Understanding surface roughness values and their manufacturing implications
| Parameter | Description | Common Range |
|---|---|---|
| Ra (Arithmetic Average) | Average deviation from mean line | 0.025 - 50 microns |
| Rz (Average Max Height) | Average of five highest peaks + five lowest valleys | 0.1 - 200 microns |
| RMS | Root mean square of deviations | Similar to Ra x 1.11 |
| Ra (microns) | Ra (microinch) | Process Examples |
|---|---|---|
| 0.025 | 1 | Lapping, superfinishing |
| 0.05 | 2 | Fine grinding, honing |
| 0.2 | 8 | Grinding |
| 0.8 | 32 | Finish machining |
| 3.2 | 125 | Standard machining |
| 6.3 | 250 | Rough machining |