| Shorter side length range | Tolerance (mm) | |----------------------------|----------------| | ≤ 100 | 0.2 | | >100 – 300 | 0.3 | | >300 – 1000 | 0.4 | | >1000 – 3000 | 0.5 |

In the world of technical drawing and mechanical engineering, specifying every single dimension with a unique tolerance is impractical, time-consuming, and clutters the blueprint. This is where general tolerances come into play. Among the most widely recognized standards globally is ISO 2768, and within that standard, the specific class "mk" represents a critical balance between manufacturing cost and precision.

This article provides an exhaustive deep dive into ISO 2768-mk, explaining what it means, when to use it, how to interpret its tables, and its real-world implications for CNC machining, quality control, and design engineering.

These tolerances apply to features like external lengths, step heights, and diameters.

| Nominal Dimension Range (mm) | Tolerance (mm) | | --- | --- | | 0.5 up to 3 | ±0.1 | | >3 up to 6 | ±0.1 | | >6 up to 30 | ±0.2 | | >30 up to 120 | ±0.3 | | >120 up to 400 | ±0.5 | | >400 up to 1000 | ±0.8 | | >1000 up to 2000 | ±1.2 |

Example: If a shaft length is specified as 50 mm with no individual tolerance, ISO 2768-mk permits a length between 49.7 mm and 50.3 mm.