Abstract: An extruder head made up of several segments including a first section made up of at least two plates bolted together. At least one plate is hingeably mounted to another plate in the first section to provide access to an extrudate passage defined by the plates. Downstream of the first section is a pair of mating blocks bolted to the first section further defining the extrudate passage. Inserts of hardened steel are provided and held by the plates and blocks forming the extruder head and the inserts define parts of the extrudate passage. A cooling liquid chamber is provided in at least one insert to cool the wall forming the passage. Although the passage is continuously restricted in the downstream direction, to increase the pressure of the elastomeric melt, intermittent portions of a slightly greater cross-sectional area are provided to allow expansion and thus intermittent lower pressure of the melt as it passes through the passage.