Lathe Speed Calculator — Safe RPM for Turning

Start slow — for a 250mm blank the calculator gives roughly 290-860 RPM, and you should begin at the bottom of that range until the blank runs true. Never exceed the 9000-rule ceiling (about 915 RPM at 250mm). Once the blank is round and balanced, increase speed gradually. An out-of-balance blank at high speed is extremely dangerous.

Finishing cuts use a higher rim speed (10-12 m/s) than roughing. For a 150mm diameter piece this is roughly 1270-1530 RPM, which gives a clean surface while staying at the 9000-rule safe limit (about 1525 RPM at 150mm). Never push beyond that ceiling — peripheral speed rises with diameter, so larger pieces must run slower.

If the lathe vibrates excessively, slow down. If the wood burns, speed up or take lighter cuts. If the surface is rough, increase speed. Always start slow with irregular blanks and increase gradually.