Official Answer
Answer
Spiral retaining rings are installed by winding them into the groove, which involves expanding the ring (for shafts) or contracting it (for bores). To prevent permanent set, the ring should not be expanded more than $1\%$ beyond its yield point. The maximum installation diameter $D_{max}$ is limited by the material's elastic strain limit $\epsilon = \sigma_y / E$. Using a tapered mandrel or a sleeve helps distribute the expansion force evenly around the circumference, preventing localized yielding at the ring's gap. If a ring is over-expanded, it will not seat tightly in the groove, leading to axial play and potential failure.
