Aircraft Bolts
Aircraft bolts are fabricated from cadmium or zinc plated corrosion resistant steel, unplated corrosion resistant steel, and anodized aluminum alloys. Most bolts used in aircraft structures are either general purpose, AN bolts, or NAS internal wrenching or close tolerance bolts, or MS bolts. In certain cases, aircraft manufacturers make bolts of different dimensions or greater strength than the standard types. Such bolts are made for a particular application, and it is of extreme importance to use like bolts in replacement. Special bolts are usually identified by the letter "S" stamped on the head.
Not sure whether you need an AN, NAS, or MS bolt? Monroe's aircraft bolt guide walks through the main bolt types and how to read head markings. For thread series and fit classes, see our overview of threaded fasteners.
