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Production M390 - Expectation vs Reality?

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

  1. Mo2


    Apr 8, 2016
    Thank you for the reply. That is better than the statement you originally made that implied something else.
  2. knifeswapper

    knifeswapper Knife Peddler Dealer / Materials Provider

    Sep 3, 2004
    If you find the time, please respond with the exact sentence/statement in which you feel something else was implied.
  3. Mo2


    Apr 8, 2016
    I already quoted the screen shot where you implied about Kurt.Your reply with more detail that was good enough for me.
  4. HappyDaddy

    HappyDaddy Gold Member Gold Member

    Dec 21, 2013
    Well isn't that just a big ol' relief.:rolleyes:
    willc, palonej, ScooterG and 2 others like this.
  5. Applecider3

    Applecider3 Gold Member Gold Member

    Feb 4, 2019
    Any tests on the new blue and red spyderco PM2’s?
  6. Banter 247

    Banter 247

    Feb 22, 2019
    2 Recent run Spyderco models in M390 (Delica, PM2) each hit at 62. This is not a reference to the previously hit 62hrc PM2. It’s a second, newer batch sample.
    DRLyman likes this.
  7. 91bravo

    91bravo Gold Member Gold Member

    Jun 29, 2008
    Good, let's squash this whole M390 hardness thing then...

    Mine cuts and holds a sharp edge just fine.
  8. David Richardson

    David Richardson Gold Member Gold Member

    Nov 30, 2018
    I can't message you here. Can I get you on IG or somewhere else?

    There's nothing wrong with most M390/20CV. The knives I have are good. I don't find the edge retention to be great. Maybe slightly better than S30V in some cases. It's really a matter of value rather then good vs. not good steel. I will say it's easier to sharpen than S30V, so it's got that going for it. Which is nice.
    Banter 247 likes this.
  9. Applecider3

    Applecider3 Gold Member Gold Member

    Feb 4, 2019
    Banter thanks for your reply, mind reposting the link to the database?

    I’d heard that the smaller knives E.g. Delica were less hard than the larger PM2 guess the data shows that is wrong.

    Do you know anywhere that shows how much harder a 62 is than a say 58? I’ve read that the hrc scale is not linear, but not what the relationship is. Perhaps the steel ball bounce method would show this in that the height of bounce could reflect hardness and height could be graphed. Of course that method doesn’t sound useable for knife blades, but it could maybe answer my question.
  10. halden.doerge

    halden.doerge I'll Sharpen Your Knife Gold Member

    Aug 17, 2014
    A poster falsely claimed above that smaller Spyderco knives in M390 tend to come in low (I believe 58 HRC was the number that thrown out). It's caused some confusion since.
  11. Tseg


    Aug 25, 2018
    This is why I buy Shirogorov... I pay for the name and the M390 is for free!
  12. David Richardson

    David Richardson Gold Member Gold Member

    Nov 30, 2018
    If you're referring to the Blade Banter spreadsheet, it's here.

    If there's a correlation between Rockwell number and difference in hardness I haven't found it. Because it's number representing the depth of penetration you can't draw any conclusions about the amount of hardness difference without knowing the formula (or shape of the curve) of hardness to penetration depth. If this exists I haven't seen it. I would guess it's not linear and is likely closer to log scale. But this is a wild guess.
  13. miso2

    miso2 Gold Member Gold Member

    Nov 19, 2014
  14. David Richardson

    David Richardson Gold Member Gold Member

    Nov 30, 2018
    That shows the relationship between different hardness test values. This doesn't help me know how much harder HRC 60 is relative to HRC 58. Am I missing something that's there?

    If another one of those tests has defined the hardness difference between their scale numbers youu could use those curves to figure out what it means for HRC. I haven't found another hardness test that does this. I haven't look very hard so it could be out there. I'm guessing Rockwell numbers a dimensionless for a reason.
    Last edited: Jul 22, 2019
  15. DeadboxHero


    Mar 22, 2014
    Steel ball bounce would be very bad because the mass of what's being tested will effect what the hardness is, that is why portable leeb testers that use that method are not used on steel for knives because of the thin stock we use.

    This is why the Rockwell test C uses a preload at 10kgf to rule out the elastic rebound before delivery of the major 140kgf for the 150kgf total, also the major load is held for a few moments to also mitigate the elastic rebound as well.

    The test measures depth of permanent plastic deformation in mm

    Each line on the test C dial is 0.5hrc incriminates this equals 0.001mm per 0.5hrc
    0.002mm(2um) for 1 point hrc

    SIZE reference 0.002mm is 2um
    (0.002mm is under 0.0001" inch roughly 0.0000787")

    HRC equals 100 subtracted from the mm of permanent deformation over 0.002mm increments.

    So 62rc is 0.076mm of permeant deformation depth

    58rc is 0.084mm of permeant deformation depth

    So the difference is that 58hrc would have 0.012mm deeper deformation from the 120° conical diamond penatrator than 62hrc.

    So the Rockwell will tell use how resistant to displacement the steel is and will give us an idea of how hard the matrix of the steel is but it obviously doesn't till us anything about stability or wear resistance.

    There can be hundreds of different vartions to the microstructure from heat treatment so the HRC is not universal to high performance but if the microstructure is badass and the HRC is higher with the Geometry to express it for the job at hand than the higher HRC measurement can be a factor for more more resistance to plastic deformation which means less annoying rounding over of a sub micron apex with use and can increase the Stability since a harder matrix can support the Carbides better.

    Last edited: Aug 3, 2019
    attila., Banter 247 and Eli Chaps like this.
  16. miso2

    miso2 Gold Member Gold Member

    Nov 19, 2014
    Some of these tables have a column for tensile strength.
    I would like to hear from experts what that means.
  17. DeadboxHero


    Mar 22, 2014
    8 microns of depth is what sets them apart on the tester. The harder steel will resist being deformed with a fixed load.

    0.5hrc =0.002mm =2um depth
    2hrc =0.008mm =8um depth
    ~three ten thousandths of an inch ~0.0003"

    Most here are probably familiar with 1 thousandths of an inch 0.001" like what is found on calipers which is roughly 26um or 0.026mm. So 0.001" of depth is roughly 6.5hrc difference
    Last edited: Jul 22, 2019
  18. David Richardson

    David Richardson Gold Member Gold Member

    Nov 30, 2018
    Thanks BBB. I get how the testing works. What I'm not seeing is a way to say with any confidence that one HRC test number is X% harder than another HRC test number. Increasing numbers are an indication of more hardness. I haven't seen anything that lets us quantity how much more hardness it is. Is the harness scale linear? Curved? Log scale? I haven't found a reference for this yet.
  19. DeadboxHero


    Mar 22, 2014
    David, we can see that the test measures depth and shows values in 0.002mm /0.5hrc increments in a linear fashion with a analog dial.
  20. Applecider3

    Applecider3 Gold Member Gold Member

    Feb 4, 2019
    So is an HRC of 51 2% harder than one of 50? See this is why I’m confused. Sure the bottom line is does the edge do what you want, but I’d like to understand the relationship between the HRC number and the actual hardness. And consequently what a difference between say 59 and 62 means in the case of m390.

    Attached Files:

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