Patent ID: 8579557
Filing Date: 2013-11-12
Classification: B23B,B24B,Y10T

Abstract:
1. A drill with a tip part on which thinning is performed, comprising two cutting blades which are formed symmetrical about an axis of rotation, said cutting blades consisting of a thinning cutting blade extending from a chisel edge toward a peripheral side of the drill to become a shape including curves, and a main cutting blade extending from an end part of said thinning cutting blade to the peripheral end of the drill, when seen from tip side of the drill, wherein a ridge line of a boundary between a slot for emitting chips and a thinning surface shaped by said thinning cutting blade is substantially u-shaped, inclining toward the drill axis direction and toward a direction in which the ridge line moves from the thinning cutting blade side to the main cutting blade side as it moves from the drill's tip side to the base end side, when seen from front side of the drill which is an aperture side of said slot, and wherein a rake angle θ1 formed by said main cutting blade and a rake angle θ2 formed by said thinning cutting blade satisfy θ1>θ2>0°, except for a part just below the chisel.