hollow grinding Nirvana
That may sound a little extreme - but it is accurate.
While I was in Calgary I had the good fortune to stay with a friend. During one of our many tool fetish moments, I noticed a pale blue wheel in his grinder. So I asked about it. He said it was the best grinding wheel he has ever used - it does not produce any heat. That was a pretty tall order - so I asked if I could give it a try. I have a 1725RPM Baldor grinder with 2 Norton white wheels on it - both 60 grit. They are fantastic wheels, but they can produce heat and even burn steel if you are not careful.
This wheel is completely different. The first thing I tried was a huge high carbon steel iron from a jointing plane. I gave it a pretty light touch and was amazed at how much metal it took off. I did another pass and pressed a little harder - expecting to feel a little warmth in the iron. I felt nothing and started worrying that my caloused fingers were loosing sensation. The blade wasn't even warm! I was going to take another heavy pass, but realized that I had already completely re-ground the iron. Holy smokes this thing was fast!
So I grabbed another iron, and had similar results - fast cutting and no heat to speak of. Then I realized I was using some pretty stout plane irons - I wonder what would happen on a small chisel? So I tried a little 3/4" "blue chip" that was in pretty rough shape. I started again with a light touch. Fast cutting - no heat. I pressed harder... even faster cutting - still no heat. At this point I was totally sold - this was fantastic! So we finished up the chisel and a few other tools that needed some work. There was not a single instance where I felt any warmth in any of the tools we were working on.
I ordered one of these wheels (Norton 3X, 46 grit) from Joel at Tools for Working wood in NY.