CNC – Why a helical end mill is preferable to a straight one
Each time that the edge of an end mill comes in contact with the part, there is an impact and a sudden shock load. If the end mill has 4 edges and is rotating at 1000 RPM, that’s 4000 impacts and vibration of 66 Hz (4000 / 60, to convert to seconds).
With a helical end mill, some edge or the other always in contact with the part. There is no periodic impact, and cutting is therefore smoother. Helical end mills give you better part quality, and are kinder to the machine’s spinde bearings.
Pics. and text source: Cadem NCyclopedia multimedia CNC training software.