内螺纹攻丝前底孔及钻头尺寸
用于不以螺纹作压力密封联接的场合（按GB/T 7307-2001）
| * 除另有说明外尺寸单位都以毫米计 | |||||
| 螺纹 | 麻花钻 | ||||
| 公称直径 | 每吋牙数 | 螺距 | 小径 | 直径 | |
| in | 最大 | 最小 | |||
| 1/16 | 28 | 0.907 | 6.843 | 6.561 | 6.8① |
| 1/8 | 28 | 0.907 | 8.848 | 8.566 | 8.8 |
| 1/4 | 19 | 1.337 | 11.89 | 11.445 | 11.8 |
| 3/8 | 19 | 1.337 | 16.395 | 14.95 | 15.25 |
| 1/2 | 14 | 1.814 | 19.172 | 18.631 | 19 |
| 5/8 | 14 | 1.814 | 21.128 | 20.587 | 21 |
| 3/4 | 14 | 1.814 | 24.658 | 24.117 | 24.5 |
| 7/8 | 14 | 1.814 | 28.418 | 27.877 | 28.25 |
| 1 | 11 | 2.309 | 30.931 | 30.291 | 30.75 |
| 1–1/8 | 11 | 2.309 | 35.579 | 34.939 | 35.5① |
| 1–1/4 | 11 | 2.309 | 39.592 | 38.952 | 39.5 |
| 1–1/2 | 11 | 2.309 | 45.485 | 44.845 | 45 |
| 1–3/4 | 11 | 2.309 | 51.428 | 50.788 | 51 |
| 2 | 11 | 2.309 | 57.296 | 56.656 | 57 |
| ① 该数值近似于螺纹大径-螺距。 | |||||
用于以螺纹作压力密封联接的场合（按GB/T 7306.1-2000）
| * 除另有说明外尺寸单位都以毫米计 | |||||
| 螺纹 | 麻花钻 | ||||
| 公称直径 | 每吋牙数 | 螺距 | 小径 | 直径 | |
| in | 最大 | 最小 | |||
| 1/16 | 28 | 0.907 | 6.632 | 6.49 | 6.6① |
| 1/8 | 28 | 0.907 | 8.637 | 8.495 | 8.6 |
| 1/4 | 19 | 1.337 | 11.549 | 11.341 | 11.5 |
| 3/8 | 19 | 1.337 | 15.054 | 14.846 | 15 |
| 1/2 | 14 | 1.814 | 18.773 | 18.489 | 18.5 |
| 3/4 | 14 | 1.814 | 24.259 | 23.975 | 24 |
| 1 | 11 | 2.309 | 30.471 | 30.111 | 30.25 |
| 1–1/4 | 11 | 2.309 | 39.132 | 38.772 | 39 |
| 1–1/2 | 11 | 2.309 | 45.025 | 44.665 | 45 |
| 2 | 11 | 2.309 | 56.836 | 56.476 | 56.5 |
| ① 该数来源于 BSI 1157-75。 | |||||