Table 3. Recommended Hole Size Limits Before Tapping Unified Threads Table 3. (Continued) Recommended Hole Size Limits Before Tapping Unified Threads
Classes 1B and 2B
Class 3B
Length of Engagement ( D = Nominal Size of Thread)
Thread Size
Above 2 ∕ 3 D to 1 1 ∕ 2 D
Above 1 1 ∕ 2 D to 3 D
Above 2 ∕ 3 D to 1 1 ∕ 2 D
Above 1 1 ∕ 2 D to 3 D
Above 1 ∕ 3 D to 2 ∕ 3 D
Above 1 ∕ 3 D to 2 ∕ 3 D
To and Including 1 ∕ 3 D
To and Including 1 ∕ 3 D
Recommended Hole Size Limits
Min a 2.115 2.160 2.182 2.196 2.245 2.285 2.307 2.370 2.229 2.365 2.410 2.432 2.446 2.535 2.557 2.479 2.615 2.660 2.682 2.785 2.807 2.729 2.865 2.910 2.932 3.035 3.057
Max b 2.140 2.178 2.196 2.207 2.259 2.303 2.321 2.384 2.267 2.390 2.428 2.446 2.457 2.553 2.571 2.517 2.640 2.678 2.696 2.803 2.821 2.767 2.890 2.928 2.946 3.053 3.071
Min a
Max b
Max 2.128 2.169 2.189 2.202 2.252 2.294 2.314 2.377 2.248 2.378 2.419 2.439 2.452 2.544 2.564 2.498 2.628 2.669 2.689 2.794 2.814 2.748 2.878 2.919 2.939 3.044 3.064
Min 2.121 2.165 2.186 2.199 2.249 2.290 2.311 2.374 2.238 2.371 2.415 2.436 2.449 2.540 2.561 2.489 2.621 2.665 2.686 2.790 2.811 2.739 2.871 2.915 2.936 3.040 3.061
Max 2.134 2.174 2.193 2.204 2.256 2.299 2.318 2.381 2.258 2.384 2.424 2.443 2.454 2.549 2.568 2.508 2.634 2.674 2.693 2.809 2.818 2.758 2.884 2.924 2.943 3.049 3.068
Min 2.128 2.169 2.189 2.202 2.252 2.294 2.314 2.377 2.248 2.378 2.419 2.439 2.452 2.544 2.564 2.498 2.628 2.669 2.689 2.794 2.814 2.748 2.878 2.919 2.939 3.044 3.064
Min 2.134 2.174 2.193 2.204 2.256 2.299 2.318 2.381 2.258 2.384 2.424 2.443 2.454 2.549 2.568 2.508 2.634 2.674 2.693 2.809 2.818 2.758 2.884 2.924 2.943 3.049 3.068
Max 2.146 2.182 2.200 2.210 2.263 2.308 2.325 2.388 2.277 2.396 2.433 2.450 2.460 2.558 2.575 2.527 2.644 2.683 2.700 2.808 2.825 2.777 2.896 2.933 2.950 3.058 3.075
Max
Min
Max
Min
Min
Max
2.1150 2.1222 2.1184 2.1259 2.1222 2.1297 2.1260 2.1335 2.1600 2.1648 2.1623 2.1673 2.1648 2.1698 2.1673 2.1723 2.1820 2.1866 2.1844 2.1887 2.1865 2.1908 2.1886 2.1929 2.1960 2.1998 2.1977 2.2017 2.1997 2.2037 2.2016 2.2056 2.2450 2.2491 2.2469 2.2512 2.2490 2.2533 2.2511 2.2554 2.2850 2.2898 2.2873 2.2923 2.2898 2.2948 2.2923 2.2973 2.3070 2.3116 2.3094 2.3137 2.3115 2.3158 2.3136 2.3179 2.3700 2.3741 2.3719 2.3762 2.3740 2.3783 2.3761 2.3804 2.2290 2.2444 2.2369 2.2519 2.2444 2.2594 2.2519 2.2669 2.3650 2.3722 2.3684 2.3759 2.3722 2.3797 2.3760 2.3835 2.4100 2.4148 2.4123 2.4173 2.4148 2.4198 2.4173 2.4223 2.4320 2.4366 2.4344 2.4387 2.4365 2.4408 2.4386 2.4429 2.4460 2.4498 2.4478 2.4517 2.4497 2.4537 2.4516 2.4556 2.5350 2.5398 2.5373 2.5423 2.5398 2.5448 2.5423 2.5473 2.5570 2.5616 2.5594 2.5637 2.5615 2.5658 2.5636 2.5679 2.4790 2.4944 2.4869 2.5019 2.4944 2.5094 2.5019 2.5169 2.6150 2.6222 2.6184 2.6259 2.6222 2.6297 2.6260 2.6335 2.6600 2.6648 2.6623 2.6673 2.6648 2.6698 2.6673 2.6723 2.6820 2.6866 2.6844 2.6887 2.6865 2.6908 2.6886 2.6929 2.7850 2.7898 2.7873 2.7923 2.7898 2.7948 2.7923 2.7973 2.8070 2.8116 2.8094 2.8137 2.8115 2.8158 2.8136 2.8179 2.7290 2.7444 2.7369 2.7519 2.7444 2.7594 2.7519 2.7669 2.8650 2.8722 2.8684 2.8759 2.8722 2.8797 2.8760 2.8835 2.9100 2.9148 2.9123 2.9173 2.9148 2.9198 2.9173 2.9223 2.9320 2.9366 2.9344 2.9387 2.9365 2.9408 2.9386 2.9429 3.0350 3.0398 3.0373 3.0423 3.0398 3.0448 3.0423 3.0473 3.0570 3.0616 3.0594 3.0637 3.0615 3.0658 3.0636 3.0679
2 1 ∕ 4 -8 2 1 ∕ 4 -12 2 1 ∕ 4 -16 2 1 ∕ 4 -20 2 5 ∕ 16 -16 2 3 ∕ 8 -12 2 3 ∕ 8 -16 2 7 ∕ 16 -16 2 1 ∕ 2 -4 2 1 ∕ 2 -8 2 1 ∕ 2 -12 2 1 ∕ 2 -16 2 1 ∕ 2 -20 2 5 ∕ 8 -12 2 5 ∕ 8 -16 2 3 ∕ 4 -4 2 3 ∕ 4 -8 2 3 ∕ 4 -12 2 3 ∕ 4 -16 2 7 ∕ 8 -12 2 7 ∕ 8 -16
3-4 3-8 3-12 3-16
3 1 ∕ 8 -12 3 1 ∕ 8 -16
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