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 3.2500 3.2500 3.2500 3.2500 3.2500 3.2500 3.2500 3.2500 3.2500 3.3750 3.3750 3.3750 3.3750 3.3750 3.3750 3.3750 3.3750 3.5000 3.5000 3.5000 3.5000 3.5000 3.5000 3.5000 3.5000 3.5000 3.5000
Class
2A 0.0026 3.2474 3.2324 3.2249 3.1662 3.1575
3.0986 3.1012 3.1288 3.1489 3.1508 3.1631 3.1739 3.1756 3.1823 3.1736 3.1765 3.2236 3.2262 3.2739 3.2758 3.2989 3.3006 3.1990 3.1990 3.2023 3.2986 3.3015 3.3486 3.3512 3.3788 3.3989 3.4008
2B 3.115
3.140
3.1688 3.1801 3.1688 3.1773 3.1850 3.1939 3.1959 3.2042 3.1959 3.2021 3.2036 3.2114 3.2094 3.2168 3.2094 3.2150 3.2139 3.2210 3.2667 3.2791 3.2667 3.2760 3.2938 3.3052 3.2938 3.3023 3.3209 3.3292 3.3209 3.3272 3.3344 3.3419 3.3344 3.3400 3.3376 3.3591 3.3376 3.3519 3.3376 3.3484 3.3917 3.4042 3.3917 3.4011 3.4188 3.4303 3.4188 3.4274 3.4350 3.4440 3.4459 3.4543 3.4459 3.4522
3 1 ∕ 4 -8 UN
3A 0.0000 3.2500 3.2350 2A 0.0021 3.2479 3.2350 2A 0.0019 3.2481 3.2367 3A 0.0000 3.2500 3.2386 2A 0.0018 3.2482 3.2379 2A 0.0017 3.2483 3.2389 3A 0.0000 3.2500 3.2406 2A 0.0016 3.2484 3.2397 2A 0.0029 3.3721 3.3539 3A 0.0000 3.3750 3.3568 2A 0.0026 3.3724 3.3574 3A 0.0000 3.3750 3.3600 2A 0.0019 3.3731 3.3617 3A 0.0000 3.3750 3.3636 2A 0.0017 3.3733 3.3639 3A 0.0000 3.3750 3.3656 1A 0.0033 3.4967 3.4610 3A 0.0000 3.5000 3.4762 2A 0.0029 3.4971 3.4789 3A 0.0000 3.5000 3.4818 3A 0.0000 3.5000 3.4850 2A 0.0021 3.4979 3.4850 2A 0.0019 3.4981 3.4867 3A 0.0000 3.5000 3.4886
— 3.1688 3.1623 — 3.1829 3.1760 — 3.1940 3.1876 — 3.1959 3.1911 — 3.2018 3.1958 — 3.2077 3.2020 — 3.2094 3.2051 — 3.2123 3.2068 — 3.2638 3.2543 — 3.2667 3.2595 — 3.2912 3.2824 — 3.2938 3.2872 — 3.3190 3.3126 — 3.3209 3.3161 — 3.3327 3.3270 — 3.3344 3.3301 — 3.3343 3.3177 — 3.3376 3.3293 — 3.3888 3.3792 — 3.3917 3.3845 — 3.4188 3.4122 — 3.4329 3.4260 — 3.4440 3.4376 — 3.4459 3.4411
3B 3.1150 3.1297
2B 3.142 2B 3.160 2B 3.173 2B 3.182 2B 3.190 2B 3.195
3.163 3.178 3.188 3.196 3.203 3.225
3 1 ∕ 4 -10 UNS 3 1 ∕ 4 -12 UN 3 1 ∕ 4 -14 UNS 3 1 ∕ 4 -16 UN 3 1 ∕ 4 -18 UNS 3 3 ∕ 8 -6 UN
3B 3.1600 3.1698
3B 3.1820 3.1909
3B 3.1950 3.2146
2B 3.240
3.265
3 3 ∕ 8 -8 UN
3B 3.2400 3.2547
2B 3.285
3.303
3 3 ∕ 8 -12 UN
3B 3.2850 3.2948
2B 3.307
3.321
3 3 ∕ 8 -16 UN
3B 3.3070 3.3159
1B 3.229 2B 3.229
3.267 3.267
3 1 ∕ 2 -4 UNC
2A 0.0033 3.4967 3.4729 3.4610 3.3343 3.3233
3B 3.2290 3.2594
2B 3.320
3.350
3 1 ∕ 2 -6 UN
3B 3.3200 3.3396
2A 0.0026 3.4974 3.4824 3.4749 3.4162 3.4074
2B 3.365
3.390
3 1 ∕ 2 -8 UN
3B 3.3650 3.3797
2B 3.392 2B 3.410
3.413 3.428
3 1 ∕ 2 -10 UNS 3 1 ∕ 2 -12 UN
3B 3.4100 3.4198
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