A cutter head assembly (11, 40) is disclosed comprising a cutter head (11) and a cutter (40). The cutter head (11) has first and second substantially planar and parallel flanges spaced so as to define a channel there between and in which channel the cutter (40) is releasably and pivotally retained therein. The cutter (40) is characterised by a length of cable (31), plastic reinforcement (32) surrounding a portion of the cable (31) , a retaining portion (34) attached to a bare portion of the cable (33) for retaining the cutter in an external cutter head and a collar (41) attached to the retaining portion (34) and axially surrounding a portion of the cable (31).
