I have a router with a screw missing. I can't figure out what kind of screw it is, and McMaster Carr seems to have nothing close. I have seen this screw before in computer equipment, such as routers.
My best guess is a #4-16. There are very few threads per inch. Literally a few turns inserts this 1/2" screw.
I do think this is standard, so I hope my description sufficies.