What is ANSI B18.2.1?
Often times, ANSI (American National Standards Institute) or ASME (American Society of Mechanical Engineers) B18.2.1 will show up on a drawing, some certification documents, and even our website . This number simply refers to dimensional standards for a variety of common bolts, such as hex bolts, heavy hex head bolts, and square head bolts. Most ASTM specifications do not address dimensional tolerances of fasteners. Instead, most ASTM bolt specifications refer to an ASME standard for this information. Bolt manufacturers must comply with ASME standards for dimensions such as head height, width across the flats, body diameter, bolt length tolerances, thread lengths, and dimensional tolerances in general. ASME B18.2.1 does not have any bearing on the strength or the chemistry of the bolt, which is typically called out by an ASTM or SAE grade designation.