Hex Nuts Basics
Hex nuts are six-sided, hexagonal fasteners that are internally threaded and can be mated with externally threaded fasteners, such as a bolt, and by rotation, develop high clamping forces on structure contained between the nut and bolt bearing surfaces. A nut of a given thread size, material, heat treatment and adequate wall thickness has about 1.75 times the axial strength (tensile strength) of its mating bolt of the same material and heat treatment, provided that the effective thread length within the nut is equal to, or greater than, the major diameter of the bolt thread. This makes bolts the critical members in nut/bolt assemblies and makes nuts of the appropriate material and heat treatment ideal for bolt testing.
A finished hex nut, also known as a standard hex nut, has a smaller width across the flats and corners compared to a heavy hex nut. Heavy hex nuts are thicker and heavier in weight. The proof load strength is higher than a standard hex nut.
Hex nuts are available in several different grades and finishes based on the mechanical and chemical properties of the material, and the intended application of the hex nut.