Lathe Accessories
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Transcript of Lathe Accessories
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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
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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 shank60º centers, steel with carbide tips
• Care to adjust and lubricate occasionally
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Revolving Tailstock Centers• Replaced solid dead centers for most
machining operations• Used to support work held in chuck or
when work is being machined between centers
• Contains antifriction bearings which allow center to revolve with workpiece
• No lubrication required between center and work
• Types: revolving dead center, long point center, and changeable point center
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Microset Adjustable Center• Fits into tailstock spindle
• Provides means of aligning lathe centers or producing slight tapers on work machined between centers
• Eccentric slide (dovetail) allows center to be adjusted limited amount to each side of center
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Self-Driving Live Center
• Mounted in headstock spindle• Used when entire length of workpiece is being
machined in one operation• Chuck or lathe dog could not be used to drive work
• Grooves ground around circumference of lathe center point provide drive
• Work usually soft material such as aluminum
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Chucks
• Used extensively for holding work for lathe machining operations
• Work large or unusual shape
• Most commonly used lathe chucks• Three-jaw universal• Four-jaw independent• Collet chuck
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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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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
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Headstock Spindle Types1. Threaded spindle nose
• Screws on in a clockwise direction
2. Tapered spindle nose• Held by lock nut that tightens on chuck
3. Cam-lock spindle nose• Held by tightening cam-locks using T-
wrench• Chuck aligned by taper on spindle nose
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Collet Chucks
• 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
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Spring Collet Chucks
• Spring-collet chuck• One form: Handwheel draws collet into
tapered adapter• Another form: Uses chuck wrench to
tighten collet on workpiece• Can hold larger work than draw-in type
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Jacobs Collet Chuck
• Jacobs collet chuck• Utilizes impact-tightening handwheel to
close collets• Wider range than spring-collet chuck
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Magnetic Chucks
• Used to hold iron or steel parts that are too thin or may be damaged if held in conventional chuck
• Fitted to an adapter mounted on headstock spindle
• Used only for light cuts and for special grinding applications
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Faceplates
• Used to hold work too large or shaped so it cannot be held in chuck or between centers
• Usually equipped with several slots to permit use of bolts to secure work
• Angle plate used so axis of workpiece may be aligned with lathe centers
• Counterbalance fastened to faceplate when work mounted off center
• Prevent imbalance and resultant vibrations
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Steadyrest• Used to support long work held in chuck
or between lathe centers• Prevent springing
• Located on and aligned by ways of the lathe
• Positioned at any point along lathe bed
• Three jaws tipped with plastic, bronze or rollers may be adjusted to support any work diameter with steadyrest capacity
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Follower Rest
• Mounted on saddle
• Travels with carriage to prevent work from springing up and away from cutting tool
• Cutting tool generally positioned just ahead of follower rest
• Provide smooth bearing surface for two jaws of follower rest
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Mandrel
• Holds internally machined workpiece between centers so further machining operations are concentric with bore
• Several types, but most common• Plain mandrel• Expanding mandrel• Gang mandrel• Stub mandrel
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Lathe Dogs
• Drives work machined between centers
• Has opening to receive work and setscrew to fasten the dog to work
• Tail of dog fits into slot on driveplate and provides drive to workpiece
• Made in variety of sizes and types to suit various workpieces
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Standard bent-tail lathe dog• Most commonly used for
round workpieces• Available with square-head
setscrews of headless setscrews
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Cutting-Tool-Holding Devices• Available in three styles
• Left-hand offset• Right-hand offset• Straight
• Each has square hole to accommodate square toolbit held in place by setscrew
• Angle of approximately 15º to 30º to base of toolholder
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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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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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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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Carbide Toolholder
• Has square hole parallel to base of toolholder to accommodate carbide-tipped toolbits
• Holds toolbit with little or no back rake
• Designated by letter C
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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
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Threading Toolholder
• Designed to hold special form-relieved thread-cutting tool
• Has accurately ground 60º angle• Maintained throughout life of tool• Only top of cutting surface sharpened
when becomes dull
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Styles of Boring Toolholders• Held in standard toolpost
• Light boring toolholder• Used for small holes and light cuts
• Medium boring toolholder• Suitable for heavier cuts• May be held at 45º or 90º to axis of bar
• Mounted on compound rest of lathe• Heavy-duty boring bar holder
• Three bars of different diameters• May be held at 45º or 90º to axis of bar
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Compound Rest Tooling Systems• Standard, or round, toolpost
• Generally supplied with conventional engine lathe
• Fits into T-slot of compound rest• Provides means of holding and adjusting
type of toolholder or cutting tool required• Concave ring and the wedge or rocker
provide for adjustment of cutting-tool height
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Modular (Quick-Change) Tooling• Initially developed for CNC machine
tools to improve accuracy, reduce tool-change time and increase productivity
• Benefits realized on conventional lathes with systems designed for these machines
• Modular tooling system must be rigid, accurate and have quick-change capabilities
• Basic clamping unit or turret can hold variety of cutting tool modules
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Modular (Quick-Change) Tooling• Initially developed for CNC machine
tools to improve accuracy, reduce tool-change time and increase productivity
• Benefits realized on conventional lathes with systems designed for these machines
• Modular tooling system must be rigid, accurate and have quick-change capabilities
• Basic clamping unit or turret can hold variety of cutting tool modules
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Modular Tooling System• Principal function is to reduce cost of
keeping large tool inventory• Tools can be specifically mounted to suit
characteristics of workpiece• More common systems available
• The Super Quick-Change Toolpost• The Quadra* Index Toolpost• The Super-Six Index Turret• The Vertical Index Turret
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Super Quick-Change Toolpost• Provides fast, accurate, and reliable
method of quickly changing and setting various toolholders for different operations
• Locking system has two sliding gibs forced out against toolholder
• Handle pulled into lock position• Provides rigid, positive lock with zero
backlash
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Quadr* Index Toolpost
• Allows four tools to be mounted on turret at same time
• Each tool locked independently• Provides flexibility to use from one to four
tools simultaneously
• Unique indexing system of turret allows it to be set in 24 positions (every 15º)
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Super-Six Index Turret
• Designed to simplify and increase machining productivity on engine lathes when multi-operation jobs require use of more than one tool
• Up to six tools for external and internal machining operations
• Allows height adjustment for each tool
• Tool changes can be made in less than 1 sec