| 摘要 |
PROBLEM TO BE SOLVED: To prevent the occurrence of troublesome cracks on the inner peripheral surface of a through-hole bored in a glass plate. SOLUTION: A pair of drills having a conical peripheral surface where the grinding surface at the side peripheral part of the drill is reduced in diameter toward a tip part are used. A drill is intruded from one surface of the glass plate, a hole having an inner peripheral surface being reduced in diameter toward an intermediate part in the thickness direction of the glass plate from the surface of the glass plate and being the conical peripheral surface is bored and then the drill is made to go backward. Another drill is intruded from another surface of the glass plate to the opposite part of the hole, a hole having an inner peripheral surface being reduced in diameter toward the intermediate part in the thickness direction of the glass plate from the surface of the glass plate to the substantially middle part of the thickness of the glass plate and being the conical peripheral surface is bored and the drill is made to go backward and then the through-hole is bored in the glass plate. COPYRIGHT: (C)2011,JPO&INPIT
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