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 bottom cutting step up reamer incorporates a shaft having a first end with attachment features adapted to be received in a chuck. A plurality of bottom cutting edges substantially perpendicular to the shaft are located at a second end distal from the first end. At least one step up land is provided proximate the plurality of bottom cutting edges and spaced toward the first end with a plurality of parallel cutting edges substantially parallel to the shaft.

A drill includes a blade tip part that is formed of diamond and a trunk part that is formed of diamond and is continuous with the blade tip part, the drill rotating about a drill axis, the blade tip part includes N cutting edges where N is an integer of no less than 4, and a proportion of S1 to S2 is no less than 30% and no more than 60%, where S1 is an area of the drill in a cross-section with the drill axis as a normal line, the cross-section including a boundary between the blade tip part and the trunk part, r is a maximum value of a distance from the drill axis to an outer edge of the drill in the cross-section and S2 is an area of a circle with r as a radius.

A one-piece cutting head for a drill bit includes a main cutting edge that extends between radial extremities of the cutting head. The main cutting edge is disposed between main rake surfaces and main relief surfaces. Each main rake surface includes one or more rake facets, and each main relief surface includes one or more relief facets. Adjacent rake facets and relief facets define a primary transverse edge therebetween that extends away from the main cutting edge. The cutting head further includes a plurality of side cutters that are transverse to the main cutting edge and that propagate from the primary transverse edge to a radial extremity of the cutting head. Each side cutter includes a side cutting edge between a side cutting rake facet and a side cutting relief facet.

A rotary tool may include a base. The base may be extended from a first end to a second end. The base may include a first part and a second part. The first part may include the first end. The second part may have a larger outer diameter than the first part. The first part may include a first flute. The second part may include a second flute. In a first cross section of the first part, the first flute may include a first bottom part. A center of a first imaginary circle overlapping with the first bottom part may be located outside a circumscribed circle of the first part. In a second cross section of the second part, the second flute may include a second bottom part. A center of the second imaginary circle overlapping with the second bottom part may be located inside a circumscribed circle of the second part.