DRILL FOR FORMING STEPPED HOLE

PROBLEM TO BE SOLVED: To provide a drill for forming a stepped hole capable of forming the inner face of the stepped hole as a highly accurate smooth face, and also forming a smooth R face on the inner face of the stepped hole when grinding a hard, brittle material and forming the stepped hole. SOLUTION: A diamond abrasive wheel 2 comprises a cylinder side face abrasive wheel part 2a, a cylinder front end face abrasive wheel part 2b and a protruded abrasive wheel part 4 having a taper face 5 formed on the tip end of the cylinder front end face abrasive wheel part 2b. To a first step part α to be a boundary between the cylinder side face abrasive wheel part 2a and the cylinder end face abrasive wheel part 2b, and a second step part β to be a boundary between the cylinder front end face abrasive wheel part 2b and the protruded abrasive wheel part 4, an R face having a predetermined curvature is formed. To the core of a shank 3 and the inside of the diamond abrasive wheel part 2, a cavity 6 to which fluid is supplied is formed. The cut grooves 7 and 8 in a longitudinal direction communicated with the cavity 6 are formed so as to cross at least the first step part α and the second step part β. COPYRIGHT: (C)2005,JPO&NCIPI