Geometric specifications
ISO recommendations for micro and macro geometry tolerancing of mechanical parts and their significance.

There are four main types of geometric specifications defined in ISO 1101 :

• geometric shape specifications ;

• geometric orientation specifications ;

• geometric position specifications ;

• geometric runout specifications.

A geometric specification is used to describe a requirement by defining :

• the toleranced element (the geometric element to be observed) ;

• the tolerance zone with or without orientation or position constraints.

The tolerance zone is the area of variation allowed for the toleranced element.

To fulfill certain functions, it is often necessary to specify certain geometric surface qualities: this is the role...