Abstract: A cutting head is formed at one end of the shank and comprises a cylindrical member having an annular wall defining a circular cutting edge. A cutting blade having a sharp cutting edge extends from adjacent a centering point to adjacent the cutting edge. The cutting head is formed of a first material and the cutting blade is formed of a second material. The cutting blade is brazed to the cutting head. A method of making a drill bit comprises investment casting a shank and a cutting head of a first material. A pocket is formed that extends to the cutting edge. A coupon of a second material is brazed in the pocket. A sharp edge is ground in the coupon.

Abstract: A bit body formed of a mixture of matrix material and superabrasive powder and including pockets lined with superabrasive-free matrix material, and a method for forming the same, are provided. The pockets are shaped to receive cutting elements therein. The superabrasive-free matrix material enhances braze strength when a cutting element is brazed to surfaces of the pocket. The method for forming the drill bit body includes providing a mold and displacements. The displacements are coated with a mixture of superabrasive free matrix-material and an organic binder. The mold is packed with a mixture of matrix material and superabrasive powder and the arrangement heated to form a solid drill bit body. When the solid bit body is removed from the mold, pockets are formed by the displacements in the bit body and are lined with the layer of superabrasive-free matrix material. The superabrasive material may be diamond, polycrystalline cubic boron nitride, SiC or TiB2 in exemplary embodiments.

Abstract: A Christmas tree stand, a method for affixing a Christmas tree to a Christmas tree stand, and a drill bit for forming a groove in the bottom of a Christmas tree are provided. The Christmas tree stand includes a base having a male member extending upwardly therefrom with at least a portion of the male member received in the groove in the bottom of the Christmas tree. Preferably an insert in the form of a cylinder is received within the groove. Upon the receipt of the male member in the groove, the Christmas tree is stabilized on the base.

Abstract: A twist drill for use, predominantly by non-professional do-it-yourself workers incorporates a flute architecture with an internal ridge for promoting the break up of chips into short length components. The tip of the twist drill includes an axial relief construction for improved performance across a wide variety of materials, and a highly sloped face for prompting transport of chips away from the drill tip.

Abstract: A metal-working twist drill is provided with inner cutting edges that form a point (18) having an angle, A, of 130°. An outer, peripheral, part of each cutting edge (55, 57) forms an outer cutting portion (59, 61). The outer cutting portions slope in the opposite direction to the corresponding inner cutting edges and form an angle B, of 3° with respect to a plane normal to the axis of rotation of the twist drill. The width of the outer cutting portion, D as measured at the cutting edge, is 10.5% of the diameter of the twist drill. The metal-working twist drill produces bores having a reduced exit burr height.

Abstract: The present invention relates to a twist drill comprising a cemented carbide or high speed steel substrate and a multilayered aperiodic (Ti,Al)N-coating having a binary A/B/A/B/A/B structure, where the composition of layer A is AlxTi1-xN, where x preferably is from about 0.40 to about 0.75, more preferably from about 0.50 to about 0.70, and most preferably from about 0.60 to about 0.68, and the composition of layer B is TiyAl1-yN, where y preferably is from about 0.50 to about 1.0, more preferably from about 0.60 to about 0.90, and most preferably from about 0.70 to about 0.80 and the composition for the whole coating is TizAl1-zN, where z preferably is from about 0.35 to about 0.75, more preferably from about 0.40 to about 0.65 and where the average thickness of layer A and B is between about 1 to about 200 nm, preferably about 2 to about 50 nm. The present invention also relates to a method of making a twist drill.

Abstract: Contoured solid polycrystalline superabrasive material such as twist drill tips and endmill flank segments can be formed by preparing a precursor mold having a plurality of shaped openings each corresponding to a predetermined shape. A specially prepared charge feed can be placed into the shaped openings to form a charged precursor. The charge feed can include a substantially homogeneous mixture of superabrasive source particulates, sintering binder, and optional inorganic bonding medium. A loaded reaction cup-assembly including the charged precursor can be subjected to a pressure, temperature and time sufficient for sintering and formation of the contoured polycrystalline superabrasive material. Reduced finishing steps and increased tailorability of grade and quality of final polycrystalline products can be readily achieved.

Abstract: A metal cutting tool has a cutting head releasably mounted on a front end of a tool shank, in a self-clamping manner. The tool shank's forward end is provided with a pair of shank coupling portions, each having a forwardly facing shank support surface. A pocket recess is defined between the shank's coupling portions. Within the pocket recess are a plurality of shank fixation surfaces which are parallel to a longitudinal axis of the tool shank. The cutting head has a cap portion and a fixation portion extending in rearward direction therefrom. The cap portion includes a pair of head segments, each having a rearwardly facing head base surface. The cutting head's fixation portion has a plurality of head fixation surfaces which are parallel to a longitudinal axis of the cutting head.

Abstract: A spiral drill bit for forming holes of a variety of sizes has a main body which provides first and second helical grooves. First and second flutes extend along the length of the main body to provide first and second helical groove segments. Cutting segments are provided between the helical groove segments. The method for forming the spiral drill bit includes turning the helical groove segments onto a round stock. An axial clearance and an initial diametral clearance are provided upon turning the helical grooves. A grinding process is used to form a radial clearance and a final diametral clearance. The reduction to the amount of grinding required to form the spiral drill bit results in a reduction to the cost of production and a reduction in the time necessary to produce the spiral drill bit.

Abstract: A method for manufacturing a rotary tool for chip removing machining with at least one chip flute that extends in the longitudinal direction of the tool. The method involves preparing a mixture of a cemented carbide, cermet or ceramics powder and a carrier, such as a polymer, and placing the mixture in an extruding machine. The mixture is extruded in a feed direction by means of a die to form the diameter of the mixture body. The mixture body passes against a chisel which forms a chip flute in the outer periphery of the mixture body by chip-removing machining. When the chisel is displaced away from the mixture body, a non-fluted shaft portion is formed. By rotating the mixture body while contacted by the chisel, a helical chip flute can be formed. Alternatively, the body could be twisted after a straight flute has been formed, whereupon the flute becomes helical.

Abstract: A blank for a rotary tool for chip removing machining, such as a helix drill or an end mill is formed by advancing a mixture of hard metal powder and carrier through an extrusion passage. The mixture is fed past a core having pins secured thereto for forming respective internal holes through the mixture. Then the mixture is advanced through a rotary part that is rotating about a center axis of the extrusion passage, wherein the rotary part and the internal holes become twisted to a predetermined pitch. The mixture is also advanced past a plurality of shaping parts which project transversely into the extrusion passage for shaping exterior chip flutes in the mixture, e.g., by embossing or cutting. The mixture is allowed to harden into a green body, and the green body is then sintered to form a blank.

Abstract: A method for manufacturing a rotary tool for chip removing machining with at least one chip flute that extends in the longitudinal direction of the tool. The method involves preparing a mixture of a cemented carbide, cermet or ceramics powder and a carrier, such as a polymer, and placing the mixture in an extruding machine. The mixture is extruded in a feed direction by means of a die to form the diameter of the mixture body. The mixture body passes against a chisel which forms a chip flute in the outer periphery of the mixture body by chip-removing machining. When the chisel is displaced away from the mixture body, a non-fluted shaft portion is formed. By rotating the mixture body while contacted by the chisel, a helical chip flute can be formed. Alternatively, the body could be twisted after a straight flute has been formed, whereupon the flute becomes helical.

Abstract: The present invention relates to a method for manufacturing a drill blank or a mill blank by extrusion, said method comprising the forming of a first blank portion (B1) having external, axially extending external flutes and the forming of a further blank portion (B3) in the shape of a shaft. The invention also relates to a device for manufacturing a drill blank or a mill blank. The method according to the invention is characterised by: extruding a first blank portion (B1) having a free end and external flutes; allowing the extrusion to continue to supply further extruding mass into a cavity (6), said supply of extruding mass completely filling out the external flutes of the first blank portion (B1) to produce a second blank portion (B2) integral with the first blank portion (B1); allowing the extrusion to continue to produce a desired length of the first blank portion (B1); and cutting off the first blank portion (B1) at the end facing away from the second blank portion (B2).

Abstract: A cutting tool and a method for the production of cutting tools for metalworking characterized in that the holder body of the tool first is submitted to a surface hardening that results in the formation of compressive stresses in the surface and then submitted to a surface treatment that gives additional contribution of compressive stresses in the surface. In this way, it is allowed to, on one hand, be able to modify/machine or remove parts of or the entire phase-transition layer obtained in the surface hardening at the same time as additional compressive stresses are built up in the surface of a hardened steel material in the tool body.

Abstract: The present invention is directed to a helical drill configuration that allows substantially flat bottomed holes to be machined. At the cutting end of the body member, there are at least two cutting edges that are symmetrically oriented on apposing sides of the rotational axis of the drill. In an embodiment of the invention, first and second cutting edge portions form a continuous surface which provides strength and tool stability. The height of the second portions of each of the cutting edges remains relatively consistent along the horizontal for formation of a generally flat bottom hole. In the embodiment, a center point is defined by two sloped peak surfaces. A central straight chisel edge is formed by the intersection of the two sloped peak surfaces. The first cutting edge section extends from the chisel edge to the second cutting edge section. The first cutting edge section for both cutting edges is formed by symmetrically thinning the two peak surface.

Abstract: A drill including a shank portion and a cylindrical body portion contiguous to each other. The cylindrical body portion includes (a) primary cutting edges and secondary cutting edges formed in its axially distal end portion such that each of the secondary cutting edges is located on a radially inner side of the corresponding primary cutting edge; (b) primary rake surfaces of the primary cutting edges and secondary rake surfaces of the secondary cutting edges; and (c) inclined surfaces each of which extends from the corresponding secondary rake surface to a periphery of the cylindrical body portion, and is inclined such that an axial distance between each of the inclined surfaces and the shank portion is reduced as viewed in a direction substantially perpendicular to the corresponding secondary cutting edge, from the corresponding secondary rake surface toward the periphery of the cylindrical body portion.

Abstract: A polishing apparatus includes a table on which a polishing target member is placed, and at least one nozzle which sprays a polishing solution to a surface of the polishing target member so as to form, by polishing, the surface of the polishing target member. The nozzle and the polishing target member move relative to each other, and an angle of the nozzle is changeable.

Abstract: Boring bits and methods for manufacturing boring bits. The method includes the acts of forming a shank including one end connectable to a power tool and an opposite end, molding a cutting head separate from the shank, the cutting head including a base wall and a side wall extending from the base wall, the base wall having an interior base surface and an exterior base surface, and bonding the shank and the cutting head as a unit including bonding the opposite end of the shank to the exterior base surface.

Abstract: A method for producing a powdered metal compact for a cutting head to be used in a metal cutting tool uses a punch and die assembly. The resulting cutting head has apertures communicating between a coolant channel and recesses.

Abstract: A cutting tip having a three-layer laminated structure is provided. The tip is made from a disc-shaped three-layer laminate wherein a second layer consisting of a hard sintered compact of CBN or diamond is sandwiched by a first layer and a third layer consisting of a tool material such as cemented carbide. Prismatic blanks of rectangular cross-section are cut out by cutting the three-layer laminate in strips. Semi-completed tips of a desired shape are obtained by cutting up the prismatic blanks. Desired cutting edges are formed on the semi-completed tips to produce completed tips. Because prismatic blanks are obtained from a three-layer laminate and semi-completed tips are cut out from the prismatic blanks like this, the semi-completed tips can be obtained in large numbers, yield is high, and the manufacturing cost of the tip can be reduced.

Abstract: A method of making a drill comprising a tip (16), a shank (10) and a flute area having chip spaces (12, 14) formed therein, the drill being substantially completely coated with a hard material, and is characterized by applying an abrasive material to merely the tip (16) before coating the drill with the hard material. The drill may more particularly be a solid carbide drill.

Abstract: A drill bit sharpener includes a motor assembly and a drill bit grinding assembly. The motor assembly has a motor with a drive shaft to drive the drill bit grinding assembly, which includes a driven assembly, a sharpener housing, a grinding wheel assembly and a bit guide assembly. The sharpener housing is attached to the motor assembly, and the grinding wheel assembly is rotatably mounted in the sharpener housing and is rotated by the driven assembly. The bit guide assembly is mounted in the sharpener housing above the grinding wheel assembly. An adjusting screw in the bit guide assembly is used to adjust the grinding wheel assembly relative to the bit guide assembly. Multiple bit guide holes correspond to the grinding wheel assembly are defined in the bit guide assembly and allow a drill bit to pass through to abut the grinding wheel.

Abstract: A rotary tool such as a helix drill and an end mill for example, is manufactured by forming a blank by an extrusion process, and then sintering the blank. During the extrusion, a mixture is passed through a die which provides a cylindrical shape to the outer peripheral surface of the mixture. A plurality of jaws are disposed downstream of the die for conducting the mixture. Each jaw includes a helical ridge for engaging the outer surface of the extrudate to cause a helical groove to be formed therein which constitutes a chip flute in the tool. During the extrusion, the jaws are moved away from the mixture to terminate formation of the chip groove, whereby a shank portion of the tool is formed.

Abstract: Boring bits and methods for manufacturing boring bits. The method includes the acts of forming a shank including one end connectable to a power tool and an opposite end, molding a cutting head separate from the shank, the cutting head including a base wall and a side wall extending from the base wall, the base wall having an interior base surface and an exterior base surface, and bonding the shank and the cutting head as a unit including bonding the opposite end of the shank to the exterior base surface.

Abstract: The invention relates to a method for the production of a tool, in particular a drill (6) or milling cutter, having at least one conveying helix (8a, 8b), proceeding from a bar-shaped blank (1). In this case, there is provision for introducing the conveying helix (8a, 8b) in a single operation by means of a machine tool, the blank (1) having a diameter (DR) which is larger than a diameter (dF) of the conveying helix (8a, 8b).

Abstract: The invention is a tool bit for use in a socket or chuck mechanism. The tool bit includes an elongated shank having an operative tip end and an opposite tail end. A polymer jacket is molded about the tail end of the shank, and the jacket in the lateral cross-section, has a hex-shaped outer surface.

Abstract: A drill having a cutting edge that is less prone to chipping or fracturing when used in drilling operations, and that can be sharpened or resharpened uniformly and consistently from drill to drill by machine grinding. The drill comprises a body and at least one flute formed in the body that terminates in a cutting edge at the cutting end of the drill. The flute has a cutting surface, the cutting surface having formed therein a dub face having a substantially planar surface over at least a portion thereof that is proximate to the cutting edge. The cutting edge has formed therein a cutting land having a substantially planar surface over at least a portion thereof connected at an edge to the planar surface portion of the dub face.

Abstract: A multi or single cutter reaming tool has a shaft and a shaped head with at least one cutter. The shaped head is produced from a blank having a base body of a base material on its envelope surface with at least one rectilinear or helical groove-shaped recess running around it, into which high hardness cutting material is sintered. The high hardness cutting material includes at least one cutter having cutting surfaces formed by the introduction of a chip groove by a grinding wheel into the base body and movement of the grinding wheel toward the high hardness cutting material.

Abstract: Two-piece drill bits and methods of manufacturing same provide a preferably hexagonal shank, and a drill portion having a proximal end inserted into an axial hole in a distal end of the shank. In a preferred embodiment, at least part of the area adjacent the proximal end of the drill portion is knurled. Alternative embodiments have wings, polygons, tapers or other irregular shapes, or combinations of same. A variety of means may be employed to mechanically capture the drill portion in the shank.

Abstract: A drill-chuck jaw is made by first forming an elongated metal body with a toothed back face and a planar front face and thereafter laser-welding an insert to the body on the face. After machining the body but before laser-welding the inserts to it, the body is heat-treated and surface hardened. After the heat-treating and surface-hardening step and before the laser-welding step, the body in tampered.

Abstract: The invention relates to a drilling tool for machine tools and to a method for the production thereof. The drilling tool has at least one chip conveyor groove (16) and at least one functional channel (20). In order to produce the body of the drill (10), the wall of a tubular metal blank is simultaneously impinged upon by substantially radially oscillating form-giving forces in several forming sections spread over the periphery, moving in an axial direction along the surface of the blank, whereby at least one chip conveyor groove (16) is shaped and at least one functional channel (20) is formed. When the chip conveyor grooves (16) are formed on at least two interspaced forming sections in a peripheral direction in the wall of the blank (50), the parts of the wall in the area of two opposite-lying chip conveyor grooves (16) come to rest against each other in a sealed manner, defining at least two functional channels (20, 24) on the inner surfaces thereof.

Abstract: A cutting tool is provided with a margin that includes a modified margin portion adjacent the terminal end of a circumferential face of the cutting tool that is smaller in width than the width of the base portion of the margin. The cutting tool is manufactured from a blank by removing portions of the blank to create flutes and interposed circumferential faces. A recessed portion on the circumferential faces is created to provide the margins, a point is provided at the cutting end, and a portion of the margin is removed on at least one of the circumferential faces between the terminal end of the circumferential face and a distance L from the terminal end. A cutting tool may be provided with a modified margin during reconditioning of the cutting tool. The modification may be done before or after the removal of worn or damaged sections of the cutting tool.

Abstract: Carbide drilling and cutting tools for use in manufacturing printed circuit boards are provided by a process that recycles used tools as the starting raw materials. The used tools have a working portion and shank with a diameter of, for example, approximately 0.125 inches. The working portion of the used tool is removed and a new carbide head is attached to the remaining shank. The new carbide head, which also has a diameter of approximately 0.125 inches, is then machined to create a new working portion. The new tool is distributed for use and then recovered after use for recycling and manufacture of new tools from the shanks of the recycled tools.

Abstract: A cutting tool material rod for machining of printed circuit boards and method of fabricating the same, adapted for recycling worn cutting tools, includes the following process steps: cutting off the edge section of a worn cutting tool to form a base portion, supplementing one end of the base portion to the total desired length, and making the other end of the base section a machining section for forming a new edge section of the recycled cutting tool. The cutting tool thus formed may be used to fabricate drills or routers, for machining printed circuit boards without dimensional limitations.

Abstract: A method of producing a fluted drill in which the flutes are formed by grinding a generally cylindrical blank using a grinding wheel having a profiled circumferential face for generating the cross-sectional form of the flutes is characterized in that the radial cross-section of the profiled circumferential face of the grinding wheel includes a main cutting portion having a convexly curved profile, and a secondary cutting portion forming a continuation of the main cutting portion, there being a change in profile shape at the junction between the main and secondary cutting portions with the secondary cutting portion extending outwardly, away from the extended curve of the main cutting portion profile, to a radially outermost peak of the circumferential face.

Abstract: A twist drill, having a replaceable drill tip, comprising a drill bit shaft (1), a cutting insert (2) which is detachably fixed thereto and which forms the tip area of the twist drill, and comprises a flute (3) that continues into the cutting insert (2). The cutting insert rests, with a bearing surface (6) extending orthogonal to the center longitudinal axis (8) of the drill bit, on the face (7) of the drill bit shaft (1) and extends with a fixing stud (9), which centrally protrudes from the bearing surface (6), into a receiving recess (10) which is configured complementary thereto and which is provided in the face (7) of the drill bit shaft (1).

Abstract: A tool for chip-forming machining is made by passing first and second compounds through first and second coaxial dies, respectively, whereby the first material forms a center core of the tool, and the second material forms an outer rod of the material. The material of the core is tougher and less wear-resistant than the material of the outer rod. The coaxial first and second compounds are passed through a shaping die and then through a flute-forming structure which forms chip flutes in the outer rod.

Abstract: A rotary tool such as a helix drill and an end mill for example, is manufactured by forming a blank by an extrusion process, and then sintering the blank. During the extrusion, a mixture is passed through a die which provides a cylindrical shape to the outer peripheral surface of the mixture. A plurality of jaws are disposed downstream of the die for conducting the mixture. Each jaw includes a helical ridge for engaging the outer surface of the extrudate to cause a helical groove to be formed therein which constitutes a chip flute in the tool. During the extrusion, the jaws are moved away from the mixture to terminate formation of the chip groove, whereby a shank portion of the tool is formed.

Abstract: A drill-chuck jaw is made by first forming an elongated metal body with a toothed back face and a front face, then machining a longitudinally extending groove having sides and a floor in the front face, and forming inwardly projecting and longitudinally spaced retaining bumps on the groove sides. A hard-metal insert is fitted into the groove between the retaining bumps and then bonded to the body in the groove. the body is heat-treated, that is annealed, before machining the groove in it to reduce internal stresses. Then the body is cleaned and oiled to prepare it for machining and to eliminate any oxidation created by the heat treatment. After machining the body and before fitting the insert the body is deburred and cleaned again. Normally the insert is bonded to the body by soldering or brazing In order to allow the insert to seat directly on the jaw and not be held off it by the solder a channel is formed between the insert and the body in the groove.

Abstract: A helical drill bit (1) for rock has an axially extending shank (2) located between a chuck insert end (3) and an opposite drilling head (4) with at least one axially extending helical discharge groove (7) extending radially inwardly from the outer circumferential surface of the shank. A radially projecting groove reinforcement (9) is arranged in the base of the radial groove (8), with the reinforcement changing its geometric form or its position within the discharge groove (7) along the discharge groove (7).

Abstract: A spade blade drill having blended open notch forms on either side of an apex. The notches transition into elliptical flutes which extend outwardly toward sides of the insert. The elliptical flute profiles inhibit chip curling and packing. The sides incorporate a pair of surfaces having a reduced clearance angle for preventing chip packing. The blended open notches are deep and extend across the entire width of the flutes, enhancing heat transfer surface area and allowing chips to flow along the entire flute surfaces. A plurality of chip splitters extend from the flutes across two relief surfaces. The chip splitters have a rounded profile, inhibiting chips from becoming hung in the splitters.

Abstract: A twist drill bit (1) for use in rock has a helical land (7) arranged between a chuck insert end (2) and a tool head (3), and extends helically around a rotational axis (A) extending along a shaft (5).

Abstract: A drill steel-chuck assembly which includes a drill steel which has a plurality of faces and opposite ends. The drill steel has one portion adjacent one of the opposite ends thereof and a mediate portion spaced apart from the one portion. The drill steel further has one transition portion between the one portion and the mediate portion so as to join the one portion and the mediate portion. The one portion of the drill steel presents a first orientation of the faces. The mediate portion of the drill steel presents a second orientation of the faces. The one transition portion of the drill steel presents a twisted orientation of the faces comprising a generally constant twist of the faces from the first orientation of the one portion to the second orientation of the mediate portion. There is a chuck for attachment to the drill steel through engagement with the transition portion of the drill steel.

Abstract: Two-piece drill bits and methods of manufacturing same provide a preferably hexagonal shank, and a drill portion having a proximal end inserted into an axial hole in a distal end of the shank. In a preferred embodiment, at least part of the area adjacent the proximal end of the drill portion is knurled. Alternative embodiments have wings, polygons, tapers or other irregular shapes, or combinations of same. A variety of means may be employed to mechanically capture the drill portion in the shank.

Abstract: Two-piece drill bit and methods of manufacturing same provide a preferably hexagonal shank, and a drill having a proximal end inserted into an axial hole in a distal end of the shank. In a preferred embodiment, at least part of the area adjacent the pr drill portion is knurled. Alternative embodiments have wings, polygons, tapers or other irregular shapes, or combinations of same. A variety of means may be employed to mechanically capture the drill portion in the shank.

Abstract: In a method for the manufacture of a drilling tool a conical seat is constructed by abrasion on the drilling tool (11) for the preferably positionally accurate, oriented connection of drill head and drill shank. Abrasion preferably takes place by milling or erosion.

Abstract: The invention is a tool bit for use in a socket or chuck mechanism. The tool bit includes an elongated shank having an operative tip end and an opposite tail end. A polymer jacket is molded about the tail end of the shank, and the jacket in the lateral cross-section, has a hex-shaped outer surface.

Abstract: A method for producing cutting tools incorporated in the present invention is carried out as follows: a shank portion and a drill portion are formed separately such that the inner diameter of a hole made in the shank portion is slightly smaller than the outer diameter of the drill portion. The rear of the drill portion is forcibly inserted into the hole of the shank portion at normal temperature which is room temperature. The diameter of the inner wall of the hole is thereby enlarged, resulting in a tight fitting. After the insertion of the drill portion in the shank portion, the drill portion may be ground to form a drill edge. Before the insertion of the drill portion in the shank portion, the shank portion may be quenched under vacuum or the like, or the surface of the shank portion may be hardened by nitriding.

Abstract: A method for producing cutting tools incorporated in the present invention is carried out as follows: a shank portion and a drill portion are formed separately such that the inner diameter of a hole made in the shank portion is slightly smaller than the outer diameter of the drill portion. The rear of the drill portion is forcibly inserted into the hole of the shank portion at normal temperature which is room temperature. The diameter of the inner wall of the hole is thereby enlarged, resulting in a tight fitting. After the insertion of the drill portion in the shank portion, the drill portion may be ground to form a drill edge. Before the insertion of the drill portion in the shank portion, the shank portion may be quenched under vacuum or the like, or the surface of the shank portion may be hardened by nitriding.

Abstract: A tool includes a tool body and a cutting portion detachably mounted thereon, the tool being rotatable about a longitudinal center axis. The tool body includes flutes formed in an outer surface thereof, and a pair of forward projections at a front end thereof. The cutting portion includes front flutes formed in an external side thereof, and a pair of recesses extending circumferentially in communication with respective ones of the front flutes. To connect the cutting portion to the tool body, the cutting portion and tool body are converged longitudinally so that the projections enter the front flutes. Then, relative rotation is produced between the cutting portion and tool body to align the front flutes with the rear flutes while causing the projections to enter the recesses and form therewith a bayonet coupling.