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 2.3750 2.3750 2.4375 2.4375 2.5000 2.5000 2.5000 2.5000 2.5000 2.5000 2.5000 2.5000 2.5000 2.5000 2.5000 2.5000 2.5000 2.5000 2.5000 2.5000 2.6250 2.6250 2.6250 2.6250 2.6250 2.6250 2.6250 2.6250
Class
2A 0.0015 2.3735 2.3654 3A 0.0000 2.3750 2.3669 2A 0.0017 2.4358 2.4264 3A 0.0000 2.4375 2.4281 1A 0.0031 2.4969 2.4612 3A 0.0000 2.5000 2.4762 2A 0.0027 2.4973 2.4791 3A 0.0000 2.5000 2.4818 3A 0.0000 2.5000 2.4850 2A 0.0020 2.4980 2.4851 2A 0.0019 2.4981 2.4867 3A 0.0000 2.5000 2.4886 2A 0.0017 2.4983 2.4880 2A 0.0017 2.4983 2.4889 3A 0.0000 2.5000 2.4906 2A 0.0016 2.4984 2.4897 2A 0.0015 2.4985 2.4904 3A 0.0000 2.5000 2.4919 2A 0.0027 2.6223 2.6041 3A 0.0000 2.6250 2.6068 2A 0.0025 2.6225 2.6075 3A 0.0000 2.6250 2.6100 2A 0.0019 2.6231 2.6117 3A 0.0000 2.6250 2.6136 2A 0.0017 2.6233 2.6139 3A 0.0000 2.6250 2.6156
— 2.3410 2.3360 — 2.3425 2.3387 — 2.3952 2.3897 — 2.3969 2.3928 — 2.3345 2.3190 — 2.3376 2.3298 — 2.3890 2.3800 — 2.3917 2.3850 — 2.4188 2.4127 — 2.4330 2.4263 — 2.4440 2.4378 — 2.4459 2.4413 — 2.4519 2.4461 — 2.4577 2.4522 — 2.4594 2.4553 — 2.4623 2.4570 — 2.4660 2.4609 — 2.4675 2.4637 — 2.5140 2.5050 — 2.5167 2.5099 — 2.5413 2.5331 — 2.5438 2.5376 — 2.5690 2.5628 — 2.5709 2.5662 — 2.5827 2.5771 — 2.5844 2.5802
2.3140 2.3155 2.3614 2.3631 2.1992 2.1992 2.2023 2.2988 2.3015 2.3488 2.3512 2.3789 2.3989 2.4008 2.4132 2.4239 2.4256 2.4322 2.4390 2.4405 2.4238 2.4265 2.4737 2.4762 2.5239 2.5258 2.5489 2.5506
2B 2.321
2.332
2.3425 2.3491 2.3425 2.3474 2.3969 2.4041 2.3969 2.4023 2.3376 2.3578 2.3376 2.3511 2.3376 2.3477 2.3917 2.4033 2.3917 2.4004 2.4188 2.4294 2.4188 2.4268 2.4350 2.4437 2.4459 2.4540 2.4459 2.4519 2.4536 2.4612 2.4594 2.4666 2.4594 2.4648 2.4639 2.4708 2.4675 2.4741 2.4675 2.4725 2.5167 2.5285 2.5167 2.5255 2.5438 2.5545 2.5438 2.5518 2.5709 2.5790 2.5709 2.5770 2.5844 2.5916 2.5844 2.5898
2 3 ∕ 8 -20 UN
3B 2.3210 2.3286
2B 2.370
2.384
2 7 ∕ 16 -16 UNS
3B 2.3700 2.3784
1B 2.229 2B 2.229
2.267 2.267
2 1 ∕ 2 -4 UNC
2A 0.0031 2.4969 2.4731 2.4612 2.3345 2.3241
3B 2.2290 2.2594
2B 2.320
2.350
2 1 ∕ 2 -6 UN
3B 2.3200 2.3396
2A 0.0024 2.4976 2.4826 2.4751 2.4164 2.4082
2B 2.365
2.390
2 1 ∕ 2 -8 UN
3B 2.3650 2.3797
2B 2.392 2B 2.410 2B 2.423 2B 2.432 2B 2.440 2B 2.446
2.413 2.428 2.438 2.446 2.453 2.457
2 1 ∕ 2 -10 UNS 2 1 ∕ 2 -12 UN 2 1 ∕ 2 -14 UNS 2 1 ∕ 2 -16 UN 2 1 ∕ 2 -18 UNS 2 1 ∕ 2 -20 UN
3B 2.4100 2.4198
3B 2.4320 2.4409
3B 2.4460 2.4536
2B 2.445
2.475
2 5 ∕ 8 -6 UN
3B 2.4450 2.4646
2B 2.490
2.515
2 5 ∕ 8 -8 UN
3B 2.4900 2.5047
2B 2.535
2.553
2 5 ∕ 8 -12 UN
3B 2.5350 2.5448
2B 2.557
2.571
2 5 ∕ 8 -16 UN
3B 2.5570 2.5659
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