Originally Posted by Henry Highrise
I have used a router speed control with my 2 and a half horse power router for years...never had a problem with it...yes the motor is AC. I did not use a HF controller though...I got mine at Sears. I have never tried to slow down a grinder with it...but I don't see why it would not work for that.
Nothing wrong with that, it is for an AC motor and should work with most tools as long as they don't exceed the rated current on the speed controller.
The Harbor Freight speed controller is for AC use also and will work with most AC motors but if you open up either one of these controllers you find that it is a heck of a lot more than just a simple rheostat. Using a light dimmer (which appears to be a rheostat) would be no different than using an extension cord that is too long which will cause a voltage drop and can damage an AC motor.