Abstract: The internal core of a molding apparatus does not have to be axially moved for molding a plastic pipe provided with a peripheral groove therein. This is accomplished by providing the internal core with a groove of such narrow width as to always be open to the surrounding cooperating mold body while at the same time preventing plastic material from entering the groove as the plastic material is being introduced into the mold cavity.

Abstract: An injection molding apparatus, including a mold having a mold cavity therein defining the outer periphery of a pipe fitting, has a core pin assembly adapted to be positioned in the cavity and which comprises opposing distal core sections whose proximal ends abut an intermediate core section therebetween. The core sections are mutually separable and have passages for accommodating a fluid coolant therein, and when the core sections are assembled, at least certain passages in either or both distal core sections are in fluid intercommunicating relation with passages in the intermediate core section.