ah, squareness.....Yes the chinese machines are all over the shop by the time you remove them from the crate and worse when you want to use them. It comes with using the aluminium extrusion unfortunately.

If the Z is the issue, then you can skim the spoil board but realistically you will need to check each axis against the other.

We can go into details if you want.

For cutting aluminium, I recommended you get some cooling first. You may be more efficient with the single flute but that does not exclude 2 flute endmills, if you go shallow and fast as you note, but you may need to clear chips well when going deeper than an 1mm. You could get a shallower angle 2 flute endmill though which is specific to ali. I always wanted to give a mist cooling things a go.


With composite materials like the alu comp you are thinking of, you will need to experiment a bit. Typically on ply material it is recommended to use a downdraft or compression bit when doing the edges so as not to rip the top and bottom ply. Not sure if this will apply to your case but the option is there.