Lathe Accessories. Work-holding, -supporting, and driving devices

Transcription

1 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

2 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

3 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

4 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

5 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

6 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

7 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

8 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

9 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.

10 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

11 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

12 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

13 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

14 46-14 Straight Toolholder General-purpose type Used for taking cuts in either direction and for general machining operations Designated by letter S

15 46-15 Toolholders for Indexable Carbide Inserts Held in holder by cam action or clamps Types available Conventional Turret-type Heavy-duty toolposts

16 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

17 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

18 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

19 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

20 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

21 50-21 Cutting edge ~ ½ In long and extend over ¼ width of toolbit 10º side relief or clearance angle

22 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

23 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

24 Using toolbit grinding gage, check amount of end relief when toolbit is in toolholder

25 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

26 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

27 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 Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

28 52-28 Heavy Cuts: Set toolholder at right angles to work Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

29 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

30 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

31 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.

32 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

33 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

34 Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display

35 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 Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

36 52-36 Three Types of Shoulders Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

37 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

38 53-38 Knurling Diamond- and straight-pattern rolls available in three styles Fine Medium Course

39 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

40 53-40 Grooving Done at end of thread to permit full travel of nut up to a shoulder or at edge of shoulder for proper fit Also called recessing, undercutting, or necking Rounded grooves used where there is strain on part Square V-shaped Round