01-17-2018, 10:53 AM
Your post timing is excellent Grepper and made even better by the fact that we couldn't get this post up yesterday due to our host's server issues.
But now we're getting someplace. We decided that rather than take the time to repeat our first test that we'd just jump the weight up and see if we were on the right track at all. 4.7 lbs didn't seem to have much effect but 9.7 lbs. did. Same knife and edge location as the first test but we began this time with a little lower initial sharpness number after additional leather only honing on the edge. The edge, this time, measured 159 to begin.
We put the knife in the test fixture and applied the 9.7 lbs at the platen and then removed the knife. Measured 429 and 445 at two different points. That's a lot of roll! But was it roll or crush? If the edge is crushed it won't come back with leather honing. We straightened the edge on a Sharp Pad and then took a lot of measurements and additional honing. The story didn't change with the additional honing/measurement efforts. At the estimated epicenter of the 5/16" diameter test point we got 229. Not bad but not perfect either. 1/16th inch to the side of that point we got 160 and we got 160 again when we moved the measurement point a 1/16th of an inch to the other side of the 229. These numbers were very reproducible. So, in a nutshell, the 229 was in the middle and flanked equidistant on both sides by 160's. Everywhere else inside the test area measured very close to 160. The reason/cause for 229 versus 160 was not visually discernible using an optical microscope.
So it was almost a perfect test sans our one 229. We got the kind of edge movement we were looking for, approximately 280 points, and fell just short of restoring the edge to its original sharpness level. A few adjustments and we might just get there. Past experience tells us that 300 points of roll on stainless steel knives is just about the limit. Beyond that, edges usually cannot be fully restored. A well designed edge test system might more accurately define this limit though.
This second set of measurements is very encouraging. Please keep in mind with these reports that, at this juncture, we're only testing the tester and the edge information presented is secondary to that purpose. Once we get our test fixture and procedure tuned in that's going to change. Then we might not have to speculate about many of the factors we think might be germane to producing long lasting and serviceable edges, we'll just know.
But now we're getting someplace. We decided that rather than take the time to repeat our first test that we'd just jump the weight up and see if we were on the right track at all. 4.7 lbs didn't seem to have much effect but 9.7 lbs. did. Same knife and edge location as the first test but we began this time with a little lower initial sharpness number after additional leather only honing on the edge. The edge, this time, measured 159 to begin.
We put the knife in the test fixture and applied the 9.7 lbs at the platen and then removed the knife. Measured 429 and 445 at two different points. That's a lot of roll! But was it roll or crush? If the edge is crushed it won't come back with leather honing. We straightened the edge on a Sharp Pad and then took a lot of measurements and additional honing. The story didn't change with the additional honing/measurement efforts. At the estimated epicenter of the 5/16" diameter test point we got 229. Not bad but not perfect either. 1/16th inch to the side of that point we got 160 and we got 160 again when we moved the measurement point a 1/16th of an inch to the other side of the 229. These numbers were very reproducible. So, in a nutshell, the 229 was in the middle and flanked equidistant on both sides by 160's. Everywhere else inside the test area measured very close to 160. The reason/cause for 229 versus 160 was not visually discernible using an optical microscope.
So it was almost a perfect test sans our one 229. We got the kind of edge movement we were looking for, approximately 280 points, and fell just short of restoring the edge to its original sharpness level. A few adjustments and we might just get there. Past experience tells us that 300 points of roll on stainless steel knives is just about the limit. Beyond that, edges usually cannot be fully restored. A well designed edge test system might more accurately define this limit though.
This second set of measurements is very encouraging. Please keep in mind with these reports that, at this juncture, we're only testing the tester and the edge information presented is secondary to that purpose. Once we get our test fixture and procedure tuned in that's going to change. Then we might not have to speculate about many of the factors we think might be germane to producing long lasting and serviceable edges, we'll just know.