When a power transmission component fails, it can adversely affect the performance of the assembly, often making the machine inoperable. Such failures can not only harm the reputation of the manufacturer, but can lead to litigation, recalls and delays in delivery due to quality concerns. Some failures can even result in bodily injury or death. Understanding why a part failed is critical to preventing similar failures from reoccurring. In the study of a failed part, the analyst must consider a broad range of possibilities for the failure. Although some failures can be attributed to a single primary cause, it is common for multiple secondary factors to contribute. The failure analyst must evaluate all of the evidence available to prepare a hypothesis about the causes of failure.