0.390-27 UNS Threads. Why?

CGID

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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.
 
You have overlooked the fact that it is simply 1/8" PIPE thread (although straight rather than tapered) and light fixtures have used it for longer than any of us on here have been alive, perhaps since the gaslight days, IDK!

NO conspiracy theory here, at all!
 
Thanks for the information. But, I'm still up-a-creek with the coupler. It's male on one end and female on the other. The male stub is what is stripped. I'm headed to the store one way or another so I'm going to buy a new fixture. I can see a use for these threads along with gas-light fixtures. That may explain why the threaded rods are still hollow.
 
If you want to keep the fixture, no problem.

There's all sorts of "lamp kits" and even individual parts available on-line or at hardware or big box stores.

All you need is a length of threaded lamp tubing and a coupler. Cut the tubing to the needed length and couple it up. Should be a rack of that sort of stuff at your favorite store.
 
If you go to the supply house you can get a longer threaded rod with any joint.They make those up to 3 feet maybe more.
 

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