chinese atc spindle ?

[JAZZCNC]

I've noticed from some of your other machine builds that you are using a fixed BK12 bearing in both ends of the X-axis (don't know about Y-axis). What is the reason for that?

I do this on all ball-screws longer than 1000mm on both X & Y. The reason is to lower ballscrew whip, 2 fixed bearings provides more support and also allow the screw to be pre-loaded with tension.

Also in this video, you are not using any floating bearing on the Z-axis. Is it not needed because of the very short Z-axis length?

Not required on ball-screws less than 350mm.