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  • So, heat-treating.

    Most of my pieces are in place now, I'm going to fire up the Turret and punch out some blanks, then grind them into knives.... then make handles.


    My mentor told me what steel to buy, which I did. It's a carbon-steel, that's all I know.

    Once I get the blank made I grind the edges to clean the punch-nibbles off then I "back" one side of the blank and pack them up to send to heat-treat.

    I tell the heat-treat company what sort of steel I have and I tell them "knife heat treat please" and a week later the blanks come back to me.


    The heat-treat is pure black-box. All I know is the blanks are quite soft and bendy when I send them, and when I come back they do NOT bend anymore, in fact if you try to bend them in a press-brake you will %*&*! up the tooling. (shuddup, gotta learn somehow. )

    Anyway, any insight on what this "heat treating" process might be? I'm curious, maybe it's something I can duplicate on a small scale to do 2-5 blades at a time.
    "The Administration does not support blowing up planets." --- Finally some SENSIBLE policy from the Gov!

  • #2
    Heat-treating knife blades is not rocket science, though it demands a bit of attention to get the blade hard enough to take a good edge, while still maintaining enough toughness and resilience in the spine.

    Here's a link to someone doing it in "primitive" fashion:

    http://theguncounter.com/forum/viewt...p?f=36&t=18542

    The magic about sending parts out for professional heat treatment is that it pretty much guarantees consistency from part to part and from batch to batch. If you only want to do a few for your own use, and don't mind ruining one from time to time (see link above), go ahead and try doing it yourself. If you search for "knife heat treatment" on the web, you'll find plenty of how-to information.

    ETA: you should be able to pick up a copy of Wayne Goddard's book, the "$50 Knife Shop", for about US$12 new - it covers what you need to get started doing your own heat treatment.
    Last edited by Euph0ny; 04-27-2012, 10:26 AM.

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    • #3
      Knife people have their own way about them, the following is in the context of general heat treating not knife stuff. Volumes have been written on heat treating, but i'll attempt to do it in a paragraph

      inside the black box: certain steels, tool steels such as O1, have a enough carbon in them that when brought to the right temp, bright red, undergo a crystalline change that gets 'locked' in place if its quenched (rapidly cooled). The steel is then as hard as it can be. Often you let it down some or temper it by warming slightly - trading some hardness for toughness, i.e. make it less brittle.

      lots more you can add, that's why there are volumes, but that's it in a nutshell

      It is very easy to do; drill rod is usually O1 meaning it works best with an oil quench (different media = different rate of cooling). Make what you want, heat it up red hot (propane and IFB is my preference) and quench in a coffee can (not plastic!) of old oil. Voila, you have a hardened piece of steel. Temper, stone, grind as required. Some want to complicate it, I think a carryover from production where you need to be consitently within a hardness tolerance and reduce scrap, but in my experience you don't need much more than this to make all manner of tooling and cutters, its enough to get you started anyway.
      Last edited by Mcgyver; 04-27-2012, 11:06 AM.
      .

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      • #4
        That simple, eh?

        What sort of oil? Can I use (say) old press-oil or motor oil drained from the car? I got both of those in abundance.

        If so this is something I can experiment with over the weekend. This would be great for "experimental" knives, one-offs, and novelty/gift knives that I sometimes make.




        I have a product, a specific knife for a specific application that I've made off and on over the years. Recently I was given the chance to buy some machinery, looks like I'll be able to bring this knife to a wider market, perhaps.

        If that happens I forsee myself learning injection-molding as I can't make zillions of wooden handles.

        Anyway, it's a specific style of butchering knife for the poultry industry... I make a knife and a specialized scissor too, and I sell them to small chicken-processing companies... mainly regional mom-and-pops or local-butcher-shops.

        THESE would continue to be professionally heat-treated, simply for liability issues. Blade fails in service I can blame Jerk-O Heat Treating Service. :P
        "The Administration does not support blowing up planets." --- Finally some SENSIBLE policy from the Gov!

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        • #5
          Not a bad place to start:
          http://www.cashenblades.com/info.html

          More detail:
          http://www.google.com/#hl=en&sclient...=1227&bih=1052

          David Merrill

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          • #6
            what kind of oil?....the quench fluid determines the speed of the quench; there's o1 that uses oil, A1 uses air and W1 uses water. You can also use cold brine for an even faster quench.

            Point being the difference between air and water and oil are what matter...not whether its 30 or 40 weight oil. I use whatever I've drained from a machine and it works, old motor oil will as well. While the engineer at a commercial facility probably can measure and influence the quench behavior by differing oils, not sure it makes any difference to what we're doing. There is also no law that you can't quench O1 in water but it's likely to crack; quenching W1 in oil will also work but it won't be as hard. We're pounding spikes with a 16oz hammer here, not putting Cartier's together

            The only meaningful difference with proper quench oil I've heard is that it doesn't smoke as much. This would be nice if you doing it frequently as i does stink up the shop.

            its use is a lot more than experimental knives etc, the most handy use imo is for making your own cutting tools. yeah I buy them where possible, but often you need specialty item, commercial is too expensive for a one time use or its just quicker. I've made taps (left hand, double start), d bits, milling cutters, hex and square broaches, gear cutters etc

            but get some drill rod and have it. take pics and post them
            Last edited by Mcgyver; 04-27-2012, 11:05 AM.
            .

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            • #7
              Originally posted by Mcgyver
              Knife people have their own way about them, the following is in the context of general heat treating not knife stuff.
              As a "Knife people", I should explain that in high-end knife making, more than any other craft, the quality of the heat treat makes the difference between a good and a great knife. There are generally three schools of thought in knifemaking:
              • The "heat it to non-magnetic and dunk it in some kind of oil" crew. These guys don't like the idea that metallurgy is a known science, and that you can look up the optimal heat treat recipe in an engineering book. For simple steels like 1084, W1/W2 and O1, this works fine. They use a variety of thin viscosity oils: canola, transmission fluid, ... You won't get complete martensite conversion, but it's good enough for most applications.

              • The "quench tank should be facing north, and done on a full moon" crew. These guys often have complex protocols involving multiple quenches, putting the blades in the freezer, etc.

              • The ASM Heat Treater's Guide crew. These guys have read, and understood, all the metallurgy books, follow careful, scientific protocols, test the blade after quench with a Rockwell hardness tester to check how much martensite conversion they got... These guys are often in the acknowledgments section of Dr. John Veerhooven (an emeritus metallurgist) books and scholarly articles: Howard Clark, Kevin Cashen (who David Merrill linked), Al Pendray...


              As a rough generalization, most bladesmiths ("Hammer jocks") do their own heat treat. Most stock removal guys send their blades off for commercial heat treat to a place familiar with heat treating very thin cross sections at high hardness: Peter's Heat Treat, Paul Bos, etc. Peter's et al use salt pots, exotic vacuum furnaces with nitrogen quench, but they're firmly in the third camp, so if you're sending your blades off for heat treat, you're in the third category as well.

              The datasheets from most tool steel vendors provide data showing the Charpy Toughness, hardness, retained austentite percentages for various austentizing temperatures, hold times, etc. Ideally, you want the crossover point between Charpy (edge) toughness and hardness -- for most common tool steels, that's at 59 - 61 Rockwell.
              "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

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              • #8
                Originally posted by Mcgyver
                quenching W1 in oil will also work but it won't be as hard. We're pounding spikes with a 16oz hammer here, not putting Cartier's together

                The only meaningful difference with proper quench oil I've heard is that it doesn't smoke as much.
                Quench oils are rated according to speed. Like commercial hydraulic oils, commercial quench oils are a mineral oil base with "add packs" -- additives to modify viscosity, thermal properties, shelf life, ... The mostly commonly used quench oil in industry is Parks AAA, which is a medium speed (11 second) quench oil intended for medium speed tool steels like O1. Gunsmiths use Brownell's Tough Quench, which is relabeled Houghto-quench "G". Same stuff. Canola and mineral oil is pretty close to Parks AAA in speed.

                W1/W2 are shallow hardening tool steels. They need to be quenched below the pearlite nose (800°) under 4.5 seconds. I make a lot of blades in W2, and I use Parks 50, which is their high-speed quench oil. If you were to quench W1/W2 or high carbon steel in Parks AAA or canola, you'll get incomplete martensite conversion -- crappy heat treat, which is most visible in the form of lower hardness. But you can radically improve the quench speed of slower oils by preheating them: bladesmiths just heat a scrap bar and stick it in the quench oil. 120 - 150° is a good range if you want to speed the oil up.

                Kevin Cashen's site has the transition diagrams for all the common tool steels on his web page, along with very straightforward cookbook recipes for heat treating them.
                Last edited by lazlo; 04-27-2012, 12:04 PM.
                "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

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                • #9
                  GB,

                  Sending them out will make you the best knife right now. But, if you're anything like me, you'll want to do it yourself!

                  McGyver's comment that it's enough to get you started was true for me. I have quickly evolved in the direction of Lazlo's "3rd camp."

                  I started by heating O-1 to non-magnetic and quenching in oil. It's a lot of fun, but I ended up having to grind off some of the steel due to de-carburization (not sure of spelling).

                  Now I heat treat a stainless tool steel in a kiln with foil. [edit: the foil is to keep oxygen away from the super-hot steel. I also regularly test hardness of blades coming out of the kiln].

                  Fortunately, the journey has been a lot of fun.
                  Last edited by Tait; 04-27-2012, 03:18 PM.
                  Hemi-proprietor,
                  Esoteric Garage

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                  • #10
                    "All I know is the blanks are quite soft and bendy when I send them, and when I come back they do NOT bend anymore,"

                    somehow i always wondered about that: soft steel is "bendy" and hardened steel is rigid. but we all know youngs modulus is the same for all steels in any state. so whats the storry?

                    also, i got some soft t-nuts recently. your supposed to heat them to 880°c for 45 minutes before quenching. so apparently its not just "heat it read hot and quench". although iv done exactly that with drill rod many times succesfully.
                    but why would anybody make t-nuts from some crazy stell, where this doesnt work?

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                    • #11
                      The ones I sell will be heat-treated.

                      However I want to play around with other knife designs, blank designs, and just noodle around with the process, that's why I'm keen on learning about the heat-treat.


                      At lunch I acquired two bottles of torch-gas, two metal buckets, some wire for hanging and a face-shield. Tonight when I get home I'm going to take a soft blank and have at it using some old transmission fluid.

                      I'll report back tomorrow either from my computer or my laptop at the hospital.
                      "The Administration does not support blowing up planets." --- Finally some SENSIBLE policy from the Gov!

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                      • #12
                        Originally posted by dian
                        also, i got some soft t-nuts recently. your supposed to heat them to 880°c for 45 minutes before quenching. so apparently its not just "heat it read hot and quench". although iv done exactly that with drill rod many times succesfully.
                        If you just heat it up and don't hold the heat long enough, the crystalline change in structure of the steel is incomplete (austenite formation) and thus only the portion that had time (mainly the surface layer) to transform will harden properly.

                        The amount of holding at heat depends on the steel and its dimensions (rule of thumb is an hour per 25 mm thickness), so you need an oven for anything you want to heat treat "properly".
                        Amount of experience is in direct proportion to the value of broken equipment.

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                        • #13
                          Originally posted by dian
                          " i got some soft t-nuts recently.
                          Good god man, hopefully nothing to do with this thread!


                          http://bbs.homeshopmachinist.net/showthread.php?t=53988




















                          couldn't help meself
                          .

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                          • #14
                            Originally posted by Mcgyver
                            Good god man, hopefully nothing to do with this thread!


                            http://bbs.homeshopmachinist.net/showthread.php?t=53988

                            couldn't help meself

                            Aye lad, that'll harden your nuts right quick no doubt about it.












                            ...what?
                            "The Administration does not support blowing up planets." --- Finally some SENSIBLE policy from the Gov!

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                            • #15
                              The steel should go pretty much from the heat into the quench medium with minimal delay (for O-1, somethin like 6 seconds before you start losing some of the hardening potential).

                              When you quench, insert the steel more or less straight: an angle will cause torsion.

                              Also, submerging the steel will lessen the opportunity for the fluid to smoke and maybe catch fire.

                              You might want to decide whether you'd rather breathe ATF smoke or Canola smoke...
                              Hemi-proprietor,
                              Esoteric Garage

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