Method and rotor for a compressor. The rotor includes a solid first stub having a first end configured to engage with a corresponding bearing and a second end having a flange configured to be attached by bolts to a corresponding flange of a first impeller of the compressor; a tie rod configured to pass through the first impeller of the compressor; a nut being configured to engage a threaded region of the first end of the tie rod; and a solid second stub having a first end configured to receive the threaded portion of the second end of the tie rod and a second end configured to engage with a corresponding bearing. The tie rod does not contact the solid first stub.