Quote Originally Posted by Bohdan View Post
A tool fitted with a universal electric motor (i.e. one with brushes) will run at the same speed for every frequency, even DC.
This made no sense to me at all having worked with AC motors which are speed controlled via frequency. As such, I have just spend the last half hour learning about the simplicity of universal motors, and the ingenious methods they use to control their speed. So thanks Bohdan for piping my interest with what I'm sure you considered a rather innocuous statement.

For anyone else interested, the following resources are a good starting point.
Explanation of how the motors work: How a universal Motor Works - YouTube
Which will no doubt lead you to wonder how they don't just continue accelerating to destruction: How Speed of a Universal Electric Motor is Controlled - Bright Hub Engineering