Page 220 - CITS - ED - Mechanical

ENGINEERING DRAWING - CITS

TABLE 2

Indication of special surface roughness characteristics.
In certain circumstances, for functional reasons, it may be necessary to specify additional special requirements
concerning surface roughness.
If it is required that the final surface roughness be produced by one particular production method, this method
should be indicated in plain language on an extension of the longer leg of the symbol shown in Fig 8.
Also on this extension line should be given any indications relating to treatment or coating.
Unless otherwise stated, the numerical value of the roughness applies to the surface roughness after treatment
of coating.
If it is necessary to define surface roughness both before and after treatment, this should be explained in a suitable
note or in accordance with Fig 9.
If it is necessary to indicate the sampling length, it should be selected from the series given in IS:3073-1967 `As-
sessment of surface roughness', and be stated adjacent to the symbol, as shown in Fig 10a.
If it is necessary to control the direction of lay, it is specified bya symbol (see Table 3) added to the surface rough-
ness symbol as shown in Fig 10b.

Note: The direction of lay is the direction of the predominant surface pattern, ordinarily determined
by the production method employed.
Symbols for the direction of lay: The series of symbols for the common directions of lay are specified in Table 3.

Fig 8 Fig 10

Fig 9

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CITS :Engineering Drawing (Mechanical) - Exercise 9 CITS :Engineering Drawing (Mechanical) - Exercise 9