Tight tolerance machining controls the allowable size variation of a feature, while GD&T controls a part’s geometry, orientation, location, form, profile, and rotational behavior. The most effective CNC drawings use tight tolerances for critical fits such as shafts, bores, seals, and press-fit features, then use GD&T to define how those features relate to functional datums and mating components. This approach improves manufacturability, inspection consistency, assembly reliability, and total production efficiency.
