Selecting a Corner Radius End Mill on Amazon.com
A corner radius end mill, also called a bull nose or torus end mill, is a rotary cutting tool with multiple edges used in machining applications, producing a radius in the corner of a slot or pocket in a workpiece. It has a rounded edge ground onto the tips of the flutes for lower resistance, which strengthens the end mill by reducing chipping and providing longer tool life. It has a corner radius that is fairly large, although less than the spherical radius of a ball mill. A corner radius end mill will remove more material and leave a better surface finish than a ball end mill, and it can be used at higher speeds, which improves productivity.
A corner radius end mill is similar to a drill bit, except that it produces a lateral cut as the workpiece is advanced at a perpendicular angle, while a drill bit cuts in a downward motion. It is typically made of high speed steel (HSS), often with tungsten or vanadium content, for its hardness and resistance to abrasion. It is then coated to increase hardness and cutting efficiency, usually with diamond, titanium nitride (TiN), titanium carbonitride (TiCN), or titanium aluminum nitride (TiAIN).
Corner radius end mills vary in length, diameter, and the number of flutes. Fewer flutes offer the most efficient chip removal, but more flutes provide a smoother finish and higher rate of speed. They come in a single-end design or double-end with a milling cutter on both ends of the tool, allowing a new cutting surface to be substituted when the first shows wear.