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| author | Roger Frank <rfrank@pglaf.org> | 2025-10-14 20:00:44 -0700 |
|---|---|---|
| committer | Roger Frank <rfrank@pglaf.org> | 2025-10-14 20:00:44 -0700 |
| commit | f4f058c0bb8a43509b2dcba48064a80d011477ed (patch) | |
| tree | 7d68ae6cf798fcef376e9e3338f64fd10b60a23e /34030-h | |
Diffstat (limited to '34030-h')
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diff --git a/34030-h/34030-h.htm b/34030-h/34030-h.htm new file mode 100644 index 0000000..0d1d564 --- /dev/null +++ b/34030-h/34030-h.htm @@ -0,0 +1,13818 @@ +<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" + "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> + +<html xmlns="http://www.w3.org/1999/xhtml"> + <head> + <meta http-equiv="Content-Type" content="text/html;charset=iso-8859-1" /> + <title> + The Project Gutenberg eBook of Turning and Boring, by Franklin D. 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Jones + +This eBook is for the use of anyone anywhere at no cost and with +almost no restrictions whatsoever. You may copy it, give it away or +re-use it under the terms of the Project Gutenberg License included +with this eBook or online at www.gutenberg.org + + +Title: Turning and Boring + A specialized treatise for machinists, students in the + industrial and engineering schools, and apprentices, on + turning and boring methods, etc. + +Author: Franklin D. Jones + +Release Date: October 4, 2010 [EBook #34030] + +Language: English + +Character set encoding: ISO-8859-1 + +*** START OF THIS PROJECT GUTENBERG EBOOK TURNING AND BORING *** + + + + +Produced by Juliet Sutherland, Harry Lamé and the Online +Distributed Proofreading Team at https://www.pgdp.net + + + + + + +</pre> + + +<p class="center fsize275 gesp"><b>TURNING AND<br />BORING</b></p> + +<div class="ind40"> +<p class="center">A SPECIALIZED TREATISE FOR MACHINISTS, +STUDENTS IN INDUSTRIAL AND ENGINEERING +SCHOOLS, AND APPRENTICES, ON +TURNING AND BORING METHODS, INCLUDING +MODERN PRACTICE WITH ENGINE +LATHES, TURRET LATHES, VERTICAL AND +HORIZONTAL BORING MACHINES</p> +</div> + +<p> </p> + +<p class="center smcap"><b>By<span class="gesp"> FRANKLIN D. JONES</span></b></p> + +<p class="smcap center fsize80">Associate Editor of MACHINERY<br /> +Author of “Planing and Milling”</p> +<p> </p> + +<hr class="c10" /> + +<p class="center fsize80"><i><span class="gesp">FIRST EDITION</span></i><br /> +FIFTH PRINTING</p> + +<hr class="c10" /> + +<p> </p> + +<p class="center"><span class="fsize80">NEW YORK</span><br /> +<span class="gesp">THE INDUSTRIAL PRESS</span><br /> +<span class="smcap fsize80">London: THE MACHINERY PUBLISHING CO., Ltd.<br /> +1919</span></p> + +<hr class="c25" /> + +<p class="center"><span class="smcap fsize80">Copyright, 1914</span><br /> +<span class="fsize80">BY</span><br /> +<span class="gesp">THE INDUSTRIAL PRESS</span><br /> +NEW YORK</p> + +<hr class="c25" /> +<span class="pagenum"><a name="Pg_v" id="Pg_v">[v]</a></span> +<h2>PREFACE</h2> +<hr class="c05" /> + +<p>Specialization in machine-tool manufacture has been developed +to such a degree that there is need also for treatises which +specialize on different classes of tools and their application in +modern practice. This book deals exclusively with the use of +various types of turning and boring machines and their attachments, +and is believed to be unusually complete. In addition +to standard practice, it describes many special operations +seldom or never presented in text-books. Very little space is +given to mere descriptions of different types of machine tools, the +principal purpose being to explain the use of the machine and the +practical problems connected with its operation, rather than +the constructional details. No attempt has been made to +describe every machine or tool which might properly be included, +but rather to deal with the more important and useful +operations, especially those which illustrate general principles.</p> + +<p>Readers of mechanical literature are familiar with <span class="smcap">Machinery's</span> +25-cent Reference Books, of which one hundred and +twenty-five different titles have been published during the past +six years. Many subjects, however, cannot be adequately +covered in all their phases in books of this size, and in response +to a demand for more comprehensive and detailed treatments +on the more important mechanical subjects, it has been deemed +advisable to bring out a number of larger volumes, of which this +is one. This work includes much of the material published in +<span class="smcap">Machinery's</span> Reference Books Nos. 91, 92 and 95, together +with a great amount of additional information on modern boring +and turning methods.</p> + +<p>It is a pleasure to acknowledge our indebtedness to the manufacturers +who generously supplied illustrations and data, including +many interesting operations from actual practice. +Much valuable information was also obtained from <span class="smcap">Machinery</span>.</p> + +<p class="textright">F. D. J.</p> + +<p><span class="smcap">New York</span>, <i>May, 1914</i>.</p> +<p> </p> + +<hr class="c25" /> +<p class="pagenum"><a name="Pg_vii" id="Pg_vii">[vii]</a></p> +<h2>CONTENTS</h2> +<hr class="c05" /> + +<table border="0" cellpadding="1" cellspacing="1" summary="ToC" class="tab70"> + +<tr><td> </td><td align="right"><span class="smcap">Pages</span></td></tr> + +<tr><td align="center" colspan="2" style="padding-bottom: 0.7em;"><span class="smcap"><a href="#Chapnum_1">Chapter I</a></span></td></tr> +<tr><td align="center" colspan="2" style="padding-bottom: 0.7em;"><a href="#Chapnum_1">THE ENGINE LATHE—TURNING AND BORING OPERATIONS</a></td></tr> +<tr><td class="toc"> +<a href="#Secnum_1_1">General Description of an Engine Lathe</a>—<a href="#Secnum_1_2">Example of Cylindrical +Turning</a>—<a href="#Secnum_1_3">Facing the Ends Square with a Side-tool</a>—<a href="#Secnum_1_4">Turning +Tool—Turning Work Cylindrical</a>—<a href="#Secnum_1_5">Roughing and Finishing Cuts</a>—<a href="#Secnum_1_6">Filing +and Finishing</a>—<a href="#Secnum_1_7">Aligning Centers for Cylindrical Turning</a>—<a href="#Secnum_1_8">Application +of Drivers or Dogs</a>—<a href="#Secnum_1_9">Lathe Arbors or Mandrels</a>—<a href="#Secnum_1_10">Different Types of +Lathe Arbors</a>—<a href="#Secnum_1_11">Mandrel or Arbor Press</a>—<a href="#Secnum_1_12">Steadyrest for Supporting +Flexible Parts</a>—<a href="#Secnum_1_13">Application of Steadyrest when Boring</a>—<a href="#Secnum_1_14">The +Follow-rest</a>—<a href="#Secnum_1_15">Centering Parts to be Turned</a>—<a href="#Secnum_1_16">Centering +Machine</a>—<a href="#Secnum_1_17">Different Forms of Centers</a>—<a href="#Secnum_1_18">Precaution When Centering Tool +Steel</a>—<a href="#Secnum_1_19">Facing the Ends of Centered Stock</a>—<a href="#Secnum_1_20">Truing Lathe +Centers</a>—<a href="#Secnum_1_21">Universal, Independent and Combination Chucks</a>—<a href="#Secnum_1_22">Application +of Chucks</a>—<a href="#Secnum_1_23">Example of Boring</a>—<a href="#Secnum_1_24">Measuring Bored +Holes</a>—<a href="#Secnum_1_25">Setting Work in the Chuck</a>—<a href="#Secnum_1_26">Inaccuracy from Pressure of Chuck +Jaws</a>—<a href="#Secnum_1_27">Drilling and Reaming</a>—<a href="#Secnum_1_28">Holding Work on +Faceplate</a>—<a href="#Secnum_1_29">Application of Angle-plate to Faceplate</a>—<a href="#Secnum_1_30">Supporting Outer +End of Chucked Work</a>—<a href="#Secnum_1_31">Boring Large Castings in the Lathe</a>—<a href="#Secnum_1_32">Boring Holes +to a Given Center Distance</a>—<a href="#Secnum_1_33">Turning Brass, Bronze and Copper</a>—<a href="#Secnum_1_34">Machining +Aluminum</a></td><td style="width: 10%" align="right" valign="bottom"> <a href="#Pg_1">1-53</a> </td></tr> +<tr><td colspan="2"> </td></tr> + +<tr><td align="center" colspan="2" style="padding-bottom: 0.7em;"><span class="smcap"><a href="#Chapnum_2">Chapter II</a></span></td></tr> +<tr><td align="center" colspan="2" style="padding-bottom: 0.7em;"><a href="#Chapnum_2">LATHE TURNING TOOLS AND CUTTING SPEEDS</a></td></tr> +<tr><td class="toc"> +<a href="#Secnum_2_1">Turning Tools for General Work</a>—<a href="#Secnum_2_2">Tool-holders with Inserted +Cutters</a>—<a href="#Secnum_2_3">The Position of Turning Tools</a>—<a href="#Secnum_2_4">Tool +Grinding</a>—<a href="#Secnum_2_5">Shape or Contour of Cutting Edge</a>—<a href="#Secnum_2_6">Direction of Top Slope for +Turning Tools</a>—<a href="#Secnum_2_7">Clearance for the Cutting Edge</a>—<a href="#Secnum_2_8">Angle of Tool-point and +Amount of Top Slope</a>—<a href="#Secnum_2_9">Grinding a Lathe Tool</a>—<a href="#Secnum_2_10">Cutting Speeds and +Feeds</a>—<a href="#Secnum_2_11">Average Cutting Speeds for Turning</a>—<a href="#Secnum_2_12">Factors which Limit the +Cutting Speed</a>—<a href="#Secnum_2_13">Rules for Calculating Cutting Speeds</a>—<a href="#Secnum_2_14">Feed of Tool and +Depth of Cut</a>—<a href="#Secnum_2_15">Effect of Lubricant on Cutting Speed</a>—<a href="#Secnum_2_16">Lubricants Used for +Turning</a>—<a href="#Secnum_2_17">Lard Oil as a Cutting Lubricant</a> +</td><td align="right" valign="bottom"> <a href="#Pg_54">54-79</a> +</td></tr><tr><td colspan="2"> </td></tr> + +<tr><td align="center" colspan="2" style="padding-bottom: 0.7em;"><span class="smcap"><a href="#Chapnum_3">Chapter III</a></span></td></tr> +<tr><td align="center" colspan="2" style="padding-bottom: 0.7em;"><a href="#Chapnum_3">TAPER TURNING—SPECIAL OPERATIONS—FITTING</a></td></tr> +<tr><td class="toc"> +<a href="#Secnum_3_1">Setting Tailstock Center for Taper Turning</a>—<a href="#Secnum_3_2">Example of Taper +Turning</a>—<a href="#Secnum_3_3">Setting the Tailstock Center with a Caliper Tool</a>—<a href="#Secnum_3_4">Setting the +Tailstock Center with a Square</a>—<a href="#Secnum_3_5">The Taper Attachment</a>—<a href="#Secnum_3_6">Application of +Taper Attachment</a>—<a href="#Secnum_3_7">Height of Tool when Turning Tapers</a>—<a href="#Secnum_3_8">Taper Turning with +the Compound Rest</a>—<a href="#Secnum_3_9">Accurate Measurement of Angles and Tapers</a>—<a href="#Secnum_3_10">To Find +Center Distance for a Given Taper</a>—<a href="#Secnum_3_11">To Find Center Distance for a Given +Angle</a>—<a href="#Secnum_3_12">To Find Angle for Given Taper per Foot</a>—<a href="#Secnum_3_13">To Find Angle for Given +Disk Dimensions</a>—<a href="#Secnum_3_14">Use of the Center Indicator</a>—<a href="#Secnum_3_15">Locating Work by the Button +Method</a>—<a href="#Secnum_3_16">Eccentric Turning</a>—<a href="#Secnum_3_17">Turning a Crankshaft in a +Lathe</a>—<a href="#Secnum_3_18">Special Crankshaft Lathe</a>—<a href="#Secnum_3_19">Operation of Special Crankshaft +Lathe</a>—<a href="#Secnum_3_20">Spherical Turning</a>—<a href="#Secnum_3_21">Spherical Turning Attachments</a>—<a +href="#Secnum_3_22">Turning with Front and Rear Tools</a>—<a href="#Secnum_3_23">A Multiple-tool Lathe</a>—<a +href="#Secnum_3_24">Examples of Multiple Turning</a>—<a href="#Secnum_3_25">Knurling in the Lathe</a>—<a +href="#Secnum_3_26">Relieving Attachment</a>—<a href="#Secnum_3_27">Application of Relieving Attachment</a>—<a +href="#Secnum_3_28">Relieving Hobs or Taps Having Spiral Flutes</a>—<a href="#Secnum_3_29">Classes of Fits Used in Machine +Construction</a>—<a href="#Secnum_3_30">Forced Fits</a>—<a href="#Secnum_3_31">Allowance for Forced Fits</a>—<a +href="#Secnum_3_32">Pressure for Forced Fits</a>—<a href="#Secnum_3_33">Allowance for Given Pressure</a>—<a +href="#Secnum_3_34">Shrinkage Fits</a> +</td><td align="right" valign="bottom"> <a href="#Pg_80">80-134</a> </td></tr> +<tr><td colspan="2"> </td></tr> + +<tr><td colspan="2"></td></tr><tr><td align="center" colspan="2" style="padding-bottom: 0.7em;"><span class="smcap"><a href="#Chapnum_4">Chapter IV</a></span> +<span class="pagenum"><a name="Pg_viii" id="Pg_viii">[viii]</a></span></td></tr> +<tr><td align="center" colspan="2" style="padding-bottom: 0.7em;"><a href="#Chapnum_4">THREAD CUTTING IN THE LATHE</a></td></tr> +<tr><td class="toc"> +<a href="#Secnum_4_1">Selecting the Change Gears for Thread Cutting</a>—<a href="#Secnum_4_2">The Thread Tool</a>—<a +href="#Secnum_4_3">Cutting the Thread</a>—<a href="#Secnum_4_4">Indicator or Chasing Dial for Catching Threads</a>—<a +href="#Secnum_4_5">Principle of the Thread Indicator</a>—<a href="#Secnum_4_6">Replacing Sharpened Thread Tool</a>—<a +href="#Secnum_4_7">Use of Compound Rest for Thread Cutting</a>—<a href="#Secnum_4_8">Threads Commonly Used</a>—<a +href="#Secnum_4_9">Multiple Threads</a>—<a href="#Secnum_4_10">Cutting a U. S. Standard Thread</a>—<a +href="#Secnum_4_11">Cutting a Left-hand Thread</a>—<a href="#Secnum_4_12">Cutting a Square Thread</a>—<a +href="#Secnum_4_13">Cutting Multiple Threads</a>—<a href="#Secnum_4_14">Setting Tool When Cutting Multiple Threads</a>—<a +href="#Secnum_4_15">Taper Threading</a>—<a href="#Secnum_4_16">Internal Threading</a>—<a href="#Secnum_4_17">Stop for Thread +Tools</a>—<a href="#Secnum_4_18">The Acme Standard Thread</a>—<a href="#Secnum_4_19">The Whitworth Thread</a>—<a +href="#Secnum_4_20">Worm Threads</a>—<a href="#Secnum_4_21">Coarse Threading Attachment</a>—<a href="#Secnum_4_22">Testing +the Size of a Thread</a>—<a href="#Secnum_4_23">The Thread Micrometer</a>—<a href="#Secnum_4_24">Three-wire System of +Measuring Threads</a>—<a href="#Secnum_4_25">Rivett-Dock Threading Tool</a>—<a href="#Secnum_4_26">Cutting Screws to +Compensate for Shrinkage</a>—<a href="#Secnum_4_27">Calculating Change Gears for Thread Cutting</a>—<a +href="#Secnum_4_28">Lathes with Compound Gearing</a>—<a href="#Secnum_4_29">Fractional Threads</a>—<a +href="#Secnum_4_30">Change Gears for Metric Pitches</a>—<a href="#Secnum_4_31">Quick Change-gear Type of Lathe</a> +</td><td align="right" valign="bottom"> <a href="#Pg_135">135-177</a> </td></tr> +<tr><td colspan="2"> </td></tr> + +<tr><td align="center" colspan="2" style="padding-bottom: 0.7em;"><span class="smcap"><a href="#Chapnum_5">Chapter V</a></span></td></tr> +<tr><td align="center" colspan="2" style="padding-bottom: 0.7em;"><a href="#Chapnum_5">TURRET LATHE PRACTICE</a></td></tr> +<tr><td class="toc"> +<a href="#Secnum_5_1">General Description of a Turret Lathe</a>—<a href="#Secnum_5_2">Example of Turret Lathe Work</a>—<a +href="#Secnum_5_3">Machining Flywheels in Turret Lathe</a>—<a href="#Secnum_5_4">Finishing a Flywheel at One Setting in Turret +Lathe</a>—<a href="#Secnum_5_5">Finishing a Webbed Flywheel in Two Settings</a>—<a href="#Secnum_5_6">Tools for Turret +Lathes</a>—<a href="#Secnum_5_7">Box-tools</a>—<a href="#Secnum_5_8">Examples of Box-tool Turning</a>—<a +href="#Secnum_5_9">Hollow Mills</a>—<a href="#Secnum_5_10">Releasing Die and Tap Holders</a>—<a +href="#Secnum_5_11">Self-opening Die Heads</a>—<a href="#Secnum_5_12">Collapsing Taps</a>—<a href="#Secnum_5_13">Miscellaneous +Turret Lathe Tools</a>—<a href="#Secnum_5_14">Turning Gasoline Engine Pistons in Turret Lathe</a>—<a +href="#Secnum_5_15">Turning Piston Rings in Turret Lathe</a>—<a href="#Secnum_5_16">Piston Turning in Pratt and Whitney Turret +Lathe</a>—<a href="#Secnum_5_17">Attachment for Turning Piston Rings</a>—<a href="#Secnum_5_18">Turning Worm-gear Blanks in +Turret Lathe</a>—<a href="#Secnum_5_19">Turning Bevel Gear Blanks</a>—<a href="#Secnum_5_20">Shell Turning Operation in Flat +Turret Lathe</a>—<a href="#Secnum_5_21">Chuck Work in Flat Turret Lathe</a>—<a href="#Secnum_5_22">Double-spindle Flat Turret +Lathe</a>—<a href="#Secnum_5_23">Automatic Chucking and Turning Machine</a>—<a href="#Secnum_5_24">Example of Work on +Automatic Turning Machine</a>—<a href="#Secnum_5_25">Determining Speed and Feed Changes</a>—<a href="#Secnum_5_26">Setting the +Turret Slide</a>—<a href="#Secnum_5_27">Setting the Cross-slide Cam</a>—<a href="#Secnum_5_28">Setting the Boring Tool for +Recessing</a>—<a href="#Secnum_5_29">Adjustments for Automatic Feed and Speed Changes</a>—<a href="#Secnum_5_30">Turning +Flywheel in Automatic Chucking and Turning Machine</a>—<a href="#Secnum_5_31">Automatic Multiple-spindle Chucking +Machine</a>—<a href="#Secnum_5_32">Selecting Type of Turning Machine</a></td> +<td align="right" valign="bottom"> <a href="#Pg_178">178-241</a> </td></tr> +<tr><td colspan="2"> </td></tr> + +<tr><td align="center" colspan="2" style="padding-bottom: 0.7em;"><span class="smcap"><a href="#Chapnum_6">Chapter VI</a></span> +<span class="pagenum"><a name="Pg_ix" id="Pg_ix">[ix]</a></span></td></tr> +<tr><td align="center" colspan="2" style="padding-bottom: 0.7em;"><a href="#Chapnum_6">VERTICAL BORING MILL PRACTICE</a></td></tr> +<tr><td class="toc"> +<a href="#Secnum_6_1">Boring and Turning in a Vertical Boring Mill</a>—<a href="#Secnum_6_2">Holding and Setting Work on Boring Mill +Table</a>—<a href="#Secnum_6_3">Turning in a Boring Mill</a>—<a href="#Secnum_6_4">Boring Operations</a>—<a +href="#Secnum_6_5">Turning Tools for the Vertical Boring Mill</a>—<a href="#Secnum_6_6">Turning a Flywheel on a Vertical +Mill</a>—<a href="#Secnum_6_7">Convex Turning Attachment for Boring Mills</a>—<a href="#Secnum_6_8">Turning Taper or Conical +Surfaces</a>—<a href="#Secnum_6_9">Turret-lathe Type of Vertical Boring Mill</a>—<a href="#Secnum_6_10">Examples of Vertical +Turret Lathe Work</a>—<a href="#Secnum_6_11">Floating Reamer Holders</a>—<a href="#Secnum_6_12">Multiple Cylinder Boring +Machine</a> +</td><td align="right" valign="bottom"> <a href="#Pg_242">242-274</a> +</td></tr> +<tr><td colspan="2"> </td></tr> + +<tr><td align="center" colspan="2" style="padding-bottom: 0.7em;"><span class="smcap"><a href="#Chapnum_7">Chapter VII</a></span></td></tr> +<tr><td align="center" colspan="2" style="padding-bottom: 0.7em;"><a href="#Chapnum_7">HORIZONTAL BORING MACHINES</a></td></tr> +<tr><td class="toc"> +<a href="#Secnum_7_1">Horizontal Boring Machine with Vertical Table Adjustment</a>—<a href="#Secnum_7_2">Drilling and +Boring—Cutters Used</a>—<a href="#Secnum_7_3">Cutter-heads for Boring Large Holes</a>—<a href="#Secnum_7_4">Cylinder +Boring</a>—<a href="#Secnum_7_5">Boring a Duplex Gasoline Engine Cylinder</a>—<a href="#Secnum_7_6">Examples of Boring, Radial +Facing and Milling</a>—<a href="#Secnum_7_7">Fixture for Cylinder Lining or Bushing</a>—<a href="#Secnum_7_8">Horizontal +Boring Machine of Floor Type</a> +</td><td align="right" valign="bottom"> <a href="#Pg_275">275-297</a> </td></tr> +<tr><td colspan="2"> </td></tr> + +<tr><td align="justify"><a href="#Pg_299">Index</a></td><td align="right" valign="bottom"><a href="#Pg_299">299</a> </td></tr> +</table> +<p> </p> + +<hr class="c25" /> +<p class="pagenum"><a name="Pg_1" id="Pg_1">[1]</a></p> +<h1>TURNING AND BORING</h1> +<hr class="c25" /> + +<a name="Chapnum_1" id="Chapnum_1"></a><h2>CHAPTER I</h2> +<h3>THE ENGINE LATHE—TURNING AND BORING OPERATIONS</h3> +<hr class="c05" /> + +<a name="Secnum_1_1" id="Secnum_1_1"></a><p>The standard “engine” lathe, which is the type commonly +used by machinists for doing general work, is one of the most +important tools in a machine shop, because it is adapted to a +great variety of operations, such as turning all sorts of cylindrical +and taper parts, boring holes, cutting threads, etc. The +illustration <a href="#Fig_1_1">Fig. 1</a> shows a lathe which, in many respects, represents +a typical design, and while some of the parts are arranged +differently on other makes, the general construction is practically +the same as on the machine illustrated.</p> + +<a name="Fig_1_1" id="Fig_1_1"></a> +<div class="figcenter"><img src="images/010sm.jpg" alt="Bradford Belt-driven Lathe—View of Front or Operating Side" /> +<p class="caption750">Fig. 1. Bradford Belt-driven Lathe—View of Front or Operating Side</p></div> + +<p>The principal parts are the bed <i>B</i>, the headstock <i>H</i>, the tailstock +<i>T</i>, and the carriage <i>C</i>. The headstock contains a spindle +which is rotated by a belt that passes over the cone-pulley <i>P</i>, +and this spindle rotates the work, which is usually held between +pointed or conical centers <i>h</i> and <i>h<sub>1</sub></i> in the headstock and +tailstock, or in a chuck screwed onto the spindle instead of the +faceplate <i>F</i>. The carriage <i>C</i> can be moved lengthwise along +the bed by turning handle <i>d</i>, and it can also be moved by power, +the movement being transmitted from the headstock spindle +either through gears <i>a</i>, <i>b</i>, <i>c</i>, and lead-screw <i>S</i>, or by a belt operating +on pulleys <i>p</i> and <i>p<sub>1</sub></i>, which drive the feed-rod <i>R</i>. The +lead-screw <i>S</i> is used when cutting threads, and the feed-rod <i>R</i> +for ordinary turning operations; in this way the wear on the +lead-screw is reduced and its accuracy is preserved.</p> + +<span class="pagenum"><a name="Pg_2" id="Pg_2">[2]</a></span> + +<p>On the carriage, there is a cross-slide <i>D</i> which can be moved +at right angles to the lathe bed by handle <i>e</i>, and on <i>D</i> there is +an upper or compound slide <i>E</i> which can be swiveled to different +positions. The tool <i>t</i>, that does the turning, is clamped to the +<span class="pagenum"><a name="Pg_3" id="Pg_3">[3]</a></span> +upper slide, as shown, and it can be moved with relation to the +work by the movement of the carriage <i>C</i> along the bed, or by +moving slide <i>D</i> crosswise. The lengthwise movement is used to +feed the tool along the work when turning, boring or cutting a +screw, and the crosswise movement for facing the ends of shafts, +etc., or for radial turning. When the tool is to be fed at an +angle, other than at right angles to the bed, slide <i>E</i>, which can +be set to the required angle, is used. The lengthwise and crosswise +feeding movements can be effected by power, the lengthwise +feed being engaged by tightening knob <i>k</i>, and the cross-feed by +tightening knob <i>l</i>. The direction of either of these movements +can also be reversed by shifting lever <i>r</i>. Ordinarily the carriage +and slide are adjusted by hand to bring the tool into the +proper position for turning to the required diameter, and then +the power feed (operating in the desired direction) is engaged. +The tailstock <i>T</i> can be clamped in different positions along the +bed, to suit the length of the work, and its center <i>h<sub>1</sub></i> can be +moved in or out for a short distance, when adjusting it to the +work, by turning handle <i>n</i>.</p> + +<a name="Fig_1_2" id="Fig_1_2"></a> +<div class="figcenter"><div class="illobox450"><img src="images/011sm.png" alt="Plan View of Lathe Headstock showing Back-gears" /></div> +<p class="caption750">Fig. 2. Plan View of Lathe Headstock showing Back-gears</p> +</div> + +<p>As some metals are much harder than others, and as the<span class="pagenum"><a name="Pg_4" id="Pg_4">[4]</a></span> +diameters of parts to be turned also vary considerably, speed +changes are necessary, because if the speed is excessive, the +turning tool will become dull in too short a time. These speed +changes (with a belt-driven lathe) are obtained by placing the +driving belt on different steps of cone-pulley <i>P</i>, and also by the +use of back-gears. The cone-pulley can be connected directly +with the spindle or be disengaged from it by means of bolt <i>m</i>. +When the pulley and spindle are connected, five speeds (with +this particular lathe) are obtained by simply shifting the driving +belt to different steps of the cone. When a slower speed is +required than can be obtained with the belt on the largest step +of the cone, the latter is disconnected from the spindle, and the +back-gears <i>G</i> and <i>G<sub>1</sub></i> (shown in the plan view <a href="#Fig_1_2">Fig. 2</a>) are moved +forward into mesh by turning handle <i>O</i>; the drive is then from +cone-pulley <i>P</i> and gear <i>L</i> to gear <i>G</i>, and from gear <i>G<sub>1</sub></i> to the +large gear <i>J</i> on the spindle. When driving through the back-gears, +five more speed changes are obtained by shifting the +position of the driving belt, as before. The fastest speed with +the back-gears in mesh is somewhat slower than the slowest +speed when driving direct or with the back-gears out of mesh; +hence, with this particular lathe, a series of ten gradually increasing +speeds is obtained. Changes of feed for the turning<span class="pagenum"><a name="Pg_5" id="Pg_5">[5]</a></span> +tool are also required, and these are obtained by shifting the +belt operating on pulleys <i>p</i> and <i>p<sub>1</sub></i> to different-sized steps. On +some lathes these feed changes are obtained through gears +which can be shifted to give different ratios. Many lathes also +have gears in the headstock for changing the speeds.</p> + +<a name="Fig_1_3" id="Fig_1_3"></a> +<div class="figcenter"><div class="illobox450"><img src="images/012sm.png" alt="Feed Mechanism of Lathe Apron" /></div> +<p class="caption750">Fig. 3. Feed Mechanism of Lathe Apron</p> +</div> + +<p>Front and rear views of the carriage apron, which contains +the feeding mechanism, are shown in <a href="#Fig_1_3">Figs. 3</a> and <a href="#Fig_1_4">4</a>, to indicate +how the feeds are engaged and reversed. The feed-rod <i>R</i> +(<a href="#Fig_1_1">Fig. 1</a>) drives the small bevel gears <i>A</i> and <i>A<sub>1</sub></i> (<a href="#Fig_1_3">Figs. 3</a> +and <a href="#Fig_1_4">4</a>), which are mounted on a slide <i>S</i> that can be moved by lever <i>r</i> +to bring either bevel gear into mesh with gear <i>B</i>. Gear <i>B</i> is +attached to pinion <i>b</i> (see <a href="#Fig_1_3">Fig. 3</a>) meshing with gear <i>C</i>, which, +when knob <i>k</i> (<a href="#Fig_1_1">Fig. 1</a>) is tightened, is locked by a friction clutch +to pinion <i>c</i>. The latter pinion drives gear <i>D</i> which rotates +shaft <i>E</i>. A pinion cut on the end of shaft <i>E</i> engages rack <i>K</i> +(<a href="#Fig_1_1">Fig. 1</a>) attached to the bed, so that the rotation of <i>E</i> (which is +controlled by knob <i>k</i>) moves the carriage along the bed. To +reverse the direction of the movement, it is only necessary to +throw gear <i>A</i> into mesh and gear <i>A<sub>1</sub></i> out, or <i>vice versa</i>, by operating +lever <i>r</i>. When the carriage is traversed by hand, shaft +<i>E</i> and gear <i>D</i> are rotated by pinion <i>d<sub>1</sub></i> connected with handle <i>d</i> +(<a href="#Fig_1_1">Fig. 1</a>).</p> + +<a name="Fig_1_4" id="Fig_1_4"></a> +<div class="figcenter"><img src="images/013sm.jpg" alt="Rear View of Lathe Apron" /> +<p class="caption750">Fig. 4. Rear View of Lathe Apron</p> +</div> + +<p>The drive for the cross-feed is from gear <i>C</i> to gear <i>F</i> which +<span class="pagenum"><a name="Pg_6" id="Pg_6">[6]</a></span> +can be engaged through a friction clutch (operated by knob <i>l</i>, +<a href="#Fig_1_1">Fig. 1</a>) with gear <i>G</i> meshing with a pinion <i>H</i>. The latter rotates +the cross-feed screw, which passes through a nut attached to +slide <i>D</i> (<a href="#Fig_1_1">Fig. 1</a>), thus moving the latter at right angles to the +ways of the bed. The cross-feed is also reversed by means of +lever <i>r</i>. As previously explained, lead-screw <i>S</i> is only used for +feeding the carriage when cutting threads. The carriage is engaged +with this screw by means of two half-nuts <i>N</i> (<a href="#Fig_1_4">Fig. 4</a>) +that are free to slide vertically and are closed around the screw +by operating lever <i>u</i>. These half-nuts can only be closed when +lever <i>r</i> is in a central or neutral position, so that the screw feed +and the regular turning feed cannot be engaged at the same +time. As previously mentioned, lead-screw <i>S</i>, <a href="#Fig_1_1">Fig. 1</a>, is rotated +from the lathe spindle, through gears <i>a</i>, <i>b</i> and <i>c</i>, called change +gears. An assortment of these gears, of various sizes, is provided +with the lathe, for cutting screws of different pitch. The +gears to use for any pitch within the range of the lathe are +given on the plate <i>I</i>.</p> + +<a name="Fig_1_5" id="Fig_1_5"></a> +<div class="figcenter"><div class="illobox450"><img src="images/015sm.png" alt="Mounted Work" /></div> +<p class="caption750">Fig. 5. Plan View showing Work Mounted between Centers of Lathe</p> +</div> + +<a name="Secnum_1_2" id="Secnum_1_2"></a><p><b>Example of Cylindrical Turning.</b>—Having now considered +the principal features of what might be called a standard lathe, +the method of using it in the production of machine parts will +be explained. To begin with a simple example of work, suppose +a steel shaft is to be turned to a diameter of 2<sup class="enum">1</sup>/<sub class="denom">4</sub> inches and a +length of 14<sup class="enum">1</sup>/<sub class="denom">2</sub> inches, these being the finished dimensions. We +will assume that the rough stock is cut off to a length of 14<sup class="enum">5</sup>/<sub class="denom">8</sub> +inches and has a diameter of 2<sup class="enum">5</sup>/<sub class="denom">8</sub> inches. The first step in this +operation is to form conically shaped center-holes in each end +of the piece as indicated at <i>c</i> in <a href="#Fig_1_5">Fig. 5</a>. As all work of this +kind is held, while being turned, between the centers <i>h</i> and <i>h<sub>1</sub></i>, +holes corresponding in shape to these centers are necessary to +keep the work in place. There are several methods of forming +these center-holes, as explained later.</p> + +<p>After the work is centered, a dog <i>A</i> is clamped to one end by +tightening screw <i>s</i>; it is then placed between the centers of the +lathe. The dog has a projecting end or “tail,” as it is commonly +called, which enters a slot in the faceplate <i>F</i> and thereby drives +<span class="pagenum"><a name="Pg_7" id="Pg_7">[7]</a></span> +or rotates the work, when power is applied to the lathe spindle +onto which the faceplate is screwed. The tailstock center <i>h<sub>1</sub></i>, +after being oiled, should be set up just tight enough to eliminate +all play, without interfering with a free rotary movement of the +work. This is done by turning handle <i>n</i>, and when the center +is properly adjusted, the tailstock spindle containing the center +is locked by tightening handle <i>p</i>. (Ordinary machine oil is +commonly used for lubricating lathe centers, but a lubricant +having more “body” should be used, especially when turning +heavy parts. The following mixtures are recommended: 1. Dry +or powdered red lead mixed with a good grade of mineral oil to +the consistency of cream. 2. White lead mixed with sperm oil +with enough graphite added to give the mixture a dark lead +color.)</p> + +<a name="Fig_1_6" id="Fig_1_6"></a> +<div class="figcenter"><div class="illobox450"><img src="images/016sm.png" alt="Lathe Side-tool for Facing Ends of Shafts, etc." /></div> +<p class="caption750">Fig. 6. Lathe Side-tool for Facing Ends of Shafts, etc.</p> +</div> + +<a name="Secnum_1_3" id="Secnum_1_3"></a><p><b>Facing the Ends Square with a Side-tool.</b>—Everything is +now ready for the turning operation. The ends of the piece +should be faced square before turning the body to size, and the +tool for this squaring operation is shown in <a href="#Fig_1_6">Fig. 6</a>; this is known +as a side-tool. It has a cutting edge <i>e</i> which shaves off the +metal as indicated in the end view by the dotted lines. The +side <i>f</i> is ground to an angle so that when the tool is moved in +the direction shown by the arrow, the cutting edge will come in +contact with the part to be turned; in other words, side <i>f</i> is<span class="pagenum"><a name="Pg_8" id="Pg_8">[8]</a></span> +ground so as to provide clearance for the cutting edge. In addition, +the top surface against which the chip bears, is beveled +to give the tool keenness so that it will cut easily. As the principles +of tool grinding are treated separately in <a href="#Chapnum_2">Chapter II</a> we +shall for the present consider the tool's use rather than its form.</p> + +<a name="Fig_1_7" id="Fig_1_7"></a> +<div class="figcenter"><div class="illobox450"><img src="images/017sm.png" alt="Facing End with Side-tool and Turning Work Cylindrical" /></div> +<p class="caption750">Fig. 7. Facing End with Side-tool and Turning Work Cylindrical</p> +</div> + +<p>For facing the end, the side tool is clamped in the toolpost by +tightening the screw <i>u</i>, <a href="#Fig_1_5">Fig. 5</a>, and it should be set with the +cutting edge slightly inclined from a right-angled position, the +point being in advance so that it will first come into contact +with the work. The cutting edge should also be about the same +height as the center of the work. When the tool is set, the +lathe (if belt-driven) is started by shifting an overhead belt and +the tool is then moved in until the point is in the position shown +at <i>A</i>, <a href="#Fig_1_7">Fig. 7</a>. The tool-point is then fed against the end by +handle <i>d</i>, <a href="#Fig_1_5">Fig. 5</a>, until a light chip is being turned off, and then +it is moved outward by handle <i>e</i> (as indicated by the arrow at +<i>B</i>, <a href="#Fig_1_7">Fig. 7</a>), the carriage remaining stationary. As the movement +of the tool-point is guided by the cross-slide <i>D</i>, which is at +right angles with the axis of the work, the end will be faced +square. For short turning operations of this kind, the power +feeds ordinarily are not used as they are intended for comparatively +long cuts. If it were necessary to remove much +metal from the end, a number of cuts would be taken across it; +in this case, however, the rough stock is only <sup class="enum">1</sup>/<sub class="denom">8</sub> inch too long so +that this end need only be made true.</p> + +<p>After taking a cut as described, the surface, if left rough by<span class="pagenum"><a name="Pg_9" id="Pg_9">[9]</a></span> +the tool-point, should be made smooth by a second or finishing +cut. If the tool is ground slightly round at the point and the +cutting edge is set almost square, as at <i>C</i>, <a href="#Fig_1_7">Fig. 7</a>, a smooth finish +can be obtained; the cut, however, should be light and the outward +feed uniform. The work is next reversed in the centers +and the driving dog is placed on the end just finished; the other +end is then faced, enough metal being removed to make the +piece 14<sup class="enum">1</sup>/<sub class="denom">2</sub> inches long, as required in this particular case. This +completes the facing operation. If the end of the work does +not need to be perfectly square, the facing operation can be performed +by setting the tool in a right-angled position and then +feeding it sidewise, thus removing a chip equal to the width of +one side. Evidently this method is confined to comparatively +small diameters and the squareness of the turned end will be +determined by the position of the tool's cutting edge.</p> + +<a name="Fig_1_8" id="Fig_1_8"></a> +<div class="figcenter"><div class="illobox450"><img src="images/018sm.png" alt="Tool used for Cylindrical Turning" /></div> +<p class="caption750">Fig. 8. Tool used for Cylindrical Turning</p> +</div> + +<a name="Secnum_1_4" id="Secnum_1_4"></a><p><b>Turning Tool—Turning Work Cylindrical.</b>—The tool used to +turn the body to the required diameter is shaped differently +from the side-tool, the cutting edge <i>E</i> of most tools used for +plain cylindrical turning being curved as shown in <a href="#Fig_1_8">Fig. 8</a>. A +<span class="pagenum"><a name="Pg_10" id="Pg_10">[10]</a></span> +tool of this shape can be used for a variety of cylindrical turning +operations. As most of the work is done by that part of +the edge marked by arrow <i>a</i>, the top of the tool is ground to +slope back from this part to give it keenness. The end <i>F</i>, or +the flank, is also ground to an angle to provide clearance for the +cutting edge. If the tool did not have this clearance, the flank +would rub against the work and prevent the cutting edge from +entering the metal. This type of tool is placed about square +with the work, for turning, and with the cutting end a little +above the center.</p> + +<a name="Fig_1_9" id="Fig_1_9"></a> +<div class="figcenter"><div class="illobox450"><img src="images/019sm.png" alt="Setting Calipers by Scale—Setting by Gage—Fixed Gage" /></div> +<p class="caption750">Fig. 9. Setting Calipers by Scale—Setting by Gage—Fixed Gage</p> +</div> + +<p>Before beginning to turn, a pair of outside calipers or a micrometer +should be set to 2<sup class="enum">1</sup>/<sub class="denom">4</sub> inches, which, in this case, is the +finished diameter of the work. Calipers are sometimes set by +using a graduated scale as at <i>A</i>, <a href="#Fig_1_9">Fig. 9</a>, or they can be adjusted +to fit a standard cylindrical gage of the required size as at <i>B</i>. +Very often fixed caliper gages <i>C</i> are used instead of the adjustable +spring calipers. These fixed gages, sometimes called “snap” +gages, are accurately made to different sizes, and they are particularly +useful when a number of pieces have to be turned to +exactly the same size.</p> + +<a name="Fig_1_10" id="Fig_1_10"></a> +<div class="figcenter"><img src="images/020sm.jpg" alt="Views showing how the Cross-slide and Carriage are Manipulated by Hand when Starting a Cut" /> +<p class="caption750">Fig. 10. Views showing how the Cross-slide and Carriage are Manipulated<br />by +Hand when Starting a Cut—<br />View to Left, Feeding Tool Laterally;<br />View to +Right, Feeding Tool in a Lengthwise Direction</p> +</div> + +<p>The turning tool is started at the right-hand end of the work +and the tool should be adjusted with the left hand when beginning +a cut, as shown in <a href="#Fig_1_10">Fig. 10</a>, in order to have the right hand +free for calipering. A short space is first turned by hand feeding, +as at <i>D</i>, <a href="#Fig_1_7">Fig. 7</a>, and when the calipers show that the diameter is +slightly greater than the finished size (to allow for a light finishing +<span class="pagenum"><a name="Pg_11" id="Pg_11">[11]</a></span> +cut, either in the lathe or grinding machine) the power feed +for the carriage is engaged; the tool then moves along the work, +reducing it as at <i>E</i>. Evidently, if the movement is along a +line <i>b—b</i>, parallel with the axis <i>a—a</i>, the diameter <i>d</i> will be the +same at all points, and a true cylindrical piece will be turned. +On the other hand, if the axis <i>a—a</i> is inclined one way or the +other, the work will be made tapering; in fact, the tailstock +center <i>h<sub>1</sub></i> can be adjusted laterally for turning tapers, but for +straight turning, both centers must be in alignment with the +carriage travel. Most lathes have lines on the stationary and +movable parts of the tailstock base which show when the centers +are set for straight turning. These lines, however, may not be +absolutely correct, and it is good practice to test the alignment +of the centers before beginning to turn. This can be done by +taking trial cuts, at each end of the work (without disturbing +the tool's crosswise position), and then comparing the diameters, +or by testing the carriage travel with a true cylindrical piece +held between the centers as explained later.</p> + +<p>If the relative positions of the lathe centers are not known, +the work should be calipered as the cut progresses to see if +the diameter <i>d</i> is the same at all points. In case the diameter +gradually increases, the tailstock center should be shifted +slightly to the rear before taking the next cut, but if the diameter<span class="pagenum"><a name="Pg_12" id="Pg_12">[12]</a></span> +gradually diminishes, the adjustment would, of course, be made +in the opposite direction. The diameter is tested by attempting +to pass the calipers over the work. When the measuring points +just touch the work as they are gently passed across it, the +diameter being turned is evidently the same as the size to which +the calipers are set.</p> + +<p>As the driving dog is on one end, the cut cannot be taken +over the entire length, and when the tool has arrived at say +position <i>x</i>, <a href="#Fig_1_5">Fig. 5</a>, it is returned to the starting point and the +work is reversed in the centers, the dog being placed upon the +other end. The unfinished part is then turned, and if the cross-slide +is not moved, the tool will meet the first cut. It is not +likely that the two cuts will be joined or blended together perfectly, +however, and for this reason a cut should be continuous +when this is possible.</p> + +<a name="Secnum_1_5" id="Secnum_1_5"></a><p><b>Roughing and Finishing Cuts.</b>—Ordinarily in lathe work, as +well as in other machine work, there are two classes of cuts, +known as “roughing” and “finishing” cuts. +Roughing cuts are<span class="pagenum"><a name="Pg_13" id="Pg_13">[13]</a></span> +for reducing the work as quickly as possible almost to the required +size, whereas finishing cuts, as the name implies, are intended +to leave the part smooth and of the proper size. When +the rough stock is only a little larger than the finished diameter, +a single cut is sufficient, but if there is considerable metal to +turn away, one or more deep roughing cuts would have to be +taken, and, finally, a light cut for finishing. In this particular +case, one roughing and one finishing cut would doubtless be +taken, as the diameter has to be reduced <sup class="enum">3</sup>/<sub class="denom">8</sub> inch. Ordinarily the +roughing cut would be deep enough to leave the work about <sup class="enum">1</sup>/<sub class="denom">32</sub> +or perhaps <sup class="enum">1</sup>/<sub class="denom">16</sub> inch above the finished size. When there is considerable +metal to remove and a number of roughing cuts have +to be taken, the depth of each cut and the feed of the tool are +governed largely by the pulling power of the lathe and the +strength of the work to withstand the strain of a heavy cut. +The depth of roughing cuts often has to be reduced considerably +because the part being turned is so flexible that a heavy cut +would spring the work and cause the tool to gouge in. Of +course, just as few cuts as possible should be taken in order to +save time. The speed of the work should also be as fast as the +conditions will allow for the same reason, but as there are many +things which govern the speed, the feed of the tool, and the +depth of the cut, these important points are referred to separately +in <a href="#Chapnum_2">Chapter II</a>.</p> + +<a name="Fig_1_11" id="Fig_1_11"></a> +<div class="figcenter"><img src="images/022sm.jpg" alt="Filing Work" /> +<p class="caption750">Fig. 11. Filing Work after Finishing Cut is taken</p> +</div> + +<a name="Secnum_1_6" id="Secnum_1_6"></a><p><b>Filing and Finishing.</b>—In many cases the last or finishing +cut does not leave as smooth a surface as is required and it is +necessary to resort to other means. The method commonly +employed for finishing in the lathe is by the use of a file and +emery cloth. The work is rotated considerably faster for filing +than for turning, and the entire surface is filed by a flat, single-cut +file, held as shown in <a href="#Fig_1_11">Fig. 11</a>. The file is passed across the +work and advanced sidewise for each forward stroke, until the +entire surface is finished. The file should be kept in contact +with the work continually, but on the return stroke the pressure +should be relieved. The movement of the file during the forward +or cutting stroke should be much slower than when filing +in a vise. By moving the file slowly, the work can make a<span class="pagenum"><a name="Pg_14" id="Pg_14">[14]</a></span> +number of revolutions for each stroke, which tends to keep it +round, as practically the same amount of metal is removed from +the entire circumference. On the other hand, short rapid strokes +tend to produce flat spots, or at least an irregular surface, especially +if the work can only make part of a revolution for +each cutting stroke. The pressure on the file during the forward +stroke should also be kept as nearly uniform as possible.</p> + +<p>It is very difficult to file a part smooth and at the same time +to keep it round and cylindrical, and the more filing that has to +be done, the greater the chance of error. For this reason, the +amount left for filing should be very small; in fact, the metal +removed by filing should be just enough to take out the tool +marks and give a smooth finish. Very often a satisfactory +finish can be obtained with a turning tool, and filing is not +necessary at all. The file generally used for lathe work is a +“single-cut bastard” of “mill” section, having a length of from +12 to 14 inches.</p> + +<p>Sometimes particles of metal collect between the teeth of a +file and make deep scratches as the file is passed across the +work. When this occurs, the teeth should be cleaned by using<span class="pagenum"><a name="Pg_15" id="Pg_15">[15]</a></span> +a wire brush or a file card, which is drawn across the file in the +direction of the teeth. This forming of tiny particles between +the teeth is known as “pinning” and it can sometimes be avoided +by rubbing chalk on the file. Filing is not only done to obtain +a smooth finish, but also to reduce the work to an exact diameter, +as a very slight reduction can be made in this way.</p> + +<p>If a polish is desired, this can be obtained by holding a piece +of emery cloth tightly around the work as it revolves. The +coarseness of emery cloth is indicated by letters and numbers +corresponding to the grain number of loose emery. The letters +and numbers for grits ranging from fine to coarse are as follows: +<i>FF</i>, <i>F</i>, 120, 100, 90, 80, 70, 60, 54, 46, 40. For large work +roughly filed, use coarse cloth such as Nos. 46 or 54, and then +finer grades to obtain the required polish. If the work has been +carefully filed, a good polish can be obtained with Nos. 60 and +90 cloth, and a brilliant polish by finishing with No. 120 and +flour-emery.</p> + +<p>Most cylindrical parts can be finished more quickly and +accurately in the grinder than in the lathe, and many classes of +work are, at the present time, simply rough-turned in the lathe +and then ground to size in a cylindrical grinding machine.</p> + +<a name="Fig_1_12" id="Fig_1_12"></a> +<div class="figcenter"><div class="illobox450"><img src="images/023sm.png" alt="Two Methods of Aligning Centers for Cylindrical Turning" /></div> +<p class="caption750">Fig. 12. Two Methods of Aligning Centers for Cylindrical Turning</p> +</div> + +<a name="Secnum_1_7" id="Secnum_1_7"></a><p><span class="pagenum"><a name="Pg_16" id="Pg_16">[16]</a></span> +<b>Aligning Centers for Cylindrical Turning.</b>—Whena rod or +shaft must be turned cylindrical or to the same diameter throughout +its entire length, it is good practice to test the alignment +of the centers, before inserting the work. The position of the +tailstock center for cylindrical turning may be indicated by the +coincidence of graduation marks on the base, but if accuracy is +necessary, the relative position of the two centers should be determined +in a more positive way. A very simple and convenient +method of testing the alignment is shown at <i>A</i> in <a href="#Fig_1_12">Fig. 12</a>. The +work is first turned for a short distance, near the dogged end, as +shown, and the tool is left as set for this cut; then the tailstock +center is withdrawn and the work is moved sufficiently to +permit running the tool back to the tailstock end without changing +its original setting. A short cut is then taken at this end +and the diameters <i>d</i> and <i>d<sub>1</sub></i> are carefully compared. In case +there is any variation, the tailstock center is adjusted laterally, +other trial cuts are taken, and the test repeated.</p> + +<p>Another method is illustrated at <i>B</i>, which requires the use of +a test-bar <i>t</i>. This bar should have accurately made centers and +the ends finished to exactly the same diameter. The lathe +centers are aligned by placing the bar between them and then +testing the position of the ends. This can be done by comparing +each end with a tool held in the toolpost and moved from +one to the other by shifting the carriage, but a better method +is to clamp a test indicator <i>i</i> in the toolpost and bring it in contact +with first one end of the bar and then the other. If the dial +does not register the same at each end, it shows that the lathe +centers are not in line. Even when centers are correctly set, +lathes that have been in use a long time do not always turn +cylindrical or straight, because if the ways that guide the carriage +are worn unevenly, the tool as it moves along does not +remain in the same plane and this causes a variation in the +diameter of the part being turned.</p> + +<a name="Fig_1_13" id="Fig_1_13"></a> +<div class="figcenter"><div class="illobox450"><img src="images/025sm.png" alt="Dog that is too Short for Faceplate and Straight Driving Dog" /></div> +<p class="caption750">Fig. 13. (A) Dog that is too Short for Faceplate.<br />(B) Straight Driving Dog</p> +</div> + +<a name="Secnum_1_8" id="Secnum_1_8"></a><p><b>Application of Drivers or Dogs.</b>—Work that is turned between +centers is sometimes driven by a dog which is so short +for the faceplate that the bent driving end bears against the +bottom <i>a</i> of the faceplate slot, as shown at <i>A</i>, <a href="#Fig_1_13">Fig. 13</a>. If the +<span class="pagenum"><a name="Pg_17" id="Pg_17">[17]</a></span> +dog is nearly the right length, it may allow the headstock center +to enter the center in the work part way, with the result that +the turned surface is not true with the centers. When a driving +dog of this type is used, care should be taken to see that it moves +freely in the faceplate slot and does not bind against the bottom. +By using a straight dog (<i>B</i>), which is driven by a pin <i>b</i> bolted +to the faceplate, all danger from this source is eliminated. The +straight dog, however, is used more particularly to do away +with the leverage <i>l</i> of a bent dog, as this leverage tends to spring +a flexible part when a cut is being taken.</p> + +<p>Straight dogs are also made with two driving ends which +engage pins on opposite sides of the faceplate. This type is +preferable because it applies the power required for turning, +evenly to the work, which still further reduces the tendency to +spring it out of shape. The principal objection to the double-ended +type lies in the difficulty of adjusting the driving pins +so that each bears with equal pressure against the dog. The +double-ended driver is often used for large work especially if +deep roughing cuts are necessary.</p> + +<a name="Fig_1_14" id="Fig_1_14"></a> +<div class="figcenter"><div class="illobox450"><img src="images/026sm.png" alt="Bushing mounted on Arbor for Turning" /></div> +<p class="caption750">Fig. 14. Bushing mounted on Arbor for Turning</p> +</div> + +<a name="Secnum_1_9" id="Secnum_1_9"></a><p><b>Lathe Arbors or Mandrels.</b>—When it is necessary to turn +the outside of a part having a hole through it, centers cannot, +of course, be drilled in the ends and other means must be resorted +to. We shall assume that the bushing <i>B</i>, <a href="#Fig_1_14">Fig. 14</a>, has a +<span class="pagenum"><a name="Pg_18" id="Pg_18">[18]</a></span> +finished hole through the center, and it is desired to turn the +outside cylindrical and concentric with the hole. This could be +done by forcing a tightly-fitted arbor <i>M</i>, having accurately-centered +ends, into the bushing and inserting the mandrel and +work between the lathe centers <i>h</i> and <i>h<sub>1</sub></i> as shown. Evidently, +if the arbor runs true on its centers, the hole in the bushing will +also run true and the outside can be turned the same as though +the arbor and bushing were a solid piece. From this it will be +seen that an arbor simply forms a temporary support for parts +that are bored and therefore cannot be centered.</p> + +<a name="Fig_1_15" id="Fig_1_15"></a> +<div class="figcenter"><div class="illobox450"><img src="images/027sm.png" alt="Turning Pulley Held on an Arbor" /></div> +<p class="caption750">Fig. 15. Turning Pulley Held on an Arbor</p> +</div> + +<p>Another example of work that would be turned on an arbor +is shown in <a href="#Fig_1_15">Fig. 15</a>. This is a small cast-iron wheel having a +finished hole through the hub, and the outer surface and sides +of the rim are to be turned true with this hole. In this case, the +casting would also be held by pressing a mandrel through the +hub; as shown. This method, however, would only apply to +comparatively small wheels because it would be difficult, if not +impossible, to prevent a large wheel from turning on the arbor +when taking a cut, and even if it could be driven, large work +could be done to better advantage on another type of machine. +(The vertical boring mill is used extensively for turning large +wheels, as explained in <a href="#Chapnum_6">Chapter VI</a>.) When turning the outside +of the rim, a tool similar to that shown at <i>t</i> should be used, but +for facing or turning the sides, it might be better, if not necessary, +to use tools having bent ends as shown by the dotted lines; in<span class="pagenum"><a name="Pg_19" id="Pg_19">[19]</a></span> +fact, turning tools of various kinds are made with the ends bent +to the right or left, as this enables them to be used on surfaces +that could not be reached very well with a straight tool. If a +comparatively large pulley is mounted near the end of the +arbor, it can be driven directly by pins attached to the faceplate +and engaging the pulley arms. This method of driving is +often employed when the diameter to be turned is large and the +hole for the arbor is so small that there will not be sufficient +friction for driving.</p> + +<a name="Fig_1_16" id="Fig_1_16"></a> +<div class="figcenter"><div class="illobox450"><img src="images/028sm.png" alt="Different Types of Lathe Arbors" /></div> +<p class="caption750">Fig. 16. Different Types of Lathe Arbors</p> +</div> + +<a name="Secnum_1_10" id="Secnum_1_10"></a><p><b>Different Types of Lathe Arbors.</b>—Three different types of +lathe arbors are shown in <a href="#Fig_1_16">Fig. 16</a>. The kind shown at <i>A</i> is +usually made of tool steel and the body is finished to a standard +size. The ends are somewhat reduced and flat spots are milled, +as shown, to give the clamping screw of the dog a good grip. +The body of the arbor is usually tapered about 0.006 inch per +foot. This taper makes it easier to insert the arbor in a close-fitting +hole, and it also permits slight variations in the diameter +of different holes. As to hardening, the practice at the present +time among manufacturers is to harden arbors all over, but for +extremely accurate work, an arbor having hardened ends and a +soft body is generally considered superior, as there is less tendency +of distortion from internal stresses. Hardened arbors are “seasoned” +before finish-grinding to relieve these internal stresses.</p> + +<p>The solid type <i>A</i>, <a href="#Fig_1_16">Fig. 16</a>, is used very extensively, but in +<span class="pagenum"><a name="Pg_20" id="Pg_20">[20]</a></span> +shops where a great variety of work is being done and there are +many odd-sized holes, some form of expanding arbor <i>B</i> can be +used to advantage. This type, instead of being solid, consists +of a tapering inner arbor <i>M</i> on which is placed a split bushing +that can be expanded, within certain limits, by driving in the +tapering member. The advantage of this type is that a comparatively +small stock of arbors is required, as different-sized +bushings can be used. This type can also be fitted to holes of +odd sizes, whereas a solid arbor must be provided for each +different size hole, unless the variation is very slight. The latter +are, however, more accurate than the expanding type.</p> + +<p>Another form of expanding arbor is shown at <i>C</i>. This type +has a straight body <i>N</i> in which four tapering grooves are cut +lengthwise, as shown, and there is a sleeve <i>S</i>, containing four +slots that are located to correspond with the tapering grooves. +Strips s are fitted into these slots, and as the part <i>N</i> is driven in, +the strips are moved outward as they ascend the tapering grooves. +By having different sets of these strips of various heights, one +arbor of this type can be made to cover quite a range of sizes. +It is not suited, however, to thin work, as the pressure, being +concentrated in four places, would spring a flexible part out of +shape.</p> + +<a name="Fig_1_17" id="Fig_1_17"></a> +<div class="figcenter"><div class="illobox450"><img src="images/029sm.png" alt="Cone Arbor, Nut Arbor, Pipe Center" /></div> +<p class="caption750">Fig. 17. (A) Cone Arbor.<br />(B) Nut Arbor.<br />(C) Pipe Center</p> +</div> + +<p>The cone arbor or mandrel shown at <i>A</i>, in <a href="#Fig_1_17">Fig. 17</a>, is convenient +<span class="pagenum"><a name="Pg_21" id="Pg_21">[21]</a></span> +for holding parts having comparatively large holes, as +it can be adjusted for quite a range of diameters. The work is +gripped between the two cones <i>c</i> and <i>c<sub>1</sub></i> which are forced together +by nut <i>n</i>. The cones are prevented from turning upon the +arbor by keys. This style of arbor should not be used for +accurate work. The threaded arbor <i>B</i> is used for facing the sides +of nuts square with the tapped hole. When a nut is first put +upon the arbor, the rough side comes against an equalizing +washer <i>w</i>. This washer rests against a spherical seat so that it +can shift to provide a uniform bearing for the rough side of the +nut, even though it is not square with the tapped hole. This +feature prevents the nut from being canted on the arbor and +insures an accurately faced nut. The revolving conical center +shown at <i>C</i> is often used for holding a pipe or tube while turning +the outside. The cone is adjusted to fit into the hole of +the pipe, by means of the tailstock spindle, and the opposite +end is usually held in a chuck.</p> + +<p>Particular care should be taken to preserve the accuracy of<span class="pagenum"><a name="Pg_22" id="Pg_22">[22]</a></span> +the centers of lathe arbors by keeping them clean and well-oiled +while in use.</p> + +<div class="figcenter"><a name="Fig_1_18" id="Fig_1_18"></a> +<img src="images/030sm.jpg" alt="Press for Forcing Arbors into Work" /> +<p class="caption750">Fig. 18. Press for Forcing Arbors into Work</p> +</div> + +<a name="Secnum_1_11" id="Secnum_1_11"></a><p><b>Mandrel or Arbor Press.</b>—The best method of inserting an +arbor of the solid type in a hole is by using a press, <a href="#Fig_1_18">Fig. 18</a>, +designed for that purpose, but if such a press is not available +and it is necessary to drive the mandrel in, a “soft” hammer, +made of copper, lead or other soft material, should be used to protect +the centered end of the arbor. In either case, the arbor should +not be forced in too tightly, for if it fits properly, this will not +be necessary in order to hold the work securely. On the other +hand, the work might easily be broken by attempting to force +the arbor in as far and as tightly as possible. In using the +arbor press, the work is placed on the base <i>B</i> with the hole in a +vertical position, and the arbor (which +should be oiled slightly) is forced down into it by ram <i>R</i>, +operated by lever <i>L</i>. Slots are provided in the base, as shown, +so that the end of the arbor can come through at the bottom +of the hole. The lever of this particular press is counter-weighted +so that it rises to a vertical position when released. +The ram can then be adjusted quickly to any required height +by the handwheel seen at the left.</p> + +<p>Some shops are equipped with power-driven mandrel or<span class="pagenum"><a name="Pg_23" id="Pg_23">[23]</a></span> +arbor presses. This type is particularly desirable for large +work, owing to the greater pressure required for inserting mandrels +that are comparatively large in diameter. One well-known +type of power press is driven by a belt, and the downward +pressure of the ram is controlled by a handwheel. The ram is +raised or lowered by turning this handwheel in one direction or +the other, and a gage shows how much pressure is being applied. +This type of press can also be used for other purposes, such as +forcing bushings or pins into or out of holes, bending or straightening +parts, or for similar work.</p> + +<div class="figcenter"> +<a name="Fig_1_19" id="Fig_1_19"></a><div class="illobox450"> +<img src="images/031sm.png" alt="Steadyrest and Follow-rest for Supporting Flexible Parts" /></div> +<p class="caption750">Fig. 19. Steadyrest and Follow-rest for Supporting Flexible Parts</p> +</div> + +<a name="Secnum_1_12" id="Secnum_1_12"></a><p><b>Steadyrest for Supporting Flexible Parts.</b>—Occasionally +long slender shafts, rods, etc., which have to be turned, are so +flexible that it is necessary to support them at some point between +the lathe centers. An attachment for the lathe known +as a steadyrest is often used for this purpose. A steadyrest is +composed of a frame containing three jaws <i>J</i> (<a href="#Fig_1_19">Fig. 19</a>), that can +be adjusted in or out radially by turning screws <i>S</i>. The frame +is hinged at <i>h</i>, thus allowing the upper half to be swung back +(as shown by the dotted lines) for inserting or removing the +work. The bolt-clamp <i>c</i> holds the hinged part in the closed +position. The base of the frame has V-grooves in it that fit +the ways of the lathe bed. When the steadyrest is in use, it is +<span class="pagenum"><a name="Pg_24" id="Pg_24">[24]</a></span> +secured to the bed by clamp <i>C</i>, and the jaws <i>J</i> are set in against +the work, thus supporting or steadying it during the turning +operation. The steadyrest must, of course, be located at a +point where it will not interfere with the turning tool.</p> + +<div class="figcenter"><a name="Fig_1_20" id="Fig_1_20"></a> +<div class="illobox450"><img src="images/032sm.png" alt="Application of Steadyrest to a Flexible Rod" /></div> +<p class="caption750">Fig. 20. Application of Steadyrest to a Flexible Rod</p> +</div> + +<p><a href="#Fig_1_20">Fig. 20</a> shows the application of the steadyrest to a long +forged rod, having one small end, which makes it too flexible to +be turned without support. As this forging is rough, a true +surface <i>n</i> a little wider than the jaws <i>J</i> (<a href="#Fig_1_19">Fig. 19</a>) is first turned +as a bearing for the jaws. This should be done very carefully +to prevent the work from mounting the tool. A sharp pointed +tool should be used and very light cuts taken. The steadyrest +is next clamped to the lathe bed opposite the turned surface, +and the jaws are adjusted in against this surface, thus forming +a bearing. Care should be taken not to set up the jaws too +tightly, as the work should turn freely but without play. The +large part of the rod and central collar are then turned to size, +this half being machined while the small part is in the rough and +as stiff as possible. The rod is then reversed and the steadyrest +is applied to the part just finished, as shown at <i>B</i>, thus supporting +the work while the small end is being turned. That +part against which the jaws bear should be kept well oiled, and +if the surface is finished it should be protected by placing a +strip of emery cloth beneath the jaws with the emery side out;<span class="pagenum"><a name="Pg_25" id="Pg_25">[25]</a></span> +a strip of belt leather is also used for this purpose, the object +in each case being to prevent the jaws from scratching and +marring the finished surface, as they tend to do, especially if at +all rough.</p> + +<p>If the work were too flexible to permit turning a spot at <i>n</i>, +this could be done by first “spotting” it at some point <i>o</i>, and +placing the steadyrest at that point while turning another spot +at <i>n</i>.</p> + +<div class="figcenter"><a name="Fig_1_21" id="Fig_1_21"></a> +<div class="illobox450"><img src="images/033sm.png" alt="Cat-head which is sometimes used as Bearing for Steadyrest" /></div> +<p class="caption750">Fig. 21. Cat-head which is sometimes used as Bearing for Steadyrest</p> +</div> + +<p>Sometimes it is desirable to apply a steadyrest to a surface +that does not run true and one which is not to be turned; in +such a case a device called a “cat-head” is used. This is simply +a sleeve <i>S</i> (<a href="#Fig_1_21">Fig. 21</a>) which is placed over the untrue surface to +serve as a bearing for the steadyrest. The sleeve is made to +run true by adjusting the four set-screws at each end, and the +jaws of the steadyrest are set against it, thus supporting the +work.</p> + +<a name="Fig_1_22" id="Fig_1_22"></a> +<div class="figcenter"><div class="illobox450"><img src="images/034sm.png" +alt="Shaft supported by Steadyrest for Drilling and Boring End" /></div> +<p class="caption750">Fig. 22. Shaft supported by Steadyrest for Drilling and Boring End</p> +</div> + +<a name="Secnum_1_13" id="Secnum_1_13"></a><p><b>Application of Steadyrest when Boring.</b>—Another example +illustrating the use of the steadyrest is shown in <a href="#Fig_1_22">Fig. 22</a>. The +rod <i>R</i> is turned on the outside and a hole is to be bored in the +end (as shown by dotted lines) true with the outer surface. If +the centers used for turning the rod are still in the ends, as they +would be ordinarily, this work could be done very accurately by +the following method: The rod is first placed between the centers +as for turning, with a driving dog <i>D</i> attached, and the steadyrest +jaws <i>J</i> are set against it near the outer end, as shown.</p> + +<div class="figcenter"><div class="illobox450"><a name="Fig_1_23" id="Fig_1_23"></a><img src="images/035sm.png" +alt="Hold-back used when Outer End of Work is held in Steadyrest" /></div> +<p class="caption750">Fig. 23. Hold-back used when Outer End of Work is held in Steadyrest</p> +</div> + +<p>Before any machine work is done, means must be provided +for holding the rod back against the headstock center <i>h</i>, because, +for an operation of this kind, the outer end cannot be supported<span class="pagenum"><a name="Pg_26" id="Pg_26">[26]</a></span> +by the tailstock center; consequently the work tends to shift +to the right. One method of accomplishing this is shown in the +illustration. A hardwood piece <i>w</i>, having a hole somewhat +larger than the work, is clamped against the dog, in a crosswise +position, by the swinging bolts and thumb-screws shown. If the +dog is not square with the work, the wood piece should be canted +so that the bearing will not be all on one side. For large heavy +parts a similar “bridle” or “hold-back”—as this is commonly +called—is made by using steel instead of wood for the +part <i>w</i>. Another very common method which requires no +special equipment is illustrated in <a href="#Fig_1_23">Fig. 23</a>. An ordinary leather +belt lacing <i>L</i> is attached to the work and faceplate while the +latter is screwed off a few turns as shown. Then the lacing is +drawn up by hand and tied, and the faceplate is screwed onto +the spindle, thus tightening the lacing and drawing the work +against the headstock center. The method of applying the +lacing is quite clearly indicated in the illustration. If a small +driving faceplate is used, it may be necessary to drill holes for +the belt lacing, as shown.</p> + +<a name="Fig_1_24" id="Fig_1_24"></a> +<div class="figcenter"><div class="illobox450"><img src="images/036sm.png" alt="Testing Work with Dial Indicator" /></div> +<p class="caption750">Fig. 24. Testing Work with Dial Indicator</p> +</div> + +<p>A hole is next drilled in the end of the rod by using a twist +drill in the tailstock. If the hole is finished by boring, a depth<span class="pagenum"><a name="Pg_27" id="Pg_27">[27]</a></span> +mark should be made on the tool shank that will warn the workman +of the cutting end's approach to the bottom. A chuck can +also be used in connection with a steadyrest for doing work of +this kind, as shown in <a href="#Fig_1_24">Fig. 24</a>, the end of the rod being held and +driven by the chuck <i>C</i>. If the piece is centered, it can be held +on these centers while setting the steadyrest and adjusting the +chuck, but if the ends are without centers, a very good way is to +make light centers in the ends with a punch; after these are +properly located they are used for holding the work until the +steadyrest and chuck jaws have been adjusted. In case it is +necessary to have the end hole very accurate with the outside +of the finished rod, a test indicator <i>I</i> should be applied to the +shaft as shown. This is an instrument which shows with great +accuracy whether a rotating part runs true and it is also used +for many other purposes in machine shops. The indicator is +held in the lathe toolpost and the contact point beneath the +dial is brought against the work. If the latter does not run +true, the hand of the indicator vibrates and the graduations on +the dial show how much the work is out in thousandths of an +inch.</p> + +<a name="Secnum_1_14" id="Secnum_1_14"></a><p><b>The Follow-rest.</b>—When turning long slender parts, such as +shafts, etc., a follow-rest is often used for supporting the work. +The follow-rest differs from the steadyrest in that it is attached<span class="pagenum"><a name="Pg_28" id="Pg_28">[28]</a></span> +to and travels with the lathe carriage. The type illustrated to +the right in <a href="#Fig_1_19">Fig. 19</a> has two adjustable jaws which are located +nearly opposite the turning tool, thus providing support where +it is most needed. In using this rest, a cut is started at the +end and the jaws are adjusted to this turned part. The tool is +then fed across the shaft, which cannot spring away from the +cut because of the supporting jaws. Some follow-rests have, +instead of jaws, a bushing bored to fit the diameter being turned, +different bushings being used for different diameters. The +bushing forms a bearing for the work and holds it rigidly. +Whether a bushing or jaws are used, the turning tool is slightly +in advance of the supporting member.</p> + +<a name="Fig_1_25" id="Fig_1_25"></a> +<div class="figcenter"><div class="illobox450"><img src="images/037sm.png" alt="Centering End with Punch preparatory to Drilling" /></div> +<p class="caption750">Fig. 25. Centering End with Punch preparatory to Drilling</p> +</div> + +<a name="Secnum_1_15" id="Secnum_1_15"></a><p><b>Centering Parts to be Turned.</b>—As previously mentioned, +there are a number of different methods of forming center-holes +in the ends of parts that have to be turned while held +between lathe centers. A method of centering light work, and +one that requires few special tools, is first to locate a central +point on the end and then drill and ream the center-hole by +using the lathe itself. Hermaphrodite dividers are useful for +finding the center, as illustrated at <i>A</i>, <a href="#Fig_1_25">Fig. 25</a>, but if the work is +fairly round, a center-square <i>B</i> is preferable. A line is scribed +across the end and then another line at right angles to the first +by changing the position of the square; the intersection of these +two lines will be the center, which should be marked by striking<span class="pagenum"><a name="Pg_29" id="Pg_29">[29]</a></span> +a pointed punch <i>C</i> with a hammer. If a cup or bell center-punch +<i>D</i> is available, it will not be necessary to first make +center lines, as the conical part shown locates the punch in a +central position. This style of punch should only be used on +work which is fairly round.</p> + +<p>After small centers have been located in both ends, their +position can be tested by placing the work between the lathe +centers and rotating it rapidly by drawing the hand quickly +across it. By holding a piece of chalk close to the work as it +spins around, a mark will be made on the “high” side if the +centers are not accurate; the centers are then shifted toward +these marks. If the work is close to the finished diameter, the +centers should, of course, be located quite accurately in order +that the entire surface of the work will be turned true when it +is reduced to the finished size.</p> + +<a name="Fig_1_26" id="Fig_1_26"></a> +<div class="figcenter"><div class="illobox450"><img src="images/038asm.png" alt="Drilling Centers in the Lathe" /></div> +<p class="caption750">Fig. 26. Drilling Centers in the Lathe</p> +</div> + +<p>One method of forming these center-holes is indicated in <a href="#Fig_1_26">Fig. +26</a>. A chuck <i>C</i> is screwed onto the spindle in place of the faceplate, +and a combination center drill and reamer <i>R</i> is gripped +by the chuck jaws and set to run true. The center is then +drilled and reamed at one end by pressing the work against the +revolving drill with the tailstock spindle, which is fed out by +turning handle <i>n</i>. The piece is then reversed for drilling the +opposite end. The work may be kept from revolving while the +centers are being drilled and reamed, by attaching a dog to it +close to the tailstock end and then adjusting the cross-slide<span class="pagenum"><a name="Pg_30" id="Pg_30">[30]</a></span> +until the dog rests upon the slide. Many parts can be held by +simply gripping them with one hand. From the foregoing it +will be seen that the small centers made by punch <i>C</i>, <a href="#Fig_1_25">Fig. 25</a>, +serve as a starting point for the drill and also as a support for +the outer end of the work while the first hole is being drilled.</p> + +<a name="Fig_1_27" id="Fig_1_27"></a> +<div class="figcenter"><div class="illobox450"><img src="images/038bsm.png" alt="Centers of Incorrect and Correct Form" /></div> +<p class="caption750">Fig. 27. Centers of Incorrect and Correct Form</p> +</div> + +<p>The form of center-hole produced by a combination drill and +reamer is shown by the lower left-hand view in <a href="#Fig_1_27">Fig. 27</a>. A +small straight hole a in the bottom prevents the point of the +lathe center from coming in contact with the work and insures +a good bearing on the conical surface <i>c</i>. The standard angle +for lathe centers is sixty degrees, as the illustration shows, and +the tapering part of all center-holes should be made to this +angle.</p> + +<a name="Fig_1_28" id="Fig_1_28"></a> +<div class="figcenter"><img src="images/039sm.jpg" alt="Special Machine for Centering Parts to be Turned" /> +<p class="caption750">Fig. 28. Special Machine for Centering Parts to be Turned</p> +</div> + +<a name="Secnum_1_16" id="Secnum_1_16"></a><p><b>Centering Machine.</b>—Many shops have a special machine +for forming centers which enables the operation to be performed<span class="pagenum"><a name="Pg_31" id="Pg_31">[31]</a></span> +quickly. One type of centering machine is shown in <a href="#Fig_1_28">Fig. 28</a>. +The work is gripped in a chuck <i>C</i> that automatically locates it +in a central position so that it is not necessary to lay out the +end before drilling. There are two spindles <i>s</i>, one of which +holds the drill and the other the countersink, and these are +rotated by a belt passing over pulley <i>P</i>. Each of these spindles +is advanced by lever <i>L</i> and either of them can be moved to a +position central with the work, as they are mounted in a swiveling +frame. In operating this machine, a small straight hole is +first made by a twist drill held in one of the spindles; the other +spindle is then moved over to the center and the hole is reamed +tapering. The arrangement is such that neither spindle can be +advanced by the feeding lever except when in a central position.<span class="pagenum"><a name="Pg_32" id="Pg_32">[32]</a></span> +The amount that each spindle can be advanced is limited by a +fixed collar inside the head, and there is also a swinging adjustable +stop against which the end of the work should be placed +before tightening the chuck. These two features make it possible +to ream center holes of the same size or depth in any +number of pieces.</p> + +<a name="Fig_1_29" id="Fig_1_29"></a> +<div class="figcenter"><div class="illobox450"><img src="images/040sm.png" alt="The Imperfect Center Bearing is the Result of Centering before Straightening" /></div> +<p class="caption750">Fig. 29. The Imperfect Center Bearing is the Result of Centering +before Straightening</p> +</div> + +<a name="Secnum_1_17" id="Secnum_1_17"></a><p><b>Different Forms of Centers.</b>—In some poorly equipped shops +it is necessary to form centers by the use of a center-punch +only, as there is no better tool. If the end of the punch has a +sixty-degree taper, a fair center can be formed in this way, but +it is not a method to be recommended, especially when accurate +work is required. Sometimes centers are made with punches +that are too blunt, producing a shallow center, such as the one +shown in the upper left-hand view, <a href="#Fig_1_27">Fig. 27</a>. In this case all the +bearing is on the point of the lathe center, which is the worst +possible place for it. Another way is to simply drill a straight +hole as in the upper view to the right; this is also bad practice +in more than one respect. The lower view to the right shows +a form of center which is often found in the ends of lathe arbors, +the mouth of the center being rounded, at <i>r</i>, and the arbor end +recessed as shown. The rounded corner prevents the point of +the lathe center from catching when it is moved rapidly towards +work which is not being held quite centrally (as shown by the +illustration), and the end is recessed to protect the center against +bruises. Stock that is bent should always be straightened before +the centers are drilled and reamed. If the work is first +centered and then straightened the bearing on the lathe center +would be as shown in <a href="#Fig_1_29">Fig. 29</a>. The center will then wear unevenly +<span class="pagenum"><a name="Pg_33" id="Pg_33">[33]</a></span> +with the result that the surfaces last turned will not be +concentric with those which were finished first.</p> + +<a name="Fig_1_30" id="Fig_1_30"></a> +<div class="figcenter"><div class="illobox450"><img src="images/041sm.png" alt="Tool Steel should be centered Concentric, in order to remove the Decarbonized Outer Surface" /></div> +<p class="caption750">Fig. 30. Tool Steel should be centered Concentric, in order to remove +the Decarbonized Outer Surface</p> +</div> + +<a name="Secnum_1_18" id="Secnum_1_18"></a><p><b>Precaution When Centering Tool Steel.</b>—Ordinarily centers +are so located that the stock runs approximately true before +being turned, but when centering tool steel to be used in making +tools, such as reamers, mills, etc., which need to be hardened, +particular care should be taken to have the rough surface run +fairly true. This is not merely to insure that the piece will +“true-up,” as there is a more important consideration, the disregard +of which often affects the quality of the finished tool. +As is well known, the degree of hardness of a piece of tool steel +that has been heated and then suddenly cooled depends upon +the amount of carbon that it contains, steel that is high in carbon +becoming much harder than that which contains less carbon. +Furthermore, the amount of carbon found at the surface, and +to some little depth below the surface of a bar of steel, is less +than the carbon content in the rest of the bar. This is illustrated +diagrammatically in <a href="#Fig_1_30">Fig. 30</a> by the shaded area in the +view to the left. (This decarbonization is probably due to the +action of the oxygen of the air on the bar during the process of +manufacture.) If stock for a reamer is so centered that the +tool removes the decarbonized surface only on one side, as +illustrated to the right, evidently when the reamer is finished +and hardened the teeth on the side <i>A</i> will be harder than those +on the opposite side, which would not have been the case if the +rough bar had been centered true. To avoid any trouble of +this kind, stock that is to be used for hardened tools should be<span class="pagenum"><a name="Pg_34" id="Pg_34">[34]</a></span> +enough larger than the finished diameter and so centered that +this decarbonized surface will be entirely removed in turning.</p> + +<a name="Fig_1_31" id="Fig_1_31"></a> +<div class="figcenter"><div class="illobox450"><img src="images/042sm.png" alt="Three Methods Facing the Ends Square" /></div> +<p class="caption750">Fig. 31. Three Methods of Facing the Ends Square</p> +</div> + +<a name="Secnum_1_19" id="Secnum_1_19"></a><p><b>Facing the Ends of Centered Stock.</b>—As a piece of work is +not properly centered until the ends are faced square, we will +consider this operation in connection with centering. Some +machinists prefer lathe centers that are cut away as shown at +<i>A</i>, <a href="#Fig_1_31">Fig. 31</a>, so that the point of the side tool can be fed in far +enough to face the end right up to the center hole. Others, instead +of using a special center, simply loosen the regular one +slightly and then, with the tool in a position as at <i>B</i>, face the +projecting teat by feeding both tool and center inward as shown +by the arrow. Whenever this method is employed, care should +be taken to remove any chips from the center hole which may +have entered. A method which makes it unnecessary to loosen +the regular center, or to use a special one, is to provide clearance +for the tool-point by grinding it to an angle of approximately +forty-five degrees, as shown at <i>C</i>. If the tool is not set +too high, it can then be fed right up to the lathe center and the +end squared without difficulty. As for the special center <i>A</i>, +the use of special tools and appliances should always be avoided +unless they effect a saving in time or their use makes it possible +to accomplish the same end with less work.</p> + +<a name="Secnum_1_20" id="Secnum_1_20"></a><p><b>Truing Lathe Centers.</b>—The lathe centers should receive +careful attention especially when accurate work must be turned. +If the headstock center does not run true as it revolves with +the work, a round surface may be turned, but if the position of +the driving dog with reference to the faceplate is changed, the +turned surface will not run true because the turned surface is<span class="pagenum"><a name="Pg_35" id="Pg_35">[35]</a></span> +not true with the work centers. Furthermore, if it is necessary +to reverse the work for finishing the dogged or driving end, the last +part turned will be eccentric to the first. Therefore, the lathe +centers should be kept true in order to produce turned surfaces +that are true or concentric with the centered ends, as it is often +necessary to change the part being turned “end for end” for +finishing, and any eccentricity between the different surfaces +would, in many cases, spoil the work.</p> + +<a name="Fig_1_32" id="Fig_1_32"></a> +<div class="figcenter"><div class="illobox450"><img src="images/043sm.png" alt="Grinder for Truing Lathe Centers" /></div> +<p class="caption750">Fig. 32. Grinder for Truing Lathe Centers</p> +</div> + +<p>Some lathes are equipped with hardened centers in both the +head-and tailstock and others have only one hardened center +which is in the tailstock. The object in having a soft or unhardened +headstock center is to permit its being trued by turning, +but as a soft center is quite easily bruised and requires +truing oftener than one that is hard, it is better to have both +centers hardened. Special grinders are used for truing these +hardened centers. One type that is very simple and easily applied +to a lathe is shown in <a href="#Fig_1_32">Fig. 32</a>. This grinder is held in the +lathe toolpost and is driven by a wheel <i>A</i> that is held in contact +with the cone-pulley. The emery wheel <i>B</i> is moved to a position +for grinding by adjusting the carriage and cross-slide, and it is<span class="pagenum"><a name="Pg_36" id="Pg_36">[36]</a></span> +traversed across the conical surface of the center by handle <i>C</i>. +As the grinding proceeds, the wheel is fed inward slightly by +manipulating the cross-slide.</p> + +<p>This grinder is set to the proper angle by placing the two +centered ends <i>D</i> and <i>D<sub>1</sub></i> between the lathe centers, which should +be aligned as for straight turning. The grinding spindle will +then be 30 degrees from the axis of the lathe spindle. The +grinder should be carefully clamped in the toolpost so that it +will remain as located by the centered ends. After the tailstock +center is withdrawn, the emery wheel is adjusted for grinding. +As the wheel spindle is 30 degrees from the axis of the lathe +spindle, the lathe center is not only ground true but to an +included angle of 60 degrees, which is the standard angle for +lathe centers. There are many other styles of center grinders +on the market, some of which are driven by a small belt from +the cone-pulley and others by electric motors which are connected +with ordinary lighting circuits. The tailstock center is +ground by inserting it in the spindle in place of the headstock +center. Before a center is replaced in its spindle, the hole +should be perfectly clean as even a small particle of dirt may +affect the alignment. The center in the headstock is usually +referred to as the “live center” because it turns around when +the lathe is in use, and the center in the tailstock as the “dead +center,” because it remains stationary.</p> + +<a name="Fig_1_33" id="Fig_1_33"></a> +<div class="figcenter"><img src="images/045sm.jpg" alt="Lathe Chuck, Faceplate Jaw" /> +<p class="caption750">Fig. 33. (A) Lathe Chuck.<br />(B) Faceplate Jaw</p> +</div> + +<a name="Secnum_1_21" id="Secnum_1_21"></a><p><b>Universal, Independent and Combination Chucks.</b>—Many +parts that are turned in the lathe are so shaped that they cannot +be held between the lathe centers like shafts and other +similar pieces and it is often necessary to hold them in a chuck +<i>A</i>, <a href="#Fig_1_33">Fig. 33</a>, which is screwed onto the lathe spindle instead of +the faceplate. The work is gripped by the jaws <i>J</i> which can be +moved in or out to accommodate various diameters. There are +three classes of chucks ordinarily used on the lathe, known as +the independent, universal and combination types. The independent +chuck is so named because each jaw can be adjusted in +or out independently of the others by turning the jaw screws S +with a wrench. The jaws of the universal chuck all move together +and keep the same distance from the center, and they<span class="pagenum"><a name="Pg_37" id="Pg_37">[37]</a></span> +can be adjusted by turning any one of the screws <i>S</i>, whereas +with the independent type the chuck wrench must be applied +to each jaw screw. The combination chuck, as the name implies, +may be changed to operate either as an independent or +universal type. The advantage of the universal chuck is that +round and other parts of a uniform shape are located in a central +position for turning without any adjustment. The independent +type is, however, preferable in some respects as it is usually +stronger and adapted for holding odd-shaped pieces because +each jaw can be set to any required position.</p> + +<a name="Fig_1_34" id="Fig_1_34"></a> +<div class="figcenter"><div class="illobox450"><img src="images/046sm.png" alt="Radial Facing, Boring Pulley Held in Chuck" /></div> +<p class="caption750">Fig. 34. (A) Radial Facing.<br />(B) Boring Pulley Held in Chuck</p> +</div> + +<a name="Secnum_1_22" id="Secnum_1_22"></a><p><b>Application of Chucks.</b>—As an example of chuck work, we +shall assume that the sides of disk <i>D</i>, <a href="#Fig_1_34">Fig. 34</a>, are to be turned +flat and parallel with each other and that an independent chuck +is to be used. First the chuck is screwed onto the lathe spindle +after removing the faceplate. The chuck jaws are then moved +out or in, as the case may be, far enough to receive the disk +and each jaw is set about the same distance from the center +by the aid of concentric circles on the face of the chuck. The +jaws are then tightened while the disk is held back against +them to bring the rough inner surface in a vertical plane. If +the work is quite heavy, it can be held against the chuck, before +the jaws are tightened, by inserting a piece of wood between +it and the tailstock center; the latter is then run out far<span class="pagenum"><a name="Pg_38" id="Pg_38">[38]</a></span> +enough to force the work back. The outside or periphery of +the disk should run nearly true and it may be necessary to +move the jaws in on one side and out on the other to bring the +disk to a central position. To test its location, the lathe is +run at a moderate speed and a piece of chalk is held near the +outer surface. If the latter runs out, the “high” side will be +marked by the chalk, and this mark can be used as a guide in +adjusting the jaws. It should be remembered that the jaws are +moved only one-half the amount that the work runs out.</p> + +<a name="Fig_1_35" id="Fig_1_35"></a> +<div class="figcenter"><div class="illobox450"><img src="images/047sm.png" alt="Tools Ground so that Top Slopes away from Working Part of Cutting Edge" /></div> +<p class="caption750">Fig. 35. Tools Ground so that Top Slopes away from Working Part of +Cutting Edge</p> +</div> + +<p>A round-nosed tool <i>t</i> of the shape shown can be used for +radial facing or turning operations of the kind illustrated. +This tool is similar to the form used when turning between +centers, the principal difference being in the direction of the +top slope. The radial facing tool should be ground to slope +downward toward <i>a</i> (see <a href="#Fig_1_35">Fig. 35</a>) whereas the regular turning +tool slopes toward <i>b</i>, the inclination in each case being away +from that part of the cutting edge which does the work. The +cutting edge should be the same height as the lathe centers, and +the cut is taken by feeding the tool from the outside in to the +center. The cut is started by hand and then the power feed is +engaged, except for small surfaces. The first cut should, if +possible, be deep enough to get beneath the scale, especially if +turning cast iron, as a tool which just grazes the hard outer +surface will be dulled in a comparatively short time.</p> + +<p>If it were simply necessary to turn a true flat surface and the<span class="pagenum"><a name="Pg_39" id="Pg_39">[39]</a></span> +thickness of the disk were immaterial, two cuts would be sufficient, +unless the surface were very uneven, the first or roughing +cut being followed by a light finishing cut. For a finishing cut, +the same tool could be used, but if there were a number of disks +to be faced, a square-nosed tool <i>F</i>, <a href="#Fig_1_35">Fig. 35</a>, could probably be +used to better advantage. This type has a broad flat cutting +edge that is set parallel with the rough-turned surface and this +broad edge enables a coarse feed to be taken, thus reducing the +time required for the finishing cut. If a coarse feed were taken +with the round tool, the turned surface would have spiral grooves +in it, whereas with the broad cutting edge, a smooth surface is +obtained even though the feed is coarse. The amount of feed +per revolution of the work, however, should always be less than +the width <i>w</i> of the cutting edge. Very often broad tools cannot +be used for finishing cuts, especially when turning steel, +because their greater contact causes chattering and results in a +rough surface. An old and worn lathe is more liable to chatter +than one that is heavy and well-built, and as the diameter of +the work also makes a difference, a broad tool cannot always +be used for finishing, even though, theoretically, it would be +preferable. After one side of the disk is finished, it is reversed +in the chuck, the finished surface being placed against the jaws. +The remaining rough side is then turned, care being taken when +starting the first cut to caliper the width of the disk at several +points to make sure that the two sides are parallel.</p> + +<a name="Secnum_1_23" id="Secnum_1_23"></a><p><b>Example of Boring.</b>—Another example of chuck work is +shown at <i>B</i>, <a href="#Fig_1_34">Fig. 34</a>. In this case a cast-iron pulley is to have a<span class="pagenum"><a name="Pg_40" +id="Pg_40">[40]</a></span> +true hole <i>h</i> bored through the hub. (The finishing of internal +cylindrical surfaces in a lathe is referred to as boring rather than +turning.) The casting should be set true by the rim instead of +by the rough-cored hole in the hub; this can be done by the use +of chalk as previously explained. Even though a universal type +of chuck were used, the jaws of which, as will be recalled, are +self-centering, it might be necessary to turn the pulley relative +to the chuck as a casting sometimes runs out because of rough +spots or lumps which happen to come beneath one or more of +the jaws.</p> + +<div class="figcenter"> +<a name="Fig_1_36" id="Fig_1_36"></a> +<div class="illobox450"><img src="images/048sm.png" alt="Boring Tool" /></div> +<p class="caption750">Fig. 36. Boring Tool</p> +</div> + +<p>The shape of tool <i>t</i> for boring is quite different from one used +for outside turning, as shown by <a href="#Fig_1_36">Fig. 36</a>. The cutting end of a +solid type of tool is forged approximately at right angles to the +body or shank, and the top surface is ground to slope away from +the working part <i>w</i> of the cutting edge, as with practically all +turning tools. The front part or flank, <i>f</i> is also ground away to +give the edge clearance. This type of tool is clamped in the +toolpost with the body about parallel with the lathe spindle, +and ordinarily the cutting edge would be about as high as the +center of the hole, or a little below, if anything. When starting +a cut, the tool is brought up to the work by moving the carriage +and it is then adjusted radially to get the right depth of cut, by +shifting the cross-slide. The power feed for the carriage is then +used, the tool feeding back through the hole as indicated by +the arrow, <a href="#Fig_1_34">Fig. 34</a>. In this case, as with all turning operations, +the first cut should be deep enough to remove the hard outer +scale at every part of the hole. Usually a rough-cored hole is +so much smaller than the finished size that several cuts are +necessary; in any case, the last or finishing cut should be very<span class="pagenum"><a name="Pg_41" id="Pg_41">[41]</a></span> +light to prevent the tool from springing away from the work, +so that the hole will be as true as possible. Boring tools, particularly +for small holes, are not as rigid as those used for outside +turning, as the tool has to be small enough to enter the hole +and for this reason comparatively light cuts have to be taken. +When boring a small hole, the largest tool that will enter it +without interference should be used to get the greatest rigidity +possible.</p> + +<a name="Fig_1_37" id="Fig_1_37"></a> +<div class="figcenter"><div class="illobox450"><img src="images/049sm.png" alt="Setting Outside Calipers, Transferring Measurements to Inside Calipers, Micrometer Gage" /></div> +<p class="caption750">Fig. 37 (A) Setting Outside Calipers.<br />(B) Transferring Measurements to +Inside Calipers.<br />(C) Micrometer Gage</p> +</div> + +<a name="Fig_1_38" id="Fig_1_38"></a> +<div class="figcenter"><img src="images/050sm.jpg" alt="Plug Gage" /> +<p class="caption750">Fig. 38. Standard Plug Gage</p> +</div> + +<a name="Secnum_1_24" id="Secnum_1_24"></a><p><b>Measuring Bored Holes.</b>—The diameters of small holes +that are being bored are usually measured with inside calipers +or standard gages. If the pulley were being bored to fit over +some shaft, the diameter of the shaft would first be measured by +using outside calipers, as shown at <i>A</i>, <a href="#Fig_1_37">Fig. 37</a>, the measuring +points of the calipers being adjusted until they just made contact +with the shaft when passed over it. The inside calipers +are then set as at <i>B</i> to correspond with the size of the shaft, and +the hole is bored just large enough to admit the inside calipers +easily. Very accurate measurements can be made with calipers, +but to become expert in their use requires experience. Some +mechanics never become proficient in the art of calipering because +their hands are “heavy” and they lack the sensitiveness +and delicacy of touch that is necessary. For large holes, a +gage <i>C</i> is often used, the length <i>l</i> being adjusted to the diameter<span class="pagenum"><a name="Pg_42" +id="Pg_42">[42]</a></span> +desired. Small holes are often bored to fit hardened steel plug +gages (<a href="#Fig_1_38">Fig. 38</a>), the cylindrical measuring ends of which are +made with great accuracy to standard sizes. This type of gage +is particularly useful when a number of holes have to be bored +to the same size, all holes being made just large enough to fit +the gage without any perceptible play.</p> + +<a name="Fig_1_39" id="Fig_1_39"></a> +<div class="figcenter"><div class="illobox450"><img src="images/051asm.png" alt="Diagram Illustrating Importance of Setting Work with Reference to Surfaces to be Turned" /></div> +<p class="caption750">Fig. 39. Diagram Illustrating Importance of Setting Work with Reference +to Surfaces to be Turned</p> +</div> + +<a name="Secnum_1_25" id="Secnum_1_25"></a><p><b>Setting Work in the Chuck.</b>—When setting a part in a chuck, +care should be taken to so locate it that every surface to be +turned will be true when machined to the finished size. As a +simple illustration, let us assume that the hole through the cast-iron +disk, <a href="#Fig_1_39">Fig. 39</a>, has been cored considerably out of center, as +shown. If the work is set by the outside surface <i>S</i>, as it would +be ordinarily, the hole is so much out of center that it will not +be true when bored to the finished size, as indicated by the +dotted lines. On the other hand, if the rough hole is set true, +the outside cannot be finished all over, without making the +diameter too small, when it is finally turned. In such a case, +the casting should be shifted, as shown by the arrow, to divide +the error between the two surfaces, both of which can then be +turned as shown by the dotted lines in the view to the right. +This principle of dividing the error when setting work can often +be applied in connection with turning and boring. After a casting +or other part has been set true by the most important surface, +all other surfaces which require machining should be tested to +make sure that they all can be finished to the proper size.</p> + +<a name="Secnum_1_26" id="Secnum_1_26"></a><p><b>Inaccuracy from Pressure of Chuck Jaws.</b>—Work that is +held in a chuck is sometimes sprung out of shape by the pressure<span class="pagenum"><a name="Pg_43" id="Pg_43">[43]</a></span> +of the chuck jaws so that when the part is bored or turned, +the finished surfaces are untrue after the jaws are released and +the work has resumed its normal shape. This applies more particularly +to frail parts, such as rings, thin cylindrical parts, etc. +Occasionally the distortion can be prevented by so locating the +work with relation to the chuck jaws that the latter bear against +a rigid part. When the work cannot be held tightly enough for +the roughing cuts without springing it, the jaws should be released +somewhat before taking the finishing cut, to permit the +part to spring back to its natural shape.</p> + +<a name="Fig_1_40" id="Fig_1_40"></a> +<div class="figcenter"><div class="illobox450"><img src="images/051bsm.png" alt="Drilling in the Lathe" /></div> +<p class="caption750">Fig. 40. Drilling in the Lathe</p> +</div> + +<a name="Secnum_1_27" id="Secnum_1_27"></a><p><b>Drilling and Reaming.</b>—When a hole is to be bored from the +solid, it is necessary to drill a hole before a boring tool can be +used. One method of drilling in the lathe is to insert an ordinary +twist drill in a holder or socket <i>S</i>, <a href="#Fig_1_40">Fig. 40</a>, which is inserted +<span class="pagenum"><a name="Pg_44" id="Pg_44">[44]</a></span> +in the tailstock spindle in place of the center. The drill is then +fed through the work by turning the handle <i>n</i> and feeding the +spindle outward as shown by the arrow. Before beginning to +drill, it is well to turn a conical spot or center for the drill point +so the latter will start true. This is often done by using a special +tool having a point like a flat drill. This tool is clamped in +the toolpost with the point at the same height as the lathe +centers. It is then fed against the center of the work and a +conical center is turned. If the drill were not given this true +starting point, it probably would enter the work more or less +off center. Drills can also be started without turning a center +by bringing the square end or butt of a tool-shank held in +the toolpost in contact with the drill near the cutting end. If +the point starts off center, thus causing the drill to wobble, the +stationary tool-shank will gradually force or bump it over to +the center.</p> + +<a name="Fig_1_41" id="Fig_1_41"></a> +<div class="figcenter"><div class="illobox450"><img src="images/052sm.png" alt="Flat Drill and Holder" /></div> +<p class="caption750">Fig. 41. Flat Drill and Holder</p> +</div> + +<p>Small holes are often finished in the lathe by drilling and +reaming without the use of a boring tool. The form of drill +that is used quite extensively for drilling cored holes in castings +is shown in <a href="#Fig_1_41">Fig. 41</a>, at <i>A</i>. This drill is flat and the right end has +a large center hole for receiving the center of the tailstock. To<span class="pagenum"><a name="Pg_45" id="Pg_45">[45]</a></span> +prevent the drill from turning, a holder <i>B</i>, having a slot <i>s</i> in its +end through which the drill passes, is clamped in the toolpost, +as at <i>C</i>. This slot should be set central with the lathe centers, +and the drill, when being started, should be held tightly in the +slot by turning or twisting it with a wrench as indicated in the +end view at <i>D</i>; this steadies the drill and causes it to start +fairly true even though the cored hole runs out considerably.</p> + +<a name="Fig_1_42" id="Fig_1_42"></a> +<div class="figcenter"><div class="illobox450"><img src="images/053sm.png" alt="Rose and Fluted Reamers" /></div> +<p class="caption750">Fig. 42. Rose and Fluted Reamers</p> +</div> + +<p>Another style of tool for enlarging cored holes is shown in +<a href="#Fig_1_42">Fig. 42</a>, at <i>A</i>. This is a rose chucking reamer, having beveled +cutting edges on the end and a cylindrical body, which fits +closely in the reamed hole, thus supporting and guiding the +cutting end. The reamer shown at <i>B</i> is a fluted type with +cutting edges that extend from <i>a</i> to <i>b</i>; it is used for finishing +holes and the drill or rose reamer preceding it should leave the +hole very close to the required size. These reamers are held +while in use in a socket inserted in the tailstock spindle, as when +using a twist drill.</p> + +<a name="Fig_1_43" id="Fig_1_43"></a> +<div class="figcenter"><div class="illobox450"><img src="images/054sm.png" alt="Casting Clamped to Faceplate for Turning and Boring" /></div> +<p class="caption750">Fig. 43. Casting Clamped to Faceplate for Turning and Boring</p> +</div> + +<a name="Secnum_1_28" id="Secnum_1_28"></a><p><b>Holding Work on Faceplate.</b>—Some castings or forgings are +so shaped that they cannot be held in a chuck very well, or perhaps +not at all, and work of this kind is often clamped to a faceplate +which is usually larger than the faceplate used for driving +parts that are turned between the centers. An example of faceplate +work is shown in <a href="#Fig_1_43">Fig. 43</a>. This is a rectangular-shaped +casting having a round boss or projection, the end <i>e</i> of which is +to be turned parallel with the back face of the casting previously +finished on a planer. A rough cored hole through the +center of the boss also needs to be bored true.</p> + +<p>The best way to perform this operation in the lathe would be<span class="pagenum"><a name="Pg_46" id="Pg_46">[46]</a></span> +to clamp the finished surface of the casting directly against the +faceplate by bolts and clamps <i>a</i>, <i>b</i>, <i>c</i>, and <i>d</i>, as shown; the +work would then be turned just as though it were held in a +chuck. By holding the casting in this way, face <i>e</i> will be finished +parallel with the back surface because the latter is clamped +directly against the true-running surface of the faceplate. If a +casting of this shape were small enough it could also be held in +the jaws of an independent chuck, but if the surface e needs to +be exactly parallel with the back face, it is better to clamp the +work to the faceplate. Most lathes have two faceplates: One +of small diameter used principally for driving work turned between +centers, and a large one for holding heavy or irregularly +shaped pieces; either of these can be screwed onto the spindle, +and the large faceplate has a number of slots through which +clamping bolts can be inserted.</p> + +<p>The proper way to clamp a piece to the faceplate depends, of +course, largely on its shape and the location of the surface to be +machined, but in any case it is necessary to hold it securely to +prevent any shifting after a cut is started. Sometimes castings +can be held by inserting bolts through previously drilled holes, +but when clamps are used in connection with the bolts, their +outer ends are supported by hardwood or metal blocks which +should be just high enough to make the clamp bear evenly on<span class="pagenum"><a name="Pg_47" id="Pg_47">[47]</a></span> +the work. When deep roughing cuts have to be taken, especially +on large diameters, it is well to bolt a piece to the faceplate +and against one side of the casting, as at <i>D</i>, to act as a +driver and prevent the work from shifting; but a driver would +not be needed in this particular case. Of course a faceplate +driver is always placed to the rear, as determined by the direction +of rotation, because the work tends to shift backward when a +cut is being taken. If the surface which is clamped against the +faceplate is finished as in this case, the work will be less likely to +shift if a piece of paper is placed between it and the faceplate.</p> + +<p>Work mounted on the faceplate is generally set true by some +surface before turning. As the hole in this casting should be +true with the round boss, the casting is shifted on the faceplate +until the rough outer surface of the boss runs true; the clamps +which were previously set up lightly are then tightened. The +face e is first turned by using a round-nosed tool. This tool is +then replaced by a boring tool and the hole is finished to the +required diameter. If the hole being bored is larger than the +central hole in the faceplate, the casting should be clamped +against parallel pieces, and not directly against the faceplate, +to provide clearance for the tool when it reaches the inner end +of the hole and prevent it from cutting the faceplate. The +parallel pieces should be of the same thickness and be located +near the clamps to prevent springing the casting.</p> + +<a name="Fig_1_44" id="Fig_1_44"></a> +<div class="figcenter"><div class="illobox450"><img src="images/055sm.png" alt="Cast Elbow held on Angle-plate attached to Faceplate" /></div> +<p class="caption750">Fig. 44. Cast Elbow held on Angle-plate attached to Faceplate</p> +</div> + +<p><span class="pagenum"><a name="Pg_48" id="Pg_48">[48]</a></span> +<a name="Secnum_1_29" id="Secnum_1_29"></a><b>Application of Angle-plate to Faceplate.</b>—Another example +of faceplate work is shown in <a href="#Fig_1_44">Fig. 44</a>. This is a cast-iron elbow +<i>E</i>, the two flanges of which are to be faced true and square +with each other. The shape of this casting is such that it would +be very difficult to clamp it directly to the faceplate, but it is +easily held on an angle-plate <i>P</i>, which is bolted to the faceplate. +The two surfaces of this angle-plate are square with +each other so that when one flange of the elbow is finished and +bolted against the angle-plate, the other will be faced square. +When setting up an angle-plate for work of this kind, the distance +from its work-holding side to the center of the faceplate is +made equal to the distance <i>d</i> between the center of one flange +and the face of the other, so that the flange to be faced will run +about true when bolted in place. As the angle-plate and work +are almost entirely on one side of the faceplate, a weight <i>W</i> is +attached to the opposite side for counterbalancing. Very often +weights are also needed to counterbalance offset parts that +are bolted directly to the faceplate. The necessity of counterbalancing +depends somewhat upon the speed to be used for +turning. If the surface to be machined is small in diameter so +that the lathe can be run quite rapidly, any unbalanced part +should always be counterbalanced.</p> + +<p>Sometimes it is rather difficult to hold heavy pieces against +the vertical surface of the faceplate while applying the clamps, +and occasionally the faceplate is removed and placed in a horizontal +position on the bench; the work can then be located +about right, and after it is clamped, the faceplate is placed on +the lathe spindle by the assistance of a crane.</p> + +<p>Special faceplate jaws, such as the one shown to the right in +<a href="#Fig_1_33">Fig. 33</a>, can often be used to advantage for holding work on +large faceplates. Three or four of these jaws are bolted to the +faceplate which is converted into a kind of independent chuck. +These faceplate jaws are especially useful for holding irregularly +shaped parts, as the different jaws can be located in any position.</p> + +<a name="Fig_1_45" id="Fig_1_45"></a> +<div class="figcenter"><img src="images/057sm.jpg" alt="Rough Turning a Cylinder Lining" /> +<p class="caption750">Fig. 45. Rough Turning a Cylinder Lining—Note Method of Supporting +Outer End</p> +</div> + +<a name="Secnum_1_30" id="Secnum_1_30"></a><p><b>Supporting Outer End of Chucked Work.</b>—<a href="#Fig_1_45">Fig. 45</a> shows +how the tailstock center is sometimes used for supporting the +outer end of a long casting, the opposite end of which is held in<span class="pagenum"><a name="Pg_49" id="Pg_49">[49]</a></span> +a chuck. This particular casting is to be turned and bored to +make a lining for the cylinder of a locomotive in order to reduce +the diameter of the cylinder which has been considerably enlarged +by re-boring a number of times. These bushings are +rough-turned on the outside while the outer end is supported by +the cross-shaped piece or “spider” which forms a center-bearing +for the tailstock. This spider has set screws in the flanged +ends of the arms, which are tightened against the inner surface +of the casting and are adjusted one way or the other in order +to locate it in a concentric position. After roughing the outside, +the inside is bored to the finish size; then centered disks, which +fit into the bore, are placed in the ends of the bushing and the +latter is finish-turned. The object in rough turning the outside +prior to boring is to avoid the distortion which might occur if +this hard outer surface were removed last.</p> + +<a name="Secnum_1_31" id="Secnum_1_31"></a><p><b>Boring Large Castings in +the Lathe.</b>—An ordinary engine +lathe is sometimes used for boring engine or pump cylinders, +linings, etc., which are too large to be held in the chuck or on a +faceplate, and must be attached to the lathe carriage. As a +rule, work of this class is done in a special boring machine (see<span class="pagenum"><a name="Pg_50" id="Pg_50">[50]</a></span> +<a href="#Chapnum_7">“Horizontal Boring Machines”</a>), but if such a machine is not +available, it may be necessary to use a lathe. There are two +general methods of boring.</p> + +<a name="Fig_1_46" id="Fig_1_46"></a> +<div class="figcenter"><img src="images/058sm.jpg" alt="Boring a Cylinder Lining in an Ordinary Engine Lathe" /> +<p class="caption750">Fig. 46. Boring a Cylinder Lining in an Ordinary Engine Lathe</p> +</div> + +<p><a href="#Fig_1_46">Fig. 46</a> shows how the lining illustrated in <a href="#Fig_1_45">Fig. 45</a> is bored +in a large engine lathe. The casting is held in special fixtures +which are attached to the lathe carriage, and the boring-bar is +rotated by the lathe spindle. The tool-head of this boring-bar +carries two tools located 180 degrees apart and it is fed along +the bar by a star-feed mechanism shown attached to the bar +and the tailstock spindle. Each time the bar revolves, the star +wheel strikes a stationary pin and turns the feed-screw which, +as the illustration shows, extends along a groove cut in one +side of the bar. This feed-screw passes through a nut attached +to the tool-head so that the latter is slowly fed through the +bore. When using a bar of this type, the carriage, of course, +remains stationary.</p> + +<p>Cylindrical parts attached to the carriage can also be bored +by using a plain solid bar mounted between the centers. The +bar must be provided with a cutter for small holes or a tool-head +for larger diameters (preferably holding two or more tools)<span class="pagenum"><a name="Pg_51" id="Pg_51">[51]</a></span> +and the boring is done by feeding the carriage along the bed by +using the regular power feed of the lathe. A symmetrically +shaped casting like a bushing or lining is often held upon wooden +blocks bolted across the carriage. These are first cut away to +form a circular seat of the required radius, by using the boring-bar +and a special tool having a thin curved edge. The casting +is then clamped upon these blocks by the use of straps and +bolts, and if the curved seats were cut to the correct radius, +the work will be located concentric with the boring-bar. When +using a boring-bar of this type, the bar must be long enough to +allow the part being bored to feed from one side of the cutter-head +to the other, the cutter-head being approximately in a +central location.</p> + +<a name="Fig_1_47" id="Fig_1_47"></a> +<div class="figcenter"><div class="illobox450"><img src="images/059sm.png" alt="Method of Setting Circle on Work Concentric with Lathe Spindle" /></div> +<p class="caption750">Fig. 47. Method of Setting Circle on Work Concentric with Lathe Spindle</p> +</div> + +<a name="Secnum_1_32" id="Secnum_1_32"></a><p><b>Boring Holes to a Given Center Distance.</b>—In connection +with faceplate work, it is often necessary to bore two or more +holes at a given distance apart. The best method of doing this +may depend upon the accuracy required. For ordinary work +sometimes two or more circles <i>A</i> and <i>B</i> (<a href="#Fig_1_47">Fig. 47</a>) are drawn +upon the part to be bored, in the position for the holes; the +piece is then clamped to the faceplate and one of the circles is +centered with the lathe spindle by testing it with a pointer C +held in the toolpost; that is, when the pointer follows the circle +as the work is turned, evidently the circle is concentric with +the spindle. The hole is then drilled and bored. The other<span class="pagenum"><a name="Pg_52" id="Pg_52">[52]</a></span> +circle is then centered in the same way for boring the second +hole. As will be seen, the accuracy of this method depends +first, upon the accuracy with which the circles were laid out, +and second; upon the care taken in setting them concentric. +For a more accurate way of locating parts for boring, see “<a href="#Secnum_3_14">Use +of Center Indicator</a>” and “<a href="#Secnum_3_15">Locating Work by the Button +Method</a>.”</p> + +<a name="Secnum_1_33" id="Secnum_1_33"></a><p><b>Turning Brass, Bronze and +Copper.</b>—When turning soft +yellow brass, a tool should be used having very little or no +slope or rake on the top surface against which the chip bears, +and for plain cylindrical turning, the point of the tool is drawn +out quite thin and rounded, by grinding, to a radius of about +<sup class="enum">1</sup>/<sub class="denom">8</sub> or <sup class="enum">3</sup>/<sub class="denom">16</sub> +inch. If a tool having very much top slope is used for +brass, there is danger of its gouging into the metal, especially if +the part being turned is at all flexible. The clearance angle of +a brass tool is usually about 12 or 14 degrees, which is 3 or 4 +degrees greater than the clearance for steel turning tools. Most +brass is easily turned, as compared with steel, and for that +reason this increase in clearance is desirable, because it facilitates +feeding the tool into the metal, especially when the carriage +and cross-slide movements are being controlled by hand +as when turning irregular shapes.</p> + +<p>The speed for turning soft brass is much higher than for +steel, being ordinarily between 150 and 200 feet per minute. +When turning phosphor, tobin or other tough bronze compositions, +the tool should be ground with rake the same as for +turning steel, and lard oil is sometimes used as a lubricant. +The cutting speed for bronzes varies from 35 or 40 to 80 feet +per minute, owing to the difference in the composition of bronze +alloys.</p> + +<p>Turning tools for copper are ground with a little more top +rake than is given steel turning tools, and the point should be +slightly rounded. It is important to have a keen edge, and +a grindstone is recommended for sharpening copper turning +tools. Milk is generally considered the best lubricant to use +when turning copper. The speed can be nearly as fast as for +brass.</p> + +<p><span class="pagenum"><a name="Pg_53" id="Pg_53">[53]</a></span> +<a name="Secnum_1_34" id="Secnum_1_34"></a><b>Machining Aluminum.</b>—Tools for turning aluminum should +have acute cutting angles. After rough-grinding the tool, it is +advisable to finish sharpening the cutting edge on a grindstone +or with an oilstone for fine work, as a keen edge is very essential. +High speeds and comparatively light cuts are recommended. +The principal difficulty in the machining of aluminum and aluminum +alloys is caused by the clogging of the chips, especially +when using such tools as counterbores and milling cutters. +This difficulty can be avoided largely by using the right kind +of cutting lubricant. Soap-water and kerosene are commonly +employed. The latter enables a fine finish to be obtained, provided +the cutting tool is properly ground.</p> + +<p>The following information on this subject represents the experience +of the Brown-Lipe Gear Co., where aluminum parts +are machined in large quantities: For finishing bored holes, a +bar equipped with cutters has been found more practicable than +reamers. The cutters used for machining 4-inch holes have a +clearance of from 20 to 22 degrees and no rake or slope on the +front faces against which the chips bear. The roughing cutters +for this work have a rather sharp nose, being ground on the +point to a radius of about <sup class="enum">3</sup>/<sub class="denom">32</sub> inch, but for securing a smooth +surface, the finishing tools are rounded to a radius of about +<sup class="enum">3</sup>/<sub class="denom">4</sub> inch. The cutting speed, as well as the feed, for machining +aluminum is from 50 to 60 per cent faster than the speeds and +feeds for cast iron. The lubricant used by this company is +composed of one part “aqualine” and 20 parts water. This +lubricant not only gives a smooth finish but preserves a keen +cutting edge and enables tools to be used much longer without +grinding. Formerly, a lubricant composed of one part of high-grade +lard oil and one part of kerosene was used. This mixture +costs approximately 30 cents per gallon, whereas the aqualine +and water mixture now being used costs less than 4 cents per +gallon, and has proved more effective than the lubricant formerly +employed.</p> + +<hr class="c25" /> +<span class="pagenum"><a name="Pg_54" id="Pg_54">[54]</a></span> +<a name="Chapnum_2" id="Chapnum_2"></a><h2>CHAPTER II</h2> +<h3>LATHE TURNING TOOLS AND CUTTING SPEEDS</h3> +<hr class="c05" /> + +<p>Notwithstanding the fact that a great variety of work can +be done in the lathe, the number of turning tools required is +comparatively small. <a href="#Fig_2_1">Fig. 1</a> shows the forms of tools that are +used principally, and typical examples of the application of +these various tools are indicated in <a href="#Fig_2_2">Fig. 2</a>. The reference letters +used in these two illustrations correspond for tools of the same +type, and both views should be referred to in connection with +the following description.</p> + +<a name="Fig_2_1" id="Fig_2_1"></a> +<div class="figcenter"><div class="illobox450"><img src="images/063sm.png" alt="Set of Lathe Turning Tools for General Work" /></div> +<p class="caption750">Fig. 1. Set of Lathe Turning Tools for General Work</p> +</div> + +<a name="Fig_2_2" id="Fig_2_2"></a> +<div class="figcenter"><div class="illobox450"><img src="images/064sm.png" alt="Views illustrating Use of Various Types of Lathe Tools" /></div> +<p class="caption750">Fig. 2. Views illustrating Use of Various Types of Lathe Tools</p> +</div> + +<a name="Secnum_2_1" id="Secnum_2_1"></a><p><b>Turning Tools for General Work.</b>—The tool shown at <i>A</i> is +the form generally used for rough turning, that is for taking +deep cuts when considerable metal has to be removed. At <i>B</i> a +tool of the same type is shown, having a bent end which enables +it to be used close up to a shoulder or surface <i>s</i> that might come +in contact with the tool-rest if the straight form were employed. +Tool <i>C</i>, which has a straight cutting end, is used on certain +classes of work for taking light finishing cuts, with a coarse +feed. This type of tool has a flat or straight cutting edge at +the end, and will leave a smooth finish even though the feed is +coarse, provided the cutting edge is set parallel with the tool's +travel so as to avoid ridges. Broad-nosed tools and wide feeds +are better adapted for finishing cast iron than steel. When +turning steel, if the work is at all flexible, a broad tool tends to +gouge into it and for this reason round-nosed tools and finer +feeds are generally necessary. A little experience in turning +will teach more on this point than a whole chapter on the subject.</p> + +<p>The side-tools shown at <i>D</i> and <i>E</i> are for facing the ends of +shafts, collars, etc. The first tool is known as a right side-tool +because it operates on the right end or side of a shaft or collar, +whereas the left side-tool <i>E</i> is used on the opposite side, as shown +in <a href="#Fig_2_2">Fig. 2</a>. Side-tools are also bent to the right or left because +<span class="pagenum"><a name="Pg_55" id="Pg_55">[55]</a></span> +the cutting edge of a straight tool cannot always be located +properly for facing certain surfaces. A bent right side-tool is +shown at <i>F</i>. A form of tool that is frequently used is shown at +<i>G</i>; this is known as a parting tool and is used for severing pieces +and for cutting grooves, squaring corners, etc. The same type +of tool having a bent end is shown at <i>H</i> (<a href="#Fig_2_2">Fig. 2</a>) severing a piece +held in the chuck. Work that is held between centers should +not be entirely severed with a parting tool unless a steadyrest is<span class="pagenum"><a name="Pg_56" id="Pg_56">[56]</a></span> +placed between the tool and faceplate, as otherwise the tool may +be broken by the springing of the work just before the piece is +cut in two. It should be noted that the sides of this tool slope<span class="pagenum"><a name="Pg_57" id="Pg_57">[57]</a></span> +inward back of the cutting edge to provide clearance when +cutting in a narrow groove.</p> + +<p>At <i>I</i> a thread tool is shown for cutting a U. S. standard thread. +This thread is the form most commonly used in this country at +the present time. A tool for cutting a square thread is shown +at <i>J</i>. This is shaped very much like a parting tool except that +the cutting end is inclined slightly to correspond with the helix +angle of the thread, as explained in <a href="#Chapnum_4">Chapter IV</a>, which contains +descriptions of different thread forms and methods of cutting +them. Internal thread tools are shown at <i>K</i> and <i>L</i> for cutting +U. S. standard and square threads in holes. It will be seen +that these tools are somewhat like boring tools excepting the +ends which are shaped to correspond with the thread which +they are intended to cut.</p> + +<p>A tool for turning brass is shown at <i>M</i>. Brass tools intended +for general work are drawn out quite thin and they are given a +narrow rounded point. The top of the brass tool is usually +ground flat or without slope as otherwise it tends to gouge into +the work, especially if the latter is at all flexible. The end of a +brass tool is sometimes ground with a straight cutting edge for +turning large rigid work, such as brass pump linings, etc., so +that a coarse feed can be used without leaving a rough surface. +The tools at <i>N</i> and <i>O</i> are for boring or finishing drilled or cored +holes. Two sizes are shown, which are intended for small and +large holes, respectively.</p> + +<p>The different tools referred to in the foregoing might be called +the standard types because they are the ones generally used, +and as <a href="#Fig_2_2">Fig. 2</a> indicates, they make it possible to turn an almost +<span class="pagenum"><a name="Pg_58" id="Pg_58">[58]</a></span> +endless variety of forms. Occasionally some special form of +tool is needed for doing odd jobs, having, perhaps, an end bent +differently or a cutting edge shaped to some particular form. +Tools of the latter type, which are known as “form tools,” are +sometimes used for finishing surfaces that are either convex, +concave, or irregular in shape. The cutting edges of these +tools are carefully filed or ground to the required shape, and +the form given the tool is reproduced in the part turned. Ornamental +or other irregular surfaces can be finished very neatly +by the use of such tools. It is very difficult, of course, to turn +convex or concave surfaces with a regular tool; in fact, it would +not be possible to form a true spherical surface, for instance, +without special equipment, because the tool could not be moved +along a true curve by simply using the longitudinal and cross +feeds. Form tools should be sharpened by grinding entirely on +the top surface, as any grinding on the end or flank would alter +the shape of the tool.</p> + +<a name="Fig_2_3" id="Fig_2_3"></a> +<div class="figcenter"><img src="images/065sm.jpg" alt="Turning Tool with Inserted Cutter" /> +<p class="caption750">Fig. 3. Turning Tool with Inserted Cutter</p> +</div> + +<a name="Fig_2_4" id="Fig_2_4"></a> +<div class="figcenter"><img src="images/066sm.jpg" alt="Heavy Inserted-cutter Turning Tool" /> +<p class="caption750">Fig. 4. Heavy Inserted-cutter Turning Tool</p> +</div> + +<a name="Secnum_2_2" id="Secnum_2_2"></a><p><b>Tool-holders with Inserted Cutters.</b>—All of the tools shown +in Fig. 1 are forged from the bar, and when the cutting ends +have been ground down considerably it is necessary to forge a +new end. To eliminate the expense of this continual dressing of +tools and also to effect a great reduction in the amount of tool +steel required, tool-holders having small inserted cutters are +used in many shops. A tool-holder of this type, for outside +turning, is shown in <a href="#Fig_2_3">Fig. 3</a>. The cutter <i>C</i> is held in a fixed +position by the set-screw shown, and it is sharpened, principally, +by grinding the end, except when it is desired to give the top of<span class="pagenum"><a name="Pg_59" id="Pg_59">[59]</a></span> +the cutter a different slope from that due to its angular position. +Another inserted-cutter turning tool is shown in <a href="#Fig_2_4">Fig. 4</a>, which +is a heavy type intended for roughing. The cutter in this case +has teeth on the rear side engaging with corresponding teeth +cut in the clamping block which is tightened by a set-screw on +the side opposite that shown. With this arrangement, the cutter +can be adjusted upward as the top is ground away.</p> + +<a name="Fig_2_5" id="Fig_2_5"></a> +<div class="figcenter"><img src="images/067asm.jpg" alt="Parting Tool with Inserted Blade" /> +<p class="caption750">Fig. 5. Parting Tool with Inserted Blade</p> +</div> + +<a name="Fig_2_6" id="Fig_2_6"></a> +<div class="figcenter"><img src="images/067bsm.jpg" alt="Boring Tool with Inserted Cutter and Adjustable Bar" /> +<p class="caption750">Fig. 6. Boring Tool with Inserted Cutter and Adjustable Bar</p> +</div> + +<a name="Fig_2_7" id="Fig_2_7"></a> +<div class="figcenter"><img src="images/068sm.jpg" alt="Threading Tool" /> +<p class="caption750">Fig. 7. Threading Tool</p> +</div> + +<p>A parting tool of the inserted blade type is shown in <a href="#Fig_2_5">Fig. 5</a>. +The blade <i>B</i> is clamped by screw <i>S</i> and also by the spring of +the holder when the latter is clamped in the toolpost. The +blade can, of course, be moved outward when necessary. <a href="#Fig_2_6">Fig. 6</a> +shows a boring tool consisting of a holder <i>H</i>, a bar <i>B</i> that can +be clamped in any position, and an inserted cutter <i>C</i>. With this +type of boring tool, the bar can be extended beyond the holder +just far enough to reach through the hole to be bored, which +makes the tool very rigid. A thread tool of the holder type is +shown in <a href="#Fig_2_7">Fig. 7</a>. The angular edge of the cutter <i>C</i> is accurately +<span class="pagenum"><a name="Pg_60" id="Pg_60">[60]</a></span> +ground by the manufacturers, so that the tool is sharpened by +simply grinding it flat on the top. As the top is ground away, +the cutter is raised by turning screw <i>S</i>, which can also be used +for setting the tool to the proper height.</p> + +<a name="Fig_2_8" id="Fig_2_8"></a> +<div class="figcenter"><div class="illobox450"><img src="images/069sm.png" alt="To Avoid springing, Overhang A of Tool should not be Excessive" /></div> +<p class="caption750">Fig. 8. To avoid springing, Overhang A of Tool should not be Excessive</p> +</div> + +<a name="Secnum_2_3" id="Secnum_2_3"></a><p><b>The Position of Turning Tools.</b>—The production of accurate +lathe work depends partly on the condition of the lathe used +and also on the care and judgment exercised by the man operating +it. Even though a lathe is properly adjusted and in good +condition otherwise, errors are often made which are due to +other causes which should be carefully avoided. If the turning +tool is clamped so that the cutting end extends too far from the +supporting block, the downward spring of the tool, owing to +the thrust of the cut, sometimes results in spoiled work, especially +when an attempt is made to turn close to the finished +size by taking a heavy roughing cut. Suppose the end of a +cylindrical part is first reduced for a short distance by taking +several trial cuts until the diameter <i>d</i>, <a href="#Fig_2_8">Fig. 8</a>, is slightly above +the finished size and the power feed is then engaged. When +the tool begins to take the full depth <i>e</i> of the cut, the point, +which ordinarily would be set a little above the center, tends to +spring downward into the work, and if there were considerable +springing action, the part would probably be turned below the +finished size, the increased reduction beginning at the point +where the full cut started.</p> + +<p>This springing action, as far as the tool is concerned, can be +practically eliminated by locating the tool so that the distance<span class="pagenum"><a name="Pg_61" id="Pg_61">[61]</a></span> +<i>A</i> between the tool-block and cutting end, or the “overhang,” +is as short as possible. Even though the tool has little overhang +it may tilt downward because the toolslide is loose on its ways, +and for this reason the slide should have a snug adjustment +that will permit an easy movement without unnecessary play. +The toolslides of all lathes are provided with gibs which can +be adjusted by screws to compensate for wear, or to secure a +more rigid bearing.</p> + +<a name="Fig_2_9" id="Fig_2_9"></a> +<div class="figcenter"><div class="illobox450"><img src="images/070sm.png" alt="Tool Displacement" /></div> +<p class="caption750">Fig. 9. (A) The Way in which Tool is sometimes displaced by Thrust of Cut, +when set at an Angle.<br />(B) Tool Set for Finishing both Cylindrical and +Radial Surfaces</p> +</div> + +<p>When roughing cuts are to be taken, the tool should be located +so that any change in its position which might be caused by the +pressure of the cut will not spoil the work. This point is illustrated +at <i>A</i> in <a href="#Fig_2_9">Fig. 9</a>. Suppose the end of a rod has been reduced +by taking a number of trial cuts, until it is <sup class="enum">1</sup>/<sub class="denom">32</sub> inch above the +finished size. If the power feed is then engaged with the tool +clamped in an oblique position, as shown, when the full cut is +encountered at <i>c</i>, the tool, unless very tightly clamped, may be +shifted backward by the lateral thrust of the cut, as indicated +by the dotted lines. The point will then begin turning smaller +than the finished size and the work will be spoiled. To prevent +any change of position, it is good practice, especially when +roughing, to clamp the tool square with the surface being turned, +or in other words, at right angles to its direction of movement. +Occasionally, however, there is a decided advantage in having<span class="pagenum"><a name="Pg_62" id="Pg_62">[62]</a></span> +the tool set at an angle. For example, if it is held about as +shown at <i>B</i>, when turning the flange casting <i>C</i>, the surfaces <i>s</i> +and <i>s<sub>1</sub></i> can be finished without changing the tool's position. +Cylindrical and radial surfaces are often turned in this way +in order to avoid shifting the tool, especially when machining +parts in quantity.</p> + +<a name="Secnum_2_4" id="Secnum_2_4"></a><p><b>Tool Grinding.</b>—In the grinding of lathe tools there are +three things of importance to be considered: First, the cutting +edge of the tool (as viewed from the top) needs to be given a +certain shape; second, there must be a sufficient amount of +clearance for the cutting edge; and third, tools, with certain +exceptions, are ground with a backward slope or a side slope, +or with a combination of these two slopes on that part against +which the chip bears when the tool is in use.</p> + +<a name="Fig_2_10" id="Fig_2_10"></a> +<div class="figcenter"><div class="illobox450"><img src="images/071sm.png" alt="Illustration showing the Meaning of Terms used in Tool Grinding as applied to Tools of Different Types" /></div> +<p class="caption750">Fig. 10. Illustration showing the Meaning of Terms used<br />in Tool +Grinding as applied to Tools of Different Types</p> +</div> + +<p>In <a href="#Fig_2_10">Fig. 10</a> a few of the different types of tools which are used +in connection with lathe work are shown. This illustration also +indicates the meaning of the various terms used in tool grinding. +As shown, the clearance of the tool is represented by the +angle <i>α</i>, the back slope is represented by the angle <i>β</i>, and the +side slope by the angle <i>γ</i>. The angle <i>δ</i> for a tool without side +slope is known as the lip angle or the angle of keenness. When,<span class="pagenum"><a name="Pg_63" id="Pg_63">[63]</a></span> +however, the tool has both back and side slopes, this lip angle +would more properly be the angle between the flank <i>f</i> and the +top of the tool, measured diagonally along a line <i>z—z</i>. It will +be seen that the lines <i>A—B</i> and <i>A—C</i> from which the angles +of clearance and back slope are measured are parallel with the +top and sides of the tool shank, respectively. For lathe tools, +however, these lines are not necessarily located in this way +when the tool is in use, as the height of the tool point with +relation to the work center determines the position of these +lines, so that the <i>effective</i> angles of back slope, clearance and +keenness are changed as the tool point is lowered or raised. +The way the position of the tool affects these angles will be +explained later.</p> + +<p>While tools must, of necessity, be varied considerably in shape +to adapt them to various purposes, there are certain underlying +principles governing their shape which apply generally; +so in what follows we shall not attempt to explain in detail just +what the form of each tool used on the lathe should be, as it is +more important to understand how the cutting action of the +tool and its efficiency is affected when it is improperly ground.<span class="pagenum"><a name="Pg_64" id="Pg_64">[64]</a></span> +When the principle is understood, the grinding of tools of various +types and shapes is comparatively easy.</p> + +<a name="Fig_2_11" id="Fig_2_11"></a> +<div class="figcenter"><div class="illobox450"><img src="images/072sm.png" alt="Plan View of Lathe Turning and Threading Tools" /></div> +<p class="caption750">Fig. 11. Plan View of Lathe Turning and Threading Tools</p> +</div> + +<a name="Secnum_2_5" id="Secnum_2_5"></a><p><b>Shape or Contour of Cutting Edge.</b>—In the first place we +shall consider the shape or contour of the cutting edge of the +tool as viewed from the top, and then take up the question of +clearance and slope, the different elements being considered +separately to avoid confusion. The contour of the cutting edge +depends primarily upon the purpose for which the tool is intended. +For example, the tool <i>A</i>, in <a href="#Fig_2_11">Fig. 11</a>, where a plan view +of a number of different lathe tools is shown, has a very different +shape from that of, say, tool <i>D</i>, as the first tool is used for rough +turning, while tool <i>D</i> is intended for cutting grooves or severing +a turned part. Similarly, tool <i>E</i> is V-shaped because it is used +for cutting V-threads. Tools <i>A</i>, <i>B</i> and <i>C</i>, however, are regular +turning tools; that is, they are all intended for turning plain +cylindrical surfaces, but the contour of the cutting edges varies +considerably, as shown. In this case it is the characteristics of +the work and the cut that are the factors which determine the +shape. To illustrate, tool <i>A</i> is of a shape suitable for rough-turning +large and rigid work, while tool <i>B</i> is adapted for smaller +and more flexible parts. The first tool is well shaped for roughing +because experiments have shown that a cutting edge of a +large radius is capable of higher cutting speed than could be +used with a tool like <i>B</i>, which has a smaller point. This increase<span class="pagenum"> +<a name="Pg_65" id="Pg_65">[65]</a></span> +in the cutting speed is due to the fact that the tool <i>A</i> +removes a thinner chip for a given feed than tool <i>B</i>; therefore, +the speed may be increased without injuring the cutting edge +to the same extent. If, however, tool <i>A</i> were to be used for +turning a long and flexible part, chattering might result; consequently, +a tool <i>B</i> having a point with a smaller radius would +be preferable, if not absolutely necessary.</p> + +<p>The character of the work also affects the shape of tools. +The tool shown at <i>C</i> is used for taking light finishing cuts with +a wide feed. Obviously, if the straight or flat part of the cutting +edge is in line with the travel of the tool, the cut will be smooth +and free from ridges, even though the feed is coarse, and by +using a coarse feed the cut is taken in less time; but such a +tool cannot be used on work that is not rigid, as chattering +would result. Therefore, a smaller cutting point and a reduced +feed would have to be employed. Tools with broad flat cutting +edges and coarse feeds are often used for taking finishing cuts +in cast iron, as this metal offers less resistance to cutting than +steel, and is less conducive to chattering.</p> + +<p>The shape of a tool (as viewed from the top) which is intended +for a more specific purpose than regular turning, can be largely +determined by simply considering the tool under working conditions. +This point may be illustrated by the parting tool <i>D</i> +which, as previously stated, is used for cutting grooves, squaring +corners, etc. Evidently this tool should be widest at the +cutting edge; that is, the sides <i>d</i> should have a slight amount +of clearance so that they will not bind as the tool is fed into a +groove. As the tool at <i>E</i> is for cutting a V-thread, the angle <i>α</i> +between its cutting edges must equal the angle between the +sides of a V-thread, or 60 degrees. The tool illustrated at <i>F</i> is +for cutting inside square threads. In this case the width <i>w</i> +should be made equal to one-half the pitch of the thread (or +slightly greater to provide clearance for the screw), and the +sides should be given a slight amount of side clearance, the +same as with the parting tool <i>D</i>. So we see that the outline of +the tool, as viewed from the top, must conform to and be governed +by its use.</p> + +<a name="Secnum_2_6" id="Secnum_2_6"></a><p><span class="pagenum"><a name="Pg_66" id="Pg_66">[66]</a></span> +<b>Direction of Top Slope for Turning Tools.</b>—Aside from the +question of the shape of the cutting edge as viewed from the +top, there remains to be determined the amount of clearance +that the tool shall have, and also the slope (and its direction) of +the top of the tool. By the top is meant that surface against +which the chip bears while it is being severed. It may be stated, +in a general way, that the direction in which the top of the tool +should slope should be away from what is to be the <i>working +part</i> of the cutting edge. For example, the working edge of a +roughing tool <i>A</i> (<a href="#Fig_2_11">Fig. 11</a>), which is used for heavy cuts, would +be, practically speaking, between points <i>a</i> and <i>b</i>, or, in other +words, most of the work would be done by this part of the cutting +edge; therefore the top should slope back from this part +of the edge. Obviously, a tool ground in this way will have +both a back and a side slope.</p> + +<p>When most of the work is done on the point or nose of the +tool, as, for example, with the lathe finishing tool <i>C</i> which takes +light cuts, the slope should be straight back from the point or +cutting edge <i>a—b</i>. As the side tool shown in <a href="#Fig_2_10">Fig. 10</a> does its +cutting along the edge <i>a—b</i>, the top is given a slope back from +this edge as shown in the end view. This point should be +remembered, for when the top slopes in the right direction, less +power is required for cutting. Tools for certain classes of work, +such as thread tools, or those for turning brass or chilled iron, +are ground flat on top, that is, without back or side slope.</p> + +<a name="Secnum_2_7" id="Secnum_2_7"></a><p><b>Clearance for the Cutting Edge.</b>—In order that the cutting +edge may work without interference, it must have clearance; +that is, the flank <i>f</i> (Fig. 10) must be ground to a certain angle <i>α</i> +so that it will not rub against the work and prevent the cutting +edge from entering the metal. This clearance should be just +enough to permit the tool to cut freely. A clearance angle of +eight or ten degrees is about right for lathe turning tools.</p> + +<a name="Fig_2_12" id="Fig_2_12"></a> +<div class="figcenter"><div class="illobox450"><img src="images/075sm.png" alt="Illustrations showing how Effective Angles of Slope and Clearance change as Tool is raised or lowered" /></div> +<p class="caption750">Fig. 12. Illustrations showing how Effective Angles of Slope<br />and +Clearance change as Tool is raised or lowered</p> +</div> + +<p>The back slope of a tool is measured from a line <i>A—B</i> which is +parallel to the shank, and the clearance angle, from a line <i>A—C</i> +at right angles to line <i>A—B</i>. These lines do not, however, always +occupy this position with relation to the tool shank when +the tool is in use. As shown to the left in <a href="#Fig_2_12">Fig. 12</a>, the base line +<span class="pagenum"><a name="Pg_67" id="Pg_67">[67]</a></span> +<i>A—B</i> for a turning tool in use intersects with the point of the +tool and center of the work, while the line <i>A—C</i> remains at right +angles to the first. It will be seen, then, that by raising the +tool, as shown to the right, the <i>effective</i> clearance angle <i>α</i> will +be diminished, whereas lowering it, as shown by the dotted +lines, will have the opposite effect.</p> + +<p>A turning tool for brass or other soft metal, particularly +where considerable hand manipulation is required, could advantageously +have a clearance of twelve or fourteen degrees, +as it would then be easier to feed the tool into the metal; but, +generally speaking, the clearance for turning tools should be +just enough to permit them to cut freely. Excessive clearance +weakens the cutting edge and may cause it to crumble under +the pressure of the cut.</p> + +<a name="Secnum_2_8" id="Secnum_2_8"></a><p><b>Angle of Tool-point and Amount of Top Slope.</b>—The lip +angle or the angle of keenness <i>δ</i> (<a href="#Fig_2_10">Fig. 10</a>) is another important +consideration in connection with tool grinding, for it is upon +this angle that the efficiency of the tool largely depends. By +referring to the illustration it will be seen that this angle is +governed by the clearance and the slope <i>β</i>, and as the clearance +remains practically the same, it is the slope which is varied to +meet different conditions. Now, the amount of slope a tool +should have depends on the work for which it is intended. If, +for example, a turning tool is to be used for roughing medium +or soft steel, it should have a back slope of about eight degrees +and a side slope ranging from fourteen to twenty degrees, while +<span class="pagenum"><a name="Pg_68" id="Pg_68">[68]</a></span> +a tool for cutting very hard steel should have a back slope of +about five degrees and a side slope of nine degrees.</p> + +<a name="Fig_2_13" id="Fig_2_13"></a> +<div class="figcenter"><img src="images/076sm.jpg" alt="Blunt Tool for Turning Hard Steel, Tool-point Ground to give Keenness" /> +<p class="caption750">Fig. 13. (A) Blunt Tool for Turning Hard Steel.<br />(B) Tool-point +Ground to give Keenness</p> +</div> + +<p>The reason for decreasing the slope and thus increasing the +lip angle for harder metals is to give the necessary increased +strength to the cutting edge to prevent it from crumbling under +the pressure of the cut. The tool illustrated at <i>A</i>, <a href="#Fig_2_13">Fig. 13</a>, is +much stronger than it would be if ground as shown at <i>B</i>, as +the former is more blunt. If a tool ground as at <i>A</i>, however, +were used for cutting very soft steel, there would be a greater +chip pressure on the top and, consequently, a greater resistance +to cutting, than if a keener tool had been employed; furthermore +the cutting speed would have to be lower, which is of +even greater importance than the chip pressure; therefore, the +lip angle, as a general rule, should be as small as possible without +weakening the tool so that it cannot do the required work. +In order to secure a strong and well-supported cutting edge, +tools used for turning very hard metal, such as chilled rolls, +etc., are ground with practically no slope and with very little +clearance. Brass tools, while given considerable clearance, as +previously stated, are ground flat on top or without slope; this +is not done, however, to give strength to the cutting edge, but +rather to prevent the tool from gouging into the work, which it +is likely to do if the part being turned is at all flexible and the +tool has top slope.</p> + +<p>Experiments conducted by Mr. F. W. Taylor to determine +the most efficient form for lathe roughing tools showed that the<span class="pagenum"><a name="Pg_69" id="Pg_69">[69]</a></span> +nearer the lip angle approached sixty-one degrees, the higher +the cutting speed. This, however, does not apply to tools for +turning cast iron, as the latter will work more efficiently with a +lip angle of about sixty-eight degrees. This is doubtless because +the chip pressure, when turning cast iron, comes closer +to the cutting edge which should, therefore, be more blunt to +withstand the abrasive action and heat. Of course, the foregoing +remarks concerning lip angles apply more particularly to +tools used for roughing.</p> + +<a name="Fig_2_14" id="Fig_2_14"></a> +<div class="figcenter"><img src="images/077sm.jpg" alt="Grinding the Top and Flank of a Turning Tool" /> +<p class="caption750">Fig. 14. Grinding the Top and Flank of a Turning Tool</p> +</div> + +<a name="Secnum_2_9" id="Secnum_2_9"></a><p><b>Grinding a Lathe Tool.</b>—The way a turning tool is held +while the top surface is being ground is shown to the left in +<a href="#Fig_2_14">Fig. 14</a>. By inclining the tool with the wheel face, it will be +seen that both the back and side slopes may be ground at the +same time. When grinding the flank of the tool it should be +held on the tool-rest of the emery wheel or grindstone, as shown +by the view to the right. In order to form a curved cutting +edge, the tool is turned about the face of the stone while it is +being ground. This rotary movement can be effected by supporting +the inner end of the tool with one hand while the shank +is moved to and fro with the other.</p> + +<p>Often a tool which has been ground properly in the first place +is greatly misshapen after it has been sharpened a few times. +This is usually the result of attempts on the part of the workman +to re-sharpen it hurriedly; for example, it is easier to secure<span class="pagenum"><a name="Pg_70" id="Pg_70">[70]</a></span> +a sharp edge on the turning tool shown to the left in <a href="#Fig_2_12">Fig. 12</a>, by +grinding the flank as indicated by the dotted line, than by +grinding the entire flank. The clearance is, however, reduced +and the lip angle changed.</p> + +<p>There is great danger when grinding a tool of burning it or +drawing the temper from the fine cutting edge, and, aside from +the actual shape of the cutting end, this is the most important +point in connection with tool grinding. If a tool is pressed +hard against an emery or other abrasive wheel, even though the +latter has a copious supply of water, the temper will sometimes +be drawn. When grinding a flat surface, to avoid burning, the +tool should frequently be withdrawn from the stone so that the +cooling water (a copious supply of which should be provided) +can reach the surface being ground. A moderate pressure +should also be applied, as it is better to spend an extra minute +or two in grinding than to ruin the tool by burning, in an attempt +to sharpen it quickly. Of course, what has been said +about burning applies more particularly to carbon steel, but +even self-hardening steels are not improved by being over-heated +at the stone. In some shops, tools are ground to the +theoretically correct shape in special machines instead of by +hand. The sharpened tools are then kept in the tool-room and +are given out as they are needed.</p> + +<a name="Secnum_2_10" id="Secnum_2_10"></a><p><b>Cutting Speeds and Feeds.</b>—The term cutting speed as applied +to turning operations is the speed in feet per minute of +the surface being turned, or, practically speaking, it is equivalent +to the length of a chip, in feet, which would be turned in +one minute. The term cutting speed should not be confused +with revolutions per minute, because the cutting speed depends +not only upon the speed of the work but also upon its diameter. +The feed of a tool is the amount it moves across the surface +being turned for each revolution; that is, when turning a cylindrical +piece, the feed is the amount that the tool moves sidewise +for each revolution of the work. Evidently the time required +for turning is governed largely by the cutting speed, the feed, +and the depth of the cut; therefore, these elements should be +carefully considered.</p> + +<p class="pagenum"><a name="Pg_71" id="Pg_71">[71]</a></p> +<h4>Cutting Speeds and Feeds for Turning Tools<a name="Fnanchor_1" id="Fnanchor_1"></a><a href="#Fn_1" class="fnanchor">[1]</a></h4> + +<table align="center" class="center" width="80%" cellpadding="0" cellspacing="0" summary="Cutting Speeds"> + +<tr><td class="bt bl" colspan="8">Steel—Standard <sup class="enum">7</sup>/<sub class="denom">8</sub>-inch Tool</td> +<td class="bt bl br" colspan="8">Cast Iron—Standard <sup class="enum">7</sup>/<sub class="denom">8</sub>-inch Tool +</td></tr> + +<tr><td class="bt bl" rowspan="2">Depth of Cut in Inches</td> +<td class="bt bl" rowspan="2">Feed in Inches</td> +<td class="bt bl" colspan="6">Speed in Feet per Minute for a Tool which is to last 1<sup class="enum">1</sup>/<sub class="denom">2</sub> +Hour before Re-grinding</td> +<td class="bt bl" rowspan="2">Depth of Cut in Inches</td> +<td class="bt bl" rowspan="2">Feed in Inches</td> +<td class="bt bl br" colspan="6">Speed in Feet per Minute for a Tool which is to last 1<sup class="enum">1</sup>/<sub class="denom">2</sub> +Hour before Re-grinding</td></tr> + +<tr><td class="bt bl" colspan="2">Soft<br />Steel</td> +<td class="bt bl" colspan="2">Medium<br />Steel</td> +<td class="bt bl" colspan="2">Hard<br />Steel</td> +<td class="bt bl" colspan="2">Soft<br />Cast Iron</td> +<td class="bt bl" colspan="2">Medium<br />Cast Iron</td> +<td class="bt bl br" colspan="2">Hard<br />Cast Iron</td></tr> + +<tr> +<td class="bt bl" rowspan="4" style="width: 10%"><sup class="enum">3</sup>/<sub class="denom">32</sub></td> +<td class="bt bl" style="width: 10%"><sup class="enum">1</sup>/<sub class="denom">64</sub></td> +<td class="bt bl" align="right" style="width: 6%">476</td> +<td class="bt" align="left" style="width: 4%"> </td> +<td class="bt bl" align="right" style="width: 6%">238</td> +<td class="bt" align="left" style="width: 4%"> </td> +<td class="bt bl" align="right" style="width: 6%">108</td> +<td class="bt" align="left" style="width: 4%"> </td> +<td class="bt bl" rowspan="3" style="width: 10%"><sup class="enum">3</sup>/<sub class="denom">32</sub></td> +<td class="bt bl" style="width: 10%"><sup class="enum">1</sup>/<sub class="denom">16</sub></td> +<td class="bt bl" align="right" style="width: 6%">122</td> +<td class="bt" align="left" style="width: 4%"> </td> +<td class="bt bl" align="right" style="width: 6%">61</td> +<td class="bt" align="left" style="width: 4%">.2</td> +<td class="bt bl" align="right" style="width: 6%">35</td> +<td class="bt br" align="left" style="width: 4%">.7</td> +</tr> + +<tr> +<td class="bt bl" ><sup class="enum">1</sup>/<sub class="denom">32</sub></td> +<td class="bt bl" align="right">325</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">162</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">73</td> +<td class="bt" align="left">.8</td> +<td class="bt bl" ><sup class="enum">1</sup>/<sub class="denom">8</sub></td> +<td class="bt bl" align="right">86</td> +<td class="bt" align="left">.4</td> +<td class="bt bl" align="right">43</td> +<td class="bt" align="left">.2</td> +<td class="bt bl" align="right">25</td> +<td class="bt br" align="left">.2</td> +</tr> + +<tr> +<td class="bt bl" ><sup class="enum">1</sup>/<sub class="denom">16</sub></td> +<td class="bt bl" align="right">222</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">111</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">50</td> +<td class="bt" align="left">.4</td> +<td class="bt bl" ><sup class="enum">3</sup>/<sub class="denom">16</sub></td> +<td class="bt bl" align="right">70</td> +<td class="bt" align="left">.1</td> +<td class="bt bl" align="right">35</td> +<td class="bt" align="left">.1</td> +<td class="bt bl" align="right">20</td> +<td class="bt br" align="left">.5</td> +</tr> + +<tr> +<td class="bt bl" ><sup class="enum">3</sup>/<sub class="denom">32</sub></td> +<td class="bt bl" align="right">177</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">88</td> +<td class="bt" align="left">.4</td> +<td class="bt bl" align="right">40</td> +<td class="bt" align="left">.2</td> +<td class="bt bl" rowspan="4"><sup class="enum">1</sup>/<sub class="denom">8</sub></td> +<td class="bt bl" ><sup class="enum">1</sup>/<sub class="denom">32</sub></td> +<td class="bt bl" align="right">156</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">77</td> +<td class="bt" align="left">.8</td> +<td class="bt bl" align="right">45</td> +<td class="bt br" align="left">.4</td> +</tr> + +<tr> +<td class="bt bl" rowspan="4"><sup class="enum">1</sup>/<sub class="denom">8</sub></td> +<td class="bt bl"><sup class="enum">1</sup>/<sub class="denom">64</sub></td> +<td class="bt bl" align="right">420</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">210</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">95</td> +<td class="bt" align="left">.5</td> +<td class="bt bl"><sup class="enum">1</sup>/<sub class="denom">16</sub></td> +<td class="bt bl" align="right">112</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">56</td> +<td class="bt" align="left">.2</td> +<td class="bt bl" align="right">32</td> +<td class="bt br" align="left">.8</td> +</tr> + +<tr> +<td class="bt bl"><sup class="enum">1</sup>/<sub class="denom">32</sub></td> +<td class="bt bl" align="right">286</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">143</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">65</td> +<td class="bt" align="left">.0</td> +<td class="bt bl"><sup class="enum">1</sup>/<sub class="denom">8</sub></td> +<td class="bt bl" align="right">79</td> +<td class="bt" align="left">.3</td> +<td class="bt bl" align="right">39</td> +<td class="bt" align="left">.7</td> +<td class="bt bl" align="right">23</td> +<td class="bt br" align="left">.2</td> +</tr> + +<tr> +<td class="bt bl"><sup class="enum">1</sup>/<sub class="denom">16</sub></td> +<td class="bt bl" align="right">195</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">97</td> +<td class="bt" align="left">.6</td> +<td class="bt bl" align="right">44</td> +<td class="bt" align="left">.4</td> +<td class="bt bl"><sup class="enum">3</sup>/<sub class="denom">16</sub></td> +<td class="bt bl" align="right">64</td> +<td class="bt" align="left">.3</td> +<td class="bt bl" align="right">32</td> +<td class="bt" align="left">.2</td> +<td class="bt bl" align="right">18</td> +<td class="bt br" align="left">.8</td> +</tr> + +<tr> +<td class="bt bl"><sup class="enum">1</sup>/<sub class="denom">8</sub></td> +<td class="bt bl" align="right">133</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">66</td> +<td class="bt" align="left">.4</td> +<td class="bt bl" align="right">30</td> +<td class="bt" align="left">.2</td> +<td rowspan="4" class="bl bt"><sup class="enum">3</sup>/<sub class="denom">16</sub></td> +<td class="bt bl"><sup class="enum">1</sup>/<sub class="denom">32</sub></td> +<td class="bt bl" align="right">137</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">68</td> +<td class="bt" align="left">.6</td> +<td class="bt bl" align="right">40</td> +<td class="bt br" align="left">.1</td> +</tr> + +<tr> +<td rowspan="4" class="bl bt"><sup class="enum">3</sup>/<sub class="denom">16</sub></td> +<td class="bt bl"><sup class="enum">1</sup>/<sub class="denom">64</sub></td> +<td class="bt bl" align="right">352</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">176</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">80</td> +<td class="bt" align="left">.0</td> +<td class="bt bl"><sup class="enum">1</sup>/<sub class="denom">16</sub></td> +<td class="bt bl" align="right">99</td> +<td class="bt" align="left">.4</td> +<td class="bt bl" align="right">49</td> +<td class="bt" align="left">.7</td> +<td class="bt bl" align="right">29</td> +<td class="bt br" align="left">.0</td> +</tr> + +<tr> +<td class="bt bl"><sup class="enum">1</sup>/<sub class="denom">32</sub></td> +<td class="bt bl" align="right">240</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">120</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">54</td> +<td class="bt" align="left">.5</td> +<td class="bt bl"><sup class="enum">1</sup>/<sub class="denom">8</sub></td> +<td class="bt bl" align="right">70</td> +<td class="bt" align="left">.1</td> +<td class="bt bl" align="right">35</td> +<td class="bt" align="left">.0</td> +<td class="bt bl" align="right">20</td> +<td class="bt br" align="left">.5</td> +</tr> + +<tr> +<td class="bt bl"><sup class="enum">1</sup>/<sub class="denom">16</sub></td> +<td class="bt bl" align="right">164</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">82</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">37</td> +<td class="bt" align="left">.3</td> +<td class="bt bl"><sup class="enum">3</sup>/<sub class="denom">16</sub></td> +<td class="bt bl" align="right">56</td> +<td class="bt" align="left">.8</td> +<td class="bt bl" align="right">28</td> +<td class="bt" align="left">.4</td> +<td class="bt bl" align="right">16</td> +<td class="bt br" align="left">.6</td> +</tr> + +<tr> +<td class="bt bl"><sup class="enum">1</sup>/<sub class="denom">8</sub></td> +<td class="bt bl" align="right">112</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">56</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">25</td> +<td class="bt" align="left">.5</td> +<td rowspan="4" class="bt bl"><sup class="enum">1</sup>/<sub class="denom">4</sub></td> +<td class="bt bl"><sup class="enum">1</sup>/<sub class="denom">32</sub></td> +<td class="bt bl" align="right">126</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">62</td> +<td class="bt" align="left">.9</td> +<td class="bt bl" align="right">36</td> +<td class="bt br" align="left">.7</td> +</tr> + +<tr> +<td class="bt bl" rowspan="4"><sup class="enum">1</sup>/<sub class="denom">4</sub></td> +<td class="bt bl"><sup class="enum">1</sup>/<sub class="denom">64</sub></td> +<td class="bt bl" align="right">312</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">156</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">70</td> +<td class="bt" align="left">.9</td> +<td class="bt bl"><sup class="enum">1</sup>/<sub class="denom">16</sub></td> +<td class="bt bl" align="right">90</td> +<td class="bt" align="left">.8</td> +<td class="bt bl" align="right">45</td> +<td class="bt" align="left">.4</td> +<td class="bt bl" align="right">26</td> +<td class="bt br" align="left">.5</td> +</tr> + +<tr> +<td class="bt bl"><sup class="enum">1</sup>/<sub class="denom">32</sub></td> +<td class="bt bl" align="right">213</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">107</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">48</td> +<td class="bt" align="left">.4</td> +<td class="bt bl"><sup class="enum">1</sup>/<sub class="denom">8</sub></td> +<td class="bt bl" align="right">64</td> +<td class="bt" align="left">.1</td> +<td class="bt bl" align="right">32</td> +<td class="bt" align="left">.0</td> +<td class="bt bl" align="right">18</td> +<td class="bt br" align="left">.7</td> +</tr> + +<tr> +<td class="bt bl"><sup class="enum">1</sup>/<sub class="denom">16</sub></td> +<td class="bt bl" align="right">145</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">72</td> +<td class="bt" align="left">.6</td> +<td class="bt bl" align="right">33</td> +<td class="bt" align="left">.0</td> +<td class="bt bl"><sup class="enum">3</sup>/<sub class="denom">16</sub></td> +<td class="bt bl" align="right">52</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">26</td> +<td class="bt" align="left">.0</td> +<td class="bt bl" align="right">15</td> +<td class="bt br" align="left">.2</td> +</tr> + +<tr> +<td class="bt bl"><sup class="enum">3</sup>/<sub class="denom">32</sub></td> +<td class="bt bl" align="right">116</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">58</td> +<td class="bt" align="left">.1</td> +<td class="bt bl" align="right">26</td> +<td class="bt" align="left">.4</td> +<td class="bt bl" rowspan="3"><sup class="enum">3</sup>/<sub class="denom">8</sub></td> +<td class="bt bl"><sup class="enum">1</sup>/<sub class="denom">32</sub></td> +<td class="bt bl" align="right">111</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">55</td> +<td class="bt" align="left">.4</td> +<td class="bt bl" align="right">32</td> +<td class="bt br" align="left">.3</td> +</tr> + +<tr> +<td class="bt bl" rowspan="3"><sup class="enum">3</sup>/<sub class="denom">8</sub></td> +<td class="bt bl"><sup class="enum">1</sup>/<sub class="denom">64</sub></td> +<td class="bt bl" align="right">264</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">132</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">60</td> +<td class="bt" align="left">.0</td> +<td class="bt bl"><sup class="enum">1</sup>/<sub class="denom">16</sub></td> +<td class="bt bl" align="right">80</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">40</td> +<td class="bt" align="left">.0</td> +<td class="bt bl" align="right">23</td> +<td class="bt br" align="left">.4</td> +</tr> + +<tr> +<td class="bt bl"><sup class="enum">1</sup>/<sub class="denom">32</sub></td> +<td class="bt bl" align="right">180</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">90</td> +<td class="bt" align="left">.2</td> +<td class="bt bl" align="right">41</td> +<td class="bt" align="left">.0</td> +<td class="bt bl"><sup class="enum">1</sup>/<sub class="denom">8</sub></td> +<td class="bt bl" align="right">56</td> +<td class="bt" align="left">.4</td> +<td class="bt bl" align="right">28</td> +<td class="bt" align="left">.2</td> +<td class="bt bl" align="right">16</td> +<td class="bt br" align="left">.5</td> +</tr> + +<tr> +<td class="bt bl"><sup class="enum">1</sup>/<sub class="denom">16</sub></td> +<td class="bt bl" align="right">122</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">61</td> +<td class="bt" align="left">.1</td> +<td class="bt bl" align="right">27</td> +<td class="bt" align="left">.8</td> +<td class="bt bl" rowspan="3"><sup class="enum">1</sup>/<sub class="denom">2</sub></td> +<td class="bt bl"><sup class="enum">1</sup>/<sub class="denom">32</sub></td> +<td class="bt bl" align="right">104</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">52</td> +<td class="bt" align="left">.1</td> +<td class="bt bl" align="right">30</td> +<td class="bt br" align="left">.4</td> +</tr> + +<tr> +<td class="bt bl" rowspan="2"><sup class="enum">1</sup>/<sub class="denom">2</sub></td> +<td class="bt bl"><sup class="enum">1</sup>/<sub class="denom">64</sub></td> +<td class="bt bl" align="right">237</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">118</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">53</td> +<td class="bt" align="left">.8</td> +<td class="bt bl"><sup class="enum">1</sup>/<sub class="denom">16</sub></td> +<td class="bt bl" align="right">75</td> +<td class="bt" align="left">.2</td> +<td class="bt bl" align="right">37</td> +<td class="bt" align="left">.6</td> +<td class="bt bl" align="right">22</td> +<td class="bt br" align="left">.0</td> +</tr> + +<tr> +<td class="bt bl"><sup class="enum">1</sup>/<sub class="denom">32</sub></td> +<td class="bt bl" align="right">162</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">80</td> +<td class="bt" align="left">.8</td> +<td class="bt bl" align="right">36</td> +<td class="bt" align="left">.7</td> +<td class="bt bl"><sup class="enum">1</sup>/<sub class="denom">8</sub></td> +<td class="bt bl" align="right">43</td> +<td class="bt" align="left">.1</td> +<td class="bt bl" align="right">21</td> +<td class="bt" align="left">.6</td> +<td class="bt bl" align="right">12</td> +<td class="bt br" align="left">.6</td> +</tr> + +<tr> +<td class="bl bt" colspan="8">Steel—Standard <sup class="enum">5</sup>/<sub class="denom">8</sub>-inch Tool</td> +<td class="bt br bl" colspan="8">Cast Iron—Standard <sup class="enum">5</sup>/<sub class="denom">8</sub>-inch Tool</td> +</tr> + +<tr> +<td class="bl bt">Depth of Cut</td> +<td class="bl bt">Feed</td> +<td colspan="2" class="bl bt">Soft<br />Steel</td> +<td colspan="2" class="bl bt">Medium<br />Steel</td> +<td colspan="2" class="bl bt">Hard<br />Steel</td> +<td class="bl bt">Depth of Cut</td> +<td class="bl bt">Feed</td> +<td colspan="2" class="bl bt">Soft<br />Cast Iron</td> +<td colspan="2" class="bl bt">Medium<br />Cast Iron</td> +<td colspan="2" class="bl bt br">Hard<br />Cast Iron</td> +</tr> + +<tr> +<td class="bt bl" rowspan="3"><sup class="enum">1</sup>/<sub class="denom">16</sub></td> +<td class="bt bl"><sup class="enum">1</sup>/<sub class="denom">64</sub></td> +<td class="bt bl" align="right">548</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">274</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">125</td> +<td class="bt" align="left"> </td> +<td class="bt bl" rowspan="3"><sup class="enum">3</sup>/<sub class="denom">32</sub></td> +<td class="bt bl"><sup class="enum">1</sup>/<sub class="denom">32</sub></td> +<td class="bt bl" align="right">160</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">80</td> +<td class="bt" align="left">.0</td> +<td class="bt bl" align="right">46</td> +<td class="bt br" align="left">.6</td> +</tr> + +<tr> +<td class="bt bl"><sup class="enum">1</sup>/<sub class="denom">32</sub></td> +<td class="bt bl" align="right">358</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">179</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">81</td> +<td class="bt" align="left">.6</td> +<td class="bt bl"><sup class="enum">1</sup>/<sub class="denom">16</sub></td> +<td class="bt bl" align="right">110</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">55</td> +<td class="bt" align="left">.0</td> +<td class="bt bl" align="right">32</td> +<td class="bt br" align="left">.2</td> +</tr> + +<tr> +<td class="bt bl"><sup class="enum">1</sup>/<sub class="denom">16</sub></td> +<td class="bt bl" align="right">235</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">117</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">53</td> +<td class="bt" align="left">.3</td> +<td class="bt bl"><sup class="enum">1</sup>/<sub class="denom">8</sub></td> +<td class="bt bl" align="right">75</td> +<td class="bt" align="left">.4</td> +<td class="bt bl" align="right">37</td> +<td class="bt" align="left">.7</td> +<td class="bt bl" align="right">22</td> +<td class="bt br" align="left">.0</td> +</tr> + +<tr> +<td class="bt bl" rowspan="4"><sup class="enum">3</sup>/<sub class="denom">32</sub></td> +<td class="bt bl"><sup class="enum">1</sup>/<sub class="denom">64</sub></td> +<td class="bt bl" align="right">467</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">234</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">106</td> +<td class="bt" align="left"> </td> +<td class="bt bl" rowspan="3"><sup class="enum">1</sup>/<sub class="denom">8</sub></td> +<td class="bt bl"><sup class="enum">1</sup>/<sub class="denom">32</sub></td> +<td class="bt bl" align="right">148</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">74</td> +<td class="bt" align="left">.0</td> +<td class="bt bl" align="right">43</td> +<td class="bt br" align="left">.3</td> +</tr> + +<tr> +<td class="bt bl"><sup class="enum">1</sup>/<sub class="denom">32</sub></td> +<td class="bt bl" align="right">306</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">153</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">69</td> +<td class="bt" align="left">.5</td> +<td class="bt bl"><sup class="enum">1</sup>/<sub class="denom">16</sub></td> +<td class="bt bl" align="right">104</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">51</td> +<td class="bt" align="left">.8</td> +<td class="bt bl" align="right">32</td> +<td class="bt br" align="left">.0</td> +</tr> + +<tr> +<td class="bt bl"><sup class="enum">1</sup>/<sub class="denom">16</sub></td> +<td class="bt bl" align="right">200</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">100</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">45</td> +<td class="bt" align="left">.5</td> +<td class="bt bl"><sup class="enum">1</sup>/<sub class="denom">8</sub></td> +<td class="bt bl" align="right">69</td> +<td class="bt" align="left">.6</td> +<td class="bt bl" align="right">34</td> +<td class="bt" align="left">.8</td> +<td class="bt bl" align="right">20</td> +<td class="bt br" align="left">.3</td> +</tr> + +<tr> +<td class="bt bl"><sup class="enum">3</sup>/<sub class="denom">32</sub></td> +<td class="bt bl" align="right">156</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">78</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">35</td> +<td class="bt" align="left">.5</td> +<td class="bt bl" rowspan="4"><sup class="enum">3</sup>/<sub class="denom">16</sub></td> +<td class="bt bl"><sup class="enum">1</sup>/<sub class="denom">64</sub></td> +<td class="bt bl" align="right">183</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">91</td> +<td class="bt" align="left">.6</td> +<td class="bt bl" align="right">68</td> +<td class="bt br" align="left">.0</td> +</tr> + +<tr> +<td class="bt bl" rowspan="4"><sup class="enum">1</sup>/<sub class="denom">8</sub></td> +<td class="bt bl"><sup class="enum">1</sup>/<sub class="denom">64</sub></td> +<td class="bt bl" align="right">417</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">209</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">94</td> +<td class="bt" align="left">.8</td> +<td class="bt bl"><sup class="enum">1</sup>/<sub class="denom">32</sub></td> +<td class="bt bl" align="right">135</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">67</td> +<td class="bt" align="left">.5</td> +<td class="bt bl" align="right">39</td> +<td class="bt br" align="left">.4</td> +</tr> + +<tr> +<td class="bt bl"><sup class="enum">1</sup>/<sub class="denom">32</sub></td> +<td class="bt bl" align="right">273</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">136</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">62</td> +<td class="bt" align="left">.0</td> +<td class="bt bl"><sup class="enum">1</sup>/<sub class="denom">16</sub></td> +<td class="bt bl" align="right">94</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">47</td> +<td class="bt" align="left">.0</td> +<td class="bt bl" align="right">27</td> +<td class="bt br" align="left">.4</td> +</tr> + +<tr> +<td class="bt bl"><sup class="enum">1</sup>/<sub class="denom">16</sub></td> +<td class="bt bl" align="right">179</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">89</td> +<td class="bt" align="left">.3</td> +<td class="bt bl" align="right">40</td> +<td class="bt" align="left">.6</td> +<td class="bt bl"><sup class="enum">1</sup>/<sub class="denom">8</sub></td> +<td class="bt bl" align="right">64</td> +<td class="bt" align="left">.3</td> +<td class="bt bl" align="right">32</td> +<td class="bt" align="left">.2</td> +<td class="bt bl" align="right">18</td> +<td class="bt br" align="left">.8</td> +</tr> + +<tr> +<td class="bt bl"><sup class="enum">3</sup>/<sub class="denom">32</sub></td> +<td class="bt bl" align="right">140</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">69</td> +<td class="bt" align="left">.8</td> +<td class="bt bl" align="right">31</td> +<td class="bt" align="left">.7</td> +<td class="bt bl" rowspan="4"><sup class="enum">1</sup>/<sub class="denom">4</sub></td> +<td class="bt bl"><sup class="enum">1</sup>/<sub class="denom">64</sub></td> +<td class="bt bl" align="right">171</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">85</td> +<td class="bt" align="left">.7</td> +<td class="bt bl" align="right">50</td> +<td class="bt br" align="left">.1</td> +</tr> + +<tr> +<td class="bt bl" rowspan="3"><sup class="enum">3</sup>/<sub class="denom">16</sub></td> +<td class="bt bl"><sup class="enum">1</sup>/<sub class="denom">64</sub></td> +<td class="bt bl" align="right">362</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">181</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">82</td> +<td class="bt" align="left">.2</td> +<td class="bt bl"><sup class="enum">1</sup>/<sub class="denom">32</sub></td> +<td class="bt bl" align="right">126</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">63</td> +<td class="bt" align="left">.2</td> +<td class="bt bl" align="right">36</td> +<td class="bt br" align="left">.9</td> +</tr> + +<tr> +<td class="bt bl"><sup class="enum">1</sup>/<sub class="denom">32</sub></td> +<td class="bt bl" align="right">236</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">118</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">53</td> +<td class="bt" align="left">.8</td> +<td class="bt bl"><sup class="enum">1</sup>/<sub class="denom">16</sub></td> +<td class="bt bl" align="right">87</td> +<td class="bt" align="left">.8</td> +<td class="bt bl" align="right">43</td> +<td class="bt" align="left">.9</td> +<td class="bt bl" align="right">25</td> +<td class="bt br" align="left">.6</td> +</tr> + +<tr> +<td class="bt bl"><sup class="enum">1</sup>/<sub class="denom">16</sub></td> +<td class="bt bl" align="right">155</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">77</td> +<td class="bt" align="left">.4</td> +<td class="bt bl" align="right">35</td> +<td class="bt" align="left">.2</td> +<td class="bt bl"><sup class="enum">3</sup>/<sub class="denom">32</sub></td> +<td class="bt bl" align="right">70</td> +<td class="bt" align="left">.4</td> +<td class="bt bl" align="right">35</td> +<td class="bt" align="left">.2</td> +<td class="bt bl" align="right">20</td> +<td class="bt br" align="left">.6</td> +</tr> + +<tr> +<td class="bt bl" rowspan="2"><sup class="enum">1</sup>/<sub class="denom">4</sub></td> +<td class="bt bl"><sup class="enum">1</sup>/<sub class="denom">64</sub></td> +<td class="bt bl" align="right">328</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">164</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">74</td> +<td class="bt" align="left">.5</td> +<td class="bt bl bb" rowspan="3"><sup class="enum">3</sup>/<sub class="denom">8</sub></td> +<td class="bt bl"><sup class="enum">1</sup>/<sub class="denom">64</sub></td> +<td class="bt bl" align="right">156</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">77</td> +<td class="bt" align="left">.8</td> +<td class="bt bl" align="right">45</td> +<td class="bt br" align="left">.4</td> +</tr> + +<tr> +<td class="bt bl"><sup class="enum">1</sup>/<sub class="denom">32</sub></td> +<td class="bt bl" align="right">215</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">107</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">48</td> +<td class="bt" align="left">.8</td> +<td class="bt bl"><sup class="enum">1</sup>/<sub class="denom">32</sub></td> +<td class="bt bl" align="right">116</td> +<td class="bt" align="left"> </td> +<td class="bt bl" align="right">57</td> +<td class="bt" align="left">.8</td> +<td class="bt bl" align="right">33</td> +<td class="bt br" align="left">.8</td> +</tr> + +<tr> +<td class="bb bt bl"><sup class="enum">3</sup>/<sub class="denom">8</sub></td> +<td class="bb bt bl"><sup class="enum">1</sup>/<sub class="denom">64</sub></td> +<td class="bb bt bl" align="right">286</td> +<td class="bb bt" align="left"> </td> +<td class="bb bt bl" align="right">143</td> +<td class="bb bt" align="left"> </td> +<td class="bb bt bl" align="right">65</td> +<td class="bb bt" align="left">.0</td> +<td class="bb bt bl"><sup class="enum">1</sup>/<sub class="denom">16</sub></td> +<td class="bb bt bl" align="right">79</td> +<td class="bb bt" align="left">.7</td> +<td class="bb bt bl" align="right">39</td> +<td class="bb bt" align="left">.9</td> +<td class="bb bt bl" align="right">23</td> +<td class="bb bt br" align="left">.3</td> +</tr> + +</table> +<p> </p> + +<hr class="l10" /> +<div class="footnote"><a name="Fn_1" id="Fn_1"></a><span class="label"><a href="#Fnanchor_1">[1]</a></span>Cutting speeds for tools of +a good grade of high-speed steel, properly ground and heat-treated.—From <span class="smcap">Machinery's Handbook</span>.</div> +<hr class="l10" /> + +<p><span class="pagenum"><a name="Pg_72" id="Pg_72">[72]</a></span> +<a name="Secnum_2_11" id="Secnum_2_11"></a><b>Average Cutting Speeds for Turning.</b>—The cutting speed is +governed principally by the hardness of the metal to be turned; +the kind of steel of which the turning tool is made; the shape +of the tool and its heat-treatment; the feed and depth of cut; +whether or not a cooling lubricant is used on the tool; the +power of the lathe and also its construction; hence it is impossible +to give any definite rule for determining either the +speed, feed, or depth of cut, because these must be varied to +suit existing conditions. A general idea of the speeds used in +ordinary machine shop practice may be obtained from the following +figures:</p> + +<p>Ordinary machine steel is generally turned at a speed varying +between 45 and 65 feet per minute. For ordinary gray cast +iron, the speed usually varies from 40 to 50 feet per minute; +for annealed tool steel, from 25 to 35 feet per minute; for soft +yellow brass, from 150 to 200 feet per minute; for hard bronze, +from 35 to 80 feet per minute, the speed depending upon the +composition of the alloy. While these speeds correspond +closely to general practice, they can be exceeded for many +machining operations.</p> + +<p>The most economical speeds for a given feed and depth of +cut, as determined by the experiments conducted by Mr. F. W. +Taylor, are given in the table, “<a href="#Fnanchor_1">Cutting Speeds and Feeds for +Turning Tools</a>.” The speeds given in this table represent results +obtained with tools made of a good grade of high-speed +steel properly heat-treated and correctly ground. It will be +noted that the cutting speed is much slower for cast iron than +for steel. Cast iron is cut with less pressure or resistance than +soft steel, but the slower speed required for cast iron is probably +due to the fact that the pressure of the chip is concentrated +closer to the cutting edge, combined with the fact that cast +iron wears the tool faster than steel. The speeds given are +higher than those ordinarily used, and, in many cases, a slower +rate would be necessary to prevent chattering or because of +some other limiting condition.</p> + +<a name="Secnum_2_12" id="Secnum_2_12"></a><p><b>Factors which limit the Cutting Speed.</b>—It is the durability +of the turning tool or the length of time that it will turn effectively<span class="pagenum"><a name="Pg_73" id="Pg_73">[73]</a></span> +without grinding, that limits the cutting speed; and the +hardness of the metal being turned combined with the quality +of the tool are the two factors which largely govern the time +that a tool can be used before grinding is necessary. The cutting +speed for very soft steel or cast iron can be three or four +times faster than the speed for hard steel or hard castings, but +whether the material is hard or soft, the kind and quality of +the tool used must also be considered, as the speed for a tool +made of ordinary carbon steel will have to be much slower than +for a tool made of modern “high-speed” steel.</p> + +<p>When the cutting speed is too high, even though high-speed +steel is used, the point of the tool is softened to such an extent +by the heat resulting from the pressure and friction of the chip, +that the cutting edge is ruined in too short a time. On the +other hand, when the speed is too slow, the heat generated is +so slight as to have little effect and the tool point is dulled by +being slowly worn or ground away by the action of the chip. +While a tool operating at such a low speed can be used a comparatively +long time without re-sharpening, this advantage is +more than offset by the fact that too much time is required for +removing a given amount of metal when the work is revolving +so slowly.</p> + +<p>Generally speaking, the speed should be such that a fair +amount of work can be done before the tool requires re-grinding. +Evidently, it would not pay to grind a tool every few +minutes in order to maintain a high cutting speed; neither +would it be economical to use a very slow speed and waste considerable +time in turning, just to save the few minutes required +for grinding. For example, if a number of roughing cuts had +to be taken over a heavy rod or shaft, time might be saved by +running at such a speed that the tool would have to be sharpened +(or be replaced by a tool previously sharpened) when it had +traversed half-way across the work; that is, the time required +for sharpening or changing the tool would be short as compared +with the gain effected by the higher work speed. On the +other hand, it might be more economical to run a little slower +and take a continuous cut across the work with one tool.</p> + +<p><span class="pagenum"><a name="Pg_74" id="Pg_74">[74]</a></span>The experiments of Mr. Taylor led to the conclusion that, as +a rule, it is not economical to use roughing tools at a speed so +slow as to cause them to last more than 1<sup class="enum">1</sup>/<sub class="denom">2</sub> hour without being +re-ground; hence the speeds given in the <a href="#Fnanchor_1">table</a> previously referred +to are based upon this length of time between grindings. +Sometimes the work speed cannot be as high as the tool will +permit, because of the chattering that often results when the +lathe is old and not massive enough to absorb the vibrations, or +when there is unnecessary play in the working parts. The shape +of the tool used also affects the work speed, and as there are so +many things to be considered, the proper cutting speed is best +determined by experiment.</p> + +<a name="Secnum_2_13" id="Secnum_2_13"></a><p><b>Rules for Calculating Cutting Speeds.</b>—The number of revolutions +required to give any desired cutting speed can be found +by multiplying the cutting speed, in feet per minute, by 12 and +dividing the product by the circumference of the work in inches. +Expressing this as a formula we have</p> + +<div class="formula center"> +<table border="0" cellpadding="0" cellspacing="0" summary="Formula 74_1"> +<tr><td> </td><td> </td><td><i>C</i> × 12</td></tr> +<tr><td><i> R </i></td><td> = </td><td> ——— </td></tr> +<tr><td> </td><td> </td><td><i>πd</i></td></tr> +</table> +</div> + +<p>in which</p> + +<div class="formsymb"> +<table border="0" cellpadding="0" cellspacing="0" summary="Formula 74_1 symbols"> +<tr><td><i> R </i></td><td> = </td><td> revolutions per minute;</td></tr> +<tr><td><i> C </i></td><td> = </td><td> the cutting speed in feet per minute;</td></tr> +<tr><td><i> π </i></td><td> = </td><td> 3.1416;</td></tr> +<tr><td><i> d </i></td><td> = </td><td> the diameter in inches.</td></tr> +</table></div> + +<p>For example if a cutting speed of 60 feet per minute is wanted +and the diameter of the work is 5 inches, the required speed +would be found as follows:</p> + +<div class="formula center"> +<table border="0" cellpadding="0" cellspacing="0" summary="Formula 74_2"> +<tr><td> </td><td> </td><td>60 × 12</td><td> </td><td> </td></tr> +<tr><td><i> R </i></td><td> = </td><td> ————— </td> +<td> = </td><td> 46 revolutions per minute.</td></tr> +<tr><td> </td><td> </td><td>3.1416 × 5</td><td> </td><td> </td></tr> +</table></div> + +<p>If the diameter is simply multiplied by 3 and the fractional +part is omitted, the calculation can easily be made, and the result +will be close enough for practical purposes. In case the cutting +speed, for a given number of revolutions and diameter, is wanted, +the following formula can be used:</p> + +<div class="formula center"> +<table border="0" cellpadding="0" cellspacing="0" summary="Formula 74_3"> +<tr><td> </td><td> </td><td> <i>Rπd</i> </td></tr> +<tr><td> <i>C</i> </td><td> = </td><td> —— </td></tr> +<tr><td> </td><td> </td><td>12</td></tr> +</table></div> + +<p><span class="pagenum"><a name="Pg_75" id="Pg_75">[75]</a></span>Machinists who operate lathes do not know, ordinarily, what +cutting speeds, in feet per minute, are used for different classes +of work, but are guided entirely by past experience.</p> + +<a name="Secnum_2_14" id="Secnum_2_14"></a><p><b>Feed of Tool and Depth of Cut.</b>—The amount of feed and +depth of cut also vary like the cutting speed, for different conditions. +When turning soft machine steel the feed under +ordinary conditions would vary between <sup class="enum">1</sup>/<sub +class="denom">32</sub> and <sup class="enum">1</sup>/<sub class="denom">16</sub> inch per +revolution. For turning soft cast iron the feed might be increased +to from <sup class="enum">1</sup>/<sub class="denom">16</sub> to <sup class="enum">1</sup>/<sub +class="denom">8</sub> inch per revolution. These feeds +apply to fairly deep roughing cuts. Coarser feeds might be +used in many cases especially when turning large rigid parts in +a powerful lathe. The depth of a roughing cut in machine +steel might vary from <sup class="enum">1</sup>/<sub class="denom">8</sub> to <sup class="enum">3</sup>/<sub +class="denom">8</sub> inch, and in cast iron from <sup class="enum">3</sup>/<sub class="denom">16</sub> to +<sup class="enum">1</sup>/<sub class="denom">2</sub> inch. These figures are intended simply to give the reader a +general idea of feeds and cuts that are feasible under average +conditions.</p> + +<p>Ordinarily coarser feeds and a greater depth of cut can be +used for cast iron than for soft steel, because cast iron offers +less resistance to turning, but in any case, with a given depth of +cut, metal can be removed more quickly by using a coarse feed +and the necessary slower speed, than by using a fine feed and +the higher speed which is possible when the feed is reduced. +When the turning operation is simply to remove metal, the feed +should be coarse, and the cut as deep as practicable. Sometimes +the cut must be comparatively light, either because the +work is too fragile and springy to withstand the strain of a +heavy cut, or the lathe has not sufficient pulling power. The +difficulty with light slender work is that a heavy cut may cause +the part being turned to bend under the strain, thus causing the +tool to gouge in, which would probably result in spoiling the +work. Steadyrests can often be used to prevent flexible parts +from springing, as previously explained, but there are many +kinds of light work to which the steadyrest cannot be applied +to advantage.</p> + +<a name="Fig_2_15" id="Fig_2_15"></a> +<div class="figcenter"><img src="images/084sm.jpg" alt="Roughing Cut—Light Finishing Cut and Coarse Feed" /> +<p class="caption750">Fig. 15. Roughing Cut—Light Finishing Cut and Coarse Feed</p> +</div> + +<p>The amount of feed to use for a finishing cut might, properly, be +either fine or coarse. Ordinarily, fine feeds are used for finishing +steel, especially if the work is at all flexible, whereas finishing<span class="pagenum"><a name="Pg_76" id="Pg_76">[76]</a></span> +cuts in cast iron are often accompanied by a coarse feed. +<a href="#Fig_2_15">Fig. 15</a> illustrates the feeds that are often used when turning +cast iron. The view to the left shows a deep roughing cut and +the one to the right, a finishing cut. By using a broad flat +cutting edge set parallel to the tool's travel, and a coarse feed +for finishing, a smooth cut can be taken in a comparatively +short time. Castings which are close to the finished size in +the rough can often be finished to advantage by taking a single +cut with a broad tool, provided the work is sufficiently rigid. +It is not always practicable to use these broad tools and coarse +feeds, as they sometimes cause chattering, and when used on +steel, a broad tool tends to gouge or “dig in” unless the part +being turned is rigid. Heavy steel parts, however, are sometimes +finished in this way. The modern method of finishing +many steel parts is to simply rough them out in a lathe to +within, say, <sup class="enum">1</sup>/<sub class="denom">32</sub> inch of the required diameter and take the finishing +cut in a cylindrical grinding machine.</p> + +<a name="Secnum_2_15" id="Secnum_2_15"></a><p><b>Effect of Lubricant on Cutting Speed.</b>—When turning iron +or steel a higher cutting speed can be used, if a stream of soda +water or other cooling lubricant falls upon the chip at the point +where it is being removed by the tool. In fact, experiments +have shown that the cutting speed, when using a large stream of +cooling water and a high-speed steel tool, can be about 40 percent +higher than when turning dry or without a cooling lubricant.<span class="pagenum"><a name="Pg_77" id="Pg_77">[77]</a></span> +For ordinary carbon steel tools, the gain was about +25 per cent. The most satisfactory results were obtained from +a stream falling at a rather slow velocity but in large volume. +The gain in cutting speed, by the use of soda water or other +suitable fluids, was found to be practically the same for all +qualities of steel from the softest to the hardest.</p> + +<p>Cast iron is usually turned dry or without a cutting lubricant. +Experiments, however, made to determine the effect of applying +a heavy stream of cooling water to a tool turning cast iron, +showed the following results: Cutting speed without water, 47 +feet per minute; cutting speed with a heavy stream of water, +nearly 54 feet per minute; increase in speed, 15 per cent. The +dirt caused by mixing the fine cast-iron turnings with a cutting +lubricant is an objectionable feature which, in the opinion of +many, more than offsets the increase in cutting speed that +might be obtained.</p> + +<p>Turret lathes and automatic turning machines are equipped +with a pump and piping for supplying cooling lubricant to the +tools in a continuous stream. Engine lathes used for general +work, however, are rarely provided with such equipment and +a lubricant, when used, is often supplied by a can mounted at +the rear of the carriage, having a spout which extends above the +tool. Owing to the inconvenience in using a lubricant on an +engine lathe, steel, as well as cast iron, is often turned dry +especially when the work is small and the cuts light and comparatively +short.</p> + +<a name="Secnum_2_16" id="Secnum_2_16"></a><p><b>Lubricants Used for Turning.</b>—A good grade of lard oil is +an excellent lubricant for use when turning steel or wrought +iron and it is extensively used on automatic screw machines, +especially those which operate on comparatively small work. +For some classes of work, especially when high-cutting speeds +are used, lard oil is not as satisfactory as soda water or some of +the commercial lubricants, because the oil is more sluggish and +does not penetrate to the cutting point with sufficient rapidity. +Many lubricants which are cheaper than oil are extensively +used on “automatics” for general machining operations. These +usually consist of a mixture of sal-soda (carbonate of soda) and<span class="pagenum"><a name="Pg_78" id="Pg_78">[78]</a></span> +water, to which is added some ingredient such as lard oil or soft +soap to thicken or give body to the lubricant.</p> + +<p>A cheap lubricant for turning, milling, etc., and one that has +been extensively used, is made in the following proportions: +1 pound of sal-soda, 1 quart of lard oil, 1 quart of soft soap, +and enough water to make 10 or 12 gallons. This mixture is +boiled for one-half hour, preferably by passing a steam coil +through it. If the solution should have an objectionable odor, +this can be eliminated by adding 2 pounds of unslaked lime. The +soap and soda in this solution improve the lubricating quality +and also prevent the surfaces from rusting. For turning and +threading operations, plain milling, deep-hole drilling, etc., a +mixture of equal parts of lard oil and paraffin oil will be found +very satisfactory, the paraffin being added to lessen the expense.</p> + +<p>Brass or bronze is usually machined dry, although lard oil is +sometimes used for automatic screw machine work. Babbitt +metal is also worked dry, ordinarily, although kerosene or +turpentine is sometimes used when boring or reaming. If +babbitt is bored dry, balls of metal tend to form on the tool +point and score the work. Milk is generally considered the best +lubricant for machining copper. A mixture of lard oil and +turpentine is also used for copper. For aluminum, the following +lubricants can be used: Kerosene, a mixture of kerosene +and gasoline, soap-water, or “aqualine” one part, water 20 +parts.</p> + +<a name="Secnum_2_17" id="Secnum_2_17"></a><p><b>Lard Oil as a Cutting Lubricant.</b>—After being used for a considerable +time, lard oil seems to lose some of its good qualities +as a cooling compound. There are several reasons for this: +Some manufacturers use the same oil over and over again on +different materials, such as brass, steel, etc. This is objectionable, +for when lard oil has been used on brass it is practically +impossible to get the fine dust separated from it in a centrifugal +separator. When this impure oil is used on steel, especially +where high-speed steels are employed, it does not give satisfactory +results, owing to the fact that when the cutting tool +becomes dull, the small brass particles “freeze” to the cutting +tool and thus produce rough work. The best results are obtained<span class="pagenum"><a name="Pg_79" id="Pg_79">[79]</a></span> +from lard oil by keeping it thin, and by using it on the +same materials—that is, not transferring the oil from a machine +in which brass is being cut to one where it would be employed +on steel. If the oil is always used on the same class of material, +it will not lose any of its good qualities.</p> + +<p>Prime lard oil is nearly colorless, having a pale yellow or +greenish tinge. The solidifying point and other characteristics +of the oil depend upon the temperature at which it was expressed, +winter-pressed lard oil containing less solid constituents of the +lard than that expressed in warm weather. The specific gravity +should not exceed 0.916; it is sometimes increased by adulterants, +such as cotton-seed and maize oils.</p> + +<hr class="c25" /> +<span class="pagenum"><a name="Pg_80" id="Pg_80">[80]</a></span> +<h2><a name="Chapnum_3" id="Chapnum_3">CHAPTER III</a></h2> +<h3>TAPER TURNING—SPECIAL OPERATIONS—FITTING</h3> +<hr class="c05" /> + +<p>It is often necessary, in connection with lathe work, to turn +parts tapering instead of straight or cylindrical. If the work is +mounted between the centers, one method of turning a taper is +to set the tailstock center out of alignment with the headstock +center. When both of these centers are in line, the movement +of the tool is parallel to the axis of the work and, consequently, a +cylindrical surface is produced; but if the tailstock <i>h<sub>1</sub></i> is set out +of alignment, as shown in <a href="#Fig_3_1">Fig. 1</a>, the work will then be turned +tapering as the tool is traversed from <i>a</i> to <i>b</i>, because the axis +<i>x—x</i> is at an angle with the movement of the tool. Furthermore +<span class="pagenum"><a name="Pg_81" id="Pg_81">[81]</a></span> +the amount of taper or the difference between the diameters +at the ends for a given length, will depend on how much +center <i>h<sub>1</sub></i> is set over from the central position.</p> + +<a name="Fig_3_1" id="Fig_3_1"></a> +<div class="figcenter"><div class="illobox450"><img src="images/088sm.png" alt="Taper Turning by the Offset-center Method" /></div> +<p class="caption750">Fig. 1. Taper Turning by the Offset-center Method</p> +</div> + +<p>The amount of taper is usually given on drawings in inches +per foot, or the difference in the diameter at points twelve +inches apart. For example, the taper of the piece shown at <i>A</i>, +<a href="#Fig_3_2">Fig. 2</a>, is 1 inch per foot, as the length of the tapering surface +is just twelve inches and the difference between the diameters +at the ends is 1 inch. The conical roller shown at <i>B</i> has a total +length of 9 inches and a tapering surface 6 inches long, and in +this case the taper per foot is also 1 inch, there being a difference +of <sup class="enum">1</sup>/<sub class="denom">2</sub> inch in a length of 6 inches or 1 inch in twice that +length. When the taper per foot is known, the amount that +the tailstock center should be set over for turning that taper +can easily be estimated, but it should be remembered that the +setting obtained in this way is not absolutely correct, and is +only intended to locate the center approximately. When a +taper needs to be at all accurate, it is tested with a gage, or by +other means, after taking a trial cut, as will be explained later, +and the tailstock center is readjusted accordingly. There are +also more accurate methods of setting the center, than by figuring +<span class="pagenum"><a name="Pg_82" id="Pg_82">[82]</a></span> +the amount of offset, but as the latter is often convenient +this will be referred to first.</p> + +<a name="Fig_3_2" id="Fig_3_2"></a> +<div class="figcenter"><div class="illobox450"><img src="images/089sm.png" alt="Examples of Taper Work" /></div> +<p class="caption750">Fig. 2. Examples of Taper Work</p> +</div> + +<a name="Secnum_3_1" id="Secnum_3_1"></a><p><b>Setting Tailstock Center for Taper Turning.</b>—Suppose the +tailstock center is to be set for turning part <i>C</i>, <a href="#Fig_3_2">Fig. 2</a>, to a taper +of approximately 1 inch per foot. In this case the center would +simply be moved toward the front of the machine <sup class="enum">1</sup>/<sub class="denom">2</sub> inch, or +one-half the required taper per foot, because the total length +of the work happens to be just 12 inches. This setting, however, +would not be correct for all work requiring a taper of 1 +inch per foot, as the adjustment depends not only on the <i>amount</i> +of the taper but on the <i>total length</i> of the piece.</p> + +<a name="Fig_3_3" id="Fig_3_3"></a> +<div class="figcenter"><img src="images/090sm.jpg" alt="Detail View of Lathe Tailstock" /> +<p class="caption750">Fig. 3. Detail View of Lathe Tailstock</p> +</div> + +<p>For example, the taper +roller <i>B</i> has a taper of +1 inch per foot, but the +center, in this case, would +be offset less than one-half +the taper per foot, +because the total length +is only 9 inches. For +lengths longer or shorter +than twelve inches, the +taper per inch should be +found first; this is then +multiplied by the <i>total</i> length of the work (not the length of the +taper) which gives the taper for that length, and one-half this +taper is the amount to set over the center. For example, the +taper per inch of part <i>B</i> equals 1 inch divided by 12 = <sup class="enum">1</sup>/<sub class="denom">12</sub> inch. +The total length of 9 inches multiplied by <sup class="enum">1</sup>/<sub class="denom">12</sub> inch = +<sup class="enum">3</sup>/<sub class="denom">4</sub> inch, and +<sup class="enum">1</sup>/<sub class="denom">2</sub> of <sup class="enum">3</sup>/<sub class="denom">4</sub> = +<sup class="enum">3</sup>/<sub class="denom">8</sub>, which is the distance that the tailstock center should +be offset. In this example if the taper per foot were not known, +and only the diameters of the large and small ends of the tapered +part were given, the difference between these diameters should +first be found (2<sup class="enum">1</sup>/<sub class="denom">2</sub> - 2 = <sup class="enum">1</sup>/<sub class="denom">2</sub>); +this difference should then be divided +by the length of the taper (<sup class="enum">1</sup>/<sub class="denom">2</sub> ÷ 6 = <sup class="enum">1</sup>/<sub +class="denom">12</sub> inch) to obtain the taper +per inch. The taper per inch times the <i>total</i> length represents +what the taper would be if it extended throughout the entire +length, and one-half of this equals the offset, which is <sup class="enum">3</sup>/<sub class="denom">8</sub> inch.</p> + +<a name="Fig_3_4" id="Fig_3_4"></a> +<div class="figcenter"><div class="illobox450"><img src="images/091sm.png" alt="Taper Plug and Gage" /></div> +<p class="caption750">Fig. 4. Taper Plug and Gage</p> +</div> + +<a name="Secnum_3_2" id="Secnum_3_2"></a><p><span class="pagenum"><a name="Pg_83" id="Pg_83">[83]</a></span> +<b>Example of Taper Turning.</b>—As a practical example of taper +turning let us assume that the piece A, <a href="#Fig_3_4">Fig. 4</a>, which has been +centered and rough-turned as shown, is to be made into a taper +plug, as indicated at <i>B</i>, to fit a ring gage as at <i>C</i>. If the required +taper is 1<sup class="enum">1</sup>/<sub class="denom">2</sub> inch per foot and the total length is 8 inches, +the tailstock center would be offset <sup class="enum">1</sup>/<sub class="denom">2</sub> inch.</p> + +<p>To adjust the tailstock, the nuts <i>N</i> (<a href="#Fig_3_3">Fig. 3</a>) are first loosened +and then the upper part <i>A</i> is shifted sidewise by turning screw <i>S</i>. +Scales are provided on some tailstocks for measuring the amount +of this adjustment; if there is no scale, draw a line across the +movable and stationary parts <i>A</i> and <i>B</i>, when the tailstock is +set for straight turning. The movement of the upper line in +relation to the lower will then show the offset, which can be +measured with a scale.</p> + +<p>When the adjustment has been made, nuts <i>N</i> are tightened +and the part to be turned, with a dog attached, is placed between +the centers the same as for straight turning. The taper +end is then reduced by turning, but before it is near the finished +size, the work is removed and the taper tested by inserting it +in the gage. If it is much out, this can be felt, as the end that +is too small can be shaken in the hole. Suppose the plug did +not taper enough and only the small end came into contact with +the gage, as shown somewhat exaggerated at <i>D</i>; in that case<span class="pagenum"><a name="Pg_84" id="Pg_84">[84]</a></span> +the center would be shifted a little more towards the front, +whereas if the taper were too steep, the adjustment would, of +course, be in the opposite direction. A light cut would then be +taken, to be followed by another test. If the plug should fit +the gage so well that there was no perceptible shake, it could be +tested more closely as follows: Draw three or four chalk lines +along the tapering surface, place the work in the gage and turn +it a few times. The chalk marks will then show whether the +taper of the plug corresponds to that of the gage; for example, +if the taper is too great, the marks will be rubbed out on the +large end, but if the taper is correct, the lines throughout their +length will be partially erased.</p> + +<p>Another and more accurate method of testing tapers is to +apply a thin coat of Prussian-blue to one-half of the tapering +surface, in a lengthwise direction. The work is then inserted in +the hole or gage and turned to mark the bearing. If the taper +is correct, the bearing marks will be evenly distributed, whereas +if the taper is incorrect, they will appear at one end. Tapering +pieces that have to be driven tightly into a hole, such as a piston-rod, +can be tested by the location of the bearing marks produced +by actual contact.</p> + +<p>After the taper is found to be correct, the plug is reduced in +size until it just enters the gage as at <i>C</i>. The final cut should +leave it slightly above the required size, so that a smooth surface<span class="pagenum"><a name="Pg_85" id="Pg_85">[85]</a></span> +can be obtained by filing. It should be mentioned that on +work of this kind, especially if great accuracy is required, the +final finish is often obtained by grinding in a regular grinding +machine, instead of by filing. When this method is employed, +a lathe is used merely to rough-turn the part close to size.</p> + +<a name="Fig_3_5" id="Fig_3_5"></a> +<div class="figcenter"><div class="illobox450"><img src="images/092sm.png" alt="Setting Work for Taper Turning by use of Caliper Gage" /></div> +<p class="caption750">Fig. 5. Setting Work for Taper Turning by use of Caliper Gage</p> +</div> + +<p>When the amount that the tailstock center should be offset +is determined by calculating, as in the foregoing example, it is +usually necessary to make slight changes afterward, and the +work should be tested before it is too near the finished size so +that in case one or more trial cuts are necessary, there will be +material enough to permit this. When there are a number of +tapered pieces to be turned to the same taper, the adjustment +of the tailstock center will have to be changed unless the total +length of each piece and the depth of the center holes are the +same in each case.</p> + +<a name="Fig_3_6" id="Fig_3_6"></a> +<div class="figcenter"><div class="illobox450"><img src="images/093sm.png" alt="Side View showing Relative Positions of Gage and Work" /></div> +<p class="caption750">Fig. 6. Side View showing Relative Positions of Gage and Work</p> +</div> + +<a name="Secnum_3_3" id="Secnum_3_3"></a><p><b>Setting the Tailstock Center with a Caliper Tool.</b>—Another +method of setting the tailstock center for taper turning is illustrated +in <a href="#Fig_3_5">Fig. 5</a>. The end of an engine piston-rod is to be made +tapering as at A and to dimensions <i>a</i>, <i>b</i>, <i>c</i> and <i>d</i>. It is first +turned with the centers in line as at <i>B</i>. The end <i>d</i> is reduced to +diameter <i>b</i> up to the beginning of the taper and it is then turned +to diameter <i>a</i> as far as the taper part <i>c</i> extends. The tailstock +center is next set over by guess and a caliper tool is clamped in +the toolpost. This tool, a side view of which is shown in <a href="#Fig_3_6">Fig. 6</a>, +<span class="pagenum"><a name="Pg_86" id="Pg_86">[86]</a></span> +has a pointer <i>p</i> that is free to swing about pivot <i>r</i>, which should +be set to about the same height as the center of the work. The +tailstock center is adjusted until this pointer just touches the +work when in the positions shown by the full and dotted lines +at <i>C</i>, <a href="#Fig_3_5">Fig. 5</a>; that is, until the pointer makes contact at the beginning +and end of the taper part. The travel of the carriage +will then be parallel to a line <i>x—x</i>, representing the taper; consequently, +if a tool is started at the small end, as shown by the +dotted lines at <i>D</i>, with the nose just grazing the work, it will +also just graze it when fed to the extreme left as shown. Of +course, if the taper were at all steep, more than one cut would +be taken.</p> + +<a name="Fig_3_7" id="Fig_3_7"></a> +<div class="figcenter"><div class="illobox450"><img src="images/094sm.png" alt="Obtaining Tailstock Center Adjustment by use of Square" /></div> +<p class="caption750">Fig. 7. Obtaining Tailstock Center Adjustment by use of Square</p> +</div> + +<p>If these various operations are carefully performed, a fairly +accurate taper can be produced. The straight end <i>d</i> is reduced +to size after the tail-center is set back to the central +position. Some mechanics turn notches or grooves at the beginning +and end of the tapering part, having diameters equal to +the largest and smallest part of the taper; the work is then set +by these grooves with a caliper tool. The advantage of the<span class="pagenum"><a name="Pg_87" id="Pg_87">[87]</a></span> +first method is that most of the metal is removed while the +centers are in alignment.</p> + +<a name="Secnum_3_4" id="Secnum_3_4"></a><p><b>Setting the Tailstock Center with a Square.</b>—Still another +method of adjusting the tailstock for taper turning, which is +very simple and eliminates all figuring, is as follows: The part +to be made tapering is first turned cylindrical or straight for +3 or 4 inches of its length, after the ends have been properly +centered and faced square. The work is then removed and the +tailstock is shifted along the bed until the distance <i>a—b</i> between +the extreme points of the centers is exactly 1 foot. The center +is next offset a distance <i>b—c</i> equal to one-half the required +taper per foot, after which a parallel strip <i>D</i>, having true sides, +is clamped in the toolpost. Part <i>D</i> is then set at right angles +to a line passing from one center point to the other. This can +be done conveniently by holding a 1-foot square (preferably with +a sliding head) against one side of <i>D</i> and adjusting the latter in +the toolpost until edge <i>E</i> of the square blade is exactly in line +with both center points. After part <i>D</i> is set, it should be +clamped carefully to prevent changing the position. The angle +between the side of <i>D</i> and an imaginary line which is perpendicular +to axis <i>a—b</i> is now equal to one-half the angle of the +required taper.</p> + +<a name="Fig_3_8" id="Fig_3_8"></a> +<div class="figcenter"><div class="illobox450"><img src="images/095sm.png" alt="Second Step in Adjusting Tailstock Center by use of Square" /></div> +<p class="caption750">Fig. 8. Second Step in Adjusting Tailstock Center by use of Square</p> +</div> + +<p><span class="pagenum"><a name="Pg_88" id="Pg_88">[88]</a></span>The axis of the part to be turned should be set parallel with +line <i>E</i>, which can be done by setting the cylindrical surface +which was previously finished, at right angles to the side of <i>D</i>. +In order to do this the work is first placed between centers, the +tailstock being shifted along the bed if necessary; the tail-center +is then adjusted laterally until the finished cylindrical +surface is square with the side of <i>D</i>. A small try-square can be +used for testing +the position of the +work, as indicated +in <a href="#Fig_3_8">Fig. 8</a>. If the +length of the work +is less than 1 foot, +it will be necessary +to move the +center toward the +rear of the machine, +and if the +length is greater +than 1 foot, the +adjustment is, of +course, in the opposite +direction.</p> + +<a name="Secnum_3_5" id="Secnum_3_5"></a><p><b>The Taper Attachment.</b>—Turning +tapers by +setting over the +tailstock center has some objectionable features. When the +lathe centers are not in alignment, as when set for taper turning, +they bear unevenly in the work centers because the axis +of the work is at an angle with them; this causes the work +centers to wear unevenly and results in inaccuracy. Furthermore, +the adjustment of the tailstock center must be changed +when turning duplicate tapers, unless the length of each piece +and the depth of the center holes are the same. To overcome +these objections, many modern lathes are equipped with a +special device for turning tapers, known as a taper attachment,<span class="pagenum"><a name="Pg_89" id="Pg_89">[89]</a></span> +which permits the lathe centers to be kept in alignment, as +for cylindrical turning, and enables more accurate work to be +done.</p> + +<a name="Fig_3_9" id="Fig_3_9"></a> +<div class="figcenter"><img src="images/096sm.jpg" alt="A Lathe Taper Attachment" /> +<p class="caption750">Fig. 9. A Lathe Taper Attachment</p> +</div> + +<p>Taper attachments, like lathes, vary some in their construction, +but all operate on the same principle. An improved form +of taper attachment is illustrated in <a href="#Fig_3_9">Figs. 9</a> and <a href="#Fig_3_10">10</a>. <a href="#Fig_3_9">Fig. 9</a> +shows a plan view of a lathe carriage with an attachment +fitted to it, and <a href="#Fig_3_10">Fig. 10</a> a sectional view. This attachment has +an arm <i>A</i> on which is mounted a slide <i>S</i> that can be turned +about a central pivot by adjusting screw <i>D</i>. The arm <i>A</i> is +supported by, and is free to slide on, a bracket <i>B</i> (see also sectional +view) that is fastened to the carriage, and on one end of +the arm there is a clamp <i>C</i> that is attached to the lathe bed +when turning tapers. On the slide <i>S</i> there is a shoe <i>F</i> that is +connected to bar <i>E</i> which passes beneath the toolslide. The +rear end of the cross-feed screw is connected to this bar, and +the latter is clamped to the toolslide when the attachment is +in use.</p> + +<a name="Fig_3_10" id="Fig_3_10"></a> +<div class="figcenter"><img src="images/097sm.jpg" alt="Sectional View of Taper Attachment" /> +<p class="caption750">Fig. 10. Sectional View of Taper Attachment</p> +</div> + +<p>When a taper is to be turned, the carriage is moved opposite +the taper part and clamp <i>C</i> is fastened to the bed; this holds +arm <i>A</i> and slide <i>S</i> stationary so that the carriage, with bracket +<i>B</i> and shoe <i>F</i>, can be moved with relation to the slide. If this +slide <i>S</i> is set at an angle, as shown, the shoe as it moves along +causes the toolslide and tool to move in or out, but if the slide +is set parallel to the carriage travel, the toolslide remains +stationary. Now if the tool, as it feeds lengthwise of the work, +is also gradually moved crosswise, it will turn a taper, and as<span class="pagenum"><a name="Pg_90" id="Pg_90">[90]</a></span> +this crosswise movement is caused by the angularity of slide <i>S</i>, +different tapers are obtained by setting the slide to different +positions.</p> + +<p>By means of a graduated scale <i>G</i> at the end of slide <i>S</i>, the +taper that will be obtained for any angular position of the slide +is shown. On some attachments there are two sets of graduations, +one giving the taper in inches per foot and the other in +degrees. While tapers are ordinarily given in inches per foot +on drawings, sometimes the taper is given in degrees instead. +The attachment is set for turning tapers by adjusting slide <i>S</i> +until pointer <i>p</i> is opposite the division or fractional part of a +division representing the taper. The whole divisions on the +scale represent taper in inches per foot, and by means of the +sub-divisions, the slide can be set for turning fractional parts of +an inch per foot. When slide <i>S</i> is properly set, it is clamped to +arm <i>A</i> by the nuts <i>N</i>. Bar <i>E</i> is also clamped to the toolslide by +bolt <i>H</i>, as previously stated. The attachment is disconnected +for straight turning by simply loosening clamp <i>C</i> and the bolt <i>H</i>.</p> + +<a name="Fig_3_11" id="Fig_3_11"></a> +<div class="figcenter"><div class="illobox450"><img src="images/099sm.png" alt="Lathe with Taper Attachment arranged for Boring Taper Hole in Engine Piston" /></div> +<p class="caption750">Fig. 11. Lathe with Taper Attachment arranged for Boring Taper Hole in Engine Piston</p> +</div> + +<a name="Secnum_3_6" id="Secnum_3_6"></a><p><b>Application of Taper Attachment.</b>—Practical examples of +lathe work, which illustrate the use of the taper attachment, +are shown in <a href="#Fig_3_11">Figs. 11</a> and <a href="#Fig_3_12">12</a>. <a href="#Fig_3_11">Fig. 11</a> shows how a taper hole +is bored in an engine piston-head, preparatory to reaming. +The casting must be held either in a chuck <i>C</i> or on a faceplate +if too large for the chuck. The side of the casting (after it has +been “chucked”) should run true, and also the circumference, +unless the cored hole for the rod is considerably out of center, +in which case the work should be shifted to divide the error. +The side of the casting for a short space around the hole is faced +true with a round nose turning tool, after which the rough-cored +hole is bored with an ordinary boring tool <i>t</i>, and then it is +finished with a reamer to exactly the right size and taper.</p> + +<a name="Fig_3_12" id="Fig_3_12"></a> +<div class="figcenter"><div class="illobox450"><img src="images/101sm.png" alt="Taper Attachment Set for Turning Taper End of Piston-rod" /></div> +<p class="caption750">Fig. 12. Taper Attachment Set for Turning Taper End of Piston-rod</p> +</div> + +<p>This particular taper attachment is set to whatever taper is +given on the drawing, by loosening nuts <i>N</i> and turning slide <i>S</i> +until pointer <i>P</i> is opposite that division on the scale which represents +the taper. The attachment is then ready, after bolt <i>H</i> +and nuts <i>N</i> are tightened, and clamp <i>C</i> is fastened to the lathe +bed. The hole is bored just as though it were straight, and<span class="pagenum"><a name="Pg_91" id="Pg_91">[91]</a></span> +as the carriage advances, the tool is gradually moved inward by +the attachment. If the lathe did not have a taper attachment, +the taper hole could be bored by using the compound rest.</p> + +<p>The hole should be bored slightly less than the finish size to +allow for reaming. When a reamer is used in the lathe, the +outer end is supported by the tailstock center and should have +a deep center-hole. The lathe is run very slowly for reaming +and the reamer is fed into the work by feeding out the tailstock +spindle. The reamer can be kept from revolving, either by attaching +a heavy dog to the end or, if the end is squared, by the +use of a wrench long enough to rest against the lathe carriage. +A common method is to clamp a dog to the reamer shank, and +then place the tool-rest beneath it to prevent rotation. If the<span class="pagenum"><a name="Pg_92" id="Pg_92">[92]</a></span> +shank of a tool is clamped to the toolpost so that the dog rests +against it, the reamer will be prevented from slipping off the +center as it tends to do; with this arrangement, the carriage is +gradually moved along as the tailstock spindle is fed outward. +Some reamers are provided with stop-collars which come against +the finished side of the casting when the hole has been reamed +to size.</p> + +<p>After the reaming operation, the casting is removed from the +chuck and a taper mandrel is driven into the hole for turning +the outside of the piston. This mandrel should run true on its +centers, as otherwise the outside surface of the piston will not +be true with the bored hole. The driving dog, especially for +large work of this kind, should be heavy and stiff, because light +flexible clamps or dogs vibrate and frequently cause chattering. +For such heavy work it is also preferable to drive at two points +on opposite sides of the faceplate, but the driving pins should +be carefully adjusted to secure a uniform bearing on both sides.</p> + +<p>The foregoing method of machining a piston is one that +would ordinarily be followed when using a standard engine +lathe, and it would, perhaps, be as economical as any if only one +piston were being made; but where such work is done in large +quantities, time could be saved by proceeding in a different +way. For example, the boring and reaming operation could be +performed much faster in a turret lathe, which is a type designed +for just such work, but a turret lathe cannot be used for +as great a variety of turning operations as a lathe of the regular +type. There are also many other classes of work that can be +turned more quickly in special types of machines, but as more +or less time is required for arranging these special machines and +often special tools have to be made, the ordinary lathe is frequently +indispensable when only a few parts are needed; in +addition, it is better adapted to some turning operations than +any other machine.</p> + +<p><a href="#Fig_3_12">Fig. 12</a> illustrates how a taper attachment would be used for +turning the taper fitting for the crosshead end of an engine +piston-rod. Even though this taper corresponds to the taper of +the hole in the piston, slide <i>S</i> would have to be reset to the corresponding +<span class="pagenum"><a name="Pg_93" id="Pg_93">[93]</a></span> +division on the opposite side of the central zero +mark, because the taper of the hole decreased in size during the +boring operation, whereas the rod is smallest at the beginning +of the cut, so that the tool must move outward rather than inward +as it advances. The taper part is turned practically the +same as a cylindrical part; that is, the power feed is used and, +as the carriage moves along the bed, the tool is gradually moved +outward by the taper attachment.</p> + +<p>If the rod is being fitted directly to the crosshead (as is usually +the case), the approximate size of the small end of the taper +could be determined by calipering, the calipers being set to the +size of the hole at a distance from the shoulder or face side of +the crosshead, equal to the length of the taper fitting on the +rod. If the crosshead were bored originally to fit a standard +plug gage, the taper on the rod could be turned with reference +to this gage, but, whatever the method, the taper should be +tested before turning too close to the finished size. The test is +made by removing the rod from the lathe and driving it tightly<span class="pagenum"><a name="Pg_94" id="Pg_94">[94]</a></span> +into the crosshead. This shows how near the taper is to size, +and when the rod is driven out, the bearing marks show whether +the taper is exactly right or not. If the rod could be driven in +until the shoulder is, say, <sup class="enum">1</sup>/<sub class="denom">8</sub> inch from the crosshead face, it +would then be near enough to finish to size by filing. When +filing, the lathe is run much faster than for turning, and most +of the filing should be done where the bearing marks are the +heaviest, to distribute the bearing throughout the length of the +taper. Care should be taken when driving the rod in or out, +to protect the center-holes in the ends by using a “soft” hammer +or holding a piece of soft metal against the driving end.</p> + +<p>After the crosshead end is finished, the rod is reversed in the +lathe for turning the piston end. The dog is clamped to the +finished end, preferably over a piece of sheet copper to prevent +the surface from being marred. When turning this end, either +the piston reamer or the finished hole in the piston can be calipered. +The size and angle of the taper are tested by driving the +rod into the piston, and the end should be fitted so that by +driving tightly, the shoulder will just come up against the +finished face of the piston. When the taper is finished, the attachment +is disengaged and a finishing cut is taken over the +body of the rod, unless it is to be finished by grinding, which is +the modern and most economical method.</p> + +<a name="Fig_3_13" id="Fig_3_13"></a> +<div class="figcenter"><div class="illobox450"><img src="images/102sm.png" alt="Tool Point should be in same Horizontal Plane as Axis of Work for Taper Turning" /></div> +<p class="caption750">Fig. 13. Tool Point should be in same Horizontal Plane as Axis +of Work for Taper Turning</p> +</div> + +<a name="Secnum_3_7" id="Secnum_3_7"></a><p><b>Height of Tool when Turning Tapers.</b>—The cutting edge of +the tool, when turning tapers, should be at the same height as +the center or axis of the work, whether an attachment is used or<span class="pagenum"><a name="Pg_95" id="Pg_95">[95]</a></span> +not. The importance of this will be apparent by referring to +<a href="#Fig_3_13">Fig. 13</a>. To turn the taper shown, the tool <i>T</i> would be moved +back a distance <i>x</i> (assuming that an attachment is used) while +traversing the length <i>l</i>. As an illustration, if the tool could +be placed as high as point <i>a</i>, the setting of the attachment remaining +as before, the tool would again move back a distance <i>x</i>, +while traversing a distance <i>l</i>, but the large end would be under-sized +(as shown by the dotted line) if the diameters of the small +ends were the same in each case. Of course, if the tool point +were only slightly above or below the center, the resulting error +would also be small. The tool can easily be set central by comparing +the height of the cutting edge at the point of the tool with +one of the lathe centers before placing the work in the lathe.</p> + +<a name="Fig_3_14" id="Fig_3_14"></a> +<div class="figcenter"><div class="illobox450"><img src="images/103sm.png" alt="Plan View showing Method of Turning a Taper with the Compound Rest" /></div> +<p class="caption750">Fig. 14. Plan View showing Method of Turning a Taper with the Compound Rest</p> +</div> + +<a name="Secnum_3_8" id="Secnum_3_8"></a><p><b>Taper Turning with the Compound Rest.</b>—The amount of +taper that can be turned by setting over the tailstock center +and by the taper attachment is limited, as the centers can +only be offset a certain distance, and the slide <i>S</i> (<a href="#Fig_3_9">Fig. 9</a>) of the +attachment cannot be swiveled beyond a certain position. For +steep tapers, the compound rest <i>E</i> is swiveled to the required<span class="pagenum"><a name="Pg_96" id="Pg_96">[96]</a></span> +angle and used as indicated in <a href="#Fig_3_14">Fig. 14</a>, which shows a plan view +of a rest set for turning the valve <i>V</i>. This compound rest is an +upper slide mounted on the lower or main cross-slide <i>D</i>, and it +can be turned to any angular position so that the tool, which +ordinarily is moved either lengthwise or crosswise of the bed, +can be fed at an angle. The base of the compound rest is +graduated in degrees and the position of these graduations +shows to what angle the upper slide is set. Suppose the seat of +valve <i>V</i> is to be turned to an angle of 45 degrees with the axis +or center, as shown on the drawing at <i>A</i>, <a href="#Fig_3_15">Fig. 15</a>. To set the +compound rest, nuts <i>n</i> on either side, which hold it rigidly to +the lower slide, are first loosened and the slide is then turned +until the 45-degree graduation is exactly opposite the zero line; +the slide is then tightened in this position. A cut is next taken +across the valve by operating handle <i>w</i> and feeding the tool in +the direction of the arrow.</p> + +<a name="Fig_3_15" id="Fig_3_15"></a> +<div class="figcenter"><div class="illobox450"><img src="images/104sm.png" alt="Example of Taper Work Turned by using Compound Rest" /></div> +<p class="caption750">Fig. 15. Example of Taper Work Turned by using Compound Rest</p> +</div> + +<p>In this particular instance the compound rest is set to the +same angle given on the drawing, but this is not always the +case. If the draftsman had given the included angle of 90 +degrees, as shown at <i>B</i>, which would be another way of expressing +it, the setting of the compound rest would, of course, +be the same as before, or to 45 degrees, but the number of degrees +marked on the drawing does not correspond with the angle +to which the rest must be set. As another illustration, suppose +the valve were to be turned to an angle of 30 degrees with the<span class="pagenum"><a name="Pg_97" id="Pg_97">[97]</a></span> +axis as shown at <i>C</i>. In this case the compound rest would not +be set to 30 degrees but to 60 degrees, because in order to turn +the work to an angle of 30 degrees, the rest must be 60 degrees +from its zero position, as shown. From this it will be seen +that the number of degrees marked on the drawing does not +necessarily correspond to the angle to which the rest must be +set, as the graduations on the rest show the number of degrees +that it is moved from its zero position, which corresponds to +the line <i>a—b</i>. The angle to which the compound rest should be +set can be found, when the drawing is marked as at <i>A</i> or <i>C</i>, +by subtracting the angle given from 90 degrees. When the included +angle is given, as at <i>B</i>, subtract one-half the included +angle from 90 degrees to obtain the required setting. Of course, +when using a compound rest, the lathe centers are set in line as +for straight turning, as otherwise the angle will be incorrect.</p> + +<h4>Rules for Figuring Tapers</h4> + +<table class="left" align="center" width="60%" border="0" cellpadding="5" cellspacing="0" summary="Figuring Tapers"> + +<tr> +<td style="width: 33%" class="center bt br bb bl">Given</td> +<td style="width: 33%" class="center bt bb br">To Find</td> +<td style="width: 33%" class="center bt bb br">Rule</td> +</tr> + +<tr valign="top"> +<td class="bl br">The taper per foot.</td> +<td class="br">The taper per inch.</td> +<td class="br">Divide the taper per foot by 12.</td> +</tr> + +<tr valign="top"> +<td class="bl br">The taper per inch.</td> +<td class="br">The taper per foot.</td> +<td class="br">Multiply the taper per inch by 12.</td> +</tr> + +<tr valign="top"> +<td class="bl br">End diameters and length of taper in inches.</td> +<td class="br">The taper per foot.</td> +<td class="br">Subtract small diameter from large; divide by length of taper, and multiply quotient by 12.</td> +</tr> + +<tr valign="top"> +<td class="bl br">Large diameter and length of taper in inches and taper per foot.</td> +<td class="br">Diameter at small end in inches.</td> +<td class="br">Divide taper per foot by 12; multiply by length of taper, and subtract result from large diameter.</td> +</tr> + +<tr valign="top"> +<td class="bl br">Small diameter and length of taper in inches, and taper per foot.</td> +<td class="br">Diameter at large end in inches.</td> +<td class="br">Divide taper per foot by 12; multiply by length of taper, and add result to small diameter.</td> +</tr> + +<tr valign="top"> +<td class="bl br">The taper per foot and two diameters in inches.</td> +<td class="br">Distance between two given diameters in inches.</td> +<td class="br">Subtract small diameter from large; divide remainder by taper per foot, and multiply quotient by 12.</td> +</tr> + +<tr valign="top"> +<td class="bl br bb">The taper per foot.</td> +<td class="br bb">Amount of taper in a certain length given in inches.</td> +<td class="br bb">Divide taper per foot by 12; multiply by given length of tapered part.</td> +</tr> + +</table> +<p> </p> + +<a name="Fig_3_16" id="Fig_3_16"></a> +<div class="figcenter"><div class="illobox450"><img src="images/106sm.png" alt="Disk Gage for Accurate Measurement of Angles and Tapers" /></div> +<p class="caption750">Fig. 16. Disk Gage for Accurate Measurement of Angles and Tapers</p> +</div> + +<a name="Secnum_3_9" id="Secnum_3_9"></a><p><b>Accurate Measurement of Angles and Tapers.</b>—When great +accuracy is required in the measurement of angles, or when<span class="pagenum"><a name="Pg_98" id="Pg_98">[98]</a></span> +originating tapers, disks are commonly used. The principle of +the disk method of taper measurement is that if two disks of +unequal diameters are placed either in contact or a certain distance +apart, lines tangent to their peripheries will represent an +angle or taper, the degree of which depends upon the diameters +of the two disks and the distance between them. The gage +shown in <a href="#Fig_3_16">Fig. 16</a>, which is a form commonly used for originating +tapers or measuring angles accurately, is set by means of disks. +This gage consists of two adjustable straight-edges <i>A</i> and <i>A<sub>1</sub></i>, +which are in contact with disks <i>B</i> and <i>B<sub>1</sub></i>. The angle <i>α</i> or the +taper between the straight-edges depends, of course, upon the +diameters of the disks and the center distance <i>C</i>, and as these +three dimensions can be measured accurately, it is possible to +set the gage to a given angle within very close limits. Moreover, +if a record of the three dimensions is kept, the exact setting +of the gage can be reproduced quickly at any time. The following +rules may be used for adjusting a gage of this type.</p> + +<a name="Secnum_3_10" id="Secnum_3_10"></a><p><b>To Find Center Distance for a Given Taper.</b>—When the +taper, in inches per foot, is given, to determine center distance +<i>C</i>. <i>Rule:</i> Divide the taper by 24 and find the angle corresponding +to the quotient in a table of tangents; then find the +sine corresponding to this angle and divide the difference between +the disk diameters by twice the sine.</p> + +<p><span class="pagenum"><a name="Pg_99" id="Pg_99">[99]</a></span> +<i>Example:</i> Gage is to be set to <sup class="enum">3</sup>/<sub class="denom">4</sub> inch per foot, and disk diameters +are 1.25 and 1.5 inch, respectively. Find the required +center distance for the disks.</p> + +<table class="formula" summary="Formula 99_1"> +<tr><td> 0.75 </td><td> </td><td> </td></tr> +<tr><td> —— </td><td> = </td><td> 0.03125.</td></tr> +<tr><td> 24 </td><td> </td><td> </td></tr> +</table> + +<p>The angle whose tangent is 0.03125 equals 1 degree 47.4 minutes;</p> + +<table class="formula" summary="Formula 99_22"> +<tr><td> sin 1° 47.4' = 0.03123; 1.50 - 1.25 = 0.25 inch;</td></tr> +</table> + +<p class="fsize60"> </p> + +<table class="formula" summary="Formula 99_3"> +<tr><td> 0.25 </td><td> </td><td> </td></tr> +<tr><td> ————— </td><td> = </td><td> 4.002 inches = center distance <i>C</i>. +</td></tr> +<tr><td> 2 × 0.03123 </td><td> </td><td> </td></tr> +</table> + +<a name="Secnum_3_11" id="Secnum_3_11"></a><p><b>To Find Center Distance for a Given Angle.</b>—When straight-edges +must be set to a given angle <i>α</i>, to determine center distance +<i>C</i> between disks of known diameter. <i>Rule:</i> Find the sine +of half the angle <i>α</i> in a table of sines; divide the difference +between the disk diameters by double this sine.</p> + +<p><i>Example:</i> If an angle <i>α</i> of 20 degrees is required, and the +disks are 1 and 3 inches in diameter, respectively, find the required +center distance <i>C</i>.</p> + +<table class="formula" summary="Formula 99_4"> +<tr><td> 20 </td><td> </td><td> </td></tr> +<tr><td> —— </td><td> = </td><td> 10 degrees; sin 10° = 0.17365;</td></tr> +<tr><td> 2 </td><td> </td><td> </td></tr> +</table> + +<p class="fsize60"> </p> + +<table class="formula" summary="Formula 99_5"> +<tr><td> 3 - 1 </td><td> </td><td> </td></tr> +<tr><td> ————— </td><td> = </td><td>5.759 inches = center distance <i>C</i>.</td></tr> +<tr><td> 2 × 0.17365 </td><td> </td><td> </td></tr> +</table> + +<a name="Secnum_3_12" id="Secnum_3_12"></a><p><b>To Find Angle for Given Taper per Foot.</b>—When the taper +in inches per foot is known, and the corresponding angle <i>α</i> is +required. <i>Rule:</i> Divide the taper in inches per foot by 24; +find the angle corresponding to the quotient, in a table of tangents, +and double this angle.</p> + +<p><i>Example:</i> What angle <i>α</i> is equivalent to a taper of 1<sup class="enum">1</sup>/<sub class="denom">2</sub> inch +per foot?</p> + +<table class="formula" summary="Formula 99_6"> +<tr><td> 1.5 </td><td> </td><td> </td></tr> +<tr><td> —— </td><td> = </td><td> 0.0625. </td></tr> +<tr><td> 24 </td><td> </td><td> </td></tr> +</table> + +<p>The angle whose tangent is 0.0625 equals 3 degrees 35 minutes, +nearly; then, 3 deg. 35 min. × 2 = 7 deg. 10 min.</p> + +<a name="Secnum_3_13" id="Secnum_3_13"></a><p><b>To Find Angle for Given Disk Dimensions.</b>—When the +diameters of the large and small disks and the center distance +are given, to determine the angle <i>α</i>. <i>Rule:</i> Divide the difference +<span class="pagenum"><a name="Pg_100" id="Pg_100">[100]</a></span> +between the disk diameters by twice the center distance; +find the angle corresponding to the quotient, in a table of sines, +and double the angle.</p> + +<p><i>Example:</i> If the disk diameters are 1 and 1.5 inch, respectively, +and the center distance is 5 inches, find the included +angle <i>α</i>.</p> + +<table class="formula" summary="Formula 100_1"> +<tr><td> 1.5 - 1 </td><td> </td><td> </td></tr> +<tr><td> ——— </td><td> = </td><td> 0.05.</td></tr> +<tr><td> 2 × 5 </td><td> </td><td> </td></tr> +</table> + +<p>The angle whose sine is 0.05 equals 2 degrees 52 minutes; then, +2 deg. 52 min. × 2 = 5 deg. 44 min. = angle <i>α</i>.</p> + +<a name="Fig_3_17" id="Fig_3_17"></a> +<div class="figcenter"><div class="illobox450"><img src="images/108sm.png" alt="Setting Center Mark in Line with Axis of Lathe Spindle by use of Test Indicator" /></div> +<p class="caption750">Fig. 17. Setting Center Mark in Line with Axis of Lathe Spindle +by use of Test Indicator</p> +</div> + +<a name="Secnum_3_14" id="Secnum_3_14"></a><p><b>Use of the Center Indicator.—</b>The center test indicator is +used for setting a center-punch mark, the position of which +corresponds with the center or axis of the hole to be bored, in +alignment with the axis of the lathe spindle. To illustrate, if +two holes are to be bored, say 5 inches apart, small punch +marks having that center-to-center distance would be laid out +as accurately as possible. One of these marks would then be +set central with the lathe spindle by using a center test indicator +as shown in <a href="#Fig_3_17">Fig. 17</a>. This indicator has a pointer <i>A</i> the +end of which is conical and enters the punch mark. The pointer +is held by shank <i>B</i> which is fastened in the toolpost. The +joint <i>C</i> by means of which the pointer is held to the shank is +universal; that is, it allows the pointer to move in any direction. +Now when the part being tested is rotated by running the<span class="pagenum"><a name="Pg_101" id="Pg_101">[101]</a></span> +lathe, if the center-punch mark is not in line with the axes of +the lathe spindle, obviously the outer end of pointer <i>A</i> will +vibrate, and as joint <i>C</i> is quite close to the inner end, a very +slight error in the location of the center-punch mark will cause +a perceptible movement of the outer end, as indicated by the +dotted lines. When the work has been adjusted until the +pointer remains practically stationary, the punch mark is central, +and the hole is bored. The other center-punch mark is +then set in the same way for boring the second hole. The +accuracy of this method depends, of course, upon the location +of the center-punch marks. A still more accurate way of +setting parts for boring holes to a given center-to-center distance +is described in the following:</p> + +<a name="Secnum_3_15" id="Secnum_3_15"></a><p><b>Locating Work by the Button Method.</b>—Among the different +methods employed by machinists and toolmakers for accurately +locating work such as jigs, etc., on the faceplate of a lathe, the +one most commonly used is known as the button method. +This scheme is so named because cylindrical bushings or buttons +are attached to the work in positions corresponding to the +holes to be bored, after which they are used in locating the +work. These buttons, which are ordinarily about <sup class="enum">1</sup>/<sub class="denom">2</sub> inch in +diameter, are ground and lapped to the same size and the ends +squared. The diameter should, preferably, be such that the<span class="pagenum"><a name="Pg_102" id="Pg_102">[102]</a></span> +radius can be determined easily, and the hole through the center +should be about <sup class="enum">1</sup>/<sub class="denom">8</sub> inch larger than the retaining screw, so that +the button can be shifted.</p> + +<a name="Fig_3_18" id="Fig_3_18"></a> +<div class="figcenter"><div class="illobox450"><img src="images/109sm.png" alt="Jig Plate with Buttons attached, ready for Boring" /></div> +<p class="caption750">Fig. 18. Jig-plate with Buttons attached, ready for Boring</p> +</div> + +<p>As an illustration of the practical application of the button +method, we shall consider, briefly, the way the holes would be +accurately machined in the jig-plate in <a href="#Fig_3_18">Fig. 18</a>. First the centers +of the seven holes should be laid off approximately correct +by the usual methods, after which small holes should be drilled +and tapped for the clamping screws <i>S</i>. After the buttons <i>B</i> +are clamped lightly in place, they are all set in correct relation +with each other and with the jig-plate. The proper location of +the buttons is very important as their positions largely determine +the accuracy of the work. A definite method of procedure +that would be applicable in all cases cannot, of course, +be given, as the nature of the work as well as the tools available +make it necessary to employ different methods.</p> + +<p>In this particular case, the three buttons <i>a</i>, <i>b</i> and <i>c</i> should be +set first, beginning with the one in the center. As this central +hole must be 2.30 and 2.65 inches from the finished sides <i>A</i> and +<i>A<sub>1</sub></i>, respectively, the work is first placed on an accurate surface-plate +as shown; by resting it first on one of these sides and then +on the other, and measuring with a vernier height gage, the +central button can be accurately set. The buttons <i>a</i> and <i>c</i> are +also set to the correct height from side <i>A<sub>1</sub></i> by using the height +<span class="pagenum"><a name="Pg_103" id="Pg_103">[103]</a></span> +gage, and in proper relation to the central button by using a +micrometer or a vernier caliper and measuring the over-all +dimension <i>x</i>. When measuring in this way, the diameter of one +button would be deducted to obtain the correct center-to-center +distance. After buttons <i>a</i>, <i>b</i> and <i>c</i> are set equidistant from +side A<sub>1</sub> and in proper relation to each other, the remaining +buttons should be set radially from the central button <i>b</i> and the +right distance apart. By having two micrometers or gages, +one set for the radial dimension <i>x</i> and the other for the chordal +distance <i>y</i>, the work may be done in a comparatively short +time.</p> + +<a name="Fig_3_19" id="Fig_3_19"></a> +<div class="figcenter"><div class="illobox450"><img src="images/110sm.png" alt="Setting a Button True Preparatory to Boring, by use of Test Indicator" /></div> +<p class="caption750">Fig. 19. Setting a Button True Preparatory to Boring, by use of +Test Indicator</p> +</div> + +<p>After the buttons have been tightened, all measurements +should be carefully checked; the work is then mounted on the +faceplate of the lathe, and one of the buttons, say <i>b</i>, is set true +by the use of a test indicator as shown in <a href="#Fig_3_19">Fig. 19</a>. When the +end of this indicator (which is one of a number of types on +the market) is brought into contact with the revolving button, +the vibration of the pointer <i>I</i> shows how much the button runs +out of true. When the pointer remains practically stationary, +thus showing that the button runs true, the latter should be +removed. The hole is then drilled nearly to the required size, +after which it is bored to the finish diameter. In a similar<span class="pagenum"><a name="Pg_104" id="Pg_104">[104]</a></span> +manner the other buttons are indicated and the holes bored, +one at a time. It is evident that if each button is correctly +located and set perfectly true in the lathe, the various holes +will be located at the required center-to-center dimensions +within very close limits.</p> + +<a name="Fig_3_20" id="Fig_3_20"></a> +<div class="figcenter"><img src="images/111sm.jpg" alt="Testing Concentricity of Button with Dial Gage" /> +<p class="caption750">Fig. 20. Testing Concentricity of Button with Dial Gage</p> +</div> + +<a name="Fig_3_21" id="Fig_3_21"></a> +<div class="figcenter"><img src="images/112sm.jpg" alt="Drilling a Bushing Hole" /> +<p class="caption750">Fig. 21. Drilling a Bushing Hole</p> +</div> + +<p><a href="#Fig_3_20">Fig. 20</a> shows how one of the buttons attached to a plate +in which three holes are to be bored is set true or concentric. +The particular indicator illustrated is of the dial type, any +error in the location of the button being shown by a hand over +a dial having graduations representing thousandths of an inch. +<a href="#Fig_3_21">Fig. 21</a> shows how the hole is drilled after the button is removed. +It will be noted that the drill is held in a chuck, the +taper shank of which fits into the tailstock spindle, this being +the method of holding small drills. After drilling, the hole is +bored as shown in <a href="#Fig_3_22">Fig. 22</a>. The boring tool should have a +keen edge to avoid springing, and if the work when clamped in +position, throws the faceplate out of balance, it is advisable to +restore the balance, before boring, by the use of a counter-weight, +because the lathe can be rotated quite rapidly when +boring such a small hole.</p> + +<a name="Fig_3_22" id="Fig_3_22"></a> +<div class="figcenter"><img src="images/113sm.jpg" alt="Boring a Bushing Hole" /> +<p class="caption750">Fig. 22. Boring a Bushing Hole</p> +</div> + +<a name="Fig_3_23" id="Fig_3_23"></a> +<div class="figcenter"><div class="illobox450"><img src="images/114asm.png" alt="Example of Work illustrating Accumulation of Errors" /></div> +<p class="caption750">Fig. 23. Example of Work illustrating Accumulation of Errors</p> +</div> + +<p>When doing precision work of this kind, the degree of accuracy +will depend upon the instruments used, the judgment<span class="pagenum"><a name="Pg_105" id="Pg_105">[105]</a></span> +and skill of the workman and the care exercised. A good +general rule to follow when locating bushings or buttons is to +use the method which is the most direct and which requires +the least number of measurements. As an illustration of how +errors may accumulate, let us assume that seven holes are to +be bored in the jig-plate shown in <a href="#Fig_3_23">Fig. 23</a>, so that they are the +same distance from each other and in a straight line. The +buttons may be brought into alignment by the use of a straight-edge, +and to simplify matters, it will be taken for granted that +they have been ground and lapped to the same size. If the +diameter of the buttons is first determined by measuring with a +micrometer, and then this diameter is deducted from the center +distance <i>x</i>, the difference will be the distance <i>y</i> between adjacent +buttons. Now if a temporary gage is made to length <i>y</i>, +all the buttons can be set practically the same distance apart, +the error between any two adjacent ones being very slight. +If, however, the total length <i>z</i> over the end buttons is measured +by some accurate means, the chances are that this distance will +not equal six times dimension <i>x</i> plus the diameter of one button, +as it should, because even a very slight error in the gage for +distance <i>y</i> would gradually accumulate as each button was +set. If a micrometer were available that would span two of<span class="pagenum"><a name="Pg_106" id="Pg_106">[106]</a></span> +the buttons, the measurements could be taken direct and greater +accuracy would doubtless be obtained. On work of this kind +where there are a number of holes that need to have accurate +over-all dimensions, the long measurements should first be +taken when setting the buttons, providing, of course, there are +proper facilities for so doing, and then the short ones. For example, +the end buttons in this case should first be set, then the +central one and finally those for the sub-divisions.</p> + +<a name="Fig_3_24" id="Fig_3_24"></a> +<div class="figcenter"><div class="illobox450"><img src="images/114bsm.png" alt="Special Arbor for Turning Eccentrics" /></div> +<p class="caption750">Fig. 24. Special Arbor for Turning Eccentrics</p> +</div> + +<a name="Secnum_3_16" id="Secnum_3_16"></a><p><b>Eccentric Turning.</b>—When one cylindrical surface must be +turned eccentric to another, as when turning the eccentric of +a steam engine, an arbor having two sets of centers is commonly +used, as shown in <a href="#Fig_3_24">Fig. 24</a>. The distance <i>x</i> between the +centers must equal one-half the total “throw” or stroke of the +eccentric. The hub of the eccentric is turned upon the centers +<i>a—a</i>, and the tongued eccentric surface, upon the offset centers, +as indicated by the illustration. Sometimes eccentrics are +turned while held upon special fixtures attached to the faceplate.</p> + +<p>When making an eccentric arbor, the offset center in each +end should be laid out upon radial lines which can be drawn<span class="pagenum"><a name="Pg_107" id="Pg_107">[107]</a></span> +across the arbor ends by means of a surface gage. Each center +is then drilled and reamed to the same radius <i>x</i> as near as +possible. The uniformity of the distance <i>x</i> at each end is then +tested by placing the mandrel upon the offset centers and rotating +it, by hand, with a dial indicator in contact at first one end +and then the other. The amount of offset can also be tested +either by measuring from the point of a tool held in the toolpost, +or by setting the tool to just graze the mandrel at extreme +inner and outer positions, and noting the movement of +the cross-slide by referring to the dial gage of the cross-feed +screw.</p> + +<a name="Fig_3_25" id="Fig_3_25"></a> +<div class="figcenter"><div class="illobox450"><img src="images/115sm.png" alt="Turning Engine Crank-pin in an Ordinary Lathe" /></div> +<p class="caption750">Fig. 25. Turning an Engine Crank-pin in an Ordinary Lathe</p> +</div> + +<a name="Secnum_3_17" id="Secnum_3_17"></a><p><b>Turning a Crankshaft in a Lathe.</b>—Another example of +eccentric turning is shown in <a href="#Fig_3_25">Fig. 25</a>. The operation is that of +turning the crank-pin of an engine crankshaft, in an ordinary +lathe. The main shaft is first rough-turned while the forging +revolves upon its centers <i>C</i> and <i>C<sub>1</sub></i> and the ends are turned to +fit closely the center-arms <i>A</i> and <i>A<sub>1</sub></i>. After the sides <i>B</i> and +<i>B<sub>1</sub></i> of the crank webs have been rough-faced, the center-arms +are attached to the ends of the shaft as shown in the illustration. +These arms have centers at <i>D</i> and <i>D<sub>1</sub></i> (located at the required +crank radius) which should be aligned with the rough pin, when<span class="pagenum"><a name="Pg_108" id="Pg_108">[108]</a></span> +attaching the arms, and it is advisable to insert braces <i>E</i> between +the arms and crank to take the thrust of the lathe centers. +With the forging supported in this way, the crank-pin and inner +sides of the webs are turned and faced, the work revolving +about the axis of the pin. The turning tools must extend beyond +the tool-holder far enough to allow the crank to clear as it +swings around. Owing to this overhang, the tool should be as +heavy as possible to make it rigid and it is necessary to take +comparatively light cuts and proceed rather cautiously. After +finishing the crank-pin and inside of the crank, the center-arms +are removed and the main body of the shaft and the sides <i>B</i> +and <i>B<sub>1</sub></i> are finished. This method of turning crankshafts is +often used in general repair shops, etc., especially where new +shafts do not have to be turned very often. It is slow and inefficient, +however, and where crankshafts are frequently turned, +special machines or attachments are used.</p> + +<a name="Fig_3_26" id="Fig_3_26"></a> +<div class="figcenter"><img src="images/116sm.jpg" alt="LeBlond Lathe with Special Equipment for Crankshaft Turning" /> +<p class="caption750">Fig. 26. LeBlond Lathe with Special Equipment for Crankshaft Turning</p> +</div> + +<a name="Secnum_3_18" id="Secnum_3_18"></a><p><b>Special Crankshaft Lathe.</b>—A lathe having special equipment +for rough-turning gas engine crankshaft pins is shown in<span class="pagenum"><a name="Pg_109" id="Pg_109">[109]</a></span> +<a href="#Fig_3_26">Fig. 26</a>. This lathe is a heavy-duty type built by the R. K. +LeBlond Machine Tool Co. It is equipped with special adjustable +headstock and tailstock fixtures designed to take crankshafts +having strokes up to about 6 inches. The tools are held +in a three-tool turret type of toolpost and there are individual +cross-stops for each tool. This lathe also has a roller steadyrest +for supporting the crankshaft; automatic stops for the +longitudinal feed, and a pump for supplying cutting lubricant. +The headstock fixture is carried on a faceplate mounted on the +spindle and so arranged as to be adjustable for cranks of different +throw. When the proper adjustment for a given throw has +been made, the slide is secured by four T-bolts. A graduated +scale and adjusting screw permit of accurate adjustments.</p> + +<p>The revolving fixture is accurately indexed for locating different +crank-pins in line with the lathe centers, by a hardened steel +plunger in the slide which engages with hardened bushings in +the fixture. The index is so divided that the fixture may be +rotated 120 or 180 degrees, making it adjustable for 2-, 4- and +6-throw cranks. After indexing, the fixture is clamped by two +T-bolts which engage a circular T-slot. The revolving fixture +is equipped with removable split bushings which can be replaced +to fit the line bearings of different sized crankshafts. +The work is driven by a V-shaped dovetail piece having a +hand-nut adjustment, which also centers the pin by the cheek +or web. The crank is held in position by a hinged clamp on +the fixture. The tailstock fixture is also adjustable and it is +mounted on a spindle which revolves in a bushing in the tailstock +barrel. The adjustment is obtained in the same manner +as on the headstock fixture, and removable split bushings as +well as a hinged clamp are also employed.</p> + +<p>The method of chucking a four-throw crank is as follows: +The two fixtures are brought into alignment by two locking +pins. One of these is located in the head and enters a bushing +in the large faceplate and the other is in the tailstock and engages +the tailstock fixture. The crankshaft is delivered to the +machine with the line bearings rough-turned and it is clamped +by the hinged clamp previously referred to and centered by the<span class="pagenum"><a name="Pg_110" id="Pg_110">[110]</a></span> +V-shaped driver. The locking pins for both fixtures are then +withdrawn and the machine is ready to turn two of the pins. +After these have been machined, the fixtures are again aligned +by the locking pins, the two T-bolts of the headstock fixture +and the hinged clamp at the tailstock are released, the indexing +plunger is withdrawn and the headstock fixture and crank are +turned 180 degrees or until the index plunger drops into place. +The crank is then clamped at the tailstock end and the revolving +fixture is secured by the two T-bolts previously referred to. +After the locking pins are withdrawn, the lathe is ready to +turn the two opposite pins.</p> + +<a name="Fig_3_27" id="Fig_3_27"></a> +<div class="figcenter"><div class="illobox450"><img src="images/118sm.png" alt="Diagrams showing Arrangements of Tools on LeBlond Lathe" /></div> +<p class="caption750">Fig. 27. Diagrams showing Arrangements of Tools on LeBlond Lathe</p> +</div> + +<a name="Secnum_3_19" id="Secnum_3_19"></a><p><b>Operation of Special Crankshaft Lathe.</b>—The total equipment +of this machine (see <a href="#Fig_3_27">Fig. 27</a>) is carried on a three-tool +turret tool-block. The method of turning a crankshaft is as +follows: A round-nosed turning tool is first fed into a cross stop +as illustrated in the plan view at <i>A</i>, which gives the proper +diameter. The feed is then engaged and the tool feeds across +the pin until the automatic stop lever engages the first stop, +which throws out the feed automatically. The carriage is then +moved against a positive stop by means of the handwheel. +The roller back-rest is next adjusted against the work by the +cross-feed handwheel operating through a telescopic screw, and<span class="pagenum"><a name="Pg_111" id="Pg_111">[111]</a></span> +the filleting tools are brought into position as at <i>B</i>. These are +run in against a stop, removing the part left by the turning tool +and giving the pin the proper width and fillets of the correct +radius. If the crankshaft has straight webs which must be +finished, two tools seen at <i>b</i> are used for facing the webs to +the correct width. During these last two operations, the crank +is supported by the roller back-rest, thus eliminating any tendency +of the work to spring.</p> + +<p>After one pin is finished in the manner described, the back-rest +is moved out of the way, the automatic stop lever raised, +the carriage shifted to the next pin, and the operation repeated. +The tools are held in position on the turret by studs, +and they can be moved and other tools quickly substituted for +pins of different widths. This machine is used for rough-turning +the pins close to the required size, the finishing operation +being done in a grinder. It should be mentioned, in +passing, that many crankshafts, especially the lighter designs +used in agricultural machinery, etc., are not turned at all but +are ground from the rough.</p> + +<a name="Fig_3_28" id="Fig_3_28"></a> +<div class="figcenter"><div class="illobox450"><img src="images/119sm.png" alt="Spherical Turning with Compound Rest, Concave Turning" /></div> +<p class="caption750">Fig. 28. (A) Spherical Turning with Compound Rest.<br />(B) Concave Turning</p> +</div> + +<a name="Secnum_3_20" id="Secnum_3_20"></a><p><b>Spherical Turning.</b>—Occasionally it may be necessary to +turn a spherical surface in the lathe. Sketch <i>A</i>, <a href="#Fig_3_28">Fig. 28</a>, shows +<span class="pagenum"><a name="Pg_112" id="Pg_112">[112]</a></span> +how a small ball-shaped end can be turned on a piece held in a +chuck. The lathe carriage is adjusted so that the pin around +which the compound rest swivels is directly under the center a. +The bolts which hold the swivel are slightly loosened to allow +the top slide to be turned, as indicated by the dotted lines; +this causes the tool point to move in an arc about center <i>a</i>, and +a spherical surface is turned. Light cuts must be taken as +otherwise it would be difficult to turn the slide around by +hand.</p> + +<p>Sketch <i>B</i> illustrates how a concave surface can be turned. +The cross-slide is adjusted until swivel pin is in line with the +lathe centers, and the carriage is moved along the bed until +the horizontal distance between center <i>b</i> of the swivel, and the +face of the work, equals the desired radius of the concave surface. +The turning is then done by swinging the compound +rest as indicated by the dotted lines. The slide can be turned +more evenly by using the tailstock center to force it around. +A projecting bar is clamped across the end of the slide at <i>d</i>, to +act as a lever, and a centered bar is placed between this lever +and the tailstock center; then by screwing out the tailstock +spindle, the slide is turned about pivot <i>b</i>. The alignment between +the swivel pin and the lathe centers can be tested by +taking a trial cut; if the swivel pin is too far forward, the tool +will not touch the turned surface if moved past center <i>c</i>, and if +the pin is too far back, the tool will cut in on the rear side.</p> + +<a name="Fig_3_29" id="Fig_3_29"></a> +<div class="figcenter"><div class="illobox450"><img src="images/120sm.png" alt="Spherical Turning Attachment for Engine Lathe" /></div> +<p class="caption750">Fig. 29. Spherical Turning Attachment for Engine Lathe</p> +</div> + +<a name="Secnum_3_21" id="Secnum_3_21"></a><p><span class="pagenum"><a name="Pg_113" id="Pg_113">[113]</a></span> +<b>Spherical Turning Attachments.</b>—When spherical turning +must be done repeatedly, special attachments are sometimes +used. <a href="#Fig_3_29">Fig. 29</a> shows an attachment applied to a lathe for turning +the spherical ends of ball-and-socket joints. The height or +radius of the cutting tool and, consequently, the diameter of +the turned ball, is regulated by adjusting screw <i>A</i>. The tool is +swung around in an arc, by turning handle <i>B</i> which revolves a +worm meshing with an enclosed worm-wheel. As will be seen, +the work is held in a special chuck, owing to its irregular +shape.</p> + +<a name="Fig_3_30" id="Fig_3_30"></a> +<div class="figcenter"><div class="illobox450"><img src="images/121sm.png" alt="Attachment for Turning Spherical End of Gasoline Engine Piston" /></div> +<p class="caption750">Fig. 30. Attachment for Turning Spherical End of Gasoline +Engine Piston</p> +</div> + +<p>Another spherical turning attachment is shown in <a href="#Fig_3_30">Fig. 30</a>. +This is used for machining the ends of gasoline engine pistons. +The cross-slide has bolted to it a bar <i>A</i> carrying a roller which +is pressed against a forming plate <i>B</i> by a heavy spring <i>C</i>. The +forming plate <i>B</i>, which is attached to a cross-piece fastened to +the ways of the lathe bed, is curved to correspond with the +radius required on the piston end, and when the tool is fed +laterally by moving the cross-slide, it follows the curve of plate<span class="pagenum"><a name="Pg_114" id="Pg_114">[114]</a></span> +<i>B</i>. The piston is held in a special hollow chuck which locates +it in a central position and holds it rigidly.</p> + +<p>In connection with lathe work, special attachments and tools +are often used, especially when considerable work of one class +must be turned; however, if a certain part is required in large +quantities, it is usually more economical to use some semi-automatic +or automatic turning machine, especially designed +for repetition work.</p> + +<a name="Fig_3_31" id="Fig_3_31"></a> +<div class="figcenter"><img src="images/122sm.jpg" alt="Front and Rear Tools used for Roughing" /> +<p class="caption750">Fig. 31. Front and Rear Tools used for Roughing</p> +</div> + +<a name="Secnum_3_22" id="Secnum_3_22"></a><p><b>Turning with Front and Rear Tools.</b>—In ordinary engine +lathe practice, one tool is used at a time, but some lathes are +equipped with tool-holders at the front and rear of the carriage +so that two tools can be used simultaneously. <a href="#Fig_3_31">Fig. 31</a> shows a +detail view of a lathe in which front and rear tools are being +used. These tools are of the inserted cutter type and the one +at the rear is inverted, as the rotary movement of the work is, +of course, upward on the rear side. This particular lathe was +designed for taking heavy roughing cuts and has considerable +driving power.</p> + +<p>The part shown in this illustration is a chrome-nickel steel +bar which is being roughed out to form a milling machine<span class="pagenum"><a name="Pg_115" id="Pg_115">[115]</a></span> +spindle. It is necessary to reduce the diameter of the bar from +5<sup class="enum">7</sup>/<sub class="denom">16</sub> inches to 3<sup class="enum">3</sup>/<sub +class="denom">4</sub> inches for a length of 27 inches, because of a +collar on one end. This reduction is made in one passage of the +two tools, with a feed of <sup class="enum">1</sup>/<sub class="denom">32</sub> inch per revolution and a speed of +60 revolutions per minute. The use of two tools for such heavy +roughing cuts is desirable, especially when the parts are required +in large quantities, because the thrust of the cut on one +side, which tends to deflect the work, is counteracted by the +thrust on the opposite side.</p> + +<p>Sometimes special tool-holders are made for the lathe, so +that more than one tool can be used for turning different surfaces +or diameters at the same time, the tools being set in the +proper relation to each other. The advantage of this method +has resulted in the design of a special lathe for multiple-tool +turning.</p> + +<a name="Fig_3_32" id="Fig_3_32"></a> +<div class="figcenter"><img src="images/123sm.jpg" alt="Lo-swing Lathe for Multiple Turning" /> +<p class="caption750">Fig. 32. Lo-swing Lathe for Multiple Turning</p> +</div> + +<a name="Secnum_3_23" id="Secnum_3_23"></a><p><b>A Multiple-tool Lathe.</b>—The lathe shown in <a href="#Fig_3_32">Fig. 32</a> (which +is built by the Fitchburg Machine Works and is known as the +Lo-swing) is designed especially for turning shafts, pins and +forgings not exceeding 3<sup class="enum">1</sup>/<sub class="denom">2</sub> inches in diameter. It has two carriages +<span class="pagenum"><a name="Pg_116" id="Pg_116">[116]</a></span> +<i>A</i> and <i>B</i> which, in conjunction with special tool-holders, +make it possible to turn several different diameters simultaneously. +At the front of this lathe there is an automatic stop-rod +<i>C</i> for disengaging the feed when the tools have turned a +surface to the required length. This stop-rod carries adjustable +stops <i>D</i> which are set to correspond with shoulders, etc., +on the work. The rod itself is also adjustable axially, so that +the tools, which are usually arranged in groups of two or more +(depending upon the nature of the work), can be disengaged at +a point nearer or farther from the headstock as may be required, +owing to a variation in the depth of center holes. For example, +if it were necessary to feed a group of tools farther toward the +headstock after they had been automatically disengaged, the +entire rod with its stops would be adjusted the required amount +in that direction.</p> + +<p>The gage <i>G</i>, which is attached to a swinging arm, is used to +set the stop bar with reference to a shoulder near the end of +the work, when it is necessary to finish other parts to a given +distance from such a shoulder or other surface. The use of<span class="pagenum"><a name="Pg_117" id="Pg_117">[117]</a></span> +this gage will be explained more fully later. Cooling lubricant +for the tools is supplied through the tubes <i>E</i>. The lathe shown +in the illustration is arranged for turning Krupp steel bars. +A rough bar and also one that has been turned may be seen to +the right. The plain cylindrical bar is turned to five different +diameters, by groups of tools held on both carriages.</p> + +<a name="Fig_3_33" id="Fig_3_33"></a> +<div class="figcenter"><img src="images/124sm.jpg" alt="Plan View showing Method of driving Steering Knuckle and Arrangement of Tools" /> +<p class="caption750">Fig. 33. Plan View showing Method of driving Steering Knuckle and Arrangement of Tools</p> +</div> + +<a name="Secnum_3_24" id="Secnum_3_24"></a><p><b>Examples of Multiple Turning.</b>—<a href="#Fig_3_33">Figs. 33</a> +and <a href="#Fig_3_34">34</a> show how a Lo-swing lathe is used for turning the steering knuckle of an +automobile. Four tools are used in this case, three cylindrical +surfaces and one tapering surface being turned at the same +time. For this job, the four tools are mounted on one carriage. +The taper part is turned by the second tool from the +headstock, which is caused to feed outward as the carriage<span class="pagenum"><a name="Pg_118" id="Pg_118">[118]</a></span> +advances by a taper attachment. This tool is held in a special +holder and bears against a templet at the rear, which is tapered +to correspond with the taper to be turned. This templet is +attached to a bar which, in turn, is fastened to a stationary +bracket seen to the extreme left in <a href="#Fig_3_33">Fig. 33</a>. This part is finished +in two operations, the tool setting being identical for each +operation, except for diameter adjustments. As the illustrations +show, three of the four tools employed are used for straight +turning on different diameters, while the fourth finishes the +taper.</p> + +<a name="Fig_3_34" id="Fig_3_34"></a> +<div class="figcenter"><div class="illobox450"><img src="images/125sm.png" alt="Plan View showing Method of driving Steering Knuckle and Arrangement of Tools" /></div> +<p class="caption750">Fig. 34. Plan View showing Method of driving Steering Knuckle and +Arrangement of Tools</p> +</div> + +<p>These pieces, which are rough drop forgings, are first reduced +to the approximate size. When it becomes necessary to +grind the tools, they are reset and those parts which have been +roughed out are turned to the finished size. The average time +for the first operation, which includes starting, stopping, turning +and replacing the piece, is one minute, while for the second +operation with the finer feed, an average time of two minutes +is required. The work is driven by sleeve <i>S</i>, which fits over the +spindle and is held in position by the regular driver, as shown. +This sleeve is notched to fit the knuckle, so that the latter can +easily and quickly be replaced when finished.</p> + +<p>One of the interesting features of this job lies in the method +of locating the shoulders on each knuckle, at the same distance +from the hole <i>H</i> which is drilled previously, and which receives +the bolt on which the knuckle swivels when assembled +in a car. As soon as the knuckle has been placed between the +centers, a close-fitting plug <i>P</i> (<a href="#Fig_3_33">Fig. 33</a>) is inserted in this hole +and the indicator arm with its attached gage or caliper <i>G</i> is +swung up to the position shown. The stop-rod on which the +stops have been previously set for the correct distance between +the shoulders is next adjusted axially until the gage <i>G</i> +just touches the plug <i>P</i>. The indicator is then swung out of +the way, and the piece turned. If the next knuckle were +centered, say, deeper than the previous one which would, of +course, cause it to be located nearer the headstock, obviously +all the shoulders would be located farther from the finished +hole, provided the position of the stops remained the same as<span class="pagenum"><a name="Pg_119" id="Pg_119">[119]</a></span> +before. In such a case their position would, however, be changed +by shifting the stop-rod until the gage <i>G</i> again touched the plug +thus locating all the stops with reference to the hole. As the +adjustment of the stop-rod changes the position of the taper +templet as well as the stops, it is evident that both the shoulders +and the taper are finished the same distance from the hole in +each case. The connection of the bracket (to which the templet +arm is attached) with the stop-rod is clearly shown in <a href="#Fig_3_33">Fig. 33</a>. +This bracket can either be locked to the ways or adjusted to +slide when the stop-rod is moved.</p> + +<a name="Fig_3_35" id="Fig_3_35"></a> +<div class="figcenter"><div class="illobox450"><img src="images/127sm.png" alt="First and Second Operations on Automobile Transmission Shaft—Lo-swing Lathe" /></div> +<p class="caption750">Fig. 35. First and Second Operations on Automobile Transmission +Shaft—Lo-swing Lathe</p> +</div> + +<p>The part illustrated in <a href="#Fig_3_35">Fig. 35</a> is an automobile transmission +shaft. In this particular case, cylindrical, tapering and spherical +surfaces are turned. The upper view shows, diagrammatically, +the arrangement of the tools and work for the first operation. +After the shaft is “spotted” at <i>A</i> for the steadyrest, the<span class="pagenum"><a name="Pg_120" id="Pg_120">[120]</a></span> +straight part <i>C</i> and the collar <i>B</i> are sized with tools <i>S</i> and <i>R</i> +which are mounted on the left-hand carriage. A concave groove +is then cut in collar <i>B</i> by tool <i>R</i>, after which spherical end <i>D</i> is +formed by a special attachment mounted on the right-hand carriage. +This attachment is the same, in principle, as the regular +taper-turning attachment, the substitution of a circular templet +<i>T</i> for the straight kind used on taper work being the only practical +difference.</p> + +<p>After the surfaces mentioned have been finished on a number +of pieces, the work is reversed and the tools changed as shown +by the lower view. The first step in the second operation is to +turn the body <i>E</i> of the shaft with the tool <i>T</i> on the left-hand +carriage. The taper <i>F</i> and the straight part <i>G</i> are then finished, +which completes the turning. It will be noted that in setting +up the machine for this second operation, it is arranged for +taper turning by simply replacing the circular templet with the +straight one shown. When this taper attachment is not in use, +the swiveling arm <i>M</i>, which is attached to a bracket, is swung +out of the way.</p> + +<p><span class="pagenum"><a name="Pg_121" id="Pg_121">[121]</a></span>The method of driving this shaft is worthy of note. A dog +having two driving arms each of which bears against a pin <i>N</i> +that passes through a hole in the spindle is used. As the ends +of this pin, against which the dog bears, are beveled in opposite +directions, the pin turns in its hole when the dog makes contact +with it and automatically adjusts itself against the two driving +members of the dog. The advantage of driving by a two-tailed +dog, as most mechanics know, is in equalizing the tendency +to spring slender parts while they are being turned.</p> + +<a name="Fig_3_36" id="Fig_3_36"></a> +<div class="figcenter"><div class="illobox450"><img src="images/128sm.png" alt="Axle End turned in One Traverse of the Five Tools shown" /></div> +<p class="caption750">Fig. 36. Axle End turned in One Traverse of the Five Tools shown</p> +</div> + +<p>In <a href="#Fig_3_36">Fig. 36</a> another turning operation on a lathe of this type +is shown, the work in this case being a rear axle for a motor +truck. The turning of this part is a good example of that class +of work where the rapid removal of metal is the important +feature. As the engraving shows, the stock, prior to turning, +is 3<sup class="enum">1</sup>/<sub class="denom">2</sub> inches in diameter and it is reduced to a minimum diameter +of 1<sup class="enum">1</sup>/<sub class="denom">16</sub> inch. This metal is turned off with one traverse of +the carriage or by one passage of the five tools, and the weight +of the chips removed from each end of the axle is approximately +12 pounds. The time required for the actual turning is about +9 minutes, while the total time for the operation, which includes +placing the heavy piece in the machine, turning, and<span class="pagenum"><a name="Pg_122" id="Pg_122">[122]</a></span> +removing the work from the lathe, is 12 minutes. The axle revolves, +while being turned, at 110 revolutions per minute and a +feed equivalent to 1 inch of tool travel to 60 revolutions of the +work is used. It will be noticed that the taper attachment is also +employed on this part, the taper being turned by the second +tool from the left. As the axle is equipped with roller bearings, +it was found desirable to finish the bearing part by a separate +operation; therefore, in the operation shown the axle is simply +roughed down rather close to the finished dimensions, leaving +enough material for a light finishing cut.</p> + +<a name="Fig_3_37" id="Fig_3_37"></a> +<div class="figcenter"><div class="illobox450"><img src="images/129sm.png" alt="Lathe Knurling Tool having Three Pairs of Knurls—Coarse, Medium and Fine" /></div> +<p class="caption750">Fig. 37. Lathe Knurling Tool having Three Pairs of Knurls—Coarse, +Medium and Fine</p> +</div> + +<a name="Secnum_3_25" id="Secnum_3_25"></a><p><b>Knurling in the Lathe.</b>—Knurling is done either to provide +a rough surface which can be firmly gripped by the hand or for +producing an ornamental effect. The handles of gages and +other tools are often knurled, and the thumb-screws used on +instruments, etc., usually have knurled edges. A knurled surface +consists of a series of small ridges or diamond-shaped projections, +and is produced in the lathe by the use of a tool similar +to the one shown in <a href="#Fig_3_37">Fig. 37</a>, this being one of several different +designs in common use. The knurling is done by two knurls +<i>A</i> and <i>B</i> having teeth or ridges which incline to the right on one +knurl and to the left on the opposite knurl, as shown by the +end view. When these two knurls are pressed against the work +as the latter revolves, one knurl forms a series of left-hand +ridges and the other knurl right-hand ridges, which cross and +form the diamond-shaped knurling which is generally used.</p> + +<p>If the surface to be knurled is wider than the knurls, the +power feed of the lathe should be engaged and the knurling tool +be traversed back and forth until the diamond-shaped projections +are well formed. To prevent forming a double set of +projections, feed the knurl in with considerable pressure at the +start, then partially relieve the pressure before engaging the +power feed. Use oil when knurling.</p> + +<p>The knurls commonly used for lathe work have spiral teeth +and ordinarily there are three classes, known as coarse, medium +and fine. The medium pitch is generally used. The teeth of +coarse knurls have a spiral angle of 36 degrees and the pitch +of the knurled cut (measured parallel to the axis of the work)<span class="pagenum"><a name="Pg_123" id="Pg_123">[123]</a></span> +should be about 8 per inch. For medium knurls, the spiral +angle is 29<sup class="enum">1</sup>/<sub class="denom">2</sub> degrees and the pitch, measured as before, is 12 +per inch. For fine knurls, the spiral angle is 25<sup class="enum">3</sup>/<sub class="denom">4</sub> degrees and +the pitch 20 per inch. The knurls should be about <sup class="enum">3</sup>/<sub class="denom">4</sub> inch in +diameter and <sup class="enum">3</sup>/<sub class="denom">8</sub> inch wide. When made to these dimensions, +coarse knurls have 34 teeth; medium, 50 teeth; and fine knurls, +80 teeth.</p> + +<p>The particular tool illustrated in <a href="#Fig_3_37">Fig. 37</a> has three pairs of +knurls of coarse, medium and fine pitch. These are mounted +in a revolving holder which not only serves to locate the required +set of knurls in the working position, but enables each +knurl to bear against the surface with equal pressure. Concave +knurls are sometimes used for knurling rounded edges on screw +heads, etc.</p> + +<a name="Secnum_3_26" id="Secnum_3_26"></a><p><b>Relieving Attachment.</b>—Some lathes, particularly those used +in toolrooms, are provided with relieving attachments which +are used for “backing off” the teeth of milling cutters, taps, +hobs, etc. If a milling cutter of special shape is to be made, the +cutter blank is first turned to the required form with a special +tool having a cutting edge that corresponds with the shape or +profile of the cutter to be made. The blank is then fluted or +gashed to form the teeth, after which the tops of the teeth are<span class="pagenum"><a name="Pg_124" id="Pg_124">[124]</a></span> +relieved or backed off to provide clearance for the cutting edges. +The forming tool used for turning the blank is set to match the +turned surface, and the teeth are backed off as the result of a +reciprocating action imparted to the toolslide by the relieving +attachment. The motion of the toolslide is so adjusted that +the tool will meet the front of each tooth and the return movement +begin promptly after the tool leaves the back end of the +tooth.</p> + +<a name="Fig_3_38" id="Fig_3_38"></a> +<div class="figcenter"><img src="images/131sm.jpg" alt="Hendey Relieving Attachment applied to a Lathe" /> +<p class="caption750">Fig. 38. Hendey Relieving Attachment applied to a Lathe</p> +</div> + +<p>These attachments differ somewhat in their construction and +arrangement but the principle of their operation is similar. +<a href="#Fig_3_38">Fig. 38</a> shows a Hendey relieving attachment applied to a lathe. +A bracket carrying the gearing <i>A</i> through which the attachment +is driven is mounted upon the main gear box of the lathe, and +the special slide <i>B</i>, which is used when relieving, is placed on +the cross-slide after removing the regular compound rest. The +gears at <i>A</i> are changed to suit the number of flutes or gashes in +the cutter, tap or whatever is to be relieved. If we assume that +the work is a formed milling cutter having nine teeth, then with +this particular attachment, a gear having 90 teeth would be +placed on the “stud” and a 40-tooth gear on the cam-shaft, the +two gears being connected by a 60-tooth intermediate gear.<span class="pagenum"><a name="Pg_125" id="Pg_125">[125]</a></span> +With this combination of gearing, the toolslide would move in +and out nine times for each revolution of the work, so that the +tool could back off the top of each tooth. (The gearing to use +for various numbers of flutes is shown by an index plate on the +attachment.) The amount of relief is varied to suit the work +being done, by means of a toothed coupling which makes it +possible to change the relative position between the eccentric +which actuates the toolslide and the cam lever, thereby lengthening +or shortening the reciprocating travel of the tool.</p> + +<a name="Fig_3_39" id="Fig_3_39"></a> +<div class="figcenter"><img src="images/132sm.jpg" alt="Relieving a Formed Cutter" /> +<p class="caption750">Fig. 39. Relieving a Formed Cutter</p> +</div> + +<a name="Secnum_3_27" id="Secnum_3_27"></a><p><b>Application of Relieving Attachment.</b>—Some typical examples +of the kind of work for which the relieving attachment +is used are shown in <a href="#Fig_3_39">Figs. 39</a> to <a href="#Fig_3_42">42</a>, inclusive. <a href="#Fig_3_39">Fig. 39</a> shows +how a formed milling cutter is relieved. The toolslide is set at +right angles to the axis of the work, and the tool moves in as +each tooth passes, and out while crossing the spaces or flutes +between the teeth. As the result of this movement, the tops of +the teeth are backed off eccentrically but the form or shape is +the same from the front to the back of the tooth; hence, a +cutter that has been relieved in this way can be ground repeatedly +without changing the profile of the teeth, provided the +faces are ground so as to lie in a radial plane.</p> + +<p><span class="pagenum"><a name="Pg_126" id="Pg_126">[126]</a></span>When relieving, the cutting speed should be much less than +when turning in order to give the toolslide time to operate +properly. A maximum of 180 teeth per minute is recommended, +and, if wide forming tools are used, it might be advisable +to reduce the speed so low that only 8 teeth per minute +would be relieved. It is also essential to use a tool having a keen +edge, and the toolslide should work freely but be closely adjusted +to the dovetail of the lower slide. Before beginning to +back off the teeth, it is a good plan to color the work either by +heating it or dipping into a strong solution of copper sulphate. +This will enable one to see plainly the cutting action of the +tool in order to stop relieving at the proper time.</p> + +<a name="Fig_3_40" id="Fig_3_40"></a> +<div class="figcenter"><img src="images/133sm.jpg" alt="Relieving Side of Angular Milling Cutter" /> +<p class="caption750">Fig. 40. Relieving Side of Angular Milling Cutter</p> +</div> + +<p><a href="#Fig_3_40">Fig. 40</a> shows a method of relieving the teeth of an angular +cutter. For an operation of this kind the toolslide is swiveled +around at right angles to the side that is to be relieved. By +the use of an additional universal joint and bearing to permit +the toolslide to be swung to a 90-degree angle, the teeth of +counterbores, etc., can be relieved on the ends. When the attachment +is used for relieving inside work, such as hollow mills +and threading dies, the eccentric which controls the travel of +the toolslide is set so that the relieving movement is away from<span class="pagenum"><a name="Pg_127" id="Pg_127">[127]</a></span> +the axis of the cutter instead of toward it. This change is +made by the toothed coupling previously referred to, which +connects the cam lever and oscillating shaft, the latter being +turned beyond the zero mark in a clockwise direction as far as +is necessary to obtain the desired amount of travel. For internal +work it is also necessary to change the position of the +opposing spring of the toolslide, so that it will press against +the end of the slide and prevent the tool from jumping into +the work.</p> + +<a name="Fig_3_41" id="Fig_3_41"></a> +<div class="figcenter"><img src="images/134sm.jpg" alt="Relieving a Right-hand Tap" /> +<p class="caption750">Fig. 41. Relieving a Right-hand Tap</p> +</div> + +<p><a href="#Fig_3_41">Fig. 41</a> shows how a right-hand tap is relieved. The ordinary +practice is to first set the tool the same as for cutting a thread. +The motion of the toolslide is then adjusted so that the tool on +the forward stroke will meet the front of each tooth, and start +back as soon as the tool leaves the end of the land or top of the +tooth. Taps having a left-hand thread can be relieved by two +different methods. With the first method the cut starts at the +cutting edge of each tooth, and ends at the “heel,” the tool +moving in toward the center of the work. With the second +method, the cut begins at the heel and discontinues at the cutting +edge, the tool being drawn away from the work during the<span class="pagenum"><a name="Pg_128" id="Pg_128">[128]</a></span> +cut. When using the first method the tap must be placed with +the point toward the headstock, the shank end being supported +by the tailstock center. This is done by providing an +extension or blank end at the point of the tap long enough to +hold the driving dog. With the second method, the tap is held +between centers the same as one having a right-hand thread, +but the travel of the toolslide is set the same as for inside relief.</p> + +<a name="Fig_3_42" id="Fig_3_42"></a> +<div class="figcenter"><img src="images/135sm.jpg" alt="Relieving a Hob having Spiral Flutes" /> +<p class="caption750">Fig. 42. Relieving a Hob having Spiral Flutes</p> +</div> + +<a name="Secnum_3_28" id="Secnum_3_28"></a><p><b>Relieving Hobs or Taps Having Spiral Flutes.</b>—With +this attachment, taps or hobs having “spiral” or helical flutes +can also be relieved. (A spiral flute is preferable to one that is +parallel to the axis, because with the former the tool has cutting +edges which are square with the teeth; this is of especial importance +when the lead of the hob or tap thread is considerable.) +When relieving work having spiral flutes (as illustrated in <a href="#Fig_3_42">Fig. +42</a>), the lead of the spiral and the gears necessary to drive the +attachment are first determined. After the attachment is +geared for the number of flutes and to compensate for the spiral, +the lead-screw is engaged and the backing-off operation is +performed the same as though the flutes were straight. The +carriage should not be disengaged from the lead-screw after +starting the cut, the tool being returned by reversing the lathe.</p> + +<p>When gearing the attachment for relieving a tap or hob +having spiral flutes, the gears are not selected for the actual +number of flutes around the circumference but for a somewhat +larger number which depends upon the lead of the hob thread +and the lead of the spiral flutes. Let us assume that a hob +has 6 spiral flutes and that the attachment is geared for that +number. The result would be that as the tool advanced along +the thread, it would not keep “in step” with the teeth because +the faces of the teeth lie along a spiral (or helix which is the +correct name for this curve); in other words, the tool would +soon be moving in too late to begin cutting at the proper time, +and to compensate for this, the attachment is geared so that the +tool will make a greater number of strokes per revolution of the +work than the actual number of flutes around the circumference.</p> + +<p>With this attachment, the two gears listed on the index plate +for the actual number of flutes are selected, and then two compensating +<span class="pagenum"><a name="Pg_129" id="Pg_129">[129]</a></span> +gears are added, thus forming a compound train of +gearing. The ratio <i>R</i> of these compensating gears is determined +as follows:</p> + +<table class="formula" summary="Formula 129_1"> +<tr><td> </td><td> </td><td> <i>r</i> + 1 </td></tr> +<tr><td> <i>R</i> </td><td> = </td><td> ——— </td></tr> +<tr><td> </td><td> </td><td> <i>r</i> </td></tr> +</table> + +in which + +<table class="formsymb" summary="Formula 129_2"> +<tr><td> <i>r</i> </td><td> = </td><td> <i>L</i> ÷ <i>l</i>; </td></tr> +<tr><td> <i>L</i> </td><td> = </td><td> lead of spiral;</td></tr> +<tr><td> <i>l</i> </td><td> = </td><td> lead of hob thread. </td></tr> +</table> + +<p>For example, if a hob has a pitch circumference of 3.25, a +single thread of 0.75 inch lead, and 6 spiral flutes, what compensating +gears would be required?</p> + +<p>The lead <i>L</i> of the spiral flutes is first determined by dividing +the square of the circumference <i>C</i> of the hob at the pitch line by +the lead <i>l</i> of the hob thread. Thus lead <i>L = C<sup>2</sup> ÷ l</i>, or, in this case, +<i>L</i> = 3.25<sup>2</sup> ÷ 0.75 = 14 inches, approximately. Then <i>r</i> = 14 ÷ 0.75 = +18<sup class="enum">2</sup>/<sub class="denom">3</sub>. Inserting these values in the formula for ratio R,</p> + +<table class="formula2" summary="Formula 129_3"> +<tr> +<td> </td> +<td> </td> +<td>18<sup class="enum">2</sup>/<sub class="denom">3</sub> + 1 </td> +<td> </td> +<td> 19<sup class="enum">2</sup>/<sub class="denom">3</sub> </td> +<td> </td> +<td>19<sup class="enum">2</sup>/<sub class="denom">3</sub> × 3 </td> +<td> </td> +<td> 59 </td> +</tr> + +<tr> +<td> <i>R</i> </td> +<td> = </td> +<td> ———— </td> +<td> = </td> +<td> ——— </td> +<td> = </td> +<td> ———— </td> +<td> = </td> +<td> —— </td> +</tr> + +<tr> +<td> </td> +<td> </td> +<td>18<sup class="enum">2</sup>/<sub class="denom">3</sub></td> +<td> </td> +<td>18<sup class="enum">2</sup>/<sub class="denom">3</sub></td> +<td> </td> +<td>18<sup class="enum">2</sup>/<sub class="denom">3</sub> × 3</td> +<td> </td> +<td> 56 </td> +</tr> +</table> + +<p>Hence, the compensating gears will have 56 and 59 teeth, respectively, +the latter being the driver. As the gears for 6 flutes +listed on the regular index plate are, stud-gear 60 teeth, cam-shaft +gear 40 teeth, the entire train of gears would be as follows: +Gear on stud, 60; <i>driven</i> intermediate gear, 56; <i>driving</i> intermediate +gear, 59; cam-shaft gear, 40. It will be understood that +the position of the driving gears or the driven gears can be +transposed without affecting the ratio.</p> + +<a name="Secnum_3_29" id="Secnum_3_29"></a><p><b>Classes of Fits Used in Machine Construction.</b>—In assembling +machine parts it is necessary to have some members fit +together tightly, whereas other parts such as shafts, etc., must be +free to move or revolve with relation to each other. The accuracy +required for a fitting varies for different classes of work. +A shaft that revolves in its bearing must be slightly smaller +than the bearing so that there will be room for a film of lubricant. +A crank-pin that must be forced into the crank-disk is<span class="pagenum"><a name="Pg_130" id="Pg_130">[130]</a></span> +made a little larger in diameter than the hole, to secure a tight +fit. When a very accurate fitting between two cylindrical parts +that must be assembled without pressure is required, the +diameter of the inner member is made as close to the diameter +of the outer member as is possible. In ordinary machine construction, +five classes of fits are used, <i>viz</i>; running fit, push +fit, driving fit, forced fit and shrinkage fit. The running fit, +as the name implies, is employed when parts must rotate; the +push fit is not sufficiently free to rotate; the other classes referred +to are used for assembling parts that must be held in +fixed positions.</p> + +<a name="Secnum_3_30" id="Secnum_3_30"></a><p><b>Forced Fits.</b>—This is the term used when a pin, shaft or +other cylindrical part is forced into a hole of slightly smaller +diameter, by the use of a hydraulic press or other means. As a +rule, forced fits are restricted to parts of small and medium +size, while shrinkage fits have no such limitations and are especially +applicable when a maximum “grip” is desired, or when +(as in the construction of ordnance) accurate results as to the +intensity of stresses produced in the parts united are required. +The proper allowance for a forced fit depends upon the mass of +metal surrounding the hole, the size of the work, the kind and +quality of the material of which the parts are composed and the +smoothness and accuracy of the pin and bore. When a pin or +other part is pressed into a hole a second time, the allowance +for a given tonnage should be diminished somewhat because the +surface of the bore is smoother and the metal more compact. +The pressure required in assembling a forced fit will also vary +for cast hubs of the same size, if they are not uniform in hardness. +Then there is the personal factor which is much in evidence +in work of this kind; hence, data and formulas for forced +fit allowances must be general in their application.</p> + +<span class="pagenum"><a name="Pg_131" id="Pg_131">[131]</a></span> + +<h4>Allowances for Different Classes of Fits</h4> + +<p class="fsize80 center">(Newall Engineering Co.)</p> + +<table align="center" class="center" width="55%" cellpadding="0" cellspacing="0" summary="Allowances for Fits"> + +<tr> +<td class="bt bl" rowspan="2">Class</td> +<td class="bt bl br" colspan="11">Tolerances in Standard Holes<a name="Fnanchor_2"></a><a href="#Fn_2" class="fnanchor">[1]</a></td> +</tr> + +<tr> +<td class="bt bl">Nominal Diameters</td> +<td class="bt bl" colspan="2">Up to <sup class="enum">1</sup>/<sub class="denom">2</sub>"</td> +<td class="bt bl" colspan="2"> <sup class="enum">9</sup>/<sub class="denom">16</sub>" - 1" </td> +<td class="bt bl" colspan="2"> 1<sup class="enum">1</sup>/<sub class="denom">16</sub>" - 2" </td> +<td class="bt bl" colspan="2"> 2<sup class="enum">1</sup>/<sub class="denom">16</sub>" - 3" </td> +<td class="bt bl br" colspan="2"> 3<sup class="enum">1</sup>/<sub class="denom">16</sub>" - 4" </td> +</tr> + +<tr> +<td class="bt bl" style="width: 15%" rowspan="3">A</td> +<td class="bt bl" style="width: 20%">High Limit</td> +<td class="bt bl" align="right" style="width: 3%">+</td> +<td class="bt" align="left" style="width: 10%">0.0002</td> +<td class="bt bl" align="right" style="width: 3%">+</td> +<td class="bt" align="left" style="width: 10%">0.0005</td> +<td class="bt bl" align="right" style="width: 3%">+</td> +<td class="bt" align="left" style="width: 10%">0.0007</td> +<td class="bt bl" align="right" style="width: 3%">+</td> +<td class="bt" align="left" style="width: 10%">0.0010</td> +<td class="bt bl" align="right" style="width: 3%">+</td> +<td class="bt br" align="left" style="width: 10%">0.0010</td> +</tr> + +<tr> +<td class="bl">Low Limit</td> +<td class="bl" align="right">-</td> +<td align="left">0.0002</td> +<td class="bl" align="right">-</td> +<td align="left">0.0002</td> +<td class="bl" align="right">-</td> +<td align="left">0.0002</td> +<td class="bl" align="right">-</td> +<td align="left">0.0005</td> +<td class="bl" align="right">-</td> +<td class="br" align="left">0.0005</td> +</tr> + +<tr> +<td class="bl">Tolerance</td> +<td class="bl" align="right"> </td> +<td align="left">0.0004</td> +<td class="bl" align="right"> </td> +<td align="left">0.0007</td> +<td class="bl" align="right"> </td> +<td align="left">0.0009</td> +<td class="bl" align="right"> </td> +<td align="left">0.0015</td> +<td class="bl" align="right"> </td> +<td class="br" align="left">0.0015</td> +</tr> + +<tr> +<td class="bt bl" rowspan="3">B</td> +<td class="bt bl" >High Limit</td> +<td class="bt bl" align="right">+</td> +<td class="bt" align="left">0.0005</td> +<td class="bt bl" align="right">+</td> +<td class="bt" align="left">0.0007</td> +<td class="bt bl" align="right">+</td> +<td class="bt" align="left">0.0010</td> +<td class="bt bl" align="right">+</td> +<td class="bt" align="left">0.0012</td> +<td class="bt bl" align="right">+</td> +<td class="bt br" align="left">0.0015</td> +</tr> + +<tr> +<td class="bl">Low Limit</td> +<td class="bl" align="right">-</td> +<td align="left">0.0005</td> +<td class="bl" align="right">-</td> +<td align="left">0.0005</td> +<td class="bl" align="right">-</td> +<td align="left">0.0005</td> +<td class="bl" align="right">-</td> +<td align="left">0.0007</td> +<td class="bl" align="right">-</td> +<td class="br" align="left">0.0007</td> +</tr> + +<tr> +<td class="bl">Tolerance</td> +<td class="bl" align="right"> </td> +<td align="left">0.0010</td> +<td class="bl" align="right"> </td> +<td align="left">0.0012</td> +<td class="bl" align="right"> </td> +<td align="left">0.0015</td> +<td class="bl" align="right"> </td> +<td align="left">0.0019</td> +<td class="bl" align="right"> </td> +<td class="br" align="left">0.0022</td> +</tr> + +<tr> +<td class="bt br bl" colspan="12">Allowances for Forced Fits</td> +</tr> + +<tr> +<td class="bt bl" rowspan="3">F</td> +<td class="bt bl">High Limit</td> +<td class="bt bl" align="right">+</td> +<td class="bt" align="left">0.0010</td> +<td class="bt bl" align="right">+</td> +<td class="bt" align="left">0.0020</td> +<td class="bt bl" align="right">+</td> +<td class="bt" align="left">0.0040</td> +<td class="bt bl" align="right">+</td> +<td class="bt" align="left">0.0060</td> +<td class="bt bl" align="right">+</td> +<td class="bt br" align="left">0.0080</td> +</tr> + +<tr> +<td class="bl">Low Limit</td> +<td class="bl" align="right">+</td> +<td align="left">0.0005</td> +<td class="bl" align="right">+</td> +<td align="left">0.0015</td> +<td class="bl" align="right">+</td> +<td align="left">0.0030</td> +<td class="bl" align="right">+</td> +<td align="left">0.0045</td> +<td class="bl" align="right">+</td> +<td class="br" align="left">0.0060</td> +</tr> + +<tr> +<td class="bl">Tolerance</td> +<td class="bl" align="right"> </td> +<td align="left">0.0005</td> +<td class="bl" align="right"> </td> +<td align="left">0.0005</td> +<td class="bl" align="right"> </td> +<td align="left">0.0010</td> +<td class="bl" align="right"> </td> +<td align="left">0.0015</td> +<td class="bl" align="right"> </td> +<td class="br" align="left">0.0020</td> +</tr> + +<tr> +<td class="bt br bl" colspan="12">Allowances for Driving Fits</td> +</tr> + +<tr> +<td class="bt bl" rowspan="3">D</td> +<td class="bt bl">High Limit</td> +<td class="bt bl" align="right">+</td> +<td class="bt" align="left">0.0005</td> +<td class="bt bl" align="right">+</td> +<td class="bt" align="left">0.0010</td> +<td class="bt bl" align="right">+</td> +<td class="bt" align="left">0.0015</td> +<td class="bt bl" align="right">+</td> +<td class="bt" align="left">0.0025</td> +<td class="bt bl" align="right">+</td> +<td class="bt br" align="left">0.0030</td> +</tr> + +<tr> +<td class="bl">Low Limit</td> +<td class="bl" align="right">+</td> +<td align="left">0.0002</td> +<td class="bl" align="right">+</td> +<td align="left">0.0007</td> +<td class="bl" align="right">+</td> +<td align="left">0.0010</td> +<td class="bl" align="right">+</td> +<td align="left">0.0015</td> +<td class="bl" align="right">+</td> +<td class="br" align="left">0.0020</td> +</tr> + +<tr> +<td class="bl">Tolerance</td> +<td class="bl" align="right"> </td> +<td align="left">0.0003</td> +<td class="bl" align="right"> </td> +<td align="left">0.0003</td> +<td class="bl" align="right"> </td> +<td align="left">0.0005</td> +<td class="bl" align="right"> </td> +<td align="left">0.0010</td> +<td> </td> +<td class="br" align="left">0.0010</td> +</tr> + +<tr> +<td class="bt br bl" colspan="12">Allowances for Push Fits</td> +</tr> + +<tr> +<td class="bt bl" rowspan="3">P</td> +<td class="bt bl">High Limit</td> +<td class="bt bl" align="right">-</td> +<td class="bt" align="left">0.0002</td> +<td class="bt bl" align="right">-</td> +<td class="bt" align="left">0.0002</td> +<td class="bt bl" align="right">-</td> +<td class="bt" align="left">0.0002</td> +<td class="bt bl" align="right">-</td> +<td class="bt" align="left">0.0005</td> +<td class="bt bl" align="right">-</td> +<td class="bt br" align="left">0.0005</td> +</tr> + +<tr> +<td class="bl">Low Limit</td> +<td class="bl" align="right">-</td> +<td align="left">0.0007</td> +<td class="bl" align="right">-</td> +<td align="left">0.0007</td> +<td class="bl" align="right">-</td> +<td align="left">0.0007</td> +<td class="bl" align="right">-</td> +<td align="left">0.0010</td> +<td class="bl" align="right">-</td> +<td class="br" align="left">0.0010</td> +</tr> + +<tr> +<td class="bl">Tolerance</td> +<td class="bl" align="right"> </td> +<td align="left">0.0005</td> +<td class="bl" align="right"> </td> +<td align="left">0.0005</td> +<td class="bl" align="right"> </td> +<td align="left">0.0005</td> +<td class="bl" align="right"> </td> +<td align="left">0.0005</td> +<td class="bl" align="right"> </td> +<td class="br" align="left">0.0005</td> +</tr> + +<tr> +<td class="bt br bl" colspan="12">Allowances for Running Fits<a name="Fnanchor_3"></a><a href="#Fn_3" class="fnanchor">[2]</a></td> +</tr> + +<tr> +<td class="bt bl" rowspan="3">X</td> +<td class="bt bl">High Limit</td> +<td class="bt bl" align="right">-</td> +<td class="bt" align="left">0.0010</td> +<td class="bt bl" align="right">-</td> +<td class="bt" align="left">0.0012</td> +<td class="bt bl" align="right">-</td> +<td class="bt" align="left">0.0017</td> +<td class="bt bl" align="right">-</td> +<td class="bt" align="left">0.0020</td> +<td class="bt bl" align="right">-</td> +<td class="bt br" align="left">0.0025</td> +</tr> + +<tr> +<td class="bl">Low Limit</td> +<td class="bl" align="right">-</td> +<td align="left">0.0020</td> +<td class="bl" align="right">-</td> +<td align="left">0.0027</td> +<td class="bl" align="right">-</td> +<td align="left">0.0035</td> +<td class="bl" align="right">-</td> +<td align="left">0.0042</td> +<td class="bl" align="right">-</td> +<td class="br" align="left">0.0050</td> +</tr> + +<tr> +<td class="bl">Tolerance</td> +<td class="bl" align="right"> </td> +<td align="left">0.0010</td> +<td class="bl" align="right"> </td> +<td align="left">0.0015</td> +<td class="bl" align="right"> </td> +<td align="left">0.0018</td> +<td class="bl" align="right"> </td> +<td align="left">0.0022</td> +<td class="bl" align="right"> </td> +<td class="br" align="left">0.0025</td> +</tr> + +<tr> +<td class="bt bl" rowspan="3">Y</td> +<td class="bt bl">High Limit</td> +<td class="bt bl" align="right">-</td> +<td class="bt" align="left">0.0007</td> +<td class="bt bl" align="right">-</td> +<td class="bt" align="left">0.0010</td> +<td class="bt bl" align="right">-</td> +<td class="bt" align="left">0.0012</td> +<td class="bt bl" align="right">-</td> +<td class="bt" align="left">0.0015</td> +<td class="bt bl" align="right">-</td> +<td class="bt br" align="left">0.0020</td> +</tr> + +<tr> +<td class="bl">Low Limit</td> +<td class="bl" align="right">-</td> +<td align="left">0.0012</td> +<td class="bl" align="right">-</td> +<td align="left">0.0020</td> +<td class="bl" align="right">-</td> +<td align="left">0.0025</td> +<td class="bl" align="right">-</td> +<td align="left">0.0030</td> +<td class="bl" align="right">-</td> +<td class="br" align="left">0.0035</td> +</tr> + +<tr> +<td class="bl">Tolerance</td> +<td class="bl" align="right"> </td> +<td align="left">0.0005</td> +<td class="bl" align="right"> </td> +<td align="left">0.0010</td> +<td class="bl" align="right"> </td> +<td align="left">0.0013</td> +<td class="bl" align="right"> </td> +<td align="left">0.0015</td> +<td class="bl" align="right"> </td> +<td class="br" align="left">0.0015</td> +</tr> + +<tr> +<td class="bt bl bb" rowspan="3">Z</td> +<td class="bt bl">High Limit</td> +<td class="bt bl" align="right">-</td> +<td class="bt" align="left">0.0005</td> +<td class="bt bl" align="right">-</td> +<td class="bt" align="left">0.0007</td> +<td class="bt bl" align="right">-</td> +<td class="bt" align="left">0.0007</td> +<td class="bt bl" align="right">-</td> +<td class="bt" align="left">0.0010</td> +<td class="bt bl" align="right">-</td> +<td class="bt br" align="left">0.0010</td> +</tr> + +<tr> +<td class="bl">Low Limit</td> +<td class="bl" align="right">-</td> +<td align="left">0.0007</td> +<td class="bl" align="right">-</td> +<td align="left">0.0012</td> +<td class="bl" align="right">-</td> +<td align="left">0.0015</td> +<td class="bl" align="right">-</td> +<td align="left">0.0020</td> +<td class="bl" align="right">-</td> +<td class="br" align="left">0.0022</td> +</tr> + +<tr> +<td class="bl bb">Tolerance</td> +<td class="bl bb" align="right"> </td> +<td class="bb" align="left">0.0002</td> +<td class="bl bb" align="right"> </td> +<td class="bb" align="left">0.0005</td> +<td class="bl bb" align="right"> </td> +<td class="bb" align="left">0.0008</td> +<td class="bl bb" align="right"> </td> +<td class="bb" align="left">0.0010</td> +<td class="bl bb" align="right"> </td> +<td class="br bb" align="left">0.0012</td> +</tr> + +</table> +<p> </p> + +<hr class="l10" /> +<p class="footnote"><a name="Fn_2" id="Fn_2"></a><span class="label"><a href="#Fnanchor_2">[1]</a> +</span>Tolerance is provided for holes, which ordinary standard reamers can produce, in two grades, +Classes A and B, the selection of which is a question for the user's decision and dependent upon +the quality of the work required; some prefer to use Class A as working limits and Class B as +inspection limits.</p> + +<p class="footnote"><a name="Fn_3" id="Fn_3"></a><span class="label"><a href="#Fnanchor_3">[2]</a> +</span>Running fits, which are the most commonly required, are divided into three grades: +Class X for engine and other work where easy fits are wanted; Class Y for high speeds and good +average machine work; Class Z for fine tool work.</p> +<hr class="l10" /> + +<a name="Secnum_3_31" id="Secnum_3_31"></a><p><b>Allowance for Forced Fits.</b>—The allowance per inch of +diameter usually ranges from 0.001 inch to 0.0025 inch, 0.0015 +being a fair average. Ordinarily, the allowance per inch decreases +as the diameter increases; thus the total allowance for +a diameter of 2 inches might be 0.004 inch, whereas for a diameter +of 8 inches the total allowance might not be over 0.009 or<span class="pagenum"><a name="Pg_132" id="Pg_132">[132]</a></span> +0.010 inch. In some shops the allowance is made practically +the same for all diameters, the increased surface area of the +larger sizes giving sufficient increase in pressure. The parts to +be assembled by forced fits are usually made cylindrical, although +sometimes they are slightly tapered. The advantages +of the taper form are that the possibility of abrasion of the +fitted surfaces is reduced; that less pressure is required in +assembling; and that the parts are more readily separated +when renewal is required. On the other hand, the taper fit is +less reliable, because if it loosens, the entire fit is free with but +little axial movement. Some lubricant, such as white lead and +lard oil mixed to the consistency of paint, should be applied to +the pin and bore before assembling, to reduce the tendency of +abrasion.</p> + +<a name="Secnum_3_32" id="Secnum_3_32"></a><p><b>Pressure for Forced Fits.</b>—The pressure required for assembling +cylindrical parts depends not only upon the allowance for +the fit, but also upon the area of the fitted surfaces, the pressure +increasing in proportion to the distance that the inner member +is forced in. The approximate ultimate pressure in pounds can +be determined by the use of the following formula in conjunction +with the accompanying table of “<a href="#Pg_132">Pressure Factors</a>.”</p> + +<h4>Pressure Factors</h4> + +<table align="center" class="center" width="60%" frame="border" rules="all" cellpadding="4" cellspacing="4" summary="Pressure Factors"> + +<tr> +<td>Diameter, Inches</td> +<td class="br2">Pressure Factor</td> +<td>Diameter, Inches</td> +<td class="br2">Pressure Factor</td> +<td>Diameter, Inches</td> +<td class="br2">Pressure Factor</td> +<td>Diameter, Inches</td> +<td class="br2">Pressure Factor</td> +<td>Diameter, Inches</td> +<td>Pressure Factor</td> +</tr> + +<tr> +<td>1</td> +<td class="br2">500</td> +<td>3<sup class="enum">1</sup>/<sub class="denom">2</sub></td> +<td class="br2">132</td> +<td>6</td> +<td class="br2">75</td> +<td>9</td> +<td class="br2">48.7</td> +<td>14</td> +<td>30.5</td> +</tr> + +<tr> +<td>1<sup class="enum">1</sup>/<sub class="denom">4</sub></td> +<td class="br2">395</td> +<td>3<sup class="enum">3</sup>/<sub class="denom">4</sub></td> +<td class="br2">123</td> +<td>6<sup class="enum">1</sup>/<sub class="denom">4</sub></td> +<td class="br2">72</td> +<td>9<sup class="enum">1</sup>/<sub class="denom">2</sub></td> +<td class="br2">46.0</td> +<td>14<sup class="enum">1</sup>/<sub class="denom">2</sub></td> +<td>29.4</td> +</tr> + +<tr> +<td>1<sup class="enum">1</sup>/<sub class="denom">2</sub></td> +<td class="br2">325</td> +<td>4</td> +<td class="br2">115</td> +<td>6<sup class="enum">1</sup>/<sub class="denom">2</sub></td> +<td class="br2">69</td> +<td>10</td> +<td class="br2">43.5</td> +<td>15</td> +<td>28.3</td> +</tr> + +<tr> +<td>1<sup class="enum">3</sup>/<sub class="denom">4</sub></td> +<td class="br2">276</td> +<td>4<sup class="enum">1</sup>/<sub class="denom">4</sub></td> +<td class="br2">108</td> +<td>6<sup class="enum">3</sup>/<sub class="denom">4</sub></td> +<td class="br2">66</td> +<td>10<sup class="enum">1</sup>/<sub class="denom">2</sub></td> +<td class="br2">41.3</td> +<td>15<sup class="enum">1</sup>/<sub class="denom">2</sub></td> +<td>27.4</td> +</tr> + +<tr> +<td>2</td> +<td class="br2">240</td> +<td>4<sup class="enum">1</sup>/<sub class="denom">2</sub></td> +<td class="br2">101</td> +<td>7</td> +<td class="br2">64</td> +<td>11</td> +<td class="br2">39.3</td> +<td>16</td> +<td>26.5</td> +</tr> + +<tr> +<td>2<sup class="enum">1</sup>/<sub class="denom">4</sub></td> +<td class="br2">212</td> +<td>4<sup class="enum">3</sup>/<sub class="denom">4</sub></td> +<td class="br2">96</td> +<td>7<sup class="enum">1</sup>/<sub class="denom">4</sub></td> +<td class="br2">61</td> +<td>11<sup class="enum">1</sup>/<sub class="denom">2</sub></td> +<td class="br2">37.5</td> +<td>16<sup class="enum">1</sup>/<sub class="denom">2</sub></td> +<td>25.6</td> +</tr> + +<tr> +<td>2<sup class="enum">1</sup>/<sub class="denom">2</sub></td> +<td class="br2">189</td> +<td>5</td> +<td class="br2">91</td> +<td>7<sup class="enum">1</sup>/<sub class="denom">2</sub></td> +<td class="br2">59</td> +<td>12</td> +<td class="br2">35.9</td> +<td>17</td> +<td>24.8</td> +</tr> + +<tr> +<td>2<sup class="enum">3</sup>/<sub class="denom">4</sub></td> +<td class="br2">171</td> +<td>5<sup class="enum">1</sup>/<sub class="denom">4</sub></td> +<td class="br2">86</td> +<td>7<sup class="enum">3</sup>/<sub class="denom">4</sub></td> +<td class="br2">57</td> +<td>12<sup class="enum">1</sup>/<sub class="denom">2</sub></td> +<td class="br2">34.4</td> +<td>17<sup class="enum">1</sup>/<sub class="denom">2</sub></td> +<td>24.1</td> +</tr> + +<tr> +<td>3</td> +<td class="br2">156</td> +<td>5<sup class="enum">1</sup>/<sub class="denom">2</sub></td> +<td class="br2">82</td> +<td>8</td> +<td class="br2">55</td> +<td>13</td> +<td class="br2">33.0</td> +<td>18</td> +<td>23.4</td> +</tr> + +<tr> +<td>3<sup class="enum">1</sup>/<sub class="denom">4</sub></td> +<td class="br2">143</td> +<td>5<sup class="enum">3</sup>/<sub class="denom">4</sub></td> +<td class="br2">78</td> +<td>8<sup class="enum">1</sup>/<sub class="denom">2</sub></td> +<td class="br2">52</td> +<td>13<sup class="enum">1</sup>/<sub class="denom">2</sub></td> +<td class="br2">31.7</td> +<td>....</td> +<td>....</td> +</tr> + +</table> + +<p>Assuming that <i>A</i> = area of fitted surface; <i>a</i> = total allowance +in inches; <i>P</i> = ultimate pressure required, in tons; <i>F</i> = +pressure factor based upon assumption that the diameter of the<span class="pagenum"><a name="Pg_133" id="Pg_133">[133]</a></span> +hub is twice the diameter of the bore, that the shaft is of machine +steel, and the hub of cast iron, then,</p> + +<table class="formula" summary="Formula 133_1"> +<tr><td> </td><td> </td><td><i>A</i> × <i>a</i> × <i>F</i> </td></tr> +<tr><td> <i>P</i> </td><td> = </td><td> ————— </td></tr> +<tr><td> </td><td> </td><td> 2 </td></tr> +</table> + +<p><i>Example:</i>—What will be the approximate pressure required +for forcing a 4-inch machine steel shaft having an allowance of +0.0085 inch into a cast-iron hub 6 inches long?</p> + +<p class="ind05"><i>A</i> = 4 × 3.1416 × 6 = 75.39 square inches;</p> + +<p><i>F</i>, for a diameter of 4 inches, = 115 (see table of “<a href="#Pg_132">Pressure +Factors</a>”). Then,</p> + +<p class="ind05"><i>P</i> = (75.39 × 0.0085 × 115)/2 = 37 tons, approximately.</p> + +<a name="Secnum_3_33" id="Secnum_3_33"></a><p><b>Allowance for Given Pressure.</b>—By transposing the preceding +formula, the approximate allowance for a required ultimate +tonnage can be determined. Thus, <i>a</i> = 2<i>P</i> ÷ <i>AF</i>. The average +ultimate pressure in tons commonly used ranges from 7 to 10 +times the diameter in inches. Assuming that the diameter of a +machine steel shaft is 4 inches and an ultimate pressure of about +30 tons is desired for forcing it into a cast-iron hub having a +length of 5<sup class="enum">1</sup>/<sub class="denom">2</sub> inches, what should be the allowance?</p> + +<p class="ind05"><i>A</i> = 4 × 3.1416 × 5<sup class="enum">1</sup>/<sub class="denom">2</sub> = 69 square inches,</p> + +<p><i>F</i>, for a diameter of 4 inches, = 115. Then,</p> + +<table class="formula" summary="Formula 133_2"> +<tr><td> </td><td> </td><td> 2 × 30 </td><td> </td><td> </td></tr> +<tr><td> <i>a</i> </td><td> = </td><td>————— </td><td> = </td> +<td>0.0075 inch. </td></tr> +<tr><td> </td><td> </td><td> 69 × 115 </td><td> </td><td> </td></tr> +</table> + +<a name="Secnum_3_34" id="Secnum_3_34"></a><p><b>Shrinkage Fits.</b>—When heat is applied to a piece of metal, +such as iron or steel, as is commonly known, a certain amount +of expansion takes place which increases as the temperature +is increased, and also varies somewhat with different kinds of +metal, copper and brass expanding more for a given increase in +temperature than iron and steel. When any part which has +been expanded by the application of heat is cooled, it contracts +and resumes its original size. This expansive property of +metals has been taken advantage of by mechanics in assembling +various machine details. A cylindrical part which is to be held +in position by a shrinkage fit is first turned a few thousandths<span class="pagenum"><a name="Pg_134" id="Pg_134">[134]</a></span> +of an inch larger than the hole; the diameter of the latter is +then increased by heating, and after the part is inserted, the +heated outer member is cooled, causing it to grip the pin or +shaft with tremendous pressure.</p> + +<p>General practice seems to favor a smaller allowance for +shrinkage fits than for forced fits, although in many shops the +allowances are practically the same in each case, and for some +classes of work, shrinkage allowances exceed those for forced +fits. In any case, the shrinkage allowance varies to a great extent +with the form and construction of the part which has to be +shrunk into place. The thickness or amount of metal around +the hole is the most important factor. The way in which the +metal is distributed also has an influence on the results. Shrinkage +allowances for locomotive driving wheel tires adopted by the +American Railway Master Mechanics Association are as follows:</p> + +<table class="center" align="center" border="0" summary="Shrinkage allowances"> +<tr><td class="left">Center diameter, inches </td><td> 38 </td><td> 44 </td><td> 50 </td> +<td> 56 </td><td> 62 </td><td> 66 </td></tr> +<tr><td class="left">Allowance, inches </td><td> 0.040 </td><td> 0.047 </td><td> 0.053 </td> +<td> 0.060 </td><td> 0.066 </td><td> 0.070 </td></tr> +</table> + +<p>Whether parts are to be assembled by forced or shrinkage +fits depends upon conditions. For example, to press a driving +wheel tire over its wheel center, without heating, would ordinarily +be a rather awkward and difficult job. On the other +hand, pins, etc., are easily and quickly forced into place with a +hydraulic press and there is the additional advantage of knowing +the exact pressure required in assembling, whereas there is +more or less uncertainty connected with a shrinkage fit, unless +the stresses are calculated. Tests to determine the difference +in the quality of shrinkage and forced fits showed that the resistance +of a shrinkage fit to slippage was, for an axial pull, +3.66 times greater than that of a forced fit, and in rotation or +torsion, 3.2 times greater. In each comparative test, the dimensions +and allowances were the same.</p> + +<p>The most important point to consider when calculating +shrinkage fits is the stress in the hub at the bore, which depends +chiefly upon the shrinkage allowance. If the allowance +is excessive, the elastic limit of the material will be exceeded +and permanent set will occur, or, in extreme cases, the ultimate +strength of the metal will be exceeded and the hub will burst.</p> + +<hr class="c25" /> +<span class="pagenum"><a name="Pg_135" id="Pg_135">[135]</a></span> +<h2><a name="Chapnum_4" id="Chapnum_4"></a>CHAPTER IV</h2> +<h3>THREAD CUTTING IN THE LATHE</h3> +<hr class="c05" /> + +<p>When threads are cut in the lathe a tool <i>t</i> is used (see <a href="#Fig_4_2">Fig. 2</a>), +having a point corresponding to the shape of the thread, and +the carriage is moved along the bed a certain distance for each +revolution of the work (the distance depending on the number +of threads to the inch being cut) by the lead-screw <i>S</i> which is +rotated by gears <i>a</i>, <i>b</i> and <i>c</i>, which receive their motion from the +spindle. As the amount that the carriage travels per revolution +of the work, and, consequently, the number of threads +per inch that is cut, depends on the size of the gears <i>a</i> and <i>c</i> +(called change gears) the latter have to be changed for cutting +different threads. The proper change gears to use for cutting +a given number of threads to the inch is ordinarily determined +by referring to a table or “index plate” <i>I</i> which shows what the +size of gears <i>a</i> and <i>c</i> should be, or the number of teeth each +should have, for cutting any given number of threads per inch.</p> + +<a name="Fig_4_1" id="Fig_4_1"></a> +<div class="figcenter"><div class="illobox450"><img src="images/143sm.png" alt="Measuring Number of Threads per Inch—Setting Thread Tool" /></div> +<p class="caption750">Fig. 1. Measuring Number of Threads per Inch—Setting Thread Tool</p> +</div> + +<a name="Fig_4_2" id="Fig_4_2"></a> +<span class="pagenum"><a name="Pg_136" id="Pg_136">[136]</a></span> +<div class="figcenter"><div class="illobox750"><img src="images/144sm.png" alt="Plan and Elevations of Engine Lathe" /></div> +<p class="center"><span class="caption750">Fig. 2. Plan and Elevations of Engine Lathe</span></p> +</div> + +<a name="Secnum_4_1" id="Secnum_4_1"></a><p><b>Selecting the Change Gears for Thread Cutting.</b>—Suppose a +V-thread is to be cut on the end of the bolt <i>B</i>, Fig. 2, having +a diameter of 1<sup class="enum">1</sup>/<sub class="denom">4</sub> inch and seven threads per inch of length, as +<span class="pagenum"><a name="Pg_137" id="Pg_137">[137]</a></span> +shown at <i>A</i> in <a href="#Fig_4_1">Fig. 1</a>, which is the standard number of threads +per inch for that diameter. First the change gears to use are +found on plate <i>I</i> which is shown enlarged in <a href="#Fig_4_3">Fig. 3</a>. This plate +has three columns: The first contains different numbers of +threads to the inch, the second the size gear to place on the +“spindle” or “stud” at <i>a</i> (<a href="#Fig_4_2">Fig. 2</a>) for different threads, and the +third the size of gear <i>c</i> for the lead-screw. +As the thread selected as +an example has 7 threads per inch, +gear <i>a</i> should have 48 teeth, this +being the number given in the +second column opposite figure 7 +in the first. By referring to the +last column, we find that the +lead-screw gear should have 84 +teeth. These gears are selected +from an assortment provided with +the lathe and they are placed on +the spindle and lead-screw, respectively.</p> + +<p>Intermediate gear <i>b</i> does not +need to be changed as it is simply +an “idler” for connecting gears <i>a</i> +and <i>c</i>. Gear <i>b</i> is mounted on a +swinging yoke <i>Y</i> so that it can +be adjusted to mesh properly with +different gear combinations; after +this adjustment is made, the lathe +is geared for cutting 7 threads to +the inch. (The change gears of +many modern lathes are so arranged that different combinations +are obtained by simply shifting a lever. A lathe having this +quick-change gear mechanism is described in the latter part of +this chapter.) The work <i>B</i> is placed between the centers just +as it would be for turning, with the end to be threaded turned +to a diameter of 1<sup class="enum">1</sup>/<sub class="denom">4</sub> inch, which is the outside diameter of the +thread.</p> + +<a name="Fig_4_3" id="Fig_4_3"></a> +<div class="figcenter"><img src="images/145sm.png" alt="Index Plate showing Gear Changes for Threading" /> +<p class="caption750">Fig. 3. Index Plate showing Gear Changes for Threading</p> +</div> + +<p><span class="pagenum"><a name="Pg_138" id="Pg_138">[138]</a></span> +<a name="Secnum_4_2" id="Secnum_4_2"></a><b>The Thread Tool.</b>—The form of tool used for cutting a +V-thread is shown at <i>A</i>, <a href="#Fig_4_4">Fig. 4</a>. The end is ground V-shaped +and to an angle of 60 degrees, which corresponds to the angle of +a standard V-thread. The front or flank, <i>f</i> of the tool is ground +back at an angle to provide clearance, but the top is left flat or +without slope. As it is very important to grind the end to exactly +60 degrees, a gage <i>G</i> is used, having 60-degree notches to +which the tool-point is fitted. The tool is clamped in the toolpost +as shown in the plan view, <a href="#Fig_4_2">Fig. 2</a>, square with the work, so +that both sides of the thread will be cut to the same angle with +the axis of the work. A very convenient way to set a thread +tool square is illustrated at <i>B</i>, <a href="#Fig_4_1">Fig. 1</a>. The thread gage is placed +against the part to be threaded, as shown, and the tool is adjusted +until the angular sides of the point bear evenly in the +60-degree notch of the gage. The top of the tool point should +be at the same height as the lathe centers, as otherwise the +angle of the thread will not be correct.</p> + +<a name="Fig_4_4" id="Fig_4_4"></a> +<div class="figcenter"><div class="illobox450"><img src="images/146sm.png" alt="Thread Tools and Gage for testing Angle of End" /></div> +<p class="caption750">Fig. 4. Thread Tools and Gage for testing Angle of End</p> +</div> + +<a name="Secnum_4_3" id="Secnum_4_3"></a><p><b>Cutting the Thread.</b>—The lathe is now ready for cutting the +thread. This is done by taking several cuts, as indicated at <i>A</i>, +<i>B</i>, <i>C</i> and <i>D</i> in <a href="#Fig_4_5">Fig. 5</a>, the tool being fed in a little farther for +each successive cut until the thread is finished. When these +cuts are being taken, the carriage is moved along the bed, as +previously explained, by the lead-screw <i>S</i>, <a href="#Fig_4_2">Fig. 2</a>. The carriage +is engaged with the lead-screw by turning lever <i>u</i> which causes +the halves of a split nut to close around the screw. The way a +lathe is handled when cutting a thread is as follows: After the<span class="pagenum"><a name="Pg_139" id="Pg_139">[139]</a></span> +lathe is started, the carriage is moved until the tool-point is +slightly beyond the right end of the work, and the tool is fed +in far enough to take the first cut which, ordinarily, would be +about <sup class="enum">1</sup>/<sub class="denom">16</sub> inch deep. The carriage is then engaged with the +lead-screw, by operating lever <i>u</i>, and the tool moves to the left +(in this case <sup class="enum">1</sup>/<sub class="denom">7</sub> inch for each revolution of the work) and cuts a +winding groove as at <i>A</i>, <a href="#Fig_4_5">Fig. 5</a>. When the tool has traveled as +far as the thread is wanted, it is withdrawn by a quick turn of +cross-slide handle <i>e</i>, and the carriage is returned to the starting +point for another cut. The tool is then fed in a little farther +and a second cut is taken as at <i>B</i>, <a href="#Fig_4_5">Fig. 5</a>, and this operation is +repeated as at <i>C</i> and <i>D</i> until a “full” thread is cut or until the +top of the thread is sharp. The thread is then tested for size +but before referring to this part of the work, the way the carriage +is returned to the starting point after each cut should be +explained.</p> + +<a name="Fig_4_5" id="Fig_4_5"></a> +<div class="figcenter"><div class="illobox450"><img src="images/147sm.png" alt="Thread is formed by taking a Number of Successive Cuts" /></div> +<p class="caption750">Fig. 5. Thread is formed by taking a Number of Successive Cuts</p> +</div> + +<p>When the tool is withdrawn at the end of the first cut, if the +carriage is disengaged from the lead-screw and returned by +hand, the tool may or may not follow the first cut when the carriage +is again engaged with the lead-screw. If the number of +threads to the inch being cut is a multiple of the number on the +lead-screw <i>S</i>, then the carriage can be returned by hand and<span class="pagenum"><a name="Pg_140" id="Pg_140">[140]</a></span> +engaged with the lead-screw at random and the tool will follow +the first cut. For example, if the lead-screw has six threads per +inch, and 6, 12, 18 or any number of threads is being cut that is +a multiple of six, the carriage can be engaged at any time and the +tool will always follow the original cut. This is not the case, +however, when the number of threads being cut is not a multiple +of the number on the lead-screw.</p> + +<p>One method of bringing the carriage back to the starting point, +when cutting threads which are not multiples, is to reverse the +lathe (by shifting the overhead driving belts) in order to bring +the tool back to the starting point without disengaging the +carriage; in this way the tool is kept in the same relation to the +work, and the carriage is not disengaged from the lead-screw +until the thread is finished. This is a good method when cutting +short threads having a length of say two or three inches; +but when they are longer, and especially when the diameter is +comparatively large (which means a slower speed), it is rather +slow as considerable time is wasted while the tool is moving +back to its starting point. This is due to the fact that the +carriage is moved slowly by the lead-screw, but when disengaged, +it can be traversed quickly by turning handle <i>d</i>, <a href="#Fig_5_2">Fig. 2</a>.</p> + +<p>A method of returning the carriage by hand when the number +of threads being cut is not a multiple of the number on the +lead-screw is as follows: The tool is moved a little beyond the +right end of the work and the carriage or split nut is engaged +with the lead-screw. The lathe is then turned forward by hand +to take up any lost motion, and a line is made on the lathe +bed showing the position of the carriage. The positions of the +spindle and lead-screw are also marked by chalking a tooth on +both the spindle and lead-screw gears, which happens to be +opposite a corner or other point on the bed. After a cut is +taken, the carriage is returned by hand to the original starting +point as shown by the line on the bed, and is again engaged +when the chalk marks show that the spindle and lead-screw are +in their original position; the tool will then follow the first cut. +If the body of the tailstock is moved against the bridge of the +carriage before starting the first cut, the carriage can be located<span class="pagenum"><a name="Pg_141" id="Pg_141">[141]</a></span> +for each following cut by moving it back against the tailstock, +and it will not be necessary to have a line on the bed.</p> + +<a name="Fig_4_6" id="Fig_4_6"></a> +<div class="figcenter"><div class="illobox450"><img src="images/149sm.png" alt="Indicator used when Cutting Threads" /></div> +<p class="caption750">Fig. 6. Indicator used when Cutting Threads</p> +</div> + +<a name="Secnum_4_4" id="Secnum_4_4"></a><p><b>Indicator or Chasing Dial for Catching Threads.</b>—On some +lathes there is an indicator for “catching threads,” as this is +called in shop language. This is a simple device attached to +the carriage and consists +of a graduated +dial <i>D</i> and a worm-wheel +<i>W</i> (see <a href="#Fig_4_2">Figs. 2</a> +and <a href="#Fig_4_6">6</a>) which meshes +with the lead-screw, +so that the dial is +revolved by the lead-screw +when the carriage +is stationary, +and when the carriage +is moved by the screw, +the dial remains stationary. +The indicator +is used by engaging +the carriage when +one of the graduation +lines is opposite the +arrow mark; after a +cut is taken the carriage +is returned by +hand and when one of +the graduation lines +again moves opposite +the arrow, the half-nuts are thrown into mesh, as before, and +this is repeated for each successive cut, thus causing the tool to +always come right with the thread. If the number of threads per +inch is even, engagement can be made when any line is opposite +the arrow, but for odd numbers such as 3, 7, 9, 11, etc., one of +the four long or numbered lines must be used. Of course, if the +thread being cut is a multiple of the number on the lead-screw, +engagement can be made at any time, as previously mentioned.</p> + +<a name="Secnum_4_5" id="Secnum_4_5"></a><p><span class="pagenum"><a name="Pg_142" id="Pg_142">[142]</a></span> +<b>Principle of the Thread Indicator.</b>—The principle upon +which the thread indicator operates is as follows: The number +of teeth in worm-wheel <i>W</i> is some multiple of the number of +threads per inch of the lead-screw, and the number of teeth in +the worm-wheel, divided by the pitch of the screw, equals the +number of graduations on the dial. For example, if the lead-screw +has six threads per inch, the worm-wheel could have +twenty-four teeth, in which case the dial would have four divisions, +each representing an inch of carriage travel, and by sub-dividing +the dial into eighths (as shown) each line would correspond +to <sup class="enum">1</sup>/<sub class="denom">2</sub> inch of travel. The dial, therefore, would enable +the carriage to be engaged with the lead-screw at points equal +to a travel of one-half inch. To illustrate the advantage of this +suppose ten threads per inch are being cut and (with the lathe +stationary) the carriage is disengaged and moved <sup class="enum">1</sup>/<sub class="denom">6</sub> inch or one +thread on the lead-screw; the tool point will also have moved +<sup class="enum">1</sup>/<sub class="denom">6</sub> inch, but it will not be opposite the next thread groove in the +work as the pitch is <sup class="enum">1</sup>/<sub class="denom">10</sub> inch. If the carriage is moved another +thread on the lead-screw, or <sup class="enum">2</sup>/<sub class="denom">6</sub> inch, the tool will still be out of +line with the thread on the work, but when it has moved three +threads, or <sup class="enum">1</sup>/<sub class="denom">2</sub> inch, the tool will then coincide with the original +cut because it has passed over exactly five threads. This would +be true for any number of threads per inch that is divisible by +2. If the thread being cut had nine threads per inch or any +other odd number, the tool would only coincide with the thread +at points 1 inch apart. Therefore, the carriage can only be +engaged when one of the four graduations representing an inch +of travel is opposite the arrow, when cutting odd threads; +whereas even numbers can be “caught” by using any one of the +eight lines.</p> + +<p>This indicator can also be used for “catching” fractional +threads. As an illustration, suppose 11<sup class="enum">1</sup>/<sub class="denom">2</sub> threads per inch are +to be cut, and the carriage is engaged for the first cut when +graduation line 1 is opposite the arrow; engagement would then +be made for each successive cut, when either line 1 or 3 were +opposite the arrow, or in other words at spaces equal to a carriage +movement of 2 inches. As the use of the indicator when<span class="pagenum"><a name="Pg_143" id="Pg_143">[143]</a></span> +cutting fractional threads is liable to result in error, it is better +to keep the half-nuts in engagement and return the carriage by +reversing the lathe.</p> + +<a name="Secnum_4_6" id="Secnum_4_6"></a><p><b>Replacing Sharpened Thread Tool.</b>—If it is necessary to +sharpen the thread tool before the thread is finished, it should +be reset square with the work by testing with the thread gage +as at <i>B</i>, <a href="#Fig_4_1">Fig. 1</a>. The carriage is then engaged with the lead-screw +and the lathe is turned forward to bring the tool opposite +the partly finished thread and also to take up any backlash or +lost motion in the gears or half-nut. If the tool-point is not +in line with the thread groove previously cut, it can be shifted +sidewise by feeding the compound rest <i>E</i> in or out, provided +the latter is set in an angular position as shown in the plan +view, <a href="#Fig_4_2">Fig. 2</a>.</p> + +<p>If the thread tool is ground flat on the top as at <i>A</i>, <a href="#Fig_4_4">Fig. 4</a>, it +is not a good tool for removing metal rapidly as neither of its +two cutting edges has any slope. In order to give each cutting +edge a backward slope, it would be necessary to grind the +top surface hollow or concave, which would be impracticable. +When a course thread is to be cut, a tool shaped as at <i>B</i> can be +used to advantage for rough turning the thread groove, which +is afterward finished to the correct depth and angle by tool <i>A</i>. +This roughing tool is ground with a backward slope from the +point and the latter is rounded to make it stronger.</p> + +<a name="Fig_4_7" id="Fig_4_7"></a> +<div class="figcenter"><div class="illobox450"><img src="images/152sm.png" alt="Cutting Thread by using Compound Rest" /></div> +<p class="caption750">Fig. 7. Cutting Thread by using Compound Rest</p> +</div> + +<a name="Secnum_4_7" id="Secnum_4_7"></a><p><b>Use of Compound Rest for Thread Cutting.</b>—Another form +of thread tool is shown at <i>A</i>, <a href="#Fig_4_7">Fig. 7</a>, which is very good for +cutting V-threads especially of coarse pitch. When this tool is +used, the compound rest <i>E</i> is set to an angle of 30 degrees, as +shown, and it is fed in for the successive cuts by handle <i>w</i> in the +direction indicated by the arrow. It will be seen that the point +a of the tool moves at an angle of 60 degrees with the axis of +the work, thus forming one side of the thread, and the cutting +edge <i>a—b</i>, which can be set as shown at <i>B</i>, forms the opposite +side and does all the cutting. As this edge is given a backward +slope, as shown, it cuts easily and enables threading operations +to be performed quickly. Threads cut in this way are often +finished by taking a light cut with a regular thread tool. The<span class="pagenum"><a name="Pg_144" id="Pg_144">[144]</a></span> +cutting edge <i>a—b</i> is ground to an angle of 60 degrees (or slightly +less, if anything) with the side, as shown by sketch <i>A</i>.</p> + +<p>When cutting threads in steel or wrought iron, some sort of +lubricant is usually applied to the tool to preserve the cutting +end and give a smooth finish to the thread. Lard oil or a mixture +of equal parts of lard oil and paraffin oil are often used for this +purpose. If the thread is small, the lubricant may be applied +from an ordinary oil can, but when cutting comparatively large +threads, it is better to have a stream of oil constantly playing +upon the tool-point. This constant flow may be obtained by +mounting a can having a spout leading to the tool, on a bracket +at the rear of the carriage.</p> + +<a name="Fig_4_8" id="Fig_4_8"></a> +<div class="figcenter"><div class="illobox450"><img src="images/153sm.png" alt="Threads" /></div> +<p class="caption750">Fig. 8. (A) V-thread.<br />(B) U. S. Standard Thread.<br />(C) Square Thread.<br />(D) +Left-hand Thread.<br />(E) Double Square Thread.<br />(F) Triple Square Thread</p> +</div> + +<a name="Secnum_4_8" id="Secnum_4_8"></a><p><b>Threads Commonly Used.</b>—Three forms of threads or screws +which are in common use are shown in <a href="#Fig_4_8">Fig. 8</a>; these are the +V-thread (<i>A</i>), the U. S. standard (<i>B</i>), and the square thread +(<i>C</i>). The shapes of these threads are shown by the sectioned +parts. The V-thread has straight sides which incline at an<span class="pagenum"><a name="Pg_145" id="Pg_145">[145]</a></span> +angle of 60 degrees with each other and at the same angle with +the axis of the screw. The U. S. standard thread is similar +to the V-thread except that the top of the thread and bottom of +the groove is left flat, as shown, and the width of these flats is +made equal to <sup class="enum">1</sup>/<sub class="denom">8</sub> of the pitch. The square thread is square in +section, the width <i>a</i>, depth <i>b</i> and space <i>c</i> being all equal. All +of these threads are right-hand, which means that the grooves +wind around to the right so that a nut will have to be turned<span class="pagenum"><a name="Pg_146" id="Pg_146">[146]</a></span> +toward the right to enter it on the thread. A left-hand thread +winds in the other direction, as shown at <i>D</i>, and a nut is screwed +on by turning it to the left.</p> + +<a name="Secnum_4_9" id="Secnum_4_9"></a><p><b>Multiple Threads.</b>—Threads, in addition to being right-and +left-handed, are single, as at <i>A</i>, <i>B</i>, <i>C</i> and <i>D</i>, double, as at <i>E</i>, +and triple, as at <i>F</i>, and for certain purposes quadruple threads +or those of a higher multiple are employed. A double thread +is different from a single thread in that it has two grooves, +starting diametrically opposite, whereas a triple thread has three +grooves cut as shown at <i>F</i>. The object of these multiple +threads is to obtain an increase in lead without weakening the +screw. For example, the threads shown at <i>C</i> and <i>E</i> have the +same pitch <i>p</i> but the lead <i>l</i> of the double-threaded screw is +twice that of the one with a single thread so that a nut would +advance twice as far in one revolution, which is often a very +desirable feature. To obtain the same lead with a single thread, +the pitch would have to be double, thus giving a much coarser +thread, which would weaken the screw, unless its diameter +were increased. (The lead is the distance <i>l</i> that one thread advances +in a single turn, or the distance that a nut would advance +in one turn, and it should not be confused with the pitch <i>p</i>, +which is the distance between the centers of adjacent threads. +Obviously the lead and pitch of a single thread are the same.)</p> + +<a name="Fig_4_9" id="Fig_4_9"></a> +<div class="figcenter"><div class="illobox450"><img src="images/155sm.png" alt="U. S. Standard Thread, Thread Tool, and Gage" /></div> +<p class="caption750">Fig. 9. U. S. Standard Thread, Thread Tool, and Gage</p> +</div> + +<a name="Secnum_4_10" id="Secnum_4_10"></a><p><b>Cutting a U. S. Standard Thread.</b>—The method of cutting a +U. S. standard thread is the same as described for a V-thread, +so far as handling the lathe is concerned. The thread tool +must correspond, of course, to the shape of a U. S. standard +thread. This tool is first ground to an angle of 60 degrees, as +it would be for cutting a V-thread, and then the point is made +flat as shown in <a href="#Fig_4_9">Fig. 9</a>. As will be recalled, the width of this +flat should be equal to <sup class="enum">1</sup>/<sub class="denom">8</sub> of the pitch. By using a gage like the +one shown at <i>G</i>, the tool can easily be ground for any pitch, as +the notches around the periphery of the gage are marked for +different pitches and the tool-point is fitted into the notch corresponding +to the pitch wanted. If such a gage is not available, the +width of the flat at the point can be tested by using, as a gage, +a U. S. standard tap of the same pitch as the thread to be cut.</p> + +<p><span class="pagenum"><a name="Pg_147" id="Pg_147">[147]</a></span> +When cutting the thread, the tool is set square with the blank, +and a number of successive cuts are taken, the tool being fed +in until the width w of the flat at the top of the thread is equal +to the width at the bottom. The thread will then be the right +size provided the outside diameter <i>D</i> is correct and the tool is +of the correct form. As it would be difficult to measure the +width of this flat accurately, the thread can be tested by screwing +a standard nut over it if a standard thread is being cut. If +it is being fitted to a tapped hole, the tap itself is a very convenient +gage to use, the method being to caliper the tap and +then compare its size with the work.</p> + +<p>A good method of cutting a U. S. standard thread to a given +size is as follows: First turn the outside of the blank accurately +to diameter <i>D</i>, and then turn a small part of the end to diameter +<i>r</i> of the thread at the root. The finishing cut for the thread +is then taken with the tool point set to just graze diameter <i>r</i>. +If ordinary calipers were set to diameter <i>r</i> and measurements +taken in the thread groove, the size would be incorrect owing to<span class="pagenum"><a name="Pg_148" id="Pg_148">[148]</a></span> +the angularity of the groove, which makes it necessary to hold +the calipers at an angle when measuring. To determine the +root diameter divide 1.299 by the number of threads per inch +and subtract the quotient from the outside diameter. Expressing +this rule as a formula,</p> + +<table class="formula" summary="Formula 148_1"> + +<tr> +<td> </td> +<td> </td> +<td> </td> +<td> </td> +<td> </td> +<td rowspan="3"><span class="row3">(</span></td> +<td>1.299</td> +<td rowspan="3"><span class="row3">)</span></td> +<td> </td> +</tr> + +<tr> +<td> <i>r</i> </td> +<td> = </td> +<td> <i>D</i> </td> +<td> - </td> +<td> </td> +<td>———</td> +</tr> + +<tr> +<td> </td> +<td> </td> +<td> </td> +<td> </td> +<td> </td> +<td><i>N</i></td> +<td> </td> +</tr> + +</table> + +<p>in which <i>D</i> equals outside diameter; <i>N</i>, the number of threads +per inch; and <i>r</i>, the root diameter. The number 1.299 is a constant +that is always used.</p> + +<a name="Fig_4_10" id="Fig_4_10"></a> +<div class="figcenter"><div class="illobox450"><img src="images/156sm.png" alt="End View of Lathe Headstock" /></div> +<p class="caption750">Fig. 10. End View of Lathe Headstock</p> +</div> + +<a name="Secnum_4_11" id="Secnum_4_11"></a><p><b>Cutting a Left-hand Thread.</b>—The only difference between +cutting left-hand and right-hand threads in the lathe is in the +movement of the tool with relation to the work. When cutting +a right-hand thread, the tool moves from right to left, but this +movement is reversed for left-hand threads because the thread +winds around in the opposite direction. To make the carriage +travel from left to right, the lead-screw is rotated backwards +by means of reversing gears <i>a</i> and <i>b</i> (<a href="#Fig_4_10">Fig. 10</a>) located in the +<span class="pagenum"><a name="Pg_149" id="Pg_149">[149]</a></span> +headstock. Either of these gears can be engaged with the +spindle gear by changing the position of lever <i>R</i>. When gear <i>a</i> +is in engagement, as shown, the drive from the spindle to gear +<i>c</i> is through gears <i>a</i> and <i>b</i>, but when lever <i>R</i> is raised thus shifting +<i>b</i> into mesh, the drive is direct and the direction of rotation +is reversed. The thread is cut by starting the tool at <i>a</i>, <a href="#Fig_4_8">Fig. 8</a>, +instead of at the end.</p> + +<a name="Fig_4_11" id="Fig_4_11"></a> +<div class="figcenter"><div class="illobox450"><img src="images/157sm.png" alt="End of Square Thread Tool, and Graphic Method of Determining Helix Angle of Thread" /></div> +<p class="caption750">Fig. 11. End of Square Thread Tool, and Graphic Method of +Determining Helix Angle of Thread</p> +</div> + +<a name="Secnum_4_12" id="Secnum_4_12"></a><p><b>Cutting a Square Thread.</b>—The form of tool used for cutting +a square thread is shown in <a href="#Fig_4_11">Fig. 11</a>. The width <i>w</i> is made +equal to one-half the pitch of the thread to be cut and the end <i>E</i> +is at an angle with the shank, which corresponds to the inclination +<i>x—y</i> of the threads. This angle <i>A</i> depends upon the +diameter of the screw and the lead of the thread; it can be determined +graphically by drawing a line <i>a—b</i> equal in length to +the circumference of the screw to be cut, and a line <i>b—c</i>, at right +angles, equal in length to the lead of the thread. The angle α +between lines <i>a—b</i> and <i>a—c</i> will be the required angle <i>A</i>. (See +end view of thread tool). It is not necessary to have this angle +accurate, ordinarily, as it is simply to prevent the tool from +binding against the sides of the thread. The end of a square +thread tool is shown in section to the right, to illustrate its +position with relation to the threads. The sides <i>e</i> and <i>e<sub>1</sub></i> are +ground to slope inward, as shown, to provide additional clearance.</p> + +<p><span class="pagenum"><a name="Pg_150" id="Pg_150">[150]</a></span> +When cutting multiple threads, which, owing to their increased +lead, incline considerably with the axis of the screw, +the angles for each side of the tool can be determined independently +as follows: Draw line <i>a—b</i> equal in length to the circumference +of the thread, as before, to obtain the required +angle <i>f</i> of the rear or following side <i>e<sub>1</sub></i>; the angle <i>l</i> of the opposite +or leading side is found by making <i>a—b</i> equal to the circumference +at the root of the thread. The tool illustrated is for +cutting right-hand threads; if it were intended for a left-hand +thread, the end, of course, would incline in the opposite direction. +The square thread is cut so that the depth <i>d</i> is equal to +the width. When threading a nut for a square thread screw, it +is the usual practice to use a tool having a width slightly greater +than one-half the pitch, to provide clearance for the screw, and +the width of a tool for threading square-thread taps to be used +for tapping nuts is made slightly less than one-half the pitch.</p> + +<a name="Fig_4_12" id="Fig_4_12"></a> +<div class="figcenter"><div class="illobox450"><img src="images/159sm.png" alt="Views illustrating how a Double Square Thread is Cut" /></div> +<p class="caption750">Fig. 12. Views illustrating how a Double Square Thread is Cut</p> +</div> + +<a name="Secnum_4_13" id="Secnum_4_13"></a><p><b>Cutting Multiple Threads.</b>—When a multiple thread is to be +cut, such as a double or triple thread, the lathe is geared with +reference to the number of single threads to the inch. For example, +the lead of the double thread, shown at <i>B</i>, <a href="#Fig_4_12">Fig. 12</a>, is +one-half inch, or twice the pitch, and the number of single +threads to the inch equals 1 ÷ <sup class="enum">1</sup>/<sub class="denom">2</sub> = 2. Therefore, the lathe is +geared for cutting two threads per inch. The first cut is taken +just as though a single thread were being cut, leaving the work +as shown at <i>A</i>. When this cut is finished the work is turned +one-half a revolution (for a double thread) without disturbing +the position of the lead-screw or carriage, which brings the tool +midway between the grooves of the single thread as indicated +by dotted lines. The second groove is then cut, producing a +double thread as shown at <i>B</i>. In the case of a triple thread, +the work would be indexed one-third of a revolution after turning +the first groove, and then another third revolution to locate +the tool for cutting the last groove. Similarly, for a quadruple +thread, it would be turned one-quarter revolution after cutting +each successive groove or thread.</p> + +<p>There are different methods of indexing the work when +cutting multiple threads, in order to locate the tool in the<span class="pagenum"><a name="Pg_151" id="Pg_151">[151]</a></span> +proper position for cutting another thread groove. Some machinists, +when cutting a double thread, simply remove the +work from the lathe and turn it one-half a revolution by placing +the tail of the driving dog in the opposite slot of the faceplate. +This is a very simple method, but if the slots are not +directly opposite or 180 degrees apart, the last thread will not be +central with the first. Another and better method is to disengage +the idler gear from the gear on the stud, turn the spindle +and work one-half, or one-third, of a revolution, as the case +might be, and then connect the gears. For example, if the +stud gear had 96 teeth, the tooth meshing with the idler gear +would be marked with chalk, the gears disengaged, and the +spindle turned until the chalked tooth had made the required +part of a revolution, which could be determined by counting +the teeth. When this method is used, the number of teeth in +the stud gear must be evenly divisible by two if a double thread +is being cut, or by three for a triple thread, etc. If the stud is +not geared to the spindle so that each makes the same number +of revolutions, the ratio of the gearing must be considered.</p> + +<p><span class="pagenum"><a name="Pg_152" id="Pg_152">[152]</a></span> +<a name="Secnum_4_14" id="Secnum_4_14"></a><b>Setting Tool When Cutting Multiple Threads.</b>—Another +method, which can sometimes be used for setting the tool after +cutting the first groove of a multiple thread, is to disengage the +lock-nuts from the lead-screw (while the spindle is stationary) +and move the carriage back whatever distance is required to +locate the tool in the proper position for taking the second cut. +Evidently this distance must not only locate the tool in the right +place, but be such that the lock-nuts can be re-engaged with +the lead-screw. Beginning with a simple illustration, suppose a +double thread is being cut having a lead of 1 inch. After the +first thread groove is cut, the tool can be set in a central position +for taking the second cut, by simply moving the carriage back +<sup class="enum">1</sup>/<sub class="denom">2</sub> inch (one-half the lead), or <sup class="enum">1</sup>/<sub class= +"denom">2</sub> inch plus the lead or any +multiple of the lead. If the length of the threaded part were +5 inches, the tool would be moved back far enough to clear the +end of the work, or say <sup class="enum">1</sup>/<sub class="denom">2</sub> + 5 = 5<sup class= +"enum">1</sup>/<sub class="denom">2</sub> inches. In order to disengage +the lock-nuts and re-engage them after moving the carriage +5<sup class="enum">1</sup>/<sub class="denom">2</sub> inches (or any distance equal, in this case, to one-half +plus a whole number), the lead-screw must have an even number +of threads per inch.</p> + +<p>Assume that a double thread is being cut having 1<sup class="enum">1</sup>/<sub class="denom">4</sub> single +threads per inch. The lead then would equal 1 ÷ 1<sup class="enum">1</sup>/<sub class="denom">4</sub> = 0.8 +inch, and if the carriage is moved back 0.8 ÷ 2 = 0.4 inch, the +tool will be properly located for the second cut; but the lock-nuts +could not be re-engaged unless the lead-screw had ten +threads per inch, which is finer than the pitch found on the +lead-screws of ordinary engine lathes. However, if the movement +were 0.4 + 0.8 × 2 = 2 inches, the lock-nuts could be re-engaged +regardless of the number of threads per inch on the +lead-screw. The rule then, is as follows:</p> + +<p><i>Divide the lead of the thread by 2 for a double thread, 3 for a +triple thread, 4 for a quadruple thread, etc., thus obtaining the +pitch; then add the pitch to any multiple of the lead, which will +give a movement, in inches, that will enable the lock-nuts to be re-engaged +with the lead-screw.</i></p> + +<p>Whenever the number obtained by this rule is a whole number, +obviously, the movement can be obtained with a lead-screw<span class="pagenum"><a name="Pg_153" id="Pg_153">[153]</a></span> +of any pitch. If the number is fractional, the number of threads +per inch on the lead-screw must be divisible by the denominator +of the fraction.</p> + +<p>To illustrate the application of the foregoing rule, suppose a +quadruple thread is to be cut having 1<sup class="enum">1</sup>/<sub class="denom">2</sub> single threads per inch +(which would be the number the lathe would be geared to cut). +Then the lead of the thread = 1 ÷ 1<sup class="enum">1</sup>/<sub class="denom">2</sub> = 0.6666 inch and the +pitch = 0.6666 ÷ 4 = 0.1666 inch; adding the pitch to twice +the lead we have 0.1666 + 2 × 0.6666 = 1.499 inch. Hence, if +the carriage is moved 1<sup class="enum">1</sup>/<sub class="denom">2</sub> inch (which will require a lead-screw +having an even number of threads per inch), the tool will be +located accurately enough for practical purposes. When the +tool is set in this way, if it does not clear the end of the part +being threaded, the lathe can be turned backward to place the +tool in the proper position.</p> + +<p>The foregoing rule, as applied to triple threads or those of a +higher number, does not always give the only distance that the +carriage can be moved. To illustrate, in the preceding example +the carriage movement could be equal to 0.499, or what is practically +one-half inch, instead of 1<sup class="enum">1</sup>/<sub class="denom">2</sub> inch, and the tool would be +properly located. The rule, however, has the merit of simplicity +and can be used in most cases.</p> + +<a name="Fig_4_13" id="Fig_4_13"></a> +<div class="figcenter"><div class="illobox450"><img src="images/161sm.png" alt="Indexing Faceplate used for Multiple Thread Cutting" /></div> +<p class="caption750">Fig. 13. Indexing Faceplate used for Multiple Thread Cutting</p> +</div> + +<p>Special faceplates are sometimes used for multiple thread +cutting, that enable work to be easily and accurately indexed. +One of these is illustrated in <a href="#Fig_4_13">Fig. 13</a>; it consists of two parts <i>A</i> +<span class="pagenum"><a name="Pg_154" id="Pg_154">[154]</a></span> +and <i>B</i>, part <i>A</i> being free to rotate in relation to <i>B</i> when bolts <i>C</i> +are loosened. The driving pin for the lathe dog is attached to +plate <i>A</i>. When one groove of a multiple thread is finished, +bolts <i>C</i> are loosened and plate <i>A</i> is turned around an amount +corresponding to the type of thread being cut. The periphery +of plate <i>A</i> is graduated in degrees, as shown, and for a double +thread it would be turned one-half revolution or 180 degrees, +for a triple thread, 120 degrees, etc. This is a very good arrangement +where multiple thread cutting is done frequently.</p> + +<a name="Fig_4_14" id="Fig_4_14"></a> +<div class="figcenter"><div class="illobox450"><img src="images/162sm.png" alt="Correct and Incorrect Positions of Tool for Taper Thread Cutting" /></div> +<p class="caption750">Fig. 14. Correct and Incorrect Positions of Tool for Taper Thread Cutting</p> +</div> + +<a name="Secnum_4_15" id="Secnum_4_15"></a><p><b>Taper Threading.</b>—When a taper thread is to be cut, the +tool should be set square with axis <i>a—a</i> as at <i>A</i>, <a href="#Fig_4_14">Fig. 14</a>, and +not by the tapering surface as at <i>B</i>. If there is a cylindrical +part, the tool can be set as indicated by the dotted lines. All +taper threads should be cut by the use of taper attachments. +If the tailstock is set over to get the required taper, and an +ordinary bent-tail dog is used for driving, the curve of the +thread will not be true, or in other words the thread will not +advance at a uniform rate; this is referred to by machinists as +a “drunken thread.” This error in the thread is due to the +angularity between the driving dog and the faceplate, which +causes the work to be rotated at a varying velocity. The pitch +of a taper thread that is cut with the tailstock set over will also +be slightly finer than the pitch for which the lathe is geared. +The amount of these errors depends upon the angle of the taper +and the distance that the center must be offset.</p> + +<a name="Fig_4_15" id="Fig_4_15"></a> +<div class="figcenter"><div class="illobox450"><img src="images/163sm.png" alt="Method of setting and using Inside Thread Tool" /></div> +<p class="caption750">Fig. 15. Method of setting and using Inside Thread Tool</p> +</div> + +<a name="Secnum_4_16" id="Secnum_4_16"></a><p><b>Internal Threading.</b>—Internal threading, or cutting threads +in holes, is an operation performed on work held in the chuck or<span class="pagenum"><a name="Pg_155" id="Pg_155">[155]</a></span> +on a faceplate, as for boring. The tool used is similar to a +boring tool except that the working end is shaped to conform +to the thread to be cut. The method of procedure, when cutting +an internal thread, is similar to that for outside work, as +far as handling the lathe is concerned. The hole to be threaded +is first bored to the root diameter <i>D</i>, <a href="#Fig_4_15">Fig. 15</a>, of the screw that is +to fit into it. The tool-point (of a tool for a U. S. standard or +V-thread) is then set square by holding a gage <i>G</i> against the +true side of the work and adjusting the point to fit the notch in +the gage as shown. The view to the right shows the tool taking +the first cut.</p> + +<p>Very often the size of a threaded hole can be tested by using +as a gage the threaded part that is to fit into it. When making +such a test, the tool is, of course, moved back out of the way. +It is rather difficult to cut an accurate thread in a small hole, +especially when the hole is quite deep, owing to the flexibility +of the tool; for this reason threads are sometimes cut slightly +under size with the tool, after which a tap with its shank end +held straight by the tailstock center is run through the hole. +In such a case, the tap should be calipered and the thread made +just small enough with the tool to give the tap a light cut. +Small square-threaded holes are often finished in this way, and +if a number of pieces are to be threaded, the use of a tap makes +the holes uniform in size.</p> + +<a name="Fig_4_16" id="Fig_4_16"></a> +<div class="figcenter"><div class="illobox450"><img src="images/164sm.png" alt="Cross-slide equipped with Stop for Regulating Depth of Cut when Threading" /></div> +<p class="caption750">Fig. 16. Cross-slide equipped with Stop for Regulating Depth +of Cut when Threading</p> +</div> + +<a name="Secnum_4_17" id="Secnum_4_17"></a><p><b>Stop for Thread Tools.</b>—When cutting a thread, it is rather +difficult to feed in the tool just the right amount for each successive +cut, because the tool is moved in before it feeds up to<span class="pagenum"><a name="Pg_156" id="Pg_156">[156]</a></span> +the work. A stop is sometimes used for threading which overcomes +this difficulty. This stop consists of a screw <i>S</i>, <a href="#Fig_4_16">Fig. 16</a>, +which enters the tool slide and passes through a block <i>B</i> clamped +in front of the slide. The hole in the block through which the +stop-screw passes is not threaded, but is large enough to permit +the screw to move freely. When cutting a thread, the tool is +set for the first cut and the screw is adjusted until the head is +against the fixed block. After taking the first cut, the stop-screw +is backed out, say one-half revolution, which allows the +tool to be fed in far enough for a second cut. If this cut is +about right for depth, the screw is again turned about one-half +revolution for the next cut and this is continued for each successive +cut until the thread is finished. By using a stop of this +kind, there is no danger of feeding the tool in too far as is often +done when the tool is set by guess. If this form of stop is used +for internal threading, the screw, instead of passing through the +fixed block, is placed in the slide so that the end or head will +come against the stop <i>B</i>. This change is made because the tool +is fed outward when cutting an internal thread.</p> + +<a name="Fig_4_17" id="Fig_4_17"></a> +<div class="figcenter"><div class="illobox450"><img src="images/165sm.png" alt="Gage for grinding and setting Acme Thread Tools" /></div> +<p class="caption750">Fig. 17. Gage for grinding and setting Acme Thread Tools</p> +</div> + +<a name="Secnum_4_18" id="Secnum_4_18"></a><p><b>The Acme Standard Thread.</b>—The Acme thread is often +used, at the present time, in place of a square thread. The +angle between the sides of the Acme thread is 29 degrees (see +<a href="#Fig_4_21">Fig. 21</a>) and the depth is made equal to one-half the pitch plus +<span class="pagenum"><a name="Pg_157" id="Pg_157">[157]</a></span> +0.010 inch to provide clearance and insure a bearing upon the +sides. The thread tool is ordinarily ground to fit a gage having +notches representing different pitches. An improved form of +Acme thread gage is shown in <a href="#Fig_4_17">Fig. 17</a>. The tool point is first +ground to the correct angle by fitting it to the 29-degree notch +in the end of the gage, as at <i>A</i>. The end is then ground to the +proper width for the pitch to be cut, by testing it, as at <i>B</i>. The +numbers opposite the shallow notches for gaging the width represent +the number of threads per inch. With this particular gage, +the tool can be set square by placing edge <i>D</i> against the turned +surface to be threaded, and adjusting the tool until the end is in +line with the gage, as at <i>C</i>. By placing the tool in this position, +the angle between the side and the end can also be tested.</p> + +<a name="Fig_4_18" id="Fig_4_18"></a> +<div class="figcenter"><div class="illobox450"><img src="images/166sm.png" alt="Measuring Width of Acme Thread Tool with Vernier Gear-tooth Caliper" /></div> +<p class="caption750">Fig. 18. Measuring Width of Acme Thread Tool with Vernier Gear-tooth +Caliper</p> +</div> + +<p>In case it should be necessary to measure the end width of +an Acme thread tool, for a pitch not on the regular gage, this +can be done by using a vernier gear-tooth caliper, as indicated +in <a href="#Fig_4_18">Fig. 18</a>. If we assume that the caliper jaws bear on the sides +of the tool at a distance <i>A</i> from the top, equal to <sup class="enum">1</sup>/<sub class="denom">4</sub> inch, then +the width of the tool point equals the caliper reading (as shown +by the horizontal scale) minus 0.1293 inch. For example, if the +caliper reading was 0.315 inch, the width at the point would +equal 0.315 - 0.1293 = 0.1857 inch, assuming that the sides +were ground to the standard angle of 29 degrees. The constant<span class="pagenum"><a name="Pg_158" id="Pg_158">[158]</a></span> +to be subtracted from the caliper reading equals 2 <i>A</i> tan 14° 30' +or, in this case, 2 × 0.25 × 0.2586 = 0.1293.</p> + +<a name="Secnum_4_19" id="Secnum_4_19"></a><p><b>The Whitworth Thread.</b>—The Whitworth (or British Standard +Whitworth) thread, which is used principally in Great +Britain, has an included angle of 55 degrees, and the threads +are rounded at the top and at the root, as shown in <a href="#Fig_4_23">Fig. 23</a>. +The shape of the tool used for cutting this thread is also shown +in this illustration. The end is rounded to form the fillet at +the root of the thread, and the round corners on the sides give +the top of the thread the required curvature. Every pitch requires +a different tool, and the cutting end is given the curved +form by milling or hobbing. The hob used for this purpose is +accurately threaded to correspond with the pitch for which +the tool is required, and then it is fluted to form cutting edges, +and is hardened. The hob is then used like a milling cutter +for forming the end of the thread tool. The tool is sharpened +by grinding on the top. The method of cutting a Whitworth +thread is, of course, similar to that followed for a U. S. standard +or V-thread, in that the tool is set square with the unthreaded +blank and at the same height as the lathe centers, in order to +secure a thread of the proper form. Care should be taken to +turn the blank to the right diameter so that the top of the +thread will be fully rounded when the screw is the required size. +</p> + +<p class="pagenum"><a name="Pg_159" id="Pg_159">[159]</a></p> +<a name="Fig_4_19" id="Fig_4_19"></a> +<a name="Fig_4_20" id="Fig_4_20"></a> +<div class="figcenter"><div class="illobox450"><img src="images/167asm.png" alt="United States Standard Thread and Standard Sharp V-Thread" /></div> +<p class="caption750">Fig. 19. United States Standard Thread<br />Fig. 20. Standard Sharp V-thread</p> +</div> + +<a name="Fig_4_21" id="Fig_4_21"></a> +<a name="Fig_4_22" id="Fig_4_22"></a> +<div class="figcenter"><div class="illobox450"><img src="images/167bsm.png" alt="Acme Standard and Square Thread" /></div> +<p class="caption750">Fig. 21. Acme Standard Thread<br />Fig. 22. Square Thread</p> +</div> + +<a name="Fig_4_23" id="Fig_4_23"></a> +<a name="Fig_4_24" id="Fig_4_24"></a> +<div class="figcenter"><div class="illobox450"><img src="images/167csm.png" alt="Whitworth Standard and Standard Worm Thread" /></div> +<p class="caption750">Fig. 23. Whitworth Standard Thread<br />Fig. 24. Standard Worm Thread</p> +</div> + +<a name="Secnum_4_20" id="Secnum_4_20"></a><p><span class="pagenum"><a name="Pg_160" id="Pg_160">[160]</a></span> +<b>Worm Threads.</b>—The standard worm thread has an angle +of 29 degrees between the sides, the same as an Acme thread, +but the depth of a worm thread and the width of the flat at the +top and bottom differ from the Acme standard, as will be seen +by comparing <a href="#Fig_4_21">Figs. 21</a> and <a href="#Fig_4_24">24</a>. The whole depth of the thread +equals the linear pitch multiplied by 0.6866, and the width of +the thread tool at the end equals the linear pitch multiplied by +0.31. Gages notched for threads of different pitch are ordinarily +used when grinding worm thread tools.</p> + +<p>When it is necessary to cut multiple-threaded worms of large +lead in an ordinary lathe, difficulty is sometimes experienced +because the lead-screw must be geared to run much faster than +the spindle, thus imposing excessive strains on the gearing. +This difficulty is sometimes overcome by mounting a belt pulley +on the lead-screw, beside the change gear, and connecting +it to the countershaft by a belt; the spindle is then driven +through the change gearing from the lead-screw, instead of <i>vice +versa</i>.</p> + +<a name="Secnum_4_21" id="Secnum_4_21"></a><p><b>Coarse Threading Attachment.</b>—To avoid the difficulties +connected with cutting threads of large lead, some lathes are +equipped with a coarse screw-cutting attachment. The arrangement +of this attachment, as made by the Bradford Machine +Tool Co., is as follows: On the usual reversing shaft, and inside +of the headstock, there is a sliding double gear, so arranged as +to be engaged with either the usual gear on the spindle, or with +a small pinion at the end of the cone. The gears are so proportioned +that the ratio of the two engagements is as 10 to 1; +that is, when engaged with the cone gear (the back-gears being +thrown in) the mating gear will make ten revolutions to one of +the spindle, so that when the lathe is ordinarily geared to cut +one thread per inch, it will, when driven by the cone pinion, +cut one thread in ten inches. This construction dispenses with +the extra strain on the reverse gears due to moving the carriage +at the rapid rate that would be necessary for such a large +lead, when not using an attachment. These attachments are +not only extensively used for the cutting of coarse screws but +for cutting oil grooves on cylindrical parts.</p> + +<p><span class="pagenum"><a name="Pg_161" id="Pg_161">[161]</a></span>When cutting a thread +of large lead or “steep pitch,” the top +of the thread tool should be ground so that it is at right angles +to the thread; then the thread groove will be cut to the same +width as the tool.</p> + +<a name="Secnum_4_22" id="Secnum_4_22"></a><p><b>Testing the Size of a Thread.</b>—When the thread tool has +been fed in far enough to form a complete thread, the screw is +then tested for size. If we assume that a bolt is being threaded +for a standard nut, it would be removed from the lathe and the +test made by screwing a nut on the end. If the thread were +too large, the nut might screw on very tightly or not at all; in +either case, the work would again be placed in the lathe and a +light cut taken over it to reduce the thread to the proper size. +When replacing a threaded part between the centers, it should +be put back in the original position, that is, with the “tail” of +the driving dog in the same slot of the faceplate it previously +occupied.</p> + +<a name="Fig_4_25" id="Fig_4_25"></a> +<div class="figcenter"><div class="illobox450"><img src="images/169sm.png" alt="Testing Diameter of Thread with Calipers and Micrometer" /></div> +<p class="caption750">Fig. 25. Testing Diameter of Thread with Calipers and Micrometer</p> +</div> + +<p>As it is difficult to tell just when a thread is cut to the exact +size, special thread calipers having wedge-shaped ends are +sometimes used for measuring the diameter of a V-thread or a +U. S. standard thread, at the bottom of the grooves or the root +diameter, as shown at <i>A</i> in <a href="#Fig_4_25">Fig. 25</a>. These calipers can be set +from a tap corresponding to the size of the thread being cut, or +from a previously threaded piece of the right size.</p> + +<p><span class="pagenum"><a name="Pg_162" id="Pg_162">[162]</a></span> +<a name="Secnum_4_23" id="Secnum_4_23"></a><b>The Thread Micrometer.</b>—Another form of caliper for testing +threads is shown at <i>B</i>. This is one of the micrometer type +and is intended for very accurate work. The spindle of this +micrometer has a conical end and the “anvil” is V-shaped, +and these ends bear on the sides of the thread or the surfaces +which form the bearing when the screw is inserted in a nut or +threaded hole. The cone-shaped point is slightly rounded so +that it will not bear in the bottom of the thread. There is also +sufficient clearance at the bottom of the V-shaped anvil to prevent +it from bearing on top of the thread. The diameter as +indicated by this micrometer is the “pitch diameter” of the +thread and is equal to the outside diameter minus the depth of +one thread. This depth may be determined as follows:</p> + +<p class="ind05">Depth of a V-thread = 0.866 ÷ No. of threads per inch;</p> + +<p class="ind05">Depth of a U. S. standard thread = 0.6495 ÷ No. of threads +per inch;</p> + +<p class="ind05">Depth of Whitworth thread = 0.6403 ÷ No. of threads per inch.</p> + +<p>The movable point measures all pitches, but the fixed anvil +is limited in its capacity, for if made large enough to measure a +thread of, say, <sup class="enum">1</sup>/<sub class="denom">4</sub>-inch pitch, it would be too wide at the top to +measure a thread of <sup class="enum">1</sup>/<sub class="denom">24</sub>-inch pitch, hence each caliper is limited +in the range of threads that the anvil can measure. When +measuring the “angle diameter” of a thread, the micrometer +should be passed back and forth across the thread, in order to +make sure that the largest dimension or the actual diameter is +being measured. If the micrometer is placed over what seems +to be the center of the screw and the reading is taken by simply +adjusting in the anvil or point against the thread, without moving +the micrometer back and forth across it, an incorrect reading +may be obtained.</p> + +<a name="Fig_4_26" id="Fig_4_26"></a> +<div class="figcenter"><div class="illobox450"><img src="images/171sm.png" alt="Testing Thread" /></div> +<p class="caption750">Fig. 26. (A) Testing Size of Thread with Ball-point Micrometer.<br />(B) Testing Size +of V-thread by the Three-wire System.<br />(C) Testing the Size of a U. S. Standard Thread</p> +</div> + +<p>If standard threaded reference gages are available, the size +of the thread being cut can be tested by comparing it with the +gage. Micrometers having small spherical measuring ends (see +sketch <i>A</i>, <a href="#Fig_4_26">Fig. 26</a>) are sometimes used for this purpose. The +ball points are small enough to bear against the sides of the +thread and the diameter, as compared with the reference gage, +can be determined with great accuracy.</p> + +<p><span class="pagenum"><a name="Pg_163" id="Pg_163">[163]</a></span> +<a name="Secnum_4_24" id="Secnum_4_24"></a><b>Three-wire System of Measuring Threads.</b>—A method of +measuring threads by using an ordinary micrometer and three +wires of equal diameter is illustrated at <i>B</i> and <i>C</i>, <a href="#Fig_4_26">Fig. 26</a>. Two +wires are placed between the threads on one side and one on the +opposite side of the screw. The dimension <i>M</i> over the wires is +then measured with an ordinary micrometer. When the thread +is cut to a standard size, the dimension <i>M</i> for different threads +is as follows:</p> + +<p>For a U. S. standard thread:</p> + +<p class="ind05"><i>m</i> = <i>d</i> - 1.5155<i>p</i> + 3<i>w</i></p> + +<p>For a sharp V-thread:</p> + +<p class="ind05"><i>m</i> = <i>d</i> - 1.732<i>p</i> + 3<i>w</i></p> + +<p>For a Whitworth standard thread:</p> + +<p class="ind05"><i>m</i> = <i>d</i> - 1.6008<i>p</i> + 3.1657<i>w</i></p> + +<p>In these formulas, <i>d</i> = standard outside diameter of screw; +<i>m</i> = measurement over wires; <i>w</i> = diameter of wires; <i>p</i> = +pitch of thread = 1 ÷ number of threads per inch.</p> + +<p>To illustrate the use of the formula for the U. S. standard +thread, let us assume that a screw having 6 threads per inch +(<sup class="enum">1</sup>/<sub class="denom">6</sub>-inch pitch) is to be cut to a diameter of 1<sup class="enum">1</sup>/<sub +class="denom">2</sub> inch, and that wires<span class="pagenum"><a name="Pg_164" id="Pg_164">[164]</a></span> +0.140 inch diameter are to be used in conjunction with a micrometer +for measurement. Then the micrometer reading <i>m</i> should +be</p> + +<p class="ind05">1<sup class="enum">1</sup>/<sub class="denom">2</sub> - 1.5155 × <sup class="enum">1</sup>/<sub +class="denom">6</sub> + 3 × 0.140 = 1.6674 inch</p> + +<p>If the micrometer reading were 1.670 inch, it would indicate +that the pitch diameter of the screw was too large, the error +being equal to difference between 1.667 and the actual reading.</p> + +<a name="Fig_4_27" id="Fig_4_27"></a> +<div class="figcenter"><img src="images/172sm.jpg" alt="Rivett-Dock Circular Threading Tool in Working Position" /> +<p class="caption750">Fig. 27. Rivett-Dock Circular Threading Tool in Working Position</p> +</div> + +<a name="Secnum_4_25" id="Secnum_4_25"></a><p><b>Rivett-Dock Threading Tool.</b>—A special form of thread tool, +which overcomes a number of disadvantages common to an +ordinary single-point thread tool, is shown in <a href="#Fig_4_27">Fig. 27</a>. This +tool has a circular-shaped cutter <i>C</i>, having ten teeth around its +circumference, which, beginning with tooth No. 1, gradually increase +in height, cutter No. 2 being higher than No. 1, etc. +This cutter is mounted on a slide <i>S</i>, that is fitted to the frame +<i>F</i>, and can be moved in or out by lever <i>L</i>. The hub of this lever +has an eccentric stud which moves slide <i>S</i> and locks it when +in the forward or cutting position. The action of the lever in +moving the slide engages the cutter with pawl <i>P</i>, thus rotating +the cutter one tooth at a time and presenting a different tooth +to the work for each movement of the lever. When the slide is<span class="pagenum"><a name="Pg_165" id="Pg_165">[165]</a></span> +moved forward, the heel or underside of the tooth which is in +the working position rests on a stop that takes the thrust of +the cut.</p> + +<p>When the tool is in use, it is mounted on the tool-block of the +lathe as shown in the illustration. The cutter is set for height +by placing a tooth in the working position and setting the top +level with the lathe center. The cutter is also set square with +the work by using an ordinary square, and it is tilted slightly +from the vertical to correspond with the angle of the thread to +be cut, by adjusting frame <i>F</i>. At first a light cut is taken with +lever <i>L</i> moved forward and tooth No. 1 on the stop. After +this cut is completed, the lever is reversed which rotates the +cutter one tooth, and the return movement places tooth No. 2 +in the working position. This operation is repeated until the +tenth tooth finishes the thread. It is often necessary, when +using a single-point thread tool, to re-sharpen it before taking +the finishing cut, but with a circular tool this is not necessary, +for by using the different teeth successively, the last tooth, +which only takes finishing cuts, is kept in good condition.</p> + +<a name="Secnum_4_26" id="Secnum_4_26"></a><p><b>Cutting Screws to Compensate for Shrinkage.</b>—Some tool +steels are liable to shrink more or less when they are hardened; +consequently if a very accurate hardened screw is required, it is +sometimes cut so that the pitch is slightly greater than standard, +to compensate for the shrinkage due to the hardening +operation. As the amount of contraction incident to hardening +is very little, it is not practicable to use change gears that will +give the exact pitch required. A well-known method of obtaining +this increase of pitch is by the use of a taper attachment.</p> + +<a name="Fig_4_28" id="Fig_4_28"></a> +<div class="figcenter"><div class="illobox450"><img src="images/174sm.png" alt="Diagram Illustrating Method of Cutting a Thread to Compensate for the Error in Pitch due to Shrinkage in Hardening" /></div> +<p class="caption750">Fig. 28. Diagram Illustrating Method of Cutting a Thread to<br />Compensate for the Error in Pitch +due to Shrinkage in Hardening</p> +</div> + +<p>For example, suppose a tap having 8 threads per inch is to be +threaded, and, owing to the contraction of the steel, the pitch +must be 0.12502 inch instead of 0.125 inch. The lathe is geared +to cut 8 threads per inch or 0.125 inch pitch, and then the +taper attachment is set to an angle <i>a</i>, <a href="#Fig_4_28">Fig. 28</a>, the cosine of +which equals 0.125÷0.12502; that is, the cosine of angle <i>a</i> equals <i>the +pitch required after hardening</i>, divided by the <i>pitch necessary to +compensate for shrinkage</i>. The angle is then found by referring<span class="pagenum"><a name="Pg_166" id="Pg_166">[166]</a></span> +to a table of cosines. The tap blank is also set to the same +angle a by adjusting the tailstock center, thus locating the axis +of the work parallel with the slide of the taper attachment. +When the carriage moves a distance <i>x</i>, the tool point will have +moved a greater distance <i>y</i> along the work, the difference between +x and y depending upon angle <i>a</i>; hence the tool will cut +a thread of slightly greater pitch than the lathe is geared to cut.</p> + +<p>To illustrate by using the preceding example, cosine of angle +<i>a</i> = 0.125÷0.12502 = 0.99984. By referring to a table of cosines, we +find that 0.99984 is the cosine of 1 degree, approximately; +hence, the taper attachment slide and the work should be set +to this angle. (The angle <i>a</i> in <a href="#Fig_4_28">Fig. 28</a> has been exaggerated in +order to more clearly illustrate the principle.)</p> + +<p>As is well known, it is objectionable to cut a thread with the +tailstock center offset, because the work is not rotated at a +uniform velocity, owing to the fact that the driving dog is at an +angle with the faceplate. For a small angle such as 1 degree, +however, the error resulting from this cause would be very +small.</p> + +<p>If a thread having a pitch slightly less than standard is +needed to fit a threaded part which has contracted in hardening, +the taper attachment can also be used provided the lathe +is equipped with special gears to cut a little less than the required +<span class="pagenum"><a name="Pg_167" id="Pg_167">[167]</a></span> +pitch. Suppose a screw having a pitch of 0.198 inch is +required to fit the thread of a nut the pitch of which has been +reduced from 0.200 inch to 0.198 inch. If gears having 83 and +84 teeth are available, these can be inserted in a compound +train, so as to reduce the 0.200 inch pitch that would be obtained +with the regular gearing, to <sup class="enum">83</sup>/<sub class="denom">84</sub> of 0.200 or 0.19762 inch. +This pitch, which is less than the 0.198 inch pitch required, is +then increased by using the taper attachment as previously described. +(This method was described by Mr. G. H. Gardner +in <span class="smcap">Machinery</span>, February, 1914.)</p> + +<a name="Secnum_4_27" id="Secnum_4_27"></a><p><b>Calculating Change Gears for Thread Cutting.</b>—As previously +mentioned, the change gears for cutting threads of various +pitches are shown by a table or “index plate” attached to +the lathe. The proper gears to be used can be calculated, but +the use of the table saves time and tends to avoid mistakes. +Every machinist, however, should know how to determine the +size of gears used for cutting any number of threads to the +inch. Before referring to any rules, let us first consider why a +lathe cuts a certain number of threads to the inch and how this +number is changed by the use of different gears.</p> + +<a name="Fig_4_29" id="Fig_4_29"></a> +<div class="figcenter"><div class="illobox450"><img src="images/176sm.png" alt="Lathe with Simple Gearing for Thread Cutting, Compound Geared Lathe" /></div> +<p class="caption750">Fig. 29. (A) Lathe with Simple Gearing for Thread Cutting.<br />(B) Compound Geared Lathe</p> +</div> + +<p>As the carriage <i>C</i> and the tool are moved by the lead-screw +<i>S</i> (see <a href="#Fig_4_2">Fig. 2</a>), which is geared to the spindle, the number of +threads to the inch that are cut depends, in every case, upon the +number of turns the work makes while the lead-screw is moving +the carriage one inch. If the lead-screw has six threads per +inch, it will make six revolutions while the carriage and the +thread tool travel one inch along the piece to be threaded. +Now if the change gears <i>a</i> and <i>c</i> (see also sketch <i>A</i>, <a href="#Fig_4_29">Fig. 29</a>) are +so proportioned that the spindle makes the same number of +revolutions as the lead-screw, in a given time, it is evident that +the tool will cut six threads per inch. If the spindle revolved +twice as fast as the lead-screw, it would make twelve turns +while the tool moved one inch, and, consequently, twelve threads +per inch would be cut; but to get this difference in speeds it is +necessary to use a combination of gearing that will cause the +lead-screw to revolve once while the lathe spindle and work +make two revolutions.</p> + +<p><span class="pagenum"><a name="Pg_168" id="Pg_168">[168]</a></span>Suppose that nine threads to the inch are to be cut and the +lead-screw has six threads per inch. In this case the work must +make nine revolutions while the lead-screw makes six and causes +the carriage and thread tool to move one inch, or in other words, +one revolution of the lead-screw corresponds to one and one-half +revolution of the spindle; therefore, if the lead-screw gear +<i>c</i> has 36 teeth, the gear <i>a</i> on the spindle stud should have +24 teeth. The spindle will then revolve one and one-half times +faster than the lead-screw, provided the stud rotates at the +same rate of speed as the main lathe spindle. The number of +teeth in the change gears that is required for a certain pitch +can be found by multiplying the number of threads per inch of +the lead-screw, and the number of threads per inch to be cut, +by the same trial multiplier. The formula which expresses the +relation between threads per inch of lead-screw, threads per<span class="pagenum"><a name="Pg_169" id="Pg_169">[169]</a></span> +inch to be cut, and the number of teeth in the change gears, is +as follows:</p> + +<table class="formula" summary="Formula 169_1"> +<tr><td> threads per inch of lead-screw</td><td> </td><td> teeth in gear on spindle stud </td></tr> +<tr><td> ———————————— </td><td> = </td><td> ———————————— </td></tr> +<tr><td> threads per inch to be cut </td><td> </td><td> teeth in gear on lead-screw </td></tr> +</table> + +<p>Applying this to the example given, we have 6÷9 = 24÷36. The +values of 36 and 24 are obtained by multiplying 6 and 9, respectively, +by 4, which, of course, does not change the proportion. +Any other number could be used as a multiplier, and if gears +having 24 and 36 teeth were not available, this might be necessary. +For example, if there were no gears of this size, some +other multiplier as 5 or 6 might be used.</p> + +<p>Suppose the number of teeth in the change gears supplied +with the lathe are 24, 28, 32, 36, etc., increasing by four teeth +up to 100, and assume that the lead-screw has 6 threads per +inch and that 10 threads per inch are to be cut. Then,</p> + +<table class="formula" summary="Formula 169_2"> + +<tr> +<td> 6 </td> +<td> </td> +<td> 6 × 4 </td> +<td> </td> +<td> 24 </td> +</tr> + +<tr> +<td> — </td> +<td> = </td> +<td> ——— </td> +<td> = </td> +<td> — </td> +</tr> + +<tr> +<td> 10 </td> +<td> </td> +<td> 10 × 4 </td> +<td> </td> +<td> 40 </td> +</tr> + +</table> + +<p>By multiplying both numerator and denominator by 4, we +obtain two available gears having 24 and 40 teeth, respectively. +The 24-tooth gear goes on the spindle stud and, the 40-tooth gear +on the lead-screw. The number of teeth in the intermediate or +“idler” gear <i>b</i>, which connects the stud and lead-screw gears, is +not considered as it does not affect the ratios between gears <i>a</i> +and <i>c</i>, but is used simply to transmit motion from one gear to +the other.</p> + +<p>We have assumed in the foregoing that the spindle stud (on +which gear <i>a</i> is mounted) and the main spindle of the lathe are +geared in the ratio of one to one and make the same number of +revolutions. In some lathes, however, these two members do +not rotate at the same speed, so that if equal gears were placed +on the lead-screw and spindle stud, the spindle would not make +the same number of revolutions as the lead-screw. In that case +if the actual number of threads per inch in the lead-screw were +used when calculating the change gears, the result would be +incorrect; hence, to avoid mistakes, the following general rule<span class="pagenum"><a name="Pg_170" id="Pg_170">[170]</a></span> +should be used as it gives the correct result, regardless of the +ratios of the gears which connect the spindle and spindle stud:</p> + +<p><i>Rule.—First find the number of threads per inch that is cut +when gears of the same size are placed on the lead-screw and spindle, +either by actual trial or by referring to the index plate. Then +place this number as the numerator of a fraction and the number +of threads per inch to be cut, as the denominator; multiply both +numerator and denominator by some trial number, until numbers +are obtained which correspond to numbers of teeth in gears that are +available.</i> The product of the trial number and the numerator +(or “lathe screw constant”) represents the gear <i>a</i> for the spindle +stud, and the product of the trial number and the denominator, +the gear for the lead-screw.</p> + +<a name="Secnum_4_28" id="Secnum_4_28"></a><p><b>Lathes with Compound Gearing.</b>—When gearing is arranged +as shown at <i>A</i>, <a href="#Fig_4_29">Fig. 29</a>, it is referred to as simple gearing, but +sometimes it is necessary to introduce two gears between the +stud and screw as at <i>B</i>, which is termed compound gearing. +The method of figuring compound gearing is practically the same +as that for simple gearing. To find the change gears used in +compound gearing, place the “screw constant” obtained by the +foregoing rule, as the numerator, and the number of threads per +inch to be cut as the denominator of a fraction; resolve both +numerator and denominator into two factors each, and multiply +each “pair” of factors by the same number, until values are +obtained representing numbers of teeth in available change +gears. (One factor in the numerator and one in the denominator +make a “pair” of factors.)</p> + +<p>Suppose the lathe cuts 6 threads per inch when gears of equal +size are used, and that the number of teeth in the gears available +are 30, 35, 40 and so on, increasing by 5 up to 100. If 24 +threads per inch are to be cut, the screw constant 6 is placed in +the numerator and 24 in the denominator. The numerator and +denominator are then divided into factors and each pair of +factors is multiplied by the same number to find the gears, +thus:</p> + +<table class="formula" summary="Formula 170_1"> + +<tr> +<td> 6 </td> +<td> </td> +<td> 2 × 3 </td> +<td> </td> +<td> (2 × 20) × (3 × 10)</td> +<td> </td> +<td> 40 × 30 </td> +</tr> + +<tr> +<td> — </td> +<td> = </td> +<td> ——— </td> +<td> = </td> +<td> ———————— </td> +<td> = </td> +<td> ——— </td> +</tr> + +<tr> +<td> 24 </td> +<td> </td> +<td> 4 × 6 </td> +<td> </td> +<td> (4 × 20) × (6 × 10)</td> +<td> </td> +<td> 80 × 60 </td> +</tr> + +</table> + +<p><span class="pagenum"><a name="Pg_171" id="Pg_171">[171]</a></span>The last four numbers indicate the gears which should be used. +The upper two having 40 and 30 teeth are the <i>driving</i> gears +and the lower two having 80 and 60 teeth are the <i>driven</i> gears. +The driving gears are gear <i>a</i> on the spindle stud and gear <i>c</i> on +the intermediate stud, meshing with the lead-screw gear, and +the driven gears are gears <i>b</i> and <i>d</i>. It makes no difference which +of the driving gears is placed on the spindle stud, or which of +the driven is placed on the lead-screw.</p> + +<a name="Secnum_4_29" id="Secnum_4_29"></a><p><b>Fractional Threads.</b>—Sometimes the lead of a thread is +given as a fraction of an inch instead of stating the number +of threads per inch. For example, a thread may be required +to be cut, having <sup class="enum">3</sup>/<sub class="denom">8</sub>-inch lead. The expression “<sup +class="enum">3</sup>/<sub class="denom">8</sub>-inch lead” +should first be transformed to “number of threads per inch.” +The number of threads per inch (the thread being single) equals:</p> + +<table class="formula2" summary="Formula 171_1"> + +<tr> +<td> 1 </td> +<td> </td> +<td> </td> +<td> 3 </td> +<td> </td> +<td> 8 </td> +<td> </td> +</tr> + +<tr> +<td> ——— </td> +<td> = </td> +<td> 1 ÷ </td> +<td> — </td> +<td> = </td> +<td> — </td> +<td> = 2<sup class="enum">2</sup>/<sub class="denom">3</sub></td> +</tr> + +<tr> +<td> 3 </td> +<td> </td> +<td> </td> +<td> 8 </td> +<td> </td> +<td> 3 </td> +<td> </td> +</tr> + +<tr> +<td> — </td> +<td> </td> +<td> </td> +<td> </td> +<td> </td> +<td> </td> +<td> </td> +</tr> + +<tr> +<td> 8 </td> +<td> </td> +<td> </td> +<td> </td> +<td> </td> +<td> </td> +<td> </td> +</tr> + +</table> + +<p>To find the change gears to cut 2<sup class="enum">2</sup>/<sub class="denom">3</sub> threads per inch in a lathe +having a screw constant of 8 and change gears varying from 24 +to 100 teeth, increasing by 4, proceed as follows:</p> + +<table class="formula2" summary="Formula 171_2"> + +<tr> +<td> 8 </td> +<td> </td> +<td> 2 × 4 </td> +<td> </td> +<td> (2 × 36) × (4 × 24) </td> +<td> </td> +<td> 72 × 96 </td> +</tr> + +<tr> +<td> — </td> +<td> = </td> +<td> ——— </td> +<td> = </td> +<td> ————————— </td> +<td> = </td> +<td> ———— </td> +</tr> + +<tr> +<td> 2<sup class="enum">2</sup>/<sub class="denom">3</sub> </td> +<td> </td> +<td> 1 × 2<sup class="enum">2</sup>/<sub class="denom">3</sub> </td> +<td> </td> +<td> (1 × 36) × (2<sup class="enum">2</sup>/<sub class="denom">3</sub> × 24) </td> +<td> </td> +<td> 36 × 64 </td> +</tr> + +</table> + +<p>As another illustration, suppose we are to cut 1<sup class="enum">3</sup>/<sub class="denom">4</sub> thread per +inch on a lathe having a screw constant of 8, and that the gears +have 24, 28, 32, 36, 40 teeth, etc., increasing by four up to one +hundred. Following the rule:</p> + +<table class="formula2" summary="Formula 171_3"> + +<tr> +<td> 8 </td> +<td> </td> +<td> 2 × 4 </td> +<td> </td> +<td> (2 × 36) × (4 × 16) </td> +<td> </td> +<td> 72 × 64 </td> +</tr> + +<tr> +<td> — </td> +<td> = </td> +<td> ——— </td> +<td> = </td> +<td> ————————— </td> +<td> = </td> +<td> ———— </td> +</tr> + +<tr> +<td> 1<sup class="enum">3</sup>/<sub class="denom">4</sub> </td> +<td> </td> +<td> 1 × 1<sup class="enum">3</sup>/<sub class="denom">4</sub> </td> +<td> </td> +<td> (1 × 36) × (1<sup class="enum">3</sup>/<sub class="denom">4</sub> × 16) </td> +<td> </td> +<td> 36 × 28 </td> +</tr> + +</table> + +<p>The gears having 72 and 64 teeth are the <i>driving</i> gears, and +those with 36 and 28 teeth are the <i>driven</i> gears.</p> + +<a name="Secnum_4_30" id="Secnum_4_30"></a><p><b>Change Gears for Metric Pitches.</b>—When screws are cut in +accordance with the metric system, it is the usual practice to +give the lead of the thread in millimeters, instead of the number +of threads per unit of measurement. To find the change +gears for cutting metric threads, when using a lathe having an +English lead-screw, first determine the number of threads per<span class="pagenum"><a name="Pg_172" id="Pg_172">[172]</a></span> +inch corresponding to the given lead in millimeters. Suppose a +thread of 3 millimeters lead is to be cut in a lathe having an +English lead-screw and a screw constant of 6. As there are +25.4 millimeters per inch, the number of threads per inch will +equal 25.4 ÷ 3. Place the screw constant as the numerator, +and the number of threads per inch to be cut as the denominator:</p> + +<table class="formula" summary="Formula 172_1"> + +<tr> +<td> 6 </td> +<td> </td> +<td> </td> +<td> 25.4 </td> +<td> </td> +<td> 6 × 3 </td> +</tr> + +<tr> +<td> ———— </td> +<td> = </td> +<td> 6 ÷ </td> +<td> —— </td> +<td> = </td> +<td> —— </td> +</tr> + +<tr> +<td> 25.4 </td> +<td> </td> +<td> </td> +<td> 3 </td> +<td> </td> +<td> 25.4 </td> +</tr> + +<tr> +<td> —— </td> +<td> </td> +<td> </td> +<td> </td> +<td> </td> +<td> </td> +</tr> + +<tr> +<td> 3 </td> +<td> </td> +<td> </td> +<td> </td> +<td> </td> +<td> </td> +</tr> + +</table> + +<p>The numerator and denominator of this fractional expression +of the change-gear ratio are next multiplied by some trial number +to determine the size of the gears. The first whole number +by which 25.4 can be multiplied so as to get a whole number as +the result is 5. Thus, 25.4 × 5 = 127; hence, one gear having +127 teeth is always used when cutting metric threads with +an English lead-screw. The other gear required in this case +has 90 teeth. Thus:</p> + +<table class="formula" summary="Formula 172_2"> + +<tr> +<td> 6 × 3 × 5 </td> +<td> </td> +<td> 90 </td> +</tr> + +<tr> +<td> ————</td> +<td> = </td> +<td> ——</td> +</tr> + +<tr> +<td> 25.4 × 5 </td> +<td> </td> +<td> 127 </td> +</tr> + +</table> + +<p>Therefore, the following rule can be used to find the change +gears for cutting metric pitches with an English lead-screw:</p> + +<p><i>Rule.—Place the lathe screw constant multiplied by the lead of +the required thread in millimeters multiplied by 5, as the numerator +of the fraction, and 127 as the denominator. The product of the +numbers in the numerator equals the number of teeth for the spindle-stud +gear, and 127 is the number of teeth for the lead-screw gear.</i></p> + +<p>If the lathe has a metric pitch lead-screw, and a screw having +a given number of threads per inch is to be cut, first find the +“metric screw constant” of the lathe or the lead of thread in +millimeters that would be cut with change gears of equal size +on the lead-screw and spindle stud; then the method of determining +the change gears is simply the reverse of the one already +explained for cutting a metric thread with an English lead-screw.</p> + +<p><i>Rule.—To find the change gears for cutting English threads +with a metric lead-screw, place 127 in the numerator and the threads +per inch to be cut, multiplied by the metric screw constant multiplied</i> +<span class="pagenum"><a name="Pg_173" id="Pg_173">[173]</a></span> +<i>by 5, in the denominator; 127 is the number of teeth on the +spindle-stud gear and the product of the numbers in the denominator +equals the number of teeth in the lead-screw gear.</i></p> + +<a name="Fig_4_30" id="Fig_4_30"></a> +<div class="figcenter"><img src="images/181sm.jpg" alt="Lathe having Quick Change-gear Mechanism" /> +<p class="caption750">Fig. 30. Lathe having Quick Change-gear Mechanism</p> +</div> + +<a name="Secnum_4_31" id="Secnum_4_31"></a><p><b>Quick Change-gear Type of Lathe.</b>—A type of lathe that is +much used at the present time is shown in <a href="#Fig_4_30">Fig. 30</a>. This is +known as the quick change-gear type, because it has a system +of gearing which makes it unnecessary to remove the change +gears and replace them with different sizes for cutting threads +of various pitches. Changes of feed are also obtained by the +same mechanism, but the feeding movement is transmitted to +the carriage by the rod <i>R</i>, whereas the screw <i>S<sub>1</sub></i> is used for screw +cutting. As previously explained, the idea of using the screw exclusively +for threading is to prevent it from being worn excessively, +as it would be if continually used in place of rod <i>R</i>, for +feeding the carriage when turning.</p> + +<a name="Fig_4_31" id="Fig_4_31"></a> +<span class="pagenum"><a name="Pg_174" id="Pg_174">[174]</a></span> +<div class="figcenter"><div class="illobox750"><img src="images/182sm.png" alt="End and Side Views of Quick Change-gear Mechanism" /></div> +<p class="caption750">Fig. 31. End and Side Views of Quick Change-gear Mechanism</p> +</div> + +<p>The general construction of this quick change gear mechanism<span class="pagenum"><a name="Pg_175" id="Pg_175">[175]</a></span> +and the way the changes are made for cutting threads of different +pitch, will be explained in connection with <a href="#Fig_4_30">Figs. 30</a>, <a href="#Fig_4_31">31</a> and +<a href="#Fig_4_32">32</a>, which are marked with the same reference letters for corresponding +parts. Referring to <a href="#Fig_4_30">Fig. 30</a>, the movement is transmitted +from gear <i>s</i> on the spindle stud through idler gear <i>I</i>, +which can be moved sidewise to mesh with either of the three +gears <i>a</i>, <i>b</i> or <i>c</i>, <a href="#Fig_4_31">Fig. 31</a>. This cone of three gears engages gears +<i>d</i>, <i>e</i> and <i>f</i>, any one of which can be locked with shaft <i>T</i> (<a href="#Fig_4_32">Fig. +32</a>) by changing the position of knob <i>K</i>. On shaft <i>T</i> there is +a gear <i>S</i> which can be moved along the shaft by hand lever <i>L</i> +and, owing to the spline or key <i>t</i>, both the sliding gear and shaft +rotate together. Shaft <i>T</i>, carrying gears <i>d</i>, <i>e</i> and <i>f</i> and the +sliding gear <i>S</i>, is mounted in a yoke <i>Y</i>, which can be turned +about shaft <i>N</i>, thus making it possible to lower sliding gear <i>S</i> +into mesh with any one of a cone of eight gears <i>C</i>, <a href="#Fig_4_31">Fig. 31</a>. The +shaft on which the eight gears are mounted has at the end a +small gear <i>m</i> meshing with gear <i>n</i> on the feed-rod, and the latter, +in turn, drives the lead-screw, unless gear <i>o</i> is shifted to the +right out of engagement, which is its position except when +cutting threads.</p> + +<a name="Fig_4_32" id="Fig_4_32"></a> +<div class="figcenter"><div class="illobox450"><img src="images/183sm.png" alt="Sectional Views of Quick Change-gear Mechanism" /></div> +<p class="caption750">Fig. 32. Sectional Views of Quick Change-gear Mechanism</p> +</div> + +<p>With this mechanism, eight changes for different threads or +feeds are obtained by simply placing gear <i>S</i> into mesh with the +<span class="pagenum"><a name="Pg_176" id="Pg_176">[176]</a></span> +various sized gears in cone <i>C</i>. As the speed of shaft <i>T</i> depends +on which of the three gears <i>d</i>, <i>e</i> and <i>f</i> are locked to it, the eight +changes are tripled by changing the position of knob <i>K</i>, making +twenty-four. Now by shifting idler gear <i>I</i>, three speed changes +may be obtained for gears <i>a</i>, <i>b</i> and <i>c</i>, which rotate together, so +that the twenty-four changes are also tripled, giving a total of +seventy-two variations without +removing any gears, and if a +different sized gear <i>s</i> were placed +on the spindle stud, an entirely +different range could be obtained, +but such a change would +rarely be necessary. As shown +in <a href="#Fig_4_30">Fig. 30</a>, there are eight hardened +steel buttons <i>B</i>, or one for +each gear of the cone <i>C</i>, placed +at different heights in the casing. +When lever <i>L</i> is shifted sidewise +to change the position of sliding +gear <i>S</i>, it is lowered onto one +of these buttons (which enters a +pocket on the under side) and in +this way gear <i>S</i> is brought into +proper mesh with any gear of the +cone <i>C</i>. To shift lever <i>L</i>, the +handle is pulled outward against +the tension of spring <i>r</i> (<a href="#Fig_4_32">Fig. 32</a>), +which disengages latch <i>l</i> and enables +the lever to be lifted clear of the button; yoke <i>Y</i> is then +raised or lowered, as the case may be, and lever <i>L</i> with the +sliding gear is shifted laterally to the required position.</p> + +<a name="Fig_4_33" id="Fig_4_33"></a> +<div class="figcenter"><img src="images/184sm.png" alt="Index Plate showing Position of Control Levers for Cutting Threads of Different Pitch" /> +<p class="caption750">Fig. 33. Index Plate showing Position of Control Levers<br />for Cutting Threads of Different Pitch</p> +</div> + +<p>The position of lever <i>L</i> and knob <i>K</i> for cutting threads of +different pitches is shown by an index plate or table attached +to the lathe and arranged as shown in <a href="#Fig_4_33">Fig. 33</a>. The upper +section <i>a</i> of this table shows the different numbers of threads to +the inch that can be obtained when idler gear <i>I</i> is in the position +shown by the diagram <i>A</i>. Section <i>b</i> gives the changes when +<span class="pagenum"><a name="Pg_177" id="Pg_177">[177]</a></span> +the idler gear is moved, as shown at <i>B</i>, and, similarly, section +<i>c</i> gives the changes for position <i>C</i> of the idler. The horizontal +row of figures from 1 to 8 below the word “stops” represents +the eight positions for lever <i>L</i>, which has a plate <i>p</i> (<a href="#Fig_4_30">Fig. 30</a>) just +beneath it with corresponding numbers, and the column to the +left shows whether knob <i>K</i> should be out, in a central position, +or in.</p> + +<p>In order to find what the position of lever <i>L</i> and knob <i>K</i> +should be for cutting any given number of threads to the inch, +find what “stop” number is directly above the number of threads +to be cut, which will indicate the location of lever <i>L</i>, and also what +position should be occupied by knob <i>K</i>, as shown in the column +to the left. For example, suppose the lathe is to be geared for +cutting eight threads to the inch. By referring to section a we +see that lever <i>L</i> should be in position 4 and knob <i>K</i> in the center, +provided the idler gear <i>I</i> were in position <i>A</i>, as it would be +ordinarily, because all standard numbers of threads per inch +(U. S. standard) from <sup class="enum">1</sup>/<sub class="denom">4</sub> inch up to and including 4 inches in +diameter can be cut with the idler gear in that position. As +another illustration, suppose we want to cut twenty-eight threads +per inch. This is listed in section <i>c</i>, which shows that lever <i>L</i> +must be placed in position 3 with knob <i>K</i> pushed in and the +idler gear shifted to the left as at <i>C</i>.</p> + +<p>The simplicity of this method as compared with the time-consuming +operation of removing and changing gears is apparent. +The diagram <i>D</i> to the right shows an arrangement of +gearing for cutting nineteen threads per inch. A 20-tooth gear +is placed on the spindle stud (in place of the regular one having +16 teeth) and one with 95 teeth on the lead-screw, thus driving +the latter direct as with ordinary change gears. Of course it +will be understood that the arrangement of a quick change-gear +mechanism varies somewhat on lathes of different make.</p> + +<hr class="c25" /> +<span class="pagenum"><a name="Pg_178" id="Pg_178">[178]</a></span> +<h2><a name="Chapnum_5" id="Chapnum_5">CHAPTER V</a></h2> +<h3>TURRET LATHE PRACTICE</h3> +<hr class="c05" /> + +<p>Turret lathes are adapted for turning duplicate parts in quantity. +The characteristic feature of a turret lathe is the turret +which is mounted upon a carriage and contains the tools which +are successively brought into the working position by indexing +or rotating the turret. In many instances, all the tools required +can be held in the turret, although it is often necessary to use +other tools, held on a cross-slide, for cutting off the finished +part, facing a radial surface, knurling, or for some other operation. +After a turret lathe is equipped with the tools needed +for machining a certain part, it produces the finished work much +more rapidly than would be possible by using an ordinary engine +lathe, principally because each tool is carefully set for turning +or boring to whatever size is required and the turret makes it +possible to quickly place any tool in the working position. Turret +lathes also have systems of stops or gages for controlling the +travel of the turret carriage and cross-slide, in order to regulate +the depth of a bored hole, the length of a cylindrical part or its +diameter; hence, turning machines of this type are much more +efficient than ordinary lathes for turning duplicate parts, unless +the quantity is small, in which case, the advantage of the turret +lathe might be much more than offset by the cost of the special +tool equipment and the time required for “setting up” the +machine. (See “<a href="#Secnum_5_32">Selecting Type of Turning Machine</a>.”)</p> + +<a name="Fig_5_1" id="Fig_5_1"></a><span class="pagenum"><a name="Pg_179" id="Pg_179">[179]</a></span> +<div class="figcenter"><img src="images/187sm.jpg" alt="Turret Lathe of Motor-driven Geared-head Type" /> +<p class="caption750">Fig. 1. Bardons & Oliver Turret Lathe of Motor-driven Geared-head Type</p> +</div> + +<a name="Secnum_5_1" id="Secnum_5_1"></a><p><b>General Description of a Turret Lathe.</b>—The turret lathe +shown in <a href="#Fig_5_1">Fig. 1</a> has a hexagonal shaped turret <i>A</i> with a hole in +each side in which the tools are held. This turret is mounted on +a slide <i>B</i> which is carried by a saddle <i>C</i> that can be moved along +the bed to locate the turret slide with reference to the length of +the tools in the turret and the room required for indexing. The +turret slide can be moved longitudinally by turning the pilot<span class="pagenum"><a name="Pg_180" id="Pg_180">[180]</a></span> +wheel or turnstile <i>D</i>, or it can be fed by power. Ordinarily, +the hand adjustment is used for quickly moving the carriage +when the tools are not cutting, although sometimes the hand +feed is preferable to a power feed when the tools are at work, +especially if the cuts are short. After a turret tool has finished +its cut, the turnstile is used to return the slide to the starting +point, and at the end of this backward movement the turret +is automatically indexed or turned one-sixth of a revolution, +thus bringing the next tool into the working position. The +turret is accurately located in each of its six positions by a lock +bolt which engages notches formed in a large index ring at the +turret base. A binder lever <i>E</i> at the top of the turret stud is +used to clamp the turret rigidly to the slide when the tools are +cutting.</p> + +<p>The forward movement of the slide for each position of the +turret is controlled by stops at <i>F</i>, which are set to suit the work +being turned. When parts are being turned from bar stock, the +latter passes through the hollow spindle of the headstock and +extends just far enough beyond the end of the spindle to permit +turning one of the parts. The bar is held while the turning tools +are at work, by a chuck of the collet type at <i>G</i>. This chuck is +opened or closed around the bar by turning handwheel <i>H</i>. After +a finished part has been cut off by a tool held in cross-slide <i>J</i>, +the chuck is released and further movement of wheel <i>H</i> causes +ratchet feed dog <i>K</i>, and the bar which passes through it, to +be drawn forward. This forward movement is continued until +the end of the bar comes against a stop gage held in one of the +turret holes, to insure feeding the bar out just the right amount +for turning the next piece. On some turret lathes, the lever +which operates the chuck also controls a power feed for the +bar stock, the latter being pushed through the spindle against +the stop.</p> + +<p>The machine illustrated has a power feed for the cross-slide +as well as for the turret. The motion is obtained from the same +shaft <i>L</i> which actuates the turret slide, but the feed changes +are independent. The cross-slide feed changes are varied by +levers <i>M</i> and those for the turret by levers <i>N</i>. For many +<span class="pagenum"><a name="Pg_181" id="Pg_181">[181]</a></span> +turret lathe operations, such as turning castings, etc., a jawed +chuck is screwed onto the spindle and the work is held the same +as when a chuck is used on an engine lathe. Sometimes chucks +are used having special jaws for holding castings of irregular +shape, or special work-holding fixtures which are bolted to the +faceplate. The small handle at <i>O</i> is for moving the cross-slide +along the bed when this is necessary in order to feed a tool +sidewise.</p> + +<p>This particular machine is driven by a motor at the rear of +the headstock, connection being made with the spindle through +gearing. The necessary speed changes are obtained both by +varying the speed of the motor and by shifting gears in the +headstock. The motor is controlled by the turnstile <i>P</i> and the +gears are shifted by the vertical levers shown.</p> + +<p>While many of the features referred to are common to turret +lathes in general, it will be understood that the details such as +the control levers, arrangement of stops, etc., vary on turret +lathes of different make.</p> + +<a name="Fig_5_2" id="Fig_5_2"></a><span class="pagenum"><a name="Pg_182" id="Pg_182">[182]</a></span> +<a name="Fig_5_3" id="Fig_5_3"></a> +<div class="figcenter"><div class="illobox750"><img src="images/190sm.png" alt="Diagrams showing Turret Lathe Tool Equipment for Machining Automobile Hub Casting" /></div> +<p class="caption750">Figs. 2 and 3. Diagrams showing Turret Lathe Tool Equipment for Machining Automobile Hub Casting</p> +</div> + +<a name="Secnum_5_2" id="Secnum_5_2"></a><p><b>Example of Turret Lathe Work.</b>—The diagrams <a href="#Fig_5_2">Figs. 2</a> and +<a href="#Fig_5_3">3</a> show a turret lathe operation which is typical in many respects. +The part to be turned is a hub casting for an automobile and it +is machined in two series of operations. The first series is shown +by the plan view, <a href="#Fig_5_2">Fig. 2</a>. The casting <i>A</i> is held in a three-jaw +chuck <i>B</i>. Tool No. 1 on the cross-slide is equipped with two +cutters and rough faces the flange and end, while the inner and +outer surfaces of the cylindrical part are rough bored and turned +by combination boring and turning tool No. 2. This tool has, +in addition to a regular boring-bar, a bracket or tool-holder +which projects above the work and carries cutters that operate +on the top surface. Tools Nos. 3 and 4 next come into action, +No. 3 finishing the surfaces roughed out by No. 2, and No. 4 +finish-facing the flange and end of the hub. The detailed side +view of Tool No. 3 (which is practically the same as No. 2), +shows the arrangement of the cutters <i>C</i> and <i>D</i>, one of which +turns the cylindrical surface and the other bevels the end of +the hub. The hole in the hub is next finished by tool No. 5 +which is a stepped reamer that machines the bore and counterbore<span class="pagenum"><a name="Pg_183" id="Pg_183">[183]</a></span> +to the required size within very close limits. The surfaces +machined by the different tools referred to are indicated by +the sectional view <i>E</i> of the hub, which shows by the numbers +what tools are used on each surface.</p> + +<p>For the second series of operations, the position of the hub +is reversed and it is held in a spring or collet type of chuck as +shown by the plan view <a href="#Fig_5_3">Fig. 3</a>. The finished cylindrical end +of the hub is inserted in the split collet <i>F</i> which is drawn back +into the tapering collet ring by rod <i>G</i> (operated by turnstile <i>H</i>, +<a href="#Fig_5_1">Fig. 1</a>) thus closing the collet tightly around the casting. The +first operation is that of facing the side of the flange and end of +the hub with tool No. 6 on the cross-slide, which is shown in the +working position. A broad cutter <i>H</i> is used for facing the +flange and finishing the large fillet, and the end is faced by a +smaller cutter <i>I</i>. When these tools are withdrawn, tool No. 7 +is moved up for rough turning the outside of the cylindrical end +(preparatory to cutting a thread) and rough boring the hole. +These same surfaces are then finished by tool No. 8. The arrangement +of tools Nos. 7 and 8 is shown by the detailed view. +Tool <i>J</i> turns the part to be threaded; tool <i>K</i> turns the end beyond +the threaded part; and tool <i>L</i> bevels the corner or edge. +The reaming tool No. 9 is next indexed to the working position +for finishing the hole and beveling the outer edge slightly. At +the same time, the form tool No. 10, held at the rear of the cross-slide, +is fed up for beveling the flange to an angle of 60 degrees. +The final operation is that of threading the end, which is done +with die No. 11. The boring-bars of tools Nos. 2, 3, 7 and 8 +are all provided with pilots <i>N</i> which enter close fitting bushings +held in the spindle, to steady the bar while taking the +cut. This is a common method of supporting turret lathe +tools.</p> + +<p>The feed of the turret for both the first and second series of +operations is <sup class="enum">1</sup>/<sub class="denom">27</sub> inch per revolution and the speeds 60 revolutions +per minute for the roughing cuts and 90 revolutions per +minute for the finishing cuts. The total time for machining +one of these castings complete is about 7<sup class="enum">1</sup>/<sub class="denom">2</sub> minutes, which includes +the time required for placing the work in the chuck.</p> + +<a name="Fig_5_4" id="Fig_5_4"></a> +<div class="figcenter"><div class="illobox450"><img src="images/192sm.png" alt="First Cycle of Operations in Finishing Gasoline Engine Flywheels on a Pond Turret Lathe" /></div> +<p class="caption750">Fig. 4. First Cycle of Operations in Finishing Gasoline Engine<br />Flywheels on a Pond Turret Lathe</p> +</div> + +<p><span class="pagenum"><a name="Pg_184" id="Pg_184">[184]</a></span> +<a name="Secnum_5_3" id="Secnum_5_3"></a><b>Machining Flywheels in Turret Lathe.</b>—<a href="#Fig_5_4">Figs. 4</a> +to <a href="#Fig_5_6">6</a>, inclusive,illustrate how a gasoline engine flywheel is finished all over in +two cycles of operations. First the flywheel is turned complete +on one side, the hole bored and reamed, and the outside of the +rim finished; in the second cycle the other side of the flywheel +is completed.</p> + +<p>During the first operation, the work is held by the inside of +the rim by means of a four-jaw chuck equipped with hard jaws. +The side of the rim, the tapering circumference of the recess, +the web, and the hub are first rough-turned, using tools held in +the carriage toolpost. The hole is then rough-bored by bar <i>C</i>, +which is supported in a bushing in the chuck, as shown in <a href="#Fig_5_4">Fig. 4.</a> +The outside of the wheel rim is rough-turned at the same time +by a cutter held in the extension turret tool-holder <i>T</i> (<a href="#Fig_5_5">Fig. 5</a>), +and the taper fit on the inside of the flywheel is turned by means +of cutter <i>A</i> (<a href="#Fig_5_4">Fig. 4</a>) held in a tool-holder attached to the turret.</p> + +<a name="Fig_5_5" id="Fig_5_5"></a> +<div class="figcenter"><div class="illobox450"><img src="images/193sm.png" alt="Elevation of Turret and Tools for Finishing Flywheels—First Operation" /></div> +<p class="caption750">Fig. 5. Elevation of Turret and Tools for Finishing Flywheels—First Operation</p> +</div> + +<p>The outside of the wheel rim is next finish-turned with cutter +<i>V</i> (<a href="#Fig_5_5">Fig. 5</a>) held in an extension turret tool-holder the same as +<span class="pagenum"><a name="Pg_185" id="Pg_185">[185]</a></span> +the roughing tool <i>T</i>. At the same time, the bore is finished +by a cutter in boring-bar <i>D</i> (<a href="#Fig_5_4">Fig. 4</a>). The side of the rim and +the hub of the wheel are also finished at this time by two facing +cutters <i>H</i> and <i>K</i>, held in tool-holders on the face of the turret. +When the finishing cuts on the rim and hub are being taken, +the work is supported by a bushing on the boring-bar which enters +the bore of the wheel, the boring cutter and facing tools being +set in such relation to each other that the final boring of the hole +is completed before the facing cuts are taken.</p> + +<p>The web of the wheel is next finish-faced with the facing cutter +held in the holder <i>E</i>, and the taper surface on the inside of the +rim is finished by the tool <i>L</i>, at the same time. While these +last operations are performed, the work is supported by a bushing +on a supporting arbor <i>J</i>, which enters the bore of the wheel. +The bore is finally reamed to size by a reamer <i>F</i> held in a “floating” +reamer-holder. When the reaming operation is completed, +a clearance groove <i>N</i> is cut on the inside of the rim, using a +tool <i>G</i> held in the carriage toolpost. The first cycle of operations +on the flywheel is now completed.</p> + +<a name="Fig_5_6" id="Fig_5_6"></a> +<div class="figcenter"><div class="illobox450"><img src="images/194sm.png" alt="Second Cycle of Operations on Flywheel" /></div> +<p class="caption750">Fig. 6. Second Cycle of Operations on Flywheel</p> +</div> + +<p>The flywheel is then removed from the chuck, turned around, +and held in “soft” jaws for the second cycle of operations, the<span class="pagenum"><a name="Pg_186" id="Pg_186">[186]</a></span> +jaws fitting the outside of the wheel rim. (Soft unhardened +jaws are used to prevent marring the finished surface of the +rim.) The operations on this side are very similar to those performed +on the other side. First, the side of the rim, the inside +of the rim, the web, and hub are rough-turned, using tools held +in the carriage toolpost. The inside of the rim and the web are +then finished by a cutter held in a tool-holder at <i>P</i>, <a href="#Fig_5_6">Fig. 6</a>, which +is bolted to the face of the turret. The work is supported +during this operation by a bushing held on a supporting arbor +<i>U</i>, having a pilot which enters a bushing in the chuck. Finally, +the rim and hub are finished, by the facing cutters <i>R</i> and <i>S</i>, +the work being supported by an arbor, as before.</p> + +<p>These operations illustrate the methods employed in automobile +factories, and other shops where large numbers of engine +flywheels, etc., must be machined.</p> + +<a name="Fig_5_7" id="Fig_5_7"></a><span class="pagenum"><a name="Pg_188" id="Pg_188">[188]</a></span> +<div class="figcenter"><div class="illobox450"><img src="images/196sm.png" alt="Turret Lathe Tool Equipment for Machining Flywheels" /></div> +<p class="caption750">Fig. 7. Turret Lathe Tool Equipment for Machining Flywheels</p> +</div> + +<a name="Secnum_5_4" id="Secnum_5_4"></a><p><b>Finishing a Flywheel at One Setting in Turret Lathe.</b>—The +plan view <i>A</i>, <a href="#Fig_5_7">Fig. 7</a>, shows an arrangement of tools for finishing +a flywheel complete at one setting. The hole for the shaft has +to be bored and reamed and the hub faced on both sides. The +sides and periphery of the rim also have to be finished and all +four corners of the rim rounded. The tools for doing this work +consist of boring-bars, a reamer, facing heads on the main turret,<span class="pagenum"><a name="Pg_187" id="Pg_187">[187]</a></span> +a turret toolpost on the slide rest (carrying, in this case, three +tools) and a special supplementary wing rest attached to the +front of the carriage at the extreme left.</p> + +<p>The casting is held by three special hardened jaws <i>b</i> in a universal +chuck. These jaws grip the work on the inner side of the +rim, leaving room for a tool to finish the rear face without striking +the chuck body or jaws. Three rests <i>c</i> are provided between +the chuck jaws. The work is pressed against these rests while +being tightened in the chuck, and they serve to locate it so that +the arms will run true so far as sidewise movement is concerned. +These rests also locate the casting with relation to the stops for +the turret and carriage movements. The chuck carries a bushing +<i>r</i> of suitable diameter to support the boring-bars in the main +turret, as will be described.</p> + +<p>In the first operation, boring-bar <i>m</i> is brought in line with the +spindle and is entered in bushing <i>r</i> in the chuck. Double-ended +cutter <i>n</i> is then fed through the hub of the pulley to true up the +cored hole. While boring the hole, the scale on the front face +of the rim and hub is removed by tool <i>j</i>. Tool <i>k</i> is then brought +into action to rough turn the periphery, after which tool <i>e</i>, in +the wing rest, is fed down to clean up the back face of the rim. +As soon as the scale is removed, the hole is bored nearly to size +by cutter <i>n<sub>1</sub></i> in bar <i>m<sub>1</sub></i>, and it is finally finished with reamer <i>q</i> +mounted on a floating arbor.</p> + +<p>The cutters <i>f</i>, <i>g</i> and <i>h</i>, in the facing head, are next brought up +to rough face the hub and rim, and round the corners of the rim +on the front side. This operation is all done by broad shaving +cuts. The facing head in which the tools are held is provided +with a pilot bar <i>t</i> which fits the finished hole in the flywheel hub, +and steadies the head during the operation. The cutters <i>f</i>, <i>g</i> +and <i>h</i> are mounted in holders which may be so adjusted as to +bring them to the proper setting for the desired dimensions. +This completes the roughing operations.</p> + +<p>The periphery of the rim is now finished by cutter <i>l</i> in the +turret toolpost which is indexed to the proper position for this +operation. The rear face of the rim is finished by the same +tool <i>e</i> with which the roughing was done. Tool <i>e</i> is then removed +<span class="pagenum"><a name="Pg_189" id="Pg_189">[189]</a></span> +and replaced with <i>d</i> which rounds the inner corner of the +rim. Tool <i>d</i> is also replaced with a third tool for rounding the +outer corner of the rear side. For finishing the front faces of +the rim and hub and rounding the corners of the rim, a second +facing head, identical with the first one, is employed. This is +shown in position in the illustration. Cutters <i>f<sub>1</sub></i>, <i>g<sub>1</sub></i> and <i>h<sub>1</sub></i> correspond +with the cutters <i>f</i>, <i>g</i> and <i>h</i>, previously referred to, and +perform the same operations.</p> + +<p>The remaining operation of finishing the back of the hub is +effected by cutter <i>p</i>. This cutter is removed from the bar, which +is then inserted through the bore; the cutter is then replaced in +its slot and the rear end of the hub is faced by feeding the carriage +away from the headstock. This completes the operations, the +flywheel being finished at one setting.</p> + +<a name="Secnum_5_5" id="Secnum_5_5"></a><p><b>Finishing a Webbed Flywheel in Two Settings.</b>—The plan +views <i>B</i> and <i>C</i>, <a href="#Fig_5_7">Fig. 7</a>, show the arrangement of tools for finishing +a webbed flywheel which has to be machined all over. This, +of course, requires two operations. In the first of these (see +sketch <i>B</i>) the rough casting is chucked on the inside of the rim +with regular inside hard chuck jaws <i>b</i>. The cored hole is first +rough bored with cutter <i>n</i> attached to the end of boring-bar <i>m</i>, +and guided by the drill support <i>d</i> pivoted to the carriage. Next, +the boring-bar <i>m<sub>1</sub></i> is brought into position, the drill support +being swung back out of the way. This bar is steadied by its +bearing in bushing <i>r</i> in the chuck. Two cutters, <i>n<sub>1</sub></i> and <i>n<sub>2</sub></i>, are +used to roughly shape the hole to the desired taper, the small +end being finished to within 0.002 inch of the required diameter. +While boring with the bar <i>m<sub>1</sub></i>, the scale is broken on the web +and hub of the casting by the tool <i>k</i> in the turret toolpost. The +latter is then shifted to bring the tool <i>j</i> into position for removing +the scale on the periphery of the wheel. Next, the hole is +reamed with taper reamer <i>q</i>, the pilot of which is supported by +bushing <i>r</i>.</p> + +<p>The first of the facing heads is now brought into action. This +facing head carries a guide <i>t</i> which is steadied in a taper bushing +<i>c</i>, driven into the taper hole of the hub for that purpose. The +top cutter <i>f</i> turns the periphery, cutter <i>g</i> turns the hub and faces +<span class="pagenum"><a name="Pg_190" id="Pg_190">[190]</a></span> +the web, and cutter <i>h</i> faces the rim. A fourth cutter <i>e</i> on the +under side of the head faces the hub. This casting is now +machined approximately to size.</p> + +<p>For finishing, similar cutters, <i>e<sub>1</sub></i>, <i>f<sub>1</sub></i>, <i>g<sub>1</sub></i> and <i>h<sub>1</sub></i>, in the other +facing head are used, the latter being supported by the taper +bushing <i>c</i> in the same way. A very light cut is taken for finishing. +Tool <i>l</i> in the carriage turret is used to round the outer and +inner corners of the rim, which completes the work on this face +of the casting.</p> + +<p>In the second cycle of operations, shown at <i>C</i>, the casting is +chucked on the outside with the soft jaws <i>b</i>, which are bored to +the exact diameter of the finished rim. The work is further +supported and centered by sliding bushing <i>c</i>, which is tapered +to fit the finished hole in the hub, and has an accurate bearing +in bushing <i>r</i> in the chuck. This bushing is provided with a +threaded collar for forcing it into the work and withdrawing it. +The scale on the web and the inside and face of the rim is first +broken with the tool <i>k</i> in the turret toolpost. These surfaces +are then roughed off with cutters <i>f</i>, <i>g</i> and <i>h</i>, in the facing head. +This latter is steadied by a pilot <i>t</i> which enters the hole in the +sliding bushing <i>c</i> on which the work is supported. A light cut +is next taken with cutters <i>f<sub>1</sub></i>, <i>g<sub>1</sub></i> and <i>h<sub>1</sub></i>, in the finishing facing +head, which completes the operation.</p> + +<a name="Secnum_5_6" id="Secnum_5_6"></a><p><b>Tools for Turret Lathes.</b>—The operation of a turret lathe after +the tools have been properly arranged is not particularly difficult, +but designing and making the tools, determining what +order of operations will give the most efficient and accurate +results, and setting the tools on the machine, requires both skill +and experience. For some classes of work, especially if of a +rather complicated nature, many of the tools must be specially +designed, although there are certain standard types used on +turret lathes which are adapted to general turning operations. +Some of the principal types are referred to in the following.</p> + +<a name="Fig_5_8" id="Fig_5_8"></a> +<div class="figcenter"><div class="illobox450"><img src="images/199sm.png" alt="Different Types of Box-tools for Turret Lathe" /></div> +<p class="caption750">Fig. 8. Different Types of Box-tools for Turret Lathe</p> +</div> + +<a name="Secnum_5_7" id="Secnum_5_7"></a><p><b>Box-tools.</b>—Tools of this type are used for turning bar +stock. There are many different designs, some of which are +shown in <a href="#Fig_5_8">Figs. 8</a>, <a href="#Fig_5_9">9</a> and <a href="#Fig_5_10">10</a>. Box-tools are held in the turret and +they have back-rests opposite the turning tools, for supporting<span class="pagenum"><a name="Pg_191" id="Pg_191">[191]</a></span> +the part being turned. The box-tool shown at <i>A</i>, <a href="#Fig_5_8">Fig. 8</a>, is for +roughing. The cutter <i>a</i> is a piece of high-speed steel beveled +on the cutting end to produce a keen edge. It takes a shearing +tangent cut on top of the bar and the latter is kept from springing +away by means of the adjustable, hardened tool-steel back-rest +<i>b</i>. This tool is considered superior to a hollow mill whenever +a fair amount of stock must be removed. If considerable +smoothness and accuracy are necessary, the finishing box-tool +shown at <i>B</i> should follow the roughing box tool, but in most +cases, especially if the part is to be threaded by a die, a finishing +cut is unnecessary.</p> + +<p><span class="pagenum"><a name="Pg_192" id="Pg_192">[192]</a></span> +The finishing box-tool <i>B</i> is also used to follow a hollow mill if +special accuracy or smoothness is desired. This tool is only +intended for light finishing cuts, the allowances varying from +0.005 inch to 0.015 inch in diameter. The cutters are made of +square tool steel of commercial size, and are ground and set to +take a scraping end cut. This particular tool has two tool-holders +which permit finishing two diameters at once. If a +larger number of sizes must be turned, extra tool-holders can +be applied.</p> + +<p>The single-cutter box-tool shown at <i>C</i> is bolted directly to the +face of the turret instead of being held by a shank in the turret +hole, and it is adapted for heavy cuts such as are necessary +when turning comparatively large bar stock. The tool-holder <i>a</i> +swivels on a stud, thus allowing the cutter to be withdrawn +from the work while being returned, which prevents marring the +turned surface. The high-speed steel cutter is ground to take +a side cut on the end of the bar. The latter is supported by +hardened and ground tool-steel rolls <i>b</i> which revolve on hardened +and ground studs. These rolls are mounted on swinging arms +which have a screw adjustment for different diameters. They +can also be adjusted parallel to the bar, thus enabling them to +be set either in advance of or back of the cutter. The opening +in the base allows the stock to pass into the turret when it is not +larger than the turret hole.</p> + +<p>The box-tool shown at <i>D</i> is similar to the one just described, +except that it has two or more cutters and roller back-rests, thus +enabling different diameters to be turned simultaneously. The +cutters are ground to take a side cut. Ordinarily this gives a +satisfactory finish, but if special accuracy and smoothness are +desired, two tools should be used, one for roughing and one for +finishing, the latter being ground to take a light scraping end cut.</p> + +<p>The taper-turning box-tool shown at <i>E</i> is designed for accurately +turning tapers on brass or cast-iron parts, when there is a +small amount of stock to be removed. The taper is obtained by +cross motion imparted to the cutter slide as the turret advances. +The taper-turning box-tool shown at <i>F</i>, instead of having a +single-point cutter, is provided with a wide cutter <i>a</i>. This tool +<span class="pagenum"><a name="Pg_193" id="Pg_193">[193]</a></span> +is designed to turn tapering parts of small or medium diameter, +requiring the use of a support which cannot be provided with a +straight forming tool and holder mounted on the cut-off slide. +The cutter is backed up by the screws shown, which also provide +adjustment for different tapers within a limited range. +The bar is supported by the three back-rests shown, which also +have screw adjustment.</p> + +<a name="Fig_5_9" id="Fig_5_9"></a><span class="pagenum"><a name="Pg_194" id="Pg_194">[194]</a></span> +<div class="figcenter"><div class="illobox450"><img src="images/202sm.png" alt="Box-tools and Work for which they are Intended" /></div> +<p class="caption750">Fig. 9. Box-tools and Work for which they are Intended</p> +</div> + +<a name="Secnum_5_8" id="Secnum_5_8"></a><p><b>Examples of Box-tool Turning.</b>—Box-tools are not only used +for cylindrical and taper turning on the end of a bar, but for +many other operations. <a href="#Fig_5_9">Figs. 9</a> and <a href="#Fig_5_10">10</a> show a number of box-tools +of different designs, with examples of the work for which +each is intended. While these tools are designed for some +specific part, they can, of course, with slight modifications be +adapted to other work.</p> + +<p>A box-tool of the pilot type that is used for finishing, after +the surplus stock has been removed by roughing tools, is shown +at <i>A</i>, <a href="#Fig_5_9">Fig. 9</a>. The work, which is the cone for a ball bearing, is +shown at <i>a</i> by the dotted lines and also by the detail view to the +right. The pilot <i>b</i> enters the work before either of the cutters +begins to operate on its respective surface. The inverted cutter +<i>c</i>, which sizes the flange of the cone, is held in position by a clamp +<i>d</i>, which is forced down by a collar-head screw. The cutter is +further secured against a beveled shoulder at <i>g</i> by the set-screws <i>f</i>, +and it is adjusted forward by the screw <i>e</i>. By loosening the +screws <i>f</i> and the collar-head screw, the cutter may be removed +for sharpening. The cutter <i>h</i> is adjusted to cut to the proper +diameter, by the screws <i>l</i>, after which the clamp <i>k</i> is made level +by the screw <i>j</i>. The collar-screw <i>m</i> is then used to secure the +tool in place. The cutter is made from drill rod and it is slightly +cupped out on the cutting end to give keenness to the cutting +edge. The adjusting screw <i>o</i>, which passes through plate <i>p</i>, prevents +the cutter from backing away from the work. This adjusting +screw plate has its screw holes slotted to avoid removing the +screws when it becomes necessary to remove the plate and +cutter for sharpening. Pilot <i>b</i> is held firmly to the tool body +by set-screw <i>r</i>. The hole <i>s</i> through the shank makes it easy to +remove the pilot, in case this is necessary.</p> + +<p><span class="pagenum"><a name="Pg_195" id="Pg_195">[195]</a></span> +A pilot box-tool for finishing another type of ball bearing cone +is shown at <i>B</i>. The shape of the work itself is indicated by the +dotted lines <i>a</i> and by the detail view. This tool is somewhat +similar in its construction to the one just described. The cutters +<i>b</i> and <i>c</i> are inverted and are used to face the flange at <i>d</i> and to +turn it to the proper diameter. These cutters are held by the +clamp <i>f</i> and screws <i>g</i> and are adjusted forward by the screw <i>h</i>. +The cutter <i>j</i>, which operates on top of the stock, rests on a +bolster, of the proper angle and is adjusted up or down by the +screws <i>k</i>. The clamp <i>l</i>, which binds against this tool, is beveled +to correspond with the angle of the tool. This clamp is secured +by the collar-screw shown and it is leveled by set-screws <i>s</i>. The +adjusting screw <i>p</i> prevents the cutter from slipping back. The +holes in the adjusting-screw plate are also slotted in this case so +that it will not be necessary to remove any screws when the +cutter has to be taken out of the holder.</p> + +<p>A box-tool for finishing a treadle-rod cone for a sewing machine +is shown at <i>C</i>. This tool is also of the pilot type. The +cutters in it operate on opposite sides of the cone <i>a</i>. The inverted +cutter <i>b</i> sizes the cylindrical part of the cone, while the +front cutter <i>d</i> is set at the proper angle to finish the tapered +part. The rear cutter <i>b</i> is held in place by the clamp <i>g</i> and a +collar screw. It is adjusted forward by the screw <i>h</i> in the plate +<i>i</i> which is held by screws as shown. The pilot is retained by a +set-screw, and it is easily removed by inserting a small rod in +the hole <i>l</i> which passes through the shank. The cutter <i>d</i> is held +by clamp <i>m</i> and is adjusted by screw <i>n</i> which passes through a +tapped hole in plate <i>o</i>. The screw holes in both the adjusting +plates <i>i</i> and <i>o</i> are slotted to facilitate their removal.</p> + +<a name="Fig_5_10" id="Fig_5_10"></a><span class="pagenum"><a name="Pg_197" id="Pg_197">[197]</a></span> +<div class="figcenter"><div class="illobox450"><img src="images/205sm.png" alt="Examples of Box-tool Designs" /></div> +<p class="caption750">Fig. 10. Examples of Box-tool Designs</p> +</div> + +<p>The box-tool illustrated at <i>A</i>, <a href="#Fig_5_10">Fig. 10</a>, is used for finishing +the bushing of a double-taper cone bearing <i>a</i>. The cutters are +so arranged that they all cut on the center; that is, the cutting +edges lie in a horizontal plane. The inverted cutter <i>b</i> at the +rear forms the short angular surface, and the cutter <i>c</i> in front +forms the long tapering part of the bearing. The large diameter +is turned, to size by cutter <i>d</i>. The pilot <i>e</i> has a bearing in the +bore nearly equal to the length of the work and it is provided<span class="pagenum"><a name="Pg_196" id="Pg_196">[196]</a></span> +with oil grooves, as shown. The taper shank of this pilot is +tapped for the screw <i>i</i> which extends the whole length of the +shank and is used to draw the pilot back to its seat. It is not +necessary to remove adjusting-screw plate <i>k</i> to take out the cutter +<i>b</i>, as the latter can be drawn out from the front after the collar-screw +<i>m</i> is loosened. The cutter <i>c</i> is removed by taking off the +adjusting-screw plate <i>s</i> after loosening the collar-screw <i>n</i>. The +cutter <i>d</i> is held in a dove-tailed slot by two headless set-screws <i>q</i>. +It is also backed up by an adjusting screw in the plate <i>s</i>. These +adjusting screws should all have fine threads, say from 32 to +40 per inch, and be nicely fitted so they will not loosen after being +adjusted.</p> + +<p>The box-tools shown at <i>B</i> and <i>C</i>, <a href="#Fig_5_10">Fig. 10</a>, are for turning the +sides of a loose pulley for a sewing machine. This pulley (shown +by the dotted lines) is finished in two operations. The box-tool +for finishing the side of the pulley on which the hub projects +beyond the rim, is shown at <i>B</i>. The inverted cutter <i>a</i>, +which faces the end of the hub, is held by a clamp <i>c</i> (clearly +shown in the end view) from the under side and it has no adjustment. +The collar-screw <i>d</i> is tapped into this clamp, which +is prevented from getting out of place by the dowel-pin <i>f</i>. The +pilot <i>g</i> is made small in the shank, so that tool <i>a</i> can be so placed +as to insure the removal of all burrs around the bore of the +hub. The pilot is held by a set-screw and it is provided with oil +grooves. The cutter <i>j</i> sizes the outside of the hub, and the cutter +<i>k</i> faces the side of the pulley rim. These cutters are both held +by the clamp <i>l</i> and the collar-screw <i>m</i>. No side plates are used +on this tool, and the cutters are all easily removed.</p> + +<p>Sketch <i>C</i> shows the box-tool used for the second operation. +As the hub is flush with the rim on the side for which this tool +is intended, it needs only one cutter to face both. This is done +by the wide cutter <i>a</i> which is held in a dove-tailed slot in the +front of the tool and is fastened by the clamp <i>b</i> and collar-screw +<i>c</i>. The bushing <i>d</i>, in which the end of the work arbor is supported, +is held by the collar-screw <i>e</i>, and to obtain the necessary +compression, the body of the tool is slotted as far back as <i>f</i>. This +bushing is provided with oil grooves and one side is cut away<span class="pagenum"><a name="Pg_198" id="Pg_198">[198]</a></span> +to clear the cutter <i>a</i>. The pilot end of the arbor on which the +work is mounted is <sup class="enum">1</sup>/<sub class="denom">16</sub> inch smaller than the bore of the pulley, +which allows the cutter to be set in far enough to prevent any +burr which might form at the edge of the bore. A disk <i>i</i> is inserted +back of bushing <i>d</i>, so that the latter may be easily removed +by passing a rod through the hollow shank. The special chuck +used for this second operation on the loose pulley is screwed +onto the spindle, and the work is mounted on a projecting arbor +and driven by the pins engaging holes in the pulley web. The +arbor is made a driving fit for the work, and the end or pilot is +a running fit in the bushing of the box-tool. A counterbore +in the arbor hub provides clearance for the hub of the pulley +which projects beyond the rim on one side.</p> + +<a name="Fig_5_11" id="Fig_5_11"></a> +<div class="figcenter"><div class="illobox450"><img src="images/206sm.png" alt="Hollow Mill and Holder, Spring Screw-threading Die" /></div> +<p class="caption750">Fig. 11. (A) Hollow Mill and Holder.<br />(B) Spring Screw-threading Die +and Releasing Die-holder</p> +</div> + +<a name="Secnum_5_9" id="Secnum_5_9"></a><p><b>Hollow Mills.</b>—A hollow mill such as is shown at +<i>A</i> in <a href="#Fig_5_11">Fig. 11</a> +is sometimes used in place of a box-tool (especially when turning +brass) for short roughing cuts preceding a threading operation. +The turning is done by the cutting edges <i>e</i>, and the turned part +enters the mill and is steadied by it. If this type of tool is used +for long, straight cuts, especially on square stock and when +making screws with large heads from the bar, it should always +be followed by a finishing box-tool to insure accurate work. A<span class="pagenum"><a name="Pg_199" id="Pg_199">[199]</a></span> +hollow mill can be sharpened readily by grinding the ends without +materially changing the cutting size. A slight adjustment +can be obtained by means of the clamp collar shown to the +left, although this is not generally used. When making these +mills, they should be reamed out tapering from the rear to give +clearance to the cutting edges. For turning steel, the cutting +edge should be about <sup class="enum">1</sup>/<sub class="denom">10</sub> of the diameter ahead of the center, +whereas for brass, it should be on the center-line.</p> + +<a name="Fig_5_12" id="Fig_5_12"></a> +<div class="figcenter"><div class="illobox450"><img src="images/207sm.png" alt="Geometric Adjustable Hollow Milling Tool" /></div> +<p class="caption750">Fig. 12. Geometric Adjustable Hollow Milling Tool</p> +</div> + +<p>Hollow mills are also made adjustable. The design shown in +<a href="#Fig_5_12">Fig. 12</a> is especially adapted for brass finishing. It can also be +used for taking light cuts on cast iron or steel but its use in +place of roughing or finishing box-tools for general use is not +recommended. With the exception of the cutters and screws, +the complete tool consists of three parts, <i>viz.</i>, the holder, cam, +and ring. The cam serves to adjust the cutters for different +diameters. The adjustment is made by the two screws shown, +the amount being indicated by a micrometer scale. When adjusting +the cutters for a given diameter, the use of a hardened +steel plug of the required size is advisable, the cutters being +adjusted against the plug.</p> + +<a name="Secnum_5_10" id="Secnum_5_10"></a><p><b>Releasing Die and Tap Holders.</b>—Threads are cut in the +turret lathe by means of dies for external threading, and taps for +internal threading, the die or tap being held in a holder attached +to the turret. A simple form of releasing die holder is shown<span class="pagenum"><a name="Pg_200" id="Pg_200">[200]</a></span> +at <i>B</i>, <a href="#Fig_5_11">Fig. 11</a>. This holder was designed for the spring-screw +type of threading die shown to the left. The die is clamped in +the holder <i>a</i> by the set-screw shown, and the shank <i>b</i> of the holder +is inserted in the turret hole. Holder <i>a</i> has an extension <i>c</i> which +passes through the hollow shank. When the die is pressed +against the end of the work, holder <i>a</i> and its extension moves +back until lug <i>d</i> on the holder engages lug <i>e</i> on the shank. The +die and holder are then prevented from rotating with the work +and the die begins to cut a thread. It continues to screw itself +onto the work with the turret following, until the thread has +been cut to the required length; the turret is then stopped and +as the die and holder <i>a</i> are drawn forward, lugs <i>d</i> and <i>e</i> disengage +so that the die simply rotates with the work without continuing +to advance. The lathe spindle is then reversed and as the turret +is moved back by hand, pin <i>f</i> comes around and enters notch <i>g</i>, +thus holding the die stationary; the die then backs off from the +threaded end. Some tap holders are also constructed the same +as this die holder, so far as the releasing mechanism is concerned. +There are also many other designs in use, some of which +operate on this same principle.</p> + +<a name="Secnum_5_11" id="Secnum_5_11"></a><p><b>Self-opening Die Heads.</b>—The type of die holder shown at +<i>B</i> in <a href="#Fig_5_11">Fig. 11</a> is objectionable because of the time required for +backing the die off the threaded end; hence, self-opening dies +are extensively used in turret lathe work. As the name implies,<span class="pagenum"><a name="Pg_201" id="Pg_201">[201]</a></span> +this type of die, instead of being solid, has several chasers +which are opened automatically when the thread has been cut +to the required length. The turret can then be returned without +reversing the lathe spindle. The dies are opened by simply +stopping the travel of the turret slide, the stop-rod for the feed +of the turret being adjusted to give the proper amount of travel.</p> + +<a name="Fig_5_13" id="Fig_5_13"></a> +<div class="figcenter"><div class="illobox450"><img src="images/208sm.png" alt="Self-opening and Adjustable Screw-cutting Die Head" /></div> +<p class="caption750">Fig. 13. Geometric Self-opening and Adjustable Screw-cutting Die Head</p> +</div> + +<p>A well-known die head of the self-opening type is shown in +<a href="#Fig_5_13">Fig. 13</a>. The dies open automatically as soon as the travel of +the head is retarded, or they can be opened at any point by simply +holding back on the turnstile or lever by which the turret slide +is moved. The die is closed again by means of the small handle +seen projecting at right-angles from the side of the head. The +closing may be done by hand or automatically by screwing a pin +into a threaded hole opposite the handle and attaching a small +piece of flat steel to the back edge of the turret slide. The latter +will then engage the pin as the turret revolves, thus closing +the die head. This die head has a roughing and finishing attachment +which is operated by handle <i>A</i>. When this handle +is moved forward, the dies are adjusted outward 0.01 inch for +the roughing cut, whereas returning the handle closes and locks +the dies for the finishing cut. The die head has a micrometer +scale which is used when making slight adjustments to compensate +for the wear of the chasers or to make either a tight-or +a loose-fitting thread.</p> + +<a name="Fig_5_14" id="Fig_5_14"></a> +<div class="figcenter"><div class="illobox450"><img src="images/209sm.png" alt="Geometric Collapsing Tap" /></div> +<p class="caption750">Fig. 14. Geometric Collapsing Tap</p> +</div> + +<p><span class="pagenum"><a name="Pg_202" id="Pg_202">[202]</a></span> +<a name="Secnum_5_12" id="Secnum_5_12"></a><b>Collapsing Taps.</b>—The collapsing tap shown in <a href="#Fig_5_14">Fig. 14</a> is one +of many different designs that are manufactured. They are +often used in turret lathe practice in place of solid taps. When +using this particular style of collapsing tap, the adjustable gage +<i>A</i> is set for the length of thread required. When the tap has +been fed to this depth, the gage comes into contact with the +end of the work, which causes the chasers to collapse automatically. +The tool is then withdrawn, after which the chasers +are again expanded and locked in position by the handle seen at +the side of the holder. In all threading operations, whether +using taps or dies, a suitable lubricant should be used, as a better +thread is obtained and there is less wear on the tools. Lard oil +is a good lubricant, although cheaper compounds give satisfactory +results on many classes of work.</p> + +<a name="Fig_5_15" id="Fig_5_15"></a> +<div class="figcenter"><div class="illobox450"><img src="images/211sm.png" alt="Various Types of Tools for the Turret Lathe" /></div> +<p class="caption750">Fig. 15. Various Types of Tools for the Turret Lathe</p> +</div> + +<a name="Secnum_5_13" id="Secnum_5_13"></a><p><b>Miscellaneous Turret Lathe Tools.</b>—The chamfering tool +shown at <i>A</i>, <a href="#Fig_5_15">Fig. 15</a>, is used for pointing the end of a bar before +running on a roughing box-tool. This not only finishes the +end of the bar but provides an even surface for the box-tool to +start on. The cutter is beveled on the end to form a cutting +edge and it is held at an angle. The back-rest consists of a +bell-mouthed, hardened tool-steel bushing which supports the +bar while the cut is being taken.</p> + +<p>The stop gages <i>B</i> and <i>C</i> are used in the turret to govern the +length of stock that is fed through the spindle. When a finished +piece has been cut off, the rough bar is fed through the spindle +and up against the stop gage, thus locating it for another operation. +This gage may be a plain cylindrical piece of hardened +steel, as at <i>B</i>, or it may have an adjusting screw as at <i>C</i>; for +special work, different forms or shapes are also required. The +stop gages on some machines, instead of being held in the turret, +are attached to a swinging arm or bracket that is fastened to +the turret slide and is swung up in line with the spindle when +the stock is fed forward.</p> + +<p>The center drilling tool <i>D</i> is designed to hold a standard combination +center drill and reamer. This type of tool is often used +when turning parts that must be finished afterwards by grinding, +to form a center for the grinding machine. The adjustable turning<span class="pagenum"><a name="Pg_203" id="Pg_203">[203]</a></span> +tool <i>E</i> is used for turning the outside of gear blanks, pulley +hubs or the rims of small pulleys. The pilot <i>a</i> enters the finished +bore to steady the tool, and cutter <i>b</i> is adjusted to turn to the +required diameter.</p> + +<p>The cutting-off tool-holder <i>F</i> (which is held on the cross-slide +of the turret lathe) is usually more convenient than a regular +toolpost, as the blade can be set closer to the chuck. The +blade is held in an inclined position, as shown, to provide rake +for the cutting edge; the inclined blade can also be adjusted +vertically, a limited amount, by moving it in or out. The +multiple cutting-off tool <i>G</i> holds two or more blades and is used +for cutting off several washers, collars, etc., simultaneously. +By changing the distance pieces between the cutters, the latter +are spaced for work of different widths. The flat drill holder<span class="pagenum"><a name="Pg_204" id="Pg_204">[204]</a></span> +<i>H</i> is used for drilling short holes, and also to form a true “spot” +or starting point for other drills.</p> + +<p>Knurling tools are shown at <i>I</i> and <i>J</i>. The former is intended +for knurling short lengths and is sometimes clamped on +top of the cut-off tool on the cross-slide, the end being swung +back after knurling (as shown by the dotted lines) to prevent +interference with the work when the cutting-off tool is in operation. +The knurling tool <i>J</i> has a shank and is held in the turret. +The two knurls are on opposite sides of the work so that the +pressure of knurling is equalized. By adjusting the arms which +hold the knurls, the tool can be set for different diameters.</p> + +<p>Three styles of drill holders are shown at <i>K</i>, <i>L</i> and <i>M</i>. Holder +<i>K</i> is provided with a split collet (seen to the left) which is tightened +on the drill shank by a set-screw in the holder. This +holder requires a separate collet for each size drill. The taper +shank drill holder <i>L</i> has a standard taper hole into which the +shank of the drill is inserted. The adjustable type of holder <i>M</i> is +extensively used, especially on small and medium sized machines +when several sizes of drills are necessary. This holder is simply +a drill chuck fitted with a special shank. For large drills the +plain style of holder <i>K</i> is recommended, and if only a few sizes +of drills are required, it is more satisfactory and economical +than the adjustable type.</p> + +<p>The various types of small turret lathe tools referred to in +the foregoing for turning, threading, tapping, knurling, etc., are +a few of the many different designs of tools used in turret lathe +practice. Naturally, the tool equipment for each particular +job must be changed somewhat to suit the conditions governing +each case. The tools referred to, however, represent in a general +way, the principal types used in ordinary practice. Some +of the more special tools are shown in connection with examples +of turret lathe work, which are referred to in the following.</p> + +<a name="Fig_5_16" id="Fig_5_16"></a> +<div class="figcenter"><div class="illobox450"><img src="images/213sm.png" alt="Method of Boring and Turning Pistons in Gisholt Lathe, Special Chuck and Tools for Turning, Boring and Cutting Off Eccentric Piston Rings" /></div> +<p class="caption750">Fig. 16. (A) Method of Boring and Turning Pistons in Gisholt Lathe.<br />(B) +Special Chuck and Tools for Turning, Boring and Cutting Off Eccentric +Piston Rings</p> +</div> + +<a name="Secnum_5_14" id="Secnum_5_14"></a><p><b>Turning Gasoline Engine Pistons in Turret Lathe.</b>—The +making of pistons for gas engines, especially in automobile factories, +is done on such a large scale that rapid methods of machining +them are necessary. The plan view <i>A</i>, <a href="#Fig_5_16">Fig. 16</a>, shows +the turret lathe tools used in one shop for doing this work. As +<span class="pagenum"><a name="Pg_205" id="Pg_205">[205]</a></span> +is often advisable with work done in large quantities, the rough +castings are made with extra projections so arranged as to assist +in holding them. These projections are, of course, removed +when the piece is completed. In this case the piston casting <i>a</i> +has a ring about 1<sup class="enum">1</sup>/<sub class="denom">4</sub> inch long and a little less in diameter than +the piston, at the chucking end. The piston is held in suitable +chuck jaws <i>b</i> which are tightened against the inside of this ring. +The set-screws in these special jaws are then tightened, thus +clamping the casting between the points of the screws and the +jaws. This method of holding permits the whole exterior of +the piston to be turned, since it projects beyond the chuck jaws. +This is the object in providing the piston with the projecting +ring by which it is held.</p> + +<p>The first operation consists in rough-boring the front end of +the piston. The double-ended cutter <i>n</i> is held in boring-bar <i>m</i>, +which is, in turn, supported by a drill-holder, clamped to one<span class="pagenum"><a name="Pg_206" id="Pg_206">[206]</a></span> +of the faces of the turret. This bar is steadied by a bushing in +the drill support <i>c</i> which is attached to the carriage, and may be +swung into or out of the operating position, as required. After +this cut is completed, the turret is revolved half way around and +the casting is finish-bored in a similar manner, with double-ended +cutter <i>n<sub>1</sub></i> held in bar <i>m<sub>1</sub></i>, the drill support being used as in +the previous case. The support is then turned back out of the +way to allow the turning tools in the turret toolpost to be used.</p> + +<p>The outside of the piston is next rough-turned with tool <i>k</i> +in the turret toolpost, which is revolved to bring this cutter into +action. The toolpost is then turned to the position shown, +and the outside is finish-turned by tool <i>j</i>, which takes a broad +shaving cut. The turret tool-holder is again revolved to bring +form tool <i>l</i> into position. This tool cuts the grooves for the +piston rings. Suitable positive stops are, of course, provided +for both the longitudinal and cross movements of the turret +toolpost.</p> + +<p>In the second operation, the piston <i>a</i> is reversed and held in +soft jaws, which are used in place of the hardened jaws <i>b</i> shown in +the illustration. These jaws are bored to the outside diameter +of the piston, so that when closed, they hold the work true or +concentric with the lathe spindle. In this operation the chucking +ring by which the piston was previously held is cut off, and +the end of the piston is faced true. If the crank-pin hole is to +be finished, a third operation is necessary, a self-centering chuck-plate +and boring and reaming tools being used. (These are not +shown in the illustration.)</p> + +<a name="Secnum_5_15" id="Secnum_5_15"></a><p><b>Turning Piston Rings in Turret Lathe.</b>—One method of turning +piston rings is shown at <i>B</i> in <a href="#Fig_5_16">Fig. 16</a>. The piston rings are +cut from a cast-iron cylindrical piece which has three lugs <i>b</i> +cast on one end and so arranged that they may be held in a three-jawed +chuck. This cylindrical casting is about 10 inches long, +and when the rings are to have their inside and outside surfaces +concentric, the casting is held by the lugs in the regular jaws +furnished with the chuck. (The arrangement used for turning +and boring eccentric rings, which is that shown in the illustration, +will be described later.)</p> + +<p><span class="pagenum"><a name="Pg_207" id="Pg_207">[207]</a></span> +The casting <i>a</i>, from which the rings are made, is first rough-bored +with double-ended cutter <i>n</i> in boring-bar <i>m</i>, after which +it is finish-bored with cutter <i>n<sub>1</sub></i> in bar <i>m<sub>1</sub></i>. While taking these +cuts, the bars <i>m</i> and <i>m<sub>1</sub></i> are supported by their extension ends +which enter bushing <i>r</i> located in the central hole of the chuck. +This furnishes a rigid support so that a heavy cut can be +taken.</p> + +<p>The outside of the casting is next rough-turned with tool <i>k</i>, +held in the turret toolpost. This toolpost is then revolved to +bring tool <i>j</i> into position, by which the outside is turned true to +size, a broad shaving chip being taken. The toolpost is again +swung around, to bring the cutting-off tool-holder <i>l</i> into position. +This holder contains four blades set the proper distance apart +to give rings of the desired width. Each blade, from right to +left, is set a little back of the preceding one, so that the rings are +cut off one after the other, the outer rings being supported until +they are completely severed. After the first four rings are cut +off, the carriage is moved ahead to a second stop, and four more +rings are severed, this operation being continued until the casting +has been entirely cut up into rings.</p> + +<p>When the bore of the ring is to be eccentric with the outside, +the holding arrangement shown in the illustration is used. The +casting a is bolted to a sliding chuck-plate <i>c</i>, and the outside is +rough-turned with tool <i>k</i> in the toolpost. Finishing tool <i>j</i> is +then brought into action, and the outside diameter is turned +accurately to size. Then the sliding chuck-plate <i>c</i>, carrying the +work, is moved over a distance equal to the eccentricity desired, +and the work is bored with cutters <i>n</i> and <i>n<sub>1</sub></i> as in the previous +case. The turret toolpost is next revolved and the tools <i>l</i> are +used for cutting off the rings. The reason for finishing the +outside first is to secure smooth rings in cutting off, as this +operation should be done when the work is running concentric +with the bore, rather than with the exterior surface.</p> + +<p>It will be evident that this method gives a far greater output +of rings than is possible by finishing them in the more primitive +way on engine lathes. The faces of the rings may be finished in +a second operation if desired, or they may be ground, depending<span class="pagenum"><a name="Pg_208" id="Pg_208">[208]</a></span> +on the method used in the shop where the work is being done, +and the accuracy required.</p> + +<a name="Fig_5_17" id="Fig_5_17"></a> +<div class="figcenter"><img src="images/216sm.jpg" alt="Turning Gasoline Engine Pistons in Pratt & Whitney Turret Lathe" /> +<p class="caption750">Fig. 17. Turning Gasoline Engine Pistons in Pratt & Whitney Turret Lathe</p> +</div> + +<a name="Secnum_5_16" id="Secnum_5_16"></a><p><b>Piston Turning in Pratt and Whitney Turret Lathe.</b>—A turret +lathe equipped with tools for turning, facing and grooving automobile +gasoline engine pistons is shown in <a href="#Fig_5_17">Fig. 17</a>. The piston +is held on an expanding pin chuck which is so constructed that +all of the pins are forced outward with equal pressure and automatically +conform to any irregularities on the inside of the +piston. Tool <i>A</i> rough-turns the outside, and just as this tool +completes its cut, a center hole is drilled and reamed in the end +of the piston by combination drill and reamer <i>B</i>. The turret +is then indexed one-half a revolution and a finishing cut is taken +by tool <i>C</i>. After the cylindrical body of the piston has been +turned, tools held in a special holder <i>E</i> attached to the cut-off +slide are used to face the ends of the piston and cut the packing-ring +grooves. While the grooves are being cut, the outer +end of the piston is supported by center <i>D</i>. The center hole in +the end also serves to support the piston while being ground to +the required diameter in a cylindrical grinding machine. The +edge at the open end of the piston may also be faced square and<span class="pagenum"><a name="Pg_209" id="Pg_209">[209]</a></span> +the inner corner beveled by a hook tool mounted on the rear +cross-slide, although this is usually done in a separate operation. +(This provides a true surface by which to hold this end when +grinding.)</p> + +<p>This illustration (<a href="#Fig_5_17">Fig. 17</a>) shows very clearly the stops which +automatically disengage the turret feed. A bracket <i>F</i> is bolted +to the front of the bed and contains six stop-rods <i>G</i> (one for each +position or side of the turret). When one of these stop-rods +strikes lever <i>H</i>, the feed is disengaged, the stop being adjusted +to throw out the feed when the tool has completed its cut. +Lever <i>H</i> is automatically aligned with the stop-rods for different +sides of the turret by a cam <i>J</i> on the turret base. A roller +<i>K</i> bears against this cam and, through the connecting shaft and +lever shown, causes lever <i>H</i> to move opposite the stop-rod for +whatever turret face is in the working position. Lever <i>L</i> is +used for engaging the feed and lever <i>R</i> for disengaging it by +hand.</p> + +<p>The indexing of the turret at the end of the backward movement +of the slide is controlled by stop <i>M</i> against which rod <i>N</i> +<span class="pagenum"><a name="Pg_210" id="Pg_210">[210]</a></span> +strikes, thus disengaging the lock bolt so that the turret can turn. +This stop <i>M</i> is adjusted along the bed to a position depending +upon the length of the turret tools and the distance the turret +must move back to allow the tools to clear as they swing around.</p> + +<a name="Fig_5_18" id="Fig_5_18"></a> +<div class="figcenter"><img src="images/217sm.jpg" alt="Pratt & Whitney Turret Lathe equipped with Special Attachment for Turning Eccentric Piston Rings" /> +<p class="caption750">Fig. 18. Pratt & Whitney Turret Lathe equipped with Special<br />Attachment +for Turning Eccentric Piston Rings</p> +</div> + +<a name="Secnum_5_17" id="Secnum_5_17"></a><p><b>Attachment for Turning Piston Rings.</b>—<a href="#Fig_5_18">Fig. +18</a> shows a special attachment applied to a Pratt & Whitney turret lathe for +turning eccentric, gas-engine piston rings. The boring of the +ring casting, turning the outside and cutting off the rings, is +done simultaneously. The interior of the casting is turned concentric +with the lathe spindle by a heavy boring-bar, the end of +which is rigidly supported by a bushing in the spindle. The +slide which carries the outside turning tool is mounted on a +heavy casting which straddles the turret. The outside of the +ring casting is turned eccentric to the bore as a result of an in-and-out +movement imparted to the tool by a cam on shaft <i>A</i> +which is rotated from the lathe spindle through the gearing +shown. For each revolution of the work, the tool recedes from +the center and advances toward it an amount sufficient to give<span class="pagenum"><a name="Pg_211" id="Pg_211">[211]</a></span> +the required eccentricity. When the turning and boring tools +have fed forward about 2 inches, then the cutting-off tools which +are held in holder <i>B</i> come into action. The end of each cutting-off +tool, from right to left, is set a little farther away from the +work than the preceding tool, so that the end rings are always +severed first as the tools are fed in by the cross-slide. A number +of the completed rings may be seen in the pan of the machine.</p> + +<a name="Fig_5_19" id="Fig_5_19"></a> +<div class="figcenter"><img src="images/218sm.jpg" alt="Tool Equipment for Worm Gear Blanks—Davis Turret Lathe" /> +<p class="caption750">Fig. 19. Tool Equipment for Machining Worm Gear Blanks—Davis Turret Lathe</p> +</div> + +<a name="Secnum_5_18" id="Secnum_5_18"></a><p><b>Turning Worm-gear Blanks in Turret Lathe.</b>—This is a second +operation, the hub of worm-gear blank <i>G</i> (<a href="#Fig_5_19">Fig. 19</a>) having +previously been bored, reamed, and faced on the rear side. The +casting is mounted upon a close-fitting arbor attached to a +plate bolted to the faceplate of the lathe, and is driven by two +pins which engage holes on the rear side. The rim is first rough-turned +by a tool <i>A</i> which operates on top, and the side is rough-faced +by a toothed or serrated cutter <i>B</i>. A similar tool-holder<span class="pagenum"><a name="Pg_212" id="Pg_212">[212]</a></span> +having a tool <i>C</i> and a smooth cutter <i>D</i> is then used to turn the +rim to the required diameter and finish the side. The end of +the hub is faced by cutters mounted in the end of bars <i>E</i> and <i>F</i>, +one being the roughing cutter and the other the finishing cutter. +The work arbor projects beyond the hub, as will be seen, and +forms a pilot that steadies these cutter bars. The curved rim +of the gear is turned to the required radius (preparatory to +gashing and bobbing the worm-wheel teeth) by a formed tool +<i>H</i> held on the cross-slide.</p> + +<a name="Fig_5_20" id="Fig_5_20"></a> +<div class="figcenter"><img src="images/219sm.jpg" alt="Turning Bevel Gear Blanks in Davis Turret Lathe—First Operation" /> +<p class="caption750">Fig. 20. Turning Bevel Gear Blanks in Davis Turret Lathe—First Operation</p> +</div> + +<a name="Secnum_5_19" id="Secnum_5_19"></a><p><b>Turning Bevel Gear Blanks.</b>—<a href="#Fig_5_20">Fig. 20</a> shows a plan view of +the tools used for the first turning operation on bevel gear blanks +(these gears are used for driving drill press spindles). The cored +hole is beveled true at the end by flat drill <i>A</i> to form a true starting +surface for the three-fluted drill <i>B</i> which follows. The hole +is bored close to the required size by a tool (not shown) held in +the end of bar <i>C</i>, and it is finished by reamer <i>D</i>. The cylindrical +end of the gear blank or hub is rough-and finish-turned by<span class="pagenum"><a name="Pg_213" id="Pg_213">[213]</a></span> +tools held in holders <i>E</i> and <i>F</i>, respectively. (These holders +were made to set at an angle of 45 degrees, instead of being +directly over the work, as usual, so that the cutters would be in +view when setting up the machine.) It will be noted that the +chuck is equipped with special jaws which fit the beveled part +of the casting.</p> + +<a name="Fig_5_21" id="Fig_5_21"></a> +<div class="figcenter"><img src="images/220sm.jpg" alt="Second Operation on Bevel Gear Blanks" /> +<p class="caption750">Fig. 21. Second Operation on Bevel Gear Blanks</p> +</div> + +<p>The second and final operation on this blank is shown in <a href="#Fig_5_21">Fig. +21</a>. The work <i>A</i> is held by a special driver plate attached to +the faceplate of the machine. This driver plate has two pins +which engage holes drilled in the gear blank and prevent it from +rotating. The blank is also held by a bolt <i>B</i> which forces a bushing +against the cylindrical end. First, the broad beveled side +which is to be the toothed part of the gear, is rough-turned by +toothed cutters <i>C</i>, and a recess is formed in the end of the blank, +by a turning tool in this same tool-holder. A similar tool-holder +<i>E</i>, having finishing cutters, is then used to finish the bevel face +and recess. The other tools seen in the turret are not used for +this second operation. The rear bevel is roughed and finished +by tools and held on the cross-slide.</p> + +<a name="Secnum_5_20" id="Secnum_5_20"></a><p><b>Shell Turning Operation in Flat Turret Lathe.</b>—The “flat +turret lathe” is so named because the turret is a flat circular +plate mounted on a low carriage to secure direct and rigid support +from the lathe bed. The tools, instead of being held by<span class="pagenum"><a name="Pg_214" id="Pg_214">[214]</a></span> +shanks inserted in holes in the turret, are designed so that they +can be clamped firmly onto the low circular turret plate.</p> + +<a name="Fig_5_22" id="Fig_5_22"></a> +<div class="figcenter"><div class="illobox450"><img src="images/221sm.png" alt="Sectional View of Tapering Mold Shell which is turned in Hartness Flat Turret Lathe" /></div> +<p class="caption750">Fig. 22. Sectional View of Tapering Mold Shell which is turned in<br />Hartness +Flat Turret Lathe, as illustrated in <a href="#Fig_5_23">Figs. 23</a> to <a href="#Fig_5_27">27</a>, Inclusive</p> +</div> + +<p>An interesting example of flat turret lathe work is shown in +<a href="#Fig_5_22">Fig. 22</a>. This is a steel shell which must be accurately finished +to a slight taper, both inside and out, threaded and plain recesses +are required at the ends, and, in addition, one or two minor +operations are necessary. This work is done in the Hartness +flat turret lathe, built by the Jones & Lamson Machine Co. +The shells are turned from cold-drawn seamless steel tubing, +having a carbon content of 0.20 per cent, and they are finished +at the rate of one in nine minutes. The tubing comes to the +machine in 12-foot lengths, and the tube being operated upon +is, of course, fed forward through the hollow spindle as each +successive shell is severed.</p> + +<a name="Fig_5_23" id="Fig_5_23"></a> +<div class="figcenter"><img src="images/222sm.jpg" alt="Rough-turning and Boring" /> +<p class="caption750">Fig. 23. First Operation on Shell Illustrated in <a href="#Fig_5_22">Fig. 22</a>—Rough-turning and Boring</p> +</div> + +<p>In finishing this shell, five different operations are required. +During the first operation the shell is rough-bored and turned by +one passage of a box-tool, <a href="#Fig_5_23">Fig. 23</a>, and the recess <i>A</i>, <a href="#Fig_5_22">Fig. 22</a>, +at the outer end, is finished to size by a second cutter located in +the boring-bar close to the turret. The turret is then indexed +to the second station which brings the threading attachment <i>G</i> +into position, as shown in <a href="#Fig_5_24">Fig. 24</a>. After the thread is finished, +<span class="pagenum"><a name="Pg_215" id="Pg_215">[215]</a></span> +the recess <i>B</i>, <a href="#Fig_5_22">Fig. 22</a>, is turned by a flat cutter <i>K</i>, <a href="#Fig_5_25">Fig. 25</a>. The +inner and outer surfaces are then finished to size by a box-tool +mounted on the fourth station of the turret and shown in position +in <a href="#Fig_5_26">Fig. 26</a>. The final operation, <a href="#Fig_5_27">Fig. 27</a>, is performed by three +tools held on an auxiliary turret cross-slide, and consists in +rounding the corners at <i>b</i> and <i>c</i>, <a href="#Fig_5_22">Fig. 22</a>, and severing the finished +shell.</p> + +<p>One of the interesting features connected with the machining +of this shell is the finishing of the inner and outer tapering surfaces. +The taper on the outside is <sup class="enum">3</sup>/<sub class="denom">32</sub> inch per foot, while the +bore has a taper of only <sup class="enum">1</sup>/<sub class="denom">64</sub> inch per foot, and these surfaces are +finished simultaneously. The box-tool employed is of a standard +type, with the exception of an inserted boring-bar, and the +taper on the outside is obtained by the regular attachment which +consists of a templet <i>D</i> (<a href="#Fig_5_23">Fig. 23</a>) of the required taper, that +causes the turning tool to recede at a uniform rate as it feeds along. +To secure the internal taper, the headstock of the machine is +swiveled slightly on its transverse ways by the use of tapering +gibs. By this simple method, the double taper is finished to +the required accuracy without special tools or equipment.</p> + +<a name="Fig_5_24" id="Fig_5_24"></a> +<div class="figcenter"><img src="images/223sm.jpg" alt="Cutting Internal Thread" /> +<p class="caption750">Fig. 24. Second Operation—Cutting Internal Thread</p> +</div> + +<a name="Fig_5_25" id="Fig_5_25"></a> +<div class="figcenter"><img src="images/224sm.jpg" alt="Turning Recess at Rear End; Tool is shown withdrawn" /> +<p class="caption750">Fig. 25. Third Operation—Turning Recess at Rear End; Tool is shown withdrawn</p> +</div> + +<a name="Fig_5_26" id="Fig_5_26"></a> +<div class="figcenter"><img src="images/225sm.jpg" alt="Finishing the Bore and Outside" /> +<p class="caption750">Fig. 26. Fourth Operation—Finishing the Bore and Outside</p> +</div> + +<a name="Fig_5_27" id="Fig_5_27"></a> +<div class="figcenter"><img src="images/226sm.jpg" alt="Rounding Ends, Scoring Large End, and Cutting Off" /> +<p class="caption750">Fig. 27. Fifth Operation—Rounding Ends, Scoring Large End, and Cutting Off</p> +</div> + +<p>As those familiar with this machine know, the longitudinal<span class="pagenum"><a name="Pg_216" id="Pg_216">[216]</a></span> +movements of the turret as well as the transverse movements +of the headstock are controlled by positive stops. The headstock +of this machine has ten stops which are mounted in a revolving +holder and are brought into position, as required, by +manipulating a lever at the front. The stops for length, or those +controlling the turret travel, are divided into two general groups, +known as “A” and “B”. Each of these groups has six stops +so that there are two stops for each of the six positions or stations +of the turret, and, in addition, five extra stops are available for +any one tool, by the engagement of a pin at the rear of the turret. +The change from the “A” to the “B” stops is made by adjusting +lever <i>L</i>, <a href="#Fig_5_26">Fig. 26</a>, which also has a neutral position.</p> + +<p>After the box-tool for the roughing cut, shown at work in +<a href="#Fig_5_23">Fig. 23</a>, has reached the end of its travel, further movement is +arrested by a stop of the “A” group. The outside turning tool +is then withdrawn by operating lever <i>E</i> and the turret is run +back and indexed to the second station, thus bringing the threading +attachment into position. The surface speed of 130 feet per +minute which is used for turning is reduced to about 30 feet per +minute for threading by manipulating levers <i>H</i>, <a href="#Fig_5_24">Fig. 24</a>. After +the turret is located by another stop of the “A” group, +the<span class="pagenum"><a name="Pg_217" id="Pg_217">[217]</a></span> +threading attachment is made operative by depressing a small +plunger <i>I</i>, which connects a vertical driving shaft from the +spindle with the splined transmission shaft <i>J</i>. A reciprocating +movement is then imparted to the thread chaser <i>t</i> which advances +on the cutting stroke and then automatically retreats to clear +the thread on the return. This movement is repeated until +the thread is cut to the proper depth, as determined by one +of the stops for the headstock. While the thread is being cut, +the carriage is locked to the bed by the lever <i>N</i>, <a href="#Fig_5_26">Fig. 26</a>. It was +found necessary to perform the threading operation before taking +the outside finishing cut, owing to a slight distortion of the +shell wall, caused by the threading operation.</p> + +<p>After the thread is finished, the turret is turned to the third +station as shown in <a href="#Fig_5_25">Fig. 25</a>, and tool <i>K</i> for the inner recess <i>B</i>, +<a href="#Fig_5_22">Fig. 22</a>, is brought into position and fed to the proper depth, +as determined by another cross-stop. The turret is also locked +in position for this operation. The finishing cuts for the bore +and the outside are next taken by a box-tool which is shown +near the end of its cut in <a href="#Fig_5_26">Fig. 26</a>. This box-tool is similar to +the one used for roughing, but it is equipped with differently +shaped cutters to obtain the required finish. The outside turning<span class="pagenum"><a name="Pg_218" id="Pg_218">[218]</a></span> +tool has a straight cutting edge set tangent to the cylindrical +surface and at an angle, while the boring tool has a cutting +edge of large radius. An end view of this box-tool is shown in +<a href="#Fig_5_27">Fig. 27</a>. A reduced feed is employed for the finishing cut, and +the speed is increased to 130 feet per minute, which is the same +as that used for roughing.</p> + +<p>During the next and final operation, the turret, after being +indexed to the position shown in <a href="#Fig_5_27">Fig. 27</a>, is first located by a +stop of the “A” group so that the cutting-off tool <i>R</i> in front can +be used for rounding the corner <i>b</i>, <a href="#Fig_5_22">Fig. 22</a>. The stop lever <i>L</i> +is then shifted and the turret is moved to a second stop of the +“B” group. The corner <i>c</i> is then rounded and the shell is +scored at <i>d</i> by two inverted tools <i>S</i> and <i>T</i> at the rear, after which +the finished work is severed by the cut-off tool at the front. +The cross-movement of these three tools is controlled by positive +stops on the cross-slide, and the latter is moved to and fro by +hand lever <i>O</i>. After the shell is cut off, the stop <i>M</i>, mounted +on the turret, <a href="#Fig_5_26">Fig. 26</a>, is swung into position, and the tube is +automatically fed forward to the swinging stop by the roll feed, +as soon as the chuck is released by operating lever <i>Q</i>. This +completes the cycle of operations. A copious supply of lubricant<span class="pagenum"><a name="Pg_219" id="Pg_219">[219]</a></span> +is, of course, furnished to the tools during these operations, +and the two boring-tool shanks are hollow so that lubricant +can be forced through them and be made to play directly upon +the cutters.</p> + +<a name="Fig_5_28" id="Fig_5_28"></a> +<div class="figcenter"><img src="images/227sm.jpg" alt="Tool Equipment for Turning Scroll Gear Blank on Acme Flat Turret Lathe" /> +<p class="caption750">Fig. 28. Tool Equipment for Turning Scroll Gear Blank on Acme Flat Turret Lathe</p> +</div> + +<a name="Secnum_5_21" id="Secnum_5_21"></a><p><b>Chuck Work in Flat Turret Lathe.</b>—Two examples of chuck +work on the Acme combination flat turret lathe are shown in +<a href="#Fig_5_28">Figs. 28</a> and <a href="#Fig_5_29">29</a>. <a href="#Fig_5_28">Fig. 28</a> shows the tool equipment for turning +a cylindrical part <i>A</i> which is held in a three-jaw universal chuck. +The front flange is first rough-turned by a bent turning tool <i>B</i>. +The diameter is regulated by one of the cross-stops at <i>D</i> which +has been previously set and controls the movement of the turret +cross-slide. The longitudinal feed is disengaged when the flange +has been turned, by an independent stop. This machine has twelve +longitudinal stops, there being one for each turret face and six +auxiliary stops, in addition to the stops for the cross-slide.</p> + +<p>After roughing the flange, the turret carriage is locked or +clamped rigidly to the bed to prevent any lengthwise movement, +and the back face of the front flange is rough-turned by tool <i>B</i> +<span class="pagenum"><a name="Pg_220" id="Pg_220">[220]</a></span> +in to the diameter of the hub which is indicated by a micrometer +dial on the cross-feed screw. The carriage is then unlocked +and auxiliary stop No. 7 is engaged (by turning a knob at the +front of the slide) and the cylindrical hub is turned back to the +rear flange, the feed being disengaged by the auxiliary stop just +as the tool reaches the flange. The cross-slide is now moved +outward, longitudinal auxiliary stop No. 8 is engaged, the +turret slide is moved against the stop, the carriage is locked and +the front sides of both the front and rear flanges are rough-faced +by tools <i>B</i> and <i>C</i>. The turret is next indexed and the hole +rough-bored by cutter <i>E</i>. After again indexing the turret, the +hub and flanges are finish-turned and faced by tools <i>F</i> and <i>G</i>, +as described for the rough-turning operation. The final operation +is that of finishing the bore by cutter <i>H</i>.</p> + +<a name="Fig_5_29" id="Fig_5_29"></a> +<div class="figcenter"><img src="images/228sm.jpg" alt="Acme Flat Turret Lathe Arranged for Turning Roller Feed Body" /> +<p class="caption750">Fig. 29. Acme Flat Turret Lathe Arranged for Turning Roller Feed Body</p> +</div> + +<p>The operation shown in <a href="#Fig_5_29">Fig. 29</a> is that of turning the body +of a roller feed mechanism for a turret lathe. The casting is +held in a three-jaw universal chuck and it is first rough-bored +by tool <i>A</i>. The turret is then indexed and the side of the body +and end of the hub are rough-faced by tools at <i>B</i>. The turret +is again indexed for rough-turning the outside of the hub and<span class="pagenum"><a name="Pg_221" id="Pg_221">[221]</a></span> +body, by tools <i>C</i> and <i>D</i>. Similar tools <i>E</i> and <i>F</i> are then used +to finish these same surfaces, after which the end of the hub +and side of the body are finished by tools <i>G</i> and <i>H</i> similar to +those located at <i>B</i>. The final operation is that of finishing +the bore by tool <i>J</i> and cutting a groove in the outside of the +hub by the bent tool <i>K</i>.</p> + +<a name="Fig_5_30" id="Fig_5_30"></a> +<div class="figcenter"><img src="images/229sm.jpg" alt="Turret and Head of Jones & Lamson Double-spindle Flat Turret Lathe" /> +<p class="caption750">Fig. 30. Turret and Head of Jones & Lamson Double-spindle Flat Turret Lathe</p> +</div> + +<a name="Secnum_5_22" id="Secnum_5_22"></a><p><b>Double-spindle Flat Turret Lathe.</b>—The extent to which +modern turning machines have been developed, especially for +turning duplicate parts in quantity, is illustrated by the design +of turret lathe the turret and head of which is shown in <a href="#Fig_5_30">Fig. 30</a>. +This machine has two spindles and a large flat turret which holds +a double set of tools, so that two duplicate castings or forgings +can be turned at the same time. It was designed primarily for +chuck work and can be used as a single-spindle machine if desirable. +When two spindles are employed for machining two duplicate +parts simultaneously, considerably more time is required for +setting up the machine than is necessary for the regular single-spindle +type, but it is claimed that the increased rate of production +obtained with the two-spindle design more than offsets<span class="pagenum"><a name="Pg_222" id="Pg_222">[222]</a></span> +this initial handicap. The manufacturers consider the single-spindle +machine the best type for ordinary machine building +operations, regardless of whether the work is turned from the +bar or is of the chucking variety. On the other hand, the double-spindle +type is preferred when work is to be produced in such +quantities that the time for setting up the machine becomes a +secondary consideration.</p> + +<p>When the double-spindle machine is used as a single-spindle +type, a chuck 17 inches in diameter is used, and when both +spindles are in operation, two 9-inch chucks are employed. +The general outline of the turret is square, and the tools are +rigidly held, with a minimum amount of overhang, by means +of tool-blocks and binding screws connected with the clamping +plates. Two duplicate sets of tools are clamped to each side of +the turret and these operate simultaneously on the two pieces +held in the chucks or on faceplates. Primarily the turret is used<span class="pagenum"><a name="Pg_223" id="Pg_223">[223]</a></span> +in but four positions, but when a 17-inch chuck or faceplate is +employed, corner blocks may be held by the clamping plates in +which tools are supported, giving, if necessary, four additional +operations by indexing the turret to eight positions.</p> + +<a name="Fig_5_31" id="Fig_5_31"></a> +<div class="figcenter"><div class="illobox450"><img src="images/230sm.png" alt="Diagram showing Tool Equipment and Successive Steps in Machining Sprocket Blanks on Double-spindle Flat Turret Lathe" /></div> +<p class="caption750">Fig. 31. Diagram showing Tool Equipment and Successive Steps<br />in +Machining Sprocket Blanks on Double-spindle Flat Turret Lathe</p> +</div> + +<p>A typical job to demonstrate the application of the double-spindle +flat turret lathe is illustrated in <a href="#Fig_5_31">Fig. 31</a>. The parts to +be turned are sprocket wheels which are held in the two 9-inch +chucks. At the first position of the turret (which is the one +illustrated), the inside is rough-bored by tools <i>A</i>. At the second +position of the turret, tools <i>B</i> rough-face the inner sides of the +flanges; tools <i>C</i> face the outer sides of the flanges, while tools <i>D</i> +turn the faces of the flanges. At the third position of the turret, +tools <i>E</i> finish-turn the inside of the flanges; tools <i>F</i> finish-turn +the outside of the flanges, while tools <i>G</i> finish the faces of the +flanges. At the fourth position of the turret, tools <i>H</i> finish-bore +the sprockets; tools <i>I</i> complete the turning on the outside of the +flanges, while tools <i>J</i> accurately size the interior of the flanges.</p> + +<p>With the double-spindle flat turret lathe, each operation is a +double operation, and the speeds are varied according to the +nature of the cut; thus, if at one position of the turret, the tools +are required to rough out the work, this may be done rapidly, +for it has no bearing on the other operations that are subsequently +performed. Furthermore, if the following operation +has to be performed with great care, this may be done without +reducing the speed of the less exacting operations.</p> + +<a name="Fig_5_32" id="Fig_5_32"></a><span class="pagenum"><a name="Pg_224" id="Pg_224">[224]</a></span> +<div class="figcenter"><img src="images/232sm.jpg" alt="Potter & Johnston Machine" /> +<p class="caption750">Fig. 32. Potter & Johnston Automatic Chucking and Turning Machine</p> +</div> + +<a name="Secnum_5_23" id="Secnum_5_23"></a><p><b>Automatic Chucking and Turning Machine.</b>—The chucking +and turning machine shown in <a href="#Fig_5_32">Fig. 32</a> is automatic in its operation, +the feeding of the tools, indexing of the turret, etc., being +done automatically after the machine is properly arranged, and +the work is placed in the chuck. This machine is adapted to +turning and boring a great variety of castings, forgings or parts +from bar stock, and it is often used in preference to the hand-operated +turret lathe, especially when a great many duplicate +parts are required. It is provided with mechanism for +operating the cross-slide, feeding the turret slide forward, returning +it rapidly, rotating the turret to a new position, and +feeding it forward quickly for taking a new cut. The cross-slide +<span class="pagenum"><a name="Pg_225" id="Pg_225">[225]</a></span> +and turret-slide movements are effected by cams mounted on +the large drum <i>E</i> seen beneath the turret, while the various +speed and feed changes are effected by dogs and pins carried on +disk <i>D</i> which is keyed to the same shaft that the cam drum is +mounted upon. This shaft with the cam drum and governing +disk <i>D</i>, makes one revolution for each piece of work completed. +The cams for operating the turret slide are mounted upon the +periphery of drum <i>E</i>. The roll which engages the angular faces +of these cams and imparts movement to the turret is carried +by an intermediate slide which has rack teeth engaging a pinion +on the square shaft <i>C</i>. By turning this shaft with a crank, the +position of the turret-slide, with relation to the cam, may be +adjusted for long or short work and long or short tools, as may +be required.</p> + +<a name="Fig_5_33" id="Fig_5_33"></a> +<div class="figcenter"><img src="images/233sm.jpg" alt="Rear View of Machine showing the Cross-slide Mechanism, Driving Gearing, etc." /> +<p class="caption750">Fig. 33. Rear View of Machine showing the Cross-slide Mechanism, Driving Gearing, etc.</p> +</div> + +<p>The cams which operate the cross-slide are mounted on the +right-hand end of drum <i>E</i> and actuate the yoke <i>A</i> (see <a href="#Fig_5_33">Fig. 33</a>) +which extends diagonally upward. The rear end of this yoke +has rack teeth meshing with the teeth of a segmental pinion,<span class="pagenum"><a name="Pg_226" id="Pg_226">[226]</a></span> +which is fastened to rock-shaft <i>B</i>. At the headstock end, this +rock-shaft carries another segmental pinion meshing with rack +teeth formed on the cross-slide. The movement imparted to +the yoke by the cams is thus transmitted through the pinions +and rock-shaft to the cross-slide.</p> + +<a name="Fig_5_34" id="Fig_5_34"></a> +<div class="figcenter"><img src="images/234sm.jpg" alt="The Automatic Controlling Mechanism for Feeds and Speeds" /> +<p class="caption750">Fig. 34. The Automatic Controlling Mechanism for Feeds and Speeds</p> +</div> + +<p>The cam drum <i>E</i> is driven by a pinion meshing with a gear +attached to its front side. This pinion is driven through a train +of gearing from pulley <i>L</i> (see <a href="#Fig_5_34">Fig. 34</a>) which is belted to the +spindle. The feeds are thus always dependent on the spindle +speed. By means of epicyclic gearing and suitable clutches, +the motion thus derived from the spindle may be made rapid +for returning the turret to be indexed and then advancing it to +the cutting position again, or very slow for the forward feed when +the tools are at work. These changes from slow to fast or <i>vice +versa</i> are controlled by disk <i>D</i>. This disk carries pins which +strike a star wheel located back of the disk at the top, and as +this star wheel is turned, the speeds are changed by operation +of the gearing and clutches referred to. The first pin <i>M</i> that +<span class="pagenum"><a name="Pg_227" id="Pg_227">[227]</a></span> +strikes the star wheel advances it one-sixth of a rotation, changing +the feed from fast to slow; the next pin that strikes it advances +it another sixth of a rotation, changing the feed from slow to +fast and so on. By adjusting the pins for each piece of work, +the feed changes are made to take place at the proper time. +Handwheel <i>E</i> is geared with the cam-shaft on which the star +wheel is mounted, so that the feeds may be changed by hand +if desired.</p> + +<p>In addition to these feed-changing pins, disk <i>D</i> has a dog +which operates a lever by which the feed movement is stopped +when the work has been completed. Four rates of feed are +provided by quick change gearing of the sliding gear type, operated +by handle <i>K</i>. With this handle set in the central position, +the feed is disengaged. On the periphery of disk <i>D</i> are also +clamped dogs or cams <i>N</i>, which operate a horizontal swinging +lever <i>P</i> connected by a link with vertical lever <i>J</i>, which controls +the two spindle speeds with which the machine is provided. +Either one of these speeds can be automatically engaged +at any time, by adjusting the cams <i>N</i> on disk <i>D</i>.</p> + +<p>Lever <i>H</i> connects or disconnects the driving pulley from the +shaft on which it is mounted, thus starting or stopping the +machine. The square shaft <i>G</i> serves to operate the drums by +hand and is turned with a crank. The rotation of the turret, +which takes place at the rear of its travel, is, of course, effected +automatically. A dog, which may be seen in <a href="#Fig_5_32">Fig. 32</a> at the side +of the bed, is set to trip the turret revolving mechanism at the +proper point in the travel, to avoid interference between the +tools and the work. The turret is provided with an automatic +clamping device. The mechanism first withdraws the locking +pin, unclamps the turret, revolves it, then throws in the locking +pin and clamps the turret again.</p> + +<a name="Fig_5_35" id="Fig_5_35"></a> +<div class="figcenter"><div class="illobox450"><img src="images/236sm.png" alt="Example of Work done in Automatic Chucking and Turning Machine" /></div> +<p class="caption750">Fig. 35. Simple Example of Work done in Automatic Chucking and Turning Machine</p> +</div> + +<a name="Secnum_5_24" id="Secnum_5_24"></a><p><b>Example of Work on Automatic Turning Machine.</b>—The +piece selected for illustrating the “setting up” and operation +of the automatic chucking and turning machine is shown in +<a href="#Fig_5_35">Fig. 35</a>. This is a second operation, and a very simple one +which will clearly illustrate the principles involved. In the first +operation, the hole was drilled, bored and reamed, the small end<span class="pagenum"><a name="Pg_228" id="Pg_228">[228]</a></span> +of the bushing faced, and the outside diameter finished, as indicated +by the sketch to the left. (The enlarged diameter at the +end was used for holding the work in the chuck.) In the second +operation (illustrated to the right), the enlarged chucking end +is cut off and, in order to prevent wasting this piece, it is made +into a collar for another part of the machine for which the bushing +is intended; hence, the outside diameter is turned and the +outside end faced, before cutting off the collar. In addition, +the bushing is recessed in the second operation, and the outer +end faced. In order to have the surfaces finished in the second +operation, concentric with those machined in the first operation, +the chuck is equipped with a set of soft “false jaws” which have +been carefully bored to exactly the diameter of the work to be +held.</p> + +<p>The first thing to determine when setting up a machine of +this type is the order of operations. In this particular case, +the order is as follows: At the first position of the turret, the +outside collar is rough-turned and the outer end rough-faced. +At the second position, the collar is turned to the required diameter +and the outer face is finished. The third face of the turret +is not equipped with tools, this part of the cycle being taken up +in cutting off the collar with a cut-off tool on the rear cross-slide. +The fourth operation is that of recessing the bushing, and the +fifth operation, facing the end to remove the rough surface left +by the cutting-off tool.</p> + +<a name="Fig_5_36" id="Fig_5_36"></a> +<div class="figcenter"><img src="images/237sm.jpg" alt="Front View of Machine set up for the Finishing Operation on the Recessed Bushing and Collar shown in the Foreground and in Fig. 35" /> +<p class="caption750">Fig. 36. Front View of Machine set up for the Finishing Operation on the +Recessed Bushing and Collar shown in the Foreground and in <a href="#Fig_5_35">Fig. 35</a></p> +</div> + +<p>The tools <i>A</i> and <i>B</i>, <a href="#Fig_5_36">Fig. 36</a>, used for turning the outside of +the flange, are held in brackets <i>C</i> bolted to the face of the turret. +<span class="pagenum"><a name="Pg_229" id="Pg_229">[229]</a></span> +These brackets are each provided with three holes for carrying +turning tool-holders. This arrangement provides for turning a +number of diameters at different positions, simultaneously, but +for this particular operation, a single cutting tool for each tool-holder +is all that is necessary. A special device is used for recessing +and will be described later.</p> + +<a name="Fig_5_37" id="Fig_5_37"></a> +<div class="figcenter"><img src="images/238sm.png" alt="Plate on the Headstock of Machine Illustrated in Fig. 32" /> +<p class="caption750">Fig. 37. Plate on the Headstock of Machine Illustrated in<br /><a href="#Fig_5_32">Fig. 32</a> +giving the Speeds and Feeds</p> +</div> + +<a name="Secnum_5_25" id="Secnum_5_25"></a><p><b>Determining Speed and Feed Changes.</b>—As previously mentioned, +the particular machine illustrated in <a href="#Fig_5_32">Fig. 32</a> can be +arranged for two automatic changes of speed to suit different +diameters on the work. The change gears that will give the +required spindle speeds should first be selected. These change +gears for different speeds are listed on a speed and feed plate +attached to the headstock of the machine (see <a href="#Fig_5_37">Fig. 37</a>). It is +possible to use one speed from the list given for the fast train +of gears, and one from the list for the slow train, so long as the +same gears are not used in each case. The diameter of the +collar on the work shown in <a href="#Fig_5_35">Fig. 35</a> is 2<sup class="enum">1</sup>/<sub class= +"denom">2</sub> inches, and the diameter +of the body is 2 inches. Assuming that the surface speed +for this job should be about 40 feet per minute, a little calculation +<span class="pagenum"><a name="Pg_230" id="Pg_230">[230]</a></span> +shows that the 66 revolutions per minute, given by the fast +train of gears, is equivalent to a surface speed of 43 feet per +minute on a diameter of 2<sup class="enum">1</sup>/<sub class="denom">2</sub> inches. Moreover, the 78 revolutions +per minute obtained from the slow train of gearing, gives +about 41 feet per minute on a diameter of 2 inches. The spindle +gearing indicated for these speeds is, therefore, placed in position +on the proper studs at the back of the machine.</p> + +<p>Next we have to determine on which faces of the turret to +place the different tools. Each turret face is numbered to +agree with the corresponding feed cam on the drum. The speed +and feed plate (<a href="#Fig_5_37">Fig. 37</a>) gives the various feeds obtainable per +revolution of the spindle. As will be seen, the different cams +give different feeds. Cam No. 1 has a coarse feed suitable for +roughing; cam No. 2 a finer feed adapted to finishing, and so on. +Since the first operation consists in rough-turning, cam No. 1 +is used. Cam No. 2, which gives a finer feed, is used for the +finish-turning operation. Cam No. 4, which is ordinarily used<span class="pagenum"><a name="Pg_231" id="Pg_231">[231]</a></span> +for reaming, could, in this case, be used for recessing, as this +recess is for clearance only and may be bored with a coarse feed.</p> + +<p>The final operation, which is that of facing, can be done with +any cam and cam No. 5 may be used. It will be understood +that for facing operations, the feeds given do not apply. As +the roll passes over the point of the feed cam at the extreme +end of the movement, the feed of the turret slide is gradually +slowed down to zero; since the facing takes place in the last +eighth or sixteenth inch of this movement, it is done at a feed +which is gradually reduced to zero. This is, of course, as it +should be, and it is not necessary to pay any attention to the +tabulated feeds in facing operations.</p> + +<a name="Secnum_5_26" id="Secnum_5_26"></a><p><b>Setting the Turret Slide.</b>—The next adjustment is that of +setting the turret slide. In making this adjustment the turret +is set in such relation to the work that the tools will have but +a small amount of overhang, the cam-shaft being revolved by +hand until the cam-roll is at the extreme top of the forward +feeding cam, so that the turret slide is at the extreme of its forward +movement. When this adjustment has been made by the +means provided, set the turret index tripping dog so as to revolve +the turret at the proper point. After a turning tool-holder and +tool is attached to the face of the turret, cam No. 1 is placed +in its operating position and is revolved by hand until the roll +is on the point of the cam and the turret at the forward extreme +of its motion. At this point the tool-holder is set so that the +cutter will be far enough forward to complete its turning operation. +The feed cam is then turned backward, thus returning +the turret slide, and the cutter is set to turn the flange to the +proper diameter for the roughing cut. The turret slide is fed +forward and back while the cutter is adjusted, and when it is +properly set, the flange is turned, the cam-drum being fed by +hand. This is the first trial cut on the piece.</p> + +<p>A facing tool, shown in the working position in <a href="#Fig_5_36">Fig. 36</a>, is placed +at this station of the turret, being held in the turret hole. This +tool has a pilot bar and a holder which contains a facing blade. +Feeding by hand, as before, the tool is adjusted lengthwise so +as to rough-face the work to the dimension desired. In a similar<span class="pagenum"><a name="Pg_232" id="Pg_232">[232]</a></span> +way the finish-turning and facing tools for the second position +of the turret are set, the cam-shaft being revolved by hand to +bring this second face and second cam into the working position. +(The finish-facing tool is not shown in place in <a href="#Fig_5_36">Fig. 36</a>.)</p> + +<a name="Secnum_5_27" id="Secnum_5_27"></a><p><b>Setting the Cross-slide Cam.</b>—As previously mentioned, the +third turret face has no tool, the cutting off of the collar being +done during this part of the cycle of operations. It has been +taken for granted that in setting the turret slide, room has been +left between it and the chuck for the cross-slide. The cross-slide +is clamped in a longitudinal position on the bed, convenient +for the cutting-off operation, which is done with a tool <i>D</i> (<a href="#Fig_5_36">Fig. 36</a>) +in the rear toolpost, thus leaving the front unobstructed for the +operator. When both forming and cutting off are to be done, +the forming tool is generally held at the front and the cutting-off +tool at the back because heavier and more accurate forming +can be done with the work revolving downward toward a tool +in the front toolpost, than with the tool at the rear where it is +subjected to a lifting action.</p> + +<a name="Fig_5_38" id="Fig_5_38"></a> +<div class="figcenter"><div class="illobox450"><img src="images/240sm.png" alt="Diagram of Cross-slide Cams and Feeding Mechanism" /></div> +<p class="caption750">Fig. 38. Diagram of Cross-slide Cams and Feeding Mechanism</p> +</div> + +<p><span class="pagenum"><a name="Pg_233" id="Pg_233">[233]</a></span> +The arrangement of the cross-slide cams is shown in <a href="#Fig_5_38">Fig. 38</a>, +which is an end view of the large drum <i>E</i>, <a href="#Fig_5_32">Fig. 32</a>. The rear +feed cam is the one to be used, and since this cutting-off operation +is a short one, it may be done during the return of the turret for +position No. 3. The cam drum is, therefore, rotated by hand +until the turret face No. 3 has begun to return. The cross-slide +cams are then loosened and the rear feed cam is swung around +to just touch the roller <i>R</i> which operates arm <i>A</i>, the cross-slide +having been adjusted out to nearly the limit of its forward +travel, leaving approximately enough movement for cutting off +the collar. The rear feed cam is then clamped in this position.</p> + +<p>A cutting-off tool is next placed in the rear toolpost at the +proper height. The rear toolpost slide is then adjusted to bring +the point of the cutting-off tool up to the work, and the cam +drum is revolved by hand until the piece is cut off. The cross-slide +tool is, of course, set in the proper position to make a collar +of the required thickness. Feeding by hand is discontinued +when the roll is on the point of the cam; the cutting-off tool +slide is then permanently set on the cross-slide so that the point +of the cutting-off tool enters the bore just far enough to completely +sever the collar from the bushing. The motion of the +cam drum is continued, by hand, until the roll is over the point +of the feed cam. The cross-slide is then pushed back, by hand, +until the cam and roll are again in contact, when the return +cam is brought up and clamped in position, so that there is just +room for the roll between the feed cam and the return cam. +The rear return cam (as the hand feed of the cam drum is continued) +brings the cross-slide back to its central position. Since +there is no front tool used for this series of operations (although +a tool is shown in the front toolpost, <a href="#Fig_5_36">Fig. 36</a>), the first feed and +return cams are allowed to remain wherever they happen to be. +These cam adjustments can all be made from the front of the +machine.</p> + +<a name="Fig_5_39" id="Fig_5_39"></a> +<div class="figcenter"><div class="illobox450"><img src="images/242sm.png" alt="Flexible Boring Tool used for Recessing a Bushing in Automatic Chucking and Turning Machine" /></div> +<p class="caption750">Fig. 39. Flexible Boring Tool used for Recessing<br />a Bushing in Automatic +Chucking and Turning Machine</p> +</div> + +<a name="Secnum_5_28" id="Secnum_5_28"></a><p><b>Setting the Boring Tool for Recessing.</b>—The feeding of the +turret slide is now continued to make sure that the cutting-off +tool is returned to its normal position before the facing tool in +the next face of the turret begins to work. The facing of the<span class="pagenum"><a name="Pg_234" id="Pg_234">[234]</a></span> +bushing, so far as the setting of the tool is concerned, is merely +a repetition of the facing operation at the first position of the +turret. The recessing tool is next set. This tool, which is +shown diagrammatically in <a href="#Fig_5_39">Fig. 39</a>, is very simple as compared +with the somewhat complex operation it has to perform. This +recess is for clearance only, and accurate dimensions and fine +finish are not necessary. The recessing tool consists simply of a +slender boring-bar held in the turret and carrying a cutter suitably +located about midway the bar. The forward end of the bar +is small enough to enter a bell-mouthed bushing held in the +chuck. The boring-bar is bent to one side far enough so that +the cutter clears the hole as the bar enters, but is forced into +the work as the rounded hole of the bushing engages the end of +the bar and deflects it into the working position. The upper +diagram shows the position of the bar as it enters the hole, and +the lower one the position after it has entered the bushing and +is engaged in turning the recess. This bar is set in the turret +so that at the extreme forward travel of the turret slide, the +recess will be bored to the required length. The cutter must +also be adjusted to bore to the desired diameter. This completes +the setting of the cutting tools.</p> + +<a name="Secnum_5_29" id="Secnum_5_29"></a><p><span class="pagenum"><a name="Pg_235" id="Pg_235">[235]</a></span> +<b>Adjustments for Automatic Feed and Speed Changes.</b>—The +machine must now be set to perform automatically the desired +changes of spindle speed and the fast and slow cam movements +for the tools. After placing a new piece of work in the machine +(the first one having been completed in the setting-up operation), +the cam-shaft is revolved by hand until the turning tool in turret +face No. 1 is just about to begin its cut. The control wheel <i>D</i>, +<a href="#Fig_5_34">Fig. 34</a>, is rotated in its normal direction until the next graduation +marked “slow” is in line with an index mark on the base of the +machine. Then the nearest pin <i>M</i> is moved up until it bears +against a tooth of the star wheel (previously referred to) and is +clamped in this position. The pin should now be in the proper +location, but to test its position, rotate the cam shaft backward +by hand and throw in the automatic feed; then watch the cut +to see if the drum slows down just before the tool begins to work. +If it does not, the pin should be adjusted a little, one way or the +other, as may be required. (In going over a piece of work for +the first time, it is best to have the feed set to the smallest rate, +feed change handle <i>K</i> being in position No. 1.)</p> + +<p>After the cut has been completed and the turret feed cam-roll +is on the high part of the cam, the power feed should again be +stopped and the handwheel revolved until the next graduation +marked “fast” is opposite the index mark. The next stop pin +is then moved up until it just touches the star wheel, where it +is clamped in position. The feed being again thrown in, the +turret will be returned rapidly, indexed, and moved forward for +the second operation. After stopping the automatic movement, +the pins are set for this face, and so on for all the operations, +including that in which the cross-slide is used for cutting off +the finished collar.</p> + +<p>As the first, second, and third operations are on comparatively +large diameters, they should be done at the slow speed, handle <i>J</i>, +<a href="#Fig_5_34">Fig. 34</a>, being set to give that speed. While the turret slide is +being returned between operations 3 and 4, one of the spindle +speed-changing dogs <i>N</i> should be clamped to the rim of disk <i>D</i> +so as to change the spindle speed to the fast movement. This +speed is continued until the last operation is completed, when a<span class="pagenum"><a name="Pg_236" id="Pg_236">[236]</a></span> +second dog is clamped in place to again throw in the slow movement. +The feed knock-off dog should also be clamped in place +on the disk to stop the machine at the completion of the fifth +operation, when the turret is in its rear position. This completes +the setting up of the machine. If the feed is finer than is necessary, +the feed change handle <i>K</i> may now be moved to a position +which will give the maximum feed that can be used.</p> + +<p>It has taken considerable time to describe the setting up of +the machine for this simple operation, but in the hands of a +competent man it can be done quite rapidly. While a simple +operation has been referred to in the foregoing, it will be understood +that a great variety of work can be done on a machine of +this type. It is not unusual to see as many as ten cutting tools +operating simultaneously on a piece of work, the tools being +carried by the turret, cross-slide and back facing attachment. +The latter is operated from a separate cam applied to the cam-shaft +and acting through levers on a back facing bar which passes +through a hole in the spindle. In this back facing bar may +be mounted drills, cutters, facing tools, etc. for machining the +rear face of a casting held in the chuck jaws. Where extreme +accuracy is required, a double back facing attachment may be +used, arranged with cutters for taking both roughing and finishing +cuts. The use of this attachment often saves a second operation. +This automatic chucking and turning machine is also adapted +for bar work, especially in diameters varying from 3 to 6 inches.</p> + +<a name="Fig_5_40" id="Fig_5_40"></a> +<div class="figcenter"><img src="images/245sm.jpg" alt="Machining Flywheels in Potter & Johnston Automatic Chucking and Turning Machine" /> +<p class="caption750">Fig. 40. Machining Flywheels in Potter & Johnston Automatic<br />Chucking +and Turning Machine</p> +</div> + +<a name="Secnum_5_30" id="Secnum_5_30"></a><p><b>Turning Flywheel in Automatic Chucking and Turning Machine.</b>—A +typical operation on the Potter & Johnston automatic +chucking and turning machine is illustrated in <a href="#Fig_5_40">Fig. 40</a>, +which shows the machine arranged for turning the cast-iron flywheel +for the engine of a motor truck. The rim is turned and +faced on both sides and the hub is bored, reamed and faced on +both sides. The flywheel casting is held in a chuck by three +special jaws which grip the inside of the rim. The order of the +operations is as follows:</p> + +<p>The rear end of the hub is faced by the back facing bar; the +cored hole is started by a four-lipped drill in the turret and +the front end of the hub is rough-faced. (These tools are on the<span class="pagenum"><a name="Pg_237" id="Pg_237">[237]</a></span> +rear side of the turret when the latter is in the position shown +in the illustration.) After the turret indexes, the hole is rough-bored +by tool <i>A</i> and while this is being done, the outside of the +rim is rough-turned by tool <i>B</i> held in a special bracket attached +to the turret. Both sides of the rim are also rough-faced by +tools <i>C</i> and <i>D</i> held at the front of the cross-slide, this operation +taking place at the same time that the rim is turned and the +hole is being bored.</p> + +<p>The turret again automatically recedes and indexes, thus locating +bar <i>E</i> and turning tool <i>G</i> in the working position. The +hole is then finish-bored by tool <i>E</i> and the hub is finish-faced by +blade <i>F</i>; at the same time the rim is finish-turned by tool <i>G</i> and +the sides are finish-faced to the proper width by two tools held +at the rear of the cross-slide. The turret automatically recedes +and indexes a third time, thus locating the flat-cutter reamer-bar +<i>H</i> in the working position and then the hole is reamed to the +required diameter. This completes the cycle of operations. +The total time for machining this flywheel is forty minutes.</p> + +<a name="Fig_5_41" id="Fig_5_41"></a> +<div class="figcenter"><img src="images/246sm.jpg" alt="New Britain Multiple-spindle Automatic Chucking Machine of Single-head Type" /> +<p class="caption750">Fig. 41. New Britain Multiple-spindle Automatic<br />Chucking Machine of +Single-head Type</p> +</div> + +<a name="Secnum_5_31" id="Secnum_5_31"></a><p><span class="pagenum"><a name="Pg_238" id="Pg_238">[238]</a></span> +<b>Automatic Multiple-spindle Chucking Machine.</b>—An example +of the specialized machines now used for producing +duplicate parts, is shown in <a href="#Fig_5_41">Fig. 41</a>. This is a “New Britain” +automatic multiple-spindle chucking machine of the single-head +type and it is especially adapted for boring, reaming and facing +operations on castings or forgings which can readily be held in +chuck jaws. This particular machine has five spindles, which +carry and revolve the tools. The work being machined is held +stationary in the multiple chuck turret <i>A</i> which holds each part +in line with one of the spindles and automatically indexes, so that +the work passes from one spindle to another until it is finished. +The turret then indexes the finished piece to a sixth or “loading +position” which is not opposite a spindle, where the part is removed +and replaced with a rough casting. Each pair of chuck +jaws is operated independently of the others by the use of a chuck +wrench. These jaws are made to suit the shape of the work.</p> + +<p>When a single-head machine is in operation, the turret advances +and feeds the work against the revolving tools so that a number +of pieces are operated upon at the same time. The turret is fed +by a cam drum <i>B</i>. Cam strips are bolted to the outside of this<span class="pagenum"><a name="Pg_239" id="Pg_239">[239]</a></span> +drum and act directly against a roller attached to the yoke <i>C</i> +which can be clamped in different positions on the spindle <i>D</i>, +the position depending upon the length of the work. On the +opposite end of the turret spindle is the indexing mechanism <i>E</i>. +An automatically spring-operated latch <i>F</i> engages notches in +the rim of the dividing wheel, thus accurately locating the turret. +The turret is locked by a steadyrest <i>G</i>, which, for each working +position, automatically slides into engagement with one of the +notches in the turret. This relieves the indexing mechanism of +all strain.</p> + +<p>This type of machine is also built with two spindle heads, +the double-head design being used for work requiring operations +on both ends. When the double-head machine is in operation, +the revolving spindles and tools advance on both sides of the +chuck turret, the latter remaining stationary except when +indexing. The feed drums on the double-head machine are +located directly beneath each group of spindles.</p> + +<a name="Fig_5_42" id="Fig_5_42"></a> +<div class="figcenter"><img src="images/247sm.jpg" alt="Detail View of New Britain Double-head Eight-spindle Machine, Boring, Reaming and Facing Castings" /> +<p class="caption750">Fig. 42. Detail View of New Britain Double-head Eight-spindle<br />Machine, +Boring, Reaming and Facing Castings</p> +</div> + +<p><a href="#Fig_5_42">Fig. 42</a> shows an example of work on a machine of the double-head +design. This is an eight-spindle machine, there being two +groups of four spindles on each side of the turret. The castings<span class="pagenum"><a name="Pg_240" id="Pg_240">[240]</a></span> +<i>E</i> are for the wheel hubs of automobiles. The order of the operations +on one of the castings, as it indexes around, is as follows: +The hole in the hub is first rough-reamed by taper reamer <i>A</i> +and the opposite end of the hub is rough-faced and counterbored +by a tool in spindle <i>A<sub>1</sub></i>. When the turret indexes, this same +casting is reamed close to the finished size by reamer <i>B</i> and the +left end of the hub is rough-faced by cutter <i>F</i>, while a tool in the +opposite spindle <i>B<sub>1</sub></i> finishes the counterboring and facing operation. +At the third position, reamer <i>C</i> finishes the hole accurately +to size, and when the work is indexed to the fourth position, +the hub on the left side is finish-faced by a tool in spindle <i>D</i>. +(The third and fourth spindles of the right-hand group are not +used for this particular operation.) When the turret again +indexes, the finished casting is removed and replaced with a +rough one. While the successive operations on a single casting +have just been described, it will be understood that all of the +tools operate simultaneously and that a finished casting arrives +at the unloading and loading position each time the turret indexes. +Three hundred of these malleable castings are machined +in nine hours.</p> + +<a name="Secnum_5_32" id="Secnum_5_32"></a><p><b>Selecting Type of Turning Machine.</b>—The variety of machine +tools now in use is very extensive, and as different types can +often be employed for the same kind of work, the selection of +the best and most efficient machine is often a rather difficult +problem. To illustrate, there are many different types and +designs of turning machines, such as the ordinary engine lathe, +the hand-operated turret lathe, the semi-automatic turning +machine, and the fully automatic type, which, after it is “set +up” and started, is entirely independent. Hence, when a certain +part must be turned, the question is, what kind of machine +should be used, assuming that it would be possible to employ +several different machines? The answer to this question usually +depends principally upon the number of parts that must be +turned.</p> + +<p>For example, a certain casting or forging might be turned in +a lathe, which could be finished in some form of automatic or +semi-automatic turning machine much more quickly. It does<span class="pagenum"><a name="Pg_241" id="Pg_241">[241]</a></span> +not necessarily follow, however, that the automatic is the best +machine to use, because the lathe is designed for general work +and the part referred to could doubtless be turned with the +regular lathe equipment, whereas the automatic machine would +require special tools and it would also need to be carefully adjusted. +Therefore, if only a few parts were needed, the lathe +might be the best tool to use, but if a large number were required, +the automatic or semi-automatic machine would doubtless +be preferable, because the saving in time effected by the latter +type would more than offset the extra expense for tool equipment +and setting the machine. It is also necessary, in connection +with some work, to consider the degree of accuracy required, +as well as the rate of production, and it is because of these varying +conditions that work of the same general class is often done +in machines of different types, in order to secure the most efficient +results.</p> + +<hr class="c25" /><span class="pagenum"><a name="Pg_242" id="Pg_242">[242]</a></span> +<h2><a name="Chapnum_6" id="Chapnum_6">CHAPTER VI</a></h2> +<h3>VERTICAL BORING MILL PRACTICE</h3> +<hr class="c05" /> + +<p>All the different types of turning machines now in use originated +from the lathe. Many of these tools, however, do not +resemble the lathe because, in the process of evolution, there +have been many changes made in order to develop turning +machines for handling certain classes of work to the best advantage. +The machine illustrated in <a href="#Fig_6_1">Fig. 1</a> belongs to the lathe +family and is known as a vertical boring and turning mill. +This type, as the name implies, is used for boring and turning +operations, and it is very efficient for work within its range. +The part to be machined is held to the table <i>B</i> either by clamps +or in chuck jaws attached to the table. When the machine is +in operation, the table revolves and the turning or boring tools +(which are held in tool-blocks <i>T</i>) remain stationary, except for +the feeding movement. Very often more than one tool is used +at a time, as will be shown later by examples of vertical boring +mill work. The tool-blocks <i>T</i> are inserted in tool-bars <i>T<sub>1</sub></i> carried +by saddles <i>S</i> which are mounted on cross-rail <i>C</i>. Each +tool-head (consisting of a saddle and tool-bar) can be moved +horizontally along cross-rail <i>C</i>, and the tool-bars <i>T<sub>1</sub></i> have a +vertical movement. These movements can be effected either +by hand or power.</p> + +<a name="Fig_6_1" id="Fig_6_1"></a> +<div class="figcenter"><img src="images/251sm.jpg" alt="Gisholt Vertical Boring and Turning Mill" /> +<p class="caption750">Fig. 1. Gisholt Vertical Boring and Turning Mill</p> +</div> + +<p>When a surface is being turned parallel to the work table, +the entire tool-head moves horizontally along the cross-rail, but +when a cylindrical surface is being turned, the tool-bar moves +vertically. The tool-heads are moved horizontally by the +screws <i>H</i> and <i>H<sub>1</sub></i>, and the vertical feed for the tool-bars is obtained +from the splined shafts <i>V</i> and <i>V<sub>1</sub></i>, there being a separate +screw and shaft for each head so that the feeding movements +are independent. These feed shafts are rotated for the power +feed by vertical shafts <i>A</i> and <i>A<sub>1</sub></i> on each side of the machine. +<span class="pagenum"><a name="Pg_243" id="Pg_243">[243]</a></span> +These vertical shafts connect with the feed shafts through bevel +and spur gears located at the ends of the cross-rail. On most +boring mills, connection is made with one of the splined shafts +<i>V</i> or screw <i>H</i>, by a movable gear, which is placed on whichever +shaft will give the desired direction of feed. The particular +machine illustrated is so arranged that either the right +or left screw or feed shaft can be engaged by simply shifting +levers <i>D<sub>1</sub></i> or <i>D</i>.</p> + +<p>The amount of feed per revolution of the table is varied for +each tool-head by feed-changing mechanisms <i>F</i> on each side of +the machine. These feed boxes contain gears of different sizes, +and by changing the combinations of these gears, the amount +of feed is varied. Five feed changes are obtained on this machine<span class="pagenum"><a name="Pg_244" id="Pg_244">[244]</a></span> +by shifting lever <i>E</i>, and this number is doubled by shifting +lever <i>G</i>. By having two feed boxes, the feeding movement +of each head can be varied independently. The direction of +either the horizontal or vertical feed can be reversed by lever +<i>R</i>, which is also used for engaging or disengaging the feeds. +This machine is equipped with the dials <i>I</i> and <i>I<sub>1</sub></i> which can be +set to automatically disengage the feed at any predetermined +point. There are also micrometer dials graduated to thousandths +of an inch and used for adjusting the tools without the +use of measuring instruments.</p> + +<p>The work table <i>B</i> is driven indirectly from a belt pulley at +the rear, which transmits the power through gearing. The +speed of the table can be varied for turning large or small parts, +by levers <i>J</i> and <i>K</i> and the table can be started, stopped or +rotated part of a revolution by lever <i>L</i> which connects with a +friction clutch. There are corresponding feed and speed levers +on the opposite side, so that the machine can be controlled from +either position.</p> + +<p>The heads can be adjusted along the cross-rail for setting the +tools by hand-cranks <i>N</i>, and the tool slides can be moved vertically +by turning shafts <i>V</i> with the same cranks. With this +machine, however, these adjustments do not have to be made +by hand, ordinarily, as there are rapid power movements controlled +by levers <i>M</i>. These levers automatically disengage the +feeds and enable the tool-heads to be rapidly shifted to the required +position, the direction of the movement depending upon +the position of the feed reverse lever <i>R</i> and lever <i>D</i>. This rapid +traverse, which is a feature applied to modern boring mills of +medium and large size, saves time and the labor connected with +hand adjustments. The cross-rail <i>C</i> has a vertical adjustment +on the faces of the right and left housings which support it, in +order to locate the tool-heads at the right height for the work. +This adjustment is effected by power and is controlled by +levers at the sides of the housings. Normally, the cross-rail is +bolted to the housings, and these bolts must be loosened before +making the adjustment, and must always be tightened afterwards.</p> + +<p><span class="pagenum"><a name="Pg_245" id="Pg_245">[245]</a></span>The function of these different levers has been explained to +show, in a general way, how a vertical boring machine is operated. +It should be understood, however, that the arrangement +differs considerably on machines of other makes. The construction +also varies considerably on machines of the same +make but of different size.</p> + +<a name="Fig_6_2" id="Fig_6_2"></a> +<div class="figcenter"><img src="images/253sm.jpg" alt="Small Boring and Turning Mill with Single Turret-head" /> +<p class="caption750">Fig. 2. Small Boring and Turning Mill<br />with Single Turret-head</p> +</div> + +<p>All modern vertical boring mills of medium and large sizes +are equipped with two tool-heads, as shown in <a href="#Fig_6_1">Fig. 1</a>, because a +great deal of work done on a machine of this type can have two +surfaces machined simultaneously. On the other hand, small<span class="pagenum"><a name="Pg_246" id="Pg_246">[246]</a></span> +mills of the type illustrated in <a href="#Fig_6_2">Fig. 2</a> have a single head. The +toolslide of this machine, instead of having a single tool-block, +carries a five-sided turret <i>T</i> in which different tools can be +mounted. These tools are shifted to the working position as +they are needed, by loosening binder lever <i>L</i> and turning or +“indexing” the turret. The turret is located and locked in any +of its five positions by lever <i>I</i>, which controls a plunger that +engages notches at the rear. Frequently, all the tools for +machining a part can be held in the turret, so that little time +is required for changing from one tool to the next. Some large +machines having two tool-heads are also equipped with a turret +on one head.</p> + +<a name="Secnum_6_1" id="Secnum_6_1"></a><p><b>Boring and Turning in a Vertical Boring Mill.</b>—The vertical +boring mill is, in many respects, like a lathe placed in a vertical +position, the table of the mill corresponding to the faceplate +or chuck of the lathe and the tool-head to the lathe carriage. +Much of the work done by a vertical mill could also be machined +in a lathe, but the former is much more efficient for work +within its range. To begin with, it is more convenient to clamp +work to a horizontal table than to the vertical surface of a lathe +faceplate, or, as someone has aptly said, “It is easier to lay a +piece down than to hang it up.” This is especially true of the +heavy parts for which the boring mill is principally used. Very +deep roughing cuts can also be taken with a vertical mill. This +type of machine mill is designed for turning and boring work +which, generally speaking, is quite large in diameter in proportion +to the width or height. The work varies greatly, +especially in regard to its diameter, so that boring mills are +built in a large range of sizes. The small and medium sizes +will swing work varying from about 30 inches to 6 or 7 feet in +diameter, whereas large machines, such as are used for turning +very large flywheels, sheaves, etc., have a swing of 16 or 20 feet, +and larger sizes are used in some shops. The size of a vertical +mill, like any other machine tool, should be somewhat in proportion +to the size of the work for which it is intended, as a +very large machine is unwieldy, and, therefore, inefficient for +machining comparatively small parts.</p> + +<p><span class="pagenum"><a name="Pg_247" id="Pg_247">[247]</a></span> +<a name="Secnum_6_2" id="Secnum_6_2"></a><b>Holding and Setting Work on Boring Mill Table.</b>—There +are three general methods of holding work to the table of a +boring mill; namely, by the use of chucks, by ordinary bolts +and clamps, or in special fixtures. Chucks which are built into +the table (as illustrated in <a href="#Fig_6_2">Fig. 2</a>) and have both universal and +independent adjustments for the jaws can be used to advantage +for holding castings that are either round or irregular in shape. +The universal adjustment is used for cylindrical parts, such as +disks, flywheels, gear blanks, etc., and the independent adjustment, +for castings of irregular shape. Chucks which have +either an independent or universal movement for the jaws are +known as a “combination” type and usually have three jaws. +There is also a four-jaw type which has the independent adjustment +only. This style is preferable for work that is not cylindrical +and which must be held very securely. Chuck jaws that do +not form a part of the machine table, but are bolted to it in the +required position, are also employed extensively, especially on +comparatively large machines.</p> + +<p>Most of the work done in a vertical mill is held in a chuck. +Occasionally, however, it is preferable to clamp a part directly +to the table. This may be desirable because of the shape and +size of the work, or because it is necessary to hold a previously +machined surface directly against the table in order to secure +greater accuracy. Sometimes a casting is held in the chuck for +turning one side, and then the finished side is clamped against +the table for turning the opposite side. Parts which are to be +machined in large quantities are often held in special fixtures. +This method is employed when it enables the work to be set up +more quickly than would be possible if regular clamps or chuck +jaws were used.</p> + +<a name="Fig_6_3" id="Fig_6_3"></a> +<div class="figcenter"><div class="illobox450"><img src="images/256sm.png" alt="Plan View showing Flywheel Casting Chucked for Turning" /></div> +<p class="caption750">Fig. 3. Plan View showing Flywheel Casting Chucked for Turning</p> +</div> + +<p>Work that is to be turned or bored should first be set so that +the part to be machined is about central with the table. For +example, the rim of a flywheel should be set to run true so that +it can be finished by removing about the same amount of metal +around the entire rim; in other words, the rim should be set +concentric with the table, as shown in <a href="#Fig_6_3">Fig. 3</a>, and the sides of +the rim should also be parallel to the table.</p> + +<p><span class="pagenum"><a name="Pg_248" id="Pg_248">[248]</a></span>A simple tool that is very useful for testing the position of +any cylindrical casting consists of a wooden shank into which +is inserted a piece of wire, having one end bent. This tool is +clamped in the toolpost and as the work revolves the wire is +adjusted close to the cylindrical surface being tested. The +movement of the work with relation to the stationary wire point +will, of course, show whether or not the part runs true. The +advantage of using a piece of wire for testing, instead of a rigid +tool, is that the wire, owing to its flexibility, will simply be +bent backward if it is moved too close to a surface which is +considerably out of true. The upper surface of a casting can +be tested for parallelism with the table by using this same +wire gage, or by comparing the surface, as the table is revolved +slowly, with a tool held in the toolpost. An ordinary +surface gage is also used for this purpose. The proper surface +to set true, in any case, depends upon the requirements. +A plain cylindrical disk would be set so that the outside ran +true and the top surface was parallel with the table. When +setting a flywheel, if the inside of the rim is to remain rough, +the casting should be set by this surface rather than by the +outside, so that the rim, when finished, will be uniform in<span class="pagenum"><a name="Pg_249" id="Pg_249">[249]</a></span> +thickness.</p> + +<p>As far as possible, chucks should be used for holding cylindrical +parts, owing to their convenience. The jaws should be set +against an interior cylindrical surface whenever this is feasible. +To illustrate, the flywheel in <a href="#Fig_6_3">Fig. 3</a> is gripped by the inside of +the rim which permits the outside to be turned at this setting +of the work. It is also advisable to set a flywheel casting in +the chuck so that a spoke rests against one of the jaws as at +<i>d</i>, if this is possible. This jaw will then act as a driver and prevent +the casting from slipping or turning in the chuck jaws, +owing to the tangential pressure of the turning tool. When a +cut is being taken, the table and work rotate as shown by +arrow <i>a</i>, and the thrust of the cut (taken by tool <i>t</i>) tends to +move the wheel backward against the direction of rotation, as +shown by arrow <i>b</i>. If one of the chuck jaws bears against one +of the spokes, this movement is prevented. It is not always +feasible to use a chuck jaw as a driver and then a special driver +having the form of a small angle-plate or block is sometimes +bolted directly to the table. Another method of driving is to +set a brace between a spoke or projection on the work and a +chuck jaw or strip attached to the table. Drivers are not only +used when turning flywheels, but in connection with any large +casting, especially when heavy cuts have to be taken. Of +course, some castings are so shaped that drivers cannot be +employed.</p> + +<a name="Fig_6_4" id="Fig_6_4"></a> +<div class="figcenter"><div class="illobox450"><img src="images/258sm.png" alt="Turning Flat and Cylindrical Surfaces" /></div> +<p class="caption750">Fig. 4. (A) Turning a Flat Surface.<br />(B) Turning a Cylindrical Surface</p> +</div> + +<a name="Secnum_6_3" id="Secnum_6_3"></a><p><b>Turning in a Boring Mill.</b>—The vertical type of boring mill is +used more for turning cylindrical surfaces than for actual boring, +although a large part of the work requires both turning +and boring. We shall first consider, in a general way, how +surfaces are turned and then refer to some boring operations. +The diagram <i>A</i>, <a href="#Fig_6_4">Fig. 4</a>, illustrates how a horizontal surface +would be turned. The tool <i>t</i> is clamped in tool-block <i>t<sub>1</sub></i>, in a +vertical position, and it is fed horizontally as the table and +work rotate. The tool is first adjusted by hand for the proper +depth of cut and the automatic horizontal feed is then engaged. +When a cylindrical surface is to be turned, the tool (provided a<span class="pagenum"><a name="Pg_250" id="Pg_250">[250]</a></span> +straight tool is used) is clamped in a horizontal position and is +fed downward as indicated at <i>B</i>. The amount that the tool +should feed per revolution of the work, depends upon the kind +of material being turned, the diameter of the turned part and +the depth of the cut.</p> + +<p>Most of the parts machined in a vertical boring mill are made +of cast iron and, ordinarily, at least one roughing and one finishing +cut is taken. The number of roughing cuts required in any +case depends, of course, upon the amount of metal to be removed. +An ordinary roughing cut in soft cast iron might vary +in depth from <sup class="enum">1</sup>/<sub class="denom">8</sub> or <sup class= +"enum">3</sup>/<sub class="denom">16</sub> inch to <sup class="enum">3</sup>/<sub class="denom">8</sub> or <sup class= +"enum">1</sup>/<sub class="denom">2</sub> inch and the tool would +probably have a feed per revolution of from <sup class="enum">1</sup>/<sub class= +"denom">16</sub> to <sup class="enum">1</sup>/<sub class="denom">8</sub> inch, although +deeper cuts and coarser feeds are sometimes taken. +These figures are merely given to show, in a general way, what +cuts and feeds are practicable. The tool used for roughing +usually has a rounded end which leaves a ridged or rough surface. +To obtain a smooth finish, broad flat tools are used. The +flat cutting edge is set parallel to the tool's travel and a coarse +feed is used in order to reduce the time required for taking the +cut. The finishing feeds for cast iron vary from <sup class="enum">1</sup>/<sub class= +"denom">4</sub> to <sup class="enum">3</sup>/<sub class="denom">4</sub> inch on +ordinary work. The different tools used on the vertical mill +will be referred to more in detail later.</p> + +<p>All medium and large sized vertical boring mills are equipped +with two tool-heads and two tools are frequently used at the<span class="pagenum"><a name="Pg_251" id="Pg_251">[251]</a></span> +same time, especially on large work. <a href="#Fig_6_9">Fig. 9</a> illustrates the use +of two tools simultaneously. The casting shown is a flywheel, +and the tool on the right side turns the upper side of the rim, +while the tool on the left side turns the outside or cylindrical +surface. As a boring mill table rotates in a counter-clockwise +direction, the left-hand tool is reversed to bring the cutting edge +at the rear. By turning two surfaces at once, the total time +for machining the casting is, of course, greatly reduced. The +turning of flywheels is a common vertical boring mill operation, +and this work will be referred to in detail later on.</p> + +<a name="Fig_6_5" id="Fig_6_5"></a> +<div class="figcenter"><div class="illobox450"><img src="images/259sm.png" alt="Tools for Boring and Reaming Holes" /></div> +<p class="caption750">Fig. 5. Tools for Boring and Reaming Holes</p> +</div> + +<a name="Secnum_6_4" id="Secnum_6_4"></a><p><b>Boring Operations.</b>—There are several methods of machining +holes when using a vertical boring mill. Ordinarily, small holes +are cored in castings and it is simply necessary to finish the +rough surface to the required diameter. Some of the tools +used for boring and finishing comparatively small holes are +shown in <a href="#Fig_6_5">Fig. 5</a>. Sketch <i>A</i> shows a boring tool consisting of a +cutter <i>c</i> inserted in a shank, which, in turn, is held in the tool +slide, or in a turret attached to the tool slide. With a tool of +this type, a hole is bored by taking one or more cuts down +through it. The tool shown at <i>B</i> is a four-lipped drill which is +used for drilling cored holes preparatory to finishing by a cutter +or reamer. This drill would probably finish a hole to within +about <sup class="enum">1</sup>/<sub class="denom">32</sub> inch of the finish diameter, thus leaving a small amount +of metal for the reamer to remove. The tool illustrated at <i>C</i><span class="pagenum"><a name="Pg_252" id="Pg_252">[252]</a></span> +has a double-ended flat cutter <i>c</i>, which cuts on both sides. +These cutters are often made in sets for boring duplicate parts. +Ordinarily, there are two cutters in a set, one being used for +roughing and the other for finishing. The cutter passes through +a rectangular slot in the bar and this particular style is centrally +located by shoulders <i>s</i>, and is held by a taper pin <i>p</i>. Some +cutter bars have an extension end, or “pilot” as it is called, +which passes through a close-fitting bushing in the table to +steady the bar. Sketch <i>D</i> shows a finishing reamer. This tool +takes a very light cut and is intended to finish holes that have +been previously bored close to the required size. Sometimes a +flat cutter <i>C</i> is used for roughing and a reamer for finishing. +The reamer is especially desirable for interchangeable work, +when all holes must have a smooth finish and be of the same +diameter. When a reamer is held rigidly to a turret or toolslide, +it is liable to produce a hole that is either tapering or +larger than the reamer diameter. To prevent this, the reamer +should be held in a “floating” holder which, by means of a +slight adjustment, allows the reamer to align itself with the +hole. There are several methods of securing this “floating” +movement. (See “<a href="#Secnum_6_11">Floating Reamer Holders</a>.”)</p> + +<a name="Fig_6_6" id="Fig_6_6"></a> +<div class="figcenter"><div class="illobox450"><img src="images/260sm.png" alt="Boring with Regular Turning Tools" /></div> +<p class="caption750">Fig. 6. Boring with Regular Turning Tools</p> +</div> + +<p>Large holes or interior cylindrical surfaces are bored by tools +held in the regular tool-head. The tool is sometimes clamped +in a horizontal position as shown at <i>A</i>, <a href="#Fig_6_6">Fig. 6</a>, or a bent type is +used as at <i>B</i>. Cast iron is usually finished by a broad flat tool +as at <i>C</i>, the same as when turning exterior surfaces. Obviously +<span class="pagenum"><a name="Pg_253" id="Pg_253">[253]</a></span> +a hole that is bored in this way must be large enough to admit +the tool-block.</p> + +<a name="Fig_6_7" id="Fig_6_7"></a> +<div class="figcenter"><div class="illobox450"><img src="images/261sm.png" alt="Set of Boring Mill Tools" /></div> +<p class="caption750">Fig. 7. Set of Boring Mill Tools</p> +</div> + +<a name="Secnum_6_5" id="Secnum_6_5"></a><p><b>Turning Tools for the Vertical Boring Mill.</b>—A set of turning +tools for the vertical boring mill is shown in <a href="#Fig_6_7">Fig. 7</a>. These +tools can be used for a wide variety of ordinary turning operations. +When a great many duplicate parts are to be machined, +special tool equipment can often be used to advantage, but as +the form of this equipment depends upon the character of the +work, only standard tools have been shown in this illustration. +The tool shown at <i>A</i> is a right-hand, roughing tool, and a left-hand +tool of the same type is shown at <i>B</i>. Tool <i>C</i> is an offset +or bent, left-hand round nose for roughing, and <i>D</i> is a right-hand +offset roughing tool. A straight round nose is shown +at <i>E</i>. Tool <i>F</i> has a flat, broad cutting edge and is used for +finishing. Left-and right-hand finishing tools of the offset<span class="pagenum"><a name="Pg_254" id="Pg_254">[254]</a></span> +type are shown at <i>G</i> and <i>H</i>, respectively. Tool <i>I</i> has a square +end and is used for cutting grooves. Right-and left-hand +parting tools are shown at <i>J</i> and <i>K</i>, and tool <i>L</i> is a form frequently +used for rounding corners.</p> + +<a name="Fig_6_8" id="Fig_6_8"></a> +<div class="figcenter"><div class="illobox450"><img src="images/262sm.png" alt="Diagrams Illustrating Use of Different Forms of Tools" /></div> +<p class="caption750">Fig. 8. Diagrams Illustrating Use of Different Forms of Tools</p> +</div> + +<p>The diagrams in <a href="#Fig_6_8">Fig. 8</a> show, in a general way, how each of +the tools illustrated in <a href="#Fig_6_7">Fig. 7</a> are used, and corresponding tools +are marked by the same reference letters in both of these illustrations. +The right-and left-hand roughing tools <i>A</i> and <i>B</i> are +especially adapted for taking deep roughing cuts. One feeds +away from the center of the table, or to the right (when held in +the right-hand tool-block) and the other tool is ground to feed +in the opposite direction. Ordinarily, when turning plain flat +surfaces, the cut is started at the outside and the tool feeds +toward the center, as at <i>B</i>, although it is sometimes more convenient +to feed in the opposite direction, as at <i>A</i>, especially when +there is a rim or other projecting part at the outside edge. The +tool shown at <i>A</i> could also be used for turning cylindrical +surfaces, by clamping it in a horizontal position across the bottom +<span class="pagenum"><a name="Pg_255" id="Pg_255">[255]</a></span> +of the tool-block. The feeding movement would then be +downward or at right-angles to the work table.</p> + +<p>The offset round-nose tools <i>C</i> and <i>D</i> are for turning exterior +or interior cylinder surfaces. The shank of this tool is clamped +in the tool-block in a vertical position and as the bent end extends +below the tool-block, it can be fed down close to a shoulder. +The straight type shown at <i>E</i> is commonly used for turning steel +or iron, and when the point is drawn out narrower, it is also +used for brass, although the front is then ground without slope. +Tool <i>F</i> is for light finishing cuts and broad feeds. The amount +of feed per revolution of the work should always be less than +the width of the cutting edge as otherwise ridges will be left +on the turned surface. The offset tools <i>G</i> and <i>H</i> are for finishing +exterior and interior cylindrical surfaces. These tools also +have both vertical and horizontal cutting edges and are sometimes +used for first finishing a cylindrical and then a horizontal +surface, or <i>vice versa</i>. Tool <i>I</i> is adapted to such work as cutting +packing-ring grooves in engine pistons, forming square or rectangular +grooves, and similar work. The parting tools <i>J</i> and +<i>K</i> can also be used for forming narrow grooves or for cutting +off rings, etc. The sketch <i>K</i> (<a href="#Fig_6_8">Fig. 8</a>) indicates how a tool of +this kind might be used for squaring a corner under a shoulder. +Tool <i>L</i> is frequently used on boring mills for rounding the +corners of flywheel rims, in order to give them a more finished +appearance. It has two cutting edges so that either side can +be used as when rounding the inner and outer corners of a rim.</p> + +<p>The turning tools of a vertical boring mill are similar, in +many respects, to those used in a lathe, although the shanks of +the former are shorter and more stocky than those of lathe +tools. The cutting edges of some of the tools also differ somewhat +in form, but the principles which govern the grinding of +lathe and boring mill tools are identical, and those who are +not familiar with tool grinding are referred to <a href="#Chapnum_2">Chapter II</a>, in +which this subject is treated.</p> + +<a name="Fig_6_9" id="Fig_6_9"></a> +<div class="figcenter"><img src="images/264sm.jpg" alt="Turning the Rim of a Flywheel" /> +<p class="caption750">Fig. 9. Turning the Rim of a Flywheel</p> +</div> + +<a name="Secnum_6_6" id="Secnum_6_6"></a><p><b>Turning a Flywheel on a Vertical Mill.</b>—The turning of a +flywheel is a good example of the kind of work for which a vertical +boring mill is adapted. A flywheel should preferably be<span class="pagenum"><a name="Pg_256" id="Pg_256">[256]</a></span> +machined on a double-head mill so that one side and the periphery +of the rim can be turned at the same time. A common method +of holding a flywheel is shown in <a href="#Fig_6_9">Fig. 9</a>. The rim is gripped by +four chuck jaws <i>D</i> which, if practicable, should be on the inside +where they will not interfere with the movement of the tool. +Two of the jaws, in this case, are set against the spokes on opposite +sides of the wheel, to act as drivers and prevent any +backward shifting of work when a heavy cut is being taken. +The illustration shows the tool to the right rough turning the +side of the rim, while the left-hand tool turns the periphery. +Finishing cuts are also taken over the rim, at this setting, and +the hub is turned on the outside, faced on top, and the hole +bored.</p> + +<a name="Fig_6_10" id="Fig_6_10"></a> +<div class="figcenter"><img src="images/265sm.jpg" alt="Tool B set for Boring the Hub" /> +<p class="caption750">Fig. 10. Tool B set for Boring the Hub</p> +</div> + +<p>The three tools <i>A</i>, <i>B</i> and <i>C</i>, for finishing the hole, are mounted +in the turret. Bar <i>A</i>, which carries a cutter at its end, first +rough bores the hole. The sizing cutter <i>B</i> is then used to +straighten it before inserting the finishing reamer <i>C</i>. <a href="#Fig_6_10">Fig. 10</a> +shows the turret moved over to a central position and the sizing +cutter <i>B</i> set for boring. The head is centrally located (on this +particular machine) by a positive center-stop. The turret is indexed<span class="pagenum"><a name="Pg_257" id="Pg_257">[257]</a></span> +for bringing the different tools into the working position, +by loosening the clamping lever <i>L</i> and pulling down lever <i>I</i> +which disengages the turret lock-pin. When all the flywheels +in a lot have been machined as described, the opposite side is +finished.</p> + +<a name="Fig_6_11" id="Fig_6_11"></a><span class="pagenum"><a name="Pg_258" id="Pg_258">[258]</a></span> +<div class="figcenter"><div class="illobox750"><img src="images/266sm.png" alt="Diagrams showing Method of Turning and Boring a Flywheel on a Double-head Mill having one Turret Head" /></div> +<p class="caption750">Fig. 11. Diagrams showing Method of Turning and Boring a Flywheel on a Double-head Mill having one Turret Head</p> +</div> + +<p>In order to show more clearly the method of handling work of +this class, the machining of a flywheel will be explained more in +detail in connection with <a href="#Fig_6_11">Fig. 11</a>, which illustrates practically +the same equipment as is shown in <a href="#Fig_6_9">Figs. 9</a> and <a href="#Fig_6_10">10</a>. The successive +order in which the various operations are performed is +as follows: Tool <i>a</i> (see sketch <i>A</i>) rough turns the side of the +rim, while tool <i>b</i>, which is set with its cutting edge toward the +rear, rough turns the outside. The direction of the feeding +movement for each tool is indicated by the arrows. When tool +<i>a</i> has crossed the rim, it is moved over for facing the hub, as +shown by the dotted lines. The side and periphery of the rim +are next finished by the broad-nose finishing tools <i>c</i> and <i>d</i> (see +sketch <i>B</i>). The feed should be increased for finishing, so that +each tool will have a movement of say <sup class="enum">1</sup>/<sub class="denom">4</sub> or +<sup class="enum">3</sup>/<sub class="denom">8</sub> inch per revolution +of the work, and the cuts should, at least, be deep enough to<span class="pagenum"><a name="Pg_259" id="Pg_259">[259]</a></span> +remove the marks made by the roughing tools. Tool <i>c</i> is also +used for finishing the hub as indicated by the dotted lines. +After these cuts are taken, the outside of the hub and inner +surface of the rim are usually turned down as far as the spokes, +by using offset tools similar to the ones shown at <i>C</i> and <i>D</i> in +<a href="#Fig_6_7">Fig. 7</a>. The corners of the rim and hub are also rounded to +give the work a more finished appearance, by using a tool <i>L</i>.</p> + +<p>The next operation is that of finishing the hole through the +hub. The hard scale is first removed by a roughing cutter <i>r</i> +(sketch <i>C</i>), which is followed by a “sizing” cutter <i>s</i>. The hole +is then finished smooth and to the right diameter by reamer <i>f</i>. +The bars carrying cutters <i>r</i> and <i>s</i> have extensions or “pilots” +which enter a close-fitting bushing in the table, in order to +steady the bar and hold it in alignment.</p> + +<p>When the hole is finished, the wheel is turned over, so that +the lower side of the rim and hub can be faced. The method +of holding the casting for the final operation is shown at <i>D</i>. +The chuck jaws are removed, and the finished side of the rim is +clamped against parallels <i>p</i> resting on the table. The wheel is +centrally located for turning this side by a plug <i>e</i> which is inserted +in a hole in the table and fits the bore of the hub. The +wheel is held by clamps which bear against the spokes. Roughing +and finishing cuts are next taken over the top surface of the +rim and hub and the corners are rounded, which completes the +machining operations. If the rim needs to be a certain width, +about the same amount of metal should be removed from each +side, unless sandy spots or “blow-holes” in the casting make it +necessary to take more from one side than from the other. That +side of the rim which was up in the mold when the casting was +made should be turned first, because the porous, spongy spots +usually form on the “cope” or top side of a casting.</p> + +<a name="Fig_6_12" id="Fig_6_12"></a> +<div class="figcenter"><img src="images/268sm.jpg" alt="Gisholt Mill equipped with Convex Turning Attachment" /> +<p class="caption750">Fig. 12. Gisholt Mill equipped with Convex Turning Attachment</p> +</div> + +<a name="Secnum_6_7" id="Secnum_6_7"></a><p><b>Convex Turning Attachment for Boring Mills.</b>—<a href="#Fig_6_12">Fig. 12</a> +shows a vertical boring mill arranged for turning pulleys having +convex rims; that is, the rim, instead of being cylindrical, is +rounded somewhat so that it slopes from the center toward +either side. (The reason for turning a pulley rim convex is to +prevent the belt from running off at one side, as it sometimes<span class="pagenum"><a name="Pg_260" id="Pg_260">[260]</a></span> +tends to do when a cylindrical pulley is used.) The convex +surface is produced by a special attachment which causes the +turning tool to gradually move outward as it feeds down, until +the center of the rim is reached, after which the movement is +inward.</p> + +<p>The particular attachment shown in <a href="#Fig_6_12">Fig. 12</a> consists of a +special box-shaped tool-head <i>F</i> containing a sliding holder <i>G</i>, in +which the tool is clamped by set-screws passing through elongated +slots in the front of the tool-head. In addition, there is +a radius link <i>L</i> which swivels on a stud at the rear of the tool-head +and is attached to vertical link <i>H</i>. Link <i>L</i> is so connected +to the sliding tool-block that any downward movement of the +tool-bar <i>I</i> causes the tool to move outward until the link is in +a horizontal position, after which the movement is reversed. +When the attachment is first set up, the turning tool is placed +at the center of the rim and then link <i>L</i> is clamped to the vertical +link while in a horizontal position. The cut is started at +the top edge of the rim, and the tool is fed downward by power,<span class="pagenum"><a name="Pg_261" id="Pg_261">[261]</a></span> +the same as when turning a cylindrical surface. The amount of +curvature or convexity of a rim can be varied by inserting the +clamp bolt <i>J</i> in different holes in link <i>L</i>.</p> + +<p>The tools for machining the hub and sides of the rim are held +in a turret mounted on the left-hand head, as shown. The +special tool-holder <i>A</i> contains two bent tools for turning the +upper and lower edges of the pulley rim at the same time as +the tool-head is fed horizontally. Roughing and finishing tools +<i>B</i> are for facing the hub, and the tools <i>C</i>, <i>D</i>, and <i>E</i> rough bore, +finish bore, and ream the hole for the shaft.</p> + +<a name="Fig_6_13" id="Fig_6_13"></a> +<div class="figcenter"><div class="illobox450"><img src="images/269sm.png" alt="Turning a Taper or Conical Surface" /></div> +<p class="caption750">Fig. 13. Turning a Taper or Conical Surface</p> +</div> + +<a name="Secnum_6_8" id="Secnum_6_8"></a><p><b>Turning Taper or Conical Surfaces.</b>—Conical or taper surfaces +are turned in a vertical boring mill by swiveling the tool-bar +to the proper angle as shown in <a href="#Fig_6_13">Fig. 13</a>. When the taper is +given in degrees, the tool-bar can be set by graduations on the +edge of the circular base <i>B</i>, which show the angle <i>a</i> to which the +bar is swiveled from a vertical position. The base turns on a +central stud and is secured to the saddle <i>S</i> by the bolts shown, +which should be tightened after the tool-bar is set. The vertical +power feed can be used for taper turning the same as for +cylindrical work.</p> + +<a name="Fig_6_14" id="Fig_6_14"></a> +<div class="figcenter"><div class="illobox450"><img src="images/270sm.png" alt="Turning a Conical Surface by using the Combined Vertical and Horizontal Feeds" /></div> +<p class="caption750">Fig. 14. Turning a Conical Surface by using the<br />Combined Vertical +and Horizontal Feeds</p> +</div> + +<p><span class="pagenum"><a name="Pg_262" id="Pg_262">[262]</a></span> +Occasionally it is necessary to machine a conical surface which +has such a large included angle that the tool-bar cannot be +swiveled far enough around to permit turning by the method +illustrated in <a href="#Fig_6_13">Fig. 13</a>. Another method, which is sometimes resorted +to for work of this class, is to use the combined vertical +and horizontal feeds. Suppose we want to turn the conical +casting <i>W</i> (<a href="#Fig_6_14">Fig. 14</a>), to an angle of 30 degrees, as shown, and +that the tool-head of the boring mill moves horizontally <sup class="enum">1</sup>/<sub class="denom">4</sub> inch +per turn of the feed-screw and has a vertical movement of <sup class="enum">3</sup>/<sub class="denom">16</sub> +inch per turn of the upper feed-shaft. If the two feeds are +used simultaneously, the tool will move a distance <i>h</i> of say 8 +inches, while it moves downward a distance <i>v</i> of 6 inches, thus +turning the surface to an angle <i>y</i>. This angle is greater (as +measured from a horizontal plane) than the angle required, but, +if the tool-bar is swiveled to an angle <i>x</i>, the tool, as it moves +downward, will also be advanced horizontally, in addition to +the regular horizontal movement. The result is that the angle +<i>y</i> is diminished and if the tool-bar is set over the right amount, +<span class="pagenum"><a name="Pg_263" id="Pg_263">[263]</a></span> +the conical surface can be turned to an angle <i>a</i> of 30 degrees. +The problem, then, is to determine what the angle <i>x</i> should be +for turning to a given angle <i>a</i>.</p> + +<a name="Fig_6_15" id="Fig_6_15"></a> +<div class="figcenter"><div class="illobox450"><img src="images/271sm.png" alt="Diagram showing Method of Obtaining Angular Position of Tool-head when Turning Conical Surfaces by using Vertical and Horizontal Feeding Movements" /></div> +<p class="caption750">Fig. 15. Diagram showing Method of Obtaining Angular Position<br />of Tool-head +when Turning Conical Surfaces by using Vertical and<br />Horizontal +Feeding Movements</p> +</div> + +<p>The way angle <i>x</i> is calculated will be explained in connection +with the enlarged diagram, <a href="#Fig_6_15">Fig. 15</a>, which shows one-half of the +casting. The sine of the known angle <i>a</i> is first found in a table +of natural sines. Then the sine of angle <i>b</i>, between the taper +surface and center-line of the tool-head, is determined as follows: +sin <i>b</i> = (sin <i>a</i> × <i>h</i>) ÷ <i>v</i>, in which <i>h</i> represents the rate +of horizontal +feed and <i>v</i> the rate of vertical feed. The angle corresponding +to sine <i>b</i> is next found in a table of sines. We now +have angles <i>b</i> and <i>a</i>, and by subtracting the sum of these angles +from 90 degrees, the desired angle <i>x</i> is obtained. To illustrate:</p> + +<p>The sine of 30 degrees is 0.5; then sin <i>b</i> = (0.5 × <sup class="enum">1</sup>/<sub class= +"denom">4</sub>) ÷ <sup class="enum">3</sup>/<sub class="denom">16</sub> = 0.6666; +hence angle <i>b</i> = 41 degrees 49 minutes, and <i>x</i> = 90° - (30° + +41° 49') = 18 degrees 11 minutes. Hence to turn the casting to +angle <i>a</i> in a boring mill having the horizontal and vertical feeds +given, the tool-head would be set over from the vertical 18 degrees +and 11 minutes which is equivalent to about 18<sup class="enum">1</sup>/<sub class="denom">6</sub> degrees.</p> + +<p><span class="pagenum"><a name="Pg_264" id="Pg_264">[264]</a></span> +If the required angle <i>a</i> were greater than angle <i>y</i> obtained +from the combined feeds with the tool-bar in a vertical position, +it would then be necessary to swing the lower end of the bar to +the left rather than to the right of a vertical plane. When the +required angle <i>a</i> exceeds angle <i>y</i>, the sum of angles <i>a</i> and <i>b</i> is +greater than 90 degrees so that angle <i>x</i> for the tool-head = +(<i>a</i> + <i>b</i>) - 90 degrees.</p> + +<a name="Fig_6_16" id="Fig_6_16"></a> +<div class="figcenter"><img src="images/273sm.jpg" alt="Bullard Vertical Turret Lathe" /> +<p class="caption750">Fig. 16. Bullard Vertical Turret Lathe</p> +</div> + +<a name="Secnum_6_9" id="Secnum_6_9"></a><p><b>Turret-lathe Type of Vertical Boring Mill.</b>—The machine +illustrated in <a href="#Fig_6_16">Fig. 16</a> was designed to combine the advantages of +the horizontal turret lathe and the vertical boring mill. It is +known as a “vertical turret lathe,” but resembles, in many +respects, a vertical boring mill. This machine has a turret on +the cross-rail the same as many vertical boring mills, and, in +addition, a side-head <i>S</i>. The side-head has a vertical feeding +movement, and the tool-bar <i>T</i> can be fed horizontally. The +tool-bar is also equipped with a four-sided turret for holding +turning tools. This arrangement of the tool-heads makes it +possible to use two tools simultaneously upon comparatively +small work. When both heads are mounted on the cross-rail, +as with a double-head boring mill, it is often impossible to +machine certain parts to advantage, because one head interferes +with the other.</p> + +<p>The drive to the table (for the particular machine illustrated) +is from a belt pulley at the rear, and fifteen speed changes are +available. Five changes are obtained by turning the pilot-wheel +<i>A</i> and this series of five speeds is compounded three +times by turning lever <i>B</i>. Each spoke of pilot-wheel <i>A</i> indicates +a speed which is engaged only when the spoke is in a +vertical position, and the three positions for <i>B</i> are indicated, +by slots in the disk shown. The number of table revolutions +per minute for different positions of pilot-wheel <i>A</i> and lever +<i>B</i> are shown by figures seen through whichever slot is at <i>C</i>. +There are five rows of figures corresponding to the five spokes +of the pilot-wheel and three figures in a row, and the speed +is shown by arrows on the sides of the slots. The segment +disk containing these figures also serves as an interlocking +device which prevents moving more than one speed controlling<span class="pagenum"><a name="Pg_265" id="Pg_265">[265]</a></span> +lever at a time, in order to avoid damaging the driving +mechanism.</p> + +<p>The feeding movement for each head is independent. Lever +<i>D</i> controls the engagement or disengagement of the vertical or +cross feeds for the head on the cross-rail. The feed for the +side-head is controlled by lever <i>E</i>. When this lever is pushed +inward, the entire head feeds vertically, but when it is pulled +out, the tool-bar feeds horizontally. These two feeds can be +disengaged by placing the lever in a neutral position. The<span class="pagenum"><a name="Pg_266" id="Pg_266">[266]</a></span> +direction of the feeding movement for either head can be reversed +by lever <i>R</i>. The amount of feed is varied by feed-wheel +<i>F</i> and clutch-rod <i>G</i>. When lever <i>E</i> is in the neutral +position, the side-head or tool-bar can be adjusted by the hand-cranks +<i>H</i> and <i>I</i>, respectively. The cross-rail head and its +turret slide have rapid power traverse movements for making +quick adjustments. This rapid traverse is controlled by the +key-handles <i>J</i>.</p> + +<p>The feed-screws for the vertical head have micrometer dials +<i>K</i> for making accurate adjustments. There are also large dials +at <i>L</i> which indicate vertical movements of the side head and +horizontal movements of the tool slide. All of these dials have +small adjustable clips <i>c</i> which are numbered to correspond to +numbers on the faces of the respective turrets. These clips or +“observation stops” are used in the production of duplicate +parts. For example, suppose a tool in face No. 1 for the main +turret is set for a given diameter and height of shoulder on a +part which is to be duplicated. To obtain the same setting of +the tools for the next piece, clips No. 1, on both the vertical +feed rod and screw dials, are placed opposite the graduations +which are intersected by stationary pointers secured to the cross-rail. +The clips are set in this way after the first part has been +machined to the required size and before disturbing the final +position of the tools. For turning a duplicate part, the tools +are simply brought to the same position by turning the feed +screws until the clips and stationary pointers again coincide. +For setting tools on other faces of either turret, this operation +is repeated, except that clips are used bearing numbers corresponding +to the turret face in use.</p> + +<p>The main turret of this machine has five holes in which are +inserted the necessary boring and turning tools, drills or reamers, +as may be required. By having all the tools mounted in the +turret, they can be quickly and accurately set in the working +position. When the turret is indexed from one face to the next, +binder lever <i>N</i> is first loosened. The turret then moves forward, +away from its seat, thus disengaging the indexing and registering +pins which accurately locate it in any one of the five positions.<span class="pagenum"><a name="Pg_267" id="Pg_267">[267]</a></span> +The turret is revolved by turning crank <i>M</i>, one turn of +this handle moving the turret <sup class="enum">1</sup>/<sub class="denom">5</sub> revolution or from one hole to +the next. The side-head turret is turned by loosening lever <i>O</i>. +The turret slide can be locked rigidly in any position by lever +<i>P</i> and its saddle is clamped to the cross-rail by lever <i>Q</i>. The +binder levers for the saddle and toolslide of the side-head are +located at <i>U</i> and <i>V</i>, respectively. A slide that does not require +feeding movements is locked in order to obtain greater rigidity. +To illustrate, if the main tool slide were to feed vertically and +not horizontally, it might be advisable to lock the saddle to the +cross-rail, while taking the vertical cut.</p> + +<p>The vertical slide can be set at an angle for taper turning, +and the turret is accurately located over the center of the table +for boring or reaming, by a positive center stop. The machine is +provided with a brake for stopping the work table quickly, which +is operated by lifting the shaft of pilot-wheel <i>A</i>. The side-and +cross-rails are a unit and are adjusted together to accommodate +work of different heights. This adjustment is effected by power<span class="pagenum"><a name="Pg_268" id="Pg_268">[268]</a></span> +on the particular machine illustrated, and it is controlled by a +lever near the left end of the cross-rail. Before making this +adjustment, all binder bolts which normally hold the rails rigidly +to the machine column must be released, and care should be +taken to tighten them after the adjustment is made.</p> + +<a name="Fig_6_17" id="Fig_6_17"></a> +<div class="figcenter"><img src="images/275sm.jpg" alt="Turning a Gear Blank on a Vertical Turret Lathe" /> +<p class="caption750">Fig. 17. Turning a Gear Blank on a Vertical Turret Lathe</p> +</div> + +<a name="Secnum_6_10" id="Secnum_6_10"></a><p><b>Examples of Vertical Turret Lathe Work.</b>—In order to illustrate +how a vertical turret lathe is used, one or two examples of +work will be referred to in detail. These examples also indicate, +in a general way, the class of work for which this type of machine +is adapted. <a href="#Fig_6_17">Fig. 17</a> shows how a cast-iron gear blank is machined. +The work is gripped on the inside of the rim by three +chuck jaws, and all of the tools required for the various operations +are mounted in the main and side turrets. The illustration<span class="pagenum"><a name="Pg_269" id="Pg_269">[269]</a></span> +shows the first operation which is that of rough turning the +hub, the top side of the blank and its periphery. The tools <i>A</i> +for facing the hub and upper surface are both held in one tool-block +on the main turret, and tool <i>A<sub>1</sub></i> for roughing the periphery +is in the side turret. With this arrangement, the three surfaces +can be turned simultaneously.</p> + +<p>The main turret is next indexed one-sixth of a revolution +which brings the broad finishing tools <i>B</i> into position, and the +side turret is also turned to locate finishing tool <i>B<sub>1</sub></i> at the front. +(The indexing of the main turret on this particular machine is +effected by loosening binder lever n and raising the turret lock-pin +by means of lever <i>p</i>.) The hub, side and periphery of the +blank are then finished. When tools <i>B</i> are clamped in the tool-blocks, +<span class="pagenum"><a name="Pg_270" id="Pg_270">[270]</a></span> +they are, of course, set for turning the hub to the required +height. The third operation is performed by the tools at <i>C</i>, one +of which “breaks” or chamfers the corner of the cored hole in +the hub, to provide a starting surface for drill <i>D</i>, and the other +turns the outside of the hub, after the chamfering tool is removed. +The four-lipped shell-drill <i>D</i> is next used to drill the cored hole +and then this hole is bored close to the finished size and concentric +with the circumference of the blank by boring tool <i>E</i>, +which is followed by the finishing reamer <i>F</i>. When the drill, +boring tool and reamer are being used, the turret is set over the +center or axis of the table, by means of a positive center stop +on the left-side of the turret saddle. If it is necessary to move<span class="pagenum"><a name="Pg_271" id="Pg_271">[271]</a></span> +the turret beyond the central position, this stop can be swung +out of the way.</p> + +<a name="Fig_6_18" id="Fig_6_18"></a> +<div class="figcenter"><img src="images/276sm.jpg" alt="Turning Gasoline Engine Flywheel on Vertical Turret Lathe—First Position" /> +<p class="caption750">Fig. 18. Turning Gasoline Engine Flywheel on Vertical Turret +Lathe—First Position</p> +</div> + +<a name="Fig_6_19" id="Fig_6_19"></a> +<div class="figcenter"><img src="images/277sm.jpg" alt="Turning Gasoline Engine Flywheel—Second Position" /> +<p class="caption750">Fig. 19. Turning Gasoline Engine Flywheel—Second Position</p> +</div> + +<p><a href="#Fig_6_18">Figs. 18</a> and <a href="#Fig_6_19">19</a> illustrate the turning of an automobile flywheel, +which is another typical example of work for a machine +of this type. The flywheel is finished in two settings. Its +position for the first series of operations is shown in <a href="#Fig_6_18">Fig. 18</a>, and +the successive order of the four operations for the first setting +is shown by the diagrams, <a href="#Fig_6_20">Fig. 20</a>. The first operation requires +four tools which act simultaneously. The three held in tool-block +<i>A</i> of the turret, face the hub, the web and the rim of the +flywheel, while tool <i>a</i> in the side-head rough turns the outside +diameter. The outside diameter is also finished by broad-nosed +tool <i>b</i> which is given a coarse feed. In the second operation, +the under face of the rim is finished by tool <i>c</i>, the outer +corners are rounded by tool <i>d</i> and the inner surface of the rim +is rough turned by a bent tool <i>B</i>, which is moved into position +by indexing the main turret. In the third operation, the side-head +is moved out of the way and the inside of the rim is finished +by another bent tool <i>B<sub>1</sub></i>. The final operation at this setting is +the boring of the central hole, which is done with a bar <i>C</i> having +interchangeable cutters which make it possible to finish the hole +at one setting of the turret.</p> + +<a name="Fig_6_20" id="Fig_6_20"></a> +<div class="figcenter"><div class="illobox450"><img src="images/278sm.png" alt="Diagrams showing How Successive Operations are Performed by Different Tools in the Turret" /></div> +<p class="caption750">Fig. 20. Diagrams showing How Successive Operations<br />are Performed +by Different Tools in the Turret</p> +</div> + +<p>The remaining operations are performed on the opposite side +of the work which is held in “soft” jaws <i>J</i> accurately bored to +fit the finished outside diameter as indicated in <a href="#Fig_6_19">Fig. 19</a>. The +tool in the main turret turns the inside of the rim, and the side-head +is equipped with two tools for facing the web and hub +simultaneously. As the tool in the main turret operates on the +left side of the rim, it is set with the cutting edge toward the +rear. In order to move the turret to this position, which is beyond +the center of the table, the center stop previously referred +to is swung out of the way.</p> + +<a name="Secnum_6_11" id="Secnum_6_11"></a><p><b>Floating Reamer Holders.</b>—If a reamer is held rigidly in the +turret of a boring mill or turret lathe, it is liable to produce a +hole which tapers slightly or is too large. When a hole is bored +with a single-point boring tool, it is concentric with the axis of +rotation, and if a reamer that is aligned exactly with the bored<span class="pagenum"><a name="Pg_272" id="Pg_272">[272]</a></span> +hole is fed into the work, the finished hole should be cylindrical +and the correct size. It is very difficult, however, to locate a +reamer exactly in line with a bored hole, because of slight variations +in the indexing of the turret, or errors resulting from wear +of the guiding ways or other important parts of the machine.</p> + +<p>To prevent inaccuracies due to this cause, reamers are often +held in what is known as a “floating” holder. This type of +holder is so arranged that the reamer, instead of being held +rigidly, is allowed a slight free or floating movement so that it +can follow a hole which has been bored true, without restraint. +In this way the hole is reamed straight and to practically the +same size as the reamer.</p> + +<a name="Fig_6_21" id="Fig_6_21"></a> +<div class="figcenter"><div class="illobox450"><img src="images/280sm.png" alt="Two Types of Floating Reamer Holders" /></div> +<p class="caption750">Fig. 21. Two Types of Floating Reamer Holders</p> +</div> + +<p>There are many different designs of floating holders but the +general principle upon which they are based is illustrated by +the two types shown in <a href="#Fig_6_21">Fig. 21</a>. The reamer and holder shown +to the left has a ball-shank <i>A</i> which bears against a backing-up +screw <i>B</i> inserted in the end of holder <i>C</i> through which the driving +pin passes. The lower end of the reamer shank is also +spherical-shaped at <i>D</i>, and screw-pin <i>E</i> secures the shell reamer +to this end. It will be noted that the hole in the shank for pin +<i>E</i> is “bell-mouthed” on each side of the center and that +there<span class="pagenum"><a name="Pg_273" id="Pg_273">[273]</a></span> +is clearance at <i>F</i> between the shank and reamer shell; hence the +reamer has a free floating action in any direction. This holder +has given very satisfactory results.</p> + +<p>The holder shown to the right is attached to the face of the +turret by four fillister-head screws. Sleeve <i>C</i> is held in plate <i>A</i> +by means of two steel pins <i>B</i> which are tight in plate <i>A</i> and made +to fit freely in bayonet grooves <i>D</i>. Reamer holder <i>E</i> floats on +sleeve <i>C</i>, the floating motion being obtained through the four +steel pins <i>G</i> extending into driving ring <i>F</i>. Two of the pins are +tight in the holder <i>E</i> and two in sleeve <i>C</i>. The faces of sleeve +<i>C</i>, driving ring <i>F</i>, and reamer holder <i>E</i> are held tightly against +each other by means of spring <i>H</i> which insures the reamer being +held perfectly true. Spring <i>H</i> is adjusted by means of nut <i>I</i> +which is turned with a spanner wrench furnished with each +holder. The reamer is so held that its axis is always maintained +parallel to the center of the hole, and, at the same time, it has +a slight self-adjusting tendency radially, so that the hole and<span class="pagenum"><a name="Pg_274" id="Pg_274">[274]</a></span> +reamer will automatically keep in perfect alignment with each +other.</p> + +<a name="Fig_6_22" id="Fig_6_22"></a> +<div class="figcenter"><img src="images/281sm.jpg" alt="Multiple-spindle Cylinder Boring Machine" /> +<p class="caption750">Fig. 22. Multiple-spindle Cylinder Boring Machine</p> +</div> + +<a name="Secnum_6_12" id="Secnum_6_12"></a><p><b>Multiple Cylinder Boring Machine.</b>—In automobile and +other factories where a great many gasoline engine cylinders are +required, multiple-spindle boring machines of the vertical type +are commonly used. The machine shown in <a href="#Fig_6_22">Fig. 22</a> is a special +design for boring four cylinders which are cast <i>en bloc</i> or in one +solid casting. The work is held in a box jig which has a top +plate equipped with guide bearings for holding the spindles +rigidly while boring. The lower end of each spindle has attached +to it a cutter-head and the boring is done by feeding the table +and casting vertically. This feeding movement is effected by +power and it is disengaged automatically when the cutters have +bored to the required depth. The particular machine illustrated +is used for rough boring only, the cylinders being finished +by reaming in another similar machine. The cylinders are +bored to a diameter of 3<sup class="enum">5</sup>/<sub class="denom">8</sub> inches, and about +<sup class="enum">3</sup>/<sub class="denom">8</sub> inch of metal is +removed by the roughing cut. The spindles have fixed center-to-center +distances as the machine is intended for constant use +on cylinders of one size, so that adjustment is not necessary. +Of course, a special machine of this kind is only used in shops +where large numbers of cylinders of one design are required +continually. Some cylinder boring machines of the vertical type +have spindles which can be adjusted for different center-to-center +distances if this should be necessary in order to accommodate +a cylinder of another size.</p> + +<hr class="c25" /> +<span class="pagenum"><a name="Pg_275" id="Pg_275">[275]</a></span> +<h2><a name="Chapnum_7" id="Chapnum_7">CHAPTER VII</a></h2> +<h3>HORIZONTAL BORING MACHINES</h3> +<hr class="c05" /> + +<p>A boring machine of the horizontal type is shown in <a href="#Fig_7_1">Fig. 1</a>. +The construction and operation of this machine is very different +from that of a vertical boring mill and it is also used for an +entirely different class of work. The horizontal machine is +employed principally for boring, drilling or milling, whereas the +vertical design is especially adapted to turning and boring. +The horizontal type is also used for turning or facing flanges +or similar surfaces when such an operation can be performed to +advantage in connection with other machine work on the same +part.</p> + +<a name="Fig_7_1" id="Fig_7_1"></a><span class="pagenum"><a name="Pg_276" id="Pg_276">[276]</a></span> +<div class="figcenter"><img src="images/284sm.jpg" alt="Lucas Horizontal Boring, Drilling and Milling Machine" /> +<p class="caption750">Fig. 1. Lucas Horizontal Boring, Drilling and Milling Machine</p> +</div> + +<p>The type of machine illustrated in <a href="#Fig_7_1">Fig. 1</a> has a heavy base or +bed to which is bolted the column <i>C</i> having vertical ways on +which the spindle-head <i>H</i> is mounted. This head contains a +sleeve or quill in which the spindle <i>S</i> slides longitudinally. +The spindle carries cutters for boring, whereas milling cutters +or the auxiliary facing arm are bolted to the end <i>A</i> of the +spindle sleeve. The work itself is attached either directly or +indirectly to the table or platen <i>P</i>. When the machine is in +operation, the cutter or tool revolves with the spindle sleeve +or spindle and either the cutter or the part being machined is +given a feeding movement, depending on the character of the +work. The spindle can be moved in or out by hand for adjustment, +or by power for feeding the cutter, as when boring or +drilling.</p> + +<p>The entire spindle-head <i>H</i> can also be moved vertically on +the face of the column <i>C</i>, by hand, for setting the spindle to the +proper height, or by power for feeding a milling cutter in a +vertical direction. When the vertical position of the spindle-head +is changed, the outboard bearing block <i>B</i> also moves +up or down a corresponding amount, the two parts being connected<span class="pagenum"><a name="Pg_277" id="Pg_277">[277]</a></span> +by shafts and gearing. Block <i>B</i> steadies the outer end +of the boring-bar and the back-rest in which this block is +mounted can be shifted along the bed to suit the length of the +work, by turning the squared end of shaft <i>D</i> with a crank. +The platen <i>P</i> has a cross-feed, and the saddle <i>E</i> on which it is +mounted can be traversed lengthwise on the bed; both of these +movements can also be effected by hand or power. There is a +series of power feeding movements for the cutters and, in addition, +rapid power movements <i>in a reverse direction from the +feed</i> for returning a cutter quickly to its starting position, when +this is desirable.</p> + +<p>This machine is driven by a belt connecting pulley <i>G</i> with an +overhead shaft. When the machine is in operation, this pulley +is engaged with the main driving shaft by a friction clutch <i>F</i> +controlled by lever <i>L</i>. This main shaft drives through gearing +a vertical shaft <i>I</i>, which by means of other gears in the spindle-head +imparts a rotary movement to the spindle. As a machine +of this type is used for boring holes of various diameters and +for a variety of other work, it is necessary to have a number +of speed changes for the spindle. Nine speeds are obtained by +changing the position of the sliding gears controlled by levers +<i>R</i> and this number is doubled by back-gears in the spindle-head +and controlled by lever <i>J</i>.</p> + +<p>The amount of feed for the spindle, spindle-head, platen or +saddle is varied by two levers <i>K</i> and <i>K<sub>1</sub></i> which control the position +of sliding gears through which the feeding movements are +transmitted. The direction of the feed can be reversed by shifting +lever <i>O</i>. With this particular machine, nine feed changes +are available for each position of the spindle back-gears, making +a total of eighteen changes. The feeding movement is transmitted +to the spindle-head, spindle, platen or saddle, as required, +by the three distributing levers <i>T</i>, <i>U</i> and <i>V</i>, which control +clutches connecting with the transmission shafts or feed +screws. When lever <i>T</i> is turned to the left, the longitudinal +power feed for the spindle is engaged, whereas turning it to the +right throws in the vertical feed for the spindle-head. Lever <i>U</i> +engages the cross-feed for platen <i>P</i> and lever <i>V</i>, the longitudinal +<span class="pagenum"><a name="Pg_278" id="Pg_278">[278]</a></span> +feed for saddle <i>E</i>. These levers have a simple but ingenious +interlocking device which makes it impossible to engage more +than one feed at a time. For example, if lever <i>T</i> is set for feeding +the spindle, levers <i>U</i> and <i>V</i> are locked against movement.</p> + +<p>The feeds are started and stopped by lever <i>M</i> which also +engages the rapid power traverse when thrown in the opposite +direction. This rapid traverse operates for whatever feed is +engaged by the distributing levers and, as before stated, in a +reverse direction. For example, if the reverse lever <i>O</i> is set for +feeding the spindle to the right, the rapid traverse would be to +the left, and <i>vice versa</i>. The cross-feed for the platen can be +automatically tripped at any point by setting an adjustable +stop in the proper position and the feed can also be tripped by +a hand lever at the side of the platen.</p> + +<p>All the different feeding movements can be effected by hand +as well as by power. By means of handwheel <i>N</i>, the spindle +can be moved in or out slowly, for feeding a cutter by hand. +When the friction clamp <i>Q</i> is loosened, the turnstile <i>W</i> can be +used for traversing the spindle, in case a hand adjustment is desirable. +The spindle-head can be adjusted vertically by turning +squared shaft <i>X</i> with a crank, and the saddle can be shifted +along the bed by turning shaft <i>Y</i>. The hand adjustment of the +platen is effected by shaft <i>Z</i>. The spindle-head, platen and +saddle can also be adjusted from the end of the machine, when +this is more convenient. Shafts <i>X</i>, <i>Y</i> and <i>Z</i> are equipped with +micrometer dials which are graduated to show movements of +one-thousandth inch. These dials are used for accurately adjusting +the spindle or work and for boring holes or milling +surfaces that must be an exact distance apart.</p> + +<a name="Fig_7_2" id="Fig_7_2"></a> +<div class="figcenter"><img src="images/287sm.jpg" alt="Horizontal Boring and Drilling Machine with Vertical Table Adjustment" /> +<p class="caption750">Fig. 2. Horizontal Boring and Drilling Machine with Vertical Table Adjustment</p> +</div> + +<a name="Secnum_7_1" id="Secnum_7_1"></a><p><b>Horizontal Boring Machine with Vertical Table Adjustment.</b>—Another +horizontal boring machine is partly shown in <a href="#Fig_7_2">Fig. 2</a>. +This machine is of the same type as that illustrated in Fig. 1, +but its construction is quite different, as will be seen. The spindle +cannot be adjusted vertically as with the first design described, but +it is mounted and driven very much like the spindle of a lathe, +and adjustment for height is obtained by raising or lowering +the work table. The design is just the reverse, in this respect,<span class="pagenum"><a name="Pg_279" id="Pg_279">[279]</a></span> +of the machine shown in <a href="#Fig_7_1">Fig. 1</a>, which has a vertical adjustment +for the spindle, and a work table that remains in the same +horizontal plane. The raising or lowering of the table is effected +by shaft <i>E</i>, which rotates large nuts engaging the screws <i>S</i>. +Shaft <i>E</i> is turned either by hand or power.</p> + +<p>The main spindle is driven by a cone pulley <i>P</i>, either directly, +or indirectly through the back-gears shown. This arrangement +gives six spindle speeds, and double this number is +obtained by using a two-speed countershaft overhead. The +motion for feeding the spindle longitudinally is transmitted +through a cone of gears, which gives the required changes, to a +pinion meshing with a rack which traverses the spindle. The +large handwheel <i>H</i> and a corresponding wheel on the opposite +side are used for adjusting the spindle rapidly by hand. The +yoke or outboard bearing <i>B</i> for the boring-bars can be clamped +in any position along the bed for supporting the bar as close to +the work as possible.</p> + +<p>Horizontal boring machines are built in many other designs, +but they all have the same general arrangement as the machines +illustrated and operate on the same principle, with the exception<span class="pagenum"><a name="Pg_280" id="Pg_280">[280]</a></span> +of special types intended for handling certain classes of +work exclusively. The horizontal boring, drilling and milling +machine is very efficient for certain classes of work because it +enables all the machining operations on some parts to be completed +at one setting. To illustrate, a casting which requires +drilling, boring and milling at different places, can often be +finished without disturbing its position on the platen after it is +clamped in place. Frequently a comparatively small surface +needs to be milled after a part has been bored. If this milling +operation can be performed while the work is set up for boring, +accurate results will be obtained (provided the machine is in +good condition) and the time saved that would otherwise be +required for re-setting the part on another machine. Some +examples of work on which different operations are performed +at the same setting will be referred to later. The horizontal +boring machine also makes it possible to machine duplicate +parts without the use of jigs, which is important, especially on +large work, owing to the cost of jigs.</p> + +<a name="Secnum_7_2" id="Secnum_7_2"></a><p><b>Drilling and Boring—Cutters Used.</b>—Holes are drilled in a +horizontal machine by simply inserting a drill of required size +either directly in the spindle <i>S</i> (see <a href="#Fig_7_1">Fig. 1</a>), or in a reducing +socket, and then feeding the spindle outward either by hand or +power. When a hole is to be bored, a boring-bar <i>B<sub>1</sub></i> is inserted +in the spindle and the cutter is attached to this bar. The +latter is then fed through the hole as the cutter revolves. The +distinction made by machinists between drilling and boring is as +follows: A hole is said to be drilled when it is formed by sinking +a drill into solid metal, whereas boring means the enlargement +of a drilled or cored hole either by the use of a single boring +tool, a double-ended cutter which operates on both sides of the +hole, or a cutter-head having several tools.</p> + +<a name="Fig_7_3" id="Fig_7_3"></a> +<div class="figcenter"><div class="illobox450"><img src="images/289sm.png" alt="Boring-cutters of Different Types" /></div> +<p class="caption750">Fig. 3. Boring-cutters of Different Types</p> +</div> + +<p>There are various methods of attaching cutters to boring-bars +and the cutters used vary for different classes of work. A +simple style of cutter which is used widely for boring small holes +is shown at <i>A</i> in <a href="#Fig_7_3">Fig. 3</a>. The cutter <i>c</i> is made from flat stock +and the cutting is done by the front edges <i>e</i> and <i>e<sub>1</sub></i>, which are +beveled in opposite directions. The cutter is held in the bar<span class="pagenum"><a name="Pg_281" id="Pg_281">[281]</a></span> +by a taper wedge <i>w</i> and it is centered by shoulders at <i>s</i>, so that +the diameter of the hole will equal the length across the cutter. +The outer corners at the front should be slightly rounded, as a +sharp corner would be dulled quickly. These cutters are made +in different sizes and also in sets for roughing and finishing. +The roughing cutter bores holes to within about <sup class="enum">1</sup>/<sub class="denom">32</sub> inch of the +finish size and it is then replaced by the finishing cutter. A +cutter having rounded ends, as shown by the detail sketch <i>a</i>, is +sometimes used for light finishing cuts. These rounded ends +form the cutting edges and give a smooth finish.</p> + +<p>Another method of holding a flat cutter is shown at <i>B</i>. The +conical end of a screw bears against a conical seat in, the cutter, +thus binding the latter in its slot. The conical seat also centers +the cutter. A very simple and inexpensive form of cutter is +shown at <i>C</i>. This is made from a piece of round steel, and it +is held in the bar by a taper pin which bears against a circular<span class="pagenum"><a name="Pg_282" id="Pg_282">[282]</a></span> +recess in the side of the cutter. This form has the advantage +of only requiring a hole through the boring-bar, whereas it is +necessary to cut a rectangular slot for the flat cutter.</p> + +<a name="Fig_7_4" id="Fig_7_4"></a> +<div class="figcenter"><div class="illobox450"><img src="images/290sm.png" alt="Boring with a Flat Double-ended Cutter" /></div> +<p class="caption750">Fig. 4. Boring with a Flat Double-ended Cutter</p> +</div> + +<p><a href="#Fig_7_4">Fig. 4</a> shows how a hole is bored by cutters of the type referred +to. The bar rotates as indicated by the arrow <i>a</i> and at +the same time feeds longitudinally as shown by arrow <i>b</i>. The +speed of rotation depends upon the diameter of the hole and +the kind of material being bored, and the feed per revolution +must also be varied to suit conditions. No definite rule can be +given for speed or feed. On some classes of work a long boring-bar +is used, which passes through the hole to be bored and is +steadied at its outer end by the back-rest <i>B</i>, <a href="#Fig_7_1">Figs. 1</a> and <a href="#Fig_7_2">2</a>. +On other work, a short bar is inserted in the spindle having a +cutter at the outer end. An inexpensive method of holding a +cutter at the end of a bar is shown at <i>D</i>, <a href="#Fig_7_3">Fig. 3</a>. The cutter +passes through a slot and is clamped by a bolt as shown. When +it is necessary to bore holes that are “blind” or closed at the +bottom, a long boring-bar which passes through the work cannot, +of course, be used.</p> + +<p>Sometimes it is necessary to have a cutter mounted at the +extreme end of a bar in order to bore close to a shoulder or the +bottom of a hole. One method of holding a cutter so that it +projects beyond the end of a bar is indicated at <i>E</i>. A screw +similar to the one shown at <i>B</i> is used, and the conical end bears +in a conical hole in the cutter. This hole should be slightly<span class="pagenum"><a name="Pg_283" id="Pg_283">[283]</a></span> +offset so that the cutter will be forced back against its seat. +The tool shown at <i>F</i> has adjustable cutters. The inner end of +each cutter is tapering and bears against a conical-headed screw +<i>b</i> which gives the required outward adjustment. The cutters +are held against the central bolt by fillister-head screws <i>f</i> and +they are clamped by the screws <i>c</i>. Boring tools are made in +many different designs and the number and form of the cutters +is varied somewhat for different kinds of work.</p> + +<a name="Fig_7_5" id="Fig_7_5"></a> +<div class="figcenter"><div class="illobox450"><img src="images/291sm.png" alt="Cutter-heads for Boring Large Holes" /></div> +<p class="caption750">Fig. 5. Cutter-heads for Boring Large Holes</p> +</div> + +<a name="Secnum_7_3" id="Secnum_7_3"></a><p><b>Cutter-heads for Boring Large Holes.</b>—When large holes are +to be bored, the cutters are usually held in a cast-iron head +which is mounted on the boring-bar. One type of cutter-head +is shown in <a href="#Fig_7_5">Fig. 5</a>. This particular head is double-ended and +carries two cutters <i>c</i>. The cutter-head is bored to fit the bar +closely and it is prevented from turning by a key against which +a set-screw is tightened. By referring to the end view, it will be +seen that each cutter is offset with relation to the center of the +bar, in order to locate the front of the tool on a radial line. +The number of cutters used in a cutter-head varies. By having +several cutters, the work of removing a given amount of metal in +boring is distributed, and holes can be bored more quickly with +a multiple cutter-head, although more power is required to +drive the boring-bar. The boring-bar is also steadied by a +multiple cutter-head, because the tendency of any one cutter<span class="pagenum"><a name="Pg_284" id="Pg_284">[284]</a></span> +to deflect the bar is counteracted by the cutters on the opposite +side.</p> + +<a name="Fig_7_6" id="Fig_7_6"></a> +<div class="figcenter"><div class="illobox450"><img src="images/292sm.png" alt="Cutter-head with Four Boring Tools" /></div> +<p class="caption750">Fig. 6. Cutter-head with Four Boring Tools</p> +</div> + +<p>A disk-shaped head having four cutters is illustrated in <a href="#Fig_7_6">Fig. +6</a>. The cutters are inserted in slots or grooves in the face of +the disk and they are held by slotted clamping posts. The +shape of these posts is shown by the sectional view. The tool +passes through an elongated slot and it is tightly clamped +against the disk by tightening nut <i>n</i>. This head is also driven +by a key which engages a keyway in the boring-bar.</p> + +<a name="Fig_7_7" id="Fig_7_7"></a> +<div class="figcenter"><div class="illobox450"><img src="images/293sm.png" alt="Cutter-heads equipped with Adjustable Tools" /></div> +<p class="caption750">Fig. 7. Cutter-heads equipped with Adjustable Tools</p> +</div> + +<p>Two other designs of cutter-heads are shown in <a href="#Fig_7_7">Fig. 7</a>. The +one illustrated at <i>A</i> has three equally spaced cutters which are +held in an inclined position. The cutters are clamped by screws +<i>c</i> and they can be adjusted within certain limits by screws <i>s</i>. +The cutters are placed at an angle so that they will extend beyond +the front of the head, thus permitting the latter to be +moved up close to a shoulder. The cutter-heads shown in +<a href="#Fig_7_5">Figs. 5</a> and <a href="#Fig_7_6">6</a> can also be moved up close to a shoulder if bent +cutters are used as shown in the right-hand view, <a href="#Fig_7_5">Fig. 5</a>. The +idea in bending the cutters is to bring the cutting edges in +advance of the clamping posts so that they will reach a shoulder +before the binding posts strike it. The arrangement of cutter-head +<i>B</i> (<a href="#Fig_7_7">Fig. 7</a>) is clearly shown by the illustration.</p> + +<p><span class="pagenum"><a name="Pg_285" id="Pg_285">[285]</a></span>Cutter-heads are often provided with two sets of cutters, one +set being used for roughing and the other for finishing. It is a +good plan to make these cutters so that the ends <i>e</i> (<a href="#Fig_7_6">Fig. 6</a>) will +rest against the bar or bottom of the slot, when the cutting edge +is set to the required radius. The cutters can then be easily +set for boring duplicate work. One method of making cutters +in sets is to clamp the annealed stock in the cutter-head and +then turn the ends to the required radius by placing the head +in the lathe. After both sets of cutters have been turned in +this way, they are ground to shape and then hardened.</p> + +<a name="Fig_7_8" id="Fig_7_8"></a> +<div class="figcenter"><div class="illobox450"><img src="images/294sm.png" alt="Boring Tools for Roughing and Finishing Cuts" /></div> +<p class="caption750">Fig. 8. Boring Tools for Roughing and Finishing Cuts</p> +</div> + +<p>Boring cutters intended for roughing and finishing cuts are +shown in the detail view <a href="#Fig_7_8">Fig. 8</a> at <i>A</i> and <i>B</i>, respectively. The +side of the roughing cutter <i>A</i> is ground to a slight angle <i>c</i> to +provide clearance for the cutting edge, and the front has a +backward slope <i>s</i> to give the tool keenness. This tool is a good +form to use for roughing cuts in cast iron. The finishing tool +at <i>B</i> has a broad flat edge <i>e</i> and it is intended for coarse feeds +and light cuts in cast iron. If a round cutting edge is used for +finishing, a comparatively fine feed is required in order to obtain +a smooth surface. The corners of tool <i>B</i> are rounded and they +should be ground to slope inward as shown in the plan view. +The top or ends <i>d</i> of both of these tools are “backed off” slightly +<span class="pagenum"><a name="Pg_286" id="Pg_286">[286]</a></span> +to provide clearance. This clearance should be just enough to +prevent the surface back of the cutting edge from dragging over +the work. Excessive end clearance not only weakens the cutting +edge, but tends to cause chattering. As a finishing tool +cuts on the upper end instead of on the side, the front should +slope backward as shown in the side view, rather than sidewise +as with a roughing cutter. The angle of the slope should +be somewhat greater for steel than cast iron, unless the steel is +quite hard, thus requiring a strong blunt tool.</p> + +<a name="Fig_7_9" id="Fig_7_9"></a> +<div class="figcenter"><div class="illobox450"><img src="images/295sm.png" alt="Cylinder mounted on Horizontal Machine for Boring" /></div> +<p class="caption750">Fig. 9. Cylinder mounted on Horizontal Machine for Boring</p> +</div> + +<a name="Secnum_7_4" id="Secnum_7_4"></a><p><b>Cylinder Boring.</b>—<a href="#Fig_7_9">Fig. 9</a> +illustrates the use of a cutter-head for cylinder boring. After the cylinder casting is set on the +platen of the machine, the boring-bar with the cutter-head +mounted on it is inserted in the spindle. The bar <i>B</i> has a taper +shank and a driving tang similar to a drill shank, which fits a +taper hole in the end of the spindle. The cutter-head <i>C</i> is +fastened to the bar so that it will be in the position shown when +the spindle is shifted to the right, as the feeding movement +(with this particular machine) is to be in the opposite direction. +The casting <i>A</i> should be set central with the bar by adjusting +the work-table vertically and laterally, if necessary, and the +outer support <i>F</i> should be moved close to the work, to make the +bar as rigid as possible.</p> + +<p>The cylinder is now ready to be bored. Ordinarily, one or +two roughing cuts and one finishing cut would be sufficient, unless +the rough bore were considerably below the finish diameter.<span class="pagenum"><a name="Pg_287" id="Pg_287">[287]</a></span> +As previously explained, the speed and feed must be governed +by the kind of material being bored and the diameter of the +cut. The power and rigidity of the boring machine and the +quality of the steel used for making the cutters also affect +the cutting speed and feed. As the finishing cut is very light, a +tool having a flat cutting edge set parallel to the bar is ordinarily +used when boring cast iron. The coarse feed enables the +cut to be taken in a comparatively short time and the broad-nosed +tool gives a smooth finish if properly ground.</p> + +<p>The coarse finishing feed is not always practicable, especially +if the boring machine is in poor condition, owing to the chattering +of the tool, which results in a rough surface. The last or +finishing cut should invariably be a continuous one, for if the +machine is stopped before the cut is completed, there will be a +ridge in the bore at the point where the tool temporarily left off +cutting. This ridge is caused by the cooling and resulting contraction +and shortening of the tool during the time that it is +stationary. For this reason independent drives are desirable +for boring machines.</p> + +<p><span class="pagenum"><a name="Pg_288" id="Pg_288">[288]</a></span>Facing arms are attached to the bar on either side of the +cylinder for facing the flanges after the boring operation. The +turning tool of a facing arm is fastened to a slide which is fed +outward a short distance each revolution, by a star-wheel that +is caused to turn as it strikes against a stationary pin. By +facing the flanges in this way, they are finished square with the +bore.</p> + +<p>When setting a cylinder which is to be bored it should, when +the design will permit, be set true by the outside of the flange, +or what is even better, by the outside of the cylinder itself, +rather than by the rough bore, in order that the walls of the +finished cylinder will have a uniform thickness. The position +of very large cylinders, while they are being bored, is an important +consideration. Such cylinders should be bored in the +position which they will subsequently occupy when assembled. +For example, the cylinder for a large horizontal engine should +be bored while in a horizontal position, as the bore is liable to +spring to a slight oval shape when the cylinder is placed horizontal +after being bored while standing in a vertical position. If, +however, the cylinder is bored while in the position in which it +will be placed in the assembled engine, this trouble is practically +eliminated.</p> + +<p>There is a difference of opinion among machinists as to the +proper shape of the cutting point of a boring tool for finishing +cuts, some contending that a wide cutting edge is to be preferred, +while others advocate the use of a comparatively narrow +edge with a reduced feed. It is claimed, that the narrow tool +produces a more perfect bore, as it is not so easily affected by +hard spots in the iron, and it is also pointed out that the minute +ridges left by the narrow tool are an advantage rather than a +disadvantage, as they form pockets for oil and aid in lubricating +the cylinder. It is the modern practice, however, to use a +broad tool and a coarse feed for the light finishing cut, provided +the tool does not chatter.</p> + +<p>The type of machine tool used for boring cylinders, and also +the method of procedure is determined largely by the size of +the work and the quantity which is to be machined. The<span class="pagenum"><a name="Pg_289" id="Pg_289">[289]</a></span> +turret lathe, as well as horizontal and vertical boring mills, is +used for this work, and in automobile factories or other shops +where a great many cylinders are bored, special machines and +fixtures are often employed.</p> + +<a name="Fig_7_10" id="Fig_7_10"></a> +<div class="figcenter"><img src="images/297sm.jpg" alt="Boring a Duplex Cylinder on Horizontal Machine" /> +<p class="caption750">Fig. 10. Boring a Duplex Cylinder on a Horizontal Machine</p> +</div> + +<a name="Secnum_7_5" id="Secnum_7_5"></a><p><b>Boring a Duplex Gasoline Engine Cylinder.</b>—The method of +holding work on a horizontal boring machine depends on its +shape. A cylinder or other casting having a flat base can be +clamped directly to the platen, but pieces of irregular shape are +usually held in special fixtures. <a href="#Fig_7_10">Fig. 10</a> shows how the cylinder +casting of a gasoline engine is set up for the boring operation. +The casting <i>W</i> is placed in a fixture <i>F</i> which is clamped to the +machine table. One end of the casting rests on the adjustable +screws <i>S</i> and it is clamped by set-screws located in the top and +sides of the fixture. There are two cylinders cast integral and +these are bored by a short stiff bar mounted in the end of the +spindle and having cutters at the outer end. A long bar of +the type which passes through the work and is supported by the +outboard bearing <i>B</i>, could not be used for this work, because +the top of each cylinder is closed.</p> + +<p>When one cylinder is finished the other is set in line with the<span class="pagenum"><a name="Pg_290" id="Pg_290">[290]</a></span> +spindle by adjusting the work-table laterally. This adjustment +is effected by screw <i>C</i>, and the required center-to-center +distance between the two cylinders can be gaged by the micrometer +dial <i>M</i> on the cross-feed screw, although positive stops +are often used in preference. After the first cylinder is bored, +the dial is set to the zero position by loosening the small knurled +screw shown, and turning the dial around. The feed screw is +then rotated until the dial shows that the required lateral +adjustment is made, which locates the casting for boring the +second cylinder. The end of the casting is also faced true by a +milling cutter. Ordinarily, milling cutters are bolted directly +to the spindle sleeve <i>A</i> on this particular machine, which gives +a rigid support for the cutter and a powerful drive.</p> + +<a name="Fig_7_11" id="Fig_7_11"></a> +<div class="figcenter"><img src="images/298sm.jpg" alt="Cylinder turned around for Machining Valve Seats" /> +<p class="caption750">Fig. 11. Cylinder turned around for Machining Valve Seats</p> +</div> + +<p>The next operation is that of boring and milling the opposite +end of the cylinder. This end is turned toward the spindle +(as shown in <a href="#Fig_7_11">Fig. 11</a>) without unclamping the work or fixture, +by simply turning the circular table <i>T</i> half way around. This +table is an attachment which is clamped to the main table for +holding work that must be turned to different positions for +machining the various parts. Its position is easily changed, and<span class="pagenum"><a name="Pg_291" id="Pg_291">[291]</a></span> +as the work remains fixed with relation to the table, the alignment +between different holes or surfaces is assured, if the table +is turned the right amount. In this case, the casting needs to +be rotated one-half a revolution or 180 degrees, and this is done +by means of angular graduations on the base of the table. +The illustration shows the casting set for boring the inlet and +exhaust valve chambers. The different cutters required for +boring are mounted on one bar as shown, and the casting is +adjusted crosswise to bring each valve chamber in position, by +using the micrometer dial. The single-ended cutter <i>c</i> forms a +shallow circular recess or seat in the raised pad which surrounds +the opening. The cover joint directly back of the cylinders is +finished by milling.</p> + +<a name="Fig_7_12" id="Fig_7_12"></a> +<div class="figcenter"><img src="images/299sm.jpg" alt="Boring Differential Gear Casing" /> +<p class="caption750">Fig. 12. Boring Differential Gear Casing</p> +</div> + +<a name="Secnum_7_6" id="Secnum_7_6"></a><p><b>Examples of Boring, Radial Facing and Milling.</b>—Another +example of boring, in which the circular table is used, is shown +in <a href="#Fig_7_12">Fig. 12</a>. The work <i>W</i> is a casing for the differential gears of +an automobile. It is mounted in a fixture <i>F</i> which is bolted to +the table. The casting has round ends, which are clamped in +V-blocks, thus aligning the work. This fixture has a guide-bushing<span class="pagenum"><a name="Pg_292" id="Pg_292">[292]</a></span> +<i>G</i> which is centered with the bar and cutter in order to +properly locate the casting. There is a bearing at each end of +the casing, and two larger ones in the center. These are bored +by flat cutters similar to the style illustrated at <i>A</i> in <a href="#Fig_7_3">Fig. 3</a>. +The cutter for the inner bearings is shown at <i>c</i>.</p> + +<a name="Fig_7_13" id="Fig_7_13"></a> +<div class="figcenter"><img src="images/300sm.jpg" alt="Facing and Turning Flange of Differential Gear Casing" /> +<p class="caption750">Fig. 13. Facing and Turning Flange of Differential Gear Casing</p> +</div> + +<p>After the bearings are bored, the circular table is turned 90 +degrees and the work is moved closer to the spindle (as shown +in <a href="#Fig_7_13">Fig. 13</a>) for facing flange <i>F</i> at right angles to the bearings. +Circular flanges of this kind are faced in a horizontal boring +machine by a special facing-arm or head <i>H</i>. For this particular +job this head is clamped directly to the spindle sleeve, +but it can also be clamped to the spindle if necessary. The +turning tool is held in a slotted toolpost, and it is fed radially +for turning the side or face of the flange, by the well-known +star feed at <i>S</i>. When this feed is in operation the bent finger +<i>E</i> is turned downward so that it strikes one of the star wheel +arms for each revolution; this turns the wheel slightly, and<span class="pagenum"><a name="Pg_293" id="Pg_293">[293]</a></span> +the movement is transmitted to the tool-block by a feed-screw. +The illustration shows the tool set for turning the outside or +periphery of the flange. This is done by setting the tool to the +proper radius and then feeding the work horizontally by shifting +the work-table along the bed. By referring to <a href="#Fig_7_12">Fig. 12</a> it will be +seen that the facing head does not need to be removed for boring, +as it is attached to the spindle driving quill and does not interfere +with the longitudinal adjustment of the spindle. This +facing head is also used frequently for truing the flanges of +cylinders which are to be bored, and for similar work.</p> + +<a name="Fig_7_14" id="Fig_7_14"></a> +<div class="figcenter"><img src="images/301sm.jpg" alt="Example of Work requiring Boring and Milling" /> +<p class="caption750">Fig. 14. Example of Work requiring Boring and Milling</p> +</div> + +<p><a href="#Fig_7_14">Fig. 14</a> shows another example of work which requires boring +and milling. This casting is mounted on a fixture which is +bolted to the main table. In this case the circular table is not +necessary, because the work can be finished without swiveling +it around. After the boring is completed the edge <i>E</i> is trued +by the large-face milling cutter <i>M</i> bolted to the spindle sleeve. +The irregular outline of the edge is followed by moving the table +crosswise and the spindle vertically, as required.</p> + +<a name="Fig_7_15" id="Fig_7_15"></a> +<div class="figcenter"><div class="illobox450"><img src="images/302sm.png" alt="Cylinder Lining mounted in Fixture for Boring" /></div> +<p class="caption750">Fig. 15. Cylinder Lining mounted in Fixture for Boring</p> +</div> + +<a name="Secnum_7_7" id="Secnum_7_7"></a><p><b>Fixture for Cylinder Lining or Bushing.</b>—A method of holding +a cylinder lining or bushing while it is being bored is shown<span class="pagenum"><a name="Pg_294" id="Pg_294">[294]</a></span> +in <a href="#Fig_7_15">Fig. 15</a>. The lining <i>L</i> is mounted in two cast-iron ring-shaped +fixtures <i>F</i>. These fixtures are circular in shape and have +flat bases which are bolted to the table of the machine. On the +inside of each fixture, there are four equally spaced wedges <i>W</i> +which fit into grooves as shown in the end view. These wedges +are drawn in against the work by bolts, and they prevent the +lining from rotating when a cut is being taken. This form of +fixture is especially adapted for holding thin bronze linings, +such as are used in pump cylinders, because only a light pressure +against the wedges is required, and thin work can be +held without distorting it. If a very thin lining is being +bored, it is well to loosen the wedges slightly before taking the +finishing cut, so that the work can spring back to its normal +shape.</p> + +<a name="Fig_7_16" id="Fig_7_16"></a><span class="pagenum"><a name="Pg_295" id="Pg_295">[295]</a></span> +<div class="figcenter"><img src="images/303sm.jpg" alt="Detrick & Harvey Horizontal Boring Machine of the Floor Type Boring Engine Bed Casting" /> +<p class="caption750">Fig. 16. Detrick & Harvey Horizontal Boring Machine of the Floor Type Boring Engine Bed Casting</p> +</div> + +<a name="Secnum_7_8" id="Secnum_7_8"></a><p><b>Horizontal Boring Machine of Floor Type.</b>—The type of +horizontal boring, drilling and milling machine, shown in <a href="#Fig_7_16">Fig. 16</a>, +is intended for boring heavy parts such as the cylinders of large +engines or pumps, the bearings of heavy machine beds and +similar work. This machine can also be used for drilling and +milling, although it is intended primarily for boring, and the +other operations are usually secondary. This design is ordinarily +referred to as the “floor type,” because the work-table +is low for accommodating large heavy castings. The spindle <i>S</i> +which drives the boring-bar, and the spindle feeding mechanism, +are carried by a saddle. This saddle is free to move vertically<span class="pagenum"><a name="Pg_296" id="Pg_296">[296]</a></span> +on the face of column <i>C</i> which is mounted on transverse ways +extending across the right-hand end of the main bed. This +construction permits the spindle to move vertically or laterally +(by traversing the column) either for adjusting it to the required +position or for milling operations. The spindle also +has a longitudinal movement for boring. There is an outer +bearing <i>B</i> for supporting the boring-bar, which also has lateral +and vertical adjustments, so that it can be aligned with the +bar.</p> + +<p>The work done on a machine of this type is either clamped +directly to the large bed-plate <i>A</i> (which has a number of T-slots +for receiving the heads of the clamping bolts) or, in some cases, +a special fixture may be used or an auxiliary table. Boring +machines of this same general construction are built in many +different sizes. The main spindle of the machine illustrated is +driven by a motor located at the rear of the vertical column +<i>C</i>, the motion being transmitted to the spindle through shafts +and gearing. The casting <i>D</i>, shown in this particular illustration, +is for a steam engine of the horizontal type, and the operation +is that of boring the cylindrical guides or bearings for the +crosshead. These bearings have a diameter of 15<sup class="enum">3</sup>/<sub class="denom">4</sub> inches and +are 37<sup class="enum">3</sup>/<sub class="denom">4</sub> inches long. In boring them, two roughing cuts and one +finishing cut are taken. The end of the casting, which in the +assembled engine bears against the cylinder, is then faced by +means of a regular facing arm.</p> + +<p>After removing the boring-bar the table <i>E</i> of the special +fixture on which the casting is mounted is turned one quarter +of a revolution. A large milling cutter 24 inches in diameter is +next mounted on the spindle of the machine, and one side of +the main bearing, as well as the pads for the valve-rod guide-bar +brackets, are milled. The table is then revolved and the opposite +side of the main bearing is milled in the same way, the +table being accurately located in the different positions by an +index plunger <i>F</i> which engages holes on the under side. The +spindle is now moved upward to allow the table to be turned so +as to locate the bearing end of the frame next to the headstock +of the machine. The milling cutter is then used to machine<span class="pagenum"><a name="Pg_297" id="Pg_297">[297]</a></span> +the inside and top surfaces of the main bearing. By turning the +fixture and not changing the position of the casting after it is +bolted into place, the various surfaces are machined in the correct +relation to one another without difficulty. This is a good +example of the work done on horizontal boring machines of the +floor type.</p> +<hr class="c25" /> + +<p class="pagenum"><a name="Pg_299" id="Pg_299">[299]</a></p> + +<h2>INDEX</h2> +<hr class="c05" /> + +<table align="center" class="center" width="50%" cellpadding="0" cellspacing="0" summary="Index"> + +<tr> +<td width="1%"> </td> +<td width="10%"> </td> +<td width="2%" class="right"><span class="smcap">Page</span></td> +</tr> + +<tr><td colspan="3"> </td></tr> + +<tr> +<td colspan="2" class="left" valign="bottom"><span class="dropcap">A</span>cme flat turret lathe, examples of chuck work</td> +<td class="right" valign="bottom"><a href="#Pg_219">219</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Acme standard thread and tool for cutting</td> +<td class="right"><a href="#Pg_159">159</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Acme standard thread gage</td> +<td class="right"><a href="#Pg_157">157</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Acme thread tool, measuring width with vernier caliper</td> +<td class="right"><a href="#Pg_157">157</a>, <a href="#Pg_158">158</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Accumulation of errors</td> +<td class="right"><a href="#Pg_105">105</a>, <a href="#Pg_106">106</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Aligning lathe centers for cylindrical turning</td> +<td class="right"><a href="#Pg_16">16</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Allowances, average, for forced fits</td> +<td class="right"><a href="#Pg_130">130</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">for different classes of fits</td> +<td class="right"><a href="#Pg_131">131</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">for driving fits</td> +<td class="right"><a href="#Pg_131">131</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">for forced fits of given pressure</td> +<td class="right"><a href="#Pg_133">133</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">for push fits</td> +<td class="right"><a href="#Pg_131">131</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">for running fits</td> +<td class="right"><a href="#Pg_131">131</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">for shrinkage fits</td> +<td class="right"><a href="#Pg_133">133</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Aluminum, lubricant for machining</td> +<td class="right"><a href="#Pg_53">53</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">shape of tools for turning</td> +<td class="right"><a href="#Pg_53">53</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">speed and feed for machining</td> +<td class="right"><a href="#Pg_53">53</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Angle-plate applied to lathe faceplate</td> +<td class="right"><a href="#Pg_48">48</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Angles, gage for accurate measurement of</td> +<td class="right"><a href="#Pg_97">97</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Apron of lathe</td> +<td class="right"><a href="#Pg_4">4</a>, <a href="#Pg_5">5</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Arbor or mandrel press</td> +<td class="right"><a href="#Pg_22">22</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Arbors or mandrels for lathe work, types of</td> +<td class="right"><a href="#Pg_49">19</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">use of</td> +<td class="right"><a href="#Pg_17">17</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Attachment, application of Hendey relieving</td> +<td class="right"><a href="#Pg_125">125</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">convex turning for vertical boring mill</td> +<td class="right"><a href="#Pg_259">259</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">for coarse threading in lathe</td> +<td class="right"><a href="#Pg_160">160</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">for spherical turning</td> +<td class="right"><a href="#Pg_113">113</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">for taper turning in lathe</td> +<td class="right"><a href="#Pg_88">88</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">Hendey relieving</td> +<td class="right"><a href="#Pg_123">123</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Automatic chucking and turning machine, Potter & Johnston</td> +<td class="right"><a href="#Pg_223">223</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">Potter & Johnston, method of “setting-up”</td> +<td class="right"><a href="#Pg_227">227</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">Potter & Johnston, turning flywheel in</td> +<td class="right"><a href="#Pg_236">236</a></td> +</tr> + +<tr> +<td colspan="3"> </td> +</tr> + +<tr> +<td colspan="2" class="left" valign="bottom"><span class="dropcap">B</span>ack-gears of lathe</td> +<td class="right" valign="bottom"><a href="#Pg_3">3</a>, <a href="#Pg_4">4</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Bardons & Oliver turret lathe, general description</td> +<td class="right"><a href="#Pg_178">178</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Bored holes, measuring diameter of</td> +<td class="right"><a href="#Pg_41">41</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Boring and reaming tools for vertical mill</td> +<td class="right"><a href="#Pg_251">251</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Boring and turning mill, vertical, general description</td> +<td class="right"><a href="#Pg_242">242</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">vertical, holding and setting work</td> +<td class="right"><a href="#Pg_247">247</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">vertical, turning in</td> +<td class="right"><a href="#Pg_249">249</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">turning tools for +<span class="pagenum"><a name="Pg_300" id="Pg_300">[300]</a></span> +</td> +<td class="right"><a href="#Pg_253">253</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Boring-bar cutters and methods of holding</td> +<td class="right"><a href="#Pg_280">280</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Boring cutters for roughing and finishing cuts</td> +<td class="right"><a href="#Pg_285">285</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Boring cylinders on horizontal machine</td> +<td class="right"><a href="#Pg_286">286</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Boring holes to given center distance in lathe</td> +<td class="right"><a href="#Pg_51">51</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Boring in lathe, example of</td> +<td class="right"><a href="#Pg_39">39</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Boring large castings in lathe</td> +<td class="right"><a href="#Pg_49">49</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Boring large holes, cutter-heads used for</td> +<td class="right"><a href="#Pg_283">283</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Boring machine, horizontal</td> +<td class="right"><a href="#Pg_275">275</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">horizontal, examples of work on</td> +<td class="right"><a href="#Pg_289">289-297</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">horizontal, floor type</td> +<td class="right"><a href="#Pg_294">294</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">vertical, multiple-spindle type</td> +<td class="right"><a href="#Pg_274">274</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Boring tool, lathe</td> +<td class="right"><a href="#Pg_40">40</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Box-tools, different designs and examples of work</td> +<td class="right"><a href="#Pg_193">193</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">for general turret lathe work</td> +<td class="right"><a href="#Pg_190">190</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Bradford belt-driven lathe, general description</td> +<td class="right"><a href="#Pg_1">1</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Bradford quick change-gear type of lathe</td> +<td class="right"><a href="#Pg_173">173</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Brass, speed for turning</td> +<td class="right"><a href="#Pg_52">52</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">tool for turning in lathe</td> +<td class="right"><a href="#Pg_52">52</a></td> +</tr> + +<tr> +<td colspan="2" class="left">“Bridle” or “hold-back” for lathe</td> +<td class="right"><a href="#Pg_26">26</a>, <a href="#Pg_27">27</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Bullard vertical turret lathe</td> +<td class="right"><a href="#Pg_264">264</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">examples of work</td> +<td class="right"><a href="#Pg_268">268</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Button method of locating work</td> +<td class="right"><a href="#Pg_101">101</a></td> +</tr> + +<tr> +<td colspan="3"> </td> +</tr> + +<tr> +<td colspan="2" class="left" valign="bottom"><span class="dropcap">C</span>aliper tool for taper turning</td> +<td class="right" valign="bottom"><a href="#Pg_85">85</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Calipers, methods of setting</td> +<td class="right"><a href="#Pg_10">10</a>, <a href="#Pg_11">11</a></td> +</tr> + +<tr> +<td colspan="2" class="left">“Cat-head,” application in lathe work</td> +<td class="right"><a href="#Pg_25">25</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Center holes, incorrect and correct forms</td> +<td class="right"><a href="#Pg_32">32</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Center indicator, use of</td> +<td class="right"><a href="#Pg_100">100</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Centered stock, methods of facing ends</td> +<td class="right"><a href="#Pg_34">34</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Centers, lathe, aligning for cylindrical turning</td> +<td class="right"><a href="#Pg_16">16</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">lathe, grinder for truing</td> +<td class="right"><a href="#Pg_34">34</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Centering machine</td> +<td class="right"><a href="#Pg_30">30</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Centering parts to be turned</td> +<td class="right"><a href="#Pg_28">28</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Centering, precaution for tool steel</td> +<td class="right"><a href="#Pg_33">33</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Change gears, calculating for thread cutting</td> +<td class="right"><a href="#Pg_167">167</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">compound, for thread cutting</td> +<td class="right"><a href="#Pg_170">170</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">for cutting fractional threads</td> +<td class="right"><a href="#Pg_171">171</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">for cutting metric pitches</td> +<td class="right"><a href="#Pg_171">171</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">for thread cutting</td> +<td class="right"><a href="#Pg_135">135</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Chasing dial for “catching threads” when screw cutting</td> +<td class="right"><a href="#Pg_141">141</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Chuck, inaccuracy from pressure of jaws</td> +<td class="right"><a href="#Pg_42">42</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">lathe, application of</td> +<td class="right"><a href="#Pg_37">37</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">setting work in</td> +<td class="right"><a href="#Pg_42">42</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">universal, independent and combination</td> +<td class="right"><a href="#Pg_36">36</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Chucking and turning machine, Potter & Johnston automatic</td> +<td class="right"><a href="#Pg_223">223</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">Potter & Johnston automatic, method of “setting-up”</td> +<td class="right"><a href="#Pg_227">227</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">Potter & Johnston automatic, turning flywheel in</td> +<td class="right"><a href="#Pg_236">236</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Chucking machine, New Britain, multiple-spindle type</td> +<td class="right"><a href="#Pg_238">238</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Clearance angle for turning tools +<span class="pagenum"><a name="Pg_301" id="Pg_301">[301]</a></span></td> +<td class="right"><a href="#Pg_66">66</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Clearance of turning tools, meaning of</td> +<td class="right"><a href="#Pg_62">62</a>, <a href="#Pg_63">63</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Coarse threading attachment for lathe</td> +<td class="right"><a href="#Pg_160">160</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Collapsing tap, Geometric</td> +<td class="right"><a href="#Pg_202">202</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Combination chuck for lathe</td> +<td class="right"><a href="#Pg_36">36</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Compound rest, applied to screw or thread cutting</td> +<td class="right"><a href="#Pg_143">143</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">applied to taper turning</td> +<td class="right"><a href="#Pg_95">95</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Convex turning attachment for vertical boring mills</td> +<td class="right"><a href="#Pg_259">259</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Copper, tool for turning in lathe</td> +<td class="right"><a href="#Pg_52">52</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Crankshaft lathe, description of R. K. LeBlond special</td> +<td class="right"><a href="#Pg_108">108</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">operation of R. K. LeBlond</td> +<td class="right"><a href="#Pg_110">110</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Crankshaft turning in engine lathe</td> +<td class="right"><a href="#Pg_107">107</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Cross-slide stop for threading</td> +<td class="right"><a href="#Pg_155">155</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Cuts, average depth for turning</td> +<td class="right"><a href="#Pg_75">75</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">roughing and finishing in lathe</td> +<td class="right"><a href="#Pg_12">12</a>, <a href="#Pg_75">75</a>, <a href="#Pg_76">76</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Cutter-heads, for boring, equipped with adjustable tools</td> +<td class="right"><a href="#Pg_284">284</a>, <a href="#Pg_285">285</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">for horizontal boring machine</td> +<td class="right"><a href="#Pg_283">283</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Cutters, boring, roughing and finishing types</td> +<td class="right"><a href="#Pg_285">285</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">for boring-bars</td> +<td class="right"><a href="#Pg_280">280</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Cutting lubricants for turning tools</td> +<td class="right"><a href="#Pg_77">77</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Cutting speeds, average for turning</td> +<td class="right"><a href="#Pg_72">72</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">based on Taylor's experiments</td> +<td class="right"><a href="#Pg_71">71</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">effect of lubricant on</td> +<td class="right"><a href="#Pg_76">76</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">factors which limit speeds for turning</td> +<td class="right"><a href="#Pg_72">72</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">rules for calculating</td> +<td class="right"><a href="#Pg_74">74</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Cylinder boring machine, multiple-spindle type</td> +<td class="right"><a href="#Pg_274">274</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Cylinder boring on horizontal machine</td> +<td class="right"><a href="#Pg_286">286</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Cylinder lining, fixture for holding when boring</td> +<td class="right"><a href="#Pg_293">293</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Cylindrical turning, simple example of</td> +<td class="right"><a href="#Pg_6">6</a></td> +</tr> + +<tr> +<td colspan="3"> </td> +</tr> + +<tr> +<td colspan="2" class="left" valign="bottom"><span class="dropcap">D</span>avis turret lathe, turning bevel gear blanks</td> +<td class="right" valign="bottom"><a href="#Pg_212">212</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">turning worm-gear blanks</td> +<td class="right"><a href="#Pg_211">211</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Depth of cut for turning, average</td> +<td class="right"><a href="#Pg_75">75</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Detrick & Harvey horizontal boring machine, floor type</td> +<td class="right"><a href="#Pg_294">294</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Dial for “catching threads” when screw cutting</td> +<td class="right"><a href="#Pg_141">141</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Dial gage, testing concentricity of button with</td> +<td class="right"><a href="#Pg_103">103</a>, <a href="#Pg_104">104</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Die and tap holders, releasing</td> +<td class="right"><a href="#Pg_199">199</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Die-heads, self-opening type</td> +<td class="right"><a href="#Pg_200">200</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Disk gage, for angles and tapers</td> +<td class="right"><a href="#Pg_97">97</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">rules for setting</td> +<td class="right"><a href="#Pg_98">98</a>, <a href="#Pg_99">99</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Dogs or drivers, lathe, application of</td> +<td class="right"><a href="#Pg_16">16</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Drill, flat, for lathe</td> +<td class="right"><a href="#Pg_44">44</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Drilling and reaming in lathe</td> +<td class="right"><a href="#Pg_43">43</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Drivers or dogs, lathe, application of</td> +<td class="right"><a href="#Pg_16">16</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Driving fits, allowances for</td> +<td class="right"><a href="#Pg_131">131</a></td> +</tr> + +<tr> +<td colspan="3"> </td> +</tr> + +<tr> +<td colspan="2" class="left" valign="bottom"><span class="dropcap">E</span>ccentric turning in lathe</td> +<td class="right" valign="bottom"><a href="#Pg_106">106</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Engine lathe, general description</td> +<td class="right"><a href="#Pg_1">1</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Errors, accumulation of</td> +<td class="right"><a href="#Pg_105">105</a>, <a href="#Pg_106">106</a></td> +</tr> + +<tr> +<td colspan="3"> </td> +</tr> + +<tr> +<td colspan="2" class="left" valign="bottom"><span class="dropcap">F</span>aceplate, indexing for multiple-thread cutting +<span class="pagenum"><a name="Pg_302" id="Pg_302">[302]</a></span></td> +<td class="right" valign="bottom"><a href="#Pg_153">153</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">lathe, application of angle-plate to</td> +<td class="right"><a href="#Pg_48">48</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">lathe, holding work on</td> +<td class="right"><a href="#Pg_45">45</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Facing ends of centered stock, different methods</td> +<td class="right"><a href="#Pg_34">34</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Feed and depth of cut for turning, average</td> +<td class="right"><a href="#Pg_75">75</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Feeds and speeds for turning based on Taylor's experiments</td> +<td class="right"><a href="#Pg_71">71</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Filing and polishing in lathe</td> +<td class="right"><a href="#Pg_13">13</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Finishing and roughing cuts in lathe</td> +<td class="right"><a href="#Pg_75">75</a>, <a href="#Pg_76">76</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Fits, allowances for different classes</td> +<td class="right"><a href="#Pg_131">131</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">different classes used in machine construction</td> +<td class="right"><a href="#Pg_129">129</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">driving, allowances for</td> +<td class="right"><a href="#Pg_131">131</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">forced, allowances for given pressure</td> +<td class="right"><a href="#Pg_133">133</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">forced, average allowance for</td> +<td class="right"><a href="#Pg_130">130</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">forced, pressure for</td> +<td class="right"><a href="#Pg_132">132</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">push, allowances for</td> +<td class="right"><a href="#Pg_131">131</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">running, allowances for</td> +<td class="right"><a href="#Pg_131">131</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">shrinkage, allowances for</td> +<td class="right"><a href="#Pg_133">133</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Fixture for holding thin lining when boring</td> +<td class="right"><a href="#Pg_293">293</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Flat drill and holder for lathe</td> +<td class="right"><a href="#Pg_44">44</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Flat turret lathe, Acme, examples of chuck work</td> +<td class="right"><a href="#Pg_219">219</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">Hartness, example of turning</td> +<td class="right"><a href="#Pg_213">213</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">Jones & Lamson double-spindle type</td> +<td class="right"><a href="#Pg_221">221</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Floating reamer holders</td> +<td class="right"><a href="#Pg_271">271</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Flywheel, finishing in one setting in turret lathe</td> +<td class="right"><a href="#Pg_186">186</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">finishing in two settings in turret lathe</td> +<td class="right"><a href="#Pg_189">189</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">machining in turret lathe</td> +<td class="right"><a href="#Pg_184">184</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">turning in Potter & Johnston automatic</td> +<td class="right"><a href="#Pg_236">236</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">turning in vertical boring mill</td> +<td class="right"><a href="#Pg_255">255</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Follow-rest for lathe</td> +<td class="right"><a href="#Pg_27">27</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Forced fits, allowances for given pressure</td> +<td class="right"><a href="#Pg_133">133</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">average allowance for</td> +<td class="right"><a href="#Pg_130">130</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">pressure generally used in assembling</td> +<td class="right"><a href="#Pg_132">132</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Fractional threads, change gears for cutting</td> +<td class="right"><a href="#Pg_171">171</a></td> +</tr> + +<tr> +<td colspan="3"> </td> +</tr> + +<tr> +<td colspan="2" class="left" valign="bottom"><span class="dropcap">G</span>age, disk, for angles and tapers</td> +<td class="right" valign="bottom"><a href="#Pg_97">97</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">disk, rules for setting</td> +<td class="right"><a href="#Pg_98">98</a>, <a href="#Pg_99">99</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">for testing V-thread tool</td> +<td class="right"><a href="#Pg_138">138</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">standard plug, for holes</td> +<td class="right"><a href="#Pg_42">42</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">thread, Acme standard</td> +<td class="right"><a href="#Pg_157">157</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Geometric collapsing tap</td> +<td class="right"><a href="#Pg_202">202</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Geometric self-opening die-head</td> +<td class="right"><a href="#Pg_200">200</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Gisholt convex attachment for vertical mill</td> +<td class="right"><a href="#Pg_259">259</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Gisholt vertical boring mill, general description</td> +<td class="right"><a href="#Pg_242">242</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Grinder for truing lathe centers</td> +<td class="right"><a href="#Pg_34">34</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Grinding lathe tools</td> +<td class="right"><a href="#Pg_62">62</a></td> +</tr> + +<tr> +<td colspan="3"> </td> +</tr> + +<tr> +<td colspan="2" class="left" valign="bottom"><span class="dropcap">H</span>artness flat turret lathe, example of turning</td> +<td class="right" valign="bottom"><a href="#Pg_213">213</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Hendey relieving attachment</td> +<td class="right"><a href="#Pg_123">123</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">application of, for relieving taps, cutters and hobs</td> +<td class="right"><a href="#Pg_125">125</a></td> +</tr> + +<tr> +<td colspan="2" class="left">“Hold-back” or “bridle” for lathe</td> +<td class="right"><a href="#Pg_26">26</a>, <a href="#Pg_27">27</a> +<span class="pagenum"><a name="Pg_303" id="Pg_303">[303]</a></span></td> +</tr> + +<tr> +<td colspan="2" class="left">Hollow mills for turret lathe</td> +<td class="right"><a href="#Pg_198">198</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Horizontal boring machine</td> +<td class="right"><a href="#Pg_275">275</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">Detrick & Harvey floor type</td> +<td class="right"><a href="#Pg_294">294</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">examples of work</td> +<td class="right"><a href="#Pg_289">289-297</a></td> +</tr> + +<tr> +<td colspan="3"> </td> +</tr> + +<tr> +<td colspan="2" class="left" valign="bottom"><span class="dropcap">I</span>ndependent chuck for lathe</td> +<td class="right" valign="bottom"><a href="#Pg_36">36</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Index plate, change gear, for lathe</td> +<td class="right"><a href="#Pg_137">137</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Indicator, center, use on lathe</td> +<td class="right"><a href="#Pg_100">100</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">for “catching threads” when screw cutting</td> +<td class="right"><a href="#Pg_141">141</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">test, truing buttons with</td> +<td class="right"><a href="#Pg_102">102</a>, <a href="#Pg_103">103</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">thread, for lathe apron, principle of</td> +<td class="right"><a href="#Pg_142">142</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Inserted cutter turning tools for lathe</td> +<td class="right"><a href="#Pg_58">58</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Internal threading</td> +<td class="right"><a href="#Pg_154">154</a></td> +</tr> + +<tr> +<td colspan="3"> </td> +</tr> + +<tr> +<td colspan="2" class="left" valign="bottom"><span class="dropcap">J</span>ones & Lamson double-spindle flat turret lathe</td> +<td class="right" valign="bottom"><a href="#Pg_221">221</a></td> +</tr> + +<tr> +<td colspan="3"> </td> +</tr> + +<tr> +<td colspan="2" class="left" valign="bottom"><span class="dropcap">K</span>nurling in lathe and tool used</td> +<td class="right" valign="bottom"><a href="#Pg_122">122</a></td> +</tr> + +<tr> +<td colspan="3"> </td> +</tr> + +<tr> +<td colspan="2" class="left" valign="bottom"><span class="dropcap">L</span>ard oil as a cutting lubricant</td> +<td class="right" valign="bottom"><a href="#Pg_78">78</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Lathe, boring holes to given center distance in</td> +<td class="right"><a href="#Pg_51">51</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">boring large castings in</td> +<td class="right"><a href="#Pg_49">49</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">boring small hole with</td> +<td class="right"><a href="#Pg_104">104</a>, <a href="#Pg_105">105</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">cutting threads in</td> +<td class="right"><a href="#Pg_135">135</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">drilling small hole with</td> +<td class="right"><a href="#Pg_104">104</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">general description of Bradford</td> +<td class="right"><a href="#Pg_1">1</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">LeBlond crankshaft, operation of</td> +<td class="right"><a href="#Pg_110">110</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">Lo-swing, general description</td> +<td class="right"><a href="#Pg_115">115</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">method of handling when cutting threads</td> +<td class="right"><a href="#Pg_138">138</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">quick change-gear type</td> +<td class="right"><a href="#Pg_173">173</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">R. K. LeBlond special crankshaft</td> +<td class="right"><a href="#Pg_108">108</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">turret type, general description</td> +<td class="right"><a href="#Pg_178">178</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Lathe centers, grinder for truing</td> +<td class="right"><a href="#Pg_34">34</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Lathe chucks, application of</td> +<td class="right"><a href="#Pg_37">37</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">universal, independent and combination</td> +<td class="right"><a href="#Pg_36">36</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Lathe faceplate, holding work on</td> +<td class="right"><a href="#Pg_45">45</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Lathe follow-rest</td> +<td class="right"><a href="#Pg_27">27</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Lathe steadyrest</td> +<td class="right"><a href="#Pg_23">23</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">application of, when boring</td> +<td class="right"><a href="#Pg_25">25</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Lathe taper attachment</td> +<td class="right"><a href="#Pg_88">88</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">practical application of</td> +<td class="right"><a href="#Pg_90">90</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Lathe tool grinding</td> +<td class="right"><a href="#Pg_62">62</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Lathe tools, angle of clearance</td> +<td class="right"><a href="#Pg_66">66</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">angle of keenness</td> +<td class="right"><a href="#Pg_67">67</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">application of various types</td> +<td class="right"><a href="#Pg_56">56</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">slope of cutting edge</td> +<td class="right"><a href="#Pg_66">66</a>, <a href="#Pg_67">67</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Lathe turning tools, inserted-cutter type</td> +<td class="right"><a href="#Pg_58">58</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">set of tools for general work</td> +<td class="right"><a href="#Pg_54">54</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Lead of thread, definition of</td> +<td class="right"><a href="#Pg_146">146</a></td> +</tr> + +<tr> +<td colspan="2" class="left">LeBlond, R. K., lathe for crankshaft turning</td> +<td class="right"><a href="#Pg_108">108</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Left-hand thread, method of cutting +<span class="pagenum"><a name="Pg_304" id="Pg_304">[304]</a></span></td> +<td class="right"><a href="#Pg_148">148</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Lining, fixture for holding when boring</td> +<td class="right"><a href="#Pg_293">293</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Lo-swing lathe, general description</td> +<td class="right"><a href="#Pg_115">115</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">example of multiple-turning</td> +<td class="right"><a href="#Pg_117">117</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Lubricant, effect on cutting speed</td> +<td class="right"><a href="#Pg_76">76</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">for cooling turning tools</td> +<td class="right"><a href="#Pg_77">77</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">for machining aluminum</td> +<td class="right"><a href="#Pg_53">53</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">lard oil as a cutting</td> +<td class="right"><a href="#Pg_78">78</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Lucas horizontal boring machine</td> +<td class="right"><a href="#Pg_275">275</a></td> +</tr> + +<tr> +<td colspan="3"> </td> +</tr> + +<tr> +<td colspan="2" class="left" valign="bottom"><span class="dropcap">M</span>andrel or arbor press</td> +<td class="right" valign="bottom"><a href="#Pg_22">22</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">Mandrels or arbors for lathe work, types of</td> +<td class="right"><a href="#Pg_19">19</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">for lathe work, use of</td> +<td class="right"><a href="#Pg_17">17</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Metric pitches, change gears for cutting</td> +<td class="right"><a href="#Pg_171">171</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Micrometer for measuring threads</td> +<td class="right"><a href="#Pg_162">162</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Mills, hollow, for turret lathe</td> +<td class="right"><a href="#Pg_198">198</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Multiple-spindle chucking machine, New Britain</td> +<td class="right"><a href="#Pg_238">238</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Multiple-thread cutting, indexing faceplate for</td> +<td class="right"><a href="#Pg_153">153</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Multiple threads</td> +<td class="right"><a href="#Pg_146">146</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">method of cutting</td> +<td class="right"><a href="#Pg_150">150</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">setting tool when cutting</td> +<td class="right"><a href="#Pg_152">152</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Multiple-turning in Lo-swing lathe</td> +<td class="right"><a href="#Pg_117">117</a></td> +</tr> + +<tr> +<td colspan="3"> </td> +</tr> + +<tr> +<td colspan="2" class="left" valign="bottom"><span class="dropcap">N</span>ew Britain multiple-spindle chucking machine</td> +<td class="right" valign="bottom"><a href="#Pg_238">238</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">Newall Engineering Co's fit allowances</td> +<td class="right"><a href="#Pg_131">131</a></td> +</tr> + +<tr> +<td colspan="3"> </td> +</tr> + +<tr> +<td colspan="2" class="left" valign="bottom"><span class="dropcap">P</span>istons, gasoline engine, turning in turret lathe</td> +<td class="right" valign="bottom"><a href="#Pg_204">204</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">Piston rings, attachment for turning in turret lathe</td> +<td class="right"><a href="#Pg_210">210</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">turning in turret lathe</td> +<td class="right"><a href="#Pg_206">206</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Piston turning in Pratt & Whitney turret lathe</td> +<td class="right"><a href="#Pg_208">208</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Pitch, metric, change gears for cutting</td> +<td class="right"><a href="#Pg_171">171</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Pitch of thread, definition of</td> +<td class="right"><a href="#Pg_146">146</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Plug gage, standard</td> +<td class="right"><a href="#Pg_42">42</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Polishing and filing in lathe</td> +<td class="right"><a href="#Pg_13">13</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Potter & Johnston automatic chucking and turning machine</td> +<td class="right"><a href="#Pg_223">223</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">method of “setting-up”</td> +<td class="right"><a href="#Pg_227">227</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">turning flywheel in</td> +<td class="right"><a href="#Pg_236">236</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Pratt & Whitney turret lathe, arranged for piston turning</td> +<td class="right"><a href="#Pg_208">208</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">equipped with piston ring turning attachment</td> +<td class="right"><a href="#Pg_210">210</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Press for arbors or mandrels</td> +<td class="right"><a href="#Pg_22">22</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Pressure generally used in assembling forced fits</td> +<td class="right"><a href="#Pg_132">132</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Push fits, allowances for</td> +<td class="right"><a href="#Pg_131">131</a></td> +</tr> + +<tr> +<td colspan="3"> </td> +</tr> + +<tr> +<td colspan="2" class="left" valign="bottom"><span class="dropcap">Q</span>uick change-gear type of lathe</td> +<td class="right" valign="bottom"><a href="#Pg_173">173</a></td> +</tr> + +<tr> +<td colspan="3"> </td> +</tr> + +<tr> +<td colspan="2" class="left" valign="bottom"><span class="dropcap">R</span>eamer holders, floating type</td> +<td class="right" valign="bottom"><a href="#Pg_271">271</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">Reaming and drilling in lathe</td> +<td class="right"><a href="#Pg_43">43</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Releasing die and tap holders</td> +<td class="right"><a href="#Pg_199">199</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Relieving attachment, Hendey</td> +<td class="right"><a href="#Pg_123">123</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">application of +<span class="pagenum"><a name="Pg_305" id="Pg_305">[305]</a></span></td> +<td class="right"><a href="#Pg_125">125</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Relieving hobs or taps having spiral flutes</td> +<td class="right"><a href="#Pg_128">128</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Rivett-Dock threading tool</td> +<td class="right"><a href="#Pg_164">164</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Roughing and finishing cuts in lathe</td> +<td class="right"><a href="#Pg_75">75</a>, <a href="#Pg_76">76</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Running fits, allowances for</td> +<td class="right"><a href="#Pg_131">131</a></td> +</tr> + +<tr> +<td colspan="3"> </td> +</tr> + +<tr> +<td colspan="2" class="left" valign="bottom"><span class="dropcap">S</span>crew cutting, calculating change gears for</td> +<td class="right" valign="bottom"><a href="#Pg_167">167</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">compound gearing for</td> +<td class="right"><a href="#Pg_170">170</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">in engine lathe</td> +<td class="right"><a href="#Pg_135">135</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">method of handling lathe</td> +<td class="right"><a href="#Pg_138">138</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">selecting change gears for</td> +<td class="right"><a href="#Pg_135">135</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">with compound rest</td> +<td class="right"><a href="#Pg_143">143</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Screws, cutting to compensate for shrinkage</td> +<td class="right"><a href="#Pg_165">165</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">metric, change gears for cutting</td> +<td class="right"><a href="#Pg_171">171</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">testing size of</td> +<td class="right"><a href="#Pg_161">161</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Selecting type of turning machine</td> +<td class="right"><a href="#Pg_240">240</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Shrinkage, cutting screws to compensate for</td> +<td class="right"><a href="#Pg_165">165</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Shrinkage fits, allowances for</td> +<td class="right"><a href="#Pg_133">133</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Side-tool, facing with</td> +<td class="right"><a href="#Pg_7">7</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Speeds for turning, average</td> +<td class="right"><a href="#Pg_72">72</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">based on Taylor's experiments</td> +<td class="right"><a href="#Pg_71">71</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">effect of lubricant</td> +<td class="right"><a href="#Pg_76">76</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">factors which limit</td> +<td class="right"><a href="#Pg_72">72</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">rules for calculating</td> +<td class="right"><a href="#Pg_74">74</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Spherical turning</td> +<td class="right"><a href="#Pg_111">111</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">attachments for</td> +<td class="right"><a href="#Pg_113">113</a></td> +</tr> + +<tr> +<td colspan="2" class="left">“Spider” for supporting bushing while turning</td> +<td class="right"><a href="#Pg_48">48</a>, <a href="#Pg_49">49</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Spiral flutes, method of relieving hobs or taps with</td> +<td class="right"><a href="#Pg_128">128</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Square thread and method of cutting</td> +<td class="right"><a href="#Pg_149">149</a>, <a href="#Pg_159">159</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Steadyrest, application of when boring</td> +<td class="right"><a href="#Pg_25">25</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">for engine lathe</td> +<td class="right"><a href="#Pg_23">23</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Stop for lathe cross-slide when threading</td> +<td class="right"><a href="#Pg_155">155</a></td> +</tr> + +<tr> +<td colspan="3"> </td> +</tr> + +<tr> +<td colspan="2" class="left" valign="bottom"><span class="dropcap">T</span>ap and die holders, releasing type</td> +<td class="right" valign="bottom"><a href="#Pg_199">199</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Taper attachment for lathe</td> +<td class="right"><a href="#Pg_88">88</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">practical application of</td> +<td class="right"><a href="#Pg_90">90</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Taper boring with taper attachment</td> +<td class="right"><a href="#Pg_90">90</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Taper threading, position of tool for</td> +<td class="right"><a href="#Pg_154">154</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Taper turning, adjustment of tailstock center for</td> +<td class="right"><a href="#Pg_82">82</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">by offset-center method</td> +<td class="right"><a href="#Pg_80">80</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">examples of</td> +<td class="right"><a href="#Pg_83">83</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">height of tool for</td> +<td class="right"><a href="#Pg_94">94</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">in vertical boring mill</td> +<td class="right"><a href="#Pg_261">261</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">in vertical mill with horizontal and vertical feeds</td> +<td class="right"><a href="#Pg_262">262</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">setting tailstock center with caliper tool</td> +<td class="right"><a href="#Pg_85">85</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">setting tailstock center with square</td> +<td class="right"><a href="#Pg_87">87</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">with compound rest</td> +<td class="right"><a href="#Pg_95">95</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">with taper attachment</td> +<td class="right"><a href="#Pg_92">92</a>, <a href="#Pg_93">93</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Tapers, gage for accurate measurement of</td> +<td class="right"><a href="#Pg_97">97</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">rules for figuring +<span class="pagenum"><a name="Pg_306" id="Pg_306">[306]</a></span></td> +<td class="right"><a href="#Pg_97">97</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Test indicator, truing buttons with</td> +<td class="right"><a href="#Pg_102">102</a>, <a href="#Pg_103">103</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Test or center indicator for use on lathe</td> +<td class="right"><a href="#Pg_100">100</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Thread cutting, calculating change gears for</td> +<td class="right"><a href="#Pg_167">167</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">compound gearing for</td> +<td class="right"><a href="#Pg_170">170</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">cross-slide stop used for</td> +<td class="right"><a href="#Pg_155">155</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">indexing faceplate for multiple threads</td> +<td class="right"><a href="#Pg_153">153</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">in engine lathe</td> +<td class="right"><a href="#Pg_135">135</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">internal</td> +<td class="right"><a href="#Pg_154">154</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">method of handling lathe</td> +<td class="right"><a href="#Pg_138">138</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">selecting change gears for</td> +<td class="right"><a href="#Pg_135">135</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">taper, position of tool for</td> +<td class="right"><a href="#Pg_154">154</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">with compound rest</td> +<td class="right"><a href="#Pg_143">143</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Thread gage, Acme standard</td> +<td class="right"><a href="#Pg_157">157</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Thread indicator for lathe apron</td> +<td class="right"><a href="#Pg_141">141</a>, <a href="#Pg_142">142</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Thread micrometer</td> +<td class="right"><a href="#Pg_162">162</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Thread tool, Acme, measuring width with vernier caliper</td> +<td class="right"><a href="#Pg_157">157</a>, <a href="#Pg_158">158</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">for cutting V-thread</td> +<td class="right"><a href="#Pg_138">138</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Thread tools for standard threads</td> +<td class="right"><a href="#Pg_159">159</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Threads, Acme standard, and tool for cutting</td> +<td class="right"><a href="#Pg_159">159</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">change gears for fractional</td> +<td class="right"><a href="#Pg_171">171</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">cutting to compensate for shrinkage</td> +<td class="right"><a href="#Pg_165">165</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">different forms of</td> +<td class="right"><a href="#Pg_144">144</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">left-hand, method of cutting</td> +<td class="right"><a href="#Pg_148">148</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">metric, change gears for cutting</td> +<td class="right"><a href="#Pg_171">171</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">multiple</td> +<td class="right"><a href="#Pg_146">146</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">multiple, method of cutting</td> +<td class="right"><a href="#Pg_150">150</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">multiple, setting tool when cutting</td> +<td class="right"><a href="#Pg_152">152</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">sharp V, and tool for cutting</td> +<td class="right"><a href="#Pg_159">159</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">square, and method of cutting</td> +<td class="right"><a href="#Pg_149">149</a>, <a href="#Pg_159">159</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">testing size of</td> +<td class="right"><a href="#Pg_161">161</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">three-wire system for measuring</td> +<td class="right"><a href="#Pg_163">163</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">U. S. standard, and tool for cutting</td> +<td class="right"><a href="#Pg_146">146</a>, <a href="#Pg_159">159</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">Whitworth standard, and tool for cutting</td> +<td class="right"><a href="#Pg_158">158</a>, <a href="#Pg_159">159</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">worm, and tool for cutting</td> +<td class="right"><a href="#Pg_159">159</a>, <a href="#Pg_160">160</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Threading attachment, lathe, for coarse threads</td> +<td class="right"><a href="#Pg_160">160</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Threading tool, Rivett-Dock</td> +<td class="right"><a href="#Pg_164">164</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Tool grinding</td> +<td class="right"><a href="#Pg_62">62</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Tools for lathe, set for general turning</td> +<td class="right"><a href="#Pg_54">54</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Tools for turning, angle of clearance</td> +<td class="right"><a href="#Pg_66">66</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">angle of keenness</td> +<td class="right"><a href="#Pg_67">67</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">inserted-cutter type</td> +<td class="right"><a href="#Pg_58">58</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">slope of cutting edge</td> +<td class="right"><a href="#Pg_66">66</a>, <a href="#Pg_67">67</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Tools for turret lathe</td> +<td class="right"><a href="#Pg_190">190</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Tools, lathe, application of various types</td> +<td class="right"><a href="#Pg_56">56</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Turning, cylindrical, simple example of</td> +<td class="right"><a href="#Pg_6">6</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">eccentric</td> +<td class="right"><a href="#Pg_106">106</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">multiple, in Lo-swing lathe</td> +<td class="right"><a href="#Pg_117">117</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">with front and rear tools</td> +<td class="right"><a href="#Pg_114">114</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Turning speeds, average for lathe +<span class="pagenum"><a name="Pg_307" id="Pg_307">[307]</a></span></td> +<td class="right"><a href="#Pg_72">72</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">based on Taylor's experiments</td> +<td class="right"><a href="#Pg_71">71</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">factors which limit</td> +<td class="right"><a href="#Pg_72">72</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">rules for calculating</td> +<td class="right"><a href="#Pg_74">74</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Turning tools, angle of clearance</td> +<td class="right"><a href="#Pg_66">66</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">angle of keenness</td> +<td class="right"><a href="#Pg_67">67</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">for aluminum</td> +<td class="right"><a href="#Pg_53">53</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">for brass</td> +<td class="right"><a href="#Pg_52">52</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">for copper</td> +<td class="right"><a href="#Pg_52">52</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">for lathe, position of</td> +<td class="right"><a href="#Pg_60">60</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">for lathe, set of, for general work</td> +<td class="right"><a href="#Pg_54">54</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">inserted-cutter type for lathe</td> +<td class="right"><a href="#Pg_58">58</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">slope of cutting edge</td> +<td class="right"><a href="#Pg_66">66</a>, <a href="#Pg_67">67</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Turret lathe, Bardons & Oliver, general description</td> +<td class="right"><a href="#Pg_178">178</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">examples of chuck work in Acme flat</td> +<td class="right"><a href="#Pg_219">219</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">Hartness flat, example of turning</td> +<td class="right"><a href="#Pg_213">213</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">Jones & Lamson double-spindle type</td> +<td class="right"><a href="#Pg_221">221</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">machining flywheels in</td> +<td class="right"><a href="#Pg_184">184</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">Pratt & Whitney arranged for piston turning</td> +<td class="right"><a href="#Pg_208">208</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">piston ring turning attachment for</td> +<td class="right"><a href="#Pg_210">210</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">tools for general work</td> +<td class="right"><a href="#Pg_190">190</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">turning bevel gear blanks in Davis</td> +<td class="right"><a href="#Pg_212">212</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">turning gasoline engine pistons in</td> +<td class="right"><a href="#Pg_204">204</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">turning piston rings in</td> +<td class="right"><a href="#Pg_206">206</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">turning worm-gear blanks in Davis</td> +<td class="right"><a href="#Pg_211">211</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">typical example of turret lathe work</td> +<td class="right"><a href="#Pg_181">181</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Turret lathe tools, miscellaneous types</td> +<td class="right"><a href="#Pg_202">202</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Turret lathe type of vertical boring mill</td><td class="right"><a href="#Pg_264">264</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Type of turning machine, factors which govern selection</td> +<td class="right"><a href="#Pg_240">240</a></td> +</tr> + +<tr> +<td colspan="3"> </td> +</tr> + +<tr> +<td colspan="2" class="left" valign="bottom"><span class="dropcap">U</span>. S. standard thread</td> +<td class="right" valign="bottom"><a href="#Pg_159">159</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">method of cutting</td> +<td class="right"><a href="#Pg_146">146</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Universal chuck for lathe</td> +<td class="right"><a href="#Pg_36">36</a></td> +</tr> + +<tr> +<td colspan="3"> </td> +</tr> + +<tr> +<td colspan="2" class="left" valign="bottom"><span class="dropcap">V</span>-thread and tool for cutting</td> +<td class="right" valign="bottom"><a href="#Pg_159">159</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Vertical boring mill, Bullard turret lathe type</td> +<td class="right"><a href="#Pg_264">264</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">convex turning attachment</td> +<td class="right"><a href="#Pg_259">259</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">general description</td> +<td class="right"><a href="#Pg_242">242</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">holding and setting work</td> +<td class="right"><a href="#Pg_247">247</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">taper turning in</td> +<td class="right"><a href="#Pg_261">261</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">taper turning with horizontal and vertical feeds</td> +<td class="right"><a href="#Pg_262">262</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">tools for boring and reaming</td> +<td class="right"><a href="#Pg_251">251</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">turning flywheel in</td> +<td class="right"><a href="#Pg_255">255</a></td> +</tr> + +<tr> +<td> </td> +<td class="left">turning tools for</td> +<td class="right"><a href="#Pg_253">253</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Vertical turret lathe, Bullard, examples of work</td> +<td class="right"><a href="#Pg_268">268</a></td> +</tr> + +<tr> +<td colspan="3"> </td> +</tr> + +<tr> +<td colspan="2" class="left" valign="bottom"><span class="dropcap">W</span>hitworth standard thread and tool for cutting</td> +<td class="right" valign="bottom"><a href="#Pg_158">158</a>, <a href="#Pg_159">159</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Wire system for measuring threads</td> +<td class="right"><a href="#Pg_163">163</a></td> +</tr> + +<tr> +<td colspan="2" class="left">Worm thread and tool for cutting</td> +<td class="right"><a href="#Pg_159">159</a>, <a href="#Pg_160">160</a></td> +</tr> + +</table> + +<p> </p> +<hr class="c25" /> +<p> </p> + +<div class="tnbox"> + +<p class="center"><b>Transcriber's notes:</b></p> + +<ul> + + <li>Inconsistencies encountered: + + <ul> + <li>Left as in original: + <ul> + <li>use of degree, deg. and °;</li> + <li>use of minute, min. and '.</li> + </ul> + </li> + </ul> + + <ul> + <li>Standardised to the most commonly used in the book: + <ul> + <li>backgear(s) to back-gear(s);</li> + <li>camshaft to cam-shaft;</li> + <li>crankpin to crank-pin;</li> + <li>face-plate to faceplate;</li> + <li>out-board to outboard;</li> + <li>over-hang to overhang;</li> + <li>setscrew to set-screw;</li> + <li>steady-rest to steadyrest;</li> + <li>subdivision(s) to sub-division(s);</li> + <li>tail-stock to tailstock;</li> + <li>thumbscrew to thumb-screw;</li> + <li>tool-post to toolpost;</li> + <li>tool-slide to toolslide;</li> + <li>hand-wheel to handwheel;</li> + <li>U.S. to U. S.</li> + </ul> + </li> + </ul> + </li> + <li>Page 64 had a blotched (illegible) word, this has been replaced by (large and rigid) <i>work</i>.</li> + <li>Table of Contents: largely re-compiled to create one-to-one links with named paragraphs and sections in text.</li> + <li>Illustrations: generally moved to the paragraph they refer to.</li> +</ul> + +</div> + + + + + + + + +<pre> + + + + + +End of the Project Gutenberg EBook of Turning and Boring, by Franklin D. 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