Hi,
I've recently been grinding a lot of toolbits after a long hiatus from machining. One thing that crops up in my mind - why do some wheels heat the part so much more than others? The obvious answer is the sharpness of the cutting media. When I sand brass on a fresh belt, there is much less heat than with an old belt because presumably the heat goes away with the chips, and there is more cutting and less rubbing. I have various wheels for shaping and sharpening, from stone to various hardness of abrasive impregnated rubber. It seems the harder the wheel, the more heat. Finer grits heat more, but that seems a smaller issue. Is the answer simply that the surface of the softer wheels wear away faster and continually expose fresh abrasive?