The most remarkable thing about high-helix end mills is that no one can agree what they’re called. They’re a special type of high-performance cutter designed for use with soft materials, especially aluminum, and you’ll find them called high-helix, high-spiral, shallow wedge, and high helix angle.
Feed rates can be much higher with these cutters. They can run higher-than-usual feed rates, since the shallow angle of the cutting teeth means more of the cutting force is directed along the axis of the cutter instead of trying to bend it. If that’s a bit confusing, imagine trying to break a stick by bending it over your knee or pulling on the ends. The latter is what a high-helix cutter does.
While stronger, high-helix cutters don’t produce very good surface finish in steel, so low-helix cutters also exist for that purpose. However, since they require very high-grade materials to stand up to machining stresses, they’re significantly more expensive than high-helix cutters for softer metals, putting them outside the reach of all but the best-equipped shops and Toolmongers.
High-spiral end mills [Production Tool Supply]