Ok, if you're not mechanically inclined, this may not be the thread for you </disclaimer>
I've been trying to figure this out for some time, starting back when I was team armorer in college and our M6 thread taper wouldn't thread onto a (good) 6mm tang (I would thread the tapper on first, then cut the tang). I also noticed a standard M6 nut from home depot wouldn't fit the tang either. I kept standard nuts around to sort out the 6mm vs. 12-24 mysteries that cropped up with our eclectic armoring closet.
So recently, I got two practice blades, that appear to be 6mm.. (as in, my 6mm inside hex nut fits fine) but when I try to put a standard M6 nut on, they won't fit. Is the thread on a 6mm tang different from a standard metric M6x1 thread? Has anyone run into this issue before?
FYI - I've never had this problem with a 12-24 tang or pommel, they all work interchangeably.
( New to the board, plenty of questions )