Tap and Die Set
A set of cutting tools used to clean, repair, or cut internal threads (taps) and external threads (dies).
A tap and die set is a collection of cutting tools used to create and repair screw threads in metal components. A tap is a fluted screw-like tool used to cut or clean internal threads in a hole (such as in an engine block or nut), while a die is a circular, hardened metal cutter used to cut or clean external threads on a cylinder (such as a bolt or stud).
In automotive repair, taps and dies are frequently used to clean rust, dirt, and old adhesive out of threaded holes before reassembly (a process called thread chasing). They are also used to repair threads that have been cross-threaded or stripped, ensuring that bolts can be torqued accurately without binding.
Using a tap and die set requires patience and the application of cutting oil to lubricate the cutter and prevent overheating. The tool is rotated forward (clockwise) to cut the thread and then backed up (counter-clockwise) frequently to break the metal shavings, preventing the tool from binding and snapping inside the hole.