Level of tolerances required and possible tolerances depending on production processes
ISO recommendations for micro and macro geometry tolerancing of mechanical parts and their significance.

Having defined the dimensional characteristics and tolerances, the design office must ensure that its requirements are feasible, in terms of manufacturing and measurement or control.

This requires :

• the measurement uncertainty is relatively small compared with the tolerance, or take this into account in the conformity decision (see ISO 14253-1);

• the variability of manufacturing processes is compatible with the required tolerance (concept of capability indicator).

The dimensional tolerances permitted by the processes are generally related to the nominal value of the toleranced dimension, the material, or other parameters.