HSS BSPF Bottoming Hand and Machine Tap. British Standard Pipe (G Series) is a pipe thread which is used mainly for mechanical coupling. The angle of thread is mainly 55° however for the US method some threads have a 60° angle. It is specified according to JIS and ISO R228. Bottoming Taps have a lead of two threads and are used to ensure minimum thread run-out when tapping to the bottom of a blind hole. Bottoming Taps are typically preceded by the use of a Taper or Intermediate Tap. Manufactured from HSS this general purpose tap is designed for use in medium tensile materials and is for hand or general machine use.