Dimensions of ASME B18.6.3 Plain and Slotted Hex Washer Head Machine Screws

Nominal Size or Basic Screw Diameter	Width Across Flats, A		Across Corners, W, Min	Head Height, H		Washers Diameter, B		Washers Thickness, U		Slot Width, J		Slot Depth, T		Protrusion Beyond Gaging Ring, F, Min
	Max	Min		Max	Min	Max	Min	Max	Min	Max	Min	Max	Min
2	0.125	0.120	0.134	0.050	0.040	0.166	0.154	0.016	0.010	-	-	-	-	0.024
3	0.125	0.120	0.134	0.055	0.044	0.177	0.163	0.016	0.010	-	-	-	-	0.026
4	0.188	0.181	0.202	0.060	0.049	0.243	0.225	0.019	0.011	0.039	0.031	0.042	0.025	0.029
5	0.188	0.181	0.202	0.070	0.058	0.260	0.240	0.025	0.015	0.043	0.035	0.049	0.030	0.035
6	0.250	0.244	0.272	0.093	0.080	0.328	0.302	0.025	0.015	0.048	0.039	0.053	0.033	0.048
8	0.250	0.244	0.272	0.110	0.096	0.348	0.322	0.031	0.019	0.054	0.045	0.074	0.052	0.058
10	0.312	0.305	0.340	0.120	0.105	0.414	0.384	0.031	0.019	0.060	0.050	0.080	0.057	0.063
12	0.312	0.305	0.340	0.155	0.139	0.432	0.398	0.039	0.022	0.067	0.056	0.103	0.077	0.083
1/4	0.375	0.367	0.409	0.190	0.172	0.520	0.480	0.050	0.030	0.075	0.064	0.111	0.083	0.103
5/16	0.500	0.489	0.545	0.230	0.208	0.676	0.624	0.055	0.035	0.084	0.072	0.134	0.100	0.125
3/8	0.562	0.551	0.614	0.295	0.270	0.780	0.720	0.063	0.037	0.094	0.081	0.168	0.131	0.162

Notes :

• Unless otherwise specified by purchaser, hex head machine screws sre not slotted.
• Fillet Radius R at junction of sides of hex and top of washers shall not exceed 0.15 times the basic screw diameter.
• A slight rounding of all edges and corners of the hex surfaces shall be permissible.
• Where specifying nominal size in decimals, zeros preceding the decimal and in the fourth decimal place shall be omitted.
• Dimensions across flats and across corners of the head shall be measured at the point of maximum metal. Taper of sides of hex (angle between one side and the axis) shall not exceed 2 deg or 0.004 in., whichever is greater, the specified width across flats being the large dimensions.
• The rounding due to lack of fill on all six corners of the head shall be reasonably uniform and the width across corners of the head shall be such that when a sharp ring having an inside diameter equal to the specified minimum width across corners is placed on the top and bottom of the head, the head shall protrude by an amount equal to, or greater than the F value tabulated.
• Slot depth beyond bottom of indentation on indented heads shall not be less than one-third of the minimum slot depth specified.