Recommended title block note examples:
| Nominal Size Range (mm) | Tolerance (mm) | |------------------------|----------------| | 0.5 up to 3 | ±0.2 | | >3 up to 6 | ±0.5 | | >6 up to 30 | ±1.0 | | >30 up to 120 | ±2.0 | | >120 up to 400 | ±4.0 |
Myth: "ISO 2768-mh allows anything to be sloppy." Reality: A 0.2mm deviation on a 6mm shaft is a 3.3% error. For general machinery, that is acceptable. For a wristwatch, it is a disaster. The standard is not "sloppy"; it is "economical." iso 2768-mh tolerance chart
Myth: "If I write ISO 2768-mh, I never have to tolerance diameters." Reality: Diameters (like a Ø10mm hole) follow the SAME linear chart. A Ø10mm hole could be Ø10.2mm. That is an H11 tolerance loose fit. For a running fit, you still need an explicit H7 or G6.
Myth: "The 'H' means the same as the 'm'." Reality: No. 'H' is specifically from ISO 2768-2. It defines geometry, not size. A part can be the wrong size (within 'm') but perfectly flat (within 'H'). Recommended title block note examples: | Nominal Size
Limitations:
Pitfalls:
Best practices:
If you are a quality engineer receiving parts with this note, follow these guidelines: Myth: "ISO 2768-mh allows anything to be sloppy
| Nominal Dimension Range (mm) | Tolerance (mm) | Interpretation | | :--- | :--- | :--- | | 0.5 up to 3 | ±0.1 | +/- 0.1mm (100 microns) | | >3 up to 6 | ±0.1 | +/- 0.1mm (100 microns) | | >6 up to 30 | ±0.2 | +/- 0.2mm (200 microns) | | >30 up to 120 | ±0.3 | +/- 0.3mm (300 microns) | | >120 up to 400 | ±0.5 | +/- 0.5mm (500 microns) | | >400 up to 1000 | ±0.8 | +/- 0.8mm (800 microns) | | >1000 up to 2000 | ±1.2 | +/- 1.2mm (1.2mm) | | >2000 up to 4000 | ±2.0 | +/- 2.0mm (2mm) |
Practical Example: If you design a shaft with a length of 50mm and do not write a tolerance, ISO 2768-mh applies. Looking at the chart, 50mm falls into the ">30 up to 120" row. Therefore, the acceptable length is 50mm ±0.3mm (49.7mm to 50.3mm).