A rotatable cutter head comprising an inner hub having a centrally-disposed bore therethrough and an outer surface for carrying at least one cutter plate concentrically thereon for rotation therewith, an outer hub having a centrally-disposed bore therethrough and an outer surface for carrying at least one cutter plate thereon for rotation therewith. The bore of the outer hub is adapted for receiving the inner hub concentrically therein for rotation therewith. An outer pressure-expansible sleeve is provided for being concentrically-mounted within the bore of said outer hub and pressurized for locking the outer hub onto the inner hub. An inner pressure-expansible sleeve is concentrically-positioned in the bore of the inner hub and pressurized for locking the inner hub onto a rotatable spindle, whereby the inner hub and outer hub and the respective cutter plates mounted thereon are locked in fixed, concentric relation relative to each other and to the rotatable spindle.