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
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 2.0000 2.0000 2.0000 2.0000 2.0000 2.0000 2.0000 2.0000 2.0000 2.0000 2.0000 2.0000 2.0000 2.0000 2.0000 2.0000 2.0625 2.0625 2.1250 2.1250 2.1250 2.1250 2.1250 2.1250 2.1250 2.1250 2.1250 2.1250
Class
1A 0.0029 1.9971 1.9641
— 1.8528 1.8385
1.7325 1.7325 1.7354 1.7989 1.8015 1.8489 1.8512 1.8789 1.8990 1.9008 1.9132 1.9240 1.9256 1.9323 1.9390 1.9405 1.9865 1.9881 1.9239 1.9265 1.9738 1.9762 2.0240 2.0258 2.0490 2.0506 2.0640 2.0655
1B 1.759 2B 1.759
1.795 1.795
1.8557 1.8743 1.8557 1.8681 1.8557 1.8650 1.8917 1.9028 1.8917 1.9000 1.9188 1.9289 1.9188 1.9264 1.9350 1.9435 1.9459 1.9538 1.9459 1.9518 1.9536 1.9610 1.9594 1.9664 1.9594 1.9646 1.9639 1.9706 1.9675 1.9739 1.9675 1.9723 2.0219 2.0289 2.0219 2.0272 2.0167 2.0280 2.0167 2.0251 2.0438 2.0540 2.0438 2.0515 2.0709 2.0788 2.0709 2.0768 2.0844 2.0914 2.0844 2.0897 2.0925 2.0990 2.0925 2.0973
2-4 1 ∕ 2 UNC
2A 0.0029 1.9971 1.9751 1.9641 1.8528 1.8433
3A 0.0000 2.0000 1.9780 2A 0.0026 1.9974 1.9792 3A 0.0000 2.0000 1.9818 3A 0.0000 2.0000 1.9850 2A 0.0020 1.9980 1.9851 2A 0.0018 1.9982 1.9868 3A 0.0000 2.0000 1.9886 2A 0.0017 1.9983 1.9880 2A 0.0016 1.9984 1.9890 3A 0.0000 2.0000 1.9906 2A 0.0015 1.9985 1.9898 2A 0.0015 1.9985 1.9904 3A 0.0000 2.0000 1.9919 2A 0.0016 2.0609 2.0515 3A 0.0000 2.0625 2.0531 2A 0.0026 2.1224 2.1042 3A 0.0000 2.1250 2.1068 3A 0.0000 2.1250 2.1100 2A 0.0018 2.1232 2.1118 3A 0.0000 2.1250 2.1136 2A 0.0016 2.1234 2.1140 3A 0.0000 2.1250 2.1156 2A 0.0015 2.1235 2.1154 3A 0.0000 2.1250 2.1169
— 1.8557 1.8486 — 1.8891 1.8805 — 1.8917 1.8853 — 1.9188 1.9130 — 1.9330 1.9265 — 1.9441 1.9380 — 1.9459 1.9414 — 1.9519 1.9462 — 1.9578 1.9524 — 1.9594 1.9554 — 1.9624 1.9573 — 1.9660 1.9611 — 1.9675 1.9638 — 2.0203 2.0149 — 2.0219 2.0179 — 2.0141 2.0054 — 2.0167 2.0102 — 2.0438 2.0379 — 2.0691 2.0630 — 2.0709 2.0663 — 2.0828 2.0774 — 2.0844 2.0803 — 2.0910 2.0860 — 2.0925 2.0888
3B 1.7590 1.7861
2-6 UN
2B 1.820
1.850
3B 1.8200 1.8396
2-8 UN
2A 0.0023 1.9977 1.9827 1.9752 1.9165 1.9087
2B 1.865
1.890
3B 1.8650 1.8797
2-10 UNS 2-12 UN 2-14 UNS 2-16 UN 2-18 UNS 2-20 UN
2B 1.892 2B 1.910 2B 1.923 2B 1.932 2B 1.940 2B 1.946
1.913 1.928 1.938 1.946 1.953 1.957
3B 1.9100 1.9198
3B 1.9320 1.9409
3B 1.9460 1.9536
2B 1.995
2.009
2 1 ∕ 16 -16 UNS
3B 1.9950 2.0034
2B 1.945
1.975
2 1 ∕ 8 -6 UN
3B 1.9450 1.9646
2A 0.0024 2.1226 2.1076 2.1001 2.0414 2.0335
2B 1.990
2.015
2 1 ∕ 8 -8 UN
3B 1.9900 2.0047
2B 2.035
2.053
2 1 ∕ 8 -12 UN
3B 2.0350 2.0448
2B 2.057
2.071
2 1 ∕ 8 -16 UN
3B 2.0570 2.0659
2B 2.071
2.082
2 1 ∕ 8 -20 UN
3B 2.0710 2.0786
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