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 0.3750 0.3750 0.3750 0.3750 0.3750 0.3750 0.3750 0.3750 0.3750 0.3750 0.3900 0.4375 0.4375 0.4375 0.4375 0.4375 0.4375 0.4375 0.4375 0.4375 0.4375 0.4375 0.4375 0.4375 0.4375 0.4375
Class
1A 0.0011 0.3739 0.3631 2A 0.0011 0.3739 0.3667 3A 0.0000 0.3750 0.3678 2A 0.0011 0.3739 0.3672 2A 0.0011 0.3739 0.3674 3A 0.0000 0.3750 0.3685 2A 0.0010 0.3740 0.3680 3A 0.0000 0.3750 0.3690 2A 0.0010 0.3740 0.3685 2A 0.0009 0.3741 0.3690 2A 0.0011 0.3889 0.3822 1A 0.0014 0.4361 0.4206 3A 0.0000 0.4375 0.4272 2A 0.0014 0.4361 0.4267 3A 0.0000 0.4375 0.4281 2A 0.0013 0.4362 0.4275 1A 0.0013 0.4362 0.4240 2A 0.0013 0.4362 0.4281 3A 0.0000 0.4375 0.4294 2A 0.0012 0.4363 0.4291 2A 0.0011 0.4364 0.4297 2A 0.0011 0.4364 0.4299 3A 0.0000 0.4375 0.4310 2A 0.0010 0.4365 0.4305 3A 0.0000 0.4375 0.4315
— 0.3468 0.3411 — 0.3468 0.3430 — 0.3479 0.3450 — 0.3498 0.3462 — 0.3507 0.3471 — 0.3518 0.3491 — 0.3537 0.3503 — 0.3547 0.3522 — 0.3560 0.3528 — 0.3579 0.3548 — 0.3648 0.3612 — 0.3897 0.3826 — 0.3911 0.3876 — 0.3955 0.3909 — 0.3969 0.3934 — 0.4001 0.3957 — 0.4037 0.3974 — 0.4037 0.3995 — 0.4050 0.4019 — 0.4092 0.4053 — 0.4123 0.4086 — 0.4132 0.4096 — 0.4143 0.4116 — 0.4162 0.4128 — 0.4172 0.4146
0.3243 0.3243 0.3254 0.3298 0.3314 0.3325 0.3368 0.3378 0.3409 0.3443 0.3448 0.3510 0.3510 0.3524 0.3617 0.3631 0.3700 0.3767 0.3767 0.3780 0.3867 0.3923 0.3939 0.3950 0.3993 0.4003
1B 0.330 2B 0.330 2B 0.335 2B 0.336
0.340 0.340 0.344 0.345
0.3479 0.3553 0.3479 0.3528 0.3479 0.3516 0.3509 0.3556 0.3518 0.3564 0.3518 0.3553 0.3547 0.3591 0.3547 0.3580 0.3570 0.3612 0.3588 0.3628 0.3659 0.3706 0.3911 0.4003 0.3911 0.3972 0.3911 0.3957 0.3969 0.4029 0.3969 0.4014 0.4014 0.4071 0.4050 0.4131 0.4050 0.4104 0.4050 0.4091 0.4104 0.4154 0.4134 0.4182 0.4143 0.4190 0.4143 0.4178 0.4172 0.4216 0.4172 0.4205
3 ∕ 8 -24 UNF
3B 0.3300 0.3372
3 ∕ 8 -27 UNS 3 ∕ 8 -28 UN
3B 0.3360 0.3426
2B 0.341
0.349
3 ∕ 8 -32 UNEF
3B 0.3410 0.3469
2B 0.345 2B 0.348 2B 0.350 1B 0.360 2B 0.360
0.352 0.354 0.359 0.376 0.376
3 ∕ 8 -36 UNS 3 ∕ 8 -40 UNS
0.390-27 UNS 7 ∕ 16 -14 UNC
2A 0.0014 0.4361 0.4258 0.4206 0.3897 0.3850
3B 0.3600 0.3717
2B 0.370
0.384
7 ∕ 16 -16 UN
3B 0.3700 0.3800
2B 0.377 1B 0.383 2B 0.383 2B 0.392 2B 0.397 2B 0.399
0.390 0.395 0.395 0.402 0.406 0.407
7 ∕ 16 -18 UNS 7 ∕ 16 -20 UNF
3B 0.3830 0.3916
7 ∕ 16 -24 UNS 7 ∕ 16 -27 UNS 7 ∕ 16 -28 UNEF
3B 0.3990 0.4051
2B 0.404
0.411
7 ∕ 16 -32 UN
3B 0.4040 0.4094
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