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I am trying to mount a new light fixture which has a decorative head for the screws that hold the fixture to the plate.

One of the screws is too long for the existing fixture, so I attempted to look for the same screw but 1/4" in shorter.

I took the screw and decorative nut to the hardware store to try matching the size. I am 99% sure the screw is 32 threads/inch by comparison with an 8-32 screw at the store. However, the 8-32 screw is barely too large for the decorative nut, and a 6-32 is too small.

I looked into metric screws, and M4-0.70 is too large and M3 too small.

What might I be missing here? My other option is to just cut the existing screw, but I'd rather figure out what's going on first, just in case.

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  • Well, there's M3.5 x 0.6 and M3.5 x 0.35 but neither is all that close to 32 TPI. 42.3 & 72.5 TPI respectively. 0.8mm is close enough to 32 TPI to be confusable, at 31.75 TPI, but does not show up until M5 x 0.8 – Ecnerwal Dec 30 '20 at 0:28
  • Many home improvement centers have a board with nuts of the most common sizes that you can try threading the screw into until you find something that fits. If you can find a local mom-n-pop hardware store (there are still a few around), there's a good chance that pop will know just by looking at it. – FreeMan Dec 30 '20 at 0:56
  • You could sidestep the issue and just grind off the excess length – whatsisname Dec 30 '20 at 1:29
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If your located in the States or Canada most light fixture screws will be SAE or imperial measurements. The most common screw size used for fixtures will be a 8/32. The next sizes closest to this are the smaller 6/32 and the larger 10/24.

Why not shorten the original screw? Thread the nut down the screw to below the length yyou want it to be. Cut the shaft to the desired length. Unthread the nut so it straightens the cut hreads. Voila!

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  • I do this all the time, my apprentice brought me a 8-32 he said was impossible to cut I was able to then showed him how to grind it off and straighten the threads with the nut. – Ed Beal Dec 30 '20 at 17:56

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