DRILL FOR METAL WORKING

PROBLEM TO BE SOLVED: To reduce thrust and enhance biting capability and centering capability by sufficiently reducing a chisel edge while maintaining the strength of an edge at the end center part in a twist drill for metal working. SOLUTION: A thinning part 7 so formed as to correspond to a cutting edge 3 is overlapped a predetermined amount Y in the direction in which a thinning part cutting edge 3b extends in front view by intruding it to the flank 5 side of the opposite side cutting edge beyond a drill center O. A negative land 8 for reinforcing the end is formed at the cutting edge 3. The width cw1 of the portion of the negative land 8 along the thinning part cutting edge 3b when viewed from the front of the drill is larger than the width cw2 of the portion thereof along the main cutting edge 3a, and the width W of the chisel edge 6 is reduced. COPYRIGHT: (C)2009,JPO&INPIT