Cutting: Aluminium
Tool Details: Seco Dia.10 4 Flute long series carbide endmill
(Seco Code: 91L100)

Seco Recomendations: Spin - 7000RPM (max. our machine can do)
Feed - 5600mm/min (Relevant to spin)
ap - 5mm
ae - 0.3mm

This produced a very poor finish (looks like chatter)
We reduced the feed to 2500mm/min much better, not as good as I had hoped. We then reduced spin to 6000RPM and feed to 600mm/min, this finish is good enough the problem is that it is now very slow.... The tool was bought with the intention of speeding things up, instead it is slowing us down.

Any suggestions to maintain speed but improve surface finish?