When I'm cutting the 18mm thick MDF with a 2mm dia cutter with 3 flutes I set at 3 equal depth cuts and around 18000 rpm at 750mm/min.

Obviously with the long series cutter it suffers from vibration, so my finish isn't quite as nice as I would like it on the edges of the finished product.

So, more flutes, less speed, more speed, less feed or what ?

Limited to around 18000 rpm by the machine head and rating, so higher revs unavailable unless I convert the head to a better faster one.