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.