Dimensions of ASME B18.6.3 Combination Slotted Type 3 Square Recessed Truss Head Machine Screws

Nominal Size or Basic Screw Diameter	Head Diameter, A		Head Height, H		Slot Width, J		Slot Depth, D		Recess Across Flats, M	Recess Depth, T	Recess Size	Recess Penetration Gaging Depth, P
	Max	Min	Max	Min	Max	Min	Max	Min				Max	Min
2	0.194	0.180	0.053	0.044	0.031	0.023	0.031	0.020	0.050	0.057	00	0.033	0.028
3	0.226	0.211	0.061	0.051	0.035	0.027	0.036	0.023	0.070	0.066	0	0.038	0.028
4	0.257	0.241	0.069	0.059	0.039	0.031	0.040	0.027	0.070	0.066	0	0.038	0.028
5	0.289	0.272	0.078	0.066	0.043	0.035	0.045	0.030	0.091	0.096	1S	0.055	0.040
6	0.321	0.303	0.086	0.074	0.048	0.039	0.050	0.033	0.091	0.096	1S	0.055	0.040
8	0.384	0.364	0.102	0.088	0.054	0.045	0.058	0.040	0.112	0.115	2S	0.063	0.048
10	0.448	0.425	0.128	0.113	0.060	0.050	0.068	0.048	0.112	0.115	2R	0.075	0.060
12	0.511	0.487	0.134	0.118	0.067	0.056	0.077	0.055	0.133	0.143	3S	0.080	0.065
1/4	0.573	0.546	0.150	0.133	0.075	0.064	0.087	0.063	0.133	0.143	3S	0.080	0.065
5/16	0.698	0.666	0.183	0.162	0.084	0.072	0.106	0.076	0.191	0.194	4R	0.100	0.085
3/8	0.823	0.787	0.215	0.191	0.094	0.081	0.124	0.090	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.
• Due to the underfill of material caused by the combination recess, the minimum slot depths are approximately 10% lower than slotted truss heads.
• "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.