Unified External Screw Threads
Data for industrial machine screws, threaded fasteners and standard industrial fasteners from MW includes unified external screw threads. Diameters and sizes for class 2A and 3A UNRC. and UNRF. and ISO metric threads are listed in the chart below.
Classes 2A & 3A UNRC. UNRF. | |||||
| Nominal Size & TPI | Class 2A | Class 3A | |||
| Major Diameter | Pitch Diameter | Major Diameter | Pitch Diameter | Blank Size | |
| 4-40 | .1061 .1112 | .0925 .0950 | .1069 .1120 | .0939 .0958 | .0938 .0943 |
| 4-48 | .1068 .1113 | .0954 .0978 | .1075 .1120 | .0967 .0985 | .0968 .0971 |
| 5-40 | .1191 .1242 | .1054 .1080 | .1199 .1250 | .1060 .1088 | .1067 .1072 |
| 5-44 | .1195 .1243 | .1070 .1095 | .1202 .1250 | .1083 .1102 | .1083 .1088 |
| 6-32 | .1312 .1372 | .1141 .1169 | .1320 .1380 | .1156 .1177 | .1155 .1161 |
| 6-40 | .1321 .1372 | .1184 .1210 | .1329 .1380 | .1198 .1218 | .1197 .1202 |
| 8-32 | .1571 .1631 | .1399 .1428 | .1580 .1640 | .1415 .1437 | .1414 .1419 |
| 8-36 | .1577 .1632 | .1424 .1452 | .1585 .1640 | .1439 .1460 | .1438 .1444 |
| 10-24 | .1818 .1890 | .1586 .1619 | .1828 .1900 | .1604 .1629 | .1603 .1609 |
| 10-32 | .1831 .1891 | .1658 .1688 | .1840 .1900 | .1674 .1697 | .1673 .1679 |
| 12-24 | .2078 .2150 | .1845 .1879 | .2088 .2160 | .1863 .1889 | .1862 .1867 |
| 12-28 | .2085 .2150 | .1888 .1918 | .2095 .2160 | .1904 .1928 | .1903 .1908 |
| 1/4-20 | .2408 .2489 | .2127 .2164 | .2419 .2500 | .2147 .2175 | .2146 .2153 |
| 1/4-28 | .2425 .2490 | .2225 .2258 | .2435 .2500 | .2243 .2268 | .2242 .2248 |
| 5/16-18 | .3026 .3113 | .2712 .2752 | .3038 .3125 | .2734 .2764 | .2732 .2740 |
| 5/16-24 | .3042 .3114 | .2806 .2843 | .3053 .3125 | .2827 .2854 | .2825 .2832 |
| 3/8-16 | .3643 .3737 | .3287 .3331 | .3656 .3750 | .3311 .3344 | .3309 .3318 |
| 3/8-24 | .3667 .3739 | .3430 .3468 | .3678 .3750 | .3450 .3479 | .3449 .3457 |
| 7/16-14 | .4258 .4361 | .3850 .3897 | .4272 .4375 | .3876 .3911 | .3874 .3883 |
| 7/16-20 | .4281 .4362 | .3995 .4037 | .4294 .4375 | .4019 .4050 | .4016 .4024 |
| 1/2-13 | .4876 .4985 | .4435.4485 | .4891 .5000 | .4463 .4500 | .4480 .4470 |
| 1/2-20 | .4906 .4987 | .4619 .4662 | .4919 .5000 | .4643 .4675 | .4641 .4649 |
| 9/16-12 | .5016 .5068 | .5495 .5609 | .5045 .5084 | .5511 .5625 | .5050 .5070 |
| 9/16-18 | .5205 .5250 | .5524 .5611 | .523 .5264 | .5538 .5625 | .5170 .5190 |
| 5/8-11 | .5589 .5644 | .6113 .6234 | .5619 .5660 | .6129 .6250 | .5630 .5650 |
| 5/8-18 | .5828 .5875 | .6149 .6236 | .5854 .5889 | .6163 .6250 | .5840 .5860 |
ISO Metric Threads CLASS 6g | ||||||
| Metric Size | Inch Measurement | Millimeters | ||||
| Nominal Size | Major Diameter | Pitch Diameter | Blank Size | Major Diameter | Pitch Diameter | Blank Size |
| M3 x .5 | .1173 .1131 | .1045 .1016 | .1037 .1030 | 2.980 2.874 | 2.655 2.580 | 2.635 2.615 |
| M3.5 x .6 | .1370 .1320 | .1216 .1183 | .1205 .1195 | 3.479 3.354 | 3.089 3.004 | 3.060 3.035 |
| M4 x .7 | .1566 .1511 | .1387 .1352 | .1376 .1364 | 3.978 3.938 | 3.523 3.438 | 3.495 3.465 |
| M5 x .8 | .1959 .1900 | .1754 .1717 | .1742 .1730 | 4.976 4.826 | 4.456 4.361 | 4.425 4.395 |
| M6 x 1.0 | .2352 .2281 | .2096 .2052 | .2087 .2071 | 5.974 5.794 | 5.324 5.212 | 5.300 5.260 |
| M7 x 1.0 | .2746 .2675 | .2490 .2446 | .2480 .2465 | 6.974 6.794 | 6.324 6.212 | 6.300 6.260 |
| M8 x 1.25 | .3139 .3055 | .2819 .2772 | .2807 .2791 | 7.972 7.760 | 7.160 7.042 | 7.130 7.090 |
| M10 x 1.25 | .3926 .3856 | .3606 .3560 | .3594 .3579 | 9.972 9.794 | 9.160 9.042 | 9.130 9.090 |
| M10 x 1.5 | .3924 .3831 | .3541 .3489 | .3528 .3512 | 9.968 9.732 | 8.994 8.862 | 8.960 8.920 |
| M11 x 1.5 | .4318 .4225 | .3935 .3883 | .3921 .3902 | 10.968 10.732 | 9.994 9.862 | 9.960 9.910 |
| M12 x 1.25 | .4713 .4630 | .4394 .4342 | .4382 .4366 | 11.972 11.760 | 11.160 11.028 | 11.130 11.090 |
| M12 x 1.75 | .4711 .4607 | .4263 .4204 | .4252 .4232 | 11.966 11.701 | 10.829 10.679 | 10.800 10.750 |
ISO Metric Threads CLASS 4h | ||||||
| Metric Size | Inch Measurement | Millimeters | ||||
| Nominal Size | Major Diameter | Pitch Diameter | Blank Size | Major Diameter | Pitch Diameter | Blank Size |
| M3 x .5 | .1181 .1155 | .1053 .1034 | .1051 .1046 | 3.000 2.933 | 2.675 2.627 | 2.669 2.656 |
| M3 .5 x .6 | .1378 .1321 | .1216 .1183 | .1212 .1205 | 3.500 3.355 | 3.088 3.004 | 3.078 3.060 |
| M4 x .7 | .1575 .1539 | .1396 .1374 | .1394 .1387 | 4.000 3.910 | 3.545 3.489 | 3.540 3.522 |
| M5 x .8 | .1968 .1931 | .1751 .1740 | .1748 .1741 | 5.000 4.905 | 4.480 4.420 | 4.439 4.422 |
| M6 x 1.0 | .2362 .2318 | .2106 .2078 | .2100 .2093 | 6.000 5.888 | 5.350 5.279 | 5.334 5.316 |
| M7 x 1.0 | .2756 .2712 | .2500 .2472 | .2494 .2487 | 7.000 6.888 | 6.350 6.279 | 6.334 6.316 |
| M8 x 1.25 | .3150 .3098 | .2830 .2800 | .2826 .2819 | 8.000 7.868 | 7.188 7.113 | 7.178 7.160 |
| M10 x 1.0 | .3937 .3893 | .3681 .3653 | .3675 .3668 | 10.000 9.888 | 9.350 9.279 | 9.334 8.554 |
| M10 x 1.25 | .3937 .3885 | .3617 .3588 | .3610 .3603 | 10.000 9.868 | 9.188 9.113 | 9.169 9.151 |
| M10 x 1.5 | .3937 .3878 | .3553 .3520 | .3551 .3544 | 10.000 9.850 | 9.026 8.941 | 9.020 9.001 |
| M12 x 1.25 | .4724 .4672 | .4405 .4371 | .4397 .4390 | 12.000 11.868 | 11.188 11.103 | 11.168 11.150 |
| M12 x 1.5 | .4724 .4665 | .4341 .4305 | .4335 | 12.000 11.850 | 11.026 10.936 | 11.010 10.993 |
| M12 x 1.75 | .4724 .4657 | .4277 .4239 | .4273 .4265 | 12.000 11.830 | 10.863 10.768 | 10.853 10.833 |