Geometric Dimensioning and Tolerancing — a symbolic language for specifying allowable variation.
GD&T controls form, orientation, location and runout, which size tolerances alone cannot. A cylindrical part specified only by diameter can be oval, tapered or bent and still pass; a GD&T callout constrains those.
The system is defined by ASME Y14.5 in North America and ISO 1101 internationally, and the two are similar but not identical — mixing them on one drawing is a real hazard.
Using a feature control frame without a datum reference. Without a datum the tolerance has nothing to be measured against.
This site uses Google Analytics to count visits and see which pages are useful. It sets cookies only if you agree. See the privacy policy.