46-1
Lathe Accessories
• Divided into two categories
– Work-holding, -supporting, and –driving devices
• Lathe centers, chucks, faceplates
• Mandrels, steady and follower rests
• Lathe dogs, drive plates
– Cutting-tool-holding devices
• Straight and offset toolholders
• Threading toolholders, boring bars
• Turret-type toolposts
46-2
Lathe Centers
• Work to be turned between centers must
have center hole drilled in each end
– Provides bearing surface
• Support during cutting
• Most common have
solid Morse taper shank
60º centers, steel with carbide tips
• Care to adjust and lubricate occasionally
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46-3
Chucks
• Used extensively for holding work for
machining operations
– Work large or unusual shape
• Most commonly used lathe chucks
– Three-jaw universal
– Four-jaw independent
– Collet chuck
46-4
Three-jaw Universal Chuck
• Holds round and hexagonal work
• Grasps work quickly and accurate within
few thousandths/inch
• Three jaws move
simultaneously when
adjusted by chuck wrench
– Caused by scroll plate into
which all three jaws fit
• Two sets of jaw: outside chucking and
inside chucking
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46-5
Four-Jaw Independent Chuck
• Used to hold round, square, hexagonal, and
irregularly shaped workpieces
• Has four jaws
– Each can be adjusted independently by chuck
wrench
• Jaws can be reversed to hold work by inside
diameter
46-6
Headstock Spindles
Universal and independent chuck fitted to
three types of headstock spindles
1. Threaded spindle nose
–
Screws on in a
clockwise direction
2. Tapered spindle nose
–
Held by lock nut
that tightens on chuck
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46-7
Headstock Spindles
3. Cam-lock spindle nose
•
•
Held by tightening cam-locks using T-wrench
Chuck aligned by taper
on spindle nose
Registration lines on spindle nose
Registration lines on cam-lock
Cam-locks
Cam-lock mating stud on
chuck or faceplate
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46-8
Collet Chuck
• Most accurate chuck
• Used for high-precision work
• Spring collets available to hold round,
square, or hexagon-shaped workpieces
• Each collet has range of only few
thousandths of an inch over or under size
stamped on collet
46-9
Collet Chuck
|
Special adapter fitted into taper of headstock spindle,
and hollow draw bar having internal thread inserted
in opposite end of headstock spindle. It draws collet
into tapered adapter causing collet to tighten on workpiece.
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46-10
Types of Lathe Dogs
• Standard bent-tail lathe dog
– Most commonly used for round
workpieces
– Available with square-head
setscrews of headless setscrews
• Straight-tail lathe dog
– Driven by stud in driveplate
– Used in precision turning
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46-11
Types of Lathe Dogs
• Safety clamp lathe dog
– Used to hold variety of work
– Wide range of adjustment
• Clamp lathe dog
– Wider range
than others
– Used on all shapes
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46-12
Left-Hand Offset Toolholder
• Offset to the right
• Designed for machining work close to
chuck or faceplate and cutting right to left
• Designated by letter L
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46-13
Right-Hand Offset Toolholder
• Offset to the left
• Designed for machining work close to the
tailstock and cutting left to right
– Also for facing operations
• Designated by letter R
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46-14
Straight Toolholder
• General-purpose type
• Used for taking cuts in either direction and
for general machining operations
• Designated by letter S
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46-15
Toolholders for Indexable
Carbide Inserts
• Held in holder by cam action or clamps
• Types available
– Conventional
– Turret-type
– Heavy-duty toolposts
46-16
Cutting-Off (Parting) Tools
• Used when work must be grooved or
parted off
• Long, thin cutting-off blade locked
securely in toolholder by either cam lock
or locking nut
• Three types of parting toolholders
– Left-hand
– Right-hand
– Straight
49-17
Alignment of Lathe Centers
•
•
Parallel diameter produced when lathe
center aligned
Three common methods
used to align
1. Aligning centerlines
on back of tailstock
with each other
–
Only a visual check
and not too accurate
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49-18
Alignment of Lathe Centers
2. Using the trial-cut
method where small
cut taken from each
end of work and
diameters measured with a micrometer
3. Using parallel test bar and dial indicator
•
Fastest and most accurate method
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50-19
Grinding Lathe Cutting Tool
• Wide variety of cutting tools for lathe
– All have certain angles and clearances regardless
of shape
Shape and Dimensions of General-purpose Lathe Toolbit
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50-20
To Grind a
General-Purpose Toolbit
1. Dress face of grinding wheel
2. Grip toolbit firmly, supporting hands on grinder
toolrest
3. Hold toolbit at proper
angel to grind cutting
edge angle
•
Tilt bottom of toolbit
toward wheel and
grind 10º side relief
or clearance angle
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50-21
Cutting edge ~ ½ In long and extend
over ¼ width of toolbit
10º side relief or
clearance angle
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50-22
4. While grinding, move toolbit back and
forth across face of wheel
•
Prevents grooving wheel
5. Toolbit must be cooled frequently during
grinding
•
•
•
Never overheat toolbit!
Never quench stellite or cemented-carbide
tools
Never grind carbides with aluminum oxide
wheel
50-23
6. Grind end cutting edge so it forms angle of
a little less than 90º with side cutting edge
–
Hold tool so that end cutting edge angle and
end relief angle of 15º ground at same time
70º to 80º Point Angle
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50-24
7. Using toolbit grinding gage, check amount
of end relief when toolbit is in toolholder
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50-25
8. Hold top of toolbit approximately 45º to
axis of wheel and grind side rake to
approximately 14º
–
Do not grind below top of toolbit
•
Creates a chip trap
Side rake ground the length
of the cutting edge
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50-26
9. Grind slight radius on point of cutting
tool, being sure to maintain same front and
side clearance angle
10. With oilstone, hone cutting edge of toolbit
slightly
•
•
Lengthen life of toolbit
Enable it to produce better surface finish on
workpiece
52-27
Setting Up a Cutting Tool
1. Move toolpost to the left-hand side of the T-slot
in the
compound
rest
2. Mount toolholder in
toolpost so
setscrew in
toolholder 1 in.
beyond toolpost
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Permission required for reproduction or display.
52-28
Heavy Cuts: Set toolholder at right
angles to work
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Permission required for reproduction or display.
52-29
Setting Up a Cutting Tool: cont.
3. Insert proper cutting tool into toolholder,
having tool extend .500 in. beyond
toolholder and never more than twice its
thickness
4. Set cutting-tool point to center height
•
Check it against lathe center point
5. Tighten toolpost securely to prevent it
from moving during a cut
52-30
Purposes of a Trial Cut
•
Produce accurate turned diameter
–
Measured with micrometer
•
Set cutting-tool point to the diameter
•
Set crossfeed micrometer collar to the
diameter
52-31
Rough Turning
• Removes as much metal as possible in
shortest length of time
• Accuracy and surface finish are not
important in this operation
– .020- to .030-in. feed recommended
• Work rough-turned to
– Within .030 in. of finished size when
removing up to .500 in. diameter
– Within .060 in. when removing > .500 in.
52-32
Finish Turning
• Follows rough turning
• Produces smooth surface finish and cuts
work to an accurate size
• Factors affecting type of surface finish
– Condition of cutting tool
– Rigidity of machine and work
– Lathe speeds and feeds
52-33
Filing in a Lathe
• Only to remove small amount of stock,
remove burrs, or round off sharp corners
• Work should be turned to within .002 to .003
in. of size
• For safety, file with left hand so arms and
hands kept clear of revolving chuck
• Remove toolbit from toolholder before filing
• Cover lathe bed with paper before filing
52-34
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Permission required for reproduction or display.
52-35
Shoulder
• Shoulder: the change in diameters, or step,
when turning more than one diameter on a
piece of work
• Three common types of shoulders
– Square
– Filleted
– Angular or Tapered
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Permission required for reproduction or display.
52-36
Three Types of Shoulders
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Permission required for reproduction or display.
53-37
Knurling
• Process if impressing a diamond-shaped or
straight-line patter into the surface of the
workpiece
– Improve its appearance
– Provide better gripping surface
– Increase workpiece diameter when press fit
required
53-38
Knurling
• Diamond- and
straight-pattern
rolls available in
three styles
– Fine
– Medium
– Course
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53-39
Knurling Tool
• Toolpost-type toolholder on which pair of
hardened-steel rolls mounted
Knurling tool with
one set of rolls in
self-centering head
Knurling tool with
three sets of rolls
in revolving head
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53-40
Grooving
• Done at end of thread to
permit full travel of nut up
to a shoulder or at edge of
Square
shoulder for proper fit
• Also called recessing,
undercutting, or necking
• Rounded grooves used
Round
where there is strain on
part
V-shaped
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