The rubber gaskets at the ends make the seal.
Of course it does, I wasn't questioning that. The tightening I am doing is not extreme. I've always had an good sense of correct torque on fasteners having working on mechanical things all the time.
It does appear however that the brass center does not fit into the compression fitting on the valve body and that makes contact first before the gasket makes contact, hence the torque on the nut going up, then leveling off, then going up when the gasket contacts. The initial torque makes you feel like it's done being tight.
I just verified the interference fit by taking apart one of the connections that has been together and working fine for the past couple of days.
- I had to 'pull' the flex out of the angle stop as the brass center was now wedged into the fitting.
- the gasket appears fine and is at the same depth it is in the picture above of a new flex.
- the top 'rib' of the center brass tube has broken off and is now a thin ring of brass shaving. (the ribbing sheared off, but the brass tube is the same overall length/protrusion.)
I wonder why Brasscraft would machine that center brass piece that way. All 6 flexes I have have the same machining and dimensions.
Edit: just measured the "turns to tightness"
- 2 turns the torque abruptly changes - this is when the center brass contacts the valve fitting opening.
- another 1-3/4 turns and the gasket is reached as this final 'tightness' is mushy like a gasket is being compressed.
Again, not paying attention, the first tightness one might think the joint is now tight and done with.