[Zumba]

Hi Bill, looking at the design, in post #9, gives me a bit of doubt as to whether the offset drive would be strong enough to remain true without flexing under load.

I don't think the offset is that big of a problem.

The problem is that in the photo, the bracket that attaches to the quill is only 1/4" thick. Adding another ballscrew to the other side would help, but no more than thickening the bracket and using a larger ballscrew.

The real issue to consider is the quality of the quill. Most bench mills have pretty crappy quills. If your quill deflects as it goes through its travel, even the sturdiest drive setup will not be good enough. It would be like using precision ground ballscrews with crappy linear motion guides.