Dimensions of ASME B18.6.3 Square and Hex Machine Screw Nuts

Nominal Size or Basic Screw Diameter	Width Across Flats, F			Width Across Corners				Thickness, H
				Square, G		Hex, G1
	Basic	Max	Min	Max	Min	Max	Min	Max	Min
0	5/32	0.156	0.150	0.221	0.206	0.180	0.171	0.050	0.043
1	5/32	0.156	0.150	0.221	0.206	0.180	0.171	0.050	0.043
2	3/16	0.188	0.180	0.265	0.247	0.217	0.205	0.066	0.057
3	3/16	0.188	0.180	0.265	0.247	0.217	0.205	0.066	0.057
4	1/4	0.250	0.241	0.354	0.331	0.289	0.275	0.098	0.087
5	5/16	0.312	0.302	0.442	0.415	0.361	0.344	0.114	0.102
6	5/16	0.312	0.302	0.442	0.415	0.361	0.344	0.114	0.102
8	11/32	0.344	0.332	0.486	0.456	0.397	0.378	0.130	0.117
10	3/8	0.375	0.362	0.530	0.497	0.433	0.413	0.130	0.117
12	7/16	0.438	0.423	0.619	0.581	0.505	0.482	0.161	0.148
1/4	7/16	0.438	0.423	0.619	0.581	0.505	0.482	0.193	0.178
5/16	9/16	0.562	0.545	0.795	0.748	0.650	0.621	0.225	0.208
3/8	5/8	0.625	0.607	0.884	0.833	0.722	0.692	0.257	0.239

Notes :

• Square macine screw nuts shall have tops and bottoms flat, and un-chamfered. The flat surfaces shall be perpendicular to the axis of the threaded hole pitch cylinder within a tolerance of 4 deg.
• Hexagon machine screw nuts shall have top and bottom surfaces flat, with chamfered corners. the flat surfaces diameter shall ne equal to the maximum width acroos flats, with a tolerance of minus 15%. The bearing surface shall be perpendicular to the axis of the threaded hole pitch cylinder within a tolerance of 4 deg.
• Bottoms of hexagon machine screw nuts may be supplied with flat, but un-chamfered surfaces at the options of the manufacturers.
• Where specifying nominal size in decimals, zeros preceding the decimal and in the fourth decimal place shall be omitted.