Hitachi, Ltd.

Toshihiro Mine

Kenji Morita

Hideaki Sasaki

Shinichi Kazui

Takeji Shiokawa

Hiroyuki Ogino

A drilling method and a drilling apparatus of a hard brittle material in which a core drill is used for abrasive grinding of high accuracy and high durability. Therefore, the structure of this invention comprises: a tubular core drill; a collet chuck for holding the core drill, including a chuck main body of an integral shape which is hollow, a seal joint provided on the chuck at the inlet side of the lubricant, a slit portion of a pin vise type for holding the core drill, which slit portion is provided on the chuck at the outlet side of the lubricant, and a seal portion provided axially inside of the slit portion, which seal portion has an inner diameter substantially equal to an outer diameter of the core drill applied to the seal portion, and a threaded portion formed on the outer periphery of a portion further axially inside of the seal portion, so that after inserting the core drill into the seal portion, a fastening nut is engaged with and tightened on the threaded portion to thereby seal and fix the core drill, and that the lubricant at a high pressure can be supplied into a central space of the core drill; and a structure for delivering the lubricant through the inner passage of the core drill.

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Hadano, Japan

Toshihiro Mine