Abstract: An improved stepping motor rotor assembly comprises a rotor having a shaft and a driving member such as a gear pinion, a centering washer disposed on the shaft and a recess with a short finished cylindrical wall coaxial with the shaft and annular abutment surface at the bottom of the recess, a rare earth permanent magnet having a rough center hole preferably drilled by laser beam defining an annular clearance with the shaft and having a finished outer cylindrical wall extending into the recess with a loose fit to center the magnet with respect to the rotor axis, and a holding washer forming an interference fit with the shaft and pressing the magnet axially against the abutment surface on the centering washer. The centering washer may be restrained in axial position by a light interference fit with the shaft or it may be held by contacting the driving member.