I have a friend who is a professional at sharpening. Been doing it for 62 yrs. He said HSS and Cryo tools that have turned blue are not ruined. He said it take a heck of a lot more heat than can be generated on a grinding wheel to ruin a piece. Carbon Steel like Rich said throw it away if you blue it because he told me you have to grind past the blue and by the time you get there it will be blued again. He said buy a new one.
Retirement: That’s when you return from work one day
and say, “Hi, Honey, I’m home – forever.”
To succeed in life, you need three things: a wishbone, a backbone and a funnybone.