FAQs

FAQs on Securing Bolted Connections and Using Wedge Lock Washers

1. What is a bolted connection, and why is it important to secure it?

A bolted connection is a way to join two or more parts together using a bolt (a threaded rod), a nut, and often washers. It's common in everything from furniture assembly to bridges and machinery. Securing it means ensuring the bolt doesn't loosen over time, which is crucial because loose bolts can lead to failures, accidents, or breakdowns. Factors like vibration, temperature changes, or repeated loading can cause loosening, so proper securing helps maintain safety and reliability.

2. What is preload in a bolted connection?

Preload is the initial tension or "stretch" applied to the bolt when you tighten it. Think of it like stretching a rubber band—it creates a clamping force that holds the parts together tightly. Maintaining preload is key because if it drops (due to settling or vibration), the connection can weaken, leading to gaps, leaks, or even complete failure.

3. Why do bolted connections loosen over time?

Bolts can loosen due to several reasons: vibration from machinery or vehicles shakes them free; thermal expansion/contraction from heat changes; embedding or settling of surfaces; or even improper initial tightening. Without countermeasures, this can reduce preload and compromise the joint's strength.

4. What are wedge lock washers, and how do they work?

Wedge lock washers are specialized washers designed to prevent bolt loosening. They come in pairs (an inner and outer washer) with ramped or wedge-shaped surfaces and radial teeth. When the bolt is tightened, the wedges "lock" into each other and the surfaces, creating friction that resists turning. If vibration tries to loosen the bolt, the wedges actually tighten the grip, helping maintain preload.

5. What are the main advantages of using wedge lock washers?

• High resistance to vibration: They're excellent for high-vibration environments like engines, railways, or heavy equipment, as they actively prevent loosening.
• Reusable: Unlike some locking methods (e.g., adhesives), they can be reused multiple times without losing effectiveness.
• Maintains preload: They help keep the initial tension consistent, reducing the risk of joint failure.
• Comparably little damage to surfaces: The teeth grip without marring the bolted parts, making them suitable for sensitive applications.
• Easy to install: No special tools needed beyond standard wrenches, and they work with most bolt types.

6. What are the disadvantages of wedge lock washers?

• Higher cost:** They're more expensive than plain or split lock washers, which might add up for large projects.
• Not ideal for all surfaces:** They work best on hard surfaces; soft materials like aluminum might get damaged by the teeth.
• Requires proper pairing:** You must use them in matched pairs, and incorrect installation (e.g., wrong orientation) can reduce effectiveness.
• Bulkier design:** They add thickness to the connection, which might not fit in tight spaces.
• Limited for extreme conditions:** In very high-temperature or corrosive environments, specialized versions are needed, or they might underperform compared to other methods.

7. How do wedge lock washers compare to other securing methods like split lock washers or thread-locking adhesives?

Split lock washers (helical spring types) are cheaper and simpler but less effective against strong vibrations—they can flatten and lose grip. Thread-locking adhesives (like Loctite) provide strong hold but aren't reusable and can be messy to remove. Wedge lock washers outperform both in vibration resistance and reusability but cost more and require more space. Choose based on your needs: adhesives for permanent fixes, split washers for low-vibe/low-cost scenarios, and wedge locks for demanding, reusable applications.

8. Are wedge lock washers suitable for DIY home projects?

Yes, for vibration-prone items like lawnmowers, bikes, or furniture, but they're overkill for static uses like hanging shelves. For laymen, they're user-friendly—just ensure the wedges face each other and tighten to the recommended torque. Start with smaller packs to test, and always check manufacturer guidelines.

9. How do I install wedge lock washers correctly?

Place the inner washer (with radial teeth) against the surface or nut, then the outer washer on top, ensuring the wedge ramps face each other. Tighten the bolt to the specified torque. The key is orientation: if installed backward, they won't lock properly. Always use a torque wrench for accurate preload, and inspect periodically in high-vibe settings.

10. Can wedge lock washers be used in all industries or environments?

They're widely used in automotive, aerospace, construction, and manufacturing, but check for compatibility. In corrosive settings (e.g., marine), opt for stainless steel versions. For very high temperatures (above 200°C/392°F), they might need special coatings. Consult standards like ISO or ASME for your specific application.

11. What are common mistakes to avoid when using wedge lock washers?

• Mixing brands or sizes—they're designed as pairs.
• Over- or under-tightening, which can damage the washers or fail to achieve preload.
• Ignoring surface cleanliness; dirt can reduce grip.
• Assuming they're maintenance-free; regular inspections are still wise in critical setups.
• Using them without due care on painted or coated surfaces without testing, as the teeth might strip the coating.

12. Can I use a wedge-locking washer against SOFT surfaces?

Not if you want to achieve a secure bolted joint. A soft material on the contact surface cannot hold the serrations, or it could be too brittle, and the bolt could start to rotate. This is the case for wood, soft plastic or any other similar materials.

How do large settlements affect wedge lock washers?

Clamp load in the bolted joint requires the bolt to be stretched appropriately. If the material settles, even just a few micrometres, the stretching of the bolt will decrease and will lead to a loss of preload. The loss of preload means the wedge-locking effect will not work as intended, and the bolt could loosen. This is true for rubber gaskets and multi-layered joints, for example.

13. Can I use a plain washer underneath a wedge-locking washer?

No. We do not recommend using a Nord-Lock wedge-locking washer in combination with a plain washer. Serrations on the Nord-Lock washer will grip the bolt head and your plain washer, successfully locking these two together, however this plain washer will not be locked against the contact surface which means it can rotate. Effectively, this method would utilise friction (between the plain washer and contact surface) and not the wedge-locking effect that occurs between wedge-lock-washers and the clamped parts, making it virtually impossible to loosen unintentionally.

14. How much should I tighten my bolted and nut when using a Conical Wedge Lock washer pair?

This 1-pager provides a summary of target preload, and required torque , by bolt size and bolt class, for a range of k-factors.

15. Where can I buy wedge lock washers, and what should I look for?

You are at the right place! We have an online store for your convenience. When shopping around and doing price comparisons, check material (e.g., steel, stainless), size compatibility with your bolts, and certifications for quality. Read reviews for real-world performance in similar uses.