A 13/16-in. hex socket failed while in use. Analysis (hardness testing, optical and scanning electron microscopy, and EDS) revealed that the socket was made of low carbon steel formed in a powder metallurgy process. A number of flaws were found including nonuniform wall thickness, poor geometric design with sharp corners as stress raisers, and incomplete sintering evidenced by unsintered particles. These were determined to be the primary cause of failure, although inclusions on the fracture surface containing S and Al may have played a role as well.

A maintenance worker was injured when his 3/4 in. (19 mm) open-ended wrench failed, fracturing in overload fashion along the jaw. The failed wrench was unavailable for testing, but an identical one that failed in the same manner was acquired and subjected to hardness, chemistry, SEM, and metallurgical analyses. SEM imaging revealed microvoid coalescence within the fracture zone. The microvoids were flat and smooth edged indicating insufficient bonding. In addition, a cross sectional sample, mounted and etched using alkaline chromate, revealed an oxygen-rich zone in the jaw. It was concluded that the failures stemmed from forging laps in the jaw that broaching failed to remove.