if not a rhetorical question, i believe your answer lies not in the screws, but in the backlash compensation and the x-y point compensations (in the exec file) for the machine. these must be periodically checked and calibrated to maintain repeatability.
Wow,
you have grabbed a tiger by the tail. Your choice of ballscrew for a 5 axis is not a trivial thing. Simple or compound attachment, drive system, repeatability required (there is a much ignored difference from accruacy here.) Speed, Force, lubrication possibilities, cycle life (how many million inches of travel), shock loading, serviceability.
Ballscrews Inc. is a name I remember from when I did such things. Saginaw Gear also make them I think. NSK, NTK, and other folks who make linear bearing way systems will either make ballscrews or have links.
Ingersol Machinery make an interesting screw - like an ACME, but with pressurized oil, so it acts like a sort of plain bearing - hell for strong and stiff, no stiction, big mess of recirculating oil.
nice new ball-nuts out there too, they have little pushers between the balls - acts like a cage in a ball bearing, and keeps the balls from scuffing on each other.
Don't forget that these things get warm and grow as you use them!!!
