Page 2 of 3 FirstFirst 123 LastLast
Results 11 to 20 of 21

Thread: Cheap K type thermometer

  1. #11
    Senior Member
    Join Date
    Dec 2010
    Location
    Vienna, Austria
    Posts
    733
    Blog Entries
    4
    Thanks Richard, I picked up on that on some of the earlier threads.

    With 20mm Graphite, then a bit of an air gap between the hole and the probe, then the stainless probe shield, then another air gap, and then the thermocouple, I wonder whether the reading will stabilize fast enough in practice to be usable.

    Mark

  2. #12
    Senior Member
    Join Date
    Nov 2012
    Location
    Ontario, Canada
    Posts
    2,187
    Better than staring at the charge and guessing regardless of how long it takes...lol.

    I'm sure if Richard got to reply before me right now I know he would add to "preheat" the probe by letting it soak in the furnace exhaust. This gets you into the melt range so reading a stabilized value from your crucible doesn't take nearly as long. I've done it with success. That said, I've also used his design without any preheat, and it worked just as well but it took a handful of seconds longer.

    The way to make these probes is to design them long enough that you can measure through the vent. That way you don't need to open the lid so in turn the time it takes to stabilize is moot.

  3. #13
    The lathe is a good idea, pity I dont have one. (yet, lol) I bought a 12inch drill bit and did it by hand on the workbench. Nailed it the first time. Total luck!
    Visit me: WWW.HandcraftedLanterns.com
    "Sometimes by losing a battle you find a new way to win the war"
    -- Donald Trump --

  4. #14
    Administrator Site Admin
    Join Date
    Dec 2005
    Location
    Huatulco, Mexico
    Posts
    3,119
    I bought a 12inch drill bit and did it by hand on the workbench. Nailed it the first time. Total luck!
    Maybe not all luck. You must have a good eye.

    I drilled mine with a drill press. I set up an accurate holding jig. Once you get the hole started about three inches with a normal length drill bit, the long bit will stay true to the beginning hole. (If it is accurately sharpened. A mis-ground bit will wander off to one side.)

    Richard
    When I die, Heaven can wait—I want to go to McMaster-Carr.

  5. #15
    Junior Member
    Join Date
    Jun 2016
    Location
    Detroit, MI - USA
    Posts
    24
    I've just been reading some degassing and fluxing threads and how temperature effects the process so I see that I should have some type of pyro on hand.
    However, a few things I read here aren't clear to me.

    Rasper says NOT to use absolute temperature. Why is this? I thought that was the point of a thermometer. Does the pot temperature need to be scaled against ambient somehow?
    I tracked the display unit above to a US seller ($9) but no mention is made of any temp compensation taking place.

    Is there a way to ID a sensor? I think I have one from a multi-meter kicking around but it's the blob-on-a-wire type. Is a sleeved sensor critical or can I pot it with something like core sand into some graphite?

    I also see various K-type kits with differing ranges. Is that just due to the construction of the sensor - SS sleeve vs handheld melty plastic bits?
    ___________________________
    Eddie daGrouch
    Making the world a messier place one project at a time.

  6. #16
    Administrator Site Admin
    Join Date
    Dec 2005
    Location
    Huatulco, Mexico
    Posts
    3,119
    Rasper says NOT to use absolute temperature. Why is this?
    I did not say exactly that. I said that pyrometers don't measure absolute temperature. They measure the temperature difference between the two points in the circuit where the thermocouple wires connect, one of which is usually, but not always, the meter. If you have a fancy meter that compensates for this, then you don't need to account for it, but if you use a simple ten dollar millivolt multimeter, then you do.

    Richard
    When I die, Heaven can wait—I want to go to McMaster-Carr.

  7. #17
    Senior Member
    Join Date
    Dec 2010
    Location
    Vienna, Austria
    Posts
    733
    Blog Entries
    4
    I have used the pyrometer for a few pours now. It is pretty slow acting with the carbon and air gap, but that is a good thing. Good advice to preheat it in the exhaust.

    I used to always hurry to pour, but now I can see that I am normally too hot, and wait for the temp to fall into range, the whole pouring process feels much less hectic. We did have the carbon rod fall off into the melt once. It is threaded on and the carbon on steel is pretty slick, and I think it just rotated off down the thread. I'll keep an eye on it, but it might need a some sort of clamp to secure it.
    Mark

  8. #18
    Administrator Site Admin
    Join Date
    Dec 2005
    Location
    Huatulco, Mexico
    Posts
    3,119
    I secure my carbon rods by cutting a shallow groove in the rod near the end. The rod is a close fit in the metal conduit. I wrap a piece of #12 copper wire around the groove which prevents the carbon rod from sliding out.

    When I die, Heaven can wait—I want to go to McMaster-Carr.

  9. #19
    Senior Member
    Join Date
    Dec 2010
    Location
    Vienna, Austria
    Posts
    733
    Blog Entries
    4
    That is a nice simple solution. I might even have 20mm circlips.
    Mark

  10. #20
    Quote Originally Posted by jagboy69 View Post
    The lathe is a good idea, pity I dont have one...
    If you are in the DFW area, you can stop by and use mine. I am in Fairview (McKinney/Allen area).

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •