A milling machine is used to shape, round or flatten materials like wood and metal, and it can also cut gears or make slots or square corners on a piece of material, notes Massachusetts Institute of Technology. This machine uses a cutter that has several teeth that can vary in size, shape and number. There are a variety of milling machines, and each differs in the direction in which it moves and its position.
In order to cut down the surface of a material, a machinist would use a facing cutter on the milling machine, while an end mill would be used if slots were needed, states MIT. An item called a machinist's square can be used with the milling machine to make square corners.