Note: Allpar does not take responsibility for the veracity of any information or opinions here, does not claim expertise, and is not responsible for any consequences. Please proceed at your own risk.




Torque specifications for fasteners

A bolt of the same size, thread, and material in a given grade can generally be tightened to a given torque; for example, grade-5, 1/4-20 should be torqued no more than 7 ft-lb in cast iron or 6 ft-lb in aluminum. In grade 8, those numbers are 11 and 9. This should apply universally to all such bolts, with some exceptions, e.g. for different alloys.

This information is for the bolt shaft size, not the bolt head size. Bolt and fastened material alloys change these numbers.

These numbers are for reference only; compare them to the bolt maker’s specifications for confirmation. We suggest using them as a guide when you cannot obtain the car manufacturer’s or bolt maker’s specifications.

Metric Class 4T
Dia Pitch Standard Hex-head Bolt Flange-Headed Bolt
mm mm N•m Ft-lb N•m Ft-lb
6 1 55 kgf-cm 48 in-lb 60 kgf-cm 52 in-lb
8 1.25 130 kgf-cm 108 in-lb 145 kgf-cm 10
10 1.25 26 19 29 21
12 1.25 47 35 53 39
14 1.5 74 55 84 61
16 1.5 115 83 -

Metric Class 5T
Dia Pitch Standard Hex-head Bolt Flange-Headed Bolt
mm mm N•m Ft-lb N•m Ft-lb
6 1 65 kgf-cm 56 in-lb 75 kgf-cm 65 in-lb
8 1.25 160 kgf-cm 12 175 kgf-cm 13
10 1.25 32 24 36 26
12 1.25 59 43 65 48
14 1.5 91 67 100 76
16 1.5 140 101 - -

Metric Class 6T
Dia Pitch Standard Hex-head Bolt Flange-Headed Bolt
mm mm N•m Ft-lb N•m Ft-lb
6 1 80 kgf-cm 69 in-lb 90 kgf-cm 78 in-lb
8 1.25 19 14 21 15
10 1.25 39 29 44 32
12 1.25 71 53 80 90
14 1.5 110 80 125 90
16 1.5 170 127 - -

Metric Class 7T
Dia Pitch Standard Hex-head Bolt Flange-Headed Bolt
mm mm N•m Ft-lb N•m Ft-lb
6 1 110 kgf-cm 96 in-lb 120 kgf-cm 108 in-lb
8 1.25 25 19 28 21
10 1.25 52 38 58 43
12 1.25 95 70 105 76
14 1.5 145 108 165 123
16 1.5 230 166 - -

Metric Class 8T
Dia Pitch Standard Hex-head Bolt Flange-Headed Bolt
mm mm N•m Ft-lb N•m Ft-lb
8 1.25 29 22 33 24
10 1.25 61 45 68 50
12 1.25 110 80 120 90

Metric Class 9T
Dia Pitch Standard Hex-head Bolt Flange-Headed Bolt
mm mm N•m Ft-lb N•m Ft-lb
8 1.25 34 25 37 27
10 1.25 70 51 78 57
12 1.25 125 94 140 105

Metric Class 10T
Dia Pitch Standard Hex-head Bolt Flange-Headed Bolt
mm mm N•m Ft-lb N•m Ft-lb
8 1.25 38 28 42 31
10 1.25 78 58 88 64
12 1.25 140 105 155 116

Metric Class 11T
Dia Pitch Standard Hex-head Bolt Flange-Headed Bolt
mm mm N•m Ft-lb N•m Ft-lb
8 1.25 42 31 47 35
10 1.25 87 64 97 72
12 1.25 155 116 175 130

 

Metric Grade 9.8
Dia Cast Iron Aluminum
mm N•m Ft-lb N•m Ft-lb
6 9 5 7 4
7 14 9 11 7
8 25 18 18 14
10 40 30 30 25
12 70 55 55 40
14 115 85 90 65
16 180 130 140 100
18 230 170 180 135

Metric Grade 10.9
Dia Cast Iron Aluminum
mm N•m Ft-lb N•m Ft-lb
6 14 9 11 7
7 18 14 14 11
8 32 23 25 18
10 60 45 45 35
12 105 75 80 60
14 160 120 125 95
16 240 175 190 135
18 320 240 250 185

Metric Grade 12.9
Dia Cast Iron Aluminum
mm N•m Ft-lb N•m Ft-lb
6 14 9 11 7
7 25 18 18 14
8 36 27 25 21
10 70 50 55 40
12 125 95 100 75
14 195 145 150 110
16 290 210 220 165
18 400 290 310 230

 

SAE Grade 5   SAE Grade 8
Size Cast Iron Aluminum Size Cast Iron Aluminum
Dia - tpi N•m Ft-lb N•m Ft-lb Dia - tpi N•m Ft-lb N•m Ft-lb
1/4 – 20 9 7 8 6 1/4 – 201511129
1/4 – 28 12 9 9 7 1/4 – 2818131410
5/16 – 18 20 15 16 12 5/16 – 1830222418
5/16 – 24 23 17 19 14 5/16 – 2433242519
3/8 – 16 40 30 25 20 3/8 – 1655404030
3/8 – 24 40 30 35 25 3/8 – 2460454535
7/16 – 14 60 45 45 35 7/16 – 1490656550
7/16 – 20 65 50 55 40 7/16 – 2095707555
1/2 – 13 95 70 75 55 1/2 – 131309510075
1/2 – 20 100 75 80 60 1/2 – 2015011012090
9/16 – 12 135 100 110 80 9/16 – 12190140150110
9/16 – 18 150 110 115 85 9/16 – 18210155170125
5/8 – 11 180 135 150 110 5/8 – 11255190205150
5/8 – 18 210 155 160 120 5/8 – 18290215230170
3/4 – 10 325 240 255 190 3/4 – 10460340365270
3/4 – 16 365 270 285 210 3/4 – 16515380410300
7/8 –  9 480 360 380 280 7/8 –  9745550600440
7/8 – 14 530 390 420 310 7/8 – 14825610660490
1 –  8 720 530 570 420 1 –  81100820890660
1 – 14 800 590 650 480 1 – 141200890960710
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