# Engineering Metrology Questions and Answers – Meaning of Surface Texture

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

1. What is the importance of the valley in any irregular surface?
a) Reduce metal to metal contact
b) Retain film of lubricating oil
c) Reduce stress concentration
d) Improve surface texture

Explanation: The hills in any irregular surface helps in reducing metal to metal contact and valleys are useful to retain the film of lubricating oil on the surface otherwise it will be difficult to maintain lubricating oil film on the surface.

2. What is the relation between rate of wear and contact surface area?
a) Rate of wear is inversely proportional to the contact surface area
b) Rate of wear is directly proportional to the contact surface area
c) Rate of wear is inversely proportional to the square of contact surface area
d) Rate of wear is directly proportional to the square of contact surface area

Explanation: If any surface has large number of irregularities i.e. hills and valley then the surface will obtain good bearing properties. Rate of wear is proportional to the load per unit area and surface area in contact.

3. Which of the following option is true for given statements about surface texture?
Statement 1: Concept of surface roughness is sensory.
Statement 2: Failure due to fatigue starts always at sharp corners.
a) T, F
b) F, T
c) F, F
d) T, T

Explanation: Concept of a roughness of surface is sensory. Surface roughness has been understood by a sense of touch and light. Failure due to Fatigue starts at sharp corner because at sharp corners stress concentration is more and that part fails earlier.

4. Which of the following is not true about first order irregularities?
a) Arising due to irregularities in machine tool itself
b) Arising due to weight of material itself
c) Arise due to vibrations
d) May arises due to deformation of work under action

Explanation: First order irregularities includes the irregularities arising out of inaccuracies in the machine tool itself. This includes the irregularities on surface arising due to work deformation under the action of cutting forces and the material weight itself.

5. Under which group, does waviness in surface falls?
a) Primary texture
b) Secondary texture
c) Tertiary texture
d) Quaternary texture

Explanation: If the hills and valleys are not close to each other or they both are far apart, it is due to the machine tool imperfections and this is referred to as waviness or secondary texture.
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6. In how many categories, geometrical irregularities can be classified?
a) 3
b) 2
c) 4
d) 5

Explanation: Geometrical irregularities can be classified into four categories i.e. First Order, Second Order, Third Order, Fourth Order and these four categories are further grouped under two groups.

7. Match the following order with their irregularities.

```A. First Order		-	1. Feed marks of cutting tool
B. Second Order 	-	2. Lack of straightness of guideways
C. Third Order		-	3. Rupture of material during chip removal
D. Fourth Order	        -	4. Vibrations```

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

Explanation: Second order Irregularities caused by vibrations due to any reason such as chatter marks. If the machine is perfect and free of vibrations, some irregularities can be caused by machining itself due to the characteristic of the process, such type of irregularities include third order. Fourth order includes the irregularities due to rupture of the material during the chip removal.

8. Under which group, does third order irregularities fall?
a) Primary group
b) Secondary group
c) First group
d) Second group

Explanation: Irregularities of small wavelength falls under second group and caused by the direct action of the cutting element or by some disturbance such as friction. It includes irregularities of third and fourth order.

9. Which type of irregularities comes under the first group?
a) First and second order
b) Second and third order
c) Third and fourth order
d) First and fourth order

Explanation: First group includes irregularities of considerable wave-length. These errors include irregularities of first and second order. These are mainly due to misalignment of centres. These errors are also referred to as Waviness.

10. Which of the following is true about texture in case of finishing process?
a) Directional and irregular
b) Regular and directional
c) Irregular and non-directional
d) Regular and non-directional

Explanation: In case of finishing process, the texture is non-directional and non regular while if the surface is machined by a single point cutting tool then the surface will have roughness which is directional and uniformly spaced.

11. Under which category, does the error arises due to non-linear feed motion falls?
a) Second group
b) Primary texture
c) Waviness
d) Roughness

Explanation: The error caused by lack of straightness of guide-ways and non-linear feed motion are also referred to as Waviness or Secondary Texture. These errors or irregularities are of considerable wavelength.

12. Which of the following option is true if hills and valleys on any surface are very close?
a) Wavelength is more
b) Wavelength is small
c) Surface appears more wavy
d) Surface appears rough but wavelength is more

Explanation: If the hills and valleys are close to each other on any surface then the wavelength is very small and the surface appears rough and if they are far apart then the wavelength is more and appears more wavy.

13. Which term is used for errors of first and second order?
a) Micro geometrical error
b) Macro geometrical error
c) Mini geometrical error
d) Mili geometrical error

Explanation: The error or irregularity falls under first and second order are also termed as macro-geometrical errors and the irregularities or error of third and fourth order are termed as micro-geometrical errors.

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