, a standardized coding method used in the aerospace industry to communicate fastener installation requirements on technical drawings. Instead of writing out lengthy instructions for every rivet, engineers use a four-quadrant "cross" symbol that provides all necessary data at a glance. The NAS 523 Quadrant System
-inch increments and the manufactured head position. The letter "N" (Near) or "F" (Far) indicates which side the head should be placed on relative to the technician.
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Applications: Primarily used for identifying rivets for skin attachment, stringer attachments, and structural frames in aircraft construction.
Northeast (NE - Upper Right): Specifies the rivet diameter in , a standardized coding method used in the
designates an MS20470AD universal-head rivet made from 2117 aluminum alloy. NE (Northeast - Upper Right): Specifies the rivet diameter in 1/32" increments and the location of the manufactured head Head on the "Near" side. Head on the "Far" side. SW (Southwest - Lower Left): Indicates the hole preparation method required for flush installations. Countersinking. Dimple top two sheets and countersink the third. SE (Southeast - Lower Right): Specifies the fastener length in 1/16" increments. A "-6" would indicate a 3/8" rivet. Common Aircraft Rivets (Reference) Material Code Alloy Markings on Head Material Type None (Plain) 1100 Aluminum Non-structural Single Dimple 2117 Aluminum Most common structural Raised Dot 2017 Aluminum "Icebox" rivet; must be frozen Raised Double Dashes 2024 Aluminum "Icebox" rivet; high strength Raised Cross 5056 Aluminum Magnesium structures Double Dimples Nickel-Copper High temp/Firewalls Practical Installation Guidelines Diameter Rule: Use a rivet diameter at least the thickness of the thickest sheet being joined. Length Calculation:
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The standard is widely adopted by major aircraft manufacturers to ensure consistency in structural repairs and new builds. Permanent Deformation: