Okay, so, about 1400 feet of cardboard cut later... I have really come to like T15 quite a lot.
Spine Thickness: .115"
Primary blade grind: 2.5 Degrees Per Side
Edge angle: 15 Degrees Per Side
I started off re-profiling the edge to 15 degrees per side. The edge from the factory was pretty close to this as measured with a laser goniometer, though with a few spots where it wavered by about 2 degrees. I figured that as well as making sure there was no "burnt" metal, that I could probably get it more even (no shade). I set the edge with a 400 grit Atoma, and it was insanely sharp. First time I ever regretted doing a 3-finger test, as I immediately cut myself. But, since my past edge-retention tests have been done with a 2k polish, followed with a 600-grit finish, I decided to follow suit. I ended up with an edge that was 15 dps +/- 1 degree, and 114 BESS. It would tree-top my beard-hair, whittle it, etc. and pop off arm-hair. Wasn't quite as aggressive as off of the 400 grit, but certainly in tune with what I'd call sharp.
So I started off performing the tests I did in my K294 and 10V testing:viewtopic.php?f=15&t=95675
Using 8.5" wide slats of single-layer corrugation cardboard that I get from Chewy pet supply shipments. I draw-cut downward through the corrugations at 8.5" lengths, going from heel-to-tip of the blade. The slats are held by hand suspended in the air so there's no cutting-board or anything to consider.
100 cuts in, it was already outperforming 10V or K294 in terms of holding the up-front sharpness. The latter steels tend to degrade from their initial sharpness quite immediately into a "working sharp" state, and hold that for a while. On the other hand, this seemed to show almost no dulling after 100 cuts, or about 70 feet worth of cardboard. In fact the BESS difference per foot remained basically static through the first 500 cuts.
Through 500 cuts, or 354 feet, the BESS score dropped to 205, which is still quite respectable. Anecdotally, it was still "hair scraping" sharp. Meaning it would shave off some arm/leg hairs, but still kind of scrape some skin off along with it. Still quite sharp, and sharper than 10V/K294 at the same state both in terms of BESS score, and especially in terms of the feel on a 3-finger test. This is kind of the "transitional" phase where 10V/K294 would go into a "working-edge". In terms of BESS, the T15 was still about 50 points ahead of both 10V/K294 at this point.
I didn't really have enough cardboard to test the T15 out to the same extent I had done the 10V/K294, but honestly I don't really think it's necessary either. Larrin Thomas has CATRA data showing exhaustive edge retention figures, and so I'm really more interested in trying to map out the front-end sharpness. There's also some questionable variability in my BESS testing, where some of the figures would seem to suggest T15 having twice the edge retention of 10V at the same amount of cutting, but I have a theory about that I'll share further down.
That said, my anecdotal experience matches the initial drops in BESS scores among all three steels, and I have heard similar reports about T15 holding it's initial sharpness longer as well. It would take cutting into literal miles worth of cardboard to start seeing differences in absolute edge retention.
I'm kind of curious about why T15 would hold the front-end sharpness longer than the more carbide-rich steels. Looking at some comparative micrographs from Knife Steel Nerds, I have a theory...
T15:
10v:
The interesting thing is that while 10V/K294 clearly has more carbide volume, the size of them is roughly the same in T15. I think that might explain why it holds the initial sharpness longer than 10V, because that ferrous matrix is basically going to degrade at a similar rate for each steel, meaning the point in which it's the carbides holding the edge structure comes sooner for the 10V/K294. Since the T15 steel has more of a ferrous matrix with smaller grain sizes, it maintains an apex that is narrower than the size of the vanadium/tungsten carbides. Say each steel starts with a 1 micron apex, and the vanadium carbides and vanadium/tungsten carbides are 3 microns wide, the T15 actually has more sub-3-micron grains to lose than the 10V/K294, so it's apex will remain narrower than 3 microns for longer. I think the only issue with that theory is that edge apexes seldom get down to 1 micron in general, but I think the same effect would scale to apexes that are much wider and more carbides present in the cross-sectional volume of the apex.
As far as the numbers suggesting T15 will outcut 10V/K294 goes...
I wish the CATRA numbers showed the loss in sharpness along the duration of the test, because while there's no reason to believe that T15 will outcut 10V/K294 based on CATRA results, I also have to wonder just how sharp the 10V and K294 really are once they get up to the 675 TCC level that T15 sits at. Obviously it reaches a threshold where it will no longer cut the CATRA media, but I wonder where both steels sit in terms of a BESS score at these points. Personally, I consider a knife dull and in need of touch ups at about 300-400 BESS, but I am guessing that the minimal BESS score needed to cut the CATRA media is well above that.
If you look at the BESS scores of K294 and T15 at 991 and 1,416 feet respectively, they're nearly the same. The K294 and 10V don't drop down to what I would call dull until 2,125 feet, with BESS scores around 450. But, if you look at the 10V and K294 at 708 feet, they're already at 383 and 323 BESS respectively, while at that point T15 is still only 217 at twice that amount.
By the BESS scores it would seem like you could predict that T15 stays sharper for longer, but with the 10V and K294 outperforming T15 on the CATRA, you have to wonder what that BESS threshold is where it will no longer cut cardstock. I am just speculating, but given that CATRA uses 1mm thick, 5% silica, card stock, I am guessing that it has to be somewhere over 1000 BESS just based on when I can no longer cut cardboard of similar thickness.
In a way, and at the risk of sounding like I am disparaging the CATRA test--which I am not--it seems like that test doesn't test how long it takes a knife to get dull, but rather tests how long it takes a knife to stop cutting at all, even after it would be called dull. Yet I think that's the point. "Dull" is subjective. Failure to cut is objective.
So my final conclusion is this: 1400 feet of cardboard is a lot of cardboard. I mean, it literally took me hours to complete this test, cutting slivers of cardboard that were maybe 1/8" to 1/4" wide. While 10V/K294 may ultimately hold an edge through more feet of cardboard, I think the fact that T15 holds a finer edge for longer is a really huge factor.
It's very likely that a person would do a touch-up before cutting that much, and so if you think about it in those terms, the ability for 10V/K294 to hold a working edge for longer isn't as valuable. I mean, we are talking about literal hours of time, and literal miles worth of material. The idea that a person couldn't find the time to perform a small touch-up in the interim would really depend a lot on the actual task at hand. I wouldn't want to stop and sharpen it if my knife was all covered in blood, for example. But if we're talking about EDC edges that you want to just stay sharp and not have to sharpen as frequently, I think T15 might have the advantage there since it seems like it holds an initial level of sharpness for much longer.
Before this testing I would have put 10V/K294 firmly as my favorite, but now I'm thinking that T15 may supplant it. Personally I think this is more of a revelation that I just don't actually need to exhaustive level of edge retention 10V/K294 provides, but want a steel that preserves initial sharpness for longer as a trade-off.
?
We collectively can't seem to even agree on what exactly explains steel performance in some of our tests and ceramic is very different from steel.