ASME B1.20.1 pdf download Pipe Threads, General Purpose (Inch) For a symmetrical straight screw thread with a 30-deg flank angle, Hp cot ␣ /2n p 0.86602540P. For a symmet- rical taper screw thread with a 30-deg flank angle and diametral taper of 0.750 in./ft, H p (cot ␣ − tan 2  tan ␣ )/2n p 0.86574320P. For an 8-pitch...