Answer
The shear strength of a spiral retaining ring is the maximum axial thrust load it can withstand before the material is physically sheared through its cross-section. It is calculated as $P_s = \pi \cdot D \cdot t \cdot \tau_{ult}$, where $D$ is the shaft/bore diameter, $t$ is the ring thickness, and $\tau_{ult}$ is the ultimate shear strength. $\tau_{ult}$ is typically estimated as $0.6$ to $0.75$ times the ultimate tensile strength $S_{ut}$ for most steels. Unlike tensile strength, which measures the resistance to pulling apart, shear strength measures the resistance to adjacent planes of the material sliding past one another. In ring design, the shear capacity of the ring usually exceeds the yield capacity of the groove, making the groove the critical design limit.
