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UNS Unified National Thread

UNS screw threads that have special combinations of diameter and pitch with tolerance to Unified formulation have the basic form designation set out first followed always by the limits of size.

#10 - 1/4" 5/16" - 1/2" 9/16" - 1" 1 1/8"- 1 7/8" 2"- 2 1/2" 2 3/4" - 3 3/4" 4" - 6"

UNS Unified National Thread

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
#10 - 28UNS 2A 0.001 4.801 4.636 . . . 4.211 4.128 3.719 2B 3.835 4.064 4.237 4.346 4.826
#10 - 36UNS 2A 0.0009 4.803 4.663 . . . 4.346 4.27 3.962 2B 4.064 4.216 4.369 4.468 4.826
#10 - 40UNS 2A 0.0009 4.803 4.674 . . . 4.392 4.318 4.044 2B 4.14 4.293 4.415 4.509 4.826
#10 - 48UNS 2A 0.0008 4.806 4.691 . . . 4.463 4.397 4.176 2B 4.242 4.369 4.483 4.569 4.826
#10 - 56UNS 2A 0.0007 4.808 4.704 . . . 4.514 4.45 4.27 2B 4.343 4.445 4.531 4.613 4.826
#12 - 36UNS 2A 0.0009 5.464 5.324 . . . 5.006 4.93 4.625 2B 4.724 4.877 5.029 5.128 5.486
#12 - 40UNS 2A 0.0009 5.464 5.334 . . . 5.052 4.978 4.661 2B 4.801 4.953 5.075 5.169 5.486
#12 - 48UNS 3A 0.0008 5.466 5.352 . . . 5.123 5.057 4.836 2B 4.902 5.029 5.144 5.23 5.486
#12 - 56UNS 2A 0.0007 5.469 5.364 . . . 5.174 5.11 4.93 2B 5.004 5.105 5.192 5.273 5.486
1/4" - 24 UNS 2A 0.0011 6.322 6.139 . . . 5.634 5.54 5.062 2B 5.207 5.461 5.662 5.784 6.35
1/4" - 24 UNS 2A 0.001 6.325 6.154 . . . 5.712 5.624 5.204 2B 5.334 5.563 5.738 5.852 6.35
1/4" - 24 UNS 1A 0.001 6.325 6.076 . . . 5.735 5.608 5.243 1B 5.359 5.588 5.761 5.926 6.35
1/4" - 24 UNS 2A 0.001 6.325 6.16 . . . 5.735 5.652 5.243 2B 5.359 5.588 5.761 5.87 6.35
1/4" - 24 UNS 3A 0 6.35 6.185 . . . 5.761 5.697 5.268 3B 5.359 5.563 5.761 5.842 6.35
1/4" - 36 UNS 2A 0.0009 6.327 6.187 . . . 5.87 5.791 5.489 2B 5.588 5.74 5.893 5.994 6.35
1/4" - 40 UNS 2A 0.0009 6.327 6.198 . . . 5.916 5.842 5.57 2B 5.664 5.817 5.939 6.035 6.35
1/4" - 48UNS 2A 0.0008 6.33 6.215 . . . 5.987 5.918 5.697 2B 5.766 5.893 6.007 6.099 6.35
1/4" - 56 UNS 2A 0.0008 6.33 6.226 . . . 6.035 5.969 5.791 2B 5.867 5.969 6.055 6.139 6.35
5/16" - 27 UNS 2A 0.001 7.912 7.742 . . . 7.3 7.211 6.792 2B 6.909 7.137 7.325 7.44 7.938
5/16" - 36 UNS 2A 0.0009 7.915 7.775 . . . 7.457 7.379 7.074 2B 7.163 7.341 7.48 7.582 7.938
5/16" - 40 UNS 2A 0.0009 7.915 7.785 . . . 7.503 7.43 7.158 2B 7.239 7.391 7.526 7.623 7.938
5/16" - 48UNS 2A 0.0008 7.917 7.803 . . . 7.574 7.506 7.287 2B 7.366 7.493 7.595 7.686 7.938
3/8" - 18UNS 2A 0.0013 9.492 9.271 . . . 8.575 8.466 7.813 2B 8.001 8.331 8.608 8.75 9.525
3/8" - 27 UNS 2A 0.0011 9.497 9.327 . . . 8.885 8.793 8.377 2B 8.509 8.738 8.913 9.032 9.525
3/8" - 36 UNS 2A 0.001 9.5 9.36 . . . 9.042 8.961 8.659 2B 8.763 8.941 9.068 9.174 9.525
3/8" - 40 UNS 2A 0.0009 9.502 9.373 . . . 9.091 9.012 8.745 2B 8.839 8.992 9.114 9.215 9.525
0.390" - 27 UNS 2A 0.0011 9.878 9.708 . . . 9.266 9.174 8.758 2B 8.89 9.119 9.294 9.413 9.906
7/16" - 18UNS 2A 0.0013 11.079 10.859 . . . 10.163 10.053 9.401 2B 9.576 9.906 10.196 10.338 11.113
7/16" - 24 UNS 2A 0.0011 11.085 10.902 . . . 10.396 10.3 9.825 2B 9.957 10.211 10.424 10.549 11.113
7/16" - 27 UNS 2A 0.0011 11.085 10.914 . . . 10.472 10.381 9.964 2B 10.084 10.312 10.5 10.62 11.113
1/2" - 12UNS 2A 0.0016 12.659 12.37 . . . 11.285 11.148 10.14 2B 10.414 10.871 11.326 11.504 12.7
1/2" - 12UNS 3A 0 12.7 12.41 . . . 11.326 11.224 10.18 3B 10.414 10.726 11.326 11.458 12.7
1/2" - 14 UNS 2A 0.0015 12.662 12.4 . . . 11.483 11.356 10.503 2B 10.744 11.125 11.521 11.687 12.7
1/2" - 18UNS 2A 0.0013 12.667 12.446 . . . 11.75 11.638 10.988 2B 11.176 11.506 11.783 11.93 12.7
1/2" - 24 UNS 2A 0.0012 12.67 12.487 . . . 11.981 11.882 11.41 2B 11.557 11.811 12.012 12.141 12.7
1/2" - 27 UNS 2A 0.0011 12.672 12.502 . . . 12.06 11.966 11.552 2B 11.684 11.913 12.088 12.21 12.7
9/16" -14 UNS 2A 0.0015 14.249 13.988 . . . 13.071 12.944 12.09 2B 12.319 12.725 13.109 13.274 14.288
9/16" -27 UNS 2A 0.0011 14.26 14.089 . . . 13.647 13.553 13.139 2B 13.259 13.487 13.675 13.797 14.288
5/8" - 14 UNS 2A 0.0015 15.837 15.575 . . . 14.658 14.529 13.678 2B 13.919 14.326 14.696 14.864 15.875
5/8" - 27 UNS 2A 0.0011 15.847 15.677 . . . 15.235 15.138 14.727 2B 14.859 15.088 15.263 15.39 15.875
3/4" - 14 UNS 2A 0.0015 19.012 18.75 . . . 17.833 17.704 16.853 2B 17.094 17.475 17.871 18.042 19.05
3/4" - 18UNS 2A 0.0014 19.014 18.793 . . . 18.098 17.981 17.336 2B 17.526 17.856 18.133 18.285 19.05
3/4" - 24 UNS 2A 0.0012 19.02 18.837 . . . 18.331 18.227 17.76 2B 17.907 18.161 18.362 18.496 19.05
3/4" - 24 UNS 2A 0.0012 19.02 18.849 . . . 18.407 18.308 17.899 2B 18.034 18.263 18.438 18.567 19.05
7/8" - 10 UNS 2A 0.0018 22.179 21.852 . . . 20.528 20.376 19.157 2B 19.482 20.015 20.574 20.772 22.225
7/8" - 18UNS 2A 0.0014 22.189 21.968 . . . 21.273 21.156 20.511 2B 20.701 21.031 21.308 21.46 22.225
7/8" - 24 UNS 2A 0.0012 22.195 22.012 . . . 21.506 21.402 20.935 2B 21.082 21.336 21.537 21.671 22.225
7/8" - 27 UNS 2A 0.0012 22.195 22.024 . . . 21.582 21.483 21.074 2B 21.209 21.438 21.613 21.742 22.225
1" - 10 UNS 2A 0.0018 25.354 25.027 . . . 23.703 23.546 22.332 2B 22.657 23.19 23.749 23.952 25.4
1" - 14 UNSf 1A 0.0017 25.357 24.963 . . . 24.178 23.965 23.195 1B 23.444 23.825 24.221 24.498 25.4
1" - 14 UNSf 2A 0.0017 25.357 25.095 . . . 24.178 24.036 23.195 2B 23.444 23.825 24.221 24.407 25.4
1" - 14 UNSf 3A 0 25.4 25.138 . . . 24.221 24.115 23.238 3B 23.444 23.66 24.221 24.359 25.4
1" - 18UNS 2A 0.0014 25.364 25.143 . . . 24.448 24.328 23.686 2B 23.876 24.206 24.483 24.641 25.4
1" - 24 UNS 2A 0.0013 25.367 25.184 . . . 24.679 24.572 24.107 2B 24.257 24.511 24.712 24.851 25.4
1" - 27 UNS 2A 0.0012 25.37 25.199 . . . 24.757 24.656 24.249 2B 24.384 24.613 24.788 24.92 25.4
1 1/8" - 10 UNS 2A 0.0018 28.529 28.202 . . . 26.878 26.721 25.507 2B 25.832 26.365 26.924 27.127 28.575
1 1/8" - 14 UNS 2A 0.0016 28.534 28.273 . . . 27.356 27.221 26.375 2B 26.619 27.026 27.396 27.572 28.575
1 1/8" - 24 UNS 2A 0.0013 28.542 28.359 . . . 27.854 27.747 27.285 2B 27.432 27.686 27.887 28.026 28.575
1 1/4" -10 UNS 2A 0.0019 31.702 31.374 . . . 30.051 29.891 28.679 2B 29.007 29.54 30.099 30.307 31.75
1 1/4" -14 UNS 2A 0.0016 31.709 31.448 . . . 30.531 30.394 29.55 2B 29.794 30.175 30.571 30.749 31.75
1 1/4" -24 UNS 2A 0.0013 31.717 31.534 . . . 31.029 30.919 30.457 2B 30.607 30.861 31.062 31.204 31.75
1 3/8" - 10 UNS 2A 0.0019 34.877 34.549 . . . 33.226 33.066 31.854 2B 32.182 32.715 33.274 33.482 34.925
1 3/8" - 14 UNS 2A 0.0016 34.884 34.623 . . . 33.706 33.569 32.725 2B 32.969 33.376 33.746 33.924 34.925
1 3/8" - 24 UNS 2A 0.0013 34.892 34.709 . . . 34.204 34.094 33.632 2B 33.782 34.036 34.237 34.379 34.925
1 1/2" - 10 UNS 2A 0.0019 38.052 37.724 . . . 36.401 36.238 35.029 2B 35.357 35.89 36.449 36.66 38.1
1 1/2" - 14 UNS 2A 0.0017 38.057 37.795 . . . 36.878 36.739 35.898 2B 36.144 36.525 36.921 37.104 38.1
1 1/2" - 24 UNS 2A 0.0013 38.067 37.884 . . . 37.379 37.267 36.807 2B 36.957 37.211 37.412 37.559 38.1
1 5/8" - 10 UNS 2A 0.0019 41.227 40.899 . . . 39.576 39.413 38.204 2B 38.532 39.065 39.624 39.835 41.275
1 5/8" - 14 UNS 2A 0.0017 41.232 40.97 . . . 40.053 39.914 39.073 2B 39.319 39.726 40.096 40.279 41.275
1 5/8" - 24 UNS 2A 0.0013 41.242 41.059 . . . 40.554 40.442 39.982 2B 40.132 40.386 40.587 40.734 41.275
1 3/4" - 10 UNS 2A 0.0019 44.402 44.074 . . . 42.751 42.586 41.379 2B 41.707 42.24 42.799 43.012 44.45
1 3/4" - 14 UNS 2A 0.0017 44.407 44.145 . . . 43.228 43.086 42.245 2B 42.494 42.875 43.271 43.457 44.45
1 3/4" - 18UNS 2A 0.0015 44.412 44.191 . . . 43.495 43.365 42.733 2B 42.926 43.256 43.533 43.701 44.45
1 7/8" - 10 UNS 2A 0.0019 47.577 47.249 . . . 45.926 45.761 44.554 2B 44.882 45.415 45.974 46.187 47.625
1 7/8" - 14 UNS 2A 0.0017 47.582 47.32 . . . 46.403 46.261 45.423 2B 45.669 46.076 46.446 46.632 47.625
1 7/8" - 18UNS 2A 0.0015 47.587 47.366 . . . 46.67 46.54 45.908 2B 46.101 46.431 46.708 46.876 47.625
2" - 10 UNS 2A 0.002 50.749 50.422 . . . 49.098 48.933 47.727 2B 48.057 48.59 49.149 49.365 50.8
2" - 14 UNS 2A 0.0017 50.757 50.495 . . . 49.578 49.433 48.598 2B 48.844 49.225 49.621 49.809 50.8
2" - 18UNS 2A 0.0015 50.762 50.541 . . . 49.845 49.715 49.083 2B 49.276 49.606 49.883 50.053 50.8
2 1/16" - 16UNS 2A 0.0016 52.347 52.108 . . . 51.316 51.178 50.455 2B 50.673 51.029 51.356 51.534 52.388
2 1/16" - 16UNS 3A 0 52.388 52.149 . . . 51.356 51.255 50.495 3B 50.673 50.884 51.356 51.488 52.388
2 3/16" UNS 2A 0.0016 55.522 55.283 . . . 54.491 54.353 53.63 2B 53.848 54.204 54.531 54.709 55.563
2 3/16" UNS 3A 0 55.563 55.324 . . . 54.531 54.427 53.67 3B 53.848 54.059 54.531 54.663 55.563
2 1/4" - 10 UNS 2A 0.002 57.099 56.772 . . . 55.448 55.283 54.077 2B 54.407 54.94 55.499 55.715 57.15
2 1/4" - 14 UNS 2A 0.0017 57.107 56.845 . . . 55.928 55.783 54.948 2B 55.194 55.575 55.971 56.159 57.15
2 1/4" - 18UNS 2A 0.0015 57.112 56.891 . . . 56.195 56.065 55.433 2B 55.626 55.956 56.233 56.403 57.15
2 5/16" - 16UNS 2A 0.0017 58.694 58.456 . . . 57.663 57.523 56.802 2B 57.023 57.379 57.706 57.889 58.738
2 5/16" - 16UNS 3A 0 58.738 58.499 . . . 57.706 57.602 56.845 3B 57.023 57.234 57.706 57.843 58.738
2 7/16" - 16UNS 2A 0.0017 61.869 61.631 . . . 60.838 60.698 59.977 2B 60.198 60.554 60.881 61.064 61.913
2 7/16" - 16UNS 3A 0 61.913 61.674 . . . 60.881 60.777 60.02 3B 60.198 60.409 60.881 61.018 61.913
2 1/2" - 10 UNS 2A 0.002 63.449 63.122 . . . 61.798 61.628 60.427 2B 60.757 61.29 61.849 62.07 63.5
2 1/2" - 14 UNS 2A 0.0017 63.457 63.195 . . . 62.278 62.131 61.298 2B 61.544 61.925 62.321 62.514 63.5
2 1/2" - 18UNS 2A 0.0016 63.459 63.238 . . . 62.542 62.408 61.78 2B 61.976 62.306 62.583 62.758 63.5
2 3/4" - 10 UNS 2A 0.002 69.799 69.472 . . . 68.148 67.978 66.777 2B 67.107 67.64 68.199 68.42 69.85
2 3/4" - 14 UNS 2A 0.0017 69.807 69.545 . . . 68.628 68.481 67.648 2B 67.894 68.275 68.671 68.864 69.85
2 3/4" - 18UNS 2A 0.0016 69.809 69.588 . . . 68.892 68.758 68.13 2B 68.326 68.656 68.933 69.108 69.85
3" - 10 UNS 2A 0.002 76.149 75.822 . . . 74.498 74.325 73.127 2B 73.457 73.99 74.549 74.775 76.2
3" - 14 UNS 2A 0.0018 76.154 75.893 . . . 74.976 74.826 73.995 2B 74.244 74.625 75.021 75.217 76.2
3" - 18UNS 2A 0.0016 76.159 75.938 . . . 75.242 75.105 74.48 2B 74.676 75.006 75.283 75.461 76.2
3 1/4" - 10 UNS 2A 0.002 82.499 82.172 . . . 80.848 80.675 79.477 2B 79.807 80.34 80.899 81.125 82.55
3 1/4" - 14 UNS 2A 0.0018 82.504 82.243 . . . 81.326 81.176 80.345 2B 80.594 80.975 81.371 81.567 82.55
3 1/4" - 18UNS 2A 0.0016 82.509 82.288 . . . 81.592 81.455 80.83 2B 81.026 81.356 81.633 81.811 82.55
3 1/2" - 10 UNS 2A 0.0021 88.847 88.519 . . . 87.196 87.02 85.824 2B 86.157 86.69 87.249 87.478 88.9
3 1/2" - 14 UNS 2A 0.0018 88.854 88.593 . . . 87.676 87.521 86.695 2B 86.944 87.325 87.721 87.922 88.9
3 1/2" - 18UNS 2A 0.0017 88.857 88.636 . . . 87.94 87.8 87.178 2B 87.376 87.706 87.983 88.166 88.9
3 3/4" - 10 UNS 2A 0.0021 95.197 94.869 . . . 93.546 93.37 92.174 2B 92.507 93.04 93.599 93.828 95.25
3 3/4" - 14 UNS 2A 0.0018 95.204 94.943 . . . 94.026 93.871 93.045 2B 93.294 93.675 94.071 94.272 95.25
3 3/4" - 18UNS 2A 0.0017 95.207 94.986 . . . 94.29 94.15 93.528 2B 93.726 94.056 94.333 94.516 95.25
4" - 10 UNS 2A 0.0021 101.547 101.219 . . . 99.896 99.718 98.471 2B 98.857 99.39 99.949 100.18 101.6
4" - 14 UNS 2A 0.0018 101.554 101.293 . . . 100.376 100.218 99.395 2B 99.644 100.025 100.421 100.625 101.6
4 1/4" - 10 UNS 2A 0.0021 107.897 107.569 . . . 106.246 106.068 104.874 2B 105.207 105.74 106.299 106.53 107.95
4 1/4" - 14 UNS 2A 0.0018 107.904 107.643 . . . 106.726 106.568 105.745 2B 105.994 106.375 106.771 106.975 107.95
4 1/2" - 10 UNS 2A 0.0021 114.247 113.919 . . . 112.596 112.418 111.224 2B 111.557 112.09 112.649 112.88 114.3
4 1/2" - 14 UNS 2A 0.0018 114.254 113.993 . . . 113.076 112.918 112.095 2B 112.344 112.725 113.121 113.325 114.3
5 3/4" - 10UNS 2A 0.0022 145.994 145.666 . . . 144.343 144.155 142.972 2B 143.307 143.84 144.399 144.643 146.05
5 3/4" - 14 UNS 2A 0.002 145.999 145.738 . . . 144.821 144.656 143.84 2B 144.094 144.475 144.871 145.087 146.05
6" - 10 UNS 2A 0.0022 152.344 152.016 . . . 150.693 150.505 149.322 2B 149.657 150.19 150.749 150.993 152.4
6" - 14 UNS 2A 0.002 152.349 152.088 . . . 151.171 151.006 150.19 2B 150.444 150.825 151.221 151.437 152.4