Table 3. Standard Series and Selected Combinations—Unified Screw Threads Table 3. (Continued) Standard Series and Selected Combinations—Unified Screw Threads
External b
Internal b
Nominal Size, Threads per Inch, and Series Designation a 1-20 UNEF
Major Diameter
UNR Minor Dia., c Max (Ref.)
Major Diameter
Pitch Diameter
Minor Diameter
Pitch Diameter
Allow ance
Max d
Min e
Max d
Class
Min
Min
Min
Max
Min
Max
Min 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0625 1.0625 1.0625 1.0625 1.0625 1.0625 1.0625 1.0625 1.0625 1.0625 1.0625 1.0625 1.1250 1.1250 1.1250 1.1250 1.1250 1.1250 1.1250 1.1250 1.1250
Class
2A 0.0014 0.9986 0.9905 3A 0.0000 1.0000 0.9919 2A 0.0013 0.9987 0.9915 2A 0.0012 0.9988 0.9921 2A 0.0012 0.9988 0.9923 3A 0.0000 1.0000 0.9935 2A 0.0011 0.9989 0.9929 3A 0.0000 1.0000 0.9940 2A 0.0020 1.0605 1.0455 3A 0.0000 1.0625 1.0475 2A 0.0017 1.0608 1.0494 3A 0.0000 1.0625 1.0511 2A 0.0015 1.0610 1.0516 3A 0.0000 1.0625 1.0531 2A 0.0014 1.0611 1.0524 3A 0.0000 1.0625 1.0538 2A 0.0014 1.0611 1.0530 3A 0.0000 1.0625 1.0544 2A 0.0012 1.0613 1.0548 3A 0.0000 1.0625 1.0560 1A 0.0022 1.1228 1.0982
— 0.9661 0.9616 — 0.9675 0.9641 — 0.9716 0.9674 — 0.9747 0.9707 — 0.9756 0.9716 — 0.9768 0.9738 — 0.9786 0.9748 — 0.9797 0.9769 — 0.9793 0.9725 — 0.9813 0.9762 — 1.0067 1.0010 — 1.0084 1.0041 — 1.0204 1.0154 — 1.0219 1.0181 — 1.0250 1.0202 — 1.0264 1.0228 — 1.0286 1.0240 — 1.0300 1.0266 — 1.0381 1.0341 — 1.0393 1.0363 — 1.0300 1.0191
0.9391 0.9405 0.9491 0.9547 0.9562 0.9575 0.9617 0.9628 0.9117 0.9137 0.9616 0.9633 0.9866 0.9881 0.9949 0.9963 1.0016 1.0030 1.0188 1.0200 0.9527 0.9527 0.9549 0.9741 0.9762 1.0040 1.0240 1.0240 1.0258
2B 0.946
0.957
0.9675 0.9734 0.9675 0.9719 0.9729 0.9784 0.9759 0.9811 0.9768 0.9820 0.9768 0.9807 0.9797 0.9846 0.9797 0.9834 0.9813 0.9902 0.9813 0.9880 1.0084 1.0158 1.0084 1.0139 1.0219 1.0284 1.0219 1.0268 1.0264 1.0326 1.0264 1.0311 1.0300 1.0359 1.0300 1.0345 1.0393 1.0445 1.0393 1.0432 1.0322 1.0463 1.0322 1.0416 1.0322 1.0393 1.0438 1.0528 1.0438 1.0505 1.0600 1.0681 1.0709 1.0826 1.0709 1.0787 1.0709 1.0768
3B 0.9460 0.9536
1-24 UNS 1-27 UNS 1-28 UN
2B 0.955 2B 0.960 2B 0.961
0.965 0.969 0.970
3B 0.9610 0.9676
1-32 UN
2B 0.966
0.974
3B 0.9660 0.9719
2B 0.927
0.952
1 1 ∕ 16 -8 UN
3B 0.9270 0.9422
2B 0.972
0.990
1 1 ∕ 16 -12 UN
3B 0.9720 0.9823
2B 0.995
1.009
1 1 ∕ 16 -16 UN
3B 0.9950 1.0034
2B 1.002
1.015
1 1 ∕ 16 -18 UNEF
3B 1.0020 1.0105
2B 1.008
1.020
1 1 ∕ 16 -20 UN
3B 1.0080 1.0161
2B 1.024
1.032
1 1 ∕ 16 -28 UN
3B 1.0240 1.0301
1B 0.970 2B 0.970
0.998 0.998
1 1 ∕ 8 -7 UNC
2A 0.0022 1.1228 1.1064 1.0982 1.0300 1.0228
3A 0.0000 1.1250 1.1086
— 1.0322 1.0268
3B 0.9700 0.9875
2A 0.0021 1.1229 1.1079 1.1004 1.0417 1.0348
2B 0.990
1.015
1 1 ∕ 8 -8 UN
3A 0.0000 1.1250 1.1100 2A 0.0019 1.1231 1.1102 1A 0.0018 1.1232 1.1060 2A 0.0018 1.1232 1.1118 3A 0.0000 1.1250 1.1136
— 1.0438 1.0386 — 1.0581 1.0519 — 1.0691 1.0601 — 1.0691 1.0631 — 1.0709 1.0664
3B 0.9900 1.0047
2B 1.017 1B 1.035 2B 1.035
1.038 1.053 1.053
1 1 ∕ 8 -10 UNS 1 1 ∕ 8 -12 UNF
3B 1.0350 1.0448
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