美制螺纹标准对照表
美制外螺纹（2A）常用规格极限尺寸表（粗牙）
公称尺寸和每英寸牙
数螺纹系
列代号
大径极限中径极限
小径max
螺胚直径最小最大最小最大最小最大
8-32
UNC 0.1571 0.1631 0.1399 0.1428 0.1248
3.58 3.61
(0.164-32) 3.9903 4.1427 3.5535 3.6271 3.1699
10-24 0.1818 0.1890 0.1586 0.1619 0.1379
4.07 4.10 (0.190-24) 4.6177 4.8006 4.0284 4.1123 3.5027
12-24 0.2078 0.2150 0.1845 0.1879 0.1639
4.72 4.75 (0.216-24)
5.2781 5.4610 4.6863 4.7727 4.1631
1/4-20 0.2408 0.2489 0.2127 0.2164 0.1876
5.45 5.48 (0.250-20)
6.1163 6.3221 5.4026 5.4966 4.7650
5/16-18 0.3026 0.3113 0.2712 0.2752 0.2431
6.94 6.98 (0.3175-18)
7.6860 7.9070 6.8885 6.9901 6.1747
3/8-16 0.3643 0.3737 0.3287 0.3331 0.2970
8.40 8.44 (0.375-16) 9.2532 9.4920 8.3490 8.4607 7.5438
7/16-14 0.4258 0.4361 0.3850 0.3897 0.3485
9.83 9.87 (0.4375-14) 10.8153 11.0769 9.7790 9.8984 8.8519
1/2-13 0.4876 0.4985 0.4435 0.4485 0.4041
11.34 11.38 (0.50-13) 12.3850 12.6619 11.2649 11.3919 10.2641
9/16-12 0.5495 0.5609 0.5016 0.5068 0.4587
12.80 12.84 (0.5625-12) 13.9573 14.2469 12.7406 12.8727 11.6510
5/8-11 0.6113 0.6234 0.5589 0.5644 0.5119
14.27 14.32 (0.625-11) 15.5270 15.8344 14.1961 14.3358 13.0023
3/4-10 0.7353 0.7482 0.6773 0.6832 0.6255
17.28 17.33 (0.750-10) 18.6766 19.0043 17.2034 17.3533 15.8877
7/8-9 0.8592 0.8731 0.7946 0.8009 0.7368
20.27 20.32 (0.875-9) 21.8237 22.1767 20.1828 20.3429 18.7147
1"-8 0.9830 0.9980 0.9100 0.9168 0.8446
23.22 23.27 (1.000-8) 24.9682 25.3492 23.1140 23.2867 21.4528
1.螺胚直径指滚丝前的尺寸，数值为依经验公式计算而得，在实践中需验证。
2.标记示例：10-24UNC-2A(或0.190-24UNC-2A)、3/8-16UNC-2A(或0.375-16UNC-2A) （注：表中上行斜体数值单位为英寸，下行为毫米）
美制外螺纹（2A）常用规格极限尺寸表（细牙）
公称尺寸和每英寸牙数螺纹系
列代号
大径极限中径极限
小径max
螺胚直径最小最大最小最大最小最大
8-36
UNF 0.1577 0.1632 0.1424 0.1452 0.1291
3.65 3.67
(0.164-36) 4.0056 4.1453 3.6170 3.6881 3.2791
10-32 0.1831 0.1891 0.1658 0.1688 0.1508
4.24 4.27 (0.190-32) 4.6507 4.8031 4.2113 4.2875 3.8303
12-28 0.2085 0.2150 0.1886 0.1918 0.1712
4.82 4.85 (0.216-28)
5.2959 5.4610 4.7904 4.8717 4.3485
1/4-28 0.2425 0.2490 0.2225 0.2258 0.2052
5.69 5.71 (0.250-28)
6.1595 6.3246 5.6515 5.7353 5.2121
5/16-24 0.3042 0.3114 0.2806 0.2843 0.2603
7.17 7.20 (0.3175-24) 7.7267 7.9096 7.1272 7.2212 6.6116
3/8-24 0.3667 0.3739 0.3430 0.3468 0.3228
8.75 8.78 (0.375-24) 9.3142 9.4971 8.7122 8.8087 8.1991
7/16-20 0.4281 0.4362 0.3995 0.4037 0.3749
10.19 10.23 (0.4375-20) 10.8737 11.0795 10.1473 10.2540 9.5225
1/2-20 0.4906 0.4987 0.4619 0.4662 0.4374
11.78 11.82 (0.50-20) 12.4612 12.6670 11.7323 11.8415 11.1100
9/16-18 0.5524 0.5611 0.5205 0.5250 0.4929
13.27 13.31 (0.5625-18) 14.0310 14.2519 13.2207 13.3350 12.5197
5/8-18 0.6149 0.6236 0.5828 0.5875 0.5554
14.85 14.89 (0.625-18) 15.6185 15.8394 14.8031 14.9225 14.1072
3/4-16 0.7391 0.7485 0.7029 0.7079 0.6718
17.91 17.95 (0.750-16) 18.7731 19.0119 17.8537 17.9807 17.0637
7/8-14 0.8631 0.8734 0.8216 0.8270 0.7858
20.93 20.97 (0.875-14) 21.9227 22.1844 20.8686 21.0058 19.9593
1"-12 0.9868 0.9982 0.9382 0.9441 0.8960
23.90 23.95 (1.000-12) 25.0647 25.3543 23.8303 23.9801 22.7584
1.螺胚直径指滚丝前的尺寸，数值为依经验公式计算而得，在实践中需验证。
2.标记示例：10-32UNF-2A(或0.190-32UNF-2A)、3/8-24UNF-2A(或0.375-24UNF-2A)
