I was working a thin (3mm) piece of aluminum plate with a rotating disc on a hand drill. On the disc was a cutout of scotchbrite. *All of a sudden* the aluminum went from having beautifully fine arcing scratch marks to this hard marble orange peely crap. I assume that *something I did was wrong* and that the work is now "work-hardened"?
If so, or not, how would I prevent such a thing? Is it a matter of use, speed, heat, or what? And how can I remove it from the piece I have.
As always TIA.