I had a screw that I wished to replace with a longer one, so I measured the diameter and ended up with a replacement too thin.
My rough measurement of the original screw was 3.5mm, so I ordered an M3.5. I've since measured the original with a calliper and got 3.75mm. The replacement M3.5 screw is 3.25mm on the calliper. What gives?
Anyone wishing to check my calliper - the screws in a lightswitch are identical in diameter to the incorrect replacement M3.5, which my calliper says is 3.25mm.
This says I'm measuring correctly: