M20 (2.50) HSS Second Cut Tap

Second-cut (or second) taps are primarily used to continue threading in blind holes that have already been started with a taper tap, or for through holes where the thread does not need to go all the way to the bottom. They have a shorter lead than a taper tap, which makes them suitable for opening up the thread diameter slightly to its full size after the taper tap has created the initial lead.