02-21-2018, 04:11 PM
I see several interesting things in this post Jan. The knife is perfect. I attended a rural grade school grades 1-8 and the curriculum was a little different than today. In addition to the standard school art fare I learned hand sewing, knitting and in my 7th & 8th grade years, wood carving. Can't say that i was terribly proficient at any of them but it was good experience. I think that the wash cloth that I knitted began at about 12 inches wide and finished at 14 and today, I don't imagine that they'd let a kid spread his own butter if it involved a knife. Seeing your wood carving knife makes me want to take it up again.
When you say "core" HRC I assume you mean exactly what you say but are you actually distinguishing hardness levels between the core metal of the blade and the surface? If so, then A; what leads you to believe that the two are different and B; how did you arrive at an estimation of the core hardness? If I've misunderstood your intent here then pardon me.
I've seen your optical knife angle instrument before but studied the picture a bit more this time. It's quite ingenuous. Reminds me of the HRC question we just took on in that I've seen this question asked a thousand times as well. The difference being that everybody has a suggestion for determining grind angle but none are even remotely as elegant or accurate as your solution. I realize that the mechanics here are key. Have you ever attempted an edge with a secondary bevel? If so, do you get two sets of reflections or just one? Next question, is the reflected laser line width indicative of the behind the edge measurement/sharpening angle and if so, is this readily apparent? This last question is with regard to thicker metal sharpened at more acute angle = wider bevel. Of course the limiting factor here might be the original width of the projected laser line.
As usual, great stuff Jan!
When you say "core" HRC I assume you mean exactly what you say but are you actually distinguishing hardness levels between the core metal of the blade and the surface? If so, then A; what leads you to believe that the two are different and B; how did you arrive at an estimation of the core hardness? If I've misunderstood your intent here then pardon me.
I've seen your optical knife angle instrument before but studied the picture a bit more this time. It's quite ingenuous. Reminds me of the HRC question we just took on in that I've seen this question asked a thousand times as well. The difference being that everybody has a suggestion for determining grind angle but none are even remotely as elegant or accurate as your solution. I realize that the mechanics here are key. Have you ever attempted an edge with a secondary bevel? If so, do you get two sets of reflections or just one? Next question, is the reflected laser line width indicative of the behind the edge measurement/sharpening angle and if so, is this readily apparent? This last question is with regard to thicker metal sharpened at more acute angle = wider bevel. Of course the limiting factor here might be the original width of the projected laser line.
As usual, great stuff Jan!