Why must larger bits run slower?

The tip of a large bit travels much faster than a small bit at the same RPM. If the peripheral speed is too high, the wood burns, the bit overheats, and the cut quality suffers. A 50mm bit at 24000 RPM has a tip speed of nearly 63 m/s — dangerously fast.

What happens if the router speed is too high?

Too high a speed causes burning, premature bit wear, and poor cut quality. It can also be dangerous with large bits. Always start at the lower end of the recommended range and increase if needed.

What speed should I use for a 12mm bit?

For a 12mm router bit in hardwood, aim for about 18,000-24,000 RPM. In softwood, the full 24,000 RPM is fine. Reduce speed for larger bits and increase feed rate to prevent burning.

WoodCalcs

Router Bit Speed Calculator — Safe RPM

Calculate safe router speeds based on bit diameter and material.

Bit Diameter

Material

How We Calculate This

RPM = (Peripheral speed × 60,000) ÷ (π × Bit diameter in mm)

Safe peripheral speed for wood routing: 15-25 m/s. Larger bits need lower RPM to stay within this range.

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.