Unit III metal cuttingopeartion milling grinding.pptx

milling and grinding

1. COURSE: MACHINING PROCESSS CODE: A40315 V Semester Regulation: R-23 G. Pullaiah College of Engineering and Technology (Autonomous) Pasupula , Kurnool- 518002 Dr G Praveen Kumar Assistant Professor Mechanical Engineering Prepared by

2. Course objectives:   Gain knowledge on working principle of different metal cutting processes and familiarize with cutting forces, machining calculations and cutting fluids. Make the student learn about principles of lathe and Drilling machines. Make the student learn about principles of Grinding and Milling machines. To acquire knowledge in the elementary mechanism and machinability of materials with different Mechanical and Electrical energy-based Machining Processes. To make student familiar with various advanced machining operations.  

3. Course Outcomes (COs) After the completion of the course, the student will be able to: A40315.1 - Operation of various machines like lathe, drilling, grinding, slotting, shaping, milling etc. A40315.2 - Practical exposure on flat surface machining, milling and grinding operations. A40315.3 - Illustrate advanced machining processes, cutting tools and cutting fluids for a specific material and part features. A40315.4 - Differentiate Electrical Energy Based machining processes, mechanism of metal removal, machine tool selection. A40315.5 - Interpret Electro Chemical machining process, economic aspects of ECM

4. Course Syllabus UNIT I Elementary treatment of metal cutting theory – Elements of cutting process – Geometry of single point tool and angles, chip formation and types of chips – built up edge and its effects, chip breakers. Mechanics of orthogonal cutting –Merchant‘s Force diagram, cutting forces – cutting speeds, feed, depth of cut, heat generation, tool life, coolants, machinability –economics of machining. cutting Tool materials and cutting fluids –types and characteristics.   UNIT II Engine lathe – Principle of working- specification of lathe – types of lathes – work holders and tool holders –Taper turning, thread cutting operations and attachments for Lathes. Drilling, Boring Machines, Shaping, Slotting and planning machines - Principles of working, specifications, types, Tools and tool holding devices – operations performed, machining time calculation.  

5. UNIT III Milling machine – Principles of working – specifications – classifications of milling machines – methods of indexing, milling cutters - machining operation, Accessories to milling machines. Grinding machine –Theory of grinding – classification– cylindrical and surface grinding machine – Tool and cutter grinding machine – Grinding wheel specification - types of abrasives – bonds, Truing and Dressing of wheels. Lapping, Honing and Broaching machines – comparison of grinding, lapping and honing. Principles of design of Jigs and fixtures and uses, Classification of Jigs & Fixtures – Principles of location and clamping –types. UNIT IV Mechanical Energy Based Processes: Abrasive Jet Machining, Water Jet Machining, Abrasive Water Jet Machining, Ultra Sonic Machining – Working Principle, Description of Equipment, Process Parameters, Metal Removal Rate, Applications, Advantages and Limitations. Electrical Energy Based Processes: Electric Discharge Machining – Wire cut EDM - Working Principles, Process Parameters, Applications Advantages and Limitations.

6. UNIT V Chemical and Electro Chemical Energy Based Processes: Chemical Machining and Electro Chemical Machining – Working Principle, Etchants, Maskants, Techniques of Applying - Process Parameters, Electro Chemical Grinding, Electro Chemical Honing, Applications, Advantages and Limitations. Thermal Energy Based Processes: Laser Beam Machining and Drilling, Plasma Arc Machining, Electron Beam Machining – Working Principle, Process Parameters, Applications, Advantages and Limitations.

7. . Books and References   Text Books: 1. Manufacturing Technology-Kalpakzian- Pearson Seventh edition. (2018) 2. Production Technology by R.K. Jain and S.C. Gupta, Khanna Publishers, 17th edition. 3. Jain V.K., Advanced Machining Processes, 1st Edition, Allied Publishers Pvt. Ltd., New Delhi, 2007. 4. Jain V.K., Advanced Machining Processes, 1st Edition, published by CRC Press (Taylor & Francis), September 7, 2022   Reference Books: 1. Pandey P.C and Shan H.S., Modern Machining Processes, 1/e, McGraw Hill, New Delhi, 2007. 2. Modern Machining Processes by Anand Pandey, published by Ane Books Pvt. Ltd, 2019 3. Production Technology by H.M.T. (Hindustan Machine Tools),TMH, 1st edition, 2001 4. Manufacturing Technology Vol II by P.N. Rao, Tata McGraw Hill, 4th edition, 2013 5. Machine Technology Machine tools and operations by Halmi A Yousuf & Harson, CRC Press Taylor and Francies. 6. Workshop Technology – Vol II, B.S.Raghu Vamshi, Dhanpat Rai & Co, 10th edition, 2013

8. Chapter :3 Milling machine – Principles of working – specifications – classifications of milling machines – methods of indexing, milling cutters - machining operation, Accessories to milling machines. Grinding machine –Theory of grinding – classification– cylindrical and surface grinding machine – Tool and cutter grinding machine – Grinding wheel specification - types of abrasives – bonds, Truing and Dressing of wheels. Lapping, Honing and Broaching machines – comparison of grinding, lapping and honing. Principles of design of Jigs and fixtures and uses, Classification of Jigs & Fixtures – Principles of location and clamping –types

9. MILLING MACHINE

10. MILLING A milling machine is a machine tool that removes metal as the work is fed against a rotating multipoint cutter. The milling cutter rotates at high speed and it removes metal at a very fast rate with the help of multiple cutting edges. One or more number of cutters can be mounted simultaneously on the arbor of milling machine. This is the reason that a milling machine finds wide application in production work. Milling machine is used for machining flat surfaces, contoured surfaces, surfaces of revolution, external and internal threads, and helical surfaces of various cross- sections. In many applications, due to its higher production rate and accuracy, milling machine has even replaced shapers and slotters.

11. PRINCIPLE OF MILLING In milling machine, the metal is cut by means of a rotating cutter having multiple cutting edges. For cutting operation, the work piece is fed against the rotary cutter. As the work piece moves against the cutting edges of milling cutter, metal is removed in form chips of trochoid shape. Machined surface is formed in one or more passes of the work. The work to be machined is held in a vice, a rotary table, a three jaw chuck, an index head, between centers, in a special fixture or bolted to machine table. The rotator speed of the cutting tool and the feed rate of the work piece depend upon the type of material being machined .

12. MILLING METHODS There are two distinct methods of milling classified as follows: Up- milling or conventional milling, and Down milling or climb milling.

13. RE UP- MILLING OR CONVENTIONAL MILLING PROCEDU In the up- milling or conventional milling, as shown in the metal is removed in form of small chips by a cutter rotating against the direction of travel of the workpiece. In this type of milling, the chip thickness is minimum at the start of the cut and maximum at the end of cut. As a result the cutting force also varies from zero to the maximum value per tooth movement of the milling cutter. The major disadvantages of up- milling process are the tendency of cutting force to lift the work from the fixtures and poor surface finish obtained. But being a safer process, it is commonly used method of milling.

14. DOWN- MILLING OR CLIMB MILLING PROCEDURE     Down milling is shown in Fig. It is also known as climb milling. In this method, the metal is removed by a cutter rotating in the same direction of feed of the work piece. The effect of this is that the teeth cut downward instead of upwards.  Chip thickness is maximum at the start of the cut and minimum in the end.  friction In this method, it is claimed that there is less involved and consequently less heat is generated on the contact surface of the cutter and workpiece.    Climb milling can be used advantageously on many kinds of work to increase the number of pieces per sharpening and to produce a better finish. With climb milling, saws cut long thin slots more satisfactorily than with standard milling. Another advantage is that slightly lower power consumption is obtainable by climb milling, since there is no need to drive the table against the cutter.

15. TYPES OF MILLING CUTTERS Plain milling cutters, Side milling cutters, Face milling cutter, Angle milling cutters, End milling cutter, Fly cutter, T- slot milling cutter, Formed cutters, Metal slitting saw,

16. TYPES OF MILLING CUTTERS Milling cutters may have teeth on the periphery or ends only, or on both the periphery and ends. Peripheral teeth may be straight or parallel to the cutter axis, or they may be helical, sometimes referred as spiral teeth.

17. TYPES OF MILLING MACHINES Milling machine rotates the cutter mounted on the arbor of the machine and at the same time automatically feed the work in the required direction. The milling machine may be classified in several forms, but the choice of any particular machine is determined primarily by the size of the workpiece to be undertaken and operations to be performed. With the above function or requirement in mind, milling machines are made in a variety of types and sizes.

18. TYPES OF MILLING MACHINES According to general design, the distinctive types of milling machines are: 1. Column and Knee Type Milling Machine Head milling machine Plain milling machine Universal milling machine Omniversal milling machine Vertical milling machine 2. 3. Planer milling machine Fixed- bed type milling machine (a) (b) (c) Simplex milling machine. Duplex milling machine. Triplex milling machine. 4. 5. Machining center machines Special types of milling machines Rotary table milling machine. Planetary milling machine. Profiling machine. Duplicating machine. Pantograph milling machine. Continuous milling machine. Drum milling machine Profiling and tracer controlled milling machine

19. COLUMN AND KNEE TYPE MILLING MACHINE Fig. shows a simple column and knee type milling machine. It is the most commonly used milling machine used for general shop work. In this type of milling machine the table is mounted on the knee casting which in turn is mounted on the vertical slides of the main column. The knee is vertically adjustable on the column so that the table can be moved up and down to accommodate work of various heights. The column and knee type milling machines are classified on the basis of various methods of supplying power to the table, different movements of the table and different axis of rotation of the main spindle.

20. COLUMN AND KNEE TYPE MILLING MACHINE Column and knee type milling machine comprises of the following important parts: Base Column Saddle Table Elevating screw Knee Knee elevating handle Cross feed handle Front brace Arbor support Arbor Overhanging arm Cutter Cone pulley Telescopic feed shaft.

21. COLUMN AND KNEE TYPE MILLING MACHINE Base : It is a foundation member for all the other parts, which rest upon it. It carries the column at its one end. In some machines, the base is hollow and serves as a reservoir for cutting fluid. Column : The column is the main supporting member mounted vertically on the base. It is box shaped, heavily ribbed inside and houses all the driving mechanism for the spindle and table feed. The front vertical face of the column is accurately machined and is provided with dovetail guideway for supporting the knee. Knee :   The knee is a rigid grey iron casting which slides up and down on the vertical ways of the column face. An elevating screw mounted on the base is used to adjust the height of the knee and it also supports the knee. The knee houses the feed mechanism of the table, and different controls to operate it.

22. COLUMN AND KNEE TYPE MILLING MACHINE Saddle The saddle is placed on the top of the knee and it slides on guide ways set exactly at 90° to the column face. The top of the saddle provides guide- ways for the table. Table   The table rests on ways on the saddle and travels longitudinally. A lead screw under the table engages a nut on the saddle to move the table horizontally by hand or power. In universal machines, the table may also be swiveled horizontally. For this purpose the table is mounted on a circular base. The top of the table is accurately finished and T - slots are provided for clamping the work and other fixtures on it. Overhanging arm It is mounted on the top of the column, which extends beyond the column face and serves as a bearing support for the other end of the arbor.

23. COLUMN AND KNEE TYPE MILLING MACHINE Front brace It is an extra support, which is fitted between the knee and the over- arm to ensure further rigidity to the arbor and the knee. Spindle It is situated in the upper part of the column and receives power from the motor through belts, gears. and clutches and transmit it to the arbor. Arbor It is like an extension of the machine spindle on which milling cutters are securely mounted and rotated.   The arbors are made with taper shanks for proper alignment with the machine spindles having taper holes at their nose. The draw bolt is used for managing for locking the arbor with the spindle and the whole assembly.

24. COLUMN AND KNEE TYPE MILLING MACHINE The arbor assembly consists of the following components. 1. Arbor 2. Spindle 3. Spacing collars 4. Bearing bush 6. Draw bolt 8. Key block 5. Cutter 7. Lock nut 9. Set screw

25. COLUMN AND KNEE TYPE MILLING MACHINE The arbor assembly consists of the following components. 1. Arbor 2. Spindle 3. Spacing collars 4. Bearing bush 6. Draw bolt 8. Key block 5. Cutter 7. Lock nut 9. Set screw

26. COLUMN AND KNEE TYPE MILLING MACHINE Types of Column and Knee type milling machine : Hand milling machine Plain milling machine Universal milling machine Omniversal milling machine Vertical milling machine

27. COLUMN AND KNEE TYPE MILLING MACHINE Hand milling machine In case of hand milling machine feed motion is given by hand and movements of the machine are provided by motor. This is simple and light duty milling machine meant for basic operations. Plain Milling Machine Plain milling machine is similar to hand milling machine but feed movement can be powered controlled in addition to manual control.

28. COLUMN AND KNEE TYPE MILLING MACHINE Universal Milling Machine A universal milling machine is named so as it is used to do a large variety of operations. The distinguishing feature of this milling machine is it table which is mounted on a circular swiveling base which has degree graduations. The table can be swiveled to any angle upto 45 o on either side of normal position. Helical milling operation is possible on universal milling machine as its table can be fed to cutter at an angle. Provision of large number of auxiliaries like dividing head, vertical milling attachments, rotary table, etc. make it suitable for wide variety of operations.

29. COLUMN AND KNEE TYPE MILLING MACHINE Omniversal Milling Machine Omniversal milling machine is like a universal milling machine with additional feature that its table can be tilted in a vertical plane by providing a swivel arrangement at the knee. This enables it to make taper spiral grooves in reamers, bevel gears, etc.

30. COLUMN AND KNEE TYPE MILLING MACHINE Vertical Milling Machine to the Position of spindle is kept vertical or perpendicular worktable in case of vertical milling machine.

31. FIXED BED TYPE MILLING MACHINE The fixed bed type milling machines are comparatively large, heavy, and rigid. The table is mounted directly on the ways of fixed bed. reciprocate at right angles to The table movement is restricted to the spindle axis with no provision for cross or vertical adjustment. The name simplex, duplex and triplex indicates that the machine is provided with single, double and triple spindle heads respectively.

32. PLANER TYPE MILLING MACHINE It is a heavy duty milling machine, its spindle head is adjustable in vertical and transverse directions. It is different from planner as feed is given to the worktable. This can accommodate a number of independent spindles carrying milling cutters on the rail. Independent driving spindles is possible of the different so multiple operations are possible simultaneously.

33. SPECIAL TYPE MILLING MACHINE These are the special purpose milling machines, entirely different in design and construction from the conventional milling machines. In case of rotary table milling machine face milling cutters are mounted on two or more vertical spindles and a number of workpieces are clamped on the horizontal surface of a circular table which rotates about a vertical axis. Different milling cutters are mounted at different heights. Loading and unloading are possible while milling is in progress. In case of drum milling machine the worktable rotates about a horizontal axis and is called drum. In a planetary milling machine , the work is held stationary while the revolving cutters in a planetary path. It is used to finish cylindrical surface of a work piece internally or externally or both.

34. SPECIAL TYPE MILLING MACHINE Pantograph milling machine reproduced the work piece at any desired scale of pre- decided model. Profiling machine duplicates full size of the template attached to the machine. Tracer milling machine can produce any pre- decided irregular or complex shapes of dies, moulds by synchronizing movements of the cutter and tracing elements.

35. SPECIFICATIONS OF A MILLING MACHINE Along with the type of a milling machine, it has to be specified by its size. Generally size of a typical milling machine is designated as given below : Size (dimensions) of the worktable and its movement range table length x table width as 900 x 275 mm . Table movements : Longitudinal travel x Cross x Vertical as 600 x 200 x 400 mm . Above travels indicate maximum movement in a direction. Number of feeds available (specify their values) Number of spindle speeds (specify their values) Total power available Spindle nose taper Floor space required Net weight

36. CUTTING PARAMETERS Where, 1000 d = Diameter of milling cutter in mm, V = Cutting speed (linear) in meter per minute, and n = Cutter speed in revolution per minute. Spindle speed of a milling machine is selected to give the desired peripheral speed of cutter. There are three major cutting parameters to be controlled in any milling operation. These three parameters are cutting speed , feed rate and depth of cut . These parameters are described below. Cutting Speed Cutting speed of a milling cutter is its peripheral linear speed resulting from operation. It is expressed in meters per minute . The cutting speed can be derived from the above formula. v   dn

37. CUTTING PARAMETERS Feed Rate It is the rate with which the work piece under process advances under the revolving milling cutter. It is known that revolving cutter remains stationary and feed is given to the work piece through worktable. Generally feed is expressed in three Ways. Feed per Tooth It is the distance traveled by the work piece (its advance) between engagement by the two successive teeth. It is expressed as mm/tooth (f t ). Feed per Revolution Travel of work piece during one revolution of milling cutter. It is expressed as mm/rev. and denoted by f (rev) . Feed per Unit of Time Feed can also be expressed as feed/minute or feed/sec . It is the distance advances by the work piece in unit time (f m ).

38. CUTTING PARAMETERS Feed Rate It is the rate with which the work piece under process advances under the revolving milling cutter. It is known that revolving cutter remains stationary and feed is given to the work piece through worktable. Generally feed is expressed in three Ways. Feed per Tooth (f t ). Feed per Revolution : mm/rev. or f (rev) Feed per Unit of Time : (f m ) f m  n  f rev . f m  z  n  f t Where, n = rpm of cutter. z = Number of teeth in milling cutter.

39. CUTTING PARAMETERS Depth of Cut Depth of cut in milling operation is the measure of penetration of cutter into the work piece. It is thickness of the material removed in one pairs of cutter under process. One pairs of cutter means when cutter completes the milling operation from one end of the work piece to another end. In other words, it is the perpendicular distance measured between the original and final surface of work piece. It is measured in mm .

40. MILLING CUTTERS Milling cutters are classified into different categories depending on different criteria as described below : According to the Construction of Milling Cutter According to Relief Characteristics of the Cutter Teeth According to Method of Mounting the Cutters According to Direction of Rotation of the Cutter According to the Direction of Helix of the Cutter Teeth According to Purpose of Use of the Cutter

41. MILLING CUTTERS According to the Construction of Milling Cutter Solid milling cutter Inserted teeth cutter Tipped solid cutter   Solid cutter consists of teeth integral with the cutter body, in tipped cutter, teeth are made of cemented carbide or satellite, teeth are brazed to steel cutter body called shank. Inserted teeth cutter are larger in diameter, teeth of hard material are inserted and secured in the shank.

42. MILLING CUTTERS According to Relief Characteristics of the Cutter Teeth  Profile relieved cutter Form relieved cutter In case of profile relieved cutter, a relief to cutting edges is provided by grinding a narrow land at their back. In case of form relieved cutters a curved relief is provided at the back of the cutting edges. According to Method of Mounting the Cutters (a) Arbor type (b) Facing cutter (c) Shank cutter   Arbor type cutters have a central hole and keyways for their mounting on arbor. Shank type cutters are provided with straight or tapered shanks inserted into the spindle nose and clamped there. Facing type milling cutter are used to produce flat surfaces. These are balled or attached to the spindle nose or the face of a short arbor (stub arbor).

43. MILLING CUTTERS According to Direction of Rotation of the Cutter Right hand rotational cutter Left hand rotational cutter  A right hand rotational cutter rotates in an anticlockwise direction when viewed from end of the spindle while left hand rotational cutter rotates in a clockwise direction. According to the Direction of Helix of the Cutter Teeth (a) Parallel straight teeth (b) Right hand helical (c) Left hand helical (d) Alternate helical teeth     Parallel or straight teeth cutter consists of teeth parallel to axis of rotation of the cutter with zero helix angle. In case of right hand and left hand helical teeth cutters, teeth cut at an angle to the axis of rotation of the cutter. Teeth have opposite inclination in both the cutters. Alternate helical teeth cutter has alternate teeth of right hand and left hand helical teeth cutters.

44. MILLING CUTTERS According to Purpose of Use of the Cutter Standard milling cutter Special milling cutter (a) (b)  Special milling cutters are designed to perform special operations which may be  combination of several conventional operations. Standard milling cutters are the  conventional cutters which are classified as given bellow.

45. STANDARD MILLING CUTTERS Plain Milling Cutter Light Duty Plain milling cutter Heavy Duty Plain milling cutter Helical Plain milling cutter Side Milling Cutter Plain Side milling cutter Staggered teeth Side milling cutter Half Side milling cutter Interlocking Side milling cutter Metal Slitting Milling Cutter Plain Metal Slitting milling cutter Staggered teeth Metal Slitting milling cutter Angle Milling Cutter Single Angle milling cutter Double Angle milling cutter

46. STANDARD MILLING CUTTERS End Mill Taper Shank end mill Straight Shank end mill Shell End Mill T- Slot milling cutter Woodruff key slot milling cutter Fly cutter Formed cutter Convex milling cutter Concave milling cutter Corner round milling cutter Gear cutter Thread milling cutter Tap and Reamer Cutter

47. STANDARD MILLING CUTTERS Plain Milling Cutter Light Duty Plain milling cutter Heavy Duty Plain milling cutter Helical Plain milling cutter These cutters are cylindrical in shape having teeth on their circumference, used to produce flat surfaces parallel to axis of rotation. Plain milling cutter is depending upon the size and applications categorized as light duty, heavy duty and helical plain milling cutters.

48. STANDARD MILLING CUTTERS Plain Milling Cutter (a) Light Duty Plain milling cutter     Less than ¾ in. wide, straight teeth Used for light milling operations Those over ¾ in have helix angle of 25º Too many teeth to permit chip clearance (b) Heavy Duty Plain milling cutter Have fewer teeth than light- duty type.   of shearing action and    Produces smoother surface because reduced chatter. Provide for better chip clearance. Helix angle varies up to 45º. Less power required.

49. STANDARD MILLING CUTTERS Plain Milling Cutter (c) Helical Plain milling cutter    Have helix angles from 45º to over 60º Suited to milling of wide and intermittent surfaces on contour and profile milling. Sometimes shank- mounted with pilot on end and used for milling elongated slots.

50. STANDARD MILLING CUTTERS Side Milling Cutter (a) Plain Side milling cutter Comparatively narrow cylindrical milling cutters with teeth on each side and on periphery. Used for cutting slots and for face and straddle milling operations. Free cutting action at high speeds and feeds. Suited for milling deep, narrow slots.     (b) Half Side milling cutter Used when only one side of cutter required Also make with interlocking faces so two cutter may be placed side by side for slot milling Have considerable rake Able to take heavy cuts

51. STANDARD MILLING CUTTERS Angular Cutters    (a) Single Angular milling cutter Teeth on angular surface May or may not have teeth on flat 45º or 60º  cutting (b) Double Angular milling cutter Two intersecting angular surfaces with teeth on both.  Equal angles on both side of line at right angle to axis.

52. STANDARD MILLING CUTTERS Formed Cutters       Incorporate exact shape of part to be produced. Useful for production of small parts. Each tooth identical in shape. Sharpened by grinding tooth face (may have positive, zero or negative rake). Important to maintain original rake. Difficult to sharpen. Concave Convex Gear Tooth

53. STANDARD MILLING CUTTERS Metal- Slitting Saws     Basically thin plain milling cutters with sides relieved or "dished" to prevent rubbing or binding when used. Widths from 1/32 to 3/16 in. Operated at approximately 1/4 to 1/8 of feed per tooth used for other cutters. Not advisable to key saw to milling arbor. Backlash eliminator should be engaged.

54. STANDARD MILLING CUTTERS End Mills   Cutting teeth on end as well as periphery. Fitted to spindle by suitable adapter. Two types     Solid end mill : shank and cutter integral Smaller with either straight or helical flutes Two flute or four flute Shell end mill : separate shank T- Slot Milling Cutter    Used to cut wide horizontal groove at bottom of T- slot . After narrow vertical groove machined with end mill or side milling cutter. Consists of small side milling cutter with teeth on both sides and integral shank for mounting.

55. STANDARD MILLING CUTTERS Woodruff Key Slot Milling Cutter Right- hand two digits give nominal diameter in eighths of an inch, preceding digits give width of cutter in thirty- seconds of an inch. Diameter 06 x 1/8 = 3/4 in. Width 4 x 1/32 = 1/8 in. Fly cutter Single- pointed cutting tool with cutting end ground to desired shape Mounted in special adapter or arbor Fine feed must be used Used in experimental work instead of a specially shaped cutter

56. MILLING MACHINE OPERATIONS on major Milling operations described earlier were based categorization of milling. These were differentiated on the basis of relative position of milling cutter and workpiece. Their detailed description is given below. Following different operations can be performed on a milling machine : Plain milling operation Face milling operation Side milling operation Straddle milling operation Angular milling operation Gang milling operation Form milling operation Profile milling operation End milling operation Saw milling operation Slot milling operation Gear cutting operation Helical milling operation Cam milling operation Thread milling operation

57. MILLING MACHINE OPERATIONS Plain Milling Operation This is also called slab milling . This operation produces flat surfaces on the work piece. Feed and depth of cut are selected, rotating milling cutter is moved from one end of the work piece to other end to complete the one pairs of plain milling operation. Face Milling Operation    This operation produces flat surface at the face o the work piece. This surface is perpendicular to the surface prepared in plain milling operation. This operation is performed by face milling cutter mounted on stub arbor of milling machine. Depth of cut is set according to the need and cross feed is given to the work table. Side Milling Operation This operation produces flat and vertical surfaces at the sides of the workpiece. In this operation depth of cut is adjusted by adjusting vertical feed screw of the workpiece.

58. MILLING MACHINE OPERATIONS Straddle Milling Operation    This is similar to the side milling operation. Two side milling cutters are mounted on the same arbor. Distance between them is so adjusted that both sides of the workpiece can be milled simultaneously. Hexagonal bolt can be produced by this operation by rotating the work piece only two times as this operation produces two parallel faces of bolt simultaneously. Angular Milling Operation   Angular milling operation is used to produce angular surface on the work piece. The produced surface makes an angle with the axis of spindle which is not right angle. Production of „V ‟ shaped groove is the example of angular milling operation.

59. MILLING MACHINE OPERATIONS Gang Milling Operation As the name indicates, this operation produces several surfaces of a workpiece simultaneously using a gang of milling cutters. During this operation, the workpiece mounted on the table is fed against the revolving milling cutters. Form Milling Operation This operation produces irregular contours on the work surface. These irregular contours may be convex, concave, or of any other shape. This operation is done comparatively at very low cutter speed than plain milling operation. Profile Milling Operation In this operation a template of complex shape or master die is used. A tracer and milling cutter are synchronized together with respect to their movements. Tracer reads the template or master die and milling cutter generates the same shape on the workpiece. Profile milling is an operation used to generate shape of a template or

60. MILLING MACHINE OPERATIONS Profile Milling Operation    In this operation a template of complex shape or master die is used. A tracer and milling cutter are synchronized together with respect to their movements. Tracer reads the template or master die and milling cutter generates the same shape on the work piece. Profile milling is an operation used to generate shape of a template or die. End Milling Operation End milling operation produces flat vertical surfaces, flat horizontal surfaces and other flat  surfaces making an angle from table surface using milling cutter named as end mill. This operation is preferably carried out on vertical milling machine.

61. MILLING MACHINE OPERATIONS Saw Milling Operation  Saw milling operation produces narrow slots or grooves into the workpiece using saw milling cutter. This operation is also used to cut the workpiece into two equal or unequal pieces which cut is also known as “parting off”. In case of parting off operation cutter and workpiece are set in a manner so that the cutter is directly placed over one of the „T ‟ slot of the worktable as illustrated in Figure.

62. MILLING MACHINE OPERATIONS Slot Milling Operation   The operation of producing keyways, grooves, slots of varying shapes and sizes is called slot milling operation. Slot milling operation can use any type of milling cutter like plain milling cutter, metal slitting saw or side milling cutter. Selection of a cutter depends upon type and size of slot or groove to be produced. Right placement of milling cutter important in this operation as axis of is very cutter should be at the middle of geometry of slot or groove to be produced.

63. MILLING MACHINE OPERATIONS Gear Cutting Operation The operation of gear cutting is cutting of equally spaced, identical gear teeth on a   gear blank by handling it on a universal dividing head and then indexing it. The cutter used for this operation is cylindrical type or end mill type. The cutter selection also depends upon tooth profile and their spacing.

64. MILLING MACHINE OPERATIONS Helical Milling Operation Helical milling produces helical flutes or grooves on the periphery of a cylindrical or conical workpiece. This is performed by swiveling the table to the required helix angle, then rotating and feeding the workpiece against revolving cutting edges of milling cutter. Helical gears and drills and reamers are made by this operation. Cam Milling Operation The operation cam milling is used to produce the cam on milling machine. In this operation cam blank is mounted at the end of the dividing head spindle and theend mill is held in the vertical milling attachment. Thread Milling Operation The operation thread milling produces threads using thread milling centres. This operation needs three simultaneous movements revolving movement of cutter, simultaneous longitudinal movement of cutter, feed movement to the workpiece through table. For each thread, the revolving cutter is fed longitudinal by a distance equal to pitch of the thread. Depth of cut is normally adjusted equal to the full depth of threads.

65. INDEXING or DIVIDING HEAD Indexing is the operation of dividing the periphery of a work piece into any number of equal parts. Ex: If we want to make a hexagonal bolt. Head of the bolt is given hexagonal shape. We do indexing to divide circular work piece into six equal parts and then all the six parts are milled to an identical flat surface. If we want to cut “n” number of teeth in a gear blank. The circumference of gear blank is divided into „n ‟ number of equal parts and teeth are made by milling operation one by one. The main component used in indexing operation is universal dividing head.

66. INDEXING or DIVIDING HEAD

67. UNIVERSAL DIVIDING HEAD It is most popular and common type of indexing arrangement. As indicated by its name “universal”, it can be used to do all types of indexing on a milling machine. Universal dividing head can set the work piece in vertical, or in inclined relative to horizontal, position worktable the in addition to working principle is explained below with the help of illustration in Figure.

68. UNIVERSAL DIVIDING HEAD The worm gear has 40 teeth and the worm has simple thread. Crank is directly attached with the worm. If we revolve crank by 40 revolutions the spindle attached with worm gear will revolve by only one revolution and one complete turn of the crank will revolve the spindle only by 1/40 th revolution (turn). In order to turn the crank precisely a fraction of a revolution, used. an indexing plate is

69. UNIVERSAL DIVIDING HEAD An indexing plate is like a circular disc having concentric rings of different number of equally spaced holes. Normally indexing plate is kept stationary by a lock pin. A spring loaded pin is fixed to the crank which can be fixed into any hole of indexing plate. The turning movement of the work piece is stably controlled by the movement of crank as explained below.

70. UNIVERSAL DIVIDING HEAD If the pin is moved by one hole on the indexing plate in the circle of 20 holes, the spindle will revolve by 1/800 th turn of one revolution. 1  1  1 40 20 800

71. INDEXING METHOD There are different indexing methods in popularity. These are : Direct or Rapid indexing Plain or Simple indexing Compound indexing Differential indexing Angular indexing

72. INDEXING METHOD It is also named as rapid indexing. For this direct indexing plate is used which has 24 equally spaced holes in a circle. It is possible to divide the surface of work piece into any number of equal divisions out of 2, 3, 4, 56, 8, 12, 24 parts. These all numbers are the factors of 24. In this case fist of all worm and worm wheel is disengaged. We find number of holes by which spring loaded pin is to be moved. Rule: If we want to divide the surface into 6 parts than number of holes by which pin is to be moved 24/N

73. INDEXING METHOD Ex: Find out the indexing movement required to mill a hexagonal bolt by direct indexing. The rapid indexing plate has 24 holes. Sol : No. of hole to be moved = 24/N = 4. Where, N= no. of divisions required. After machining one side of the bolt the indexing plate will have to be moved by 4 hole for five number of times to machine the remaining faces of the bolt.

74. SIMPLE INDEXING It is also named as plain indexing. the major It over comes limitation of direct that is possibility of indexing dividing circumference of work piece into some fixed number of divisions. In this case worm and worm gear is first engaged. indexing crank revolves So one complete turn of the work piece by 1/40 th revolution.

75. SIMPLE INDEXING To facilitate indexing to fractions of a turn, indexing plates are used to cover practically all numbers. Here, three indexing plates are used. These plates have concentric circles of holes with their different numbers as described below : These plates are the standard indexing plates followed by all machine tool manufacturers.

76. SIMPLE INDEXING : PROCEDURE 1. Divide 40 by the number of divisions to be done on the circumference of work piece to find the movement of indexing crank. 2. If the above number is a whole number, then crank is rotated by that much number of revolutions after each milling operations, till the completion of the work ( same as Direct Indexing method ).  Ex: If we want to divide the circumference into 10 number of parts.  Ex: If we want to divide the circumference into 10 number of parts.  That is the indexing crank is given 4 revolutions after each of milling operation for 9 more milling operations. Indexicnragnmkovem  e 4 n t  40  4revolust N 10 Indexicnragnmkovem  e 4 n t  40  4revolust N 10

77. SIMPLE INDEXING : PROCEDURE Ex: If we want to divide the circumference into 10 number of parts. That is the indexing crank is given 4 revolutions after each of milling operation for 9 more milling operations. If indexing crank movement calculated by “40/N” is not whole number. It is simplified and then expressed as a whole number and a fraction. Indexicnragnmkovem  e 4 n t  40  4revolust N 10

78. SIMPLE INDEXING : PROCEDURE If indexing crank movement calculated by is not whole number. It is simplified and then expressed as a whole number and a fraction. The fractional part of the above number is further processed by multiplying its denominator and numerator by a suitable common number so that the denominator will turn to a number equal to any number of holes available on the any of indexing plates . That particular holes circle is selected for the movement of crank pin. The numerator of the process fraction stands for the number of holes to be moved by the indexing crank in the selected hole circle in addition to complete turns of indexing crank equal to whole number part of “40/N”.

79. SIMPLE INDEXING : PROCEDURE Denominator becomes “15” so we will select 15 hole circle of plate 1 . After each milling operation we will rotate indexing crank by one complete turn and 5 holes in 15 holes circle . This way we do milling total 30 times. Indcerxaminokgv  e me 4  04  n t1 1  1 1 revo N 30303 Ex 1: The indexing to cut 30 teeth on a spur gear blank that means we need to divide the circumference of gear blank into 30 identical, parts. Crank movement is calculated as given below. 4 4 1 1 Indcerxaminokgv  em  e  1 n t  1 revo N 30303 Let us multiply both numerator and denominator by 5.

80. SIMPLE INDEXING : PROCEDURE Denominator becomes “21” so we will select 21 hole circle of plate 2 . After each milling operation we will rotate indexing crank by one complete turn and 7 holes in 21 holes circle . This way we do milling total 30 times. Indcerxaminokgv  e m 4  04 e  n t1 1  1 1 revo N 30303 Ex 2: The indexing to cut 30 teeth on a spur gear blank that means we need to divide the circumference of gear blank into 30 identical, parts. Crank movement is calculated as given below. 4 4 1 1 Indcerxaminokgv  em  e  1 n t  1 revo N 30303 Let us multiply both numerator and denominator by 7.

81. SIMPLE INDEXING : LIMITATION This method can used for indexing up to 50 for any number of divisions after 50 this method is not capable for some numbers like 96, etc. Compound indexing overcomes the limitations.

82. Grinding is a metal cutting operation performed by means of a rotating abrasive tool called grinding wheel . Grinding process consists of removing material from the work piece by the use of a rotating wheel that has a surface composed of abrasive grains. Grinding is considered to be the most accurate of the existing machining processes. Grinding processes are used when high accuracies , close dimensional tolerances , and a fine surface finishes are required. Grinding processes also allow for high production rates. This allows for a lowered cost of production. Hard materials can also be machined. ABRASIVE PROCESSES : GRINDING

83. abrasive Grinding is the most common form of machining. It is a material cutting process which engages an abrasive tool whose cutting elements are grains of abrasive material known as grit. These grits are characterized by sharp cutting points , high hot hardness , chemical stability and wear resistance . The grits are held together by a suitable bonding material to give shape of an abrasive tool. ABRASIVE PROCESSES : GRINDING

84. Advantages : Dimensional accuracy. Good surface finish. Good form and locational accuracy. Applicable to both hardened and unhardened material. Applications : Surface finishing. Slitting and parting. Descaling, Deburring. Stock removal (abrasive milling). Finishing of flat as well as cylindrical surface. Grinding of tools and cutters and re- sharpening of the same. ABRASIVE PROCESSES : GRINDING

85. Grinding is done on the surfaces of almost all conceivable shapes and materials of all kinds. Grinding can be classified broadly in to two groups : Rough or Non- Precision grinding. Precision grinding. Non- precision grinding : The common forms are called, snagging and off- hand grinding . Both are done primarily to remove stock that can not be taken off as conveniently by other methods. The work is pressed hard against the wheel or vice versa. The accuracy and surface finish are of secondary importance. KINDS OF GRINDING

86. Precision grinding : Precision grinding is concerned with producing good surface finishes and accurate dimensions. The wheel or work both are guided in precise path. Three types of precision grinding exists : External cylindrical grinding Internal cylindrical grinding Surface grinding Form grinding KINDS OF GRINDING

87. External cylindrical grinding produces a straight or tapered surface on work piece. The work piece must be rotated about its own axis between centers as it passes lengthwise across the face of revolving grinding wheel. Internal cylindrical grinding produces internal cylindrical holes and tapers. The work pieces are chucked and precisely rotated about their own axis. The grinding wheel or in the case of small bore holes, the cylinder wheel rotates against the sense of rotation of the work piece. KINDS OF GRINDING

88. Surface grinding produces flat surface. The work may be ground by either the periphery or by the end face of the grinding wheel. The work piece is reciprocated at constant speed bellow or on the end face of the grinding wheel. Form grinding is done with specially shaped grinding wheels that grind the formed surfaces as in grinding gear teeth, threads, spindle shafts, holes, and spheres, etc. KINDS OF GRINDING

89. the quality of surface Grinding machines according to finish, may be classified as : Rough Grinders. Precision Grinders. Rough Grinders : Rough grinders are those grinding machines whose chief work is the removal of stock with out any reference to the accuracy of the result. These are mainly of the following types : Floor stand and bench grinders. Portable and flexible shaft grinders. Swing frame grinders. Abrasive belt grinders. GRINDING MACHINES

90. Schematic illustration of a horizontal spindle surface grinder GRINDING MACHINES

91. Precision Grinders : these grinders are finish the parts to a very accurate dimensions. Classification : GRINDING MACHINES Surface Grinders Reciprocating Table Horizontal spindle Vertical Spindle Rotating Table Horizontal spindle Vertical Spindle Tool and Cutter Grinders Universal Special Special Grinding Machines Cylindrical Grinders Centre type (plain) Centre type ( universal) Centreless Internal Grinders (a) Chucking (Plain & Universal) Planetary Centreless

92. Plain Centre Type Cylindrical Grinder Figure illustrates schematically this machine and various motions required for grinding action. The machine is similar to a centre lathe in many respects. The workpiece is held between head stock and tailstock centres. A disc type grinding wheel performs the grinding action with its peripheral surface. Both traverse and plunge grinding can be carried out in this machine as shown in Fig. GRINDING MACHINES

93. GRINDING MACHINES Plain Centre Type Cylindrical Grinder

94. Universal Centre Type Cylindrical Grinder These grinders are usually used in tool rooms for grinding tools. A universal machine has the following additional features : The head stock spindle may be alived or dead, so that the work can be held and revolved by chuck as well as ground between centres. The head stock can be swiveled at an angle in a horizontal plane. The wheel head and slide can be swiveled and traversed at any angle. The wheel can also be arranged for internal grinding by the addition of an auxiliary wheel head to revolve small wheels at high speeds. GRINDING MACHINES

95. Centreless Grinders Centerless grinding is a method when the workpiece is supported by a blade instead of by centers or chucks. Two wheels are used. The larger one is used to grind the surface of the workpiece and the smaller wheel is used to regulate the axial movement of the workpiece. Types of centerless grinding include: through- feed grinding, in- feed/plunge grinding, and internal centerless grinding. GRINDING MACHINES

96. Centreless Grinders Through- feed grinding : The work is passed completely through the space between the grinding wheel and the regulating wheel. In- feed/plunge grinding : The regulating wheel is drawn back so that the work piece may be placed on the work rest blade. Endfeed grinding : Used to produce taper, either the grinding wheel or regulating wheel or both are formed to a taper. The work is fed lengthwise between the wheels and is ground as it advances until it reaches the end stop. GRINDING MACHINES

97. Internal Grinders These are used to finish straight, tapered, or formed holes to the correct size, shape and finish. The depth of cut depends up on the diameter of the hole being ground and may vary from 0.02 to 0.05mm in roughing and from 0.002 to 0.01mm in finishing operations. There are three types of internal grinders : Chucking grinders Planetary grinders Centreless grinders GRINDING MACHINES

98. Internal Grinders Chucking grinders : In this the work piece is chucked and rotated about its own axis to bring all parts of the bore or other surfaces to be ground in contact with the grinding wheel. Checking grinders are best whenever the work itself applied can be conveniently chucked and rotated. GRINDING MACHINES

99. Internal Grinders Chucking grinders : According to general construction there are three types of internal grinders: The wheel is rotated but has no longitudinal movement while the work is slowly rotated and transverse back and forth.  The work head is mounted on a longitudinal slide at the left end of the machine so that the work piece may be traversed past.  The grinding wheel, and the wheel head is mounted on a cross-slide at the right end so that the wheel may be fed for depth of cut. GRINDING MACHINES

100. Internal Grinders Chucking grinders : According to general construction there are three types of internal grinders: The wheel is rotated at the same time reciprocated back and forth through the length of the hole.  The work is rotated slowly but has no lateral and cross movement.  In this type of machine the design traverses the wheel head and cross feed the work. GRINDING MACHINES

101. Internal Grinders Chucking grinders : According to general construction there are three types of internal grinders: The grinder has two wheels side by side mounted on a horizontal overhead bar.  One has a small wheel to grind the hole, and the other has a large wheel for facing in the same setup and squaring with the hole.  This is known as internal and face grinder. GRINDING MACHINES

102. Internal Grinders Chucking grinders : Internal grinders of chucking type may be classified as : Plain internal grinder : the work head can be swiveled to grind a straight hole tapers up to 45 included angle. The wheel head is moved into and away from the hole and can be cross fed into the work. Universal grinder : it is basically the same as a plain internal grinder, the work head is mounted on a cross slide as in the wheel head, and can be swiveled through a 90 angle. GRINDING MACHINES

103. Internal Grinders Planetary : In a planetary grinder the work is mounted on the reciprocating table and is not reveled. Instead, the grinding wheel is given rotary and planetary motions to grind cylindrical holes. Planetary grinding is usually limited to large work pieces that can not be conveniently rotated by chuck. GRINDING MACHINES

104. Internal Grinders Centreless grinders : In internal centerless grinding, the work is supported by three rolls. One is the regulating roll, and the other is a pressure roll to hold the work piece firmly against the support and regulating rolls. The grinding wheel contacts the inside diameter of the work piece directly opposite to the regulating roll, thus assuming a part of absolutely uniform thickness and concentricity. The pressure roll is mounted to swing aside to permit loading and unloading. GRINDING MACHINES

105. Surface grinders Surface grinding is employed to finish plane or flat surfaces. They are also capable of grinding irregular, curved, convex and concave surfaces. grinders tot two Conventional surface may be classified in classes : One class has reciprocating tables for work ground along the straight lines. Other covers the machines with rotating work tables for continuous rapid grinding. GRINDING MACHINES

106. Types of Surface grinders Horizontal spindle reciprocating table Horizontal spindle rotary table Vertical spindle reciprocating table Vertical spindle rotary table GRINDING MACHINES

107. Types of Surface grinders Horizontal spindle reciprocating table: These machines use the circumference of straight grinding wheels, and are able to deal with a wide range of work needing super finish and extremely fine limits of accuracy. They yield a greater out put and take off metal faster than similar machines using cup- shaped, segmental or annular wheels. If a rotating work table is used, a finish comprising concentric circles can be obtained. GRINDING MACHINES

108. Types of Surface grinders Vertical spindle flat grinding machines: These machines remove metal faster when using a cup, cylindrical or segmental wheel than when using a straight wheel. They have a great precision, and if strong and rigidly built can grind to extremely fine limits. GRINDING MACHINES

109. Types of Surface grinders Disc grinding machines: In it one disc of abrasive type is mounted on a vertical spindle so that the plan of the disc is horizontal, the work resting on the surface of a flat, rotating carrier or work table. GRINDING MACHINES

110. Tool and cutter grinder machine Tool and cutter grinders are used mainly to sharpen and recondition multiple tooth cutters like reamers, milling cutters, drills, taps, hobs and other type of tools used in the shop. They are classified according to the purpose of grinding as : Universal tool and cutter grinder Single - purpose tool and cutter grinders GRINDING MACHINES

111. Tool and cutter grinding machine Universal tool and cutter grinders are particularly intended for sharpening of miscellaneous cutters. Single - purpose tool and cutter grinders are used for grinding tools such as drills, tool bits, etc. in large production plants and in large amount of grinding work is necessary to keep production tools in proper cutting conditions. Tools can be ground uniformly and with accurate cutting angles. GRINDING MACHINES

112. Universal tool and cutter grinders These are used for grinding tools such as drills, tool bits, etc. in large production plants and in large amount of grinding work is necessary to keep production tools in proper cutting conditions. Tools can be ground uniformly and with accurate cutting angles. Principal parts : Base Saddle Table Headstock and tailstock Wheel head Grinding wheel GRINDING MACHINES

113. Universal tool and cutter grinders Base : Base gives rigidity and stability to the machine. It is heavy, rigid and box type. Saddle : the saddle is mounted directly on the top of the base. It moves on anti- frictional ball bearings on hardened ways. The column supporting the wheelhead is mounted on the saddle and it can be moved up and down and swiveled to either side. The saddle is also provides the means for moving the work forward and backward. Table : it rests and moves on the top base which is mounted over the saddle. The top of the base contains the gears mechanism which control the table movement. The work table is mounted on the sub- table which has T- slots for mounting the work and attachments used on the machines. The table can be swiveled to enable taper grinding. GRINDING MACHINES

114. Universal tool and cutter grinders Head stock and tail stock : These are mounted on either side of the table similar to those on a cylindrical grinding. The work piece is positioned between the centers and driven exactly as in a cylindrical grinder. Wheel head : The wheelhead is mounted on a column on the back of the machine. Grinding wheel : Three types of grinding wheels. The straight or disc shaped wheel. The cup type in either the straight or flaring form. The dish type. GRINDING MACHINES

115. PRINCIPLE GRINDING OPERATIONS Taper surfaces Formed surfaces Gear teeth Threaded surfaces GRINDING MACHINES

116. Abrasive : It is a substance that is used for grinding and polishing operations. It should be pure and have uniform physical properties of hardness, toughness, and resistance to facture to be useful in manufacturing grinding wheels. Abrasives may be classified in to 2 groups : Natural Artificial or manufactured ABRASIVE WHEELS

117. Natural Abrasive : Sand stone, Emery, Corundum, Diamonds are the natural abrasives. The sand stone is used only for sharpening wood working tools. Emery is a natural aluminum oxide. It contains from 55 to 65 % alumina, the remainder consist of iron oxide and other impurities. Corundum is a natural aluminum oxide. It contains from 75 to 95 % alumina, the remainder consist of impurities. Diamonds of less than gem quality are crushed to produce abrasive grains for making grinding wheels to grind cemented carbide tools an to make lapping compounds. ABRASIVE WHEELS

118. Artificial Abrasive : SiC, Al 2 O 3 Silicon carbide (SiC) is manufactured from 56 parts of silica sand , 34 parts of powdered coke , 2 parts of salt , 12 parts of saw dust in a long, rectangular electric furnace of the resistance type that is built up of loose brick work. saw dust Sand furnishes silicon, coke furnishes carbon, make the charge porous, salt helps to fuse it. There are two type of silicon carbide abrasives : Green grit : consists of 97% SiC. Black grit : consists at least 95%SiC. Aluminum oxide (Al 2 O 3 ) manufactured by heating mineral bauxite, hydrated aluminum oxide clay containing silica, iron oxide, titanium oxide, etc., mixed through ground coke and iron borings in a arc type electric furnace. ABRASIVE WHEELS

119. Bonding materials and processing: Verified bond used for making verified grinding wheels. Silicate bond for making silicate wheels Shellac bond for making elastic wheels Resinoid bonds for making resinoid wheels Rubber bond used for making vulcanized wheels. Oxychloride bond for making Oxychloride wheels. BONDINGS and BONDING PROCESSES

120. TYPES OF GRINDING WHEELS

121. LAPPING Lapping is an abrading or finishing process used to produce geometrically true surfaces, correct minor surface imperfections, improve dimensional accuracy, or provide a very close fit between two contact surfaces.  Very thin layers of metal (0.005 to 0.01 mm) are removed in lapping.

122. LAPPING Characteristics of lapping process: Use of loose abrasive between lap and the workpiece. Usually lap and workpiece are not positively driven but are guided in contact with each other. Relative motion between the lap and the work should change continuously so that path of the abrasive grains of the lap is not repeated on the workpiece.

123. LAPPING Schematic illustration of the lapping process. Production lapping on flat surfaces. Production lapping on cylindrical surfaces.

124. LAPPING Abrasives of lapping: Al 2 O 3 and SiC, grain size 5~100 μ m Cr 2 O 3 , grain size 1~2 μ m B 4 C 3 , grain size 5- 60 μ m Diamond, grain size 0.5~5 V Vehicle materials for lapping Machine oil Rape oil Grease Technical parameters affecting lapping processes are: Unit pressure The grain size of abrasive Concentration of abrasive in the vehicle Lapping speed

125. LAPPING Hand lapping : Hand lapping of flat surface is carried out by rubbing the component over accurately finished flat surface of master lap usually made of a thick soft close- grained cast iron block. Abrading action is accomplished by very fine abrasive powder held in a vehicle. Manual lapping requires high personal skill because the lapping pressure and speed have to be controlled manually. Lapping Machine : Machine lapping is meant for economic lapping of batch qualities. In machine lapping, where high accuracy is demanded, metal laps and abrasive powder held in suitable vehicles are used. Bonded abrasives in the form wheel are chosen for commercial lapping. Machine lapping can also employ abrasive paper or abrasive cloth as the lapping medium.

126. LAPPING Production lapping of both flat and cylindrical surfaces are illustrated in Figures.

127. LAPPING Lapping Machine : In this case cast iron plate with loose abrasive carried in a vehicle can be used. Alternatively, bonded abrasive plates may also be used. Centreless roll lapping uses two cast iron rolls, one of which serves as the lapping roller twice in diameter than the other one known as the regulating roller. During lapping the abrasive compound is applied to the rolls rotating in the same direction while the workpiece is fed across the rolls. This process is suitable for lapping a single piece at a time and mostly used for lapping plug gauges, measuring wires and similar straight or tapered cylindrical parts.

128. LAPPING Lapping Machine : Centreless lapping is carried out in the same principle as that of centreless grinding. The bonded abrasive lapping wheel as well as the regulating wheel are much wider than those used in centreless grinding. This technique is used to produce high roundness accuracy and fine finish, the workpiece requires multi- pass lapping each with progressively finer lapping wheel. This is a high production operation and suitable for small amount of rectification on shape of workpiece. Therefore, parts are to be pre- ground to obtain substantial straightness and roundness. The process finds use in lapping piston rings, shafts and bearing races.

129. LAPPING Advantages It can lap any type of material of any shape, if it is flat. As the parts are not clamped and no heat is generated, there is no warping. It produces no burrs, rather removes those left in the earlier process. Disadvantages Large variables involved and are to be control in proper way to achieve the requirement. High skill is required. Flatness, surface finish and polished surface are not obtained all at the same time.

130. HONING Honing is grinding or a abrading process mostly for finishing round holes by means of bonded abrasive stones, called hones. In honing the material is removed by abrasive sticks (Al 2 O 3 and SiC) mounted on a mandrel or fixture. By floating action between the work and tool, the pressure exerted in the tool is transmitted equally to all sides. The honing tool is given a slow reciprocating motion as it rotates. This action results in rapid removal of stock and at the same time generation of a straight and round surfaces.

131. HONING

132. HONING When honing is done manually the tool is rotated, and the work piece is passed back and forth over the tool. Honing is done on general purpose machines, such as the lathe, drilling press, and portable drills. There are two general types of honing machines : horizontal and vertical .

133. HONING Schematic illustration of the super finishing process for a cylindrical part: cylindrical micro- honing; centerless micro- honing.

134. HONING Advantages Correction of geometrical accuracy : Out of roundness Taper Axial distortion. Dimensional accuracy.  Relatively high productivity as compared to lapping.  Holes of any diameter or length may be honed. Disadvantages  Tough non- ferrous metals cause glazing or clogging of the voids of the abrasive sticks and thus they are difficult to hone.

135. POLISHING Polishing is surface finish operation performed by a polishing wheel for the purpose of removing appreciable metal to take out scratches , tool marks , pits and other defects from the rough surfaces. In polishing usually accuracy of size and shape of the finished surface is not important, but some times tolerances of 0.025 mm or less can be obtained in machine polishing. The polishing wheels are made of leather , papers , canvas , felt or wool. The polishing method is very similar to grinding, and the work may be pressed by hand to wheels mounted on floor stand grinders. The polishing machines may be broadly classified as : endless belt machine and coated abrasive wheels .

136. POLISHING Polishing is surface finish operation performed by a polishing wheel for the purpose of removing appreciable metal to take out scratches , tool marks , pits and other defects from the rough surfaces. In polishing usually accuracy of size and shape of the finished surface is not important, but some times tolerances of 0.025 mm or less can be obtained in machine polishing. The polishing wheels are made of leather , papers , canvas , felt or wool. The polishing method is very similar to grinding, and the work may be pressed by hand to wheels mounted on floor stand grinders. The polishing machines may be broadly classified as : endless belt machine and coated abrasive wheels .

137. BUFFING Buffing is used to give much higher, lustrous, reflective finish that can not be obtained by polishing. The buffing process consists of applying a very fine abrasive with a rotating wheel. Buffing wheels are made of felts passed and glued layers of duck or other cloth, and also of leather. The abrasive is mixed with a binder and is applied either on the buffing wheel or on the work. The buffing wheel rotates with a high peripheral speed up to 40 m/sec. The abrasive may consists of iron oxide, chromium oxide, emery, etc. The binder is paste consisting of wax, mixed with grease, paraffin and kerosene.