Drill

A coated drill having a coated layer formed on a surface thereof, in which:

• a chip discharge groove which extends toward a base end is formed in an outer periphery of an edge portion serving as a leading end side portion of a drill body rotated around an axis;
• and a cutting edge is formed in an intersecting edge between a rake surface of a leading end side region of an inner wall surface of the chip discharge groove and a leading end flank of the edge portion, such inner wall surface facing forward with respect to a drill rotating direction, the coated drill comprising:
• a margin portion intersecting with the rake surface and facing toward the outer periphery;
• a shoulder portion being an intersecting edge between the margin portion and the leading end flank of the edge portion and extending, from an outer peripheral end of the cutting edge, backward with respect to the drill rotating direction;
• and
• a web thinning portion extending toward a leading end of the inner wall surface of the chip discharge groove, wherein
• the cutting edge comprises, in order from a rotation center, a first cutting edge portion formed in the web thinning portion, a second cutting edge portion formed closer to the outer periphery than the first cutting edge portion, a shoulder cutting edge portion formed in the shoulder portion, and a margin cutting edge portion formed in the margin portion,
• honing is performed on the second cutting edge portion, the margin cutting edge portion and the shoulder cutting edge portion,
• when a honing width at a boundary P1 between the margin cutting edge portion and the shoulder cutting edge portion is defined as R1, and a honing width at a position P2 separated 3 mm from the boundary P1 in a direction opposite to the second cutting edge portion is defined as R2 in the margin cutting edge portion,
• the honing width gradually decreases from the boundary P1 toward the position P2, and conditions represented by expression (1) and expression (2) below are satisfied:
• honing width of second cutting edge portion≤R1 (1)
• 2.0<R1/R2<5.0 (2),
• when an arithmetic mean roughness of a honed portion in a first range from the boundary P1 to the position P2 is defined as Ra1, and an arithmetic mean roughness of a honed portion in a second range other than the first range in the margin cutting edge portion is defined as Ra2, a condition represented by expression (3) below is satisfied:
• Ra1<Ra2 (3), and
• Ra1 is 0.1 μm or more and 1.0 μm or less, and Ra2 is 0.2 μm or more and 2.0 μm or less.