What grade of Ali are you using?

The shop said it was 1050. It's very soft...

I'd very much doubt any form of Shapeoko will manage to cut aluminium well, as they just don't have the rigidity.To give some idea of required feeds in 6061 alu, Suggested feed rate for a 1mm two flute endmill is 100mm/min, at 10'000rpm, for slotting with a depth of cut of about 0.75mm...

We are only talking about shallow cutting here - but I can see that I need to up the feed considerably! Thanks for the calculator reference....