There’s been talk on some forums that the external speed controls you can plug into routers actually aren’t that good for the router. Some say it shortens the life of the motor. Is this true?
Michael Dresdner: It’s common for routers to have a built in cooling fan that runs off the motor. When you slow the motor, you slow the cooling fan, thus creating a potential overheating problem. Nevertheless, used judiciously, the speed reductions do more good than harm. Running a large diameter router bit at too high a speed is dangerous to the humans using the machine, and they mean more to me than a router with a shortened lifespan.