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 0.7500 0.7500 0.7500 0.7500 0.8125 0.8125 0.8125 0.8125 0.8125 0.8125 0.8125 0.8125 0.8125 0.8125 0.8750 0.8750 0.8750 0.8750 0.8750 0.8750 0.8750 0.8750 0.8750 0.8750 0.8750 0.8750 0.8750 0.8750
Class
2A 0.0012 0.7488 0.7423 3A 0.0000 0.7500 0.7435 2A 0.0011 0.7489 0.7429 3A 0.0000 0.7500 0.7440 2A 0.0017 0.8108 0.7994 3A 0.0000 0.8125 0.8011 2A 0.0015 0.8110 0.8016 3A 0.0000 0.8125 0.8031 2A 0.0013 0.8112 0.8031 3A 0.0000 0.8125 0.8044 2A 0.0012 0.8113 0.8048 3A 0.0000 0.8125 0.8060 2A 0.0011 0.8114 0.8054 3A 0.0000 0.8125 0.8065 1A 0.0019 0.8731 0.8523 3A 0.0000 0.8750 0.8611 2A 0.0018 0.8732 0.8603 2A 0.0017 0.8733 0.8619 3A 0.0000 0.8750 0.8636 1A 0.0016 0.8734 0.8579 2A 0.0016 0.8734 0.8631 3A 0.0000 0.8750 0.8647 2A 0.0015 0.8735 0.8641 3A 0.0000 0.8750 0.8656 2A 0.0014 0.8736 0.8649 2A 0.0013 0.8737 0.8656 3A 0.0000 0.8750 0.8669
— 0.7256 0.7218 — 0.7268 0.7239 — 0.7286 0.7250 — 0.7297 0.7270 — 0.7567 0.7511 — 0.7584 0.7542 — 0.7704 0.7655 — 0.7719 0.7682 — 0.7787 0.7743 — 0.7800 0.7767 — 0.7881 0.7842 — 0.7893 0.7864 — 0.7911 0.7874 — 0.7922 0.7894 — 0.8009 0.7914 — 0.8028 0.7981 — 0.8082 0.8021 — 0.8192 0.8136 — 0.8209 0.8167 — 0.8270 0.8189 — 0.8270 0.8216 — 0.8286 0.8245 — 0.8329 0.8280 — 0.8344 0.8307 — 0.8375 0.8328 — 0.8412 0.8367 — 0.8425 0.8391
0.7063 0.7075 0.7117 0.7128 0.7116 0.7133 0.7366 0.7381 0.7517 0.7530 0.7688 0.7700 0.7742 0.7753 0.7408 0.7408 0.7427 0.7541 0.7741 0.7758 0.7883 0.7883 0.7899 0.7991 0.8006 0.8074 0.8142 0.8155
2B 0.711
0.720
0.7268 0.7318 0.7268 0.7305 0.7297 0.7344 0.7297 0.7333 0.7584 0.7656 0.7584 0.7638 0.7719 0.7783 0.7719 0.7767 0.7800 0.7858 0.7800 0.7843 0.7893 0.7943 0.7893 0.7931 0.7922 0.7970 0.7922 0.7958 0.8028 0.8151 0.8028 0.8110 0.8028 0.8089 0.8100 0.8179 0.8209 0.8282 0.8209 0.8264 0.8286 0.8392 0.8286 0.8356 0.8286 0.8339 0.8344 0.8408 0.8344 0.8392 0.8389 0.8450 0.8425 0.8483 0.8425 0.8469
3 ∕ 4 -28 UN
3B 0.7110 0.7176
2B 0.716
0.724
3 ∕ 4 -32 UN
3B 0.7160 0.7219
2B 0.722
0.740
13 ∕ 16 -12 UN
3B 0.7220 0.7329
2B 0.745
0.759
13 ∕ 16 -16 UN
3B 0.7450 0.7534
2B 0.758
0.770
13 ∕ 16 -20 UNEF
3B 0.7580 0.7661
2B 0.774
0.782
13 ∕ 16 -28 UN
3B 0.7740 0.7801
2B 0.779
0.786
13 ∕ 16 -32 UN
3B 0.7790 0.7844
1B 0.755 2B 0.755 2B 0.767 2B 0.785 1B 0.798 2B 0.798
0.778 0.778 0.788 0.803 0.813 0.813
7 ∕ 8 -9 UNC
2A 0.0019 0.8731 0.8592 0.8523 0.8009 0.7946
3B 0.7550 0.7681
7 ∕ 8 -10 UNS 7 ∕ 8 -12 UN
3B 0.7850 0.7952
7 ∕ 8 -14 UNF
3B 0.7980 0.8067
2B 0.807
0.821
7 ∕ 8 -16 UN
3B 0.8070 0.8159
2B 0.815 2B 0.821
0.828 0.832
7 ∕ 8 -18 UNS 7 ∕ 8 -20 UNEF
3B 0.8210 0.8286
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