Spiral flute bottoming tap, ground from solid high speed steel (HSS) with ground thread.

Two flute fine thread, with an H3 thread allowance (plus 0.0010 to plus 0.0015).

Having 1-2 lead threads, and little to no taper, a bottoming tap is used to continue threading a blind hole. This allows the tap to cut threads to the bottom or nearly to the bottom of the hole. This design however makes bottoming taps ill designed for starting a hole and another type of tap should be used for that purpose. Use the bottoming tap to continue the partially threaded hole to the bottom.

*Bottoming taps are not necessarily flat on the bottom, they sometimes have a 60 degree tapered point from the manufacturing process.