The knowledge of the threading dies
2.HSS dies: (High-Speed Steel)
BSPT: British Standard Pipe Taper
BSPP: British Standard Pipe Parallel
NPT: National Pipe Taper
NPSM: National Pipe Straight Mechanical
ISO: International Standards Organization ,Metric threads.
BSPT，widely use in Asian,Middle East,Europ,Africa.
NPT，widely use America countryBSPP，Russia