Abstract: The invention is applied to a compressor comprising: a cylinder block (10) provided with a radial bearing (11) and an axial bearing (12); an eccentric shaft (20) having an upper end extension (21), around which a rotor (30) is mounted and supported on the axial bearing (12). A sliding ring (40) is mounted around said upper end extension (21), which is provided with an indexing means (22) to which is coupled a positioning means (42) of the sliding ring (40), rotatively locking the latter to the eccentric shaft (20). The mounting process comprises the steps of: mounting the eccentric shaft (20) in the radial bearing (11); descendingly mounting the sliding ring (40) around the upper end extension (21) of the eccentric shaft (20), until reaching an axial positioning stop (22c) therein, rotationally locking the sliding ring (40) to the eccentric shaft (20); and mounting the rotor (30) to the eccentric shaft (20) until seating a lower face portion (32) of the rotor (30) on the sliding ring (40).