Hi Rich,
I have Nema 24, 3.1Nm Steppers on all three axis connected to spider couplings and 5 terns per inch ball screws. I have attached pictures of the Coupling on the Z axis but all axis are the same. I've also attached a picture of my Mill, a Grizzly G8689 CNC controlled using a GECKO G540 4 axis controller and Mach3 licensed.
The flood is under construction... also the home switches for X and Y are under construction.
I've searched for the original manufacturer of the parts but can't find them. Out-of-Business or my migraines are getting in the way.
BTW - I have all axis calibrated to less then 0.0005 in all directions except Z in Up direction (I am now thinking the Z is under a heavy load due to the weight of the head). The direction of Z that makes a difference for me is Down which is good. Up is not nearly as good, something like 10X the down accuracy.