Tolerances
How tolerances, nominal values, min/max limits, fits, and geometric controls affect comparison of mechanical and manufactured parts.
Back to Engineering FAQsView Engineering GuidesA nominal dimension does not show the allowed variation. Two parts can share the same nominal size but differ in tolerance, geometric control, surface finish, hole position, or material condition. The comparison should preserve tolerance and drawing context.
Compare the full acceptable range, not only the nominal value. A 10.00 +/- 0.05 mm part has a different acceptance window than a 10.00 +/- 0.20 mm part, even though the center value is identical.
Flatness, parallelism, perpendicularity, concentricity, runout, profile, and position control different aspects of geometry. They should not be collapsed into a generic dimensional tolerance field.
