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Clearance and press fits

A fit describes how a shaft and a hole with the same nominal size go together. In a clearance fit the shaft is always a bit smaller than the hole, so the parts slide together by hand. In a press fit the shaft is a bit larger, and the parts must be pressed or shrink-fitted together to grip by friction.

\text{Clearance: } d_{shaft} < D_{hole}

the parts always have clearance

\text{Press: } d_{shaft} > D_{hole}

the parts always have interference

Symbols

$d_{shaft}$	shaft diameter	mm
$D_{hole}$	hole diameter	mm

Example

H7/g6 is a clearance fit:

the g shaft is always below nominal size, the H hole always above.

H7/g6 always gives clearance, H7/p6 always gives interference – the shaft letter decides the type.

Practise tolerances and fits for free →

← Bending stress and section modulus · Hole-basis system (IT tolerances) →

Part of Machine Design: Tolerances and fits.