Electrical – Do European/Italian light fixtures & boxes use metric threads


I installed a fancy light fixture in a US single wall box, and had a terrible time with the mount and trim until I tapped out the fixture's mounting caps with a 8-24 tap and replaced the mounting screws with my own cut-to-size 8-24 bolts.

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Looking back, my box has normal mounting lugs at 2-3/4" (69.85mm?), but the fixture's plate has its mounting rings a little narrower at maybe 2-9/16 (60mm?) and I had to force the box screws in a bit crooked.

I think when I threaded the mounting screws into my bolt-cutter/wirestripper to cut them to length, it formed the thread to 8-32 to make them not quite match the knurl knob, which made it much harder to thread onto the stub and made the matching the proper length much more awkward.

The whole job took 10x as long as normal with all the fiddling around with everything not quite right.

So, what are the non-US standard box lug spacings and mounting screw threads? (With US spacings being 2-3/4" with #8-32 threads)

Best Answer

On http://internationalconfig.com/icc6.asp?item=72350-F I found this diagram with M3.5 lugs spaced at 60mm, which matches the mounting plate/mounting strap packaged with the fixture with its inner 60mm rings.

An M3.5 thread is a 3.5mm OD by 0.7mm pitch thread, while an #8-32 thread is 0.164" (4.156mm) with a 1/32" (0.794mm) pitch. A #6-32 thread is 0.136" (3.45mm) with 1/32" (0.793mm) pitch. They don't quite match, but visually they look close.

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