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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 · 300 SFM | Mid · 550 SFM | High · 800 SFM | Low · 800 SFM | Mid · 1400 SFM | High · 2000 SFM | |
| 1/8″ | 9,167 | 16,807 | 24,446 | 24,446 | 42,781 | 61,115 |
| 1/4″ | 4,584 | 8,403 | 12,223 | 12,223 | 21,390 | 30,558 |
| 3/8″ | 3,056 | 5,602 | 8,149 | 8,149 | 14,260 | 20,372 |
| 1/2″ | 2,292 | 4,202 | 6,112 | 6,112 | 10,695 | 15,279 |
| 3/4″ | 1,528 | 2,801 | 4,074 | 4,074 | 7,130 | 10,186 |
| 1″ | 1,146 | 2,101 | 3,056 | 3,056 | 5,348 | 7,639 |
The existing SFM-to-RPM calculator is preset to Plastic (Delrin), a 1/2-inch tool, and the 550 SFM HSS midpoint. Change any input to recalculate.
The stored starting range is 300–800 SFM for HSS tooling and 800–2000 SFM for carbide tooling.
800 SFM with a 0.500-inch tool calculates to 6,112 RPM using RPM = SFM × 12 ÷ (π × diameter).
The material library stores 0.006 inch per tooth as the 1/4-inch end-mill starting chip load.
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