No outlet box found in ceiling light.

I suspect that the round plastic disc is actually an old black enameled metal pancake box. The 1" screw rod may be an old gas pipe from an former gas light fixture or just a fixture mounting stud.

I hope that you are in the mood for an electrical challenge. Turn off the power. You will need to remove the old box. Do it carefully so as to not damage the existing wiring. Make sure that you identify each conductor in the box before you take apart the splices. Most likely the color coding is almost gone on these wires. I'm guessing that the wires are soldered and taped. Most likely the insulation on the wires is brittle and will break off as you separate the conductors. Get a roll of white and a roll of black electrical tape. You may need a roll of red also.

If there aren't too many wires in the box, you may be able to get away with installing a new larger pancake box which will easily accept your fixture mounting bracket. If there is a gas pipe coming from the ceiling it will have to be removed. If there are too many wires then you may have to install a 4" round electrical box.

Plan on spending a few hours doing all of this.

John Grabowski

Heat shrink tubing.

Why? Gas pipes are very stable strong mounts for the heaviest of fixtures.

The OP needs a hickey to screw on the end of the nipple or sometimes he can mount the cross support directly on the nipple with an appropriate lock nut.

Alternatively the black round plastic (?) disk may be an old...er not sure of the name... maybe "end-wire-terminator-for-fixtures-attached-to-gas-lines" . Quite ingenious actually. It's about the diameter and thickness of a hockey puck and made out a some sort of junky electrically conductive metal and has a blind threaded hole in the center one side of which terminates the gas line and the other takes a nipple + hickey + nipple (as required) to support the fixture. Around the center hole there are four or six (I suppose they came in various sizes) holes the same diameter as an AC box connector and like the AC box connector there's a screw (in this case with a captive nut) coming in at an angle which engages the AC cable, prevents it pulling out, and provides electrical continuity for the equipment ground. The " box" is really supplied by the canopy of the fixture which itself was metal (usually brass).

Although I'm sure it would freak out the code fanatics, it's not really a bad arrangement supplying all the protection and grounding that a modern setup would. Any heat (lamps) is a couple of feet below and behind the wiring is non-combustible plaster. The only thing you have to ensure is that the canopy is big enough for the connections.