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UNEF - 60 Degree Unified National Extra Fine Threads

UNEF Thread Series / UNREF, is applicable where even finer pitches of threads are desirable, as for short lengths of engagement and for thin-walled tubes, nuts, ferrules, or couplings. It is also generally applicable under the conditions stated above for the fine threads.

#12 - 3/4" 13/16" - 1 3/8" 1 7/16" - 1 11/16"

UNEF Threads

Nominal Size External (b) Internal (b)
Threads per Inch and Series Designation Class Allowance Major Diameter Minor Diameter UNR Minor Dia.,c Max (Ref.) Class Minor Diameter Pitch Diameter Major Diameter
Max (d) Min Min (e) Max (d) Min Min Max Min Max Min
#12 - 32UNEF 2A 0.0009 5.464 5.311 . . . 4.948 4.869 4.519 2B 4.623 4.826 4.971 5.075 5.486
#12 - 32UNEF 3A 0 5.486 5.334 . . . 4.971 4.91 4.542 3B 4.623 4.813 4.971 5.05 5.486
1/4" - 32UNEF 2A 0.001 6.325 6.172 . . . 5.809 5.728 5.38 2B 5.486 5.69 5.834 5.941 6.35
1/4" - 32UNEF 3A 0 6.35 6.198 . . . 5.834 5.773 5.405 3B 5.486 5.662 5.834 5.913 6.35
5/16" - 32UNEF 2A 0.001 7.912 7.76 . . . 7.396 7.315 6.967 2B 7.087 7.264 7.422 7.529 7.938
5/16" - 32UNEF 3A 0 7.938 7.785 . . . 7.422 7.361 6.993 3B 7.087 7.231 7.422 7.501 7.938
3/8" - 32UNEF 2A 0.001 9.5 9.347 . . . 8.984 8.898 8.555 2B 8.661 8.865 9.009 9.121 9.525
3/8" - 32UNEF 3A 0 9.525 9.373 . . . 9.009 8.946 8.58 3B 8.661 8.811 9.009 9.093 9.525
7/16" - 28UNEF 2A 0.0011 11.085 10.919 . . . 10.495 10.404 10.003 2B 10.135 10.338 10.523 10.64 11.113
7/16" - 28UNEF 3A 0 11.113 10.947 . . . 10.523 10.455 10.03 3B 10.135 10.29 10.523 10.612 11.113
1/2" - 28UNEF 2A 0.0011 12.672 12.507 . . . 12.083 11.989 11.59 2B 11.709 11.938 12.111 12.233 12.7
1/2" - 28UNEF 3A 0 12.7 12.535 . . . 12.111 12.04 11.618 3B 11.709 11.877 12.111 12.202 12.7
9/16" - 24UNEF 2A 0.0012 14.257 14.074 . . . 13.569 13.47 12.997 2B 13.132 13.386 13.599 13.729 14.288
9/16" - 24UNEF 3A 0 14.288 14.105 . . . 13.599 13.526 13.028 3B 13.132 13.32 13.599 13.696 14.288
5/8" - 24UNEF 2A 0.0012 15.845 15.662 . . . 15.156 15.055 14.585 2B 14.732 14.986 15.187 15.319 15.875
5/8" - 24 UNEF 3A 0 15.875 15.692 . . . 15.187 15.11 14.615 3B 14.732 14.907 15.187 15.286 15.875
11/16" - 24UNEF 2A 0.0012 17.432 17.249 . . . 16.744 16.642 16.172 2B 16.307 16.561 16.774 16.906 17.463
11/16" - 24UNEF 3A 0 17.463 17.28 . . . 16.774 16.698 16.203 3B 16.307 16.495 16.774 16.873 17.463
3/4" - 20UNEF 2A 0.0013 19.017 18.811 . . . 18.191 18.08 17.506 2B 17.678 17.958 18.225 18.369 19.05
3/4" - 20UNEF 3A 0 19.05 18.844 . . . 18.225 18.141 17.539 3B 17.678 17.874 18.225 18.334 19.05
13/16" - 20UNEF 2A 0.0013 20.604 20.399 . . . 19.779 19.667 19.093 2B 19.253 19.558 19.812 19.957 20.638
13/16" - 20UNEF 3A 0 20.638 20.432 . . . 19.812 19.728 19.126 3B 19.253 19.461 19.812 19.921 20.638
7/8" - 20UNEF 2A 0.0013 22.192 21.986 . . . 21.366 21.255 20.681 2B 20.853 21.133 21.4 21.544 22.225
7/8" - 20UNEF 3A 0 22.225 22.019 . . . 21.4 21.316 20.714 3B 20.853 21.049 21.4 21.509 22.225
15/16" - 20UNEF 2A 0.0014 23.777 23.571 . . . 22.951 22.837 22.266 2B 22.428 22.733 22.987 23.137 23.813
15/16" - 20UNEF 3A 0 23.813 23.607 . . . 22.987 22.901 22.301 3B 22.428 22.636 22.987 23.099 23.813
1" - 20UNEF 2A 0.0014 25.364 25.159 . . . 24.539 24.425 23.853 2B 24.028 24.308 24.575 24.724 25.4
1" - 20UNEF 3A 0 25.4 25.194 . . . 24.575 24.488 23.889 3B 24.028 24.224 24.575 24.686 25.4
1 1/16" - 18UNEF 2A 0.0014 26.952 26.731 . . . 26.035 25.916 25.273 2B 25.451 25.781 26.071 26.228 26.988
1 1/16" - 18UNEF 3A 0 26.988 26.767 . . . 26.071 25.979 25.309 3B 25.451 25.667 26.071 26.187 26.988
1 1/8" - 18UNEF 2A 0.0014 28.539 28.318 . . . 27.623 27.503 26.861 2B 27.051 27.381 27.658 27.816 28.575
1 1/8" - 18UNEF 3A 0 28.575 28.354 . . . 27.658 27.567 26.896 3B 27.051 27.254 27.658 27.775 28.575
1 3/8" - 18UNEF 2A 0.0015 30.124 29.903 . . . 29.207 29.083 28.445 2B 28.626 28.956 29.246 29.406 30.163
1 3/8" - 18UNEF 3A 0 30.163 29.942 . . . 29.246 29.154 28.484 3B 28.626 28.842 29.246 29.365 30.163
1 1/4" - 1 8UNEF 2A 0.0015 31.712 31.491 . . . 30.795 30.671 30.033 2B 30.226 30.556 30.833 30.993 31.75
1 1/4" - 1 8UNEF 3A 0 31.75 31.529 . . . 30.833 30.742 30.071 3B 30.226 30.429 30.833 30.952 31.75
1 5/16" - 18UNEF 2A 0.0015 33.299 33.078 . . . 32.382 32.258 31.62 2B 31.801 32.131 32.421 32.581 33.338
1 5/16" - 18UNEF 3A 0 33.338 33.117 . . . 32.421 32.329 31.659 3B 31.801 32.017 32.421 32.54 33.338
1 3/8" - 18UNEF 2A 0.0015 34.887 34.666 . . . 33.97 33.846 33.208 2B 33.401 33.731 34.008 34.168 34.925
1 3/8" - 18UNEF 3A 0 34.925 34.704 . . . 34.008 33.917 33.246 3B 33.401 33.604 34.008 34.127 34.925
1 7/16" - 18UNEF 2A 0.0015 36.474 36.253 . . . 35.557 35.43 34.795 2B 34.976 35.306 35.596 35.761 36.513
1 7/16" - 18UNEF 3A 0 36.513 36.292 . . . 35.596 35.502 34.834 3B 34.976 35.192 35.596 35.717 36.513
1 1/2" - 18UNEF 2A 0.0015 38.062 37.841 . . . 37.145 37.018 36.383 2B 36.576 36.881 37.183 37.348 38.1
1 1/2" - 18UNEF 3A 0 38.1 37.879 . . . 37.183 37.089 36.421 3B 36.576 36.779 37.183 37.305 38.1
1 9/16" - 18UNEF 2A 0.0015 39.649 39.428 . . . 38.732 38.605 37.97 2B 38.151 38.481 38.771 38.936 39.688
1 9/16" - 18UNEF 3A 0 39.688 39.467 . . . 38.771 38.677 38.009 3B 38.151 38.367 38.771 38.892 39.688
1 5/8" - 18UNEF 2A 0.0015 41.237 41.016 . . . 40.32 40.193 39.558 2B 39.751 40.081 40.358 40.523 41.275
1 5/8" - 18UNEF 3A 0 41.275 41.054 . . . 40.358 40.264 39.596 3B 39.751 39.954 40.358 40.48 41.275
1 11/16" - 18UNEF 2A 0.0015 42.824 42.603 . . . 41.907 41.778 41.145 2B 41.326 41.656 41.946 42.113 42.863
1 11/16" - 18UNEF 3A 0 42.863 42.642 . . . 41.946 41.849 41.184 3B 41.326 41.542 41.946 42.07 42.863