Abstract: Drilling tool with a drill head with an end face pointing in the feed direction and which has a main bit, which forms a drill point located in the drill axis and the bit is inclined on either side in a substantially roof-shaped manner and the tool has drilling dust grooves. The main bit has a primary cutting edge, which extends radially over at least one side of the main bit, and a secondary cutting edge, which extends radially over substantially the remaining length of the main bit and is axially set back with respect to the primary cutting edge counter to the feed direction by at least the amount of feed in millimeters per revolution.

Abstract: A single point drill particularly adapted to producing small diameter deep holes utilizing a peck feed cycle routine. The preferred embodiment features a limited flute length with a depth approximately 1/3 the drill diameter and a dual point edge consisting of a shallow cutting angle and a steep relief angle. A negative rake angle runs along this edge functioning as a knife edge that will cut on opposite rotation, countering the unbalanced forces inherent in a single point tool. A sharpening fixture consisting of 2 parallel slates secured with a T-headed bolt and an anti-rotation pin. The lower plate features a central groove to locate the drill, the upper plate having a short land that facilitates orienting and clamping the drill flute. The forward end of the fixture mimics the drill point allowing the drill to be sharpened on a grinder table or by hand with a suitable abrasive stone or file.

Abstract: The invention concerns a drilling tool for machine tools. The drilling tool comprises a drill body with two chip-conveying grooves which are delimited at their flanks by helically curved ribs. Disposed at the end of the drill body is a drill head which comprises two segment parts, which are separated from each other by opposite axially aligned chip spaces, and two cutting plates which are each disposed in a recess in the segment parts in the region of an axially parallel radial chip-guide surface at different radial spacings from the drill axis with mutually partially overlapping working regions. At a transition point, the chip-guide surfaces merge into the flanks of the adjacent chip-conveying grooves. Disposed at at least one of the transition points is a transition surface which is gradually recessed so that it widens the cross-section of the chip space and merges into a flank of the adjacent chip-conveying groove.

Abstract: A hole cutter having a body provided with first and second types of cutting teeth. The cutter facilitates the discharge of cutting chips during machining of a workpiece. The tooth depth of the left and right sections of each of the second type of teeth is smaller than that of the left and right sections of each of the first type of teeth. The tooth depth of the middle section of each tooth of the second type is greater than that of the middle section of each tooth of the first type. A linear flattening section is provided at the middle portion of a second blade edge of each tooth of the second type. The flattening section causes each cutting chip to be shaped in a strip-like manner when removed from the workpiece. This separates the ends of the cutting chips from each other and prevents the chips from becoming entangled to one another.

Abstract: A drill insert has a polygon plate-shaped body that defines a top face and a central shaft extending substantially perpendicular to the top face. A pair of first cutting edges are formed on the top face in a dot symmetrical relation with respect to the central shaft. A pair of second cutting edges are formed on the top face in a dot symmetrical relation with respect to the central shaft. The second cutting edges are disposed adjacent to the first cutting edges. A projected cutting edge portion is provided in each of the second cutting edges. The projected cutting edge portion outwardly projects from each of the second cutting edges in a radial direction with respect to the central shaft.

Abstract: A drilling tool includes a one-piece drill body having axially spaced front and rear ends. The front end includes pockets for receiving cutting inserts spaced by respective radial distances from a center axis of rotation of the drill body. Chip canals are formed in the front end, and a frustoconical chip space is formed in the drill body for connecting the chip canals to an axial passage which discharges chips through the rear end of the drill body.

Abstract: A high speed drill bit is formed of a longitudinal body designed to rotate about a longitudinal axis. Each flute has a leading edge with a positive rake angle and a trailing edge with a neutral or negative rake angle. The bit cutting face is formed by surfaces and cutting edges that are asymmetrical with respect to each other.

Abstract: A spiral drill includes a rear shank portion; a front tip; and a spiral (helical) middle portion extending therebetween. Spiral ribs are formed in the middle portion, and coolant channels extend through the drill to the tip for conducting coolant fluid. The coolant channels form exit openings in the tip which are spaced at different radial distances from a centerline of the drill. Each coolant channel extends spirally through a respective rib, and the portion of each coolant channel disposed in the shank is straight. Those straight portions are spaced by different radial distances from the centerline.

Abstract: A tool-bit holder (1) for tool bits (3, 5) of cemented carbide or other hard material, in which the tool-bit holder has vibration-damping properties and the bits are specifically oriented. In particular, the tool-bit holder (1) in all essentials consists of a material, e.g. mild steel, with vibration-damping properties. The effect achieved is that the tool-bit holder may be made in one piece. The vibration-damping properties makes it possible to place the bits (3, 5) in a manner which would otherwise cause instability and consequent machining marks on the workpiece.

Abstract: A cutting tool for forming complex ports within metal workpieces. The present invention provides a cylindrical body to one end of which are attached indexable cutting inserts. One set of inserts is provided at a reduced diameter portion of the shaft for forming a boring section which enlarges and uniformly shapes the diameter of a pilot hole. A second set of inserts is provided at an enlarged diameter section of the shaft for performing multiple functions such as forming both the countersink and the spot face areas of the port. Each set of cutting inserts is substantially equidistantly disposed about the circumference of the shaft to reduce the chatter or deflection of the porting tool and therefore allow a port to be formed in adherence with very tight tolerances. In addition, since at least two inserts are provided at each diameter, the axial feed rate of the porting tool is relatively high in that a full revolution of the tool is not required to form a cut as is required by prior art porting tools.

Abstract: A drilling tool having a cylindrical body with a central axis. A first cutting insert with a cutting edge extending from a datum plane from a position about half way between the central axis and the outer edge of the holes and extending toward the first end of the tool at a first acute angle and a second cutting insert extending from the datum plane extending generally outwardly at a second acute angle substantially less than the first acute angle so that the cutting path of the second insert intersects the cutting path of the first insert whereby four chips are cut by the cutting tool.

Abstract: A spiral drill includes a rear shank portion; a front tip; and a spiral (helical) middle portion extending therebetween. Spiral ribs are formed in the middle portion, and coolant channels extend through the drill to the tip for conducting coolant fluid. The coolant channels form exit openings in the tip which are spaced at different radial distances from a centerline of the drill. Each coolant channel extends spirally through a respective rib, and the portion of each coolant channel disposed in the shank is straight. Those straight portions are spaced by different radial distances from the centerline.

Abstract: A flat drill bit having a shaft with an axis of rotation and a flat drill bit head connected to the shaft. The flat drill bit head includes opposing flat front and back faces, left and right edgewalls between the front and back faces, and a bottom endwall connected to the left and right edgewalls. The left and right edgewalls are angled relative to the front and back faces so as to define left and right cutting edges that are parallel to the axis of rotation. The bottom endwall includes left and right sections, each being angled in opposite directions relative to the front and back faces so as to define left and right bottom cutting edges. The bottom endwall of the drill bit head has a rounded shape thereby providing curved left and right bottom cutting edges. In an alternate embodiment the bottom endwall is generally straight, thereby providing straight left and right bottom cutting edges.

Abstract: A drill includes a substantially cylindrical bit body 10 having an axis O. The bit body 10 has a flange portion 13 which includes a converging portion 13a which reduces its diameter progressively towards the front end of the bit body and a flange 13b which is provided with a rearwardly facing annular surface 13c. The annular end surface is contactable with the front end surface of a drill holding portion of a machine too. Chip discharging flutes 14A,14B, each having an inner surface constituted by first and second inner surface portions 14a,14b and a third inner surface portion 14c arcuately recessed therefrom, are formed in the front end portion of the tip body 10. An inner peripheral cutting insert 16A and an outer peripheral cutting insert 16B are mounted on the ends of the chip-discharging flutes 14A,14B. The cross-sectional area S.sub.A of the first-mentioned chip-discharging flute 14A is determined to be greater than that S.sub.B of the second-mentioned chip-discharging flute 14B.

Abstract: A cutting edge 18 is provided on the end of a cutter tip 12 on a gun drill body 1. The cutting edge 18 has: a radially inner region providing a convex curved cutting edge portion 23, a radially outer region providing a straight cutting edge portion 19 and an intermediate region which provides a concave cutting edge portion 22 having a tapered portion 20 and a concave portion 21. The convex curved cutting edge portion 23, when viewed in the direction of the axis O, presents an arc shape, the radius R of the curvature of which is determined in relation to the outside diameter D of the gun drill so as to range from 0.1.times.D to 0.4.times.D. Thus, a gun drill is provided which exhibits an enhanced severing effect to cut metal chips into pieces so as to prevent clogging, as well as to prevent an increase in the cutting resistance, thus meeting the demand for a greater feed rate.

Abstract: Spiral drill comprising a cylindrical part with two chip grooves (15,16) and a principal maximum stiffness direction (22,23), an attachment part (30) with larger diameter connecting to the cylindrical part at a transition (14), and a tip with indexable cutting inserts (12,13), the chip grooves spirally encircling the cylindrical part to make the principal direction turn an angle C which is at least 110 degrees and at most 125 degrees.

Abstract: A drilling tool for drilling bores in solid metal, with a shank having at its front end several geometrically similar indexable inserts arranged at various radial distances and staggered with respect to each other by the same peripheral angle, whose working areas overlap, each of them having two equally long cutting edges, two of the respectively contiguous cutting edges inclined with respect to each other at an obtuse angle being simultaneously engaged, whereby the radial inner indexable insert extends slightly with one of its engaged cutting edges beyond the drill axis, at least one of the bisectors of the two pair set cutting edges of indexable inserts being inclined with respect to the longitudinal shank axis by an angle up to 25.degree. m and at least one of the bisectors running at an angle differing from zero with respect to another bisector, so that the sum total differing from zero of the radial force component (F.sub.

Abstract: A drill has a pair of cutting edges (4) which are arranged at positions that are substantially uniformly circumferentially spaced about its rotation axis. Each of the cutting edges (4) has a first linear cutting region (4a) and a second linear cutting region (4b) which are aligned with each other on the same straight line, and a curved cutting region (4c) which is located between the first and second linear cutting regions (4a, 4b). The curved cutting region (4c) has a third linear cutting region (4e, 4f) which extends in a direction intersecting with the second linear cutting region (4b) at a prescribed angle. With this structure, it is possible to prevent chip loading etc. which may be caused during perforation drilling operations. In a throw-away tipped drill, a notch (118a) is formed in a received portion of an insert (110) which is mounted on a shank (130). A holding portion (131a, 131b, 133a, 133b) of the shank (130) corresponding to the notch (118a) is provided with a through screw hole (138).

Abstract: This patent discloses a method of manufacturing an insert drill having three or more flutes and a three flute insert drill that may be manufactured by the disclosed method. The method allows accurate machining of insert pockets without requiring removal of a large volume of material from an adjacent flute. The drill disclosed by this patent has three or more cutting inserts which cut chips that are smaller than drills of similar size that have a smaller number of cutting tip inserts. Smaller chips allow easier evacuation of chips and enhance cooling of the drill and workpiece.

Abstract: A cutting tool in the form of a drill bit or end-milling tool has an elongated body formed with at least one cutting edge defined by a flank of a flute running primarily along a rotation axis of the body and having leading and trailing flanks one of which is formed with wavelike and spaced projections and recesses. The depth of these grooves and, hence, the height of the projections increases toward the end cutting edge to break up chips.

Abstract: To permit boring with replaceable cutter elements (10, 10a, 10b), particularly into materials where, upon withdrawal of the boring tool from a bore hole (40), grooves or scratches are to be avoided, two cutter elements are positioned on a fluted cylindrical body (1), the cutter elements being so located that the inner cutter element (10b) is positioned on the body so that an effective cutting edge (19) thereof is radially inwardly of the theoretical circle (33) formed by the outer cutter element (10a) upon rotation of the tool, the cutting corner of each cutter element is formed as a relieved or chamfered corner (15) and forms a chopped corner cutting edge (22).

Abstract: A drill bit blade for masonry and rock drills incudes first and second lateral side surfaces, first and second flank side surfaces, and converging first and second tip face surfaces. A first lateral cutting edge is defined by the intersection of the first tip face surface with the first lateral side surface, and a first lateral trailing edge is defined by the intersection of the first tip face surface with the second lateral side surface. A first lateral cutting edge is defined by the intersection of the first tip face surface with the second lateral side surface, and a second lateral trailing edge is defined by the intersection of the second tip face surface with the first lateral side surface. A chisel edge is defined at the converging intersection of the first and second tip face surfaces.

Abstract: In a ball end mill, a rotational locus is described by cutting edges of respective throw-away tips mounted to a tool body. The cutting edge of one of the tips and the cutting edge of the adjacent tip overlap with each other, and the center of the overlapping portion is located at a position that is substantially 45.degree. from a forward end of the cutting edge along a 1/4 arc of the rotational locus therefrom. The overlapping length is 1/4 to 1/3 of a diameter of the rotational locus in an arcuate length thereof. A planar section is formed at a side surface of at least one of the tips, which is located at a forward end of the tool body. The side surface is located adjacent a forward end of the cutting edge. A planar surface is formed at at least one of the tip pockets formed in the tool body, at a position facing toward the planar section. The planar surface is subject to a radial cutting force acting from the throw-away tip having the planar section. The planar section is abutted against the planar surface.

Abstract: The annular cutter of the present invention has a body portion with a plurality of teeth circumferentially spaced about the lower end thereof and a plurality of flutes extending upwardly around the outer periphery of the body portion between the teeth. Each of the teeth has at least two circumferentially stepped cutting edges with the trailing edge being the outermost cutting edge. These two cutting edges are separated by a shoulder which in the preferred embodiment is defined by the bottom wall of the flute. This shoulder has a radial clearance adjacent the outermost cutting edge to accommodate the growth of the outermost chip cut by the outermost cutting edge to facilitate discharge of the chips through the flute.

Abstract: An insert boring tool includes a tool body and a cutting insert releasably mounted thereon. The insert includes a plate defined by front and rear surfaces and a plurality of side faces and having a plurality of corners where adjacent side faces intersect one another. At least one of the corners is removed to provide a corner face. A first cutting edge is defined by the front surface and one of the side faces adjacent to the corner face, and a straight second cutting edge is defined by the front surface and the corner side face. The first and second cutting edges intersect each other at an obtuse angle, and are indexed in an end cutting position. The front surface has a marginal portion extending along the second cutting edge and inclined in such a manner that a thickness of the plate between the marginal portion and the rear surface is progressively reduced toward the second cutting edge.

Abstract: A drill for performing a roughing cut in a workpiece as the drill is advanced, and performing a finishing cut as the drill is retracted. A blade carrier is mounted eccentrically on the drill to be movable between first and second positions. In the first position, the blade is located for a roughing cut. In the second position, the blade is shifted radially for a finishing cut. A spring biases the carrier toward the second position and yields when the carrier moves to the first position. The spring bias is too weak to overcome reaction forces acting on the blade during a roughing cut, wherein the roughing cut reaction forces cause the carrier to be shifted to the first (roughing cut) position. The spring bias is strong enough to overcome the weaker reaction forces occurring during a finishing cut, so that the carrier is automatically shifted to the second (finishing cut) position when the drill is withdrawn through the workpiece.

Abstract: The invention relates to a short-hole drill and a cutting insert therefor, for drilling of metallic work pieces. The drill comprises a drill shank with two chip flutes formed therein and with two cutting insert sites and two mainly rectangular cutting inserts having mutually identical shaping. The cutting inserts are accommodated in the cutting insert sites and secured thereto by means of lock screws such that the broken non-active cutting edge abuts against a broken support surface in each cutting insert site while the active cutting edge projects axially forwards. The cutting insert which is arranged radially outermost is inclined such that it determines the size of the bore while the longitudinal axis of the other cutting insert is arranged parallel to the center line (CL) of the drill. The distance between the outermost parts of each cutting edge is longer than the shortest distance between the long side surfaces of the cutting insert.

Abstract: A drill is provided having opposed primary and secondary cutting edges extending perpendicular to the longitudinal axis of the drill. The primary cutting edge extends across the longitudinal axis of the drill to a terminus intermediate the longitudinal axis and the periphery of the drill. The secondary cutting edge extends inwardly from the periphery of the drill to a point intermediate the periphery and the longitudinal axis of the drill. The primary and secondary cutting edges are spaced from one another along the longitudinal axis so that the primary cutting edge leads the secondary cutting edge during a drilling operation. The primary cutting edge drills the inner part of the hole and the secondary cutting edge drills the outer part of the hole. The primary and secondary cutting edges are designed to generate substantially balanced forces about the longitudinal axis of the drill. Flutes extend from each cutting edge for efficient and reliable removal of chips.

Abstract: An annular hole cutter having a shank and an integral cylindrical body provided with a plurality of axially extended cutting teeth which each has an inner cutting edge and an outer cutting edge. The inner and outer cutting edges are equal in radial width and their inner ends meet in a common leading cutter point. The outer and inner cutting edges on each cutting teeth share a substantially mutual radial face.

Abstract: An improved spade type bit for use in drilling metal, masonry and the like. This bit has a replaceable transverse bar of hardened material in the tip thereof with symmetrical end surfaces sloping away from a central chisel point located on the axis of the bit. One of these surfaces is provided along its length with a groove extending from a cutting lip to the trailing edge, with the groove width and depth at the trailing edge having at least the same dimensions as at the cutting edge. Preferably the dimensions of the groove at the trailing edge are slightly greater than those at the cutting edge. The second of the surfaces has an outer portion with a reduced angle with respect to the axis of the bit as compared to the angle of the inner portion. This construction provides for the accurate drilling of holes in metal, masonry and the like and further accomplishes the drilling at increased penetration rates with the same or lower axial force applied to the bit.

Abstract: A hole cutter having a generally cylindrical cutter body provided around its lower end with a plurality of first cutting teeth each having a plurality of cutting edges, and a plurality of second cutting teeth adapted to scrape a surface cut by the first cutting teeth.

Abstract: An indexable insert drill is disclosed that avoids formation of a breakout slug and therefore is particularly suited for drilling a laminate workpiece or stacked workpieces. The tool includes a cylindrical body provided with opposed flutes. A radially inner indexable carbide insert is releasably secured in the back wall of one flute at the leading end of the body and a radially outer insert is similarly secured in the back wall of the opposed flute. The inserts present an active cutting edge generally disposed in a transverse plane containing the axis of the tool and in axially leading relation relative to the tool body, and together are adapted to cut a hole of given diameter with the active cutting edges providing for overlap therebetween.

Abstract: This invention relates to a tapered finishing reamer having an overall taper of about ten degrees and having only two teeth diametrically opposite one another. Each tooth is formed to present a negative cutting angle on the order of ten degrees leading a diameter extending between the apexes of the two teeth. The tapered body of the reamer between the two teeth being cylindrical in cross-section and forms guiding surfaces of slightly less diameters than the diameter through the apexes of the teeth.

Abstract: The present invention provides a drilling tool having a shank and at least one pair of identical cutting inserts, the inserts having an octagonal shape having alternate equal obtuse angles. Each of the inserts is arranged such that they each have a different radial displacement from the turning axis of the drill, the inner insert having a cutting path which overlaps the turning axis of the drill and the next outer insert having a cutting path which overlaps the cutting path of the inner insert. The cutting path of each insert is formed by the cutting edges either side of the obtuse angles of the insert.

Abstract: A cutting tool having an upper cylindrical body and a lower cylindrical body with flat surfaces on opposite sides of the lower cylindrical body, flutes in said lower cylindrical body and three triangular cutting elements indexible to three separate positions secured in said lower cylindrical body and means for detachably securing said triangular cutting elements, one of said cutting elements having three cutting edges for each position and the other two of said cutting elements having one cutting edge for each position.

Abstract: O-rings, which are disposed within pneumatic couplings and which are recurrently moved past ports within those pneumatic couplings, tend to be abraded as they recurrently engage the changes of surface at the mouths of those ports. The present invention minimizes the abrading of the O-rings by providing the ports with bell mouths which merge smoothly into at least two spaced points on the surface of the body in which the ports are located.

Abstract: A twist drill (20) is provided which has an improved tip (26) including at least one spiral groove (42) which extends from the leading face of a cutting edge of a tip portion of the drill. This groove is positioned at a spaced location from the cutting lip (40) and extends to the trailing face of the cutting blade tip such that a portion of the material to be drilled initially passes through the spiral groove (42) during the drilling operation as the drill is fed into the work piece. The portion of the material which passes through the groove (42) is at least partially cut by a subsequent pass of the cutting edge of the further cutting blade tip and causes shavings of the material to be broken into smaller sizes thereby enhancing the travel of the shavings along the length of the flutes (70') and reducing the binding forces applied to the twist drill during drilling operations. The flutes (70') are also enlarged in accordance with a specified criteria to enhance the drilling efficiency.

Abstract: An improved twist drill (20) is provided which includes at least one spiral groove (42) which extends from the leading face of a cutting edge of a tip portion of the drill. This groove is positioned at a spaced location from the cutting lip (40) and extends to the trailing face of the cutting blade tip such that a portion of the material to be drilled initially passes through the spiral groove during the drilling operation as the drill is fed into the work piece. The portion of the material which passes through the groove is at least partially cut by a subsequent pass of the cutting edge of the further cutting blade tip and causes shavings of the material to be broken into smaller sizes thereby enhancing the travel of the shavings along the length of the flutes and reducing the binding forces applied to the twist drill during drilling operations.

Abstract: A drill bit comprises a body having a shank portion and an end face at its forward end. The drill bit body has at the forward end a cutting means having at least one cutting edge provided on the end face. The cutting edge is spaced from the axis of rotation of the body. The body has a rake surface which terminates in the cutting edge and extends along the axis of rotation.

Abstract: To reduce the requirement for stocking different types of holder plates for cutting chips 9, at least the chip holder plate 16 carrying the radially outermost chip, and the next adjacent chip holder plate 6 carrying the radially more inwardly positioned chip, have mutually engaged common abutment surfaces 19, 27. The tool body 1 is formed with a recess 5 in which the radially outermost chip holder plate and the next adjacent plate are commonly secured, for example by clamping bolts or screws extending inwardly into the tool body at an angle with respect to the tool body axis 26. All of the radially inwardly positioned chip holder plates 6 are of equal size and shape. The boring or drilling diameter of the tool is defined by the width of the radially outermost chip holder plate and the chip positioned thereon.

Abstract: The milling cutter of the invention comprises a cutting section having a plurality of blades positioned on the surface and separated one from the other by flutes. At least two blades have one or more smooth segments, exhibiting an even and unbroken land and cutting edge, interspersed with one or more serrated segments containing a row of cutting teeth. The positions of the smooth and serrated segments are staggered from blade to blade so that in the course of one complete revolution of the cutter, each point along a surface being worked by the cutter will be contacted by at least one smooth segment and at least one serrated segment.

Abstract: Improved throw away insert and end mills suitable for use with such an insert. The throw away insert has cutting edges which have a convex arcuate shape and have an identical radius of curvature larger than that of the circle circumscribing it at the noses thereof.

Abstract: In a boring tool for making borings in solid metal material of workpieces, at least one cutting bit is interchangeably arranged in a recess, at the end of the borer shank. The polygonal cutting bit has a plurality of cutting edges of equal length, of which two are in engagement with the workpiece at each time. For the purposes of improved centering of the borer, these two operative cutting edges each form approximately the same angle to a line parallel to the borer axis. A plurality of cutting bits at different radial distances may also be arranged in the boring tool, with two cutting edges of each cutting bit being in engagement with the workpiece and the working regions of the cutting edges of adjacent cutting bits each overlapping somewhat.

Abstract: A drill body for drilling solid metal and for finish boring having, at the working end, two or more replaceable, indexable, hard metal inserts dimensioned and spaced radially to cut equal volumes of metal. The inserts are retained in pockets by a headed screw with a through passage for a wrench. The outside insert is also shaped and positioned so the drill body may be shifted radially from the drilling axis and used as a boring bar.

Abstract: A boring tool having asymmetric disposition of cutting edges providing smooth, balanced cutting permitting the use of a lighter tool for a given job and having proportions providing a range of lateral adjustment for increasing hole size when desired while preserving smooth cutting characteristics; in simplest embodiment the tool comprises a unitary, substantially rectangular shape block for mounting a pilot bar with a cutting edge on each side of the axis, one cutting edge being closer to the axis and being longer than the other, the two cutting edges located for making contiguous cuts; on one side a relieved portion adjacent one cutting edge (on the outboard end of the inboard cutting edge) automatically engages the work when positioned more inboard as result of lateral resetting of the tool to bore a larger hole than the holesize for which nominally designed.

Abstract: An indexable insert drill employing a pair of radially opposed inserts having either positive or negative axial lead cutting edges extending in the same cone of revolution. One of the inserts has a radially inner arcuate corner intersecting and extending across the axial center line. The other insert is located relatively overlapping but outward radially with an outermost corner adapted to finish cut the side wall diameter of the hole. Insert cutting edges provide for chip interruption and breakage.

Abstract: A spade drill characterized in that the slotted blade clamping end of the holder has oppositely beveled end surfaces which are perpendicular to the respective side faces of the blade and which are at an angle less than the angle of the respective cutting edges of the blade to define convergent passages of right angle cross section for funneling or tracking chips to diametrically opposite obtuse angle cross section longitudinal grooves in the holder.

Abstract: A twist drill having primary lands and associated secondary lands the primary lands being relieved adjacent the major flanks so that each secondary land protrudes outwardly and forms a sizing flank for taking a "skimming" cut. The primary lands may be relieved either by being chamfered off at an angle or by the diameter across said primary lands being reduced for a limited distance from the major flanks.