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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 · 200 SFM | Mid · 300 SFM | High · 400 SFM | Low · 400 SFM | Mid · 600 SFM | High · 800 SFM | |
| 1/8″ | 6,112 | 9,167 | 12,223 | 12,223 | 18,335 | 24,446 |
| 1/4″ | 3,056 | 4,584 | 6,112 | 6,112 | 9,167 | 12,223 |
| 3/8″ | 2,037 | 3,056 | 4,074 | 4,074 | 6,112 | 8,149 |
| 1/2″ | 1,528 | 2,292 | 3,056 | 3,056 | 4,584 | 6,112 |
| 3/4″ | 1,019 | 1,528 | 2,037 | 2,037 | 3,056 | 4,074 |
| 1″ | 764 | 1,146 | 1,528 | 1,528 | 2,292 | 3,056 |
The existing SFM-to-RPM calculator is preset to Lead, a 1/2-inch tool, and the 300 SFM HSS midpoint. Change any input to recalculate.
The stored starting range is 200–400 SFM for HSS tooling and 400–800 SFM for carbide tooling.
400 SFM with a 0.500-inch tool calculates to 3,056 RPM using RPM = SFM × 12 ÷ (π × diameter).
The material library stores 0.005 inch per tooth as the 1/4-inch end-mill starting chip load.
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