X axis yaw on G8689

I thought I'd start a new topic for this (as opposed to continuing the tool size > hole dia). I have a G8689 converted to CNC and it still has ACME screws. In cutting the holes using the CNC, I get holes that aren't too round. PArt of the problem is that I need to better characterize the backlash in MACH, but I also noticed that I have some significant yaw issues with the X axis - except at the end points of travel, where the ways tighten up so much that the steppers miss steps. So, it looks like I need to rework the ways on this mini mill - any suggestions???? I have a pretty good Bridgeport that I could toss this little table on and try to straighten the ways, or is this a dumb idea? thanks, C