PURPOSE: To eliminate the severe dimensional accuracy and to reduce the improper rate by forming a tapered protrusion on the side face of a molding set and cutting chip accumulating groove on the periphery, and engaging it with the hole of an end bracket in size of the degree of generating cutting chips.

CONSTITUTION: A tapered protrusion 1 is formed on the side face of a molding set. A cutting chip accumulating groove 3 for accumulating cutting chips is formed on the periphery of the root of the protrusion 1. A hole having an extrusion rounded shape is formed on the flange of an end bracket 1 corresponding to the protrusion 1. The diameter of the hole is formed slightly smaller in the degree of generating cutting chips when the protrusion 1 is engaged with the hole. The protrusion 1 is engaged with the hole, the chips 4 are received by the groove 3, and the bracket 2 is secured to the set. Thus, the generating rates of the displacement of an axial center and fluctuation noise can be reduced.