Hollow body such as a golf-club head, made of molded thermoplastic material comprising an imprisoned insert, and method for the manufacture thereof

A method of manufacturing a hollow body such as a golf club head, having an external hollow body of molded thermal plastic material and an insert in the hollow by which it is possible to adjust the position of the center of gravity and the weight of the hollow body. An insert which is to remain within the hollow body is overmolded with a soft fusible metal to define with the insert a shape for the interior hollow of the hollow body. The hollow body of plastic material is overmolded over the combination of the insert and the overmolded core. The insert is then melted without melting the hollow body around it, and the melted insert material is removed from within the hollow body. For holding the insert and/or the fusible material core in place during the overmolding, either the insert is so shaped or a pin passes through the overmolded region defining an opening in the molded body through which the fusible material may be removed later, and that opening may be plugged.