Surface Roughness Converter
Enter Ra value (µm) to automatically convert to other roughness parameters.
Max Height
—
Max Profile Height
—
RMS Roughness
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Machining Process Ra Reference
| Process | Ra Min (µm) | Ra Max (µm) |
|---|---|---|
| Grinding | 0.025 | 0.4 |
| Milling | 0.4 | 6.3 |
| Turning | 0.8 | 12.5 |
| Drilling | 1.6 | 25 |
Ra：Arithmetic mean roughness — the most widely used roughness metric.
Rz：Average max peak-to-valley height across sampling length.
Rmax：Maximum profile height in sampling length (single largest value).
Rq (RMS)：RMS roughness — more sensitive to large deviations.
A customer drawing specifies surface roughness Ra ≤ 1.6 µm, but the supplier's measurement report is expressed in Rz. The engineer needs the Ra-Rz conversion relationship and the typical Ra ranges of machining processes (milling, grinding, polishing) to verify the part meets the customer requirement.
Ra = 1.6 µm conversion: / Estimated Rz ≈ 4 × Ra = 6.4 µm (approximation; the ratio varies with material and process) / Rq ≈ 1.25 × Ra = 2.0 µm / Process check: / Milling: typical Ra 0.4~6.3 µm → Ra 1.6 µm is within milling range (achievable with finish milling) / Grinding: typical Ra 0.025~0.4 µm → switch to grinding if Ra 0.1 µm is required / Drilling: typical Ra 1.6~25 µm → Ra 1.6 µm is at the boundary (requires drilling precision control)
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