Cutting head and rotary cutting tool having four cutting portions and two convex clamping surfaces

Abstract

The cutting head (20) rotatable about a head axis AH has a cap portion (22) and a rigid mounting projection (24) joined to the cap portion. The cap portion has exactly four cutting portions (26) arranged circumferentially in alternating fashion with four head flutes (28), and a head base surface (30) facing in an axially rearward direction DR. The mounting projection has two convex clamping surfaces (38) extending axially rearward from the head base surface and spaced apart circumferentially. In a cross section taken along a first horizontal plane PH1 perpendicular to the head axis and intersecting the mounting projection, only the two clamping surfaces are circumscribed by an imaginary first circle C1 having a first diameter D1 and a center coincident with the head axis. The rotary cutting tool (56) has an elongated tool shank (58) having a head receiving pocket (60) at its forward end in which a cutting head of the type previously described is removably secured.

Description

[Technical field]

[0001] The present invention relates generally to a rotary cutting tool for use in metal cutting processes, particularly for drilling operations, and an associated cutting head having four cutting portions removably secured to a tool shank. [Background technology]

[0002] In the field of cutting tools used in drilling operations, there are several examples of cutting heads having three or more cutting portions removably secured to their associated tool shanks.

[0003] U.S. Patent No. 10,173,271 discloses a tool shank having a head receiving pocket at a front end and a plurality of tip flutes extending rearwardly from the head receiving pocket along a longitudinal axis. The head receiving pocket has a support surface transverse to the longitudinal axis. A central recess is formed in the support surface and extends rearwardly from the support surface. The central recess has a plurality of elastically displaceable abutment portions circumferentially alternated with and spaced apart from a plurality of intermediate portions. Each abutment portion has an abutment surface facing radially inward, and each intermediate portion has an intermediate surface intersecting two circumferentially adjacent abutment surfaces. A rotary cutting tool includes a shank and a cutting head removably mounted on the shank. The cutting head has a mounting portion provided with a base surface and an engagement member protruding from the base surface. In an assembled position, the engagement member is elastically held in the central recess against the abutment surfaces.

[0004] US Patent No. 11,110,521 discloses a cutting head rotatable about a first axis having a cap portion and a rigid mounting projection coupled to the cap portion. The cap portion has a plurality of cutting portions circumferentially alternating with a plurality of head tip flutes and a head base surface facing in an axially rearward direction. The mounting projection is rotationally symmetric about the first axis and extends axially rearward from the head base surface, and has a plurality of circumferentially spaced convex clamping surfaces. The plurality of cutting portions defines a cutting diameter, the plurality of head tip flutes are inscribed by an imaginary first circle having a first diameter, and the plurality of clamping surfaces are circumscribed by an imaginary second circle having a second diameter. The first diameter is greater than the second diameter, and the second diameter is less than 40% of the cutting diameter.

[0005] SUMMARY OF THE PRESENT EMBODIMENT It is an object of the present invention to provide an improved cutting head having four cutting sections.

[0006] It is also an object of the present invention to provide an improved cutting head which has good stability when removably secured to a tool shank.

[0007] It is a further object of the present invention to provide an improved tool shank having an extended service life. Summary of the Invention

[0008] According to the present invention there is provided a cutting head rotatable about a head axis in a first rotational direction, said head axis establishing an axial forward direction and an axial rearward direction opposite said axial forward direction, said cutting head comprising: A cap portion having exactly four cutting portions circumferentially alternating with four head longitudinal grooves, and a head base surface facing in the axial rearward direction, a cap portion having a front surface facing the axial forward direction, and each cutting portion intersects with a head longitudinal groove in a circumferential direction adjacent to the first rotational direction to form a cutting edge extending in a radial direction; a rigid mounting projection extending axially rearward from the head base surface and having exactly two circumferentially spaced convex clamping surfaces; In a cross section along a first horizontal plane perpendicular to the head axis and intersecting the mounting projection at two of the clamping surfaces, only the two clamping surfaces are circumscribed by an imaginary first circle having a first diameter and a center coincident with the head axis.

[0009] According to the present invention, there is also provided a rotary cutting tool, comprising: an elongated tool shank having a head receiving pocket at a forward end thereof and four shank flutes extending along a shank axis away from the forward end; a cutting head of the type previously described which is removably secured in said head receiving pocket.

[0010] For a better understanding, the invention will now be described, by way of example only, with reference to the accompanying drawings, in which dashed lines represent cutting boundaries of partial views of elements, in which: [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a perspective view of a cutting head according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a side view of the cutting head shown in FIG. [Diagram 3] FIG. 2 is a plan view of the cutting head shown in FIG. [Figure 4] 4 is a cross-sectional view taken along line IV-IV of the cutting head shown in FIG. 2. [Diagram 5] 3 is a cross-sectional view taken along line VV of the cutting head shown in FIG. 2. [Figure 6] 3 is a cross-sectional view taken along line VI-VI of the cutting head shown in FIG. 2. [Figure 7] 7 is a cross-sectional view taken along line VII-VII of the cutting head shown in FIG. 3. [Figure 8] FIG. 1 is an exploded perspective view of a rotary cutting tool according to an embodiment of the present invention. [Figure 9]FIG. 2 is an end view of a tool shank according to an embodiment of the present invention. [Figure 10] FIG. 10 is a side view of the tool shank shown in FIG. [Figure 11] FIG. 11 is a cross-sectional view taken along line XI-XI of the tool shank shown in FIG. [Figure 12] FIG. 9 is a side view of the clamp assembly of the rotary cutting tool shown in FIG. 8. [Figure 13] 13 is a cross-sectional view taken along line XIII-XIII of the rotary cutting tool shown in FIG. 12. [Figure 14] FIG. 9 is a side view of the unclamped assembly of the rotary cutting tool shown in FIG. 8. [Figure 15] 15 is a cross-sectional view taken along line XV-XV of the rotary cutting tool shown in FIG. 14. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] A first aspect of the invention relates to a cutting head 20 rotatable about a head axis AH in a first rotational direction R1, the head axis AH establishing an axial forward direction DF and an axial rearward direction DR opposite the axial forward direction DF.

[0013] In one embodiment of the present invention, the cutting head 20 may be manufactured by molding, pressing and sintering a cemented carbide such as tungsten carbide, and may be coated or uncoated.

[0014] As shown in FIGS. 1 to 3, the cutting head 20 includes a cap portion 22 and a rigid mounting projection 24 joined to the cap portion 22. As shown in FIG.

[0015] The cutting head 20 may have a single, unitary structure and the mounting projection 24 may have the same rigidity as the cap portion 22 and may not have any resiliently displaceable elements.

[0016] As will be described below, the cap portion 22 has a number of first cut-out portions 26 that is exactly twice the number of the number of second convex clamping surfaces 38 provided on the mounting projection 24 .

[0017] As shown in FIGS. 1 to 3, the cap portion 22 has four head longitudinal grooves 28 and exactly four cutting portions 26 arranged alternately in the circumferential direction, and a head base surface 30 facing in the axial rear direction DR.

[0018] As shown in Figures 1 to 3, each cutting portion 26 has a front surface 32 facing the axial forward direction DF, and each front surface 32 is adjacent to the first rotational direction R1 in the circumferential direction and intersects with the head longitudinal groove 28 forward in the rotational direction to form a cutting edge 34 extending radially.

[0019] In some embodiments of the present invention, the four cutting edges 34 may be identical.

[0020] In addition, in one embodiment of the present invention, the four cutting edges 34 may be disposed at equal intervals in the circumferential direction around the head axis AH.

[0021] Furthermore, in one embodiment of the present invention, except for a pair of key slots 36 formed in two diametrically opposed cutting portions 26, the cap portion 22 may exhibit four-fold rotational symmetry about the head axis AH.

[0022] As shown in FIG. 3, the four cutting edges 34 may define a cutting diameter DC that corresponds to an imaginary cutting circle CC.

[0023] It should be noted throughout this description and the claims that the four radially outermost points of the four cutting edges 34 define a cutting diameter DC and lie on an imaginary cutting circle CC.

[0024] In some embodiments of the present invention, the cutting head 20 may be used for drilling operations.

[0025] As shown in FIGS. 1-3, the rigid mounting projection 24 extends axially rearward from the head base surface 30 and has exactly two circumferentially spaced convex clamping surfaces 38. As shown in FIG.

[0026] In one embodiment of the present invention, a first vertical plane PV1 including the head axis AH may intersect two clamping surfaces 38, which may be described as a pair of diametrically opposed clamping surfaces 38.

[0027] In addition, in one embodiment of the present invention, the two clamping surfaces 38 may be formed in a partially cylindrical shape, and as shown in FIG. 4, in a cross section along the first vertical plane PV1, the two clamping surfaces 38 may extend parallel to the head axis AH.

[0028] In another embodiment of the invention (not shown), the two clamping surfaces 38 may be formed partially conically, such that in a cross section along a vertical plane that includes the head axis AH and intersects the two clamping surfaces 38, the two clamping surfaces 38 diverge away from the head axis AH in the axial rearward direction DR. In other words, in the rearward direction of the mounting projection 24, the diameter dimension of an imaginary circle circumscribing the two clamping surfaces 38 increases.

[0029] As shown in FIGS. 1 and 2, the mounting projection 24 may have at least two circumferentially spaced apart axial stop portions 39 located axially rearward of the two clamping surfaces 38 .

[0030] In one embodiment of the present invention, the first vertical plane PV1 may intersect two of the at least two circumferentially spaced axial stop portions 39, and, as shown in FIG. 4, in a cross section along the first vertical plane PV1, the two axial stop portions 39 may extend radially beyond the two clamping surfaces 38.

[0031] In an embodiment of the invention, each axial stop portion 39 may have a stop surface 41 facing in the axial forward direction DF.

[0032] Also, in one embodiment of the present invention, the mounting projection 24 may have four axial stop portions 39 equally spaced circumferentially about the head axis AH and forming a bulge 43 at its distal end.

[0033] As shown in FIG. 5, according to the first aspect of the present invention, in a cross section along a first horizontal plane PH1 that is perpendicular to the head axis AH and intersects the mounting projection 24 at the two clamping surfaces 38, only the two clamping surfaces 38 are circumscribed by an imaginary first circle CL having a first diameter D1 and a center coinciding with the head axis AH.

[0034] 4 and referring to FIG 5, each of the four axial stopper portions 39 extends radially outward of the axial projection of the first imaginary circle C1. In other words, a virtual circle that is perpendicular to the head axis AH, has a center coincident with the head axis AH, and circumscribes the four axial stopper portions 39 has a diameter larger than the first diameter D1.

[0035] It should be noted that in one embodiment of the present invention, in a cross section along the first horizontal plane PH1, no portion of the mounting projection 24 may be located outside the imaginary first circle CL, and that throughout this description and claims, the imaginary first circle CL circumscribes the entire mounting projection 24 by only the two clamping surfaces 38.

[0036] Furthermore, in one embodiment of the present invention, in a cross section along the first horizontal plane PH1, the two clamping surfaces 38 may form two clamping arcs 40 that coincide with the imaginary first circle CL.

[0037] Furthermore, in some embodiments of the present invention, the first vertical plane PV1 may bisect the two clamping arcs 40 at its midpoint.

[0038] Still further, in some embodiments of the present invention, the first vertical plane PV1 may bisect the two clamping surfaces 38.

[0039] As shown in FIG. 5, the first diameter D1 may be less than 40% of the cutting diameter DC, ie, D1<0.40×DC.

[0040] As shown in FIG. 6, in a cross section along a second horizontal plane PH2 perpendicular to the head axis AH and intersecting the cap portion 22, the four head longitudinal grooves 28 have a second diameter D2 and are inscribed by an imaginary second circle C2 having a center coincident with the head axis AH, the imaginary second circle C2 passing through the four radially innermost head longitudinal groove points NH, and each head longitudinal groove point NH is associated with a corresponding one of the four head longitudinal grooves 28.

[0041] In some embodiments of the present invention, the second diameter D2 may be greater than the first diameter D1, ie, D2>D1.

[0042] As shown in Figures 1 to 3, the rigid mounting projection 24 may have two convex guide surfaces 42 spaced apart in the circumferential direction, and the two guide surfaces 42 may be circumferentially alternating with the two clamping surfaces 38.

[0043] As shown in FIG. 5, in a cross section taken along the first horizontal plane PH1, the two guide surfaces 42 may be disposed inside an imaginary first circle C1.

[0044] Also as shown in FIG. 5, in a cross section along the first horizontal plane PH1, the two guide surfaces 42 may be circumscribed by an imaginary third circle C3 having a third diameter D3 and having a center coincident with the head axis AH, and the third diameter D3 may be less than the first diameter D1 but greater than 85% of the first diameter D1, i.e., D1>D3>0.85×D1.

[0045] It should be understood that throughout this description and the claims, the imaginary third circle C3 circumscribes the two guide surfaces 42 in a cross section along the first horizontal plane PH1, but that the imaginary third circle C3 does not circumscribe the entire mounting projection 24, and in particular the two clamping surfaces 38.

[0046] As shown in FIG. 5, in a cross section along the first horizontal plane PH1, the two guide surfaces 42 may form two guide arcs 37 that coincide with an imaginary third circle C3.

[0047] In one embodiment of the present invention, a second vertical plane PV2 including the head axis AH may intersect two guide surfaces 42, which may be described as a pair of diametrically opposed guide surfaces 42.

[0048] Additionally, in some embodiments of the present invention, the second vertical plane PV2 may bisect the two guiding arcs 37 at its midpoint.

[0049] Furthermore, in an embodiment of the present invention, the second vertical plane PV2 may bisect the two guide surfaces 42.

[0050] As shown in FIG. 5, the first vertical plane PV1 and the second vertical plane PV2 may be perpendicular to each other.

[0051] In one embodiment of the present invention, the mounting projection 24 may exhibit two-fold rotational symmetry about the head axis AH.

[0052] As shown in FIGS. 1, 2 and 5, the rigid mounting projection 24 may have four transition surfaces 45 circumferentially spaced apart by two clamping surfaces 38 and two guide surfaces 42.

[0053] In some embodiments of the present invention, each transition surface 45 may be a planar surface.

[0054] Additionally, in some embodiments of the present invention, each transition surface 45 may be parallel to the head axis AH.

[0055] As shown in FIGS. 1 and 2, a rake face 44 is located on each head flute 28 adjacent its associated cutting edge 34 .

[0056] As shown in FIG. 7, in a cross section along a third vertical plane PV3 that is parallel to the head axis AH and intersects one of the cutting edges 34 along at least its radially outer portion, the cutting face 44 may be inclined at a positive rake angle α1.

[0057] It should be noted that throughout this description and the claims, the term “positive rake angle” refers to the acute exterior angle formed between the rake face 44 and an imaginary reference line parallel to the head axis AH and intersecting the associated cutting edge 34.

[0058] In some embodiments of the present invention, the rake angle α1 may be greater than 7 degrees, ie, α1 > 7°.

[0059] As shown in Figures 1 and 5, the head base surface 30 includes a central base region 46 and four radially outer base regions 48, and each head longitudinal groove 28 intersects one of the four radially outer base regions 48 to form a radially outer base edge 50.

[0060] As shown in FIG. 5, the central base region 46 may completely surround the mounting projection 24 .

[0061] In some embodiments of the present invention, the four radially outer base regions 48 and the central base region 46 may be coplanar.

[0062] As shown in FIG. 5, the third vertical plane PV3 intersects one of the radially outer base edges 50.

[0063] In one embodiment of the present invention, as shown in FIGS. 1 and 5, an interface surface 52 may be disposed on each head flute 28 adjacent its associated radially outer base edge 50. As shown in FIG.

[0064] As shown in FIG. 7, in a cross section taken along the third vertical plane PV3, a straight line tangent LT to the joint surface 52 may be inclined at a zero or positive joint angle β1.

[0065] It should be noted that throughout this description and the claims, the term "zero mating angle" refers to a configuration in which the straight tangent LT is parallel to the head axis AH, and the term "positive mating angle" refers to the acute included angle formed between the straight tangent LT and an imaginary reference line that is parallel to the head axis AH and intersects the associated radially outer base edge 50.

[0066] In some embodiments of the present invention, the joint angle β1 may be smaller than the tilt angle α1, ie, β1<α1.

[0067] It should be noted that for embodiments of the present invention in which the joint angle β1 is less than the tilt angle α1, the joint surface 52 may be concave in cross section along the third vertical plane PV3, as shown in FIG.

[0068] Also, it should be noted that for embodiments of the present invention in which the interface angle β1 is less than the rake angle α1, the surface area of ​​each of the four radially outer base regions 48 may be advantageously increased while providing an optimally sized flute volume for each of the four head flutes 28.

[0069] In such an embodiment, the increased surface area of ​​each radially outer base region 48 contributes to increased stability of the cutting tool when the cutting head 20 is removably secured to a tool shank, and it should be noted that providing an optimally large flute volume for each head flute 28 is more important when the cutting head 20 is configured to have four circumferentially spaced head flutes 28 compared to alternative cutting head configurations (not shown) having, for example, only two or three circumferentially spaced head flutes.

[0070] As shown in FIGS. 1 to 3, each cutting portion 26 may have a torque transmission surface 54 facing away from the first rotational direction R1.

[0071] For an embodiment of the present invention in which each cutting portion 26 has a torque transmission surface 54 and the cap portion 22 exhibits substantially four-fold rotational symmetry about the head axis AH, it should be noted that the cutting head 20 may be mounted to the tool shank in four index positions whereby each of the four torque transmission surfaces 54 contacts a different one of the four shank drive surfaces, and the four torque transmission surfaces 54 and four index positions are exactly twice the number of the plurality of convex second clamping surfaces 38 provided on the mounting projection 24.

[0072] In certain embodiments of the present invention, each torque transfer surface 54 may be disposed between the forward surface 32 of its associated cutting portion and one of the radially outer base regions 48 .

[0073] Additionally, in some embodiments of the present invention, each torque transmission surface 54 may be planar.

[0074] Further, in certain embodiments of the present invention, as shown in FIG. 2, each torque transmission surface 54 may be inclined in a first rotational direction R1 as it extends in the axial rearward direction DR away from the front surface 32 of its associated cutting portion.

[0075] 8 to 13, a second aspect of the present invention relates to a rotary cutting tool 56 having a cutting head 20 secured to an elongated tool shank 58. The tool shank 58 is provided with a head receiving pocket 60 at a front end 62 thereof and is provided with four shank longitudinal grooves 64 extending along a shank axis AS away from the front end 62, and the cutting head 20 is removably secured in the head receiving pocket 60.

[0076] In some embodiments, the cutting head 20 may be removably secured to the head-receiving pocket 60 without the need for additional fasteners, such as clamp screws.

[0077] It should be noted throughout this description and claims that when the cutting head 20 is removably secured in the head receiving pocket 60 and the rotary cutting tool 56 is in an assembled state, the four shank longitudinal grooves 64 extend in the axial rearward direction DR away from the front end 62 of the tool shank.

[0078] As shown in FIGS. 8 to 10, four shank longitudinal grooves 64 may be formed in a cylindrical shank peripheral surface 65 of the tool shank 58 .

[0079] In some embodiments of the present invention, the head axis AH may coincide with the shank axis AS.

[0080] Additionally, in one embodiment of the present invention, the four shank flutes 64 may extend helically along the shank axis AS, and the four head flutes 28 may function as corresponding extensions of the four shank flutes 64.

[0081] Furthermore, in certain embodiments of the present invention, the tool shank 58 may preferably be manufactured from tool steel.

[0082] Still further, in some embodiments of the present invention, the rotary cutting tool 56 may be used for drilling operations.

[0083] As shown in FIGS. 8 and 9, the head receiving pocket 60 has a shank support surface 66 transverse to the shank axis AS and a central recess 68 formed in the shank support surface 66.

[0084] In some embodiments of the present invention, the central recess 68 may not intersect any of the four shank flutes 64 .

[0085] As shown in FIG. 9, the shank support surface 66 includes a central support region 70 and four radially outer support regions 72.

[0086] In some embodiments of the present invention, the central recess 68 may be formed in a central support region 70 .

[0087] Additionally, in some embodiments of the present invention, each radially outer support region 72 may intersect the shank circumferential surface 65 .

[0088] Furthermore, in some embodiments of the present invention, the four radially outer support regions 72 may be coplanar and located axially forward of the central support region 70 .

[0089] As shown in Figures 9 and 11, the central recess 68 has four circumferentially spaced elastically displaceable abutment portions 74, each of which has an abutment surface 76 facing radially inward.

[0090] In one embodiment of the present invention, the four abutment portions 74 may be identical, and the four abutment surfaces 76 may be arranged as two diametrically opposed pairs of abutment surfaces 76. Thus, the tool shank 58 has a plurality of third abutment surfaces 76, the same number as the plurality of first cutting portions 26, and exactly twice the number of the plurality of convex second clamping surfaces 38.

[0091] It should be noted that in some embodiments of the present invention, the four abutment portions 74 may be independently elastically displaceable, and in such embodiments, radial displacement of one of the four abutment portions 74 does not cause radial displacement of any of the other three abutment portions 74.

[0092] Also, in one embodiment of the present invention, the central recess 68 may include four intermediate portions 78 arranged alternately with the four abutment portions 74 in the circumferential direction, and each intermediate portion 78 may have an intermediate surface 80 that intersects two circumferentially adjacent abutment surfaces 76.

[0093] Furthermore, in certain embodiments of the present invention, each intermediate surface 80 may extend radially outward from two circumferentially adjacent abutment surfaces 76 .

[0094] In an embodiment of the present invention in which the four abutment surfaces 76 are circumferentially alternating with the four intermediate surfaces 80, the head-receiving pocket 60 has a “circumferentially confined” central recess 68, thereby improving the resiliency of the four abutment portions 74 and extending the service life of the tool shank 58.

[0095] As shown in Figures 9 and 11, before the cutting head 20 is removably secured in the head-receiving pocket 60, the head-receiving pocket 60 may exhibit four-fold rotational symmetry about the shank axis AS.

[0096] Additionally, before the cutting head 20 is removably secured in the head-receiving pocket 60, the tool shank 58 may exhibit four-fold rotational symmetry about the shank axis AS.

[0097] In accordance with a second aspect of the present invention, as shown in FIGS. 12 and 13, the mounting projection 24 is resiliently retained within the central recess 68 in one of four index positions, and in each index position: The head base surface 30 faces the shank support surface 66, The two clamping surfaces 38 are in clamping contact with two of the four abutment surfaces 76', No clamping contact occurs between the rigid mounting projection 24 and two of the four abutment surfaces 76 ″, which are non-operative abutment surfaces.

[0098] It should be noted throughout this description and the claims that clamping contact between the two clamping surfaces 38 and the two operative abutment surfaces 76' causes the associated two abutment portions 74 to be displaced radially outward.

[0099] It should also be noted throughout this description and the claims that no clamping contact occurs between the rigid mounting projection 24 and the two non-operative abutment surfaces 76'', and that the two guide surfaces 42 of the mounting projection may face the two non-operative abutment surfaces 76'' with a minimal spacing between them.

[0100] In one embodiment of the present invention, at each index position, the head receiving pocket 60 may exhibit two-fold rotational symmetry about the shank axis AS.

[0101] It will be noted that the tool shank 58 of the cutting tool has two operating configurations, namely a first operating configuration in which the mounting projection 24 of the removably fixed cutting head 20 is resiliently held in the central recess 68 of the tool shank at a first or second index position of said four index positions in which the same first pair of diametrically opposed abutment surfaces 76 are active, and a second operating configuration in which the mounting projection 24 of the removably fixed cutting head 20 is resiliently held in the central recess 68 of the tool shank at a third or fourth index position of said four index positions in which the same second pair of diametrically opposed abutment surfaces 76 are active.

[0102] In the rotary cutting tool 56 of the present invention, the tool shank 58 has in its central recess 68 exactly twice the number of clamping surfaces 38 that the cutting head 20 has on its mounting projection 24. Thus, in a fully assembled rotary cutting tool 56, only alternating ones of the plurality of third abutment surfaces 76 are operative around the circumferential direction of the tool shank central recess 68. More specifically, the plurality of circumferentially spaced second convex clamping surfaces 38 on the cutting head mounting projection 24 abut alternating ones of the plurality of circumferentially spaced, radially inwardly facing third abutment surfaces 76 around the circumferential direction of the tool shank central recess 68.

[0103] It should also be noted that by having two actuation configurations, the useful life of the tool shank 58 of the rotary cutting tool may be advantageously extended.

[0104] It should further be noted that visual markings or indicia (not shown) may be provided on the front end 62 of the tool shank to enable the pair of diametrically opposed first and second abutment surfaces 76 to be distinguished from one another.

[0105] It should further be noted that the key slot 36 located in the cap portion 22 of the cutting head may provide a visual indication for the position of the two clamping surfaces 38 on the mounting projection 24 of the cutting head, which may be relied upon when selecting a desired index position of the cutting head 20 within the central recess 68 of the tool shank.

[0106] It should be noted that in the case of an embodiment of the present invention in which the four abutment portions 74 are independently elastically displaceable, the service life of the tool shank 58 of the rotary cutting tool may be doubled.

[0107] It should further be noted that during the service life of each of the first and second operative configurations of the tool shank, multiple cutting heads 20 may be removably secured to the head-receiving pockets 60 of the tool shank and used in drilling operations before being replaced after wear.

[0108] As shown in Figures 12 and 13, when the cutting head 20 is removably secured in the head receiving pocket 60 and the rotary cutting tool 56 is in the clamped assembly, the head base surface 30 contacts the shank support surface 66 and other portions of the mounting projection 24 may not be in clamping contact with the central recess 68, except for the two clamping surfaces 38 which are in clamping contact with the two operative abutment surfaces 76'.

[0109] In some embodiments of the present invention, at least three of the four radially outer base regions 48 may contact at least three of the four radially outer support regions 72 .

[0110] It should be noted that during the drilling operation, the axially rearward cutting force overcomes the inaccuracies normally associated with the coplanarity of the four radially outer support regions 72, resulting in contact between all four radially outer base regions 48 and all four radially outer support regions 72.

[0111] Additionally, in some embodiments of the present invention, the central base region 46 may be spaced apart from the central support region 70 .

[0112] As shown in FIG. 13, in a cross-section along a third horizontal plane PH3 that is perpendicular to the shank axis AS and passes through the central recess 68, a virtual fourth circle C4 having a fourth diameter D4 and a center coinciding with the shank axis AS is inscribed in the two operating contact surfaces 76', while a virtual fifth circle C5 having a fifth diameter D5 and a center coinciding with the shank axis AS is inscribed in the two non-operating contact surfaces 76'', and the fourth diameter D4 is larger than the fifth diameter D5, that is, D4 > D5.

[0113] It should be noted that throughout this description and the claims, in a cross-section along the third horizontal plane PH3, none of the four contact portions 74 and the four intermediate portions 78 of the central recess need to cross the virtual fifth circle C5.

[0114] In an embodiment of the present invention, the first horizontal plane PH1 and the third horizontal plane PH3 may coincide, and the first diameter D1 may be larger than the fifth diameter D5, that is, D1 > D5.

[0115] Also, in the case of an embodiment of the present invention where the first horizontal plane PH1 and the third horizontal plane PH3 coincide, the first diameter D1 may be equal to the fourth diameter D4, that is, D1 = D4. In other words, the diameter of the outermost portion of the clamping surface 38 may coincide with the diameter of the operating contact surface 76'.

[0116] Furthermore, in the case of an embodiment of the present invention where the first horizontal plane PH1 and the third horizontal plane PH3 coincide, the third diameter D3 may be smaller than the fifth diameter D5, that is, D3 < D5. In other words, the diameter of the outermost portion of the guide surface 42 may be smaller than the diameter of the non-operating contact surface 76''.

[0117] In an embodiment of the present invention where the four elastically displaceable contact portions 74 spaced apart in the circumferential direction are the same, as shown in FIG. 11, it should be noted that in a cross-section along the third horizontal plane PH3, before the cutting head 20 is removably fixed to the head receiving pocket 60, the virtual fifth circle C5 is inscribed in all of the four contact surfaces 76.

[0118] Also, in the case of an embodiment of the present invention in which the four circumferentially spaced apart elastically displaceable abutment portions 74 are identical, as shown in FIG. 11, in a cross section taken along the third horizontal plane PH3, before the cutting head 20 is removably secured to the head receiving pocket 60, the four shank longitudinal grooves 64 are arranged such that the four first longitudinal groove points N are disposed on an imaginary sixth circle C6 having a sixth diameter D6 and a center coincident with the shank axis AS. F Note that it is inscribed at 1.

[0119] In one embodiment of the present invention, the four first groove points N F A radial groove axis AF including one of the first groove points N F 1 may be disposed at a first minimum wall thickness T1 from its adjacent abutment surface 76 along its associated radial flute axis AF.

[0120] Also, in one embodiment of the present invention, the sixth diameter D6 is between 90 percent and 110 percent of the second diameter D2, i.e., D2×0.90. <D6<D2×1.10であってもよい。

[0121] As shown in FIG. 11, in a cross section taken along the third horizontal plane PH3, before the cutting head 20 is removably secured to the head receiving pocket 60, each shank flute 64 is aligned with a first flute point N F 1 and a second groove point N located a minimum second wall thickness T2 from its adjacent intermediate surface 80. F 2.

[0122] In one embodiment of the present invention, the minimum second wall thickness T2 is equal to or less than the minimum first wall thickness T1, i.e., T2 <T1であってもよい。

[0123] It should be noted that for embodiments of the present invention in which the minimum second wall thickness T2 is equal to or less than the minimum first wall thickness T1, the proximity of each shank flute 64 to its adjacent intermediate surface 80 is the primary parameter for adjusting the elasticity of the associated abutment portion 74.

[0124] As shown in Figures 8-10, the front end 62 of the tool shank may have four drive lugs 82 projecting from the shank support surface 66, and each drive lug 82 may have a drive surface 84 adjacent one of the radially outer support regions 72 facing the first rotational direction R1.

[0125] In some embodiments of the present invention, each drive surface 84 may intersect the shank circumferential surface 65 .

[0126] When the cutting head 20 is removably secured in the head receiving pocket 60 and the rotary cutting tool 56 is in a clamped assembly as shown in FIG. 12, at least two of the four drive surfaces 84 may contact at least two of the four torque transmission surfaces 54.

[0127] With clamping contact between the two clamping surfaces 38 and the two operative abutment surfaces 76', and no clamping contact between the rigid mounting projection 24 and the two non-operative abutment surfaces 76'', the front end 62 of the tool shank may be subjected to very slight torsional bending such that only two diametrically opposed drive surfaces 84 of the four drive surfaces 84 may contact two diametrically opposed torque transmission surfaces 54 of the four torque transmission surfaces 54; however, during a drilling operation, the rotating cutting forces will normally overcome said slight torsional bending such that all four drive surfaces 84 are in contact with all four torque transmission surfaces 54.

[0128] In some embodiments of the present invention, the four drive surfaces 84 and the four torque transmission surfaces 54 may be correspondingly inclined with respect to the first direction of rotation R1.

[0129] It should be noted that by configuring each drive face 84 to slope away from the first rotational direction R1 as it extends away from its associated radially outer support region 72, as shown in FIG. 12, a component of the rotational cutting force is directed axially rearward and improves the robustness of the four drive lugs 82.

[0130] The present invention further relates to a method of assembling a rotary cutting tool 56, the method comprising: a) orienting the head base surface 30 to face the shank support surface 66; b) aligning the head axis AH with the shank axis AS; c) rotationally aligning the two clamping surfaces 38 with two of the four intermediate portions 78; d) inserting the mounting projection 24 into the central recess 68 until the head base surface 30 contacts the shank support surface 66, as shown in FIG. 14; e) rotating the cutting head 20 about its head axis AH in a direction opposite to the first rotation direction R1 until the two clamping surfaces 38 are resiliently held against two of the four abutment surfaces 76', as shown in FIG. 12.

[0131] In one embodiment of the present invention, in step d), the rotary cutting tool 56 is in an unclamped assembly state, whereby none of the four abutment portions 74 are elastically displaced, and as shown in FIG. 15, in a cross section along the third horizontal plane PH3, an imaginary seventh circle C7 having a seventh diameter D7 and a center coinciding with the shank axis AS may be inscribed in all of the four abutment surfaces 76.

[0132] In an embodiment of the present invention in which the first horizontal plane PH1 and the third horizontal plane PH3 are coincident, the first diameter D1 is greater than the seventh diameter D7, i.e., D1>D7, but because the two clamping surfaces 38 are rotationally aligned with two of the four intermediate portions 78, no radially outward force FR acts on any of the four abutment portions 74, and the head receiving pocket 60 has the same configuration as it had before the cutting head 20 was removably secured thereto.

[0133] Also, in one embodiment of the present invention, in step d), the head receiving pocket 60 may exhibit four-fold rotational symmetry about the shank axis AS.

[0134] It should be noted that step e) is typically performed using an assembly tool (not shown) that engages with key slot 36 in the cutting head.

[0135] In one embodiment of the present invention, in step e), the cutting head 20 may be rotated approximately 45 degrees about its head axis AH relative to the central recess 68 of the tool shank until the rotary cutting tool 56 is in the clamped assembly.

[0136] Also, it should be noted that step e) is typically performed until at least two of the four drive surfaces 84 contact at least two of the four torque transmission surfaces 54 .

[0137] Also, in one embodiment of the present invention, in step e), the two abutment portions 74 associated with the two actuating abutment surfaces 76' are elastically displaced, and as shown in FIG. 13, in a cross section along the third horizontal plane PH3, an imaginary fourth circle C4 is inscribed in the two actuating abutment surfaces 76', and the fourth diameter D4 is greater than the seventh diameter D7, i.e., D4>D7.

[0138] Furthermore, it is to be noted that in step e), a radially outward force FR is exerted by the two clamping surfaces 38 on said two abutment portions 74 associated with the two active abutment surfaces 76'.

[0139] Furthermore, in one embodiment of the present invention, in step e), the two abutment portions 74 associated with the two non-operating abutment surfaces 76'' are not elastically displaced, and as shown in FIG. 13, in a cross section along the third horizontal plane PH3, an imaginary fifth circle C5 is inscribed in the two non-operating abutment surfaces 76'', and the fifth diameter D5 is equal to the seventh diameter D7, i.e., D5=D7.

[0140] It is further noted that in step e), no radially outward force FR acts on said two abutment portions 74 associated with the two non-operating abutment surfaces 76''.

[0141] Furthermore, in some embodiments of the present invention, in step e), the head receiving pocket 60 may exhibit two-fold rotational symmetry about the shank axis AS.

[0142] Although the present invention has been described in some detail, it should be noted that various changes and modifications are possible without departing from the scope of the invention as claimed below.

Claims

1. A cutting head (20) rotatable in a first rotational direction (R1) about a head axis (AH), said head axis (AH) establishing an axial forward direction (DF) and an axial rearward direction (DR) opposite said axial forward direction (DF), said cutting head comprising: A cap portion (22) having exactly four cutting portions (26) circumferentially alternated with four head longitudinal grooves (28), and a head base surface (30) facing in the axial rearward direction (DR), a cap portion (22) in which each cutting portion (26) has a front surface (32) facing the axial forward direction (DF) and intersecting a circumferentially adjacent and rotationally forward head flute (28) with respect to the first rotational direction (R1) to form a radially extending cutting edge (34); a rigid mounting projection (24) extending axially rearward from the head base surface (30) and having exactly two circumferentially spaced convex clamping surfaces (38); A cutting head (20) in which, in a cross section along a first horizontal plane (PH1) perpendicular to the head axis (AH) and intersecting the mounting projection (24) at two of the clamping surfaces (38), only the two clamping surfaces (38) are circumscribed by an imaginary first circle (C1) having a first diameter (D1) and a center coincident with the head axis (AH).

2. 2. The cutting head (20) of claim 1, wherein the four cutting edges (34) are identical and the four cutting edges (34) are equally spaced circumferentially about the head axis (AH).

3. 2. The cutting head (20) of claim 1, wherein the mounting projection (34) exhibits two-fold rotational symmetry about the head axis (AH).

4. 2. The cutting head (20) of claim 1, wherein each cutting portion (26) has a torque transmission surface (54) facing away from said first direction of rotation (R1).

5. The rigid mounting projection (24) has two circumferentially spaced convex guide surfaces (42); The two guide surfaces (42) are arranged alternately with the two clamping surfaces (38) in the circumferential direction; In a cross section along the first horizontal plane (PH1), the two guide surfaces (42) are arranged inside the imaginary first circle (CL), In a cross section along the first horizontal plane (PH1), 2. The cutting head (20) of claim 1, wherein the two guide surfaces (42) are circumscribed by an imaginary third circle (C3) having a third diameter (D3) and a center coincident with the head axis (AH).

6. The mounting projection (24) has four circumferentially spaced apart axial stop portions (39) arranged axially rearward of the two clamping surfaces (38), 2. The cutting head (20) according to claim 1, wherein each of the four axial stop portions (39) extends radially outward of an axial projection of the imaginary first circle (C1) circumscribing the two clamping surfaces (38).

7. In a cross section along a second horizontal plane (PH2) perpendicular to the head axis (AH) and intersecting the cap portion (22), the four head flutes (28) are inscribed by an imaginary second circle (C2) having a second diameter (D2) and a center coincident with the head axis (AH), the imaginary second circle (C2) passing through four radially innermost head flute points (NH), each head flute point (NH) being associated with a corresponding one of the four head flutes (28); The cutting head (20) of claim 1, wherein the second diameter (D2) is greater than the first diameter (D1).

8. The four cutting edges (34) define a cutting diameter (DC) corresponding to a cutting circle (CC); The cutting head (20) of claim 1, wherein the first diameter (D1) is less than 40% of the cutting diameter (DC).

9. a rake face (44) disposed on each head flute (28) adjacent its associated cutting edge (34); 2. The cutting head (20) of claim 1, wherein the rake face (44) is inclined at a positive rake angle (α1) in a cross section along a third vertical plane (PV3) parallel to the head axis (AH) and transverse to one of the cutting edges (34) along at least a radially outer portion thereof.

10. The head base surface (30) includes a central base region (46) and four radially outer base regions (48); Each head flute (28) intersects with one of the four radially outer base regions (48) to form a radially outer base edge (50); The cutting head (20) of claim 9, wherein the third vertical plane (PV3) intersects one of the radially outer base edges (50).

11. an interface surface (52) disposed on each head flute (28) adjacent its associated radially outer base edge (50); In a cross section along the third vertical plane (PV3), a straight tangent (LT) tangent to the joint surface (52) is inclined at a zero or positive joint angle (β1), The cutting head (20) according to claim 10, wherein the joint angle (β1) is smaller than the rake angle (α1).

12. an elongated tool shank (58) having a head receiving pocket (60) at a forward end (62) thereof and four shank flutes (64) extending away from said forward end (62) along a shank axis (AS); A rotary cutting tool (56) comprising: a cutting head (20) according to claim 1 removably secured to said head-receiving pocket (60).

13. The head receiving pocket (60) has a shank support surface (66) transverse to the shank axis (AS) and a central recess (68) formed in the shank support surface (66); the central recess (68) has four circumferentially spaced apart elastically displaceable abutment portions (74), each abutment portion (74) having a radially inwardly facing abutment surface (76); The mounting projection (24) is resiliently retained within the central recess (68) in any one of four index positions; At each index position, The head base surface (30) faces the shank support surface (66), two of said clamping surfaces (38) are in clamping contact with two of said four abutment surfaces (76), 13. The rotary cutting tool (56) of claim 12, wherein no clamping contact occurs between the rigid mounting projection (24) and two of the four non-operating abutment surfaces (76'').

14. The rotary cutting tool (56) of claim 13, wherein the four abutment portions (74) are independently resiliently displaceable.

15. The rigid mounting projection (24) has two circumferentially spaced convex guide surfaces (42); The two guide surfaces (42) are arranged alternately with the two clamping surfaces (38) in the circumferential direction; In a cross section along the first horizontal plane (PH1), the two guide surfaces (42) are arranged inside the imaginary first circle (CL), 14. The rotary cutting tool (56) of claim 13, wherein two of said guide surfaces (42) face two of said non-operating abutment surfaces (76').

16. The head base surface (30) contacts the shank support surface (66), 14. The rotary cutting tool (56) of claim 13, wherein, except for the two clamping surfaces (38) that are in clamping contact with the two operative abutment surfaces (76′), no other portion of the mounting projection (24) is in clamping contact with the central recess (68).

17. In a cross section along a third horizontal plane (PH3) perpendicular to the shank axis (AS) and passing through the central recess (68), an imaginary fourth circle (C4) having a fourth diameter (D4) and a center coincident with the shank axis (AS) is inscribed in the two operating abutment surfaces (76'); an imaginary fifth circle (C5) having a fifth diameter (D5) and a center coincident with the shank axis (AS) is inscribed in the two non-operating abutment surfaces (76''); The rotary cutting tool (56) of claim 13, wherein the fourth diameter (D4) is greater than the fifth diameter (D5).

18. The first horizontal plane (PH1) and the third horizontal plane (PH3) coincide with each other, 18. The rotary cutting tool (56) of claim 17, wherein the first diameter (D1) is greater than the fifth diameter (D5).

19. The first horizontal plane (PH1) and the third horizontal plane (PH3) coincide with each other, 18. The rotary cutting tool (56) of claim 17, wherein the first diameter (D1) is equal to the fourth diameter (D4).

20. 14. A method of assembling the rotary cutting tool (56) of claim 13, comprising the steps of: The central recess (68) further comprises four intermediate portions (78) arranged alternately with the four abutment portions (74) in the circumferential direction, The method comprises: a) orienting the head base surface (30) to face the shank support surface (66); b) aligning the head axis (AH) with the shank axis (AS); c) rotationally aligning two of said clamping surfaces (38) with two of said four intermediate portions (78); d) inserting the mounting projection (24) into the central recess (68) until the head base surface (30) contacts the shank support surface (66); e) rotating the cutting head (20) about its head axis (AH) opposite to the first direction of rotation (R1) until the two clamping surfaces (38) are resiliently held against two of the four working abutment surfaces (76').

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