
| 螺纹规格 | 螺距 | 外径C1 | 底径 | 螺纹标号 | 螺牙角度 | 备注 |
| NPT1/4 | 1.411 | 13.616 | 18 | 60 | ||
| NPT3/8 | 1.411 | 17.055 | 18 | 60 | ||
| NPT1/2 | 1.814 | 21.223 | 14 | 60 | ||
| NPT5/8 | 1.814 | 26.568 | 14 | 60 | ||
| NPT1 | 2.208 | 33.227 | 11 1/2 | 60 | ||
| NPT1 1/4 | 2.208 | 41.984 | 11 1/2 | 60 | ||
| NPT1 1/2 | 2.208 | 48.053 | 11 1/2 | 60 | ||
| NPT2 | 2.208 | 60.091 | 11 1/2 | 60 | ||
| NPT2 1/2 | 3.175 | 72.699 | 8 | 60 | ||
| NPT3 | 3.175 | 88.608 | 8 | 60 | ||
| NPT3 1/2 | 3.175 | 100.013 | 8 | 60 |
美制一般密封管螺纹的基本尺寸:
尺寸
| 代号 | 牙数 n | 螺距 P | 牙型 高度 h | 基准平面内的基本直径 | 基准距离L1 | 装配余量L3 | 外螺纹 小端面 内的基 本小径 | ||||
| 大径d=D | 中径d1=D2 | 小径d1=D1 | |||||||||
| mm | 圈数 | mm | 圈数 | mm | mm | ||||||
| 1/16 | 27 | 0.941 | 0.752 | 7.4 | 7.142 | 6.3 | 4.32 | 4.0 | 3 | 2.822 | 6.137 |
| 1/8 | 27 | 0.941 | 0.752 | 10.242 | 9.4 | 8.737 | 4.36 | 4.102 | 3 | 2.822 | 8.481 |
| 1/4 | 18 | 1.411 | 1.129 | 13.616 | 12.487 | 11.358 | 4.10 | 5.785 | 3 | 4.233 | 10.996 |
| 3/8 | 18 | 1.411 | 1.129 | 17.055 | 15.926 | 14.797 | 4.32 | 6.096 | 3 | 4.233 | 14.417 |
| 1/2 | 14 | 1.814 | 1.451 | 21.224 | 19.772 | 18.321 | 4.48 | 8.128 | 3 | 5.443 | 17.813 |
| 3/4 | 14 | 1.814 | 1.451 | 26.569 | 25.117 | 23.666 | 4.75 | 8.618 | 3 | 5.443 | 23.127 |
| 1 | 11.5 | 2.209 | 1.767 | 33.228 | 31.461 | 29.694 | 4.60 | 10.160 | 3 | 6.626 | 29.060 |
| 11/4 | 11.5 | 2.209 | 1.767 | 41.985 | 40.218 | 38.451 | 4.83 | 10.668 | 3 | 6.350 | 37.788 |
| 11/2 | 11.5 | 2.209 | 1.767 | 48.054 | 46.287 | 44.520 | 4.83 | 10.668 | 3 | 6.350 | 43.853 |
| 2 | 11.5 | 2.209 | 1.767 | 60.092 | 58.325 | 56.558 | 5.01 | 11.065 | 3 | 6.350 | 55.867 |
| 21/2 | 8 | 3.175 | 2.540 | 72.699 | 70.159 | 67.619 | 5.46 | 17.335 | 2 | 6.350 | 66.535 |
| 3 | 8 | 3.175 | 2.540 | 88.608 | 86.068 | 83.528 | 6.13 | 19.463 | 2 | 6.350 | 62.311 |
| 31/2 | 8 | 3.175 | 2.540 | 101.316 | 98.776 | 96.236 | 6.57 | 20.860 | 2 | 6.350 | 94.932 |
| 4 | 8 | 3.175 | 2.540 | 113.973 | 111.433 | 108.3 | 6.75 | 21.431 | 2 | 6.350 | 107.554 |
| 5 | 8 | 3.175 | 2.540 | 140.952 | 138.412 | 135.872 | 7.50 | 23.812 | 2 | 6.350 | 134.384 |
| 6 | 8 | 3.175 | 2.540 | 167.792 | 165.252 | 162.712 | 7.66 | 24.320 | 2 | 6.350 | 161.191 |
| 8 | 8 | 3.175 | 2.540 | 218.441 | 215.901 | 213.361 | 8.50 | 26.988 | 2 | 6.350 | 211.673 |
| 10 | 8 | 3.175 | 2.540 | 272.312 | 269.772 | 267.232 | 9.68 | 30.734 | 2 | 6.350 | 265.311 |
| 12 | 8 | 3.175 | 2.540 | 323.032 | 320.492 | 317.952 | 10.88 | 34.544 | 2 | 6.350 | 315.793 |
| 14O.D. | 8 | 3.175 | 2.540 | 354.904 | 352.3 | 349.824 | 12.50 | 39.688 | 2 | 6.350 | 347.345 |
| 16O.D. | 8 | 3.175 | 2.540 | 405.784 | 403.244 | 400.704 | 14.50 | 46.038 | 2 | 6.350 | 397.828 |
| 18O.D. | 8 | 3.175 | 2.540 | 456.565 | 454.025 | 451.485 | 16.00 | 50.800 | 2 | 6.350 | 448.310 |
| 20O.D. | 8 | 3.175 | 2.540 | 507.246 | 504.706 | 502.166 | 17.00 | 53.975 | 2 | 6.350 | 498.792 |
| 24O.D. | 8 | 3.175 | 2.540 | 608.608 | 606.068 | 603.528 | 19.00 | 60.325 | 2 | 6.350 | 599.758 |
② 螺纹收尾长度(V)为3.47 P;
③ O.D.是英文管子外径(outside diameter)的缩写。
标记:美制一般密封管螺纹的完整标记由螺纹特征代号,螺纹尺寸代号和旋向代号组成。左旋螺纹的旋向代号为LH;右旋螺纹的旋向代号省略不标。
例如:1/8 NPT-LH,1/8表示螺纹尺寸,NPT为螺纹特征代号,LH表示左旋。
美制管螺纹的米制化方法:将管螺纹的原英寸尺寸乘以25.4就转化为毫米尺寸。
