A method for attaching a plastic barrel configured to guide an output shaft of a mechanical device to a housing for the mechanical device is disclosed. The housing includes a chimney delimited by an upper edge and a base, the chimney being arranged to partially surround the output shaft, the plastic barrel having a lateral protuberance. The method involves at least the following steps: inserting a first end of the plastic barrel into the chimney of the housing until the lateral protuberance axially abuts against the upper edge of the chimney, and at least partially deforming the first end of the plastic barrel in order to form an axial counter-abutment.