knurling grooving and form turning

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PowerPoint to accompany

Krar • Gill • Smid

Technology of Machine Tools6th Edition

Knurling, Grooving,

and Form Turning Unit 53

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Objectives

• Set up and use knurling tools to produce diamond-shaped or straight patterns on diameters

• Cut square, round, and V-shaped grooves on work between centers or in a chuck

• Machine convex or concave forms on diameters freehand

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Knurling, Grooving, and Form Turning

• Alter either the shape or finish of a round workpiece

• Normally performed on work mounted in chuck– Can also be done on work mounted between

lathe centers

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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

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Knurling

• Diamond- and straight-pattern rolls available in three styles– Fine

– Medium

– Course


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Knurling Tool

• Toolpost-type toolholder on which pair of hardened-steel rolls mounted

Knurling tool withone set of rolls inself-centering head

Knurling tool with three sets of rollsin revolving head


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Universal Knurling Tool System

• Dovetailed shank and as many as seven interchangeable knurling heads that can produce wide range of knurling patterns

• Combines in one tool– Versatility– Rigidity– Ease of handling– Simplicity

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Small Diameter DiamondCutting Knurling Tool

Single Wheel Knurling HeadShoulder Knurling Head

Standard Diamond Knurling HeadStraddle Forming Knurling Head

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Procedure to Knurl in a Lathe

1. Mount work between centers and mark required length to be knurled

• If work held in chuck for knurling, right end of work should be supported with revolving tailstock center

2. Set lathe to run at one-quarter speed required for turning

3. Set carriage feed to .015 to .030 in.

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4. Set center of floating head of knurling tool even with dead-center point


5. Set knurling tool at right angles to workpiece and tighten it securely

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6. Start machine and lightly touch rolls against work to check tracking

7. Move knurling tool to end of work so only half the roll face bears against work

8. Force knurling tool into work approximately .025 in. and start lathe

OR

Start lathe and then force knurling tool into work until diamond pattern come to point

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9. Stop lathe and examine pattern10. Once pattern correct, engage automatic

carriage feed and apply cutting fluid to knurling rolls

11. Knurl to proper length and depth• Do not disengage feed until full length has

been knurled; otherwise, rings will be formed on knurled pattern

12. If knurling pattern not to point after length has been knurled, reverse lathe feed and take another pass across work

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Grooving


Square

Round

V-shaped

• 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

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Procedure to Cut a Groove

1. Grind toolbit to desired size and shape of groove required

2. Lay out location of groove

3. Set lathe to half the speed for turning

4. Mount workpiece in lathe

5. Set toolbit to center height

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6. Locate toolbit on work at position where groove is to be cut

7. Start lathe and feed cutting tool toward work using crossfeed handle until toolbit marks work lightly

8. Hold crossfeed handle in position and set graduated collar to zero

9. Calculate how far crossfeed screw must be turned to cut groove to proper depth

10. Feed toolbit into work slowly using crossfeed handle

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11. Apply cutting fluid to point of cutting tool• To ensure cutting tool will not bind in

groove, move carriage slightly to left and to right while grooving

• Should chatter develop, reduce spindle speed

12. Stop lathe and check depth of groove with outside calipers or knife-edge verniers

Safety note: Always wear safety goggles when grooving on a lathe

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Form Turning

• Need irregular shapes or contours from workpiece

• Done on lathe by four methods:– Freehand– Form-turning tool– Spherical tool– Hydraulic tracer attachment

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Turning a Freehand Form or Radius

• Presents greatest problem to beginning lathe operator

• Coordination of both hands is required and practice important in master skill

• Let's use an example to walk through the steps:– Turn a .500 in. radius on the end of a

workpiece

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Example: Turn a .500 Radius

1. Mount workpiece in chuck and face end

2. With work revolving, mark a line .500 in. from end using a pencil


3. Mount a round-noseturning tool on center

4. Start lathe and adjust toolbit until it touches diameter about .250 in. from end

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5. Place one hand on crossfeed handle and other on carriage handwheel

6. turn carriage handwheel (not the handle) to feed toolbit slowly toward end of work; at same time, turn crossfeed handle to move tool into work

7. Back toolbit out and move carriage to left

8. Take successive cuts as in step 6 until toolbit starts to cut close to the .500 in. line

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9. Test radius with a .500 in. gage

10. If radius not correct, it may have to be recut

• Often possible to finish radius to required shape by filing


Note: Follow same procedure as in step 6when cutting internal radii – always start atlarge diameter

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Form-Turning Tools

• Used to form smaller radii and contours

• Lathe toolbit ground to desired radius and used to form contour– Also concave radius


• Eliminates need forchecking with gage

• Leave collar of desired sizeon workpiece when producing convex radius

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Form-Turning Tools

• Produce good finish work should be revolved slowly

• Cutting oil applied as tool fed into work

• Eliminate chatter during cutting– Move cutting tool slightly back and forth

(longitudinally)

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Procedure for Form Turning Using a Template and Follower

1. Make accurate template to form desired2. Mount template on bracket fastened to

back of lathe3. Position template lengthwise in relation to

workpiece4. Mount a round-nose cutting tool in toolpost5. Fasten follower, face must have same form

as point of cutting tool, on cross-slide of lathe

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6. Rough-out form on workpiece freehand by keeping follower close to template

• Final roughing cut .030 in. of template

7. Disconnect cross-slide from crossfeed screw

8. Apply light hand pressure on cross-slide to keep follower in contact with template

9. Engage automatic carriage feed and take finish cut from workpiece, while keeping follower in contact with template

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Spherical Tool

• Can make a perfect spherical ball or spherical cavity to within .0001-in accuracy

• Consists of dovetailed turret that holds cutting tool and drive mechanism that can be hand fed or power driven

• Dial microscrew indicates depth of cut and diameter

• Concave forms can be cut when internal toolholder installed

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Hydraulic Tracer Attachment

• Used when many duplicate parts having several radii or contours to produce required

• Incorporates means of moving cross-slide by controlled oil pressure supplied by hydraulic pump– Flat template mounted on lathe– Stylus bears against template surface and

actuates control value regulating flow of oil into cylinder which moves piston and causes toolbit to move in or out

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Advantages of a Tracer Attachment

• Intricate forms can be readily produced

• Various forms, tapers, and shoulders can be produced in one cut

• Duplicate parts can be produced rapidly and accurately

• Accuracy and finish of part do not depend on skill of operator

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Hints on the Use of a Tracer Attachment

1. Toolbit point and stylus should have same form and radius

2. Radius on toolbit should be smaller than smallest radius on template

3. Stylus must be set to point on template giving smallest diameter of work

4. Centerline of template must be parallel to ways of the lathe

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5. Form of template must be smooth6. No angle larger than 30º, or equivalent

radius, should be incorporated in form of template

7. Duplicate parts produced between centers must be same length and have center holes drilled to same depth

8. Duplicate parts held in chuck should project same distance from chuck jaws

9. Included angle of tool point should be less than smallest angle on template

knurling grooving and form turning

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