Every fit falls into one of three categories based on the interaction between the hole and shaft tolerance zones.
In engineering, describes the relationship between two mating parts (typically a "hole" and a "shaft") and determines how tightly or loosely they fit together. This relationship is governed by tolerances , which are the allowable variations in dimensions to account for manufacturing imperfections. 1. The Three Main Types of Fits
: High-precision location where parts need to be snug but removable. Examples : H7/k6 (locational transition for dowel pins). 2. ISO 286 Notation System Fit Tolerance
: H7/p6 (light press), H7/s6 (medium drive fit for gear hubs).
: The shaft is always larger than the hole, requiring force or thermal expansion/contraction for assembly. Every fit falls into one of three categories
: The tolerance zones overlap; the resulting fit could be a slight clearance or a slight interference depending on the actual manufactured size.
: The shaft is always smaller than the hole, ensuring a gap for movement. : The tolerance zones overlap
The ISO 286 Standard uses an alphanumeric code (e.g., ) to define fits.