An end mill is a tool used on a milling machine. A milling machine is a machine found in a metal working shop that is used to remove material from a metal block to make it into a finished part. An end mill is one of the tools used on the milling machine to make a particular type of cut.

End mills come in single ended and double ended varieties. A single ended end mill has only one useful working end; the other end is just a smooth shank for holding the end mill in the tooling holder on the milling machine. A double ended end mill has two useful working ends. When one end becomes dull and no longer useful, the end mill can be installed such that the opposite end can be used.

End mills are made of carbide steels, with the cutting surfaces sometimes made entirely of carbides. It is also common for end mills to be coated with a very thin layer of titanium nitrate. Titanium nitrate is a gold colored coating that prevents the metal chips being removed from the part from sticking to the end mill, reducing its life and the quality of the cut. End mills come in a wide variety of shapes and sizes. To those unfamiliar with metal machining, an end mill will look like an odd drill bit.

While an end mill can be used to drill a hole, its function is much larger than that. In many ways, a milling machine with an end mill is very similar to a router in wood working. An end mill can be used to cut blind holes or grooves, bevel edges, cut a flat edge, and make holes in a block of material. An end mill can also be used to make bearing raceways and cylinders. You cannot make a square hole with an end mill, but you can make a square post. An end mill coupled with a milling machine is possibly the most versatile machine in the shop.