Cliff Stamp
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- Joined
- Oct 5, 1998
- Messages
- 17,562
Recently, mainly to show one aspect of the edge retention advantage of a KX06 utility kitchen knife from Spyderco, I compared it on cardboard to a Henckles paring knife. The 1/8" ridged, cardboard was cut on a draw, across the ridges, though three centimeters of edge. The knives had micro-bevels applied at 20 degrees with the medium ceramic rods off of a Sharpmaker, the bevels were 0.15 mm wide.
The numerical details will be given in full detail in the review of the KX06, but in short, the blades were equal in sharpness at the beginning, and after extensive cutting (166 m), the KX06 had a significant advantage. This really isn't surprising, nor overly interesting as it is a harder and higher alloy steel, so its as expected, that being said it is nice to confirm such behavior on occasion.
What is interesting is that even though the Henckels wore much fast enough that the difference could be see under magnification, it continued to cut well because of the primary edge bevel, which was ground at 5.4 (1) degrees per side, almost flat to the spine. As pointed out by Mike Swaim and Alvin Johnson on rec.knives back in the mid 90's, geometry makes a significant impact on cutting edge lifetime (not simply sharpness), and that the behavior is opposite as what is commonly presented (lower profile -> reduced edge lifetime).
In fact, comparing the Henckels to the KX06, even when the Henckels was wore so much that the microbevel was completely removed, it could still continued to cut well because the primary edge bevel was so acute. In fact given its overall much lower profile than the KX06, it actually outcut it (by force required to cut the cardboard), even though the KX06 was significantly sharper.
Now of course the point could be made that this isn't a fair comparison of the two knives, which is true, but the point isn't to do so (well, it started that way, but became something else). The point here is that a significantly inferior steel can be made to outcut a superior one, not simple in regards to initial performance, but also with extended used, due to a more suitable geometry - which of course is task specific. The very acute edge on the Henckles makes it very fragile.
It also brings up a specific point, which is when cutting very soft materials like cardboard and ropes, edge angles can be made very thin and acute and the performance just increases as the durability requirements for such materials is very low. Of course different performance would be seen on harder materials like carving hardwoods, or cutting around bones, shelled lobsters, etc. .
Note that the amount of cardboard cut was large, there were four runs made, and averages takes to stabilize the results. Each individual run was 166 m, thus x2 for both knives, then x4 for the runs gives ~5000 cuts of a foot long each. I intended to cut until the knives could no longer cut the cardboard, but stopped after 166 m because it didn't look like the performance of the Henckles would change significantly because at this point it had wore off the secondard edge and thus subsequent changes would be slight.
As well of course, the performance of the KX06 could be improved by refining its edge bevel similar to the Henckels, which did not come that way NIB, it was reground awhile back on a belt sander.
-Cliff
The numerical details will be given in full detail in the review of the KX06, but in short, the blades were equal in sharpness at the beginning, and after extensive cutting (166 m), the KX06 had a significant advantage. This really isn't surprising, nor overly interesting as it is a harder and higher alloy steel, so its as expected, that being said it is nice to confirm such behavior on occasion.
What is interesting is that even though the Henckels wore much fast enough that the difference could be see under magnification, it continued to cut well because of the primary edge bevel, which was ground at 5.4 (1) degrees per side, almost flat to the spine. As pointed out by Mike Swaim and Alvin Johnson on rec.knives back in the mid 90's, geometry makes a significant impact on cutting edge lifetime (not simply sharpness), and that the behavior is opposite as what is commonly presented (lower profile -> reduced edge lifetime).
In fact, comparing the Henckels to the KX06, even when the Henckels was wore so much that the microbevel was completely removed, it could still continued to cut well because the primary edge bevel was so acute. In fact given its overall much lower profile than the KX06, it actually outcut it (by force required to cut the cardboard), even though the KX06 was significantly sharper.
Now of course the point could be made that this isn't a fair comparison of the two knives, which is true, but the point isn't to do so (well, it started that way, but became something else). The point here is that a significantly inferior steel can be made to outcut a superior one, not simple in regards to initial performance, but also with extended used, due to a more suitable geometry - which of course is task specific. The very acute edge on the Henckles makes it very fragile.
It also brings up a specific point, which is when cutting very soft materials like cardboard and ropes, edge angles can be made very thin and acute and the performance just increases as the durability requirements for such materials is very low. Of course different performance would be seen on harder materials like carving hardwoods, or cutting around bones, shelled lobsters, etc. .
Note that the amount of cardboard cut was large, there were four runs made, and averages takes to stabilize the results. Each individual run was 166 m, thus x2 for both knives, then x4 for the runs gives ~5000 cuts of a foot long each. I intended to cut until the knives could no longer cut the cardboard, but stopped after 166 m because it didn't look like the performance of the Henckles would change significantly because at this point it had wore off the secondard edge and thus subsequent changes would be slight.
As well of course, the performance of the KX06 could be improved by refining its edge bevel similar to the Henckels, which did not come that way NIB, it was reground awhile back on a belt sander.
-Cliff
