Thanks. I bought a couple of 4 flute upcutters recently but your right I should try a new sharp downcutter to compare. Looking at the endmills specifically sold for polystyrene and foams lots of them are upcutters but what i am adviced is to run these bits below 6000rpm so just about to see how my spindle, which currently has a minimum of 12,000rpm likes running at half that.