I've removed an old and ugly looking ceiling mounted fan (probably installed 30 years ago) which I'm replacing with a modern light fixture.
The round (not octagonal) junction box in the ceiling (behind sheet rock) that the fan was attached to has two mounting bolt holes that are 2.75" apart and the new light fixture has mounting bolt holes that are 3.50" apart.
The problem is how to attached the new light fixture to the existing box given that the holes of the fitting are 0.5" wider than the electric box?
I've tried using an all-purpose crossbar but it doesn't work because the mounting bolts from the new light fixture coincide with the sheetrock cutout for the electric box.
I thought about drilling holes in the new light fixture but think this would be dangerous because the light fixture has wires running between two pieces of metal and I obviously need to avoid drilling into them, also I cannot easily separate the two layers of metal.
Best Answer
I managed to attach the light fixture using the universal crossbar, but with some improvisation.
The light fixture included two combo truss bolts that were designed to screw into the junction box but this didn't work because of the incompatible sizes(3.5" and 2.75").
The solution was to bolt the crossbar to the junction box and hang the combo truss bolts (to attach the fixture) from the top side of the crossbar, with the bolt heads resting on the top of the cross bar. Then I secured the fixture to the bolts using nuts.
Not perfect but the fixture is stable and secure.
Thanks for your comments guys!