11-12-2018, 11:57 AM
For context, some of the lore comes from Cliff Stamp and his forum. There were a few tests (if I recall correctly) where he was surprised at a low edge retention result in his testing of a factory edge, after completely removing the edge and re-forming it the wear resistance was much better.
I was away from the knife scene while all this was going on, but it's my understanding that Cliff's tests originated the speculation about heating the apex.
I think most of us who grew up with access to a 8" grinding wheel have probably seen steel go through the surface oxide colors that correspond to tempering heat. Many of us were warned to stay far away from "grinders" when sharpening, and the intuition that follows (belt grinders less bad, but still bad) feels sound.
I've definitely got an edge hot enough in my early experiments re-grinding a thick edge on a 2x72 belt that I saw the tell-tale straw color. It took a lot of work, and it happened at the tip of the knife while I was holding the handle, but it happened when I didn't expect it.
Water-cooled grinders further reinforce the intuition about grinders=bad, though interestingly they also establish (in my estimation) a clear methodology for evaluating your grinder setup: dip your blade in water before each pass and see what happens to water on the secondary bevel as you grind. Won't work for every grinder setup, but it gives you a feel for how hot things are getting if you can do a freehand test with your preferred belt speed/speed of each pass.
I was away from the knife scene while all this was going on, but it's my understanding that Cliff's tests originated the speculation about heating the apex.
I think most of us who grew up with access to a 8" grinding wheel have probably seen steel go through the surface oxide colors that correspond to tempering heat. Many of us were warned to stay far away from "grinders" when sharpening, and the intuition that follows (belt grinders less bad, but still bad) feels sound.
I've definitely got an edge hot enough in my early experiments re-grinding a thick edge on a 2x72 belt that I saw the tell-tale straw color. It took a lot of work, and it happened at the tip of the knife while I was holding the handle, but it happened when I didn't expect it.
Water-cooled grinders further reinforce the intuition about grinders=bad, though interestingly they also establish (in my estimation) a clear methodology for evaluating your grinder setup: dip your blade in water before each pass and see what happens to water on the secondary bevel as you grind. Won't work for every grinder setup, but it gives you a feel for how hot things are getting if you can do a freehand test with your preferred belt speed/speed of each pass.