大径极限 中径极限 螺胚直径公称尺寸和每英寸牙数螺纹系列代号最小最大最小最大小径max 最小 最大8-320.1571 0.1631 0.1399 0.1428 0.1248 (0.164-32)3.99034.1427 3.5535 3.6271 3.1699 3.58 3.61 10-240.1818 0.1890 0.1586 0.1619 0.1379 (0.190-24)4.6177 4.8006 4.0284 4.1123 3.5027 4.07 4.10 12-240.2078 0.2150 0.1845 0.1879 0.1639 (0.216-24)5.2781 5.4610 4.6863 4.7727 4.1631 4.72 4.75 1/4-200.2408 0.2489 0.2127 0.2164 0.1876 (0.250-20)6.1163 6.3221 5.4026 5.4966 4.7650 5.45 5.48 5/16-180.3026 0.3113 0.2712 0.2752 0.2431 (0.3175-18)7.6860 7.9070 6.8885 6.9901 6.1747 6.94 6.98 3/8-160.3643 0.3737 0.3287 0.3331 0.2970 (0.375-16)9.2532 9.4920 8.3490 8.4607 7.5438 8.40 8.44 7/16-140.4258 0.4361 0.3850 0.3897 0.3485 (0.4375-14)10.8153 11.0769 9.77909.8984 8.8519 9.83 9.87 1/2-130.4876 0.4985 0.4435 0.4485 0.4041 (0.50-13)12.3850 12.6619 11.2649 11.3919 10.2641 11.34 11.38 9/16-120.5495 0.5609 0.5016 0.5068 0.4587 (0.5625-12)13.9573 14.2469 12.7406 12.8727 11.6510 12.80 12.84 5/8-110.6113 0.6234 0.5589 0.5644 0.5119 (0.625-11)15.5270 15.8344 14.1961 14.3358 13.0023 14.27 14.32 3/4-100.7353 0.7482 0.6773 0.6832 0.6255 (0.750-10)18.6766 19.0043 17.2034 17.3533 15.8877 17.28 17.33 7/8-90.8592 0.8731 0.7946 0.8009 0.7368 (0.875-9)21.8237 22.1767 20.1828 20.3429 18.7147 20.27 20.32 1"-80.9830 0.99800.9100 0.9168 0.8446 (1.000-8)UNC24.9682 25.3492 23.1140 23.2867 21.452823.22 23.271.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）大径极限 中径极限 螺胚直径 公称尺寸和每英寸牙数 螺纹系列代号最小最大最小最大小径max 最小最大8-360.1577 0.1632 0.1424 0.1452 0.1291 (0.164-36)4.0056 4.1453 3.6170 3.6881 3.2791 3.65 3.67 10-320.1831 0.1891 0.1658 0.1688 0.1508 (0.190-32)4.6507 4.8031 4.2113 4.2875 3.8303 4.24 4.27 12-280.2085 0.2150 0.1886 0.1918 0.1712 (0.216-28)5.2959 5.4610 4.7904 4.8717 4.3485 4.82 4.85 1/4-280.2425 0.2490 0.2225 0.2258 0.2052 (0.250-28)6.1595 6.3246 5.6515 5.7353 5.2121 5.69 5.71 5/16-240.3042 0.3114 0.2806 0.2843 0.2603 (0.3175-24)7.7267 7.9096 7.1272 7.2212 6.6116 7.17 7.20 3/8-240.3667 0.3739 0.3430 0.3468 0.3228 (0.375-24)9.3142 9.4971 8.7122 8.8087 8.1991 8.75 8.78 7/16-200.4281 0.4362 0.3995 0.4037 0.3749 (0.4375-20)10.8737 11.0795 10.1473 10.2540 9.5225 10.19 10.23 1/2-200.4906 0.4987 0.4619 0.4662 0.4374 (0.50-20)12.4612 12.6670 11.7323 11.8415 11.1100 11.78 11.82 9/16-180.5524 0.5611 0.5205 0.5250 0.4929 (0.5625-18)14.0310 14.2519 13.2207 13.3350 12.5197 13.27 13.31 5/8-180.6149 0.6236 0.5828 0.5875 0.5554 (0.625-18)15.6185 15.8394 14.8031 14.9225 14.1072 14.85 14.89 3/4-160.7391 0.7485 0.7029 0.7079 0.6718 (0.750-16)18.7731 19.0119 17.8537 17.9807 17.0637 17.91 17.95 7/8-140.8631 0.8734 0.8216 0.8270 0.7858 (0.875-14)21.9227 22.1844 20.8686 21.0058 19.9593 20.93 20.97 1"-120.9868 0.99820.9382 0.9441 0.8960 (1.000-12)UNF25.0647 25.3543 23.8303 23.9801 22.758423.90 23.951.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)小径极限 中径极限 底孔直径 公称尺寸和每英寸牙数 螺纹系列代号最小最大最小最大大径min 最小最大8-320.1300 0.1390 0.1437 0.1475 0.1640 (0.164-32)3.3020 3.5306 3.6500 3.74654.1656 3.40 3.50 10-240.1450 0.1560 0.1629 0.1672 0.1900 (0.190-24)3.6830 3.96244.1377 4.2469 4.8260 3.75 3.90 12-240.1710 0.1810 0.1889 0.1933 0.2160 (0.216-24)4.3434 4.5974 4.7981 4.90985.4864 4.40 4.55 1/4-200.1960 0.2070 0.2175 0.2224 0.2500 (0.250-20)4.97845.2578 5.5245 5.64906.3500 5.05 5.20 5/16-180.2520 0.2650 0.2764 0.2817 0.3125 (0.3175-18)6.4008 6.73107.0206 7.1552 7.9375 6.45 6.60 3/8-160.3070 0.3210 0.3344 0.3401 0.3750 (0.375-16)7.7978 8.1534 8.4938 8.6385 9.5250 7.85 8.00 7/16-140.3600 0.3760 0.3911 0.3972 0.4375 (0.4375-14)9.1440 9.5504 9.9339 10.0889 11.11259.20 9.40 1/2-130.4170 0.4340 0.4500 0.4565 0.5000 (0.50-13)10.5918 11.0236 11.4300 11.5951 12.7000 10.65 10.90 9/16-120.4720 0.4900 0.5084 0.5152 0.5625 (0.5625-12)11.9888 12.4460 12.9134 13.0861 14.2875 12.05 12.30 5/8-110.5270 0.5460 0.5660 0.5732 0.6250 (0.625-11)13.3858 13.8684 14.3764 14.5593 15.8750 13.45 13.70 3/4-100.6420 0.6630 0.6850 0.6927 0.7500 (0.750-10)16.3068 16.8402 17.3990 17.5946 19.0500 16.40 16.70 7/8-90.7550 0.7780 0.8028 0.8110 0.8750 (0.875-9)19.1770 19.7612 20.3911 20.5994 22.2250 19.30 19.60 1"-80.8650 0.89000.9188 0.9276 1.0000 (1.000-8)UNC21.9710 22.6060 23.3375 23.5610 25.400022.10 22.401.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)小径极限 中径极限 底孔直径 公称尺寸和每英寸牙数 螺纹系列代号最小最大最小最大大径min 最小最大8-360.1340 0.1420 0.1460 0.1496 0.1640 (0.164-36)3.4036 3.6068 3.7084 3.79984.1656 3.45 3.67 10-320.1560 0.1640 0.1697 0.1736 0.1900 (0.190-32)3.96244.1656 4.3104 4.4094 4.8260 4.00 4.27 12-280.1770 0.1860 0.1928 0.1970 0.2160 (0.216-28)4.4958 4.7244 4.89715.0038 5.4864 4.55 4.85 1/4-280.2110 0.2200 0.2268 0.2311 0.2500 (0.250-28)5.3594 5.5880 5.7607 5.86996.3500 5.40 5.71 5/16-240.2670 0.2770 0.2854 0.2902 0.3125 (0.3175-24)6.78187.0358 7.2492 7.3711 7.9375 6.85 7.20 3/8-240.3300 0.3400 0.3479 0.3528 0.3750 (0.375-24)8.38208.6360 8.8367 8.9611 9.5250 8.45 8.78 7/16-200.3830 0.3950 0.4050 0.4104 0.4375 (0.4375-20)9.7282 10.0330 10.2870 10.4242 11.1125 9.85 10.23 1/2-200.4460 0.4570 0.4675 0.4731 0.5000 (0.50-20)11.3284 11.6078 11.8745 12.0167 12.7000 11.40 11.82 9/16-180.5020 0.5150 0.5264 0.5323 0.5625 (0.5625-18)12.7508 13.0810 13.3706 13.5204 14.2875 12.85 13.31 5/8-180.5650 0.5780 0.5889 0.5949 0.6250 (0.625-18)14.3510 14.6812 14.9581 15.1105 15.8750 14.45 14.89 3/4-160.6820 0.6960 0.7094 0.7159 0.7500 (0.750-16)17.3228 17.6784 18.0188 18.1839 19.0500 17.40 17.95 7/8-140.7980 0.8140 0.8286 0.8356 0.8750 (0.875-14)20.2692 20.6756 21.0464 21.2242 22.2250 20.35 20.97 1"-120.91000.92800.94590.95351.0000 (1.000-12)UNF23.1140 23.5712 24.0259 24.2189 25.400023.90 23.951.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。