Official Answer
Answer
The groove in the shaft or bore should ideally have a sharp 'square' corner to provide maximum contact area. However, all machining processes leave a small 'radius' ($r$) at the bottom of the groove. If this radius is too large (e.g., $r > 0.1 · t$), the ring will 'ride up' on the radius, leading to 'Dishing' and a significant reduction in thrust capacity. The ring's edge is typically deburred but not radiused to $0.005"$ max. Designers must specify a maximum allowable groove radius ($R_{max}$) in the drawing. In high-performance racing engines, the groove is often 'undercut' to ensure the ring sits perfectly flat against the load-bearing wall, maximizing the shear area.
