A rotary cutting tool includes a main body and a shank. The main body has a tip end. The shank is continuous with the main body on the side opposite to the tip end. The main body is provided with a first cutting edge having a positive twist angle, and a second cutting edge having a negative twist angle and separated from the first cutting edge. Each of the first cutting edge and the second cutting edge extends continuously from the tip end to the shank.

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.

The drill of the invention has: two cutting edges, each having a main cutting edge and a thinned cutting edge, wherein two relief surfaces formed symmetrically around rotation axis, first and second margin portions are formed, the first margin portions have a forward-end small-diameter portion with diameter smaller than the drill diameter, that is formed from the side of the drill forward-end toward the drill rearward-end, the second margin portions have a second forward-end small-diameter portion with diameter smaller than the first forward-end small-diameter portion, that is formed from the side of the drill forward-end toward the side of the drill rearward-end, the first forward-end small-diameter portion and the second forward-end small-diameter portion have inclination portions, the diameters of which gradually increase from the side of the drill forward-end toward the side of the drill rearward-end, and the inclination portions of the first forward-end small-diameter portion have relief surfaces.

A deburring chamfer tool has a main body including a working end for engaging a workpiece to be deburred. The working end is of a conical shape and has a first and a second cutting edge respectively extending lengthwise with reference to different slant reference lines which delimit the conical shape. Each of the first and the second cutting edges slope from a first end adjacent to the vertex of the conical shape to a second end adjacent to the base of the conical shape in a first length and a second length respectively. The second length is smaller than the first length.

The invention relates to a drill comprising a drill tip, wherein the drill tip comprises at least one main cutting edge having a cutting corner, from which the main cutting edge extends to a center, wherein the drill tip comprises at least one additional cutting edge having an additional cutting corner, from which the additional cutting edge extends in the direction of the center, wherein the additional cutting edge is formed only on an outer portion of the drill tip and is thus shorter than the main cutting edge, wherein the additional cutting corner projects beyond the cutting corner.

A drill may include a body extending from a first end toward a second end, and the body may include an outer peripheral surface and a cutting edge. The cutting edge may include a first cutting edge and a second cutting edge. The second cutting edge may be positioned closer to the second end and the outer peripheral surface than the first cutting edge. The second cutting edge may include a first part, a second part and a third part. The second part may be positioned closer to the outer peripheral surface than the first part and may be positioned closer to the second end as close to the first part. The third part may be positioned closer to the first cutting edge than the first part and may be positioned closer to the second end as close to the first part.

For improving a drill, in particular a spiral drill, comprising a base body extending substantially longitudinally in a direction axial to a drill axis, said base body comprising a drilling portion, wherein a radially inward core region in relation to the drill axis and a radially outer region are provided in the base body in the drilling portion, and the drilling portion comprises a plurality of spiral-shaped recesses in the outer region, and arranged between each two spiral-shaped recesses is a wall part, it is proposed that the drill comprises at least four main cutting edges, in particular exactly four main cutting edge and/or the drill comprises at least three central cutting edge portions.

A rotary cutting tool includes a main body and a shank. The main body has a tip end. The shank is continuous with the main body on the side opposite to the tip end. The main body is provided with a first cutting edge having a positive twist angle, and a second cutting edge having a negative twist angle and separated from the first cutting edge. Each of the first cutting edge and the second cutting edge extends continuously from the tip end to the shank.

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 (x) than the outer partial cutting edge and the short main cutting edges.