1. UNIT-II TURNING MACHINES
Work Holding Devices And Thread Cutting Methods
PREPARED BY
SOUNDHAR.A

2. Work Holding Devices Chuck Centers Face Plates Angle plate Mandrel
Steady & follower rest

3. Work Holding Devices

4. Chuck Attached to head stock spindle
Hold small length work pieces & irregular shape work pieces
Work pieces are held in jaws of the chuck
Types
Three jaw chuck or self centering
Four jaw chuck or independent chuck
Magnetic chuck

5. Chuck - Types
Three jaw chuck or self centering (hold regular shaped work piece)
Has 3 jaws – move in equal distance – radial direction – chuck key
9 circular discs
Front – Spiral scroll
Back – bevel teeth – 3 bevel pinions fitted
Chuck key turned – bevel pinion & disc rotate
Four jaw chuck or Independent chuck (hold regular or irregular shaped work piece)
Has 4 jaws – each moved individually
Each jaw fitted to screw with the help of slots at backside
The screws have square hole at the top to receive chuck key & can be rotated
When chuck key turned in the slot, the particular jaw will only move
So, irregular shape work piece & large work piece can be held
Magnetic chuck
Has a flat surface
Chuck has magnetic power – electromagnet
Work piece held on chuck by magnetic power
Only magnetic material can be held on the chuck

6. Three jaw chuck or self centering
Has 3 jaws – move in equal distance – radial direction – chuck key
9 circular discs
Front – Spiral scroll
Back – bevel teeth – 3 bevel pinions fitted
Chuck key turned – bevel pinion & disc rotate
Used to hold regular shaped work piece – round & hexagonal

7. Three jaw chuck
back

8. Four jaw chuck or Independent chuck
Hold regular / irregular shaped work piece
Has 4 jaws – each moved individually
Each jaw fitted to screw - slots at backside
Screws - square hole at the top to receive chuck key & can be rotated
When chuck key turned in the slot, the particular jaw will only move
So, irregular shape work piece & large work piece can be held

9. Four jaw chuck
back

10. Magnetic Chuck Has a flat surface
Chuck has magnetic power – electromagnet
Work piece held on chuck by magnetic power
Only magnetic material can be held on the chuck

11. Centers Hold & centering the work pieces Conical end - machined to 60º
Shank – made by taper turning
Live center - Center in head stock
Dead center - Center in tail stock

12. Dog Carrier or Catch Plate
Hold job & work piece in b/w the centers
Catch plate – circular disc – screwed on spindle
Tail part  catch plate
When spindle rotates, work pieces also rotate thru catch plate & carrier arrangement

13. Dog Carrier or Catch Plate

14. Face Plate Hold irregular shaped work pieces
Screwed – spindle – when spindle rotates, face plate too rotates
It’s a circular disc – has 4 T-slots & a number of plain radial slots
Slots –hold work pieces

15. Face Plates

16. Angle Plate
Made of cast iron- has 2 machined right angle to each other
Has holes & slots
One face - work piece
Other face - face plate
When spindle rotates, face plate with angle plate & work piece will also rotate
Angle plate used for holding elbow pieces

17. Mandrel Hold hollow work pieces
Mandrel inserted into the hollow work pieces – held b/w live center & dead center
Different types of mandrels are used for diff types of jobs

18. Plain Mandrel

19. Mandrel

20. Mandrel

21. Steady Rest Has a cast iron base – rest on guide ways of lathe bed
Top – one end for removing job without disturbing steady rest
Work piece – held b/w 3 jaws – move radially & separately
Turning operation - 2 stages - carriage will not pass
So, work piece turned to 1st half , then reversing it to second half

22. Follower Rest Has a C type casting
2 adjustable jaws – support work piece
Follower rest mounted on saddle – move together with tool
Used to give continuous support to work piece

23. Lathe Operations Centering Straight Turning Grooving Parting Off
Rough Turning
Finish Turning
Shoulder Turning
Facing
Chamfering
Knurling
Forming
Grooving
Parting Off
Eccentric Turning
Drilling
Reaming
Boring
Milling
Grinding

24. Lathe Operations

25. Centering
Producing conical shape holes – ends of work piece (Longer work pieces)
Centers marked at the ends - centre punch
Work piece - chuck & rotated
Drill bit - tail stock – fed into the work piece by turning the hand wheel

26. Straight Turning
Producing cylindrical surface by removing the material from outside diameter of the work piece
Work piece held b/w live & dead centers
Right hand turning tool clamped on tool post
Work piece rotated
Tool fed parallel to lathe axis also depth of cut given to tool
Two types of turning
Rough Turning
Finish Turning

27. Straight Turning - Types
Rough Turning
Feed rate – fast (0.3 mm – 1.5 mm per revolution)
Depth of cut – heavy (2 mm – 5 mm)
Finish Turning
Feed rate – slow (0.1 mm – 0.3 mm per revolution)
Depth of cut – small (0.5 mm – 1 mm)

28. Shoulder Turning Operation - shoulder of stepped diameter work piece
Right hand facing tool – square shoulder
Round nose tool – radius shoulder
Types of shoulders
Square
Bevelled
Filleted
Grooved

29. Facing Making flat surface at the end of work piece
Work piece held in chuck or b/w centers
Work piece rotated
Facing tool fed perpendicular to lathe axis

30. Chamfering
Making bevelled surface or to turn a slope at the end of the work piece
It is done after knurling, rough turning & thread cutting
Remove burrs & sharp edges
Work piece rotated – tool fed perpendicular to the lathe axis

31. Knurling
Produce impression (any shape) on the outer surface of work piece
Give good gripping surface
Knurling tool - two hardened steel rollers with cutting teeth
Tool held in tool post & pressed against the rotating work piece – moved parallel to lathe axis
Speed & feed should be very low

32. Forming
Making concave, convex or any other irregular shape on the work piece
Cutting tool should be made to the required form
Work piece held b/w centers & form tool moved perpendicular to the revolving work piece

33. Grooving
Reducing the diameter of work piece over a very narrow surface
Also called recessing, undercutting or necking
Work piece held in chuck
Grooving tool fed against revolving work piece

34. Parting Off
Process of cutting of work piece after the completion of all machining operations
Parting tool is used
Work piece held in chuck & rotated
Carriage locked at the required position
Spindle speed reduced
Tool fed slowly perpendicular to lathe axis

35. Eccentric Turning Making of eccentric Set up Operation
Center of one cylinder is out of the center of other cylinder – crank shaft, cam shaft, eccentric on a shaft
Two set of center holes (offset from the normal axis of the work piece) are drilled – end of work piece
Amount of offset = half of eccentricity required
Operation
Work piece - one axis of rotation – in b/w centers
One cylindrical surface turned
Work piece removed & held in other axis of rotation for turning the other cylindrical surface

36. Drilling Producing cylindrical hole in a work piece
Methods used for making a drill
First method
Work piece - chuck or face plate
Drill bit - tail stock spindle
Tail stock clamped near work piece
Work piece rotated & drill bit fed into the work piece – turning tail stock hand wheel
Second method
Drill held in chuck
Work piece - pad supported by tail stock spindle
Work piece fed by tail stock hand wheel while the drill bit is revolving

37. Drilling

38. Reaming
Operation of finishing & sizing of already drilled hole – dimensionally more accurate
Tool – Reamer – has multiple cutting edges
Work piece - chuck & revolves slowly
Reamer – tail stock – fed into the work piece for reaming

39. Reaming & Remears

40. Boring Enlargement of hole
Done when correct size drill bit not available
Work piece - chuck/face plate - rotated
Boring tool - tool post - fed parallel to lathe axis
Boring tool - smaller holes
Boring bar - larger holes

41. Milling Removing metal – rotating cutter (multiple cutting edges)
Work piece - vice
Vice - compound rest
Milling cutter rotated
Work piece fed by moving carriage

42. Slab Milling & Face Milling

43. End Milling

44. Grinding Removing metal – grinding wheel External grinding
Work piece revolved b/w centers
Grinding wheel – compound rest – tool post – fed against the work piece
Internal grinding
Work piece – chuck or face plate
Grinding wheel – tool post – compound rest
Feed - carriage
Depth of cut given by cross slide

45. Thread Cutting
Setup
Producing helical groove on a cylindrical work piece
Feed – lock nut, lead screw
Longitudinal feed = pitch of the thread
Pitch – ratio b/w spindle & longitudinal feed
Lead screw & spindle – connected by change gears

46. Thread Cutting Operation Carriage  lead screw by engaging half nut
When spindle rotates, lead screw will be rotated at the same speed
Pitch of work = pitch of lead screw

47. Thread Cutting Driver Headstock Spindle Work Tailstock Spindle
Threading tool
Changing gears
Carriage
Driven
Lead screw
Movement of carriage tool

48. Gear Trains
Driver

49. Gear Trains Second stud First stud Driver A B Intermediate gears C
Driven
Lead screw

50. Lathe Attachment Milling attachment Copying attachment
Grinding attachment
Taper turning attachment

51. Grinding Attachment Attached to cross slide
Work piece & grinding wheel rotate
External grinding
Work piece – b/w centers - & rotated
Internal grinding
Work piece – chuck & rotated
Feed – moving carriage
Depth – moving cross slide

52. Grinding Attachment
Work
Belt drive
Head
stock
Chuck
Grinder spindle

53. Milling Attachment 1st method 2nd method
Milling cutter – chuck – rotated
Work piece – cross slide
Work fed against rotating milling cutter
Depth – vertical adjustment of work piece
Used to cut key ways & grooves
2nd method
Milling mounted on carriage
Work piece – held b/w centers – not rotated
Cutter driven by motor vertically
Feed given by carriage

54. Milling Attachment Vertical slide Clamping screw Packing piece
Swivel base
Cross slide
Chuck
End mill
Work
Carriage
Bed