The tolerance is the difference between the permissible maximum and minimum value of a measurable property such as dimension, hardness, surface quality etc.
A property of particular importance in connection with straightening is "dimension", e.g. in the geometry of a straightener and in the curvature of the product to be straightened.
See Also
Adapted from “"We do it straight" — Wire Straightening”, p. 191 (ISBN 3-00-005897-4).