Abstract: A dual worm extruder includes a worm housing having a cavity and a wear resistant insert accommodated in the cavity. The insert has two parallel extruder bores defining, when viewed together in cross section, passages of circular areas having an overlap. The outer surface portions of the insert situated on opposite sides adjacent the overlap are peripherally concave, whereby the cross-sectional outline of the insert has the shape of an hourglass.

Abstract: A method of providing a wear-resistant layer on the inner bore faces of the housing of a dual-worm extruder having two longitudinally communicating parallel bores for accommodating extruder worms therein. According to the method, a relatively soft sheet metal blank and a relatively hard, wear-resistant sheet metal blank are metallurgically bonded to one another in a face-to-face relationship, then the thus obtained "sandwich" is deformed into two longitudinally open tubular blanks, with the relatively soft sheet metal blank forming the outer, convex side of each tubular blank. Thereafter, the tubular blanks are welded to one another along respective longitudinal edges thereof for obtaining a composite body having a cross-sectional outline of a FIG. 8, generally corresponding to, but being smaller than the cross-sectional outline of the bores.