Machine Drawing

Limits, Tolerances and Fits 229

dharm
d:\N-Design\Des15-2.pm5

15.4.3.2 Maximum interference

It is the magnitude of the difference between the minimum size of the hole and the maximum

size of the shaft in an interference or a transition fit before assembly.

The shaft in Fig. 15.12 is larger than the hole, so it requires a press fit, which has an

effect similar to welding of two parts. The value of minimum interference is 30.25 – 30.30

= – 0.05 mm and maximum interference is 30.15 – 30.40 = – 0.25 mm.

Max. size of shaft

Shaft tolerance

Max. interference (Allowance)

Min. size of hole =

basic size

Hole tolerance

Max. diameter of hole

f30.40

Min. dia. of shaft

f30.15

f30.30

f30.25

Min. interference

Fig. 15.12 Interference fit

Figure 15.13 shows the conventional representation of these three classes of fits.

Hole Hole

Shaft

Shaft

Clearance fit

Hole

Shaft

Shaft

Shaft

Transition fit

Hole Hole

Shaft

Shaft

Interference fit

Fig. 15.13 Schematic representation of fits