The helix is the angle of the flutes relative to the axis of the cutter. On a high helix end mill, the flutes have to go around the cutter more revolutions than a standard end mill. High helix is analogous to a finer pitch screw thread. The advantage of the high helix is usually better surface finish. The disadvantage is that the chips have to travel farther up the flutes to be ejected from the cutting zone. So high helix are not good at deep slotting in aluminum but leave a lovely finish when profiling steel.
I agree that the 4 flute is probably loading up and cannot clear the chips. |