Simple Machine (help and advice needed)

[Ross77]

Steel would be stronger but heavier and the weight could be a disadvantage.

The best advantage of using Ali would be if you use tooling plate so it is perfectly parallel so mounting the rails and spindle mount would be easier and more accurate.

[Gregor]

Hi
Could someone please explain how you measure ballscrews and what fixing you need to order in order to fix the ballscrew.The ballscrew in the picture is the x axis off the machine and there is an end plate at each end welded to the frame . there is an outer and an inner measurement.
Cheers.