Materials & Finishing
Surface Roughness (Ra) Chart
ISO roughness grade numbers (N-grades), their corresponding Ra (arithmetic mean roughness) values, and machining processes typically capable of achieving them.
| Grade | Ra (µm) | Typical Process |
|---|---|---|
| N4 | 0.1 | Fine grinding / lapping |
| N6 | 0.4 | Grinding |
| N7 | 0.8 | Fine turning / grinding |
| N8 | 1.6 | Turning |
| N9 | 3.2 | Turning / milling |
| N10 | 6.3 | Milling |
| N11 | 12.5 | Rough machining |
Reference values only. Verify against the current governing standard (e.g. ISO, ANSI, ASME, DIN) before using in production drawings or manufacturing. Provided by Micro Components as a free engineering resource.
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