Surface Finish Chart
ISO 1302 roughness grades with Ra in µm and µin, Rq, and typical producing processes.
| Grade | Ra (µm) | Ra (µin) | Rq (µm) | Typical process |
|---|---|---|---|---|
| N1 | 0.025 | 1 | 0.03 | — |
| N2 | 0.05 | 2 | 0.06 | — |
| N3 | 0.1 | 4 | 0.11 | — |
| N4 | 0.2 | 8 | 0.22 | ground, honed |
| N5 | 0.4 | 16 | 0.44 | ground |
| N6 | 0.8 | 31 | 0.89 | finish machined |
| N7 | 1.6 | 63 | 1.78 | machined |
| N8 | 3.2 | 126 | 3.55 | machined |
| N9 | 6.3 | 248 | 6.99 | rough machined |
| N10 | 12.5 | 492 | 13.88 | sand cast, sawn |
| N11 | 25 | 984 | 27.75 | — |
| N12 | 50 | 1969 | 55.50 | — |
Convert a specific value with the Surface Finish tool.
A reference aid, not a substitute for engineering judgment. Verify against the governing standard.