Heat treating thin 15N20 in a 2 brick forge?

Discussion in 'Shop Talk - BladeSmith Questions and Answers' started by Fitzhugh, Oct 7, 2019.

  1. Fitzhugh

    Fitzhugh Basic Member Basic Member

    Feb 5, 2013
    Any suggestions on heat treating really thin, 0.049" stock in a 2 brick forge?

    On a whim I added an 18x1.5 piece of 0.049 thick 15b20 to an order from Sheffield*, thinking I'd try making a paring knife.

    I haven't used 15n20 but read here you can get good, if not ideal, results when doing a simple home ht like 1084. I've had good luck heat treating 1084 I'm my 2 brick forge, but never anything this thin overall.

    Should I just ht the blank prior to adding the bevel? I don't have a proper grinder (just a 1x30), so it's either filing before HT, or doing it all by sanding after HT.

    Any tips on keeping it straight or straightening it if it gets a little warped?

    Is it silly to even try something this thin? I've got enough to experiment a bit.

    *I emailed about aking about filling jigs and they offered one for cheap because of light rust, so I wanted to find a few things to add to the order at full cost.
    I was impressed - "light rust" was actually a bit overly dramatic, more of a light discoloration that a just a few moments on worn 1000 paper in a surface plate removed. It's a nicely made hardened steel guide, better than the one I had made.
  2. Bigfattyt

    Bigfattyt Gold Member Gold Member

    Jun 23, 2007
    I'll be interested to see responses.

    I have a stack of .07 15n20 and was thinking of trying a thin puko. Probably send out for heat treat, but might try charcoal or torch with edge quench.....
  3. Joel Mercier

    Joel Mercier

    Dec 3, 2017
    I'd HT before putting bevels. That's what I do with stock that thin. Now, with the 2 brick forge, you gotta take your time and try to heat the blade evenly. Then I'd pull it out when you think it's hot enough and watch for recalescence. It has to be very dark or you may not see it at all. Better do it at night. If it never happens, it means you did not heat enough. If it happens after a while, it means you overheated. If it happens within the next seconds, it means you were right on.
  4. weo

    weo KnifeMaker / Craftsman / Service Provider Knifemaker / Craftsman / Service Provider

    Sep 21, 2014
  5. Travis_Wright


    Jan 27, 2019
    Grind the profile prior to heat treat and drill holes for pins. The rest of the work is to be done after heat treat. You're going to have a warp or two so it'd be good to have some sort of quench plates ready.
  6. milkbaby


    Aug 1, 2016
    I have been happy with results from HT of 15N20 in a 2 brick. That thin I agree HT before grinding bevels. I just straighten warps by clamping with an overbend in the opposite direction while tempering.
  7. Fitzhugh

    Fitzhugh Basic Member Basic Member

    Feb 5, 2013
    Thanks, I'm encouraged by the answers.

    I'm familiar with the concept of plate quenching but had not thought about looking at it for this, as the recipes I'd seen were 1084-like canola oil quench. I'll do some reading.

    milkbaby - I'm glad you mentioned overbend. I found a photo of a 3 point jaw for a benchtop vise that will be easy to copy.

    This reminded me... had forgotten all about a jig I made to straighten my first knife (it was a few years ago). A piece of unistrut with rows of bolts coming in each side to straighten the blade, and a row from the bottom to support it in position. The jig was a loose copy of a nice one I'd seen here somewhere, but mine was inadequate in design and worse in execution, as it turned out. It was too awkward to set up quickly, the blade could twist a little and slide off the support bolts, unistrut sides aren't actually square and I didn't use a drill press vise so my holes were slightly angled, etc.

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