A method for drilling through an assembly forming a stack of at least two different materials uses a drill bit having at least a first cutting edge and a second cutting edge inclined in an axial plane of the drill bit so that the end of the drill bit has a projecting conical shape. The first cutting edge is configured to drill a first material. The second cutting edge is made differently from the first cutting edge, to drill a second material. A first rotational drive axis of the drill bit is laterally offset during the drilling by an offset distance D relative to the axis of the drill bit in a direction opposite the first cutting edge when the drill bit is drilling through the first material, and alternately, in a direction opposite the second cutting edge when the drill bit is drilling through the second material.

A three-flute drill having: a tool main body with cutting edges at an axially distal end thereof, a flute portion having discharge flutes in a distal-end side portion of the body, and a cutting fluid supply hole for supplying fluid toward the edges, a rear inner wall surface on the radial direction on a rear side in the drill rotation direction and opposed to the front inner wall surface in a drill circumferential direction, an outer circumferential inner wall surface made up of a partially cylindrical surface whose center lies on an axis of the drill, and an inner circumferential inner wall surface having a partially cylindrical surface whose center lies on the drill axis and opposed to the outer circumferential inner wall surface in the radial direction, the inner circumferential inner wall having a curvature radius smaller than that of the outer circumferential inner wall surface.

A cutting head rotatable about a first axis, comprising an intermediate portion and a tip portion. The intermediate portion has a plurality of leading edges defining a cutting diameter, and the tip portion has an axially forwardmost tip point and a plurality of front surfaces with outer and inner cutting edges. An outer rake surface adjacent to each outer cutting edge has a positive outer rake angle, and an inner rake surface adjacent to each inner cutting edge has a negative inner rake angle. Each outer rake surface is disposed on a head flute intersecting one of the leading edges, and each inner rake surface is disposed on a gash intersecting one of the head flutes. Each gash extends to a gash path end point located a first distance axially rearward of the tip point, and the first distance is greater than thirty percent of the cutting diameter.