Variable speed router

[Randy Cohen]

I've never owned one of these and yesterday i got my free one from Hitachi for buying the SCMS. So when would I use the slower speeds? Is it for larger size bits? My other router is single speed.

[Glenn Clabo]

Randy,
You are right. Primary reason for speed change is the size of the bit...secondary is tocontrol the speed to keep burning down. Here's a chart that gives you a ballpark number for use in a table. Large diameter bits should never be used hand held. You should check with the bit manufacturor to be sure.
Bit Diameter ........Maximum Speed (RPM)
Up to 1".....................24,000
1 1/4" to 2"................18,000
2 1/4" to 2 1/2"...........16,000
3" to 3 1/2"................12,000

[John Grossi]

Glenn is right on. That is a very helpful chart. After a while, you will be adjusting your speed by the router's sound. If you still get burning or chattering, you can adjust your feed rate, and the use of featherboards will be helpful (if mounted to a router table). John

[Glenn Clabo]

Good points John...and to further the discussion...burning is usually caused by a feed rate being too slow while chattering is usually caused by a speed rate that is too slow.
I only say this because intuitively most people feel if they slow down the feed rate it will make a smoother cut and stop burning.

[Rick Christopherson]

I know that this table most likely came from a router manufacturer (but the same table is often repeated in many other sources), but in my opinion, these numbers are way too high. I believe these numbers are based on the Maximum rpm, not necessarily the Optimum rpm. Choosing a router bit speed is more complex than just looking at the bit diameter.

Not long ago, the maximum speed of a router was 20,000 rpm, but the speeds keep creeping up higher in order for router manufacturers to claim higher "peak" horsepower. As a result, this table keeps creeping up higher too.

Running the bit at too high of an rpm will result in burning of the wood and overheating of the bit. This is especially true on the smaller bits where there is less time between cuts for the tips to cool off.

The best gauge for setting router speeds is personal experience, but for new woodworkers, all they have to rely on is a table such as this. I have a vast collection of router bits, and there is not a single one of them that I would ever run at over 20,000 rpm. For a new woodworker starting out, I would suggest starting out with a slightly lower speed, and then gauge your optimal speed based on the performance of the specific bit. This will vary with knife profile and tip geometry for each bit.

[Glenn Clabo]

I know that this table most likely came from a router manufacturer (but the same table is often repeated in many other sources), but in my opinion, these numbers are way too high. I believe these numbers are based on the Maximum rpm, not necessarily the Optimum rpm.

You are absolutely right Rick...that's why I labeled the chart..."Maximum Speed (RPM)" and suggested contacting the bit maker.

Feel...results...experience always count more than a general chart.

[pat warner]

Speed x experience, no. 5. (http://patwarner.com/faq.html)

[Glenn Clabo]

Love your website Pat.;)