All I wanted to do was change out a light bulb in a modern, two bulb ceiling fixture. A hollow threaded rod runs down the center of the fixture. The rod's top end holds the fixture to the ceiling and the finial, which holds the glass, screws onto the other end. While taking off the glass I discovered a coupling nut in this assembly with stripped threads and I cannot reassemble the fixture. The rod and coupling nut could be changed out with anything compatible with the treads in the finial. All the threaded components are 0.390-27 UNS. Why? The finial is pot-metal and I don't think it would take to being re-threaded. I know there is a joke in here somewhere about the number of people necessary to change a light bulb.