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Lathe Accessories

Session 7

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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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Lathe Centers

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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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Revolving Tailstock Centers

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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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Microset Adjustable 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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Self-Driving Live Center

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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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Three-jaw Universal Chuck

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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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Four-Jaw Independent Chucks

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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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Threaded Spindle Nose

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Tapered Spindle Nose

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Cam Lock 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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Spring Collet Chucks

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Spring Collet Chucks

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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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Jacobs 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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Magnetic Chucks

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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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Faceplates

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Faceplates

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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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Steadyrest

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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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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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Plain Mandrel

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Expanding Mandrel

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Gang Mandrel

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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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Standard bent-tail lathe dog• Bent tail engages in slot on

drive plate

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Straight-tail lathe dog

• Driven by stud in driveplate• Used in precision turning

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Safety clamp lathe dog

• Used to hold variety of work

• Wide range of adjustment

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Heavy Duty Lathe Dog

• Wider range than others

• Used on all shapes

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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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Conventional ToolPosts

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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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Super Quick-Change Toolpost

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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

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Vertical Index Turret (VIT)• Designed to give highest accuracy,

fastest tool change and greatest rigidity of any tool system available for engine lathes

• Same concept as indexing turrets on CNC lathes

• Can hold up to six or eight tools• Closest to performance of CNC lathes