Abstract: In a rotary cutter block each blade (14) is clamped in an inwardly divergent recess (12) by a wedge (16). The wedges (16) may be clamped simultaneously against their associated blades (14) by application of high pressure grease at any of one or more grease nipples (52, 54) which actuates by hydraulic plungers (22) in the bases of the wedge recesses (12). The angle of the wedges (16) is such as to provide a taper-lock between the wedges (16), the blades (14) and the recesses (12), which means that after depressurization the cutterblock can be stored or moved from one machine spindle to another without slackening of the wedges. The invention is of considerable advantage in reducing the amount of setting-up time involved in setting and grinding the blades of a rotary cutter head, since one pressurization is sufficient to tighten all the wedges simultaneously and to the same degree.