Unit 2 Lathe and reciprocating machine tool.pptx
- 3. Machine Tools for Metal Cutting I: a) Lathe: Introduction, Working principle, types, specifications, principle parts, accessories, attachments, and various lathe operations, Calculations of Change gears for thread cutting. b) Capstan, turret lathe: Principle parts, Working, Turret indexing mechanism, bar feeding mechanism, Comparison with centre lathe. c) Drilling & Boring Machines: Classification of drilling machines, Construction and working of radial drilling machine, Various accessories and various operations. Introduction to boring machines, Types of boring machine, different operations.
- 5. Working principle of lathe The main function of a lathe is to remove metal from a piece of work to give it the required shape and size. The lathe is used to machine cylindrical shapes. In a lathe workpiece is held and rotated about its axis. Generally single point cutting tool is used as the cutting tool.
- 6. specifications of lathe 1. The length between the centres 2. The length of bed 3. The height of the centre’s 4. The maximum diameter 5. The swing diameter of the bed 6. The swing diameter over carriage
- 7. Types of lathe Speed Lathes
- 8. Engine lathe
- 9. Bench lathe:
- 10. Tool room lathe
- 11. Turret lathe and capstan lathe
- 13. Automatic lathe
- 15. Layout of lathe machine
- 16. Bed It is supported on broad box-section columns and is made of cast iron. Its upper surface is either scraped or ground and the guiding and sliding surfaces are provided. The bed consists of two heavy metal slides running lengthwise, with ways or V's formed upon them. It is rigidly supported by cross girths. The outer guide ways provide bearing and sliding surface for the carriage, and the inner ways for the tailstock. Three major units mounted on bed are the headstock, the tailstock, and the carriage.
- 17. Headstock It supports the main spindle in the bearings and aligns it properly. It also houses Necessary transmission mechanism with speed changing levers to obtain different Speeds cone pulley or gears or combination of both could be used to change speed Of spindle.
- 18. Tailstock It is movable casting located opposite to the headstock on the ways of the bed. It is used for two purposes, (i) to support the other end of the work when beingmachined, and (ii) to hold a tool for performing operations like drilling, reaming,taping etc. it contains the dead centers the adjusting screw and the hand wheel.
- 19. Carriage: It is located between the headstock and tailstock. It is fitted on the bed and slides. Along the bed guide ways and can be locked on the bed at any desired position by Tightening the carriage lock screw. It can be moved manually with a hand wheel or With power feed. It consists of following 5 main parts 1) Saddle 2) Cross slide 3) Compound rest consisting of a swivel and top slide 4) Tool post 5) Apron.
- 20. Tool Post It is used to hold various cutting tool holders. The holders rest on a wedge which is Shaped on the bottom to fit into a concave-shaped ring (segmental type), which permits the height of the cutting edge to be adjusted by tilting the tool It is fixed on the top slide. It gets its movement by the movement of the saddle, cross slide and top slide.
- 21. Turning Operation Turning is the most generally used operation in a lathe. In this the work held in the spindle is rotated while the tool is fed past the work-piece in a direction parallel to the axis of rotation. The surface thus generated is the cylindrical surface.
- 22. Facing Facing is an operation for generating flat surfaces in lathes. The feed in this case is given in a direction perpendicular to the axis of revolution. The tool used should thus have an approach angle suitable so that it would not interfere with the work-piece during the tool feeding.
- 23. Knurling Knurling is a metal working operation done in a lathe. In this a knurling tool having the requisite serrations is forced ori the work-piece material, thus deforming the top layers .This forms atop surface which is rough and provides a proper gripping surface.
- 24. Parting Parting and grooving are similar operations. In this a flat nosed tool plunge cuts the Work-piece with a feed in the direction perpendicular to the axis of revolution as This operation is generally carried out for cutting off the part from the parent material. When the tool goes beyond the center, the part would be severed. Other wise a rectangular groove would be obtained. It is also possible in similar operations to use a special form of tool to obtain the specific groove shape.
- 25. Drilling Drilling is the operation of making cylindrical holes in to the solid material. A twist drill is held in the quill of the tailstock and is fed in to the rotating work-piece by feeding the tailstock quill. Since the work-piece keeps rotating, the axis of the hole is very well maintained, even when the drill enters at an angle initially
- 26. Boring Boring is the operation of enlarging a hole already made by a single point boring tool termed as boring bar. The operation is somewhat similar to the external turning operation.
- 27. Lathe Operations
- 28. work holding devices 3 Jaw chuck 4 Jaw Chuck Work held between centres
- 29. Steady Rest Plane Mandrel Gang Mandrel
- 30. Tool holding devices Straight cutter holder Multiple cutter holder Knee tool holder Flange tool holder
- 31. B) Capstan, Turret Lathe
- 32. A capstan and turret lathe is a production lathe. It is used to manufacture any number of identical pieces in the minimum time. These lathes were first developed in the United States of America by Pratt and Whitney in 1960. Capstan lathe is one of the types of semi-automatic lathe. In semi-automatic lathes machining operations are done automatically. Functions other than machining like loading and unloading of a job, the positioning of tools coolant operations are done manually.
- 33. Capstan lathe
- 34. Turret lathe
- 35. Capstan and Turret Lathe Working: The workpiece is held in collet or chucks which are actuated hydraulically or pneumatically. All the needed tools are held in the respective holes on the turret head. According to the sequence of operation, the tool is moved with the help of a turret head. Drilling, boring, turning, reaming, threading tools are mounted on the turret head. Forming, chamfering, knurling tools are mounted on the front end of the turret. The Parting tool is mounted in an inverted position on the rear end of the turret. After completing each operation the turret head is moved back to its initial position which indexes the tools automatically.
- 37. Capstan and Turret Lathe Advantages The rate of production is higher Different ranges of speeds are obtained. A number of tools can be accommodated. Chucking of larger workpieces can be done. Operators of less skill are required hence lowers the labor cost. Higher rigidity so can withstand heavy loads.
- 38. Shaping Machines: The shaper is a machine tool having a reciprocating cutting tool of the lathe type, which takes a straight line cut. It is primarily intended to produce flat surfaces. These surfaces may be horizontal, vertical or inclined. The main significance of this machine lies in its greater flexibility on account of ease in work holding, quick adjustment and use of tools of relatively simple design.
- 39. Shaper
- 41. Base The base is the necessary bed or support required for all machine tools. The base may be rigidly bolted to the floor of the shop or on the bench according to the size of the machine. It is so designed that it can take up the entire load of the machine and the forces set up by the cutting tool over the work. It is made of cast iron to resist vibration and take up high compressive load.
- 42. Column The column is a box like casting mounted upon the base. It encloses the ram driving mechanism. Two accurately machined guide ways are provided on the top of the column on which the ram reciprocates. The front vertical face of the column contains levers, handles, etc, for operating the machine.
- 43. Cross Rail The cross rail is mounted on the front vertical guide ways of the column. It has two parallel guide ways on its top in the vertical plane that are perpendicular to the ram axis. The table may be raised or lowered to accommodate different sizes of jobs by rotating an elevating screw which causes the cross rail to slide up and down on the vertical face of the column. A horizontal cross feed screw which is fitted within the cross rail and parallel to the top guide ways of the cross rail actuates the table to move in a crosswise direction.
- 44. Saddle The saddle is mounted on the crossrail which holds the table firmly on its top. Crosswise movement of the saddle by rotating the cross feed screw by hand or power causes the table to move sideways.
- 45. Table The table, which is bolted to the saddle receives cross wise and vertical movements from the saddle and crossrail. It is a box like casting having T-slots both on the top and sides for clamping the work. In a universal shaper the table may be swiveled on a horizontal axis and the upper part of the table may be tilted up or down. In a heavier type shaper, the front face of the table is clamped with a table support to make it more rigid.
- 46. Ram The ram is the reciprocating member of the shaper. This is semi- cylindrical in from and heavily ribbed inside to make it more rigid. It slides on the accurately machined dovetail guideways on the top of the column and is connected to the reciprocating mechanism contained within the column. It houses a screwed shaft for altering the position of the ram with respect to the work and holds the tool head at the extreme forward end.
- 47. Tool head The tool head of a shaper holds the tool rigidly provides vertical and angular feed movement of the tool and allows the tool to have an automatic relief during its return stroke. The vertical slide of the tool head swivel base, which is held on seat on the ram.
- 48. Specification Maximum ram stroke in mm Maximum tool overhang in mm Distance between table surface and ram Maximum and Minimum Dimensions of table working surface Maximum travel of table Horizontal and Vertical Horizontal feed per double stroke Principal movement motor power Overall dimensions L X B X H
- 49. operations The different operations, which a shaper can perform, are as follows: 1) Machining horizontal surface 2) Machining vertical surface 3) Machining angular surface 4) Cutting slots, grooves, and key ways 5) Machining or cutting gears.
- 51. Planer Machine A planer is a machine having reciprocating work and fixed tool. The work traverses the tool and feeds over at the end of each stroke the tool is clamped in the tool holder and the work on the table. The type of work is very similar to that done on a shaper except that a plane is adopted to much large work. The cuts are all plain surfaces, but they may be horizontal, vertical or at any angle.
- 52. Operations of planer machine: The planer is used for: 1. Planning flat horizontal, vertical and curved surfaces. 2. Planning at an angle and machining dovetails. 3. Planning slots and grooves.
- 53. Construction
- 54. Bed It is a very strong and robust structure. It is made of cast iron. Cross ribs are provided to make it more strong and stable. The length of the bed is usually-twice the length of the table, so that the table may have complete stroke on the bed surface. For, supporting and permitting the table to reciprocate in constrained form, ways are provided on the top of the bed. Mechanisms for driving the table are accommodated inside the bed.
- 55. Table The table is supported on the bed ways. T-slots are provided through out the length of the table for tightening the work-piece by T-bolts. A trough is provided at either end of the table to collect chips. Adjustable dogs are provided at aside of the table, which operate some mechanism for reversing the table automatically at the end of each the stroke. The arrangements are also made to avoid the running away of the moving, loaded table. The table is usually cast in one piece; long table, may be cast in several pieces and bolted together.
- 56. Column or Uprights A planer has to columns one at each side of the bed at its centre and opposite to each other. The columns support a horizontal cross rail across the length of the bed. The cross rail may slide up or down on the columns and may be clamped in any position. Within the body of the columns, the vertical feed shaft, elevating screw for cross rail, end feed bar, etc. are accommodated within the body of the columns. The column may also support a tool head for side machining.
- 57. Cross-Rail It is supported horizontally by the two vertical column at the centre of the bed and across it. The cross rail may be operated manually, hydraulically;. It may be clamped horizontally in any position on the columns. It carries tool heads usually two in number. For feeding the tool, the feed screws are enclosed in the cross rail.
- 58. Tool Head Usually two tool heads are mounted on the horizontal cross rail and one on each column. The tool head carries a tool post to hold the cutting tool. The tool post is hinged on the tool head for lifting the tool in the return stroke. The tool may be adjusted at an angle also, if desired.
- 59. Specifications Planning width Length Height Clamping surface of table Vertical movement of the Slide Speeds (working) Main drive motor
- 62. Slotting Machine
- 63. Rotary Table • The rotary table is a circular table which is mounted on the top of the cross-slide. • The table may be rotated by rotating a worm which meshes with a worm gear connected to the underside of the table. • The rotation of the table may be effected either by hand or power. • T-slots are cut on the top of the table Ram & Tool head assembly:- The ram is the reciprocating member of the machine mounted on the guideways of the column. • It supports the tool at its bottom end on a tool head. • A slot is cut on the body of the ram for changing the position of the stroke.
- 64. Withworth Quick Return Mechanism is used in slotter machine