I seem to run into quite a bit of parts with longish tooling necessary, but never have much luck with it. For instance, right now I'm using a Helical 82856 in 6061. .375", 3" flute length, 45 degree endmill. MAP says .020" WOC, 15K rpm, and .0029ipt. HSM Advisor says .005" WOC, 15K rpm, .0045ipt. Realistically though, I always end up with my SFM on the floor. Then I see Youtube videos and stuff, and they're moving at speeds similar to what I posted. So what gives? What could I be doing wrong? I'm almost always using high quality holders on a very new, high end machine, and all I seem to get at those speeds is chatter and vibrations.