The center pin extends from the end of the main body about a half an inch.
The sleeve barrel screws on from the cable side and is not allowed to come off, but when engaged with the SO-239 female part the sleeve roughly matches the position of the center pin.
So the barrel end will start flush with the major base area of the pin, then when connected, the barrel is screwed on to the socket to hold it in place.
Thanks for the excellent reference and explanation on the UHF connector. I suppose there is some variability in connectors of all types but it's good to know the min/max allowable. Here is the N and SMA together, the SMA looks a little large or the N looks a little small, I'll have to recheck my measurements in MoI, or maybe it's my environment / camera settings in Thearender. The inner ring and screw threads look a little thick on the N type, I think I'll tweak those and put in a few more fillets to catch the light.
