Thermocouple/forge questions

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Dixieblade57

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Jun 20, 2007
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From a post on the forum.

http://www.bladeforums.com/forums/showthread.php?t=635924

The post talks about using a thermoucouple and PID with the potential for a trmperature regulated forge.

"This thermocouple might be better suited as it has a higher working range up to 2300F which will easily be seen in most forge situations. You'll also want to look into a protective cover as fuel exposure can easily shorten the life of the probe. Here's the cover for the above TC.

This PID would work great for a simple pyrometer reading, and it also has the potential to be used as a solenoid controller in the future if you decide you want a temperature regulated forge."

My question is this on a forge like mine and here are pics of my forge,

000_1150.jpg


000_1148.jpg


Where would be the best place to locate the thermocouple?

Would it be better to penetrate the top, side, bottom of the forge with the thermocouple or just lay in on the firebrick on the bottom to get a true reading on temps? I am trying to think ahead before I put the inswool in and the fire brick on the bottom for how the thermocouple is going to need to be routed to where is picks up the heat.
Any suggestions from someone who has a similar set up?
 
Hey DIxieblade, This is just my opinion but I think if what you want it a even heat and a true heat throughout the entire forge you might want to build yourself a forge just for heat treating. I have found that smaller diameter forges have alot of hot spots in them since the flame is not that far away from the metal. Check out my Ht forge here I built, Its probaly on the second page by now but it works amazing!!!! and it didnt cost me but 150.00 dollars. Now you might be able to get the one you got going but if my goal was to Heat Treat I would definitely look into making another one. I hope I helped some, Take care,Charlie
 
right now I'm just using the probe and PID to read temps and I don't use it much during forging; maybe a little more so at the moment while I'm still tweaking the oil burner but I mostly use it for heat treating.

I use a pipe muffle for heat treating and the delay when I manually adjust the heat to the time it actually registers on the PID is around 10 seconds. I'm not sure if the 'smart' software in the PID is smart enough to compensate for that condition or not.

Anyway the pipe muffle is open at the front of the forge and I stick the thermocouple near the hottest spot inside it. when I put a cold blade in I rest it on the TC and it drops the temp 200 - 300 degreesF and I can watch as it comes up to temp.
 
Thanks Charlie, I can't say this forge won't have hot spots but Ed Caffery seen a pic of it way back when I was just getting started and he's the one that helped to redesign the burners angles to create the "Vortex Effect" which helps to elimate hot spots!
My intention is to use the PID to keep up with my heat while forgeing so I won't need a pyrometer for now, (like this).http://www.truechoice.com/prodinfo.asp?number=LON 50612 I can do that set up cheaper than I can buy one of these and most won't read high enough temperature wise to be useful in heat treating later.


Down the road the PID along with gas solenoids the PID setup can allow you to maintain a almost constant heat, for heat treatment! Stacey has got a set up for that, down towards the bottom of this thread.

http://www.bladeforums.com/forums/showthread.php?t=523845

This is a new forge and has yet to be fired the first time. So I want to make sure I have either a channel into the interior of the forge in the right place for the thermocoupling, before the inswool goes in and is sealed!
My question is where to place the thermocouple to get the most accurate reading? Anyone want to take a shot at the location?
 
If I had to guess, I'd say basically in line with the burner holes but about 4"-5" toward the front.
 
You can put the thermocouple well pretty much anywhere, as long as it is reading the chamber temp. Avoid putting it right in the flame. I usually try to run it in from the back and have it stick in as far as possible toward the center of the forge. If the TC end is in the center, it reads the best average, usually. On vertical forge, run it in from the top and have the TC tip just above the area the steel will be in. Some sort of sheath or tube should cover the actual thermocouple to avoid improper readings, and extend the life of the TC.

It is perfectly fine to have it enter from the top or side in the center of the forge,too. Wherever it enters, make a pipe entry, just like the burner ports, that fits your TC sheath ( ceramic thermocouple well) with enough play to avoid being too tight. A little furnace cement on the outer end will seal it up nicely once all is installed and adjusted.You can also seal/plug the thermo-well with some kaowool. In the absence of a proper ceramic sheath, use a piece of heavy walled 1/2" stainless pipe. Forge the end shut, weld it closed, and grind it down so it fits in the entry pipe. This will have to be replaced occasionally, but will work well.

Stacy
 
my probe just goes in the back door, I have a little block of fiber board pluging it up as i dont need it to be open right now and there is a little v notch cut i the side for the probe. i like it coming in the back as i can move the probe around where i want. when i heat treat i have the probe right on the blade and it works great. my forge is realy even when up to temp with no real noticble hot spots.
 
Thank you gentlemen I do appreciate the info!!!!! :thumbup:

Here is what I am thinking if I were to put a SS tube into the forge for the TC, where it was just at the level of the top of the brick floor of the forge it should give me a fairly accurate reading as to what the temp is on the floor of the forge. Which is where the blade is going to be resting.
How does that idea sound? Here is a crude drawing of what I am talking about doing!



Clicking the pic will enlarge, sorry about the quality.
If I were to cut a groove in the brick to accomodate the SS tube would that give an accurate reading at floor level or would it be better to above floor level slightly? I am wondering if the fact it was grooved into the brick that the brick might shield it some from accurate reading!!!!!!!
 
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Looks fine. I would open the groove a little on each side of the SS well. That way it will get more exposure.
Stacy
 
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