Official Answer
Answer
Spiral retaining rings are installed by spreading the coils and 'winding' them into the groove. To avoid permanent set, the ring must not be expanded beyond its elastic limit. The maximum expansion $S_{max}$ is limited by the fiber stress $\sigma = \frac{E t (D_g - D_f)}{(D_f)(D_g)}$ where $D_g$ is the groove diameter and $D_f$ is the free diameter. Using an installation mandrel or a tapered sleeve is recommended for high-volume assembly to ensure even distribution of the expansion stress. If the ring is over-expanded such that $\sigma > S_{yield}$, the ring will not snap back tightly into the groove, reducing its thrust load capacity $P_a = \frac{D d S_y \pi}{K}$.
