Interpretation of part dimensional limits
Limit gauges for checking smooth parts

As no real surface has a perfect shape, the numerical value defining a limit remains an abstraction until it is materialized by a measuring instrument. The latter, through its structure and methods of use, gives concrete meaning to this value.

On the other hand, the nature of the criteria verified and the methods used to verify them must be determined with a view to ensuring the necessary and sufficient conditions for the surface to be fit for purpose.