ASME B18.2.1 Hex Cap Screws
| Nominal Size or Basic Product Diameter | Body Diameter, E (See Para. 4.6) | Width Across Flats, F (See Para. 2.1.2) | Width Across Corners, G | Head Height, H | Minimum Wrenching Height, J | Thread Length for Screw Lengths, LT (See Para. 4.7) | Transition Thread Length, Y (See Para. 4.7) | Maximum Total Runout of Bearing Surface FIM (See Para. 4.4) | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Max. | Min. | Basic | Max. | Min. | Max. | Min. | Basic | Max. | Min. | 6 in. and Shorter | Over 6 in. | Reference | ||||
| ASME B18.2.1 - 1⁄4 | 0.25 | 0.25 | 0.245 | 7⁄16 | 0.438 | 0.428 | 0.505 | 0.488 | 5⁄32 | 0.163 | 0.15 | 0.106 | 0.75 | 1 | 0.25 | 0.01 |
| ASME B18.2.1 - 5⁄16 | 0.3125 | 0.3125 | 0.3065 | 1⁄2 | 0.5 | 0.489 | 0.577 | 0.557 | 13⁄64 | 0.211 | 0.195 | 0.14 | 0.875 | 1.125 | 0.278 | 0.011 |
| ASME B18.2.1 - 3⁄8 | 0.375 | 0.375 | 0.369 | 9⁄16 | 0.562 | 0.551 | 0.65 | 0.628 | 15⁄64 | 0.243 | 0.226 | 0.16 | 1 | 1.25 | 0.312 | 0.012 |
| ASME B18.2.1 - 7⁄16 | 0.4375 | 0.4375 | 0.4305 | 5⁄8 | 0.625 | 0.612 | 0.722 | 0.698 | 9⁄32 | 0.291 | 0.272 | 0.195 | 1.125 | 1.375 | 0.357 | 0.013 |
| ASME B18.2.1 - 1⁄2 | 0.5 | 0.5 | 0.493 | 3⁄4 | 0.75 | 0.736 | 0.866 | 0.84 | 5⁄16 | 0.323 | 0.302 | 0.215 | 1.25 | 1.5 | 0.385 | 0.014 |
| ASME B18.2.1 - 9⁄16 | 0.5625 | 0.5625 | 0.5545 | 13⁄16 | 0.812 | 0.798 | 0.938 | 0.91 | 23⁄64 | 0.371 | 0.348 | 0.25 | 1.375 | 1.625 | 0.417 | 0.015 |
| ASME B18.2.1 - 5⁄8 | 0.625 | 0.625 | 0.617 | 15⁄16 | 0.938 | 0.922 | 1.083 | 1.051 | 25⁄64 | 0.403 | 0.378 | 0.269 | 1.5 | 1.75 | 0.455 | 0.017 |
| ASME B18.2.1 - 3⁄4 | 0.75 | 0.75 | 0.741 | 1 1⁄8 | 1.125 | 1.1 | 1.299 | 1.254 | 15⁄32 | 0.483 | 0.455 | 0.324 | 1.75 | 2 | 0.5 | 0.02 |
| ASME B18.2.1 - 7⁄8 | 0.875 | 0.875 | 0.866 | 1 5⁄16 | 1.312 | 1.285 | 1.516 | 1.465 | 35⁄64 | 0.563 | 0.531 | 0.378 | 2 | 2.25 | 0.556 | 0.023 |
| ASME B18.2.1 - 1 | 1 | 1 | 0.99 | 1 1⁄2 | 1.5 | 1.469 | 1.732 | 1.675 | 39⁄64 | 0.627 | 0.591 | 0.416 | 2.25 | 2.5 | 0.625 | 0.026 |
| ASME B18.2.1 - 11⁄8 | 1.125 | 1.125 | 1.114 | 1 11⁄16 | 1.688 | 1.631 | 1.949 | 1.859 | 11⁄16 | 0.718 | 0.658 | 0.461 | 2.5 | 2.75 | 0.714 | 0.029 |
| ASME B18.2.1 - 11⁄4 | 1.25 | 1.25 | 1.239 | 1 7⁄8 | 1.875 | 1.812 | 2.165 | 2.066 | 25⁄32 | 0.813 | 0.749 | 0.53 | 2.75 | 3 | 0.714 | 0.033 |
| ASME B18.2.1 - 13⁄8 | 1.375 | 1.375 | 1.363 | 2 1⁄16 | 2.062 | 1.994 | 2.382 | 2.273 | 27⁄32 | 0.878 | 0.81 | 0.569 | 3 | 3.25 | 0.833 | 0.036 |
| ASME B18.2.1 - 11⁄2 | 1.5 | 1.5 | 1.488 | 2 1⁄4 | 2.25 | 2.175 | 2.598 | 2.48 | 15⁄16 | 0.974 | 0.902 | 0.64 | 3.25 | 3.5 | 0.833 | 0.039 |
| ASME B18.2.1 - 15⁄8 | 1.625 | 1.625 | 1.613 | 2 7⁄16 | 2.438 | 2.356 | 2.815 | 2.686 | 1 | 1.038 | 0.962 | 0.694 | 3.5 | 3.75 | 0.909 | 0.043 |
| ASME B18.2.1 - 1 3⁄4 | 1.75 | 1.75 | 1.738 | 2 5⁄8 | 2.625 | 2.538 | 3.031 | 2.893 | 1 3⁄32 | 1.134 | 1.054 | 0.748 | 3.75 | 4 | 1 | 0.046 |
| ASME B18.2.1 - 17⁄8 | 1.875 | 1.875 | 1.863 | 2 13⁄16 | 2.812 | 2.719 | 3.248 | 3.099 | 1 5⁄32 | 1.198 | 1.114 | 0.802 | 4 | 4.25 | 1 | 0.049 |
| ASME B18.2.1 - 2 | 2 | 2 | 1.988 | 3 | 3 | 2.9 | 3.464 | 3.306 | 1 7⁄32 | 1.263 | 1.175 | 0.825 | 4.25 | 4.5 | 1.111 | 0.052 |
| ASME B18.2.1 - 21⁄4 | 2.25 | 2.25 | 2.238 | 3 3⁄8 | 3.375 | 3.262 | 3.897 | 3.719 | 1 3⁄8 | 1.423 | 1.327 | 0.933 | ... | 5 | 1.111 | 0.059 |
| ASME B18.2.1 - 21⁄2 | 2.5 | 2.5 | 2.488 | 3 3⁄4 | 3.75 | 3.625 | 4.33 | 4.133 | 1 17⁄32 | 1.583 | 1.479 | 1.042 | ... | 5.5 | 1.25 | 0.065 |
| ASME B18.2.1 - 23⁄4 | 2.75 | 2.75 | 2.738 | 4 1⁄8 | 4.125 | 3.988 | 4.763 | 4.546 | 1 11⁄16 | 1.744 | 1.632 | 1.151 | ... | 6 | 1.25 | 0.072 |
| ASME B18.2.1 - 3 | 3 | 3 | 2.988 | 4 1⁄2 | 4.5 | 4.35 | 5.196 | 4.959 | 1 7⁄8 | 1.935 | 1.815 | 1.29 | ... | 6.5 | 1.25 | 0.079 |
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