Answer
The mathematical models for thrust capacity assume a perfectly square corner on both the groove and the retained component. In reality, manufacturing tools leave a corner radius, and components often have chamfers.
Impact and Calculation Adjustment:
1. Radius/Chamfer Effect: A radius ($r$) or chamfer ($ch$) on the retained component shifts the point of contact outward from the groove root, creating a bending moment on the retaining ring that can twist it out of the groove.
2. De-rating Factor Curve: If the chamfer ($ch$) on the mating part exceeds $0.1 \times H$ (where $H$ is the radial wall of the ring), the thrust capacity drops exponentially.
3. Thrust Load Reduction Formula:
$$P_{corrected} = P_g \times \left( 1 - \frac{r_{mating}}{d_{groove}} \right)$$
Where $r_{mating}$ is the corner radius of the retained part, and $d_{groove}$ is the groove depth. To offset this, a thicker, heavy-duty 2-turn or 3-turn spiral ring should be specified to resist twisting forces.
