Official Answer
Answer
Wave springs exert localized pressure at the wave crests. If the mating surface (e.g., a bearing race or a housing shoulder) is too rough, the concentrated stress leads to fretting and micro-shaving of the spring material. A surface finish of $R_a 32 \mu in$ or better is generally recommended. In dynamic applications, where the spring is cycling at high frequencies, a rough mating surface acts as an abrasive, creating stress risers that can initiate fatigue cracks. Lubrication (grease or dry film molybdenum disulfide) is often applied at the contact points to reduce the coefficient of friction and heat generation during rapid cycling.
