Spindle motor including magnetic element for pre-loading a ball bearing set

A disk drive comprising:

• a disk drive base;
• and
• a spindle motor attached to the disk drive base, the spindle motor including;
• a spindle motor base attached to the disk drive base;
• a motor shaft in mechanical communication with the spindle motor base, the motor shaft having a central axis and a distal end;
• a spindle motor hub rotatably coupled to the spindle motor base, the spindle motor hub including a central magnetic metal portion disposed adjacent the distal end;
• a ball bearing set disposed between and in mechanical communication with the spindle motor hub and the motor shaft for rotatably coupling the spindle motor hub and the spindle motor base;
• and
• a shaft magnetic element attached to the motor shaft at the distal end adjacent the central magnetic metal portion;
• wherein the shaft magnetic element being sized and configured to apply an attractive magnetic force to the central magnetic metal portion in a direction along the central axis for pre-loading the ball bearing set.