PURPOSE: To correctly let mating surfaces of two parts coincide with each other by forming the mating surface of the first part to have a protruded part having a head at a tip, and the mating surface of the second part to have a recessed place to enclose the protruded part to catch the head, and composing them in such a way that the head is cut at the protruded part to separate the first part from the second part.

CONSTITUTION: On the mating surface 28 of a first part 12 of a bearing cap 10, the protruded part 30 of a trancated cone having a diameter-expanded tip part 34 is formed. When a second part 14 is cast, the recessed place 66 of a mating surface 60 of the second part 14 encloses the protruded part 30 to catch the tip part 34. With any type of machining applied, therefore, the two parts can be tightly held to each other during machining. In separating the two parts from each other, the protruded part 30 is broken at a neck part 36. Separation of the parts can thus be achieved by a relatively small force without bending the parts. Since the second part 14 can be molded at a specified position relative to the first part 12, the two parts can be correctly mated with each other.