ASME B18.6.3 Type 3 Square Recessed Round Head Machine Screws

ASME B18.6.3 Type 3 Square Recessed Round Head Machine Screws

Dimensions of Type 3 Square Recessed Round Head Machine Screws

Nominal Size or Basic Screw Diameter Head Diameter, A Head Height, H Recess Across Flats, M Recess Depth, T Recess Size Recess Penetration Gaging Depth
Max Min Max Min Max Min
3 0.187 0.169 0.078 0.067 0.070 0.066 0 0.038 0.028
4 0.211 0.193 0.086 0.075 0.070 0.066 0 0.038 0.028
5 0.236 0.217 0.095 0.083 0.091 0.106 1R 0.065 0.050
6 0.260 0.240 0.103 0.091 0.091 0.096 1R 0.065 0.050
8 0.309 0.287 0.120 0.107 0.112 0.115 2R 0.075 0.060
10 0.359 0.334 0.137 0.123 0.112 0.115 2R 0.075 0.060
12 0.408 0.382 0.153 0.139 0.133 0.143 3R 0.95 0.080
1/4 0.472 0.443 0.175 0.160 0.133 0.143 3R 0.095 0.080
5/16 0.590 0.557 0.216 0.198 0.191 0.194 4R 0.100 0.085
3/8 0.708 0.670 0.256 0.237 0.191 0.194 4R 0.100 0.085

Note :

  • Where specifying nominal size in decimals, zeros preceding the decimals and in the fourth decimal place shall be omitted.
  • "R" in the recess size tabulation means regular depth recess
  • Square recesses incorporate a slight taper on the sides od the recess. This taper can result in loss of penetration gaging depth on finished fasteners due to the build up of plating in recesses. The recess penetrations dimensions specified here are for finished (plated) product. Manufactures should be advised that they should not use all this tolerance in the heading process, or an out of tolerance condition could exist after plating.