~ Article courtesy of Henkel LOCTITE

Threadlockers offer a universal, reliable adhesive solution to an age-old problem in many OEM (original equipment manufacturer) and MRO (maintenance, repair, and operations) applications. Typically applied to the threads of fasteners before assembly, they form a secure bond that helps maintain the integrity of the connection once cured.

Threadlockers protect fasteners from working loose when subject to harsh vibration, shock, bending, or environmental factors. However, this chemical option is a relatively recent solution to this issue.

The problem with threaded fasteners
Threaded fasteners have long been used to reliably join assemblies, thanks to their impressive clamp load performance. But their design means they’re susceptible to failure over time. Depending on the application and environment, these components can potentially work themselves loose — which means they must be backed up with additional locking methods.

For years, methods of locking these assemblies meant using mechanical devices to prevent a fastener from rotating or loosening over time. This includes alternative products to threadlocker, such as lock nuts, washers, and nylon insert nuts.

These devices are one option for securing threaded connections and can offer ease of installation and reusability benefits. And while many of these mechanical solutions perform a decent job of locking threads, they also present risks to assemblies, including:

1. Susceptibility to loosening over time
2. Subject to corrosion
3. Permitting contamination

Some of the most common mechanical locking devices include:

• Tab washers– A type of lock washer, these metal devices have multiple tabs and notches around them, which fit around a fastener to lock it in place. They tend to bend with use over time and often need replacing.
• Wedge locking washers– A free-spinning component with radial teeth that grips the surface below the bolt head to stay in place. However, the thread is liable to corrosion as it’s not sealed, and its teeth can damage bearing surfaces.
• Nylon insert nuts– These nuts are a type of prevailing torque device. The nylon insert creates additional thread friction. But they fail to seal threads against corrosion or maintain a reliable clamp load in high-vibration environments.

In reality, mechanical devices fail to “lock” assemblies and cannot reliably maintain the clamp load over time. These components often loosen under vibration, thermal expansion, bending, and improper torque, which can be fatal to the operation of key machinery.

A threadlocking alternative
Quality threadlocking adhesives effectively overcome many of the limitations of mechanical locking devices. They limit loosening and reduce the effects of corrosion and contaminants.

Additionally, threadlocking compounds can effectively reduce the impact of costly failures, repairs, maintenance, and downtime.

Threadlockers are designed to:

Fill gaps and voids. One of the most prominent issues with mechanical locking devices is that air gaps, no matter how small, will always exist between a thread and a bolt. These minute gaps allow a degree of freedom to move when an assembly is subjected to torque, vibration, or shock. But they also cause the threads to loosen  gradually.

Gaps are of no concern for chemical threadlockers, which flow into them, removing the air between the two parts of an assembly. When applied properly, the liquid displaces the air as it disperses between the threads. This guarantees a surface-to-surface seal across the thread.

One major advantage of a treadlocker is that it tightly locks fasteners into place and negates any air gaps between threads, significantly limiting the ability of the assembly to move while in operation.

Eliminate corrosion. Environmental factors impact how well assemblies perform over time. Extreme temperatures and atmospheric conditions can seriously affect bolts and other threaded assemblies.

Corrosion is one of the most common concerns, often resulting from moisture, water, or other liquids seeping into threaded fasteners. Of course, rusted or corroded threaded fasteners can seriously affect an assembly. Rust can also restrict the ability to disassemble fasteners for maintenance without cutting the bolt or using mechanical methods. This can extend assembly downtime and create unnecessary expenses.

By eliminating the gaps between two metal surfaces with a strong bond, threadlockers reduce the risk of liquids wicking into assemblies.

When choosing threadlockers, ensure they’re from a reliable brand that will not be compromised by the presence of water, salt, or chemicals that may cause corrosion in other fasteners. Also, choose the correct type for the application.

Threadlockers are typically graded by strength, operating temperature range, and maximum thread size.

They’re also labeled by color. Understanding the difference between threadlocker colors ensures the ideal product is chosen for the job. For example, a purple threadlocker is ideal for low-strength and blue is best for medium-strength assemblies. Red threadlockers, labeled for high strength, are only deployed for the strongest, most permanent applications. These include heavy equipment, suspension, and bearing cap bolts.

Choosing the ideal threadlocker for an assembly, along with the proper application, will ensure your assemblies stay locked in place over time.

 

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Filed Under: Fastener adhesives
Tagged With: henkel
 

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