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Wood Lathe Speed Calculator (Safe RPM for Woodturning)

Find a safe wood lathe speed for a bowl or spindle blank from its diameter with the 6,000–9,000 rule: starting RPM for rough or unbalanced blanks, top speed for balanced work and rim speed.

Units

Blank diameter

Blank condition

Lathe maximum speed

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How it works

diameter (inches) × RPM = 6,000 (rough or unbalanced) to 9,000 (round and balanced) · RPM = 6,000 ÷ D or 9,000 ÷ D · diameter in inches = mm ÷ 25.4 · rim speed = π × D × RPM

The danger in woodturning is the speed of the rim, not the RPM: a big blank at a modest RPM has a rim moving as fast as a small one at high RPM, and an unbalanced blank can pull the lathe across the floor or come off the chuck. The common turners' rule, used in American Association of Woodturners safety guidance and club handouts, keeps diameter (in inches) × RPM between about 6,000 and 9,000. Start rough, cracked or out-of-round blanks at the bottom of the range — or lower — and only speed up once the piece is trued and running without vibration. Always start the lathe at its lowest speed and stand out of the line of fire.

Worked example

A 250 mm (9.8 in) rough bowl blank: 6,000 ÷ 9.84 = 610 RPM to start, rising to about 914 RPM once it is round and balanced. At 610 RPM the rim moves at 7.98 m/s.

Sources: American Association of Woodturners — Safety · Hill Country Turners — Selecting a safe lathe speed

Frequently asked questions

What speed should I turn a bowl at?

Use diameter in inches × RPM ≈ 6,000–9,000. A 10 in bowl starts around 600 RPM and can run at about 900 RPM when balanced; a 6 in bowl at 1,000–1,500 RPM.

What speed for spindle turning?

Thin spindles (1–2 in) can run at 1,500–3,000 RPM, but long thin work whips, so slow down if it vibrates and use a steady rest.

Why start at the lowest speed?

If the last job left the lathe at high speed, a large unbalanced blank can fly off the moment you switch on. Always check the speed dial before starting and stand to the side.

Is faster better for a smooth finish?

Slightly higher speed helps with a final shear cut and sanding, but sharp tools and good technique matter far more. Never exceed what the blank tolerates without vibration.

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This calculator is for educational purposes. Double-check important results before acting on them.