Patent ID: 11325194

Abstract:
[Problem] To protect a leading end part of a drill having a coolant hole which is adapted for drilling a thin diameter or very thin diameter hole in a workpiece.[Solution] A coolant hole 33 is formed in a shank 3 and a shaft body 7 so as to extend through from a rear end surface 31 of the shank 3 to a leading end surface 15 of the shaft body 7 along an axis thereof. A leading end part of the coolant hole 33 is branched into a pair of discharge holes 35, at a position slightly toward a base end relative to the leading end surface 15 of the shaft body 13. The discharge holes 35 extend in the opposite directions, perpendicular to the coolant hole 33, respectively, and open at opposite side surfaces 37, 37 to define discharge ports 39, 39. A leading end opening 41 of the coolant hole 33 is closed by a bottom face 17 of the drill part 9.