Interesting thread - I've kind of wondered how metal shrinkers work. The 6200 rpm grinder speed as read on Metal Meet is kind of unexpected. One of my LEAST favorite suppliers has a set of on-line instructions
that suggests much less - like 2-3000 rpm. Of course, I have no experience with a shrinking disc, so really don't know but would like to try to repair a couple hood sides that I have for my '31 that I screwed up.