These are the ones I have used - http://www.cutweltools.co.uk/files/w...lu%20power.pdf

2 Flute solid carbide - the cutting angles on these prevent the chips from sticking and blocking the cutter up, also plenty of fluid needed when cutting to wash away the swarf and keep the cutter lubricated.

The more solid the machine the better, if you have any play anywhere in your machine then you will find it when cutting aluminium, also realistic speeds and feeds need to be used to keep the cutter cutting and not just rubbing away the aluminium, too slow a feed rate combined with a not so solid machine and they wont last too long, you have to make them work to get the best results.