Helix angles generally come as low as 12° to as high as 60°. Most general purpose end mills use between a 25° and 30° angle where basic sharpness and cutting edge strength is maintained. Increasing the helix angle improves stock removal and is useful in machining at increased speeds and feeds. A higher helix angle also reduces tool deflection and transfers stress vertically through the spindle, as opposed to horizontally. In addition, it also reduces the amount of torque needed and the amount of heat generated. Chip evacuation is also increased, though the smaller flute spacing may cause build up when machining gummy materials or in slotting operations. Difficult to machine materials use a lower helix, where maximum edge strength and rigidity are imperative to efficient machining.

Edge build-up can accumulate immediately with straight flutes, creating excessive chatter. Chip load in higher flute angles is ejected progressively along the entire flute length. Thus, the cutting force is more consistent with less chatter. Higher helix end mills produce a finer finish. 45° and higher helix angles significantly reduce side loading and make it possible to periphery mill thin wall sections with much less deflection.

While selecting a tool, it is also important to consider other tool characteristics which may enhance the performance of the tool by eliminating traditional negative characteristics of the helix. For instance, as helix angle is increased, flute strength and core stability are diminished. That’s why we’ve designed our higher helix tools with maximum core diameters and eccentrically relieved flutes to increase edge strength and stability, achieving performances that were once not possible. Below are some common angles and their characteristics: