PURPOSE: To enable two cores to be coated with the same kind of a coating material by constituting a device of a plate in which two bores for receiving a die or a molding tool are formed and a connecting pipe which extends deep inside and is connected to the bores through another passageway.

CONSTITUTION: A plate 1 is fixed at the outlet part of an extrusion machine with a fixing nut. The fixing nut is kept in contact with a connecting pipe 3 screwed into the plate 1. Therefore, even when the plate 1 is rotated, an interface between the cylinder of the extrusion machine and a center supply passageway 4 is filled airtightly to a liquid. The number of bores 2 for receiving a die F or any other optional molding tool or a machine shop tool, is at least two. This number of the bores 2 can be increased depending upon the type and the complicacy of the core to be coated, and may be 10 or more as the case may be.