How much backlash is there on a 5/8 nook industries ballscrew, non preloaded. Would it be better to go with a 1/2"precision lead screw, at 10 tpi and make my own anti-backlash setup.

rocks101,
First off, what do you plan to use this on? There are tables on critical lengths vs speed etc that you have to look at. Secondly, the change between the typical 5 TPI and 10TPI will also affect speed. Thirdly, the coeficient of friction between ball and lead screw is great. This will affect the required power to move the axis.
Why not use the ball screw and make a pre-loaded nut??? I did and it was fairly easy to do. Zero Backlash.
To possibly answer your origional question, I was told by Roton their rolled ballscrew single nut had a typical .006" backlash!

Thanks for the info Bubba, I plan to use it on a 3 axis router im building, im really leaning twoard the ball screw, but i dont want to buy to ball screw nuts to eliminate backlash, I heard you could use slightly bigger steel balls.How would this affect the performance of the ball screw Any suggestions appreciated.