engineering fundamentals Unified Screw Threads, Standard Series
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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. 5/8-11 UNC 1A 0.0016 0.6234 0.6052 - 0.5644 0.5561 0.5152
Int.   1B   0.5460 0.5270   0.5767 0.5660 0.6250
Ext. 5/8-11 UNC 2A 0.0016 0.6234 0.6113 0.6052 0.5644 0.5589 0.5152
Int.   2B   0.5460 0.5270   0.5732 0.5660 0.6250
Ext. 5/8-11 UNC 3A 0.0000 0.6250 0.6129 - 0.5660 0.5619 0.5168
Int.   3B   0.5391 0.5270   0.5714 0.5660 0.6250
Ext. 5/8-12 UN 2A 0.0016 0.6234 0.6120 - 0.5693 0.5639 0.5242
Int.   2B   0.5530 0.5350   0.5780 0.5709 0.6250
Ext. 5/8-12 UN 3A 0.0000 0.6250 0.6136 - 0.5709 0.5668 0.5258
Int.   3B   0.5463 0.5350   0.5762 0.5709 0.6250
Ext. 5/8-14 UNS 2A 0.0015 0.6235 0.6132 - 0.5771 0.5720 0.5385
Int.   2B   0.5640 0.5480   0.5852 0.5786 0.6250
Ext. 5/8-16 UN 2A 0.0014 0.6236 0.6142 - 0.5830 0.5782 0.5491
Int.   2B   0.5710 0.5570   0.5906 0.5844 0.6250
Ext. 5/8-16 UN 3A 0.0000 0.6250 0.6156 - 0.5844 0.5808 0.5505
Int.   3B   0.5662 0.5570   0.5890 0.5844 0.6250
Ext. 5/8-18 UNF 1A 0.0014 0.6236 0.6105 - 0.5875 0.5805 0.5575
Int.   1B   0.5780 0.5650   0.5980 0.5889 0.6250
Ext. 5/8-18 UNF 2A 0.0014 0.6236 0.6149 - 0.5875 0.5828 0.5575
Int.   2B   0.5780 0.5650   0.5949 0.5889 0.6250
Ext. 5/8-18 UNF 3A 0.0000 0.6250 0.6163 - 0.5889 0.5854 0.5589
Int.   3B   0.5730 0.5650   0.5934 0.5889 0.6250
Ext. 5/8-20 UN 2A 0.0013 0.6237 0.6156 - 0.5912 0.5869 0.5642
Int.   2B   0.5820 0.5710   0.5981 0.5925 0.6250
Ext. 5/8-20 UN 3A 0.0000 0.6250 0.6169 - 0.5925 0.5893 0.5655
Int.   3B   0.5787 0.5710   0.5967 0.5925 0.6250
Ext. 5/8-24 UNEF 2A 0.0012 0.6238 0.6166 - 0.5967 0.5927 0.5742
Int.   2B   0.5900 0.5800   0.6031 0.5979 0.6250
Ext. 5/8-24 UNEF 3A 0.0000 0.6250 0.6178 - 0.5979 0.5949 0.5754
Int.   3B   0.5869 0.5800   0.6018 0.5979 0.6250
Ext. 5/8-27 UNS 2A 0.0011 0.6239 0.6172 - 0.5998 0.5960 0.5798
Int.   2B   0.5940 0.5850   0.6059 0.6009 0.6250
Ext. 5/8-28 UN 2A 0.0011 0.6239 0.6174 - 0.6007 0.5969 0.5813
Int.   2B   0.5950 0.5860   0.6067 0.6018 0.6250
Ext. 5/8-28 UN 3A 0.0000 0.6250 0.6185 - 0.6018 0.5990 0.5824
Int.   3B   0.5926 0.5860   0.6055 0.6018 0.6250
Ext. 5/8-32 UN 2A 0.0011 0.6239 0.6179 - 0.6036 0.6000 0.5867
Int.   2B   0.5990 0.5910   0.6093 0.6047 0.6250
Ext. 5/8-32 UN 3A 0.0000 0.6250 0.6190 - 0.6047 0.6020 0.5878
Int.   3B   0.5969 0.5910   0.6082 0.6047 0.6250
Ext. 11/16-12 UN 2A 0.0016 0.6859 0.6745 - 0.6318 0.6264 0.5867
Int.   2B   0.6150 0.5970   0.6405 0.6334 0.6875
Ext. 11/16-12 UN 3A 0.0000 0.6875 0.6761 - 0.6334 0.6293 0.5883
Int.   3B   0.6085 0.5970   0.6387 0.6334 0.6875
Ext. 11/16-16 UN 2A 0.0014 0.6861 0.6767 - 0.6455 0.6407 0.6116
Int.   2B   0.6340 0.6200   0.6531 0.6469 0.6875
Ext. 11/16-16 UN 3A 0.0000 0.6875 0.6781 - 0.6469 0.6433 0.6130
Int.   3B   0.6284 0.6200   0.6515 0.6469 0.6875
Ext. 11/16-20 UN 2A 0.0013 0.6862 0.6781 - 0.6537 0.6494 0.6267
Int.   2B   0.6450 0.6330   0.6606 0.6550 0.6875
Ext. 11/16-20 UN 3A 0.0000 0.6875 0.6794 - 0.6550 0.6518 0.6280
Int.   3B   0.6412 0.6330   0.6592 0.6550 0.6875
Ext. 11/16-24 UNEF 2A 0.0012 0.6863 0.6791 - 0.6592 0.6552 0.6367
Int.   2B   0.6520 0.6420   0.6656 0.6604 0.6875
Ext. 11/16-24 UNEF 3A 0.0000 0.6875 0.6803 - 0.6604 0.6574 0.6379
Int.   3B   0.6494 0.6420   0.6643 0.6604 0.6875
Ext. 11/16-28 UN 2A 0.0011 0.6864 0.6799 - 0.6632 0.6594 0.6438
Int.   2B   0.6570 0.6490   0.6692 0.6643 0.6875
Ext. 11/16-28 UN 3A 0.0000 0.6875 0.6810 - 0.6643 0.6615 0.6449
Int.   3B   0.6551 0.6490   0.6680 0.6643 0.6875
Ext. 11/16-32 UN 2A 0.0011 0.6864 0.6804 - 0.6661 0.6625 0.6492
Int.   2B   0.6610 0.6540   0.6718 0.6672 0.6875
Ext. 11/16-32 UN 3A 0.0000 0.6875 0.6815 - 0.6672 0.6645 0.6503
Int.   3B   0.6594 0.6540   0.6707 0.6672 0.6875
Ext. 3/4-10 UNC 1A 0.0018 0.7482 0.7288 - 0.6832 0.6744 0.6291
Int.   1B   0.6630 0.6420   0.6965 0.6850 0.7500
Ext. 3/4-10 UNC 2A 0.0018 0.7482 0.7353 0.7288 0.6832 0.6773 0.6291
Int.   2B   0.6630 0.6420   0.6927 0.6850 0.7500
Ext. 3/4-10 UNC 3A 0.0000 0.7500 0.7371 - 0.6850 0.6806 0.6309
Int.   3B   0.6545 0.6420   0.6907 0.6850 0.7500
Ext. 3/4-12 UN 2A 0.0017 0.7483 0.7369 - 0.6942 0.6887 0.6491
Int.   2B   0.6780 0.6600   0.7031 0.6959 0.7500
Ext. 3/4-12 UN 3A 0.0000 0.7500 0.7386 - 0.6959 0.6918 0.6508
Int.   3B   0.6707 0.6600   0.7103 0.6959 0.7500
Ext. 3/4-14 UNS 2A 0.0015 0.7485 0.7382 - 0.7021 0.6970 0.6635
Int.   2B   0.6880 0.6730   0.7103 0.7036 0.7500
Ext. 3/4-16 UNF 1A 0.0015 0.7485 0.7343 - 0.7079 0.7004 0.6740
Int.   1B   0.6960 0.6820   0.7192 0.7094 0.7500
Ext. 3/4-16 UNF 2A 0.0015 0.7485 0.7391 - 0.7079 0.7029 0.6740
Int.   2B   0.6960 0.6820   0.7159 0.7094 0.7500
Ext. 3/4-16 UNF 3A 0.0000 0.7500 0.7406 - 0.7094 0.7056 0.6755
Int.   3B   0.6908 0.6820   0.7143 0.7094 0.7500
Ext. 3/4-18 UNS 2A 0.0014 0.7486 0.7399 - 0.7125 0.7079 0.6825
Int.   2B   0.7030 0.6900   0.7199 0.7139 0.7500
Ext. 3/4-20 UNEF 2A 0.0013 0.7487 0.7406 - 0.7162 0.7118 0.6892
Int.   2B   0.7070 0.6960   0.7232 0.7175 0.7500
Ext. 3/4-20 UNEF 3A 0.0000 0.7500 0.7419 - 0.7175 0.7142 0.6905
Int.   3B   0.7037 0.6960   0.7218 0.7175 0.7500
Ext. 3/4-24 UNS 2A 0.0012 0.7488 0.7416 - 0.7217 0.7176 0.6992
Int.   2B   0.7150 0.7050   0.7282 0.7229 0.7500
Ext. 3/4-27 UNS 2A 0.0012 0.7488 0.7421 - 0.7247 0.7208 0.7047
Int.   2B   0.7190 0.7100   0.7310 0.7259 0.7500
Ext. 3/4-28 UN 2A 0.0012 0.7488 0.7423 - 0.7256 0.7218 0.7062
Int.   2B   0.7200 0.7110   0.7318 0.7268 0.7500
Ext. 3/4-28 UN 3A 0.0000 0.7500 0.7435 - 0.7268 0.7239 0.7074
Int.   3B   0.7176 0.7110   0.7305 0.7268 0.7500
Ext. 3/4-32 UN 2A 0.0011 0.7489 0.7429 - 0.7286 0.7250 0.7114
Int.   2B   0.7240 0.7160   0.7344 0.7297 0.7500
Ext. 3/4-32 UN 3A 0.0000 0.7500 0.7440 - 0.7297 0.7270 0.7128
Int.   3B   0.7219 0.7160   0.7333 0.7297 0.7500
Ext. 13/16-12 UN 2A 0.0017 0.8108 0.7994 - 0.7567 0.7512 0.7116
Int.   2B   0.7400 0.7220   0.7656 0.7584 0.8125
Ext. 13/16-12 UN 3A 0.0000 0.8125 0.8011 - 0.7584 0.7543 0.7133
Int.   3B   0.7329 0.7220   0.7638 0.7584 0.8125
Ext. 13/16-16 UN 2A 0.0015 0.8110 0.8016 - 0.7704 0.7655 0.7365
Int.   2B   0.7590 0.7450   0.7782 0.7719 0.8125
Ext. 13/16-16 UN 3A 0.0000 0.8125 0.8031 - 0.7719 0.7683 0.7380
Int.   3B   0.7533 0.7450   0.7766 0.7719 0.8125
Ext. 13/16-20 UNEF 2A 0.0013 0.8112 0.8031 - 0.7787 0.7743 0.7517
Int.   2B   0.7700 0.7580   0.7857 0.7800 0.8125
Ext. 13/16-20 UNEF 3A 0.0000 0.8125 0.8044 - 0.7800 0.7767 0.7530
Int.   3B   0.7662 0.7580   0.7843 0.7800 0.8125
Ext. 13/16-28 UN 2A 0.0012 0.8113 0.8048 - 0.7881 0.7843 0.7687
Int.   2B   0.7820 0.7740   0.7943 0.7893 0.8125
Ext. 13/16-28 UN 3A 0.0000 0.8125 0.8060 - 0.7893 0.7864 0.7699
Int.   3B   0.7801 0.7740   0.7930 0.7893 0.8125
Ext. 13/16-32 UN 2A 0.0011 0.8114 0.8054 - 0.7911 0.7875 0.7742
Int.   2B   0.7860 0.7790   0.7969 0.7922 0.8125
Ext. 13/16-32 UN 3A 0.0000 0.8125 0.8065 - 0.7922 0.7895 0.7753
Int.   3B   0.7844 0.7790   0.7958 0.7922 0.8125
Ext. 7/8-9 UNC 1A 0.0019 0.8731 0.8523 - 0.8009 0.7914 0.7408
Int.   1B   0.7780 0.7550   0.8151 0.8028 0.8750
Ext. 7/8-9 UNC 2A 0.0019 0.8731 0.8592 0.8523 0.8009 0.7946 0.7408
Int.   2B   0.7780 0.7550   0.8110 0.8028 0.8750
Ext. 7/8-9 UNC 3A 0.0000 0.8750 0.8611 - 0.8028 0.7981 0.7427
Int.   3B   0.7681 0.7550   0.8089 0.8028 0.8750
Ext. 7/8-10 UNS 2A 0.0018 0.8732 0.8603 - 0.8082 0.8022 0.7542
Int.   2B   0.7880 0.7670   0.8178 0.8100 0.8750
Ext. 7/8-12 UN 2A 0.0017 0.8733 0.8619 - 0.8192 0.8137 0.7741
Int.   2B   0.8030 0.7850   0.8281 0.8209 0.8750
Ext. 7/8-12 UN 3A 0.0000 0.8750 0.8636 - 0.8209 0.8168 0.7758
Int.   3B   0.7948 0.7850   0.8263 0.8209 0.8750
Ext. 7/8-14 UNF 1A 0.0016 0.8734 0.8579 - 0.8270 0.8189 0.7884
Int.   1B   0.8140 0.7980   0.8392 0.8286 0.8750
Ext. 7/8-14 UNF 2A 0.0016 0.8734 0.8631 - 0.8270 0.8216 0.7884
Int.   2B   0.8140 0.7980   0.8356 0.8286 0.8750
Ext. 7/8-14 UNF 3A 0.0000 0.8750 0.8647 - 0.8286 0.8245 0.7900
Int.   3B   0.8068 0.7980   0.8339 0.8286 0.8750
Ext. 7/8-16 UN 2A 0.0015 0.8735 0.8641 - 0.8329 0.8280 0.7900
Int.   2B   0.8210 0.8070   0.8407 0.8344 0.8750
Ext. 7/8-16 UN 3A 0.0000 0.8750 0.8656 - 0.8344 0.8308 0.8005
Int.   3B   0.8158 0.8070   0.8391 0.8344 0.8750
Ext. 7/8-18 UNS 2A 0.0014 0.8736 0.8649 - 0.8375 0.8329 0.8075
Int.   2B   0.8280 0.8150   0.8449 0.8389 0.8750
Ext. 7/8-20 UNEF 2A 0.0013 0.8737 0.8656 - 0.8412 0.8368 0.8142
Int.   2B   0.8320 0.8210   0.8482 0.8425 0.8750
Ext. 7/8-20 UNEF 3A 0.0000 0.8750 0.8669 - 0.8425 0.8392 0.8155
Int.   3B   0.8287 0.8210   0.8468 0.8425 0.8750
Ext. 7/8-24 UNS 2A 0.0012 0.8738 0.8666 - 0.8467 0.8426 0.8242
Int.   2B   0.8400 0.8300   0.8532 0.8479 0.8750
Ext. 7/8-27 UNS 2A 0.0012 0.8738 0.8671 - 0.8497 0.8458 0.8297
Int.   2B   0.8440 0.8350   0.8560 0.8509 0.8750
Ext. 7/8-28 UN 2A 0.0012 0.8738 0.8673 - 0.8506 0.8468 0.8312
Int.   2B   0.8450 0.8360   0.8568 0.8518 0.8750
Ext. 7/8-28 UN 3A 0.0000 0.8750 0.8685 - 0.8518 0.8489 0.8324
Int.   3B   0.8426 0.8360   0.8555 0.8518 0.8750
Ext. 7/8-32 UN 2A 0.0011 0.8739 0.8679 - 0.8536 0.8500 0.8367
Int.   2B   0.8490 0.8410   0.8594 0.8547 0.8750
Ext. 7/8-32 UN 3A 0.0000 0.8750 0.8690 - 0.8547 0.8520 0.8378
Int.   3B   0.8469 0.8410   0.8583 0.8547 0.8750
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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