I took apart a failed angle grinder the other day. I saw brushes, so I figured "oh, it must be DC, so I will check the rectifier" - there was no rectifier. I have learned of a new type of motor! I checked here and I see it's a "AC commutator motor" (Single phase series motor )- but I don't understand from reading that, how does it work? it seems to me like that motor is exactly the same as a DC motor, yet works on AC? If you were to put AC through a DC motor (which is how I perceive this motor to operate) I would think it would oscillate at 60HZ or just burn up.