There was a question in one of the blade forums about chipping and one response alluded to the possibility of overheating during factory grind. I've had a few blades that were prone to chipping, and always thought that they didn't get proper tempering to soften up the metal.
The overheating and ruined temper are sometimes used synonymously, and I'm wondering if this is true. If you overheat, aren't you always going to soften up the metal? I.e. small amount of heat tempers the hardness, large amount of heat anneals, either way it would soften the blade and prevent chipping rather than cause it. Does anyone have any explanation for why overheating on belt grinder could lead to making the metal more brittle?