Is horsepower a meaningful measure of a wood router’s capabilities? In truth, it may not be the best: There’s more than one way to measure horsepower, and some aren’t a good indication of how a router will work in an actual woodworking situation. Manufacturers aren’t all that likely to tell you which one they used, but most will supply a more useful measure: rated amperage. Even that isn’t the perfect guide in selecting a power tool, but it does have certain advantages.
Horsepower ratings on routers are only semi-useful for comparison purposes for the simple reason that there are so many ways to interpret and report this measure of power. Obviously, a 3 HP router isn’t as powerful as a 3 HP table saw. Amperage ratings are more objective, but they can’t be taken as the final word on power either, since the amount of amperage a universal motor draws is affected by its efficiency and several other factors.
Rated amperage is definitely useful for one thing: It’s an objective way to narrow the field. The type of router work you’ll be doing will, of course, be the biggest influence on the amount of power you should look for in a router. If you need a router mainly for light -duty, handheld machining for inlay and other small projects, a king-sized 15 amp model might not be the best choice. And by the same token, a lightweight, easy to handle 10 amp-or-less router will turn out to be a disappointment if you need it to crank out raised panels for cabinet doors all day long.
Picking the best router based on the quality and power of it’s motor may involve further research. The best place to start is by learning more about how power tool motors work, and what makes a good one. “Electric Motors Frequently Asked Questions” [ftp://ftp.cs.rochester.edu/pub/archives/rec.woodworking/woodwork-motors] on rec.woodworking is an excellent introduction to power tool motors. But reading reviews and asking other woodworkers what worked out best for them is probably the best basis for a judgment. There’s no shortage of discussions on woodworking forums about which routers live up to their manufacturers’ claims.