I have never had good luck with helical milling (tornado milling) in hard material. I have tried different pitch lengths, new endmills after a few cut (even though the tool looks brand new still), slower, faster. I even tried helical with a pitch and a second helix at the same height with no pitch, then the next move with a pitch followed by a second with no height change. Did that all the way down. I end up with a 1 inch deep hole that tapers about .002". Anyone have any good suggestions on how to fix this? Hard milling holes this way is my enemy. The only thing I cannot figure out for the life of me.