Dimensions of ASME B18.6.3 Slotted Undercut Flat Countersunk Head Machine Screws

Nominal Size or Basic Screw Diameter	Length, L	Head Diameter, A		Head Height, H		Slot Width, J		Slot Depth, T		Protrusion Above Gaging Diameter, F		Gaging Diameter, G
		Max	Min	Max	Min	Max	Min	Max	Min	Max	Min
0	1/8	0.112	0.096	0.025	0.018	0.023	0.016	0.011	0.007	Note 4	Note 4	Note 4
1	1/8	0.137	0.120	0.031	0.023	0.026	0.019	0.014	0.009	Note 4	Note 4	Note 4
2	1/8	0.162	0.144	0.036	0.028	0.031	0.023	0.016	0.011	0.029	0.017	0.124
3	1/8	0.187	0.167	0.042	0.033	0.035	0.027	0.019	0.012	0.031	0.018	0.148
4	3/16	0.212	0.191	0.047	0.038	0.039	0.031	0.022	0.014	0.032	0.019	0.172
5	3/16	0.237	0.215	0.053	0.043	0.043	0.035	0.024	0.016	0.034	0.020	0.196
6	3/16	0.262	0.238	0.059	0.048	0.048	0.039	0.027	0.017	0.036	0.021	0.220
8	1/4	0.312	0.285	0.070	0.058	0.054	0.045	0.032	0.021	0.039	0.023	0.267
10	5/16	0.362	0.333	0.081	0.068	0.060	0.050	0.037	0.024	0.042	0.025	0.313
12	3/8	0.412	0.380	0.092	0.078	0.067	0.056	0.043	0.028	0.045	0.027	0.362
1/4	7/16	0.477	0.442	0.107	0.092	0.075	0.064	0.050	0.032	0.050	0.029	0.424
5/16	1/2	0.597	0.556	0.134	0.116	0.084	0.072	0.062	0.041	0.057	0.034	0.539
3/8	9/16	0.717	0.670	0.161	0.140	0.094	0.081	0.075	0.049	0.065	0.039	0.653
7/16	5/8	0.760	0.715	0.156	0.133	0.094	0.081	0.072	0.045	0.073	0.044	0.690
1/2	3/4	0.815	0.765	0.156	0.130	0.106	0.091	0.072	0.046	0.081	0.049	0.739

Note :

• Where specifying nominal size in decimals, zeros preceding the decimals and in the fourth decimal place shall be omitted.
• Screws of these lengths and shorter are undercut. Screws of longer lengths shall have head heights.
• No tolerance for gaging diameter is given. If the gaging diameter of the gage used differs from tabulated value, the protrusion will be affected accordingly and the proper protusion values must be recalculated using the formulas.
• Not practical to gage.