Update for 76925HEAD main

author: pgww <pgww@lists.pglaf.org> 2025-09-24 17:22:01 -0700
committer: pgww <pgww@lists.pglaf.org> 2025-09-24 17:22:01 -0700
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+<body>
+<div style='text-align:center'>*** START OF THE PROJECT GUTENBERG EBOOK 76925 ***</div>
+
+<div class="transnote">
+<strong>TRANSCRIBER’S NOTE</strong>
+<p class="noindent">Some minor changes to the text are noted at the end of the book.</p>
+</div>
+
+<hr class="chap x-ebookmaker-drop">
+<div class="chapter"></div>
+
+    <figure class="figcenter illowp60" id="Illustration_COVER" >
+      <img class="w100" src="images/cover.jpg" alt="Book cover">
+    </figure>
+    <hr class="chap x-ebookmaker-drop">
+
+    <div class="chapter"></div>
+
+
+<div class="bbx1">
+<div class="bbx2">
+<div class="h1_box">
+<h1>
+Elementary Lathe Practice
+</h1>
+</div>
+
+<p class="center wsp pb4 fs110">
+AS ADAPTED TO THE TEACHING OF<br>
+<br>
+<span class="fs135 lspp5">MACHINE SHOP PRACTICE<br>
+IN TECHNICAL SCHOOLS.</span><br>
+</p>
+<hr class="r30">
+<p class="center p2 wsp lh15">
+<span class=fs135>BY T. J. PALMATEER</span><br>
+INSTRUCTOR IN MACHINE WORK<br>
+<span class=fs90>Leland Stanford Junior University</span><br>
+</p>
+<hr class="r30 fs90">
+<p class="center wsp">
+Copyright 1917, by T. J. Palmateer<br>
+</p>
+
+<p class="center p6">
+<span class=wsp>FIRST EDITION</span><br>
+<br>
+<span class=fs120>1917</span><br>
+<br>
+Press of Nolte Bros.
+<img  style="max-height: 1.1em; display: inline-block; margin-bottom: -.4em" src="images/pbug.jpg" alt="Union Printer Mark">
+ San Jose, California
+</p>
+</div>
+</div>
+<hr class="chap x-ebookmaker-drop">
+<div class="chapter">
+  <h2 class="nobreak p4" id="PREFACE">
+    PREFACE
+  </h2>
+</div>
+
+<p>The object of this instruction book is to help beginners to
+acquire some familiarity with the more common lathe operations
+in the shortest practicable period of time. For this purpose three
+exercises have been designed with the view of giving the student
+the maximum amount of information in the small amount of time
+usually allowed for this purpose. The repetition of operations
+has therefore been avoided wherever it was considered advisable
+and the time lost in simply cutting off metal has been reduced as
+much as possible.</p>
+
+<p>It is assumed that beginners will receive oral instruction on
+the manipulation of the lathe, as in shifting the belt, the feed control,
+etc. It will also be necessary for the instructor to give a
+practical demonstration of most of the operations.</p>
+
+<p>The lathe speeds for the different operations as indicated in
+this book are only approximately correct since the actual cutting
+speed of the tool in feet per minute varies with the size and kind
+of lathe used. The instructor is expected to designate the proper
+speeds although the belt connections given herein will generally
+be close enough for beginners.</p>
+
+<p>In case it is considered advisable to devote to the elementary
+lathe operations less time than would be necessary to complete the
+three exercises presented herein, very good results can be obtained
+if the student will read all of the instructions carefully and
+then do only <a href="#EXERCISE_No_1">Exercise No. 1</a> and
+<a href="#PIECE_B">piece B of Exercise No. 3.</a></p>
+
+<p>The instructions here given are not intended as fixed rules for
+it is recognized that some of the operations may be done by other
+methods with equally good results.</p>
+
+<p class="right">
+  T. J. PALMATEER.
+</p>
+
+<p class="noindent">
+  Stanford University, Cal.<br>
+  <span class="pad2">January 1917.</span>
+</p>
+
+<hr class="chap x-ebookmaker-drop">
+<div class="chapter">
+
+<p><span class="pagenum" id="Page_5">[Pg 5]</span></p>
+
+  <h2 class="nobreak" id="EXERCISE_No_1">
+    <span class=norm>EXERCISE No. 1.</span>
+    <br>
+    <b>FIT SHAFT TO COLLAR—RUNNING FIT</b>
+  </h2>
+</div>
+
+<figure class="figcenter illowp100" id="ex_1" >
+  <img class="w100" src="images/ex_1.jpg" alt="Diagram showing machined tube, 6', 3/4 Outer diameter, 13/16 Inner Diameter">
+</figure>
+
+<p>Cut off with a power hack-saw a piece of steel 6¹⁄₁₆ inches
+long from a bar 1 inch in diameter. This will allow ¹⁄₁₆ of an
+inch for finishing the ends and ³⁄₁₆ of an inch for turning the
+diameter.</p>
+
+<p>An experienced lathe operator would use a piece of steel ⅝
+of an inch in diameter, but for beginners it is better to use larger
+stock to allow for practice turning.</p>
+
+<h4>CENTERING</h4>
+
+<p>Center both ends in the centering machine. The size of the
+center in this shaft should be from ³⁄₁₆ to ¼ of an inch in
+diameter. Larger work should have deeper centers.</p>
+
+<figure class="figcenter illowp100" id="fig01" >
+  <img class="w100" src="images/fig01.jpg" alt="">
+  <figcaption>
+      <p>Fig. 1</p>
+  </figcaption>
+</figure>
+
+<figure class="figcenter illowp100" id="fig02" >
+  <img class="w100" src="images/fig02.jpg" alt="">
+  <figcaption>
+      <p>Fig. 2</p>
+  </figcaption>
+</figure>
+
+<figure class="figcenter illowp100" id="fig03_4" >
+  <img class="w100" src="images/fig03_4.jpg" alt="">
+  <figcaption>
+<table class="autotable wd100">
+<tr>
+<td class="tdc">Fig. 3</td>
+<td class="tdc">Fig. 4</td>
+</tr>
+</table>
+  </figcaption>
+</figure>
+
+<p><span class="pagenum" id="Page_6">[6]</span></p>
+
+<p>If a centering machine is not available, the work may be centered
+by first locating the center with a pair of dividers and center
+punch and then using a combination drill and countersink in
+the lathe as shown in <a href="#fig01">Fig.&nbsp;1</a>. In this case the work is held by
+hand to prevent it from turning. As this work is to be turned, it
+is necessary to center it only approximately true.</p>
+
+<p><b>Accurate Centering.</b>—When the work is to be centered accurately,
+it may be done by putting one end in the lathe chuck and
+the other in a steady rest. A pointed tool is then used in the tool
+post as shown in <a href="#fig02">Fig.&nbsp;2</a>. The point of this tool has an angle of 60
+degrees, the same as the lathe centers, and is ground like a flat
+drill so that it cuts on both sides.</p>
+
+<p>After the shaft is centered with this tool, a center hole about
+⅛ of an inch in diameter should be drilled. This is done by
+holding the drill in the tail-stock of the lathe with a drill-chuck,
+as shown in <a href="#fig03_4">Fig.&nbsp;3</a>. The object of this center hole is to give the
+center of the shaft a bearing on the lathe center a short distance
+back from the point, as at A in <a href="#fig03_4">Fig.&nbsp;4</a>.</p>
+
+<h4>PLACING WORK IN LATHE</h4>
+
+<p>The work is made to rotate on the lathe centers by fastening
+a lathe dog to the shaft at the head-stock end, as shown at A in
+<a href="#fig05">Fig.&nbsp;5</a>.</p>
+
+<figure class="figcenter illowp100" id="fig05" >
+  <img class="w100" src="images/fig05.jpg" alt="">
+  <figcaption>
+      <p>Fig. 5</p>
+  </figcaption>
+</figure>
+
+<p>The tail-stock center is adjusted so that the shaft will rotate
+freely, yet be tight enough to allow no slack, or lost motion. Since
+the shaft rotates on this center, it should be kept well lubricated
+by using machine oil, or a mixture of graphite and oil.</p>
+
+<p>To get the best results in turning this sort of work, it is necessary
+to face both ends before turning and to rough turn the whole
+piece to within about 0.03, or 0.04 of an inch of the finished size
+before any part of it is finished. However, it is not always necessary
+to do this. The object of first rough turning the shaft all
+over is to remove the internal strains of the steel and to wear the
+centers down to a good bearing before any finishing cuts are
+<span class="pagenum" id="Page_7">[7]</span>taken. The purpose of facing the ends is to get them square, or
+true, and smooth.</p>
+
+<h4>FINISHING END OF SHAFT</h4>
+
+<p>To face the ends, use a regular turning tool starting to cut
+from the outside and feeding by hand towards the center with the
+cross feed. Such a tool will leave a ridge near the center, as
+shown in <a href="#fig06_7">Fig.&nbsp;6</a>. This ridge is cut off with a sharp pointed, side
+cutting tool, as shown in <a href="#fig06_7">Fig.&nbsp;7</a>, which is also used for taking the
+finishing cut across the whole end of the bar. When taking this
+finishing cut, lard oil, or some other lubricant, should be used.</p>
+
+<figure class="figcenter illowp100" id="fig06_7" >
+  <img class="w100" src="images/fig06_7.jpg" alt="">
+  <figcaption>
+<table class="autotable wd100">
+<tr>
+<td class="tdc"></td>
+<td class="tdc">Fig. 6</td>
+<td class="tdc">Fig. 7</td>
+</tr>
+</table>
+  </figcaption>
+</figure>
+
+<p>After the finishing cut has been taken, any small ridge, or fin
+that remains at the edge of the center is removed by slightly
+changing the angle of the tool in the tool post and allowing about
+¹⁄₆₄ of an inch play between the centers. Having the work loose
+like this when the lathe is running, allows the extreme point of
+the side tool to extend beyond the edge of the center and cut a
+smooth end.</p>
+
+<p>The lathe should run slow for the finishing cut and fast when
+the regular turning tool is used.</p>
+
+<h4>TURNING THE SHAFT</h4>
+
+<p>The first, or roughing cut, is taken with a high-speed steel
+tool, or bit, fastened in a tool holder. The tool holder is clamped
+in the tool post of the lathe so that the point of the tool is at, or
+a little above, the center, or axis, of the lathe, as in <a href="#fig08_10">Fig.&nbsp;8</a>.</p>
+
+<p>If the point of the bit is too high, it is easy to see that, as the
+shaft rotates, the tool will not cut at all, <a href="#fig08_10">Fig.&nbsp;9</a>. In case the tool
+is set below the center, the cutting action is very poor so that
+turning tools are never set as in <a href="#fig08_10">Fig.&nbsp;10</a>.</p>
+
+<p><span class="pagenum" id="Page_8">[8]</span></p>
+
+<figure class="figcenter illowp100" id="fig08_10" >
+  <img class="w100" src="images/fig08_10.jpg" alt="">
+  <figcaption>
+<table class="autotable wd100">
+<tr>
+<td class="tdc"></td>
+<td class="tdc">Fig. 8</td>
+<td class="tdc">Fig. 9</td>
+<td class="tdc">Fig. 10</td>
+</tr>
+</table>
+  </figcaption>
+</figure>
+
+<figure class="figcenter illowp100" id="fig11" >
+  <img class="w100" src="images/fig11.jpg" alt="">
+  <figcaption>
+      <p>Fig. 11</p>
+  </figcaption>
+</figure>
+
+<p><b>Speed of the Lathe.</b>—In taking the heavy roughing cuts, the
+belt may be placed on the second largest step of the cone, while
+for the finishing cuts the lathe should run a little faster, say with
+the belt in the next smaller step.</p>
+
+<p><b>Grinding Turning Tool.</b>—The front, or point, and the sides of
+the tool are ground at an angle, which is called the clearance. If
+the tool has too little clearance, it will not cut freely, while if it
+has too much clearance, the point will be so thin that it will break
+off or become dull quickly.</p>
+
+<p>The top of the tool is also ground at an angle. This is called
+the rake. If the tool has too little rake, it will not cut freely and
+if it has too much, the edge will soon break down.</p>
+
+<p>It requires some practice for a beginner to learn the proper
+rake and clearance that should be given to a tool. <a href="#fig11">Fig.&nbsp;11</a> shows
+a tool ground with clearance and rake that will give very good
+results.</p>
+
+<p><b>Direction Tool Should Travel.</b>—The depth of the first cut
+should be about ¹⁄₁₆ of an inch and the travel of the tool should
+always be from the tail-stock end towards the head-stock. If the
+travel is in the opposite direction, the pressure on the tail-stock
+center is increased, causing it to heat quickly.</p>
+
+<p>The length of the cut should be as great as possible without
+the lathe dog striking the tool, or cross-rest.</p>
+
+<p><b>Adjusting the Lathe to Turn Straight.</b>—After the first cut,
+the work should be calipered and if it is not the same diameter
+<span class="pagenum" id="Page_9">[9]</span>at both ends the tail-stock should be adjusted so that the lathe
+will turn straight.</p>
+
+<p>The tail-stock adjustment is made by loosening the main
+clamping nut B and one of the screws C and then tightening the
+other screw C on the opposite side of the tail-stock, <a href="#fig05">Fig.&nbsp;5</a>.</p>
+
+<p>If the shaft is larger at the tail-stock end, the tail-stock should
+be moved towards the front of the lathe one half the difference
+between the diameters of the shaft at the two ends.</p>
+
+<p>In doing close work, the tail-stock should be adjusted as
+closely as possible, but in this case if it is off center only a little,
+say 0.002 or 0.003 of an inch, it will be close enough providing it
+is set so that the shaft will be turned larger at the head-stock end.
+If the tail-stock is set so that the shaft is turned larger at the tail-stock
+end, the shaft will be too small at the other end after the
+finishing cut is taken.</p>
+
+<p><b>Fitting Shaft to the Collar.</b>—After the roughing cut is taken
+and the lathe has been adjusted so that it turns approximately
+<ins class="corr" title="Transcriber's Note—original text: straght" id="straght">straight</ins>, the end of the shaft is turned for about ¼ of an inch so
+that it will just fit the hole in the collar, shown in the drawing
+of Exercise 1. To measure this: first set the inside calipers to the
+diameter of the hole in the collar, then set the outside calipers to
+the inside calipers and caliper the shaft as accurately as possible.
+For a final test of this diameter, remove the work from the lathe
+and try it with the collar itself.</p>
+
+<p>The advantage of turning but ¼ of an inch at the end of the
+shaft is this; if the finishing cut were set too deep, only ¼ of an
+inch of the shaft would be too small, while if this cut were taken
+the whole length, the entire shaft would be too small.</p>
+
+<p>After the shaft has been turned at the end so that it fits the
+collar, the rest of the shaft should be turned a little larger, say
+0.002 or 0.003 of an inch, in diameter. This will leave enough to
+finish with a file.</p>
+
+<p><b>Filing.</b>—The object of filing is to take out the tool marks, but
+it is also found to be much easier to make a close fit by filing off
+the last 0.002 or 0.003 of an inch than to take so small a cut with
+a tool. The amount of allowance for filing depends upon the
+character of the finishing cut. Since the less filing required the
+better, the finishing cut should be made as smooth as possible.</p>
+
+<p>The tool used for the roughing cut may also be used for finishing,
+but it is usually necessary to re-sharpen it. After it is reset
+in the tool post, the point should be flattened a little wider
+<span class="pagenum" id="Page_10">[10]</span>than the pitch of the feed, say about ¹⁄₃₂ of an inch, and parallel
+with the work. This is done with an oilstone.</p>
+
+<p>For filing work on a lathe, a single cut file is used. This is
+called a lathe, or mill file.</p>
+
+<p>The stroke of the file should be slow, steady, and straight
+across the shaft. The lathe should run a little faster for filing
+than for turning, the object being to have the work make several
+revolutions for a single stroke of the file. If the lathe runs too
+slow and the stroke of the file is too fast, the shaft, instead of
+being filed round, will have a series of flat places on the surface.</p>
+
+<p>After the work is finished as close to the dog as possible, reverse
+it in the lathe and finish that part where the dog was fastened.</p>
+
+<hr class="chap x-ebookmaker-drop">
+<div class="chapter">
+  <h2 class="nobreak" id="EXERCISE_No_2">
+    <span class=norm>EXERCISE No. 2.</span>
+  </h2>
+</div>
+
+<figure class="figcenter illowp100" id="ex_2" >
+  <img class="w100" src="images/ex_2.jpg" alt="Diagram of tapered shaft, with threads on each end">
+</figure>
+
+<p>The finished shaft in Exercise No. 1 may be used for Exercise
+No. 2.</p>
+
+<p>Place the shaft in the bench vise and with a rule and scriber
+lay off the dimensions: 1¾ in., 3 in., and 1¼ in. Then center
+punch the lines just deep enough so that they can be easily seen
+when the work is in the lathe.</p>
+
+<p>Turn the large end first.</p>
+
+<p>When it is necessary to turn a fixed distance, or to a line as
+in this case, it is well to disconnect the feed when the tool is within
+about ⅛ of an inch from the end of the cut and to feed the
+tool the rest of the distance by hand. If this is not done, the tool
+may travel farther than it is intended to.</p>
+
+<p>It is better to turn the portions to be threaded a little under
+rather than over size. For if they are over size, the threads will
+not fit the standard size nut, but if under size the threads do not
+need to be cut so deep in order to fit the nut.</p>
+
+<p>For measuring the diameters of this piece set the calipers as
+<span class="pagenum" id="Page_11">[11]</span>accurately as possible by measuring from the end of the rule, as
+shown in <a href="#fig12_13">Fig.&nbsp;12</a>.</p>
+
+<figure class="figcenter illowp100" id="fig12_13" >
+  <img class="w100" src="images/fig12_13.jpg" alt="">
+  <figcaption>
+<table class="autotable wd100">
+<tr>
+<td class="tdc">Fig. 12</td>
+<td class="tdc">Fig. 13</td>
+</tr>
+</table>
+  </figcaption>
+</figure>
+
+<p><b>Cutting Recess.</b>—The surface at the end as well as the recesses
+between the threads and the taper are cut with a square-nose, or
+cutting-off tool, <a href="#fig12_13">Fig.&nbsp;13</a>.</p>
+
+<p>This tool <ins class="corr" title="Transcriber's Note—original text: shoull" id="shoull">should</ins> have a sharp smooth edge, the
+point being set level with the center of the lathe.</p>
+
+<p>To produce a smooth finished surface lard oil should be used
+with a slow feed and lathe speed.</p>
+
+<p>After the end is turned to size, reverse the work in the lathe
+and turn the other end and the taper before cutting the threads.</p>
+
+<p><b>Turning Taper.</b>—The drawing calls for a taper of 1 inch per
+foot. This is cut by using a taper attachment, or by setting the
+tail-stock off center. As most lathes are not provided with a
+taper attachment, the latter method will be used.</p>
+
+<p>If the work was 12 inches long, the tail-stock would be moved
+off center ½ inch to turn a taper of 1 inch per foot. It being
+only 6 inches long, the tail-stock is set off center but half that
+amount, or ¼ inch.</p>
+
+<p>Before taking the finishing cut, caliper both ends to prove
+that the lathe is cutting the correct taper.</p>
+
+<h4>THREAD CUTTING</h4>
+
+<p>The threads are cut to fit ½ inch and ⅝ inch nuts having
+United States Standard threads. These threads are flattened at
+the top and bottom to the amount of ⅛ of the pitch instead of
+being sharp pointed as in the case of Standard V-threads.</p>
+
+<p><b>Pitch.</b>—The pitch of the thread is the distance from the center
+of one thread to the center of the one adjoining. On the end of
+the exercise having 13 threads per inch the pitch is ¹⁄₁₃ of an
+inch so that the width of the flat at the top and bottom of this
+<span class="pagenum" id="Page_12">[12]</span>thread should be ⅛ of ¹⁄₁₃ of an inch, or about .009 of an inch.</p>
+
+<p><b>Lead.</b>—The lead of the thread is the distance a nut on the
+screw will travel in making one complete turn. For single threads
+the pitch and lead are the same, but for double threads the lead
+is twice the pitch.</p>
+
+<p><b>Grinding Tool.</b>—The sides of U. S. S. threads form an angle of
+60 degrees. To cut this thread in a lathe, a tool the same shape as
+the threads is used. A gauge for grinding this tool accurately is
+shown in <a href="#fig14_16">Fig.&nbsp;14</a>.</p>
+
+<figure class="figcenter illowp100" id="fig14_16" >
+  <img class="w100" src="images/fig14_16.jpg" alt="">
+  <figcaption>
+<table class="autotable wd100">
+<tr>
+<td class="tdc">Fig. 14</td>
+<td class="tdc">Fig. 15</td>
+<td class="tdc">Fig. 16</td>
+</tr>
+</table>
+  </figcaption>
+</figure>
+
+<p>If a U. S. S. thread gauge is not available, the tool can be
+ground with the aid of a regular thread and center gauge, shown
+in <a href="#fig14_16">Fig.&nbsp;15</a>. With such a gauge the angle can be ground accurately,
+but it will be necessary to measure the flat point with a rule.</p>
+
+<p>The top of the tool should be ground so that it will be approximately
+in a horizontal plane when set in the lathe.</p>
+
+<p>Where the thread to be cut is as fine as 13 per inch the flat
+surface at the point of the tool is so small that the extreme point
+can be oil-stoned off instead of being taken off with the grinding
+wheel. The flat point should never be wider than the standard
+size, but if it is a little too narrow it will make very little difference
+in ordinary lathe work.</p>
+
+<p><b>Setting Tool.</b>—To set the tool so that both sides of the thread
+will have the same angle, the thread gauge is used as shown in
+<a href="#fig14_16">Fig.&nbsp;16</a>. The tool should be set on a level with the center of the
+lathe.</p>
+
+<p><b>How Lathe is Geared.</b>—To cut 13 threads per inch the work
+must make 13 revolutions while the carriage, which carries the
+tool, travels one inch. For this purpose the lathe spindle is connected
+<span class="pagenum" id="Page_13">[13]</span>to the lead screw with the proper size gears and the lead
+screw to the carriage by a split nut. This split nut is back of the
+carriage apron and is opened and closed by the lever E, <a href="#fig17">Fig.&nbsp;17</a>.</p>
+
+<figure class="figcenter illowp100" id="fig17" >
+  <img class="w100" src="images/fig17.jpg" alt="">
+  <figcaption>
+      <p>Fig. 17</p>
+  </figcaption>
+</figure>
+
+<figure class="figright illowp50" id="fig18" >
+  <img class="w100" src="images/fig18.jpg" alt="">
+  <figcaption>
+      <p>Fig. 18</p>
+</figcaption>
+</figure>
+      <p class="noindent lh15">
+      A. Index Plate<br>
+      B. Stud Gear<br>
+      C. Screw Gear<br>
+      D. Intermediate or Idle Gear<br>
+      E. Lever for connecting Carriage to Lead Screw<br>
+      J. Lever for Disconnecting and Reversing Feed<br>
+      K. Adjustable Stop for Thread Cutting</p>
+
+      <p class="clearx">If the lead screw of the lathe has 6 threads per inch, the gearing
+    to cut 13 threads per inch must have the same ratio as 6 is to
+    13. To cut 16 threads the ratio would be 6 to 16.</p>
+      <p>It is not necessary to figure the size of gears for the different
+    <span class="pagenum" id="Page_14">[14]</span>threads as all lathes are provided with an index plate that designates
+    the proper size gears to be placed on the stud B and screw
+    C, <a href="#fig17">Fig.&nbsp;17</a>, for the desired thread.</p>
+      <p><b>To Set Change Gear.</b>—To change these gears, first loosen the
+    nuts holding the stud and screw gears B and C. Next loosen the
+    nut G. This will allow the intermediate gear to drop away from
+    the stud gear B. Then loosen the nut H so that the intermediate
+    gear can be drawn back away from the gear on the lead screw C.</p>
+      <p>When the gears are put together, they should be set so that
+    there will be a little slack, or lost motion, between the different
+    gears. If they are set too close together, they will make a great
+    deal of noise when running and there is also danger of breaking
+    the teeth.</p>
+      <p>While all lathes are not designed alike the method of changing
+    the gears is very much the same on all machines except those having
+    the quick change-gear device. With a lathe having such a device,
+    instead of changing the gears on the stud and screw the same
+    result is obtained by shifting a combination of levers.</p>
+      <p><b>Why Feed Should Be Disconnected.</b>—The mechanism that
+    controls the feed, or travel, of the tool when cutting threads is
+    independent of that used for the feed when doing plain turning.
+    The two feeds usually run at different speeds so that if they are
+    both in action at the same time the gears in the carriage will
+    break. For this reason all lathes are provided with some means
+    of disconnecting the feed used for plain turning when cutting
+    threads.</p>
+      <p>To disconnect the feed on the lathe shown in <a href="#fig17">Fig.&nbsp;17</a>, move the
+    lever J to the central, or neutral, position. This should always
+    be done before starting to cut the threads.</p>
+      <p><b>Speed of Lathe.</b>—The lathe should run slower for cutting
+    threads than for plain turning. With most lathes if the belt is
+    on the largest step of the cone it will give about the right speed
+    for cutting the threads in this exercise.</p>
+      <p>The object of running the lathe slow is to give the operator
+    time to draw back the tool at the end of the cut and to obtain a
+    smoother cut. If the speed of the lathe is too fast, the cutting
+    action will be so quick that the tool, instead of cutting clean and
+    smooth, will tear out the metal leaving a rough surface.</p>
+      <p>The slower the lathe runs the easier it is to cut the threads,
+    but it will also take longer to do the job. It therefore requires
+    <span class="pagenum" id="Page_15">[15]</span>practical experience to determine the proper speed to be used for
+    cutting the different size threads.</p>
+      <p><b>Chamfering.</b>—After the lathe and tool are properly set, chamfer
+    off the sharp corners where the threads begin and end with
+    the side of the thread tool. The depth of this cut should be about
+    the same as that of the threads when finished. If the corners are
+    not chamfered, the threads, when cut, will form a very thin edge,
+    or fin, at the ends.</p>
+      <p><b>Use of Adjustable Stop.</b>—To regulate the depth of each cut
+    an adjustable stop is used as shown at K. First move the tool so
+    that the point just touches the work, then adjust the screw on
+    the attachment K so that the cross-rest will not go in any farther.
+    Now move the carriage by hand until the point of the tool is a
+    little past the tail-stock end of the work; close the split nut on
+    the lead screw with the lever E; and turn the screw on the attachment
+    K so that the tool can be moved in just enough to take
+    a very light cut.</p>
+      <p>Start the lathe and when the tool has reached the end of the
+    cut back it out and reverse the lathe. By reversing the lathe the
+    tool is returned to the starting point without disconnecting any
+    of the gearing. The object of drawing the tool back is to prevent
+    it from dragging on the work during its return.</p>
+      <p>The tool will never travel over the same path on the reverse
+    as on the forward movement of the lathe on account of the slack,
+    or lost motion, in the gears.</p>
+      <p>This first cut is taken to prove that the lathe is properly
+    geared, so the work should be measured with a rule, or screw
+    pitch gauge.</p>
+      <p>Adjust the screw at K until the tool can be moved in deeper
+    for the next cut and repeat the operation until the thread is
+    nearly finished. Then the tool should be reset so that it will cut
+    on only one side at a time.</p>
+      <p><b>Finishing Side of Thread.</b>—When roughing out the threads,
+    the tool cuts on both sides of the point since it is fed straight into
+    the work. It is much easier, though, to finish the threads smooth
+    if the tool cuts on one side only. This is done by rapping the end
+    of the tool holder so that it is turned in the tool post just enough
+    to change the position of the point of the tool about .01, or .02 of
+    an inch.</p>
+      <p>To prove that the tool is set over the proper amount, turn the
+    <span class="pagenum" id="Page_16">[16]</span>lathe forward by hand a few revolutions, to take out all the slack,
+    or lost, motion in the gears, then move the tool into the groove of
+    the thread until one side just touches the side of the thread. The
+    other side of the tool should then be about .01, or .02 of an inch
+    away from the side of the thread.</p>
+      <p>After the tool is properly adjusted, set the stop K. The tool
+    is then drawn back and the lathe reversed until the tool is at the
+    end of the work ready for a cut. It usually requires several finishing
+    cuts to take out all the rough marks left by the roughing
+    cuts.</p>
+      <p>When this side of the thread is finished, the other side is finished
+    in the same manner.</p>
+      <p>If the lathe is provided with a compound rest, a somewhat
+    different procedure is usually followed since the rest can be set
+    at an angle of 30 degrees with the work, as in <a href="#fig18">Fig.&nbsp;18</a>.</p>
+      <p>In this case the tool is moved in by turning the small hand-crank
+    M until the side at O has been cut to the proper depth.
+    While making these first cuts, the stop K is merely used to bring
+    the cross-rest to the same position each time. The tool is then
+    drawn back slightly with the hand-crank M and the stop K adjusted
+    so that the tool can be moved straight in by means of the
+    hand-crank Q. This will finish the other side of the thread at P.</p>
+      <p>To determine when the thread is cut to the proper size the
+    work is removed from the lathe and tested with a standard nut
+    having U. S. S. threads.</p>
+      <p>After the threads are cut on this end of the exercise, it is reversed
+    in the lathe and the other end threaded in a similar manner.</p>
+      <p>To prevent the screw of the dog from marring the portion
+    already threaded two nuts should be screwed on and the dog fastened
+    to the nuts.</p>
+      <p><b>How to Reset the Tool.</b>—When cutting threads of this size and
+    larger, the tool usually becomes dull from taking the heavy roughing
+    cuts. It is then necessary to resharpen it before taking the
+    fine finishing cuts.</p>
+      <p>To reset the tool in the lathe first get the angles correct, as
+    shown in <a href="#fig14_16">Fig.&nbsp;16</a>. Then revolve the lathe forward by hand to
+    take up the slack in the gears and move the tool in close to the
+    threads. If the tool is in a position so that it will cut too much
+    off one side of the thread, it may be changed by disengaging the
+    reversing gears with the lever R and turning the lathe by hand.
+    <span class="pagenum" id="Page_17">[17]</span>When the tool is in the proper position relative to the groove of
+    the thread, the reverse gear lever R is reset.</p>
+      <p>In a case where the tool is off the desired position only a very
+    little, it may be corrected by the rapping process.</p>
+      <p>If the lathe has a compound rest the tool may be brought to
+    the correct position by turning the hand-crank M.</p>
+      <p>It would be well for beginners to practice thread cutting on a
+    piece of scrap steel before trying to cut them on the exercise.</p>
+
+
+<hr class="chap x-ebookmaker-drop">
+    <div class="chapter">
+      <h2 class="nobreak" id="EXERCISE_No_3">
+        <span class=norm>EXERCISE No. 3.</span>
+        <br>
+        CAST IRON FINISHED ALL OVER.
+      </h2>
+    </div>
+
+
+<figure class="figcenter illowp80" id="ex_3">
+  <img class="w100" src="images/ex_3.jpg"
+alt="Two piece, outer casing with inside threads, and inner mandrel with threads.">
+</figure>
+      <p class="noindent hang2"><b>Sequence of Operations</b>:<br>
+      1. Finish the inside of Piece A.<br>
+      2. Drill and Ream the hole in Piece B.<br>
+      3. Mount B on mandrel and finish outside.<br>
+      4. Screw A on B and finish the outside of A.</p>
+
+<h3 id="PIECE_A" class="nosep">Piece A.</h3>
+
+<figure class="figcenter illowp100" id="fig19_20" >
+  <img class="w100" src="images/fig19_20.jpg" alt="">
+  <figcaption>
+
+<table class="autotable wd100">
+<tr>
+<td class="tdc">Fig. 19 Rough Casting</td>
+<td class="tdc">Fig. 20 Finished Casting</td>
+</tr>
+</table>
+     <p class="fs75">10 Thrds. per 1″ U. S. S.</p>
+  </figcaption>
+</figure>
+
+<p><span class="pagenum" id="Page_18">[18]</span></p>
+
+<h4>USE OF 4-JAW CHUCK.</h4>
+
+<p>To machine the inside of piece A it is necessary to hold it in
+the lathe by means of an independent four-jaw chuck, as shown
+in <a href="#fig21">Fig.&nbsp;21</a>. Work of this kind is usually chucked so that the outside
+surfaces will be within ¹⁄₃₂ of an inch of running true.</p>
+
+<figure class="figcenter illowp100" id="fig21" >
+  <img class="w100" src="images/fig21.jpg" alt="">
+  <figcaption>
+      <p>Fig. 21</p>
+  </figcaption>
+</figure>
+
+<p>The process of chucking the work is as follows:</p>
+
+<p><b>Centering Work in the Chuck.</b>—Place the work in the chuck
+and adjust the jaws until they are all at approximately equal
+distances from the circles on the face of the chuck. Then put a
+cutting-off tool loosely in the tool post and move it close to the
+work and as near as possible to the end of the chuck jaws. Revolve
+the lathe by hand to prove if the work is centered. If it is
+not centered to within ¹⁄₃₂ of an inch, readjust the jaws until it
+is. Now move the cutting-off tool to the end of the work and
+turn the lathe by hand. If the end runs out of true, rap it with a
+hammer at such points as will correct its position.</p>
+
+<p><b>Advantage of Proper Chucking.</b>—<a href="#fig21">Fig.&nbsp;21</a> shows the work held
+by the middle step of the cone. One reason for holding it in this
+way is to permit the rough turning of the larger step while in
+the chuck. If the work were held by the small end, it would be
+apt to work loose when taking the heavy roughing cuts on account
+of the distance that the work projects out and the small diameter
+on which the chuck grips compared with that of the large end
+which is to be turned.</p>
+
+<h4>ROUGH TURNING AND BORING.</h4>
+
+<p>After the work has been properly chucked, rough turn the
+end and the largest diameter to within ¹⁄₃₂ of an inch of the finished
+size.</p>
+
+<p>All cast iron has a hard surface, or scale, from ¹⁄₆₄ to ¹⁄₃₂
+of an inch deep so that it is necessary to run the lathe slower
+for the first cut than for those made after the scale has been removed.
+<span class="pagenum" id="Page_19">[19]</span>In taking this first cut the tool should be set deep
+enough to permit the point to cut under the scale.</p>
+
+<p><b>Speed of Lathe.</b>—The speed of the lathe in taking the roughing
+cut on work of this size should be about right if the belt is on
+the smallest step of the cone and the back gears are used. After
+the scale is removed, the lathe may be run faster.</p>
+
+<p>A beginner will require experience before being able to determine
+the proper speeds and feeds for the <ins class="corr" title="Transcriber's Note—original text: diffrent" id="diffrent">different</ins> kinds of
+lathe work.</p>
+
+<p><b>Advantage of Roughing Inside.</b>—As the inside of piece A must
+fit the outside of the piece B, the 1⅛ inch hole, the threads,
+and the taper must be machine true with each other, or else A will
+not fit into B properly. Now if the taper should be finished and
+the work moved in the chuck before the threads and the 1⅛
+inch hole are finished, they would not be true with each other.
+For this reason it would be well to rough bore the inside to within
+¹⁄₃₂ of an inch of the finished size before any of these three parts
+are finished.</p>
+
+<p><b>Roughing Inside.</b>—To rough bore the taper use a regular turning
+tool. Set the compound rest to the correct angle and feed the
+tool in at that angle.</p>
+
+<p>If the lathe is not provided with a compound rest, the taper
+may be rough bored by turning both feeds by hand and following
+the cored surface as closely as possible.</p>
+
+<p>The cored hole in the rough casting, <a href="#fig19_20">Fig.&nbsp;19</a>, is ¹⁵⁄₁₆ of an
+inch in diameter which allows ³⁄₁₆ of an inch for finishing the
+1⅛ inch hole and ⁵⁄₁₆ for the portion where the threads are to
+be cut.</p>
+
+<p><b>Use of Flat Drill.</b>—To rough bore the hole a 1¹⁄₁₆ flat, or
+lathe, drill is used as shown in <a href="#fig21">Fig.&nbsp;21</a>. The holder A is clamped
+in the tool post so that the slot in it will hold the drill at the center
+of the lathe. If the drill is held above or below the center, the
+hole will be drilled larger than the drill. To prove that the slot
+in the holder is at the center, move it close to the tail-stock center.
+After the holder is properly set, move it as close to the work as
+possible and feed the drill into the exercise by turning the hand-crank
+on the tail-stock.</p>
+
+<p>This drill removes the hard surface, or scale, and also trues
+up, or centers, the hole to within ¹⁄₆₄, or ¹⁄₃₂ of an inch. Now
+enlarge the portion of the hole where the threads are to be cut
+with a 1³⁄₁₆ drill.</p>
+
+<p><span class="pagenum" id="Page_20">[20]</span></p>
+
+<p>To determine when this drill has been fed in far enough, mark
+on the drill with a piece of chalk the distance from the end of the
+work to the point where the recess is to be cut. By sighting
+across the end of the work the operator can then see when the
+drill has been fed in the proper distance.</p>
+
+<p><b>Use of Boring Bar.</b>—To cut the square shoulder where the
+threads begin and the recess where they end, use a tool and boring
+bar, as shown in <a href="#fig22">Fig.&nbsp;22</a>, held in the tool post. The width of this
+tool is ⁵⁄₃₂ of an inch so that it will be necessary to take two cuts
+to make the recess wide enough. Such a narrow tool is used because
+it is less liable to chatter.</p>
+
+<figure class="figcenter illowp100" id="fig22" >
+  <img class="w100" src="images/fig22.jpg" alt="">
+  <figcaption>
+      <p>Fig. 22</p>
+  </figcaption>
+</figure>
+
+<p>This tool is ground with clearance at the sides as well as at
+the front and it should also be noticed that it is wider at the cutting
+edge than back close to the boring bar. This is done so that
+when the tool is fed into the work there will be little, or no chance
+of its binding on the side.</p>
+
+<p>To obtain the correct setting for the tool, move the boring bar
+into the hole and bring it up close to one side. The tool should
+then be adjusted until its cutting edge is parallel to the elements
+of this surface.</p>
+
+<p>The work is now all roughed out so that it makes very little
+difference which of the three fitting parts is finished first.</p>
+
+<h4>FINISHING INSIDE</h4>
+
+<p>The 1⅛ inch hole has been drilled with a ¹¹⁄₁₆ inch lathe
+drill, but as such a tool cannot be relied upon to drill true to center,
+or size, it is necessary to turn it out with a boring tool. With
+<span class="pagenum" id="Page_21">[21]</span>this tool the hole can be bored true to center and within .01 of an
+inch of the finished size.</p>
+
+<p>The boring bar used in this case is the same as shown in
+<a href="#fig22">Fig.&nbsp;22</a>, but the cutter has a rounded point and is similar to the tool
+used for outside turning except that it is ground with less clearance.</p>
+
+<p>To insure accuracy and conserve time, the hole is then finished
+with a shell reamer held in the lathe as shown in <a href="#fig23">Fig.&nbsp;23</a>.</p>
+
+<figure class="figcenter illowp100" id="fig23" >
+  <img class="w100" src="images/fig23.jpg" alt="">
+  <figcaption>
+      <p>Fig. 23</p>
+  </figcaption>
+</figure>
+
+<p><b>Reaming the Hole.</b>—Before starting the reamer, the hole
+should be bored at the end, for a distance of about ⅛ of an inch,
+to the size which will just permit the reamer to enter. This diameter
+must be calipered very carefully and should be tested with
+the reamer itself. The rest of the hole is then bored about .01 of
+an inch smaller in diameter to allow enough material for finishing
+with the reamer. Since the reamer used in this case cuts on
+the sides as well as on the end, the hole must be bored true to center
+in order to be reamed true.</p>
+
+<p>If the reamer has a tapered shank, it is held in the lathe by a
+square shank socket and wrench, as shown in <a href="#fig23">Fig.&nbsp;23</a>, and is fed
+into the work by turning the hand-crank on the tail-stock.</p>
+
+<figure class="figcenter illowp100" id="fig24" >
+  <img class="w100" src="images/fig24.jpg" alt="">
+  <figcaption>
+      <p>Fig. 24</p>
+  </figcaption>
+</figure>
+
+<p>In case the reamer has a straight shank, it is held as shown in
+<a href="#fig24">Fig.&nbsp;24</a>. Here a dog is fastened to the end of the reamer and prevented
+from turning by a tool clamped at an angle in the tool post.
+The end of the tool presses against the dog near the shank
+of the reamer so that as the reamer is fed into the work the carriage
+of the lathe is forced along with it. This causes the tool
+<span class="pagenum" id="Page_22">[22]</span>to hold the end of the reamer against the center of the tail-stock.</p>
+
+<p>When reaming work in a lathe, if the tail-stock is off center
+the hole will be reamed too large at the front end.</p>
+
+<p><b>Accurate Boring with Boring Bar.</b>—In turning out holes with
+a boring bar, if all the cuts are started from one end, that end will
+be bored larger than the other. In case the hole is to be reamed,
+the reamer will correct this, but if the hole is to be finished with
+the boring bar it will be necessary to bore the hole from both ends.
+This is done by reversing the feed of the carriage.</p>
+
+<p><b>Speed of Lathe.</b>—The speed of the lathe for reaming should be
+slower than when using the boring bar. If the belt is on the second
+smallest step of the cone with the back gears in, the lathe
+should have about the right speed for reaming. When using the
+boring bar, the belt should be on the largest step of the cone without
+the back gear.</p>
+
+<h4>INSIDE THREADING</h4>
+
+<p>The inside threads are cut in very much the same manner as
+the outside ones. The cutting tool is held in the boring bar and,
+like all boring tools, is ground with less clearance than tools used
+for outside work.</p>
+
+<p>To regulate the depth of each cut, the screw in the adjustable
+stop is placed between the stop and the cross-rest. Then by turning
+the screw in after a cut has been taken the cross-rest can be
+drawn back to permit a deeper cut with the tool.</p>
+
+<p><b>Cause of Threads Breaking.</b>—When cutting threads in cast
+iron, they will break if the roughing cuts are too heavy and are
+liable to if they are cut to a sharp point. Another cause for the
+breaking of cast iron threads is the use of a dull tool, or one with
+too little clearance.</p>
+
+<p><b>Finishing Threads.</b>—As a general rule cast iron is machined
+without using a lubricant, but in finishing threads a little lard oil
+will aid in producing a smooth finish.</p>
+
+<h4>FINISHING ENDS</h4>
+
+<p>The end of the work may be finished by taking a very light
+cut with the turning tool and then scraping it with a lathe scraper,
+<span class="pagenum" id="Page_23">[23]</span>as shown in <a href="#fig25_26">Fig.&nbsp;25</a>. To provide a rest for the scraper a tool
+is clamped in the tool post and as close as possible to the surface
+being scraped.</p>
+
+<figure class="figcenter illowp100" id="fig25_26" >
+  <img class="w100" src="images/fig25_26.jpg" alt="">
+  <figcaption>
+<table class="autotable wd100">
+<tr>
+<td class="tdc">Fig. 25</td>
+<td class="tdc">Fig. 26</td>
+</tr>
+</table>
+  </figcaption>
+</figure>
+
+<p>A scraper is usually made from an old file ground smooth on
+the two sides and with a little clearance at the end.</p>
+
+<h4>FINISHING TAPER</h4>
+
+<p>To finish the taper, set the compound rest at an angle of 30
+degrees with the axis of the lathe. Such a rest is normally at
+right angles with the lathe axis so that it must be turned through
+60 degrees to cut the 30 degree angle. A regular turning tool
+may be used to finish this angle, but it should be set so that the
+straight side will be nearly parallel with the tapered surface.</p>
+
+<p>If the lathe is not provided with a compound rest, the angle
+may be cut with the side of a tool set at the proper angle. To set
+this tool, use the thread and center gauge, as shown in <a href="#fig25_26">Fig.&nbsp;26</a>.</p>
+
+<p>In case the angle is any other than 30, or 60 degrees, it is
+necessary to set the tool with a bevel and bevel protractor.</p>
+
+<p>After the taper has been cut, it may be finished smooth by
+scraping with a lathe scraper in very much the same manner as
+shown in <a href="#fig25_26">Fig.&nbsp;25</a>. The tool that is used as a rest is set in as close
+as possible to the taper. If this rest is too far away from the surface
+being finished, the scraper will chatter leaving a rough surface.</p>
+
+<p><span class="pagenum" id="Page_24">[24]</span></p>
+<h3 id="PIECE_B" class="nosep">Piece B.</h3>
+
+
+<figure class="figcenter illowp100" id="fig27" >
+  <img class="w100" src="images/fig27.jpg" alt="">
+  <figcaption>
+
+<table class="autotable wd100">
+<tr>
+<td class="tdc">Rough Casting</td>
+<td class="tdc">Fig. 27</td>
+<td class="tdc">Finished Casting</td>
+</tr>
+</table>
+<p class="fs75">10 Thrds. per 1″ U. S. S.</p>
+  </figcaption>
+</figure>
+
+<h4>DRILLING AND REAMING.</h4>
+
+<p>This piece is first placed in the chuck, as shown in <a href="#fig28">Fig.&nbsp;28</a>,
+and the end rough turned to see if it is a good casting. The hole
+is then drilled with a ²³⁄₃₂ inch twist drill and reamed out to
+size with a ¾ inch rose reamer.</p>
+
+<figure class="figcenter illowp100" id="fig28" >
+  <img class="w100" src="images/fig28.jpg" alt="">
+  <figcaption>
+      <p>Fig. 28</p>
+  </figcaption>
+</figure>
+
+<p><b>Centering Twist Drill.</b>—This drill will not bore a hole in the
+center unless the point is controlled in some way. To do this, a
+cutting-off tool is clamped in the tool post with its point well
+above the center of the lathe and is then moved close to the point
+of the drill. As the drill starts to cut, it wabbles a little on account
+of the point being off center. The cutting-off tool is then
+gradually brought against the drill which is at the same time being
+slowly fed into the work by turning the hand-crank on the
+tail-stock. It is necessary to have the drill centered true before it
+begins to cut the full diameter.</p>
+
+<p>The drill should be placed in the tail-stock so that the cutting
+edges are vertical. If they are horizontal, it will be difficult to
+make the drill center.</p>
+
+<p>If the hole in this piece were larger, it would be cast with a
+core and then machined in the same manner as the 1⅛ inch hole
+in piece A, but since it is cast solid, the hole can be machined
+more advantageously by using a twist drill and a rose reamer.</p>
+
+<p><b>Reaming.</b>—After the hole has been drilled with the ²³⁄₃₂
+<span class="pagenum" id="Page_25">[25]</span>drill, bore it out with a small boring tool for about ⅛ of an inch
+from the end to the diameter that will just fit over the reamer
+and insure its starting true. Ream the hole with the reamer held
+in the same manner as the twist drill in <a href="#fig28">Fig.&nbsp;28</a>.</p>
+
+<p><b>Speed of Lathe.</b>—The lathe should run slower for reaming
+than for drilling. The speed will be about right for this size
+reamer if the belt is on the largest step of the cone without the
+back gears being used. The speed for the drill may be much
+faster. With a high-speed steel drill, the belt can be run on the
+second smallest step of the cone. If the drill is made of carbon
+steel, a slower speed should be used.</p>
+
+<p><b>Advantage of Rose Reamer.</b>—In drilling long holes like this,
+the drill is very apt to get off center a little as it is fed deeper into
+the work, even though it may have been started dead true.</p>
+
+<p>The reamer used in this case is called a rose reamer, or rose
+bit, and cuts on the end only. For this reason, if the hole is approximately
+true, say within ¹⁄₆₄ of an inch, it will ream the hole
+straight and true to size if it is once started true.</p>
+
+<h4>FINISHING CORNER</h4>
+
+<p>After the hole is bored and reamed, the work may be finished
+at the end by using a tool ground like a threading tool, but having
+an angle at the point a little less than 90 degrees, as in
+<a href="#fig29">Fig.&nbsp;29</a>.</p>
+
+<figure class="figcenter illowp60" id="fig29" >
+  <img class="w100" src="images/fig29.jpg" alt="">
+  <figcaption>
+      <p>Fig. 29</p>
+  </figcaption>
+</figure>
+
+<p>The boss, or hub, which is 1⅜ inches in diameter, is finished
+with one cutting edge of this tool set nearly parallel to the work,
+the point being a trifle deeper than the rest. This will insure the
+full depth of cut for the entire length and also a good sharp corner.
+The direction of feed for this tool should be from the end
+and towards the square corner or shoulder. If it is fed in the opposite
+direction the tool is apt to chatter.</p>
+
+<p>This tool is also used to finish the end, but it is turned a little
+<span class="pagenum" id="Page_26">[26]</span>in the tool post so that the other cutting edge is nearly parallel
+to the surface to be cut. After using this tool, the work may be
+finished smoother by scraping the ends, as in <a href="#fig25_26">Fig.&nbsp;25</a>, and by filing
+the boss, or hub.</p>
+
+<h4>USE OF MANDREL, OR ARBOR</h4>
+
+<p>Before this piece can be finished on the outside, it must be
+forced on a mandrel, or arbor, and placed in the lathe, as shown
+in <a href="#fig30">Fig.&nbsp;30</a>. Most commercial shops are provided with hardened
+steel mandrels for this purpose, but if one is not available it can
+be made from soft steel in the following manner:</p>
+
+<figure class="figcenter illowp100" id="fig30" >
+  <img class="w100" src="images/fig30.jpg" alt="">
+  <figcaption>
+      <p>Fig. 30</p>
+  </figcaption>
+</figure>
+
+<p><b>Making Mandrel.</b>—Cut off a piece of steel of suitable length,
+say 6 inches, and rough turn it to within ¹⁄₃₂ of an inch of the
+diameter of the hole. Then turn it at the end for a distance of
+about ⅛ of an inch to the size that will just fit the hole. The
+rest of the distance is now turned .002, or .003 of an inch larger
+and filed for about 3 inches until it will just fit the hole. The
+next 2 inches are filed with a slight taper so that when the mandrel
+is pressed into the hole it will fit tight enough to hold the
+casting while it is being turned. This kind of a fit is called a
+forced, or driving fit.</p>
+
+<p>When making such a mandrel, it is not necessary to turn that
+portion to which the dog is fastened.</p>
+
+<p><b>Mounting Work on Mandrel.</b>—Before pressing the mandrel in,
+it should be oiled to prevent it from being marred, or scored.
+Mandrels are usually forced in with a mandrel press, but if one
+is not available, they may be driven in with a hammer. When
+this method is used, a piece of lead, or some other soft material,
+must be held on the end of the mandrel to keep the hammer from
+marring the center.</p>
+
+<h4>FINISHING OUTSIDE OF PIECE B TO FIT A</h4>
+
+<p>This casting is rough turned to within ¹⁄₃₂ of an inch of the
+finished size before any part of it is finished. The 1⅛ inch end
+is then turned until it fits the corresponding part of the hole in
+<span class="pagenum" id="Page_27">[27]</span>piece A as closely as possible and yet not so tight that it cannot
+be freely rotated. This kind of a fit is called a close running fit.</p>
+
+<p><b>Cutting Threads.</b>—The portion to be threaded should be
+turned a little smaller than the diameter at the bottom of the
+threads in piece A. This size is measured by means of the inside
+spring-thread calipers.</p>
+
+<p>There is no recess, or groove, cut at the end of this thread so
+that if the threading tool is allowed to travel farther than the end
+of the preceding cut, either the point of the tool or the threads
+may break. To prevent this, the lathe is stopped when the tool is
+within a half a thread of the end and the cut finished by turning
+the lathe by hand. In this way the lathe is kept under control
+and the tool may be drawn back when it reaches the end of the
+preceding cut. Experienced lathe operators do not, as a rule,
+turn the lathe by hand, but control the lathe entirely by the
+shipper.</p>
+
+<p>The speed of the lathe for cutting this thread will be about
+right for beginners if the belt is on the second smallest step of the
+cone and the back gears are thrown in.</p>
+
+<p><b>Finishing the Angle, or Taper.</b>—The 30 degree angle may be
+cut by setting the compound rest to the correct angle and using a
+regular turning tool. In case the tool leaves a few tool marks,
+they may be removed by filing.</p>
+
+<p>If the lathe is not provided with a compound rest, this angle
+may be cut by setting a square-nose tool, as in <a href="#fig31">Fig.&nbsp;31</a>, with the
+aid of a thread gauge. Any other angle would have to be set
+with a bevel and bevel protractor.</p>
+
+<figure class="figcenter illowp60" id="fig31" >
+  <img class="w100" src="images/fig31.jpg" alt="">
+  <figcaption>
+      <p>Fig. 31</p>
+  </figcaption>
+</figure>
+
+<p>This tool is not as wide as the surface to be cut because one
+that will cut the full width is very liable to chatter. It is therefore
+better to make several cuts with a narrow tool. The surface
+can then be finished smooth by filing.</p>
+
+<p>The closeness of the fit of this taper with that in A can be
+<span class="pagenum" id="Page_28">[28]</span>tested by rubbing black paint, which consists of lamp black and
+oil, on the tapered surface in A. When B is screwed into A,
+marks will be made on B indicating the high spots. If these are
+not too high, they may be removed by filing.</p>
+
+<h4>FINISHING OUTSIDE OF PIECE A.</h4>
+
+<p>Piece A may now be screwed on B and the outside rough
+turned to within ¹⁄₃₂ of an inch of the finished size.</p>
+
+<p>The ends of the different steps are finished to the proper
+length with the tool shown in <a href="#fig29">Fig.&nbsp;29</a>. This same tool can then be
+used to turn the different diameters to within 0.002 or 0.003 of an
+inch of the required size. These steps are brought to the final
+size by filing.</p>
+
+<p><b>Filing.</b>—The file for this work should be less than 1 inch in
+width. If it is wider than the steps, a beginner will usually file
+the portion at the end of each step smaller in diameter than that
+which is close to the square corners.</p>
+
+<p>The different diameters may be measured accurately with the
+micrometer calipers.</p>
+
+<h4>KNURLING</h4>
+
+<p>After piece A is finished, it is removed from B and B is reversed
+in the lathe so that the boss may be knurled.</p>
+
+<p>In case there is enough room between the dog and the work,
+when held as in <a href="#fig30">Fig.&nbsp;30</a>, there is no need to reverse the work for
+knurling since it can be done in this position.</p>
+
+<p>The boss at the end of B is used as a handle so that if it were
+left smooth it would be hard to turn by hand. The surface is
+therefore made rough with a knurling tool as shown in <a href="#fig32">Fig.&nbsp;32</a>.</p>
+
+<figure class="figcenter illowp100" id="fig32" >
+  <img class="w100" src="images/fig32.jpg" alt="">
+  <figcaption>
+      <p>Fig. 32</p>
+  </figcaption>
+</figure>
+
+<p>The speed of the lathe should be about the same for knurling
+as for thread cutting. If the lathe runs too fast, the knurling tool
+does not cut satisfactorily.</p>
+
+<p>The tool is set so that the face of the rollers is parallel with
+<span class="pagenum" id="Page_29">[29]</span>the surface to be knurled. When starting the cut, the rollers can
+be forced into the piece easier if about half of their width extends
+past the end of the work.</p>
+
+<p>The knurling tool should be pressed into the work fast enough
+so that about one half the depth of the finished knurl will be cut
+while the lathe makes three or four revolutions. If the tool is
+forced in too slow, it will cut a finer knurled surface than the
+rollers are intended to cut.</p>
+
+<p>The tool is fed along the surface in the same manner as in
+plain turning. The speed at which the carriage of the lathe moves
+has no effect upon the pitch of the knurled surface since this is
+controlled by the pitch of the grooves in the rollers. If a finer
+knurled surface is desired, a knurling tool having rollers with
+finer grooves would have to be used.</p>
+
+<hr class="chap x-ebookmaker-drop">
+
+<div class="chapter">
+<div class="transnote">
+<strong>TRANSCRIBER’S NOTE</strong>
+
+<p class="noindent">Illustrations in this eBook have been positioned between paragraphs
+and outside quotations. </p>
+
+<p class="noindent">Obvious typographical errors and punctuation errors have been
+corrected after careful comparison with other occurrences within
+the text and consultation of external sources.</p>
+
+<p class="noindent">Some hyphens in words have been silently removed, some added,
+when a predominant preference was found in the original book.</p>
+
+<p class="noindent">Except for those changes noted below, all misspellings in the text,
+and inconsistent or archaic usage, have been retained.</p>
+
+<table class="autotable">
+<tr>
+<td class="tdl">Pg <a href="#straght">9</a>:</td>
+<td class="tdl">‘straght’ replaced with ‘straight’</td>
+</tr>
+<tr>
+<td class="tdl">Pg <a href="#shoull">11</a>:</td>
+<td class="tdl">‘shoull’ replaced with ‘should’</td>
+</tr>
+<tr>
+<td class="tdl">Pg <a href="#diffrent">19</a>:</td>
+<td class="tdl">‘diffrent’ replaced with ‘different.’</td>
+</tr>
+</table>
+</div>
+</div>
+<div style='text-align:center'>*** END OF THE PROJECT GUTENBERG EBOOK 76925 ***</div>
+</body>
+</html>
+
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author	pgww <pgww@lists.pglaf.org>	2025-09-24 17:22:01 -0700
committer	pgww <pgww@lists.pglaf.org>	2025-09-24 17:22:01 -0700
commit	38d2168e6bfcf5293d8af01d80c4078a69efdab9 (patch)
tree	9ae89d983e33e91027a0dc3d8b275b68c18160d4 /76925-h