When a bolted joint is subjected to vibrations, movement, or alternating loads, there is always a risk that it will loosen over time. To counteract this, various locking mechanisms are used. But which one should you choose – lock nut, lock washer, or threadlocker?
In this guide, we compare the most common options and explain when each solution is best.
Why is locking needed in bolted joints?
A bolted joint can loosen for several reasons:
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Vibrations (machines, vehicles, railings)
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Temperature fluctuations
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Settlement in the material
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Dynamic load
Without the right locking, you risk:
Looseness and noise
Reduced structural integrity
Safety risks
Lock nut – simple and effective locking
What is a lock nut?
A lock nut is a nut with a built-in locking function, e.g.:
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Nylon insert (DIN 985)
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All-metal locknut
Advantages
✔ Easy to assemble
✔ Requires no extra parts
✔ Reliable under vibration
Disadvantages
➖ Nylon insert is affected by high temperatures
➖ Slightly higher price than standard nuts
When is a lock nut best?
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Machines and installations with vibration
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Assemblies where disassembly may occur
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When you want a clean and compact solution
Lock washer – classic solution with several variants
Common types of lock washers
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Spring washer
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Toothed washer
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Wedge lock washer (e.g., Nord-Lock type)
Advantages
✔ Easy to combine with standard nuts
✔ Provides extra security in many applications
✔ Available in stainless A2 and A4
Disadvantages
➖ Not all types work equally well under heavy vibration
➖ Requires correct assembly and the right type
When is a lock washer best?
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Constructions with moderate vibration
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Where a lock nut cannot be used
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When load distribution and locking are combined
Threadlocking – chemical thread locking
What is threadlocking?
Threadlocking is a liquid adhesive applied to the threads that cures after assembly.
Available in different strengths:
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Low strength – easy disassembly
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Medium strength – standard solution
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High strength – permanent locking
Advantages
✔ Very effective against vibration
✔ Protects against moisture and corrosion
✔ Invisible locking
Disadvantages
➖ Requires cleaning of the threads
➖ High strength can make disassembly difficult
When is threadlocking best?
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Small screws with no room for a lock washer
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Precision assembly
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Where absolute locking is required
Comparison – which locking should you choose?
| Situation | Recommended solution |
|---|---|
| Heavy vibrations | Lock nut or wedge lock washer |
| Limited space | Threadlocking |
| Regular disassembly | Lock nut |
| Permanent assembly | Threadlocking (high strength) |
| Stainless environment (A4) | Match locking in the same material |
Common mistakes to avoid
No locking at all under vibration
Wrong materials (stainless + galvanized)
Wrong type of threadlocking
Excessive tightening instead of correct locking
Summary
There is no universal solution – the right locking mechanism depends on application, environment, and load.
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Lock nut → smooth and reliable
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Lock washer → flexible solution in many cases
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Threadlocking → maximum safety where space is limited
At rostfri.nu you will find lock nuts, lock washers, and accessories in stainless A2 and A4, adapted for both professionals and demanding environments.