ASME B1.13M is the cornerstone American standard for Metric Screw Threads with the M Profile. It provides the technical basis for the design, dimensions, and tolerances of metric fasteners used in the North American industrial and automotive sectors, ensuring full compatibility with ISO 68-1 and ISO 261 basic thread profiles.

While similar to ISO standards, ASME B1.13M offers specialized engineering data focused on precision fits and boundary conditions required for high-performance machinery. It establishes the limits of sizes for the internal and external threads, facilitating the global transition toward metric standardization in engineering design.

The technical focus of ASME B1.13M is the Thread Tolerance Quality and Position. The standard uses a combination of numeric grades (e.g., 6) and letter positions (e.g., g, h for external; G, H for internal). A key feature is the "Allowance" (fundamental deviation), which ensures a minimum clearance between mating parts under maximum material conditions, preventing galling during assembly.