Router Bit Speed Chart: RPM by Bit Diameter

QUICK ANSWER: Router bit RPM scales inversely with bit diameter. Small bits run fast (24,000 RPM); big bits run slow (10,000 RPM or less). The reason is tip speed — the velocity of the bit's outer edge — which scales linearly with diameter at any fixed RPM. Above 200 mph tip speed, carbide tips run hot, cuts burn, and at the extreme the bit can fail. Use the chart below as a starting point, then adjust by 10–20% slower for hardwoods and 10–20% faster for softwoods. Trim routers with no speed control are limited to bits 1" diameter and under — see why fixed-speed trim routers can't run large bits.

The Speed Chart

The recommended starting RPM for any cut depends on bit diameter. Numbers below are pulled from Freud's official speed chart and Whiteside Router Bits speed recommendations — they agree closely on every diameter.

Reading the chart: pick the row matching your largest bit diameter; set your variable-speed dial to the listed RPM. The tip-speed column is for understanding only — you don't need to calculate it for every cut, but it explains why the RPMs have to drop as bits get bigger.

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Why Tip Speed (Not RPM) Is the Real Rule

The actual physical limit on a router bit is tip speed — how fast the outer cutting edge is moving through the air, in feet per minute or miles per hour. Tip speed = π × diameter × RPM. Carbide cutting edges are designed for a target tip-speed range, generally 80–200 mph for clean cutting. Above that range, the carbide runs hot, the cut surface burns, and at extremes the brazing holding the carbide tip to the bit body can fail. The Bosch router-bit guidance covers this engineering rationale.

Because tip speed scales linearly with diameter at any fixed RPM, doubling the bit diameter doubles the tip speed. A 1/2" bit at 22,000 RPM is at 98 mph (clean cutting); the same RPM with a 2" bit is at 392 mph (well past failure). That's why the chart drops RPM steeply as diameter rises — to keep tip speed in the safe zone for every diameter.

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When to Drop Below the Recommended RPM

Three situations call for going below the chart's recommended RPM by 10–20%.

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Hard or dense wood species — hard maple, oak, hickory, exotic hardwoods. Slower RPM gives the bit more time to clean up its chip-load and reduces friction burn. The Wood Magazine bit-speed guidance recommends dropping 10–15% for typical North American hardwoods, more for very hard exotics.

Cope-and-stick or other multi-profile bits with multiple cutting edges at different diameters. Set RPM for the largest diameter on the bit, not the average — the largest tip is the safety constraint, and slower RPM is fine for the smaller cutters.

Spinning at full depth on a single pass (which you should avoid anyway — see router feed rate for the multi-pass discussion). If you're forced into a single deep pass, drop RPM to give the bit more dwell time per cut.

Bits Without Published RPM Caps

Some specialty and budget bits ship without an RPM rating. Three rules of thumb fill the gap:

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• Match diameter to the chart above if the bit is from a reputable manufacturer (Freud, Whiteside, Amana, CMT). Their unrated bits follow the same tip-speed engineering.
• Drop one tier on the chart if the bit is a cheap import or no-name. The carbide quality is unknown; running slower buys margin.
• Don't run any bit over 1" diameter on a fixed-speed trim router — trim routers have no speed control, so the chart is unenforceable. See trim router large bits for why this is a hard rule.

Sources

This guide draws on router-bit-manufacturer speed-chart documentation and woodworking publication references.

• Freud Router Bit Speed Chart — primary RPM-by-diameter source
• Whiteside Router Bits: Speed Recommendations — independent confirmation
• Bosch: Router Bit Operating Guidance — engineering rationale on tip-speed limits
• Wood Magazine: Router Bit Speeds — wood-species adjustments to the base chart
• Rockler: Router Bit Speed Chart — retailer-side reference matching manufacturer data