BS 916 Square Head Bolt

Square Head Bolts

Nominal size D	No. of threads per inch	Approx. max. width across corners C		Radius under head R	Thickness of head F hex.and sqaure		Nominal size D
Nominal size D	B.S.W	hex.	square.	max.	max.	basic.	Nominal size D
in.		in.	in.	in.	in.	in.	in.
¼	20	0.51	0.63	¹⁄₃₂	0.186	0.166	¼
⁵⁄₁₆	18	0.61	0.74	¹⁄₃₂	0.228	0.208	⁵⁄₁₆
⅜	16	0.69	0.85	¹⁄₃₂	0.270	0.250	⅜
⁷⁄₁₆	16	0.69	0.85	¹⁄₃₂	0.270	0.250	⁷⁄₁₆
½	12	0.95	1.16	¹⁄₃₂	0.363	0.333	½
⁹⁄₁₆	12	1.06	1.30	³⁄₆₄	0.405	0.375	⁹⁄₁₆
⅝	0.11	1.17	1.43	³⁄₆₄	0.447	0.417	⅝
¾	10	1.39	1.70	³⁄₆₄	0.530	0.500	¾
⅞	9	1.50	1.84	¹⁄₁₆	0.623	0.583	⅞
1	8	1.71	2.09	¹⁄₁₆	0.706	0.666	1
1⅛	7	1.93	2.36	⅛	0.79	0.75	1⅛
1¼	7	215	2.63	⅛	0.89	0.83	1¼
1⅜^a	6	2.37	2.90	⅛	0.98	0.92	1⅜^a
1½	6	2.56	3.14	⅛	1.06	1.00	1½
1⅝^a	5	2.78	3.41	⅛	1.18	1.08	1⅝^a
1¾	5	2.98	3.65	⅛	1.27	1.17	1¾
2	4.5	3.19	3.90	⅛	1.43	1.33	2
2¼	4	3.64	3.90	⅛	1.43	1.33	2¼
2½	4	4.10	5.02	³⁄₁₆	1.77	1.67	2½
2¾	3.5	4.49	5.50	³⁄₁₆	1.93	1.83	2¾
3	3.5	4.83	5.91	³⁄₁₆	2.15	2.00	3
3¼^a	3.25	5.23	6.41	¼	2.32	2.17	3¼^a
3½	3.25	5.60	6.86	¼	2.48	2.33	3½
3¾^a	3.	5.98	7.33	¼	2.65	2.50	3¾^a
4	3	6.41	7.85	¼	2.82	2.67	4
4½	2.875	7.37	9.02	¼	3.20	3.00	4½
5	2.750	8.43	10.32	¼	3.53	3.33	5
5½	2.625	9.64	11.81	¼	3.87	3.67	5½
5½	2.5	10.91	13.36	¼	4.20	4.00	6
^a To be dispensed with wherever possible.