No worries Nick - no, alas mechanically it is far from perfect!! I suspect I just need to address that first....

JAZZ - I also suspected end float on the screws right from the start, but measured it at something around 0.04mm by putting the DTI on the end of the ballscrew and moving the gantry back and forwards. Seemed surprisingly small, considering it just uses twin-row angular contact bearings at the fixed end with no preload. But if I move one of the axes by 1.00mm using MDI and measure with a DTI, and then go back to zero, the gauge zeros repeatedly with very little lash indicated. All seems good. But is it different under a cutting load?

Cheers
Graeme