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Common Fastener Failures and How to Prevent Them

Blake Marciszewski

Blake Marciszewski

Metric Bolt is a family run company with an inventory of military fasteners.

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In the world of manufacturing and construction, quality fasteners serve as unsung heroes, silently securing structures, machines, and countless products we use daily. But when these heroes falter, the implications can be severe. 

Understanding common fastener failures and how to prevent them is crucial for manufacturers, defense contractors, builders, and maintenance teams alike.

Spotting the Warning Signs – Common Indicators of Fastener Failure

Before delving into the types of fastener failures, it’s important to understand how to recognize impending fastener failure. 

Knowing these warning signs can help prevent catastrophic failures by addressing issues before they escalate.

  • Unexpected loosening – One of the earliest and most noticeable signs of fastener failure is unexpected loosening. If a fastener that was previously tightened securely becomes loose, it’s a clear indication that something is amiss. This loosening can result from several factors, including vibrations, incorrect torque during installation, or wear and tear.
  • Visible corrosion or rust – Corrosion or rust on fasteners is another significant indicator of potential failure. When fasteners corrode, they lose their structural integrity and can easily break under load. If you notice any discoloration, flaking, or rusting on your fasteners, it’s time to replace them.
  • Surface cracks – Surface cracks on fasteners, even the smallest ones, can be an early warning sign of impending failure. Cracks often develop due to stress concentration or hydrogen embrittlement. They may be hard to detect visually, especially in the early stages, which is why routine inspections and non-destructive testing methods like dye penetrant inspection are crucial.
  • Stripped threads – Stripped threads can also indicate fastener failure. If the threads on a fastener become worn or damaged, the fastener may not be able to maintain its grip, leading to loosening or failure.
  • Deformation – Any visible deformation, such as bending or stretching, is a sure sign of a problem. Deformation often indicates that the fastener is subjected to loads higher than it was designed to handle.

Recognizing these warning signs can facilitate timely intervention, potentially averting disastrous fastener failures.

Coupled with regular maintenance checks and proactive quality control measures, this knowledge serves as the first line of defense against fastener failure.

Now, let’s delve deeper into the common types of fastener failures and how to prevent them.

Strip-Out – When Threads Give Way

One of the most frequent failures is a strip-out, a situation where the threads of a screw or bolt give way under tension or torque. 

This failure often leads to the loss of clamping force, compromising the integrity of the assembly. 

Strip-outs typically happen due to over-tightening or when a fastener is driven into a hole with misaligned threads.

How to prevent this issue

Preventing strip-outs involves understanding the torque limits of your fasteners and the material into which they’re driven. 

The use of calibrated torque wrenches can ensure that fasteners aren’t over-tightened. 

Properly aligning the fastener with the hole can also prevent cross-threading and subsequent strip-outs.

Hydrogen Embrittlement – The Invisible Saboteur

Hydrogen embrittlement is a silent but devastating fastener failure, especially prevalent in high-strength steel fasteners. 

In this phenomenon, hydrogen atoms infiltrate the steel, reducing its ductility and leading to sudden, catastrophic fractures under stress.

 The source of hydrogen is often corrosive environments or manufacturing processes like electroplating.

How to prevent this issue

To prevent hydrogen embrittlement, manufacturers must adhere to precise process controls during coating or plating processes, ensuring excess hydrogen is baked out. 

Additionally, fasteners exposed to corrosive environments can be designed with corrosion-resistant materials or protective coatings.

Shear Failures – Overburdening the Fastener

Shear failures occur when the force applied to a fastener exceeds its shear strength, causing it to snap. 

This can happen when a fastener is incorrectly specified for its intended application, often due to misunderstanding the forces it will encounter.

How to prevent this issue

The best way to prevent shear failures is by understanding the load a fastener will bear and choosing one with a suitable shear strength. 

Using larger or stronger fasteners or redistributing the load across multiple fasteners can also help.

Corrosion – The Slow Deterioration

Corrosion is a slow, but insidious enemy of fasteners, gradually eroding their strength and functionality. 

Fasteners exposed to harsh environments, moisture, or certain chemicals are particularly vulnerable. 

Corrosion can lead to a loss of preload, galling, or complete fastener failure.

How to prevent this issue

Using fasteners made of corrosion-resistant materials or ones coated with corrosion inhibitors can prevent this issue. 

Additionally, regular inspections can identify and address corrosion before it leads to failure.

Wear and Tear – The Unavoidable Failure

Over time, fasteners can undergo wear and tear, compromising their functionality.

This failure is especially common in applications with moving parts or where fasteners are exposed to vibrations.

How to prevent this issue

Periodic maintenance checks can help identify wear and tear early and replace failing fasteners before they lead to larger issues. 

For applications prone to vibration, using lock washers, thread-locking fluid, or vibration-resistant fasteners can help.

Improper Installation – The Human Element

Finally, one of the most common causes of fastener failure isn’t related to the fastener itself but to the person installing it.

Incorrect hole size, misalignment, over-tightening, or under-tightening can all lead to fastener failures.

How to prevent this issue

Training installers properly, providing clear instructions, and using the correct tools can all help to prevent these failures. 

Automated fastening systems can also ensure consistent, correct installation.

Understanding Common Fastener Failures & How To Prevent Them

All in all, fastener failures can pose significant challenges, but a solid understanding of these common issues and their prevention strategies can go a long way in ensuring the reliability of any assembly. 

To benefit from the highest quality fasteners, please don’t hesitate to contact our team at Metric Bolt today. 

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