What do the letters "MS" in a rivet designation indicate?

The designation "MS" in a rivet specification denotes "Military Standard." It indicates that the rivet meets specific criteria and requirements set forth by military standards, ensuring a level of consistency, quality, and performance in aerospace and defense applications. Military standards (often referred to as "Mil-Specs") provide guidelines and specifications to ensure that materials and components can withstand rigorous operational conditions, contributing to the overall safety and reliability of military and aerospace equipment.

This designation is important in the context of aerospace materials, as the rigorous testing and quality assurance associated with military standards are critical for components that will be subjected to extreme stresses and environmental conditions. Therefore, "MS" signifies adherence to a recognized standard that is essential for aviation and military applications where performance and safety are paramount.