Official Answer
Answer
The edge margin $Y$ (the distance from the groove to the end of the shaft or housing) is critical for preventing 'blowout.' The material between the groove and the end must be able to withstand the shear and bending forces from the thrust load $P$. A general rule of thumb is $Y \ge 3 \cdot d$, where $d$ is the groove depth. For thin-walled housings, the hoop stress $\sigma_h = \frac{P \cdot r}{t}$ must also be considered. If the edge margin is insufficient, the material will yield and 'roll over,' allowing the ring to escape. In aerospace applications, finite element analysis (FEA) is typically performed to optimize the $Y$ dimension to save weight while maintaining a safety factor of 1.5.
