These taps are used to produce a thread close to the bottom of a blind hole and therefore have a very short lead. The right hand spiral cut of the flutes acts to force the swarf away from the cutting teeth to the rear of the flutes and out of the hole.
They are better on materials which form long continuous stringy swarf, rather than chips. They are also better to tap a thread in a hole where there is a break in the material, e.g. another hole, as the spiral fluting helps the tap to pick up on the other side.
Spiral flute taps can have slow or fast helix angles. Slow spirals are used for non ferrous materials, and fast spirals for most other materials.
Surface black oxide treated HSS spiral flute taps for blind hole tapping. Chips flow out against tapping direction.
Pointed end for sizes up to 1/4".
Flat end for sizes from 5/16" onward.