FF-W-84 Spring Lock Washers — Helical & Split

FF-W-84 describes a helical spring-type washer utilized heavily with nuts, bolts, machine screws, and studs to prevent them from vibrating loose over time. A helical spring lock washer is essentially a single coil of split, rectangular-section wire formed into a washer shape. When compressed under a bolted joint, its sharp edges and two bearing surfaces bring spring tension and a biting locking principle into play that materially resists any tendency of the joint to turn or back off.

The specification is strictly organized by material class and style/duty level. While Revision A was approved in 1967, later administrative notices (2000 and 2013) confirm the document is now officially inactive for new design. This means modern engineering designs should consider alternative active locking methods or current commercial standards. However, it remains fully valid for use, especially regarding legacy replacement procurement.

The primary mechanical function of helical spring lock washers is to compensate for slight losses in joint tension caused by thermal expansion, heavy vibration, or minor seating wear. A split helical washer acts as a highly compressed, loaded spring when flattened between the fastener head (or mating nut) and the installation surface. As the structural joint experiences dynamic loads, the split edges of the washer bite into the metal, creating a frictional lock that resists loosening.

These components are extremely common in older industrial machinery, automotive assemblies, and legacy military hardware. For verification of the latest notices and active status codes, engineers can reference the Defense Logistics Agency (DLA) ASSIST database.