Thanks to you both for replying,
I noticed both of you talk about feed speeds and RPM but not depth of cut? According to GWizard I could get away with a 2mm DOC, 300mm / m feed rate, and an 8000RPM spindle speed, and that won't come even close to using the the 800w available on the spindle. Sound reasonable? I'll take your advice and pay attention to the chips. At the moment they are kind of like dust, reasonable size but they weight nothing... thiner than tin foil.

I wouldn't mind loosing an endmill in the name of experimentation... its more ruining the bearings in the spindle or something.

Thanks again,
David.