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  1. #1
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    DIY heat treat oven

    Well in the British Blades tradition of making everything yourself and seeing Andy and Alistair make such cracking heat treat ovens, I decided to give it a go with lots of help and kit from Tim Gunn. So here it is...frame made up from welded mild steel angle 25 x 25 x 3 and the side panels, floor and top panels are all stainless steel sheet. The door was fabricated for me by a local company that sold me the steel. Very useful!

    Anyway Tim provided me with the little PID controller, thermocouple and I got the 20amp SSR from RS. It's wired up but I'm not entirely sure I got it right so am waiting for Tim to pop round for a look see to make sure.

    Oh the kanthal elements were from a seller on ebay and the hi temp wires from Omega Engineering in Irlam, Manchester.

    Hope you like it - oh, I have always fancied putting one of those missile cover thingies so I picked one up from Maplin along with the switch.











    Last edited by Ken_Lau; 09-02-10 at 05:40 PM.

  2. #2
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    Re: DIY heat treat oven

    Nice one Ken.

    Are we going to see some knives soon?

  3. #3
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    Re: DIY heat treat oven

    Oh yes....my first blade is nearly done. Fully flat ground blade. It's been HT'd already so just got a finish it up.

    Sneak peek....
    Last edited by Ken_Lau; 09-02-10 at 05:42 PM.

  4. #4
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    Re: DIY heat treat oven

    Very nice looking superb bit of kit, but as a person who does PAT testing I think you would be better with some form of interlock on the door, Double Insulated cables from the control box(try 3183TQ Butyl Flex for immersion heater) to the element and an enclosure over the element teminals.You never know when you may reach round the back to move it while it is still plugged in. Use it carefully while testing.

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    Re: DIY heat treat oven

    Without meaning to sound thick but knowing that I will....what's a door interlock? As for an enclosure for the terminals, yes, that sounds like a good idea, but my little plastic tubes will have to do for now. Internally, I've got some spare pieces of soft insulating brick that I'm going to throw to the back of the oven to make sure my blades don't touch the elements at the rear wall.
    Oh the wires connecting the elements to the PID are mica glass insulated ultra high temp heater hook up wires - rated to 842 deg F or 450 deg C which should be sufficient!

  6. #6
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    Re: DIY heat treat oven

    I dont think anyone who produces an appliance to that standard could ever be considered to sound thick.
    When the oven is heating the bare elements are live to a voltage of up to 230volts (and very little current limiting) depending which part of the element you touch, moving a metal blade with metal tongs will bring you very close to the elements.
    An interlock can be either mechanical or electrical and ensures that the supply is isolated before opening the door.
    Probably the easiest method at this stage in your construction(and the least visible) would be to use a Micro Switch wired into the circuit to isolate the supply when the door is open. A bracket on the door will be needed to operate the switch.
    I have seen some pretty close things over the years when things have failed with appliances, and had a couple of close ones myself when tired and distracted.
    Not trying to knock your work at all as that oven looks every bit as good as some of the professional kilns etc that I have seen and worked on over the years.
    If you want a micro switch I think I have an unused Burgess enclosed one at work that I will send you FOC if you want to PM me your delivery address.

    Ken

  7. #7
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    Re: DIY heat treat oven

    great stuff ken in the middle of making one up myself mate
    that looks the business
    so might have to pick your brain if thats ok

    kindest regards mick

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    Re: DIY heat treat oven

    -
    Last edited by steveinthewoods; 28-06-12 at 03:05 PM.

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    Re: DIY heat treat oven

    Ken - gotcha....I get it. I think that I will do the low tech approach and make sure that I switch off the oven before opening the door. But thanks for the offer - appreciate it.

    Mick - no probs. Pls PM me and I'll help where I can.

  10. #10
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    Re: DIY heat treat oven

    ken, you have built a very fine heat treat oven, im impressed, looks better than the factory made ovens i have had in the past, i think this will be my next build, going to be tough to build a oven as nice as yours, congratulations on a top notch build.

  11. #11
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    Re: DIY heat treat oven

    very nice looking Ken

    how do one test to find out if a PID controller is working or broken as I have 4 used ones.
    2 high temp 1350C and 2 800C old turn a dial type and one digital ?

    DC
    Daniel Claville

    Flames and Fire is forever my Desire, And my Desire shall bend the will of Steel

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    Re: DIY heat treat oven

    Cheers Steve and Permafrost.

    DC - I'm afraid I'm not expert with the electrics or electronics. Tim Gunn is the resident expert and guru for all things involving electricity and heat! In fact Tim came over this afternoon and helped me rewire it correctly (ahem!) and after a shaky start cos the switch I bought was suitable (under rated) and it started smoking...we took it out and make do without for the moment. And it worked a treat. Tim knew where he was with the PID and was setting all the parameters. He made the PID do an autotune, then changed a few more parameters and it was really pretty accurate. It did overshoot a little but not much. It ran at 900 deg C for a good 30-40mins and it's probably worked as hard as it ever will need to. And it passed with flying colours. I did notice that one of the kanthal elements came away from the brick on one side, so I'll pin that back with a small bit of nichrome wire. Well pleased with it - only need to get a 20amp switch and it'll be done and dusted.

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    Re: DIY heat treat oven

    Very nice, id love one myself but I have no idea where to start.

    Jamie

  14. #14
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    Re: DIY heat treat oven

    I was impressed.

    Ken's done a far tidier job than I ever would with the build.

    The safety issues raised in some of the earlier posts are currently dealt with by a combination of common sense and an RCD. It seems safe enough to use, but not safe enough to sell.

    Realistically, overshoot is not an issue with it: I tend to get awfully anal about stuff like this, and it looks like it's infectious.

    It's pretty damn good for a quick tuning job; overshoot was about 10 degrees and it settled pretty quickly to within 3 or 4 degrees on the display. Though I'd have happily faffed about with it for hours to get it a tiny bit better, it probably performs as well as anything of similar size available from any of the well-known manufacturers.

    I was fairly surprised at how well it autotuned. I'd had quite a bit of trouble getting my oven to control reasonably well and thought this one might be awkward, too. I put the difference down to having the exposed elements on this one. Response is very rapid compared to mine, which has the elements buried in the insulation. Safer, as you can't touch them, but makes for lousy control.

    We had a brief discussion about cost, never clear-cut with any project that involves using parts that are readily available to the individual. It looks as if "anyone" should be able to build something very similar, using new parts, for around 500. Obviously adding bells and whistles would take this up, and scrounging bits would take it down.

    I'd certainly recommend it as a project for anyone who fancies a go.

    Tim

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    Re: DIY heat treat oven

    Hi Ken,
    I am planning on building something similar to that oven and even though I have been reading as much as I can about it (found a nice tutorial for building one just like yours, have a list of providers for the elements, etc) I still have a few doubts.

    I hope galvanized doesn't give me trouble with fumes or anything.

    My questions are the following:
    Structure: I plan on making the structure out of welded angle iron just like you and the sides will be made out of galvanized steel, since I have a shitload of 2mm sheets (I guess they are 1m x 2m, go figure).
    PID controllers: There seems to be lots of them for little money on eBay and they seem ok (enough range, etc).
    Thermocouple: Most of the ones I see are not rated to 1300C which is the most Kanthal wire is going to provide. For SS I will need close to 1150C I guess. And the few ones I have seen rated for those temps are plug like thermocouples. I have no idea how to attach it to the oven and where to place them. Since heat tends to rise, I guess it should be placed on the lower part of the oven, just by the knife blades you intend to heat treat. Could you elaborate a bit more the Thermocouple issue, how to attach it to the oven and where to place it? Pictures are wellcome.
    Wires comming in and out: I see you are mentioning some kind of heat resistant wire. I may be able to fetch some from a friend who repairs heaters and alike, otherwise I will need to buy it. My question is about how to insulate those wires. I guess you made a big hole in the steel plate (lets say 20mm) and a big enough hole centered in the middle of it for the SS screw that goes through the soft brick. That assures you the screw won't touch the cage. What is that insulating material you placed over the holes (rectangular shape) so you have something to tighthen the nuts? I have a load of hard bricks. Could I just cut one in half (thickness-wise) and use it for that?

    BTW, since I will need to buy the PID, controller, solid state relay and such on the internet, if Tim Gunn is able to provide such items, I would be happy to buy them from him. That will assure me everything works well together. Tim, could you give me a quotation for such items by PM?

    Thanks in advance,
    Mikel

 

 

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