Taps and dies are tools used to create screw threads, which is called threading. Many are cutting tools; others are forming tools. A tap is used to cut or form the female portion of the mating pair (e.g., a nut). A die is used to cut or form 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 be used to clean up a thread, which is called chasing.

 Taps and Die Set :

• Taper - 8 to 10 threads chamfered for easy thread starting in rough materials
• Plug - 3 to 5 threads chamfered; general use when tapping to bottom of holes is not critical. (This is the most widely used type of tap.)
• Bottoming - 1 1/2 thread chamfered - use after threads have been started for tappping to bottom of hole