A method of producing a drill has a step of preparing a workpiece to be processed to produce a drill, and a step of forming a ground groove. The workpiece has a cutting blade, a chip discharge flute helically extending, and a rake surface which have been formed therein. The drill is rotated around a drill axial center. The formation step rotates a rotary whetstone around its whetstone axial center, and grinds the rake surface to form the ground groove along the chip discharge flute. The formation step uses the rotary whetstone so that the whetstone axial center intersects a longitudinal direction of the chip discharge flute. The rotary whetstone has a rotating body shape projecting in a radial outward direction of the rotary whetstone axial center and around the rotary whetstone axial center.

The invention relates to a four-edged drill having two long main cutting edges, arranged in a point-symmetric manner with regard to the axis of rotation, which each extend from an outer circumferential cutting corner to a chisel edge in the middle of the drill tip, and two short main cutting edges, arranged in a point-symmetric manner with regard to the axis of rotation, which each extend from an outer circumferential cutting corner in the direction of the middle of the drill tip. According to the invention, each long main cutting edge has an outer partial cutting edge, extending from the cutting corner as far as a shoulder, and an inner partial cutting edge, extending from the shoulder as far as the chisel edge, said inner partial cutting edge having a greater cutting height (Δx) than the outer partial cutting edge and the short main cutting edges.

A rotary tool according to an aspect includes a body, a flank face positioned at a side of a tip end of the body, a flute extending from the flank face toward a rear end of the body, and a ridge line positioned at an intersection of the flank face and the flute. The ridge line includes a recessed portion recessed toward the rear end of the body, an inner edge extending from the recessed portion toward the tip end of the body, and an outer edge extending from the recessed portion toward an outer periphery of the body. The flute includes a recessed groove extending along the outer edge. The recessed groove is connected to the recessed portion and the outer edge, and is separated from the inner edge.

An insert includes a main body extending from a first end toward a second end. The main body includes a cutting edge, a rake face, and a flute. In the rake face, a second rake angle of a second surface region positioned closer to the second end than a first surface region connected to the cutting edge is smaller than a first rake angle of the first surface region. A third rake angle of a third surface region is smaller than the second rake angle, the third surface region being adjacent to the flute rearward in a rotational direction and on an outer peripheral side of the main body.

A drill point for machining of light alloys, such as aluminium alloys, includes a body having a front end with an apex area, a central axis of rotation and at least one cutting structure. Each cutting structure has a primary rake surface, a primary clearance surface, a cutting edge at an intersection between the primary rake surface and the primary clearance surface, and a peripheral cutting corner. The cutting edge extends radially outward from the apex area to the cutting corner. The primary clearance surface, as seen in a front end view, has a breadth that is a distance extending perpendicular to and from the cutting edge to a primary clearance surface edge, which is rotationally trailing the cutting edge. The body further has a nominal cutting radius, which is a radial distance outward from the central axis of rotation to the cutting corner, and which is at least 1 mm.

A method of manufacturing a drill bit includes providing a piece of bar stock having a first end, a second end opposite the first end, and an axis of rotation extending centrally through the bar stock between the first and second ends, cutting the first end of the bar stock to form a first tip angle at an oblique angle measured through the axis of rotation, cutting the first end of the bar stock at a second tip angle measured through the axis of rotation to form first tip surfaces and second tip surfaces. The first tip surfaces have the first tip angle and the second tip surfaces have the second tip angle. The second tip angle is smaller than the first tip angle. Finally forming a flute in the bar stock between the first and second ends and forming a shank at the second end of the bar stock.

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.

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.

In this small-diameter drill bit, two cutting blades having main cutting blades, of which a difference between lengths are 0.04 mm or less, are formed on a tip of a double-margin drill bit body having a diameter of 2 mm or less and a margin length/diameter ratio of 3 or more. Two tip flank faces are formed such that a first extension line extending from a linear first intersecting ridgeline between a first tip flank face and a second tip flank face of one of the flank faces to the linear first intersecting ridgeline of the other flank face is located on a side in the drill bit rotation direction with respect to the other linear first intersecting ridgeline. A distance between the first extension line and the linear first intersecting ridgeline is in a range of 0.04 mm-0.08 mm.