Dimensions of ASME B18.5 Round Head Ribbed Neck Bolts

Nominal Size or Basic Bolt Diameter		Body Diameter, E		Head Diameter, A		Head Height, H		Max Head to Rib Length, M		Number of Ribs, N	Min Diameter Over Ribs, O	Length of Depth Over Ribs, P			Maximum Fillet Radius, R
												=<7/8 Inch	1 in. and 1 1/8	>= 1 1/4 in.
		Max	Min	Max	Min	Max	Min	=<7/8 Inch	>= 1 in.	Apporx.		(+ -) 0.031	(+ -) 0.031	(+ -) 0.031
No. 10	0.19	0.199	0.182	0.469	0.438	0.114	0.094	0.062	0.094	9	0.21	0.25	0.407	0.594	0.031
1/4	0.25	0.26	0.237	0.594	0.563	0.145	0.125	0.062	0.094	10	0.274	0.25	0.407	0.594	0.031
5/16	0.3125	0.324	0.298	0.719	0.688	0.176	0.156	0.062	0.094	12	0.34	0.25	0.407	0.594	0.031
3/8	0.375	0.388	0.360	0.844	0.782	0.208	0.188	0.062	0.094	12	0.405	0.25	0.407	0.594	0.031
7/16	0.4375	0.452	0.421	0.969	0.907	0.239	0.219	0.062	0.094	14	0.47	0.25	0.407	0.594	0.031
1/2	0.5	0.515	0.483	1.094	1.032	0.270	0.250	0.062	0.094	16	0.534	0.25	0.407	0.594	0.031
5/8	0.625	0.642	0.605	1.344	1.219	0.344	0.313	0.125	0.125	19	0.66	0.313	0.438	0.625	0.062
3/4	0.75	0.768	0.729	1.594	1.469	0.406	0.375	0.125	0.125	22	0.785	0.313	0.438	0.625	0.062

Note :

• Where specifying nominal size in decimals, zeros preceding decimal and in the fourth decimal place shall be omitted.
• The minimum radius is one half of the value shown.