A United States defense standard, often called a military standard, is used to achieve standardization objectives by the U.S. Department of Defense. They are also referred to as “MIL-SPEC” or “MIL-STD.” Military defense standards evolved from the need to ensure proper performance, maintainability, and reparability. The main benefit was that standardization allowed for interchangeability of parts.
Mil-Spec criteria covers every aspect of a part, ranging from the materials it’s made from to the treatment of those materials, dimensions of components made from those materials, testing of the parts, wear and durability, and service life. Every detail is specified and has to be met in order to be classified as Mil-Spec of Mil-Std. Most importantly, military standard parts must be tested and inspected by the U.S. government. Defense standards are also used by non-defense government organizations and technical organizations. According to the Government Accountability Office (GAO), military specifications describe the physical and/or operational characteristics of a product while military standards describe the processes and materials to be used to make the product. However, these terms (MIL-SPEC and MIL-STD) are often used interchangeably.
MIL-STD-961 covers the content and format for defense specifications while MIL-STD-962 covers the content and format for defense standards. These are documents that describe the uniform engineering and technical requirements for military-unique or modified commercial processes. There are five types of defense standards: interface standards, design criteria standards, manufacturing process standards, standard practices, and test method standards. There is a long list of documents that are MIL-STD, followed by a number to denote a specific area in which its requirements are described.