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8-32UNC 0.1571 0.1631 0.1399 0.1428 0.12483.58 3.61(0.164-32) 3.9903 4.1427 3.5535 3.6271 3.169910-24 0.1818 0.1890 0.1586 0.1619 0.13794.07 4.10(0.190-24) 4.6177 4.8006 4.0284 4.1123 3.502712-24 0.2078 0.2150 0.1845 0.1879 0.16394.72 4.75(0.216-24) 5.2781 5.4610 4.6863 4.7727 4.16311/4-20 0.2408 0.2489 0.2127 0.2164 0.18765.45 5.48(0.250-20) 6.1163 6.3221 5.4026 5.4966 4.76505/16-18 0.3026 0.3113 0.2712 0.2752 0.24316.94 6.98(0.3175-18) 7.6860 7.9070 6.8885 6.9901 6.17473/8-16 0.3643 0.3737 0.3287 0.3331 0.29708.40 8.44(0.375-16) 9.2532 9.4920 8.3490 8.4607 7.54387/16-14 0.4258 0.4361 0.3850 0.3897 0.34859.83 9.87(0.4375-14) 10.8153 11.0769 9.7790 9.8984 8.85191/2-13 0.4876 0.4985 0.4435 0.4485 0.404111.34 11.38(0.50-13) 12.3850 12.6619 11.2649 11.3919 10.26419/16-12 0.5495 0.5609 0.5016 0.5068 0.458712.80 12.84(0.5625-12) 13.9573 14.2469 12.7406 12.8727 11.65105/8-11 0.6113 0.6234 0.5589 0.5644 0.511914.27 14.32(0.625-11) 15.5270 15.8344 14.1961 14.3358 13.00233/4-10 0.7353 0.7482 0.6773 0.6832 0.625517.28 17.33(0.750-10) 18.6766 19.0043 17.2034 17.3533 15.88777/8-9 0.8592 0.8731 0.7946 0.8009 0.736820.27 20.32(0.875-9) 21.8237 22.1767 20.1828 20.3429 18.71471"-8 0.9830 0.9980 0.9100 0.9168 0.844623.22 23.27(1.000-8) 24.9682 25.3492 23.1140 23.2867 21.45281.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8-36UNF 0.1577 0.1632 0.1424 0.1452 0.12913.65 3.67(0.164-36) 4.0056 4.1453 3.6170 3.6881 3.279110-32 0.1831 0.1891 0.1658 0.1688 0.15084.24 4.27 (0.190-32) 4.6507 4.8031 4.2113 4.2875 3.830312-28 0.2085 0.2150 0.1886 0.1918 0.17124.82 4.85 (0.216-28)5.2959 5.4610 4.7904 4.8717 4.34851/4-28 0.2425 0.2490 0.2225 0.2258 0.20525.69 5.71 (0.250-28)6.1595 6.3246 5.6515 5.7353 5.21215/16-24 0.3042 0.3114 0.2806 0.2843 0.26037.17 7.20 (0.3175-24) 7.7267 7.9096 7.1272 7.2212 6.61163/8-24 0.3667 0.3739 0.3430 0.3468 0.32288.75 8.78 (0.375-24) 9.3142 9.4971 8.7122 8.8087 8.19917/16-20 0.4281 0.4362 0.3995 0.4037 0.374910.19 10.23 (0.4375-20) 10.8737 11.0795 10.1473 10.2540 9.52251/2-20 0.4906 0.4987 0.4619 0.4662 0.437411.78 11.82 (0.50-20) 12.4612 12.6670 11.7323 11.8415 11.11009/16-18 0.5524 0.5611 0.5205 0.5250 0.492913.27 13.31 (0.5625-18) 14.0310 14.2519 13.2207 13.3350 12.51975/8-18 0.6149 0.6236 0.5828 0.5875 0.555414.85 14.89 (0.625-18) 15.6185 15.8394 14.8031 14.9225 14.10723/4-16 0.7391 0.7485 0.7029 0.7079 0.671817.91 17.95 (0.750-16) 18.7731 19.0119 17.8537 17.9807 17.06377/8-14 0.8631 0.8734 0.8216 0.8270 0.785820.93 20.97 (0.875-14) 21.9227 22.1844 20.8686 21.0058 19.95931"-12 0.9868 0.9982 0.9382 0.9441 0.896023.90 23.95 (1.000-12) 25.0647 25.3543 23.8303 23.9801 22.75841.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)美制内螺纹（2B）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小径极限中径极限大径min底孔直径最小最大最小最大最小最大8-32UNC 0.1300 0.1390 0.1437 0.1475 0.16403.40 3.50(0.164-32) 3.3020 3.5306 3.6500 3.7465 4.165610-24 0.1450 0.1560 0.1629 0.1672 0.19003.75 3.90 (0.190-24) 3.6830 3.96244.1377 4.2469 4.826012-24 0.1710 0.1810 0.1889 0.1933 0.21604.40 4.55 (0.216-24) 4.3434 4.5974 4.7981 4.90985.48641/4-20 0.1960 0.2070 0.2175 0.2224 0.25005.05 5.20 (0.250-20) 4.9784 5.2578 5.5245 5.64906.35005/16-18 0.2520 0.2650 0.2764 0.2817 0.31256.45 6.60 (0.3175-18) 6.4008 6.73107.0206 7.1552 7.93753/8-16 0.3070 0.3210 0.3344 0.3401 0.37507.85 8.00 (0.375-16) 7.7978 8.1534 8.4938 8.6385 9.52507/16-14 0.3600 0.3760 0.3911 0.3972 0.43759.20 9.40 (0.4375-14) 9.1440 9.5504 9.9339 10.0889 11.11251/2-13 0.4170 0.4340 0.4500 0.4565 0.500010.65 10.90 (0.50-13) 10.5918 11.0236 11.4300 11.5951 12.70009/16-12 0.4720 0.4900 0.5084 0.5152 0.562512.05 12.30 (0.5625-12) 11.9888 12.4460 12.9134 13.0861 14.28755/8-11 0.5270 0.5460 0.5660 0.5732 0.6250 13.45 13.70(0.625-11) 13.3858 13.8684 14.3764 14.5593 15.87503/4-10 0.6420 0.6630 0.6850 0.6927 0.750016.40 16.70 (0.750-10) 16.3068 16.8402 17.3990 17.5946 19.05007/8-9 0.7550 0.7780 0.8028 0.8110 0.875019.30 19.60 (0.875-9) 19.1770 19.7612 20.3911 20.5994 22.22501"-8 0.8650 0.8900 0.9188 0.9276 1.000022.10 22.40 (1.000-8) 21.9710 22.6060 23.3375 23.5610 25.40001.底孔直径指攻丝前钻孔直径，铸铁、黄铜等较软料取小值，钢、青铜等较硬料取大值。

2.标记示例：10-24UNC-2B(或0.190-24UNC-2B)、3/8-16UNC-2B(或0.375-16UNC-2B)美制内螺纹（2B）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小径极限中径极限大径min底孔直径最小最大最小最大最小最大8-36UNF 0.1340 0.1420 0.1460 0.1496 0.16403.45 3.67(0.164-36) 3.4036 3.6068 3.7084 3.7998 4.165610-32 0.1560 0.1640 0.1697 0.1736 0.19004.00 4.27 (0.190-32) 3.9624 4.1656 4.3104 4.4094 4.826012-28 0.1770 0.1860 0.1928 0.1970 0.21604.55 4.85 (0.216-28) 4.4958 4.7244 4.89715.0038 5.48641/4-28 0.2110 0.2200 0.2268 0.2311 0.25005.40 5.71 (0.250-28) 5.3594 5.5880 5.7607 5.86996.35005/16-24 0.2670 0.2770 0.2854 0.2902 0.31256.857.20 (0.3175-24) 6.7818 7.0358 7.2492 7.3711 7.93753/8-24 0.3300 0.3400 0.3479 0.3528 0.37508.45 8.78 (0.375-24) 8.3820 8.6360 8.8367 8.9611 9.52507/16-20 0.3830 0.3950 0.4050 0.4104 0.43759.85 10.23 (0.4375-20) 9.7282 10.0330 10.2870 10.4242 11.11251/2-20 0.4460 0.4570 0.4675 0.4731 0.500011.40 11.82 (0.50-20) 11.3284 11.6078 11.8745 12.0167 12.70009/16-18 0.5020 0.5150 0.5264 0.5323 0.562512.85 13.31 (0.5625-18) 12.7508 13.0810 13.3706 13.5204 14.28755/8-18 0.5650 0.5780 0.5889 0.5949 0.625014.45 14.89 (0.625-18) 14.3510 14.6812 14.9581 15.1105 15.87503/4-16 0.6820 0.6960 0.7094 0.7159 0.750017.40 17.95 (0.750-16) 17.3228 17.6784 18.0188 18.1839 19.05007/8-14 0.7980 0.8140 0.8286 0.8356 0.875020.35 20.97 (0.875-14) 20.2692 20.6756 21.0464 21.2242 22.22501"-12 0.9100 0.9280 0.9459 0.9535 1.000023.90 23.95 (1.000-12) 23.1140 23.5712 24.0259 24.2189 25.40001.底孔直径指攻丝前钻孔直径，铸铁、黄铜等较软料取小值，钢、青铜等较硬料取大值。