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Broke A Chef Knife Trying To Correct A Warped Tang.

Discussion in 'Working the Steel' started by Wuatt, Nov 12, 2021.

  1. Wuatt

    Wuatt New Member

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    Howdy all, so I unfortunately broke one of the 8" chef knives I've been working on while trying to correct a pretty rough warp in the tang (happened during cryo).
    What do you think I should do? Am I able to anneal and then weld it back together? or is it a scrap piece now?
    Also, first time making a chef knife, so other than the snap, what do you all think?
    [​IMG]
     
  2. Dave Hodson

    Dave Hodson Member

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    Tough luck for sure. Sorry I don't have any welding experience so can't help you there but hopefully somebody can.

    It's a nice looking profile and you've done most of the hard work so I'd be tempted to carry on - experiment to see what happens. Obviously it's compromised and you wouldn't put a lot of effort into finishing but how else are you going to learn? You'd never to this on purpose so seems like a good opportunity. Unfortunately I seem to have a drawer of these learning experiences that I keep adding to. I'd be interested to hear how you make out so keep us posted.

    Regards
    Dave
     
  3. Joelsund

    Joelsund Active Member

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    If it’s a simple high carbon steel I’m sure it could be welded back together. But I’m pretty sure that looks like stainless from the colors on the tip. In that case I don’t think you’ll be able to weld that very easily. I’d say just make a smaller knife out of it lol.

    For the future, tang warps for hidden tangs are super easy to hide in the handle and imo should have no effect on the knifes performance in any way.

    Usually what if found is warps will always occur during the quench, but become worse during cryo.

    Some things to keep in mind to prevent warpage would be to grind everything evenly, have your quench plates vertical rather than horizontal and close the plates making simultaneous contact on both sides. By having them horizontal and laying the knife down on 1 side, that side will cool faster, shrinking at a quicker rate than the other causing a warp. This also would apply to blowing compressed air on your tangs if they stick out of the plates, blowing air on 1 side will cause a warp to that side (this is what I would guess happened in your case).

    Now for getting warps out, what I like to do is set up the knife with a thick piece of steel and a 1/4 pin under the warp, then gently clamp on either end with C clamps just to hold everything in place. Then put it in your oven at your previous tempering temp, let it warm up for 30 mins, then tighten your clamps to warp the other way slightly beyond being straight, then put it back in the oven for an hour. Take it out and let it cool with the clamps on to room temp.
     
  4. Wuatt

    Wuatt New Member

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    It is indeed stainless, All of them seemed to warp a little to one side starting about half way up the blade. But very mild warps, somewhere 1/16" or less. After trying to correct this one and having it snap, it made me a bit nervous to try and correct the others lol. I may try and weld this one back together while the blade is submerged in water, and then just use it as an abuse tester.
     
  5. Wuatt

    Wuatt New Member

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    Thanks! yeah, I have a few of these laying in a drawer, but they were out of O1 and 1095 mostly. This is my first time messing around with stainless and I didn't realize how expensive that foil rap for heat treat was :eek:. But oh-well, all part of the experience I guess :)
     
  6. Scott Kozub

    Scott Kozub Active Member

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    AEBL? That stuff warps like crazy. I'd consider welding it but I have a tig. When welding stainless like this you get a lot of stress as it cools and the weld starts to crack. Preheating is a good idea and then an oven for a slow cool. Grind clean, aneal and reheat treat. Finish and use for testing being aware that the tang may break again. It's a lot of work for $20 worth of steel. You could profile a new blade in a quarter of the time and not have to worry about it breaking on you.
     
  7. Joelsund

    Joelsund Active Member

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    I think once I use up the AEBL that I currently have i'll switch to s35vn for most things just to avoid the warping issues of AEBL.
     
  8. Wuatt

    Wuatt New Member

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    Yeah, I was amazed with how much warpage I got, especially because there was no grinding done pre heat treat (other than profiling). I spent all afternoon fixing the warpage on just one of the knives. And even now it isn't perfectly straight. Is AEB-L really that bad for warping usually?
     
  9. Joelsund

    Joelsund Active Member

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    it's notoriously very bad for warping. I'd say 90% of the ones I've done have had some degree of warp. I've only had 2 that were so bad I couldn't get it out.
    the 3 I've done in s35vn I ground the bevels about 80% before hardening and they had no warp whatsoever. same for the few I've done in A2.
     
  10. Vladimir

    Vladimir New Member

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    There was a line in the Knife Engineering Book that talked about steel that is rolled first at the mill, then unrolled "straightened" and cut to size. And the issue we face is that the straightening process is not complete and the steel still has a memory of the cast it had on the role and when we heat and cool the steel it goes back to that shape.
     
  11. Wuatt

    Wuatt New Member

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    I only have a few feet of AEB-L left, S35VN is about double the price, but I think I might switch over just to avoid the headache of fixing warps for two full days after heat treat. Do you think the average home cook would be able to even discern the difference between AEB-L and S35VN?
     
  12. Joelsund

    Joelsund Active Member

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    I like to think that if you pregrind s35vn and not get warping, your time saved in grinding and fixing warps on aebl with no pregrind more than makes up for the cost. Based on Larrin's tests s35vn at the same hardness as aebl should have 1.6x the edge retention, but whether that's noticeable to anyone I'm not really sure. I don't think the loss of toughness would matter or be noticeable in any way for a chef knife designated to normal chopping. For a fillet knife, I would still opt for aebl though.
     
  13. Vladimir

    Vladimir New Member

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    I mostly use 440C, I've made 12" brisket knives pre ground plate quenched, cold treatment in the frezzer and no warping....yet.
     
  14. Nieman Knives

    Nieman Knives New Member

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    I’ve been sending out batches of aebl and getting many of them back with some warping.

    What I started doing was “dimpling” (not sure if that is the correct term) the steel using a carbide tipped masonry bit and a hammer. Essentially all I do is place the bit on the inside of the cup of the warp and tap the bit with a hammer creating dimples. This causes the steel expand on the cupped side and force the steel to push out. This actually works like a charm. It may take a few dozen to several dozen dimples in the area to fix the warp. If I ever find the video/s I watched I’ll post a link.

    If your warp is in the tang which will be hidden, I would say this is definitely the way to go, just be sure to only do a few dimples at a time before checking because depending on how hard you are hitting/how deep you are making the dimples, the results can happen surprisingly fast.
     

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