1. Tolerances and fits

1.1 General

The inevitable imprecision of manufacturing processes, combined with the fact that perfect dimensional accuracy is not necessary for most machined parts, has led to the concept of tolerances.

In fact, for a feature of a part to fulfil its function correctly, it is sufficient for its actual dimensions to lie between two permissible limit dimensions, the difference between which constitutes the dimensional tolerance.

On the other hand, interchangeability - the basic concept of modern, economical manufacturing - and the need to increase international trade opportunities led to the principle of adjustment....