How do I prevent burning when routing?

I get burn marks when rounding over the ends of glued-up cutting boards. I thought I was moving the trim router fast enough, and the bit is sharp and clean, so why does the wood scorch?
—Curtis Severson, North Platte, Neb.

Curtis, some wood species, such as cherry and maple, tend to burn easier than others, so your situation is not uncommon. And your idea to use a quicker feed rate usually helps.

If you've ruled out feed rate as the problem, and you have a sharp bit, consider the router as the culprit. If it has a single speed—usually around 25,000 rpm or faster—that high speed could be causing the burns. In that case, rout the profile in two passes, removing most of the wood the first time through, and then following up with a quicker, shaving-thin pass. If your router has variable speed, dial it back to about 18,000 rpm or so. That should alleviate the friction burns.