Limits, Tolerances and Fits 229
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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