Thread mills cut threads into an existing hole or onto the external surface of a part. A single thread mill can create internal threads in a range of hole diameters, eliminating the need to change tools when threading multiple holes of different sizes. Thread mills are used in production milling applications over 3/8" and in applications where a variety of parts will be produced on the same machine. They are also used as an alternative to taps when threading soft, nonferrous alloys that may break standard taps. Thread mills can only be used in CNC machines that have helical interpolation capability.