Originally Posted by
Spaghetti Legs
Top pic is with the fixed cup. Experiment was done with the caged bearings in place. Pretty sure it's the right spindle with the cups. I'm no frame guru - always assumed thread chasing was strictly to clean up the threads, but I wonder if a proper thread chasing, along with facing will address any subtle misalignment between left side and right side threading.
Yeah that's the idea. BB shells get literally red hot when they are brazed in. Metal warps when it's hot. Chase and face with a precision tool ensures everything is perfectly aligned, as well as cleaned of any brazing debris, paint, etc.