ISO IT grade → typical tolerance (µm) for 10–18 mm feature
| IT grade | Tolerance | Process |
|---|---|---|
| IT01 – IT4 | 0.3 – 8 µm | Gauge blocks / precision grinding |
| IT5 | 9 µm | Precision grinding / reaming |
| IT6 | 11 µm | Fine grinding / turning / reaming |
| IT7 | 18 µm | Fine turning / grinding |
| IT8 | 27 µm | Turning / milling / drilling |
| IT9 | 43 µm | Rough turning / drilling |
| IT10 | 70 µm | Drilling / rough machining |
| IT11 | 110 µm | Cold rolling / flame cutting |
| IT12 | 180 µm | Casting / hot rolling |
| IT13 – IT16 | 0.27 – 2.5 mm | Sand casting / large forging |
Typical process capabilities
| Process | Typical tolerance | Surface finish (Ra) |
|---|---|---|
| CNC milling (precision) | ±0.005 mm | 0.8–1.6 µm |
| CNC milling (general) | ±0.025 mm | 1.6–3.2 µm |
| CNC turning | ±0.013 mm | 0.8–1.6 µm |
| Grinding | ±0.002 mm | 0.2–0.8 µm |
| EDM (wire) | ±0.005 mm | 0.4–1.6 µm |
| Sheet metal (laser) | ±0.1 mm | 3.2 µm |
| Sheet metal (punch) | ±0.15 mm | 6.3 µm |
| Injection molding | ±0.05 mm | 0.4–1.6 µm |
| 3D print (FDM) | ±0.2 mm | 12–25 µm |
| 3D print (SLA/DLP) | ±0.1 mm | 0.8–6 µm |
| 3D print (SLS) | ±0.2 mm | 6–15 µm |
| 3D print (MJF / metal SLM) | ±0.1 mm | 6 µm |
| Sand casting | ±0.5 – 1 mm | 6–25 µm |
| Die casting | ±0.1 – 0.3 mm | 1.6 µm |
Notes
- Tight tolerances cost exponentially more — specify only what the design requires.
- GD&T allows per-feature control of form, orientation, location, and runout — more expressive than ±tolerance.
Was this article helpful?