Most people don't have access to or own a lathe. This is a quick way to polish or grind/shape round parts by using a ordinary hand drill. Preferably one with a brake to reduce the chance of loosing a finger. Unlike a lathe that doesn't mind plucking off digits in the chuck.
In this case I made a tool to hold these small interior trim rings for shaping and polishing. You can also spin round parts in conjunction with a right angle grinder or sand paper to shape the part. Run the drill in the opposite direction of the sanding disk rotation of your grinder. You can do things as simple as a chamfer or make a chess set if your that dedicated
