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Maybe OT: Need input for turning self cleaning electric oven into a tempering furnace

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  • Maybe OT: Need input for turning self cleaning electric oven into a tempering furnace

    Hi Everyone,

    I have an older Hotpoint electric range with a self-cleaning oven that I am thinking of using for tempering after hardening and also for preheating prior to welding.

    What I have found so far is these typically reach 900 to 1000 F. for the cleaning cycle. The owner's manual doesn't specify what temperature this one reaches. It only gives a 3 hour time for a heavy cleaning. I haven't been able to find a service manual/schematic yet.

    I can't think of a reason why the door needs to stay locked during these higher temps other than liability issues for the manufacturer.

    My evil plan is to either bypass the door lock circuit for the cleaning cycle or see about adjusting the thermostat to achieve higher temperatures w/o using the cleaning cycle.

    Anyone see any problems with this idea?

    Thanks in advance for any insights!
    Best wishes to ya’ll.

    Sincerely,

    Jim

    "To invent you need a good imagination and a pile of junk" - Thomas Edison

    "I've always wanted to get a job as a procrastinator but I keep putting off going out to find one so I guess I'll never realize my life's dream. Frustrating!" - Me

  • #2
    If you could open the door at 1000 degrees you would probably loose your eyebrows
    “I know lots of people who are educated far beyond their intelligence”

    Lewis Grizzard

    Comment


    • #3
      Which is a good reason to wear face protection when opening a heat treat furnace - and to be aware that there will be radiant heat coming from the furnace.

      I just realized that it might also be a good idea to elevate the oven to eye level so I wouldn't have to bend over to open the door all the way.

      Sooooo, thanks for mentioning that!

      Last edited by jhe.1973; 11-25-2019, 04:33 AM.
      Best wishes to ya’ll.

      Sincerely,

      Jim

      "To invent you need a good imagination and a pile of junk" - Thomas Edison

      "I've always wanted to get a job as a procrastinator but I keep putting off going out to find one so I guess I'll never realize my life's dream. Frustrating!" - Me

      Comment


      • #4
        That is pretty hot fr tempering. You do not need or really want to go that high.

        Comment


        • #5
          Turn it upside down so the heat doesn't escape quite so fast when you open it .

          Fit an electronic pid controller with a proper thermocouple to get the temperature desired, the current control on the oven will not allow the control you will need. Here are some examples:
          https://www.amazon.com/s?k=pid+contr...b_sb_ss_i_3_14

          Comment


          • #6
            Originally posted by BCRider View Post
            That is pretty hot fr tempering. You do not need or really want to go that high.
            Depends on what youre tempering. If youre making knives thats too hot, but if youre drawing back a fully hard piece of 4140 to 30rhc, 1000f is actually right where you want to be.

            To the original question, so long as the lock isnt integrated somehow into any complicated electronics i cant see why you wouldnt be able to disable it. I do agree with the statement that opening a 1000f oven can be a rather warm experience, but its nowhere near searing your eyebrows off. Dont stand directly over the door and youll be fine, i do it all the time for much hotter temperatures for knife making. For the record, double that temperature will light a leather glove on fire at 4 inches from the opening...

            The suggestion for a PID controller is a good one as well, but it really depends on what your needs are for tempering. Its really up to you if your welding preheats need to be within a few degrees, or if you want to be trying to split hairs with rockwell hardness. Personally, for my knifemaking outfit i try to keep my initial hardening temperatures +-10f of what my book says they need to be before the quench. Wide swings can have noticeable effects when youre trying to squeeze out every bit of cutting performance. For that preformance, my heat treat kiln does have a PID controller, which is honestly needed for higher temperatures. That said though, for tempering i honestly go by color for the carbon steel alloys i use, and use a basic toaster oven to do so. I wouldnt want to go +-50f for tempering, and youll want to test your oven, but honestly most of the temperature controllers in ovens could probably keep you within +-20f of setpoint, least at the lower temperatures, and unless you know you need more precision you probably dont

            Comment


            • #7
              opening the door at 1000 degrees will probably ruin the heating elements in short order, thermal shock. The industrial furnaces I maintained at work spent their entire lives at temperature, only coming down for a complete overhaul. The usual temperature cycle took 2-3 weeks to avoid thermal shock issues. Otherwise I think you have a *great* idea, I would want to pipe some argon into there at a slow rate, say 10 CFH. I bet you old stove will work great.
              Last edited by nickel-city-fab; 11-25-2019, 10:09 AM. Reason: typo

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              • #8
                DZER

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                • #9
                  Just saying !

                  -Doozer
                  DZER

                  Comment


                  • #10
                    setting your house on fire to act as a tempering oven seems a bit of an extreme suggestion Doozer, if only because it's a one shot deal

                    Comment


                    • #11
                      Originally posted by mattthemuppet View Post
                      setting your house on fire to act as a tempering oven seems a bit of an extreme suggestion Doozer, if only because it's a one shot deal
                      Coffee on the keyboard !
                      Thanks.
                      --D
                      DZER

                      Comment


                      • #12
                        The oven is designed so that the insulation needed for the cleaning cycle time is just adequate to prevent over-heating the external structure. If your HT cycles are longer, you might want to retrofit your oven with some better insulation, like Koawool ceramic fiber. If there's enough space, fill it with the better insulation. Also, as has been stated, the controls will need to be reworked to better control the temps. With that much heat, I would worry about the glass in the door. You might want to remove the glass and put a sheet of steel over it and fill the resulting void with Kaowool.

                        Comment


                        • #13
                          This stuff is pretty good, its what we used at work for lower temp zones: http://www.nutec.com/ceramic-fiber-blanket

                          Comment


                          • #14
                            I know I've said it often, but I so appreciate the help, humor, and general camaraderie of ya'll and wish I could spend more time here!

                            Thanks for all the input and keep it coming!

                            Now for the rest of the story.....................

                            My immediate need is for a preheat oven to salvage the right engine case for the motorcycle build I am detailing elsewhere on this forum.

                            As I have done with later engines, strengthening the case in this area was to be a piece of cake but it led to this disaster:



                            Turns out this area is MUCH thinner than later castings ............. to the tune of 3/16 inch blending to 3/4 inch and thicker in a short space. After trying all the tricks I knew, I had to give up and I am now replacing the entire rear half of the case with a later version that never had the built in weakness I was trying to improve.

                            Being a race engine, it is doubtful I could find a case half at ANY price, so I need to get as many variables in my favor. Hence the preheat oven idea.
                            Best wishes to ya’ll.

                            Sincerely,

                            Jim

                            "To invent you need a good imagination and a pile of junk" - Thomas Edison

                            "I've always wanted to get a job as a procrastinator but I keep putting off going out to find one so I guess I'll never realize my life's dream. Frustrating!" - Me

                            Comment


                            • #15
                              Originally posted by mattthemuppet View Post
                              setting your house on fire to act as a tempering oven seems a bit of an extreme suggestion Doozer, if only because it's a one shot deal
                              But just think of the slow cool down and annealing it would provide if it weren't for those pesky firefighters!

                              Best wishes to ya’ll.

                              Sincerely,

                              Jim

                              "To invent you need a good imagination and a pile of junk" - Thomas Edison

                              "I've always wanted to get a job as a procrastinator but I keep putting off going out to find one so I guess I'll never realize my life's dream. Frustrating!" - Me

                              Comment

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