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 drill bit includes a body having a first end, a second end opposite the first end, and an axis of rotation extending centrally through the body. The drill bit includes a cutting head with a cutting tip on the axis of rotation and a cutting portion. The cutting portion includes first tip surfaces on opposite sides of the axis of rotation and second tip surfaces on opposite sides of the axis of rotation. Each first tip surface extends radially outward from the cutting tip to a corresponding second tip surface. Each second tip surface extends from a corresponding first tip surface to an outer periphery of the body. The first tip surfaces define a first tip angle measured through the axis of rotation that is oblique. The second tip surfaces define a second tip angle measured through the axis of rotation that is smaller than the first tip angle.

According to one implementation, a drill includes the first cutting edges, the second cutting edges and a deflection reducer. The first cutting edges drill a prepared hole to a workpiece. The first cutting edges are formed in a tip side of the drill. The first point angle and each first relief angle of the first cutting edges continuously or intermittently decrease from the tip side toward a rear end side of the drill. The second cutting edges ream the prepared hole. The second cutting edges are formed at positions away in the rear end side from the first cutting edges. The second cutting edges have the second relief angles at a maximum diameter position. The deflection reducer reduces deflection of the second cutting edges. The deflection reducer is formed between the first cutting edges and the second cutting edges. The deflection reducer is inserted into the prepared hole.

A drill bit includes a shank extending along a bit axis and a body with a proximal end adjacent the shank and a distal end opposite the proximal end. The body defines a plurality of axially stacked, progressively sized steps including a first step at the distal end and a terminal step at the proximal end. The drill bit also includes a flute in the body. The flute defines an elongated groove that extends from the distal end to the proximal end. The drill bit further includes a plurality of cutting edges formed in the body. Each cutting edge is disposed along one of the plurality of steps and defines a helix angle and a rake angle. The helix angle of the cutting edge at the terminal step is greater than the helix angle of the cutting edge at the first step. A ratio of the helix angle to the rake angle of the cutting edge at the first step is in a range from 0.5 to 2.4, and a ratio of the helix angle to the rake angle of the cutting edge at the terminal step is in a range of 0.9 to 1.7.

A drill bit includes a body having a first end, a second end, and an axis of rotation extending centrally through the body from the first end to the second end. The drill bit also includes a shank adjacent the second end. The drill bit further includes a cutting head adjacent the first end. The cutting head includes a pilot tip and a cutting portion. The cutting portion has first tip surfaces and second tip surfaces on opposite sides of the pilot tip. Each first tip surface extends radially outward from the pilot tip to a corresponding second tip surface. The first tip surfaces define a first tip angle through the axis of rotation that is less than 180 degrees. The second tip surfaces define a second tip angle through the axis of rotation that is smaller than the first tip angle.

According to one implementation, a drill includes the first cutting edges, the second cutting edges and a deflection reducer. The first cutting edges drill a prepared hole to a workpiece. The first cutting edges are formed in a tip side of the drill. The first point angle and each first relief angle of the first cutting edges continuously or intermittently decrease from the tip side toward a rear end side of the drill. The second cutting edges finish the prepared hole. The second cutting edges are formed at positions away in the rear end side from the first cutting edges. The second cutting edges have the second relief angles at a maximum diameter position. The deflection reducer reduces deflection of the second cutting edges. The deflection reducer is formed between the first cutting edges and the second cutting edges. The deflection reducer is inserted into the prepared hole.

A drilling tool for producing a bore with a cylindrical inner wall can be rotatable in a rotary movement with a predetermined rotational direction (VD) about a tool axis (A) extending through the drilling tool, and at the same time is movable in an axial forward movement (VB) in a forward direction axially to the tool axis. The drilling tool comprises at least one drilling area (3) arranged in a forwardly located region of the drilling tool at a forward or free end, but preferably not having a thread forming region. The drilling area has a number n of drilling edges which are arranged offset to each other in the rotational direction, and at least one chip divider is arranged on at least one or each of the n drill cutting edges, where the chip divider forms an interruption of the respective drill cutting edge.

A step drill bit includes a shank and a body having a proximal end adjacent the shank and a distal end opposite the proximal end. The body defines a plurality of axially stacked, progressively sized steps including a first step at the distal end, a terminal step at the proximal end, and a plurality of intermediate steps having incrementally increasing diameters disposed between the first and terminal steps. The step drill bit also includes a plurality of cutting edges each disposed along one of the plurality of steps. Each edge defines a helix angle and a radial rake angle. The radial rake angle and the helix angle of the cutting edge at the terminal step is greater than the radial rake angle and the helix angle of the cutting edge at the first step.

The drill has a rake face, a flank face, and an outer circumferential surface. The flank face is continuous to the rake face. The outer circumferential surface is continuous to both the rake face and the flank face. A ridgeline between the rake face and the flank face constitutes a cutting edge. A ridgeline between the rake face and the outer circumferential surface constitutes an outer circumferential end. A groove is provided cyclically in the rake face to extend at an angle relative to an axis of the drill, the angle being larger than a helix angle of the drill. The groove has a depth of more than or equal to 1.5 μm.

A twist drill and an exchangeable head for a twist drill, the twist drill extending along a central axis of rotation and having a front end formed as a drill point with two cutting edges and at least two clearance surfaces. Two helical chip flutes conduct chips away from the cutting edges. Each cutting edge extends in a transition between the clearance surfaces. One of the chip flutes extends from an inner position adjacent to the central axis to a peripheral envelope surface and has a main portion closest to the peripheral envelope surface. Each chip flute is delimited by a side surface including a main rake face, which extends rearward from the main portion of the cutting edge. The cutting edges are contained in an imaginary conical surface, such that the twist drill is operable to generate a bottom profile having the shape of an inverted cone.