This is basically a follow-up of my previous question.
I am talking about the nut between the frame and the cassette (see attached image). In other words not the "external nut" which fixes the axis to the frame.
This nut was loose, but I realized that tightening it too much locks the axis together with the hub/cassette: in other words when the cassette was rotating, it was also moving the axis along itself, which of course is not supposed to happen.
So what I ended up doing was tightening this nut by hand, just enough so that the hub can still move freely, without taking the axis with it. However, I'm not sure this is the right thing (maybe you are supposed to tighten it all the way, and something is wrong with my wheel and that's why doing so locked the hub and the axis together?)
So the question is: what is the proper way and amount to tighten this nut? (Also, if it has some more proper name than "internal" nut, I can gladly edit the question.)