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Diameter - Pitch Combinations For Class of Fit Nominal Size Threads Internal° Per Inch and Series *Minor Diameter Pitch Diameter Major Diameter Designation Class Min. Max. Min. Max. Min. 0–80 UNF 1–64 UNC 1–72 UNF 2B 3B 2B B 2B .0465 .0465 .0561 .0561 .0580 .0514 .0514 .0623 .0623 .0635 .0519 .0519 .0629 .0629 .0640 .0542 .0536 .0655 .0648 .0665 .0600 .0600 .0730 .0730 .0730 2–56 UNC 2–64 UNF 3B 2B 3B 2B 3B .0580 .0667 .0667 .0691 .0691 .0635 .0737 .0737 .0753 .0753 .0640 .0744 .0744 .0759 .0759 .0659 .0772 .0765 .0786 .0779 .0730 .0860 .0860 .0860 .0860 3–48 UNC 3–56 UNF 4–40 UNC 2B 3B 2B 3B 2B .0764 .0764 .0797 .0797 .0849 .0845 .0845 .0865 .0865 .0939 .0855 .0855 .0874 .0874 .0958 .0885 .0877 .0902 .0895 .0991 .0990 .0990 .0990 .0990 .1120 4–48 UNF 5–40 UNC 3B 2B 3B 2B 3B .0849 .0894 .0894 .0979 .0979 .0939 .0968 .0968 .1062 .1062 .0958 .0985 .0985 .1088 .1088 .0982 .1016 .1008 .1121 .1113 .1120 .1120 .1120 .1250 .1250 5–44 UNF 6–32 UNC 6–40 UNF 2B 3B 2B 3B 2B .1004 .1004 .1040 .1040 .1110 .1079 .1079 .1140 .1140 .1190 .1102 .1102 .1177 .1177 .1218 .1134 .1126 .1214 .1204 .1252 .1250 .1250 .1380 .1380 .1380 8–32 UNC 8–36 UNF 3B 2B 3B 2B 3B .1110 .1300 .1300 .1340 .1340 .1186 .1390 .1389 .1420 .1416 .1218 .1437 .1437 .1460 .1460 .1243 .1475 .1465 .1496 .1487 .1380 .1640 .1640 .1640 .1640 10–24 UNC 10–32 UNF 12–24 UNC 2B 3B 2B 3B 2B .1450 .1450 .1560 .1560 .1710 .1560 .1555 .1640 .1641 .1810 .1629 .1629 .1697 .1697 .1889 .1672 .1661 .1736 .1726 .1933 .1900 .1900 .1900 .1900 .2160 12–28 UNF 3B 2B 3B .1710 .1770 .1770 .1807 .1860 .1857 .1889 .1928 .1928 .1922 .1970 .1959 .2160 .2160 .2160		Fractional Sizes Nominal Size Threads Internal° Per Inch and Series *Minor Diameter Pitch Diameter Major Diameter Designation Class Min. Max. Min. Max. Min. 1/4–20 UNC 1/4–28 UNF 1B 2B 3B 1B 2B .1960 .1960 .1960 .2110 .2110 .2070 .2070 .2067 .2200 .2200 .2175 .2175 .2175 .2268 .2268 .2248 .2224 .2211 .2333 .2311 .2500 .2500 .2500 .2500 .2500 5/16–18 UNC 5/16–24 UNF 3B 1B 2B 3B 1B .2110 .2520 .2520 .2520 .2670 .2190 .2650 .2650 .2630 .2770 .2268 .2764 .2764 .2764 .2854 .2300 .2843 .2817 .2803 .2925 .2500 .3125 .3125 .3125 .3125 3/8–16 UNC 2B 3B 1B 2B 3B .2670 .2670 .3070 .3070 .3070 .2770 .2754 .3210 .3210 .3182 .2854 .2854 .3344 .3344 .3344 .2902 .2890 .3429 .3401 .3387 .3125 .3125 .3750 .3750 .3750 3/8–24 UNF 7/16–14 UNC 1B 2B 3B 1B 2B .3300 .3300 .3300 .3600 .3600 .3400 .3400 .3372 .3760 .3760 .3479 .3479 .3479 .3911 .3911 .3553 .3528 .3516 .4003 .3972 .3750 .3750 .3750 .4375 .4375 7/16–20 UNF 1/2–13 UNC 3B 1B 2B 3B 1B .3600 .3830 .3830 .3830 .4170 .3717 .3950 .3950 .3916 .4340 .3911 .4050 .4050 .4050 .4500 .3957 .4131 .4104 .4091 .4597 .4375 .4375 .4375 .4375 .5000 1/2–20 UNF 2B 3B 1B 2B 3B .4170 .4170 .4460 .4460 .4460 .4340 .4284 .4570 .4570 .4537 .4500 .4500 .4675 .4675 .4675 .4565 .4548 .4759 .4731 .4717 .5000 .5000 .5000 .5000 .5000
Metric Sizes (ANSA B1.13M-1983) All dimensions are in millimeters. Basic Thread Toler. Minor Diameter Pitch Diameter Major Diameter Description Class Min. Max. Min. Max. Tol Min. Max. M1.6 x 0.35 M2 x 0.4 M2.5 x 0.45 M3 x 0.5 M3.5 x 0.6 6H 6H 6H 6H 6H 1.221 1.567 2.013 2.459 2.850 1.321 1.679 2.138 2.599 3.010 1.373 1.740 2.208 2.675 3.110 1.458 1.830 2.303 2.775 3.222 .085 .090 .095 .100 .112 1.600 2.000 2.500 3.000 3.500 1.736 2.148 2.660 3.172 3.699 M4 x 0.7 M5 x 0.8 M6 x 1 M8 x 1.25 M8 x 1 6H 6H 6H 6H 6H 3.242 4.134 4.917 6.647 6.917 3.422 4.334 5.153 6.912 7.153 3.545 4.480 5.350 7.188 7.350 3.663 4.605 5.500 7.348 7.500 .118 .125 .150 .160 .150 4.000 5.000 6.000 8.000 8.000 4.219 5.240 6.294 8.340 8.294 10 x 1.5 M10 x 1.25 M10 x 0.75 M12 x 1.75 M12 x 1.5 6H 6H 6H 6H 6H 8.376 8.647 9.188 10.106 10.376 8.676 8.912 9.378 10.441 10.676 9.026 9.188 9.513 10.863 11.026 9.206 9.348 9.645 11.063 11.216 .180 .160 .132 .200 .190 10.000 10.000 10.000 12.000 12.000 10.396 10.340 10.240 12.453 12.406 M12 x 1.25 M12 x 1 6H 6H 10.647 10.917 10.912 11.153 11.188 11.350 11.368 11.510 .180 .160 12.000 12.000 12.360 12.304
*Internal Thread Minor Diameter Tolerances. Internal thread minor diameter tolerances are based on a length of engagement equal to the nominal diameter. For general applications these tolerances are suitable for lengths of engagement up to 11/2 diameters. However, some thread applications have lengths of engagement which are greater than 11/2 diameters or less than the nominal diameter. For such applications it may be advantageous to increase or decrease the tolerance, respectively, as explained in the following section.