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  • Heat treat oven choice

    If you choose a heat treat furnace for your HSM needs, what chamber size would YOU prefer (apart from the usual "the bigger the better" or "the smaller the hotter")? Size for YOUR own needs (mine could be different, I know).

    I'm trying to choose between knife makers kiln configurations (18"-24"long chambers with about 10"x6" opening) and square chambers (13" cube or so). The latter are significantly more expensive though (although have less Watts per cubic inch). I'm not a knife or gun maker, so my needs are not obvious in this respect. I'm trying to choose a nice and not overly expensive kiln for the tasks that an average HSM with larger machine tools (Monarch, Bridgeport, etc.) may encounter.

    Presently, I'm looking into 220v Evenheat and Sugar Creek ovens with digital controls. Do you have any experience with those? Which would you prefer and why?

    Thank you.

    P.S. Please let's not discuss a DIY, "use your torch" or "buy a used ceramic/potters kiln on eBay" options here. It is a completely different subject.
    Last edited by MichaelP; 12-29-2011, 10:31 AM.
    Mike
    WI/IL border, USA

  • #2
    What is it you want to treat, this is assuming you want an electric oven.

    size-big or small

    what temp range do you need

    what can you afford IE:Purchase cost and most important operating cost, bigger, higher temp. range will cost significantly more to operate, at least if it is an electric one, unless you have cheap power you need to consider this.
    The shortest distance between two points is a circle of infinite diameter.

    Bluewater Model Engineering Society at https://sites.google.com/site/bluewatermes/

    Southwestern Ontario. Canada

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    • #3
      I posted these questions on PM too to get a wider audience/more opinions.
      There I explained my needs further and asked more questions.

      I'd be very greatful to anyone who shares his experience and thoughts. Please feel free to post them here or there. Whatever is more convenient for you.

      Here it is: http://www.practicalmachinist.com/vb...e-shop-238079/
      Mike
      WI/IL border, USA

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      • #4
        I can't help you a lot.

        I have the evenheat, 22.5" depth, and use it a lot; but, then, I am a knife/pocket tool maker.

        I was going to get the 13.5", but my wife pointed out that I would probably end up wishing I had a longer one (!?!). So, I looked at the space and realized I could fit a 22.5" in the same width as I could have fit a 13.5", so I went with the 22.5. Out dozens of firings, I've only needed the full depth once. So, I might consider getting a smaller one in addition to this one, but I'm keeping this one.

        The hinges and door latch seem cheap but work. The control takes a bit of getting used to but works great.

        I think the trade-off in size is whether you will need the length more often or the additional width/height more often. I don't anticipate heat treating many things that won't fit into this one. Do you want to heat treat any long skinny stuff, like axles or control rods?

        The newest knifemaking kilns go up to 2400 degrees for treating really high alloy steels.

        Not sure whether that helped or not...
        Hemi-proprietor,
        Esoteric Garage

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        • #5
          Of course!

          How long does it take your kiln to get to 1950F or so? What about 1550F?

          How quickly can you return the parts to the oven for tempering (= how quickly the chamber cools)?

          Thank you.
          Mike
          WI/IL border, USA

          Comment


          • #6
            > How long does it take your kiln to get to 1950F or so? What about 1550F?

            1550 seems quick, 1950 a little slower.

            I've never timed it - will be happy to on the next HT batch. I just remembered I owe a friend a golf pick (in High Alloy Stainless, no less), so I should have numbers for you by the end of the weekend/month/year.

            > How quickly can you return the parts to the oven for tempering (= how quickly the chamber cools)?

            Not quickly enough! Even with a subzero treatment, kiln is still way too hot when the pieces are ready to temper, even if the kiln door was open and a fan blowing in it (which warms up the garage nicely in winter). I currently temper in a toaster oven which reliably hits 455 (F) when set to 500.

            My eventual goal is to use liquid nitrogen as a cryo treatment. ETA carbide formation (which is supposedly good) takes a soak of several hours, so I will be able to use the kiln for tempering then.

            I'll get back to you in a couple of days.
            Hemi-proprietor,
            Esoteric Garage

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            • #7
              Originally posted by MichaelP
              Presently, I'm looking into 220v Evenheat and Sugar Creek ovens with digital controls. Do you have any experience with those? Which would you prefer and why?
              I've used the Evenheat ovens, and they're pretty much what you can make in an afternoon with some refractory brick and kanthal wire. It has a very thin sheetmetal shell, the structure is actually the firebrick.

              Building a furnace, like building a forge, seems complicated, but it's dirt simple:

              http://www.machinistweb.com/forum/showthread.php?t=1343
              http://www.viddler.com/explore/rashid11/videos/3/

              The Paragon ovens are considerably nicer -- they have a substantial reinforced structure, shell, and door... and they're more expensive. They're essentially a rebranded muffle furnace (which is a positive).

              http://www.usaknifemaker.com/index.p...x&cPath=57_168
              Last edited by lazlo; 12-29-2011, 11:59 AM.
              "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 lazlo
                The Paragon ovens are considerably nicer --
                They also advertise in HSM and Machinist's Workshop regularly Sorry -- couldn't resist the note

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                • #9
                  From ambient (~70F) to 1500F was 32 minutes.

                  From 1500 to 1900 was another 26 minutes.

                  Many of the hardcore knifemakers think that heating up steel even that quickly is too fast to ensure good results. I was not able to measure a difference with rapid heating though, so I don't worry about it very much.
                  Hemi-proprietor,
                  Esoteric Garage

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                  • #10
                    Originally posted by Tait
                    From ambient (~70F) to 1500F was 32 minutes.

                    From 1500 to 1900 was another 26 minutes.

                    Many of the hardcore knifemakers think that heating up steel even that quickly is too fast to ensure good results.
                    At the ABS bladesmithing school, we did all our heat treat in forges. ambient - 1500° in about 5 minutes. No worries
                    "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

                    Comment


                    • #11
                      Originally posted by Tait
                      From ambient (~70F) to 1500F was 32 minutes.

                      From 1500 to 1900 was another 26 minutes.

                      Many of the hardcore knifemakers think that heating up steel even that quickly is too fast to ensure good results. I was not able to measure a difference with rapid heating though, so I don't worry about it very much.
                      Not bad at all. Tait, thank you.
                      Mike
                      WI/IL border, USA

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