Grey Bar

Recommended Tightening Torque

The following tables of tightening torques for various strengths of bolt are provided as a general guide.

Projection Weld Bolts

Care should be taken when using them because plating finishes can act as a lubricant resulting in lower torque values corresponding with higher tensile values. Thus a lower torque value could result in a higher than expected tensile load which in some cases could be greater than the ultimate tensile strength of the fastener resulting in failure.

What must also be taken into consideration is the variation in stress area between minimum and maximum rolling diameter - the smaller the fastener the more significant this becomes.

The fastener should not therefore be tested by use of torque to failure and then computing the tensile load. Instead a direct axial tensile load to failure should be applied. The tables represent maximum tightening torque values. You should always thoroughly test the products to ensure suitability for your particular application.


Standard Series - Course & Fine - All Torques figures in Nm (Newton Metres)
Nominal
Thread
Diameter
mm
4:6
Quality
4:8
Quality
5:6
Quality
Course Fine Course Fine Course Fine
Nm Nm Nm Nm Nm Nm
M3 0.57   0.76   0.71  
M4 1.3   1.8   1.7  
M5 2.7   3.6   3.3  
M6 4.5   6.0   5.7  
M7 7.6   10.2   9.5  
M8 11.0 11.8 14.0 15.7 13.8 14.8
M10 21.8 23.0 29.0 30.7 27.3 28.8
M12 38.1 41.6 50.8 55.5 47.6 52.0
M14 60.6 66.0 80.0 88.0 76.0 82.0
M16 95.0 101.0 126.0 134.0 118.0 126.0
M18 130.0 146.0 173.0 195.0 163.0 183.0
M20 185.0 205.0 246.0 273.0 231.0 256.0

Nominal
Thread
Diameter
mm
5:8
Quality
6:6
Quality

8:8
Quality

Course Fine Course Fine Course Fine
Nm Nm Nm Nm Nm Nm
M3 0.95   0.85   1.5  
M4 2.2   2.0   3.5  
M5 4.5   4.0   7.1  
M6 7.6   6.8   12.1  
M7 12.7   11.4   20.3  
M8 18.4 19.7 16.5 17.7 29.4 31.5
M10 36.4 38.4 32.8 34.6 58.3 61.0
M12 64.0 69.0 57.0 62.0 101.0 111.0
M14 101.0 110.0 91.0 99.0 161.0 176.0
M16 158.0 168.0 142.0 151.0 252.0 268.0
M18 217.0 244.0   220.0 347.0 390.0
M20 308.0 342.0     492.0 546.0

Nominal
Thread
Diameter
mm
9.8
Quality
10:9
Quality
12:9
Quality
14:9
Quality
Course Fine Course Fine Course Fine Course Fine
Nm Nm Nm Nm Nm Nm Nm Nm
M3 1.7   2.1   2.6   3.0  
M4 4.0   5.0   6.0   7.0  
M5 8.0   10.0   12.0   14.0  
M6 13.6 13.0 17.0 18.0 20.4 22.0 23.8  
M7 22.8   28.6   34.3   40.0  
M8 33.1 35.4 41.3 44.3 49.6 53.2 57.9 62.0
M10 66.0 69.0 82.0 86.0 98.0 104.0 115.0 121.0
M12 114.0 125.0 143.0 156.0 171.0 187.0 200.0 219.0
M14 182.0 198.0 227.0 247.0 273.0 297.0 318.0 346.0
M16 284.0 302.0 355.0 377.0 426.0 453.0 497.0 528.0
M18 391.0 439.0 488.0 549.0 586.0 659.0 683.0 769.0
M20 554.0 615.0 693.0 768.0 830.0 922.0 969.0 1076.0

BSW, BSF, UNC & UNF

Nominal Thread Diameter mm

 'A'  Quality

'P'  Quality

BSW
BSF
UNC
UNF
BSW
BSF
UNC
UNF
lbf ft
lbf ft
lbf ft
lbf ft
lbf ft
lbf ft
lbf ft
lbf ft
1/4 3.6 4.0 3.6 4.0 5.3 5.9 5.3 6.0
3/16 7.4 7.9 7.4 8.2 11.0 12.0 11.0 12.0
3/8 13.0 14.0 13.0 15.0 19.0 21.0 19.0 22.0
7/16 21.0 23.0 21.0 23.0 31.0 33.0 31.0 34.0
1/2 31.0 34.0 32.0 36.0 46.0 50.0 47.0 53.0
9/16 46.0 50.0 46.0 52.0 68.0 73.0 68.0 76.0
5/8 64.0 68.0 64.0 72.0 93.0 100.0 94.0 108.0
3/4 113.0 118.0 114.0 126.0 166.0 173.0 167.0 185.0

Nominal Thread Diameter mm

 'R'  Quality

'S'  Quality

BSW
BSF
UNC
UNF
BSW
BSF
UNC
UNF
lbf ft
lbf ft
lbf ft
lbf ft
lbf ft
lbf ft
lbf ft
lbf ft
1/4 8.2 9.1 8.2 9.3 9.1 9.1 10.0 10.0
3/16 17.0 16.0 17.0 19.0 19.0 19.0 20.0 31.0
3/8 30.0 32.0 30.0 34.0 33.0 33.0 36.0 38.0
7/16 48.0 51.0 48.0 53.0 53.0 53.0 58.0 60.0
1/2 70.0 77.0 73.0 82.0 79.0 82.0 86.0 91.0
9/16 104.0 113.0 105.0 117.0 117.0 117.0 126.0 131.0
5/8 144.0 154.0 145.0 164.0 161.0 162.0 172.0 183.0
3/4 256.0 268.0 256.0 286.0 286.0 288.0 300.0 319.0
Nominal Thread Diameter mm

 'T'  Quality

'X'  Quality

BSW
BSF
UNC
UNF
BSW
BSF
UNC
UNF
lbf ft
lbf ft
lbf ft
lbf ft
lbf ft
lbf ft
lbf ft
lbf ft
1/4 11.0 12.0 11.0 12.0 15.0 17.0 15.0 17.0
3/16 22.0 23.0 22.0 24.0 31.0 33.0 31.0 34.0
3/8 38.0 41.0 39.0 44.0 55.0 59.0 55.0 63.0
7/16 62.0 67.0 62.0 69.0 88.0 95.0 89.0 99.0
1/2 91.0 100.0 94.0 106.0 130.0 143.0 135.0 152.0
9/16 135.0 146.0 137.0 152.0 194.0 210.0 195.0 217.0
5/8 187.0 200.0 188.0 212.0 267.0 286.0 269.0 304.0
3/4 331.0 347.0 333.0   474.0 497.0 477.0 529.0

Unified Fine Numbered Series

Nominal Thread Diameter mm

    Quality

'A'
'P'
'R'
'S'
'T'
'X'
lbf in
lbf in
lbf in
lbf in
lbf in
lbf in
No. 2 1.8 2.7 4.1 4.6 5.3 7.6
No. 3 2.8 4.1 6.3 7.0 8.1 11.6
No. 4 3.9 5.7 8.9 9.9 11.5 16.4
No. 5 5.5 8.1 12.5 14.0 16.2 23.1
No. 6 7.5 11.0 17.0 19.0 22.0 31.5
No. 8 12.9 18.9 29.2 32.6 37.8 54.0
No. 10 20.3 29.8 46.1 51.9   85.4
No. 12 29.9 43.8 67.7 75.6 87.5 125.0

British BA Series

Nominal Thread Diameter mm

    Quality

'A'
'P'
'R'
'S'
'T'
'X'
lbf in
lbf in
lbf in
lbf in
lbf in
lbf in
8 BA 1.9 2.8 4.4 4.9 5.6 8.1
7 BA 2.7 4.0 6.2 6.9 8.0 11.5
6 BA 3.9 5.6 8.7 10.0 11.3 16.1
5 BA 5.9 8.6 13.4 14.9 17.3 24.8
4 BA 8.4 12.3 19.0 21.3 24.6 35.3
3 BA 12.5 18.3 28.2 31.6 36.6 52.4
2 BA 19.1 28.0 43.3 48.4 56.0 80.2
1 BA 27.4 40.2 62.1 69.4 80.0 115.0
0 BA 40.2 59.0 91.1 101.9 118.0 169.0