Taps and internal threading tools create threads on the interior surfaces of holes and parts so that they can be connected to fasteners or other parts with matching exterior threads. Chip-free thread-forming taps press against the sides of a hole to form threads. Acme taps create trapezoidal threads with a 29° included angle. Extension, nut, and pulley taps can thread deep holes and access holes that standard taps cannot reach. Garden hose taps create threads that meet the garden hose thread (GHT) standard. Oversized taps are used to make threads in a hole before a coating or treatment is applied to the hole. Pipe and conduit thread taps create threads that meet the thread standards used for pipe and conduit systems. STI taps create an oversized thread inside a hole so that a helical-coil screw thread insert can be inserted in the hole. Combination threading tools can drill, tap, and/or countersink a hole in one pass.
