What's the best router speed for a given router bit? It’s not always the manufacturers recommended maximum. Maximum speeds can be used as a guideline, but the actual performance of any bit will always depend on a number of factors - speed is just one. Below, in answer to a Woodworker's Journal eZine reader's question, two expert woodworkers expand on the conditions that make for a good router cut:
Q. Are there better guidelines for determining router speeds than those provided by the manufacturer in the owner's manual? (This particular woodworker didn't think the recommended speeds produced good results.)
A. (Rob Johnstone) "With very large router bits, you need to slow down the RPMs for safe cutting. Smaller bits should spin faster (for more information on large bits, check out Woodworker's Journal, April 2000, page 66). But this is a complex question and without more information, I wonder if the poor results were due to the speed settings per se. Manufacturers' recommendations are the correct place to start. Then, if experience tells you all is not working well, make your bit speed adjustments.
There is a relationship between bit speed, sharpness and feed rate (the speed at which you move the bit through the wood or the stock across the bit) and how well your bit cuts, as well as the characteristics of the individual piece of wood you are working with. So to suggest that a specific speed setting would solve this problem is questionable. The correct answer, as with much of woodworking, is to start with the recommendations and make adjustments if all is not working well."
A. (Ian Kirby) "The answer to the question lies in this particular woodworker's thoughts or experiences. The results of all wood machining are related to cutter speeds, depth of cut, feed rate and hardness of the stock. And all of these assume that the setup of fences, guide blocks and holddowns are correctly in place. Good results come from the totality; picking out one link in this chain doesn't make a strong chain. Put the parts together as you think appropriate and then begin the task of methodically improving the processes if improvement is needed. That's the most important guideline."
From the Woodworker's Journal eZine archives
Manufacturers don't always agree on top speeds for router bits of a given diameter, and as mentioned above, there are other factors to consider. For a rough guide, here's a typical maximum router bit speed chart:
|Router Bit Diameter||Maximum Speed|
|Up to 1"||22,000 - 24,000 rpm|
|1" to 2"||18,000 - 22,000 rpm|
|2" to 2-1/2"||12,000 - 16,000 rpm|
|2-1/2" to 3-1/2"||8,000 - 12,000 rpm|
Remember, that's just a reference; Always follow manufacturers recommendations and the sage advice that if something doesn't feel like it's working right, there's a good chance that it isn't. Better yet, pick up a Router Book and get to know your router inside and out. Or, for a beginning-level overview of router bits, read Rockler's article "Router Bit Basics".