ASME B18.2.2 Hex Nuts

ASME B18.2.2 hex nuts, also called hexagon nuts, are internally threaded fasteners with six flat sides for wrench engagement. They mate with compatible inch-series bolts, screws, or studs to form detachable threaded joints in machinery, equipment assemblies, fabricated steelwork, and general maintenance.

ASME B18.2.2 specifies dimensional requirements for inch-series nuts, including wrenching dimensions and nut geometry. It covers several nut styles, so the term “hex nut” alone does not define every dimensional detail. Standard-pattern hex nuts, heavy hex nuts, and thinner jam nuts differ in proportions and intended joint arrangements. A jam nut may be paired with another nut where a thin secondary nut is required, while a heavy hex nut has larger dimensions than a standard-pattern nut.

ASME B18.2.2 is a dimensional standard, not a complete material or mechanical-property specification. Material and strength requirements must be specified separately where applicable. Selection depends on the nut style, nominal diameter, thread series and fit, and the strength requirements of the mating bolt or stud. Inch-series threads commonly use UNC coarse or UNF fine pitches; the nut and mating fastener must have matching thread specifications.