A cutter assembly for a tunnel boring machine comprising: a first housing mount and a second housing mount, the first and second housing mounts being configured to be fixed to the tunnel boring machine, each housing mount having a plate portion, an abutment flange, and a plurality of spaced-apart seats; a cutter ring assembly comprising at least two spaced-apart bridging supports, a shaft supported by the at least two bridging supports, and at least one cutter ring mounted for rotation on the shaft, wherein the at least two bridging supports each comprise a shaft-mounting portion, a first end portion extending from the shaft-mounting portion and configured to abut the first housing mount abutment flange and a second end portion extending from the shaft-mounting portion and configured to abut the second housing mount abutment flange, wherein the first and second end portions each define a first wedge face; a first wedge member attachable to the first housing mount between the abutment flange and the plurality of spaced-apart seats, the first wedge member defining a second wedge face that slidably engages the first wedge faces of the first end portions of each of the at least two bridging supports; and a second wedge member attachable to the second housing mount between the abutment flange and the plurality of spaced-apart seats, the second wedge member defining a second wedge face that slidably engages the first wedge faces of the second end portions of each of the at least two bridging supports; characterized in that the first and second housing mounts define a plurality of channels at a back end of the first and second housing mounts and configured to slidably engage the at least two bridging supports and the at least one cutter ring such that the cutter ring assembly is slidable along a straight path from a back end of the housing mounts to a position wherein the first and second end members of the bridging supports abut the abutment flange of the first and second housing mounts. a first housing mount and a second housing mount, the first and second housing mounts being configured to be fixed to the tunnel boring machine, each housing mount having a plate portion, an abutment flange, and a plurality of spaced-apart seats; a cutter ring assembly comprising at least two spaced-apart bridging supports, a shaft supported by the at least two bridging supports, and at least one cutter ring mounted for rotation on the shaft, wherein the at least two bridging supports each comprise a shaft-mounting portion, a first end portion extending from the shaft-mounting portion and configured to abut the first housing mount abutment flange and a second end portion extending from the shaft-mounting portion and configured to abut the second housing mount abutment flange, wherein the first and second end portions each define a first wedge face; a first wedge member attachable to the first housing mount between the abutment flange and the plurality of spaced-apart seats, the first wedge member defining a second wedge face that slidably engages the first wedge faces of the first end portions of each of the at least two bridging supports; and a second wedge member attachable to the second housing mount between the abutment flange and the plurality of spaced-apart seats, the second wedge member defining a second wedge face that slidably engages the first wedge faces of the second end portions of each of the at least two bridging supports; characterized in that the first and second housing mounts define a plurality of channels at a back end of the first and second housing mounts and configured to slidably engage the at least two bridging supports and the at least one cutter ring such that the cutter ring assembly is slidable along a straight path from a back end of the housing mounts to a position wherein the first and second end members of the bridging supports abut the abutment flange of the first and second housing mounts.