226 Machine Drawing
dharm
d:\N-Design\Des15-1.pm5
f25H7 f25h9
40 C11
10 H10
40 h11
10 h9
Fig. 15.4 Toleranced dimensions for internal and external features
The terms φ 40 H11 and 10h9 refer to external features, since the terms involve lower
case letters. The letter ‘h’ signifies that the upper deviation is zero (Fig. 15.3) and the number
symbol 11 signifies the grade, the value of which is 160 microns (Table 15.1), which in-turn is
equal to the lower deviation.
Method 2
In this method, the basic size and the tolerance values are indicated above the dimension line;
the tolerance values being in a size smaller than that of the basic size and the lower deviation
value being indicated in line with the basic size.
55
±0.02
40
- 0.03
60.5
±0.05
40
- 0.02
40
+ 0.02
+ 0.02
- 0.06
+ 0.06
Fig. 15.5 Bilateral tolerance of Fig. 15.6 Bilateral tolerance of
equal variation unequal variation
60
– 0.05 50.05
50.00
50.00
49.90
- 0.00
55
+ 0.00
+ 0.05
Fig. 15.7 Unilateral tolerance with zero Fig. 15.8 Maximum and minimum
variation in one direction size directly indicated