While fibre discs grind faster and grinding wheels last longer, they don’t offer the application versatility of flap discs, which leave a finer finish after the grinding step.
.General rule of thumb is that die width creates the radius on steel, and punch tip creates the radius on aluminum. In your case, match your punch radius to what you're trying to achieve,
.It is important to use flap discs at the correct angle and on the correct surface. Using the incorrect angle or surface can cause epoxy wear, backing
.For effective grinding of aluminum, choose from flap wheels, resin-bonded wheels, silicon carbide wheels and wire
.There are flap wheels for use on aluminum and non ferrous metals, makes a big difference in performance. Listen to episode 80 of the WTT podcast for some great info on choosing