Michael Chen
TVWBB Fan
May I ask, what did you use on the back side of the kettle lid to secure the NPT threads?
The Tel Tru thermometers I purchased from Amazon included a locking nut like the one in the pictures Chris posted here: https://www.virtualweberbullet.com/installing-thermometer/#industrial
You can also use one of these. I had one lying around from something else I had purchased: https://www.amazon.com/dp/B07GJSC8PQ/?tag=tvwb-20