Glossary

A tap and die set is a collection of tools used to cut, repair, or clean screw threads, which are the helical grooves that allow bolts, screws, and nuts to fasten securely. These sets are widely used in metalworking, automotive repair, maintenance, and fabrication because they make it possible to either create new threads or restore damaged ones.

The tap is the tool used for cutting or forming internal threads inside a hole so that a screw or bolt can be inserted. Taps are typically made of hardened steel and have flutes cut along their length, which allow chips of material to escape during the cutting process. They come in several variations: taper taps for starting threads easily, plug taps for cutting closer to the bottom of a hole, and bottoming taps for completing threads at the very bottom of blind holes.

The die is used to cut or repair external threads on rods, bolts, or pipes. Shaped as a round or hexagonal tool with sharp cutting edges, a die matches specific thread sizes and pitches. It is typically mounted into a die stock handle, which provides the leverage needed to rotate it around the material being threaded.

Together, taps and dies serve two main functions: creating new threads in raw material or repairing existing ones that have been damaged by rust, wear, or mishandling. They are also used for chasing threads to clean and realign them, ensuring smooth assembly.

These tools have many applications, such as fixing spark plug holes in automotive repair, restoring fasteners in general maintenance, cutting custom-sized threaded parts in metalworking, or threading rods and pipes in construction and plumbing. Their versatility makes them a cost-effective solution for extending the life of parts and avoiding replacements.

While highly useful, tap and die sets do have limitations. They require precise alignment to avoid cross-threading, may weaken softer or thin materials when used incorrectly, and are not efficient for high-volume industrial thread production, which relies on automated machinery. Nonetheless, they remain an essential part of most toolkits for repairing and creating threaded fasteners.