Abstract: The invention relates to a single-lip drill and a double-lip drill having a plurality of chip-forming devices or depressions in the rake face which are arranged in succession and at a distance from one another. As soon as a cutting edge and/or the associated chip-forming device or the associated depression is worn, the deep hole drill according to the invention can be reground using simple means.

Abstract: In some embodiments, the present disclosure relates to a method for forming an integrated chip (IC), including forming a plurality of image sensing elements including a first doping type within a substrate, performing a first removal process to form deep trenches within the substrate, the deep trenches separating the plurality of image sensing elements from one another, performing an epitaxial growth process to form an isolation epitaxial precursor including a first material within the deep trenches and to form a light absorbing layer including a second material different than the first material within the deep trenches and between sidewalls of the isolation epitaxial precursor, performing a dopant activation process on the light absorbing layer and the isolation epitaxial precursor to form a doped isolation layer including a second doping type opposite the first doping type, and filling remaining portions of the deep trenches with an isolation filler structure.

Abstract: A machining tool is a machining tool rotated about an axis and is provided with a machining blade portion having a rake face and a machining blade, wherein in a case where the rake face faces and is parallel to an virtual plane including the axis, the rake face is arranged at a position shifted from the virtual plane in the direction opposite to the rotational direction of the machining tool.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: A drilling tool, in particular a reamer, for drilling out a workpiece core bore to a nominal diameter by means of a main blade formed on a drill body is disclosed. The main blade has a radially external cutting edge which extends along a drill-body longitudinal axis as far as a blade corner arranged at the drill tip, wherein during the drilling-out operation, the drilling tool is drivable into the workpiece core bore with a rotary movement and a feed movement. The drilling tool has at least one groove blade which is arranged so as to precede the blade corner of the main blade in the direction of rotation of the tool. During the drilling-out operation, the groove blade produces a groove in the inner wall of the core bore drilling, the blade corner of the main blade being guided in the groove with an at least reduced cutting load.

Abstract: One automated process for evenly applying a thin layer within a device housing includes applying a vacuum hold from a curved surface applicator to the thin layer, pressing the thin layer against the device housing with the applicator, wherein said pressing includes applying pressure from the center of the applicator first and then radially expanding said pressure, and pressing the cylindrical outer housing against an outer region of the thin layer to effect a hard pressed application at the outer surface thereof.

Abstract: A method for manufacturing a drill bit (1), wherein in a first step the chip flutes (12) are ground into a round rod, in a second step the round rod is ground down to its outer diameter (15, 16) with simultaneous grinding of the drill-bit back (13), and wherein in a third step the drill-bit front (4) is ground, and a drill bit (1) having at least one chip flute (12) and one secondary cutting edge and one drill-bit back (13) adjoining the secondary cutting edge, the drill-bit back (13) sloping downwards as the distance from the secondary cutting edge increases, in order to create a clearance that becomes continuously larger as the distance from the point of intersection (19) of the secondary cutting edge with the drill-bit back (13) increases.

Abstract: This document provides novel drills and/or reamers that are well-suited for making holes in a variety of materials including, but not limited to, metals, ceramics, glass, wood, plasterboard, plastics, stone, composites, synthetics, silicon or multi-layered or hybridized substrates. In some embodiments, these drilling devices have some centers of mass that are offset from the axis of rotation. Accordingly, such drills and/or reamers may rotate and cut using a precessional pattern of motion. Precessional cutting devices may display a mechanical wave pattern in relationship to the longitudinal axis of the device. If the cutting device is fabricated from a flexible material, for example Nickel-Titanium, bodily deflection of the device may result during rotation.

Abstract: Twist drill for short hole drilling with two chip flutes opening in a clearance surface of a front tip to form, with the clearance surface, two cutting edges. Chip flutes have three different part surfaces having different curvatures—a bottom surface with arc radius less than 10 mm and two other ones with radius of curvature approaching infinity. Boundary line between concave bottom surface and heading frontal surface meets a main edge that is included in the individual cutting edge and divided into two edge segments imparting a J-like shape to the main edge. The chip flute is extraordinary deep with the diameter (DC) of the core reduced to a minimum and the opening angle (?) smaller than the angle of divergence (?) of two bars, between which the flutes are countersunk. The drill improves-formation and evacuation of chips, is easy-cutting and requires a minimum of energy.

Abstract: An adjustable drill is provided comprising a drill body having at least one face surface with a plurality of serrations provided therewith. The drill further has at least one cartridge having a cooperating plurality of second serrations, to be driven with the drill body when assembled therewith. The at least one cartridge includes at least one insert pocket, and at least one insert is releasably affixed in the insert pocket provided in the cartridge. In further examples, the adjustable drill may have a central cutting system in combination with the adjustable cartridge type system, wherein the central cutting system may be modular. There may also be provided a modular type of holder arrangement to provide flexibility to adapt the system for various applications.

Abstract: The present disclosure relates to a deep hole drill tool of the type that includes a basic body, a cutting insert having a cutting edge, which is formed between a chip surface and a clearance surface. The chip surface includes a chamfer surface adjacent to the cutting edge and the clearance surface, the chamfer surface having a width of at least 0.2 mm defined between two boundary lines, and which, in each infinitesimal part along the cutting edge, forms an angle (?) of at least 25° and at most 50° with a reference plane extending perpendicular to the center or rotation axis of the tool.

Abstract: Drill with a straight chucking groove, with a convexly curved main cutting edge with, adjacent to the main cutting edge, a convexly designed region of groove base and with, adjacent to the convexly designed region of the groove base, a concavely designed groove base or a concavely curved main cutting edge with, adjacent to the main cutting edge, a concavely designed groove base with, adjacent to the concavely design region of the groove base, a convexly design region of the groove base.

Abstract: A cutting tool according to an embodiment of the invention includes: a column-like shaped body having a cutting edge located at a front end part thereof and a flute which is located at an outer peripheral part thereof and is continuous with the cutting edge; a front taper connected to a rear end part of the body and having a larger diameter as separating from the body; a column-like shaped step connected to a rear end part of the front taper and having a larger diameter than the body; a rear taper connected to a rear end part of the step and having a larger diameter as separating from the step; a column-like shaped shank connected to a rear end part of the rear taper and having a larger diameter than the step; and a front connection member located in a region including the front taper and the step.

Abstract: A drill including: a chip discharge flute; and a cutting edge, the cutting edge being made up of a concavely-curved cutting edge portion formed on an inner circumferential side and a convexly-curved cutting edge portion formed on an outer circumferential side, the drill further including a cross section orthogonal to an axial center having a first convex curve corresponding to the convexly-curved cutting edge portion and a first concave curve corresponding to the concavely-curved cutting edge portion intersecting with each other, a flank following the cutting edge on the tip surface having an orthogonal clearance angle ? formed within an angular range of 9 to 20 degrees, and a ridgeline of the cutting edge having a chamfer formed with a width CW within a range of 0.002D to 0.02D (where D is a drill diameter).

Abstract: A drill bit, has a front side (5) and a circumferential surface (19) adjoining the front side (5). The front side (5) has a main cutting edge (7) including a transverse cutting edge (3) extending through a center axis (11) of the drill bit (1), and has two first and second main cutting-edge regions (13, 15) adjoining the transverse cutting edge (9) and extending radially toward the circumferential surface (19). The circumferential surface (19) comprises at least two chip flutes (21, 23), which between them delimit a first and a second web (25, 27), and three lands, of which a first land adjoins the end of the first main cutting-edge region (13) facing away from the transverse cutting edge (9), and serves as a free cutting-edge land (33), and additionally has a free cutting edge (39), a second land adjoins the end of the second main cutting-edge region (15) facing away from the transverse cutting edge (9), and serves as a guide land (35), and a third land serves as a support land (37).

Abstract: A method of joining a plurality of parts to form a unitary body includes providing at least two sintered parts. Each of the parts is formed of a hard metal composition of material. The sintered parts are assembled into the shape of a unitary body. Each of the sintered parts has a joining surface and when each joining surface is brought into contact the surfaces form a bonding interface therebetween. The assembled sintered parts are subjected to a temperature sufficient to fuse the sintered parts together at the bonding interface to form the unitary body. A wear resistant tool includes a plurality of sintered parts, each of the sintered parts is formed of a hard metal composition of material, wherein the plurality of sintered parts can be assembled into a unitary body, wherein the assembled parts are fused together at a respective bonding interface to form the unitary body.

Abstract: A drill includes: a chip discharge flute opened in a tip surface; and a cutting edge formed at an intersecting portion between an inner wall surface of the chip discharge flute on a side of a drill rotation direction and a tip flank formed on the tip surface, the cutting edge being made up of a concavely-curved cutting edge portion formed on an inner circumferential side and a convexly-curved cutting edge portion formed on an outer circumferential side, a cross section orthogonal to an axial center having a first convex curve corresponding to the convexly-curved cutting edge portion and a first concave curve corresponding to the concavely-curved cutting edge portion intersecting with each other.

Abstract: A combination drill bit for use in both hand held drills and stationary drill presses has a shanking end, a working end and a helical flute portion between the shanking and working ends. The helical portion has a helix length (L) of L = ( D × ? tan ? ? ? ) . The drill bit has a core that is tapered from the working end to the shanking end. A web thickness length at the working end is 10% to 35% of the diameter and the thickness length at the junction of the shanking end is 70% to 90% of the diameter. The drill bit is manufactured from a high speed steel including at least 5% by weight of cobalt.

Abstract: A cutting insert has a head portion and a coupling portion protruding rearwards from the head portion, along a longitudinal insert axis. The head portion has a base surface at a rearward end thereof, defining a base plane, and two major surfaces. A coupling portion rear surface is longitudinally spaced apart from the base surface and a cylindrical coupling peripheral surface extends between the coupling portion rear surface and the base surface. A resilience slit has two opposite inner walls converging forwards towards a slit inner end terminating at a slit inner end plane. The slit inner end plane is parallel to the base plane and spaced apart therefrom by a longitudinal distance. The inner walls of the resilience slit form an acute slit angle therebetween.

Abstract: A drill includes a pair of main cutting edges extending from a distal portion of the drill to a position close to a proximal end of the drill to entirely define a two-edge configuration, and a pair of auxiliary cutting edges extending between positions at the distal and proximal sides of a maximum diameter position to partly define a four-edge configuration. A ridgeline of each auxiliary cutting edge is located within an angle smaller than 90° from a ridgeline of the corresponding main cutting edge toward the rear in a rotation direction of the drill. The point angle of the auxiliary cutting edges increases at a higher rate than the point angle of the main cutting edges in a predetermined range from the maximum diameter position toward a distal end of the drill.

Abstract: A cutting tool having a shaft with a longitudinal axis, wherein the cutting tool includes a first flute extending about the longitudinal shaft along a helix angle and a first cutting edge adjacent the first flute. The cutting tool also includes a second flute extending about the longitudinal shaft along a helix angle and a second cutting edge adjacent a second flute. The cutting tool further includes a third flute extending about the longitudinal shaft along a helix angle and a third cutting edge adjacent the third flute. The first cutting edge, the second cutting edge, and the third cutting edge are unequally angularly spaced from each other.

Abstract: One non-limiting aspect of the present disclosure is directed to a multi-piece spade drill head for a spade drill, wherein the spade drill includes an elongate body portion and a cutting portion removably secured to an end of the body portion. The multi-piece spade drill head includes at least two insert pieces, each piece including a cutting edge. The at least two insert pieces are configured to be removably secured to the body portion of the spade drill adjacent one another and with the cutting edges of the insert pieces aligned to together form a cutting edge on an end of the spade drill.

Abstract: A countersink cutter or drill/countersink combination or similar rotary cutter or assembly for drilling/countersinking or performing similar cutting operation to precise depths in various applications, including aerospace applications, uses a pneumatically driven pistol grip motor attached to a tool assembly or countersink tool assembly. The countersink tool assembly, which has a multi-fluted cutter, is coupled to and is coaxial with the spindle. The cutter can be preset to a precise depth at the back end of assembly through the slot or using gage stops on the guide rods fastened to brackets by setting the gage between gage stops and the bracket.

Abstract: A countersink cutter or assembly for countersinking to precise depths in various applications, including aerospace applications, uses a pneumatically driven pistol grip motor attached to a countersink tool assembly. The countersink tool assembly, which has a multi-fluted cutter, is coupled to and is coaxial with the spindle. The cutter can be preset to a precise depth at the back end of assembly through the slot using a gage.

Abstract: A bit for a rotary drill, the bit including a cylindrical body having at least two flutes provided therein, the cylindrical body terminating in a cutting end; and a cylindrical land defined by a peripheral face of the cylindrical body between adjacent flutes, the cylindrical land including a margin that is radially elevated relative to a remainder of the cylindrical land; the margin having a width that varies along the length of the cylindrical land.

Abstract: A drill comprises a drill body that is rotatable on an axis. Chip evacuating flutes, which are open on front flanks of the drill body and are extended rearwards, are formed in a periphery of the drill body on its front side. Cutting edges are formed along ridge lines where the front flanks intersect with wall surfaces of the chip evacuating flutes facing a drill rotating direction. At least first and second front flanks are formed on the front flanks in order of their locations in the drill rotating direction from its leading side to its trailing side. A clearance angle of the second front flank is greater than that of the first front flank. Intersection lines of the first and second front flanks cross the cutting edges.

Abstract: A drilling tool for machining structural components made of a titanium alloy includes: a support, which extends along an axis of rotation in the axial direction, the support having an end face with a receptacle disposed centrally therein; a plurality of cutting inserts inserted at the end face in a manner that forms a flat drill, each cutting insert having an active insert cutting edge extending transversely to the axial direction; and a drilling tip disposed in the receptacle and having at least two tip cutting edges, the tip cutting edges extending outward from the axis of rotation and being adjoined in each case by at least one active insert cutting edge.

Abstract: An adjustable drill has a drill body having a face surface with a directional feature provided therewith. At least one cartridge is mounted adjacent the face surface and selectively slidable along the directional feature to provide adjustment. At least one insert is releasably affixed in an insert pocket provided in the cartridge. In further examples, the adjustable drill may have a central cutting system in combination with the adjustable cartridge type system, wherein the central cutting system may be modular. There may also be provided a modular type of holder arrangement to provide flexibility to adapt the system for various applications.

Abstract: A cutting tool has a tool shank and a replaceable cutting head resiliently secured to the tool shank by an interference fit between a male fixation member of the cutting head and a female fixation member of the tool shank. The male fixation member has a resilience slit. In each cross section of the cutting tool taken perpendicular to an axis of rotation of the cutting tool through mutual abutment regions, the cross sectional profiles of the mutual abutment regions are arcuate sectors.

Abstract: The present invention relates to a rotary cutting tool consisting of a shank and at least one cutting section comprising a plurality of cutting teeth, the cutting section being conceptionaly and functionally divided into several sub-sections along the tool axis (“zones” for brevity), wherein each zone has its own core form and its own cutting edges, its own teeth land form and its own zone cutting length, these being selected according to the perceived task for which each zone of the tool is to be optimized.

Abstract: A drilling head for a tubular shank having an inside diameter and threads may comprise an axial body comprising a duct exiting through a first end; threads adjacent the first end corresponding to the threads on the shank and aligning the duct with the shank inside diameter; a bore from an outer surface of the body to the duct; and two axially extending approximately parallel and offset surfaces adjacent a second end; and an insert affixed between the offset surfaces, the insert comprising: a first face at least partially contacting one offset surface and a second face at least partially contacting the other offset surface; one or more cutting edges adjacent the first face, the second face, or both; and a cutting lip adjacent one or more cutting edges.

Abstract: A cutting head having a cutting end and an opposite coupling end along a longitudinal cutting head axis; having a cutting head length; and including two major surfaces and a peripheral surface. A male coupling portion extends rearwards from the coupling end, between a base portion and a rear surface, with a circumferential peripheral surface, having a coupling length. A flexibility slot extends from the rear surface opening to the major surfaces, along the cutting head axis, having a slot length and a head slot length. The coupling length is equal to or less than half the head slot length, and the slot length is equal to or greater than half the cutting head length. The cutting head is self-clamped into a tool shank with female coupling portion, by a friction fit between the male and female portion peripheral surfaces, causing the cutting head to elastically deform.

Abstract: The present invention relates to a tool for machining workpieces, having a shank and a cutting part, wherein the cutting part has a cutting edge section that defines the nominal diameter of the tool, or an insert seat for a cutting insert, the seat having a cutting edge section that defines the nominal diameter of the tool, and wherein the tool has a rotational axis about which the tool rotates in the functionally mounted state.

Abstract: An adjustable drill has a drill body having a face surface with a directional feature provided therewith. At least one cartridge is mounted adjacent the face surface and selectively slidable along the directional feature to provide adjustment. At least one insert is releasably affixed in an insert pocket provided in the cartridge. In further examples, the adjustable drill may have a central cutting system in combination with the adjustable cartridge type system, wherein the central cutting system may be modular. There may also be provided a modular type of holder arrangement to provide flexibility to adapt the system for various applications.

Abstract: An adjustable drill has a drill body having a face surface with a directional feature provided therewith. At least one cartridge is mounted adjacent the face surface and selectively slidable along the directional feature to provide adjustment. At least one insert is releasably affixed in an insert pocket provided in the cartridge. In further examples, the adjustable drill may have a central cutting system in combination with the adjustable cartridge type system, wherein the central cutting system may be modular. There may also be provided a modular type of holder arrangement to provide flexibility to adapt the system for various applications.

Abstract: An adjustable drill having a drill body having a longitudinal axis, and a face surface including an aperture extending into the drill body. A directional feature adjacent the aperture extends toward an edge of the drill body, and a longitudinal gullet extends from the face surface along at least a portion of the drill body. A cartridge adjacent the face surface is selectively slidable along the directional feature, and a cutting face having an insert pocket positioned adjacent the edge of the drill body in which an insert is releasably affixed.

Abstract: The invention relates to a drilling tool comprising a clamping shaft and cutting element contiguous with said clamping shaft. The cutting element comprises at least one flute having a flute surface that has a concave cross-section. The at least one flute has a cut-in section in the chip-forming zone adjacent to the main cutting edge in the area of the flute front and/or the back segment to enlarge the flute cross-section.

Abstract: [Problem] To provide a drill which enables a great reduction in cutting resistance and easy performance of a drilling operation by human power using a hand drill, a drilling machine, or the like. [Solution] A drill has two cutting edges formed symmetrically with respect to a rotation axis, and is subjected to thinning at the tip thereof. The cutting edge is configured from a thinned cutting edge (1) which extends in a shape including a curved line from a chisel edge to the outer peripheral side of the drill, and a main cutting edge (2) which extends from the end of the thinned cutting edge to the outer peripheral end of the drill when viewed from the tip side of the drill, and a thinned surface formed by the thinned cutting edge is formed into an approximately parabolic shape inclined in a drill axis direction when viewed from the front side of the drill.

Abstract: The description shows a chip breaker system for a drilling, turning, milling or reaming tool, wherein the chip breaker system comprises: a portion of a flute and a first area which is produced by a progressive cut, wherein a first edge is arranged between the portion and the first area in such a way that chips produced by a cutting movement of the drilling, turning, milling or reaming tool can be broken at the first edge. The application further relates to a high-speed reamer comprising such a chip breaker system, a reamer made of solid carbide, a reamer with axially extending cooling channels which are disposed in a decentralized manner, a reamer with cooling channels which are unevenly distributed in the peripheral direction, and a reamer with cooling channels, wherein the outlet openings of the cooling channels are arranged on different cutting planes.

Abstract: A cutting bit for a pruning tool includes an elongate body having a first end and a second end. At least one flute extends at least part of a distance between the first end and the second end of the elongate body. A shank is located at the first end of the elongate body and is adapted for connection to an associated pruning tool. The second end of the elongate body defines a boring tip.

Abstract: A drilling tool includes at least two chip flutes and a chisel edge with a thinned region. The thinned region merges continuously into the chip flutes in such a way that the thinned region forms the end of the respective chip flute in the region of the chisel edge.

Abstract: A method for manufacturing a drill bit (1), wherein in a first step the chip flutes (12) are ground into a round rod, in a second step the round rod is ground down to its outer diameter (15, 16) with simultaneous grinding of the drill-bit back (13), and wherein in a third step the drill-bit front (4) is ground, and a drill bit (1) having at least one chip flute (12) and one secondary cutting edge and one drill-bit back (13) adjoining the secondary cutting edge, the drill-bit back (13) sloping downwards as the distance from the secondary cutting edge increases, in order to create a clearance that becomes continuously larger as the distance from the point of intersection (19) of the secondary cutting edge with the drill-bit back (13) increases.

Abstract: One non-limiting aspect of the present disclosure is directed to a multi-piece twist drill head. The multi-piece twist drill head includes a core piece formed from a first hard material, and a peripheral piece formed from a second hard material. The core piece and peripheral piece each comprise a cutting edge and are adapted to mate to provide a central region and a peripheral region, respectively, of the multi-piece twist drill head. A twist drill including the multi-piece twist drill head is also disclosed.

Abstract: Rotatable drilling tool has an insert top detachably connectable to a basic body and at least one chip flute. In each cross-section, each chip flute has a depth equal to the difference between the radius of a cutting circle and a radius of a greatest possible core circle centered on the longitudinal axis and tangential to a limiting curve of the respective chip flute. The basic body is divided longitudinally into a coupling segment, extending axially rearward from a coupling end, and a transportation segment that is situated axially behind the coupling segment, extends rearward toward a fixing end, and is longer than the coupling segment. Each chip flute extends through the coupling segment and the transportation segment. At least essentially the entire female part is situated in the coupling segment, and each chip flute has a smaller depth in the coupling segment than in the transportation segment.

Abstract: A bit for removing a broken fastener comprises a tip from which extend two or more notches separated by traction or biting surfaces formed from two-sided frusto-conically-shaped regions. The surfaces are bounded on one side by a nonlinear cutting edge and on the other side by a non-cutting edge and are configured to cut into the fastener when the bit is rotated in a direction opposite to the fastener's direction of engagement. Specific embodiments include configurations where the cutting edges extend at different angles with respect to the bit axis, where the biting surfaces comprise a plurality of serrations, and where the cutting edges are separated by flutes which spiral along a longitudinally extending periphery of the bit.

Abstract: A drill for producing a drilled hole in work pieces has at least one main cutting edge on an end face. At least one secondary cutting edge is provided in the region of a circumferential surface of the drill. At least one circularly ground land circumferentially adjoins the at least one secondary cutting edge. The circularly ground lands extend over a first longitudinal section in the front area of the secondary cutting edge. In a following second longitudinal section, a secondary flank circumferentially adjoins the secondary cutting edge.

Abstract: A drilling tool includes a tool shank disposed about a center longitudinal axis. The tool shank having a holding region structured to be chucked in the chuck of a machine tool and an active region extending from the holding region. The drilling tool further includes at least two partial cutting edges formed on an end face of the active region and running at right angles to the center longitudinal axis and form a drill main cutting edge and a clearance formed in the end face between the partial cutting edges. The clearance being recessed axially along the center longitudinal axis toward the tool shank.

Abstract: A fluted drill has a drill body with a fluted drill cutting head removably secured thereto. The cutting head has two drilling portions facing axially opposite directions. In axial view, the cutting head has at least four through openings. Each drilling portion includes a plurality of head flute portions and a plurality of cutting head coupling portions.