How should 'Chamfered' mating parts be handled when they bear against a spiral retaining ring?

If the part being retained has a large chamfer or radius, it will contact the ring at a point further away from the groove wall. This increases the 'moment arm' and the 'Dish Effect.' To prevent the ring from being cammed out, the designer must either: 1) Use a 'Back-up Washer' (a flat shim) between the chamfered part and the ring to provide a square face, or 2) Calculate the maximum allowable chamfer $Ch_{max} = 0.5 imes (b - d)$, where $b$ is the radial wall and $d$ is the groove depth. Exceeding this limit leads to premature failure due to the ring 'rolling' over the edge of the groove.