Questions:

I'm in the market for a new router and have seen models with variable speed options. What is the purpose of this option?

Answer:

When working with larger router bits it is necessary to slow down the bit. In addition to safety concerns, the router's speed can affect the finish. If the router is burning the wood or leaving a rough finish, try turning down the speed. If the router is chattering the wood's surface or leaving marks, try turning the speed up.

Electronic Variable Speed (EVS)

Electronic Variable Speed (EVS) routers are relatively new on the woodworking scene. The EVS feature allows the operator to adjust the speed of the router bit. The main reason you'd want to do this is to slow down a larger bit for safety reasons. Smaller bits operating at high speeds are not a major concern. If your project plans don't include raised panel doors and other projects requiring larger (2"+) bits, EVS should not be a major concern. Even if you scale up to larger projects in the future you can still purchase an external speed adjusting unit from most woodworking supply stores. Make sure the unit is designed for routers. The units contain special feedback circuits that adjusts the power levels as the load changes. These devices are designed to work with the motor to drop the speed without damaging the router. We can not emphasize the importance of avoiding variable speed controllers not specifically designed for routers, as these units may burn out your motor.

The following guide will help you select the MAXIMUM speed for your router.

(Note: This table is only a guideline. Please use reasonable judgment when working with router bits.)