Alloy 6061 10mm x 200mm x 620mm. The alloy is extruded, so its kind of straight but not if you know what I mean. I guess its about 0.5mm out.

I am too tight to pay someone to machine it flat and my router is not good enough. Its for a new Z axis in order to make a machine that can make things flat.

So. I am thinking a block with something like 600 grit wet and dry? I tried a stone but dont see that working.

Thoughts from a metalwork Guru? Thanks