After threading the “nut” I used a 3/8” end mill to make a .093” recess on one end. This engages the cap part.
Then I made the caps out of ½ brass rod. I decreased the diameter to .480” to get a tiny step for the silver braze.
I cut .130” thick blanks because it suited my tooling but making the .24 protrusion and 3/8 diameter step, then parting it off is an excellent method. The important part is to make the .24 part clean because it compresses the Teflon seal, and get the .015” step at 3/8” sized properly to engage the diameter of the relief in the “nuts”.
I then mounted the cap by the .24” part and filed a radius on the top edge.