Retaining rings and snap rings are fasteners used to axially position a component on a shaft or in a bore. The primary retaining ring type can be internal or external. Internal retaining rings fit into a housing or bore. External retaining rings fit over a shaft or pin. The retaining ring style can be circlip, radially assembled, wire formed snap rings, grooveless or self-locking, spiral, beveled, bowed, and interlocking. Circlip are the most common style for axial installation, usually has ears with holes for assembly tool. Radially assembled include E-style and other radially installed rings (external only). These rings are also called snap-on style. Wire formed rings are of uniform cross section with no ears. They are also called "Eaton" style. Grooveless retaining rings do not require a groove. They often have prongs that grip shaft or housing bore. These rings are also called self-locking. Spiral retaining rings are coiled, flat rings with no gap or protruding ears. Beveled retaining rings are used for endplay take-up; the ring has beveled angle (usually 15°). The beveled angle on the ring mates to a complimentary angle on the groove wall during installation, creating a rigid assembly. Bowed retaining rings are used for endplay take-up; bowed or curved, includes EL type. Bowed rings exert a pre-load on the assembly and act like a spring, keeping the assembly in compression. Interlocking retaining rings have two identical, interlocking halves (external only). They are installed radially. Design units for retaining rings and snap rings can be English or metric. Some suppliers may specify both.
Important size specifications to consider when searching for retaining rings and snap rings include shaft diameter, housing diameter, and thickness. The shaft diameter is specified for external rings. The housing diameter is specified for internal rings. The maximum thrust load is also important to consider. The maximum thrust load is also called the ring shear. Common materials of construction for retaining rings and snap rings include beryllium copper, spring steel, and stainless steel. Beryllium copper is chosen when the ring is required to conduct electricity. Spring steel is the most commonly used material. Stainless steel includes steel alloys, bronze and plastics. Common finish, coating or plating for spring steel retaining rings and snap rings are: oil dip, phosphate coating, zinc plating, zinc dichromate lacquer, black oxide, cadmium plating. Common treatment for stainless steel is passivation.