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一、英制螺紋（螺紋牙型角55度）Thread of British standard ( Thread pitch shape angle 55°) BSW----英國標準惠氏螺紋（粗牙）British Standard Whitworth Thread ( Coarse ) BSF----英國標準惠氏螺紋（細牙）British Standard Whitworth Thread ( Fine ) G----直管螺紋（外螺紋分A、B兩面級、絲錐分G、G－D）Straight pipe thread ( Outside ) thread in A\B: taps in G、G－D ) R----錐管外螺紋（舊代號ZG;KG）Outside paper pipe thread ( Old thread code ZG,KG ) RC----錐管內螺紋（舊代號ZG;KG）Inside taper pipe thread ( Old thread code ZG,KG ) 二、美制螺紋（螺紋牙型角60度）Thread of American standard ( Thread pitch shape angle 60° UNC----統一制粗牙螺紋（代替NC）Unified coarse pitch thread ( Instead of NC ) UNF----統一制細牙螺紋（代替NF）Unified fine pitch thread ( Instead of NF ) UNEF----統一制超細牙螺紋Unified superfine pitch thread UN----－統一制不變螺距螺紋Unified thread UNS----統一制特殊螺紋Unified Special thread NPT----一般用途錐管螺紋（舊代號Z;K）Taper pipe thread for general purpose ( Old thread code Z,K ) NPSC----管接頭直管內螺紋Internal straight pipe thread for connection NPSM----設備上自由配合，機械連接用直管螺紋Straight pipe thread for general purpose NPTF----干密封錐管螺紋Dryseal taper pipe thread NPSF----干密封燃油直管螺紋Dryseal straight pipe internal thread NGT----氣瓶用錐螺紋Special thread for gas cylinder 三、米制螺紋Metric thread ZM----－米制錐管螺紋 Metric taper pipe thread 四、其它螺紋Other threads SM----縫紉機螺紋Thread for sewing machine PZ----氣瓶用錐螺紋Special thread for gas cylinder 5V1－20V1－氣門芯螺紋5V1－20V1－Tyre valve thread 螺紋代號說明示例：Explanation of thread code. e. g. 1/4－20UNC 1/4－公稱直徑1/4" nominal dia. 1/4"