Where should I install a thermocouple on 2-brick mini forge

[ashwinearl]

Hi All,

I just built a 2-brick mini forge following the "virtual BBQ" instructions from Atlas a few years ago. The purpose is heat treating small blades made from simple steels (1084, 15N20, 80CrV2, 8670).

I purchased an Atlas 30k burner, regulator, and multimeter/ 4" thermocouple kit as well. Any suggestions for where to place the thermocouple. Do I drill a hole into the cavity from the side and have the tip sticking in, or just place it inside the front free standing.

Here are some pictures. Note the single brick on the left is just to hold the burner. The burner entry hole is angled towards the back and is 1" in diameter. The burner tubing is 0.85" Outer diameter.

Thanks.

 

[JTknives]

I think your most likely going to have issues or wild inaccuracy. Most TC need to be mounted at least 5x diameter inside the heated area and if it’s shielded like yours then further. What happens is if the TC is not far enough in the the heat just travles down the TC to the outside air. There is not enough surface area of the Tc exposed to the heated area to over come the thermal conductivity of the TC and shielding. I also don’t think you have a large enough chamber to actualy drop the flame temp and idle along at a set temp. Running a forge at 1450° inside temp can be tricky and normally requires a pid and solenoid valve and a blown burner. You could use the TC to show forge temp inside but I don’t think it’s going to accurately depict the temp of the blade. Plus in a forge that small your going to have one hot zone and cold ends. So your going to have to pump that blade back and forth to get the temp even in the blade. This is normally done with a forge that is much hotter then the temp you want the blade at. This is becaus time is your enemy. You need to pump enough heat into the blade fast enough that the other heated section does not cool off befor you get that part back in the hot spot. I wish you luck but honestly I would not waste the money on trying to stick a TC in the baby forge. Just run it full blast and pump the blade till a magnet stops sticking.

 

[Atlas Knife Company]

To use the thermocouple, I recommend placing the probe under the metal
as it sits in the forge. This will give the most accurate reading.
Typical use is to learn the correlation between temp and color. After
a while, you will no longer need the thermocouple except for HT.

Slightly bigger chamber will work better. Looks like you have 2" or slightly smaller. 2.5" will work great.