Try (Constant Surface cutting speed, around 300 roughing, to 400 finishing, * 318.3) all over the cutter diameter.

So try around (350*318.3)/8 = rounds up to around 14k rpm.

so with ur rpm speed u need the appropriate feedrate, this is speed in rpm * no of teeth (or flutes same difference) * chip load per tooth (0.04mm finishing to 0.08mm roughing)

So say 14k * 3flutes * 0.06 = 2520mm/m

That probably wont help you, this might: Speeds and feeds - Wikipedia, the free encyclopedia

However those values are for HSS, your are using carbide so see above?