General tolerances according to ISO 2768
Table of permissible deviations f, m, c and v with practical tips for drawings and large parts
ISO 2768 defines general tolerances for dimensions that have no individual tolerance on the drawing. Part 1 covers linear and angular dimensions in the classes f (fine), m (medium), c (coarse) and v (very coarse), Part 2 covers form and position in the classes H, K and L. The drawing states, for example, “ISO 2768-mK”.
MWA – Mechanische Werkstätten Anhalt GmbH in Halberstadt manufactures components to drawing in contract manufacturing up to 12,000 mm. With every enquiry, we check the tolerances on your drawing for feasibility free of charge.
Guide: general tolerances according to ISO 2768
The most important questions about general tolerances at a glance: click on a topic to expand it. This guide is a general overview; the text of the standard is authoritative.
Which permissible deviations apply according to ISO 2768-1?
Permissible deviations for linear dimensions without tolerance indication in mm, depending on the nominal size range and tolerance class:
| Nominal size (mm) | f (fine) | m (medium) | c (coarse) | v (very coarse) |
|---|---|---|---|---|
| 0.5 to 3 | ±0.05 | ±0.1 | ±0.2 | – |
| over 3 to 6 | ±0.05 | ±0.1 | ±0.3 | ±0.5 |
| over 6 to 30 | ±0.1 | ±0.2 | ±0.5 | ±1 |
| over 30 to 120 | ±0.15 | ±0.3 | ±0.8 | ±1.5 |
| over 120 to 400 | ±0.2 | ±0.5 | ±1.2 | ±2.5 |
| over 400 to 1,000 | ±0.3 | ±0.8 | ±2 | ±4 |
| over 1,000 to 2,000 | ±0.5 | ±1.2 | ±3 | ±6 |
| over 2,000 to 4,000 | – | ±2 | ±4 | ±8 |
What does “ISO 2768-mK” on the drawing mean?
Linear and angular dimensions without their own tolerance indication are subject to class m (medium) of ISO 2768-1, form and position tolerances to class K of ISO 2768-2. The indication is usually found in the title block of the drawing.
What does ISO 2768-2 cover?
With the classes H, K and L, Part 2 covers general form and position tolerances, for example straightness, flatness, perpendicularity, symmetry and run-out, unless these are toleranced individually. H is the finest class, L the coarsest.
Which class is common in mechanical engineering?
In mechanical engineering, class m or mK is usually used. Class f is used for precision mechanical parts, classes c and v mainly for welded assemblies and blanks.
What applies to large parts over 4,000 mm?
The ISO 2768-1 table ends at 4,000 mm. For larger components such as machine beds, frames or long welded assemblies, functionally important dimensions, flatness and parallelism should be toleranced directly on the drawing.
Equally important are the datum from which measurements are taken and the temperature during measurement: with 10 m of steel, 1 °C already causes a change in length of around 0.12 mm. Read more about large components on the Large part machining page.
When should you specify an individual tolerance?
- on fits, for example bearing seats H7/k6 according to ISO 286,
- on sealing surfaces and guideways (flatness, roughness Ra),
- on hole patterns that must align with other parts (position tolerance),
- on all dimensions over 4,000 mm.
Where the general tolerance is sufficient, you should deliberately not specify a finer tolerance: every tighter tolerance costs time in machining and measuring.
Is ISO 2768 still valid?
Yes, it is still widely used in practice. For new drawings, ISO 22081 (general geometrical specifications) is increasingly recommended. Today, you will find both on drawings.
How does MWA check the tolerances on your drawing?
With every enquiry, we check feasibility, tolerances and material and clarify any open points; you will receive our feedback within 24 hours on working days. Every component is inspected before delivery, on request with a measurement report on the characteristics of your drawing and a first article inspection report (FAI).
Send us your drawing via the enquiry form with file upload. You can read which tolerances are usual for each process on the CNC milling and Turning and grinding pages.
Would you like us to check your drawing?
Send us your drawing (PDF, STEP, DXF, DWG or IGES) with material, quantity and desired delivery date. We check feasibility free of charge and get back to you with a quote within 24 hours on working days.