10-19-2018, 11:08 AM
Very useful and not confusing Geno so thank you. As we detailed in our description of the Tempilaq test, the procedure leaned toward giving belt sharpening every opportunity not to overheat the edge. Just like all of you, we've seen metal turn cherry red during a grinding operation so we know that, given enough force and time while grinding, metal can get very hot. We did everything we reasonably could in the early phases of the test (outside of water cooling) to avoid overheating including beginning with a knife that was already sharp. We never really "leaned in" with much force nor did we maintain contact with the belt for long periods of time. In the later phases we did begin working, back and forth, over a relatively small area and that might tend to create some additional heat. Generally, we would describe the final stages of the test as "normal grinding methodology" as if we were simply, "sharpening a knife".
Hardening on the surface and softening beneath? Sounds like the fodder that many Knife Forum discussions are made up of and, possibly, could be quite accurate but, of course, very difficult to test for and validate. This applies to all discussion of HRC levels of edge apexes because, once again, we can't actually conduct an HRC test at or near the edge apex. If someone has actually figured out how to accomplish this then we will stand corrected.
There is at least one variable in our test that might prove significant; our test knife was a cheap stainless steel model purchased at the discount store some time ago. We'd guess HRC55 or so. We'd could do better than a guess at hardness because we do own a Rockwell bench tester but Mark Reich won't fly down here and show us how to use it. Harder knives are harder to grind. A different steel and a higher HRC number could add up to a significantly higher grind temperature. Just how significant we don't know. Also, higher HRC knives are tempered, generally, at lower temperatures making the potential for altering hardness, it might seem, more likely. This would assume that tempering temperatures are among those that we are concerned with but the answer to that question is not yet clear to us.
Here's an unexpected benefit of our test and one that gives us additional confidence in our results; as you already know, the business end of a knife is the edge apex. This is the area of our concern and is only a very few microns in height and much less in thickness. To observe melting Tempilaq in the immediate area surrounding a region so small is a questionable task even with the aid of a digital microscope. We were successful, during the grinding process, of raising a contiguous burr that was several thousandths of an inch in height (25.4 microns = .001"). The thickness, or thinness as you prefer, of the burr metal should approximate the thickness of the edge apex (therefore approximating the thermo mass characteristics of the apex ) but over a much larger and more easily observable area. The Tempilaq that was adhered to the backside of the burr steel remained opaque.
Note on the above: We would have liked to have described the Tempilaq on the backside of the burr as being "clearly opaque" but that just doesn't sound right does it?
Hardening on the surface and softening beneath? Sounds like the fodder that many Knife Forum discussions are made up of and, possibly, could be quite accurate but, of course, very difficult to test for and validate. This applies to all discussion of HRC levels of edge apexes because, once again, we can't actually conduct an HRC test at or near the edge apex. If someone has actually figured out how to accomplish this then we will stand corrected.
There is at least one variable in our test that might prove significant; our test knife was a cheap stainless steel model purchased at the discount store some time ago. We'd guess HRC55 or so. We'd could do better than a guess at hardness because we do own a Rockwell bench tester but Mark Reich won't fly down here and show us how to use it. Harder knives are harder to grind. A different steel and a higher HRC number could add up to a significantly higher grind temperature. Just how significant we don't know. Also, higher HRC knives are tempered, generally, at lower temperatures making the potential for altering hardness, it might seem, more likely. This would assume that tempering temperatures are among those that we are concerned with but the answer to that question is not yet clear to us.
Here's an unexpected benefit of our test and one that gives us additional confidence in our results; as you already know, the business end of a knife is the edge apex. This is the area of our concern and is only a very few microns in height and much less in thickness. To observe melting Tempilaq in the immediate area surrounding a region so small is a questionable task even with the aid of a digital microscope. We were successful, during the grinding process, of raising a contiguous burr that was several thousandths of an inch in height (25.4 microns = .001"). The thickness, or thinness as you prefer, of the burr metal should approximate the thickness of the edge apex (therefore approximating the thermo mass characteristics of the apex ) but over a much larger and more easily observable area. The Tempilaq that was adhered to the backside of the burr steel remained opaque.
Note on the above: We would have liked to have described the Tempilaq on the backside of the burr as being "clearly opaque" but that just doesn't sound right does it?