How is the shear strength of a spiral retaining ring calculated, and how does it relate to the safety factor $K$?

The axial thrust capacity based on ring shear is calculated as $P_r = \frac{D t \pi S_s}{K}$ where $D$ is the shaft/bore diameter, $t$ is the ring thickness, $S_s$ is the shear strength of the ring material, and $K$ is the safety factor (usually 3). For most spring steels, $S_s \approx 0.6 \times S_{ut}$ (ultimate tensile strength). It is critical to compare $P_r$ (ring shear) with $P_g$ (groove yield). The lower value determines the system's limit. In high-impact applications, $K$ should be increased to 5 or higher to account for dynamic loading and potential fatigue at the groove interface.