Abstract: A step bearing is provided for the end of the shaft of an open-end spinning rotor. The step bearing has a cartridge which is clamped fixedly by a cylindrical outer surface in a corresponding hollow cylindrical receiver surface of a supporting part. The cartridge includes a freely rotatable supporting ball for supporting the shaft; a thrust bearing screwed fixedly onto the cartridge for supporting the supporting ball; and a take-up receptacle for lubricating grease. The cartridge, including the supporting ball and the thrust bearing, can be exchanged for another cartridge with fresh lubricating grease.