Had a go using motorcalc sheet but does not look right.

[irving2008]

Ah right, so your max cutting speed is 1.5mm/s = 90mm/min? That still seems for too slow to be a useful cutting speed, esp for alloy.. even with your high speed spindle. I was expecting 500mm/min+, i.e. something around 10mm/sec

Increasing delay between steps by root 2 on an 'X and Y step' is a neat approximation to maintaining a constant tangential linear speed in a curve. :)