Abstract: Machine parts subject to relative vibration motion, in particular a metal spindle fitting with some play in the socket of another member as in the case of an ignition distributor arm joint, are provided, on at least one of the relatively moving surfaces, with closely spaced cavities in which wear products may accumulate, leaving a web-like engagement surface. The cavities do not permit displacement of materials in the direction of vibration, which has the advantage, if the engagement is greased, of holding the grease in the engagement area. Instead of providing the cavities by pits or grooves on one or both of the relatively vibrating surfaces, a perforated or woven and rolled insert of metal or tough synthetic material may be used.