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Production M390 - Expectation vs Reality?

Discussion in 'General Knife Discussion' started by Cosmodragoon, Jun 11, 2019.

  1. Rykjeklut

    Rykjeklut Basic Member Basic Member

    May 23, 2018
  2. scott.livesey

    scott.livesey

    Nov 10, 2011
    another "Tempest in a Teapot." Does anyone know the Rc tester model the knifemaker or the video maker used? What level of calibration was done to the tester? What is the tolerance of the tester? Unless you are using "Standard" level equipment, +/- 1 unit would be the best expected.
    What is the tolerance of the calibration blocks? anywhere from +/-1 to +/-3 is what is sold. expect to spend $200 for one Rc60 +/-1 test block
    How is the calibration block being used? If you test too close to a previous test, your results are going to be high. When one side was covered with test marks, did you turn it over? if you did, your results are skewed, because the reverse side does not have the same surface finish. How close to the edge are you testing. too close and results are skewed. How thick is material being tested, if less than 10x the test hole depth, results skewed. is spot being tested flat and 90* to the test arm, if not more error
    So here we are, Little Johnny and Scott have the same model tester, calibrated by same calibration lab, same test blocks. Johnny tests a knife and gets a reading Rc64. Mails Scott the knife which he tests and gets a reading of Rc60. Who is right? Knife and the testers are sent to third party who has higher tolerance equipment and the blade measures Rc62. Scott's tester was -1 and the calibration block was -1. Jason's tester and cal block both read +1. So both were right.
    the old sailor
     
    Last edited: Jun 21, 2019
    miso2, ArchVV and Pomsbz like this.
  3. Pomsbz

    Pomsbz

    Jul 31, 2015
    @Larrin I would be interested in your take on this, you have a bunch of expertise and test data. What is the optimum hardness for a user M390 blade? What would you consider too hard? How much difference is there between 58 and 60 in real world use?

    The video in the OP suggests that 62 is a base limit, that anything under 60 is appalling. I personally haven't got a clue if either of those suggestions are true or what context they are being presented. I know my car doesn't get the advertised gas mileage (I wish!), it would be interesting to be presented with the context of claimed optimal values and testing variations so that we can slot the information into the buying matrix considering the hardness in relation to grind, edge angle, thickness BTE, etc, etc.
     
  4. Banter 247

    Banter 247

    374
    Feb 22, 2019
    I hope the new model is hitting that hard, using a good process to get into that range. The best outcome for all involved is a company thriving, based on delivery of a good product.

    As for the existing samples which have hit low, Kurt is working things out to go visit Peters ht to provide third party confirmation of results. Edge retention tests have been done, and should be up soon.

    An important thing to remember is that each test tells us only the hardness of a single sample. It doesn’t tell us how or why it’s that hard, only that it is.

    It is entirely possible that the tests on those BestMan samples are accurate, and that the tests on the ones that hit low are also accurate.

    I’m expecting a few days of heated exchanges between now and when Kurt gets to Peters ht, followed by a flurry after those hits come out.
     
    cwsmith17 and Rykjeklut like this.
  5. 353

    353

    972
    Feb 20, 2015
    Låll!! :D
     
  6. Larrin

    Larrin Gold Member Gold Member

    Jan 17, 2004
    I don't tend to provide specific recommendations on hardness because of all of the different factors that go into it. I certainly have my own opinions about what steel/hardness combinations are best for certain knives/applications. In toughness testing of M390 we got pretty decent results (compared to other steels in its category) at about 62 Rc. So I think the steel can handle that range. Whether 60 Rc, 58 Rc, etc. is "bad" is more opinion. The thinner the edge of the knife, the more you are going to notice the effect of hardness, in that a lack of strength becomes more relevant. Cutting operations that tend to lead to rolling are also going to make it more apparent. The wear resistance is still going to be relatively high on M390 even at 58 Rc, but the slicing edge retention can definitely be reduced by about 5-10% per 1 Rc. Toughness can also be improved by reducing hardness, of course, depending on the heat treatment chosen. Moving to a tougher steel provides a much larger toughness improvement compared with dropping the hardness a couple points, though. Softer steel is easier to wear away in sharpening, but de-burring is more difficult.

    I have an article from last November about what Rockwell hardness means and what it doesn't: https://knifesteelnerds.com/2018/11/12/rockwell-hardness/
     
    attila., steff27, miso2 and 9 others like this.
  7. Pomsbz

    Pomsbz

    Jul 31, 2015
    Good information, thanks!
     
  8. Mrs_Esterhouse

    Mrs_Esterhouse

    36
    Apr 9, 2019
    I want 62HRC M390 and I want it now! :eek:
     
  9. J-RAY1989

    J-RAY1989 Gold Member Gold Member

    223
    Jun 14, 2019
    After using the m390 delica 4 for about a week, I can at least voucher for my unit. I've cut 18 gauge copper wire, injection molded urethane, gum rubber, zip ties, and multiple boxes over that time, with no rolling and no noticeable wear to the edge. Even hit metal with it a couple times. Haven't abused it, but it seems Spyderco got the heat treat right.
     
    cistercian and Banter 247 like this.
  10. Batmanacw

    Batmanacw

    16
    Mar 28, 2018
    What are we seeing for HRC from 20CV? Isn't it nearly identical?
     
  11. ScooterG

    ScooterG You mean Ireland? Yeah, it’s mine. Gold Member

    Mar 15, 2016
  12. Banter 247

    Banter 247

    374
    Feb 22, 2019
    Small sample size, so far. Most has hit 57-59.
     
  13. ShannonSteelLabs

    ShannonSteelLabs KnifeMaker / Craftsman / Service Provider Knifemaker / Craftsman / Service Provider

    Sep 9, 2015
    They are essentially identical.
    M390, 204P, 20CV.
    I would reccomend 61.
    But that's the only experience I have working with it. Great edge holding pretty decent toughness. (Heat treat by Peters)

    I know you can get 61-63. And I think it may be possible for 64HRC I believe @DeadboxHero would know more on that particular aspect than myself.

    My personal opinion is anything less than 60 is unnecessary for this steel. Its definitely tough enough to support about 60HRC. And with a great heat treat it will perform awesome. Not always about how hard it is. It's a knife not a prybar. Made to CUT.

    Take D2/PSF27.
    You can get if from some companies (some chinese companies) that boost the HRC to like 62. But the edge holding is crap or it doesnt perform well.
    Why? Bad heat treating protocol. Or poor sharpening.
    Conversely, you can get some D2 from a good company say Carothers, and have AWESOME results. Why? Perfect heat treat. Dialed in for the steel, and will smoke a poor heat treat.

    Seems like everyone is just going on and on about the hardness. It has more to do with the process of how it gets to the desired hardness.
     
    attila., cwsmith17, Mo2 and 7 others like this.
  14. Banter 247

    Banter 247

    374
    Feb 22, 2019
    I keep using the analogy of a table, where the table is performance, and the four legs are geometry, composition, ht process, and hrc. If any of them is out of whack, the table won’t stand up right.
     
    Rykjeklut, Mo2, Pomsbz and 2 others like this.
  15. BigWillie

    BigWillie

    182
    Jun 4, 2019
    any one of those ever magically lost an edge?

    I was responding to the guy who made a silly meme talking about magically losing edges

    Which again doesn't happen

    Quite a scroll there tho. If I'm supposed to be impressed by you rotating and taking pictures of your knives...I'm not
     
  16. Banter 247

    Banter 247

    374
    Feb 22, 2019
    Are you under the impression that it matters if you’re impressed?

    “Magically lost an edge” doesn’t happen, because we live in a world of physics. In this realm of rules and predictable behaviors, it is known that there are 3 primary ways in which edges are said to be “lost”. Those 3 ways are dulling, chipping, or rolling. Two of these have to do with edge stability. One correlates to wear resistance. Wear resistance and edge stability are each influenced in part by hardness.

    At certain extreme lows of hardness, dulling or edge deformation can happen very quickly.

    No magic. Just effects of ht process, composition, geometry, and matrix hardness working together to produce tangible results.

    Everything stated in this reply will remain true, whether or not you believe in them, understand them, or are impressed by them.
     
    attila., marrenmiller, Mo2 and 4 others like this.
  17. BigWillie

    BigWillie

    182
    Jun 4, 2019
    Yea and no matter those variables you're gonna know them after the first time it gets dull or if you change them via grind or whatever. So no edge will ever magically be lost.

    They don't go poof

    You just didn't maintain your tool

    If you knew you had a blade that would go dull after cutting a few pieces of cardboard up then you should be carrying something to sharpen in your pocket. And the same applies for any blade that held an edge longer. You know what's gonna happen. Maintain your tool don't blame it.

    This is off topic but it's crazy some of you imagine a blade being dull is ever the blades fault after the first needed sharpening. You should know by then how the tool performs even if it makes you wanna huck it in a river

    edit - probably some russian guy with some chinese crmov tools hand crafting himself a log cabin that will last decades right now. Many of our fore fathers managed just fine too. We know how to deal with crap blades it's almost never the blades fault in conventional scenarios.
     
    Mistman68 likes this.
  18. T.L.E. Sharp

    T.L.E. Sharp I support the 3rd amendment! Platinum Member

    Jun 30, 2016
    Your perspective on the issue is off I think. The problem with an m390 blade at a low hrc isn't that it's a bad knife or that it can no longer be used when it goes dull, it's that the end user paid a large premium for that m390 upgrade expecting an increase in performance that wasn't delivered.

    A Ferrari with a 3 cylinder diesel engine will still get you where you need to go, but you're going to be pissed if you were expecting a 12 cylinder fire breather.

    All blades will need maintenance. High end super steels should need less maintenance. A lot less. When it comes to this recent flood of m390, 20cv, 204p knives that hasn't been the case.
     
  19. Banter 247

    Banter 247

    374
    Feb 22, 2019
    No one at all is suggesting to not maintain your tools.

    1. Sharpening is removing material.

    2. When you buy a knife, your cutting potential is basically determined by your behind the edge measurement, grind height, and stock thickness.

    3. As you sharpen/remove material, you’re thickening the knife “behind the edge”, or slowly degrading it’s cutting efficiency.

    4. The more frequently you have to sharpen in order to maintain a good apex, the faster your tool becomes less efficient. You’re also spending more time doing it.

    5. In a perfect scenario, the end user has to spend less time, removing less material, to preserve the best cutting experience possible with the blade.

    6. Well treated, properly hardened, appropriately selected steels, ground well, and maintained by removing as little material as possible to maintain a good apex -> where we want to be.
     
  20. ShannonSteelLabs

    ShannonSteelLabs KnifeMaker / Craftsman / Service Provider Knifemaker / Craftsman / Service Provider

    Sep 9, 2015
    I completely agree with that.
    It is a system.
     
    Banter 247 likes this.

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