Lathe How To Use 1

8/12/2019 Lathe How To Use 1

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INSTRUCTIONS TO LEARN HO TO USE A LATHE

PAGE 1 OF 2This webpage is best printed in Landscape format.

This information was originally compiled by the ! Army.

The lathe is a machine tool "sed principally for shaping pieces of metal #and sometimes wood orother materials$ by ca"sing the wor%piece to be held and rotated by the lathe while a tool bit isad&anced into the wor% ca"sing the c"tting action. The basic lathe that was designed to c"tcylindrical metal stoc% has been de&eloped f"rther to prod"ce screw threads' tapered wor%' drilledholes' %n"rled s"rfaces' and cran%shafts. (odern lathes offer a &ariety of rotating speeds and ameans to man"ally and a"tomatically mo&e the c"tting tool into the wor%piece. (achinists andmaintenance shop personnel m"st be thoro"ghly familiar with the lathe and its operations to

accomplish the repair and fabrication of needed parts.

T!"ES O# LATHES

Lathes can be di&ided into three types for easy identification) engine lathe' t"rret lathe' andspecial p"rpose lathes. !ome smaller ones are bench mo"nted and semi*portable. The largerlathes are floor mo"nted and may re+"ire special transportation if they m"st be mo&ed. Field andmaintenance shops generally "se a lathe that can be adapted to many operations and that is nottoo large to be mo&ed from one wor% site to another. The engine lathe #Fig"re ,*1$ is ideallys"ited for this p"rpose. A trained operator can accomplish more machining -obs with the enginelathe than with any other machine tool. T"rret lathes and special p"rpose lathes are "s"ally "sedin prod"ction or -ob shops for mass prod"ction or specialied parts' while basic engine lathes are"s"ally "sed for any type of lathe wor%. F"rther reference to lathes in this chapter will be abo"tthe &ario"s engine lathes.



EN$INE LATHES

Si%es

The sie of an engine lathe is determined by the largest piece of stoc% that can be machined./efore machining a wor%piece' the following meas"rements m"st be considered) the diameter of the wor% that will swing o&er the bed and the length between lathe centers #Fig"re ,*1$.

Cate&ories

!light differences in the &ario"s engine lathes ma%e it easy to gro"p them into three categories)lightweight bench engine lathes' precision tool room lathes' and gap lathes' which are also %nown

as e0tension*type lathes. These lathe categories are shown in Fig"re ,*2 ifferent man"fact"rersmay "se different lathe categories.

Li&ht'ei&ht

Lightweight bench engine lathes are generally small lathes with a swing of 1 inches or less'



mo"nted to a bench or table top. These lathes can accomplish most machining -obs' b"t may belimited d"e to the sie of the material that can be t"rned.

"re(ision

Precision tool room lathes are also %nown as standard man"fact"ring lathes and are "sed for alllathe operations' s"ch as t"rning' boring' drilling' reaming' prod"cing screw threads' taper t"rning'%n"rling' and radi"s forming' and can be adapted for special milling operations with the

appropriate fi0t"re. This type of lathe can handle wor%pieces "p to 23 inches in diameter and "pto 2 inches long. 4owe&er' the general sie is abo"t a 13*inch swing with 56 to 78 inchesbetween centers. (any tool room lathes are "sed for special tool and die prod"ction d"e to thehigh acc"racy of the machine.

$A" OR E)TENSION-T!"E LATHES

Gap or e0tension*type lathes are similar to toolroom lathes e0cept that gap lathes can bead-"sted to machine larger diameter and longer wor%pieces The operator can increase the swingby mo&ing the bed a distance from the headstoc%' which is "s"ally one or two feet. /y sliding thebed away from the headstoc%' the gap lathe can be "sed to t"rn &ery long wor%pieces between

centers.

LATHE COM"ONENTS

Engine lathes all ha&e the same general f"nctional parts' e&en tho"gh the specific location orshape of a certain part may differ from one man"fact"rer The bed is the fo"ndation of the

wor%ing parts of the lathe to another #Fig"re ,*5$.

The main feat"re of its constr"ction are the ways which are formed on its "pper s"rface and r"nthe f"ll length of the bed.

9ays pro&ide the means for holding the tailstoc% and carriage' which slide along the ways' inalignment with the permanently attached headstoc%

The headstoc% is located on the operator:s left end of the lathe bed. ;t contains the main spindleand oil reser&oir and the gearing mechanism for obtaining &ario"s spindle speeds and fortransmitting power to the feeding and threading mechanism. The headstoc% mechanism is dri&enby an electric motor connected either to a belt or p"lley system or to a geared system. The mainspindle is mo"nted on bearings in the headstoc% and is hardened and specially gro"nd to fit



different lathe holding de&ices. The spindle has a hole thro"gh its entire length to accommodatelong wor%pieces. The hole in the nose of the spindle "s"ally has a standard (orse taper which&aries with the sie of the lathe. <enters' collets' drill ch"c%s' tapered shan% drills and reamersmay be inserted into the spindle. <h"c%s' dri&e plates' and faceplates may be screwed onto thespindle or clamped onto the spindle nose.

The tailstoc% is located on the opposite end of the lathe from the headstoc%. ;t s"pports one endof the wor% when machining between centers' s"pports long pieces held in the ch"c%' and holds

&ario"s forms of c"tting tools' s"ch as drills' reamers' and taps. The tailstoc% is mo"nted on theways and is designed to be clamped at any point along the ways. ;t has a sliding spindle that isoperated by a hand wheel and clamped in position by means of a spindle clamp. The tailstoc% may be ad-"sted laterally #toward or away from the operator$ by ad-"sting screws. ;t sho"ld be"nclamped from the ways before any lateral ad-"stments are made' as this will allow the tailstoc% to be mo&ed freely and pre&ent damage to the lateral ad-"stment screws.

The carriage incl"des the apron' saddle' compo"nd rest' cross slide' tool post' and the c"ttingtool. ;t sits across the lathe ways and in front of the lathe bed. The f"nction of the carriage is tocarry and mo&e the c"tting tool. ;t can be mo&ed by hand or by power and can be clamped intoposition with a loc%ing n"t. The saddle carries the cross slide and the compo"nd rest. The cross

slide is mo"nted on the do&etail ways on the top of the saddle and is mo&ed bac% and forth at=> to the a0is of the lathe by the cross slide lead screw. The lead screw can be hand or poweracti&ated. A feed re&ersing le&er' located on the carriage or headstoc%' can be "sed to ca"se thecarriage and the cross slide to re&erse the direction of tra&el. The compo"nd rest is mo"nted onthe cross slide and can be swi&eled and clamped at any angle in a horiontal plane. Thecompo"nd rest is "sed e0tensi&ely in c"tting steep tapers and angles for lathe centers. Thec"tting tool and tool holder are sec"red in the tool post which is mo"nted directly to thecompo"nd rest. The apron contains the gears and feed cl"tches which transmit motion from thefeed rod or lead screw to the carriage and cross slide.

CARE AN* MAINTENANCE O# LATHES

Lathes are highly acc"rate machine tools designed to operate aro"nd the cloc% if properlyoperated and maintained. Lathes m"st be l"bricated and chec%ed for ad-"stment beforeoperation. ;mproper l"brication or loose n"ts and bolts can ca"se e0cessi&e wear and dangero"soperating conditions.

The lathe ways are precision gro"nd s"rfaces and m"st not be "sed as tables for other tools andsho"ld be %ept clean of grit and dirt. The lead screw and gears sho"ld be chec%ed fre+"ently forany metal chips that co"ld be lodged in the gearing mechanisms. <hec% each lathe prior tooperation for any missing parts or bro%en shear pins. ?efer to the operator:s instr"ctions beforeattempting to lift any lathe. @ewly installed lathes or lathes that are transported in mobile &ehiclessho"ld be properly le&eled before any operation to pre&ent &ibration and wobble. Any lathes thatare transported o"t of a normal shop en&ironment sho"ld be protected from d"st' e0cessi&e heat'and &ery cold conditions. <hange the l"bricant fre+"ently if wor%ing in d"sty conditions. ;n hotwor%ing areas' "se care to a&oid o&erheating the motor or damaging any seals. Operate the latheat slower speeds than normal when wor%ing in cold en&ironments.

SA#ET!

All lathe operators m"st be constantly aware of the safety haards that are associated with "singthe lathe and m"st %now all safety preca"tions to a&oid accidents and in-"ries. <arelessness andignorance are two great menaces to personal safety. Other haards can be mechanically relatedto wor%ing with the lathe' s"ch as proper machine maintenance and set"p. !ome important safety

preca"tions to follow when "sing lathes are)

<orrect dress is important' remo&e rings and watches' roll slee&es abo&e elbows.



Always stop the lathe before ma%ing ad-"stments.

o not change spindle speeds "ntil the lathe comes to a complete stop.

4andle sharp c"tters' centers' and drills with care.

?emo&e ch"c% %eys and wrenches before operating

Always wear protecti&e eye protection.

4andle hea&y ch"c%s with care and protect the lathe ways with a bloc% of wood wheninstalling a ch"c%.

now where the emergency stop is before operating the lathe.

se pliers or a br"sh to remo&e chips and swarf' ne&er yo"r hands.

@e&er lean on the lathe.

@e&er lay tools directly on the lathe ways. ;f a separate table is not a&ailable' "se a wide

board with a cleat on each side to lay on the ways.

eep tools o&erhang as short as possible.

@e&er attempt to meas"re wor% while it is t"rning.

@e&er file lathe wor% "nless the file has a handle.

File left*handed if possible.

Protect the lathe ways when grinding or filing.

se two hands when sanding the wor%piece. o not wrap sand paper or emory cloth aro"ndthe wor%piece.

TOOLS AN* E+UI"MENT

$ENERAL "UR"OSE CUTTIN$ TOOLS

The lathe c"tting tool or tool bit m"st be made of the correct material and gro"nd to the correctangles to machine a wor%piece efficiently. The most common tool bit is the general all*p"rpose bitmade of high*speed steel. These tool bits are generally ine0pensi&e' easy to grind on a bench orpedestal grinder' ta%e lots of ab"se and wear' and are strong eno"gh for all*aro"nd repair andfabrication. 4igh*speed steel tool bits can handle the high heat that is generated d"ring c"ttingand are not changed after cooling. These tool bits are "sed for t"rning' facing' boring and otherlathe operations. Tool bits made from special materials s"ch as carbides' ceramics' diamonds' castalloys are able to machine wor%pieces at &ery high speeds b"t are brittle and e0pensi&e fornormal lathe wor%. 4igh*speed steel tool bits are a&ailable in many shapes and sies toaccommodate any lathe operation.

SIN$LE "OINT TOOL ,ITS

!ingle point tool bits can be one end of a high*speed steel tool bit or one edge of a carbide orceramic c"tting tool or insert. /asically' a single point c"tter bit is a tool that has only one c"ttingaction proceeding at a time. A machinist or machine operator sho"ld %now the &ario"s termsapplied to the single point tool bit to properly identify and grind different tool bits #Fig"re ,*7$.

The shan% is the main body of the tool bit.



The nose is the part of the tool bit which is shaped to a point and forms the corner betweenthe side c"tting edge and the end c"tting edge. The nose radi"s is the ro"nded end of thetool bit.

The face is the top s"rface of the tool bit "pon which the chips slide as they separate fromthe wor% piece.

The side or flan% of the tool bit is the s"rface -"st below and ad-acent to the c"tting edge.

The c"tting edge is the part of the tool bit that act"ally c"ts into the wor%piece' locatedbehind the nose and ad-acent to the side and face.

The base is the bottom s"rface of the tool bit' which "s"ally is gro"nd flat d"ring tool bitman"fact"ring.

The end of the tool bit is the near*&ertical s"rface which' with the side of the bit' forms theprofile of the bit. The end is the trailing s"rface of the tool bit when c"tting.

The heel is the portion of the tool bit base immediately below and s"pporting the face.

An&les o Tool ,its

The s"ccessf"l operation of the lathe and the +"ality of wor% that may be achie&ed dependlargely on the angles that form the c"tting edge of the tool bit #Fig"re ,*7$. (ost tools are handgro"nd to the desired shape on a bench or pedestal grinder. The c"tting tool geometry for thera%e and relief angles m"st be properly gro"nd' b"t the o&erall shape of the tool bit is determinedby the preference of the machinist or machine operator. Lathe tool bit shapes can be pointed'

ro"nded' s+"ared off' or irreg"lar in shape and still c"t +"ite well as long as the tool bit angles areproperly gro"nd for the type of material being machined. The angles are the side and bac% ra%eangles' the side and end c"tting edge angles' and the side and end relief angles. Other angles tobe considered are the radi"s on the end of the tool bit and the angle of the tool holder. After%nowing how the angles affect the c"tting action' some recommended c"tting tool shapes can beconsidered.

?a%e angle pertains to the top s"rface of the tool bit. There are two types of ra%e angles' theside and bac% ra%e angles #Fig"re ,*7$. The ra%e angle can be positi&e' negati&e' or ha&e no ra%eangle at all. The tool holder can ha&e an angle' %nown as the tool holder angle' which a&eragesabo"t 13>' depending on the model of tool holder selected. The tool holder angle combines with

the bac% ra%e angle to pro&ide clearance for the heel of the tool bit from the wor%piece and tofacilitate chip remo&al. The side ra%e angle is meas"red bac% from the c"tting edge and can be apositi&e ra%e angle or ha&e no ra%e at all.

?a%e angles cannot be too great or the c"tting edge will lose strength to s"pport the c"tting



action. The side ra%e angle determines the type and sie of chip prod"ced d"ring the c"ttingaction and the direction that the chip tra&els when lea&ing the c"tting tool. <hip brea%ers can beincl"ded in the side ra%e angle to ens"re that the chips brea% "p and do not become a safetyhaard.

!ide and relief angles' or clearance angles' are the angles formed behind and beneath the c"ttingedge that pro&ide clearance or relief to the c"tting action of the tool. There are two types of relief angles' side relief and end relief. !ide relief is the angle gro"nd into the tool bit' "nder the side of

the c"tting edge' to pro&ide clearance in the direction of tool bit tra&el. End relief is the anglegro"nd into the tool bit to pro&ide front clearance to %eep the tool bit heel from r"bbing. The endrelief angle is s"pplemented by the tool holder angle and ma%es "p the effecti&e relief angle forthe end of the tool bit.

!ide and c"tting edge angles are the angles formed by the c"tting edge with the end of the toolbit #the end c"tting edge angle$' or with the side of the tool bit #the side c"tting edge angle$. Theend c"tting edge angle permits the nose of the tool bit to ma%e contact with the wor% and aids infeeding the tool bit into the wor%. The side c"tting edge angle red"ces the press"re on the tool bitas it begins to c"t. The side ra%e angle and the side relief angle combine to form the wedge angle#or lip angle$ of the tool bit that pro&ides for the c"tting action #Fig"re ,*7$.

A radi"s gro"nd onto the nose of the tool bit can help strengthen the tool bit and pro&ide for asmooth c"tting action.

Shapes o Tool ,its

The o&erall shape of the lathe tool bits can be ro"nded' s+"ared' or another shape as long as theproper angles are incl"ded. Tool bits are identified by the f"nction they perform' s"ch as t"rningor facing. They can also be identified as ro"ghing tools or finishing tools. Generally' a ro"ghingtool has a radi"s gro"nd onto the nose of the tool bit that is smaller than the radi"s for a finishingor general*p"rpose tool bit. E0perienced machinists ha&e fo"nd the following shapes to be "sef"lfor different lathe operations.

A right*hand t"rning tool bit is shaped to be fed from right to left. The c"tting edge is on the leftside of the tool bit and the face slopes down away from the c"tting edge. The left side and end of the tool bit are gro"nd with s"fficient clearance to permit the c"tting edge to bear "pon thewor%piece witho"t the heel r"bbing on the wor%. The right*hand t"rning tool bit is ideal for ta%inglight ro"ghing c"ts as well as general all*aro"nd machining.

A left*hand t"rning tool bit is the opposite of the right*hand t"rning tool bit' designed to c"t whenfed from left to right. This tool bit is "sed mainly for machining close in to a right sho"lder.

The ro"nd*nose t"rning tool bit is &ery &ersatile and can be "sed to t"rn in either direction forro"ghing and finishing c"ts. @o side ra%e angle is gro"nd into the top face when "sed to c"t in

either direction' b"t a small bac% ra%e angle may be needed for chip remo&al. The nose radi"s is"s"ally gro"nd in the shape of a half*circle with a diameter of abo"t 1B52 inch.

The right*hand facing tool bit is intended for facing on right*hand side sho"lders and the right endof a wor%piece. The c"tting edge is on the left*hand side of the bit' and the nose is gro"nd &erysharp for machining into a s+"are corner. The direction of feed for this tool bit sho"ld be awayfrom the center a0is of the wor%' not going into the center a0is.

A left*hand facing tool bit is the opposite of the right*hand facing tool bit and is intend to machineand face the left sides of sho"lders.



The parting tool bit' Fig"re ,*6' is also %nown as the c"toff tool bit. This tool bit has the principalc"tting edge at the s+"ared end of the bit that is ad&anced at a right angle into the wor%piece.

/oth sides sho"ld ha&e s"fficient clearance to pre&ent binding and sho"ld be gro"nd slightlynarrower at the bac% than at the c"tting edge. /esides being "sed for parting operations' this tool

bit can be "sed to machine s+"are corners and groo&es.

Thread*c"tting tool bits' Fig"re ,*,' are gro"nd to c"t the type and style of threads desired. !ideand front clearances m"st be gro"nd' pl"s the special point shape for the type of thread desired.



Thread*c"tting tool bits can be gro"nd for standard 6> thread forms or for s+"are' Acme' orspecial threads. Thread*c"tting forms are disc"ssed in greater detail later in this chapter.

S"ECIAL T!"ES O# LATHE CUTTIN$ TOOLS

/esides the common shaped tool bits' special lathe operations and hea&y prod"ction wor% re+"irespecial types of c"tting tools. !ome of the more common of these tools are listed below.

T"ngsten carbide' tantal"m carbide' titani"m carbide' ceramic' o0ide' and diamond*tipped tool bits#Fig"re ,*8$. and c"tting tool inserts are commonly "sed in high*speed prod"ction wor% whenhea&y c"ts are necessary and where e0ceptionally hard and to"gh materials are enco"ntered.!tandard shapes for tipped tool bits are similar to high*speed steel*c"tting tool shapes. <arbideand ceramic inserts can be s+"are' triang"lar' ro"nd' or other shapes. The inserts are designed tobe inde0ed or rotated as each c"tting edge gets d"ll and then discarded. <"tting tool inserts are

not intended for re"se after sharpening.

!pecially formed thread c"tter mo"nted in a thread c"tter holder #Fig"re ,*=$. This tool isdesigned for prod"ction high*speed thread c"tting operations. The special design of the c"tterallows for sharp and strong c"tting edges which need only to be resharpened occasionally bygrinding the face. The c"tter mo"nts into a special tool holder that mo"nts to the lathe tool post.



The common %n"rling tool' Fig"re ,*1' consists of two cylindrical c"tters' called %n"rls' whichrotate in a specially designed tool holder. The %n"rls contain teeth which are rolled against the

s"rface of the wor%piece to form depressed patterns on the wor%piece. The common %n"rling tool

accepts different pairs of %n"rls' each ha&ing a different pattern or pitch. The diamond pattern ismost widely "sed and comes in three pitches) 17' 21' or 55. These pitches prod"ce coarse'

medi"m' and fine %n"rled patterns.

/oring tool bits' Fig"re ,*11' are gro"nd similar to left*hand t"rning tool bits and thread*c"ttingtool bits' b"t with more end clearance angle to pre&ent the heel of the tool bit from r"bbingagainst the s"rface of the bored hole. The boring tool bit is "s"ally clamped to a boring toolholder' b"t it can be a one*piece "nit . The boring tool bit and tool holder clamp into the lathe tool

post.



There is no set proced"re to grinding lathe tool bit angles and shapes' b"t there are generalg"idelines that sho"ld be followed. o not attempt to "se the bench or pedestal grinder witho"tbecoming f"lly ed"cated as to its safety' operation' and capabilities. ;n order to effecti&ely grind atool bit' the grinding wheel m"st ha&e a tr"e and clean face and be of the appropriate materialfor the c"tting tool to be gro"nd. <arbide tool bits m"st be gro"nd on a silicon carbide grindingwheel to remo&e the &ery hard metal.

4igh*speed steel tool bits are the only tool bits that can effecti&ely be gro"nd on the bench orpedestal grinder when e+"ipped with the al"min"m o0ide grinding wheel which is standard formost field and maintenance shops. /efore grinding' shaping' or sharpening a high*speed steel toolbit' inspect the entire grinder for a safe set"p and ad-"st the tool rests and g"ards as needed for

tool bit grinding #Fig"re ,*12$.



!et the tool rest 1B8 inch or less from the wheel' and ad-"st the spar% arrestor 1B7 inch or less.Each grinder is "s"ally e+"ipped with a coarse*grained wheel for ro"gh grinding and afine*grained wheel for fine and finish grinding. ress the face of the grinding wheels as needed to%eep a smooth' flat grinding s"rface for the tool bit. 9hen grinding the side and bac% ra%e angles'ens"re the grinding wheel has a sharp corner for shaping the angle. ip the tool bit in wateroccasionally while grinding to %eep the tool bit cool eno"gh to handle and to a&oid changing theproperty of the metal by o&erheating. Fre+"ently inspect the tool bit angles with a protractor orspecial grinding gage. Grind the tool bit to the recommended angles in the reference for tool bitgeometry #Table ,*l in Appendi0 A$. After grinding to the finished shape' the tool bit sho"ld be

honed lightly on an oilstone to remo&e any b"rrs or irreg"lar high spots. The smoother the finishon the c"tting tool' the smoother the finish on the wor%. Fig"re ,*15 shows the steps in&ol&ed ingrinding a ro"nd nose tool bit to be "sed for t"rning in either direction. As a safety note' ne&er"se the side of the grinding wheel to grind a tool bit' as this co"ld wea%en the bonding of thewheel and ca"se it to crac% and e0plode.



TOOL HOL*ERS AN* TOOL "OSTS

Lathe tool holders are designed to sec"rely and rigidly hold the tool bit at a fi0ed angle forproperly machining a wor%piece #Fig"re ,*17$. Tool holders are designed to wor% in con-"nction

with &ario"s lathe tool posts' onto which the tool holders are mo"nted. Tool holders for highspeed steel tool bits come in &ario"s types for different "ses. These tool holders are designed tobe "sed with the standard ro"nd tool post that "s"ally is s"pplied with each engine lathe #Fig"re

,*13 $. This tool post consists of the post' screw' washer' collar' and roc%er' and fits into the T*slotof the compo"nd rest.



!tandard tool holders for high*speed steel c"tting tools ha&e a s+"are slot made to fit a standardsie tool bit shan%. Tool bit shan%s can be 1B7*inch' 3B16*inch' 5B8*inch' and greater' with all the&ario"s sies being man"fact"red for all the different lathe man"fact"rer:s tool holder models.!ome standard tool holders for steel tool bits are the straight tool holder' right and left offset toolholder' and the ero ra%e tool holder designed for special carbide tool bits. Other tool holders to f itthe standard ro"nd tool post incl"de straight' left' and right parting tool holders' %n"rling toolholders' boring bar tool holders' and specially formed thread c"tting tool holders.

The t"rret tool post #Fig"re ,*16 $ is a swi&eling bloc% that can hold many different tool bits ortool holders. Each c"tting tool can +"ic%ly be swi&eled into c"tting position and clamped into place"sing a +"ic% clamping handle. The t"rret tool post is "sed mainly for high*speed prod"ction

operations.



The hea&y*d"ty or open*sided tool post #Fig"re ,*1,$ is "sed for holding a single carbide*tippedtool bit or tool holder. ;t is "sed mainly for &ery hea&y c"ts that re+"ire a rigid tool holder.

The +"ic%*change tool system #Fig"re ,*18$ consists of a +"ic%*change do&etail tool post with acomplete set of matching do&etailed tool holders that can be +"ic%ly changed as different latheoperations become necessary. This system has a +"ic%*release %nob on the top of the tool postthat allows tool changes in less than 3 seconds' which ma%es this system &al"able for prod"ctionmachine shops.



OR. HOL*IN$ *E/ICES

(any different de&ices' s"ch as ch"c%s' collets' faceplates' dri&e plates' mandrels' and lathecenters' are "sed to hold and dri&e the wor% while it is being machined on a lathe. The sie andtype of wor% to be machined and the partic"lar operation that needs to be done will determinewhich wor% holding de&ice is best for any partic"lar -ob. Another consideration is how m"chacc"racy is needed for a -ob' since some wor% holding de&ices are more acc"rate than others.Operational details for some of the more common wor% holding de&ices follow.

The "ni&ersal scroll ch"c%' Fig"re ,*1=' "s"ally has three -aws which mo&e in "nison as anad-"sting pinion is rotated. The ad&antage of the "ni&ersal scroll ch"c% is its ease of operation incentering wor% for concentric t"rning. This ch"c% is not as acc"rate as the independent ch"c%' b"twhen in good condition it will center wor% within .2 to .5 inches of r"no"t.



The -aws are mo&ed sim"ltaneo"sly within the ch"c% by a scroll or spiral*threaded plate. The -aws

are threaded to the scroll and mo&e an e+"al distance inward or o"tward as the scroll is rotatedby the ad-"sting pinion. !ince the -aws are indi&id"ally aligned on the scroll' the -aws cannot"s"ally be re&ersed. !ome man"fact"res s"pply two sets of -aws' one for internal wor% and onefor e0ternal wor%. Other man"fact"res ma%e the -aws in two pieces so the o"tside' or grippings"rface may be re&ersed. which can be interchanged.

The "ni&ersal scroll ch"c% can be "sed to hold and a"tomatically center ro"nd or he0agonalwor%pieces. 4a&ing only three -aws' the ch"c% cannot be "sed effecti&ely to hold s+"are'octagonal' or irreg"lar shapes.

The independent ch"c%' Fig"re ,*1=' generally has fo"r -aws which are ad-"sted indi&id"ally onthe ch"c% face by means of ad-"sting screws. The ch"c% face is scribed with concentric circles

which are "sed for ro"gh alignment of the -aws when ch"c%ing ro"nd wor%pieces. The finalad-"stment is made by t"rning the wor%piece slowly by hand and "sing a dial indicator todetermine it:s concentricity. The -aws are then read-"sted as necessary to align the wor%piecewithin the desired tolerances.



The -aws of the independent ch"c% may be "sed as ill"strated or may be re&ersed so that thesteps face in the opposite directionC th"s wor%pieces can be gripped either e0ternally or internally.The independent ch"c% can be "sed to hold s+"are' ro"nd' octagonal' or irreg"larly shapedwor%pieces in either a concentric or eccentric position d"e to the independent operation of each -aw.

/eca"se of its &ersatility and capacity for fine ad-"stment' the independent ch"c% is commonly"sed for mo"nting odd*shaped wor%pieces which m"st be held with e0treme acc"racy.

A combination ch"c% combines the feat"res of the independent ch"c% and the "ni&ersal scrollch"c% and can ha&e either three or fo"r -aws. The -aws can be mo&ed in "nison on a scroll fora"tomatic centering or can be mo&ed indi&id"ally if desired by separate ad-"sting screws.

The drill ch"c%' Fig"re ,*1=' is a small "ni&ersal ch"c% which can be "sed in either the headstoc% spindle or the tailstoc% for holding straight*shan% drills' reamers' taps' or small diameterwor%pieces. The drill ch"c% has three or fo"r hardened steel -aws which are mo&ed together orapart by ad-"sting a tapered slee&e within which they are contained. The drill ch"c% is capable of centering tools and small*diameter wor%pieces to within .2 or .5 inch when firmlytightened.

The collet ch"c% is the most acc"rate means of holding small wor%pieces in the lathe. The colletch"c% consists of a spring machine collet #Fig"re ,*2$ and a collet attachment which sec"res andreg"lates the collet on the headstoc% spindle of the lathe.

The spring machine collet is a thin metal b"shing with an acc"rately machined bore and a tapered

e0terior. The collet has three lengthwise slots to permit its sides being spr"ng slightly inward togrip the wor%piece. To grip the wor%piece acc"rately' the collet m"st be no more than .3 inchlarger or smaller than the diameter of the piece to be ch"c%ed. For this reason' spring machinecollets are a&ailable in increments of 1B67 inch. For general p"rposes' the spring machine collets



are limited in capacity to 1 1B8 inch in diameter.

For general p"rposes' the spring machine collets are limited in capacity to 1 1B8 inch in diameter.

The collet attachment consists of a collet slee&e' a drawbar' and a handwheel or hand le&er tomo&e the drawbar. The spring machine collet and collet attachment together form the colletch"c%. Fig"re ,*2 ill"strates a typical collet ch"c% installation. The collet slee&e is fitted to theright end of the headstoc% spindle. The drawbar passes thro"gh the headstoc% spindle and is

threaded to the spring machine collet. 9hen the drawbar is rotated by means of the hand wheel'it draws the collet into the tapered adapter' ca"sing the collet to tighten on the wor%piece. !pringmachine collets are a&ailable in different shapes to ch"c% s+"are and he0agonal wor%pieces of small dimensions as well as ro"nd wor%pieces.

The Dacob:s spindle*nose collet ch"c% #Fig"re ,*21$ is a special ch"c% is "sed for the Dacob:sr"bber fle0 collets. This ch"c% combines the f"nctions of the standard collet ch"c% and drawbarinto one single compact "nit. The ch"c% ho"sing has a handwheel on the o"ter diameter thatt"rns to tighten or loosen the tapered spindle which holds the r"bber fle0 collets. ?"bber fle0collets are comprised of de&ices made of hardened steel -aws in a solid r"bber ho"sing. Thesecollets ha&e a range of 1B8 inch per collet. The gripping power and acc"racy remain constant

thro"gho"t the entire collet capacity. Dacob:s r"bber fle0 collets are designed for hea&y d"tyt"rning and possess two to fo"r times the grip of the con&entional split steel collet. The differentsets of these collets are stored in steel bo0es designed for holding the collets. <ollets are normallystored in steel bo0es designed for holding the collets.

The step ch"c%' Fig"re ,*22' is a &ariation of the collet ch"c%' and it is intended for holding smallro"nd wor%pieces or discs for special machining -obs. !tep ch"c%s are blan% when new' and then

are machined in the lathe for an e0act fit for the discs to be t"rned. The step ch"c% machinecollet' which is split into three sections li%e the spring machine collet' is threaded to the drawbarof the collet attachment.



The lathe tailstoc% ch"c%' Fig"re ,*22' is a de&ice designed to s"pport the ends of wor%pieces inthe tailstoc% when a lathe center cannot be "sed con&eniently. The ch"c% has a taper arbor thatfits into the lathe tailstoc% spindle. The three brone self*centering -aws of the ch"c% willacc"rately close "pon wor%pieces between 1B7 and 1 inch in diameter. The brone -aws pro&ide agood bearing s"rface for the wor%piece. The -aws are ad-"sted to the diameter of the wor%pieceand then loc%ed in place.

A lathe faceplate' Fig"re ,*25' is a f lat' ro"nd plate that threads to the headstoc% spindle of thelathe. The faceplate is "sed for irreg"larly shaped wor%pieces that cannot be s"ccessf"lly held by

ch"c%s or mo"nted between centers. The wor%piece is either attached to the faceplate "singangle plates or brac%ets or bolted directly to the plate. ?adial T*slots in the faceplate s"rfacefacilitate mo"nting wor%pieces. The faceplate is &al"able for mo"nting wor%pieces in which aneccentric hole or pro-ection is to be machined. The n"mber of applications of the faceplatesdepends "pon the ingen"ity of the machinist. A small faceplate %nown as a dri&ing faceplate is"sed to dri&e the lathe dog for wor%pieces mo"nted between centers. The dri&ing faceplate"s"ally has fewer T*slots than the larger faceplates. 9hen the wor%piece is s"pported betweencenters' a lathe dog is fastened to the wor%piece and engaged in a slot of the dri&ing faceplate.

Lathe centers' are the most common de&ices for s"pporting wor%pieces in the lathe. (ost lathecenters ha&e a tapered point with a 6> incl"ded angle to fit wor%piece holes with the sameangle. The wor%piece is s"pported between two centers' one in the headstoc% spindle and one inthe tailstoc% spindle. <enters for lathe wor% ha&e standard tapered shan%s that fit directly into the



tailstoc% and into the headstoc% spindle "sing a center slee&e to con&ert the larger bore of thespindle to the smaller tapered sie of the lathe center. The centers are referred to as li&e centersor dead centers. A li&e center re&ol&es with the wor% and does not need to be l"bricated andhardened. A dead center does not re&ol&e with the wor% and m"st be hardened and hea&ilyl"bricated when holding wor%. Li&e and dead centers commonly come in matched sets' with thehardened dead center mar%ed with a groo&e near the conical end point.

The ball bearing li&e center is a special center mo"nted in a ball bearing ho"sing that lets thecenter t"rn with the wor% and eliminates the need for a hea&ily l"bricated dead center. /allbearing types of centers can ha&e interchangeable points which ma%e this center a &ersatile toolin all lathe operations. (odern centers of this type can be &ery acc"rate. escriptions for somecommon lathe centers follow.

The male center or plain center is "sed in pairs for most general lathe t"rning operations. Thepoint is gro"nd to a 6> cone angle. 9hen "sed in the headstoc% spindle where it re&ol&es withthe wor%piece' it is commonly called a li&e center. 9hen "sed in the tailstoc% spindle where itremains stationary when the wor%piece is t"rned' it is called a dead center. ead centers arealways made of hardened steel and m"st be l"bricated &ery often to pre&ent o&erheating.

The half male center is a male center that has a portion of the 6> cone c"t away. The half malecenter is "sed as a dead center in the tailstoc% where facing is to be performed. The c"tawayportion of the center faces the c"tting tool and pro&ides the necessary clearance for the tool



when facing the s"rface immediately aro"nd the drilled center in the wor%piece.

The *center is "sed to s"pport ro"nd wor%pieces at right angles to the lathe a0is for specialoperations s"ch as drilling or reaming. The pipe center is similar to the male center b"t its cone isgro"nd to a greater angle and is larger in sie. ;t is "sed for holding pipe and t"bing in the lathe.The female center is conically bored at the tip and is "sed to s"pport wor%pieces that are pointedon the end. A self*dri&ing lathe center is a center with serrated gro"nd sides that can grip thewor% while t"rning between centers witho"t ha&ing to "se lathe dogs.

A self dri&ing center is a center that has grips installed on the o"ter edge of the center diameterthat can be forced into the wor% to hold and dri&e the wor% when t"rning between centerswitho"t "sing lathe dogs.

Lathe dogs are cast metal de&ices "sed to pro&ide a firm connection between the headstoc% spindle and the wor%piece mo"nted between centers. This firm connection permits the wor%pieceto be dri&en at the same speed as the spindle "nder the strain of c"tting. Three common lathedogs are ill"strated in Fig"re ,*23. Lathe dogs may ha&e bent tails or straight tails. 9hen bent*taildogs are "sed' the tail fits into a slot of the dri&ing faceplate. 9hen straight*tail dogs are "sed'the tail bears against a st"d pro-ecting from the faceplate. The bent*tail lathe dog with headless

setscrew is considered safer than the dog with the s+"are head screw beca"se the headlesssetscrew red"ces the danger of the dog catching in the operator:s clothing and ca"sing anaccident. The bent*tail clamp lathe dog is "sed primarily for rectang"lar wor%pieces.



MAN*RELS

A wor%piece which cannot be held between centers beca"se its a0is has been drilled or bored'and which is not s"itable for holding in a ch"c% or against a faceplate' is "s"ally machined on amandrel. A mandrel is a tapered a0le pressed into the bore of the wor%piece to s"pport itbetween centers.

A mandrel sho"ld not be conf"sed with an arbor' which is a similar de&ice b"t "sed for holdingtools rather than wor%pieces. To pre&ent damage to the wor%' the mandrel sho"ld always be oiledbefore being forced into the hole. 9hen t"rning wor% on a mandrel' feed toward the large endwhich sho"ld be nearest the headstoc% of the lathe.

A solid machine mandrel is generally made from hardened steel and gro"nd to a slight taper of from .3 to .6 inch per inch. ;t has &ery acc"rately co"nters"n% centers at each end formo"nting between centers. The ends of the mandrel are smaller than the body and ha&emachined flats for the lathe dog to grip. The sie of the solid machine mandrel is always stampedon the large end of the taper. !ince solid machine mandrels ha&e a &ery slight taper' they arelimited to wor%pieces with specific inside diameters.

An e0pansion mandrel will accept wor%pieces ha&ing a greater range of sies. The e0pansionmandrel is' in effect' a ch"c% arranged so that the grips can be forced o"tward against theinterior of the hole in the wor%piece.

LATHE ATTACHMENTS

The &ariety of wor% that can be performed on the lathe is greatly increased by the "se of &ario"slathe attachments. !ome lathes come e+"ipped with special attachmentsC some attachments m"stbe ordered separately. !ome common lathe attachments are the steady rest with cathead' thefollower rest' the tool post grinding machine' the lathe micrometer stop' the lathe milling fi0t"re'the lathe coolant attachment' the lathe inde0ing fi0t"re' and the milling*grinding*drilling*slottingattachment #or ersa*(il$. The lathe inde0ing fi0t"re and ersa*(il "nit are detailed in <hapter =.escriptions for the other lathe attachments follows.

RESTS

9or%pieces often need e0tra s"pport' especially long' thin wor%pieces that tend to spring awayfrom the tool bit. Three common s"pports or rests are the steady rest' the cathead' and the



follower rest #Fig"re ,*2,$.

Steady Rest

The steady rest' also called a center rest' is "sed to s"pport long wor%pieces for t"rning andboring operations. ;t is also "sed for internal threading operations where the wor%piece pro-ects aconsiderable distance from the ch"c% or faceplate. The steady rest is clamped to the lathe bed atthe desired location and s"pports the wor%piece within three ad-"stable -aws. The wor%piece m"stbe machined with a concentric bearing s"rface at the point where the steady rest is to be applied.The -aws m"st be caref"lly ad-"sted for proper alignment and loc%ed in position. The area of



contact m"st be l"bricated fre+"ently. The top section of the steady rest swings away from thebottom section to permit remo&al of the wor%piece witho"t dist"rbing the -aw setting.

Cathead

9hen the wor% is too small to machine a bearing s"rface for the ad-"stable -aws to hold' then acathead sho"ld be "sed. The cathead has a bearing s"rface' a hole thro"gh which the wor% e0tends' and ad-"sting screws. The ad-"sting screws fasten the cathead to the wor%. They are

also "sed to align the bearing s"rface so that it is concentric to the wor% a0is. A dial indicatorm"st be "sed to set "p the cathead to be concentric and acc"rate.

#ollo'er Rest

The follower rest has one or two -aws that bear against the wor%piece. The rest is fastened tothe lathe carriage so that it will follow the tool bit and bear "pon the portion of the wor%piece thathas -"st been t"rned. The c"t m"st first be started and contin"ed for a short longit"dinal distancebefore the follower rest may be applied. The rest is generally "sed only for straight t"rning andfor threading long' thin wor%pieces. !teady rests and follower rests can be e+"ipped withball*bearing s"rfaces on the ad-"stable -aws. These types of rests can be "sed witho"t e0cessi&el"bricant or ha&ing to machine a polished bearing s"rface.

Mi(rometer Carria&e Stop

The micrometer carriage stop' Fig"re ,*28' is "sed to acc"rately position the lathe carriage. Themicrometer stop is designed so the carriage can be mo&ed into position against the retractablespindle of the stop and loc%ed into place. A micrometer gage on the stop enables carriagemo&ement of as little as .1 inch. This tool is &ery "sef"l when facing wor% to length' t"rning asho"lder' or c"tting an acc"rate groo&e.

Tool "ost $rinder

The tool post grinder #Fig"re ,*2=$ is a machine tool attachment specially designed for cylindricalgrinding operations on the lathe. ;t consists primarily of a 1B7*or 1B5*horsepower electric motorand a wheel spindle connected by p"lleys and a belt. The machine fastens to the compo"nd restof the lathe with a T*slot bolt which fits in the slot of the compo"nd rest in the same manner as

the lathe tool post. The tool post grinding machine mo"nts grinding abrasi&e wheels ranging from1B7 inch to 5 or 7 inches in diameter for internal and e0ternal grinding operations. The p"lleys onthe wheel spindle and motor shaft are interchangeable to pro&ide proper c"tting speeds for the&ario"s wheel sies. The larger grinding abrasi&e wheels "sed for e0ternal grinding are attachedto the wheel spindle with an arbor. !mall' mo"nted grinding abrasi&e wheels for internal grinding



are fi0ed in a ch"c% which screws to the wheel spindle. The electric motor is connected to anelectrical power so"rce by a cable and pl"g. A switch is "s"ally pro&ided at the attachment tofacilitate starting and stopping the motor.

Lathe Millin& #i0ture

This is a fi0t"re designed to pro&ide the ability for limited milling operations. (any repair andfabrication -obs cannot be satisfactorily completed on the standard engine lathe' b"t with thelathe milling attachment' the small machine shop that is not e+"ipped with a milling machine canmill %eyslots' %eyways' flats' angles' he0 heads' s+"ares' splines' and holes. For specific operatinginstr"ctions and parts' refer to T( =*5763*2*1.

TOOLS NECESSAR! #OR LATHE OR.

;n order to properly set"p and operate most engine lathes' it is recommended to ha&e the

following tools on hand. A machinist tool bo0 with all wrenches' screwdri&ers' and common handtools. A dial indicator may be necessary for some proced"res on the lathe. ?eferences' charts'tables' and other predetermined data on machine operations may be "sef"l to lathe operators.eep all safety e+"ipment' along with necessary cleaning mar%ing' and l"bricating e+"ipment' inthe immediate lathe area to "se as needed.



CUTTIN$ #LUI*S

The p"rposes of "sing c"tting fl"ids on the lathe are to cool the tool bit and wor%piece that arebeing machined' increase the life of the c"tting tool' ma%e a smoother s"rface f inish' deter r"st'and wash away chips. <"tting fl"ids can be sprayed' dripped' wiped' or flooded onto the pointwhere the c"tting action is ta%ing place. Generally' c"tting fl"ids sho"ld only be "sed if the speedor c"tting action re+"ires the "se of c"tting fl"ids. escriptions of some common c"tting fl"ids"sed on the lathe follow.

Lard Oil

P"re lard oil is one of the oldest and best c"tting oils. ;t is especially good for thread c"tting'tapping' deep hole drilling' and reaming. Lard oil has a high degree of adhesion or oiliness' a

relati&ely high specific heat' and its fl"idity changes only slightly with temperat"re. ;t is ane0cellent r"st pre&enti&e and prod"ces a smooth finish on the wor%piece. /eca"se lard oil ise0pensi&e' it is seldom "sed in a p"re state b"t is combined with other ingredients to form goodc"tting oil mi0t"res.

Mineral Oil

(ineral oils are petrole"m*base oils that range in &iscosity from %erosene to light paraffin oils.(ineral oil is &ery stable and does not de&elop disagreeable odors li%e lard oilC howe&er' it lac%ssome of the good +"alities of lard oil s"ch as adhesion' oiliness' and high specific heat. /eca"se itis relati&ely ine0pensi&e' it is commonly mi0ed with lard oil or other chemicals to pro&ide c"tting

oils with desirable characteristics. Two mineral oils' %erosene and t"rpentine' are often "sed alonefor machining al"min"m and magnesi"m. Paraffin oil is "sed alone or with lard oil for machiningcopper and brass.

Mineral-Lard Cuttin& Oil Mi0ture

ario"s mi0t"res of mineral oils and lard oil are "sed to ma%e c"tting oils which combine the goodpoints of both ingredients b"t pro&e more economical and often as effecti&e as p"re lard oil.

Suluri%ed #atty-Mineral Oil

(ost good c"tting oils contain mineral oil and lard oil with &ario"s amo"nts of s"lf"r and chlorine

which gi&e the oils good antiweld properties and promote free machining. These oils play animportant part in present*day machining beca"se they pro&ide good f inishes on most materialsand aid the c"tting of to"gh material.

Solu1le Cuttin& Oils



9ater is an e0cellent cooling medi"m b"t has little l"bricating &al"e and hastens r"st andcorrosion. Therefore' mineral oils or lard oils which can be mi0ed with water are often "sed toform a c"tting oil. A sol"ble oil and water mi0 has l"bricating +"alities dependent "pon thestrength of the sol"tion. Generally' sol"ble oil and water is "sed for ro"gh c"tting where +"ic% dissipation of heat is most important. /ora0 and trisodi"m phosphate #T!P$ are sometimes addedto the sol"tion to impro&e its corrosion resistance.

Soda-ater Mi0tures

!alts s"ch as soda ash and T!P are sometimes added to water to help control r"st. This mi0t"reis the cheapest of all coolants and has practically no l"bricating &al"e. Lard oil and soap in small+"antities are sometimes added to the mi0t"re to impro&e its l"bricating +"alities. Generally' sodawater is "sed only where cooling is the prime consideration and l"brication a secondaryconsideration. ;t is especially s"itable in reaming and threading operations on cast iron where abetter finish is desired.

hite Lead and Lard Oil Mi0ture

9hite lead can be mi0ed with either lard oil or mineral oil to form a c"tting oil which is especiallys"itable for diffic"lt machining of &ery hard metals.

LA!IN$ OUT AN* MOUNTIN$ OR.

There is relati&ely little layo"t wor% to be done for most lathe wor% beca"se of the lathe:s abilityto g"ide the c"tting tool acc"rately to the wor%piece. ;f center holes m"st be located and drilledinto the end of a wor%piece for t"rning lay o"t and center*p"nch the wor%piece "sing othermethods. !ome s"ggested methods are to "se a bell*type center p"nch between centers and thiscannot be accomplished on the lathe' #Fig"re ,*52$' "se hermaphrodite calipers to scribeintersecting arcs' "se the centering head of the combination s+"are' or "se di&iders #Fig"re ,*55$.



METHO*S O# MOUNTIN$ OR.

Mountin& or2pie(es in Chu(2s

9hen installing the ch"c% or any attachment that screws onto the lathe headstoc% spindle' thethreads and bearing s"rfaces of both spindle and ch"c% m"st be cleaned and oiled. ;n cleaning

the internal threads of the ch"c%' a spring thread cleaner is &ery "sef"l #Fig"re ,*57$.

T"rn the spindle so that the %ey is facing "p and loc% the spindle in position. (a%e s"re that thespindle and ch"c% taper are free of grit and chips. Place the ch"c% in position on the spindle.

Engage the draw n"t thread and tighten by applying fo"r or fi&e hammer blows on the spannerwrench engaged with the draw n"t. ?otate the spindle 18>' engage the spanner wrench' and

gi&e fo"r or fi&e solid hammer blows to the spanner wrench handle. The wor%piece is now readyfor mo"nting.

9or% a"tomatically centers itself in the "ni&ersal #5 -aw$ scroll ch"c%' drill ch"c%' collet ch"c%s'

and step ch"c%' b"t m"st be man"ally centered in the independent #7 -aw$ ch"c%. To center wor% in the independent ch"c%' line the fo"r -aws "p to the concentric rings on the face of the ch"c%'as close to the re+"ired diameter as possible.

(o"nt the wor%piece and tighten the -aws loosely onto the wor%piece #Fig"re ,*53$. !pin thewor%piece by hand and ma%e appro0imate centering ad-"stments as needed' then firmly tighten

the -aws.



For ro"gh centering irreg"larly shaped wor%' first meas"re the o"tside diameter of the wor%piece'then open the fo"r -aws of the ch"c% "ntil the wor%piece slides in. @e0t tighten each opposing -awa little at a time "ntil the wor%piece is held firmly' b"t not too tightly. 4old a piece of chal% nearthe wor%piece and re&ol&e the ch"c% slowly with yo"r left hand. 9here the chal% to"ches isconsidered the high side.

Loosen the -aw opposite and tighten the -aw where the chal% mar%s are fo"nd. ?epeat theprocess "ntil the wor%piece is satisfactorily aligned.

To center a wor%piece ha&ing a smooth s"rface s"ch as ro"nd stoc%' the best method is to "se adial test indicator. Place the point of the indicator against the o"tside or inside diameter of thewor%piece. ?e&ol&e the wor%piece slowly by hand and notice any de&iations on the dial. Thismethod will indicate any inacc"racy of the centering in tho"sandths of an inch.

;f an irreg"larly shaped wor%piece is to be mo"nted in the independent ch"c%' then a straight'hardened steel bar can be "sed with a dial indicator to align the wor%piece. E0periencedmachinists fabricate se&eral sies of hardened steel bars' gro"nd with a 6> point' that can bemo"nted into the drill ch"c% of the tailstoc% spindle and g"ided into the center*p"nched mar% onthe wor%piece. A dial indicator can then be "sed to finish aligning the wor%piece to within .1inch. ;f a hardened steel bar is not readily a&ailable' a hardened center mo"nted in the tailstoc%

spindle may be "sed to align the wor% while "sing a dial indicator on the ch"c% -aws. This methodis one of se&eral ways to align a wor%piece in an independent ch"c%. ;ngen"ity and e0periencewill increase the awareness of the machine operator to find the best method to set "p the wor% for machining.

9hen remo&ing ch"c%s from the lathe' always "se a wooden ch"c% bloc% "nder the ch"c% tos"pport the ch"c% on the lathe ways. se care to a&oid dropping the ch"c% on the ways' sincethis can greatly damage the lathe ways or cr"sh the operator:s hands.

Mountin& or2 to #a(eplates

(o"nt faceplates in the same manner as ch"c%s. <hec% the acc"racy of the faceplate s"rface"sing a dial indicator' and tr"e the*faceplate s"rface by ta%ing a light c"t if necessary. o not "se

faceplates on different lathes' since this will ca"se e0cessi&e wear of the faceplate d"e torepeated tr"ing c"ts ha&ing to be ta%en. (o"nt the wor%piece "sing T*bolts and clamps of the

correct sies #Fig"re ,*56 $. Ens"re all s"rfaces are wiped clean of b"rrs' chips' and dirt. 9hen a



hea&y piece of wor% is mo"nted off center' s"ch as when "sing an angle plate' "se aco"nterweight to offset the throw of the wor% and to minimie &ibration and chatter. se paper orbrass shims between the wor% and the faceplate to protect the delicate s"rface of the faceplate.

After mo"nting the wor% to an appro0imate center location' "se a dial indicator to finish acc"ratealignment.

Mountin& or2 ,et'een Centers

/efore mo"nting a wor%*piece between centers' the wor%piece ends m"st be center*drilled andco"nters"n%. This can be done "sing a small twist drill followed by a 6> center co"ntersin% or'more commonly' "sing a co"ntersin% and drill #also commonly called a center drill$. ;t is &eryimportant that the center holes are drilled and co"nters"n% so that they will fit the lathe centerse0actly. ;ncorrectly drilled holes will s"b-ect the lathe centers to "nnecessary wear and the

wor%piece will not r"n tr"e beca"se of poor bearing s"rfaces. A correctly drilled and co"nters"n% hole has a "niform 6> taper and has clearance at the bottom for the point of the lathe center.Fig"re ,*5, ill"strates correctly and incorrectly drilled center holes. The holes sho"ld ha&e apolished appearance so as not to score the lathe centers. The act"al drilling and co"ntersin%ing of center holes can be done on a drilling machine or on the lathe itself. /efore attempting to centerdrill "sing the lathe' the end of the wor%piece m"st be machined flat to %eep the center drill fromr"nning off center.



(o"nt the wor% in a "ni&ersal or independent ch"c% and mo"nt the center drill in the lathetailstoc% #Fig"re ,*58$. ?efer to the section of this chapter on facing and drilling on the lathe' priorto doing this operation. <enter drills come in &ario"s sies for different diameters of wor% #Fig"re,*5=$. <alc"late the correct speed and hand feed into the wor%piece. Only drill into the wor%piece

abo"t 2B5 of the body diameter. high speeds and feed them into the wor% slowly to a&oidbrea%ing off the drill point inside the wor%. ;f this happens' the wor% m"st be remo&ed from the

ch"c% and the point e0tracted. This is a time*cons"ming -ob and co"ld r"in the wor%piece.



To mo"nt wor% between centers' the operator m"st %now how to insert and remo&e lathecenters. The +"ality of wor%manship depends as m"ch on the condition of the lathe centers as onthe proper drilling of the center holes. /efore mo"nting lathe centers in the headstoc% or tailstoc%'

thoro"ghly clean the centers' the center slee&e' and the tapered soc%ets in the headstoc% andtailstoc% spindles. Any dirt or chips on the centers or in their soc%ets will pre&ent the centers from

seating properly and will ca"se the centers to r"n o"t of tr"e.

;nstall the lathe center in the tailstoc% spindle with a light twisting motion to ens"re a clean fit.;nstall the center slee&e into the headstoc% spindle and install the lathe center into the center

slee&e with a light twisting motion.

To remo&e the center from the headstoc% spindle' hold the pointed end with a cloth or rag in onehand and gi&e the center a sharp tap with a rod or %noc%o"t bar inserted thro"gh the hollow

headstoc% spindle.

To remo&e the center from the tailstoc%' t"rn the tailstoc% handwheel to draw the tailstoc% spindleinto the tailstoc%. The center will contact the tailstoc% screw and will be b"mped loose from its

soc%et.

After mo"nting the headstoc% and tailstoc% centers' the acc"racy of the 6> point sho"ld bechec%ed "sing a center gage or a dial indicator. ;f the center in the headstoc% is not at 6>' or is

scarred and b"rred' it m"st be tr"ed while inserted in the lathe headstoc% spindle. ;f theheadstoc% center is a soft center #a center that is not heat*treated and hardened$' it can be



t"rned tr"e with the lathe tool bit. ;f the center in the headstoc% is hardened' it m"st be gro"ndwith a tool post grinding machine to get a tr"e s"rface #Fig"re ,*7$.

To t"rn a soft center tr"e with the lathe' first set "p the tool bit for right hand t"rning' center thetool bitC then' rotate the compo"nd rest to an angle of 5> to the a0is of the lathe #Fig"re ,*71$.The lathe speed sho"ld be set for a finish c"t' and the feed is s"pplied by cran%ing the handwheel

of the compo"nd rest' th"s prod"cing a clean and short steep taper with an incl"ded angle of 6>.Once tr"ed' the center sho"ld stay in place "ntil the operation is completed. ;f the center m"st be

remo&ed' mar% the position on the center and headstoc% for easy realignment later.

Lathe centers m"st be parallel with the ways of the lathe in order to t"rn wor%pieces straight andtr"e. /efore beginning each t"rning operation' the center alignment sho"ld be chec%ed.

The tailstoc% may be mo&ed laterally to accomplish this alignment by means of ad-"sting screwsafter it has been released from the ways. Two ero lines are located at the rear of the tailstoc%

and the centers are appro0imately aligned when these lines coincide #Fig"re ,*72$. This alignmentmay be chec%ed by mo&ing the tailstoc% "p close to the headstoc% so that the centers almost



to"ch' and obser&ing their relati&e positions #Fig"re ,*72$.

The most acc"rate method of chec%ing alignment of centers is by mo"nting the wor%piecebetween centers and ta%ing light c"ts at both ends witho"t changing the carriage ad-"stments.

(eas"re each end of this c"t with calipers or a micrometer. ;f the tailstoc% end is greater indiameter than the headstoc% end' the tailstoc% is mo&ed toward the operator. ;f the tailstoc% end

is smaller in diameter than the headstoc% end' the tailstoc% is mo&ed away from the operator.Ta%e additional c"ts in the same manner after each ad-"stment "ntil both c"ts meas"re the same.

To set"p the wor%piece between centers on the lathe' a dri&ing faceplate #dri&e plate$ and lathedog m"st be "sed.

#Fig"re ,*75$. (a%e headstoc% spindle are faceplate. !crew the s"re that the e0ternal threads of the clean before screwing on the dri&ing faceplate sec"rely onto the spindle. <lamp the lathe dogon the wor%piece so that its tail hangs o&er the end of the wor%piece. ;f the wor%piece is finished'

place a shim of soft material s"ch as brass between the setscrew of the dog and wor%piece.(o"nt the wor%piece between the centers. (a%e s"re that the lathe dog tail tits freely in the slotof the faceplate and does not bind. !ometimes' the tailstoc% center is a dead center and does not

re&ol&e with the wor%piece' so it may re+"ire l"brication. A few drops of oil mi0ed with white leadsho"ld be applied to the center before the wor%piece is set "p. The tailstoc% sho"ld be ad-"sted

so that the tailstoc% center fits firmly into the center hole of the wor%piece b"t does not bind. Thelathe sho"ld be stopped at inter&als and additional oil and white lead mi0t"re applied to the dead



center to pre&ent o&erheating harm to the center and the wor%piece.

Mountin& or2 on Mandrels

To machine a wor%piece of an odd shape' s"ch as a wheel p"lley' a tapered mandrel is "sed tohold and t"rn the wor%. The mandrel m"st be mo"nted between centers and a dri&e plate andlathe dog m"st be "sed. The centers m"st be aligned and the mandrel m"st be free of b"rrs.

(o"nt the wor%piece onto a l"bricated mandrel of the proper sie by "sing an arbor press. Ens"rethat the lathe dog is sec"red to the machined flat on the end of the mandrel and not on the

smooth s"rface of the mandrel taper #Fig"re ,*77$. ;f e0pansion b"shings are to be "sed with amandrel' clean and care for the e0pansion b"shings in the same manner as a normal mandrel.

Always feed the tool bit in the direction of the large end of the mandrel' which is "s"ally towardthe headstoc% end' to a&oid p"lling the wor% o"t of the mandrel. ;f facing on a mandrel' a&oid



c"tting into the mandrel with the tool bit..

$ENERAL LATHE O"ERATIONS

LATHE S"EE*S3 #EE*S3 AN* *E"TH O# CUTS

General operations on the lathe incl"de straight and sho"lder t"rning' facing' groo&ing' parting'

t"rning tapers' and c"tting &ario"s screw threads. /efore these operations can be done' athoro"gh %nowledge of the &ariable factors of lathe speeds' feeds' and depth of c"t m"st be

"nderstood. These factors differ for each lathe operation' and fail"re to "se these factors properlywill res"lt in machine fail"re or wor% damage. The %ind of material being wor%ed' the type of toolbit' the diameter and length of the wor%piece' the type of c"t desired #ro"ghing or f inishing$' and

the wor%ing condition of the lathe will determine which speed' feed' or depth of c"t is best forany partic"lar operation. The g"idelines which follow for selecting speed' feed' and depth of c"t

are general in nat"re and may need to be changed as conditions dictate.

Cuttin& Speeds4

The c"tting speed of a tool bit is defined as the n"mber of feet of wor%piece s"rface' meas"red

at the circ"mference' that passes the tool bit in one min"te. The c"tting speed' e0pressed in FP('m"st not be conf"sed with the spindle speed of the lathe which is e0pressed in ?P(. To obtain

"niform c"tting speed' the lathe spindle m"st be re&ol&ed faster for wor%pieces of small diameterand slower for wor%pieces of large diameter. The proper c"tting speed for a gi&en -ob depends"pon the hardness of the material being machined' the material of the tool bit' and how m"ch

feed and depth of c"t is re+"ired. <"tting speeds for metal are "s"ally e0pressed in s"rface feetper min"te' meas"red on the circ"mference of the wor%. !pindle re&ol"tions per min"te #?P($

are determined by "sing the form"la)

9hich is simplified to)

9here S#M is the rated s"rface feet per min"te' also e0pressed as c"tting speed.

R"M is the spindle speed in re&ol"tions per min"te

* is the diameter of the wor% in inches.

;n order to "se the form"la simply insert the c"tting speed of the metal and the diameter of the

wor%piece into the form"la and yo" will ha&e the ?P(.

T"rning a one*half inch piece of al"min"m' c"tting speed of 2 !F(' wo"ld res"lt in thefollowing)

Table ,*2 in Appendi0 A lists specific ranges of c"tting speeds for t"rning and threading &ario"smaterials "nder normal lathe conditions' "sing normal feeds and depth of c"ts. @ote that in Table,*2 the meas"rement calc"lations are in inch and metric meas"res. The diameter meas"rements

"sed in these calc"lations are the act"al wor%ing diameters that are being machined' and notnecessarily the largest diameter of the material. The c"tting speeds ha&e a wide range so thatthe lower end of the c"tting speed range can be "sed for ro"gh c"tting and the higher end forfinish c"tting. ;f no c"tting speed tables are a&ailable' remember that' generally' hard materials



re+"ire a slower c"tting speed than soft or d"ctile materials. (aterials that are machined dry'witho"t coolant' re+"ire a slower c"tting speed than operations "sing coolant. Lathes that areworn and in poor condition will re+"ire slower speeds than machines that are in good shape. ;f carbide*tipped tool bits are being "sed' speeds can be increased two to three times the speed

"sed for high*speed tool bits.

#eed

Feed is the term applied to the distance the tool bit ad&ances along the wor% for each re&ol"tionof the lathe spindle. Feed is meas"red in inches or millimeters per re&ol"tion' depending on thelathe "sed and the operator:s system of meas"rement. Table ,*5 in Appendi0 A is a g"ide thatcan be "sed to select feed for general ro"ghing and finishing operations. A light feed m"st be"sed on slender and small wor%pieces to a&oid damage. ;f an irreg"lar finish or chatter mar%s

de&elop while t"rning' red"ce the feed and chec% the tool bit for alignment and sharpness.?egardless of how the wor% is held in the lathe' the tool sho"ld feed toward the headstoc%. This

res"lts in most of the press"re of the c"t being p"t on the wor% holding de&ice. ;f the c"t m"st befed toward the tailstoc%' "se light feeds and light c"ts to a&oid p"lling the wor%piece loose.

*epth o Cut

epth of c"t is the distance that the tool bit mo&es into the wor%' "s"ally meas"red intho"sandths of an inch or in millimeters. General machine practice is to "se a depth of c"t "p tofi&e times the rate of feed' s"ch as ro"gh c"tting stainless steel "sing a feed of .2 inch perre&ol"tion and a depth of c"t of .1 inch' which wo"ld red"ce the diameter by .2 inch. ;f

chatter mar%s or machine noise de&elops' red"ce the depth of c"t.

MICROMETER COLLAR

Grad"ated micrometer collars can be "sed to acc"rately meas"re this tool bit mo&ement to andaway from the lathe center a0is. Th"s' the depth of c"t can be acc"rately meas"red when mo&ing

the tool bit on the cross slide by "sing the cross slide micrometer collar. The compo"nd rest isalso e+"ipped with a micrometer collar. These collars can meas"re in inches or in millimeters' orthey can be e+"ipped with a d"al reado"t collar that has both. !ome collars meas"re the e0acttool bit mo&ement' while others are designed to meas"re the amo"nt of material remo&ed from

the wor%piece #twice the tool bit mo&ement$. <ons"lt the operator:s instr"ction man"al for specificinformation on grad"ated collar "se.

#ACIN$



Facing is machining the ends and sho"lders of a piece of stoc% smooth' flat' and perpendic"lar tothe lathe a0is. Facing is "sed to c"t wor% to the desired length and to prod"ce a s"rface from

which acc"rate meas"rements may be ta%en.

#a(in& or2 in a Chu(2

Facing is "s"ally performed with the wor% held in a ch"c% or collet. Allow the wor%piece to e0tenda distance no more than 1 1B2 times the wor% diameter from the ch"c% -aws' and "se finishing

speeds and feeds calc"lated "sing the largest diameter of the wor%piece. The tool bit may be fedfrom the o"ter edge to the center or from the center to the o"ter edge. @ormal facing is done

from the o"ter edge to the center since this method permits the operator to obser&e the tool bitand layo"t line while starting the c"t. This method also eliminates the problem of feeding the toolbit into the solid center portion of the wor%piece to get a c"t started.. se a left*hand finishingtool bit and a right*hand tool holder when facing from the o"ter edge toward the center. 9or%

that has a drilled or bored hole in the center may be faced from the center o"t to the o"ter edgeif a right*hand finishing tool bit is "sed. A&oid e0cessi&e tool holder and tool bit o&erhang when

setting "p the facing operation. !et the tool bit e0actly on center to a&oid lea&ing a center n"b onthe wor%piece #Fig"re ,*76 $. se the tailstoc% center point as a reference point when setting the

tool bit e0actly on center. ;f no tailstoc% center is a&ailable' ta%e a trial c"t and read-"st as

needed. ;f "sing the cross slide power feed to mo&e the tool bit #into the center$' disengagepower when the tool bit is within lB16 inch of the center and finish the facing c"t "sing hand feed.

#a(in& or2 ,et'een Centers

!ometimes the wor%piece will not fit into a ch"c% or collet' so facing m"st be done betweencenters. To properly accomplish facing between centers' the wor%piece m"st be center*drilled

before mo"nting into the lathe. A half male center #with the tip well l"bricated with a white leadand oil mi0t"re$ m"st be "sed in the lathe tailstoc% to pro&ide ade+"ate clearance for the tool bit.

The tool bit m"st be gro"nd with a sharp angle to permit facing to the &ery edge of the centerdrilled hole #Fig"re ,*7,$. !tart the facing c"t at the edge of the center*drilled hole after chec%ingfor tool bit clearance' and feed the c"tting tool o"t to the edge. se light c"ts and finishing feeds'

which will red"ce the tension p"t on the half male center. ?eplace the half male center with astandard center after the facing operation' since the half male center will not pro&ide ade+"ates"pport for general t"rning operations. Only a small amo"nt of material can be remo&ed while

facing between centers. ;f too m"ch material is remo&ed' the center*drilled hole will become toosmall to s"pport the wor%piece.



"re(ision #a(in&

!pecial methods m"st be "sed to face materials to a precise length. One method is to mo"nt thewor% in a ch"c% and lightly face one end with a clean"p c"t. Then' re&erse the stoc% and face itto the scribed layo"t line. This method may not be as acc"rate as other methods' b"t it will wor% for most -obs. A more precise method to face a piece of stoc% to a specified length is to t"rn the

compo"nd rest to an angle of 5 degrees to the cross slide and then "se the grad"atedmicrometer collar to meas"re tool bit mo&ement' Fig"re ,*78. At this angle of the compo"nd rest'the mo&ement of the c"tting tool will always be half of the reading of the grad"ated collar. Th"s'if the compo"nd rest feed is t"rned .1 inch' the tool bit will face off .3 inch of material.

9ith the compo"nd rest angled at 5>' a light c"t may be made on the first end' then the piecere&ersed and faced to acc"rate length. Always loc% the carriage down to the bed. This pro&idesthe most sec"re and acc"rate base for the c"tting tool and helps eliminate "nwanted &ibrationd"ring facing operations. Another way to face to a precise length is to "se the lathe carriage

micrometer stop to meas"re the carriage and tool bit mo&ement. sing the micrometer stop cansometimes be faster and easier than "sing the compo"nd rest grad"ated collar for meas"ring tool

bit mo&ement.

STRAI$HT TURNIN$

!traight t"rning' sometimes called cylindrical t"rning' is the process of red"cing the wor% diameter



to a specific dimension as the carriage mo&es the tool along the wor%. The wor% is machined on aplane parallel to its a0is so that there is no &ariation in the wor% diameter thro"gho"t the lengthof the c"t. !traight t"rning "s"ally consists of a ro"ghing c"t followed by a finishing c"t. 9hen a

large amo"nt of material is to be remo&ed' se&eral ro"ghing c"ts may need to be ta%en. Thero"ghing c"t sho"ld be as hea&y as the machine and tool bit can withstand. The finishing c"t

sho"ld be light and made to c"t to the specified dimension in -"st one pass of the tool bit. 9hen"sing power feed to machine to a specific length' always disengage the feed appro0imately1B16*inch away from the desired length dimension' and then finish the c"t "sing hand feed.

Settin& *epth o Cut

;n straight t"rning' the cross feed or compo"nd rest grad"ated collars are "sed to determine thedepth of c"t' which will remo&e a desired amo"nt from the wor%piece diameter. 9hen "sing thegrad"ated collars for meas"rement' ma%e all readings when rotating the handles in the forwarddirection. The lost motion in the gears' called bac%lash' pre&ents ta%ing acc"rate readings when

the feed is re&ersed. ;f the feed screw m"st be re&ersed' s"ch as to restart a c"t' then thebac%lash m"st be ta%en "p by t"rning the feed screw handle in the opposite direction "ntil themo&ement of the screw act"ates the mo&ement of the cross slide or compo"nd rest. Then t"rn

the feed screw handle in the original or desired direction bac% to the re+"ired setting.

Settin& Tool ,it or Strai&ht Turnin&

!ee Fig"re ,*7=. For most straight t"rning operations' the compo"nd rest sho"ld be aligned at anangle perpendic"lar to the cross slide' and then sw"ng 5> to the right and clamped in position.

The tool post sho"ld be set on the left*hand side of the compo"nd rest T*slot' with a minim"m of tool bit and tool holder o&erhang.

9hen the compo"nd rest and tool post are in these positions' the danger of r"nning the c"ttingtool into the ch"c% or damaging the cross slide are minimied. Position the ro"ghing tool bit abo"t3> abo&e center height for the best c"tting action. This is appro0imately 5B67*inch abo&e center

for each inch of the wor%piece diameter. The finishing tool bit sho"ld be positioned at centerheight since there is less tor+"e d"ring finishing. The position of the tool bit to the wor% sho"ld beset so that if anything occ"rs d"ring the c"tting process to change the tool bit alignment' the tool



bit will not dig into the wor%' b"t instead will mo&e away from the wor%. Also' by setting the toolbit in this position' chatter will be red"ced. se a right*hand t"rning tool bit with a slight ro"ndradi"s on the nose for straight t"rning. Always feed the tool bit toward the headstoc% "nless

t"rning "p to an inside sho"lder. ifferent wor%pieces can be mo"nted in a ch"c%' in a collet' orbetween centers. 9hich wor% holding de&ice to "se will depend on the sie of the wor% and the

partic"lar operation that needs to be performed.

Turnin& or2 ,et'een Centers

T"rning wor% that is held between centers is one acc"rate method that is a&ailable. The chief ad&antage of "sing this method is that the wor% can be remo&ed from the lathe and later

replaced for s"bse+"ent machining operations witho"t dist"rbing the tr"eness of the t"rneds"rface in relation to the center holes of the wor%piece. The lathe centers m"st be in good

condition and caref"lly aligned if the t"rning operation is to be acc"rate. ;f necessary' tr"e thecenters and realign as needed. After the wor%piece is center*drilled' place a lathe dog #that isslightly larger in diameter than the wor%piece$ on the end of the wor% that will be toward the

headstoc%' and tighten the lathe dog bolt sec"rely to the wor%piece$. ;f "sing a dead center in thetailstoc%' l"bricate the center with a mi0t"re of white lead and motor oil. A ball bearing li&e center

is best for the tailstoc% center since this center wo"ld not need l"brication and can properly

s"pport the wor%. E0tend the tailstoc% spindle o"t abo"t 5 inches and loosen the tailstoc% clamp*down n"t. Place the wor% with the lathe dog end on the headstoc% li&e center and slide thetailstoc% forward "ntil the tailstoc% center will s"pport the wor%C then' sec"re the tailstoc% with theclamp*down n"t. Ad-"st the tail of the lathe dog in the dri&e plate slot' ma%ing s"re that the taildoes not bind into the slot and force the wor% o"t of the center. A good fit for the lathe dog iswhen there is clearance at the top and bottom of the dri&e plate slot on both sides of the lathe

dog tail. Tension sho"ld be applied to hold the wor% in place' b"t not so m"ch tension that the tailof the lathe dog will not mo&e freely in the dri&e *plate slot.

<hec% tool bit clearance by mo&ing the tool bit to the f"rthest position that can be c"t witho"tr"nning into the lathe dog or the dri&e plate. !et the lathe carriage stop or micrometer carriagestop at this point to reference for the end of the c"t and to protect the lathe components fromdamage. !et the speed' feed' and depth of c"t for a ro"ghing c"t and then ro"gh c"t to within.2 inch of the final dimension. Perform a finish c"t' flip the piece o&er' and change the lathe

dog to the opposite end. Then ro"gh and finish c"t the second side to final dimensions.

Turnin& or2 in Chu(2s

!ome wor% can be machined more efficiently by "sing ch"c%s' collets' mandrels' or faceplates tohold the wor%. ?o"gh and finish t"rning "sing these de&ices is basically the same as for t"rning

between centers. The wor%piece sho"ld not e0tend too far from the wor% holding de&ice witho"tade+"ate s"pport. ;f the wor% e0tends more than three times the diameter of the wor%piece from

the ch"c% or collet' additional s"pport m"st be "sed s"ch as a steady rest or a tailstoc% center

s"pport. 9hen t"rning "sing a mandrel or faceplate to hold an odd*shaped wor%piece' "se lightc"ts and always feed the c"tting tool toward the headstoc%. E&ery -ob may re+"ire a different

set"p and a different le&el of s%ill. Thro"gh e0perience' each machine operator will learn the bestmethods for holding wor% to be t"rned.

MACHININ$ SHOUL*ERS3 CORNERS3 UN*ERCUTS3 $ROO/ES3 AN* "ARTIN$

Shoulders

Fre+"ently' it will be necessary to machine wor% that has two or more diameters in its length. Theabr"pt step' or meeting place' of the two diameters is called a sho"lder. The wor%piece may be

mo"nted in a ch"c%' collet' or mandrel' or between centers as in straight t"rning. !ho"lders aret"rned' or formed' to &ario"s shapes to s"it the re+"irements of a partic"lar part. !ho"lders aremachined to add strength for parts that are to be fitted together' ma%e a corner' or impro&e theappearance of a part. The three common sho"lders are the s+"are' the filleted' and the ang"lar

sho"lder #Fig"re ,*3$.



!+"are sho"lders are "sed on wor% that is not s"b-ect to e0cessi&e strain at the corners. Thisshape pro&ides a f lat clamping s"rface and permits parts to be fitted s+"arely together. There aremany different ways to acc"rately machine a s+"are sho"lder. One method is to "se a parting toolbit to locate and c"t to depth the position of the sho"lder. !traight*t"rning the diameter down to

the desired sie is then the same as normal straight t"rning. Another method to machine a s+"aresho"lder is to ro"gh o"t the sho"lder slightly o&ersie with a ro"nd*nosed tool bit' and then finishs+"are the sho"lders to sie with a side*finishing tool bit. /oth of these methods are fine for most

wor%' b"t may be too time*cons"ming for precise -obs. !ho"lders can be machined +"ic%ly and

acc"rately by "sing one type of tool bit that is gro"nd and angled to straight t"rn and face in oneoperation #Fig"re ,*31$.

!et "p the micrometer carriage stop to align the sho"lder dimensionC then' in one pass of the toolbit' feed the tool bit left to t"rn the smaller diameter "ntil contact is made with the carriage stop.

<hange the direction to feed o"t from center and face the sho"lder o"t to the edge of thewor%piece. The lathe micrometer stop meas"res the length of the sho"lder and pro&ides for a

stop or reference for the tool bit. !ho"lder t"rning in this manner can be accomplished with a fewro"ghing c"ts and a finishing c"t.

#illeted Shoulders

Filleted sho"lders or corners' are ro"nded to be "sed on parts which re+"ire additional strength atthe sho"lder. These sho"lders are machined with a ro"nd*nose tool bit or a specially formed toolbit #Fig"re ,*32$. This type of sho"lder can be t"rned and formed in the same manner as s+"are

sho"lders. Filleted corners are commonly c"t to do"ble*sided sho"lders #see nderc"ts$.



An&ular Shoulders

Ang"lar sho"lders altho"gh not as common as filleted sho"lders' are sometimes "sed to gi&eadditional strength to corners' to eliminate sharp corners' and to add to the appearance of the

wor%. Ang"lar sho"lders do not ha&e all the strength of filleted corners b"t are more economicalto prod"ce d"e to the simpler c"tting tools. These sho"lders are t"rned in the same manner ass+"are sho"lders by "sing a side t"rning tool set at the desired angle of the sho"lder' or with a

s+"are*nosed tool set straight into the wor% #Fig"re ,*35$.

Corners

<orners are t"rned on the edges of wor% to brea% down sharp edges and to add to the generalappearance of the wor%. <ommon types of corners are chamfered' ro"nded' and s+"are #Fig"re

,*37$. <hamfered #or ang"lar$ corners may be t"rned with the side of a t"rning tool or the end of

a s+"are tool bit' as in ang"lar sho"lder t"rning. ?o"nd corners are prod"ced by t"rning a smallradi"s on the ends of the wor%. The radi"s may be formed by hand manip"lation of the cross

slide and carriage "sing a t"rning tool. An easier method is to "se a tool bit specifically gro"nd forthe shape of the desired corner. !till another method is to file the radi"s with a standard file. A



s+"are corner is simply what is left when ma%ing a sho"lder' and no machining is needed.

Under(uts

nderc"ts are the red"ctions in diameter machined onto the center portion of wor%pieces #Fig"re,*33$ to lighten the piece or to red"ce an area of the part for special reasons' s"ch as holding anoil seal ring. !ome tools' s"ch as drills and reamers' re+"ire a red"ction in diameter at the endsof the f l"tes to pro&ide clearance or r"no"t for a milling c"tter or grinding wheel. ?ed"cing the

diameter of a shaft or wor%piece at the center with filleted sho"lders at each end may beaccomplished by the "se of a ro"nd*nosed t"rning tool bit. This tool bit may or may not ha&e aside ra%e angle' depending on how m"ch machining needs to be done. A tool bit witho"t any sidera%e is best when machining in either direction. nderc"tting is done by feeding the tool bit into

the wor%piece while mo&ing the carriage bac% and forth slightly. This pre&ents go"ging andchatter occ"rring on the wor% s"rface.

$roo5es

Groo&ing #or nec%ing$ is the process of t"rning a groo&e or f"rrow on a cylinder' shaft' orwor%piece. The shape of the tool and the depth to which it is fed into the wor% go&ern the shape

and sie of the groo&e. The types of groo&es most commonly "sed are s+"are' ro"nd' and *shaped #Fig"re ,*36$. !+"are and ro"nd groo&es are fre+"ently c"t on wor% to pro&ide a space

for tool r"no"t d"ring s"bse+"ent machining operations' s"ch as threading or %n"rling. Thesegroo&es also pro&ide a clearance for assembly of different parts. The *shaped groo&e is "sed

e0tensi&ely on step p"lleys made to fit a *type belt. The groo&ing tool is a type of forming tool.;t is gro"nd witho"t side or bac% ra%e angles and set to the wor% at center height with a minim"m

of o&erhang. The side and end relief angles are generally somewhat less than for t"rning tools.



;n order to c"t a ro"nd groo&e of a definite radi"s on a cylindrical s"rface' the tool bit m"st begro"nd to fit the proper radi"s gage #Fig"re ,*3,$. !mall *groo&es may be machined by "sing a

form tool gro"nd to sie or -"st slightly "ndersie. Large *groo&es may be machined with thecompo"nd rest by finishing each side separately at the desired angle. This method red"ces toolbit and wor% contact area' th"s red"cing chatter' go"ging' and tearing. !ince the c"tting s"rfaceof the tool bit is generally broad' the c"tting speed m"st be slower than that "sed for general

t"rning. A good g"ide is to "se half of the speed recommended for normal t"rning. The depth of the groo&e' or the diameter of the "nderc"t' may be chec%ed by "sing o"tside calipers or by "sing

two wires and an o"tside micrometer #Fig"re ,*38$.



9hen a micrometer and two wires are "sed' the micrometer reading is e+"al to the meas"reddiameter of the groo&e pl"s two wire diameters.

To calc"late meas"rement o&er the wires' "se the following form"la)

Measurement 6 Outside *iameter 7 89 0 'ires: - 9 0 radius:4

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Lathe How To Use 1

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