I ran some new 3 flute carbides for a project on Sunday. I've got to work on my recipe for those. I adjusted using FSWizard to compensate for going from 4 flutes to 3 but it just did not like it. Chattered hard enough to break one and then I broke another when a tool offset failed to be applied. This part requires a good bit of stick out so that didn't help. These are variable flute end mills which in all the research meant possibly less chatter but so far the 4 flute cutter I used last time I cut this part did a better job.