Warped knife blade

Discussion in 'The Craftsman' started by kswan, Jun 12, 2019.

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  1. Jun 12, 2019 #1

    kswan

    kswan

    kswan

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    Hello all.
    I've just started building knives and I'm now working on my second knife. The blade came out of the quench a little warped. I've heat treated it 3 times at 400 degrees with the blade C clamped onto a 3/4 inch steel plate with a shim. Most of the warp came out but there is still a slight warp towards the tip. Is there any other methods which could straighten out the blade? The blade itself is 1084, 5/32 x 1 1/2 x 7.

    Thanks for reading.
     
  2. Jun 12, 2019 #2

    LRB

    LRB

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    You can continue to re-temper as many times as it takes to unwarp it. At the same temp of course. Re-temper at the same heat will not hurt anything. There is another method, but it carries a risk. Lock in a vise after polishing where you can see colors in the warp area. Heat the spine carefully while bending the blade to over flex a bit at the apex of the curve in the warp. Have a can of water ready to pour on it. When you have the heat at a blue in the warp area at the spine, but before the color reaches the edge, pour on the water while keeping the blade flexed over. This will not work up near a point. You will end up over heating the point area. You can also re-temper as you were with C clamp and wedge, but once you are confident that the heat is soaked through well, quench in water while still clamped. Or just pour plenty of water on it. As mentioned, you can repeat this over and over. Your other option is to regrind the area, if possible, while not over heating it. You may have to settle for less length.
     
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  3. Jun 12, 2019 #3

    hamanky

    hamanky

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    The way I do it if I have a blade warp when I quench. I take the blade from the kiln to the quench tank, after a few dunks I sight down the blade if I see a curve I take it too the vice and straighten it while it’s still hot. You have a short window to do this but it works good for me.
    When I say still hot, I’m not talking about red hot I mean still to warm to handle without gloves. Before it cools down completely I find the steel to still be workable. If you allow it to cool to far it will snap while bending.
    Then test the hardness with a file and temper as normal. Hope that makes sense.

    Joe
     
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  4. Jun 12, 2019 #4

    kswan

    kswan

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    Thanks very much for the advice. Because the warp was so close to the point, I did the re temper method you described and that has solved the problem.
     
  5. Jun 12, 2019 #5

    kswan

    kswan

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    Thanks, This will help on my next knife.
     
  6. Jun 13, 2019 at 11:48 AM #6

    LRB

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    I do about the same HAMANKY, using hand pressure, but it was too late for KSWAN unless he wanted to repeat the entire process. It seems his problem is solved now.
    As far as window times on hand straightening, it varies with steel types. I used 01 and it would allow as long as 8 to 10 minutes to straighten, but I always tried for 5 minutes or less. The 10XX steels offer the shortest time frames in this practice. With 10XX steels the risk of breaking accelerates rapidly under 400°, while 01 continues to allow some amount of straightening even nearing ambient temp.
     
    Last edited by a moderator: Jun 14, 2019 at 1:26 AM
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  7. Jun 13, 2019 at 7:59 PM #7

    kswan

    kswan

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    I dont have alot of knowledge working with steel. I did't realize I could have started the process from the start again. As well, I didn't think I could use water at any point in the process. All very good advice for my next one.
     
  8. Jun 13, 2019 at 9:59 PM #8

    LRB

    LRB

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    Never said it was good to start the whole process again, but you can. However, you will lose a little carbon just below the surface at each extra go at it. You can temper a hundred times with no ill effect, but it is best to get the hardening quench right just once. Yes. You can water quench a TEMPER cycle, but not the hardening quench process. Well, actually you can do it also, but be ready for broken blades. Once you gain a little experience, you can experiment with brine quenching, only with 10XX steels though. Brine is 13 oz salt per one gallon of water. It will give maximum hardness, although safer than water alone, but still carries some risk of breakage.
     
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  9. Jun 14, 2019 at 5:08 PM #9

    Rifleman1776

    Rifleman1776

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    I'm not a bladesmith but I watch them on TV. :rolleyes: OK, I have proven my lack of personal knowledge. But, sharing what I frequently see on the 'Forged in Fire' tv show, there are often problems with warping and blade failure. Most of the contestants who get warping reheat the blade in the forge and hammer as straight as they can then reheat and quench. Sometimes they do this several times. Often those blades fail (break) during testing. The judges will say the reheating/quenching destroyed the grain structure of the steel weakening it. What I have learned from this forum and that show is that blade making with a forge is neither simple or instantly learned. I have great respect for those who do it well. And despite my frequent jabs at LRB for being a knife maker not from Arkansas, I include him in that group I respect.
     
  10. Jun 14, 2019 at 7:27 PM #10

    LRB

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    Warp can be caused by a number of things. Uneven heat in the blade, uneven cooling in the quench, uneven/asymmetrical blade bevels, or shape, stresses in the steel from forging, stresses from grinding, lateral movement of the blade when it is in the quench, and a few other reasons. The one thing that does NOT cause warp, but is a wide spread belief that has been disproven over and over, is a horizonal quench that is not aligned north & south. If you intend to do a full quench, your best method is to have a tank allowing the blade to go into the quenchant point down first in. If you want an edge quench only, or just want a horizonal quench, it does matter in the slightest bit which direction the blade is pointing. It has been my experience that a vertical blade quench seems less likely to warp, but you may not have a tank that allows that.
    RIFLEMAN1776, thank you for your words. We all just cannot be from that great state.
     
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  11. Jun 18, 2019 at 2:21 AM #11

    hamanky

    hamanky

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    Everything LRB said is right in my limited experience. That said, I still place my quench tank north to south. Why? Because it makes me feel better lol. I figure I need all the help I can get some days.
     
  12. Jun 18, 2019 at 10:27 PM #12

    kswan

    kswan

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    I'm not sure how I could place my 1 gallon tin can north to south.
     
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  13. Jun 19, 2019 at 12:49 AM #13

    nhmoose

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    Lay it down on it's side after soldering both ends and cutting a top opening.:confused::D
     
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  14. Jun 19, 2019 at 3:55 AM #14

    ohio ramrod

    ohio ramrod

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    I have found that a warped blade can be best straightened by anealing the blade. straightening, then rehardening and tempering. When hardening and tempering blades I always do it "hanging" never laid in the side.
     

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