One curious thing that I have seen is some equipment from other countries (metric countries) came with M4 screws and nut plates that fit behind a set of three 10-32 holes in the rails. And you could order non-standard mounting rails with the 10-24 threads, but almost no one ever did. I am not aware of how this usage started in professional electronics. There are many other examples of fine threads being used in professional, electronic equipment. Those mounting screws are usually a combination of an oval head with an integral imitation of a countersunk washer to provide a wider head to better grip the usually slotted holes in the equipment being mounted. We would buy the mounting screws by boxes of 1000. Only one example is the mounting rails in standard electronic racks almost always have 10-32 holes.
But 10-32s are used all over in electronics. I come from a professional electronics/radio/TV background and I almost never saw a 10-24 in use there.
