Size of screw holes

[dolemitecomputer]

I'll be making a few modifications to a black cube server case and need to know what size are the standard screw holes for fans/grills. I might need to buy a drill bit and need to know what size that will have to be.

[klosters64a]

5/32". However, they need just a touch of a round needle file to make them big enough to accommodate the self-tapping screws. But I've never tried the next larger size drill bits, which would be 3/16"--I think, anyway. The self-tapping variety seem to be the most common, and easy to get along with the fans from cooling specialist etailers.

Frankly, the self-tappers look like crud. The Philips heads on them get mangled, and they often don't go in perfectly straight.
Can't beat them for convenience, though.