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?

A 12mm (about 1/2 inch) router bit is small enough to run at the router's full speed — typically the maximum 24,000 RPM. The spindle speed chart is the same for softwood, hardwood and MDF; the wood species mainly affects your feed rate, not the RPM. Step the speed down only as bit diameter grows, 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

Cutting diameter of the router bit in mm (measure across the widest point of the cutter)

MaterialMaterial you are routing — plastics run slower to avoid melting

How We Calculate This

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

Solid wood is cut at a tip (peripheral) speed of roughly 40-60 m/s. Larger bits reach that speed at fewer revolutions, so they need lower RPM — which is why a 50mm panel-raising bit runs at around 15,000-23,000 RPM (most charts centre on 16,000-18,000, with ~23,000 the upper bound at 60 m/s) while a 12mm bit can spin at the router\'s full 24,000 RPM.

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.