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# Reduced Torque with Lubricated Bolts

## Lubrication effect on bolt tension and torque.

When a bolt is lubricated - less torque is required to achieve bolt axial load or tension. Reduction of torques for lubricated vs. dry bolts are indicated in the table below.

Lubricated Bolts - Reduced Torque
LubricantTorque Reduction
(%)
Graphite 50 - 55
White Grease 35 - 45
SAE 30 oil 35 - 45
SAE 40 oil 30 - 40
No lube 0

### Example - Reduction of Torque when Bolt is Lubricated

The maximum tightening torque for a slightly lubricated 1" Grade 5 coarse bolt is 483 lbf ft. Dry bolt torque is approximately 30% higher - or 628 lbf ft.

Tdry = (483 lbf ft) (1 + (30%) / (100%))

= 628 lbf ft

If the bolt is lubricated with SAE 30 oil - the torque compared to a dry bolt is reduced with approximately 40%.

TSAE30 = (628 lbf ft) (1 - (40%) / (100%))

= 377 lbf ft

Note that if torque specified for a dry or slightly oiled bolt torque is applied to a lubricated bolt  - the bolt may overload and break.

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## Citation

• The Engineering ToolBox (2010). Reduced Torque with Lubricated Bolts. [online] Available at: https://www.engineeringtoolbox.com/torque-lubrication-effects-d_1693.html [Accessed Day Month Year].

Modify the access date according your visit.

6.3.17

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