Lathe How To Use 2

8/12/2019 Lathe How To Use 2

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INSTRUCTIONS TO LEARN HOW TO USE A LATHE

A!E " O# "

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This we!age is est !rinte" in Lan"sca!e for#at$

arting

Parting is the !rocess of cutting off a !iece of stock while it is eing hel" in the lathe$ This!rocess uses a s!eciall% sha!e" tool it with a cutting e"ge si#ilar to that of a s&uare-nose" toolit$ When !arting' e sure to use !lent% of coolant' such as a sulfuri(e" cutting oil )#achine cast

iron "r%*$ Parting tools nor#all% ha+e a , si"e rake an" no ack rake angles$ The la"es areshar!ene" % grin"ing the en"s onl%$ Parting is use" to cut off stock' such as tuing' that is

i#!ractical to saw off with a !ower hacksaw$

Parting is also use" to cut off work after other #achining o!erations ha+e een co#!lete").igure /-,0*$ Parting tools can e of the forge" t%!e' inserte" la"e t%!e' or groun" fro# a

stan"ar" tool lank$ n or"er for the tool to ha+e #ai#u# strength' the length of the cutting!ortion of the la"e shoul" eten" onl% enough to e slightl% longer than half of the work!iece

"ia#eter )ale to reach the center of the work*$ 3e+er atte#!t to !art while the work is#ounte" etween centers$


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Work that is to e !arte" shoul" e hel" rigi"l% in a chuck or collet' with the area to e !arte"as close to the hol"ing "e+ice as !ossile$ Alwa%s #ake the !arting cut at a right angle to the

centerline of the work$ .ee" the tool it into the re+ol+ing work with the cross sli"e until the toolco#!letel% se+ers the work$ S!ee"s for !arting shoul" e aout half that use" for straight

turning$ .ee"s shoul" e light ut continuous$ f chatter occurs' "ecrease the fee" an" s!ee"'an" check for loose lathe !arts or a loose setu!$ The !arting tool shoul" e !ositione" at centerheight unless cutting a !iece that is o+er 1-inch thick$ Thick !ieces shoul" ha+e the cutting tool4ust slightl% ao+e center to account for the stronger tor&ue in+ol+e" in !arting$ The length ofthe !ortion to e cut off can e #easure" % using the #icro#eter carriage sto! or % usingla%out lines scrie" on the work!iece$ Alwa%s ha+e the carriage locke" "own to the e" to

re"uce +iration an" chatter$ 3e+er tr% to catch the cutoff !art in the han"5 it will e hot an"coul" urn$

RA$II AN$ #OR% TURNIN!

Occasionall%' a ra"ius or irregular sha!e #ust e #achine" on the lathe$ .or# turning is the!rocess of #achining ra"ii an" these irregular sha!es$ The #etho" use" to for#-turn will

"e!en" on the si(e an" sha!e of the o4ect' the accurac% "esire"' the ti#e allowe"' an" thenu#er of !ieces that nee" to e for#e"$ Of the se+eral wa%s to for#-turn' using a for#turning tool that is groun" to the sha!e of the "esire" ra"ius is the #ost co##on$ Other

co##on #etho"s are using han" #ani!ulation an" filing' using a te#!late an" following ro"' orusing the co#!oun" rest an" tool to !i+ot an" cut$ Two ra"ii are cut in for# turning' conca+e

an" con+e$ A conca+e ra"ius cur+es inwar" an" a con+e ra"ius cur+es outwar"$

#orming a Ra&iu' U'ing a #orm Turning Tool

Using a for# turning tool to cut a ra"ius is a wa% to for# s#all ra"ii an" contours that will fit thesha!e of the tool$ .or#ing tools can e groun" to an% "esire" sha!e or contour ).igure /-67*'

with the onl% re&uire#ents eing that the !ro!er relief an" rake angles #ust e groun" into the


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tool8s sha!e$ The #ost !ractical use of the groun" for#ing tool is in #achining se+eral "u!licate!ieces' since the #achining of one or two !ieces will not warrant the ti#e s!ent on grin"ing thefor# tool$ Use the !ro!er ra"ius gage to check for correct fit$ A for#ing tool has a lot of contact

with the work surface' which can result in +iration an" chatter$ Slow the s!ee"' increase thefee"' an" tighten the work setu! if these !role#s occur$

#orming a Ra&iu' U'ing Han& %anipulation

Han" #ani!ulation' or free han"' is the #ost "ifficult #etho" of for# turning to #aster$ The

cutting tool #o+es on an irregular !ath as the carriage an" cross sli"e are si#ultaneousl%#ani!ulate" % han"$ The "esire" for# is achie+e" % watching the tool as it cuts an" #akings#all a"4ust#ents in the #o+e#ent of the carriage an" cross sli"e$ 3or#all%' the right han"

works the cross fee" #o+e#ent while the left han" works the carriage #o+e#ent$ The accurac%of the ra"ius "e!en"s on the skill of the o!erator$ After the a!!roi#ate ra"ius is for#e"' the

work!iece is file" an" !olishe" to a finishe" "i#ension$

#orming a Ra&iu' U'ing a Template

To use a te#!late with a follower ro" to for# a ra"ius' a full scale for# of the work is lai" outan" cut fro# thin sheet #etal$ This for# is then attache" to the cross sli"e in such a wa% that

the cutting tool will follow the te#!late$ The accurac% of the te#!late will "eter#ine theaccurac% of the work!iece$ Each lathe #o"el has a cross sli"e an" carriage that are slightl%

"ifferent fro# one another' ut the% all o!erate in asicall% the sa#e wa%$ A #ounting racket#ust e faricate" to hol" the te#!late to allow the cutting tool to follow its sha!e$ This

#ounting racket can e utili(e" for se+eral "ifferent o!erations' ut shoul" e stur"% enoughfor hol"ing cla#!s an" te#!lates$ The #ounting racket #ust e !ositione" on the carriage toallow for a follower )that is attache" to the cross sli"e* to contact the te#!late an" gui"e the

cutting tool$ .or this o!eration' the cross sli"e #ust e "isconnecte" fro# the cross fee" screwan" han" !ressure a!!lie" to hol" the cross sli"e against the follower an" te#!late$ 9ough-cut

the for# to the a!!roi#ate sha!e efore "isconnecting the cross fee" screw$ This wa%' a finishcut is all that is re&uire" while a!!l%ing han" !ressure to the cross sli"e$ So#e filing #a% e

nee"e" to co#!letel% finish the work to "i#ension$

#orming a Ra&iu' U'ing t(e Compoun& Re't

To use the co#!oun" rest an" tool to !i+ot an" cut ).igure /-61*' the co#!oun" rest olts #uste loosene" to allow the co#!oun" rest to swi+el$ When using this #etho"' the co#!oun" restan" tool are swung fro# si"e to si"e in an arc$ The "esire" ra"ius is for#e" % fee"ing the toolin or out with the co#!oun" sli"e$ The !i+ot !oint is the center swi+el !oint of the co#!oun"rest$ A conca+e ra"ius can e turne" % !ositioning the tool in front of the !i+ot !oint' while acon+e ra"ius can e turne" % !lacing the tool ehin" the !i+ot !oint$ Use the #icro#eter

carriage sto! to #easure !recision "e!ths of "ifferent ra"ii$


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TAER TURNIN!

When the "ia#eter of a !iece changes unifor#l% fro# one en" to the other' the !iece is sai" toe ta!ere"$ Ta!er turning as a #achining o!eration is the gra"ual re"uction in "ia#eter fro#

one !art of a c%lin"rical work!iece to another !art$ Ta!ers can e either eternal or internal$ f a

work!iece is ta!ere" on the outsi"e' it has an eternal ta!er5 if it is ta!ere" on the insi"e' it hasan internal ta!er$ There are three asic #etho"s of turning ta!ers with a lathe$ :e!en"ing onthe "egree' length' location of the ta!er )internal or eternal*' an" the nu#er of !ieces to e

"one' the o!erator will either use the co#!oun" rest' offset the tailstock' or use the ta!erattach#ent$ With an% of these #etho"s the cutting e"ge of the tool it #ust e set eactl% oncenter with the ais of the work!iece or the work will not e trul% conical an" the rate of ta!er

will +ar% with each cut$

Compoun& Re't'

The co#!oun" rest is fa+orale for turning or oring short' stee! ta!ers' ut it can also e use"

for longer' gra"ual ta!ers !ro+i"ing the length of ta!er "oes not ecee" the "istance theco#!oun" rest will #o+e u!on its sli"e$ This #etho" can e use" with a high "egree of

accurac%' ut is so#ewhat li#ite" "ue to lack of auto#atic fee" an" the length of ta!er eingrestricte" to the #o+e#ent of the sli"e$


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The co#!oun" rest ase is gra"uate" in "egrees an" can e set at the re&uire" angle for ta!erturning or oring$ With this #etho"' it is necessar% to know the inclu"e" angle of the ta!er to e#achine"$ The angle of the ta!er with the centerline is one-half the inclu"e" angle an" will ethe angle the co#!oun" rest is set for$ .or ea#!le' to true u! a lathe center which has an

inclu"e" angle of 67' the co#!oun" rest woul" e set at ;7 fro# !arallel to the wa%s ).igure/-


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Using the trig charts in TC 0-,1, or an% other source of trig charts' the TA3 of 7$


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Since the work!iece is #ounte" etween centers' this #etho" of ta!er turning can onl% e use"for eternal ta!ers$ The length of the ta!er is fro# hea"stock center to tailstock center' whichallows for longer ta!ers than can e #achine" using the co#!oun" rest or ta!er attach#ent

#etho"s$

The tool it tra+els along a line which is !arallel with the wa%s of the lathe$ When the lathecenters are aligne" an" the work!iece is #achine" etween these centers' the "ia#eter will

re#ain constant fro# one en" of the !iece to the other$ f the tailstock is offset' as shown in.igure /-6


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The offset tailstock #etho" is a!!licale onl% to co#!arati+el% gra"ual ta!ers ecause the lathecenters' eing out of align#ent' "o not ha+e full earing on the work!iece$ Center holes arelikel% to wear out of their true !ositions if the lathe centers are offset too far' causing !oor

results an" !ossile "a#age to centers$

The #ost "ifficult o!eration in ta!er turning % the offset tailstock #etho" is "eter#ining the!ro!er "istance the tailstock shoul" e #o+e" o+er to otain a gi+en ta!er$ Two factors affect

the a#ount the tailstock is offset= the ta!er "esire" an" the length of the work!iece$ f theoffset re#ains constant' work!ieces of "ifferent lengths' or with "ifferent "e!th center holes'

will e #achine" with "ifferent ta!ers ).igure /-6,*$

The for#ula for calculating the tailstock offset when the ta!er is gi+en in ta!er inches !er foot)t!f* is as follows

W(ere+ Off'et)tail'tock off'et ,in inc(e'-T#)taper ,in inc(e' per foot-

L)lengt( of taper ,in feet- mea'ure& along t(e a.i' of t(e workpiece

.or ea#!le' the a#ount of offset re&uire" to #achine a ar


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Where O##SETBtailstock offsetTIBta!er !er inch

LBlength of ta!er in inches

.or ea#!le' the a#ount of offset re&uire" to #achine a ar


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ta!er$

etric ta!ers can also e calculate" for ta!er turning % using the offset tailstock #etho"$ etricta!ers are e!resse" as a ratio of 1 ## !er unit of length$ .igure /-66 shows how the work

woul" ta!er 1 ## in a "istance of 27 ##$ This ta!er woul" then e gi+en as a ratio of 1=27 an"woul" e annotate" on s#all "ia#eter )"* will e 1 ## greater )" D *$ 9efer to the following

for#ula for calculating the "i#ensions of a #etric ta!er$ f the s#all "ia#eter )"*' the unit length

of ta!er )k*' an" the total length of ta!er )1* are known' then the large "ia#eter ):* #a% ecalculate"$ The large "ia#eter ):* will e e&ual to the s#all "ia#eter !lus the a#ount of ta!er$The a#ount of ta!er for the unit length )k* is )" D 1* -)"*$ Therefore' the a#ount of ta!er !er#illi#eter of unit length B )l@k*$ The total a#ount of ta!er will e the ta!er !er #illi#eter )l@k*

#ulti!lie" % the total length of ta!er )l*$

.or ea#!le' to calculate for the large "ia#eter : for a 1=;7

ta!er ha+ing a s#all "ia#eter of 17 ## an" a length of 67 ##' "o the following=

Since the ta!er is the ratio 1=;7' then )k*B ;7' since ;7 is the unit of length$

Tailstock offset is calculate" as follows=

Tailstock offset B

$B large "ia#eter


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&B s#all "ia#eterI B length of ta!erL B length of the work!iece

Thus' to "eter#ine the tailstock offset in #illi#eters for the ta!er in .igure /-6/' sustitute thenu#ers an" sol+e for the offset$ Calculate the tailstock offset re&uire" to turn a 1=,7 ta!er 277

## long on a work!iece 77 ## long$ The s#all "ia#eter of the ta!ere" section is


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One #etho" is to gage the "istance the lineu! #arks on the rear of the tailstock ha+e #o+e"

out of align#ent$ This can e "one % using a 6-inch rule !lace" near the lineu! #arks or %transferring the "istance etween the #arks to the rule8s surface using a !air of "i+i"ers$

Another co##on #etho" uses a rule to check the a#ount of offset when the tailstock is roughtclose to the hea"stock$

Where accurac% is re&uire"' the a#ount of offset #a% e #easure" % #eans of the gra"uate"collar on the cross fee" screw$ .irst co#!ute the a#ount of offset5 net' set the tool hol"er inthe tool !ost so the utt en" of the hol"er faces the tailstock s!in"le$ Using the cross fee"' runthe tool hol"er in % han" until the utt en" touches the tailstock s!in"le$ The !ressure shoul"e 4ust enough to hol" a sli! of !a!er !lace" etween the tool hol"er an" the s!in"le$ 3et'

#o+e the cross sli"e to ring the tool hol"er towar" %ou to re#o+e the acklash$ The rea"ing onthe cross fee" #icro#eter collar #a% e recor"e"' or the gra"uate" collar on the cross fee"screw #a% e set at (ero$ Using either the recor"e" rea"ing or the (ero setting for a starting!oint' ring the cross sli"e towar" %ou the "istance co#!ute" % the offset$ Loosen an" offsetthe tailstock until the sli! of !a!er "rags when !ulle" etween the tool hol"er an" the s!in"le$Cla#! the tailstock to the lathe e"$

Another an" !ossil% the #ost !recise #etho" of #easuring the offset is to use a "ial in"icator$The in"icator is set on the center of the tailstock s!in"le while the centers are still aligne"$ Aslight loa"ing of the in"icator is a"+ise" since the first 7$717 or 7$727 inches of #o+e#ent of thein"icator #a% e inaccurate "ue to #echanis# wear causing fluctuating rea"ings$ Loa" the "ial

in"icators follows= Set the e(el to (ero an" #o+e tailstock towar"s the o!erator the calculate".a#ount$ Then cla#! the tailstock to the wa%$

Whiche+er #etho" is use" to offset the tailstock' the offset #ust still e checke" efore startingto cut$ Set the "ial in"icator in the tool !ost with its s!in"le 4ust arel% touching far right si"e ofthe work!iece$ Then' rotate the carriage towar" the hea"stock eactl% 1 inch an" take therea"ing fro# the "ial in"icator$ One inch is easil% acco#!lishe" using the threa" chasing "ial$ t is1 inch fro# one nu#er to another$

Alternati+el%' 1 inch can e "rawn out on the work!iece$ The "ial in"icator will in"icate the ta!erfor that 1 inch an"' if nee"e"' the tailstock can e a"4uste" as nee"e" to the !recise ta!er

"esire"$ f this #etho" of checking the ta!er is not use"' then an etensi+e trial an" error#etho" is necessar%$

To cut the ta!er' start the rough turning at the en" which will e the s#all "ia#eter an" fee"


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longitu"inall% towar" the large en" ).igure /-6


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carriage fee"s along' the tool is alwa%s the sa#e "istance fro# the centerline$ The !ur!ose ofthe ta!er attach#ent is to #ake it !ossile to kee! the lathe centers in line' ut % freeing thecross sli"e an" then gui"ing it )an" the tool it* gra"uall% awa% fro# the centerline' a ta!er cane cut or' % gui"ing it gra"uall% nearer the centerline ).igure /-/7*' a ta!er hole can e ore"$

A !lain ta!er attach#ent for the lathe is illustrate" in .igure /-60$ A e" racket attaches to thelathe e" an" kee!s the angle !late fro# #o+ing to the left or the right$ The carriage racket#o+es along the un"ersi"e of the angle !late in a "o+etail an" kee!s the angle !late fro##o+ing in or out on the e" racket$ The ta!er to e cut is set % !lacing the gui"e ar' whichcla#!s to the angle !late' at an angle to the wa%s of the lathe e"$ ra"uations on one or othen"s of the gui"e ar are use" to #ake this a"4ust#ent$ A sli"ing lock which ri"es on a "o+etailon the u!!er surface of the gui"e ar is secure" "uring the #achining o!eration to the cross

sli"e ar of the carriage' with the cross fee" screw of the carriage eing "isconnecte"$Therefore' as the carriage is tra+erse" "uring the fee"ing o!eration' the cross sli"e ar followsthe gui"e ar' #o+ing at the !re"eter#ine" angle fro# the wa%s of the e" to cut the ta!er$ t isnot necessar% to re#o+e the ta!er attach#ent when straight turning is "esire"$ The gui"e arcan e set !arallel to the wa%s' or the cla#! han"le can e release" !er#itting the sli"ing lockto #o+e without affecting the cross sli"e ar' an" the cross fee" screw can e reengage" to!er#it !ower cross fee" an" control of the cross sli"e fro# the a!ron of the carriage$

o"ern lathes often use a telesco!ic ta!er attach#ent$ This attach#ent allows for using thecross fee"' an" set u! is a it faster than using a stan"ar" ta!er attach#ent$ To use thetelesco!ic attach#ent' first set the tool it for the re&uire" "ia#eter of the work an" engage the

attach#ent % tightening the in"ing screws' the location an" nu#er of which "e!en" u!on the"esign of the attach#ent$ The !ur!ose of the in"ing screws is to in" the cross sli"e so it #a%e #o+e" onl% % turning the cross fee" han"le' or' when loosene"' to free the cross sli"e foruse with the ta!er attach#ent$ To change ack to straight turning with the telesco!ic


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attach#ent' it is necessar% onl% to loosen the in"ing screws$

When cutting a ta!er using the ta!er attach#ent' the "irection of fee" shoul" e fro# theinten"e" s#all "ia#eter towar" the inten"e" large "ia#eter$ Cutting in this #anner' the "e!th ofcut will "ecrease as the tool it !asses along the work!iece surface an" will assist the o!eratorin !re+enting !ossile "a#age to the tool it' work!iece' an" lathe % forcing too "ee! a cut$

The length of the ta!er the gui"e ar will allow is usuall% not o+er 12 to 2< inches' "e!en"ing onthe si(e of the lathe$ t is !ossile to #achine a ta!er longer than the gui"e ar allows %#o+ing the attach#ent after a !ortion of the "esire" ta!er length has een #achine"5 then there#ain"er of the ta!er can e cut$ Howe+er' this o!eration re&uires e!erience$

f a !lain stan"ar" ta!er attach#ent is eing use"' re#o+e the in"ing screw in the cross sli"ean" set the co#!oun" rest !er!en"icular to the wa%s$ Use the co#!oun" rest gra"uate" collarfor "e!th a"4ust#ents$

When using the ta!er attach#ent' there #a% e a certain a#ount of Flost #otionF )acklash*which #ust e eli#inate" or serious !role#s will result$ n e+er% sli"e an" e+er% freel%

re+ol+ing screw there is a certain a#ount of lost #otion which is +er% noticeale if the !arts areworn$ Care #ust e taken to re#o+e lost #otion efore !rocee"ing to cut or the work!iece wille turne" or ore" straight for a short "istance efore the ta!er attach#ent egins to work$ Totake u! lost #otion when turning ta!ers' run the carriage ack towar" the "ea" center as far as!ossile' then fee" forwar" % han" to the en" of the work!iece where the !ower fee" isengage" to finish the cut$ This !roce"ure #ust e re!eate" for e+er% cut$

The est wa% to ore a ta!er with a lathe is to use the ta!er attach#ent$ ?acklash #ust ere#o+e" when ta!ers are eing ore" with the ta!er attach#ent' otherwise the hole will eore" straight for a "istance efore the ta!er starts$ Two i#!ortant factors to consi"er= theoring tool #ust e set eactl% on center with the work!iece ais' an" it #ust e s#all enough

in si(e to !ass through the hole without ruing at the s#all "ia#eter$ A +iolation of either ofthese factors will result in a !oorl% for#e"' inaccurate ta!er or "a#age to the tool an"work!iece$ The clearance of the cutter it shank an" oring tool ar #ust e "eter#ine" for thes#aller "ia#eter of the ta!er$ Ta!er oring is acco#!lishe" in the sa#e #anner as ta!erturning$

To set u! the lathe attach#ent for turning a ta!er' the !ro!er TP. #ust e calculate" an" theta!er attach#ent set-o+er #ust e checke" with a "ial in"icator !rior to cutting$ Calculate theta!er !er foot % using the for#ula=

T# ) taper per foot*$ ) large &iameter ,in inc(e'-*& ) 'mall &iameter ,in inc(e'-*L ) lengt( of taper

After the TP. is "eter#ine"' the a!!roi#ate angle can e set on the gra"uate" TP. scale ofthe ta!er attach#ent$ Use a "ial in"icator an" a test ar to set u! for the eact ta!er$ Check theta!er in the sa#e #anner as cutting the ta!er % allowing for acklash an" #o+ing the "ialin"icator along the test ar fro# the tailstock en" of the hea" stock en"$ Check the TP % using

the threa"-chasing "ial' or using la%out lines of 1-inch si(e' an" #ulti!l% % 12 to check the TP.$ake an% a"4ust#ents nee"e"' set u! the work to e ta!ere"' an" take a trial cut$ Afterchecking the trial cut an" #aking final a"4ust#ents' continue to cut the ta!er to re&uire""i#ensions as in straight turning$ So#e lathes are set u! in #etric #easure#ent instea" of inch


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#easure#ent$ The ta!er attach#ent has a scale gra"uate" in "egrees' an" the gui"e ar cane set o+er for the angle of the "esire" ta!er$ f the angle of the ta!er is not gi+en' use thefollowing for#ula to "eter#ine the a#ount of the gui"e ar set o+er=

ui"e ?ar Set O+er )in #illi#eters* B

$ ) large &iameter of taper ,mm-

& ) 'mall &iameter of taper ,mm-

I ) lengt( of taper ,mm-

L ) lengt( of gui&e bar ,mm-

9eference lines #ust e #arke" on the gui"e ar an e&ual "istance fro# the center for estresults$

A #etric "ial in"icator can e use" to #easure the gui"e ar set o+er' or the +alues can echange" to inch +alues an" an inch "ial in"icator use"$

C(ecking Taper' for Accurac0

Ta!ers #ust e checke" for unifor#it% after cutting a trial cut$ La% a goo" straight e"ge alongthe length of the ta!er an" look for an% "e+iation of the angle or surface$ :e+iation is cause" %acklash or a lathe with loose or worn !arts$ A ore" ta!er #a% e checke" with a !lug gage).igure /-/1* % #arking the gage with chalk or Prussian lue !ig#ent$ nsert the gage into theta!er an" turn it one re+olution$ f the #arking on the gage has een rue" e+enl%' the angleof ta!er is correct$ The angle of ta!er #ust e increase" when there is not enough contact atthe s#all en" of the !lug gage' an" it #ust e "ecrease" when there is not enough contact atthe large en" of the gage$ After the correct ta!er has een otaine" ut the gage "oes notenter the work!iece far enough' a""itional cuts #ust e taken to increase the "ia#eter of theore$

An eternal ta!er #a% e checke" with a ring gage ).igure /-/1*$ This is achie+e" % the sa#e#etho" as for checking internal ta!ers' ece!t that the work!iece will e #arke" with the chalk

or Prussian lue !ig#ent rather than the gage$ Also' the angle of ta!er #ust e "ecrease" whenthere is not enough contact at the s#all en" of the ring gage an" it #ust e increase" whenthere is not enough contact at the large en" of the gage$ f no gage is a+ailale' the work!ieceshoul" e teste" in the hole it is to fit$ When e+en contact has een otaine"' ut the ta!ere"


17/59

!ortion "oes not enter the gage or hole far enough' the "ia#eter of the !iece is too large an"#ust e "ecrease" % a""itional "e!th of cut

Another goo" #etho" of checking eternal ta!ers is to scrie lines on the work!iece 1 inch a!art).igure /-/2*5 then' take #easure#ents with an outsi"e #icro#eter$ Sutracting the s#allrea"ing fro# the large rea"ing will gi+e the ta!er !er inch$

$uplicating a Tapere& iece

When the ta!er on a !iece of work is to e "u!licate" an" the original !iece is a+ailale' it #a%e !lace" etween centers on the lathe an" checke" with a "ial in"icator #ounte" in the tool!ost$$ When the setting is correct' the "ial in"icator rea"ing will re#ain constant when #o+e"

along the length of ta!er$

This sa#e #etho" can e use" on work!ieces without centers !ro+i"e" one en" of thework!iece can e #ounte" an" hel" securel% on center in the hea"stock of the lathe$ .orea#!le' a lathe center coul" e #ounte" in the lathe s!in"le % use of the s!in"le slee+e' or a!artiall% ta!ere" work!iece coul" e hel" % the nonta!ere" !ortion #ounte" in a collet or achuck$ Using either of these two #etho"s of hol"ing the work' the o!erator coul" use onl% theco#!oun" rest or the ta!er attach#ent for "eter#ining an" #achining the ta!ers$

Stan&ar& Taper'

There are +arious stan"ar" ta!ers in co##ercial use' the #ost co##on ones eing the orseta!ers' the ?rown an" Shar!e ta!ers' the A#erican Stan"ar" achine ta!ers' the Garno ta!ers'an" the Stan"ar" ta!er !ins$

orse ta!ers are use" on a +ariet% of tool shanks' an" eclusi+el% on the shanks of twist "rills$The ta!er for "ifferent nu#ers of orse ta!ers is slightl% "ifferent' ut is a!!roi#atel% ,@inch !er foot in #ost cases$ :i#ensions for orse ta!ers are gi+en in Tale /-< in A!!en"i A$

?rown an" Shar!e ta!ers are use" for ta!er shanks on tools such as en" #ills an" rea#ers$ Theta!er is a!!roi#atel% inch !er foot for all si(es ece!t for ta!er 3o 17' where the ta!er is

7$,161 inch !er foot$

The A#erican Stan"ar" #achine ta!ers are co#!ose" of a self-hol"ing series an" a stee! ta!erseries$ The self-hol"ing ta!er series consists of 22 si(es which are gi+en in Tale /-, in A!!en"i

A$ The na#e Fself-hol"ingF has een a!!lie" where the angle of the ta!er is onl% 2 or ; an"


18/59

the shank of the tool is so fir#l% seate" in its socket that there is consi"erale frictionalresistance to an% force ten"ing to$ turn or rotate the tool in the hol"er$ The self-hol"ing ta!ersare co#!ose" of selecte" ta!ers fro# the orse' the ?rown an" Shar!e' an" the I-inch-!erfoot #achine ta!er series$ The s#aller si(es of self-hol"ing ta!ere" shanks are !ro+i"e" with atang to "ri+e the cutting tool$ Larger si(es e#!lo% a tang "ri+e with the shank hel" % a ke%' ora ke% "ri+e with the shank hel" with a "raw olt$ The stee! #achine ta!ers consist of a!referre" series an" an inter#e"iate series as gi+en in Tale /-6 in A!!en"i A$ A stee! ta!er is

"efine" as a ta!er ha+ing an angle large enough to ensure the eas% or self-releasing feature$Stee! ta!ers ha+e a ; -inch ta!er !er foot an" are use" #ainl% for aligning #illing #achinearors an" s!in"les' an" on so#e lathe s!in"les an" their accessories$

The Garno ta!er is ase" on such si#!le for#ulas that !racticall% no calculations are re&uire"when the nu#er of ta!er is known$ The ta!er !er foot of all Garno ta!ers is 7$677 inch !erfoot$ The "ia#eter at the large en" is as #an% eighths' the "ia#eter at the s#all en" is as#an% tenths' an" the length as #an% half-inches as in"icate" % the nu#er of the ta!er$ .orea#!le= A 3o / Garno ta!er is /@ inch in "ia#eter at the large en"5 /@17 or 7$/ inch in"ia#eter at the s#all en"5 an" /@2' or ; inches long$ Therefore' for#ulas for these"i#ensions woul" rea"=

The Garno ta!er is use" on +arious #achine tools' es!eciall% !rofiling #achines an" "ie-sinking#achines$ t has also een use" for the hea"stock an" tailstock s!in"les on so#e lathes$

The Stan"ar" ta!er !ins are use" for !ositioning an" hol"ing !arts together an" ha+e a J-inchta!er !er foot$ Stan"ar" si(es in these !ins range fro# 3o /@7 to 3o 17 an" are gi+en in Tale/-/ in A!!en"i A$ The ta!ere" holes use" in con4unction with the ta!ere" !ins utili(e the!rocesses of ste!-"rilling an" ta!er rea#ing$

To !reser+e the accurac% an" efficienc% of ta!ers )shanks an" holes*' the% #ust e ke!t freefro# "irt' chi!s' nicks' or urrs$ The #ost i#!ortant thing in regar" to ta!ers is to kee! the#clean$ The net #ost i#!ortant thing is to re#o+e all oil % wi!ing the ta!ere" surfaces with asoft' "r% cloth efore use' ecause an oil% ta!er will not hol"$

SCREW THREA$ CUTTIN!

Screw threa"s are cut with the lathe for accurac% an" for +ersatilit%$ ?oth inch an" #etric screwthrea"s can e cut using the lathe$ A threa" is a unifor# helical groo+e cut insi"e of a c%lin"ricalwork!iece' or on the outsi"e of a tue or shaft$ Cutting threa"s % using the lathe re&uires athorough knowle"ge of the "ifferent !rinci!les of threa"s an" !roce"ures of cutting$ Han"coor"ination' lathe #echanis#s' an" cutting tool angles are all interrelate" "uring the threa"cutting !rocess$ ?efore atte#!ting to cut threa"s on the lathe a #achine o!erator #ust ha+e athorough knowle"ge of the !rinci!les' ter#inolog% an" uses of threa"s$


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Screw T(rea& Terminolog0

The co##on ter#s an" "efinitions elow are use" in screw threa" work an" will e use" in"iscussing threa"s an" threa" cutting$

Eternal or #ale threa" is a threa" on the outsi"e of a c%lin"er or cone$

nternal or fe#ale threa" is a threa" on the insi"e of a hollow c%lin"er or ore$

Pitch is the "istance fro# a gi+en !oint on one threa" to a si#ilar !oint on a threa" net toit' #easure" !arallel to the ais of the c%lin"er$ The !itch in inches is e&ual to one "i+i"e"% the nu#er of threa"s !er inch$

Lea" is the "istance a screw threa" a"+ances aiall% in one co#!lete re+olution$ On asingle-threa" screw' the lea" is e&ual to the !itch$ On a "oule-threa" screw' the lea" ise&ual to twice the !itch' an" on a tri!le-threa" screw' the lea" is e&ual to three ti#es the!itch ).igure /-/


20/59

groo+e is e&ual to one-half of the !itch$ This is the critical "i#ension of threa"ing as the fitof the threa" is "eter#ine" % the !itch "ia#eter )3ot use" for #etric threa"s*$

Threa"s !er inch is the nu#er of threa"s !er inch #a% e counte" % !lacing a ruleagainst the threa"e" !arts an" counting the nu#er of !itches in 1 inch$ A secon" #etho"is to use the screw !itch gage$ This #etho" is es!eciall% suitale for checking the finer!itches of screw threa"s$

A single threa" is a threa" #a"e % cutting one single groo+e aroun" a ro" or insi"e ahole$ ost har"ware #a"e' such as nuts an" olts' has single threa"s$ :oule threa"sha+e two groo+es cut aroun" the c%lin"er$ There can e two' three' or four threa"s cutaroun" the outsi"e or insi"e of a c%lin"er$ These t%!es of s!ecial threa"s are so#eti#escalle" #ulti!le threa"s$

A right-han" threa" is a threa" in which the olt or nut #ust e turne" to the right)clockwise* to tighten$

A left han" threa" is a threa" in which the olt or nut #ust turn to the left

)counterclockwise* to tighten$

Threa" fit is the wa% a olt an" nut fit together as to eing too loose or too tight$

etric threa"s are threa"s that are #easure" in #etric #easure#ent instea" of inch#easure#ent$

Screw T(rea& #orm'


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The #ost co##onl% use" screw threa" for#s are "etaile" in the following !aragra!hs$ One ofthe #a4or !role#s in in"ustr% is the lack of a stan"ar" for# for fastening "e+ices$ The screwthrea" for#s that follow atte#!t to sol+e this !role#5 howe+er' there is still #ore than onestan"ar" for# eing use" in each in"ustrial nation$ The nternational Organi(ation forStan"ar"i(ation )S7* #et in 10/, an" "rew u! a stan"ar" #etric #easure#ent for screwthrea"s' the new S7 etric threa" Stan"ar" )!re+iousl% known as the O!ti#u# etric .astenerS%ste#*$ Other threa" for#s are still in general use to"a%' inclu"ing the A#erican )3ational*

screw threa" for#' the s&uare threa"' the Ac#e threa"' the ?rown an" Shar!e 20 wor# screwthrea"' the ?ritish Stan"ar" Whitworth threa"' the Unifie" threa"' an" "ifferent !i!e threa"s$ Allof these threa"s can e cut % using the lathe$

The S7 etric threa" stan"ar" is a si#!le threa" s%ste# that has threa"e" si(es rangingin "ia#eter fro# 1$6 ## to 177 ## )see Tale /- in A!!en"i A*$ These #etric threa"sare i"entifie" % the ca!ital ' the no#inal "ia#eter' an" the !itch$ .or ea#!le' a #etricthrea" with an outsi"e "ia#eter of , ## an" a !itch of 7$ ## woul" e gi+en as , 7$$ The S7 #etric threa" stan"ar" si#!lifies threa" "esign' !ro+i"es for goo" strongthrea"s' an" re&uires a s#aller in+entor% of screw fasteners than use" % other threa"for#s$ This S7 etric threa" has a 67 inclu"e" angle an" a crest that is 1$2, ti#es the

!itch )which is si#ilar to the 3ational threa" for#*$ The "e!th of threa" is 7$61;< ti#esthe !itch' an" the flat on the root of the threa" is wi"er than the crest$ The root of theSO etric threa" is 7$2,7 ti#es the !itch )Tale /-0*$

The A#erican )3ational* screw threa" for# is "i+i"e" into four series' the 3ational Coarse)3C*' 3ational .ine )3.*' 3ational S!ecial )3S*' an" 3ational Pi!e threa"s )3PT*$ 11 seriesof this threa" for# ha+e the sa#e sha!e an" !ro!ortions$ This threa" has a 67 inclu"e"angle$ The root an" crest are 7$12, ti#es the !itch$ This threa" for# is wi"el% use" inin"ustrial a!!lications for farication an" eas% asse#l% an" construction of #achine !arts$Tale /-0 in A!!en"i A gi+es the "ifferent +alues for this threa" for#$

The ?ritish Stan"ar" Whitworth threa" for# threa" has a ,, threa" for# in the K-sha!e$t has roun"e" crests an" roots$

The Unifie" threa" for# is now use" instea" of the A#erican )3ational* threa" for#$ twas "esigne" for interchangeailit% etween #anufacturing units in the Unite" States'Cana"a' an" reat ?ritain$ This threa" is a co#ination of the A#erican )3ational* screwthrea" for# an" the ?ritish Whitworth screw threa" for#s$ The threa" has a 67 anglewith a roun"e" root' while the crest can e roun"e" or flat$ )n the Unite" States' a flatcrest is !referre"$* The internal threa" of the unifie" for# is like the A#erican )3ational*threa" for# ut is not cut as "ee!' lea+ing a crest of one-fourth the !itch instea" ofone-eighth the !itch$ The coarse threa" series of the unifie" s%ste# is "esignate" U3C'while the fine threa" series is "esignate" U3.$ )See Tale /-0 in A!!en"i A for threa"for# an" +alues$

The A#erican 3ational 20 Ac#e was "esigne" to re!lace the stan"ar" s&uare threa"'which is "ifficult to #achine using nor#al ta!s an" #achine "ies$ This threa" is a !owertrans#itting t%!e of threa" for use in 4acks' +ises' an" fee" screws$ Tale /-0 lists the+alues for Ac#e threa"s$

The ?rown an" Shar!e 20 wor# screw threa" uses a 20 angle' si#ilar to the Ac#e threa"$The "e!th is greater an" the wi"ths of the crest an" root are "ifferent )Tale /-0 in A!!en"i

A*$ This is a s!ecial threa" use" to #esh with wor# gears an" to trans#it #otion etween twoshafts at right angles to each other that are on se!arate !lanes$ This threa" has a self-lockingfeature #aking it useful for winches an" steering #echanis#s$

The s&uare screw threa" is a !ower trans#itting threa" that is eing re!lace" % the Ac#e


22/59

threa"$ So#e +ises an" lea" screws #a% still e e&ui!!e" with s&uare threa"s$ Contactareas etween the threa"s are s#all' causing screws to resist we"ging' an" frictionetween the !arts is #ini#al )Tale /-0 in A!!en"i A*$

The s!ark !lug threa" )international #etric threa" t%!e* is a s!ecial threa" use"etensi+el% in Euro!e' ut seen onl% on so#e s!ark !lugs in the Unite" States$ t has aninclu"e" angle of 67 with a crest an" root that are 7$12, ti#es the "e!th$

:ifferent t%!es of !i!e threa" for#s are in use that ha+e generall% the sa#echaracteristics ut "ifferent fits$ Consult the achiner%8s Han"ook or a si#ilar referencefor this t%!e of threa"$

THREA$ #IT AN$ CLASSI#ICATIONS

The Unifie" an" A#erican )3ational* threa" for#s "esignate classifications for fit to ensure that#ate" threa"e" !arts fit to the tolerances s!ecifie"$ The unifie" screw threa" for# s!ecifiesse+eral classes of threa"s which are Classes 1A' 2A' an" ;A for screws or eternal threa"e"!arts' an" 1?' 2?' an" ;? for nuts or internal threa"e" !arts$ Classes 1 A an" 1 ? are for a

loose fit where &uick asse#l% an" ra!i" !ro"uction are i#!ortant an" shake or !la% is noto4ectionale$ Classes 2A an" 2? !ro+i"e a s#all a#ount of !la% to !re+ent galling an" sei(urein asse#l% an" use' an" sufficient clearance for so#e !lating$ Classes 2A an" 2? arereco##en"e" for stan"ar" !ractice in #aking co##ercial screws' olts' an" nuts$ Classes ;Aan" ;? ha+e no allowance an" /, !ercent of the tolerance of Classes 2A an" 2? A screw an"nut in this class #a% +ar% fro# a fit ha+ing no !la% to one with a s#all a#ount of !la%$ Onl% highgra"e !ro"ucts are hel" to Class ; s!ecifications$

.our "istinct classes of screw threa" fits etween #ating threa"s )as etween olt an" nut*ha+e een "esignate" for the A#erican )3ational* screw threa" for#$ .it is "efine" as Ftherelation etween two #ating !arts with reference to ease of asse#l%$ F These four fits are!ro"uce" % the a!!lication of tolerances which are liste" in the stan"ar"s$

The four fits are "escrie" as follows=

Class 1 fit is reco##en"e" onl% for screw threa" work where clearance etween #ating!arts is essential for ra!i" asse#l% an" where shake or !la% is not o4ectionale$

Class 2 fit re!resents a high &ualit% of threa" !ro"uct an" is reco##en"e" for the greatulk of interchangeale screw threa" work$

Class ; fit re!resents an ece!tionall% high &ualit% of co##erciall% threa"e" !ro"uct an" is

reco##en"e" onl% in cases where the high cost of !recision tools an" continual checkingare warrante"$

Class < fit is inten"e" to #eet +er% unusual re&uire#ents #ore eacting than those forwhich Class ; is inten"e"$ t is a selecti+e fit if initial asse#l% % han" is re&uire"$ t isnot' as %et' a"a!tale to &uantit% !ro"uction$

T(rea& $e'ignation'

n general' screw threa" "esignations gi+e the screw nu#er )or "ia#eter* first' then the threa"!er inch$ 3et is the threa" series containing the initial letter of the series' 3C )3ational Coarse*'

U3. )Unifie" .ine*' 3S )3ational S!ecial*' an" so forth' followe" % the class of fit$ f a threa" isleft-han"' the letters LH follow the fit$ An ea#!le of "esignations is as follows=


23/59

Two sa#!les an" e!lanations of threa" "esignations are as follows=

3o 12 )7$216* - 2< 3C-;$ This is a nu#er 12 )7$216-inch "ia#eter* threa"' 2< 3ationalCoarse threa"s !er inch' an" Class ; wa%s of "esignating the fit etween !arts' inclu"ingtolerance gra"es' tolerance !ositions' an" tolerance classes$ A si#!ler fit$

1@


24/59

it ).igure /-/6*' !er!en"icular to the center line of the 677 threa" angle$ See the threa" for#tale for the a!!ro!riate threa" to "eter#ine the wi"th of the Sat$ .or unifie" threa" for#s' theti! of the tool it shoul" e groun" with a ra"ius for#e" to fit the si(e of the root of the threa"$nternal unifie" threa"s ha+e a flat on the ti! of the tool it$ n all threa"s liste" ao+e' the tool

it shoul" e groun" with enough si"e relief angle an" enough front clearance angle ).igure/-/6*$ .igure /-// illustrates the correct ste!s in+ol+e" in grin"ing a threa"-cutting tool it$

.or Ac#e an" 20 wor# screw threa"s' the cutter it #ust e groun" to for# a !oint angle of20$ Si"e clearances #ust e sufficient to !re+ent ruing on threa"s of stee! !itch$ The en" ofthe it is then groun" to a flat which agrees with the wi"th of the root for the s!ecific !itcheing cut$ Threa"-cutting tool gages ).igure /-/* are a+ailale to si#!lif% the !roce"ure an"#ake co#!utations unnecessar%$


25/59

To cut s&uare threa"s' a s!ecial threa"-cutter it is re&uire"$ ?efore the s&uare threa"-cutter itcan e groun"' it is necessar% to co#!ute the heli angle of the threa" to e cut ).igure /-/0*$

Co#!ute the heli angle % "rawing a line e&ual in length to the threa" circu#ference at its#inor "ia#eter )this is acco#!lishe" % #ulti!l%ing the #inor "ia#eter % ;$1


26/59

The tool it shoul" e groun" to the heli angle$ The clearance angles for the si"es shoul" ewithin the heli angle$ 3ote that the si"es are also groun" in towar" the shank to !ro+i"ea""itional clearance$

The en" of the tool shoul" e groun" flat' the flat eing e&ual to one-half the !itch of the threa"to !ro"uce e&ual flats an" s!aces on the threa"e" !art$

When !ositioning the threa"-cutter it for use' !lace it eactl% on line hori(ontall% with the aisof the work!iece$ This is es!eciall% i#!ortant for threa"-cutter its since a slight +ariation in the+ertical !osition of the it will change the threa" angle eing cut$

The threa"-cutter it #ust e !ositione" so that the centerline of the threa" angle groun" onthe it is eactl% !er!en"icular to the ais of the work!iece$ The easiest wa% to #ake thisalign#ent is % use of a center gage$ The center gage will !er#it checking the !oint angle at thesa#e ti#e as the align#ent is eing effecte"$ The center gage is !lace" against the work!iece

an" the cutter it is a"4uste" on the tool !ost so that its !oint fits snugl% in the 67 angle notchof the center gage ).igure /-7*$


27/59

n cutting threa"s on a lathe' the !itch of the threa" or nu#er of threa"s !er inch otaine" is"eter#ine" % the s!ee" ratio of the hea"stock s!in"le an" the lea" screw which "ri+es thecarriage$ Lathes e&ui!!e" for threa" cutting ha+e gear arrange#ents for +ar%ing the s!ee" ofthe lea" screw$ o"ern lathes ha+e a &uick-change gearo for +ar%ing the lea" screw tos!in"le ratio so that the o!erator nee" onl% follow the instructions on the "irection !lates of thelathe to set the !ro!er fee" to !ro"uce the "esire" nu#er of threa"s !er inch$ Once set to as!ecific nu#er of threa"s !er inch' the s!in"le s!ee" can e +arie" "e!en"ing u!on the#aterial eing cut an" the si(e of the work!iece without affecting the threa"s !er inch$

The carriage is connecte" to the lea" screw of the lathe for threa"ing o!erations % engagingthe half nut on the carriage a!ron with the lea" screw$ A control is a+ailale to re+erse the"irection of the lea" screw for left or right-han" threa"ing as "esire"$ ?e sure the lea" screwturns in the !ro!er "irection$ .ee" the cutter it fro# right to left to !ro"uce a right-han"

threa"$ .ee" the cutter it fro# left to right to !ro"uce a left-han" threa"$

:irection of fee"$ .or cutting stan"ar" 67 right-han" threa"s of the shar! K-t%!e' such as the#etric for#' the A#erican )3ational* for#' an" the Unifie" for#' the tool it shoul" e #o+e" inat an angle of 20 to the right ).igure /-1*$ )Set the angle at 20 to the left for left-han"threa"s*$ Cutting threa"s with the co#!oun" rest at this angle allows for the left si"e of the toolit to "o #ost of the cutting' thus relie+ing so#e strain an" !ro"ucing a free curling chi!$ The"irection is controlle" % setting the co#!oun" rest at the 20 angle efore a"4usting the cutterit !er!en"icular to the work!iece ais$ The "e!th of cut is then controlle" % the co#!oun" restfee" han"le$


28/59


29/59

in the first "e!th of cut % using the gra"uate" collar of the co#!oun" rest$ Position the carriagehalf nut le+er to engage the half nut to the lea" screw in or"er to start the threa"ing o!eration$The first cut shoul" e a scratch cut of no #ore than 7$77; inch so the !itch can e checke"$Engaging the half nut with the lea" screw causes the carriage to #o+e as the lea" screwre+ol+es$ Cut the threa" % #aking a series of cuts in which the threa"ing tool follows theoriginal groo+e for each cut$ Use the threa" chasing "ial' .igure /-2' to "eter#ine when toengage the half nut so that the threa"ing tool will track !ro!erl%$ The "ial is attache" to the

carriage an" is "ri+en % #eans of the lea" screw$ .ollow the "irections of the threa" chasing"ial' .igure /-;' to "eter#ine when to engage the half nut le+er$


30/59

After #aking the first !ass check for !ro!er !itch of threa"s % using one of the three #etho"sin .igure /-


31/59

%etric T(rea& Cutting Operation'

etric threa"s' are cut one of two wa%s % using the lathe' "esigne" an" e&ui!!e" for #etric#easure#ent or % using a stan"ar" inch lathe an" con+erting its o!eration to cut #etricthrea"s$ A #etric #easure#ent lathe has a &uick-change gear o use" to set the !ro!er screw!itch in #illi#eters$ An inch-"esigne" lathe #ust e con+erte" to cut #etric threa"s % switchinggears in the lathe hea"stock accor"ing to the "irections su!!lie" with each lathe$

ost lathes co#e e&ui!!e" with a set of changeale gears for cutting "ifferent' or nonstan"ar"screw threa"s$ .ollow the "irections in the lathe o!erator #anual for setting the !ro!er #etric!itch$ )A #etric "ata !late #a% e attache" to the lathe hea"stock$* ost lathes ha+e theca!ailit% of &uickl% attaching these change gears o+er the eisting gears then realigning thegearing$ One change gear in nee"e" for the lea" screw gear an" one for the s!in"le' or "ri+egear$

The #etric threa" "ia#eter an" !itch can e easil% #easure" with a #etric #easuring tool$ fthere are no #etric #easuring tools a+ailale' the !itch an" "ia#eter #ust e con+erte" fro##illi#eters to inch #easure#ent' an" then a inch #icro#eter an" #easuring tools can e use"

to "eter#ine the !ro!er !itch an" "ia#eter$ illi#eters #a% e con+erte" to inch #easure#enteither % "i+i"ing #illi#eters % 2,$< inches or #ulti!l%ing % 7$7;0;/ inches$

.or ea#!le' a threa" with a "esignation 27 2$, 6g@6h is rea" as follows= the "esignatesthe threa" is #etric$ The 27 "esignates the #a4or "ia#eter in #illi#eters$ The 2$, "esignatesthe linear !itch in #illi#eters$ The 6g@6h "esignates that a general !ur!ose fit etween nut an"olt is inten"e"$ Therefore' to #achine this #etric threa" on a inch "esigne" lathe' con+ert theoutsi"e "ia#eter in #illi#eters to a "eci#al fraction of an inch an" #achine the #a4or "ia#eterto the "esire" "ia#eter #easure#ent$ Con+ert the linear !itch in #illi#eters' to threa"s !er inch% "i+i"ing the linear !itch of 2$, % 2,$< to get the threa"s !er inch )17$16 TP*$

3ow$ a -1; TP threa" #icro#eter can e use" to #easure the !itch "ia#eter for this #etricthrea"$

To su# u! how to con+ert #etric threa"s to inch #easure#ent=

Con+ert #a4or "ia#eter fro# #illi#eters to inch #easure$

Con+ert !itch an" !itch "ia#eter to inch #easure$

Set &uick change gears accor"ing to instructions$

Set u! the lathe for threa" cutting as in the !rece"ing !aragra!hs on screw threa" cutting$ Takea light trial cut an" check that the threa"s are of the correct !itch using a #etric screw !itchgage$ At the en" of this trial cut' an" an% cut when #etric threa"ing' turn off the lathe an" ackout the tool it fro# the work!iece without "isengaging the half-nut-le+er$ 3e+er "isengage thele+er until the #etric threa" is cut to the !ro!er !itch "ia#eter' or the tool it will ha+e to erealigne" an" set for chasing into the threa"$

After acking the tool it out fro# the work!iece' tra+erse the tool it ack to the starting !oint% re+ersing the lathe s!in"le "irection while lea+ing the half-nut le+er engage"$ f the correct!itch is eing cut' continue to #achine the threa" to the "esire" "e!th$

NOTE+f the tool it nee"s to e realigne" an" chase" into the threa" "ue to "isengage#ent'of the half-nut le+er or ha+ing to re#o+e the !iece an" start again' then the lathe #ust e resetfor threa"ing$ Start the lathe' with the tool it clear of the work!iece engage the le+er$ Allow thecarriage to tra+el until the tool it is o!!osite an% !ortion of the unfinishe" threa"5 an" then turnoff the lathe' lea+ing the engage"$ 3ow the tool it can e set ack into a threa" groo+e %


32/59

a"+ancing the cross sli"e an" reference$ 9estart the lathe' an" the tool it shoul" follow thegroo+e that was !re+iousl% cut' as long as the half-nut le+er sta%s engage"$

TAERE$ SCREW THREA$S

Ta!ere" screw threa"s or !i!e threa"s can e cut on the lathe % setting the tailstock o+er or %using a ta!er attach#ent$ 9efer to the references for ta!er !er inch an" no#inal #easure#ents

of ta!ere" threa" for#s$ When cutting a ta!ere" threa"' the tool it shoul" e set at rightangles to the ais of the work$ :o not set the tool it at a right angle to the ta!er of the threa"$Check the threa" tool it carefull% for clearances efore cutting since the it will not e entering

the work at right angles to the ta!ere" work!iece surface$

%EASURIN! E2TERNAL 34SHAE$ SCREW THREA$S

The fit of the threa" is "eter#ine" % its !itch "ia#eter$ The !itch "ia#eter is the "ia#eter ofthe threa" at an i#aginar% !oint on the threa" where the wi"th of the s!ace an" the wi"th ofthe threa" are e&ual$ The fact that the #ating !arts ear on this !oint or angle of the threa"'

an" not on the to! of it' #akes the !itch "ia#eter an i#!ortant "i#ension to use in #easuringscrew threa"s$

The threa" #icro#eter ).igure /-,* is an instru#ent use" to gage the threa" on the !itch"ia#eter$ The an+il is K-Sha!e" to fit o+er the K-threa"$ The s!in"le' or #o+ale !oint' iscone-sha!e" )!ointe" to a K* to fit etween the threa"s$ Since the an+il an" s!in"le oth contactthe si"es of the threa"s' the !itch "ia#eter is gage" an" the rea"ing is gi+en on the slee+e an"s!in"le where it can e rea" % the o!erator$

Threa" #icro#eters are #arke" on the fra#e to s!ecif% the !itch "ia#eters which the#icro#eter is use" to #easure$ One will e #arke"' for instance' to #easure fro# to 1;threa"s !er inch' while others are #arke" 1< to 27' 22 to ;7' or ;2 to


33/59

#icro#eters are also a+ailale in "ifferent si(es$

The !roce"ure in checking the threa" is first to select the !ro!er #icro#eter' then calculate orselect fro# a tale of threa"s the correct !itch "ia#eter of the screw$ Lastl%' fit the threa" intothe #icro#eter an" take the rea"ing$

The ;-wire #etho" is another #etho" of #easuring the !itch "ia#eter for A#erican 3ational )67

"egree* an" Unifie" threa"s$ t is consi"ere" the FestF #etho" for etre#el% accurate#easure#ent$ A!!en"i A shows three wires of correct "ia#eter !lace" in threa"s with the#icro#eter #easuring o+er the#$ The !itch "ia#eter can e foun" % sutracting the wireconstant fro# the #easure" "istance o+er the wires$ t can e rea"il% seen that this #etho" is"e!en"ent on the use of the F8est8F wire for the !itch of the threa"$ The FestF wire is the si(eof wire which touches the threa" at the #i""le of the slo!ing si"es$ in other wor"s' at the !itch"ia#eter$ A for#ula % which the !ro!er si(e wire #a% e foun" is as follows= :i+i"e theconstant 7$,//;, % the nu#er of threa"s !er inch to cut$ f$ for ea#!le' threa"s !er inchha+e een cut' we woul" calculate 7$,//;, B 7$7/2$ The "ia#eter of wire to use for#easuring an -!itch threa" is 7$7/2$

The wires use" in the three-wire #etho" shoul" e har"ene" an" la!!e" steel wires$ the%'shoul" e three ti#es as accurate as the accurac% "esire" in #easure#ent of the threa"s$ The?ureau of Stan"ar"s has s!ecifie" an accurac% of 7$7772 inch$ The suggeste" !roce"ure for#easuring threa"s is as follows=

After the three wires of e&ual "ia#eter ha+e een selecte" % using the ao+e for#ula' the% are!ositione" in the threa" groo+es as shown in A!!en"i A$ The an+il an" s!in"le of an or"inar%#icro#eter are then !lace" against the three wires an" the rea"ing is taken$ To "eter#ine whatthe rea"ing of the #icro#eter shoul" e if a threa" is the correct finish si(e$ use the followingfor#ula )for #easuring Unifie" 3ational Coarse threa"s*= a"" three ti#es the "ia#eter of thewire to the "ia#eter of the screw5 fro# the su#' sutract the &uotient otaine" % "i+i"ing the

constant 1$,1,, % the nu#er of threa"s !er inch$ Written concisel%' the for#ula is=

W(ere m)micrometer mea'urement o5er wire'*$)&iameter of t(e t(rea&*n)number of t(rea&' per inc(*

W)&iameter of wire u'e&

Ea#!le= :eter#ine # )#easure#ent o+er wires* for 1@2 inch' 12-!itch U3C threa"$ We woul"

!rocee" to sol+e as follows=

w(ere W)67689// inc($)67:66 inc(n)/"

T(en m)

m),67:66 ; 67/88


34/59

etric threa"s can also e checke" % using the three-wire #etho" % using "ifferent nu#erical+alues in the for#ula$ Three-wire threa"s of #etric "i#ensions #ust ha+e a 67 angle for this#etho"$

% )$; C$ ) %4C% )mea'urement o5er t(e wire'

$)pitc( &iameterC )N con'tant ,T(i' i' foun& in Table >4// in Appen&i. A-

The FestF wire si(e can e foun" % con+erting fro# inch to #etric' or % using Tale/-11 in A!!en"i A$

An o!tical co#!arator #ust e use" to check the threa"s if the tolerance "esire" is lessthan 7$771 inch )7$72 ##*$ This t%!e of threa" #easure#ent is nor#all% use" in in"ustrial

sho!s "oing !ro"uction work$

CUTTIN! INTERNAL THREA$S

nternal threa"s are cut into nuts an" castings in the sa#e general #anner as eternalthrea"s$ f a han" ta! is not a+ailale to cut the internal threa"s' the% #ust e #achine"

on the lathe$

An internal threa"ing o!eration will usuall% follow a oring an" "rilling o!eration' thus the#achine o!erator #ust know "rilling an" oring !roce"ures efore atte#!ting to cutinternal threa"s$ The sa#e hol"er use" for oring can e use" to hol" the tool it for

cutting internal threa"s$ Lathe s!ee" is the sa#e as the s!ee" for eternal threa" cutting$

To !re+ent ruing' the clearance of the cutter it shank an" oring tool ar #ust e

greater for threa"ing than for straight oring ecause of the necessit% of #o+ing the itclear of the threa"s when returning the it to the right after each cut$

The co#!oun" rest shoul" e set at a 20 angle to the sa""le so that the cutter it willfee" after each cut towar" the o!erator an" to his left$

Although the setu! shown in .igure /-6 woul" e i#!ractical on etre#el% large lathes' itallows a "egree of safet% on co##on si(e" #achines % ha+ing the co#!oun" all crank

!ositione" awa% fro# an% work hol"ing "e+ice that woul" e in use on the lathe'eli#inating the !ossiilit% of the o!erator8s han"s or the co#!oun" rest contacting the

re+ol+ing s!in"le an" work hol"ing "e+ices$


35/59


36/59

the right en" of the Ac#e threa" gage$

f a gage is not a+ailale' the wi"th of the tool it !oint #a% e calculate" % the for#ula=

Wi&t( of point ) 676> 4 6766:" inc(

W(ere ) Number of t(rea&' per inc(

?e sure to grin" this tool with sufficient si"e clearance so that it will cut$ :e!en"ing u!onthe nu#er of threa"s !er inch to e cut' the !oint of the tool is groun" flat to fit into theslot on the Ac#e threa" gage that is #arke" with the nu#er of threa"s !er inch the toolis to cut$ The si(e of the flat on the tool !oint will +ar% "e!en"ing u!on the threa" !er inch

to e #achine"$

After grin"ing the tool' set the co#!oun" rest to one-half the inclu"e" angle of the threa")1< 1@2* to the right of the +ertical centerline of the #achine ).igure /-0*$ ount the

tool in the hol"er or tool !ost so that the to! of the tool is on the ais or center line of thework!iece$ The tool is set s&uare to the work' using the Ac#e threa" gage$ This threa" iscut using the co#!oun" fee"$ The "e!th to which %ou fee" the co#!oun" rest to otain

total threa" "e!th is "eter#ine" % the for#ula gi+en an" illustrate" in Tale /-0 inA!!en"i A$ The re#ain"er of the Ac#e threa"-cutting o!eration is the sa#e as the

K-threa"ing o!eration !re+iousl% "escrie"$ The co#!oun" rest shoul" e fe" into thework onl% 7$772 inch to 7$77; inch !er cut until the "esire" "e!th of threa" is otaine"$


37/59

The for#ulas use" to calculate Ac#e threa" "e!th are in Tale /-0 in A!!en"i A$ Thesingle wire #etho" can e use" to #easure the accurac% of the threa" ).igure /-07*$ Asingle wire or !in of the correct "ia#eter is !lace" in the threa"e" groo+e an" #easure"

with a #icro#eter$ The threa" is the correct si(e when the #icro#eter rea"ing o+er thewire is the sa#e as the #a4or "ia#eter of the threa" an" the wire is !lace" tightl% into the

threa" groo+e$ The "ia#eter of the wire to e use" can e calculate" % using thisfor#ula=

Wire &iameter ) 6789>" . pitc(

Thus' if 6 threa"s !er inch are eing cut' the wire si(e woul" e=

6789>" . /?= ) 6769/ inc(


38/59

Cutting the 20 wor# screw threa" )?rown an" Shar!e*$ The tool it use" to cut 20 wor#screw threa"s will e si#ilar to the Ac#e threa"ing tool' ut slightl% longer with a "ifferentti!$ Use Tale /-0 in A!!en"i A to calculate the length of the tool it an" ti! wi"th$ The

cutting is "one 4ust like cutting an Ac#e threa"$

CUTTIN! S@UARE THREA$S

?ecause of their "esign an" strength' s&uare threa"s are use" for +ise screws' 4ackscrews'an" other "e+ices where #ai#u# trans#ission of !ower is nee"e"$ All surfaces of thes&uare threa" for# are s&uare with each other' an" the si"es are !er!en"icular to the

center ais of the threa"e" !art$ The "e!th' the wi"th of the crest' an" root are of e&ual

"i#ensions$ ?ecause the contact areas are relati+el% s#all an" "o not we"ge together'friction etween #atching threa"s is re"uce" to a #ini#u#$ This fact e!lains wh% s&uare

threa"s are use" for !ower trans#ission$

?efore the s&uare threa" cutting tool can e groun"' it is necessar% first to "eter#ine theheli angle of the threa"$ The si"es of the tool for cutting the s&uare threa" shoul"

confor# with the heli angle of the threa" ).igure /-/0*$

.or cutting the threa"' the cutting e"ge of the tool shoul" e groun" to a wi"th eactl%one-half that of the !itch$ .or cutting the nut' it shoul" e fro# 7$771 to 7$77; of an inch

larger to !er#it a free fit of the nut on the screw$

The cutting of the s&uare threa" for# !resents so#e "ifficult%$ Although it is s&uare' thisthrea"' like an% other' !rogresses in the for# of a heli' an" thus assu#es a slight twist$So#e o!erators !refer to !ro"uce this threa" in two cuts' the first with a narrow tool tothe full "e!th an" the secon" with a tool groun" to si(e$ This !roce"ure relie+es cutting!ressure on the tool nose an" #a% !re+ent s!ringing the work$ The cutting o!eration for

s&uare threa"s "iffers fro# cutting threa"s !re+iousl% e!laine" in that the co#!oun" restis set !arallel to the ais of the work!iece an" fee"ing is "one onl% with the cross fee"$

The cross fee" is fe" onl% 7$772 inch or 7$77; inch !er cut$ The finish "e!th of the threa"is "eter#ine" % the for#ula$

$ept( ) /?"

The wi"th of the tool !oint is "eter#ine" % this for#ula also an" will "e!en" u!on thenu#er of threa"s !er inch to e #achine"$ t is #easure" with a #icro#eter' as s&uare


39/59

threa" gages are not a+ailale$

SECIAL OERATIONS ON THE LATHE

NURLIN! ON THE LATHE

Nnurling is a !rocess of i#!ressing a "ia#on" sha!e" or straight line !attern into thesurface of a work!iece % using s!eciall% sha!e" har"ene" #etal wheels to i#!ro+e itsa!!earance an" to !ro+i"e a etter gri!!ing surface$ Straight knurling is often use" to

increase the work!iece "ia#eter when a !ress fit is re&uire" etween two !arts$

Hol&ing $e5ice' for nurling

The setu! for knurling can e #a"e etween centers or #ounte" in a soli" chuck$ 3e+eratte#!t to knurl % hol"ing the work in a ruer or #etal collet chuck' since the great!ressures of knurling coul" "a#age these "e+ices$ t is i#!ortant to su!!ort the work

while knurling$ f #ounting the work etween centers' #ake the center holes as large as!ossile to allow for the strongest hol"$ f using a chuck to hol" the work' use the tailstockcenter to su!!ort the en" of the work$ f "oing a long knurl' use a stea"% rest to su!!ort

the work an" kee! the !iece fro# s!ringing awa% fro# the tool$

nurling Tool'

The knurling tool ).igure /-17* can e "esigne" "ifferentl%' ut all acco#!lish the sa#eo!eration$ Two co##on t%!es of knurling tools are the knuckle 4oint an" re+ol+ing hea"t%!e of knurling tools$ The knuckle 4oint t%!e is e&ui!!e" with a single !air of rollers thatre+ol+e with the work as it is eing knurle"$ The re+ol+ing hea" t%!e of tool is fitte" with

three !airs of rollers so that the !itch can e change" to a "ifferent knurl without ha+ing tochange the setu!$ There are two knurl !atterns' "ia#on" an" straight$

There are three !itches of rollers' coarse' #e"iu#' an" fine ).igure /-01*$

The "ia#on" is the #ost co##on !attern an" the #e"iu# !itch is use" #ost often$ Thecoarse !itch is use" for large-"ia#eter work5 the fine !itch is use" for s#all-"ia#eter

work$

nurling

The knurling o!eration is starte" % "eter#ining the location an" length of the knurl' an"then setting the #achine for knurling$ A slow s!ee" is nee"e" with a #e"iu# fee"$

Co##onl%' the s!ee" is set to 67 to 7 9P' while the fee" is est fro# 7$71, to 7$7;7


40/59

inch !er re+olution of the s!in"le$ The knurling tool #ust e set in the tool !ost with theais of the knurling hea" at center height an" the face of the knurls !arallel with the worksurface$ Check that the rollers #o+e freel% an" are in goo" cutting con"ition5 then oil theknurling tool cutting wheels where the% contact the work!iece$ ?ring the cutting wheels)rollers* u! to the surface of the work with a!!roi#atel% 1@2 of the face of the roller in

contact with the work$

f the face of the roller is !lace" in this #anner' the initial !ressure that is re&uire" to startthe knurl will e lessene" an" the knurl #a% cut s#oother$ A!!l% oil generousl% o+er the

area to e knurle"$ Start the lathe while forcing the knurls into the work aout 7$717 inch$As the i#!ression starts to for#' engage the carriage fee" le+er ).igure /-02*$ Oser+ethe knurl for a few re+olutions an" shut off the #achine$ Check to see that the knurl is

tracking !ro!erl%' an" that it is not on a F"oule trackF ).igure /-0;*$

9eset the tool if nee"e"5 otherwise' #o+e the carriage an" tool ack to the starting !ointan" lightl% ring the tool ack into the !re+iousl% knurle" !ortion$ The rollers will align

the#sel+es with the knurle" i#!ressions$ .orce the knurling tool into the work to a "e!thof aout 1@6< inch an" si#ultaneousl% engage the carriage to fee" towar" the hea"stock$

Oser+e the knurling action an" allow the tool to knurl to within 1@;2 inch of the "esire"en" of cut' an" "isengage the fee"$ Han" fee" to the !oint where onl% one-half of the

knurling wheel is off the work' change the fee" "irection towar" the tailstock an" force thetool "ee!er into the work$

Engage the carriage fee" an" cut ack to the starting !oint$ Sto! the lathe an" check theknurl for co#!leteness$ 3e+er allow the knurling tool to fee" entirel% off the en" of the

work' or it coul" cause "a#age to the work or lathe centers$ The knurl is co#!lete whenthe "ia#on" sha!e ) or straight knurl* is full% "e+elo!e"$ Ecessi+e knurling after the knurl

has for#e" will wear off the full knurl an" ruin the work "ia#eter$ o+e the tool awa%fro# the work as the centers$ The knurl is co#!lete when the "ia#on" sha!e )or work

re+ol+es an" shut off the lathe$ Clean the knurl with a rush an" then re#o+e an% urrswith a file$

Special nurling recaution'


41/59

3e+er sto! the carriage while the tool is in contact with the work an" the work is stillre+ol+ing as this will cause wear rings on the work surface ).igure /-0


42/59

Ta!ere"-shank twist "rills #a% e hel" "irectl% in the tailstock ta!ere" s!in"le as long as a

goo" fit eists$ f the "rill shank is not the correct si(e' then a "rill socket or slee+e #a% euse" in the tailstock s!in"le$

A twist "rill hol"er is use" to su!!ort large twist "rills with the tailstock center$ The "rill isinserte" into the hol"er an" the tailstock center is !lace" in the center hole which is

locate" at the rear of the "rill hol"er$ The hol"er will rest on the cross sli"e or co#!oun"rest an" #ust e su!!orte" % han" until it is hel" secure % !ressure etween the

tailstock an" hea"stock$ When using this #etho"' ne+er with"raw or loosen the tailstocks!in"le while the lathe is rotating or the work!iece can e thrown out at the o!erator$

Alwa%s sto! the #achine efore atte#!ting to with"raw the twist "rill$

Another #etho" of su!!orting a large twist "rill in the tailstock is to fasten a lathe "og tothe "rill shank an" su!!ort the rear of the "rill with the tailstock center in the center hole

in the tang of the "rill$


43/59

Supporting $rill' in t(e Hea&'tock

The "rill can also e hel" an" rotate" in the hea"stock with the work hel" stationar%against the tailstock$ Straight shank twist "rills are su!!orte" in the hea"stock % a "rill

chuck or collet which is #ounte" in the hea"stock s!in"le$ A uni+ersal or in"e!en"ent 4awchuck can also e use" to hol" an" turn twist "rills if a hea"stock "rill chuck is not

a+ailale$ Ta!ere" shank twist "rills can e #ounte" in the hea"stock % using a s!ecial

a"a!ter' such as a slee+e with an internal ta!er to hol" the ta!ere" "rill' while the outsi"eof the slee+e is #a"e to fit into the hea"stock s!in"le$

%ounting Work for $rilling

f the work is to e rotate" an" the twist "rill will e fe" into the en" of the work' thework shoul" e #ounte" in a chuck' on a face!late' or in a collet$ The center of the hole to

e "rille" shoul" e accuratel% #arke" an" !unche" as "escrie" for "rilling setu!s$

Alwa%s start holes % using a center "rill' since this #etho" will e the #ost accurate an"the #ost efficient$ Center-"rill % rotating the s!in"le at co#!ute" "rill s!ee" an" gentl%

ringing the !oint of the center "rill into the en" of the work until the !ro!er "e!th isreache"$

f the twist "rill is to e rotate" % the hea"stock s!in"le an" the work!iece is to esu!!orte" % a K-center #ounte" in the tailstock' the work shoul" e carefull% !ositione"

% han" an" the "rill #o+e" lightl% into contact with the work!iece efore starting thelathe$ The work!iece #ust e well su!!orte" "uring "rilling o!erations to !re+ent the work

fro# eing thrown fro# the lathe or rotating with the "rill$

$rilling Operation'

To start the "rilling o!eration' co#!ute the correct 9P for the "rill an" set the s!in"les!ee" accor"ingl%$ Ensure the tailstock is cla#!e" "own on the lathe wa%s$ The fee" iscontrolle" % turning the tailstock han"wheel$ The gra"uations on the tailstock s!in"le are

use" to "eter#ine the "e!th of cut$

f a large twist "rill is use"' it shoul" e !rocee"e" % a !ilot "rill' the "ia#eter of whichshoul" e wi"er than the larger "rills we$

Use a suitale cutting flui" while "rilling )Tale


44/59

1ORIN! WITH THE LATHE

?oring is the enlarging an" truing of a hole % re#o+ing #aterial fro# internal surfaceswith a single-!oint cutter it$ On the lathe' oring is acco#!lishe" in either of these two

#etho"s=

ounting the hol"er an" oring tool ar with cutter it on the tool !ost an" re+ol+ingthe work!iece$

ounting the work!iece in a fie" !osition to the carriage an" re+ol+ing the oringtool ar an" cutter it in a chuck attache" to the hea"stock s!in"le$ )This is a s!ecial

!rocess an" not use" in #ost #achine sho!s*$

%ounting Workpiece for 1oring

The work!iece #a% e su!!orte" in a chuck or fastene" to a face!late for oringo!erations "e!en"ing u!on of the #aterial to e #achine"$ When oring is to e

!erfor#e" on the en"s of long stock' the work!iece is #ounte" in a chuck an" a stea"%rest is use" to su!!ort the right en" near the cutter it$ So#e oring o!erations re&uire

the use of s!ecial chuck-#ounte" #an"rels to hol" work!ieces that cannot e successfull%#ounte" otherwise$

urpo'e for 1oring

?oring is necessar% in #an% cases to !ro"uce accurate holes$ :rille" holes are sel"o#straight "ue to i#!erfections in the #aterial which cause "rills to #o+e out of align#ent$

Therefore' where accurac% is i#!ortant' "rille" holes are usuall% #a"e un"ersi(e an" thenore" or rea#e" to the !ro!er "i#ensions$ ?oring is also useful in truing large holes in flat#aterial$ n this case' the hole is cut un"ersi(e using a an"saw or tre!anning tool an" is

true" to !ro!er "i#ensions % oring$

1oring Cutter 1it Setup

The cutter it use" for oring is si#ilar to that use" for eternal turning on the lathe$ Theit is usuall% hel" in a soft or se#isoft ar calle" a oring tool ar$ The oring tool ar).igure /-11* is su!!orte" % a cutting tool hol"er which fits into the lathe tool !ost$

?oring tool ars are su!!lie" in se+eral t%!es an" si(es for hol"ing "ifferent cutter its$ Theit is su!!orte" in the oring tool ar at a 07' ;7' or


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it is necessar% to cut u! to the otto# of a hole or finish the si"e of an internal shoul"er$ tis "esirale that the oring tool ar e as large as !ossile without interfering with the

walls of the hole$ The cutter it shoul" not eten" far e%on" the oring tool ar an" theit securel% in the ar' %et not ha+e the shank-en" !rotru"e far fro# the ar$

The cutter its use" for oring are sha!e" like left-han" turning an" facing cutter its$reater attention #ust e gi+en to the en" clearance angle an" the ack rake angle

ecause of the cur+ature of the hole ).igure /-0/*$

The oring tool ar shoul" e cla#!e" as close to the hol"er an" tool !ost as !ossileconsi"ering the "e!th of oring to e "one$ The ar will ha+e a ten"enc% to s!ring awa%

fro# the work!iece if the ar o+erhangs the tool !ost too far$ f "ee! oring is to e!erfor#e"' it will e necessar% that the ar e as thick as !ossile to counteract this

s!ringing ten"enc%$

Straig(t 1oring Operation

The cutter it is !ositione" for straight oring o!erations with its cutting e"ge set slightl%ao+e center$ :e!en"ing on the rigi"it% of the setu!' the oring tool will ha+e a ten"enc%

to s!ring "ownwar" as !ressure is a!!lie" to the cutting e"ge$ ?% setting the cutter slightl%ao+e center' co#!ensation has een #a"e for the "ownwar" s!ring an" the cutter willactuall% e !ositione" on the eact center of the work!iece "uring #achining o!erations

).igure /-0*$ The cutting e"ge faces forwar" for #ost o!erations so the lathe can turn inits nor#al counterclockwise "irection$ f it eco#es necessar% to !osition the cutter it

against the rear wall of the hole for a s!ecial o!eration' a right-han" turning cutter it isuse" an" the s!in"le rotation is re+erse"$


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Position the cutter it so that the cutting e"ge is i##e"iatel% to the right of the work!iece

an" clears the wall of the hole % aout 1@16 inch$ Tra+erse the carriage % han"' withoutstarting the lathe' to #o+e the cutter it an" oring tool ar into the hole to the "e!th ofthe inten"e" oring an" out again to "eter#ine whether there is sufficient clearance to!re+ent the ack of the cutter it an" the oring tool ar fro# ruing the insi"e of the

hole$ When the clearance is satisfactor%' !osition the cutter it to the right of thework!iece rea"% for the first cut$ Use the #icro#eter carriage sto! to control the "e!th of

tool tra+el$

The sa#e s!ee"s reco##en"e" for straight turning shoul" e use" for straight oring$.ee"s for oring shoul" e consi"eral% s#aller than fee"s use" for straight turning

ecause there is less rigi"it% in the setu!$ :ecrease the "e!th of cut for each !ass of the

tool it for the sa#e reason$ t is often a"+isale to fee" the cutter it into the hole to the"esire" "e!th an" then re+erse the fee" an" let the cutter it #o+e out of the holewithout changing the "e!th of fee"$ t is also goo" !ractice to take a free cut e+er%

se+eral !asses to hel! eli#inate ell #outhing of the work!iece$ This !ractice will correctan% irregularities cause" % the it or oring tool ar s!ringing ecause of the !ressure

a!!lie" to the it$

TAIN! AN$ HAN$ $IE THREA$IN!

The lathe can e use" as a "e+ice to hol" an" align a ta! or han" "ie to cut internal or

eternal threa"s &uickl% for threa"s that "o not re&uire a high "egree of accurac% or a finefinish$ ore infor#ation on ta!s an" "ies can e foun" in T 0-2


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The work will rotate when ta!!ing using lathe !ower$ Use a +er% slow s!in"le s!ee" )17 to

;7 9P* an" !lent% of cutting flui" or coolant$ nstall a ta! an" rea#er wrench on the en"of the ta! to kee! it fro# turning$ Su!!ort the wrench on the co#!oun" rest$ Power is notreco##en"e" for ta!s un"er 1@2 inch in "ia#eter or when ta!!ing steel$ Ensure that theta! wrench han"le contacts the co#!oun" rest efore engaging !ower or the en" of thehan"le will whi! aroun" an" coul" crush a finger or cause other in4ur% or "a#age$ :o notatte#!t to start the ta! into the hole with the work re+ol+ing$ Alwa%s kee! the ta! snug inthe center hole to !re+ent the ta! fro# co#ing out of align#ent an" ruining the threa"s$

The setu! for han" ta!!ing in a lathe is si#ilar to that use" in !ower ta!!ing$ Thehea"stock chuck is hel" stea"% an" not rotate"$ The ta! is turne" % using an a"4ustalewrench$ Lock the lathe gears so that the hea"stock will not #o+e when using a large ta!$

?ack off the ta! fre&uentl% when ta!!ing to reak the chi!s an" allow for a clean threa"$

Han& $ie T(rea&ing on t(e Lat(e

:ie threa"ing on a lathe is +er% si#ilar to ta!!ing on a lathe' ece!t that the "ie is aligne"!er!en"icular to the work ais % !ressure eerte" against the ack surface of the "ie$

This !ressure can e eerte" % #eans of a "rill !a"' % using the tailstock s!in"le' or %using the hea" of the "rill chuck for s#all "ies$ :ie threa"ing can e "one using !ower or

% han"' using the sa#e !roce"ures as ta!!ing$ Power can e use" to re#o+e the "iefro# the work if the "ie stock han"le is swung to the o!!osite si"e an" low re+erse !oweris use"$ t is "ifficult to cut +er% coarse threa"s with a "ie ecause of the great a#ount of

force nee"e" to turn the "ie$ t is a"+isale to o!en u! the "ie to its full wi"th' rough-cutthe threa"s' an" then close u! the "ie an" go o+er the threa"s for a finishe" si(e$ Alwa%s

use a luricant or coolant for this o!eration$

REA%IN! ON THE LATHE

9ea#ers are use" to finish "rille" holes or ores &uickl% an" accuratel% to a s!ecifie""ia#eter$ When a hole is to e rea#e"' it #ust first e "rille" or ore" to within 7$77< to7$712 inch of the finishe" si(e since the rea#er is not "esigne" to re#o+e #uch #aterial$

Reaming wit( a %ac(ine Reamer

The hole to e rea#e" with a #achine rea#er #ust e "rille" or ore" to within 7$712inch of the finishe" si(e so that the #achine rea#er will onl% ha+e to re#o+e the cutter it

#arks$


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The work!iece is #ounte" in a chuck at the hea"stock s!in"le an" the rea#er is su!!orte"% the tailstock in one of the #etho"s "escrie" for hol"ing a twist "rill in the tailstock$

The lathe s!ee" for #achine rea#ing shoul" e a!!roi#atel% one-half that use" for"rilling$

Reaming wit( a Han& Reamer

The hole to e rea#e" % han" #ust e within 7$77, inch of the re&uire" finishe" si(e$

The work!iece is #ounte" to the hea"stock s!in"le in a chuck an" the hea"stock s!in"le islocke" after the !iece is accuratel% setu! The han" rea#er is #ounte" in an a"4ustale ta!an" rea#er wrench an" su!!orte" with the tailstock center$ As the wrench is re+ol+e" %

han"' the han" rea#er is fe" into the hole si#ultaneousl% % turning the tailstockhan"wheel$

The rea#er shoul" e with"rawn fro# the hole carefull%' turning it in the sa#e "irection aswhen rea#ing$ 3e+er turn a rea#er ackwar"$ See Tale


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Since filing shoul" e use" for little #ore than to re#o+e tool #arks fro# the work!iece'onl% 7$772 to 7$77, inch shoul" e left for the filing o!eration$

oli'(ing on t(e Lat(e

Polishing with either arasi+e cloth or arasi+e !a!er is "esirale to i#!ro+e the surfacefinish after filing$ E#er% arasi+e cloth is est for ferrous #etals while arasi+e !a!er

often gi+es etter results on nonferrous #aterials$ The #ost effecti+e s!ee" for !olishingwith or"inar% arasi+es is a!!roi#atel% ,'777 feet !er #inute$ Since #ost lathes are notca!ale of a s!ee" this great for an a+erage si(e work!iece' it is necessar% to select as

high a s!ee" as con"itions will !er#it$

n #ost cases the arasi+e cloth or !a!er is hel" "irectl% in the han" an" a!!lie" to thework!iece' although it #a% e tacke" o+er a !iece of woo" an" use" in the sa#e #anner

as a file$ #!ro+ise" cla#!s #a% also e use" to !olish !lain roun" work$

Since !olishing will slightl% re"uce the "i#ensions of the work!iece' 7$7772, to 7$777, inchshoul" e allowe" for this o!eration$ .igure /-171 shows how to hol" the arasi+e stri!

when !olishing$ 3ote that the en"s of the stri! are se!arate"$ This !re+ents the stri! fro#graing an" win"ing aroun" the work' which coul" !ull the o!erator8s han" into the work$o+e the !olishing stri! slowl% ack an" forth to !re+ent #aterial uil"ing u! on the stri!

which causes !olishing rings to for# on the work$ To !ro"uce a right surface' !olish thework "r%$ To !ro"uce a "ull satin finish' a!!l% oil as the !olishing o!eration is in !rogress$


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ECCENTRIC WOR ON THE LATHE

Eccentric work is work that is turne" off center' or not on the nor#al center ais$ Anengine crankshaft is a goo" ea#!le of an eccentric work!iece$ Crankshafts nor#all% ha+ea #ain center ais' calle" a #ain 4ournal' an" offset aes' which !ro"uce the throw an"

the eccentric "ia#eters of the #echanis#$ An eccentric shaft #a% ha+e two or #ore"ia#eters an" se+eral "ifferent center aes$ The a#ount of eccentricit%' or half of thethrow' is the linear "istance that a set of center holes has een offset fro# the nor#al

center ais of the work!iece$ Eccentric turning on the lathe is use" for the followingeccentric turning situations=

When the throw is large enough to allow all centers to e locate" on the work!iece at thesa#e ti#e$

When the throw is too s#all to allow all centers to fit into the en" of a work!iece at thesa#e ti#e$ )The center "rille" holes are too large$*

When the throw is so great that all centers cannot e locate" on the work' or in otherwor"s' a throw larger than the largest "ia#eter of the work!iece$ )This t%!e of crank is

usuall% #a"e in se!arate !ieces an" connecte" together' since the cost of waste" #aterialwoul" e too great if constructe" fro# one !iece on the lathe*$

Turning an Eccentric wit( Center Hole'

?efore an eccentric work!iece can e #achine"' it is necessar% to center-"rill oth en"s ofthe work!iece' inclu"ing the offset centers$ f the work!iece is large enough to !osition allcenter aes on the work at the sa#e ti#e' the #achining o!eration will e si#!le an"

eas%$

.irst "eter#ine the stock re&uire" % a""ing the throws !lus 1@ inch for #achining).igure /-172*$

.ace the work to length in a chuck$

9e#o+e the !iece an" a!!l% la%out "%e to oth en"s$

ount the work in a K- lock an"' using a surface !late an" +enire height scrier' la%out the nor#al center ais an" the offset center aes on oth en"s$

Accuratel% !rick !unch the inten"e" centers' check for accurac%' an" then enlarge the


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A""itional throws are #achine" in the sa#e #anner$ Throw !ositions #a% e starte" %cutting with a !arting tool to estalish the shoul"ers' which #a% ai" the turning o!eration$The tool it selecte" will "e!en" on the #aterial to e #achine" an" on the "e!th of cut

"esire"$

Turning an Eccentric wit( Clo'e Center Hole'


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f turning an eccentric that has the "ifferent centers !lace" too close together' a "ifferent!roce"ure shoul" e use"$ Cut the stock ;@< inch o+ersi(e" an" 4ust face oth en"s to

clean u! the saw cuts La% out an" center-"rill the nor#al$ center ais an" turn "own those"ia#eters on the center ais with the work #ounte" etween centers$ 9e#o+e the work

an" re#ount into a chuck$ .ace oth en"s to the re&uire" length an" center-"rill the offsetcenters$ 9e#ount the work etween these centers an" #achine the eccentric "ia#eters to

si(e$ .or eccentric work that has a li#ite" "istance etween each center' this #etho" is

safer than tr%ing to use a +er% shallow center-"rille" hole to hol" the work etweencenters ).igure /-172*$

Turning an Eccentric U'ing T(row late'

f the lathe is to e use" to turn a crank with a great throw' or a throw that is greaterthan nor#all% #achine" on a lathe ).igure /-172*' s!ecial throw !lates #ust e faricate"to hol" the en"s of the work while turning$ The s!ecial throw !lates will e use" as su!!ortlocks to enale the offset center holes to e #achine" into the throw !lates an" allow for

eccentric turning$ eccentric turning' it is not reco##en"e" for nor#al lathe o!erations$S!ecial crankshaft turning an" grin"ing e&ui!#ent is a+ailale for this t%!e of #achining$

RECESSIN! $RILLE$ AN$ 1ORE$ HOLES

!eneral

9ecessing' so#eti#es calle" channeling or ca#ering' is the !rocess of cutting a groo+einsi"e of a "rille"' ore"' or rea#e" hole$ 9ecesses ).igure /-17;* are usuall% #achine" to

!ro+i"e roo# for the tool runout nee"e" for suse&uent o!erations such as internalthrea"ing$

A oring ar an" hol"er #a% e use" as a recessing tool' since recessing tools ha+e thesa#e tool angles an" are si#ilar in sha!e to oring tools$ A high-s!ee" steel cutting tool

it' groun" with a s&uare nose' #akes a satisfactor% tool for cutting s#all cha#ers).igure /-17;*$ The si"es of the tool it ta!er in fro# the cutting e"ge so that the nose of

the tool is the wi"est !art$ The tool it #ust eten" fro# the hol"er a "istance slightl%greater than the "e!th of the cha#er to !re+ent the hol"er fro# ruing the ore of the

work$

%ac(ining a Rece''

To cut a recess' set u! the lathe as in a oring o!eration$ 9eference the face of the tool


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it to the face of the work5 then #o+e the tool it forwar" the re&uire" "istance to therecess % using the #icro#eter sto! or % using the co#!oun" rest gra"uate" collar$ The

co#!oun" rest #ust e set !arallel with the wa%s of the e" for this #etho"$ A"" thewi"th of the tool it into the #easure#ent or the recess will not e cut correctl%$ Position A).igure /-17;* is the tool aligning to the work' !osition ? is set o+er to the front shoul"erof the recess' an" !osition C is the set o+er to the ack of the recess$ Use the cross sli"egra"uate" collar to #easure the "istance to #o+e the tool it towar" the o!erator' insi"e

of the hole$ S!in"le s!ee" #a% ha+e to e re"uce" "ue to the sha!e of the tool it causingchatter on the work$ After cutting the recess' use insi"e cali!ers to check the "ia#eter$

LATHE TOOL OST !RIN$ER

!eneral

The tool !ost grin"er is a !ortale grin"ing #achine that can e #ounte" on the co#!oun"rest of a lathe in !lace of the tool !ost$ t can e use" to #achine work that is too har" to

cut % or"inar% #eans or to #achine work that re&uires a +er% fine finish$ .igure /-20shows a t%!ical tool !ost grin"er$ The grin"er #ust e set on center' as shown in .igure/-17


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:uring all grin"ing o!erations' wear goggles to !rotect %our e%es fro# fl%ing arasi+e#aterial$

$re''ing t(e !rin&ing W(eel

The grin"ing wheel #ust e "resse" an" true"$ Use a "ia#on" wheel "resser to "ress an"true the wheel$ The "resser is hel" in a hol"er that is cla#!e" to the "ri+e !late$ Set the

!oint of the "ia#on" at center height an" at a 17 to 1, angle in the "irection of thegrin"ing wheel rotation$ The 17 to 1, angle !re+ents the "ia#on" fro# gouging thewheel$ Lock the lathe s!in"le % !lacing the s!in"le s!ee" control le+er in the low 9P

!osition$

3OTE= The lathe s!in"le "oes not re+ol+e when %ou are "ressing the grin"ing wheel$

9e#o+e the "ia#on" "resser hol"er as soon as the "ressing o!eration is co#!lete"$ ?ringthe grin"ing wheel in contact with the "ia#on" % carefull% fee"ing the cross sli"e % han"$

o+e the wheel clear of the "ia#on" an" #ake a cut % #eans of the cross sli"e$ The#ai#u# "e!th of cut is 7$772 inch$ o+e the wheel slowl% % han" ack an" forth o+er

the !oint of the "ia#on"$ o+e the carriage if the face of the wheel is !arallel to the wa%of the lathe$ o+e the co#!oun" rest if the face of the wheel is at an angle$ ake thefinal "e!th of cut of 7$777, inch with a slow' e+en fee" to otain a goo" wheel finish$

?efore %ou egin the grin"ing o!eration' co+er the wa%s with a hea+% !iece of !a!er oruse a shallow !an of water !lace" on the wa%s to collect the grin"ing "ust that will

accu#ulate fro# the grin"ing$ This is to ensure none of the grin"ing urns to the wa%s orgets un"er the carriage which will cause the lathe !re#ature wear$ f %ou use a !iece of!a!er' !a% close attention that the s!arks fro# the grin"ing o!eration "o not cause the!a!er to ignite$ f %ou use a shallow !an of water' #ake sure water is not s!ille" on the

wa%s of the lathe$ After all grin"ing o!erations' thoroughl% clean an" oil the lathe to

re#o+e an% grin"ing "ust that the !a!er !an of water #isse"$

!rin&ing #ee&'* Spee&'* an& $ept( of Cut'

9otate the work at a fairl% low s!ee" "uring the grin"ing o!erations$ The reco##en"e"surface foot s!ee" is 67 to 177 .P$ The "e!th of cut "e!en"s u!on the har"ness of the

work' the t%!e of grin"ing wheel' an" the "esire" finish$

3e+er take grin"ing cuts "ee!er than 7$772 inch Use a fairl% low rate of fee"$ ou will soone ale to 4u"ge whether the fee" shoul" e increase" or "ecrease"$ 3e+er sto! therotation of the work or the grin"ing wheel while the% are in contact with each other$

%arking o'ition of Lat(e Center'

Tool !ost grin"ers are often use" to refinish "a#age" lathe centers$ f the lathe is to euse" for turning etween centers in the near future' grin" the tailstock center first' then

the hea"stock center$ Lea+e the hea"stock center in !osition for the turning o!eration$ This#etho" !ro+i"es the greatest "egree of accurac%$ f %ou #ust re#o+e the hea"stock

center in or"er to !erfor# other o!erations' #arks !lace" on the hea"stock center' theslee+e' an" the center will enale %ou to install the# in the sa#e !osition the% were in

when the center was groun"$ This will ensure the greatest "egree of accurac% for futureo!erations in+ol+ing turning work etween centers$

Setup for !rin&ing Lat(e Center'

To refinish a "a#age" lathe center' %ou shoul" first install hea"stock an" tailstock centersafter ensuring that the s!in"le holes' "rill slee+es' an" centers are clean an" free of urrs$


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3et' !osition the co#!oun" rest !arallel to the wa%s5 then' #ount the tool !ost grin"er onthe co#!oun" rest$ ake sure that the grin"ing wheel s!in"le is at center height an"aligne" with the lathe centers$ o+e the co#!oun" rest ;7 to the right of the lathe

s!in"le ais' as shown in .igure /-


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carriage can e accuratel% !ositione" within 7$771 inch$ This is +e

Lathe How To Use 2

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Transcript of Lathe How To Use 2