Milling is a machining process in which a rotating milling tool removes material from the surface of a piece of stock. It is used to create parts with a wide range of shapes and features, such as pockets and slots. Milling tools are installed on a CNC (computer numerical control) or manually controlled milling machine to perform milling tasks. End mills have cutting edges on their nodes and sides and are used to create parts with complex shapes and profiles. Thread mills form internal and external threads on existing holes. Keyseat cutters create grooves in shafts for mating keyed parts to the shafts. Mold and die milling tools have tapered sides and are used for creating molds and dies. Engraving tools are used to cut letters, numbers, and designs on parts. Router bits remove material from workpieces to create decorative edges and other features.