An arrangement that can be turned by an assigned hydraulic pressure and flow, related to a chain saw supported by a harvesting unit for crosscutting timber, wherein a bearing arrangement is arranged for the chain saw and oriented between a guide bar housing and the chain saw's drive motor unit, wherewith an oscillatory motion can be activated by a hydraulic control valve, through which hydraulic flow is alternatively controlled via feed or connection lines to the bearing arrangement, for a first or second operating mode. The arrangement is activated via hydrostatic pressure and coordinated with the guide bar housing, and with the drive motor unit, via surrounding perforated discs oriented in parallel and aligned around an axis of rotation for a drive shaft. The hydrostatic affects the arrangement's oscillatory motion for a reciprocal motion pattern, while spent hydraulic oil serves as a lubricating film between the opposing bearing surfaces.
