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Copyright © The McGraw-Hill Companies, Inc.Permission required or reproduction or display.
PowerPoint to accompany
Krar • Gill • Smid
Technology o Machine Tools!th "dition
The Lathe
Section 11
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History
• Lathe forerunner of all machine tools
• First application was potter's wheel
– Rotated clay and enabled it to be formed intocylindrical shape
• Very versatile (many attachments)
– Used for turnin! taperin! form turnin! screw
cuttin! facin! drillin! borin! spinnin!
rindin and polishin operations
• "uttin tool fed either parallel or riht anles
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Special Types of Lathes
• #nine lathe – $ot production lathe! found in school shops!
toolrooms! and %obbin shops– Basic to all lathes
• &urret lathe
– Used when many duplicate parts reuired – #uipped with multisided toolpost (turret) to
which several different cuttin tools mounted• #mployed in iven seuence
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PowerPoint to accompany
Krar • Gill • Smid
Technology o Machine Tools!th "dition
Engine Lathe Parts
Unit 45
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Engine Lathe
• ccurate and versatile machine
• perations
– &urnin! taperin! form turnin! threadin!facin! drillin! borin! rindin! and polishin
• &hree common
– &oolroom – *eavy+duty
– ,ap+bed
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Lathe Size and Capacity
• -esinated by larest wor. diameter thatcan be swun over lathe ways and enerally
the ma/imum distance between centers• 0anufactured in wide rane of si1es
– 0ost common2 3+ to 45+ in6 swin with
capacity of 78 in6 to 79 feet between centers – &ypical lathe2 74 in6 swin! 8 ft lon bed! 48 in6
– verae metric lathe2 945+445 mm swin and bed lenth of :55 – 4555 mm
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Indicated y the swingand the length of the ed
Lathe Size
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Parts of the Lathe
Copyright © The McGraw-Hill Companies, Inc.Permission required or reproduction or display.
!ed
Headstoc"
#$ic"
Change
Gearo%
Tailstoc"
Carriage
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Copyright © The McGraw-Hill Companies, Inc.
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Copyright © The McGraw-Hill Companies, Inc.
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Setting Speeds on a Lathe
• ;peeds measured in revolutions per minute – "haned by stepped pulleys or ear levers
•
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Shear Pins and Slip Cl$tches
• >revents damae to feed mechanism fromoverload or sudden torue
• ;hear pins – 0ade of brass
– Found on feed rod! lead screw! and end ear train
• ;prin+loaded slip clutches – Found only on feed rods – ?hen feed mechanism overloaded! shear pin will
brea. or slip clutch will slip causin feed to stop
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Copyright © The McGraw-Hill Companies, Inc.
Permission required or reproduction or display.
;hear pin in end ear
train prevents damae
to the ears in case
of an overload
;prin+ball clutchwill slip when too
much strain is
applied to feed rod
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PowerPoint to accompany
Krar • Gill • Smid
Technology o Machine Tools!th "dition
Lathe Accessories
Unit 46
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+,-./
Lathe 0ccessories
• -ivided into two cateories
– ?or.+holdin! +supportin! and –drivin devices
• Lathe centers! chuc.s! faceplates
• 0andrels! steady and follower rests
• Lathe dos! drive plates
– "uttin+tool+holdin devices• ;traiht and offset toolholders
• &hreadin toolholders! borin bars
• &urret+type toolposts
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+,-.,
Lathe Centers
• ?or. to be turned between centers musthave center hole drilled in each end
– >rovides bearin surface• ;upport durin cuttin
• 0ost common havesolid 0orse taper shan. 85@ centers! steel with carbide tips
• "are to ad%ust and lubricate occasionally
Copyright © The McGraw-Hill Companies, Inc. Permission required or reproduction or display.
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+,-.1
Ch$c"s
• Used e/tensively for holdin wor. for
machinin operations
– ?or. lare or unusual shape
• 0ost commonly used lathe chuc.s
– &hree+%aw universal
– Four+%aw independent
– "ollet chuc.
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+,-.2
Three-3aw 4ni5ersal Ch$c"
• *olds round and he/aonal wor.
• ,rasps wor. uic.ly and accurate withinfew thousandths=inch
• &hree %aws movesimultaneously whenad%usted by chuc. wrench
– "aused by scroll plate intowhich all three %aws fit
• &wo sets of %aw2 outside chuc.in andinside chuc.in
Copyright © The McGraw-Hill Companies, Inc. Permission required or reproduction or display.
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+,-.6
7o$r-8aw Independent Ch$c"
• Used to hold round! suare! he/aonal! and
irreularly shaped wor.pieces
• *as four %aws
– #ach can be ad%usted independently by chuc.
wrench
• Aaws can be reversed to hold wor. by inside
diameter
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+,-9:
Headstoc" Spindles
Copyright © The McGraw-Hill Companies, Inc. Permission required or reproduction or display.
Universal and independent chuc. fitted to
three types of headstoc. spindles
76 &hreaded spindle nose
– ;crews on in a
cloc.wise direction
96 &apered spindle nose – *eld by loc. nut
that tihtens on chuc.
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+,-9.
Headstoc" Spindles
46 "am+loc. spindle nose
• *eld by tihtenin cam+loc.s usin &+wrench
• "huc. alined by taper
on spindle nose
Copyright © The McGraw-Hill Companies, Inc. Permission required or reproduction or display.
Reistration lines on spindle nose
Reistration lines on cam+loc.
"am+loc.s
"am+loc. matin stud on
chuc. or faceplate
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+,-99
Collet Ch$c"
• 0ost accurate chuc.
• Used for hih+precision wor.
• ;prin collets available to hold round!
suare! or he/aon+shaped wor.pieces
•#ach collet has rane of only fewthousandths of an inch over or under si1e
stamped on collet
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+,-9;
Copyright © The McGraw-Hill Companies, Inc. Permission required or reproduction or display.
B
Collet Ch$c"
;pecial adapter fitted into taper of headstoc. spindle!and hollow draw bar havin internal thread inserted
in opposite end of headstoc. spindle6 Ct draws collet
into tapered adapter causin collet to tihten on wor.piece6
+, 9+
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Types of Lathe
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Types of Lathe
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+,-9,
Left-Hand =ffset Toolholder
Copyright © The McGraw-Hill Companies, Inc. Permission required or reproduction or display.
• ffset to the riht
• -esined for machinin wor. close to
chuc. or faceplate and cuttin riht to left
• -esinated by letter L
+, 91
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+,-91
)ight-Hand =ffset Toolholder
Copyright © The McGraw-Hill Companies, Inc. Permission required or reproduction or display.
• ffset to the left
• -esined for machinin wor. close to the
tailstoc. and cuttin left to riht – lso for facin operations
• -esinated by letter R
+, 92
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+,-92
Straight Toolholder
• ,eneral+purpose type
• Used for ta.in cuts in either direction and
for eneral machinin operations
• -esinated by letter ;
Copyright © The McGraw-Hill Companies, Inc. Permission required or reproduction or display.
+, 96
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+,-96
Toolholders for Inde%ale
Caride Inserts• *eld in holder by cam action or clamps
• &ypes available – "onventional
– &urret+type
– *eavy+duty toolposts
+, ;:
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+,-;:
C$tting-=ff >Parting? Tools
• Used when wor. must be rooved or parted off
• Lon! thin cuttin+off blade loc.edsecurely in toolholder by either cam loc. orloc.in nut
• &hree types of partin toolholders
– Left+hand
– Riht+hand
– ;traiht
+, ;.
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+,-;.
Threading Toolholder
• -esined to hold special form+relieved
thread+cuttin tool
• *as accurately round 85@ anle
– 0aintained throuhout life of tool
• nly top of cuttin surface sharpened when
becomes dull
+, ;9
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+,-;9
S$per #$ic"-Change Toolpost
Copyright © The McGraw-Hill Companies, Inc. Permission required or reproduction or display.
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Copyright © The McGraw-Hill Companies, Inc.Permission required or reproduction or display.
PowerPoint to accompany
Krar • Gill • Smid
Technology o Machine Tools!th "dition
Cutting Speed,Feed, and Depth
of Cut Unit 47
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+1-;+
C$tting Speed
• Rate at which point on wor. circumference
travels past cuttin tool
• lways e/pressed in feet per minute (ft=min)
or meters per minute (m=min)
• Cmportant to use correct speed for material
– &oo hih2 cuttin+tool brea.s down rapidly
– &oo low2 time lost! low production rates
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+1-;/
Lathe C$tting Speeds in 7eet and @eters per
@in$te 4sing High-Speed Steel Toolit
Turning and Boring
Rough CutFinish Cut Threading
Materia ft!"in "!"in ft!"in "!"i
Machine steel 90 27 100 30 35 11
Tool steel 70 21 90 27 30 9
Cast iron 60 1 0 24 25
Bron!e 90 27 100 30 25 "l#$in#$ 200 61 300 93 60 1
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+1-;,
Calc$lating Lathe Spindle Speed
• ,iven in revolutions per minute
• "uttin speed of metal and diameter of
wor. must be .nown• >roper spindle speed set by dividin
"; (in=min) by circumference of wor. (in)
-
D/";
-
79/"; r=min ==π
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+1 ;1
E%ampleA
-
D/";
r=min =
"alculate r=min reuired to rouh+turn 9 in6 diameter
piece of machine steel ("; 35)2
7E59
D/35 r=min ==
-
495/"; r=min =0etric Formula
+1-;2
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+1 ;2
Lathe 7eed
• -istance cuttin tool advances alon lenth
of wor. for every revolution of the spindle
• Feed of enine lathe dependent on speed of
lead screw for feed rod
– ;peed controlled by chane ears in
uic.+chane earbo/
+1-;6
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+1 ;6
Two C$ts 4sed to !ring
urpose to remove e/cess material uic.ly
– "oarse feed2 surface finish not too important
• 6575+ to 657:+in6 (569:+ to 56D+mm)
• Finishin cut
– Used to brin diameter to si1e
– Fine feed2 >roduce ood finish
• 6554+ to 655:+in (565+ to 56579+mm)
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+1 +:
7eeds for (ario$s @aterials
>$sing high-speed steel c$tting tool?
Rough Cuts Finish Cut
Materia in# "" in#
Machine steel %010–%020 0%25–0%5 %003–%010
Tool steel %010–%020 0%25–0%5 %003–%010 0%07–
Cast iron %015–%025 0%4–0%65 %005–%012 0%13–
Bron!e %015–%025 0%4–0%65 %003–%010"l#$in#$ %015–%030 0%4–0%75 %005–%010 0%13–
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+1 +.
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Copyright © The McGraw-Hill Companies, Inc.
Permission required or reproduction or display.
#/ample2 -epth of cut on a lathe
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7actors
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Inch System
• "ircumference of crossfeed and compound
rest screw collars divided into 755+79:
eual divisions – #ach has value of 6557 in6
• &urn crossfeed screw cloc.wise 75 raduations!
cuttin tool moved 6575 in6 toward wor.
• Lathe revolves! so 6575 depth of cut ta.en fromentire wor. circumference reducin diameter 6595 in6
• "hec. machine for its' raduations
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Copyright © The McGraw-Hill Companies, Inc.
Permission required or reproduction or display.
=n machines where the wor"piece re5ol5esB
the c$tting tool sho$ld e set in for only half
the amo$nt to e remo5ed from the diameter*
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Copyright © The McGraw-Hill Companies, Inc.
Permission required or reproduction or display.
=n machines where the wor"piece does not
re5ol5eB the c$tting tool sho$ld e set in forthe amo$nt of material to e remo5ed*
+1-+1
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Hints on Grad$ated Collar 4se
76 0a.e sure collar is secure before settin adepth of cut
96 ll depths of cut must be made by feedin
cuttin tool toward wor.piece46 Cf raduated collar turned past desired
settin! must be turned bac.ward half+turnand fed into proper settin to remove
bac.lashD6 $ever hold raduated collar when settin
depth of cut
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:6 ,raduated collar on compound rest can be
used for accurately settin depth of cut• ;houlder turnin• "ompound rest set at 35@ to cross+slide
• Loc. carriae in place
• ;pacin of shoulders to within 6557 in6 accuracy• Facin
• "ompound rest swun to 45@! amount removed fromlenth of wor. G H amount of feed on collar
• 0achinin accurate diameters• ;et compound rest to ED@78' to the cross+slide
• 6557 in movement G 65557+in6 infeed movement
+1-+6
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Copyright © The McGraw-Hill Companies, Inc.
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The compo$nd rest is set at 2+.,D for
ma"ing fine settings*
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Copyright © The McGraw-Hill Companies, Inc.Permission required or reproduction or display.
PowerPoint to accompany
Krar • Gill • Smid
Technology o Machine Tools!th "dition
Lathe Safet$
Unit 4
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Safety
•
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Safety Preca$tions
• Lathe ha1ardous if not operated properly
• Cmportant to .eep machine and surroundin
area clean and tidy
• ccidents usually caused by carelessness
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Safety Preca$tions
• lways wear approved safety lasses
• Rollup sleeves! remove tie and tuc. in loose
clothin
• $ever wear rin or watch
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Safety Preca$tions
• -o not operate lathe until understand controls
• $ever operate machine if safety uards
removed• ;top lathe before measure wor. or clean! oil
or ad%ust machine
• -o not use ra to clean wor. or machinewhen in operation – Ra can et cauht and dra in hand
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Safety Preca$tions
• $ever attempt to stop a lathe chuc. or
driveplate by hand
•
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Safety Preca$tions
• 0ove carriae to farthest position of cut and
revolve lathe spindle one turn by hand
– #nsure all parts clear without %ammin – >revent accident and damae to lathe
• Ieep floor around machine free from rease!
oil! metal cuttins! tools and wor.pieces – il and rease can cause falls
– b%ects on floor become trippin ha1ards
+2-/1
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Safety Preca$tions
• void horseplay at all times
• lways remove chips with brush
– "hips can cause cuts if use hands
– "hips become embedded if use cloths
• lways remove sharp toolbit from
toolholder when polishin! filin! cleanin!or ma.in ad%ustments
P P i t t
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Technology o Machine Tools!th "dition
Mounting,Re"o%ing, andAigning Lathe
Centers Unit 49
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&'(ecti%es
& Mo#nt an'(or re$o)e lathe
centers *ro*erl+
& "lign lathe centers ,+ )is#al- trial.
c#t- an' 'ial.in'icator $etho's
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Lathe Centers
• ?or. machined between centers turned for
some portion of lenth! then reversed! and
other end finished• "ritical when machinin wor. between
centers that live center be absolutely true
– "oncentric wor.
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To @o$nt Lathe Centers
• Remove any burrs from lathe spindle!centers! or spindle sleeves
•"lean tapers on lathe centers and inheadstoc. and tailstoc. spindles
• >artially insert cleaned center in lathe spindle
• Force center into spindle
• Follow same procedure when mountintailstoc. center
• "hec. trueness of center
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To )emo5e Lathe Centers
• Live center – Use .noc.out bar pushed throuh headstoc.
spindle (sliht tap)
– Use cloth over center and hold to prevent damae
• -ead center – &urn tailstoc. handwheel to draw spindle bac.
into tailstoc. • #nd of screw contacts end of dead center! forcin it out
of spindle
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0lignment of Lathe Centers
• >arallel diameter produced when lathecenter alined
• &hree common methodsused to alin
76 linin centerlineson bac. of tailstoc.
with each other – nly a visual chec.
and not too accurate
Copyright © The McGraw-Hill Companies, Inc. Permission required or reproduction or display.
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0lignment of Lathe Centers
96 Usin the trial+cut
method where small
cut ta.en from eachend of wor. and
diameters measured with a micrometer
46 Usin parallel test bar and dial indicator • Fastest and most accurate method
Copyright © The McGraw-Hill Companies, Inc. Permission required or reproduction or display.
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To 0lign Centers y 0d3$sting
the Tailstoc" 76 Loosen tailstoc. clamp nut or level
96 Loosen on of the ad%ustin screws!
dependin on direction tailstoc. must bemoved and tihten other until line on topalins with line on bottom half
46 &ihten screw to loc. both halves in placeD6 0a.e sure tailstoc. lines still alined
:6 Loc. tailstoc. clamp nut or lever
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To 0lign Centers y
Trial-C$t @ethod76 &a.e a liht cut (J655: in6) to true
diameter from section at tailstoc. end
for 69:5 in6 lon96 ;top feed and note readin on raduated
collar of crossfeed handle
46 0ove cuttin tool away from wor. withcrossfeed handle
D6
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To 0lign Centers y
Trial-C$t @ethod
:6 Return cuttin tool to same raduated
collar settin as at section 86 "ut a 6:55+in (74 mm) lenth at section <
and stop lathe
6 0easure both diameters with micrometer
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To 0lign Centers y
Trial-C$t @ethodE6 Cf both diameters not same si1e! ad%ust
tailstoc. either toward or away from
cuttin tool H difference of two readins
36 &a.e another liht cut at and < at same
crossfeed raduated collar settin6
0easure diameters and ad%ust tailstoc.6
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To 0lign Centers 4sing
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To 0lign Centers 4sing
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To 0lign Centers 4sing
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Technology o Machine Tools!th "dition
)rinding LatheCutting Toos
Unit 50
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Grinding Lathe C$tting Tool
• ?ide variety of cuttin tools for lathe – ll have certain anles and clearances reardless
of shape
Shape and
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To Grind a
General-P$rpose Toolit76 -ress face of rindin wheel
96 ,rip toolbit firmly! supportin hands on rinder
toolrest46 *old toolbit at proper
anel to rind cuttinede anle
• &ilt bottom of toolbittoward wheel andrind 75@ side relief or clearance anle
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"uttin ede J H Cn lon and e/tendover K width of toolbit
75@ side relief or
clearance anle
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D6 ?hile rindin! move toolbit bac. and
forth across face of wheel• >revents roovin wheel
:6 &oolbit must be cooled freuently durin
rindin• Never overheat toolbit
• Never uench stellite or cemented+carbide
tools• Never rind carbides with aluminum o/ide
wheel
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86 ,rind end cuttin ede so it forms anle of
a little less than 35@ with side cuttin ede – *old tool so that end cuttin ede anle and
end relief anle of 7:@ round at same time
Copyright © The McGraw-Hill Companies, Inc. Permission required or reproduction or display.
1: to 2: Point 0ngle
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6 Usin toolbit rindin ae! chec. amount
of end relief when toolbit is in toolholder
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E6 *old top of toolbit appro/imately D:@ to
a/is of wheel and rind side ra.e toappro/imately 7D@
– -o not rind below top of toolbit
• "reates a chip trap
Copyright © The McGraw-Hill Companies, Inc. Permission required or reproduction or display.
Side ra"e gro$nd the length
of the c$tting edge
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36 ,rind sliht radius on point of cuttin
tool! bein sure to maintain same frontand side clearance anle
756 ?ith oilstone! hone cuttin ede of toolbit
slihtly• Lenthen life of toolbit
• #nable it to produce better surface finish on
wor.piece
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Copyright © The McGraw-Hill Companies, Inc.
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Krar • Gill • Smid
Technology o Machine Tools!th "dition
MachiningBet*een Centers
Unit 52
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@achining !etween Centers
• &rainin prorams (schools) – Remove and replace wor. in lathe many times
before completed
– $eed assurance that machined diameter will runtrue with other diameters
• 0achinin between centers saves time in settin up
• "ommon operations – Facin! rouh and finish+turnin! shoulder
turnin! filin and polishin
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Setting 4p a C$tting Tool
76 0ove toolpost to the left+hand side of the &+slotin thecompoundrest
96 0ount tool+holder intoolpost sosetscrew intoolholder 7 in6
beyond toolpost
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Copyright © The McGraw-Hill Companies, Inc.Permission required or reproduction or display.
Hea5y C$tsA Set toolholder at right
angles to wor"
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Setting 4p a C$tting ToolA cont*
46 Cnsert proper cuttin tool into toolholder!havin tool e/tend 6:55 in6 beyond
toolholder and never more than twice its
thic.nessD6 ;et cuttin+tool point to center heiht
• "hec. it aainst lathe center point
:6 &ihten toolpost securely to prevent itfrom movin durin a cut
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P$rposes of a Trial C$t
• >roduce accurate turned diameter
– 0easured with micrometer
• ;et cuttin+tool point to the diameter
• ;et crossfeed micrometer collar to the
diameter
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Proced$re to Ta"e a Trial C$t
76 ;et up wor.piece and cuttin tool as for
turnin
96 ;et proper speeds and feed to suit material
46 ;tart lathe and position toolbit over wor.
appro/imately 679: in6 from end
D6 &urn compound rest handle cloc.wise K
of a turn to remove any bac.lash
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:6 feed toolbit into wor. by turnin crossfeedhandle cloc.wise until liht rin appearsaround entire circumference of wor.
86 -o $& move crossfeed handle settin
6 &urn carriae handwheel until toolbit
clears end of wor.piece by about 6585 in6E6 &urn crossfeed handle cloc.wise about 6
575 in6 and ta.e trial cut 69:5 in6 alon
lenth of wor. 36 -isenae automatic feed and clear toolbit
past end of wor. with carriae handwheel
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756 ;top the lathe
776 &est accuracy of micrometer by cleaninand closin measurin faces and then
measure trial+cut diameter
796 "alculate how much material must still be
removed from diameter of wor.
746 &urn crossfeed handle cloc.wise H
amount of material to be removed
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7D6 &a.e another trial cut 69:5 in6 lon and
stop the lathe7:6 "lear toolbit over end of wor. with
carriae handwheel
786 0easure diameter and read%ust crossfeed
handle until diameter is correct
76 0achine diameter to lenth
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)o$gh T$rning
• Removes as much metal as possible inshortest lenth of time
•ccuracy and surface finish are notimportant in this operation – 6595+ to 6545+in6 feed recommended
• ?or. rouh+turned to
– ?ithin 6545 in6 of finished si1e when removinup to 6:55 in6 diameter
– ?ithin 6585 in6 when removin M 6:55 in6
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Proced$re for )o$gh T$rning
76 ;et lathe to correct speed for type and si1eof material bein cut
96 d%ust uic.+chane earbo/ for a 6575+to 6545+in6 feed
• -epends on depth of cut and condition ofmachine
46 0ove toolholder to left+hand side ofcompound rest and set toolbit heiht tocenter
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D6 &ihten toolpost securely to prevent
toolholder from movin durin machinin:6 &a.e liht trial cut at riht+hand end of
wor. for a 69:5 in6 lenth
86 0easure wor. and ad%ust toolbit for proper depth of cut
6 "ut alon for 69:5 in6! stop lathe! andchec. diameter for si1e
76 -iameter 6545 in6 over finish si1e
E6 Read%ust depth of cut! if necessary
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7inish T$rning
• Follows rouh turnin
• >roduces smooth surface finish and cuts
wor. to an accurate si1e
• Factors affectin type of surface finish
– "ondition of cuttin tool
– Riidity of machine and wor.
– Lathe speeds and feeds
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Proced$re 7or 7inish T$rning
76 0a.e sure cuttin ede of toolbit free
from nic.s! burrs! etc6
96 ;et toolbit on centerN chec. it aainst lathe
center point
46 ;et lathe to recommended speed and feed
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D6 &a.e liht trial cut 69:5 in6 lon at riht+
hand end of wor. • >roduce true diameter
• ;et cuttin tool to diameter
• ;et raduated collar to diameter
:6 ;top lathe and measure diameter
86 ;et depth of cut for half amount ofmaterial to be removed
6 "ut alon for 69:5 in6! stop lathe! chec.
E6 Read%ust depth of cut and finish+turn
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7iling in a Lathe
• nly to remove small amount of stoc.!remove burrs! or round off sharp corners
• ?or. should be turned to within 6559 to 6554in6 of si1e
• For safety! file with left hand so arms andhands .ept clear of revolvin chuc.
• Remove toolbit from toolholder before filin
• "over lathe bed with paper before filin
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Proced$re to 7ile in a Lathe
76 ;et spindle speed to twice that for turnin
96 0ount wor. between centers! lubricate!
and carefully ad%ust dead center in wor. 46 0ove carriae as far to riht as possible
and remove toolpost
D6 -isenae lead screw and feed rod:6 ;elect 75+ or 79+in6 mill file or lon+anle
lathe file
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86 ;tart lathe
6 ,rasp file handle in left hand and supportfile point with finers of riht hand
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E6 pply liht pressure and push file forwardto its full lenthN release pressure onreturn stro.e
36 0ove file about half width of file for eachstro.e and continue filin until finished
• Use 45+D5 stro.es per minute756 ;afety precautions
• Roll sleeves above elbow
• Remove watches and rins
• $ever use file without properly fitted handle• $ever apply too much pressure
• "lean file freuently with file brush
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Proced$re forPolishing in a Lathe
76 ;elect correct type and rade of abrasivecloth for finish desired
• >iece about 8 – E in6 lon and 7 in6 wide• Use aluminum o/ide abrasive cloth forferrous metals
• Use silicon carbide abrasive cloth should be
used for nonferrous metals96 ;et lathe to run at hih speed
46 -isenae feed rod and lead screw
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D6 Remove toolpost and toolholder
:6 Lubricate and ad%ust dead center 86 Roll sleeves up above elbows and tuc. in
any loose clothin
6 ;tart latheE6 *old abrasive cloth on wor.
36 ?ith riht hand! press cloth firmly on
wor. while tihtly holdin other end ofabrasive cloth with left hand
756 0ove cloth slowly bac. and forth
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Sho$lder
• ;houlder2 the chane in diameters! or step!
when turnin more than one diameter on a
piece of wor. • &hree common types of shoulders
– ;uare
– Filleted – nular or &apered
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f S
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Three Types of Sho$lders
Copyright © The McGraw-Hill Companies, Inc.
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Krar • Gill • Smid
Technology o Machine Tools!th "dition
+nuring,)roo%ing,
and For" Turning Unit 53
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Kn$rling
• >rocess if impressin a diamond+shaped or
straiht+line patter into the surface of the
wor.piece – Cmprove its appearance
– >rovide better rippin surface
– Cncrease wor.piece diameter when press fitreuired
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Kn$rling
• -iamond+ and
straiht+pattern
rolls available inthree styles
– Fine
– 0edium
– "ourse
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Kn$rling Tool
• &oolpost+type toolholder on which pair of
hardened+steel rolls mounted
Inurlin tool with
one set of rolls in
self+centerin head
Inurlin tool with
three sets of rolls
in revolvin head
Copyright © The McGraw-Hill Companies, Inc. Permission required or reproduction or display.
/;-.:6
4 i l K li T l S t
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4ni5ersal Kn$rling Tool System
• -ovetailed shan. and as many as seven
interchaneable .nurlin heads that can
produce wide rane of .nurlin patterns• "ombines in one tool
– Versatility
– Riidity
– #ase of handlin
– ;implicity
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P d K l i L h
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Proced$re to Kn$rl in a Lathe
76 0ount wor. between centers and mar.
reuired lenth to be .nurled
•Cf wor. held in chuc. for .nurlin! riht endof wor. should be supported with revolvin
tailstoc. center
96 ;et lathe to run at one+uarter speed
reuired for turnin
46 ;et carriae feed to 657: to 6545 in6
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D6 ;et center of floatin head of .nurlin tool
even with dead+center point
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:6 ;et .nurlin tool at riht anles to
wor.piece and tihten it securely
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8 ; hi d li h l h ll
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86 ;tart machine and lihtly touch rolls
aainst wor. to chec. trac.in6 0ove .nurlin tool to end of wor. so
only half the roll face bears aainst wor.
E6 Force .nurlin tool into wor.appro/imately 659: in6 and start lathe
R
;tart lathe and then force .nurlin tool intowor. until diamond pattern come to point
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36 ;top lathe and e/amine pattern
756 nce pattern correct! enae automaticcarriae feed and apply cuttin fluid to.nurlin rolls
776 Inurl to proper lenth and depth• -o not disenae feed until full lenth has
been .nurledN otherwise! rins will be formedon .nurled pattern
796 Cf .nurlin pattern not to point after lenthhas been .nurled! reverse lathe feed andta.e another pass across wor.
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Groo5ing
Copyright © The McGraw-Hill Companies, Inc. Permission required or reproduction or display.
S$are
)o$nd
(-shaped
• -one at end of thread to
permit full travel of nut up
to a shoulder or at ede of
shoulder for proper fit• lso called recessin!
undercuttin! or nec.in
• Rounded rooves usedwhere there is strain on
part
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Proced$re to C$t a Groo5e
76 ,rind toolbit to desired si1e and shape of
roove reuired
96 Lay out location of roove
46 ;et lathe to half the speed for turnin
D6 0ount wor.piece in lathe
:6 ;et toolbit to center heiht
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86 Locate toolbit on wor. at position whereroove is to be cut
6 ;tart lathe and feed cuttin tool towardwor. usin crossfeed handle until toolbitmar.s wor. lihtly
E6 *old crossfeed handle in position and setraduated collar to 1ero
36 "alculate how far crossfeed screw must be
turned to cut roove to proper depth756 Feed toolbit into wor. slowly usin
crossfeed handle
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776 pply cuttin fluid to point of cuttin tool
• &o ensure cuttin tool will not bind inroove! move carriae slihtly to left and to
riht while roovin
• ;hould chatter develop! reduce spindle speed
796 ;top lathe and chec. depth of roove with
outside calipers or .nife+ede verniers
Safety noteA 0lways wear safety goggles when
groo5ing on a lathe
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Krar • Gill • Smid
Technology o Machine Tools!th "dition
Threads andThread Cutting
Unit 55
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Threads
• Used for hundreds of years for holdin parts
toether! ma.in ad%ustments! and
transmittin power and motion• rt of producin threads continually
improved
• 0assed+produced by taps! dies! threadrollin! thread millin! and rindin
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Threads
• &hread – *elical ride of uniform section formed on
inside or outside of cylinder or cone
• Used for several purposes2 – Fasten devices such as screws! bolts! studs! and
nuts
– >rovide accurate measurement! as in micrometer – &ransmit motion
– Cncrease force
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Thread
TerminologyCopyright © The McGraw-Hill Companies, Inc.
Permission required or reproduction or display.
//-.99
Th d T i l
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Thread Terminology
• ;crew thread
– *elical ride of uniform section formed on
inside or outside of cylinder or cone
• #/ternal thread
– "ut on e/ternal surface or cone
• Cnternal thread – >roduced on inside of cylinder or cone
//-.9;
• 0a%or diameter
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• 0a%or diameter – Larest diameter of e/ternal or internal thread
• 0inor diameter – ;mallest diameter of e/ternal or internal thread
• >itch diameter – -iameter of imainary cylinder that passes
throuh thread at point where roove and threadwidths are eual
– #ual to ma%or diameter minus sinle depth ofthread
– &olerance and allowances iven at pitchdiameter line
//-.9+
• $umber of threads per inch
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• $umber of threads per inch
– $umber of crests or roots per inch of threaded
section (-oes not apply to metric threads)
• >itch
– -istance from point on one thread to
correspondin point on ne/t thread! measured
parallel to a/is
– #/pressed in millimeters for metric threads
• Lead – -istance screw thread advances a/ially in one
revolution (sinle+start thread! lead G pitch)
//-.9/
• Root
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• Root –
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//-.91
• Riht hand thread
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• Riht+hand thread
– *elical ride of uniform cross section onto
which nut is threaded in cloc.wise direction
– ?hen cut on lathe! toolbit
advanced from riht to left
• Left+hand thread
– *elical ride of uniform cross section onto
which nut is threaded in countercloc.wise
direction – ?hen cut on lathe! toolbit
advanced from left to riht
Copyright © The McGraw-Hill Companies, Inc.
Permission required or reproduction or display.
//-.92
Th d 7
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Thread 7orms
• pril! 73: C; came to an areement
coverin standard metric thread profile
– ;pecifies si1es and pitches for various threadsin new C; 0etric &hread ;tandard
– *as 9: thread si1es! rane in diameter from 768
to 755 mm
– Cdentified by letter 0! nominal diameter! and
pitch @ / F :*2
//-.96
0merican &ational Standard Thread
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0merican &ational Standard Thread
• -ivided into four main series! all havinsame shape and proportions – $ational "oarse ($")
– $ational Fine ($F) – $ational ;pecial ($;)
– $ational >ipe ($>&)
• *as 85@ anle with root and crest truncatedto 7=Eth the pitch
• Used in fabrication! machine construction
//-.;:
0merican &ational Standard Thread
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N P F
N P D
679:or/679:
6874Dor/874D6
=
=
Copyright © The McGraw-Hill Companies, Inc.
Permission required or reproduction or display.
//-.;.
4nified Thread
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4nified Thread
• -eveloped by U6;6!
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N
P F
N P F
N P D
N
69:5or/69:5thread)(internal
679:or/679:thread)(e/ternal
6:D74or/:D746thread)(internal
=
=
=
Copyright © The McGraw-Hill Companies, Inc.
Permission required or reproduction or display.
//-.;;
0merican &ational 0cme Thread
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0merican &ational 0cme Thread
• Replacin suare thread in many cases
• Used for feed screws! %ac.s! and vises D / minimum .500P
/ maximum .500P 0.010
F / .3707P
C / .3707P . .0052 (for maximum depth)
Copyright © The McGraw-Hill Companies, Inc.
Permission required or reproduction or display.
//-.;+
! Sh Th d
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!rown Sharpe orm Thread
• Used to mesh worm ears and transmitmotion between two shafts at riht anles toeach other but not in same plane
D / .6866P
F / .335P
C / .310P
Copyright © The McGraw-Hill Companies, Inc.
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//-.;/
S are Thread
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S$are Thread
•
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International @etric thread
• ;tandardi1ed thread used in #urope
F G 5679: P
R G 565844 P (ma/imum) G 565:D P (minimum)
D G 5654: P (ma/imum)
G 568E:: P (minimum)
Copyright © The McGraw-Hill Companies, Inc.
Permission required or reproduction or display.
//-.;1
Thread 7its and Classifications
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Thread 7its and Classifications
• Fit – Relationship between two matin parts
– -etermined by amount of clearance or
interference when they are assembled
• $ominal si1e – -esination used to identify si1e of part
• ctual si1e – 0easured si1e of thread or part
–
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0llowance
• >ermissible difference between lareste/ternal thread and smallest internal thread
• -ifference produces tihtest fit acceptable
for any iven classification&he allowance for a 7 in6PE U$" "lass 9 and 9< fit is2
0inimum pitch diameter of the
internal thread (9
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Tolerance
• Variation permitted in part si1e
• 0ay be e/pressed as plus! minus! or both
• &otal tolerance is sum of plus and minus tolerances
• Cn Unified and $ational systems! tolerance is pluson e/ternal threads and minus on internal threads
0a/imum pitch diameter of the
e/ternal thread (9) G 6378E in60inimum pitch diameter of the
e/ternal thread (9) G 63755 in6
&olerance G 6558E in6
&he tolerance for a 7 in6PE U$" "lass 9 thread is2
//-.+:
Limits
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Limits
• 0a/imum and minimum dimensions of part
0a/imum pitch diameter of the
e/ternal thread (9) G 6378E in66
0inimum pitch diameter of the
e/ternal thread (9) G 63755 in6
&he limits for a 7 in6PE U$" "lass 9 thread are2
//-.+.
Three Categories of 4nified
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gThread 7its
• #/ternal threads classified as 7! 9! and 4 andinternal threads as 7
• "lasses 7 and 7<
– &hreads for wor. that must be assembled – Loosest fit
• "lasses 9 and 9< – Used for most commercial fasteners
– 0edium or free fit• "lasses 4 and 4<
– Used where more accurate fit and lead reuired
– $o allowance provided
//-.+9
Thread Calc$lationsA E%ample .
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Thread Calc$lationsA E%ample .
&o cut a correct thread on a lathe! it is necessary first to ma.ecalculations so thread will have the proper dimensions6
D / single depth of thread
P / pitch
in665876755/6874D4
/874D46
in67556
75
77
==
=
===
P Dtpi
P
"alculate pitch! depth! minor diameter! and width of flat
for a QP75 U$" thread6
in6579:6
75
7 /
E
7
E flatof ?idth
in689E6
6587)(6587+6:
)(+dia0a%ordia0inor
=
==
=
+=
+=
P
D D
//-.+;
Thread Calc$lationsA E%ample 9
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Thread Calc$lationsA E%ample 9
P / pitch = 1 mm
D / 0.54127 x 1
= 0.54 mm
?hat are the pitch! depth! minor diameter! width of crest
and width of root for an 0 864 7 threadS
mm79:65
7/79:65
/679:5crestof ?idth
mm996:
6:D)(6:D+864
)(+dia0a%ordia0inor
=
=
=
=
+=
+=
P
D D
mm9:65
7/569:
/9:65rootof ?idth
=
=
= P
//-.++
Proced$re to Set the #$ic"-
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#Change Gearo% for Threading
76 "hec. drawin for thread pitch reuired
96 From chart on uic.+chane earbo/! find
whole number that represents pitch inthreads per inch or in millimeters
46 ?ith lathe stopped! enae tumbler lever
in hole! which is in line with the pitchD6 ;et top lever in proper position as
indicated on chart
//-.+/
: # lidi i t i d
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:6 #nae slidin ear in or out as reuired
86 &urn lathe spindle by hand to ensure thatlead screw revolves
6 Rechec. lever settins to avoid errors
//-.+,
Thread-Chasing dial
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Thread Chasing dial
• Lathe spindle andlead screw must bein same relative
position for each cut
– &hread+chasin dialattached to carriae for this purpose
• -ial has eiht divisions – #ven threads use any division
– dd threads either numberedor unnumbered2 not both
Copyright © The McGraw-Hill Companies, Inc.
Permission required or reproduction or display.
//-.+1
Thread C$tting
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Thread C$tting
• >roduces a helical ride of uniform section
on wor.piece
• >erformed by ta.in successive cuts withthreadin toolbit of same shape as thread
form reuired
• ?or. may be held between centers or inchuc.
//-.+2
Proced$re to Set 4p a Lathe for
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Threading >,: Thread?
76 ;et lathe speed to K speed used for turnin
96 ;et uic.+chane earbo/ for reuired pitch
in threads per inch or in millimeters46 #nae lead screw
D6 ;ecure 85@ threadin toolbit and chec.
anle usin thread center ae:6 ;et compound rest at 93@ to rihtN set to left
for left+hand thread
//-.+6
8 ;et cuttin tool to heiht of lathe center
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86 ;et cuttin tool to heiht of lathe center
point6 0ount wor. between centers
• 0a.e sure lathe do is tiht on wor.
• Cf wor. mounted in chuc.! it must be heldtihtly
E6 ;et toolbit at riht anles to wor.! usin
thread center ae
36 rrane apron controls to allow split+nut
lever to be enaed
//-./:
Thread-C$tting =peration
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Thread-C$tting =peration
Proced$re to c$t a ,: thread
76 "hec. ma%or diameter of wor. for si1e
96 ;tart lathe and chamfer end of wor.piecewith side of threadin tool to %ust below
minor diameter of thread
46 0ar. lenth to be threaded by cuttinliht roove at this point with threadin
tool while lathe revolvin
//-./.
D6 0ove carriae until point of threadin tool
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p
near riht+hand end of wor.
:6 &urn crossfeed handle until threadin tool
close to diameter! but stop when handle is at
4 o'cloc. position86 *old crossfeed handle in this position and
set raduated collar to 1ero
6 &urn compound rest handle until threadintool lihtly mar.s wor.
//-./9
E6 0ove carriae to riht until toolbit clears
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E6 ove ca ae to t u t too b t c ea s
end of wor. 36 Feed compound rest cloc.wise about 6554 in6
756 #nae split+nut lever on correct line of
thread+chasin dial and ta.e trial cut alonlenth to be threaded
776 t end of cut! turn crossfeed handle
countercloc.wise to move toolbit away from
wor. and disenae split+nut lever
//-./;
796 ;top lathe and chec. number of tpi with
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p p
thread pitch ae! rule! or center ae746 fter each cut! turn carriae handwheel to
brin toolbit to start of thread and return
crossfeed handle to 1ero7D6 ;et depth of all threadin cuts with
compound rest handle
• ;ee &able ::69 and &able ::64
//-./+
hen tool is fed in at 96B most of the c$tting
i i f i
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is done y the leading edge of toolit*
Copyright © The McGraw-Hill Companies, Inc.
Permission required or reproduction or display.
//-.//
Ta'e 55#- Depth settings forcutting ./0 nationa for"
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cutting ./ nationa for"
threadsCo"pound Rest Settingtpi /0 2/0 -30
24 %027 %031 %030
20 %0325%0375%0371 %036 %0417%041
16 %0405%046%046
14 %0465%0537%0525
13 %050 %0577%057
11 %059 %06 %0674
Portion of tale ta"en
from te%too"
//-./,
7:6 pply cuttin fluid and ta.e successive
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pp y
cuts until top (crest) and bottom (root) ofthread are same width
786 Remove burrs from top of thread with file
76 "hec. thread with master nut and ta.efurther cuts
//-./1
Si% ays to Chec" Threads
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Si% ays to Chec" Threads
• -epends on accuracy reuired2
76 0aster nut or screw
96 &hread micrometer 46 &hree wires
D6 &hread roll or snap ae
:6 &hread rin or plu ae8 i l