Lathe machine

Lathe machine

1. Unit 2 – CENTRE LATHE

2. HISTORY OF LATHE STRAP LATHE: On these lathes the work-piece is held between two iron spikes supported by a crude wooden framework. The tool rest is formed by a long rod, which runs parallel to the axis. The motive power is transmitted by a strap which takes a couple of turns around the end of the work-piece; the strap is pulled backwards and forwards by the turner's assistant to provide a reciprocating motion. Usually, both the turner and his assistant had to sit on the ground to operate this device .

3. HISTORY OF LATHE….. BOW LATHE: The bow lathe is very similar to the strap lathe but the motive power is supplied by a bow. The string of the bow is wrapped around the work piece and a reciprocating motion is created by moving the bow backwards and forwards. Whereas the strap lathe requires two people to work it the bow lathe requires only one. The drawback is that less power is available and the turner has only one hand with which to control the tool. In some cases the turner used his foot to help to steady the tool. Because of these deficiencies only small work is done on the bow lathe .

4. HISTORY OF LATHE….. POLE LATHE: The basic construction is shown in the diagram. It can be seen that the upper end of the driving cord is attached to the tip of a flexible pole and the other end is fastened to a simple treadle arrangement below the bed of the lathe. It should be noted that function of the pole is to act as a return spring and to keep the string taught-nothing more . 

5. HISTORY OF LATHE….. GREAT WHEEL: There is some evidence from a detailed examination of bronze vessels that the Romans employed lathes using continuous motion. It has been suggested that the drive could have been provided by means of a pulley system utilising an independent "great wheel" as illustrated in Figure.

6. HISTORY OF LATHE….. TREADLE LATHE: The turning speed for a treadle lathe was increased by using a flywheel and belt to drive a small pulley on the headstock. Note that the flywheel and the pulley are provided with a number of stepped grooves so that a variety of speed ranges could be obtained by moving the belt. 

7. PRINCIPLE OF LATHE MACHINE T he lathe is a machine tool which holds the w/p b/w two rigid & strong supports called centres or in a chuck or in face plate which revolves. T he cutting tool is held and fed against the revolving work. C utting tool fed either parallel or at right angles to the axis of w/p or may also at an angle.

8. LATHE SPECIFICATION A -SWING B -DISTANCE B/W CENTERS C -LENGTH OF BED D -RADIUS(ONE HALF OF SWING

9. PRINCIPLE PARTS OF LATHE

10. PRINCIPLE PARTS OF LATHE 1-BED AND WAYS The bed of the lathe provides the foundation for the whole machine and holds the headstock, tailstock and carriage in alignment. The surfaces of the bed that are finely machined - and upon which the carriage and tailstock slide - are known as "ways". Some beds have a gap near the headstock to allow extra-large diameters to be turned. Sometimes the gap is formed by the machined ways stopping short of the headstock, sometimes by a piece of bed that can be unbolted, removed--and lost.

11. HEADSTOCK & SPINDLE The headstock comprises the rectangular metal casting at the left end of the lathe. It contains the spindle shaft and it supports bearings and high/low speed shift lever and gears. Spindle is the main rotating shaft on which the chuck is mounted it supported by precision thrust bearings.

12. TAILSTOCK The unit is arranged to slide along the bed and can be locked to it at any convenient point; the upper portion of the unit is fitted with what is variously called a "barrel", "spindle" "ram" or "shoot" that can be moved in and out of the main casting by hand, lever or screw feed and carries a "Dead Centre" that supports the other end of work held (by various means) in the headstock.

13. CARRIAGE Carriage is located between the headstock and tailstock on the lathe bed guide ways. It can be moved along the bed either towards or away from the headstock. It has several parts to support, move and control the cutting tool. The parts of the carriage are :saddle, apron, cross-slide, compound rest, compound slide, tool post.

14. SADDLE It is an “H” shaped casting. It connects the pair of bed guideways like a bridge. It fits over the bed and slides along the bed between headstock and tailstock. The saddle or the entire carriage can be moved by providing hand feed or automatic feed.

15. CROSS-SLIDE AND COMPOUND REST Cross-slide is situated on the saddle and slides on the dovetail guideways at right angles to the bed guideways . It carries compound rest, compound slide and tool post. Cross slide handwheel is rotated to move it at right angles to the lathe axis. It can also be power driven . The cross slide hand wheel is graduated on its rim to enable to give known amount of feed as accurate as 0.05mm . Compound rest is a part which connects cross slide and compound slide. It is mounted on the cross-slide by tongue and groove joint. It has a circular base on which angular graduations are marked. The compound rest can be swiveled to the required angle while turning tapers. A top slide known as compound slide is attached to the compound rest by dove tail joint. The tool post is situated on the compound slide.

16. CROSS-SLIDE AND COMPOUND REST

17. TOOL POST This is located on top of the compound slide. It is used to hold the tools rigidly. Tools are selected according to the type of operation and mounted on the tool post and adjusted to a convenient working position .

18. TYPES OF TOOL POST Single Screw Tool Post:

19. Open side Tool post

20. Four bolt Tool post

21. Four way Tool post

22. Head Stock Mechanisms Back geared headstock

23. Head Stock Mechanisms Back geared headstock

24. Head Stock Mechanisms All geared headstock

25. Head Stock Mechanisms All geared headstock

26. FEED MECHANISM Tumbler gear reversing mechanism

27. Tumbler gear reversing mechanism

28. Quick change gearbox

29. Apron Mechanism

30. WORK HOLDING DEVICES Chucks : Three jaw or self centering chuck:

31. Three jaw or self centering chuck :

32. Four jaw chuck:

33. Four jaw chuck:

34. Thin jobs can be held by means of magnetic chucks. Collet Chuck Magnetic Chuck Collet chuck is used to hold small workpieces Thin jobs can be held by means of magnetic chucks.

35. Lathe Centers Work to be turned between centers must have center hole drilled in each end Support during cutting Most common have solid morse taper shank 60 º centers, steel with carbide tips Care to adjust and lubricate occasionally

36. LATHE DOGS Lathe dogs are cast metal devices used to provide a firm connection between the headstock spindle and the w/p mounted between centres.

37. MANDRELS Mandrels is used to held the hollow/drilled w/p

38. RESTS Long w/p need extra support that tend to spring away from the tool bit. We use the rest for provide support.

39. FACE PLATES A lathe face plate is a flat round plate that threads to the headstock spindle to the lathe. The faceplate is used for irregularly shaped w/p that cannot successfully held by chucks.

40. Lathe Operations Turning: produce straight, conical, curved, or grooved work pieces Facing : to produce a flat surface at the end of the part or for making face grooves . Boring: to enlarge a hole or cylindrical cavity made by a previous process or to produce circular internal grooves . Drilling: to produce a hole by fixing a drill in the tailstock Threading: to produce external or internal threads   Knurling: to produce a regularly shaped roughness on cylindrical surfaces

41. Lathe Operations

42. THREAD CUTTING

43. TAPER TURNING METHODS Form tool method:

44. TAPER TURNING METHODS Tailstock set over method:

45. TAPER TURNING METHODS Compound rest method:

46. TAPER TURNING METHODS Taper turning attachment method:

47. TYPES OF LATHE Speed Lathe : It is the simplest type lathe. It is mainly used for metal spinning, polishing etc. Bench Lathe : It is small sized engine lathe mounted on bench. It is used for turning small and light weight workpiece . Tool Room Lathe : It is used for production of small tools, gauges, fixtures and accurate parts in tool room.

48. TYPES OF LATHE Turret Lathe : These lathes are used in mass production and for heavy duty work pieces. Capsten Lathe : These lathes are used in mass production used for light duty work pieces. Special Purpose Lathe : These lathes are modification of engine lathes developed for machining special types of work pieces.

49. ENGINE LATHE

50. BENCH LATHE AUTOMATIC LATHE

51. CAPSTAN AND TURRET LATHE The  turret lathe  is a form of metalworking  lathe that is used for repetitive production of duplicate parts, which by the nature of their cutting process are usually interchangeable.

52. CAPSTAN LATHE

53. TURRET LATHE

54. RAM OF CAPSTAN LATHE

55. SADDLE OF TURRET LATHE

56. S.No Capstan lathe Turret lathe 1 It is a light duty machine It is a heavy duty machine 2 The turret head is mounted on the ram and the ram is mounted on the saddle. The turret head is directly mounted on the saddle and the saddle slides over the bed ways 3 The saddle will not be moved during machining The saddle is moved along with the turret head during machining 4 The lengthwise movement of turret is less The lengthwise movement of turret is more 5 Short work pieces only can be machined. Long work pieces can be machined 6 It is easy to move the turret head as it slides over the ram It is difficult to move the turret head along with saddle 7 The turret head cannot be moved crosswise The turret head can bbe moved crosswise in some turret lathes 8 As the construction of lathe is not rigid, heavy cut cannot be given As the construction of lathe is rigid, heavy cut can be given 9 It is used for machining work pieces up to 60mm diameter It is used for machining work pieces up to 200mm diameter 10 Collet is used to hold the work piece Jaw chuck is used to hold the work piece

57. GENEVA MECHANISM The Geneva drive or Maltese cross is a gear mechanism that translates a continuous rotation into an intermittent rotary motion. The rotating drive wheel has a pin that reaches into a slot of the driven wheel advancing it by one step.