Rotatable cutting head having a tip portion with three radially extending cutting edges forming a straight rotational profile

Abstract

A cutting head (20) rotatable about a central axis (A1) includes a tip portion (22) and an intermediate portion (24). The tip portion (22) has an axially forward-most tip point (NT) contained in the central axis (A1), and three axially forward-facing front surfaces (26) forming three lateral edges (28) extending axially rearward away from the tip point (NT), each front surface (26) having a radially extending cutting edge including a minor cutting edge portion (32) extending radially outward from one of the lateral edges (28), and a major cutting edge portion (34) extending radially outward from the minor cutting edge portion (32). Each major cutting edge portion (34) is contained in an imaginary annular ring surface having an annular ring width spanning at least its radially inner and outer endpoints. In a front end view of the cutting head, each major cutting edge portion (34) is concave, and a radial plane intersects the imaginary annular surface to form an imaginary straight line each having a length equal to the annular ring width.

Description

Technical Field

[0001] The present invention relates to a rotatable cutting head having an end portion with three radially extending cutting edges, generally for use in metal cutting processes, and particularly for drilling operations. Background Technology

[0002] Within the field of cutting tools used in drilling operations, there are numerous examples of rotatable cutting heads with radially extending cutting edges whose cutting edge portions form an approximately straight rotational profile.

[0003] US7,832,966 discloses a spiral drill configuration that allows machining of a substantially flat bottom hole. At the cutting end of the body component, there are two cutting edges symmetrically oriented on opposite sides of the drill's axis of rotation. In an embodiment, a first cutting edge portion and a second cutting edge portion form a continuous surface providing strength and tool stability. The height of the second portion of each of the cutting edges remains relatively consistent in the horizontal direction for forming a substantially flat bottom hole. In an embodiment, the center point is defined by two inclined peak surfaces. A central chisel edge is formed by the intersection of the two inclined peak surfaces. A first cutting edge section extends from the chisel edge to the second cutting edge section. The first cutting edge section for the two cutting edges is formed by symmetrically thinning the bi-peaked surfaces. The stress at the center portion of the spiral cutting tool is limited by the chisel edge and the first section of the cutting edge near the center portion, which has a balanced geometry. The balanced geometry of the spiral drill also prevents drill wobbling and deviations in the formed hole. The chisel edge may be combined with a first curved cutting edge, and the first curved cutting edge may also have a positive rake angle to facilitate cutting.

[0004] US2019 / 262910A1 discloses a drill comprising a plurality of cutting edges extending to a cutting edge, wherein adjacent cutting edges are separated by grooves, the grooves comprising a base profile arranged in a generally helical configuration along a central axis of the drill body. The drill also includes a plurality of profiled drill tips, each having a linear portion extending toward the outer diameter of the drill body and an arcuate portion extending from the linear portion toward the chisel edge of the drill body. The drill further includes a plurality of slit profiles positioned within the plurality of grooves. The slit profiles extend from the chisel edge of the drill body and are inclined with respect to the base profiles of the grooves.

[0005] The object of the present invention is to provide an improved rotatable cutting head having three radially extending cutting edges whose cutting edge portions are configured to form a rotational profile that is truly straight.

[0006] Another object of the present invention is to provide an improved rotatable cutting head having three circumferentially spaced chip removal passages, wherein the head recess is configured to maximize the volume of the chip removal passages.

[0007] Another object of the present invention is to provide an improved rotatable cutting head capable of machining an almost flat shoulder surface between two coaxial through holes of different diameters. Summary of the Invention

[0008] According to the present invention, a cutting head capable of rotating about a central axis in a rotational direction is provided, the central axis defining a front-to-back axial direction, and the cutting head comprises:

[0009] The end portion has an axially foremost end point contained in the central axis, and three axially forward-facing front surfaces forming three transverse blades extending axially rearward away from the end point.

[0010] Each front surface has a radially extending cutting edge, comprising a secondary cutting edge portion extending radially outward from one of the transverse cutting edges, and a primary cutting edge portion extending radially outward directly from or via a transition cutting edge portion; and

[0011] Each front surface further includes a main clearance surface adjacent to its corresponding main cutting edge portion, and

[0012] The middle section has three cutting edge bands that alternate circumferentially with three chip discharge passages. Each cutting edge band has a leading edge extending axially rearward from the end portion, and each chip discharge passage has a head groove extending axially rearward from the end portion and intersecting one of the leading edges.

[0013] in:

[0014] Each main cutting edge portion has a radially inner main endpoint and a radially outer main endpoint, as well as a main midpoint between the radially inner main endpoint and the radially outer main endpoint. The three radially outer main endpoints define a first imaginary circle with a first diameter, the three main midpoints define a second imaginary circle with a second diameter, and the three radially inner main endpoints define a third imaginary circle with a third diameter.

[0015] The radially outer principal endpoint, principal midpoint, and radially inner principal endpoint of one of the main cutting edge portions are respectively contained in a first imaginary radial plane, a second imaginary radial plane, and a third imaginary radial plane, each of the first imaginary radial plane, the second imaginary radial plane, and the third imaginary radial plane containing a central axis.

[0016] Each main cutting edge portion is contained within a first imaginary annular ring surface, the first imaginary annular ring surface having a first annular ring width spanning at least the radially inner main endpoint and the radially outer main endpoint, and

[0017] In the front view of the cutting head, each main cutting edge is concave.

[0018] And among them:

[0019] The first, second, and third imaginary radial planes intersect the surface of the first imaginary annular ring to form the first, second, and third imaginary straight lines, respectively, each having a length equal to the width of the first annular ring. Attached Figure Description

[0020] For better understanding, the invention will now be described by way of example only with reference to the accompanying drawings, in which dashed lines denote cutoff boundaries for partial views of components, and in which:

[0021] Figure 1 This is a perspective view of the cutting head according to the present invention;

[0022] Figure 2 yes Figure 1 The top view of the cutting head shown in the image;

[0023] Figure 3 yes Figure 1 The side view of the cutting head shown in the image;

[0024] Figure 4 yes Figure 2 The cross-sectional view shown is taken along line IV-IV by the cutting head;

[0025] Figure 5 yes Figure 2 The cross-sectional view shown is taken along line VV by the cutting head;

[0026] Figure 6 yes Figure 2 The cross-sectional view shown is taken along line VI-VI of the cutting head;

[0027] Figure 7 yes Figure 2 The cross-sectional view taken along line VII-VII by the cutting head is shown in the figure;

[0028] Figure 8 yes Figure 2 The cross-sectional view shown is taken along line VIII-VIII by the cutting head;

[0029] Figure 9 yes Figure 2 The cross-sectional view shown is taken along line IX-IX by the cutting head;

[0030] Figure 10 It is viewed along an imaginary tilted plane. Figure 1 The top view of the cutting head shown in the image;

[0031] Figure 11 yes Figure 10 The side view of the cutting head shown in the image;

[0032] Figure 12 yes Figure 11 A detailed view of a portion of the cutting head is shown in the image;

[0033] Figure 13 yes Figure 10 The cross-sectional view shown is taken along line XIII-XIII by the cutting head;

[0034] Figure 14 yes Figure 13 A detailed view of a portion of the cutting head is shown in the image;

[0035] Figure 15 yes Figure 2 The cross-sectional view shown is taken along line XV-XV by the cutting head;

[0036] Figure 16 yes Figure 2 The cross-sectional view shown is taken along line XVI-XVI of the cutting head;

[0037] Figure 17 This is a perspective view of a rotary cutting tool according to the present invention; and

[0038] Figure 18 yes Figure 17 An exploded view of a rotary cutting tool is shown in the image. Detailed Implementation

[0039] First, pay attention Figures 1 to 3 The image shows a cutting head 20 capable of rotating about a central axis A1 in the direction of rotation RD, which includes an end portion 22 and a middle portion 24.

[0040] The central axis A1 defines the front-to-back axial directions DF and DR.

[0041] In some embodiments of the invention, the cutting head 20 may be made by shape pressing and sintering a cemented carbide (such as tungsten carbide) and may be coated or uncoated.

[0042] like Figures 1 to 3 As shown, the end portion 22 has an axially foremost end point NT contained in the central axis A1 and three axially forward-facing front surfaces 26 forming three transverse blades 28 extending axially backward away from the end point NT.

[0043] like Figure 2 As shown, each front surface 26 has a radially extending cutting edge 30, which includes a secondary cutting edge portion 32 extending axially rearward and radially outward from one of the transverse cutting edges 28, and a main cutting edge portion 34 extending radially outward directly from said secondary cutting edge portion 32 or via a transition cutting edge portion 36.

[0044] It should be recognized that providing three radially extending cutting edges 30 to the cutting head 20, compared to, for example, two radially extending cutting edges, enables the cutting head 20 to perform drilling operations at a higher feed rate.

[0045] In some embodiments of the invention, the cutting head 20 may exhibit triple rotational symmetry about the central axis A1.

[0046] Each front surface 26 includes a primary clearance surface 38 adjacent to its corresponding primary cutting edge portion 34 and a secondary clearance surface 40 adjacent to its corresponding secondary cutting edge portion 32.

[0047] like Figures 1 to 3 As shown, the middle portion 24 has three head blades 42 that alternate circumferentially with three chip discharge passages 44, each head blade 42 having a leading edge 46 extending axially rearward from the end portion 22, and each chip discharge passage 44 having a head groove 48 extending axially rearward from the end portion 22 and intersecting one of the leading edges 46.

[0048] In some embodiments of the invention, each main cutting edge portion 34 may be formed at the intersection of one of the head grooves 48 and one of the main clearance surfaces 38.

[0049] like Figure 2 As shown, the three leading edges 46 can define the cutting diameter DC.

[0050] In some embodiments of the invention, each leading edge 46 may extend in the opposite direction of rotation RD as it extends axially rearward from the end portion 22.

[0051] Moreover, in some embodiments of the invention, each leading edge 46 may extend helically along the central axis A1.

[0052] like Figures 1 to 3 As shown, each head blade 42 may include a radially outwardly oriented edge surface 50 intersecting its leading edge 46.

[0053] In some embodiments of the invention, each edge surface 50 may extend helically along the central axis A1.

[0054] Furthermore, in some embodiments of the invention, each edge surface 50 may be spaced apart from one of the front surfaces 26 by an edge chamfer 52.

[0055] Furthermore, in some embodiments of the invention, the cutting diameter DC can be measured immediately axially behind the three chamfered edges 52.

[0056] Throughout the specification and claims, it should be appreciated that the three leading edges 46 may undergo a slight axial taper in the rearward axial direction DR, such that the cutting diameter DC is reduced by up to 0.01 mm along the length of the three leading edges 46.

[0057] like Figures 1 to 3 As shown, each main cutting edge portion 34 has a radially inner main endpoint NIP and a radially outer main endpoint NOP.

[0058] Moreover, such as Figures 1 to 3 As shown, each main cutting edge portion 34 has a main midpoint NMP located between its radially inner main endpoint NIP and radially outer main endpoint NOP.

[0059] like Figure 2 As shown, the three radially outer principal endpoints NOP define a first imaginary circle C1 with a first diameter D1, the three principal midpoints NMP define a second imaginary circle C2 with a second diameter D2, and the three radially inner principal endpoints NOP define a third imaginary circle C3 with a third diameter D3.

[0060] In some embodiments of the present invention, the difference between the first diameter D1 and the third diameter D3 may be greater than 35 percent of the cutting diameter DC, that is, D1-D3>0.35*DC.

[0061] In some embodiments of the present invention, the first diameter D1 may be greater than 90% of the cutting diameter DC, that is, D1>0.90*DC.

[0062] Moreover, in some embodiments of the present invention, the first diameter D1 may be smaller than the cutting diameter DC.

[0063] like Figure 2 As shown in the front view of the cutting head 20, each main cutting edge portion 34 is concave, that is, each main cutting edge portion 34 has a concave shape.

[0064] In some embodiments of the invention, each master midpoint NMP may be located behind the rotational direction of its corresponding radially inner master endpoint NIP and radially outer master endpoint NOP.

[0065] Throughout the specification and claims, it should be understood that the position of a point "behind" or "in front of" another point along the same cutting edge 30 is considered to be with respect to the rotation direction RD and within the rotation range of the cutting edge 30.

[0066] like Figure 2As shown, the radially outer main endpoint NOP, the main midpoint NMP, and the radially inner main endpoint NIP of one of the main cutting edge portions 34 are respectively contained in the first imaginary radial plane PR1, the second imaginary radial plane PR2, and the third imaginary radial plane PR3, and each of the first imaginary radial plane PR1, the second imaginary radial plane PR2, and the third imaginary radial plane PR3 contains a central axis A1.

[0067] In some embodiments of the present invention, the second imaginary radial plane PR2 may be positioned behind the rotational direction of the first imaginary radial plane PR1 and the third imaginary radial plane PR3.

[0068] Furthermore, in some embodiments of the present invention, the third imaginary radial plane PR3 may be positioned in front of the first imaginary radial plane PR1 in the direction of rotation.

[0069] Throughout the specification and claims, it should be appreciated that the position of the imaginary radial plane "behind" or "in front of" another imaginary radial plane associated with the same cutting edge 30 is considered to be with respect to the rotation direction RD and within the rotation range of the cutting edge 30.

[0070] In some embodiments of the present invention, the second imaginary radial plane PR2 and the third imaginary radial plane PR3 may form an acute hook angle θ of at least 10 degrees, that is, θ≥10°.

[0071] For embodiments of the invention in which each of the main cutting edge portions 34 is concave in the front view of the cutting head 20, and the second imaginary radial plane PR2 and the third imaginary radial plane PR3 form an acute hook angle θ of at least 10 degrees, it should be appreciated that each head recess 48 is advantageously configured to maximize the volume of its associated chip removal passage 44 and provide sufficient space for smooth and efficient chip removal, which can be limited by the cutting head 20 having more than two circumferentially spaced chip removal passages 44.

[0072] like Figure 2 As shown in the front view of the cutting head 20, each secondary cutting edge portion 32 may be straight.

[0073] In some embodiments of the invention, each secondary cutting edge portion 32 may extend rearward in a rotatable manner as it extends radially outward.

[0074] Moreover, in some embodiments of the invention, each secondary cutting edge portion 32 may extend rearward in a continuously rotating manner as it extends radially outward along its entire length.

[0075] In embodiments of the invention where the secondary cutting edge portion 32 and the primary cutting edge portion 34 of each cutting edge 30 are separated by a transition cutting edge portion 36, such as... Figure 2 As shown in the front view of the cutting head 20, each transition cutting edge portion 36 may be convex, that is, each transition cutting edge portion 36 may have a convex shape.

[0076] like Figures 1 to 3 As shown, each main cutting edge portion 34 is contained in a first imaginary annular ring surface SA1, which has a first annular ring width WA1 that spans at least the radially inner main endpoint NIP and the radially outer main endpoint NOP.

[0077] According to the present invention, such as Figures 4 to 6 As shown, the first imaginary radial plane PR1, the second imaginary radial plane PR2, and the third imaginary radial plane PR3 intersect with the first imaginary annular surface SA1 to form the first imaginary straight line LR1, the second imaginary straight line LR2, and the third imaginary straight line LR3, respectively, all of which have a length equal to the width WA1 of the first annular ring.

[0078] It should be recognized that any imaginary radial plane containing the central axis A1 may intersect the first imaginary annular ring surface SA1 to form an imaginary straight line with a length equal to the width WA1 of the first annular ring.

[0079] It should also be recognized that the first imaginary annular surface SA1 exhibits circular symmetry about the central axis A1, that is, the first imaginary annular surface SA1 has rotational symmetry of infinite order.

[0080] It should also be recognized that the first imaginary line LR1, the second imaginary line LR2 and the third imaginary line LR3 all have high straightness, and the three main cutting edge portions 34 are constructed to form a true straight-line rotation profile.

[0081] like Figures 7 to 9 As shown, in the cross sections taken from the first transverse plane PT1, the second transverse plane PT2, and the third transverse plane PT3, which are perpendicular to the first imaginary radial plane PR1, the second imaginary radial plane PR2, and the third imaginary radial plane PR3 respectively and contain the associated main cutting edge portion 34, adjacent main clearance surfaces 38 form a first acute clearance angle α1, a second acute clearance angle α2, and a third acute clearance angle α3 relative to the first imaginary horizontal reference line HL1, the second imaginary horizontal reference line HL2, and the third imaginary horizontal reference line HL3, which are perpendicular to the central axis A1.

[0082] In some embodiments of the present invention, the first transverse plane PT1, the second transverse plane PT2, and the third transverse plane PT3 may be perpendicular to the first imaginary line LR1, the second imaginary line LR2, and the third imaginary line LR3, respectively.

[0083] Although in the specific construction where the first imaginary line LR1, the second imaginary line LR2, and the third imaginary line LR3 are perpendicular to the central axis A1 (not shown), the first transverse plane PT1, the second transverse plane PT2, and the third transverse plane PT3 may only be parallel to the central axis A1, it should be understood that, for convenience, Figure 2 The first transverse plane PT1, the second transverse plane PT2, and the third transverse plane PT3, which are parallel to the central axis A1, are shown.

[0084] Throughout the specification and claims, it should be appreciated that at any section taken in a transverse plane intersecting one of the main cutting edge portions 34, the adjacent main clearance surface 38 extends axially rearward as it extends away from the main cutting edge portion 34.

[0085] In some embodiments of the present invention, the first acute gap angle α1, the second acute gap angle α2 and the third acute gap angle α3 may be equal, that is, α1=α2=α3.

[0086] It should be recognized that the first acute clearance angle α1, the second acute clearance angle α2, and the third acute clearance angle α3 may have an accuracy that is one degree greater or smaller than the nominal value.

[0087] It should also be recognized that setting the first acute clearance angle α1, the second acute clearance angle α2, and the third acute clearance angle α3 to be equal can advantageously improve the uniform wear distribution along the main cutting edge portion 34.

[0088] In some embodiments of the present invention, the first gap angle α1, the second gap angle α2 and the third gap angle α3 may each have a minimum nominal value of 5 degrees and a maximum nominal value of 12 degrees, that is, 5°≤α1, α2, α3≤12°.

[0089] In the present embodiment of the invention, the first acute gap angle α1, the second acute gap angle α2 and the third acute gap angle α3 have a nominal value of 8°.

[0090] like Figure 8 As shown, the imaginary inclined plane PI containing the second imaginary straight line LR2 forms an inclined angle π with the second imaginary radial plane PR2 and intersects with the main gap surface 38 of the corresponding front surface 26.

[0091] In some embodiments of the present invention, the tilt angle π may be equal to the second acute clearance angle α2.

[0092] For an embodiment of the present invention where the tilt angle π is equal to the second acute gap angle α2, such as Figure 8 As shown in the diagram, it should be recognized that the hypothetical inclined plane PI, near the principal midpoint NMP, forms a right angle with the principal gap surface 38.

[0093] In some embodiments of the invention, the hypothetical inclined plane PI may intersect with the secondary clearance surface 40 of the corresponding front surface 26.

[0094] Figure 10 A top view of the cutting head 20 as seen along the imaginary inclined plane PI is shown.

[0095] like Figure 11 and Figure 12 As shown in the view perpendicular to the imaginary inclined plane PI, the radially outer main endpoint NOP and the radially inner main endpoint NIP of the associated main cutting edge portion 34 are spaced apart from the second imaginary straight line LR2.

[0096] It should be recognized that, such as Figure 11 and Figure 12 As shown, the main midpoint NMP of the associated main cutting edge portion 34 is located on the second imaginary straight line LR2.

[0097] In some embodiments of the present invention, such as Figure 11 and Figure 12 As shown, the radially outer main endpoint NOP and the radially inner main endpoint NIP of the associated main cutting edge portion 34 may be located on the same side of the second imaginary straight line LR2.

[0098] Moreover, in some embodiments of the present invention, such as Figure 11 and Figure 12 As shown, in a view perpendicular to the imaginary inclined plane PI, the radially inner main endpoint NIP can be separated from the second imaginary straight line LR2 by a correction height HC, and the correction height HC can be greater than one percent of the difference between the second diameter D2 and the third diameter D3, i.e., HC>0.01*(D2-D3).

[0099] It should be recognized that, for embodiments of the invention in which the hook angle θ and / or the second clearance angle α2 are increased, the correction height HC may be increased.

[0100] like Figure 13 and Figure 14 As shown, in the cross section taken in the imaginary inclined plane PI, the main gap surface 38 can be convex, that is, the main gap surface 38 can have a convex shape.

[0101] In an embodiment of the invention in which each primary gap surface 38 is convex in a cross section taken in the imaginary inclined plane PI, and the first imaginary straight line LR1, the second imaginary straight line LR2 and the third imaginary straight line LR3 all have high straightness, it should be recognized that each primary gap surface 38 can be produced by means of a very precise manufacturing method and has a complex radial range.

[0102] In some embodiments of the invention, each primary clearance surface 38 may be produced by a grinding process.

[0103] like Figures 4 to 6 As shown, in the cross-sections taken from the first imaginary radial plane PR1, the second imaginary radial plane PR2, and the third imaginary radial plane PR3, the first imaginary line LR1, the second imaginary line LR2, and the third imaginary line LR3 can all form an acute or right-angled internal cutting angle φ relative to the central axis A1.

[0104] It should be recognized that the first imaginary line LR1, the second imaginary line LR2, and the third imaginary line LR3 can all form the same acute or right angle internal cutting angle φ relative to the central axis A1. For embodiments of the invention where the cutting angle φ is acute, it should be recognized that the first imaginary annular surface SA1 can define a 3D truncated cone shape, and for embodiments of the invention where the cutting angle φ is right, it should be recognized that the first imaginary annular surface SA1 can define a 2D annular disk shape.

[0105] It should also be recognized that the term "internal cutting angle" is used throughout the specification and claims to refer to the angle formed between the first imaginary line LR1, the second imaginary line LR2 and the third imaginary line LR3 and the portion of the central axis A1 extending through the middle portion 24 of the cutting head.

[0106] In an embodiment of the invention where the cutting angle φ is an acute angle, such that each main cutting edge portion 34 has at least a minimum inclination relative to a first horizontal plane PH1 perpendicular to the central axis A1 and intersecting with the end portion 22, it should be recognized that the axial cutting force acting on at least three main cutting edge portions 34 during the initial contact with the workpiece during drilling operations will gradually spread along the at least three main cutting edge portions 34.

[0107] In some embodiments of the present invention, such as Figures 4 to 6 As shown, the cutting angle φ can be greater than 88 degrees, that is, 88°≤φ≤90°.

[0108] It should be recognized that the cutting angle φ can have an accuracy greater than or less than half a degree of the nominal value.

[0109] In the present embodiment of the invention, the cutting angle φ has a nominal value of 89.5°.

[0110] In embodiments of the invention where the cutting angle φ is greater than 88 degrees, it should be appreciated that at least three main cutting edge portions 34 can be configured to form a nearly flat rotary cutting profile, and the chip head 20 can be advantageously used in drilling operations to machine a nearly flat shoulder surface (not shown) between two coaxial through holes of different diameters.

[0111] In other embodiments of the invention (not shown), the cutting angle φ can be exactly ninety degrees, that is, φ = 90°.

[0112] In embodiments of the invention where the cutting angle φ is exactly ninety degrees, it should be recognized that at least three main cutting edge portions 34 can be configured to form a truly flat rotary cutting profile.

[0113] like Figures 1 to 3 As shown, each secondary cutting edge portion 32 has a secondary midpoint NMS located midway along its length.

[0114] like Figure 2 As shown, the three secondary midpoints NMS define a fourth imaginary circle C4 with a fourth diameter D4.

[0115] In some embodiments of the present invention, the difference between the first diameter D1 and the fourth diameter D4 may be greater than 50% of the cutting diameter DC, that is, D1-D4>0.50*DC.

[0116] like Figure 2 As shown, the secondary midpoint NMS of one of the main cutting edge portions 34 is contained in the fourth imaginary radial plane PR4, and the fourth imaginary radial plane PR4 contains the central axis A1.

[0117] like Figures 1 to 3 As shown, the combined cutting edge portion 54 of each cutting edge 30 extending from the radially outer main endpoint NOP to the secondary midpoint NMS may be contained in the first imaginary annular surface SA1.

[0118] In an embodiment of the invention where each combined cutting edge portion 54 is contained in the first imaginary annular ring surface SA1, and the difference between the first diameter D1 and the fourth diameter D4 is greater than fifty percent of the cutting diameter DC, it should be recognized that the width of the first annular ring WA1 may be greater than fifty percent of half of the cutting diameter DC, i.e., WA1>0.50*DC / 2.

[0119] like Figure 15 As shown, the fourth imaginary radial plane PR4 intersects the first imaginary annular surface SA1 to form a fourth imaginary straight line LR4 with a length equal to the width WA1 of the first annular ring.

[0120] like Figure 1As shown in Figure 5, in the section taken from the fourth imaginary radial plane PR4, the fourth imaginary straight line LR4 can form an acute or right-angled internal cutting angle φ relative to the central axis A1.

[0121] In some embodiments of the present invention, it should be understood that the first imaginary line LR1, the second imaginary line LR2, the third imaginary line LR3, and the fourth imaginary line LR4 can all form the same acute or right-angled inner cutting angle φ relative to the central axis A1.

[0122] In some embodiments of the invention, the secondary midpoint NMS may be located in front of the radially inner primary endpoint NIP of its associated primary cutting edge portion 34 in the direction of rotation.

[0123] like Figure 2 As shown, each secondary cutting edge portion 32 can extend axially forward as it extends radially inward from its secondary midpoint NMS.

[0124] In some embodiments of the present invention, such as Figures 1 to 3 As shown, each secondary cutting edge portion 32 may include a peak cutting edge sub-portion 56 located radially inside its secondary midpoint NMS, and the peak cutting edge portion 56 may form an acute entry angle λ relative to a second horizontal plane PH2 that is perpendicular to the central axis A1 and intersects with the end portion 22.

[0125] Moreover, in some embodiments of the present invention, such as Figure 3 As shown, the entry angle λ can be at least 15 degrees and at most 30 degrees, that is, 15°≤λ≤30°.

[0126] Furthermore, in some embodiments of the present invention, the first horizontal plane PH1 and the second horizontal plane PH2 may be coplanar.

[0127] It should be recognized that the three-peak cutting edge portion 56 may be contained in a second imaginary annular ring surface (not shown), which, compared to the first imaginary annular ring surface SA1, may not form an imaginary straight line when intersecting with the radial plane.

[0128] It should also be recognized that a portion of each secondary clearance surface 40 of the adjacent associated peak cutting edge portion 56 may not have a complex radial range.

[0129] like Figures 1 to 3 As shown, the main rake surface 58 may be disposed on each head recess 48 adjacent to the associated main cutting edge portion 34.

[0130] In some embodiments of the present invention, a plurality of main front blade surfaces 58 may be oriented toward the rotation direction RD.

[0131] like Figures 7 to 9As shown, in the cross sections taken from the first transverse plane PT1, the second transverse plane PT2, and the third transverse plane PT3, the main rake surface 58 is inclined with a first axial rake angle β1, a second axial rake angle β2, and a third axial rake angle β3 relative to the first imaginary radial plane PR1, the second imaginary radial plane PR2, and the third imaginary radial plane PR3, respectively.

[0132] In some embodiments of the present invention, each of the first axial rake angle β1, the second axial rake angle β2, and the third axial rake angle β3 may be positive.

[0133] Throughout the specification and claims, it should be appreciated that the first axial rake angle β1, the second axial rake angle β2, and the third axial rake angle β3 are positive in a configuration in which the corresponding portions of the main rake surface 58 extend rearward in a rotational manner as they extend away from the associated main cutting edge portion 34.

[0134] It should also be recognized that the main cutting edge portion 34 is more susceptible to wear than the secondary cutting edge portion 32 due to its relatively higher cutting speed, and that configuring the first axial rake angle β1, the second axial rake angle β1 and the third axial rake angle β3 as positive reduces wear on the main cutting edge portion 34, thus extending its service life.

[0135] like Figure 16 As shown, in the section taken from the fourth imaginary transverse plane PT4, which is perpendicular to the fourth imaginary radial plane PR4 and includes the associated secondary cutting edge portion 32 midpoint NMS, the adjacent secondary clearance surfaces 40 form a fourth acute clearance angle α4 relative to the fourth imaginary horizontal reference line HL4, which is perpendicular to the central axis A1.

[0136] In some embodiments of the present invention, the fourth imaginary transverse plane PT4 may be perpendicular to the fourth imaginary line LR4, but for convenience, Figure 2 The fourth imaginary transverse plane PT4 is shown, which is parallel to the central axis A1.

[0137] Throughout the specification and claims, it should be appreciated that at any section taken in a transverse plane parallel to the central axis A1 and intersecting one of the secondary cutting edge portions 32, the secondary clearance surface 40 extends axially rearward as it extends away from the primary cutting edge portion 34.

[0138] In some embodiments of the present invention, the fourth acute gap angle α4 may be equal to the first acute gap angle α1, the second acute gap angle α2 and the third acute gap angle α3.

[0139] like Figures 1 to 3 As shown, each chip discharge passage 44 may have a cut 60 extending axially rearward from the end portion 22 and intersecting one of the head grooves 48.

[0140] In some embodiments of the invention, each secondary cutting edge portion 32 may be formed at the intersection of one of the cuts 60 and one of the secondary clearance surfaces 40.

[0141] like Figures 1 to 3 As shown, the secondary front cutting edge surface 62 may be disposed adjacent to the associated secondary cutting edge portion 32 on each cut 60.

[0142] In some embodiments of the present invention, a plurality of secondary front blade surfaces 62 may be oriented toward the rotation direction RD.

[0143] like Figure 16 As shown in the figure, in the cross section taken in the fourth imaginary transverse plane PT4, the secondary front cutter surface 62 is inclined relative to the fourth imaginary radial plane PR4 at the fourth axial front cutter angle β4.

[0144] In some embodiments of the present invention, the fourth axial rake angle β4 may be negative.

[0145] Furthermore, in some embodiments of the present invention, the negative fourth axial rake angle β4 may be greater than 4 degrees.

[0146] Throughout the specification and claims, it should be recognized that in a configuration where the corresponding portion of the secondary rake surface 62 extends forward in a rotational manner as it extends away from the secondary cutting edge portion 32, the fourth axial rake angle β4 is negative.

[0147] It should also be recognized that the secondary cutting edge portion 32 is more susceptible to greater impact forces than the primary cutting edge portion 34 due to their relatively lower cutting speed, especially at high feed rates, and that constructing the fourth axial rake angle β4 as negative increases the stability and robustness of the secondary cutting edge portion 32, thus extending its service life.

[0148] In an embodiment of the invention where the first diameter D1 is smaller than the cutting diameter DC, each cutting edge 30 may include a third cutting edge portion 64 extending radially outward from the radially outer main endpoint NOP of its main cutting edge portion 34.

[0149] like Figure 2 As shown in the front view of the cutting head 20, each third cutting edge portion 64 may be convex, that is, each third cutting edge portion 64 may have a convex shape.

[0150] In some embodiments of the invention, each third cutting edge portion 64 may be included in the first imaginary annular surface SA1.

[0151] like Figures 1 to 3As shown, each third cutting edge portion 64 has a radially inner third endpoint NIT and a radially outer third endpoint NOT.

[0152] In some embodiments of the invention, the radially inner third endpoint NIT of each third cutting edge portion 64 may coincide with the radially outer main endpoint NOP of the associated main cutting edge portion 34.

[0153] like Figure 2 As shown in the front view of the cutting head 20, a first imaginary line L1, which is tangent to one of the third cutting edge portions 64 and adjacent to its radially outer third endpoint NOT, can form a negative radial rake angle δ relative to a second imaginary line L2 that includes the radially outer third endpoint NOT and intersects the central axis A1.

[0154] Throughout the specification and claims, it should be recognized that in the configuration where the first imaginary straight line L1 extends backward in a radially outward manner from the third cutting edge portion 64, the radial rake angle δ is negative.

[0155] Now pay attention Figure 17 and Figure 18 The diagram shows a rotary cutting tool 66 according to the invention, which includes a cutting head 20 and a shank 68 having a longitudinal axis AL.

[0156] The handle 68 has three handle grooves 70 that alternate circumferentially with the three handle blades 72, and each handle groove 70 can extend spirally along the longitudinal axis AL.

[0157] like Figure 17 and Figure 18 As shown, the cutting head 20 may have an axially rearward-facing bottom surface 74, the shank 68 may have a support surface 76 transverse to the longitudinal axis AL, and the cutting head 20 may be removably mounted on the shank 68, wherein the bottom surface 74 contacts the support surface 76.

[0158] The cutting head 20 is configured to be removably mounted on the shank 68 such that the cutting head 20 can be made of a material of suitable hardness (such as tungsten carbide), and the shank 68 can be made of a material of lower hardness and lower cost (such as high-speed steel). After the worn or damaged cutting head 20 is disposed of, the shank 68 can be reused.

[0159] In some embodiments of the invention, each head recess 48 may intersect with the bottom surface 74 and cooperate with one of the handle recesses 70.

[0160] Furthermore, in some embodiments of the present invention, the bottom surface 74 may be perpendicular to the central axis A1, the support surface 76 may be perpendicular to the longitudinal axis AL, and the central axis A1 may be coaxial with the longitudinal axis AL.

[0161] like Figure 17 and Figure 1 As shown in Figure 8, the intermediate portion 24 of the cutting head 20 may include three torque transmission surfaces 78 facing opposite to the rotation direction RD, and the shank 68 may include three drive protrusions 80, wherein each drive protrusion 80 has a drive surface 82 facing the rotation direction RD, and each torque transmission surface 78 may contact one of the drive surfaces 82.

[0162] In some embodiments of the invention, each torque transmission surface 78 may intersect with one of the front surfaces 26.

[0163] like Figure 17 and Figure 18 As shown, the cutting head 20 may include a mounting protrusion 84 extending axially rearward from the bottom surface 74.

[0164] In other embodiments of the invention (not shown), the cutting head 20 and the shank 68 may be integral parts of a one-piece construction (e.g., a solid drill), and each head recess 48 may be merged with one of the shank recesses 70.

[0165] Although the invention has been described with a certain degree of specificity, it should be understood that various modifications and alterations may be made without departing from the spirit or scope of the invention as claimed below.

Claims

1. A cutting head (20) capable of rotating about a central axis (A1) in a rotational direction (RD), said central axis (A1) defining a front-rear axial direction (DF, DR), and said cutting head (20) comprising: The end portion (22) has an axially foremost end point (NT) contained in the central axis (A1), and three axially forward-facing front surfaces (26) forming three transverse blades (28) extending axially rearward away from the end point (NT). Each front surface (26) has a radially extending cutting edge (30), which includes a secondary cutting edge portion (32) extending radially outward from one of the transverse cutting edges (28), and a primary cutting edge portion (34) extending radially outward directly from the secondary cutting edge portion (32) or via a transition cutting edge portion (36); and Each front surface (26) further includes a main clearance surface (38) adjacent to its corresponding main cutting edge portion (34), and The middle portion (24) has three head blades (42) that alternate circumferentially with three chip discharge passages (44), each head blade (42) having a leading edge (46) extending axially rearward from the end portion (22), and each chip discharge passage (44) having a head groove (48) extending axially rearward from the end portion (22) and intersecting one of the leading edges (46). in: Each main cutting edge portion (34) has a radially inner main endpoint (NIP) and a radially outer main endpoint (NOP), and a main midpoint (NMP) between the radially inner main endpoint (NIP) and the radially outer main endpoint (NOP). The three radially outer main endpoints (NOP) define a first imaginary circle (C1) with a first diameter (D1), the three main midpoints (NMP) define a second imaginary circle (C2) with a second diameter (D2), and the three radially inner main endpoints (NIP) define a third imaginary circle (C3) with a third diameter (D3). The radially outer main endpoint (NOP), the main midpoint (NMP), and the radially inner main endpoint (NIP) of one of the main cutting edge portions (34) are respectively contained in a first imaginary radial plane (PR1), a second imaginary radial plane (PR2), and a third imaginary radial plane (PR3), each of the first imaginary radial plane (PR1), the second imaginary radial plane (PR2), and the third imaginary radial plane (PR3) containing the central axis (A1). Each main cutting edge portion (34) is contained in a first imaginary annular ring surface (SA1), the first imaginary annular ring surface (SA1) having a first annular ring width (WA1) that spans at least the radially inner main endpoint (NIP) and the radially outer main endpoint (NOP), and In the front view of the cutting head (20), each main cutting edge portion (34) is concave. And among them: The first imaginary radial plane (PR1), the second imaginary radial plane (PR2), and the third imaginary radial plane (PR3) intersect the first imaginary annular surface (SA1) to form the first imaginary straight line (LR1), the second imaginary straight line (LR2), and the third imaginary straight line (LR3), respectively, all of which have a length equal to the width of the first annular ring (WA1). in: In cross-sections taken from the first transverse plane (PT1), second transverse plane (PT2), and third transverse plane (PT3) of the radially outer main endpoint (NOP), the main midpoint (NMP), and the radially inner main endpoint (NIP) respectively, which are perpendicular to the first imaginary radial plane (PR1), the second imaginary radial plane (PR2), and the third imaginary radial plane (PR3) and contain the associated main cutting edge portion (34), adjacent main clearance surfaces (38) form a first acute clearance angle (α1), a second acute clearance angle (α2), and a third acute clearance angle (α3) respectively relative to the first imaginary horizontal reference line (HL1), the second imaginary horizontal reference line (HL2), and the third imaginary horizontal reference line (HL3) perpendicular to the central axis (A1). An imaginary inclined plane (PI) containing the second imaginary straight line (LR2) forms an inclination angle (π) with the second imaginary radial plane (PR2) and intersects the main gap surface (38) of the corresponding front surface (26). The tilt angle (π) is equal to the second acute gap angle (α2); In a view perpendicular to the imaginary inclined plane (PI), the radially outer main endpoint (NOP) and the radially inner main endpoint (NIP) of the associated main cutting edge portion (34) are spaced apart from the second imaginary line (LR2); and In a view perpendicular to the imaginary inclined plane (PI), the radially outer main endpoint (NOP) and the radially inner main endpoint (NIP) of the associated main cutting edge portion (34) are located on the same side of the second imaginary straight line (LR2).

2. The cutting head (20) according to claim 1, characterized in that: In the cross-sections taken from the first imaginary radial plane (PR1), the second imaginary radial plane (PR2), and the third imaginary radial plane (PR3), the first imaginary line (LR1), the second imaginary line (LR2), and the third imaginary line (LR3) all form an acute or right-angled internal cutting angle (φ) relative to the central axis (A1), and The internal cutting angle (φ) is greater than 88 degrees.

3. The cutting head (20) according to claim 2, characterized in that: In the cross-sections taken from the first imaginary radial plane (PR1), the second imaginary radial plane (PR2), and the third imaginary radial plane (PR3), the first imaginary line (LR1), the second imaginary line (LR2), and the third imaginary line (LR3) all form the same acute or right-angled inner cutting angle (φ) relative to the central axis (A1).

4. The cutting head (20) according to claim 1, characterized in that: The second imaginary radial plane (PR2) is positioned behind the rotational direction of the first imaginary radial plane (PR1) and the third imaginary radial plane (PR3).

5. The cutting head (20) according to claim 1, characterized in that: The second imaginary radial plane (PR2) and the third imaginary radial plane (PR3) form an acute hook angle (θ) of at least 10 degrees.

6. The cutting head (20) according to claim 1, characterized in that: In a view perpendicular to the imaginary tilt plane (PI), the radially inner main endpoint (NIP) is spaced apart from the second imaginary line (LR2) by a correction height (HC), and The corrected height (HC) is greater than one percent of the difference between the second diameter (D2) and the third diameter (D3).

7. The cutting head (20) according to claim 1, characterized in that: In the cross section taken in the imaginary inclined plane (PI), the main gap surface (38) is convex.

8. The cutting head (20) according to claim 1, characterized in that: The first acute gap angle (α1), the second acute gap angle (α2), and the third acute gap angle (α3) all have a minimum nominal value of 5 degrees and a maximum nominal value of 12 degrees.

9. The cutting head (20) according to claim 1, characterized in that: The first acute gap angle (α1), the second acute gap angle (α2), and the third acute gap angle (α3) are equal.

10. The cutting head (20) according to claim 1, characterized in that: Each main cutting edge portion (34) is formed at the intersection of one of the head grooves (48) and one of the main clearance surfaces (38). The main rake surface (58) adjacent to the associated main cutting edge portion (34) is disposed on each head groove (48). In the cross-sections taken from the first transverse plane (PT1), the second transverse plane (PT2), and the third transverse plane (PT3), the main rake surface (58) is inclined relative to the first imaginary radial plane (PR1), the second imaginary radial plane (PR2), and the third imaginary radial plane (PR3) with a first axial rake angle (β1), a second axial rake angle (β2), and a third axial rake angle (β3), respectively. Each of the first axial rake angle (β1), the second axial rake angle (β2), and the third axial rake angle (β3) is positive.

11. The cutting head (20) according to claim 9, characterized in that: Each secondary cutting edge portion (32) has a secondary midpoint (NMS) located midway along its length, and the three secondary midpoints (NMS) define a fourth imaginary circle (C4) with a fourth diameter (D4). The midpoint (NMS) of one of the secondary cutting edge portions (32) is contained within a fourth imaginary radial plane (PR4), and the fourth imaginary radial plane (PR4) contains the central axis (A1). The combined cutting edge portion (54) of each cutting edge (30) extending from the radially outer main endpoint (NOP) to the secondary midpoint (NMS) is contained in the first imaginary annular surface (SA1), and The fourth imaginary radial plane (PR4) intersects the first imaginary annular surface (SA1) to form a fourth imaginary straight line (LR4) with a length equal to the width of the first annular surface (WA1).

12. The cutting head (20) according to claim 11, characterized in that: Each front surface (26) has a secondary clearance surface (40) adjacent to its corresponding secondary cutting edge portion (32). In a cross-section taken in the fourth transverse plane (PT4) perpendicular to the fourth imaginary radial plane (PR4) and containing the associated secondary cutting edge portion (32) at the secondary midpoint (NMS), adjacent secondary clearance surfaces (40) form a fourth acute clearance angle (α4) relative to the fourth imaginary horizontal reference line (HL4) perpendicular to the central axis (A1), and The fourth acute gap angle (α4) is equal to the first acute gap angle (α1), the second acute gap angle (α2), and the third acute gap angle (α3).

13. The cutting head (20) according to claim 12, characterized in that: Each chip discharge passage (44) has a cut (60) extending axially rearward from the end portion (22) and intersecting one of the head grooves (48). Each secondary cutting edge portion (32) is formed at the intersection of one of the cuts (60) and one of the secondary clearance surfaces (40). The secondary front cutting edge surface (62) adjacent to the associated secondary cutting edge portion (32) is disposed on each cut (60). In the cross-section taken in the fourth transverse plane (PT4), the secondary rake surface (62) is inclined relative to the fourth imaginary radial plane (PR4) at a fourth axial rake angle (β4), and The fourth axial rake angle (β4) is negative.

14. The cutting head (20) according to claim 13, characterized in that, The negative fourth-axis rake angle (β4) has a magnitude greater than 4 degrees.

15. The cutting head (20) according to claim 11, characterized in that: The three leading edges (46) define the cutting diameter (DC), and The difference between the first diameter (D1) and the third diameter (D3) is greater than 35 percent of the cutting diameter (DC).

16. The cutting head (20) according to claim 15, characterized in that: The difference between the first diameter (D1) and the fourth diameter (D4) is greater than fifty percent of the cutting diameter (DC).

17. The cutting head (20) according to claim 11, characterized in that: Each secondary cutting edge portion (32) extends axially forward as it extends radially inward from its secondary midpoint (NMS).

18. The cutting head (20) according to claim 11, characterized in that: Each secondary cutting edge portion (32) includes a peak cutting edge sub-portion (56) located radially inside its secondary midpoint (NMS). The peak cutting edge portion (56) forms an acute entry angle (λ) relative to the second horizontal plane (PH2) perpendicular to the central axis (A1), and The entry angle (λ) is at least 15 degrees and at most 30 degrees.

19. The cutting head (20) according to claim 1, characterized in that: In the front view of the cutting head (20), each secondary cutting edge portion (32) is straight.

20. The cutting head (20) according to claim 19, characterized in that: Each secondary cutting edge portion (32) extends rearward in a rotating manner as it extends radially outward.

21. The cutting head (20) according to claim 1, characterized in that: In the front view of the cutting head (20), each transition cutting edge portion (36) is convex.

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