A cutting and dust collecting assembly comprises a rotatable, circular saw blade (4) having a first side (20), a second side (21), and a cover device (6) with a terminal member (52). The bottom surface (36) of the cover device extends in a plane. A longitudinal passage (45, 46) for the saw blade extends through the cover device from its top surface to its bottom surface. The terminal member comprises a terminal chamber (60) having an inlet (45a), the mouth of which coincides with the plane of said bottom surface. An outlet (58) can be connected to a vacuum source. The direction of rotation of the operating blade is such that the rear part (4a) of the saw blade which has passed beyond the bottom surface of the cover device will move in a direction upwards-rearwards towards the bottom surface. The invention also concerns the cover device, a sealing body belonging to the cover device and a working machine which is provided with the cutting and dust collecting assembly.