+  wrought
+
+Jump weld
+
+Lap welding
+Lead
+Linde process
+Liquid air oxygen
+
+Magnalium
+Malleable iron
+  welding
+Melting points of metals
+Metal alloys, table of
+Metals
+  characteristics of
+  conductivity of
+  expansion of
+  heat treatment of
+  melting points of
+  tensile strength of
+  weight of
+
+Nickel
+Nozzle sizes, torch
+
+Open hearth steel
+Oxy-acetylene cutting
+  welding practice
+Oxygen
+  cylinders
+  weight of
+
+Pipes, bending
+Platinum
+Preheating
+
+Removal of carbon by oxygen process
+Resistance method of electric welding
+Restoration of steel
+Rods, welding
+
+Safety devices
+Scarfing
+Solder
+Soldering
+  flux
+  holes
+  seams
+  steel and iron
+  wires
+Spelter
+Spot welding
+Steel
+  alloys
+  Bessemer
+  crucible
+  heat treatment of
+  open hearth
+  restoration of
+  tensile strength of
+  welding
+Strength of metals
+
+Tank valves
+Tapering
+Tables of welding information
+Tempering steel
+Thermit metal
+  preheating
+  preparation
+  welding
+Tin
+Torch
+  acetylene-air
+  care
+  construction
+  cutting
+  high pressure
+  low pressure
+  medium pressure
+  nozzles
+  practice
+
+Valves, regulating
+  tank
+
+Water
+  to carbide generator
+Welding aluminum
+  brass
+  bronze
+  butt
+  cast iron
+  copper
+  electric
+  electric arc
+  flame
+  forge
+  information and tables
+  instruments
+  lap
+  malleable iron
+  materials
+  practice, oxy-acetylene
+  rods
+  spot
+  steel
+  table
+  thermit
+  torches
+  various metals
+  wrought iron
+Wrought iron
+  welding
+
+Zinc
+
+
+
+
+
+
+
+
+
+
+End of the Project Gutenberg EBook of Oxy-Acetylene Welding and Cutting, by 
+Harold P. Manly
+
+*** END OF THIS PROJECT GUTENBERG EBOOK OXY-ACETYLENE WELDING AND CUTTING ***
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+<title>The Project Gutenberg eBook of Oxy-Acetylene Welding and Cutting, by Harold P. Manly</title>
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+<pre>
+
+Project Gutenberg's Oxy-Acetylene Welding and Cutting, by Harold P. Manly
+
+This eBook is for the use of anyone anywhere at no cost and with
+almost no restrictions whatsoever.  You may copy it, give it away or
+re-use it under the terms of the Project Gutenberg License included
+with this eBook or online at www.gutenberg.org
+
+
+Title: Oxy-Acetylene Welding and Cutting
+       Electric, Forge and Thermit Welding together with related
+              methods and materials used in metal working and the oxygen
+              process for removal of carbon
+
+Author: Harold P. Manly
+
+Posting Date: April 12, 2014 [EBook #7969]
+Release Date: April, 2005
+First Posted: June 7, 2003
+
+Language: English
+
+Character set encoding: ISO-8859-1
+
+*** START OF THIS PROJECT GUTENBERG EBOOK OXY-ACETYLENE WELDING AND CUTTING ***
+
+
+
+
+Produced by Juliet Sutherland, John Argus, Tonya Allen,
+Charles Franks and the Online Distributed Proofreading Team.
+
+
+
+
+
+
+</pre>
+
+
+<h1>Oxy-Acetylene Welding and Cutting</h1>
+
+<h2>Electric, Forge and Thermit Welding</h2>
+
+<h3>Together with Related Methods and Materials Used in Metal Working
+And
+The Oxygen Process for Removal of Carbon</h3>
+
+<h3>By</h3>
+
+<h2>HAROLD P. MANLY</h2>
+
+<br>
+<br>
+<br>
+
+<h2>PREFACE</h2>
+
+<p>
+In the preparation of this work, the object has been to cover not only the
+several processes of welding, but also those other processes which are so
+closely allied in method and results as to make them a part of the whole
+subject of joining metal to metal with the aid of heat.
+</p>
+
+<p>
+The workman who wishes to handle his trade from start to finish finds that
+it is necessary to become familiar with certain other operations which
+precede or follow the actual joining of the metal parts, the purpose of
+these operations being to add or retain certain desirable qualities in the
+materials being handled. For this reason the following subjects have been
+included: Annealing, tempering, hardening, heat treatment and the
+restoration of steel.
+</p>
+
+<p>
+In order that the user may understand the underlying principles and the
+materials employed in this work, much practical information is given on the
+uses and characteristics of the various metals; on the production, handling
+and use of the gases and other materials which are a part of the equipment;
+and on the tools and accessories for the production and handling of these
+materials.
+</p>
+
+<p>
+An examination will show that the greatest usefulness of this book lies in
+the fact that all necessary information and data has been included in one
+volume, making it possible for the workman to use one source for securing a
+knowledge of both principle and practice, preparation and finishing of the
+work, and both large and small repair work as well as manufacturing methods
+used in metal working.
+</p>
+
+<p>
+An effort has been made to eliminate all matter which is not of direct
+usefulness in practical work, while including all that those engaged in
+this trade find necessary. To this end, the descriptions have been limited
+to those methods and accessories which are found in actual use today. For
+the same reason, the work includes the application of the rules laid down
+by the insurance underwriters which govern this work as well as
+instructions for the proper care and handling of the generators, torches
+and materials found in the shop.
+</p>
+
+<p>
+Special attention has been given to definite directions for handling the
+different metals and alloys which must be handled. The instructions have
+been arranged to form rules which are placed in the order of their use
+during the work described and the work has been subdivided in such a way
+that it will be found possible to secure information on any one point
+desired without the necessity of spending time in other fields.
+</p>
+
+<p>
+The facts which the expert welder and metalworker finds it most necessary
+to have readily available have been secured, and prepared especially for
+this work, and those of most general use have been combined with the
+chapter on welding practice to which they apply.
+</p>
+
+<p>
+The size of this volume has been kept as small as possible, but an
+examination of the alphabetical index will show that the range of subjects
+and details covered is complete in all respects. This has been accomplished
+through careful classification of the contents and the elimination of all
+repetition and all theoretical, historical and similar matter that is not
+absolutely necessary.
+</p>
+
+<p>
+Free use has been made of the information given by those manufacturers who
+are recognized as the leaders in their respective fields, thus insuring
+that the work is thoroughly practical and that it represents present day
+methods and practice.
+</p>
+
+<p>
+THE AUTHOR.
+</p>
+
+<br>
+<br>
+<br>
+
+<h3>
+CONTENTS
+</h3>
+
+<p>
+<a href="#i">CHAPTER I</a>
+</p>
+
+<p>
+METALS AND ALLOYS--HEAT TREATMENT:--The Use and Characteristics of the
+Industrial Alloys and Metal Elements--Annealing, Hardening, Tempering and
+Case Hardening of Steel
+</p>
+
+<p>
+<a href="#ii">CHAPTER II</a>
+</p>
+
+<p>
+WELDING MATERIALS:--Production, Handling and Use of the Gases, Oxygen and
+Acetylene--Welding Rods--Fluxes--Supplies and Fixtures
+</p>
+
+<p>
+<a href="#iii">CHAPTER III</a>
+</p>
+
+<p>
+ACETYLENE GENERATORS:--Generator Requirements and Types--Construction--Care
+and Operation of Generators.
+</p>
+
+<p>
+<a href="#iv">CHAPTER IV</a>
+</p>
+
+<p>
+WELDING INSTRUMENTS:--Tank and Regulating Valves and Gauges--High, Low and
+Medium Pressure Torches--Cutting Torches--Acetylene-Air Torches
+</p>
+
+<p>
+<a href="#v">CHAPTER V</a>
+</p>
+
+<p>
+OXY-ACETYLENE WELDING PRACTICE:--Preparation of Work--Torch Practice--
+Control of the Flame--Welding Various Metals and Alloys--Tables of
+Information Required in Welding Operations
+</p>
+
+<p>
+<a href="#vi">CHAPTER VI</a>
+</p>
+
+<p>
+ELECTRIC WELDING:--Resistance Method--Butt, Spot and Lap Welding--Troubles
+and Remedies--Electric Arc Welding
+</p>
+
+<p>
+<a href="#vii">CHAPTER VII</a>
+</p>
+
+<p>
+HAND FORGING AND WELDING:--Blacksmithing, Forging and Bending--Forge
+Welding Methods
+</p>
+
+<p>
+<a href="#viii">CHAPTER VIII</a>
+</p>
+
+<p>
+SOLDERING, BRAZING AND THERMIT WELDING:--Soldering Materials and Practice--
+Brazing--Thermit Welding
+</p>
+
+<p>
+<a href="#ix">CHAPTER IX</a>
+</p>
+
+<p>
+OXYGEN PROCESS FOR REMOVAL OF CARBON
+</p>
+
+<p>
+<a href="#index">INDEX</a>
+</p>
+
+<br>
+<br>
+<br>
+
+<p>
+OXY-ACETYLENE WELDING AND CUTTING, ELECTRIC AND THERMIT WELDING
+</p>
+
+<br>
+<br>
+<br>
+
+<h2><a name="i">CHAPTER I</a></h2>
+
+<h3>METALS AND THEIR ALLOYS--HEAT TREATMENT</h3>
+
+<p>
+THE METALS
+</p>
+
+<p>
+<i>Iron.</i>--Iron, in its pure state, is a soft, white, easily worked
+metal. It is the most important of all the metallic elements, and is, next
+to aluminum, the commonest metal found in the earth.
+</p>
+
+<p>
+Mechanically speaking, we have three kinds of iron: wrought iron, cast iron
+and steel. Wrought iron is very nearly pure iron; cast iron contains carbon
+and silicon, also chemical impurities; and steel contains a definite
+proportion of carbon, but in smaller quantities than cast iron.
+</p>
+
+<p>
+Pure iron is never obtained commercially, the metal always being mixed with
+various proportions of carbon, silicon, sulphur, phosphorus, and other
+elements, making it more or less suitable for different purposes. Iron is
+magnetic to the extent that it is attracted by magnets, but it does not
+retain magnetism itself, as does steel. Iron forms, with other elements,
+many important combinations, such as its alloys, oxides, and sulphates.
+</p>
+
+<p class="ctr">
+<a href="images/009.png"><img src="images/009th.png" alt="Figure 1.--Section Through a Blast Furnace"></a>
+</p>
+
+<p>
+<i>Cast Iron.</i>--Metallic iron is separated from iron ore in the blast
+furnace (Figure 1), and when allowed to run into moulds is called cast
+iron. This form is used for engine cylinders and pistons, for brackets,
+covers, housings and at any point where its brittleness is not
+objectionable. Good cast iron breaks with a gray fracture, is free from
+blowholes or roughness, and is easily machined, drilled, etc. Cast iron is
+slightly lighter than steel, melts at about 2,400 degrees in practice, is
+about one-eighth as good an electrical conductor as copper and has a
+tensile strength of 13,000 to 30,000 pounds per square inch. Its
+compressive strength, or resistance to crushing, is very great. It has
+excellent wearing qualities and is not easily warped and deformed by heat.
+Chilled iron is cast into a metal mould so that the outside is cooled
+quickly, making the surface very hard and difficult to cut and giving great
+resistance to wear. It is used for making cheap gear wheels and parts that
+must withstand surface friction.
+</p>
+
+<p>
+<i>Malleable Cast Iron.</i>--This is often called simply malleable iron. It
+is a form of cast iron obtained by removing much of the carbon from cast
+iron, making it softer and less brittle. It has a tensile strength of
+25,000 to 45,000 pounds per square inch, is easily machined, will stand a
+small amount of bending at a low red heat and is used chiefly in making
+brackets, fittings and supports where low cost is of considerable
+importance. It is often used in cheap constructions in place of steel
+forgings. The greatest strength of a malleable casting, like a steel
+forging, is in the surface, therefore but little machining should be done.
+</p>
+
+<p>
+<i>Wrought Iron.</i>--This grade is made by treating the cast iron to
+remove almost all of the carbon, silicon, phosphorus, sulphur, manganese
+and other impurities. This process leaves a small amount of the slag from
+the ore mixed with the wrought iron.
+</p>
+
+<p>
+Wrought iron is used for making bars to be machined into various parts. If
+drawn through the rolls at the mill once, while being made, it is called
+"muck bar;" if rolled twice, it is called "merchant bar" (the commonest
+kind), and a still better grade is made by rolling a third time. Wrought
+iron is being gradually replaced in use by mild rolled steels.
+
+Wrought iron is slightly heavier than cast iron, is a much better
+electrical conductor than either cast iron or steel, has a tensile strength
+of 40,000 to 60,000 pounds per square inch and costs slightly more than
+steel. Unlike either steel or cast iron, wrought iron does not harden when
+cooled suddenly from a red heat.
+</p>
+
+<p>
+<i>Grades of Irons.</i>--The mechanical properties of cast iron differ
+greatly according to the amount of other materials it contains. The most
+important of these contained elements is carbon, which is present to a
+degree varying from 2 to 5-1/2 per cent. When iron containing much carbon
+is quickly cooled and then broken, the fracture is nearly white in color
+and the metal is found to be hard and brittle. When the iron is slowly
+cooled and then broken the fracture is gray and the iron is more malleable
+and less brittle. If cast iron contains sulphur or phosphorus, it will show
+a white fracture regardless of the rapidity of cooling, being brittle and
+less desirable for general work.
+</p>
+
+<p>
+<i>Steel.</i>--Steel is composed of extremely minute particles of iron and
+carbon, forming a network of layers and bands. This carbon is a smaller
+proportion of the metal than found in cast iron, the percentage being from
+3/10 to 2-1/2 per cent.
+</p>
+
+<p>
+Carbon steel is specified according to the number of "points" of carbon, a
+point being one one-hundredth of one per cent of the weight of the steel.
+Steel may contain anywhere from 30 to 250 points, which is equivalent to
+saying, anywhere from 3/10 to 2-1/2 per cent, as above. A 70-point steel
+would contain 70/100 of one per cent or 7/10 of one per cent of carbon by
+weight. The percentage of carbon determines the hardness of the steel, also
+many other qualities, and its suitability for various kinds of work. The
+more carbon contained in the steel, the harder the metal will be, and, of
+course, its brittleness increases with the hardness. The smaller the grains
+or particles of iron which are separated by the carbon, the stronger the
+steel will be, and the control of the size of these particles is the object
+of the science of heat treatment.
+</p>
+
+<p>
+In addition to the carbon, steel may contain the following:
+</p>
+
+<p>
+Silicon, which increases the hardness, brittleness, strength and difficulty
+  of working if from 2 to 3 per cent is present.
+</p>
+
+<p>
+Phosphorus, which hardens and weakens the metal but makes it easier to
+  cast. Three-tenths per cent of phosphorus serves as a hardening agent and
+  may be present in good steel if the percentage of carbon is low. More
+  than this weakens the metal.
+</p>
+
+<p>
+Sulphur, which tends to make the metal hard and filled with small holes.
+</p>
+
+<p>
+Manganese, which makes the steel so hard and tough that it can with
+  difficulty be cut with steel tools. Its hardness is not lessened by
+  annealing, and it has great tensile strength.
+</p>
+
+<p>
+Alloy steel has a varying but small percentage of other elements mixed with
+it to give certain desired qualities. Silicon steel and manganese steel are
+sometimes classed as alloy steels. This subject is taken up in the latter
+part of this chapter under <i>Alloys</i>, where the various combinations
+and their characteristics are given consideration.
+</p>
+
+<p>
+Steel has a tensile strength varying from 50,000 to 300,000 pounds per
+square inch, depending on the carbon percentage and the other alloys
+present, as well as upon the texture of the grain. Steel is heavier than
+cast iron and weighs about the same as wrought iron. It is about one-ninth
+as good a conductor of electricity as copper.
+</p>
+
+<p>
+Steel is made from cast iron by three principal processes: the crucible,
+Bessemer and open hearth.
+</p>
+
+<p>
+<i>Crucible steel</i> is made by placing pieces of iron in a clay or
+graphite crucible, mixed with charcoal and a small amount of any desired
+alloy. The crucible is then heated with coal, oil or gas fires until the
+iron melts, and, by absorbing the desired elements and giving up or
+changing its percentage of carbon, becomes steel. The molten steel is then
+poured from the crucible into moulds or bars for use. Crucible steel may
+also be made by placing crude steel in the crucibles in place of the iron.
+This last method gives the finest grade of metal and the crucible process
+in general gives the best grades of steel for mechanical use.
+</p>
+
+<p class="ctr">
+<a href="images/013.png"><img src="images/013th.png" alt="Figure 2.--A Bessemer Converter"></a>
+</p>
+
+<p>
+<i>Bessemer steel</i> is made by heating iron until all the undesirable
+elements are burned out by air blasts which furnish the necessary oxygen.
+The iron is placed in a large retort called a converter, being poured,
+while at a melting heat, directly from the blast furnace into the
+converter. While the iron in the converter is molten, blasts of air are
+forced through the liquid, making it still hotter and burning out the
+impurities together with the carbon and manganese. These two elements are
+then restored to the iron by adding spiegeleisen (an alloy of iron, carbon
+and manganese). A converter holds from 5 to 25 tons of metal and requires
+about 20 minutes to finish a charge. This makes the cheapest steel.
+</p>
+
+<p class="ctr">
+<a href="images/014.png"><img src="images/014th.png" alt="Figure 3.--An Open Hearth Furnace"></a>
+</p>
+
+<p>
+<i>Open hearth steel</i> is made by placing the molten iron in a receptacle
+while currents of air pass over it, this air having itself been highly
+heated by just passing over white hot brick (Figure. 3). Open hearth steel
+is considered more uniform and reliable than Bessemer, and is used for
+springs, bar steel, tool steel, steel plates, etc.
+</p>
+
+<p>
+<i>Aluminum</i> is one of the commonest industrial metals. It is used for
+gear cases, engine crank cases, covers, fittings, and wherever lightness
+and moderate strength are desirable.
+</p>
+
+<p>
+Aluminum is about one-third the weight of iron and about the same weight as
+glass and porcelain; it is a good electrical conductor (about one-half as
+good as copper); is fairly strong itself and gives great strength to other
+metals when alloyed with them. One of the greatest advantages of aluminum
+is that it will not rust or corrode under ordinary conditions. The granular
+formation of aluminum makes its strength very unreliable and it is too soft
+to resist wear.
+</p>
+
+<p>
+<i>Copper</i> is one of the most important metals used in the trades, and
+the best commercial conductor of electricity, being exceeded in this
+respect only by silver, which is but slightly better. Copper is very
+malleable and ductile when cold, and in this state may be easily worked
+under the hammer. Working in this way makes the copper stronger and harder,
+but less ductile. Copper is not affected by air, but acids cause the
+formation of a green deposit called verdigris.
+</p>
+
+<p>
+Copper is one of the best conductors of heat, as well as electricity, being
+used for kettles, boilers, stills and wherever this quality is desirable.
+Copper is also used in alloys with other metals, forming an important part
+of brass, bronze, german silver, bell metal and gun metal. It is about
+one-eighth heavier than steel and has a tensile strength of about 25,000 to
+50,000 pounds per square inch.
+</p>
+
+<p>
+<i>Lead.</i>--The peculiar properties of lead, and especially its quality
+of showing but little action or chemical change in the presence of other
+elements, makes it valuable under certain conditions of use. Its principal
+use is in pipes for water and gas, coverings for roofs and linings for vats
+and tanks. It is also used to coat sheet iron for similar uses and as an
+important part of ordinary solder.
+</p>
+
+<p>
+Lead is the softest and weakest of all the commercial metals, being very
+pliable and inelastic. It should be remembered that lead and all its
+compounds are poisonous when received into the system. Lead is more than
+one-third heavier than steel, has a tensile strength of only about 2,000
+pounds per square inch, and is only about one-tenth as good a conductor of
+electricity as copper.
+</p>
+
+<p>
+<i>Zinc.</i>--This is a bluish-white metal of crystalline form. It is
+brittle at ordinary temperatures and becomes malleable at about 250 to 300
+degrees Fahrenheit, but beyond this point becomes even more brittle than at
+ordinary temperatures. Zinc is practically unaffected by air or moisture
+through becoming covered with one of its own compounds which immediately
+resists further action. Zinc melts at low temperatures, and when heated
+beyond the melting point gives off very poisonous fumes.
+</p>
+
+<p>
+The principal use of zinc is as an alloy with other metals to form brass,
+bronze, german silver and bearing metals. It is also used to cover the
+surface of steel and iron plates, the plates being then called galvanized.
+</p>
+
+<p>
+Zinc weighs slightly less than steel, has a tensile strength of 5,000
+pounds per square inch, and is not quite half as good as copper in
+conducting electricity.
+</p>
+
+<p>
+<i>Tin</i> resembles silver in color and luster. Tin is ductile and
+malleable and slightly crystalline in form, almost as heavy as steel, and
+has a tensile strength of 4,500 pounds per square inch.
+</p>
+
+<p>
+The principal use of tin is for protective platings on household utensils
+and in wrappings of tin-foil. Tin forms an important part of many alloys
+such as babbitt, Britannia metal, bronze, gun metal and bearing metals.
+</p>
+
+<p>
+<i>Nickel</i> is important in mechanics because of its combinations with
+other metals as alloys. Pure nickel is grayish-white, malleable, ductile
+and tenacious. It weighs almost as much as steel and, next to manganese, is
+the hardest of metals. Nickel is one of the three magnetic metals, the
+others being iron and cobalt. The commonest alloy containing nickel is
+german silver, although one of its most important alloys is found in nickel
+steel. Nickel is about ten per cent heavier than steel, and has a tensile
+strength of 90,000 pounds per square inch.
+</p>
+
+<p>
+<i>Platinum.</i>--This metal is valuable for two reasons: it is not
+affected by the air or moisture or any ordinary acid or salt, and in
+addition to this property it melts only at the highest temperatures. It is
+a fairly good electrical conductor, being better than iron or steel. It is
+nearly three times as heavy as steel and its tensile strength is 25,000
+pounds per square inch.
+</p>
+
+<p>
+ALLOYS
+</p>
+
+<p>
+An alloy is formed by the union of a metal with some other material, either
+metal or non-metallic, this union being composed of two or more elements
+and usually brought about by heating the substances together until they
+melt and unite. Metals are alloyed with materials which have been found to
+give to the metal certain characteristics which are desired according to
+the use the metal will be put to.
+</p>
+
+<p>
+The alloys of metals are, almost without exception, more important from an
+industrial standpoint than the metals themselves. There are innumerable
+possible combinations, the most useful of which are here classed under the
+head of the principal metal entering into their composition.
+</p>
+
+<p>
+<i>Steel.</i>--Steel may be alloyed with almost any of the metals or
+elements, the combinations that have proven valuable numbering more than a
+score. The principal ones are given in alphabetical order, as follows:
+</p>
+
+<p>
+Aluminum is added to steel in very small amounts for the purpose of
+preventing blow holes in castings.
+</p>
+
+<p>
+Boron increases the density and toughness of the metal.
+</p>
+
+<p>
+Bronze, added by alloying copper, tin and iron, is used for gun metal.
+</p>
+
+<p>
+Carbon has already been considered under the head of steel in the section
+devoted to the metals. Carbon, while increasing the strength and hardness,
+decreases the ease of forging and bending and decreases the magnetism and
+electrical conductivity. High carbon steel can be welded only with
+difficulty. When the percentage of carbon is low, the steel is called "low
+carbon" or "mild" steel. This is used for rods and shafts, and called
+"machine" steel. When the carbon percentage is high, the steel is called
+"high carbon" steel, and it is used in the shop as tool steel. One-tenth
+per cent of carbon gives steel a tensile strength of 50,000 to 65,000
+pounds per square inch; two-tenths per cent gives from 60,000 to 80,000;
+four-tenths per cent gives 70,000 to 100,000, and six-tenths per cent
+gives 90,000 to 120,000.
+</p>
+
+<p>
+Chromium forms chrome steel, and with the further addition of nickel is
+called chrome nickel steel. This increases the hardness to a high degree
+and adds strength without much decrease in ductility. Chrome steels are
+used for high-speed cutting tools, armor plate, files, springs, safes,
+dies, etc.
+</p>
+
+<p>
+Manganese has been mentioned under <i>Steel</i>. Its alloy is much used for
+high-speed cutting tools, the steel hardening when cooled in the air and
+being called self-hardening.
+</p>
+
+<p>
+Molybdenum is used to increase the hardness to a high degree and makes the
+steel suitable for high-speed cutting and gives it self-hardening
+properties.
+</p>
+
+<p>
+Nickel, with which is often combined chromium, increases the strength,
+springiness and toughness and helps to prevent corrosion.
+</p>
+
+<p>
+Silicon has already been described. It suits the metal for use in
+high-speed tools.
+</p>
+
+<p>
+Silver added to steel has many of the properties of nickel.
+</p>
+
+<p>
+Tungsten increases the hardness without making the steel brittle. This
+makes the steel well suited for gas engine valves as it resists corrosion
+and pitting. Chromium and manganese are often used in combination with
+tungsten when high-speed cutting tools are made.
+</p>
+
+<p>
+Vanadium as an alloy increases the elastic limit, making the steel
+stronger, tougher and harder. It also makes the steel able to stand much
+bending and vibration.
+</p>
+
+<p>
+<i>Copper.</i>--The principal copper alloys include brass, bronze, german
+silver and gun metal.
+</p>
+
+<p>
+Brass is composed of approximately one-third zinc and two-thirds copper. It
+is used for bearings and bushings where the speeds are slow and the loads
+rather heavy for the bearing size. It also finds use in washers, collars
+and forms of brackets where the metal should be non-magnetic, also for many
+highly finished parts.
+</p>
+
+<p>
+Brass is about one-third as good an electrical conductor as copper, is
+slightly heavier than steel and has a tensile strength of 15,000 pounds
+when cast and about 75,000 to 100,000 pounds when drawn into wire.
+</p>
+
+<p>
+Bronze is composed of copper and tin in various proportions, according to
+the use to which it is to be put. There will always be from six-tenths to
+nine-tenths of copper in the mixture. Bronze is used for bearings,
+bushings, thrust washers, brackets and gear wheels. It is heavier than
+steel, about 1/15 as good an electrical conductor as pure copper and has a
+tensile strength of 30,000 to 60,000 pounds.
+</p>
+
+<p>
+Aluminum bronze, composed of copper, zinc and aluminum has high tensile
+strength combined with ductility and is used for parts requiring this
+combination.
+</p>
+
+<p>
+Bearing bronze is a variable material, its composition and proportion
+depending on the maker and the use for which it is designed. It usually
+contains from 75 to 85 per cent of copper combined with one or more
+elements, such as tin, zinc, antimony and lead.
+</p>
+
+<p>
+White metal is one form of bearing bronze containing over 80 per cent of
+zinc together with copper, tin, antimony and lead. Another form is made
+with nearly 90 per cent of tin combined with copper and antimony.
+</p>
+
+<p>
+Gun metal bronze is made from 90 per cent copper with 10 per cent of tin
+and is used for heavy bearings, brackets and highly finished parts.
+</p>
+
+<p>
+Phosphor bronze is used for very strong castings and bearings. It is
+similar to gun metal bronze, except that about 1-1/2 per cent of phosphorus
+has been added.
+</p>
+
+<p>
+Manganese bronze contains about 1 per cent of manganese and is used for
+parts requiring great strength while being free from corrosion.
+</p>
+
+<p>
+German silver is made from 60 per cent of copper with 20 per cent each of
+zinc and nickel. Its high electrical resistance makes it valuable for
+regulating devices and rheostats.
+</p>
+
+<p>
+<i>Tin</i> is the principal part of <i>babbitt</i> and <i>solder</i>. A
+commonly used babbitt is composed of 89 per cent tin, 8 per cent antimony
+and 3 per cent of copper. A grade suitable for repairing is made from
+80 per cent of lead and 20 per cent antimony. This last formula should not
+be used for particular work or heavy loads, being more suitable for
+spacers. Innumerable proportions of metals are marketed under the name of
+babbitt.
+</p>
+
+<p>
+Solder is made from 50 per cent tin and 50 per cent lead, this grade being
+called "half-and-half." Hard solder is made from two-thirds tin and
+one-third lead.
+</p>
+
+<p>
+Aluminum forms many different alloys, giving increased strength to whatever
+metal it unites with.
+</p>
+
+<p>
+Aluminum brass is composed of approximately 65 per cent copper, 30 per cent
+zinc and 5 per cent aluminum. It forms a metal with high tensile strength
+while being ductile and malleable.
+</p>
+
+<p>
+Aluminum zinc is suitable for castings which must be stiff and hard.
+</p>
+
+<p>
+Nickel aluminum has a tensile strength of 40,000 pounds per square inch.
+</p>
+
+<p>
+Magnalium is a silver-white alloy of aluminum with from 5 to 20 per cent of
+magnesium, forming a metal even lighter than aluminum and strong enough to
+be used in making high-speed gasoline engines.
+</p>
+
+<p>
+HEAT TREATMENT OF STEEL
+</p>
+
+<p>
+The processes of heat treatment are designed to suit the steel for various
+purposes by changing the size of the grain in the metal, therefore the
+strength; and by altering the chemical composition of the alloys in the
+metal to give it different physical properties. Heat treatment, as applied
+in ordinary shop work, includes the three processes of annealing, hardening
+and tempering, each designed to accomplish a certain definite result.
+</p>
+
+<p>
+All of these processes require that the metal treated be gradually brought
+to a certain predetermined degree of heat which shall be uniform throughout
+the piece being handled and, from this point, cooled according to certain
+rules, the selection of which forms the difference in the three methods.
+</p>
+
+<p>
+<i>Annealing.</i>--This is the process which relieves all internal strains
+and distortion in the metal and softens it so that it may more easily be
+cut, machined or bent to the required form. In some cases annealing is used
+only to relieve the strains, this being the case after forging or welding
+operations have been performed. In other cases it is only desired to soften
+the metal sufficiently that it may be handled easily. In some cases both of
+these things must be accomplished, as after a piece has been forged and
+must be machined. No matter what the object, the procedure is the same.
+</p>
+
+<p>
+The steel to be annealed must first be heated to a dull red. This heating
+should be done slowly so that all parts of the piece have time to reach the
+same temperature at very nearly the same time. The piece may be heated in
+the forge, but a much better way is to heat in an oven or furnace of some
+type where the work is protected against air currents, either hot or cold,
+and is also protected against the direct action of the fire.
+</p>
+
+<p class="ctr">
+<a href="images/023.png"><img src="images/023th.png" alt="Figure 4.--A Gaspipe Annealing Oven"></a>
+</p>
+
+<p>
+Probably the simplest of all ovens for small tools is made by placing a
+piece of ordinary gas pipe in the fire (Figure 4), and heating until the
+inside of the pipe is bright red. Parts placed in this pipe, after one end
+has been closed, may be brought to the desired heat without danger of
+cooling draughts or chemical change from the action of the fire. More
+elaborate ovens may be bought which use gas, fuel oils or coal to produce
+the heat and in which the work may be placed on trays so that the fire will
+not strike directly on the steel being treated.
+</p>
+
+<p>
+If the work is not very important, it may be withdrawn from the fire or
+oven, after heating to the desired point, and allowed to cool in the air
+until all traces of red have disappeared when held in a dark place. The
+work should be held where it is reasonably free from cold air currents. If,
+upon touching a pine stick to the piece being annealed, the wood does not
+smoke, the work may then be cooled in water.
+</p>
+
+<p>
+Better annealing is secured and harder metal may be annealed if the cooling
+is extended over a number of hours by placing the work in a bed of
+non-heat-conducting material, such as ashes, charred bone, asbestos fibre,
+lime, sand or fire clay. It should be well covered with the heat retaining
+material and allowed to remain until cool. Cooling may be accomplished by
+allowing the fire in an oven or furnace to die down and go out, leaving the
+work inside the oven with all openings closed. The greater the time taken
+for gradual cooling from the red heat, the more perfect will be the results
+of the annealing.
+</p>
+
+<p>
+While steel is annealed by slow cooling, copper or brass is annealed by
+bringing to a low red heat and quickly plunging into cold water.
+</p>
+
+<p>
+<i>Hardening.</i>--Steel is hardened by bringing to a proper temperature,
+slowly and evenly as for annealing, and then cooling more or less quickly,
+according to the grade of steel being handled. The degree of hardening is
+determined by the kind of steel, the temperature from which the metal is
+cooled and the temperature and nature of the bath into which it is plunged
+for cooling.
+</p>
+
+<p>
+Steel to be hardened is often heated in the fire until at some heat around
+600 to 700 degrees is reached, then placed in a heating bath of molten
+lead, heated mercury, fused cyanate of potassium, etc., the heating bath
+itself being kept at the proper temperature by fires acting on it. While
+these baths have the advantage of heating the metal evenly and to exactly
+the temperature desired throughout without any part becoming over or under
+heated, their disadvantages consist of the fact that their materials and
+the fumes are poisonous in most all cases, and if not poisonous, are
+extremely disagreeable.
+</p>
+
+<p>
+The degree of heat that a piece of steel must be brought to in order that
+it may be hardened depends on the percentage of carbon in the steel. The
+greater the percentage of carbon, the lower the heat necessary to harden.
+</p>
+
+<p class="ctr">
+<a href="images/025.png"><img src="images/025th.png" alt="Figure 5.--Cooling the Test Bar for Hardening"></a>
+</p>
+
+<p>
+To find the proper heat from which any steel must be cooled, a simple test
+may be carried out provided a sample of the steel, about six inches long
+can be secured. One end of this test bar should be heated almost to its
+melting point, and held at this heat until the other end just turns red.
+Now cool the piece in water by plunging it so that both ends enter at the
+same time (Figure 5), that is, hold it parallel with the surface of the
+water when plunged in. This serves the purpose of cooling each point along
+the bar from a different heat. When it has cooled in the water remove the
+piece and break it at short intervals, about 1/2 inch, along its length.
+The point along the test bar which was cooled from the best possible
+temperature will show a very fine smooth grain and the piece cannot be cut
+by a file at this point. It will be necessary to remember the exact color
+of that point when taken from the fire, making another test if necessary,
+and heat all pieces of this same steel to this heat. It will be necessary
+to have the cooling bath always at the same temperature, or the results
+cannot be alike.
+</p>
+
+<p>
+While steel to be hardened is usually cooled in water, many other liquids
+may be used. If cooled in strong brine, the heat will be extracted much
+quicker, and the degree of hardness will be greater. A still greater degree
+of hardness is secured by cooling in a bath of mercury. Care should be used
+with the mercury bath, as the fumes that arise are poisonous.
+</p>
+
+<p>
+Should toughness be desired, without extreme hardness, the steel may be
+cooled in a bath of lard oil, neatsfoot oil or fish oil. To secure a result
+between water and oil, it is customary to place a thick layer of oil on top
+of water. In cooling, the piece will pass through the oil first, thus
+avoiding the sudden shock of the cold water, yet producing a degree of
+hardness almost as great as if the oil were not used.
+</p>
+
+<p>
+It will, of course, be necessary to make a separate test for each cooling
+medium used. If the fracture of the test piece shows a coarse grain, the
+steel was too hot at that point; if the fracture can be cut with a file,
+the metal was not hot enough at that point.
+</p>
+
+<p>
+When hardening carbon tool steel its heat should be brought to a cherry
+red, the exact degree of heat depending on the amount of carbon and the
+test made, then plunged into water and held there until all hissing sound
+and vibration ceases. Brine may be used for this purpose; it is even better
+than plain water. As soon as the hissing stops, remove the work from the
+water or brine and plunge in oil for complete cooling.
+</p>
+
+<p class="ctr">
+<a href="images/027.png"><img src="images/027th.png" alt="Figure 6.--Cooling the Tool for Tempering"></a>
+</p>
+
+<p>
+In hardening high-speed tool steel, or air hardening steels, the tool
+should be handled as for carbon steel, except that after the body reaches
+a cherry red, the cutting point must be quickly brought to a white heat,
+almost melting, so that it seems ready for welding. Then cool in an oil
+bath or in a current of cool air.
+</p>
+
+<p>
+Hardening of copper, brass and bronze is accomplished by hammering or
+working them while cold.
+</p>
+
+<p>
+<i>Tempering</i> is the process of making steel tough after it has been
+hardened, so that it will hold a cutting edge and resist cracking.
+Tempering makes the grain finer and the metal stronger. It does not affect
+the hardness, but increases the elastic limit and reduces the brittleness
+of the steel. In that tempering is usually performed immediately after
+hardening, it might be considered as a continuation of the former process.
+</p>
+
+<p>
+The work or tool to be tempered is slowly heated to a cherry red and the
+cutting end is then dipped into water to a depth of 1/2 to 3/4 inch above
+the point (Figure 6). As soon as the point cools, still leaving the tool
+red above the part in water, remove the work from the bath and quickly rub
+the end with a fine emery cloth.
+</p>
+
+<p>
+As the heat from the uncooled part gradually heats the point again, the
+color of the polished portion changes rapidly. When a certain color is
+reached, the tool should be completely immersed in the water until cold.
+</p>
+
+<p>
+For lathe, planer, shaper and slotter tools, this color should be a light
+straw.
+</p>
+
+<p>
+Reamers and taps should be cooled from an ordinary straw color.
+</p>
+
+<p>
+Drills, punches and wood working tools should have a brown color.
+</p>
+
+<p>
+Blue or light purple is right for cold chisels and screwdrivers.
+</p>
+
+<p>
+Dark blue should be reached for springs and wood saws.
+</p>
+
+<p>
+Darker colors than this, ranging through green and gray, denote that the
+piece has reached its ordinary temper, that is, it is partially annealed.
+</p>
+
+<p>
+After properly hardening a spring by dipping in lard or fish oil, it should
+be held over a fire while still wet with the oil. The oil takes fire and
+burns off, properly tempering the spring.
+</p>
+
+<p>
+Remember that self-hardening steels must never be dipped in water, and
+always remember for all work requiring degrees of heat, that the more
+carbon, the less heat.
+</p>
+
+<p>
+<i>Case Hardening.</i>--This is a process for adding more carbon to the
+surface of a piece of steel, so that it will have good wear-resisting
+qualities, while being tough and strong on the inside. It has the effect of
+forming a very hard and durable skin on the surface of soft steel, leaving
+the inside unaffected.
+</p>
+
+<p>
+The simplest way, although not the most efficient, is to heat the piece to
+be case hardened to a red heat and then sprinkle or rub the part of the
+surface to be hardened with potassium ferrocyanide. This material is a
+deadly poison and should be handled with care. Allow the cyanide to fuse on
+the surface of the metal and then plunge into water, brine or mercury.
+Repeating the process makes the surface harder and the hard skin deeper
+each time.
+</p>
+
+<p>
+Another method consists of placing the piece to be hardened in a bed of
+powdered bone (bone which has been burned and then powdered) and cover with
+more powdered bone, holding the whole in an iron tray. Now heat the tray
+and bone with the work in an oven to a bright red heat for 30 minutes to an
+hour and then plunge the work into water or brine.
+</p>
+
+<br>
+<br>
+<br>
+
+<h2><a name="ii">CHAPTER II</a></h2>
+
+<h3>OXY-ACETYLENE WELDING AND CUTTING MATERIALS</h3>
+
+<p>
+<i>Welding.</i>--Oxy-acetylene welding is an autogenous welding process, in
+which two parts of the same or different metals are joined by causing the
+edges to melt and unite while molten without the aid of hammering or
+compression. When cool, the parts form one piece of metal.
+</p>
+
+<p>
+The oxy-acetylene flame is made by mixing oxygen and acetylene gases in a
+special welding torch or blowpipe, producing, when burned, a heat of 6,300
+degrees, which is more than twice the melting temperature of the common
+metals. This flame, while being of intense heat, is of very small size.
+</p>
+
+<p>
+<i>Cutting.</i>--The process of cutting metals with the flame produced from
+oxygen and acetylene depends on the fact that a jet of oxygen directed upon
+hot metal causes the metal itself to burn away with great rapidity,
+resulting in a narrow slot through the section cut. The action is so fast
+that metal is not injured on either side of the cut.
+</p>
+
+<p>
+<i>Carbon Removal.</i>--This process depends on the fact that carbon will
+burn and almost completely vanish if the action is assisted with a supply
+of pure oxygen gas. After the combustion is started with any convenient
+flame, it continues as long as carbon remains in the path of the jet of
+oxygen.
+</p>
+
+<p>
+<i>Materials.</i>--For the performance of the above operations we require
+the two gases, oxygen and acetylene, to produce the flames; rods of metal
+which may be added to the joints while molten in order to give the weld
+sufficient strength and proper form, and various chemical powders, called
+fluxes, which assist in the flow of metal and in doing away with many of
+the impurities and other objectionable features.
+</p>
+
+<p>
+<i>Instruments.</i>--To control the combustion of the gases and add to the
+convenience of the operator a number of accessories are required.
+</p>
+
+<p>
+The pressure of the gases in their usual containers is much too high for
+their proper use in the torch and we therefore need suitable valves which
+allow the gas to escape from the containers when wanted, and other
+specially designed valves which reduce the pressure. Hose, composed of
+rubber and fabric, together with suitable connections, is used to carry the
+gas to the torch.
+</p>
+
+<p>
+The torches for welding and cutting form a class of highly developed
+instruments of the greatest accuracy in manufacture, and must be thoroughly
+understood by the welder. Tables, stands and special supports are provided
+for holding the work while being welded, and in order to handle the various
+metals and allow for their peculiarities while heated use is made of ovens
+and torches for preheating. The operator requires the protection of
+goggles, masks, gloves and appliances which prevent undue radiation of the
+heat.
+</p>
+
+<p>
+<i>Torch Practice.</i>--The actual work of welding and cutting requires
+preliminary preparation in the form of heat treatment for the metals,
+including preheating, annealing and tempering. The surfaces to be joined
+must be properly prepared for the flame, and the operation of the torches
+for best results requires careful and correct regulation of the gases and
+the flame produced.
+</p>
+
+<p>
+Finally, the different metals that are to be welded require special
+treatment for each one, depending on the physical and chemical
+characteristics of the material.
+</p>
+
+<p>
+It will thus be seen that the apparently simple operations of welding and
+cutting require special materials, instruments and preparation on the part
+of the operator and it is a proved fact that failures, which have been
+attributed to the method, are really due to lack of these necessary
+qualifications.
+</p>
+
+<p>
+OXYGEN
+</p>
+
+<p>
+Oxygen, the gas which supports the rapid combustion of the acetylene in the
+torch flame, is one of the elements of the air. It is the cause and the
+active agent of all combustion that takes place in the atmosphere. Oxygen
+was first discovered as a separate gas in 1774, when it was produced by
+heating red oxide of mercury and was given its present name by the famous
+chemist, Lavoisier.
+</p>
+
+<p>
+Oxygen is prepared in the laboratory by various methods, these including
+the heating of chloride of lime and peroxide of cobalt mixed in a retort,
+the heating of chlorate of potash, and the separation of water into its
+elements, hydrogen and oxygen, by the passage of an electric current. While
+the last process is used on a large scale in commercial work, the others
+are not practical for work other than that of an experimental or temporary
+nature.
+</p>
+
+<p>
+This gas is a colorless, odorless, tasteless element. It is sixteen times
+as heavy as the gas hydrogen when measured by volume under the same
+temperature and pressure. Under all ordinary conditions oxygen remains in
+a gaseous form, although it turns to a liquid when compressed to 4,400
+pounds to the square inch and at a temperature of 220° below zero.
+</p>
+
+<p>
+Oxygen unites with almost every other element, this union often taking
+place with great heat and much light, producing flame. Steel and iron will
+burn rapidly when placed in this gas if the combustion is started with a
+flame of high heat playing on the metal. If the end of a wire is heated
+bright red and quickly plunged into a jar containing this gas, the wire
+will burn away with a dazzling light and be entirely consumed except for
+the molten drops that separate themselves. This property of oxygen is used
+in oxy-acetylene cutting of steel.
+</p>
+
+<p>
+The combination of oxygen with other substances does not necessarily cause
+great heat, in fact the combination may be so slow and gradual that the
+change of temperature can not be noticed. An example of this slow
+combustion, or oxidation, is found in the conversion of iron into rust as
+the metal combines with the active gas. The respiration of human beings
+and animals is a form of slow combustion and is the source of animal heat.
+It is a general rule that the process of oxidation takes place with
+increasing rapidity as the temperature of the body being acted upon rises.
+Iron and steel at a red heat oxidize rapidly with the formation of a scale
+and possible damage to the metal.
+</p>
+
+<p>
+<i>Air.</i>--Atmospheric air is a mixture of oxygen and nitrogen with
+traces of carbonic acid gas and water vapor. Twenty-one per cent of the
+air, by volume, is oxygen and the remaining seventy-nine per cent is the
+inactive gas, nitrogen. But for the presence of the nitrogen, which deadens
+the action of the other gas, combustion would take place at a destructive
+rate and be beyond human control in almost all cases. These two gases exist
+simply as a mixture to form the air and are not chemically combined. It is
+therefore a comparatively simple matter to separate them with the processes
+now available.
+</p>
+
+<p>
+<i>Water.</i>--Water is a combination of oxygen and hydrogen, being
+composed of exactly two volumes of hydrogen to one volume of oxygen. If
+these two gases be separated from each other and then allowed to mix in
+these proportions they unite with explosive violence and form water. Water
+itself may be separated into the gases by any one of several means, one
+making use of a temperature of 2,200° to bring about this separation.
+</p>
+
+<p class="ctr">
+<a href="images/034.png"><img src="images/034th.png" alt="Figure 7--Obtaining Oxygen by Electrolysis"></a>
+</p>
+
+<p>
+The easiest way to separate water into its two parts is by the process
+called electrolysis (Figure 7). Water, with which has been mixed a small
+quantity of acid, is placed in a vat through the walls of which enter the
+platinum tipped ends of two electrical conductors, one positive and the
+other negative.
+</p>
+
+<p>
+Tubes are placed directly above these wire terminals in the vat, one tube
+being over each electrode and separated from each other by some distance.
+With the passage of an electric current from one wire terminal to the
+other, bubbles of gas rise from each and pass into the tubes. The gas that
+comes from the negative terminal is hydrogen and that from the positive
+pole is oxygen, both gases being almost pure if the work is properly
+conducted. This method produces electrolytic oxygen and electrolytic
+hydrogen.
+</p>
+
+<p>
+<i>The Liquid Air Process.</i>--While several of the foregoing methods of
+securing oxygen are successful as far as this result is concerned, they are
+not profitable from a financial standpoint. A process for separating oxygen
+from the nitrogen in the air has been brought to a high state of perfection
+and is now supplying a major part of this gas for oxy-acetylene welding. It
+is known as the Linde process and the gas is distributed by the Linde Air
+Products Company from its plants and warehouses located in the large cities
+of the country.
+</p>
+
+<p>
+The air is first liquefied by compression, after which the gases are
+separated and the oxygen collected. The air is purified and then compressed
+by successive stages in powerful machines designed for this purpose until
+it reaches a pressure of about 3,000 pounds to the square inch. The large
+amount of heat produced is absorbed by special coolers during the process
+of compression. The highly compressed air is then dried and the
+temperature further reduced by other coolers.
+</p>
+
+<p>
+The next point in the separation is that at which the air is introduced
+into an apparatus called an interchanger and is allowed to escape through a
+valve, causing it to turn to a liquid. This liquid air is sprayed onto
+plates and as it falls, the nitrogen return to its gaseous state and leaves
+ the oxygen to run to the bottom of the container. This liquid oxygen is
+then allowed to return to a gas and is stored in large gasometers or tanks.
+</p>
+
+<p>
+The oxygen gas is taken from the storage tanks and compressed to
+approximately 1,800 pounds to the square inch, under which pressure it is
+passed into steel cylinders and made ready for delivery to the customer.
+This oxygen is guaranteed to be ninety-seven per cent pure.
+</p>
+
+<p>
+Another process, known as the Hildebrandt process, is coming into use in
+this country. It is a later process and is used in Germany to a much
+greater extent than the Linde process. The Superior Oxygen Co. has secured
+the American rights and has established several plants.
+</p>
+
+<p>
+<i>Oxygen Cylinders</i>.--Two sizes of cylinders are in use, one containing
+100 cubic feet of gas when it is at atmospheric pressure and the other
+containing 250 cubic feet under similar conditions. The cylinders are made
+from one piece of steel and are without seams. These containers are tested
+at double the pressure of the gas contained to insure safety while
+handling.
+</p>
+
+<p>
+One hundred cubic feet of oxygen weighs nearly nine pounds (8.921), and
+therefore the cylinders will weigh practically nine pounds more when full
+than after emptying, if of the 100 cubic feet size. The large cylinders
+weigh about eighteen and one-quarter pounds more when full than when empty,
+making approximately 212 pounds empty and 230 pounds full.
+</p>
+
+<p>
+The following table gives the number of cubic feet of oxygen remaining in
+the cylinders according to various gauge pressures from an initial pressure
+of 1,800 pounds. The amounts given are not exactly correct as this would
+necessitate lengthy calculations which would not make great enough
+difference to affect the practical usefulness of the table:
+</p>
+
+<pre>
+Cylinder of 100 Cu. Ft. Capacity at 68° Fahr.
+
+ Gauge     Volume     Gauge     Volume
+Pressure  Remaining  Pressure  Remaining
+
+ 1800        100       700        39
+ 1620         90       500        28
+ 1440         80       300        17
+ 1260         70       100         6
+ 1080         60        18         1
+  900         50         9          1/2
+
+Cylinder of 250 Cu. Ft. Capacity at 68° Fahr.
+
+ Gauge     Volume     Gauge     Volume
+Pressure  Remaining  Pressure  Remaining
+
+ 1800        250       700        97
+ 1620        225       500        70
+ 1440        200       300        42
+ 1260        175       100        15
+ 1080        150        18         8
+  900        125         9         1-1/4
+</pre>
+
+<p>
+The temperature of the cylinder affects the pressure in a large degree, the
+pressure increasing with a rise in temperature and falling with a fall in
+temperature. The variation for a 100 cubic foot cylinder at various
+temperatures is given in the following tabulation:
+</p>
+
+<pre>
+At 150° Fahr........................ 2090 pounds.
+At 100° Fahr........................ 1912 pounds.
+At  80° Fahr........................ 1844 pounds.
+At  68° Fahr........................ 1800 pounds.
+At  50° Fahr........................ 1736 pounds.
+At  32° Fahr........................ 1672 pounds.
+At   0  Fahr........................ 1558 pounds.
+At -10° Fahr........................ 1522 pounds.
+</pre>
+
+<p>
+<i>Chlorate of Potash Method.</i>--In spite of its higher cost and the
+inferior gas produced, the chlorate of potash method of producing oxygen is
+used to a limited extent when it is impossible to secure the gas in
+cylinders.
+</p>
+
+<p class="ctr">
+<a href="images/038.png"><img src="images/038th.png" alt="Figure 8.--Oxygen from Chlorate of Potash"></a>
+</p>
+
+<p>
+An iron retort (Figure 8) is arranged to receive about fifteen pounds of
+chlorate of potash mixed with three pounds of manganese dioxide, after
+which the cylinder is closed with a tight cap, clamped on. This retort is
+carried above a burner using fuel gas or other means of generating heat and
+this burner is lighted after the chemical charge is mixed and compressed in
+the tube.
+</p>
+
+<p>
+The generation of gas commences and the oxygen is led through water baths
+which wash and cool it before storing in a tank connected with the plant.
+From this tank the gas is compressed into portable cylinders at a pressure
+of about 300 pounds to the square inch for use as required in welding
+operations.
+</p>
+
+<p>
+Each pound of chlorate of potash liberates about three cubic feet of
+oxygen, and taking everything into consideration, the cost of gas produced
+in this way is several times that of the purer product secured by the
+liquid air process.
+</p>
+
+<p>
+These chemical generators are oftentimes a source of great danger,
+especially when used with or near the acetylene gas generator, as is
+sometimes the case with cheap portable outfits. Their use should not be
+tolerated when any other method is available, as the danger from accident
+alone should prohibit the practice except when properly installed and
+cared for away from other sources of combustible gases.
+</p>
+
+<p>
+ACETYLENE
+</p>
+
+<p>
+In 1862 a chemist, Woehler, announced the discovery of the preparation of
+acetylene gas from calcium carbide, which he had made by heating to a high
+temperature a mixture of charcoal with an alloy of zinc and calcium. His
+product would decompose water and yield the gas. For nearly thirty years
+these substances were neglected, with the result that acetylene was
+practically unknown, and up to 1892 an acetylene flame was seen by very few
+persons and its possibilities were not dreamed of. With the development of
+the modern electric furnace the possibility of calcium carbide as a
+commercial product became known.
+</p>
+
+<p>
+In the above year, Thomas L. Willson, an electrical engineer of Spray,
+North Carolina, was experimenting in an attempt to prepare metallic
+calcium, for which purpose he employed an electric furnace operating on a
+mixture of lime and coal tar with about ninety-five horse power. The result
+was a molten mass which became hard and brittle when cool. This apparently
+useless product was discarded and thrown in a nearby stream, when, to the
+astonishment of onlookers, a large volume of gas was immediately
+liberated, which, when ignited, burned with a bright and smoky flame and
+gave off quantities of soot. The solid material proved to be calcium
+carbide and the gas acetylene.
+</p>
+
+<p>
+Thus, through the incidental study of a by-product, and as the result of an
+accident, the possibilities in carbide were made known, and in the spring
+of 1895 the first factory in the world for the production of this substance
+was established by the Willson Aluminum Company.
+</p>
+
+<p>
+When water and calcium carbide are brought together an action takes place
+which results in the formation of acetylene gas and slaked lime.
+</p>
+
+<p>
+CARBIDE
+</p>
+
+<p>
+Calcium carbide is a chemical combination of the elements carbon and
+calcium, being dark brown, black or gray with sometimes a blue or red
+tinge. It looks like stone and will only burn when heated with oxygen.
+</p>
+
+<p>
+Calcium carbide may be preserved for any length of time if protected from
+the air, but the ordinary moisture in the atmosphere gradually affects it
+until nothing remains but slaked lime. It always possesses a penetrating
+odor, which is not due to the carbide itself but to the fact that it is
+being constantly affected by moisture and producing small quantities of
+acetylene gas.
+</p>
+
+<p>
+This material is not readily dissolved by liquids, but if allowed to come
+in contact with water, a decomposition takes place with the evolution of
+large quantities of gas. Carbide is not affected by shock, jarring or age.
+</p>
+
+<p>
+A pound of absolutely pure carbide will yield five and one-half cubic feet
+of acetylene. Absolute purity cannot be attained commercially, and in
+practice good carbide will produce from four and one-half to five cubic
+feet for each pound used.
+</p>
+
+<p>
+Carbide is prepared by fusing lime and carbon in the electric furnace under
+a heat in excess of 6,000 degrees Fahrenheit. These materials are among the
+most difficult to melt that are known. Lime is so infusible that it is
+frequently employed for the materials of crucibles in which the highest
+melting metals are fused, and for the pencils in the calcium light because
+it will stand extremely high temperatures.
+</p>
+
+<p>
+Carbon is the material employed in the manufacture of arc light electrodes
+and other electrical appliances that must stand extreme heat. Yet these two
+substances are forced into combination in the manufacture of calcium
+carbide. It is the excessively high temperature attainable in the electric
+furnace that causes this combination and not any effect of the electricity
+other than the heat produced.
+</p>
+
+<p>
+A mixture of ground coke and lime is introduced into the furnace through
+which an electric arc has been drawn. The materials unite and form an ingot
+of very pure carbide surrounded by a crust of less purity. The poorer crust
+is rejected in breaking up the mass into lumps which are graded according
+to their size. The largest size is 2 by 3-1/2 inches and is called "lump,"
+a medium size is 1/2 by 2 inches and is called "egg," an intermediate size
+for certain types of generators is 3/8 by 1-1/4 inches and called "nut,"
+and the finely crushed pieces for use in still other types of generators
+are 1/12 by 1/4 inch in size and are called "quarter." Instructions as to
+the size best suited to different generators are furnished by the makers
+of those instruments.
+</p>
+
+<p>
+These sizes are packed in air-tight sheet steel drums containing 100 pounds
+each. The Union Carbide Company of Chicago and New York, operating under
+patents, manufactures and distributes the supply of calcium carbide for the
+entire United States. Plants for this manufacture are established at
+Niagara Falls, New York, and Sault Ste. Marie, Michigan. This company
+maintains a system of warehouses in more than one hundred and ten cities,
+where large stocks of all sizes are carried.
+</p>
+
+<p>
+The National Board of Fire Underwriters gives the following rules for the
+storage of carbide:
+</p>
+
+<p>
+Calcium carbide in quantities not to exceed six hundred pounds may be
+stored, when contained in approved metal packages not to exceed one hundred
+pounds each, inside insured property, provided that the place of storage be
+dry, waterproof and well ventilated and also provided that all but one of
+the packages in any one building shall be sealed and that seals shall not
+be broken so long as there is carbide in excess of one pound in any other
+unsealed package in the building.
+</p>
+
+<p>
+Calcium carbide in quantities in excess of six hundred pounds must be
+stored above ground in detached buildings, used exclusively for the storage
+of calcium carbide, in approved metal packages, and such buildings shall be
+constructed to be dry, waterproof and well ventilated.
+</p>
+
+<p>
+<i>Properties of Acetylene.</i>--This gas is composed of twenty-four parts
+of carbon and two parts of hydrogen by weight and is classed with natural
+gas, petroleum, etc., as one of the hydrocarbons. This gas contains the
+highest percentage of carbon known to exist in any combination of this form
+and it may therefore be considered as gaseous carbon. Carbon is the fuel
+that is used in all forms of combustion and is present in all fuels from
+whatever source or in whatever form. Acetylene is therefore the most
+powerful of all fuel gases and is able to give to the torch flame in
+welding the highest temperature of any flame.
+</p>
+
+<p>
+Acetylene is a colorless and tasteless gas, possessed of a peculiar and
+penetrating odor. The least trace in the air of a room is easily noticed,
+and if this odor is detected about an apparatus in operation, it is certain
+to indicate a leakage of gas through faulty piping, open valves, broken
+hose or otherwise. This leakage must be prevented before proceeding with
+the work to be done.
+</p>
+
+<p>
+All gases which burn in air will, when mixed with air previous to ignition,
+produce more or less violent explosions, if fired. To this rule acetylene
+is no exception. One measure of acetylene and twelve and one-half of air
+are required for complete combustion; this is therefore the proportion for
+the most perfect explosion. This is not the only possible mixture that will
+explode, for all proportions from three to thirty per cent of acetylene in
+air will explode with more or less force if ignited.
+</p>
+
+<p>
+The igniting point of acetylene is lower than that of coal gas, being about
+900 degrees Fahrenheit as against eleven hundred degrees for coal gas. The
+gas issuing from a torch will ignite if allowed to play on the tip of a
+lighted cigar.
+</p>
+
+<p>
+It is still further true that acetylene, at some pressures, greater than
+normal, has under most favorable conditions for the effect, been found to
+explode; yet it may be stated with perfect confidence that under no
+circumstances has anyone ever secured an explosion in it when subjected to
+pressures not exceeding fifteen pounds to the square inch.
+</p>
+
+<p>
+Although not exploded by the application of high heat, acetylene is injured
+by such treatment. It is partly converted, by high heat, into other
+compounds, thus lessening the actual quantity of the gas, wasting it and
+polluting the rest by the introduction of substances which do not belong
+there. These compounds remain in part with the gas, causing it to burn with
+a persistent smoky flame and with the deposit of objectionable tarry
+substances. Where the gas is generated without undue rise of temperature
+these difficulties are avoided.
+</p>
+
+<p>
+<i>Purification of Acetylene.</i>--Impurities in this gas are caused by
+impurities in the calcium carbide from which it is made or by improper
+methods and lack of care in generation. Impurities from the material will
+be considered first.
+</p>
+
+<p>
+Impurities in the carbide may be further divided into two classes: those
+which exert no action on water and those which act with the water to throw
+off other gaseous products which remain in the acetylene. Those impurities
+which exert no action on the water consist of coke that has not been
+changed in the furnace and sand and some other substances which are
+harmless except that they increase the ash left after the acetylene has
+been generated.
+</p>
+
+<p>
+An analysis of the gas coming from a typical generator is as follows:
+</p>
+
+<pre>
+                                          Per cent
+  Acetylene ................................ 99.36
+  Oxygen ...................................   .08
+  Nitrogen .................................   .11
+  Hydrogen .................................   .06
+  Sulphuretted Hydrogen ....................   .17
+  Phosphoretted Hydrogen ...................   .04
+  Ammonia ..................................   .10
+  Silicon Hydride ..........................   .03
+  Carbon Monoxide ..........................   .01
+  Methane ..................................   .04
+</pre>
+
+<p>
+The oxygen, nitrogen, hydrogen, methane and carbon monoxide are either
+harmless or are present in such small quantities as to be neglected. The
+phosphoretted hydrogen and silicon hydride are self-inflammable gases when
+exposed to the air, but their quantity is so very small that this
+possibility may be dismissed. The ammonia and sulphuretted hydrogen are
+almost entirely dissolved by the water used in the gas generator. The
+surest way to avoid impure gas is to use high-grade calcium carbide in the
+generator and the carbide of American manufacture is now so pure that it
+never causes trouble.
+</p>
+
+<p>
+The first and most important purification to which the gas is subjected is
+its passage through the body of water in the generator as it bubbles to the
+top. It is then filtered through felt to remove the solid particles of lime
+dust and other impurities which float in the gas.
+</p>
+
+<p>
+Further purification to remove the remaining ammonia, sulphuretted hydrogen
+and phosphorus containing compounds is accomplished by chemical means. If
+this is considered necessary it can be easily accomplished by readily
+available purifying apparatus which can be attached to any generator or
+inserted between the generator and torch outlets. The following mixtures
+have been used.
+</p>
+
+<p>
+"<i>Heratol,</i>" a solution of chromic acid or sulphuric acid absorbed in
+porous earth.
+</p>
+
+<p>
+"<i>Acagine,</i>" a mixture of bleaching powder with fifteen per cent of
+lead chromate.
+</p>
+
+<p>
+"<i>Puratylene,</i>" a mixture of bleaching powder and hydroxide of lime,
+made very porous, and containing from eighteen to twenty per cent of active
+chlorine.
+</p>
+
+<p>
+"<i>Frankoline,</i>" a mixture of cuprous and ferric chlorides dissolved in
+strong hydrochloric acid absorbed in infusorial earth.
+</p>
+
+<p>
+A test for impure acetylene gas is made by placing a drop of ten per cent
+solution of silver nitrate on a white blotter and holding the paper in a
+stream of gas coming from the torch tip. Blackening of the paper in a short
+length of time indicates impurities.
+</p>
+
+<p>
+<i>Acetylene in Tanks.</i>--Acetylene is soluble in water to a very limited
+extent, too limited to be of practical use. There is only one liquid that
+possesses sufficient power of containing acetylene in solution to be of
+commercial value, this being the liquid acetone. Acetone is produced in
+various ways, oftentimes from the distillation of wood. It is a
+transparent, colorless liquid that flows with ease. It boils at 133°
+Fahrenheit, is inflammable and burns with a luminous flame. It has a
+peculiar but rather agreeable odor.
+</p>
+
+<p>
+Acetone dissolves twenty-four times its own bulk of acetylene at ordinary
+atmospheric pressure. If this pressure is increased to two atmospheres,
+14.7 pounds above ordinary pressure, it will dissolve just twice as much of
+the gas and for each atmosphere that the pressure is increased it will
+dissolve as much more.
+</p>
+
+<p>
+If acetylene be compressed above fifteen pounds per square inch at ordinary
+temperature without first being dissolved in acetone a danger is present of
+self-ignition. This danger, while practically nothing at fifteen pounds,
+increases with the pressure until at forty atmospheres it is very
+explosive. Mixed with acetone, the gas loses this dangerous property and is
+safe for handling and transportation. As acetylene is dissolved in the
+liquid the acetone increases its volume slightly so that when the gas has
+been drawn out of a closed tank a space is left full of free acetylene.
+</p>
+
+<p>
+This last difficulty is removed by first filling the cylinder or tank with
+some porous material, such as asbestos, wood charcoal, infusorial earth,
+etc. Asbestos is used in practice and by a system of packing and supporting
+the absorbent material no space is left for the free gas, even when the
+acetylene has been completely withdrawn.
+</p>
+
+<p>
+The acetylene is generated in the usual way and is washed, purified and
+dried. Great care is used to make the gas as free as possible from all
+impurities and from air. The gas is forced into containers filled with
+acetone as described and is compressed to one hundred and fifty pounds to
+the square inch. From these tanks it is transferred to the smaller portable
+cylinders for consumers' use.
+</p>
+
+<p>
+The exact volume of gas remaining in a cylinder at atmospheric temperature
+may be calculated if the weight of the cylinder empty is known. One pound
+of the gas occupies 13.6 cubic feet, so that if the difference in weight
+between the empty cylinder and the one considered be multiplied by 13.6.
+the result will be the number of cubic feet of gas contained.
+</p>
+
+<p>
+The cylinders contain from 100 to 500 cubic feet of acetylene under
+pressure. They cannot be filled with the ordinary type of generator as they
+require special purifying and compressing apparatus, which should never be
+installed in any building where other work is being carried on, or near
+other buildings which are occupied, because of the danger of explosion.
+</p>
+
+<p>
+Dissolved acetylene is manufactured by the Prest-O-Lite Company, the
+Commercial Acetylene Company and the Searchlight Gas Company and is
+distributed from warehouses in various cities.
+</p>
+
+<p>
+These tanks should not be discharged at a rate per hour greater than
+one-seventh of their total capacity, that is, from a tank of 100 cubic feet
+capacity, the discharge should not be more than fourteen cubic feet per
+hour. If discharge is carried on at an excessive rate the acetone is drawn
+out with the gas and reduces the heat of the welding flame.
+</p>
+
+<p>
+For this reason welding should not be attempted with cylinders designed for
+automobile and boat lighting. When the work demands a greater delivery than
+one of the larger tanks will give, two or more tanks may be connected with
+a special coupler such as may be secured from the makers and distributers
+of the gas. These couplers may be arranged for two, three, four or five
+tanks in one battery by removing the plugs on the body of the coupler and
+attaching additional connecting pipes. The coupler body carries a pressure
+gauge and the valve for controlling the pressure of the gas as it flows to
+the welding torches. The following capacities should be provided for:
+</p>
+
+<pre>
+Acetylene Consumption         Combined Capacity of
+ of Torches per Hour           Cylinders in Use
+Up to 15 feet.......................100 cubic feet
+16 to 30 feet.......................200 cubic feet
+31 to 45 feet.......................300 cubic feet
+46 to 60 feet.......................400 cubic feet
+61 to 75 feet.......................500 cubic feet
+</pre>
+
+<p>
+WELDING RODS
+</p>
+
+<p>
+The best welding cannot be done without using the best grade of materials,
+and the added cost of these materials over less desirable forms is so
+slight when compared to the quality of work performed and the waste of
+gases with inferior supplies, that it is very unprofitable to take any
+chances in this respect. The makers of welding equipment carry an
+assortment of supplies that have been standardized and that may be relied
+upon to produce the desired result when properly used. The safest plan is
+to secure this class of material from the makers.
+</p>
+
+<p>
+Welding rods, or welding sticks, are used to supply the additional metal
+required in the body of the weld to replace that broken or cut away and
+also to add to the joint whenever possible so that the work may have the
+same or greater strength than that found in the original piece. A rod of
+the same material as that being welded is used when both parts of the work
+are the same. When dissimilar metals are to be joined rods of a composition
+suited to the work are employed.
+</p>
+
+<p>
+These filling rods are required in all work except steel of less than 16
+gauge. Alloy iron rods are used for cast iron. These rods have a high
+silicon content, the silicon reacting with the carbon in the iron to
+produce a softer and more easily machined weld than would otherwise be the
+case. These rods are often made so that they melt at a slightly lower point
+than cast iron. This is done for the reason that when the part being welded
+has been brought to the fusing heat by the torch, the filling material can
+be instantly melted in without allowing the parts to cool. The metal can be
+added faster and more easily controlled.
+</p>
+
+<p>
+Rods or wires of Norway iron are used for steel welding in almost all
+cases. The purity of this grade of iron gives a homogeneous, soft weld of
+even texture, great ductility and exceptionally good machining qualities.
+For welding heavy steel castings, a rod of rolled carbon steel is employed.
+For working on high carbon steel, a rod of the steel being welded must be
+employed and for alloy steels, such as nickel, manganese, vanadium, etc.,
+special rods of suitable alloy composition are preferable.
+</p>
+
+<p>
+Aluminum welding rods are made from this metal alloyed to give the even
+flowing that is essential. Aluminum is one of the most difficult of all the
+metals to handle in this work and the selection of the proper rod is of
+great importance.
+</p>
+
+<p>
+Brass is filled with brass wire when in small castings and sheets. For
+general work with brass castings, manganese bronze or Tobin bronze may be
+used.
+</p>
+
+<p>
+Bronze is welded with manganese bronze or Tobin bronze, while copper is
+filled with copper wire.
+</p>
+
+<p>
+These welding rods should always be used to fill the weld when the
+thickness of material makes their employment necessary, and additional
+metal should always be added at the weld when possible as the joint cannot
+have the same strength as the original piece if made or dressed off flush
+with the surfaces around the weld. This is true because the metal welded
+into the joint is a casting and will never have more strength than a
+casting of the material used for filling.
+</p>
+
+<p>
+Great care should be exercised when adding metal from welding rods to make
+sure that no metal is added at a point that is not itself melted and molten
+when the addition is made. When molten metal is placed upon cooler surfaces
+the result is not a weld but merely a sticking together of the two parts
+without any strength in the joint.
+</p>
+
+<p>
+FLUXES
+</p>
+
+<p>
+Difficulty would be experienced in welding with only the metal and rod to
+work with because of the scale that forms on many materials under heat, the
+oxides of other metals and the impurities found in almost all metals. These
+things tend to prevent a perfect joining of the metals and some means are
+necessary to prevent their action.
+</p>
+
+<p>
+Various chemicals, usually in powder form, are used to accomplish the
+result of cleaning the weld and making the work of the operator less
+difficult. They are called fluxes.
+</p>
+
+<p>
+A flux is used to float off physical impurities from the molten metal; to
+furnish a protecting coating around the weld; to assist in the removal of
+any objectionable oxide of the metals being handled; to lower the
+temperature at which the materials flow; to make a cleaner weld and to
+produce a better quality of metal in the finished work.
+</p>
+
+<p>
+The flux must be of such composition that it will accomplish the desired
+result without introducing new difficulties. They may be prepared by the
+operator in many cases or may be secured from the makers of welding
+apparatus, the same remarks applying to their quality as were made
+regarding the welding rods, that is, only the best should be considered.
+</p>
+
+<p>
+The flux used for cast iron should have a softening effect and should
+prevent burning of the metal. In many cases it is possible and even
+preferable to weld cast iron without the use of a flux, and in any event
+the smaller the quantity used the better the result should be. Flux should
+not be added just before the completion of the work because the heat will
+not have time to drive the added elements out of the metal or to
+incorporate them with the metal properly.
+</p>
+
+<p>
+Aluminum should never be welded without using a flux because of the oxide
+formed. This oxide, called alumina, does not melt until a heat of 5,000°
+Fahrenheit is reached, four times the heat needed to melt the aluminum
+itself. It is necessary that this oxide be broken down or dissolved so that
+the aluminum may have a chance to flow together. Copper is another metal
+that requires a flux because of its rapid oxidation under heat.
+</p>
+
+<p>
+While the flux is often thrown or sprinkled along the break while welding,
+much better results will be obtained by dipping the hot end of the welding
+rod into the flux whenever the work needs it. Sufficient powder will stick
+on the end of the rod for all purposes, and with some fluxes too much will
+adhere. Care should always be used to avoid the application of excessive
+flux, as this is usually worse than using too little.
+
+</p>
+
+<p>
+SUPPLIES AND FIXTURES
+</p>
+
+<p>
+<i>Goggles.</i>--The oxy-acetylene torch should not be used without the
+protection to the eyes afforded by goggles. These not only relieve
+unnecessary strain, but make it much easier to watch the exact progress of
+the work with the molten metal. The difficulty of protecting the sight
+while welding is even greater than when cutting metal with the torch.
+</p>
+
+<p>
+Acetylene gives a light which is nearest to sunlight of any artificial
+illuminant. But for the fact that this gas light gives a little more green
+and less blue in its composition, it would be the same in quality and
+practically the same in intensity. This light from the gas is almost absent
+during welding, being lost with the addition of the extra oxygen needed to
+produce the welding heat. The light that is dangerous comes from the molten
+metal which flows under the torch at a bright white heat.
+</p>
+
+<p>
+Goggles for protection against this light and the heat that goes with it
+may be secured in various tints, the darker glass being for welding and
+the lighter for cutting. Those having frames in which the metal parts do
+not touch the flesh directly are most desirable because of the high
+temperature reached by these parts.
+</p>
+
+<p>
+<i>Gloves.</i>--While not as necessary as are the goggles, gloves are a
+convenience in many cases. Those in which leather touches the hands
+directly are really of little value as the heat that protection is desired
+against makes the leather so hot that nothing is gained in comfort. Gloves
+are made with asbestos cloth, which are not open to this objection in so
+great a degree.
+</p>
+
+<p class="ctr">
+<a href="images/054.png"><img src="images/054th.png" alt="Figure 9.--Frame for Welding Stand"></a>
+</p>
+
+<p>
+<i>Tables and Stands.</i>--Tables for holding work while being welded
+(Figure 9) are usually made from lengths of angle steel welded together.
+The top should be rectangular, about two feet wide and two and one-half
+feet long. The legs should support the working surface at a height of
+thirty-two to thirty-six inches from the floor. Metal lattice work may be
+fastened or laid in the top framework and used to support a layer of
+firebrick bound together with a mixture of one-third cement and two-thirds
+fireclay. The piece being welded is braced and supported on this table with
+pieces of firebrick so that it will remain stationary during the operation.
+</p>
+
+<p>
+Holders for supporting the tanks of gas may be
+made or purchased in forms that rest directly on the floor or that are
+mounted on wheels. These holders are quite useful where the floor or ground
+is very uneven.
+</p>
+
+<p>
+<i>Hose.</i>--All permanent lines from tanks and generators to the torches
+are made with piping rigidly supported, but the short distance from the end
+of the pipe line to the torch itself is completed with a flexible hose so
+that the operator may be free in his movements while welding. An accident
+through which the gases mix in the hose and are ignited will burst this
+part of the equipment, with more or less painful results to the person
+handling it. For that reason it is well to use hose with great enough
+strength to withstand excessive pressure.
+</p>
+
+<p>
+A poor grade of hose will also break down inside and clog the flow of gas,
+both through itself and through the parts of the torch. To avoid outside
+damage and cuts this hose is sometimes encased with coiled sheet metal.
+Hose may be secured with a bursting strength of more than 1,000 pounds to
+the square inch. Many operators prefer to distinguish between the oxygen
+and acetylene lines by their color and to allow this, red is used for the
+oxygen and black for acetylene.
+</p>
+
+<p>
+<i>Other Materials.</i>--Sheet asbestos and asbestos fibre in flakes are
+used to cover parts of the work while preparing them for welding and during
+the operation itself. The flakes and small pieces that become detached from
+the large sheets are thrown into a bin where the completed small work is
+placed to allow slow and even cooling while protected by the asbestos.
+</p>
+
+<p>
+Asbestos fibre and also ordinary fireclay are often used to make a backing
+or mould into a form that may be placed behind aluminum and some other
+metals that flow at a low heat and which are accordingly difficult to
+handle under ordinary methods. This forms a solid mould into which the
+metal is practically cast as melted by the torch so that the desired shape
+is secured without danger of the walls of metal breaking through and
+flowing away.
+</p>
+
+<p>
+Carbon blocks and rods are made in various shapes and sizes so that they
+may be used to fill threaded holes and other places that it is desired to
+protect during welding. These may be secured in rods of various diameters
+up to one inch and in blocks of several different dimensions.
+</p>
+
+<br>
+<br>
+<br>
+
+<h2><a name="iii">CHAPTER III</a></h2>
+
+<h3>ACETYLENE GENERATORS</h3>
+
+<p>
+Acetylene generators used for producing the gas from the action of water on
+calcium carbide are divided into three principal classes according to the
+pressure under which they operate.
+</p>
+
+<p>
+Low pressure generators are designed to operate at one pound or less per
+square inch. Medium pressure systems deliver the gas at not to exceed
+fifteen pounds to the square inch while high pressure types furnish gas
+above fifteen pounds per square inch. High pressure systems are almost
+unknown in this country, the medium pressure type being often referred to
+as "high pressure."
+</p>
+
+<p>
+Another important distinction is formed by the method of bringing the
+carbide and water together. The majority of those now in use operate by
+dropping small quantities of carbide into a large volume of water, allowing
+the generated gas to bubble up through the water before being collected
+above the surface. This type is known as the "carbide to water" generator.
+</p>
+
+<p>
+A less used type brings a measured and small quantity of water to a
+comparatively large body of the carbide, the gas being formed and collected
+from the chamber in which the action takes place. This is called the "water
+to carbide" type. Another way of expressing the difference in feed is that
+of designating the two types as "carbide feed" for the former and "water
+feed" for the latter.
+</p>
+
+<p>
+A further division of the carbide to water machines is made by mentioning
+the exact method of feeding the carbide. One type, called "gravity feed"
+operates by allowing the carbide to escape and fall by the action of its
+own weight, or gravity; the other type, called "forced feed," includes a
+separate mechanism driven by power. This mechanism feeds definite amounts
+of the carbide to the water as required by the demands on the generator.
+The action of either feed is controlled by the withdrawal of gas from the
+generator, the aim being to supply sufficient carbide to maintain a nearly
+constant supply.
+</p>
+
+<p>
+<i>Generator Requirements.</i>--The qualities of a good generator are
+outlined as follows: [Footnote: See Pond's "Calcium Carbide and
+Acetylene."]
+</p>
+
+<p>
+It must allow no possibility of the existence of an explosive mixture in
+any of its parts at any time. It is not enough to argue that a mixture,
+even if it exists, cannot be exploded unless kindled. It is necessary to
+demand that a dangerous mixture can at no time be formed, even if the
+machine is tampered with by an ignorant person. The perfect machine must be
+so constructed that it shall be impossible at any time, under any
+circumstances, to blow it up.
+</p>
+
+<p>
+It must insure cool generation. Since this is a relative term, all machines
+being heated somewhat during the generation of gas, this amounts to saying
+that a machine must heat but little. A pound of carbide decomposed by water
+develops the same amount of heat under all circumstances, but that heat
+can be allowed to increase locally to a high point, or it can be equalized
+by water so that no part of the material becomes heated enough to do
+damage.
+</p>
+
+<p>
+It must be well constructed. A good generator does not need, perhaps, to be
+"built like a watch," but it should be solid, substantial and of good
+material. It should be built for service, to last and not simply to sell;
+anything short of this is to be avoided as unsafe and unreliable.
+</p>
+
+<p>
+It must be simple. The more complicated the machine the sooner it will get
+out of order. Understand your generator. Know what is inside of it and
+beware of an apparatus, however attractive its exterior, whose interior is
+filled with pipes and tubes, valves and diaphragms whose functions you do
+not perfectly understand.
+</p>
+
+<p>
+It should be capable of being cleaned and recharged and of receiving all
+other necessary attention without loss of gas, both for economy's sake, and
+more particularly to avoid danger of fire.
+</p>
+
+<p>
+It should require little attention. All machines have to be emptied and
+recharged periodically; but the more this process is simplified and the
+more quickly this can be accomplished, the better.
+</p>
+
+<p>
+It should be provided with a suitable indicator to designate how low the
+charge is in order that the refilling may be done in good season.
+</p>
+
+<p>
+It should completely use up the carbide, generating the maximum amount of
+gas.
+</p>
+
+<p>
+<i>Overheating.</i>--A large amount of heat is liberated when acetylene gas
+is formed from the union of calcium carbide and water. Overheating during
+this process, that is to say, an intense local heat rather than a large
+amount of heat well distributed, brings about the phenomenon of
+polymerization, converting the gas, or part of it, into oily matters, which
+can do nothing but harm. This tarry mass coming through the small openings
+in the torches causes them to become partly closed and alters the
+proportions of the gases to the detriment of the welding flame. The only
+remedy for this trouble is to avoid its cause and secure cool generation.
+</p>
+
+<p>
+Overheating can be detected by the appearance of the sludge remaining after
+the gas has been made. Discoloration, yellow or brown, shows that there has
+been trouble in this direction and the resultant effects at the torches may
+be looked for. The abundance of water in the carbide to water machines
+effects this cooling naturally and is a characteristic of well designed
+machines of this class. It has been found best and has practically become a
+fundamental rule of generation that a gallon of water must be provided for
+each pound of carbide placed in the generator. With this ratio and a
+generator large enough for the number of torches to be supplied, little
+trouble need be looked for with overheating.
+</p>
+
+<p>
+<i>Water to Carbide Generators.</i>--It is, of course, much easier to
+obtain a measured and regular flow of water than to obtain such a flow of
+any solid substance, especially when the solid substance is in the form of
+lumps, as is carbide This fact led to the use of a great many water-feed
+generators for all classes of work, and this type is still in common use
+for the small portable machines, such, for instance, as those used on motor
+cars for the lamps. The water-feed machine is not, however, favored for
+welding plants, as is the carbide feed, in spite of the greater
+difficulties attending the handling of the solid material.
+</p>
+
+<p>
+A water-feed generator is made up of the gas producing part and a holder
+for the acetylene after it is made. The carbide is held in a tray formed of
+a number of small compartments so that the charge in each compartment is
+nearly equal to that in each of the others. The water is allowed to flow
+into one of these compartments in a volume sufficient to produce the
+desired amount of gas and the carbide is completely used from this one
+division. The water then floods the first compartment and finally overflows
+into the next one, where the same process is repeated. After using the
+carbide in this division, it is flooded in turn and the water passing on to
+those next in order, uses the entire charge of the whole tray.
+</p>
+
+<p>
+These generators are charged with the larger sizes of carbide and are
+easily taken care of. The residue is removed in the tray and emptied,
+making the generator ready for a fresh supply of carbide.
+</p>
+
+<p>
+<i>Carbide to Water Generators.</i>--This type also is made up of two
+principal parts, the generating chamber and a gas holder, the holder being
+part of the generating chamber or a separate device. The generator (Figure
+10) contains a hopper to receive the charge of carbide and is fitted with
+the feeding mechanism to drop the proper amount of carbide into the water
+as required by the demands of the torches. The charge of carbide is of one
+of the smaller sizes, usually "nut" or "quarter."
+</p>
+
+<p>
+<i>Feed Mechanisms.</i>--The device for dropping the carbide into the water
+is the only part of the machine that is at all complicated. This
+complication is brought about by the necessity of controlling the mass of
+carbide so that it can never be discharged into the water at an excessive
+rate, feeding it at a regular rate and in definite amounts, feeding it
+positively whenever required and shutting off the feed just as positively
+when the supply of gas in the holder is enough for the immediate needs.
+</p>
+
+<p class="ctr">
+<a href="images/062.png"><img src="images/062th.png" alt="Figure 10--Carbide to Water Generator"></a>
+</p>
+
+<p>
+The charge of carbide is unavoidably acted upon by the water vapor in the
+generator and will in time become more or less pasty and sticky. This is
+more noticeable if the generator stands idle for a considerable length of
+time This condition imposes another duty on the feeding mechanism; that is,
+the necessity of self-cleaning so that the carbide, no matter in what
+condition, cannot prevent the positive action of this part of the device,
+especially so that it cannot prevent the supply from being stopped at the
+proper time.
+</p>
+
+<p>
+The gas holder is usually made in the bell form so that the upper portion
+rises and falls with the addition to or withdrawal from the supply of gas
+in the holder. The rise and fall of this bell is often used to control the
+feed mechanism because this movement indicates positively whether enough
+gas has been made or that more is required. As the bell lowers it sets the
+feed mechanism in motion, and when the gas passing into the holder has
+raised the bell a sufficient distance, the movement causes the feed
+mechanism to stop the fall of carbide into the water. In practice, the
+movement of this part of the holder is held within very narrow limits.
+</p>
+
+<p>
+<i>Gas Holders.</i>--No matter how close the adjustment of the feeding
+device, there will always be a slight amount of gas made after the fall of
+carbide is stopped, this being caused by the evolution of gas from the
+carbide with which water is already in contact. This action is called
+"after generation" and the gas holder in any type of generator must
+provide sufficient capacity to accommodate this excess gas. As a general
+rule the water to carbide generator requires a larger gas holder than the
+carbide to water type because of the greater amount of carbide being acted
+upon by the water at any one time, also because the surface of carbide
+presented to the moist air within the generating chamber is greater with
+this type.
+</p>
+
+<p>
+<i>Freezing.</i>--Because of the rather large body of water contained in
+any type of generator, there is always danger of its freezing and
+rendering the device inoperative unless placed in a temperature above the
+freezing point of the water. It is, of course, dangerous and against the
+insurance rules to place a generator in the same room with a fire of any
+kind, but the room may be heated by steam or hot water coils from a furnace
+in another building or in another part of the same building.
+</p>
+
+<p>
+When the generator is housed in a separate structure the walls should be
+made of materials or construction that prevents the passage of heat or
+cold through them to any great extent. This may be accomplished by the use
+of hollow tile or concrete blocks or by any other form of double wall
+providing air spaces between the outer and inner facings. The space between
+the parts of the wall may be filled with materials that further retard the
+loss of heat if this is necessary under the conditions prevailing.
+</p>
+
+<p>
+<i>Residue From Generators.</i>--The sludge remaining in the carbide to
+water generator may be drawn off into the sewer if the piping is run at a
+slant great enough to give a fall that carries the whole quantity, both
+water and ash, away without allowing settling and consequent clogging.
+Generators are provided with agitators which are operated to stir the ash
+up with the water so that the whole mass is carried off when the drain cock
+is opened.
+</p>
+
+<p>
+If sewer connections cannot be made in such a way that the ash is entirely
+carried away, it is best to run the liquid mass into a settling basin
+outside of the building. This should be in the form of a shallow pit which
+will allow the water to pass off by soaking into the ground and by
+evaporation, leaving the comparatively dry ash in the pit. This ash which
+remains is essentially slaked lime and can often be disposed of to more or
+less advantage to be used in mortar, whitewash, marking paths and any other
+use for which slaked lime is suited. The disposition of the ash depends
+entirely on local conditions. An average analysis of this ash is as
+follows:
+</p>
+
+<pre>
+Sand.......................  1.10 per cent.
+Carbon.....................  2.72    "
+Oxide of iron and alumina..  2.77    "
+Lime....................... 64.06    "
+Water and carbonic acid.... 29.35    "
+                           ------
+                           100.00
+</pre>
+
+<p>
+GENERATOR CONSTRUCTION
+</p>
+
+<p>
+The water for generating purposes is carried in the large tank-like
+compartment directly below the carbide chamber. See Figure 11. This water
+compartment is filled through a pipe of such a height that the water level
+cannot be brought above the proper point or else the water compartment is
+provided with a drain connection which accomplishes this same result by
+allowing an excess to flow away.
+</p>
+
+<p>
+The quantity of water depends on the capacity of the generator inasmuch as
+there must be one gallon for each pound of carbide required. The generator
+should be of sufficient capacity to furnish gas under working conditions
+from one charge of carbide to all torches installed for at least five hours
+continuous use.
+</p>
+
+<p>
+After calculating the withdrawal of the whole number of torches according
+to the work they are to do for this period of five hours the proper
+generator capacity may be found on the basis of one cubic foot of gas per
+hour for each pound of carbide. Thus if the torches were to use sixty cubic
+feet of gas per hour, five hours would call for three hundred cubic feet
+and a three hundred pound generator should be installed. Generators are
+rated according to their carbide capacity in pounds.
+</p>
+
+<p>
+<i>Charging.</i>--The carbide capacity of the generator should be great
+enough to furnish a continuous supply of gas for the maximum operating
+time, basing the quantity of gas generated on four and one-half cubic feet
+from each pound of lump carbide and on four cubic feet from each pound of
+quarter, intermediate sizes being in proportion.
+</p>
+
+<p>
+Generators are built in such a way that it is impossible for the acetylene
+to escape from the gas holding compartment during the recharging process.
+This is accomplished (1) by connecting the water inlet pipe opening with a
+shut off valve in such a way that the inlet cannot be uncovered or opened
+without first closing the shut off valve with the same movement of the
+operator; (2) by incorporating an automatic or hydraulic one-way valve so
+that this valve closes and acts as a check when the gas attempts to flow
+from the holder back to the generating chamber, or by any other means that
+will positively accomplish this result.
+</p>
+
+<p>
+In generators having no separate gas holding chamber but carrying the
+supply in the same compartment in which it is generated, the gas contained
+under pressure is allowed to escape through vent pipes into the outside
+air before recharging with carbide. As in the former case, the parts are
+so interlocked that it is impossible to introduce carbide or water without
+first allowing the escape of the gas in the generator.
+</p>
+
+<p>
+It is required by the insurance rules that the entire change of carbide
+while in the generator be held in such a way that it may be entirely
+removed without difficulty in case the necessity should arise.
+</p>
+
+<p>
+Generators should be cleaned and recharged at regular stated intervals.
+This work should be done during daylight hours only and likewise all
+repairs should be made at such a time that artificial light is not needed.
+Where it is absolutely necessary to use artificial light it should be
+provided only by incandescent electric lamps enclosed in gas tight globes.
+</p>
+
+<p>
+In charging generating chambers the old ash and all residue must first be
+cleaned out and the operator should be sure that no drain or other pipe has
+become clogged. The generator should then be filled with the required
+amount of water. In charging carbide feed machines be careful not to place
+less than a gallon of water in the water compartment for each pound of
+carbide to be used and the water must be brought to, but not above, the
+proper level as indicated by the mark or the maker's instructions. The
+generating chamber must be filled with the proper amount of water before
+any attempt is made to place the carbide in its holder. This rule must
+always be followed. It is also necessary that all automatic water seals
+and valves, as well as any other water tanks, be filled with clean water
+at this time.
+</p>
+
+<p>
+Never recharge with carbide without first cleaning the generating chamber
+and completely refilling with clean water. Never test the generator or
+piping for leaks with any flame, and never apply flame to any open pipe or
+at any point other than the torch, and only to the torch after it has a
+welding or cutting nozzle attached. Never use a lighted match, lamp,
+candle, lantern, cigar or any open flame near a generator. Failure to
+observe these precautions is liable to endanger life and property.
+</p>
+
+<p>
+<i>Operation and Care of Generators.</i>--The following instructions apply
+especially to the Davis Bournonville pressure generator, illustrated in
+Figure 11. The motor feed mechanism is illustrated in Figure 12.
+</p>
+
+<p>
+Before filling the machine, the cover should be removed and the hopper
+taken out and examined to see that the feeding disc revolves freely; that
+no chains have been displaced or broken, and that the carbide displacer
+itself hangs barely free of the feeding disc when it is revolved. After
+replacing the cover, replace the bolts and tighten them equally, a little
+at a time all around the circumference of the cover--not screwing tight in
+one place only. Do not screw the cover down any more than is necessary to
+make a tight fit.
+</p>
+
+<p>
+To charge the generator, proceed as follows: Open the vent valve by turning
+the handle which extends over the filling tube until it stands at a right
+angle with the generator. Open the valve in the water filling pipe, and
+through this fill with water until it runs out of the overflow pipe of the
+drainage chamber, then close the valve in the water filling pipe and vent
+valve. Remove the carbide filling plugs and fill the hopper with
+1-1/4"x3/8" carbide ("nut" size). Then replace the plugs and the
+safety-locking lever chains. Now rewind the motor weight. Run the pressure
+up to about five pounds by raising the controlling diaphragm valve lever
+by hand (Figure 12, lever marked <i>E</i>). Then raise the blow-off lever,
+allowing the gas to blow off until the gauge shows about two pounds; this
+to clear the generator of air mixture. Then run the pressure up to about
+eight pounds by raising the controlling valve lever <i>E</i>, or until
+this controlling lever rests against the upper wing of the fan governor,
+and prevents operation of the feed motor. After this is done, the motor
+will operate automatically as the gas is consumed.
+</p>
+
+<p class="ctr">
+<a href="images/069.png"><img src="images/069th.png" alt="Figure 11.--Pressure Generator (Davis Bournonville)"></a>
+</p>
+
+<p class="ctr">
+<a href="images/070.png"><img src="images/070th.png" alt="Figure 12.--Feed Mechanism of Pressure Generator"></a>
+</p>
+
+<p>
+Should the pressure rise much above the blow-off point, the safety
+controlling diaphragm valve will operate and throw the safety clutch in
+interference and thus stop the motor. This interference clutch will then
+have to be returned to its former position before the motor will operate,
+but cannot be replaced before the pressure has been reduced below the
+blow-off point.
+</p>
+
+<p>
+The parts of the feed mechanism illustrated in Figure 12 are as follows:
+<i>A</i>, motor drum for weight cable. <i>B</i>, carbide filling plugs.
+<i>C</i>, chains for connecting safety locking lever of motor to pins on
+the top of the carbide plugs. <i>D</i>, interference clutch of motor.
+<i>E</i>, lever on feed controlling diaphragm valve. <i>F</i>, lever of
+interference controlling diaphragm valve that operates interference clutch.
+<i>G</i>, feed controlling diaphragm valve. <i>H</i>, diaphragm valve
+controlling operation of interference clutch. <i>I</i>, interference pin
+to engage emergency clutch. <i>J</i>, main shaft driving carbide feeding
+disc. <i>Y</i>, safety locking lever.
+
+<i>Recharging Generator.</i>--Turn the agitator handle rapidly for several
+revolutions, and then open the residuum valve, having five or six pounds
+gas pressure on the machine. If the carbide charge has been exhausted and
+the motor has stopped, there is generally enough carbide remaining in the
+feeding disc that can be shaken off, and fed by running the motor to
+obtain some pressure in the generator. The desirability of discharging
+the residuum with some gas pressure is because the pressure facilitates
+the discharge and at the same time keeps the generator full of gas,
+preventing air mixture to a great extent. As soon as the pressure is
+relieved by the withdrawal of the residuum, the vent valve should be
+opened, as if the pressure is maintained until all of the residuum is
+discharged gas would escape through the discharge valve.
+</p>
+
+<p>
+Having opened the vent pipe valve and relieved the pressure, open the
+valve in the water filling tube. Close the residuum valve, then run in
+several gallons of water and revolve the agitator, after which draw out the
+remaining residuum; then again close the residuum valve and pour in water
+until it discharges from the overflow pipe of the drainage chamber. It is
+desirable in filling the generator to pour the water in rapidly enough to
+keep the filling pipe full of water, so that air will not pass in at the
+same time.
+</p>
+
+<p>
+After the generator is cleaned and filled with water, fill with carbide and
+proceed in the same manner as when first charging.
+</p>
+
+<p>
+<i>Carbide Feed Mechanism.</i>--Any form of carbide to water machine should
+be so designed that the carbide never falls directly from its holder into
+the water, but so that it must take a more or less circuitous path. This
+should be true, no matter what position the mechanism is in. One of the
+commonest types of forced feed machine carries the carbide in a hopper with
+slanting sides, this hopper having a large opening in the bottom through
+which the carbide passes to a revolving circular plate. As the pieces of
+carbide work out toward the edge of the plate under the influence of the
+mass behind them, they are thrown off into the water by small stationary
+fins or plows which are in such a position that they catch the pieces
+nearest the edges and force them off as the plate revolves. This
+arrangement, while allowing a free passage for the carbide, prevents an
+excess from falling should the machine stop in any position.
+</p>
+
+<p>
+When, as is usually the case, the feed mechanism is actuated by the rise
+or fall of pressure in the generator or of the level of some part of the
+gas holder, it must be built in such a way that the feeding remains
+inoperative as long as the filling opening on the carbide holder remains
+open.
+</p>
+
+<p>
+The feed of carbide should always be shut off and controlled so that under
+no condition can more gas be generated than could be cared for by the
+relief valve provided. It is necessary also to have the feed mechanism at
+least ten inches above the surface of the water so that the parts will
+never become clogged with damp lime dust.
+</p>
+
+<p>
+<i>Motor Feed.</i>--The feed mechanism itself is usually operated by power
+secured from a slowly falling weight which, through a cable, revolves a
+drum. To this drum is attached suitable gearing for moving the feed parts
+with sufficient power and in the way desired. This part, called the motor,
+is controlled by two levers, one releasing a brake and allowing the motor
+to operate the feed, the other locking the gearing so that no more carbide
+will be dropped into the water. These levers are moved either by the
+quantity of gas in the holder or by the pressure of the gas, depending on
+the type of machine.
+</p>
+
+<p>
+With a separate gas holder, such as used with low pressure systems, the
+levers are operated by the rise and fall of the bell of the holder or
+gasometer, alternately starting and stopping the motor as the bell falls
+and rises again. Medium pressure generators are provided with a diaphragm
+to control the feed motor.
+</p>
+
+<p>
+This diaphragm is carried so that the pressure within the generator acts
+on one side while a spring, whose tension is under the control of the
+operator, acts on the other side. The diaphragm is connected to the brake
+and locking device on the motor in such a way that increasing the tension
+on the spring presses the diaphragm and moves a rod that releases the brake
+and starts the feed. The gas pressure, increasing with the continuation of
+carbide feed, acts on the other side and finally overcomes the pressure of
+the spring tension, moving the control rod the other way and stopping the
+motor and carbide feed. This spring tension is adjusted and checked with
+the help of a pressure gauge attached to the generating chamber.
+</p>
+
+<p>
+<i>Gravity Feed.</i>--This type of feed differs from the foregoing in that
+the carbide is simply released and is allowed to fall into the water
+without being forced to do so. Any form of valve that is sufficiently
+powerful in action to close with the carbide passing through is used and is
+operated by the power secured from the rise and fall of the gas holder
+bell. When this valve is first opened the carbide runs into the water until
+sufficient pressure and volume of gas is generated to raise the bell. This
+movement operates the arm attached to the carbide shut off valve and slowly
+closes it. A fall of the bell occasioned by gas being withdrawn again opens
+the valve and more gas is generated.
+</p>
+
+<p>
+<i>Mechanical Feed.</i>--The previously described methods of feeding
+carbide to the water have all been automatic in action and do not depend
+on the operator for their proper action.
+</p>
+
+<p>
+Some types of large generating plants have a power-driven feed, the power
+usually being from some kind of motor other than one operated by a weight,
+such as a water motor, for instance. This motor is started and stopped by
+the operator when, in his judgment, more gas is wanted or enough has been
+generated. This type of machine, often called a "non-automatic generator,"
+is suitable for large installations and is attached to a gas holder of
+sufficient size to hold a day's supply of acetylene. The generator can then
+be operated until a quantity of gas has been made that will fill the large
+holder, or gasometer, and then allowed to remain idle for some time.
+</p>
+
+<p>
+<i>Gas Holders.</i>--The commonest type of gas container is that known as a
+gasometer. This consists of a circular tank partly filled with water, into
+which is lowered another circular tank, inverted, which is made enough
+smaller in diameter than the first one so that three-quarters of an inch is
+left between them. This upper and inverted portion, called the bell,
+receives the gas from the generator and rises or falls in the bath of water
+provided in the lower tank as a greater or less amount of gas is contained
+in it.
+</p>
+
+<p>
+These holders are made large enough so that they will provide a means of
+caring for any after generation and so that they maintain a steady and even
+flow. The generator, however, must be of a capacity great enough so that
+the gas holder will not be drawn on for part of the supply with all torches
+in operation. That is, the holder must not be depended on for a reserve
+supply.
+</p>
+
+<p>
+The bell of the holder is made so that when full of gas its lower edge is
+still under a depth of at least nine inches of water in the lower tank. Any
+further rise beyond this point should always release the gas, or at least
+part of it, to the escape pipe so that the gas will under no circumstances
+be forced into the room from, between the bell and tank. The bell is guided
+in its rise and fall by vertical rods so that it will not wedge at any
+point in its travel.
+</p>
+
+<p>
+A condensing chamber to receive the water which condenses from the
+acetylene gas in the holder is usually placed under this part and is
+provided with a drain so that this water of condensation may be easily
+removed.
+</p>
+
+<p>
+<i>Filtering.</i>--A small chamber containing some closely packed but
+porous material such as felt is placed in the pipe leading to the torch
+lines. As the acetylene gas passes through this filter the particles of
+lime dust and other impurities are extracted from it so that danger of
+clogging the torch openings is avoided as much as possible.
+</p>
+
+<p>
+The gas is also filtered to a large extent by its passage through the water
+in the generating chamber, this filtering or "scrubbing" often being
+facilitated by the form of piping through which the gas must pass from the
+generating chamber into the holder. If the gas passes out of a number of
+small openings when going into the holder the small bubbles give a better
+washing than large ones would.
+</p>
+
+<p>
+<i>Piping.</i>--Connections from generators to service pipes should
+preferably be made with right and left couplings or long thread nipples
+with lock nuts. If unions are used, they should be of a type that does not
+require gaskets. The piping should be carried and supported so that any
+moisture condensing in the lines will drain back toward the generator and
+where low points occur they should be drained through tees leading into
+drip cups which are permanently closed with screw caps or plugs. No pet
+cocks should be used for this purpose.
+</p>
+
+<p>
+For the feed pipes to the torch lines the following pipe sizes are
+recommended.
+</p>
+
+<pre>
+    3/8 inch pipe.  26 feet long.   2 cubic feet per hour.
+    1/2 inch pipe.  30 feet long.   4 cubic feet per hour.
+    3/4 inch pipe.  50 feet long.  15 cubic feet per hour.
+  1     inch pipe.  70 feet long.  27 cubic feet per hour.
+  1-1/4 inch pipe. 100 feet long.  50 cubic feet per hour.
+  1-1/2 inch pipe. 150 feet long.  65 cubic feet per hour.
+  2     inch pipe. 200 feet long. 125 cubic feet per hour.
+  2-1/2 inch pipe. 300 feet long. 190 cubic feet per hour.
+  3     inch pipe. 450 feet long. 335 cubic feet per hour.
+</pre>
+
+<p>
+When drainage is possible into a sewer, the generator should not be
+connected directly into the sewer but should first discharge into an open
+receptacle, which may in turn be connected to the sewer.
+</p>
+
+<p>
+No valves or pet cocks should open into the generator room or any other
+room when it would be possible, by opening them for draining purposes, to
+allow any escape of gas. Any condensation must be removed without the use
+of valves or other working parts, being drained into closed receptacles. It
+should be needless to say that all the piping for gas must be perfectly
+tight at every point in its length.
+</p>
+
+<p>
+<i>Safety Devices.</i>--Good generators are built in such a way that the
+operator must follow the proper order of operation in charging and cleaning
+as well as in all other necessary care. It has been mentioned that the gas
+pressure is released or shut off before it is possible to fill the water
+compartment, and this same idea is carried further in making the generator
+inoperative and free from gas pressure before opening the residue drain of
+the carbide filling opening on top of the hopper. Some machines are made so
+that they automatically cease to generate should there be a sudden and
+abnormal withdrawal of gas such as would be caused by a bad leak. This
+method of adding safety by automatic means and interlocking parts may be
+carried to any extent that seems desirable or necessary to the maker.
+</p>
+
+<p>
+All generators should be provided with escape or relief pipes of large size
+which lead to the open air. These pipes are carried so that condensation
+will drain back toward the generator and after being led out of the
+building to a point at least twelve feet above ground, they end in a
+protecting hood so that no rain or solid matter can find its way into them.
+Any escape of gas which might ordinarily pass into the generator room is
+led into these escape pipes, all parts of the system being connected with
+the pipe so that the gas will find this way out.
+</p>
+
+<p>
+Safety blow off valves are provided so that any excess gas which cannot be
+contained by the gas holder may be allowed to escape without causing an
+undue rise in pressure. This valve also allows the escape of pressure above
+that for which the generator was designed. Gas released in this way passes
+into the escape pipe just described.
+</p>
+
+<p>
+Inasmuch as the pressure of the oxygen is much greater than that of the
+acetylene when used in the torch, it will be seen that anything that caused
+the torch outlet to become closed would allow the oxygen to force the
+acetylene back into the generator and the oxygen would follow it, making a
+very explosive mixture. This return of the gas is prevented by a hydraulic
+safety valve or back pressure valve, as it is often called.
+</p>
+
+<p>
+Mechanical check valves have been found unsuitable for this use and those
+which employ water as a seal are now required by the insurance rules. The
+valve itself (Figure 13) consists of a large cylinder containing water to a
+certain depth, which is indicated on the valve body. Two pipes come into
+the upper end of this cylinder and lead down into the water, one being
+longer than the other. The shorter pipe leads to the escape pipe mentioned
+above, while the longer one comes from the generator. The upper end of the
+cylinder has an opening to which is attached the pipe leading to the
+torches.
+</p>
+
+<p class="ctr">
+<a href="images/079.png"><img src="images/079th.png" alt="Figure 13.--Hydraulic Back-Pressure Valve"></a>
+</p>
+
+<p>
+The gas coming from the generator through the longer pipe passes out of the
+lower end of the pipe which is under water and bubbles up through the water
+to the space in the top of the cylinder. From there the gas goes to the
+pipe leading to the torches. The shorter pipe is closed by the depth of
+water so that the gas does not escape to the relief pipe. As long as the
+gas flows in the normal direction as described there will be no escape to
+the air. Should the gas in the torch line return into the hydraulic valve
+its pressure will lower the level of water in the cylinder by forcing some
+of the liquid up into the two pipes. As the level of the water lowers, the
+shorter pipe will be uncovered first, and as this is the pipe leading to
+the open air the gas will be allowed to escape, while the pipe leading back
+to the generator is still closed by the water seal. As soon as this reverse
+flow ceases, the water will again resume its level and the action will
+continue. Because of the small amount of water blown out of the escape pipe
+each time the valve is called upon to perform this duty, it is necessary to
+see that the correct water level is always maintained.
+</p>
+
+<p>
+While there are modifications of this construction, the same principle is
+used in all types. The pressure escape valve is often attached to this
+hydraulic valve body.
+</p>
+
+<p>
+<i>Construction Details.</i>--Flexible tubing (except at torches), swing
+pipe joints, springs, mechanical check valves, chains, pulleys and lead or
+fusible piping should never be used on acetylene apparatus except where the
+failure of those parts will not affect the safety of the machine or permit,
+either directly or indirectly, the escape of gas into a room. Floats should
+not be used except where failure will only render the machine inoperative.
+</p>
+
+<p>
+It should be said that the National Board of Fire Underwriters have
+established an inspection service for acetylene generators and any
+apparatus which bears their label, stating that that particular model and
+type has been passed, is safe to use. This service is for the best
+interests of all concerned and looks toward the prevention of accidents.
+Such inspection is a very important and desirable feature of any outfit and
+should be insisted upon.
+</p>
+
+<p>
+<i>Location of Generators.</i>--Generators should preferably be placed
+outside of insured buildings and in properly constructed generator houses.
+The operating mechanism should have ample room to work in and there should
+be room enough for the attendant to reach the various parts and perform the
+required duties without hindrance or the need of artificial light. They
+should also be protected from tampering by unauthorized persons.
+</p>
+
+<p>
+Generator houses should not be within five feet of any opening into, nor
+have any opening toward, any adjacent building, and should be kept under
+lock and key. The size of the house should be no greater than called for by
+the requirements mentioned above and it should be well ventilated.
+</p>
+
+<p>
+The foundation for the generator itself should be of brick, stone, concrete
+or iron, if possible. If of wood, they should be extra heavy, located in a
+dry place and open to circulation of air. A board platform is not
+satisfactory, but the foundation should be of heavy planking or timber to
+make a firm base and so that the air can circulate around the wood.
+</p>
+
+<p>
+The generator should stand level and no strain should be placed on any of
+the pipes or connections or any parts of the generator proper.
+</p>
+
+<p>
+
+</p>
+
+<h2><a name="iv">CHAPTER IV</a></h2>
+
+<h3>WELDING INSTRUMENTS</h3>
+
+<p>
+VALVES
+</p>
+
+<p>
+<i>Tank Valves.</i>--The acetylene tank valve is of the needle type, fitted
+with suitable stuffing box nuts and ending in an exposed square shank to
+which the special wrench may be fitted when the valve is to be opened or
+closed.
+</p>
+
+<p>
+The valve used on Linde oxygen cylinders is also a needle type, but of
+slightly more complex construction. The body of the valve, which screws
+into the top of the cylinder, has an opening below through which the gas
+comes from the cylinder, and another opening on the side through which it
+issues to the torch line. A needle screws down from above to close this
+lower opening. The needle which closes the valve is not connected directly
+to the threaded member, but fits loosely into it. The threaded part is
+turned by a small hand wheel attached to the upper end. When this hand
+wheel is turned to the left, or up, as far as it will go, opening the
+valve, a rubber disc is compressed inside of the valve body and this disc
+serves to prevent leakage of the gas around the spindle.
+</p>
+
+<p>
+The oxygen valve also includes a safety nut having a small hole through it
+closed by a fusible metal which melts at 250° Fahrenheit. Melting of this
+plug allows the gas to exert its pressure against a thin copper diaphragm,
+this diaphragm bursting under the gas pressure and allowing the oxygen to
+escape into the air.
+</p>
+
+<p>
+The hand wheel and upper end of the valve mechanism are protected during
+shipment by a large steel cap which covers them when screwed on to the end
+of the cylinder. This cap should always be in place when tanks are received
+from the makers or returned to them.
+</p>
+
+<p class="ctr">
+<a href="images/083.png"><img src="images/083th.png" alt="Figure 14.--Regulating Valve"></a>
+</p>
+
+<p>
+<i>Regulating Valves.</i>--While the pressure in the gas containers may be
+anything from zero to 1,800 pounds, and will vary as the gas is withdrawn,
+the pressure of the gas admitted to the torch must be held steady and at a
+definite point. This is accomplished by various forms of automatic
+regulating valves, which, while they differ somewhat in details of
+construction, all operate on the same principle.
+</p>
+
+<p>
+The regulator body (Figure 14) carries a union which attaches to the side
+outlet on the oxygen tank valve. The gas passes through this union,
+following an opening which leads to a large gauge which registers the
+pressure on the oxygen remaining in the tank and also to a very small
+opening in the end of a tube. The gas passes through this opening and into
+the interior of the regulator body. Inside of the body is a metal or rubber
+diaphragm placed so that the pressure of the incoming gas causes it to
+bulge slightly. Attached to the diaphragm is a sleeve or an arm tipped
+with a small piece of fibre, the fibre being placed so that it is directly
+opposite the small hole through which the gas entered the diaphragm
+chamber. The slight movement of the diaphragm draws the fibre tightly over
+the small opening through which the gas is entering, with the result that
+further flow is prevented.
+</p>
+
+<p>
+Against the opposite side of the diaphragm is the end of a plunger. This
+plunger is pressed against the diaphragm by a coiled spring. The tension on
+the coiled spring is controlled by the operator through a threaded spindle
+ending in a wing or milled nut on the outside of the regulator body.
+Screwing in on the nut causes the tension on the spring to increase, with a
+consequent increase of pressure on the side of the diaphragm opposite to
+that on which the gas acts. Inasmuch as the gas pressure acted to close the
+small gas opening and the spring pressure acts in the opposite direction
+from the gas, it will be seen that the spring pressure tends to keep the
+valve open.
+</p>
+
+<p>
+When the nut is turned way out there is of course, no pressure on the
+spring side of the diaphragm and the first gas coming through automatically
+closes the opening through which it entered. If now the tension on the
+spring be slightly increased, the valve will again open and admit gas until
+the pressure of gas within the regulator is just sufficient to overcome the
+spring pressure and again close the opening. There will then be a pressure
+of gas within the regulator that corresponds to the pressure placed on the
+spring by the operator. An opening leads from the regulator interior to the
+torch lines so that all gas going to the torches is drawn from the
+diaphragm chamber.
+</p>
+
+<p>
+Any withdrawal of gas will, of course, lower the pressure of that remaining
+inside the regulator. The spring tension, remaining at the point determined
+by the operator, will overcome this lessened pressure of the gas, and the
+valve will again open and admit enough more gas to bring the pressure back
+to the starting point. This action continues as long as the spring tension
+remains at this point and as long as any gas is taken from the regulator.
+Increasing the spring tension will require a greater gas pressure to close
+the valve and the pressure of that in the regulator will be correspondingly
+higher.
+</p>
+
+<p>
+When the regulator is not being used, the hand nut should be unscrewed
+until no tension remains on the spring, thus closing the valve. After the
+oxygen tank valve is open, the regulator hand nut is slowly screwed in
+until the spring tension is sufficient to give the required pressure in the
+torch lines. Another gauge is attached to the regulator so that it
+communicates with the interior of the diaphragm chamber, this gauge showing
+the gas pressure going to the torch. It is customary to incorporate a
+safety valve in the regulator which will blow off at a dangerous pressure.
+</p>
+
+<p>
+In regulating valves and tank valves, as well as all other parts with which
+the oxygen comes in contact, it is not permissible to use any form of oil
+or grease because of danger of ignition and explosion. The mechanism of a
+regulator is too delicate to be handled in the ordinary shop and should any
+trouble or leakage develop in this part of the equipment it should be sent
+to a company familiar with this class of work for the necessary repairs.
+Gas must never be admitted to a regulator until the hand nut is all the way
+out, because of danger to the regulator itself and to the operator as well.
+A regulator can only be properly adjusted when the tank valve and torch
+valves are fully opened.
+</p>
+
+<p class="ctr">
+<a href="images/086.png"><img src="images/086th.png" alt="Figure 15.--High and Low Pressure Gauges with Regulator"></a>
+</p>
+
+<p>
+Acetylene regulators are used in connection with tanks of compressed gas.
+They are built on exactly the same lines as the oxygen regulating valve and
+operate in a similar way. One gauge only, the low pressure indicator, is
+used for acetylene regulators, although both high and low pressure may be
+used if desired. (See Figure 15.)
+</p>
+
+<p>
+TORCHES
+</p>
+
+<p>
+Flame is always produced by the combustion of a gas with oxygen and in no
+other way. When we burn oil or candles or anything else, the material of
+the fuel is first turned to a gas by the heat and is then burned by
+combining with the oxygen of the air. If more than a normal supply of air
+is forced into the flame, a greater heat and more active burning follows.
+If the amount of air, and consequently oxygen, is reduced, the flame
+becomes smaller and weaker and the combustion is less rapid. A flame may be
+easily extinguished by shutting off all of its air supply.
+</p>
+
+<p>
+The oxygen of the combustion only forms one-fifth of the total volume of
+air; therefore, if we were to supply pure oxygen in place of air, and in
+equal volume, the action would be several times as intense. If the oxygen
+is mixed with the fuel gas in the proportion that burns to the very best
+advantage, the flame is still further strengthened and still more heat is
+developed because of the perfect combustion. The greater the amount of fuel
+gas that can be burned in a certain space and within a certain time, the
+more heat will be developed from that fuel.
+</p>
+
+<p>
+The great amount of heat contained in acetylene gas, greater than that
+found in any other gaseous fuel, is used by leading this gas to the
+oxy-acetylene torch and there combining it with just the right amount of
+oxygen to make a flame of the greatest power and heat than can possibly be
+produced by any form of combustion of fuels of this kind. The heat
+developed by the flame is about 6300° Fahrenheit and easily melts all the
+metals, as well as other solids.
+</p>
+
+<p>
+Other gases have been and are now being used in the torch. None of them,
+however, produce the heat that acetylene does, and therefore the
+oxy-acetylene process has proved the most useful of all. Hydrogen was used
+for many years before acetylene was introduced in this field. The
+oxy-hydrogen flame develops a heat far below that of oxy-acetylene, namely
+4500° Fahrenheit. Coal gas, benzine gas, blaugas and others have also been
+used in successful applications, but for the present we will deal
+exclusively with the acetylene fuel.
+</p>
+
+<p>
+It was only with great difficulty that the obstacles in the way of
+successfully using acetylene were overcome by the development of
+practicable controlling devices and torches, as well as generators. At
+present the oxy-acetylene process is the most universally adaptable, and
+probably finds the most widely extended field of usefulness of any welding
+process.
+</p>
+
+<p>
+The theoretical proportion of the gases for perfect combustion is two and
+one-half volumes of oxygen to one of acetylene. In practice this proportion
+is one and one-eighth or one and one-quarter volumes of oxygen to one
+volume of acetylene, so that the cost is considerably reduced below what it
+would be if the theoretical quantity were really necessary, as oxygen costs
+much more than acetylene in all cases.
+</p>
+
+<p>
+While the heat is so intense as to fuse anything brought into the path of
+the flame, it is localized in the small "welding cone" at the torch tip so
+that the torch is not at all difficult to handle without special protection
+except for the eyes, as already noted. The art of successful welding may be
+acquired by any operator of average intelligence within a reasonable time
+and with some practice. One trouble met with in the adoption of this
+process has been that the operation looks so simple and so easy of
+performance that unskilled and unprepared persons have been tempted to try
+welding, with results that often caused condemnation of the process, when
+the real fault lay entirely with the operator.
+</p>
+
+<p>
+The form of torch usually employed is from twelve to twenty-four inches
+long and is composed of a handle at one end with tubes leading from this
+handle to the "welding head" or torch proper. At or near one end of the
+handle are adjustable cocks or valves for allowing the gases to flow into
+the torch or to prevent them from doing so. These cocks are often used for
+regulating the pressure and amount of gas flowing to the welding head, but
+are not always constructed for this purpose and should not be so used when
+it is possible to secure pressure adjustment at the regulators (Figure 16).
+</p>
+
+<p>
+Figure 16 shows three different sizes of torches. The number 5 torch is
+designed especially for jewelers' work and thin sheet steel welding. It is
+eleven inches in length and weighs nineteen ounces. The tips for the number
+10 torch are interchangeable with the number 5. The number 10 torch is
+adapted for general use on light and medium heavy work. It has six tips and
+its length is sixteen inches, with a weight of twenty-three ounces.
+</p>
+
+<p>
+The number 15 torch is designed for heavy work, being twenty-five inches in
+length, permitting the operator to stand away from the heat of the metal
+being worked. These heavy tips are in two parts, the oxygen check being
+renewable.
+</p>
+
+<p class="ctr">
+<a href="images/090.png"><img src="images/090th.png" alt="Figure 16.--Three Sizes of Torches, with Tips"></a>
+</p>
+
+<p>
+Figures 17 and 18 show two sizes of another welding torch. Still another
+type is shown in Figure 19 with four interchangeable tips, the function of
+each being as follows:
+</p>
+
+<pre>
+  No. 1. For heavy castings.<br>
+  No. 2. Light castings and heavy sheet metal.<br>
+  No. 3. Light sheet metal.<br>
+  No. 4. Very light sheet metal and wire.
+</pre>
+
+<p class="ctr">
+<a href="images/091.png"><img src="images/091th.png" alt="Figure 17.--Cox Welding Torch (No. 1)"></a>
+</p>
+
+<p class="ctr">
+<a href="images/091a.png"><img src="images/091ath.png" alt="Figure 18.--Cox Welding Torch (No. 2)"></a>
+</p>
+
+<p class="ctr">
+<a href="images/091b.png"><img src="images/091bth.png" alt="Figure 19.--Monarch Welding Torch"></a>
+</p>
+
+<p>
+At the side of the shut off cock away from the torch handle the gas tubes
+end in standard forms of hose nozzles, to which the rubber hose from the
+gas supply tanks or generators can be attached. The tubes from the handle
+to the head may be entirely separate from each other, or one may be
+contained within the other. As a general rule the upper one of two
+separate tubes carries the oxygen, while this gas is carried in the inside
+tube when they are concentric with each other.
+</p>
+
+<p>
+In the welding head is the mixing chamber designed to produce an intimate
+mixture of the two gases before they issue from the nozzle to the flame.
+The nozzle, or welding tip, of a suitable size are design for the work to
+be handled and the pressure of gases being used, is attached to the welding
+head and consists essentially of the passage at the outer end of which the
+flame appears.
+</p>
+
+<p>
+The torch body and tubes are usually made of brass, although copper is
+sometimes used. The joint must be very strong, and are usually threaded and
+soldered with silver solder. The nozzle proper is made from copper, because
+it withstands the heat of the flame better than other less suitable metals.
+The torch must be built in such a way that it is not at all liable to come
+apart under the influence of high temperatures.
+</p>
+
+<p>
+All torches are constructed in such a way that it is impossible for the
+gases to mix by any possible chance before they reach the head, and the
+amount of gas contained in the head and tip after being mixed is made as
+small as possible. In order to prevent the return of the flame through the
+acetylene tube under the influence of the high pressure oxygen some form of
+back flash preventer is usually incorporated in the torch at or near the
+point at which the acetylene enters. This preventer takes the form of some
+porous and heat absorbing material, such as aluminum shavings, contained in
+a small cavity through which the gas passes on its way to the head.
+</p>
+
+<p>
+<i>High Pressure Torches.</i>--Torches are divided into the same classes as
+are the generators; that is, high pressure, medium pressure and low
+pressure. As mentioned before, the medium pressure is usually called the
+high pressure, because there are very few true high pressure systems in
+use, and comparatively speaking the medium pressure type is one of high
+pressure.
+</p>
+
+<p class="ctr">
+<a href="images/093.png"><img src="images/093th.png" alt="Figure 20.--High Pressure Torch Head"></a>
+</p>
+
+<p>
+With a true high pressure torch (Figure 20) the gases are used at very
+nearly equal heads so that the mixing before ignition is a simple matter.
+This type admits the oxygen at the inner end of a straight passage leading
+to the tip of the nozzle. The acetylene comes into this same passage from
+openings at one side and near the inner end. The difference in direction of
+the two gases as they enter the passage assists in making a homogeneous
+mixture. The construction of this nozzle is perfectly simple and is easily
+understood. The true high pressure torch nozzle is only suited for use with
+compressed and dissolved acetylene, no other gas being at a sufficient
+pressure to make the action necessary in mixing the gases.
+</p>
+
+<p>
+<i>Medium Pressure Torches.</i>--The medium pressure (usually called high
+pressure) torch (Figure 21) uses acetylene from a medium pressure generator
+or from tanks of compressed gas, but will not take the acetylene from low
+pressure generators.
+</p>
+
+<p class="ctr">
+<a href="images/094.png"><img src="images/094th.png" alt="Figure 21.--Medium Pressure Torch Head"></a>
+</p>
+
+<p>
+The construction of the mixing chamber and nozzle is very similar to that
+of the high pressure torch, the gases entering in the same way and from the
+same positions of openings. The pressure of the acetylene is but little
+lower than that of the oxygen, and the two gases, meeting at right angles,
+form a very intimate mixture at this point of juncture. The mixture in its
+proportions of gases depends entirely on the sizes of the oxygen and
+acetylene openings into the mixing chamber and on the pressures at which
+the gases are admitted. There is a very slight injector action as the fast
+moving stream of oxygen tends to draw the acetylene from the side openings
+into the chamber, but the operation of the torch does not depend on this
+action to any extent.
+</p>
+
+<p>
+<i>Low Pressure Torches.</i>--The low pressure torch (Figure 22) will use
+gas from low pressure generators from medium pressure machines or from
+tanks in which it has been compressed and dissolved. This type depends for
+a perfect mixture of gas upon the principle of the injector just as it is
+applied in steam boiler practice.
+</p>
+
+<p class="ctr">
+<a href="images/095.png"><img src="images/095th.png" alt="Figure 22.--Low Pressure Torch with Separate Injector Nozzle"></a>
+</p>
+
+<p>
+The oxygen enters the head at considerable pressure and passes through its
+tube to a small jet within the head. The opening of this jet is directly
+opposite the end of the opening through the nozzle which forms the mixing
+chamber and the path of the gases to the flame. A small distance remains
+between the opening from which the oxygen issues and the inner opening into
+the mixing passage. The stream of oxygen rushes across this space and
+enters the mixing chamber, being driven by its own pressure.
+</p>
+
+<p>
+The acetylene enters the head in an annular space surrounding the oxygen
+tube. The space between oxygen jet and mixing chamber opening is at one end
+of this acetylene space and the stream of oxygen seizes the acetylene and
+under the injector action draws it into the mixing chamber, it being
+necessary only to have a sufficient supply of acetylene flowing into the
+head to allow the oxygen to draw the required proportion for a proper
+mixture.
+</p>
+
+<p>
+The volume of gas drawn into the mixing chamber depends on the size of the
+injector openings and the pressure of the oxygen. In practice the oxygen
+pressure is not altered to produce different sized flames, but a new nozzle
+is substituted which is designed to give the required flame. Each nozzle
+carries its own injector, so that the design is always suited to the
+conditions. While torches are made having the injector as a permanent part
+of the torch body, the replaceable nozzle is more commonly used because it
+makes the one torch suitable for a large range of work and a large number
+of different sized flames. With the replaceable head a definite pressure of
+oxygen is required for the size being used, this pressure being the one for
+which the injector and corresponding mixing chamber were designed in
+producing the correct mixture.
+</p>
+
+<p>
+<i>Adjustable Injectors.</i>-Another form of low pressure torch operates on
+the injector principle, but the injector itself is a permanent part of the
+torch, the nozzle only being changed for different sizes of work and flame.
+The injector is placed in or near the handle and its opening is the largest
+required by any work that can be handled by this particular torch. The
+opening through the tip of the injector through which the oxygen issues on
+its way to the mixing chamber may be wholly or partly closed by a needle
+valve which may be screwed into the opening or withdrawn from it, according
+to the operator's judgment. The needle valve ends in a milled nut outside
+the torch handle, this being the adjustment provided for the different
+nozzles.
+</p>
+
+<p>
+<i>Torch Construction.</i>--A well designed torch is so designed that the
+weight distribution is best for holding it in the proper position for
+welding. When a torch is grasped by its handle with the gas hose attached,
+it should balance so that it does not feel appreciably heavier on one end
+than on the other.
+</p>
+
+<p>
+The head and nozzle may be placed so that the flame issues in a line at
+right angles with the torch body, or they may be attached at an angle
+convenient for the work to be done. The head set at an angle of from 120 to
+170 degrees with the body is usually preferred for general work in welding,
+while the cutting torch usually has its head at right angles to the body.
+</p>
+
+<p>
+Removable nozzles have various size openings through them and the different
+sizes are designated by numbers from 1 up. The same number does not always
+indicate the same size opening in torches of different makes, nor does it
+indicate a nozzle of the same capacity.
+</p>
+
+<p>
+The design of the nozzle, the mixing chamber, the injector, when one is
+used, and the size of the gas openings must be such that all these things
+are suited to each other if a proper mixture of gas is to be secured. Parts
+that are not made to work together are unsafe if used because of the danger
+of a flash back of the flame into the mixing chamber and gas tubes. It is
+well known that flame travels through any inflammable gas at a certain
+definite rate of speed, depending on the degree of inflammability of the
+gas. The easier and quicker the gas burns, the faster will the flame travel
+through it.
+</p>
+
+<p>
+If the gas in the nozzle and mixing chamber stood still, the flame would
+immediately travel back into these parts and produce an explosion of more
+or less violence. The speed with which the gases issue from the nozzle
+prevent this from happening because the flame travels back through the gas
+at the same speed at which the gas issues from the torch tip. Should the
+velocity of the gas be greater than the speed of flame propagation through
+it, it will be impossible to keep the flame at the tip, the tendency being
+for a space of unburned gas to appear between tip and flame. On the other
+hand, should the speed of the flame exceed the velocity with which the gas
+comes from the torch there will result a flash back and explosion.
+</p>
+
+<p>
+<i>Care of Torches.</i>--An oxy-acetylene torch is a very delicate and
+sensitive device, much more so that appears on the surface. It must be
+given equally as good care and attention as any other high-priced piece of
+machinery if it is to be maintained in good condition for use.
+</p>
+
+<p>
+It requires cleaning of the nozzles at regular intervals if used regularly.
+This cleaning is accomplished with a piece of copper or brass wire run
+through the opening, and never with any metal such as steel or iron that is
+harder than the nozzle itself, because of the danger of changing the size
+of the openings. The torch head and nozzle can often be cleaned by allowing
+the oxygen to blow through at high pressure without the use of any tools.
+</p>
+
+<p>
+In using a torch a deposit of carbon will gradually form inside of the
+head, and this deposit will be more rapid if the operator lights the stream
+of acetylene before turning any oxygen into the torch. This deposit may be
+removed by running kerosene through the nozzle while it is removed from the
+torch, setting fire to the kerosene and allowing oxygen to flow through
+while the oil is burning.
+</p>
+
+<p>
+Should a torch become clogged in the head or tubes, it may usually be
+cleaned by removing the oxygen hose from the handle end, closing the
+acetylene cock on the torch, placing the end of the oxygen hose over the
+opening in the nozzle and turning on the oxygen under pressure to blow the
+obstruction back through the passage that it has entered. By opening the
+acetylene cock and closing the oxygen cock at the handle, the acetylene
+passages may then be cleaned in the same way. Under no conditions should a
+torch be taken apart any more than to remove the changeable nozzle, except
+in the hands of those experienced in this work.
+</p>
+
+<p>
+<i>Nozzle Sizes.</i>--The size of opening through the nozzle is determined
+according to the thickness and kind of metal being handled. The following
+sizes are recommended for steel:
+</p>
+
+<pre>
+                      Davis-Bournonville.   Oxweld Low
+  Thickness of Metal  (Medium Pressure.)      Pressure
+  1/32                     Tip No. 1        Head No. 2
+  1/16                             2
+  5/64                                               3
+  3/32                             3                 4
+  3/8                              4                 5
+  3/16                             5                 6
+  1/4                              6                 7
+  5/16                             7
+  3/8                              8                 8
+  1/2                              9                10
+  5/8                             10                12
+  3/4                             11                15
+  Very heavy                      12                15
+</pre>
+
+<p>
+<i>Cutting Torches.</i>--Steel may be cut with a jet of oxygen at a rate of
+speed greater than in any other practicable way under usual conditions. The
+action consists of burning away a thin section of the metal by allowing a
+stream of oxygen to flow onto it while the gas is at high pressure and the
+metal at a white heat.
+</p>
+
+<p class="ctr">
+<a href="images/100.png"><img src="images/100th.png" alt="Figure 23--Cutting Torch"></a>
+</p>
+
+<p>
+The cutting torch (Figure 23) has the same characteristics as the welding
+torch, but has an additional nozzle or means for temporarily using the
+welding opening for the high pressure oxygen. The oxygen issues from the
+opening while cutting at a pressure of from ten to 100 pounds to the square
+inch.
+</p>
+
+<p>
+The work is first heated to a white heat by adjusting the torch for a
+welding flame. As soon as the metal reaches this temperature, the high
+pressure oxygen is turned on to the white-hot portion of the steel. When
+the jet of gas strikes the metal it cuts straight through, leaving a very
+narrow slot and removing but little metal. Thicknesses of steel up to ten
+inches can be economically handled in this way.
+</p>
+
+<p>
+The oxygen nozzle is usually arranged so that it is surrounded by a number
+of small jets for the heating flame. It will be seen that this arrangement
+makes the heating flame always precede the oxygen jet, no matter in which
+direction the torch is moved.
+</p>
+
+<p>
+The torch is held firmly, either by hand or with the help of special
+mechanism for guiding it in the desired path, and is steadily advanced in
+the direction it is desired to extend the cut, the rate of advance being
+from three inches to two feet per minute through metal from nine inches
+down to one-quarter of an inch in thickness.
+</p>
+
+<p>
+The following data on cutting is given by the Davis-Bournonville Company:
+</p>
+
+<pre>
+                            Cubic
+                            Feet                          Cost of
+Thickness                   of Gas               Inches   Gases
+of        Cutting  Heating  per Foot  Oxygen     Cut per  per Foot
+Steel     Oxygen   Oxygen   of Cut    Acetylene  Min.     of Cut
+  1/4     10 lbs.  4 lbs.     .40      .086      24        $ .013
+  1/2     20       4          .91      .150      15          .029
+  3/4     30       4         1.16      .150      15          .036
+1         30       4         1.45      .172      12          .045
+1 1/2     30       5         2.40      .380      12          .076
+2         40       5         2.96      .380      12          .093
+4         50       5         9.70      .800       7          .299
+6         70       6        21.09     1.50        4          .648
+9        100       6        43.20     2.00        3         1.311
+</pre>
+
+<p>
+<i>Acetylene-Air Torch.</i>--A form of torch which burns the acetylene after
+mixing it with atmospheric air at normal pressure rather than with the
+oxygen under higher pressures has been found useful in certain pre-heating,
+brazing and similar operations. This torch (Figure 24) is attached by a
+rubber gas hose to any compressed acetylene tank and is regulated as to
+flame size and temperature by opening or closing the tank valve more or
+less.
+</p>
+
+<p>
+After attaching the torch to the tank, the gas is turned on very slowly and
+is lighted at the torch tip. The adjustment should cause the presence of a
+greenish-white cone of flame surrounded by a larger body of burning gas,
+the cone starting at the mouth of the torch.
+</p>
+
+<p class="ctr">
+<a href="images/102.png"><img src="images/102th.png" alt="Figure 24.--Acetylene-Air Torch"></a>
+</p>
+
+<p>
+By opening the tank valve more, a longer and hotter flame is produced, the
+length being regulated by the tank valve also. This torch will give
+sufficient heat to melt steel, although not under conditions suited to
+welding. Because of the excess of acetylene always present there is no
+danger of oxidizing the metal being heated.
+</p>
+
+<p>
+The only care required by this torch is to keep the small air passages at
+the nozzle clean and free from carbon deposits. The flame should be
+extinguished when not in use rather than turned low, because this low flame
+rapidly deposits large quantities of soot in the burner.
+</p>
+
+<br>
+<br>
+<br>
+
+<h2><a name="v">CHAPTER V</a></h2>
+
+<h3>OXY-ACETYLENE WELDING PRACTICE</h3>
+
+<p>
+PREPARATION OF WORK
+</p>
+
+<p>
+<i>Preheating.</i>--The practice of heating the metal around the weld
+before applying the torch flame is a desirable one for two reasons. First,
+it makes the whole process more economical; second, it avoids the danger of
+breakage through expansion and contraction of the work as it is heated and
+as it cools.
+</p>
+
+<p>
+When it is desired to join two surfaces by welding them, it is, of course,
+necessary to raise the metal from the temperature of the surrounding air to
+its melting point, involving an increase in temperature of from one
+thousand to nearly three thousand degrees. To obtain this entire increase
+of temperature with the torch flame is very wasteful of fuel and of the
+operator's time. The total amount of heat necessary to put into metal is
+increased by the conductivity of that metal because the heat applied at the
+weld is carried to other parts of the piece being handled until the whole
+mass is considerably raised in temperature. To secure this widely
+distributed increase the various methods of preheating are adopted.
+</p>
+
+<p>
+As to the second reason for preliminary heating. It is understood that the
+metal added to the joint is molten at the time it flows into place. All the
+metals used in welding contract as they cool and occupy a much smaller
+space than when molten. If additional metal is run between two adjoining
+surfaces which are parts of a surrounding body of cool metal, this added
+metal will cool while the surfaces themselves are held stationary in the
+position they originally occupied. The inevitable result is that the metal
+added will crack under the strain, or, if the weld is exceptionally strong,
+the main body of the work will be broken by the force of contraction. To
+overcome these difficulties is the second and most important reason for
+preheating and also for slow cooling following the completion of the weld.
+</p>
+
+<p>
+There are many ways of securing this preheating. The work may be brought to
+a red heat in the forge if it is cast iron or steel; it may be heated in
+special ovens built for the purpose; it may be placed in a bed of charcoal
+while suitably supported; it may be heated by gas or gasoline preheating
+torches, and with very small work the outer flame of the welding torch
+automatically provides means to this end.
+</p>
+
+<p>
+The temperature of the parts heated should be gradually raised in all
+cases, giving the entire mass of metal a chance to expand equally and to
+adjust itself to the strains imposed by the preheating. After the region
+around the weld has been brought to a proper temperature the opening to be
+filled is exposed so that the torch flame can reach it, while the remaining
+surfaces are still protected from cold air currents and from cooling
+through natural radiation.
+</p>
+
+<p>
+One of the commonest methods and one of the best for handling work of
+rather large size is to place the piece to be welded on a bed of fire brick
+and build a loose wall around it with other fire brick placed in rows, one
+on top of the other, with air spaces left between adjacent bricks in each
+row. The space between the brick retaining wall and the work is filled with
+charcoal, which is lighted from below. The top opening of the temporary
+oven is then covered with asbestos and the fire kept up until the work has
+been uniformly raised in temperature to the desired point.
+</p>
+
+<p>
+When much work of the same general character and size is to be handled, a
+permanent oven may be constructed of fire brick, leaving a large opening
+through the top and also through one side. Charcoal may be used in this
+form of oven as with the temporary arrangement, or the heat may be secured
+from any form of burner or torch giving a large volume of flame. In any
+method employing flame to do the heating, the work itself must be protected
+from the direct blast of the fire. Baffles of brick or metal should be
+placed between the mouth of the torch and the nearest surface of the work
+so that the flame will be deflected to either side and around the piece
+being heated.
+</p>
+
+<p>
+The heat should be applied to bring the point of welding to the highest
+temperature desired and, except in the smallest work, the heat should
+gradually shade off from this point to the other parts of the piece. In the
+case of cast iron and steel the temperature at the point to be welded
+should be great enough to produce a dull red heat. This will make the whole
+operation much easier, because there will be no surrounding cool metal to
+reduce the temperature of the molten material from the welding rod below
+the point at which it will join the work. From this red heat the mass of
+metal should grow cooler as the distance from the weld becomes greater, so
+that no great strain is placed upon any one part. With work of a very
+irregular shape it is always best to heat the entire piece so that the
+strains will be so evenly distributed that they can cause no distortion or
+breakage under any conditions.
+</p>
+
+<p>
+The melting point of the work which is being preheated should be kept in
+mind and care exercised not to approach it too closely. Special care is
+necessary with aluminum in this respect, because of its low melting
+temperature and the sudden weakening and flowing without warning. Workmen
+have carelessly overheated aluminum castings and, upon uncovering the piece
+to make the weld, have been astonished to find that it had disappeared.
+Six hundred degrees is about the safe limit for this metal. It is possible
+to gauge the exact temperature of the work with a pyrometer, but when this
+instrument cannot be procured, it might be well to secure a number of
+"temperature cones" from a chemical or laboratory supply house. These cones
+are made from material that will soften at a certain heat and in form they
+are long and pointed. Placed in position on the part being heated, the
+point may be watched, and when it bends over it is sure that the metal
+itself has reached a temperature considerably in excess of the temperature
+at which that particular cone was designed to soften.
+</p>
+
+<p>
+The object in preheating the metal around the weld is to cause it to expand
+sufficiently to open the crack a distance equal to the contraction when
+cooling from the melting point. In the case of a crack running from the
+edge of a piece into the body or of a crack wholly within the body, it is
+usually satisfactory to heat the metal at each end of the opening. This
+will cause the whole length of the crack to open sufficiently to receive
+the molten material from the rod.
+</p>
+
+<p>
+The judgment of the operator will be called upon to decide just where a
+piece of metal should be heated to open the weld properly. It is often
+possible to apply the preheating flame to a point some distance from the
+point of work if the parts are so connected that the expansion of the
+heated part will serve to draw the edges of the weld apart. Whatever part
+of the work is heated to cause expansion and separation, this part must
+remain hot during the entire time of welding and must then cool slowly at
+the same time as the metal in the weld cools.
+</p>
+
+<p class="ctr">
+<a href="images/107.png"><img src="images/107th.png" alt="Figure 25.--Preheating at A While Welding at B.  C also May Be Heated."></a>
+</p>
+
+<p>
+An example of heating points away from the crack might be found in welding
+a lattice work with one of the bars cracked through (Figure 25). If the
+strips parallel and near to the broken bar are heated gradually, the work
+will be so expanded that the edges of the break are drawn apart and the
+weld can be successfully made. In this case, the parallel bars next to the
+broken one would be heated highest, the next row not quite so hot and so on
+for some distance away. If only the one row were heated, the strains set up
+in the next ones would be sufficient to cause a new break to appear.
+</p>
+
+<p class="ctr">
+<a href="images/108.png"><img src="images/108th.png" alt="Figure 26.--Cutting Through the Rim of a Wheel (Cut Shown at A)"></a>
+</p>
+
+<p>
+If welding is to be done near the central portion of a large piece, the
+strains will be brought to bear on the parts farthest away from the center.
+Should a fly wheel spoke be broken and made ready to weld, the greatest
+strain will come on the rim of the wheel. In cases like this it is often
+desirable to cut through at the point of greatest strain with a saw or
+cutting torch, allowing free movement while the weld is made at the
+original break (Figure 26). After the inside weld is completed, the cut may
+be welded without danger, for the reason that it will always be at some
+point at which severe strains cannot be set up by the contraction of the
+cooling metal.
+</p>
+
+<p class="ctr">
+<a href="images/109.png"><img src="images/109th.png" alt="Figure 27.--Using a Wedge While Welding"></a>
+</p>
+
+<p>
+In materials that will spring to some extent without breakage, that is, in
+parts that are not brittle, it may be possible to force the work out of
+shape with jacks or wedges (Figure 27) in the same way that it would be
+distorted by heating and expanding some portion of it as described. A
+careful examination will show whether this method can be followed in such a
+way as to force the edges of the break to separate. If the plan seems
+feasible, the wedges may be put in place and allowed to remain while the
+weld is completed. As soon as the work is finished the wedges should be
+removed so that the natural contraction can take place without damage.
+</p>
+
+<p>
+It should always be remembered that it is not so much the expansion of the
+work when heated as it is the contraction caused by cooling that will do
+the damage. A weld may be made that, to all appearances, is perfect and it
+may be perfect when completed; but if provision has not been made to allow
+for the contraction that is certain to follow, there will be a breakage at
+some point. It is not possible to weld the simplest shapes, other than
+straight bars, without considering this difficulty and making provision to
+take care of it.
+</p>
+
+<p>
+The exact method to employ in preheating will always call for good judgment
+on the part of the workman, and he should remember that the success or
+failure of his work will depend fully as much on proper preparation as on
+correct handling of the weld itself. It should be remembered that the outer
+flame of the oxy-acetylene torch may be depended on for a certain amount of
+preheating, as this flame gives a very large volume of heat, but a heat
+that is not so intense nor so localized as the welding flame itself. The
+heat of this part of the flame should be fully utilized during the
+operation of melting the metal and it should be so directed, when possible,
+that it will bring the parts next to be joined to as high a temperature as
+possible.
+</p>
+
+<p>
+When the work has been brought to the desired temperature, all parts except
+the break and the surface immediately surrounding it on both sides should
+be covered with heavy sheet asbestos. This protecting cover should remain
+in place throughout the operation and should only be moved a distance
+sufficient to allow the torch flame to travel in the path of the weld. The
+use of asbestos in this way serves a twofold purpose. It retains the heat
+in the work and prevents the breakage that would follow if a draught of air
+were to strike the heated metal, and it also prevents such a radiation of
+heat through the surrounding air as would make it almost impossible for the
+operator to perform his work, especially in the case of large and heavy
+castings when the amount of heat utilized is large.
+</p>
+
+<p>
+<i>Cleaning and Champfering.</i>--A perfect weld can never be made unless
+the surfaces to be joined have been properly prepared to receive the new
+metal.
+</p>
+
+<p>
+All spoiled, burned, corroded and rough particles must positively be
+removed with chisel and hammer and with a free application of emery cloth
+and wire brush. The metal exposed to the welding flame should be perfectly
+clean and bright all over, or else the additional material will not unite,
+but will only stick at best.
+</p>
+
+<p class="ctr">
+<a href="images/111.png"><img src="images/111th.png" alt="Figure 28.--Tapering the Opening Formed by a Break"></a>
+</p>
+
+<p>
+Following the cleaning it is always necessary to bevel, or champfer, the
+edges except in the thinnest sheet metal. To make a weld that will hold,
+the metal must be made into one piece, without holes or unfilled portions
+at any point, and must be solid from inside to outside. This can only be
+accomplished by starting the addition of metal at one point and gradually
+building it up until the outside, or top, is reached. With comparatively
+thin plates the molten metal may be started from the side farthest from the
+operator and brought through, but with thicker sections the addition is
+started in the middle and brought flush with one side and then with the
+other.
+</p>
+
+<p>
+It will readily be seen that the molten material cannot be depended upon to
+flow between the tightly closed surfaces of a crack in a way that can be at
+all sure to make a true weld. It will be necessary for the operator to
+reach to the farthest side with the flame and welding rod, and to start the
+new surfaces there. To allow this, the edges that are to be joined are
+beveled from one side to the other (Figure 28), so that when placed
+together in approximately the position they are to occupy they will leave a
+grooved channel between them with its sides at an angle with each other
+sufficient in size to allow access to every point of each surface.
+</p>
+
+<p class="ctr">
+<a href="images/112.png"><img src="images/112th.png" alt="Figure 29.--Beveling for Thin Work"></a>
+</p>
+
+<p class="ctr">
+<a href="images/112a.png"><img src="images/112ath.png" alt="Figure 30.--Beveling for Thick Work"></a>
+</p>
+
+<p>
+With work less than one-fourth inch thick, this angle should be forty-five
+degrees on each piece (Figure 29), so that when they are placed together
+the extreme edges will meet at the bottom of a groove whose sides are
+square, or at right angles, to each other. This beveling should be done so
+that only a thin edge is left where the two parts come together, just
+enough points in contact to make the alignment easy to hold. With work of a
+thickness greater than a quarter of an inch, the angle of bevel on each
+piece may be sixty degrees (Figure 30), so that when placed together the
+angle included between the sloping sides will also be sixty degrees. If the
+plate is less than one-eighth of an inch thick the beveling is not
+necessary, as the edges may be melted all the way through without danger of
+leaving blowholes at any point.
+</p>
+
+<p class="ctr">
+<a href="images/113.png"><img src="images/113th.png" alt="Figure 31.--Beveling Both Sides of a Thick Piece"></a>
+</p>
+
+<p class="ctr">
+<a href="images/113a.png"><img src="images/113ath.png" alt="Figure 32.--Beveling the End of a Pipe"></a>
+</p>
+
+<p>
+This beveling may be done in any convenient way. A chisel is usually most
+satisfactory and also quickest. Small sections may be handled by filing,
+while metal that is too hard to cut in either of these ways may be shaped
+on the emery wheel. It is not necessary that the edges be perfectly
+finished and absolutely smooth, but they should be of regular outline and
+should always taper off to a thin edge so that when the flame is first
+applied it can be seen issuing from the far side of the crack. If the work
+is quite thick and is of a shape that will allow it to be turned over, the
+bevel may be brought from both sides (Figure 31), so that there will be two
+grooves, one on each surface of the work. After completing the weld on one
+side, the piece is reversed and finished on the other side. Figure 32 shows
+the proper beveling for welding pipe. Figure 33 shows how sheet metal may
+be flanged for welding.
+</p>
+
+<p>
+Welding should not be attempted with the edges separated in place of
+beveled, because it will be found impossible to build up a solid web of new
+metal from one side clear through to the other by this method. The flame
+cannot reach the surfaces to make them molten while receiving new material
+from the rod, and if the flame does not reach them it will only serve to
+cause a few drops of the metal to join and will surely cause a weak and
+defective weld.
+</p>
+
+<p class="ctr">
+<a href="images/114.png"><img src="images/114th.png" alt="Figure 33.--Flanging Sheet Metal for Welding"></a>
+</p>
+
+<p>
+<i>Supporting Work.</i>--During the operation of welding it is necessary
+that the work be well supported in the position it should occupy. This may
+be done with fire brick placed under the pieces in the correct position,
+or, better still, with some form of clamp. The edges of the crack should
+touch each other at the point where welding is to start and from there
+should gradually separate at the rate of about one-fourth inch to the foot.
+This is done so that the cooling of the molten metal as it is added will
+draw the edges together by its contraction.
+</p>
+
+<p>
+Care must be used to see that the work is supported so that it will
+maintain the same relative position between the parts as must be present
+when the work is finished. In this connection it must be remembered that
+the expansion of the metal when heated may be great enough to cause serious
+distortion and to provide against this is one of the difficulties to be
+overcome.
+</p>
+
+<p>
+Perfect alignment should be secured between the separate parts that are to
+be joined and the two edges must be held up so that they will be in the
+same plane while welding is carried out. If, by any chance, one drops
+below the other while molten metal is being added, the whole job may have
+to be undone and done over again. One precaution that is necessary is that
+of making sure that the clamping or supporting does not in itself pull the
+work out of shape while melted.
+</p>
+
+<p>
+TORCH PRACTICE
+</p>
+
+<p class="ctr">
+<a href="images/115.png"><img src="images/115th.png" alt="Figure 34.--Rotary Movement of Torch in Welding"></a>
+</p>
+
+<p>
+The weld is made by bringing the tip of the welding flame to the edges of
+the metals to be joined. The torch should be held in the right hand and
+moved slowly along the crack with a rotating motion, traveling in small
+circles (Figure 34), so that the Welding flame touches first on one side of
+the crack and then on the other. On large work the motion may be simply
+back and forth across the crack, advancing regularly as the metal unites.
+It is usually best to weld toward the operator rather than from him,
+although this rule is governed by circumstances. The head of the torch
+should be inclined at an angle of about 60 degrees to the surface of the
+work. The torch handle should extend in the same line with the break
+(Figure 35) and not across it, except when welding very light plates.
+</p>
+
+<p class="ctr">
+<a href="images/116.png"><img src="images/116th.png" alt="Figure 35.--Torch Held in Line with the Break"></a>
+</p>
+
+<p>
+If the metal is 1/16 inch or less in thickness it is only necessary to
+circle along the crack, the metal itself furnishing enough material to
+complete the weld without additions. Heat both sides evenly until they flow
+together.
+</p>
+
+<p>
+Material thicker than the above requires the addition of more metal of the
+same or different kind from the welding rod, this rod being held by the
+left hand. The proper size rod for cast iron is one having a diameter equal
+to the thickness of metal being welded up to a one-half inch rod, which is
+the largest used. For steel the rod should be one-half the thickness of the
+metal being joined up to one-fourth inch rod. As a general rule, better
+results will be obtained by the use of smaller rods, the very small sizes
+being twisted together to furnish enough material while retaining the free
+melting qualities.
+</p>
+
+<p class="ctr">
+<a href="images/117.png"><img src="images/117th.png" alt="Figure 36,--The Welding Rod Should Be Held in the Molten Metal"></a>
+</p>
+
+<p>
+The tip of the rod must at all times be held in contact with the pieces
+being welded and the flame must be so directed that the two sides of the
+crack and the end of the rod are melted at the same time (Figure 36).
+Before anything is added from the rod, the sides of the crack are melted
+down sufficiently to fill the bottom of the groove and join the two sides.
+Afterward, as metal comes from the rod in filling the crack, the flame is
+circled along the joint being made, the rod always following the flame.
+</p>
+
+<p class="ctr">
+<a href="images/117a.png"><img src="images/117ath.png" alt="Figure 37.--Welding Pieces of Unequal Thickness"></a>
+</p>
+
+<p>
+Figure 37 illustrates the welding of pieces of unequal thickness.
+</p>
+
+<p>
+Figure 38 illustrates welding at an angle.
+</p>
+
+<p>
+The molten metal may be directed as to where it should go by the tip of the
+welding flame, which has considerable force, but care must be taken not to
+blow melted metal on to cooler surfaces which it cannot join. If, while
+welding, a spot appears which does not unite with the weld, it may be
+handled by heating all around it to a white heat and then immediately
+welding the bad place.
+</p>
+
+<p class="ctr">
+<a href="images/118.png"><img src="images/118th.png" alt="Figure 38,--Welding at an Angle"></a>
+</p>
+
+<p>
+Never stop in the middle of a weld, as it is extremely difficult to
+continue smoothly when resuming work.
+</p>
+
+<p>
+<i>The Flame.</i>--The welding flame must have exactly the right
+proportions of each gas. If there is too much oxygen, the metal will be
+burned or oxidized; the presence of too much acetylene carbonizes the
+metal; that is to say, it adds carbon and makes the work harder. Just the
+right mixture will neither burn nor carbonize and is said to be a "neutral"
+flame. The neutral flame, if of the correct size for the work, reduces the
+metal to a melted condition, not too fluid, and for a width about the same
+as the thickness of the metal being welded.
+</p>
+
+<p>
+When ready to light the torch, after attaching the right tip or head as
+directed in accordance with the thickness of metal to be handled, it will
+be necessary to regulate the pressure of gases to secure the neutral flame.
+</p>
+
+<p>
+The oxygen will have a pressure of from 2 to 20 pounds, according to the
+nozzle used. The acetylene will have much less. Even with the compressed
+gas, the pressure should never exceed 10 pounds for the largest work, and
+it will usually be from 4 to 6. In low pressure systems, the acetylene will
+be received at generator pressure. It should first be seen that the
+hand-screws on the regulators are turned way out so that the springs are
+free from any tension. It will do no harm if these screws are turned back
+until they come out of the threads. This must be done with both oxygen and
+acetylene regulators.
+</p>
+
+<p>
+Next, open the valve from the generator, or on the acetylene tank, and
+carefully note whether there is any odor of escaping gas. Any leakage of
+this gas must be stopped before going on with the work.
+</p>
+
+<p>
+The hand wheel controlling the oxygen cylinder valve should now be turned
+very slowly to the left as far as it will go, which opens the valve, and
+it should be borne in mind the pressure that is being released. Turn in the
+hand screw on the oxygen regulator until the small pressure gauge shows a
+reading according to the requirements of the nozzle being used. This oxygen
+regulator adjustment should be made with the cock on the torch open, and
+after the regulator is thus adjusted the torch cock may be closed.
+</p>
+
+<p>
+Open the acetylene cock on the torch and screw in on the acetylene
+regulator hand-screw until gas commences to come through the torch. Light
+this flow of acetylene and adjust the regulator screw to the pressure
+desired, or, if there is no gauge, so that there is a good full flame. With
+the pressure of acetylene controlled by the type of generator it will only
+be necessary to open the torch cock.
+</p>
+
+<p>
+With the acetylene burning, slowly open the oxygen cock on the torch and
+allow this gas to join the flame. The flame will turn intensely bright and
+then blue white. There will be an outer flame from four to eight inches
+long and from one to three inches thick. Inside of this flame will be two
+more rather distinctly defined flames. The inner one at the torch tip is
+very small, and the intermediate one is long and pointed. The oxygen should
+be turned on until the two inner flames unite into one blue-white cone from
+one-fourth to one-half inch long and one-eighth to one-fourth inch in
+diameter. If this single, clearly defined cone does not appear when the
+oxygen torch cock has been fully opened, turn off some of the acetylene
+until it does appear.
+</p>
+
+<p>
+If too much oxygen is added to the flame, there will still be the central
+blue-white cone, but it will be smaller and more or less ragged around the
+edges (Figure 39). When there is just enough oxygen to make the single
+cone, and when, by turning on more acetylene or by turning off oxygen, two
+cones are caused to appear, the flame is neutral (Figure 40), and the small
+blue-white cone is called the welding flame.
+</p>
+
+<p class="ctr">
+<a href="images/121.png"><img src="images/121th.png" alt="Figure 39.--Oxidizing Flame--Too Much Oxygen"></a>
+</p>
+
+<p class="ctr">
+<a href="images/121a.png"><img src="images/121ath.png" alt="Figure 40.--Neutral Flame"></a>
+</p>
+
+<p class="ctr">
+<a href="images/121b.png"><img src="images/121bth.png" alt="Figure 41.--Reducing Flame--Showing an Excess of Acetylene"></a>
+</p>
+
+<p>
+While welding, test the correctness of the flame adjustment occasionally by
+turning on more acetylene or by turning off some oxygen until two flames or
+cones appear. Then regulate as before to secure the single distinct cone.
+Too much oxygen is not usually so harmful as too much acetylene, except
+with aluminum. (See Figure 41.) An excessive amount of sparks coming from
+the weld denotes that there is too much oxygen in the flame. Should the
+opening in the tip become partly clogged, it will be difficult to secure a
+neutral flame and the tip should be cleaned with a brass or copper
+wire--never with iron or steel tools or wire of any kind. While the torch
+is doing its work, the tip may become excessively hot due to the heat
+radiated from the molten metal. The tip may be cooled by turning off the
+acetylene and dipping in water with a slight flow of oxygen through the
+nozzle to prevent water finding its way into the mixing chamber.
+</p>
+
+<p>
+The regulators for cutting are similar to those for welding, except that
+higher pressures may be handled, and they are fitted with gauges reading up
+to 200 or 250 pounds pressure.
+</p>
+
+<p>
+In welding metals which conduct the heat very rapidly it is necessary to
+use a much larger nozzle and flame than for metals which have not this
+property. This peculiarity is found to the greatest extent in copper,
+aluminum and brass.
+</p>
+
+<p>
+Should a hole be blown through the work, it may be closed by withdrawing
+the flame for a few seconds and then commencing to build additional metal
+around the edges, working all the way around and finally closing the small
+opening left at the center with a drop or two from the welding rod.
+</p>
+
+<p>
+WELDING VARIOUS METALS
+</p>
+
+<p>
+Because of the varying melting points, rates of expansion and contraction,
+and other peculiarities of different metals, it is necessary to give
+detailed consideration to the most important ones.
+</p>
+
+<p>
+<i>Characteristics of Metals.</i>--The welder should thoroughly understand
+the peculiarities of the various metals with which he has to deal. The
+metals and their alloys are described under this heading in the first
+chapter of this book and a tabulated list of the most important points
+relating to each metal will be found at the end of the present chapter.
+All this information should be noted by the operator of a welding
+installation before commencing actual work.
+</p>
+
+<p>
+Because of the nature of welding, the melting point of a metal is of great
+importance. A metal melting at a low temperature should have more careful
+treatment to avoid undesired flow than one which melts at a temperature
+which is relatively high. When two dissimilar metals are to be joined, the
+one which melts at the higher temperature must be acted upon by the flame
+first and when it is in a molten condition the heat contained in it will in
+many cases be sufficient to cause fusion of the lower melting metal and
+allow them to unite without playing the flame on the lower metal to any
+great extent.
+</p>
+
+<p>
+The heat conductivity bears a very important relation to welding, inasmuch
+as a metal with a high rate of conductance requires more protection from
+cooling air currents and heat radiation than one not having this quality to
+such a marked extent. A metal which conducts heat rapidly will require a
+larger volume of flame, a larger nozzle, than otherwise, this being
+necessary to supply the additional heat taken away from the welding point
+by this conductance.
+</p>
+
+<p>
+The relative rates of expansion of the various metals under heat should be
+understood in order that parts made from such material may have proper
+preparation to compensate for this expansion and contraction. Parts made
+from metals having widely varying rates of expansion must have special
+treatment to allow for this quality, otherwise breakage is sure to occur.
+</p>
+
+<p>
+<i>Cast Iron.</i>--All spoiled metal should be cut away and if the work is
+more than one-eighth inch in thickness the sides of the crack should be
+beveled to a 45 degree angle, leaving a number of points touching at the
+bottom of the bevel so that the work may be joined in its original
+relation.
+</p>
+
+<p>
+The entire piece should be preheated in a bricked-up oven or with charcoal
+placed on the forge, when size does not warrant building a temporary oven.
+The entire piece should be slowly heated and the portion immediately
+surrounding the weld should be brought to a dull red. Care should be used
+that the heat does not warp the metal through application to one part more
+than the others. After welding, the work should be slowly cooled by
+covering with ashes, slaked lime, asbestos fibre or some other
+non-conductor of heat. These precautions are absolutely essential in the
+case of cast iron.
+</p>
+
+<p>
+A neutral flame, from a nozzle proportioned to the thickness of the work,
+should be held with the point of the blue-white cone about one-eighth inch
+from the surface of the iron.
+</p>
+
+<p>
+A cast iron rod of correct diameter, usually made with an excess of
+silicon, is used by keeping its end in contact with the molten metal and
+flowing it into the puddle formed at the point of fusion. Metal should be
+added so that the weld stands about one-eighth inch above the surrounding
+surface of the work.
+</p>
+
+<p>
+Various forms of flux may be used and they are applied by dipping the end
+of the welding rod into the powder at intervals. These powders may contain
+borax or salt, and to prevent a hard, brittle weld, graphite or
+ferro-silicon may be added. Flux should be added only after the iron is
+molten and as little as possible should be used. No flux should be used
+just before completion of the work.
+</p>
+
+<p>
+The welding flame should be played on the work around the crack and
+gradually brought to bear on the work. The bottom of the bevel should be
+joined first and it will be noted that the cast iron tends to run toward
+the flame, but does not stick together easily. A hard and porous weld
+should be carefully guarded against, as described above, and upon
+completion of the work the welded surface should be scraped with a file,
+while still red hot, in order to remove the surface scale.
+</p>
+
+<p>
+<i>Malleable Iron.</i>--This material should be beveled in the same way
+that cast iron is handled, and preheating and slow cooling are equally
+desirable. The flame used is the same as for cast iron and so is the flux.
+The welding rod may be of cast iron, although better results are secured
+with Norway iron wire or else a mild steel wire wrapped with a coil of
+copper wire.
+</p>
+
+<p>
+It will be understood that malleable iron turns to ordinary cast iron when
+melted and cooled. Welds in malleable iron are usually far from
+satisfactory and a better joint is secured by brazing the edges together
+with bronze. The edges to be joined are brought to a heat just a little
+below the point at which they will flow and the opening is then
+quickly-filled from a rod of Tobin bronze or manganese bronze, a brass or
+bronze flux being used in this work.
+</p>
+
+<p>
+<i>Wrought Iron or Semi-Steel.</i>--This metal should be beveled and heated
+in the same way as described for cast iron. The flame should be neutral, of
+the same size as for steel, and used with the tip of the blue-white cone
+just touching the work. The welding rod should be of mild steel, or, if
+wrought iron is to be welded to steel, a cast iron rod may be used. A cast
+iron flux is well suited for this work. It should be noted that wrought
+iron turns to ordinary cast iron if kept heated for any length of time.
+</p>
+
+<p>
+<i>Steel.</i>--Steel should be beveled if more than one-eighth inch in
+thickness. It requires only a local preheating around the point to be
+welded. The welding flame should be absolutely neutral, without excess of
+either gas. If the metal is one-sixteenth inch or less in thickness, the
+tip of the blue-white cone must be held a short distance from the surface
+of the work; in all other cases the tip of this cone is touched to the
+metal being welded.
+</p>
+
+<p>
+The welding rod may be of mild, low carbon steel or of Norway iron. Nickel
+steel rods may be used for parts requiring great strength, but vanadium
+alloys are very difficult to handle. A very satisfactory rod is made by
+twisting together two wires of the required material. The rod must be kept
+constantly in contact with the work and should not be added until the edges
+are thoroughly melted. The flux may or may not be used. If one is wanted,
+it may be made from three parts iron filings, six parts borax and one part
+sal ammoniac.
+</p>
+
+<p>
+It will be noticed that the steel runs from the flame, but tends to hold
+together. Should foaming commence in the molten metal, it shows an excess
+of oxygen and that the metal is being burned.
+</p>
+
+<p>
+High carbon steels are very difficult to handle. It is claimed that a drop
+or two of copper added to the weld will assist the flow, but will also
+harden the work. An excess of oxygen reduces the amount of carbon and
+softens the steel, while an excess of acetylene increases the proportion of
+carbon and hardens the metal. High speed steels may sometimes be welded if
+first coated with semi-steel before welding.
+</p>
+
+<p>
+<i>Aluminum.</i>--This is the most difficult of the commonly found metals
+to weld. This is caused by its high rate of expansion and contraction and
+its liability to melt and fall away from under the flame. The aluminum
+seems to melt on the inside first, and, without previous warning, a portion
+of the work will simply vanish from in front of the operator's eyes. The
+metal tends to run from the flame and separate at the same time. To keep
+the metal in shape and free from oxide, it is worked or puddled while in a
+plastic condition by an iron rod which has been flattened at one end.
+Several of these rods should be at hand and may be kept in a jar of salt
+water while not being used. These rods must not become coated with aluminum
+and they must not get red hot while in the weld.
+</p>
+
+<p>
+The surfaces to be joined, together with the adjacent parts, should be
+cleaned thoroughly and then washed with a 25 per cent solution of nitric
+acid in hot water, used on a swab. The parts should then be rinsed in clean
+water and dried with sawdust. It is also well to make temporary fire clay
+moulds back of the parts to be heated, so that the metal may be flowed into
+place and allowed to cool without danger of breakage.
+</p>
+
+<p>
+Aluminum must invariably be preheated to about 600 degrees, and the whole
+piece being handled should be well covered with sheet asbestos to prevent
+excessive heat radiation.
+</p>
+
+<p>
+The flame is formed with an excess of acetylene such that the second cone
+extends about an inch, or slightly more, beyond the small blue-white point.
+The torch should be held so that the end of this second cone is in contact
+with the work, the small cone ordinarily used being kept an inch or an inch
+and a half from the surface of the work.
+</p>
+
+<p>
+Welding rods of special aluminum are used and must be handled with their
+end submerged in the molten metal of the weld at all times.
+</p>
+
+<p>
+When aluminum is melted it forms alumina, an oxide of the metal. This
+alumina surrounds small masses of the metal, and as it does not melt at
+temperatures below 5000 degrees (while aluminum melts at about 1200), it
+prevents a weld from being made. The formation of this oxide is retarded
+and the oxide itself is dissolved by a suitable flux, which usually
+contains phosphorus to break down the alumina.
+</p>
+
+<p>
+<i>Copper.</i>--The whole piece should be preheated and kept well covered
+while welding. The flame must be much larger than for the same thickness of
+steel and neutral in character. A slight excess of acetylene would be
+preferable to an excess of oxygen, and in all cases the molten metal should
+be kept enveloped with the flame. The welding rod is of copper which
+contains phosphorus; and a flux, also containing phosphorus, should be
+spread for about an inch each side of the joint. These assist in preventing
+oxidation, which is sure to occur with heated copper.
+</p>
+
+<p>
+Copper breaks very easily at a heat slightly under the welding temperature
+and after cooling it is simply cast copper in all cases.
+</p>
+
+<p>
+<i>Brass and Bronze.</i>--It is necessary to preheat these metals, although
+not to a very high temperature. They must be kept well covered at all times
+to prevent undue radiation. The flame should be produced with a nozzle one
+size larger than for the same thickness of steel and the small blue-white
+cone should be held from one-fourth to one-half inch above the surface of
+the work. The flame should be neutral in character.
+</p>
+
+<p>
+A rod or wire of soft brass containing a large percentage of zinc is
+suitable for adding to brass, while copper requires the use of copper or
+manganese bronze rods. Special flux or borax may be used to assist the
+flow.
+</p>
+
+<p>
+The emission of white smoke indicates that the zinc contained in these
+alloys is being burned away and the heat should immediately be turned away
+or reduced. The fumes from brass and bronze welding are very poisonous and
+should not be breathed.
+</p>
+
+<p>
+RESTORATION OF STEEL
+</p>
+
+<p>
+The result of the high heat to which the steel has been subjected is that
+it is weakened and of a different character than before welding. The
+operator may avoid this as much as possible by first playing the outer
+flame of the torch all over the surfaces of the work just completed until
+these faces are all of uniform color, after which the metal should be well
+covered with asbestos and allowed to cool without being disturbed. If a
+temporary heating oven has been employed, the work and oven should be
+allowed to cool together while protected with the sheet asbestos. If the
+outside air strikes the freshly welded work, even for a moment, the result
+will be breakage.
+</p>
+
+<p>
+A weld in steel will always leave the metal with a coarse grain and with
+all the characteristics of rather low grade cast steel. As previously
+mentioned in another chapter, the larger the grain size in steel the weaker
+the metal will be, and it is the purpose of the good workman to avoid, as
+far as possible, this weakening.
+</p>
+
+<p>
+The structure of the metal in one piece of steel will differ according to
+the heat that it has under gone. The parts of the work that have been at
+the melting point will, therefore, have the largest grain size and the
+least strength. Those parts that have not suffered any great rise in
+temperature will be practically unaffected, and all the parts between these
+two extremes will be weaker or stronger according to their distance from
+the weld itself. To restore the steel so that it will have the best grain
+size, the operator may resort to either of two methods: (1) The grain may
+be improved by forging. That means that the metal added to the weld and the
+surfaces that have been at the welding heat are hammered much as a
+blacksmith would hammer his finished work to give it greater strength. The
+hammering should continue from the time the metal first starts to cool
+until it has reached the temperature at which the grain size is best for
+strength. This temperature will vary somewhat with the composition of the
+metal being handled, but in a general way, it may be stated that the
+hammering should continue without intermission from the time the flame is
+removed from the weld until the steel just begins to show attraction for a
+magnet presented to it. This temperature of magnetic attraction will always
+be low enough and the hammering should be immediately discontinued at this
+point. (2) A method that is more satisfactory, although harder to apply, is
+that of reheating the steel to a certain temperature throughout its whole
+mass where the heat has had any effect, and then allowing slow and even
+cooling from this temperature. The grain size is affected by the
+temperature at which the reheating is stopped, and not by the cooling, yet
+the cooling should be slow enough to avoid strains caused by uneven
+contraction.
+</p>
+
+<p>
+After the weld has been completed the steel must be allowed to cool until
+below 1200° Fahrenheit. The next step is to heat the work slowly until all
+those parts to be restored have reached a temperature at which the magnet
+just ceases to be attracted. While the very best temperature will vary
+according to the nature and hardness of the steel being handled, it will be
+safe to carry the heating to the point indicated by the magnet in the
+absence of suitable means of measuring accurately these high temperatures.
+In using a magnet for testing, it will be most satisfactory if it is an
+electromagnet and not of the permanent type. The electric current may be
+secured from any small battery and will be the means of making sure of the
+test. The permanent magnet will quickly lose its power of attraction under
+the combined action of the heat and the jarring to which it will be
+subjected.
+</p>
+
+<p>
+In reheating the work it is necessary to make sure that no part reaches a
+temperature above that desired for best grain size and also to see that all
+parts are brought to this temperature. Here enters the greatest difficulty
+in restoring the metal. The heating may be done so slowly that no part of
+the work on the outside reaches too high a temperature and then keeps the
+outside at this heat until the entire mass is at the same temperature. A
+less desirable way is to heat the outside higher than this temperature and
+allow the conductivity of the metal to distribute the excess to the inside.
+</p>
+
+<p>
+The most satisfactory method, where it can be employed, is to make use of a
+bath of some molten metal or some chemical mixture that can be kept at the
+exact heat necessary by means of gas fires that admit of close regulation.
+The temperature of these baths may be maintained at a constant point by
+watching a pyrometer, and the finished work may be allowed to remain in the
+bath until all parts have reached the desired temperature.
+</p>
+
+<p>
+WELDING INFORMATION
+</p>
+
+<p>
+The following tables include much of the information that the operator must
+use continually to handle the various metals successfully. The temperature
+scales are given for convenience only. The composition of various alloys
+will give an idea of the difficulties to be contended with by consulting
+the information on welding various metals. The remaining tables are of
+self-evident value in this work.
+</p>
+
+<pre>
+TEMPERATURE SCALES
+Centigrade  Fahrenheit      Centigrade  Fahrenheit
+   200°        392°            1000°      1832°
+   225°        437°            1050°      1922°
+   250°        482°            1100°      2012°
+   275°        527°            1150°      2102°
+   300°        572°            1200°      2192°
+   325°        617°            1250°      2282°
+   350°        662°            1300°      2372°
+   375°        707°            1350°      2462°
+   400°        752°            1400°      2552°
+   425°        797°            1450°      2642°
+   450°        842°            1500°      2732°
+   475°        887°            1550°      2822°
+   500°        932°            1600°      2912°
+   525°        977°            1650°      3002°
+   550°       1022°            1700°      3092°
+   575°       1067°            1750°      3182°
+   600°       1112°            1800°      3272°
+   625°       1157°            1850°      3362°
+   650°       1202°            1900°      3452°
+   675°       1247°            2000°      3632°
+   700°       1292°            2050°      3722°
+   725°       1337°            2100°      3812°
+   750°       1382°            2150°      3902°
+   775°       1427°            2200°      3992°
+   800°       1472°            2250°      4082°
+   825°       1517°            2300°      4172°
+   850°       1562°            2350°      4262°
+   875°       1607°            2400°      4352°
+   900°       1652°            2450°      4442°
+   925°       1697°            2500°      4532°
+   950°       1742°            2550°      4622°
+   975°       1787°            2600°      4712°
+
+METAL ALLOYS
+(Society of Automobile Engineers)
+
+Babbitt--
+  Tin...........................           84.00%
+  Antimony......................            9.00%
+  Copper........................            7.00%
+
+Brass, White--
+  Copper........................  3.00% to  6.00%
+  Tin (minimum) ................           65.00%
+  Zinc.......................... 28.00% to 30.00%
+
+Brass, Red Cast--
+  Copper........................           85.00%
+  Tin...........................            5.00%
+  Lead..........................            5.00%
+  Zinc..........................            5.00%
+
+Brass, Yellow--
+  Copper........................ 62.00% to 65.00%
+  Lead..........................  2.00% to  4.00%
+  Zinc.......................... 36.00% to 31.00%
+
+Bronze, Hard--
+  Copper........................ 87.00% to 88.00%
+  Tin...........................  9.50% to 10.50%
+  Zinc..........................  1.50% to  2.50%
+
+Bronze, Phosphor--
+  Copper........................           80.00%
+  Tin...........................           10.00%
+  Lead..........................           10.00%
+  Phosphorus....................   .50% to   .25%
+
+Bronze, Manganese--
+  Copper (approximate) .........           60.00%
+  Zinc (approximate) ...........           40.00%
+  Manganese (variable) .........            small
+
+Bronze, Gear--
+  Copper........................ 88.00% to 89.00%
+  Tin........................... 11.00% to 12.00%
+
+Aluminum Alloys--
+          Aluminum   Copper   Zinc   Manganese
+  No. 1.. 90.00%    8.5-7.0%
+  No. 2.. 80.00%    2.0-3.0%  15%  Not over 0.40%
+  No. 3.. 65.00%              35.0%
+
+Cast Iron--
+                      Gray Iron      Malleable
+  Total carbon........3.0 to 3.5%
+  Combined carbon.....0.4 to 0.7%
+  Manganese...........0.4 to 0.7%    0.3 to 0.7%
+  Phosphorus..........0.6 to 1.0%  Not over 0.2%
+  Sulphur...........Not over 0.1%  Not over 0.6%
+  Silicon............1.75 to 2.25% Not over 1.0%
+
+Carbon Steel (10 Point)--
+  Carbon........................     .05% to .15%
+  Manganese.....................     .30% to .60%
+  Phosphorus (maximum)..........             .045%
+  Sulphur (maximum).............             .05%
+(20 Point)--
+  Carbon........................     .15% to .25%
+  Manganese.....................     .30% to .60%
+  Phosphorus (maximum)..........             .045%
+  Sulphur (maximum).............             .05%
+(35 Point)--
+  Manganese.....................     .50% to .80%
+  Carbon........................     .30% to .40%
+  Phosphorus (maximum)..........             .05%
+  Sulphur (maximum).............             .05%
+(95 Point)--
+  Carbon........................    .90% to 1.05%
+  Manganese.....................    .25% to  .50%
+  Phosphorus (maximum)..........             .04%
+  Sulphur (maximum).............             .05%
+
+HEATING POWER OF FUEL GASES
+
+(In B.T.U. per Cubic Foot.)
+  Acetylene....... 1498.99   Ethylene....... 1562.9
+  Hydrogen........  291.96   Methane........  953.6
+  Alcohol......... 1501.76
+
+MELTING POINTS OF METALS
+  Platinum....................3200°
+  Iron, wrought...............2900°
+    malleable.................2500°
+    cast......................2400°
+    pure......................2760°
+  Steel, mild.................2700°
+    Medium....................2600°
+    Hard......................2500°
+  Copper......................1950°
+  Brass.......................1800°
+  Silver......................1750°
+  Bronze......................1700°
+  Aluminum....................1175°
+  Antimony....................1150°
+  Zinc........................ 800°
+  Lead........................ 620°
+  Babbitt..................500-700°
+  Solder...................500-575°
+  Tin......................... 450°
+</pre>
+
+<p>
+<i>NOTE.--These melting points are for average compositions and conditions.
+The exact proportion of elements entering into the metals affects their
+melting points one way or the other in practice.</i>
+</p>
+
+<p>
+TENSILE STRENGTH OF METALS
+</p>
+
+<p>
+Alloy steels can be made with tensile strengths as high as 300,000 pounds
+per square inch. Some carbon steels are given below according to "points":
+</p>
+
+<pre>
+                           Pounds per Square Inch
+Steel, 10 point................ 50,000 to  65,000
+  20 point..................... 60,000 to  80,000
+  40 point..................... 70,000 to 100,000
+  60 point..................... 90,000 to 120,000
+Iron, Cast..................... 13,000 to  30,000
+  Wrought...................... 40,000 to  60,000
+  Malleable.................... 25,000 to  45,000
+Copper......................... 24,000 to  50,000
+Bronze......................... 30,000 to  60,000
+Brass, Cast.................... 12,000 to  18,000
+  Rolled....................... 30,000 to  40,000
+  Wire......................... 60,000 to  75,000
+Aluminum....................... 12,000 to  23,000
+Zinc...........................  5,000 to  15,000
+Tin............................  3,000 to   5,000
+Lead...........................  1,500 to   2,500
+
+CONDUCTIVITY OF METALS
+
+(Based on the Value of Silver as 100)
+
+                          Heat  Electricity
+Silver....................100     100
+Copper.................... 74      99
+Aluminum.................. 38      63
+Brass..................... 23      22
+Zinc...................... 19      29
+Tin....................... 14      15
+Wrought Iron.............. 12      16
+Steel..................... 11.5    12
+Cast Iron................. 11      12
+Bronze....................  9       7
+Lead......................  8       9
+
+WEIGHT OF METALS
+
+(Per Cubic Inch)
+                 Pounds                  Pounds
+Lead............  .410  Wrought Iron.....  .278
+Copper..........  .320  Tin..............  .263
+Bronze..........  .313  Cast Iron........  .260
+Brass...........  .300  Zinc.............  .258
+Steel...........  .283  Aluminum.........  .093
+
+EXPANSION OF METALS
+
+(Measured in Thousandths of an Inch per Foot of
+Length When Raised 1000 Degrees in Temperature)
+                  Inch                     Inch
+Lead............  .188  Brass............  .115
+Zinc............  .168  Copper...........  .106
+Aluminum........  .148  Steel............  .083
+Silver..........  .129  Wrought Iron.....  .078
+Bronze..........  .118  Cast Iron........  .068
+</pre>
+
+<br>
+<br>
+<br>
+
+<h2><a name="vi">CHAPTER VI</a></h2>
+
+<h3>ELECTRIC WELDING</h3>
+
+<p>
+RESISTANCE METHOD
+</p>
+
+<p>
+Two distinct forms of electric welding apparatus are in use, one producing
+heat by the resistance of the metal being treated to the passage of
+electric current, the other using the heat of the electric arc.
+</p>
+
+<p>
+The resistance process is of the greatest use in manufacturing lines where
+there is a large quantity of one kind of work to do, many thousand pieces
+of one kind, for instance. The arc method may be applied in practically any
+case where any other form of weld may be made. The resistance process will
+be described first.
+</p>
+
+<p>
+It is a well known fact that a poor conductor of electricity will offer so
+much resistance to the flow of electricity that it will heat. Copper is a
+good conductor, and a bar of iron, a comparatively poor conductor, when
+placed between heavy copper conductors of a welder, becomes heated in
+attempting to carry the large volume of current. The degree of heat depends
+on the amount of current and the resistance of the conductor.
+</p>
+
+<p>
+In an electric circuit the ends of two pieces of metal brought together
+form the point of greatest resistance in the electric circuit, and the
+abutting ends instantly begin to heat. The hotter this metal becomes, the
+greater the resistance to the flow of current; consequently, as the edges
+of the abutting ends heat, the current is forced into the adjacent cooler
+parts, until there is a uniform heat throughout the entire mass. The heat
+is first developed in the interior of the metal so that it is welded there
+as perfectly as at the surface.
+</p>
+
+<p class="ctr">
+<a href="images/140.png"><img src="images/140th.png" alt="Figure 42.--Spot Welding Machine"></a>
+</p>
+
+<p>
+The electric welder (Figure 42) is built to hold the parts to be joined
+between two heavy copper dies or contacts. A current of three to five
+volts, but of very great volume (amperage), is allowed to pass across
+these dies, and in going through the metal to be welded, heats the edges
+to a welding temperature. It may be explained that the voltage of an
+electric current measures the pressure or force with which it is being sent
+through the circuit and has nothing to do with the quantity or volume
+passing. Amperes measure the rate at which the current is passing through
+the circuit and consequently give a measure of the quantity which passes in
+any given time. Volts correspond to water pressure measured by pounds to
+the square inch; amperes represent the flow in gallons per minute. The low
+voltage used avoids all danger to the operator, this pressure not being
+sufficient to be felt even with the hands resting on the copper contacts.
+</p>
+
+<p>
+Current is supplied to the welding machine at a higher voltage and lower
+amperage than is actually used between the dies, the low voltage and high
+amperage being produced by a transformer incorporated in the machine
+itself. By means of windings of suitable size wire, the outside current may
+be received at voltages ranging from 110 to 550 and converted to the low
+pressure needed.
+</p>
+
+<p>
+The source of current for the resistance welder must be alternating, that
+is, the current must first be negative in value and then positive, passing
+from one extreme to the other at rates varying from 25 to 133 times a
+second. This form is known as alternating current, as opposed to direct
+current, in which there is no changing of positive and negative.
+</p>
+
+<p>
+The current must also be what is known as single phase, that is, a current
+which rises from zero in value to the highest point as a positive current
+and then recedes to zero before rising to the highest point of negative
+value. Two-phase of three-phase currents would give two or three positive
+impulses during this time.
+</p>
+
+<p>
+As long as the current is single phase alternating, the voltage and cycles
+(number of alternations per second) may be anything convenient. Various
+voltages and cycles are taken care of by specifying all these points when
+designing the transformer which is to handle the current.
+</p>
+
+<p>
+Direct current is not used because there is no way of reducing the voltage
+conveniently without placing resistance wires in the circuit and this uses
+power without producing useful work. Direct current may be changed to
+alternating by having a direct current motor running an alternating current
+dynamo, or the change may be made by a rotary converter, although this last
+method is not so satisfactory as the first.
+</p>
+
+<p>
+The voltage used in welding being so low to start with, it is absolutely
+necessary that it be maintained at the correct point. If the source of
+current supply is not of ample capacity for the welder being used, it will
+be very hard to avoid a fall of voltage when the current is forced to pass
+through the high resistance of the weld. The current voltage for various
+work is calculated accurately, and the efficiency of the outfit depends to
+a great extent on the voltage being constant.
+</p>
+
+<p>
+A simple test for fall of voltage is made by connecting an incandescent
+electric lamp across the supply lines at some point near the welder. The
+lamp should burn with the same brilliancy when the weld is being made as at
+any other time. If the lamp burns dim at any time, it indicates a drop in
+voltage, and this condition should be corrected.
+</p>
+
+<p>
+The dynamo furnishing the alternating current may be in the same building
+with the welder and operated from a direct current motor, as mentioned
+above, or operated from any convenient shafting or source of power. When
+the dynamo is a part of the welding plant it should be placed as close to
+the welding machine as possible, because the length of the wire used
+affects the voltage appreciably.
+</p>
+
+<p>
+In order to hold the voltage constant, the Toledo Electric Welder Company
+has devised connections which include a rheostat to insert a variable
+resistance in the field windings of the dynamo so that the voltage may be
+increased by cutting this resistance out at the proper time. An auxiliary
+switch is connected to the welder switch so that both switches act
+together. When the welder switch is closed in making a weld, that portion
+of the rheostat resistance between two arms determining the voltage is
+short circuited. This lowers the resistance and the field magnets of the
+dynamo are made stronger so that additional voltage is provided to care for
+the resistance in the metal being heated.
+</p>
+
+<p>
+A typical machine is shown in the accompanying cut (Figure 43). On top of
+the welder are two jaws for holding the ends of the pieces to be welded.
+The lower part of the jaws is rigid while the top is brought down on top of
+the work, acting as a clamp. These jaws carry the copper dies through which
+the current enters the work being handled. After the work is clamped
+between the jaws, the upper set is forced closer to the lower set by a long
+compression lever. The current being turned on with the surfaces of the
+work in contact, they immediately heat to the welding point when added
+pressure on the lever forces them together and completes the weld.
+</p>
+
+<p class="ctr">
+<a href="images/144.png"><img src="images/144th.png" alt="Figure 43--Operating Parts of a Toledo Spot Welder"></a>
+</p>
+
+<p class="ctr">
+<a href="images/145.png"><img src="images/145th.png" alt="Figure 43a.--Method of Testing Electric Welder"></a>
+</p>
+
+<p class="ctr">
+<a href="images/145a.png"><img src="images/145ath.png" alt="Figure 44.--Detail of Water-Cooled Spot Welding Head"></a>
+</p>
+
+<p>
+The transformer is carried in the base of the machine and on the left-hand
+side is a regulator for controlling the voltage for various kinds of work.
+The clamps are applied by treadles convenient to the foot of the operator.
+A treadle is provided which instantly releases both jaws upon the
+completion of the weld. One or both of the copper dies may be cooled by a
+stream of water circulating through it from the city water mains
+(Figure 44). The regulator and switch give the operator control of the
+heat, anything from a dull red to the melting point being easily obtained
+by movement of the lever (figure 45).
+</p>
+
+<p class="ctr">
+<a href="images/146.png"><img src="images/146th.png" alt="Figure 45.--Welding Head of a Water-Cooled Welder"></a>
+</p>
+
+<p>
+<i>Welding.</i>--It is not necessary to give the metal to be welded any
+special preparation, although when very rusty or covered with scale, the
+rust and scale should be removed sufficiently to allow good contact of
+clean metal on the copper dies. The cleaner and better the stock, the less
+current it takes, and there is less wear on the dies. The dies should be
+kept firm and tight in their holders to make a good contact. All bolts and
+nuts fastening the electrical contacts should be clean and tight at all
+times.
+</p>
+
+<p>
+The scale may be removed from forgings by immersing them in a pickling
+solution in a wood, stone or lead-lined tank.
+</p>
+
+<p>
+The solution is made with five gallons of commercial sulphuric acid in
+150 gallons of water. To get the quickest and best results from this
+method, the solution should be kept as near the boiling point as possible
+by having a coil of extra heavy lead pipe running inside the tank and
+carrying live steam. A very few minutes in this bath will remove the scale
+and the parts should then be washed in running water. After this washing
+they should be dipped into a bath of 50 pounds of unslaked lime in 150
+gallons of water to neutralize any trace of acid.
+</p>
+
+<p>
+Cast iron cannot be commercially welded, as it is high in carbon and
+silicon, and passes suddenly from a crystalline to a fluid state when
+brought to the welding temperature. With steel or wrought iron the
+temperature must be kept below the melting point to avoid injury to the
+metal. The metal must be heated quickly and pressed together with
+sufficient force to push all burnt metal out of the joint.
+</p>
+
+<p>
+High carbon steel can be welded, but must be annealed after welding to
+overcome the strains set up by the heat being applied at one place. Good
+results are hard to obtain when the carbon runs as high as 75 points, and
+steel of this class can only be handled by an experienced operator. If the
+steel is below 25 points in carbon content, good welds will always be the
+result. To weld high carbon to low carbon steel, the stock should be
+clamped in the dies with the low carbon stock sticking considerably further
+out from the die than the high carbon stock. Nickel steel welds readily,
+the nickel increasing the strength of the weld.
+</p>
+
+<p>
+Iron and copper may be welded together by reducing the size of the copper
+end where it comes in contact with the iron. When welding copper and brass
+the pressure must be less than when welding iron. The metal is allowed to
+actually fuse or melt at the juncture and the pressure must be sufficient
+to force the burned metal out. The current is cut off the instant the metal
+ends begin to soften, this being done by means of an automatic switch which
+opens when the softening of the metal allows the ends to come together. The
+pressure is applied to the weld by having the sliding jaw moved by a weight
+on the end of an arm.
+</p>
+
+<p>
+Copper and brass require a larger volume of current at a lower voltage than
+for steel and iron. The die faces are set apart three times the diameter of
+the stock for brass and four times the diameter for copper.
+</p>
+
+<p>
+Light gauges of sheet steel can be welded to heavy gauges or to solid bars
+of steel by "spot" welding, which will be described later. Galvanized iron
+can be welded, but the zinc coating will be burned off. Sheet steel can be
+welded to cast iron, but will pull apart, tearing out particles of the
+iron.
+</p>
+
+<p>
+Sheet copper and sheet brass may be welded, although this work requires
+more experience than with iron and steel. Some grades of sheet aluminum can
+be spot-welded if the slight roughness left on the surface under the die
+is not objectionable.
+</p>
+
+<p>
+<i>Butt Welding.</i>--This is the process which joins the ends of two
+pieces of metal as described in the foregoing part of this chapter. The
+ends are in plain sight of the operator at all times and it can easily be
+seen when the metal reaches the welding heat and begins to soften (Figure
+46). It is at this point that the pressure must be applied with the lever
+and the ends forced together in the weld.
+</p>
+
+<p class="ctr">
+<a href="images/149.png"><img src="images/149th.png" alt="Figure 46.--Butt Welder"></a>
+</p>
+
+<p>
+The parts are placed in the clamping jaws (Figure 47) with 1/8 to 1/2 inch
+of metal extending beyond the jaw. The ends of the metal touch each other
+and the current is turned on by means of a switch. To raise the ends to the
+proper heat requires from 3 seconds for 1/4-inch rods to 35 seconds for a
+1-1/2-inch bar.
+</p>
+
+<p>
+This method is applicable to metals having practically the same area of
+metal to be brought into contact on each end. When such parts are forced
+together a slight projection will be left in the form of a fin or an
+enlarged portion called an upset. The degree of heat required for any work
+is found by moving the handle of the regulator one way or the other while
+testing several parts. When this setting is right the work can continue as
+long as the same sizes are being handled.
+</p>
+
+<p class="ctr">
+<a href="images/150.png"><img src="images/150th.png" alt="Figure 47.--Clamping Dies of a Butt Welder"></a>
+</p>
+
+<p>
+Copper, brass, tool steel and all other metals that are harmed by high
+temperatures must be heated quickly and pressed together with sufficient
+force to force all burned metal from the weld.
+</p>
+
+<p>
+In case it is desired to make a weld in the form of a capital letter T, it
+is necessary to heat the part corresponding to the top bar of the T to a
+bright red, then bring the lower bar to the pre-heated one and again turn
+on the current, when a weld can be quickly made.
+</p>
+
+<p>
+<i>Spot Welding.</i>--This is a method of joining metal sheets together at
+any desired point by a welded spot about the size of a rivet. It is done on
+a spot welder by fusing the metal at the point desired and at the same
+instant applying sufficient pressure to force the particles of molten metal
+together. The dies are usually placed one above the other so that the work
+may rest on the lower one while the upper one is brought down on top of the
+upper sheet to be welded.
+</p>
+
+<p>
+One of the dies is usually pointed slightly, the opposing one being left
+flat. The pointed die leaves a slight indentation on one side of the metal,
+while the other side is left smooth. The dies may be reversed so that the
+outside surface of any work may be left smooth. The current is allowed to
+flow through the dies by a switch which is closed after pressure is applied
+to the work.
+</p>
+
+<p>
+There is a limit to the thickness of sheet metal that can be welded by this
+process because of the fact that the copper rods can only carry a certain
+quantity of current without becoming unduly heated themselves. Another
+reason is that it is difficult to make heavy sections of metal touch at the
+welding point without excessive pressure.
+</p>
+
+<p>
+<i>Lap welding</i> is the process used when two pieces of metal are caused
+to overlap and when brought to a welding heat are forced together by
+passing through rollers, or under a press, thus leaving the welded joint
+practically the same thickness as the balance of the work.
+</p>
+
+<p>
+Where it is desirable to make a continuous seam, a special machine is
+required, or an attachment for one of the other types. In this form of work
+the stock must be thoroughly cleaned and is then passed between copper
+rollers which act in the same capacity as the copper dies.
+</p>
+
+<p>
+<i>Other Applications.</i>--Hardening and tempering can be done by clamping
+the work in the welding dies and setting the control and time to bring the
+metal to the proper color, when it is cooled in the usual manner.
+</p>
+
+<p>
+Brazing is done by clamping the work in the jaws and heating until the
+flux, then the spelter has melted and run into the joint. Riveting and
+heading of rivets can be done by bringing the dies down on opposite ends of
+the rivet after it has been inserted in the hole, the dies being shaped to
+form the heads properly.
+</p>
+
+<p>
+Hardened steel may be softened and annealed so that it can be machined by
+connecting the dies of the welder to each side of the point to be softened.
+The current is then applied until the work has reached a point at which it
+will soften when cooled.
+</p>
+
+<p>
+<i>Troubles and Remedies.</i>--The following methods have been furnished by
+the Toledo Electric Welder Company and are recommended for this class of
+work whenever necessary.
+</p>
+
+<p>
+To locate grounds in the primary or high voltage side of the circuit,
+connect incandescent lamps in series by means of a long piece of lamp cord,
+as shown, in Figure 43a. For 110 volts use one lamp, for 220 volts use two
+lamps and for 440 volts use four lamps. Attach one end of the lamp cord to
+one side of the switch, and close the switch. Take the other end of the
+cord in the hand and press it against some part of the welder frame where
+the metal is clean and bright. Paint, grease and dirt act as insulators and
+prevent electrical contact. If the lamp lights, the circuit is in
+electrical contact with the frame; in other words, grounded. If the lamps
+do not light, connect the wire to a terminal block, die or slide. If the
+lamps then light, the circuit, coils or leads are in electrical contact
+with the large coil in the transformer or its connections.
+</p>
+
+<p>
+If, however, the lamps do not light in either case, the lamp cord should be
+disconnected from the switch and connected to the other side, and the
+operations of connecting to welder frame, dies, terminal blocks, etc., as
+explained above, should be repeated. If the lamps light at any of these
+connections, a "ground" is indicated. "Grounds" can usually be found by
+carefully tracing the primary circuit until a place is found where the
+insulation is defective. Reinsulate and make the above tests again to make
+sure everything is clear. If the ground can not be located by observation,
+the various parts of the primary circuit should be disconnected, and the
+transformer, switch, regulator, etc., tested separately.
+</p>
+
+<p>
+To locate a ground in the regulator or other part, disconnect the lines
+running to the welder from the switch. The test lamps used in the previous
+tests are connected, one end of lamp cord to the switch, the other end to a
+binding post of the regulator. Connect the other side of the switch to some
+part of the regulator housing. (This must be a clean connection to a bolt
+head or the paint should be scraped off.) Close the switch. If the lamps
+light, the regulator winding or some part of the switch is "grounded" to
+the iron base or core of the regulator. If the lamps do not light, this
+part of the apparatus is clear.
+</p>
+
+<p>
+This test can be easily applied to any part of the welder outfit by
+connecting to the current carrying part of the apparatus, and to the iron
+base or frame that should not carry current. If the lamps light, it
+indicates that the insulation is broken down or is defective.
+</p>
+
+<p>
+An A.C. voltmeter can, of course, be substituted for the lamps, or a D.C.
+voltmeter with D.C. current can be used in making the tests.
+</p>
+
+<p>
+A short circuit in the primary is caused by the insulation of the coils
+becoming defective and allowing the bare copper wires to touch each other.
+This may result in a "burn out" of one or more of the transformer coils, if
+the trouble is in the transformer, or in the continued blowing of fuses in
+the line. Feel of each coil separately. If a short circuit exists in a coil
+it will heat excessively. Examine all the wires; the insulation may have
+worn through and two of them may cross, or be in contact with the frame or
+other part of the welder. A short circuit in the regulator winding is
+indicated by failure of the apparatus to regulate properly, and sometimes,
+though not always, by the heating of the regulator coils.
+</p>
+
+<p>
+The remedy for a short circuit is to reinsulate the defective parts. It is
+a good plan to prevent trouble by examining the wiring occasionally and see
+that the insulation is perfect.
+</p>
+
+<p>
+<i>To Locate Grounds and Short Circuits in the Secondary, or Low Voltage
+Side.</i>--Trouble of this kind is indicated by the machine acting sluggish
+or, perhaps, refusing to operate. To make a test, it will be necessary to
+first ascertain the exciting current of your particular transformer. This
+is the current the transformer draws on "open circuit," or when supplied
+with current from the line with no stock in the welder dies. The following
+table will give this information close enough for all practical purposes:
+</p>
+
+<pre>
+K.W.      ----------------- Amperes at ----------------
+Rating    110 Volts   220 Volts   440 Volts   550 Volts
+3         1.5         .75         .38         .3
+5         2.5         1.25        .63         .5
+8         3.6         1.8         .9          .72
+10        4.25        2.13        1.07        .85
+15        6.          3.          1.5         1.2
+20        7.          3.5         1.75        1.4
+30        9.          4.5         2.25        1.8
+35        9.6         4.8         2.4         1.92
+50        10.         5.          2.5         2
+</pre>
+
+<p>
+Remove the fuses from the wall switch and substitute fuses just large
+enough to carry the "exciting" current. If no suitable fuses are at hand,
+fine strands of copper from an ordinary lamp cord may be used. These
+strands are usually No. 30 gauge wire and will fuse at about 10 amperes.
+One or more strands should be used, depending on the amount of exciting
+current, and are connected across the fuse clips in place of fuse wire.
+Place a piece of wood or fibre between the welding dies in the welder as
+though you were going to weld them. See that the regulator is on the
+highest point and close the welder switch. If the secondary circuit is
+badly grounded, current will flow through the ground, and the small fuses
+or small strands of wire will burn out. This is an indication that both
+sides of the secondary circuit are grounded or that a short circuit exists
+in a primary coil. In either case the welder should not be operated until
+the trouble is found and removed. If, however, the small fuses do not
+"blow," remove same and replace the large fuses, then disconnect wires
+running from the wall switch to the welder and substitute two pieces of
+No. 8 or No. 6 insulated copper wire, after scraping off the insulation for
+an inch or two at each end. Connect one wire from the switch to the frame
+of welder; this will leave one loose end. Hold this a foot or so away from
+the place where the insulation is cut off; then turn on the current and
+strike the free end of this wire lightly against one of the copper dies,
+drawing it away quickly. If no sparking is produced, the secondary circuit
+is free from ground, and you will then look for a broken connection in the
+circuit. Some caution must be used in making the above test, as in case one
+terminal is heavily grounded the testing wire may be fused if allowed to
+stay in contact with the die.
+</p>
+
+<p>
+<i>The Remedy.</i>--Clean the slides, dies and terminal blocks thoroughly
+and dry out the fibre insulation if it is damp. See that no scale or metal
+has worked under the sliding parts, and that the secondary leads do not
+touch the frame. If the ground is very heavy it may be necessary to remove
+the slides in order to facilitate the examination and removal of the
+ground. Insulation, where torn or worn through, must be carefully replaced
+or taped. If the transformer coils are grounded to the iron core of the
+transformer or to the secondary, it may be necessary to remove the coils
+and reinsulate them at the points of contact. A short circuited coil will
+heat excessively and eventually burn out. This may mean a new coil if you
+are unable to repair the old one. In all cases the transformer windings
+should be protected from mechanical injury or dampness. Unless excessively
+overloaded, transformers will last for years without giving a moment's
+trouble, if they are not exposed to moisture or are not injured
+mechanically.
+</p>
+
+<p>
+The most common trouble arises from poor electrical contacts, and they are
+the cause of endless trouble and annoyance. See that all connections are
+clean and bright. Take out the dies every day or two and see that there is
+no scale, grease or dirt between them and the holders. Clean them
+thoroughly before replacing. Tighten the bolts running from the transformer
+leads to the work jaws.
+</p>
+
+<p>
+ELECTRIC ARC WELDING
+</p>
+
+<p>
+This method bears no relation to the one just considered, except that the
+source of heat is the same in both cases. Arc welding makes use of the
+flame produced by the voltaic arc in practically the same way that
+oxy-acetylene welding uses the flame from the gases.
+</p>
+
+<p>
+If the ends of two pieces of carbon through which a current of electricity
+is flowing while they are in contact are separated from each other quite
+slowly, a brilliant arc of flame is formed between them which consists
+mainly of carbon vapor. The carbons are consumed by combination with the
+oxygen in the air and through being turned to a gas under the intense heat.
+</p>
+
+<p>
+The most intense action takes place at the center of the carbon which
+carries the positive current and this is the point of greatest heat. The
+temperature at this point in the arc is greater than can be produced by any
+other means under human control.
+</p>
+
+<p>
+An arc may be formed between pieces of metal, called electrodes, in the
+same way as between carbon. The metallic arc is called a flaming arc and as
+the metal of the electrode burns with the heat, it gives the flame a color
+characteristic of the material being used. The metallic arc may be drawn
+out to a much greater length than one formed between carbon electrodes.
+</p>
+
+<p>
+Arc Welding is carried out by drawing a piece of carbon which is of
+negative polarity away from the pieces of metal to be welded while the
+metal is made positive in polarity. The negative wire is fastened to the
+carbon electrode and the work is laid on a table made of cast or wrought
+iron to which the positive wire is made fast. The direction of the flame is
+then from the metal being welded to the carbon and the work is thus
+prevented from being saturated with carbon, which would prove very
+detrimental to its strength. A secondary advantage is found in the fact
+that the greatest heat is at the metal being welded because of its being
+the positive electrode.
+</p>
+
+<p>
+The carbon electrode is usually made from one quarter to one and a half
+inches in diameter and from six to twelve inches in length. The length of
+the arc may be anywhere from one inch to four inches, depending on the size
+of the work being handled.
+</p>
+
+<p>
+While the parts are carefully insulated to avoid danger of shock, it is
+necessary for the operator to wear rubber gloves as a further protection,
+and to wear some form of hood over the head to shield him against the
+extreme heat liberated. This hood may be made from metal, although some
+material that does not conduct electricity is to be preferred. The work is
+watched through pieces of glass formed with one sheet, which is either blue
+or green, placed over another which is red. Screens of glass are sometimes
+used without the head protector. Some protection for the eyes is absolutely
+necessary because of the intense white light.
+</p>
+
+<p>
+It is seldom necessary to preheat the work as with the gas processes,
+because the heat is localized at the point of welding and the action is so
+rapid that the expansion is not so great. The necessity of preheating,
+however, depends entirely on the material, form and size of the work being
+handled. The same advice applies to arc welding as to the gas flame method
+but in a lesser degree. Filling rods are used in the same way as with any
+other flame process.
+</p>
+
+<p>
+It is the purpose of this explanation to state the fundamental principles
+of the application of the electric arc to welding metals, and by applying
+the principles the following questions will be answered:
+</p>
+
+<p>
+What metals can be welded by the electric arc?
+</p>
+
+<p>
+What difficulties are to be encountered in applying the electric arc to
+welding?
+</p>
+
+<p>
+What is the strength of the weld in comparison with the original piece?
+</p>
+
+<p>
+What is the function of the arc welding machine itself?
+</p>
+
+<p>
+What is the comparative application of the electric arc and the
+oxy-acetylene method and others of a similar nature?
+</p>
+
+<p>
+The answers to these questions will make it possible to understand the
+application of this process to any work. In a great many places the use of
+the arc is cutting the cost of welding to a very small fraction of what it
+would be by any other method, so that the importance of this method may be
+well understood.
+</p>
+
+<p>
+Any two metals which are brought to the melting temperature and applied to
+each other will adhere so that they are no more apt to break at the weld
+than at any other point outside of the weld. It is the property of all
+metals to stick together under these conditions. The electric arc is used
+in this connection merely as a heating agent. This is its only function in
+the process.
+</p>
+
+<p>
+It has advantages in its ease of application and the cheapness with which
+heat can be liberated at any given point by its use. There is nothing in
+connection with arc welding that the above principles will not answer; that
+is, that metals at the melting point will weld and that the electric arc
+will furnish the heat to bring them to this point. As to the first
+question, what metals can be welded, all metals can be welded.
+</p>
+
+<p>
+The difficulties which are encountered are as follows:
+</p>
+
+<p>
+In the case of brass or zinc, the metals will be covered with a coat of
+zinc oxide before they reach a welding heat. This zinc oxide makes it
+impossible for two clean surfaces to come together and some method has to
+be used for eliminating this possibility and allowing the two surfaces to
+join without the possibility of the oxide intervening. The same is true of
+aluminum, in which the oxide, alumina, will be formed, and with several
+other alloys comprising elements of different melting points.
+</p>
+
+<p>
+In order to eliminate these oxides, it is necessary in practical work, to
+puddle the weld; this is, to have a sufficient quantity of molten metal at
+the weld so that the oxide is floated away. When this is done, the two
+surfaces which are to be joined are covered with a coat of melted metal on
+which floats the oxide and other impurities. The two pieces are thus
+allowed to join while their surfaces are protected. This precaution is not
+necessary in working with steel except in extreme cases.
+</p>
+
+<p>
+Another difficulty which is met with in the welding of a great many metals
+is their expansion under heat, which results in so great a contraction when
+the weld cools that the metal is left with a considerable strain on it. In
+extreme cases this will result in cracking at the weld or near it. To
+eliminate this danger it is necessary to apply heat either all over the
+piece to be welded or at certain points. In the case of cast iron and
+sometimes with copper it is necessary to anneal after welding, since
+otherwise the welded pieces will be very brittle on account of the
+chilling. This is also true of malleable iron.
+</p>
+
+<p>
+Very thin metals which are welded together and are not backed up by
+something to carry away the excess heat, are very apt to burn through,
+leaving a hole where the weld should be. This difficulty can be eliminated
+by backing up the weld with a metal face or by decreasing the intensity of
+the arc so that this melting through will not occur. However, the practical
+limit for arc welding without backing up the work with a metal face or
+decreasing the intensity of the arc is approximately 22 gauge, although
+thinner metal can be welded by a very skillful and careful operator.
+</p>
+
+<p>
+One difficulty with arc welding is the lack of skillful operators. This
+method is often looked upon as being something out of the ordinary and
+governed by laws entirely different from other welding. As a matter of
+fact, it does not take as much skill to make a good arc weld as it does to
+make a good weld in a forge fire as the blacksmith does it. There are few
+jobs which cannot be handled successfully by an operator of average
+intelligence with one week's instructions, although his work will become
+better and better in quality as he continues to use the arc.
+</p>
+
+<p>
+Now comes the question of the strength of the weld after it has been made.
+This strength is equally as great as that of the metal that is used to make
+the weld. It should be remembered, however, that the metal which goes into
+the weld is put in there as a casting and has not been rolled. This would
+make the strength of the weld as great as the same metal that is used for
+filling if in the cast form.
+</p>
+
+<p>
+Two pieces of steel could be welded together having a tensile strength at
+the weld of 50,000 pounds. Higher strengths than this can be obtained by
+the use of special alloys for the filling material or by rolling. Welds
+with a tensile strength as great as mentioned will give a result which is
+perfectly satisfactory in almost all cases.
+</p>
+
+<p>
+There are a great many jobs where it is possible to fill up the weld, that
+is, make the section at the point of the weld a little larger than the
+section through the rest of the piece. By doing this, the disadvantages
+of the weld being in the form of a casting in comparison with the rest of
+the piece being in the form of rolled steel can be overcome, and make the
+weld itself even stronger than the original piece.
+</p>
+
+<p>
+The next question is the adaptability of the electric arc in comparison
+with forge fire, oxy-acetylene or other method. The answer is somewhat
+difficult if made general. There are no doubt some cases where the use of a
+drop hammer and forge fire or the use of the oxy-acetylene torch will make,
+all things being considered, a better job than the use of the electric arc,
+although a case where this is absolutely proved is rare.
+</p>
+
+<p>
+The electric arc will melt metal in a weld for less than the same metal can
+be melted by the use of the oxy-acetylene torch, and, on account of the
+fact that the heat can be applied exactly where it is required and in the
+amount required, the arc can in almost all cases supply welding heat for
+less cost than a forge fire or heating furnace.
+</p>
+
+<p>
+The one great advantage of the oxy-acetylene method in comparison with
+other methods of welding is the fact that in some cases of very thin sheet,
+the weld can be made somewhat sooner than is possible otherwise. With metal
+of 18 gauge or thicker, this advantage is eliminated. In cutting steel, the
+oxy-acetylene torch is superior to almost any other possible method.
+</p>
+
+<p>
+<i>Arc Welding Machines.</i>--A consideration of the function and purpose
+of the various types of arc welding machines shows that the only reason for
+the use of any machine is either for conversion of the current from
+alternating to direct, or, if the current is already direct, then the
+saving in the application of this current in the arc.
+</p>
+
+<p>
+It is practically out of the question to apply an alternating current arc
+to welding for the reason that in any arc practically all the heat is
+liberated at the positive electrode, which means that, in alternating
+current, half the heat is liberated at each electrode as the current
+changes its direction of flow or alternates. Another disadvantage of the
+alternating arc is that it is difficult of control and application.
+</p>
+
+<p>
+In all arc welding by the use of the carbon arc, the positive electrode is
+made the piece to be welded, while in welding with metallic electrodes this
+may be either the piece to be welded of the rod that is used as a filler.
+The voltage across the arc is a variable quantity, depending on the length
+of the flame, its temperature and the gases liberated in the arc. With a
+carbon electrode the voltage will vary from zero to forty-five volts. With
+the metallic electrode the voltage will vary from zero to thirty volts. It
+is, therefore, necessary for the welding machine to be able to furnish to
+the arc the requisite amount of current, this amount being varied, and
+furnish it at all times at the voltage required.
+</p>
+
+<p>
+The simplest welding apparatus is a resistance in series with the arc. This
+is entirely satisfactory in every way except in cost of current. By the use
+of resistance in series with the arc and using 220 volts as the supply,
+from eighty to ninety per cent of the current is lost in heat at the
+resistance. Another disadvantage is the fact that most materials change
+their resistance as their temperature changes, thus making the amount of
+current for the arc a variable quantity, depending on the temperature of
+the resistance.
+</p>
+
+<p>
+There have been various methods originated for saving the power mentioned
+and a good many machines have been put on the market for this purpose. All
+of them save some power over what a plain resistance would use. Practically
+all arc welding machines at the present time are motor generator sets, the
+motor of which is arranged for the supply voltage and current, this motor
+being direct connected to a compound wound generator delivering
+approximately seventy-five volts direct current. Then by the use of a
+resistance, this seventy-five volt supply is applied to the arc. Since the
+voltage across the arc will vary from zero to fifty volts, this machine
+will save from zero up to seventy per cent of the power that the machine
+delivers. The rest of the power, of course, has to be dissipated in the
+resistance used in series with the arc.
+</p>
+
+<p>
+A motor generator set which can be purchased from any electrical company,
+with a long piece of fence wire wound around a piece of asbestos, gives
+results equally as good and at a very small part of the first cost.
+</p>
+
+<p>
+It is possible to construct a machine which will eliminate all losses in
+the resistance; in other words, eliminate all resistance in series with the
+arc. A machine of this kind will save its cost within a very short time,
+providing the welder is used to any extent.
+</p>
+
+<p>
+Putting it in figures, the results are as follows for average conditions.
+Current at 2c per kilowatt hour, metallic electrode arc of 150 amperes,
+carbon arc 500 amperes; voltage across the metallic electrode arc 20,
+voltage across the carbon arc 35. Supply current 220 volts, direct. In the
+case of the metallic electrode, if resistance is used, the cost of running
+this arc is sixty-six cents per hour. With the carbon electrode, $2.20 per
+hour. If a motor generator set with a seventy volt constant potential
+machine is used for a welder, the cost will be as follows:
+</p>
+
+<p>
+Metallic electrode 25.2c. Carbon electrode 84c per hour. With a machine
+which will deliver the required voltage at the arc and eliminate all the
+resistance in series with the arc, the cost will be as follows: Metallic
+electrode 7.2c per hour; carbon electrode 42c per hour. This is with the
+understanding that the arc is held constant and continuously at its full
+value. This, however, is practically impossible and the actual load factor
+is approximately fifty per cent, which would mean that operating a welder
+as it is usually operated, this result will be reduced to one-half of that
+stated in all cases.
+</p>
+
+<br>
+<br>
+<br>
+
+<h2><a name="vii">CHAPTER VII</a></h2>
+
+<h3>HAND FORGING AND WELDING</h3>
+
+<p>
+Smithing, or blacksmithing, is the process of working heated iron, steel or
+other metals by forging, bending or welding them.
+</p>
+
+<p>
+<i>The Forge.</i>--The metal is heated in a forge consisting of a shallow
+pan for holding the fire, in the center of which is an opening from below
+through which air is forced to make a hot fire.
+</p>
+
+<p class="ctr">
+<a href="images/167.png"><img src="images/167th.png" alt="Figure 48.--Tuyere Construction on a Forge"></a>
+</p>
+
+<p>
+Air is forced through this hole, called a "tuyere" (Figure 48) by means of
+a hand bellows, a rotary fan operated with crank or lever, or with a fan
+driven from an electric motor. The harder the air is driven into the fire
+above the tuyere the more oxygen is furnished and the hotter the fire
+becomes.
+</p>
+
+<p>
+Directly below the tuyere is an opening through which the ashes that drop
+from the fire may be cleaned out.
+</p>
+
+<p>
+<i>The Fire.</i>--The fire is made by placing a small piece of waste soaked
+in oil, kerosene or gasoline, over the tuyere, lighting the waste, then
+starting the fan or blower slowly. Gradually cover the waste, while it is
+burning brightly, with a layer of soft coal. The coal will catch fire and
+burn after the waste has been consumed. A piece of waste half the size of a
+person's hand is ample for this purpose.
+</p>
+
+<p>
+The fuel should be "smithing coal." A lump of smithing coal breaks easily,
+shows clean and even on all sides and should not break into layers. The
+coal is broken into fine pieces and wet before being used on the fire.
+</p>
+
+<p>
+The fire should be kept deep enough so that there is always three or four
+inches of fire below the piece of metal to be heated and there should be
+enough fire above the work so that no part of the metal being heated comes
+in contact with the air. The fire should be kept as small as possible while
+following these rules as to depth.
+</p>
+
+<p>
+To make the fire larger, loosen the coal around the edges. To make the fire
+smaller, pack wet coal around the edges in a compact mass and loosen the
+fire in the center. Add fresh coal only around the edges of the fire. It
+will turn to coke and can then be raked onto the fire. Blow only enough air
+into the fire to keep it burning brightly, not so much that the fire is
+blown up through the top of the coal pack. To prevent the fire from going
+out between jobs, stick a piece of soft wood into it and cover with fresh
+wet coal.
+</p>
+
+<p>
+<i>Tools.</i>--The <i>hammer</i> is a ball pene, or blacksmith's hammer,
+weighing about a pound and a half.
+</p>
+
+<p>
+The <i>sledge</i> is a heavy hammer, weighing from 5 to 20 pounds and
+having a handle 30 to 36 inches long.
+</p>
+
+<p>
+The <i>anvil</i> is a heavy piece of wrought iron (Figure 49), faced with
+steel and having four legs. It has a pointed horn on one end, an
+overhanging tail on the other end and a flat top. In the tail there is a
+square hole called the "hardie" hole and a round one called the "spud"
+hole.
+</p>
+
+<p class="ctr">
+<a href="images/169.png"><img src="images/169th.png" alt="Figure 49.--Anvil, Showing Horn, Tail, Hardie Hole and Spud Hole"></a>
+</p>
+
+<p>
+<i>Tongs</i>, with handles about one foot long and jaws suitable for
+holding the work, are used. To secure a firm grip on the work, the jaws may
+be heated red hot and hammered into shape over the piece to be held, thus
+giving a properly formed jaw. Jaws should touch the work along their entire
+length.
+</p>
+
+<p>
+The <i>set hammer</i> is a hammer, one end of whose head is square and
+flat, and from this face the head tapers evenly to the other face. The
+large face is about 1-1/4 inches square.
+</p>
+
+<p>
+The <i>flatter</i> is a hammer having one face of its head flat and about
+2-1/2 inches square.
+</p>
+
+<p>
+<i>Swages</i> are hammers having specially formed faces for finishing
+rounds, squares, hexagons, ovals, tapers, etc.
+</p>
+
+<p>
+<i>Fullers</i> are hammers having a rounded face, long in one direction.
+They are used for spreading metal in one direction only.
+</p>
+
+<p>
+The <i>hardy</i> is a form of chisel with a short, square shank which may
+be set into the hardie hole for cutting off hot bars.
+</p>
+
+<p>
+<i>Operations.</i>--Blacksmithing consists of bending, drawing or upsetting
+with the various hammers, or in punching holes.
+</p>
+
+<p>
+Bending is done over the square corners of the anvil if square cornered
+bends are desired, or over the horn of the anvil if rounding bends, eyes,
+hooks, etc., are wanted.
+</p>
+
+<p>
+To bend a ring or eye in the end of a bar, first figure the length of stock
+needed by multiplying the diameter of the hole by 31/7, then heat the piece
+to a good full red at a point this distance back from the end. Next bend
+the iron over at a 90 degree angle (square) at this point. Next, heat the
+iron from the bend just made clear to the point and make the eye by laying
+the part that was bent square over the horn of the anvil and bending the
+extreme tip into part of a circle. Keep pushing the piece farther and
+farther over the horn of the anvil, bending it as you go. Do not hammer
+directly over the horn of the anvil, but on the side where you are doing
+the bending.
+</p>
+
+<p>
+To make the outside of a bend square, sharp and full, rather than slightly
+rounding, the bent piece must be laid edgewise on the face of the anvil.
+That is, after making the bend over the corner of the anvil, lay the piece
+on top of the anvil so that its edge and not the flat side rests on the
+anvil top. With the work in this position, strike directly against the
+corner with the hammer so that the blows come in line, first with one leg
+of the work, then the other, and always directly on the corner of the
+piece. This operation cannot be performed by laying the work so that one
+leg hangs over the anvil's corner.
+</p>
+
+<p>
+To make a shoulder on a rod or bar, heat the work and lay flat across the
+top of the anvil with the point at which the shoulder is desired at the
+edge of the anvil. Then place the set hammer on top of the piece, with the
+outside edge of the set hammer directly over the edge of the anvil. While
+hammering in this position keep the work turning continually.
+</p>
+
+<p>
+To draw stock means to make it longer and thinner by hammering. A piece to
+be drawn out is usually laid across the horn of the anvil while being
+struck with the hammer. The metal is then spread in only one direction in
+place of being spread in every direction, as it would be if laid on the
+anvil face. To draw the work, heat it to as high a temperature as it will
+stand without throwing sparks and burning. The fuller may be used for
+drawing metal in place of laying the work over the horn of the anvil.
+</p>
+
+<p>
+When drawing round stock, it should be first drawn out square, and when
+almost down to size it may be rounded. When pointing stock, the same rule
+of first drawing out square applies.
+</p>
+
+<p>
+Upsetting means to make a piece shorter in length and greater in thickness
+or width, or both shorter and thicker. To upset short pieces, heat to a
+bright red at the place to be upset, then stand on end on the anvil face
+and hammer directly down on top until of the right form. Longer pieces may
+be swung against the anvil or placed upright on a heavy piece of metal
+lying on the floor or that is sunk into the floor. While standing on this
+heavy piece the metal may be upset by striking down on the end with a heavy
+hammer or the sledge. If a bend appears while upsetting, it should be
+straightened by hammering back into shape on the anvil face.
+</p>
+
+<p>
+Light blows affect the metal for only a short distance from the point of
+striking, but heavy blows tend to swell the metal more equally through its
+entire length. In driving rivets that should fill the holes, heavy blows
+should be struck, but to shape the end of a rivet or to make a head on a
+rod, light blows should be used.
+</p>
+
+<p>
+The part of the piece that is heated most will upset the most.
+</p>
+
+<p>
+To punch a hole through metal, use a tool steel punch with its end slightly
+tapering to a size a little smaller than the hole to be punched. The end of
+the punch must be square across and never pointed or rounded.
+</p>
+
+<p>
+First drive the punch part way through from one side and then turn the work
+over. When you turn it over, notice where the bulge appears and in that way
+locate the hole and drive the punch through from the second side. This
+makes a cleaner and more even hole than to drive completely through from
+one side. When the punch is driven in from the second side, the place to be
+punched through should be laid over the spud hole in the tail of the anvil
+and the piece driven out of the work.
+</p>
+
+<p>
+Work when hot is larger than it will be after cooling. This must be
+remembered when fitting parts or trouble will result. A two-foot bar of
+steel will be 1/4 inch longer when red hot than when cold.
+</p>
+
+<p>
+The temperatures of iron correspond to the following colors:
+</p>
+
+<pre>
+  Dullest red seen in the dark...  878°
+  Dullest red seen in daylight...  887°
+  Dull red....................... 1100°
+  Full red....................... 1370°
+  Light red...................... 1550°
+  Orange......................... 1650°
+  Light orange................... 1725°
+  Yellow......................... 1825°
+  Light yellow................... 1950°
+</pre>
+
+<p>
+<i>Bending Pipes and Tubes.</i>--It is difficult to make bends or curves in
+pipes and tubing without leaving a noticeable bulge at some point of the
+work. Seamless steel tubing may be handled without very great danger of
+this trouble if care is used, but iron pipe, having a seam running
+lengthwise, must be given special attention to avoid opening the seam.
+</p>
+
+<p>
+Bends may be made without kinking if the tube or pipe is brought to a full
+red heat all the way around its circumference and at the place where the
+bend is desired. Hold the cool portion solidly in a vise and, by taking
+hold of the free end, bend very slowly and with a steady pull. The pipe
+must be kept at full red heat with the flames from one or more torches and
+must not be hammered to produce the bend. If a sufficient purchase cannot
+be secured on the free end by the hand, insert a piece of rod or a smaller
+pipe into the opening.
+</p>
+
+<p>
+While making the bend, should small bulges appear, they may be hammered
+back into shape before proceeding with the work.
+</p>
+
+<p>
+Tubing or pipes may be bent while being held between two flat metal
+surfaces while at a bright red heat. The metal plates at each side of the
+work prevent bulging.
+</p>
+
+<p>
+Another method by which tubing may be bent consists of filling completely
+with tightly packed sand and fitting a solid cap or plug at each end.
+</p>
+
+<p>
+Thin brass tubing may be filled with melted resin and may be bent after the
+resin cools. To remove the resin it is necessary to heat the tube, allowing
+it to run out.
+</p>
+
+<p>
+Large jobs of bending should be handled in special pipe bending machines in
+which the work is forced through formed rolls which prevent its bulging.
+</p>
+
+<p>
+WELDING
+</p>
+
+<p>
+Welding with the heat of a blacksmith forge fire, or a coal or illuminating
+gas fire, can only be performed with iron and steel because of the low heat
+which is not localized as with the oxy-acetylene and electric processes.
+Iron to be welded in this manner is heated until it reaches the temperature
+indicated by an orange color, not white, as is often stated, this orange
+color being slightly above 3600 degrees Fahrenheit. Steel is usually welded
+at a bright red heat because of the danger of oxidizing or burning the
+metal if the temperature is carried above this point.
+</p>
+
+<p>
+<i>The Fire.</i>--If made in a forge, the fire should be built from good
+smithing coal or, better still, from coke. Gas fires are, of course,
+produced by suitable burners and require no special preparation except
+adjustment of the heat to the proper degree for the size and thickness of
+the metal being welded so that it will not be burned.
+</p>
+
+<p>
+A coal fire used for ordinary forging operations should not be used for
+welding because of the impurities it contains. A fresh fire should be built
+with a rather deep bed of coal, four to eight inches being about right for
+work ordinarily met with. The fire should be kept burning until the coal
+around the edges has been thoroughly coked and a sufficient quantity of
+fuel should be on and around the fire so that no fresh coal will have to
+be added while working.
+</p>
+
+<p>
+After the coking process has progressed sufficiently, the edges should be
+packed down and the fire made as small as possible while still surrounding
+the ends to be joined. The fire should not be altered by poking it while
+the metal is being heated. The best form of fire to use is one having
+rather high banks of coked coal on each side of the mass, leaving an
+opening or channel from end to end. This will allow the added fuel to be
+brought down on top of the fire with a small amount of disturbance.
+</p>
+
+<p>
+<i>Preparing to Weld.</i>--If the operator is not familiar with the metal
+to be handled, it is best to secure a test piece if at all possible and try
+heating it and joining the ends. Various grades of iron and steel call for
+different methods of handling and for different degrees of heat, the proper
+method and temperature being determined best by actual test under the
+hammer.
+</p>
+
+<p>
+The form of the pieces also has a great deal to do with their handling,
+especially in the case of a more or less inexperienced workman. If the
+pieces are at all irregular in shape, the motions should be gone through
+with before the metal is heated and the best positions on the anvil as well
+as in the fire determined with regard to the convenience of the workman and
+speed of handling the work after being brought to a welding temperature.
+Unnatural positions at the anvil should be avoided as good work is most
+difficult of performance under these conditions.
+</p>
+
+<p>
+<i>Scarfing.</i>--While there are many forms of welds, depending on the
+relative shape of the pieces to be joined, the portions that are to meet
+and form one piece are always shaped in the same general way, this shape
+being called a "scarf." The end of a piece of work, when scarfed, is
+tapered off on one side so that the extremity comes to a rather sharp edge.
+The other side of the piece is left flat and a continuation in the same
+straight plane with its side of the whole piece of work. The end is then in
+the form of a bevel or mitre joint (Figure 50).
+</p>
+
+<p class="ctr">
+<a href="images/176.png"><img src="images/176th.png" alt="Figure 50.--Scarfing Ends of Work Ready for Welding"></a>
+</p>
+
+<p>
+Scarfing may be produced in any one of several ways. The usual method is to
+bring the ends to a forging heat, at which time they are upset to give a
+larger body of metal at the ends to be joined. This body of metal is then
+hammered down to the taper on one side, the length of the tapered portion
+being about one and a half times the thickness of the whole piece being
+handled. Each piece should be given this shape before proceeding farther.
+</p>
+
+<p>
+The scarf may be produced by filing, sawing or chiseling the ends, although
+this is not good practice because it is then impossible to give the desired
+upset and additional metal for the weld. This added thickness is called for
+by the fact that the metal burns away to a certain extent or turns to
+scale, which is removed before welding.
+</p>
+
+<p>
+When the two ends have been given this shape they should not fit as closely
+together as might be expected, but should touch only at the center of the
+area to be joined (Figure 51). That is to say, the surface of the beveled
+portion should bulge in the middle or should be convex in shape so that the
+edges are separated by a little distance when the pieces are laid together
+with the bevels toward each other. This is done so that the scale which is
+formed on the metal by the heat of the fire can have a chance to escape
+from the interior of the weld as the two parts are forced together.
+</p>
+
+<p class="ctr">
+<a href="images/177.png"><img src="images/177th.png" alt="Figure 51.--Proper Shape of Scarfed Ends"></a>
+</p>
+
+<p>
+If the scarf were to be formed with one or more of the edges touching each
+other at the same time or before the centers did so, the scale would be
+imprisoned within the body of the weld and would cause the finished work to
+be weak, while possibly giving a satisfactory appearance from the outside.
+</p>
+
+<p>
+<i>Fluxes.</i>--In order to assist in removing the scale and other
+impurities and to make the welding surfaces as clean as possible while
+being joined, various fluxing materials are used as in other methods of
+welding.
+</p>
+
+<p>
+For welding iron, a flux of white sand is usually used, this material being
+placed on the metal after it has been brought to a red heat in the fire.
+Steel is welded with dry borax powder, this flux being applied at the same
+time as the iron flux just mentioned. Borax may also be used for iron
+welding and a mixture of borax with steel borings may also be used for
+either class of work. Mixtures of sal ammoniac with borax have been
+successfully used, the proportions being about four parts of borax to one
+of sal ammoniac. Various prepared fluxing powders are on the market for
+this work, practically all of them producing satisfactory results.
+</p>
+
+<p>
+After the metal has been in the fire long enough to reach a red heat, it is
+removed temporarily and, if small enough in size, the ends are dipped into
+a box of flux. If the pieces are large, they may simply be pulled to the
+edge of the fire and the flux then sprinkled on the portions to be joined.
+A greater quantity of flux is required in forge welding than in electric or
+oxy-acetylene processes because of the losses in the fire. After the powder
+has been applied to the surfaces, the work is returned to the fire and
+heated to the welding temperature.
+</p>
+
+<p>
+<i>Heating the Work.</i>--After being scarfed, the two pieces to be welded
+are placed in the fire and brought to the correct temperature. This
+temperature can only be recognized by experiment and experience. The metal
+must be just below that point at which small sparks begin to be thrown out
+of the fire and naturally this is a hard point to distinguish. At the
+welding heat the metal is almost ready to flow and is about the consistency
+of putty. Against the background of the fire and coal the color appears to
+be a cream or very light yellow and the work feels soft as it is handled.
+</p>
+
+<p>
+It is absolutely necessary that both parts be heated uniformly and so that
+they reach the welding temperature at the same time. For this reason they
+should be as close together in the fire as possible and side by side. When
+removed to be hammered together, time is saved if they are picked up in
+such a way that when laid together naturally the beveled surfaces come
+together. This makes it necessary that the workman remember whether the
+scarfed side is up or down, and to assist in this it is a good thing to
+mark the scarfed side with chalk or in some other noticeable manner, so
+that no mistake will be made in the hurry of placing the work on the anvil.
+</p>
+
+<p>
+The common practice in heating allows the temperature to rise until the
+small white sparks are seen to come from the fire. Any heating above this
+point will surely result in burning that will ruin the iron or steel being
+handled. The best welding heat can be discerned by the appearance of the
+metal and its color after experience has been gained with this particular
+material. Test welds can be made and then broken, if possible, so that the
+strength gained through different degrees of heat can be known before
+attempting more important work.
+</p>
+
+<p>
+<i>Welding.</i>--When the work has reached the welding temperature after
+having been replaced in the fire with the flux applied, the two parts are
+quickly tapped to remove the loose scale from their surfaces. They are then
+immediately laid across the top of the anvil, being placed in a diagonal
+position if both pieces are straight. The lower piece is rested on the
+anvil first with the scarf turned up and ready to receive the top piece in
+the position desired. The second piece must be laid in exactly the position
+it is to finally occupy because the two parts will stick together as soon
+as they touch and they cannot well be moved after having once been allowed
+to come in contact with each other. This part of the work must be done
+without any unnecessary loss of time because the comparatively low heat at
+which the parts weld allows them to cool below the working temperature in
+a few seconds.
+</p>
+
+<p>
+The greatest difficulty will be experienced in withdrawing the metal from
+the fire before it becomes burned and in getting it joined before it cools
+below this critical point. The beveled edges of the scarf are, of course,
+the first parts to cool and the weld must be made before they reach a point
+at which they will not join, or else the work will be defective in
+appearance and in fact.
+</p>
+
+<p>
+If the parts being handled are of such a shape that there is danger of
+bending a portion back of the weld, this part may be cooled by quickly
+dipping it into water before laying the work on the anvil to be joined.
+</p>
+
+<p>
+The workman uses a heavy hand hammer in making the joint, and his helper,
+if one is employed, uses a sledge. With the two parts of the work in place
+on the anvil, the workman strikes several light blows, the first ones being
+at a point directly over the center of the weld, so that the joint will
+start from this point and be worked toward the edges. After the pieces have
+united the helper strikes alternate blows with his sledge, always striking
+in exactly the same place as the last stroke of the workman. The hammer
+blows are carried nearer and nearer to the edges of the weld and are made
+steadily heavier as the work progresses.
+</p>
+
+<p>
+The aim during the first part of the operation should be to make a perfect
+joint, with every part of the surfaces united, and too much attention
+should not be paid to appearance, at least not enough to take any chance
+with the strength of the work.
+</p>
+
+<p>
+It will be found, after completion of the weld, that there has been a loss
+in length equal to one-half the thickness of the metal being welded. This
+loss is occasioned by the burned metal and the scale which has been formed.
+</p>
+
+<p>
+<i>Finishing the Weld.</i>--If it is possible to do so, the material should
+be hammered into the shape that it should remain with the same heat that
+was used for welding. It will usually be found, however, that the metal has
+cooled below the point at which it can be worked to advantage. It should
+then be replaced in the fire and brought back to a forging heat.
+</p>
+
+<p class="ctr">
+<a href="images/181.png"><img src="images/181th.png" alt="Figure 52.--Upsetting and Scarfing the End of a Rod"></a>
+</p>
+
+<p>
+While shaping the work at this forging heat every part that has been at a
+red heat should be hammered with uniformly light and even blows as it
+cools. This restores the grain and strength of the iron or steel to a great
+extent and makes the unavoidable weakness as small as possible.
+</p>
+
+<p>
+<i>Forms of Welds.</i>--The simplest of all welds is that called a "lap
+weld." This is made between the ends of two pieces of equal size and
+similar form by scarfing them as described and then laying one on top of
+the other while they are hammered together.
+</p>
+
+<p>
+A butt weld (Figure 52) is made between the ends of two pieces of shaft or
+other bar shapes by upsetting the ends so that they have a considerable
+flare and shaping the face of the end so that it is slightly higher in the
+center than around the edges, this being done to make the centers come
+together first. The pieces are heated and pushed into contact, after which
+the hammering is done as with any other weld.
+</p>
+
+<p class="ctr">
+<a href="images/182.png"><img src="images/182th.png" alt="Figure 53.--Scarfing for a T Weld"></a>
+</p>
+
+<p>
+A form similar to the butt weld in some ways is used for joining the end of
+a bar to a flat surface and is called a jump weld. The bar is shaped in the
+same way as for a butt weld. The flat plate may be left as it is, but if
+possible a depression should be made at the point where the shaft is to be
+placed. With the two parts heated as usual, the bar is dropped into
+position and hammered from above. As soon as the center of the weld has
+been made perfect, the joint may be finished with a fuller driven all the
+way around the edge of the joint.
+</p>
+
+<p>
+When it is required to join a bar to another bar or to the edge of any
+piece at right angles the work is called a "T" weld from its shape when
+complete (Figure 53). The end of the bar is scarfed as described and the
+point of the other bar or piece where the weld is to be made is hammered so
+that it tapers to a thin edge like one-half of a circular depression. The
+pieces are then laid together and hammered as for a lap weld.
+</p>
+
+<p>
+The ends of heavy bar shapes are often joined with a "V," or cleft, weld.
+One bar end is shaped so that it is tapering on both sides and comes to a
+broad edge like the end of a chisel. The other bar is heated to a forging
+temperature and then slit open in a lengthwise direction so that the
+V-shaped opening which is formed will just receive the pointed edge of the
+first piece. With the work at welding heat, the two parts are driven
+together by hammering on the rear ends and the hammering then continues as
+with a lap weld, except that the work is turned over to complete both sides
+of the joint.
+</p>
+
+<p class="ctr">
+<a href="images/183.png"><img src="images/183th.png" alt="Figure 54.-Splitting Ends to Be Welded in Thin Work"></a>
+</p>
+
+<p>
+The forms so far described all require that the pieces be laid together in
+the proper position after removal from the fire, and this always causes a
+slight loss of time and a consequent lowering of the temperature. With very
+light stock, this fall of temperature would be so rapid that the weld would
+be unsuccessful, and in this case the "lock" weld is resorted to. The ends
+of the two pieces to be joined are split for some distance back, and
+one-half of each end is bent up and the other half down (Figure 54). The
+two are then pushed together and placed in the fire in this position. When
+the welding heat is reached, it is only necessary to take the work out of
+the fire and hammer the parts together, inasmuch as they are already in the
+correct position.
+</p>
+
+<p>
+Other forms of welds in which the parts are too small to retain their heat,
+can be made by first riveting them together or cutting them so that they
+can be temporarily fastened in any convenient way when first placed in the
+fire.
+</p>
+
+<br>
+<br>
+<br>
+
+<h2><a name="viii">CHAPTER VIII</a></h2>
+
+<h3>SOLDERING, BRAZING AND THERMIT WELDING</h3>
+
+<p>
+SOLDERING
+</p>
+
+<p>
+Common solder is an alloy of one-half lead with one-half tin, and is called
+"half and half." Hard solder is made with two-thirds tin and one-third
+lead. These alloys, when heated, are used to join surfaces of the same or
+dissimilar metals such as copper, brass, lead, galvanized iron, zinc,
+tinned plate, etc. These metals are easily joined, but the action of solder
+with iron, steel and aluminum is not so satisfactory and requires greater
+care and skill.
+</p>
+
+<p>
+The solder is caused to make a perfect union with the surfaces treated with
+the help of heat from a soldering iron. The soldering iron is made from a
+piece of copper, pointed at one end and with the other end attached to an
+iron rod and wooden handle. A flux is used to remove impurities from the
+joint and allow the solder to secure a firm union with the metal surface.
+The iron, and in many cases the work, is heated with a gasoline blow torch,
+a small gas furnace, an electric heater or an acetylene and air torch.
+</p>
+
+<p>
+The gasoline torch which is most commonly used should be filled two-thirds
+full of gasoline through the hole in the bottom, which is closed by a screw
+plug. After working the small hand pump for 10 to 20 strokes, hold the palm
+of your hand over the end of the large iron tube on top of the torch and
+open the gasoline needle valve about a half turn. Hold the torch so that
+the liquid runs down into the cup below the tube and fills it. Shut the
+gasoline needle valve, wipe the hands dry, and set fire to the fuel in the
+cup. Just as the gasoline fire goes out, open the gasoline needle valve
+about a half turn and hold a lighted match at the end of the iron tube to
+ignite the mixture of vaporized gasoline and air. Open or close the needle
+valve to secure a flame about 4 inches long.
+</p>
+
+<p>
+On top of the iron tube from which the flame issues there is a rest for
+supporting the soldering iron with the copper part in the flame. Place the
+iron in the flame and allow it to remain until the copper becomes very hot,
+not quite red, but almost so.
+</p>
+
+<p>
+A new soldering iron or one that has been misused will have to be "tinned"
+before using. To do this, take the iron from the fire while very hot and
+rub the tip on some flux or dip it into soldering acid. Then rub the tip of
+the iron on a stick of solder or rub the solder on the iron. If the solder
+melts off the stick without coating the end of the iron, allow a few drops
+to fall on a piece of tin plate, then nil the end of the iron on the tin
+plate with considerable force. Alternately rub the iron on the solder and
+dip into flux until the tip has a coating of bright solder for about half
+an inch from the end. If the iron is in very bad shape, it may be necessary
+to scrape or file the end before dipping in the flux for the first time.
+After the end of the iron is tinned in this way, replace it on the rest of
+the torch so that the tinned point is not directly in the flame, turning
+the flame down to accomplish this.
+</p>
+
+<p>
+<i>Flux.</i>--The commonest flux, which is called "soldering acid," is made
+by placing pieces of zinc in muriatic (hydrochloric) acid contained in a
+heavy glass or porcelain dish. There will be bubbles and considerable heat
+evolved and zinc should be added until this action ceases and the zinc
+remains in the liquid, which is now chloride of zinc.
+</p>
+
+<p>
+This soldering acid may be used on any metal to be soldered by applying
+with a brush or swab. For electrical work, this acid should be made neutral
+by the addition of one part ammonia and one part water to each three parts
+of the acid. This neutralized flux will not corrode metal as will the
+ordinary acid.
+</p>
+
+<p>
+Powdered resin makes a good flux for lead, tin plate, galvanized iron and
+aluminum. Tallow, olive oil, beeswax and vaseline are also used for this
+purpose. Muriatic acid may be used for zinc or galvanized iron without the
+addition of the zinc, as described in making zinc chloride. The addition of
+two heaping teaspoonfuls of sal ammoniac to each pint of the chloride of
+zinc is sometimes found to improve its action.
+</p>
+
+<p>
+<i>Soldering Metal Parts.</i>--All surfaces to be joined should be fitted
+to each other as accurately as possible and then thoroughly cleaned with a
+file, emery cloth, scratch bush or by dipping in lye. Work may be cleaned
+by dipping it into nitric acid which has been diluted with an equal volume
+of water. The work should be heated as hot as possible without danger of
+melting, as this causes the solder to flow better and secure a much better
+hold on the surfaces. Hard solder gives better results than half and half,
+but is more difficult to work. It is very important that the soldering iron
+be kept at a high heat during all work, otherwise the solder will only
+stick to the surfaces and will not join with them.
+</p>
+
+<p>
+Sweating is a form of soldering in which the surfaces of the work are first
+covered with a thin layer of solder by rubbing them with the hot iron after
+it has been dipped in or touched to the soldering stick. These surfaces are
+then placed in contact and heated to a point at which the solder melts and
+unites. Sweating is much to be preferred to ordinary soldering where the
+form of the work permits it. This is the only method which should ever be
+used when a fitting is to be placed over the end of a length of tube.
+</p>
+
+<p>
+<i>Soldering Holes.</i>--Clean the surfaces for some distance around the
+hole until they are bright, and apply flux while holding the hot iron near
+the hole. Touch the tip of the iron to some solder until the solder is
+picked up on the iron, and then place this solder, which was just picked
+up, around the edge of the hole. It will leave the soldering iron and stick
+to the metal. Keep adding solder in this way until the hole has been closed
+up by working from the edges and building toward the center. After the hole
+is closed, apply more flux to the job and smooth over with the hot iron
+until there are no rough spots. Should the solder refuse to flow smoothly,
+the iron is not hot enough.
+</p>
+
+<p>
+<i>Soldering Seams.</i>--Clean back from the seam or split for at least
+half an inch all around and then build up the solder in the same way as was
+done with the hole. After closing the opening, apply more flux to the work
+and run the hot iron lengthwise to smooth the job.
+</p>
+
+<p>
+<i>Soldering Wires.</i>--Clean all insulation from the ends to be soldered
+and scrape the ends bright. Lay the ends parallel to each other and,
+starting at the middle of the cleaned portion, wrap the ends around each
+other, one being wrapped to the right, the other to the left. Hold the hot
+iron under the twisted joint and apply flux to the wire. Then dip the iron
+in the solder and apply to the twisted portion until the spaces between the
+wires are filled with solder. Finish by smoothing the joint and cleaning
+away all excess metal by rubbing the hot iron lengthwise. The joint should
+now be covered with a layer of rubber tape and this covered with a layer of
+ordinary friction tape.
+</p>
+
+<p>
+<i>Steel and Iron.</i>--Steel surfaces should be cleaned, then covered with
+clear muriatic acid. While the acid is on the metal, rub with a stick of
+zinc and then tin the surfaces with the hot iron as directed. Cast iron
+should be cleaned and dipped in strong lye to remove grease. Wash the lye
+away with clean water and cover with muriatic acid as with steel. Then rub
+with a piece of zinc and tin the surfaces by using resin as a flux.
+</p>
+
+<p>
+It is very difficult to solder aluminum with ordinary solder. A special
+aluminum solder should be secured, which is easily applied and makes a
+strong joint. Zinc or phosphor tin may be used in place of ordinary solder
+to tin the surfaces or to fill small holes or cracks. The aluminum must be
+thoroughly heated before attempting to solder and the flux may be either
+resin or soldering acid. The aluminum must be thoroughly cleaned with
+dilute nitric acid and kept hot while the solder is applied by forcible
+rubbing with the hot iron.
+</p>
+
+<p>
+BRAZING
+</p>
+
+<p>
+This is a process for joining metal parts, very similar to soldering,
+except that brass is used to make the joint in place of the lead and zinc
+alloys which form solder. Brazing must not be attempted on metals whose
+melting point is less than that of sheet brass.
+</p>
+
+<p>
+Two pieces of brass to be brazed together are heated to a temperature at
+which the brass used in the process will melt and flow between the
+surfaces. The brass amalgamates with the surfaces and makes a very strong
+and perfect joint, which is far superior to any form of soldering where the
+work allows this process to be used, and in many cases is the equal of
+welding for the particular field in which it applies.
+</p>
+
+<p>
+<i>Brazing Heat and Tools.</i>--The metal commonly used for brazing will
+melt at heats between 1350° and 1650° Fahrenheit. To bring the parts to
+this temperature, various methods are in use, using solid, liquid or
+gaseous fuels. While brazing may be accomplished with the fire of the
+blacksmith forge, this method is seldom satisfactory because of the
+difficulty of making a sufficiently clean fire with smithing coal, and it
+should not be used when anything else is available. Large jobs of brazing
+may be handled with a charcoal fire built in the forge, as this fuel
+produces a very satisfactory and clean fire. The only objection is in the
+difficulty of confining the heat to the desired parts of the work.
+</p>
+
+<p>
+The most satisfactory fire is that from a fuel gas torch built for this
+work. These torches are simply forms of Bunsen burners, mixing the proper
+quantity of air with the gas to bring about a perfect combustion. Hose
+lines lead to the mixing tube of the gas torch, one line carrying the gas
+and the other air under a moderate pressure. The air line is often
+dispensed with, allowing the gas to draw air into the burner on the
+injector principle, much the same as with illuminating gas burners for use
+with incandescent mantles. Valves are provided with which the operator may
+regulate the amount of both gas and air, and ordinarily the quality and
+intensity of the flame.
+</p>
+
+<p>
+When gas is not available, recourse may be had to the gasoline torch made
+for brazing. This torch is built in the same way as the small portable
+gasoline torches for soldering operations, with the exception that two
+regulating needle valves are incorporated in place of only one.
+</p>
+
+<p>
+The torches are carried on a framework, which also supports the work being
+handled. Fuel is forced to the torch from a large tank of gasoline into
+which air pressure is pumped by hand. The torches are regulated to give
+the desired flame by means of the needle valves in much the same way as
+with any other form of pressure torch using liquid fuel.
+</p>
+
+<p>
+Another very satisfactory form of torch for brazing is the acetylene-air
+combination described in the chapter on welding instruments. This torch
+gives the correct degree of heat and may be regulated to give a clean and
+easily controlled flame.
+</p>
+
+<p>
+Regardless of the source of heat, the fire or flame must be adjusted so
+that no soot is deposited on the metal surfaces of the work. This can only
+be accomplished by supplying the exact amounts of gas and air that will
+produce a complete burning of the fuel. With the brazing torches in common
+use two heads are furnished, being supplied from the same source of fuel,
+but with separate regulating devices. The torches are adjustably mounted in
+such a way that the flames may be directed toward each other, heating two
+sides of the work at the same time and allowing the pieces to be completely
+surrounded with the flame.
+</p>
+
+<p>
+Except for the source of heat, but one tool is required for ordinary
+brazing operations, this being a spatula formed by flattening one end of a
+quarter-inch steel rod. The spatula is used for placing the brazing metal
+on the work and for handling the flux that is required in this work as in
+all other similar operations.
+</p>
+
+<p>
+<i>Spelter.</i>--The metal that is melted into the joint is called spelter.
+While this name originally applied to but one particular grade or
+composition of metal, common use has extended the meaning until it is
+generally applied to all grades.
+</p>
+
+<p>
+Spelter is variously composed of alloys containing copper, zinc, tin and
+antimony, the mixture employed depending on the work to be done. The
+different grades are of varying hardness, the harder kinds melting at
+higher temperatures than the soft ones and producing a stronger joint when
+used. The reason for not using hard spelter in all cases is the increased
+difficulty of working it and the fact that its melting point is so near to
+some of the metals brazed that there is great danger of melting the work as
+well as the spelter.
+</p>
+
+<p>
+The hardest grade of spelter is made from three-fourths copper with
+one-fourth zinc and is used for working on malleable and cast iron and for
+steel.
+</p>
+
+<p>
+This hard spelter melts at about 1650° and is correspondingly difficult to
+handle.
+</p>
+
+<p>
+A spelter suitable for working with copper is made from equal parts of
+copper and zinc, melting at about 1400° Fahrenheit, 500° below the melting
+point of the copper itself. A still softer brazing metal is composed of
+half copper, three-eighths zinc and one-eighth tin. This grade is used for
+fastening brass to iron and copper and for working with large pieces of
+brass to brass. For brazing thin sheet brass and light brass castings, a
+metal is used which contains two-thirds tin and one-third antimony. The
+low melting point of this last composition makes it very easy to work with
+and the danger of melting the work is very slight. However, as might be
+expected, a comparatively weak joint is secured, which will not stand any
+great strain.
+</p>
+
+<p>
+All of the above brazing metals are used in powder form so that they may be
+applied with the spatula where the joint is exposed on the outside of the
+work. In case it is necessary to braze on the inside of a tube or any deep
+recess, the spelter may be placed on a flat rod long enough to reach to
+the farthest point. By distributing the spelter at the proper points along
+the rod it may be placed at the right points by turning the rod over after
+inserting into the recess.
+</p>
+
+<p>
+<i>Flux.</i>--In order to remove the oxides produced under brazing heat and
+to allow the brazing metal to flow freely into place, a flux of some kind
+must be used. The commonest flux is simply a pure calcined borax powder,
+that is, a borax powder that has been heated until practically all the
+water has been driven off.
+</p>
+
+<p>
+Calcined borax may also be mixed with about 15 per cent of sal ammoniac to
+make a satisfactory fluxing powder. It is absolutely necessary to use flux
+of some kind and a part of whatever is used should be made into a paste
+with water so that it can be applied to the joint to be brazed before
+heating. The remainder of the powder should be kept dry for use during the
+operation and after the heat has been applied.
+</p>
+
+<p>
+<i>Preparing the Work.</i>--The surfaces to be brazed are first thoroughly
+cleaned with files, emery cloth or sand paper. If the work is greasy, it
+should be dipped into a bath of lye or hot soda water so that all trace of
+oil is removed. The parts are then placed in the relation to each other
+that they are to occupy when the work has been completed. The edges to be
+joined should make a secure and tight fit, and should match each other at
+all points so that the smallest possible space is left between them. This
+fit should not be so tight that it is necessary to force the work into
+place, neither should it be loose enough to allow any considerable space
+between the surfaces. The molten spelter will penetrate between surfaces
+that water will flow between when the work and spelter have both been
+brought to the proper heat. It is, of course, necessary that the two parts
+have a sufficient number of points of contact so that they will remain in
+the proper relative position.
+</p>
+
+<p>
+The work is placed on the surface of the brazing table in such a position
+that the flame from the torches will strike the parts to be heated, and
+with the joint in such a position that the melted spelter will flow down
+through it and fill every possible part of the space between the surfaces
+under the action of gravity. That means that the edge of the joint must be
+uppermost and the crack to be filled must not lie horizontal, but at the
+greatest slant possible. Better than any degree of slant would be to have
+the line of the joint vertical.
+</p>
+
+<p>
+The work is braced up or clamped in the proper position before commencing
+to braze, and it is best to place fire brick in such positions that it will
+be impossible for cooling draughts of air to reach the heated metal should
+the flame be removed temporarily during the process. In case there is a
+large body of iron, steel or copper to be handled, it is often advisable to
+place charcoal around the work, igniting this with the flame of the torch
+before starting to braze so that the metal will be maintained at the
+correct heat without depending entirely on the torch.
+</p>
+
+<p>
+When handling brass pieces having thin sections there is danger of melting
+the brass and causing it to flow away from under the flame, with the result
+that the work is ruined. If, in the judgment of the workman, this may
+happen with the particular job in hand, it is well to build up a mould of
+fire clay back of the thin parts or preferably back of the whole piece, so
+that the metal will have the necessary support. This mould may be made by
+mixing the fire clay into a stiff paste with water and then packing it
+against the piece to be supported tightly enough so that the form will be
+retained even if the metal softens.
+</p>
+
+<p>
+<i>Brazing.</i>--With the work in place, it should be well covered with the
+paste of flux and water, then heated until this flux boils up and runs over
+the surfaces. Spelter is then placed in such a position that it will run
+into the joint and the heat is continued or increased until the spelter
+melts and flows in between the two surfaces. The flame should surround the
+work during the heating so that outside air is excluded as far as is
+possible to prevent excessive oxidization.
+</p>
+
+<p>
+When handling brass or copper, the flame should not be directed so that its
+center strikes the metal squarely, but so that it glances from one side or
+the other. Directing the flame straight against the work is often the cause
+of melting the pieces before the operation is completed. When brazing two
+different metals, the flame should play only on the one that melts at the
+higher temperature, the lower melting part receiving its heat from the
+other. This avoids the danger of melting one before the other reaches the
+brazing point.
+</p>
+
+<p>
+The heat should be continued only long enough to cause the spelter to flow
+into place and no longer. Prolonged heating of any metal can do nothing but
+oxidize and weaken it, and this practice should be avoided as much as
+possible. If the spelter melts into small globules in place of flowing, it
+may be caused to spread and run into the joint by lightly tapping the work.
+More dry flux may be added with the spatula if the tapping does not produce
+the desired result.
+</p>
+
+<p>
+Excessive use of flux, especially toward the end of the work, will result
+in a very hard surface on all the work, a surface which will be extremely
+difficult to finish properly. This trouble will be present to a certain
+extent anyway, but it may be lessened by a vigorous scraping with a wire
+brush just as soon as the work is removed from the fire. If allowed to cool
+before cleaning, the final appearance will not be as good as with the
+surplus metal and scale removed immediately upon completing the job.
+</p>
+
+<p>
+After the work has been cleaned with the brush it may be allowed to cool
+and finished to the desired shape, size and surface by filing and
+polishing. When filed, a very thin line of brass should appear where the
+crack was at the beginning of the work. If it is desired to avoid a square
+shoulder and fill in an angle joint to make it rounding, the filling is
+best accomplished by winding a coil of very thin brass wire around the part
+of the work that projects and then causing this to flow itself or else
+allow the spelter to fill the spaces between the layers of wire. Copper
+wire may also be used for this purpose, the spaces being filled with
+melted spelter.
+</p>
+
+<p>
+THERMIT WELDING
+</p>
+
+<p>
+The process of welding which makes use of the great heat produced by oxygen
+combining with aluminum is known as the Thermit process and was perfected
+by Dr. Hans Goldschmidt. The process, which is controlled by the
+Goldschmidt Thermit Company, makes use of a mixture of finely powdered
+aluminum with an oxide of iron called by the trade name, Thermit.
+</p>
+
+<p>
+The reaction is started with a special ignition powder, such as barium
+superoxide and aluminum, and the oxygen from the iron oxide combining with
+the aluminum, producing a mass of superheated steel at about 5000 degrees
+Fahrenheit. After the reaction, which takes from. 30 seconds to a minute,
+the molten metal is drawn from the crucible on to the surfaces to be
+joined. Its extreme heat fuses the metal and a perfect joint is the result.
+This process is suited for welding iron or steel parts of comparatively
+large size.
+</p>
+
+<p>
+<i>Preparation.</i>--The parts to be joined are thoroughly cleaned on the
+surfaces and for several inches back from the joint, after which they are
+supported in place. The surfaces between which the metal will flow are
+separated from 1/4 to 1 inch, depending on the size of the parts, but
+cutting or drilling part of the metal away. After this separation is made
+for allowing the entrance of new metal, the effects of contraction of the
+molten steel are cared for by preheating adjacent parts or by forcing the
+ends apart with wedges and jacks. The amount of this last separation must
+be determined by the shape and proportions of the parts in the same way as
+would be done for any other class of welding which heats the parts to a
+melting point.
+</p>
+
+<p>
+Yellow wax, which has been warmed until plastic, is then placed around the
+joint to form a collar, the wax completely filling the space between the
+ends and being provided with vent holes by imbedding a piece of stout cord,
+which is pulled out after the wax cools.
+</p>
+
+<p>
+A retaining mould (Figure 55) made from sheet steel or fire brick is then
+placed around the parts. This mould is then filled with a mixture of one
+part fire clay, one part ground fire brick and one part fire sand. These
+materials are well mixed and moistened with enough water so that they will
+pack. This mixture is then placed in the mould, filling the space between
+the walls and the wax, and is packed hard with a rammer so that the
+material forms a wall several inches thick between any point of the mould
+and the wax. The mixture must be placed in the mould in small quantities
+and packed tight as the filling progresses.
+</p>
+
+<p class="ctr">
+<a href="images/199.png"><img src="images/199th.png" alt="Figure 55.--Thermit Mould Construction"></a>
+</p>
+
+<p>
+Three or more openings are provided through this moulding material by the
+insertion of wood or pipe forms. One of these openings will lead from the
+lowest point of the wax pattern and is used for the introduction of the
+preheating flame. Another opening leads from the top of the mould into this
+preheating gate, opening into the preheating gate at a point about one inch
+from the wax pattern. Openings, called risers, are then provided from each
+of the high points of the wax pattern to the top of the mould, these risers
+ending at the top in a shallow basin. The molten metal comes up into these
+risers and cares for contraction of the casting, as well as avoiding
+defects in the collar of the weld. After the moulding material is well
+packed, these gate patterns are tapped lightly and withdrawn, except in the
+case of the metal pipes which are placed at points at which it would be
+impossible to withdraw a pattern.
+</p>
+
+<p>
+<i>Preheating.</i>--The ends to be welded are brought to a bright red heat
+by introducing the flame from a torch through the preheating gate. The
+torch must use either gasoline or kerosene, and not crude oil, as the crude
+oil deposits too much carbon on the parts. Preheating of other adjacent
+parts to care for contraction is done at this time by an additional torch
+burner.
+</p>
+
+<p>
+The heating flame is started gently at first and gradually increased. The
+wax will melt and may be allowed to run out of the preheating gate by
+removing the flame at intervals for a few seconds. The heat is continued
+until the mould is thoroughly dried and the parts to be joined are brought
+to the red heat required. This leaves a mould just the shape of the wax
+pattern.
+</p>
+
+<p>
+The heating gate should then be plugged with a sand core, iron plug or
+piece of fitted fire brick, and backed up with several shovels full of the
+moulding mixture, well packed.
+</p>
+
+<p class="ctr">
+<a href="images/201.png"><img src="images/201th.png" alt="Figure 56--Thermit Crucible Plug."></a>
+</p>
+
+<p>
+<i>Thermit Metal.</i>--The reaction takes place in a special crucible lined
+with magnesia tar, which is baked at a red heat until the tar is driven off
+and the magnesia left. This lining should last from twelve to fifteen
+reactions. This magnesia lining ends at the bottom of the crucible in a
+ring of magnesia stone and this ring carries a magnesia thimble through
+which the molten steel passes on its way to the mould. It will usually be
+necessary to renew this thimble after each reaction. This lower opening is
+closed before filling the crucible with thermit by means of a small disc or
+iron carrying a stem, which is called a tapping pin (Figure 56). This pin,
+<i>F</i>, is placed in the thimble with the stem extending down through the
+opening and exposing about two inches. The top of this pin is covered with
+an asbestos, washer, <i>E</i>, then with another iron disc. <i>D</i>, and
+finally with a layer of refractory sand. The crucible is tapped by knocking
+the stem of the pin upwards with a spade or piece of flat iron about four
+feet long.
+</p>
+
+<p>
+The charge of thermit is added by placing a few handfuls over the
+refractory sand and then pouring in the balance required. The amount of
+thermit required is calculated from the wax used. The wax is weighed before
+and after filling <i>the entire space that the thermit will occupy</i>.
+This does not mean only the wax collar, but the space of the mould with all
+gates filled with wax. The number of pounds of wax required for this
+filling multiplied by 25 will give the number of pounds of thermit to be
+used. To this quantity of thermit should be added I per cent of pure
+manganese, 1 per cent nickel thermit and 15 per cent of steel punchings.
+</p>
+
+<p>
+It is necessary, when more than 10 pounds of thermit will be used, to mix
+steel punchings not exceeding 3/8 inch diameter by 1/8 inch thick with the
+powder in order to sufficiently retard the intensity of the reaction.
+</p>
+
+<p>
+Half a teaspoonful of ignition powder is placed on top of the thermit
+charge and ignited with a storm match or piece of red hot iron. The cover
+should be immediately closed on the top of the crucible and the operator
+should get away to a safe distance because of the metal that may be thrown
+out of the crucible.
+</p>
+
+<p>
+After allowing about 30 seconds to a minute for the reaction to take place
+and the slag to rise to the top of the crucible, the tapping pin is struck
+from below and the molten metal allowed to run into the mould. The mould
+should be allowed to remain in place as long as possible, preferably over
+night, so as to anneal the steel in the weld, but in no case should it be
+disturbed for several hours after pouring. After removing the mould, drill
+through the metal left in the riser and gates and knock these sections off.
+No part of the collar should be removed unless absolutely necessary.
+</p>
+
+<br>
+<br>
+<br>
+
+<h2><a name="ix">CHAPTER IX</a></h2>
+
+<h3>OXYGEN PROCESS FOR REMOVAL OF CARBON</h3>
+
+<p>
+Until recently the methods used for removing carbon deposits from gas
+engine cylinders were very impractical and unsatisfactory. The job meant
+dismantling the motor, tearing out all parts, and scraping the pistons and
+cylinder walls by hand.
+</p>
+
+<p>
+The work was never done thoroughly. It required hours of time to do it, and
+then there was always the danger of injuring the inside of the cylinders.
+</p>
+
+<p>
+These methods have been to a large extent superseded by the use of oxygen
+under pressure. The various devices that are being manufactured are known
+as carbon removers, decarbonizers, etc., and large numbers of them are in
+use in the automobile and gasoline traction motor industry.
+</p>
+
+<p>
+<i>Outfit.</i>--The oxygen carbon cleaner consists of a high pressure
+oxygen cylinder with automatic reducing valve, usually constructed on the
+diaphragm principle, thus assuring positive regulation of pressure. This
+valve is fitted with a pressure gauge, rubber hose, decarbonizing torch
+with shut off and flexible tube for insertion into the chamber from which
+the carbon is to be removed.
+</p>
+
+<p>
+There should also be an asbestos swab for swabbing out the inside of the
+cylinder or other chamber with kerosene previous to starting the operation.
+The action consists in simply burning the carbon to a fine dust in the
+presence of the stream of oxygen, this dust being then blown out.
+</p>
+
+<p>
+<i>Operation.</i>--The following are instructions for operating the
+cleaner:--
+</p>
+
+<p>
+(1) Close valve in gasoline supply line and start the motor, letting it run
+until the gasoline is exhausted.
+</p>
+
+<p>
+(2) If the cylinders be T or L head, remove either the inlet or the exhaust
+valve cap, or a spark plug if the cap is tight. If the cylinders have
+overhead valves, remove a spark plug. If any spark plug is then remaining
+in the cylinder it should be removed and an old one or an iron pipe plug
+substituted.
+</p>
+
+<p>
+(3) Raise the piston of the cylinder first to be cleaned to the top of the
+compression stroke and continue this from cylinder to cylinder as the work
+progresses.
+</p>
+
+<p>
+(4) In motors where carbon has been burned hard, the cylinder interior
+should then be swabbed with kerosene before proceeding. Work the swab,
+saturated with kerosene, around the inside of the cylinder until all the
+carbon has been moistened with the oil. This same swab may be used to
+ignite the gas in the cylinder in place of using a match or taper.
+</p>
+
+<p>
+(5) Make all connections to the oxygen cylinder.
+</p>
+
+<p>
+(6) Insert the torch nozzle in the cylinder, open the torch valve gradually
+and regulate to about two lbs. pressure. Manipulate the nozzle inside the
+cylinder and light a match or other flame at the opening so that the carbon
+starts to burn. Cover the various points within the cylinder and when there
+is no further burning the carbon has been removed. The regulating and
+oxygen tank valves are operated in exactly the same way as for welding as
+previously explained.
+</p>
+
+<p>
+It should be carefully noted that when the piston is up, ready to start the
+operation, both valves must be closed. There will be a considerable display
+of sparks while this operation is taking place, but they will not set fire
+to the grease and oil. Care should be used to see that no gasoline is
+about.
+</p>
+
+<br>
+<br>
+<br>
+
+<h2><a name="index">INDEX</a></h2>
+
+<pre>
+Acetylene
+  filtering
+  generators
+  in tanks
+  piping
+  properties of
+  purification of
+Acetylene-air torches
+Air
+  oxygen from
+Alloys
+  table of
+Alloy steel
+Aluminum
+  alloys
+  welding
+Annealing
+Anvil
+Arc welding, electric
+  machines
+Asbestos, use of, in welding
+
+Babbitt
+Bending pipes and tubes
+Bessemer steel
+Beveling
+Brass
+  welding
+Brazing
+  electric
+  heat and tools
+  spelter
+Bronze
+  welding
+Butt welding
+
+Calcium carbide
+Carbide
+  storage of, Fire Underwriters' Rules
+  to water generator
+Carbon removal
+  by oxygen process
+Case hardening steel
+Cast iron
+  welding
+Champfering
+Charging generator
+Chlorate of potash oxygen
+Conductivity of metals
+Copper
+  alloys
+  welding
+Crucible steel
+Cutting, oxy-acetylene
+  torches
+
+Dissolved acetylene
+
+Electric arc welding
+Electric welding
+  troubles and remedies
+Expansion of metals
+
+Flame, welding
+Fluxes
+  for brazing
+  for soldering
+Forge
+  fire
+  practice
+  tools
+  tuvere construction of
+  welding
+  welding preparation
+  welds, forms of
+Forging
+
+Gas holders
+Gases, heating power of
+Generator, acetylene
+  carbide to water
+  construction
+Generator
+  location of
+  operation and care of
+  overheating
+  requirements
+  water to carbide
+German silver
+Gloves
+Goggles
+
+Hand forging
+Hardening steel
+Heat treatment of steel
+Hildebrandt process
+Hose
+
+Injectors, adjuster
+Iron
+  cast
+  grades of
+  malleable cast
+  wrought
+
+Jump weld
+
+Lap welding
+Lead
+Linde process
+Liquid air oxygen
+
+Magnalium
+Malleable iron
+  welding
+Melting points of metals
+Metal alloys, table of
+Metals
+  characteristics of
+  conductivity of
+  expansion of
+  heat treatment of
+  melting points of
+  tensile strength of
+  weight of
+
+Nickel
+Nozzle sizes, torch
+
+Open hearth steel
+Oxy-acetylene cutting
+  welding practice
+Oxygen
+  cylinders
+  weight of
+
+Pipes, bending
+Platinum
+Preheating
+
+Removal of carbon by oxygen process
+Resistance method of electric welding
+Restoration of steel
+Rods, welding
+
+Safety devices
+Scarfing
+Solder
+Soldering
+  flux
+  holes
+  seams
+  steel and iron
+  wires
+Spelter
+Spot welding
+Steel
+  alloys
+  Bessemer
+  crucible
+  heat treatment of
+  open hearth
+  restoration of
+  tensile strength of
+  welding
+Strength of metals
+
+Tank valves
+Tapering
+Tables of welding information
+Tempering steel
+Thermit metal
+  preheating
+  preparation
+  welding
+Tin
+Torch
+  acetylene-air
+  care
+  construction
+  cutting
+  high pressure
+  low pressure
+  medium pressure
+  nozzles
+  practice
+
+Valves, regulating
+  tank
+
+Water
+  to carbide generator
+Welding aluminum
+  brass
+  bronze
+  butt
+  cast iron
+  copper
+  electric
+  electric arc
+  flame
+  forge
+  information and tables
+  instruments
+  lap
+  malleable iron
+  materials
+  practice, oxy-acetylene
+  rods
+  spot
+  steel
+  table
+  thermit
+  torches
+  various metals
+  wrought iron
+Wrought iron
+  welding
+
+Zinc
+</pre>
+
+
+
+
+
+
+
+
+
+<pre>
+
+
+
+
+
+End of the Project Gutenberg EBook of Oxy-Acetylene Welding and Cutting, by
+Harold P. Manly
+
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+Project Gutenberg's Oxy-Acetylene Welding and Cutting, by Harold P. Manly
+
+This eBook is for the use of anyone anywhere at no cost and with
+almost no restrictions whatsoever.  You may copy it, give it away or
+re-use it under the terms of the Project Gutenberg License included
+with this eBook or online at www.gutenberg.org
+
+
+Title: Oxy-Acetylene Welding and Cutting
+       Electric, Forge and Thermit Welding together with related
+       methods and materials used in metal working and the oxygen
+       process for removal of carbon
+
+Author: Harold P. Manly
+
+Posting Date: April 12, 2014 [EBook #7969]
+Release Date: April, 2005
+First Posted: June 7, 2003
+
+Language: English
+
+Character set encoding: ASCII
+
+*** START OF THIS PROJECT GUTENBERG EBOOK OXY-ACETYLENE WELDING AND CUTTING ***
+
+
+
+
+Produced by Juliet Sutherland, John Argus, Tonya Allen,
+Charles Franks and the Online Distributed Proofreading Team.
+
+
+
+
+
+
+
+
+
+
+Oxy-Acetylene Welding and Cutting
+
+Electric, Forge and Thermit Welding
+
+Together with Related Methods and Materials Used in Metal Working
+And
+The Oxygen Process for Removal of Carbon
+
+By
+HAROLD P. MANLY
+
+
+
+
+PREFACE
+
+In the preparation of this work, the object has been to cover not only the
+several processes of welding, but also those other processes which are so
+closely allied in method and results as to make them a part of the whole
+subject of joining metal to metal with the aid of heat.
+
+The workman who wishes to handle his trade from start to finish finds that
+it is necessary to become familiar with certain other operations which
+precede or follow the actual joining of the metal parts, the purpose of
+these operations being to add or retain certain desirable qualities in the
+materials being handled. For this reason the following subjects have been
+included: Annealing, tempering, hardening, heat treatment and the
+restoration of steel.
+
+In order that the user may understand the underlying principles and the
+materials employed in this work, much practical information is given on the
+uses and characteristics of the various metals; on the production, handling
+and use of the gases and other materials which are a part of the equipment;
+and on the tools and accessories for the production and handling of these
+materials.
+
+An examination will show that the greatest usefulness of this book lies in
+the fact that all necessary information and data has been included in one
+volume, making it possible for the workman to use one source for securing a
+knowledge of both principle and practice, preparation and finishing of the
+work, and both large and small repair work as well as manufacturing methods
+used in metal working.
+
+An effort has been made to eliminate all matter which is not of direct
+usefulness in practical work, while including all that those engaged in
+this trade find necessary. To this end, the descriptions have been limited
+to those methods and accessories which are found in actual use today. For
+the same reason, the work includes the application of the rules laid down
+by the insurance underwriters which govern this work as well as
+instructions for the proper care and handling of the generators, torches
+and materials found in the shop.
+
+Special attention has been given to definite directions for handling the
+different metals and alloys which must be handled. The instructions have
+been arranged to form rules which are placed in the order of their use
+during the work described and the work has been subdivided in such a way
+that it will be found possible to secure information on any one point
+desired without the necessity of spending time in other fields.
+
+The facts which the expert welder and metalworker finds it most necessary
+to have readily available have been secured, and prepared especially for
+this work, and those of most general use have been combined with the
+chapter on welding practice to which they apply.
+
+The size of this volume has been kept as small as possible, but an
+examination of the alphabetical index will show that the range of subjects
+and details covered is complete in all respects. This has been accomplished
+through careful classification of the contents and the elimination of all
+repetition and all theoretical, historical and similar matter that is not
+absolutely necessary.
+
+Free use has been made of the information given by those manufacturers who
+are recognized as the leaders in their respective fields, thus insuring
+that the work is thoroughly practical and that it represents present day
+methods and practice.
+
+THE AUTHOR.
+
+
+
+
+CONTENTS
+
+   CHAPTER I
+
+METALS AND ALLOYS--HEAT TREATMENT:--The Use and Characteristics of the
+Industrial Alloys and Metal Elements--Annealing, Hardening, Tempering and
+Case Hardening of Steel
+
+   CHAPTER II
+
+WELDING MATERIALS:--Production, Handling and Use of the Gases, Oxygen and
+Acetylene--Welding Rods--Fluxes--Supplies and Fixtures
+
+   CHAPTER III
+
+ACETYLENE GENERATORS:--Generator Requirements and Types--Construction--Care
+and Operation of Generators.
+
+   CHAPTER IV
+
+WELDING INSTRUMENTS:--Tank and Regulating Valves and Gauges--High, Low and
+Medium Pressure Torches--Cutting Torches--Acetylene-Air Torches
+
+   CHAPTER V
+
+OXY-ACETYLENE WELDING PRACTICE:--Preparation of Work--Torch Practice--
+Control of the Flame--Welding Various Metals and Alloys--Tables of
+Information Required in Welding Operations
+
+   CHAPTER VI
+
+ELECTRIC WELDING:--Resistance Method--Butt, Spot and Lap Welding--Troubles
+and Remedies--Electric Arc Welding
+
+   CHAPTER VII
+
+HAND FORGING AND WELDING:--Blacksmithing, Forging and Bending--Forge
+Welding Methods
+
+   CHAPTER VIII
+
+SOLDERING, BRAZING AND THERMIT WELDING:--Soldering Materials and Practice--
+Brazing--Thermit Welding
+
+   CHAPTER IX
+
+OXYGEN PROCESS FOR REMOVAL OF CARBON
+
+INDEX
+
+
+
+
+
+OXY-ACETYLENE WELDING AND CUTTING, ELECTRIC AND THERMIT WELDING
+
+
+
+
+CHAPTER I
+
+METALS AND THEIR ALLOYS--HEAT TREATMENT
+
+
+THE METALS
+
+_Iron._--Iron, in its pure state, is a soft, white, easily worked
+metal. It is the most important of all the metallic elements, and is, next
+to aluminum, the commonest metal found in the earth.
+
+Mechanically speaking, we have three kinds of iron: wrought iron, cast iron
+and steel. Wrought iron is very nearly pure iron; cast iron contains carbon
+and silicon, also chemical impurities; and steel contains a definite
+proportion of carbon, but in smaller quantities than cast iron.
+
+Pure iron is never obtained commercially, the metal always being mixed with
+various proportions of carbon, silicon, sulphur, phosphorus, and other
+elements, making it more or less suitable for different purposes. Iron is
+magnetic to the extent that it is attracted by magnets, but it does not
+retain magnetism itself, as does steel. Iron forms, with other elements,
+many important combinations, such as its alloys, oxides, and sulphates.
+
+[Illustration: Figure 1.--Section Through a Blast Furnace]
+
+_Cast Iron._--Metallic iron is separated from iron ore in the blast
+furnace (Figure 1), and when allowed to run into moulds is called cast
+iron. This form is used for engine cylinders and pistons, for brackets,
+covers, housings and at any point where its brittleness is not
+objectionable. Good cast iron breaks with a gray fracture, is free from
+blowholes or roughness, and is easily machined, drilled, etc. Cast iron is
+slightly lighter than steel, melts at about 2,400 degrees in practice, is
+about one-eighth as good an electrical conductor as copper and has a
+tensile strength of 13,000 to 30,000 pounds per square inch. Its
+compressive strength, or resistance to crushing, is very great. It has
+excellent wearing qualities and is not easily warped and deformed by heat.
+Chilled iron is cast into a metal mould so that the outside is cooled
+quickly, making the surface very hard and difficult to cut and giving great
+resistance to wear. It is used for making cheap gear wheels and parts that
+must withstand surface friction.
+
+_Malleable Cast Iron._--This is often called simply malleable iron. It
+is a form of cast iron obtained by removing much of the carbon from cast
+iron, making it softer and less brittle. It has a tensile strength of
+25,000 to 45,000 pounds per square inch, is easily machined, will stand a
+small amount of bending at a low red heat and is used chiefly in making
+brackets, fittings and supports where low cost is of considerable
+importance. It is often used in cheap constructions in place of steel
+forgings. The greatest strength of a malleable casting, like a steel
+forging, is in the surface, therefore but little machining should be done.
+
+_Wrought Iron._--This grade is made by treating the cast iron to
+remove almost all of the carbon, silicon, phosphorus, sulphur, manganese
+and other impurities. This process leaves a small amount of the slag from
+the ore mixed with the wrought iron.
+
+Wrought iron is used for making bars to be machined into various parts. If
+drawn through the rolls at the mill once, while being made, it is called
+"muck bar;" if rolled twice, it is called "merchant bar" (the commonest
+kind), and a still better grade is made by rolling a third time. Wrought
+iron is being gradually replaced in use by mild rolled steels.
+
+Wrought iron is slightly heavier than cast iron, is a much better
+electrical conductor than either cast iron or steel, has a tensile strength
+of 40,000 to 60,000 pounds per square inch and costs slightly more than
+steel. Unlike either steel or cast iron, wrought iron does not harden when
+cooled suddenly from a red heat.
+
+_Grades of Irons._--The mechanical properties of cast iron differ
+greatly according to the amount of other materials it contains. The most
+important of these contained elements is carbon, which is present to a
+degree varying from 2 to 5-1/2 per cent. When iron containing much carbon
+is quickly cooled and then broken, the fracture is nearly white in color
+and the metal is found to be hard and brittle. When the iron is slowly
+cooled and then broken the fracture is gray and the iron is more malleable
+and less brittle. If cast iron contains sulphur or phosphorus, it will show
+a white fracture regardless of the rapidity of cooling, being brittle and
+less desirable for general work.
+
+_Steel._--Steel is composed of extremely minute particles of iron and
+carbon, forming a network of layers and bands. This carbon is a smaller
+proportion of the metal than found in cast iron, the percentage being from
+3/10 to 2-1/2 per cent.
+
+Carbon steel is specified according to the number of "points" of carbon, a
+point being one one-hundredth of one per cent of the weight of the steel.
+Steel may contain anywhere from 30 to 250 points, which is equivalent to
+saying, anywhere from 3/10 to 2-1/2 per cent, as above. A 70-point steel
+would contain 70/100 of one per cent or 7/10 of one per cent of carbon by
+weight. The percentage of carbon determines the hardness of the steel, also
+many other qualities, and its suitability for various kinds of work. The
+more carbon contained in the steel, the harder the metal will be, and, of
+course, its brittleness increases with the hardness. The smaller the grains
+or particles of iron which are separated by the carbon, the stronger the
+steel will be, and the control of the size of these particles is the object
+of the science of heat treatment.
+
+In addition to the carbon, steel may contain the following:
+
+Silicon, which increases the hardness, brittleness, strength and difficulty
+  of working if from 2 to 3 per cent is present.
+
+Phosphorus, which hardens and weakens the metal but makes it easier to
+  cast. Three-tenths per cent of phosphorus serves as a hardening agent and
+  may be present in good steel if the percentage of carbon is low. More
+  than this weakens the metal.
+
+Sulphur, which tends to make the metal hard and filled with small holes.
+
+Manganese, which makes the steel so hard and tough that it can with
+  difficulty be cut with steel tools. Its hardness is not lessened by
+  annealing, and it has great tensile strength.
+
+Alloy steel has a varying but small percentage of other elements mixed with
+it to give certain desired qualities. Silicon steel and manganese steel are
+sometimes classed as alloy steels. This subject is taken up in the latter
+part of this chapter under _Alloys_, where the various combinations
+and their characteristics are given consideration.
+
+Steel has a tensile strength varying from 50,000 to 300,000 pounds per
+square inch, depending on the carbon percentage and the other alloys
+present, as well as upon the texture of the grain. Steel is heavier than
+cast iron and weighs about the same as wrought iron. It is about one-ninth
+as good a conductor of electricity as copper.
+
+Steel is made from cast iron by three principal processes: the crucible,
+Bessemer and open hearth.
+
+_Crucible steel_ is made by placing pieces of iron in a clay or
+graphite crucible, mixed with charcoal and a small amount of any desired
+alloy. The crucible is then heated with coal, oil or gas fires until the
+iron melts, and, by absorbing the desired elements and giving up or
+changing its percentage of carbon, becomes steel. The molten steel is then
+poured from the crucible into moulds or bars for use. Crucible steel may
+also be made by placing crude steel in the crucibles in place of the iron.
+This last method gives the finest grade of metal and the crucible process
+in general gives the best grades of steel for mechanical use.
+
+[Illustration: Figure 2.--A Bessemer Converter]
+
+_Bessemer steel_ is made by heating iron until all the undesirable
+elements are burned out by air blasts which furnish the necessary oxygen.
+The iron is placed in a large retort called a converter, being poured,
+while at a melting heat, directly from the blast furnace into the
+converter. While the iron in the converter is molten, blasts of air are
+forced through the liquid, making it still hotter and burning out the
+impurities together with the carbon and manganese. These two elements are
+then restored to the iron by adding spiegeleisen (an alloy of iron, carbon
+and manganese). A converter holds from 5 to 25 tons of metal and requires
+about 20 minutes to finish a charge. This makes the cheapest steel.
+
+[Illustration: Figure 3.--An Open Hearth Furnace]
+
+_Open hearth steel_ is made by placing the molten iron in a receptacle
+while currents of air pass over it, this air having itself been highly
+heated by just passing over white hot brick (Figure. 3). Open hearth steel
+is considered more uniform and reliable than Bessemer, and is used for
+springs, bar steel, tool steel, steel plates, etc.
+
+_Aluminum_ is one of the commonest industrial metals. It is used for
+gear cases, engine crank cases, covers, fittings, and wherever lightness
+and moderate strength are desirable.
+
+Aluminum is about one-third the weight of iron and about the same weight as
+glass and porcelain; it is a good electrical conductor (about one-half as
+good as copper); is fairly strong itself and gives great strength to other
+metals when alloyed with them. One of the greatest advantages of aluminum
+is that it will not rust or corrode under ordinary conditions. The granular
+formation of aluminum makes its strength very unreliable and it is too soft
+to resist wear.
+
+_Copper_ is one of the most important metals used in the trades, and
+the best commercial conductor of electricity, being exceeded in this
+respect only by silver, which is but slightly better. Copper is very
+malleable and ductile when cold, and in this state may be easily worked
+under the hammer. Working in this way makes the copper stronger and harder,
+but less ductile. Copper is not affected by air, but acids cause the
+formation of a green deposit called verdigris.
+
+Copper is one of the best conductors of heat, as well as electricity, being
+used for kettles, boilers, stills and wherever this quality is desirable.
+Copper is also used in alloys with other metals, forming an important part
+of brass, bronze, german silver, bell metal and gun metal. It is about
+one-eighth heavier than steel and has a tensile strength of about 25,000 to
+50,000 pounds per square inch.
+
+_Lead._--The peculiar properties of lead, and especially its quality
+of showing but little action or chemical change in the presence of other
+elements, makes it valuable under certain conditions of use. Its principal
+use is in pipes for water and gas, coverings for roofs and linings for vats
+and tanks. It is also used to coat sheet iron for similar uses and as an
+important part of ordinary solder.
+
+Lead is the softest and weakest of all the commercial metals, being very
+pliable and inelastic. It should be remembered that lead and all its
+compounds are poisonous when received into the system. Lead is more than
+one-third heavier than steel, has a tensile strength of only about 2,000
+pounds per square inch, and is only about one-tenth as good a conductor of
+electricity as copper.
+
+_Zinc._--This is a bluish-white metal of crystalline form. It is
+brittle at ordinary temperatures and becomes malleable at about 250 to 300
+degrees Fahrenheit, but beyond this point becomes even more brittle than at
+ordinary temperatures. Zinc is practically unaffected by air or moisture
+through becoming covered with one of its own compounds which immediately
+resists further action. Zinc melts at low temperatures, and when heated
+beyond the melting point gives off very poisonous fumes.
+
+The principal use of zinc is as an alloy with other metals to form brass,
+bronze, german silver and bearing metals. It is also used to cover the
+surface of steel and iron plates, the plates being then called galvanized.
+
+Zinc weighs slightly less than steel, has a tensile strength of 5,000
+pounds per square inch, and is not quite half as good as copper in
+conducting electricity.
+
+_Tin_ resembles silver in color and luster. Tin is ductile and
+malleable and slightly crystalline in form, almost as heavy as steel, and
+has a tensile strength of 4,500 pounds per square inch.
+
+The principal use of tin is for protective platings on household utensils
+and in wrappings of tin-foil. Tin forms an important part of many alloys
+such as babbitt, Britannia metal, bronze, gun metal and bearing metals.
+
+_Nickel_ is important in mechanics because of its combinations with
+other metals as alloys. Pure nickel is grayish-white, malleable, ductile
+and tenacious. It weighs almost as much as steel and, next to manganese, is
+the hardest of metals. Nickel is one of the three magnetic metals, the
+others being iron and cobalt. The commonest alloy containing nickel is
+german silver, although one of its most important alloys is found in nickel
+steel. Nickel is about ten per cent heavier than steel, and has a tensile
+strength of 90,000 pounds per square inch.
+
+_Platinum._--This metal is valuable for two reasons: it is not
+affected by the air or moisture or any ordinary acid or salt, and in
+addition to this property it melts only at the highest temperatures. It is
+a fairly good electrical conductor, being better than iron or steel. It is
+nearly three times as heavy as steel and its tensile strength is 25,000
+pounds per square inch.
+
+
+ALLOYS
+
+An alloy is formed by the union of a metal with some other material, either
+metal or non-metallic, this union being composed of two or more elements
+and usually brought about by heating the substances together until they
+melt and unite. Metals are alloyed with materials which have been found to
+give to the metal certain characteristics which are desired according to
+the use the metal will be put to.
+
+The alloys of metals are, almost without exception, more important from an
+industrial standpoint than the metals themselves. There are innumerable
+possible combinations, the most useful of which are here classed under the
+head of the principal metal entering into their composition.
+
+_Steel._--Steel may be alloyed with almost any of the metals or
+elements, the combinations that have proven valuable numbering more than a
+score. The principal ones are given in alphabetical order, as follows:
+
+Aluminum is added to steel in very small amounts for the purpose of
+preventing blow holes in castings.
+
+Boron increases the density and toughness of the metal.
+
+Bronze, added by alloying copper, tin and iron, is used for gun metal.
+
+Carbon has already been considered under the head of steel in the section
+devoted to the metals. Carbon, while increasing the strength and hardness,
+decreases the ease of forging and bending and decreases the magnetism and
+electrical conductivity. High carbon steel can be welded only with
+difficulty. When the percentage of carbon is low, the steel is called "low
+carbon" or "mild" steel. This is used for rods and shafts, and called
+"machine" steel. When the carbon percentage is high, the steel is called
+"high carbon" steel, and it is used in the shop as tool steel. One-tenth
+per cent of carbon gives steel a tensile strength of 50,000 to 65,000
+pounds per square inch; two-tenths per cent gives from 60,000 to 80,000;
+four-tenths per cent gives 70,000 to 100,000, and six-tenths per cent
+gives 90,000 to 120,000.
+
+Chromium forms chrome steel, and with the further addition of nickel is
+called chrome nickel steel. This increases the hardness to a high degree
+and adds strength without much decrease in ductility. Chrome steels are
+used for high-speed cutting tools, armor plate, files, springs, safes,
+dies, etc.
+
+Manganese has been mentioned under _Steel_. Its alloy is much used for
+high-speed cutting tools, the steel hardening when cooled in the air and
+being called self-hardening.
+
+Molybdenum is used to increase the hardness to a high degree and makes the
+steel suitable for high-speed cutting and gives it self-hardening
+properties.
+
+Nickel, with which is often combined chromium, increases the strength,
+springiness and toughness and helps to prevent corrosion.
+
+Silicon has already been described. It suits the metal for use in
+high-speed tools.
+
+Silver added to steel has many of the properties of nickel.
+
+Tungsten increases the hardness without making the steel brittle. This
+makes the steel well suited for gas engine valves as it resists corrosion
+and pitting. Chromium and manganese are often used in combination with
+tungsten when high-speed cutting tools are made.
+
+Vanadium as an alloy increases the elastic limit, making the steel
+stronger, tougher and harder. It also makes the steel able to stand much
+bending and vibration.
+
+_Copper._--The principal copper alloys include brass, bronze, german
+silver and gun metal.
+
+Brass is composed of approximately one-third zinc and two-thirds copper. It
+is used for bearings and bushings where the speeds are slow and the loads
+rather heavy for the bearing size. It also finds use in washers, collars
+and forms of brackets where the metal should be non-magnetic, also for many
+highly finished parts.
+
+Brass is about one-third as good an electrical conductor as copper, is
+slightly heavier than steel and has a tensile strength of 15,000 pounds
+when cast and about 75,000 to 100,000 pounds when drawn into wire.
+
+Bronze is composed of copper and tin in various proportions, according to
+the use to which it is to be put. There will always be from six-tenths to
+nine-tenths of copper in the mixture. Bronze is used for bearings,
+bushings, thrust washers, brackets and gear wheels. It is heavier than
+steel, about 1/15 as good an electrical conductor as pure copper and has a
+tensile strength of 30,000 to 60,000 pounds.
+
+Aluminum bronze, composed of copper, zinc and aluminum has high tensile
+strength combined with ductility and is used for parts requiring this
+combination.
+
+Bearing bronze is a variable material, its composition and proportion
+depending on the maker and the use for which it is designed. It usually
+contains from 75 to 85 per cent of copper combined with one or more
+elements, such as tin, zinc, antimony and lead.
+
+White metal is one form of bearing bronze containing over 80 per cent of
+zinc together with copper, tin, antimony and lead. Another form is made
+with nearly 90 per cent of tin combined with copper and antimony.
+
+Gun metal bronze is made from 90 per cent copper with 10 per cent of tin
+and is used for heavy bearings, brackets and highly finished parts.
+
+Phosphor bronze is used for very strong castings and bearings. It is
+similar to gun metal bronze, except that about 1-1/2 per cent of phosphorus
+has been added.
+
+Manganese bronze contains about 1 per cent of manganese and is used for
+parts requiring great strength while being free from corrosion.
+
+German silver is made from 60 per cent of copper with 20 per cent each of
+zinc and nickel. Its high electrical resistance makes it valuable for
+regulating devices and rheostats.
+
+_Tin_ is the principal part of _babbitt_ and _solder_. A
+commonly used babbitt is composed of 89 per cent tin, 8 per cent antimony
+and 3 per cent of copper. A grade suitable for repairing is made from
+80 per cent of lead and 20 per cent antimony. This last formula should not
+be used for particular work or heavy loads, being more suitable for
+spacers. Innumerable proportions of metals are marketed under the name of
+babbitt.
+
+Solder is made from 50 per cent tin and 50 per cent lead, this grade being
+called "half-and-half." Hard solder is made from two-thirds tin and
+one-third lead.
+
+Aluminum forms many different alloys, giving increased strength to whatever
+metal it unites with.
+
+Aluminum brass is composed of approximately 65 per cent copper, 30 per cent
+zinc and 5 per cent aluminum. It forms a metal with high tensile strength
+while being ductile and malleable.
+
+Aluminum zinc is suitable for castings which must be stiff and hard.
+
+Nickel aluminum has a tensile strength of 40,000 pounds per square inch.
+
+Magnalium is a silver-white alloy of aluminum with from 5 to 20 per cent of
+magnesium, forming a metal even lighter than aluminum and strong enough to
+be used in making high-speed gasoline engines.
+
+
+HEAT TREATMENT OF STEEL
+
+The processes of heat treatment are designed to suit the steel for various
+purposes by changing the size of the grain in the metal, therefore the
+strength; and by altering the chemical composition of the alloys in the
+metal to give it different physical properties. Heat treatment, as applied
+in ordinary shop work, includes the three processes of annealing, hardening
+and tempering, each designed to accomplish a certain definite result.
+
+All of these processes require that the metal treated be gradually brought
+to a certain predetermined degree of heat which shall be uniform throughout
+the piece being handled and, from this point, cooled according to certain
+rules, the selection of which forms the difference in the three methods.
+
+_Annealing._--This is the process which relieves all internal strains
+and distortion in the metal and softens it so that it may more easily be
+cut, machined or bent to the required form. In some cases annealing is used
+only to relieve the strains, this being the case after forging or welding
+operations have been performed. In other cases it is only desired to soften
+the metal sufficiently that it may be handled easily. In some cases both of
+these things must be accomplished, as after a piece has been forged and
+must be machined. No matter what the object, the procedure is the same.
+
+The steel to be annealed must first be heated to a dull red. This heating
+should be done slowly so that all parts of the piece have time to reach the
+same temperature at very nearly the same time. The piece may be heated in
+the forge, but a much better way is to heat in an oven or furnace of some
+type where the work is protected against air currents, either hot or cold,
+and is also protected against the direct action of the fire.
+
+[Illustration: Figure 4.--A Gaspipe Annealing Oven]
+
+Probably the simplest of all ovens for small tools is made by placing a
+piece of ordinary gas pipe in the fire (Figure 4), and heating until the
+inside of the pipe is bright red. Parts placed in this pipe, after one end
+has been closed, may be brought to the desired heat without danger of
+cooling draughts or chemical change from the action of the fire. More
+elaborate ovens may be bought which use gas, fuel oils or coal to produce
+the heat and in which the work may be placed on trays so that the fire will
+not strike directly on the steel being treated.
+
+If the work is not very important, it may be withdrawn from the fire or
+oven, after heating to the desired point, and allowed to cool in the air
+until all traces of red have disappeared when held in a dark place. The
+work should be held where it is reasonably free from cold air currents. If,
+upon touching a pine stick to the piece being annealed, the wood does not
+smoke, the work may then be cooled in water.
+
+Better annealing is secured and harder metal may be annealed if the cooling
+is extended over a number of hours by placing the work in a bed of
+non-heat-conducting material, such as ashes, charred bone, asbestos fibre,
+lime, sand or fire clay. It should be well covered with the heat retaining
+material and allowed to remain until cool. Cooling may be accomplished by
+allowing the fire in an oven or furnace to die down and go out, leaving the
+work inside the oven with all openings closed. The greater the time taken
+for gradual cooling from the red heat, the more perfect will be the results
+of the annealing.
+
+While steel is annealed by slow cooling, copper or brass is annealed by
+bringing to a low red heat and quickly plunging into cold water.
+
+_Hardening._--Steel is hardened by bringing to a proper temperature,
+slowly and evenly as for annealing, and then cooling more or less quickly,
+according to the grade of steel being handled. The degree of hardening is
+determined by the kind of steel, the temperature from which the metal is
+cooled and the temperature and nature of the bath into which it is plunged
+for cooling.
+
+Steel to be hardened is often heated in the fire until at some heat around
+600 to 700 degrees is reached, then placed in a heating bath of molten
+lead, heated mercury, fused cyanate of potassium, etc., the heating bath
+itself being kept at the proper temperature by fires acting on it. While
+these baths have the advantage of heating the metal evenly and to exactly
+the temperature desired throughout without any part becoming over or under
+heated, their disadvantages consist of the fact that their materials and
+the fumes are poisonous in most all cases, and if not poisonous, are
+extremely disagreeable.
+
+The degree of heat that a piece of steel must be brought to in order that
+it may be hardened depends on the percentage of carbon in the steel. The
+greater the percentage of carbon, the lower the heat necessary to harden.
+
+[Illustration: Figure 5.--Cooling the Test Bar for Hardening]
+
+To find the proper heat from which any steel must be cooled, a simple test
+may be carried out provided a sample of the steel, about six inches long
+can be secured. One end of this test bar should be heated almost to its
+melting point, and held at this heat until the other end just turns red.
+Now cool the piece in water by plunging it so that both ends enter at the
+same time (Figure 5), that is, hold it parallel with the surface of the
+water when plunged in. This serves the purpose of cooling each point along
+the bar from a different heat. When it has cooled in the water remove the
+piece and break it at short intervals, about 1/2 inch, along its length.
+The point along the test bar which was cooled from the best possible
+temperature will show a very fine smooth grain and the piece cannot be cut
+by a file at this point. It will be necessary to remember the exact color
+of that point when taken from the fire, making another test if necessary,
+and heat all pieces of this same steel to this heat. It will be necessary
+to have the cooling bath always at the same temperature, or the results
+cannot be alike.
+
+While steel to be hardened is usually cooled in water, many other liquids
+may be used. If cooled in strong brine, the heat will be extracted much
+quicker, and the degree of hardness will be greater. A still greater degree
+of hardness is secured by cooling in a bath of mercury. Care should be used
+with the mercury bath, as the fumes that arise are poisonous.
+
+Should toughness be desired, without extreme hardness, the steel may be
+cooled in a bath of lard oil, neatsfoot oil or fish oil. To secure a result
+between water and oil, it is customary to place a thick layer of oil on top
+of water. In cooling, the piece will pass through the oil first, thus
+avoiding the sudden shock of the cold water, yet producing a degree of
+hardness almost as great as if the oil were not used.
+
+It will, of course, be necessary to make a separate test for each cooling
+medium used. If the fracture of the test piece shows a coarse grain, the
+steel was too hot at that point; if the fracture can be cut with a file,
+the metal was not hot enough at that point.
+
+When hardening carbon tool steel its heat should be brought to a cherry
+red, the exact degree of heat depending on the amount of carbon and the
+test made, then plunged into water and held there until all hissing sound
+and vibration ceases. Brine may be used for this purpose; it is even better
+than plain water. As soon as the hissing stops, remove the work from the
+water or brine and plunge in oil for complete cooling.
+
+[Illustration: Figure 6.--Cooling the Tool for Tempering]
+
+In hardening high-speed tool steel, or air hardening steels, the tool
+should be handled as for carbon steel, except that after the body reaches
+a cherry red, the cutting point must be quickly brought to a white heat,
+almost melting, so that it seems ready for welding. Then cool in an oil
+bath or in a current of cool air.
+
+Hardening of copper, brass and bronze is accomplished by hammering or
+working them while cold.
+
+_Tempering_ is the process of making steel tough after it has been
+hardened, so that it will hold a cutting edge and resist cracking.
+Tempering makes the grain finer and the metal stronger. It does not affect
+the hardness, but increases the elastic limit and reduces the brittleness
+of the steel. In that tempering is usually performed immediately after
+hardening, it might be considered as a continuation of the former process.
+
+The work or tool to be tempered is slowly heated to a cherry red and the
+cutting end is then dipped into water to a depth of 1/2 to 3/4 inch above
+the point (Figure 6). As soon as the point cools, still leaving the tool
+red above the part in water, remove the work from the bath and quickly rub
+the end with a fine emery cloth.
+
+As the heat from the uncooled part gradually heats the point again, the
+color of the polished portion changes rapidly. When a certain color is
+reached, the tool should be completely immersed in the water until cold.
+
+For lathe, planer, shaper and slotter tools, this color should be a light
+straw.
+
+Reamers and taps should be cooled from an ordinary straw color.
+
+Drills, punches and wood working tools should have a brown color.
+
+Blue or light purple is right for cold chisels and screwdrivers.
+
+Dark blue should be reached for springs and wood saws.
+
+Darker colors than this, ranging through green and gray, denote that the
+piece has reached its ordinary temper, that is, it is partially annealed.
+
+After properly hardening a spring by dipping in lard or fish oil, it should
+be held over a fire while still wet with the oil. The oil takes fire and
+burns off, properly tempering the spring.
+
+Remember that self-hardening steels must never be dipped in water, and
+always remember for all work requiring degrees of heat, that the more
+carbon, the less heat.
+
+_Case Hardening._--This is a process for adding more carbon to the
+surface of a piece of steel, so that it will have good wear-resisting
+qualities, while being tough and strong on the inside. It has the effect of
+forming a very hard and durable skin on the surface of soft steel, leaving
+the inside unaffected.
+
+The simplest way, although not the most efficient, is to heat the piece to
+be case hardened to a red heat and then sprinkle or rub the part of the
+surface to be hardened with potassium ferrocyanide. This material is a
+deadly poison and should be handled with care. Allow the cyanide to fuse on
+the surface of the metal and then plunge into water, brine or mercury.
+Repeating the process makes the surface harder and the hard skin deeper
+each time.
+
+Another method consists of placing the piece to be hardened in a bed of
+powdered bone (bone which has been burned and then powdered) and cover with
+more powdered bone, holding the whole in an iron tray. Now heat the tray
+and bone with the work in an oven to a bright red heat for 30 minutes to an
+hour and then plunge the work into water or brine.
+
+
+
+
+CHAPTER II
+
+OXY-ACETYLENE WELDING AND CUTTING MATERIALS
+
+
+_Welding._--Oxy-acetylene welding is an autogenous welding process, in
+which two parts of the same or different metals are joined by causing the
+edges to melt and unite while molten without the aid of hammering or
+compression. When cool, the parts form one piece of metal.
+
+The oxy-acetylene flame is made by mixing oxygen and acetylene gases in a
+special welding torch or blowpipe, producing, when burned, a heat of 6,300
+degrees, which is more than twice the melting temperature of the common
+metals. This flame, while being of intense heat, is of very small size.
+
+_Cutting._--The process of cutting metals with the flame produced from
+oxygen and acetylene depends on the fact that a jet of oxygen directed upon
+hot metal causes the metal itself to burn away with great rapidity,
+resulting in a narrow slot through the section cut. The action is so fast
+that metal is not injured on either side of the cut.
+
+_Carbon Removal._--This process depends on the fact that carbon will
+burn and almost completely vanish if the action is assisted with a supply
+of pure oxygen gas. After the combustion is started with any convenient
+flame, it continues as long as carbon remains in the path of the jet of
+oxygen.
+
+_Materials._--For the performance of the above operations we require
+the two gases, oxygen and acetylene, to produce the flames; rods of metal
+which may be added to the joints while molten in order to give the weld
+sufficient strength and proper form, and various chemical powders, called
+fluxes, which assist in the flow of metal and in doing away with many of
+the impurities and other objectionable features.
+
+_Instruments._--To control the combustion of the gases and add to the
+convenience of the operator a number of accessories are required.
+
+The pressure of the gases in their usual containers is much too high for
+their proper use in the torch and we therefore need suitable valves which
+allow the gas to escape from the containers when wanted, and other
+specially designed valves which reduce the pressure. Hose, composed of
+rubber and fabric, together with suitable connections, is used to carry the
+gas to the torch.
+
+The torches for welding and cutting form a class of highly developed
+instruments of the greatest accuracy in manufacture, and must be thoroughly
+understood by the welder. Tables, stands and special supports are provided
+for holding the work while being welded, and in order to handle the various
+metals and allow for their peculiarities while heated use is made of ovens
+and torches for preheating. The operator requires the protection of
+goggles, masks, gloves and appliances which prevent undue radiation of the
+heat.
+
+_Torch Practice._--The actual work of welding and cutting requires
+preliminary preparation in the form of heat treatment for the metals,
+including preheating, annealing and tempering. The surfaces to be joined
+must be properly prepared for the flame, and the operation of the torches
+for best results requires careful and correct regulation of the gases and
+the flame produced.
+
+Finally, the different metals that are to be welded require special
+treatment for each one, depending on the physical and chemical
+characteristics of the material.
+
+It will thus be seen that the apparently simple operations of welding and
+cutting require special materials, instruments and preparation on the part
+of the operator and it is a proved fact that failures, which have been
+attributed to the method, are really due to lack of these necessary
+qualifications.
+
+
+OXYGEN
+
+Oxygen, the gas which supports the rapid combustion of the acetylene in the
+torch flame, is one of the elements of the air. It is the cause and the
+active agent of all combustion that takes place in the atmosphere. Oxygen
+was first discovered as a separate gas in 1774, when it was produced by
+heating red oxide of mercury and was given its present name by the famous
+chemist, Lavoisier.
+
+Oxygen is prepared in the laboratory by various methods, these including
+the heating of chloride of lime and peroxide of cobalt mixed in a retort,
+the heating of chlorate of potash, and the separation of water into its
+elements, hydrogen and oxygen, by the passage of an electric current. While
+the last process is used on a large scale in commercial work, the others
+are not practical for work other than that of an experimental or temporary
+nature.
+
+This gas is a colorless, odorless, tasteless element. It is sixteen times
+as heavy as the gas hydrogen when measured by volume under the same
+temperature and pressure. Under all ordinary conditions oxygen remains in
+a gaseous form, although it turns to a liquid when compressed to 4,400
+pounds to the square inch and at a temperature of 220 deg. below zero.
+
+Oxygen unites with almost every other element, this union often taking
+place with great heat and much light, producing flame. Steel and iron will
+burn rapidly when placed in this gas if the combustion is started with a
+flame of high heat playing on the metal. If the end of a wire is heated
+bright red and quickly plunged into a jar containing this gas, the wire
+will burn away with a dazzling light and be entirely consumed except for
+the molten drops that separate themselves. This property of oxygen is used
+in oxy-acetylene cutting of steel.
+
+The combination of oxygen with other substances does not necessarily cause
+great heat, in fact the combination may be so slow and gradual that the
+change of temperature can not be noticed. An example of this slow
+combustion, or oxidation, is found in the conversion of iron into rust as
+the metal combines with the active gas. The respiration of human beings
+and animals is a form of slow combustion and is the source of animal heat.
+It is a general rule that the process of oxidation takes place with
+increasing rapidity as the temperature of the body being acted upon rises.
+Iron and steel at a red heat oxidize rapidly with the formation of a scale
+and possible damage to the metal.
+
+_Air._--Atmospheric air is a mixture of oxygen and nitrogen with
+traces of carbonic acid gas and water vapor. Twenty-one per cent of the
+air, by volume, is oxygen and the remaining seventy-nine per cent is the
+inactive gas, nitrogen. But for the presence of the nitrogen, which deadens
+the action of the other gas, combustion would take place at a destructive
+rate and be beyond human control in almost all cases. These two gases exist
+simply as a mixture to form the air and are not chemically combined. It is
+therefore a comparatively simple matter to separate them with the processes
+now available.
+
+_Water._--Water is a combination of oxygen and hydrogen, being
+composed of exactly two volumes of hydrogen to one volume of oxygen. If
+these two gases be separated from each other and then allowed to mix in
+these proportions they unite with explosive violence and form water. Water
+itself may be separated into the gases by any one of several means, one
+making use of a temperature of 2,200 deg. to bring about this separation.
+
+[Illustration: Figure 7.--Obtaining Oxygen by Electrolysis]
+
+The easiest way to separate water into its two parts is by the process
+called electrolysis (Figure 7). Water, with which has been mixed a small
+quantity of acid, is placed in a vat through the walls of which enter the
+platinum tipped ends of two electrical conductors, one positive and the
+other negative.
+
+Tubes are placed directly above these wire terminals in the vat, one tube
+being over each electrode and separated from each other by some distance.
+With the passage of an electric current from one wire terminal to the
+other, bubbles of gas rise from each and pass into the tubes. The gas that
+comes from the negative terminal is hydrogen and that from the positive
+pole is oxygen, both gases being almost pure if the work is properly
+conducted. This method produces electrolytic oxygen and electrolytic
+hydrogen.
+
+_The Liquid Air Process._--While several of the foregoing methods of
+securing oxygen are successful as far as this result is concerned, they are
+not profitable from a financial standpoint. A process for separating oxygen
+from the nitrogen in the air has been brought to a high state of perfection
+and is now supplying a major part of this gas for oxy-acetylene welding. It
+is known as the Linde process and the gas is distributed by the Linde Air
+Products Company from its plants and warehouses located in the large cities
+of the country.
+
+The air is first liquefied by compression, after which the gases are
+separated and the oxygen collected. The air is purified and then compressed
+by successive stages in powerful machines designed for this purpose until
+it reaches a pressure of about 3,000 pounds to the square inch. The large
+amount of heat produced is absorbed by special coolers during the process
+of compression. The highly compressed air is then dried and the
+temperature further reduced by other coolers.
+
+The next point in the separation is that at which the air is introduced
+into an apparatus called an interchanger and is allowed to escape through a
+valve, causing it to turn to a liquid. This liquid air is sprayed onto
+plates and as it falls, the nitrogen return to its gaseous state and leaves
+ the oxygen to run to the bottom of the container. This liquid oxygen is
+then allowed to return to a gas and is stored in large gasometers or tanks.
+
+The oxygen gas is taken from the storage tanks and compressed to
+approximately 1,800 pounds to the square inch, under which pressure it is
+passed into steel cylinders and made ready for delivery to the customer.
+This oxygen is guaranteed to be ninety-seven per cent pure.
+
+Another process, known as the Hildebrandt process, is coming into use in
+this country. It is a later process and is used in Germany to a much
+greater extent than the Linde process. The Superior Oxygen Co. has secured
+the American rights and has established several plants.
+
+_Oxygen Cylinders_.--Two sizes of cylinders are in use, one containing
+100 cubic feet of gas when it is at atmospheric pressure and the other
+containing 250 cubic feet under similar conditions. The cylinders are made
+from one piece of steel and are without seams. These containers are tested
+at double the pressure of the gas contained to insure safety while
+handling.
+
+One hundred cubic feet of oxygen weighs nearly nine pounds (8.921), and
+therefore the cylinders will weigh practically nine pounds more when full
+than after emptying, if of the 100 cubic feet size. The large cylinders
+weigh about eighteen and one-quarter pounds more when full than when empty,
+making approximately 212 pounds empty and 230 pounds full.
+
+The following table gives the number of cubic feet of oxygen remaining in
+the cylinders according to various gauge pressures from an initial pressure
+of 1,800 pounds. The amounts given are not exactly correct as this would
+necessitate lengthy calculations which would not make great enough
+difference to affect the practical usefulness of the table:
+
+Cylinder of 100 Cu. Ft. Capacity at 68 deg. Fahr.
+
+ Gauge     Volume     Gauge     Volume
+Pressure  Remaining  Pressure  Remaining
+
+ 1800        100       700        39
+ 1620         90       500        28
+ 1440         80       300        17
+ 1260         70       100         6
+ 1080         60        18         1
+  900         50         9          1/2
+
+Cylinder of 250 Cu. Ft. Capacity at 68 deg. Fahr.
+
+ Gauge     Volume     Gauge     Volume
+Pressure  Remaining  Pressure  Remaining
+
+ 1800        250       700        97
+ 1620        225       500        70
+ 1440        200       300        42
+ 1260        175       100        15
+ 1080        150        18         8
+  900        125         9         1-1/4
+
+The temperature of the cylinder affects the pressure in a large degree, the
+pressure increasing with a rise in temperature and falling with a fall in
+temperature. The variation for a 100 cubic foot cylinder at various
+temperatures is given in the following tabulation:
+
+At 150 deg. Fahr........................ 2090 pounds.
+At 100 deg. Fahr........................ 1912 pounds.
+At  80 deg. Fahr........................ 1844 pounds.
+At  68 deg. Fahr........................ 1800 pounds.
+At  50 deg. Fahr........................ 1736 pounds.
+At  32 deg. Fahr........................ 1672 pounds.
+At   0  Fahr........................ 1558 pounds.
+At -10 deg. Fahr........................ 1522 pounds.
+
+_Chlorate of Potash Method._--In spite of its higher cost and the
+inferior gas produced, the chlorate of potash method of producing oxygen is
+used to a limited extent when it is impossible to secure the gas in
+cylinders.
+
+[Illustration: Figure 8.--Oxygen from Chlorate of Potash]
+
+An iron retort (Figure 8) is arranged to receive about fifteen pounds of
+chlorate of potash mixed with three pounds of manganese dioxide, after
+which the cylinder is closed with a tight cap, clamped on. This retort is
+carried above a burner using fuel gas or other means of generating heat and
+this burner is lighted after the chemical charge is mixed and compressed in
+the tube.
+
+The generation of gas commences and the oxygen is led through water baths
+which wash and cool it before storing in a tank connected with the plant.
+From this tank the gas is compressed into portable cylinders at a pressure
+of about 300 pounds to the square inch for use as required in welding
+operations.
+
+Each pound of chlorate of potash liberates about three cubic feet of
+oxygen, and taking everything into consideration, the cost of gas produced
+in this way is several times that of the purer product secured by the
+liquid air process.
+
+These chemical generators are oftentimes a source of great danger,
+especially when used with or near the acetylene gas generator, as is
+sometimes the case with cheap portable outfits. Their use should not be
+tolerated when any other method is available, as the danger from accident
+alone should prohibit the practice except when properly installed and
+cared for away from other sources of combustible gases.
+
+
+ACETYLENE
+
+In 1862 a chemist, Woehler, announced the discovery of the preparation of
+acetylene gas from calcium carbide, which he had made by heating to a high
+temperature a mixture of charcoal with an alloy of zinc and calcium. His
+product would decompose water and yield the gas. For nearly thirty years
+these substances were neglected, with the result that acetylene was
+practically unknown, and up to 1892 an acetylene flame was seen by very few
+persons and its possibilities were not dreamed of. With the development of
+the modern electric furnace the possibility of calcium carbide as a
+commercial product became known.
+
+In the above year, Thomas L. Willson, an electrical engineer of Spray,
+North Carolina, was experimenting in an attempt to prepare metallic
+calcium, for which purpose he employed an electric furnace operating on a
+mixture of lime and coal tar with about ninety-five horse power. The result
+was a molten mass which became hard and brittle when cool. This apparently
+useless product was discarded and thrown in a nearby stream, when, to the
+astonishment of onlookers, a large volume of gas was immediately
+liberated, which, when ignited, burned with a bright and smoky flame and
+gave off quantities of soot. The solid material proved to be calcium
+carbide and the gas acetylene.
+
+Thus, through the incidental study of a by-product, and as the result of an
+accident, the possibilities in carbide were made known, and in the spring
+of 1895 the first factory in the world for the production of this substance
+was established by the Willson Aluminum Company.
+
+When water and calcium carbide are brought together an action takes place
+which results in the formation of acetylene gas and slaked lime.
+
+
+CARBIDE
+
+Calcium carbide is a chemical combination of the elements carbon and
+calcium, being dark brown, black or gray with sometimes a blue or red
+tinge. It looks like stone and will only burn when heated with oxygen.
+
+Calcium carbide may be preserved for any length of time if protected from
+the air, but the ordinary moisture in the atmosphere gradually affects it
+until nothing remains but slaked lime. It always possesses a penetrating
+odor, which is not due to the carbide itself but to the fact that it is
+being constantly affected by moisture and producing small quantities of
+acetylene gas.
+
+This material is not readily dissolved by liquids, but if allowed to come
+in contact with water, a decomposition takes place with the evolution of
+large quantities of gas. Carbide is not affected by shock, jarring or age.
+
+A pound of absolutely pure carbide will yield five and one-half cubic feet
+of acetylene. Absolute purity cannot be attained commercially, and in
+practice good carbide will produce from four and one-half to five cubic
+feet for each pound used.
+
+Carbide is prepared by fusing lime and carbon in the electric furnace under
+a heat in excess of 6,000 degrees Fahrenheit. These materials are among the
+most difficult to melt that are known. Lime is so infusible that it is
+frequently employed for the materials of crucibles in which the highest
+melting metals are fused, and for the pencils in the calcium light because
+it will stand extremely high temperatures.
+
+Carbon is the material employed in the manufacture of arc light electrodes
+and other electrical appliances that must stand extreme heat. Yet these two
+substances are forced into combination in the manufacture of calcium
+carbide. It is the excessively high temperature attainable in the electric
+furnace that causes this combination and not any effect of the electricity
+other than the heat produced.
+
+A mixture of ground coke and lime is introduced into the furnace through
+which an electric arc has been drawn. The materials unite and form an ingot
+of very pure carbide surrounded by a crust of less purity. The poorer crust
+is rejected in breaking up the mass into lumps which are graded according
+to their size. The largest size is 2 by 3-1/2 inches and is called "lump,"
+a medium size is 1/2 by 2 inches and is called "egg," an intermediate size
+for certain types of generators is 3/8 by 1-1/4 inches and called "nut,"
+and the finely crushed pieces for use in still other types of generators
+are 1/12 by 1/4 inch in size and are called "quarter." Instructions as to
+the size best suited to different generators are furnished by the makers
+of those instruments.
+
+These sizes are packed in air-tight sheet steel drums containing 100 pounds
+each. The Union Carbide Company of Chicago and New York, operating under
+patents, manufactures and distributes the supply of calcium carbide for the
+entire United States. Plants for this manufacture are established at
+Niagara Falls, New York, and Sault Ste. Marie, Michigan. This company
+maintains a system of warehouses in more than one hundred and ten cities,
+where large stocks of all sizes are carried.
+
+The National Board of Fire Underwriters gives the following rules for the
+storage of carbide:
+
+Calcium carbide in quantities not to exceed six hundred pounds may be
+stored, when contained in approved metal packages not to exceed one hundred
+pounds each, inside insured property, provided that the place of storage be
+dry, waterproof and well ventilated and also provided that all but one of
+the packages in any one building shall be sealed and that seals shall not
+be broken so long as there is carbide in excess of one pound in any other
+unsealed package in the building.
+
+Calcium carbide in quantities in excess of six hundred pounds must be
+stored above ground in detached buildings, used exclusively for the storage
+of calcium carbide, in approved metal packages, and such buildings shall be
+constructed to be dry, waterproof and well ventilated.
+
+_Properties of Acetylene._--This gas is composed of twenty-four parts
+of carbon and two parts of hydrogen by weight and is classed with natural
+gas, petroleum, etc., as one of the hydrocarbons. This gas contains the
+highest percentage of carbon known to exist in any combination of this form
+and it may therefore be considered as gaseous carbon. Carbon is the fuel
+that is used in all forms of combustion and is present in all fuels from
+whatever source or in whatever form. Acetylene is therefore the most
+powerful of all fuel gases and is able to give to the torch flame in
+welding the highest temperature of any flame.
+
+Acetylene is a colorless and tasteless gas, possessed of a peculiar and
+penetrating odor. The least trace in the air of a room is easily noticed,
+and if this odor is detected about an apparatus in operation, it is certain
+to indicate a leakage of gas through faulty piping, open valves, broken
+hose or otherwise. This leakage must be prevented before proceeding with
+the work to be done.
+
+All gases which burn in air will, when mixed with air previous to ignition,
+produce more or less violent explosions, if fired. To this rule acetylene
+is no exception. One measure of acetylene and twelve and one-half of air
+are required for complete combustion; this is therefore the proportion for
+the most perfect explosion. This is not the only possible mixture that will
+explode, for all proportions from three to thirty per cent of acetylene in
+air will explode with more or less force if ignited.
+
+The igniting point of acetylene is lower than that of coal gas, being about
+900 degrees Fahrenheit as against eleven hundred degrees for coal gas. The
+gas issuing from a torch will ignite if allowed to play on the tip of a
+lighted cigar.
+
+It is still further true that acetylene, at some pressures, greater than
+normal, has under most favorable conditions for the effect, been found to
+explode; yet it may be stated with perfect confidence that under no
+circumstances has anyone ever secured an explosion in it when subjected to
+pressures not exceeding fifteen pounds to the square inch.
+
+Although not exploded by the application of high heat, acetylene is injured
+by such treatment. It is partly converted, by high heat, into other
+compounds, thus lessening the actual quantity of the gas, wasting it and
+polluting the rest by the introduction of substances which do not belong
+there. These compounds remain in part with the gas, causing it to burn with
+a persistent smoky flame and with the deposit of objectionable tarry
+substances. Where the gas is generated without undue rise of temperature
+these difficulties are avoided.
+
+_Purification of Acetylene._--Impurities in this gas are caused by
+impurities in the calcium carbide from which it is made or by improper
+methods and lack of care in generation. Impurities from the material will
+be considered first.
+
+Impurities in the carbide may be further divided into two classes: those
+which exert no action on water and those which act with the water to throw
+off other gaseous products which remain in the acetylene. Those impurities
+which exert no action on the water consist of coke that has not been
+changed in the furnace and sand and some other substances which are
+harmless except that they increase the ash left after the acetylene has
+been generated.
+
+An analysis of the gas coming from a typical generator is as follows:
+
+                                          Per cent
+  Acetylene ................................ 99.36
+  Oxygen ...................................   .08
+  Nitrogen .................................   .11
+  Hydrogen .................................   .06
+  Sulphuretted Hydrogen ....................   .17
+  Phosphoretted Hydrogen ...................   .04
+  Ammonia ..................................   .10
+  Silicon Hydride ..........................   .03
+  Carbon Monoxide ..........................   .01
+  Methane ..................................   .04
+
+The oxygen, nitrogen, hydrogen, methane and carbon monoxide are either
+harmless or are present in such small quantities as to be neglected. The
+phosphoretted hydrogen and silicon hydride are self-inflammable gases when
+exposed to the air, but their quantity is so very small that this
+possibility may be dismissed. The ammonia and sulphuretted hydrogen are
+almost entirely dissolved by the water used in the gas generator. The
+surest way to avoid impure gas is to use high-grade calcium carbide in the
+generator and the carbide of American manufacture is now so pure that it
+never causes trouble.
+
+The first and most important purification to which the gas is subjected is
+its passage through the body of water in the generator as it bubbles to the
+top. It is then filtered through felt to remove the solid particles of lime
+dust and other impurities which float in the gas.
+
+Further purification to remove the remaining ammonia, sulphuretted hydrogen
+and phosphorus containing compounds is accomplished by chemical means. If
+this is considered necessary it can be easily accomplished by readily
+available purifying apparatus which can be attached to any generator or
+inserted between the generator and torch outlets. The following mixtures
+have been used.
+
+"_Heratol,_" a solution of chromic acid or sulphuric acid absorbed in
+porous earth.
+
+"_Acagine,_" a mixture of bleaching powder with fifteen per cent of
+lead chromate.
+
+"_Puratylene,_" a mixture of bleaching powder and hydroxide of lime,
+made very porous, and containing from eighteen to twenty per cent of active
+chlorine.
+
+"_Frankoline,_" a mixture of cuprous and ferric chlorides dissolved in
+strong hydrochloric acid absorbed in infusorial earth.
+
+A test for impure acetylene gas is made by placing a drop of ten per cent
+solution of silver nitrate on a white blotter and holding the paper in a
+stream of gas coming from the torch tip. Blackening of the paper in a short
+length of time indicates impurities.
+
+_Acetylene in Tanks._--Acetylene is soluble in water to a very limited
+extent, too limited to be of practical use. There is only one liquid that
+possesses sufficient power of containing acetylene in solution to be of
+commercial value, this being the liquid acetone. Acetone is produced in
+various ways, oftentimes from the distillation of wood. It is a
+transparent, colorless liquid that flows with ease. It boils at 133 deg.
+Fahrenheit, is inflammable and burns with a luminous flame. It has a
+peculiar but rather agreeable odor.
+
+Acetone dissolves twenty-four times its own bulk of acetylene at ordinary
+atmospheric pressure. If this pressure is increased to two atmospheres,
+14.7 pounds above ordinary pressure, it will dissolve just twice as much of
+the gas and for each atmosphere that the pressure is increased it will
+dissolve as much more.
+
+If acetylene be compressed above fifteen pounds per square inch at ordinary
+temperature without first being dissolved in acetone a danger is present of
+self-ignition. This danger, while practically nothing at fifteen pounds,
+increases with the pressure until at forty atmospheres it is very
+explosive. Mixed with acetone, the gas loses this dangerous property and is
+safe for handling and transportation. As acetylene is dissolved in the
+liquid the acetone increases its volume slightly so that when the gas has
+been drawn out of a closed tank a space is left full of free acetylene.
+
+This last difficulty is removed by first filling the cylinder or tank with
+some porous material, such as asbestos, wood charcoal, infusorial earth,
+etc. Asbestos is used in practice and by a system of packing and supporting
+the absorbent material no space is left for the free gas, even when the
+acetylene has been completely withdrawn.
+
+The acetylene is generated in the usual way and is washed, purified and
+dried. Great care is used to make the gas as free as possible from all
+impurities and from air. The gas is forced into containers filled with
+acetone as described and is compressed to one hundred and fifty pounds to
+the square inch. From these tanks it is transferred to the smaller portable
+cylinders for consumers' use.
+
+The exact volume of gas remaining in a cylinder at atmospheric temperature
+may be calculated if the weight of the cylinder empty is known. One pound
+of the gas occupies 13.6 cubic feet, so that if the difference in weight
+between the empty cylinder and the one considered be multiplied by 13.6.
+the result will be the number of cubic feet of gas contained.
+
+The cylinders contain from 100 to 500 cubic feet of acetylene under
+pressure. They cannot be filled with the ordinary type of generator as they
+require special purifying and compressing apparatus, which should never be
+installed in any building where other work is being carried on, or near
+other buildings which are occupied, because of the danger of explosion.
+
+Dissolved acetylene is manufactured by the Prest-O-Lite Company, the
+Commercial Acetylene Company and the Searchlight Gas Company and is
+distributed from warehouses in various cities.
+
+These tanks should not be discharged at a rate per hour greater than
+one-seventh of their total capacity, that is, from a tank of 100 cubic feet
+capacity, the discharge should not be more than fourteen cubic feet per
+hour. If discharge is carried on at an excessive rate the acetone is drawn
+out with the gas and reduces the heat of the welding flame.
+
+For this reason welding should not be attempted with cylinders designed for
+automobile and boat lighting. When the work demands a greater delivery than
+one of the larger tanks will give, two or more tanks may be connected with
+a special coupler such as may be secured from the makers and distributers
+of the gas. These couplers may be arranged for two, three, four or five
+tanks in one battery by removing the plugs on the body of the coupler and
+attaching additional connecting pipes. The coupler body carries a pressure
+gauge and the valve for controlling the pressure of the gas as it flows to
+the welding torches. The following capacities should be provided for:
+
+Acetylene Consumption         Combined Capacity of
+ of Torches per Hour           Cylinders in Use
+Up to 15 feet.......................100 cubic feet
+16 to 30 feet.......................200 cubic feet
+31 to 45 feet.......................300 cubic feet
+46 to 60 feet.......................400 cubic feet
+61 to 75 feet.......................500 cubic feet
+
+
+WELDING RODS
+
+The best welding cannot be done without using the best grade of materials,
+and the added cost of these materials over less desirable forms is so
+slight when compared to the quality of work performed and the waste of
+gases with inferior supplies, that it is very unprofitable to take any
+chances in this respect. The makers of welding equipment carry an
+assortment of supplies that have been standardized and that may be relied
+upon to produce the desired result when properly used. The safest plan is
+to secure this class of material from the makers.
+
+Welding rods, or welding sticks, are used to supply the additional metal
+required in the body of the weld to replace that broken or cut away and
+also to add to the joint whenever possible so that the work may have the
+same or greater strength than that found in the original piece. A rod of
+the same material as that being welded is used when both parts of the work
+are the same. When dissimilar metals are to be joined rods of a composition
+suited to the work are employed.
+
+These filling rods are required in all work except steel of less than 16
+gauge. Alloy iron rods are used for cast iron. These rods have a high
+silicon content, the silicon reacting with the carbon in the iron to
+produce a softer and more easily machined weld than would otherwise be the
+case. These rods are often made so that they melt at a slightly lower point
+than cast iron. This is done for the reason that when the part being welded
+has been brought to the fusing heat by the torch, the filling material can
+be instantly melted in without allowing the parts to cool. The metal can be
+added faster and more easily controlled.
+
+Rods or wires of Norway iron are used for steel welding in almost all
+cases. The purity of this grade of iron gives a homogeneous, soft weld of
+even texture, great ductility and exceptionally good machining qualities.
+For welding heavy steel castings, a rod of rolled carbon steel is employed.
+For working on high carbon steel, a rod of the steel being welded must be
+employed and for alloy steels, such as nickel, manganese, vanadium, etc.,
+special rods of suitable alloy composition are preferable.
+
+Aluminum welding rods are made from this metal alloyed to give the even
+flowing that is essential. Aluminum is one of the most difficult of all the
+metals to handle in this work and the selection of the proper rod is of
+great importance.
+
+Brass is filled with brass wire when in small castings and sheets. For
+general work with brass castings, manganese bronze or Tobin bronze may be
+used.
+
+Bronze is welded with manganese bronze or Tobin bronze, while copper is
+filled with copper wire.
+
+These welding rods should always be used to fill the weld when the
+thickness of material makes their employment necessary, and additional
+metal should always be added at the weld when possible as the joint cannot
+have the same strength as the original piece if made or dressed off flush
+with the surfaces around the weld. This is true because the metal welded
+into the joint is a casting and will never have more strength than a
+casting of the material used for filling.
+
+Great care should be exercised when adding metal from welding rods to make
+sure that no metal is added at a point that is not itself melted and molten
+when the addition is made. When molten metal is placed upon cooler surfaces
+the result is not a weld but merely a sticking together of the two parts
+without any strength in the joint.
+
+
+FLUXES
+
+Difficulty would be experienced in welding with only the metal and rod to
+work with because of the scale that forms on many materials under heat, the
+oxides of other metals and the impurities found in almost all metals. These
+things tend to prevent a perfect joining of the metals and some means are
+necessary to prevent their action.
+
+Various chemicals, usually in powder form, are used to accomplish the
+result of cleaning the weld and making the work of the operator less
+difficult. They are called fluxes.
+
+A flux is used to float off physical impurities from the molten metal; to
+furnish a protecting coating around the weld; to assist in the removal of
+any objectionable oxide of the metals being handled; to lower the
+temperature at which the materials flow; to make a cleaner weld and to
+produce a better quality of metal in the finished work.
+
+The flux must be of such composition that it will accomplish the desired
+result without introducing new difficulties. They may be prepared by the
+operator in many cases or may be secured from the makers of welding
+apparatus, the same remarks applying to their quality as were made
+regarding the welding rods, that is, only the best should be considered.
+
+The flux used for cast iron should have a softening effect and should
+prevent burning of the metal. In many cases it is possible and even
+preferable to weld cast iron without the use of a flux, and in any event
+the smaller the quantity used the better the result should be. Flux should
+not be added just before the completion of the work because the heat will
+not have time to drive the added elements out of the metal or to
+incorporate them with the metal properly.
+
+Aluminum should never be welded without using a flux because of the oxide
+formed. This oxide, called alumina, does not melt until a heat of 5,000 deg.
+Fahrenheit is reached, four times the heat needed to melt the aluminum
+itself. It is necessary that this oxide be broken down or dissolved so that
+the aluminum may have a chance to flow together. Copper is another metal
+that requires a flux because of its rapid oxidation under heat.
+
+While the flux is often thrown or sprinkled along the break while welding,
+much better results will be obtained by dipping the hot end of the welding
+rod into the flux whenever the work needs it. Sufficient powder will stick
+on the end of the rod for all purposes, and with some fluxes too much will
+adhere. Care should always be used to avoid the application of excessive
+flux, as this is usually worse than using too little.
+
+
+SUPPLIES AND FIXTURES
+
+_Goggles._--The oxy-acetylene torch should not be used without the
+protection to the eyes afforded by goggles. These not only relieve
+unnecessary strain, but make it much easier to watch the exact progress of
+the work with the molten metal. The difficulty of protecting the sight
+while welding is even greater than when cutting metal with the torch.
+
+Acetylene gives a light which is nearest to sunlight of any artificial
+illuminant. But for the fact that this gas light gives a little more green
+and less blue in its composition, it would be the same in quality and
+practically the same in intensity. This light from the gas is almost absent
+during welding, being lost with the addition of the extra oxygen needed to
+produce the welding heat. The light that is dangerous comes from the molten
+metal which flows under the torch at a bright white heat.
+
+Goggles for protection against this light and the heat that goes with it
+may be secured in various tints, the darker glass being for welding and
+the lighter for cutting. Those having frames in which the metal parts do
+not touch the flesh directly are most desirable because of the high
+temperature reached by these parts.
+
+_Gloves._--While not as necessary as are the goggles, gloves are a
+convenience in many cases. Those in which leather touches the hands
+directly are really of little value as the heat that protection is desired
+against makes the leather so hot that nothing is gained in comfort. Gloves
+are made with asbestos cloth, which are not open to this objection in so
+great a degree.
+
+[Illustration: Figure 9.--Frame for Welding Stand]
+
+_Tables and Stands._--Tables for holding work while being welded
+(Figure 9) are usually made from lengths of angle steel welded together.
+The top should be rectangular, about two feet wide and two and one-half
+feet long. The legs should support the working surface at a height of
+thirty-two to thirty-six inches from the floor. Metal lattice work may be
+fastened or laid in the top framework and used to support a layer of
+firebrick bound together with a mixture of one-third cement and two-thirds
+fireclay. The piece being welded is braced and supported on this table with
+pieces of firebrick so that it will remain stationary during the operation.
+
+Holders for supporting the tanks of gas may be
+made or purchased in forms that rest directly on the floor or that are
+mounted on wheels. These holders are quite useful where the floor or ground
+is very uneven.
+
+_Hose._--All permanent lines from tanks and generators to the torches
+are made with piping rigidly supported, but the short distance from the end
+of the pipe line to the torch itself is completed with a flexible hose so
+that the operator may be free in his movements while welding. An accident
+through which the gases mix in the hose and are ignited will burst this
+part of the equipment, with more or less painful results to the person
+handling it. For that reason it is well to use hose with great enough
+strength to withstand excessive pressure.
+
+A poor grade of hose will also break down inside and clog the flow of gas,
+both through itself and through the parts of the torch. To avoid outside
+damage and cuts this hose is sometimes encased with coiled sheet metal.
+Hose may be secured with a bursting strength of more than 1,000 pounds to
+the square inch. Many operators prefer to distinguish between the oxygen
+and acetylene lines by their color and to allow this, red is used for the
+oxygen and black for acetylene.
+
+_Other Materials._--Sheet asbestos and asbestos fibre in flakes are
+used to cover parts of the work while preparing them for welding and during
+the operation itself. The flakes and small pieces that become detached from
+the large sheets are thrown into a bin where the completed small work is
+placed to allow slow and even cooling while protected by the asbestos.
+
+Asbestos fibre and also ordinary fireclay are often used to make a backing
+or mould into a form that may be placed behind aluminum and some other
+metals that flow at a low heat and which are accordingly difficult to
+handle under ordinary methods. This forms a solid mould into which the
+metal is practically cast as melted by the torch so that the desired shape
+is secured without danger of the walls of metal breaking through and
+flowing away.
+
+Carbon blocks and rods are made in various shapes and sizes so that they
+may be used to fill threaded holes and other places that it is desired to
+protect during welding. These may be secured in rods of various diameters
+up to one inch and in blocks of several different dimensions.
+
+
+
+
+CHAPTER III
+
+ACETYLENE GENERATORS
+
+
+Acetylene generators used for producing the gas from the action of water on
+calcium carbide are divided into three principal classes according to the
+pressure under which they operate.
+
+Low pressure generators are designed to operate at one pound or less per
+square inch. Medium pressure systems deliver the gas at not to exceed
+fifteen pounds to the square inch while high pressure types furnish gas
+above fifteen pounds per square inch. High pressure systems are almost
+unknown in this country, the medium pressure type being often referred to
+as "high pressure."
+
+Another important distinction is formed by the method of bringing the
+carbide and water together. The majority of those now in use operate by
+dropping small quantities of carbide into a large volume of water, allowing
+the generated gas to bubble up through the water before being collected
+above the surface. This type is known as the "carbide to water" generator.
+
+A less used type brings a measured and small quantity of water to a
+comparatively large body of the carbide, the gas being formed and collected
+from the chamber in which the action takes place. This is called the "water
+to carbide" type. Another way of expressing the difference in feed is that
+of designating the two types as "carbide feed" for the former and "water
+feed" for the latter.
+
+A further division of the carbide to water machines is made by mentioning
+the exact method of feeding the carbide. One type, called "gravity feed"
+operates by allowing the carbide to escape and fall by the action of its
+own weight, or gravity; the other type, called "forced feed," includes a
+separate mechanism driven by power. This mechanism feeds definite amounts
+of the carbide to the water as required by the demands on the generator.
+The action of either feed is controlled by the withdrawal of gas from the
+generator, the aim being to supply sufficient carbide to maintain a nearly
+constant supply.
+
+_Generator Requirements._--The qualities of a good generator are
+outlined as follows: [Footnote: See Pond's "Calcium Carbide and
+Acetylene."]
+
+It must allow no possibility of the existence of an explosive mixture in
+any of its parts at any time. It is not enough to argue that a mixture,
+even if it exists, cannot be exploded unless kindled. It is necessary to
+demand that a dangerous mixture can at no time be formed, even if the
+machine is tampered with by an ignorant person. The perfect machine must be
+so constructed that it shall be impossible at any time, under any
+circumstances, to blow it up.
+
+It must insure cool generation. Since this is a relative term, all machines
+being heated somewhat during the generation of gas, this amounts to saying
+that a machine must heat but little. A pound of carbide decomposed by water
+develops the same amount of heat under all circumstances, but that heat
+can be allowed to increase locally to a high point, or it can be equalized
+by water so that no part of the material becomes heated enough to do
+damage.
+
+It must be well constructed. A good generator does not need, perhaps, to be
+"built like a watch," but it should be solid, substantial and of good
+material. It should be built for service, to last and not simply to sell;
+anything short of this is to be avoided as unsafe and unreliable.
+
+It must be simple. The more complicated the machine the sooner it will get
+out of order. Understand your generator. Know what is inside of it and
+beware of an apparatus, however attractive its exterior, whose interior is
+filled with pipes and tubes, valves and diaphragms whose functions you do
+not perfectly understand.
+
+It should be capable of being cleaned and recharged and of receiving all
+other necessary attention without loss of gas, both for economy's sake, and
+more particularly to avoid danger of fire.
+
+It should require little attention. All machines have to be emptied and
+recharged periodically; but the more this process is simplified and the
+more quickly this can be accomplished, the better.
+
+It should be provided with a suitable indicator to designate how low the
+charge is in order that the refilling may be done in good season.
+
+It should completely use up the carbide, generating the maximum amount of
+gas.
+
+_Overheating._--A large amount of heat is liberated when acetylene gas
+is formed from the union of calcium carbide and water. Overheating during
+this process, that is to say, an intense local heat rather than a large
+amount of heat well distributed, brings about the phenomenon of
+polymerization, converting the gas, or part of it, into oily matters, which
+can do nothing but harm. This tarry mass coming through the small openings
+in the torches causes them to become partly closed and alters the
+proportions of the gases to the detriment of the welding flame. The only
+remedy for this trouble is to avoid its cause and secure cool generation.
+
+Overheating can be detected by the appearance of the sludge remaining after
+the gas has been made. Discoloration, yellow or brown, shows that there has
+been trouble in this direction and the resultant effects at the torches may
+be looked for. The abundance of water in the carbide to water machines
+effects this cooling naturally and is a characteristic of well designed
+machines of this class. It has been found best and has practically become a
+fundamental rule of generation that a gallon of water must be provided for
+each pound of carbide placed in the generator. With this ratio and a
+generator large enough for the number of torches to be supplied, little
+trouble need be looked for with overheating.
+
+_Water to Carbide Generators._--It is, of course, much easier to
+obtain a measured and regular flow of water than to obtain such a flow of
+any solid substance, especially when the solid substance is in the form of
+lumps, as is carbide This fact led to the use of a great many water-feed
+generators for all classes of work, and this type is still in common use
+for the small portable machines, such, for instance, as those used on motor
+cars for the lamps. The water-feed machine is not, however, favored for
+welding plants, as is the carbide feed, in spite of the greater
+difficulties attending the handling of the solid material.
+
+A water-feed generator is made up of the gas producing part and a holder
+for the acetylene after it is made. The carbide is held in a tray formed of
+a number of small compartments so that the charge in each compartment is
+nearly equal to that in each of the others. The water is allowed to flow
+into one of these compartments in a volume sufficient to produce the
+desired amount of gas and the carbide is completely used from this one
+division. The water then floods the first compartment and finally overflows
+into the next one, where the same process is repeated. After using the
+carbide in this division, it is flooded in turn and the water passing on to
+those next in order, uses the entire charge of the whole tray.
+
+These generators are charged with the larger sizes of carbide and are
+easily taken care of. The residue is removed in the tray and emptied,
+making the generator ready for a fresh supply of carbide.
+
+_Carbide to Water Generators._--This type also is made up of two
+principal parts, the generating chamber and a gas holder, the holder being
+part of the generating chamber or a separate device. The generator (Figure
+10) contains a hopper to receive the charge of carbide and is fitted with
+the feeding mechanism to drop the proper amount of carbide into the water
+as required by the demands of the torches. The charge of carbide is of one
+of the smaller sizes, usually "nut" or "quarter."
+
+_Feed Mechanisms._--The device for dropping the carbide into the water
+is the only part of the machine that is at all complicated. This
+complication is brought about by the necessity of controlling the mass of
+carbide so that it can never be discharged into the water at an excessive
+rate, feeding it at a regular rate and in definite amounts, feeding it
+positively whenever required and shutting off the feed just as positively
+when the supply of gas in the holder is enough for the immediate needs.
+
+[Illustration: Figure 10.--Carbide to Water Generator. A. Feed motor weight;
+B. Carbide feed motor; C. Carbide hopper; D. Water for gas generation;
+E. Agitator for loosening residuum; F. Water seal in gas bell; G. Filter;
+H. Hydraulic Valve; J. Motor control levers.]
+
+The charge of carbide is unavoidably acted upon by the water vapor in the
+generator and will in time become more or less pasty and sticky. This is
+more noticeable if the generator stands idle for a considerable length of
+time This condition imposes another duty on the feeding mechanism; that is,
+the necessity of self-cleaning so that the carbide, no matter in what
+condition, cannot prevent the positive action of this part of the device,
+especially so that it cannot prevent the supply from being stopped at the
+proper time.
+
+The gas holder is usually made in the bell form so that the upper portion
+rises and falls with the addition to or withdrawal from the supply of gas
+in the holder. The rise and fall of this bell is often used to control the
+feed mechanism because this movement indicates positively whether enough
+gas has been made or that more is required. As the bell lowers it sets the
+feed mechanism in motion, and when the gas passing into the holder has
+raised the bell a sufficient distance, the movement causes the feed
+mechanism to stop the fall of carbide into the water. In practice, the
+movement of this part of the holder is held within very narrow limits.
+
+_Gas Holders._--No matter how close the adjustment of the feeding
+device, there will always be a slight amount of gas made after the fall of
+carbide is stopped, this being caused by the evolution of gas from the
+carbide with which water is already in contact. This action is called
+"after generation" and the gas holder in any type of generator must
+provide sufficient capacity to accommodate this excess gas. As a general
+rule the water to carbide generator requires a larger gas holder than the
+carbide to water type because of the greater amount of carbide being acted
+upon by the water at any one time, also because the surface of carbide
+presented to the moist air within the generating chamber is greater with
+this type.
+
+_Freezing._--Because of the rather large body of water contained in
+any type of generator, there is always danger of its freezing and
+rendering the device inoperative unless placed in a temperature above the
+freezing point of the water. It is, of course, dangerous and against the
+insurance rules to place a generator in the same room with a fire of any
+kind, but the room may be heated by steam or hot water coils from a furnace
+in another building or in another part of the same building.
+
+When the generator is housed in a separate structure the walls should be
+made of materials or construction that prevents the passage of heat or
+cold through them to any great extent. This may be accomplished by the use
+of hollow tile or concrete blocks or by any other form of double wall
+providing air spaces between the outer and inner facings. The space between
+the parts of the wall may be filled with materials that further retard the
+loss of heat if this is necessary under the conditions prevailing.
+
+_Residue From Generators._--The sludge remaining in the carbide to
+water generator may be drawn off into the sewer if the piping is run at a
+slant great enough to give a fall that carries the whole quantity, both
+water and ash, away without allowing settling and consequent clogging.
+Generators are provided with agitators which are operated to stir the ash
+up with the water so that the whole mass is carried off when the drain cock
+is opened.
+
+If sewer connections cannot be made in such a way that the ash is entirely
+carried away, it is best to run the liquid mass into a settling basin
+outside of the building. This should be in the form of a shallow pit which
+will allow the water to pass off by soaking into the ground and by
+evaporation, leaving the comparatively dry ash in the pit. This ash which
+remains is essentially slaked lime and can often be disposed of to more or
+less advantage to be used in mortar, whitewash, marking paths and any other
+use for which slaked lime is suited. The disposition of the ash depends
+entirely on local conditions. An average analysis of this ash is as
+follows:
+
+Sand.......................  1.10 per cent.
+Carbon.....................  2.72    "
+Oxide of iron and alumina..  2.77    "
+Lime....................... 64.06    "
+Water and carbonic acid.... 29.35    "
+                           ------
+                           100.00
+
+
+GENERATOR CONSTRUCTION
+
+The water for generating purposes is carried in the large tank-like
+compartment directly below the carbide chamber. See Figure 11. This water
+compartment is filled through a pipe of such a height that the water level
+cannot be brought above the proper point or else the water compartment is
+provided with a drain connection which accomplishes this same result by
+allowing an excess to flow away.
+
+The quantity of water depends on the capacity of the generator inasmuch as
+there must be one gallon for each pound of carbide required. The generator
+should be of sufficient capacity to furnish gas under working conditions
+from one charge of carbide to all torches installed for at least five hours
+continuous use.
+
+After calculating the withdrawal of the whole number of torches according
+to the work they are to do for this period of five hours the proper
+generator capacity may be found on the basis of one cubic foot of gas per
+hour for each pound of carbide. Thus if the torches were to use sixty cubic
+feet of gas per hour, five hours would call for three hundred cubic feet
+and a three hundred pound generator should be installed. Generators are
+rated according to their carbide capacity in pounds.
+
+_Charging._--The carbide capacity of the generator should be great
+enough to furnish a continuous supply of gas for the maximum operating
+time, basing the quantity of gas generated on four and one-half cubic feet
+from each pound of lump carbide and on four cubic feet from each pound of
+quarter, intermediate sizes being in proportion.
+
+Generators are built in such a way that it is impossible for the acetylene
+to escape from the gas holding compartment during the recharging process.
+This is accomplished (1) by connecting the water inlet pipe opening with a
+shut off valve in such a way that the inlet cannot be uncovered or opened
+without first closing the shut off valve with the same movement of the
+operator; (2) by incorporating an automatic or hydraulic one-way valve so
+that this valve closes and acts as a check when the gas attempts to flow
+from the holder back to the generating chamber, or by any other means that
+will positively accomplish this result.
+
+In generators having no separate gas holding chamber but carrying the
+supply in the same compartment in which it is generated, the gas contained
+under pressure is allowed to escape through vent pipes into the outside
+air before recharging with carbide. As in the former case, the parts are
+so interlocked that it is impossible to introduce carbide or water without
+first allowing the escape of the gas in the generator.
+
+It is required by the insurance rules that the entire change of carbide
+while in the generator be held in such a way that it may be entirely
+removed without difficulty in case the necessity should arise.
+
+Generators should be cleaned and recharged at regular stated intervals.
+This work should be done during daylight hours only and likewise all
+repairs should be made at such a time that artificial light is not needed.
+Where it is absolutely necessary to use artificial light it should be
+provided only by incandescent electric lamps enclosed in gas tight globes.
+
+In charging generating chambers the old ash and all residue must first be
+cleaned out and the operator should be sure that no drain or other pipe has
+become clogged. The generator should then be filled with the required
+amount of water. In charging carbide feed machines be careful not to place
+less than a gallon of water in the water compartment for each pound of
+carbide to be used and the water must be brought to, but not above, the
+proper level as indicated by the mark or the maker's instructions. The
+generating chamber must be filled with the proper amount of water before
+any attempt is made to place the carbide in its holder. This rule must
+always be followed. It is also necessary that all automatic water seals
+and valves, as well as any other water tanks, be filled with clean water
+at this time.
+
+Never recharge with carbide without first cleaning the generating chamber
+and completely refilling with clean water. Never test the generator or
+piping for leaks with any flame, and never apply flame to any open pipe or
+at any point other than the torch, and only to the torch after it has a
+welding or cutting nozzle attached. Never use a lighted match, lamp,
+candle, lantern, cigar or any open flame near a generator. Failure to
+observe these precautions is liable to endanger life and property.
+
+_Operation and Care of Generators._--The following instructions apply
+especially to the Davis Bournonville pressure generator, illustrated in
+Figure 11. The motor feed mechanism is illustrated in Figure 12.
+
+Before filling the machine, the cover should be removed and the hopper
+taken out and examined to see that the feeding disc revolves freely; that
+no chains have been displaced or broken, and that the carbide displacer
+itself hangs barely free of the feeding disc when it is revolved. After
+replacing the cover, replace the bolts and tighten them equally, a little
+at a time all around the circumference of the cover--not screwing tight in
+one place only. Do not screw the cover down any more than is necessary to
+make a tight fit.
+
+To charge the generator, proceed as follows: Open the vent valve by turning
+the handle which extends over the filling tube until it stands at a right
+angle with the generator. Open the valve in the water filling pipe, and
+through this fill with water until it runs out of the overflow pipe of the
+drainage chamber, then close the valve in the water filling pipe and vent
+valve. Remove the carbide filling plugs and fill the hopper with
+1-1/4"x3/8" carbide ("nut" size). Then replace the plugs and the
+safety-locking lever chains. Now rewind the motor weight. Run the pressure
+up to about five pounds by raising the controlling diaphragm valve lever
+by hand (Figure 12, lever marked _E_). Then raise the blow-off lever,
+allowing the gas to blow off until the gauge shows about two pounds; this
+to clear the generator of air mixture. Then run the pressure up to about
+eight pounds by raising the controlling valve lever _E_, or until
+this controlling lever rests against the upper wing of the fan governor,
+and prevents operation of the feed motor. After this is done, the motor
+will operate automatically as the gas is consumed.
+
+[Illustration: Figure 11.--Pressure Generator (Davis Bournonville).
+_A_, Feed motor weight;
+_B_, Carbide feed motor;
+_C_, Motor Control diaphragm;
+_D_, Carbide hopper;
+_E_, Carbide feed disc;
+_F_, Overflow pipe;
+_G_, Overflow pipe seal;
+_H_, Overflow pipe valve;
+_J_, Filling funnel;
+_K_, Hydraulic valve;
+_L_, Expansion chamber;
+_M_, Escape pipe;
+_N_, Feed pipe;
+_O_, Agitator for residuum;
+_P_, Residuum valve;
+_Q_, Water level]
+
+[Illustration: Figure 12.--Feed Mechanism of Pressure Generator]
+
+Should the pressure rise much above the blow-off point, the safety
+controlling diaphragm valve will operate and throw the safety clutch in
+interference and thus stop the motor. This interference clutch will then
+have to be returned to its former position before the motor will operate,
+but cannot be replaced before the pressure has been reduced below the
+blow-off point.
+
+The parts of the feed mechanism illustrated in Figure 12 are as follows:
+_A_, motor drum for weight cable. _B_, carbide filling plugs.
+_C_, chains for connecting safety locking lever of motor to pins on
+the top of the carbide plugs. _D_, interference clutch of motor.
+_E_, lever on feed controlling diaphragm valve. _F_, lever of
+interference controlling diaphragm valve that operates interference clutch.
+_G_, feed controlling diaphragm valve. _H_, diaphragm valve
+controlling operation of interference clutch. _I_, interference pin
+to engage emergency clutch. _J_, main shaft driving carbide feeding
+disc. _Y_, safety locking lever.
+
+_Recharging Generator._--Turn the agitator handle rapidly for several
+revolutions, and then open the residuum valve, having five or six pounds
+gas pressure on the machine. If the carbide charge has been exhausted and
+the motor has stopped, there is generally enough carbide remaining in the
+feeding disc that can be shaken off, and fed by running the motor to
+obtain some pressure in the generator. The desirability of discharging
+the residuum with some gas pressure is because the pressure facilitates
+the discharge and at the same time keeps the generator full of gas,
+preventing air mixture to a great extent. As soon as the pressure is
+relieved by the withdrawal of the residuum, the vent valve should be
+opened, as if the pressure is maintained until all of the residuum is
+discharged gas would escape through the discharge valve.
+
+Having opened the vent pipe valve and relieved the pressure, open the
+valve in the water filling tube. Close the residuum valve, then run in
+several gallons of water and revolve the agitator, after which draw out the
+remaining residuum; then again close the residuum valve and pour in water
+until it discharges from the overflow pipe of the drainage chamber. It is
+desirable in filling the generator to pour the water in rapidly enough to
+keep the filling pipe full of water, so that air will not pass in at the
+same time.
+
+After the generator is cleaned and filled with water, fill with carbide and
+proceed in the same manner as when first charging.
+
+_Carbide Feed Mechanism._--Any form of carbide to water machine should
+be so designed that the carbide never falls directly from its holder into
+the water, but so that it must take a more or less circuitous path. This
+should be true, no matter what position the mechanism is in. One of the
+commonest types of forced feed machine carries the carbide in a hopper with
+slanting sides, this hopper having a large opening in the bottom through
+which the carbide passes to a revolving circular plate. As the pieces of
+carbide work out toward the edge of the plate under the influence of the
+mass behind them, they are thrown off into the water by small stationary
+fins or plows which are in such a position that they catch the pieces
+nearest the edges and force them off as the plate revolves. This
+arrangement, while allowing a free passage for the carbide, prevents an
+excess from falling should the machine stop in any position.
+
+When, as is usually the case, the feed mechanism is actuated by the rise
+or fall of pressure in the generator or of the level of some part of the
+gas holder, it must be built in such a way that the feeding remains
+inoperative as long as the filling opening on the carbide holder remains
+open.
+
+The feed of carbide should always be shut off and controlled so that under
+no condition can more gas be generated than could be cared for by the
+relief valve provided. It is necessary also to have the feed mechanism at
+least ten inches above the surface of the water so that the parts will
+never become clogged with damp lime dust.
+
+_Motor Feed._--The feed mechanism itself is usually operated by power
+secured from a slowly falling weight which, through a cable, revolves a
+drum. To this drum is attached suitable gearing for moving the feed parts
+with sufficient power and in the way desired. This part, called the motor,
+is controlled by two levers, one releasing a brake and allowing the motor
+to operate the feed, the other locking the gearing so that no more carbide
+will be dropped into the water. These levers are moved either by the
+quantity of gas in the holder or by the pressure of the gas, depending on
+the type of machine.
+
+With a separate gas holder, such as used with low pressure systems, the
+levers are operated by the rise and fall of the bell of the holder or
+gasometer, alternately starting and stopping the motor as the bell falls
+and rises again. Medium pressure generators are provided with a diaphragm
+to control the feed motor.
+
+This diaphragm is carried so that the pressure within the generator acts
+on one side while a spring, whose tension is under the control of the
+operator, acts on the other side. The diaphragm is connected to the brake
+and locking device on the motor in such a way that increasing the tension
+on the spring presses the diaphragm and moves a rod that releases the brake
+and starts the feed. The gas pressure, increasing with the continuation of
+carbide feed, acts on the other side and finally overcomes the pressure of
+the spring tension, moving the control rod the other way and stopping the
+motor and carbide feed. This spring tension is adjusted and checked with
+the help of a pressure gauge attached to the generating chamber.
+
+_Gravity Feed._--This type of feed differs from the foregoing in that
+the carbide is simply released and is allowed to fall into the water
+without being forced to do so. Any form of valve that is sufficiently
+powerful in action to close with the carbide passing through is used and is
+operated by the power secured from the rise and fall of the gas holder
+bell. When this valve is first opened the carbide runs into the water until
+sufficient pressure and volume of gas is generated to raise the bell. This
+movement operates the arm attached to the carbide shut off valve and slowly
+closes it. A fall of the bell occasioned by gas being withdrawn again opens
+the valve and more gas is generated.
+
+_Mechanical Feed._--The previously described methods of feeding
+carbide to the water have all been automatic in action and do not depend
+on the operator for their proper action.
+
+Some types of large generating plants have a power-driven feed, the power
+usually being from some kind of motor other than one operated by a weight,
+such as a water motor, for instance. This motor is started and stopped by
+the operator when, in his judgment, more gas is wanted or enough has been
+generated. This type of machine, often called a "non-automatic generator,"
+is suitable for large installations and is attached to a gas holder of
+sufficient size to hold a day's supply of acetylene. The generator can then
+be operated until a quantity of gas has been made that will fill the large
+holder, or gasometer, and then allowed to remain idle for some time.
+
+_Gas Holders._--The commonest type of gas container is that known as a
+gasometer. This consists of a circular tank partly filled with water, into
+which is lowered another circular tank, inverted, which is made enough
+smaller in diameter than the first one so that three-quarters of an inch is
+left between them. This upper and inverted portion, called the bell,
+receives the gas from the generator and rises or falls in the bath of water
+provided in the lower tank as a greater or less amount of gas is contained
+in it.
+
+These holders are made large enough so that they will provide a means of
+caring for any after generation and so that they maintain a steady and even
+flow. The generator, however, must be of a capacity great enough so that
+the gas holder will not be drawn on for part of the supply with all torches
+in operation. That is, the holder must not be depended on for a reserve
+supply.
+
+The bell of the holder is made so that when full of gas its lower edge is
+still under a depth of at least nine inches of water in the lower tank. Any
+further rise beyond this point should always release the gas, or at least
+part of it, to the escape pipe so that the gas will under no circumstances
+be forced into the room from, between the bell and tank. The bell is guided
+in its rise and fall by vertical rods so that it will not wedge at any
+point in its travel.
+
+A condensing chamber to receive the water which condenses from the
+acetylene gas in the holder is usually placed under this part and is
+provided with a drain so that this water of condensation may be easily
+removed.
+
+_Filtering._--A small chamber containing some closely packed but
+porous material such as felt is placed in the pipe leading to the torch
+lines. As the acetylene gas passes through this filter the particles of
+lime dust and other impurities are extracted from it so that danger of
+clogging the torch openings is avoided as much as possible.
+
+The gas is also filtered to a large extent by its passage through the water
+in the generating chamber, this filtering or "scrubbing" often being
+facilitated by the form of piping through which the gas must pass from the
+generating chamber into the holder. If the gas passes out of a number of
+small openings when going into the holder the small bubbles give a better
+washing than large ones would.
+
+_Piping._--Connections from generators to service pipes should
+preferably be made with right and left couplings or long thread nipples
+with lock nuts. If unions are used, they should be of a type that does not
+require gaskets. The piping should be carried and supported so that any
+moisture condensing in the lines will drain back toward the generator and
+where low points occur they should be drained through tees leading into
+drip cups which are permanently closed with screw caps or plugs. No pet
+cocks should be used for this purpose.
+
+For the feed pipes to the torch lines the following pipe sizes are
+recommended.
+
+    3/8 inch pipe.  26 feet long.   2 cubic feet per hour.
+    1/2 inch pipe.  30 feet long.   4 cubic feet per hour.
+    3/4 inch pipe.  50 feet long.  15 cubic feet per hour.
+  1     inch pipe.  70 feet long.  27 cubic feet per hour.
+  1-1/4 inch pipe. 100 feet long.  50 cubic feet per hour.
+  1-1/2 inch pipe. 150 feet long.  65 cubic feet per hour.
+  2     inch pipe. 200 feet long. 125 cubic feet per hour.
+  2-1/2 inch pipe. 300 feet long. 190 cubic feet per hour.
+  3     inch pipe. 450 feet long. 335 cubic feet per hour.
+
+When drainage is possible into a sewer, the generator should not be
+connected directly into the sewer but should first discharge into an open
+receptacle, which may in turn be connected to the sewer.
+
+No valves or pet cocks should open into the generator room or any other
+room when it would be possible, by opening them for draining purposes, to
+allow any escape of gas. Any condensation must be removed without the use
+of valves or other working parts, being drained into closed receptacles. It
+should be needless to say that all the piping for gas must be perfectly
+tight at every point in its length.
+
+_Safety Devices._--Good generators are built in such a way that the
+operator must follow the proper order of operation in charging and cleaning
+as well as in all other necessary care. It has been mentioned that the gas
+pressure is released or shut off before it is possible to fill the water
+compartment, and this same idea is carried further in making the generator
+inoperative and free from gas pressure before opening the residue drain of
+the carbide filling opening on top of the hopper. Some machines are made so
+that they automatically cease to generate should there be a sudden and
+abnormal withdrawal of gas such as would be caused by a bad leak. This
+method of adding safety by automatic means and interlocking parts may be
+carried to any extent that seems desirable or necessary to the maker.
+
+All generators should be provided with escape or relief pipes of large size
+which lead to the open air. These pipes are carried so that condensation
+will drain back toward the generator and after being led out of the
+building to a point at least twelve feet above ground, they end in a
+protecting hood so that no rain or solid matter can find its way into them.
+Any escape of gas which might ordinarily pass into the generator room is
+led into these escape pipes, all parts of the system being connected with
+the pipe so that the gas will find this way out.
+
+Safety blow off valves are provided so that any excess gas which cannot be
+contained by the gas holder may be allowed to escape without causing an
+undue rise in pressure. This valve also allows the escape of pressure above
+that for which the generator was designed. Gas released in this way passes
+into the escape pipe just described.
+
+Inasmuch as the pressure of the oxygen is much greater than that of the
+acetylene when used in the torch, it will be seen that anything that caused
+the torch outlet to become closed would allow the oxygen to force the
+acetylene back into the generator and the oxygen would follow it, making a
+very explosive mixture. This return of the gas is prevented by a hydraulic
+safety valve or back pressure valve, as it is often called.
+
+Mechanical check valves have been found unsuitable for this use and those
+which employ water as a seal are now required by the insurance rules. The
+valve itself (Figure 13) consists of a large cylinder containing water to a
+certain depth, which is indicated on the valve body. Two pipes come into
+the upper end of this cylinder and lead down into the water, one being
+longer than the other. The shorter pipe leads to the escape pipe mentioned
+above, while the longer one comes from the generator. The upper end of the
+cylinder has an opening to which is attached the pipe leading to the
+torches.
+
+[Illustration: Figure 13.--Hydraulic Back-Pressure Valve.
+_A_, Acetylene supply line;
+_B_, Vent pipe;
+_C_, Water filling plug;
+_D_, Acetylene service cock;
+_E_, Plug to gauge height of water;
+_F_, Gas openings under water;
+_G_, Return pipe for sealing water;
+_H_, Tube to carry gas below water line;
+_I_, Tube to carry gas to escape pipe;
+_J_, Gas chamber;
+_K_, Plug in upper gas chamber;
+_L_, High water level;
+_M_, Opening through which water returns;
+_O_, Bottom clean out casting]
+
+The gas coming from the generator through the longer pipe passes out of the
+lower end of the pipe which is under water and bubbles up through the water
+to the space in the top of the cylinder. From there the gas goes to the
+pipe leading to the torches. The shorter pipe is closed by the depth of
+water so that the gas does not escape to the relief pipe. As long as the
+gas flows in the normal direction as described there will be no escape to
+the air. Should the gas in the torch line return into the hydraulic valve
+its pressure will lower the level of water in the cylinder by forcing some
+of the liquid up into the two pipes. As the level of the water lowers, the
+shorter pipe will be uncovered first, and as this is the pipe leading to
+the open air the gas will be allowed to escape, while the pipe leading back
+to the generator is still closed by the water seal. As soon as this reverse
+flow ceases, the water will again resume its level and the action will
+continue. Because of the small amount of water blown out of the escape pipe
+each time the valve is called upon to perform this duty, it is necessary to
+see that the correct water level is always maintained.
+
+While there are modifications of this construction, the same principle is
+used in all types. The pressure escape valve is often attached to this
+hydraulic valve body.
+
+_Construction Details._--Flexible tubing (except at torches), swing
+pipe joints, springs, mechanical check valves, chains, pulleys and lead or
+fusible piping should never be used on acetylene apparatus except where the
+failure of those parts will not affect the safety of the machine or permit,
+either directly or indirectly, the escape of gas into a room. Floats should
+not be used except where failure will only render the machine inoperative.
+
+It should be said that the National Board of Fire Underwriters have
+established an inspection service for acetylene generators and any
+apparatus which bears their label, stating that that particular model and
+type has been passed, is safe to use. This service is for the best
+interests of all concerned and looks toward the prevention of accidents.
+Such inspection is a very important and desirable feature of any outfit and
+should be insisted upon.
+
+_Location of Generators._--Generators should preferably be placed
+outside of insured buildings and in properly constructed generator houses.
+The operating mechanism should have ample room to work in and there should
+be room enough for the attendant to reach the various parts and perform the
+required duties without hindrance or the need of artificial light. They
+should also be protected from tampering by unauthorized persons.
+
+Generator houses should not be within five feet of any opening into, nor
+have any opening toward, any adjacent building, and should be kept under
+lock and key. The size of the house should be no greater than called for by
+the requirements mentioned above and it should be well ventilated.
+
+The foundation for the generator itself should be of brick, stone, concrete
+or iron, if possible. If of wood, they should be extra heavy, located in a
+dry place and open to circulation of air. A board platform is not
+satisfactory, but the foundation should be of heavy planking or timber to
+make a firm base and so that the air can circulate around the wood.
+
+The generator should stand level and no strain should be placed on any of
+the pipes or connections or any parts of the generator proper.
+
+
+
+
+CHAPTER IV
+
+WELDING INSTRUMENTS
+
+
+VALVES
+
+_Tank Valves._--The acetylene tank valve is of the needle type, fitted
+with suitable stuffing box nuts and ending in an exposed square shank to
+which the special wrench may be fitted when the valve is to be opened or
+closed.
+
+The valve used on Linde oxygen cylinders is also a needle type, but of
+slightly more complex construction. The body of the valve, which screws
+into the top of the cylinder, has an opening below through which the gas
+comes from the cylinder, and another opening on the side through which it
+issues to the torch line. A needle screws down from above to close this
+lower opening. The needle which closes the valve is not connected directly
+to the threaded member, but fits loosely into it. The threaded part is
+turned by a small hand wheel attached to the upper end. When this hand
+wheel is turned to the left, or up, as far as it will go, opening the
+valve, a rubber disc is compressed inside of the valve body and this disc
+serves to prevent leakage of the gas around the spindle.
+
+The oxygen valve also includes a safety nut having a small hole through it
+closed by a fusible metal which melts at 250 deg. Fahrenheit. Melting of this
+plug allows the gas to exert its pressure against a thin copper diaphragm,
+this diaphragm bursting under the gas pressure and allowing the oxygen to
+escape into the air.
+
+The hand wheel and upper end of the valve mechanism are protected during
+shipment by a large steel cap which covers them when screwed on to the end
+of the cylinder. This cap should always be in place when tanks are received
+from the makers or returned to them.
+
+[Illustration: Figure 14.--Regulating Valve]
+
+_Regulating Valves._--While the pressure in the gas containers may be
+anything from zero to 1,800 pounds, and will vary as the gas is withdrawn,
+the pressure of the gas admitted to the torch must be held steady and at a
+definite point. This is accomplished by various forms of automatic
+regulating valves, which, while they differ somewhat in details of
+construction, all operate on the same principle.
+
+The regulator body (Figure 14) carries a union which attaches to the side
+outlet on the oxygen tank valve. The gas passes through this union,
+following an opening which leads to a large gauge which registers the
+pressure on the oxygen remaining in the tank and also to a very small
+opening in the end of a tube. The gas passes through this opening and into
+the interior of the regulator body. Inside of the body is a metal or rubber
+diaphragm placed so that the pressure of the incoming gas causes it to
+bulge slightly. Attached to the diaphragm is a sleeve or an arm tipped
+with a small piece of fibre, the fibre being placed so that it is directly
+opposite the small hole through which the gas entered the diaphragm
+chamber. The slight movement of the diaphragm draws the fibre tightly over
+the small opening through which the gas is entering, with the result that
+further flow is prevented.
+
+Against the opposite side of the diaphragm is the end of a plunger. This
+plunger is pressed against the diaphragm by a coiled spring. The tension on
+the coiled spring is controlled by the operator through a threaded spindle
+ending in a wing or milled nut on the outside of the regulator body.
+Screwing in on the nut causes the tension on the spring to increase, with a
+consequent increase of pressure on the side of the diaphragm opposite to
+that on which the gas acts. Inasmuch as the gas pressure acted to close the
+small gas opening and the spring pressure acts in the opposite direction
+from the gas, it will be seen that the spring pressure tends to keep the
+valve open.
+
+When the nut is turned way out there is of course, no pressure on the
+spring side of the diaphragm and the first gas coming through automatically
+closes the opening through which it entered. If now the tension on the
+spring be slightly increased, the valve will again open and admit gas until
+the pressure of gas within the regulator is just sufficient to overcome the
+spring pressure and again close the opening. There will then be a pressure
+of gas within the regulator that corresponds to the pressure placed on the
+spring by the operator. An opening leads from the regulator interior to the
+torch lines so that all gas going to the torches is drawn from the
+diaphragm chamber.
+
+Any withdrawal of gas will, of course, lower the pressure of that remaining
+inside the regulator. The spring tension, remaining at the point determined
+by the operator, will overcome this lessened pressure of the gas, and the
+valve will again open and admit enough more gas to bring the pressure back
+to the starting point. This action continues as long as the spring tension
+remains at this point and as long as any gas is taken from the regulator.
+Increasing the spring tension will require a greater gas pressure to close
+the valve and the pressure of that in the regulator will be correspondingly
+higher.
+
+When the regulator is not being used, the hand nut should be unscrewed
+until no tension remains on the spring, thus closing the valve. After the
+oxygen tank valve is open, the regulator hand nut is slowly screwed in
+until the spring tension is sufficient to give the required pressure in the
+torch lines. Another gauge is attached to the regulator so that it
+communicates with the interior of the diaphragm chamber, this gauge showing
+the gas pressure going to the torch. It is customary to incorporate a
+safety valve in the regulator which will blow off at a dangerous pressure.
+
+In regulating valves and tank valves, as well as all other parts with which
+the oxygen comes in contact, it is not permissible to use any form of oil
+or grease because of danger of ignition and explosion. The mechanism of a
+regulator is too delicate to be handled in the ordinary shop and should any
+trouble or leakage develop in this part of the equipment it should be sent
+to a company familiar with this class of work for the necessary repairs.
+Gas must never be admitted to a regulator until the hand nut is all the way
+out, because of danger to the regulator itself and to the operator as well.
+A regulator can only be properly adjusted when the tank valve and torch
+valves are fully opened.
+
+[Illustration: Figure 15.--High and Low Pressure Gauges with Regulator]
+
+Acetylene regulators are used in connection with tanks of compressed gas.
+They are built on exactly the same lines as the oxygen regulating valve and
+operate in a similar way. One gauge only, the low pressure indicator, is
+used for acetylene regulators, although both high and low pressure may be
+used if desired. (See Figure 15.)
+
+
+TORCHES
+
+Flame is always produced by the combustion of a gas with oxygen and in no
+other way. When we burn oil or candles or anything else, the material of
+the fuel is first turned to a gas by the heat and is then burned by
+combining with the oxygen of the air. If more than a normal supply of air
+is forced into the flame, a greater heat and more active burning follows.
+If the amount of air, and consequently oxygen, is reduced, the flame
+becomes smaller and weaker and the combustion is less rapid. A flame may be
+easily extinguished by shutting off all of its air supply.
+
+The oxygen of the combustion only forms one-fifth of the total volume of
+air; therefore, if we were to supply pure oxygen in place of air, and in
+equal volume, the action would be several times as intense. If the oxygen
+is mixed with the fuel gas in the proportion that burns to the very best
+advantage, the flame is still further strengthened and still more heat is
+developed because of the perfect combustion. The greater the amount of fuel
+gas that can be burned in a certain space and within a certain time, the
+more heat will be developed from that fuel.
+
+The great amount of heat contained in acetylene gas, greater than that
+found in any other gaseous fuel, is used by leading this gas to the
+oxy-acetylene torch and there combining it with just the right amount of
+oxygen to make a flame of the greatest power and heat than can possibly be
+produced by any form of combustion of fuels of this kind. The heat
+developed by the flame is about 6300 deg. Fahrenheit and easily melts all the
+metals, as well as other solids.
+
+Other gases have been and are now being used in the torch. None of them,
+however, produce the heat that acetylene does, and therefore the
+oxy-acetylene process has proved the most useful of all. Hydrogen was used
+for many years before acetylene was introduced in this field. The
+oxy-hydrogen flame develops a heat far below that of oxy-acetylene, namely
+4500 deg. Fahrenheit. Coal gas, benzine gas, blaugas and others have also been
+used in successful applications, but for the present we will deal
+exclusively with the acetylene fuel.
+
+It was only with great difficulty that the obstacles in the way of
+successfully using acetylene were overcome by the development of
+practicable controlling devices and torches, as well as generators. At
+present the oxy-acetylene process is the most universally adaptable, and
+probably finds the most widely extended field of usefulness of any welding
+process.
+
+The theoretical proportion of the gases for perfect combustion is two and
+one-half volumes of oxygen to one of acetylene. In practice this proportion
+is one and one-eighth or one and one-quarter volumes of oxygen to one
+volume of acetylene, so that the cost is considerably reduced below what it
+would be if the theoretical quantity were really necessary, as oxygen costs
+much more than acetylene in all cases.
+
+While the heat is so intense as to fuse anything brought into the path of
+the flame, it is localized in the small "welding cone" at the torch tip so
+that the torch is not at all difficult to handle without special protection
+except for the eyes, as already noted. The art of successful welding may be
+acquired by any operator of average intelligence within a reasonable time
+and with some practice. One trouble met with in the adoption of this
+process has been that the operation looks so simple and so easy of
+performance that unskilled and unprepared persons have been tempted to try
+welding, with results that often caused condemnation of the process, when
+the real fault lay entirely with the operator.
+
+The form of torch usually employed is from twelve to twenty-four inches
+long and is composed of a handle at one end with tubes leading from this
+handle to the "welding head" or torch proper. At or near one end of the
+handle are adjustable cocks or valves for allowing the gases to flow into
+the torch or to prevent them from doing so. These cocks are often used for
+regulating the pressure and amount of gas flowing to the welding head, but
+are not always constructed for this purpose and should not be so used when
+it is possible to secure pressure adjustment at the regulators (Figure 16).
+
+Figure 16 shows three different sizes of torches. The number 5 torch is
+designed especially for jewelers' work and thin sheet steel welding. It is
+eleven inches in length and weighs nineteen ounces. The tips for the number
+10 torch are interchangeable with the number 5. The number 10 torch is
+adapted for general use on light and medium heavy work. It has six tips and
+its length is sixteen inches, with a weight of twenty-three ounces.
+
+The number 15 torch is designed for heavy work, being twenty-five inches in
+length, permitting the operator to stand away from the heat of the metal
+being worked. These heavy tips are in two parts, the oxygen check being
+renewable.
+
+[Illustration: Figure 16.--Three Sizes of Torches, with Tips]
+
+Figures 17 and 18 show two sizes of another welding torch. Still another
+type is shown in Figure 19 with four interchangeable tips, the function of
+each being as follows:
+
+  No. 1. For heavy castings.
+  No. 2. Light castings and heavy sheet metal.
+  No. 3. Light sheet metal.
+  No. 4. Very light sheet metal and wire.
+
+[Illustration: Figure 17.--Cox Welding Torch (No. 1)]
+
+[Illustration: Figure 18.--Cox Welding Torch (No. 2)]
+
+[Illustration: Figure 19.--Monarch Welding Torch]
+
+At the side of the shut off cock away from the torch handle the gas tubes
+end in standard forms of hose nozzles, to which the rubber hose from the
+gas supply tanks or generators can be attached. The tubes from the handle
+to the head may be entirely separate from each other, or one may be
+contained within the other. As a general rule the upper one of two
+separate tubes carries the oxygen, while this gas is carried in the inside
+tube when they are concentric with each other.
+
+In the welding head is the mixing chamber designed to produce an intimate
+mixture of the two gases before they issue from the nozzle to the flame.
+The nozzle, or welding tip, of a suitable size are design for the work to
+be handled and the pressure of gases being used, is attached to the welding
+head and consists essentially of the passage at the outer end of which the
+flame appears.
+
+The torch body and tubes are usually made of brass, although copper is
+sometimes used. The joint must be very strong, and are usually threaded and
+soldered with silver solder. The nozzle proper is made from copper, because
+it withstands the heat of the flame better than other less suitable metals.
+The torch must be built in such a way that it is not at all liable to come
+apart under the influence of high temperatures.
+
+All torches are constructed in such a way that it is impossible for the
+gases to mix by any possible chance before they reach the head, and the
+amount of gas contained in the head and tip after being mixed is made as
+small as possible. In order to prevent the return of the flame through the
+acetylene tube under the influence of the high pressure oxygen some form of
+back flash preventer is usually incorporated in the torch at or near the
+point at which the acetylene enters. This preventer takes the form of some
+porous and heat absorbing material, such as aluminum shavings, contained in
+a small cavity through which the gas passes on its way to the head.
+
+_High Pressure Torches._--Torches are divided into the same classes as
+are the generators; that is, high pressure, medium pressure and low
+pressure. As mentioned before, the medium pressure is usually called the
+high pressure, because there are very few true high pressure systems in
+use, and comparatively speaking the medium pressure type is one of high
+pressure.
+
+[Illustration: Figure 20.--High Pressure Torch Head]
+
+With a true high pressure torch (Figure 20) the gases are used at very
+nearly equal heads so that the mixing before ignition is a simple matter.
+This type admits the oxygen at the inner end of a straight passage leading
+to the tip of the nozzle. The acetylene comes into this same passage from
+openings at one side and near the inner end. The difference in direction of
+the two gases as they enter the passage assists in making a homogeneous
+mixture. The construction of this nozzle is perfectly simple and is easily
+understood. The true high pressure torch nozzle is only suited for use with
+compressed and dissolved acetylene, no other gas being at a sufficient
+pressure to make the action necessary in mixing the gases.
+
+_Medium Pressure Torches._--The medium pressure (usually called high
+pressure) torch (Figure 21) uses acetylene from a medium pressure generator
+or from tanks of compressed gas, but will not take the acetylene from low
+pressure generators.
+
+[Illustration: Figure 21.--Medium Pressure Torch Head]
+
+The construction of the mixing chamber and nozzle is very similar to that
+of the high pressure torch, the gases entering in the same way and from the
+same positions of openings. The pressure of the acetylene is but little
+lower than that of the oxygen, and the two gases, meeting at right angles,
+form a very intimate mixture at this point of juncture. The mixture in its
+proportions of gases depends entirely on the sizes of the oxygen and
+acetylene openings into the mixing chamber and on the pressures at which
+the gases are admitted. There is a very slight injector action as the fast
+moving stream of oxygen tends to draw the acetylene from the side openings
+into the chamber, but the operation of the torch does not depend on this
+action to any extent.
+
+_Low Pressure Torches._--The low pressure torch (Figure 22) will use
+gas from low pressure generators from medium pressure machines or from
+tanks in which it has been compressed and dissolved. This type depends for
+a perfect mixture of gas upon the principle of the injector just as it is
+applied in steam boiler practice.
+
+[Illustration: Figure 22.--Low Pressure Torch with Separate Injector
+Nozzle]
+
+The oxygen enters the head at considerable pressure and passes through its
+tube to a small jet within the head. The opening of this jet is directly
+opposite the end of the opening through the nozzle which forms the mixing
+chamber and the path of the gases to the flame. A small distance remains
+between the opening from which the oxygen issues and the inner opening into
+the mixing passage. The stream of oxygen rushes across this space and
+enters the mixing chamber, being driven by its own pressure.
+
+The acetylene enters the head in an annular space surrounding the oxygen
+tube. The space between oxygen jet and mixing chamber opening is at one end
+of this acetylene space and the stream of oxygen seizes the acetylene and
+under the injector action draws it into the mixing chamber, it being
+necessary only to have a sufficient supply of acetylene flowing into the
+head to allow the oxygen to draw the required proportion for a proper
+mixture.
+
+The volume of gas drawn into the mixing chamber depends on the size of the
+injector openings and the pressure of the oxygen. In practice the oxygen
+pressure is not altered to produce different sized flames, but a new nozzle
+is substituted which is designed to give the required flame. Each nozzle
+carries its own injector, so that the design is always suited to the
+conditions. While torches are made having the injector as a permanent part
+of the torch body, the replaceable nozzle is more commonly used because it
+makes the one torch suitable for a large range of work and a large number
+of different sized flames. With the replaceable head a definite pressure of
+oxygen is required for the size being used, this pressure being the one for
+which the injector and corresponding mixing chamber were designed in
+producing the correct mixture.
+
+_Adjustable Injectors._-Another form of low pressure torch operates on
+the injector principle, but the injector itself is a permanent part of the
+torch, the nozzle only being changed for different sizes of work and flame.
+The injector is placed in or near the handle and its opening is the largest
+required by any work that can be handled by this particular torch. The
+opening through the tip of the injector through which the oxygen issues on
+its way to the mixing chamber may be wholly or partly closed by a needle
+valve which may be screwed into the opening or withdrawn from it, according
+to the operator's judgment. The needle valve ends in a milled nut outside
+the torch handle, this being the adjustment provided for the different
+nozzles.
+
+_Torch Construction._--A well designed torch is so designed that the
+weight distribution is best for holding it in the proper position for
+welding. When a torch is grasped by its handle with the gas hose attached,
+it should balance so that it does not feel appreciably heavier on one end
+than on the other.
+
+The head and nozzle may be placed so that the flame issues in a line at
+right angles with the torch body, or they may be attached at an angle
+convenient for the work to be done. The head set at an angle of from 120 to
+170 degrees with the body is usually preferred for general work in welding,
+while the cutting torch usually has its head at right angles to the body.
+
+Removable nozzles have various size openings through them and the different
+sizes are designated by numbers from 1 up. The same number does not always
+indicate the same size opening in torches of different makes, nor does it
+indicate a nozzle of the same capacity.
+
+The design of the nozzle, the mixing chamber, the injector, when one is
+used, and the size of the gas openings must be such that all these things
+are suited to each other if a proper mixture of gas is to be secured. Parts
+that are not made to work together are unsafe if used because of the danger
+of a flash back of the flame into the mixing chamber and gas tubes. It is
+well known that flame travels through any inflammable gas at a certain
+definite rate of speed, depending on the degree of inflammability of the
+gas. The easier and quicker the gas burns, the faster will the flame travel
+through it.
+
+If the gas in the nozzle and mixing chamber stood still, the flame would
+immediately travel back into these parts and produce an explosion of more
+or less violence. The speed with which the gases issue from the nozzle
+prevent this from happening because the flame travels back through the gas
+at the same speed at which the gas issues from the torch tip. Should the
+velocity of the gas be greater than the speed of flame propagation through
+it, it will be impossible to keep the flame at the tip, the tendency being
+for a space of unburned gas to appear between tip and flame. On the other
+hand, should the speed of the flame exceed the velocity with which the gas
+comes from the torch there will result a flash back and explosion.
+
+_Care of Torches._--An oxy-acetylene torch is a very delicate and
+sensitive device, much more so that appears on the surface. It must be
+given equally as good care and attention as any other high-priced piece of
+machinery if it is to be maintained in good condition for use.
+
+It requires cleaning of the nozzles at regular intervals if used regularly.
+This cleaning is accomplished with a piece of copper or brass wire run
+through the opening, and never with any metal such as steel or iron that is
+harder than the nozzle itself, because of the danger of changing the size
+of the openings. The torch head and nozzle can often be cleaned by allowing
+the oxygen to blow through at high pressure without the use of any tools.
+
+In using a torch a deposit of carbon will gradually form inside of the
+head, and this deposit will be more rapid if the operator lights the stream
+of acetylene before turning any oxygen into the torch. This deposit may be
+removed by running kerosene through the nozzle while it is removed from the
+torch, setting fire to the kerosene and allowing oxygen to flow through
+while the oil is burning.
+
+Should a torch become clogged in the head or tubes, it may usually be
+cleaned by removing the oxygen hose from the handle end, closing the
+acetylene cock on the torch, placing the end of the oxygen hose over the
+opening in the nozzle and turning on the oxygen under pressure to blow the
+obstruction back through the passage that it has entered. By opening the
+acetylene cock and closing the oxygen cock at the handle, the acetylene
+passages may then be cleaned in the same way. Under no conditions should a
+torch be taken apart any more than to remove the changeable nozzle, except
+in the hands of those experienced in this work.
+
+_Nozzle Sizes._--The size of opening through the nozzle is determined
+according to the thickness and kind of metal being handled. The following
+sizes are recommended for steel:
+
+                      Davis-Bournonville.   Oxweld Low
+  Thickness of Metal  (Medium Pressure.)      Pressure
+  1/32                     Tip No. 1        Head No. 2
+  1/16                             2
+  5/64                                               3
+  3/32                             3                 4
+  3/8                              4                 5
+  3/16                             5                 6
+  1/4                              6                 7
+  5/16                             7
+  3/8                              8                 8
+  1/2                              9                10
+  5/8                             10                12
+  3/4                             11                15
+  Very heavy                      12                15
+
+_Cutting Torches._--Steel may be cut with a jet of oxygen at a rate of
+speed greater than in any other practicable way under usual conditions. The
+action consists of burning away a thin section of the metal by allowing a
+stream of oxygen to flow onto it while the gas is at high pressure and the
+metal at a white heat.
+
+[Illustration: Figure 23.--Cutting Torch]
+
+The cutting torch (Figure 23) has the same characteristics as the welding
+torch, but has an additional nozzle or means for temporarily using the
+welding opening for the high pressure oxygen. The oxygen issues from the
+opening while cutting at a pressure of from ten to 100 pounds to the square
+inch.
+
+The work is first heated to a white heat by adjusting the torch for a
+welding flame. As soon as the metal reaches this temperature, the high
+pressure oxygen is turned on to the white-hot portion of the steel. When
+the jet of gas strikes the metal it cuts straight through, leaving a very
+narrow slot and removing but little metal. Thicknesses of steel up to ten
+inches can be economically handled in this way.
+
+The oxygen nozzle is usually arranged so that it is surrounded by a number
+of small jets for the heating flame. It will be seen that this arrangement
+makes the heating flame always precede the oxygen jet, no matter in which
+direction the torch is moved.
+
+The torch is held firmly, either by hand or with the help of special
+mechanism for guiding it in the desired path, and is steadily advanced in
+the direction it is desired to extend the cut, the rate of advance being
+from three inches to two feet per minute through metal from nine inches
+down to one-quarter of an inch in thickness.
+
+The following data on cutting is given by the Davis-Bournonville Company:
+
+                            Cubic
+                            Feet                          Cost of
+Thickness                   of Gas               Inches   Gases
+of        Cutting  Heating  per Foot  Oxygen     Cut per  per Foot
+Steel     Oxygen   Oxygen   of Cut    Acetylene  Min.     of Cut
+  1/4     10 lbs.  4 lbs.     .40      .086      24        $ .013
+  1/2     20       4          .91      .150      15          .029
+  3/4     30       4         1.16      .150      15          .036
+1         30       4         1.45      .172      12          .045
+1 1/2     30       5         2.40      .380      12          .076
+2         40       5         2.96      .380      12          .093
+4         50       5         9.70      .800       7          .299
+6         70       6        21.09     1.50        4          .648
+9        100       6        43.20     2.00        3         1.311
+
+_Acetylene-Air Torch._--A form of torch which burns the acetylene after
+mixing it with atmospheric air at normal pressure rather than with the
+oxygen under higher pressures has been found useful in certain pre-heating,
+brazing and similar operations. This torch (Figure 24) is attached by a
+rubber gas hose to any compressed acetylene tank and is regulated as to
+flame size and temperature by opening or closing the tank valve more or
+less.
+
+After attaching the torch to the tank, the gas is turned on very slowly and
+is lighted at the torch tip. The adjustment should cause the presence of a
+greenish-white cone of flame surrounded by a larger body of burning gas,
+the cone starting at the mouth of the torch.
+
+[Illustration: Figure 24.--Acetylene-Air Torch]
+
+By opening the tank valve more, a longer and hotter flame is produced, the
+length being regulated by the tank valve also. This torch will give
+sufficient heat to melt steel, although not under conditions suited to
+welding. Because of the excess of acetylene always present there is no
+danger of oxidizing the metal being heated.
+
+The only care required by this torch is to keep the small air passages at
+the nozzle clean and free from carbon deposits. The flame should be
+extinguished when not in use rather than turned low, because this low flame
+rapidly deposits large quantities of soot in the burner.
+
+
+
+
+CHAPTER V
+
+OXY-ACETYLENE WELDING PRACTICE
+
+
+PREPARATION OF WORK
+
+_Preheating._--The practice of heating the metal around the weld
+before applying the torch flame is a desirable one for two reasons. First,
+it makes the whole process more economical; second, it avoids the danger of
+breakage through expansion and contraction of the work as it is heated and
+as it cools.
+
+When it is desired to join two surfaces by welding them, it is, of course,
+necessary to raise the metal from the temperature of the surrounding air to
+its melting point, involving an increase in temperature of from one
+thousand to nearly three thousand degrees. To obtain this entire increase
+of temperature with the torch flame is very wasteful of fuel and of the
+operator's time. The total amount of heat necessary to put into metal is
+increased by the conductivity of that metal because the heat applied at the
+weld is carried to other parts of the piece being handled until the whole
+mass is considerably raised in temperature. To secure this widely
+distributed increase the various methods of preheating are adopted.
+
+As to the second reason for preliminary heating. It is understood that the
+metal added to the joint is molten at the time it flows into place. All the
+metals used in welding contract as they cool and occupy a much smaller
+space than when molten. If additional metal is run between two adjoining
+surfaces which are parts of a surrounding body of cool metal, this added
+metal will cool while the surfaces themselves are held stationary in the
+position they originally occupied. The inevitable result is that the metal
+added will crack under the strain, or, if the weld is exceptionally strong,
+the main body of the work will be broken by the force of contraction. To
+overcome these difficulties is the second and most important reason for
+preheating and also for slow cooling following the completion of the weld.
+
+There are many ways of securing this preheating. The work may be brought to
+a red heat in the forge if it is cast iron or steel; it may be heated in
+special ovens built for the purpose; it may be placed in a bed of charcoal
+while suitably supported; it may be heated by gas or gasoline preheating
+torches, and with very small work the outer flame of the welding torch
+automatically provides means to this end.
+
+The temperature of the parts heated should be gradually raised in all
+cases, giving the entire mass of metal a chance to expand equally and to
+adjust itself to the strains imposed by the preheating. After the region
+around the weld has been brought to a proper temperature the opening to be
+filled is exposed so that the torch flame can reach it, while the remaining
+surfaces are still protected from cold air currents and from cooling
+through natural radiation.
+
+One of the commonest methods and one of the best for handling work of
+rather large size is to place the piece to be welded on a bed of fire brick
+and build a loose wall around it with other fire brick placed in rows, one
+on top of the other, with air spaces left between adjacent bricks in each
+row. The space between the brick retaining wall and the work is filled with
+charcoal, which is lighted from below. The top opening of the temporary
+oven is then covered with asbestos and the fire kept up until the work has
+been uniformly raised in temperature to the desired point.
+
+When much work of the same general character and size is to be handled, a
+permanent oven may be constructed of fire brick, leaving a large opening
+through the top and also through one side. Charcoal may be used in this
+form of oven as with the temporary arrangement, or the heat may be secured
+from any form of burner or torch giving a large volume of flame. In any
+method employing flame to do the heating, the work itself must be protected
+from the direct blast of the fire. Baffles of brick or metal should be
+placed between the mouth of the torch and the nearest surface of the work
+so that the flame will be deflected to either side and around the piece
+being heated.
+
+The heat should be applied to bring the point of welding to the highest
+temperature desired and, except in the smallest work, the heat should
+gradually shade off from this point to the other parts of the piece. In the
+case of cast iron and steel the temperature at the point to be welded
+should be great enough to produce a dull red heat. This will make the whole
+operation much easier, because there will be no surrounding cool metal to
+reduce the temperature of the molten material from the welding rod below
+the point at which it will join the work. From this red heat the mass of
+metal should grow cooler as the distance from the weld becomes greater, so
+that no great strain is placed upon any one part. With work of a very
+irregular shape it is always best to heat the entire piece so that the
+strains will be so evenly distributed that they can cause no distortion or
+breakage under any conditions.
+
+The melting point of the work which is being preheated should be kept in
+mind and care exercised not to approach it too closely. Special care is
+necessary with aluminum in this respect, because of its low melting
+temperature and the sudden weakening and flowing without warning. Workmen
+have carelessly overheated aluminum castings and, upon uncovering the piece
+to make the weld, have been astonished to find that it had disappeared.
+Six hundred degrees is about the safe limit for this metal. It is possible
+to gauge the exact temperature of the work with a pyrometer, but when this
+instrument cannot be procured, it might be well to secure a number of
+"temperature cones" from a chemical or laboratory supply house. These cones
+are made from material that will soften at a certain heat and in form they
+are long and pointed. Placed in position on the part being heated, the
+point may be watched, and when it bends over it is sure that the metal
+itself has reached a temperature considerably in excess of the temperature
+at which that particular cone was designed to soften.
+
+The object in preheating the metal around the weld is to cause it to expand
+sufficiently to open the crack a distance equal to the contraction when
+cooling from the melting point. In the case of a crack running from the
+edge of a piece into the body or of a crack wholly within the body, it is
+usually satisfactory to heat the metal at each end of the opening. This
+will cause the whole length of the crack to open sufficiently to receive
+the molten material from the rod.
+
+The judgment of the operator will be called upon to decide just where a
+piece of metal should be heated to open the weld properly. It is often
+possible to apply the preheating flame to a point some distance from the
+point of work if the parts are so connected that the expansion of the
+heated part will serve to draw the edges of the weld apart. Whatever part
+of the work is heated to cause expansion and separation, this part must
+remain hot during the entire time of welding and must then cool slowly at
+the same time as the metal in the weld cools.
+
+[Illustration: Figure 25.--Preheating at _A_ While Welding at
+_B_. _C_ also May Be Heated.]
+
+An example of heating points away from the crack might be found in welding
+a lattice work with one of the bars cracked through (Figure 25). If the
+strips parallel and near to the broken bar are heated gradually, the work
+will be so expanded that the edges of the break are drawn apart and the
+weld can be successfully made. In this case, the parallel bars next to the
+broken one would be heated highest, the next row not quite so hot and so on
+for some distance away. If only the one row were heated, the strains set up
+in the next ones would be sufficient to cause a new break to appear.
+
+[Illustration: Figure 26.--Cutting Through the Rim of a Wheel (Cut Shown
+at A)]
+
+If welding is to be done near the central portion of a large piece, the
+strains will be brought to bear on the parts farthest away from the center.
+Should a fly wheel spoke be broken and made ready to weld, the greatest
+strain will come on the rim of the wheel. In cases like this it is often
+desirable to cut through at the point of greatest strain with a saw or
+cutting torch, allowing free movement while the weld is made at the
+original break (Figure 26). After the inside weld is completed, the cut may
+be welded without danger, for the reason that it will always be at some
+point at which severe strains cannot be set up by the contraction of the
+cooling metal.
+
+[Illustration: Figure 27.--Using a Wedge While Welding]
+
+In materials that will spring to some extent without breakage, that is, in
+parts that are not brittle, it may be possible to force the work out of
+shape with jacks or wedges (Figure 27) in the same way that it would be
+distorted by heating and expanding some portion of it as described. A
+careful examination will show whether this method can be followed in such a
+way as to force the edges of the break to separate. If the plan seems
+feasible, the wedges may be put in place and allowed to remain while the
+weld is completed. As soon as the work is finished the wedges should be
+removed so that the natural contraction can take place without damage.
+
+It should always be remembered that it is not so much the expansion of the
+work when heated as it is the contraction caused by cooling that will do
+the damage. A weld may be made that, to all appearances, is perfect and it
+may be perfect when completed; but if provision has not been made to allow
+for the contraction that is certain to follow, there will be a breakage at
+some point. It is not possible to weld the simplest shapes, other than
+straight bars, without considering this difficulty and making provision to
+take care of it.
+
+The exact method to employ in preheating will always call for good judgment
+on the part of the workman, and he should remember that the success or
+failure of his work will depend fully as much on proper preparation as on
+correct handling of the weld itself. It should be remembered that the outer
+flame of the oxy-acetylene torch may be depended on for a certain amount of
+preheating, as this flame gives a very large volume of heat, but a heat
+that is not so intense nor so localized as the welding flame itself. The
+heat of this part of the flame should be fully utilized during the
+operation of melting the metal and it should be so directed, when possible,
+that it will bring the parts next to be joined to as high a temperature as
+possible.
+
+When the work has been brought to the desired temperature, all parts except
+the break and the surface immediately surrounding it on both sides should
+be covered with heavy sheet asbestos. This protecting cover should remain
+in place throughout the operation and should only be moved a distance
+sufficient to allow the torch flame to travel in the path of the weld. The
+use of asbestos in this way serves a twofold purpose. It retains the heat
+in the work and prevents the breakage that would follow if a draught of air
+were to strike the heated metal, and it also prevents such a radiation of
+heat through the surrounding air as would make it almost impossible for the
+operator to perform his work, especially in the case of large and heavy
+castings when the amount of heat utilized is large.
+
+_Cleaning and Champfering._--A perfect weld can never be made unless
+the surfaces to be joined have been properly prepared to receive the new
+metal.
+
+All spoiled, burned, corroded and rough particles must positively be
+removed with chisel and hammer and with a free application of emery cloth
+and wire brush. The metal exposed to the welding flame should be perfectly
+clean and bright all over, or else the additional material will not unite,
+but will only stick at best.
+
+[Illustration: Figure 28.--Tapering the Opening Formed by a Break]
+
+Following the cleaning it is always necessary to bevel, or champfer, the
+edges except in the thinnest sheet metal. To make a weld that will hold,
+the metal must be made into one piece, without holes or unfilled portions
+at any point, and must be solid from inside to outside. This can only be
+accomplished by starting the addition of metal at one point and gradually
+building it up until the outside, or top, is reached. With comparatively
+thin plates the molten metal may be started from the side farthest from the
+operator and brought through, but with thicker sections the addition is
+started in the middle and brought flush with one side and then with the
+other.
+
+It will readily be seen that the molten material cannot be depended upon to
+flow between the tightly closed surfaces of a crack in a way that can be at
+all sure to make a true weld. It will be necessary for the operator to
+reach to the farthest side with the flame and welding rod, and to start the
+new surfaces there. To allow this, the edges that are to be joined are
+beveled from one side to the other (Figure 28), so that when placed
+together in approximately the position they are to occupy they will leave a
+grooved channel between them with its sides at an angle with each other
+sufficient in size to allow access to every point of each surface.
+
+[Illustration: Figure 29.--Beveling for Thin Work]
+
+[Illustration: Figure 30.--Beveling for Thick Work]
+
+With work less than one-fourth inch thick, this angle should be forty-five
+degrees on each piece (Figure 29), so that when they are placed together
+the extreme edges will meet at the bottom of a groove whose sides are
+square, or at right angles, to each other. This beveling should be done so
+that only a thin edge is left where the two parts come together, just
+enough points in contact to make the alignment easy to hold. With work of a
+thickness greater than a quarter of an inch, the angle of bevel on each
+piece may be sixty degrees (Figure 30), so that when placed together the
+angle included between the sloping sides will also be sixty degrees. If the
+plate is less than one-eighth of an inch thick the beveling is not
+necessary, as the edges may be melted all the way through without danger of
+leaving blowholes at any point.
+
+[Illustration: Figure 31.--Beveling Both Sides of a Thick Piece]
+
+[Illustration: Figure 32.--Beveling the End of a Pipe]
+
+This beveling may be done in any convenient way. A chisel is usually most
+satisfactory and also quickest. Small sections may be handled by filing,
+while metal that is too hard to cut in either of these ways may be shaped
+on the emery wheel. It is not necessary that the edges be perfectly
+finished and absolutely smooth, but they should be of regular outline and
+should always taper off to a thin edge so that when the flame is first
+applied it can be seen issuing from the far side of the crack. If the work
+is quite thick and is of a shape that will allow it to be turned over, the
+bevel may be brought from both sides (Figure 31), so that there will be two
+grooves, one on each surface of the work. After completing the weld on one
+side, the piece is reversed and finished on the other side. Figure 32 shows
+the proper beveling for welding pipe. Figure 33 shows how sheet metal may
+be flanged for welding.
+
+Welding should not be attempted with the edges separated in place of
+beveled, because it will be found impossible to build up a solid web of new
+metal from one side clear through to the other by this method. The flame
+cannot reach the surfaces to make them molten while receiving new material
+from the rod, and if the flame does not reach them it will only serve to
+cause a few drops of the metal to join and will surely cause a weak and
+defective weld.
+
+[Illustration: Figure 33.--Flanging Sheet Metal for Welding]
+
+_Supporting Work._--During the operation of welding it is necessary
+that the work be well supported in the position it should occupy. This may
+be done with fire brick placed under the pieces in the correct position,
+or, better still, with some form of clamp. The edges of the crack should
+touch each other at the point where welding is to start and from there
+should gradually separate at the rate of about one-fourth inch to the foot.
+This is done so that the cooling of the molten metal as it is added will
+draw the edges together by its contraction.
+
+Care must be used to see that the work is supported so that it will
+maintain the same relative position between the parts as must be present
+when the work is finished. In this connection it must be remembered that
+the expansion of the metal when heated may be great enough to cause serious
+distortion and to provide against this is one of the difficulties to be
+overcome.
+
+Perfect alignment should be secured between the separate parts that are to
+be joined and the two edges must be held up so that they will be in the
+same plane while welding is carried out. If, by any chance, one drops
+below the other while molten metal is being added, the whole job may have
+to be undone and done over again. One precaution that is necessary is that
+of making sure that the clamping or supporting does not in itself pull the
+work out of shape while melted.
+
+
+TORCH PRACTICE
+
+[Illustration: Figure 34.--Rotary Movement of Torch in Welding]
+
+The weld is made by bringing the tip of the welding flame to the edges of
+the metals to be joined. The torch should be held in the right hand and
+moved slowly along the crack with a rotating motion, traveling in small
+circles (Figure 34), so that the Welding flame touches first on one side of
+the crack and then on the other. On large work the motion may be simply
+back and forth across the crack, advancing regularly as the metal unites.
+It is usually best to weld toward the operator rather than from him,
+although this rule is governed by circumstances. The head of the torch
+should be inclined at an angle of about 60 degrees to the surface of the
+work. The torch handle should extend in the same line with the break
+(Figure 35) and not across it, except when welding very light plates.
+
+[Illustration: Figure 35.--Torch Held in Line with the Break]
+
+If the metal is 1/16 inch or less in thickness it is only necessary to
+circle along the crack, the metal itself furnishing enough material to
+complete the weld without additions. Heat both sides evenly until they flow
+together.
+
+Material thicker than the above requires the addition of more metal of the
+same or different kind from the welding rod, this rod being held by the
+left hand. The proper size rod for cast iron is one having a diameter equal
+to the thickness of metal being welded up to a one-half inch rod, which is
+the largest used. For steel the rod should be one-half the thickness of the
+metal being joined up to one-fourth inch rod. As a general rule, better
+results will be obtained by the use of smaller rods, the very small sizes
+being twisted together to furnish enough material while retaining the free
+melting qualities.
+
+[Illustration: Figure 36.--The Welding Rod Should Be Held in the Molten
+Metal]
+
+The tip of the rod must at all times be held in contact with the pieces
+being welded and the flame must be so directed that the two sides of the
+crack and the end of the rod are melted at the same time (Figure 36).
+Before anything is added from the rod, the sides of the crack are melted
+down sufficiently to fill the bottom of the groove and join the two sides.
+Afterward, as metal comes from the rod in filling the crack, the flame is
+circled along the joint being made, the rod always following the flame.
+
+[Illustration: Figure 37.--Welding Pieces of Unequal Thickness]
+
+Figure 37 illustrates the welding of pieces of unequal thickness.
+
+Figure 38 illustrates welding at an angle.
+
+The molten metal may be directed as to where it should go by the tip of the
+welding flame, which has considerable force, but care must be taken not to
+blow melted metal on to cooler surfaces which it cannot join. If, while
+welding, a spot appears which does not unite with the weld, it may be
+handled by heating all around it to a white heat and then immediately
+welding the bad place.
+
+[Illustration: Figure 38.--Welding at an Angle]
+
+Never stop in the middle of a weld, as it is extremely difficult to
+continue smoothly when resuming work.
+
+_The Flame._--The welding flame must have exactly the right
+proportions of each gas. If there is too much oxygen, the metal will be
+burned or oxidized; the presence of too much acetylene carbonizes the
+metal; that is to say, it adds carbon and makes the work harder. Just the
+right mixture will neither burn nor carbonize and is said to be a "neutral"
+flame. The neutral flame, if of the correct size for the work, reduces the
+metal to a melted condition, not too fluid, and for a width about the same
+as the thickness of the metal being welded.
+
+When ready to light the torch, after attaching the right tip or head as
+directed in accordance with the thickness of metal to be handled, it will
+be necessary to regulate the pressure of gases to secure the neutral flame.
+
+The oxygen will have a pressure of from 2 to 20 pounds, according to the
+nozzle used. The acetylene will have much less. Even with the compressed
+gas, the pressure should never exceed 10 pounds for the largest work, and
+it will usually be from 4 to 6. In low pressure systems, the acetylene will
+be received at generator pressure. It should first be seen that the
+hand-screws on the regulators are turned way out so that the springs are
+free from any tension. It will do no harm if these screws are turned back
+until they come out of the threads. This must be done with both oxygen and
+acetylene regulators.
+
+Next, open the valve from the generator, or on the acetylene tank, and
+carefully note whether there is any odor of escaping gas. Any leakage of
+this gas must be stopped before going on with the work.
+
+The hand wheel controlling the oxygen cylinder valve should now be turned
+very slowly to the left as far as it will go, which opens the valve, and
+it should be borne in mind the pressure that is being released. Turn in the
+hand screw on the oxygen regulator until the small pressure gauge shows a
+reading according to the requirements of the nozzle being used. This oxygen
+regulator adjustment should be made with the cock on the torch open, and
+after the regulator is thus adjusted the torch cock may be closed.
+
+Open the acetylene cock on the torch and screw in on the acetylene
+regulator hand-screw until gas commences to come through the torch. Light
+this flow of acetylene and adjust the regulator screw to the pressure
+desired, or, if there is no gauge, so that there is a good full flame. With
+the pressure of acetylene controlled by the type of generator it will only
+be necessary to open the torch cock.
+
+With the acetylene burning, slowly open the oxygen cock on the torch and
+allow this gas to join the flame. The flame will turn intensely bright and
+then blue white. There will be an outer flame from four to eight inches
+long and from one to three inches thick. Inside of this flame will be two
+more rather distinctly defined flames. The inner one at the torch tip is
+very small, and the intermediate one is long and pointed. The oxygen should
+be turned on until the two inner flames unite into one blue-white cone from
+one-fourth to one-half inch long and one-eighth to one-fourth inch in
+diameter. If this single, clearly defined cone does not appear when the
+oxygen torch cock has been fully opened, turn off some of the acetylene
+until it does appear.
+
+If too much oxygen is added to the flame, there will still be the central
+blue-white cone, but it will be smaller and more or less ragged around the
+edges (Figure 39). When there is just enough oxygen to make the single
+cone, and when, by turning on more acetylene or by turning off oxygen, two
+cones are caused to appear, the flame is neutral (Figure 40), and the small
+blue-white cone is called the welding flame.
+
+[Illustration: Figure 39.--Oxidizing Flame--Too Much Oxygen]
+
+[Illustration: Figure 40.--Neutral Flame]
+
+[Illustration: Figure 41.--Reducing Flame--Showing an Excess of Acetylene]
+
+While welding, test the correctness of the flame adjustment occasionally by
+turning on more acetylene or by turning off some oxygen until two flames or
+cones appear. Then regulate as before to secure the single distinct cone.
+Too much oxygen is not usually so harmful as too much acetylene, except
+with aluminum. (See Figure 41.) An excessive amount of sparks coming from
+the weld denotes that there is too much oxygen in the flame. Should the
+opening in the tip become partly clogged, it will be difficult to secure a
+neutral flame and the tip should be cleaned with a brass or copper
+wire--never with iron or steel tools or wire of any kind. While the torch
+is doing its work, the tip may become excessively hot due to the heat
+radiated from the molten metal. The tip may be cooled by turning off the
+acetylene and dipping in water with a slight flow of oxygen through the
+nozzle to prevent water finding its way into the mixing chamber.
+
+The regulators for cutting are similar to those for welding, except that
+higher pressures may be handled, and they are fitted with gauges reading up
+to 200 or 250 pounds pressure.
+
+In welding metals which conduct the heat very rapidly it is necessary to
+use a much larger nozzle and flame than for metals which have not this
+property. This peculiarity is found to the greatest extent in copper,
+aluminum and brass.
+
+Should a hole be blown through the work, it may be closed by withdrawing
+the flame for a few seconds and then commencing to build additional metal
+around the edges, working all the way around and finally closing the small
+opening left at the center with a drop or two from the welding rod.
+
+
+WELDING VARIOUS METALS
+
+Because of the varying melting points, rates of expansion and contraction,
+and other peculiarities of different metals, it is necessary to give
+detailed consideration to the most important ones.
+
+_Characteristics of Metals._--The welder should thoroughly understand
+the peculiarities of the various metals with which he has to deal. The
+metals and their alloys are described under this heading in the first
+chapter of this book and a tabulated list of the most important points
+relating to each metal will be found at the end of the present chapter.
+All this information should be noted by the operator of a welding
+installation before commencing actual work.
+
+Because of the nature of welding, the melting point of a metal is of great
+importance. A metal melting at a low temperature should have more careful
+treatment to avoid undesired flow than one which melts at a temperature
+which is relatively high. When two dissimilar metals are to be joined, the
+one which melts at the higher temperature must be acted upon by the flame
+first and when it is in a molten condition the heat contained in it will in
+many cases be sufficient to cause fusion of the lower melting metal and
+allow them to unite without playing the flame on the lower metal to any
+great extent.
+
+The heat conductivity bears a very important relation to welding, inasmuch
+as a metal with a high rate of conductance requires more protection from
+cooling air currents and heat radiation than one not having this quality to
+such a marked extent. A metal which conducts heat rapidly will require a
+larger volume of flame, a larger nozzle, than otherwise, this being
+necessary to supply the additional heat taken away from the welding point
+by this conductance.
+
+The relative rates of expansion of the various metals under heat should be
+understood in order that parts made from such material may have proper
+preparation to compensate for this expansion and contraction. Parts made
+from metals having widely varying rates of expansion must have special
+treatment to allow for this quality, otherwise breakage is sure to occur.
+
+_Cast Iron._--All spoiled metal should be cut away and if the work is
+more than one-eighth inch in thickness the sides of the crack should be
+beveled to a 45 degree angle, leaving a number of points touching at the
+bottom of the bevel so that the work may be joined in its original
+relation.
+
+The entire piece should be preheated in a bricked-up oven or with charcoal
+placed on the forge, when size does not warrant building a temporary oven.
+The entire piece should be slowly heated and the portion immediately
+surrounding the weld should be brought to a dull red. Care should be used
+that the heat does not warp the metal through application to one part more
+than the others. After welding, the work should be slowly cooled by
+covering with ashes, slaked lime, asbestos fibre or some other
+non-conductor of heat. These precautions are absolutely essential in the
+case of cast iron.
+
+A neutral flame, from a nozzle proportioned to the thickness of the work,
+should be held with the point of the blue-white cone about one-eighth inch
+from the surface of the iron.
+
+A cast iron rod of correct diameter, usually made with an excess of
+silicon, is used by keeping its end in contact with the molten metal and
+flowing it into the puddle formed at the point of fusion. Metal should be
+added so that the weld stands about one-eighth inch above the surrounding
+surface of the work.
+
+Various forms of flux may be used and they are applied by dipping the end
+of the welding rod into the powder at intervals. These powders may contain
+borax or salt, and to prevent a hard, brittle weld, graphite or
+ferro-silicon may be added. Flux should be added only after the iron is
+molten and as little as possible should be used. No flux should be used
+just before completion of the work.
+
+The welding flame should be played on the work around the crack and
+gradually brought to bear on the work. The bottom of the bevel should be
+joined first and it will be noted that the cast iron tends to run toward
+the flame, but does not stick together easily. A hard and porous weld
+should be carefully guarded against, as described above, and upon
+completion of the work the welded surface should be scraped with a file,
+while still red hot, in order to remove the surface scale.
+
+_Malleable Iron._--This material should be beveled in the same way
+that cast iron is handled, and preheating and slow cooling are equally
+desirable. The flame used is the same as for cast iron and so is the flux.
+The welding rod may be of cast iron, although better results are secured
+with Norway iron wire or else a mild steel wire wrapped with a coil of
+copper wire.
+
+It will be understood that malleable iron turns to ordinary cast iron when
+melted and cooled. Welds in malleable iron are usually far from
+satisfactory and a better joint is secured by brazing the edges together
+with bronze. The edges to be joined are brought to a heat just a little
+below the point at which they will flow and the opening is then
+quickly-filled from a rod of Tobin bronze or manganese bronze, a brass or
+bronze flux being used in this work.
+
+_Wrought Iron or Semi-Steel._--This metal should be beveled and heated
+in the same way as described for cast iron. The flame should be neutral, of
+the same size as for steel, and used with the tip of the blue-white cone
+just touching the work. The welding rod should be of mild steel, or, if
+wrought iron is to be welded to steel, a cast iron rod may be used. A cast
+iron flux is well suited for this work. It should be noted that wrought
+iron turns to ordinary cast iron if kept heated for any length of time.
+
+_Steel._--Steel should be beveled if more than one-eighth inch in
+thickness. It requires only a local preheating around the point to be
+welded. The welding flame should be absolutely neutral, without excess of
+either gas. If the metal is one-sixteenth inch or less in thickness, the
+tip of the blue-white cone must be held a short distance from the surface
+of the work; in all other cases the tip of this cone is touched to the
+metal being welded.
+
+The welding rod may be of mild, low carbon steel or of Norway iron. Nickel
+steel rods may be used for parts requiring great strength, but vanadium
+alloys are very difficult to handle. A very satisfactory rod is made by
+twisting together two wires of the required material. The rod must be kept
+constantly in contact with the work and should not be added until the edges
+are thoroughly melted. The flux may or may not be used. If one is wanted,
+it may be made from three parts iron filings, six parts borax and one part
+sal ammoniac.
+
+It will be noticed that the steel runs from the flame, but tends to hold
+together. Should foaming commence in the molten metal, it shows an excess
+of oxygen and that the metal is being burned.
+
+High carbon steels are very difficult to handle. It is claimed that a drop
+or two of copper added to the weld will assist the flow, but will also
+harden the work. An excess of oxygen reduces the amount of carbon and
+softens the steel, while an excess of acetylene increases the proportion of
+carbon and hardens the metal. High speed steels may sometimes be welded if
+first coated with semi-steel before welding.
+
+_Aluminum._--This is the most difficult of the commonly found metals
+to weld. This is caused by its high rate of expansion and contraction and
+its liability to melt and fall away from under the flame. The aluminum
+seems to melt on the inside first, and, without previous warning, a portion
+of the work will simply vanish from in front of the operator's eyes. The
+metal tends to run from the flame and separate at the same time. To keep
+the metal in shape and free from oxide, it is worked or puddled while in a
+plastic condition by an iron rod which has been flattened at one end.
+Several of these rods should be at hand and may be kept in a jar of salt
+water while not being used. These rods must not become coated with aluminum
+and they must not get red hot while in the weld.
+
+The surfaces to be joined, together with the adjacent parts, should be
+cleaned thoroughly and then washed with a 25 per cent solution of nitric
+acid in hot water, used on a swab. The parts should then be rinsed in clean
+water and dried with sawdust. It is also well to make temporary fire clay
+moulds back of the parts to be heated, so that the metal may be flowed into
+place and allowed to cool without danger of breakage.
+
+Aluminum must invariably be preheated to about 600 degrees, and the whole
+piece being handled should be well covered with sheet asbestos to prevent
+excessive heat radiation.
+
+The flame is formed with an excess of acetylene such that the second cone
+extends about an inch, or slightly more, beyond the small blue-white point.
+The torch should be held so that the end of this second cone is in contact
+with the work, the small cone ordinarily used being kept an inch or an inch
+and a half from the surface of the work.
+
+Welding rods of special aluminum are used and must be handled with their
+end submerged in the molten metal of the weld at all times.
+
+When aluminum is melted it forms alumina, an oxide of the metal. This
+alumina surrounds small masses of the metal, and as it does not melt at
+temperatures below 5000 degrees (while aluminum melts at about 1200), it
+prevents a weld from being made. The formation of this oxide is retarded
+and the oxide itself is dissolved by a suitable flux, which usually
+contains phosphorus to break down the alumina.
+
+_Copper._--The whole piece should be preheated and kept well covered
+while welding. The flame must be much larger than for the same thickness of
+steel and neutral in character. A slight excess of acetylene would be
+preferable to an excess of oxygen, and in all cases the molten metal should
+be kept enveloped with the flame. The welding rod is of copper which
+contains phosphorus; and a flux, also containing phosphorus, should be
+spread for about an inch each side of the joint. These assist in preventing
+oxidation, which is sure to occur with heated copper.
+
+Copper breaks very easily at a heat slightly under the welding temperature
+and after cooling it is simply cast copper in all cases.
+
+_Brass and Bronze._--It is necessary to preheat these metals, although
+not to a very high temperature. They must be kept well covered at all times
+to prevent undue radiation. The flame should be produced with a nozzle one
+size larger than for the same thickness of steel and the small blue-white
+cone should be held from one-fourth to one-half inch above the surface of
+the work. The flame should be neutral in character.
+
+A rod or wire of soft brass containing a large percentage of zinc is
+suitable for adding to brass, while copper requires the use of copper or
+manganese bronze rods. Special flux or borax may be used to assist the
+flow.
+
+The emission of white smoke indicates that the zinc contained in these
+alloys is being burned away and the heat should immediately be turned away
+or reduced. The fumes from brass and bronze welding are very poisonous and
+should not be breathed.
+
+
+RESTORATION OF STEEL
+
+The result of the high heat to which the steel has been subjected is that
+it is weakened and of a different character than before welding. The
+operator may avoid this as much as possible by first playing the outer
+flame of the torch all over the surfaces of the work just completed until
+these faces are all of uniform color, after which the metal should be well
+covered with asbestos and allowed to cool without being disturbed. If a
+temporary heating oven has been employed, the work and oven should be
+allowed to cool together while protected with the sheet asbestos. If the
+outside air strikes the freshly welded work, even for a moment, the result
+will be breakage.
+
+A weld in steel will always leave the metal with a coarse grain and with
+all the characteristics of rather low grade cast steel. As previously
+mentioned in another chapter, the larger the grain size in steel the weaker
+the metal will be, and it is the purpose of the good workman to avoid, as
+far as possible, this weakening.
+
+The structure of the metal in one piece of steel will differ according to
+the heat that it has under gone. The parts of the work that have been at
+the melting point will, therefore, have the largest grain size and the
+least strength. Those parts that have not suffered any great rise in
+temperature will be practically unaffected, and all the parts between these
+two extremes will be weaker or stronger according to their distance from
+the weld itself. To restore the steel so that it will have the best grain
+size, the operator may resort to either of two methods: (1) The grain may
+be improved by forging. That means that the metal added to the weld and the
+surfaces that have been at the welding heat are hammered much as a
+blacksmith would hammer his finished work to give it greater strength. The
+hammering should continue from the time the metal first starts to cool
+until it has reached the temperature at which the grain size is best for
+strength. This temperature will vary somewhat with the composition of the
+metal being handled, but in a general way, it may be stated that the
+hammering should continue without intermission from the time the flame is
+removed from the weld until the steel just begins to show attraction for a
+magnet presented to it. This temperature of magnetic attraction will always
+be low enough and the hammering should be immediately discontinued at this
+point. (2) A method that is more satisfactory, although harder to apply, is
+that of reheating the steel to a certain temperature throughout its whole
+mass where the heat has had any effect, and then allowing slow and even
+cooling from this temperature. The grain size is affected by the
+temperature at which the reheating is stopped, and not by the cooling, yet
+the cooling should be slow enough to avoid strains caused by uneven
+contraction.
+
+After the weld has been completed the steel must be allowed to cool until
+below 1200 deg. Fahrenheit. The next step is to heat the work slowly until all
+those parts to be restored have reached a temperature at which the magnet
+just ceases to be attracted. While the very best temperature will vary
+according to the nature and hardness of the steel being handled, it will be
+safe to carry the heating to the point indicated by the magnet in the
+absence of suitable means of measuring accurately these high temperatures.
+In using a magnet for testing, it will be most satisfactory if it is an
+electromagnet and not of the permanent type. The electric current may be
+secured from any small battery and will be the means of making sure of the
+test. The permanent magnet will quickly lose its power of attraction under
+the combined action of the heat and the jarring to which it will be
+subjected.
+
+In reheating the work it is necessary to make sure that no part reaches a
+temperature above that desired for best grain size and also to see that all
+parts are brought to this temperature. Here enters the greatest difficulty
+in restoring the metal. The heating may be done so slowly that no part of
+the work on the outside reaches too high a temperature and then keeps the
+outside at this heat until the entire mass is at the same temperature. A
+less desirable way is to heat the outside higher than this temperature and
+allow the conductivity of the metal to distribute the excess to the inside.
+
+The most satisfactory method, where it can be employed, is to make use of a
+bath of some molten metal or some chemical mixture that can be kept at the
+exact heat necessary by means of gas fires that admit of close regulation.
+The temperature of these baths may be maintained at a constant point by
+watching a pyrometer, and the finished work may be allowed to remain in the
+bath until all parts have reached the desired temperature.
+
+
+WELDING INFORMATION
+
+The following tables include much of the information that the operator must
+use continually to handle the various metals successfully. The temperature
+scales are given for convenience only. The composition of various alloys
+will give an idea of the difficulties to be contended with by consulting
+the information on welding various metals. The remaining tables are of
+self-evident value in this work.
+
+TEMPERATURE SCALES
+Centigrade  Fahrenheit      Centigrade  Fahrenheit
+   200 deg.        392 deg.            1000 deg.      1832 deg.
+   225 deg.        437 deg.            1050 deg.      1922 deg.
+   250 deg.        482 deg.            1100 deg.      2012 deg.
+   275 deg.        527 deg.            1150 deg.      2102 deg.
+   300 deg.        572 deg.            1200 deg.      2192 deg.
+   325 deg.        617 deg.            1250 deg.      2282 deg.
+   350 deg.        662 deg.            1300 deg.      2372 deg.
+   375 deg.        707 deg.            1350 deg.      2462 deg.
+   400 deg.        752 deg.            1400 deg.      2552 deg.
+   425 deg.        797 deg.            1450 deg.      2642 deg.
+   450 deg.        842 deg.            1500 deg.      2732 deg.
+   475 deg.        887 deg.            1550 deg.      2822 deg.
+   500 deg.        932 deg.            1600 deg.      2912 deg.
+   525 deg.        977 deg.            1650 deg.      3002 deg.
+   550 deg.       1022 deg.            1700 deg.      3092 deg.
+   575 deg.       1067 deg.            1750 deg.      3182 deg.
+   600 deg.       1112 deg.            1800 deg.      3272 deg.
+   625 deg.       1157 deg.            1850 deg.      3362 deg.
+   650 deg.       1202 deg.            1900 deg.      3452 deg.
+   675 deg.       1247 deg.            2000 deg.      3632 deg.
+   700 deg.       1292 deg.            2050 deg.      3722 deg.
+   725 deg.       1337 deg.            2100 deg.      3812 deg.
+   750 deg.       1382 deg.            2150 deg.      3902 deg.
+   775 deg.       1427 deg.            2200 deg.      3992 deg.
+   800 deg.       1472 deg.            2250 deg.      4082 deg.
+   825 deg.       1517 deg.            2300 deg.      4172 deg.
+   850 deg.       1562 deg.            2350 deg.      4262 deg.
+   875 deg.       1607 deg.            2400 deg.      4352 deg.
+   900 deg.       1652 deg.            2450 deg.      4442 deg.
+   925 deg.       1697 deg.            2500 deg.      4532 deg.
+   950 deg.       1742 deg.            2550 deg.      4622 deg.
+   975 deg.       1787 deg.            2600 deg.      4712 deg.
+
+METAL ALLOYS
+(Society of Automobile Engineers)
+
+Babbitt--
+  Tin...........................           84.00%
+  Antimony......................            9.00%
+  Copper........................            7.00%
+
+Brass, White--
+  Copper........................  3.00% to  6.00%
+  Tin (minimum) ................           65.00%
+  Zinc.......................... 28.00% to 30.00%
+
+Brass, Red Cast--
+  Copper........................           85.00%
+  Tin...........................            5.00%
+  Lead..........................            5.00%
+  Zinc..........................            5.00%
+
+Brass, Yellow--
+  Copper........................ 62.00% to 65.00%
+  Lead..........................  2.00% to  4.00%
+  Zinc.......................... 36.00% to 31.00%
+
+Bronze, Hard--
+  Copper........................ 87.00% to 88.00%
+  Tin...........................  9.50% to 10.50%
+  Zinc..........................  1.50% to  2.50%
+
+Bronze, Phosphor--
+  Copper........................           80.00%
+  Tin...........................           10.00%
+  Lead..........................           10.00%
+  Phosphorus....................   .50% to   .25%
+
+Bronze, Manganese--
+  Copper (approximate) .........           60.00%
+  Zinc (approximate) ...........           40.00%
+  Manganese (variable) .........            small
+
+Bronze, Gear--
+  Copper........................ 88.00% to 89.00%
+  Tin........................... 11.00% to 12.00%
+
+Aluminum Alloys--
+          Aluminum   Copper   Zinc   Manganese
+  No. 1.. 90.00%    8.5-7.0%
+  No. 2.. 80.00%    2.0-3.0%  15%  Not over 0.40%
+  No. 3.. 65.00%              35.0%
+
+Cast Iron--
+                      Gray Iron      Malleable
+  Total carbon........3.0 to 3.5%
+  Combined carbon.....0.4 to 0.7%
+  Manganese...........0.4 to 0.7%    0.3 to 0.7%
+  Phosphorus..........0.6 to 1.0%  Not over 0.2%
+  Sulphur...........Not over 0.1%  Not over 0.6%
+  Silicon............1.75 to 2.25% Not over 1.0%
+
+Carbon Steel (10 Point)--
+  Carbon........................     .05% to .15%
+  Manganese.....................     .30% to .60%
+  Phosphorus (maximum)..........             .045%
+  Sulphur (maximum).............             .05%
+(20 Point)--
+  Carbon........................     .15% to .25%
+  Manganese.....................     .30% to .60%
+  Phosphorus (maximum)..........             .045%
+  Sulphur (maximum).............             .05%
+(35 Point)--
+  Manganese.....................     .50% to .80%
+  Carbon........................     .30% to .40%
+  Phosphorus (maximum)..........             .05%
+  Sulphur (maximum).............             .05%
+(95 Point)--
+  Carbon........................    .90% to 1.05%
+  Manganese.....................    .25% to  .50%
+  Phosphorus (maximum)..........             .04%
+  Sulphur (maximum).............             .05%
+
+HEATING POWER OF FUEL GASES
+
+(In B.T.U. per Cubic Foot.)
+  Acetylene....... 1498.99   Ethylene....... 1562.9
+  Hydrogen........  291.96   Methane........  953.6
+  Alcohol......... 1501.76
+
+MELTING POINTS OF METALS
+  Platinum....................3200 deg.
+  Iron, wrought...............2900 deg.
+    malleable.................2500 deg.
+    cast......................2400 deg.
+    pure......................2760 deg.
+  Steel, mild.................2700 deg.
+    Medium....................2600 deg.
+    Hard......................2500 deg.
+  Copper......................1950 deg.
+  Brass.......................1800 deg.
+  Silver......................1750 deg.
+  Bronze......................1700 deg.
+  Aluminum....................1175 deg.
+  Antimony....................1150 deg.
+  Zinc........................ 800 deg.
+  Lead........................ 620 deg.
+  Babbitt..................500-700 deg.
+  Solder...................500-575 deg.
+  Tin......................... 450 deg.
+
+_NOTE.--These melting points are for average compositions and conditions.
+The exact proportion of elements entering into the metals affects their
+melting points one way or the other in practice._
+
+TENSILE STRENGTH OF METALS
+
+Alloy steels can be made with tensile strengths as high as 300,000 pounds
+per square inch. Some carbon steels are given below according to "points":
+
+                           Pounds per Square Inch
+Steel, 10 point................ 50,000 to  65,000
+  20 point..................... 60,000 to  80,000
+  40 point..................... 70,000 to 100,000
+  60 point..................... 90,000 to 120,000
+Iron, Cast..................... 13,000 to  30,000
+  Wrought...................... 40,000 to  60,000
+  Malleable.................... 25,000 to  45,000
+Copper......................... 24,000 to  50,000
+Bronze......................... 30,000 to  60,000
+Brass, Cast.................... 12,000 to  18,000
+  Rolled....................... 30,000 to  40,000
+  Wire......................... 60,000 to  75,000
+Aluminum....................... 12,000 to  23,000
+Zinc...........................  5,000 to  15,000
+Tin............................  3,000 to   5,000
+Lead...........................  1,500 to   2,500
+
+CONDUCTIVITY OF METALS
+
+(Based on the Value of Silver as 100)
+
+                          Heat  Electricity
+Silver....................100     100
+Copper.................... 74      99
+Aluminum.................. 38      63
+Brass..................... 23      22
+Zinc...................... 19      29
+Tin....................... 14      15
+Wrought Iron.............. 12      16
+Steel..................... 11.5    12
+Cast Iron................. 11      12
+Bronze....................  9       7
+Lead......................  8       9
+
+WEIGHT OF METALS
+
+(Per Cubic Inch)
+                 Pounds                  Pounds
+Lead............  .410  Wrought Iron.....  .278
+Copper..........  .320  Tin..............  .263
+Bronze..........  .313  Cast Iron........  .260
+Brass...........  .300  Zinc.............  .258
+Steel...........  .283  Aluminum.........  .093
+
+EXPANSION OF METALS
+
+(Measured in Thousandths of an Inch per Foot of
+Length When Raised 1000 Degrees in Temperature)
+                  Inch                     Inch
+Lead............  .188  Brass............  .115
+Zinc............  .168  Copper...........  .106
+Aluminum........  .148  Steel............  .083
+Silver..........  .129  Wrought Iron.....  .078
+Bronze..........  .118  Cast Iron........  .068
+
+
+
+
+CHAPTER VI
+
+ELECTRIC WELDING
+
+
+RESISTANCE METHOD
+
+Two distinct forms of electric welding apparatus are in use, one producing
+heat by the resistance of the metal being treated to the passage of
+electric current, the other using the heat of the electric arc.
+
+The resistance process is of the greatest use in manufacturing lines where
+there is a large quantity of one kind of work to do, many thousand pieces
+of one kind, for instance. The arc method may be applied in practically any
+case where any other form of weld may be made. The resistance process will
+be described first.
+
+It is a well known fact that a poor conductor of electricity will offer so
+much resistance to the flow of electricity that it will heat. Copper is a
+good conductor, and a bar of iron, a comparatively poor conductor, when
+placed between heavy copper conductors of a welder, becomes heated in
+attempting to carry the large volume of current. The degree of heat depends
+on the amount of current and the resistance of the conductor.
+
+In an electric circuit the ends of two pieces of metal brought together
+form the point of greatest resistance in the electric circuit, and the
+abutting ends instantly begin to heat. The hotter this metal becomes, the
+greater the resistance to the flow of current; consequently, as the edges
+of the abutting ends heat, the current is forced into the adjacent cooler
+parts, until there is a uniform heat throughout the entire mass. The heat
+is first developed in the interior of the metal so that it is welded there
+as perfectly as at the surface.
+
+[Illustration: Figure 42.--Spot Welding Machine]
+
+The electric welder (Figure 42) is built to hold the parts to be joined
+between two heavy copper dies or contacts. A current of three to five
+volts, but of very great volume (amperage), is allowed to pass across
+these dies, and in going through the metal to be welded, heats the edges
+to a welding temperature. It may be explained that the voltage of an
+electric current measures the pressure or force with which it is being sent
+through the circuit and has nothing to do with the quantity or volume
+passing. Amperes measure the rate at which the current is passing through
+the circuit and consequently give a measure of the quantity which passes in
+any given time. Volts correspond to water pressure measured by pounds to
+the square inch; amperes represent the flow in gallons per minute. The low
+voltage used avoids all danger to the operator, this pressure not being
+sufficient to be felt even with the hands resting on the copper contacts.
+
+Current is supplied to the welding machine at a higher voltage and lower
+amperage than is actually used between the dies, the low voltage and high
+amperage being produced by a transformer incorporated in the machine
+itself. By means of windings of suitable size wire, the outside current may
+be received at voltages ranging from 110 to 550 and converted to the low
+pressure needed.
+
+The source of current for the resistance welder must be alternating, that
+is, the current must first be negative in value and then positive, passing
+from one extreme to the other at rates varying from 25 to 133 times a
+second. This form is known as alternating current, as opposed to direct
+current, in which there is no changing of positive and negative.
+
+The current must also be what is known as single phase, that is, a current
+which rises from zero in value to the highest point as a positive current
+and then recedes to zero before rising to the highest point of negative
+value. Two-phase of three-phase currents would give two or three positive
+impulses during this time.
+
+As long as the current is single phase alternating, the voltage and cycles
+(number of alternations per second) may be anything convenient. Various
+voltages and cycles are taken care of by specifying all these points when
+designing the transformer which is to handle the current.
+
+Direct current is not used because there is no way of reducing the voltage
+conveniently without placing resistance wires in the circuit and this uses
+power without producing useful work. Direct current may be changed to
+alternating by having a direct current motor running an alternating current
+dynamo, or the change may be made by a rotary converter, although this last
+method is not so satisfactory as the first.
+
+The voltage used in welding being so low to start with, it is absolutely
+necessary that it be maintained at the correct point. If the source of
+current supply is not of ample capacity for the welder being used, it will
+be very hard to avoid a fall of voltage when the current is forced to pass
+through the high resistance of the weld. The current voltage for various
+work is calculated accurately, and the efficiency of the outfit depends to
+a great extent on the voltage being constant.
+
+A simple test for fall of voltage is made by connecting an incandescent
+electric lamp across the supply lines at some point near the welder. The
+lamp should burn with the same brilliancy when the weld is being made as at
+any other time. If the lamp burns dim at any time, it indicates a drop in
+voltage, and this condition should be corrected.
+
+The dynamo furnishing the alternating current may be in the same building
+with the welder and operated from a direct current motor, as mentioned
+above, or operated from any convenient shafting or source of power. When
+the dynamo is a part of the welding plant it should be placed as close to
+the welding machine as possible, because the length of the wire used
+affects the voltage appreciably.
+
+In order to hold the voltage constant, the Toledo Electric Welder Company
+has devised connections which include a rheostat to insert a variable
+resistance in the field windings of the dynamo so that the voltage may be
+increased by cutting this resistance out at the proper time. An auxiliary
+switch is connected to the welder switch so that both switches act
+together. When the welder switch is closed in making a weld, that portion
+of the rheostat resistance between two arms determining the voltage is
+short circuited. This lowers the resistance and the field magnets of the
+dynamo are made stronger so that additional voltage is provided to care for
+the resistance in the metal being heated.
+
+A typical machine is shown in the accompanying cut (Figure 43). On top of
+the welder are two jaws for holding the ends of the pieces to be welded.
+The lower part of the jaws is rigid while the top is brought down on top of
+the work, acting as a clamp. These jaws carry the copper dies through which
+the current enters the work being handled. After the work is clamped
+between the jaws, the upper set is forced closer to the lower set by a long
+compression lever. The current being turned on with the surfaces of the
+work in contact, they immediately heat to the welding point when added
+pressure on the lever forces them together and completes the weld.
+
+[Illustration: Figure 43--Operating Parts of a Toledo Spot Welder]
+
+[Illustration: Figure 43a.--Method of Testing Electric Welder]
+[Illustration: Figure 44.--Detail of Water-Cooled Spot Welding Head]
+
+The transformer is carried in the base of the machine and on the left-hand
+side is a regulator for controlling the voltage for various kinds of work.
+The clamps are applied by treadles convenient to the foot of the operator.
+A treadle is provided which instantly releases both jaws upon the
+completion of the weld. One or both of the copper dies may be cooled by a
+stream of water circulating through it from the city water mains
+(Figure 44). The regulator and switch give the operator control of the
+heat, anything from a dull red to the melting point being easily obtained
+by movement of the lever (figure 45).
+
+[Illustration: Figure 45.--Welding Head of a Water-Cooled Welder]
+
+_Welding._--It is not necessary to give the metal to be welded any
+special preparation, although when very rusty or covered with scale, the
+rust and scale should be removed sufficiently to allow good contact of
+clean metal on the copper dies. The cleaner and better the stock, the less
+current it takes, and there is less wear on the dies. The dies should be
+kept firm and tight in their holders to make a good contact. All bolts and
+nuts fastening the electrical contacts should be clean and tight at all
+times.
+
+The scale may be removed from forgings by immersing them in a pickling
+solution in a wood, stone or lead-lined tank.
+
+The solution is made with five gallons of commercial sulphuric acid in
+150 gallons of water. To get the quickest and best results from this
+method, the solution should be kept as near the boiling point as possible
+by having a coil of extra heavy lead pipe running inside the tank and
+carrying live steam. A very few minutes in this bath will remove the scale
+and the parts should then be washed in running water. After this washing
+they should be dipped into a bath of 50 pounds of unslaked lime in 150
+gallons of water to neutralize any trace of acid.
+
+Cast iron cannot be commercially welded, as it is high in carbon and
+silicon, and passes suddenly from a crystalline to a fluid state when
+brought to the welding temperature. With steel or wrought iron the
+temperature must be kept below the melting point to avoid injury to the
+metal. The metal must be heated quickly and pressed together with
+sufficient force to push all burnt metal out of the joint.
+
+High carbon steel can be welded, but must be annealed after welding to
+overcome the strains set up by the heat being applied at one place. Good
+results are hard to obtain when the carbon runs as high as 75 points, and
+steel of this class can only be handled by an experienced operator. If the
+steel is below 25 points in carbon content, good welds will always be the
+result. To weld high carbon to low carbon steel, the stock should be
+clamped in the dies with the low carbon stock sticking considerably further
+out from the die than the high carbon stock. Nickel steel welds readily,
+the nickel increasing the strength of the weld.
+
+Iron and copper may be welded together by reducing the size of the copper
+end where it comes in contact with the iron. When welding copper and brass
+the pressure must be less than when welding iron. The metal is allowed to
+actually fuse or melt at the juncture and the pressure must be sufficient
+to force the burned metal out. The current is cut off the instant the metal
+ends begin to soften, this being done by means of an automatic switch which
+opens when the softening of the metal allows the ends to come together. The
+pressure is applied to the weld by having the sliding jaw moved by a weight
+on the end of an arm.
+
+Copper and brass require a larger volume of current at a lower voltage than
+for steel and iron. The die faces are set apart three times the diameter of
+the stock for brass and four times the diameter for copper.
+
+Light gauges of sheet steel can be welded to heavy gauges or to solid bars
+of steel by "spot" welding, which will be described later. Galvanized iron
+can be welded, but the zinc coating will be burned off. Sheet steel can be
+welded to cast iron, but will pull apart, tearing out particles of the
+iron.
+
+Sheet copper and sheet brass may be welded, although this work requires
+more experience than with iron and steel. Some grades of sheet aluminum can
+be spot-welded if the slight roughness left on the surface under the die
+is not objectionable.
+
+_Butt Welding._--This is the process which joins the ends of two
+pieces of metal as described in the foregoing part of this chapter. The
+ends are in plain sight of the operator at all times and it can easily be
+seen when the metal reaches the welding heat and begins to soften (Figure
+46). It is at this point that the pressure must be applied with the lever
+and the ends forced together in the weld.
+
+[Illustration: Figure 46.--Butt Welder]
+
+The parts are placed in the clamping jaws (Figure 47) with 1/8 to 1/2 inch
+of metal extending beyond the jaw. The ends of the metal touch each other
+and the current is turned on by means of a switch. To raise the ends to the
+proper heat requires from 3 seconds for 1/4-inch rods to 35 seconds for a
+1-1/2-inch bar.
+
+This method is applicable to metals having practically the same area of
+metal to be brought into contact on each end. When such parts are forced
+together a slight projection will be left in the form of a fin or an
+enlarged portion called an upset. The degree of heat required for any work
+is found by moving the handle of the regulator one way or the other while
+testing several parts. When this setting is right the work can continue as
+long as the same sizes are being handled.
+
+[Illustration: Figure 47.--Clamping Dies of a Butt Welder]
+
+Copper, brass, tool steel and all other metals that are harmed by high
+temperatures must be heated quickly and pressed together with sufficient
+force to force all burned metal from the weld.
+
+In case it is desired to make a weld in the form of a capital letter T, it
+is necessary to heat the part corresponding to the top bar of the T to a
+bright red, then bring the lower bar to the pre-heated one and again turn
+on the current, when a weld can be quickly made.
+
+_Spot Welding._--This is a method of joining metal sheets together at
+any desired point by a welded spot about the size of a rivet. It is done on
+a spot welder by fusing the metal at the point desired and at the same
+instant applying sufficient pressure to force the particles of molten metal
+together. The dies are usually placed one above the other so that the work
+may rest on the lower one while the upper one is brought down on top of the
+upper sheet to be welded.
+
+One of the dies is usually pointed slightly, the opposing one being left
+flat. The pointed die leaves a slight indentation on one side of the metal,
+while the other side is left smooth. The dies may be reversed so that the
+outside surface of any work may be left smooth. The current is allowed to
+flow through the dies by a switch which is closed after pressure is applied
+to the work.
+
+There is a limit to the thickness of sheet metal that can be welded by this
+process because of the fact that the copper rods can only carry a certain
+quantity of current without becoming unduly heated themselves. Another
+reason is that it is difficult to make heavy sections of metal touch at the
+welding point without excessive pressure.
+
+_Lap welding_ is the process used when two pieces of metal are caused
+to overlap and when brought to a welding heat are forced together by
+passing through rollers, or under a press, thus leaving the welded joint
+practically the same thickness as the balance of the work.
+
+Where it is desirable to make a continuous seam, a special machine is
+required, or an attachment for one of the other types. In this form of work
+the stock must be thoroughly cleaned and is then passed between copper
+rollers which act in the same capacity as the copper dies.
+
+_Other Applications._--Hardening and tempering can be done by clamping
+the work in the welding dies and setting the control and time to bring the
+metal to the proper color, when it is cooled in the usual manner.
+
+Brazing is done by clamping the work in the jaws and heating until the
+flux, then the spelter has melted and run into the joint. Riveting and
+heading of rivets can be done by bringing the dies down on opposite ends of
+the rivet after it has been inserted in the hole, the dies being shaped to
+form the heads properly.
+
+Hardened steel may be softened and annealed so that it can be machined by
+connecting the dies of the welder to each side of the point to be softened.
+The current is then applied until the work has reached a point at which it
+will soften when cooled.
+
+_Troubles and Remedies._--The following methods have been furnished by
+the Toledo Electric Welder Company and are recommended for this class of
+work whenever necessary.
+
+To locate grounds in the primary or high voltage side of the circuit,
+connect incandescent lamps in series by means of a long piece of lamp cord,
+as shown, in Figure 43a. For 110 volts use one lamp, for 220 volts use two
+lamps and for 440 volts use four lamps. Attach one end of the lamp cord to
+one side of the switch, and close the switch. Take the other end of the
+cord in the hand and press it against some part of the welder frame where
+the metal is clean and bright. Paint, grease and dirt act as insulators and
+prevent electrical contact. If the lamp lights, the circuit is in
+electrical contact with the frame; in other words, grounded. If the lamps
+do not light, connect the wire to a terminal block, die or slide. If the
+lamps then light, the circuit, coils or leads are in electrical contact
+with the large coil in the transformer or its connections.
+
+If, however, the lamps do not light in either case, the lamp cord should be
+disconnected from the switch and connected to the other side, and the
+operations of connecting to welder frame, dies, terminal blocks, etc., as
+explained above, should be repeated. If the lamps light at any of these
+connections, a "ground" is indicated. "Grounds" can usually be found by
+carefully tracing the primary circuit until a place is found where the
+insulation is defective. Reinsulate and make the above tests again to make
+sure everything is clear. If the ground can not be located by observation,
+the various parts of the primary circuit should be disconnected, and the
+transformer, switch, regulator, etc., tested separately.
+
+To locate a ground in the regulator or other part, disconnect the lines
+running to the welder from the switch. The test lamps used in the previous
+tests are connected, one end of lamp cord to the switch, the other end to a
+binding post of the regulator. Connect the other side of the switch to some
+part of the regulator housing. (This must be a clean connection to a bolt
+head or the paint should be scraped off.) Close the switch. If the lamps
+light, the regulator winding or some part of the switch is "grounded" to
+the iron base or core of the regulator. If the lamps do not light, this
+part of the apparatus is clear.
+
+This test can be easily applied to any part of the welder outfit by
+connecting to the current carrying part of the apparatus, and to the iron
+base or frame that should not carry current. If the lamps light, it
+indicates that the insulation is broken down or is defective.
+
+An A.C. voltmeter can, of course, be substituted for the lamps, or a D.C.
+voltmeter with D.C. current can be used in making the tests.
+
+A short circuit in the primary is caused by the insulation of the coils
+becoming defective and allowing the bare copper wires to touch each other.
+This may result in a "burn out" of one or more of the transformer coils, if
+the trouble is in the transformer, or in the continued blowing of fuses in
+the line. Feel of each coil separately. If a short circuit exists in a coil
+it will heat excessively. Examine all the wires; the insulation may have
+worn through and two of them may cross, or be in contact with the frame or
+other part of the welder. A short circuit in the regulator winding is
+indicated by failure of the apparatus to regulate properly, and sometimes,
+though not always, by the heating of the regulator coils.
+
+The remedy for a short circuit is to reinsulate the defective parts. It is
+a good plan to prevent trouble by examining the wiring occasionally and see
+that the insulation is perfect.
+
+_To Locate Grounds and Short Circuits in the Secondary, or Low Voltage
+Side._--Trouble of this kind is indicated by the machine acting sluggish
+or, perhaps, refusing to operate. To make a test, it will be necessary to
+first ascertain the exciting current of your particular transformer. This
+is the current the transformer draws on "open circuit," or when supplied
+with current from the line with no stock in the welder dies. The following
+table will give this information close enough for all practical purposes:
+
+K.W.      ----------------- Amperes at ----------------
+Rating    110 Volts   220 Volts   440 Volts   550 Volts
+3         1.5         .75         .38         .3
+5         2.5         1.25        .63         .5
+8         3.6         1.8         .9          .72
+10        4.25        2.13        1.07        .85
+15        6.          3.          1.5         1.2
+20        7.          3.5         1.75        1.4
+30        9.          4.5         2.25        1.8
+35        9.6         4.8         2.4         1.92
+50        10.         5.          2.5         2
+
+Remove the fuses from the wall switch and substitute fuses just large
+enough to carry the "exciting" current. If no suitable fuses are at hand,
+fine strands of copper from an ordinary lamp cord may be used. These
+strands are usually No. 30 gauge wire and will fuse at about 10 amperes.
+One or more strands should be used, depending on the amount of exciting
+current, and are connected across the fuse clips in place of fuse wire.
+Place a piece of wood or fibre between the welding dies in the welder as
+though you were going to weld them. See that the regulator is on the
+highest point and close the welder switch. If the secondary circuit is
+badly grounded, current will flow through the ground, and the small fuses
+or small strands of wire will burn out. This is an indication that both
+sides of the secondary circuit are grounded or that a short circuit exists
+in a primary coil. In either case the welder should not be operated until
+the trouble is found and removed. If, however, the small fuses do not
+"blow," remove same and replace the large fuses, then disconnect wires
+running from the wall switch to the welder and substitute two pieces of
+No. 8 or No. 6 insulated copper wire, after scraping off the insulation for
+an inch or two at each end. Connect one wire from the switch to the frame
+of welder; this will leave one loose end. Hold this a foot or so away from
+the place where the insulation is cut off; then turn on the current and
+strike the free end of this wire lightly against one of the copper dies,
+drawing it away quickly. If no sparking is produced, the secondary circuit
+is free from ground, and you will then look for a broken connection in the
+circuit. Some caution must be used in making the above test, as in case one
+terminal is heavily grounded the testing wire may be fused if allowed to
+stay in contact with the die.
+
+_The Remedy._--Clean the slides, dies and terminal blocks thoroughly
+and dry out the fibre insulation if it is damp. See that no scale or metal
+has worked under the sliding parts, and that the secondary leads do not
+touch the frame. If the ground is very heavy it may be necessary to remove
+the slides in order to facilitate the examination and removal of the
+ground. Insulation, where torn or worn through, must be carefully replaced
+or taped. If the transformer coils are grounded to the iron core of the
+transformer or to the secondary, it may be necessary to remove the coils
+and reinsulate them at the points of contact. A short circuited coil will
+heat excessively and eventually burn out. This may mean a new coil if you
+are unable to repair the old one. In all cases the transformer windings
+should be protected from mechanical injury or dampness. Unless excessively
+overloaded, transformers will last for years without giving a moment's
+trouble, if they are not exposed to moisture or are not injured
+mechanically.
+
+The most common trouble arises from poor electrical contacts, and they are
+the cause of endless trouble and annoyance. See that all connections are
+clean and bright. Take out the dies every day or two and see that there is
+no scale, grease or dirt between them and the holders. Clean them
+thoroughly before replacing. Tighten the bolts running from the transformer
+leads to the work jaws.
+
+
+ELECTRIC ARC WELDING
+
+This method bears no relation to the one just considered, except that the
+source of heat is the same in both cases. Arc welding makes use of the
+flame produced by the voltaic arc in practically the same way that
+oxy-acetylene welding uses the flame from the gases.
+
+If the ends of two pieces of carbon through which a current of electricity
+is flowing while they are in contact are separated from each other quite
+slowly, a brilliant arc of flame is formed between them which consists
+mainly of carbon vapor. The carbons are consumed by combination with the
+oxygen in the air and through being turned to a gas under the intense heat.
+
+The most intense action takes place at the center of the carbon which
+carries the positive current and this is the point of greatest heat. The
+temperature at this point in the arc is greater than can be produced by any
+other means under human control.
+
+An arc may be formed between pieces of metal, called electrodes, in the
+same way as between carbon. The metallic arc is called a flaming arc and as
+the metal of the electrode burns with the heat, it gives the flame a color
+characteristic of the material being used. The metallic arc may be drawn
+out to a much greater length than one formed between carbon electrodes.
+
+Arc Welding is carried out by drawing a piece of carbon which is of
+negative polarity away from the pieces of metal to be welded while the
+metal is made positive in polarity. The negative wire is fastened to the
+carbon electrode and the work is laid on a table made of cast or wrought
+iron to which the positive wire is made fast. The direction of the flame is
+then from the metal being welded to the carbon and the work is thus
+prevented from being saturated with carbon, which would prove very
+detrimental to its strength. A secondary advantage is found in the fact
+that the greatest heat is at the metal being welded because of its being
+the positive electrode.
+
+The carbon electrode is usually made from one quarter to one and a half
+inches in diameter and from six to twelve inches in length. The length of
+the arc may be anywhere from one inch to four inches, depending on the size
+of the work being handled.
+
+While the parts are carefully insulated to avoid danger of shock, it is
+necessary for the operator to wear rubber gloves as a further protection,
+and to wear some form of hood over the head to shield him against the
+extreme heat liberated. This hood may be made from metal, although some
+material that does not conduct electricity is to be preferred. The work is
+watched through pieces of glass formed with one sheet, which is either blue
+or green, placed over another which is red. Screens of glass are sometimes
+used without the head protector. Some protection for the eyes is absolutely
+necessary because of the intense white light.
+
+It is seldom necessary to preheat the work as with the gas processes,
+because the heat is localized at the point of welding and the action is so
+rapid that the expansion is not so great. The necessity of preheating,
+however, depends entirely on the material, form and size of the work being
+handled. The same advice applies to arc welding as to the gas flame method
+but in a lesser degree. Filling rods are used in the same way as with any
+other flame process.
+
+It is the purpose of this explanation to state the fundamental principles
+of the application of the electric arc to welding metals, and by applying
+the principles the following questions will be answered:
+
+What metals can be welded by the electric arc?
+
+What difficulties are to be encountered in applying the electric arc to
+welding?
+
+What is the strength of the weld in comparison with the original piece?
+
+What is the function of the arc welding machine itself?
+
+What is the comparative application of the electric arc and the
+oxy-acetylene method and others of a similar nature?
+
+The answers to these questions will make it possible to understand the
+application of this process to any work. In a great many places the use of
+the arc is cutting the cost of welding to a very small fraction of what it
+would be by any other method, so that the importance of this method may be
+well understood.
+
+Any two metals which are brought to the melting temperature and applied to
+each other will adhere so that they are no more apt to break at the weld
+than at any other point outside of the weld. It is the property of all
+metals to stick together under these conditions. The electric arc is used
+in this connection merely as a heating agent. This is its only function in
+the process.
+
+It has advantages in its ease of application and the cheapness with which
+heat can be liberated at any given point by its use. There is nothing in
+connection with arc welding that the above principles will not answer; that
+is, that metals at the melting point will weld and that the electric arc
+will furnish the heat to bring them to this point. As to the first
+question, what metals can be welded, all metals can be welded.
+
+The difficulties which are encountered are as follows:
+
+In the case of brass or zinc, the metals will be covered with a coat of
+zinc oxide before they reach a welding heat. This zinc oxide makes it
+impossible for two clean surfaces to come together and some method has to
+be used for eliminating this possibility and allowing the two surfaces to
+join without the possibility of the oxide intervening. The same is true of
+aluminum, in which the oxide, alumina, will be formed, and with several
+other alloys comprising elements of different melting points.
+
+In order to eliminate these oxides, it is necessary in practical work, to
+puddle the weld; this is, to have a sufficient quantity of molten metal at
+the weld so that the oxide is floated away. When this is done, the two
+surfaces which are to be joined are covered with a coat of melted metal on
+which floats the oxide and other impurities. The two pieces are thus
+allowed to join while their surfaces are protected. This precaution is not
+necessary in working with steel except in extreme cases.
+
+Another difficulty which is met with in the welding of a great many metals
+is their expansion under heat, which results in so great a contraction when
+the weld cools that the metal is left with a considerable strain on it. In
+extreme cases this will result in cracking at the weld or near it. To
+eliminate this danger it is necessary to apply heat either all over the
+piece to be welded or at certain points. In the case of cast iron and
+sometimes with copper it is necessary to anneal after welding, since
+otherwise the welded pieces will be very brittle on account of the
+chilling. This is also true of malleable iron.
+
+Very thin metals which are welded together and are not backed up by
+something to carry away the excess heat, are very apt to burn through,
+leaving a hole where the weld should be. This difficulty can be eliminated
+by backing up the weld with a metal face or by decreasing the intensity of
+the arc so that this melting through will not occur. However, the practical
+limit for arc welding without backing up the work with a metal face or
+decreasing the intensity of the arc is approximately 22 gauge, although
+thinner metal can be welded by a very skillful and careful operator.
+
+One difficulty with arc welding is the lack of skillful operators. This
+method is often looked upon as being something out of the ordinary and
+governed by laws entirely different from other welding. As a matter of
+fact, it does not take as much skill to make a good arc weld as it does to
+make a good weld in a forge fire as the blacksmith does it. There are few
+jobs which cannot be handled successfully by an operator of average
+intelligence with one week's instructions, although his work will become
+better and better in quality as he continues to use the arc.
+
+Now comes the question of the strength of the weld after it has been made.
+This strength is equally as great as that of the metal that is used to make
+the weld. It should be remembered, however, that the metal which goes into
+the weld is put in there as a casting and has not been rolled. This would
+make the strength of the weld as great as the same metal that is used for
+filling if in the cast form.
+
+Two pieces of steel could be welded together having a tensile strength at
+the weld of 50,000 pounds. Higher strengths than this can be obtained by
+the use of special alloys for the filling material or by rolling. Welds
+with a tensile strength as great as mentioned will give a result which is
+perfectly satisfactory in almost all cases.
+
+There are a great many jobs where it is possible to fill up the weld, that
+is, make the section at the point of the weld a little larger than the
+section through the rest of the piece. By doing this, the disadvantages
+of the weld being in the form of a casting in comparison with the rest of
+the piece being in the form of rolled steel can be overcome, and make the
+weld itself even stronger than the original piece.
+
+The next question is the adaptability of the electric arc in comparison
+with forge fire, oxy-acetylene or other method. The answer is somewhat
+difficult if made general. There are no doubt some cases where the use of a
+drop hammer and forge fire or the use of the oxy-acetylene torch will make,
+all things being considered, a better job than the use of the electric arc,
+although a case where this is absolutely proved is rare.
+
+The electric arc will melt metal in a weld for less than the same metal can
+be melted by the use of the oxy-acetylene torch, and, on account of the
+fact that the heat can be applied exactly where it is required and in the
+amount required, the arc can in almost all cases supply welding heat for
+less cost than a forge fire or heating furnace.
+
+The one great advantage of the oxy-acetylene method in comparison with
+other methods of welding is the fact that in some cases of very thin sheet,
+the weld can be made somewhat sooner than is possible otherwise. With metal
+of 18 gauge or thicker, this advantage is eliminated. In cutting steel, the
+oxy-acetylene torch is superior to almost any other possible method.
+
+_Arc Welding Machines._--A consideration of the function and purpose
+of the various types of arc welding machines shows that the only reason for
+the use of any machine is either for conversion of the current from
+alternating to direct, or, if the current is already direct, then the
+saving in the application of this current in the arc.
+
+It is practically out of the question to apply an alternating current arc
+to welding for the reason that in any arc practically all the heat is
+liberated at the positive electrode, which means that, in alternating
+current, half the heat is liberated at each electrode as the current
+changes its direction of flow or alternates. Another disadvantage of the
+alternating arc is that it is difficult of control and application.
+
+In all arc welding by the use of the carbon arc, the positive electrode is
+made the piece to be welded, while in welding with metallic electrodes this
+may be either the piece to be welded of the rod that is used as a filler.
+The voltage across the arc is a variable quantity, depending on the length
+of the flame, its temperature and the gases liberated in the arc. With a
+carbon electrode the voltage will vary from zero to forty-five volts. With
+the metallic electrode the voltage will vary from zero to thirty volts. It
+is, therefore, necessary for the welding machine to be able to furnish to
+the arc the requisite amount of current, this amount being varied, and
+furnish it at all times at the voltage required.
+
+The simplest welding apparatus is a resistance in series with the arc. This
+is entirely satisfactory in every way except in cost of current. By the use
+of resistance in series with the arc and using 220 volts as the supply,
+from eighty to ninety per cent of the current is lost in heat at the
+resistance. Another disadvantage is the fact that most materials change
+their resistance as their temperature changes, thus making the amount of
+current for the arc a variable quantity, depending on the temperature of
+the resistance.
+
+There have been various methods originated for saving the power mentioned
+and a good many machines have been put on the market for this purpose. All
+of them save some power over what a plain resistance would use. Practically
+all arc welding machines at the present time are motor generator sets, the
+motor of which is arranged for the supply voltage and current, this motor
+being direct connected to a compound wound generator delivering
+approximately seventy-five volts direct current. Then by the use of a
+resistance, this seventy-five volt supply is applied to the arc. Since the
+voltage across the arc will vary from zero to fifty volts, this machine
+will save from zero up to seventy per cent of the power that the machine
+delivers. The rest of the power, of course, has to be dissipated in the
+resistance used in series with the arc.
+
+A motor generator set which can be purchased from any electrical company,
+with a long piece of fence wire wound around a piece of asbestos, gives
+results equally as good and at a very small part of the first cost.
+
+It is possible to construct a machine which will eliminate all losses in
+the resistance; in other words, eliminate all resistance in series with the
+arc. A machine of this kind will save its cost within a very short time,
+providing the welder is used to any extent.
+
+Putting it in figures, the results are as follows for average conditions.
+Current at 2c per kilowatt hour, metallic electrode arc of 150 amperes,
+carbon arc 500 amperes; voltage across the metallic electrode arc 20,
+voltage across the carbon arc 35. Supply current 220 volts, direct. In the
+case of the metallic electrode, if resistance is used, the cost of running
+this arc is sixty-six cents per hour. With the carbon electrode, $2.20 per
+hour. If a motor generator set with a seventy volt constant potential
+machine is used for a welder, the cost will be as follows:
+
+Metallic electrode 25.2c. Carbon electrode 84c per hour. With a machine
+which will deliver the required voltage at the arc and eliminate all the
+resistance in series with the arc, the cost will be as follows: Metallic
+electrode 7.2c per hour; carbon electrode 42c per hour. This is with the
+understanding that the arc is held constant and continuously at its full
+value. This, however, is practically impossible and the actual load factor
+is approximately fifty per cent, which would mean that operating a welder
+as it is usually operated, this result will be reduced to one-half of that
+stated in all cases.
+
+
+
+
+CHAPTER VII
+
+HAND FORGING AND WELDING
+
+
+Smithing, or blacksmithing, is the process of working heated iron, steel or
+other metals by forging, bending or welding them.
+
+_The Forge._--The metal is heated in a forge consisting of a shallow
+pan for holding the fire, in the center of which is an opening from below
+through which air is forced to make a hot fire.
+
+[Illustration: Figure 48.--Tuyere Construction on a Forge]
+
+Air is forced through this hole, called a "tuyere" (Figure 48) by means of
+a hand bellows, a rotary fan operated with crank or lever, or with a fan
+driven from an electric motor. The harder the air is driven into the fire
+above the tuyere the more oxygen is furnished and the hotter the fire
+becomes.
+
+Directly below the tuyere is an opening through which the ashes that drop
+from the fire may be cleaned out.
+
+_The Fire._--The fire is made by placing a small piece of waste soaked
+in oil, kerosene or gasoline, over the tuyere, lighting the waste, then
+starting the fan or blower slowly. Gradually cover the waste, while it is
+burning brightly, with a layer of soft coal. The coal will catch fire and
+burn after the waste has been consumed. A piece of waste half the size of a
+person's hand is ample for this purpose.
+
+The fuel should be "smithing coal." A lump of smithing coal breaks easily,
+shows clean and even on all sides and should not break into layers. The
+coal is broken into fine pieces and wet before being used on the fire.
+
+The fire should be kept deep enough so that there is always three or four
+inches of fire below the piece of metal to be heated and there should be
+enough fire above the work so that no part of the metal being heated comes
+in contact with the air. The fire should be kept as small as possible while
+following these rules as to depth.
+
+To make the fire larger, loosen the coal around the edges. To make the fire
+smaller, pack wet coal around the edges in a compact mass and loosen the
+fire in the center. Add fresh coal only around the edges of the fire. It
+will turn to coke and can then be raked onto the fire. Blow only enough air
+into the fire to keep it burning brightly, not so much that the fire is
+blown up through the top of the coal pack. To prevent the fire from going
+out between jobs, stick a piece of soft wood into it and cover with fresh
+wet coal.
+
+_Tools._--The _hammer_ is a ball pene, or blacksmith's hammer,
+weighing about a pound and a half.
+
+The _sledge_ is a heavy hammer, weighing from 5 to 20 pounds and
+having a handle 30 to 36 inches long.
+
+The _anvil_ is a heavy piece of wrought iron (Figure 49), faced with
+steel and having four legs. It has a pointed horn on one end, an
+overhanging tail on the other end and a flat top. In the tail there is a
+square hole called the "hardie" hole and a round one called the "spud"
+hole.
+
+[Illustration: Figure 49.--Anvil, Showing Horn, Tail, Hardie Hole and Spud
+Hole]
+
+_Tongs_, with handles about one foot long and jaws suitable for
+holding the work, are used. To secure a firm grip on the work, the jaws may
+be heated red hot and hammered into shape over the piece to be held, thus
+giving a properly formed jaw. Jaws should touch the work along their entire
+length.
+
+The _set hammer_ is a hammer, one end of whose head is square and
+flat, and from this face the head tapers evenly to the other face. The
+large face is about 1-1/4 inches square.
+
+The _flatter_ is a hammer having one face of its head flat and about
+2-1/2 inches square.
+
+_Swages_ are hammers having specially formed faces for finishing
+rounds, squares, hexagons, ovals, tapers, etc.
+
+_Fullers_ are hammers having a rounded face, long in one direction.
+They are used for spreading metal in one direction only.
+
+The _hardy_ is a form of chisel with a short, square shank which may
+be set into the hardie hole for cutting off hot bars.
+
+_Operations._--Blacksmithing consists of bending, drawing or upsetting
+with the various hammers, or in punching holes.
+
+Bending is done over the square corners of the anvil if square cornered
+bends are desired, or over the horn of the anvil if rounding bends, eyes,
+hooks, etc., are wanted.
+
+To bend a ring or eye in the end of a bar, first figure the length of stock
+needed by multiplying the diameter of the hole by 31/7, then heat the piece
+to a good full red at a point this distance back from the end. Next bend
+the iron over at a 90 degree angle (square) at this point. Next, heat the
+iron from the bend just made clear to the point and make the eye by laying
+the part that was bent square over the horn of the anvil and bending the
+extreme tip into part of a circle. Keep pushing the piece farther and
+farther over the horn of the anvil, bending it as you go. Do not hammer
+directly over the horn of the anvil, but on the side where you are doing
+the bending.
+
+To make the outside of a bend square, sharp and full, rather than slightly
+rounding, the bent piece must be laid edgewise on the face of the anvil.
+That is, after making the bend over the corner of the anvil, lay the piece
+on top of the anvil so that its edge and not the flat side rests on the
+anvil top. With the work in this position, strike directly against the
+corner with the hammer so that the blows come in line, first with one leg
+of the work, then the other, and always directly on the corner of the
+piece. This operation cannot be performed by laying the work so that one
+leg hangs over the anvil's corner.
+
+To make a shoulder on a rod or bar, heat the work and lay flat across the
+top of the anvil with the point at which the shoulder is desired at the
+edge of the anvil. Then place the set hammer on top of the piece, with the
+outside edge of the set hammer directly over the edge of the anvil. While
+hammering in this position keep the work turning continually.
+
+To draw stock means to make it longer and thinner by hammering. A piece to
+be drawn out is usually laid across the horn of the anvil while being
+struck with the hammer. The metal is then spread in only one direction in
+place of being spread in every direction, as it would be if laid on the
+anvil face. To draw the work, heat it to as high a temperature as it will
+stand without throwing sparks and burning. The fuller may be used for
+drawing metal in place of laying the work over the horn of the anvil.
+
+When drawing round stock, it should be first drawn out square, and when
+almost down to size it may be rounded. When pointing stock, the same rule
+of first drawing out square applies.
+
+Upsetting means to make a piece shorter in length and greater in thickness
+or width, or both shorter and thicker. To upset short pieces, heat to a
+bright red at the place to be upset, then stand on end on the anvil face
+and hammer directly down on top until of the right form. Longer pieces may
+be swung against the anvil or placed upright on a heavy piece of metal
+lying on the floor or that is sunk into the floor. While standing on this
+heavy piece the metal may be upset by striking down on the end with a heavy
+hammer or the sledge. If a bend appears while upsetting, it should be
+straightened by hammering back into shape on the anvil face.
+
+Light blows affect the metal for only a short distance from the point of
+striking, but heavy blows tend to swell the metal more equally through its
+entire length. In driving rivets that should fill the holes, heavy blows
+should be struck, but to shape the end of a rivet or to make a head on a
+rod, light blows should be used.
+
+The part of the piece that is heated most will upset the most.
+
+To punch a hole through metal, use a tool steel punch with its end slightly
+tapering to a size a little smaller than the hole to be punched. The end of
+the punch must be square across and never pointed or rounded.
+
+First drive the punch part way through from one side and then turn the work
+over. When you turn it over, notice where the bulge appears and in that way
+locate the hole and drive the punch through from the second side. This
+makes a cleaner and more even hole than to drive completely through from
+one side. When the punch is driven in from the second side, the place to be
+punched through should be laid over the spud hole in the tail of the anvil
+and the piece driven out of the work.
+
+Work when hot is larger than it will be after cooling. This must be
+remembered when fitting parts or trouble will result. A two-foot bar of
+steel will be 1/4 inch longer when red hot than when cold.
+
+The temperatures of iron correspond to the following colors:
+
+  Dullest red seen in the dark...  878 deg.
+  Dullest red seen in daylight...  887 deg.
+  Dull red....................... 1100 deg.
+  Full red....................... 1370 deg.
+  Light red...................... 1550 deg.
+  Orange......................... 1650 deg.
+  Light orange................... 1725 deg.
+  Yellow......................... 1825 deg.
+  Light yellow................... 1950 deg.
+
+_Bending Pipes and Tubes._--It is difficult to make bends or curves in
+pipes and tubing without leaving a noticeable bulge at some point of the
+work. Seamless steel tubing may be handled without very great danger of
+this trouble if care is used, but iron pipe, having a seam running
+lengthwise, must be given special attention to avoid opening the seam.
+
+Bends may be made without kinking if the tube or pipe is brought to a full
+red heat all the way around its circumference and at the place where the
+bend is desired. Hold the cool portion solidly in a vise and, by taking
+hold of the free end, bend very slowly and with a steady pull. The pipe
+must be kept at full red heat with the flames from one or more torches and
+must not be hammered to produce the bend. If a sufficient purchase cannot
+be secured on the free end by the hand, insert a piece of rod or a smaller
+pipe into the opening.
+
+While making the bend, should small bulges appear, they may be hammered
+back into shape before proceeding with the work.
+
+Tubing or pipes may be bent while being held between two flat metal
+surfaces while at a bright red heat. The metal plates at each side of the
+work prevent bulging.
+
+Another method by which tubing may be bent consists of filling completely
+with tightly packed sand and fitting a solid cap or plug at each end.
+
+Thin brass tubing may be filled with melted resin and may be bent after the
+resin cools. To remove the resin it is necessary to heat the tube, allowing
+it to run out.
+
+Large jobs of bending should be handled in special pipe bending machines in
+which the work is forced through formed rolls which prevent its bulging.
+
+
+WELDING
+
+Welding with the heat of a blacksmith forge fire, or a coal or illuminating
+gas fire, can only be performed with iron and steel because of the low heat
+which is not localized as with the oxy-acetylene and electric processes.
+Iron to be welded in this manner is heated until it reaches the temperature
+indicated by an orange color, not white, as is often stated, this orange
+color being slightly above 3600 degrees Fahrenheit. Steel is usually welded
+at a bright red heat because of the danger of oxidizing or burning the
+metal if the temperature is carried above this point.
+
+_The Fire._--If made in a forge, the fire should be built from good
+smithing coal or, better still, from coke. Gas fires are, of course,
+produced by suitable burners and require no special preparation except
+adjustment of the heat to the proper degree for the size and thickness of
+the metal being welded so that it will not be burned.
+
+A coal fire used for ordinary forging operations should not be used for
+welding because of the impurities it contains. A fresh fire should be built
+with a rather deep bed of coal, four to eight inches being about right for
+work ordinarily met with. The fire should be kept burning until the coal
+around the edges has been thoroughly coked and a sufficient quantity of
+fuel should be on and around the fire so that no fresh coal will have to
+be added while working.
+
+After the coking process has progressed sufficiently, the edges should be
+packed down and the fire made as small as possible while still surrounding
+the ends to be joined. The fire should not be altered by poking it while
+the metal is being heated. The best form of fire to use is one having
+rather high banks of coked coal on each side of the mass, leaving an
+opening or channel from end to end. This will allow the added fuel to be
+brought down on top of the fire with a small amount of disturbance.
+
+_Preparing to Weld._--If the operator is not familiar with the metal
+to be handled, it is best to secure a test piece if at all possible and try
+heating it and joining the ends. Various grades of iron and steel call for
+different methods of handling and for different degrees of heat, the proper
+method and temperature being determined best by actual test under the
+hammer.
+
+The form of the pieces also has a great deal to do with their handling,
+especially in the case of a more or less inexperienced workman. If the
+pieces are at all irregular in shape, the motions should be gone through
+with before the metal is heated and the best positions on the anvil as well
+as in the fire determined with regard to the convenience of the workman and
+speed of handling the work after being brought to a welding temperature.
+Unnatural positions at the anvil should be avoided as good work is most
+difficult of performance under these conditions.
+
+_Scarfing._--While there are many forms of welds, depending on the
+relative shape of the pieces to be joined, the portions that are to meet
+and form one piece are always shaped in the same general way, this shape
+being called a "scarf." The end of a piece of work, when scarfed, is
+tapered off on one side so that the extremity comes to a rather sharp edge.
+The other side of the piece is left flat and a continuation in the same
+straight plane with its side of the whole piece of work. The end is then in
+the form of a bevel or mitre joint (Figure 50).
+
+[Illustration: Figure 50.--Scarfing Ends of Work Ready for Welding]
+
+Scarfing may be produced in any one of several ways. The usual method is to
+bring the ends to a forging heat, at which time they are upset to give a
+larger body of metal at the ends to be joined. This body of metal is then
+hammered down to the taper on one side, the length of the tapered portion
+being about one and a half times the thickness of the whole piece being
+handled. Each piece should be given this shape before proceeding farther.
+
+The scarf may be produced by filing, sawing or chiseling the ends, although
+this is not good practice because it is then impossible to give the desired
+upset and additional metal for the weld. This added thickness is called for
+by the fact that the metal burns away to a certain extent or turns to
+scale, which is removed before welding.
+
+When the two ends have been given this shape they should not fit as closely
+together as might be expected, but should touch only at the center of the
+area to be joined (Figure 51). That is to say, the surface of the beveled
+portion should bulge in the middle or should be convex in shape so that the
+edges are separated by a little distance when the pieces are laid together
+with the bevels toward each other. This is done so that the scale which is
+formed on the metal by the heat of the fire can have a chance to escape
+from the interior of the weld as the two parts are forced together.
+
+[Illustration: Figure 51.--Proper Shape of Scarfed Ends]
+
+If the scarf were to be formed with one or more of the edges touching each
+other at the same time or before the centers did so, the scale would be
+imprisoned within the body of the weld and would cause the finished work to
+be weak, while possibly giving a satisfactory appearance from the outside.
+
+_Fluxes._--In order to assist in removing the scale and other
+impurities and to make the welding surfaces as clean as possible while
+being joined, various fluxing materials are used as in other methods of
+welding.
+
+For welding iron, a flux of white sand is usually used, this material being
+placed on the metal after it has been brought to a red heat in the fire.
+Steel is welded with dry borax powder, this flux being applied at the same
+time as the iron flux just mentioned. Borax may also be used for iron
+welding and a mixture of borax with steel borings may also be used for
+either class of work. Mixtures of sal ammoniac with borax have been
+successfully used, the proportions being about four parts of borax to one
+of sal ammoniac. Various prepared fluxing powders are on the market for
+this work, practically all of them producing satisfactory results.
+
+After the metal has been in the fire long enough to reach a red heat, it is
+removed temporarily and, if small enough in size, the ends are dipped into
+a box of flux. If the pieces are large, they may simply be pulled to the
+edge of the fire and the flux then sprinkled on the portions to be joined.
+A greater quantity of flux is required in forge welding than in electric or
+oxy-acetylene processes because of the losses in the fire. After the powder
+has been applied to the surfaces, the work is returned to the fire and
+heated to the welding temperature.
+
+_Heating the Work._--After being scarfed, the two pieces to be welded
+are placed in the fire and brought to the correct temperature. This
+temperature can only be recognized by experiment and experience. The metal
+must be just below that point at which small sparks begin to be thrown out
+of the fire and naturally this is a hard point to distinguish. At the
+welding heat the metal is almost ready to flow and is about the consistency
+of putty. Against the background of the fire and coal the color appears to
+be a cream or very light yellow and the work feels soft as it is handled.
+
+It is absolutely necessary that both parts be heated uniformly and so that
+they reach the welding temperature at the same time. For this reason they
+should be as close together in the fire as possible and side by side. When
+removed to be hammered together, time is saved if they are picked up in
+such a way that when laid together naturally the beveled surfaces come
+together. This makes it necessary that the workman remember whether the
+scarfed side is up or down, and to assist in this it is a good thing to
+mark the scarfed side with chalk or in some other noticeable manner, so
+that no mistake will be made in the hurry of placing the work on the anvil.
+
+The common practice in heating allows the temperature to rise until the
+small white sparks are seen to come from the fire. Any heating above this
+point will surely result in burning that will ruin the iron or steel being
+handled. The best welding heat can be discerned by the appearance of the
+metal and its color after experience has been gained with this particular
+material. Test welds can be made and then broken, if possible, so that the
+strength gained through different degrees of heat can be known before
+attempting more important work.
+
+_Welding._--When the work has reached the welding temperature after
+having been replaced in the fire with the flux applied, the two parts are
+quickly tapped to remove the loose scale from their surfaces. They are then
+immediately laid across the top of the anvil, being placed in a diagonal
+position if both pieces are straight. The lower piece is rested on the
+anvil first with the scarf turned up and ready to receive the top piece in
+the position desired. The second piece must be laid in exactly the position
+it is to finally occupy because the two parts will stick together as soon
+as they touch and they cannot well be moved after having once been allowed
+to come in contact with each other. This part of the work must be done
+without any unnecessary loss of time because the comparatively low heat at
+which the parts weld allows them to cool below the working temperature in
+a few seconds.
+
+The greatest difficulty will be experienced in withdrawing the metal from
+the fire before it becomes burned and in getting it joined before it cools
+below this critical point. The beveled edges of the scarf are, of course,
+the first parts to cool and the weld must be made before they reach a point
+at which they will not join, or else the work will be defective in
+appearance and in fact.
+
+If the parts being handled are of such a shape that there is danger of
+bending a portion back of the weld, this part may be cooled by quickly
+dipping it into water before laying the work on the anvil to be joined.
+
+The workman uses a heavy hand hammer in making the joint, and his helper,
+if one is employed, uses a sledge. With the two parts of the work in place
+on the anvil, the workman strikes several light blows, the first ones being
+at a point directly over the center of the weld, so that the joint will
+start from this point and be worked toward the edges. After the pieces have
+united the helper strikes alternate blows with his sledge, always striking
+in exactly the same place as the last stroke of the workman. The hammer
+blows are carried nearer and nearer to the edges of the weld and are made
+steadily heavier as the work progresses.
+
+The aim during the first part of the operation should be to make a perfect
+joint, with every part of the surfaces united, and too much attention
+should not be paid to appearance, at least not enough to take any chance
+with the strength of the work.
+
+It will be found, after completion of the weld, that there has been a loss
+in length equal to one-half the thickness of the metal being welded. This
+loss is occasioned by the burned metal and the scale which has been formed.
+
+_Finishing the Weld._--If it is possible to do so, the material should
+be hammered into the shape that it should remain with the same heat that
+was used for welding. It will usually be found, however, that the metal has
+cooled below the point at which it can be worked to advantage. It should
+then be replaced in the fire and brought back to a forging heat.
+
+[Illustration: Figure 52.--Upsetting and Scarfing the End of a Rod]
+
+While shaping the work at this forging heat every part that has been at a
+red heat should be hammered with uniformly light and even blows as it
+cools. This restores the grain and strength of the iron or steel to a great
+extent and makes the unavoidable weakness as small as possible.
+
+_Forms of Welds._--The simplest of all welds is that called a "lap
+weld." This is made between the ends of two pieces of equal size and
+similar form by scarfing them as described and then laying one on top of
+the other while they are hammered together.
+
+A butt weld (Figure 52) is made between the ends of two pieces of shaft or
+other bar shapes by upsetting the ends so that they have a considerable
+flare and shaping the face of the end so that it is slightly higher in the
+center than around the edges, this being done to make the centers come
+together first. The pieces are heated and pushed into contact, after which
+the hammering is done as with any other weld.
+
+[Illustration: Figure 53.--Scarfing for a T Weld]
+
+A form similar to the butt weld in some ways is used for joining the end of
+a bar to a flat surface and is called a jump weld. The bar is shaped in the
+same way as for a butt weld. The flat plate may be left as it is, but if
+possible a depression should be made at the point where the shaft is to be
+placed. With the two parts heated as usual, the bar is dropped into
+position and hammered from above. As soon as the center of the weld has
+been made perfect, the joint may be finished with a fuller driven all the
+way around the edge of the joint.
+
+When it is required to join a bar to another bar or to the edge of any
+piece at right angles the work is called a "T" weld from its shape when
+complete (Figure 53). The end of the bar is scarfed as described and the
+point of the other bar or piece where the weld is to be made is hammered so
+that it tapers to a thin edge like one-half of a circular depression. The
+pieces are then laid together and hammered as for a lap weld.
+
+The ends of heavy bar shapes are often joined with a "V," or cleft, weld.
+One bar end is shaped so that it is tapering on both sides and comes to a
+broad edge like the end of a chisel. The other bar is heated to a forging
+temperature and then slit open in a lengthwise direction so that the
+V-shaped opening which is formed will just receive the pointed edge of the
+first piece. With the work at welding heat, the two parts are driven
+together by hammering on the rear ends and the hammering then continues as
+with a lap weld, except that the work is turned over to complete both sides
+of the joint.
+
+[Illustration: Figure 54.-Splitting Ends to Be Welded in Thin Work]
+
+The forms so far described all require that the pieces be laid together in
+the proper position after removal from the fire, and this always causes a
+slight loss of time and a consequent lowering of the temperature. With very
+light stock, this fall of temperature would be so rapid that the weld would
+be unsuccessful, and in this case the "lock" weld is resorted to. The ends
+of the two pieces to be joined are split for some distance back, and
+one-half of each end is bent up and the other half down (Figure 54). The
+two are then pushed together and placed in the fire in this position. When
+the welding heat is reached, it is only necessary to take the work out of
+the fire and hammer the parts together, inasmuch as they are already in the
+correct position.
+
+Other forms of welds in which the parts are too small to retain their heat,
+can be made by first riveting them together or cutting them so that they
+can be temporarily fastened in any convenient way when first placed in the
+fire.
+
+
+
+
+CHAPTER VIII
+
+SOLDERING, BRAZING AND THERMIT WELDING
+
+
+SOLDERING
+
+Common solder is an alloy of one-half lead with one-half tin, and is called
+"half and half." Hard solder is made with two-thirds tin and one-third
+lead. These alloys, when heated, are used to join surfaces of the same or
+dissimilar metals such as copper, brass, lead, galvanized iron, zinc,
+tinned plate, etc. These metals are easily joined, but the action of solder
+with iron, steel and aluminum is not so satisfactory and requires greater
+care and skill.
+
+The solder is caused to make a perfect union with the surfaces treated with
+the help of heat from a soldering iron. The soldering iron is made from a
+piece of copper, pointed at one end and with the other end attached to an
+iron rod and wooden handle. A flux is used to remove impurities from the
+joint and allow the solder to secure a firm union with the metal surface.
+The iron, and in many cases the work, is heated with a gasoline blow torch,
+a small gas furnace, an electric heater or an acetylene and air torch.
+
+The gasoline torch which is most commonly used should be filled two-thirds
+full of gasoline through the hole in the bottom, which is closed by a screw
+plug. After working the small hand pump for 10 to 20 strokes, hold the palm
+of your hand over the end of the large iron tube on top of the torch and
+open the gasoline needle valve about a half turn. Hold the torch so that
+the liquid runs down into the cup below the tube and fills it. Shut the
+gasoline needle valve, wipe the hands dry, and set fire to the fuel in the
+cup. Just as the gasoline fire goes out, open the gasoline needle valve
+about a half turn and hold a lighted match at the end of the iron tube to
+ignite the mixture of vaporized gasoline and air. Open or close the needle
+valve to secure a flame about 4 inches long.
+
+On top of the iron tube from which the flame issues there is a rest for
+supporting the soldering iron with the copper part in the flame. Place the
+iron in the flame and allow it to remain until the copper becomes very hot,
+not quite red, but almost so.
+
+A new soldering iron or one that has been misused will have to be "tinned"
+before using. To do this, take the iron from the fire while very hot and
+rub the tip on some flux or dip it into soldering acid. Then rub the tip of
+the iron on a stick of solder or rub the solder on the iron. If the solder
+melts off the stick without coating the end of the iron, allow a few drops
+to fall on a piece of tin plate, then nil the end of the iron on the tin
+plate with considerable force. Alternately rub the iron on the solder and
+dip into flux until the tip has a coating of bright solder for about half
+an inch from the end. If the iron is in very bad shape, it may be necessary
+to scrape or file the end before dipping in the flux for the first time.
+After the end of the iron is tinned in this way, replace it on the rest of
+the torch so that the tinned point is not directly in the flame, turning
+the flame down to accomplish this.
+
+_Flux._--The commonest flux, which is called "soldering acid," is made
+by placing pieces of zinc in muriatic (hydrochloric) acid contained in a
+heavy glass or porcelain dish. There will be bubbles and considerable heat
+evolved and zinc should be added until this action ceases and the zinc
+remains in the liquid, which is now chloride of zinc.
+
+This soldering acid may be used on any metal to be soldered by applying
+with a brush or swab. For electrical work, this acid should be made neutral
+by the addition of one part ammonia and one part water to each three parts
+of the acid. This neutralized flux will not corrode metal as will the
+ordinary acid.
+
+Powdered resin makes a good flux for lead, tin plate, galvanized iron and
+aluminum. Tallow, olive oil, beeswax and vaseline are also used for this
+purpose. Muriatic acid may be used for zinc or galvanized iron without the
+addition of the zinc, as described in making zinc chloride. The addition of
+two heaping teaspoonfuls of sal ammoniac to each pint of the chloride of
+zinc is sometimes found to improve its action.
+
+_Soldering Metal Parts._--All surfaces to be joined should be fitted
+to each other as accurately as possible and then thoroughly cleaned with a
+file, emery cloth, scratch bush or by dipping in lye. Work may be cleaned
+by dipping it into nitric acid which has been diluted with an equal volume
+of water. The work should be heated as hot as possible without danger of
+melting, as this causes the solder to flow better and secure a much better
+hold on the surfaces. Hard solder gives better results than half and half,
+but is more difficult to work. It is very important that the soldering iron
+be kept at a high heat during all work, otherwise the solder will only
+stick to the surfaces and will not join with them.
+
+Sweating is a form of soldering in which the surfaces of the work are first
+covered with a thin layer of solder by rubbing them with the hot iron after
+it has been dipped in or touched to the soldering stick. These surfaces are
+then placed in contact and heated to a point at which the solder melts and
+unites. Sweating is much to be preferred to ordinary soldering where the
+form of the work permits it. This is the only method which should ever be
+used when a fitting is to be placed over the end of a length of tube.
+
+_Soldering Holes._--Clean the surfaces for some distance around the
+hole until they are bright, and apply flux while holding the hot iron near
+the hole. Touch the tip of the iron to some solder until the solder is
+picked up on the iron, and then place this solder, which was just picked
+up, around the edge of the hole. It will leave the soldering iron and stick
+to the metal. Keep adding solder in this way until the hole has been closed
+up by working from the edges and building toward the center. After the hole
+is closed, apply more flux to the job and smooth over with the hot iron
+until there are no rough spots. Should the solder refuse to flow smoothly,
+the iron is not hot enough.
+
+_Soldering Seams._--Clean back from the seam or split for at least
+half an inch all around and then build up the solder in the same way as was
+done with the hole. After closing the opening, apply more flux to the work
+and run the hot iron lengthwise to smooth the job.
+
+_Soldering Wires._--Clean all insulation from the ends to be soldered
+and scrape the ends bright. Lay the ends parallel to each other and,
+starting at the middle of the cleaned portion, wrap the ends around each
+other, one being wrapped to the right, the other to the left. Hold the hot
+iron under the twisted joint and apply flux to the wire. Then dip the iron
+in the solder and apply to the twisted portion until the spaces between the
+wires are filled with solder. Finish by smoothing the joint and cleaning
+away all excess metal by rubbing the hot iron lengthwise. The joint should
+now be covered with a layer of rubber tape and this covered with a layer of
+ordinary friction tape.
+
+_Steel and Iron._--Steel surfaces should be cleaned, then covered with
+clear muriatic acid. While the acid is on the metal, rub with a stick of
+zinc and then tin the surfaces with the hot iron as directed. Cast iron
+should be cleaned and dipped in strong lye to remove grease. Wash the lye
+away with clean water and cover with muriatic acid as with steel. Then rub
+with a piece of zinc and tin the surfaces by using resin as a flux.
+
+It is very difficult to solder aluminum with ordinary solder. A special
+aluminum solder should be secured, which is easily applied and makes a
+strong joint. Zinc or phosphor tin may be used in place of ordinary solder
+to tin the surfaces or to fill small holes or cracks. The aluminum must be
+thoroughly heated before attempting to solder and the flux may be either
+resin or soldering acid. The aluminum must be thoroughly cleaned with
+dilute nitric acid and kept hot while the solder is applied by forcible
+rubbing with the hot iron.
+
+
+BRAZING
+
+This is a process for joining metal parts, very similar to soldering,
+except that brass is used to make the joint in place of the lead and zinc
+alloys which form solder. Brazing must not be attempted on metals whose
+melting point is less than that of sheet brass.
+
+Two pieces of brass to be brazed together are heated to a temperature at
+which the brass used in the process will melt and flow between the
+surfaces. The brass amalgamates with the surfaces and makes a very strong
+and perfect joint, which is far superior to any form of soldering where the
+work allows this process to be used, and in many cases is the equal of
+welding for the particular field in which it applies.
+
+_Brazing Heat and Tools._--The metal commonly used for brazing will
+melt at heats between 1350 deg. and 1650 deg. Fahrenheit. To bring the parts to
+this temperature, various methods are in use, using solid, liquid or
+gaseous fuels. While brazing may be accomplished with the fire of the
+blacksmith forge, this method is seldom satisfactory because of the
+difficulty of making a sufficiently clean fire with smithing coal, and it
+should not be used when anything else is available. Large jobs of brazing
+may be handled with a charcoal fire built in the forge, as this fuel
+produces a very satisfactory and clean fire. The only objection is in the
+difficulty of confining the heat to the desired parts of the work.
+
+The most satisfactory fire is that from a fuel gas torch built for this
+work. These torches are simply forms of Bunsen burners, mixing the proper
+quantity of air with the gas to bring about a perfect combustion. Hose
+lines lead to the mixing tube of the gas torch, one line carrying the gas
+and the other air under a moderate pressure. The air line is often
+dispensed with, allowing the gas to draw air into the burner on the
+injector principle, much the same as with illuminating gas burners for use
+with incandescent mantles. Valves are provided with which the operator may
+regulate the amount of both gas and air, and ordinarily the quality and
+intensity of the flame.
+
+When gas is not available, recourse may be had to the gasoline torch made
+for brazing. This torch is built in the same way as the small portable
+gasoline torches for soldering operations, with the exception that two
+regulating needle valves are incorporated in place of only one.
+
+The torches are carried on a framework, which also supports the work being
+handled. Fuel is forced to the torch from a large tank of gasoline into
+which air pressure is pumped by hand. The torches are regulated to give
+the desired flame by means of the needle valves in much the same way as
+with any other form of pressure torch using liquid fuel.
+
+Another very satisfactory form of torch for brazing is the acetylene-air
+combination described in the chapter on welding instruments. This torch
+gives the correct degree of heat and may be regulated to give a clean and
+easily controlled flame.
+
+Regardless of the source of heat, the fire or flame must be adjusted so
+that no soot is deposited on the metal surfaces of the work. This can only
+be accomplished by supplying the exact amounts of gas and air that will
+produce a complete burning of the fuel. With the brazing torches in common
+use two heads are furnished, being supplied from the same source of fuel,
+but with separate regulating devices. The torches are adjustably mounted in
+such a way that the flames may be directed toward each other, heating two
+sides of the work at the same time and allowing the pieces to be completely
+surrounded with the flame.
+
+Except for the source of heat, but one tool is required for ordinary
+brazing operations, this being a spatula formed by flattening one end of a
+quarter-inch steel rod. The spatula is used for placing the brazing metal
+on the work and for handling the flux that is required in this work as in
+all other similar operations.
+
+_Spelter._--The metal that is melted into the joint is called spelter.
+While this name originally applied to but one particular grade or
+composition of metal, common use has extended the meaning until it is
+generally applied to all grades.
+
+Spelter is variously composed of alloys containing copper, zinc, tin and
+antimony, the mixture employed depending on the work to be done. The
+different grades are of varying hardness, the harder kinds melting at
+higher temperatures than the soft ones and producing a stronger joint when
+used. The reason for not using hard spelter in all cases is the increased
+difficulty of working it and the fact that its melting point is so near to
+some of the metals brazed that there is great danger of melting the work as
+well as the spelter.
+
+The hardest grade of spelter is made from three-fourths copper with
+one-fourth zinc and is used for working on malleable and cast iron and for
+steel.
+
+This hard spelter melts at about 1650 deg. and is correspondingly difficult to
+handle.
+
+A spelter suitable for working with copper is made from equal parts of
+copper and zinc, melting at about 1400 deg. Fahrenheit, 500 deg. below the melting
+point of the copper itself. A still softer brazing metal is composed of
+half copper, three-eighths zinc and one-eighth tin. This grade is used for
+fastening brass to iron and copper and for working with large pieces of
+brass to brass. For brazing thin sheet brass and light brass castings, a
+metal is used which contains two-thirds tin and one-third antimony. The
+low melting point of this last composition makes it very easy to work with
+and the danger of melting the work is very slight. However, as might be
+expected, a comparatively weak joint is secured, which will not stand any
+great strain.
+
+All of the above brazing metals are used in powder form so that they may be
+applied with the spatula where the joint is exposed on the outside of the
+work. In case it is necessary to braze on the inside of a tube or any deep
+recess, the spelter may be placed on a flat rod long enough to reach to
+the farthest point. By distributing the spelter at the proper points along
+the rod it may be placed at the right points by turning the rod over after
+inserting into the recess.
+
+_Flux._--In order to remove the oxides produced under brazing heat and
+to allow the brazing metal to flow freely into place, a flux of some kind
+must be used. The commonest flux is simply a pure calcined borax powder,
+that is, a borax powder that has been heated until practically all the
+water has been driven off.
+
+Calcined borax may also be mixed with about 15 per cent of sal ammoniac to
+make a satisfactory fluxing powder. It is absolutely necessary to use flux
+of some kind and a part of whatever is used should be made into a paste
+with water so that it can be applied to the joint to be brazed before
+heating. The remainder of the powder should be kept dry for use during the
+operation and after the heat has been applied.
+
+_Preparing the Work._--The surfaces to be brazed are first thoroughly
+cleaned with files, emery cloth or sand paper. If the work is greasy, it
+should be dipped into a bath of lye or hot soda water so that all trace of
+oil is removed. The parts are then placed in the relation to each other
+that they are to occupy when the work has been completed. The edges to be
+joined should make a secure and tight fit, and should match each other at
+all points so that the smallest possible space is left between them. This
+fit should not be so tight that it is necessary to force the work into
+place, neither should it be loose enough to allow any considerable space
+between the surfaces. The molten spelter will penetrate between surfaces
+that water will flow between when the work and spelter have both been
+brought to the proper heat. It is, of course, necessary that the two parts
+have a sufficient number of points of contact so that they will remain in
+the proper relative position.
+
+The work is placed on the surface of the brazing table in such a position
+that the flame from the torches will strike the parts to be heated, and
+with the joint in such a position that the melted spelter will flow down
+through it and fill every possible part of the space between the surfaces
+under the action of gravity. That means that the edge of the joint must be
+uppermost and the crack to be filled must not lie horizontal, but at the
+greatest slant possible. Better than any degree of slant would be to have
+the line of the joint vertical.
+
+The work is braced up or clamped in the proper position before commencing
+to braze, and it is best to place fire brick in such positions that it will
+be impossible for cooling draughts of air to reach the heated metal should
+the flame be removed temporarily during the process. In case there is a
+large body of iron, steel or copper to be handled, it is often advisable to
+place charcoal around the work, igniting this with the flame of the torch
+before starting to braze so that the metal will be maintained at the
+correct heat without depending entirely on the torch.
+
+When handling brass pieces having thin sections there is danger of melting
+the brass and causing it to flow away from under the flame, with the result
+that the work is ruined. If, in the judgment of the workman, this may
+happen with the particular job in hand, it is well to build up a mould of
+fire clay back of the thin parts or preferably back of the whole piece, so
+that the metal will have the necessary support. This mould may be made by
+mixing the fire clay into a stiff paste with water and then packing it
+against the piece to be supported tightly enough so that the form will be
+retained even if the metal softens.
+
+_Brazing._--With the work in place, it should be well covered with the
+paste of flux and water, then heated until this flux boils up and runs over
+the surfaces. Spelter is then placed in such a position that it will run
+into the joint and the heat is continued or increased until the spelter
+melts and flows in between the two surfaces. The flame should surround the
+work during the heating so that outside air is excluded as far as is
+possible to prevent excessive oxidization.
+
+When handling brass or copper, the flame should not be directed so that its
+center strikes the metal squarely, but so that it glances from one side or
+the other. Directing the flame straight against the work is often the cause
+of melting the pieces before the operation is completed. When brazing two
+different metals, the flame should play only on the one that melts at the
+higher temperature, the lower melting part receiving its heat from the
+other. This avoids the danger of melting one before the other reaches the
+brazing point.
+
+The heat should be continued only long enough to cause the spelter to flow
+into place and no longer. Prolonged heating of any metal can do nothing but
+oxidize and weaken it, and this practice should be avoided as much as
+possible. If the spelter melts into small globules in place of flowing, it
+may be caused to spread and run into the joint by lightly tapping the work.
+More dry flux may be added with the spatula if the tapping does not produce
+the desired result.
+
+Excessive use of flux, especially toward the end of the work, will result
+in a very hard surface on all the work, a surface which will be extremely
+difficult to finish properly. This trouble will be present to a certain
+extent anyway, but it may be lessened by a vigorous scraping with a wire
+brush just as soon as the work is removed from the fire. If allowed to cool
+before cleaning, the final appearance will not be as good as with the
+surplus metal and scale removed immediately upon completing the job.
+
+After the work has been cleaned with the brush it may be allowed to cool
+and finished to the desired shape, size and surface by filing and
+polishing. When filed, a very thin line of brass should appear where the
+crack was at the beginning of the work. If it is desired to avoid a square
+shoulder and fill in an angle joint to make it rounding, the filling is
+best accomplished by winding a coil of very thin brass wire around the part
+of the work that projects and then causing this to flow itself or else
+allow the spelter to fill the spaces between the layers of wire. Copper
+wire may also be used for this purpose, the spaces being filled with
+melted spelter.
+
+
+THERMIT WELDING
+
+The process of welding which makes use of the great heat produced by oxygen
+combining with aluminum is known as the Thermit process and was perfected
+by Dr. Hans Goldschmidt. The process, which is controlled by the
+Goldschmidt Thermit Company, makes use of a mixture of finely powdered
+aluminum with an oxide of iron called by the trade name, Thermit.
+
+The reaction is started with a special ignition powder, such as barium
+superoxide and aluminum, and the oxygen from the iron oxide combining with
+the aluminum, producing a mass of superheated steel at about 5000 degrees
+Fahrenheit. After the reaction, which takes from. 30 seconds to a minute,
+the molten metal is drawn from the crucible on to the surfaces to be
+joined. Its extreme heat fuses the metal and a perfect joint is the result.
+This process is suited for welding iron or steel parts of comparatively
+large size.
+
+_Preparation._--The parts to be joined are thoroughly cleaned on the
+surfaces and for several inches back from the joint, after which they are
+supported in place. The surfaces between which the metal will flow are
+separated from 1/4 to 1 inch, depending on the size of the parts, but
+cutting or drilling part of the metal away. After this separation is made
+for allowing the entrance of new metal, the effects of contraction of the
+molten steel are cared for by preheating adjacent parts or by forcing the
+ends apart with wedges and jacks. The amount of this last separation must
+be determined by the shape and proportions of the parts in the same way as
+would be done for any other class of welding which heats the parts to a
+melting point.
+
+Yellow wax, which has been warmed until plastic, is then placed around the
+joint to form a collar, the wax completely filling the space between the
+ends and being provided with vent holes by imbedding a piece of stout cord,
+which is pulled out after the wax cools.
+
+A retaining mould (Figure 55) made from sheet steel or fire brick is then
+placed around the parts. This mould is then filled with a mixture of one
+part fire clay, one part ground fire brick and one part fire sand. These
+materials are well mixed and moistened with enough water so that they will
+pack. This mixture is then placed in the mould, filling the space between
+the walls and the wax, and is packed hard with a rammer so that the
+material forms a wall several inches thick between any point of the mould
+and the wax. The mixture must be placed in the mould in small quantities
+and packed tight as the filling progresses.
+
+[Illustration: Figure 55.--Thermit Mould Construction]
+
+Three or more openings are provided through this moulding material by the
+insertion of wood or pipe forms. One of these openings will lead from the
+lowest point of the wax pattern and is used for the introduction of the
+preheating flame. Another opening leads from the top of the mould into this
+preheating gate, opening into the preheating gate at a point about one inch
+from the wax pattern. Openings, called risers, are then provided from each
+of the high points of the wax pattern to the top of the mould, these risers
+ending at the top in a shallow basin. The molten metal comes up into these
+risers and cares for contraction of the casting, as well as avoiding
+defects in the collar of the weld. After the moulding material is well
+packed, these gate patterns are tapped lightly and withdrawn, except in the
+case of the metal pipes which are placed at points at which it would be
+impossible to withdraw a pattern.
+
+_Preheating._--The ends to be welded are brought to a bright red heat
+by introducing the flame from a torch through the preheating gate. The
+torch must use either gasoline or kerosene, and not crude oil, as the crude
+oil deposits too much carbon on the parts. Preheating of other adjacent
+parts to care for contraction is done at this time by an additional torch
+burner.
+
+The heating flame is started gently at first and gradually increased. The
+wax will melt and may be allowed to run out of the preheating gate by
+removing the flame at intervals for a few seconds. The heat is continued
+until the mould is thoroughly dried and the parts to be joined are brought
+to the red heat required. This leaves a mould just the shape of the wax
+pattern.
+
+The heating gate should then be plugged with a sand core, iron plug or
+piece of fitted fire brick, and backed up with several shovels full of the
+moulding mixture, well packed.
+
+[Illustration: Figure 56.--Thermit Crucible Plug.
+_A_, Hard burn magnesia stone;
+_B_, Magnesia thimble;
+_C_, Refractory sand;
+_D_, Metal disc;
+_E_, Asbestos washer;
+_F_, Tapping pin]
+
+_Thermit Metal._--The reaction takes place in a special crucible lined
+with magnesia tar, which is baked at a red heat until the tar is driven off
+and the magnesia left. This lining should last from twelve to fifteen
+reactions. This magnesia lining ends at the bottom of the crucible in a
+ring of magnesia stone and this ring carries a magnesia thimble through
+which the molten steel passes on its way to the mould. It will usually be
+necessary to renew this thimble after each reaction. This lower opening is
+closed before filling the crucible with thermit by means of a small disc or
+iron carrying a stem, which is called a tapping pin (Figure 56). This pin,
+_F_, is placed in the thimble with the stem extending down through the
+opening and exposing about two inches. The top of this pin is covered with
+an asbestos, washer, _E_, then with another iron disc. _D_, and
+finally with a layer of refractory sand. The crucible is tapped by knocking
+the stem of the pin upwards with a spade or piece of flat iron about four
+feet long.
+
+The charge of thermit is added by placing a few handfuls over the
+refractory sand and then pouring in the balance required. The amount of
+thermit required is calculated from the wax used. The wax is weighed before
+and after filling _the entire space that the thermit will occupy_.
+This does not mean only the wax collar, but the space of the mould with all
+gates filled with wax. The number of pounds of wax required for this
+filling multiplied by 25 will give the number of pounds of thermit to be
+used. To this quantity of thermit should be added I per cent of pure
+manganese, 1 per cent nickel thermit and 15 per cent of steel punchings.
+
+It is necessary, when more than 10 pounds of thermit will be used, to mix
+steel punchings not exceeding 3/8 inch diameter by 1/8 inch thick with the
+powder in order to sufficiently retard the intensity of the reaction.
+
+Half a teaspoonful of ignition powder is placed on top of the thermit
+charge and ignited with a storm match or piece of red hot iron. The cover
+should be immediately closed on the top of the crucible and the operator
+should get away to a safe distance because of the metal that may be thrown
+out of the crucible.
+
+After allowing about 30 seconds to a minute for the reaction to take place
+and the slag to rise to the top of the crucible, the tapping pin is struck
+from below and the molten metal allowed to run into the mould. The mould
+should be allowed to remain in place as long as possible, preferably over
+night, so as to anneal the steel in the weld, but in no case should it be
+disturbed for several hours after pouring. After removing the mould, drill
+through the metal left in the riser and gates and knock these sections off.
+No part of the collar should be removed unless absolutely necessary.
+
+
+
+
+CHAPTER IX
+
+OXYGEN PROCESS FOR REMOVAL OF CARBON
+
+
+Until recently the methods used for removing carbon deposits from gas
+engine cylinders were very impractical and unsatisfactory. The job meant
+dismantling the motor, tearing out all parts, and scraping the pistons and
+cylinder walls by hand.
+
+The work was never done thoroughly. It required hours of time to do it, and
+then there was always the danger of injuring the inside of the cylinders.
+
+These methods have been to a large extent superseded by the use of oxygen
+under pressure. The various devices that are being manufactured are known
+as carbon removers, decarbonizers, etc., and large numbers of them are in
+use in the automobile and gasoline traction motor industry.
+
+_Outfit._--The oxygen carbon cleaner consists of a high pressure
+oxygen cylinder with automatic reducing valve, usually constructed on the
+diaphragm principle, thus assuring positive regulation of pressure. This
+valve is fitted with a pressure gauge, rubber hose, decarbonizing torch
+with shut off and flexible tube for insertion into the chamber from which
+the carbon is to be removed.
+
+There should also be an asbestos swab for swabbing out the inside of the
+cylinder or other chamber with kerosene previous to starting the operation.
+The action consists in simply burning the carbon to a fine dust in the
+presence of the stream of oxygen, this dust being then blown out.
+
+_Operation._--The following are instructions for operating the
+cleaner:--
+
+(1) Close valve in gasoline supply line and start the motor, letting it run
+until the gasoline is exhausted.
+
+(2) If the cylinders be T or L head, remove either the inlet or the exhaust
+valve cap, or a spark plug if the cap is tight. If the cylinders have
+overhead valves, remove a spark plug. If any spark plug is then remaining
+in the cylinder it should be removed and an old one or an iron pipe plug
+substituted.
+
+(3) Raise the piston of the cylinder first to be cleaned to the top of the
+compression stroke and continue this from cylinder to cylinder as the work
+progresses.
+
+(4) In motors where carbon has been burned hard, the cylinder interior
+should then be swabbed with kerosene before proceeding. Work the swab,
+saturated with kerosene, around the inside of the cylinder until all the
+carbon has been moistened with the oil. This same swab may be used to
+ignite the gas in the cylinder in place of using a match or taper.
+
+(5) Make all connections to the oxygen cylinder.
+
+(6) Insert the torch nozzle in the cylinder, open the torch valve gradually
+and regulate to about two lbs. pressure. Manipulate the nozzle inside the
+cylinder and light a match or other flame at the opening so that the carbon
+starts to burn. Cover the various points within the cylinder and when there
+is no further burning the carbon has been removed. The regulating and
+oxygen tank valves are operated in exactly the same way as for welding as
+previously explained.
+
+
+It should be carefully noted that when the piston is up, ready to start the
+operation, both valves must be closed. There will be a considerable display
+of sparks while this operation is taking place, but they will not set fire
+to the grease and oil. Care should be used to see that no gasoline is
+about.
+
+
+
+
+INDEX
+
+
+Acetylene
+  filtering
+  generators
+  in tanks
+  piping
+  properties of
+  purification of
+Acetylene-air torches
+Air
+  oxygen from
+Alloys
+  table of
+Alloy steel
+Aluminum
+  alloys
+  welding
+Annealing
+Anvil
+Arc welding, electric
+  machines
+Asbestos, use of, in welding
+
+Babbitt
+Bending pipes and tubes
+Bessemer steel
+Beveling
+Brass
+  welding
+Brazing
+  electric
+  heat and tools
+  spelter
+Bronze
+  welding
+Butt welding
+
+Calcium carbide
+Carbide
+  storage of, Fire Underwriters' Rules
+  to water generator
+Carbon removal
+  by oxygen process
+Case hardening steel
+Cast iron
+  welding
+Champfering
+Charging generator
+Chlorate of potash oxygen
+Conductivity of metals
+Copper
+  alloys
+  welding
+Crucible steel
+Cutting, oxy-acetylene
+  torches
+
+Dissolved acetylene
+
+Electric arc welding
+Electric welding
+  troubles and remedies
+Expansion of metals
+
+Flame, welding
+Fluxes
+  for brazing
+  for soldering
+Forge
+  fire
+  practice
+  tools
+  tuvere construction of
+  welding
+  welding preparation
+  welds, forms of
+Forging
+
+Gas holders
+Gases, heating power of
+Generator, acetylene
+  carbide to water
+  construction
+Generator
+  location of
+  operation and care of
+  overheating
+  requirements
+  water to carbide
+German silver
+Gloves
+Goggles
+
+Hand forging
+Hardening steel
+Heat treatment of steel
+Hildebrandt process
+Hose
+
+Injectors, adjuster
+Iron
+  cast
+  grades of
+  malleable cast
+  wrought
+
+Jump weld
+
+Lap welding
+Lead
+Linde process
+Liquid air oxygen
+
+Magnalium
+Malleable iron
+  welding
+Melting points of metals
+Metal alloys, table of
+Metals
+  characteristics of
+  conductivity of
+  expansion of
+  heat treatment of
+  melting points of
+  tensile strength of
+  weight of
+
+Nickel
+Nozzle sizes, torch
+
+Open hearth steel
+Oxy-acetylene cutting
+  welding practice
+Oxygen
+  cylinders
+  weight of
+
+Pipes, bending
+Platinum
+Preheating
+
+Removal of carbon by oxygen process
+Resistance method of electric welding
+Restoration of steel
+Rods, welding
+
+Safety devices
+Scarfing
+Solder
+Soldering
+  flux
+  holes
+  seams
+  steel and iron
+  wires
+Spelter
+Spot welding
+Steel
+  alloys
+  Bessemer
+  crucible
+  heat treatment of
+  open hearth
+  restoration of
+  tensile strength of
+  welding
+Strength of metals
+
+Tank valves
+Tapering
+Tables of welding information
+Tempering steel
+Thermit metal
+  preheating
+  preparation
+  welding
+Tin
+Torch
+  acetylene-air
+  care
+  construction
+  cutting
+  high pressure
+  low pressure
+  medium pressure
+  nozzles
+  practice
+
+Valves, regulating
+  tank
+
+Water
+  to carbide generator
+Welding aluminum
+  brass
+  bronze
+  butt
+  cast iron
+  copper
+  electric
+  electric arc
+  flame
+  forge
+  information and tables
+  instruments
+  lap
+  malleable iron
+  materials
+  practice, oxy-acetylene
+  rods
+  spot
+  steel
+  table
+  thermit
+  torches
+  various metals
+  wrought iron
+Wrought iron
+  welding
+
+Zinc
+
+
+
+
+
+
+
+
+
+
+End of the Project Gutenberg EBook of Oxy-Acetylene Welding and Cutting, by
+Harold P. Manly
+
+*** END OF THIS PROJECT GUTENBERG EBOOK OXY-ACETYLENE WELDING AND CUTTING ***
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+Project Gutenberg's Oxy-Acetylene Welding and Cutting, by Harold P. Manly
+
+Copyright laws are changing all over the world. Be sure to check the
+copyright laws for your country before downloading or redistributing
+this or any other Project Gutenberg eBook.
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+*****These eBooks Were Prepared By Thousands of Volunteers!*****
+
+
+Title: Oxy-Acetylene Welding and Cutting
+       Electric, Forge and Thermit Welding together with related methods
+       and materials used in metal working and the oxygen process
+       for removal of carbon
+
+Author: Harold P. Manly
+
+Release Date: April, 2005 [EBook #7969]
+[Yes, we are more than one year ahead of schedule]
+[This file was first posted on June 7, 2003]
+
+Edition: 10
+
+Language: English
+
+Character set encoding: ASCII
+
+*** START OF THE PROJECT GUTENBERG EBOOK OXY-ACETYLENE WELDING AND CUTTING ***
+
+
+
+
+Produced by Juliet Sutherland, John Argus, Tonya Allen,
+Charles Franks and the Online Distributed Proofreading Team.
+
+
+
+
+Oxy-Acetylene Welding and Cutting
+
+Electric, Forge and Thermit Welding
+
+Together with Related Methods and Materials Used in Metal Working
+And
+The Oxygen Process for Removal of Carbon
+
+By
+HAROLD P. MANLY
+
+
+
+
+PREFACE
+
+In the preparation of this work, the object has been to cover not only the
+several processes of welding, but also those other processes which are so
+closely allied in method and results as to make them a part of the whole
+subject of joining metal to metal with the aid of heat.
+
+The workman who wishes to handle his trade from start to finish finds that
+it is necessary to become familiar with certain other operations which
+precede or follow the actual joining of the metal parts, the purpose of
+these operations being to add or retain certain desirable qualities in the
+materials being handled. For this reason the following subjects have been
+included: Annealing, tempering, hardening, heat treatment and the
+restoration of steel.
+
+In order that the user may understand the underlying principles and the
+materials employed in this work, much practical information is given on the
+uses and characteristics of the various metals; on the production, handling
+and use of the gases and other materials which are a part of the equipment;
+and on the tools and accessories for the production and handling of these
+materials.
+
+An examination will show that the greatest usefulness of this book lies in
+the fact that all necessary information and data has been included in one
+volume, making it possible for the workman to use one source for securing a
+knowledge of both principle and practice, preparation and finishing of the
+work, and both large and small repair work as well as manufacturing methods
+used in metal working.
+
+An effort has been made to eliminate all matter which is not of direct
+usefulness in practical work, while including all that those engaged in
+this trade find necessary. To this end, the descriptions have been limited
+to those methods and accessories which are found in actual use today. For
+the same reason, the work includes the application of the rules laid down
+by the insurance underwriters which govern this work as well as
+instructions for the proper care and handling of the generators, torches
+and materials found in the shop.
+
+Special attention has been given to definite directions for handling the
+different metals and alloys which must be handled. The instructions have
+been arranged to form rules which are placed in the order of their use
+during the work described and the work has been subdivided in such a way
+that it will be found possible to secure information on any one point
+desired without the necessity of spending time in other fields.
+
+The facts which the expert welder and metalworker finds it most necessary
+to have readily available have been secured, and prepared especially for
+this work, and those of most general use have been combined with the
+chapter on welding practice to which they apply.
+
+The size of this volume has been kept as small as possible, but an
+examination of the alphabetical index will show that the range of subjects
+and details covered is complete in all respects. This has been accomplished
+through careful classification of the contents and the elimination of all
+repetition and all theoretical, historical and similar matter that is not
+absolutely necessary.
+
+Free use has been made of the information given by those manufacturers who
+are recognized as the leaders in their respective fields, thus insuring
+that the work is thoroughly practical and that it represents present day
+methods and practice.
+
+THE AUTHOR.
+
+
+
+
+CONTENTS
+
+   CHAPTER I
+
+METALS AND ALLOYS--HEAT TREATMENT:--The Use and Characteristics of the
+Industrial Alloys and Metal Elements--Annealing, Hardening, Tempering and
+Case Hardening of Steel
+
+   CHAPTER II
+
+WELDING MATERIALS:--Production, Handling and Use of the Gases, Oxygen and
+Acetylene--Welding Rods--Fluxes--Supplies and Fixtures
+
+   CHAPTER III
+
+ACETYLENE GENERATORS:--Generator Requirements and Types--Construction--Care
+and Operation of Generators.
+
+   CHAPTER IV
+
+WELDING INSTRUMENTS:--Tank and Regulating Valves and Gauges--High, Low and
+Medium Pressure Torches--Cutting Torches--Acetylene-Air Torches
+
+   CHAPTER V
+
+OXY-ACETYLENE WELDING PRACTICE:--Preparation of Work--Torch Practice--
+Control of the Flame--Welding Various Metals and Alloys--Tables of
+Information Required in Welding Operations
+
+   CHAPTER VI
+
+ELECTRIC WELDING:--Resistance Method--Butt, Spot and Lap Welding--Troubles
+and Remedies--Electric Arc Welding
+
+   CHAPTER VII
+
+HAND FORGING AND WELDING:--Blacksmithing, Forging and Bending--Forge
+Welding Methods
+
+   CHAPTER VIII
+
+SOLDERING, BRAZING AND THERMIT WELDING:--Soldering Materials and Practice--
+Brazing--Thermit Welding
+
+   CHAPTER IX
+
+OXYGEN PROCESS FOR REMOVAL OF CARBON
+
+INDEX
+
+
+
+
+
+OXY-ACETYLENE WELDING AND CUTTING, ELECTRIC AND THERMIT WELDING
+
+
+
+
+CHAPTER I
+
+METALS AND THEIR ALLOYS--HEAT TREATMENT
+
+
+THE METALS
+
+_Iron._--Iron, in its pure state, is a soft, white, easily worked
+metal. It is the most important of all the metallic elements, and is, next
+to aluminum, the commonest metal found in the earth.
+
+Mechanically speaking, we have three kinds of iron: wrought iron, cast iron
+and steel. Wrought iron is very nearly pure iron; cast iron contains carbon
+and silicon, also chemical impurities; and steel contains a definite
+proportion of carbon, but in smaller quantities than cast iron.
+
+Pure iron is never obtained commercially, the metal always being mixed with
+various proportions of carbon, silicon, sulphur, phosphorus, and other
+elements, making it more or less suitable for different purposes. Iron is
+magnetic to the extent that it is attracted by magnets, but it does not
+retain magnetism itself, as does steel. Iron forms, with other elements,
+many important combinations, such as its alloys, oxides, and sulphates.
+
+[Illustration: Figure 1.--Section Through a Blast Furnace]
+
+_Cast Iron._--Metallic iron is separated from iron ore in the blast
+furnace (Figure 1), and when allowed to run into moulds is called cast
+iron. This form is used for engine cylinders and pistons, for brackets,
+covers, housings and at any point where its brittleness is not
+objectionable. Good cast iron breaks with a gray fracture, is free from
+blowholes or roughness, and is easily machined, drilled, etc. Cast iron is
+slightly lighter than steel, melts at about 2,400 degrees in practice, is
+about one-eighth as good an electrical conductor as copper and has a
+tensile strength of 13,000 to 30,000 pounds per square inch. Its
+compressive strength, or resistance to crushing, is very great. It has
+excellent wearing qualities and is not easily warped and deformed by heat.
+Chilled iron is cast into a metal mould so that the outside is cooled
+quickly, making the surface very hard and difficult to cut and giving great
+resistance to wear. It is used for making cheap gear wheels and parts that
+must withstand surface friction.
+
+_Malleable Cast Iron._--This is often called simply malleable iron. It
+is a form of cast iron obtained by removing much of the carbon from cast
+iron, making it softer and less brittle. It has a tensile strength of
+25,000 to 45,000 pounds per square inch, is easily machined, will stand a
+small amount of bending at a low red heat and is used chiefly in making
+brackets, fittings and supports where low cost is of considerable
+importance. It is often used in cheap constructions in place of steel
+forgings. The greatest strength of a malleable casting, like a steel
+forging, is in the surface, therefore but little machining should be done.
+
+_Wrought Iron._--This grade is made by treating the cast iron to
+remove almost all of the carbon, silicon, phosphorus, sulphur, manganese
+and other impurities. This process leaves a small amount of the slag from
+the ore mixed with the wrought iron.
+
+Wrought iron is used for making bars to be machined into various parts. If
+drawn through the rolls at the mill once, while being made, it is called
+"muck bar;" if rolled twice, it is called "merchant bar" (the commonest
+kind), and a still better grade is made by rolling a third time. Wrought
+iron is being gradually replaced in use by mild rolled steels.
+
+Wrought iron is slightly heavier than cast iron, is a much better
+electrical conductor than either cast iron or steel, has a tensile strength
+of 40,000 to 60,000 pounds per square inch and costs slightly more than
+steel. Unlike either steel or cast iron, wrought iron does not harden when
+cooled suddenly from a red heat.
+
+_Grades of Irons._--The mechanical properties of cast iron differ
+greatly according to the amount of other materials it contains. The most
+important of these contained elements is carbon, which is present to a
+degree varying from 2 to 5-1/2 per cent. When iron containing much carbon
+is quickly cooled and then broken, the fracture is nearly white in color
+and the metal is found to be hard and brittle. When the iron is slowly
+cooled and then broken the fracture is gray and the iron is more malleable
+and less brittle. If cast iron contains sulphur or phosphorus, it will show
+a white fracture regardless of the rapidity of cooling, being brittle and
+less desirable for general work.
+
+_Steel._--Steel is composed of extremely minute particles of iron and
+carbon, forming a network of layers and bands. This carbon is a smaller
+proportion of the metal than found in cast iron, the percentage being from
+3/10 to 2-1/2 per cent.
+
+Carbon steel is specified according to the number of "points" of carbon, a
+point being one one-hundredth of one per cent of the weight of the steel.
+Steel may contain anywhere from 30 to 250 points, which is equivalent to
+saying, anywhere from 3/10 to 2-1/2 per cent, as above. A 70-point steel
+would contain 70/100 of one per cent or 7/10 of one per cent of carbon by
+weight. The percentage of carbon determines the hardness of the steel, also
+many other qualities, and its suitability for various kinds of work. The
+more carbon contained in the steel, the harder the metal will be, and, of
+course, its brittleness increases with the hardness. The smaller the grains
+or particles of iron which are separated by the carbon, the stronger the
+steel will be, and the control of the size of these particles is the object
+of the science of heat treatment.
+
+In addition to the carbon, steel may contain the following:
+
+Silicon, which increases the hardness, brittleness, strength and difficulty
+  of working if from 2 to 3 per cent is present.
+
+Phosphorus, which hardens and weakens the metal but makes it easier to
+  cast. Three-tenths per cent of phosphorus serves as a hardening agent and
+  may be present in good steel if the percentage of carbon is low. More
+  than this weakens the metal.
+
+Sulphur, which tends to make the metal hard and filled with small holes.
+
+Manganese, which makes the steel so hard and tough that it can with
+  difficulty be cut with steel tools. Its hardness is not lessened by
+  annealing, and it has great tensile strength.
+
+Alloy steel has a varying but small percentage of other elements mixed with
+it to give certain desired qualities. Silicon steel and manganese steel are
+sometimes classed as alloy steels. This subject is taken up in the latter
+part of this chapter under _Alloys_, where the various combinations
+and their characteristics are given consideration.
+
+Steel has a tensile strength varying from 50,000 to 300,000 pounds per
+square inch, depending on the carbon percentage and the other alloys
+present, as well as upon the texture of the grain. Steel is heavier than
+cast iron and weighs about the same as wrought iron. It is about one-ninth
+as good a conductor of electricity as copper.
+
+Steel is made from cast iron by three principal processes: the crucible,
+Bessemer and open hearth.
+
+_Crucible steel_ is made by placing pieces of iron in a clay or
+graphite crucible, mixed with charcoal and a small amount of any desired
+alloy. The crucible is then heated with coal, oil or gas fires until the
+iron melts, and, by absorbing the desired elements and giving up or
+changing its percentage of carbon, becomes steel. The molten steel is then
+poured from the crucible into moulds or bars for use. Crucible steel may
+also be made by placing crude steel in the crucibles in place of the iron.
+This last method gives the finest grade of metal and the crucible process
+in general gives the best grades of steel for mechanical use.
+
+[Illustration: Figure 2.--A Bessemer Converter]
+
+_Bessemer steel_ is made by heating iron until all the undesirable
+elements are burned out by air blasts which furnish the necessary oxygen.
+The iron is placed in a large retort called a converter, being poured,
+while at a melting heat, directly from the blast furnace into the
+converter. While the iron in the converter is molten, blasts of air are
+forced through the liquid, making it still hotter and burning out the
+impurities together with the carbon and manganese. These two elements are
+then restored to the iron by adding spiegeleisen (an alloy of iron, carbon
+and manganese). A converter holds from 5 to 25 tons of metal and requires
+about 20 minutes to finish a charge. This makes the cheapest steel.
+
+[Illustration: Figure 3.--An Open Hearth Furnace]
+
+_Open hearth steel_ is made by placing the molten iron in a receptacle
+while currents of air pass over it, this air having itself been highly
+heated by just passing over white hot brick (Figure. 3). Open hearth steel
+is considered more uniform and reliable than Bessemer, and is used for
+springs, bar steel, tool steel, steel plates, etc.
+
+_Aluminum_ is one of the commonest industrial metals. It is used for
+gear cases, engine crank cases, covers, fittings, and wherever lightness
+and moderate strength are desirable.
+
+Aluminum is about one-third the weight of iron and about the same weight as
+glass and porcelain; it is a good electrical conductor (about one-half as
+good as copper); is fairly strong itself and gives great strength to other
+metals when alloyed with them. One of the greatest advantages of aluminum
+is that it will not rust or corrode under ordinary conditions. The granular
+formation of aluminum makes its strength very unreliable and it is too soft
+to resist wear.
+
+_Copper_ is one of the most important metals used in the trades, and
+the best commercial conductor of electricity, being exceeded in this
+respect only by silver, which is but slightly better. Copper is very
+malleable and ductile when cold, and in this state may be easily worked
+under the hammer. Working in this way makes the copper stronger and harder,
+but less ductile. Copper is not affected by air, but acids cause the
+formation of a green deposit called verdigris.
+
+Copper is one of the best conductors of heat, as well as electricity, being
+used for kettles, boilers, stills and wherever this quality is desirable.
+Copper is also used in alloys with other metals, forming an important part
+of brass, bronze, german silver, bell metal and gun metal. It is about
+one-eighth heavier than steel and has a tensile strength of about 25,000 to
+50,000 pounds per square inch.
+
+_Lead._--The peculiar properties of lead, and especially its quality
+of showing but little action or chemical change in the presence of other
+elements, makes it valuable under certain conditions of use. Its principal
+use is in pipes for water and gas, coverings for roofs and linings for vats
+and tanks. It is also used to coat sheet iron for similar uses and as an
+important part of ordinary solder.
+
+Lead is the softest and weakest of all the commercial metals, being very
+pliable and inelastic. It should be remembered that lead and all its
+compounds are poisonous when received into the system. Lead is more than
+one-third heavier than steel, has a tensile strength of only about 2,000
+pounds per square inch, and is only about one-tenth as good a conductor of
+electricity as copper.
+
+_Zinc._--This is a bluish-white metal of crystalline form. It is
+brittle at ordinary temperatures and becomes malleable at about 250 to 300
+degrees Fahrenheit, but beyond this point becomes even more brittle than at
+ordinary temperatures. Zinc is practically unaffected by air or moisture
+through becoming covered with one of its own compounds which immediately
+resists further action. Zinc melts at low temperatures, and when heated
+beyond the melting point gives off very poisonous fumes.
+
+The principal use of zinc is as an alloy with other metals to form brass,
+bronze, german silver and bearing metals. It is also used to cover the
+surface of steel and iron plates, the plates being then called galvanized.
+
+Zinc weighs slightly less than steel, has a tensile strength of 5,000
+pounds per square inch, and is not quite half as good as copper in
+conducting electricity.
+
+_Tin_ resembles silver in color and luster. Tin is ductile and
+malleable and slightly crystalline in form, almost as heavy as steel, and
+has a tensile strength of 4,500 pounds per square inch.
+
+The principal use of tin is for protective platings on household utensils
+and in wrappings of tin-foil. Tin forms an important part of many alloys
+such as babbitt, Britannia metal, bronze, gun metal and bearing metals.
+
+_Nickel_ is important in mechanics because of its combinations with
+other metals as alloys. Pure nickel is grayish-white, malleable, ductile
+and tenacious. It weighs almost as much as steel and, next to manganese, is
+the hardest of metals. Nickel is one of the three magnetic metals, the
+others being iron and cobalt. The commonest alloy containing nickel is
+german silver, although one of its most important alloys is found in nickel
+steel. Nickel is about ten per cent heavier than steel, and has a tensile
+strength of 90,000 pounds per square inch.
+
+_Platinum._--This metal is valuable for two reasons: it is not
+affected by the air or moisture or any ordinary acid or salt, and in
+addition to this property it melts only at the highest temperatures. It is
+a fairly good electrical conductor, being better than iron or steel. It is
+nearly three times as heavy as steel and its tensile strength is 25,000
+pounds per square inch.
+
+
+ALLOYS
+
+An alloy is formed by the union of a metal with some other material, either
+metal or non-metallic, this union being composed of two or more elements
+and usually brought about by heating the substances together until they
+melt and unite. Metals are alloyed with materials which have been found to
+give to the metal certain characteristics which are desired according to
+the use the metal will be put to.
+
+The alloys of metals are, almost without exception, more important from an
+industrial standpoint than the metals themselves. There are innumerable
+possible combinations, the most useful of which are here classed under the
+head of the principal metal entering into their composition.
+
+_Steel._--Steel may be alloyed with almost any of the metals or
+elements, the combinations that have proven valuable numbering more than a
+score. The principal ones are given in alphabetical order, as follows:
+
+Aluminum is added to steel in very small amounts for the purpose of
+preventing blow holes in castings.
+
+Boron increases the density and toughness of the metal.
+
+Bronze, added by alloying copper, tin and iron, is used for gun metal.
+
+Carbon has already been considered under the head of steel in the section
+devoted to the metals. Carbon, while increasing the strength and hardness,
+decreases the ease of forging and bending and decreases the magnetism and
+electrical conductivity. High carbon steel can be welded only with
+difficulty. When the percentage of carbon is low, the steel is called "low
+carbon" or "mild" steel. This is used for rods and shafts, and called
+"machine" steel. When the carbon percentage is high, the steel is called
+"high carbon" steel, and it is used in the shop as tool steel. One-tenth
+per cent of carbon gives steel a tensile strength of 50,000 to 65,000
+pounds per square inch; two-tenths per cent gives from 60,000 to 80,000;
+four-tenths per cent gives 70,000 to 100,000, and six-tenths per cent
+gives 90,000 to 120,000.
+
+Chromium forms chrome steel, and with the further addition of nickel is
+called chrome nickel steel. This increases the hardness to a high degree
+and adds strength without much decrease in ductility. Chrome steels are
+used for high-speed cutting tools, armor plate, files, springs, safes,
+dies, etc.
+
+Manganese has been mentioned under _Steel_. Its alloy is much used for
+high-speed cutting tools, the steel hardening when cooled in the air and
+being called self-hardening.
+
+Molybdenum is used to increase the hardness to a high degree and makes the
+steel suitable for high-speed cutting and gives it self-hardening
+properties.
+
+Nickel, with which is often combined chromium, increases the strength,
+springiness and toughness and helps to prevent corrosion.
+
+Silicon has already been described. It suits the metal for use in
+high-speed tools.
+
+Silver added to steel has many of the properties of nickel.
+
+Tungsten increases the hardness without making the steel brittle. This
+makes the steel well suited for gas engine valves as it resists corrosion
+and pitting. Chromium and manganese are often used in combination with
+tungsten when high-speed cutting tools are made.
+
+Vanadium as an alloy increases the elastic limit, making the steel
+stronger, tougher and harder. It also makes the steel able to stand much
+bending and vibration.
+
+_Copper._--The principal copper alloys include brass, bronze, german
+silver and gun metal.
+
+Brass is composed of approximately one-third zinc and two-thirds copper. It
+is used for bearings and bushings where the speeds are slow and the loads
+rather heavy for the bearing size. It also finds use in washers, collars
+and forms of brackets where the metal should be non-magnetic, also for many
+highly finished parts.
+
+Brass is about one-third as good an electrical conductor as copper, is
+slightly heavier than steel and has a tensile strength of 15,000 pounds
+when cast and about 75,000 to 100,000 pounds when drawn into wire.
+
+Bronze is composed of copper and tin in various proportions, according to
+the use to which it is to be put. There will always be from six-tenths to
+nine-tenths of copper in the mixture. Bronze is used for bearings,
+bushings, thrust washers, brackets and gear wheels. It is heavier than
+steel, about 1/15 as good an electrical conductor as pure copper and has a
+tensile strength of 30,000 to 60,000 pounds.
+
+Aluminum bronze, composed of copper, zinc and aluminum has high tensile
+strength combined with ductility and is used for parts requiring this
+combination.
+
+Bearing bronze is a variable material, its composition and proportion
+depending on the maker and the use for which it is designed. It usually
+contains from 75 to 85 per cent of copper combined with one or more
+elements, such as tin, zinc, antimony and lead.
+
+White metal is one form of bearing bronze containing over 80 per cent of
+zinc together with copper, tin, antimony and lead. Another form is made
+with nearly 90 per cent of tin combined with copper and antimony.
+
+Gun metal bronze is made from 90 per cent copper with 10 per cent of tin
+and is used for heavy bearings, brackets and highly finished parts.
+
+Phosphor bronze is used for very strong castings and bearings. It is
+similar to gun metal bronze, except that about 1-1/2 per cent of phosphorus
+has been added.
+
+Manganese bronze contains about 1 per cent of manganese and is used for
+parts requiring great strength while being free from corrosion.
+
+German silver is made from 60 per cent of copper with 20 per cent each of
+zinc and nickel. Its high electrical resistance makes it valuable for
+regulating devices and rheostats.
+
+_Tin_ is the principal part of _babbitt_ and _solder_. A
+commonly used babbitt is composed of 89 per cent tin, 8 per cent antimony
+and 3 per cent of copper. A grade suitable for repairing is made from
+80 per cent of lead and 20 per cent antimony. This last formula should not
+be used for particular work or heavy loads, being more suitable for
+spacers. Innumerable proportions of metals are marketed under the name of
+babbitt.
+
+Solder is made from 50 per cent tin and 50 per cent lead, this grade being
+called "half-and-half." Hard solder is made from two-thirds tin and
+one-third lead.
+
+Aluminum forms many different alloys, giving increased strength to whatever
+metal it unites with.
+
+Aluminum brass is composed of approximately 65 per cent copper, 30 per cent
+zinc and 5 per cent aluminum. It forms a metal with high tensile strength
+while being ductile and malleable.
+
+Aluminum zinc is suitable for castings which must be stiff and hard.
+
+Nickel aluminum has a tensile strength of 40,000 pounds per square inch.
+
+Magnalium is a silver-white alloy of aluminum with from 5 to 20 per cent of
+magnesium, forming a metal even lighter than aluminum and strong enough to
+be used in making high-speed gasoline engines.
+
+
+HEAT TREATMENT OF STEEL
+
+The processes of heat treatment are designed to suit the steel for various
+purposes by changing the size of the grain in the metal, therefore the
+strength; and by altering the chemical composition of the alloys in the
+metal to give it different physical properties. Heat treatment, as applied
+in ordinary shop work, includes the three processes of annealing, hardening
+and tempering, each designed to accomplish a certain definite result.
+
+All of these processes require that the metal treated be gradually brought
+to a certain predetermined degree of heat which shall be uniform throughout
+the piece being handled and, from this point, cooled according to certain
+rules, the selection of which forms the difference in the three methods.
+
+_Annealing._--This is the process which relieves all internal strains
+and distortion in the metal and softens it so that it may more easily be
+cut, machined or bent to the required form. In some cases annealing is used
+only to relieve the strains, this being the case after forging or welding
+operations have been performed. In other cases it is only desired to soften
+the metal sufficiently that it may be handled easily. In some cases both of
+these things must be accomplished, as after a piece has been forged and
+must be machined. No matter what the object, the procedure is the same.
+
+The steel to be annealed must first be heated to a dull red. This heating
+should be done slowly so that all parts of the piece have time to reach the
+same temperature at very nearly the same time. The piece may be heated in
+the forge, but a much better way is to heat in an oven or furnace of some
+type where the work is protected against air currents, either hot or cold,
+and is also protected against the direct action of the fire.
+
+[Illustration: Figure 4.--A Gaspipe Annealing Oven]
+
+Probably the simplest of all ovens for small tools is made by placing a
+piece of ordinary gas pipe in the fire (Figure 4), and heating until the
+inside of the pipe is bright red. Parts placed in this pipe, after one end
+has been closed, may be brought to the desired heat without danger of
+cooling draughts or chemical change from the action of the fire. More
+elaborate ovens may be bought which use gas, fuel oils or coal to produce
+the heat and in which the work may be placed on trays so that the fire will
+not strike directly on the steel being treated.
+
+If the work is not very important, it may be withdrawn from the fire or
+oven, after heating to the desired point, and allowed to cool in the air
+until all traces of red have disappeared when held in a dark place. The
+work should be held where it is reasonably free from cold air currents. If,
+upon touching a pine stick to the piece being annealed, the wood does not
+smoke, the work may then be cooled in water.
+
+Better annealing is secured and harder metal may be annealed if the cooling
+is extended over a number of hours by placing the work in a bed of
+non-heat-conducting material, such as ashes, charred bone, asbestos fibre,
+lime, sand or fire clay. It should be well covered with the heat retaining
+material and allowed to remain until cool. Cooling may be accomplished by
+allowing the fire in an oven or furnace to die down and go out, leaving the
+work inside the oven with all openings closed. The greater the time taken
+for gradual cooling from the red heat, the more perfect will be the results
+of the annealing.
+
+While steel is annealed by slow cooling, copper or brass is annealed by
+bringing to a low red heat and quickly plunging into cold water.
+
+_Hardening._--Steel is hardened by bringing to a proper temperature,
+slowly and evenly as for annealing, and then cooling more or less quickly,
+according to the grade of steel being handled. The degree of hardening is
+determined by the kind of steel, the temperature from which the metal is
+cooled and the temperature and nature of the bath into which it is plunged
+for cooling.
+
+Steel to be hardened is often heated in the fire until at some heat around
+600 to 700 degrees is reached, then placed in a heating bath of molten
+lead, heated mercury, fused cyanate of potassium, etc., the heating bath
+itself being kept at the proper temperature by fires acting on it. While
+these baths have the advantage of heating the metal evenly and to exactly
+the temperature desired throughout without any part becoming over or under
+heated, their disadvantages consist of the fact that their materials and
+the fumes are poisonous in most all cases, and if not poisonous, are
+extremely disagreeable.
+
+The degree of heat that a piece of steel must be brought to in order that
+it may be hardened depends on the percentage of carbon in the steel. The
+greater the percentage of carbon, the lower the heat necessary to harden.
+
+[Illustration: Figure 5.--Cooling the Test Bar for Hardening]
+
+To find the proper heat from which any steel must be cooled, a simple test
+may be carried out provided a sample of the steel, about six inches long
+can be secured. One end of this test bar should be heated almost to its
+melting point, and held at this heat until the other end just turns red.
+Now cool the piece in water by plunging it so that both ends enter at the
+same time (Figure 5), that is, hold it parallel with the surface of the
+water when plunged in. This serves the purpose of cooling each point along
+the bar from a different heat. When it has cooled in the water remove the
+piece and break it at short intervals, about 1/2 inch, along its length.
+The point along the test bar which was cooled from the best possible
+temperature will show a very fine smooth grain and the piece cannot be cut
+by a file at this point. It will be necessary to remember the exact color
+of that point when taken from the fire, making another test if necessary,
+and heat all pieces of this same steel to this heat. It will be necessary
+to have the cooling bath always at the same temperature, or the results
+cannot be alike.
+
+While steel to be hardened is usually cooled in water, many other liquids
+may be used. If cooled in strong brine, the heat will be extracted much
+quicker, and the degree of hardness will be greater. A still greater degree
+of hardness is secured by cooling in a bath of mercury. Care should be used
+with the mercury bath, as the fumes that arise are poisonous.
+
+Should toughness be desired, without extreme hardness, the steel may be
+cooled in a bath of lard oil, neatsfoot oil or fish oil. To secure a result
+between water and oil, it is customary to place a thick layer of oil on top
+of water. In cooling, the piece will pass through the oil first, thus
+avoiding the sudden shock of the cold water, yet producing a degree of
+hardness almost as great as if the oil were not used.
+
+It will, of course, be necessary to make a separate test for each cooling
+medium used. If the fracture of the test piece shows a coarse grain, the
+steel was too hot at that point; if the fracture can be cut with a file,
+the metal was not hot enough at that point.
+
+When hardening carbon tool steel its heat should be brought to a cherry
+red, the exact degree of heat depending on the amount of carbon and the
+test made, then plunged into water and held there until all hissing sound
+and vibration ceases. Brine may be used for this purpose; it is even better
+than plain water. As soon as the hissing stops, remove the work from the
+water or brine and plunge in oil for complete cooling.
+
+[Illustration: Figure 6.--Cooling the Tool for Tempering]
+
+In hardening high-speed tool steel, or air hardening steels, the tool
+should be handled as for carbon steel, except that after the body reaches
+a cherry red, the cutting point must be quickly brought to a white heat,
+almost melting, so that it seems ready for welding. Then cool in an oil
+bath or in a current of cool air.
+
+Hardening of copper, brass and bronze is accomplished by hammering or
+working them while cold.
+
+_Tempering_ is the process of making steel tough after it has been
+hardened, so that it will hold a cutting edge and resist cracking.
+Tempering makes the grain finer and the metal stronger. It does not affect
+the hardness, but increases the elastic limit and reduces the brittleness
+of the steel. In that tempering is usually performed immediately after
+hardening, it might be considered as a continuation of the former process.
+
+The work or tool to be tempered is slowly heated to a cherry red and the
+cutting end is then dipped into water to a depth of 1/2 to 3/4 inch above
+the point (Figure 6). As soon as the point cools, still leaving the tool
+red above the part in water, remove the work from the bath and quickly rub
+the end with a fine emery cloth.
+
+As the heat from the uncooled part gradually heats the point again, the
+color of the polished portion changes rapidly. When a certain color is
+reached, the tool should be completely immersed in the water until cold.
+
+For lathe, planer, shaper and slotter tools, this color should be a light
+straw.
+
+Reamers and taps should be cooled from an ordinary straw color.
+
+Drills, punches and wood working tools should have a brown color.
+
+Blue or light purple is right for cold chisels and screwdrivers.
+
+Dark blue should be reached for springs and wood saws.
+
+Darker colors than this, ranging through green and gray, denote that the
+piece has reached its ordinary temper, that is, it is partially annealed.
+
+After properly hardening a spring by dipping in lard or fish oil, it should
+be held over a fire while still wet with the oil. The oil takes fire and
+burns off, properly tempering the spring.
+
+Remember that self-hardening steels must never be dipped in water, and
+always remember for all work requiring degrees of heat, that the more
+carbon, the less heat.
+
+_Case Hardening._--This is a process for adding more carbon to the
+surface of a piece of steel, so that it will have good wear-resisting
+qualities, while being tough and strong on the inside. It has the effect of
+forming a very hard and durable skin on the surface of soft steel, leaving
+the inside unaffected.
+
+The simplest way, although not the most efficient, is to heat the piece to
+be case hardened to a red heat and then sprinkle or rub the part of the
+surface to be hardened with potassium ferrocyanide. This material is a
+deadly poison and should be handled with care. Allow the cyanide to fuse on
+the surface of the metal and then plunge into water, brine or mercury.
+Repeating the process makes the surface harder and the hard skin deeper
+each time.
+
+Another method consists of placing the piece to be hardened in a bed of
+powdered bone (bone which has been burned and then powdered) and cover with
+more powdered bone, holding the whole in an iron tray. Now heat the tray
+and bone with the work in an oven to a bright red heat for 30 minutes to an
+hour and then plunge the work into water or brine.
+
+
+
+
+CHAPTER II
+
+OXY-ACETYLENE WELDING AND CUTTING MATERIALS
+
+
+_Welding._--Oxy-acetylene welding is an autogenous welding process, in
+which two parts of the same or different metals are joined by causing the
+edges to melt and unite while molten without the aid of hammering or
+compression. When cool, the parts form one piece of metal.
+
+The oxy-acetylene flame is made by mixing oxygen and acetylene gases in a
+special welding torch or blowpipe, producing, when burned, a heat of 6,300
+degrees, which is more than twice the melting temperature of the common
+metals. This flame, while being of intense heat, is of very small size.
+
+_Cutting._--The process of cutting metals with the flame produced from
+oxygen and acetylene depends on the fact that a jet of oxygen directed upon
+hot metal causes the metal itself to burn away with great rapidity,
+resulting in a narrow slot through the section cut. The action is so fast
+that metal is not injured on either side of the cut.
+
+_Carbon Removal._--This process depends on the fact that carbon will
+burn and almost completely vanish if the action is assisted with a supply
+of pure oxygen gas. After the combustion is started with any convenient
+flame, it continues as long as carbon remains in the path of the jet of
+oxygen.
+
+_Materials._--For the performance of the above operations we require
+the two gases, oxygen and acetylene, to produce the flames; rods of metal
+which may be added to the joints while molten in order to give the weld
+sufficient strength and proper form, and various chemical powders, called
+fluxes, which assist in the flow of metal and in doing away with many of
+the impurities and other objectionable features.
+
+_Instruments._--To control the combustion of the gases and add to the
+convenience of the operator a number of accessories are required.
+
+The pressure of the gases in their usual containers is much too high for
+their proper use in the torch and we therefore need suitable valves which
+allow the gas to escape from the containers when wanted, and other
+specially designed valves which reduce the pressure. Hose, composed of
+rubber and fabric, together with suitable connections, is used to carry the
+gas to the torch.
+
+The torches for welding and cutting form a class of highly developed
+instruments of the greatest accuracy in manufacture, and must be thoroughly
+understood by the welder. Tables, stands and special supports are provided
+for holding the work while being welded, and in order to handle the various
+metals and allow for their peculiarities while heated use is made of ovens
+and torches for preheating. The operator requires the protection of
+goggles, masks, gloves and appliances which prevent undue radiation of the
+heat.
+
+_Torch Practice._--The actual work of welding and cutting requires
+preliminary preparation in the form of heat treatment for the metals,
+including preheating, annealing and tempering. The surfaces to be joined
+must be properly prepared for the flame, and the operation of the torches
+for best results requires careful and correct regulation of the gases and
+the flame produced.
+
+Finally, the different metals that are to be welded require special
+treatment for each one, depending on the physical and chemical
+characteristics of the material.
+
+It will thus be seen that the apparently simple operations of welding and
+cutting require special materials, instruments and preparation on the part
+of the operator and it is a proved fact that failures, which have been
+attributed to the method, are really due to lack of these necessary
+qualifications.
+
+
+OXYGEN
+
+Oxygen, the gas which supports the rapid combustion of the acetylene in the
+torch flame, is one of the elements of the air. It is the cause and the
+active agent of all combustion that takes place in the atmosphere. Oxygen
+was first discovered as a separate gas in 1774, when it was produced by
+heating red oxide of mercury and was given its present name by the famous
+chemist, Lavoisier.
+
+Oxygen is prepared in the laboratory by various methods, these including
+the heating of chloride of lime and peroxide of cobalt mixed in a retort,
+the heating of chlorate of potash, and the separation of water into its
+elements, hydrogen and oxygen, by the passage of an electric current. While
+the last process is used on a large scale in commercial work, the others
+are not practical for work other than that of an experimental or temporary
+nature.
+
+This gas is a colorless, odorless, tasteless element. It is sixteen times
+as heavy as the gas hydrogen when measured by volume under the same
+temperature and pressure. Under all ordinary conditions oxygen remains in
+a gaseous form, although it turns to a liquid when compressed to 4,400
+pounds to the square inch and at a temperature of 220  below zero.
+
+Oxygen unites with almost every other element, this union often taking
+place with great heat and much light, producing flame. Steel and iron will
+burn rapidly when placed in this gas if the combustion is started with a
+flame of high heat playing on the metal. If the end of a wire is heated
+bright red and quickly plunged into a jar containing this gas, the wire
+will burn away with a dazzling light and be entirely consumed except for
+the molten drops that separate themselves. This property of oxygen is used
+in oxy-acetylene cutting of steel.
+
+The combination of oxygen with other substances does not necessarily cause
+great heat, in fact the combination may be so slow and gradual that the
+change of temperature can not be noticed. An example of this slow
+combustion, or oxidation, is found in the conversion of iron into rust as
+the metal combines with the active gas. The respiration of human beings
+and animals is a form of slow combustion and is the source of animal heat.
+It is a general rule that the process of oxidation takes place with
+increasing rapidity as the temperature of the body being acted upon rises.
+Iron and steel at a red heat oxidize rapidly with the formation of a scale
+and possible damage to the metal.
+
+_Air._--Atmospheric air is a mixture of oxygen and nitrogen with
+traces of carbonic acid gas and water vapor. Twenty-one per cent of the
+air, by volume, is oxygen and the remaining seventy-nine per cent is the
+inactive gas, nitrogen. But for the presence of the nitrogen, which deadens
+the action of the other gas, combustion would take place at a destructive
+rate and be beyond human control in almost all cases. These two gases exist
+simply as a mixture to form the air and are not chemically combined. It is
+therefore a comparatively simple matter to separate them with the processes
+now available.
+
+_Water._--Water is a combination of oxygen and hydrogen, being
+composed of exactly two volumes of hydrogen to one volume of oxygen. If
+these two gases be separated from each other and then allowed to mix in
+these proportions they unite with explosive violence and form water. Water
+itself may be separated into the gases by any one of several means, one
+making use of a temperature of 2,200  to bring about this separation.
+
+[Illustration: Figure 7.--Obtaining Oxygen by Electrolysis]
+
+The easiest way to separate water into its two parts is by the process
+called electrolysis (Figure 7). Water, with which has been mixed a small
+quantity of acid, is placed in a vat through the walls of which enter the
+platinum tipped ends of two electrical conductors, one positive and the
+other negative.
+
+Tubes are placed directly above these wire terminals in the vat, one tube
+being over each electrode and separated from each other by some distance.
+With the passage of an electric current from one wire terminal to the
+other, bubbles of gas rise from each and pass into the tubes. The gas that
+comes from the negative terminal is hydrogen and that from the positive
+pole is oxygen, both gases being almost pure if the work is properly
+conducted. This method produces electrolytic oxygen and electrolytic
+hydrogen.
+
+_The Liquid Air Process._--While several of the foregoing methods of
+securing oxygen are successful as far as this result is concerned, they are
+not profitable from a financial standpoint. A process for separating oxygen
+from the nitrogen in the air has been brought to a high state of perfection
+and is now supplying a major part of this gas for oxy-acetylene welding. It
+is known as the Linde process and the gas is distributed by the Linde Air
+Products Company from its plants and warehouses located in the large cities
+of the country.
+
+The air is first liquefied by compression, after which the gases are
+separated and the oxygen collected. The air is purified and then compressed
+by successive stages in powerful machines designed for this purpose until
+it reaches a pressure of about 3,000 pounds to the square inch. The large
+amount of heat produced is absorbed by special coolers during the process
+of compression. The highly compressed air is then dried and the
+temperature further reduced by other coolers.
+
+The next point in the separation is that at which the air is introduced
+into an apparatus called an interchanger and is allowed to escape through a
+valve, causing it to turn to a liquid. This liquid air is sprayed onto
+plates and as it falls, the nitrogen return to its gaseous state and leaves
+ the oxygen to run to the bottom of the container. This liquid oxygen is
+then allowed to return to a gas and is stored in large gasometers or tanks.
+
+The oxygen gas is taken from the storage tanks and compressed to
+approximately 1,800 pounds to the square inch, under which pressure it is
+passed into steel cylinders and made ready for delivery to the customer.
+This oxygen is guaranteed to be ninety-seven per cent pure.
+
+Another process, known as the Hildebrandt process, is coming into use in
+this country. It is a later process and is used in Germany to a much
+greater extent than the Linde process. The Superior Oxygen Co. has secured
+the American rights and has established several plants.
+
+_Oxygen Cylinders_.--Two sizes of cylinders are in use, one containing
+100 cubic feet of gas when it is at atmospheric pressure and the other
+containing 250 cubic feet under similar conditions. The cylinders are made
+from one piece of steel and are without seams. These containers are tested
+at double the pressure of the gas contained to insure safety while
+handling.
+
+One hundred cubic feet of oxygen weighs nearly nine pounds (8.921), and
+therefore the cylinders will weigh practically nine pounds more when full
+than after emptying, if of the 100 cubic feet size. The large cylinders
+weigh about eighteen and one-quarter pounds more when full than when empty,
+making approximately 212 pounds empty and 230 pounds full.
+
+The following table gives the number of cubic feet of oxygen remaining in
+the cylinders according to various gauge pressures from an initial pressure
+of 1,800 pounds. The amounts given are not exactly correct as this would
+necessitate lengthy calculations which would not make great enough
+difference to affect the practical usefulness of the table:
+
+Cylinder of 100 Cu. Ft. Capacity at 68  Fahr.
+
+ Gauge     Volume     Gauge     Volume
+Pressure  Remaining  Pressure  Remaining
+
+ 1800        100       700        39
+ 1620         90       500        28
+ 1440         80       300        17
+ 1260         70       100         6
+ 1080         60        18         1
+  900         50         9          1/2
+
+Cylinder of 250 Cu. Ft. Capacity at 68  Fahr.
+
+ Gauge     Volume     Gauge     Volume
+Pressure  Remaining  Pressure  Remaining
+
+ 1800        250       700        97
+ 1620        225       500        70
+ 1440        200       300        42
+ 1260        175       100        15
+ 1080        150        18         8
+  900        125         9         1-1/4
+
+The temperature of the cylinder affects the pressure in a large degree, the
+pressure increasing with a rise in temperature and falling with a fall in
+temperature. The variation for a 100 cubic foot cylinder at various
+temperatures is given in the following tabulation:
+
+At 150  Fahr........................ 2090 pounds.
+At 100  Fahr........................ 1912 pounds.
+At  80  Fahr........................ 1844 pounds.
+At  68  Fahr........................ 1800 pounds.
+At  50  Fahr........................ 1736 pounds.
+At  32  Fahr........................ 1672 pounds.
+At   0  Fahr........................ 1558 pounds.
+At -10  Fahr........................ 1522 pounds.
+
+_Chlorate of Potash Method._--In spite of its higher cost and the
+inferior gas produced, the chlorate of potash method of producing oxygen is
+used to a limited extent when it is impossible to secure the gas in
+cylinders.
+
+[Illustration: Figure 8.--Oxygen from Chlorate of Potash]
+
+An iron retort (Figure 8) is arranged to receive about fifteen pounds of
+chlorate of potash mixed with three pounds of manganese dioxide, after
+which the cylinder is closed with a tight cap, clamped on. This retort is
+carried above a burner using fuel gas or other means of generating heat and
+this burner is lighted after the chemical charge is mixed and compressed in
+the tube.
+
+The generation of gas commences and the oxygen is led through water baths
+which wash and cool it before storing in a tank connected with the plant.
+From this tank the gas is compressed into portable cylinders at a pressure
+of about 300 pounds to the square inch for use as required in welding
+operations.
+
+Each pound of chlorate of potash liberates about three cubic feet of
+oxygen, and taking everything into consideration, the cost of gas produced
+in this way is several times that of the purer product secured by the
+liquid air process.
+
+These chemical generators are oftentimes a source of great danger,
+especially when used with or near the acetylene gas generator, as is
+sometimes the case with cheap portable outfits. Their use should not be
+tolerated when any other method is available, as the danger from accident
+alone should prohibit the practice except when properly installed and
+cared for away from other sources of combustible gases.
+
+
+ACETYLENE
+
+In 1862 a chemist, Woehler, announced the discovery of the preparation of
+acetylene gas from calcium carbide, which he had made by heating to a high
+temperature a mixture of charcoal with an alloy of zinc and calcium. His
+product would decompose water and yield the gas. For nearly thirty years
+these substances were neglected, with the result that acetylene was
+practically unknown, and up to 1892 an acetylene flame was seen by very few
+persons and its possibilities were not dreamed of. With the development of
+the modern electric furnace the possibility of calcium carbide as a
+commercial product became known.
+
+In the above year, Thomas L. Willson, an electrical engineer of Spray,
+North Carolina, was experimenting in an attempt to prepare metallic
+calcium, for which purpose he employed an electric furnace operating on a
+mixture of lime and coal tar with about ninety-five horse power. The result
+was a molten mass which became hard and brittle when cool. This apparently
+useless product was discarded and thrown in a nearby stream, when, to the
+astonishment of onlookers, a large volume of gas was immediately
+liberated, which, when ignited, burned with a bright and smoky flame and
+gave off quantities of soot. The solid material proved to be calcium
+carbide and the gas acetylene.
+
+Thus, through the incidental study of a by-product, and as the result of an
+accident, the possibilities in carbide were made known, and in the spring
+of 1895 the first factory in the world for the production of this substance
+was established by the Willson Aluminum Company.
+
+When water and calcium carbide are brought together an action takes place
+which results in the formation of acetylene gas and slaked lime.
+
+
+CARBIDE
+
+Calcium carbide is a chemical combination of the elements carbon and
+calcium, being dark brown, black or gray with sometimes a blue or red
+tinge. It looks like stone and will only burn when heated with oxygen.
+
+Calcium carbide may be preserved for any length of time if protected from
+the air, but the ordinary moisture in the atmosphere gradually affects it
+until nothing remains but slaked lime. It always possesses a penetrating
+odor, which is not due to the carbide itself but to the fact that it is
+being constantly affected by moisture and producing small quantities of
+acetylene gas.
+
+This material is not readily dissolved by liquids, but if allowed to come
+in contact with water, a decomposition takes place with the evolution of
+large quantities of gas. Carbide is not affected by shock, jarring or age.
+
+A pound of absolutely pure carbide will yield five and one-half cubic feet
+of acetylene. Absolute purity cannot be attained commercially, and in
+practice good carbide will produce from four and one-half to five cubic
+feet for each pound used.
+
+Carbide is prepared by fusing lime and carbon in the electric furnace under
+a heat in excess of 6,000 degrees Fahrenheit. These materials are among the
+most difficult to melt that are known. Lime is so infusible that it is
+frequently employed for the materials of crucibles in which the highest
+melting metals are fused, and for the pencils in the calcium light because
+it will stand extremely high temperatures.
+
+Carbon is the material employed in the manufacture of arc light electrodes
+and other electrical appliances that must stand extreme heat. Yet these two
+substances are forced into combination in the manufacture of calcium
+carbide. It is the excessively high temperature attainable in the electric
+furnace that causes this combination and not any effect of the electricity
+other than the heat produced.
+
+A mixture of ground coke and lime is introduced into the furnace through
+which an electric arc has been drawn. The materials unite and form an ingot
+of very pure carbide surrounded by a crust of less purity. The poorer crust
+is rejected in breaking up the mass into lumps which are graded according
+to their size. The largest size is 2 by 3-1/2 inches and is called "lump,"
+a medium size is 1/2 by 2 inches and is called "egg," an intermediate size
+for certain types of generators is 3/8 by 1-1/4 inches and called "nut,"
+and the finely crushed pieces for use in still other types of generators
+are 1/12 by 1/4 inch in size and are called "quarter." Instructions as to
+the size best suited to different generators are furnished by the makers
+of those instruments.
+
+These sizes are packed in air-tight sheet steel drums containing 100 pounds
+each. The Union Carbide Company of Chicago and New York, operating under
+patents, manufactures and distributes the supply of calcium carbide for the
+entire United States. Plants for this manufacture are established at
+Niagara Falls, New York, and Sault Ste. Marie, Michigan. This company
+maintains a system of warehouses in more than one hundred and ten cities,
+where large stocks of all sizes are carried.
+
+The National Board of Fire Underwriters gives the following rules for the
+storage of carbide:
+
+Calcium carbide in quantities not to exceed six hundred pounds may be
+stored, when contained in approved metal packages not to exceed one hundred
+pounds each, inside insured property, provided that the place of storage be
+dry, waterproof and well ventilated and also provided that all but one of
+the packages in any one building shall be sealed and that seals shall not
+be broken so long as there is carbide in excess of one pound in any other
+unsealed package in the building.
+
+Calcium carbide in quantities in excess of six hundred pounds must be
+stored above ground in detached buildings, used exclusively for the storage
+of calcium carbide, in approved metal packages, and such buildings shall be
+constructed to be dry, waterproof and well ventilated.
+
+_Properties of Acetylene._--This gas is composed of twenty-four parts
+of carbon and two parts of hydrogen by weight and is classed with natural
+gas, petroleum, etc., as one of the hydrocarbons. This gas contains the
+highest percentage of carbon known to exist in any combination of this form
+and it may therefore be considered as gaseous carbon. Carbon is the fuel
+that is used in all forms of combustion and is present in all fuels from
+whatever source or in whatever form. Acetylene is therefore the most
+powerful of all fuel gases and is able to give to the torch flame in
+welding the highest temperature of any flame.
+
+Acetylene is a colorless and tasteless gas, possessed of a peculiar and
+penetrating odor. The least trace in the air of a room is easily noticed,
+and if this odor is detected about an apparatus in operation, it is certain
+to indicate a leakage of gas through faulty piping, open valves, broken
+hose or otherwise. This leakage must be prevented before proceeding with
+the work to be done.
+
+All gases which burn in air will, when mixed with air previous to ignition,
+produce more or less violent explosions, if fired. To this rule acetylene
+is no exception. One measure of acetylene and twelve and one-half of air
+are required for complete combustion; this is therefore the proportion for
+the most perfect explosion. This is not the only possible mixture that will
+explode, for all proportions from three to thirty per cent of acetylene in
+air will explode with more or less force if ignited.
+
+The igniting point of acetylene is lower than that of coal gas, being about
+900 degrees Fahrenheit as against eleven hundred degrees for coal gas. The
+gas issuing from a torch will ignite if allowed to play on the tip of a
+lighted cigar.
+
+It is still further true that acetylene, at some pressures, greater than
+normal, has under most favorable conditions for the effect, been found to
+explode; yet it may be stated with perfect confidence that under no
+circumstances has anyone ever secured an explosion in it when subjected to
+pressures not exceeding fifteen pounds to the square inch.
+
+Although not exploded by the application of high heat, acetylene is injured
+by such treatment. It is partly converted, by high heat, into other
+compounds, thus lessening the actual quantity of the gas, wasting it and
+polluting the rest by the introduction of substances which do not belong
+there. These compounds remain in part with the gas, causing it to burn with
+a persistent smoky flame and with the deposit of objectionable tarry
+substances. Where the gas is generated without undue rise of temperature
+these difficulties are avoided.
+
+_Purification of Acetylene._--Impurities in this gas are caused by
+impurities in the calcium carbide from which it is made or by improper
+methods and lack of care in generation. Impurities from the material will
+be considered first.
+
+Impurities in the carbide may be further divided into two classes: those
+which exert no action on water and those which act with the water to throw
+off other gaseous products which remain in the acetylene. Those impurities
+which exert no action on the water consist of coke that has not been
+changed in the furnace and sand and some other substances which are
+harmless except that they increase the ash left after the acetylene has
+been generated.
+
+An analysis of the gas coming from a typical generator is as follows:
+
+                                          Per cent
+  Acetylene ................................ 99.36
+  Oxygen ...................................   .08
+  Nitrogen .................................   .11
+  Hydrogen .................................   .06
+  Sulphuretted Hydrogen ....................   .17
+  Phosphoretted Hydrogen ...................   .04
+  Ammonia ..................................   .10
+  Silicon Hydride ..........................   .03
+  Carbon Monoxide ..........................   .01
+  Methane ..................................   .04
+
+The oxygen, nitrogen, hydrogen, methane and carbon monoxide are either
+harmless or are present in such small quantities as to be neglected. The
+phosphoretted hydrogen and silicon hydride are self-inflammable gases when
+exposed to the air, but their quantity is so very small that this
+possibility may be dismissed. The ammonia and sulphuretted hydrogen are
+almost entirely dissolved by the water used in the gas generator. The
+surest way to avoid impure gas is to use high-grade calcium carbide in the
+generator and the carbide of American manufacture is now so pure that it
+never causes trouble.
+
+The first and most important purification to which the gas is subjected is
+its passage through the body of water in the generator as it bubbles to the
+top. It is then filtered through felt to remove the solid particles of lime
+dust and other impurities which float in the gas.
+
+Further purification to remove the remaining ammonia, sulphuretted hydrogen
+and phosphorus containing compounds is accomplished by chemical means. If
+this is considered necessary it can be easily accomplished by readily
+available purifying apparatus which can be attached to any generator or
+inserted between the generator and torch outlets. The following mixtures
+have been used.
+
+"_Heratol,_" a solution of chromic acid or sulphuric acid absorbed in
+porous earth.
+
+"_Acagine,_" a mixture of bleaching powder with fifteen per cent of
+lead chromate.
+
+"_Puratylene,_" a mixture of bleaching powder and hydroxide of lime,
+made very porous, and containing from eighteen to twenty per cent of active
+chlorine.
+
+"_Frankoline,_" a mixture of cuprous and ferric chlorides dissolved in
+strong hydrochloric acid absorbed in infusorial earth.
+
+A test for impure acetylene gas is made by placing a drop of ten per cent
+solution of silver nitrate on a white blotter and holding the paper in a
+stream of gas coming from the torch tip. Blackening of the paper in a short
+length of time indicates impurities.
+
+_Acetylene in Tanks._--Acetylene is soluble in water to a very limited
+extent, too limited to be of practical use. There is only one liquid that
+possesses sufficient power of containing acetylene in solution to be of
+commercial value, this being the liquid acetone. Acetone is produced in
+various ways, oftentimes from the distillation of wood. It is a
+transparent, colorless liquid that flows with ease. It boils at 133 
+Fahrenheit, is inflammable and burns with a luminous flame. It has a
+peculiar but rather agreeable odor.
+
+Acetone dissolves twenty-four times its own bulk of acetylene at ordinary
+atmospheric pressure. If this pressure is increased to two atmospheres,
+14.7 pounds above ordinary pressure, it will dissolve just twice as much of
+the gas and for each atmosphere that the pressure is increased it will
+dissolve as much more.
+
+If acetylene be compressed above fifteen pounds per square inch at ordinary
+temperature without first being dissolved in acetone a danger is present of
+self-ignition. This danger, while practically nothing at fifteen pounds,
+increases with the pressure until at forty atmospheres it is very
+explosive. Mixed with acetone, the gas loses this dangerous property and is
+safe for handling and transportation. As acetylene is dissolved in the
+liquid the acetone increases its volume slightly so that when the gas has
+been drawn out of a closed tank a space is left full of free acetylene.
+
+This last difficulty is removed by first filling the cylinder or tank with
+some porous material, such as asbestos, wood charcoal, infusorial earth,
+etc. Asbestos is used in practice and by a system of packing and supporting
+the absorbent material no space is left for the free gas, even when the
+acetylene has been completely withdrawn.
+
+The acetylene is generated in the usual way and is washed, purified and
+dried. Great care is used to make the gas as free as possible from all
+impurities and from air. The gas is forced into containers filled with
+acetone as described and is compressed to one hundred and fifty pounds to
+the square inch. From these tanks it is transferred to the smaller portable
+cylinders for consumers' use.
+
+The exact volume of gas remaining in a cylinder at atmospheric temperature
+may be calculated if the weight of the cylinder empty is known. One pound
+of the gas occupies 13.6 cubic feet, so that if the difference in weight
+between the empty cylinder and the one considered be multiplied by 13.6.
+the result will be the number of cubic feet of gas contained.
+
+The cylinders contain from 100 to 500 cubic feet of acetylene under
+pressure. They cannot be filled with the ordinary type of generator as they
+require special purifying and compressing apparatus, which should never be
+installed in any building where other work is being carried on, or near
+other buildings which are occupied, because of the danger of explosion.
+
+Dissolved acetylene is manufactured by the Prest-O-Lite Company, the
+Commercial Acetylene Company and the Searchlight Gas Company and is
+distributed from warehouses in various cities.
+
+These tanks should not be discharged at a rate per hour greater than
+one-seventh of their total capacity, that is, from a tank of 100 cubic feet
+capacity, the discharge should not be more than fourteen cubic feet per
+hour. If discharge is carried on at an excessive rate the acetone is drawn
+out with the gas and reduces the heat of the welding flame.
+
+For this reason welding should not be attempted with cylinders designed for
+automobile and boat lighting. When the work demands a greater delivery than
+one of the larger tanks will give, two or more tanks may be connected with
+a special coupler such as may be secured from the makers and distributers
+of the gas. These couplers may be arranged for two, three, four or five
+tanks in one battery by removing the plugs on the body of the coupler and
+attaching additional connecting pipes. The coupler body carries a pressure
+gauge and the valve for controlling the pressure of the gas as it flows to
+the welding torches. The following capacities should be provided for:
+
+Acetylene Consumption         Combined Capacity of
+ of Torches per Hour           Cylinders in Use
+Up to 15 feet.......................100 cubic feet
+16 to 30 feet.......................200 cubic feet
+31 to 45 feet.......................300 cubic feet
+46 to 60 feet.......................400 cubic feet
+61 to 75 feet.......................500 cubic feet
+
+
+WELDING RODS
+
+The best welding cannot be done without using the best grade of materials,
+and the added cost of these materials over less desirable forms is so
+slight when compared to the quality of work performed and the waste of
+gases with inferior supplies, that it is very unprofitable to take any
+chances in this respect. The makers of welding equipment carry an
+assortment of supplies that have been standardized and that may be relied
+upon to produce the desired result when properly used. The safest plan is
+to secure this class of material from the makers.
+
+Welding rods, or welding sticks, are used to supply the additional metal
+required in the body of the weld to replace that broken or cut away and
+also to add to the joint whenever possible so that the work may have the
+same or greater strength than that found in the original piece. A rod of
+the same material as that being welded is used when both parts of the work
+are the same. When dissimilar metals are to be joined rods of a composition
+suited to the work are employed.
+
+These filling rods are required in all work except steel of less than 16
+gauge. Alloy iron rods are used for cast iron. These rods have a high
+silicon content, the silicon reacting with the carbon in the iron to
+produce a softer and more easily machined weld than would otherwise be the
+case. These rods are often made so that they melt at a slightly lower point
+than cast iron. This is done for the reason that when the part being welded
+has been brought to the fusing heat by the torch, the filling material can
+be instantly melted in without allowing the parts to cool. The metal can be
+added faster and more easily controlled.
+
+Rods or wires of Norway iron are used for steel welding in almost all
+cases. The purity of this grade of iron gives a homogeneous, soft weld of
+even texture, great ductility and exceptionally good machining qualities.
+For welding heavy steel castings, a rod of rolled carbon steel is employed.
+For working on high carbon steel, a rod of the steel being welded must be
+employed and for alloy steels, such as nickel, manganese, vanadium, etc.,
+special rods of suitable alloy composition are preferable.
+
+Aluminum welding rods are made from this metal alloyed to give the even
+flowing that is essential. Aluminum is one of the most difficult of all the
+metals to handle in this work and the selection of the proper rod is of
+great importance.
+
+Brass is filled with brass wire when in small castings and sheets. For
+general work with brass castings, manganese bronze or Tobin bronze may be
+used.
+
+Bronze is welded with manganese bronze or Tobin bronze, while copper is
+filled with copper wire.
+
+These welding rods should always be used to fill the weld when the
+thickness of material makes their employment necessary, and additional
+metal should always be added at the weld when possible as the joint cannot
+have the same strength as the original piece if made or dressed off flush
+with the surfaces around the weld. This is true because the metal welded
+into the joint is a casting and will never have more strength than a
+casting of the material used for filling.
+
+Great care should be exercised when adding metal from welding rods to make
+sure that no metal is added at a point that is not itself melted and molten
+when the addition is made. When molten metal is placed upon cooler surfaces
+the result is not a weld but merely a sticking together of the two parts
+without any strength in the joint.
+
+
+FLUXES
+
+Difficulty would be experienced in welding with only the metal and rod to
+work with because of the scale that forms on many materials under heat, the
+oxides of other metals and the impurities found in almost all metals. These
+things tend to prevent a perfect joining of the metals and some means are
+necessary to prevent their action.
+
+Various chemicals, usually in powder form, are used to accomplish the
+result of cleaning the weld and making the work of the operator less
+difficult. They are called fluxes.
+
+A flux is used to float off physical impurities from the molten metal; to
+furnish a protecting coating around the weld; to assist in the removal of
+any objectionable oxide of the metals being handled; to lower the
+temperature at which the materials flow; to make a cleaner weld and to
+produce a better quality of metal in the finished work.
+
+The flux must be of such composition that it will accomplish the desired
+result without introducing new difficulties. They may be prepared by the
+operator in many cases or may be secured from the makers of welding
+apparatus, the same remarks applying to their quality as were made
+regarding the welding rods, that is, only the best should be considered.
+
+The flux used for cast iron should have a softening effect and should
+prevent burning of the metal. In many cases it is possible and even
+preferable to weld cast iron without the use of a flux, and in any event
+the smaller the quantity used the better the result should be. Flux should
+not be added just before the completion of the work because the heat will
+not have time to drive the added elements out of the metal or to
+incorporate them with the metal properly.
+
+Aluminum should never be welded without using a flux because of the oxide
+formed. This oxide, called alumina, does not melt until a heat of 5,000 
+Fahrenheit is reached, four times the heat needed to melt the aluminum
+itself. It is necessary that this oxide be broken down or dissolved so that
+the aluminum may have a chance to flow together. Copper is another metal
+that requires a flux because of its rapid oxidation under heat.
+
+While the flux is often thrown or sprinkled along the break while welding,
+much better results will be obtained by dipping the hot end of the welding
+rod into the flux whenever the work needs it. Sufficient powder will stick
+on the end of the rod for all purposes, and with some fluxes too much will
+adhere. Care should always be used to avoid the application of excessive
+flux, as this is usually worse than using too little.
+
+
+SUPPLIES AND FIXTURES
+
+_Goggles._--The oxy-acetylene torch should not be used without the
+protection to the eyes afforded by goggles. These not only relieve
+unnecessary strain, but make it much easier to watch the exact progress of
+the work with the molten metal. The difficulty of protecting the sight
+while welding is even greater than when cutting metal with the torch.
+
+Acetylene gives a light which is nearest to sunlight of any artificial
+illuminant. But for the fact that this gas light gives a little more green
+and less blue in its composition, it would be the same in quality and
+practically the same in intensity. This light from the gas is almost absent
+during welding, being lost with the addition of the extra oxygen needed to
+produce the welding heat. The light that is dangerous comes from the molten
+metal which flows under the torch at a bright white heat.
+
+Goggles for protection against this light and the heat that goes with it
+may be secured in various tints, the darker glass being for welding and
+the lighter for cutting. Those having frames in which the metal parts do
+not touch the flesh directly are most desirable because of the high
+temperature reached by these parts.
+
+_Gloves._--While not as necessary as are the goggles, gloves are a
+convenience in many cases. Those in which leather touches the hands
+directly are really of little value as the heat that protection is desired
+against makes the leather so hot that nothing is gained in comfort. Gloves
+are made with asbestos cloth, which are not open to this objection in so
+great a degree.
+
+[Illustration: Figure 9.--Frame for Welding Stand]
+
+_Tables and Stands._--Tables for holding work while being welded
+(Figure 9) are usually made from lengths of angle steel welded together.
+The top should be rectangular, about two feet wide and two and one-half
+feet long. The legs should support the working surface at a height of
+thirty-two to thirty-six inches from the floor. Metal lattice work may be
+fastened or laid in the top framework and used to support a layer of
+firebrick bound together with a mixture of one-third cement and two-thirds
+fireclay. The piece being welded is braced and supported on this table with
+pieces of firebrick so that it will remain stationary during the operation.
+
+Holders for supporting the tanks of gas may be
+made or purchased in forms that rest directly on the floor or that are
+mounted on wheels. These holders are quite useful where the floor or ground
+is very uneven.
+
+_Hose._--All permanent lines from tanks and generators to the torches
+are made with piping rigidly supported, but the short distance from the end
+of the pipe line to the torch itself is completed with a flexible hose so
+that the operator may be free in his movements while welding. An accident
+through which the gases mix in the hose and are ignited will burst this
+part of the equipment, with more or less painful results to the person
+handling it. For that reason it is well to use hose with great enough
+strength to withstand excessive pressure.
+
+A poor grade of hose will also break down inside and clog the flow of gas,
+both through itself and through the parts of the torch. To avoid outside
+damage and cuts this hose is sometimes encased with coiled sheet metal.
+Hose may be secured with a bursting strength of more than 1,000 pounds to
+the square inch. Many operators prefer to distinguish between the oxygen
+and acetylene lines by their color and to allow this, red is used for the
+oxygen and black for acetylene.
+
+_Other Materials._--Sheet asbestos and asbestos fibre in flakes are
+used to cover parts of the work while preparing them for welding and during
+the operation itself. The flakes and small pieces that become detached from
+the large sheets are thrown into a bin where the completed small work is
+placed to allow slow and even cooling while protected by the asbestos.
+
+Asbestos fibre and also ordinary fireclay are often used to make a backing
+or mould into a form that may be placed behind aluminum and some other
+metals that flow at a low heat and which are accordingly difficult to
+handle under ordinary methods. This forms a solid mould into which the
+metal is practically cast as melted by the torch so that the desired shape
+is secured without danger of the walls of metal breaking through and
+flowing away.
+
+Carbon blocks and rods are made in various shapes and sizes so that they
+may be used to fill threaded holes and other places that it is desired to
+protect during welding. These may be secured in rods of various diameters
+up to one inch and in blocks of several different dimensions.
+
+
+
+
+CHAPTER III
+
+ACETYLENE GENERATORS
+
+
+Acetylene generators used for producing the gas from the action of water on
+calcium carbide are divided into three principal classes according to the
+pressure under which they operate.
+
+Low pressure generators are designed to operate at one pound or less per
+square inch. Medium pressure systems deliver the gas at not to exceed
+fifteen pounds to the square inch while high pressure types furnish gas
+above fifteen pounds per square inch. High pressure systems are almost
+unknown in this country, the medium pressure type being often referred to
+as "high pressure."
+
+Another important distinction is formed by the method of bringing the
+carbide and water together. The majority of those now in use operate by
+dropping small quantities of carbide into a large volume of water, allowing
+the generated gas to bubble up through the water before being collected
+above the surface. This type is known as the "carbide to water" generator.
+
+A less used type brings a measured and small quantity of water to a
+comparatively large body of the carbide, the gas being formed and collected
+from the chamber in which the action takes place. This is called the "water
+to carbide" type. Another way of expressing the difference in feed is that
+of designating the two types as "carbide feed" for the former and "water
+feed" for the latter.
+
+A further division of the carbide to water machines is made by mentioning
+the exact method of feeding the carbide. One type, called "gravity feed"
+operates by allowing the carbide to escape and fall by the action of its
+own weight, or gravity; the other type, called "forced feed," includes a
+separate mechanism driven by power. This mechanism feeds definite amounts
+of the carbide to the water as required by the demands on the generator.
+The action of either feed is controlled by the withdrawal of gas from the
+generator, the aim being to supply sufficient carbide to maintain a nearly
+constant supply.
+
+_Generator Requirements._--The qualities of a good generator are
+outlined as follows: [Footnote: See Pond's "Calcium Carbide and
+Acetylene."]
+
+It must allow no possibility of the existence of an explosive mixture in
+any of its parts at any time. It is not enough to argue that a mixture,
+even if it exists, cannot be exploded unless kindled. It is necessary to
+demand that a dangerous mixture can at no time be formed, even if the
+machine is tampered with by an ignorant person. The perfect machine must be
+so constructed that it shall be impossible at any time, under any
+circumstances, to blow it up.
+
+It must insure cool generation. Since this is a relative term, all machines
+being heated somewhat during the generation of gas, this amounts to saying
+that a machine must heat but little. A pound of carbide decomposed by water
+develops the same amount of heat under all circumstances, but that heat
+can be allowed to increase locally to a high point, or it can be equalized
+by water so that no part of the material becomes heated enough to do
+damage.
+
+It must be well constructed. A good generator does not need, perhaps, to be
+"built like a watch," but it should be solid, substantial and of good
+material. It should be built for service, to last and not simply to sell;
+anything short of this is to be avoided as unsafe and unreliable.
+
+It must be simple. The more complicated the machine the sooner it will get
+out of order. Understand your generator. Know what is inside of it and
+beware of an apparatus, however attractive its exterior, whose interior is
+filled with pipes and tubes, valves and diaphragms whose functions you do
+not perfectly understand.
+
+It should be capable of being cleaned and recharged and of receiving all
+other necessary attention without loss of gas, both for economy's sake, and
+more particularly to avoid danger of fire.
+
+It should require little attention. All machines have to be emptied and
+recharged periodically; but the more this process is simplified and the
+more quickly this can be accomplished, the better.
+
+It should be provided with a suitable indicator to designate how low the
+charge is in order that the refilling may be done in good season.
+
+It should completely use up the carbide, generating the maximum amount of
+gas.
+
+_Overheating._--A large amount of heat is liberated when acetylene gas
+is formed from the union of calcium carbide and water. Overheating during
+this process, that is to say, an intense local heat rather than a large
+amount of heat well distributed, brings about the phenomenon of
+polymerization, converting the gas, or part of it, into oily matters, which
+can do nothing but harm. This tarry mass coming through the small openings
+in the torches causes them to become partly closed and alters the
+proportions of the gases to the detriment of the welding flame. The only
+remedy for this trouble is to avoid its cause and secure cool generation.
+
+Overheating can be detected by the appearance of the sludge remaining after
+the gas has been made. Discoloration, yellow or brown, shows that there has
+been trouble in this direction and the resultant effects at the torches may
+be looked for. The abundance of water in the carbide to water machines
+effects this cooling naturally and is a characteristic of well designed
+machines of this class. It has been found best and has practically become a
+fundamental rule of generation that a gallon of water must be provided for
+each pound of carbide placed in the generator. With this ratio and a
+generator large enough for the number of torches to be supplied, little
+trouble need be looked for with overheating.
+
+_Water to Carbide Generators._--It is, of course, much easier to
+obtain a measured and regular flow of water than to obtain such a flow of
+any solid substance, especially when the solid substance is in the form of
+lumps, as is carbide This fact led to the use of a great many water-feed
+generators for all classes of work, and this type is still in common use
+for the small portable machines, such, for instance, as those used on motor
+cars for the lamps. The water-feed machine is not, however, favored for
+welding plants, as is the carbide feed, in spite of the greater
+difficulties attending the handling of the solid material.
+
+A water-feed generator is made up of the gas producing part and a holder
+for the acetylene after it is made. The carbide is held in a tray formed of
+a number of small compartments so that the charge in each compartment is
+nearly equal to that in each of the others. The water is allowed to flow
+into one of these compartments in a volume sufficient to produce the
+desired amount of gas and the carbide is completely used from this one
+division. The water then floods the first compartment and finally overflows
+into the next one, where the same process is repeated. After using the
+carbide in this division, it is flooded in turn and the water passing on to
+those next in order, uses the entire charge of the whole tray.
+
+These generators are charged with the larger sizes of carbide and are
+easily taken care of. The residue is removed in the tray and emptied,
+making the generator ready for a fresh supply of carbide.
+
+_Carbide to Water Generators._--This type also is made up of two
+principal parts, the generating chamber and a gas holder, the holder being
+part of the generating chamber or a separate device. The generator (Figure
+10) contains a hopper to receive the charge of carbide and is fitted with
+the feeding mechanism to drop the proper amount of carbide into the water
+as required by the demands of the torches. The charge of carbide is of one
+of the smaller sizes, usually "nut" or "quarter."
+
+_Feed Mechanisms._--The device for dropping the carbide into the water
+is the only part of the machine that is at all complicated. This
+complication is brought about by the necessity of controlling the mass of
+carbide so that it can never be discharged into the water at an excessive
+rate, feeding it at a regular rate and in definite amounts, feeding it
+positively whenever required and shutting off the feed just as positively
+when the supply of gas in the holder is enough for the immediate needs.
+
+[Illustration: Figure 10.--Carbide to Water Generator. A. Feed motor weight;
+B. Carbide feed motor; C. Carbide hopper; D. Water for gas generation;
+E. Agitator for loosening residuum; F. Water seal in gas bell; G. Filter;
+H. Hydraulic Valve; J. Motor control levers.]
+
+The charge of carbide is unavoidably acted upon by the water vapor in the
+generator and will in time become more or less pasty and sticky. This is
+more noticeable if the generator stands idle for a considerable length of
+time This condition imposes another duty on the feeding mechanism; that is,
+the necessity of self-cleaning so that the carbide, no matter in what
+condition, cannot prevent the positive action of this part of the device,
+especially so that it cannot prevent the supply from being stopped at the
+proper time.
+
+The gas holder is usually made in the bell form so that the upper portion
+rises and falls with the addition to or withdrawal from the supply of gas
+in the holder. The rise and fall of this bell is often used to control the
+feed mechanism because this movement indicates positively whether enough
+gas has been made or that more is required. As the bell lowers it sets the
+feed mechanism in motion, and when the gas passing into the holder has
+raised the bell a sufficient distance, the movement causes the feed
+mechanism to stop the fall of carbide into the water. In practice, the
+movement of this part of the holder is held within very narrow limits.
+
+_Gas Holders._--No matter how close the adjustment of the feeding
+device, there will always be a slight amount of gas made after the fall of
+carbide is stopped, this being caused by the evolution of gas from the
+carbide with which water is already in contact. This action is called
+"after generation" and the gas holder in any type of generator must
+provide sufficient capacity to accommodate this excess gas. As a general
+rule the water to carbide generator requires a larger gas holder than the
+carbide to water type because of the greater amount of carbide being acted
+upon by the water at any one time, also because the surface of carbide
+presented to the moist air within the generating chamber is greater with
+this type.
+
+_Freezing._--Because of the rather large body of water contained in
+any type of generator, there is always danger of its freezing and
+rendering the device inoperative unless placed in a temperature above the
+freezing point of the water. It is, of course, dangerous and against the
+insurance rules to place a generator in the same room with a fire of any
+kind, but the room may be heated by steam or hot water coils from a furnace
+in another building or in another part of the same building.
+
+When the generator is housed in a separate structure the walls should be
+made of materials or construction that prevents the passage of heat or
+cold through them to any great extent. This may be accomplished by the use
+of hollow tile or concrete blocks or by any other form of double wall
+providing air spaces between the outer and inner facings. The space between
+the parts of the wall may be filled with materials that further retard the
+loss of heat if this is necessary under the conditions prevailing.
+
+_Residue From Generators._--The sludge remaining in the carbide to
+water generator may be drawn off into the sewer if the piping is run at a
+slant great enough to give a fall that carries the whole quantity, both
+water and ash, away without allowing settling and consequent clogging.
+Generators are provided with agitators which are operated to stir the ash
+up with the water so that the whole mass is carried off when the drain cock
+is opened.
+
+If sewer connections cannot be made in such a way that the ash is entirely
+carried away, it is best to run the liquid mass into a settling basin
+outside of the building. This should be in the form of a shallow pit which
+will allow the water to pass off by soaking into the ground and by
+evaporation, leaving the comparatively dry ash in the pit. This ash which
+remains is essentially slaked lime and can often be disposed of to more or
+less advantage to be used in mortar, whitewash, marking paths and any other
+use for which slaked lime is suited. The disposition of the ash depends
+entirely on local conditions. An average analysis of this ash is as
+follows:
+
+Sand.......................  1.10 per cent.
+Carbon.....................  2.72    "
+Oxide of iron and alumina..  2.77    "
+Lime....................... 64.06    "
+Water and carbonic acid.... 29.35    "
+                           ------
+                           100.00
+
+
+GENERATOR CONSTRUCTION
+
+The water for generating purposes is carried in the large tank-like
+compartment directly below the carbide chamber. See Figure 11. This water
+compartment is filled through a pipe of such a height that the water level
+cannot be brought above the proper point or else the water compartment is
+provided with a drain connection which accomplishes this same result by
+allowing an excess to flow away.
+
+The quantity of water depends on the capacity of the generator inasmuch as
+there must be one gallon for each pound of carbide required. The generator
+should be of sufficient capacity to furnish gas under working conditions
+from one charge of carbide to all torches installed for at least five hours
+continuous use.
+
+After calculating the withdrawal of the whole number of torches according
+to the work they are to do for this period of five hours the proper
+generator capacity may be found on the basis of one cubic foot of gas per
+hour for each pound of carbide. Thus if the torches were to use sixty cubic
+feet of gas per hour, five hours would call for three hundred cubic feet
+and a three hundred pound generator should be installed. Generators are
+rated according to their carbide capacity in pounds.
+
+_Charging._--The carbide capacity of the generator should be great
+enough to furnish a continuous supply of gas for the maximum operating
+time, basing the quantity of gas generated on four and one-half cubic feet
+from each pound of lump carbide and on four cubic feet from each pound of
+quarter, intermediate sizes being in proportion.
+
+Generators are built in such a way that it is impossible for the acetylene
+to escape from the gas holding compartment during the recharging process.
+This is accomplished (1) by connecting the water inlet pipe opening with a
+shut off valve in such a way that the inlet cannot be uncovered or opened
+without first closing the shut off valve with the same movement of the
+operator; (2) by incorporating an automatic or hydraulic one-way valve so
+that this valve closes and acts as a check when the gas attempts to flow
+from the holder back to the generating chamber, or by any other means that
+will positively accomplish this result.
+
+In generators having no separate gas holding chamber but carrying the
+supply in the same compartment in which it is generated, the gas contained
+under pressure is allowed to escape through vent pipes into the outside
+air before recharging with carbide. As in the former case, the parts are
+so interlocked that it is impossible to introduce carbide or water without
+first allowing the escape of the gas in the generator.
+
+It is required by the insurance rules that the entire change of carbide
+while in the generator be held in such a way that it may be entirely
+removed without difficulty in case the necessity should arise.
+
+Generators should be cleaned and recharged at regular stated intervals.
+This work should be done during daylight hours only and likewise all
+repairs should be made at such a time that artificial light is not needed.
+Where it is absolutely necessary to use artificial light it should be
+provided only by incandescent electric lamps enclosed in gas tight globes.
+
+In charging generating chambers the old ash and all residue must first be
+cleaned out and the operator should be sure that no drain or other pipe has
+become clogged. The generator should then be filled with the required
+amount of water. In charging carbide feed machines be careful not to place
+less than a gallon of water in the water compartment for each pound of
+carbide to be used and the water must be brought to, but not above, the
+proper level as indicated by the mark or the maker's instructions. The
+generating chamber must be filled with the proper amount of water before
+any attempt is made to place the carbide in its holder. This rule must
+always be followed. It is also necessary that all automatic water seals
+and valves, as well as any other water tanks, be filled with clean water
+at this time.
+
+Never recharge with carbide without first cleaning the generating chamber
+and completely refilling with clean water. Never test the generator or
+piping for leaks with any flame, and never apply flame to any open pipe or
+at any point other than the torch, and only to the torch after it has a
+welding or cutting nozzle attached. Never use a lighted match, lamp,
+candle, lantern, cigar or any open flame near a generator. Failure to
+observe these precautions is liable to endanger life and property.
+
+_Operation and Care of Generators._--The following instructions apply
+especially to the Davis Bournonville pressure generator, illustrated in
+Figure 11. The motor feed mechanism is illustrated in Figure 12.
+
+Before filling the machine, the cover should be removed and the hopper
+taken out and examined to see that the feeding disc revolves freely; that
+no chains have been displaced or broken, and that the carbide displacer
+itself hangs barely free of the feeding disc when it is revolved. After
+replacing the cover, replace the bolts and tighten them equally, a little
+at a time all around the circumference of the cover--not screwing tight in
+one place only. Do not screw the cover down any more than is necessary to
+make a tight fit.
+
+To charge the generator, proceed as follows: Open the vent valve by turning
+the handle which extends over the filling tube until it stands at a right
+angle with the generator. Open the valve in the water filling pipe, and
+through this fill with water until it runs out of the overflow pipe of the
+drainage chamber, then close the valve in the water filling pipe and vent
+valve. Remove the carbide filling plugs and fill the hopper with
+1-1/4"x3/8" carbide ("nut" size). Then replace the plugs and the
+safety-locking lever chains. Now rewind the motor weight. Run the pressure
+up to about five pounds by raising the controlling diaphragm valve lever
+by hand (Figure 12, lever marked _E_). Then raise the blow-off lever,
+allowing the gas to blow off until the gauge shows about two pounds; this
+to clear the generator of air mixture. Then run the pressure up to about
+eight pounds by raising the controlling valve lever _E_, or until
+this controlling lever rests against the upper wing of the fan governor,
+and prevents operation of the feed motor. After this is done, the motor
+will operate automatically as the gas is consumed.
+
+[Illustration: Figure 11.--Pressure Generator (Davis Bournonville).
+_A_, Feed motor weight;
+_B_, Carbide feed motor;
+_C_, Motor Control diaphragm;
+_D_, Carbide hopper;
+_E_, Carbide feed disc;
+_F_, Overflow pipe;
+_G_, Overflow pipe seal;
+_H_, Overflow pipe valve;
+_J_, Filling funnel;
+_K_, Hydraulic valve;
+_L_, Expansion chamber;
+_M_, Escape pipe;
+_N_, Feed pipe;
+_O_, Agitator for residuum;
+_P_, Residuum valve;
+_Q_, Water level]
+
+[Illustration: Figure 12.--Feed Mechanism of Pressure Generator]
+
+Should the pressure rise much above the blow-off point, the safety
+controlling diaphragm valve will operate and throw the safety clutch in
+interference and thus stop the motor. This interference clutch will then
+have to be returned to its former position before the motor will operate,
+but cannot be replaced before the pressure has been reduced below the
+blow-off point.
+
+The parts of the feed mechanism illustrated in Figure 12 are as follows:
+_A_, motor drum for weight cable. _B_, carbide filling plugs.
+_C_, chains for connecting safety locking lever of motor to pins on
+the top of the carbide plugs. _D_, interference clutch of motor.
+_E_, lever on feed controlling diaphragm valve. _F_, lever of
+interference controlling diaphragm valve that operates interference clutch.
+_G_, feed controlling diaphragm valve. _H_, diaphragm valve
+controlling operation of interference clutch. _I_, interference pin
+to engage emergency clutch. _J_, main shaft driving carbide feeding
+disc. _Y_, safety locking lever.
+
+_Recharging Generator._--Turn the agitator handle rapidly for several
+revolutions, and then open the residuum valve, having five or six pounds
+gas pressure on the machine. If the carbide charge has been exhausted and
+the motor has stopped, there is generally enough carbide remaining in the
+feeding disc that can be shaken off, and fed by running the motor to
+obtain some pressure in the generator. The desirability of discharging
+the residuum with some gas pressure is because the pressure facilitates
+the discharge and at the same time keeps the generator full of gas,
+preventing air mixture to a great extent. As soon as the pressure is
+relieved by the withdrawal of the residuum, the vent valve should be
+opened, as if the pressure is maintained until all of the residuum is
+discharged gas would escape through the discharge valve.
+
+Having opened the vent pipe valve and relieved the pressure, open the
+valve in the water filling tube. Close the residuum valve, then run in
+several gallons of water and revolve the agitator, after which draw out the
+remaining residuum; then again close the residuum valve and pour in water
+until it discharges from the overflow pipe of the drainage chamber. It is
+desirable in filling the generator to pour the water in rapidly enough to
+keep the filling pipe full of water, so that air will not pass in at the
+same time.
+
+After the generator is cleaned and filled with water, fill with carbide and
+proceed in the same manner as when first charging.
+
+_Carbide Feed Mechanism._--Any form of carbide to water machine should
+be so designed that the carbide never falls directly from its holder into
+the water, but so that it must take a more or less circuitous path. This
+should be true, no matter what position the mechanism is in. One of the
+commonest types of forced feed machine carries the carbide in a hopper with
+slanting sides, this hopper having a large opening in the bottom through
+which the carbide passes to a revolving circular plate. As the pieces of
+carbide work out toward the edge of the plate under the influence of the
+mass behind them, they are thrown off into the water by small stationary
+fins or plows which are in such a position that they catch the pieces
+nearest the edges and force them off as the plate revolves. This
+arrangement, while allowing a free passage for the carbide, prevents an
+excess from falling should the machine stop in any position.
+
+When, as is usually the case, the feed mechanism is actuated by the rise
+or fall of pressure in the generator or of the level of some part of the
+gas holder, it must be built in such a way that the feeding remains
+inoperative as long as the filling opening on the carbide holder remains
+open.
+
+The feed of carbide should always be shut off and controlled so that under
+no condition can more gas be generated than could be cared for by the
+relief valve provided. It is necessary also to have the feed mechanism at
+least ten inches above the surface of the water so that the parts will
+never become clogged with damp lime dust.
+
+_Motor Feed._--The feed mechanism itself is usually operated by power
+secured from a slowly falling weight which, through a cable, revolves a
+drum. To this drum is attached suitable gearing for moving the feed parts
+with sufficient power and in the way desired. This part, called the motor,
+is controlled by two levers, one releasing a brake and allowing the motor
+to operate the feed, the other locking the gearing so that no more carbide
+will be dropped into the water. These levers are moved either by the
+quantity of gas in the holder or by the pressure of the gas, depending on
+the type of machine.
+
+With a separate gas holder, such as used with low pressure systems, the
+levers are operated by the rise and fall of the bell of the holder or
+gasometer, alternately starting and stopping the motor as the bell falls
+and rises again. Medium pressure generators are provided with a diaphragm
+to control the feed motor.
+
+This diaphragm is carried so that the pressure within the generator acts
+on one side while a spring, whose tension is under the control of the
+operator, acts on the other side. The diaphragm is connected to the brake
+and locking device on the motor in such a way that increasing the tension
+on the spring presses the diaphragm and moves a rod that releases the brake
+and starts the feed. The gas pressure, increasing with the continuation of
+carbide feed, acts on the other side and finally overcomes the pressure of
+the spring tension, moving the control rod the other way and stopping the
+motor and carbide feed. This spring tension is adjusted and checked with
+the help of a pressure gauge attached to the generating chamber.
+
+_Gravity Feed._--This type of feed differs from the foregoing in that
+the carbide is simply released and is allowed to fall into the water
+without being forced to do so. Any form of valve that is sufficiently
+powerful in action to close with the carbide passing through is used and is
+operated by the power secured from the rise and fall of the gas holder
+bell. When this valve is first opened the carbide runs into the water until
+sufficient pressure and volume of gas is generated to raise the bell. This
+movement operates the arm attached to the carbide shut off valve and slowly
+closes it. A fall of the bell occasioned by gas being withdrawn again opens
+the valve and more gas is generated.
+
+_Mechanical Feed._--The previously described methods of feeding
+carbide to the water have all been automatic in action and do not depend
+on the operator for their proper action.
+
+Some types of large generating plants have a power-driven feed, the power
+usually being from some kind of motor other than one operated by a weight,
+such as a water motor, for instance. This motor is started and stopped by
+the operator when, in his judgment, more gas is wanted or enough has been
+generated. This type of machine, often called a "non-automatic generator,"
+is suitable for large installations and is attached to a gas holder of
+sufficient size to hold a day's supply of acetylene. The generator can then
+be operated until a quantity of gas has been made that will fill the large
+holder, or gasometer, and then allowed to remain idle for some time.
+
+_Gas Holders._--The commonest type of gas container is that known as a
+gasometer. This consists of a circular tank partly filled with water, into
+which is lowered another circular tank, inverted, which is made enough
+smaller in diameter than the first one so that three-quarters of an inch is
+left between them. This upper and inverted portion, called the bell,
+receives the gas from the generator and rises or falls in the bath of water
+provided in the lower tank as a greater or less amount of gas is contained
+in it.
+
+These holders are made large enough so that they will provide a means of
+caring for any after generation and so that they maintain a steady and even
+flow. The generator, however, must be of a capacity great enough so that
+the gas holder will not be drawn on for part of the supply with all torches
+in operation. That is, the holder must not be depended on for a reserve
+supply.
+
+The bell of the holder is made so that when full of gas its lower edge is
+still under a depth of at least nine inches of water in the lower tank. Any
+further rise beyond this point should always release the gas, or at least
+part of it, to the escape pipe so that the gas will under no circumstances
+be forced into the room from, between the bell and tank. The bell is guided
+in its rise and fall by vertical rods so that it will not wedge at any
+point in its travel.
+
+A condensing chamber to receive the water which condenses from the
+acetylene gas in the holder is usually placed under this part and is
+provided with a drain so that this water of condensation may be easily
+removed.
+
+_Filtering._--A small chamber containing some closely packed but
+porous material such as felt is placed in the pipe leading to the torch
+lines. As the acetylene gas passes through this filter the particles of
+lime dust and other impurities are extracted from it so that danger of
+clogging the torch openings is avoided as much as possible.
+
+The gas is also filtered to a large extent by its passage through the water
+in the generating chamber, this filtering or "scrubbing" often being
+facilitated by the form of piping through which the gas must pass from the
+generating chamber into the holder. If the gas passes out of a number of
+small openings when going into the holder the small bubbles give a better
+washing than large ones would.
+
+_Piping._--Connections from generators to service pipes should
+preferably be made with right and left couplings or long thread nipples
+with lock nuts. If unions are used, they should be of a type that does not
+require gaskets. The piping should be carried and supported so that any
+moisture condensing in the lines will drain back toward the generator and
+where low points occur they should be drained through tees leading into
+drip cups which are permanently closed with screw caps or plugs. No pet
+cocks should be used for this purpose.
+
+For the feed pipes to the torch lines the following pipe sizes are
+recommended.
+
+    3/8 inch pipe.  26 feet long.   2 cubic feet per hour.
+    1/2 inch pipe.  30 feet long.   4 cubic feet per hour.
+    3/4 inch pipe.  50 feet long.  15 cubic feet per hour.
+  1     inch pipe.  70 feet long.  27 cubic feet per hour.
+  1-1/4 inch pipe. 100 feet long.  50 cubic feet per hour.
+  1-1/2 inch pipe. 150 feet long.  65 cubic feet per hour.
+  2     inch pipe. 200 feet long. 125 cubic feet per hour.
+  2-1/2 inch pipe. 300 feet long. 190 cubic feet per hour.
+  3     inch pipe. 450 feet long. 335 cubic feet per hour.
+
+When drainage is possible into a sewer, the generator should not be
+connected directly into the sewer but should first discharge into an open
+receptacle, which may in turn be connected to the sewer.
+
+No valves or pet cocks should open into the generator room or any other
+room when it would be possible, by opening them for draining purposes, to
+allow any escape of gas. Any condensation must be removed without the use
+of valves or other working parts, being drained into closed receptacles. It
+should be needless to say that all the piping for gas must be perfectly
+tight at every point in its length.
+
+_Safety Devices._--Good generators are built in such a way that the
+operator must follow the proper order of operation in charging and cleaning
+as well as in all other necessary care. It has been mentioned that the gas
+pressure is released or shut off before it is possible to fill the water
+compartment, and this same idea is carried further in making the generator
+inoperative and free from gas pressure before opening the residue drain of
+the carbide filling opening on top of the hopper. Some machines are made so
+that they automatically cease to generate should there be a sudden and
+abnormal withdrawal of gas such as would be caused by a bad leak. This
+method of adding safety by automatic means and interlocking parts may be
+carried to any extent that seems desirable or necessary to the maker.
+
+All generators should be provided with escape or relief pipes of large size
+which lead to the open air. These pipes are carried so that condensation
+will drain back toward the generator and after being led out of the
+building to a point at least twelve feet above ground, they end in a
+protecting hood so that no rain or solid matter can find its way into them.
+Any escape of gas which might ordinarily pass into the generator room is
+led into these escape pipes, all parts of the system being connected with
+the pipe so that the gas will find this way out.
+
+Safety blow off valves are provided so that any excess gas which cannot be
+contained by the gas holder may be allowed to escape without causing an
+undue rise in pressure. This valve also allows the escape of pressure above
+that for which the generator was designed. Gas released in this way passes
+into the escape pipe just described.
+
+Inasmuch as the pressure of the oxygen is much greater than that of the
+acetylene when used in the torch, it will be seen that anything that caused
+the torch outlet to become closed would allow the oxygen to force the
+acetylene back into the generator and the oxygen would follow it, making a
+very explosive mixture. This return of the gas is prevented by a hydraulic
+safety valve or back pressure valve, as it is often called.
+
+Mechanical check valves have been found unsuitable for this use and those
+which employ water as a seal are now required by the insurance rules. The
+valve itself (Figure 13) consists of a large cylinder containing water to a
+certain depth, which is indicated on the valve body. Two pipes come into
+the upper end of this cylinder and lead down into the water, one being
+longer than the other. The shorter pipe leads to the escape pipe mentioned
+above, while the longer one comes from the generator. The upper end of the
+cylinder has an opening to which is attached the pipe leading to the
+torches.
+
+[Illustration: Figure 13.--Hydraulic Back-Pressure Valve.
+_A_, Acetylene supply line;
+_B_, Vent pipe;
+_C_, Water filling plug;
+_D_, Acetylene service cock;
+_E_, Plug to gauge height of water;
+_F_, Gas openings under water;
+_G_, Return pipe for sealing water;
+_H_, Tube to carry gas below water line;
+_I_, Tube to carry gas to escape pipe;
+_J_, Gas chamber;
+_K_, Plug in upper gas chamber;
+_L_, High water level;
+_M_, Opening through which water returns;
+_O_, Bottom clean out casting]
+
+The gas coming from the generator through the longer pipe passes out of the
+lower end of the pipe which is under water and bubbles up through the water
+to the space in the top of the cylinder. From there the gas goes to the
+pipe leading to the torches. The shorter pipe is closed by the depth of
+water so that the gas does not escape to the relief pipe. As long as the
+gas flows in the normal direction as described there will be no escape to
+the air. Should the gas in the torch line return into the hydraulic valve
+its pressure will lower the level of water in the cylinder by forcing some
+of the liquid up into the two pipes. As the level of the water lowers, the
+shorter pipe will be uncovered first, and as this is the pipe leading to
+the open air the gas will be allowed to escape, while the pipe leading back
+to the generator is still closed by the water seal. As soon as this reverse
+flow ceases, the water will again resume its level and the action will
+continue. Because of the small amount of water blown out of the escape pipe
+each time the valve is called upon to perform this duty, it is necessary to
+see that the correct water level is always maintained.
+
+While there are modifications of this construction, the same principle is
+used in all types. The pressure escape valve is often attached to this
+hydraulic valve body.
+
+_Construction Details._--Flexible tubing (except at torches), swing
+pipe joints, springs, mechanical check valves, chains, pulleys and lead or
+fusible piping should never be used on acetylene apparatus except where the
+failure of those parts will not affect the safety of the machine or permit,
+either directly or indirectly, the escape of gas into a room. Floats should
+not be used except where failure will only render the machine inoperative.
+
+It should be said that the National Board of Fire Underwriters have
+established an inspection service for acetylene generators and any
+apparatus which bears their label, stating that that particular model and
+type has been passed, is safe to use. This service is for the best
+interests of all concerned and looks toward the prevention of accidents.
+Such inspection is a very important and desirable feature of any outfit and
+should be insisted upon.
+
+_Location of Generators._--Generators should preferably be placed
+outside of insured buildings and in properly constructed generator houses.
+The operating mechanism should have ample room to work in and there should
+be room enough for the attendant to reach the various parts and perform the
+required duties without hindrance or the need of artificial light. They
+should also be protected from tampering by unauthorized persons.
+
+Generator houses should not be within five feet of any opening into, nor
+have any opening toward, any adjacent building, and should be kept under
+lock and key. The size of the house should be no greater than called for by
+the requirements mentioned above and it should be well ventilated.
+
+The foundation for the generator itself should be of brick, stone, concrete
+or iron, if possible. If of wood, they should be extra heavy, located in a
+dry place and open to circulation of air. A board platform is not
+satisfactory, but the foundation should be of heavy planking or timber to
+make a firm base and so that the air can circulate around the wood.
+
+The generator should stand level and no strain should be placed on any of
+the pipes or connections or any parts of the generator proper.
+
+
+
+
+CHAPTER IV
+
+WELDING INSTRUMENTS
+
+
+VALVES
+
+_Tank Valves._--The acetylene tank valve is of the needle type, fitted
+with suitable stuffing box nuts and ending in an exposed square shank to
+which the special wrench may be fitted when the valve is to be opened or
+closed.
+
+The valve used on Linde oxygen cylinders is also a needle type, but of
+slightly more complex construction. The body of the valve, which screws
+into the top of the cylinder, has an opening below through which the gas
+comes from the cylinder, and another opening on the side through which it
+issues to the torch line. A needle screws down from above to close this
+lower opening. The needle which closes the valve is not connected directly
+to the threaded member, but fits loosely into it. The threaded part is
+turned by a small hand wheel attached to the upper end. When this hand
+wheel is turned to the left, or up, as far as it will go, opening the
+valve, a rubber disc is compressed inside of the valve body and this disc
+serves to prevent leakage of the gas around the spindle.
+
+The oxygen valve also includes a safety nut having a small hole through it
+closed by a fusible metal which melts at 250  Fahrenheit. Melting of this
+plug allows the gas to exert its pressure against a thin copper diaphragm,
+this diaphragm bursting under the gas pressure and allowing the oxygen to
+escape into the air.
+
+The hand wheel and upper end of the valve mechanism are protected during
+shipment by a large steel cap which covers them when screwed on to the end
+of the cylinder. This cap should always be in place when tanks are received
+from the makers or returned to them.
+
+[Illustration: Figure 14.--Regulating Valve]
+
+_Regulating Valves._--While the pressure in the gas containers may be
+anything from zero to 1,800 pounds, and will vary as the gas is withdrawn,
+the pressure of the gas admitted to the torch must be held steady and at a
+definite point. This is accomplished by various forms of automatic
+regulating valves, which, while they differ somewhat in details of
+construction, all operate on the same principle.
+
+The regulator body (Figure 14) carries a union which attaches to the side
+outlet on the oxygen tank valve. The gas passes through this union,
+following an opening which leads to a large gauge which registers the
+pressure on the oxygen remaining in the tank and also to a very small
+opening in the end of a tube. The gas passes through this opening and into
+the interior of the regulator body. Inside of the body is a metal or rubber
+diaphragm placed so that the pressure of the incoming gas causes it to
+bulge slightly. Attached to the diaphragm is a sleeve or an arm tipped
+with a small piece of fibre, the fibre being placed so that it is directly
+opposite the small hole through which the gas entered the diaphragm
+chamber. The slight movement of the diaphragm draws the fibre tightly over
+the small opening through which the gas is entering, with the result that
+further flow is prevented.
+
+Against the opposite side of the diaphragm is the end of a plunger. This
+plunger is pressed against the diaphragm by a coiled spring. The tension on
+the coiled spring is controlled by the operator through a threaded spindle
+ending in a wing or milled nut on the outside of the regulator body.
+Screwing in on the nut causes the tension on the spring to increase, with a
+consequent increase of pressure on the side of the diaphragm opposite to
+that on which the gas acts. Inasmuch as the gas pressure acted to close the
+small gas opening and the spring pressure acts in the opposite direction
+from the gas, it will be seen that the spring pressure tends to keep the
+valve open.
+
+When the nut is turned way out there is of course, no pressure on the
+spring side of the diaphragm and the first gas coming through automatically
+closes the opening through which it entered. If now the tension on the
+spring be slightly increased, the valve will again open and admit gas until
+the pressure of gas within the regulator is just sufficient to overcome the
+spring pressure and again close the opening. There will then be a pressure
+of gas within the regulator that corresponds to the pressure placed on the
+spring by the operator. An opening leads from the regulator interior to the
+torch lines so that all gas going to the torches is drawn from the
+diaphragm chamber.
+
+Any withdrawal of gas will, of course, lower the pressure of that remaining
+inside the regulator. The spring tension, remaining at the point determined
+by the operator, will overcome this lessened pressure of the gas, and the
+valve will again open and admit enough more gas to bring the pressure back
+to the starting point. This action continues as long as the spring tension
+remains at this point and as long as any gas is taken from the regulator.
+Increasing the spring tension will require a greater gas pressure to close
+the valve and the pressure of that in the regulator will be correspondingly
+higher.
+
+When the regulator is not being used, the hand nut should be unscrewed
+until no tension remains on the spring, thus closing the valve. After the
+oxygen tank valve is open, the regulator hand nut is slowly screwed in
+until the spring tension is sufficient to give the required pressure in the
+torch lines. Another gauge is attached to the regulator so that it
+communicates with the interior of the diaphragm chamber, this gauge showing
+the gas pressure going to the torch. It is customary to incorporate a
+safety valve in the regulator which will blow off at a dangerous pressure.
+
+In regulating valves and tank valves, as well as all other parts with which
+the oxygen comes in contact, it is not permissible to use any form of oil
+or grease because of danger of ignition and explosion. The mechanism of a
+regulator is too delicate to be handled in the ordinary shop and should any
+trouble or leakage develop in this part of the equipment it should be sent
+to a company familiar with this class of work for the necessary repairs.
+Gas must never be admitted to a regulator until the hand nut is all the way
+out, because of danger to the regulator itself and to the operator as well.
+A regulator can only be properly adjusted when the tank valve and torch
+valves are fully opened.
+
+[Illustration: Figure 15.--High and Low Pressure Gauges with Regulator]
+
+Acetylene regulators are used in connection with tanks of compressed gas.
+They are built on exactly the same lines as the oxygen regulating valve and
+operate in a similar way. One gauge only, the low pressure indicator, is
+used for acetylene regulators, although both high and low pressure may be
+used if desired. (See Figure 15.)
+
+
+TORCHES
+
+Flame is always produced by the combustion of a gas with oxygen and in no
+other way. When we burn oil or candles or anything else, the material of
+the fuel is first turned to a gas by the heat and is then burned by
+combining with the oxygen of the air. If more than a normal supply of air
+is forced into the flame, a greater heat and more active burning follows.
+If the amount of air, and consequently oxygen, is reduced, the flame
+becomes smaller and weaker and the combustion is less rapid. A flame may be
+easily extinguished by shutting off all of its air supply.
+
+The oxygen of the combustion only forms one-fifth of the total volume of
+air; therefore, if we were to supply pure oxygen in place of air, and in
+equal volume, the action would be several times as intense. If the oxygen
+is mixed with the fuel gas in the proportion that burns to the very best
+advantage, the flame is still further strengthened and still more heat is
+developed because of the perfect combustion. The greater the amount of fuel
+gas that can be burned in a certain space and within a certain time, the
+more heat will be developed from that fuel.
+
+The great amount of heat contained in acetylene gas, greater than that
+found in any other gaseous fuel, is used by leading this gas to the
+oxy-acetylene torch and there combining it with just the right amount of
+oxygen to make a flame of the greatest power and heat than can possibly be
+produced by any form of combustion of fuels of this kind. The heat
+developed by the flame is about 6300  Fahrenheit and easily melts all the
+metals, as well as other solids.
+
+Other gases have been and are now being used in the torch. None of them,
+however, produce the heat that acetylene does, and therefore the
+oxy-acetylene process has proved the most useful of all. Hydrogen was used
+for many years before acetylene was introduced in this field. The
+oxy-hydrogen flame develops a heat far below that of oxy-acetylene, namely
+4500  Fahrenheit. Coal gas, benzine gas, blaugas and others have also been
+used in successful applications, but for the present we will deal
+exclusively with the acetylene fuel.
+
+It was only with great difficulty that the obstacles in the way of
+successfully using acetylene were overcome by the development of
+practicable controlling devices and torches, as well as generators. At
+present the oxy-acetylene process is the most universally adaptable, and
+probably finds the most widely extended field of usefulness of any welding
+process.
+
+The theoretical proportion of the gases for perfect combustion is two and
+one-half volumes of oxygen to one of acetylene. In practice this proportion
+is one and one-eighth or one and one-quarter volumes of oxygen to one
+volume of acetylene, so that the cost is considerably reduced below what it
+would be if the theoretical quantity were really necessary, as oxygen costs
+much more than acetylene in all cases.
+
+While the heat is so intense as to fuse anything brought into the path of
+the flame, it is localized in the small "welding cone" at the torch tip so
+that the torch is not at all difficult to handle without special protection
+except for the eyes, as already noted. The art of successful welding may be
+acquired by any operator of average intelligence within a reasonable time
+and with some practice. One trouble met with in the adoption of this
+process has been that the operation looks so simple and so easy of
+performance that unskilled and unprepared persons have been tempted to try
+welding, with results that often caused condemnation of the process, when
+the real fault lay entirely with the operator.
+
+The form of torch usually employed is from twelve to twenty-four inches
+long and is composed of a handle at one end with tubes leading from this
+handle to the "welding head" or torch proper. At or near one end of the
+handle are adjustable cocks or valves for allowing the gases to flow into
+the torch or to prevent them from doing so. These cocks are often used for
+regulating the pressure and amount of gas flowing to the welding head, but
+are not always constructed for this purpose and should not be so used when
+it is possible to secure pressure adjustment at the regulators (Figure 16).
+
+Figure 16 shows three different sizes of torches. The number 5 torch is
+designed especially for jewelers' work and thin sheet steel welding. It is
+eleven inches in length and weighs nineteen ounces. The tips for the number
+10 torch are interchangeable with the number 5. The number 10 torch is
+adapted for general use on light and medium heavy work. It has six tips and
+its length is sixteen inches, with a weight of twenty-three ounces.
+
+The number 15 torch is designed for heavy work, being twenty-five inches in
+length, permitting the operator to stand away from the heat of the metal
+being worked. These heavy tips are in two parts, the oxygen check being
+renewable.
+
+[Illustration: Figure 16.--Three Sizes of Torches, with Tips]
+
+Figures 17 and 18 show two sizes of another welding torch. Still another
+type is shown in Figure 19 with four interchangeable tips, the function of
+each being as follows:
+
+  No. 1. For heavy castings.
+  No. 2. Light castings and heavy sheet metal.
+  No. 3. Light sheet metal.
+  No. 4. Very light sheet metal and wire.
+
+[Illustration: Figure 17.--Cox Welding Torch (No. 1)]
+
+[Illustration: Figure 18.--Cox Welding Torch (No. 2)]
+
+[Illustration: Figure 19.--Monarch Welding Torch]
+
+At the side of the shut off cock away from the torch handle the gas tubes
+end in standard forms of hose nozzles, to which the rubber hose from the
+gas supply tanks or generators can be attached. The tubes from the handle
+to the head may be entirely separate from each other, or one may be
+contained within the other. As a general rule the upper one of two
+separate tubes carries the oxygen, while this gas is carried in the inside
+tube when they are concentric with each other.
+
+In the welding head is the mixing chamber designed to produce an intimate
+mixture of the two gases before they issue from the nozzle to the flame.
+The nozzle, or welding tip, of a suitable size are design for the work to
+be handled and the pressure of gases being used, is attached to the welding
+head and consists essentially of the passage at the outer end of which the
+flame appears.
+
+The torch body and tubes are usually made of brass, although copper is
+sometimes used. The joint must be very strong, and are usually threaded and
+soldered with silver solder. The nozzle proper is made from copper, because
+it withstands the heat of the flame better than other less suitable metals.
+The torch must be built in such a way that it is not at all liable to come
+apart under the influence of high temperatures.
+
+All torches are constructed in such a way that it is impossible for the
+gases to mix by any possible chance before they reach the head, and the
+amount of gas contained in the head and tip after being mixed is made as
+small as possible. In order to prevent the return of the flame through the
+acetylene tube under the influence of the high pressure oxygen some form of
+back flash preventer is usually incorporated in the torch at or near the
+point at which the acetylene enters. This preventer takes the form of some
+porous and heat absorbing material, such as aluminum shavings, contained in
+a small cavity through which the gas passes on its way to the head.
+
+_High Pressure Torches._--Torches are divided into the same classes as
+are the generators; that is, high pressure, medium pressure and low
+pressure. As mentioned before, the medium pressure is usually called the
+high pressure, because there are very few true high pressure systems in
+use, and comparatively speaking the medium pressure type is one of high
+pressure.
+
+[Illustration: Figure 20.--High Pressure Torch Head]
+
+With a true high pressure torch (Figure 20) the gases are used at very
+nearly equal heads so that the mixing before ignition is a simple matter.
+This type admits the oxygen at the inner end of a straight passage leading
+to the tip of the nozzle. The acetylene comes into this same passage from
+openings at one side and near the inner end. The difference in direction of
+the two gases as they enter the passage assists in making a homogeneous
+mixture. The construction of this nozzle is perfectly simple and is easily
+understood. The true high pressure torch nozzle is only suited for use with
+compressed and dissolved acetylene, no other gas being at a sufficient
+pressure to make the action necessary in mixing the gases.
+
+_Medium Pressure Torches._--The medium pressure (usually called high
+pressure) torch (Figure 21) uses acetylene from a medium pressure generator
+or from tanks of compressed gas, but will not take the acetylene from low
+pressure generators.
+
+[Illustration: Figure 21.--Medium Pressure Torch Head]
+
+The construction of the mixing chamber and nozzle is very similar to that
+of the high pressure torch, the gases entering in the same way and from the
+same positions of openings. The pressure of the acetylene is but little
+lower than that of the oxygen, and the two gases, meeting at right angles,
+form a very intimate mixture at this point of juncture. The mixture in its
+proportions of gases depends entirely on the sizes of the oxygen and
+acetylene openings into the mixing chamber and on the pressures at which
+the gases are admitted. There is a very slight injector action as the fast
+moving stream of oxygen tends to draw the acetylene from the side openings
+into the chamber, but the operation of the torch does not depend on this
+action to any extent.
+
+_Low Pressure Torches._--The low pressure torch (Figure 22) will use
+gas from low pressure generators from medium pressure machines or from
+tanks in which it has been compressed and dissolved. This type depends for
+a perfect mixture of gas upon the principle of the injector just as it is
+applied in steam boiler practice.
+
+[Illustration: Figure 22.--Low Pressure Torch with Separate Injector
+Nozzle]
+
+The oxygen enters the head at considerable pressure and passes through its
+tube to a small jet within the head. The opening of this jet is directly
+opposite the end of the opening through the nozzle which forms the mixing
+chamber and the path of the gases to the flame. A small distance remains
+between the opening from which the oxygen issues and the inner opening into
+the mixing passage. The stream of oxygen rushes across this space and
+enters the mixing chamber, being driven by its own pressure.
+
+The acetylene enters the head in an annular space surrounding the oxygen
+tube. The space between oxygen jet and mixing chamber opening is at one end
+of this acetylene space and the stream of oxygen seizes the acetylene and
+under the injector action draws it into the mixing chamber, it being
+necessary only to have a sufficient supply of acetylene flowing into the
+head to allow the oxygen to draw the required proportion for a proper
+mixture.
+
+The volume of gas drawn into the mixing chamber depends on the size of the
+injector openings and the pressure of the oxygen. In practice the oxygen
+pressure is not altered to produce different sized flames, but a new nozzle
+is substituted which is designed to give the required flame. Each nozzle
+carries its own injector, so that the design is always suited to the
+conditions. While torches are made having the injector as a permanent part
+of the torch body, the replaceable nozzle is more commonly used because it
+makes the one torch suitable for a large range of work and a large number
+of different sized flames. With the replaceable head a definite pressure of
+oxygen is required for the size being used, this pressure being the one for
+which the injector and corresponding mixing chamber were designed in
+producing the correct mixture.
+
+_Adjustable Injectors._-Another form of low pressure torch operates on
+the injector principle, but the injector itself is a permanent part of the
+torch, the nozzle only being changed for different sizes of work and flame.
+The injector is placed in or near the handle and its opening is the largest
+required by any work that can be handled by this particular torch. The
+opening through the tip of the injector through which the oxygen issues on
+its way to the mixing chamber may be wholly or partly closed by a needle
+valve which may be screwed into the opening or withdrawn from it, according
+to the operator's judgment. The needle valve ends in a milled nut outside
+the torch handle, this being the adjustment provided for the different
+nozzles.
+
+_Torch Construction._--A well designed torch is so designed that the
+weight distribution is best for holding it in the proper position for
+welding. When a torch is grasped by its handle with the gas hose attached,
+it should balance so that it does not feel appreciably heavier on one end
+than on the other.
+
+The head and nozzle may be placed so that the flame issues in a line at
+right angles with the torch body, or they may be attached at an angle
+convenient for the work to be done. The head set at an angle of from 120 to
+170 degrees with the body is usually preferred for general work in welding,
+while the cutting torch usually has its head at right angles to the body.
+
+Removable nozzles have various size openings through them and the different
+sizes are designated by numbers from 1 up. The same number does not always
+indicate the same size opening in torches of different makes, nor does it
+indicate a nozzle of the same capacity.
+
+The design of the nozzle, the mixing chamber, the injector, when one is
+used, and the size of the gas openings must be such that all these things
+are suited to each other if a proper mixture of gas is to be secured. Parts
+that are not made to work together are unsafe if used because of the danger
+of a flash back of the flame into the mixing chamber and gas tubes. It is
+well known that flame travels through any inflammable gas at a certain
+definite rate of speed, depending on the degree of inflammability of the
+gas. The easier and quicker the gas burns, the faster will the flame travel
+through it.
+
+If the gas in the nozzle and mixing chamber stood still, the flame would
+immediately travel back into these parts and produce an explosion of more
+or less violence. The speed with which the gases issue from the nozzle
+prevent this from happening because the flame travels back through the gas
+at the same speed at which the gas issues from the torch tip. Should the
+velocity of the gas be greater than the speed of flame propagation through
+it, it will be impossible to keep the flame at the tip, the tendency being
+for a space of unburned gas to appear between tip and flame. On the other
+hand, should the speed of the flame exceed the velocity with which the gas
+comes from the torch there will result a flash back and explosion.
+
+_Care of Torches._--An oxy-acetylene torch is a very delicate and
+sensitive device, much more so that appears on the surface. It must be
+given equally as good care and attention as any other high-priced piece of
+machinery if it is to be maintained in good condition for use.
+
+It requires cleaning of the nozzles at regular intervals if used regularly.
+This cleaning is accomplished with a piece of copper or brass wire run
+through the opening, and never with any metal such as steel or iron that is
+harder than the nozzle itself, because of the danger of changing the size
+of the openings. The torch head and nozzle can often be cleaned by allowing
+the oxygen to blow through at high pressure without the use of any tools.
+
+In using a torch a deposit of carbon will gradually form inside of the
+head, and this deposit will be more rapid if the operator lights the stream
+of acetylene before turning any oxygen into the torch. This deposit may be
+removed by running kerosene through the nozzle while it is removed from the
+torch, setting fire to the kerosene and allowing oxygen to flow through
+while the oil is burning.
+
+Should a torch become clogged in the head or tubes, it may usually be
+cleaned by removing the oxygen hose from the handle end, closing the
+acetylene cock on the torch, placing the end of the oxygen hose over the
+opening in the nozzle and turning on the oxygen under pressure to blow the
+obstruction back through the passage that it has entered. By opening the
+acetylene cock and closing the oxygen cock at the handle, the acetylene
+passages may then be cleaned in the same way. Under no conditions should a
+torch be taken apart any more than to remove the changeable nozzle, except
+in the hands of those experienced in this work.
+
+_Nozzle Sizes._--The size of opening through the nozzle is determined
+according to the thickness and kind of metal being handled. The following
+sizes are recommended for steel:
+
+                      Davis-Bournonville.   Oxweld Low
+  Thickness of Metal  (Medium Pressure.)      Pressure
+  1/32                     Tip No. 1        Head No. 2
+  1/16                             2
+  5/64                                               3
+  3/32                             3                 4
+  3/8                              4                 5
+  3/16                             5                 6
+  1/4                              6                 7
+  5/16                             7
+  3/8                              8                 8
+  1/2                              9                10
+  5/8                             10                12
+  3/4                             11                15
+  Very heavy                      12                15
+
+_Cutting Torches._--Steel may be cut with a jet of oxygen at a rate of
+speed greater than in any other practicable way under usual conditions. The
+action consists of burning away a thin section of the metal by allowing a
+stream of oxygen to flow onto it while the gas is at high pressure and the
+metal at a white heat.
+
+[Illustration: Figure 23.--Cutting Torch]
+
+The cutting torch (Figure 23) has the same characteristics as the welding
+torch, but has an additional nozzle or means for temporarily using the
+welding opening for the high pressure oxygen. The oxygen issues from the
+opening while cutting at a pressure of from ten to 100 pounds to the square
+inch.
+
+The work is first heated to a white heat by adjusting the torch for a
+welding flame. As soon as the metal reaches this temperature, the high
+pressure oxygen is turned on to the white-hot portion of the steel. When
+the jet of gas strikes the metal it cuts straight through, leaving a very
+narrow slot and removing but little metal. Thicknesses of steel up to ten
+inches can be economically handled in this way.
+
+The oxygen nozzle is usually arranged so that it is surrounded by a number
+of small jets for the heating flame. It will be seen that this arrangement
+makes the heating flame always precede the oxygen jet, no matter in which
+direction the torch is moved.
+
+The torch is held firmly, either by hand or with the help of special
+mechanism for guiding it in the desired path, and is steadily advanced in
+the direction it is desired to extend the cut, the rate of advance being
+from three inches to two feet per minute through metal from nine inches
+down to one-quarter of an inch in thickness.
+
+The following data on cutting is given by the Davis-Bournonville Company:
+
+                            Cubic
+                            Feet                          Cost of
+Thickness                   of Gas               Inches   Gases
+of        Cutting  Heating  per Foot  Oxygen     Cut per  per Foot
+Steel     Oxygen   Oxygen   of Cut    Acetylene  Min.     of Cut
+  1/4     10 lbs.  4 lbs.     .40      .086      24        $ .013
+  1/2     20       4          .91      .150      15          .029
+  3/4     30       4         1.16      .150      15          .036
+1         30       4         1.45      .172      12          .045
+1 1/2     30       5         2.40      .380      12          .076
+2         40       5         2.96      .380      12          .093
+4         50       5         9.70      .800       7          .299
+6         70       6        21.09     1.50        4          .648
+9        100       6        43.20     2.00        3         1.311
+
+_Acetylene-Air Torch._--A form of torch which burns the acetylene after
+mixing it with atmospheric air at normal pressure rather than with the
+oxygen under higher pressures has been found useful in certain pre-heating,
+brazing and similar operations. This torch (Figure 24) is attached by a
+rubber gas hose to any compressed acetylene tank and is regulated as to
+flame size and temperature by opening or closing the tank valve more or
+less.
+
+After attaching the torch to the tank, the gas is turned on very slowly and
+is lighted at the torch tip. The adjustment should cause the presence of a
+greenish-white cone of flame surrounded by a larger body of burning gas,
+the cone starting at the mouth of the torch.
+
+[Illustration: Figure 24.--Acetylene-Air Torch]
+
+By opening the tank valve more, a longer and hotter flame is produced, the
+length being regulated by the tank valve also. This torch will give
+sufficient heat to melt steel, although not under conditions suited to
+welding. Because of the excess of acetylene always present there is no
+danger of oxidizing the metal being heated.
+
+The only care required by this torch is to keep the small air passages at
+the nozzle clean and free from carbon deposits. The flame should be
+extinguished when not in use rather than turned low, because this low flame
+rapidly deposits large quantities of soot in the burner.
+
+
+
+
+CHAPTER V
+
+OXY-ACETYLENE WELDING PRACTICE
+
+
+PREPARATION OF WORK
+
+_Preheating._--The practice of heating the metal around the weld
+before applying the torch flame is a desirable one for two reasons. First,
+it makes the whole process more economical; second, it avoids the danger of
+breakage through expansion and contraction of the work as it is heated and
+as it cools.
+
+When it is desired to join two surfaces by welding them, it is, of course,
+necessary to raise the metal from the temperature of the surrounding air to
+its melting point, involving an increase in temperature of from one
+thousand to nearly three thousand degrees. To obtain this entire increase
+of temperature with the torch flame is very wasteful of fuel and of the
+operator's time. The total amount of heat necessary to put into metal is
+increased by the conductivity of that metal because the heat applied at the
+weld is carried to other parts of the piece being handled until the whole
+mass is considerably raised in temperature. To secure this widely
+distributed increase the various methods of preheating are adopted.
+
+As to the second reason for preliminary heating. It is understood that the
+metal added to the joint is molten at the time it flows into place. All the
+metals used in welding contract as they cool and occupy a much smaller
+space than when molten. If additional metal is run between two adjoining
+surfaces which are parts of a surrounding body of cool metal, this added
+metal will cool while the surfaces themselves are held stationary in the
+position they originally occupied. The inevitable result is that the metal
+added will crack under the strain, or, if the weld is exceptionally strong,
+the main body of the work will he broken by the force of contraction. To
+overcome these difficulties is the second and most important reason for
+preheating and also for slow cooling following the completion of the weld.
+
+There are many ways of securing this preheating. The work may be brought to
+a red heat in the forge if it is cast iron or steel; it may he heated in
+special ovens built for the purpose; it may be placed in a bed of charcoal
+while suitably supported; it may be heated by gas or gasoline preheating
+torches, and with very small work the outer flame of the welding torch
+automatically provides means to this end.
+
+The temperature of the parts heated should be gradually raised in all
+cases, giving the entire mass of metal a chance to expand equally and to
+adjust itself to the strains imposed by the preheating. After the region
+around the weld has been brought to a proper temperature the opening to be
+filled is exposed so that the torch flame can reach it, while the remaining
+surfaces are still protected from cold air currents and from cooling
+through natural radiation.
+
+One of the commonest methods and one of the best for handling work of
+rather large size is to place the piece to be welded on a bed of fire brick
+and build a loose wall around it with other fire brick placed in rows, one
+on top of the other, with air spaces left between adjacent bricks in each
+row. The space between the brick retaining wall and the work is filled with
+charcoal, which is lighted from below. The top opening of the temporary
+oven is then covered with asbestos and the fire kept up until the work has
+been uniformly raised in temperature to the desired point.
+
+When much work of the same general character and size is to be handled, a
+permanent oven may be constructed of fire brick, leaving a large opening
+through the top and also through one side. Charcoal may be used in this
+form of oven as with the temporary arrangement, or the heat may be secured
+from any form of burner or torch giving a large volume of flame. In any
+method employing flame to do the heating, the work itself must be protected
+from the direct blast of the fire. Baffles of brick or metal should be
+placed between the mouth of the torch and the nearest surface of the work
+so that the flame will be deflected to either side and around the piece
+being heated.
+
+The heat should be applied to bring the point of welding to the highest
+temperature desired and, except in the smallest work, the heat should
+gradually shade off from this point to the other parts of the piece. In the
+case of cast iron and steel the temperature at the point to be welded
+should be great enough to produce a dull red heat. This will make the whole
+operation much easier, because there will be no surrounding cool metal to
+reduce the temperature of the molten material from the welding rod below
+the point at which it will join the work. From this red heat the mass of
+metal should grow cooler as the distance from the weld becomes greater, so
+that no great strain is placed upon any one part. With work of a very
+irregular shape it is always best to heat the entire piece so that the
+strains will be so evenly distributed that they can cause no distortion or
+breakage under any conditions.
+
+The melting point of the work which is being preheated should be kept in
+mind and care exercised not to approach it too closely. Special care is
+necessary with aluminum in this respect, because of its low melting
+temperature and the sudden weakening and flowing without warning. Workmen
+have carelessly overheated aluminum castings and, upon uncovering the piece
+to make the weld, have been astonished to find that it had disappeared.
+Six hundred degrees is about the safe limit for this metal. It is possible
+to gauge the exact temperature of the work with a pyrometer, but when this
+instrument cannot be procured, it might be well to secure a number of
+"temperature cones" from a chemical or laboratory supply house. These cones
+are made from material that will soften at a certain heat and in form they
+are long and pointed. Placed in position on the part being heated, the
+point may be watched, and when it bends over it is sure that the metal
+itself has reached a temperature considerably in excess of the temperature
+at which that particular cone was designed to soften.
+
+The object in preheating the metal around the weld is to cause it to expand
+sufficiently to open the crack a distance equal to the contraction when
+cooling from the melting point. In the case of a crack running from the
+edge of a piece into the body or of a crack wholly within the body, it is
+usually satisfactory to heat the metal at each end of the opening. This
+will cause the whole length of the crack to open sufficiently to receive
+the molten material from the rod.
+
+The judgment of the operator will be called upon to decide just where a
+piece of metal should be heated to open the weld properly. It is often
+possible to apply the preheating flame to a point some distance from the
+point of work if the parts are so connected that the expansion of the
+heated part will serve to draw the edges of the weld apart. Whatever part
+of the work is heated to cause expansion and separation, this part must
+remain hot during the entire time of welding and must then cool slowly at
+the same time as the metal in the weld cools.
+
+[Illustration: Figure 25.--Preheating at _A_ While Welding at
+_B_. _C_ also May Be Heated.]
+
+An example of heating points away from the crack might be found in welding
+a lattice work with one of the bars cracked through (Figure 25). If the
+strips parallel and near to the broken bar are heated gradually, the work
+will be so expanded that the edges of the break are drawn apart and the
+weld can be successfully made. In this case, the parallel bars next to the
+broken one would be heated highest, the next row not quite so hot and so on
+for some distance away. If only the one row were heated, the strains set up
+in the next ones would be sufficient to cause a new break to appear.
+
+[Illustration: Figure 26.--Cutting Through the Rim of a Wheel (Cut Shown
+at A)]
+
+If welding is to be done near the central portion of a large piece, the
+strains will be brought to bear on the parts farthest away from the center.
+Should a fly wheel spoke be broken and made ready to weld, the greatest
+strain will come on the rim of the wheel. In cases like this it is often
+desirable to cut through at the point of greatest strain with a saw or
+cutting torch, allowing free movement while the weld is made at the
+original break (Figure 26). After the inside weld is completed, the cut may
+be welded without danger, for the reason that it will always be at some
+point at which severe strains cannot be set up by the contraction of the
+cooling metal.
+
+[Illustration: Figure 27.--Using a Wedge While Welding]
+
+In materials that will spring to some extent without breakage, that is, in
+parts that are not brittle, it may be possible to force the work out of
+shape with jacks or wedges (Figure 27) in the same way that it would be
+distorted by heating and expanding some portion of it as described. A
+careful examination will show whether this method can be followed in such a
+way as to force the edges of the break to separate. If the plan seems
+feasible, the wedges may be put in place and allowed to remain while the
+weld is completed. As soon as the work is finished the wedges should be
+removed so that the natural contraction can take place without damage.
+
+It should always be remembered that it is not so much the expansion of the
+work when heated as it is the contraction caused by cooling that will do
+the damage. A weld may be made that, to all appearances, is perfect and it
+may be perfect when completed; but if provision has not been made to allow
+for the contraction that is certain to follow, there will be a breakage at
+some point. It is not possible to weld the simplest shapes, other than
+straight bars, without considering this difficulty and making provision to
+take care of it.
+
+The exact method to employ in preheating will always call for good judgment
+on the part of the workman, and he should remember that the success or
+failure of his work will depend fully as much on proper preparation as on
+correct handling of the weld itself. It should be remembered that the outer
+flame of the oxy-acetylene torch may be depended on for a certain amount of
+preheating, as this flame gives a very large volume of heat, but a heat
+that is not so intense nor so localized as the welding flame itself. The
+heat of this part of the flame should be fully utilized during the
+operation of melting the metal and it should be so directed, when possible,
+that it will bring the parts next to be joined to as high a temperature as
+possible.
+
+When the work has been brought to the desired temperature, all parts except
+the break and the surface immediately surrounding it on both sides should
+be covered with heavy sheet asbestos. This protecting cover should remain
+in place throughout the operation and should only be moved a distance
+sufficient to allow the torch flame to travel in the path of the weld. The
+use of asbestos in this way serves a twofold purpose. It retains the heat
+in the work and prevents the breakage that would follow if a draught of air
+were to strike the heated metal, and it also prevents such a radiation of
+heat through the surrounding air as would make it almost impossible for the
+operator to perform his work, especially in the case of large and heavy
+castings when the amount of heat utilized is large.
+
+_Cleaning and Champfering._--A perfect weld can never be made unless
+the surfaces to be joined have been properly prepared to receive the new
+metal.
+
+All spoiled, burned, corroded and rough particles must positively be
+removed with chisel and hammer and with a free application of emery cloth
+and wire brush. The metal exposed to the welding flame should be perfectly
+clean and bright all over, or else the additional material will not unite,
+but will only stick at best.
+
+[Illustration: Figure 28.--Tapering the Opening Formed by a Break]
+
+Following the cleaning it is always necessary to bevel, or champfer, the
+edges except in the thinnest sheet metal. To make a weld that will hold,
+the metal must be made into one piece, without holes or unfilled portions
+at any point, and must be solid from inside to outside. This can only be
+accomplished by starting the addition of metal at one point and gradually
+building it up until the outside, or top, is reached. With comparatively
+thin plates the molten metal may be started from the side farthest from the
+operator and brought through, but with thicker sections the addition is
+started in the middle and brought flush with one side and then with the
+other.
+
+It will readily be seen that the molten material cannot be depended upon to
+flow between the tightly closed surfaces of a crack in a way that can be at
+all sure to make a true weld. It will be necessary for the operator to
+reach to the farthest side with the flame and welding rod, and to start the
+new surfaces there. To allow this, the edges that are to be joined are
+beveled from one side to the other (Figure 28), so that when placed
+together in approximately the position they are to occupy they will leave a
+grooved channel between them with its sides at an angle with each other
+sufficient in size to allow access to every point of each surface.
+
+[Illustration: Figure 29.--Beveling for Thin Work]
+
+[Illustration: Figure 30.--Beveling for Thick Work]
+
+With work less than one-fourth inch thick, this angle should be forty-five
+degrees on each piece (Figure 29), so that when they are placed together
+the extreme edges will meet at the bottom of a groove whose sides are
+square, or at right angles, to each other. This beveling should be done so
+that only a thin edge is left where the two parts come together, just
+enough points in contact to make the alignment easy to hold. With work of a
+thickness greater than a quarter of an inch, the angle of bevel on each
+piece may be sixty degrees (Figure 30), so that when placed together the
+angle included between the sloping sides will also be sixty degrees. If the
+plate is less than one-eighth of an inch thick the beveling is not
+necessary, as the edges may be melted all the way through without danger of
+leaving blowholes at any point.
+
+[Illustration: Figure 31.--Beveling Both Sides of a Thick Piece]
+
+[Illustration: Figure 32.--Beveling the End of a Pipe]
+
+This beveling may be done in any convenient way. A chisel is usually most
+satisfactory and also quickest. Small sections may be handled by filing,
+while metal that is too hard to cut in either of these ways may be shaped
+on the emery wheel. It is not necessary that the edges be perfectly
+finished and absolutely smooth, but they should be of regular outline and
+should always taper off to a thin edge so that when the flame is first
+applied it can be seen issuing from the far side of the crack. If the work
+is quite thick and is of a shape that will allow it to be turned over, the
+bevel may be brought from both sides (Figure 31), so that there will be two
+grooves, one on each surface of the work. After completing the weld on one
+side, the piece is reversed and finished on the other side. Figure 32 shows
+the proper beveling for welding pipe. Figure 33 shows how sheet metal may
+be flanged for welding.
+
+Welding should not be attempted with the edges separated in place of
+beveled, because it will be found impossible to build up a solid web of new
+metal from one side clear through to the other by this method. The flame
+cannot reach the surfaces to make them molten while receiving new material
+from the rod, and if the flame does not reach them it will only serve to
+cause a few drops of the metal to join and will surely cause a weak and
+defective weld.
+
+[Illustration: Figure 33.--Flanging Sheet Metal for Welding]
+
+_Supporting Work._--During the operation of welding it is necessary
+that the work be well supported in the position it should occupy. This may
+be done with fire brick placed under the pieces in the correct position,
+or, better still, with some form of clamp. The edges of the crack should
+touch each other at the point where welding is to start and from there
+should gradually separate at the rate of about one-fourth inch to the foot.
+This is done so that the cooling of the molten metal as it is added will
+draw the edges together by its contraction.
+
+Care must be used to see that the work is supported so that it will
+maintain the same relative position between the parts as must be present
+when the work is finished. In this connection it must be remembered that
+the expansion of the metal when heated may be great enough to cause serious
+distortion and to provide against this is one of the difficulties to be
+overcome.
+
+Perfect alignment should be secured between the separate parts that are to
+be joined and the two edges must be held up so that they will be in the
+same plane while welding is carried out. If, by any chance, one drops
+below the other while molten metal is being added, the whole job may have
+to be undone and done over again. One precaution that is necessary is that
+of making sure that the clamping or supporting does not in itself pull the
+work out of shape while melted.
+
+
+TORCH PRACTICE
+
+[Illustration: Figure 34.--Rotary Movement of Torch in Welding]
+
+The weld is made by bringing the tip of the welding flame to the edges of
+the metals to be joined. The torch should be held in the right hand and
+moved slowly along the crack with a rotating motion, traveling in small
+circles (Figure 34), so that the Welding flame touches first on one side of
+the crack and then on the other. On large work the motion may be simply
+back and forth across the crack, advancing regularly as the metal unites.
+It is usually best to weld toward the operator rather than from him,
+although this rule is governed by circumstances. The head of the torch
+should be inclined at an angle of about 60 degrees to the surface of the
+work. The torch handle should extend in the same line with the break
+(Figure 35) and not across it, except when welding very light plates.
+
+[Illustration: Figure 35.--Torch Held in Line with the Break]
+
+If the metal is 1/16 inch or less in thickness it is only necessary to
+circle along the crack, the metal itself furnishing enough material to
+complete the weld without additions. Heat both sides evenly until they flow
+together.
+
+Material thicker than the above requires the addition of more metal of the
+same or different kind from the welding rod, this rod being held by the
+left hand. The proper size rod for cast iron is one having a diameter equal
+to the thickness of metal being welded up to a one-half inch rod, which is
+the largest used. For steel the rod should be one-half the thickness of the
+metal being joined up to one-fourth inch rod. As a general rule, better
+results will be obtained by the use of smaller rods, the very small sizes
+being twisted together to furnish enough material while retaining the free
+melting qualities.
+
+[Illustration: Figure 36.--The Welding Rod Should Be Held in the Molten
+Metal]
+
+The tip of the rod must at all times be held in contact with the pieces
+being welded and the flame must be so directed that the two sides of the
+crack and the end of the rod are melted at the same time (Figure 36).
+Before anything is added from the rod, the sides of the crack are melted
+down sufficiently to fill the bottom of the groove and join the two sides.
+Afterward, as metal comes from the rod in filling the crack, the flame is
+circled along the joint being made, the rod always following the flame.
+
+[Illustration: Figure 37.--Welding Pieces of Unequal Thickness]
+
+Figure 37 illustrates the welding of pieces of unequal thickness.
+
+Figure 38 illustrates welding at an angle.
+
+The molten metal may be directed as to where it should go by the tip of the
+welding flame, which has considerable force, but care must be taken not to
+blow melted metal on to cooler surfaces which it cannot join. If, while
+welding, a spot appears which does not unite with the weld, it may be
+handled by heating all around it to a white heat and then immediately
+welding the bad place.
+
+[Illustration: Figure 38.--Welding at an Angle]
+
+Never stop in the middle of a weld, as it is extremely difficult to
+continue smoothly when resuming work.
+
+_The Flame._--The welding flame must have exactly the right
+proportions of each gas. If there is too much oxygen, the metal will be
+burned or oxidized; the presence of too much acetylene carbonizes the
+metal; that is to say, it adds carbon and makes the work harder. Just the
+right mixture will neither burn nor carbonize and is said to be a "neutral"
+flame. The neutral flame, if of the correct size for the work, reduces the
+metal to a melted condition, not too fluid, and for a width about the same
+as the thickness of the metal being welded.
+
+When ready to light the torch, after attaching the right tip or head as
+directed in accordance with the thickness of metal to be handled, it will
+be necessary to regulate the pressure of gases to secure the neutral flame.
+
+The oxygen will have a pressure of from 2 to 20 pounds, according to the
+nozzle used. The acetylene will have much less. Even with the compressed
+gas, the pressure should never exceed 10 pounds for the largest work, and
+it will usually be from 4 to 6. In low pressure systems, the acetylene will
+be received at generator pressure. It should first be seen that the
+hand-screws on the regulators are turned way out so that the springs are
+free from any tension. It will do no harm if these screws are turned back
+until they come out of the threads. This must be done with both oxygen and
+acetylene regulators.
+
+Next, open the valve from the generator, or on the acetylene tank, and
+carefully note whether there is any odor of escaping gas. Any leakage of
+this gas must be stopped before going on with the work.
+
+The hand wheel controlling the oxygen cylinder valve should now be turned
+very slowly to the left as far as it will go, which opens the valve, and
+it should be borne in mind the pressure that is being released. Turn in the
+hand screw on the oxygen regulator until the small pressure gauge shows a
+reading according to the requirements of the nozzle being used. This oxygen
+regulator adjustment should be made with the cock on the torch open, and
+after the regulator is thus adjusted the torch cock may be closed.
+
+Open the acetylene cock on the torch and screw in on the acetylene
+regulator hand-screw until gas commences to come through the torch. Light
+this flow of acetylene and adjust the regulator screw to the pressure
+desired, or, if there is no gauge, so that there is a good full flame. With
+the pressure of acetylene controlled by the type of generator it will only
+be necessary to open the torch cock.
+
+With the acetylene burning, slowly open the oxygen cock on the torch and
+allow this gas to join the flame. The flame will turn intensely bright and
+then blue white. There will be an outer flame from four to eight inches
+long and from one to three inches thick. Inside of this flame will be two
+more rather distinctly defined flames. The inner one at the torch tip is
+very small, and the intermediate one is long and pointed. The oxygen should
+be turned on until the two inner flames unite into one blue-white cone from
+one-fourth to one-half inch long and one-eighth to one-fourth inch in
+diameter. If this single, clearly defined cone does not appear when the
+oxygen torch cock has been fully opened, turn off some of the acetylene
+until it does appear.
+
+If too much oxygen is added to the flame, there will still be the central
+blue-white cone, but it will be smaller and more or less ragged around the
+edges (Figure 39). When there is just enough oxygen to make the single
+cone, and when, by turning on more acetylene or by turning off oxygen, two
+cones are caused to appear, the flame is neutral (Figure 40), and the small
+blue-white cone is called the welding flame.
+
+[Illustration: Figure 39.--Oxidizing Flame--Too Much Oxygen]
+
+[Illustration: Figure 40.--Neutral Flame]
+
+[Illustration: Figure 41.--Reducing Flame--Showing an Excess of Acetylene]
+
+While welding, test the correctness of the flame adjustment occasionally by
+turning on more acetylene or by turning off some oxygen until two flames or
+cones appear. Then regulate as before to secure the single distinct cone.
+Too much oxygen is not usually so harmful as too much acetylene, except
+with aluminum. (See Figure 41.) An excessive amount of sparks coming from
+the weld denotes that there is too much oxygen in the flame. Should the
+opening in the tip become partly clogged, it will be difficult to secure a
+neutral flame and the tip should be cleaned with a brass or copper
+wire--never with iron or steel tools or wire of any kind. While the torch
+is doing its work, the tip may become excessively hot due to the heat
+radiated from the molten metal. The tip may be cooled by turning off the
+acetylene and dipping in water with a slight flow of oxygen through the
+nozzle to prevent water finding its way into the mixing chamber.
+
+The regulators for cutting are similar to those for welding, except that
+higher pressures may be handled, and they are fitted with gauges reading up
+to 200 or 250 pounds pressure.
+
+In welding metals which conduct the heat very rapidly it is necessary to
+use a much larger nozzle and flame than for metals which have not this
+property. This peculiarity is found to the greatest extent in copper,
+aluminum and brass.
+
+Should a hole be blown through the work, it may be closed by withdrawing
+the flame for a few seconds and then commencing to build additional metal
+around the edges, working all the way around and finally closing the small
+opening left at the center with a drop or two from the welding rod.
+
+
+WELDING VARIOUS METALS
+
+Because of the varying melting points, rates of expansion and contraction,
+and other peculiarities of different metals, it is necessary to give
+detailed consideration to the most important ones.
+
+_Characteristics of Metals._--The welder should thoroughly understand
+the peculiarities of the various metals with which he has to deal. The
+metals and their alloys are described under this heading in the first
+chapter of this book and a tabulated list of the most important points
+relating to each metal will be found at the end of the present chapter.
+All this information should be noted by the operator of a welding
+installation before commencing actual work.
+
+Because of the nature of welding, the melting point of a metal is of great
+importance. A metal melting at a low temperature should have more careful
+treatment to avoid undesired flow than one which melts at a temperature
+which is relatively high. When two dissimilar metals are to be joined, the
+one which melts at the higher temperature must be acted upon by the flame
+first and when it is in a molten condition the heat contained in it will in
+many cases be sufficient to cause fusion of the lower melting metal and
+allow them to unite without playing the flame on the lower metal to any
+great extent.
+
+The heat conductivity bears a very important relation to welding, inasmuch
+as a metal with a high rate of conductance requires more protection from
+cooling air currents and heat radiation than one not having this quality to
+such a marked extent. A metal which conducts heat rapidly will require a
+larger volume of flame, a larger nozzle, than otherwise, this being
+necessary to supply the additional heat taken away from the welding point
+by this conductance.
+
+The relative rates of expansion of the various metals under heat should be
+understood in order that parts made from such material may have proper
+preparation to compensate for this expansion and contraction. Parts made
+from metals having widely varying rates of expansion must have special
+treatment to allow for this quality, otherwise breakage is sure to occur.
+
+_Cast Iron._--All spoiled metal should he cut away and if the work is
+more than one-eighth inch in thickness the sides of the crack should be
+beveled to a 45 degree angle, leaving a number of points touching at the
+bottom of the bevel so that the work may be joined in its original
+relation.
+
+The entire piece should be preheated in a bricked-up oven or with charcoal
+placed on the forge, when size does not warrant building a temporary oven.
+The entire piece should be slowly heated and the portion immediately
+surrounding the weld should be brought to a dull red. Care should be used
+that the heat does not warp the metal through application to one part more
+than the others. After welding, the work should be slowly cooled by
+covering with ashes, slaked lime, asbestos fibre or some other
+non-conductor of heat. These precautions are absolutely essential in the
+case of cast iron.
+
+A neutral flame, from a nozzle proportioned to the thickness of the work,
+should be held with the point of the blue-white cone about one-eighth inch
+from the surface of the iron.
+
+A cast iron rod of correct diameter, usually made with an excess of
+silicon, is used by keeping its end in contact with the molten metal and
+flowing it into the puddle formed at the point of fusion. Metal should be
+added so that the weld stands about one-eighth inch above the surrounding
+surface of the work.
+
+Various forms of flux may be used and they are applied by dipping the end
+of the welding rod into the powder at intervals. These powders may contain
+borax or salt, and to prevent a hard, brittle weld, graphite or
+ferro-silicon may be added. Flux should be added only after the iron is
+molten and as little as possible should be used. No flux should be used
+just before completion of the work.
+
+The welding flame should be played on the work around the crack and
+gradually brought to bear on the work. The bottom of the bevel should be
+joined first and it will be noted that the cast iron tends to run toward
+the flame, but does not stick together easily. A hard and porous weld
+should be carefully guarded against, as described above, and upon
+completion of the work the welded surface should be scraped with a file,
+while still red hot, in order to remove the surface scale.
+
+_Malleable Iron._--This material should be beveled in the same way
+that cast iron is handled, and preheating and slow cooling are equally
+desirable. The flame used is the same as for cast iron and so is the flux.
+The welding rod may be of cast iron, although better results are secured
+with Norway iron wire or else a mild steel wire wrapped with a coil of
+copper wire.
+
+It will be understood that malleable iron turns to ordinary cast iron when
+melted and cooled. Welds in malleable iron are usually far from
+satisfactory and a better joint is secured by brazing the edges together
+with bronze. The edges to be joined are brought to a heat just a little
+below the point at which they will flow and the opening is then
+quickly-filled from a rod of Tobin bronze or manganese bronze, a brass or
+bronze flux being used in this work.
+
+_Wrought Iron or Semi-Steel._--This metal should be beveled and heated
+in the same way as described for cast iron. The flame should be neutral, of
+the same size as for steel, and used with the tip of the blue-white cone
+just touching the work. The welding rod should be of mild steel, or, if
+wrought iron is to be welded to steel, a cast iron rod may be used. A cast
+iron flux is well suited for this work. It should be noted that wrought
+iron turns to ordinary cast iron if kept heated for any length of time.
+
+_Steel._--Steel should be beveled if more than one-eighth inch in
+thickness. It requires only a local preheating around the point to be
+welded. The welding flame should be absolutely neutral, without excess of
+either gas. If the metal is one-sixteenth inch or less in thickness, the
+tip of the blue-white cone must be held a short distance from the surface
+of the work; in all other cases the tip of this cone is touched to the
+metal being welded.
+
+The welding rod may be of mild, low carbon steel or of Norway iron. Nickel
+steel rods may be used for parts requiring great strength, but vanadium
+alloys are very difficult to handle. A very satisfactory rod is made by
+twisting together two wires of the required material. The rod must be kept
+constantly in contact with the work and should not be added until the edges
+are thoroughly melted. The flux may or may not be used. If one is wanted,
+it may be made from three parts iron filings, six parts borax and one part
+sal ammoniac.
+
+It will be noticed that the steel runs from the flame, but tends to hold
+together. Should foaming commence in the molten metal, it shows an excess
+of oxygen and that the metal is being burned.
+
+High carbon steels are very difficult to handle. It is claimed that a drop
+or two of copper added to the weld will assist the flow, but will also
+harden the work. An excess of oxygen reduces the amount of carbon and
+softens the steel, while an excess of acetylene increases the proportion of
+carbon and hardens the metal. High speed steels may sometimes be welded if
+first coated with semi-steel before welding.
+
+_Aluminum._--This is the most difficult of the commonly found metals
+to weld. This is caused by its high rate of expansion and contraction and
+its liability to melt and fall away from under the flame. The aluminum
+seems to melt on the inside first, and, without previous warning, a portion
+of the work will simply vanish from in front of the operator's eyes. The
+metal tends to run from the flame and separate at the same time. To keep
+the metal in shape and free from oxide, it is worked or puddled while in a
+plastic condition by an iron rod which has been flattened at one end.
+Several of these rods should be at hand and may be kept in a jar of salt
+water while not being used. These rods must not become coated with aluminum
+and they must not get red hot while in the weld.
+
+The surfaces to be joined, together with the adjacent parts, should be
+cleaned thoroughly and then washed with a 25 per cent solution of nitric
+acid in hot water, used on a swab. The parts should then be rinsed in clean
+water and dried with sawdust. It is also well to make temporary fire clay
+moulds back of the parts to be heated, so that the metal may be flowed into
+place and allowed to cool without danger of breakage.
+
+Aluminum must invariably be preheated to about 600 degrees, and the whole
+piece being handled should be well covered with sheet asbestos to prevent
+excessive heat radiation.
+
+The flame is formed with an excess of acetylene such that the second cone
+extends about an inch, or slightly more, beyond the small blue-white point.
+The torch should be held so that the end of this second cone is in contact
+with the work, the small cone ordinarily used being kept an inch or an inch
+and a half from the surface of the work.
+
+Welding rods of special aluminum are used and must be handled with their
+end submerged in the molten metal of the weld at all times.
+
+When aluminum is melted it forms alumina, an oxide of the metal. This
+alumina surrounds small masses of the metal, and as it does not melt at
+temperatures below 5000 degrees (while aluminum melts at about 1200), it
+prevents a weld from being made. The formation of this oxide is retarded
+and the oxide itself is dissolved by a suitable flux, which usually
+contains phosphorus to break down the alumina.
+
+_Copper._--The whole piece should be preheated and kept well covered
+while welding. The flame must be much larger than for the same thickness of
+steel and neutral in character. A slight excess of acetylene would be
+preferable to an excess of oxygen, and in all cases the molten metal should
+be kept enveloped with the flame. The welding rod is of copper which
+contains phosphorus; and a flux, also containing phosphorus, should be
+spread for about an inch each side of the joint. These assist in preventing
+oxidation, which is sure to occur with heated copper.
+
+Copper breaks very easily at a heat slightly under the welding temperature
+and after cooling it is simply cast copper in all cases.
+
+_Brass and Bronze._--It is necessary to preheat these metals, although
+not to a very high temperature. They must be kept well covered at all times
+to prevent undue radiation. The flame should be produced with a nozzle one
+size larger than for the same thickness of steel and the small blue-white
+cone should be held from one-fourth to one-half inch above the surface of
+the work. The flame should be neutral in character.
+
+A rod or wire of soft brass containing a large percentage of zinc is
+suitable for adding to brass, while copper requires the use of copper or
+manganese bronze rods. Special flux or borax may be used to assist the
+flow.
+
+The emission of white smoke indicates that the zinc contained in these
+alloys is being burned away and the heat should immediately be turned away
+or reduced. The fumes from brass and bronze welding are very poisonous and
+should not be breathed.
+
+
+RESTORATION OF STEEL
+
+The result of the high heat to which the steel has been subjected is that
+it is weakened and of a different character than before welding. The
+operator may avoid this as much as possible by first playing the outer
+flame of the torch all over the surfaces of the work just completed until
+these faces are all of uniform color, after which the metal should be well
+covered with asbestos and allowed to cool without being disturbed. If a
+temporary heating oven has been employed, the work and oven should be
+allowed to cool together while protected with the sheet asbestos. If the
+outside air strikes the freshly welded work, even for a moment, the result
+will be breakage.
+
+A weld in steel will always leave the metal with a coarse grain and with
+all the characteristics of rather low grade cast steel. As previously
+mentioned in another chapter, the larger the grain size in steel the weaker
+the metal will be, and it is the purpose of the good workman to avoid, as
+far as possible, this weakening.
+
+The structure of the metal in one piece of steel will differ according to
+the heat that it has under gone. The parts of the work that have been at
+the melting point will, therefore, have the largest grain size and the
+least strength. Those parts that have not suffered any great rise in
+temperature will be practically unaffected, and all the parts between these
+two extremes will be weaker or stronger according to their distance from
+the weld itself. To restore the steel so that it will have the best grain
+size, the operator may resort to either of two methods: (1) The grain may
+be improved by forging. That means that the metal added to the weld and the
+surfaces that have been at the welding heat are hammered much as a
+blacksmith would hammer his finished work to give it greater strength. The
+hammering should continue from the time the metal first starts to cool
+until it has reached the temperature at which the grain size is best for
+strength. This temperature will vary somewhat with the composition of the
+metal being handled, but in a general way, it may be stated that the
+hammering should continue without intermission from the time the flame is
+removed from the weld until the steel just begins to show attraction for a
+magnet presented to it. This temperature of magnetic attraction will always
+be low enough and the hammering should be immediately discontinued at this
+point. (2) A method that is more satisfactory, although harder to apply, is
+that of reheating the steel to a certain temperature throughout its whole
+mass where the heat has had any effect, and then allowing slow and even
+cooling from this temperature. The grain size is affected by the
+temperature at which the reheating is stopped, and not by the cooling, yet
+the cooling should be slow enough to avoid strains caused by uneven
+contraction.
+
+After the weld has been completed the steel must be allowed to cool until
+below 1200  Fahrenheit. The next step is to heat the work slowly until all
+those parts to be restored have reached a temperature at which the magnet
+just ceases to be attracted. While the very best temperature will vary
+according to the nature and hardness of the steel being handled, it will be
+safe to carry the heating to the point indicated by the magnet in the
+absence of suitable means of measuring accurately these high temperatures.
+In using a magnet for testing, it will be most satisfactory if it is an
+electromagnet and not of the permanent type. The electric current may be
+secured from any small battery and will be the means of making sure of the
+test. The permanent magnet will quickly lose its power of attraction under
+the combined action of the heat and the jarring to which it will be
+subjected.
+
+In reheating the work it is necessary to make sure that no part reaches a
+temperature above that desired for best grain size and also to see that all
+parts are brought to this temperature. Here enters the greatest difficulty
+in restoring the metal. The heating may be done so slowly that no part of
+the work on the outside reaches too high a temperature and then keeps the
+outside at this heat until the entire mass is at the same temperature. A
+less desirable way is to heat the outside higher than this temperature and
+allow the conductivity of the metal to distribute the excess to the inside.
+
+The most satisfactory method, where it can be employed, is to make use of a
+bath of some molten metal or some chemical mixture that can be kept at the
+exact heat necessary by means of gas fires that admit of close regulation.
+The temperature of these baths may be maintained at a constant point by
+watching a pyrometer, and the finished work may be allowed to remain in the
+bath until all parts have reached the desired temperature.
+
+
+WELDING INFORMATION
+
+The following tables include much of the information that the operator must
+use continually to handle the various metals successfully. The temperature
+scales are given for convenience only. The composition of various alloys
+will give an idea of the difficulties to be contended with by consulting
+the information on welding various metals. The remaining tables are of
+self-evident value in this work.
+
+TEMPERATURE SCALES
+Centigrade  Fahrenheit      Centigrade  Fahrenheit
+   200         392             1000       1832 
+   225         437             1050       1922 
+   250         482             1100       2012 
+   275         527             1150       2102 
+   300         572             1200       2192 
+   325         617             1250       2282 
+   350         662             1300       2372 
+   375         707             1350       2462 
+   400         752             1400       2552 
+   425         797             1450       2642 
+   450         842             1500       2732 
+   475         887             1550       2822 
+   500         932             1600       2912 
+   525         977             1650       3002 
+   550        1022             1700       3092 
+   575        1067             1750       3182 
+   600        1112             1800       3272 
+   625        1157             1850       3362 
+   650        1202             1900       3452 
+   675        1247             2000       3632 
+   700        1292             2050       3722 
+   725        1337             2100       3812 
+   750        1382             2150       3902 
+   775        1427             2200       3992 
+   800        1472             2250       4082 
+   825        1517             2300       4172 
+   850        1562             2350       4262 
+   875        1607             2400       4352 
+   900        1652             2450       4442 
+   925        1697             2500       4532 
+   950        1742             2550       4622 
+   975        1787             2600       4712 
+
+METAL ALLOYS
+(Society of Automobile Engineers)
+
+Babbitt--
+  Tin...........................           84.00%
+  Antimony......................            9.00%
+  Copper........................            7.00%
+
+Brass, White--
+  Copper........................  3.00% to  6.00%
+  Tin (minimum) ................           65.00%
+  Zinc.......................... 28.00% to 30.00%
+
+Brass, Red Cast--
+  Copper........................           85.00%
+  Tin...........................            5.00%
+  Lead..........................            5.00%
+  Zinc..........................            5.00%
+
+Brass, Yellow--
+  Copper........................ 62.00% to 65.00%
+  Lead..........................  2.00% to  4.00%
+  Zinc.......................... 36.00% to 31.00%
+
+Bronze, Hard--
+  Copper........................ 87.00% to 88.00%
+  Tin...........................  9.50% to 10.50%
+  Zinc..........................  1.50% to  2.50%
+
+Bronze, Phosphor--
+  Copper........................           80.00%
+  Tin...........................           10.00%
+  Lead..........................           10.00%
+  Phosphorus....................   .50% to   .25%
+
+Bronze, Manganese--
+  Copper (approximate) .........           60.00%
+  Zinc (approximate) ...........           40.00%
+  Manganese (variable) .........            small
+
+Bronze, Gear--
+  Copper........................ 88.00% to 89.00%
+  Tin........................... 11.00% to 12.00%
+
+Aluminum Alloys--
+          Aluminum   Copper   Zinc   Manganese
+  No. 1.. 90.00%    8.5-7.0%
+  No. 2.. 80.00%    2.0-3.0%  15%  Not over 0.40%
+  No. 3.. 65.00%              35.0%
+
+Cast Iron--
+                      Gray Iron      Malleable
+  Total carbon........3.0 to 3.5%
+  Combined carbon.....0.4 to 0.7%
+  Manganese...........0.4 to 0.7%    0.3 to 0.7%
+  Phosphorus..........0.6 to 1.0%  Not over 0.2%
+  Sulphur...........Not over 0.1%  Not over 0.6%
+  Silicon............1.75 to 2.25% Not over 1.0%
+
+Carbon Steel (10 Point)--
+  Carbon........................     .05% to .15%
+  Manganese.....................     .30% to .60%
+  Phosphorus (maximum)..........             .045%
+  Sulphur (maximum).............             .05%
+(20 Point)--
+  Carbon........................     .15% to .25%
+  Manganese.....................     .30% to .60%
+  Phosphorus (maximum)..........             .045%
+  Sulphur (maximum).............             .05%
+(35 Point)--
+  Manganese.....................     .50% to .80%
+  Carbon........................     .30% to .40%
+  Phosphorus (maximum)..........             .05%
+  Sulphur (maximum).............             .05%
+(95 Point)--
+  Carbon........................    .90% to 1.05%
+  Manganese.....................    .25% to  .50%
+  Phosphorus (maximum)..........             .04%
+  Sulphur (maximum).............             .05%
+
+HEATING POWER OF FUEL GASES
+
+(In B.T.U. per Cubic Foot.)
+  Acetylene....... 1498.99   Ethylene....... 1562.9
+  Hydrogen........  291.96   Methane........  953.6
+  Alcohol......... 1501.76
+
+MELTING POINTS OF METALS
+  Platinum....................3200 
+  Iron, wrought...............2900 
+    malleable.................2500 
+    cast......................2400 
+    pure......................2760 
+  Steel, mild.................2700 
+    Medium....................2600 
+    Hard......................2500 
+  Copper......................1950 
+  Brass.......................1800 
+  Silver......................1750 
+  Bronze......................1700 
+  Aluminum....................1175 
+  Antimony....................1150 
+  Zinc........................ 800 
+  Lead........................ 620 
+  Babbitt..................500-700 
+  Solder...................500-575 
+  Tin......................... 450 
+
+_NOTE.--These melting points are for average compositions and conditions.
+The exact proportion of elements entering into the metals affects their
+melting points one way or the other in practice._
+
+TENSILE STRENGTH OF METALS
+
+Alloy steels can be made with tensile strengths as high as 300,000 pounds
+per square inch. Some carbon steels are given below according to "points":
+
+                           Pounds per Square Inch
+Steel, 10 point................ 50,000 to  65,000
+  20 point..................... 60,000 to  80,000
+  40 point..................... 70,000 to 100,000
+  60 point..................... 90,000 to 120,000
+Iron, Cast..................... 13,000 to  30,000
+  Wrought...................... 40,000 to  60,000
+  Malleable.................... 25,000 to  45,000
+Copper......................... 24,000 to  50,000
+Bronze......................... 30,000 to  60,000
+Brass, Cast.................... 12,000 to  18,000
+  Rolled....................... 30,000 to  40,000
+  Wire......................... 60,000 to  75,000
+Aluminum....................... 12,000 to  23,000
+Zinc...........................  5,000 to  15,000
+Tin............................  3,000 to   5,000
+Lead...........................  1,500 to   2,500
+
+CONDUCTIVITY OF METALS
+
+(Based on the Value of Silver as 100)
+
+                          Heat  Electricity
+Silver....................100     100
+Copper.................... 74      99
+Aluminum.................. 38      63
+Brass..................... 23      22
+Zinc...................... 19      29
+Tin....................... 14      15
+Wrought Iron.............. 12      16
+Steel..................... 11.5    12
+Cast Iron................. 11      12
+Bronze....................  9       7
+Lead......................  8       9
+
+WEIGHT OF METALS
+
+(Per Cubic Inch)
+                 Pounds                  Pounds
+Lead............  .410  Wrought Iron.....  .278
+Copper..........  .320  Tin..............  .263
+Bronze..........  .313  Cast Iron........  .260
+Brass...........  .300  Zinc.............  .258
+Steel...........  .283  Aluminum.........  .093
+
+EXPANSION OF METALS
+
+(Measured in Thousandths of an Inch per Foot of
+Length When Raised 1000 Degrees in Temperature)
+                  Inch                     Inch
+Lead............  .188  Brass............  .115
+Zinc............  .168  Copper...........  .106
+Aluminum........  .148  Steel............  .083
+Silver..........  .129  Wrought Iron.....  .078
+Bronze..........  .118  Cast Iron........  .068
+
+
+
+
+CHAPTER VI
+
+ELECTRIC WELDING
+
+
+RESISTANCE METHOD
+
+Two distinct forms of electric welding apparatus are in use, one producing
+heat by the resistance of the metal being treated to the passage of
+electric current, the other using the heat of the electric arc.
+
+The resistance process is of the greatest use in manufacturing lines where
+there is a large quantity of one kind of work to do, many thousand pieces
+of one kind, for instance. The arc method may be applied in practically any
+case where any other form of weld may be made. The resistance process will
+be described first.
+
+It is a well known fact that a poor conductor of electricity will offer so
+much resistance to the flow of electricity that it will heat. Copper is a
+good conductor, and a bar of iron, a comparatively poor conductor, when
+placed between heavy copper conductors of a welder, becomes heated in
+attempting to carry the large volume of current. The degree of heat depends
+on the amount of current and the resistance of the conductor.
+
+In an electric circuit the ends of two pieces of metal brought together
+form the point of greatest resistance in the electric circuit, and the
+abutting ends instantly begin to heat. The hotter this metal becomes, the
+greater the resistance to the flow of current; consequently, as the edges
+of the abutting ends heat, the current is forced into the adjacent cooler
+parts, until there is a uniform heat throughout the entire mass. The heat
+is first developed in the interior of the metal so that it is welded there
+as perfectly as at the surface.
+
+[Illustration: Figure 42.--Spot Welding Machine]
+
+The electric welder (Figure 42) is built to hold the parts to be joined
+between two heavy copper dies or contacts. A current of three to five
+volts, but of very great volume (amperage), is allowed to pass across
+these dies, and in going through the metal to be welded, heats the edges
+to a welding temperature. It may be explained that the voltage of an
+electric current measures the pressure or force with which it is being sent
+through the circuit and has nothing to do with the quantity or volume
+passing. Amperes measure the rate at which the current is passing through
+the circuit and consequently give a measure of the quantity which passes in
+any given time. Volts correspond to water pressure measured by pounds to
+the square inch; amperes represent the flow in gallons per minute. The low
+voltage used avoids all danger to the operator, this pressure not being
+sufficient to be felt even with the hands resting on the copper contacts.
+
+Current is supplied to the welding machine at a higher voltage and lower
+amperage than is actually used between the dies, the low voltage and high
+amperage being produced by a transformer incorporated in the machine
+itself. By means of windings of suitable size wire, the outside current may
+be received at voltages ranging from 110 to 550 and converted to the low
+pressure needed.
+
+The source of current for the resistance welder must be alternating, that
+is, the current must first be negative in value and then positive, passing
+from one extreme to the other at rates varying from 25 to 133 times a
+second. This form is known as alternating current, as opposed to direct
+current, in which there is no changing of positive and negative.
+
+The current must also be what is known as single phase, that is, a current
+which rises from zero in value to the highest point as a positive current
+and then recedes to zero before rising to the highest point of negative
+value. Two-phase of three-phase currents would give two or three positive
+impulses during this time.
+
+As long as the current is single phase alternating, the voltage and cycles
+(number of alternations per second) may be anything convenient. Various
+voltages and cycles are taken care of by specifying all these points when
+designing the transformer which is to handle the current.
+
+Direct current is not used because there is no way of reducing the voltage
+conveniently without placing resistance wires in the circuit and this uses
+power without producing useful work. Direct current may be changed to
+alternating by having a direct current motor running an alternating current
+dynamo, or the change may be made by a rotary converter, although this last
+method is not so satisfactory as the first.
+
+The voltage used in welding being so low to start with, it is absolutely
+necessary that it be maintained at the correct point. If the source of
+current supply is not of ample capacity for the welder being used, it will
+be very hard to avoid a fall of voltage when the current is forced to pass
+through the high resistance of the weld. The current voltage for various
+work is calculated accurately, and the efficiency of the outfit depends to
+a great extent on the voltage being constant.
+
+A simple test for fall of voltage is made by connecting an incandescent
+electric lamp across the supply lines at some point near the welder. The
+lamp should burn with the same brilliancy when the weld is being made as at
+any other time. If the lamp burns dim at any time, it indicates a drop in
+voltage, and this condition should be corrected.
+
+The dynamo furnishing the alternating current may be in the same building
+with the welder and operated from a direct current motor, as mentioned
+above, or operated from any convenient shafting or source of power. When
+the dynamo is a part of the welding plant it should be placed as close to
+the welding machine as possible, because the length of the wire used
+affects the voltage appreciably.
+
+In order to hold the voltage constant, the Toledo Electric Welder Company
+has devised connections which include a rheostat to insert a variable
+resistance in the field windings of the dynamo so that the voltage may be
+increased by cutting this resistance out at the proper time. An auxiliary
+switch is connected to the welder switch so that both switches act
+together. When the welder switch is closed in making a weld, that portion
+of the rheostat resistance between two arms determining the voltage is
+short circuited. This lowers the resistance and the field magnets of the
+dynamo are made stronger so that additional voltage is provided to care for
+the resistance in the metal being heated.
+
+A typical machine is shown in the accompanying cut (Figure 43). On top of
+the welder are two jaws for holding the ends of the pieces to be welded.
+The lower part of the jaws is rigid while the top is brought down on top of
+the work, acting as a clamp. These jaws carry the copper dies through which
+the current enters the work being handled. After the work is clamped
+between the jaws, the upper set is forced closer to the lower set by a long
+compression lever. The current being turned on with the surfaces of the
+work in contact, they immediately heat to the welding point when added
+pressure on the lever forces them together and completes the weld.
+
+[Illustration: Figure 43--Operating Parts of a Toledo Spot Welder]
+
+[Illustration: Figure 43a.--Method of Testing Electric Welder]
+[Illustration: Figure 44.--Detail of Water-Cooled Spot Welding Head]
+
+The transformer is carried in the base of the machine and on the left-hand
+side is a regulator for controlling the voltage for various kinds of work.
+The clamps are applied by treadles convenient to the foot of the operator.
+A treadle is provided which instantly releases both jaws upon the
+completion of the weld. One or both of the copper dies may be cooled by a
+stream of water circulating through it from the city water mains
+(Figure 44). The regulator and switch give the operator control of the
+heat, anything from a dull red to the melting point being easily obtained
+by movement of the lever (figure 45).
+
+[Illustration: Figure 45.--Welding Head of a Water-Cooled Welder]
+
+_Welding._--It is not necessary to give the metal to be welded any
+special preparation, although when very rusty or covered with scale, the
+rust and scale should be removed sufficiently to allow good contact of
+clean metal on the copper dies. The cleaner and better the stock, the less
+current it takes, and there is less wear on the dies. The dies should be
+kept firm and tight in their holders to make a good contact. All bolts and
+nuts fastening the electrical contacts should be clean and tight at all
+times.
+
+The scale may be removed from forgings by immersing them in a pickling
+solution in a wood, stone or lead-lined tank.
+
+The solution is made with five gallons of commercial sulphuric acid in
+150 gallons of water. To get the quickest and best results from this
+method, the solution should be kept as near the boiling point as possible
+by having a coil of extra heavy lead pipe running inside the tank and
+carrying live steam. A very few minutes in this bath will remove the scale
+and the parts should then be washed in running water. After this washing
+they should be dipped into a bath of 50 pounds of unslaked lime in 150
+gallons of water to neutralize any trace of acid.
+
+Cast iron cannot be commercially welded, as it is high in carbon and
+silicon, and passes suddenly from a crystalline to a fluid state when
+brought to the welding temperature. With steel or wrought iron the
+temperature must be kept below the melting point to avoid injury to the
+metal. The metal must be heated quickly and pressed together with
+sufficient force to push all burnt metal out of the joint.
+
+High carbon steel can be welded, but must be annealed after welding to
+overcome the strains set up by the heat being applied at one place. Good
+results are hard to obtain when the carbon runs as high as 75 points, and
+steel of this class can only be handled by an experienced operator. If the
+steel is below 25 points in carbon content, good welds will always be the
+result. To weld high carbon to low carbon steel, the stock should be
+clamped in the dies with the low carbon stock sticking considerably further
+out from the die than the high carbon stock. Nickel steel welds readily,
+the nickel increasing the strength of the weld.
+
+Iron and copper may be welded together by reducing the size of the copper
+end where it comes in contact with the iron. When welding copper and brass
+the pressure must be less than when welding iron. The metal is allowed to
+actually fuse or melt at the juncture and the pressure must be sufficient
+to force the burned metal out. The current is cut off the instant the metal
+ends begin to soften, this being done by means of an automatic switch which
+opens when the softening of the metal allows the ends to come together. The
+pressure is applied to the weld by having the sliding jaw moved by a weight
+on the end of an arm.
+
+Copper and brass require a larger volume of current at a lower voltage than
+for steel and iron. The die faces are set apart three times the diameter of
+the stock for brass and four times the diameter for copper.
+
+Light gauges of sheet steel can be welded to heavy gauges or to solid bars
+of steel by "spot" welding, which will be described later. Galvanized iron
+can be welded, but the zinc coating will be burned off. Sheet steel can be
+welded to cast iron, but will pull apart, tearing out particles of the
+iron.
+
+Sheet copper and sheet brass may be welded, although this work requires
+more experience than with iron and steel. Some grades of sheet aluminum can
+be spot-welded if the slight roughness left on the surface under the die
+is not objectionable.
+
+_Butt Welding._--This is the process which joins the ends of two
+pieces of metal as described in the foregoing part of this chapter. The
+ends are in plain sight of the operator at all times and it can easily be
+seen when the metal reaches the welding heat and begins to soften (Figure
+46). It is at this point that the pressure must be applied with the lever
+and the ends forced together in the weld.
+
+[Illustration: Figure 46.--Butt Welder]
+
+The parts are placed in the clamping jaws (Figure 47) with 1/8 to 1/2 inch
+of metal extending beyond the jaw. The ends of the metal touch each other
+and the current is turned on by means of a switch. To raise the ends to the
+proper heat requires from 3 seconds for 1/4-inch rods to 35 seconds for a
+1-1/2-inch bar.
+
+This method is applicable to metals having practically the same area of
+metal to be brought into contact on each end. When such parts are forced
+together a slight projection will be left in the form of a fin or an
+enlarged portion called an upset. The degree of heat required for any work
+is found by moving the handle of the regulator one way or the other while
+testing several parts. When this setting is right the work can continue as
+long as the same sizes are being handled.
+
+[Illustration: Figure 47.--Clamping Dies of a Butt Welder]
+
+Copper, brass, tool steel and all other metals that are harmed by high
+temperatures must be heated quickly and pressed together with sufficient
+force to force all burned metal from the weld.
+
+In case it is desired to make a weld in the form of a capital letter T, it
+is necessary to heat the part corresponding to the top bar of the T to a
+bright red, then bring the lower bar to the pre-heated one and again turn
+on the current, when a weld can be quickly made.
+
+_Spot Welding._--This is a method of joining metal sheets together at
+any desired point by a welded spot about the size of a rivet. It is done on
+a spot welder by fusing the metal at the point desired and at the same
+instant applying sufficient pressure to force the particles of molten metal
+together. The dies are usually placed one above the other so that the work
+may rest on the lower one while the upper one is brought down on top of the
+upper sheet to be welded.
+
+One of the dies is usually pointed slightly, the opposing one being left
+flat. The pointed die leaves a slight indentation on one side of the metal,
+while the other side is left smooth. The dies may be reversed so that the
+outside surface of any work may be left smooth. The current is allowed to
+flow through the dies by a switch which is closed after pressure is applied
+to the work.
+
+There is a limit to the thickness of sheet metal that can be welded by this
+process because of the fact that the copper rods can only carry a certain
+quantity of current without becoming unduly heated themselves. Another
+reason is that it is difficult to make heavy sections of metal touch at the
+welding point without excessive pressure.
+
+_Lap welding_ is the process used when two pieces of metal are caused
+to overlap and when brought to a welding heat are forced together by
+passing through rollers, or under a press, thus leaving the welded joint
+practically the same thickness as the balance of the work.
+
+Where it is desirable to make a continuous seam, a special machine is
+required, or an attachment for one of the other types. In this form of work
+the stock must be thoroughly cleaned and is then passed between copper
+rollers which act in the same capacity as the copper dies.
+
+_Other Applications._--Hardening and tempering can be done by clamping
+the work in the welding dies and setting the control and time to bring the
+metal to the proper color, when it is cooled in the usual manner.
+
+Brazing is done by clamping the work in the jaws and heating until the
+flux, then the spelter has melted and run into the joint. Riveting and
+heading of rivets can be done by bringing the dies down on opposite ends of
+the rivet after it has been inserted in the hole, the dies being shaped to
+form the heads properly.
+
+Hardened steel may be softened and annealed so that it can be machined by
+connecting the dies of the welder to each side of the point to be softened.
+The current is then applied until the work has reached a point at which it
+will soften when cooled.
+
+_Troubles and Remedies._--The following methods have been furnished by
+the Toledo Electric Welder Company and are recommended for this class of
+work whenever necessary.
+
+To locate grounds in the primary or high voltage side of the circuit,
+connect incandescent lamps in series by means of a long piece of lamp cord,
+as shown, in Figure 43a. For 110 volts use one lamp, for 220 volts use two
+lamps and for 440 volts use four lamps. Attach one end of the lamp cord to
+one side of the switch, and close the switch. Take the other end of the
+cord in the hand and press it against some part of the welder frame where
+the metal is clean and bright. Paint, grease and dirt act as insulators and
+prevent electrical contact. If the lamp lights, the circuit is in
+electrical contact with the frame; in other words, grounded. If the lamps
+do not light, connect the wire to a terminal block, die or slide. If the
+lamps then light, the circuit, coils or leads are in electrical contact
+with the large coil in the transformer or its connections.
+
+If, however, the lamps do not light in either case, the lamp cord should be
+disconnected from the switch and connected to the other side, and the
+operations of connecting to welder frame, dies, terminal blocks, etc., as
+explained above, should be repeated. If the lamps light at any of these
+connections, a "ground" is indicated. "Grounds" can usually be found by
+carefully tracing the primary circuit until a place is found where the
+insulation is defective. Reinsulate and make the above tests again to make
+sure everything is clear. If the ground can not be located by observation,
+the various parts of the primary circuit should be disconnected, and the
+transformer, switch, regulator, etc., tested separately.
+
+To locate a ground in the regulator or other part, disconnect the lines
+running to the welder from the switch. The test lamps used in the previous
+tests are connected, one end of lamp cord to the switch, the other end to a
+binding post of the regulator. Connect the other side of the switch to some
+part of the regulator housing. (This must be a clean connection to a bolt
+head or the paint should be scraped off.) Close the switch. If the lamps
+light, the regulator winding or some part of the switch is "grounded" to
+the iron base or core of the regulator. If the lamps do not light, this
+part of the apparatus is clear.
+
+This test can be easily applied to any part of the welder outfit by
+connecting to the current carrying part of the apparatus, and to the iron
+base or frame that should not carry current. If the lamps light, it
+indicates that the insulation is broken down or is defective.
+
+An A.C. voltmeter can, of course, be substituted for the lamps, or a D.C.
+voltmeter with D.C. current can be used in making the tests.
+
+A short circuit in the primary is caused by the insulation of the coils
+becoming defective and allowing the bare copper wires to touch each other.
+This may result in a "burn out" of one or more of the transformer coils, if
+the trouble is in the transformer, or in the continued blowing of fuses in
+the line. Feel of each coil separately. If a short circuit exists in a coil
+it will heat excessively. Examine all the wires; the insulation may have
+worn through and two of them may cross, or be in contact with the frame or
+other part of the welder. A short circuit in the regulator winding is
+indicated by failure of the apparatus to regulate properly, and sometimes,
+though not always, by the heating of the regulator coils.
+
+The remedy for a short circuit is to reinsulate the defective parts. It is
+a good plan to prevent trouble by examining the wiring occasionally and see
+that the insulation is perfect.
+
+_To Locate Grounds and Short Circuits in the Secondary, or Low Voltage
+Side._--Trouble of this kind is indicated by the machine acting sluggish
+or, perhaps, refusing to operate. To make a test, it will be necessary to
+first ascertain the exciting current of your particular transformer. This
+is the current the transformer draws on "open circuit," or when supplied
+with current from the line with no stock in the welder dies. The following
+table will give this information close enough for all practical purposes:
+
+K.W.      ----------------- Amperes at ----------------
+Rating    110 Volts   220 Volts   440 Volts   550 Volts
+3         1.5         .75         .38         .3
+5         2.5         1.25        .63         .5
+8         3.6         1.8         .9          .72
+10        4.25        2.13        1.07        .85
+15        6.          3.          1.5         1.2
+20        7.          3.5         1.75        1.4
+30        9.          4.5         2.25        1.8
+35        9.6         4.8         2.4         1.92
+50        10.         5.          2.5         2
+
+Remove the fuses from the wall switch and substitute fuses just large
+enough to carry the "exciting" current. If no suitable fuses are at hand,
+fine strands of copper from an ordinary lamp cord may be used. These
+strands are usually No. 30 gauge wire and will fuse at about 10 amperes.
+One or more strands should be used, depending on the amount of exciting
+current, and are connected across the fuse clips in place of fuse wire.
+Place a piece of wood or fibre between the welding dies in the welder as
+though you were going to weld them. See that the regulator is on the
+highest point and close the welder switch. If the secondary circuit is
+badly grounded, current will flow through the ground, and the small fuses
+or small strands of wire will burn out. This is an indication that both
+sides of the secondary circuit are grounded or that a short circuit exists
+in a primary coil. In either case the welder should not be operated until
+the trouble is found and removed. If, however, the small fuses do not
+"blow," remove same and replace the large fuses, then disconnect wires
+running from the wall switch to the welder and substitute two pieces of
+No. 8 or No. 6 insulated copper wire, after scraping off the insulation for
+an inch or two at each end. Connect one wire from the switch to the frame
+of welder; this will leave one loose end. Hold this a foot or so away from
+the place where the insulation is cut off; then turn on the current and
+strike the free end of this wire lightly against one of the copper dies,
+drawing it away quickly. If no sparking is produced, the secondary circuit
+is free from ground, and you will then look for a broken connection in the
+circuit. Some caution must be used in making the above test, as in case one
+terminal is heavily grounded the testing wire may be fused if allowed to
+stay in contact with the die.
+
+_The Remedy._--Clean the slides, dies and terminal blocks thoroughly
+and dry out the fibre insulation if it is damp. See that no scale or metal
+has worked under the sliding parts, and that the secondary leads do not
+touch the frame. If the ground is very heavy it may be necessary to remove
+the slides in order to facilitate the examination and removal of the
+ground. Insulation, where torn or worn through, must be carefully replaced
+or taped. If the transformer coils are grounded to the iron core of the
+transformer or to the secondary, it may be necessary to remove the coils
+and reinsulate them at the points of contact. A short circuited coil will
+heat excessively and eventually burn out. This may mean a new coil if you
+are unable to repair the old one. In all cases the transformer windings
+should be protected from mechanical injury or dampness. Unless excessively
+overloaded, transformers will last for years without giving a moment's
+trouble, if they are not exposed to moisture or are not injured
+mechanically.
+
+The most common trouble arises from poor electrical contacts, and they are
+the cause of endless trouble and annoyance. See that all connections are
+clean and bright. Take out the dies every day or two and see that there is
+no scale, grease or dirt between them and the holders. Clean them
+thoroughly before replacing. Tighten the bolts running from the transformer
+leads to the work jaws.
+
+
+ELECTRIC ARC WELDING
+
+This method bears no relation to the one just considered, except that the
+source of heat is the same in both cases. Arc welding makes use of the
+flame produced by the voltaic arc in practically the same way that
+oxy-acetylene welding uses the flame from the gases.
+
+If the ends of two pieces of carbon through which a current of electricity
+is flowing while they are in contact are separated from each other quite
+slowly, a brilliant arc of flame is formed between them which consists
+mainly of carbon vapor. The carbons are consumed by combination with the
+oxygen in the air and through being turned to a gas under the intense heat.
+
+The most intense action takes place at the center of the carbon which
+carries the positive current and this is the point of greatest heat. The
+temperature at this point in the arc is greater than can be produced by any
+other means under human control.
+
+An arc may be formed between pieces of metal, called electrodes, in the
+same way as between carbon. The metallic arc is called a flaming arc and as
+the metal of the electrode burns with the heat, it gives the flame a color
+characteristic of the material being used. The metallic arc may be drawn
+out to a much greater length than one formed between carbon electrodes.
+
+Arc Welding is carried out by drawing a piece of carbon which is of
+negative polarity away from the pieces of metal to be welded while the
+metal is made positive in polarity. The negative wire is fastened to the
+carbon electrode and the work is laid on a table made of cast or wrought
+iron to which the positive wire is made fast. The direction of the flame is
+then from the metal being welded to the carbon and the work is thus
+prevented from being saturated with carbon, which would prove very
+detrimental to its strength. A secondary advantage is found in the fact
+that the greatest heat is at the metal being welded because of its being
+the positive electrode.
+
+The carbon electrode is usually made from one quarter to one and a half
+inches in diameter and from six to twelve inches in length. The length of
+the arc may be anywhere from one inch to four inches, depending on the size
+of the work being handled.
+
+While the parts are carefully insulated to avoid danger of shock, it is
+necessary for the operator to wear rubber gloves as a further protection,
+and to wear some form of hood over the head to shield him against the
+extreme heat liberated. This hood may be made from metal, although some
+material that does not conduct electricity is to be preferred. The work is
+watched through pieces of glass formed with one sheet, which is either blue
+or green, placed over another which is red. Screens of glass are sometimes
+used without the head protector. Some protection for the eyes is absolutely
+necessary because of the intense white light.
+
+It is seldom necessary to preheat the work as with the gas processes,
+because the heat is localized at the point of welding and the action is so
+rapid that the expansion is not so great. The necessity of preheating,
+however, depends entirely on the material, form and size of the work being
+handled. The same advice applies to arc welding as to the gas flame method
+but in a lesser degree. Filling rods are used in the same way as with any
+other flame process.
+
+It is the purpose of this explanation to state the fundamental principles
+of the application of the electric arc to welding metals, and by applying
+the principles the following questions will be answered:
+
+What metals can be welded by the electric arc?
+
+What difficulties are to be encountered in applying the electric arc to
+welding?
+
+What is the strength of the weld in comparison with the original piece?
+
+What is the function of the arc welding machine itself?
+
+What is the comparative application of the electric arc and the
+oxy-acetylene method and others of a similar nature?
+
+The answers to these questions will make it possible to understand the
+application of this process to any work. In a great many places the use of
+the arc is cutting the cost of welding to a very small fraction of what it
+would be by any other method, so that the importance of this method may be
+well understood.
+
+Any two metals which are brought to the melting temperature and applied to
+each other will adhere so that they are no more apt to break at the weld
+than at any other point outside of the weld. It is the property of all
+metals to stick together under these conditions. The electric arc is used
+in this connection merely as a heating agent. This is its only function in
+the process.
+
+It has advantages in its ease of application and the cheapness with which
+heat can be liberated at any given point by its use. There is nothing in
+connection with arc welding that the above principles will not answer; that
+is, that metals at the melting point will weld and that the electric arc
+will furnish the heat to bring them to this point. As to the first
+question, what metals can be welded, all metals can be welded.
+
+The difficulties which are encountered are as follows:
+
+In the case of brass or zinc, the metals will be covered with a coat of
+zinc oxide before they reach a welding heat. This zinc oxide makes it
+impossible for two clean surfaces to come together and some method has to
+be used for eliminating this possibility and allowing the two surfaces to
+join without the possibility of the oxide intervening. The same is true of
+aluminum, in which the oxide, alumina, will be formed, and with several
+other alloys comprising elements of different melting points.
+
+In order to eliminate these oxides, it is necessary in practical work, to
+puddle the weld; this is, to have a sufficient quantity of molten metal at
+the weld so that the oxide is floated away. When this is done, the two
+surfaces which are to be joined are covered with a coat of melted metal on
+which floats the oxide and other impurities. The two pieces are thus
+allowed to join while their surfaces are protected. This precaution is not
+necessary in working with steel except in extreme cases.
+
+Another difficulty which is met with in the welding of a great many metals
+is their expansion under heat, which results in so great a contraction when
+the weld cools that the metal is left with a considerable strain on it. In
+extreme cases this will result in cracking at the weld or near it. To
+eliminate this danger it is necessary to apply heat either all over the
+piece to be welded or at certain points. In the case of cast iron and
+sometimes with copper it is necessary to anneal after welding, since
+otherwise the welded pieces will be very brittle on account of the
+chilling. This is also true of malleable iron.
+
+Very thin metals which are welded together and are not backed up by
+something to carry away the excess heat, are very apt to burn through,
+leaving a hole where the weld should be. This difficulty can be eliminated
+by backing up the weld with a metal face or by decreasing the intensity of
+the arc so that this melting through will not occur. However, the practical
+limit for arc welding without backing up the work with a metal face or
+decreasing the intensity of the arc is approximately 22 gauge, although
+thinner metal can be welded by a very skillful and careful operator.
+
+One difficulty with arc welding is the lack of skillful operators. This
+method is often looked upon as being something out of the ordinary and
+governed by laws entirely different from other welding. As a matter of
+fact, it does not take as much skill to make a good arc weld as it does to
+make a good weld in a forge fire as the blacksmith does it. There are few
+jobs which cannot be handled successfully by an operator of average
+intelligence with one week's instructions, although his work will become
+better and better in quality as he continues to use the arc.
+
+Now comes the question of the strength of the weld after it has been made.
+This strength is equally as great as that of the metal that is used to make
+the weld. It should be remembered, however, that the metal which goes into
+the weld is put in there as a casting and has not been rolled. This would
+make the strength of the weld as great as the same metal that is used for
+filling if in the cast form.
+
+Two pieces of steel could be welded together having a tensile strength at
+the weld of 50,000 pounds. Higher strengths than this can be obtained by
+the use of special alloys for the filling material or by rolling. Welds
+with a tensile strength as great as mentioned will give a result which is
+perfectly satisfactory in almost all cases.
+
+There are a great many jobs where it is possible to fill up the weld, that
+is, make the section at the point of the weld a little larger than the
+section through the rest of the piece. By doing this, the disadvantages
+of the weld being in the form of a casting in comparison with the rest of
+the piece being in the form of rolled steel can be overcome, and make the
+weld itself even stronger than the original piece.
+
+The next question is the adaptability of the electric arc in comparison
+with forge fire, oxy-acetylene or other method. The answer is somewhat
+difficult if made general. There are no doubt some cases where the use of a
+drop hammer and forge fire or the use of the oxy-acetylene torch will make,
+all things being considered, a better job than the use of the electric arc,
+although a case where this is absolutely proved is rare.
+
+The electric arc will melt metal in a weld for less than the same metal can
+be melted by the use of the oxy-acetylene torch, and, on account of the
+fact that the heat can be applied exactly where it is required and in the
+amount required, the arc can in almost all cases supply welding heat for
+less cost than a forge fire or heating furnace.
+
+The one great advantage of the oxy-acetylene method in comparison with
+other methods of welding is the fact that in some cases of very thin sheet,
+the weld can be made somewhat sooner than is possible otherwise. With metal
+of 18 gauge or thicker, this advantage is eliminated. In cutting steel, the
+oxy-acetylene torch is superior to almost any other possible method.
+
+_Arc Welding Machines._--A consideration of the function and purpose
+of the various types of arc welding machines shows that the only reason for
+the use of any machine is either for conversion of the current from
+alternating to direct, or, if the current is already direct, then the
+saving in the application of this current in the arc.
+
+It is practically out of the question to apply an alternating current arc
+to welding for the reason that in any arc practically all the heat is
+liberated at the positive electrode, which means that, in alternating
+current, half the heat is liberated at each electrode as the current
+changes its direction of flow or alternates. Another disadvantage of the
+alternating arc is that it is difficult of control and application.
+
+In all arc welding by the use of the carbon arc, the positive electrode is
+made the piece to be welded, while in welding with metallic electrodes this
+may be either the piece to be welded of the rod that is used as a filler.
+The voltage across the arc is a variable quantity, depending on the length
+of the flame, its temperature and the gases liberated in the arc. With a
+carbon electrode the voltage will vary from zero to forty-five volts. With
+the metallic electrode the voltage will vary from zero to thirty volts. It
+is, therefore, necessary for the welding machine to be able to furnish to
+the arc the requisite amount of current, this amount being varied, and
+furnish it at all times at the voltage required.
+
+The simplest welding apparatus is a resistance in series with the arc. This
+is entirely satisfactory in every way except in cost of current. By the use
+of resistance in series with the arc and using 220 volts as the supply,
+from eighty to ninety per cent of the current is lost in heat at the
+resistance. Another disadvantage is the fact that most materials change
+their resistance as their temperature changes, thus making the amount of
+current for the arc a variable quantity, depending on the temperature of
+the resistance.
+
+There have been various methods originated for saving the power mentioned
+and a good many machines have been put on the market for this purpose. All
+of them save some power over what a plain resistance would use. Practically
+all arc welding machines at the present time are motor generator sets, the
+motor of which is arranged for the supply voltage and current, this motor
+being direct connected to a compound wound generator delivering
+approximately seventy-five volts direct current. Then by the use of a
+resistance, this seventy-five volt supply is applied to the arc. Since the
+voltage across the arc will vary from zero to fifty volts, this machine
+will save from zero up to seventy per cent of the power that the machine
+delivers. The rest of the power, of course, has to be dissipated in the
+resistance used in series with the arc.
+
+A motor generator set which can be purchased from any electrical company,
+with a long piece of fence wire wound around a piece of asbestos, gives
+results equally as good and at a very small part of the first cost.
+
+It is possible to construct a machine which will eliminate all losses in
+the resistance; in other words, eliminate all resistance in series with the
+arc. A machine of this kind will save its cost within a very short time,
+providing the welder is used to any extent.
+
+Putting it in figures, the results are as follows for average conditions.
+Current at 2c per kilowatt hour, metallic electrode arc of 150 amperes,
+carbon arc 500 amperes; voltage across the metallic electrode arc 20,
+voltage across the carbon arc 35. Supply current 220 volts, direct. In the
+case of the metallic electrode, if resistance is used, the cost of running
+this arc is sixty-six cents per hour. With the carbon electrode, $2.20 per
+hour. If a motor generator set with a seventy volt constant potential
+machine is used for a welder, the cost will be as follows:
+
+Metallic electrode 25.2c. Carbon electrode 84c per hour. With a machine
+which will deliver the required voltage at the arc and eliminate all the
+resistance in series with the arc, the cost will be as follows: Metallic
+electrode 7.2c per hour; carbon electrode 42c per hour. This is with the
+understanding that the arc is held constant and continuously at its full
+value. This, however, is practically impossible and the actual load factor
+is approximately fifty per cent, which would mean that operating a welder
+as it is usually operated, this result will be reduced to one-half of that
+stated in all cases.
+
+
+
+
+CHAPTER VII
+
+HAND FORGING AND WELDING
+
+
+Smithing, or blacksmithing, is the process of working heated iron, steel or
+other metals by forging, bending or welding them.
+
+_The Forge._--The metal is heated in a forge consisting of a shallow
+pan for holding the fire, in the center of which is an opening from below
+through which air is forced to make a hot fire.
+
+[Illustration: Figure 48.--Tuyere Construction on a Forge]
+
+Air is forced through this hole, called a "tuyere" (Figure 48) by means of
+a hand bellows, a rotary fan operated with crank or lever, or with a fan
+driven from an electric motor. The harder the air is driven into the fire
+above the tuyere the more oxygen is furnished and the hotter the fire
+becomes.
+
+Directly below the tuyere is an opening through which the ashes that drop
+from the fire may be cleaned out.
+
+_The Fire._--The fire is made by placing a small piece of waste soaked
+in oil, kerosene or gasoline, over the tuyere, lighting the waste, then
+starting the fan or blower slowly. Gradually cover the waste, while it is
+burning brightly, with a layer of soft coal. The coal will catch fire and
+burn after the waste has been consumed. A piece of waste half the size of a
+person's hand is ample for this purpose.
+
+The fuel should be "smithing coal." A lump of smithing coal breaks easily,
+shows clean and even on all sides and should not break into layers. The
+coal is broken into fine pieces and wet before being used on the fire.
+
+The fire should be kept deep enough so that there is always three or four
+inches of fire below the piece of metal to be heated and there should be
+enough fire above the work so that no part of the metal being heated comes
+in contact with the air. The fire should be kept as small as possible while
+following these rules as to depth.
+
+To make the fire larger, loosen the coal around the edges. To make the fire
+smaller, pack wet coal around the edges in a compact mass and loosen the
+fire in the center. Add fresh coal only around the edges of the fire. It
+will turn to coke and can then be raked onto the fire. Blow only enough air
+into the fire to keep it burning brightly, not so much that the fire is
+blown up through the top of the coal pack. To prevent the fire from going
+out between jobs, stick a piece of soft wood into it and cover with fresh
+wet coal.
+
+_Tools._--The _hammer_ is a ball pene, or blacksmith's hammer,
+weighing about a pound and a half.
+
+The _sledge_ is a heavy hammer, weighing from 5 to 20 pounds and
+having a handle 30 to 36 inches long.
+
+The _anvil_ is a heavy piece of wrought iron (Figure 49), faced with
+steel and having four legs. It has a pointed horn on one end, an
+overhanging tail on the other end and a flat top. In the tail there is a
+square hole called the "hardie" hole and a round one called the "spud"
+hole.
+
+[Illustration: Figure 49.--Anvil, Showing Horn, Tail, Hardie Hole and Spud
+Hole]
+
+_Tongs_, with handles about one foot long and jaws suitable for
+holding the work, are used. To secure a firm grip on the work, the jaws may
+be heated red hot and hammered into shape over the piece to be held, thus
+giving a properly formed jaw. Jaws should touch the work along their entire
+length.
+
+The _set hammer_ is a hammer, one end of whose head is square and
+flat, and from this face the head tapers evenly to the other face. The
+large face is about 1-1/4 inches square.
+
+The _flatter_ is a hammer having one face of its head flat and about
+2-1/2 inches square.
+
+_Swages_ are hammers having specially formed faces for finishing
+rounds, squares, hexagons, ovals, tapers, etc.
+
+_Fullers_ are hammers having a rounded face, long in one direction.
+They are used for spreading metal in one direction only.
+
+The _hardy_ is a form of chisel with a short, square shank which may
+be set into the hardie hole for cutting off hot bars.
+
+_Operations._--Blacksmithing consists of bending, drawing or upsetting
+with the various hammers, or in punching holes.
+
+Bending is done over the square corners of the anvil if square cornered
+bends are desired, or over the horn of the anvil if rounding bends, eyes,
+hooks, etc., are wanted.
+
+To bend a ring or eye in the end of a bar, first figure the length of stock
+needed by multiplying the diameter of the hole by 31/7, then heat the piece
+to a good full red at a point this distance back from the end. Next bend
+the iron over at a 90 degree angle (square) at this point. Next, heat the
+iron from the bend just made clear to the point and make the eye by laying
+the part that was bent square over the horn of the anvil and bending the
+extreme tip into part of a circle. Keep pushing the piece farther and
+farther over the horn of the anvil, bending it as you go. Do not hammer
+directly over the horn of the anvil, but on the side where you are doing
+the bending.
+
+To make the outside of a bend square, sharp and full, rather than slightly
+rounding, the bent piece must be laid edgewise on the face of the anvil.
+That is, after making the bend over the corner of the anvil, lay the piece
+on top of the anvil so that its edge and not the flat side rests on the
+anvil top. With the work in this position, strike directly against the
+corner with the hammer so that the blows come in line, first with one leg
+of the work, then the other, and always directly on the corner of the
+piece. This operation cannot be performed by laying the work so that one
+leg hangs over the anvil's corner.
+
+To make a shoulder on a rod or bar, heat the work and lay flat across the
+top of the anvil with the point at which the shoulder is desired at the
+edge of the anvil. Then place the set hammer on top of the piece, with the
+outside edge of the set hammer directly over the edge of the anvil. While
+hammering in this position keep the work turning continually.
+
+To draw stock means to make it longer and thinner by hammering. A piece to
+be drawn out is usually laid across the horn of the anvil while being
+struck with the hammer. The metal is then spread in only one direction in
+place of being spread in every direction, as it would be if laid on the
+anvil face. To draw the work, heat it to as high a temperature as it will
+stand without throwing sparks and burning. The fuller may be used for
+drawing metal in place of laying the work over the horn of the anvil.
+
+When drawing round stock, it should be first drawn out square, and when
+almost down to size it may be rounded. When pointing stock, the same rule
+of first drawing out square applies.
+
+Upsetting means to make a piece shorter in length and greater in thickness
+or width, or both shorter and thicker. To upset short pieces, heat to a
+bright red at the place to be upset, then stand on end on the anvil face
+and hammer directly down on top until of the right form. Longer pieces may
+be swung against the anvil or placed upright on a heavy piece of metal
+lying on the floor or that is sunk into the floor. While standing on this
+heavy piece the metal may be upset by striking down on the end with a heavy
+hammer or the sledge. If a bend appears while upsetting, it should be
+straightened by hammering back into shape on the anvil face.
+
+Light blows affect the metal for only a short distance from the point of
+striking, but heavy blows tend to swell the metal more equally through its
+entire length. In driving rivets that should fill the holes, heavy blows
+should be struck, but to shape the end of a rivet or to make a head on a
+rod, light blows should be used.
+
+The part of the piece that is heated most will upset the most.
+
+To punch a hole through metal, use a tool steel punch with its end slightly
+tapering to a size a little smaller than the hole to be punched. The end of
+the punch must be square across and never pointed or rounded.
+
+First drive the punch part way through from one side and then turn the work
+over. When you turn it over, notice where the bulge appears and in that way
+locate the hole and drive the punch through from the second side. This
+makes a cleaner and more even hole than to drive completely through from
+one side. When the punch is driven in from the second side, the place to be
+punched through should be laid over the spud hole in the tail of the anvil
+and the piece driven out of the work.
+
+Work when hot is larger than it will be after cooling. This must be
+remembered when fitting parts or trouble will result. A two-foot bar of
+steel will be 1/4 inch longer when red hot than when cold.
+
+The temperatures of iron correspond to the following colors:
+
+  Dullest red seen in the dark...  878 
+  Dullest red seen in daylight...  887 
+  Dull red....................... 1100 
+  Full red....................... 1370 
+  Light red...................... 1550 
+  Orange......................... 1650 
+  Light orange................... 1725 
+  Yellow......................... 1825 
+  Light yellow................... 1950 
+
+_Bending Pipes and Tubes._--It is difficult to make bends or curves in
+pipes and tubing without leaving a noticeable bulge at some point of the
+work. Seamless steel tubing may be handled without very great danger of
+this trouble if care is used, but iron pipe, having a seam running
+lengthwise, must be given special attention to avoid opening the seam.
+
+Bends may be made without kinking if the tube or pipe is brought to a full
+red heat all the way around its circumference and at the place where the
+bend is desired. Hold the cool portion solidly in a vise and, by taking
+hold of the free end, bend very slowly and with a steady pull. The pipe
+must be kept at full red heat with the flames from one or more torches and
+must not be hammered to produce the bend. If a sufficient purchase cannot
+be secured on the free end by the hand, insert a piece of rod or a smaller
+pipe into the opening.
+
+While making the bend, should small bulges appear, they may be hammered
+back into shape before proceeding with the work.
+
+Tubing or pipes may be bent while being held between two flat metal
+surfaces while at a bright red heat. The metal plates at each side of the
+work prevent bulging.
+
+Another method by which tubing may be bent consists of filling completely
+with tightly packed sand and fitting a solid cap or plug at each end.
+
+Thin brass tubing may be filled with melted resin and may be bent after the
+resin cools. To remove the resin it is necessary to heat the tube, allowing
+it to run out.
+
+Large jobs of bending should be handled in special pipe bending machines in
+which the work is forced through formed rolls which prevent its bulging.
+
+
+WELDING
+
+Welding with the heat of a blacksmith forge fire, or a coal or illuminating
+gas fire, can only be performed with iron and steel because of the low heat
+which is not localized as with the oxy-acetylene and electric processes.
+Iron to be welded in this manner is heated until it reaches the temperature
+indicated by an orange color, not white, as is often stated, this orange
+color being slightly above 3600 degrees Fahrenheit. Steel is usually welded
+at a bright red heat because of the danger of oxidizing or burning the
+metal if the temperature is carried above this point.
+
+_The Fire._--If made in a forge, the fire should be built from good
+smithing coal or, better still, from coke. Gas fires are, of course,
+produced by suitable burners and require no special preparation except
+adjustment of the heat to the proper degree for the size and thickness of
+the metal being welded so that it will not be burned.
+
+A coal fire used for ordinary forging operations should not be used for
+welding because of the impurities it contains. A fresh fire should be built
+with a rather deep bed of coal, four to eight inches being about right for
+work ordinarily met with. The fire should be kept burning until the coal
+around the edges has been thoroughly coked and a sufficient quantity of
+fuel should be on and around the fire so that no fresh coal will have to
+be added while working.
+
+After the coking process has progressed sufficiently, the edges should be
+packed down and the fire made as small as possible while still surrounding
+the ends to be joined. The fire should not be altered by poking it while
+the metal is being heated. The best form of fire to use is one having
+rather high banks of coked coal on each side of the mass, leaving an
+opening or channel from end to end. This will allow the added fuel to be
+brought down on top of the fire with a small amount of disturbance.
+
+_Preparing to Weld._--If the operator is not familiar with the metal
+to be handled, it is best to secure a test piece if at all possible and try
+heating it and joining the ends. Various grades of iron and steel call for
+different methods of handling and for different degrees of heat, the proper
+method and temperature being determined best by actual test under the
+hammer.
+
+The form of the pieces also has a great deal to do with their handling,
+especially in the case of a more or less inexperienced workman. If the
+pieces are at all irregular in shape, the motions should be gone through
+with before the metal is heated and the best positions on the anvil as well
+as in the fire determined with regard to the convenience of the workman and
+speed of handling the work after being brought to a welding temperature.
+Unnatural positions at the anvil should be avoided as good work is most
+difficult of performance under these conditions.
+
+_Scarfing._--While there are many forms of welds, depending on the
+relative shape of the pieces to be joined, the portions that are to meet
+and form one piece are always shaped in the same general way, this shape
+being called a "scarf." The end of a piece of work, when scarfed, is
+tapered off on one side so that the extremity comes to a rather sharp edge.
+The other side of the piece is left flat and a continuation in the same
+straight plane with its side of the whole piece of work. The end is then in
+the form of a bevel or mitre joint (Figure 50).
+
+[Illustration: Figure 50.--Scarfing Ends of Work Ready for Welding]
+
+Scarfing may be produced in any one of several ways. The usual method is to
+bring the ends to a forging heat, at which time they are upset to give a
+larger body of metal at the ends to be joined. This body of metal is then
+hammered down to the taper on one side, the length of the tapered portion
+being about one and a half times the thickness of the whole piece being
+handled. Each piece should be given this shape before proceeding farther.
+
+The scarf may be produced by filing, sawing or chiseling the ends, although
+this is not good practice because it is then impossible to give the desired
+upset and additional metal for the weld. This added thickness is called for
+by the fact that the metal burns away to a certain extent or turns to
+scale, which is removed before welding.
+
+When the two ends have been given this shape they should not fit as closely
+together as might be expected, but should touch only at the center of the
+area to be joined (Figure 51). That is to say, the surface of the beveled
+portion should bulge in the middle or should be convex in shape so that the
+edges are separated by a little distance when the pieces are laid together
+with the bevels toward each other. This is done so that the scale which is
+formed on the metal by the heat of the fire can have a chance to escape
+from the interior of the weld as the two parts are forced together.
+
+[Illustration: Figure 51.--Proper Shape of Scarfed Ends]
+
+If the scarf were to be formed with one or more of the edges touching each
+other at the same time or before the centers did so, the scale would be
+imprisoned within the body of the weld and would cause the finished work to
+be weak, while possibly giving a satisfactory appearance from the outside.
+
+_Fluxes._--In order to assist in removing the scale and other
+impurities and to make the welding surfaces as clean as possible while
+being joined, various fluxing materials are used as in other methods of
+welding.
+
+For welding iron, a flux of white sand is usually used, this material being
+placed on the metal after it has been brought to a red heat in the fire.
+Steel is welded with dry borax powder, this flux being applied at the same
+time as the iron flux just mentioned. Borax may also be used for iron
+welding and a mixture of borax with steel borings may also be used for
+either class of work. Mixtures of sal ammoniac with borax have been
+successfully used, the proportions being about four parts of borax to one
+of sal ammoniac. Various prepared fluxing powders are on the market for
+this work, practically all of them producing satisfactory results.
+
+After the metal has been in the fire long enough to reach a red heat, it is
+removed temporarily and, if small enough in size, the ends are dipped into
+a box of flux. If the pieces are large, they may simply be pulled to the
+edge of the fire and the flux then sprinkled on the portions to be joined.
+A greater quantity of flux is required in forge welding than in electric or
+oxy-acetylene processes because of the losses in the fire. After the powder
+has been applied to the surfaces, the work is returned to the fire and
+heated to the welding temperature.
+
+_Heating the Work._--After being scarfed, the two pieces to be welded
+are placed in the fire and brought to the correct temperature. This
+temperature can only be recognized by experiment and experience. The metal
+must be just below that point at which small sparks begin to be thrown out
+of the fire and naturally this is a hard point to distinguish. At the
+welding heat the metal is almost ready to flow and is about the consistency
+of putty. Against the background of the fire and coal the color appears to
+be a cream or very light yellow and the work feels soft as it is handled.
+
+It is absolutely necessary that both parts be heated uniformly and so that
+they reach the welding temperature at the same time. For this reason they
+should be as close together in the fire as possible and side by side. When
+removed to be hammered together, time is saved if they are picked up in
+such a way that when laid together naturally the beveled surfaces come
+together. This makes it necessary that the workman remember whether the
+scarfed side is up or down, and to assist in this it is a good thing to
+mark the scarfed side with chalk or in some other noticeable manner, so
+that no mistake will be made in the hurry of placing the work on the anvil.
+
+The common practice in heating allows the temperature to rise until the
+small white sparks are seen to come from the fire. Any heating above this
+point will surely result in burning that will ruin the iron or steel being
+handled. The best welding heat can be discerned by the appearance of the
+metal and its color after experience has been gained with this particular
+material. Test welds can be made and then broken, if possible, so that the
+strength gained through different degrees of heat can be known before
+attempting more important work.
+
+_Welding._--When the work has reached the welding temperature after
+having been replaced in the fire with the flux applied, the two parts are
+quickly tapped to remove the loose scale from their surfaces. They are then
+immediately laid across the top of the anvil, being placed in a diagonal
+position if both pieces are straight. The lower piece is rested on the
+anvil first with the scarf turned up and ready to receive the top piece in
+the position desired. The second piece must be laid in exactly the position
+it is to finally occupy because the two parts will stick together as soon
+as they touch and they cannot well be moved after having once been allowed
+to come in contact with each other. This part of the work must be done
+without any unnecessary loss of time because the comparatively low heat at
+which the parts weld allows them to cool below the working temperature in
+a few seconds.
+
+The greatest difficulty will be experienced in withdrawing the metal from
+the fire before it becomes burned and in getting it joined before it cools
+below this critical point. The beveled edges of the scarf are, of course,
+the first parts to cool and the weld must be made before they reach a point
+at which they will not join, or else the work will be defective in
+appearance and in fact.
+
+If the parts being handled are of such a shape that there is danger of
+bending a portion back of the weld, this part may be cooled by quickly
+dipping it into water before laying the work on the anvil to be joined.
+
+The workman uses a heavy hand hammer in making the joint, and his helper,
+if one is employed, uses a sledge. With the two parts of the work in place
+on the anvil, the workman strikes several light blows, the first ones being
+at a point directly over the center of the weld, so that the joint will
+start from this point and be worked toward the edges. After the pieces have
+united the helper strikes alternate blows with his sledge, always striking
+in exactly the same place as the last stroke of the workman. The hammer
+blows are carried nearer and nearer to the edges of the weld and are made
+steadily heavier as the work progresses.
+
+The aim during the first part of the operation should be to make a perfect
+joint, with every part of the surfaces united, and too much attention
+should not be paid to appearance, at least not enough to take any chance
+with the strength of the work.
+
+It will be found, after completion of the weld, that there has been a loss
+in length equal to one-half the thickness of the metal being welded. This
+loss is occasioned by the burned metal and the scale which has been formed.
+
+_Finishing the Weld._--If it is possible to do so, the material should
+be hammered into the shape that it should remain with the same heat that
+was used for welding. It will usually be found, however, that the metal has
+cooled below the point at which it can be worked to advantage. It should
+then be replaced in the fire and brought back to a forging heat.
+
+[Illustration: Figure 52.--Upsetting and Scarfing the End of a Rod]
+
+While shaping the work at this forging heat every part that has been at a
+red heat should be hammered with uniformly light and even blows as it
+cools. This restores the grain and strength of the iron or steel to a great
+extent and makes the unavoidable weakness as small as possible.
+
+_Forms of Welds._--The simplest of all welds is that called a "lap
+weld." This is made between the ends of two pieces of equal size and
+similar form by scarfing them as described and then laying one on top of
+the other while they are hammered together.
+
+A butt weld (Figure 52) is made between the ends of two pieces of shaft or
+other bar shapes by upsetting the ends so that they have a considerable
+flare and shaping the face of the end so that it is slightly higher in the
+center than around the edges, this being done to make the centers come
+together first. The pieces are heated and pushed into contact, after which
+the hammering is done as with any other weld.
+
+[Illustration: Figure 53.--Scarfing for a T Weld]
+
+A form similar to the butt weld in some ways is used for joining the end of
+a bar to a flat surface and is called a jump weld. The bar is shaped in the
+same way as for a butt weld. The flat plate may be left as it is, but if
+possible a depression should be made at the point where the shaft is to be
+placed. With the two parts heated as usual, the bar is dropped into
+position and hammered from above. As soon as the center of the weld has
+been made perfect, the joint may be finished with a fuller driven all the
+way around the edge of the joint.
+
+When it is required to join a bar to another bar or to the edge of any
+piece at right angles the work is called a "T" weld from its shape when
+complete (Figure 53). The end of the bar is scarfed as described and the
+point of the other bar or piece where the weld is to be made is hammered so
+that it tapers to a thin edge like one-half of a circular depression. The
+pieces are then laid together and hammered as for a lap weld.
+
+The ends of heavy bar shapes are often joined with a "V," or cleft, weld.
+One bar end is shaped so that it is tapering on both sides and comes to a
+broad edge like the end of a chisel. The other bar is heated to a forging
+temperature and then slit open in a lengthwise direction so that the
+V-shaped opening which is formed will just receive the pointed edge of the
+first piece. With the work at welding heat, the two parts are driven
+together by hammering on the rear ends and the hammering then continues as
+with a lap weld, except that the work is turned over to complete both sides
+of the joint.
+
+[Illustration: Figure 54.-Splitting Ends to Be Welded in Thin Work]
+
+The forms so far described all require that the pieces be laid together in
+the proper position after removal from the fire, and this always causes a
+slight loss of time and a consequent lowering of the temperature. With very
+light stock, this fall of temperature would be so rapid that the weld would
+be unsuccessful, and in this case the "lock" weld is resorted to. The ends
+of the two pieces to be joined are split for some distance back, and
+one-half of each end is bent up and the other half down (Figure 54). The
+two are then pushed together and placed in the fire in this position. When
+the welding heat is reached, it is only necessary to take the work out of
+the fire and hammer the parts together, inasmuch as they are already in the
+correct position.
+
+Other forms of welds in which the parts are too small to retain their heat,
+can be made by first riveting them together or cutting them so that they
+can be temporarily fastened in any convenient way when first placed in the
+fire.
+
+
+
+
+CHAPTER VIII
+
+SOLDERING, BRAZING AND THERMIT WELDING
+
+
+SOLDERING
+
+Common solder is an alloy of one-half lead with one-half tin, and is called
+"half and half." Hard solder is made with two-thirds tin and one-third
+lead. These alloys, when heated, are used to join surfaces of the same or
+dissimilar metals such as copper, brass, lead, galvanized iron, zinc,
+tinned plate, etc. These metals are easily joined, but the action of solder
+with iron, steel and aluminum is not so satisfactory and requires greater
+care and skill.
+
+The solder is caused to make a perfect union with the surfaces treated with
+the help of heat from a soldering iron. The soldering iron is made from a
+piece of copper, pointed at one end and with the other end attached to an
+iron rod and wooden handle. A flux is used to remove impurities from the
+joint and allow the solder to secure a firm union with the metal surface.
+The iron, and in many cases the work, is heated with a gasoline blow torch,
+a small gas furnace, an electric heater or an acetylene and air torch.
+
+The gasoline torch which is most commonly used should be filled two-thirds
+full of gasoline through the hole in the bottom, which is closed by a screw
+plug. After working the small hand pump for 10 to 20 strokes, hold the palm
+of your hand over the end of the large iron tube on top of the torch and
+open the gasoline needle valve about a half turn. Hold the torch so that
+the liquid runs down into the cup below the tube and fills it. Shut the
+gasoline needle valve, wipe the hands dry, and set fire to the fuel in the
+cup. Just as the gasoline fire goes out, open the gasoline needle valve
+about a half turn and hold a lighted match at the end of the iron tube to
+ignite the mixture of vaporized gasoline and air. Open or close the needle
+valve to secure a flame about 4 inches long.
+
+On top of the iron tube from which the flame issues there is a rest for
+supporting the soldering iron with the copper part in the flame. Place the
+iron in the flame and allow it to remain until the copper becomes very hot,
+not quite red, but almost so.
+
+A new soldering iron or one that has been misused will have to be "tinned"
+before using. To do this, take the iron from the fire while very hot and
+rub the tip on some flux or dip it into soldering acid. Then rub the tip of
+the iron on a stick of solder or rub the solder on the iron. If the solder
+melts off the stick without coating the end of the iron, allow a few drops
+to fall on a piece of tin plate, then nil the end of the iron on the tin
+plate with considerable force. Alternately rub the iron on the solder and
+dip into flux until the tip has a coating of bright solder for about half
+an inch from the end. If the iron is in very bad shape, it may be necessary
+to scrape or file the end before dipping in the flux for the first time.
+After the end of the iron is tinned in this way, replace it on the rest of
+the torch so that the tinned point is not directly in the flame, turning
+the flame down to accomplish this.
+
+_Flux._--The commonest flux, which is called "soldering acid," is made
+by placing pieces of zinc in muriatic (hydrochloric) acid contained in a
+heavy glass or porcelain dish. There will be bubbles and considerable heat
+evolved and zinc should be added until this action ceases and the zinc
+remains in the liquid, which is now chloride of zinc.
+
+This soldering acid may be used on any metal to be soldered by applying
+with a brush or swab. For electrical work, this acid should be made neutral
+by the addition of one part ammonia and one part water to each three parts
+of the acid. This neutralized flux will not corrode metal as will the
+ordinary acid.
+
+Powdered resin makes a good flux for lead, tin plate, galvanized iron and
+aluminum. Tallow, olive oil, beeswax and vaseline are also used for this
+purpose. Muriatic acid may be used for zinc or galvanized iron without the
+addition of the zinc, as described in making zinc chloride. The addition of
+two heaping teaspoonfuls of sal ammoniac to each pint of the chloride of
+zinc is sometimes found to improve its action.
+
+_Soldering Metal Parts._--All surfaces to be joined should be fitted
+to each other as accurately as possible and then thoroughly cleaned with a
+file, emery cloth, scratch bush or by dipping in lye. Work may be cleaned
+by dipping it into nitric acid which has been diluted with an equal volume
+of water. The work should be heated as hot as possible without danger of
+melting, as this causes the solder to flow better and secure a much better
+hold on the surfaces. Hard solder gives better results than half and half,
+but is more difficult to work. It is very important that the soldering iron
+be kept at a high heat during all work, otherwise the solder will only
+stick to the surfaces and will not join with them.
+
+Sweating is a form of soldering in which the surfaces of the work are first
+covered with a thin layer of solder by rubbing them with the hot iron after
+it has been dipped in or touched to the soldering stick. These surfaces are
+then placed in contact and heated to a point at which the solder melts and
+unites. Sweating is much to be preferred to ordinary soldering where the
+form of the work permits it. This is the only method which should ever be
+used when a fitting is to be placed over the end of a length of tube.
+
+_Soldering Holes._--Clean the surfaces for some distance around the
+hole until they are bright, and apply flux while holding the hot iron near
+the hole. Touch the tip of the iron to some solder until the solder is
+picked up on the iron, and then place this solder, which was just picked
+up, around the edge of the hole. It will leave the soldering iron and stick
+to the metal. Keep adding solder in this way until the hole has been closed
+up by working from the edges and building toward the center. After the hole
+is closed, apply more flux to the job and smooth over with the hot iron
+until there are no rough spots. Should the solder refuse to flow smoothly,
+the iron is not hot enough.
+
+_Soldering Seams._--Clean back from the seam or split for at least
+half an inch all around and then build up the solder in the same way as was
+done with the hole. After closing the opening, apply more flux to the work
+and run the hot iron lengthwise to smooth the job.
+
+_Soldering Wires._--Clean all insulation from the ends to be soldered
+and scrape the ends bright. Lay the ends parallel to each other and,
+starting at the middle of the cleaned portion, wrap the ends around each
+other, one being wrapped to the right, the other to the left. Hold the hot
+iron under the twisted joint and apply flux to the wire. Then dip the iron
+in the solder and apply to the twisted portion until the spaces between the
+wires are filled with solder. Finish by smoothing the joint and cleaning
+away all excess metal by rubbing the hot iron lengthwise. The joint should
+now be covered with a layer of rubber tape and this covered with a layer of
+ordinary friction tape.
+
+_Steel and Iron._--Steel surfaces should be cleaned, then covered with
+clear muriatic acid. While the acid is on the metal, rub with a stick of
+zinc and then tin the surfaces with the hot iron as directed. Cast iron
+should be cleaned and dipped in strong lye to remove grease. Wash the lye
+away with clean water and cover with muriatic acid as with steel. Then rub
+with a piece of zinc and tin the surfaces by using resin as a flux.
+
+It is very difficult to solder aluminum with ordinary solder. A special
+aluminum solder should be secured, which is easily applied and makes a
+strong joint. Zinc or phosphor tin may be used in place of ordinary solder
+to tin the surfaces or to fill small holes or cracks. The aluminum must be
+thoroughly heated before attempting to solder and the flux may be either
+resin or soldering acid. The aluminum must be thoroughly cleaned with
+dilute nitric acid and kept hot while the solder is applied by forcible
+rubbing with the hot iron.
+
+
+BRAZING
+
+This is a process for joining metal parts, very similar to soldering,
+except that brass is used to make the joint in place of the lead and zinc
+alloys which form solder. Brazing must not be attempted on metals whose
+melting point is less than that of sheet brass.
+
+Two pieces of brass to be brazed together are heated to a temperature at
+which the brass used in the process will melt and flow between the
+surfaces. The brass amalgamates with the surfaces and makes a very strong
+and perfect joint, which is far superior to any form of soldering where the
+work allows this process to be used, and in many cases is the equal of
+welding for the particular field in which it applies.
+
+_Brazing Heat and Tools._--The metal commonly used for brazing will
+melt at heats between 1350  and 1650  Fahrenheit. To bring the parts to
+this temperature, various methods are in use, using solid, liquid or
+gaseous fuels. While brazing may be accomplished with the fire of the
+blacksmith forge, this method is seldom satisfactory because of the
+difficulty of making a sufficiently clean fire with smithing coal, and it
+should not be used when anything else is available. Large jobs of brazing
+may be handled with a charcoal fire built in the forge, as this fuel
+produces a very satisfactory and clean fire. The only objection is in the
+difficulty of confining the heat to the desired parts of the work.
+
+The most satisfactory fire is that from a fuel gas torch built for this
+work. These torches are simply forms of Bunsen burners, mixing the proper
+quantity of air with the gas to bring about a perfect combustion. Hose
+lines lead to the mixing tube of the gas torch, one line carrying the gas
+and the other air under a moderate pressure. The air line is often
+dispensed with, allowing the gas to draw air into the burner on the
+injector principle, much the same as with illuminating gas burners for use
+with incandescent mantles. Valves are provided with which the operator may
+regulate the amount of both gas and air, and ordinarily the quality and
+intensity of the flame.
+
+When gas is not available, recourse may be had to the gasoline torch made
+for brazing. This torch is built in the same way as the small portable
+gasoline torches for soldering operations, with the exception that two
+regulating needle valves are incorporated in place of only one.
+
+The torches are carried on a framework, which also supports the work being
+handled. Fuel is forced to the torch from a large tank of gasoline into
+which air pressure is pumped by hand. The torches are regulated to give
+the desired flame by means of the needle valves in much the same way as
+with any other form of pressure torch using liquid fuel.
+
+Another very satisfactory form of torch for brazing is the acetylene-air
+combination described in the chapter on welding instruments. This torch
+gives the correct degree of heat and may be regulated to give a clean and
+easily controlled flame.
+
+Regardless of the source of heat, the fire or flame must be adjusted so
+that no soot is deposited on the metal surfaces of the work. This can only
+be accomplished by supplying the exact amounts of gas and air that will
+produce a complete burning of the fuel. With the brazing torches in common
+use two heads are furnished, being supplied from the same source of fuel,
+but with separate regulating devices. The torches are adjustably mounted in
+such a way that the flames may be directed toward each other, heating two
+sides of the work at the same time and allowing the pieces to be completely
+surrounded with the flame.
+
+Except for the source of heat, but one tool is required for ordinary
+brazing operations, this being a spatula formed by flattening one end of a
+quarter-inch steel rod. The spatula is used for placing the brazing metal
+on the work and for handling the flux that is required in this work as in
+all other similar operations.
+
+_Spelter._--The metal that is melted into the joint is called spelter.
+While this name originally applied to but one particular grade or
+composition of metal, common use has extended the meaning until it is
+generally applied to all grades.
+
+Spelter is variously composed of alloys containing copper, zinc, tin and
+antimony, the mixture employed depending on the work to be done. The
+different grades are of varying hardness, the harder kinds melting at
+higher temperatures than the soft ones and producing a stronger joint when
+used. The reason for not using hard spelter in all cases is the increased
+difficulty of working it and the fact that its melting point is so near to
+some of the metals brazed that there is great danger of melting the work as
+well as the spelter.
+
+The hardest grade of spelter is made from three-fourths copper with
+one-fourth zinc and is used for working on malleable and cast iron and for
+steel.
+
+This hard spelter melts at about 1650  and is correspondingly difficult to
+handle.
+
+A spelter suitable for working with copper is made from equal parts of
+copper and zinc, melting at about 1400  Fahrenheit, 500  below the melting
+point of the copper itself. A still softer brazing metal is composed of
+half copper, three-eighths zinc and one-eighth tin. This grade is used for
+fastening brass to iron and copper and for working with large pieces of
+brass to brass. For brazing thin sheet brass and light brass castings, a
+metal is used which contains two-thirds tin and one-third antimony. The
+low melting point of this last composition makes it very easy to work with
+and the danger of melting the work is very slight. However, as might be
+expected, a comparatively weak joint is secured, which will not stand any
+great strain.
+
+All of the above brazing metals are used in powder form so that they may be
+applied with the spatula where the joint is exposed on the outside of the
+work. In case it is necessary to braze on the inside of a tube or any deep
+recess, the spelter may be placed on a flat rod long enough to reach to
+the farthest point. By distributing the spelter at the proper points along
+the rod it may be placed at the right points by turning the rod over after
+inserting into the recess.
+
+_Flux._--In order to remove the oxides produced under brazing heat and
+to allow the brazing metal to flow freely into place, a flux of some kind
+must be used. The commonest flux is simply a pure calcined borax powder,
+that is, a borax powder that has been heated until practically all the
+water has been driven off.
+
+Calcined borax may also be mixed with about 15 per cent of sal ammoniac to
+make a satisfactory fluxing powder. It is absolutely necessary to use flux
+of some kind and a part of whatever is used should be made into a paste
+with water so that it can be applied to the joint to be brazed before
+heating. The remainder of the powder should be kept dry for use during the
+operation and after the heat has been applied.
+
+_Preparing the Work._--The surfaces to be brazed are first thoroughly
+cleaned with files, emery cloth or sand paper. If the work is greasy, it
+should be dipped into a bath of lye or hot soda water so that all trace of
+oil is removed. The parts are then placed in the relation to each other
+that they are to occupy when the work has been completed. The edges to be
+joined should make a secure and tight fit, and should match each other at
+all points so that the smallest possible space is left between them. This
+fit should not be so tight that it is necessary to force the work into
+place, neither should it be loose enough to allow any considerable space
+between the surfaces. The molten spelter will penetrate between surfaces
+that water will flow between when the work and spelter have both been
+brought to the proper heat. It is, of course, necessary that the two parts
+have a sufficient number of points of contact so that they will remain in
+the proper relative position.
+
+The work is placed on the surface of the brazing table in such a position
+that the flame from the torches will strike the parts to be heated, and
+with the joint in such a position that the melted spelter will flow down
+through it and fill every possible part of the space between the surfaces
+under the action of gravity. That means that the edge of the joint must be
+uppermost and the crack to be filled must not lie horizontal, but at the
+greatest slant possible. Better than any degree of slant would be to have
+the line of the joint vertical.
+
+The work is braced up or clamped in the proper position before commencing
+to braze, and it is best to place fire brick in such positions that it will
+be impossible for cooling draughts of air to reach the heated metal should
+the flame be removed temporarily during the process. In case there is a
+large body of iron, steel or copper to be handled, it is often advisable to
+place charcoal around the work, igniting this with the flame of the torch
+before starting to braze so that the metal will be maintained at the
+correct heat without depending entirely on the torch.
+
+When handling brass pieces having thin sections there is danger of melting
+the brass and causing it to flow away from under the flame, with the result
+that the work is ruined. If, in the judgment of the workman, this may
+happen with the particular job in hand, it is well to build up a mould of
+fire clay back of the thin parts or preferably back of the whole piece, so
+that the metal will have the necessary support. This mould may be made by
+mixing the fire clay into a stiff paste with water and then packing it
+against the piece to be supported tightly enough so that the form will be
+retained even if the metal softens.
+
+_Brazing._--With the work in place, it should be well covered with the
+paste of flux and water, then heated until this flux boils up and runs over
+the surfaces. Spelter is then placed in such a position that it will run
+into the joint and the heat is continued or increased until the spelter
+melts and flows in between the two surfaces. The flame should surround the
+work during the heating so that outside air is excluded as far as is
+possible to prevent excessive oxidization.
+
+When handling brass or copper, the flame should not be directed so that its
+center strikes the metal squarely, but so that it glances from one side or
+the other. Directing the flame straight against the work is often the cause
+of melting the pieces before the operation is completed. When brazing two
+different metals, the flame should play only on the one that melts at the
+higher temperature, the lower melting part receiving its heat from the
+other. This avoids the danger of melting one before the other reaches the
+brazing point.
+
+The heat should be continued only long enough to cause the spelter to flow
+into place and no longer. Prolonged heating of any metal can do nothing but
+oxidize and weaken it, and this practice should be avoided as much as
+possible. If the spelter melts into small globules in place of flowing, it
+may be caused to spread and run into the joint by lightly tapping the work.
+More dry flux may be added with the spatula if the tapping does not produce
+the desired result.
+
+Excessive use of flux, especially toward the end of the work, will result
+in a very hard surface on all the work, a surface which will be extremely
+difficult to finish properly. This trouble will be present to a certain
+extent anyway, but it may be lessened by a vigorous scraping with a wire
+brush just as soon as the work is removed from the fire. If allowed to cool
+before cleaning, the final appearance will not be as good as with the
+surplus metal and scale removed immediately upon completing the job.
+
+After the work has been cleaned with the brush it may be allowed to cool
+and finished to the desired shape, size and surface by filing and
+polishing. When filed, a very thin line of brass should appear where the
+crack was at the beginning of the work. If it is desired to avoid a square
+shoulder and fill in an angle joint to make it rounding, the filling is
+best accomplished by winding a coil of very thin brass wire around the part
+of the work that projects and then causing this to flow itself or else
+allow the spelter to fill the spaces between the layers of wire. Copper
+wire may also be used for this purpose, the spaces being filled with
+melted spelter.
+
+
+THERMIT WELDING
+
+The process of welding which makes use of the great heat produced by oxygen
+combining with aluminum is known as the Thermit process and was perfected
+by Dr. Hans Goldschmidt. The process, which is controlled by the
+Goldschmidt Thermit Company, makes use of a mixture of finely powdered
+aluminum with an oxide of iron called by the trade name, Thermit.
+
+The reaction is started with a special ignition powder, such as barium
+superoxide and aluminum, and the oxygen from the iron oxide combining with
+the aluminum, producing a mass of superheated steel at about 5000 degrees
+Fahrenheit. After the reaction, which takes from. 30 seconds to a minute,
+the molten metal is drawn from the crucible on to the surfaces to be
+joined. Its extreme heat fuses the metal and a perfect joint is the result.
+This process is suited for welding iron or steel parts of comparatively
+large size.
+
+_Preparation._--The parts to be joined are thoroughly cleaned on the
+surfaces and for several inches back from the joint, after which they are
+supported in place. The surfaces between which the metal will flow are
+separated from 1/4 to 1 inch, depending on the size of the parts, but
+cutting or drilling part of the metal away. After this separation is made
+for allowing the entrance of new metal, the effects of contraction of the
+molten steel are cared for by preheating adjacent parts or by forcing the
+ends apart with wedges and jacks. The amount of this last separation must
+be determined by the shape and proportions of the parts in the same way as
+would be done for any other class of welding which heats the parts to a
+melting point.
+
+Yellow wax, which has been warmed until plastic, is then placed around the
+joint to form a collar, the wax completely filling the space between the
+ends and being provided with vent holes by imbedding a piece of stout cord,
+which is pulled out after the wax cools.
+
+A retaining mould (Figure 55) made from sheet steel or fire brick is then
+placed around the parts. This mould is then filled with a mixture of one
+part fire clay, one part ground fire brick and one part fire sand. These
+materials are well mixed and moistened with enough water so that they will
+pack. This mixture is then placed in the mould, filling the space between
+the walls and the wax, and is packed hard with a rammer so that the
+material forms a wall several inches thick between any point of the mould
+and the wax. The mixture must be placed in the mould in small quantities
+and packed tight as the filling progresses.
+
+[Illustration: Figure 55.--Thermit Mould Construction]
+
+Three or more openings are provided through this moulding material by the
+insertion of wood or pipe forms. One of these openings will lead from the
+lowest point of the wax pattern and is used for the introduction of the
+preheating flame. Another opening leads from the top of the mould into this
+preheating gate, opening into the preheating gate at a point about one inch
+from the wax pattern. Openings, called risers, are then provided from each
+of the high points of the wax pattern to the top of the mould, these risers
+ending at the top in a shallow basin. The molten metal comes up into these
+risers and cares for contraction of the casting, as well as avoiding
+defects in the collar of the weld. After the moulding material is well
+packed, these gate patterns are tapped lightly and withdrawn, except in the
+case of the metal pipes which are placed at points at which it would be
+impossible to withdraw a pattern.
+
+_Preheating._--The ends to be welded are brought to a bright red heat
+by introducing the flame from a torch through the preheating gate. The
+torch must use either gasoline or kerosene, and not crude oil, as the crude
+oil deposits too much carbon on the parts. Preheating of other adjacent
+parts to care for contraction is done at this time by an additional torch
+burner.
+
+The heating flame is started gently at first and gradually increased. The
+wax will melt and may be allowed to run out of the preheating gate by
+removing the flame at intervals for a few seconds. The heat is continued
+until the mould is thoroughly dried and the parts to be joined are brought
+to the red heat required. This leaves a mould just the shape of the wax
+pattern.
+
+The heating gate should then be plugged with a sand core, iron plug or
+piece of fitted fire brick, and backed up with several shovels full of the
+moulding mixture, well packed.
+
+[Illustration: Figure 56.--Thermit Crucible Plug.
+_A_, Hard burn magnesia stone;
+_B_, Magnesia thimble;
+_C_, Refractory sand;
+_D_, Metal disc;
+_E_, Asbestos washer;
+_F_, Tapping pin]
+
+_Thermit Metal._--The reaction takes place in a special crucible lined
+with magnesia tar, which is baked at a red heat until the tar is driven off
+and the magnesia left. This lining should last from twelve to fifteen
+reactions. This magnesia lining ends at the bottom of the crucible in a
+ring of magnesia stone and this ring carries a magnesia thimble through
+which the molten steel passes on its way to the mould. It will usually be
+necessary to renew this thimble after each reaction. This lower opening is
+closed before filling the crucible with thermit by means of a small disc or
+iron carrying a stem, which is called a tapping pin (Figure 56). This pin,
+_F_, is placed in the thimble with the stem extending down through the
+opening and exposing about two inches. The top of this pin is covered with
+an asbestos, washer, _E_, then with another iron disc. _D_, and
+finally with a layer of refractory sand. The crucible is tapped by knocking
+the stem of the pin upwards with a spade or piece of flat iron about four
+feet long.
+
+The charge of thermit is added by placing a few handfuls over the
+refractory sand and then pouring in the balance required. The amount of
+thermit required is calculated from the wax used. The wax is weighed before
+and after filling _the entire space that the thermit will occupy_.
+This does not mean only the wax collar, but the space of the mould with all
+gates filled with wax. The number of pounds of wax required for this
+filling multiplied by 25 will give the number of pounds of thermit to be
+used. To this quantity of thermit should be added I per cent of pure
+manganese, 1 per cent nickel thermit and 15 per cent of steel punchings.
+
+It is necessary, when more than 10 pounds of thermit will be used, to mix
+steel punchings not exceeding 3/8 inch diameter by 1/8 inch thick with the
+powder in order to sufficiently retard the intensity of the reaction.
+
+Half a teaspoonful of ignition powder is placed on top of the thermit
+charge and ignited with a storm match or piece of red hot iron. The cover
+should be immediately closed on the top of the crucible and the operator
+should get away to a safe distance because of the metal that may be thrown
+out of the crucible.
+
+After allowing about 30 seconds to a minute for the reaction to take place
+and the slag to rise to the top of the crucible, the tapping pin is struck
+from below and the molten metal allowed to run into the mould. The mould
+should be allowed to remain in place as long as possible, preferably over
+night, so as to anneal the steel in the weld, but in no case should it be
+disturbed for several hours after pouring. After removing the mould, drill
+through the metal left in the riser and gates and knock these sections off.
+No part of the collar should be removed unless absolutely necessary.
+
+
+
+
+CHAPTER IX
+
+OXYGEN PROCESS FOR REMOVAL OF CARBON
+
+
+Until recently the methods used for removing carbon deposits from gas
+engine cylinders were very impractical and unsatisfactory. The job meant
+dismantling the motor, tearing out all parts, and scraping the pistons and
+cylinder walls by hand.
+
+The work was never done thoroughly. It required hours of time to do it, and
+then there was always the danger of injuring the inside of the cylinders.
+
+These methods have been to a large extent superseded by the use of oxygen
+under pressure. The various devices that are being manufactured are known
+as carbon removers, decarbonizers, etc., and large numbers of them are in
+use in the automobile and gasoline traction motor industry.
+
+_Outfit._--The oxygen carbon cleaner consists of a high pressure
+oxygen cylinder with automatic reducing valve, usually constructed on the
+diaphragm principle, thus assuring positive regulation of pressure. This
+valve is fitted with a pressure gauge, rubber hose, decarbonizing torch
+with shut off and flexible tube for insertion into the chamber from which
+the carbon is to be removed.
+
+There should also be an asbestos swab for swabbing out the inside of the
+cylinder or other chamber with kerosene previous to starting the operation.
+The action consists in simply burning the carbon to a fine dust in the
+presence of the stream of oxygen, this dust being then blown out.
+
+_Operation._--The following are instructions for operating the
+cleaner:--
+
+(1) Close valve in gasoline supply line and start the motor, letting it run
+until the gasoline is exhausted.
+
+(2) If the cylinders be T or L head, remove either the inlet or the exhaust
+valve cap, or a spark plug if the cap is tight. If the cylinders have
+overhead valves, remove a spark plug. If any spark plug is then remaining
+in the cylinder it should be removed and an old one or an iron pipe plug
+substituted.
+
+(3) Raise the piston of the cylinder first to be cleaned to the top of the
+compression stroke and continue this from cylinder to cylinder as the work
+progresses.
+
+(4) In motors where carbon has been burned hard, the cylinder interior
+should then be swabbed with kerosene before proceeding. Work the swab,
+saturated with kerosene, around the inside of the cylinder until all the
+carbon has been moistened with the oil. This same swab may be used to
+ignite the gas in the cylinder in place of using a match or taper.
+
+(5) Make all connections to the oxygen cylinder.
+
+(6) Insert the torch nozzle in the cylinder, open the torch valve gradually
+and regulate to about two lbs. pressure. Manipulate the nozzle inside the
+cylinder and light a match or other flame at the opening so that the carbon
+starts to burn. Cover the various points within the cylinder and when there
+is no further burning the carbon has been removed. The regulating and
+oxygen tank valves are operated in exactly the same way as for welding as
+previously explained.
+
+
+It should be carefully noted that when the piston is up, ready to start the
+operation, both valves must be closed. There will be a considerable display
+of sparks while this operation is taking place, but they will not set fire
+to the grease and oil. Care should be used to see that no gasoline is
+about.
+
+
+
+
+INDEX
+
+
+Acetylene
+  filtering
+  generators
+  in tanks
+  piping
+  properties of
+  purification of
+Acetylene-air torches
+Air
+  oxygen from
+Alloys
+  table of
+Alloy steel
+Aluminum
+  alloys
+  welding
+Annealing
+Anvil
+Arc welding, electric
+  machines
+Asbestos, use of, in welding
+
+Babbitt
+Bending pipes and tubes
+Bessemer steel
+Beveling
+Brass
+  welding
+Brazing
+  electric
+  heat and tools
+  spelter
+Bronze
+  welding
+Butt welding
+
+Calcium carbide
+Carbide
+  storage of, Fire Underwriters' Rules
+  to water generator
+Carbon removal
+  by oxygen process
+Case hardening steel
+Cast iron
+  welding
+Champfering
+Charging generator
+Chlorate of potash oxygen
+Conductivity of metals
+Copper
+  alloys
+  welding
+Crucible steel
+Cutting, oxy-acetylene
+  torches
+
+Dissolved acetylene
+
+Electric arc welding
+Electric welding
+  troubles and remedies
+Expansion of metals
+
+Flame, welding
+Fluxes
+  for brazing
+  for soldering
+Forge
+  fire
+  practice
+  tools
+  tuvere construction of
+  welding
+  welding preparation
+  welds, forms of
+Forging
+
+Gas holders
+Gases, heating power of
+Generator, acetylene
+  carbide to water
+  construction
+Generator
+  location of
+  operation and care of
+  overheating
+  requirements
+  water to carbide
+German silver
+Gloves
+Goggles
+
+Hand forging
+Hardening steel
+Heat treatment of steel
+Hildebrandt process
+Hose
+
+Injectors, adjuster
+Iron
+  cast
+  grades of
+  malleable cast
+  wrought
+
+Jump weld
+
+Lap welding
+Lead
+Linde process
+Liquid air oxygen
+
+Magnalium
+Malleable iron
+  welding
+Melting points of metals
+Metal alloys, table of
+Metals
+  characteristics of
+  conductivity of
+  expansion of
+  heat treatment of
+  melting points of
+  tensile strength of
+  weight of
+
+Nickel
+Nozzle sizes, torch
+
+Open hearth steel
+Oxy-acetylene cutting
+  welding practice
+Oxygen
+  cylinders
+  weight of
+
+Pipes, bending
+Platinum
+Preheating
+
+Removal of carbon by oxygen process
+Resistance method of electric welding
+Restoration of steel
+Rods, welding
+
+Safety devices
+Scarfing
+Solder
+Soldering
+  flux
+  holes
+  seams
+  steel and iron
+  wires
+Spelter
+Spot welding
+Steel
+  alloys
+  Bessemer
+  crucible
+  heat treatment of
+  open hearth
+  restoration of
+  tensile strength of
+  welding
+Strength of metals
+
+Tank valves
+Tapering
+Tables of welding information
+Tempering steel
+Thermit metal
+  preheating
+  preparation
+  welding
+Tin
+Torch
+  acetylene-air
+  care
+  construction
+  cutting
+  high pressure
+  low pressure
+  medium pressure
+  nozzles
+  practice
+
+Valves, regulating
+  tank
+
+Water
+  to carbide generator
+Welding aluminum
+  brass
+  bronze
+  butt
+  cast iron
+  copper
+  electric
+  electric arc
+  flame
+  forge
+  information and tables
+  instruments
+  lap
+  malleable iron
+  materials
+  practice, oxy-acetylene
+  rods
+  spot
+  steel
+  table
+  thermit
+  torches
+  various metals
+  wrought iron
+Wrought iron
+  welding
+
+Zinc
+
+
+
+
+
+End of the Project Gutenberg EBook of Oxy-Acetylene Welding and Cutting
+by Harold P. Manly
+
+*** END OF THE PROJECT GUTENBERG EBOOK OXY-ACETYLENE WELDING AND CUTTING ***
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+Project Gutenberg's Oxy-Acetylene Welding and Cutting, by Harold P. Manly
+
+Copyright laws are changing all over the world. Be sure to check the
+copyright laws for your country before downloading or redistributing
+this or any other Project Gutenberg eBook.
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+
+Title: Oxy-Acetylene Welding and Cutting
+       Electric, Forge and Thermit Welding together with related methods
+       and materials used in metal working and the oxygen process
+       for removal of carbon
+
+Author: Harold P. Manly
+
+Release Date: April, 2005 [EBook #7969]
+[Yes, we are more than one year ahead of schedule]
+[This file was first posted on June 7, 2003]
+
+Edition: 10
+
+Language: English
+
+Character set encoding: ISO-Latin-1
+
+*** START OF THE PROJECT GUTENBERG EBOOK OXY-ACETYLENE WELDING AND CUTTING ***
+
+
+
+
+Produced by Juliet Sutherland, John Argus, Tonya Allen,
+Charles Franks and the Online Distributed Proofreading Team.
+
+
+
+
+Oxy-Acetylene Welding and Cutting
+
+Electric, Forge and Thermit Welding
+
+Together with Related Methods and Materials Used in Metal Working
+And
+The Oxygen Process for Removal of Carbon
+
+By
+HAROLD P. MANLY
+
+
+
+
+PREFACE
+
+In the preparation of this work, the object has been to cover not only the
+several processes of welding, but also those other processes which are so
+closely allied in method and results as to make them a part of the whole
+subject of joining metal to metal with the aid of heat.
+
+The workman who wishes to handle his trade from start to finish finds that
+it is necessary to become familiar with certain other operations which
+precede or follow the actual joining of the metal parts, the purpose of
+these operations being to add or retain certain desirable qualities in the
+materials being handled. For this reason the following subjects have been
+included: Annealing, tempering, hardening, heat treatment and the
+restoration of steel.
+
+In order that the user may understand the underlying principles and the
+materials employed in this work, much practical information is given on the
+uses and characteristics of the various metals; on the production, handling
+and use of the gases and other materials which are a part of the equipment;
+and on the tools and accessories for the production and handling of these
+materials.
+
+An examination will show that the greatest usefulness of this book lies in
+the fact that all necessary information and data has been included in one
+volume, making it possible for the workman to use one source for securing a
+knowledge of both principle and practice, preparation and finishing of the
+work, and both large and small repair work as well as manufacturing methods
+used in metal working.
+
+An effort has been made to eliminate all matter which is not of direct
+usefulness in practical work, while including all that those engaged in
+this trade find necessary. To this end, the descriptions have been limited
+to those methods and accessories which are found in actual use today. For
+the same reason, the work includes the application of the rules laid down
+by the insurance underwriters which govern this work as well as
+instructions for the proper care and handling of the generators, torches
+and materials found in the shop.
+
+Special attention has been given to definite directions for handling the
+different metals and alloys which must be handled. The instructions have
+been arranged to form rules which are placed in the order of their use
+during the work described and the work has been subdivided in such a way
+that it will be found possible to secure information on any one point
+desired without the necessity of spending time in other fields.
+
+The facts which the expert welder and metalworker finds it most necessary
+to have readily available have been secured, and prepared especially for
+this work, and those of most general use have been combined with the
+chapter on welding practice to which they apply.
+
+The size of this volume has been kept as small as possible, but an
+examination of the alphabetical index will show that the range of subjects
+and details covered is complete in all respects. This has been accomplished
+through careful classification of the contents and the elimination of all
+repetition and all theoretical, historical and similar matter that is not
+absolutely necessary.
+
+Free use has been made of the information given by those manufacturers who
+are recognized as the leaders in their respective fields, thus insuring
+that the work is thoroughly practical and that it represents present day
+methods and practice.
+
+THE AUTHOR.
+
+
+
+
+CONTENTS
+
+   CHAPTER I
+
+METALS AND ALLOYS--HEAT TREATMENT:--The Use and Characteristics of the
+Industrial Alloys and Metal Elements--Annealing, Hardening, Tempering and
+Case Hardening of Steel
+
+   CHAPTER II
+
+WELDING MATERIALS:--Production, Handling and Use of the Gases, Oxygen and
+Acetylene--Welding Rods--Fluxes--Supplies and Fixtures
+
+   CHAPTER III
+
+ACETYLENE GENERATORS:--Generator Requirements and Types--Construction--Care
+and Operation of Generators.
+
+   CHAPTER IV
+
+WELDING INSTRUMENTS:--Tank and Regulating Valves and Gauges--High, Low and
+Medium Pressure Torches--Cutting Torches--Acetylene-Air Torches
+
+   CHAPTER V
+
+OXY-ACETYLENE WELDING PRACTICE:--Preparation of Work--Torch Practice--
+Control of the Flame--Welding Various Metals and Alloys--Tables of
+Information Required in Welding Operations
+
+   CHAPTER VI
+
+ELECTRIC WELDING:--Resistance Method--Butt, Spot and Lap Welding--Troubles
+and Remedies--Electric Arc Welding
+
+   CHAPTER VII
+
+HAND FORGING AND WELDING:--Blacksmithing, Forging and Bending--Forge
+Welding Methods
+
+   CHAPTER VIII
+
+SOLDERING, BRAZING AND THERMIT WELDING:--Soldering Materials and Practice--
+Brazing--Thermit Welding
+
+   CHAPTER IX
+
+OXYGEN PROCESS FOR REMOVAL OF CARBON
+
+INDEX
+
+
+
+
+
+OXY-ACETYLENE WELDING AND CUTTING, ELECTRIC AND THERMIT WELDING
+
+
+
+
+CHAPTER I
+
+METALS AND THEIR ALLOYS--HEAT TREATMENT
+
+
+THE METALS
+
+_Iron._--Iron, in its pure state, is a soft, white, easily worked
+metal. It is the most important of all the metallic elements, and is, next
+to aluminum, the commonest metal found in the earth.
+
+Mechanically speaking, we have three kinds of iron: wrought iron, cast iron
+and steel. Wrought iron is very nearly pure iron; cast iron contains carbon
+and silicon, also chemical impurities; and steel contains a definite
+proportion of carbon, but in smaller quantities than cast iron.
+
+Pure iron is never obtained commercially, the metal always being mixed with
+various proportions of carbon, silicon, sulphur, phosphorus, and other
+elements, making it more or less suitable for different purposes. Iron is
+magnetic to the extent that it is attracted by magnets, but it does not
+retain magnetism itself, as does steel. Iron forms, with other elements,
+many important combinations, such as its alloys, oxides, and sulphates.
+
+[Illustration: Figure 1.--Section Through a Blast Furnace]
+
+_Cast Iron._--Metallic iron is separated from iron ore in the blast
+furnace (Figure 1), and when allowed to run into moulds is called cast
+iron. This form is used for engine cylinders and pistons, for brackets,
+covers, housings and at any point where its brittleness is not
+objectionable. Good cast iron breaks with a gray fracture, is free from
+blowholes or roughness, and is easily machined, drilled, etc. Cast iron is
+slightly lighter than steel, melts at about 2,400 degrees in practice, is
+about one-eighth as good an electrical conductor as copper and has a
+tensile strength of 13,000 to 30,000 pounds per square inch. Its
+compressive strength, or resistance to crushing, is very great. It has
+excellent wearing qualities and is not easily warped and deformed by heat.
+Chilled iron is cast into a metal mould so that the outside is cooled
+quickly, making the surface very hard and difficult to cut and giving great
+resistance to wear. It is used for making cheap gear wheels and parts that
+must withstand surface friction.
+
+_Malleable Cast Iron._--This is often called simply malleable iron. It
+is a form of cast iron obtained by removing much of the carbon from cast
+iron, making it softer and less brittle. It has a tensile strength of
+25,000 to 45,000 pounds per square inch, is easily machined, will stand a
+small amount of bending at a low red heat and is used chiefly in making
+brackets, fittings and supports where low cost is of considerable
+importance. It is often used in cheap constructions in place of steel
+forgings. The greatest strength of a malleable casting, like a steel
+forging, is in the surface, therefore but little machining should be done.
+
+_Wrought Iron._--This grade is made by treating the cast iron to
+remove almost all of the carbon, silicon, phosphorus, sulphur, manganese
+and other impurities. This process leaves a small amount of the slag from
+the ore mixed with the wrought iron.
+
+Wrought iron is used for making bars to be machined into various parts. If
+drawn through the rolls at the mill once, while being made, it is called
+"muck bar;" if rolled twice, it is called "merchant bar" (the commonest
+kind), and a still better grade is made by rolling a third time. Wrought
+iron is being gradually replaced in use by mild rolled steels.
+
+Wrought iron is slightly heavier than cast iron, is a much better
+electrical conductor than either cast iron or steel, has a tensile strength
+of 40,000 to 60,000 pounds per square inch and costs slightly more than
+steel. Unlike either steel or cast iron, wrought iron does not harden when
+cooled suddenly from a red heat.
+
+_Grades of Irons._--The mechanical properties of cast iron differ
+greatly according to the amount of other materials it contains. The most
+important of these contained elements is carbon, which is present to a
+degree varying from 2 to 5-1/2 per cent. When iron containing much carbon
+is quickly cooled and then broken, the fracture is nearly white in color
+and the metal is found to be hard and brittle. When the iron is slowly
+cooled and then broken the fracture is gray and the iron is more malleable
+and less brittle. If cast iron contains sulphur or phosphorus, it will show
+a white fracture regardless of the rapidity of cooling, being brittle and
+less desirable for general work.
+
+_Steel._--Steel is composed of extremely minute particles of iron and
+carbon, forming a network of layers and bands. This carbon is a smaller
+proportion of the metal than found in cast iron, the percentage being from
+3/10 to 2-1/2 per cent.
+
+Carbon steel is specified according to the number of "points" of carbon, a
+point being one one-hundredth of one per cent of the weight of the steel.
+Steel may contain anywhere from 30 to 250 points, which is equivalent to
+saying, anywhere from 3/10 to 2-1/2 per cent, as above. A 70-point steel
+would contain 70/100 of one per cent or 7/10 of one per cent of carbon by
+weight. The percentage of carbon determines the hardness of the steel, also
+many other qualities, and its suitability for various kinds of work. The
+more carbon contained in the steel, the harder the metal will be, and, of
+course, its brittleness increases with the hardness. The smaller the grains
+or particles of iron which are separated by the carbon, the stronger the
+steel will be, and the control of the size of these particles is the object
+of the science of heat treatment.
+
+In addition to the carbon, steel may contain the following:
+
+Silicon, which increases the hardness, brittleness, strength and difficulty
+  of working if from 2 to 3 per cent is present.
+
+Phosphorus, which hardens and weakens the metal but makes it easier to
+  cast. Three-tenths per cent of phosphorus serves as a hardening agent and
+  may be present in good steel if the percentage of carbon is low. More
+  than this weakens the metal.
+
+Sulphur, which tends to make the metal hard and filled with small holes.
+
+Manganese, which makes the steel so hard and tough that it can with
+  difficulty be cut with steel tools. Its hardness is not lessened by
+  annealing, and it has great tensile strength.
+
+Alloy steel has a varying but small percentage of other elements mixed with
+it to give certain desired qualities. Silicon steel and manganese steel are
+sometimes classed as alloy steels. This subject is taken up in the latter
+part of this chapter under _Alloys_, where the various combinations
+and their characteristics are given consideration.
+
+Steel has a tensile strength varying from 50,000 to 300,000 pounds per
+square inch, depending on the carbon percentage and the other alloys
+present, as well as upon the texture of the grain. Steel is heavier than
+cast iron and weighs about the same as wrought iron. It is about one-ninth
+as good a conductor of electricity as copper.
+
+Steel is made from cast iron by three principal processes: the crucible,
+Bessemer and open hearth.
+
+_Crucible steel_ is made by placing pieces of iron in a clay or
+graphite crucible, mixed with charcoal and a small amount of any desired
+alloy. The crucible is then heated with coal, oil or gas fires until the
+iron melts, and, by absorbing the desired elements and giving up or
+changing its percentage of carbon, becomes steel. The molten steel is then
+poured from the crucible into moulds or bars for use. Crucible steel may
+also be made by placing crude steel in the crucibles in place of the iron.
+This last method gives the finest grade of metal and the crucible process
+in general gives the best grades of steel for mechanical use.
+
+[Illustration: Figure 2.--A Bessemer Converter]
+
+_Bessemer steel_ is made by heating iron until all the undesirable
+elements are burned out by air blasts which furnish the necessary oxygen.
+The iron is placed in a large retort called a converter, being poured,
+while at a melting heat, directly from the blast furnace into the
+converter. While the iron in the converter is molten, blasts of air are
+forced through the liquid, making it still hotter and burning out the
+impurities together with the carbon and manganese. These two elements are
+then restored to the iron by adding spiegeleisen (an alloy of iron, carbon
+and manganese). A converter holds from 5 to 25 tons of metal and requires
+about 20 minutes to finish a charge. This makes the cheapest steel.
+
+[Illustration: Figure 3.--An Open Hearth Furnace]
+
+_Open hearth steel_ is made by placing the molten iron in a receptacle
+while currents of air pass over it, this air having itself been highly
+heated by just passing over white hot brick (Figure. 3). Open hearth steel
+is considered more uniform and reliable than Bessemer, and is used for
+springs, bar steel, tool steel, steel plates, etc.
+
+_Aluminum_ is one of the commonest industrial metals. It is used for
+gear cases, engine crank cases, covers, fittings, and wherever lightness
+and moderate strength are desirable.
+
+Aluminum is about one-third the weight of iron and about the same weight as
+glass and porcelain; it is a good electrical conductor (about one-half as
+good as copper); is fairly strong itself and gives great strength to other
+metals when alloyed with them. One of the greatest advantages of aluminum
+is that it will not rust or corrode under ordinary conditions. The granular
+formation of aluminum makes its strength very unreliable and it is too soft
+to resist wear.
+
+_Copper_ is one of the most important metals used in the trades, and
+the best commercial conductor of electricity, being exceeded in this
+respect only by silver, which is but slightly better. Copper is very
+malleable and ductile when cold, and in this state may be easily worked
+under the hammer. Working in this way makes the copper stronger and harder,
+but less ductile. Copper is not affected by air, but acids cause the
+formation of a green deposit called verdigris.
+
+Copper is one of the best conductors of heat, as well as electricity, being
+used for kettles, boilers, stills and wherever this quality is desirable.
+Copper is also used in alloys with other metals, forming an important part
+of brass, bronze, german silver, bell metal and gun metal. It is about
+one-eighth heavier than steel and has a tensile strength of about 25,000 to
+50,000 pounds per square inch.
+
+_Lead._--The peculiar properties of lead, and especially its quality
+of showing but little action or chemical change in the presence of other
+elements, makes it valuable under certain conditions of use. Its principal
+use is in pipes for water and gas, coverings for roofs and linings for vats
+and tanks. It is also used to coat sheet iron for similar uses and as an
+important part of ordinary solder.
+
+Lead is the softest and weakest of all the commercial metals, being very
+pliable and inelastic. It should be remembered that lead and all its
+compounds are poisonous when received into the system. Lead is more than
+one-third heavier than steel, has a tensile strength of only about 2,000
+pounds per square inch, and is only about one-tenth as good a conductor of
+electricity as copper.
+
+_Zinc._--This is a bluish-white metal of crystalline form. It is
+brittle at ordinary temperatures and becomes malleable at about 250 to 300
+degrees Fahrenheit, but beyond this point becomes even more brittle than at
+ordinary temperatures. Zinc is practically unaffected by air or moisture
+through becoming covered with one of its own compounds which immediately
+resists further action. Zinc melts at low temperatures, and when heated
+beyond the melting point gives off very poisonous fumes.
+
+The principal use of zinc is as an alloy with other metals to form brass,
+bronze, german silver and bearing metals. It is also used to cover the
+surface of steel and iron plates, the plates being then called galvanized.
+
+Zinc weighs slightly less than steel, has a tensile strength of 5,000
+pounds per square inch, and is not quite half as good as copper in
+conducting electricity.
+
+_Tin_ resembles silver in color and luster. Tin is ductile and
+malleable and slightly crystalline in form, almost as heavy as steel, and
+has a tensile strength of 4,500 pounds per square inch.
+
+The principal use of tin is for protective platings on household utensils
+and in wrappings of tin-foil. Tin forms an important part of many alloys
+such as babbitt, Britannia metal, bronze, gun metal and bearing metals.
+
+_Nickel_ is important in mechanics because of its combinations with
+other metals as alloys. Pure nickel is grayish-white, malleable, ductile
+and tenacious. It weighs almost as much as steel and, next to manganese, is
+the hardest of metals. Nickel is one of the three magnetic metals, the
+others being iron and cobalt. The commonest alloy containing nickel is
+german silver, although one of its most important alloys is found in nickel
+steel. Nickel is about ten per cent heavier than steel, and has a tensile
+strength of 90,000 pounds per square inch.
+
+_Platinum._--This metal is valuable for two reasons: it is not
+affected by the air or moisture or any ordinary acid or salt, and in
+addition to this property it melts only at the highest temperatures. It is
+a fairly good electrical conductor, being better than iron or steel. It is
+nearly three times as heavy as steel and its tensile strength is 25,000
+pounds per square inch.
+
+
+ALLOYS
+
+An alloy is formed by the union of a metal with some other material, either
+metal or non-metallic, this union being composed of two or more elements
+and usually brought about by heating the substances together until they
+melt and unite. Metals are alloyed with materials which have been found to
+give to the metal certain characteristics which are desired according to
+the use the metal will be put to.
+
+The alloys of metals are, almost without exception, more important from an
+industrial standpoint than the metals themselves. There are innumerable
+possible combinations, the most useful of which are here classed under the
+head of the principal metal entering into their composition.
+
+_Steel._--Steel may be alloyed with almost any of the metals or
+elements, the combinations that have proven valuable numbering more than a
+score. The principal ones are given in alphabetical order, as follows:
+
+Aluminum is added to steel in very small amounts for the purpose of
+preventing blow holes in castings.
+
+Boron increases the density and toughness of the metal.
+
+Bronze, added by alloying copper, tin and iron, is used for gun metal.
+
+Carbon has already been considered under the head of steel in the section
+devoted to the metals. Carbon, while increasing the strength and hardness,
+decreases the ease of forging and bending and decreases the magnetism and
+electrical conductivity. High carbon steel can be welded only with
+difficulty. When the percentage of carbon is low, the steel is called "low
+carbon" or "mild" steel. This is used for rods and shafts, and called
+"machine" steel. When the carbon percentage is high, the steel is called
+"high carbon" steel, and it is used in the shop as tool steel. One-tenth
+per cent of carbon gives steel a tensile strength of 50,000 to 65,000
+pounds per square inch; two-tenths per cent gives from 60,000 to 80,000;
+four-tenths per cent gives 70,000 to 100,000, and six-tenths per cent
+gives 90,000 to 120,000.
+
+Chromium forms chrome steel, and with the further addition of nickel is
+called chrome nickel steel. This increases the hardness to a high degree
+and adds strength without much decrease in ductility. Chrome steels are
+used for high-speed cutting tools, armor plate, files, springs, safes,
+dies, etc.
+
+Manganese has been mentioned under _Steel_. Its alloy is much used for
+high-speed cutting tools, the steel hardening when cooled in the air and
+being called self-hardening.
+
+Molybdenum is used to increase the hardness to a high degree and makes the
+steel suitable for high-speed cutting and gives it self-hardening
+properties.
+
+Nickel, with which is often combined chromium, increases the strength,
+springiness and toughness and helps to prevent corrosion.
+
+Silicon has already been described. It suits the metal for use in
+high-speed tools.
+
+Silver added to steel has many of the properties of nickel.
+
+Tungsten increases the hardness without making the steel brittle. This
+makes the steel well suited for gas engine valves as it resists corrosion
+and pitting. Chromium and manganese are often used in combination with
+tungsten when high-speed cutting tools are made.
+
+Vanadium as an alloy increases the elastic limit, making the steel
+stronger, tougher and harder. It also makes the steel able to stand much
+bending and vibration.
+
+_Copper._--The principal copper alloys include brass, bronze, german
+silver and gun metal.
+
+Brass is composed of approximately one-third zinc and two-thirds copper. It
+is used for bearings and bushings where the speeds are slow and the loads
+rather heavy for the bearing size. It also finds use in washers, collars
+and forms of brackets where the metal should be non-magnetic, also for many
+highly finished parts.
+
+Brass is about one-third as good an electrical conductor as copper, is
+slightly heavier than steel and has a tensile strength of 15,000 pounds
+when cast and about 75,000 to 100,000 pounds when drawn into wire.
+
+Bronze is composed of copper and tin in various proportions, according to
+the use to which it is to be put. There will always be from six-tenths to
+nine-tenths of copper in the mixture. Bronze is used for bearings,
+bushings, thrust washers, brackets and gear wheels. It is heavier than
+steel, about 1/15 as good an electrical conductor as pure copper and has a
+tensile strength of 30,000 to 60,000 pounds.
+
+Aluminum bronze, composed of copper, zinc and aluminum has high tensile
+strength combined with ductility and is used for parts requiring this
+combination.
+
+Bearing bronze is a variable material, its composition and proportion
+depending on the maker and the use for which it is designed. It usually
+contains from 75 to 85 per cent of copper combined with one or more
+elements, such as tin, zinc, antimony and lead.
+
+White metal is one form of bearing bronze containing over 80 per cent of
+zinc together with copper, tin, antimony and lead. Another form is made
+with nearly 90 per cent of tin combined with copper and antimony.
+
+Gun metal bronze is made from 90 per cent copper with 10 per cent of tin
+and is used for heavy bearings, brackets and highly finished parts.
+
+Phosphor bronze is used for very strong castings and bearings. It is
+similar to gun metal bronze, except that about 1-1/2 per cent of phosphorus
+has been added.
+
+Manganese bronze contains about 1 per cent of manganese and is used for
+parts requiring great strength while being free from corrosion.
+
+German silver is made from 60 per cent of copper with 20 per cent each of
+zinc and nickel. Its high electrical resistance makes it valuable for
+regulating devices and rheostats.
+
+_Tin_ is the principal part of _babbitt_ and _solder_. A
+commonly used babbitt is composed of 89 per cent tin, 8 per cent antimony
+and 3 per cent of copper. A grade suitable for repairing is made from
+80 per cent of lead and 20 per cent antimony. This last formula should not
+be used for particular work or heavy loads, being more suitable for
+spacers. Innumerable proportions of metals are marketed under the name of
+babbitt.
+
+Solder is made from 50 per cent tin and 50 per cent lead, this grade being
+called "half-and-half." Hard solder is made from two-thirds tin and
+one-third lead.
+
+Aluminum forms many different alloys, giving increased strength to whatever
+metal it unites with.
+
+Aluminum brass is composed of approximately 65 per cent copper, 30 per cent
+zinc and 5 per cent aluminum. It forms a metal with high tensile strength
+while being ductile and malleable.
+
+Aluminum zinc is suitable for castings which must be stiff and hard.
+
+Nickel aluminum has a tensile strength of 40,000 pounds per square inch.
+
+Magnalium is a silver-white alloy of aluminum with from 5 to 20 per cent of
+magnesium, forming a metal even lighter than aluminum and strong enough to
+be used in making high-speed gasoline engines.
+
+
+HEAT TREATMENT OF STEEL
+
+The processes of heat treatment are designed to suit the steel for various
+purposes by changing the size of the grain in the metal, therefore the
+strength; and by altering the chemical composition of the alloys in the
+metal to give it different physical properties. Heat treatment, as applied
+in ordinary shop work, includes the three processes of annealing, hardening
+and tempering, each designed to accomplish a certain definite result.
+
+All of these processes require that the metal treated be gradually brought
+to a certain predetermined degree of heat which shall be uniform throughout
+the piece being handled and, from this point, cooled according to certain
+rules, the selection of which forms the difference in the three methods.
+
+_Annealing._--This is the process which relieves all internal strains
+and distortion in the metal and softens it so that it may more easily be
+cut, machined or bent to the required form. In some cases annealing is used
+only to relieve the strains, this being the case after forging or welding
+operations have been performed. In other cases it is only desired to soften
+the metal sufficiently that it may be handled easily. In some cases both of
+these things must be accomplished, as after a piece has been forged and
+must be machined. No matter what the object, the procedure is the same.
+
+The steel to be annealed must first be heated to a dull red. This heating
+should be done slowly so that all parts of the piece have time to reach the
+same temperature at very nearly the same time. The piece may be heated in
+the forge, but a much better way is to heat in an oven or furnace of some
+type where the work is protected against air currents, either hot or cold,
+and is also protected against the direct action of the fire.
+
+[Illustration: Figure 4.--A Gaspipe Annealing Oven]
+
+Probably the simplest of all ovens for small tools is made by placing a
+piece of ordinary gas pipe in the fire (Figure 4), and heating until the
+inside of the pipe is bright red. Parts placed in this pipe, after one end
+has been closed, may be brought to the desired heat without danger of
+cooling draughts or chemical change from the action of the fire. More
+elaborate ovens may be bought which use gas, fuel oils or coal to produce
+the heat and in which the work may be placed on trays so that the fire will
+not strike directly on the steel being treated.
+
+If the work is not very important, it may be withdrawn from the fire or
+oven, after heating to the desired point, and allowed to cool in the air
+until all traces of red have disappeared when held in a dark place. The
+work should be held where it is reasonably free from cold air currents. If,
+upon touching a pine stick to the piece being annealed, the wood does not
+smoke, the work may then be cooled in water.
+
+Better annealing is secured and harder metal may be annealed if the cooling
+is extended over a number of hours by placing the work in a bed of
+non-heat-conducting material, such as ashes, charred bone, asbestos fibre,
+lime, sand or fire clay. It should be well covered with the heat retaining
+material and allowed to remain until cool. Cooling may be accomplished by
+allowing the fire in an oven or furnace to die down and go out, leaving the
+work inside the oven with all openings closed. The greater the time taken
+for gradual cooling from the red heat, the more perfect will be the results
+of the annealing.
+
+While steel is annealed by slow cooling, copper or brass is annealed by
+bringing to a low red heat and quickly plunging into cold water.
+
+_Hardening._--Steel is hardened by bringing to a proper temperature,
+slowly and evenly as for annealing, and then cooling more or less quickly,
+according to the grade of steel being handled. The degree of hardening is
+determined by the kind of steel, the temperature from which the metal is
+cooled and the temperature and nature of the bath into which it is plunged
+for cooling.
+
+Steel to be hardened is often heated in the fire until at some heat around
+600 to 700 degrees is reached, then placed in a heating bath of molten
+lead, heated mercury, fused cyanate of potassium, etc., the heating bath
+itself being kept at the proper temperature by fires acting on it. While
+these baths have the advantage of heating the metal evenly and to exactly
+the temperature desired throughout without any part becoming over or under
+heated, their disadvantages consist of the fact that their materials and
+the fumes are poisonous in most all cases, and if not poisonous, are
+extremely disagreeable.
+
+The degree of heat that a piece of steel must be brought to in order that
+it may be hardened depends on the percentage of carbon in the steel. The
+greater the percentage of carbon, the lower the heat necessary to harden.
+
+[Illustration: Figure 5.--Cooling the Test Bar for Hardening]
+
+To find the proper heat from which any steel must be cooled, a simple test
+may be carried out provided a sample of the steel, about six inches long
+can be secured. One end of this test bar should be heated almost to its
+melting point, and held at this heat until the other end just turns red.
+Now cool the piece in water by plunging it so that both ends enter at the
+same time (Figure 5), that is, hold it parallel with the surface of the
+water when plunged in. This serves the purpose of cooling each point along
+the bar from a different heat. When it has cooled in the water remove the
+piece and break it at short intervals, about 1/2 inch, along its length.
+The point along the test bar which was cooled from the best possible
+temperature will show a very fine smooth grain and the piece cannot be cut
+by a file at this point. It will be necessary to remember the exact color
+of that point when taken from the fire, making another test if necessary,
+and heat all pieces of this same steel to this heat. It will be necessary
+to have the cooling bath always at the same temperature, or the results
+cannot be alike.
+
+While steel to be hardened is usually cooled in water, many other liquids
+may be used. If cooled in strong brine, the heat will be extracted much
+quicker, and the degree of hardness will be greater. A still greater degree
+of hardness is secured by cooling in a bath of mercury. Care should be used
+with the mercury bath, as the fumes that arise are poisonous.
+
+Should toughness be desired, without extreme hardness, the steel may be
+cooled in a bath of lard oil, neatsfoot oil or fish oil. To secure a result
+between water and oil, it is customary to place a thick layer of oil on top
+of water. In cooling, the piece will pass through the oil first, thus
+avoiding the sudden shock of the cold water, yet producing a degree of
+hardness almost as great as if the oil were not used.
+
+It will, of course, be necessary to make a separate test for each cooling
+medium used. If the fracture of the test piece shows a coarse grain, the
+steel was too hot at that point; if the fracture can be cut with a file,
+the metal was not hot enough at that point.
+
+When hardening carbon tool steel its heat should be brought to a cherry
+red, the exact degree of heat depending on the amount of carbon and the
+test made, then plunged into water and held there until all hissing sound
+and vibration ceases. Brine may be used for this purpose; it is even better
+than plain water. As soon as the hissing stops, remove the work from the
+water or brine and plunge in oil for complete cooling.
+
+[Illustration: Figure 6.--Cooling the Tool for Tempering]
+
+In hardening high-speed tool steel, or air hardening steels, the tool
+should be handled as for carbon steel, except that after the body reaches
+a cherry red, the cutting point must be quickly brought to a white heat,
+almost melting, so that it seems ready for welding. Then cool in an oil
+bath or in a current of cool air.
+
+Hardening of copper, brass and bronze is accomplished by hammering or
+working them while cold.
+
+_Tempering_ is the process of making steel tough after it has been
+hardened, so that it will hold a cutting edge and resist cracking.
+Tempering makes the grain finer and the metal stronger. It does not affect
+the hardness, but increases the elastic limit and reduces the brittleness
+of the steel. In that tempering is usually performed immediately after
+hardening, it might be considered as a continuation of the former process.
+
+The work or tool to be tempered is slowly heated to a cherry red and the
+cutting end is then dipped into water to a depth of 1/2 to 3/4 inch above
+the point (Figure 6). As soon as the point cools, still leaving the tool
+red above the part in water, remove the work from the bath and quickly rub
+the end with a fine emery cloth.
+
+As the heat from the uncooled part gradually heats the point again, the
+color of the polished portion changes rapidly. When a certain color is
+reached, the tool should be completely immersed in the water until cold.
+
+For lathe, planer, shaper and slotter tools, this color should be a light
+straw.
+
+Reamers and taps should be cooled from an ordinary straw color.
+
+Drills, punches and wood working tools should have a brown color.
+
+Blue or light purple is right for cold chisels and screwdrivers.
+
+Dark blue should be reached for springs and wood saws.
+
+Darker colors than this, ranging through green and gray, denote that the
+piece has reached its ordinary temper, that is, it is partially annealed.
+
+After properly hardening a spring by dipping in lard or fish oil, it should
+be held over a fire while still wet with the oil. The oil takes fire and
+burns off, properly tempering the spring.
+
+Remember that self-hardening steels must never be dipped in water, and
+always remember for all work requiring degrees of heat, that the more
+carbon, the less heat.
+
+_Case Hardening._--This is a process for adding more carbon to the
+surface of a piece of steel, so that it will have good wear-resisting
+qualities, while being tough and strong on the inside. It has the effect of
+forming a very hard and durable skin on the surface of soft steel, leaving
+the inside unaffected.
+
+The simplest way, although not the most efficient, is to heat the piece to
+be case hardened to a red heat and then sprinkle or rub the part of the
+surface to be hardened with potassium ferrocyanide. This material is a
+deadly poison and should be handled with care. Allow the cyanide to fuse on
+the surface of the metal and then plunge into water, brine or mercury.
+Repeating the process makes the surface harder and the hard skin deeper
+each time.
+
+Another method consists of placing the piece to be hardened in a bed of
+powdered bone (bone which has been burned and then powdered) and cover with
+more powdered bone, holding the whole in an iron tray. Now heat the tray
+and bone with the work in an oven to a bright red heat for 30 minutes to an
+hour and then plunge the work into water or brine.
+
+
+
+
+CHAPTER II
+
+OXY-ACETYLENE WELDING AND CUTTING MATERIALS
+
+
+_Welding._--Oxy-acetylene welding is an autogenous welding process, in
+which two parts of the same or different metals are joined by causing the
+edges to melt and unite while molten without the aid of hammering or
+compression. When cool, the parts form one piece of metal.
+
+The oxy-acetylene flame is made by mixing oxygen and acetylene gases in a
+special welding torch or blowpipe, producing, when burned, a heat of 6,300
+degrees, which is more than twice the melting temperature of the common
+metals. This flame, while being of intense heat, is of very small size.
+
+_Cutting._--The process of cutting metals with the flame produced from
+oxygen and acetylene depends on the fact that a jet of oxygen directed upon
+hot metal causes the metal itself to burn away with great rapidity,
+resulting in a narrow slot through the section cut. The action is so fast
+that metal is not injured on either side of the cut.
+
+_Carbon Removal._--This process depends on the fact that carbon will
+burn and almost completely vanish if the action is assisted with a supply
+of pure oxygen gas. After the combustion is started with any convenient
+flame, it continues as long as carbon remains in the path of the jet of
+oxygen.
+
+_Materials._--For the performance of the above operations we require
+the two gases, oxygen and acetylene, to produce the flames; rods of metal
+which may be added to the joints while molten in order to give the weld
+sufficient strength and proper form, and various chemical powders, called
+fluxes, which assist in the flow of metal and in doing away with many of
+the impurities and other objectionable features.
+
+_Instruments._--To control the combustion of the gases and add to the
+convenience of the operator a number of accessories are required.
+
+The pressure of the gases in their usual containers is much too high for
+their proper use in the torch and we therefore need suitable valves which
+allow the gas to escape from the containers when wanted, and other
+specially designed valves which reduce the pressure. Hose, composed of
+rubber and fabric, together with suitable connections, is used to carry the
+gas to the torch.
+
+The torches for welding and cutting form a class of highly developed
+instruments of the greatest accuracy in manufacture, and must be thoroughly
+understood by the welder. Tables, stands and special supports are provided
+for holding the work while being welded, and in order to handle the various
+metals and allow for their peculiarities while heated use is made of ovens
+and torches for preheating. The operator requires the protection of
+goggles, masks, gloves and appliances which prevent undue radiation of the
+heat.
+
+_Torch Practice._--The actual work of welding and cutting requires
+preliminary preparation in the form of heat treatment for the metals,
+including preheating, annealing and tempering. The surfaces to be joined
+must be properly prepared for the flame, and the operation of the torches
+for best results requires careful and correct regulation of the gases and
+the flame produced.
+
+Finally, the different metals that are to be welded require special
+treatment for each one, depending on the physical and chemical
+characteristics of the material.
+
+It will thus be seen that the apparently simple operations of welding and
+cutting require special materials, instruments and preparation on the part
+of the operator and it is a proved fact that failures, which have been
+attributed to the method, are really due to lack of these necessary
+qualifications.
+
+
+OXYGEN
+
+Oxygen, the gas which supports the rapid combustion of the acetylene in the
+torch flame, is one of the elements of the air. It is the cause and the
+active agent of all combustion that takes place in the atmosphere. Oxygen
+was first discovered as a separate gas in 1774, when it was produced by
+heating red oxide of mercury and was given its present name by the famous
+chemist, Lavoisier.
+
+Oxygen is prepared in the laboratory by various methods, these including
+the heating of chloride of lime and peroxide of cobalt mixed in a retort,
+the heating of chlorate of potash, and the separation of water into its
+elements, hydrogen and oxygen, by the passage of an electric current. While
+the last process is used on a large scale in commercial work, the others
+are not practical for work other than that of an experimental or temporary
+nature.
+
+This gas is a colorless, odorless, tasteless element. It is sixteen times
+as heavy as the gas hydrogen when measured by volume under the same
+temperature and pressure. Under all ordinary conditions oxygen remains in
+a gaseous form, although it turns to a liquid when compressed to 4,400
+pounds to the square inch and at a temperature of 220° below zero.
+
+Oxygen unites with almost every other element, this union often taking
+place with great heat and much light, producing flame. Steel and iron will
+burn rapidly when placed in this gas if the combustion is started with a
+flame of high heat playing on the metal. If the end of a wire is heated
+bright red and quickly plunged into a jar containing this gas, the wire
+will burn away with a dazzling light and be entirely consumed except for
+the molten drops that separate themselves. This property of oxygen is used
+in oxy-acetylene cutting of steel.
+
+The combination of oxygen with other substances does not necessarily cause
+great heat, in fact the combination may be so slow and gradual that the
+change of temperature can not be noticed. An example of this slow
+combustion, or oxidation, is found in the conversion of iron into rust as
+the metal combines with the active gas. The respiration of human beings
+and animals is a form of slow combustion and is the source of animal heat.
+It is a general rule that the process of oxidation takes place with
+increasing rapidity as the temperature of the body being acted upon rises.
+Iron and steel at a red heat oxidize rapidly with the formation of a scale
+and possible damage to the metal.
+
+_Air._--Atmospheric air is a mixture of oxygen and nitrogen with
+traces of carbonic acid gas and water vapor. Twenty-one per cent of the
+air, by volume, is oxygen and the remaining seventy-nine per cent is the
+inactive gas, nitrogen. But for the presence of the nitrogen, which deadens
+the action of the other gas, combustion would take place at a destructive
+rate and be beyond human control in almost all cases. These two gases exist
+simply as a mixture to form the air and are not chemically combined. It is
+therefore a comparatively simple matter to separate them with the processes
+now available.
+
+_Water._--Water is a combination of oxygen and hydrogen, being
+composed of exactly two volumes of hydrogen to one volume of oxygen. If
+these two gases be separated from each other and then allowed to mix in
+these proportions they unite with explosive violence and form water. Water
+itself may be separated into the gases by any one of several means, one
+making use of a temperature of 2,200° to bring about this separation.
+
+[Illustration: Figure 7.--Obtaining Oxygen by Electrolysis]
+
+The easiest way to separate water into its two parts is by the process
+called electrolysis (Figure 7). Water, with which has been mixed a small
+quantity of acid, is placed in a vat through the walls of which enter the
+platinum tipped ends of two electrical conductors, one positive and the
+other negative.
+
+Tubes are placed directly above these wire terminals in the vat, one tube
+being over each electrode and separated from each other by some distance.
+With the passage of an electric current from one wire terminal to the
+other, bubbles of gas rise from each and pass into the tubes. The gas that
+comes from the negative terminal is hydrogen and that from the positive
+pole is oxygen, both gases being almost pure if the work is properly
+conducted. This method produces electrolytic oxygen and electrolytic
+hydrogen.
+
+_The Liquid Air Process._--While several of the foregoing methods of
+securing oxygen are successful as far as this result is concerned, they are
+not profitable from a financial standpoint. A process for separating oxygen
+from the nitrogen in the air has been brought to a high state of perfection
+and is now supplying a major part of this gas for oxy-acetylene welding. It
+is known as the Linde process and the gas is distributed by the Linde Air
+Products Company from its plants and warehouses located in the large cities
+of the country.
+
+The air is first liquefied by compression, after which the gases are
+separated and the oxygen collected. The air is purified and then compressed
+by successive stages in powerful machines designed for this purpose until
+it reaches a pressure of about 3,000 pounds to the square inch. The large
+amount of heat produced is absorbed by special coolers during the process
+of compression. The highly compressed air is then dried and the
+temperature further reduced by other coolers.
+
+The next point in the separation is that at which the air is introduced
+into an apparatus called an interchanger and is allowed to escape through a
+valve, causing it to turn to a liquid. This liquid air is sprayed onto
+plates and as it falls, the nitrogen return to its gaseous state and leaves
+ the oxygen to run to the bottom of the container. This liquid oxygen is
+then allowed to return to a gas and is stored in large gasometers or tanks.
+
+The oxygen gas is taken from the storage tanks and compressed to
+approximately 1,800 pounds to the square inch, under which pressure it is
+passed into steel cylinders and made ready for delivery to the customer.
+This oxygen is guaranteed to be ninety-seven per cent pure.
+
+Another process, known as the Hildebrandt process, is coming into use in
+this country. It is a later process and is used in Germany to a much
+greater extent than the Linde process. The Superior Oxygen Co. has secured
+the American rights and has established several plants.
+
+_Oxygen Cylinders_.--Two sizes of cylinders are in use, one containing
+100 cubic feet of gas when it is at atmospheric pressure and the other
+containing 250 cubic feet under similar conditions. The cylinders are made
+from one piece of steel and are without seams. These containers are tested
+at double the pressure of the gas contained to insure safety while
+handling.
+
+One hundred cubic feet of oxygen weighs nearly nine pounds (8.921), and
+therefore the cylinders will weigh practically nine pounds more when full
+than after emptying, if of the 100 cubic feet size. The large cylinders
+weigh about eighteen and one-quarter pounds more when full than when empty,
+making approximately 212 pounds empty and 230 pounds full.
+
+The following table gives the number of cubic feet of oxygen remaining in
+the cylinders according to various gauge pressures from an initial pressure
+of 1,800 pounds. The amounts given are not exactly correct as this would
+necessitate lengthy calculations which would not make great enough
+difference to affect the practical usefulness of the table:
+
+Cylinder of 100 Cu. Ft. Capacity at 68° Fahr.
+
+ Gauge     Volume     Gauge     Volume
+Pressure  Remaining  Pressure  Remaining
+
+ 1800        100       700        39
+ 1620         90       500        28
+ 1440         80       300        17
+ 1260         70       100         6
+ 1080         60        18         1
+  900         50         9          1/2
+
+Cylinder of 250 Cu. Ft. Capacity at 68° Fahr.
+
+ Gauge     Volume     Gauge     Volume
+Pressure  Remaining  Pressure  Remaining
+
+ 1800        250       700        97
+ 1620        225       500        70
+ 1440        200       300        42
+ 1260        175       100        15
+ 1080        150        18         8
+  900        125         9         1-1/4
+
+The temperature of the cylinder affects the pressure in a large degree, the
+pressure increasing with a rise in temperature and falling with a fall in
+temperature. The variation for a 100 cubic foot cylinder at various
+temperatures is given in the following tabulation:
+
+At 150° Fahr........................ 2090 pounds.
+At 100° Fahr........................ 1912 pounds.
+At  80° Fahr........................ 1844 pounds.
+At  68° Fahr........................ 1800 pounds.
+At  50° Fahr........................ 1736 pounds.
+At  32° Fahr........................ 1672 pounds.
+At   0  Fahr........................ 1558 pounds.
+At -10° Fahr........................ 1522 pounds.
+
+_Chlorate of Potash Method._--In spite of its higher cost and the
+inferior gas produced, the chlorate of potash method of producing oxygen is
+used to a limited extent when it is impossible to secure the gas in
+cylinders.
+
+[Illustration: Figure 8.--Oxygen from Chlorate of Potash]
+
+An iron retort (Figure 8) is arranged to receive about fifteen pounds of
+chlorate of potash mixed with three pounds of manganese dioxide, after
+which the cylinder is closed with a tight cap, clamped on. This retort is
+carried above a burner using fuel gas or other means of generating heat and
+this burner is lighted after the chemical charge is mixed and compressed in
+the tube.
+
+The generation of gas commences and the oxygen is led through water baths
+which wash and cool it before storing in a tank connected with the plant.
+From this tank the gas is compressed into portable cylinders at a pressure
+of about 300 pounds to the square inch for use as required in welding
+operations.
+
+Each pound of chlorate of potash liberates about three cubic feet of
+oxygen, and taking everything into consideration, the cost of gas produced
+in this way is several times that of the purer product secured by the
+liquid air process.
+
+These chemical generators are oftentimes a source of great danger,
+especially when used with or near the acetylene gas generator, as is
+sometimes the case with cheap portable outfits. Their use should not be
+tolerated when any other method is available, as the danger from accident
+alone should prohibit the practice except when properly installed and
+cared for away from other sources of combustible gases.
+
+
+ACETYLENE
+
+In 1862 a chemist, Woehler, announced the discovery of the preparation of
+acetylene gas from calcium carbide, which he had made by heating to a high
+temperature a mixture of charcoal with an alloy of zinc and calcium. His
+product would decompose water and yield the gas. For nearly thirty years
+these substances were neglected, with the result that acetylene was
+practically unknown, and up to 1892 an acetylene flame was seen by very few
+persons and its possibilities were not dreamed of. With the development of
+the modern electric furnace the possibility of calcium carbide as a
+commercial product became known.
+
+In the above year, Thomas L. Willson, an electrical engineer of Spray,
+North Carolina, was experimenting in an attempt to prepare metallic
+calcium, for which purpose he employed an electric furnace operating on a
+mixture of lime and coal tar with about ninety-five horse power. The result
+was a molten mass which became hard and brittle when cool. This apparently
+useless product was discarded and thrown in a nearby stream, when, to the
+astonishment of onlookers, a large volume of gas was immediately
+liberated, which, when ignited, burned with a bright and smoky flame and
+gave off quantities of soot. The solid material proved to be calcium
+carbide and the gas acetylene.
+
+Thus, through the incidental study of a by-product, and as the result of an
+accident, the possibilities in carbide were made known, and in the spring
+of 1895 the first factory in the world for the production of this substance
+was established by the Willson Aluminum Company.
+
+When water and calcium carbide are brought together an action takes place
+which results in the formation of acetylene gas and slaked lime.
+
+
+CARBIDE
+
+Calcium carbide is a chemical combination of the elements carbon and
+calcium, being dark brown, black or gray with sometimes a blue or red
+tinge. It looks like stone and will only burn when heated with oxygen.
+
+Calcium carbide may be preserved for any length of time if protected from
+the air, but the ordinary moisture in the atmosphere gradually affects it
+until nothing remains but slaked lime. It always possesses a penetrating
+odor, which is not due to the carbide itself but to the fact that it is
+being constantly affected by moisture and producing small quantities of
+acetylene gas.
+
+This material is not readily dissolved by liquids, but if allowed to come
+in contact with water, a decomposition takes place with the evolution of
+large quantities of gas. Carbide is not affected by shock, jarring or age.
+
+A pound of absolutely pure carbide will yield five and one-half cubic feet
+of acetylene. Absolute purity cannot be attained commercially, and in
+practice good carbide will produce from four and one-half to five cubic
+feet for each pound used.
+
+Carbide is prepared by fusing lime and carbon in the electric furnace under
+a heat in excess of 6,000 degrees Fahrenheit. These materials are among the
+most difficult to melt that are known. Lime is so infusible that it is
+frequently employed for the materials of crucibles in which the highest
+melting metals are fused, and for the pencils in the calcium light because
+it will stand extremely high temperatures.
+
+Carbon is the material employed in the manufacture of arc light electrodes
+and other electrical appliances that must stand extreme heat. Yet these two
+substances are forced into combination in the manufacture of calcium
+carbide. It is the excessively high temperature attainable in the electric
+furnace that causes this combination and not any effect of the electricity
+other than the heat produced.
+
+A mixture of ground coke and lime is introduced into the furnace through
+which an electric arc has been drawn. The materials unite and form an ingot
+of very pure carbide surrounded by a crust of less purity. The poorer crust
+is rejected in breaking up the mass into lumps which are graded according
+to their size. The largest size is 2 by 3-1/2 inches and is called "lump,"
+a medium size is 1/2 by 2 inches and is called "egg," an intermediate size
+for certain types of generators is 3/8 by 1-1/4 inches and called "nut,"
+and the finely crushed pieces for use in still other types of generators
+are 1/12 by 1/4 inch in size and are called "quarter." Instructions as to
+the size best suited to different generators are furnished by the makers
+of those instruments.
+
+These sizes are packed in air-tight sheet steel drums containing 100 pounds
+each. The Union Carbide Company of Chicago and New York, operating under
+patents, manufactures and distributes the supply of calcium carbide for the
+entire United States. Plants for this manufacture are established at
+Niagara Falls, New York, and Sault Ste. Marie, Michigan. This company
+maintains a system of warehouses in more than one hundred and ten cities,
+where large stocks of all sizes are carried.
+
+The National Board of Fire Underwriters gives the following rules for the
+storage of carbide:
+
+Calcium carbide in quantities not to exceed six hundred pounds may be
+stored, when contained in approved metal packages not to exceed one hundred
+pounds each, inside insured property, provided that the place of storage be
+dry, waterproof and well ventilated and also provided that all but one of
+the packages in any one building shall be sealed and that seals shall not
+be broken so long as there is carbide in excess of one pound in any other
+unsealed package in the building.
+
+Calcium carbide in quantities in excess of six hundred pounds must be
+stored above ground in detached buildings, used exclusively for the storage
+of calcium carbide, in approved metal packages, and such buildings shall be
+constructed to be dry, waterproof and well ventilated.
+
+_Properties of Acetylene._--This gas is composed of twenty-four parts
+of carbon and two parts of hydrogen by weight and is classed with natural
+gas, petroleum, etc., as one of the hydrocarbons. This gas contains the
+highest percentage of carbon known to exist in any combination of this form
+and it may therefore be considered as gaseous carbon. Carbon is the fuel
+that is used in all forms of combustion and is present in all fuels from
+whatever source or in whatever form. Acetylene is therefore the most
+powerful of all fuel gases and is able to give to the torch flame in
+welding the highest temperature of any flame.
+
+Acetylene is a colorless and tasteless gas, possessed of a peculiar and
+penetrating odor. The least trace in the air of a room is easily noticed,
+and if this odor is detected about an apparatus in operation, it is certain
+to indicate a leakage of gas through faulty piping, open valves, broken
+hose or otherwise. This leakage must be prevented before proceeding with
+the work to be done.
+
+All gases which burn in air will, when mixed with air previous to ignition,
+produce more or less violent explosions, if fired. To this rule acetylene
+is no exception. One measure of acetylene and twelve and one-half of air
+are required for complete combustion; this is therefore the proportion for
+the most perfect explosion. This is not the only possible mixture that will
+explode, for all proportions from three to thirty per cent of acetylene in
+air will explode with more or less force if ignited.
+
+The igniting point of acetylene is lower than that of coal gas, being about
+900 degrees Fahrenheit as against eleven hundred degrees for coal gas. The
+gas issuing from a torch will ignite if allowed to play on the tip of a
+lighted cigar.
+
+It is still further true that acetylene, at some pressures, greater than
+normal, has under most favorable conditions for the effect, been found to
+explode; yet it may be stated with perfect confidence that under no
+circumstances has anyone ever secured an explosion in it when subjected to
+pressures not exceeding fifteen pounds to the square inch.
+
+Although not exploded by the application of high heat, acetylene is injured
+by such treatment. It is partly converted, by high heat, into other
+compounds, thus lessening the actual quantity of the gas, wasting it and
+polluting the rest by the introduction of substances which do not belong
+there. These compounds remain in part with the gas, causing it to burn with
+a persistent smoky flame and with the deposit of objectionable tarry
+substances. Where the gas is generated without undue rise of temperature
+these difficulties are avoided.
+
+_Purification of Acetylene._--Impurities in this gas are caused by
+impurities in the calcium carbide from which it is made or by improper
+methods and lack of care in generation. Impurities from the material will
+be considered first.
+
+Impurities in the carbide may be further divided into two classes: those
+which exert no action on water and those which act with the water to throw
+off other gaseous products which remain in the acetylene. Those impurities
+which exert no action on the water consist of coke that has not been
+changed in the furnace and sand and some other substances which are
+harmless except that they increase the ash left after the acetylene has
+been generated.
+
+An analysis of the gas coming from a typical generator is as follows:
+
+                                          Per cent
+  Acetylene ................................ 99.36
+  Oxygen ...................................   .08
+  Nitrogen .................................   .11
+  Hydrogen .................................   .06
+  Sulphuretted Hydrogen ....................   .17
+  Phosphoretted Hydrogen ...................   .04
+  Ammonia ..................................   .10
+  Silicon Hydride ..........................   .03
+  Carbon Monoxide ..........................   .01
+  Methane ..................................   .04
+
+The oxygen, nitrogen, hydrogen, methane and carbon monoxide are either
+harmless or are present in such small quantities as to be neglected. The
+phosphoretted hydrogen and silicon hydride are self-inflammable gases when
+exposed to the air, but their quantity is so very small that this
+possibility may be dismissed. The ammonia and sulphuretted hydrogen are
+almost entirely dissolved by the water used in the gas generator. The
+surest way to avoid impure gas is to use high-grade calcium carbide in the
+generator and the carbide of American manufacture is now so pure that it
+never causes trouble.
+
+The first and most important purification to which the gas is subjected is
+its passage through the body of water in the generator as it bubbles to the
+top. It is then filtered through felt to remove the solid particles of lime
+dust and other impurities which float in the gas.
+
+Further purification to remove the remaining ammonia, sulphuretted hydrogen
+and phosphorus containing compounds is accomplished by chemical means. If
+this is considered necessary it can be easily accomplished by readily
+available purifying apparatus which can be attached to any generator or
+inserted between the generator and torch outlets. The following mixtures
+have been used.
+
+"_Heratol,_" a solution of chromic acid or sulphuric acid absorbed in
+porous earth.
+
+"_Acagine,_" a mixture of bleaching powder with fifteen per cent of
+lead chromate.
+
+"_Puratylene,_" a mixture of bleaching powder and hydroxide of lime,
+made very porous, and containing from eighteen to twenty per cent of active
+chlorine.
+
+"_Frankoline,_" a mixture of cuprous and ferric chlorides dissolved in
+strong hydrochloric acid absorbed in infusorial earth.
+
+A test for impure acetylene gas is made by placing a drop of ten per cent
+solution of silver nitrate on a white blotter and holding the paper in a
+stream of gas coming from the torch tip. Blackening of the paper in a short
+length of time indicates impurities.
+
+_Acetylene in Tanks._--Acetylene is soluble in water to a very limited
+extent, too limited to be of practical use. There is only one liquid that
+possesses sufficient power of containing acetylene in solution to be of
+commercial value, this being the liquid acetone. Acetone is produced in
+various ways, oftentimes from the distillation of wood. It is a
+transparent, colorless liquid that flows with ease. It boils at 133°
+Fahrenheit, is inflammable and burns with a luminous flame. It has a
+peculiar but rather agreeable odor.
+
+Acetone dissolves twenty-four times its own bulk of acetylene at ordinary
+atmospheric pressure. If this pressure is increased to two atmospheres,
+14.7 pounds above ordinary pressure, it will dissolve just twice as much of
+the gas and for each atmosphere that the pressure is increased it will
+dissolve as much more.
+
+If acetylene be compressed above fifteen pounds per square inch at ordinary
+temperature without first being dissolved in acetone a danger is present of
+self-ignition. This danger, while practically nothing at fifteen pounds,
+increases with the pressure until at forty atmospheres it is very
+explosive. Mixed with acetone, the gas loses this dangerous property and is
+safe for handling and transportation. As acetylene is dissolved in the
+liquid the acetone increases its volume slightly so that when the gas has
+been drawn out of a closed tank a space is left full of free acetylene.
+
+This last difficulty is removed by first filling the cylinder or tank with
+some porous material, such as asbestos, wood charcoal, infusorial earth,
+etc. Asbestos is used in practice and by a system of packing and supporting
+the absorbent material no space is left for the free gas, even when the
+acetylene has been completely withdrawn.
+
+The acetylene is generated in the usual way and is washed, purified and
+dried. Great care is used to make the gas as free as possible from all
+impurities and from air. The gas is forced into containers filled with
+acetone as described and is compressed to one hundred and fifty pounds to
+the square inch. From these tanks it is transferred to the smaller portable
+cylinders for consumers' use.
+
+The exact volume of gas remaining in a cylinder at atmospheric temperature
+may be calculated if the weight of the cylinder empty is known. One pound
+of the gas occupies 13.6 cubic feet, so that if the difference in weight
+between the empty cylinder and the one considered be multiplied by 13.6.
+the result will be the number of cubic feet of gas contained.
+
+The cylinders contain from 100 to 500 cubic feet of acetylene under
+pressure. They cannot be filled with the ordinary type of generator as they
+require special purifying and compressing apparatus, which should never be
+installed in any building where other work is being carried on, or near
+other buildings which are occupied, because of the danger of explosion.
+
+Dissolved acetylene is manufactured by the Prest-O-Lite Company, the
+Commercial Acetylene Company and the Searchlight Gas Company and is
+distributed from warehouses in various cities.
+
+These tanks should not be discharged at a rate per hour greater than
+one-seventh of their total capacity, that is, from a tank of 100 cubic feet
+capacity, the discharge should not be more than fourteen cubic feet per
+hour. If discharge is carried on at an excessive rate the acetone is drawn
+out with the gas and reduces the heat of the welding flame.
+
+For this reason welding should not be attempted with cylinders designed for
+automobile and boat lighting. When the work demands a greater delivery than
+one of the larger tanks will give, two or more tanks may be connected with
+a special coupler such as may be secured from the makers and distributers
+of the gas. These couplers may be arranged for two, three, four or five
+tanks in one battery by removing the plugs on the body of the coupler and
+attaching additional connecting pipes. The coupler body carries a pressure
+gauge and the valve for controlling the pressure of the gas as it flows to
+the welding torches. The following capacities should be provided for:
+
+Acetylene Consumption         Combined Capacity of
+ of Torches per Hour           Cylinders in Use
+Up to 15 feet.......................100 cubic feet
+16 to 30 feet.......................200 cubic feet
+31 to 45 feet.......................300 cubic feet
+46 to 60 feet.......................400 cubic feet
+61 to 75 feet.......................500 cubic feet
+
+
+WELDING RODS
+
+The best welding cannot be done without using the best grade of materials,
+and the added cost of these materials over less desirable forms is so
+slight when compared to the quality of work performed and the waste of
+gases with inferior supplies, that it is very unprofitable to take any
+chances in this respect. The makers of welding equipment carry an
+assortment of supplies that have been standardized and that may be relied
+upon to produce the desired result when properly used. The safest plan is
+to secure this class of material from the makers.
+
+Welding rods, or welding sticks, are used to supply the additional metal
+required in the body of the weld to replace that broken or cut away and
+also to add to the joint whenever possible so that the work may have the
+same or greater strength than that found in the original piece. A rod of
+the same material as that being welded is used when both parts of the work
+are the same. When dissimilar metals are to be joined rods of a composition
+suited to the work are employed.
+
+These filling rods are required in all work except steel of less than 16
+gauge. Alloy iron rods are used for cast iron. These rods have a high
+silicon content, the silicon reacting with the carbon in the iron to
+produce a softer and more easily machined weld than would otherwise be the
+case. These rods are often made so that they melt at a slightly lower point
+than cast iron. This is done for the reason that when the part being welded
+has been brought to the fusing heat by the torch, the filling material can
+be instantly melted in without allowing the parts to cool. The metal can be
+added faster and more easily controlled.
+
+Rods or wires of Norway iron are used for steel welding in almost all
+cases. The purity of this grade of iron gives a homogeneous, soft weld of
+even texture, great ductility and exceptionally good machining qualities.
+For welding heavy steel castings, a rod of rolled carbon steel is employed.
+For working on high carbon steel, a rod of the steel being welded must be
+employed and for alloy steels, such as nickel, manganese, vanadium, etc.,
+special rods of suitable alloy composition are preferable.
+
+Aluminum welding rods are made from this metal alloyed to give the even
+flowing that is essential. Aluminum is one of the most difficult of all the
+metals to handle in this work and the selection of the proper rod is of
+great importance.
+
+Brass is filled with brass wire when in small castings and sheets. For
+general work with brass castings, manganese bronze or Tobin bronze may be
+used.
+
+Bronze is welded with manganese bronze or Tobin bronze, while copper is
+filled with copper wire.
+
+These welding rods should always be used to fill the weld when the
+thickness of material makes their employment necessary, and additional
+metal should always be added at the weld when possible as the joint cannot
+have the same strength as the original piece if made or dressed off flush
+with the surfaces around the weld. This is true because the metal welded
+into the joint is a casting and will never have more strength than a
+casting of the material used for filling.
+
+Great care should be exercised when adding metal from welding rods to make
+sure that no metal is added at a point that is not itself melted and molten
+when the addition is made. When molten metal is placed upon cooler surfaces
+the result is not a weld but merely a sticking together of the two parts
+without any strength in the joint.
+
+
+FLUXES
+
+Difficulty would be experienced in welding with only the metal and rod to
+work with because of the scale that forms on many materials under heat, the
+oxides of other metals and the impurities found in almost all metals. These
+things tend to prevent a perfect joining of the metals and some means are
+necessary to prevent their action.
+
+Various chemicals, usually in powder form, are used to accomplish the
+result of cleaning the weld and making the work of the operator less
+difficult. They are called fluxes.
+
+A flux is used to float off physical impurities from the molten metal; to
+furnish a protecting coating around the weld; to assist in the removal of
+any objectionable oxide of the metals being handled; to lower the
+temperature at which the materials flow; to make a cleaner weld and to
+produce a better quality of metal in the finished work.
+
+The flux must be of such composition that it will accomplish the desired
+result without introducing new difficulties. They may be prepared by the
+operator in many cases or may be secured from the makers of welding
+apparatus, the same remarks applying to their quality as were made
+regarding the welding rods, that is, only the best should be considered.
+
+The flux used for cast iron should have a softening effect and should
+prevent burning of the metal. In many cases it is possible and even
+preferable to weld cast iron without the use of a flux, and in any event
+the smaller the quantity used the better the result should be. Flux should
+not be added just before the completion of the work because the heat will
+not have time to drive the added elements out of the metal or to
+incorporate them with the metal properly.
+
+Aluminum should never be welded without using a flux because of the oxide
+formed. This oxide, called alumina, does not melt until a heat of 5,000°
+Fahrenheit is reached, four times the heat needed to melt the aluminum
+itself. It is necessary that this oxide be broken down or dissolved so that
+the aluminum may have a chance to flow together. Copper is another metal
+that requires a flux because of its rapid oxidation under heat.
+
+While the flux is often thrown or sprinkled along the break while welding,
+much better results will be obtained by dipping the hot end of the welding
+rod into the flux whenever the work needs it. Sufficient powder will stick
+on the end of the rod for all purposes, and with some fluxes too much will
+adhere. Care should always be used to avoid the application of excessive
+flux, as this is usually worse than using too little.
+
+
+SUPPLIES AND FIXTURES
+
+_Goggles._--The oxy-acetylene torch should not be used without the
+protection to the eyes afforded by goggles. These not only relieve
+unnecessary strain, but make it much easier to watch the exact progress of
+the work with the molten metal. The difficulty of protecting the sight
+while welding is even greater than when cutting metal with the torch.
+
+Acetylene gives a light which is nearest to sunlight of any artificial
+illuminant. But for the fact that this gas light gives a little more green
+and less blue in its composition, it would be the same in quality and
+practically the same in intensity. This light from the gas is almost absent
+during welding, being lost with the addition of the extra oxygen needed to
+produce the welding heat. The light that is dangerous comes from the molten
+metal which flows under the torch at a bright white heat.
+
+Goggles for protection against this light and the heat that goes with it
+may be secured in various tints, the darker glass being for welding and
+the lighter for cutting. Those having frames in which the metal parts do
+not touch the flesh directly are most desirable because of the high
+temperature reached by these parts.
+
+_Gloves._--While not as necessary as are the goggles, gloves are a
+convenience in many cases. Those in which leather touches the hands
+directly are really of little value as the heat that protection is desired
+against makes the leather so hot that nothing is gained in comfort. Gloves
+are made with asbestos cloth, which are not open to this objection in so
+great a degree.
+
+[Illustration: Figure 9.--Frame for Welding Stand]
+
+_Tables and Stands._--Tables for holding work while being welded
+(Figure 9) are usually made from lengths of angle steel welded together.
+The top should be rectangular, about two feet wide and two and one-half
+feet long. The legs should support the working surface at a height of
+thirty-two to thirty-six inches from the floor. Metal lattice work may be
+fastened or laid in the top framework and used to support a layer of
+firebrick bound together with a mixture of one-third cement and two-thirds
+fireclay. The piece being welded is braced and supported on this table with
+pieces of firebrick so that it will remain stationary during the operation.
+
+Holders for supporting the tanks of gas may be
+made or purchased in forms that rest directly on the floor or that are
+mounted on wheels. These holders are quite useful where the floor or ground
+is very uneven.
+
+_Hose._--All permanent lines from tanks and generators to the torches
+are made with piping rigidly supported, but the short distance from the end
+of the pipe line to the torch itself is completed with a flexible hose so
+that the operator may be free in his movements while welding. An accident
+through which the gases mix in the hose and are ignited will burst this
+part of the equipment, with more or less painful results to the person
+handling it. For that reason it is well to use hose with great enough
+strength to withstand excessive pressure.
+
+A poor grade of hose will also break down inside and clog the flow of gas,
+both through itself and through the parts of the torch. To avoid outside
+damage and cuts this hose is sometimes encased with coiled sheet metal.
+Hose may be secured with a bursting strength of more than 1,000 pounds to
+the square inch. Many operators prefer to distinguish between the oxygen
+and acetylene lines by their color and to allow this, red is used for the
+oxygen and black for acetylene.
+
+_Other Materials._--Sheet asbestos and asbestos fibre in flakes are
+used to cover parts of the work while preparing them for welding and during
+the operation itself. The flakes and small pieces that become detached from
+the large sheets are thrown into a bin where the completed small work is
+placed to allow slow and even cooling while protected by the asbestos.
+
+Asbestos fibre and also ordinary fireclay are often used to make a backing
+or mould into a form that may be placed behind aluminum and some other
+metals that flow at a low heat and which are accordingly difficult to
+handle under ordinary methods. This forms a solid mould into which the
+metal is practically cast as melted by the torch so that the desired shape
+is secured without danger of the walls of metal breaking through and
+flowing away.
+
+Carbon blocks and rods are made in various shapes and sizes so that they
+may be used to fill threaded holes and other places that it is desired to
+protect during welding. These may be secured in rods of various diameters
+up to one inch and in blocks of several different dimensions.
+
+
+
+
+CHAPTER III
+
+ACETYLENE GENERATORS
+
+
+Acetylene generators used for producing the gas from the action of water on
+calcium carbide are divided into three principal classes according to the
+pressure under which they operate.
+
+Low pressure generators are designed to operate at one pound or less per
+square inch. Medium pressure systems deliver the gas at not to exceed
+fifteen pounds to the square inch while high pressure types furnish gas
+above fifteen pounds per square inch. High pressure systems are almost
+unknown in this country, the medium pressure type being often referred to
+as "high pressure."
+
+Another important distinction is formed by the method of bringing the
+carbide and water together. The majority of those now in use operate by
+dropping small quantities of carbide into a large volume of water, allowing
+the generated gas to bubble up through the water before being collected
+above the surface. This type is known as the "carbide to water" generator.
+
+A less used type brings a measured and small quantity of water to a
+comparatively large body of the carbide, the gas being formed and collected
+from the chamber in which the action takes place. This is called the "water
+to carbide" type. Another way of expressing the difference in feed is that
+of designating the two types as "carbide feed" for the former and "water
+feed" for the latter.
+
+A further division of the carbide to water machines is made by mentioning
+the exact method of feeding the carbide. One type, called "gravity feed"
+operates by allowing the carbide to escape and fall by the action of its
+own weight, or gravity; the other type, called "forced feed," includes a
+separate mechanism driven by power. This mechanism feeds definite amounts
+of the carbide to the water as required by the demands on the generator.
+The action of either feed is controlled by the withdrawal of gas from the
+generator, the aim being to supply sufficient carbide to maintain a nearly
+constant supply.
+
+_Generator Requirements._--The qualities of a good generator are
+outlined as follows: [Footnote: See Pond's "Calcium Carbide and
+Acetylene."]
+
+It must allow no possibility of the existence of an explosive mixture in
+any of its parts at any time. It is not enough to argue that a mixture,
+even if it exists, cannot be exploded unless kindled. It is necessary to
+demand that a dangerous mixture can at no time be formed, even if the
+machine is tampered with by an ignorant person. The perfect machine must be
+so constructed that it shall be impossible at any time, under any
+circumstances, to blow it up.
+
+It must insure cool generation. Since this is a relative term, all machines
+being heated somewhat during the generation of gas, this amounts to saying
+that a machine must heat but little. A pound of carbide decomposed by water
+develops the same amount of heat under all circumstances, but that heat
+can be allowed to increase locally to a high point, or it can be equalized
+by water so that no part of the material becomes heated enough to do
+damage.
+
+It must be well constructed. A good generator does not need, perhaps, to be
+"built like a watch," but it should be solid, substantial and of good
+material. It should be built for service, to last and not simply to sell;
+anything short of this is to be avoided as unsafe and unreliable.
+
+It must be simple. The more complicated the machine the sooner it will get
+out of order. Understand your generator. Know what is inside of it and
+beware of an apparatus, however attractive its exterior, whose interior is
+filled with pipes and tubes, valves and diaphragms whose functions you do
+not perfectly understand.
+
+It should be capable of being cleaned and recharged and of receiving all
+other necessary attention without loss of gas, both for economy's sake, and
+more particularly to avoid danger of fire.
+
+It should require little attention. All machines have to be emptied and
+recharged periodically; but the more this process is simplified and the
+more quickly this can be accomplished, the better.
+
+It should be provided with a suitable indicator to designate how low the
+charge is in order that the refilling may be done in good season.
+
+It should completely use up the carbide, generating the maximum amount of
+gas.
+
+_Overheating._--A large amount of heat is liberated when acetylene gas
+is formed from the union of calcium carbide and water. Overheating during
+this process, that is to say, an intense local heat rather than a large
+amount of heat well distributed, brings about the phenomenon of
+polymerization, converting the gas, or part of it, into oily matters, which
+can do nothing but harm. This tarry mass coming through the small openings
+in the torches causes them to become partly closed and alters the
+proportions of the gases to the detriment of the welding flame. The only
+remedy for this trouble is to avoid its cause and secure cool generation.
+
+Overheating can be detected by the appearance of the sludge remaining after
+the gas has been made. Discoloration, yellow or brown, shows that there has
+been trouble in this direction and the resultant effects at the torches may
+be looked for. The abundance of water in the carbide to water machines
+effects this cooling naturally and is a characteristic of well designed
+machines of this class. It has been found best and has practically become a
+fundamental rule of generation that a gallon of water must be provided for
+each pound of carbide placed in the generator. With this ratio and a
+generator large enough for the number of torches to be supplied, little
+trouble need be looked for with overheating.
+
+_Water to Carbide Generators._--It is, of course, much easier to
+obtain a measured and regular flow of water than to obtain such a flow of
+any solid substance, especially when the solid substance is in the form of
+lumps, as is carbide This fact led to the use of a great many water-feed
+generators for all classes of work, and this type is still in common use
+for the small portable machines, such, for instance, as those used on motor
+cars for the lamps. The water-feed machine is not, however, favored for
+welding plants, as is the carbide feed, in spite of the greater
+difficulties attending the handling of the solid material.
+
+A water-feed generator is made up of the gas producing part and a holder
+for the acetylene after it is made. The carbide is held in a tray formed of
+a number of small compartments so that the charge in each compartment is
+nearly equal to that in each of the others. The water is allowed to flow
+into one of these compartments in a volume sufficient to produce the
+desired amount of gas and the carbide is completely used from this one
+division. The water then floods the first compartment and finally overflows
+into the next one, where the same process is repeated. After using the
+carbide in this division, it is flooded in turn and the water passing on to
+those next in order, uses the entire charge of the whole tray.
+
+These generators are charged with the larger sizes of carbide and are
+easily taken care of. The residue is removed in the tray and emptied,
+making the generator ready for a fresh supply of carbide.
+
+_Carbide to Water Generators._--This type also is made up of two
+principal parts, the generating chamber and a gas holder, the holder being
+part of the generating chamber or a separate device. The generator (Figure
+10) contains a hopper to receive the charge of carbide and is fitted with
+the feeding mechanism to drop the proper amount of carbide into the water
+as required by the demands of the torches. The charge of carbide is of one
+of the smaller sizes, usually "nut" or "quarter."
+
+_Feed Mechanisms._--The device for dropping the carbide into the water
+is the only part of the machine that is at all complicated. This
+complication is brought about by the necessity of controlling the mass of
+carbide so that it can never be discharged into the water at an excessive
+rate, feeding it at a regular rate and in definite amounts, feeding it
+positively whenever required and shutting off the feed just as positively
+when the supply of gas in the holder is enough for the immediate needs.
+
+[Illustration: Figure 10.--Carbide to Water Generator. A. Feed motor weight;
+B. Carbide feed motor; C. Carbide hopper; D. Water for gas generation;
+E. Agitator for loosening residuum; F. Water seal in gas bell; G. Filter;
+H. Hydraulic Valve; J. Motor control levers.]
+
+The charge of carbide is unavoidably acted upon by the water vapor in the
+generator and will in time become more or less pasty and sticky. This is
+more noticeable if the generator stands idle for a considerable length of
+time This condition imposes another duty on the feeding mechanism; that is,
+the necessity of self-cleaning so that the carbide, no matter in what
+condition, cannot prevent the positive action of this part of the device,
+especially so that it cannot prevent the supply from being stopped at the
+proper time.
+
+The gas holder is usually made in the bell form so that the upper portion
+rises and falls with the addition to or withdrawal from the supply of gas
+in the holder. The rise and fall of this bell is often used to control the
+feed mechanism because this movement indicates positively whether enough
+gas has been made or that more is required. As the bell lowers it sets the
+feed mechanism in motion, and when the gas passing into the holder has
+raised the bell a sufficient distance, the movement causes the feed
+mechanism to stop the fall of carbide into the water. In practice, the
+movement of this part of the holder is held within very narrow limits.
+
+_Gas Holders._--No matter how close the adjustment of the feeding
+device, there will always be a slight amount of gas made after the fall of
+carbide is stopped, this being caused by the evolution of gas from the
+carbide with which water is already in contact. This action is called
+"after generation" and the gas holder in any type of generator must
+provide sufficient capacity to accommodate this excess gas. As a general
+rule the water to carbide generator requires a larger gas holder than the
+carbide to water type because of the greater amount of carbide being acted
+upon by the water at any one time, also because the surface of carbide
+presented to the moist air within the generating chamber is greater with
+this type.
+
+_Freezing._--Because of the rather large body of water contained in
+any type of generator, there is always danger of its freezing and
+rendering the device inoperative unless placed in a temperature above the
+freezing point of the water. It is, of course, dangerous and against the
+insurance rules to place a generator in the same room with a fire of any
+kind, but the room may be heated by steam or hot water coils from a furnace
+in another building or in another part of the same building.
+
+When the generator is housed in a separate structure the walls should be
+made of materials or construction that prevents the passage of heat or
+cold through them to any great extent. This may be accomplished by the use
+of hollow tile or concrete blocks or by any other form of double wall
+providing air spaces between the outer and inner facings. The space between
+the parts of the wall may be filled with materials that further retard the
+loss of heat if this is necessary under the conditions prevailing.
+
+_Residue From Generators._--The sludge remaining in the carbide to
+water generator may be drawn off into the sewer if the piping is run at a
+slant great enough to give a fall that carries the whole quantity, both
+water and ash, away without allowing settling and consequent clogging.
+Generators are provided with agitators which are operated to stir the ash
+up with the water so that the whole mass is carried off when the drain cock
+is opened.
+
+If sewer connections cannot be made in such a way that the ash is entirely
+carried away, it is best to run the liquid mass into a settling basin
+outside of the building. This should be in the form of a shallow pit which
+will allow the water to pass off by soaking into the ground and by
+evaporation, leaving the comparatively dry ash in the pit. This ash which
+remains is essentially slaked lime and can often be disposed of to more or
+less advantage to be used in mortar, whitewash, marking paths and any other
+use for which slaked lime is suited. The disposition of the ash depends
+entirely on local conditions. An average analysis of this ash is as
+follows:
+
+Sand.......................  1.10 per cent.
+Carbon.....................  2.72    "
+Oxide of iron and alumina..  2.77    "
+Lime....................... 64.06    "
+Water and carbonic acid.... 29.35    "
+                           ------
+                           100.00
+
+
+GENERATOR CONSTRUCTION
+
+The water for generating purposes is carried in the large tank-like
+compartment directly below the carbide chamber. See Figure 11. This water
+compartment is filled through a pipe of such a height that the water level
+cannot be brought above the proper point or else the water compartment is
+provided with a drain connection which accomplishes this same result by
+allowing an excess to flow away.
+
+The quantity of water depends on the capacity of the generator inasmuch as
+there must be one gallon for each pound of carbide required. The generator
+should be of sufficient capacity to furnish gas under working conditions
+from one charge of carbide to all torches installed for at least five hours
+continuous use.
+
+After calculating the withdrawal of the whole number of torches according
+to the work they are to do for this period of five hours the proper
+generator capacity may be found on the basis of one cubic foot of gas per
+hour for each pound of carbide. Thus if the torches were to use sixty cubic
+feet of gas per hour, five hours would call for three hundred cubic feet
+and a three hundred pound generator should be installed. Generators are
+rated according to their carbide capacity in pounds.
+
+_Charging._--The carbide capacity of the generator should be great
+enough to furnish a continuous supply of gas for the maximum operating
+time, basing the quantity of gas generated on four and one-half cubic feet
+from each pound of lump carbide and on four cubic feet from each pound of
+quarter, intermediate sizes being in proportion.
+
+Generators are built in such a way that it is impossible for the acetylene
+to escape from the gas holding compartment during the recharging process.
+This is accomplished (1) by connecting the water inlet pipe opening with a
+shut off valve in such a way that the inlet cannot be uncovered or opened
+without first closing the shut off valve with the same movement of the
+operator; (2) by incorporating an automatic or hydraulic one-way valve so
+that this valve closes and acts as a check when the gas attempts to flow
+from the holder back to the generating chamber, or by any other means that
+will positively accomplish this result.
+
+In generators having no separate gas holding chamber but carrying the
+supply in the same compartment in which it is generated, the gas contained
+under pressure is allowed to escape through vent pipes into the outside
+air before recharging with carbide. As in the former case, the parts are
+so interlocked that it is impossible to introduce carbide or water without
+first allowing the escape of the gas in the generator.
+
+It is required by the insurance rules that the entire change of carbide
+while in the generator be held in such a way that it may be entirely
+removed without difficulty in case the necessity should arise.
+
+Generators should be cleaned and recharged at regular stated intervals.
+This work should be done during daylight hours only and likewise all
+repairs should be made at such a time that artificial light is not needed.
+Where it is absolutely necessary to use artificial light it should be
+provided only by incandescent electric lamps enclosed in gas tight globes.
+
+In charging generating chambers the old ash and all residue must first be
+cleaned out and the operator should be sure that no drain or other pipe has
+become clogged. The generator should then be filled with the required
+amount of water. In charging carbide feed machines be careful not to place
+less than a gallon of water in the water compartment for each pound of
+carbide to be used and the water must be brought to, but not above, the
+proper level as indicated by the mark or the maker's instructions. The
+generating chamber must be filled with the proper amount of water before
+any attempt is made to place the carbide in its holder. This rule must
+always be followed. It is also necessary that all automatic water seals
+and valves, as well as any other water tanks, be filled with clean water
+at this time.
+
+Never recharge with carbide without first cleaning the generating chamber
+and completely refilling with clean water. Never test the generator or
+piping for leaks with any flame, and never apply flame to any open pipe or
+at any point other than the torch, and only to the torch after it has a
+welding or cutting nozzle attached. Never use a lighted match, lamp,
+candle, lantern, cigar or any open flame near a generator. Failure to
+observe these precautions is liable to endanger life and property.
+
+_Operation and Care of Generators._--The following instructions apply
+especially to the Davis Bournonville pressure generator, illustrated in
+Figure 11. The motor feed mechanism is illustrated in Figure 12.
+
+Before filling the machine, the cover should be removed and the hopper
+taken out and examined to see that the feeding disc revolves freely; that
+no chains have been displaced or broken, and that the carbide displacer
+itself hangs barely free of the feeding disc when it is revolved. After
+replacing the cover, replace the bolts and tighten them equally, a little
+at a time all around the circumference of the cover--not screwing tight in
+one place only. Do not screw the cover down any more than is necessary to
+make a tight fit.
+
+To charge the generator, proceed as follows: Open the vent valve by turning
+the handle which extends over the filling tube until it stands at a right
+angle with the generator. Open the valve in the water filling pipe, and
+through this fill with water until it runs out of the overflow pipe of the
+drainage chamber, then close the valve in the water filling pipe and vent
+valve. Remove the carbide filling plugs and fill the hopper with
+1-1/4"x3/8" carbide ("nut" size). Then replace the plugs and the
+safety-locking lever chains. Now rewind the motor weight. Run the pressure
+up to about five pounds by raising the controlling diaphragm valve lever
+by hand (Figure 12, lever marked _E_). Then raise the blow-off lever,
+allowing the gas to blow off until the gauge shows about two pounds; this
+to clear the generator of air mixture. Then run the pressure up to about
+eight pounds by raising the controlling valve lever _E_, or until
+this controlling lever rests against the upper wing of the fan governor,
+and prevents operation of the feed motor. After this is done, the motor
+will operate automatically as the gas is consumed.
+
+[Illustration: Figure 11.--Pressure Generator (Davis Bournonville).
+_A_, Feed motor weight;
+_B_, Carbide feed motor;
+_C_, Motor Control diaphragm;
+_D_, Carbide hopper;
+_E_, Carbide feed disc;
+_F_, Overflow pipe;
+_G_, Overflow pipe seal;
+_H_, Overflow pipe valve;
+_J_, Filling funnel;
+_K_, Hydraulic valve;
+_L_, Expansion chamber;
+_M_, Escape pipe;
+_N_, Feed pipe;
+_O_, Agitator for residuum;
+_P_, Residuum valve;
+_Q_, Water level]
+
+[Illustration: Figure 12.--Feed Mechanism of Pressure Generator]
+
+Should the pressure rise much above the blow-off point, the safety
+controlling diaphragm valve will operate and throw the safety clutch in
+interference and thus stop the motor. This interference clutch will then
+have to be returned to its former position before the motor will operate,
+but cannot be replaced before the pressure has been reduced below the
+blow-off point.
+
+The parts of the feed mechanism illustrated in Figure 12 are as follows:
+_A_, motor drum for weight cable. _B_, carbide filling plugs.
+_C_, chains for connecting safety locking lever of motor to pins on
+the top of the carbide plugs. _D_, interference clutch of motor.
+_E_, lever on feed controlling diaphragm valve. _F_, lever of
+interference controlling diaphragm valve that operates interference clutch.
+_G_, feed controlling diaphragm valve. _H_, diaphragm valve
+controlling operation of interference clutch. _I_, interference pin
+to engage emergency clutch. _J_, main shaft driving carbide feeding
+disc. _Y_, safety locking lever.
+
+_Recharging Generator._--Turn the agitator handle rapidly for several
+revolutions, and then open the residuum valve, having five or six pounds
+gas pressure on the machine. If the carbide charge has been exhausted and
+the motor has stopped, there is generally enough carbide remaining in the
+feeding disc that can be shaken off, and fed by running the motor to
+obtain some pressure in the generator. The desirability of discharging
+the residuum with some gas pressure is because the pressure facilitates
+the discharge and at the same time keeps the generator full of gas,
+preventing air mixture to a great extent. As soon as the pressure is
+relieved by the withdrawal of the residuum, the vent valve should be
+opened, as if the pressure is maintained until all of the residuum is
+discharged gas would escape through the discharge valve.
+
+Having opened the vent pipe valve and relieved the pressure, open the
+valve in the water filling tube. Close the residuum valve, then run in
+several gallons of water and revolve the agitator, after which draw out the
+remaining residuum; then again close the residuum valve and pour in water
+until it discharges from the overflow pipe of the drainage chamber. It is
+desirable in filling the generator to pour the water in rapidly enough to
+keep the filling pipe full of water, so that air will not pass in at the
+same time.
+
+After the generator is cleaned and filled with water, fill with carbide and
+proceed in the same manner as when first charging.
+
+_Carbide Feed Mechanism._--Any form of carbide to water machine should
+be so designed that the carbide never falls directly from its holder into
+the water, but so that it must take a more or less circuitous path. This
+should be true, no matter what position the mechanism is in. One of the
+commonest types of forced feed machine carries the carbide in a hopper with
+slanting sides, this hopper having a large opening in the bottom through
+which the carbide passes to a revolving circular plate. As the pieces of
+carbide work out toward the edge of the plate under the influence of the
+mass behind them, they are thrown off into the water by small stationary
+fins or plows which are in such a position that they catch the pieces
+nearest the edges and force them off as the plate revolves. This
+arrangement, while allowing a free passage for the carbide, prevents an
+excess from falling should the machine stop in any position.
+
+When, as is usually the case, the feed mechanism is actuated by the rise
+or fall of pressure in the generator or of the level of some part of the
+gas holder, it must be built in such a way that the feeding remains
+inoperative as long as the filling opening on the carbide holder remains
+open.
+
+The feed of carbide should always be shut off and controlled so that under
+no condition can more gas be generated than could be cared for by the
+relief valve provided. It is necessary also to have the feed mechanism at
+least ten inches above the surface of the water so that the parts will
+never become clogged with damp lime dust.
+
+_Motor Feed._--The feed mechanism itself is usually operated by power
+secured from a slowly falling weight which, through a cable, revolves a
+drum. To this drum is attached suitable gearing for moving the feed parts
+with sufficient power and in the way desired. This part, called the motor,
+is controlled by two levers, one releasing a brake and allowing the motor
+to operate the feed, the other locking the gearing so that no more carbide
+will be dropped into the water. These levers are moved either by the
+quantity of gas in the holder or by the pressure of the gas, depending on
+the type of machine.
+
+With a separate gas holder, such as used with low pressure systems, the
+levers are operated by the rise and fall of the bell of the holder or
+gasometer, alternately starting and stopping the motor as the bell falls
+and rises again. Medium pressure generators are provided with a diaphragm
+to control the feed motor.
+
+This diaphragm is carried so that the pressure within the generator acts
+on one side while a spring, whose tension is under the control of the
+operator, acts on the other side. The diaphragm is connected to the brake
+and locking device on the motor in such a way that increasing the tension
+on the spring presses the diaphragm and moves a rod that releases the brake
+and starts the feed. The gas pressure, increasing with the continuation of
+carbide feed, acts on the other side and finally overcomes the pressure of
+the spring tension, moving the control rod the other way and stopping the
+motor and carbide feed. This spring tension is adjusted and checked with
+the help of a pressure gauge attached to the generating chamber.
+
+_Gravity Feed._--This type of feed differs from the foregoing in that
+the carbide is simply released and is allowed to fall into the water
+without being forced to do so. Any form of valve that is sufficiently
+powerful in action to close with the carbide passing through is used and is
+operated by the power secured from the rise and fall of the gas holder
+bell. When this valve is first opened the carbide runs into the water until
+sufficient pressure and volume of gas is generated to raise the bell. This
+movement operates the arm attached to the carbide shut off valve and slowly
+closes it. A fall of the bell occasioned by gas being withdrawn again opens
+the valve and more gas is generated.
+
+_Mechanical Feed._--The previously described methods of feeding
+carbide to the water have all been automatic in action and do not depend
+on the operator for their proper action.
+
+Some types of large generating plants have a power-driven feed, the power
+usually being from some kind of motor other than one operated by a weight,
+such as a water motor, for instance. This motor is started and stopped by
+the operator when, in his judgment, more gas is wanted or enough has been
+generated. This type of machine, often called a "non-automatic generator,"
+is suitable for large installations and is attached to a gas holder of
+sufficient size to hold a day's supply of acetylene. The generator can then
+be operated until a quantity of gas has been made that will fill the large
+holder, or gasometer, and then allowed to remain idle for some time.
+
+_Gas Holders._--The commonest type of gas container is that known as a
+gasometer. This consists of a circular tank partly filled with water, into
+which is lowered another circular tank, inverted, which is made enough
+smaller in diameter than the first one so that three-quarters of an inch is
+left between them. This upper and inverted portion, called the bell,
+receives the gas from the generator and rises or falls in the bath of water
+provided in the lower tank as a greater or less amount of gas is contained
+in it.
+
+These holders are made large enough so that they will provide a means of
+caring for any after generation and so that they maintain a steady and even
+flow. The generator, however, must be of a capacity great enough so that
+the gas holder will not be drawn on for part of the supply with all torches
+in operation. That is, the holder must not be depended on for a reserve
+supply.
+
+The bell of the holder is made so that when full of gas its lower edge is
+still under a depth of at least nine inches of water in the lower tank. Any
+further rise beyond this point should always release the gas, or at least
+part of it, to the escape pipe so that the gas will under no circumstances
+be forced into the room from, between the bell and tank. The bell is guided
+in its rise and fall by vertical rods so that it will not wedge at any
+point in its travel.
+
+A condensing chamber to receive the water which condenses from the
+acetylene gas in the holder is usually placed under this part and is
+provided with a drain so that this water of condensation may be easily
+removed.
+
+_Filtering._--A small chamber containing some closely packed but
+porous material such as felt is placed in the pipe leading to the torch
+lines. As the acetylene gas passes through this filter the particles of
+lime dust and other impurities are extracted from it so that danger of
+clogging the torch openings is avoided as much as possible.
+
+The gas is also filtered to a large extent by its passage through the water
+in the generating chamber, this filtering or "scrubbing" often being
+facilitated by the form of piping through which the gas must pass from the
+generating chamber into the holder. If the gas passes out of a number of
+small openings when going into the holder the small bubbles give a better
+washing than large ones would.
+
+_Piping._--Connections from generators to service pipes should
+preferably be made with right and left couplings or long thread nipples
+with lock nuts. If unions are used, they should be of a type that does not
+require gaskets. The piping should be carried and supported so that any
+moisture condensing in the lines will drain back toward the generator and
+where low points occur they should be drained through tees leading into
+drip cups which are permanently closed with screw caps or plugs. No pet
+cocks should be used for this purpose.
+
+For the feed pipes to the torch lines the following pipe sizes are
+recommended.
+
+    3/8 inch pipe.  26 feet long.   2 cubic feet per hour.
+    1/2 inch pipe.  30 feet long.   4 cubic feet per hour.
+    3/4 inch pipe.  50 feet long.  15 cubic feet per hour.
+  1     inch pipe.  70 feet long.  27 cubic feet per hour.
+  1-1/4 inch pipe. 100 feet long.  50 cubic feet per hour.
+  1-1/2 inch pipe. 150 feet long.  65 cubic feet per hour.
+  2     inch pipe. 200 feet long. 125 cubic feet per hour.
+  2-1/2 inch pipe. 300 feet long. 190 cubic feet per hour.
+  3     inch pipe. 450 feet long. 335 cubic feet per hour.
+
+When drainage is possible into a sewer, the generator should not be
+connected directly into the sewer but should first discharge into an open
+receptacle, which may in turn be connected to the sewer.
+
+No valves or pet cocks should open into the generator room or any other
+room when it would be possible, by opening them for draining purposes, to
+allow any escape of gas. Any condensation must be removed without the use
+of valves or other working parts, being drained into closed receptacles. It
+should be needless to say that all the piping for gas must be perfectly
+tight at every point in its length.
+
+_Safety Devices._--Good generators are built in such a way that the
+operator must follow the proper order of operation in charging and cleaning
+as well as in all other necessary care. It has been mentioned that the gas
+pressure is released or shut off before it is possible to fill the water
+compartment, and this same idea is carried further in making the generator
+inoperative and free from gas pressure before opening the residue drain of
+the carbide filling opening on top of the hopper. Some machines are made so
+that they automatically cease to generate should there be a sudden and
+abnormal withdrawal of gas such as would be caused by a bad leak. This
+method of adding safety by automatic means and interlocking parts may be
+carried to any extent that seems desirable or necessary to the maker.
+
+All generators should be provided with escape or relief pipes of large size
+which lead to the open air. These pipes are carried so that condensation
+will drain back toward the generator and after being led out of the
+building to a point at least twelve feet above ground, they end in a
+protecting hood so that no rain or solid matter can find its way into them.
+Any escape of gas which might ordinarily pass into the generator room is
+led into these escape pipes, all parts of the system being connected with
+the pipe so that the gas will find this way out.
+
+Safety blow off valves are provided so that any excess gas which cannot be
+contained by the gas holder may be allowed to escape without causing an
+undue rise in pressure. This valve also allows the escape of pressure above
+that for which the generator was designed. Gas released in this way passes
+into the escape pipe just described.
+
+Inasmuch as the pressure of the oxygen is much greater than that of the
+acetylene when used in the torch, it will be seen that anything that caused
+the torch outlet to become closed would allow the oxygen to force the
+acetylene back into the generator and the oxygen would follow it, making a
+very explosive mixture. This return of the gas is prevented by a hydraulic
+safety valve or back pressure valve, as it is often called.
+
+Mechanical check valves have been found unsuitable for this use and those
+which employ water as a seal are now required by the insurance rules. The
+valve itself (Figure 13) consists of a large cylinder containing water to a
+certain depth, which is indicated on the valve body. Two pipes come into
+the upper end of this cylinder and lead down into the water, one being
+longer than the other. The shorter pipe leads to the escape pipe mentioned
+above, while the longer one comes from the generator. The upper end of the
+cylinder has an opening to which is attached the pipe leading to the
+torches.
+
+[Illustration: Figure 13.--Hydraulic Back-Pressure Valve.
+_A_, Acetylene supply line;
+_B_, Vent pipe;
+_C_, Water filling plug;
+_D_, Acetylene service cock;
+_E_, Plug to gauge height of water;
+_F_, Gas openings under water;
+_G_, Return pipe for sealing water;
+_H_, Tube to carry gas below water line;
+_I_, Tube to carry gas to escape pipe;
+_J_, Gas chamber;
+_K_, Plug in upper gas chamber;
+_L_, High water level;
+_M_, Opening through which water returns;
+_O_, Bottom clean out casting]
+
+The gas coming from the generator through the longer pipe passes out of the
+lower end of the pipe which is under water and bubbles up through the water
+to the space in the top of the cylinder. From there the gas goes to the
+pipe leading to the torches. The shorter pipe is closed by the depth of
+water so that the gas does not escape to the relief pipe. As long as the
+gas flows in the normal direction as described there will be no escape to
+the air. Should the gas in the torch line return into the hydraulic valve
+its pressure will lower the level of water in the cylinder by forcing some
+of the liquid up into the two pipes. As the level of the water lowers, the
+shorter pipe will be uncovered first, and as this is the pipe leading to
+the open air the gas will be allowed to escape, while the pipe leading back
+to the generator is still closed by the water seal. As soon as this reverse
+flow ceases, the water will again resume its level and the action will
+continue. Because of the small amount of water blown out of the escape pipe
+each time the valve is called upon to perform this duty, it is necessary to
+see that the correct water level is always maintained.
+
+While there are modifications of this construction, the same principle is
+used in all types. The pressure escape valve is often attached to this
+hydraulic valve body.
+
+_Construction Details._--Flexible tubing (except at torches), swing
+pipe joints, springs, mechanical check valves, chains, pulleys and lead or
+fusible piping should never be used on acetylene apparatus except where the
+failure of those parts will not affect the safety of the machine or permit,
+either directly or indirectly, the escape of gas into a room. Floats should
+not be used except where failure will only render the machine inoperative.
+
+It should be said that the National Board of Fire Underwriters have
+established an inspection service for acetylene generators and any
+apparatus which bears their label, stating that that particular model and
+type has been passed, is safe to use. This service is for the best
+interests of all concerned and looks toward the prevention of accidents.
+Such inspection is a very important and desirable feature of any outfit and
+should be insisted upon.
+
+_Location of Generators._--Generators should preferably be placed
+outside of insured buildings and in properly constructed generator houses.
+The operating mechanism should have ample room to work in and there should
+be room enough for the attendant to reach the various parts and perform the
+required duties without hindrance or the need of artificial light. They
+should also be protected from tampering by unauthorized persons.
+
+Generator houses should not be within five feet of any opening into, nor
+have any opening toward, any adjacent building, and should be kept under
+lock and key. The size of the house should be no greater than called for by
+the requirements mentioned above and it should be well ventilated.
+
+The foundation for the generator itself should be of brick, stone, concrete
+or iron, if possible. If of wood, they should be extra heavy, located in a
+dry place and open to circulation of air. A board platform is not
+satisfactory, but the foundation should be of heavy planking or timber to
+make a firm base and so that the air can circulate around the wood.
+
+The generator should stand level and no strain should be placed on any of
+the pipes or connections or any parts of the generator proper.
+
+
+
+
+CHAPTER IV
+
+WELDING INSTRUMENTS
+
+
+VALVES
+
+_Tank Valves._--The acetylene tank valve is of the needle type, fitted
+with suitable stuffing box nuts and ending in an exposed square shank to
+which the special wrench may be fitted when the valve is to be opened or
+closed.
+
+The valve used on Linde oxygen cylinders is also a needle type, but of
+slightly more complex construction. The body of the valve, which screws
+into the top of the cylinder, has an opening below through which the gas
+comes from the cylinder, and another opening on the side through which it
+issues to the torch line. A needle screws down from above to close this
+lower opening. The needle which closes the valve is not connected directly
+to the threaded member, but fits loosely into it. The threaded part is
+turned by a small hand wheel attached to the upper end. When this hand
+wheel is turned to the left, or up, as far as it will go, opening the
+valve, a rubber disc is compressed inside of the valve body and this disc
+serves to prevent leakage of the gas around the spindle.
+
+The oxygen valve also includes a safety nut having a small hole through it
+closed by a fusible metal which melts at 250° Fahrenheit. Melting of this
+plug allows the gas to exert its pressure against a thin copper diaphragm,
+this diaphragm bursting under the gas pressure and allowing the oxygen to
+escape into the air.
+
+The hand wheel and upper end of the valve mechanism are protected during
+shipment by a large steel cap which covers them when screwed on to the end
+of the cylinder. This cap should always be in place when tanks are received
+from the makers or returned to them.
+
+[Illustration: Figure 14.--Regulating Valve]
+
+_Regulating Valves._--While the pressure in the gas containers may be
+anything from zero to 1,800 pounds, and will vary as the gas is withdrawn,
+the pressure of the gas admitted to the torch must be held steady and at a
+definite point. This is accomplished by various forms of automatic
+regulating valves, which, while they differ somewhat in details of
+construction, all operate on the same principle.
+
+The regulator body (Figure 14) carries a union which attaches to the side
+outlet on the oxygen tank valve. The gas passes through this union,
+following an opening which leads to a large gauge which registers the
+pressure on the oxygen remaining in the tank and also to a very small
+opening in the end of a tube. The gas passes through this opening and into
+the interior of the regulator body. Inside of the body is a metal or rubber
+diaphragm placed so that the pressure of the incoming gas causes it to
+bulge slightly. Attached to the diaphragm is a sleeve or an arm tipped
+with a small piece of fibre, the fibre being placed so that it is directly
+opposite the small hole through which the gas entered the diaphragm
+chamber. The slight movement of the diaphragm draws the fibre tightly over
+the small opening through which the gas is entering, with the result that
+further flow is prevented.
+
+Against the opposite side of the diaphragm is the end of a plunger. This
+plunger is pressed against the diaphragm by a coiled spring. The tension on
+the coiled spring is controlled by the operator through a threaded spindle
+ending in a wing or milled nut on the outside of the regulator body.
+Screwing in on the nut causes the tension on the spring to increase, with a
+consequent increase of pressure on the side of the diaphragm opposite to
+that on which the gas acts. Inasmuch as the gas pressure acted to close the
+small gas opening and the spring pressure acts in the opposite direction
+from the gas, it will be seen that the spring pressure tends to keep the
+valve open.
+
+When the nut is turned way out there is of course, no pressure on the
+spring side of the diaphragm and the first gas coming through automatically
+closes the opening through which it entered. If now the tension on the
+spring be slightly increased, the valve will again open and admit gas until
+the pressure of gas within the regulator is just sufficient to overcome the
+spring pressure and again close the opening. There will then be a pressure
+of gas within the regulator that corresponds to the pressure placed on the
+spring by the operator. An opening leads from the regulator interior to the
+torch lines so that all gas going to the torches is drawn from the
+diaphragm chamber.
+
+Any withdrawal of gas will, of course, lower the pressure of that remaining
+inside the regulator. The spring tension, remaining at the point determined
+by the operator, will overcome this lessened pressure of the gas, and the
+valve will again open and admit enough more gas to bring the pressure back
+to the starting point. This action continues as long as the spring tension
+remains at this point and as long as any gas is taken from the regulator.
+Increasing the spring tension will require a greater gas pressure to close
+the valve and the pressure of that in the regulator will be correspondingly
+higher.
+
+When the regulator is not being used, the hand nut should be unscrewed
+until no tension remains on the spring, thus closing the valve. After the
+oxygen tank valve is open, the regulator hand nut is slowly screwed in
+until the spring tension is sufficient to give the required pressure in the
+torch lines. Another gauge is attached to the regulator so that it
+communicates with the interior of the diaphragm chamber, this gauge showing
+the gas pressure going to the torch. It is customary to incorporate a
+safety valve in the regulator which will blow off at a dangerous pressure.
+
+In regulating valves and tank valves, as well as all other parts with which
+the oxygen comes in contact, it is not permissible to use any form of oil
+or grease because of danger of ignition and explosion. The mechanism of a
+regulator is too delicate to be handled in the ordinary shop and should any
+trouble or leakage develop in this part of the equipment it should be sent
+to a company familiar with this class of work for the necessary repairs.
+Gas must never be admitted to a regulator until the hand nut is all the way
+out, because of danger to the regulator itself and to the operator as well.
+A regulator can only be properly adjusted when the tank valve and torch
+valves are fully opened.
+
+[Illustration: Figure 15.--High and Low Pressure Gauges with Regulator]
+
+Acetylene regulators are used in connection with tanks of compressed gas.
+They are built on exactly the same lines as the oxygen regulating valve and
+operate in a similar way. One gauge only, the low pressure indicator, is
+used for acetylene regulators, although both high and low pressure may be
+used if desired. (See Figure 15.)
+
+
+TORCHES
+
+Flame is always produced by the combustion of a gas with oxygen and in no
+other way. When we burn oil or candles or anything else, the material of
+the fuel is first turned to a gas by the heat and is then burned by
+combining with the oxygen of the air. If more than a normal supply of air
+is forced into the flame, a greater heat and more active burning follows.
+If the amount of air, and consequently oxygen, is reduced, the flame
+becomes smaller and weaker and the combustion is less rapid. A flame may be
+easily extinguished by shutting off all of its air supply.
+
+The oxygen of the combustion only forms one-fifth of the total volume of
+air; therefore, if we were to supply pure oxygen in place of air, and in
+equal volume, the action would be several times as intense. If the oxygen
+is mixed with the fuel gas in the proportion that burns to the very best
+advantage, the flame is still further strengthened and still more heat is
+developed because of the perfect combustion. The greater the amount of fuel
+gas that can be burned in a certain space and within a certain time, the
+more heat will be developed from that fuel.
+
+The great amount of heat contained in acetylene gas, greater than that
+found in any other gaseous fuel, is used by leading this gas to the
+oxy-acetylene torch and there combining it with just the right amount of
+oxygen to make a flame of the greatest power and heat than can possibly be
+produced by any form of combustion of fuels of this kind. The heat
+developed by the flame is about 6300° Fahrenheit and easily melts all the
+metals, as well as other solids.
+
+Other gases have been and are now being used in the torch. None of them,
+however, produce the heat that acetylene does, and therefore the
+oxy-acetylene process has proved the most useful of all. Hydrogen was used
+for many years before acetylene was introduced in this field. The
+oxy-hydrogen flame develops a heat far below that of oxy-acetylene, namely
+4500° Fahrenheit. Coal gas, benzine gas, blaugas and others have also been
+used in successful applications, but for the present we will deal
+exclusively with the acetylene fuel.
+
+It was only with great difficulty that the obstacles in the way of
+successfully using acetylene were overcome by the development of
+practicable controlling devices and torches, as well as generators. At
+present the oxy-acetylene process is the most universally adaptable, and
+probably finds the most widely extended field of usefulness of any welding
+process.
+
+The theoretical proportion of the gases for perfect combustion is two and
+one-half volumes of oxygen to one of acetylene. In practice this proportion
+is one and one-eighth or one and one-quarter volumes of oxygen to one
+volume of acetylene, so that the cost is considerably reduced below what it
+would be if the theoretical quantity were really necessary, as oxygen costs
+much more than acetylene in all cases.
+
+While the heat is so intense as to fuse anything brought into the path of
+the flame, it is localized in the small "welding cone" at the torch tip so
+that the torch is not at all difficult to handle without special protection
+except for the eyes, as already noted. The art of successful welding may be
+acquired by any operator of average intelligence within a reasonable time
+and with some practice. One trouble met with in the adoption of this
+process has been that the operation looks so simple and so easy of
+performance that unskilled and unprepared persons have been tempted to try
+welding, with results that often caused condemnation of the process, when
+the real fault lay entirely with the operator.
+
+The form of torch usually employed is from twelve to twenty-four inches
+long and is composed of a handle at one end with tubes leading from this
+handle to the "welding head" or torch proper. At or near one end of the
+handle are adjustable cocks or valves for allowing the gases to flow into
+the torch or to prevent them from doing so. These cocks are often used for
+regulating the pressure and amount of gas flowing to the welding head, but
+are not always constructed for this purpose and should not be so used when
+it is possible to secure pressure adjustment at the regulators (Figure 16).
+
+Figure 16 shows three different sizes of torches. The number 5 torch is
+designed especially for jewelers' work and thin sheet steel welding. It is
+eleven inches in length and weighs nineteen ounces. The tips for the number
+10 torch are interchangeable with the number 5. The number 10 torch is
+adapted for general use on light and medium heavy work. It has six tips and
+its length is sixteen inches, with a weight of twenty-three ounces.
+
+The number 15 torch is designed for heavy work, being twenty-five inches in
+length, permitting the operator to stand away from the heat of the metal
+being worked. These heavy tips are in two parts, the oxygen check being
+renewable.
+
+[Illustration: Figure 16.--Three Sizes of Torches, with Tips]
+
+Figures 17 and 18 show two sizes of another welding torch. Still another
+type is shown in Figure 19 with four interchangeable tips, the function of
+each being as follows:
+
+  No. 1. For heavy castings.
+  No. 2. Light castings and heavy sheet metal.
+  No. 3. Light sheet metal.
+  No. 4. Very light sheet metal and wire.
+
+[Illustration: Figure 17.--Cox Welding Torch (No. 1)]
+
+[Illustration: Figure 18.--Cox Welding Torch (No. 2)]
+
+[Illustration: Figure 19.--Monarch Welding Torch]
+
+At the side of the shut off cock away from the torch handle the gas tubes
+end in standard forms of hose nozzles, to which the rubber hose from the
+gas supply tanks or generators can be attached. The tubes from the handle
+to the head may be entirely separate from each other, or one may be
+contained within the other. As a general rule the upper one of two
+separate tubes carries the oxygen, while this gas is carried in the inside
+tube when they are concentric with each other.
+
+In the welding head is the mixing chamber designed to produce an intimate
+mixture of the two gases before they issue from the nozzle to the flame.
+The nozzle, or welding tip, of a suitable size are design for the work to
+be handled and the pressure of gases being used, is attached to the welding
+head and consists essentially of the passage at the outer end of which the
+flame appears.
+
+The torch body and tubes are usually made of brass, although copper is
+sometimes used. The joint must be very strong, and are usually threaded and
+soldered with silver solder. The nozzle proper is made from copper, because
+it withstands the heat of the flame better than other less suitable metals.
+The torch must be built in such a way that it is not at all liable to come
+apart under the influence of high temperatures.
+
+All torches are constructed in such a way that it is impossible for the
+gases to mix by any possible chance before they reach the head, and the
+amount of gas contained in the head and tip after being mixed is made as
+small as possible. In order to prevent the return of the flame through the
+acetylene tube under the influence of the high pressure oxygen some form of
+back flash preventer is usually incorporated in the torch at or near the
+point at which the acetylene enters. This preventer takes the form of some
+porous and heat absorbing material, such as aluminum shavings, contained in
+a small cavity through which the gas passes on its way to the head.
+
+_High Pressure Torches._--Torches are divided into the same classes as
+are the generators; that is, high pressure, medium pressure and low
+pressure. As mentioned before, the medium pressure is usually called the
+high pressure, because there are very few true high pressure systems in
+use, and comparatively speaking the medium pressure type is one of high
+pressure.
+
+[Illustration: Figure 20.--High Pressure Torch Head]
+
+With a true high pressure torch (Figure 20) the gases are used at very
+nearly equal heads so that the mixing before ignition is a simple matter.
+This type admits the oxygen at the inner end of a straight passage leading
+to the tip of the nozzle. The acetylene comes into this same passage from
+openings at one side and near the inner end. The difference in direction of
+the two gases as they enter the passage assists in making a homogeneous
+mixture. The construction of this nozzle is perfectly simple and is easily
+understood. The true high pressure torch nozzle is only suited for use with
+compressed and dissolved acetylene, no other gas being at a sufficient
+pressure to make the action necessary in mixing the gases.
+
+_Medium Pressure Torches._--The medium pressure (usually called high
+pressure) torch (Figure 21) uses acetylene from a medium pressure generator
+or from tanks of compressed gas, but will not take the acetylene from low
+pressure generators.
+
+[Illustration: Figure 21.--Medium Pressure Torch Head]
+
+The construction of the mixing chamber and nozzle is very similar to that
+of the high pressure torch, the gases entering in the same way and from the
+same positions of openings. The pressure of the acetylene is but little
+lower than that of the oxygen, and the two gases, meeting at right angles,
+form a very intimate mixture at this point of juncture. The mixture in its
+proportions of gases depends entirely on the sizes of the oxygen and
+acetylene openings into the mixing chamber and on the pressures at which
+the gases are admitted. There is a very slight injector action as the fast
+moving stream of oxygen tends to draw the acetylene from the side openings
+into the chamber, but the operation of the torch does not depend on this
+action to any extent.
+
+_Low Pressure Torches._--The low pressure torch (Figure 22) will use
+gas from low pressure generators from medium pressure machines or from
+tanks in which it has been compressed and dissolved. This type depends for
+a perfect mixture of gas upon the principle of the injector just as it is
+applied in steam boiler practice.
+
+[Illustration: Figure 22.--Low Pressure Torch with Separate Injector
+Nozzle]
+
+The oxygen enters the head at considerable pressure and passes through its
+tube to a small jet within the head. The opening of this jet is directly
+opposite the end of the opening through the nozzle which forms the mixing
+chamber and the path of the gases to the flame. A small distance remains
+between the opening from which the oxygen issues and the inner opening into
+the mixing passage. The stream of oxygen rushes across this space and
+enters the mixing chamber, being driven by its own pressure.
+
+The acetylene enters the head in an annular space surrounding the oxygen
+tube. The space between oxygen jet and mixing chamber opening is at one end
+of this acetylene space and the stream of oxygen seizes the acetylene and
+under the injector action draws it into the mixing chamber, it being
+necessary only to have a sufficient supply of acetylene flowing into the
+head to allow the oxygen to draw the required proportion for a proper
+mixture.
+
+The volume of gas drawn into the mixing chamber depends on the size of the
+injector openings and the pressure of the oxygen. In practice the oxygen
+pressure is not altered to produce different sized flames, but a new nozzle
+is substituted which is designed to give the required flame. Each nozzle
+carries its own injector, so that the design is always suited to the
+conditions. While torches are made having the injector as a permanent part
+of the torch body, the replaceable nozzle is more commonly used because it
+makes the one torch suitable for a large range of work and a large number
+of different sized flames. With the replaceable head a definite pressure of
+oxygen is required for the size being used, this pressure being the one for
+which the injector and corresponding mixing chamber were designed in
+producing the correct mixture.
+
+_Adjustable Injectors._-Another form of low pressure torch operates on
+the injector principle, but the injector itself is a permanent part of the
+torch, the nozzle only being changed for different sizes of work and flame.
+The injector is placed in or near the handle and its opening is the largest
+required by any work that can be handled by this particular torch. The
+opening through the tip of the injector through which the oxygen issues on
+its way to the mixing chamber may be wholly or partly closed by a needle
+valve which may be screwed into the opening or withdrawn from it, according
+to the operator's judgment. The needle valve ends in a milled nut outside
+the torch handle, this being the adjustment provided for the different
+nozzles.
+
+_Torch Construction._--A well designed torch is so designed that the
+weight distribution is best for holding it in the proper position for
+welding. When a torch is grasped by its handle with the gas hose attached,
+it should balance so that it does not feel appreciably heavier on one end
+than on the other.
+
+The head and nozzle may be placed so that the flame issues in a line at
+right angles with the torch body, or they may be attached at an angle
+convenient for the work to be done. The head set at an angle of from 120 to
+170 degrees with the body is usually preferred for general work in welding,
+while the cutting torch usually has its head at right angles to the body.
+
+Removable nozzles have various size openings through them and the different
+sizes are designated by numbers from 1 up. The same number does not always
+indicate the same size opening in torches of different makes, nor does it
+indicate a nozzle of the same capacity.
+
+The design of the nozzle, the mixing chamber, the injector, when one is
+used, and the size of the gas openings must be such that all these things
+are suited to each other if a proper mixture of gas is to be secured. Parts
+that are not made to work together are unsafe if used because of the danger
+of a flash back of the flame into the mixing chamber and gas tubes. It is
+well known that flame travels through any inflammable gas at a certain
+definite rate of speed, depending on the degree of inflammability of the
+gas. The easier and quicker the gas burns, the faster will the flame travel
+through it.
+
+If the gas in the nozzle and mixing chamber stood still, the flame would
+immediately travel back into these parts and produce an explosion of more
+or less violence. The speed with which the gases issue from the nozzle
+prevent this from happening because the flame travels back through the gas
+at the same speed at which the gas issues from the torch tip. Should the
+velocity of the gas be greater than the speed of flame propagation through
+it, it will be impossible to keep the flame at the tip, the tendency being
+for a space of unburned gas to appear between tip and flame. On the other
+hand, should the speed of the flame exceed the velocity with which the gas
+comes from the torch there will result a flash back and explosion.
+
+_Care of Torches._--An oxy-acetylene torch is a very delicate and
+sensitive device, much more so that appears on the surface. It must be
+given equally as good care and attention as any other high-priced piece of
+machinery if it is to be maintained in good condition for use.
+
+It requires cleaning of the nozzles at regular intervals if used regularly.
+This cleaning is accomplished with a piece of copper or brass wire run
+through the opening, and never with any metal such as steel or iron that is
+harder than the nozzle itself, because of the danger of changing the size
+of the openings. The torch head and nozzle can often be cleaned by allowing
+the oxygen to blow through at high pressure without the use of any tools.
+
+In using a torch a deposit of carbon will gradually form inside of the
+head, and this deposit will be more rapid if the operator lights the stream
+of acetylene before turning any oxygen into the torch. This deposit may be
+removed by running kerosene through the nozzle while it is removed from the
+torch, setting fire to the kerosene and allowing oxygen to flow through
+while the oil is burning.
+
+Should a torch become clogged in the head or tubes, it may usually be
+cleaned by removing the oxygen hose from the handle end, closing the
+acetylene cock on the torch, placing the end of the oxygen hose over the
+opening in the nozzle and turning on the oxygen under pressure to blow the
+obstruction back through the passage that it has entered. By opening the
+acetylene cock and closing the oxygen cock at the handle, the acetylene
+passages may then be cleaned in the same way. Under no conditions should a
+torch be taken apart any more than to remove the changeable nozzle, except
+in the hands of those experienced in this work.
+
+_Nozzle Sizes._--The size of opening through the nozzle is determined
+according to the thickness and kind of metal being handled. The following
+sizes are recommended for steel:
+
+                      Davis-Bournonville.   Oxweld Low
+  Thickness of Metal  (Medium Pressure.)      Pressure
+  1/32                     Tip No. 1        Head No. 2
+  1/16                             2
+  5/64                                               3
+  3/32                             3                 4
+  3/8                              4                 5
+  3/16                             5                 6
+  1/4                              6                 7
+  5/16                             7
+  3/8                              8                 8
+  1/2                              9                10
+  5/8                             10                12
+  3/4                             11                15
+  Very heavy                      12                15
+
+_Cutting Torches._--Steel may be cut with a jet of oxygen at a rate of
+speed greater than in any other practicable way under usual conditions. The
+action consists of burning away a thin section of the metal by allowing a
+stream of oxygen to flow onto it while the gas is at high pressure and the
+metal at a white heat.
+
+[Illustration: Figure 23.--Cutting Torch]
+
+The cutting torch (Figure 23) has the same characteristics as the welding
+torch, but has an additional nozzle or means for temporarily using the
+welding opening for the high pressure oxygen. The oxygen issues from the
+opening while cutting at a pressure of from ten to 100 pounds to the square
+inch.
+
+The work is first heated to a white heat by adjusting the torch for a
+welding flame. As soon as the metal reaches this temperature, the high
+pressure oxygen is turned on to the white-hot portion of the steel. When
+the jet of gas strikes the metal it cuts straight through, leaving a very
+narrow slot and removing but little metal. Thicknesses of steel up to ten
+inches can be economically handled in this way.
+
+The oxygen nozzle is usually arranged so that it is surrounded by a number
+of small jets for the heating flame. It will be seen that this arrangement
+makes the heating flame always precede the oxygen jet, no matter in which
+direction the torch is moved.
+
+The torch is held firmly, either by hand or with the help of special
+mechanism for guiding it in the desired path, and is steadily advanced in
+the direction it is desired to extend the cut, the rate of advance being
+from three inches to two feet per minute through metal from nine inches
+down to one-quarter of an inch in thickness.
+
+The following data on cutting is given by the Davis-Bournonville Company:
+
+                            Cubic
+                            Feet                          Cost of
+Thickness                   of Gas               Inches   Gases
+of        Cutting  Heating  per Foot  Oxygen     Cut per  per Foot
+Steel     Oxygen   Oxygen   of Cut    Acetylene  Min.     of Cut
+  1/4     10 lbs.  4 lbs.     .40      .086      24        $ .013
+  1/2     20       4          .91      .150      15          .029
+  3/4     30       4         1.16      .150      15          .036
+1         30       4         1.45      .172      12          .045
+1 1/2     30       5         2.40      .380      12          .076
+2         40       5         2.96      .380      12          .093
+4         50       5         9.70      .800       7          .299
+6         70       6        21.09     1.50        4          .648
+9        100       6        43.20     2.00        3         1.311
+
+_Acetylene-Air Torch._--A form of torch which burns the acetylene after
+mixing it with atmospheric air at normal pressure rather than with the
+oxygen under higher pressures has been found useful in certain pre-heating,
+brazing and similar operations. This torch (Figure 24) is attached by a
+rubber gas hose to any compressed acetylene tank and is regulated as to
+flame size and temperature by opening or closing the tank valve more or
+less.
+
+After attaching the torch to the tank, the gas is turned on very slowly and
+is lighted at the torch tip. The adjustment should cause the presence of a
+greenish-white cone of flame surrounded by a larger body of burning gas,
+the cone starting at the mouth of the torch.
+
+[Illustration: Figure 24.--Acetylene-Air Torch]
+
+By opening the tank valve more, a longer and hotter flame is produced, the
+length being regulated by the tank valve also. This torch will give
+sufficient heat to melt steel, although not under conditions suited to
+welding. Because of the excess of acetylene always present there is no
+danger of oxidizing the metal being heated.
+
+The only care required by this torch is to keep the small air passages at
+the nozzle clean and free from carbon deposits. The flame should be
+extinguished when not in use rather than turned low, because this low flame
+rapidly deposits large quantities of soot in the burner.
+
+
+
+
+CHAPTER V
+
+OXY-ACETYLENE WELDING PRACTICE
+
+
+PREPARATION OF WORK
+
+_Preheating._--The practice of heating the metal around the weld
+before applying the torch flame is a desirable one for two reasons. First,
+it makes the whole process more economical; second, it avoids the danger of
+breakage through expansion and contraction of the work as it is heated and
+as it cools.
+
+When it is desired to join two surfaces by welding them, it is, of course,
+necessary to raise the metal from the temperature of the surrounding air to
+its melting point, involving an increase in temperature of from one
+thousand to nearly three thousand degrees. To obtain this entire increase
+of temperature with the torch flame is very wasteful of fuel and of the
+operator's time. The total amount of heat necessary to put into metal is
+increased by the conductivity of that metal because the heat applied at the
+weld is carried to other parts of the piece being handled until the whole
+mass is considerably raised in temperature. To secure this widely
+distributed increase the various methods of preheating are adopted.
+
+As to the second reason for preliminary heating. It is understood that the
+metal added to the joint is molten at the time it flows into place. All the
+metals used in welding contract as they cool and occupy a much smaller
+space than when molten. If additional metal is run between two adjoining
+surfaces which are parts of a surrounding body of cool metal, this added
+metal will cool while the surfaces themselves are held stationary in the
+position they originally occupied. The inevitable result is that the metal
+added will crack under the strain, or, if the weld is exceptionally strong,
+the main body of the work will he broken by the force of contraction. To
+overcome these difficulties is the second and most important reason for
+preheating and also for slow cooling following the completion of the weld.
+
+There are many ways of securing this preheating. The work may be brought to
+a red heat in the forge if it is cast iron or steel; it may he heated in
+special ovens built for the purpose; it may be placed in a bed of charcoal
+while suitably supported; it may be heated by gas or gasoline preheating
+torches, and with very small work the outer flame of the welding torch
+automatically provides means to this end.
+
+The temperature of the parts heated should be gradually raised in all
+cases, giving the entire mass of metal a chance to expand equally and to
+adjust itself to the strains imposed by the preheating. After the region
+around the weld has been brought to a proper temperature the opening to be
+filled is exposed so that the torch flame can reach it, while the remaining
+surfaces are still protected from cold air currents and from cooling
+through natural radiation.
+
+One of the commonest methods and one of the best for handling work of
+rather large size is to place the piece to be welded on a bed of fire brick
+and build a loose wall around it with other fire brick placed in rows, one
+on top of the other, with air spaces left between adjacent bricks in each
+row. The space between the brick retaining wall and the work is filled with
+charcoal, which is lighted from below. The top opening of the temporary
+oven is then covered with asbestos and the fire kept up until the work has
+been uniformly raised in temperature to the desired point.
+
+When much work of the same general character and size is to be handled, a
+permanent oven may be constructed of fire brick, leaving a large opening
+through the top and also through one side. Charcoal may be used in this
+form of oven as with the temporary arrangement, or the heat may be secured
+from any form of burner or torch giving a large volume of flame. In any
+method employing flame to do the heating, the work itself must be protected
+from the direct blast of the fire. Baffles of brick or metal should be
+placed between the mouth of the torch and the nearest surface of the work
+so that the flame will be deflected to either side and around the piece
+being heated.
+
+The heat should be applied to bring the point of welding to the highest
+temperature desired and, except in the smallest work, the heat should
+gradually shade off from this point to the other parts of the piece. In the
+case of cast iron and steel the temperature at the point to be welded
+should be great enough to produce a dull red heat. This will make the whole
+operation much easier, because there will be no surrounding cool metal to
+reduce the temperature of the molten material from the welding rod below
+the point at which it will join the work. From this red heat the mass of
+metal should grow cooler as the distance from the weld becomes greater, so
+that no great strain is placed upon any one part. With work of a very
+irregular shape it is always best to heat the entire piece so that the
+strains will be so evenly distributed that they can cause no distortion or
+breakage under any conditions.
+
+The melting point of the work which is being preheated should be kept in
+mind and care exercised not to approach it too closely. Special care is
+necessary with aluminum in this respect, because of its low melting
+temperature and the sudden weakening and flowing without warning. Workmen
+have carelessly overheated aluminum castings and, upon uncovering the piece
+to make the weld, have been astonished to find that it had disappeared.
+Six hundred degrees is about the safe limit for this metal. It is possible
+to gauge the exact temperature of the work with a pyrometer, but when this
+instrument cannot be procured, it might be well to secure a number of
+"temperature cones" from a chemical or laboratory supply house. These cones
+are made from material that will soften at a certain heat and in form they
+are long and pointed. Placed in position on the part being heated, the
+point may be watched, and when it bends over it is sure that the metal
+itself has reached a temperature considerably in excess of the temperature
+at which that particular cone was designed to soften.
+
+The object in preheating the metal around the weld is to cause it to expand
+sufficiently to open the crack a distance equal to the contraction when
+cooling from the melting point. In the case of a crack running from the
+edge of a piece into the body or of a crack wholly within the body, it is
+usually satisfactory to heat the metal at each end of the opening. This
+will cause the whole length of the crack to open sufficiently to receive
+the molten material from the rod.
+
+The judgment of the operator will be called upon to decide just where a
+piece of metal should be heated to open the weld properly. It is often
+possible to apply the preheating flame to a point some distance from the
+point of work if the parts are so connected that the expansion of the
+heated part will serve to draw the edges of the weld apart. Whatever part
+of the work is heated to cause expansion and separation, this part must
+remain hot during the entire time of welding and must then cool slowly at
+the same time as the metal in the weld cools.
+
+[Illustration: Figure 25.--Preheating at _A_ While Welding at
+_B_. _C_ also May Be Heated.]
+
+An example of heating points away from the crack might be found in welding
+a lattice work with one of the bars cracked through (Figure 25). If the
+strips parallel and near to the broken bar are heated gradually, the work
+will be so expanded that the edges of the break are drawn apart and the
+weld can be successfully made. In this case, the parallel bars next to the
+broken one would be heated highest, the next row not quite so hot and so on
+for some distance away. If only the one row were heated, the strains set up
+in the next ones would be sufficient to cause a new break to appear.
+
+[Illustration: Figure 26.--Cutting Through the Rim of a Wheel (Cut Shown
+at A)]
+
+If welding is to be done near the central portion of a large piece, the
+strains will be brought to bear on the parts farthest away from the center.
+Should a fly wheel spoke be broken and made ready to weld, the greatest
+strain will come on the rim of the wheel. In cases like this it is often
+desirable to cut through at the point of greatest strain with a saw or
+cutting torch, allowing free movement while the weld is made at the
+original break (Figure 26). After the inside weld is completed, the cut may
+be welded without danger, for the reason that it will always be at some
+point at which severe strains cannot be set up by the contraction of the
+cooling metal.
+
+[Illustration: Figure 27.--Using a Wedge While Welding]
+
+In materials that will spring to some extent without breakage, that is, in
+parts that are not brittle, it may be possible to force the work out of
+shape with jacks or wedges (Figure 27) in the same way that it would be
+distorted by heating and expanding some portion of it as described. A
+careful examination will show whether this method can be followed in such a
+way as to force the edges of the break to separate. If the plan seems
+feasible, the wedges may be put in place and allowed to remain while the
+weld is completed. As soon as the work is finished the wedges should be
+removed so that the natural contraction can take place without damage.
+
+It should always be remembered that it is not so much the expansion of the
+work when heated as it is the contraction caused by cooling that will do
+the damage. A weld may be made that, to all appearances, is perfect and it
+may be perfect when completed; but if provision has not been made to allow
+for the contraction that is certain to follow, there will be a breakage at
+some point. It is not possible to weld the simplest shapes, other than
+straight bars, without considering this difficulty and making provision to
+take care of it.
+
+The exact method to employ in preheating will always call for good judgment
+on the part of the workman, and he should remember that the success or
+failure of his work will depend fully as much on proper preparation as on
+correct handling of the weld itself. It should be remembered that the outer
+flame of the oxy-acetylene torch may be depended on for a certain amount of
+preheating, as this flame gives a very large volume of heat, but a heat
+that is not so intense nor so localized as the welding flame itself. The
+heat of this part of the flame should be fully utilized during the
+operation of melting the metal and it should be so directed, when possible,
+that it will bring the parts next to be joined to as high a temperature as
+possible.
+
+When the work has been brought to the desired temperature, all parts except
+the break and the surface immediately surrounding it on both sides should
+be covered with heavy sheet asbestos. This protecting cover should remain
+in place throughout the operation and should only be moved a distance
+sufficient to allow the torch flame to travel in the path of the weld. The
+use of asbestos in this way serves a twofold purpose. It retains the heat
+in the work and prevents the breakage that would follow if a draught of air
+were to strike the heated metal, and it also prevents such a radiation of
+heat through the surrounding air as would make it almost impossible for the
+operator to perform his work, especially in the case of large and heavy
+castings when the amount of heat utilized is large.
+
+_Cleaning and Champfering._--A perfect weld can never be made unless
+the surfaces to be joined have been properly prepared to receive the new
+metal.
+
+All spoiled, burned, corroded and rough particles must positively be
+removed with chisel and hammer and with a free application of emery cloth
+and wire brush. The metal exposed to the welding flame should be perfectly
+clean and bright all over, or else the additional material will not unite,
+but will only stick at best.
+
+[Illustration: Figure 28.--Tapering the Opening Formed by a Break]
+
+Following the cleaning it is always necessary to bevel, or champfer, the
+edges except in the thinnest sheet metal. To make a weld that will hold,
+the metal must be made into one piece, without holes or unfilled portions
+at any point, and must be solid from inside to outside. This can only be
+accomplished by starting the addition of metal at one point and gradually
+building it up until the outside, or top, is reached. With comparatively
+thin plates the molten metal may be started from the side farthest from the
+operator and brought through, but with thicker sections the addition is
+started in the middle and brought flush with one side and then with the
+other.
+
+It will readily be seen that the molten material cannot be depended upon to
+flow between the tightly closed surfaces of a crack in a way that can be at
+all sure to make a true weld. It will be necessary for the operator to
+reach to the farthest side with the flame and welding rod, and to start the
+new surfaces there. To allow this, the edges that are to be joined are
+beveled from one side to the other (Figure 28), so that when placed
+together in approximately the position they are to occupy they will leave a
+grooved channel between them with its sides at an angle with each other
+sufficient in size to allow access to every point of each surface.
+
+[Illustration: Figure 29.--Beveling for Thin Work]
+
+[Illustration: Figure 30.--Beveling for Thick Work]
+
+With work less than one-fourth inch thick, this angle should be forty-five
+degrees on each piece (Figure 29), so that when they are placed together
+the extreme edges will meet at the bottom of a groove whose sides are
+square, or at right angles, to each other. This beveling should be done so
+that only a thin edge is left where the two parts come together, just
+enough points in contact to make the alignment easy to hold. With work of a
+thickness greater than a quarter of an inch, the angle of bevel on each
+piece may be sixty degrees (Figure 30), so that when placed together the
+angle included between the sloping sides will also be sixty degrees. If the
+plate is less than one-eighth of an inch thick the beveling is not
+necessary, as the edges may be melted all the way through without danger of
+leaving blowholes at any point.
+
+[Illustration: Figure 31.--Beveling Both Sides of a Thick Piece]
+
+[Illustration: Figure 32.--Beveling the End of a Pipe]
+
+This beveling may be done in any convenient way. A chisel is usually most
+satisfactory and also quickest. Small sections may be handled by filing,
+while metal that is too hard to cut in either of these ways may be shaped
+on the emery wheel. It is not necessary that the edges be perfectly
+finished and absolutely smooth, but they should be of regular outline and
+should always taper off to a thin edge so that when the flame is first
+applied it can be seen issuing from the far side of the crack. If the work
+is quite thick and is of a shape that will allow it to be turned over, the
+bevel may be brought from both sides (Figure 31), so that there will be two
+grooves, one on each surface of the work. After completing the weld on one
+side, the piece is reversed and finished on the other side. Figure 32 shows
+the proper beveling for welding pipe. Figure 33 shows how sheet metal may
+be flanged for welding.
+
+Welding should not be attempted with the edges separated in place of
+beveled, because it will be found impossible to build up a solid web of new
+metal from one side clear through to the other by this method. The flame
+cannot reach the surfaces to make them molten while receiving new material
+from the rod, and if the flame does not reach them it will only serve to
+cause a few drops of the metal to join and will surely cause a weak and
+defective weld.
+
+[Illustration: Figure 33.--Flanging Sheet Metal for Welding]
+
+_Supporting Work._--During the operation of welding it is necessary
+that the work be well supported in the position it should occupy. This may
+be done with fire brick placed under the pieces in the correct position,
+or, better still, with some form of clamp. The edges of the crack should
+touch each other at the point where welding is to start and from there
+should gradually separate at the rate of about one-fourth inch to the foot.
+This is done so that the cooling of the molten metal as it is added will
+draw the edges together by its contraction.
+
+Care must be used to see that the work is supported so that it will
+maintain the same relative position between the parts as must be present
+when the work is finished. In this connection it must be remembered that
+the expansion of the metal when heated may be great enough to cause serious
+distortion and to provide against this is one of the difficulties to be
+overcome.
+
+Perfect alignment should be secured between the separate parts that are to
+be joined and the two edges must be held up so that they will be in the
+same plane while welding is carried out. If, by any chance, one drops
+below the other while molten metal is being added, the whole job may have
+to be undone and done over again. One precaution that is necessary is that
+of making sure that the clamping or supporting does not in itself pull the
+work out of shape while melted.
+
+
+TORCH PRACTICE
+
+[Illustration: Figure 34.--Rotary Movement of Torch in Welding]
+
+The weld is made by bringing the tip of the welding flame to the edges of
+the metals to be joined. The torch should be held in the right hand and
+moved slowly along the crack with a rotating motion, traveling in small
+circles (Figure 34), so that the Welding flame touches first on one side of
+the crack and then on the other. On large work the motion may be simply
+back and forth across the crack, advancing regularly as the metal unites.
+It is usually best to weld toward the operator rather than from him,
+although this rule is governed by circumstances. The head of the torch
+should be inclined at an angle of about 60 degrees to the surface of the
+work. The torch handle should extend in the same line with the break
+(Figure 35) and not across it, except when welding very light plates.
+
+[Illustration: Figure 35.--Torch Held in Line with the Break]
+
+If the metal is 1/16 inch or less in thickness it is only necessary to
+circle along the crack, the metal itself furnishing enough material to
+complete the weld without additions. Heat both sides evenly until they flow
+together.
+
+Material thicker than the above requires the addition of more metal of the
+same or different kind from the welding rod, this rod being held by the
+left hand. The proper size rod for cast iron is one having a diameter equal
+to the thickness of metal being welded up to a one-half inch rod, which is
+the largest used. For steel the rod should be one-half the thickness of the
+metal being joined up to one-fourth inch rod. As a general rule, better
+results will be obtained by the use of smaller rods, the very small sizes
+being twisted together to furnish enough material while retaining the free
+melting qualities.
+
+[Illustration: Figure 36.--The Welding Rod Should Be Held in the Molten
+Metal]
+
+The tip of the rod must at all times be held in contact with the pieces
+being welded and the flame must be so directed that the two sides of the
+crack and the end of the rod are melted at the same time (Figure 36).
+Before anything is added from the rod, the sides of the crack are melted
+down sufficiently to fill the bottom of the groove and join the two sides.
+Afterward, as metal comes from the rod in filling the crack, the flame is
+circled along the joint being made, the rod always following the flame.
+
+[Illustration: Figure 37.--Welding Pieces of Unequal Thickness]
+
+Figure 37 illustrates the welding of pieces of unequal thickness.
+
+Figure 38 illustrates welding at an angle.
+
+The molten metal may be directed as to where it should go by the tip of the
+welding flame, which has considerable force, but care must be taken not to
+blow melted metal on to cooler surfaces which it cannot join. If, while
+welding, a spot appears which does not unite with the weld, it may be
+handled by heating all around it to a white heat and then immediately
+welding the bad place.
+
+[Illustration: Figure 38.--Welding at an Angle]
+
+Never stop in the middle of a weld, as it is extremely difficult to
+continue smoothly when resuming work.
+
+_The Flame._--The welding flame must have exactly the right
+proportions of each gas. If there is too much oxygen, the metal will be
+burned or oxidized; the presence of too much acetylene carbonizes the
+metal; that is to say, it adds carbon and makes the work harder. Just the
+right mixture will neither burn nor carbonize and is said to be a "neutral"
+flame. The neutral flame, if of the correct size for the work, reduces the
+metal to a melted condition, not too fluid, and for a width about the same
+as the thickness of the metal being welded.
+
+When ready to light the torch, after attaching the right tip or head as
+directed in accordance with the thickness of metal to be handled, it will
+be necessary to regulate the pressure of gases to secure the neutral flame.
+
+The oxygen will have a pressure of from 2 to 20 pounds, according to the
+nozzle used. The acetylene will have much less. Even with the compressed
+gas, the pressure should never exceed 10 pounds for the largest work, and
+it will usually be from 4 to 6. In low pressure systems, the acetylene will
+be received at generator pressure. It should first be seen that the
+hand-screws on the regulators are turned way out so that the springs are
+free from any tension. It will do no harm if these screws are turned back
+until they come out of the threads. This must be done with both oxygen and
+acetylene regulators.
+
+Next, open the valve from the generator, or on the acetylene tank, and
+carefully note whether there is any odor of escaping gas. Any leakage of
+this gas must be stopped before going on with the work.
+
+The hand wheel controlling the oxygen cylinder valve should now be turned
+very slowly to the left as far as it will go, which opens the valve, and
+it should be borne in mind the pressure that is being released. Turn in the
+hand screw on the oxygen regulator until the small pressure gauge shows a
+reading according to the requirements of the nozzle being used. This oxygen
+regulator adjustment should be made with the cock on the torch open, and
+after the regulator is thus adjusted the torch cock may be closed.
+
+Open the acetylene cock on the torch and screw in on the acetylene
+regulator hand-screw until gas commences to come through the torch. Light
+this flow of acetylene and adjust the regulator screw to the pressure
+desired, or, if there is no gauge, so that there is a good full flame. With
+the pressure of acetylene controlled by the type of generator it will only
+be necessary to open the torch cock.
+
+With the acetylene burning, slowly open the oxygen cock on the torch and
+allow this gas to join the flame. The flame will turn intensely bright and
+then blue white. There will be an outer flame from four to eight inches
+long and from one to three inches thick. Inside of this flame will be two
+more rather distinctly defined flames. The inner one at the torch tip is
+very small, and the intermediate one is long and pointed. The oxygen should
+be turned on until the two inner flames unite into one blue-white cone from
+one-fourth to one-half inch long and one-eighth to one-fourth inch in
+diameter. If this single, clearly defined cone does not appear when the
+oxygen torch cock has been fully opened, turn off some of the acetylene
+until it does appear.
+
+If too much oxygen is added to the flame, there will still be the central
+blue-white cone, but it will be smaller and more or less ragged around the
+edges (Figure 39). When there is just enough oxygen to make the single
+cone, and when, by turning on more acetylene or by turning off oxygen, two
+cones are caused to appear, the flame is neutral (Figure 40), and the small
+blue-white cone is called the welding flame.
+
+[Illustration: Figure 39.--Oxidizing Flame--Too Much Oxygen]
+
+[Illustration: Figure 40.--Neutral Flame]
+
+[Illustration: Figure 41.--Reducing Flame--Showing an Excess of Acetylene]
+
+While welding, test the correctness of the flame adjustment occasionally by
+turning on more acetylene or by turning off some oxygen until two flames or
+cones appear. Then regulate as before to secure the single distinct cone.
+Too much oxygen is not usually so harmful as too much acetylene, except
+with aluminum. (See Figure 41.) An excessive amount of sparks coming from
+the weld denotes that there is too much oxygen in the flame. Should the
+opening in the tip become partly clogged, it will be difficult to secure a
+neutral flame and the tip should be cleaned with a brass or copper
+wire--never with iron or steel tools or wire of any kind. While the torch
+is doing its work, the tip may become excessively hot due to the heat
+radiated from the molten metal. The tip may be cooled by turning off the
+acetylene and dipping in water with a slight flow of oxygen through the
+nozzle to prevent water finding its way into the mixing chamber.
+
+The regulators for cutting are similar to those for welding, except that
+higher pressures may be handled, and they are fitted with gauges reading up
+to 200 or 250 pounds pressure.
+
+In welding metals which conduct the heat very rapidly it is necessary to
+use a much larger nozzle and flame than for metals which have not this
+property. This peculiarity is found to the greatest extent in copper,
+aluminum and brass.
+
+Should a hole be blown through the work, it may be closed by withdrawing
+the flame for a few seconds and then commencing to build additional metal
+around the edges, working all the way around and finally closing the small
+opening left at the center with a drop or two from the welding rod.
+
+
+WELDING VARIOUS METALS
+
+Because of the varying melting points, rates of expansion and contraction,
+and other peculiarities of different metals, it is necessary to give
+detailed consideration to the most important ones.
+
+_Characteristics of Metals._--The welder should thoroughly understand
+the peculiarities of the various metals with which he has to deal. The
+metals and their alloys are described under this heading in the first
+chapter of this book and a tabulated list of the most important points
+relating to each metal will be found at the end of the present chapter.
+All this information should be noted by the operator of a welding
+installation before commencing actual work.
+
+Because of the nature of welding, the melting point of a metal is of great
+importance. A metal melting at a low temperature should have more careful
+treatment to avoid undesired flow than one which melts at a temperature
+which is relatively high. When two dissimilar metals are to be joined, the
+one which melts at the higher temperature must be acted upon by the flame
+first and when it is in a molten condition the heat contained in it will in
+many cases be sufficient to cause fusion of the lower melting metal and
+allow them to unite without playing the flame on the lower metal to any
+great extent.
+
+The heat conductivity bears a very important relation to welding, inasmuch
+as a metal with a high rate of conductance requires more protection from
+cooling air currents and heat radiation than one not having this quality to
+such a marked extent. A metal which conducts heat rapidly will require a
+larger volume of flame, a larger nozzle, than otherwise, this being
+necessary to supply the additional heat taken away from the welding point
+by this conductance.
+
+The relative rates of expansion of the various metals under heat should be
+understood in order that parts made from such material may have proper
+preparation to compensate for this expansion and contraction. Parts made
+from metals having widely varying rates of expansion must have special
+treatment to allow for this quality, otherwise breakage is sure to occur.
+
+_Cast Iron._--All spoiled metal should he cut away and if the work is
+more than one-eighth inch in thickness the sides of the crack should be
+beveled to a 45 degree angle, leaving a number of points touching at the
+bottom of the bevel so that the work may be joined in its original
+relation.
+
+The entire piece should be preheated in a bricked-up oven or with charcoal
+placed on the forge, when size does not warrant building a temporary oven.
+The entire piece should be slowly heated and the portion immediately
+surrounding the weld should be brought to a dull red. Care should be used
+that the heat does not warp the metal through application to one part more
+than the others. After welding, the work should be slowly cooled by
+covering with ashes, slaked lime, asbestos fibre or some other
+non-conductor of heat. These precautions are absolutely essential in the
+case of cast iron.
+
+A neutral flame, from a nozzle proportioned to the thickness of the work,
+should be held with the point of the blue-white cone about one-eighth inch
+from the surface of the iron.
+
+A cast iron rod of correct diameter, usually made with an excess of
+silicon, is used by keeping its end in contact with the molten metal and
+flowing it into the puddle formed at the point of fusion. Metal should be
+added so that the weld stands about one-eighth inch above the surrounding
+surface of the work.
+
+Various forms of flux may be used and they are applied by dipping the end
+of the welding rod into the powder at intervals. These powders may contain
+borax or salt, and to prevent a hard, brittle weld, graphite or
+ferro-silicon may be added. Flux should be added only after the iron is
+molten and as little as possible should be used. No flux should be used
+just before completion of the work.
+
+The welding flame should be played on the work around the crack and
+gradually brought to bear on the work. The bottom of the bevel should be
+joined first and it will be noted that the cast iron tends to run toward
+the flame, but does not stick together easily. A hard and porous weld
+should be carefully guarded against, as described above, and upon
+completion of the work the welded surface should be scraped with a file,
+while still red hot, in order to remove the surface scale.
+
+_Malleable Iron._--This material should be beveled in the same way
+that cast iron is handled, and preheating and slow cooling are equally
+desirable. The flame used is the same as for cast iron and so is the flux.
+The welding rod may be of cast iron, although better results are secured
+with Norway iron wire or else a mild steel wire wrapped with a coil of
+copper wire.
+
+It will be understood that malleable iron turns to ordinary cast iron when
+melted and cooled. Welds in malleable iron are usually far from
+satisfactory and a better joint is secured by brazing the edges together
+with bronze. The edges to be joined are brought to a heat just a little
+below the point at which they will flow and the opening is then
+quickly-filled from a rod of Tobin bronze or manganese bronze, a brass or
+bronze flux being used in this work.
+
+_Wrought Iron or Semi-Steel._--This metal should be beveled and heated
+in the same way as described for cast iron. The flame should be neutral, of
+the same size as for steel, and used with the tip of the blue-white cone
+just touching the work. The welding rod should be of mild steel, or, if
+wrought iron is to be welded to steel, a cast iron rod may be used. A cast
+iron flux is well suited for this work. It should be noted that wrought
+iron turns to ordinary cast iron if kept heated for any length of time.
+
+_Steel._--Steel should be beveled if more than one-eighth inch in
+thickness. It requires only a local preheating around the point to be
+welded. The welding flame should be absolutely neutral, without excess of
+either gas. If the metal is one-sixteenth inch or less in thickness, the
+tip of the blue-white cone must be held a short distance from the surface
+of the work; in all other cases the tip of this cone is touched to the
+metal being welded.
+
+The welding rod may be of mild, low carbon steel or of Norway iron. Nickel
+steel rods may be used for parts requiring great strength, but vanadium
+alloys are very difficult to handle. A very satisfactory rod is made by
+twisting together two wires of the required material. The rod must be kept
+constantly in contact with the work and should not be added until the edges
+are thoroughly melted. The flux may or may not be used. If one is wanted,
+it may be made from three parts iron filings, six parts borax and one part
+sal ammoniac.
+
+It will be noticed that the steel runs from the flame, but tends to hold
+together. Should foaming commence in the molten metal, it shows an excess
+of oxygen and that the metal is being burned.
+
+High carbon steels are very difficult to handle. It is claimed that a drop
+or two of copper added to the weld will assist the flow, but will also
+harden the work. An excess of oxygen reduces the amount of carbon and
+softens the steel, while an excess of acetylene increases the proportion of
+carbon and hardens the metal. High speed steels may sometimes be welded if
+first coated with semi-steel before welding.
+
+_Aluminum._--This is the most difficult of the commonly found metals
+to weld. This is caused by its high rate of expansion and contraction and
+its liability to melt and fall away from under the flame. The aluminum
+seems to melt on the inside first, and, without previous warning, a portion
+of the work will simply vanish from in front of the operator's eyes. The
+metal tends to run from the flame and separate at the same time. To keep
+the metal in shape and free from oxide, it is worked or puddled while in a
+plastic condition by an iron rod which has been flattened at one end.
+Several of these rods should be at hand and may be kept in a jar of salt
+water while not being used. These rods must not become coated with aluminum
+and they must not get red hot while in the weld.
+
+The surfaces to be joined, together with the adjacent parts, should be
+cleaned thoroughly and then washed with a 25 per cent solution of nitric
+acid in hot water, used on a swab. The parts should then be rinsed in clean
+water and dried with sawdust. It is also well to make temporary fire clay
+moulds back of the parts to be heated, so that the metal may be flowed into
+place and allowed to cool without danger of breakage.
+
+Aluminum must invariably be preheated to about 600 degrees, and the whole
+piece being handled should be well covered with sheet asbestos to prevent
+excessive heat radiation.
+
+The flame is formed with an excess of acetylene such that the second cone
+extends about an inch, or slightly more, beyond the small blue-white point.
+The torch should be held so that the end of this second cone is in contact
+with the work, the small cone ordinarily used being kept an inch or an inch
+and a half from the surface of the work.
+
+Welding rods of special aluminum are used and must be handled with their
+end submerged in the molten metal of the weld at all times.
+
+When aluminum is melted it forms alumina, an oxide of the metal. This
+alumina surrounds small masses of the metal, and as it does not melt at
+temperatures below 5000 degrees (while aluminum melts at about 1200), it
+prevents a weld from being made. The formation of this oxide is retarded
+and the oxide itself is dissolved by a suitable flux, which usually
+contains phosphorus to break down the alumina.
+
+_Copper._--The whole piece should be preheated and kept well covered
+while welding. The flame must be much larger than for the same thickness of
+steel and neutral in character. A slight excess of acetylene would be
+preferable to an excess of oxygen, and in all cases the molten metal should
+be kept enveloped with the flame. The welding rod is of copper which
+contains phosphorus; and a flux, also containing phosphorus, should be
+spread for about an inch each side of the joint. These assist in preventing
+oxidation, which is sure to occur with heated copper.
+
+Copper breaks very easily at a heat slightly under the welding temperature
+and after cooling it is simply cast copper in all cases.
+
+_Brass and Bronze._--It is necessary to preheat these metals, although
+not to a very high temperature. They must be kept well covered at all times
+to prevent undue radiation. The flame should be produced with a nozzle one
+size larger than for the same thickness of steel and the small blue-white
+cone should be held from one-fourth to one-half inch above the surface of
+the work. The flame should be neutral in character.
+
+A rod or wire of soft brass containing a large percentage of zinc is
+suitable for adding to brass, while copper requires the use of copper or
+manganese bronze rods. Special flux or borax may be used to assist the
+flow.
+
+The emission of white smoke indicates that the zinc contained in these
+alloys is being burned away and the heat should immediately be turned away
+or reduced. The fumes from brass and bronze welding are very poisonous and
+should not be breathed.
+
+
+RESTORATION OF STEEL
+
+The result of the high heat to which the steel has been subjected is that
+it is weakened and of a different character than before welding. The
+operator may avoid this as much as possible by first playing the outer
+flame of the torch all over the surfaces of the work just completed until
+these faces are all of uniform color, after which the metal should be well
+covered with asbestos and allowed to cool without being disturbed. If a
+temporary heating oven has been employed, the work and oven should be
+allowed to cool together while protected with the sheet asbestos. If the
+outside air strikes the freshly welded work, even for a moment, the result
+will be breakage.
+
+A weld in steel will always leave the metal with a coarse grain and with
+all the characteristics of rather low grade cast steel. As previously
+mentioned in another chapter, the larger the grain size in steel the weaker
+the metal will be, and it is the purpose of the good workman to avoid, as
+far as possible, this weakening.
+
+The structure of the metal in one piece of steel will differ according to
+the heat that it has under gone. The parts of the work that have been at
+the melting point will, therefore, have the largest grain size and the
+least strength. Those parts that have not suffered any great rise in
+temperature will be practically unaffected, and all the parts between these
+two extremes will be weaker or stronger according to their distance from
+the weld itself. To restore the steel so that it will have the best grain
+size, the operator may resort to either of two methods: (1) The grain may
+be improved by forging. That means that the metal added to the weld and the
+surfaces that have been at the welding heat are hammered much as a
+blacksmith would hammer his finished work to give it greater strength. The
+hammering should continue from the time the metal first starts to cool
+until it has reached the temperature at which the grain size is best for
+strength. This temperature will vary somewhat with the composition of the
+metal being handled, but in a general way, it may be stated that the
+hammering should continue without intermission from the time the flame is
+removed from the weld until the steel just begins to show attraction for a
+magnet presented to it. This temperature of magnetic attraction will always
+be low enough and the hammering should be immediately discontinued at this
+point. (2) A method that is more satisfactory, although harder to apply, is
+that of reheating the steel to a certain temperature throughout its whole
+mass where the heat has had any effect, and then allowing slow and even
+cooling from this temperature. The grain size is affected by the
+temperature at which the reheating is stopped, and not by the cooling, yet
+the cooling should be slow enough to avoid strains caused by uneven
+contraction.
+
+After the weld has been completed the steel must be allowed to cool until
+below 1200° Fahrenheit. The next step is to heat the work slowly until all
+those parts to be restored have reached a temperature at which the magnet
+just ceases to be attracted. While the very best temperature will vary
+according to the nature and hardness of the steel being handled, it will be
+safe to carry the heating to the point indicated by the magnet in the
+absence of suitable means of measuring accurately these high temperatures.
+In using a magnet for testing, it will be most satisfactory if it is an
+electromagnet and not of the permanent type. The electric current may be
+secured from any small battery and will be the means of making sure of the
+test. The permanent magnet will quickly lose its power of attraction under
+the combined action of the heat and the jarring to which it will be
+subjected.
+
+In reheating the work it is necessary to make sure that no part reaches a
+temperature above that desired for best grain size and also to see that all
+parts are brought to this temperature. Here enters the greatest difficulty
+in restoring the metal. The heating may be done so slowly that no part of
+the work on the outside reaches too high a temperature and then keeps the
+outside at this heat until the entire mass is at the same temperature. A
+less desirable way is to heat the outside higher than this temperature and
+allow the conductivity of the metal to distribute the excess to the inside.
+
+The most satisfactory method, where it can be employed, is to make use of a
+bath of some molten metal or some chemical mixture that can be kept at the
+exact heat necessary by means of gas fires that admit of close regulation.
+The temperature of these baths may be maintained at a constant point by
+watching a pyrometer, and the finished work may be allowed to remain in the
+bath until all parts have reached the desired temperature.
+
+
+WELDING INFORMATION
+
+The following tables include much of the information that the operator must
+use continually to handle the various metals successfully. The temperature
+scales are given for convenience only. The composition of various alloys
+will give an idea of the difficulties to be contended with by consulting
+the information on welding various metals. The remaining tables are of
+self-evident value in this work.
+
+TEMPERATURE SCALES
+Centigrade  Fahrenheit      Centigrade  Fahrenheit
+   200°        392°            1000°      1832°
+   225°        437°            1050°      1922°
+   250°        482°            1100°      2012°
+   275°        527°            1150°      2102°
+   300°        572°            1200°      2192°
+   325°        617°            1250°      2282°
+   350°        662°            1300°      2372°
+   375°        707°            1350°      2462°
+   400°        752°            1400°      2552°
+   425°        797°            1450°      2642°
+   450°        842°            1500°      2732°
+   475°        887°            1550°      2822°
+   500°        932°            1600°      2912°
+   525°        977°            1650°      3002°
+   550°       1022°            1700°      3092°
+   575°       1067°            1750°      3182°
+   600°       1112°            1800°      3272°
+   625°       1157°            1850°      3362°
+   650°       1202°            1900°      3452°
+   675°       1247°            2000°      3632°
+   700°       1292°            2050°      3722°
+   725°       1337°            2100°      3812°
+   750°       1382°            2150°      3902°
+   775°       1427°            2200°      3992°
+   800°       1472°            2250°      4082°
+   825°       1517°            2300°      4172°
+   850°       1562°            2350°      4262°
+   875°       1607°            2400°      4352°
+   900°       1652°            2450°      4442°
+   925°       1697°            2500°      4532°
+   950°       1742°            2550°      4622°
+   975°       1787°            2600°      4712°
+
+METAL ALLOYS
+(Society of Automobile Engineers)
+
+Babbitt--
+  Tin...........................           84.00%
+  Antimony......................            9.00%
+  Copper........................            7.00%
+
+Brass, White--
+  Copper........................  3.00% to  6.00%
+  Tin (minimum) ................           65.00%
+  Zinc.......................... 28.00% to 30.00%
+
+Brass, Red Cast--
+  Copper........................           85.00%
+  Tin...........................            5.00%
+  Lead..........................            5.00%
+  Zinc..........................            5.00%
+
+Brass, Yellow--
+  Copper........................ 62.00% to 65.00%
+  Lead..........................  2.00% to  4.00%
+  Zinc.......................... 36.00% to 31.00%
+
+Bronze, Hard--
+  Copper........................ 87.00% to 88.00%
+  Tin...........................  9.50% to 10.50%
+  Zinc..........................  1.50% to  2.50%
+
+Bronze, Phosphor--
+  Copper........................           80.00%
+  Tin...........................           10.00%
+  Lead..........................           10.00%
+  Phosphorus....................   .50% to   .25%
+
+Bronze, Manganese--
+  Copper (approximate) .........           60.00%
+  Zinc (approximate) ...........           40.00%
+  Manganese (variable) .........            small
+
+Bronze, Gear--
+  Copper........................ 88.00% to 89.00%
+  Tin........................... 11.00% to 12.00%
+
+Aluminum Alloys--
+          Aluminum   Copper   Zinc   Manganese
+  No. 1.. 90.00%    8.5-7.0%
+  No. 2.. 80.00%    2.0-3.0%  15%  Not over 0.40%
+  No. 3.. 65.00%              35.0%
+
+Cast Iron--
+                      Gray Iron      Malleable
+  Total carbon........3.0 to 3.5%
+  Combined carbon.....0.4 to 0.7%
+  Manganese...........0.4 to 0.7%    0.3 to 0.7%
+  Phosphorus..........0.6 to 1.0%  Not over 0.2%
+  Sulphur...........Not over 0.1%  Not over 0.6%
+  Silicon............1.75 to 2.25% Not over 1.0%
+
+Carbon Steel (10 Point)--
+  Carbon........................     .05% to .15%
+  Manganese.....................     .30% to .60%
+  Phosphorus (maximum)..........             .045%
+  Sulphur (maximum).............             .05%
+(20 Point)--
+  Carbon........................     .15% to .25%
+  Manganese.....................     .30% to .60%
+  Phosphorus (maximum)..........             .045%
+  Sulphur (maximum).............             .05%
+(35 Point)--
+  Manganese.....................     .50% to .80%
+  Carbon........................     .30% to .40%
+  Phosphorus (maximum)..........             .05%
+  Sulphur (maximum).............             .05%
+(95 Point)--
+  Carbon........................    .90% to 1.05%
+  Manganese.....................    .25% to  .50%
+  Phosphorus (maximum)..........             .04%
+  Sulphur (maximum).............             .05%
+
+HEATING POWER OF FUEL GASES
+
+(In B.T.U. per Cubic Foot.)
+  Acetylene....... 1498.99   Ethylene....... 1562.9
+  Hydrogen........  291.96   Methane........  953.6
+  Alcohol......... 1501.76
+
+MELTING POINTS OF METALS
+  Platinum....................3200°
+  Iron, wrought...............2900°
+    malleable.................2500°
+    cast......................2400°
+    pure......................2760°
+  Steel, mild.................2700°
+    Medium....................2600°
+    Hard......................2500°
+  Copper......................1950°
+  Brass.......................1800°
+  Silver......................1750°
+  Bronze......................1700°
+  Aluminum....................1175°
+  Antimony....................1150°
+  Zinc........................ 800°
+  Lead........................ 620°
+  Babbitt..................500-700°
+  Solder...................500-575°
+  Tin......................... 450°
+
+_NOTE.--These melting points are for average compositions and conditions.
+The exact proportion of elements entering into the metals affects their
+melting points one way or the other in practice._
+
+TENSILE STRENGTH OF METALS
+
+Alloy steels can be made with tensile strengths as high as 300,000 pounds
+per square inch. Some carbon steels are given below according to "points":
+
+                           Pounds per Square Inch
+Steel, 10 point................ 50,000 to  65,000
+  20 point..................... 60,000 to  80,000
+  40 point..................... 70,000 to 100,000
+  60 point..................... 90,000 to 120,000
+Iron, Cast..................... 13,000 to  30,000
+  Wrought...................... 40,000 to  60,000
+  Malleable.................... 25,000 to  45,000
+Copper......................... 24,000 to  50,000
+Bronze......................... 30,000 to  60,000
+Brass, Cast.................... 12,000 to  18,000
+  Rolled....................... 30,000 to  40,000
+  Wire......................... 60,000 to  75,000
+Aluminum....................... 12,000 to  23,000
+Zinc...........................  5,000 to  15,000
+Tin............................  3,000 to   5,000
+Lead...........................  1,500 to   2,500
+
+CONDUCTIVITY OF METALS
+
+(Based on the Value of Silver as 100)
+
+                          Heat  Electricity
+Silver....................100     100
+Copper.................... 74      99
+Aluminum.................. 38      63
+Brass..................... 23      22
+Zinc...................... 19      29
+Tin....................... 14      15
+Wrought Iron.............. 12      16
+Steel..................... 11.5    12
+Cast Iron................. 11      12
+Bronze....................  9       7
+Lead......................  8       9
+
+WEIGHT OF METALS
+
+(Per Cubic Inch)
+                 Pounds                  Pounds
+Lead............  .410  Wrought Iron.....  .278
+Copper..........  .320  Tin..............  .263
+Bronze..........  .313  Cast Iron........  .260
+Brass...........  .300  Zinc.............  .258
+Steel...........  .283  Aluminum.........  .093
+
+EXPANSION OF METALS
+
+(Measured in Thousandths of an Inch per Foot of
+Length When Raised 1000 Degrees in Temperature)
+                  Inch                     Inch
+Lead............  .188  Brass............  .115
+Zinc............  .168  Copper...........  .106
+Aluminum........  .148  Steel............  .083
+Silver..........  .129  Wrought Iron.....  .078
+Bronze..........  .118  Cast Iron........  .068
+
+
+
+
+CHAPTER VI
+
+ELECTRIC WELDING
+
+
+RESISTANCE METHOD
+
+Two distinct forms of electric welding apparatus are in use, one producing
+heat by the resistance of the metal being treated to the passage of
+electric current, the other using the heat of the electric arc.
+
+The resistance process is of the greatest use in manufacturing lines where
+there is a large quantity of one kind of work to do, many thousand pieces
+of one kind, for instance. The arc method may be applied in practically any
+case where any other form of weld may be made. The resistance process will
+be described first.
+
+It is a well known fact that a poor conductor of electricity will offer so
+much resistance to the flow of electricity that it will heat. Copper is a
+good conductor, and a bar of iron, a comparatively poor conductor, when
+placed between heavy copper conductors of a welder, becomes heated in
+attempting to carry the large volume of current. The degree of heat depends
+on the amount of current and the resistance of the conductor.
+
+In an electric circuit the ends of two pieces of metal brought together
+form the point of greatest resistance in the electric circuit, and the
+abutting ends instantly begin to heat. The hotter this metal becomes, the
+greater the resistance to the flow of current; consequently, as the edges
+of the abutting ends heat, the current is forced into the adjacent cooler
+parts, until there is a uniform heat throughout the entire mass. The heat
+is first developed in the interior of the metal so that it is welded there
+as perfectly as at the surface.
+
+[Illustration: Figure 42.--Spot Welding Machine]
+
+The electric welder (Figure 42) is built to hold the parts to be joined
+between two heavy copper dies or contacts. A current of three to five
+volts, but of very great volume (amperage), is allowed to pass across
+these dies, and in going through the metal to be welded, heats the edges
+to a welding temperature. It may be explained that the voltage of an
+electric current measures the pressure or force with which it is being sent
+through the circuit and has nothing to do with the quantity or volume
+passing. Amperes measure the rate at which the current is passing through
+the circuit and consequently give a measure of the quantity which passes in
+any given time. Volts correspond to water pressure measured by pounds to
+the square inch; amperes represent the flow in gallons per minute. The low
+voltage used avoids all danger to the operator, this pressure not being
+sufficient to be felt even with the hands resting on the copper contacts.
+
+Current is supplied to the welding machine at a higher voltage and lower
+amperage than is actually used between the dies, the low voltage and high
+amperage being produced by a transformer incorporated in the machine
+itself. By means of windings of suitable size wire, the outside current may
+be received at voltages ranging from 110 to 550 and converted to the low
+pressure needed.
+
+The source of current for the resistance welder must be alternating, that
+is, the current must first be negative in value and then positive, passing
+from one extreme to the other at rates varying from 25 to 133 times a
+second. This form is known as alternating current, as opposed to direct
+current, in which there is no changing of positive and negative.
+
+The current must also be what is known as single phase, that is, a current
+which rises from zero in value to the highest point as a positive current
+and then recedes to zero before rising to the highest point of negative
+value. Two-phase of three-phase currents would give two or three positive
+impulses during this time.
+
+As long as the current is single phase alternating, the voltage and cycles
+(number of alternations per second) may be anything convenient. Various
+voltages and cycles are taken care of by specifying all these points when
+designing the transformer which is to handle the current.
+
+Direct current is not used because there is no way of reducing the voltage
+conveniently without placing resistance wires in the circuit and this uses
+power without producing useful work. Direct current may be changed to
+alternating by having a direct current motor running an alternating current
+dynamo, or the change may be made by a rotary converter, although this last
+method is not so satisfactory as the first.
+
+The voltage used in welding being so low to start with, it is absolutely
+necessary that it be maintained at the correct point. If the source of
+current supply is not of ample capacity for the welder being used, it will
+be very hard to avoid a fall of voltage when the current is forced to pass
+through the high resistance of the weld. The current voltage for various
+work is calculated accurately, and the efficiency of the outfit depends to
+a great extent on the voltage being constant.
+
+A simple test for fall of voltage is made by connecting an incandescent
+electric lamp across the supply lines at some point near the welder. The
+lamp should burn with the same brilliancy when the weld is being made as at
+any other time. If the lamp burns dim at any time, it indicates a drop in
+voltage, and this condition should be corrected.
+
+The dynamo furnishing the alternating current may be in the same building
+with the welder and operated from a direct current motor, as mentioned
+above, or operated from any convenient shafting or source of power. When
+the dynamo is a part of the welding plant it should be placed as close to
+the welding machine as possible, because the length of the wire used
+affects the voltage appreciably.
+
+In order to hold the voltage constant, the Toledo Electric Welder Company
+has devised connections which include a rheostat to insert a variable
+resistance in the field windings of the dynamo so that the voltage may be
+increased by cutting this resistance out at the proper time. An auxiliary
+switch is connected to the welder switch so that both switches act
+together. When the welder switch is closed in making a weld, that portion
+of the rheostat resistance between two arms determining the voltage is
+short circuited. This lowers the resistance and the field magnets of the
+dynamo are made stronger so that additional voltage is provided to care for
+the resistance in the metal being heated.
+
+A typical machine is shown in the accompanying cut (Figure 43). On top of
+the welder are two jaws for holding the ends of the pieces to be welded.
+The lower part of the jaws is rigid while the top is brought down on top of
+the work, acting as a clamp. These jaws carry the copper dies through which
+the current enters the work being handled. After the work is clamped
+between the jaws, the upper set is forced closer to the lower set by a long
+compression lever. The current being turned on with the surfaces of the
+work in contact, they immediately heat to the welding point when added
+pressure on the lever forces them together and completes the weld.
+
+[Illustration: Figure 43--Operating Parts of a Toledo Spot Welder]
+
+[Illustration: Figure 43a.--Method of Testing Electric Welder]
+[Illustration: Figure 44.--Detail of Water-Cooled Spot Welding Head]
+
+The transformer is carried in the base of the machine and on the left-hand
+side is a regulator for controlling the voltage for various kinds of work.
+The clamps are applied by treadles convenient to the foot of the operator.
+A treadle is provided which instantly releases both jaws upon the
+completion of the weld. One or both of the copper dies may be cooled by a
+stream of water circulating through it from the city water mains
+(Figure 44). The regulator and switch give the operator control of the
+heat, anything from a dull red to the melting point being easily obtained
+by movement of the lever (figure 45).
+
+[Illustration: Figure 45.--Welding Head of a Water-Cooled Welder]
+
+_Welding._--It is not necessary to give the metal to be welded any
+special preparation, although when very rusty or covered with scale, the
+rust and scale should be removed sufficiently to allow good contact of
+clean metal on the copper dies. The cleaner and better the stock, the less
+current it takes, and there is less wear on the dies. The dies should be
+kept firm and tight in their holders to make a good contact. All bolts and
+nuts fastening the electrical contacts should be clean and tight at all
+times.
+
+The scale may be removed from forgings by immersing them in a pickling
+solution in a wood, stone or lead-lined tank.
+
+The solution is made with five gallons of commercial sulphuric acid in
+150 gallons of water. To get the quickest and best results from this
+method, the solution should be kept as near the boiling point as possible
+by having a coil of extra heavy lead pipe running inside the tank and
+carrying live steam. A very few minutes in this bath will remove the scale
+and the parts should then be washed in running water. After this washing
+they should be dipped into a bath of 50 pounds of unslaked lime in 150
+gallons of water to neutralize any trace of acid.
+
+Cast iron cannot be commercially welded, as it is high in carbon and
+silicon, and passes suddenly from a crystalline to a fluid state when
+brought to the welding temperature. With steel or wrought iron the
+temperature must be kept below the melting point to avoid injury to the
+metal. The metal must be heated quickly and pressed together with
+sufficient force to push all burnt metal out of the joint.
+
+High carbon steel can be welded, but must be annealed after welding to
+overcome the strains set up by the heat being applied at one place. Good
+results are hard to obtain when the carbon runs as high as 75 points, and
+steel of this class can only be handled by an experienced operator. If the
+steel is below 25 points in carbon content, good welds will always be the
+result. To weld high carbon to low carbon steel, the stock should be
+clamped in the dies with the low carbon stock sticking considerably further
+out from the die than the high carbon stock. Nickel steel welds readily,
+the nickel increasing the strength of the weld.
+
+Iron and copper may be welded together by reducing the size of the copper
+end where it comes in contact with the iron. When welding copper and brass
+the pressure must be less than when welding iron. The metal is allowed to
+actually fuse or melt at the juncture and the pressure must be sufficient
+to force the burned metal out. The current is cut off the instant the metal
+ends begin to soften, this being done by means of an automatic switch which
+opens when the softening of the metal allows the ends to come together. The
+pressure is applied to the weld by having the sliding jaw moved by a weight
+on the end of an arm.
+
+Copper and brass require a larger volume of current at a lower voltage than
+for steel and iron. The die faces are set apart three times the diameter of
+the stock for brass and four times the diameter for copper.
+
+Light gauges of sheet steel can be welded to heavy gauges or to solid bars
+of steel by "spot" welding, which will be described later. Galvanized iron
+can be welded, but the zinc coating will be burned off. Sheet steel can be
+welded to cast iron, but will pull apart, tearing out particles of the
+iron.
+
+Sheet copper and sheet brass may be welded, although this work requires
+more experience than with iron and steel. Some grades of sheet aluminum can
+be spot-welded if the slight roughness left on the surface under the die
+is not objectionable.
+
+_Butt Welding._--This is the process which joins the ends of two
+pieces of metal as described in the foregoing part of this chapter. The
+ends are in plain sight of the operator at all times and it can easily be
+seen when the metal reaches the welding heat and begins to soften (Figure
+46). It is at this point that the pressure must be applied with the lever
+and the ends forced together in the weld.
+
+[Illustration: Figure 46.--Butt Welder]
+
+The parts are placed in the clamping jaws (Figure 47) with 1/8 to 1/2 inch
+of metal extending beyond the jaw. The ends of the metal touch each other
+and the current is turned on by means of a switch. To raise the ends to the
+proper heat requires from 3 seconds for 1/4-inch rods to 35 seconds for a
+1-1/2-inch bar.
+
+This method is applicable to metals having practically the same area of
+metal to be brought into contact on each end. When such parts are forced
+together a slight projection will be left in the form of a fin or an
+enlarged portion called an upset. The degree of heat required for any work
+is found by moving the handle of the regulator one way or the other while
+testing several parts. When this setting is right the work can continue as
+long as the same sizes are being handled.
+
+[Illustration: Figure 47.--Clamping Dies of a Butt Welder]
+
+Copper, brass, tool steel and all other metals that are harmed by high
+temperatures must be heated quickly and pressed together with sufficient
+force to force all burned metal from the weld.
+
+In case it is desired to make a weld in the form of a capital letter T, it
+is necessary to heat the part corresponding to the top bar of the T to a
+bright red, then bring the lower bar to the pre-heated one and again turn
+on the current, when a weld can be quickly made.
+
+_Spot Welding._--This is a method of joining metal sheets together at
+any desired point by a welded spot about the size of a rivet. It is done on
+a spot welder by fusing the metal at the point desired and at the same
+instant applying sufficient pressure to force the particles of molten metal
+together. The dies are usually placed one above the other so that the work
+may rest on the lower one while the upper one is brought down on top of the
+upper sheet to be welded.
+
+One of the dies is usually pointed slightly, the opposing one being left
+flat. The pointed die leaves a slight indentation on one side of the metal,
+while the other side is left smooth. The dies may be reversed so that the
+outside surface of any work may be left smooth. The current is allowed to
+flow through the dies by a switch which is closed after pressure is applied
+to the work.
+
+There is a limit to the thickness of sheet metal that can be welded by this
+process because of the fact that the copper rods can only carry a certain
+quantity of current without becoming unduly heated themselves. Another
+reason is that it is difficult to make heavy sections of metal touch at the
+welding point without excessive pressure.
+
+_Lap welding_ is the process used when two pieces of metal are caused
+to overlap and when brought to a welding heat are forced together by
+passing through rollers, or under a press, thus leaving the welded joint
+practically the same thickness as the balance of the work.
+
+Where it is desirable to make a continuous seam, a special machine is
+required, or an attachment for one of the other types. In this form of work
+the stock must be thoroughly cleaned and is then passed between copper
+rollers which act in the same capacity as the copper dies.
+
+_Other Applications._--Hardening and tempering can be done by clamping
+the work in the welding dies and setting the control and time to bring the
+metal to the proper color, when it is cooled in the usual manner.
+
+Brazing is done by clamping the work in the jaws and heating until the
+flux, then the spelter has melted and run into the joint. Riveting and
+heading of rivets can be done by bringing the dies down on opposite ends of
+the rivet after it has been inserted in the hole, the dies being shaped to
+form the heads properly.
+
+Hardened steel may be softened and annealed so that it can be machined by
+connecting the dies of the welder to each side of the point to be softened.
+The current is then applied until the work has reached a point at which it
+will soften when cooled.
+
+_Troubles and Remedies._--The following methods have been furnished by
+the Toledo Electric Welder Company and are recommended for this class of
+work whenever necessary.
+
+To locate grounds in the primary or high voltage side of the circuit,
+connect incandescent lamps in series by means of a long piece of lamp cord,
+as shown, in Figure 43a. For 110 volts use one lamp, for 220 volts use two
+lamps and for 440 volts use four lamps. Attach one end of the lamp cord to
+one side of the switch, and close the switch. Take the other end of the
+cord in the hand and press it against some part of the welder frame where
+the metal is clean and bright. Paint, grease and dirt act as insulators and
+prevent electrical contact. If the lamp lights, the circuit is in
+electrical contact with the frame; in other words, grounded. If the lamps
+do not light, connect the wire to a terminal block, die or slide. If the
+lamps then light, the circuit, coils or leads are in electrical contact
+with the large coil in the transformer or its connections.
+
+If, however, the lamps do not light in either case, the lamp cord should be
+disconnected from the switch and connected to the other side, and the
+operations of connecting to welder frame, dies, terminal blocks, etc., as
+explained above, should be repeated. If the lamps light at any of these
+connections, a "ground" is indicated. "Grounds" can usually be found by
+carefully tracing the primary circuit until a place is found where the
+insulation is defective. Reinsulate and make the above tests again to make
+sure everything is clear. If the ground can not be located by observation,
+the various parts of the primary circuit should be disconnected, and the
+transformer, switch, regulator, etc., tested separately.
+
+To locate a ground in the regulator or other part, disconnect the lines
+running to the welder from the switch. The test lamps used in the previous
+tests are connected, one end of lamp cord to the switch, the other end to a
+binding post of the regulator. Connect the other side of the switch to some
+part of the regulator housing. (This must be a clean connection to a bolt
+head or the paint should be scraped off.) Close the switch. If the lamps
+light, the regulator winding or some part of the switch is "grounded" to
+the iron base or core of the regulator. If the lamps do not light, this
+part of the apparatus is clear.
+
+This test can be easily applied to any part of the welder outfit by
+connecting to the current carrying part of the apparatus, and to the iron
+base or frame that should not carry current. If the lamps light, it
+indicates that the insulation is broken down or is defective.
+
+An A.C. voltmeter can, of course, be substituted for the lamps, or a D.C.
+voltmeter with D.C. current can be used in making the tests.
+
+A short circuit in the primary is caused by the insulation of the coils
+becoming defective and allowing the bare copper wires to touch each other.
+This may result in a "burn out" of one or more of the transformer coils, if
+the trouble is in the transformer, or in the continued blowing of fuses in
+the line. Feel of each coil separately. If a short circuit exists in a coil
+it will heat excessively. Examine all the wires; the insulation may have
+worn through and two of them may cross, or be in contact with the frame or
+other part of the welder. A short circuit in the regulator winding is
+indicated by failure of the apparatus to regulate properly, and sometimes,
+though not always, by the heating of the regulator coils.
+
+The remedy for a short circuit is to reinsulate the defective parts. It is
+a good plan to prevent trouble by examining the wiring occasionally and see
+that the insulation is perfect.
+
+_To Locate Grounds and Short Circuits in the Secondary, or Low Voltage
+Side._--Trouble of this kind is indicated by the machine acting sluggish
+or, perhaps, refusing to operate. To make a test, it will be necessary to
+first ascertain the exciting current of your particular transformer. This
+is the current the transformer draws on "open circuit," or when supplied
+with current from the line with no stock in the welder dies. The following
+table will give this information close enough for all practical purposes:
+
+K.W.      ----------------- Amperes at ----------------
+Rating    110 Volts   220 Volts   440 Volts   550 Volts
+3         1.5         .75         .38         .3
+5         2.5         1.25        .63         .5
+8         3.6         1.8         .9          .72
+10        4.25        2.13        1.07        .85
+15        6.          3.          1.5         1.2
+20        7.          3.5         1.75        1.4
+30        9.          4.5         2.25        1.8
+35        9.6         4.8         2.4         1.92
+50        10.         5.          2.5         2
+
+Remove the fuses from the wall switch and substitute fuses just large
+enough to carry the "exciting" current. If no suitable fuses are at hand,
+fine strands of copper from an ordinary lamp cord may be used. These
+strands are usually No. 30 gauge wire and will fuse at about 10 amperes.
+One or more strands should be used, depending on the amount of exciting
+current, and are connected across the fuse clips in place of fuse wire.
+Place a piece of wood or fibre between the welding dies in the welder as
+though you were going to weld them. See that the regulator is on the
+highest point and close the welder switch. If the secondary circuit is
+badly grounded, current will flow through the ground, and the small fuses
+or small strands of wire will burn out. This is an indication that both
+sides of the secondary circuit are grounded or that a short circuit exists
+in a primary coil. In either case the welder should not be operated until
+the trouble is found and removed. If, however, the small fuses do not
+"blow," remove same and replace the large fuses, then disconnect wires
+running from the wall switch to the welder and substitute two pieces of
+No. 8 or No. 6 insulated copper wire, after scraping off the insulation for
+an inch or two at each end. Connect one wire from the switch to the frame
+of welder; this will leave one loose end. Hold this a foot or so away from
+the place where the insulation is cut off; then turn on the current and
+strike the free end of this wire lightly against one of the copper dies,
+drawing it away quickly. If no sparking is produced, the secondary circuit
+is free from ground, and you will then look for a broken connection in the
+circuit. Some caution must be used in making the above test, as in case one
+terminal is heavily grounded the testing wire may be fused if allowed to
+stay in contact with the die.
+
+_The Remedy._--Clean the slides, dies and terminal blocks thoroughly
+and dry out the fibre insulation if it is damp. See that no scale or metal
+has worked under the sliding parts, and that the secondary leads do not
+touch the frame. If the ground is very heavy it may be necessary to remove
+the slides in order to facilitate the examination and removal of the
+ground. Insulation, where torn or worn through, must be carefully replaced
+or taped. If the transformer coils are grounded to the iron core of the
+transformer or to the secondary, it may be necessary to remove the coils
+and reinsulate them at the points of contact. A short circuited coil will
+heat excessively and eventually burn out. This may mean a new coil if you
+are unable to repair the old one. In all cases the transformer windings
+should be protected from mechanical injury or dampness. Unless excessively
+overloaded, transformers will last for years without giving a moment's
+trouble, if they are not exposed to moisture or are not injured
+mechanically.
+
+The most common trouble arises from poor electrical contacts, and they are
+the cause of endless trouble and annoyance. See that all connections are
+clean and bright. Take out the dies every day or two and see that there is
+no scale, grease or dirt between them and the holders. Clean them
+thoroughly before replacing. Tighten the bolts running from the transformer
+leads to the work jaws.
+
+
+ELECTRIC ARC WELDING
+
+This method bears no relation to the one just considered, except that the
+source of heat is the same in both cases. Arc welding makes use of the
+flame produced by the voltaic arc in practically the same way that
+oxy-acetylene welding uses the flame from the gases.
+
+If the ends of two pieces of carbon through which a current of electricity
+is flowing while they are in contact are separated from each other quite
+slowly, a brilliant arc of flame is formed between them which consists
+mainly of carbon vapor. The carbons are consumed by combination with the
+oxygen in the air and through being turned to a gas under the intense heat.
+
+The most intense action takes place at the center of the carbon which
+carries the positive current and this is the point of greatest heat. The
+temperature at this point in the arc is greater than can be produced by any
+other means under human control.
+
+An arc may be formed between pieces of metal, called electrodes, in the
+same way as between carbon. The metallic arc is called a flaming arc and as
+the metal of the electrode burns with the heat, it gives the flame a color
+characteristic of the material being used. The metallic arc may be drawn
+out to a much greater length than one formed between carbon electrodes.
+
+Arc Welding is carried out by drawing a piece of carbon which is of
+negative polarity away from the pieces of metal to be welded while the
+metal is made positive in polarity. The negative wire is fastened to the
+carbon electrode and the work is laid on a table made of cast or wrought
+iron to which the positive wire is made fast. The direction of the flame is
+then from the metal being welded to the carbon and the work is thus
+prevented from being saturated with carbon, which would prove very
+detrimental to its strength. A secondary advantage is found in the fact
+that the greatest heat is at the metal being welded because of its being
+the positive electrode.
+
+The carbon electrode is usually made from one quarter to one and a half
+inches in diameter and from six to twelve inches in length. The length of
+the arc may be anywhere from one inch to four inches, depending on the size
+of the work being handled.
+
+While the parts are carefully insulated to avoid danger of shock, it is
+necessary for the operator to wear rubber gloves as a further protection,
+and to wear some form of hood over the head to shield him against the
+extreme heat liberated. This hood may be made from metal, although some
+material that does not conduct electricity is to be preferred. The work is
+watched through pieces of glass formed with one sheet, which is either blue
+or green, placed over another which is red. Screens of glass are sometimes
+used without the head protector. Some protection for the eyes is absolutely
+necessary because of the intense white light.
+
+It is seldom necessary to preheat the work as with the gas processes,
+because the heat is localized at the point of welding and the action is so
+rapid that the expansion is not so great. The necessity of preheating,
+however, depends entirely on the material, form and size of the work being
+handled. The same advice applies to arc welding as to the gas flame method
+but in a lesser degree. Filling rods are used in the same way as with any
+other flame process.
+
+It is the purpose of this explanation to state the fundamental principles
+of the application of the electric arc to welding metals, and by applying
+the principles the following questions will be answered:
+
+What metals can be welded by the electric arc?
+
+What difficulties are to be encountered in applying the electric arc to
+welding?
+
+What is the strength of the weld in comparison with the original piece?
+
+What is the function of the arc welding machine itself?
+
+What is the comparative application of the electric arc and the
+oxy-acetylene method and others of a similar nature?
+
+The answers to these questions will make it possible to understand the
+application of this process to any work. In a great many places the use of
+the arc is cutting the cost of welding to a very small fraction of what it
+would be by any other method, so that the importance of this method may be
+well understood.
+
+Any two metals which are brought to the melting temperature and applied to
+each other will adhere so that they are no more apt to break at the weld
+than at any other point outside of the weld. It is the property of all
+metals to stick together under these conditions. The electric arc is used
+in this connection merely as a heating agent. This is its only function in
+the process.
+
+It has advantages in its ease of application and the cheapness with which
+heat can be liberated at any given point by its use. There is nothing in
+connection with arc welding that the above principles will not answer; that
+is, that metals at the melting point will weld and that the electric arc
+will furnish the heat to bring them to this point. As to the first
+question, what metals can be welded, all metals can be welded.
+
+The difficulties which are encountered are as follows:
+
+In the case of brass or zinc, the metals will be covered with a coat of
+zinc oxide before they reach a welding heat. This zinc oxide makes it
+impossible for two clean surfaces to come together and some method has to
+be used for eliminating this possibility and allowing the two surfaces to
+join without the possibility of the oxide intervening. The same is true of
+aluminum, in which the oxide, alumina, will be formed, and with several
+other alloys comprising elements of different melting points.
+
+In order to eliminate these oxides, it is necessary in practical work, to
+puddle the weld; this is, to have a sufficient quantity of molten metal at
+the weld so that the oxide is floated away. When this is done, the two
+surfaces which are to be joined are covered with a coat of melted metal on
+which floats the oxide and other impurities. The two pieces are thus
+allowed to join while their surfaces are protected. This precaution is not
+necessary in working with steel except in extreme cases.
+
+Another difficulty which is met with in the welding of a great many metals
+is their expansion under heat, which results in so great a contraction when
+the weld cools that the metal is left with a considerable strain on it. In
+extreme cases this will result in cracking at the weld or near it. To
+eliminate this danger it is necessary to apply heat either all over the
+piece to be welded or at certain points. In the case of cast iron and
+sometimes with copper it is necessary to anneal after welding, since
+otherwise the welded pieces will be very brittle on account of the
+chilling. This is also true of malleable iron.
+
+Very thin metals which are welded together and are not backed up by
+something to carry away the excess heat, are very apt to burn through,
+leaving a hole where the weld should be. This difficulty can be eliminated
+by backing up the weld with a metal face or by decreasing the intensity of
+the arc so that this melting through will not occur. However, the practical
+limit for arc welding without backing up the work with a metal face or
+decreasing the intensity of the arc is approximately 22 gauge, although
+thinner metal can be welded by a very skillful and careful operator.
+
+One difficulty with arc welding is the lack of skillful operators. This
+method is often looked upon as being something out of the ordinary and
+governed by laws entirely different from other welding. As a matter of
+fact, it does not take as much skill to make a good arc weld as it does to
+make a good weld in a forge fire as the blacksmith does it. There are few
+jobs which cannot be handled successfully by an operator of average
+intelligence with one week's instructions, although his work will become
+better and better in quality as he continues to use the arc.
+
+Now comes the question of the strength of the weld after it has been made.
+This strength is equally as great as that of the metal that is used to make
+the weld. It should be remembered, however, that the metal which goes into
+the weld is put in there as a casting and has not been rolled. This would
+make the strength of the weld as great as the same metal that is used for
+filling if in the cast form.
+
+Two pieces of steel could be welded together having a tensile strength at
+the weld of 50,000 pounds. Higher strengths than this can be obtained by
+the use of special alloys for the filling material or by rolling. Welds
+with a tensile strength as great as mentioned will give a result which is
+perfectly satisfactory in almost all cases.
+
+There are a great many jobs where it is possible to fill up the weld, that
+is, make the section at the point of the weld a little larger than the
+section through the rest of the piece. By doing this, the disadvantages
+of the weld being in the form of a casting in comparison with the rest of
+the piece being in the form of rolled steel can be overcome, and make the
+weld itself even stronger than the original piece.
+
+The next question is the adaptability of the electric arc in comparison
+with forge fire, oxy-acetylene or other method. The answer is somewhat
+difficult if made general. There are no doubt some cases where the use of a
+drop hammer and forge fire or the use of the oxy-acetylene torch will make,
+all things being considered, a better job than the use of the electric arc,
+although a case where this is absolutely proved is rare.
+
+The electric arc will melt metal in a weld for less than the same metal can
+be melted by the use of the oxy-acetylene torch, and, on account of the
+fact that the heat can be applied exactly where it is required and in the
+amount required, the arc can in almost all cases supply welding heat for
+less cost than a forge fire or heating furnace.
+
+The one great advantage of the oxy-acetylene method in comparison with
+other methods of welding is the fact that in some cases of very thin sheet,
+the weld can be made somewhat sooner than is possible otherwise. With metal
+of 18 gauge or thicker, this advantage is eliminated. In cutting steel, the
+oxy-acetylene torch is superior to almost any other possible method.
+
+_Arc Welding Machines._--A consideration of the function and purpose
+of the various types of arc welding machines shows that the only reason for
+the use of any machine is either for conversion of the current from
+alternating to direct, or, if the current is already direct, then the
+saving in the application of this current in the arc.
+
+It is practically out of the question to apply an alternating current arc
+to welding for the reason that in any arc practically all the heat is
+liberated at the positive electrode, which means that, in alternating
+current, half the heat is liberated at each electrode as the current
+changes its direction of flow or alternates. Another disadvantage of the
+alternating arc is that it is difficult of control and application.
+
+In all arc welding by the use of the carbon arc, the positive electrode is
+made the piece to be welded, while in welding with metallic electrodes this
+may be either the piece to be welded of the rod that is used as a filler.
+The voltage across the arc is a variable quantity, depending on the length
+of the flame, its temperature and the gases liberated in the arc. With a
+carbon electrode the voltage will vary from zero to forty-five volts. With
+the metallic electrode the voltage will vary from zero to thirty volts. It
+is, therefore, necessary for the welding machine to be able to furnish to
+the arc the requisite amount of current, this amount being varied, and
+furnish it at all times at the voltage required.
+
+The simplest welding apparatus is a resistance in series with the arc. This
+is entirely satisfactory in every way except in cost of current. By the use
+of resistance in series with the arc and using 220 volts as the supply,
+from eighty to ninety per cent of the current is lost in heat at the
+resistance. Another disadvantage is the fact that most materials change
+their resistance as their temperature changes, thus making the amount of
+current for the arc a variable quantity, depending on the temperature of
+the resistance.
+
+There have been various methods originated for saving the power mentioned
+and a good many machines have been put on the market for this purpose. All
+of them save some power over what a plain resistance would use. Practically
+all arc welding machines at the present time are motor generator sets, the
+motor of which is arranged for the supply voltage and current, this motor
+being direct connected to a compound wound generator delivering
+approximately seventy-five volts direct current. Then by the use of a
+resistance, this seventy-five volt supply is applied to the arc. Since the
+voltage across the arc will vary from zero to fifty volts, this machine
+will save from zero up to seventy per cent of the power that the machine
+delivers. The rest of the power, of course, has to be dissipated in the
+resistance used in series with the arc.
+
+A motor generator set which can be purchased from any electrical company,
+with a long piece of fence wire wound around a piece of asbestos, gives
+results equally as good and at a very small part of the first cost.
+
+It is possible to construct a machine which will eliminate all losses in
+the resistance; in other words, eliminate all resistance in series with the
+arc. A machine of this kind will save its cost within a very short time,
+providing the welder is used to any extent.
+
+Putting it in figures, the results are as follows for average conditions.
+Current at 2c per kilowatt hour, metallic electrode arc of 150 amperes,
+carbon arc 500 amperes; voltage across the metallic electrode arc 20,
+voltage across the carbon arc 35. Supply current 220 volts, direct. In the
+case of the metallic electrode, if resistance is used, the cost of running
+this arc is sixty-six cents per hour. With the carbon electrode, $2.20 per
+hour. If a motor generator set with a seventy volt constant potential
+machine is used for a welder, the cost will be as follows:
+
+Metallic electrode 25.2c. Carbon electrode 84c per hour. With a machine
+which will deliver the required voltage at the arc and eliminate all the
+resistance in series with the arc, the cost will be as follows: Metallic
+electrode 7.2c per hour; carbon electrode 42c per hour. This is with the
+understanding that the arc is held constant and continuously at its full
+value. This, however, is practically impossible and the actual load factor
+is approximately fifty per cent, which would mean that operating a welder
+as it is usually operated, this result will be reduced to one-half of that
+stated in all cases.
+
+
+
+
+CHAPTER VII
+
+HAND FORGING AND WELDING
+
+
+Smithing, or blacksmithing, is the process of working heated iron, steel or
+other metals by forging, bending or welding them.
+
+_The Forge._--The metal is heated in a forge consisting of a shallow
+pan for holding the fire, in the center of which is an opening from below
+through which air is forced to make a hot fire.
+
+[Illustration: Figure 48.--Tuyere Construction on a Forge]
+
+Air is forced through this hole, called a "tuyere" (Figure 48) by means of
+a hand bellows, a rotary fan operated with crank or lever, or with a fan
+driven from an electric motor. The harder the air is driven into the fire
+above the tuyere the more oxygen is furnished and the hotter the fire
+becomes.
+
+Directly below the tuyere is an opening through which the ashes that drop
+from the fire may be cleaned out.
+
+_The Fire._--The fire is made by placing a small piece of waste soaked
+in oil, kerosene or gasoline, over the tuyere, lighting the waste, then
+starting the fan or blower slowly. Gradually cover the waste, while it is
+burning brightly, with a layer of soft coal. The coal will catch fire and
+burn after the waste has been consumed. A piece of waste half the size of a
+person's hand is ample for this purpose.
+
+The fuel should be "smithing coal." A lump of smithing coal breaks easily,
+shows clean and even on all sides and should not break into layers. The
+coal is broken into fine pieces and wet before being used on the fire.
+
+The fire should be kept deep enough so that there is always three or four
+inches of fire below the piece of metal to be heated and there should be
+enough fire above the work so that no part of the metal being heated comes
+in contact with the air. The fire should be kept as small as possible while
+following these rules as to depth.
+
+To make the fire larger, loosen the coal around the edges. To make the fire
+smaller, pack wet coal around the edges in a compact mass and loosen the
+fire in the center. Add fresh coal only around the edges of the fire. It
+will turn to coke and can then be raked onto the fire. Blow only enough air
+into the fire to keep it burning brightly, not so much that the fire is
+blown up through the top of the coal pack. To prevent the fire from going
+out between jobs, stick a piece of soft wood into it and cover with fresh
+wet coal.
+
+_Tools._--The _hammer_ is a ball pene, or blacksmith's hammer,
+weighing about a pound and a half.
+
+The _sledge_ is a heavy hammer, weighing from 5 to 20 pounds and
+having a handle 30 to 36 inches long.
+
+The _anvil_ is a heavy piece of wrought iron (Figure 49), faced with
+steel and having four legs. It has a pointed horn on one end, an
+overhanging tail on the other end and a flat top. In the tail there is a
+square hole called the "hardie" hole and a round one called the "spud"
+hole.
+
+[Illustration: Figure 49.--Anvil, Showing Horn, Tail, Hardie Hole and Spud
+Hole]
+
+_Tongs_, with handles about one foot long and jaws suitable for
+holding the work, are used. To secure a firm grip on the work, the jaws may
+be heated red hot and hammered into shape over the piece to be held, thus
+giving a properly formed jaw. Jaws should touch the work along their entire
+length.
+
+The _set hammer_ is a hammer, one end of whose head is square and
+flat, and from this face the head tapers evenly to the other face. The
+large face is about 1-1/4 inches square.
+
+The _flatter_ is a hammer having one face of its head flat and about
+2-1/2 inches square.
+
+_Swages_ are hammers having specially formed faces for finishing
+rounds, squares, hexagons, ovals, tapers, etc.
+
+_Fullers_ are hammers having a rounded face, long in one direction.
+They are used for spreading metal in one direction only.
+
+The _hardy_ is a form of chisel with a short, square shank which may
+be set into the hardie hole for cutting off hot bars.
+
+_Operations._--Blacksmithing consists of bending, drawing or upsetting
+with the various hammers, or in punching holes.
+
+Bending is done over the square corners of the anvil if square cornered
+bends are desired, or over the horn of the anvil if rounding bends, eyes,
+hooks, etc., are wanted.
+
+To bend a ring or eye in the end of a bar, first figure the length of stock
+needed by multiplying the diameter of the hole by 31/7, then heat the piece
+to a good full red at a point this distance back from the end. Next bend
+the iron over at a 90 degree angle (square) at this point. Next, heat the
+iron from the bend just made clear to the point and make the eye by laying
+the part that was bent square over the horn of the anvil and bending the
+extreme tip into part of a circle. Keep pushing the piece farther and
+farther over the horn of the anvil, bending it as you go. Do not hammer
+directly over the horn of the anvil, but on the side where you are doing
+the bending.
+
+To make the outside of a bend square, sharp and full, rather than slightly
+rounding, the bent piece must be laid edgewise on the face of the anvil.
+That is, after making the bend over the corner of the anvil, lay the piece
+on top of the anvil so that its edge and not the flat side rests on the
+anvil top. With the work in this position, strike directly against the
+corner with the hammer so that the blows come in line, first with one leg
+of the work, then the other, and always directly on the corner of the
+piece. This operation cannot be performed by laying the work so that one
+leg hangs over the anvil's corner.
+
+To make a shoulder on a rod or bar, heat the work and lay flat across the
+top of the anvil with the point at which the shoulder is desired at the
+edge of the anvil. Then place the set hammer on top of the piece, with the
+outside edge of the set hammer directly over the edge of the anvil. While
+hammering in this position keep the work turning continually.
+
+To draw stock means to make it longer and thinner by hammering. A piece to
+be drawn out is usually laid across the horn of the anvil while being
+struck with the hammer. The metal is then spread in only one direction in
+place of being spread in every direction, as it would be if laid on the
+anvil face. To draw the work, heat it to as high a temperature as it will
+stand without throwing sparks and burning. The fuller may be used for
+drawing metal in place of laying the work over the horn of the anvil.
+
+When drawing round stock, it should be first drawn out square, and when
+almost down to size it may be rounded. When pointing stock, the same rule
+of first drawing out square applies.
+
+Upsetting means to make a piece shorter in length and greater in thickness
+or width, or both shorter and thicker. To upset short pieces, heat to a
+bright red at the place to be upset, then stand on end on the anvil face
+and hammer directly down on top until of the right form. Longer pieces may
+be swung against the anvil or placed upright on a heavy piece of metal
+lying on the floor or that is sunk into the floor. While standing on this
+heavy piece the metal may be upset by striking down on the end with a heavy
+hammer or the sledge. If a bend appears while upsetting, it should be
+straightened by hammering back into shape on the anvil face.
+
+Light blows affect the metal for only a short distance from the point of
+striking, but heavy blows tend to swell the metal more equally through its
+entire length. In driving rivets that should fill the holes, heavy blows
+should be struck, but to shape the end of a rivet or to make a head on a
+rod, light blows should be used.
+
+The part of the piece that is heated most will upset the most.
+
+To punch a hole through metal, use a tool steel punch with its end slightly
+tapering to a size a little smaller than the hole to be punched. The end of
+the punch must be square across and never pointed or rounded.
+
+First drive the punch part way through from one side and then turn the work
+over. When you turn it over, notice where the bulge appears and in that way
+locate the hole and drive the punch through from the second side. This
+makes a cleaner and more even hole than to drive completely through from
+one side. When the punch is driven in from the second side, the place to be
+punched through should be laid over the spud hole in the tail of the anvil
+and the piece driven out of the work.
+
+Work when hot is larger than it will be after cooling. This must be
+remembered when fitting parts or trouble will result. A two-foot bar of
+steel will be 1/4 inch longer when red hot than when cold.
+
+The temperatures of iron correspond to the following colors:
+
+  Dullest red seen in the dark...  878°
+  Dullest red seen in daylight...  887°
+  Dull red....................... 1100°
+  Full red....................... 1370°
+  Light red...................... 1550°
+  Orange......................... 1650°
+  Light orange................... 1725°
+  Yellow......................... 1825°
+  Light yellow................... 1950°
+
+_Bending Pipes and Tubes._--It is difficult to make bends or curves in
+pipes and tubing without leaving a noticeable bulge at some point of the
+work. Seamless steel tubing may be handled without very great danger of
+this trouble if care is used, but iron pipe, having a seam running
+lengthwise, must be given special attention to avoid opening the seam.
+
+Bends may be made without kinking if the tube or pipe is brought to a full
+red heat all the way around its circumference and at the place where the
+bend is desired. Hold the cool portion solidly in a vise and, by taking
+hold of the free end, bend very slowly and with a steady pull. The pipe
+must be kept at full red heat with the flames from one or more torches and
+must not be hammered to produce the bend. If a sufficient purchase cannot
+be secured on the free end by the hand, insert a piece of rod or a smaller
+pipe into the opening.
+
+While making the bend, should small bulges appear, they may be hammered
+back into shape before proceeding with the work.
+
+Tubing or pipes may be bent while being held between two flat metal
+surfaces while at a bright red heat. The metal plates at each side of the
+work prevent bulging.
+
+Another method by which tubing may be bent consists of filling completely
+with tightly packed sand and fitting a solid cap or plug at each end.
+
+Thin brass tubing may be filled with melted resin and may be bent after the
+resin cools. To remove the resin it is necessary to heat the tube, allowing
+it to run out.
+
+Large jobs of bending should be handled in special pipe bending machines in
+which the work is forced through formed rolls which prevent its bulging.
+
+
+WELDING
+
+Welding with the heat of a blacksmith forge fire, or a coal or illuminating
+gas fire, can only be performed with iron and steel because of the low heat
+which is not localized as with the oxy-acetylene and electric processes.
+Iron to be welded in this manner is heated until it reaches the temperature
+indicated by an orange color, not white, as is often stated, this orange
+color being slightly above 3600 degrees Fahrenheit. Steel is usually welded
+at a bright red heat because of the danger of oxidizing or burning the
+metal if the temperature is carried above this point.
+
+_The Fire._--If made in a forge, the fire should be built from good
+smithing coal or, better still, from coke. Gas fires are, of course,
+produced by suitable burners and require no special preparation except
+adjustment of the heat to the proper degree for the size and thickness of
+the metal being welded so that it will not be burned.
+
+A coal fire used for ordinary forging operations should not be used for
+welding because of the impurities it contains. A fresh fire should be built
+with a rather deep bed of coal, four to eight inches being about right for
+work ordinarily met with. The fire should be kept burning until the coal
+around the edges has been thoroughly coked and a sufficient quantity of
+fuel should be on and around the fire so that no fresh coal will have to
+be added while working.
+
+After the coking process has progressed sufficiently, the edges should be
+packed down and the fire made as small as possible while still surrounding
+the ends to be joined. The fire should not be altered by poking it while
+the metal is being heated. The best form of fire to use is one having
+rather high banks of coked coal on each side of the mass, leaving an
+opening or channel from end to end. This will allow the added fuel to be
+brought down on top of the fire with a small amount of disturbance.
+
+_Preparing to Weld._--If the operator is not familiar with the metal
+to be handled, it is best to secure a test piece if at all possible and try
+heating it and joining the ends. Various grades of iron and steel call for
+different methods of handling and for different degrees of heat, the proper
+method and temperature being determined best by actual test under the
+hammer.
+
+The form of the pieces also has a great deal to do with their handling,
+especially in the case of a more or less inexperienced workman. If the
+pieces are at all irregular in shape, the motions should be gone through
+with before the metal is heated and the best positions on the anvil as well
+as in the fire determined with regard to the convenience of the workman and
+speed of handling the work after being brought to a welding temperature.
+Unnatural positions at the anvil should be avoided as good work is most
+difficult of performance under these conditions.
+
+_Scarfing._--While there are many forms of welds, depending on the
+relative shape of the pieces to be joined, the portions that are to meet
+and form one piece are always shaped in the same general way, this shape
+being called a "scarf." The end of a piece of work, when scarfed, is
+tapered off on one side so that the extremity comes to a rather sharp edge.
+The other side of the piece is left flat and a continuation in the same
+straight plane with its side of the whole piece of work. The end is then in
+the form of a bevel or mitre joint (Figure 50).
+
+[Illustration: Figure 50.--Scarfing Ends of Work Ready for Welding]
+
+Scarfing may be produced in any one of several ways. The usual method is to
+bring the ends to a forging heat, at which time they are upset to give a
+larger body of metal at the ends to be joined. This body of metal is then
+hammered down to the taper on one side, the length of the tapered portion
+being about one and a half times the thickness of the whole piece being
+handled. Each piece should be given this shape before proceeding farther.
+
+The scarf may be produced by filing, sawing or chiseling the ends, although
+this is not good practice because it is then impossible to give the desired
+upset and additional metal for the weld. This added thickness is called for
+by the fact that the metal burns away to a certain extent or turns to
+scale, which is removed before welding.
+
+When the two ends have been given this shape they should not fit as closely
+together as might be expected, but should touch only at the center of the
+area to be joined (Figure 51). That is to say, the surface of the beveled
+portion should bulge in the middle or should be convex in shape so that the
+edges are separated by a little distance when the pieces are laid together
+with the bevels toward each other. This is done so that the scale which is
+formed on the metal by the heat of the fire can have a chance to escape
+from the interior of the weld as the two parts are forced together.
+
+[Illustration: Figure 51.--Proper Shape of Scarfed Ends]
+
+If the scarf were to be formed with one or more of the edges touching each
+other at the same time or before the centers did so, the scale would be
+imprisoned within the body of the weld and would cause the finished work to
+be weak, while possibly giving a satisfactory appearance from the outside.
+
+_Fluxes._--In order to assist in removing the scale and other
+impurities and to make the welding surfaces as clean as possible while
+being joined, various fluxing materials are used as in other methods of
+welding.
+
+For welding iron, a flux of white sand is usually used, this material being
+placed on the metal after it has been brought to a red heat in the fire.
+Steel is welded with dry borax powder, this flux being applied at the same
+time as the iron flux just mentioned. Borax may also be used for iron
+welding and a mixture of borax with steel borings may also be used for
+either class of work. Mixtures of sal ammoniac with borax have been
+successfully used, the proportions being about four parts of borax to one
+of sal ammoniac. Various prepared fluxing powders are on the market for
+this work, practically all of them producing satisfactory results.
+
+After the metal has been in the fire long enough to reach a red heat, it is
+removed temporarily and, if small enough in size, the ends are dipped into
+a box of flux. If the pieces are large, they may simply be pulled to the
+edge of the fire and the flux then sprinkled on the portions to be joined.
+A greater quantity of flux is required in forge welding than in electric or
+oxy-acetylene processes because of the losses in the fire. After the powder
+has been applied to the surfaces, the work is returned to the fire and
+heated to the welding temperature.
+
+_Heating the Work._--After being scarfed, the two pieces to be welded
+are placed in the fire and brought to the correct temperature. This
+temperature can only be recognized by experiment and experience. The metal
+must be just below that point at which small sparks begin to be thrown out
+of the fire and naturally this is a hard point to distinguish. At the
+welding heat the metal is almost ready to flow and is about the consistency
+of putty. Against the background of the fire and coal the color appears to
+be a cream or very light yellow and the work feels soft as it is handled.
+
+It is absolutely necessary that both parts be heated uniformly and so that
+they reach the welding temperature at the same time. For this reason they
+should be as close together in the fire as possible and side by side. When
+removed to be hammered together, time is saved if they are picked up in
+such a way that when laid together naturally the beveled surfaces come
+together. This makes it necessary that the workman remember whether the
+scarfed side is up or down, and to assist in this it is a good thing to
+mark the scarfed side with chalk or in some other noticeable manner, so
+that no mistake will be made in the hurry of placing the work on the anvil.
+
+The common practice in heating allows the temperature to rise until the
+small white sparks are seen to come from the fire. Any heating above this
+point will surely result in burning that will ruin the iron or steel being
+handled. The best welding heat can be discerned by the appearance of the
+metal and its color after experience has been gained with this particular
+material. Test welds can be made and then broken, if possible, so that the
+strength gained through different degrees of heat can be known before
+attempting more important work.
+
+_Welding._--When the work has reached the welding temperature after
+having been replaced in the fire with the flux applied, the two parts are
+quickly tapped to remove the loose scale from their surfaces. They are then
+immediately laid across the top of the anvil, being placed in a diagonal
+position if both pieces are straight. The lower piece is rested on the
+anvil first with the scarf turned up and ready to receive the top piece in
+the position desired. The second piece must be laid in exactly the position
+it is to finally occupy because the two parts will stick together as soon
+as they touch and they cannot well be moved after having once been allowed
+to come in contact with each other. This part of the work must be done
+without any unnecessary loss of time because the comparatively low heat at
+which the parts weld allows them to cool below the working temperature in
+a few seconds.
+
+The greatest difficulty will be experienced in withdrawing the metal from
+the fire before it becomes burned and in getting it joined before it cools
+below this critical point. The beveled edges of the scarf are, of course,
+the first parts to cool and the weld must be made before they reach a point
+at which they will not join, or else the work will be defective in
+appearance and in fact.
+
+If the parts being handled are of such a shape that there is danger of
+bending a portion back of the weld, this part may be cooled by quickly
+dipping it into water before laying the work on the anvil to be joined.
+
+The workman uses a heavy hand hammer in making the joint, and his helper,
+if one is employed, uses a sledge. With the two parts of the work in place
+on the anvil, the workman strikes several light blows, the first ones being
+at a point directly over the center of the weld, so that the joint will
+start from this point and be worked toward the edges. After the pieces have
+united the helper strikes alternate blows with his sledge, always striking
+in exactly the same place as the last stroke of the workman. The hammer
+blows are carried nearer and nearer to the edges of the weld and are made
+steadily heavier as the work progresses.
+
+The aim during the first part of the operation should be to make a perfect
+joint, with every part of the surfaces united, and too much attention
+should not be paid to appearance, at least not enough to take any chance
+with the strength of the work.
+
+It will be found, after completion of the weld, that there has been a loss
+in length equal to one-half the thickness of the metal being welded. This
+loss is occasioned by the burned metal and the scale which has been formed.
+
+_Finishing the Weld._--If it is possible to do so, the material should
+be hammered into the shape that it should remain with the same heat that
+was used for welding. It will usually be found, however, that the metal has
+cooled below the point at which it can be worked to advantage. It should
+then be replaced in the fire and brought back to a forging heat.
+
+[Illustration: Figure 52.--Upsetting and Scarfing the End of a Rod]
+
+While shaping the work at this forging heat every part that has been at a
+red heat should be hammered with uniformly light and even blows as it
+cools. This restores the grain and strength of the iron or steel to a great
+extent and makes the unavoidable weakness as small as possible.
+
+_Forms of Welds._--The simplest of all welds is that called a "lap
+weld." This is made between the ends of two pieces of equal size and
+similar form by scarfing them as described and then laying one on top of
+the other while they are hammered together.
+
+A butt weld (Figure 52) is made between the ends of two pieces of shaft or
+other bar shapes by upsetting the ends so that they have a considerable
+flare and shaping the face of the end so that it is slightly higher in the
+center than around the edges, this being done to make the centers come
+together first. The pieces are heated and pushed into contact, after which
+the hammering is done as with any other weld.
+
+[Illustration: Figure 53.--Scarfing for a T Weld]
+
+A form similar to the butt weld in some ways is used for joining the end of
+a bar to a flat surface and is called a jump weld. The bar is shaped in the
+same way as for a butt weld. The flat plate may be left as it is, but if
+possible a depression should be made at the point where the shaft is to be
+placed. With the two parts heated as usual, the bar is dropped into
+position and hammered from above. As soon as the center of the weld has
+been made perfect, the joint may be finished with a fuller driven all the
+way around the edge of the joint.
+
+When it is required to join a bar to another bar or to the edge of any
+piece at right angles the work is called a "T" weld from its shape when
+complete (Figure 53). The end of the bar is scarfed as described and the
+point of the other bar or piece where the weld is to be made is hammered so
+that it tapers to a thin edge like one-half of a circular depression. The
+pieces are then laid together and hammered as for a lap weld.
+
+The ends of heavy bar shapes are often joined with a "V," or cleft, weld.
+One bar end is shaped so that it is tapering on both sides and comes to a
+broad edge like the end of a chisel. The other bar is heated to a forging
+temperature and then slit open in a lengthwise direction so that the
+V-shaped opening which is formed will just receive the pointed edge of the
+first piece. With the work at welding heat, the two parts are driven
+together by hammering on the rear ends and the hammering then continues as
+with a lap weld, except that the work is turned over to complete both sides
+of the joint.
+
+[Illustration: Figure 54.-Splitting Ends to Be Welded in Thin Work]
+
+The forms so far described all require that the pieces be laid together in
+the proper position after removal from the fire, and this always causes a
+slight loss of time and a consequent lowering of the temperature. With very
+light stock, this fall of temperature would be so rapid that the weld would
+be unsuccessful, and in this case the "lock" weld is resorted to. The ends
+of the two pieces to be joined are split for some distance back, and
+one-half of each end is bent up and the other half down (Figure 54). The
+two are then pushed together and placed in the fire in this position. When
+the welding heat is reached, it is only necessary to take the work out of
+the fire and hammer the parts together, inasmuch as they are already in the
+correct position.
+
+Other forms of welds in which the parts are too small to retain their heat,
+can be made by first riveting them together or cutting them so that they
+can be temporarily fastened in any convenient way when first placed in the
+fire.
+
+
+
+
+CHAPTER VIII
+
+SOLDERING, BRAZING AND THERMIT WELDING
+
+
+SOLDERING
+
+Common solder is an alloy of one-half lead with one-half tin, and is called
+"half and half." Hard solder is made with two-thirds tin and one-third
+lead. These alloys, when heated, are used to join surfaces of the same or
+dissimilar metals such as copper, brass, lead, galvanized iron, zinc,
+tinned plate, etc. These metals are easily joined, but the action of solder
+with iron, steel and aluminum is not so satisfactory and requires greater
+care and skill.
+
+The solder is caused to make a perfect union with the surfaces treated with
+the help of heat from a soldering iron. The soldering iron is made from a
+piece of copper, pointed at one end and with the other end attached to an
+iron rod and wooden handle. A flux is used to remove impurities from the
+joint and allow the solder to secure a firm union with the metal surface.
+The iron, and in many cases the work, is heated with a gasoline blow torch,
+a small gas furnace, an electric heater or an acetylene and air torch.
+
+The gasoline torch which is most commonly used should be filled two-thirds
+full of gasoline through the hole in the bottom, which is closed by a screw
+plug. After working the small hand pump for 10 to 20 strokes, hold the palm
+of your hand over the end of the large iron tube on top of the torch and
+open the gasoline needle valve about a half turn. Hold the torch so that
+the liquid runs down into the cup below the tube and fills it. Shut the
+gasoline needle valve, wipe the hands dry, and set fire to the fuel in the
+cup. Just as the gasoline fire goes out, open the gasoline needle valve
+about a half turn and hold a lighted match at the end of the iron tube to
+ignite the mixture of vaporized gasoline and air. Open or close the needle
+valve to secure a flame about 4 inches long.
+
+On top of the iron tube from which the flame issues there is a rest for
+supporting the soldering iron with the copper part in the flame. Place the
+iron in the flame and allow it to remain until the copper becomes very hot,
+not quite red, but almost so.
+
+A new soldering iron or one that has been misused will have to be "tinned"
+before using. To do this, take the iron from the fire while very hot and
+rub the tip on some flux or dip it into soldering acid. Then rub the tip of
+the iron on a stick of solder or rub the solder on the iron. If the solder
+melts off the stick without coating the end of the iron, allow a few drops
+to fall on a piece of tin plate, then nil the end of the iron on the tin
+plate with considerable force. Alternately rub the iron on the solder and
+dip into flux until the tip has a coating of bright solder for about half
+an inch from the end. If the iron is in very bad shape, it may be necessary
+to scrape or file the end before dipping in the flux for the first time.
+After the end of the iron is tinned in this way, replace it on the rest of
+the torch so that the tinned point is not directly in the flame, turning
+the flame down to accomplish this.
+
+_Flux._--The commonest flux, which is called "soldering acid," is made
+by placing pieces of zinc in muriatic (hydrochloric) acid contained in a
+heavy glass or porcelain dish. There will be bubbles and considerable heat
+evolved and zinc should be added until this action ceases and the zinc
+remains in the liquid, which is now chloride of zinc.
+
+This soldering acid may be used on any metal to be soldered by applying
+with a brush or swab. For electrical work, this acid should be made neutral
+by the addition of one part ammonia and one part water to each three parts
+of the acid. This neutralized flux will not corrode metal as will the
+ordinary acid.
+
+Powdered resin makes a good flux for lead, tin plate, galvanized iron and
+aluminum. Tallow, olive oil, beeswax and vaseline are also used for this
+purpose. Muriatic acid may be used for zinc or galvanized iron without the
+addition of the zinc, as described in making zinc chloride. The addition of
+two heaping teaspoonfuls of sal ammoniac to each pint of the chloride of
+zinc is sometimes found to improve its action.
+
+_Soldering Metal Parts._--All surfaces to be joined should be fitted
+to each other as accurately as possible and then thoroughly cleaned with a
+file, emery cloth, scratch bush or by dipping in lye. Work may be cleaned
+by dipping it into nitric acid which has been diluted with an equal volume
+of water. The work should be heated as hot as possible without danger of
+melting, as this causes the solder to flow better and secure a much better
+hold on the surfaces. Hard solder gives better results than half and half,
+but is more difficult to work. It is very important that the soldering iron
+be kept at a high heat during all work, otherwise the solder will only
+stick to the surfaces and will not join with them.
+
+Sweating is a form of soldering in which the surfaces of the work are first
+covered with a thin layer of solder by rubbing them with the hot iron after
+it has been dipped in or touched to the soldering stick. These surfaces are
+then placed in contact and heated to a point at which the solder melts and
+unites. Sweating is much to be preferred to ordinary soldering where the
+form of the work permits it. This is the only method which should ever be
+used when a fitting is to be placed over the end of a length of tube.
+
+_Soldering Holes._--Clean the surfaces for some distance around the
+hole until they are bright, and apply flux while holding the hot iron near
+the hole. Touch the tip of the iron to some solder until the solder is
+picked up on the iron, and then place this solder, which was just picked
+up, around the edge of the hole. It will leave the soldering iron and stick
+to the metal. Keep adding solder in this way until the hole has been closed
+up by working from the edges and building toward the center. After the hole
+is closed, apply more flux to the job and smooth over with the hot iron
+until there are no rough spots. Should the solder refuse to flow smoothly,
+the iron is not hot enough.
+
+_Soldering Seams._--Clean back from the seam or split for at least
+half an inch all around and then build up the solder in the same way as was
+done with the hole. After closing the opening, apply more flux to the work
+and run the hot iron lengthwise to smooth the job.
+
+_Soldering Wires._--Clean all insulation from the ends to be soldered
+and scrape the ends bright. Lay the ends parallel to each other and,
+starting at the middle of the cleaned portion, wrap the ends around each
+other, one being wrapped to the right, the other to the left. Hold the hot
+iron under the twisted joint and apply flux to the wire. Then dip the iron
+in the solder and apply to the twisted portion until the spaces between the
+wires are filled with solder. Finish by smoothing the joint and cleaning
+away all excess metal by rubbing the hot iron lengthwise. The joint should
+now be covered with a layer of rubber tape and this covered with a layer of
+ordinary friction tape.
+
+_Steel and Iron._--Steel surfaces should be cleaned, then covered with
+clear muriatic acid. While the acid is on the metal, rub with a stick of
+zinc and then tin the surfaces with the hot iron as directed. Cast iron
+should be cleaned and dipped in strong lye to remove grease. Wash the lye
+away with clean water and cover with muriatic acid as with steel. Then rub
+with a piece of zinc and tin the surfaces by using resin as a flux.
+
+It is very difficult to solder aluminum with ordinary solder. A special
+aluminum solder should be secured, which is easily applied and makes a
+strong joint. Zinc or phosphor tin may be used in place of ordinary solder
+to tin the surfaces or to fill small holes or cracks. The aluminum must be
+thoroughly heated before attempting to solder and the flux may be either
+resin or soldering acid. The aluminum must be thoroughly cleaned with
+dilute nitric acid and kept hot while the solder is applied by forcible
+rubbing with the hot iron.
+
+
+BRAZING
+
+This is a process for joining metal parts, very similar to soldering,
+except that brass is used to make the joint in place of the lead and zinc
+alloys which form solder. Brazing must not be attempted on metals whose
+melting point is less than that of sheet brass.
+
+Two pieces of brass to be brazed together are heated to a temperature at
+which the brass used in the process will melt and flow between the
+surfaces. The brass amalgamates with the surfaces and makes a very strong
+and perfect joint, which is far superior to any form of soldering where the
+work allows this process to be used, and in many cases is the equal of
+welding for the particular field in which it applies.
+
+_Brazing Heat and Tools._--The metal commonly used for brazing will
+melt at heats between 1350° and 1650° Fahrenheit. To bring the parts to
+this temperature, various methods are in use, using solid, liquid or
+gaseous fuels. While brazing may be accomplished with the fire of the
+blacksmith forge, this method is seldom satisfactory because of the
+difficulty of making a sufficiently clean fire with smithing coal, and it
+should not be used when anything else is available. Large jobs of brazing
+may be handled with a charcoal fire built in the forge, as this fuel
+produces a very satisfactory and clean fire. The only objection is in the
+difficulty of confining the heat to the desired parts of the work.
+
+The most satisfactory fire is that from a fuel gas torch built for this
+work. These torches are simply forms of Bunsen burners, mixing the proper
+quantity of air with the gas to bring about a perfect combustion. Hose
+lines lead to the mixing tube of the gas torch, one line carrying the gas
+and the other air under a moderate pressure. The air line is often
+dispensed with, allowing the gas to draw air into the burner on the
+injector principle, much the same as with illuminating gas burners for use
+with incandescent mantles. Valves are provided with which the operator may
+regulate the amount of both gas and air, and ordinarily the quality and
+intensity of the flame.
+
+When gas is not available, recourse may be had to the gasoline torch made
+for brazing. This torch is built in the same way as the small portable
+gasoline torches for soldering operations, with the exception that two
+regulating needle valves are incorporated in place of only one.
+
+The torches are carried on a framework, which also supports the work being
+handled. Fuel is forced to the torch from a large tank of gasoline into
+which air pressure is pumped by hand. The torches are regulated to give
+the desired flame by means of the needle valves in much the same way as
+with any other form of pressure torch using liquid fuel.
+
+Another very satisfactory form of torch for brazing is the acetylene-air
+combination described in the chapter on welding instruments. This torch
+gives the correct degree of heat and may be regulated to give a clean and
+easily controlled flame.
+
+Regardless of the source of heat, the fire or flame must be adjusted so
+that no soot is deposited on the metal surfaces of the work. This can only
+be accomplished by supplying the exact amounts of gas and air that will
+produce a complete burning of the fuel. With the brazing torches in common
+use two heads are furnished, being supplied from the same source of fuel,
+but with separate regulating devices. The torches are adjustably mounted in
+such a way that the flames may be directed toward each other, heating two
+sides of the work at the same time and allowing the pieces to be completely
+surrounded with the flame.
+
+Except for the source of heat, but one tool is required for ordinary
+brazing operations, this being a spatula formed by flattening one end of a
+quarter-inch steel rod. The spatula is used for placing the brazing metal
+on the work and for handling the flux that is required in this work as in
+all other similar operations.
+
+_Spelter._--The metal that is melted into the joint is called spelter.
+While this name originally applied to but one particular grade or
+composition of metal, common use has extended the meaning until it is
+generally applied to all grades.
+
+Spelter is variously composed of alloys containing copper, zinc, tin and
+antimony, the mixture employed depending on the work to be done. The
+different grades are of varying hardness, the harder kinds melting at
+higher temperatures than the soft ones and producing a stronger joint when
+used. The reason for not using hard spelter in all cases is the increased
+difficulty of working it and the fact that its melting point is so near to
+some of the metals brazed that there is great danger of melting the work as
+well as the spelter.
+
+The hardest grade of spelter is made from three-fourths copper with
+one-fourth zinc and is used for working on malleable and cast iron and for
+steel.
+
+This hard spelter melts at about 1650° and is correspondingly difficult to
+handle.
+
+A spelter suitable for working with copper is made from equal parts of
+copper and zinc, melting at about 1400° Fahrenheit, 500° below the melting
+point of the copper itself. A still softer brazing metal is composed of
+half copper, three-eighths zinc and one-eighth tin. This grade is used for
+fastening brass to iron and copper and for working with large pieces of
+brass to brass. For brazing thin sheet brass and light brass castings, a
+metal is used which contains two-thirds tin and one-third antimony. The
+low melting point of this last composition makes it very easy to work with
+and the danger of melting the work is very slight. However, as might be
+expected, a comparatively weak joint is secured, which will not stand any
+great strain.
+
+All of the above brazing metals are used in powder form so that they may be
+applied with the spatula where the joint is exposed on the outside of the
+work. In case it is necessary to braze on the inside of a tube or any deep
+recess, the spelter may be placed on a flat rod long enough to reach to
+the farthest point. By distributing the spelter at the proper points along
+the rod it may be placed at the right points by turning the rod over after
+inserting into the recess.
+
+_Flux._--In order to remove the oxides produced under brazing heat and
+to allow the brazing metal to flow freely into place, a flux of some kind
+must be used. The commonest flux is simply a pure calcined borax powder,
+that is, a borax powder that has been heated until practically all the
+water has been driven off.
+
+Calcined borax may also be mixed with about 15 per cent of sal ammoniac to
+make a satisfactory fluxing powder. It is absolutely necessary to use flux
+of some kind and a part of whatever is used should be made into a paste
+with water so that it can be applied to the joint to be brazed before
+heating. The remainder of the powder should be kept dry for use during the
+operation and after the heat has been applied.
+
+_Preparing the Work._--The surfaces to be brazed are first thoroughly
+cleaned with files, emery cloth or sand paper. If the work is greasy, it
+should be dipped into a bath of lye or hot soda water so that all trace of
+oil is removed. The parts are then placed in the relation to each other
+that they are to occupy when the work has been completed. The edges to be
+joined should make a secure and tight fit, and should match each other at
+all points so that the smallest possible space is left between them. This
+fit should not be so tight that it is necessary to force the work into
+place, neither should it be loose enough to allow any considerable space
+between the surfaces. The molten spelter will penetrate between surfaces
+that water will flow between when the work and spelter have both been
+brought to the proper heat. It is, of course, necessary that the two parts
+have a sufficient number of points of contact so that they will remain in
+the proper relative position.
+
+The work is placed on the surface of the brazing table in such a position
+that the flame from the torches will strike the parts to be heated, and
+with the joint in such a position that the melted spelter will flow down
+through it and fill every possible part of the space between the surfaces
+under the action of gravity. That means that the edge of the joint must be
+uppermost and the crack to be filled must not lie horizontal, but at the
+greatest slant possible. Better than any degree of slant would be to have
+the line of the joint vertical.
+
+The work is braced up or clamped in the proper position before commencing
+to braze, and it is best to place fire brick in such positions that it will
+be impossible for cooling draughts of air to reach the heated metal should
+the flame be removed temporarily during the process. In case there is a
+large body of iron, steel or copper to be handled, it is often advisable to
+place charcoal around the work, igniting this with the flame of the torch
+before starting to braze so that the metal will be maintained at the
+correct heat without depending entirely on the torch.
+
+When handling brass pieces having thin sections there is danger of melting
+the brass and causing it to flow away from under the flame, with the result
+that the work is ruined. If, in the judgment of the workman, this may
+happen with the particular job in hand, it is well to build up a mould of
+fire clay back of the thin parts or preferably back of the whole piece, so
+that the metal will have the necessary support. This mould may be made by
+mixing the fire clay into a stiff paste with water and then packing it
+against the piece to be supported tightly enough so that the form will be
+retained even if the metal softens.
+
+_Brazing._--With the work in place, it should be well covered with the
+paste of flux and water, then heated until this flux boils up and runs over
+the surfaces. Spelter is then placed in such a position that it will run
+into the joint and the heat is continued or increased until the spelter
+melts and flows in between the two surfaces. The flame should surround the
+work during the heating so that outside air is excluded as far as is
+possible to prevent excessive oxidization.
+
+When handling brass or copper, the flame should not be directed so that its
+center strikes the metal squarely, but so that it glances from one side or
+the other. Directing the flame straight against the work is often the cause
+of melting the pieces before the operation is completed. When brazing two
+different metals, the flame should play only on the one that melts at the
+higher temperature, the lower melting part receiving its heat from the
+other. This avoids the danger of melting one before the other reaches the
+brazing point.
+
+The heat should be continued only long enough to cause the spelter to flow
+into place and no longer. Prolonged heating of any metal can do nothing but
+oxidize and weaken it, and this practice should be avoided as much as
+possible. If the spelter melts into small globules in place of flowing, it
+may be caused to spread and run into the joint by lightly tapping the work.
+More dry flux may be added with the spatula if the tapping does not produce
+the desired result.
+
+Excessive use of flux, especially toward the end of the work, will result
+in a very hard surface on all the work, a surface which will be extremely
+difficult to finish properly. This trouble will be present to a certain
+extent anyway, but it may be lessened by a vigorous scraping with a wire
+brush just as soon as the work is removed from the fire. If allowed to cool
+before cleaning, the final appearance will not be as good as with the
+surplus metal and scale removed immediately upon completing the job.
+
+After the work has been cleaned with the brush it may be allowed to cool
+and finished to the desired shape, size and surface by filing and
+polishing. When filed, a very thin line of brass should appear where the
+crack was at the beginning of the work. If it is desired to avoid a square
+shoulder and fill in an angle joint to make it rounding, the filling is
+best accomplished by winding a coil of very thin brass wire around the part
+of the work that projects and then causing this to flow itself or else
+allow the spelter to fill the spaces between the layers of wire. Copper
+wire may also be used for this purpose, the spaces being filled with
+melted spelter.
+
+
+THERMIT WELDING
+
+The process of welding which makes use of the great heat produced by oxygen
+combining with aluminum is known as the Thermit process and was perfected
+by Dr. Hans Goldschmidt. The process, which is controlled by the
+Goldschmidt Thermit Company, makes use of a mixture of finely powdered
+aluminum with an oxide of iron called by the trade name, Thermit.
+
+The reaction is started with a special ignition powder, such as barium
+superoxide and aluminum, and the oxygen from the iron oxide combining with
+the aluminum, producing a mass of superheated steel at about 5000 degrees
+Fahrenheit. After the reaction, which takes from. 30 seconds to a minute,
+the molten metal is drawn from the crucible on to the surfaces to be
+joined. Its extreme heat fuses the metal and a perfect joint is the result.
+This process is suited for welding iron or steel parts of comparatively
+large size.
+
+_Preparation._--The parts to be joined are thoroughly cleaned on the
+surfaces and for several inches back from the joint, after which they are
+supported in place. The surfaces between which the metal will flow are
+separated from 1/4 to 1 inch, depending on the size of the parts, but
+cutting or drilling part of the metal away. After this separation is made
+for allowing the entrance of new metal, the effects of contraction of the
+molten steel are cared for by preheating adjacent parts or by forcing the
+ends apart with wedges and jacks. The amount of this last separation must
+be determined by the shape and proportions of the parts in the same way as
+would be done for any other class of welding which heats the parts to a
+melting point.
+
+Yellow wax, which has been warmed until plastic, is then placed around the
+joint to form a collar, the wax completely filling the space between the
+ends and being provided with vent holes by imbedding a piece of stout cord,
+which is pulled out after the wax cools.
+
+A retaining mould (Figure 55) made from sheet steel or fire brick is then
+placed around the parts. This mould is then filled with a mixture of one
+part fire clay, one part ground fire brick and one part fire sand. These
+materials are well mixed and moistened with enough water so that they will
+pack. This mixture is then placed in the mould, filling the space between
+the walls and the wax, and is packed hard with a rammer so that the
+material forms a wall several inches thick between any point of the mould
+and the wax. The mixture must be placed in the mould in small quantities
+and packed tight as the filling progresses.
+
+[Illustration: Figure 55.--Thermit Mould Construction]
+
+Three or more openings are provided through this moulding material by the
+insertion of wood or pipe forms. One of these openings will lead from the
+lowest point of the wax pattern and is used for the introduction of the
+preheating flame. Another opening leads from the top of the mould into this
+preheating gate, opening into the preheating gate at a point about one inch
+from the wax pattern. Openings, called risers, are then provided from each
+of the high points of the wax pattern to the top of the mould, these risers
+ending at the top in a shallow basin. The molten metal comes up into these
+risers and cares for contraction of the casting, as well as avoiding
+defects in the collar of the weld. After the moulding material is well
+packed, these gate patterns are tapped lightly and withdrawn, except in the
+case of the metal pipes which are placed at points at which it would be
+impossible to withdraw a pattern.
+
+_Preheating._--The ends to be welded are brought to a bright red heat
+by introducing the flame from a torch through the preheating gate. The
+torch must use either gasoline or kerosene, and not crude oil, as the crude
+oil deposits too much carbon on the parts. Preheating of other adjacent
+parts to care for contraction is done at this time by an additional torch
+burner.
+
+The heating flame is started gently at first and gradually increased. The
+wax will melt and may be allowed to run out of the preheating gate by
+removing the flame at intervals for a few seconds. The heat is continued
+until the mould is thoroughly dried and the parts to be joined are brought
+to the red heat required. This leaves a mould just the shape of the wax
+pattern.
+
+The heating gate should then be plugged with a sand core, iron plug or
+piece of fitted fire brick, and backed up with several shovels full of the
+moulding mixture, well packed.
+
+[Illustration: Figure 56.--Thermit Crucible Plug.
+_A_, Hard burn magnesia stone;
+_B_, Magnesia thimble;
+_C_, Refractory sand;
+_D_, Metal disc;
+_E_, Asbestos washer;
+_F_, Tapping pin]
+
+_Thermit Metal._--The reaction takes place in a special crucible lined
+with magnesia tar, which is baked at a red heat until the tar is driven off
+and the magnesia left. This lining should last from twelve to fifteen
+reactions. This magnesia lining ends at the bottom of the crucible in a
+ring of magnesia stone and this ring carries a magnesia thimble through
+which the molten steel passes on its way to the mould. It will usually be
+necessary to renew this thimble after each reaction. This lower opening is
+closed before filling the crucible with thermit by means of a small disc or
+iron carrying a stem, which is called a tapping pin (Figure 56). This pin,
+_F_, is placed in the thimble with the stem extending down through the
+opening and exposing about two inches. The top of this pin is covered with
+an asbestos, washer, _E_, then with another iron disc. _D_, and
+finally with a layer of refractory sand. The crucible is tapped by knocking
+the stem of the pin upwards with a spade or piece of flat iron about four
+feet long.
+
+The charge of thermit is added by placing a few handfuls over the
+refractory sand and then pouring in the balance required. The amount of
+thermit required is calculated from the wax used. The wax is weighed before
+and after filling _the entire space that the thermit will occupy_.
+This does not mean only the wax collar, but the space of the mould with all
+gates filled with wax. The number of pounds of wax required for this
+filling multiplied by 25 will give the number of pounds of thermit to be
+used. To this quantity of thermit should be added I per cent of pure
+manganese, 1 per cent nickel thermit and 15 per cent of steel punchings.
+
+It is necessary, when more than 10 pounds of thermit will be used, to mix
+steel punchings not exceeding 3/8 inch diameter by 1/8 inch thick with the
+powder in order to sufficiently retard the intensity of the reaction.
+
+Half a teaspoonful of ignition powder is placed on top of the thermit
+charge and ignited with a storm match or piece of red hot iron. The cover
+should be immediately closed on the top of the crucible and the operator
+should get away to a safe distance because of the metal that may be thrown
+out of the crucible.
+
+After allowing about 30 seconds to a minute for the reaction to take place
+and the slag to rise to the top of the crucible, the tapping pin is struck
+from below and the molten metal allowed to run into the mould. The mould
+should be allowed to remain in place as long as possible, preferably over
+night, so as to anneal the steel in the weld, but in no case should it be
+disturbed for several hours after pouring. After removing the mould, drill
+through the metal left in the riser and gates and knock these sections off.
+No part of the collar should be removed unless absolutely necessary.
+
+
+
+
+CHAPTER IX
+
+OXYGEN PROCESS FOR REMOVAL OF CARBON
+
+
+Until recently the methods used for removing carbon deposits from gas
+engine cylinders were very impractical and unsatisfactory. The job meant
+dismantling the motor, tearing out all parts, and scraping the pistons and
+cylinder walls by hand.
+
+The work was never done thoroughly. It required hours of time to do it, and
+then there was always the danger of injuring the inside of the cylinders.
+
+These methods have been to a large extent superseded by the use of oxygen
+under pressure. The various devices that are being manufactured are known
+as carbon removers, decarbonizers, etc., and large numbers of them are in
+use in the automobile and gasoline traction motor industry.
+
+_Outfit._--The oxygen carbon cleaner consists of a high pressure
+oxygen cylinder with automatic reducing valve, usually constructed on the
+diaphragm principle, thus assuring positive regulation of pressure. This
+valve is fitted with a pressure gauge, rubber hose, decarbonizing torch
+with shut off and flexible tube for insertion into the chamber from which
+the carbon is to be removed.
+
+There should also be an asbestos swab for swabbing out the inside of the
+cylinder or other chamber with kerosene previous to starting the operation.
+The action consists in simply burning the carbon to a fine dust in the
+presence of the stream of oxygen, this dust being then blown out.
+
+_Operation._--The following are instructions for operating the
+cleaner:--
+
+(1) Close valve in gasoline supply line and start the motor, letting it run
+until the gasoline is exhausted.
+
+(2) If the cylinders be T or L head, remove either the inlet or the exhaust
+valve cap, or a spark plug if the cap is tight. If the cylinders have
+overhead valves, remove a spark plug. If any spark plug is then remaining
+in the cylinder it should be removed and an old one or an iron pipe plug
+substituted.
+
+(3) Raise the piston of the cylinder first to be cleaned to the top of the
+compression stroke and continue this from cylinder to cylinder as the work
+progresses.
+
+(4) In motors where carbon has been burned hard, the cylinder interior
+should then be swabbed with kerosene before proceeding. Work the swab,
+saturated with kerosene, around the inside of the cylinder until all the
+carbon has been moistened with the oil. This same swab may be used to
+ignite the gas in the cylinder in place of using a match or taper.
+
+(5) Make all connections to the oxygen cylinder.
+
+(6) Insert the torch nozzle in the cylinder, open the torch valve gradually
+and regulate to about two lbs. pressure. Manipulate the nozzle inside the
+cylinder and light a match or other flame at the opening so that the carbon
+starts to burn. Cover the various points within the cylinder and when there
+is no further burning the carbon has been removed. The regulating and
+oxygen tank valves are operated in exactly the same way as for welding as
+previously explained.
+
+
+It should be carefully noted that when the piston is up, ready to start the
+operation, both valves must be closed. There will be a considerable display
+of sparks while this operation is taking place, but they will not set fire
+to the grease and oil. Care should be used to see that no gasoline is
+about.
+
+
+
+
+INDEX
+
+
+Acetylene
+  filtering
+  generators
+  in tanks
+  piping
+  properties of
+  purification of
+Acetylene-air torches
+Air
+  oxygen from
+Alloys
+  table of
+Alloy steel
+Aluminum
+  alloys
+  welding
+Annealing
+Anvil
+Arc welding, electric
+  machines
+Asbestos, use of, in welding
+
+Babbitt
+Bending pipes and tubes
+Bessemer steel
+Beveling
+Brass
+  welding
+Brazing
+  electric
+  heat and tools
+  spelter
+Bronze
+  welding
+Butt welding
+
+Calcium carbide
+Carbide
+  storage of, Fire Underwriters' Rules
+  to water generator
+Carbon removal
+  by oxygen process
+Case hardening steel
+Cast iron
+  welding
+Champfering
+Charging generator
+Chlorate of potash oxygen
+Conductivity of metals
+Copper
+  alloys
+  welding
+Crucible steel
+Cutting, oxy-acetylene
+  torches
+
+Dissolved acetylene
+
+Electric arc welding
+Electric welding
+  troubles and remedies
+Expansion of metals
+
+Flame, welding
+Fluxes
+  for brazing
+  for soldering
+Forge
+  fire
+  practice
+  tools
+  tuvere construction of
+  welding
+  welding preparation
+  welds, forms of
+Forging
+
+Gas holders
+Gases, heating power of
+Generator, acetylene
+  carbide to water
+  construction
+Generator
+  location of
+  operation and care of
+  overheating
+  requirements
+  water to carbide
+German silver
+Gloves
+Goggles
+
+Hand forging
+Hardening steel
+Heat treatment of steel
+Hildebrandt process
+Hose
+
+Injectors, adjuster
+Iron
+  cast
+  grades of
+  malleable cast
+  wrought
+
+Jump weld
+
+Lap welding
+Lead
+Linde process
+Liquid air oxygen
+
+Magnalium
+Malleable iron
+  welding
+Melting points of metals
+Metal alloys, table of
+Metals
+  characteristics of
+  conductivity of
+  expansion of
+  heat treatment of
+  melting points of
+  tensile strength of
+  weight of
+
+Nickel
+Nozzle sizes, torch
+
+Open hearth steel
+Oxy-acetylene cutting
+  welding practice
+Oxygen
+  cylinders
+  weight of
+
+Pipes, bending
+Platinum
+Preheating
+
+Removal of carbon by oxygen process
+Resistance method of electric welding
+Restoration of steel
+Rods, welding
+
+Safety devices
+Scarfing
+Solder
+Soldering
+  flux
+  holes
+  seams
+  steel and iron
+  wires
+Spelter
+Spot welding
+Steel
+  alloys
+  Bessemer
+  crucible
+  heat treatment of
+  open hearth
+  restoration of
+  tensile strength of
+  welding
+Strength of metals
+
+Tank valves
+Tapering
+Tables of welding information
+Tempering steel
+Thermit metal
+  preheating
+  preparation
+  welding
+Tin
+Torch
+  acetylene-air
+  care
+  construction
+  cutting
+  high pressure
+  low pressure
+  medium pressure
+  nozzles
+  practice
+
+Valves, regulating
+  tank
+
+Water
+  to carbide generator
+Welding aluminum
+  brass
+  bronze
+  butt
+  cast iron
+  copper
+  electric
+  electric arc
+  flame
+  forge
+  information and tables
+  instruments
+  lap
+  malleable iron
+  materials
+  practice, oxy-acetylene
+  rods
+  spot
+  steel
+  table
+  thermit
+  torches
+  various metals
+  wrought iron
+Wrought iron
+  welding
+
+Zinc
+
+
+
+
+
+End of the Project Gutenberg EBook of Oxy-Acetylene Welding and Cutting
+by Harold P. Manly
+
+*** END OF THE PROJECT GUTENBERG EBOOK OXY-ACETYLENE WELDING AND CUTTING ***
+
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