Low-strength ASTM A563 Grade A and SAE J995 coupling nuts are typically manufactured to standard hex nut dimensions across the flats and corners of the nut. The length will vary from slightly more than three diameters in smaller-diameter coupling nuts to slightly less than three diameters for larger sizes. High-strength A563 Grade DH and A194 Grade 2H coupling nuts measure three diameters in length. Note that some coupling nuts may be supplied in slightly larger hex sizes due to variances in commercially available hex bar from which most coupling nuts are produced.
Nonstandard coupling nuts can be manufactured to any ASTM or SAE nut specification and have different dimensional requirements.
Finished Hex Coupler Dimensions
| Nominal Size | F | C | H | Part Numbers | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Width Across Flats | Width Across Corners | Length/Thickness | Import | |||||||
| Basic | Max | Min | Max | Min | Basic | Max | Min | Plain | Galvanized | |
| 1⁄2 | 11⁄16 | 0.688 | 0.663 | 0.794 | 0.756 | 13⁄4 | 1.760 | 1.690 | 12338 | 17525 |
| 5⁄8 | 13⁄16 | 0.813 | 0.782 | 0.939 | 0.891 | 21⁄8 | 2.135 | 2.067 | 12559 | 18195 |
| 3⁄4 | 1 | 1.000 | 0.963 | 1.155 | 1.097 | 21⁄4 | 2.260 | 2.190 | 12557 | 17526 |
| 7⁄8 | 11⁄4 | 1.250 | 1.212 | 1.443 | 1.382 | 21⁄2 | 2.510 | 2.440 | 12558 | 19504 |
| 1 | 13⁄8 | 1.375 | 1.325 | 1.588 | 1.511 | 23⁄4 | 2.760 | 2.690 | – | 18494 |
| 11⁄8 | 11⁄2 | 1.500 | 1.450 | 1.732 | 1.653 | 3 | 3.010 | 2.940 | 18394 | – |
| 11⁄4 | 15⁄8 | 1.625 | 1.575 | 1.876 | 1.825 | 3 | 3.010 | 2.940 | 18994 | 17529 |
| 11⁄2 | 2 | 2.000 | 1.950 | 2.309 | 2.275 | 31⁄2 | 3.510 | 3.440 | – | – |
| Dimensions per ASME B18.2.2 2010 | ||||||||||
Heavy Hex Coupling Nut Pattern
| Nominal Size | F | C | H | Part Numbers | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Width Across Flats | Width Across Corners | Thickness | A563DH Domestic | |||||||
| Basic | Max | Min | Max | Min | Basic | Max | Min | Plain | Galvanized | |
| 1⁄2 | 7⁄8 | 0.875 | 0.850 | 1.010 | 0.969 | 11⁄2 | – | – | 17541 | 17542 |
| 5⁄8 | 11⁄16 | 1.062 | 1.031 | 1.227 | 1.175 | 17⁄8 | – | – | 17543 | 17544 |
| 3⁄4 | 11⁄4 | 1.250 | 1.212 | 1.443 | 1.382 | 21⁄4 | – | – | 17528 | 17527 |
| 7⁄8 | 17⁄16 | 1.438 | 1.394 | 1.660 | 1.589 | 25⁄8 | – | – | 19501 | 19502* |
| 1 | 15⁄8 | 1.625 | 1.575 | 1.876 | 1.796 | 3 | – | – | 12344 | 12343 |
| 11⁄8 | 113⁄16 | 1.812 | 1.756 | 2.093 | 2.002 | 33⁄8 | – | – | 12348 | 12349 |
| 11⁄4 | 2 | 2.000 | 1.938 | 2.309 | 2.209 | 33⁄4 | – | – | 17547 | 17548 |
| 11⁄2 | 23⁄8 | 2.375 | 2.300 | 2.742 | 2.622 | 41⁄2 | – | – | 17551 | 17552 |
| 15⁄8 | 29⁄16 | 2.562 | 2.481 | 2.959 | 2.828 | 47⁄8 | 4.91 | 4.83 | – | – |
| 13⁄4 | 23⁄4 | 2.750 | 2.662 | 3.175 | 3.035 | 51⁄4 | 5.29 | 5.21 | 17553 | 17554 |
| 17⁄8 | 215⁄16 | 2.938 | 2.844 | 3.392 | 3.242 | 55⁄8 | 5.67 | 5.58 | – | – |
| 2 | 31⁄8 | 3.125 | 3.025 | 3.608 | 3.449 | 6 | 6.04 | 5.95 | 17555 | 17556 |
| 21⁄4 | 31⁄2 | 3.500 | 3.388 | 4.041 | 3.862 | 63⁄4 | 6.80 | 6.70 | – | – |
| 21⁄2 | 37⁄8 | 3.875 | 3.750 | 4.474 | 4.275 | 71⁄2 | 7.55 | 7.44 | – | – |
| 23⁄4 | 41⁄4 | 4.250 | 4.112 | 4.907 | 4.688 | 81⁄4 | 8.31 | 8.19 | – | – |
| 3 | 45⁄8 | 4.625 | 4.475 | 5.340 | 5.102 | 9 | 9.06 | 8.94 | – | – |
| 31⁄4 | 5 | 5.000 | 4.838 | 5.774 | 5.515 | 93⁄4 | 9.81 | 9.68 | – | – |
| 31⁄2 | 53⁄8 | 5.375 | 5.200 | 6.207 | 5.928 | 101⁄2 | 10.57 | 10.43 | – | – |
| 33⁄4 | 53⁄4 | 5.750 | 5.562 | 6.640 | 6.341 | 111⁄4 | 11.32 | 11.17 | – | – |
| 4 | 61⁄8 | 6.125 | 5.925 | 7.073 | 6.755 | 12 | 12.08 | 11.92 | – | – |
| 41⁄2 | 67⁄8 | 6.875 | 6.650 | 7.939 | 7.581 | 131⁄2 | – | – | – | – |
| 5 | 75⁄8 | 7.625 | 7.375 | 8.805 | 8.408 | 15 | – | – | – | – |
| Heavy coupler dimensions are not defined by ASME 18.2.2. The width across the flats and corners match the dimensions of a heavy hex nut. * 7/8″ Galvanized Couplers are 3″ long. |
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