Tap and die

Not to be confused with Tool and die.
Tap in a wrench for creating female threads (left), and die in a wrench for creating male threads (right).

In the context of threading, taps and dies are two classes of tools used to create or repair screw threads. A tap is used to cut or form the female portion of the mating pair (e.g. a nut). A die is a cutting tool used to cut the male portion of the mating pair (e.g. a bolt). The process of cutting or forming threads using a tap is called tapping, whereas the process using a die is called threading.

Both tools can also be used to clean up or repair a thread, which is called chasing. However using an ordinary tap or die to clean threads generally removes some material, which results in looser, weaker threads. Because of this, machinists generally clean threads with special taps and dies—called chasers—made for that purpose. Chasers are made of softer materials and don't cut new threads. However they still fit tighter than actual fasteners, and are fluted like regular taps and dies so debris can escape. Car mechanics, for example, use chasers on spark plug threads, to remove corrosion and carbon build-up.

Taps and dies are available in many hardware stores, home improvement centers and automotive part retailers in common sizes and pipe (Home improvement) sizes. Online industrial suppliers also offer taps and dies. Manufacturers and DIY websites have instructions on how to use the tools.

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