BS 3692

Dimensions of Hexagon Head Bolts

Thread Diameter, A, mm	Pitch Of Thread	Dia of Shank Unthreaded, mm		Width Across Flats, E, mm		Width Across Corners, F, mm		Height of Head, D, mm		Radius Under Head, mm
Thread Diameter, A, mm	Coarse Pitch Series	Min	Max	Min	Max	Min	Max	Min	Max	Min	Max
M5	0.8	4.82	5.0	7.85	8.0	8.87	9.2	3.35	3.65	0.2	0.35
M6	1	5.82	6.0	9.78	10.0	11.05	11.5	3.85	4.15	0.25	0.4
M8	1.25	7.78	8.0	12.73	13.0	14.38	15.0	5.35	5.65	0.4	0.6
M10	1.5	9.78	10.0	16.73	17.0	18.90	19.6	6.82	7.18	0.4	0.6
M12	1.75	11.73	12.0	18.67	19.0	21.10	21.9	7.82	8.18	0.6	1.1
M14	2	13.73	14.0	21.67	22.0	24.49	25.4	8.82	9.18	0.6	1.1
M16	2	15.73	16.0	23.67	24.0	26.75	27.7	9.82	10.18	0.6	1.1
M18	2.5	17.73	18.0	26.67	27.0	30.14	31.2	11.785	12.215	0.6	1.1
M20	2.5	19.67	20.0	29.67	30.0	33.53	34.6	12.785	13.215	0.8	1.2
M22	2.5	21.67	22.0	31.61	32.0	35.72	36.9	13.785	14.215	0.8	1.2
M24	3	23.67	24.0	35.38	36.0	39.98	41.6	14.785	15.215	0.8	1.2
M27	3	26.67	27.0	40.38	41.0	45.63	47.3	16.785	17.215	1.0	1.7
M30	3.5	29.67	30.0	45.38	46.0	51.28	53.1	18.74	19.26	1.0	1.7
M33	3.5	32.61	33.0	49.38	50.0	55.80	57.7	20.74	21.26	1.0	1.7
M36	4	35.61	36.0	54.26	55.0	61.31	63.5	22.74	23.26	1.0	1.7
M39	4	38.61	39.0	59.26	60.0	66.96	69.3	24.74	25.26	1.0	1.7
M42	4.5	41.61	42.0	64.26	65.0	72.61	75.1	25.74	26.26	1.2	1.8
M45	4.5	44.61	45.0	69.26	70.0	78.26	80.8	27.74	28.26	1.2	1.8
M48	5	47.61	48.0	74.26	75.0	83.91	86.6	29.74	30.26	1.6	2.3
M52	5	51.54	52.0	79.26	80.0	89.56	92.4	32.69	33.31	1.6	2.3
M56	5.5	55.54	56.0	84.13	85.0	95.07	98.1	34.69	35.31	2.0	3.5
M60	5.5	59.54	60.0	89.13	90.0	100.72	103.9	37.69	38.31	2.0	3.5
M64	6	63.54	64.0	94.13	95.0	106.37	109.7	39.69	40.31	2.0	3.5
M68	6	67.54	68.0	99.13	100.0	112.02	115.5	42.69	43.31	2.0	3.5

Mechanical Property	Tensile strength R_m				Brinell hardness		Rock well hardness				Vickers hardness HV30		Yield stress R_e		Sress at permanent set limit R₀₂		Stress under proof load S_p			Elongation A after fracture	Strength under wedge loading	Charpy Impact Strength		Head soundness	Decarburization at root of thread	Non-decarburized zone
Strength Grade Designation	min		max		min	max	min		max		min	max	min		min		Stress under proof load S_p			Elongation A after fracture		min
Strength Grade Designation	kgf/mm²	N/mm²	kgf/mm²	N/mm²	HB	HB	HRB	HRC	HRB	HRC	min	max	kgf/mm²	N/mm²	kgf/mm²	N/mm²	S_p/R_e	kgf/mm²	N/mm²	min. percent		kgfm/cm²	ft lbf
4.6	40	392	55	539	110	170	62	–	88	–	110	170	24	235	–	–	0.94	22.6	222	25	See Note 3 for all	–	–	No Fracture (See Note 4)	Depth Not More than 1/10 of H1	Depth Not less than 2/3 of H1
4.8	40	392	55	539	110	170	62	–	88	–	110	170	32	214	–	–	0.91	29.1	286	14		–	–
5.6	50	490	70	686	140	215	77	–	97	–	140	215	30	294	–	–	0.94	28.2	276	20		–	–
5.8	50	490	70	686	140	215	77	–	97	–	140	215	40	392	–	–	0.91	36.4	357	10		–	–
6.6	60	588	80	785	170	245	88	–	102	–	170	245	36	353	–	–	0.94	33.9	333	16		–	–
6.8	60	588	80	785	170	245	88	–	102	–	170	245	48	471	–	–	0.91	43.7	429	8		–	–
8.8	80	785	100	981	225	300	–	18	–	31	225	300	–	–	64	628	0.91	58.2	571	12		6	22
10.9	100	981	120	1177	280	365	–	27	–	38	280	370	–	–	90	883	0.88	79.2	777	9		4	14
12.9	120	117	140	1373	330	425	–	34	–	44	330	440	–	–	108	1059	0.88	95.0	932	8		3	11
14.9	140	1373	160	1569	390	–	–	40	–	49	400	510	–	–	126	1236	0.88	111	1089	7		3	11

Notes:

Only for full size bolts.
The allowed permanent extensions is 12.5 micrometres.
The fracture should not take place immediately under head of the bolt.
Where screws are threaded up to the head this property will be regarded as established even if a crack
should be appear in the first thread, provided that the head does not snap off.