engineering fundamentals Unified Screw Threads, Standard Series
Directory | Career | News | Standards | Industrial | SpecSearch®
Design Home
Screw Threads
Thread System
Unified Screw Threads
  UNC Coarse
  UNF Fine
  UNEF Extra Fine
  Unified Standard Series
  Tap Drill
Constant Pitch Series
Metric Screw Threads
Torque in Bolts
Introduction
Torque Calculator
Resources
Bibliography


Login

Home Membership Store Forum Search Member Calculators

Materials
Design
Processes
Units
Formulas
Math
 
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. 2-41/2 UNC 1A 0.0029 1.9971 1.9641 - 1.8528 1.8385 1.7324
Int.   1B   1.7950 1.7590   1.8743 1.8557 2.0000
Ext. 2-41/2 UNC 2A 0.0029 1.9971 1.9751 1.9641 1.8528 1.8433 1.7324
Int.   2B   1.7950 1.7590   1.8681 1.8557 2.0000
Ext. 2-41/2 UNC 3A 0.0000 2.0000 1.9780 - 1.8557 1.8486 1.7353
Int.   3B   1.7861 1.7590   1.8650 1.8557 2.0000
Ext. 2-6 UN 2A 0.0026 1.9974 1.9792 - 1.8891 1.8805 1.7990
Int.   2B   1.8500 1.8200   1.9028 1.8917 2.0000
Ext. 2-6 UN 3A 0.0000 2.0000 1.9818 - 1.8917 1.8853 1.8016
Int.   3B   1.8396 1.8200   1.9000 1.8917 2.0000
Ext. 2-8 UN 2A 0.0023 1.9977 1.9827 1.9752 1.9165 1.9087 1.8489
Int.   2B   1.8900 1.8650   1.9289 1.9188 2.0000
Ext. 2-8 UN 3A 0.0000 2.0000 1.9850 - 1.9188 1.9130 1.8512
Int.   3B   1.8797 1.8650   1.9264 1.9188 2.0000
Ext. 2-10 UNS 2A 0.0020 1.9980 1.9851 - 1.9330 1.9265 1.8790
Int.   2B   1.9130 1.8920   1.9435 1.9350 2.0000
Ext. 2-12 UN 2A 0.0018 1.9982 1.9868 - 1.9441 1.9380 1.8990
Int.   2B   1.9280 1.9100   1.9538 1.9459 2.0000
Ext. 2-12 UN 3A 0.0000 2.0000 1.9886 - 1.9459 1.9414 1.9008
Int.   3B   1.9198 1.9100   1.9518 1.9459 2.0000
Ext. 2-14 UNS 2A 0.0017 1.9983 1.9880 - 1.9519 1.9462 1.9133
Int.   2B   1.9380 1.9230   1.9610 1.9536 2.0000
Ext. 2-16 UN 2A 0.0016 1.9984 1.9890 - 1.9578 1.9524 1.9239
Int.   2B   1.9460 1.9320   1.9664 1.9594 2.0000
Ext. 2-16 UN 3A 0.0000 2.0000 1.9906 - 1.9594 1.9554 1.9255
Int.   3B   1.9408 1.9320   1.9646 1.9594 2.0000
Ext. 2-18 UNS 2A 0.0015 1.9985 1.9898 - 1.9624 1.9573 1.9324
Int.   2B   1.9530 1.9400   1.9706 1.9639 2.0000
Ext. 2-20 UN 2A 0.0015 1.9985 1.9904 - 1.9660 1.9611 1.9390
Int.   2B   1.9570 1.9460   1.9739 1.9675 2.0000
Ext. 2-20 UN 3A 0.0000 2.0000 1.9919 - 1.9675 1.9638 1.9405
Int.   3B   1.9537 1.9460   1.9723 1.9675 2.0000
Ext. 21/16-16 UNS 2A 0.0016 2.0609 2.0515 - 2.0203 2.0149 1.9864
Int.   2B   2.0090 1.9950   2.0289 2.0219 2.0625
Ext. 21/16-16 UNS 3A 0.0000 2.0625 2.0531 - 2.0219 2.0179 1.9880
Int.   3B   2.0033 1.9950   2.0271 2.0219 2.0625
Ext. 21/8-6 UN 2A 0.0026 2.1224 2.1042 - 2.0141 2.0054 1.9240
Int.   2B   1.9750 1.9450   2.0280 2.0167 2.1250
Ext. 21/8-6 UN 3A 0.0000 2.1250 2.1068 - 2.0167 2.0102 1.9266
Int.   3B   1.9646 1.9450   2.0251 2.0167 2.1250
Ext. 21/8-8 UN 2A 0.0024 2.1226 2.1076 2.1001 2.0414 2.0335 1.9738
Int.   2B   2.0150 1.9900   2.0540 2.0438 2.1250
Ext. 21/8-8 UN 3A 0.0000 2.1250 2.1100 - 2.0438 2.0379 1.9762
Int.   3B   2.0047 1.9900   2.0515 2.0438 2.1250
Ext. 21/8-12 UN 2A 0.0018 2.1232 2.1118 - 2.0691 2.0630 2.0240
Int.   2B   2.0530 2.0350   2.0788 2.0709 2.1250
Ext. 21/8-12 UN 3A 0.0000 2.1250 2.1136 - 2.0709 2.0664 2.0258
Int.   3B   2.0448 2.0350   2.0768 2.0709 2.1250
Ext. 21/8-16 UN 2A 0.0016 2.1234 2.1140 - 2.0828 2.0774 2.0489
Int.   2B   2.0710 2.0570   2.0914 2.0844 2.1250
Ext. 21/8-16 UN 3A 0.0000 2.1250 2.1156 - 2.0844 2.0803 2.0505
Int.   3B   2.0658 2.0570   2.0896 2.0844 2.1250
Ext. 21/8-20 UN 2A 0.0015 2.1235 2.1154 - 2.0910 2.0861 2.0640
Int.   2B   2.0820 2.0710   2.0989 2.0925 2.1250
Ext. 21/8-20 UN 3A 0.0000 2.1250 2.1169 - 2.0925 2.0888 2.0655
Int.   3B   2.0787 2.0710   2.0973 2.0925 2.1250
Ext. 23/16-16 UNS 2A 0.0016 2.1859 2.1765 - 2.1453 2.1399 2.1114
Int.   2B   2.1340 2.1200   2.1539 2.1469 2.1875
Ext. 23/16-16 UNS 3A 0.0000 2.1875 2.1781 - 2.1469 2.1428 2.1130
Int.   3B   2.1283 2.1200   2.1521 2.1469 2.1875
Ext. 21/4-41/2 UNC 1A 0.0029 2.2471 2.2141 - 2.1028 2.0882 1.9824
Int.   1B   2.0450 2.0090   2.1247 2.1057 2.2500
Ext. 21/4-41/2 UNC 2A 0.0029 2.2471 2.2251 2.2141 2.1028 2.0931 1.9824
Int.   2B   2.0450 2.0090   2.1183 2.1057 2.2500
Ext. 21/4-41/2 UNC 3A 0.0000 2.2500 2.2280 - 2.1057 2.0984 1.9853
Int.   3B   2.0361 2.0090   2.1152 2.1057 2.2500
Ext. 21/4-6 UN 2A 0.0026 2.2474 2.2292 - 2.1391 2.1303 2.0490
Int.   2B   2.1000 2.0700   2.1531 2.1417 2.2500
Ext. 21/4-6 UN 3A 0.0000 2.2500 2.2318 - 2.1417 2.1351 2.0516
Int.   3B   2.0896 2.0700   2.1502 2.1417 2.2500
Ext. 21/4-8 UN 2A 0.0024 2.2476 2.2326 2.2251 2.1664 2.1584 2.0988
Int.   2B   2.1400 2.1150   2.1792 2.1688 2.2500
Ext. 21/4-8 UN 3A 0.0000 2.2500 2.2350 - 2.1688 2.1628 2.1012
Int.   3B   2.1297 2.1150   2.1766 2.1688 2.2500
Ext. 21/4-10 UNS 2A 0.0020 2.2480 2.2351 - 2.1830 2.1765 2.1290
Int.   2B   2.1630 2.1420   2.1935 2.1850 2.2500
Ext. 21/4-12 UN 2A 0.0018 2.2482 2.2368 - 2.1941 2.1880 2.1490
Int.   2B   2.1780 2.1600   2.2038 2.1959 2.2500
Ext. 21/4-12 UN 3A 0.0000 2.2500 2.2386 - 2.1959 2.1914 2.1508
Int.   3B   2.1698 2.1600   2.2018 2.1959 2.2500
Ext. 21/4-14 UNS 2A 0.0017 2.2483 2.2380 - 2.2019 2.1962 2.1633
Int.   2B   2.1880 2.1730   2.2110 2.2036 2.2500
Ext. 21/4-16 UN 2A 0.0016 2.2484 2.2390 - 2.2078 2.2024 2.1739
Int.   2B   2.1960 2.1820   2.2164 2.2094 2.2500
Ext. 21/4-16 UN 3A 0.0000 2.2500 2.2406 - 2.2094 2.2053 2.1755
Int.   3B   2.1908 2.1820   2.2146 2.2094 2.2500
Ext. 21/4-18 UNS 2A 0.0015 2.2485 2.2398 - 2.2124 2.2073 2.1824
Int.   2B   2.2030 2.1900   2.2206 2.2139 2.2500
Ext. 21/4-20 UN 2A 0.0015 2.2485 2.2404 - 2.2160 2.2111 2.1890
Int.   2B   2.2070 2.1960   2.2239 2.2175 2.2500
Ext. 21/4-20 UN 3A 0.0000 2.2500 2.2419 - 2.2175 2.2137 2.1905
Int.   3B   2.2037 2.1960   2.2223 2.2175 2.2500
Ext. 25/16-16 UNS 2A 0.0017 2.3108 2.3014 - 2.2702 2.2647 2.2363
Int.   2B   2.2590 2.2450   2.2791 2.2719 2.3125
Ext. 25/16-16 UNS 3A 0.0000 2.3125 2.3031 - 2.2719 2.2678 2.2380
Int.   3B   2.2533 2.2450   2.2773 2.2719 2.3125
Ext. 23/8-6 UN 2A 0.0027 2.3723 2.3541 - 2.2640 2.2551 2.1739
Int.   2B   2.2260 2.1950   2.2782 2.2667 2.3750
Ext. 23/8-6 UN 3A 0.0000 2.3750 2.3568 - 2.2667 2.2601 2.1766
Int.   3B   2.2146 2.1950   2.2753 2.2667 2.3750
Ext. 23/8-8 UN 2A 0.0024 2.3726 2.3576 - 2.2914 2.2833 2.2238
Int.   2B   2.2650 2.2400   2.3043 2.2938 2.3750
Ext. 23/8-8 UN 3A 0.0000 2.3750 2.3600 - 2.2938 2.2878 2.2262
Int.   3B   2.2547 2.2400   2.3017 2.2938 2.3750
Ext. 23/8-12 UN 2A 0.0019 2.3731 2.3617 - 2.3190 2.3128 2.2739
Int.   2B   2.3030 2.2850   2.3290 2.3209 2.3750
Ext. 23/8-12 UN 3A 0.0000 2.3750 2.3636 - 2.3209 2.3163 2.2758
Int.   3B   2.2948 2.2850   2.3269 2.3209 2.3750
Ext. 23/8-16 UN 2A 0.0017 2.3733 2.3639 - 2.3327 2.3272 2.2988
Int.   2B   2.3210 2.3070   2.3416 2.3344 2.3750
Ext. 23/8-16 UN 3A 0.0000 2.3750 2.3656 - 2.3344 2.3303 2.3005
Int.   3B   2.3158 2.3070   2.3398 2.3344 2.3750
Ext. 23/8-20 UN 2A 0.0015 2.3735 2.3654 - 2.3410 2.3359 2.3140
Int.   2B   2.3320 2.3210   2.3491 2.3425 2.3750
Ext. 23/8-20 UN 3A 0.0000 2.3750 2.3669 - 2.3425 2.3387 2.3155
Int.   3B   2.3287 2.3210   2.3475 2.3425 2.3750
Ext. 27/16-16 UNS 2A 0.0017 2.4358 2.4264 - 2.3952 2.3897 2.3613
Int.   2B   2.3840 2.3700   2.4041 2.3969 2.4375
Ext. 27/16-16 UNS 3A 0.0000 2.4375 2.4281 - 2.3969 2.3928 2.3630
Int.   3B   2.3783 2.3700   2.4023 2.3969 2.4375
Ext. 21/2-4 UNC 1A 0.0031 2.4969 2.4612 - 2.3345 2.3190 2.1992
Int.   1B   2.2670 2.2290   2.3578 2.3376 2.5000
Ext. 21/2-4 UNC 2A 0.0031 2.4969 2.4731 2.4612 2.3345 2.3241 2.1992
Int.   2B   2.2670 2.2290   2.3511 2.3376 2.5000
Ext. 21/2-4 UNC 3A 0.0000 2.5000 2.4762 - 2.3376 2.3298 2.2023
Int.   3B   2.2594 2.2290   2.3477 2.3376 2.5000
Ext. 21/2-6 UN 2A 0.0027 2.4973 2.4791 - 2.3890 2.3800 2.2989
Int.   2B   2.3500 2.3200   2.4033 2.3917 2.5000
Ext. 21/2-6 UN 3A 0.0000 2.5000 2.4818 - 2.3917 2.3850 2.3016
Int.   3B   2.3396 2.3200   2.4004 2.3917 2.5000
Ext. 21/2-8 UN 2A 0.0024 2.4976 2.4826 2.4751 2.4164 2.4082 2.3488
Int.   2B   2.3900 2.3650   2.4294 2.4188 2.5000
Ext. 21/2-8 UN 3A 0.0000 2.5000 2.4850 - 2.4188 2.4127 2.3512
Int.   3B   2.3797 2.3650   2.4268 2.4188 2.5000
Ext. 21/2-10 UNS 2A 0.0020 2.4980 2.4851 - 2.4330 2.4263 2.3790
Int.   2B   2.4130 2.3920   2.4437 2.4350 2.5000
Ext. 21/2-12 UN 2A 0.0019 2.4981 2.4867 - 2.4440 2.4378 2.3989
Int.   2B   2.4280 2.4100   2.4540 2.4459 2.5000
Ext. 21/2-12 UN 3A 0.0000 2.5000 2.4886 - 2.4459 2.4413 2.4008
Int.   3B   2.4198 2.4100   2.4519 2.4459 2.5000
Ext. 21/2-14 UNS 2A 0.0017 2.4983 2.4880 - 2.4519 2.4461 2.4133
Int.   2B   2.4380 2.4230   2.4612 2.4536 2.5000
Ext. 21/2-16 UN 2A 0.0017 2.4983 2.4889 - 2.4577 2.4522 2.4238
Int.   2B   2.4460 2.4320   2.4666 2.4594 2.5000
Ext. 21/2-16 UN 3A 0.0000 2.5000 2.4906 - 2.4594 2.4553 2.4255
Int.   3B   2.4408 2.4320   2.4648 2.4594 2.5000
Ext. 21/2-18 UNS 2A 0.0016 2.4984 2.4897 - 2.4623 2.4570 2.4323
Int.   2B   2.4530 2.4400   2.4708 2.4639 2.5000
Ext. 21/2-20 UN 2A 0.0015 2.4985 2.4904 - 2.4660 2.4609 2.4390
Int.   2B   2.4570 2.4460   2.4741 2.4675 2.5000
Ext. 21/2-20 UN 3A 0.0000 2.5000 2.4919 - 2.4675 2.4637 2.4405
Int.   3B   2.4537 2.4460   2.4725 2.4675 2.5000
Ext. 25/8-6 UN 2A 0.0027 2.6223 2.6041 - 2.5140 2.5050 2.4239
Int.   2B   2.4750 2.4450   2.5285 2.5167 2.6250
Ext. 25/8-6 UN 3A 0.0000 2.6250 2.6068 - 2.5167 2.5099 2.4266
Int.   3B   2.4646 2.4450   2.5255 2.5167 2.6250
Ext. 25/8-8 UN 2A 0.0025 2.6225 2.6075 - 2.5413 2.5331 2.4737
Int.   2B   2.5150 2.4900   2.5545 2.5438 2.6250
Ext. 25/8-8 UN 3A 0.0000 2.6250 2.6100 - 2.5438 2.5376 2.4762
Int.   3B   2.5047 2.4900   2.5518 2.5438 2.6250
Ext. 25/8-12 UN 2A 0.0019 2.6231 2.6117 - 2.5690 2.5628 2.5239
Int.   2B   2.5530 2.5350   2.5790 2.5709 2.6250
Ext. 25/8-12 UN 3A 0.0000 2.6250 2.6136 - 2.5709 2.5663 2.5258
Int.   3B   2.5448 2.5350   2.5769 2.5709 2.6250
Ext. 25/8-16 UN 2A 0.0017 2.6233 2.6139 - 2.5827 2.5772 2.5488
Int.   2B   2.5710 2.5570   2.5916 2.5844 2.6250
Ext. 25/8-16 UN 3A 0.0000 2.6250 2.6156 - 2.5844 2.5803 2.5505
Int.   3B   2.5658 2.5570   2.5898 2.5844 2.6250
Ext. 25/8-20 UN 2A 0.0015 2.6235 2.6154 - 2.5910 2.5859 2.5640
Int.   2B   2.5820 2.5710   2.5991 2.5925 2.6250
Ext. 25/8-20 UN 3A 0.0000 2.6250 2.6169 - 2.5925 2.5887 2.5655
Int.   3B   2.5787 2.5710   2.5975 2.5925 2.6250
Ext. 23/4-4 UNC 1A 0.0032 2.7468 2.7111 - 2.5844 2.5686 2.4491
Int.   1B   2.5170 2.4790   2.6082 2.5876 2.7500
Ext. 23/4-4 UNC 2A 0.0032 2.7468 2.7230 2.7111 2.5844 2.5739 2.4491
Int.   2B   2.5170 2.4790   2.6013 2.5876 2.7500
Ext. 23/4-4 UNC 3A 0.0000 2.7500 2.7262 - 2.5876 2.5797 2.4523
Int.   3B   2.5094 2.4790   2.5979 2.5876 2.7500
Ext. 23/4-6 UN 2A 0.0027 2.7473 2.7291 - 2.6390 2.6299 2.5489
Int.   2B   2.6000 2.5700   2.6536 2.6417 2.7500
Ext. 23/4-6 UN 3A 0.0000 2.7500 2.7318 - 2.6417 2.6349 2.5516
Int.   3B   2.5896 2.5700   2.6506 2.6417 2.7500
Ext. 23/4-8 UN 2A 0.0025 2.7475 2.7325 2.7250 2.6663 2.6580 2.5987
Int.   2B   2.6400 2.6150   2.6796 2.6688 2.7500
Ext. 23/4-8 UN 3A 0.0000 2.7500 2.7350 - 2.6688 2.6625 2.6012
Int.   3B   2.6297 2.6150   2.6769 2.6688 2.7500
Ext. 23/4-10 UNS 2A 0.0020 2.7480 2.7351 - 2.6830 2.6763 2.6290
Int.   2B   2.6630 2.6420   2.6937 2.6850 2.7500
Ext. 23/4-12 UN 2A 0.0019 2.7481 2.7367 - 2.6940 2.6878 2.6489
Int.   2B   2.6780 2.6600   2.7040 2.6959 2.7500
Ext. 23/4-12 UN 3A 0.0000 2.7500 2.7386 - 2.6959 2.6913 2.6508
Int.   3B   2.6698 2.6600   2.7019 2.6959 2.7500
Ext. 23/4-14 UNS 2A 0.0017 2.7483 2.7380 - 2.7019 2.6961 2.6633
Int.   2B   2.6880 2.6730   2.7112 2.7036 2.7500
Ext. 23/4-16 UN 2A 0.0017 2.7483 2.7389 - 2.7077 2.7022 2.6738
Int.   2B   2.6960 2.6820   2.7166 2.7094 2.7500
Ext. 23/4-16 UN 3A 0.0000 2.7500 2.7406 - 2.7094 2.7053 2.6755
Int.   3B   2.6908 2.6820   2.7148 2.7094 2.7500
Ext. 23/4-18 UNS 2A 0.0016 2.7484 2.7397 - 2.7123 2.7070 2.6832
Int.   2B   2.7030 2.6900   2.7208 2.7139 2.7500
Ext. 23/4-20 UN 2A 0.0015 2.7485 2.7404 - 2.7160 2.7109 2.6890
Int.   2B   2.7070 2.6960   2.7241 2.7175 2.7500
Ext. 23/4-20 UN 3A 0.0000 2.7500 2.7419 - 2.7175 2.7137 2.6905
Int.   3B   2.7037 2.6960   2.7225 2.7175 2.7500
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
Next
Top of Page
Home  Membership  About Us  Privacy  Disclaimer  Contact  Advertise

Copyright © 2009 eFunda, Inc.