How to disassemble SRAM PG-950 cassette It seems to me that SRAM used not rivet to hold all the cogs in one place, but long screw. This screw looks like a hex one, but I tried hex keys I have and I didn't find a match. Unfortunately the head is so small I cannot be sure it is hex in the first place (and not for example pentagonal).

So my question is am I correct with the "screw lead"? If yes, is it a hex one indeed? And what size?

I am asking to avoid drilling it through. Screw is always nicer to work with also because I can screw it back.
Hex bolts on bicycles are usually metric, and it seems that the bolts holding the cassette together are too. Inch based hex key sizes fall just in between so that none fits.