Whenever I deal with new stainless lines (specifically from Inline), I make sure that the old fittings are spotlessly clean and not galled.
I then tighten them and loosen them repeatedly. If you pay attention during this process, you will observe the gradual progression of the nut turning further as you go.
This occurs without actually increasing the amount of torque being applied on each successive tightening sequence.
What you are observing is the stainless steel flare becoming form-fitted to the brass fitting.
If you try to tighten these lines in only one gorilla-like step, you risk galling of the stainless steel flare. Stainless steel is notorious for galling.
Carl
