Abstract: This relates to a tool and a method for assembling an electric machine rotor, including a rotor body and magnetic pole elements. The process includes: placing a lower seal on a bearing element; positioning the rotor body and the magnetic pole elements on a support in such a way that they define between them spaces closed on the support side by the lower seal; placing an upper seal on the rotor body and the magnetic pole elements so that it closes the spaces on the side opposite to the support; and injecting a joining material into the spaces, through holes made in at least one of the lower seal and upper seal.