Thread milling uses a rotating tool with a smaller diameter than the thread to interpolate the thread profile. You use a 3-axis CNC milling machine capable of helical interpolation for this process.

The thread mill moves in a spiral path (G02/G03 helical move) to create the thread, typically performing a “climb milling” action. Thread milling gives you absolute control over the thread size (Pitch Diameter). You can use one tool for different thread sizes of the same pitch. This method works exceptionally well for hard alloys.

The cutting forces stay low because the arc of engagement is small. This allows for better heat dissipation into the chip rather than the workpiece. Thread milling is critical for thin-walled parts because the low lateral forces prevent wall deformation, whereas a tap acts like a wedge.

Contrary to older beliefs, modern micro-thread mills can process threads as small as M1.6, and handle materials up to 65 HRC. Many aerospace and automotive shops use thread milling for tough jobs like Titanium Grade 5. You get precise threads and longer tool life. CNC milling makes this process possible and efficient.