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 
        Z－－－－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" 
        20－每寸20牙twenty teeth per inch 
        UNC－美标统一制粗牙螺纹unified coarse pitch thread ( American standard)