[Jack21]

Years ago, Craftsman used to make die grinders with variable speed control built in. Many Pontiac, and Oldsmobile heads got ported with it.

Variable speed control is essential, and I never use one flat out.

My trusty old Craftsman gave out on this Cobra, and I had to replace it. Got the DeWalt from Grainger, and found a router speed reducer from a tool shop on-line.

Have never used an air die grinder because the electric one works so well. But using one is an art, like welding.

Need carbide bits of varying coarsness, and 3/8" is usually the only size I use. Use these on cast iron. Flutes will clog on aluminum. For aluminum, and brass, you need the non-ferrous bits. Flute pattern is entirely different, and bits are usually tool steel, rather than carbide. These bits work great on fiberglass also.