Drill for boring anchor fixing hole

Abstract

A drill for boring an anchor fixing hole 72 having an expanded configuration at a nearby area of a bottom part of the hole, wherein a stopper 4 having a diameter larger than an outside diameter of the drill main body 2 is disposed at a location near a shank 3 of the drill main body 2 and a surface 41 of the stopper 4 on a leading end side of the drill is a tapered curved surface which is expanded towards the shank 3 side from the leading end side of the drill. According to the drill of the present invention for boring an anchor fixing hole, an expanded bottom anchor fixing hole can be bored without using two kinds of drills and at a low cost.

What is claimed is:  
     
         1 . A drill for boring an anchor fixing hole having an expanded configuration at a nearby area of a bottom part of said hole, characterized in that 
 a stopper having a diameter larger than an outside diameter of said drill main body is disposed at a location near a shank of said drill main body and a surface of said stopper on a leading end side of said drill is a tapered curved surface which is expanded towards said shank side from said leading end side of said drill.    
     
     
         2 . The drill for boring an anchor fixing hole according to  claim 1 , characterized in that an angle formed between an orthogonal line with respect to an axis of said drill and lo said tapered curved surface is 6 to 30 degrees.  
     
     
         3 . The drill for boring an anchor fixing hole according to  claim 1 , characterized in that a difference (D1−D2) between an outside diameter D1 of a cutting edge disposed at a location near a leading end of said drill main body and an outside diameter D2 of said drill main body at an area where a spiral groove is formed, is 0.5 to 3 mm.  
     
     
         4 . The drill for boring an anchor fixing hole according to  claim 1 , characterized in that a distance from a leading end of said drill main body to said tapered curved surface of said stopper is 30 to 100 mm.  
     
     
         5 . A method for drilling an anchor fixing hole by using said drill for boring an anchor fixing hole according to  claim 1 , characterized by comprising the steps of 
 boring a member to be bored by using said drill for boring an anchor fixing hole until said stopper is abutted with a surface of said member to be bored, and    in a state where said drill for boring an anchor fixing hole is rotated about the axis, moving said drill for boring an anchor fixing hole so as to cause precession serving said stopper as a fulcrum while keeping said tapered curved surface of said stopper abutted with the surface of said member to be bored to cut a nearby area of a bottom part of said anchor fixing hole thereby to form an expanded bottom part having an expanded configuration.