Quote Originally Posted by Zeeflyboy View Post
That would no doubt help... maybe flip it around so you can still use your extrusion slots for mounting the rails (assuming that was your plan?).

Best option I think would probably be to use the steel as the mounting face and look into the self levelling epoxy method of getting a flat surface, but that may or may not fit in with your budget option. If not going that route, the question becomes which is the more precise mounting surface in terms of flatness - the steel or the aluminium.
It would be convenient to use the slots to mount the rails so maybe I should spin it round for now. I intend to upgrade or rebuild the machine what's most important is to get it working reasonable now and I will work out if it's better to start again or upgrade.

I really want 8*4 but I don't need it I actually need 4*2 (1/4 sheet) but I will get 1/3 sheet so happy with that.

Interesting with the self levelling epoxy will investigate but my supported rail and ballscrews on the bottom axis will be bolted into the extrusion directly.