Diameter-enlarged hole portion forming device

A diameter-enlarged hole portion forming device for forming a diameter-enlarged hole portion by cutting into a hole that is formed in a workpiece, the diameter-enlarged hole portion forming device comprising:

• a bow jaw including a shaft and a guide, the guide including a distal end surface and a first sloped surface, the distal end surface being provided on an opposite side of the guide from the shaft, the first sloped surface being sloped from the shaft side of the guide toward the distal end surface side of the guide in a direction away from a center axis of the shaft, wherein the guide includes:
• a pair of sloped surfaces that includes the first sloped surface and a second sloped surface, wherein the pair of the sloped surfaces is provided such that the center axis is interposed between the pair of the sloped surfaces;
• a recess that is open at the distal end surface and an outer peripheral surface between the pair of the sloped surfaces;
• and
• a groove that is connected to a suction port and to an opening of the recess, wherein
• the opening is formed at the distal end surface, and
• the suction port is open at the distal end surface;
• and
• a cutter blade including a cutting portion whose distal end is provided with a cutting edge, the cutting portion being slidable along the first sloped surface, wherein
• the bow jaw further includes a suction passage that includes a flow passage, the flow passage including the suction port.