End mills are machining tools which are similar in appearance to drill bits, and perform various types of cutting and machining of metals. A ball end mill is a type of end mill that is especially suited to machining three-dimensional contoured shapes, such as those in molds and dies. It has a rounded tip which is designed to give an improved surface finish to the material being cut.
A ball end mill is well suited to milling many types of materials, from plastics to steel alloys and titanium. The toughness and durability of the cutting edge is very high in these mills because of the rounded edge design. This fact is actually just a byproduct of the rounded cutting edge. Originally it was rounded for a specialized purpose, namely for milling grooves with a semi-circular cross-section. This type of groove is an important part of the metal bearings used in many machines.
Another benefit of the way the ball end mill is designed is that it can handle very high feed rates, meaning it can mill the material very quickly. This gives it great productivity for use in today’s milling machines. The smooth geometry of the cutting tip also translates into lower cutting forces, giving the cutter added strength under pressure. Since it is less likely to break under normal forces, the ball end mill is also highly cost-effective for the applications to which it is suited.
Ball end mills are almost always made of tungsten carbide, a high-strength metallic compound containing tungsten and carbon. Tungsten carbide powder is pressed into rods, which are then ground and sharpened to various specifications. A typical ball end mill will often be manufactured with a protective coating. These coatings usually contain titanium mixed with other elements such as carbon and aluminum.
The coatings are applied to reduce wear and friction, and can also prevent damage to the cutting surface. For example, the gold-colored coating called titanium nitrate helps prevent small pieces of the milled material from welding to the mill itself under high temperatures. Protective coatings have been in use since the early 1990s, and many advances have been made since then. In the mid- 2000s, amorphous diamond coatings were beginning to be seen on some higher-end mills. Even with the toughest coating, though, a ball end mill will eventually wear out and need to be replaced.