מחשבון סבולות כלליות — ISO 2768-1

ISO 2768 is an international standard that defines general tolerances for linear and angular dimensions on engineering drawings. Part 1 (ISO 2768-1) covers linear and angular tolerances, while Part 2 (ISO 2768-2) covers geometrical tolerances.

General tolerances apply to all dimensions on a drawing that do not have individual tolerances indicated. This simplifies drawings and reduces the number of tolerance notations needed.

General tolerances are appropriate when:

• Features are produced by standard machining (turning, milling, drilling)
• Normal workshop accuracy is sufficient for function
• Parts do not require tight fits or precision alignment

Do not rely on general tolerances for critical fits, mating surfaces, seal grooves, or bearing seats — these require individual tolerances.

The four tolerance classes represent increasing levels of permissible deviation:

• f (Fine) — Tightest tolerances. Precision machining with careful process control.
• m (Medium) — Most commonly used. Standard machining accuracy.
• c (Coarse) — Rough machining, welded assemblies, non-critical parts.
• v (Very Coarse) — Castings, forgings, flame-cut parts.

When in doubt, class m is the default for general machined parts.

Angular tolerances per ISO 2768-1 Table 2 depend on the shorter side of the angle being toleranced. As the shorter side length increases, the angular tolerance decreases (tighter).

For example, for class m: a 5 mm side gets ±1°, while a 200 mm side gets ±0°10′. The tolerance is given in degrees and minutes of arc.

Place the standard designation in the title block of the drawing:

• ISO 2768-m — Linear tolerances only, class m
• ISO 2768-mK — Linear class m + geometrical class K (ISO 2768-2)
• ISO 2768-fH — Linear class f + geometrical class H

No additional notation is needed on individual dimensions — the general tolerance automatically applies to all untoleranced dimensions.