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 0.5625 0.5625 0.5625 0.5625 0.5625 0.5625 0.5625 0.5625 0.5625 0.6250 0.6250 0.6250 0.6250 0.6250 0.6250 0.6250 0.6250 0.6250 0.6250 0.6250 0.6250 0.6250 0.6250 0.6250 0.6250 0.6250 0.6250
Class
2A 0.0013 0.5612 0.5531 3A 0.0000 0.5625 0.5544 2A 0.0012 0.5613 0.5541 3A 0.0000 0.5625 0.5553 2A 0.0011 0.5614 0.5547 2A 0.0011 0.5614 0.5549 3A 0.0000 0.5625 0.5560 2A 0.0011 0.5614 0.5554 3A 0.0000 0.5625 0.5565 1A 0.0017 0.6233 0.6051 3A 0.0000 0.6250 0.6129 2A 0.0016 0.6234 0.6120 3A 0.0000 0.6250 0.6136 2A 0.0015 0.6235 0.6132 2A 0.0014 0.6236 0.6142 3A 0.0000 0.6250 0.6156 1A 0.0014 0.6236 0.6105 2A 0.0014 0.6236 0.6149 3A 0.0000 0.6250 0.6163 2A 0.0013 0.6237 0.6156 3A 0.0000 0.6250 0.6169 2A 0.0012 0.6238 0.6166 3A 0.0000 0.6250 0.6178 2A 0.0011 0.6239 0.6172 2A 0.0011 0.6239 0.6174 3A 0.0000 0.6250 0.6185
— 0.5287 0.5244 — 0.5300 0.5268 — 0.5342 0.5302 — 0.5354 0.5324 — 0.5373 0.5335 — 0.5382 0.5345 — 0.5393 0.5365 — 0.5411 0.5376 — 0.5422 0.5396 — 0.5643 0.5560 — 0.5660 0.5619 — 0.5693 0.5639 — 0.5709 0.5668 — 0.5771 0.5720 — 0.5830 0.5782 — 0.5844 0.5808 — 0.5875 0.5805 — 0.5875 0.5828 — 0.5889 0.5854 — 0.5912 0.5869 — 0.5925 0.5893 — 0.5967 0.5927 — 0.5979 0.5949 — 0.5998 0.5960 — 0.6007 0.5969 — 0.6018 0.5990
0.5017 0.5030 0.5117 0.5129 0.5173 0.5189 0.5200 0.5242 0.5253 0.5150 0.5150 0.5167 0.5242 0.5258 0.5384 0.5492 0.5506 0.5574 0.5574 0.5588 0.5642 0.5655 0.5742 0.5754 0.5798 0.5814 0.5825
2B 0.508
0.520
0.5300 0.5356 0.5300 0.5342 0.5354 0.5405 0.5354 0.5393 0.5384 0.5433 0.5393 0.5441 0.5393 0.5429 0.5422 0.5468 0.5422 0.5456 0.5660 0.5767 0.5660 0.5732 0.5660 0.5714 0.5709 0.5780 0.5709 0.5762 0.5786 0.5852 0.5844 0.5906 0.5844 0.5890 0.5889 0.5980 0.5889 0.5949 0.5889 0.5934 0.5925 0.5981 0.5925 0.5967 0.5979 0.6031 0.5979 0.6018 0.6009 0.6059 0.6018 0.6067 0.6018 0.6055
9 ∕ 16 -20 UN
3B 0.5080 0.5161
2B 0.517
0.527
9 ∕ 16 -24 UNEF
3B 0.5170 0.5244
2B 0.522 2B 0.524
0.531 0.532
9 ∕ 16 -27 UNS 9 ∕ 16 -28 UN
3B 0.5240 0.5301
2B 0.529
0.536
9 ∕ 16 -32 UN
3B 0.5290 0.5344
1B 0.527 2B 0.527
0.546 0.546
5 ∕ 8 -11 UNC
2A 0.0017 0.6233 0.6112 0.6052 0.5643 0.5588
3B 0.5270 0.5391
2B 0.535
0.553
5 ∕ 8 -12 UN
3B 0.5350 0.5463
2B 0.548 2B 0.557 1B 0.565 2B 0.565
0.563 0.571 0.578 0.578
5 ∕ 8 -14 UNS 5 ∕ 8 -16 UN
3B 0.5570 0.5662
5 ∕ 8 -18 UNF
3B 0.5650 0.5730
2B 0.571
0.582
5 ∕ 8 -20 UN
3B 0.5710 0.5786
2B 0.580
0.590
5 ∕ 8 -24 UNEF
3B 0.5800 0.5869
2B 0.585 2B 0.586
0.594 0.595
5 ∕ 8 -27 UNS 5 ∕ 8 -28 UN
3B 0.5860 0.5926
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