Your result

Locking ability

2 out of 5


4 out of 5

Worker safety

4 out of 5

Initial cost


Lifetime cost


How did we calculate?

Are double nuts effective
against bolt loosening?

The double nut, also known as jam nut, is a friction locking method that uses two separate nuts on top of each other.

Care must be taken during the tightening of the second nut as overtightening will lead to thread stripping or tensile rupture of the bolt. Although the nuts used for this method require little investment, the installation process itself is time-consuming and relies on the skill of the operator. It is also an unreliable locking method that protects poorly against vibration, which means it must be inspected and maintained often – increasing long-term costs. It is particularly ineffective when lubrication of the bolted joint is required.

Scroll down to access the eBook "Why do bolts loosen?"
(A comparison between common bolt securing options)

Which bolt locking product should I use?

  • Pros & Cons of different bolt locking methods
  • A Guidance for Selection, to help you decide which product to use in your applications

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The biggest challenge for a bolted joint, causing it to lose preload and fail, is spontaneous loosening often caused by vibrationsThis Junker test shows all 5 nuts rotated loose! A steep decline in the graph indicates a failure. Read more about the Junker Test.

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Do you need guidance choosing the best bolt securing solution for your application? Let our bolting experts guide you.

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