1. Machining in a Chuck
Session 10

2. Lathe Chuck Most versatile and commonly used spindle accessory
Jaws adjustable
Three-jaw: jaws move simultaneously
Four-jaw: jaws move independently
Can handle all operations that can be performed on work between centers

3. Lathe Chucks
Must be careful when mounting and removing to prevent damage to spindle and/or chuck
Three types of spindle noses found on engine lathes
Threaded spindle nose
Tapered spindle nose
Cam-lock spindle nose

4. Procedure To Mount a Chuck
Set lathe to slowest speed
SHUT OFF ELECTRICAL SWITCH
Remove drive plate and live center
Clean all surfaces of spindle nose and mating parts of chuck
Place cradle block on lathe bed in front of spindle and place chuck on cradle
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5. Slide cradle close to lathe spindle nose and mount chuck
Threaded Spindle Nose Chucks
Revolve lathe spindle by hand in a counterclockwise direction and bring chuck up to spindle (NEVER START MACHINE)
If chuck and spindle correctly aligned, chuck should easily thread onto lathe spindle
When chuck adapter plate within .060 in. of spindle shoulder, give chuck quick turn to seat it against spindle shoulder
Do not jam chuck against shoulder too tightly

6. Taper Spindle Nose Chucks
Revolve lathe spindle by hand until key on spindle nose aligns with keyway in tapered hole of chuck
Slide chuck onto lathe spindle
Turn lock ring counter-clockwise until hand-tight
Tighten lock ring with spanner wrench striking it sharply downward

7. Cam-Lock Spindle Nose Chucks
Align registration line of each cam lock with registration line on lathe spindle nose
Revolve lathe spindle by hand until holes in spindle align with cam-lock studs of chuck
Slide chuck onto spindle
Tighten each cam lock in a clockwise direction
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8. Procedure To Remove a Chuck
Set lathe in slowest speed
STOP MOTOR
Place cradle block under chuck
Remove chuck by following methods dependent on type of spindle nose

9. Threaded Spindle Nose Chucks
Turn chuck until wrench hole is in top position
Insert chuck wrench into hole and pull sharply toward front of lathe OR
Place block or short stick under chuck jaw
Revolve lathe spindle by hand in clockwise direction until chuck loosened on spindle
Remove chuck from spindle and store it where it will not be damaged

10. Taper Spindle Nose Chucks
Secure proper C-spanner wrench
Place it around lock ring of spindle with handle in upright position
Place one hand on curve of spanner wrench to prevent it from slipping off lock ring
With palm of other hand, sharply strike handle of wrench in clockwise direction
Hold chuck with one hand, and with other hand, remove lock ring from chuck
Remove chuck from spindle and store it with jaws in up position

11. Cam-Lock Spindle Nose Chucks
With chuck wrench, turn each cam lock in counterclockwise direction until its registration line coincides with registration line on lathe spindle nose
Place one hand on chuck face and with palm of other hand, sharply strike top of chuck
Action necessary to break taper contact between chuck and lathe spindle
Slide chuck clear of spindle and place it carefully in storage compartment

12. Procedure to Mount Work in Three-Jaw Chuck
Clean chuck jaws and surfaces of workpiece
Use proper size chuck wrench and open chuck jaws slightly more than diameter of work
Place work in chuck, leaving no more than three times diameter extending beyond chuck jaws
Tighten chuck jaws with wrench in left hand while slowly rotating workpiece with right hand
Tighten chuck jaws securely using chuck wrench

13. Three-Jaw Universal Chuck
Supplied with two sets of chuck jaws
Set for outside gripping
Set for inside gripping
Jaws marked with same serial number and should never be used with another chuck
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14. Procedure To Change Chuck Jaws
Thoroughly clean jaws and jaw slides
Turn chuck wrench clockwise until start of scroll thread almost showing at back edge of slide 1
Insert jaw 1 (in slot 1) and press down with one hand while turning chuck wrench clockwise with the other

15. After scroll thread has engaged in jaw, continue turning chuck wrench clockwise until start of scroll is near back edge of groove 2
Insert second jaw and repeat steps 3 and 4
Insert third jaw in same manner
Some chucks equipped with one set of top jaws fastened on by allen screws

16. Four-Jaw Chuck Used when work must run absolutely true
Each jaw can be adjusted independently
Jaws reversible
Can hold round, square, or irregularly shaped workpieces securely
Work can be adjusted to be either concentric or off center

17. Procedure To Mount Work in Four-Jaw Chuck
Measure diameter of work to be chucked
With chuck wrench, adjust jaws to approximate size according to ring marks on face of chuck
Set work in chuck and tighten jaws snugly against work surface
True workpiece by either chalk method or surface gage method

18. Chalk Method
Start lathe and with piece of chalk, lightly mark high spot on diameter
Stop lathe and check the chalk mark
If even, lightly marked line around work, work is true
If one mark, loosen jaw opposite chalk mark and tighten jaw next to chalk mark
Continue until chalk marks lightly around work or leaves two marks opposite each other

19. Surface Gage Method
Place surface gage on lathe bed and adjust point of scriber so it is close to work
Revolve lathe by hand to find low spot on work
Loosen jaw nearest low spot and tighten jaw opposite low spot to adjust work closer to center
Repeat steps 2 and 3 until work true

20. Procedure To True Work in a Four-Jaw Chuck Using Dial Indicator
Mount work and true it approximately, using either chalk or surface gage method
Mount indicator, with rang of at least in., in toolpost of lathe
Set indicator spindle in horizontal position with contact point set to center height
Bring indicator point against work diameter so it registers approximately in and rotate lathe by hand

21. Note highest and lowest reading on dial
Slightly loosen chuck jaw at lowest reading and tighten jaw at high reading until work is moved half the difference between the two indicator readings
Continue to adjust only these two opposite jaws until indicator registers same at both jaws
Adjust other set of opposite jaws in same manner until indicator registers same at any point on work circumference
Tighten all jaws evenly to secure work firmly
Rotate lathe spindle by hand and recheck reading

22. Procedure To Face Work Held in a Chuck
True up work in chuck using chalk or dial indicator method
Have at least amount equal to diameter of work projecting from chuck jaws
Swivel compound rest at 90º to cross-slide when facing series of shoulders OR
Swivel compound rest 30º to right if only one surface on work must be faced

23. Lock carriage in position
Set up facing toolbit to height of dead center and pointing slightly to the left
Lock carriage in position
Set depth of cut by using graduated collar on compound rest screw
Twice amount to be removed if compound rest set at 30º
Same as amount to be removed if compound rest set at 90º to cross-slide
Face work to length

24. Rough- and Finish- Turn Work in a Chuck
Operations are same as turning between centers
Should be machined to size in two cuts
Usually short workpieces
If long workpiece, support must be provided
Use revolving tailstock center
Steady rest

25. Rough and Finish Turning
Mount work securely in chuck, with no more than three times diameter extending beyond chuck jaws
Move toolpost to left of compound rest and grip toolholder short
Fasten general-purpose toolbit in toolholder and set point to center
Tighten toolpost screw securely

26. Set lathe to correct speed and feed
Take light trial cut an end of work and measure diameter
Adjust crossfeed graduated collar to one-half amount of metal to be removed
Rough-turn diameter to correct length
Set lathe speed and feed for finish turning
Take light trial cut at end of workpiece
Set graduated collar in one-half amount of metal to be removed
Take another trial cut, if correct, finish-turn work

27. PCBN Tools
Cost-effective for machining materials from 45 Rc and higher
Remove material at high rates
Long tool life even under interrupted cuts
Characteristics include superior hardness, wear resistance, compressive strength and thermal conductivity

28. Guidelines for PCBN Turning
Machines should have good bearings, tight slides and enough power
Proper cutting tool selected to suit type of material being cut and machining operation
Follow manufacturer's recommendation for proper speed, feed, and depth of cut
Set cutting tools on center, short overhang
Use cutting fluid wherever possible

29. Interactive Superabrasive Machining Advisor Software
Used to select PCBN tool and machining conditions
To use, operator must know the following:
Material hardness, machine horsepower
Maximum spindle speed and carriage feed
Depth of cut and surface finish
Program recommends tool grade, tool edge preparation, tool geometry, speed, feed and type of coolant

30. Part Specifications Workpiece material Machine Tool
1 in. diameter, hardened tool steel Rc
Machine
Conventional lathe with 5 HP drive to spindle
Tool
BZN* 8100 tipped insert, CNMA 433
Machining conditions
.010 in depth of cut
.004 in. feed rate
400 sf/min cutting speed

31. Procedure For Turning the Part
Set machine spindle to correct speed
Set lathe for recommended feed per revolution
Lock PCBN insert in proper toolholder
Fasten toolholder in toolpost and adjust tool to centerline height
Use .010 in. plastic shim and set tool tip to outside diameter of part

32. Turn carriage handwheel clockwise so tool clears end of part
Turn crossfeed handle clockwise thickness of shim plus desired depth of cut
Engage automatic feed to machine diameter toward lathe headstock
At end of cut, turn crossfeed handle counterclockwise to withdraw tool from diameter
Return to starting position of cut, reset tool for depth and continue passes until part to size

33. Procedure For Cutting Off Work in a Chuck
Mount work in chuck with part to be cut off as close to jaws as possible
Mount cutoff tool on left-hand side of compound rest, with cutting edge set on center
Place holder as close to toolpost as possible

34. Extend cutting blade beyond holder half diameter of work to be cut, plus .125 in. for clearance
Set lathe to approximately ½ turning speed
Move cutting tool into position
Start lathe and feed cutoff tool into work by hand
When grooving or cutting off deeper than .250 in, good practice to move parting tool sideways slightly
Before cut completed, remove burrs from side of groove with file