Basic Of Metal Cutting | Interview Question and Answers
Basic Of Metal Cutting | Interview , VIVA, Oral Question and Answers
1. Explain the cutting shaping process?
The required shape of metal is obtained by removing the unwanted material from the work piece in the form of chips is called cutting shaping. Example: Turning, Drilling, Milling, Boring etc.
2. Classify the relative motion between work piece and cutting tool.
(i) Rotation of work against the tool. Example: Turning,
(ii) Rotation of tool against work piece. Example: Drilling, Milling,
(iii) linear movement of the work piece against the tool. Example: Planer,
(iv) Linear movement of the tool against the work. Example: Shaper.
3. What are all the different types of cutting tool?
(i) Single point cutting tool, (ii) Multiply point cutting tool.
4. Classify the various angles in cutting tool?
1) Back rake angle 2) Side rake angle 3) End relief angle 4) Side relief angle 5) Side cutting angle 6) End cutting angle.
5. What is tool signature?
The various angles of tools are mentioned in a numerical number in particular order. That order is known as tool signature.
6. What is effect of back rake angle and mention the types?
Back rake angle of tool is increases the strength of cutting tool and cutting action.
It can be classified into two types. 1. Positive rake angle. 2. Negative rake angle.
7. What is side rake angle and Mention its effects?
The angle between the tool face and the line parallel to the base of the tool. It is used to control chip flow.
8. What is clearance angle and mention the types?
These are the slopes ground downwards from the cutting edges. The clearance angle can be classified into two types. i Side relief angle. Ii. End relief angle. .
9. Explain the nose radius?
Joining of side and end cutting edges by means of small radius in order to increase the tool life and better surface finish on the work piece.
10. What are all conditions for using positive rake angle?
a. To machine the work hardened materials.
b. to machine low strength ferrous and non-ferrous metals.
c. To turn the long shaft of small diameters.
d. To machine the metal below recommended cutting speeds.
11. When will the negative rake angles be used?
a. To machine high strength alloys. b. The machine tools are more rigid. c.The feed rates are high. d. To give heavy and interrupted cuts.
12. Classify the types of metal cutting process?
The metal cutting processes are mainly classified into two types.
a. Orthogonal cutting process (two dimensional cutting),
b. Oblique cutting process (Three dimensional cutting).
13. Define orthogonal and oblique cutting?
Orthogonal cutting :- The cutting edge of tool is perpendicular to the work piece axis.
Oblique cutting :- The cutting edge is inclined at an acute angle with normal to the cutting velocity vector is called oblique cutting process.
14. What is shear plane?
The material of work piece is stressed beyond its yield point under the compressive force. This causes the material to deform plastically and shear off. The plastic flow takes place in a localized region is called shear plane.
15. What is cutting force?
The sheared material begins to flow along the cutting tool face in the form of small pieces. The compressive force applied to form the chip is called cutting force.
16. What is chip and mention its different types?
The sheared material begins to flow along the cutting tool face in the form of small pieces is called chip. The chips are mainly classified into two types.
a. Continuous chip. b. Discontinuous chip. c. Continuous chip with built up edge.
18. When will the continuous chip deformed?
The following factor favours the formation of continuous chip.
(i) Ductile material (ii) Smaller depth of cut (iii) High cutting speed (iv) Large rake angle
(v) Sharp cutting edge. (vi) Proper cutting fluid, (vii) Low friction between tool face and chips.
19. What are the favourable factors for discontinuous chip formation?
a. Machining of brittle material, b. Small rake angle, c. Higher depth of cut, d. Low cutting speeds , e. Excess cutting fluid. f. Cutting ductile material with low speed and small rake angle of the tool.
20.What are the favorable factors for continuous chip with built up edge?
a. Low cutting speed.
b. Small rake angle.
c. Coarse feed.
d .Strong adhesion between chip and tool face.
e. Insufficient cutting fluid.
19. What is chip thickness ratio?
The ratio of chip thickness before cutting, to chip thickness after cutting is called chip thickness ratio.
20. What is chip reduction co-efficient?
The reciprocal of chip thickness ratio is called chip reduction co-efficient.
21. What are purposes of chip breakers?
The chip breakers are used to break the chips into small pieces – for removal, safety and to prevent to machine and work.
22. What is the difficulty for long and continuous chip?
During machining, long and continuous chip that are formed at high cutting speed will affect machining. It will spoil tool, work and machine. These chips are hard, sharp and hot. It will be difficult to remove metal and also dangerous to safety.
23. Classify the different types of chip breakers?
The chip breakers are classified into three types. a. Step type. b.Groove type. c. Clamp type.
24. What are the cuttings forces acting on the cutting tool?
During the cutting process, the following three component of cutting forces acting mutually right angles.
a. Feed force Fx acts in a horizontal plane, but in the Direction opposite to feed.
b. Thrust force Fy acts in a direction perpendicular to the generated surface.
c. Cutting force Fz in the direction of the main cutting motion.
26. What are the assumptions made by merchant circle?
a. The chip formation will be continuous without built up edge.
b. During cutting process cutting velocity remains constant,
c. The cutting tool has a sharp cutting edge so that it does not make flank contact to the work piece.
27. What is metal removal rate?
It is defined as the volume of metal removed in unit time. It is used to calculate time required to remove specified quantity of material from the work piece.
28. What are the assumptions made in lee and Shaffer’s theory?
a. The work ahead of the tool behaves as ideal plasticmass
b. There exists a shear plane which separates the chip and work piece
c. No hardening in chip occurs.
29. Explain the total energy of the cutting process?
Total energy per unit volume is approximate equal to the sum of following four energies.
a. Shear energy per unit volume in shear plane,
b. Friction energy per unit volume in tool face,
c. Surface energy per unit volume due to the formation of a new surface area in cutting.
d. Momentum energy per unit volume, due to the change in momentum associated with the metal it crosses the shear plane.
30. Define mach inability of metal?
Mach inability is defined as the ease with which a material can be satisfactorily machined.
31. What are the factors affecting the machinability?
a. Chemical composition of work piece material,
b. Microstructure of work piece material
c. Mechanical properties like ductility, toughness etc.
d. Physical properties of work materials.
e. Method of production of the work materials.
32. What are all the tool variables affecting the machinabiliry?
a. Tool geometry and tool material.
b. Nature of engagement of tool with the work.
c. Rigidity of tool.
33. What are the machine variables affecting the machinability?
a. Rigidity of machine. b. Power and accuracy of the machine tool.
34. How the machinability can be evaluated?
The following criteria suggested for evaluating machinability.
a. Tool life per grind,
b. Rate of removal per tool grind,
c. Magnitude of cutting forces and power consumption. Surface finish.
e. Dimensional stability of finished work.
f. Heat generated during cutting.
g. Ease of chip disposal.
h. Chip hardness, shape and size.
35. Mention the advantage of high machinability?
a. Good surface finish can be produced,
b. High cutting speed can be used,
c. Less power consumption,
d. Metal removal rate is high,
e. Less tool wear.
36. What is machinability index?
It is a comparison of machinability of different material to standard material. US material standard for 100% machinability is SAE 1112 hot rolled steel.
37. Classify the tool wear?
The tool wear is generally classified as follows, (i) Flank wear or crater wear (ii) Face wear (iii) Nose wear
38. How tool life is defined?
Tool life is defined as time elapsed between two consecutive tool resharpening. During, this period tool serves effectively and efficiently.
39. What are the ways of representing tool life?
The following are some of the ways of expressing tool life.
i. Volume of metal removed per grind,
ii. Number of work piece machined per grind, iii. Time unit.
40. What are the factors affecting tool life?
i. Cutting speed ii. Feed and depth of cut iii. Tool geometry iv. Tool material v. Cutting fluid vi. Work material vii. Rigidity of work, tool and machine.
41. Express the Taylor’s tool life equation.
Taylor’s tool life equation
VT ^ n = C
V= Cutting speed in m/min.
T = Tool life in minute
C = Constant
n = Index depends upon tool and work.
42. What are all the factors considered for selection of cutting speed?
i. Tool life ii.Properties of material being machined, iii.Rate of feed iv.Depth of cut v.Tool geometry. Vi.Cutting fluid used, vii.Type of machining process viii.Surface finish to be obtained.
43. What are the factors should be considered for selection of tool materials?
i. Volume of production
ii. Tool design
iii. Type of machining process
iv. Physical & Chemical properties
v. Rigidity and condition of machine.
44. What are the important characteristics?
i. Hot hardness
ii. Wear resistance
iv. Low friction
v. Cost of tool
vi. High thermal conductivity
vii. Resistance to thermal shock
viii. Easy to grind and sharpen.
45. Name any four tools material?
i. Carbon tool steel
ii. High speed steel
iii. Cemented carbides
46. What is the function of cutting fluids?
i. It is used to cool the cutting tool and work piece,
ii. It lubricates the cutting tool and thus reduces the co-efficient of friction between tool and work,
iii. It improves the surface finish as stated earlier,
iv. It causes the chips to break up into small parts,
v. It protects the finished surface from corrosion,
vi. It washes away the chips from the tool. It prevents the tool from fouling,
vii. It prevents corrosion of work and machine.
47. What are the properties of cutting fluid?
i. It should have good lubricant properties,
ii. High heat absorbing capacity,
iii. It should have a high specific heat, high heat conductivity and high film co-efficient,
iv. High flash point.
v. It should be odorless,
vi. It should be non-corrosive to work and tool,
vii.It should have low viscosity to permit free flow of the liquid.
48. What is built up edge?
During cutting process, the interface temperature and pressure is.
49. Briefly differentiate between orthogonal cutting i cutting?
- The cutting edge of the tool is perpendicular to the cutting velocity vector.
- The chip flows over the tool face and the direction of chip-flow velocity is normal to the cutting edge.
- The cutting edge clears the width of the work piece on either ends. (i.e. No side flow)
- The maximum chip thickness occurs at its middle.
- The cutting edge is inclined at an acute angle with normal to the cutting velocity vector.
- The chip flows on the tool face making an angle with the normal on the cutting edge.
- The cutting edge may or may not clear the width of the work piece.
- The maximum chip thickness may not occur at the middle.
50. Mention the various parts single point cutting tool?
1) Shank , 2) Face , 3) Flank , 4) Base, 5) Nose, 6) Cutting edge.
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