Help with using long series endmills

[SteveGT4]

Hi, i have to mill a pocket 80mm deep in aluminium with a 10mm endmill. Is there a general rule of thumb as to how to adjust the speed and feed of a long series cutter compared to a standard lengh? I just managed to snap a brand new reduced shank 3 flute alu geometry endmill using the rpm my cam software gave me which was 6000 rpm (m/c's maximum) and i gradually crept the feed up. It got to probably no more than 100mm per min when the cutter shank broke. I didn't even get a chance to play with the rpm! Any recommendations?
Thanks
Steve

[djr76]

How about 'Plunge roughing' the cavity out then do the finish pocketing/profiling.

[dertsap]

a broken tool wouldn t be caused by the feed or speed ,especially at 6000 rpm . what was the depth of cut and engagement