标注方法：螺纹直径—每英寸牙数系列代号—精度等级 示例：
粗牙系列 3/8—16 UNC—2A
细牙系列 3/8—24 UNF—2A
特细牙系列 3/8—32 UNEF—2A
定螺距系列 3/8—20 UN—2A
第一位数字3/8表示螺纹外径，单位为英寸，转换为米制单位mm要乘以25.4，即3/8×25.4=9.525mm；第二、三位数字16、24、32、20为每英寸牙数(在25.4mm长度上的牙数)；第三位以后的文字代号UNC、UNF、UNEF、UN为系列代号，最后两位2A为精度等级。UNC：统一粗牙螺纹。
| 美制粗螺纹 |
美制细螺纹 |
||||||||
| 规格 （UNC) |
标准径 |
2级牙钻孔径 |
规格 （UNF) |
标准径 |
2级牙钻孔径 |
||||
| 最大 |
最小 |
最大 |
最小 |
||||||
| NO.1-64(1.854) |
1.55 |
1.582 |
1.425 |
NO.0-80(1.524) |
1.25 |
1.305 |
1.182 |
||
| NO.2-56(2.184) |
1.80 |
1.871 |
1.695 |
NO.1-72(1.854) |
1.55 |
1.612 |
1.474 |
||
| NO.3-48(2.515) |
2.10 |
2.146 |
1.941 |
NO.2-64(2.184) |
1.85 |
1.912 |
1.756 |
||
| NO.4-40(2.845) |
2.30 |
2.385 |
2.157 |
NO.3-56(2.515) |
2.10 |
2.197 |
2.025 |
||
| NO.5-40(3.175) |
2.60 |
2.697 |
2.487 |
NO.4-48(2.845) |
2.40 |
2.458 |
2.271 |
||
| NO.6-32(3.505) |
2.80 |
2.895 |
2.642 |
NO.5-44(3.175) |
2.70 |
2.740 |
2.551 |
||
| NO.8-32(4.166) |
3.40 |
3.530 |
3.302 |
NO.6-40(3.505) |
2.90 |
3.022 |
2.820 |
||
| NO.10-24(4.826) |
3.90 |
3.962 |
3.683 |
NO.8-36(4.166) |
3.50 |
3.606 |
3.404 |
||
| NO.12-24(5.486) |
4.50 |
4.597 |
4.344 |
NO.10-32(4.826) |
4.10 |
4.165 |
3.963 |
||
| 1/4 -20 |
5.10 |
5.257 |
4.979 |
NO.12-28(5.846) |
4.60 |
4.724 |
4.496 |
||
| 5/16 -18 |
6.60 |
6.731 |
6.401 |
1/4-28 |
5.50 |
5.588 |
5.360 |
||
| 3/8 -16 |
8.00 |
8.153 |
7.798 |
5/16-24 |
6.90 |
7.035 |
6.782 |
||
| 7/16 -14 |
9.40 |
9.550 |
9.144 |
3/8-24 |
8.50 |
8.636 |
8.382 |
||
| 1/2 -13 |
10.80 |
11.023 |
10.592 |
7/16-20 |
9.90 |
10.033 |
9.729 |
||
| 9/16 -12 |
12.20 |
12.446 |
11.989 |
1/2-20 |
11.50 |
11.607 |
11.329 |
||
| 5/8 -11 |
13.60 |
13.868 |
13.386 |
9/16-18 |
12.90 |
13.081 |
12.751 |
||
| 3/4 -10 |
16.50 |
16.840 |
16.307 |
5/8-18 |
14.50 |
14.681 |
14.351 |
||
| 7/8 -9 |
19.50 |
19.761 |
19.177 |
3/4-16 |
17.50 |
17.678 |
17.323 |
||
| 1-8 |
22.20 |
22.606 |
21.971 |
7/8-14 |
20.50 |
20.675 |
20.270 |
||
| 1-1/8-7 |
25.00 |
25.349 |
24.638 |
1-12 |
23.20 |
23.571 |
23.114 |
||
| 1-1/4-7 |
28.20 |
28.524 |
27.813 |
1-1/8-12 |
26.50 |
26.746 |
26.289 |
||
| 1-3/8-6 |
30.80 |
31.115 |
30.353 |
1-1/4-12 |
29.50 |
29.921 |
29.464 |
||
| 1-1/2-6 |
34.00 |
34.290 |
33.528 |
1-3/8-12 |
32.80 |
33.096 |
32.639 |
||
| 1-3/4-5 |
39.50 |
39.827 |
38.964 |
1-1/2-12 |
36.0 |
36.271 |
35.814 |
||
| 2-4-1/2 |
45.20 |
45.593 |
44.679 |
||||||
| 美制迫牙丝攻钻孔径 |
美制特细螺纹 |
||||||||
| 规格 |
精度等级 |
规格 （UNEF) |
标准径 |
2级牙钻孔径 |
|||||
| G4-G6 |
G7-G8 |
G9 |
最大 |
最小 |
|||||
| NO.2-56UNC |
1.94 |
- |
- |
NO.12-32 |
4.70 |
4.826 |
4.623 |
||
| NO.3-48 |
2.23 |
- |
- |
1/4--32 |
5.60 |
5.690 |
5.486 |
||
| NO.4-40 |
2.50 |
- |
- |
5/16-32 |
7.10 |
7.264 |
7.087 |
||
| NO.5-40 |
2.83 |
- |
- |
3/8-32 |
8.70 |
8.865 |
8.661 |
||
| NO.6-32 |
3.07 |
- |
- |
7/16-28 |
10.20 |
10.338 |
10.135 |
||
| NO.8-32 |
3.73 |
3.77 |
- |
1/2-28 |
11.80 |
11.938 |
11.709 |
||
| NO.10-24 |
4.24 |
4.30 |
- |
9/16-24 |
13.20 |
13.386 |
13.132 |
||
| NO.12-24 |
4.90 |
4.96 |
- |
5/8-24 |
14.80 |
14.986 |
14.732 |
||
| 1/4-20 |
- |
5.72 |
- |
3/4-20 |
17.80 |
17.958 |
17.678 |
||
| 5/16-18 |
- |
7.24 |
- |
7/8-20 |
21.00 |
21.133 |
20.853 |
||
| 3/8-16 |
- |
8.74 |
8.81 |
1-20 |
24.00 |
24.308 |
24.028 |
||
| 7/16-14 |
- |
10.20 |
10.30 |
美制管螺纹 |
|||||
| 1/2-13 |
11.27 |
11.82 |
|||||||
| NO.2-64UNF |
1.97 |
- |
- |
规格 |
钻孔径 |
||||
| NO.3-56 |
2.27 |
- |
- |
NPT |
NPS |
||||
| NO.4-48 |
2.56 |
- |
- |
使用绞刀时 |
不用绞刀时 |
||||
| NO.5-44 |
2.86 |
- |
- |
1/16-27 |
6.10 |
6.25 |
6.35 |
||
| NO.6-40 |
3.16 |
- |
- |
1/8-27 |
8.33 |
8.43 |
8.74 |
||
| NO.8-36 |
3.78 |
- |
- |
1/4-18 |
10.72 |
11.13 |
11.13 |
||
| NO.10-32 |
4.39 |
4.43 |
- |
3/8-18 |
14.27 |
14.27 |
14.68 |
||
| NO.12-28 |
4.99 |
5.04 |
- |
1/2-14 |
17.48 |
17.86 |
18.26 |
||
| 1/4-28 |
5.85 |
5.90 |
- |
3/4-14 |
22.63 |
23.01 |
23.42 |
||
| 5/16-24 |
7.36 |
7.41 |
- |
1-11-1/2 |
28.58 |
28.98 |
29.36 |
||
| 3/8-24 |
- |
9.00 |
- |
1-1/4-11-1/2 |
37.31 |
37.69 |
38.10 |
||
| 7/16-20 |
- |
10.48 |
10.54 |
1-1/2-11-1/2 |
43.66 |
44.04 |
44.45 |
||
| 1/2-20 |
- |
12.07 |
12.13 |
2-11-1/2 |
55.58 |
55.96 |
56.36 |
||
| 英制电器螺纹 |
|||||||||
| 规格 |
钻孔径 |
||||||||
| 2BA |
4.0-4.2 |
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| 3BA |
|||||||||
| 4BA |
3.0-3.2 |
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| 5BA |
2.7-2.8 |
||||||||
| 6BA |
2.4-2.5 |
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