The following data reflects standard permissible deviations for common machining workshops. 1. Linear Dimensions (ISO 2768-1) Values in mm Nominal Length (mm) m (medium) c (coarse) v (very coarse) Over 3 to 6 Over 6 to 30 Over 30 to 120 Over 120 to 400 2. Straightness & Flatness (ISO 2768-2) Values in mm Range (mm) 100 to 300 Downloadable Reference Guides
ISO 2768 is a set of international standards that specifies general tolerances for linear and angular dimensions and for geometrical tolerances on parts made by machining, stamping, casting, forging, etc., when no individual tolerance is indicated on the drawing. It prevents over-specifying tolerances for non-critical features, simplifies drawings, and reduces manufacturing cost while maintaining fit and function. iso 2768 general tolerances pdf exclusive
Angles are treated specially. For a 90° angle on a large part, a ±0.5° tolerance is massive. ISO 2768-1 uses to determine tolerance. Straightness & Flatness (ISO 2768-2) Values in mm