• Zach Byrne
    5
    I was listening to this week's episode of the podcast when I heard the question about heat treating with a "blow torch". I'm kinda assuming he means a propane or map gas torch as I know this is a very attainable item for most people. Anyway, the guys highly recommended against it and this got me thinking about my own heat treat method. I've only done a few knives so far, but am going to be making some more over my winter break.
    Thus far I've been using a literal campfire, just tons of random wood from doing yard work, taking down trees, trimming branches, old Christmas trees, etc. I build up a nice bed of coals with all that then use a hair dryer to get my steel hot enough. I test with a magnet to make sure its not magnetic, then quench in some warm canola oil. I then temper in my kitchen oven. My question is this: is there any downside to using a campfire? The knives are hard when I test them with a file, and I've smacked one of them through a log a few times to process firewood while camping and it kept an edge well enough to slice through paper like butter. If I'm getting results like this is there any reason to try something else? Recently sunk some money into a portaband I can't wait to try out so buying a forge or kiln isn't exactly an option for me right now.
  • Justin Wells
    9
    Disclaimer: I AM NO EXPERT lol. To me it seems like the issue with heat treating with a torch is that the flame is so concentrated that It would be hard to get the whole blade evenly heated at the right temp. But whenever you stick the blade in a forge (gas,coal,charcoal, ect) you are allowing the entire blade to heat up evenly to the right temp before you quench so I don't think it would matter if you are using a souped up campfire lol
  • Ross Vosloo
    21
    in short, no. your basically using a charcoal forge, even if it is in campfire form. i do the exact same thing, only mine is coal and i built a forge, but its the same principle.
  • Smith Knifeworks
    53
    You're doing the same thing people did for a long time. Knives existed way before propane forges, thermocouples, an understanding of science and heat treat ovens, you know? I think it depends on what your goal is. If you just need a knife to get hard- your method is perfectly acceptable. If your goal is to get as close to perfect on the heat treat, for the given steel, as you're humanly capable of- your method is unacceptable. If you take a notion to heat treat something in an oven and compare results I'm in Columbia. You're welcome to come use my oven to heat treat a knife or two.
  • Zach Byrne
    5
    Hadn't thought about it from a historical aspect, so good point there. At this point I'm just trying to get it hard, I've got many other aspects of the craft to work on before I worry about perfecting my heat treat. Thanks for the offer!
  • Smith Knifeworks
    53
    Yeah, dude. If you just want it to get hard, and you're using a simple carbon (excluding 1095) just heat it till a magnet doesn't stick, go a little further and quench in some sorta semi-thin benign oil. Vegetable or canola. Peanut if you're feeling spendy. Exactly what you described yourself doing.


    An observation: I wasn't aware of this, but in my experience, neodymium magnets lose their magnetism when exposed to the heat of a nearly 1500deg blade. I've had cheap ceramic-type magnets that didn't. If you don't acknowledge that, and you're using a rare earth magnet for the second time, it can really get you chasing your tail. Ask me how I know! hahaha. I was standing around going " how the hell did this piece of steel become non-magnetic at ALL temperatures?!?!?!


    I did notice something interesting re oven- If you're using an electric oven to temper, at least in my case, it will WILDLY vary the heat. I took a temp gun to a bunch of different areas of my oven. Set at 350 it would whack the knife steel up to about 400 every time the heating element cycled on. I've taken to creating a "chamber" in my oven. I'll set a sheet pan above the knife and below the knife to block some radiant heat from the coils in my shitty electric oven. It'll help soak everything and maintain an even 370 deg or so in the "chamber" when the oven is set on about 390. Just an fyi if you're concerned about an even ( or overshooting your) temper. I'd imagine a gas oven would be much more forgiving.
  • Ross Vosloo
    21
    another good trick is to use a tray of sand and bury the knife in it. it acts as a giant heat sync that levels out the temps
  • ashwinearl
    4
    Here is a relatively cost effective baby forge that is capable of heat treating simple steels (80CrV2, 1084, 8670, 15N20) O1 if you use a muffle and get good at regulating the heat to achieve a consistent soak.
    YXRuciv.jpg
    Instructions were discussed in this thread at blade forums.

    You have to use the SOFT fire bricks that pottery supply stores sell, not the hard fire bricks available from Home Depot/building supply stores. They can be purchased online from High Temp Tools. They are soft and they do break. Buy extra.

    I got a burner from Atlas Forge and paired it with propane tank. Regulating even heat is achieved by moving the blade in an out. It get too hot to leave in there. The blade forum thread mentions a model of a propane torch that works well. Combine that with a muffle (a stainless steel pipe that keeps direct flame off the blade), and you might be able to achieve a stable temperature to actually soak for extended period of time.
  • Smith Knifeworks
    53
    that's a great idea! Why didn't I think of that?
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