Edge Holding of TSEK, Vapor, Kitchen Utility and Stanley Utility

me2

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Oct 11, 2003
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Just tested the edge holding of the TSEK by Benchmade, the Vapor II by Kershaw, and a Stanley utility knife blade on cardboard. 100 cuts were made, about an inch long on about 1.5 inches of blade. All the cardboard came from the same box. At the end of the cutting, I tested to see if the knife would cut a plastic grocery bag. I find that a knife that will still shave hair a little will not cut one of these. Cutting was generally a slicing type cut.

The blades were sharpened (except the Stanley) using a belt sander at 320 grit to set the edge and raise a small burr at about 15 degrees per side, and then sharpened at 20 degrees per side (DPS) on the Spyderco Sharpmaker using the brown rod flats only. 1-2 light cuts were made into the brown rod to remove the burr from the sander, and Jeff Clarks Sharpmaker deburring technique was used, slightly modified, to remove any burr formed during sharpening. The modification was that I didnt move to the white stones, but after about 20 strokes per side, used a couple of light 80 DPS strokes to remove any burr, then did about 10 more strokes per side to finish up. All three knives would cleanly slice the plastic bags. The Stanley utility blade was new and the factory edge was used.

The Benchmade would still cut the bag after the test, but took a little effort. The Vapor II would also still cut the bag, with a barely detectable bit more effort than the Benchmade. The utility knife would not cut the bag.

Today I compared a $5 kitchen knife from Kroger to the Benchmade TSEK. I used an empty cereal box for cutting. The Benchmade was resharpened on the Sharpmaker after the last test. The Kroger knife was set with a 12 DPS backbevel, then sharpened on the 20 degree Sharpmaker slots the same as above. The first test showed that the Kroger would still cut the bag after the cardboard cutting, but the Benchmade would not. I was quite surprised by this. I repeated the test and the rolls reversed, with the Benchmadecutting the bag with difficulty and the Kroger not cutting at all. Fo the second test the knives were just resharpened on the Sharpmaker.

Since both knives were in slightly different condition, with respect to edge formation and resharpening, I intend to sharpen both on the belt sander and use the strop on the sander as a final finish. This should eliminate any burr issues, but changes the edge finish and angle, therefore it wont be in any way comparable the testing of the others in the above, other than by relation through the Benchmade. Actually, the Kershaw saw some concrete cutting, so I may be able to resharpen all 3 and run the test again with a new Stanley blade. Anyway, interesting results, and I'm quite surprised by the Kroger knife not being completely outclassed by the Benchmade.
 
The very high carbide steels sometimes have extremely low performance and by this I mean a small fraction of their optimal performance if the edge falls along the major carbides as they can tear out. I have seen wild variances in steels like that which surprised me for awhile until I saw the work that Landes had done and he saw the same thing even with highly controlled machine testing and then he had the micrographs to show the carbide disintegration being the problem.

As a suggestion, it would be very informative to know the ratios of when they would stop cutting. How much cardboard can be cut with each blade before they stop cutting the bag. This ratio could then be used to give a numerical estimate. So you could say, the Benchmade cut 50% more material or whatever. Ideally you do a number of runs and average to ensure you are not seeing just some fluke variation.

Anyway, nice work.

-Cliff
 
Cliff.... when you say high carbide ... you mean concentration and not
the size of the carbides? If so, then what about the effect
of small versus large carbides in the above phenomenon.
 
Both tend to be related, as the volume of carbides increases so does the size due to probability of aggregates. A side issue would be PM vs ingot, but Landes has tested this and found no significant increase in edge stability as the volume is still the same, so overall the intersection area of the edge through the carbides is constant and thus is the probability of premature blunting.

-Cliff
 
Ok, tested the Chinese kitchen knife today. 175 cuts before it stopped cutting the bag. It still shaves pretty easily, requires slicing instead of push cut, but its there. I'll try the Benchmade tomorrow. This is on different cardboard, double layer, from a moving box, so it cant be compared to values from before. Oh yea, for this round, sharpening was on the belt sander, 320 grit, then leather belt w/ white compound from Sears. Angle was about 15 DPS, give or take one or 2 either way.
 
Ok, round 2 with the Benchmade was just completed. So far I have 300 cuts with the BM, and 175 w/ the Kitchen knife. I'll try to get the Vapor done this week. I'm out of bags though. The brown ones are harder to cut than the white ones from Wal Mart. After failing to cut the brown ones, both knives would still cut the Wal Mart bags easily. The Benchmade would also shave after the 300 cuts dulled it to the point that it didnt cut the brown plastic bag. I want to try to run the tests again after all 3 have been dulled, and resharpened on the white Sharpmaker stone flats at about 30 DPS. This is how I usually sharpen knives between trips to the sander, just freehand some light passes, 5-10 passes per side, and I use a fairly high angle, nearly 25 DPS or so. I expect to see a drop in edgeholding after the touchup on the white stones, but I dont know how much.

I'm guessing the variation I saw earlier was from the blades not being in the same condition w/r to recent previous sharpening. I've read Cliff's comments on removing any deformed/fatigued steel from the edge to get optimal sharpening and edgeholding. I am now a firm believer in this as I had a great deal of trouble sharpening some abused blades this weekend. The have been used for about 4 years w/ only light sharpening about every 6 months, just a ceramic rod or something. The are kitchen knives of the same brand that I have. After sharpening with a 120 grit belt and removing the burr w/ fine India, a small burr was still present and very tenatious. I cut into the stone 2-3 times, and removed it, then started over. After a second trip to the 120 grit belt, the burr was still pretty stubborn, but it was at last removed with very light passes over the fine India. The edge would whittle beard hair held between my fingers. In contrast, I took one pass into the belt to remove the old steel on some knives at home (same brand/models except for handle material), and they took a very aggressive edge with only about 10 relatively firm strokes on the fine India.
 
I'm guessing the variation I saw earlier was from the blades not being in the same condition w/r to recent previous sharpening.

Yeah, this can be a big issue. Many things like this really can give bad impressions to people about knives/steel. I have had some knives people gave to me that they hated to sharpen for these exact reasons.

In contrast, I took one pass into the belt to remove the old steel on some knives at home (same brand/models except for handle material), and they took a very aggressive edge with only about 10 relatively firm strokes on the fine India.

Funny thing is that most knives used to be like that because people sharpened them on actual stones often so there was never a buildup of weakened steel plus the steels used were sensible for knives. Now the alignment based "honing" combined with the soft and high carbide steels really causes problems in this area.

-Cliff
 
What do you mean by alignment based honing? Steeling and such? I've never seen the benefit of a steel. I've always used fine ceramic for final honing and touch up between honing.
 
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