Table 3. (Continued) Standard Series and Selected Combinations—Unified Screw Threads
Table 3. Standard Series and Selected Combinations—Unified Screw Threads
External b
Internal b
Nominal Size, Threads per Inch, and Series Designation a 3 1 ∕ 2 -14 UNS
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 3.5000 3.5000 3.5000 3.5000 3.6250 3.6250 3.6250 3.6250 3.6250 3.6250 3.6250 3.6250 3.7500 3.7500 3.7500 3.7500 3.7500 3.7500 3.7500 3.7500 3.7500 3.7500 3.7500 3.7500 3.7500 3.7500
Class
2A 0.0018 3.4982 3.4879 2A 0.0017 3.4983 3.4889 3A 0.0000 3.5000 3.4906 2A 0.0017 3.4983 3.4896 2A 0.0029 3.6221 3.6039 3A 0.0000 3.6250 3.6068 2A 0.0027 3.6223 3.6073 3A 0.0000 3.6250 3.6100 2A 0.0019 3.6231 3.6117 3A 0.0000 3.6250 3.6136 2A 0.0017 3.6233 3.6139 3A 0.0000 3.6250 3.6156 1A 0.0034 3.7466 3.7109 3A 0.0000 3.7500 3.7262 2A 0.0029 3.7471 3.7289 3A 0.0000 3.7500 3.7318 3A 0.0000 3.7500 3.7350 2A 0.0021 3.7479 3.7350 2A 0.0019 3.7481 3.7367 3A 0.0000 3.7500 3.7386 2A 0.0018 3.7482 3.7379 2A 0.0017 3.7483 3.7389 3A 0.0000 3.7500 3.7406 2A 0.0017 3.7483 3.7396
— 3.4518 3.4457 — 3.4577 3.4519 — 3.4594 3.4551 — 3.4622 3.4567 — 3.5138 3.5041 — 3.5167 3.5094 — 3.5411 3.5322 — 3.5438 3.5371 — 3.5690 3.5625 — 3.5709 3.5661 — 3.5827 3.5769 — 3.5844 3.5801 — 3.5842 3.5674 — 3.5876 3.5792 — 3.6388 3.6290 — 3.6417 3.6344 — 3.6688 3.6621 — 3.6829 3.6759 — 3.6940 3.6875 — 3.6959 3.6910 — 3.7018 3.6957 — 3.7077 3.7019 — 3.7094 3.7050 — 3.7122 3.7066
3.4131 3.4239 3.4256 3.4321 3.4236 3.4265 3.4735 3.4762 3.5239 3.5258 3.5489 3.5506 3.4489 3.4489 3.4523 3.5486 3.5515 3.5985 3.6012 3.6288 3.6489 3.6508 3.6631 3.6739 3.6756 3.6821
2B 3.423 2B 3.432 2B 3.440 2B 3.445
3.438 3.446 3.453 3.475
3.4536 3.4615 3.4594 3.4669 3.4594 3.4650 3.4639 3.4711 3.5167 3.5293 3.5167 3.5262 3.5438 3.5554 3.5438 3.5525 3.5709 3.5793 3.5709 3.5772 3.5844 3.5919 3.5844 3.5900 3.5876 3.6094 3.5876 3.6021 3.5876 3.5985 3.6417 3.6544 3.6417 3.6512 3.6688 3.6805 3.6688 3.6776 3.6850 3.6941 3.6959 3.7043 3.6959 3.7022 3.7036 3.7115 3.7094 3.7170 3.7094 3.7151 3.7139 3.7211
3 1 ∕ 2 -16 UN
3B 3.4320 3.4409
3 1 ∕ 2 -18 UNS 3 5 ∕ 8 -6 UN
3B 3.4450 3.4646
2B 3.490
3.515
3 5 ∕ 8 -8 UN
3B 3.4900 3.5047
2B 3.535
3.553
3 5 ∕ 8 -12 UN
3B 3.5350 3.5448
2B 3.557
3.571
3 5 ∕ 8 -16 UN
3B 3.5570 3.5659
1B 3.479 2B 3.479
3.517 3.517
3 3 ∕ 4 -4 UNC
2A 0.0034 3.7466 3.7228 3.7109 3.5842 3.5730
3B 3.4790 3.5094
2B 3.570
3.600
3 3 ∕ 4 -6 UN
3B 3.5700 3.5896
2A 0.0027 3.7473 3.7323 3.7248 3.6661 3.6571
2B 3.615
3.640
3 3 ∕ 4 -8 UN
3B 3.6150 3.6297
2B 3.642 2B 3.660 2B 3.673 2B 3.682
3.663 3.678 3.688 3.696
3 3 ∕ 4 -10 UNS 3 3 ∕ 4 -12 UN 3 3 ∕ 4 -14 UNS 3 3 ∕ 4 -16 UN
3B 3.6600 3.6698
3B 3.6820 3.6909
2B 3.690
3.703
3 3 ∕ 4 -18 UNS
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