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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(biāo)準(zhǔn)惠氏螺紋（粗牙）British Standard Whitworth Thread ( Coarse ) 
        BSF－－－－英國標(biāo)準(zhǔn)惠氏螺紋（細(xì)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(nèi)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(tǒng)一制粗牙螺紋（代替NC）Unified coarse pitch thread ( Instead of NC ) 
        UNF－－－－統(tǒng)一制細(xì)牙螺紋（代替NF）Unified fine pitch thread ( Instead of NF ) 
        UNEF－－－－統(tǒng)一制超細(xì)牙螺紋Unified superfine pitch thread 
        UN－－－－－統(tǒng)一制不變螺距螺紋Unified thread 
        UNS－－－－統(tǒng)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(nèi)螺紋Internal straight pipe thread for connection 
        NPSM－－－－設(shè)備上自由配合，機(jī)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(jī)螺紋Thread for sewing machine 
        Z－－－－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" 
        20－每寸20牙twenty teeth per inch 
        UNC－美標(biāo)統(tǒng)一制粗牙螺紋unified coarse pitch thread ( American standard)