PURPOSE: To improve the quality of a type section and the contacting strength of the type section to the end of an arm by forming the end of the arm in a stepped flat state, and forming a taper at the end.

CONSTITUTION: When a thermosetting resin composite material is injected from a gate 8 into a space 7, the material is first fed above the space 7 for forming a character section 4a along the tapered surface of a taper 3b to form the section 4a, then fed below the space 7 for forming a detent 4b to integrally form a type section 4 at the end 3b of an arm 3. Accordingly, since the material is sequentially cast from above to below the space 7 for forming the section 4a when the section 4 is integrally formed at the end 3a of the arm 3, the generation of volatile gas is suppressed to prevent the material from improperly filling the section 4a and to effectively contact the section 4 with the end 3a.