Steel frame for 8' * 4' cnc bed ?

[flanagaj]

80 x 80 x 6 box section can still distort. The size of the machine you are building will be rather heavy, 80 x 80 x 6 box section aint light. Unless you level it very well it will still move. If you decide to bolt it down then make sure it is perfectly level on its feet or you will pull it out of alignment with the bolts.

Ian

Do you think that is over sized ?

[Web Goblin]

Do you think that is over sized ?

No I dont think the material is oversized.
If you want a really sturdy machine then you cant really oversize the frame material, within reason I might add. Box section steel itself isnt really that strong unless you start going into heavy wall thickness stuff and as Jazzcnc has said getting your construction right to start with will make all the difference and would save you £800 on machining.

Ian