EvilGnome. I have a 10 gallon cooler MLT that I want to mount a digital probe thermo like you have done with the solid stopper. Any details that you could provide would be much appreciated. Step by step, maybe. Seems straight forward just don't want to miss something. In the pic it looks like you might have bent the probe down a bit, true? What size stopper did you use does it matter?.
You can PM me if this is to much off topic, don't want to high jack the thread.
It was really pretty simple.
First I had to pick a spot where the probe was going to be located. There happens to be a plastic piece stuck on the side of the cooler (I think it's for a cup holder) and it's centered around the 4 gallon mark. I figured that would be good enough to be completely submerged, even with a small grain bill.
Then I used a small drill bit to drill all the way through the wall of the cooler. I just made sure that the hole was big enough to pass the probe and the wire through.
I don't remember what size the stopper is, but it's about 3/4 wide at the bigger end.
I then used a step bit to widen the hole on the inside of the cooler. Each time I widened it a step, I checked to see how far the stopper would go in the hole and called it good enough when the stopper fit in about halfway.
Once that was done, I drilled a hole through the center of the stopper using the smallest bit I could find.
The probe that comes with the thermometer is already bent at a 90 degree angle. I think most of them come this way.
Then I fed the probe through from the outside of the mash tun and put the stopper onto the probe. Getting the probe through the stopper was really hard at first. Then I lubed it up with some olive oil (just to make sure it was food safe) and it slid through with ease. Just make sure you have the skinny part of the stopper pointing towards the wire.
I pulled back the excess wire and jammed the stopper into the hole as hard as I could.
This has worked flawlessly for me so far.