英制管螺纹基本尺寸及公差（牙形角55º） BSPP 螺纹代号 基本直径 内螺纹 外螺纹 大径 中径 小径 中径公差 小径公差 A 级 B 级 中径公差 大径公差 中径公差 大径公差 G1/8″×28 9.728 9.147 8.566 +0.170 +0.282 0 0 -0.107 0 -0.214 0 -0.214 0 -0.214 G1/4″×19 13.157 12.301 11.445 +0.125 +0.445 -0.125 -0.250 -0.250 0-0.250 G3/8″×19 16.662 15.806 14.950 +0.125 0 +0.445 0 0 -0.125 0 -0.250 0 -0.250 0 -0.250 G1/2″×14 20.955 19.793 18.631 +0.142 0 +0.541 0 0 -0.142 0 -0.284 0 -0.284 0 -0.284 G5/8″×14 22.911 21.749 20.587 +0.142 0 +0.541 0 0 -0.142 0 -0.284 0 -0.284 0 -0.284 G3/4″×14 26.441 25.279 24.117 +0.142 0 +0.541 0 0 -0.142 0 -0.284 0 -0.284 0 -0.284 G1″×11 33.249 31.770 30.291 +0.180 0 +0.640 0 0 -0.180 0 -0.360 0 -0.360 0 -0.360 G1.1/4″×11 41.910 40.431 38.952 +0.180 0 +0.640 0 0 -0.180 0 -0.360 0 -0.360 0 -0.360 G1.1/2″×11 47.803 46.324 44.854 +0.180 0 +0.640 0 0 -0.180 0 -0.360 0 -0.360 0 -0.360 G2″×11 59.614 58.135 56.656 +0.180 0 +0.640 0 0 -0.180 0 -0.360 0 -0.360 0 -0.360 G2.1/2”X11 75.184 73.705 72.226 +0.217 0 +0.640 0 0 -0.217 0 -0.434 0 -0.434 0 -0.434 G3”X11 87.884 86.405 84.926 +0.217 0 +0.640 0 0 -0.217 0 -0.434 0 -0.434 0 -0.434 G3.1/2”X11 100.330 98.851 97.372 +0.217 0 +0.640 0 0 -0.217 0 -0.434 0 -0.434 0 -0.434 英制锥管螺纹基本尺寸及公差（牙形角55º） BSPT 螺纹代号 基面上的直径 基准长度 有效螺纹长度 圆锥内螺纹基面轴向位移偏差（±mm） 大径 中径 小径 基本 最大 最小 基本 最大 最小 R1/8″×28 9.728 9.147 8.566 4.0 4.9 3.1 6.5 7.4 5.6 1.1 R1/4″×19 13.157 12.301 11.445 6.0 7.3 4.7 9.7 11.0 8.4 1.7 R3/8″×19 16.662 15.806 14.950 6.4 7.7 5.1 10.1 11.4 8.8 1.7 R1/2″×14 20.955 19.793 18.631 8.2 10.0 6.4 13.2 15.0 11.4 2.3 R3/4″×14 26.441 25.279 24.117 9.5 11.3...
