Preload springs, spacers and washers are used to provide end-play take up or a constant preload for bearings, gears and other mechanical components and assemblies.
Spring washers are disks of metal that are formed in an irregular shape so that when the washer is loaded it deflects, acts like a spring, and provides a preload between two surfaces.
Washers are disks of metal or non-metallic material placed beneath a nut, an axle bearing, or a joint, to relieve friction, prevent leakage, isolate, prevent loosening, or distribute pressure.