ASME B18.2.1 Hex Cap Screws

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
  • GENERAL NOTE:
    • (a) See Table 10 for underhead fillet dimensions and Table 11 for LG, max. and LB, min. dimensions for fully threaded short screws.
    • (b) Refer to section 4 for further information.