Material properties and Metal Forming (Machining) Processes - Set 03

Practice Test: Question Set - 03

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1. Which type of motor is not used in axis or spindle drives of CNC machine tools?

(A) Induction motor

(B) DC servo motor

(C) Stepper motor 

(D) Linear servo motor

Answer: Option C
Explanation: A spindle motor is a small, high precision, high reliability electric motor that is used to rotate the shaft or spindle used in machine tools for performing a wide range of tasks like drilling, grinding, milling etc. A stepper motor has not all these characteristic due to change of direction of rotation with time interval.

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2. The main purpose of spheroidising treatment is to improve

(A) Hardenability of low carbon steels

(B) Machinability of low carbon steels

(C) Hardenability of high carbon steels

(D) Machinability of high carbon steels

Answer: Option D
Explanation: Spheroidising may be defined as any heat treatment process that produces a rounded or globular form of carbide. High carbon steels are spheroidized to improve machinability, especially in continuous cutting operations.

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3. NC contouring is an example of

(A) Continuous path positioning

(B) Point-to-point positioning

(C) Absolute positioning

(D) Incremental positioning

Answer: Option A
Explanation: NC contouring is a continuous path positioning system. Its function is to synchronize the axes of motion to generate a predetermined path, generally a line or a circular arc.

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4. A ring gauge is used to measure

(A) Outside diameter but not roundness

(B) Roundness but not outside diameter

(C) Both outside diameter and roundness

(D) Only external threads

Answer: Option A
Explanation: Ring gauges are used for gauging the shaft and male components i.e. measure the outside diameter. It does not able to measure the roundness of the given shaft.

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5. When the temperature of a solid metal increases,

(A) Strength of the metal decreases but ductility increases

(B) Both strength and ductility of the metal decreases

(C) Both strength and ductility of the metal increases

(D) Strength of the metal increases but ductility decreases

Answer: Option A
Explanation: When the temperature of a solid metal increases, its intra molecular bonds are brake and strength of solid metal decreases. Due to decrease its strength, the elongation of the metal increases, when we apply the load i.e. ductility increases.

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6. The strength of a brazed joint

(A) Decreases with increase in gap between the two joining surfaces

(B) Increases with increase in gap between the two joining surfaces

(C) Decreases up to certain gap between the two joining surfaces beyond which it increases

(D) Increases up to certain gap between the two joining surfaces beyond which it decreases

Answer: Option D
Explanation: We know that, the strength of the brazed joint depends on (a) joint design and (b) the adhesion at the interfaces between the work piece and the filler metal. The strength of the brazed joint increases up to certain gap between the two joining surfaces beyond which it decreases

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7. In order to have interference fit, it is essential that the lower limit of the shaft should be

(A) Greater than the upper limit of the hole

(B) Lesser than the upper limit of the hole

(C) Greater than the lower limit of the hole

(D) Lesser than the lower limit of the hole

Answer: Option A
Explanation: The interference is the amount by which the actual size of a shaft is larger than the actual finished size of the mating hole in an assembly. For interference fit, lower limit of shaft should be greater than the upper limit of the hole.

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8. When 3-2-1 principle is used to support and locate a three dimensional work-piece during machining, the number of degrees of freedom that are restricted is

(A) 7

(B) 8

(C) 9

(D) 10

Answer: Option C
Explanation: According to 3-2-1 principle, only the minimum locating points should be used to secure location of the work piece in any one plane.
(A) The work piece is resting on three pins A, B, C which are inserted in the base of fixed body. The work piece cannot rotate about the axis XX and YY and also it cannot move downward. In this case, the five degrees of freedom have been arrested.
(B) Two more pins D and E are inserted in the fixed body, in a plane perpendicular to the plane containing, the pins A, B and C. Now the work piece cannot rotate about the Z -axis and also it cannot move towards the left. Hence the addition of pins D and E restrict three more degrees of freedom.
(C) Another pin F in the second vertical face of the fixed body, arrests degree of freedom 9.

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9. Which among the NC operations given below are continuous path operations?

Arc Welding (AW), Drilling (D), Laser Cutting of Sheet Metal (LC), Milling (M), Punching in Sheet Metal (P), Spot Welding (SW)

(A) AW, LC and M

(B) AW, D, LC and M

(C) D, LC, P and SW

(D) D, LC, and SW

Answer: Option A
Explanation: Arc welding, Laser cutting of sheet and milling operations are the continuous path operations.

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10. In an interchangeable assembly, shafts of size 25.000 -_0.0100⁺⁰∙⁰⁴⁰ mm mate with holes of size 25.000 -_0.010⁺⁰∙⁰²⁰ mm. The maximum possible clearance in the assembly will be

(A) 10 microns

(B) 20 microns

(C) 30 microns

(D) 60 microns

Answer: Option C
Explanation: We know that maximum possible clearance occurs between minimum shaft size and maximum hole size.
Maximum size of shaft = 25 + 0.040 = 25.040 mm
Minimum size of shaft = 25 − 0.100 = 24.99 mm
Maximum size of hole = 25 + 0.020 = 25.020 mm
Minimum size of hole = 25 − 0.000 = 25.00 mm
25.020 − 24.99 = 0.03mm = 30 microns

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11. During the execution of a CNC part program block

      NO20 GO2 X45.0 Y25.0 R5.0 ; the type of tool motion will be

(A) Circular Interpolation − clockwise

(B) Circular Interpolation − counter clockwise

(C) Linear Interpolation

(D) Rapid feed

Answer: Option A
Explanation: Given:-NO20 GO2 X45.0 Y25.0 R5.0
Here term X45.0 Y25.0 R5.0 will produce circular motion because radius is consider in this term and GO2 will produce clockwise motion of the tool.

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12. The mechanism of material removal in EDM process is

(A) Melting and Evaporation

(B) Melting and Corrosion

(C) Erosion and Cavitations

(D) Cavitations and Evaporation

Answer: Option A
Explanation: In EDM, the thermal energy is employed to melt and vaporize tiny particles of work material by concentrating the heat energy on a small area of the work-piece.

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13. The percentage of carbon in gray cast iron is in the range of

(A) 0.25 to 0.75 percent 

(B) 1.25 to 1.75 percent

(C) 3 to 4 percent

(D) 8 to 10 percent

Answer: Option C
Explanation: Gray cast iron is the most widely used of all cast irons. In fact, it is common to speak of gray cast iron just as cast iron. It contains 3 to 4% C and 2.5 % Si.

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14. Cold working of steel is defined as working

(A) At its recrystallisation temperature

(B) Above its recrystallisation temperature

(C) Below its recrystallisation temperature

(D) At two thirds of the melting temperature of the metal

Answer: Option C
Explanation: Cold forming or cold working can be defined as the plastic deforming of metals and alloys under conditions of temperature and strain rate. Theoretically, the working temperature for cold working is below the recrystallisation temperature of the metal/alloy (which is about one-half the absolute melting temperature).

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15. Quality screw threads are produced by

(A) Thread milling

(B) Thread chasing

(C) Thread cutting with single point tool

(D) Thread casting

Answer: Option D
Explanation: Quality screw threads are produced by only thread casting. Quality screw threads are made by die-casting and permanent mould casting is very accurate and of high finish, if properly made.

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View All Answers

(1) Answer: Option C
(2) Answer: Option D
(3) Answer: Option A
(4) Answer: Option A
(5) Answer: Option A
(6) Answer: Option D
(7) Answer: Option A
(8) Answer: Option C
(9) Answer: Option A
(10) Answer: Option C
(11) Answer: Option A
(12) Answer: Option A
(13) Answer: Option C
(14) Answer: Option C
(15) Answer: Option D

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