BORING DRILL

PROBLEM TO BE SOLVED: To provide a boring drill capable of forming a ground hole having a shape where a hard-brittle material plate is hardly cracked even if handling such as holding and moving the hard-brittle material plate having the ground hole. SOLUTION: The boring drill 11 is equipped with a grinding wheel part 12 on the peripheral surface of a shank 13 operating as a rotating shaft along the axial direction, axially rotates the grinding wheel part 12 with the axis center of the shank 13 as the center, and forms the ground hole on the hard-brittle material plate to be an object to be ground. The grinding wheel part 12 is provided with a curved surface grinding part 15 having a curved surface where an inclination of the tangent line is continued along the axial direction of the rotary shaft. The curved surface where the inclination of the tangent line is continued can be formed on the inner surface of the ground hole by applying an eccentric motion between the curved surface grinding part 15 and the ground hole. COPYRIGHT: (C)2009,JPO&INPIT