Tap: Used to cut or form the female portion of the mating pair (e.g., a nut), initiating the process of tapping.

Die: Employed to cut or form the male portion of the mating pair (e.g., a bolt), initiating the process of threading.

The process of creating threads using a tap is termed tapping, while the process involving a die is known as threading.

Both tools are also adept at cleaning up threads, a process referred to as chasing. However, conventional taps and dies used for this purpose often remove some material, leading to looser and weaker threads. To address this, machinists employ special taps and dies, known as chasers, specifically designed for cleaning threads.

Chasers, crafted from softer materials, refrain from cutting new threads but ensure a tighter fit compared to conventional fasteners. They feature fluting akin to regular taps and dies, facilitating the escape of debris during the cleaning process.

In automotive maintenance, chasers find particular utility, especially in tasks like cleaning spark plug threads, effectively removing corrosion and carbon build-up without compromising thread integrity.

The tap size chart provides a comprehensive listing of standard size taps