Two mark questions and answers

TWO MARK QUESTIONS AND ANSWERS

1. What is a shaper?

The machine which is having a reciprocating type of machine tool with single point cutting tool used to produce flat surfaces called shaper.

2. List any four important parts of a shaper.

(a) Table

(b) Tool head

(c) Ram

(d) Cross-rail

3. Define chatting ratio in a shaper.

The ratio between cutting stroke time to return stroke time,

m = Cutting stroke time / Return stroke time

4. Explain the principle of Quick return motion.

To convert the rotary motion of a motor into reciprocating motion of the tool, the various types of drives are provided in the shaper because the metal is removed during forward stroke. But no metal is cut during return stroke. Due to this, the time taken for the return stroke should be reduced by making the return stroke faster than the cutting stroke. It is achieved by some quick return mechanisms.

5. List any two types of quick return mechanisms. 

(a) Hydraulic drive mechanism

(b) Crank and slotted lever mechanism.

6. How are feed and depth of cut given to the shaper?

Feed is given by rotating the down feed screws of tool head. Depth of cut is given by rotating by raising or elevating the table.

7. What are the various types of shaper according to various conditions?

(a) According to the type of driving mechanism

(i) Crank drive type

(ii) Whit worth driving mechanism type.

(iii) Hydraulic drive type.

(b) According to the position of ram.

(i) Horizontal shaper

(ii) Vertical shaper

(iii) Travelling head shaper.

(c) According to the table design

(i) Standard or plain shaper

(ii) Universal shaper.

(d) According to the type of cutting stroke

(i) Push out type

(ii) Draw cut type.

8. What are the other types of shaper?

(a) Standard or plain shaper

(b) Universal shaper

(c) Draw cut shaper.

9. Name any four work holding devices in shaper.

[Anna Univ. Apr'18]

(a) Vice

(b) Table

(c) V-block

(d) Angle plate

(e) Fixture.

10. Compare hydraulic shaper with mechanical shaper.

[Anna Univ. Dec'06]

11. What are the various types of quick return mechanism?

(a) Open and cross belt drive

(b) Electric drive

(c) Hydraulic drive

12. State the differences between a vertical shaper and a slotter.

13. List the various quick return motion mechanism used in slotter.

(a) Whitworth quick return mechanism.

(b) Variable speed reversible electric motor drive.

(c) Hydraulic drive.

14. Mention the different speeds available in slotter.

(a) Longitudinal feed

(b) Cross feed

(c) Circular feed.

15. What are operations that can be performed on a slotter?

(a) Machining flat surface

(b) Machining grooves, slots, keyways

(c) Machining cylindrical surface and (iv) Machining irregular surface.

16. How does the planer differ from a shaper?

In planer: The work reciprocates while the tool is stationary.

In shaper: The tool reciprocates while the work is stationary.

17. Under what conditions planning operation would be proffered over other machining processes like milling, broaching, shaping, etc.? 

[Anna Univ. dec'07]

In planer, the workpiece mounted on the table reciprocates but the tool is stationary. A single point cutting tool is used for machining the work surface. This tool is always fitted vertically the tool holder which moves on a cross-rail while feeding. Planer is mainly used for machining large and heavy workpieces. The machined surface may be horizontal, vertical or inclined surface.

18. How are the cross feed and vertical feed given in the planer?

The cross feed is given by moving the tool head along the cross rail and the vertical feed is given by moving down the tool.

19. Mention the operations performed by a planer.

The following operations generally performed in a planer are:

(a) Planing horizontal surface

(b) Planing of an angle

(c) Planing vertical surface

(d) Planing curved surface.

20. State the uses of planer.

[Anna Univ. Nov'05]

The planer is used for machining heavy and large castings. Example: Lathe bed guide ways, machine guide ways etc.

21. List the various types of planers.

(a) Double hosing planer

(b) Open side planer

(c) Pit planer

(d) Edge planer

(e) Divided table planer.

22. Name the various parts of a double housing planer.

(a) Bed 

(b) Table

(c) Columns

(d) Cross rail

(e) Tool head.

23. Mention any four specifications of planer.

(a) Maximum length of the table

(b) Total weight of the planer

(c) Power of the motor

(d) Range of speeds and feed available

(e) Type of drives required.

24. What is the function of clapper block in a planer?

[Anna Univ. Apr 04]

During cutting stroke, the tool block fits inside the clapper block rigidly. During the return stroke, the tool block lifts out of the clapper block to avoid rubbing of the tool on the job.

25. How do shaping and planning differ?

26. What is meant by drilling?

Drilling is the process of producing hole on the workpiece by using a rotating cutter called drill.

27. Classify drilling machines.

1. Portable drilling machine

2. Sensitive drilling machine

(a) Bench type

(b) Floor type.

3. Upright drilling machines

(a) Round column type or pillar type

(b) Box column type or square section type.

4. Radial drilling machine

(a) Plain type

(b) Semi-universal type

(c) Universal type

5. Gang drilling machine

6. Multiple spindle drilling machine

7. Automatic drilling machine

8. Deep hole drilling machine.

28. What is deep hole drilling? State its applications.

[Anna Univ. Dec'11]

Drilling any hole more than 4 to 5 times of its diameter is called a deep hole drilling. It is mainly used in: (i) components used in steel rolling industries, and (ii) making shallow holes at the place or on components.

29. Name the various parts of a upright drilling machine.

(a) Base

(b) Column

(c) Table and spindle head

(d) Driving mechanism.

30. What are the main components of a radial drilling machine?

(a) Base

(b) Column

(c) Radial arm

(d) Drill head

(e) Spindle head and feed mechanism.

31. What is the main use of multi-spindle drilling machine?

This machine is suitable for mass production. In this machine, several holes of different sizes can simultaneously be drilled.

32. What is gang-drilling machine?

When a number of single spindle with essential speed and feed are mounted side by side on one base and have common worktable, it is known as gang-drilling machine.

33. How do you specify radial drilling machine?

[Anna Univ. Nov'04]

1. Maximum size of the drill in mm that the machine can operate.

2. Table size of maximum dimensions of a job can mount on a table in square meter. 

3. Maximum spindle travel is in mm.

4. Number of spindle speed and range of spindle speeds are in rpm.

34. Write down any four operations that can be performed in a drilling machine.

1. Drilling

2. Counter sinking

3. Tapping

4. Trepanning.

35. What is meant by reaming?

Reaming is the process of sizing and finishing the existing drilled hole. The tool used for reaming is known as a reamer.

36. What are the differences between drilling and reaming?

[Anna Univ. May'11]

Drilling is the operation of producing cylindrical hole in a workpiece. It is done by rotating the cutting edge of a cutter known as drill. The work is rotated at high speed.

Reaming is the operation of finishing and sizing hole which is already drilled while the work is revolved at a very slow speed.

37. What is the difference between a blind hole and a through hole? What is the significance of that difference? 

[Anna Univ. Apr'19]

In a through hole tapping process, the component thickness is completely through drilled in such a way to machine threads completely throughout the thickness. Generally, straight flute taps are preferred for this operation.

In a blind hole process, it is not a through hole and particular depth of threading will 'be mentioned. Generally, pre-drilling should be for 3 mm to 4-mm more than the required tapping depth. Then, tapping is done. Generally, spiral flute taps are used for blind tapping.

38. What is meant by "sensitive hand feed"?

[Anna Univ. Apr'04].

In drilling machines, the manual sensing of the hand does the feeding of tool towards the workpiece. It is called sensitive hand feed.

39. What are the different ways to mount the drilling tool?

(a) Fitting directly in the spindle

(b) By using a sleeve

(c) By using a socket

(d) By means of chucks.

40. Give the functions of flutes on taps.

(a) It provides cutting edges

(b) It conducts the cutting fluid to the cutting region

(c) It periodically reverses the rotation to break the chip formed to avoid breakage during cutting process

(d) It acts channels to carry away the chips formed by cutting action.

41. Sketch the nomenclature of a drill bit.

[Anna Univ. Nov'15]

42. Define cutting speed, feed and machining time for drilling.

1. Cutting speed:

It is the peripheral speed of a point on the surface of the drill in contact with the workpiece. It is usually expressed in m/min.

2. Feed:

It is the distance of a drill moved into the work at each revolution of the spindle. It is expressed in mm/rev.

3. Machining time:

The time taken to complete the machining process without considering the idle time of machines is called machining time. The machining time can be calculated by using the following relation

Machining time, t = Length of the tool travel in mm. / Feed in mm/rev × rpm of the spindle

43. Calculate the tap drill size to cut an internal thread for bolt of outside diameter 10mm, pitch 1.5mm and depth of the thread 0.61 pitch.

 [Anna Univ. Apr'04]

Drill size = Tap size - 2 × Depth of threads

Depth of threads = 0.61 × 1.5 = 0.915 mm

So, drill size = 10 -2 × 0.915 = 8.17 mm Ans.

44. State the nomenclature of a standard drill.

1. Body

2. Shank

3. Neck

4. Point

5. Land or margin.

45. What do you know about straight fluted drill and fluted drill? [Anna Univ. June'09] 

The reamer with helical flutes provides a smooth shear cutting action and it provides

a better surface finish. The pitch of the flutes is made uneven to reduce vibration. Small size reamers are made with straight shank whereas large size reamers are made with taper shank. The different types of reamers are used for different applications. Shell reamers are used for reaming larger holes.

46. Write the difference between drilling and tapping.

[Anna Univ. dec❜08] 

Drilling is the process of producing hole on the workpiece by using a rotating cutter called drill. The different shapes of holes can be made.

Tapping is the process used for making internal threads in a machine component by a tool called tap. Internal thread can be cut in existing drilled holes.

47. What is meant by reaming?

Reaming is the process of sizing and finishing the existing drilled hole. The tool used for reaming is known as a reamer.

48. Why reaming operation is performed?

[Anna Univ. Nov'17]

Reaming operation is performed to finish drilled holes accurately to size and with a good surface finish. Reaming is a finishing operation of high-precision holes performed with a multi-edge tool. The reamer cannot produce a hole. It simply follows the path of an already drilled hole. It removes less amount of metal.

49. What are the differences between drilling and reaming?

[Anna Univ. May'11]

Drilling is the operation of producing cylindrical hole in a workpiece. It is done by rotating the cutting edge of a cutter known as drill. The work is rotated at high speed.

Reaming is the operation of finishing and sizing hole which is already drilled while the work is revolved at a very slow speed.

50. What is the use of a tapping tool?

A tap is a tool which is used for making internal threads in a machine component. 

51. What is boring?

Boring is the process of enlarging and locating previously drilled holes with a single point cutting tool.

52. What are the applications of boring?

The boring machine is designed for machining large and heavy workpiece in mass production work of engine frame, cylinder, machine housing etc.

53. What is the main difference between boring bar and boring tool?

Boring bar: The tool which is having a single point cutting edge known as boring bar.

Boring tool: The tool which is having multi point cutting edge known as boring tool. 

54. What are the types of boring machines?

(a) Horizontal boring machine.

(i) Table type

(ii) Floor type

(iii) Planer type

(iv) Multiple head type

(b) Vertical boring machine

(c) Precision boring machine

(d) Jig boring machine.

55. How is the work clamped on the table?

The workpiece is mounted on the table and clamped with ordinary strap clamps, T- slot bolts and nuts or it is held in a special boring fixture if required.

56. List the various types of horizontal boring machines.

(a) Table type horizontal boring machine

(b) Floor type horizontal boring machine

(c) Planer type horizontal boring machine

(d) Multi-spindle horizontal boring machine.

57. State any four specifications of horizontal boring machine.

(a) Type of machine - floor, planer type, or multi spindle etc.

(b) Maximum size of boring spindle diameter in mm.

(c) Maximum spindle travel in horizontal and vertical direction in mm.

(d) Maximum travel of the table in longitudinal and cross-wise directions in mm.

58. What are the three types of vertical boring machines?

(a) Vertical boring mill

(b) Vertical turret lathe boring machine

(c) Vertical precision boring machine.

59. What are the applications of vertical boring machines?

Vertical boring machines are used for machining inside and outside diameters of pressure vessels and facing of large pieces such as turbine castings, fly wheels, tables of machine tools, gear blanks, locomotive wheels etc.

60. How is the work set on a vertical turret lathe boring machine?

The workpiece clamps on rotary table by adjustable jaws and it is identical to lathe chuck which rotates in its vertical axis.

61. Name the various operations performed on a horizontal boring machine.

(a) Boring

(b) Facing or face milling

(c) Drilling

(d) Reaming.

62. List out the possible operations which can be performed on a vertical boring machine.

(a) Cylindrical turning

(b) Taper turning

(c) Boring

(d) Turning plane surface.

(e) Necking or cutting off and forming.

63. What are the different types of boring tools?

(a) Boring bar

(b) Boring head, and

(c) Facing head.

64. Why is a jig boring machine called so?

[Anna Univ. June 06]

A jig-boring machine is a precision boring machine used for boring accurate holes at proper centre-to-centre distances. It is a specially designed machine tool for the precision location and production of holes needed in jigs, fixtures, dies and templates.

65. Specify the importance of jig boring machine.

1. A jig-boring machine is a precision boring machine used for boring accurate holes at proper centre-to-centre distance.

2. It is specially designed machine tool for the precision location and production of holes needed in jigs, fixtures, dies and templates.

3. The machining accuracy of holes produced by this machine tool lies within a range of 0.0025 mm.

4. Built-in precision measuring devices for axis movement is another specialty of this machine.

66. Define "milling process".

Milling is the process of removing metal by feeding the work past against a rotating multipoint cutter.

67. Why is milling a versatile machining process?

[Anna Univ. May'15].

Metal removal is performed through the relative motions of a rotating, multi-edge cutter and multi-axis movement of the workpiece. Milling is a form of interrupted cutting where the repeated cycles of entry and exit motions of the cutting tool accomplish the actual metal removal and discontinuous chip generation.

68. What are the specifications of milling machine?

(a) The table length and width.

(b) Maximum longitudinal cross and vertical travel of the table.

(c) Number of spindle speeds and feeds.

(d) Power of driving motor.

69. Classify milling machine.

(a) Column and knee types

(i) Plain milling machine 

(ii) Vertical milling machine 

(iii) Universal milling machine

(iv) Ram-type milling machine

(v) Omniversal milling machine.

(b) Bed-Type milling machine

(i) Simplex milling machine

(ii) Duplex milling machine 

(iii) Triplex milling machine. 

(c) Plano-type milling machine 

(d) Special purpose milling machine 

(i) Rotary table milling machine

(ii) Drum milling machine

(iii) Profile milling machine.

70. What are the two types of column and knee type-milling machine?

(i) Horizontal type

(ii) Vertical type.

71. List the principle parts of horizontal or plain milling machine.

Base, column, knee, saddle, table, overarm and arbor.

72. Mention the various movements of universal milling machine table.

(a) Vertical movement-through the knee.

(b) Cross wise movement-through the saddle.

(c) Longitudinal movement of the table.

(d) Angular movement of the table-by swiveling the table on the swivel base.

73. State any two comparisons between plain and universal milling machine.

(a) In plain milling machines, the table is provided with three movements, longitudinal, cross and vertical. In universal milling machine in addition to these three movements, there is a fourth movement to the table. The table can horizontally be swiveled and can be fed at angle to the milling machine spindle. 

(b) The universal milling machine is provided with auxiliaries such as dividing head, vertical milling attachment, rotary table etc. Hence, it is possible to make spiral, bevel gears, twist drills, reamers etc. on universal milling machine.

74. How does omniversal milling machine differ from universal milling machines?

This is a modified form of a plain (horizontal) milling machine. It is provided with two spindles, one of which is in the horizontal plane while the other one is carried by a universal swiveling head.

75. Classify bed type milling machine.

The bed type milling machines are classified as simplex, duplex and triplex machine. 

76. What are the different ways for machining workpieces in Plano-milling?

(a) By moving the table, the cutters rotating in position.

(b) By keeping the table stationary and feeding the cutters by moving the milling heads.

(c) By simultaneously moving the table and the milling heads.

(d) By keeping the table stationary, moving the cross-rail downwards and the side cutters up and down.

77. What are the various types of special purpose milling machines?

(a) Rotary table or continuous milling machine

(b) Drum type milling machine

(c) Profile or contour milling machine.

78. What are the common work holding devices used on milling machines?

(a) ' V’ blocks

(b) Machine vises

(c) Milling fixture

(d) Dividing heads.

79. What are the cutter holding devices?

(a) Arbors

(b) Adapters

(c) Collets.

80. List the various types of milling attachments.

(a) Vertical milling attachment

(b) Universal milling attachment

(c) High speed milling attachment.

(d) Rotary attachment

(e) Slotting attachment

(f) Rack milling attachment

(g) Universal spiral milling attachment.

81. How do you classify milling cutters?

[Anna Univ. May'10 & Nov'18]

According to the shape of the tooth, milling cutters are classified as

(a) Milled tooth cutters

(b) Form relieved cutters

According to the type of operation

(a) Plain milling cutters 

(b) Side milling cutters 

(c) End mill cutters

(d) Angle milling cutters

(e) T-slot milling cutters

(f) Slitting saws

(g) Form milling cutters

(h) Fly cutters

(i) Woodruff key slot milling cutter.

82. What is a shell mill?

[Anna Univ. Nov'05& June 06]

A shell mill is a large type of face or end mill that mounts onto an arbor, rather than having an integral shank. Typically, there is a hollow or recess in the centre of the shell mill for mounting hardware onto a separate arbor.

83. What is meant by up-milling and down milling?

[Anna Univ. dec'06 & June'09]

In up milling process, the cutter rotates opposite to the direction of feed of the workpiece whereas in down milling, the cutter rotates in the same direction of travel of the workpiece.

84. What are the advantages of up milling processes?

(i) It does not require a backlash eliminator.

(ii) It is safe in operation due to separating forces between cutter and work.

(iii) It produces less wear on feed screw and nut due to the absence of pre-loaded. 

(iv) Milled surface does not have built up edge.

85. What is climb milling? Mention its advantage.

[Anna Univ. Dec'11]

The cutter rotates in the same direction of travel of the workpiece is called climb milling.

(i) Cutter with higher rake angles can be used. It reduces power requirements. 

(ii) Cutter wear is less because the chip thickness is maximum at the start of the cut. 

(iii) Finishing is generally good because the rubbing action with chip is eliminated.

86. What are the differences between up milling and down milling?

[Anna Univ. Nov'03, Nov'04, May'11, Nov'13, Nov '15, May'16, Nov '17 & Apr'19] 

87. Write any ten nomenclature of a plain milling cutter.

Body of cutter, cutting edge, face, fillet, gash, lead, land, outside diameter, root diameter and cutter angles.

88. Define straddle milling.

Straddle milling operation is the process of producing two vertical flat surfaces on the both sides of the job by using two side milling cutters which are separated by collars. 

89. What do you understand by Gang milling?

Gang milling is the production of many surfaces of a job simultaneously by feeding the table against a number of required cutters.

The two plain milling cutters have helical teeth of opposite hands. This method of operation saves the machining time and hence, it is widely used in mass production.

90. What is thread milling?

[Anna Univ. June'06]

A thread mill has no chamfer. The mill is inserted into the hole along the axis of the spindle and deep enough to produce full thread depth required.

91. What are the different methods of indexing?

The common methods of indexing are given below.

1. Direct or rapid indexing

2. Plain or simple indexing

3. Differential indexing

4. Compound indexing

5. Angular indexing.

92. What do you mean by differential indexing?

A method in which the difference between simultaneous movements of index plate and index crank is used to divide circle into subdivisions is called differential indexing.

First, the crank is moved in a certain direction. Next, the movement is added or subtracted by moving the plate by means of a gear train.

93. Write down the rule for gear ratio in differential indexing.

The rule for gear ratio in differential indexing is given by

where

A → Selected no which can be indexed by plain indexing and approximately equal to N. 

N → Required number of divisions to be indexed.

94. What is the combination of two movements in differential indexing?

When the index plate rotates in the same direction of the crank, the resulting movement of the crank will increase. When the index plate rotates in the opposite direction of the crank, the resulting actual movement is decreased.

95. What is gear finishing? Why it is done?

[Anna Univ. May'16]

Gear finishing is a finishing process to remove considerable amount of the metal after heat treatment to obtain predetermined quality gear.

Generally, the gear teeth are produced by any one of the gear forming or generating processes. But, the gear, does not be more accurate with the good quality surface. The rough surface of gear teeth occurs due to vibrations causing noise, excessive wear, play and backlash between meshing pair of gears. So, the gear produced by generation process leads to low power transmission and it produces incorrect velocity ratio because of poor surface finish. Therefore, the gear finishing is carried at last in gear manufacturing. 

96. What are the two methods used in gear teeth grinding?

(i) Gear generating process

(ii) Gear forming process.

97. Explain the difference between generation and forming operations.

[Anna Univ. May'10 & Apr'19]

98. What are the other forming methods for manufacturing gears?

(a) Gear cutting by single point form tool

(b) Gear cutting by shear speed shaping process

(c) Gear milling using a formed end mill

(d) Gear broaching

(e) Template method.

99. What are the advantages of speed shaping process?

(a) It is the quickest process.

(b) Both external and internal spur gears can be cut.

100. List the gear generating process.

(a) Gear shaping process

(b) Gear planing process

(c) Gear hobbing process.

101. Mention the applications of gear shaping process.

[Anna Univ. May'13]

(a) Gear shaping is used for generating both internal and external spur gears.

(b) Helical gears can also be generated using special attachments.

102. What are the advantages of gear planning process?

(a) Any given module can be cut using a single cutter.

(b) The rate of production is higher when compared to formed cutter method.

(c) It is a simple flexible and accurate method of generating gears..

103. What is gear hobbing?

[Anna Univ. May'11]

The process of generating a gear by means of a rotating cutter call hob is known as hobbing.

104. Mention any two advantages of gear hobbing.

[Anna Univ. Dec'11]

(a) Using a single hob, any number of teeth of the same module can be produced.

(b) Spur and helical gears can be produced using the same hob.

(c) It can be used in mass production.

(d) Perfect tooth profile can be obtained.

(e) Process is automatic which reduces the cost of labour.

105. What are the limitations of gear hobbing?

(a) Internal gears cannot be generated.

(b) Hobbing process cannot be applied very near to shoulders.

106. List the applications of gear hobbing.

Hobbing is used for generating spur, helical and worm gears.

107. What is roller burnishing process?

Roller burnishing is a method of cold working metal surfaces in which hardened sphere or cylindrical roller is pressed against the work to be processed. For example, in roller burnishing on a lathe, the burnishing tool is moved across the surface to be spanned.

108. Explain the difference between gear honing and gear lapping processes.

109. What is meant by grinding?

Grinding is a metal removing process in which the metal is removed with the help of a rotating grinding wheel.

110. How do you specify a grinding wheel?

[Anna Univ. May'16 & Apr'18]

(i) Grit number and grain size

(ii) Grade

(iii) Structure of wheels.

111. What is the process of self-sharpening of the grinding wheel?

During machining, the blunt abrasive grains will be released from the wheel surface. In their place, new abrasive grains project from the surface of the wheel. This process is called self-sharpening of the grinding wheel.

112. State the purpose of grinding.

(i) To remove less amount of metal from workpieces and finish them to close tolerances.

(ii) To obtain a better surface finish.

(iii) To machine hard surfaces which cannot be machined by high-speed steels.

113. Classify the various types of grinding machine.

1. Type of operation

a) Tool grinders

b) Cut off grinders.

2. Quality of surface finish

a) Precision grinders 

b) Rough grinders.

3. Type of surface generated

a) Cylindrical grinders

b) Internal grinders

c) Surface grinders

d) Tool grinders.

4. Special purpose grinding machines

5. Surface finishing grinders.

114. Classify the grinding machines according to the type of surface produced.

1. Rough grinders

a) Floor stand grinders

b) Bench grinders

c) Portable grinders

d) Abrasive belt grinders

e) Swing frame grinders.

2. Precision grinders

a) Cylindrical grinders

(i) Centre type plain grinders 

(ii) Centre type universal grinders

(iii) Centreless grinders.

b) Internal grinders

b) Internal grinders

(i) Chucking type grinders

(ii) Planetary type grinders

(iii) Centreless grinders.

c) Surface grinders

(i) Reciprocating table-horizontal spindle

(ii) Rotary table-horizontal spindle 

(iii) Reciprocating table-vertical spindle

(iv) Rotary table-vertical spindle

d) Tool and cutter grinders.

e) Special grinders.

115. State the use of rough grinding process.

Rough grinding is used for removing projections such as sprue pins from castings, grinding the projections in the forgings, finishing the weldments, sharpening of hard tool etc.

116. How can small and irregular shaped workpiece be ground?

Small and irregular shaped workpiece can be ground by using an abrasive belt grinder.

117. State the use of swing frame grinder.

A swing frame grinder is used for snagging the castings which are too heavy and large in nature.

118. Specify the importance of precision grinders.

It is used to manufacture parts of accurate dimensions with good surface finish.

119. What are the four movements in a cylindrical center type grinding?

(i) Rotation of cylindrical workpiece about its axis.

(ii) Rotation of the grinding wheel about its axis.

(iii) Longitudinal feed movement of the work past the wheel face.

(iv) Movement of wheel into the work which is perpendicular to the axis of the workpiece to give depth of cut.

120. What is the main difference between traverse and plunge grinding?

In traverse grinding, this method is used when the job length is greater than the width of the grinding wheel.

In plunge grinding, this method is used when the length of the workpiece is less than the width of the grinding wheel.

121. What is the use of plunge grinding?

Plunge grinding is used for grinding shoulders, stepping and various contours on the workpiece.

122. What are the various parts of a plain center type cylindrical grinding machine?

a) Base

b) Table

c) Headstock

d) Tailstock

e) Wheelhead.

123. What are the types of surfaces that could be produced using plain cylindrical grinders? 

[Anna Univ. Nov'06]

The types of surfaces that could be produced using plain cylindrical grinders are plain cylindrical parts, cylinders, tapers, shoulders, fillets, cams, crankshaft etc. 

124. What are the various features of a center type universal cylindrical grinding?

(a) The centre of the headstock spindle can be used live centre or dead centre. The work can be held and revolved by a chuck. It can also be held between centres and revolved.

(b) The wheelhead can be swivelled in a horizontal plane to any angle. The wheelhead can also be fed in the inclined direction.

(c) The headstock can be swivelled to any angle in the horizontal plane.

(d) The wheelhead can also be arranged for internal grinding.

125. What is meant by centreless grinding?

Centreless grinding is performed on workpieces which do not have centres, such as pistons, valves, rings, tubes, balls, wrist pins, drills, bushings, shafts etc. Centreless grinding can be done on both external and internal cylindrical surfaces.

126. With the help of a neat figure explain centerless grinders.

[Anna Univ. Nov'19]

Centreless grinding differs from centred grinding operations in such a way that no spindle or fixture is used to locate and secure the workpiece. The workpiece is secured between two rotary grinding wheels and the speed of their rotation relative to each other determines the rate at which the material is removed from the workpiece. The grinder has two wheels. A larger grinding wheel is revolving at a high speed and a small regulating wheel is revolving at a slow speed.

127. Why is the centreless grinders called specialized machine for cylindrical parts?

[Anna Univ. Apr'17]

The centreless grinders are called specialized machine for cylindrical parts because it was developed to form the rapid production of cylindrical, external taper, or external profile work.

128. What are the three methods of external cylindrical centreless grinding?

(i) Through-feed centreless grinding

(ii) In-feed centreless grinding (Plunge cutting)

(iii) End-feed centreless grinding.

129. How is end feed grinding identified at the moment of seeing?

Both grinding and regulating wheels are tapered and thus, it produces tapered workpieces.

130. State any four advantages and disadvantages of centreless grinding

Advantages:

1. Work holding devices such as chucks, dogs, centres, mandrels are not required.

2. Wide range of components can be ground.

3. A very little skill is required for the operator.

4. Large grinding wheels can be used so that wheel wear is minimized.

Disadvantages:

1. Work with flat surface and key ways cannot be ground.

2. Workpieces with step and multiple diameters cannot easily be ground.

3. In hollow work, there is no certainly that the outside diameter will be concentric with inside diameter.

131. What are the uses of internal grinders?

Internal grinders are used to finish straight, tapered or formed holes to the correct size, shape and finish.

132. State the various types of internal grinders.

a) Chucking type

b) Planetary type

c) Centreless type.

133. What is planetary grinding?

The motion of the grinding wheel is in the form of planet and hence, it is called planetary grinding.

134. What are the three rolls used in centreless grinding?

One is the regulating wheel, the second one is a supporting roll and the last one is a pressure roll to hold the workpiece against the support and regulating rolls.

135. What are the types of surface grinders?

a) Horizontal spindle reciprocating table surface grinder

b) Horizontal spindle rotary table surface grinder

c) Vertical spindle reciprocating table surface grinder

d) Vertical spindle rotary table surface grinder.

136. What is a bol post grinder?

 [Anna Univ. May'14]

The tool post grinders are used for miscellaneous and small grinding work on a lathe.

137. Classify tool and cutter grinders.

(i) Single purpose and cutter grinders

(ii) Universal tool and cutter grinders.

138. What are the three types of grinding wheels? 

(i) The straight or disc shaped wheel

(ii) The cup type

(iii) The disc'type.

139. Define the term "abrasives grains".

An abrasive is a hard material. It can be used to cut or wear away other materials. Small abrasive particles are used in grinding wheels called abrasive grains.

140. Classify the types of abrasives.

(i) Natural abrasives

(ii) Artificial abrasives.

141. State the abrasives used in manufacture of grinding wheels.

[Anna Univ. Nov'07, Dec'11 & Nov'18]

1. Natural abrasives:

b) Sandstone or solid quartz.

e) Emery (50 to 60% crystalline Al2O3 + Iron oxide).

f) Corundum (75 to 90% crystalline Al2O3 + Iron oxide) 

g) Diamond.

2. Artificial abrasives:

a) Aluminium oxide

b) Silicon carbide

c) Artificial diamond

d) Boron carbide

e) Cubic boron nitride..

142. What are the physical properties of aluminum oxide?

(i) Silicon carbide is harder than aluminium oxide.

(ii) Aluminium oxide can withstand greater stresses than silicon carbide.

(iii) Aluminium oxide is tougher than silicon carbide.

143. Name the two types of bond.

(i) Organic bond

(ii) Non-organic bond.

144. List the various advantages of using vitrified bond.

a) It is made porous and enables a quicker stock removal.

b) It is not affected by water, oil, acids and alkaline.

c) The bond itself is very hard and it acts as an abrasive.

d) The structure of the wheel is uniform due to wet mixing of the different constituents.

145. What are the different types of bonds used in grinding?

a) Vitrified bond

b) Silicate bond

c) Resinoid bond

d) Rubber bond

e) Shellac bond

f) Oxy chloride bond.

146. What is meant by grit number and grain size?

The grain size is denoted by the grit number. This number is equal to the number of meshes in 254 cm of a sieve through which the grains can pass through it.

147. What is meant by "grade" and "structure" of a grinding wheel? 

[Anna Univ. May'11]

Grade or hardness indicates the strength with which the bonding material holds the abrasive grains in the grinding wheel.

Structure denotes the spacing between abrasive grains or in other words, it is the density of the wheel.

148. What is open and dense structure?

Structure of the grinding wheel is designated by a number. Higher is the number, wider will be the spacing. When the spacing is small, the structure is called dense structure. When the spacing is wide, the structure is called open structure.

149. Define grinding ratio.

[Ana Univ. Nov'17]

Grinding ratio is the ratio of the volume of ground material removed from the workpiece to the volume of material removed from the grinding wheel.

G = Volume of material required / Volume of wheel wear

150. What are grinding points? Sketch the various grinding points? 

[Anna Univ. May '14] 

The bonded abrasive stones in the grinding process are called grinding points.

151. What are the specifications of grinding wheel?

[Anna Univ. Dec'10, May '13 & Nov '15]

 (i) Type of abrasives

(ii) Grain size or grit number

(iii) Grade of the wheel

(iv) Structure

(v) Type of bond

(vi) Manufacturer's code.

152. Define the terms 'Glazing' and 'Loading' with respect to grinding wheels.

[Anna Univ. Nov'05 & May '17]

When the bond of the abrasive is very hard, it does not dislodge an abrasive particle. Therefore, the surface of the wheel becomes smooth and gets a glassy like appearance. It is known as glazing of the wheel.

During the operation, the chips' formed get entrapped in the inner granular space of abrasive particles. It is called loading and it results to an inefficient cutting operation. 

153. How does loading differ from glazing in grinding process? 

[Anna Univ. May'15] 

A glazed wheel has cutting particles which are dull worn out bond. It will not allow the dulled particles to be torn of the wheel. A glazed wheel increases the smoothness of the wheel-face and it decreases its cutting capacity.

The loaded wheel has particles of the metal being ground adhering to it. They prevent the wheel from cutting freely due to openings and pores of the wheel-face filled up with metal.

154. What is meant by dressing and truing?

[Anna Univ. Dec'08 & Nov'13]

Dressing is the process of loading and breaking away the glazed surface so that new sharp abrasive particles are again present to work for efficient cutting.

Truing is the process of trimming the cutting surface of the wheel to run true with the axis.

155. Mention four important factors that influence the selection of grinding wheel. 

[Anna Univ. June 09, Nov'15 &Nov'18]

1. Constant factors

(i) Physical properties of material to be ground.

(ii) Amount and rate of stock to be removed

(iii) Area of contact

(iv) Type of grinding machine.

2. Variable factors

(i) Work speed

(ii) Wheel speed

(iii) Condition of the grinding machine

(iv) Personal factor.