It's easy t tell when you're "overheating" metal, it turns blue. Personally I don't think it's possible to overheat metal with a Paint Eater, the disk would probably melt first.
Keep in mind that it only removes paint. If you have deep pits with rust it's not going to get anything below the top of the metal because it won't remove metal. A grinder will get that stuff but at the expense of thinning the metal. Where I had deep pits I used phosphoric acid and Eastwood's Rust Encapsulator. Rust needs moisture and oxygen to "grow". Deprive it of either and it becomes a non-issue.
For getting into the really difficult corners use
THESE in the gray color. I've thrown away all of my rotary wire brushes. I've had those things grab my clothing once too many times. They don't work as well as the Nyalox, they throw wire and they'll tear the hell out of you if you're not careful.
Some of these newfangled things actually work
