Thermocouple placement

D

Dixieblade57

Joined
Jun 20, 2007
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I am looking for an opinion as to the placement of my thermocouple in my forge to achive the most accurate reading.
This is my forge. Before the burners were installed and plumbing to them was run.
(click thumbnails for larger view)




The burners have been angled to create a vortex, the inside is lined with 2" of inswool and the bottom has a 1" layer of firebrick.
This is the thremocouple I will be using. It is incased in cermaic sleeve blocks.

I have notched the firebrick in the floor of the forge to allow for the TC to lay flush to the top of brick. The TC would be inserted thru a hole drilled in the side of the forge directly in the center between the two burners. In theroy it should be reading the temp at the firebrick floor of the forge, directly where the knife would be laying.
So how does that sound for placement as to getting an accurate reading?
Also is there a way to test the reading your PID is giving you inside of a forge? Perhaps a container of water and check the boiling point?
 
I'm going through the same thing right now... I ended up drilling several holes so that I could move it around to really see what's going on. I just stuff some wool into the holes when I'm not using them. Just don't put one right where the main burst of the flame hits... like I did.
 
No I understand that is bad, the way my burner are directed is up! The vortex or swirl should bring the heat to the floor of the forge though. I am just trying to decide the best location for the TC!

Is there a formula or a site that you can go to find out what the true temp that water boils at for your particular location?
 
Dixieblade57 said:
Is there a formula or a site that you can go to find out what the true temp that water boils at for your particular location?
Click to expand...

I'm sure there is, however, if you are in Florida it is 212 degrees Farenheit. I am in the Atlanta area, about 1,000' ASL, and if it is off by a degree or so, I can't tell.

Ok, I just googled this link: http://www.csgnetwork.com/h2oboilcalc.html

per the calculator, water boils at 1,000' ASL at 210.2 degrees Farenheit.

I recently read a post in a forum somewhere of someone calibrating heat treating furnaces in a commercial environment using pure gold, silver and one other metal which I don't recall. They were calibrating to the tenth of a degree. The boiling point of water is too low, lower than your tempering temps. Perhaps lead, copper, aluminium, brass would suffice.. and they are cheaper also.
 
Thanks for the site! I understand that the boiling point of water is lower than the temps you will be working with when forging and heat treating. However if the PID reads the correct temp at boiling point then you have a constant with which to gauge if the system is reading correctly. Correct?

Now anyone want to offer an opinion on the proposed placement of my TC?
 
I've just trusted it to be right, but you could chunk a piece of 1095 with some salt on it in there. Salt should melt at 1475ºF.

As far as placement, I'd put it how you said in your first post. I would think you would want it to be accurate to where the steel will be.
 
jorasco312 said:
I'm sure there is, however, if you are in Florida it is 212 degrees Farenheit. I am in the Atlanta area, about 1,000' ASL, and if it is off by a degree or so, I can't tell.

Ok, I just googled this link: http://www.csgnetwork.com/h2oboilcalc.html

per the calculator, water boils at 1,000' ASL at 210.2 degrees Farenheit.

I recently read a post in a forum somewhere of someone calibrating heat treating furnaces in a commercial environment using pure gold, silver and one other metal which I don't recall. They were calibrating to the tenth of a degree. The boiling point of water is too low, lower than your tempering temps. Perhaps lead, copper, aluminium, brass would suffice.. and they are cheaper also.
Click to expand...

Pure aluminum might work, but the oxide coat would make it hard to see when it melts, brass is a horrible mess, as it is not a pure metal (it is an alloy with AT LEAST 2 components, one of which is zinc which will fume lethally in a forge (you do not want copper or zinc in a forge any way) brass has a slushy state often several hundred degrees wide, lead is also a bad idea in a forge. If you are planning to use the forge for heat treating, you should put a muffle in to protect the blade from direct flame and put the TC in the muffle with the blade

-Page
 
I just used a small piece of pure silver. Made a small box of stainless foil and set it in my oven touching my thermocouple and kept going up until it melted. I cut the silver from the side of a silver bullion coin. It looks like silver is around $17.50 a troy oz. I got mine for about $3.50 long ago. But, no matter, you can cut a lot of small pieces from an oz, so it is not that expensive to use in this way.
 
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