Threads and Threading - Sportpilot.info

Nominal Size,
Threads per Inch,
and Series
Designation a
Class
Table 3. (Continued) Standard Series and Selected Combinations — Unified Screw Threads
Allowance
Machinery's Handbook 27th Edition
Externalb Internalb Major Diameter Pitch Diameter
UNR Minor
Dia., c Max
Minor Diameter Pitch Diameter
Major
Diameter
Max (Ref.) Class
d Min Mine Maxd Min Min Max Min Max Min
31 ⁄ 4 –8 UN 2A 0.0026 3.2474 3.2324 3.2249 3.1662 3.1575 3.0986 2B 3.115 3.140 3.1688 3.1801 3.2500
3A 0.0000 3.2500 3.2350 — 3.1688 3.1623 3.1012 3B 3.1150 3.1297 3.1688 3.1773 3.2500
31 ⁄ 4 –10 UNS 2A 0.0020 3.2480 3.2351 — 3.1830 3.1762 3.1290 2B 3.142 3.163 3.1850 3.1939 3.2500
31 ⁄ 4 –12 UN 2A 0.0019 3.2481 3.2367 — 3.1940 3.1877 3.1489 2B 3.160 3.178 3.1959 3.2041 3.2500
3A 0.0000 3.2500 3.2386 — 3.1959 3.1912 3.1508 3B 3.1600 3.1698 3.1959 3.2041 3.2500
31 ⁄ 4–14 UNS 2A 0.0018 3.2482 3.2379 — 3.2018 3.1959 3.1632 2B 3.173 3.188 3.2036 3.2113 3.2500
31 ⁄ 4 –16 UN 2A 0.0017 3.2483 3.2389 — 3.2077 3.2021 3.1738 2B 3.182 3.196 3.2094 3.2167 3.2500
3A 0.0000 3.2500 3.2406 — 3.2094 3.2052 3.1755 3B 3.1820 3.1908 3.2094 3.2149 3.2500
31 ⁄ 4 –18 UNS 2A 0.0016 3.2484 3.2397 — 3.2123 3.2069 3.1823 2B 3.190 3.203 3.2139 3.2209 3.2500
33 ⁄ 8 –6 UN 2A 0.0029 3.3721 3.3539 — 3.2638 3.2543 3.1737 2B 3.195 3.225 3.2667 3.2791 3.3750
3A 0.0000 3.3750 3.3568 — 3.2667 3.2595 3.1766 3B 3.1950 3.2146 3.2667 3.2760 3.3750
33 ⁄ 8 –8 UN 2A 0.0026 3.3724 3.3574 — 3.2912 3.2824 3.2236 2B 3.240 3.265 3.2938 3.3052 3.3750
3A 0.0000 3.3750 3.3600 — 3.2938 3.2872 3.2262 3B 3.2400 3.2547 3.2938 3.3023 3.3750
33 ⁄ 8 –12 UN 2A 0.0019 3.3731 3.3617 — 3.3190 3.3126 3.2739 2B 3.285 3.303 3.3209 3.3293 3.3750
3A 0.0000 3.3750 3.3636 — 3.3209 3.3161 3.2758 3B 3.2850 3.2948 3.3209 3.3272 3.3750
33 ⁄ 8 –16 UN 2A 0.0017 3.3733 3.3639 — 3.3327 3.3269 3.2988 2B 3.307 3.321 3.3344 3.3419 3.3750
3A 0.0000 3.3750 3.3656 — 3.3344 3.3301 3.3005 3B 3.3070 3.3158 3.3344 3.3400 3.3750
31 ⁄ 2–4 UNC 1A 0.0033 3.4967 3.4610 — 3.3343 3.3177 3.1990 1B 3.229 3.267 3.3376 3.3591 3.5000
2A 0.0033 3.4967 3.4729 3.4610 3.3343 3.3233 3.1990 2B 3.229 3.267 3.3376 3.3519 3.5000
3A 0.0000 3.5000 3.4762 — 3.3376 3.3293 3.2023 3B 3.2290 3.2594 3.3376 3.3484 3.5000
31 ⁄ 2 –6 UN 2A 0.0029 3.4971 3.4789 — 3.3888 3.3792 3.2987 2B 3.320 3.350 3.3917 3.4042 3.5000
3A 0.0000 3.5000 3.4818 — 3.3917 3.3845 3.3016 3B 3.3200 3.3396 3.3917 3.4011 3.5000
31 ⁄ 2 –8 UN 2A 0.0026 3.4974 3.4824 3.4749 3.4162 3.4074 3.3486 2B 3.365 3.390 3.4188 3.4303 3.5000
3A 0.0000 3.5000 3.4850 — 3.4188 3.4122 3.3512 3B 3.3650 3.3797 3.4188 3.4274 3.5000
31 ⁄ 2 –10 UNS 2A 0.0021 3.4979 3.4850 — 3.4329 3.4260 3.3789 2B 3.392 3.413 3.4350 3.4440 3.5000
31 ⁄ 2 –12 UN 2A 0.0019 3.4981 3.4867 — 3.4440 3.4376 3.3989 2B 3.410 3.428 3.4459 3.4543 3.5000
3A 0.0000 3.5000 3.4886 — 3.4459 3.4411 3.4008 3B 3.4100 3.4198 3.4459 3.4522 3.5000
Copyright 2004, Industrial Press, Inc., New York, NY
1758
UNIFIED SCREW THREADS