Here are some of the fundamental rules of geometric dimensioning and tolerancing per ANSI Y14.5:
- All dimensions must have a tolerance.
- Dimensions and tolerances shall completely define the nominal
(ideal) geometry and allowable variation.
- Dimensions and tolerances are valid at 20 deg C unless stated otherwise.
- Dimensions and tolerances are valid when the item is in a free state unless stated otherwise.
- Dimensions and tolerances apply to the full length, width, and depth of a feature.
- Dimensions and tolerances only apply at the level of the drawing
where they are specified.