BERGEN 32pc METRIC TAP AND DIE M3-M12 SET B2553
Each size comes with 3 different finishing types of taps. A taper tap, an intermediate tap and a bottoming tap in all sizes.
Taper tap or starting tap: This is similar to a plug tap but has a more pronounced taper to the cutting edges. This feature gives the taper tap a very gradual cutting action that is less aggressive than that of the plug tap. The number of tapered threads typically ranges from 8 to 10. A taper tap is most often used when the material to be tapped is difficult to work (e.g., alloy steel).
Intermediate tap or second tap: The tap has tapered cutting edges, which assist in aligning and starting the tap into an untapped hole. The number of tapered threads typically ranges from 3 to 5. In the US they are commonly known as intermediate taps, whereas in Australia and Britain they are commonly known as second taps.
Bottoming tap or plug tap: The tap has a continuous cutting edge with almost no taper with between 1 and 1.5 threads of taper is typical. This feature enables a bottoming tap to cut threads to the bottom of a blind hole. A bottoming tap is usually used to cut threads in a hole that has already been partially threaded using one of the more tapered types of tap. The tapered end ("tap chamfer") of a bottoming tap is too short to successfully start into an unthreaded hole. In the US they are commonly known as bottoming taps, but in Australia and Britain they are also known as plug taps.