Methods, systems and apparatuses for mounting a motor rotor to a shaft of a compressor are disclosed. The shaft can include a rib region that is configured to form a press fit or a transition fit with the rotor bore. An end of the shaft can also include a plurality of crenulations that can be expanded outwardly in a radial direction relative to a centerline of the shaft. After the rotor is mounted onto the shaft, the crenulations can be expanded to eliminate the clearance between the shaft and the rotor to form a press fit with the rotor bore.