If your part requires tighter geometric control (e.g., sealing surfaces or alignment features), consider upgrading to ISO 2768-mK (Medium geometry) or applying specific GD&T callouts (like a Flatness symbol) directly on the drawing to override the general standard.
The ISO 2768 standard defines four tolerance classes: f (fine), m (medium), c (coarse), and v (very coarse). The MH tolerance class is a medium tolerance class that provides a balance between the fine and coarse tolerance classes. iso 2768-mh tolerance chart
Now go check your title block – is ISO 2768-mH the right fit for your next project? If your part requires tighter geometric control (e
| Nominal Angle Range | Tolerance Class 'm' | | :--- | :--- | | Up to 10mm length of shorter side | ±1° | | >10mm up to 50mm | ±0°30' (30 arc minutes) | | >50mm up to 120mm | ±0°20' (20 arc minutes) | | >120mm up to 400mm | ±0°10' (10 arc minutes) | | >400mm | ±0°5' (5 arc minutes) | Now go check your title block – is
If you specify , you are asking for Medium linear accuracy but Coarse geometric accuracy.
| Feature | ISO 2768-mH Allowance | |-----------------------------|---------------------------------------------| | Linear (0.5–3 mm) | ±0.1 mm | | Linear (30–120 mm) | ±0.3 mm | | Linear (120–400 mm) | ±0.5 mm | | Hole (10 mm dia.) | +0.22 / -0 mm | | Hole (50 mm dia.) | +0.39 / -0 mm | | Angle (leg ≤120 mm) | ±1° | | Flatness / Straightness | 0.2 mm / 100 mm | | Perpendicularity | 0.4 mm / 100 mm | | Runout | 0.2 mm |
ISO 2768-mH