I'm developing a sump pump monitor/alarm setup that will include an Arduino Uno as well as a Raspberry Pi. Both boards will be mounted to a piece of wood. As we all know the Arduino Uno has M3-sized screw holes. However, the Pi is designed to take M2.5 screws. The difference in diameter between these two sizes is 0.5mm (2.4mm M2.5 vs 2.9mm M3). Is this going to be close enough to be able to use the smaller M2.5 screws for both? Due to cost reasons, I want to avoid having to purchase two different sizes of screws and standoffs.
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According to this table, the head on an M2.5 is 4.5mm across, so it won't fall through the M3 hole. Is that what you're actually wondering?
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Thank you! That table is very helpful. I just ordered a kit of M2.5 screws/standoffs/nuts - I think it will work just fine 
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I made very effective standoffs from pieces cut from some plastic tubing. Can make them any length I need.
...R
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Robin2:
standoffs from pieces cut from some plastic tubing
Bic biros do the trick
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