End mills with a cutting edge that looks like a segment of a large-diameter arc were introduced approximately 25 years ago. Because the shape of the cutting edge looks like a barrel’s profile, the tools became known as barrel milling cutters, or in shop talk, often simply as barrels.

At first the use of these barrel milling cutters was limited to just a few specific applications, such as machining the 3D surfaces of complex dies and turbomachinery components. However, recent advances in 5-axis machining and CAM systems have significantly expanded the role of barrel milling cutter applications.

This is because the design principle of having a cutting edge with a large-diameter arc has been used successfully in other types of milling cutter, such as tools for high-feed milling (HFM). The concept provides a toroidal cutting geometry that helps ensure productive rough machining at very high feed rates because of the tool’s chip-thinning effect.

Finish Your Work

Unlike high-feed milling tools, though, barrel end mills are not intended for roughing but for finish and semi-finish machining of 3D surfaces with low stock removal.

Traditionally, ball-nose and toroidal cutters perform these machining operations. However, the large-diameter arc of the barrel end mill cutting edge results in a substantial reduction of the cusp height generated between passes machined by a ball-nose or toroidal cutter.

Another advantage of this type of cutting edge versus ball-nose and toroidal cutters is a significant increase in the distance between passes (the stepover or a stepdown, depending on the direction of the cutter displacement after every pass) that is at least five times greater, without any degradation of the surface finish parameters.

This means that the number of passes and, subsequently, machining time can be noticeably reduced. Increasing the distance between passes also improves tool life and, therefore, lowers tool cost per part.