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DIY Heat treat furnace

Discussion in 'Shop Talk - BladeSmith Questions and Answers' started by Fox, Dec 7, 2005.

  1. Fox


    Feb 6, 2000
    I came across this tutorial today and thought some of you DIY guys might find it of interest. It looks like a pretty stout unit. If this is a dupe, mods, please delete.
  2. Sweany


    Dec 3, 2002
    looks simple enough:D
  3. Pete Allan

    Pete Allan

    Oct 29, 2003
    About a year ago I built a HT furnace by sort of following that tutorial and to say the least it works great. The one I built is a little large to use for knife work but it works fine for my needs. Mine is used for annealling small castings (50 lb) at a time and for carbon restoration of lots of small castings that will end up being heat treated. I think I saved the cost of the furnace with the first 2 batches of castings that I didn't have to send to the local heat treater.:thumbup:
  4. David Schott

    David Schott

    Sep 27, 2004
    I thought about this but for some reason it just seems really easy to electrocute myself or burn my house down if things don't turn out right....

    But since paragons and kilns are soooooo expensive, what would we estimate for a total cost to make one of these and attach a pyrometer and controller?
  5. Rob!


    Feb 9, 2000
    Good point about the electrocution. When I was considering building one, it was brought to my attention that the insurance comany would have something to say about the lack of UL or CSA approvals.

    Hey, I'm a knifemaker (and a guy) and that means there is a good chance that I'll burn the house down someday, in spite of my wife's efforts to avoid that. Between solvents, glues and gunpowder, the insurance claim would be spread over a city block or so. :eek:

    I decided that the savings weren't worth it.
  6. jhiggins


    Jul 11, 2003
    That furnace looks pretty cool, but I will have to admit I'm thinking that it would make a decent tempering oven - not an HT furnace. I say if you bought all the materials new and spent the time to construct, and charged yourself minimum wage for the time it took, you'd be better off buying an evenheat. ;)
  7. David Schott

    David Schott

    Sep 27, 2004
    I'm with you on that one! The last thing i need is to electrocute myself, then be lying unconscius next to a 2000 degree object! Im sure it can be made safe, but ill prolly spring for a real oven before something like this....
  8. adammichael


    Sep 13, 2004
    unless you have connections.:D :D :D :jerkit:
    (the last icon doesnt apply, I just think its funny)

  9. M Wadel

    M Wadel

    Sep 11, 2005
    i am building something similar next month hopefully. with a bit more isolation than that one to save electrical costs, im not the least bit worried about electricuting myself, i mean isolate the connectors and make sure the heating wire disconnects when the oven isnt 100% closed. its 2000° inside that one so just dont put any flammable material close to it
  10. Ripper


    Jul 2, 2000
    The turtorial is also avaiable as a .pdf document for anyone who wishes to download and print it: Heat Treatment Furnace
  11. jhiggins


    Jul 11, 2003
    Actually, I've studied the pdf a bit more than the original link. I'm going to place a caveat on my original statement about buying a ready-made furnace. The design of this cute little oven is sound. In fact, I may borrow some ideas from this to make myself an electric salt pot.
  12. Dan Gray

    Dan Gray

    Jun 25, 2001
    cool when I get home i'll put that on the knife making site :)
  13. Pete Allan

    Pete Allan

    Oct 29, 2003
    I put all of the electrical in side of steel shielding. the only place a person could get near any electric is if they were to reach inside while the oven was on and touch a 2300F heating coil -- I bet they wouldn't be stupid enough to do that again:rolleyes:
  14. Stacy E. Apelt - Bladesmith

    Stacy E. Apelt - Bladesmith ilmarinen - MODERATOR Moderator Knifemaker / Craftsman / Service Provider

    Aug 20, 2004
    It is not a real big risk,but many a caster has got a good shock when removing a flask from the burnout oven and accidentally brushing the heating coils.They tend to bulge out with age.A knife blade could easily do the same.This is where a good GFI circuit becomes a necessity.The idea of a power disconnect interlock in the door is a good idea.Make sure the interlock switch can handle that much current,though.
  15. Diggerdog


    Aug 30, 2005
    I've just built this furnace identical to the specs and the only thing that bothers me is the electrical. Can anyone give me a simple diagram as to how they have connected the heating elements to the bolts and then through to the control unit etc.? I'm thinking to be safe, I'll have the wiring inspected before I use it. Any help would be appreciated. Thanks. Dave
  16. Pete Allan

    Pete Allan

    Oct 29, 2003
    The safety switch on the door can be rather small because all it has to disconnect is the relay that is sending the power to the heating coils. If you are using 2 heating coils and hooking them together you are using 240 volts and 2 sets of points on a relay. All that is needed for a safety switch is a normal open push button switch that is set up so when the door is closed it will hold the switch closed.
  17. Sweany


    Dec 3, 2002
    Just don't lick your fingers and touch the bare wires while its plugged in.
    Sheeesh. I learned basic electricity in 4-H when I was ten.
  18. Dan Gray

    Dan Gray

    Jun 25, 2001
    I agree and as a fix to the switch

    you can use a low power ground operated relay to make sure you don't have to have a big heavy switch..kind of like the old ford starter solenoids,

    the OMC marine type is made for ground operation..it's a safety interlock so the starter can't operate while the engine is in gear..the small engine industry uses this type of lock out all the time now for safety..

    is this smily shaking dice or what :jerkit: :D
  19. Peter_E_Ryt


    Oct 26, 2005
    I may have to build myself one of these...
    My dad's a master electrician, so I'll run this design past him and see if he can reccomend any improvements. Otherwise- I'm probably gonna build myself one of these once I have the spare cash.
    Thanks for the link!
  20. Peter_E_Ryt


    Oct 26, 2005
    Sorry Double Post

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