Official Answer
Answer
Edge margin is the axial distance from the groove to the end of the shaft or housing. If this margin is too small, the material between the groove and the end of the part will fail in shear (blowout). The required edge margin $Y$ can be estimated as $Y = \frac{3 · P · S_f}{π · D · σ_y}$, where $P$ is the thrust load. A general rule of thumb is $Y ≥ 3d$, where $d$ is the groove depth. For brittle materials like cast iron, this should be increased to $5d$. If space is limited, the edge margin can be reinforced with a hardened collar, but this adds complexity and cost to the assembly.
