Proper technique for connecting 7mm (APC-7) connectors.
Spin the knurled outer connector nuts on the two connectors so that
one has its threaded connector sleeve fully extended, and the other is
fully retracted. Carefully press the connectors together and thread
the connector nut onto the extended sleeve, until it is finger tight.
You should turn only the outer connector nut, and not the connector
body, so that you do not rotate and scrape the mating surfaces. Now
finish tightening the connectors with a 12 lb-in torque wrench.
When you are finished, one of the outer connector nuts should
still be loose, and you should leave it this way.
Do not tighten this nut up against the other
one, jamming them together. What this does is apply a force that tries
to push the connectors apart, thereby reducing the contact pressure
at their mating surfaces. In other words, it loosens up the
connection where it really matters. There is absolutely no reason
to jam these outer nuts together; it is a bad thing to do.