Let us talk about machining allowance vs. tolerance.
We emphasized the use of the word ‘intentional’ as it is the main distinguishing factor between the often confusing concepts of machining allowance and tolerance. While tolerance is also about how much extra/less material is on a workpiece, it is not something that is done intentionally.
Rather, it accounts for the acceptable amount of unintentional variation in the workpiece dimensions. It relates to the fact that it is impossible to achieve the exact dimensions of a part, so engineers define CNC machining tolerances to give manufacturers a target range to stay within.