December 2016 – It is critical to inspect formed metal fasteners to ensure zero defects whether for safety, mission-critical performance or to optimize the manufacturing process. Conventional methods to do this exist, such as sorting mechanically for size or hand sorting with optical comparators. 

Historically, it has been difficult to inspect internal threads for tiny defects such as chips, tears, weld spatter, or for short or missing threads.

Inspecting the vertical walls of a fastener hole and its threads is difficult for the human eye, due to the hole’s small size as well as lighting and viewing conditions. This type of inspection process is not only slow, labor intensive and subject to interpretation but also prone to human error—particularly over long periods when fatigue can degrade accuracy.

“Because many of our parts, such as small fuel fittings and unions for the auto industry, are safety parts, our customers will not accept anything but 100 percent quality, so we carefully check key areas, including internal threads,” says Chuck Abbate, vice president of operations at H&L Tool, an ISO-TS 16949:2009 registered manufacturer of precision turned and cold formed fastener products. “We needed a way to make sure that all the internal features were perfect and within the print.”

However, even typical cameras and laser-based equipment have difficulty detecting required features inside of parts, and the deeper the hole or recess, the more challenging this becomes.


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Fasteners, The Fastener Museum