一、英制螺纹（螺纹牙型角55度）Thread of British standard ( Thread pitch shape angle 55°) BSW----英国标准惠氏螺纹（粗牙）British Standard Whitworth Thread ( Coarse ) BSF----英国标准惠氏螺纹（细牙）British Standard Whitworth Thread ( Fine ) G----直管螺纹（外螺纹分A、B两面级、丝锥分G、G－D）Straight pipe thread ( Outside ) thread in A\B: taps in G、G－D ) R----锥管外螺纹（旧代号ZG;KG）Outside paper pipe thread ( Old thread code ZG,KG ) RC----锥管内螺纹（旧代号ZG;KG）Inside taper pipe thread ( Old thread code ZG,KG ) 二、美制螺纹（螺纹牙型角60度）Thread of American standard ( Thread pitch shape angle 60° UNC----统一制粗牙螺纹（代替NC）Unified coarse pitch thread ( Instead of NC ) UNF----统一制细牙螺纹（代替NF）Unified fine pitch thread ( Instead of NF ) UNEF----统一制超细牙螺纹Unified superfine pitch thread UN----－统一制不变螺距螺纹Unified thread UNS----统一制特殊螺纹Unified Special thread NPT----一般用途锥管螺纹（旧代号Z;K）Taper pipe thread for general purpose ( Old thread code Z,K ) NPSC----管接头直管内螺纹Internal straight pipe thread for connection NPSM----设备上自由配合，机械连接用直管螺纹Straight pipe thread for general purpose NPTF----干密封锥管螺纹Dryseal taper pipe thread NPSF----干密封燃油直管螺纹Dryseal straight pipe internal thread NGT----气瓶用锥螺纹Special thread for gas cylinder 三、米制螺纹Metric thread ZM----－米制锥管螺纹 Metric taper pipe thread 四、其它螺纹Other threads SM----缝纫机螺纹Thread for sewing machine PZ----气瓶用锥螺纹Special thread for gas cylinder 5V1－20V1－气门芯螺纹5V1－20V1－Tyre valve thread 螺纹代号说明示例：Explanation of thread code. e. g. 1/4－20UNC 1/4－公称直径1/4" nominal dia. 1/4"