Abstract: A hole expansion device includes a cutting portion main, body formed to have a diameter for the cutting portion, main body to be housed within a joint hole and including a cutting blade tool movable in a range from a housed position at which a blade is housed within a diameter for the cutting portion main body to an extended position at which the blade projects out of the diameter, an advancing and retracting member that is constructed to move in an axial direction by an external force and rotate about an axis of the advancing and retracting member, and a link mechanism that converts an advancing and retracting movement of the advancing and retracting member into a rotational movement of the cutting blade tool.

Abstract: A hole expansion, forming device includes a cutting portion main, body formed to have a diameter for the cutting portion, main body to be housed within a joint hole and including a cutting blade tool movable in a range from a housed position at which a blade is housed within a diameter for the cutting portion main body to an extended position at which the blade projects out of the diameter, an advancing and retracting member that is constructed to move in an axial direction by an external force and rotate about an axis of the advancing and retracting member, and a link mechanism that converts an advancing and retracting movement of the advancing and retracting member into a rotational movement of the cutting blade tool, a tip portion bearing that is provided on a tip end of the cutting portion main body, and serves as a tip end side bearing when being housed in an inner side of the joint hole.