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：Rp1/2LH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：G1/2BLH螺紋副G1/2G1/2A1、公制螺紋所標注的公稱尺寸即直徑值，而英制要所標注的尺寸乘以25.4，才等與其直徑值。2、公制螺紋的牙型角為60度，而英制螺紋的牙型角為55度。3、公制螺紋螺距就是其相鄰兩牙在中徑線上對應兩點間的軸向距離。而英制螺紋的螺距可由1英寸長度內的牙數換算出來。公稱通徑DN/mm俗稱相當管螺紋/in外徑D/mm61分管1/81082分管1/4103分管3/814或17154分管1/218或22206分管3/425或27251寸管132或34尺寸代號每25.4mm內的牙數n螺距p牙高h圓弧半徑r基面上的直徑基準長度基本有效螺紋長度裝配余量大徑（基準直徑）d=D中徑d2小徑d1=D1余量圈數1/16280.9070.5810.1257.7237.1426.56146.52.52+3/41/8280.9070.5810.1259.7289.1478.56646.52.52+3/41/4191.3370.8560.18413.15712.30111.44569.73.72+3/43/8191.3370.8560.18416.66215.80614.956.410.13.72+3/41/2141.8141.1620.24920.95519.79318.6318.213.252+3/43/4141.8141.1620.24926.44125.27924.1179.514.552+3/41112.3091.4790.31733.24931.7730.29110.416.86.42+3/41+1/4112.3091.4790.31741.9140.43138.95212.719.16.42+3/41+1/2112.3091.4790.31747.80346.32444.84512.719.16.42+3/42112.3091.4790.31759.61458.13556.65615.923.47.53+1/42+1/2112.3091.4790.31775.18473.70572.22617.526.79.243112.3091.4790.31787.88486.40584.92620.629.89.243+1/2112.3091.4790.317100.3398.85197.37222.231.49.244112.3091.4790.317113.03111.551110.07225.435.810.44+1/45112.3091.4790.317138.43136.951135.47228.640.111.556112.3091.4790.317163.83162.351160.87228.640.111.551.本標準包括了圓錐內螺紋和圓柱內螺紋與圓錐外螺紋兩種聯接形式。2.本標準適用于管子、管接頭、旋塞、閥門和其它螺紋聯接的附件。3.當內螺紋的結構無螺尾時，有效螺紋的長度不應小于表中最小值的80%。4.與圓錐外螺紋配合的圓柱內螺紋，其各直徑的極限偏差均為圓錐內螺紋基面軸向位移的確良/16。5. 標記示例：螺紋特征代號：R表示圓錐外螺紋；Rc表示圓錐內螺紋；Rp表示圓柱內螺紋公稱直徑為1 1/2的圓錐內螺紋：Rc1 1/2公稱直徑為1 1/2的圓柱內螺紋與圓錐外螺紋組成的螺紋副：Rp1 1/2 / R1 1/2公稱直徑為1 1/2的圓錐內螺紋與圓錐外螺紋組成的螺紋副：Rc1 1/2 / R1 1/2當螺紋為左旋時 Rc 1 1/2 / R1 1/2 -LH6. 示圖中：內、外圓錐螺紋