I took a flat fine file, and polished off some of the material ...
I just got this and gave it a try. The first couple of attempts, the motor quit spinning as the others mentioned. Here is what i found to be the problem on mine. When pressure is applied, the collar that holds the polishing cup rubbed against the body of the motor housing, causing it to lock up. I took a flat fine file, and polished off some of the material on the motor housing where the shaft comes out. This gave the collar a little clearance. After i did that, it worked fine, and the motor didn't stall at all. It did a decent job after that.
Rating: 4 stars