Hm, I assembled about a gazillion BNC connectors in a previous life.
They were whatever brand the Air Force bought, and they didn't contain a
wavy washer. The pieces were the shell, the tip, and the screw end; and
to hold the braid on the inside there were only the rubber washer, a
strange-shaped washer, and a flat washer (to go between the screw end
and the rubber washer to reduce the friction when tightening). One
surface of the strange washer was flat (actually, stepped), and that was
where the braid was smashed against the boss inside the shell. The other
was tapered in such a way that it would force the rubber washer to
expand outward to squeeze tightly against the shell. When disassembling
one, we'd often find that the rubber washer would be cut nearly in two.
The only pressure on the braid was from the rubber washer via the force
of the screw end.

A common mistake was to put the strange washer in upside down, since it
just looked right that way, with the braid nicely cascading over a sort
of angled surface. When that was done, the washer wasn't properly
expanded by the tapered end of the strange washer, and you could easily
yank a connector off. When properly assembled, there's no way you can
yank one off.

I have a bunch of connectors in my junk box which are essentially the
same as I've described, but with a couple of more parts relating to the
tip and insulator. I assemble one from time to time when needed and,
like their military counterparts, they've been very trouble free.

Roy Lewallen, W7EL

Ian White, G3SEK wrote:
Crazy George wrote:

All the contact pressure in a BNC derives from the rubber washer inside
the bayonet ring. A good BNC should need quite a hard twist to make the
bayonet click into place... and in old surplus plugs, this springiness
does wear out.


Ian, you need to chop one apart again and look at the construction.
The contact pressure is provided by the wavy washers behind the
shoulder. The rubber washer, which is on the other side of the
shoulder, if anything opposes the contact pressure direction as it
'seals' against the end of the female cylinder.


Well, thank you, George - they do say "Learn a little every day"! I've
sawn up several BNC plugs, but never in that particular way.

Even though it's a wavy washer, the fact remains that the spring
eventually weakens (it happens it in C plugs also).