A 6-pointed disc cuts more effectively, with less pressure than a round one. The corners dig in and dislodge the paint, primer, and surface rust better than a rounded edge, with less down pressure exerted on the metal. I can skin the paint down to bare metal and barely leave any scratches in the surface with a high speed hex disc and a little careful sweeping motion.

The same procedure works for rough-shaping body filler before going to a D-A sander and 80-grit paper.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!