# Engineering Metrology Questions and Answers – Surface Roughness

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

1. What is meant by roughness?
a) Minute succession of hills of different height
b) Minute succession of valleys and hills of different height and varied spacing
c) Minute succession of valleys and hills of same height and same gap
d) Minute succession of valleys of different depth

Explanation: Imperfections are bound to be on surface and they take the form of succession of hills and valleys which vary in height and spacing which result in irregularity of the surface. Roughness is the form of these minute imperfections.

2. Surfaces produced by straight and cylindrical grinding tools tend to create which type of roughness?
a) Regularly spaced but directional roughness
b) Regularly spaced but non directional roughness
c) Irregularly spaced but directional roughness
d) Irregularly spaced but non directional roughness

Explanation: The roughness on the surface tends to be both irregularly spaced and directional in straight and cylindrical grinding and in the case of boring or lapping process the surface roughness tends to be irregular and non-directional in nature.

3. Which of the following is necessary for the complete study of surface roughness?
a) Measurement of all the components of elements
b) Analysis of all the component element
c) Assessment of the effects of combined texture
d) Measurement and analysis of all the components and assessment of combined texture

Explanation: For the complete study of the surface roughness, it is important that the analysis and measurement of all the component elements be made and an assessment of the effects of the combined texture be made.

4. Which of the following is true for measurement of surface roughness?
a) 3 dimensional geometry can be easily measured
b) Direction of measurement is perpendicular to the lay
c) Direction of measurement is parallel to the lay
d) Direction of measurement is parallel to the direction of the predominant surface marking

Explanation: There are difficulties in the measurement of surface roughness in three dimensional geometry, but for simplification purposes, it is reduced into two dimensional geometry. To measure, the direction is generally perpendicular to the direction of the predominant surface markings or “lay”.

5. How much a stylus instrument can be magnified to plot or find minute irregularities?
a) 50 times
b) 500 times
c) 5000 times
d) 50,000 times

Explanation: The shape of the hills and valleys is best studied in a cross-section normal to the surface using a stylus instrument which plots a graph in which even the minute irregularities are magnified upto 50,000 times whereas the length over which observations are made is magnified only by 50-300 times.
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6. Which of the following is true about Tomlinson surface meter?
a) It is a mechanical instrument
b) It is an electrical instrument
c) It is a mechanical cum optical instrument
d) It is an optical instrument

Explanation: The Tomlinson surface meter uses mechanical cum optical means for magnification. It has a diamond stylus on the surface finish recorder. This instrument is given reliable results.

7. What do you mean by dominant spacing?
a) Distance between successive peaks when irregularities are comparatively uniform in shape and size
b) Distance between middle point of successive hills when irregularities are comparatively uniform in shape and size
c) Distance between middle point of successive valleys when irregularities are comparatively uniform in shape and size
d) Distance between successive peaks when irregularities are regardless of shape and size

Explanation: When the irregularities are uniform in shape and size, then the distance between the peaks or successive peaks is described as pitch or dominant spacing. These spacings are measured by using an instrument.

8. Which of the following is used for the direct measurement of surface quality and commonly used in U.S.A.?
a) Profilometer
b) Tomlinson surface meter
c) Talysurf
d) Replica method

Explanation: Profilometer is most commonly used in U.S.A. It is used for direct measurement of surface quality. It is a dynamic instrument and principle is similar to the gramophone pick-up.

9. Which of the following parameter is important for specifying surface roughness?
a) Size of irregularity
b) Spacing of irregularity
c) Height of irregularities
d) Height, spacing and form of irregularities

Explanation: The surface roughness is concerned with both the size and the shape of the irregularities. Both size and shape i.e. height of irregularities, their spacing and form are important for specifying surface roughness.

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