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How Long To Reach Temp ?

Discussion in 'Shop Talk - BladeSmith Questions and Answers' started by cootersplace, Aug 31, 2019.

  1. cootersplace

    cootersplace Gold Member Gold Member

    195
    Jun 8, 2006
    I have that Blue M electric oven and bought a new Pyrometer and Thermo thing. The scale on the oven doesn't go higher then 5-600 and I knew it was hotter. This new set tells me it has gotten to 1425 but it has taken 2 hrs. Its glowing red all over inside and this old oven is suppose to reach 2000 F So what do you think? Just wore out?
     

    Attached Files:

  2. 12345678910

    12345678910

    Jul 13, 2009
    degrees C vs F ?
     
  3. cootersplace

    cootersplace Gold Member Gold Member

    195
    Jun 8, 2006
    In F, I shut it down after over 2 hrs it finally got to 1525 degrees F , seems like a really long to
    time to me. It is a 110 volt oven.
     
  4. JTknives

    JTknives Blade Heat Treating www.jarodtodd.com Knifemaker / Craftsman / Service Provider

    Jun 11, 2006
    How do you know it’s designed to reach 2000°. A lot of those smaller ovens are burn out kilns for the dental industry and don't need to get hot. A big indicator is amp draw. If your plugging it into you 120v wall outlet then it will take along time to hit 2000 if it even can. You would be looking at hours to reach temp on a 120v circuit. To give you an idea my oven is about 5”x5”x32” and draws around 20amps which is about 4,400 watts. This comes out to 5.5watts per cubic inch. My oven takes around 40-45min to hit 1900°-2000°. So do the math and let us know what watt/in^3 your sitting at. Just to let you know I would personally not want to go less then where I’m sitting right now.
     
  5. JTknives

    JTknives Blade Heat Treating www.jarodtodd.com Knifemaker / Craftsman / Service Provider

    Jun 11, 2006
    120v ouch. If I had to guess I would say it pulls around 12-13amps. I don’t know if it would be designed for a 20amp circuit being that old. And industry standard is 20% less then breaker if it’s going to be on for a long time. That’s 1560watts and if you wanted 5.5in^3 then your chamber would have to be 284 cubic inches or less. Thats a chamber that 6.6x6.6x6.6”. So as you can see I don’t personally think it’s even capable of hitting 2k and might even have problems in the 1,500° range. Once you put a blade in there the temp is going to tank and it’s going to take a good bit of time to get back up.
     
  6. cootersplace

    cootersplace Gold Member Gold Member

    195
    Jun 8, 2006
    I had a RR spike in it while it was heating up.It did reach 1525F after that long time. And yes I just plugged it into a shared wall socket. I have the manual in a saved file let me see what it has.
     
  7. cootersplace

    cootersplace Gold Member Gold Member

    195
    Jun 8, 2006
    I have the manual in a file but it won't let me attach it here it has I think 4 pages. But the picture shows the model. If you would PM me your email address I would appreciate you looking at the specs and tell me what you think. You lost me with all the break down. Thank you for your time and effort.
     

    Attached Files:

  8. 12345678910

    12345678910

    Jul 13, 2009
    Why are you heating up a rail road spike ?
     
  9. Stacy E. Apelt - Bladesmith

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

    Aug 20, 2004
    The plate says 2KW, which would be about 16 amps draw. A 2000W oven should theoretically hit close to 2000°F, but many dental and jewelry burnout ovens won't get there. Your two hour heat up to 1500°F is too slow, though. They usually hit that temp in 15 to 30 minutes. The insulation and condition of the coils will be the factor that decides how hot it will get. I suspect one set of coils is bad and you are running on half the heating power.
     
    cootersplace likes this.
  10. JTknives

    JTknives Blade Heat Treating www.jarodtodd.com Knifemaker / Craftsman / Service Provider

    Jun 11, 2006
    I would take a peak at the coils at startup and see if thy all light up and run. After that if thy are all working I would probe the ends of the coils (unplug it first) and measure the resistance of the coils. The resistance will tell you what your actual draw is. Hell you could just measure the resistance between the prongs of your plug. That will tell you a ton of information.
     
    cootersplace likes this.
  11. cootersplace

    cootersplace Gold Member Gold Member

    195
    Jun 8, 2006
    Just to have something in the oven absorbing heat as if I were in real use. I could have thrown anything in it to see if it effected heat up.
     
  12. JTknives

    JTknives Blade Heat Treating www.jarodtodd.com Knifemaker / Craftsman / Service Provider

    Jun 11, 2006
    If I was you I would unplug the oven and flip the switch on. Then get out the ohm meter and put one probe on each of the plugs prongs. At 2000w and 120v you should be reading 7.2ohms of resistance between the prongs. This at 120v would draw 16.66amps and give you 2000w. But if one side of the oven went out then your looking at probably 14.4ohms which would be half the watts and amp draw.
     
  13. cootersplace

    cootersplace Gold Member Gold Member

    195
    Jun 8, 2006
    I will give that a shot when I go back out to the shop. Ya know whats bad is I had the itch for making knives, went thru all the building and wiring and all the belts and such, probably $3K plus and still not doing anything with it all. I keep hoping I will get that itch back. I have a small machine shop and am always busy for an old fart. So just in case I do get that itch back I want to be ready. If not then down the road someone will get a helluva a lot of equipment for half its value. :D Thank you for the help. I will check that plug in a bit.
     
  14. cootersplace

    cootersplace Gold Member Gold Member

    195
    Jun 8, 2006
    Here is what I got doing it twice.
     

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  15. Drew Riley

    Drew Riley

    Oct 17, 2007
    Looks like you've got it set to check continuity. What do you get if you set the dial to 200 ohms? If you get the same reading, then there's definitely something wrong , though it may not be reading across the coil. Next step would be to measure JUST the heating element, which means you'll have to disconnect it from the controller. If the reading is still high, try cleaning the end connections with some sand paper and testing again.
     
    Last edited: Sep 2, 2019
  16. JTknives

    JTknives Blade Heat Treating www.jarodtodd.com Knifemaker / Craftsman / Service Provider

    Jun 11, 2006
    I was under the impression that this was all mechanical inside. Meaning you adjust the knob and it just goes. If there are relays and other things in there that need power to switch the oven on then your not getting a correct ohm reading. You will need to then open the cover and measure right on the coils. I was hoping that measuring the plug would give us answers.
     
  17. cootersplace

    cootersplace Gold Member Gold Member

    195
    Jun 8, 2006
    Here is what I got with the meter set to 2000 the 200 would not read. I did it twice. Also the plate says it reaches 1832 F not 2000 F. Now I am trying a different oven I picked up.
     

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  18. cootersplace

    cootersplace Gold Member Gold Member

    195
    Jun 8, 2006
    This one was a little beat up with a cut off cord. I put a cord on it and here are the results. Once I got it to 2000 I shut it down. It melted my digital pyrometer probe. The oven was almost 100 degrees off from my digital.
     

    Attached Files:

  19. Drew Riley

    Drew Riley

    Oct 17, 2007
    Ok, your readings are probably all correct, but you’re also most likely reading resistance of the whole circuit, which is likely more than just the coil. You need to disconnect the coil and meter from each end to get a proper reading.
     

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