Straightening During The Temper Cycles

Discussion in 'Heat Treating Forum on KnifeDogs' started by Rick Marchand, Dec 20, 2011.

  1. Rick Marchand

    Rick Marchand Member

    :biggrin:Hi Folks,
    I'm kinda new to this site, though I recognise many of the members here.

    I have posted this thread on another forum with a surprisingly good response. Frankly, I didn't think it was anything new but I guess it is one of those "smack... why haven't I been doing that?" type of thing. I did a search and found nothing on what I have to present but I am new here... so maybe this isn't even the right place to post this.

    STRAIGHTENING DURING THE TEMPER CYCLE has allowed me to sleep easier. I am no longer haunted by the TINK of snapping blades in a straightening vice.:eek:

    I'd like to start by saying that proper normalization and pre heat treat practices would eliminate most of your warping issues. Tweaking during an interupted quench is very common practice, as well. Most of the makers I see, use straightening jigs after the temper and over-bend enough for the blade to take a set. I'd like to tell you that my heat treat is so good that even the most exagerated bends spring back to shape... but I'm afraid that isn't so. Some blades work out well in a straightening jig and some snap. I have also clamped the tang in a vice and used a slotted 2x4 to bend and twist the blade back to true. The sad fact is that "warp happens" and our goal is to true the blade while keeping it in one piece. That is why I felt compelled to get this thread up, as I think it could prevent some broken/scrapped blades.

    I brought this technique over from my Tool and Die days and scaled it down for knives. It is nothing new... just underestimated in its effectivenes, IMO. The basic concept is to clamp a warped blade to something straight and perform a tempering cycle to lock it in. Sometimes, is takes a few tries but, hey... we are tempering in multiple cycles anyway, right?

    This can be used for warps, twists and bows... you just have to get creative with your clamping. I don't know if certain steels(stainless in particular) aren't subject to this technique... I have personally used it on 1050/70/80/84/95, O1, 5160 and 52100.

    Here are the ingredients...

    Warped to the left...

    Clamp it straight. If you end up needing to over-bend, shim between the file and blade. (I use spare change... lol). If the warp is slight enough, I will clamp it straight even before the first temper. You are putting very little stress on the blade during this process.

    Run it through a tempering cycle. I usually water quench after each cycle to improve resistance to extreme cold embrittlement (something that Roman Landes recommends) I am not sure if that helps "lock in" the straightened blade or not. It doesn't hurt.

    The freshly straightened blade... I got it on the first shot.:3: (I don't know why the picture makes it look a bit warped... believe me, it's straight as an arrow.)

    Last edited: Dec 20, 2011
  2. Doug Lester

    Doug Lester Well-Known Member

    Now there's something to file away for future use. Thanks for putting it up.

  3. Church & Son

    Church & Son Well-Known Member

    Thanks for the wisdom Rick, I can certainly use it....Now if I had one of those oven thingies....
  4. GHEzell

    GHEzell Well-Known Member

    Good to see you here, Rick. I saw the thread on the other forum and tried this method, and it works, though sometimes it requires a couple of tries to get the blade perfect. The good thing is, no more blades broken from trying to straighten in a vise!
  5. RandyR


    Just for information, I have had the process work well on CPM 154 and ATS 34. It can definitely take several cycles and you will waste your time if you don't get back to your original tempering temperature.
  6. Bush Monkey

    Bush Monkey Guest

    Looks like the best solution of all - a simple one that makes perfect sense. Thanks for posting.
  7. ARCustomKnives

    ARCustomKnives Well-Known Member

    I've been using this method for a while now as well, and it works! I normally use a piece of 3/8" flat stock, or some 1" square tubing I have lying around for the straight edge, and a couple of flat washers for the occasional shim if needed. It usually takes me no more than 2 cycles to tweak things where I need them.

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