# Engineering Metrology Questions and Answers – Straightness

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

1. Who gave the fundamental principle of straightness measurement?
a) Bryan
b) Moire
c) Euler
d) Amedeo

Explanation: Fundamental principle of measurement of straightness is given by Bryan. According to this principle, “A straightness measurement system should be in line with the point at which it is to be measured”.

2. Which of the following represents the quality of straightness in precision engineering?
a) Spirit level
b) Straight edge
c) Autocollimator
d) Dial indicator

Explanation: At many places, it is necessary that the surface must be straight e.g. in lathe machine it is required that the tool must move in straight path. Straight line is the basis of most methods of measurements.

3. What is the tolerance of the straightness of a line?
a) Maximum deviation from the straight line joining two extremities
b) Maximum deviation from the middle point of straight line joining two extremities
c) Minimum deviation from the straight line joining two extremities
d) Minimum deviation from the middle point of straight line joining two extremities

Explanation: The tolerance on the straightness of a line can be defined as the maximum deviation in
relation to the reference straight line joining the two extremities of the line to be checked. Tolerance is used to confirm that a part is uniform over a surface. More straightness is present with less tolerance.

4. For checking straightness, straight edge is placed over a surface and these two are viewed against the light. Which of the following option true if colour of light is red?
a) Gap between 0.12 to 0.17 mm
b) Gap between 0.2 to 0.7 mm
c) Gap between 1.7 to 2 mm
d) Gap between 0.0012 to 0.0017 mm

Explanation: Straight edge and surface are viewed against the light. The gap between surface and straight edge should be negligible small for perfect straight surfaces and the measurement of straightness is observed by seeing the colour of light produced due to interference caused by diffraction of light.

5. What is the name of a pair of straight edges?
a) Drum sticks
b) Lower pair
c) Winding sticks
d) Self closed pair

Explanation: Straight edge is a measuring tool consist of a steel and is used to check the straightness. Straight edges are used in machining industry and automotive service. Winding stick is a pair of straight edges which are used in woodwork.

6. What is the position of straightness interferometer in straightness measurement optics?
b) After straightness reflector
c) Between laser head and straightness reflector
d) No need of interferometer

Explanation: Straightness interferometer is placed between laser head and reflector. Beam from the laser passes through the interferometer which splits it into two beams which diverge at an angle and are directed to the reflector. The beams are then reflected from the reflector and return to the interferometer along a new path.

7. What is the range of straightness measurement in straightness measurement optics?
a) ±2.5 mm
b) ±5 mm
c) ±10 mm
d) ±20 mm

Explanation: To measure straightness errors in a linear axis, straightness measurement optics are used. For both short range and long range measurement, length of straightness measurement is ±2.5 mm.

8. Which of the following is not the factor affecting the accuracy of straightness measurement by optics?
a) Air turbulence
b) Optics fixed rigidly
c) Slope error
d) Localised heat sources

Explanation: Factors affecting the accuracy of straightness measurement by optics are Air turbulence, Mechanical vibrations, Optic errors, Slope errors, Optics not fixed in the correct position, Optics not fixed rigidly, Localised heat sources etc.

9. At which part of the precision straight edge is generally lapped?
a) Edges only
b) Base only
c) Base and edges both
d) All over the surface

Explanation: Straight edges are extremely useful for setting up machines such as planers. Precision straight edges are hardened and lapped on the edges by a small radius, which makes a blunt knife edge straight to a few thousands of an mm.

Sanfoundry Global Education & Learning Series – Engineering Metrology.

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