These Solid Carbide Helical Flute Thread Mills are ideal for milling a wide variety of thread diameters and pitches. As a general rule thread mills can always mill a thread larger than its stated size but not smaller. For example our 5/8-10 thread mill is ideal for milling a 5/8-10 internal or external thread and a 3/4-10 as well. A M14 X 2.0 thread mill can be used to mill a M16 X 2.0 thread but should NOT be used to mill a M12 X 2.0 thread.