Lathe & Drill Press Speed Calculator
Spindle speed is a diameter problem, not a dial setting. A 12in bowl blank and a 2in spindle want the same rim speed and wildly different rpm, and a drill press only offers the pulley steps it was built with. This works the target out from diameter, snaps it to a step you actually have, and shows what the motor still gives you down there — because an inverter holding torque at half speed is also giving you half the power.
Operation
Widest swing of the blank as mounted, not the finished piece.
Top of the range in the belt position you are in.
Nameplate horsepower, quoted at full speed.
What this belt position reaches at 60 Hz — the baseline the derating works from.
Halves the starting speed until the blank runs true.
| Blank diameter | Roughing | Shaping | Fine cuts | Sanding |
|---|---|---|---|---|
| 2in | 3000 | 3750 | 4500 | 2000 |
| 4in | 1500 | 1875 | 2250 | 1000 |
| 6in | 1000 | 1250 | 1500 | 665 |
| 8in | 750 | 940 | 1125 | 500 |
| 10in | 600 | 750 | 900 | 400 |
| 12in | 500 | 625 | 750 | 335 |
| 16in | 375 | 470 | 565 | 250 |
| 20in | 300 | 375 | 450 | 200 |