This is one of my favorite convenience tools. It is a 3M brand buffing wheel made with a coarse Scotch-Brite pad impregnated with abrasive, 4 inches diameter on a 1/4 inch arbor. DO NOT EXCEED 3500 RPM. In fact it works quite well at 1000 RPM in an electric drill. It works like sandpaper, use a gentle touch, let the abrasive do the work, and it will last a good long time. If you push hard it just shreds the wheel in a hurry.

This thing will make short work of removing paint and gasket materials from iron engines, aluminum transmissions, and sheet metal covers. It is the most marvelous tool for removing carbon deposits from combustion chambers and from the tops of pistons without harming the aluminum parts. No more scraping and no more scratches. It will even buff away a thin coat of rust to leave a polished steel surface (but will not grind out pit marks).