Answer
Groove depth $d$ is a critical parameter. It is defined as $d = \frac{D_{shaft} - D_{groove}}{2}$ (for shafts) or $d = \frac{D_{groove} - D_{bore}}{2}$ (for bores). The stability of the ring is dependent on the 'percent engagement', which is the ratio of the ring's radial wall $b$ that sits inside the groove. A deeper groove increases thrust capacity but makes installation harder and increases the risk of 'over-stressing' the ring during assembly. The optimal depth $d$ ensures that even under the maximum tolerances (worst-case scenario), the ring maintains at least $50\%$ engagement. For precision medical devices, $d$ is often kept small to minimize the footprint, requiring the use of Beryllium Copper rings to maintain high spring force at low deflections.
