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 1.3750 1.3750 1.3750 1.3750 1.3750 1.3750 1.3750 1.3750 1.3750 1.3750 1.3750 1.3750 1.3750 1.3750 1.3750 1.3750 1.4375 1.4375 1.4375 1.4375 1.4375 1.4375 1.4375 1.4375 1.4375 1.4375 1.4375 1.4375
Class
2A 0.0022 1.3728 1.3578 1.3503 1.2916 1.2844
1.2240 1.2262 1.2540 1.2739 1.2739 1.2758 1.2883 1.2991 1.3006 1.3073 1.3088 1.3141 1.3155 1.3241 1.3313 1.3325 1.2366 1.2390 1.2865 1.2887 1.3365 1.3383 1.3615 1.3631 1.3698 1.3713 1.3766 1.3780
2B 1.240
1.265
1.2938 1.3031 1.2938 1.3008 1.3100 1.3182 1.3209 1.3332 1.3209 1.3291 1.3209 1.3270 1.3286 1.3357 1.3344 1.3411 1.3344 1.3394 1.3389 1.3453 1.3389 1.3437 1.3425 1.3486 1.3425 1.3471 1.3479 1.3536 1.3518 1.3572 1.3518 1.3558 1.3292 1.3396 1.3292 1.3370 1.3563 1.3657 1.3563 1.3634 1.3834 1.3910 1.3834 1.3891 1.3969 1.4036 1.3969 1.4020 1.4014 1.4078 1.4014 1.4062 1.4050 1.4112 1.4050 1.4096
1 3 ∕ 8 -8 UN
3A 0.0000 1.3750 1.3600 2A 0.0019 1.3731 1.3602 1A 0.0019 1.3731 1.3559 2A 0.0019 1.3731 1.3617 3A 0.0000 1.3750 1.3636 2A 0.0016 1.3734 1.3631 2A 0.0015 1.3735 1.3641 3A 0.0000 1.3750 1.3656 2A 0.0015 1.3735 1.3648 3A 0.0000 1.3750 1.3663 2A 0.0014 1.3736 1.3655 3A 0.0000 1.3750 1.3669 2A 0.0013 1.3737 1.3665 2A 0.0012 1.3738 1.3673 3A 0.0000 1.3750 1.3685 2A 0.0024 1.4351 1.4169 3A 0.0000 1.4375 1.4193 2A 0.0022 1.4353 1.4203 3A 0.0000 1.4375 1.4225 2A 0.0018 1.4357 1.4243 3A 0.0000 1.4375 1.4261 2A 0.0016 1.4359 1.4265 3A 0.0000 1.4375 1.4281 2A 0.0015 1.4360 1.4273 3A 0.0000 1.4375 1.4288 2A 0.0014 1.4361 1.4280 3A 0.0000 1.4375 1.4294
— 1.2938 1.2884 — 1.3081 1.3018 — 1.3190 1.3096 — 1.3190 1.3127 — 1.3209 1.3162 — 1.3270 1.3215 — 1.3329 1.3277 — 1.3344 1.3305 — 1.3374 1.3325 — 1.3389 1.3352 — 1.3411 1.3364 — 1.3425 1.3390 — 1.3466 1.3422 — 1.3506 1.3465 — 1.3518 1.3487 — 1.3268 1.3188 — 1.3292 1.3232 — 1.3541 1.3469 — 1.3563 1.3509 — 1.3816 1.3757 — 1.3834 1.3790 — 1.3953 1.3901 — 1.3969 1.3930 — 1.3999 1.3950 — 1.4014 1.3977 — 1.4036 1.3989 — 1.4050 1.4014
3B 1.2400 1.2547
2B 1.267 1B 1.285 2B 1.285 2B 1.298 2B 1.307
1.288 1.303 1.303 1.313 1.321
1 3 ∕ 8 -10 UNS 1 3 ∕ 8 -12 UNF
3B 1.2850 1.2948
1 3 ∕ 8 -14 UNS 1 3 ∕ 8 -16 UN
3B 1.3070 1.3159
2B 1.315
1.328
1 3 ∕ 8 -18 UNEF
3B 1.3150 1.3230
2B 1.321
1.332
1 3 ∕ 8 -20 UN
3B 1.3210 1.3286
2B 1.330 2B 1.336
1.340 1.345
1 3 ∕ 8 -24 UNS 1 3 ∕ 8 -28 UN
3B 1.3360 1.3426
2B 1.257
1.288
1 7 ∕ 16 -6 UN
3B 1.2570 1.2771
2B 1.302
1.327
1 7 ∕ 16 -8 UN
3B 1.3020 1.3172
2B 1.347
1.365
1 7 ∕ 16 -12 UN
3B 1.3470 1.3573
2B 1.370
1.384
1 7 ∕ 16 -16 UN
3B 1.3700 1.3784
2B 1.377
1.390
1 7 ∕ 16 -18 UNEF
3B 1.3770 1.3855
2B 1.383
1.395
1 7 ∕ 16 -20 UN
3B 1.3830 1.3911
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