I'm looking at getting a set of small Phillips head screw drivers for disassembling electronics, and I was wondering how the size of screwdrivers are measured? I know screws come in standard sizes (M1, M2, M3 ...) Is the screw head part of that standard size, or does it have another sizing scheme?
The heads of screws typically do come in standardised sizes. However the sizing scheme differs from the the standard screw sizes.
For example Philips head screwdrivers typically come in PH0, PH1, PH2, and PH3 sizes. Though smaller (e.g. PH000) and larger sizes exist.
Similarly other heads such as Torx, PoziDriv and flat head screws have standardised sizes using similar naming schemes (e.g. PZ1, PZ2 for PoziDriv).