
Pitch Diameter Limits For External and Internal Screw Threads Classes 2A, 3A and 2B, 3B, Unified Thread Form Classes 2 and 3, American National Thread Form External Thread (Bolt) Internal Thread (Nut) Threads Per Inch Unified American National Basic UnifiedPitch AmericanNational Size Maximum Minimum Max. Minimum Dia. Maximum Minimum NC NFUNCUNFClass2A Class3ABasicNo.Class2A Classes AllClass3A2, 3BasicSizeClass 2No.Class 3ClassesMin.Size2B SizeNo.3B SizeNo.2 SizeNo.3 SizeNo.No.No. 0 – 80 0.0514 0.0519 0.0496 0.0506 0.0519 0.0502 0.0506 0.0519 0.0542 0.0536 0.0536 0.0532 1 64 – 0.0623 0.0629 0.0603 0.0614 0.0629 0.0610 0.0615 0.0629 0.0655 0.0648 0.0648 0.0643–720.06340.06400.06150.06260.06400.06220.06270.06400.06650.06590.06580.0653 2 56 – 0.0738 0.0744 0.0717 0.0728 0.0744 0.0724 0.0729 0.0744 0.0772 0.0765 0.0764 0.0759–640.07530.07590.07330.07440.07590.07400.07450.07590.07860.07790.07780.0773 3 48 – 0.0848 0.0855 0.0825 0.0838 0.0855 0.0833 0.0839 0.0855 0.0885 0.0877 0.0877 0.0871–560.08670.08740.08450.08580.08740.08540.08590.08740.09020.08950.08940.0889 4 40 – 0.0950 0.0958 0.0925 0.0939 0.0958 0.0934 0.0941 0.0958 0.0991 0.0982 0.0982 0.0975480.09780.09850.09540.09670.09850.09630.09690.09850.10160.10080.10070.1001 5 40 – 0.1080 0.1088 0.1054 0.1069 0.1088 0.1064 0.1071 0.1088 0.1121 0.1113 0.1112 0.1105–440.10950.11020.10700.10830.11020.10790.10860.11020.11340.11260.11250.1118 6 32 – 0.1169 0.1177 0.1141 0.1156 0.1177 0.1150 0.1158 0.1177 0.1214 0.1204 0.1204 0.1196–400.12100.12180.11840.11980.12180.11940.12010.12180.12520.12430.12420.1235 8 32 – 0.1428 0.1437 0.1399 0.1415 0.1437 0.1410 0.1418 0.1437 0.1475 0.1465 0.1464 0.1456–360.14520.14600.14240.14390.14600.14350.14420.14600.14960.14870.14850.1478 10 24– – 0.1619 0.1629 0.1586 0.1604 0.1629 0.1596 0.1605 0.1629 0.1672 0.1661 0.1662 0.1653320.16880.16970.16580.16740.16970.16700.16780.16970.17360.17260.17240.1716 12 24– – 0.1879 0.1889 0.1845 0.1863 0.1889 0.1856 0.1865 0.1889 0.1933 0.1922 0.1922 0.1913280.19180.19280.18860.19040.19280.18970.19060.19280.19700.19590.19590.1950 1/4 20– – 0.2164 0.2175 0.2127 0.2147 0.2175 0.2139 0.2149 0.2175 0.2224 0.2211 0.2211 0.2201280.22580.22680.22250.22430.22680.22370.22460.22680.23110.23000.22990.2290 5/16 18– – 0.2752 0.2764 0.2712 0.2734 0.2764 0.2723 0.2734 0.2764 0.2817 0.2803 0.2805 0.2794240.28430.28540.28060.28270.28540.28210.28300.28540.29020.28900.28870.2878 3/8 16– – 0.3331 0.3344 0.3287 0.3311 0.3344 0.3299 0.3312 0.3344 0.3401 0.3387 0.3389 0.3376240.34680.34790.34300.34500.34790.34460.34550.34790.35280.35160.35120.3503 7/16 14– – 0.3897 0.3911 0.3850 0.3876 0.3911 0.3862 0.3875 0.3911 0.3972 0.3957 0.3960 0.3947200.40370.40500.39950.40190.40500.40140.40240.40500.41040.40910.40860.4076 1/2 13– – 0.4485 0.4500 0.4435 0.4463 0.4500 0.4448 0.4463 0.4500 0.4565 0.4548 0.4552 0.4537200.46620.46750.46190.46430.46750.46390.46490.46750.47310.47170.47110.4701 9/16 12– – 0.5068 0.5084 0.5016 0.5045 0.5084 0.5028 0.5044 0.5084 0.5152 0.5135 0.5140 0.5124180.52500.52640.52050.52300.52640.52230.52340.52640.53230.53080.53050.5294 5/8 11– – 0.5644 0.5660 0.5589 0.5619 0.5660 0.5601 0.5618 0.5660 0.5732 0.5714 0.5719 0.5702180.58750.58890.58280.58540.58890.58480.58590.58890.59490.59340.59300.5919 3/4 10– – 0.6832 0.6850 0.6773 0.6806 0.6850 0.6786 0.6805 0.6850 0.6927 0.6907 0.6914 0.6985160.70790.70940.70290.70560.70940.70490.70620.70940.71590.71430.71390.7126 7/8 9– – 0.8009 0.8028 0.7946 0.7981 0.8028 0.7958 0.7979 0.8028 0.8110 0.8089 0.8098 0.8077140.82700.82860.82160.82450.82860.82370.82500.82860.83560.83390.83350.8322 8 – 0.9168 0.9188 0.9100 0.9137 0.9188 0.9112 0.9134 0.9188 0.9276 0.9254 0.9264 0.9242 1 – 12 0.9441 0.9459 0.9382 0.9415 0.9459 0.9403 0.9419 0.9459 0.9535 0.9516 0.9515 0.9499 – 14NS 0.9519 0.9536 0.9463 0.9494 0.9536 0.9487 0.9500 0.9536 0.9609 0.9590 0.9585 0.9572 1 1/8 7– – 1.0300 1.0322 1.0228 1.0268 1.0322 1.0237 1.0263 1.0322 1.0416 1.0393 1.0407 1.0381121.06911.07091.06311.06641.07091.06531.06691.07091.07871.07681.07651.0749 1 1/4 7– – 1.1550 1.1572 1.1476 1.1517 1.1572 1.1487 1.1513 1.1572 1.1668 1.1644 1.1657 1.1631121.19411.19591.18791.19131.19591.19031.19191.19591.20391.20191.20151.1999 1 3/8 6– – 1.2643 1.2667 1.2563 1.2607 1.2667 1.2566 1.2596 1.2667 1.2771 1.2745 1.2768 1.2738121.31901.33211.31271.31621.32091.31531.31691.32091.32911.32701.32651.3249 1 1/2 6– – 1.3893 1.3917 1.3812 1.3856 1.3917 1.3816 1.3846 1.3917 1.4022 1.3996 1.4018 1.3988121.44401.44591.43761.44111.44591.44031.44191.44591.45421.45221.45151.4499 658 Threading Technical WWW.OSGTOOL.COM