PURPOSE: To make each chip cuttable to proper length by forming a cylindrical surface whose lower inner surface is equivalent to a drill outer diameter, while making the upper inner surface larger than the drill outer diameter, and projecting two blades inward from the upper inner surface, and making the cutting edge be reached to the cylindrical surface being equivalent to the drill outer diameter.

CONSTITUTION: When a drill 03 is inserted into a drilling jig bush 1 and it is rotated and a feed motion is given, a work material is drilled. In the case, in this bush 1, its upper inner surface is larger than an outer diameter of the drill 03, and since two blades 8A are projected inward from the upper inner surface, and the cutting edge is reached to a cylindrical surface being equivalent to the drill outer diameter, each chip 7 is cut off into proper length by these blades 8A and discharged in succession. In this case, a radius (R) installed in a root part of the blades 8A is conductive to a smooth discharge of the chip 7.