My new 6040 improvement plan.

[Zeeflyboy]

Aren't those just grub screws holding the bearing cartridge in place? I don't see how those would do any adjusting on the bearings other than distorting the casing or possibly forcing things out of alignment slightly.

My first (well actually second, but first was tiny) CNC machine was a similar design... was good enough to get started with and do light work, but unfortunately you will never be able to address the flex you get on those unsupported rails without just getting rid of them.

Whether that's an issue depends on what the goals are... cutting foam or other very light duty stuff will never show a problem, harder woods or light aluminium work can be done but you have to really work within the limits of the machine and accept that the tolerances and finish may not be what you hope.