A motor includes a stator, a rotor, a shaft (50) and two end caps (10, 40), which are assembled together. According to the precision requirements, the outer circumference of the rotor core (20), and the outer circumference, the inner bore (33), the end surfaces of the stator core (30) are subjected to grind. The ground rotor core (20) is nested in the ground stator core inner bore (33), wherein the punched outer diameter of the rotor core (20) is equal to the punched diameter of the inner bore (33) of the stator core (30). The shaft (50) is pressed directly into the shaft bore of the rotor core (20) so as to tightly fit with the shaft bore of the rotor core (20).