Machine Drawing

250 Machine Drawing

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z

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(a) (b)

Fig. 16.10

THEORY QUESTIONS

16.1 What is the importance of surface roughness?

16.2 Mention the geometrical characteristics of a surface.

16.3 Define the following terms :

(a) reference profile, (b) datum profile,

(c) mean roughness index (d) surface roughness number.

16.4 What are the various means that are used to determine the surface roughness value?

16.5 How surface roughness values are indicated on a drawing?

16.6 Indicate how various surface roughness specifications are placed relative to the symbol.

16.7 Indicate roughness grade symbols for the following roughness grade numbers :

(a)N 12 (b)N 10 (c)N 8

(d)N 6 (e)N 2

16.8 What is meant by direction of lay? How is it shown on a drawing? Sketch the symbols related to

the common directions of lay.

DRAWING EXERCISES

16.1 Indicate the roughness grade symbols used in shop floor practice, with their range of roughness

values.

16.2 What are the roughness values that can be normally obtained by (a) fine turning, (b) machine

reaming, (c) milling, (d) precision grinding and (e) chrome plating.

16.3 Show how the roughness is indicated on the component for the following situations.

(a) surface to be obtained by any production method,

(b) surface to be obtained without removal of material

(c) surface to be coated, and

(d) surface to be given a machining allowance.

16.4 With examples, show the method of indicating surface roughness on the following components :

(a) symmetrical surfaces requiring the same quality,

(b) cylindrical part, and (c) same surface quality all over.

16.5 Suggest suitable surface finish values and the process of obtaining them for the following compo-

nents :

(a) precision drill sleeve, (b) grade 1 milling machine column guide-ways,

(c) splines on a shaft, (d) faces of a milling arbor spacer, and

(e) precision lathe bed guide-ways.