top of page

Tension Testing: The Effect of Lubrication on K Factor

Updated: Nov 28, 2023

Surprise results testing bolt tension with different lubricants.



Test Setup



Bolt and Nut Used for the Tests



Predicted Results Before Testing



Actual Results




Thread Conditions

Measured Clamp Force (lbs)

Calculated K Factor

Link to Video

Dry​


30,000

0.18

https://youtu.be/8OwkjjqXGDE

Anti-seize paste


32,000

0.17

https://youtu.be/_V5ZhGfZZEg

Anti-seize spray


35,000

0.15

https://youtu.be/fKgE_KrrPYo

WD-40 spray oil


28,000

0.20

https://youtu.be/I3sNZw6L1L0

Oil


32,000​

0.17

Dirt

44,000

0.13​

https://youtu.be/C8cf5ZYIZ_c

0.13 is very low!


Surprise Results – This is astonishingly low and very much unexpected. The dirt used for this test was gathered from the hole on a SAG mill in a gold mining operation. Normally we’d expect dirt to increase the K value, but this material created the opposite effect. For an actual installation, if this dirt is left on the thread, the bolt could be stretched beyond it’s yield point as shown in the experiment.


The Takeaways

  • It’s important to achieve the correct clamp force, as we’ve shown in previous posts (clamp force blog post link).

  • It’s difficult to predict the bolt clamp force as we’ve shown with these results.

  • For optimal results, tests that match as closely as possible to actual conditions should be done to determine the torque required to achieve the desired clamp load.

  • It’s difficult to get it right every time. Use a Security Locknut to protect your assembly when you don’t.

Having problems with bolted joints? Give us a call. We can help.


(847) 970-4050




Kommentare


bottom of page