Fastener Failure Analysis

Full size tensile test of B7 threaded rod. Notice how the elongation of the sample stretched the threads. Checking the threads of a used part is a quick way to see if the part was over-stressed.

Fatigue failure of a 2-1/2" Hex Cap Screw. Beachmarks can be seen on nearly 100% of the failure surface.

Fastenal has an accredited A2LA laboratory with equipment that can help you uncover the causes of fastener failures.

We have processes in place to gather parts and details surrounding the failure event. We then look at both the failed piece(s) and unused parts from the same lot, while also reviewing details about the assembly, field conditions, loads experienced by the fastener, and other factors. Laboratory testing will confirm whether there are any issues with that lot of parts. The failed fastener itself may also provide clues, so don't throw away the broken fastener; save it and protect the fractured surfaces (with bubble wrap or something similar). If our fastener testing shows that the parts meet the appropriate standards, we will work with you to find the root cause of the failure.

Although the fastener is the first item that gets the blame when there is a failure, our experience is that the fastener will meet the specs it was intended to meet the vast majority of the time. At that point putting our engineers and equipment to work for you can save significant time in analyzing the situation -- and preventing future failures.

Contact us at

Additional Resources

  • Corrosion - For fasteners as well as most all other industries, corrosion is one of the most common failure modes. This article looks at some of the more common forms of corrosion.
  • Embrittlement - This may be the single most debated topic for failures in any industry. It's also one of those areas in which the more you learn about it, the less you realize you really knew. As this article points out, embrittlement failures, both internal and environmental, are preventable with proper fastener selection.
  • Galling - If you've ever had the pleasure of installing or removing stainless steel fasteners, you've more than likely experienced galling. Galling is a cold-welding process that results when the threads are in contact under heavy pressure and friction. Or in other words, when fasteners are assembled or disassembled. Read the article to learn more.