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 0.330 0.341 0.345 0.360 0.383 0.399 0.417 0.410 0.446 0.461 0.472 0.502 0.517 0.524 0.527 0.535 0.565 0.580 0.586 0.597 0.642 0.642 0.660 0.682 0.696 0.711 0.722
Max b 0.340 0.349 0.352 0.376 0.395 0.407 0.434 0.428 0.457 0.470 0.490 0.515 0.527 0.532 0.546 0.553 0.578 0.590 0.595 0.615 0.652 0.663 0.678 0.696 0.707 0.720 0.740
Min a
Max b
Max 0.335 0.345 0.349 0.368 0.389 0.403 0.426 0.414 0.452 0.467 0.476 0.509 0.522 0.528 0.536 0.544 0.572 0.585 0.591 0.606 0.647 0.653 0.669 0.689 0.702 0.716 0.731
Min 0.333 0.343 0.346 0.364 0.386 0.401 0.421 0.414 0.449 0.463 0.476 0.505 0.520 0.526 0.532 0.540 0.568 0.583 0.588 0.602 0.645 0.647 0.665 0.686 0.699 0.713 0.727
Max 0.338 0.347 0.350 0.372 0.391 0.406 0.430 0.424 0.454 0.468 0.486 0.512 0.525 0.531 0.541 0.549 0.575 0.588 0.593 0.611 0.650 0.658 0.674 0.693 0.704 0.718 0.736
Min 0.335 0.345 0.347 0.368 0.389 0.403 0.426 0.414 0.452 0.466 0.476 0.509 0.522 0.528 0.536 0.544 0.572 0.585 0.591 0.606 0.647 0.653 0.669 0.689 0.702 0.716 0.731
Min 0.338 0.347 0.349 0.372 0.391 0.406 0.430 0.424 0.454 0.468 0.486 0.512 0.525 0.531 0.541 0.549 0.575 0.588 0.593 0.611 0.650 0.658 0.674 0.693 0.704 0.718 0.736
Max 0.343 0.351 0.353 0.380 0.397 0.410 0.438 0.433 0.460 0.472 0.495 0.518 0.530 0.535 0.551 0.558 0.581 0.593 0.597 0.620 0.655 0.668 0.683 0.700 0.710 0.722 0.745
Max
Min
Max
Min
Min
Max
0.3300 0.3336 0.3314 0.3354 0.3332 0.3372 0.3351 0.3391 0.3410 0.3441 0.3415 0.3455 0.3429 0.3469 0.3444 0.3484 0.3450 0.3488 0.3449 0.3488 0.3461 0.3501 0.3474 0.3514 0.3600 0.3660 0.3630 0.3688 0.3659 0.3717 0.3688 0.3746 0.3830 0.3875 0.3855 0.3896 0.3875 0.3916 0.3896 0.3937 0.3990 0.4020 0.3995 0.4035 0.4011 0.4051 0.4017 0.4067 0.4170 0.4225 0.4196 0.4254 0.4226 0.4284 0.4255 0.4313 0.4100 0.4161 0.4129 0.4192 0.4160 0.4223 0.4192 0.4255 0.4460 0.4498 0.4477 0.4517 0.4497 0.4537 0.4516 0.4556 0.4610 0.4645 0.4620 0.4660 0.4636 0.4676 0.4652 0.4692 0.4720 0.4783 0.4753 0.4813 0.4783 0.4843 0.4813 0.4873 0.5020 0.5065 0.5045 0.5086 0.5065 0.5106 0.5086 0.5127 0.5170 0.5209 0.5186 0.5226 0.5204 0.5244 0.5221 0.5261 0.5240 0.5270 0.5245 0.5285 0.5261 0.5301 0.5277 0.5317 0.5270 0.5328 0.5298 0.5360 0.5329 0.5391 0.5360 0.5422 0.5350 0.5406 0.5377 0.5435 0.5405 0.5463 0.5434 0.5492 0.5650 0.5690 0.5670 0.5711 0.5690 0.5730 0.5711 0.5752 0.5800 0.5834 0.5811 0.5851 0.5829 0.5869 0.5846 0.5886 0.5860 0.5895 0.5870 0.5910 0.5886 0.5926 0.5902 0.5942 0.5970 0.6029 0.6001 0.6057 0.6029 0.6085 0.6057 0.6113 0.6420 0.6459 0.6436 0.6476 0.6454 0.6494 0.6471 0.6511 0.6420 0.6481 0.6449 0.6513 0.6481 0.6545 0.6513 0.6577 0.6600 0.6652 0.6626 0.6680 0.6653 0.6707 0.6680 0.6734 0.6820 0.6866 0.6844 0.6887 0.6865 0.6908 0.6886 0.6929 0.6960 0.6998 0.6977 0.7017 0.6997 0.7037 0.7016 0.7056 0.7110 0.7145 0.7120 0.7160 0.7136 0.7176 0.7152 0.7192 0.7220 0.7276 0.7250 0.7303 0.7276 0.7329 0.7303 0.7356
3 ∕ 8 -24 3 ∕ 8 -32 3 ∕ 8 -36 7 ∕ 16 -14 7 ∕ 16 -20 7 ∕ 16 -28 1 ∕ 2 -13 1 ∕ 2 -12 1 ∕ 2 -20 1 ∕ 2 -28 9 ∕ 16 -12 9 ∕ 16 -18 9 ∕ 16 -24 9 ∕ 16 -28 5 ∕ 8 -11 5 ∕ 8 -12 5 ∕ 8 -18 5 ∕ 8 -24 5 ∕ 8 -28 11 ∕ 16 -12 11 ∕ 16 -24 3 ∕ 4 -10 3 ∕ 4 -12
3 ∕ 4 -16 3 ∕ 4 -20 3 ∕ 4 -28
13 ∕ 16 -12
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