In fastener inspection, what is a major defect?

A major defect in fastener inspection is identified as a crack or missing thread that extends more than half the thread height. This type of defect is critical because it can significantly compromise the integrity and strength of the fastener, making it unsuitable for its intended application. In fasteners, maintaining the structural integrity of the threads is essential for ensuring proper engagement and load-bearing capacity. If a defect extends beyond half the thread height, it can lead to failure under load, which poses risks in safety-critical applications.

In contrast, defects such as a single small nick or a flattened thread that does not exceed specific dimensions may still allow the fastener to function adequately under certain conditions, but they are classified as minor defects. An acceptable minor defect, even if isolated, does not compromise the overall effectiveness of the fastener significantly, which is why it does not fall into the category of a major defect. Understanding the categorization of defects helps in assessing the reliability and safety of fasteners in various applications.