ASME B1.20.1 pdf download Pipe Threads, General Purpose (Inch) This formula determines the length of effective exter- nal thread. This may include two usable threads incom- plete at the crest. 3.1.8 Hand-Tight Engagement Between External and Internal TaperThreads. The basic length of engagement between external and internal taper threads when screwed together hand-tight is L 1 , shown in column...