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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 · 25 SFM | Mid · 37.5 SFM | High · 50 SFM | Low · 120 SFM | Mid · 190 SFM | High · 260 SFM | |
| 1/8″ | 764 | 1,146 | 1,528 | 3,667 | 5,806 | 7,945 |
| 1/4″ | 382 | 573 | 764 | 1,833 | 2,903 | 3,973 |
| 3/8″ | 255 | 382 | 509 | 1,222 | 1,935 | 2,648 |
| 1/2″ | 191 | 286 | 382 | 917 | 1,451 | 1,986 |
| 3/4″ | 127 | 191 | 255 | 611 | 968 | 1,324 |
| 1″ | 95 | 143 | 191 | 458 | 726 | 993 |
The existing SFM-to-RPM calculator is preset to Stainless 17-4 PH, a 1/2-inch tool, and the 37.5 SFM HSS midpoint. Change any input to recalculate.
The stored starting range is 25–50 SFM for HSS tooling and 120–260 SFM for carbide tooling.
120 SFM with a 0.500-inch tool calculates to 917 RPM using RPM = SFM × 12 ÷ (π × diameter).
The material library stores 0.002 inch per tooth as the 1/4-inch end-mill starting chip load.
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