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Nominal Thread SizeCovered Range
0-80 UNF to ¼-56 UNS Nominal thread sizes from 0-80 UNF to ¼-56 UNS
5/16-18 UNC to 9/16 -32 UN Nominal thread sizes from 5/16-18 UNC to 9/16 -32 UN
5/8-11 UNC to 7/8-32 UN Nominal thread sizes from 5/8-11 UNC to 7/8-32 UN
15/16-12 UN to 1 3/16-28 UN Nominal thread sizes from 15/16-12 UN to 1 3/16-28 UN
1 1/4-7 UNC to 1 9/16-20 UN Nominal thread sizes from 1 1/4-7 UNC to 1 9/16-20 UN
1 5/8-6 UN to 1 15/16-20 UN Nominal thread sizes from 1 5/8-6 UN to 1 15/16-20 UN
2-4½ UNC to 2¾-20 UN Nominal thread sizes from 2-4½ UNC to 2¾-20 UN
2 7/8-6 UN to 4-16 UN Nominal thread sizes from 2 7/8-6 UN to 4-16 UN
 
External Thread /Internal Thread
  Nominal Size, TPI, Series Class Allowance Maxa Major
Max Minor		 Min Major
Min Minor		 Min b Maxa Pitch Min Pitch UNRc Minor Dia
Major Dia(Min)
Ext. 27/8-6 UN 2A 0.0028 2.8722 2.8540 - 2.7639 2.7547 2.6738
Int.   2B   2.7250 2.6950   2.7787 2.7667 2.8750
Ext. 27/8-6 UN 3A 0.0000 2.8750 2.8568 - 2.7667 2.7598 2.6766
Int.   3B   2.7146 2.6950   2.7757 2.7667 2.8750
Ext. 27/8-8 UN 2A 0.0025 2.8725 2.8575 - 2.7913 2.7829 2.7237
Int.   2B   2.7650 2.7400   2.8048 2.7938 2.8750
Ext. 27/8-8 UN 3A 0.0000 2.8750 2.8600 - 2.7938 2.7875 2.7262
Int.   3B   2.7547 2.7400   2.8020 2.7938 2.8750
Ext. 27/8-12 UN 2A 0.0019 2.8731 2.8617 - 2.8190 2.8127 2.7739
Int.   2B   2.8030 2.7850   2.8291 2.8209 2.8750
Ext. 27/8-12 UN 3A 0.0000 2.8750 2.8636 - 2.8209 2.8162 2.7758
Int.   3B   2.7948 2.7850   2.8271 2.8209 2.8750
Ext. 27/8-16 UN 2A 0.0017 2.8733 2.8639 - 2.8327 2.8271 2.7988
Int.   2B   2.8210 2.8070   2.8417 2.8344 2.8750
Ext. 27/8-16 UN 3A 0.0000 2.8750 2.8656 - 2.8344 2.8302 2.8005
Int.   3B   2.8158 2.8070   2.8399 2.8344 2.8750
Ext. 27/8-20 UN 2A 0.0016 2.8734 2.8653 - 2.8409 2.8357 2.8139
Int.   2B   2.8320 2.8210   2.8493 2.8425 2.8750
Ext. 27/8-20 UN 3A 0.0000 2.8750 2.8669 - 2.8425 2.8386 2.8155
Int.   3B   2.8287 2.8210   2.8476 2.8425 2.8750
Ext. 3-4 UNC 1A 0.0032 2.9968 2.9611 - 2.8344 2.8183 2.6991
Int.   1B   2.7670 2.7290   2.8585 2.8376 3.0000
Ext. 3-4 UNC 2A 0.0032 2.9968 2.9730 2.9611 2.8344 2.8237 2.6991
Int.   2B   2.7670 2.7290   2.8515 2.8376 3.0000
Ext. 3-4 UNC 3A 0.0000 3.0000 2.9762 - 2.8376 2.8296 2.7023
Int.   3B   2.7594 2.7290   2.8480 2.8376 3.0000
Ext. 3-6 UN 2A 0.0028 2.9972 2.9790 - 2.8889 2.8796 2.7988
Int.   2B   2.8500 2.8200   2.9038 2.8917 3.0000
Ext. 3-6 UN 3A 0.0000 3.0000 2.9818 - 2.8917 2.8847 2.8016
Int.   3B   2.8396 2.8200   2.9008 2.8917 3.0000
Ext. 3-8 UN 2A 0.0026 2.9974 2.9824 2.9749 2.9162 2.9077 2.8486
Int.   2B   2.8900 2.8650   2.9299 2.9188 3.0000
Ext. 3-8 UN 3A 0.0000 3.0000 2.9850 - 2.9188 2.9124 2.8512
Int.   3B   2.8797 2.8650   2.9271 2.9188 3.0000
Ext. 3-10 UNS 2A 0.0020 2.9980 2.9851 - 2.9330 2.9262 2.8790
Int.   2B   2.9130 2.8920   2.9439 2.9350 3.0000
Ext. 3-12 UN 2A 0.0019 2.9981 2.9867 - 2.9440 2.9377 2.8989
Int.   2B   2.9280 2.9100   2.9541 2.9459 3.0000
Ext. 3-12 UN 3A 0.0000 3.0000 2.9886 - 2.9459 2.9412 2.9008
Int.   3B   2.9198 2.9100   2.9521 2.9459 3.0000
Ext. 3-14 UNS 2A 0.0018 2.9982 2.9879 - 2.9518 2.9459 2.9132
Int.   2B   2.9380 2.9230   2.9613 2.9536 3.0000
Ext. 3-16 UN 2A 0.0017 2.9983 2.9889 - 2.9577 2.9521 2.9238
Int.   2B   2.9460 2.9320   2.9667 2.9594 3.0000
Ext. 3-16 UN 3A 0.0000 3.0000 2.9906 - 2.9594 2.9552 2.9255
Int.   3B   2.9408 2.9320   2.9649 2.9594 3.0000
Ext. 3-18 UNS 2A 0.0016 2.9984 2.9897 - 2.9623 2.9569 2.9323
Int.   2B   2.9530 2.9400   2.9709 2.9639 3.0000
Ext. 3-20 UN 2A 0.0016 2.9984 2.9903 - 2.9659 2.9607 2.9389
Int.   2B   2.9570 2.9460   2.9743 2.9675 3.0000
Ext. 3-20 UN 3A 0.0000 3.0000 2.9919 - 2.9675 2.9636 2.9405
Int.   3B   2.9537 2.9460   2.9726 2.9675 3.0000
Ext. 31/8-6 UN 2A 0.0028 3.1222 3.1040 - 3.0139 3.0045 2.9238
Int.   2B   2.9750 2.9450   3.0289 3.0167 3.1250
Ext. 31/8-6 UN 3A 0.0000 3.1250 3.1068 - 3.0167 3.0097 2.9266
Int.   3B   2.9646 2.9450   3.0259 3.0167 3.1250
Ext. 31/8-8 UN 2A 0.0026 3.1224 3.1074 - 3.0412 3.0326 2.9736
Int.   2B   3.0150 2.9900   3.0550 3.0438 3.1250
Ext. 31/8-8 UN 3A 0.0000 3.1250 3.1100 - 3.0438 3.0374 2.9762
Int.   3B   3.0047 2.9900   3.0522 3.0438 3.1250
Ext. 31/8-12 UN 2A 0.0019 3.1231 3.1117 - 3.0690 3.0627 3.0239
Int.   2B   3.0530 3.0350   3.0791 3.0709 3.1250
Ext. 31/8-12 UN 3A 0.0000 3.1250 3.1136 - 3.0709 3.0662 3.0258
Int.   3B   3.0448 3.0350   3.0771 3.0709 3.1250
Ext. 31/8-16 UN 2A 0.0017 3.1233 3.1139 - 3.0827 3.0771 3.0488
Int.   2B   3.0710 3.0570   3.0917 3.0844 3.1250
Ext. 31/8-16 UN 3A 0.0000 3.1250 3.1156 - 3.0844 3.0802 3.0505
Int.   3B   3.0658 3.0570   3.0899 3.0844 3.1250
Ext. 31/4-4 UNC 1A 0.0033 3.2467 3.2110 - 3.0843 3.0680 2.9490
Int.   1B   3.0170 2.9790   3.1088 3.0876 3.2500
Ext. 31/4-4 UNC 2A 0.0033 3.2467 3.2229 3.2110 3.0843 3.0734 2.9490
Int.   2B   3.0170 2.9790   3.1017 3.0876 3.2500
Ext. 31/4-4 UNC 3A 0.0000 3.2500 3.2262 - 3.0876 3.0794 2.9523
Int.   3B   3.0094 2.9790   3.0982 3.0876 3.2500
Ext. 31/4-6 UN 2A 0.0028 3.2472 3.2290 - 3.1389 3.1294 3.0488
Int.   2B   3.1000 3.0700   3.1540 3.1417 3.2500
Ext. 31/4-6 UN 3A 0.0000 3.2500 3.2318 - 3.1417 3.1346 3.0516
Int.   3B   3.0896 3.0700   3.1509 3.1417 3.2500
Ext. 31/4-8 UN 2A 0.0026 3.2474 3.2324 3.2249 3.1662 3.1575 3.0986
Int.   2B   3.1400 3.1150   3.1801 3.1688 3.2500
Ext. 31/4-8 UN 3A 0.0000 3.2500 3.2350 - 3.1688 3.1623 3.1012
Int.   3B   3.1297 3.1150   3.1773 3.1688 3.2500
Ext. 31/4-10 UNS 2A 0.0020 3.2480 3.2351 - 3.1830 3.1762 3.1290
Int.   2B   3.1630 3.1420   3.1939 3.1850 3.2500
Ext. 31/4-12 UN 2A 0.0019 3.2481 3.2367 - 3.1940 3.1877 3.1489
Int.   2B   3.1780 3.1600   3.2041 3.1959 3.2500
Ext. 31/4-12 UN 3A 0.0000 3.2500 3.2386 - 3.1959 3.1912 3.1508
Int.   3B   3.1698 3.1600   3.2021 3.1959 3.2500
Ext. 31/4-14 UNS 2A 0.0018 3.2482 3.2379 - 3.2018 3.1959 3.1632
Int.   2B   3.1880 3.1730   3.2113 3.2036 3.2500
Ext. 31/4-16 UN 2A 0.0017 3.2483 3.2389 - 3.2077 3.2021 3.1738
Int.   2B   3.1960 3.1820   3.2167 3.2094 3.2500
Ext. 31/4-16 UN 3A 0.0000 3.2500 3.2406 - 3.2094 3.2052 3.1755
Int.   3B   3.1908 3.1820   3.2149 3.2094 3.2500
Ext. 31/4-18 UNS 2A 0.0016 3.2484 3.2397 - 3.2123 3.2069 3.1823
Int.   2B   3.2030 3.1900   3.2209 3.2139 3.2500
Ext. 33/8-6 UN 2A 0.0029 3.3721 3.3539 - 3.2638 3.2543 3.1737
Int.   2B   3.2250 3.1950   3.2791 3.2667 3.3750
Ext. 33/8-6 UN 3A 0.0000 3.3750 3.3568 - 3.2667 3.2595 3.1766
Int.   3B   3.2146 3.1950   3.2760 3.2667 3.3750
Ext. 33/8-8 UN 2A 0.0026 3.3724 3.3574 - 3.2912 3.2824 3.2236
Int.   2B   3.2650 3.2400   3.3052 3.2938 3.3750
Ext. 33/8-8 UN 3A 0.0000 3.3750 3.3600 - 3.2938 3.2872 3.2262
Int.   3B   3.2547 3.2400   3.3023 3.2938 3.3750
Ext. 33/8-12 UN 2A 0.0019 3.3731 3.3617 - 3.3190 3.3126 3.2739
Int.   2B   3.3030 3.2850   3.3293 3.3209 3.3750
Ext. 33/8-12 UN 3A 0.0000 3.3750 3.3636 - 3.3209 3.3161 3.2758
Int.   3B   3.2948 3.2850   3.3272 3.3209 3.3750
Ext. 33/8-16 UN 2A 0.0017 3.3733 3.3639 - 3.3327 3.3269 3.2988
Int.   2B   3.3210 3.3070   3.3419 3.3344 3.3750
Ext. 33/8-16 UN 3A 0.0000 3.3750 3.3656 - 3.3344 3.3301 3.3005
Int.   3B   3.3158 3.3070   3.3400 3.3344 3.3750
Ext. 31/2-4 UNC 1A 0.0033 3.4967 3.4610 - 3.3343 3.3177 3.1990
Int.   1B   3.2670 3.2290   3.3591 3.3376 3.5000
Ext. 31/2-4 UNC 2A 0.0033 3.4967 3.4729 3.4610 3.3343 3.3233 3.1990
Int.   2B   3.2670 3.2290   3.3519 3.3376 3.5000
Ext. 31/2-4 UNC 3A 0.0000 3.5000 3.4762 - 3.3376 3.3293 3.2023
Int.   3B   3.2594 3.2290   3.3484 3.3376 3.5000
Ext. 31/2-6 UN 2A 0.0029 3.4971 3.4789 - 3.3888 3.3792 3.2987
Int.   2B   3.3500 3.3200   3.4042 3.3917 3.5000
Ext. 31/2-6 UN 3A 0.0000 3.5000 3.4818 - 3.3917 3.3845 3.3016
Int.   3B   3.3396 3.3200   3.4011 3.3917 3.5000
Ext. 31/2-8 UN 2A 0.0026 3.4974 3.4824 3.4749 3.4162 3.4074 3.3486
Int.   2B   3.3900 3.3650   3.4303 3.4188 3.5000
Ext. 31/2-8 UN 3A 0.0000 3.5000 3.4850 - 3.4188 3.4122 3.3512
Int.   3B   3.3797 3.3650   3.4274 3.4188 3.5000
Ext. 31/2-10 UNS 2A 0.0021 3.4979 3.4850 - 3.4329 3.4260 3.3789
Int.   2B   3.4130 3.3920   3.4440 3.4350 3.5000
Ext. 31/2-12 UN 2A 0.0019 3.4981 3.4867 - 3.4440 3.4376 3.3989
Int.   2B   3.4280 3.4100   3.4543 3.4459 3.5000
Ext. 31/2-12 UN 3A 0.0000 3.5000 3.4886 - 3.4459 3.4411 3.4008
Int.   3B   3.4198 3.4100   3.4522 3.4459 3.5000
Ext. 31/2-14 UNS 2A 0.0018 3.4982 3.4879 - 3.4518 3.4132 3.4132
Int.   2B   3.4380 3.4230   3.4615 3.4536 3.5000
Ext. 31/2-16 UN 2A 0.0017 3.4983 3.4889 - 3.4577 3.4519 3.4238
Int.   2B   3.4460 3.4320   3.4669 3.4594 3.5000
Ext. 31/2-16 UN 3A 0.0000 3.5000 3.4906 - 3.4594 3.4551 3.4255
Int.   3B   3.4408 3.4320   3.4650 3.4594 3.5000
Ext. 31/2-18 UNS 2A 0.0017 3.4983 3.4896 - 3.4622 3.4322 3.4322
Int.   2B   3.4530 3.4400   3.4711 3.4639 3.5000
Ext. 35/8-6 UN 2A 0.0029 3.6221 3.6039 - 3.5138 3.5041 3.4237
Int.   2B   3.4750 3.4450   3.5293 3.5167 3.6250
Ext. 35/8-6 UN 3A 0.0000 3.6250 3.6068 - 3.5167 3.5094 3.4266
Int.   3B   3.4646 3.4450   3.5262 3.5167 3.6250
Ext. 35/8-8 UN 2A 0.0027 3.6223 3.6073 - 3.5411 3.5322 3.4735
Int.   2B   3.5150 3.4900   3.5554 3.5438 3.6250
Ext. 35/8-8 UN 3A 0.0000 3.6250 3.6100 - 3.5438 3.5371 3.4762
Int.   3B   3.5047 3.4900   3.5525 3.5438 3.6250
Ext. 35/8-12 UN 2A 0.0019 3.6231 3.6117 - 3.5690 3.5626 3.5239
Int.   2B   3.5530 3.5350   3.5793 3.5709 3.6250
Ext. 35/8-12 UN 3A 0.0000 3.6250 3.6136 - 3.5709 3.5661 3.5258
Int.   3B   3.5448 3.5350   3.5772 3.5709 3.6250
Ext. 35/8-16 UN 2A 0.0017 3.6233 3.6139 - 3.5827 3.5769 3.5488
Int.   2B   3.5710 3.5570   3.5919 3.5844 3.6250
Ext. 35/8-16 UN 3A 0.0000 3.6250 3.6156 - 3.5844 3.5801 3.5505
Int.   3B   3.5658 3.5570   3.5900 3.5844 3.6250
Ext. 33/4-4 UNC 1A 0.0034 3.7466 3.7109 - 3.5842 3.5674 3.4489
Int.   1B   3.5170 3.4790   3.6094 3.5876 3.7500
Ext. 33/4-4 UNC 2A 0.0034 3.7466 3.7228 3.7109 3.5842 3.5730 3.4489
Int.   2B   3.5170 3.4790   3.6021 3.5876 3.7500
Ext. 33/4-4 UNC 3A 0.0000 3.7500 3.7262 - 3.5876 3.5792 3.4523
Int.   3B   3.5094 3.4790   3.5985 3.5876 3.7500
Ext. 33/4-6 UN 2A 0.0029 3.7471 3.7289 - 3.6388 3.6290 3.5487
Int.   2B   3.6000 3.5700   3.6544 3.6417 3.7500
Ext. 33/4-6 UN 3A 0.0000 3.7500 3.7318 - 3.6417 3.6344 3.5516
Int.   3B   3.5896 3.5700   3.6512 3.6417 3.7500
Ext. 33/4-8 UN 2A 0.0027 3.7473 3.7323 3.7248 3.6661 3.6571 3.5985
Int.   2B   3.6400 3.6150   3.6805 3.6688 3.7500
Ext. 33/4-8 UN 3A 0.0000 3.7500 3.7350 - 3.6688 3.6621 3.6012
Int.   3B   3.6297 3.6150   3.6776 3.6688 3.7500
Ext. 33/4-10 UNS 2A 0.0021 3.7479 3.7350 - 3.6829 3.6289 3.6289
Int.   2B   3.6630 3.6420   3.6940 3.6850 3.7500
Ext. 33/4-12 UN 2A 0.0019 3.7481 3.7367 - 3.6940 3.6876 3.6489
Int.   2B   3.6780 3.6600   3.7043 3.6959 3.7500
Ext. 33/4-12 UN 3A 0.0000 3.7500 3.7386 - 3.6959 3.6911 3.6508
Int.   3B   3.6698 3.6600   3.7022 3.6959 3.7500
Ext. 33/4-14 UNS 2A 0.0018 3.7482 3.7379 - 3.7018 3.6632 3.6632
Int.   2B   3.6880 3.6730   3.7115 3.7036 3.7500
Ext. 33/4-16 UN 2A 0.0017 3.7483 3.7389 - 3.7077 3.7019 3.6738
Int.   2B   3.6960 3.6820   3.7169 3.7094 3.7500
Ext. 33/4-16 UN 3A 0.0000 3.7500 3.7406 - 3.7094 3.7051 3.6755
Int.   3B   3.6908 3.6820   3.7150 3.7094 3.7500
Ext. 33/4-18 UNS 2A 0.0017 3.7483 3.7396 - 3.7122 3.6822 3.6822
Int.   2B   3.7030 3.6900   3.7211 3.7139 3.7500
Ext. 37/8-6 UN 2A 0.0030 3.8720 3.8538 - 3.7637 3.7538 3.6736
Int.   2B   3.7250 3.6950   3.7795 3.7667 3.8750
Ext. 37/8-6 UN 3A 0.0000 3.8750 3.8568 - 3.7667 3.7593 3.6766
Int.   3B   3.7146 3.6950   3.7763 3.7667 3.8750
Ext. 37/8-8 UN 2A 0.0027 3.8723 3.8573 - 3.7911 3.7820 3.7235
Int.   2B   3.7650 3.7400   3.8056 3.7938 3.8750
Ext. 37/8-8 UN 3A 0.0000 3.8750 3.8600 - 3.7938 3.7870 3.7262
Int.   3B   3.7547 3.7400   3.8026 3.7938 3.8750
Ext. 37/8-12 UN 2A 0.0020 3.8730 3.8616 - 3.8189 3.8124 3.7738
Int.   2B   3.8030 3.7850   3.8294 3.8209 3.8750
Ext. 37/8-12 UN 3A 0.0000 3.8750 3.8636 - 3.8209 3.8160 3.7758
Int.   3B   3.7948 3.7850   3.8273 3.8209 3.8750
Ext. 37/8-16UN 2A 0.0018 3.8732 3.8638 - 3.8326 3.8267 3.7987
Int.   2B   3.8210 3.8070   3.8420 3.8344 3.8750
Ext. 37/8-16UN 3A 0.0000 3.8750 3.8656 - 3.8344 3.8300 3.8005
Int.   3B   3.8158 3.8070   3.8401 3.8344 3.8750
Ext. 4-4 UNC 1A 0.0034 3.9966 3.9609 - 3.8342 3.8172 3.6989
Int.   1B   3.7670 3.7290   3.8597 3.8376 4.0000
Ext. 4-4 UNC 2A 0.0034 3.9966 3.9728 - 3.8342 3.8229 3.6989
Int.   2B   3.7670 3.7290   3.8523 3.8376 4.0000
Ext. 4-4 UNC 3A 0.0000 4.0000 3.9762 - 3.8376 3.8291 3.7023
Int.   3B   3.7594 3.7290   3.8487 3.8376 4.0000
Ext. 4-6 UN 2A 0.0030 3.9970 3.9788 - 3.8887 3.8788 3.7986
Int.   2B   3.8500 3.8200   3.9046 3.8917 4.0000
Ext. 4-6 UN 3A 0.0000 4.0000 3.9818 - 3.8917 3.8843 3.8016
Int.   3B   3.8396 3.8200   3.9014 3.8917 4.0000
Ext. 4-8 UN 2A 0.0027 3.9973 3.9823 3.9748 3.9161 3.9070 3.8485
Int.   2B   3.8900 3.8650   3.9307 3.9188 4.0000
Ext. 4-8 UN 3A 0.0000 4.0000 3.9850 - 3.9188 3.9120 3.8512
Int.   3B   3.8797 3.8650   3.9277 3.9188 4.0000
Ext. 4-10 UNS 2A 0.0021 3.9979 3.9850 - 3.9329 3.9259 3.8768
Int.   2B   3.9130 3.8920   3.9441 3.9350 4.0000
Ext. 4-12 UN 2A 0.0020 3.9980 3.9866 - 3.9439 3.9374 3.8988
Int.   2B   3.9280 3.9100   3.9544 3.9459 4.0000
Ext. 4-12 UN 3A 0.0000 4.0000 3.9886 - 3.9459 3.9410 3.9008
Int.   3B   3.9198 3.9100   3.9523 3.9459 4.0000
Ext. 4-14 UNS 2A 0.0018 3.9982 3.9879 - 3.9518 3.9456 3.9132
Int.   2B   3.9380 3.9230   3.9616 3.9536 4.0000
Ext. 4-16 UN 2A 0.0018 3.9982 3.9888 - 3.9576 3.9517 3.9237
Int.   2B   3.9460 3.9320   3.9670 3.9594 4.0000
Ext. 4-16 UN 3A 0.0000 4.0000 3.9906 - 3.9594 3.9550 3.9255
Int.   3B   3.9408 3.9320   3.9651 3.9594 4.0000
a For Class 2A threads with coating (plating) the max. is increased by the allowance, to the basic size. This is the same value as Class 3A.
b For uncoated hot-rolled, but not standard fasteners with cold rolled threads
c UN series external thread, Max.Diameter = Basic - Allowance, for Class 1A and 2A
  = Basic for Class 3A
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