There's a pretty clearly hardened area at the end, that I'm more than halfway through at this point, I think. They aren't very good chisels and were rather cheap, but I use them pretty rarely so they've been fine this long. When I do finally need to replace them, I might step up a level - they've never really held edges that well.

Oh, it's not a grinder, it's a drill press! I'm just using it as a wrong-angle grinder. I was also grinding against the side of the stone, I don't know if that's considered bad or what. I never got the metal really very hot - it only got at most warm to the touch - but I did water it occasionally anyway.