Interesting machine Chaz in that video.

Spindle speed looks strangely high for steel but it seems to be working at that feed rate.

Forgot to mention that I'd been looking at double ballscrews, or using back-to-back singles with belleville washers in my machine design to remove (up to a point) the 50 microns or so backlash. Something to think about if you are really trying to max out on performance. I'm undecided on whether to bother . . .