How long is a piece of string!
There are many factors to the answer, here are a few
1. Is the machine worn
2. Are you using leadscrews or ball screws
3. Is there backlash, yaw, twist, etc.
4. What ratio of motor to screw
The list goes on and on
Mach is not the limiting factor, Mach will work to .0001" or less.
Its like this, make the machine accurate and Mach will do the rest.
Graham.