Answer
The thrust capacity of a spiral retaining ring assembly is limited by two distinct factors: the shear strength of the ring and the deformation of the groove. The shear capacity of the ring is calculated as $P_r = \frac{D \cdot T \cdot \pi \cdot S_s}{K}$, where $D$ is the shaft/bore diameter, $T$ is the ring thickness, $S_s$ is the shear strength, and $K$ is the safety factor (typically 3). However, the groove material is usually the weaker link. The groove yield capacity is given by $P_g = \frac{D \cdot d \cdot \pi \cdot \sigma_y}{K}$, where $d$ is the groove depth and $\sigma_y$ is the yield strength of the housing material. If the thrust load exceeds $P_g$, the groove wall will deform, causing the ring to dish (cone) and eventually 'walk out' of the groove. Engineers must use the lower of these two values as the design limit.
