尺寸代號每英寸牙數螺距螺紋直徑（in)np大徑D、d小徑D1、d11/16280.9077.7236.5611/8280.9079.7288.5661/4191.33713.15711.4453/8191.33716.66214.951/2141.81420.95518.6315/8141.81422.91120.5873/4141.81426.44124.1177/8141.81430.20127.8771112.30933.24930.2911-1/8112.30937.89734.9391-1/4112.30941.9138.9521-1/2112.30947.80344.8451-3/4112.30953.74650.7882112.30959.61456.6562-1/4112.30965.7162.7522-1/2112.30975.18472.2262-3/4112.30981.53478.5783112.30987.88484.9263-1/2112.309100.3397.3724112.309113.03110.0725112.309138.43135.4726112.309163.83160.872注：1in=25.4mm1、用螺紋密封的管螺紋其標記及各種螺紋的特征代號規定如下：Rc—圓錐內螺紋Rp—與圓錐外螺紋配合的圓柱內螺紋R—圓錐外螺紋標準規定將螺紋尺寸代號寫在特征代號之后，若螺紋為械旋應再加寫左旋代號LH，具體示例如下：圓錐內螺紋：Rc1/2左旋圓柱內螺紋：Rp1/2—LH圓柱內螺紋與圓錐外螺紋的配合：Rp2/R22、非螺紋密封的管螺紋標記如下：A級外螺紋：G1/2A內螺紋：G1/2左旋B級外螺紋：G1/2B—LH螺紋副G1/2G1/2A