Machine Drawing

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

Figure 15.5 shows dimensioning with a bilateral tolerance; the variation form the basic

size being equal on either side.