Anyone ever try doing edge retention testing on their own?

Discussion in 'General Knife Discussion' started by marrenmiller, Jun 26, 2020.

  1. marrenmiller

    marrenmiller Basic Member Basic Member

    Apr 6, 2017
    After years of just assuming there would be differences between different steels, heat treatments, edge angles, etc, but doing little formal testing to confirm anything, I finally decided yesterday to do some proper testing on some of my knives. Specifically, this started because I have never had great experiences with Zero Tolerance knives, and I wanted to see if this was due to my bias against ZT as a company or if they really just do a poor job heat treating their steels.

    I borrowed a Spyderco Tenacious which had been gifted to my fiancee and sharpened it on the KME at 17 dps at a 600 grit "fine" finish, then stropped it on 0.1m diamond compound on leather. Next, I put the same exact edge on a ZT 0308. Both knives had a 1" section of mild belly taped off after sharpening. Then, I prepared a ton of U-Haul cardboard box panels for the test (with a third knife not being tested) to consistent and measured lengths. My testing would entail cutting the panels into strips along the grain and recording the number of times I cut a given length panel with the 1" section of each knife before 1) the knife stopped shaving hair, and 2) the knife stopped comfortably cutting held printer paper. I used some sheets of cardboard as my cutting board to prevent the knife from hitting the ground at the end of a cut. Standard stuff for edge retention testing, or so it seemed at the time. Here's what actually happened:
    • The edges on both knives wore down at exactly the same rate, from what I could tell. Even though there's supposedly a massive difference between the knives, I could not reliably determine one knife to perform better than the other. I thought I must have screwed something up sharpening on my KME, so I very carefully sharpened the ZT up on a DMT fine plate, stropped it, and tried a second time, but saw no difference in performance.
    • The point of stopping seemed completely arbitrary, and it was very difficult to tell when I should stop cutting and move on to the next test. For shaving, I could stop when it became difficult(?) to cut hair normally but I could always just increase the pressure and angle of attack and get the knife to continue to painfully scrape some hairs. This was especially difficult to determine with the paper cutting test, where a knife could be made to slice held printer paper slowly but consistently with the right technique, but was past the point where I would in normal use consider it dull.
    • Unlike other testers I've seen, in no case did I get anywhere close to hundreds of feet of cardboard cut before a knife lost its hair shaving ability or even paper cutting ability. Both knives lost hair cutting ability after about 40' of cardboard. Knives started being frustrating to cut paper with at about 80', but could limp along making short but clean slices long after that point. I didn't go too much further with the paper cutting test as the edges would be pretty useless to me at that point.
    • In a panic and wondering if I had messed up something in the tests, I grabbed some knives I was hoping would exhibit noticeably better edge retention and started cutting the cardboard. These included a Police 4 in K390 with 600 grit ~15 dps edge, a Benchmade 570 with a 600 grit ~15 dps edge, a PM2 in Maxamet (stock edge closely followed on DMT stones), and a Manix 2 in M390 (stock edge closely followed on DMT stones). The edges were drastically different, but this wasn't intended to be an apples to apples comparison; I was expecting to see a runaway in performance. These knives were razors when I started, but like the first knives none of them were noticeably better at holding a shaving edge after cutting a fairly small amount of cardboard. The Police 4 was doing a bit better with the paper cutting test, but after about 100' of cardboard it was past the point where I'd sharpen it normally. When in the realm of edge performance I actually care about, I saw no runaway in performance between the knives, not even with Maxamet.
    • The biggest difference I could perceive between the knives was in ease of sharpening. The Tenacious got sharp easily and in next to no time at all, as expected of 8Cr13MoV, whereas the ZT took a lot more effort and required more care to get rid of the burr. Maxamet and K390 felt harder on the stones, but I liked how they feel when sharpening more than the stainless steels. The Manix 2 in M390 was easier and more pleasant to sharpen than the ZT, for whatever reason.
    • On a light-hearted note, the testing made an absolute mess and my cat loved playing in the debris field I created. Our recycling bin is full, so I really should have timed this testing better.
    To be honest, I don't know what to think about what I saw during my tests. I'm sure every part of what I did could be disputed by someone, whether it be that my edges were not consistent, or that I had a burr on my knives that I didn't detect, or that I somehow cut the cardboard wrong or something, or that the cardboard wasn't homogeneous or consistent, but I did everything as consistently as I could, and I can sharpen a knife competently freehand or with my KME. I'm reasonably confident that nothing is particularly wrong with any of my knives. Maybe cutting U-Haul cardboard is just particularly hard on a knife? I don't know.

    If I need to devise ways to be even more controlled and methodical than this, and I need to run a ton of tests back to back and average the results to start to see definitive differences between steels, then I'm not sure any of the craze over steels with high edge retention is worth it to me. At the point where the super steels might have an advantage over lesser steels in working edge retention, in real life I would have written the knife off as dull sharpened it long beforehand. At least with corrosion resistance or ease of sharpening, the differences can be palpable even in an uncontrolled setting. I'm going to continue doing tests on my other knives to see if there's something I'm missing (in particular, retesting Maxamet and seeing if my 4V manix 2 is as good at holding an edge as it is difficult to reprofile).

    Has anyone ever tried doing something like this for yourself? I'd be curious to hear your thoughts.
     
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  2. Shorttime

    Shorttime

    Oct 16, 2011
    (Unhelpfully) no. I never even thought about edge retention until I read an article about CATRA testing, years ago. It's a complicated business, as you found out.

    I like the idea of having hard data about all aspects of knives, but I feel like gathering that information is best left to people who are more organized, with better self discipline, and bigger budgets.

    I'm not saying don't do your own testing if the fancy takes you, but you're going to need some kind of mechanical force gauge to get anything like comparable results. I have the feeling this is one of those rabbit holes that knife knuts can fall down, where you eventually have laboratory equipment, and a pile of knives that you bought, just for research purposes.

    Be careful out there: science is an expensive mistress.
     
    David Mary likes this.
  3. soc_monki

    soc_monki

    816
    Apr 5, 2019
    Nope. If my knives cut I'm happy. If they don't I touch them up. However my ZTs will hold an edge much longer than any of my spyderco or Kershaws in 8cr. Maybe I'll do some cardboard tests one day but for now I'm satisfied.

    You should check out outdoors55 on YouTube. He did a comparison between spyderco 8cr and S30v and surprisingly he found the same results you did. They performed about the same.

    It's funny how a few people find results like yours, but many others don't. I think something like Catra is the only way because it is more controlled and scientific.

    Another thing... I hear so many people saying zt has soft heat treats, but has anyone ever Rockwell tested them? I kind find hrc for so many knives, but trying to find even one ZT that's been tested is like pulling teeth. That could end the "bad heat treat" argument once and for all.
     
  4. vwb563

    vwb563 Gold Member Gold Member

    Jun 29, 2007
    I have done several impromptu card board cutting test similar to yours with pretty much the same results. There was a difference but I saw no huge difference from steels like 8Cr and 420(Bos) to m390 and s110v. I did notice a big difference when resharpening the knives though. The super steels took much more effort to get back shaving sharp.
     
  5. afishhunter

    afishhunter

    Oct 21, 2014
    Why bother? Eventually every knife is going to need re-sharpened, no matter what the blade is. (steel or ceramic)

    What difference does it make if I spend a couple minutes once or twice a week to freshen up the edge, or say, "half an hour give or take, once a month or so."? Neither option is going to result in "world shattering" or "life changing" consequences. :)

    If you're that worried about edge retention, get a Stanley or Husky or whatever brand box/utility knife and a supply of replacement blades. Takes seconds to change the blade for a new one. Remember, every time you sharpen your knife, you loose a little bit of steel. Eventually, you can sharpen any blade down to a toothpick.
     
  6. marrenmiller

    marrenmiller Basic Member Basic Member

    Apr 6, 2017
    Those videos are exactly what made me start thinking about it this week.

    But I think the big takeaway from his tests is that if something as controlled as his tests were indicated no visible difference, then why bother using Catra testing at all? In the end, the goal is a better user experience, not a higher test score by a machine.
     
    Last edited: Jun 26, 2020
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  7. marrenmiller

    marrenmiller Basic Member Basic Member

    Apr 6, 2017
    I don't claim to know they do soft heat treatments. It just always seemed like their steel performed poorly for me, which can be true while still hitting their target hardness if their HT is not optimum.

    I'll be ensuring my M390 Manix 2 is at the same edge angle/finish and repeating the test today. That knife always sharpened up much nicer for me, with less burring formed. I'll see if that results in something different.
     
    Last edited: Jun 26, 2020
  8. marrenmiller

    marrenmiller Basic Member Basic Member

    Apr 6, 2017
    You could look at it that way, but to me the promise of better steels is that some knives may be able to be sharpened less often, while not being a bear to sharpen when you do need to. I don't like having to sharpen a knife. If it took less than twice as long to sharpen and I can do it less than half as often, then that's a win in my book. My issue was that there was no observable difference when so many other testers repeatedly find significant differences.
     
    Last edited: Jun 26, 2020
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  9. marrenmiller

    marrenmiller Basic Member Basic Member

    Apr 6, 2017
    I don't want to get involved in highly refined, expensive testing. To me, that just indicates that if the difference is that slight, then there's no point to any of these advancements.
     
    David Mary likes this.
  10. Alberta Ed

    Alberta Ed

    Jun 29, 1999
    My real life edge testing is pretty basic, a stick of dry pine and some whittling. I enjoy the various CATRA and hemp rope and cardboard cutting exercises by the experts but am happy to leave that hard stuff to them. I know a knife is sufficiently sharp when I see blood before I realize I've cut myself:rolleyes:.
     
  11. soc_monki

    soc_monki

    816
    Apr 5, 2019
    Because catra has much more strictly controlled media to cut, and more controlled pressure. Doesn't matter who you are, you'll never be as precise as a machine! I still enjoy watching Cedric and Ada cut tests, because Pete is awesome and makes fun videos. His results also showed that different sharpening equipment made for different results so... More questions to be answered!
     
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  12. soc_monki

    soc_monki

    816
    Apr 5, 2019
    That is true. I've always had their steel perform well for me, always have long lasting edges and good performance after lowering the edge angle. I haven't really gone to town on any spydercos yet because they come with good edge bevels anyway, and they just need touch ups, but ZT 20cv sharpens about the same as Benchmades 20cv and m390 so...? At least to me it feels similar.

    Still would like to see a Rockwell test on some ZTs so we can actually see some hrc data. Then we'll know if they are at least hitting a decent hardness.
     
    Razor likes this.
  13. marrenmiller

    marrenmiller Basic Member Basic Member

    Apr 6, 2017
    I understand that, but... humans aren't machines. If you can't demonstrate a difference in controlled use, what point is there? That's the question I'm trying to figure out. I understand an expensive machine cutting silicon impregnated card stock with precise controls and measurement systems can tell a difference, but I can't. Can you?
     
  14. marrenmiller

    marrenmiller Basic Member Basic Member

    Apr 6, 2017
    How low are you talking? This was at 17 DPS.
     
  15. soc_monki

    soc_monki

    816
    Apr 5, 2019
    Nope, not really. That's why I don't really worry about it. I buy knife designs I like, steel be damned. I can't tell much difference sharpening certain steels. 8cr or 420hc are easy and sharpen up quickly. However S30v, 20cv, m390 and m4 all feel very similar.

    S90v can go to hell. I only own one in s90 and it's such a pain. But, I like the knife so I'll deal with it!
     
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  16. soc_monki

    soc_monki

    816
    Apr 5, 2019
    14-15 dps. Usually with a 20dps microbevel, but I'm starting to get away from them.
     
  17. BITEME

    BITEME Gold Member Gold Member

    Dec 14, 2007
    I had this experience, it's a bit of a reality check- I have cut down my supersteel knife purchase by a bunch..I have really grown to love 14c28n to me I really like the feel of a super refined edge over a knife that feels dull but can supposedly cut forever
     
  18. vwb563

    vwb563 Gold Member Gold Member

    Jun 29, 2007
    I’ll tell you all a true story that I experienced. My first super steel knife was a Spyderco in S90V. I had read how the edge-holding ability of that steel was amazing so I finally broke down and bought one. Up until then I had always used stuff like Bucks in 420, Kershaws in 14c and 8Cr, and Benchmades in 154 and S30, and Victorinox knives in their stainless steel. Over the years working in a steel shop and only getting 30min lunch breaks occasionally I would be forced to use my carry knife at the time (which was normally a Victorinox Tinker or a Buck Prince) to cut the top out of a tuna can or a Campbell’s soup can. The knives edges held up fine. No chips or anything but I would certainly dull them considerably. Now fast forward to a few years ago on a Thanksgiving day. Family was over and I was carrying the Spyderco since it was a special occasion. Without really thinking about it I used the Spyderco to poke a hole in a chicken broth can. The blade did fine until I twisted it around to make the hole bigger. Big mistake. I heard this tiny “tick” sound and after pulling the blade from the can I discovered about an 1/8 of an inch of tip was missing. It had snapped off under the twisting motion. I know you’re not supposed to use a knife in that manner but it was something I had done several times before with Bucks and Swiss Army knives with no damage. I learned my lesson that day about the brittleness of the super steels. Brittleness and fact that they’re a bear to resharpen makes me shy away from the super steels. I’d rather have a medium grade steel that’s tough and reasonably easy to sharpen. But that just me. Your mileage may vary.
     
  19. Fanglekai

    Fanglekai

    Jan 7, 2007
    Why not just use the can opener on the SAK?
     
  20. AntDog

    AntDog Gold Member Gold Member Basic Member

    Apr 3, 2001
    At my last job, I cut the same stuff day in and day out. I sharpened my knives to the same angle using the same technique. I only sharpened them up when they wouldn’t cut worth a sh!t.

    They all behaved differently. Some steels lose razor sharpness pretty quickly, but retain a good working edge for a long time. Some steels go outright dull quickly.

    Just one comparison that stuck out in my mind from two knives I used extensively - I only had to sharpen my Sere 2K (VG10) a coupe of times a year, but I had to sharpen my Cold Steel mini Recon 1 (AUS8) every month. This was with both knives sharpened to the same angle, using the same technique, to the same level of sharpness, then seeing near constant use until they wouldn’t cut worth a damn anymore.

    Daily use will tell you a lot about how different steels function.
     
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