In article , Robin S. says...

Indeed, this is very important. I think Eric touched on the idea that the
effective diameter (such that it clears a nominally-sized shaft) is not the
same as the diameter at any given point in the hole, necessarily. Geometric
dimensioning and tolerancing addresses these issues. Simply having an X and
Y positional tolerance as well as a diameter tolerance will not suffice when
one is designing very precise holes. A tolerance zone must be defined that
extends at least throughout the entire length of the hole, and perhaps
beyond its physical boundaries.

Cylindricity of a bore is actually a pretty tough
issue.

Jim

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