TiN HSS Hand Taps 3pcs Set available in M2 to M12

Serial Tap Sets (designated as Rougher, Intermediate and Finisher) actually vary in thread diameter, unlike conventional tap sets (Taper, Second and Plug) where the difference between each one is the length on the taper. 

1: Rougher    2: Intermediate     3: Finisher

Because the major and pitch diameter of the "rougher" is smaller than the "intermediate" , and "intermediate" is smaller than the "finisher" , each tap removes a smaller volume of metal resulting in a extremely smooth thread.

Excellent for tapping deep holes and tough metals such as stainless steel.