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3V Heat Treat History

Discussion in 'Carothers Performance Knives' started by vkp78, Apr 14, 2019.

  1. Nathan the Machinist

    Nathan the Machinist KnifeMaker / Machinist / Evil Genius Moderator Knifemaker / Craftsman / Service Provider

    Feb 13, 2007
    The average user can tell the difference between industry standard 3V and Delta 3V pretty easily, the difference in edge stability and therefore edge retention in normal use is significant.

    The industry standard heat treat uses the secondary hardening hump and goes into temper immediately after an atmosphere quench to approximately room temperature. This heat treat was developed for tool and die where minimizing dimensional changes and reducing risk of cracking and distortion were critical and the sort of fine edge stability we need in a knife application aren't commonly seen. This industry standard heat treat stabilizes retained austenite, a lot of the martensite that is formed isn't formed in the primary quench but converts in temper, and you're increasing the carbide volume fraction while reducing cohesion in the softer (weaker) over tempered matrix, all of which leads to reduced edge stability and edge retention. Delta 3V is one of the low temper tweaks whose goal is to maximize the durability of the edge by minimizing mixed structures and maximizing the strength of the matrix. This not only improves edge stability in rough use, it allows the use of a narrower edge angle and may also support the primary carbides better leading to improved abrasion resistance. This addresses the primary shortcoming with 3V, which was a crumbly mushy edge that prevented the user from being able to fully capitalize on the alloy's inherent toughness because a knife made in 3V would otherwise go dull quickly in rough use. We fixed that and it's pretty obvious to even a casual user.

    Less obvious is the difference between some of the better low temp tweaks and Delta 3V. To see this clearly you need better controls than just casual use. But with controlled edge geometry and cut media it is clear and repeatable.

    There are a couple things that may be happening with those two well known smiths who tested forged vs stock removal. One could easily be bias, intentional or not, towards the outcome they wanted. To minimize this when I was first starting out with low temperature tweaks I would do blind controlled tests where I didn't know which was which until after the test. The other thing that could be happening in their evaluation is they may have seen a difference and misunderstood the meaning of it. This could be uncontrolled variables coming up such as unintentional differences in heat treat, a burned edge during sharpening, differences in the cut media they used, weaknesses in the criteria they used to evaluate the sharpness or durability of the test pieces or even differences in the materials being cut. But I think the most likely reason may be the forged blade legitimately out performed the stock removal blade. Not because it was hit with a hammer, but because of the multiple heats it was subjected to during the forging process that the stock removal blade didn't get. The forged blade would have gone into the heat treat as a fine homogenous pearlite while the stock removal blade may have been in a coarse sphereoidized condition (as it comes from the mill). Had the stock removal blade gone through the same thermal cycles as the forged blade it may have been a different story. If those two smiths saw two identical blades in the same steel at the same hardness perform differently I believe them because I've seen the same thing myself. And if they misunderstood the underlying reason (forging rather than thermal cycles) they would only be human, and I can relate.

    My methodology that we used when developing the Delta protocol was a skill set I developed working in product design and development where we would optimize a product's characteristics and manufacturing processes through an iterative process similar to what you experience when you go to the optometrist for an eyeglasses prescription. You develop a matrix of variables and a testing procedure to evaluate the effect of changes to those variables and compare work while also attempting to track relationships between the variables because of complex if/then interactions. Much like natural evolution you dial in an optimized process. You can have working theories about why something works, but an important distinction between science and engineering is the emphasis on optimizing an outcome more than necessarily understanding the underlying reasons. So, while we don't have an SEM in the shop, we do have the ability to control variables and measure outcomes. I can say with complete confidence that the difference between industry standard and well optimized low temper tweaks like the Delta protocol is very significant and difference between Delta and the low temp tweak that immediately preceded it is meaningful.

    A casual user can see this. If they are a real user. Obviously the difference isn't noticeable to a collector who only occasionally cuts a piece of paper or string. I'm a pretty bad abuser of knives. Yesterday I used my knife to deburr a thread in a steel part I'd just cut. I used a piece of steel as a cutting board to cleanly cut some o-ring cord stock for a gasket I was making. I shaved steel fines out of an aluminum fixture. I do all of these abusive things with a knife with a narrow edge angle and I like my knife to be sharp so I can still cut the cap off my cigar without messing it up. The difference in edge stability between an optimized heat treat and a average heat treat can be a HUGE difference in sharpness at the end of the day. So if you're a guy who might clink his knife against a beer bottle when opening a case of beer, or bump a steel staple when opening a box, or cut wire and deburr hard objects you will notice the difference. If you only cut the occasional loose string you probably won't, but it's still nice to know that you can.

    A Carothers Performance Knife in Delta 3V will be sharper than another industry standard 3V knife at the end of rigorous use such as weekend hiking trip or a week of use with a tradesman etc. And the thinner edge geometry cuts better too. Ask anyone who uses them.
     
    Last edited: May 16, 2019
  2. Odog27

    Odog27 Gold Member Gold Member

    Nov 20, 2011
    ^^^^ And this.
     
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  3. BITEME

    BITEME Gold Member Gold Member

    Dec 14, 2007
    This is why you want to buy a knife from Nathan, super thoughtful response ,thanks for your contribution to the forums it is greatly appreciated
     
  4. TRfromMT

    TRfromMT Gold Member Gold Member

    Jan 4, 2016
    I have said on more than one occasion that mere mortals will never be able to tell the difference between Nathan's routine 3V and his D3V (meaning the more pedestrian 3V he had previously was that damn good).

    And, mere mortals do not have SEM's at their disposal.

    (if you have to ask what an SEM is... you lose one CPK nerd point. @Casinostocks will keep track)
     
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  5. Nathan the Machinist

    Nathan the Machinist KnifeMaker / Machinist / Evil Genius Moderator Knifemaker / Craftsman / Service Provider

    Feb 13, 2007
    Edit: yeah, an SEM would be cool
     
    Last edited: May 17, 2019
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  6. TommyGun56

    TommyGun56 Gold Member Gold Member

    Jul 29, 2014
    ^^^Very Informative as always Nathan:confused:
    [​IMG]
     
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  7. TRfromMT

    TRfromMT Gold Member Gold Member

    Jan 4, 2016
    What he said was that the micro structure has something like little stop-drilled holes to blunt the tips of cracks. Stress goes up (exponentially, to infinity) with the sharpness of the tip of the crack. As the tip goes to zero, stress goes up. Dislocations stop that.

    Or put another way, Unicorns and Santa's elves had an orgy. Cigarette butts and beer bottles are lying everywhere, but that made it all better.

    (Where I actually snorted, and LOL'd was "Contrary to popular belief..." )
     
  8. Odog27

    Odog27 Gold Member Gold Member

    Nov 20, 2011
    There was a guy in my neighborhood growing up that had an electron microscope down his basement. He had every tool imaginable. My dad had close to no tools, so I was always borrowing tools off this guy. His basement was incredible!

    ETA: Dude was a METAL DOCTOR!
    I didn’t realize it at the time but that thing likely cost more than our house.

    ETAA: He actually had a doctorate in metallurgy, but METAL DOCTOR sounds cooler.
     
    Last edited: May 16, 2019
  9. UffDa

    UffDa Gold Member Gold Member

    Sep 11, 1999
    I understand what Nate wrote. I read the whole thing twice. I have one more question. Do the FKs without the delta heat treat have the industry standard heat treat or was it different? I don't recall anyone complaining.
     
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  10. Casinostocks

    Casinostocks Factotum Platinum Member

    Mar 20, 2016
    From Nathan's earlier Field Knife sales thread when the new D3V HT was implemented:

    "We have been tweaking 3V for cutlery for a while now, improving it for knives incrementally. There are a number of versions of these tweaks from me and other makers, but they can all be described as a "low temperature tweak". Basically, it involves avoiding the secondary hardening hump, and when done right reduces structures that are harmful to edge stability, but requires addressing retained austenite without a high temper. A happy side effect of leaving the carbon in the martensite is it doesn't tie up all the chromium, leaving 3V very nearly stainless.

    All of my 3V over the years has been tweaked in one way or another.

    Last year some of us running a tweaked 3V ran into some trouble with some that didn't respond like we expected. Those of us makers who test work from every batch noticed it. It required some re-work, but we addressed the issue, and it prompted us to try to better understand what was going on with the alloy and to pursue a fully optimized 3V. So, Guy Seiferd (Survive Knives), Dan Keffeler and I invested the time and resources to more deeply investigate variables and develop a more complete understanding of the alloy, its quirks, and develop an optimized heat treat protocol for it. This is one reason my output was low earlier in the year, because I'd spent a significant portion of the winter in R&D mode.

    Our previous tweaks to 3V had already made it significantly outperform the industry standard, so the fully optimized version is not a night and day improvement over our previous work, but the difference is significant, so in order to differentiate between this optimized 3V and previous tweaks we are putting a Delta symbol with the 3V on the knife to denote change. Otherwise, it would be difficult to differentiate.
    "
     
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  11. UffDa

    UffDa Gold Member Gold Member

    Sep 11, 1999
    ⬆︎⬆︎⬆︎⬆︎⬆︎

    "Otherwise, it would be difficult to differentiate"

    That's what I based my comment about the average guy not being able to tell the difference between Nate's 3V and D3V knives. Maybe Nate didn't understand what I was trying to say.
     
    Odog27 likes this.
  12. CataD

    CataD Platinum Member Platinum Member

    Oct 2, 2013
    ⬆︎⬆︎⬆︎⬆︎⬆︎
    Yeah, but this!!
    "so the fully optimized version is not a night and day improvement over our previous work, but the difference is significant"
     
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  13. UffDa

    UffDa Gold Member Gold Member

    Sep 11, 1999
    Not a biggie, but there is some contradiction here. That's why I brought this up. If it's not a night and day improvement, how is the difference significant? I'm not trying to be argumentative, I'm just trying to get it straight in my pea-brain.

    Here's Nate's first sentence replying to my question. I don't think that he quite understood what I was asking.
    "The average user can tell the difference between industry standard 3V and Delta 3V pretty easily, the difference in edge stability and therefore edge retention in normal use is significant."

    Go back to my original question. Is the difference between a FK with Nate's original heat treat be that much different from a FK with the D3V heat treat that in a blind test, would an average user be able to tell the difference? Am I not being clear? I don't know how to word it any other way.
     
    Last edited: May 16, 2019
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  14. UffDa

    UffDa Gold Member Gold Member

    Sep 11, 1999
    [​IMG]
     
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  15. Odog27

    Odog27 Gold Member Gold Member

    Nov 20, 2011
    I took your original comment to be: Would you be able to tell the difference between the industry standard heat treat protocol for 3V and the delta heat treat protocol?
     
  16. Odog27

    Odog27 Gold Member Gold Member

    Nov 20, 2011
    Now I think what you’re trying to ask is: Would you be able to tell the difference between this (3V)
    33997FC9-8DB7-4FCC-812E-E915BC520BA1.jpeg
    and this (D3V)
    C83411E1-03A3-41CB-B698-9173AE0C74F4.jpeg
    if they were unmarked?
    Pictures always help with us knuckleheads!
    @Casinostocks @Choppaman I stole your pics.
    Thanks
     
    Last edited: May 16, 2019
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  17. Odog27

    Odog27 Gold Member Gold Member

    Nov 20, 2011
    Shakin’ the bush, Boss. Shakin’ the bush.
     
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  18. UffDa

    UffDa Gold Member Gold Member

    Sep 11, 1999
    While blindfolded at midnight with no moon, I might have a problem.
     
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  19. Odog27

    Odog27 Gold Member Gold Member

    Nov 20, 2011
    So from what I think I know:
    @Casinostocks orange and black 3V FK does not have the industry standard 3V protocol; instead a tweaked version. It’s better than the industry standard but not Delta.

    @Nathan the Machinist is saying that there is still a significant enough difference between the tweaked 3V and the D3V that you would notice the difference in rough or extended use.


    Disclaimer: I don’t usually know what I think I know.
     
    Last edited: May 16, 2019
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  20. UffDa

    UffDa Gold Member Gold Member

    Sep 11, 1999
    I probably wouldn't notice the difference, but someone else might.
     
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