Thread mills create threads in an existing hole or on the part's outside surface. When threading many holes of various sizes, a single thread mill may make internal threads in a variety of hole diameters, reducing the need to change tools. Thread mills are utilized in production milling operations with diameters greater than 3/8" and in applications where several parts will be manufactured on the same machine. They can also be used instead of taps when threading soft, nonferrous metals that might otherwise break ordinary taps. Thread mills are only compatible with CNC machines that can do helical interpolation.