Tapping

Tapping is a machining operation that cuts internal threads in a pre-drilled hole using a threaded cutting tool called a tap, producing threads for screws, studs, and other fasteners to engage. CNC rigid tapping synchronizes spindle rotation with Z-axis feed motion (spindle speed and feed rate are electronically linked), enabling accurate thread production without the thread-chasing complexity of older machines.

Before tapping, a properly sized pilot hole must be drilled; too small a hole will overload the tap and cause breakage, while too large a hole produces incomplete threads that won't hold fasteners. The thread size, pitch (distance between threads), class of fit (loose, normal, or tight), and depth are specified on engineering drawings, and programmers select the appropriate tap and speeds to produce threads that meet specification.

Tapping requires careful technique, proper coolant, and attention to chip evacuation, as broken taps are extremely difficult to remove and can scrap expensive workpieces.