Making a hole in a thin brass fixture.

[Tony Wells]

I'd turn a "spud" to fit in the end of the housing, and use the two smaller holes to mount it on the spud with screws. The spud could be mounted any way you like. Your grip is rather precarious there, Jim.

 

[Milton Shaw]

Try a knockout punch from a electrician they may have the size you need. The 3/4 size is about 1" in diameter they will not distort the metal nearly as much as a drill bit.