What speed for roughing a large blank?

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.

What speed for finishing cuts?

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.

How do I know if the speed is right?

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.

WoodCalcs

Lathe Speed Calculator — Safe RPM for Turning

Determine safe lathe RPM based on workpiece diameter and operation type.

Workpiece Diameter

Largest diameter of the spinning blank or workpiece (mm) — this sets the rim speed and therefore the safe RPM. Larger pieces must run slower.

OperationRoughing = slow start for unbalanced blanks; Finishing = higher rim speed (10-12 m/s) for a clean cut; Sanding = low speed (3-5 m/s) to avoid heat glazing the abrasive.

How We Calculate This

RPM = (Peripheral rim speed × 60,000) ÷ (π × Diameter in mm)

Target peripheral (rim) speeds: Roughing spans your chosen centre speed ±50% (default 7.5 m/s, i.e. 3.75-11.25 m/s), Finishing 10-12 m/s, Sanding 3-5 m/s. The 12 m/s finishing ceiling matches the woodturner's 6000/9000 rule (D in inches × RPM ≤ 9000, ≈27 mph at the rim). Always start at the low end for unbalanced or irregular blanks.

Frequently Asked Questions

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Last updated: February 2026

All calculations are estimates. Always verify measurements and material quantities before cutting or purchasing.