What is the effect of 'Edge Margin' on the thrust capacity of a retaining ring groove?

The edge margin is the distance from the edge of the groove to the end of the shaft or bore. If this margin is too small, the material will fail via 'shear-out' or 'blow-out'. The rule of thumb is that the edge margin $z$ should be at least $3 \cdot d$ (three times the groove depth). The calculation for the maximum load $P_z$ before edge failure is $P_z = \frac{2 π D z τ_y}{S}$. In subsea connectors where space is at a premium, engineers often use high-strength alloys like Inconel 718 for the shaft to reduce the required edge margin, allowing for a more compact design without sacrificing the $P_z$ rating.