Provided herein is a drill having less possibility of cracks in an inner periphery of a drilled workpiece and deformation of a workpiece upon penetrating with a drill, as well as delamination.

A drill according to the present invention comprises two cutting blades which are formed symmetrical about an axis of rotation, wherein each of the cutting blades has a main cutting blade formed from a drill tip toward a peripheral side of the drill to become a shape with curves, a thinning cutting blade in a shape with curves formed in closer to the drill tip than the main cutting blade, and an U-shaped cutting blade in a shape with curves formed in closer to the periphery of the drill than the thinning cutting blade.

A drill includes a tip cutting edge provided at a tip end thereof and a main cutting edge continuous to a rearward of the tip cutting edge. A point angle of the tip cutting edge is a predetermined acute angle. A point angle of the main cutting edge decreases from a front end toward a rear end of the main cutting edge. A point angle at the front end of the main cutting edge is an acute angle greater than the point angle of the tip cutting edge.

In this drill, a cutting edge, which is formed at an intersecting ridge line part between a wall surface, facing a drill rotation direction, of a chip discharging flute formed at an outer periphery of a tip portion of a drill main body that is rotated around an axis, and a tip flank face, includes an inner peripheral cutting edge located on a radially inner peripheral side with respect to the axis; and an outer peripheral cutting edge connected to a radially outer peripheral side of the inner peripheral cutting edge. A point angle of a portion of the inner peripheral cutting edge on an inner peripheral side with respect to the axis is within a range of 90? to 170?.

The invention relates to a carbide insert (2) for a rock drill (1), which is configured as a non-percussively operating twist drill with a cylindrical drill body (11) and a working end (13) having the carbide insert (2), the carbide insert (2) having two cutting lips (22) which are radially opposite one another relative to an axis of drill rotation (d) and are arranged at an angle to one another to form a centering tip (21) and with each of which a peripheral conveyor spiral (14) may be associated. To be able to introduce a drilled hole more quickly, easily and simply and with less risk of damage into a workpiece of rock, rock-like material, hard plastics, glass or the like, it is proposed that the cutting lips (22) be configured asymmetrically to one another, wherein at least one of the cutting lips (22) defines over its radial profile, in a central region spaced from its radial ends, a tip (23) projecting in the drilling direction (b).

A drill is provided with a body having a rod shape configured to rotate about a rotational axis, a cutting edge that is located at a tip portion of the body and extends from an outer periphery of the body toward the rotational axis when viewed from the tip portion, a flank located at the tip portion and disposed along the cutting edge, a covering layer that covers at least the tip portion of the body, and one or more recessed portions disposed on the flank at positions close to the cutting edge.

A cutting body for a drilling tool has a center axis, at least one cutting element with at least one cutting edge, and at least one side face. The at least one side face has at least one radially inwardly directed cutout, which is designed to produce a drilled hole having an increased roughness, the cutout having precisely three open sides.

A drill according to an embodiment of the present invention has a pair of main cutting edges positioned at a front end of a drill body, a pair of first chisel edges each extending from the pair of main cutting edges toward a rotation axis, and a second chisel edge positioned between the pair of first chisel edges and intersecting with the rotation axis of the drill body. When viewing a locus of rotation of the pair of first chisel edges and a locus of rotation of the second chisel edge in a cross section taken so as to include the rotation axis, the respective locus of rotation of the pair of first chisel edges have a rectilinear shape, and respective imaginary straight lines obtained by extending the locus of rotation of the pair of first chisel edges toward the rotation axis are positioned further to a rear end side of the drill body than the locus of rotation of the second chisel edge.

A micro-reinforced concentric twist drill. Concentric drilling and micro-reinforcing technologies are applied to cutting faces of the twist drill, and upright micro-reinforced center drills are symmetrically arranged on spiral cutting surfaces on two sides of an axial central area, and extend to the rear cutting surface and form drill center hole cutters in a protruding manner; a micro-reinforced central cutting face is arranged on the inner side of each micro-reinforced center drill in a protruding manner, and the micro-reinforced central cutting face extends to the axial front and intersects with the rear cutting surface to form a micro-reinforced central drilling edge of the micro-reinforced concentric twist drill; and/or upright micro-reinforced reamers are symmetrically arranged on central areas of the spiral cutting surfaces on two sides of the axial center in an integral manner; a protruding reaming cutting face is formed on the inner side of each micro-reinforced reamer.

A step drill bit having a hole processing portion and at least two flutes extending on the hole processing portion, the hole processing portion comprising step sections, each step section and the at least two flutes forming at least two cutting edges distributed in a circumferential direction of the step section, each cutting edge having a tooth profile, wherein the first cutting edge and the second cutting edge are at least partially different from each other in the structure of their respective tooth profiles.

A drill bit for drilling a hard material includes a drill bit blade defining an axis of rotation and including a first side and a second side positioned respectively on first and second lateral sides of the axis of rotation. The drill bit blade further includes a blade tip point that is laterally biased relative to the axis of rotation, and a first blade edge and a second blade edge starting at the blade tip point and ending at the first side and second side, respectively. An angular bisector between the first and second blade edges is inclined at an angle relative to the axis of rotation.