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Warp On The Cutting Edge

Discussion in 'Heat Treating' started by Griff, Jul 26, 2020.

  1. Griff

    Griff Active Member

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    Besides some very careful grinding, anyone have any solutions to this kind of warp, or am I working on a paperweight lol. And yes I’ll state the obvious I know ground it too thin prior to popping it in the kiln.
     
    Last edited: Jul 26, 2020
  2. FORGE

    FORGE Maker of the Year Best Knife

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    Griff, I find when I heat treat especially San Mai or a big kitchen blade, if the cutting edge is less than .020 you can sometimes get a real nice sin wave on the edge. Then you have just made a real expensive letter opener. I have tossed a number of hours of work into the scrap bucket on a few occasions.
    It is impossible to fix unless you have enough steel to make a smaller blade out of the knife.
     
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  3. Griff

    Griff Active Member

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    That’s the boat I am in then...it’s a San-Mai billet from Alpha Knife Supply. I’ll make a smaller knife out of it maybe.
     
  4. dancom

    dancom Dust Maker Best Shop Tool

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    Curious... how thin did you go? I've heard the "dime" thickness recommended, but with dissimilar steels in the equation I wonder if thicker would be more prudent.
     
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  5. Griff

    Griff Active Member

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    Way too thin Dan. Fought this knife all the way and it kicked my butt. I was attempting a hidden, or faded plunge, because I wanted the San-Mai pattern to be the focal point. I chased that and basically I stuck it in the oven with an edge thickness most makers would sharpen! Face meet Palm!

    I’ve been chasing a few projects lately, not sure what’s up. The grinds on the last knife, ‘Ridgeback,’ were great...but for some reason I have missed the mark on the last two knives.

    And with this one you’d think I’d know better by now since it’s called ‘Thin Core,’ San Mai and only 5/32’sh at 0.160 (just over 4mm).

    I’ll see what I can make out of it...nothing to really lose now since the intended project is already a bust.

    What sucks is I did a test etch, and it was really nice look. Then again, since I’m not selling it, maybe I’ll finish it anyway and like Cal said, open my mail with it haha:D
     
    Last edited: Jul 26, 2020
  6. Griff

    Griff Active Member

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    Decided to put in a recurve. Not my intention for this knife. I hope it doesn’t take away too much of the San Mai’s transition.

    What I should have done is definitely done my heat-treat right after the profile grind and flattening on the disc grinder, and bevels post HT.

    Think I’ll order another billet.

    I followed Larrin’s HT protocol on the 26C3 core (His test was actually on AKS’s San Mai), and coated the 410SS Jacket with ATP. The 26C3 edge skated the file and the 410SS has a blue/green tinge to it.

    HT is 1475F for 10 minutes, and I went with a 400F temper x 2 for 2hrs each.
     
    Last edited: Jul 27, 2020
  7. John Noon

    John Noon Well-Known Member

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    I have found that instead of dime thickness which has no relationship to the maximum blade thickness or degree of tapered area verses flat I go with a percentage of thickness. This can be measured in several spots and accurately repeated for a specific shape of knife.
    So far 10% has worked on anything over 0.07" thick, 0.07" and thinner I grind after heat treating.

    For Damascus that is a whole other ball game depending on materials and pattern created. For starting point I would personally go 20-25% then drop in 5% increments until failure or comfort point is reached
     
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  8. Griff

    Griff Active Member

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    I fixed it. It’s an entirely different knife, but I like it. Photos soon, knife is in glue up. :beer:

    My experience from this is that the 410SS Jacket thickness means nothing, by that I mean the core thickness is what I should have paid attention too, and I should have ground the bevels post HT.

    This was my first San Mai billet and it’s a completely different experience to grinding a mono-steel. The 410SS heats up crazy fast at the grinder! This thing was getting hot in half a pass across the platen. I was very careful in post HT clean-up and mostly hand-sanded. Thinner 1/8 O1 did not heat up as fast as this stuff!

    After fighting this thing I hope I don’t screw up the handle lol!
     
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