Patent ID: 8851808

Claim:
A drill comprising: a first flank, a second flank, a third flank and a fourth flank formed on a tip end portion of a drill body, wherein the first flank includes a first ridge line and a second ridge line forming a cutting edge; the second flank is adjacent to the first flank via a third shared ridge line and includes a fourth ridge line forming a land portion, the second flank being directly adjacent to a rear side of the first flank in a rotational direction of the drill; the third flank is adjacent to the first flank via the first ridge line on the rear side of the first flank in the rotational direction of the drill, and includes a fifth ridge line forming a chisel edge; and the fourth flank is surrounded by a sixth ridge line defining the first flank, a seventh ridge line defining the third flank and a trough line defining the second flank.