Selecting the optimal helix angle can be the difference between a perfect work piece and a do-over.
Here are details on why the helix angle is important and how it affects the cutting action. Most standard end mills are manufactured with helix angles as low as 15° and as high as 60°. General-purpose end mills are typically around 30°. Any increase in the helix angle increases the effective shearing action. This reduces cutting forces and the amount of heat generated during the milling process. Chip ejection is also improved.
Lower helix angle end mills are used on more difficult to machine materials where maximum edge strength and rigidity are important.
With straight flutes, the load build-up is almost instantaneous. This situation makes the end mill prone to vibration or chatter.
With helix angles, chip load is applied to the entire flute length in a progressive siding action. This makes the cutting forces much more constant with less chance for chatter. End mills with a higher helix also tend to produce much better work piece finishes. The 50° and higher helix angles significantly reduce side loading on the mill making it possible to mill thin wall sections with much less deflection.
At Midwest Cutting Tools, we can manufacture mills with helix angles from 15° to 60°. If you have questions about the right helix angle for your applications, contact us today.