BS 4190 Bolting, BS 4190 Hex Bolts, BS 4190 Nuts

BS 4190 Chemical composition of steel nuts

Strength grade designation	Chemical composition limits
	C max. %	P max. %	S max. %
4 and 6 (see note)	0.5	0.11	0.15
8	0.58	0.06	0.15
10	0.58	0.048	0.058
NOTE 1 Free cutting steel may be used only by special agreement between the purchaser and the supplier. In such cases, the following maximum phosphorus, sulfur and lead contents are permissible: phosphorus, 0.12 %, sulfur, 0.34 %, lead, 0.35 %. NOTE 2 Alloying elements may be added if necessary to develop the mechanical properties of the nuts stipulated.

BS 4190 Mechanical properties of steel nuts

Strength grade designation	4	6	8	10	12
Proof load stress a N/mm 2	400	600	800	1000	1200	All nuts other than those exempted by agreement between the purchaser and manufacturerb
Brinell hardness (HB) max.	302	302	302	353	375	All nuts
Rockwell hardness c (HRC) max.	30	30	30	36	39	All nuts
Vickers hardness (HV) max.	310	310	310	370	395	All nuts
a The proof load is calculated by multiplying the proof load stress by the tensile stress area of the bolt. b Nuts with a specified proof load in excess of 500 000 N (see Table 16) may be exempted from proof load testing. Such nuts shall meet the minimum hardness as agreed between the purchaser and the manufacturer. c The conversion from Brinell hardness into Rockwell hardness has been calculated according to BS EN ISO 6506-1, -2 and -3 and BS EN 10109-1.

BS 4190 Proof loads for steel nuts

Nominal size of nut mm	Tensile stress area of bolt mm 2	Strength grade designation
		4	6	8	10	12
		Stress under proof load N/mm 2
		400	600	800	1 000	1 200
		Proof load N
M5	14.2	5 680	8 500	11 400	14 800	17000
M6	20.1	8 040	12000	16000	20000	24000
M8	36.6	14 600	22000	29000	36 500	43000
M10	58.0	23 200	35000	46000	58000	69 500
M12	84.3	33 700	50 500	67000	84000	100000
M16	157	62 800	94000	125000	157000	188000
M20	245	98000	147000	196000	245000	294000
M22	303	121000	182000	242000	303000	364000
M24	353	141000	212000	282000	353000	423000
M27	459	184000	276000	367000	459000	550000
M30	561	224000	336000	448000	561000	673000
M33	694	278000	416000	555000	694000	833000
M36	817	327000	490000	653000	817000	980000
M39	976	390000	585000	780000	976000	1170000
M42	1120	448000	672000	896000	1120000	1340000
M45	1300	520000	780000	1400000	1300000	1560000
M48	1470	588000	882000	1180000	1470000	1760000
M52	1760	704000	1060000	1410000	1760000	2110000
M56	2030	812000	1220000	1620000	2030000	2440000
M60	2360	944000	1420000	1890000	2360000	2830000
M64	2680	1072000	1610000	2140000	2680000	3 220000
M68	3 060	1224000	1840000	2450000	3 060000	3 670000
NOTE 1 Proof load = stress under proof load tensile stress area divided by 1 000. NOTE 2 For stress under proof load NOTE 3 Nuts with a specified proof load above 500 000 N may be exempted from proof load testing

BS 4190 Tolerance on Nominal Length

Length		Bolts faced under head only or black bolts and screws	Screws faced under head only or bolts faced under head and turned on shank
Over	Up to and including
10	18	±0.90	±0.55
18	30	±1.05	±0.65
30	50	±1.25	±0.80
50	80	±1.50	±0.95
80	120	±1.75	±1.10
120	180	±2.0	±1.25
180	250	±2.30	±1.45
250	315	±2.60	±1.60
315	400	±2.85	±1.80
400	500	±3.15	±2.00

Thread lengths

Nominal length of bolt l	Length of thread b
Up to and including 125 mm	2d + 6 mm
Over 125 mm up to and including 200 mm	2d + 12 mm
Over 200 mm	2d + 25 mm

Thread runout (bolts) and underhead distance (screws)

Nominal size and thread diameter d	Thread runout on bolts a	Distance of ring gauge from underside of head on screws
	max	max
M5	2	3
M6	2.5	4
M8	3	4.5
M10	3.5	5
M12	4	6
M16	5	7.5
M20	6	9
(M22)	6	9
M24	7	11
(M27)	7	11
M30	8	12
(M33)	8	12
M36	10	15
(M39)	10	15
M42	11	16
(M45)	11	16
M48	12	18
(M52)	12	18
M56	19	20
(M60)	19	20
M64	21	22
(M68)	21	22
NOTE : Sizes in brackets are non-preferred.

Split pin holes

Nominal size and thread diameter d	Tolerance on dimension lp
M5	-0	+0.8
M6	-0	+0.8
M8	-0	+0.8
M10	-0	+0.8
M12	-0	+0.8
M16	-0	+1.2
M20	-0	+1.2
(M22)	-0	+1.2
M24	-0	+1.2
(M27)	-0	+1.6
M30	-0	+1.6
(M33)	-0	+1.6
M36	-0	+1.6
(M39)	-0	+1.6
M42	-0	+1.6
(M45)	-0	+1.6
M48	-0	+1.6
(M52)	-0	+1.6
M56	-0	+1.6
(M60)	-0	+1.6
M64	-0	+1.6
(M68)	-0	+1.6
Sizes in brackets are non-preferred. For information, refer to BS EN ISO 1234.

Strength grade designations for steel bolts and screws

Strength grade designation	4.6	4.8	6.8	8.8	10.9
Tensile strength Rm min. N/mm2	400	400	600	800	1000
Yield stress Re min. N/mm	240	320	480	640	900

Strength grade designations for steel nuts

Strength grade designation	4	6	8	10	12
Proof load stress N/mm2	400	600	800	1000	1200

Recommended bolt and nut combinations

Grade of bolt	4.6	4.8	6.8	8.8a	8.8a	10.9a	10.9a
Recommended grade of nut	4	4	6	8	10	10	12
a When a thick protective coating is applied to a bolt of grade 8.8 or 10.9, which requires the nut thread to be overtapped, the next higher grade of nut should be used.

BS 4190 Dimensions

Dimensions of ISO metric black hexagon head bolts and screws

Nominal size and thread diameter d	Pitch of thread (coarse pitch series)	Diameter of unthreaded shank d		Width across flats s		Width across corners e		Height of head h		Radius under head r	Washer face dia. Dw	Depth of washer face c
		max.	min.	max.	min.	max.	min.	max.	min.	max.	min.	max.
M5	0.8	5.48	4.52	8.00	7.64	9.20	8.63	3.88	3.125	0.3	6.8	0.5
M6	1	6.48	5.52	10.00	9.64	11.5	10.9	4.4	3.625	0.4	8.7	0.5
M8	1.25	8.58	7.42	13.00	12.57	15.0	14.2	5.9	5.125	0.8	11.5	0.6
M10	1.5	10.58	9.42	17.00	16.57	19.6	18.7	7.5	6.55	0.8	15.5	0.6
M12	1.75	12.70	11.30	19.00	18.48	21.9	20.9	8.4	7.55	1.2	17.2	0.6
M16	2	16.70	15.30	24.00	23.16	27.7	26.2	10.4	9.55	1.2	22	0.8
M20	2.5	20.84	19.16	30.00	29.16	34.6	33.0	13.9	12.1	1.8	27.7	0.8
(M22)	2.5	22.84	21.16	32.00	31.00	36.9	35.0	14.9	13.1	1.8
M24	3	24.84	23.16	36.00	35.00	41.6	39.5	15.9	14.1	1.8	33.2	0.8
(M27)	3	27.84	26.16	41.00	40.00	47.3	45.2	17.9	16.1	2.3
M30	3.5	30.84	29.16	46.00	45.00	53.1	50.9	20.1	17.95	2.3	42.7	0.8
(M33)	3.5	34.00	32.00	50.00	49.00	57.7	55.4	22.1	19.95	2.3
M36	4	37.00	35.00	55.00	53.80	63.5	60.8	24.1	21.95	2.7	51.1	0.8
(M39)	4	40.00	38.00	60.00	58.80	69.3	66.4	26.1	23.95	2.7
M42	4.5	43.00	41.00	65.00	63.80	75.1	72.1	27.1	24.95	2.8	60.8	1.0
(M45)	4.5	46.00	44.00	70.00	68.80	80.8	77.7	29.1	26.95	3.3
M48	5	49.00	47.00	75.00	73.80	86.6	83.4	31.1	28.95	3.8	70.8	1.0
(M52)	5	53.20	50.80	80.00	78.80	92.4	89.0	34.2	31.75	4.7
M56	5.5	57.20	54.80	85.00	83.60	98.1	94.5	36.2	33.75	4.9
(M60)	5.5	61.20	58.80	90.00	88.60	103.9	100.1	39.2	36.75	4.9
M64	6	65.20	62.80	95.00	93.60	109.7	105.8	41.2	38.75	4.9
(M68)	6	69.20	62.80	100.00	98.60	115.5	111.4	44.2	41.75	4.9
Sizes in brackets are non-preferred. Calculations of washer face diameters for other sizes may be obtained from the following formulae: for sizes up to and including M20: washer face diameter (min.) = smin. - IT16; for sizes over M20: washer face diameter (min.) = smin. - IT17; where : IT stands for standard tolerance, and belongs to the ISO series of tolerances (see BS EN 20286-1 and BS EN 20286-2)

Dimensions of ISO metric hexagon head bolts and screws faced under head or faced under head and turned on shank

Nominal size and thread diameter d	Pitch of thread (coarse pitch series)	Diameter of unthreaded shank d				Width across flats s		Width across corners e		Height of head K		Radius under head R
		Faced under head		Faced under head and turned on shank
		max.	min.	max.	min.	max.	min.	max.	min.	max.	min.	max.	min.
M6	1	6.48	5.52	6.00	5.82	10.00	9.64	11.5	10.89	4.24	3.76	0.4	0.25
M8	1.25	8.58	7.42	8.00	7.78	13.00	12.57	15	14.20	5.74	5.26	0.8	0.4
M10	1.5	10.58	9.42	10.00	9.78	17.00	16.57	19.6	18.72	7.29	6.71	0.8	0.4
M12	1.75	12.70	11.30	12.00	11.73	19.00	18.48	21.9	20.88	8.29	7.71	1.25	0.6
M16	2	16.70	15.30	16.00	15.73	24.00	23.16	27.7	26.17	10.29	9.71	1.25	0.6
M20	2.5	20.84	19.16	20.00	19.67	30.00	29.16	34.6	32.95	13.35	12.65	1.78	0.8
(M22)	2.5	22.84	21.16	22.00	21.67	32.00	31.00	36.9	35.03	14.35	13.65	1.78	0.8
M24	3	24.84	23.16	24.00	23.67	36.00	35.00	41.6	39.55	15.35	14.65	1.78	0.8
(M27)	3	27.84	26.16	27.00	26.67	41.00	40.00	47.3	45.20	17.35	16.65	2.28	1
M30	3.5	30.84	29.16	30.00	29.67	46.00	45.00	53.1	50.85	19.42	18.58	2.28	1
(M33)	3.5	34.00	32.00	33.00	32.61	50.00	49.00	57.7	55.37	21.42	20.58	2.28	1
M36	4	37.00	35.00	36.00	35.61	55.00	53.80	63.5	60.79	23.42	22.58	2.7	1
(M39)	4	40.00	38.00	39.00	38.61	60.00	58.80	69.3	66.44	25.42	24.58	2.7	1
M42	4.5	43.00	41.00	42.00	41.61	65.00	63.80	75.1	72.09	26.42	25.58	2.8	1.2
(M45)	4.5	46.00	44.00	45.00	44.61	70.00	68.80	80.8	77.74	28.42	27.58	3.3	1.2
M48	5	49.00	47.00	48.00	47.61	75.00	73.80	86.6	83.39	30.42	29.58	3.8	1.6
(M52)	5	53.20	50.80	52.00	51.54	80.00	78.80	92.4	89.04	33.50	32.50	4.7	1.6
M56	5.5	57.20	54.80	56.00	55.54	85.00	83.60	98.1	94.47	35.50	34.50	4.9	2
(M60)	5.5	61.20	58.80	60.00	59.54	90.00	88.60	103.9	100.12	38.50	37.50	4.9	2
M64	6	65.20	62.80	64.00	63.54	95.00	93.60	109.7	105.77	40.50	39.50	4.9	2
(M68)	6	69.20	66.80	68.00	67.54	100.00	98.60	115.5	111.42	43.50	42.50	4.9	2
Sizes in brackets are non-preferred.

Dimensions of ISO metric hexagon nuts and hexagon thin nuts

Nominal size and thread diameter	Pitch of thread (coarse pitch series)	Width across flats s		Width across corners e		Thickness of nut m				Thickness of thin nut (faced both sides) t
						Black		Faced one side
		max.	min.	max.	min.	max.	min.	max.	min.	max.	min.
M5	0.8	8	7.64	9.2	8.63	4.375	3.625	4	3.52	-	-
M6	1	10	9.64	11.5	10.89	5.375	4.625	5	4.52	-	-
M8	1.25	13	12.57	15	14.2	6.875	6.125	6.5	5.92	5	4.52
M10	1.5	17	16.57	19.6	18.72	8.45	7.55	8	7.42	6	5.52
M12	1.75	19	18.48	21.9	20.88	10.45	9.55	10	9.42	7	6.42
M16	2	24	23.16	27.7	26.17	13.55	12.45	13	12.3	9	8.42
M20	2.5	30	29.16	34.6	32.95	16.55	15.45	16	15.3	9	8.42
(M22)	2.5	32	31	36.9	35.03	18.55	17.45	18	17.3	10	9.42
M24	3	36	35	41.6	39.55	19.65	18.35	19	18.16	10	9.42
(M27)	3	41	40	47.3	45.2	22.65	21.35	22	21.16	12	11.3
M30	3.5	46	45	53.1	50.85	24.65	23.35	24	23.16	12	11.3
(M33)	3.5	50	49	57.7	55.37	26.65	25.35	26	25.16	14	13.3
M36	4	55	53.8	63.5	60.79	29.65	28.35	29	28.16	14	13.3
(M39)	4	60	58.8	69.3	66.44	31.8	30.2	31	30	16	15.3
M42	4.5	65	63.8	75.1	72.09	34.8	33.2	34	33	16	15.3
(M45)	4.5	70	68.8	80.8	77.74	36.8	35.2	36	35	18	17.3
M48	5	75	73.8	86.6	83.39	38.8	37.2	38	37	18	17.3
(M52)	5	80	78.8	92.4	89.04	42.8	41.2	42	41	20	19.16
M56	5.5	85	83.6	98.1	94.47	45.8	44.2	45	44	-	-
(M60)	5.5	90	88.6	103.9	100.12	48.8	47.2	48	47	-	-
M64	6	95	93.6	109.7	105.77	51.95	50.05	51	49.8	-	-
(M68)	6	100	98.6	115.5	111.42	54.95	53.05	54	52.8	-	-
NOTE Sizes shown in brackets are non-preferred.

Sizes greater than 68 mm diameter

Nominal size and thread diameter d	Width across flats s		Width across corners e	Nominal height of head k	Nominal thickness of nut m
	max.	min.	min.
M72	105	103.6	117.07	45	58
(M76)	110	108.6	122.72	48	61
M80	115	113.6	128.37	50	64
(M85)	120	118.6	134.02	54	68
M90	130	128.4	145.09	57	72
(M95)	135	133.4	150.74	60	76
M100	145	143.4	162.04	63	80
(M105)	150	148.4	167.69	66	84
M110	155	153.4	173.34	69	88
(M115)	165	163.4	184.64	72	92
(M120)	170	168.4	190.29	76	96
M125	180	178.4	201.59	79	100
(M130)	185	183.15	206.96	82	104
M140	200	198.15	223.91	88	112
M150	210	208.15	235.21	95	120

BS 4190 Bolting Surface Treatment Specifications

BS 4190 Bolting Components Marking

Product Shall be Marked with our manufacturing trade mark "TorqBolt" or "TB" along with the designated Grade.
Grade and manufacturer’s identification symbols shall be applied to one end of studs and to the heads of bolts and screws of all sizes. (If the available area is inadequate, the grade symbol may be marked on one end and the manufacturer’s identification symbol marked on the other end.) For bolts and screws smaller than 1⁄4 in. [6 mm] in diameter and studs smaller than 3⁄8 in. [10 mm] in diameter and for 1⁄4 in. [6 mm] in diameter studs requiring more than a total of three symbols, the marking shall be a matter of agreement between the purchaser and the manufacturer.

BS 4190 Supplementary Requirements