On Mon, 30 Jun 2014 03:21:39 -0700 (PDT), robobass
wrote:

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?

There are lots of reasons.

1) Area of contact (angle, diameter of tool)
2) Grit size (the finer, the hotter, see 1)
3) Pressure used
4) Type of wheel/band (The harder wheels are usually finer grits.)
5) Metal of the bit or insert
6) Time taken to sharpen
7) Sharpness of the media

The answer is "All of the above", and then some.

--
You can ignore reality, but you cannot ignore
the consequences of ignoring reality.
--Ayn Rand