Quote Originally Posted by CNCRY View Post
I'm hoping I can get slight adjustment if I have to go there, from shimming either ballnut or the gantry side/ballnut fixing. I have built in a very slight tolerance by using a 1mm thick piece of rubber between gantry side and ballnut fixing, which can compress 0.5mm ish to accomodate a slight twist.

So, wasteboard, just best to start with MDF and hold down clamps screwed into it to get started?
I like the idea of deliberately designing with a built-in gap for a shim in certain places. There's no such thing as a -0.2mm shim however much you might want one when finally assembling the machine.

Having recently got away from just screwing clamps into an MDF spoilboard to using something a little more sophisticated I can honestly say it's worth the effort to do better from day one, even if it is just to get you started. One of the problems is the little dimples that form around the screw holes which must be removed before you can put another workpiece over them and it's a pain having to drill holes for where you want to fit the clamps every time. Re-using the same holes many times over isn't too reliable either. I let my machine drill a grid of holes in the plywood base board and then put M8 T-nuts underneath. A sacrificial layer of MDF goes over that and then drill again. I also put a row of hand-drilled holes at either end of the base board to hold any pieces which cover the whole cutting area of the machine.
You can always upgrade to a slotted aluminium base in the future if you need to.