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These are the HSS and carbide starting ranges stored in the ShopCalc material library. The RPM table applies the site’s SFM-to-RPM formula to each range.
RPM is computed at the low, midpoint, and high end of both stored SFM ranges. Diameter is the cutter diameter for milling or cutting diameter for turning.
| Tool diameter | HSS RPM | Carbide RPM | ||||
|---|---|---|---|---|---|---|
| Low · 10 SFM | Mid · 17.5 SFM | High · 25 SFM | Low · 60 SFM | Mid · 105 SFM | High · 150 SFM | |
| 1/8″ | 306 | 535 | 764 | 1,833 | 3,209 | 4,584 |
| 1/4″ | 153 | 267 | 382 | 917 | 1,604 | 2,292 |
| 3/8″ | 102 | 178 | 255 | 611 | 1,070 | 1,528 |
| 1/2″ | 76 | 134 | 191 | 458 | 802 | 1,146 |
| 3/4″ | 51 | 89 | 127 | 306 | 535 | 764 |
| 1″ | 38 | 67 | 95 | 229 | 401 | 573 |
The existing SFM-to-RPM calculator is preset to Inconel 718, a 1/2-inch tool, and the 17.5 SFM HSS midpoint. Change any input to recalculate.
The stored starting range is 10–25 SFM for HSS tooling and 60–150 SFM for carbide tooling.
60 SFM with a 0.500-inch tool calculates to 458 RPM using RPM = SFM × 12 ÷ (π × diameter).
The material library stores 0.0012 inch per tooth as the 1/4-inch end-mill starting chip load.
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