Dimensions of ASME B18.6.3 Type 1 Cross Recessed Indented Regular and Large Hex Head Machine Screws

Nominal Size or Basic Screw Diameter	Regular Head			Large Head			Head Height, H		Recess Diameter, M	Recess Depth, T	Recess Width, N	Driver Size	Recess Penetration Gaging Depth		Protrusion Beyond Gaging Ring, F, Min
	Width Across Flats, A		Across Corners, W, Min	Width Across Flats, A		Across Corners, W, Min
	Max	Min		Max	Min		Max	Min					Max	Min
1	0.125	0.120	0.134	-	-	-	0.044	0.036	0.072	0.052	0.014	0	0.054	0.036	0.022
2	0.125	0.120	0.134	-	-	-	0.050	0.040	0.086	0.052	0.017	1	0.054	0.036	0.024
3	0.188	0.181	0.202	-	-	-	0.055	0.044	0.092	0.058	0.017	1	0.060	0.042	0.026
4	0.188	0.181	0.202	0.219	0.213	0.238	0.060	0.049	0.097	0.065	0.017	1	0.067	0.049	0.029
5	0.188	0.181	0.202	0.250	0.244	0.272	0.070	0.058	0.105	0.074	0.017	1	0.076	0.058	0.035
6	0.250	0.244	0.272	-	-	-	0.093	0.080	0.148	0.088	0.026	2	0.089	0.064	0.048
8	0.250	0.244	0.272	0.312	0.305	0.340	0.110	0.096	0.168	0.114	0.029	2	0.115	0.090	0.058
10	0.312	0.305	0.340	-	-	-	0.120	0.105	0.178	0.126	0.029	2	0.127	0.102	0.063
12	0.312	0.305	0.340	0.375	0.367	0.409	0.155	0.139	0.247	0.157	0.033	3	0.152	0.127	0.083
1/4	0.375	0.367	0.409	0.438	0.428	0.477	0.190	0.172	0.277	0.191	0.034	3	0.186	0.161	0.103
5/16	0.500	0.489	0.545	-	-	-	0.230	0.208	0.359	0.242	0.055	4	0.234	0.210	0.125
3/8	0.0562	0.551	0.614	-	-	-	0.295	0.270	0.387	0.275	0.062	4	0.267	0.243	0.162

Notes :

• A slight rounding of all edges and corners of the hex surfaces of indented hex heads shall be permissible provided the diameter of the bearing circle is equal to no less than 90% of the specified minimum width across flats dimension.
• Where specifying nominal size in decimals, zeros preceding the decimal and in the fourth decimal place shall be omitted.
• Unless otherwise specified by purchaser, regular hex heads shall be furnished, and both regular and large head styles may be intented head, trimmed head, or fully upset head contruction, at the option of manufacturer.
• 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.
• The recess depths and penetrations given are intended to include the depth of the indentation. Due to possible variations in the indentation depths, there could be variations in these dimensions. In these cases, the requirements are to be as agreed upon between the manufacturer and his customer.