I designed and machined my own lead screw nuts out of Delrin.... I used a piece of the 3/8-12 ACME rod to fabricate a Tap to thread the Delrin, by doing that I got a real snug fit, and along with the "offset compensator" blocks, I was able to get zero backlash ....What do you use for leadscrews and nut?
The ball nuts I've looked at for zero backlash and great tolerance seem to cost more than the steppers, and stepper control board if you count the carriage rod for the ball screws on 3 axis.
I'm still unsure if buying a 3 axis mill with ball screws and solid work area already set up, then converting it to CNC would be a better alternative than building one from scratch, for "best accuracy per dollar spent".
I am actually about to convert my 3 axis manual industrial mill into a CNC