i actually tried cutting aluminum today on this thing and i was surprised by the finish quality and how well it did with modest feed rates and lighter cuts. the drive pulley is the weak link when it gets pushed to hard. the spindle will take a 3 mm depth of cut full diameter with a 3/8 2 flute HHS cutter it just vibrates to much taking that much but cut good at 1.5 to 2 mm depth of cut i had the feed up to 40 IMP but i think it will do 50 IPM and still leave a decent finish. i'm still tweaking things in and have it close but the Z axis is being stubborn. things look pretty good as far as squareness and things being parallel so that's a good thing at least.