Thermocouple Placement?

Gary Mulkey

Gary Mulkey

Joined
May 14, 2001
Messages
1,414
Since this is my first gas forge, I would appreciate some imput. I am about to install a pyrometer on the forge and am debating on the best position for the thermocouple. The forge is a 16" verticle:

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I'm planning on letting the thermocouple extend approx. 2" inside of the insulation layer. What do you think would be the best (most accurate) position for it?

I'm thinking of screwing the thermocouple tight to the forge with the pyrometer around 2-3" away. Am I thinking correctly?

Gary
 
I'd consider purchasing a ceramic sheath for the TC to protect it from the forge atomsphere for longer life and to also act a bit as a muffle for accurate readings. The sheath is probably a foot long, and I'd install it from the side at the level of the door and extend it to just beside where you're stock is being heated.

Here's the sheath I'm talking about:

http://www.auberins.com/index.php?main_page=product_info&cPath=3&products_id=40

--nathan
 
Hi Gary!

If that picture on the post is your forge, I would suggest positioning the thermocouple in the upper, right, rear of the forge, as you standing facing the forge. Place it an inch or two below the top cover of the forge. With your burner coming in on the lower right (as in the photo) that placement is going to give you the best average temp within the forge. Also, only insert the thermocouple enough to expose about 1" of the tip inside the forge. The only portion of a thermocouple that reads temp is the first 1/2"- 1"...that's were the dissimilar meal junction is in the thermocouple.

In order to provide a little protection for the pyrometer, I would somehow place it just below the forge, tiled upward where you can easily see it. I have all three of the forges sitting on one big steel table, and made a sheet metal holder for each of my pryometers, which I mounted just under the edge of the table for protection.
 
The position of the thermocouple depends on what you are trying to read.
If you are reading the forge chamber temperature, then Ed's advise is spot on.
If you are trying to determine the exact temperature of a blade being heat treated, the best placement is directly under or over the blade. I have seen Burt Foster place the blade upright, on edge, with the thermocouple laying right on the blade's spine.
Stacy
 
Thanks. I will be using the forge primarily for welding and bladesmithing. I still use my evenheat for HT.

Gary
 
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