A bearing is mounted in an axle tube of a motor and includes an axial hole for rotatably receiving a shaft of the motor. At least one guiding groove is defined in a peripheral wall defining the axial hole. The guiding groove extends axially from an end face toward but spaced from the other end face. The guiding groove includes a deposit space formed at a bottom thereof for receiving carbide and impurities to enhance the lubricating effect and to prolong the life of the motor.