Writing a separate tolerance for every dimension on a drawing is impractical. ISO 2768 defines the deviations that apply to dimensions without an individual tolerance.
Classes
The standard has classes f (fine), m (medium), c (coarse) and v (very coarse). In machining the most common is ISO 2768-m; ISO 2768-f is preferred for precision parts.
Example values (linear dimensions)
- 6–30 mm: ±0.2 mm in class m, ±0.1 mm in class f
- 30–120 mm: ±0.3 mm in class m, ±0.15 mm in class f
When do you need a specific tolerance?
Bearing seats, pin holes and mating surfaces should not be left to general tolerance. Specify fits such as H7 or g6 on these dimensions. Unnecessarily tight tolerances increase cost; our engineers advise on this in the quote.
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