Surface finish calculator
See the finish to expect from your feed and nose radius, or the feed to use for the finish on the drawing.
Geometric values for a sharp insert: Ra ≈ f² ÷ (31.2 × rε) × 1000 and Rt = f² ÷ (8 × rε) × 1000. Real finish is usually worse because of wear, built-up edge and vibration, so aim for about two thirds of the drawing value. Wiper inserts give roughly half the Ra at the same feed.
Roughness grades
| N grade | Ra µm | Ra µin |
|---|---|---|
| N12 | 50 | 2000 |
| N11 | 25 | 1000 |
| N10 | 12.5 | 500 |
| N9 | 6.3 | 250 |
| N8 | 3.2 | 125 |
| N7 | 1.6 | 63 |
| N6 | 0.8 | 32 |
| N5 | 0.4 | 16 |
| N4 | 0.2 | 8 |
| N3 | 0.1 | 4 |
| N2 | 0.05 | 2 |
| N1 | 0.025 | 1 |
ISO 1302. Ra is also called CLA or AA. Rz is typically 4 to 7 times Ra. µm = µin × 0.0254.
Finish by process
Typical production Ra in µm. Finer is possible with extra care; worn tools or shaky set-ups give rougher results. Printable version: surface finish chart (A3 PDF).
A guide only. These tools and figures are general starting points, not a guarantee for your job. Results depend on your machine, setup, material and tooling, so always check against the tool maker’s data, and talk to a Teravin sales engineer to make sure it’s right for your application. Call +61 8 9345 2099 or ask us. See our terms of use.
