# Engineering Metrology Questions and Answers – Bench Centres

This set of Engineering Metrology Multiple Choice Questions & Answers (MCQs) focuses on “Bench Centres”.

1. What is the material of the bench center’s base?
a) Copper
b) Wood
c) Cast Iron
d) Steel

Explanation: The base of Bench centre is generally made from close-grained cast iron and should be free from any casting defect. Defects may cause error and failure of materials.

2. Why T- slots are provided on the base of bench centres?
a) To reduce its weight
b) For the attachment of centre holders
c) For the attachment of base to table

3. What is the range in which distance between the centres varies?
a) 100 to 200 mm
b) 200 to 400 mm
c) 300 to 400 mm
d) 500 to 1500 mm

Explanation: Distance between the centres in centre bench depends upon the centre height and varies between 500 to 1500 mm with centre height accordingly.

4. Which of the following is incorrect about bench centre’s physical characteristics?
a) Centre holders may be located in any position
b) Box type straight edges have a rigid cross section for minimum deflection
c) Minimum hardness of bench centre’s base is 180 HB
d) Male or female centres are non-adjustable on bench centres

Explanation: Along the vees of the centre holders, male or female centres can be adjusted and locked in any desired position.

5. What will happen due to out-of-straightness of a part?
a) Less finished surface of part
b) No error in roundness
c) Failure of a part
d) Doubling run out effect

Explanation: A doubling run out effect and roundness error is caused by out-of-straightness of the part. Run out is also called as out-of true running.

6. What are the centre heights that available for Bench centres?
a) 125 mm
b) 125, 160 mm
c) 125, 250 and 300 mm
d) 125, 160, 200, 250 and 300 mm

Explanation: 125, 160, 200, 250 and 300 mm heights of centres are available in bench centres and according to these heights, centre distance is decided.

7. Match the following apparatus with the function they perform.

```A) Straight Edges         1) Checking Eccentricity
B) V-Blocks               2) Checking Flatness
C) Bench Centres          3) Small angle measurement
D) Spirit Level           4) Checking Roundness```

a) A-2, B-4, C-1, D-3
b) A-1, B-2, C-3, D-4
c) A-3, B-1, C-4, D-2
d) A-4, B-3, C-2, D-1

Explanation: Straight edges are used with surface plates to check straightness and flatness. V-blocks are used to check roundness of cylindrical pieces. Bench centres are used for rotary components to check eccentricity. Spirit levels are used to measure small inclination.

8. How much deviation is permitted in parallelism of centres axis w.r.t. guideways for 125-160 mm center height?
a) 0.01 mm/200 mm
b) 0.01 mm/300 mm
c) 0.1 mm/300 mm
d) 0.001 mm/300 mm

Explanation: This permissible deviation in parallelism is specified by IS: 1980-1978.

9. Which option is correct for given statements about out of roundness of V blocks?
Statement 1: Shafts can be out-of-roundness due to improper centre alignment.
Statement 2: Adjustable V-Blocks can be used to show out-of-roundness.
a) T, T
b) T, F
c) F, T
d) F, F

Explanation: Many factors affects the roundness of shafts like angle of centres, alignment of centres, centre holes, run-out of piece etc. Adjustable V-Blocks can be used to measure correct roundness.

Sanfoundry Global Education & Learning Series – Engineering Metrology.

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