Turning cutting tool with PCD cutting tip

Abstract

Turning cutting tool (20, 100, 300) which includes the following: an elongated body arranged around a longitudinal axis (AA), wherein the longitudinal body includes a spiral groove (32) and a cutting tip (22) made of polycrystalline diamond, the cutting tip (22) comprising: Cutting edges (30) extending radially outwards to an edge (39) on an external radial circumference of a side wall (49) of the rotary cutting tool (20); an inner section (50) with an inner apex angle (γ); and an outer section (52) with an outer tip angle (Γ), wherein the inner tip angle (γ) is in the range between 110 degrees and 140 degrees and the outer tip angle (Γ) is in the range between 145 degrees and 180 degrees and the inner section (50) projects axially beyond the outer section.

Description

[0001] The invention relates generally to rotary cutting tools and in particular to rotary cutting tools such as drills with PCD (polycrystalline diamond) cutting tips. The invention further relates to a method for producing a rotary cutting tool with a cutting tip made of polycrystalline diamond.

[0002] Historically, PCD drills were designed as straight-fluted drills with faceted tips. More recently, PCD drills with helical flutes and more complex tip geometries similar to solid carbide drills have been developed. One of the primary applications for such advanced PCD drills is drilling in composite materials such as CFRP-titanium composites (CFRP – Carbon Fiber Reinforced Polymer). Drills used to cut such materials require high wear resistance to survive in CFRP while possessing a geometry capable of effectively cutting titanium. Customers in the air cargo industry, who commonly utilize such CFRP composites, further require that the burr height of the titanium section of the drilled composite be maintained at approximately 100 micrometers.Well-known PDK drill bits produce high-quality holes in the first few holes, but soon after quickly develop unacceptable burrs (usually after about 5 holes or less). Consequently, such drill bits have to be replaced regularly, which is very expensive.

[0003] Therefore, there is room for improvement in rotary cutting tools used for drilling CRFP titanium, especially in the quality of the holes cut and the durability of the cutting tool.

[0004] EP 0 137 898 A1 discloses a solid carbide spiral drill for machining difficult-to-machine materials, the drill head of which has at least two main cutting edges, each with an internal cutting edge and an external cutting edge.

[0005] In DE 10 2008 052 743 A1 a tool for machining workpieces is described which is formed from several layers of tough and hard material.

[0006] Furthermore, US Patent 5,273,380 A discloses a drill bit having an elongated body arranged around a longitudinal axis, with a spiral flute and a cutting tip. The cutting tip comprises cutting edges extending radially outward to an edge of a circumferential wall of the drill bit, an inner section with an inner point angle, and an outer section with an outer point angle that differs from the inner point angle. The inner section also projects axially beyond the outer section.

[0007] The object of the invention is to provide an improved turning tool with a PCD cutting tip, an improved PCD cutting tip and a method for forming an improved turning tool with a PCD cutting tip.

[0008] The problem is solved by a rotary cutting tool according to claim 1, a cutting tip according to claim 6 and a method according to claim 8.

[0009] As one aspect of the invention, a rotary cutting tool is provided. The rotary cutting tool comprises an elongated body arranged around a longitudinal axis. The body contains a helical groove and a cutting tip made of polycrystalline diamond. The cutting tip comprises cutting edges extending radially outward to a rim on an external radial circumference of a side wall of the rotary cutting tool, an inner section with an inner tip angle, and an outer section with an outer tip angle that differs from the inner tip angle.

[0010] The outer tip angle is greater than the inner tip angle. The inner tip angle is in the range of approximately 110 degrees to approximately 140 degrees. The outer tip angle is in the range of approximately 145 degrees to approximately 180 degrees. The elongated body may be made of a carbide material. The elongated body may comprise: a first end opposite the cutting tip and at least two coolant passages extending through it, each coolant passage extending from the first end to the cutting tip. Each coolant passage may be of a generally helical shape.

[0011] As a further aspect of the invention, a cutting tip made of polycrystalline diamond is provided for use with a rotary cutting tool. The cutting tip comprises cutting edges extending radially outward to an edge on an external radial circumference of a side wall of the rotary cutting tool, an inner section with an inner tip angle, and an outer section with an outer tip angle that differs from the inner tip angle.

[0012] The outer tip angle is larger than the inner tip angle. The inner tip angle ranges from approximately 110 degrees to approximately 140 degrees. The outer tip angle ranges from approximately 145 degrees to approximately 180 degrees.

[0013] As a further aspect of the invention, a method for forming a rotary cutting tool with a cutting tip made of polycrystalline diamond is provided. The method comprises: forming at least two coolant passages in a generally cylindrical tool body; forming at least two coolant passages in a tip section, wherein the tip section is separate from the tool body; and coupling the tip section to the tool body to form the rotary cutting tool.

[0014] The tip section can be coupled to the tool body via a brazing process. The at least two coolant passages can be formed in the generally cylindrical tool body by an extrusion process. Alternatively, the at least two passages can be formed in the tip section via an EDM drilling process.

[0015] The tip section comprises cutting edges extending radially outwards to an edge on an external radial circumference of a side wall of the rotary cutting tool, an inner section with an inner tip angle, and an outer section with an outer tip angle different from the inner tip angle, the inner section projecting axially beyond the outer section.

[0016] A thorough understanding of the invention can be gained from the following description of preferred embodiments when read in conjunction with the accompanying drawings. These show: Fig. 1 a side view along a line generally perpendicular and within the same horizontal plane as the primary cutting edge section and the second cutting edge section of the cutting end of a twist drill according to a non-limiting embodiment of the present invention, Fig. 2 a top view of the cutting edge of the in Fig. 1 of the drills shown, Fig. 3 a top view of the cutting end of a drill bit according to a further non-limiting embodiment of the present invention, Fig. 4 an enlarged view of the in Fig. 3 top view shown, Fig. 5 a partial cross-sectional view along the arrows “5-5” in Fig. 3, Fig. 6 a side view of the in Fig. 3 drills shown along the arrows “6-6” in Fig. 3, Fig. 7 a semi-transparent view of a state-of-the-art drill showing the internal coolant passages, Fig. 8 a semi-transparent view of a drill according to a non-limiting embodiment of the present invention, showing the internal coolant passages, and Fig. 9 a top view of the cutting edge of the in Fig. 8 drills shown.

[0017] Directional terms used herein, such as left, right, front, back, top, bottom, and derivatives thereof, refer to the orientation of the elements shown in the drawings and do not limit the claims unless expressly stated herein. Identical parts are designated with the same reference number in all drawings.

[0018] The Fig. 1 and Fig. Figure 2 shows a section of an exemplary twist drill 20 according to a non-limiting embodiment of the present invention. The drill 20 is configured to be driven rotationally about a mean longitudinal axis AA, or to rotate an associated workpiece (not shown), or to rotate both the drill 20 and the workpiece relative to each other. With reference to Fig. 1. The drill 20 is designed such that a cutting end 22 is formed at the outer end of a shank 24. The shank 24 comprises a first section 24a, preferably made of carbide material, and a second section 24b, preferably made of PCD material, arranged at or around the cutting end 22. Carbon fibers contained in composite materials are highly abrasive, and a PCD tool material helps to extend the service life and edge sharpness of the drill 20. A sharp edge is critical to minimize unwanted damage to the machined composite material and further to minimize burr height when the drill 20 exits the metal of a CRFP-titanium composite material.A blunt edge generally causes excessive delamination in CRFP and is equally detrimental when cutting titanium, leading to higher stresses and temperatures, which eventually results in premature chipping of the drill bit and damage to the workpiece.

[0019] At the in Fig. 1 and Fig. In the embodiment shown in Figure 2, the shaft 24 is formed by first sintering the PCD material onto a small carbide piece, which is then brazed to a larger carbide piece, such as at a brazing line 24c. Fig. Figure 1 is shown with a dashed line. However, it is understood that other methods or steps may be used in forming the shaft 24 without deviating from the scope of protection of the present invention.

[0020] With further reference to the Fig. 1 and Fig. 2 The shank section 24 contains two chip evacuation grooves 32. The grooves 32 are formed from the tip of the cutting end 22 and extend rearward to a point at a mounting shank section of the drill 20 (not shown), which is designed to be mounted in a machine tool as is commonly known in the art. The grooves 32 are generally symmetrical and are located at equal intervals in the circumferential and axial directions and are arranged in a general helical path at a helical angle φ ( Fig. 1) is oriented with respect to the longitudinal axis AA. The grooves 32 ensure that composite fibers of the workpiece are cut well, while delamination is minimized when the drill 20 enters the workpiece. The helix angle φ of the grooves also plays an important role in the hole-cutting process. A low helix angle φ or a straight groove would not effectively evacuate the metallic chips, while a high helix angle φ would reduce the strength of the cutting edge. A preferred helix angle also allows for appropriate curling of the cut chips. In at least one embodiment of the present invention, it has been found that the preferred helix angle φ is about 22.5 degrees. In general, it has been found that such a helix angle φ lies in the range between about 18 degrees and about 30 degrees. It is understood that a different helix angle could also be used.In such embodiments, the local spiral angle near the cutting edge is preferably within the specified range, but the spiral angle towards the shank can vary within or outside the range.

[0021] The cutting end 22 contains a few cutting edges 30 ( Fig. 2), which are formed along the cutting ridge, where the front groove wall surfaces 33 ( Fig. 1) cut the upper flank 34. Each upper flank 34 contains front surface sections 34a and rear surface sections 34b on opposite sides of the drill 20. Each cutting edge 30 has at least a first cutting edge section 36 and a second cutting edge section 35, the first cutting edge section 36 extending radially from a central, generally straight chisel edge 41 to the second cutting edge section 35, and the second cutting edge section 35 extending radially outward to at least approximately near an outer edge 39 on the external radial circumference of the drill 20. The chisel edge 41 is formed by cutting tip surfaces 45. The second cutting edge section 35 extends radially outwards to a third outer cutting edge section 37. The third outer cutting edge section 37 extends radially outwards from the second straight section 35 to the drill edge 39 and axially backwards.The length of the chisel edge 41 is designed in relation to the diameter of the drill bit such that it is approximately between 1% and 10% of the drill bit diameter.

[0022] The symmetrical design of the cutting edges 30 described above greatly facilitates stability during use of the drilling system. This characteristic is achieved through the neutral or balanced geometry of the cutting surfaces, which significantly reduces any tendency of the drilling system to wobble during use. It is understood, however, that the cutting edges 30, as well as other elements described herein as symmetrical in the exemplary embodiments, can also be asymmetrical without deviating from the scope of protection of the present invention.

[0023] The front sections 34a of the upper flank 34 immediately adjacent to all sections of the cutting edge 30 are oriented at a first clearance angle generally between 5 degrees and 20 degrees, or approximately 10 degrees. The rear sections 34b of the upper flank 34 are oriented at a larger clearance angle than the front sections 34a. The rear surface sections 34b are oriented at a second clearance angle generally between 15 degrees and 50 degrees, 25 degrees to 40 degrees, or approximately 20 degrees. In the Fig. 1 and Fig. In the embodiment shown in Figure 2, the first cutting edge section 36 is convex and has a generally constant radius of curvature R when viewed from above along the central axis, as shown in Figure 2. Fig. 2. The radius of curvature R is generally set to the range of 8% to 20% of the outer diameter XD of the drill bit when viewed from a top view along the central axis of the drill bit, as shown in Fig. Figure 2 shows that the radius of curvature R generally eliminates the sharp transition between the cutting edges 30, thus preventing breakage of the cutting edges 30 regardless of drilling conditions. It is considered that the first cutting edge section 36 could also have other convex curvilinear geometries instead of a convex shape with a generally constant radius. It is also considered that the first cutting edge section 36 could be formed in other non-curvilinear shapes (e.g., without a boundary, chamfers) without deviating from the scope of protection of the present invention.

[0024] The drill bit 20 is preferably formed by thinning at the cutting end of the drill bit 20. The thinning is applied to a thick central core section at the tip of the drill bit body, and a curvilinear first cutting edge section 36 is formed by the thinning, the first cutting edge section 36 extending from the central chisel edge 41 to the second cutting edge section 35. It is understood that in the Fig. 1 and Fig. In the embodiment shown in Figure 2, the first cutting edge section 36 does not extend to the center of the drill bit 20. The first section 36 of the cutting edge is formed at a position slightly offset from the central axis of the drill bit in order to reduce weakening of the center of the drill bit caused by stress concentration.

[0025] The in Fig. 1 and Fig. The thinning surfaces 38 shown in Figure 2 at the drill tip 22 of the present invention extend from the central core of the drill 20 to the side wall 49 of the drill 20. The first thinning surface 38 extends from the rear of the chip discharge groove 32 to the rear surface 34b of the upper flank when viewed from a top view along the central axis AA of the drill 20 (as shown in Figure 2). Fig. 2 shown). At the in Fig. 1 and Fig. In the embodiment of the invention shown in Figure 2, the thinning surface 38 is arranged such that it extends from the external circumferential side wall 49 to the central core of the drill 20 near the central axis AA.

[0026] Each dilution on opposite sides of the central axis AA also consists of two dilution surfaces, the first dilution surface 38 and the second dilution surface 44. As in Fig. As can be seen in Figure 1, the second thinning surface 44 runs essentially parallel to the central axis AA of the drill 20. In an alternative embodiment of the invention, it is considered that the second thinning surface 44 may be angled slightly forward or backward with respect to the cutting direction of the drill 20 to obtain a negative or positive rake angle. The first cutting edge section 36 is formed along the cutting ridge where the second thinning surface 44 intersects the tip surface 45. The first thinning surface 44 generally extends downward through a fold 46 formed with the second thinning surface 38. The first thinning surface 44 is preferably not a flat plane, but instead a convex surface, as best represented by line 36 in Figure 1. Fig. 2 shown (note that line 36 represents the cutting edge section formed where the first thinning surface 44 intersects the tip surfaces 45).

[0027] The second thinning surface 38 is generally flat and planar and oriented at a constant back angle with respect to a plane that intersects the central axis AA of the drill 20. In one embodiment of the invention, the plane intersecting the longitudinal axis AA also runs parallel to the second cutting edge section 35, although this plane intersecting the central axis need not be parallel to the second cutting edge sections 35. The back angle is generally between 30 and 50 degrees, alternatively between 40 and 45 degrees, or may be approximately 45 degrees. It is understood that the second thinning surface 38 may be shaped differently than flat and planar without departing from the scope of protection of the present invention.

[0028] A flank edge 43 represents an upper boundary of the thinning. The flank edge 43 is defined as the intersection between the second thinning surface 38 and the rear surface section 34b of the upper flank. The flank edge 43 is oriented at an angle θ with respect to the chisel edge 41 (see Fig. 2) The angle θ is generally set within the range of 75 degrees to 105 degrees, or within the range of 85 degrees to 95 degrees, or at approximately 90 degrees (as shown).

[0029] An upwardly inclined tip surface 45 is associated with each of the upper flank surfaces 34a, 34a and cutting edges 30, 30. As in Fig. As shown in Figure 1, the first cutting edge sections 36 associated with the tip surfaces 45 are generally oriented such that they form an inner tip angle γ, which represents the angle between the tip surface 45 and the associated first cutting edge sections 36. In the illustrated embodiment, the cutting edge 30 on one side of the axis of rotation AA is symmetrical to the cutting edge 30 on the opposite side of the axis of rotation AA. However, it is understood that the cutting edges 30 could also be asymmetrical without deviating from the scope of protection of the present invention. In the embodiment shown in Fig. 1 and Fig. In the embodiment shown in Figure 2, the tip surfaces 45 are generally oriented at the same angle (not numbered) with respect to the axis of rotation AA. The inner tip angle γ is preferably in the range of approximately 110 degrees to approximately 140 degrees.

[0030] The inner point angle γ generally defines an inner point 50 near the central section of the drill bit 20. Such an inner point 50, projecting axially beyond the surrounding surfaces, generally provides improved stability and allows for good centering of the drill bit 20 when it enters a workpiece (not shown). By reducing the inner point angle γ of the inner point 50, thereby making the inner point 50 steeper, the starting performance, stability, and impact reduction of the drill bit can be improved as desired by configuring the angle γ as required for different applications. However, it is understood that while reducing the angle γ generally improves the starting performance, stability, and impact reduction of the drill bit, such a reduction also generally weakens the sharp point of the drill bit 20.

[0031] With further reference to Fig. 1. The second cutting edge sections 35 are generally oriented such that they form an outer tip angle Γ. The angle Γ is preferably in the range of approximately 145 degrees to approximately 180 degrees. The outer tip angle Γ generally defines a peripheral or outer tip geometry that forms an outer shoulder or outer tip 52. The relatively flat geometry of the outer tip 52 ensures that cutting forces are generally directed axially along the drill 20 rather than laterally, thus reducing the size of the burr that rolls along the exit edge of a drilled hole.

[0032] The third outer cutting edge section 37 can be curved and have a constant radius of rotation, or it can be chamfered. It is also considered that other embodiments of the drill may not have a third outer cutting edge section 37, but may consist only of a first cutting edge section 36 and a second cutting edge section 35 extending radially outward from the first cutting edge section 36 to the outermost edge of the drill, forming a sharp corner there.

[0033] Regarding the Fig. In references to figures 3-9, in which a second non-limiting embodiment of the present invention is shown, it is to be understood that identical parts of the drill previously discussed retain the same reference element numbers and these parts are not discussed again in detail.

[0034] In particular, Fig. 3. A view similar to the one presented previously. Fig. 2, however, the chisel edge 141 is much shorter relative to the tool's outer diameter than the previously discussed chisel edge 41. The enlarged view of Fig. 3 in Fig. Figure 4 highlights this feature. Furthermore, as discussed, the first curvilinear cutting edge section 136 has a positive axial rake angle.

[0035] With reference to the Fig. 3-6 the drill bit 100 has a longitudinal axis AA ( Fig. 6) on, which in the frontal view of Fig. 4. The center of the drill bit is 100. As in Fig. As shown in Figure 6, the drill 100, like the previously described drill 20, comprises a shank 124 with a section 124a, preferably made of carbide material, and a second section 124b, preferably made of PCD material, arranged on or around a cutting end 122. In a preferred embodiment, the shank 124 is formed by first sintering the PCD material onto a small carbide piece, which is then brazed onto a larger carbide piece, as shown by the dashed brazing line 124c. It is understood, however, that other methods or steps can be used in forming the shank 124 without departing from the scope of the present invention.

[0036] A first tip surface 45a and a second tip surface 45b intersect at the central axis AA and are generally adjacent to it, intersecting to form the chisel edge 141. An imaginary bisector 102 extends radially through the central axis AA perpendicular to the chisel edge 141 and defines a first tool half 103 on one side of the bisector 102 and a second half 104 on the other side of the bisector 102.

[0037] Each tool half 103, 104 has a first curved cutting edge section 136 extending radially from the chisel edge 141, and a second cutting edge section 135 extending radially outwards from the first cutting edge section 136. Viewed from the cutting end 122 ( Fig. 6) The chisel edge 141 is curved in such a way that it harmonizes with the curved cutting edge 136 of the first tool half 103 and the first curved cutting edge 136 of the second tool half 104. It is understood, when considering Fig. 4, that the chisel edge 141 harmonizes smoothly with the first curvilinear cutting edge 136 of the first tool half 103 and the first curvilinear cutting edge 136 of the second tool half 104 to provide a continuous ‘s’-shaped joint between each of the first curvilinear cutting edges.

[0038] In the present invention, the fact that the first curvilinear cutting edge sections 136 at the chisel edge 141 of each tool half 103, 104 each have adjacent surfaces that define a positive axial rake angle is of particular interest. In particular, the second thinning surface 144 ( Fig. 6) as the rake angle area for the first curvilinear cutting section 136. It is understood that the positive axial rake angle X ( Fig. 5) between the second dilution surface 144 and the central axis AA can generally be between 0 and 15 degrees and preferably is about 5 degrees.

[0039] Furthermore, the length L ( Fig. 4) the chisel edge 141 relative to the outer diameter XD ( Fig. 3) of the drill 100 short. In particular, the length L of the chisel edge 141 is generally between about 1% and 4%, preferably about 2.5%, of the outer diameter XD of the drill 100.

[0040] Fig. Figure 3 shows a radius of curvature R of the first curved cutting edge 136, and this radius of curvature R can generally be between about 8% and 20% of the outer diameter XD of the drill 100. As mentioned previously and regarding Fig. In section 4, the chisel edge 141 is curved such that it harmonizes with the first curved cutting edge section 136 of both the first tool half 103 and the second tool half 104. Consequently, the chisel edge 141 and the adjacent first curved cutting edge sections 136 assume an "s" shape. This "s" shape, together with the positive axial rake angle X of the first curved cutting edge section 136, provides an improved ability to center the cutting tool 100 and also gives the cutting tool 100 additional stability.

[0041] As previously discussed, the drill 100 has a chisel edge 141 with initial curved cutting edge sections 136 which form a positive rake angle X with the longitudinal axis AA of the drill 100. It is also possible to manufacture such a cutting tool without the chisel edge having a positive rake angle surface, but in which the chisel edge 141 smoothly harmonizes with the first curved edge section 136 to create a smooth "s" shape.

[0042] When drilling CRFP titanium, the drill described herein produced 100 holes with burrs of generally less than 50% of those of known drills, while lasting about twice as long as known drills.

[0043] With reference to the Fig. 8 and Fig. 9 will be a further feature of the present invention in contrast to an example of the one in Fig. The state of the art is shown in section 7. With reference to Fig. Figure 7 shows an exemplary prior art drill 200 with a carbide body 202 and a brazed tip section 204. Coolant is supplied to a pair of openings 206 in the brazed tip section 204 through a pair of straight passages 208 provided in the brazed tip section 204, extending from a single opening 210 in the brazed joint 203 to each of the openings 206. The opening 210 is located at the end of a single central coolant passage 212, which runs axially along the central axis AA of the drill 200.

[0044] In contrast to the one in Fig. The 7 designs shown represent the state of the art. Fig. 8 and Fig. 9. A drill 300 with a coolant supply system according to a non-limiting embodiment of the present invention. Similar to the prior art layout, the drill 300 comprises a carbide body 302 with a brazed tip section 304. Coolant is supplied to a pair of openings 306 in the brazed tip section 304 by a pair of straight passages 308 provided in the brazed tip section 304 and extending from a pair of openings 310 in the brazed joint 303 such that each passage 308 is arranged between one of the openings 306 and one of the openings 310. Each of the openings 310 is arranged at the end of a respective helical coolant passage 312, which extends in a generally helical manner around the central axis AA of the drill 300 along a helical angle δ relative to the central axis AA in the axial direction.

[0045] Passages 312 are formed when the carbide rods are initially extruded. The helix angle δ of the passages 312 is generally controlled by the required helix angle at the flute (i.e., the pitch of the coolant hole is usually the same as the desired pitch to achieve the required flute helix angle). In some cases, permissible deviations exist as long as the coolant does not intersect the flute profile. Typically, the coolant hole is generally positioned between 30% and 80% of the drill radius radially and approximately 25 to 60 degrees circumferentially from the edge of the cutting edge.

[0046] Typically, the passages 308 in the tip section 304 are formed on the carbide body 302 prior to brazing. Such passages 308 can be formed by EDM drilling or other suitable processes. The passages 308 are preferably oriented at an angle so that they intersect the existing coolant holes in the rod tangentially, but the passages 308 could also intersect at other angles (e.g., they could run parallel to the axis of the drill without restriction).

[0047] With such a new design as in Fig. 8 and Fig. As shown in Figure 9, strength and stiffness are not significantly compromised, unlike in the example of Fig.7, where a single central coolant passage 212 is used. In contrast to the prior art, there is no risk of a "weak" intersection at the load-bearing areas near the core. The design of the present invention with multiple coolant passages that run continuously separate from one another allows a larger volume of coolant to be delivered to the cutting edge. The design with multiple coolant passages also does not impose any limitations on smaller diameter drills. Furthermore, the design with multiple coolant passages generally does not increase manufacturing costs, since two holes must be produced through the PCD material in any case.

[0048] Although described here in connection with a drill with a PCD tip, it is understood that the multi-coolant-passage design could easily be applied to other applications involving brazing a tip section to an existing rod. Rod materials used in such applications can typically include, but are not limited to, carbide, ceramic, powder metal, high-speed steel, steel, and others. Tip materials used in such applications can include, but are not limited to, carbide, cermet, ceramic, PCD, pCBN, and others.

[0049] Drills constructed according to the present invention can be used in many applications in all industries, but are particularly well suited for use in hole-cutting operations with composite materials (e.g., without limitation, CRFP-titanium composite materials).

[0050] Other applications, embodiments and variations of the disclosed embodiments described herein are apparent to the person skilled in the art and can be produced without deviating from the concept and scope of the invention as defined in the attached claims.

[0051] Although specific embodiments of the invention have been described in detail, the person skilled in the art understands that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the disclosed particular arrangements are intended only to be illustrative and not to limit the scope of the invention, which shall encompass the full width of the appended claims and any and all equivalents thereof.

Claims

[1] Rotary cutting tool (20, 100, 300) comprising the following: an elongated body arranged around a longitudinal axis (AA), wherein the longitudinal body includes a spiral groove (32) and a cutting tip (22) made of polycrystalline diamond, the cutting tip (22) comprising: Cutting edges (30) extending radially outwards to an edge (39) on an external radial circumference of a side wall (49) of the rotary cutting tool (20); an inner section (50) with an inner apex angle (γ); and an outer section (52) with an outer tip angle (Γ), wherein the inner tip angle (γ) is in the range between 110 degrees and 140 degrees and the outer tip angle (Γ) is in the range between 145 degrees and 180 degrees and the inner section (50) projects axially beyond the outer section. [2] Rotary cutting tool (20, 100, 300) according to claim 1, wherein the elongated body is formed from a carbide material. [3] Rotary cutting tool (300) according to claim 1 or 2, wherein the elongated body comprises: a first end opposite the cutting tip (22); and at least two coolant passages (308, 312) passing through there, each coolant passage (308, 312) extending from the first end to the cutting tip (22). [4] Rotary cutting tool (300) according to claim 3, wherein each coolant passage (308, 312) is of a generally spiral shape. [5] Rotary cutting tool (300) according to claim 3 or claim 4, wherein the two coolant passages (308, 312) run continuously separate from each other. [6] Cutting tip (22) made of polycrystalline diamond for use with a rotary cutting tool (20, 100, 300), wherein the cutting tip (22) comprises: Cutting edges (30) extending radially outwards to an edge (39) on an external radial circumference of a side wall (49) of the rotary cutting tool (20); an inner section (50) with an inner apex angle (γ); and an outer section (52) with an outer tip angle (Γ), wherein the inner tip angle (γ) is in the range between 110 degrees and 140 degrees and the outer tip angle (Γ) is in the range between 145 degrees and 180 degrees and the inner section (50) projects axially beyond the outer section (52). [7] Cutting tip (22) according to claim 6, characterized by , that at least two continuously separate coolant passages (308, 312) are provided. [8] Method for forming a rotary cutting tool (300) with a cutting tip (22) made of polycrystalline diamond, the method comprising: Forming at least two axially extending coolant passages (312) in a generally cylindrical tool body (302); Forming at least two coolant passages (308) in a tip section (304), wherein the tip section (304) is separated from the tool body (302) and the coolant passages extend from a rear side of the tip section to the cutting tip of the tip section; and Coupling the tip section (304) to the tool body (302) to form the turning cutting tool (300), wherein the coolant passages of the tip section are aligned with the coolant passages of the tool body so that axially continuous coolant passages are obtained, the top section (304) comprises the following: Cutting edges (30) extending radially outwards to an edge (39) on an external radial circumference of a side wall (49) of the rotary cutting tool (20); an inner section (50) with an inner apex angle (γ); and an outer section (52) with an outer tip angle (Γ), wherein the inner tip angle (γ) is in the range between 110 degrees and 140 degrees and the outer tip angle (Γ) is in the range between 145 degrees and 180 degrees and the inner section (50) projects axially beyond the outer section (52). [9] Method according to claim 8, wherein the tip section (304) is coupled to the tool body (302) via a brazing process. [10] Method according to claim 8 or claim 9, wherein the at least two coolant passages (312) are formed by an extrusion process in the generally cylindrical tool body (302). [11] Method according to any one of claims 8 to 10, wherein the at least two passages (308) are formed in the tip section (304) via an EDM drilling process.