First cut in aluminium. Disaster.

[Zeeflyboy]

Depends what spindle you are using - when you have the 2.2kw 24krpm spindles Like I'm using there they really don't perform well at low rpm, so for good alu cutting on them you need to either have unrealistically high feed rates for a hobby machine where you start running into rigidity issues, or you need to move to something like a 2 flute or single flute cutter.

I wish there were some 12,000rpm options in the water cooled spindle variety at around 2.2kw but it seems you either drop down to 8krpm max (and those are massive!) or stick with the 24k rpm and try to make do with single flutes etc for the best results.