BS 4882

Metric series bolting

NOTE 1. This section relates to metric series bolting for use with metric series pipe flanges, valves and fittings as referred to in BS 4504 and also for general pressure containing purposes.
Dimensional requirements are given for four designs of alloy steel studbolts, three designs of alloy steel studs and associated nuts, which use ISO metric screw threads in the following nominal diameters (see figures 1 and 2).

M10	M24	M36	M52
M12	M27	M39	M56
(M14)	M30	M42	M64
M16	M33	M45	M70
M20		M48	M72
(M22)			M76 {Studbolts only} M82 M90 M95 M100

(Sizes M14 and M22 are non-preferred.) Metric hexagon bolts and screws (and associated nuts) may also be used for flange bolting and in such cases selection should be made from BS 3692 or BS 4190, except that the bearing area of bolts and nuts ordered to BS 4190 has to be full-faced to comply with this standard.
NOTE 2. BS 3692 specifies low and high tensile, medium carbon and alloy steel hexagon bolts and nuts whereas BS 4190 specifies low tensile ‘mild steel’ hexagon bolts and nuts.

Table 5. Diameter of plain portion, maximum and minimum sizes of studbolts : metric series

Nominal diameter	Nominal diameter design		Reduced diameter design
Nominal diameter	max.	min. ¹⁾	max.	min. ¹⁾
	mm	mm	mm	mm
M10 × 1.5	10.0	9.78	7.49	7.27
M12 × 1.75	12.0	11.73	9.07	8.85
(M14 × 2)	14.0	13.73	10.64	10.37
M16 × 2	16.0	15.73	12.54	12.27
M20 × 2.5	20.0	19.67	15.71	15.44
(M22 × 2.5)	22.0	21.67	17.61	17.34
M24 × 3	24.0	23.67	18.86	18.53
M27 × 3	27.0	26.67	21.71	21.38
M30 × 3	30.0	29.67	24.56	24.23
M33 × 3	33.0	32.61	27.41	27.08
M36 × 3	36.0	35.61	30.26	29.87
M39 × 3	39.0	38.61	33.11	32.72
M42 × 3	42.0	41.61	35.96	35.57
M45 × 4	45.0	44.61	37.54	37.15
M48 × 4	48.0	47.61	40.38	39.99
M52 × 4	52.0	51.54	44.18	43.79
M56 × 4	56.0	55.54	47.98	47.59
M64 × 4	64.0	63.54	55.58	55.12
M70 × 4	70.0	69.54	61.38	60.92
M72 × 4	72.0	71.54	63.18	62.72
M76 × 4	76.0	75.54	67.08	66.62
M82 × 4	82.0	81.46	72.28	72.24
M90 × 4	90.0	89.46	80.38	79.84
M95 × 4	95.0	94.46	85.11	84.57
M100 × 4	100.0	99.46	89.86	89.32
¹⁾ Based on tolerance class h13 of BS 4500

Studbolts

2.1.1. General
The forms of the studbolts shall comply with those shown in figure 1(a),(b),(c) or (d).Dimensions shall be as given in 2.1.2 to 2.1.8 and tables 5 to 8

Table 6. Tolerance on nominal length of studbolts: metric series

Nominal diameter	Length	Tolerance on length
	mm	mm
≤ M24	≤ 150	± 0.75
≤ M24	> 150	± 1.00
> M24 ≤ M48	≤ 180	± 1.00
> M24 ≤ M48	> 180	± 1.5
> M48 ≤ M100	All	± 2.00

Table 7. Preferred nominal lengths of studbolts:metric series (based on flange designs as specified in BS 4504)

Nominal diameter	Preferred lengths
Nominal diameter	40	45	50	55	60	65	70	75	80	85	90	95	100	105	110	115	120	125	130	140	150	160	170	180	190	200	220	240	260	280	300	340	360	380
M10
M12	X	X	X	X	X	X	X
(M14) ¹⁾
M16						X	X	X	X	X
M20									X	X	X	X	X	X
(M22) ¹⁾
M24													X	X	X	X	X	X	X	X
M27														X	X	X	X	X	X	X	X	X	X
M30										X	X	X	X		X	X	X	X	X	X	X	X	X	X	X	X
M33															X	X	X	X	X	X	X	X	X	X	X	X	X
M36																		X	X	X	X	X	X	X	X	X	X	X	X
M39																				X	X	X	X	X	X	X	X	X	X	X	X
M42 ¹⁾
M45																						X	X	X	X	X	X	X	X	X	X	X	X
M48																																X
M52																											X	X	X	X	X		X
M56																											X	X	X	X	X
M64																													X	X	X	X
M70 ¹⁾
M72																																		X
M76 ¹⁾
M82 ¹⁾
M90 ¹⁾
M95 ¹⁾
M100 ¹⁾
Preferred nominal lengths to be completed in a later revision of this standard. NOTE: Choice of length. (a) Minimum length. The minimum length of studs or studbolts has to ensure a full engagement of nut, i.e. with the point protruding above the face of the nut. (b) Maximum length. There is no precise limit on the maximum length of thread although under normal circumstances, unnecessarily long studs and studbolts are avoided due to cost, and preventing corrosion or unintentional damage to the exposed thread making subsequent nut removal more difficult. Studs and studbolts may be chosen as the next nominal length, greater than that required for the thicknesses and tolerances on the bolted components (e.g. flanges, gaskets, washers). The availability of ‘stocked’ lengths may also be taken into account. Unnecessary shortening of studs and studbolts should be avoided. Where studs and studbolts are shortened the original manufacturer’s identification and grade marking should be retained.

Table 7. Length of point (see 2.2.6) for studbolts: metric series

Nominal diameter	Length
	mm
M10	1.17
M12	1.32
(M14)	1.48
M16	1.48
M20	1.80
(M22)	1.80
M24	2.09
M27	2.09
M30	2.09
M33	2.09
M36	2.09
M39	2.09
M42	2.09
M45	2.70
M48	2.70
M52	2.70
M56	2.70
M64	2.70
M70	2.70
M72	2.70
M76	2.70
M82	2.70
M90	2.70
M95	2.70
M100	2.70

Nominal length

The tolerances on nominal length shall be as given in table 6.
NOTE 1. The preferred nominal lengths are given in table 7. If lengths other than these are requested (see appendix C) the increments of length should be as given in table 9.
NOTE 2. Length of point is included in nominal length (see 1.2.2.1).

Table 9. Increments of nominal length of studbolts: metric series

Nominal length		Increment
Over	Up to and including	Increment
mm	mm	mm
--	65	5
65	200	10
200	300	20
300	--	25

2.1.3 Length of thread

For studbolts having plain portions as shown in figures 1(b),1(c) and 1(d), the basic length of thread shall be the nominal diameter plus 10 mm.
For studbolts as in figures 1(b) and 1(c), the tolerances on the length of thread shall be plus 2 pitches, minus 0.

2.1.4 Length of reduced diameter portion

The basic length of the reduced diameter portion shall be 0.6 times the nominal diameter (see figure 1(d) and item (d)(5) of appendix C.
The following tolerances shall apply to this dimension:
(a) +0.75, −0 mm for lengths up to and including 28 mm;
(b) +1.50, −0 mm for lengths over 28 mm.

2.1.5 Length of thread plus length of reduced diameter portion

The following tolerances shall apply to this dimension:
(a) ±1.0 mm for nominal diameters up to and including M48;
(b) ±2.0 mm for nominal diameters over M48 and up to and including M100.

2.1.6 Ends

The ends of studbolts shall be finished with a point having an included angle of approximately 90° to a depth slightly exceeding the depth of thread. Nominal lengths of points for reference purposes shall be as given in table 8.

Dimension of studbolts

2.1.7 Diameter of plain portion

The diameter of the plain portion shall not exceed the maximum values given in table 5.
NOTE. The diameter of the reduced portion should be stated by the purchaser in the order (see appendix C).Under normal conditions a minimum of 0.95 times the minor thread diameter is used, but for studs subject to particularly onerous conditions (such as high temperature service) diameters less than this may be used.

2.1.8 Screw threads

Screw threads for studbolts for all materials other than mild or carbon steel shall comply with requirements given in table 10.

Table 10. Pitch of screw threads for studbolts: metric series

Nominal diameter	Pitch
≤ M27	ISO metric coarse (see BS 3643)
≥ M30 ≤ M43	3mm
≥ M45 ≤ M100	4mm

The ISO metric coarse pitch series shall be used throughout the range of sizes for mild or carbon steel.

NOTE. The tolerance class should be stated by the purchaser in the order (see appendix C), but for most conditions the following are applicable:
(a) class 6g for carbon steel and grades MB7, ML7, MB7A, MB16, MB16A, MB16B;
(b) class 6e for other materials.

2.2 Studs

2.2.1 General

The forms of the studs shall comply with those in figure 2(a), (b) or (c). Studs shown in figure 2(a) shall comply with BS 4439, covering sizes up to M39 and shall have ISO coarse pitches. Studs to figures 2(b) and 2(c) shall have pitches in accordance with 2.2.10.

The dimensions of studs to figure 2(b) or 2(c) shall be as given in 2.2.2 to 2.2.11 and tables 5, 6 and 8 for studbolts.

2.2.2 Nominal length

The nominal lengths shall be in increments of 5 mm.

NOTE. The length of point is included in nominal length (see 1.2). The tolerances on nominal length shall be as given in table 6.

2.2.3 Length of metal end of thread

For studs as shown in figures 2(b) and 2(c), the length of full form thread at the metal end shall equal nominal diameter except where high strength studs are used with weak flange materials, in which case the metal end threaded length shall be equal to 1.5 times the nominal diameter.

2.2.4 Length of nut end of thread

For studs as shown in figures 2(b) and 2(c), the basic length of thread shall be as given in table 11.

Table 11. Length of thread for studs : metric series

Nominal diameter	Thread length
	mm
≤ M12	Nominal dia. + 4
> M12 ≤ M20	Nominal dia. + 6
> M20 ≤ M72	Nominal dia. + 10

2.2.5 Length of reduced diameter portion

The basic length of the reduced diameter portion shall be 0.6 times the nominal diameter (see figure 2(b)), and shall be rounded up to the next whole millimetre.
The following tolerances shall apply to this dimension:
(a) +0.75, −0 mm for lengths up to and including 28 mm;
(b) +1.50, −0 mm for lengths over 28 mm.

2.2.6 Lengths of thread plus length of reduced diameter portion

The following tolerances shall apply to this dimension:

(a) ± 1.0 mm for nominal diameters up to and including M48;

(b) ± 2.0 mm for nominal diameters over M48 and up to and including M72.

2.2.7 Ends

The nut ends shall be finished with a point having an included angle of approximately 90° to a depth slightly exceeding the depth of thread. Lengths of points shall be as given in table 8.

The metal ends shall be finished as follows:
(a) for studs as illustrated in figure 2(b) the corner shall be broken at 45° to give a smooth edge;
(b) for studs as illustrated in figure 2(c) the end dimensions shall comply with the scale of sizes given in table 12.

Table 12. Stud dimensions: metric series

Nominal diameter	Ring contact diameter	Ring diameter radius	Length of plain ring portion
	mm	mm	mm
M10 to M12	Nominal dia. -5	1	5
M14 to M27	Nominal dia. -6	1.5	6
M30 to M72	Nominal dia. -8	2	8

Dimension of studs

2.2.8 Diameter of plain portion

The diameter of the plain portion shall be to the maximum and minimum sizes shown in table 5.

2.2.9 Diameter of reduced portion

The diameter of the reduced portion shall not exceed the maximum values given in table 5.

NOTE: The diameter of the reduced portion should be stated by the purchaser in the order (see appendix C). Under normal conditions a minimum of 0.95 times the minor thread diameter is used, but for studs subject to particularly onerous conditions (such as high temperature service) diameters less than this may be used.

2.2.10 Screw threads

Screw threads for studs of all materials other than low and medium carbon steel shall comply with the requirements given in table 13.

Table 13. Pitch of screw threads for studs: metric series

Nominal diameter	Pitch
≤ M27	ISO metric coarse (see BS 3643)
> M30 ≤ M42	3 mm
> M45 ≤ M72	4 mm

NOTE 1: For low and medium carbon steel, it is permissible to use the ISO metric coarse pitch series throughout the range of sizes for low and medium carbon steel.

NOTE 2: The tolerance class (see BS 3643) should be stated by the purchaser in the order (see appendix C), but for most conditions the following are applicable:

The metal end of studs should be tolerance class 4h for all materials;
The nut end of studs should be to the following classes:

Class 6g for carbon steel and grades MB7, ML7, MB7A, MB16, MB16A, MB16B;
Class 6e for other materials.

2.2.11 Tolerances on nominal length

The tolerances on nominal length shall be as shown in table 6.

2.3 Nuts for use with metric series bolts and studs

2.3.1 Dimensions

Nuts shall comply with the dimensions and tolerances given in table 14.

Table 14. Dimensions of hexagon nuts: metric series

Nominal size and pitch	Width across flats s		Width across corners e	Thickness m		Tolerance on squareness
Nominal size and pitch	max.	min.	min.	max.	min.	Tolerance on squareness
	mm	mm	mm	mm	mm	mm
M10 × 1.5	16.00	15.57	17.59	8	7.42	0.29
M12 × 1.75	18.00	17.57	19.85	10	9.42	0.32
(M14 × 2)	21.00	20.16	22.78	11	10.30	0.37
M16 × 2	24.00	23.16	26.17	13	12.30	0.41
M20 × 2.5	30.00	29.16	32.95	16	15.30	0.51
(M22 × 2.5)	34.00	33.00	37.29	18	17.30	0.54
M24 × 3	36.00	35.00	39.55	19	18.16	0.61
M27 × 3	41.00	40.00	45.20	22	21.16	0.70
M30 × 3	46.00	45.00	50.85	24	23.16	0.78
M33 × 3	50.00	49.00	55.37	26	25.16	0.85
M36 × 3	55.00	53.80	60.79	29	28.16	0.94
M39 × 3	60.00	58.80	66.44	31	30.00	1.03
M42 × 3	65.00	63.80	72.09	34	33.00	1.11
M45 × 4	70.00	68.80	77.74	36	35.00	1.20
M48 × 4	75.00	73.80	83.39	38	37.00	1.29
M52 × 4	80.00	78.80	89.04	42	41.00	1.37
M56 × 4	85.00	83.60	94.47	45	44.00	1.46
M64 × 4	95.00	93.60	105.77	51	49.80	1.63
M70 × 4	100.00	98.60	114.42	56	54.80	1.76
M72 × 4	105.00	103.60	117.07	58	56.80	1.81
M76 × 4	110.00	108.60	122.72	61	59.80	1.89
M82 × 4	120.00	118.60	134.01	66	64.80	2.02
M90 × 4	130.00	128.60	145.32	72	70.80	2.20
M95 × 4	135.00	133.60	150.97	76	74.80	2.31
M100 × 4	145.00	143.60	162.27	80	78.80	2.42
NOTE. The dimensions are illustrated in figure 3.

2.3.2 Faces

Nuts shall have a chamfer of approximately 30° on the non-bearing face only. The bearing face shall be full faced. The bearing face shall be machined, or have a surface equal to that produced by machining.

The faces of the nut shall be square to the axis of the thread of the nut within the tolerances given in table 14 (see figure 3 and appendix E).

2.3.3 Screw threads

Screw threads for all materials other than low and medium carbon steel shall comply with the requirements given in table 15.

Table 15. Pitch of screw threads for nuts: metric series

Nominal dia.	Pitch	Note
≤ M27	ISO metric coarse (see BS 3643)	Class 6H (see item (d)(6) of appendix C)
≥ M30 ≤ M42	3 mm
≥ M45 ≤ M100	4 mm

The ISO metric coarse pitch series shall be used throughout the range of sizes for low and medium carbon steel.

The screw threads in nuts shall be concentric with the hexagons within a tolerance of 2 IT13, FIM (see BS 6322 : Part 1), using the width across flats as reference datum.

Dimension of Hexagon Nuts