Control and measurement
ISO recommendations for micro and macro geometry tolerancing of mechanical parts and their significance.

The preceding paragraphs have described geometric, dimensional and surface finish requirements. To be able to justify the conformity of the parts produced, it will be necessary to set up a product verification process. This necessarily includes notions of measurement or control:

• measurement" will enable us to define a quantity for a given part with a dimensional, geometric or surface finish characteristic. This value (R) will necessarily be associated with a measurement uncertainty (U) giving the complete measurement result: R ± U (see the guide to expressing measurement uncertainties);

• control, on the other hand, will enable us to define the notion of conformity directly, as with the use of an in/out gauge, or indirectly, through measurement and comparison with the required tolerances.