I've never seen 4-40 thread standoffs (that is the size of the hold down screws for DVI, VGA, serial, etc.), but definitely have seen both 6-32 (aka hard disc screws) and M3 (aka CD-ROM screws ...

The major thread diameter of a shoulder screw must not exceed the shoulder diameter. Commercial-grade shoulder screws have UNC class 3A threads. So, a commercial-grade screw with a ¼-in.-diameter ...

I've used them for ages but never had to buy them. Is there any practical difference in the various sizes of screws and cage nuts? M6 seems to be the prolific choice, but I see 12-24 and 10-32 are ...

The size of a screw is the size that would have been 100% mesh so your 1/4 inch screw will fit into a 1/4 inch hole with a small gap. There are 3 common standards for machine screws.

They're available in different sizes, but the most useful ones are similar in diameter and length to a 16d nail. For example, Spax makes a No. 9 screw that's 3¼ inches long.

Sellers called his talk, "On a Uniform Standard of Screw Threads". He complained that American nuts, bolts and screws were all individually made by hand, and that they still had to be hand-matched ...