So, I was making these spacers to align some boards into an adhesive backing and I would like to point out that if you ever do something like this, you MUST NOT lathe the recess using the hexagonal body of the spacer. If you do, they (lathed part and center of rotation of the screw) will be very misaligned (up to 0.5mm).
Use, instead, a screw wrapped in copper foil to attach it to the chuck, then lathe away until you achieve the desired diameter. (2.52/50 in those). Also, be careful to make shallow passes or you might bend the screw and mess up something.
(yeah, not much electronics lately, I know. Just wait for it, I’m preparing something really cool, continuing a previous project)