About Hanks’ bulkhead fitting, it looks as though there is a toothy washer that prevents the inner part from spinning.
I don’t know how a person could get those threads started inside a tank though.
A better design for the tank would be to have a thicker plate in place of the one pictured above. That plate would be securely welded or brazed to the tank (brazing would allow for the plate to be brass?) , and would have a standard sized and threaded opening into which a fitting could be inserted and turned. That attachment , specific to the application of the tank, could be soldered or bedded with Permatex -
Bing bang boom , done.
The two flat surfaces soldered together make no sense to me , and are obviously prone to failure.
