So I'm retrofitting a Mori SL1 Lathe and there is .005" backlash in the Z axis. Too much to use compensation, I think. So far I've received quote from $1300-$1800 to recondition it. I've found new NSK 36mm Ballscrew and Nut with 10mm lead Grade C5 for $425.

So I'm wondering should I not bother with a new screw and have the old one reconditioned or should I try bigger balls in the old screw?

If I were to go with bigger balls how would i go about that? I mean what size should I go up from the original?