[canterburyflyer]

As I was dissembling the gantry once again to install new 2010 ballnut, I discovered deep groove ball bearings where a pair of angular contact bearings are indicated. Funny thing is that I handled the bearings before and never twigged. It just boggles the mind, the ways the manufacturer of this albeit entry level rig cut corners. I'm no seasoned pro, but I know enough to get by. Axial thrust loads are not the domain of the deep groove bearings.
I have installed the pairs over angular contact bearings measuring 30 x 10 x 9 with ease on the X and Y ballscrews and grabbed a pack of wave washers to use as I preload. So far I have no idea how the preload is done.
Anyway, I have made a 3D model of the situation I have with the Z axis 1605 rolled ballscrew. (It is not as modelled I just quickly made up an involute)

[canterburyflyer]

I just want to elaborate on the model I included. It shows the ballscrew where it is supported at its lower extremity. The new 7200ACM bearing is pictured how I gather is best practice. The lower component of the cast iron bracket pushes on the outer race and M10x1 nut will be torqued as per your suggestions. There is also the matter of lube and chip rejection. I have 30mm I.D rubber bellows on the way. I would be grateful if you might share pitfalls cautionary tails