Yup. We are on the same page Mr. KG. It was only after rereading your post that I understood that you were offering an explanation of why test results differ for edges of the same sharpness but with different bevel angles. I feel a bit meager of mind because you stated it most clearly. After all, the subject of your post is, “Why the 40° edge will not score as well as the 20° “, as opposed to Why the 40° edge is not as sharp as the 20°.
If I understand correctly, you are suggesting that test media must be penetrated to some depth before it cleaves and that this depth is enough so that the bevel interaction with test media measurably affects the sharpness reading. Additionally, the impact of bevel angle is significant, accounting for a ~40 point variation between 15 and 20 degrees of bevel angle for similar edges of the same sharpness.
I like that hypothesis because I can now blame test instrument limitations for what I had previously assigned to my own faulty technique.
Test media is some amazing stuff and I am personally hesitant to assume understanding it's qualities or how it works. With very sharp edges it severs with almost no force and yet is able to withstand 2,000g+ of force with a dull edge. I don't understand how it functions well enough to suppose if it supports the bevel hypothesis or not.
While interesting, I have no idea as to the validity of your hypothesis. Moreover, verifying it is problematic as the only accurate way I have of measuring sharpness is with the instrument in question. Yes, there is empirically derived evidence of hair splitting, etc., but in my mind that is only suggestive and not quantifiable.
This is really some cutting edge stuff here and we are considering hair splitting details. (Puns intended). I hesitate to delve into subjects like this because I think it way over complicates practical knife sharpening adding to the mysticism so prevalent in knife forums.
That said, I know you are very meticulous in your technique and when you present a 40 point sharpness difference, even though for all intents and practical purposes for cutting onions it matters little, it is curious and methinks merits a bit of head scratching.
If I understand correctly, you are suggesting that test media must be penetrated to some depth before it cleaves and that this depth is enough so that the bevel interaction with test media measurably affects the sharpness reading. Additionally, the impact of bevel angle is significant, accounting for a ~40 point variation between 15 and 20 degrees of bevel angle for similar edges of the same sharpness.
I like that hypothesis because I can now blame test instrument limitations for what I had previously assigned to my own faulty technique.
Test media is some amazing stuff and I am personally hesitant to assume understanding it's qualities or how it works. With very sharp edges it severs with almost no force and yet is able to withstand 2,000g+ of force with a dull edge. I don't understand how it functions well enough to suppose if it supports the bevel hypothesis or not.
While interesting, I have no idea as to the validity of your hypothesis. Moreover, verifying it is problematic as the only accurate way I have of measuring sharpness is with the instrument in question. Yes, there is empirically derived evidence of hair splitting, etc., but in my mind that is only suggestive and not quantifiable.
This is really some cutting edge stuff here and we are considering hair splitting details. (Puns intended). I hesitate to delve into subjects like this because I think it way over complicates practical knife sharpening adding to the mysticism so prevalent in knife forums.
That said, I know you are very meticulous in your technique and when you present a 40 point sharpness difference, even though for all intents and practical purposes for cutting onions it matters little, it is curious and methinks merits a bit of head scratching.