A hardened steel tool with cutting edges and flutes designed to cut or form internal female threads in a hole. Taps come in various profiles, such as taper, plug, and bottoming, to dictate how aggressively the threads are cut and how close they reach the bottom of a blind hole.
Use a bottoming tap to get the threads all the way down so the set screw seats properly.
Always use cutting fluid and back the tap out every half turn to break the chips, or it will bind and snap off in the hole.
Related terms
Chase
To run a tap, die or thread chaser through an existing thread to clean and reform it without cutting it oversize.
Thread cutting
Making a thread by removing metal with a tap, die, single-point tool or thread mill.
Overtapping
Tapping a nut oversize after galvanizing so it will fit over the thick zinc on a hot-dip galvanized bolt.