M3nS size and the printed Y rod holder
I am seriously considering MK2S -> MK3S upgrade so I tried to print some parts first to check whether they come out in acceptable quality and with dimensions not too far off. The hole sizes are basically OK - a M3 screw is tight but comes through, hexagonal M3 nuts fit perfectly but no way I can push a square M3 nut to the printed Y rod holder.
I am trying with the nut from the old M2S spare parts bag. Measured using a digital caliper this nut is 1.69 mm thick while the hole for it is 1.5 mm best. Using the microscope the hole is indeed 8 layers wide, which with some deformation (this is printed as a small bridge) corresponds to the 1.5 mm.
Googling for the nut sizes I found that the tolerance is relatively wide with 1.4 to 1.8 mm stated as the thickness. Is Mk3S now using a different supplier and the nuts from the upgrade kit are goint to fit flawlessly or is my print coming out different than it should? Sure I can file the hole to fit, I am just trying to assess the quality of the parts. Maybe someone with a Mk3S kit could measure the thickness of that nut if there is one in the spare parts bag?
I am using Prusament PET-G with the default profile and extruder-calibrated (the single wall thickness in a spiral vase model comes at exactly 0.45 mm).
For the record (and future searchers), the upgrade kit contains the same nuts and they are plain impossible to insert without filing the holes first slightly. Also the hole should be drilled by a 3 mm bit so the screw passes freely. If it cuts the thread in plastic with a bit of bad luck it can become seized in the nut's thread no matter how perfect the alignment is. I really recommend to print one or two spares here and test-screw before mounting it to the place it belongs. Only the Y rod holder has this problem.