I was creating a water butt for my greenhouse, and I couldn't find a brass fitting to do the job.
This nut and flanged thread are designed to go through a 30mm hole in a barrel or drum, using your favourite sealing method on the inside of the flange to seal. I used an O-ring, inside and out for good measure, but a washer or silicone would work too.
The outer thread, which mates to the printed nut is M30x3.5.
The inner thread is BSP 1/2", fitting most UK compression valves, just with the olive and nut removed. Pipe tape is probably required to seal this.
Printed in PETG
6 shells on the threaded part of the flange
25% infill on the flange
3 shells for the nut with 15% infill