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diff --git a/.gitattributes b/.gitattributes new file mode 100644 index 0000000..d7b82bc --- /dev/null +++ b/.gitattributes @@ -0,0 +1,4 @@ +*.txt text eol=lf +*.htm text eol=lf +*.html text eol=lf +*.md text eol=lf diff --git a/LICENSE.txt b/LICENSE.txt new file mode 100644 index 0000000..6312041 --- /dev/null +++ b/LICENSE.txt @@ -0,0 +1,11 @@ +This eBook, including all associated images, markup, improvements, +metadata, and any other content or labor, has been confirmed to be +in the PUBLIC DOMAIN IN THE UNITED STATES. + +Procedures for determining public domain status are described in +the "Copyright How-To" at https://www.gutenberg.org. + +No investigation has been made concerning possible copyrights in +jurisdictions other than the United States. Anyone seeking to utilize +this eBook outside of the United States should confirm copyright +status under the laws that apply to them. diff --git a/README.md b/README.md new file mode 100644 index 0000000..a2ea38a --- /dev/null +++ b/README.md @@ -0,0 +1,2 @@ +Project Gutenberg (https://www.gutenberg.org) public repository for +eBook #53064 (https://www.gutenberg.org/ebooks/53064) diff --git a/old/53064-0.txt b/old/53064-0.txt deleted file mode 100644 index 37b3cd4..0000000 --- a/old/53064-0.txt +++ /dev/null @@ -1,1903 +0,0 @@ -The Project Gutenberg EBook of Die Casting, by Chester L. Lucas - -This eBook is for the use of anyone anywhere in the United States and most -other parts of the world 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. If you are not located in the United States, you'll have -to check the laws of the country where you are located before using this ebook. - -Title: Die Casting - Dies--Machines--Methods - -Author: Chester L. Lucas - -Release Date: September 17, 2016 [EBook #53064] - -Language: English - -Character set encoding: UTF-8 - -*** START OF THIS PROJECT GUTENBERG EBOOK DIE CASTING *** - - - - -Produced by Chris Curnow, Charlie Howard, and the Online -Distributed Proofreading Team at http://www.pgdp.net (This -file was produced from images generously made available -by The Internet Archive) - - - - - - - - - -Transcriber’s Note: Subscripts are preceded by an acute accent mark `; -italic text is enclosed in _underscores_. - - - - -[Illustration] - - - - - MACHINERY’S REFERENCE SERIES - - - EACH NUMBER IS ONE UNIT IN A COMPLETE LIBRARY OF MACHINE DESIGN - AND SHOP PRACTICE REVISED AND REPUBLISHED FROM MACHINERY - - - NUMBER 109 - - DIE CASTING - DIES--MACHINES--METHODS - - By CHESTER L. LUCAS - - - - -CONTENTS - - - Die Casting 3 - - Making Dies for Die-Casting Machines 15 - - Van Wagner Mfg. Co.’s Die-Casting Practice 27 - - - Copyright, 1913, The Industrial Press, Publishers of MACHINERY, - 49-55 Lafayette Street, New York City - - - - -CHAPTER I - -DIE CASTING - - -Die-casting, a comparatively recent method for producing finished -castings, is rapidly proving itself an important factor in the -economical manufacture of interchangeable parts for adding machines, -typewriters, telephones, automobiles and numerous other products where -it is essential that the parts be nicely finished and accurate in -dimensions. The term “die-casting” is self-explanatory, meaning “to -cast by means of dies”; described briefly, the process consists of -forcing molten metal into steel dies, allowing it to cool in them, and -then opening the dies and removing the finished casting. It is the -purpose of this treatise to give a general outline of the die-casting -process, showing its possibilities and limitations, and also to give -a description of the die-casting machinery and its operation, of -the fundamental principles involved, and of the methods used in the -die-making. Illustrative examples of the best types of dies, based on -results obtained from actual experience, will also be given. - - -Origin of Die Casting - -The origin of the die-casting process is somewhat difficult to -ascertain. We may look into the history of type founding and find -that away back in 1838, the first casting machine for type, invented -by Bruce, was a machine that involved the principles of die-casting -as it is practiced to-day. More recently, in 1885, Otto Mergenthaler -brought out the linotype machine. This machine is a good example of -a die-casting machine. However, as we interpret the word to-day, -die-casting is a broader term than type-casting or linotyping, although -its development without doubt is due to the success of the linotype -machine. It is doubtful if die-casting, properly speaking, was -originated until about fifteen years ago, and it is certain that it is -only during the past few years that the activities in this line have -been very noticeable. - -One of the first experiments in the direction of die-casting was -undertaken to get out some rubber mold parts cheaply enough to leave a -profit on a job that was beginning to look dubious from the financial -side. The molds were for making rubber plates about three inches -square and one-eighth inch thick, the top side of which was decorated -with fine raised scroll work; it was this latter feature that gave -the trouble. After wasting much time and money trying to stamp the -mold parts, a metal-tight box was made as shown in Figs. 1 and 2 with -a block screwed in it, the purpose of which was to shape the mold -impression and impart to it the scroll design. As shown, the ends of -the box were removable, being screwed on. This box was placed under -a screw press and a straight plunger that just filled the top of the -box was fitted to the head of the press. After the two were lined up, -molten type metal was poured into the box, and as soon as the metal -had cooled to the “mushy” state, the ram of the press was forced down -as shown in Fig. 2. Next, the ends of the box were removed, the screw -holding the block taken out, and the die-casting pushed from the box. -The object in having the inclined side to the box was to produce a -piece shaped with the proper inclination for its position in the final -mold used for casting the rubber plates. The illustrations give an idea -of the compression that took place. The die-casting was found to be -sharp at the corners and free from flaws, and the scroll work came up -in fine shape. Naturally the rest of the mold parts were made in the -same way and the job turned from failure into success. - -[Illustration: - - Fig. 1. An Early Experiment in Die Casting--Before Applying Pressure - - Fig. 2. An Early Experiment in Die Casting--After Applying Pressure -] - -From such simple experiments as these, the die-casting industry has -developed to its present stage. In view of the advances that have been -made in die-casting, it is singular that there are to-day only about -a dozen concerns in the business in this country, but as the subject -becomes better understood, and the possibilities of the process are -realized, the demand for this class of castings will result in many -other firms going into the work, and it is not improbable that a large -number of factories will install die-casting plants of their own to aid -them in producing better work in a more economical way. - - -Advantages, Possibilities and Limitations of Die Casting - -The greatest advantage of die-casting is the fact that the castings -produced are completely and accurately finished when taken from the -dies. When we say completely, we mean that absolutely no machining is -required after the piece has been cast, as it is ready to slip into its -place in the machine or device of which it is to be a part. When we say -accurately, we mean that each piece will come from the die an exact -counterpart of the last one; and if the dies are carefully made, the -castings will be accurate within 0.001 inch on all dimensions, whether -they are outside measurements, diameters of holes or radii. All holes -are cast and come out smoother than they could be reamed; lugs and gear -teeth are cast in place; threads, external and internal, and of any -desired pitch can be cast. Oil grooves can be cast in bearings, and, in -a word, any piece that can be machined can be die-cast. - -The saving in machining works both ways; not only is all machine work -eliminated by the one operation of casting, but the machine tools and -the workmen necessary for their operation and up-keep are dispensed -with, the expense of building jigs and fixtures is stopped; and no -cutters, reamers, taps or drills are required for this branch of the -production. In addition, the labor required for operating the casting -machines may be classed as unskilled. No matter how intricate and -exacting the machine work on a piece has been, and how skillful a -workman was required to produce the work when machine-made, the same -result may be brought about by die-casting, and usually the work is -excelled, and, excluding the die-making, unskilled men can make the -parts. - -From a metallurgical standpoint a die-casting is superior to a -sand-casting on account of its density, strength and freedom from -blow-holes. Also, when the hot metal comes in contact with the cool -dies, it forms a “skin” similar to the scale on an iron sand-casting. -As the die-casting requires no machining after leaving the dies, this -skin increases the wearing qualities of the casting. - -The possibilities of die-casting are numerous. By this method of -manufacturing it is possible and practical to cast pieces that could -not possibly be machined. It is an every-day occurrence to make -castings with inserted parts of another metal, as, for instance, a -zinc wheel with a steel hub. It is also possible to make babbitt -bearings that are harder and better than can be made in any other way. -Often there are two or more parts of a device that have formerly been -made separately, machined and assembled, that can be die-cast as one -piece. In such cases the saving in production is very great. Figures -and letters may be cast sunken or in relief on wheels for counting -or printing, and of course ornamentation may be cast on pieces that -require exterior finish. As to size, there is no definite limit to the -work that can be cast. One job that is being done at the present time -is a disk 16 inches in diameter with a round flange 1 inch in diameter, -around the rim. - -[Illustration: Fig. 3. Examples of Die-castings] - -“There is no great gain without some small loss,” is just as true of a -process like die-casting as it is of anything else. The limitations of -this work are few, however, and they are here given so as to state the -situation fairly. Generally speaking, a part should not be considered -for die-casting if there are but few pieces required, because the cost -of the dies would usually be prohibitive. Often, however, it happens -that because of the large amount of accurate machine work being done on -a machine part, it is economical to make a die for the comparatively -small number of parts required and die-cast them. A case illustrating -this phase of the matter recently occurred in actual practice. In -getting out an order of two hundred vending machines, it was decided -to try die-casting on a part that was difficult to machine. The dies -were expensive, costing $200, and as there were only 200 pieces to be -cast, the die cost per piece was one dollar; but even with that initial -handicap, it was found that on account of the difficult machining that -had formerly been required, the die-cast parts effected a large saving, -and of course the results were superior. - -A rough part that would require little or no machining should not -be die-cast, because pound for pound, the die-casting metals cost -more than cast iron or steel. The casting machine cannot make parts -as rapidly or of as hard metals as the punch press or the automatic -screw machine. For this latter reason a part that necessarily must be -made of brass, iron or steel, cannot be die-cast, although mixtures -approximately equal in strength to iron and brass are readily die-cast. -To give added strength to a die-cast part it is often advisable to -add webs and ribs or to insert brass or iron pins at points that are -weak or subject to hard wear. Roughly speaking, it is the part that -has required a good deal of accurate machine operations that shows the -greatest difference in cost when die-cast, and sometimes the saving is -as great as 80 per cent. - - -The Metals used in Die Casting - -The metals that produce the best die-castings are alloys of lead, tin, -zinc, antimony, aluminum and copper, and the bulk of the die-castings -made at the present time are mixtures of the first four of these -metals. From them, compositions may be made that will meet the -requirements of nearly any part. - -For parts that perform little or no actual work, save to “lend -their weight,” such as balance weights, novelties and ornaments for -show windows, etc., a mixture consisting principally of lead, often -stiffened with a little antimony, is used. There is but little strength -to this metal, but it is used because of its weight and low cost. -For parts that are subject to wear, such as phonograph, telephone, -gas-meter and adding machine parts, an alloy composed of zinc, tin and -a small amount of copper is used. This alloy may be plated or japanned, -and is a good metal to use on general work. - -Another metal, used chiefly for casting pieces that have delicate -points in their design but are not subjected to hard wear, consists -principally of tin alloyed with lead and zinc to suit the requirements -of the work. This mixture casts freely, and the finished castings come -out exceptionally clean. Still another metal, used chiefly for casting -pieces that have letters and figures for printing, is similar to the -standard type metal--5 parts lead and 1 part antimony; but if there are -teeth cast on the sides of the printing wheel a harder mixture will be -required to give longer life to the gears. - -The following mixtures are typical of die-casting or “white brass” -alloys: copper, 10 parts; zinc, 83 parts; aluminum, 2 parts; tin, 5 -parts. Another is copper, 6 parts; zinc, 90 parts; aluminum, 3 parts; -tin, 1 part. Another containing antimony is copper, 5 parts; zinc, 85 -parts; tin, 5 parts; antimony, 5 parts. Shonberg’s patented alloy is -copper, 3 parts; zinc, 87 parts; tin, 10 parts. Alloys containing 15 to -40 per cent copper and 60 to 85 per cent zinc are brittle, having low -strength and low ductility. An alloy of 8 per cent copper, 92 per cent -zinc has greater resilience and strength but not the ductility of cast -zinc. - -Aluminum may be cast, but it is a difficult metal to run into thin -walls and fine details; it plays, however, an important part in some -good mixtures used for die casting. Experiments are now being conducted -for die-casting manganese bronze, and it is said that some very good -castings have already been made. Its wearing qualities are so valuable -that it is particularly desirable for making die-castings. - - -The Die-casting Machine - -The three important requisites for good die-casting are the machine, -the dies and the metal. The casting machine is fully as essential as -either of the other requisites, and although there are a number of -different styles of casting machines in use, each of which has its -advantages over the others, especially in the eyes of their respective -designers, the fundamental principles upon which they all operate are -the same. In each there is the melting pot and the burner, the cylinder -and the piston for forcing the metal into the dies, and the dies with -the opening and closing device. In some machines pressure is applied to -the metal by hand, in others power is used, and in still another class -the metal is forced into the dies with compressed air. The provisions -for opening and closing the dies vary in the different machines; there -are various means employed for cutting the sprue, and the styles of -heaters are numerous. - -One or two of the largest firms in the die-casting industry have -automatic casting machines for turning out duplicate work in large -quantities very rapidly. These machines are complicated and are only -profitable on large quantities of work, and for that reason their -use is not extensive. In general, their operating principles are the -same as in the case of the hand machines, but provision is made for -automatically opening and closing the dies, compressing the metal, and -ejecting the castings. - - -The Soss Die-casting Machine - -The Soss die-casting machine, manufactured and sold by the Soss -Manufacturing Co., Brooklyn, N. Y., was the first die-casting machine -to be placed on the open market. This machine is shown in Figs. 4 and -5, and in section in Fig. 6. The Soss Manufacturing Co. originally -manufactured invisible hinges exclusively. At the advent of the -die-casting era, they commenced to make these hinges from die-castings, -and placed orders with a leading die-casting concern amounting to -thousands of dollars each year. After the die-cast hinges had been on -the market for a short time, complaints commenced to come in, some to -the effect that the hinges were breaking and others that the hinges -were corroding. Either of these faults was serious enough to blast the -reputation of the hinge, but the first trouble, breakage, was the more -important. Examination of the broken hinges showed that the castings -were porous and full of flaws, and as the makers of the castings -could not produce castings sufficiently strong for the hinges, Mr. -Soss started to experiment for himself. This experimenting led to the -production of the Soss die-casting machine. - -[Illustration: Fig. 4. General View of the Soss Die-casting Machine] - -Referring to the illustrations Figs. 5 and 6, _A_ is the base and frame -of the machine, _B_ is the heating chamber located at one end of the -machine, and within this heating chamber is the tank _C_, shown in Fig. -6. This tank contains the metal from which the die-castings are made, -and the metal is heated by the burners _D_. These burners are fed by -air and gas through piping on the side of and beneath the furnace. To -facilitate lighting the burners and inspecting their condition at any -time, there is an opening (not shown) through the firebrick lining of -the furnace and the outer iron wall, on a level with the top of the -burners. There is also another opening through the furnace wall to -allow the gases due to the combustion to escape. Through the bottom of -the tank, well to the inner side of the furnace, runs the cylinder _E_. -Below the bottom of the tank, the cylinder makes a right-angle turn, -extending through the furnace wall and terminating just outside of the -wall. The orifice of this cylinder is controlled by gate _F_. In that -part of the cylinder that extends upward into the tank, there is an -opening _G_ that allows the molten metal to run into the cylinder from -the tank. Working in this cylinder, is the piston _H_, that is used in -forcing the metal into the dies. The compression lever _I_, hinged over -the inner furnace wall, is kept normally raised by spring pressure, and -is connected to the piston by means of the link _J_. - -[Illustration: Fig. 5. Working Parts of the Soss Die-casting Machine] - -At the opposite end of the machine from the furnace, is the mechanism -for operating the dies. This mechanism consists of a pair of square -rods _K_, upon which are mounted the sleeves _L_. These sleeves have -a long bearing surface and are attached to the die-plate _M_. Lever -_N_ at the end of the operating mechanism controls the movement of -these sleeves by means of links _O_. Upon these sleeves is mounted a -secondary set of sleeves _P_, attached to the other die-plate _Q_, -and whose movement is controlled by lever _R_, through links _S_. -This second set of sleeves is free to travel with the first set, and -in addition has an independent movement of its own on the primary -sleeves. It is the function of lever _R_ to bring die-plate _Q_ up -to die-plate _M_ by means of links _S_ and sleeves _P_; and it is -the function of lever _N_ to bring both of the die-plates up to the -outlet of the cylinder by means of links _O_ and sleeves _L_. This -system of sleeve-mounting is one of the distinctive patented features -of the Soss machine. The orifice of the cylinder _E_ is conical in -shape and exactly fits the cup-shaped opening in die-plate _M_, so -that when the two are brought together, the joint is metal tight. At -the center of this opening, and extending through the die-plate _M_, -is an opening that leads to the dies mounted on the inner faces of the -two die-plates, and a continuation of this opening extends through -die-plate _Q_ in which the sprue-cutter _U_ works. Attached to the -outer side of this die-plate are two slotted brackets. In the slot of -one of these is pivoted the lever _T_, and in the slot in the opposite -bracket are bolted two stops that limit the motion of the lever. This -lever operates the sprue cutter _U_, that works through the opening in -die-plate _Q_. The sprue-cutting mechanism is best shown in Figs. 5 and -6. At the left of Fig. 5 may be seen a rubber hose connected to the air -piping. This hose is used for cleaning out the dies after each casting -operation. - - -Operation of the Die-casting Machine - -The metal for the die-casting machine is mixed in the proper -proportions for the work in hand by means of a separate furnace, before -being poured into the tank of the machine itself. The burners are -lighted and the dies are set up on the two die-plates. As soon as the -machine has “warmed up,” so that the metal is in a thoroughly melted -condition, the sprue-cutting lever _T_ is thrown back, leaving a clear -passageway to the die cavities. Lever _R_ is pulled backward, thus -bringing die-plate _Q_ up to die-plate _M_, which operation closes -the two halves of the die. Then lever _N_ is thrown forward, thereby -bringing the closed die up to the body of the machine, with the nozzle -in close contact with the outlet of the cylinder. Next, the gate _F_ -is opened, and the man at the compression lever _I_ gives the lever a -quick, hard pull, forcing the metal in the cylinder downward and into -the dies. The molten metal literally “squirts” into the dies. Gate _F_ -is now closed; lever _N_ is pulled back to remove the dies from the -cylinder outlet; and the sprue-cutting lever _T_ is pushed forward, -cutting off the sprue and pushing it out of the nozzle into the kettle -placed beneath it. The lever _R_ is pushed forward, and a finished -casting is ejected from the dies. - -An important advantage that this machine has over other die-casting -machines is the fact that the metal for the castings is taken from the -_bottom_ of the melting pot, whereas most other machines use metal from -the top of the tank. At the bottom of the tank the metal is always the -best, as it is free from impurities and dross; hence, there is little -chance for the formation of blow-holes. A handful of rosin thrown -into the melting tank occasionally helps to keep the metal clean, -but the metal nearest the surface always contains more or less foreign -matter. - -[Illustration: Fig. 6. Section of Soss Die-casting Machine] - -While this description of the operation of the die-casting machine may -convey the idea that the process is a slow one, as a matter of fact, -the time required is, on the average, not over a minute and a half -for turning out a finished casting. With the ejection of the casting -from the dies, the product is completed, in theory; but in practice -there are always a few small thin fins, caused by the air vents or by -improperly fitted portions of the dies. It is, however, but the work -of a few seconds to break off these fins, and unless there are many of -them, or they are excessively thick, they are detrimental neither to -the quality nor the quantity of finished castings. - - -Points on the Operation of the Die-casting Machine - -We have now taken up the description and general operation of the -die-casting machine, but like every other machine, there are numerous -little kinds and practices in its working the observing of which makes -the difference between good and poor die-casting. Some of these points -are here given. - -The casting machine is best operated by three men, one of whom attends -to the compression lever and the metal supply in the tank. The other -two men stand on each side of the die-end of the machine, and it is -their duty to operate the sprue-cutter, open the dies and remove the -finished casting, clean the dies with air and close them, throw back -the die-plates to their casting position over the cylinder outlet, and -do any other work incident to the operation of the machine. While it -requires three men to operate a die-casting machine in the best manner, -the man who attends to the compression lever has a good deal of spare -time between strokes, and if two or even three of the machines are -conveniently placed, one man can easily pull levers for all three. - -The metal should be kept just above the melting point and at a -uniform temperature. If the metal is worked too cold, the result will -manifest itself in castings that are full of seams and creases, and it -will be difficult to “fill” the thin places in the dies. If, on the -other hand the metal is allowed to get too hot, the die will throw -excessively long fins, the castings will not cool as quickly in the -die, and consequently they cannot be made as rapidly. On account of -the importance of keeping the metal at a uniform heat, the fresh metal -that is added to that in the tank from time to time, is kept heated in -a separate furnace. Therefore, when the metal in the tank gets low, the -new supply does not reduce the temperature of the metal being worked. -Some casters use a thermometer to indicate the heat of the metal. - -Casting-dies require lubrication frequently. Just how often they should -be lubricated depends on the shape of the die, the composition of the -casting metal, and the general performance of the dies. Beeswax is -the common lubricant, and the lubrication consists in merely rubbing -the cake over the surfaces of the dies that come in contact with the -casting metal. In die-casting large parts, the dies must be kept cool -by some artificial means, for hot dies are conducive to slow work and -poor castings. To reach this end, large dies are sometimes drilled and -piped so that water may be circulated through them to keep them cool. - -In the Soss machine, the burners are so placed that the metal in the -cylinder is kept at a slightly higher heat than that in the tank -proper. This condition is brought about by having the cylinder directly -over the burners. The value of this feature lies in the fact that -gas is not wasted in heating the entire tank full of metal to this -higher heat, but still the metal under compression is at the required -temperature. The gas consumption of the average die-casting machine is -about 100 cubic feet per hour. - -The speed at which die-castings may be produced varies with the size of -the castings being made, the composition of the metal being cast, and -the style of dies that must be employed. In many cases, in die-casting, -separate brass or steel pieces are used, that must be placed in the -dies before each operation so that they will be inserted in and become -a part of the finished casting. The dies may be difficult of operation -on account of draft problems or pins and screws that must be inserted -in the dies and removed from each casting before another can be made. -These different types of dies will be more fully described in the next -chapter. Taken as a whole, from ten to sixty pieces per hour are the -maximum limits for speed in die-casting, and with a well-working die, -of simple construction, a speed of forty pieces per hour is considered -good production. It is possible, however, when the castings to be -produced are small in size and simple in shape, to gate a number of -them together, or rather to construct the dies so that six or more -castings may be made at once. By this means it is often possible to -cast five or six thousand pieces per day of ten hours, on a hand -die-casting machine. - - - - -CHAPTER II - -MAKING DIES FOR DIE-CASTING MACHINES - - -The making of casting-dies calls for ingenuity and skill of the highest -order on the part of the die-maker. There is probably no class of -die-making in which the work produced is more faithful to the dies, -both in showing up the little details in the making that reflect credit -on the dies, and in exposing the defects and shortcomings in the -workmanship, if there be any. The castings from casting-dies or molds -as they are sometimes called, may be produced in dimensions down to -ten-thousandths for accuracy if necessary, and once the dies are made -the castings will not vary in the slightest degree, if the working -conditions are kept uniform. - -In spite of the close work required in making casting-dies, the work is -very fascinating. Perhaps it is on account of this accuracy; possibly -it is on account of the fact that they are made from machine steel; -but most likely it is because there are no hardening troubles to be -contended with. Another factor that makes the work interesting is the -ingenuity required in the work, for almost every die-maker, if he is -worthy of the name, likes to figure out and plan for the best way of -building a die for a difficult job. - - -General Principles of Casting-die Making - -Casting-dies, or molds, have little in common with sand molds. It -is true that the dies for die-casting are composed of two parts -corresponding to the cope and nowel of the sand mold, but they are -so different in every other way that no benefit would result from a -comparison. - -Generally speaking, casting-dies are made of machine steel; the parts -which are exceptions are the heavy bases and frames, which are made of -cast iron, and the dowel pins and small cores, usually made of tool -steel. Except in rare instances, there are no hardened parts about a -casting-die; this is the case because the melting points of some of the -alloys that are die-cast are high enough to draw the temper from any -hardened parts of the dies. - -The ideal die is simple in construction, with as few parts as -practicable; the castings should be easily ejected and should come -from the dies as nearly free from fins as possible. To meet these -requirements in the best way is the proposition that confronts the -ingenuity of the die-maker. As the die is primarily in two parts, there -must be a parting line on the casting. This line is always placed at -the point that will permit the casting to be ejected from the dies in -the easiest manner possible, bearing in mind the effect the joint will -have on the appearance of the finished casting; this is a point far -less important than with sand casting, for, if the dies are properly -made this seam will be barely perceptible. When it is practicable to -do so, it is wise to have the parting line come on an edge of the -die-casting. Draft is unnecessary on the straight “up-and-down” -places, but of course it is impossible to draw any parts that are -undercut. Means must be provided for ejecting the casting from the -dies after completion and it is usually done by means of ejector pins, -though frequently it is better to have the bottom of the die or some -other section movable and do the ejecting on the same principle that -is used on drawing dies of the compound type. On close work, shrinkage -plays an important part, and the amount of shrinkage varies from 0.002 -to 0.007 of an inch per inch. Aluminum shrinks the greatest amount, -Parsons white brass shrinks considerably, while tin shrinks but little. -Thus, it may be easily seen that to figure the shrinkage allowance for -an alloy that contains three or four metals with different shrinkages, -requires judgment. To prevent the air from “pocketing,” air vents are -necessary at frequent intervals around the die-cavity. These vents are -made by milling a flat shallow cut from the die-cavity across the face -of the die to the outside edges of the block. From ¼ inch to ½ inch -is the usual width and from 0.003 to 0.005 of an inch, the customary -depth, varying with the size and shape of the die in question. - -[Illustration: Fig. 7. Disk cast in Simple Casting-die] - -The dies or molds for die-casting are of various styles, as are also -punch-press dies, and it would be difficult to lay down specific -rules for their classification. There are the plain dies, without -complications of any kind; slide dies with one or more slides; dies -for bearings, both of the “half-round” and of the “whole-round” types; -dies for gated work; and many other less important classes. Then there -are dies that have features that belong to more than one of these -types, so that it is easily seen that to decide upon the style of die -that would be best for a given piece of work requires a good deal of -experience. Some of the most important of these types can best be shown -by illustrating dies made in the various styles, showing, step by step, -how the dies are made and assembled. To begin with, consider the making -of a casting-die of the very simplest form. - -In Fig. 7 is shown a plain flat disk made by die-casting. In actual -practice, a die would not be made for such a simple piece, unless -there were some features about it that would prevent it being made -on a screw machine or with press tools. It might have a cam groove -cut in one of its flat sides, the sides might be covered with scroll -work, there might be gear teeth around its circumference, or a hundred -and one other conditions to make die-casting a desirable method of -manufacturing. All these complications are omitted for the sake of -simplifying this initial description of a casting-die. - -[Illustration: Fig. 8. Simple Casting-die for Casting Block shown in -Fig. 7] - -Fig. 8 shows the die for this piece in plan and sectional elevation. -_A_ is a square cast-iron frame, made from a single casting. This frame -or box, as it is generally called, is planed on the top and bottom -only. Next, the two die-halves _B_ and _C_ are shaped up from machine -steel. In this casting-die, and in the majority of others, these -die blocks are square. The lower half of the die _B_ is held to the -cast-iron frame by fillister head screws, set in counterbored holes, -thus sinking the screw-heads under the surface of the block. The upper -half of the die _C_ is located upon _B_ by dowel pins driven into _B_ -which have a sliding fit in the reamed holes in _C_. This being done, -the die-half _B_ is fixed to the faceplate of the lathe and the recess -bored for the die-cavity. This operation is a simple one in this case, -for it is merely a straight hole one-half inch deep and three inches in -diameter. Of course this recess must be carefully finished with a tool -that has been stoned up to a sharp edge, using lard oil. Emery cloth -should be used as little as possible. It is unnecessary to give this -hole draft, but it must be free from ridges or marks that would prevent -the casting from being pushed out. If the faces of the dies are spotted -with a small piece of box wood or rawhide held in the drill press and -kept charged with flour emery, the die-casting will reproduce this -“bird’s-eye” finish and the appearance will well repay the few minutes -additional time that it will take. The spotting should be done with dry -emery (without oil) to get the brightest finish. The upper die-half _C_ -is simply ground on its working face. The outside corners and edges of -the faces of both die-halves should be well rounded off so as to insure -the absence of slight dents or rough places that might prevent the dies -from fitting perfectly. - -The ejecting mechanism must next be considered. Lever _D_, pivoted -from bracket _E_, has a steel pin _F_ that engages in the elongated -hole in bracket _G_, so that an upward pull of the lever _D_ raises -bracket _G_, which is attached to ejector-pin plate _H_. This plate is -a loose fit over the guide screws _I_ that are attached to the lower -die-half _B_. The ejector pins _J_, four in number, in this die, are -riveted into the ejector-pin plate, and they work through holes drilled -and reamed through the lower die-half. The ends of these pins must be -finished off so as to lie perfectly flush with the inside of the die -when ready for operation and, of course, they must be a sliding fit in -the holes in the die. - -An important feature of a casting-die is the sprue cutter, shown in -this die at _K_. If the disk for which this die was made, had had a -hole or central opening of any kind, the sprue cutter would best be -operated at that point; but, as this disk is plain, the sprue cutter -must be placed at the edge. At the outside of the die-cavity, as shown -in Fig. 8, the opening for the sprue cutter is laid out, drilled -and filed to shape. It is obvious that the side of the sprue cutter -adjacent to the die must fit the outline of the die perfectly, so that -there will be no break in the appearance of the casting. The opening -for it is extended through the upper die-half, and from a point ¼ of an -inch from the inside face of the die this hole is flared out nearly as -large as the opening through the die-plate of the machine. Of course -the apperture in the upper die-half must be no larger than the opening -through the die-plate; otherwise the sprue could not be pushed out. The -sprue cutter itself is a long rod, whose section is of the same shape -and size as the openings just made, and it is connected to the sprue -cutting mechanism of the machine. Of course it is unnecessary to shape -the entire length of the sprue cutter to size; after the working end is -milled to shape for a distance of six or eight inches, the rest of the -rod may be left round. The sprue cutter is finished first, after which -both the openings in the die are fitted to it; and while the fit should -be metal tight, it must be perfectly free to slide. - -The dies are mounted on the die-plates of the casting machine by means -of straps, much the same as bolsters are held on punch press beds. The -position of the die on the die-plate must be such that the opening for -the sprue cutter will line up with the nozzle at the outlet of the -cylinder. At the time of casting, the position of the sprue cutter is -as shown in the illustration of this die, Fig. 8. In this position -there is room for the metal to enter the die-cavity, and yet there is -but a small amount of metal to be cut off and pushed back after the die -has been filled with metal. - -With slight modifications, the above style of die may be used for -die-casting any piece that will draw or pull out of a two-part die. If -holes must be cast through the piece, it is only necessary to add core -pins to the lower die _B_, a point that will be more fully described -later. It is unnecessary to add that both halves of the die may be -utilized in making the cavity for the die, should they be needed. Also, -it is often easier to machine out the recess larger than is needed, and -set in pieces in which parts of the outline of the die-casting have -been formed. Gear teeth are put in the die in this way; a broach is cut -similar to the gear desired, then hardened and driven through a piece -of steel plate which is afterward fitted to its place in the die. - - -Slide Dies - -The die illustrated in Fig. 9 is one of the most successful of the -various types of casting-dies, and if properly made is an interesting -piece of die work. The principal use of this particular style of die, -called a slide die, is to cast parts like the one shown in Fig. 10, -which is a disk similar to the one which the last die described was -to cast, except that it has raised letters at the edge and a hole in -the center. It is obvious that the die last described, (Fig. 8), would -not do for disks or other pieces having projections or depressions -around their edges, as, for instance, printing or counting wheels with -raised or sunken characters, or grooved pulleys. Briefly, this style -of die is similar to the simple casting-die, except that slides are -provided, to the required number, which form the edge of the casting. -A die for a plain grooved pulley would require but two slides, while -a die for a printing wheel with forty letters around its edge would -necessitate forty slides, one for each of the letters. The die about to -be described, shown in Fig. 9, was made to cast a wheel with six raised -letters. - -Referring to Fig. 9, _D_ is the cast-iron box or frame, _E_, the lower -die, and _F_ the upper die. In making the lower die-half, the stock is -first shaped to size and doweled to the blank for the upper die-half, -and the holes for attaching to the frame are drilled. For the sake of -clearness, these holes and screws are omitted from the illustration as -are also the vents, since they have been fully explained. The lower -die is next strapped to a faceplate, trued up, and bored out nearly -to the diameter of the body of the piece to be cast, exclusive of the -raised letters. The depth of this recess is equal to the thickness of -the printing wheel plus 3/16 inch to allow for the cam ring _G_ that is -used to reciprocate the slides of the die. The cam ring is made large -enough to cover the die-cavity as well as the slides that surround -it, with an allowance of an inch or two for the cam slots _H_. The six -slides _I_ are made long enough to have good bearing surfaces. With the -size of the cam ring determined, the die is next bored out to receive -this cam ring and the last inch of the recess is carried down to the -depth of the die cavity so as to make an ending space for the slots -that the slides are to work in. The die is now taken from the faceplate -and the slots for the slides laid out. - -[Illustration: Fig. 9. Slide Die for Casting the Printing Wheel shown -in Fig. 10] - -These slots may be milled or shaped, but milling is to be preferred. -The next step is the making and fitting of the slides, which are of -machine steel, having a good sliding fit in the slots. The six slides -are fitted in position and left with the ends projecting into the die -proper. The slots _H_ are next profiled in the cam ring _G_, and the -pins _J_ that work in them are made and driven into the holes in the -slides. With the slides and cam ring in place, the cam ring is rotated -to bring all the slides to their inner position where they are held -temporarily by means of the cam ring and temporary screws. The die-half -with the slides thus clamped in the inner or closed position, is set up -on the lathe faceplate and the die-cavity indicated up and bored out to -the finish size, which operation also finishes the ends of the slides -to the proper radius. The die may now be taken down and the slides -removed to engrave the letters upon their concave ends. The engraving -can be done in the best manner on a Gorton engraving machine, but if -such a machine is not available they may be cut in by hand. Stamping -should never be resorted to for putting in the letters, because the -stock displacement would be so great that it would be impossible to -refinish the surface to its original condition. Before fitting the -cam ring, an opening must be milled in the die to allow the handle to -be rotated the short distance necessary. After the cam ring has been -fitted, it is held in by the four small straps _K_, attached by screws -to the lower die-half at the corners. - -[Illustration: Fig. 10. Printing Wheel cast in a Slide Die] - -The sprue cutter, which is not shown, is operated through the hole -in the center of the piece and is, of course, round in this die. -Its action is the same as was the one previously described, and the -ejecting device is similar, with the exception that the brackets _L_ -that are attached to the ejector-pin plate M, are widely separated so -as to make room for the sprue cutter that works through a hole in the -plate _M_. - - -Die for Casting with Inserted Pieces - -For making die-castings that are to have pieces of another metal -inserted, it is necessary to have a die with provisions for receiving -the metal blank and holding it firmly in position while the metal is -being cast around it, and of course the piece must be held in such a -manner that it can be easily withdrawn from the die with the finished -casting. - -The die illustrated in Fig. 11 is for a part that is used as a swinging -weight, shown in Fig. 12. The upper part of the piece is made from a -sheet steel punching, so as to lighten this part of the piece as well -as to give increased strength, especially at the hole at the pivoted -end of the work. The cast portion of the piece is slotted lengthwise, -as the illustration shows; and three holes pass through the casting, -piercing the sides of the slot. In addition to showing the method of -making dies for inserted pieces, this die shows the principles of -simple coring. - -[Illustration: Fig. 11. Casting-die for Making Castings with Inserted -Pieces like that shown in Fig. 12] - -In making this die, two machine-steel blanks are planed up for the -upper and lower halves of the die, _A_ and _B_, the lower die being -made nearly twice as thick as the upper die because it is in this part -that the most of the die-cavity will be made. In this lower half of -the die the stock is milled out to the same shape as the outline of -the plan view of the casting, being carried down to the exact depth -of the thickness of the casting. From the wide end of this recess the -stock is milled or shaped out in a parallel slot to the outside of the -die-block. At the bottom of the side of this wide slot are T-slots -to guide the slide _E_ that is to work in this opening. The side is -milled and fitted to the T-slots and opening in the die, but is left -considerably longer than the finish size. Next, the slide is mounted -on the faceplate of a lathe and turned out on the end with the proper -radius and a tongue to form the slot that is to be in the curved end -of the casting. At the outer end of the slide is left a lug that is -drilled and tapped for the operating lever _F_ that reciprocates the -slide, using the stud in bracket _K_ as a fulcrum. - -Two pieces of machine steel are next shaped and finished up to form the -chamfered part of the casting and to locate the inserted steel punching -in the die. The combined thickness of these pieces _C_ and _D_ is equal -to the thickness of the casting, less the thickness of the inserted -piece. It is now an easy matter to seat section _D_ in the bottom of -the milled part of the lower die-half, and to locate section _C_ in its -proper position on the upper half. A pilot pin _M_ is fitted in _D_ to -hold the steel punching in position by means of the hole that is in the -extreme upper end of the punching. The pilot pin extends through this -hole into a corresponding hole in section _C_. At the lower end of the -steel part that is inserted, there are two holes the object of which -is to secure the punching to the die-casting, for the molten metal -runs through these holes, practically riveting the die-casting to the -inserted piece. - -[Illustration: Fig. 12. Die-cast Weight with Inserted Sheet-steel -Punching] - -Provision has now been made for holding the sheet-metal part that is -to be inserted, and the cavity has been completed for the casting, -including the tongue at the end; it now remains to describe the manner -of forming the holes that pierce the casting through the slotted -portion. In the lower die-half the positions of the three holes _H_ are -laid out, drilled and reamed. Then, with the two die-halves together -and the slide clamped at its inner position, the holes are transferred -through the slide and the upper die. This being done, it is an easy -matter to make core pins and drive them into the upper die at the two -end holes, the center hole being taken care of by the sprue cutter _L_ -that will be described later. The core pins should be a nice sliding -fit through the slide and in the holes in the lower die, into which -they should extend from a quarter to half an inch. In addition to -coring the holes, these pins act as a lock to hold the slide _E_ in its -proper position at the time of casting. - -The sprue cutter _L_ is most conveniently operated in the center hole, -thus doing away with the core pin that would otherwise be required. The -sprue cutter needs little description in this die, for as in the slide -die, it is merely a plain round rod that fits closely in the holes -through the dies and slide. The ejector mechanism is the same in this -die as in the dies already described; therefore further description is -unnecessary. - -[Illustration: Fig. 13. Casting-die for the Half-round Bearing shown in -Fig. 14] - -The operation of this die is very simple. The sheet-steel piece is laid -in the recess in the open die, being located by the pin _M_. Slide -_E_ is thrown in by means of lever _F_, and the dies are closed. At -the time of casting, the sprue cutter in is the position shown in -the sketch, being nearly through the die-cavity. As before explained, -this position admits the molten metal to pass into the die-cavity, but -still leaves very little sprue to be cut off after the die-casting is -completed. It should be stated that the steel piece that is inserted -must be perfectly flat and free from burrs that would prevent the -die-halves from coming together properly. - - -Bearing Dies - -Bearing dies are one of the most important of the various classes of -casting-dies. The bearings produced by die-casting are so far superior -to those made by other casting methods and machining that their use is -now very extensive. Dies are made for “half-round” and “whole-round” -bearings. There is little out of the ordinary about a whole-round die, -but the half-round die involves many interesting methods of die-making, -and for that reason is here described. - -Fig. 13 shows a casting-die for half-round bearings. Half-round bearing -dies are usually made to cast two bearings at a time, for the reason -that it is just as easy to cast two pieces of such a shape as it is to -cast one, and, in addition, the die is balanced in a better manner. As -with other dies, the first step is to machine up the frame _A_ and the -two die-halves _B_ and _C_. The pieces _D_ and _E_ that are to form -the insides of the bearings are then turned up and one side of each -shaped and keyed to fit the slots that have previously been milled in -die-half _C_. These parts are held in place by dowels and screws. One -of the bearings produced by this die is shown in Fig. 14, and it will -be noticed that there is an oil groove within that covers the length -of the bearing. To produce this groove in the die-castings, a shell -must be turned up and bored out whose inside diameter is that of the -inside of the bearing, and whose thickness equals the depth of the oil -groove. This being done, the oil grooves are laid out upon the shell -and cut out by drilling and filing. After rounding the outside corners, -these little strips are pinned to the cores _D_ and _E_ in their proper -places. - -[Illustration: Fig. 14. Die-cast Half-round Bearing, Showing the Cast -Oil Grooves] - -Another little kink in this connection is worthy of noting. So many -different styles and sizes of bearings are made by a concern doing much -die-casting that it is essential that the die-cast bearings should -bear some distinguishing number to identify them. As this number is -of no consequence to the user it is well to have the number in an -inconspicuous place, but it must be where it will not be effaced by -scraping, etc. Bearing in mind that it is much easier to produce raised -lettering by die-casting than to produce sunken lettering, it will be -readily seen that the oil groove affords a good place in which to -put the bearing number. This is easily done by stamping the figures -upon the narrow strip that forms the oil groove. In this place on the -bearing it may be easily found if needed, and of course there is no -danger of its being taken out by machining. - -The lower die consists of two blocks _F_ and _G_, each of which -contains an impression of a bearing. The best way to make these parts -is to lay out the ends of each of the blocks with the proper radius, -taking care to have the center come a little below the surface of the -face of the block. Then the blocks should be shaped out to get the bulk -of the stock out, before setting up in the lathe. After the lathe work -is done on each piece, which of course is usually done separately, the -faces of the two blocks are faced down just to the exact center of the -impression. It will be noticed that two blocks are used for the lower -part of the die. The reason is to facilitate the locating of the female -parts of the die in proper relation to the male parts. After properly -locating, they may be doweled and screwed to baseplate _B_. - -[Illustration: Fig. 15. Interesting Examples of Die-castings] - -The sprue cutter _H_, better shown in the plan view, is square in shape -and connects with the die-cavities in a thin narrow opening on either -side of the sprue cutter. The ejector pins, _I_, two to each die, are -at the ends of the bearings. The ejector-pin plate _J_ is necessarily -large, and is operated by lever _K_. - -Fig. 15 shows a number of interesting examples of die-castings. - - - - -CHAPTER III - -VAN WAGNER MFG. CO.’S DIE-CASTING PRACTICE - - -In 1907, Mr. E. B. Van Wagner, of Syracuse, N. Y., established the -E. B. Van Wagner Mfg. Co. for the production of die-castings. The -factory comprises the office section, the machine shop where the dies -and casting machines are built, the metallurgical laboratory where the -metals are alloyed, the casting department shown in Fig. 17 where the -die-castings are made, and the trimming department. - - -Possibilities and Limitations of Die Casting - -[Illustration: Fig. 16. Die-casting Constructions to be avoided] - -At the outset we may say that it is possible to die-cast almost any -piece, but it is not by any means practicable to do so. It must be -remembered that to die-cast on a practical basis the dies must be -constructed in such a manner that the cost of their operation and -up-keep will be light, or there will be no profit in die-casting. It -is impracticable to produce under-cut work, that is, work having no -draft and which is therefore impossible to draw from the die. Such -an instance is that illustrated at _A_, Fig. 16, and by the internal -section of _M_, Fig. 21, and the internal groove in _O_, also shown -in Fig. 21. If absolutely necessary, work of this kind can be done by -the use of collapsible cores; but here, again, we meet resistance in -maintaining the dies in proper condition, and, moreover, this method -is commercially impracticable, owing to the difficulty of operating -these cores rapidly. Hollow work, requiring curved cores, like faucets -and bent piping of the character illustrated at _C_ in Fig. 16, are -difficult to produce. If, in designing the piece, it can be planned to -have the parts of such a shape that the cores can be readily withdrawn, -employing a two-piece core with a slight draft in each direction, -the division coming as indicated by the core line of _C_ in Fig. 16, -the problem becomes simpler. Oftentimes this work can best be done -by casting in a straight piece, afterward bending the die-casting. -It does not pay to cast rough heavy work that can be made just as -efficiently by sand casting. Generally speaking, the greatest saving -can be effected by die-casting small pieces which have previously -required a large amount of machining to produce. On large plain work -the amount of metal required for the casting makes the cost excessive -on account of the difference in cost of the metals. If, however, the -large work must be finely finished by polishing, etc., it is oftentimes -found of advantage to die-cast. Corners, especially those joining thick -and thin sections, as at _B_, Fig. 16, should be heavily filleted -as shown on one side of this piece. Regarding the casting of thin -sections, it is not practicable to try to cast sections under 3/64 -inch in thickness, as the metal runs with difficulty into such narrow -places. A casting having walls 1/16 inch, like that shown at _X_, Fig. -24, is easily cast. Threaded sections, if the threads are fine, say, -under twenty-four to the inch, should not be die-cast, because under -moderate pressure they will strip. A good way to treat constructions of -this kind is to enclose brass or steel bushings in the die-castings in -which the threads are required. - -[Illustration: Fig. 17. View of the Casting Room] - -As to the accuracy with which die-castings may be produced, it is -possible to keep dimensions within 0.0005 inch of standard size, but to -do so requires considerable expense in keeping the dies in condition. -A limit of 0.002 inch, however, is entirely practicable, and can be -maintained easily. In specifying the accuracy with which die-castings -are to be made, only those parts which are absolutely essential should -be held to size, in order to keep the cost of the work nominal. One of -the great advantages of the use of die-castings is that no finishing is -required after the pieces leave the molds. Finish requirements should -be plainly stated in ordering die-castings, as the alloy must be suited -to these requirements. - -[Illustration: Fig. 18. Methods of attaching Die-cast Gears, etc., to -Shafts] - -Another great saving is effected on lettered work, either raised or -sunken. One of these jobs is illustrated at _Q_, Fig. 22, which shows -an example of die-cast lettering. Sunken lettering is to be preferred -to raised lettering, as the latter is more easily injured. Knurled -work may be produced easily, if straight knurls are used, and threaded -sections over ¼ inch in size are entirely practicable, either internal -or external. External die cast threads are illustrated at _R_ and _S_, -Fig. 22. The casting of gears and segments is a familiar application -of die-casting; this is illustrated by the large gear at _N_, Fig. 21, -and the segment at _W_, Fig. 23, which give an idea of the general -character of this class of work. The casting of pulleys, gears, and -similar parts on shafts may be easily effected as shown by the gear on -the shaft at _N_, in Fig. 21. The views shown in Fig. 18 are intended -to convey an idea of three methods of die-casting around shafts. At -_D_ is shown a die-casting cast around a steel shaft. If the surface -of the shaft coming within the pulley has been previously knurled, -the pulley will grip it much better, but for ordinary purposes the -shrinkage of the die-cast metal around the shaft is sufficient. If any -heavy strain is to be imposed on the work, it is better to provide -anchor holes through the shaft, like those indicated at _E_. It will be -readily seen that the die-cast metal runs through these holes in the -shaft, forming rivets which are integral with the casting. For locating -levers upon the ends of shafts, etc., a good way is to flatten opposite -sides of the shaft and cast around them, as shown at _F_, Fig. 18. The -screw seen projecting beneath the piece at _Q_, Fig. 22, was die-cast -in place. Any of these methods are to be recommended, and a proper -knowledge of possibilities of this kind will increase the scope of -die-casting. - -[Illustration: Fig. 19. A Few Possibilities of Die Casting] - -Another phase of die-casting which can well be borne in mind is the -possibility of inserting steel or other parts in the die-casting. -Such an instance is shown at _G_ in Fig. 19--a die-casting which was -made by the Van Wagner Co. as a part of an electrical apparatus, the -steel inserts being contact points. Oftentimes it is found advisable -to include brass bearing rings to give additional durability at points -where the die-cast metal would not stand up. The die-casting shown at -_U_, Fig. 23, in which the brass ring at _T_ has been incorporated, -is typical of such cases. To die-cast pieces like those shown at -_H_ in Fig. 19, and similarly at _V_ in Fig. 23, having inverted -conical openings, might at first thought seem difficult, but this is -entirely practicable. Similarly, split bushings like those shown at -_I_, Fig. 19, and at _W_, Fig. 23, may be cast with projecting lugs -for the reception of screws for clamping upon shafts, etc., but this -construction should not be used if frequent tightening or loosening -will be necessary. - -[Illustration: Fig. 20. Castings which illustrate Points of Shrinkage -and Draft] - -[Illustration: Fig. 21. Die-castings showing Impractical Under-cut -Sections; also a Large Gear die-cast on Shaft] - -[Illustration: Fig. 22. Die-castings which show Lettering and Thread -Castings] - -The shrinkage problem manifests itself in die-casting in the same -measure that it does in other casting operations. Different metals -shrink in different degrees, as will be explained later on. However, -one important point can be mentioned at this time: that is, the amount -of shrinkage is often dependent upon the shape of the piece. For -instance, pieces like those shown at _K_ in Fig. 20 or at _X_ in Fig. -24, will shrink very little on account of the fact that the steel mold -is of such shape that the central core will prevent the die-casting -from shrinking. However, pieces like those shown at _L_ in Fig. 20, -or at _V_ in Fig. 24, which have nothing to hold them from pulling -together as they cool, will shrink to the greatest extent. All of -these points must be taken into consideration when designing work for -die-casting. Practically no draft is necessary on a die-casting, except -on very deep sections, as indicated at _J_ in Fig. 20, where a draft -of 0.001 inch to the inch is desirable. Perfectly straight sections, -however, can be cast, as the shrinkage of the metal is usually enough -to free it from the die. - -[Illustration: Fig. 23. Typical Die-castings illustrating Various -Points] - -[Illustration: Fig. 24. Die-castings illustrating the Extremes of -Shrinkage] - -It is the opinion of the Van Wagner Co. that die-casting costs can -be materially reduced if designers will bear this point in mind when -bringing out new designs. Even though it is often possible to cast -special pieces, incorporating several parts in one, and thereby -accomplishing what seems to be a great stunt to the designer, it is -sometimes more practicable to make the piece in several sections and -later assemble it. Not only is this simpler for the die caster, but it -is also more economical for the customer. Such points as avoiding thin -sections, including large fillets at corners, as well as taking account -of the under-cut problem, are simply matters of common sense, but they -can profitably be considered by the designer. - - -The Van Wagner Die-casting Machine - -The first essential to good die-casting is a good casting machine. -Perhaps the best known types of casting machines are of the familiar -plunger type, of which there are several varieties, the pneumatic type -and the rotary or automatic type. (For descriptions of various types of -die-casting machines, see “Die Casting Machines,” MACHINERY’S Reference -Book No. 108.) For the economical production of die-castings, however, -the hand-operated machines are rather too slow, and automatic machines -are applicable only to a class of work which may be made in very large -quantities. For these reasons, therefore, the Van Wagner Co. employs -the compressed air type of die-casting machine which was patented by -Mr. E. B. Van Wagner in 1907. In the casting department of the Van -Wagner shop, illustrated in Fig. 17, there are installed about thirty -machines. Fig. 27 shows a die-casting machine in the open position. -Fig. 26 shows a closer view of the die-operating mechanism and Fig. 25 -is presented to give a general idea of the construction of the entire -machine. - -[Illustration: Fig. 25. Drawing illustrating Principle of Van Wagner -Die-casting Machine] - -By referring to the line illustration Fig. 25, which shows the Van -Wagner pneumatic die-casting machine in part, and comparing this -illustration with Fig. 26, which shows the general appearance of the -die-operating and other mechanism of the casting machine, a good idea -may be obtained of its construction and working. At _A_ may be seen -the base of the machine in which is located the melting pot _B_. This -melting pot is heated by means of fuel oil passing through the supply -pipe _C_ to the burners _C_`1. A vent pipe _D_ is provided to take -away the gases incident to combustion. The pressure for “shooting” the -metal into the die cavity is supplied by air through the supply pipe -_E_. A valve controls this air supply. The pressure is regulated to -suit the particular casting or die, the proper amount being determined -by experiment. Similarly, an air exhaust pipe _F_, which may be seen -directly above the supply pipe, sub-divides into two tubes which -extend to the die cavity to exhaust the air before the metal is -admitted. There are two methods of overcoming the presence of air in -the die cavity--the exhaust method and the venting method, and it is -the former that is here described. - -[Illustration: Fig. 26. View of Machine showing Die-operating Mechanism] - -A “goose-neck” _G_, shown in Fig. 25, serves to temporarily contain -the metal which is forced into the mold. An amount of metal slightly -in excess of that required for one die-casting is placed in this -goose-neck with a hand-ladle, previous to each operation of the -machine. One end of the goose-neck is connected to the air pipe, _E_, -while the other end terminates in the nozzle _G_`1. This nozzle may -best be seen by referring to the illustration of the machine shown in -Fig. 27, in connection with Fig. 25. One of the advantages in using -this goose-neck is that the entire air pressure is expended upon the -metal in the goose-neck, and, by reason of its isolated position, the -goose-neck and its contents are kept slightly hotter than the contents -of the melting pot. - - -The Die-operating Mechanism - -The die-operating mechanism of the machine is contained within a hinged -framework, shown in position for the removal of the die-casting in Fig. -27. Referring to Fig. 26, in connection with the line illustration Fig. -25, it will be seen that the die-holding mechanism is all supported -upon the lower die-holding plate _H_, which is hinged to the edge -of the base of the machine. A lock _J_ serves to hold the dies and -operating mechanism in the upright operating position, and by means -of a counterbalance, suspended from an overhead rope which connects -with the top of the mechanism at _P_, the changing of the position of -this mechanism is easily effected, and when thrown into the horizontal -position, as indicated in Fig. 27, it rests upon a support while the -dies are being opened and the castings ejected. - -[Illustration: Fig. 27. Die-casting Machine in Position for Removal of -Casting] - -The lower die is shown at _H_`1 and the upper die _K_`1 is mounted -upon the upper die-holding plate _K_. Four rods _L_ act as guiding -members for the upper die-holding plate to slide upon. These rods _L_ -are mounted in fixed positions at the corners of the lower die-holding -plate _H_, and at their upper ends the operating shaft supporting plate -_M_ is located in a fixed position, serving to support the upper ends -of these rods. The position of this plate _M_ is adjustable upon the -rods by means of check-nuts, thus providing for the accommodation of -thick as well as thin dies. A shaft _O_ is supported in this top plate, -and by means of the operating lever _N_ working through slotted levers -_O_`1 and links _O_`2, the upper die-holding plate and die can thus -be removed from contact with the lower die at will. - -The metal enters the die cavity through the nozzle _G_`1 and after -setting, it is necessary to cut the sprue formed by the surplus metal -that remains outside the die cavity. For this purpose, a sprue-cutter, -operated by means of hand-lever _Q_`1, is employed. This sprue-cutting -lever is hinged in the fulcrumed link _Q_`2, and is held in its -casting position by means of an adjustable stop on bracket _Q_`3. - -[Illustration: Fig. 28. General View of Trimming Department] - -In many dies, it is necessary that water be circulated through the -die-blocks to keep them cool during the die-casting operation. In -Fig. 26, the water pipe may be seen at _R_, and hose pipes run from -this supply to each side of the die-blocks, thus providing a cooling -circulation. In this illustration, the pipes used for exhausting the -air from the die cavity are apt to be confused with the cooling pipes, -but by following the two pipes leading vertically down to the machine, -the exhaust pipes may be seen and kept distinct from the water pipes. - - -Making a Die-casting - -In order to clearly understand the operation of the die-casting -machine, let us follow the sequence of events that takes place in -producing a casting. Two men are required to operate the machine. In -Fig. 27, the operators may be seen in their working positions. The -first step is taken by the operator at the left who, with a hand-ladle, -dips enough metal for one casting from the melting pot and pours it -through nozzle _G_`1 into the goose-neck. The second operator in the -meantime is replacing the cores in the dies, adjusting the position of -the sprue-cutter and closing the dies preparatory to making a casting. -This being done, he elevates the dies and their operating mechanism, -which are hinged and counterbalanced, as previously described, bringing -them to an upright position. The die operator now mounts the box, -raises the sprue-cutter to its open position to admit the metal; after -which the machine operator turns the air valve with his left hand. The -operation of this air valve admits the air behind the metal, forcing it -into the die, and the same movement opens the exhaust valve slightly in -advance. The exhaust valve is located upon the second length of piping -just above the air valve, and as a link connects the two valves, the -single motion exhausts the air from the die cavity and immediately -afterward the air is admitted behind the metal, thereby “shooting” the -metal into the die. This being done, the air is shut off and the die -operator cuts the sprue by means of lever _Q_`1, withdraws the cores -in the die, throws the dies to the open position (which is indicated -in Fig. 27), and operates the ejecting mechanism, thus removing the -casting from the die. In the meantime, the machine operator is tending -to his metal supply and getting a ladle full of metal ready for the -next die-casting operation. By referring to the machines shown in Fig. -17, it will be noticed that only a few are provided with exhaust piping -for venting the dies. Another venting method will be described later. - -[Illustration: Fig. 29. Trimming Die-castings on a Filing Machine] - -The number of die-castings which can be made on one machine per day of -ten hours varies with the character of the pieces being die-cast, the -number of pieces made at each operation of the machine and the ease -with which the dies may be worked, which depends, of course, upon the -number of cores and parts to be handled at each die-casting operation. -The dies shown in the machine in Fig. 26, produce four bearings at each -operation. - - -Trimming Die-castings - -At the end of each run the operators of the machines go over their -work, breaking the castings from the sprues and throwing out all that -are defective. No matter how carefully the die-casting molds have been -made, there is always a certain amount of trimming to be done on the -finished die-castings, on account of the crevices left in the die for -air vents, or which exist from improper fitting of the parts of the -dies. These “fins,” as they are called, are trimmed by hand operators -in a special department. A general view of this trimming room is shown -in Fig. 28. Usually it is sufficient to scrape these fins off with a -scraping knife, but if the casting is especially difficult to produce, -so that a large opening is required to admit the metal, it is sometimes -necessary to trim unusually thick sprue sections by filing. Fig. 29 -illustrates the method of trimming such die-castings on a filing -machine. - -[Illustration: Fig. 30. General View of E. B. Van Wagner Co.’s Die -making Department] - -[Illustration: Fig. 31. A Typical Die-casting Mold] - - -The Dies Used - -Next to the casting machine, the dies or molds are the most important -necessary factor. A general view of the Van Wagner Co.’s die-making -department is shown in Fig. 30. In order to gain a proper conception of -the work required in producing a high-grade die-casting mold, we will -follow the different steps which are necessary in making the mold. The -first and most important step is the proper planning of the die. Before -any work at all can be done, it is necessary to plan the die, _i. e._, -to decide just where the parting lines will come; just what method -will be used for ejecting the piece; what alloy will be used; where -the casting will be gated; and a hundred and one minor points, all of -which have a direct bearing upon the performance of the finished dies. -All these decisions have to be made by the diemaker, and in Fig. 37 he -is shown, micrometer in hand, computing the shrinkage allowances that -he will make in the dies. This is a very important factor on accurate -work as the shrinkage varies from 0.001 to 0.004 inch, according to the -alloy and the general shape of the piece. - -[Illustration: Fig. 32. Die-casting Mold shown in Fig. 31, disassembled] - -Before taking up the actual machining operations of the mold-making -as conducted in this factory, it will be well to take a typical -die-casting mold and note its general construction. Fig. 31 shows a -typical die-casting mold closed, while Fig. 32 shows the same mold -disassembled on the bench to show its construction. The piece for -which the mold has been made is also shown. Fig. 33 shows a similar -die in section. From the three illustrations a good idea of an average -die-casting mold can be obtained. Referring to these illustrations, the -principal parts of this die are the ejector box _A_, and the ejector -plate _B_ which is operated by the racks _C_. For operating the ejector -plate, the pinion shaft _D_ having a handle suitable for turning, is -furnished. This, of course, fits into a bored hole in the ejector box, -bringing the pinion into mesh with the racks for raising the ejector -plate. In the ejector plate are three ejector pins _E_ for removing -the casting from the mold. The ejector pins operate through holes _F_. -Beyond the pinion shaft may be seen the casting for which this mold -has been made. It will be noticed that the top side of the casting has -three projecting lugs through which are small holes. Provision for -forming this side of the die-casting is made in the lower half of the -mold _G_, while the upper half of the die-casting is taken care of -by the top plate _H_. One of the toggles for operating the core pins -through these three lugs is shown at _I_. These parts will be described -more fully later. The sprue cutter is shown in position in the die at -_J_. - - -Machining the Die Cavities - -As will be noticed from Fig. 30, the machinery in the die-making -department is of modern design, for no other class of work demands as -good tool equipment and as much skill in the making as die-casting -molds. The die-blocks are made of machinery steel. Fig. 34 illustrates -the first step in making a die-casting mold after the die-block has -been shaped approximately to size. This operation consists in carefully -facing off the die surfaces on a vertical-spindle grinding machine. -This, of course, is a quick method of surfacing the die-block, and -it insures that the top and bottom surfaces of these plates will be -parallel, permitting the die-faces to come together properly. - -[Illustration: Fig. 33. Section through a Die-casting Mold] - -The next step consists of laying out the die, as shown in Fig. 36. This -is done in the usual manner, by working on a coppered surface, using -dividers, scales, and a center punch. When laying out the die, the -necessary allowances are made for shrinkage and finish, these points -having been planned before actual work on the die has been started. As -in other phases of die-work, the machining operations are performed, -as far as possible, before any hand-work is done. In Fig. 38 may be -seen a die-maker turning the cavity in a part of the die-casting mold. -The highest type of skilled workmanship is called for on this machine -work, and as may be surmised from Fig. 38, where the die-maker is shown -measuring the die with a vernier caliper, the measurements must be -exact, for no grinding operations follow the machine work. - -[Illustration: Fig. 34. First step in making the Mold--Grinding -Surfaces of Blocks] - -[Illustration: Fig. 35. A Milling Operation on a Die] - -Figs. 35 and 39 show typical milling operations being performed on -die-casting molds. In Fig. 39 the diemaker is shown indicating a pin in -one corner of the mold cavity, preparatory to doing additional milling. -The block is held in the usual manner by being clamped on the bed of -the milling machine, and after it has been properly located under the -cutter head, tools are substituted for the indicator and the milling -of the cavity is completed. Fig. 35 shows one of the sections of the -die-casting mold which is to be used in producing the casting shown at -the right of the work. In this case the diemaker is milling the recess -for the steel arbor which may be seen directly in the foreground. This -will be fitted in place to provide for the forming of the hole in the -side of the piece. - -[Illustration: Fig. 36. Laying out One of the Mold Parts] - -[Illustration: Fig. 37. Planning the Die-casting Mold] - -[Illustration: Fig. 38. Turning out a Die-casting Mold] - -[Illustration: Fig. 39. Indicating a Mold on the Milling Machine] - -Fig. 40 illustrates several important points in the making of a -die-casting mold. This illustration shows the ejector box with the -lower half of the mold on it, the ejector plate being held against the -under side of the die-plate by means of the pinion shaft. The operation -being done is the drilling of the ejector-pin holes. Referring back to -Fig. 32, which by the way shows the die here illustrated disassembled, -the holes being drilled are those shown at _F_ for the reception of the -pins _E_. The method employed is to drill the holes through the die and -into the ejector plate, afterward reaming all holes to size and driving -the pins into position in the ejector plate, while they are allowed to -slide freely through the die-plate. We will now assume that the ejector -box and plate have been completed and fitted, a pinion shaft for -operating this plate also fitted, the lower and upper dies completed -by the machining operations previously described, and all assembled. -The final operation of the fitting of the pins is shown in Fig. 41 in -which the die-maker may be seen filing off the ends of these pins so -that when dropped to the lower position they will lie flush with the -surface. If of uneven lengths, these pins will cause irregular spots in -the casting. It now remains to describe the toggles used for operating -the cores which form the holes through the three lugs in the casting. -One of these toggles, of which there are three, is shown at _I_, in -Fig. 31, and also in Fig. 32. These toggles consist of brackets which -are attached to the die-plate, and levers which are fulcrumed at the -ends of the brackets so that their operation works the core pins. It is -necessary to remove these core pins after each casting has been made -and position them before another casting can be produced. - -[Illustration: Fig. 40. Drilling the Ejector-pin Holes] - -The fitting of the parts of a die-casting mold is one of the -most important parts of the work. It demands the highest type of -workmanship, for a poorly fitted die means a die which works hard -in addition to producing poor castings. It is very important that -all movable parts should work freely. Fig. 42 shows the assembling -operation on a die-casting mold, the casting which is to be duplicated -being shown in the immediate foreground. These parts must all be -screwed into their respective places, making the joints as nearly -air-tight as possible. One cause of poor die-castings arises from the -trapping of air in the die, and different methods are employed for -overcoming this trouble. - - -Venting the Dies - -There are two methods of preventing air from being trapped in -die-casting molds; either by constructing the dies so that the air -may be exhausted from the mold cavity before admitting the metal, or -by venting the die so that the air may be forced out by the inrushing -metal. In the first of these methods it is necessary that the joints in -the mold be made as close as possible, otherwise it will be impossible -to produce anything like a vacuum in the mold cavity. If, however, it -has many parts which must be fitted, it is usually considered advisable -to provide the die with vents consisting of milled recesses a few -thousandths inch deep. Several vents are provided, from which the air -can escape when the metal is admitted to the dies. The hot metal, of -course, “shoots” through them in thin ribbons, but not enough escapes -to affect the pressure on the metal which goes into the casting. - -[Illustration: Fig. 41. Fitting Ejector-pins] - -No matter how carefully a die may have been constructed, or how -carefully it has been assembled, there is always a certain amount of -“babying” to be done before it will work satisfactorily. The casting -may stick a little here, or there may be a rough spot there, and it -is the successful elimination of these troubles which constitutes the -production of a good die-casting. - - -Die-casting Metals - -One of the purposes of this book is to correct several erroneous -impressions which are prevalent in regard to die-casting possibilities. -Many people seem to think that nearly all metals can be die-cast, but -as a matter of fact, those metals which can be successfully die-cast -can be numbered on the fingers of one hand, being alloys of lead, zinc, -tin, copper and antimony. The tin base metals shrink very little, while -the zinc base metals shrink considerably, and those with a large per -cent of aluminum have a very high shrinkage. Without doubt, the most -used die-casting metals are the zinc base metals. A typical metal of -this class contains about 85 per cent zinc; 8 per cent tin; 4 per -cent copper and 3 per cent aluminum. The melting point of this metal -is about 850 degrees F. While this alloy is one of the most common, -it is not by any means the best, as there is too little tin employed, -but it is a comparatively cheap metal, which probably accounts for its -large use. This metal is easily affected by heat and cold, and rapidly -deteriorates with age. The lead base metals may be typified by an alloy -containing 80 per cent lead; 15 per cent antimony; 4 per cent tin; and -1 per cent copper. This composition melts at approximately 550 degrees -F. and is used for castings subjected to little wear and where no -great strength is required. The weight of this metal is its greatest -objection, and it is also quite brittle because of the large percentage -of antimony. - -[Illustration: Fig. 42. Assembling a Die-casting Mold] - -For the best class of die-castings, the tin base metals are employed. -These range from 60 to 90 per cent tin, and from 2 to 10 per cent -copper, together with a little antimony. The melting point of a -mixture of this composition is about 675 degrees F. The castings have -a good color and they are much better in quality than any of the other -alloys. It is absolutely essential that tin base metals be used for -carbureter parts or other parts coming in contact with gasoline. Also, -the tin base metals must be used for parts which come in contact with -food products, as the lead or zinc alloys have a contaminating effect. - -Aluminum alloys have been cast in France and Germany in limited -quantities, but very seldom in this country on account of their high -melting point, as well as their effect upon the die. After aluminum -alloys have been run in the dies for a short time, the surfaces of the -molds become pitted. Through some unexplained cause, the metal seems -to flake out particles of the steel in the molds. When an aluminum -alloy is to be used, a good mixture is 80 per cent aluminum, 3 per cent -copper and 17 per cent zinc. This alloy has a high shrinkage and it has -also the same deteriorating effect upon the dies, but to a much less -degree than pure aluminum. - - - - -Transcriber’s Notes - - -Punctuation, hyphenation, and spelling were made consistent when a -predominant preference was found in this book; otherwise they were not -changed. - -Simple typographical errors were corrected; occasional unbalanced -quotation marks retained. - -Ambiguous hyphens at the ends of lines were retained. - -Text uses “die-cavity” and “die cavity”, “die-maker” and “die maker”; -none changed here. - - - - - -End of the Project Gutenberg EBook of Die Casting, by Chester L. 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Lucas - -This eBook is for the use of anyone anywhere in the United States and most -other parts of the world 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. If you are not located in the United States, you'll have -to check the laws of the country where you are located before using this ebook. - -Title: Die Casting - Dies--Machines--Methods - -Author: Chester L. Lucas - -Release Date: September 17, 2016 [EBook #53064] - -Language: English - -Character set encoding: UTF-8 - -*** START OF THIS PROJECT GUTENBERG EBOOK DIE CASTING *** - - - - -Produced by Chris Curnow, Charlie Howard, and the Online -Distributed Proofreading Team at http://www.pgdp.net (This -file was produced from images generously made available -by The Internet Archive) - - - - - - -</pre> - - -<div class="figcenter" style="width: 400px;"> - <img src="images/cover.jpg" width="530" height="800" alt="Cover" /> -</div> - -<hr /> -<p class="newpage large center wspace uline"> -MACHINERY’S REFERENCE SERIES</p> - -<p class="smaller center wspace">EACH NUMBER IS ONE UNIT IN A COMPLETE LIBRARY OF<br /> -MACHINE DESIGN AND SHOP PRACTICE REVISED AND<br /> -REPUBLISHED FROM MACHINERY</p> - -<p class="p4 center larger">NUMBER 109</p> - -<h1 class="nobreak p2"><span class="larger wspace">DIE CASTING</span><br /> -<span class="subhead">DIES—MACHINES—METHODS</span></h1> - -<p class="p2 center">By <span class="smcap">Chester L. Lucas</span></p> - -<h2 class="nobreak p2"><a id="CONTENTS">CONTENTS</a></h2> - -<table summary="Contents"> - <tr> - <td class="tdl">Die Casting</td> - <td class="tdr"><a href="#CHAPTER_I">3</a></td></tr> - <tr> - <td class="tdl">Making Dies for Die-Casting Machines</td> - <td class="tdr"><a href="#CHAPTER_II">15</a></td></tr> - <tr> - <td class="tdl">Van Wagner Mfg. Co.’s Die-Casting Practice</td><td class="tdr"><a href="#CHAPTER_III">27</a></td></tr> -</table> - -<p class="p2 center small"> -Copyright, 1913, The Industrial Press, Publishers of <span class="smcap">Machinery</span>,<br /> -49–55 Lafayette Street, New York City</p> - -<hr /> - -<p><span class="pagenum"><a id="Page_3">3</a></span></p> - -<div class="chapter"> -<h2 class="vspace"><a id="CHAPTER_I">CHAPTER I</a><br /> - -<span class="subhead">DIE CASTING</span></h2> -</div> - -<p>Die-casting, a comparatively recent method for producing finished -castings, is rapidly proving itself an important factor in the economical -manufacture of interchangeable parts for adding machines, typewriters, -telephones, automobiles and numerous other products where it is essential -that the parts be nicely finished and accurate in dimensions. -The term “die-casting” is self-explanatory, meaning “to cast by means -of dies”; described briefly, the process consists of forcing molten metal -into steel dies, allowing it to cool in them, and then opening the dies -and removing the finished casting. It is the purpose of this treatise -to give a general outline of the die-casting process, showing its possibilities -and limitations, and also to give a description of the die-casting -machinery and its operation, of the fundamental principles involved, -and of the methods used in the die-making. Illustrative examples of -the best types of dies, based on results obtained from actual experience, -will also be given.</p> - -<h3>Origin of Die Casting</h3> - -<p>The origin of the die-casting process is somewhat difficult to ascertain. -We may look into the history of type founding and find that -away back in 1838, the first casting machine for type, invented by Bruce, -was a machine that involved the principles of die-casting as it is practiced -to-day. More recently, in 1885, Otto Mergenthaler brought out the -linotype machine. This machine is a good example of a die-casting -machine. However, as we interpret the word to-day, die-casting is a -broader term than type-casting or linotyping, although its development -without doubt is due to the success of the linotype machine. It is -doubtful if die-casting, properly speaking, was originated until about -fifteen years ago, and it is certain that it is only during the past few -years that the activities in this line have been very noticeable.</p> - -<p>One of the first experiments in the direction of die-casting was undertaken -to get out some rubber mold parts cheaply enough to leave a -profit on a job that was beginning to look dubious from the financial -side. The molds were for making rubber plates about three inches -square and one-eighth inch thick, the top side of which was decorated -with fine raised scroll work; it was this latter feature that gave the -trouble. After wasting much time and money trying to stamp the -mold parts, a metal-tight box was made as shown in <a href="#Fig_1">Figs. 1 and 2</a> -with a block screwed in it, the purpose of which was to shape the mold -impression and impart to it the scroll design. As shown, the ends of -the box were removable, being screwed on. This box was placed under -a screw press and a straight plunger that just filled the top of the box -was fitted to the head of the press. After the two were lined up, -molten type metal was poured into the box, and as soon as the metal -had cooled to the “mushy” state, the ram of the press was forced down<span class="pagenum"><a id="Page_4">4</a></span> -as shown in <a href="#Fig_1">Fig. 2</a>. Next, the ends of the box were removed, the screw -holding the block taken out, and the die-casting pushed from the box. -The object in having the inclined side to the box was to produce a piece -shaped with the proper inclination for its position in the final mold -used for casting the rubber plates. The illustrations give an idea of the -compression that took place. The die-casting was found to be sharp -at the corners and free from flaws, and the scroll work came up in fine -shape. Naturally the rest of the mold parts were made in the same -way and the job turned from failure into success.</p> - -<div id="Fig_1" class="figcenter" style="width: 442px;"> - <img src="images/i_004.jpg" width="442" height="600" alt="" /> - <div class="caption intact"> - <table id="tablefig1" summary="figures 1 and 2"> - <tr> - <td class="tdl">Fig. 1. An Early Experiment in Die Casting—Before Applying Pressure</td> - <td class="tdl">Fig. 2. An Early Experiment in Die Casting—After Applying Pressure</td></tr> - </table> - </div></div> - -<p>From such simple experiments as these, the die-casting industry -has developed to its present stage. In view of the advances that have -been made in die-casting, it is singular that there are to-day only<span class="pagenum"><a id="Page_5">5</a></span> -about a dozen concerns in the business in this country, but as the subject -becomes better understood, and the possibilities of the process are -realized, the demand for this class of castings will result in many -other firms going into the work, and it is not improbable that a large -number of factories will install die-casting plants of their own to aid -them in producing better work in a more economical way.</p> - -<h3>Advantages, Possibilities and Limitations of Die Casting</h3> - -<p>The greatest advantage of die-casting is the fact that the castings -produced are completely and accurately finished when taken from the -dies. When we say completely, we mean that absolutely no machining -is required after the piece has been cast, as it is ready to slip into its -place in the machine or device of which it is to be a part. When we -say accurately, we mean that each piece will come from the die an -exact counterpart of the last one; and if the dies are carefully made, -the castings will be accurate within 0.001 inch on all dimensions, -whether they are outside measurements, diameters of holes or radii. -All holes are cast and come out smoother than they could be reamed; -lugs and gear teeth are cast in place; threads, external and internal, -and of any desired pitch can be cast. Oil grooves can be cast in bearings, -and, in a word, any piece that can be machined can be die-cast.</p> - -<p>The saving in machining works both ways; not only is all machine -work eliminated by the one operation of casting, but the machine tools -and the workmen necessary for their operation and up-keep are dispensed -with, the expense of building jigs and fixtures is stopped; and -no cutters, reamers, taps or drills are required for this branch of the -production. In addition, the labor required for operating the casting -machines may be classed as unskilled. No matter how intricate and -exacting the machine work on a piece has been, and how skillful a -workman was required to produce the work when machine-made, the -same result may be brought about by die-casting, and usually the work -is excelled, and, excluding the die-making, unskilled men can make the -parts.</p> - -<p>From a metallurgical standpoint a die-casting is superior to a sand-casting -on account of its density, strength and freedom from blow-holes. -Also, when the hot metal comes in contact with the cool dies, it forms -a “skin” similar to the scale on an iron sand-casting. As the die-casting -requires no machining after leaving the dies, this skin increases the -wearing qualities of the casting.</p> - -<p>The possibilities of die-casting are numerous. By this method of -manufacturing it is possible and practical to cast pieces that could not -possibly be machined. It is an every-day occurrence to make castings -with inserted parts of another metal, as, for instance, a zinc wheel with -a steel hub. It is also possible to make babbitt bearings that are harder -and better than can be made in any other way. Often there are two or -more parts of a device that have formerly been made separately, machined -and assembled, that can be die-cast as one piece. In such cases -the saving in production is very great. Figures and letters may be -cast sunken or in relief on wheels for counting or printing, and of<span class="pagenum"><a id="Page_6">6</a></span> -course ornamentation may be cast on pieces that require exterior finish. -As to size, there is no definite limit to the work that can be cast. -One job that is being done at the present time is a disk 16 inches in -diameter with a round flange 1 inch in diameter, around the rim.</p> - -<div id="Fig_3" class="figcenter" style="width: 489px;"> - <img src="images/i_006.jpg" width="489" height="600" alt="" /> - <div class="caption">Fig. 3. Examples of Die-castings</div></div> - -<p>“There is no great gain without some small loss,” is just as true of -a process like die-casting as it is of anything else. The limitations -of this work are few, however, and they are here given so as to state -the situation fairly. Generally speaking, a part should not be considered -for die-casting if there are but few pieces required, because the -cost of the dies would usually be prohibitive. Often, however, it happens -that because of the large amount of accurate machine work being -done on a machine part, it is economical to make a die for the comparatively -small number of parts required and die-cast them. A case -illustrating this phase of the matter recently occurred in actual practice. -In getting out an order of two hundred vending machines, it -was decided to try die-casting on a part that was difficult to machine. -The dies were expensive, costing $200, and as there were only 200 pieces<span class="pagenum"><a id="Page_7">7</a></span> -to be cast, the die cost per piece was one dollar; but even with that -initial handicap, it was found that on account of the difficult machining -that had formerly been required, the die-cast parts effected a large -saving, and of course the results were superior.</p> - -<p>A rough part that would require little or no machining should not be -die-cast, because pound for pound, the die-casting metals cost more than -cast iron or steel. The casting machine cannot make parts as rapidly -or of as hard metals as the punch press or the automatic screw machine. -For this latter reason a part that necessarily must be made of brass, -iron or steel, cannot be die-cast, although mixtures approximately equal -in strength to iron and brass are readily die-cast. To give added -strength to a die-cast part it is often advisable to add webs and ribs or -to insert brass or iron pins at points that are weak or subject to hard -wear. Roughly speaking, it is the part that has required a good deal -of accurate machine operations that shows the greatest difference in -cost when die-cast, and sometimes the saving is as great as 80 per -cent.</p> - -<h3>The Metals used in Die Casting</h3> - -<p>The metals that produce the best die-castings are alloys of lead, tin, -zinc, antimony, aluminum and copper, and the bulk of the die-castings -made at the present time are mixtures of the first four of these metals. -From them, compositions may be made that will meet the requirements -of nearly any part.</p> - -<p>For parts that perform little or no actual work, save to “lend their -weight,” such as balance weights, novelties and ornaments for show -windows, etc., a mixture consisting principally of lead, often stiffened -with a little antimony, is used. There is but little strength to this -metal, but it is used because of its weight and low cost. For parts that -are subject to wear, such as phonograph, telephone, gas-meter and -adding machine parts, an alloy composed of zinc, tin and a small -amount of copper is used. This alloy may be plated or japanned, and is -a good metal to use on general work.</p> - -<p>Another metal, used chiefly for casting pieces that have delicate -points in their design but are not subjected to hard wear, consists principally -of tin alloyed with lead and zinc to suit the requirements of the -work. This mixture casts freely, and the finished castings come out -exceptionally clean. Still another metal, used chiefly for casting pieces -that have letters and figures for printing, is similar to the standard -type metal—5 parts lead and 1 part antimony; but if there are teeth -cast on the sides of the printing wheel a harder mixture will be required -to give longer life to the gears.</p> - -<p>The following mixtures are typical of die-casting or “white brass” -alloys: copper, 10 parts; zinc, 83 parts; aluminum, 2 parts; tin, 5 parts. -Another is copper, 6 parts; zinc, 90 parts; aluminum, 3 parts; tin, 1 -part. Another containing antimony is copper, 5 parts; zinc, 85 parts; -tin, 5 parts; antimony, 5 parts. Shonberg’s patented alloy is copper, 3 -parts; zinc, 87 parts; tin, 10 parts. Alloys containing 15 to 40 per -cent copper and 60 to 85 per cent zinc are brittle, having low strength<span class="pagenum"><a id="Page_8">8</a></span> -and low ductility. An alloy of 8 per cent copper, 92 per cent zinc has -greater resilience and strength but not the ductility of cast zinc.</p> - -<p>Aluminum may be cast, but it is a difficult metal to run into thin -walls and fine details; it plays, however, an important part in some -good mixtures used for die casting. Experiments are now being conducted -for die-casting manganese bronze, and it is said that some very -good castings have already been made. Its wearing qualities are so -valuable that it is particularly desirable for making die-castings.</p> - -<h3>The Die-casting Machine</h3> - -<p>The three important requisites for good die-casting are the machine, -the dies and the metal. The casting machine is fully as essential as -either of the other requisites, and although there are a number of -different styles of casting machines in use, each of which has its -advantages over the others, especially in the eyes of their respective -designers, the fundamental principles upon which they all operate are -the same. In each there is the melting pot and the burner, the cylinder -and the piston for forcing the metal into the dies, and the dies with<span class="pagenum"><a id="Page_9">9</a></span> -the opening and closing device. In some machines pressure is applied -to the metal by hand, in others power is used, and in still another class -the metal is forced into the dies with compressed air. The provisions -for opening and closing the dies vary in the different machines; there -are various means employed for cutting the sprue, and the styles of -heaters are numerous.</p> - -<p>One or two of the largest firms in the die-casting industry have -automatic casting machines for turning out duplicate work in large -quantities very rapidly. These machines are complicated and are only -profitable on large quantities of work, and for that reason their use -is not extensive. In general, their operating principles are the same -as in the case of the hand machines, but provision is made for automatically -opening and closing the dies, compressing the metal, and -ejecting the castings.</p> - -<h3>The Soss Die-casting Machine</h3> - -<p>The Soss die-casting machine, manufactured and sold by the Soss -Manufacturing Co., Brooklyn, N. Y., was the first die-casting machine -to be placed on the open market. This machine is shown in <a href="#Fig_4">Figs. 4</a> and -<a href="#Fig_5">5</a>, and in section in <a href="#Fig_6">Fig. 6</a>. The Soss Manufacturing Co. originally -manufactured invisible hinges exclusively. At the advent of the die-casting -era, they commenced to make these hinges from die-castings, -and placed orders with a leading die-casting concern amounting to -thousands of dollars each year. After the die-cast hinges had been on -the market for a short time, complaints commenced to come in, some -to the effect that the hinges were breaking and others that the hinges -were corroding. Either of these faults was serious enough to blast -the reputation of the hinge, but the first trouble, breakage, was the -more important. Examination of the broken hinges showed that the -castings were porous and full of flaws, and as the makers of the castings -could not produce castings sufficiently strong for the hinges, Mr. -Soss started to experiment for himself. This experimenting led to the -production of the Soss die-casting machine.</p> - -<div id="Fig_4" class="figcenter" style="width: 486px;"> - <img src="images/i_008.jpg" width="486" height="600" alt="" /> - <div class="caption">Fig. 4. General View of the Soss Die-casting Machine</div></div> - -<p>Referring to the illustrations <a href="#Fig_5">Figs. 5</a> and <a href="#Fig_6">6</a>, <i>A</i> is the base and frame -of the machine, <i>B</i> is the heating chamber located at one end of the -machine, and within this heating chamber is the tank <i>C</i>, shown in -<a href="#Fig_6">Fig. 6</a>. This tank contains the metal from which the die-castings are -made, and the metal is heated by the burners <i>D</i>. These burners are fed -by air and gas through piping on the side of and beneath the furnace. -To facilitate lighting the burners and inspecting their condition at -any time, there is an opening (not shown) through the firebrick lining -of the furnace and the outer iron wall, on a level with the top of the -burners. There is also another opening through the furnace wall to -allow the gases due to the combustion to escape. Through the bottom -of the tank, well to the inner side of the furnace, runs the cylinder <i>E</i>. -Below the bottom of the tank, the cylinder makes a right-angle turn, -extending through the furnace wall and terminating just outside of the -wall. The orifice of this cylinder is controlled by gate <i>F</i>. In that -part of the cylinder that extends upward into the tank, there is an<span class="pagenum"><a id="Page_10">10</a></span> -opening <i>G</i> that allows the molten metal to run into the cylinder from -the tank. Working in this cylinder, is the piston <i>H</i>, that is used in -forcing the metal into the dies. The compression lever <i>I</i>, hinged over -the inner furnace wall, is kept normally raised by spring pressure, and -is connected to the piston by means of the link <i>J</i>.</p> - -<div id="Fig_5" class="figcenter" style="width: 502px;"> - <img src="images/i_010.jpg" width="502" height="600" alt="" /> - <div class="caption">Fig. 5. Working Parts of the Soss Die-casting Machine</div></div> - -<p>At the opposite end of the machine from the furnace, is the mechanism -for operating the dies. This mechanism consists of a pair of -square rods <i>K</i>, upon which are mounted the sleeves <i>L</i>. These sleeves -have a long bearing surface and are attached to the die-plate <i>M</i>. Lever -<i>N</i> at the end of the operating mechanism controls the movement of -these sleeves by means of links <i>O</i>. Upon these sleeves is mounted a -secondary set of sleeves <i>P</i>, attached to the other die-plate <i>Q</i>, and whose<span class="pagenum"><a id="Page_11">11</a></span> -movement is controlled by lever <i>R</i>, through links <i>S</i>. This second set -of sleeves is free to travel with the first set, and in addition has an -independent movement of its own on the primary sleeves. It is the -function of lever <i>R</i> to bring die-plate <i>Q</i> up to die-plate <i>M</i> by means -of links <i>S</i> and sleeves <i>P</i>; and it is the function of lever <i>N</i> to bring -both of the die-plates up to the outlet of the cylinder by means of links -<i>O</i> and sleeves <i>L</i>. This system of sleeve-mounting is one of the distinctive -patented features of the Soss machine. The orifice of the -cylinder <i>E</i> is conical in shape and exactly fits the cup-shaped opening -in die-plate <i>M</i>, so that when the two are brought together, the joint is -metal tight. At the center of this opening, and extending through the -die-plate <i>M</i>, is an opening that leads to the dies mounted on the inner -faces of the two die-plates, and a continuation of this opening extends -through die-plate <i>Q</i> in which the sprue-cutter <i>U</i> works. Attached to -the outer side of this die-plate are two slotted brackets. In the slot of -one of these is pivoted the lever <i>T</i>, and in the slot in the opposite -bracket are bolted two stops that limit the motion of the lever. This -lever operates the sprue cutter <i>U</i>, that works through the opening in -die-plate <i>Q</i>. The sprue-cutting mechanism is best shown in <a href="#Fig_6">Figs. 5</a> -and <a href="#Fig_6">6</a>. At the left of <a href="#Fig_5">Fig. 5</a> may be seen a rubber hose connected to -the air piping. This hose is used for cleaning out the dies after each -casting operation.</p> - -<h3>Operation of the Die-casting Machine</h3> - -<p>The metal for the die-casting machine is mixed in the proper proportions -for the work in hand by means of a separate furnace, before -being poured into the tank of the machine itself. The burners are -lighted and the dies are set up on the two die-plates. As soon as the -machine has “warmed up,” so that the metal is in a thoroughly melted -condition, the sprue-cutting lever <i>T</i> is thrown back, leaving a clear -passageway to the die cavities. Lever <i>R</i> is pulled backward, thus -bringing die-plate <i>Q</i> up to die-plate <i>M</i>, which operation closes the two -halves of the die. Then lever <i>N</i> is thrown forward, thereby bringing -the closed die up to the body of the machine, with the nozzle in close -contact with the outlet of the cylinder. Next, the gate <i>F</i> is opened, and -the man at the compression lever <i>I</i> gives the lever a quick, hard pull, -forcing the metal in the cylinder downward and into the dies. The -molten metal literally “squirts” into the dies. Gate <i>F</i> is now closed; -lever <i>N</i> is pulled back to remove the dies from the cylinder outlet; and -the sprue-cutting lever <i>T</i> is pushed forward, cutting off the sprue and -pushing it out of the nozzle into the kettle placed beneath it. The -lever <i>R</i> is pushed forward, and a finished casting is ejected from the -dies.</p> - -<p>An important advantage that this machine has over other die-casting -machines is the fact that the metal for the castings is taken from the -<em>bottom</em> of the melting pot, whereas most other machines use metal from -the top of the tank. At the bottom of the tank the metal is always the -best, as it is free from impurities and dross; hence, there is little -chance for the formation of blow-holes. A handful of rosin thrown into<span class="pagenum"><a id="Page_13">13</a></span> -the melting tank occasionally helps to keep the metal clean, but the -metal nearest the surface always contains more or less foreign matter.</p> - -<div id="Fig_6" class="figcenter" style="width: 600px;"> - <img src="images/i_012.jpg" width="600" height="360" alt="" /> - <div class="caption">Fig. 6. Section of Soss Die-casting Machine</div></div> - -<p>While this description of the operation of the die-casting machine -may convey the idea that the process is a slow one, as a matter of -fact, the time required is, on the average, not over a minute and a half -for turning out a finished casting. With the ejection of the casting -from the dies, the product is completed, in theory; but in practice there -are always a few small thin fins, caused by the air vents or by improperly -fitted portions of the dies. It is, however, but the work of a -few seconds to break off these fins, and unless there are many of them, -or they are excessively thick, they are detrimental neither to the quality -nor the quantity of finished castings.</p> - -<h3>Points on the Operation of the Die-casting Machine</h3> - -<p>We have now taken up the description and general operation of the -die-casting machine, but like every other machine, there are numerous -little kinds and practices in its working the observing of which makes -the difference between good and poor die-casting. Some of these points -are here given.</p> - -<p>The casting machine is best operated by three men, one of whom -attends to the compression lever and the metal supply in the tank. The -other two men stand on each side of the die-end of the machine, and -it is their duty to operate the sprue-cutter, open the dies and remove -the finished casting, clean the dies with air and close them, throw back -the die-plates to their casting position over the cylinder outlet, and do -any other work incident to the operation of the machine. While it -requires three men to operate a die-casting machine in the best manner, -the man who attends to the compression lever has a good deal of spare -time between strokes, and if two or even three of the machines are -conveniently placed, one man can easily pull levers for all three.</p> - -<p>The metal should be kept just above the melting point and at a -uniform temperature. If the metal is worked too cold, the result will -manifest itself in castings that are full of seams and creases, and it -will be difficult to “fill” the thin places in the dies. If, on the other -hand the metal is allowed to get too hot, the die will throw excessively -long fins, the castings will not cool as quickly in the die, and -consequently they cannot be made as rapidly. On account of the importance -of keeping the metal at a uniform heat, the fresh metal that -is added to that in the tank from time to time, is kept heated in a -separate furnace. Therefore, when the metal in the tank gets low, the -new supply does not reduce the temperature of the metal being worked. -Some casters use a thermometer to indicate the heat of the metal.</p> - -<p>Casting-dies require lubrication frequently. Just how often they -should be lubricated depends on the shape of the die, the composition -of the casting metal, and the general performance of the dies. Beeswax -is the common lubricant, and the lubrication consists in merely -rubbing the cake over the surfaces of the dies that come in contact -with the casting metal. In die-casting large parts, the dies must be -kept cool by some artificial means, for hot dies are conducive to slow<span class="pagenum"><a id="Page_14">14</a></span> -work and poor castings. To reach this end, large dies are sometimes -drilled and piped so that water may be circulated through them to -keep them cool.</p> - -<p>In the Soss machine, the burners are so placed that the metal in the -cylinder is kept at a slightly higher heat than that in the tank proper. -This condition is brought about by having the cylinder directly over -the burners. The value of this feature lies in the fact that gas is not -wasted in heating the entire tank full of metal to this higher heat, but -still the metal under compression is at the required temperature. The -gas consumption of the average die-casting machine is about 100 cubic -feet per hour.</p> - -<p>The speed at which die-castings may be produced varies with the size -of the castings being made, the composition of the metal being cast, -and the style of dies that must be employed. In many cases, in die-casting, -separate brass or steel pieces are used, that must be placed in the -dies before each operation so that they will be inserted in and become -a part of the finished casting. The dies may be difficult of operation -on account of draft problems or pins and screws that must be inserted -in the dies and removed from each casting before another can be made. -These different types of dies will be more fully described in the next -chapter. Taken as a whole, from ten to sixty pieces per hour are -the maximum limits for speed in die-casting, and with a well-working -die, of simple construction, a speed of forty pieces per hour is considered -good production. It is possible, however, when the castings -to be produced are small in size and simple in shape, to gate a number -of them together, or rather to construct the dies so that six or more -castings may be made at once. By this means it is often possible -to cast five or six thousand pieces per day of ten hours, on a hand -die-casting machine.</p> - -<hr /> - -<p><span class="pagenum"><a id="Page_15">15</a></span></p> - -<div class="chapter"> -<h2 class="vspace"><a id="CHAPTER_II">CHAPTER II</a><br /> - -<span class="subhead">MAKING DIES FOR DIE-CASTING MACHINES</span></h2> -</div> - -<p>The making of casting-dies calls for ingenuity and skill of the -highest order on the part of the die-maker. There is probably no class -of die-making in which the work produced is more faithful to the dies, -both in showing up the little details in the making that reflect credit -on the dies, and in exposing the defects and shortcomings in the workmanship, -if there be any. The castings from casting-dies or molds as -they are sometimes called, may be produced in dimensions down to -ten-thousandths for accuracy if necessary, and once the dies are made -the castings will not vary in the slightest degree, if the working conditions -are kept uniform.</p> - -<p>In spite of the close work required in making casting-dies, the work -is very fascinating. Perhaps it is on account of this accuracy; possibly -it is on account of the fact that they are made from machine steel; -but most likely it is because there are no hardening troubles to be -contended with. Another factor that makes the work interesting is the -ingenuity required in the work, for almost every die-maker, if he is -worthy of the name, likes to figure out and plan for the best way of -building a die for a difficult job.</p> - -<h3>General Principles of Casting-die Making</h3> - -<p>Casting-dies, or molds, have little in common with sand molds. It -is true that the dies for die-casting are composed of two parts corresponding -to the cope and nowel of the sand mold, but they are so -different in every other way that no benefit would result from a comparison.</p> - -<p>Generally speaking, casting-dies are made of machine steel; the parts -which are exceptions are the heavy bases and frames, which are made -of cast iron, and the dowel pins and small cores, usually made of tool -steel. Except in rare instances, there are no hardened parts about a -casting-die; this is the case because the melting points of some of the -alloys that are die-cast are high enough to draw the temper from any -hardened parts of the dies.</p> - -<p>The ideal die is simple in construction, with as few parts as practicable; -the castings should be easily ejected and should come from the -dies as nearly free from fins as possible. To meet these requirements -in the best way is the proposition that confronts the ingenuity of the -die-maker. As the die is primarily in two parts, there must be a -parting line on the casting. This line is always placed at the point -that will permit the casting to be ejected from the dies in the easiest -manner possible, bearing in mind the effect the joint will have on the -appearance of the finished casting; this is a point far less important -than with sand casting, for, if the dies are properly made this seam will -be barely perceptible. When it is practicable to do so, it is wise to have -the parting line come on an edge of the die-casting. Draft is unnecessary<span class="pagenum"><a id="Page_16">16</a></span> -on the straight “up-and-down” places, but of course it is impossible -to draw any parts that are undercut. Means must be provided for -ejecting the casting from the dies after completion and it is usually -done by means of ejector pins, though frequently it is better to have -the bottom of the die or some other section movable and do the ejecting -on the same principle that is used on drawing dies of the compound -type. On close work, shrinkage plays an important part, and the amount -of shrinkage varies from 0.002 to 0.007 of an inch per inch. Aluminum -shrinks the greatest amount, Parsons white brass shrinks considerably, -while tin shrinks but little. -Thus, it may be easily seen -that to figure the shrinkage -allowance for an alloy that -contains three or four metals -with different shrinkages, -requires judgment. To prevent -the air from “pocketing,” -air vents are necessary -at frequent intervals around -the die-cavity. These vents -are made by milling a flat -shallow cut from the die-cavity -across the face of the -die to the outside edges of -the block. From ¼ inch to ½ inch is the usual width and from 0.003 -to 0.005 of an inch, the customary depth, varying with the size and -shape of the die in question.</p> - -<div id="Fig_7" class="figcenter" style="width: 600px;"> - <img src="images/i_016.jpg" width="600" height="460" alt="" /> - <div class="caption">Fig. 7. Disk cast in Simple Casting-die</div></div> - -<p>The dies or molds for die-casting are of various styles, as are also -punch-press dies, and it would be difficult to lay down specific rules -for their classification. There are the plain dies, without complications -of any kind; slide dies with one or more slides; dies for bearings, both -of the “half-round” and of the “whole-round” types; dies for gated -work; and many other less important classes. Then there are dies that -have features that belong to more than one of these types, so that it -is easily seen that to decide upon the style of die that would be best -for a given piece of work requires a good deal of experience. Some of -the most important of these types can best be shown by illustrating dies -made in the various styles, showing, step by step, how the dies are made -and assembled. To begin with, consider the making of a casting-die -of the very simplest form.</p> - -<p>In <a href="#Fig_7">Fig. 7</a> is shown a plain flat disk made by die-casting. In actual -practice, a die would not be made for such a simple piece, unless there -were some features about it that would prevent it being made on a -screw machine or with press tools. It might have a cam groove cut -in one of its flat sides, the sides might be covered with scroll work, -there might be gear teeth around its circumference, or a hundred and -one other conditions to make die-casting a desirable method of manufacturing. -All these complications are omitted for the sake of simplifying -this initial description of a casting-die.</p> - -<p><span class="pagenum"><a id="Page_17">17</a></span></p> - -<div id="Fig_8" class="figcenter" style="width: 391px;"> - <img src="images/i_017.jpg" width="391" height="600" alt="" /> - <div class="caption">Fig. 8. Simple Casting-die for Casting Block shown in <a href="#Fig_7">Fig. 7</a></div></div> - -<p><a href="#Fig_8">Fig. 8</a> shows the die for this piece in plan and sectional elevation. -<i>A</i> is a square cast-iron frame, made from a single casting. This frame -or box, as it is generally called, is planed on the top and bottom only. -Next, the two die-halves <i>B</i> and <i>C</i> are shaped up from machine steel. -In this casting-die, and in the majority of others, these die blocks are -square. The lower half of the die <i>B</i> is held to the cast-iron frame by -fillister head screws, set in counterbored holes, thus sinking the screw-heads -under the surface of the block. The upper half of the die <i>C</i> is -located upon <i>B</i> by dowel pins driven into <i>B</i> which have a sliding fit in<span class="pagenum"><a id="Page_18">18</a></span> -the reamed holes in <i>C</i>. This being done, the die-half <i>B</i> is fixed to the -faceplate of the lathe and the recess bored for the die-cavity. This -operation is a simple one in this case, for it is merely a straight hole -one-half inch deep and three inches in diameter. Of course this recess -must be carefully finished with a tool that has been stoned up to a sharp -edge, using lard oil. Emery cloth should be used as little as possible. -It is unnecessary to give this hole draft, but it must be free from ridges -or marks that would prevent the casting from being pushed out. If the -faces of the dies are spotted with a small piece of box wood or rawhide -held in the drill press and kept charged with flour emery, the die-casting -will reproduce this “bird’s-eye” finish and the appearance will well -repay the few minutes additional time that it will take. The spotting -should be done with dry emery (without oil) to get the brightest finish. -The upper die-half <i>C</i> is simply ground on its working face. The outside -corners and edges of the faces of both die-halves should be well rounded -off so as to insure the absence of slight dents or rough places that -might prevent the dies from fitting perfectly.</p> - -<p>The ejecting mechanism must next be considered. Lever <i>D</i>, pivoted -from bracket <i>E</i>, has a steel pin <i>F</i> that engages in the elongated hole -in bracket <i>G</i>, so that an upward pull of the lever <i>D</i> raises bracket <i>G</i>, -which is attached to ejector-pin plate <i>H</i>. This plate is a loose fit over -the guide screws <i>I</i> that are attached to the lower die-half <i>B</i>. The -ejector pins <i>J</i>, four in number, in this die, are riveted into the ejector-pin -plate, and they work through holes drilled and reamed through the -lower die-half. The ends of these pins must be finished off so as to lie -perfectly flush with the inside of the die when ready for operation and, -of course, they must be a sliding fit in the holes in the die.</p> - -<p>An important feature of a casting-die is the sprue cutter, shown in -this die at <i>K</i>. If the disk for which this die was made, had had a hole -or central opening of any kind, the sprue cutter would best be operated -at that point; but, as this disk is plain, the sprue cutter must be placed -at the edge. At the outside of the die-cavity, as shown in <a href="#Fig_8">Fig. 8</a>, the -opening for the sprue cutter is laid out, drilled and filed to shape. -It is obvious that the side of the sprue cutter adjacent to the die must -fit the outline of the die perfectly, so that there will be no break in -the appearance of the casting. The opening for it is extended through -the upper die-half, and from a point ¼ of an inch from the inside face -of the die this hole is flared out nearly as large as the opening through -the die-plate of the machine. Of course the apperture in the upper die-half -must be no larger than the opening through the die-plate; otherwise -the sprue could not be pushed out. The sprue cutter itself is a -long rod, whose section is of the same shape and size as the openings -just made, and it is connected to the sprue cutting mechanism of the -machine. Of course it is unnecessary to shape the entire length of -the sprue cutter to size; after the working end is milled to shape for a -distance of six or eight inches, the rest of the rod may be left round. -The sprue cutter is finished first, after which both the openings in the -die are fitted to it; and while the fit should be metal tight, it must be -perfectly free to slide.</p> - -<p><span class="pagenum"><a id="Page_19">19</a></span> -The dies are mounted on the die-plates of the casting machine by -means of straps, much the same as bolsters are held on punch press -beds. The position of the die on the die-plate must be such that the -opening for the sprue cutter will line up with the nozzle at the outlet -of the cylinder. At the time of casting, the position of the sprue cutter -is as shown in the illustration of this die, <a href="#Fig_8">Fig. 8</a>. In this position there -is room for the metal to enter the die-cavity, and yet there is but a -small amount of metal to be cut off and pushed back after the die has -been filled with metal.</p> - -<p>With slight modifications, the above style of die may be used for die-casting -any piece that will draw or pull out of a two-part die. If holes -must be cast through the piece, it is only necessary to add core pins to -the lower die <i>B</i>, a point that will be more fully described later. It is -unnecessary to add that both halves of the die may be utilized in -making the cavity for the die, should they be needed. Also, it is often -easier to machine out the recess larger than is needed, and set in -pieces in which parts of the outline of the die-casting have been formed. -Gear teeth are put in the die in this way; a broach is cut similar to the -gear desired, then hardened and driven through a piece of steel plate -which is afterward fitted to its place in the die.</p> - -<h3>Slide Dies</h3> - -<p>The die illustrated in <a href="#Fig_9">Fig. 9</a> is one of the most successful of the -various types of casting-dies, and if properly made is an interesting -piece of die work. The principal use of this particular style of die, -called a slide die, is to cast parts like the one shown in <a href="#Fig_10">Fig. 10</a>, which -is a disk similar to the one which the last die described was to cast, -except that it has raised letters at the edge and a hole in the center. -It is obvious that the die last described, (<a href="#Fig_8">Fig. 8</a>), would not do for -disks or other pieces having projections or depressions around their -edges, as, for instance, printing or counting wheels with raised or -sunken characters, or grooved pulleys. Briefly, this style of die is -similar to the simple casting-die, except that slides are provided, to the -required number, which form the edge of the casting. A die for a plain -grooved pulley would require but two slides, while a die for a printing -wheel with forty letters around its edge would necessitate forty slides, -one for each of the letters. The die about to be described, shown in -<a href="#Fig_9">Fig. 9</a>, was made to cast a wheel with six raised letters.</p> - -<p>Referring to <a href="#Fig_9">Fig. 9</a>, <i>D</i> is the cast-iron box or frame, <i>E</i>, the lower die, -and <i>F</i> the upper die. In making the lower die-half, the stock is first -shaped to size and doweled to the blank for the upper die-half, and the -holes for attaching to the frame are drilled. For the sake of clearness, -these holes and screws are omitted from the illustration as are also -the vents, since they have been fully explained. The lower die is next -strapped to a faceplate, trued up, and bored out nearly to the diameter -of the body of the piece to be cast, exclusive of the raised letters. The -depth of this recess is equal to the thickness of the printing wheel plus -3/16 inch to allow for the cam ring <i>G</i> that is used to reciprocate the -slides of the die. The cam ring is made large enough to cover the die-cavity<span class="pagenum"><a id="Page_20">20</a></span> -as well as the slides that surround it, with an allowance of an -inch or two for the cam slots <i>H</i>. The six slides <i>I</i> are made long enough -to have good bearing surfaces. With the size of the cam ring determined, -the die is next bored out to receive this cam ring and the last -inch of the recess is carried down to the depth of the die cavity so as -to make an ending space for the slots that the slides are to work in. The die is now taken from the faceplate and the slots for the slides -laid out.</p> - -<div id="Fig_9" class="figcenter" style="width: 437px;"> - <img src="images/i_020.jpg" width="437" height="600" alt="" /> - <div class="caption">Fig. 9. Slide Die for Casting the Printing Wheel shown in <a href="#Fig_10">Fig. 10</a></div></div> - -<p>These slots may be milled or shaped, but milling is to be preferred. -The next step is the making and fitting of the slides, which are of -machine steel, having a good sliding fit in the slots. The six slides are -fitted in position and left with the ends projecting into the die proper.<span class="pagenum"><a id="Page_21">21</a></span> -The slots <i>H</i> are next profiled in the cam ring <i>G</i>, and the pins <i>J</i> that -work in them are made and driven into the holes in the slides. With -the slides and cam ring in place, the cam ring is rotated to bring all -the slides to their inner position where they are held temporarily by -means of the cam ring and temporary screws. The die-half with the -slides thus clamped in the inner or closed position, is set up on the -lathe faceplate and the die-cavity indicated up and bored out to the -finish size, which operation also finishes the ends of the slides to the -proper radius. The die may now be taken down and the slides removed -to engrave the letters upon their concave ends. The engraving can be -done in the best manner on a Gorton engraving machine, but if such a -machine is not available they may be cut in by hand. Stamping should -never be resorted to for putting in the letters, because the stock displacement -would be so great that it would be impossible to refinish the -surface to its original condition. Before fitting the cam ring, an opening -must be milled in the -die to allow the handle to -be rotated the short distance -necessary. After the cam -ring has been fitted, it is -held in by the four small -straps <i>K</i>, attached by screws -to the lower die-half at the -corners.</p> - -<div id="Fig_10" class="figcenter" style="width: 600px;"> - <img src="images/i_021.jpg" width="600" height="459" alt="" /> - <div class="caption">Fig. 10. Printing Wheel cast in a Slide Die</div></div> - -<p>The sprue cutter, which is -not shown, is operated -through the hole in the -center of the piece and is, -of course, round in this -die. Its action is the same -as was the one previously described, and the ejecting device -is similar, with the exception that the brackets <i>L</i> that are attached to -the ejector-pin plate M, are widely separated so as to make room for the -sprue cutter that works through a hole in the plate <i>M</i>.</p> - -<h3>Die for Casting with Inserted Pieces</h3> - -<p>For making die-castings that are to have pieces of another metal -inserted, it is necessary to have a die with provisions for receiving the -metal blank and holding it firmly in position while the metal is being -cast around it, and of course the piece must be held in such a manner -that it can be easily withdrawn from the die with the finished casting.</p> - -<p>The die illustrated in <a href="#Fig_11">Fig. 11</a> is for a part that is used as a swinging -weight, shown in <a href="#Fig_12">Fig. 12</a>. The upper part of the piece is made from a -sheet steel punching, so as to lighten this part of the piece as well as -to give increased strength, especially at the hole at the pivoted end of -the work. The cast portion of the piece is slotted lengthwise, as the -illustration shows; and three holes pass through the casting, piercing -the sides of the slot. In addition to showing the method of making dies -for inserted pieces, this die shows the principles of simple coring.</p> - -<p><span class="pagenum"><a id="Page_22">22</a></span></p> - -<div id="Fig_11" class="figcenter" style="width: 393px;"> - <img src="images/i_022.jpg" width="393" height="600" alt="" /> - <div class="caption">Fig. 11. Casting-die for Making Castings with Inserted Pieces like -that shown in <a href="#Fig_12">Fig. 12</a></div></div> - -<p>In making this die, two machine-steel blanks are planed up for the -upper and lower halves of the die, <i>A</i> and <i>B</i>, the lower die being made -nearly twice as thick as the upper die because it is in this part that -the most of the die-cavity will be made. In this lower half of the die -the stock is milled out to the same shape as the outline of the plan -view of the casting, being carried down to the exact depth of the thickness -of the casting. From the wide end of this recess the stock is -milled or shaped out in a parallel slot to the outside of the die-block.<span class="pagenum"><a id="Page_23">23</a></span> -At the bottom of the side of this wide slot are T-slots to guide the -slide <i>E</i> that is to work in this opening. The side is milled and fitted -to the T-slots and opening in the die, but is left considerably longer -than the finish size. Next, the slide is mounted on the faceplate of a -lathe and turned out on the end with the proper radius and a tongue -to form the slot that is to be in the curved end of the casting. At the -outer end of the slide is left a lug that is drilled and tapped for the -operating lever <i>F</i> that reciprocates the slide, using the stud in bracket -<i>K</i> as a fulcrum.</p> - -<p>Two pieces of machine steel are next shaped and finished up to -form the chamfered part of the casting and to locate the inserted steel -punching in the die. The combined thickness of these pieces <i>C</i> and <i>D</i> -is equal to the thickness of the casting, less the thickness of the inserted -piece. It is now an easy -matter to seat section <i>D</i> in the -bottom of the milled part of the -lower die-half, and to locate -section <i>C</i> in its proper position -on the upper half. A pilot pin -<i>M</i> is fitted in <i>D</i> to hold the -steel punching in position by -means of the hole that is in the -extreme upper end of the -punching. The pilot pin extends -through this hole into a corresponding -hole in section <i>C</i>. -At the lower end of the steel -part that is inserted, there are -two holes the object of which is to secure the punching to the die-casting, -for the molten metal runs through these holes, practically -riveting the die-casting to the inserted piece.</p> - -<div id="Fig_12" class="figcenter" style="width: 600px;"> - <img src="images/i_023.jpg" width="600" height="507" alt="" /> - <div class="caption">Fig. 12. Die-cast Weight with Inserted -Sheet-steel Punching</div></div> - -<p>Provision has now been made for holding the sheet-metal part that is -to be inserted, and the cavity has been completed for the casting, including -the tongue at the end; it now remains to describe the manner -of forming the holes that pierce the casting through the slotted portion. -In the lower die-half the positions of the three holes <i>H</i> are -laid out, drilled and reamed. Then, with the two die-halves together -and the slide clamped at its inner position, the holes are transferred -through the slide and the upper die. This being done, it is an easy -matter to make core pins and drive them into the upper die at the two -end holes, the center hole being taken care of by the sprue cutter <i>L</i> -that will be described later. The core pins should be a nice sliding fit -through the slide and in the holes in the lower die, into which they -should extend from a quarter to half an inch. In addition to coring -the holes, these pins act as a lock to hold the slide <i>E</i> in its proper -position at the time of casting.</p> - -<p>The sprue cutter <i>L</i> is most conveniently operated in the center -hole, thus doing away with the core pin that would otherwise be required. -The sprue cutter needs little description in this die, for as in<span class="pagenum"><a id="Page_24">24</a></span> -the slide die, it is merely a plain round rod that fits closely in the -holes through the dies and slide. The ejector mechanism is the same -in this die as in the dies already described; therefore further description -is unnecessary.</p> - -<div id="Fig_13" class="figcenter" style="width: 373px;"> - <img src="images/i_024.jpg" width="373" height="600" alt="" /> - <div class="caption">Fig. 13. Casting-die for the Half-round Bearing shown in <a href="#Fig_14">Fig. 14</a></div></div> - -<p>The operation of this die is very simple. The sheet-steel piece is -laid in the recess in the open die, being located by the pin <i>M</i>. Slide -<i>E</i> is thrown in by means of lever <i>F</i>, and the dies are closed. At the<span class="pagenum"><a id="Page_25">25</a></span> -time of casting, the sprue cutter in is the position shown in the sketch, -being nearly through the die-cavity. As before explained, this -position admits the molten metal to pass into the die-cavity, but still -leaves very little sprue to be cut off after the die-casting is completed. -It should be stated that the steel piece that is inserted must be perfectly -flat and free from burrs that would prevent the die-halves from -coming together properly.</p> - -<h3>Bearing Dies</h3> - -<p>Bearing dies are one of the most important of the various classes of -casting-dies. The bearings produced by die-casting are so far superior -to those made by other casting methods and machining that their use -is now very extensive. Dies are made for “half-round” and “whole-round” -bearings. There is little out of the ordinary about a whole-round -die, but the half-round die involves many interesting methods -of die-making, and for that reason is here described.</p> - -<p><a href="#Fig_13">Fig. 13</a> shows a casting-die for half-round bearings. Half-round bearing -dies are usually made to cast two bearings at a time, for the -reason that it is just as easy to cast two pieces of such a shape as it -is to cast one, and, in addition, the die is balanced in a better manner. -As with other dies, the first step is to machine up the frame <i>A</i> and the -two die-halves <i>B</i> and <i>C</i>. The pieces <i>D</i> and <i>E</i> that are to form the -insides of the bearings are then turned up and one side of each shaped -and keyed to fit the slots that have previously been milled in die-half -<i>C</i>. These parts are held in place by dowels and screws. One of the -bearings produced by this die is shown in <a href="#Fig_14">Fig. 14</a>, and it will be -noticed that there is an oil groove within that covers the length of -the bearing. To produce this groove in the die-castings, a shell must -be turned up and bored out whose inside diameter is that of the inside -of the bearing, and whose thickness equals the depth of the oil groove. -This being done, the oil grooves are laid out upon the shell and cut -out by drilling and filing. After rounding the outside corners, these -little strips are pinned to the cores <i>D</i> and <i>E</i> in their proper places.</p> - -<div id="Fig_14" class="figcenter" style="width: 600px;"> - <img src="images/i_025.jpg" width="600" height="168" alt="" /> - <div class="caption">Fig. 14. Die-cast Half-round Bearing, Showing the Cast Oil Grooves</div></div> - -<p>Another little kink in this connection is worthy of noting. So many -different styles and sizes of bearings are made by a concern doing much -die-casting that it is essential that the die-cast bearings should bear -some distinguishing number to identify them. As this number is of no -consequence to the user it is well to have the number in an inconspicuous -place, but it must be where it will not be effaced by scraping, -etc. Bearing in mind that it is much easier to produce raised lettering -by die-casting than to produce sunken lettering, it will be readily seen<span class="pagenum"><a id="Page_26">26</a></span> -that the oil groove affords a good place in which to put the bearing -number. This is easily done by stamping the figures upon the narrow -strip that forms the oil groove. In this place on the bearing it may be -easily found if needed, and of course there is no danger of its being -taken out by machining.</p> - -<p>The lower die consists of two blocks <i>F</i> and <i>G</i>, each of which contains -an impression of a bearing. The best way to make these parts is to -lay out the ends of each of the blocks with the proper radius, taking -care to have the center come a little below the surface of the face of -the block. Then the blocks should be shaped out to get the bulk of the -stock out, before setting up in the lathe. After the lathe work is done -on each piece, which of course is usually done separately, the faces of -the two blocks are faced down just to the exact center of the impression. -It will be noticed that two blocks are used for the lower part of -the die. The reason is to facilitate the locating of the female parts -of the die in proper relation to the male parts. After properly locating, -they may be doweled and screwed to baseplate <i>B</i>.</p> - -<div id="Fig_15" class="figcenter" style="width: 579px;"> - <img src="images/i_026.jpg" width="579" height="600" alt="" /> - <div class="caption">Fig. 15. Interesting Examples of Die-castings</div></div> - -<p>The sprue cutter <i>H</i>, better shown in the plan view, is square in -shape and connects with the die-cavities in a thin narrow opening on -either side of the sprue cutter. The ejector pins, <i>I</i>, two to each die, -are at the ends of the bearings. The ejector-pin plate <i>J</i> is necessarily -large, and is operated by lever <i>K</i>.</p> - -<p><a href="#Fig_15">Fig. 15</a> shows a number of interesting examples of die-castings.</p> - -<hr /> - -<p><span class="pagenum"><a id="Page_27">27</a></span></p> - -<div class="chapter"> -<h2 class="vspace"><a id="CHAPTER_III">CHAPTER III</a><br /> - -<span class="subhead">VAN WAGNER MFG. CO.’S DIE-CASTING PRACTICE</span></h2> -</div> - -<p>In 1907, Mr. E. B. Van Wagner, of Syracuse, N. Y., established the -E. B. Van Wagner Mfg. Co. for the production of die-castings. The factory -comprises the office section, the machine shop where the dies and -casting machines are built, the metallurgical laboratory where the -metals are alloyed, the casting department shown in <a href="#Fig_17">Fig. 17</a> where the -die-castings are made, and the trimming department.</p> - -<h3>Possibilities and Limitations of Die Casting</h3> - -<div id="Fig_16" class="figcenter" style="width: 600px;"> - <img src="images/i_027.jpg" width="600" height="331" alt="" /> - <div class="caption">Fig. 16. Die-casting Constructions to be avoided</div></div> - -<p>At the outset we may say that it is possible to die-cast almost any -piece, but it is not by any means practicable to do so. It must be -remembered that to die-cast on a practical basis the dies must be constructed -in such a manner that the cost of their operation and up-keep -will be light, or there will be no profit in die-casting. It is impracticable -to produce under-cut work, that is, work having no draft and -which is therefore impossible to draw from the die. Such an instance -is that illustrated at <i>A</i>, <a href="#Fig_16">Fig. 16</a>, and by the internal section of <i>M</i>, -<a href="#Fig_21">Fig. 21</a>, and the internal groove in <i>O</i>, also shown in <a href="#Fig_21">Fig. 21</a>. If absolutely -necessary, work of this kind can be done by the use of collapsible -cores; but here, again, we meet resistance in maintaining the dies -in proper condition, and, moreover, this method is commercially impracticable, -owing to the difficulty of operating these cores rapidly. -Hollow work, requiring curved cores, like faucets and bent piping of -the character illustrated at <i>C</i> in <a href="#Fig_16">Fig. 16</a>, are difficult to produce. If, -in designing the piece, it can be planned to have the parts of such a -shape that the cores can be readily withdrawn, employing a two-piece -core with a slight draft in each direction, the division coming as indicated -by the core line of <i>C</i> in <a href="#Fig_16">Fig. 16</a>, the problem becomes simpler. -Oftentimes this work can best be done by casting in a straight piece,<span class="pagenum"><a id="Page_28">28</a></span> -afterward bending the die-casting. It does not pay to cast -rough heavy work that can be made just as efficiently by sand -casting. Generally speaking, the greatest saving can be -effected by die-casting small pieces which have previously -required a large amount of machining to produce. On large -plain work the amount of metal required for the casting -makes the cost excessive on account of the difference in cost -of the metals. If, however, the large work must be finely -finished by polishing, etc., it is oftentimes found of advantage -to die-cast. Corners, especially those joining thick and thin -sections, as at <i>B</i>, <a href="#Fig_16">Fig. 16</a>, should be heavily filleted as shown -on one side of this piece. Regarding the casting of thin sections, -it is not practicable to try to cast sections under 3/64 -inch in thickness, as the metal runs with difficulty into such -narrow places. A casting having walls 1/16 inch, like that -shown at <i>X</i>, <a href="#Fig_24">Fig. 24</a>, is easily cast. Threaded sections,<span class="pagenum"><a id="Page_29">29</a></span> -if the threads are fine, say, under twenty-four to the inch, should not -be die-cast, because under moderate pressure they will strip. A good -way to treat constructions of this kind is to enclose brass or steel -bushings in the die-castings in which the threads are required.</p> - -<div id="Fig_17" class="figcenter" style="width: 600px;"> - <img src="images/i_028.jpg" width="600" height="237" alt="" /> - <div class="caption">Fig. 17. View of the Casting Room</div></div> - -<p>As to the accuracy with which die-castings may be produced, it is -possible to keep dimensions within 0.0005 inch of standard size, but to -do so requires considerable expense in keeping the dies in condition. -A limit of 0.002 inch, however, is entirely practicable, and can be maintained -easily. In specifying the accuracy with which die-castings are -to be made, only those parts which are absolutely essential should be -held to size, in order to keep the cost of the work nominal. One of the -great advantages of the use of die-castings is that no finishing is required -after the pieces leave the molds. Finish requirements should -be plainly stated in ordering die-castings, as the alloy must be suited -to these requirements.</p> - -<div id="Fig_18" class="figcenter" style="width: 600px;"> - <img src="images/i_029.jpg" width="600" height="326" alt="" /> - <div class="caption">Fig. 18. Methods of attaching Die-cast Gears, etc., to Shafts</div></div> - -<p>Another great saving is effected on lettered work, either raised or -sunken. One of these jobs is illustrated at <i>Q</i>, <a href="#Fig_22">Fig. 22</a>, which shows an -example of die-cast lettering. Sunken lettering is to be preferred to -raised lettering, as the latter is more easily injured. Knurled work -may be produced easily, if straight knurls are used, and threaded sections -over ¼ inch in size are entirely practicable, either internal or -external. External die cast threads are illustrated at <i>R</i> and <i>S</i>, <a href="#Fig_22">Fig. 22</a>. -The casting of gears and segments is a familiar application of die-casting; -this is illustrated by the large gear at <i>N</i>, <a href="#Fig_21">Fig. 21</a>, and the -segment at <i>W</i>, <a href="#Fig_23">Fig. 23</a>, which give an idea of the general character of -this class of work. The casting of pulleys, gears, and similar parts on -shafts may be easily effected as shown by the gear on the shaft at <i>N</i>, -in <a href="#Fig_21">Fig. 21</a>. The views shown in <a href="#Fig_18">Fig. 18</a> are intended to convey an -idea of three methods of die-casting around shafts. At <i>D</i> is shown a -die-casting cast around a steel shaft. If the surface of the shaft -coming within the pulley has been previously knurled, the pulley will -grip it much better, but for ordinary purposes the shrinkage of the -die-cast metal around the shaft is sufficient. If any heavy strain is to<span class="pagenum"><a id="Page_30">30</a></span> -be imposed on the work, it is better to provide anchor holes through -the shaft, like those indicated at <i>E</i>. It will be readily seen that the -die-cast metal runs through these holes in the shaft, forming rivets -which are integral with the casting. For locating levers upon the ends -of shafts, etc., a good way is to flatten opposite sides of the shaft and -cast around them, as shown at <i>F</i>, <a href="#Fig_18">Fig. 18</a>. The screw seen projecting -beneath the piece at <i>Q</i>, <a href="#Fig_22">Fig. 22</a>, was die-cast in place. Any of these -methods are to be recommended, and a proper knowledge of possibilities -of this kind will increase the scope of die-casting.</p> - -<div id="Fig_19" class="figcenter" style="width: 600px;"> - <img src="images/i_030.jpg" width="600" height="226" alt="" /> - <div class="caption">Fig. 19. A Few Possibilities of Die Casting</div></div> - -<p>Another phase of die-casting which can well be borne in mind is -the possibility of inserting steel or other parts in the die-casting. Such -an instance is shown at <i>G</i> in <a href="#Fig_19">Fig. 19</a>—a die-casting which was made -by the Van Wagner Co. as a part of an electrical apparatus, the steel -inserts being contact points. Oftentimes it is found advisable to include -brass bearing rings to give additional durability at points where -the die-cast metal would not stand up. The die-casting shown at <i>U</i>, -<a href="#Fig_23">Fig. 23</a>, in which the brass ring at <i>T</i> has been incorporated, is typical -of such cases. To die-cast pieces like those shown at <i>H</i> in <a href="#Fig_19">Fig. 19</a>, and -similarly at <i>V</i> in <a href="#Fig_23">Fig. 23</a>, having inverted conical openings, might at -first thought seem difficult, but this is entirely practicable. Similarly, -split bushings like those shown at <i>I</i>, <a href="#Fig_19">Fig. 19</a>, and at <i>W</i>, <a href="#Fig_23">Fig. 23</a>, may -be cast with projecting lugs for the reception of screws for clamping -upon shafts, etc., but this construction should not be used if frequent -tightening or loosening will be necessary.</p> - -<div id="Fig_20" class="figcenter" style="width: 600px;"> - <img src="images/i_030b.jpg" width="600" height="229" alt="" /> - <div class="caption">Fig. 20. Castings which illustrate Points of Shrinkage and Draft</div></div> - -<div id="Fig_21" class="figcenter" style="width: 600px;"> - <img src="images/i_031.jpg" width="600" height="357" alt="" /> - <div class="caption">Fig. 21. Die-castings showing Impractical Under-cut Sections; also a -Large Gear die-cast on Shaft</div></div> - -<div id="Fig_22" class="figcenter" style="width: 600px;"> - <img src="images/i_031b.jpg" width="600" height="514" alt="" /> - <div class="caption">Fig. 22. Die-castings which show Lettering and Thread Castings</div></div> - -<p>The shrinkage problem manifests itself in die-casting in the same -measure that it does in other casting operations. Different metals<span class="pagenum"><a id="Page_31">31</a></span> -shrink in different degrees, as will be explained later on. However, one -important point can be mentioned at this time: that is, the amount of -shrinkage is often dependent upon the shape of the piece. For instance, -pieces like those shown at <i>K</i> in <a href="#Fig_20">Fig. 20</a> or at <i>X</i> in <a href="#Fig_24">Fig. 24</a>, will -shrink very little on account of the fact that the steel mold is of such -shape that the central core will prevent the die-casting from shrinking. -However, pieces like those shown at <i>L</i> in <a href="#Fig_20">Fig. 20</a>, or at <i>V</i> in <a href="#Fig_24">Fig. 24</a>, -which have nothing to hold them from pulling together as they -cool, will shrink to the greatest extent. All of these points must be -taken into consideration when designing work for die-casting. Practically -no draft is necessary on a die-casting, except on very deep sections,<span class="pagenum"><a id="Page_32">32</a></span> -as indicated at <i>J</i> in <a href="#Fig_20">Fig. 20</a>, where a draft of 0.001 inch to the -inch is desirable. Perfectly straight sections, however, can be cast, -as the shrinkage of the metal is usually enough to free it from the -die.</p> - -<div id="Fig_23" class="figcenter" style="width: 600px;"> - <img src="images/i_032.jpg" width="600" height="353" alt="" /> - <div class="caption">Fig. 23. Typical Die-castings illustrating Various Points</div></div> - -<div id="Fig_24" class="figcenter" style="width: 600px;"> - <img src="images/i_032b.jpg" width="600" height="358" alt="" /> - <div class="caption">Fig. 24. Die-castings illustrating the Extremes of Shrinkage</div></div> - -<p>It is the opinion of the Van Wagner Co. that die-casting costs can be -materially reduced if designers will bear this point in mind when -bringing out new designs. Even though it is often possible to cast -special pieces, incorporating several parts in one, and thereby accomplishing -what seems to be a great stunt to the designer, it is sometimes -more practicable to make the piece in several sections and later -assemble it. Not only is this simpler for the die caster, but it is also -more economical for the customer. Such points as avoiding thin sections, -including large fillets at corners, as well as taking account of -the under-cut problem, are simply matters of common sense, but they -can profitably be considered by the designer.</p> - -<h3>The Van Wagner Die-casting Machine</h3> - -<p>The first essential to good die-casting is a good casting machine. -Perhaps the best known types of casting machines are of the familiar<span class="pagenum"><a id="Page_33">33</a></span> -plunger type, of which there are several varieties, the pneumatic type -and the rotary or automatic type. (For descriptions of various types of -die-casting machines, see “Die Casting Machines,” <span class="smcap">Machinery’s</span> Reference -Book No. 108.) For the economical production of die-castings, -however, the hand-operated machines are rather too slow, and automatic -machines are applicable only to a class of work which may be -made in very large quantities. For these reasons, therefore, the Van -Wagner Co. employs the compressed air type of die-casting machine -which was patented by Mr. E. B. Van Wagner in 1907. In the casting -department of the Van Wagner shop, illustrated in <a href="#Fig_17">Fig. 17</a>, there are -installed about thirty machines. <a href="#Fig_27">Fig. 27</a> shows a die-casting -machine in the open position. <a href="#Fig_26">Fig. 26</a> shows a closer view of the die-operating -mechanism and <a href="#Fig_25">Fig. 25</a> is presented to give a general idea -of the construction of the entire machine.</p> - -<div id="Fig_25" class="figcenter" style="width: 600px;"> - <img src="images/i_033.jpg" width="600" height="424" alt="" /> - <div class="caption">Fig. 25. Drawing illustrating Principle of Van Wagner Die-casting -Machine</div></div> - -<p>By referring to the line illustration <a href="#Fig_25">Fig. 25</a>, which shows the Van -Wagner pneumatic die-casting machine in part, and comparing this -illustration with <a href="#Fig_26">Fig. 26</a>, which shows the general appearance of the -die-operating and other mechanism of the casting machine, a good idea -may be obtained of its construction and working. At <i>A</i> may be seen -the base of the machine in which is located the melting pot <i>B</i>. This -melting pot is heated by means of fuel oil passing through the supply -pipe <i>C</i> to the burners <i>C</i><sub>1</sub>. A vent pipe <i>D</i> is provided to take away the -gases incident to combustion. The pressure for “shooting” the metal -into the die cavity is supplied by air through the supply pipe <i>E</i>. A -valve controls this air supply. The pressure is regulated to suit the -particular casting or die, the proper amount being determined by experiment. -Similarly, an air exhaust pipe <i>F</i>, which may be seen -directly above the supply pipe, sub-divides into two tubes which extend<span class="pagenum"><a id="Page_34">34</a></span> -to the die cavity to exhaust the air before the metal is admitted. -There are two methods of overcoming the presence of air in -the die cavity—the exhaust method and the venting method, and it is -the former that is here described.</p> - -<div id="Fig_26" class="figcenter" style="width: 416px;"> - <img src="images/i_034.jpg" width="416" height="600" alt="" /> - <div class="caption">Fig. 26. View of Machine showing Die-operating Mechanism</div></div> - -<p>A “goose-neck” <i>G</i>, shown in <a href="#Fig_25">Fig. 25</a>, serves to temporarily contain -the metal which is forced into the mold. An amount of metal -slightly in excess of that required for one die-casting is placed in this -goose-neck with a hand-ladle, previous to each operation of the machine. -One end of the goose-neck is connected to the air pipe, <i>E</i>, while the -other end terminates in the nozzle <i>G</i><sub>1</sub>. This nozzle may best be seen -by referring to the illustration of the machine shown in <a href="#Fig_27">Fig. 27</a>, in -connection with <a href="#Fig_25">Fig. 25</a>. One of the advantages in using this goose-neck<span class="pagenum"><a id="Page_35">35</a></span> -is that the entire air pressure is expended upon the metal in the -goose-neck, and, by reason of its isolated position, the goose-neck and its -contents are kept slightly hotter than the contents of the melting pot.</p> - -<h3>The Die-operating Mechanism</h3> - -<p>The die-operating mechanism of the machine is contained within -a hinged framework, shown in position for the removal of the die-casting -in <a href="#Fig_27">Fig. 27</a>. Referring to <a href="#Fig_26">Fig. 26</a>, in connection with the line -illustration <a href="#Fig_25">Fig. 25</a>, it will be seen that the die-holding mechanism is -all supported upon the lower die-holding plate <i>H</i>, which is hinged to -the edge of the base of the machine. A lock <i>J</i> serves to hold the dies -and operating mechanism in the upright operating position, and by -means of a counterbalance, suspended from an overhead rope which -connects with the top of the mechanism at <i>P</i>, the changing of the position -of this mechanism is easily effected, and when thrown into the -horizontal position, as indicated in <a href="#Fig_27">Fig. 27</a>, it rests upon a support -while the dies are being opened and the castings ejected.</p> - -<div id="Fig_27" class="figcenter" style="width: 600px;"> - <img src="images/i_035.jpg" width="600" height="421" alt="" /> - <div class="caption">Fig. 27. Die-casting Machine in Position for Removal of Casting</div></div> - -<p>The lower die is shown at <i>H</i><sub>1</sub> and the upper die <i>K</i><sub>1</sub> is mounted upon -the upper die-holding plate <i>K</i>. Four rods <i>L</i> act as guiding members -for the upper die-holding plate to slide upon. These rods <i>L</i> are mounted -in fixed positions at the corners of the lower die-holding plate <i>H</i>, and -at their upper ends the operating shaft supporting plate <i>M</i> is located -in a fixed position, serving to support the upper ends of these rods. -The position of this plate <i>M</i> is adjustable upon the rods by means of -check-nuts, thus providing for the accommodation of thick as well as -thin dies. A shaft <i>O</i> is supported in this top plate, and by means of -the operating lever <i>N</i> working through slotted levers <i>O</i><sub>1</sub> and links <i>O</i><sub>2</sub>, -the upper die-holding plate and die can thus be removed from contact -with the lower die at will.</p> - -<p>The metal enters the die cavity through the nozzle <i>G</i><sub>1</sub> and after -setting, it is necessary to cut the sprue formed by the surplus metal that<span class="pagenum"><a id="Page_36">36</a></span> -remains outside the die cavity. For this purpose, a sprue-cutter, -operated by means of hand-lever <i>Q</i><sub>1</sub>, is employed. This sprue-cutting -lever is hinged in the fulcrumed link <i>Q</i><sub>2</sub>, and is held in its casting position -by means of an adjustable stop on bracket <i>Q</i><sub>3</sub>.</p> - -<div id="Fig_28" class="figcenter" style="width: 600px;"> - <img src="images/i_036.jpg" width="600" height="483" alt="" /> - <div class="caption">Fig. 28. General View of Trimming Department</div></div> - -<p>In many dies, it is necessary that water be circulated through the die-blocks -to keep them cool during the die-casting operation. In <a href="#Fig_26">Fig. 26</a>, -the water pipe may be seen at <i>R</i>, and hose pipes run from this supply -to each side of the die-blocks, thus providing a cooling circulation. In -this illustration, the pipes used for exhausting the air from the die -cavity are apt to be confused with the cooling pipes, but by following -the two pipes leading vertically down to the machine, the exhaust pipes -may be seen and kept distinct from the water pipes.</p> - -<h3>Making a Die-casting</h3> - -<p>In order to clearly understand the operation of the die-casting machine, -let us follow the sequence of events that takes place in producing -a casting. Two men are required to operate the machine. In <a href="#Fig_27">Fig. 27</a>, -the operators may be seen in their working positions. The first step -is taken by the operator at the left who, with a hand-ladle, dips enough -metal for one casting from the melting pot and pours it through nozzle -<i>G</i><sub>1</sub> into the goose-neck. The second operator in the meantime is replacing -the cores in the dies, adjusting the position of the sprue-cutter and -closing the dies preparatory to making a casting. This being done, he -elevates the dies and their operating mechanism, which are hinged and -counterbalanced, as previously described, bringing them to an upright -position. The die operator now mounts the box, raises the sprue-cutter -to its open position to admit the metal; after which the machine operator<span class="pagenum"><a id="Page_37">37</a></span> -turns the air valve with his left hand. The operation of this air -valve admits the air behind the metal, forcing it into the die, and the -same movement opens the exhaust valve slightly in advance. The -exhaust valve is located upon the second length of piping just above -the air valve, and as a link connects the two valves, the single motion -exhausts the air from the die cavity and immediately afterward the air -is admitted behind the metal, thereby “shooting” the metal into the die. -This being done, the air is shut off and the die operator cuts the sprue -by means of lever <i>Q</i><sub>1</sub>, withdraws the cores in the die, throws the dies -to the open position (which is indicated in <a href="#Fig_27">Fig. 27</a>), and operates the -ejecting mechanism, thus removing the casting from the die. In the -meantime, the machine operator is tending to his metal supply and -getting a ladle full of metal ready for the next die-casting operation. -By referring to the machines shown in <a href="#Fig_17">Fig. 17</a>, it will be noticed that -only a few are provided with exhaust piping for venting the dies. -Another venting method will be described later.</p> - -<div id="Fig_29" class="figcenter" style="width: 600px;"> - <img src="images/i_037.jpg" width="600" height="431" alt="" /> - <div class="caption">Fig. 29. Trimming Die-castings on a Filing Machine</div></div> - -<p>The number of die-castings which can be made on one machine per -day of ten hours varies with the character of the pieces being die-cast, -the number of pieces made at each operation of the machine and the -ease with which the dies may be worked, which depends, of course, -upon the number of cores and parts to be handled at each die-casting -operation. The dies shown in the machine in <a href="#Fig_26">Fig. 26</a>, produce four -bearings at each operation.</p> - -<h3>Trimming Die-castings</h3> - -<p>At the end of each run the operators of the machines go over their -work, breaking the castings from the sprues and throwing out all that -are defective. No matter how carefully the die-casting molds have been -made, there is always a certain amount of trimming to be done on the -finished die-castings, on account of the crevices left in the die for air<span class="pagenum"><a id="Page_39">39</a></span> -vents, or which exist from improper fitting of the parts of the dies. -These “fins,” as they are called, are trimmed by hand operators in a -special department. A general view of this trimming room is shown -in <a href="#Fig_28">Fig. 28</a>. Usually it is sufficient to scrape these fins off with a scraping -knife, but if the casting is especially difficult to produce, so that a large -opening is required to admit the metal, it is sometimes necessary to -trim unusually thick sprue sections by filing. <a href="#Fig_29">Fig. 29</a> illustrates the -method of trimming such die-castings on a filing machine.</p> - -<div id="Fig_30" class="figcenter" style="width: 600px;"> - <img src="images/i_038.jpg" width="600" height="325" alt="" /> - <div class="caption">Fig. 30. General View of E. B. Van Wagner Co.’s Die making Department</div></div> - -<div id="Fig_31" class="figcenter" style="width: 496px;"> - <img src="images/i_039.jpg" width="496" height="600" alt="" /> - <div class="caption">Fig. 31. A Typical Die-casting Mold</div></div> - -<h3>The Dies Used</h3> - -<p>Next to the casting machine, the dies or molds are the most important -necessary factor. A general view of the Van Wagner Co.’s die-making -department is shown in <a href="#Fig_30">Fig. 30</a>. In order to gain a proper -conception of the work required in producing a high-grade die-casting -mold, we will follow the different steps which are necessary in making -the mold. The first and most important step is the proper planning of -the die. Before any work at all can be done, it is necessary to plan the<span class="pagenum"><a id="Page_40">40</a></span> -die, <i>i. e.</i>, to decide just where the parting lines will come; just what -method will be used for ejecting the piece; what alloy will be used; -where the casting will be gated; and a hundred and one minor points, -all of which have a direct bearing upon the performance of the finished -dies. All these decisions have to be made by the diemaker, and in <a href="#Fig_37">Fig. 37</a> -he is shown, micrometer in hand, computing the shrinkage allowances -that he will make in the dies. This is a very important factor on -accurate work as the shrinkage varies from 0.001 to 0.004 inch, according -to the alloy and the general shape of the piece.</p> - -<div id="Fig_32" class="figcenter" style="width: 600px;"> - <img src="images/i_040.jpg" width="600" height="472" alt="" /> - <div class="caption">Fig. 32. Die-casting Mold shown in <a href="#Fig_31">Fig. 31</a>, disassembled</div></div> - -<p>Before taking up the actual machining operations of the mold-making -as conducted in this factory, it will be well to take a typical die-casting -mold and note its general construction. <a href="#Fig_31">Fig. 31</a> shows a typical die-casting -mold closed, while <a href="#Fig_32">Fig. 32</a> shows the same mold disassembled on -the bench to show its construction. The piece for which the mold has -been made is also shown. <a href="#Fig_33">Fig. 33</a> shows a similar die in section. From -the three illustrations a good idea of an average die-casting mold can -be obtained. Referring to these illustrations, the principal parts of this -die are the ejector box <i>A</i>, and the ejector plate <i>B</i> which is operated by -the racks <i>C</i>. For operating the ejector plate, the pinion shaft <i>D</i> having -a handle suitable for turning, is furnished. This, of course, fits into a -bored hole in the ejector box, bringing the pinion into mesh with the -racks for raising the ejector plate. In the ejector plate are three ejector -pins <i>E</i> for removing the casting from the mold. The ejector pins -operate through holes <i>F</i>. Beyond the pinion shaft may be seen the -casting for which this mold has been made. It will be noticed that -the top side of the casting has three projecting lugs through which are -small holes. Provision for forming this side of the die-casting is made -in the lower half of the mold <i>G</i>, while the upper half of the die-casting<span class="pagenum"><a id="Page_41">41</a></span> -is taken care of by the top plate <i>H</i>. One of the toggles for operating the -core pins through these three lugs is shown at <i>I</i>. These parts will be -described more fully later. The sprue cutter is shown in position in -the die at <i>J</i>.</p> - -<h3>Machining the Die Cavities</h3> - -<p>As will be noticed from <a href="#Fig_30">Fig. 30</a>, the machinery in the die-making -department is of modern design, for no other class of work demands as -good tool equipment and as much skill in the making as die-casting -molds. The die-blocks are made of machinery steel. <a href="#Fig_34">Fig. 34</a> illustrates -the first step in making a -die-casting mold after the -die-block has been shaped -approximately to size. This -operation consists in carefully -facing off the die surfaces -on a vertical-spindle -grinding machine. This, of -course, is a quick method of -surfacing the die-block, and -it insures that the top and -bottom surfaces of these -plates will be parallel, permitting -the die-faces to come -together properly.</p> - -<div id="Fig_33" class="figcenter" style="width: 321px;"> - <img src="images/i_041.jpg" width="321" height="600" alt="" /> - <div class="caption">Fig. 33. Section through a Die-casting Mold</div></div> - -<p>The next step consists of -laying out the die, as shown -in <a href="#Fig_36">Fig. 36</a>. This is done in -the usual manner, by working -on a coppered surface, -using dividers, scales, and a -center punch. When laying -out the die, the necessary -allowances are made for -shrinkage and finish, these -points having been planned -before actual work on the -die has been started. As in -other phases of die-work, -the machining operations -are performed, as far as possible, -before any hand-work -is done. In <a href="#Fig_38">Fig. 38</a> may be seen a die-maker turning the cavity in a -part of the die-casting mold. The highest type of skilled workmanship -is called for on this machine work, and as may be surmised from -<a href="#Fig_38">Fig. 38</a>, where the die-maker is shown measuring the die with a vernier -caliper, the measurements must be exact, for no grinding operations -follow the machine work.</p> - -<p><span class="pagenum"><a id="Page_42">42</a></span></p> - -<div id="Fig_34" class="figcenter" style="width: 600px;"> - <img src="images/i_042.jpg" width="600" height="461" alt="" /> - <div class="caption">Fig. 34. First step in making the Mold—Grinding Surfaces of Blocks</div></div> - -<div id="Fig_35" class="figcenter" style="width: 600px;"> - <img src="images/i_042b.jpg" width="600" height="465" alt="" /> - <div class="caption">Fig. 35. A Milling Operation on a Die</div></div> - -<p><a href="#Fig_5">Figs. 35</a> and <a href="#Fig_39">39</a> show typical milling operations being performed on -die-casting molds. In <a href="#Fig_39">Fig. 39</a> the diemaker is shown indicating a pin -in one corner of the mold cavity, preparatory to doing additional milling. -The block is held in the usual manner by being clamped on the -bed of the milling machine, and after it has been properly located under -the cutter head, tools are substituted for the indicator and the milling -of the cavity is completed. <a href="#Fig_35">Fig. 35</a> shows one of the sections of the die-casting -mold which is to be used in producing the casting shown at -the right of the work. In this case the diemaker is milling the recess<span class="pagenum"><a id="Page_43">43</a></span> -for the steel arbor which may be seen directly in the foreground. -This will be fitted in place to provide for the forming -of the hole in the side of the piece.</p> - -<div id="Fig_36" class="figcenter" style="width: 406px;"> - <img src="images/i_043.jpg" width="406" height="600" alt="" /> - <div class="caption">Fig. 36. Laying out One of the Mold Parts</div></div> - -<div id="Fig_37" class="figcenter" style="width: 406px;"> - <img src="images/i_043b.jpg" width="406" height="600" alt="" /> - <div class="caption">Fig. 37. Planning the Die-casting Mold</div></div> - -<div id="Fig_38" class="figcenter" style="width: 405px;"> - <img src="images/i_043c.jpg" width="405" height="600" alt="" /> - <div class="caption">Fig. 38. Turning out a Die-casting Mold</div></div> - -<div id="Fig_39" class="figcenter" style="width: 493px;"> - <img src="images/i_044.jpg" width="493" height="600" alt="" /> - <div class="caption">Fig. 39. Indicating a Mold on the Milling Machine</div></div> - -<p><a href="#Fig_40">Fig. 40</a> illustrates several important points in the making -of a die-casting mold. This illustration shows the ejector -box with the lower half of the mold on it, the ejector<span class="pagenum"><a id="Page_44">44</a></span> -plate being held against the under side of the die-plate by means -of the pinion shaft. The operation being done is the drilling of -the ejector-pin holes. Referring back to <a href="#Fig_32">Fig. 32</a>, which by the -way shows the die here illustrated disassembled, the holes being -drilled are those shown at <i>F</i> for the reception of the pins <i>E</i>. The -method employed is to drill the holes through the die and into the -ejector plate, afterward reaming all holes to size and driving the pins -into position in the ejector plate, while they are allowed to slide freely -through the die-plate. We will now assume that the ejector box and -plate have been completed and fitted, a pinion shaft for operating this -plate also fitted, the lower and upper dies completed by the machining -operations previously described, and all assembled. The final operation -of the fitting of the pins is shown in <a href="#Fig_41">Fig. 41</a> in which the die-maker -may be seen filing off the ends of these pins so that when dropped -to the lower position they will lie flush with the surface. If of uneven -lengths, these pins will cause irregular spots in the casting. It now -remains to describe the toggles used for operating the cores which form -the holes through the three lugs in the casting. One of these toggles, -of which there are three, is shown at <i>I</i>, in <a href="#Fig_31">Fig. 31</a>, and also in <a href="#Fig_32">Fig. 32</a>.<span class="pagenum"><a id="Page_45">45</a></span> -These toggles consist of brackets which are attached to the die-plate, -and levers which are fulcrumed at the ends of the brackets so that -their operation works the core pins. It is necessary to remove these -core pins after each casting has been made and position them before -another casting can be produced.</p> - -<div id="Fig_40" class="figcenter" style="width: 495px;"> - <img src="images/i_045.jpg" width="495" height="600" alt="" /> - <div class="caption">Fig. 40. Drilling the Ejector-pin Holes</div></div> - -<p>The fitting of the parts of a die-casting mold is one of the most -important parts of the work. It demands the highest type of workmanship, -for a poorly fitted die means a die which works hard in -addition to producing poor castings. It is very important that all movable -parts should work freely. <a href="#Fig_42">Fig. 42</a> shows the assembling operation -on a die-casting mold, the casting which is to be duplicated being -shown in the immediate foreground. These parts must all be screwed -into their respective places, making the joints as nearly air-tight as -possible. One cause of poor die-castings arises from the trapping of -air in the die, and different methods are employed for overcoming this -trouble.</p> - -<h3>Venting the Dies</h3> - -<p>There are two methods of preventing air from being trapped in die-casting -molds; either by constructing the dies so that the air may be<span class="pagenum"><a id="Page_46">46</a></span> -exhausted from the mold cavity before admitting the metal, or by -venting the die so that the air may be forced out by the inrushing -metal. In the first of these methods it is necessary that the joints in -the mold be made as close as possible, otherwise it will be impossible to -produce anything like a vacuum in the mold cavity. If, however, it -has many parts which must be fitted, it is usually considered advisable -to provide the die with vents consisting of milled recesses a few thousandths -inch deep. Several vents are provided, from which the air can -escape when the metal is admitted to the dies. The hot metal, of -course, “shoots” through them in thin ribbons, but not enough escapes -to affect the pressure on the metal which goes into the casting.</p> - -<div id="Fig_41" class="figcenter" style="width: 468px;"> - <img src="images/i_046.jpg" width="468" height="600" alt="" /> - <div class="caption">Fig. 41. Fitting Ejector-pins</div></div> - -<p>No matter how carefully a die may have been constructed, or how -carefully it has been assembled, there is always a certain amount of -“babying” to be done before it will work satisfactorily. The casting -may stick a little here, or there may be a rough spot there, and it is -the successful elimination of these troubles which constitutes the production -of a good die-casting.</p> - -<h3>Die-casting Metals</h3> - -<p><span class="pagenum"><a id="Page_47">47</a></span> -One of the purposes of this book is to correct several erroneous impressions -which are prevalent in regard to die-casting possibilities. -Many people seem to think that nearly all metals can be die-cast, but as -a matter of fact, those metals which can be successfully die-cast can be -numbered on the fingers of one hand, being alloys of lead, zinc, tin, -copper and antimony. The tin base metals shrink very little, while the -zinc base metals shrink considerably, and those with a large per -cent of aluminum have a very high shrinkage. Without doubt, the -most used die-casting metals are the zinc base metals. A typical metal -of this class contains about 85 per cent zinc; 8 per cent tin; 4 per cent -copper and 3 per cent aluminum. The melting point of this metal is -about 850 degrees F. While this alloy is one of the most common, -it is not by any means the best, as there is too little tin employed, but -it is a comparatively cheap metal, which probably accounts for its large -use. This metal is easily affected by heat and cold, and rapidly deteriorates -with age. The lead base metals may be typified by -an alloy containing 80 per cent lead; 15 per cent antimony; 4 per cent -tin; and 1 per cent copper. This composition melts at approximately -550 degrees F. and is used for castings subjected to little wear and -where no great strength is required. The weight of this metal is its -greatest objection, and it is also quite brittle because of the large percentage -of antimony.</p> - -<div id="Fig_42" class="figcenter" style="width: 600px;"> - <img src="images/i_047.jpg" width="600" height="466" alt="" /> - <div class="caption">Fig. 42. Assembling a Die-casting Mold</div></div> - -<p>For the best class of die-castings, the tin base metals are employed. -These range from 60 to 90 per cent tin, and from 2 to 10 per cent -copper, together with a little antimony. The melting point of a mixture -of this composition is about 675 degrees F. The castings have a good -color and they are much better in quality than any of the other alloys.<span class="pagenum"><a id="Page_48">48</a></span> -It is absolutely essential that tin base metals be used for carbureter -parts or other parts coming in contact with gasoline. Also, the tin -base metals must be used for parts which come in contact with food -products, as the lead or zinc alloys have a contaminating effect.</p> - -<p>Aluminum alloys have been cast in France and Germany in limited -quantities, but very seldom in this country on account of their high -melting point, as well as their effect upon the die. After aluminum -alloys have been run in the dies for a short time, the surfaces of the -molds become pitted. Through some unexplained cause, the metal seems -to flake out particles of the steel in the molds. When an aluminum -alloy is to be used, a good mixture is 80 per cent aluminum, 3 per cent -copper and 17 per cent zinc. This alloy has a high shrinkage and it -has also the same deteriorating effect upon the dies, but to a much less -degree than pure aluminum.</p> - -<div class="chapter"><div class="transnote"> -<h2 class="nobreak p1"><a id="Transcribers_Notes">Transcriber’s Notes</a></h2> - -<p>Punctuation, hyphenation, and spelling were made consistent when a predominant -preference was found in this book; otherwise they were not changed.</p> - -<p>Simple typographical errors were corrected; occasional unbalanced -quotation marks retained.</p> - -<p>Ambiguous hyphens at the ends of lines were retained.</p> - -<p>Text uses “die-cavity” and “die cavity”, “die-maker” and -“die maker”; none changed here.</p> -</div></div> - - - - - - - - -<pre> - - - - - -End of the Project Gutenberg EBook of Die Casting, by Chester L. 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