Page 232 - CITS - ED - Mechanical

ENGINEERING DRAWING - CITS

Fig 2

So the limits of the shaft are
20 - 0.007 = 19.993 mm

and 20 - 0.020 = 19.980 mm. (Fig 3)

Fig 3

Maximum clearance: In a clearance fit or transition fit, the maximum clearance is the difference between the
maximum size hole and the minimum size shaft. (Fig 4)
Minimum clearance: It is the clearance fit, the minimum clearance is the difference between the minimum hole
and the maximum shaft. (Fig 4)
The minimum clearance is 20.000 - 19.993 = 0.007 mm.

The maximum clearance is 20.021 - 19.980 = 0.041 mm. (Fig 4)
There is always a clearance between the hole and the shaft. This is the clearance fit.
Interference: It is the difference between the size of the hole and the shaft before assembly and this is negative.
In this case, the shaft is always larger than the hole size.

Fig 4

Interference fit: It is a fit which always provides interference. Here the tolerance zone of the hole will be below
the tolerance zone of the shaft. (Fig 5)
Example
Fit 25 H7/p6 (Fig 6)

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