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  5. ASME B18.3 Hexagon And Spline Socket Flat Countersunk Head Cap Screws

ASME B18.3 Hexagon And Spline Socket Flat Countersunk Head Cap Screws

ASME B18.3 Hexagon And Spline Socket Flat Countersunk Head Cap Screws

Nominal Size Body Diameter Head Diameter Head Height Spline Socket Size Hexagon Socket Size Key Engagement
Theoretical Sharp Abs. Min. Reference
Max. Min. Max. Nom. Min.
D A H M J T
ASME B18.3 - 0 0.06 0.0568 0.138 0.117 0.044 0.048 0.035 0.025
ASME B18.3 - 1 0.073 0.0695 0.168 0.143 0.054 0.06 0.05 0.031
ASME B18.3 - 2 0.086 0.0822 0.197 0.168 0.064 0.06 0.05 0.038
ASME B18.3 - 3 0.099 0.0949 0.226 0.193 0.073 0.072 1⁄16 0.044
ASME B18.3 - 4 0.112 0.1075 0.255 0.218 0.083 0.072 1⁄16 0.055
ASME B18.3 - 5 0.125 0.1202 0.281 0.24 0.09 0.096 5⁄64 0.061
ASME B18.3 - 6 0.138 0.1329 0.307 0.263 0.097 0.096 5⁄64 0.066
ASME B18.3 - 8 0.164 0.1585 0.359 0.311 0.112 0.111 3⁄32 0.076
ASME B18.3 - 10 0.19 0.184 0.411 0.359 0.127 0.145 1⁄8 0.087
ASME B18.3 - 1⁄4 0.25 0.2435 0.531 0.48 0.161 0.183 5⁄32 0.111
ASME B18.3 - 5⁄16 0.3125 0.3053 0.656 0.6 0.198 0.216 3⁄16 0.135
ASME B18.3 - 3⁄8 0.375 0.3678 0.781 0.72 0.234 0.251 7⁄32 0.159
ASME B18.3 - 7⁄16 0.4375 0.4294 0.844 0.781 0.234 0.291 1⁄4 0.159
ASME B18.3 - 1⁄2 0.5 0.4919 0.938 0.872 0.251 0.372 5⁄16 0.172
ASME B18.3 - 5⁄8 0.625 0.6163 1.188 1.112 0.324 0.454 3⁄8 0.22
ASME B18.3 - 3⁄4 0.75 0.7406 1.438 1.355 0.396 0.454 1⁄2 0.22
ASME B18.3 - 7⁄8 0.875 0.8647 1.688 1.604 0.468 ... 9⁄16 0.248
ASME B18.3 - 1 1 0.9886 1.938 1.841 0.54 ... 5⁄8 0.297
ASME B18.3 - 1 1⁄8 1.125 1.1086 2.188 2.079 0.611 ... 3⁄4 0.325
ASME B18.3 - 1 1⁄4 1.25 1.2336 2.438 2.316 0.683 ... 7⁄8 0.358
ASME B18.3 - 1 3⁄8 1.375 1.3568 2.688 2.553 0.755 ... 7⁄8 0.402
ASME B18.3 - 1 1⁄2 1.5 1.4818 2.938 2.791 0.827 ... 1 0.435
  • a Key engagement depths are minimum. Spline socket sizes are nominal.
  • All dimensions in inches. The body length LB of the screw is the length of the unthreaded cylindrical portion of the shank. The length of thread, LT, is the distance from the extreme point to the last complete (full form) thread. Standard length increments for screw diameters up to 1 inch are 1 ⁄ 16 inch for lengths 1 ⁄ 8 through 1 ⁄ 4 inch, 1 ⁄ 8 inch for lengths 1 ⁄ 4 through 1 inch, 1 ⁄ 4 inch for lengths 1 through 3 1 ⁄ 2 inches, 1 ⁄ 2 inch for lengths 3 1 ⁄ 2 through 7 inches, 1 inch for lengths 7 through 10 inches and for diameters over 1 inch are 1 ⁄ 2 inch for lengths 1 through 7 inches, 1 inch for lengths 7 through 10 inches, and 2 inches for lengths over 10 inches.