The router bit speed guide shows the maximum safe RPM for each bit diameter. Running a large panel-raising bit at full router speed is dangerous — the bit's rim speed can exceed safe limits, causing vibration, burning, and potential bit failure. Use this guide to set the correct speed before routing.
Speed Lookup by Bit Diameter
Complete Router Bit Speed Reference
| Bit Diameter | Max RPM | Rim Speed |
|---|
How to Use the Router Bit Speed Guide
The router bit speed you set is one of the most important safety decisions in routing. The governing principle is rim speed — the speed at which the cutting edge travels through the air. A 3" bit spinning at 20,000 RPM has a rim speed of nearly 942 feet per second — dangerously fast. This guide ensures you stay within safe operating limits.
Step 1: Measure Your Bit Diameter
Measure the widest cutting diameter of the bit. For straight bits, this is straightforward. For profile bits (roundover, ogee, raised panel), measure the full diameter of the body at the widest point, not just the shank. If unsure, measure with calipers.
Step 2: Set RPM Before Installing the Bit
Reduce router speed before installing large bits. Set your variable-speed router to the appropriate range from the table above, then install the bit. Starting at too high a speed and dialing down after installation means the bit ran too fast during installation — avoid this.
Step 3: Make Multiple Passes for Large Profiles
For large profile bits (1.5" and above), reduce cutting depth and make multiple passes at the correct speed. Take no more than 1/4" depth per pass in hardwood. A slightly lower speed with multiple light passes produces a better finish and is safer than a single deep cut at maximum speed.
FAQ
Why do larger router bits require slower speeds?
The critical factor is rim speed (surface speed) — the speed at which the cutting edge moves through the air. A larger bit has a larger circumference, so even at the same RPM, the rim speed is much higher. Excessively high rim speeds cause vibration, burning, rough cuts, and in severe cases, catastrophic bit failure. Router bit manufacturers specify maximum safe rim speeds around 25,000-30,000 feet per minute.
What happens if I run a router bit too fast?
Running too fast causes: burning the wood and bit, rough or torn surface finish, excessive vibration leading to chattering, possible bit failure (rare but dangerous), and faster bit dulling. Running slightly too slow just means the bit cuts more conservatively — much safer than too fast.
How do I know what speed my router is running at?
Most variable-speed routers have RPM settings marked on the speed dial. The router's manual shows the RPM range corresponding to each dial position. A basic 1-3/4 HP router might range from 8,000-24,000 RPM. A trim router (laminate trimmer) typically runs 25,000-30,000 RPM and should only be used with small bits.
Is this router speed guide free?
Yes, completely free with no signup required. All data is based on standard router bit safety guidelines from leading manufacturers.