Finish looks respectable on the flat, but a little rough on the sides?

Looks like a 2flute HSS cutter? What diameter, spindle speed, feedrate, depth of cut and stepover did you use out of interest?

My machine is currently running cutting a huge aluminium sheet at 780mm/min with an 8mm single flute carbide at 2mm depth of cut. It's been going for hours at that...