Z-axis design - help sizing materials please!

[Jonathan]

...0.1mm then you should expect no better than 1mm tolerance.

Maybe I've got to the stage where I should just try it and see and just accept that I may have to compromise on cutting depths to reduce the cutting forces.

Supported rail suffers from much less flexing but what about the opening in the base of the bearing? How much extra movement does this allow?

That's a good point. Looking at the drawing for the bearing blocks if the force is in the 'worst' direction with the supported rails then it's only supported on 2 of the little ball bearings compared to 4 on the unsupported ones.

With this in mind maybe I should mount the supported rails 'back to back' on the Z-axis aswell as the Y.

Second hand: true, you never know.

Your compromise, your budget, your choice :)

Indeed

I think I'll go for the 600 and 900 supported rails for £155. That's already much more than I was intending to spend and a much better design.
Has anyone here bought from that seller / can confirm that they're good?