Indexable drilling insert having three tip portions and rotary cutting tool in which such drilling insert is centrally mounted

Abstract

The drilling insert (20) has a central portion (22) having a central axis (AC) and three circumferentially spaced tip portions (24a, 24b, 24c). Each tip portion has a first axis (A1) and two diverging first cutting edges (30a, 30b) having radially outermost cutting points (NC1, NC2), which define a first circle on a tip plane perpendicular to the first axis and have a first cutting diameter. In a view along one of the first axes, a second circle having a second diameter circumscribes the drilling insert, and the first cutting diameter is at least 60 percent of the second diameter. A cutting tool rotatable about a tool axis having a tool cutting diameter includes the drilling insert (20) and a second cutting insert having a second cutting edge. One of the tip portions is active and has a first axis coaxial with the tool axis, and a second cutting edge extending radially outward of the first cutting diameter.

Description

[Technical field]

[0001] The present invention relates to a three-point insert for use in metal cutting operations in general, and drilling operations in particular, and to a rotary cutting tool in which such a cutting insert is centrally mounted. [Background technology]

[0002] In the field of cutting tools used in drilling operations, there are many examples for indexable cutting inserts used in drilling operations, and several examples for drilling tools in which the indexable cutting insert is centrally mounted.

[0003] US8,702,357 discloses a prefabricated spade drill head for a spade drill, the spade drill comprising a body portion and a drill head removably secured to the body portion, the prefabricated spade drill head comprising a central insert piece forming a central region of the spade drill head and including a first side and a second side and a cutting edge, a first side insert piece forming at least a portion of the first side of the spade drill head and including the cutting edge and a mating surface configured to mate with at least a region of the first side of the central insert piece, and a second side insert piece forming at least a portion of the second side region of the spade drill head, the second side insert piece having a cutting edge and a mating surface configured to mate with the second side of the central insert piece. and a mating surface configured to mate with at least a region of the central insert piece, the first side insert piece, and the second side insert piece being configured to be individually removably secured to the body portion with the mating surface of the first side insert piece mating with the first side of the central insert piece and the mating surface of the second side insert piece mating with the second side of the central insert piece, the second side of the central insert piece being aligned to abut an end point of the cutting edge of the insert piece and forming a straight continuous cutting edge region on one end of the spade drill, and at least one of the central insert piece, the first side insert piece, and the second side insert piece including two cutting edges and being indexable with at least two alternating cutting directions and being securable to the body portion.

[0004] US9,421,622 discloses a central drill insert having a bottom surface, a top surface, and a peripheral surface extending between the bottom surface and the top surface. At least three lead drill portions project outwardly from the peripheral surface, each having a drill axis and a plurality of drill cutting edges. A minor cutting edge is adjacent to each lead drill portion and extends transversely to the respective drill axis along an intersection line between the top surface and the peripheral surface. Each minor cutting edge is spaced along the drill axis from an associated drill cutting edge. A dovetail abutment side is formed on the peripheral surface along an intersection line between the top surface and the peripheral surface, and extends from each of the lead drill portions toward a minor cutting edge associated with another lead drill portion. The cutting tool has an insert pocket that holds the central drill insert, the central drill insert having an effective drill axis aligned with the tool axis.

[0005] It is an object of the present invention to provide an improved indexable drilling insert having three tip portions.

[0006] It is also an object of the present invention to provide an improved indexable drilling insert that has a high cutting range relative to its size / volume.

[0007] It is a further object of the present invention to provide an improved rotary cutting tool to which the indexable drilling insert can be stably and removably secured.

[0008] It is yet a further object of the present invention to provide an improved rotary cutting tool in which the non-effective cutting edge of the indexable drilling insert is adequately protected. Summary of the Invention

[0009] According to the present invention, there is provided an indexable drilling insert, the indexable drilling insert comprising a central portion and three tip portions, the central portion has opposing first and second sides and a central axis passing through the first and second sides; The midplane is perpendicular to the central axis and passes between the two side surfaces. the three tip portions are circumferentially spaced about the central portion; Each tip portion has a first shaft and two divergent first cutting edges; a first axis intersecting the tip portion at an apex point; The two first cutting edges extend away from the first axis to two radially outermost cutting points relative to the first axis; the tip plane is perpendicular to the first axis and includes the two radially outermost cutting points; the two radially outermost cutting points are on an imaginary first circle having a center coincident with the first axis and a first cutting diameter; The midplane includes the three first axes; In a view taken along any one of the three first axes, an imaginary second circle having a second diameter circumscribes the drilling insert; The first cutting diameter is at least 60 percent of the second diameter.

[0010] There is also provided in accordance with the present invention a rotary cutting tool rotatable about a tool axis in a rotational direction and having a tool cutting diameter, the rotary cutting tool comprising: a tool shank extending along a tool axis and having a plurality of insert-receiving pockets at a forward end thereof; a plurality of cutting inserts removably secured within the plurality of insert receiving pockets; The plurality of cutting inserts include The drilling insert described above; a second cutting insert having a different structure from the drilling insert; the second cutting insert has at least one second cutting edge; One of the tip portions of the drilling insert is active and has a first axis that is coaxial with the tool axis; One of the second cutting edges of the second cutting insert is active and extends radially outward of the first cutting diameter relative to the tool axis.

[0011] For a better understanding, the invention will now be described, purely by way of example, with reference to the accompanying drawings, in which dashed and dotted lines represent the boundaries of cuts through which parts may be partially seen, in which: [Brief description of the drawings]

[0012] [Figure 1] FIG. 2 is a perspective view of a first cutting insert according to the present invention. [Diagram 2] 2 is a side view taken along the central axis of the first cutting insert shown in FIG. 1. FIG. [Diagram 3] 2 is a circumferential view of the first cutting insert shown in FIG. 1 taken along a first axis. [Figure 4] FIG. 4 is a cross-sectional view of the cutting insert shown in FIG. 2 taken along line IV-IV. [Diagram 5] 3 is a cross-sectional view of the cutting insert shown in FIG. 2 taken along line VV. [Figure 6] FIG. 6 is a cross-sectional view of the cutting insert shown in FIG. 3 taken along line VI-VI. [Figure 7] 1 is a perspective view of a rotary cutting tool according to the present invention; [Figure 8] FIG. 8 is an end view of the rotary cutting tool shown in FIG. [Figure 9] FIG. 9 is a cross-sectional view of the rotary cutting tool shown in FIG. 8 taken along line IX-IX. [Figure 10] FIG. 10 is a cross-sectional view of the rotary cutting tool shown in FIG. 9 taken along line XX. [Figure 11] FIG. 2 is an end view of a tool shank according to the present invention. [Figure 12] FIG. 12 is a cross-sectional view of the tool shank shown in FIG. 11 taken along line XII-XII. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] As shown in FIGS. 1 to 3, one embodiment of the present invention relates to a first indexable cutting insert 20 having a central portion 22 and three tip portions 24a, 24b, and 24c.

[0014] In some embodiments of the present invention, the first cutting insert 20 may be a drilling insert.

[0015] Also, in some embodiments of the present invention, the first cutting insert 20 may be manufactured by molding pressing and sintering a cemented carbide, such as tungsten carbide, and may be coated or uncoated.

[0016] As shown in FIGS. 1 to 3, the central portion 22 has opposing first and second side surfaces 26a and 26b, and a central axis AC passing through the first and second side surfaces 26a and 26b.

[0017] In some embodiments of the present invention, the first cutting insert 20 may be indexable about a central axis AC.

[0018] Additionally, in some embodiments of the present invention, the first cutting insert 20 may exhibit three-fold rotational symmetry about the central axis AC.

[0019] Furthermore, in some embodiments of the present invention, the first side 26a and the second side 26b may be identical.

[0020] As shown in Figures 1 and 2, the through hole 28 can intersect the first side 26a and the second side 26b.

[0021] In some embodiments of the present invention, through-hole 28 may be coaxial about a central axis AC.

[0022] As shown in FIGS. 1-3, the three tip portions 24a, 24b, 24c are circumferentially spaced apart around the central portion 22. As shown in FIG.

[0023] Each tip portion 24a, 24b, 24c has a first axis A1 and two first branch cutting edges 30a, 30b that extend away from the first axis A1 to two radially outermost cutting points NC1, NC2 relative to the first axis A1.

[0024] In some embodiments of the present invention, each of the first axes A1 may intersect about a central axis AC.

[0025] Also, in some embodiments of the present invention, each first axis A1 may pass through the first cutting insert 20 between the two side surfaces 26a and 26b.

[0026] Additionally, in some embodiments of the present invention, the three tip portions 24a, 24b, 24c may be circumferentially spaced apart by three recessed interface portions 32a, 32b, 32c.

[0027] It should be appreciated that the three recessed interfaces 32a, 32b, 32c may not have cutting edges.

[0028] Furthermore, in some embodiments of the present invention, the two first cutting edges 30a, 30b of each tip portion 24a, 24b, 24c may be the same.

[0029] Still further, in some embodiments of the present invention, each tip portion 24a, 24b, 24c may exhibit two-fold (ie, 180°) rotational symmetry about its respective first axis A1.

[0030] It should be appreciated that in embodiments of the present invention in which each tip portion 24a, 24b, 24c has two identical radially extending first cutting edges 30a, 30b, the cutting range of each tip portion 24a, 24b, 24c may be advantageously increased.

[0031] As shown in FIGS. 1-3, each tip portion 24a, 24b, 24c may have two abutment surfaces 34a, 34b.

[0032] It should be appreciated that configuring each tip portion 24a, 24b, 24c to include two first cutting edges 30a, 30b and two abutment surfaces 34a, 34b provides for highly efficient use of the size / volume of the insert.

[0033] In some embodiments of the present invention, the two abutment surfaces 34a, 34b of each tip portion 24a, 24b, 24c may be spaced from the two respective first cutting edges 30a, 30b by two respective clearance surfaces 36a, 36b.

[0034] Also, in some embodiments of the present invention, the two abutment surfaces 34a, 34b of each tip portion 24a, 24b, 24c may be spaced apart from one another.

[0035] It will be appreciated that the embodiment of the present invention in which the two abutment surfaces 34a, 34b of each tip portion 24a, 24b, 24c are spaced apart from the two respective first cutting edges 30a, 30b reduces the risk of unintentional damage to the first cutting edges 30a, 30b when at least one of the two abutment surfaces 34a, 34b comes into contact with a corresponding supporting surface, e.g. the tool body / shank.

[0036] In some embodiments of the present invention, the two abutment surfaces 34a, 34b of each tip portion 24a, 24b, 24c may intersect different first and second sides 26a, 26b.

[0037] 2, in a side view of the first cutting insert 20, each of the three visible abutment surfaces 34b intersects the first side surface 26a at a side edge 35b. The three side edges 35b may define a first imaginary equilateral triangle T1. A second equilateral triangle (not shown) may be formed by the three side edges formed at the intersections of the three abutment surfaces 34a and the second side surface 26b.

[0038] Also, in some embodiments of the present invention, each abutment surface 34a, 34b may intersect one of the three recessed interface portions 32a, 32b, 32c.

[0039] Furthermore, in some embodiments of the present invention, each abutment surface 34a, 34b may be flat.

[0040] As shown in FIGS. 1-3, each first axis A1 may intersect a respective tip portion 24a, 24b, 24c at a tip point NT.

[0041] In some embodiments of the present invention, the two first cutting edges 30a, 30b of each tip portion 24a, 24b, 24c may meet at a respective tip point NT.

[0042] Also, in some embodiments of the present invention, each first cutting edge 30a, 30b of each tip portion 24a, 24b, 24c may extend continuously from a respective tip point NT to a respective radially outermost cutting point NC1, NC2.

[0043] 2 and 3, a tip plane PT perpendicular to the first axis A1 includes two radially outermost cutting points NC1, NC2, and the two radially outermost cutting points NC1, NC2 are on an imaginary first circle C1 having a center coincident with the first axis A1 and the first cutting diameter DC1. The tip plane PT includes the imaginary first circle C1.

[0044] As shown in FIG. 2, in a view taken along a central axis AC, each tip point NT may be located on one side of a respective tip plane PT, and the central axis AC may be located on the opposite side of said tip plane PT.

[0045] In some embodiments of the invention, no point along the two first cutting edges 30a, 30b of each tip portion 24a, 24b, 24c is located further from the respective tip plane PT than the respective tip point NT.

[0046] As shown in FIG. 3, a midplane M perpendicular to the central axis AC includes three first axes A1.

[0047] In some embodiments of the present invention, the two radially outermost cutting points NC1, NC2 of each tip portion 24a, 24b, 24c may be located on either side of a mid-plane M.

[0048] Also, the mid-plane M passes between the two side surfaces 26a, 26b. In some embodiments of the invention, the mid-plane M may be located halfway between the first side surface 26a and the second side surface 26b.

[0049] As shown in FIG. 4, each abutment surface 34a, 34b may form a first abutment acute angle α1 with the central plane M.

[0050] In some embodiments of the present invention, the first abutment angle α1 may be greater than 50 degrees and less than 80 degrees, ie, 50°<α1<80°.

[0051] Also, in some embodiments of the present invention, the two abutment surfaces 34a, 34b of each tip portion 24a, 24b, 24c may lie completely on either side of the mid-plane M.

[0052] As shown in FIG. 2, each tip portion 24a, 24b, 24c may be bisected by a bisector plane PB that is perpendicular to midplane M and includes central axis AC.

[0053] In some embodiments of the present invention, as shown in FIG. 2, in a side view of the first cutting insert 20, each abutment surface 34a, 34b may form a second abutment acute angle α2 with a respective bisector plane PB.

[0054] Also, in some embodiments of the present invention, the second abutment angle α2 may be greater than 60 degrees, ie, α2>60°.

[0055] Furthermore, in some embodiments of the present invention, the two abutment surfaces 34a, 34b of each tip portion 24a, 24b, 24c may be located on either side of a respective bisector plane PB.

[0056] As shown in FIGS. 1 and 2, each of the first side 26a and the second side 26b may have three circumferentially spaced notches 38a, 38b, and each first cutting edge 30a, 30b of each tip portion 24a, 24b, 24c may have an adjacent cutting face 40a, 40b disposed within a corresponding one of the notches 38a, 38b.

[0057] In some embodiments of the present invention, a radially inner portion of each cutting face 40a, 40b may be disposed over a thinning groove 42a, 42b of a corresponding notch 38a, 38b.

[0058] As shown in Figures 1-3, each thinning groove 42a, 42b can have a groove path GP defined by a number of groove apexes from a series of cross sections taken in planes perpendicular to the respective first axis A1 and intersecting the thinning grooves 42a, 42b.

[0059] In some embodiments of the present invention, each gullet path GP extends away from a respective tip point NT and therefore may extend away from mid-plane M.

[0060] It will be understood that throughout the specification and claims, for each cross section taken in a plane perpendicular to any one of the first axes A1 shown in, for example, FIG. 5, and intersecting a respective thinning groove 42a, 42b, the associated groove apex is located at the midpoint of the associated contour section having the smallest radius.

[0061] 3, in a view taken along any one of the three first axes A1, an imaginary second circle C2 having a second diameter D2 circumscribes the first cutting insert 20. That is, the second circle C2 is the smallest size circle within which the entire insert can fit in the view.

[0062] In some embodiments of the present invention, the imaginary second circle C2 may have a center that coincides with the respective first axis A1.

[0063] According to the present invention, the first cutting diameter DC1 is at least 60 percent of the second diameter D2, ie, DC1 >= D2 x 0.60.

[0064] Because the first cutting diameter DC1 is at least 60 percent of the second diameter D2 for each tip portion 24a, 24b, 24c, the cutting range of the first cutting insert 20 relative to its size / volume is advantageously high, resulting in highly efficient use of the cemented carbide from which the first cutting insert 20 is typically manufactured.

[0065] In some embodiments of the present invention, the first cutting diameter DC1 may be at least 70 percent of the second diameter D2, ie, DC1 >= D2 x 0.70.

[0066] Also, in some embodiments of the present invention, the first cutting diameter DC1 may be at most 90 percent of the second diameter D2, ie, DC1≦D2×0.90.

[0067] Furthermore, in some embodiments of the present invention, as shown in FIG. 3, in a view taken along any one of three first axes A1, one of the two radially outermost cutting points NC1, NC2 of each of the two non-attached tip portions 24a, 24b, 24c may be on an imaginary second circle C2, whereby the two non-attached tip portions 24a, 24b, 24c are the two tip portions 24a, 24b, 24c that are not attached to the first axis A1 along which the view is taken.

[0068] As shown in FIG. 3, the first side 26a and the second side 26b define a first side plane P1 and a second side plane P2, and the first side plane P1 and the second side plane P2 define a maximum insert thickness T1 in a direction along the central axis AC.

[0069] In some embodiments of the present invention, the first cutting insert 20 has no portion extending outside the maximum insert thickness TI, i.e., no portion extending beyond the first side plane P1 and the second side plane P2 in each direction away from the central plane M.

[0070] Additionally, in some embodiments of the present invention, the first side plane P1 and the second side plane P2 may be parallel to the central plane M.

[0071] Further, in some embodiments of the present invention, the first cutting diameter DC1 may be at least twice the maximum insert thickness TI, ie, DC1≧TI×2.

[0072] It should be appreciated that for embodiments of the present invention in which the first cutting diameter DC1 is at least twice the maximum insert thickness TI, the cutting range of the first cutting insert 20 relative to its size or volume is advantageously high, resulting in highly efficient use of the cemented carbide from which the first cutting insert 20 is typically manufactured.

[0073] As shown in FIG. 3, the two radially outermost cutting points NC1, NC2 of each tip portion 24a, 24b, 24c may be located between the first side plane P1 and the second side plane P2, and thus, each of the two radially outermost cutting points NC1, NC2 is not included in either the first side plane P1 or the second side plane P2.

[0074] In some embodiments of the present invention, the two first cutting edges 30a, 30b of each tip portion 24a, 24b, 24c may be located completely between the first side plane P1 and the second side plane P2.

[0075] It should be appreciated that in an embodiment of the present invention in which the two first cutting edges 30a, 30b of each tip portion 24a, 24b, 24c are completely located between the first side plane P1 and the second side plane P2, the first cutting edges 30a, 30b associated with the non-effective tip portions 24a, 24b, 24c may be better protected from unintentional contact / damage during assembly of the first cutting insert 20 to a cutting tool and during cutting operations.

[0076] As shown in FIG. 3, each imaginary first circle C1 intersects with the midplane M at two intersection points NI1 and NI2.

[0077] As shown in FIG. 6, in a cross-sectional view taken on the midplane M, each intersection point NI1, NI2 is on an imaginary radial straight line RL1, RL2 including the central axis AC, and the two imaginary radial straight lines RL1, RL2 associated with each imaginary first circle form a first cutting angle β1.

[0078] In some embodiments of the present invention, the first cutting angle β1 may be greater than 70 degrees, ie, β1>70°.

[0079] Also, in some embodiments of the present invention, the first cutting angle β1 may be greater than 90 degrees, ie, β1>90°.

[0080] As shown in Figures 7-12, another aspect of the invention relates to a rotary cutting tool 44 rotatable about a tool axis AH in a rotational direction DR, the rotary cutting tool 44 having a tool cutting diameter DCT.

[0081] The rotary cutting tool 44 includes a tool shank 46 extending along a tool axis AT and having a plurality of insert receiving pockets 48, 148, 248 at a front end 50, and the plurality of cutting inserts 20, 120, 220 are removably secured within the plurality of insert receiving pockets 48, 148, 248.

[0082] In some embodiments of the present invention, the rotary cutting tool 44 may be a drilling tool.

[0083] Also, in some embodiments of the present invention, the tool shank 46 may have two groove portions 52 a , 52 b circumferentially alternating with the first land portion 54 and the second land portion 56 .

[0084] Additionally, in some embodiments of the present invention, the two groove portions 52a, 52b may extend helically from the shank front end 50 along the tool axis AT.

[0085] As shown in FIGS. 7-10, the plurality of cutting inserts 20, 120, 220 includes one of the first cutting insert 20 and the second cutting insert 120 described above, where the second cutting insert 120 has at least one second cutting edge 130a, 130b, 130c, 130d. The second cutting insert 120 has a different configuration from the first cutting insert 20. The plurality of cutting inserts may also include a third cutting insert 220 having at least one third cutting edge 230a, 230b, 230c, 230d. The third cutting insert 220 may be the same as the second cutting insert 120. Although these figures show a rotary cutting tool 44 having both the second cutting insert 120 and the third cutting insert 220, in other embodiments, only the second cutting insert 120 may be provided.

[0086] As shown in Figures 7-9, one of the tip portions 24a, 24b, 24c is active and has a first axis A1 that is coaxial with the tool axis AT, and one of the second cutting edges 130a, 130b, 130c, 130d is active and extends radially outward of a first cutting diameter DC1 relative to the tool axis AT. Also, one of the third cutting edges 230a, 230b, 230c, 230d is active and extends radially outward of the first cutting diameter DC1 relative to the tool axis AT. In the illustrated embodiment, the active third cutting edge 230a, 230b, 230c, 230d radially overlaps the active second cutting edge 130a, 130b, 130c, 130d. Also, in the illustrated embodiment, the effective cutting edges of the first cutting insert 20, the second cutting insert 120, and the third cutting insert 220 together establish a tool cutting diameter DCT.

[0087] With the first axis A1 of the effective tip portion being coaxial with the tool axis AT, the first cutting insert 20 may be described as center mounted.

[0088] In some embodiments of the present invention, the tool cutting diameter DCT may be greater than the first cutting diameter DC1.

[0089] With the first cutting diameter DC1 being at least 60 percent of the second diameter D2 for each tip portion 24a, 24b, 24c, the effective tip portions 24a, 24b, 24c and the two radially extending first cutting edges 30a, 30b can advantageously contribute more than 50 percent of the tool cutting diameter DCT, if desired.

[0090] As shown in Figures 7-12, the multiple insert receiving pockets 48, 148, 248 may include a first insert receiving pocket 48 having a seating surface 58 and spaced apart from a first support wall 60 and a second support wall 62 that intersect the seating surface 58.

[0091] In some embodiments of the present invention, the two groove portions 52 a , 52 b may communicate with the first insert-receiving pocket 48 .

[0092] Also, in some embodiments of the present invention, the first support wall 60 and the second support wall 62 may be flat, and the seating surface 58 may be flat.

[0093] Additionally, in some embodiments of the present invention, at least one of the first support wall 60 and the second support wall 62 may form a first outer support acute angle δ1 with the bearing surface 58 .

[0094] Still further, in some embodiments of the present invention, the first support angle δ1 may be equal to the first abutment angle α1.

[0095] In the assembled position of the rotary cutting tool 44 shown in FIGS. One of the first sides 26a, 26b of the first cutting insert 20 may contact the seat surface 58, One of the two abutment surfaces 34 a , 34 b of each of the two non-effective tip portions 24 a , 24 b , 24 c of the first cutting insert 20 may contact a corresponding one of the first support wall 60 and the second support wall 62 .

[0096] It should be appreciated that by configuring at least one of the first support walls 60, 62 to form a first outer support acute angle δ1 with the seat surface 58, cutting forces acting on the first support wall 60 and / or the second support wall 62 are directed partially toward the seat surface 58, thus providing a stable clamping configuration of the cutting insert 20 within the first insert receiving pocket 48.

[0097] It will be appreciated that the embodiment of the present invention in which the two abutment surfaces 34a, 34b of each tip portion 24a, 24b, 24c are spaced from the two respective first cutting edges 30a, 30b reduces the risk of unintentional damage to the first cutting edges 30a, 30b of the two non-effective tip portions 24a, 24b, 24c when one of the two abutment surfaces 34a, 34b of each of the two non-effective tip portions 24a, 24b, 24c contacts the first support wall 60 and the second support wall 62.

[0098] In some embodiments of the present invention, a fastening screw 64 may pass through the through hole 28 and threadably engage a threaded hole 66 in the seat 58 .

[0099] Also, in some embodiments of the present invention, a seating surface 58 may be formed on the first land portion 54 .

[0100] Additionally, in some embodiments of the present invention, a through opening 68 may be formed on the second land portion 56 .

[0101] It should be appreciated that in the embodiment of the present invention in which the through opening 68 is formed on the second land portion 56, the through opening 68 provides an operator access to pass the fastening screw 64 through the through hole 28 and also allows the fastening screw 64 to be tightened or loosened with a torque wrench.

[0102] As shown in FIG. 11, the second land portion 56 may include an inner wall 70 that faces the seating surface 58 of the first land portion 54 .

[0103] As shown in FIGS. 8 and 10, in the assembled position of the rotary cutting tool 44, one of the first side 26a and the second side 26b that is not in contact with the seating surface 58 may be spaced apart from the inner wall 70.

[0104] In some embodiments of the present invention, other than one of the first side surface 26a and the second side surface 26b that contacts the seat surface 58, and one of the two abutment surfaces 34a, 34b of each of the two non-effective tip portions 24a, 24b, 24c that contact the first support wall 60 and the second support wall 62, respectively, no other surfaces of the first cutting insert 20 contact any other surfaces of the first insert receiving pocket 48.

[0105] As shown in FIG. 12, the threaded hole 66 has a hole axis AB.

[0106] In some embodiments of the present invention, at each cutting edge replacement position of the first cutting insert 20, the center axis AC may be non-coaxial with the hole axis AB, and the screw hole 66 may be eccentric with respect to the through hole 28, so that when the clamping screw 64 is tightened, good contact is provided between the two abutment surfaces 34a, 34b of the two non-effective tip portions 24a, 24b, 24c and the first support wall 60 and the second support wall 62.

[0107] It should be understood that in some embodiments of the present invention, the first support wall 60 and the second support wall 62 may be arranged on different structural portions of the first insert-receiving pocket 48 so as to be elastically displaceable relative to each other, and thus the first support wall 60 and the second support wall 62 can fully correspond to the two abutment surfaces 34a, 34b of the two non-effective tip portions 24a, 24b, 24c when the tightening screw 64 is tightened.

[0108] As shown in Figures 7, 8 and 11, the multiple insert receiving pockets 48, 148, 248 may include a second insert receiving pocket 148 formed on one of the two land portions 54, 56, and the second cutting insert 120 may be removably secured within the second insert receiving pocket 148.

[0109] As shown in Figures 7, 8 and 11, the multiple insert receiving pockets 48, 148, 248 may include a third insert receiving pocket 248 formed on one of the two land portions 54, 56 that does not have the second insert receiving pocket 148, and the third cutting insert 220 may be removably secured within the third insert receiving pocket 248.

[0110] Although the invention has been described to a certain degree of detail, it should be understood that various substitutions and modifications can be made without departing from the spirit or scope of the invention as claimed below.

Claims

1. An indexable drilling insert (20), comprising: A central portion (22) and three tip portions (24a, 24b, 24c), The central portion (22) has opposing first and second sides (26a) and (26b), and a central axis (AC) passing through the first and second sides (26a) and (26b); a mid-plane (M) perpendicular to said central axis (AC) and passing between said two side surfaces (26a, 26b); the three tip portions (24a, 24b, 24c) are circumferentially spaced about the central portion (22) via three recessed interface portions (32a, 32b, 32c); Each of the tip portions (24a, 24b, 24c) has a first axis (A1) and two divergent first cutting edges (30a, 30b); The first axis (A1) intersects the tip portions (24a, 24b, 24c) at a tip point (NT), the two first cutting edges (30a, 30b) extend away from the first axis (A1) to two radially outermost cutting points (NC1, NC2) relative to the first axis (A1); a tip plane (PT) perpendicular to said first axis (A1) and including said two radially outermost cutting points (NC1, NC2); the two radially outermost cutting points (NC1, NC2) are on an imaginary first circle (C1) having a center coinciding with the first axis (A1) and the first cutting diameter (DC1); The central plane (M) includes the three first axes (A1), In a view taken along any one of the three first axes (A1), an imaginary second circle (C2) having a second diameter (D2) circumscribes the drilling insert (20), the imaginary second circle (C2) having a center coinciding with the respective first axis (A1); The drilling insert (20), wherein said first cutting diameter (DC1) is at least 60 percent of said second diameter (D2).

2. 2. The drilling insert (20) of claim 1, wherein no point along the two first cutting edges (30a, 30b) of each tip portion (24a, 24b, 24c) is located farther from the respective tip plane (PT) than the respective tip point (NT).

3. Each of the first axes (A1) intersects the central axis (AC), The drilling insert (20) according to claim 1, wherein each tip portion (24a, 24b, 24c) exhibits two-fold rotational symmetry about the respective first axis (A1).

4. The drilling insert (20) according to claim 1, wherein the two radially outermost cutting points (NC1, NC2) of each tip portion (24a, 24b, 24c) are located on either side of the mid-plane (M).

5. 2. The drilling insert (20) of claim 1, wherein the mid-plane (M) is located midway between the first side (26a) and the second side (26b).

6. the first side surface (26a) and the second side surface (26b) define a first side plane (P1) and a second side plane (P2); the first side plane (P1) and the second side plane (P2) define a maximum insert thickness (TI) in a direction along the central axis (AC); The drilling insert (20) of claim 1, wherein the drilling insert (20) has no portion extending outside the maximum insert thickness (TI).

7. The drilling insert (20) according to claim 6, wherein the first cutting diameter (DC1) is at least twice the maximum insert thickness (TI).

8. 7. The drilling insert (20) according to claim 6, wherein the two radially outermost cutting points (NC1, NC2) of each tip portion (24a, 24b, 24c) are located between the first side plane (P1) and the second side plane (P2).

9. Each of the imaginary first circles (C1) intersects with the mid-plane (M) at two intersection points (NI1, NI2), In a cross-sectional view taken on the mid-plane (M), each of the intersections (NI1, NI2) is on a virtual radial straight line (RL1, RL2) including the central axis (AC); 2. The drilling insert (20) according to claim 1, wherein the two imaginary radial straight lines (RL1, RL2) associated with each imaginary first circle (C1) form a first cutting angle (β1) greater than 70 degrees.

10. In a view taken along any one of the three first axes (A1), For the two tip portions not associated with any one of the first axes (A1) from which the figure is taken, The drilling insert (20) according to claim 1, wherein one of the two radially outermost cutting points (NC1, NC2) is on the imaginary second circle (C2).

11. The drilling insert (20) of claim 1, wherein each of said tip portions (24a, 24b, 24c) has two abutment surfaces (34a, 34b).

12. 12. The drilling insert (20) according to claim 11, wherein the two abutment surfaces (34a, 34b) of each tip portion (24a, 24b, 24c) intersect different first and second side surfaces (26a, 26b).

13. 12. The drilling insert (20) according to claim 11, wherein the two abutment surfaces (34a, 34b) of each tip portion (24a, 24b, 24c) are spaced from the two respective first cutting edges (30a, 30b) by two respective flank surfaces (36a, 36b).

14. The drilling insert (20) according to claim 11, wherein each of the abutment surfaces (34a, 34b) forms a first abutment internal acute angle (α1) with the mid-plane (M).

15. The drilling insert (20) of claim 1, wherein the first cutting diameter (DC1) is at least 70 percent of the second diameter (D2).

16. each of the first side (26a) and the second side (26b) has three circumferentially spaced apart notches (38a, 38b); 2. The drilling insert (20) of claim 1, wherein each of the first cutting edges (30a, 30b) of each of the tip portions (24a, 24b, 24c) has an adjacent cutting surface (40a, 40b) disposed within a corresponding one of the notches (38a, 38b).

17. 17. The drilling insert (20) of claim 16, wherein a radially inner portion of each cutting face (40a, 40b) is disposed on a thinning groove (42a, 42b) of a corresponding notch (38a, 38b).

18. A rotary cutting tool (44) rotatable about a tool axis (AT) in a direction of rotation (DR) and having a tool cutting diameter (DCT), a tool shank (46) extending along said tool axis (AT) and having a plurality of insert receiving pockets (48, 148, 248) at a front end (50); a plurality of cutting inserts (20, 120, 220) removably secured within the plurality of insert receiving pockets (48, 148, 248); The plurality of cutting inserts (20, 120, 220) are A drilling insert (20) according to claim 1; a second cutting insert (120) having a different structure from the drilling insert (20); the second cutting insert (120) has at least one second cutting edge (130a, 130b, 130c, 130d); one of the tip portions (24a, 24b, 24c) of the drilling insert (20) is active and has the first axis (A1) coaxial with the tool axis (AT); Two of the tip portions (24a, 24b, 24c) of the drilling insert (20) are inactive; a rotary cutting tool (44), wherein one of the second cutting edges (130a, 130b, 130c, 130d) of the second cutting insert (120) is active and extends radially outward of the first cutting diameter (DC1) relative to the tool axis (AT).

19. 20. The rotary cutting tool (44) of claim 18, wherein the tool cutting diameter (DCT) is greater than the first cutting diameter (DC1).

20. Each tip portion (24a, 24b, 24c) of the drilling insert (20) has two abutment surfaces (34a, 34b); The plurality of insert receiving pockets (48, 148, 248) includes a first insert receiving pocket (48); The first insert receiving pocket (48) has a seating surface (58) and is spaced apart from a first support wall (60) and a second support wall (62) transverse to the seating surface (58); one of the first side (26a) and the second side (26b) of the drilling insert (20) contacts the seat surface (58); 20. The rotary cutting tool (44) of claim 18, wherein one of the two abutment surfaces (34a, 34b) of each of the two ineffective tip portions (24a, 24b, 24c) of the drilling insert (20) contacts a corresponding one of the first support wall (60) and the second support wall (62).

21. a through hole (28) intersects the first side surface (26a) and the second side surface (26b); 21. The rotary cutting tool (44) of claim 20, wherein a fastening screw (64) passes through the through hole (28) and threadably engages a threaded hole (66) in the seat (58).

22. The tool shank (46) has two groove portions (52a, 52b) circumferentially alternating with first and second land portions (54, 56); The rotary cutting tool (44) of claim 20, wherein the seating surface (58) is formed on the first land portion (54).

23. the plurality of cutting inserts (20, 120, 220) further includes a third cutting insert (220) that is identical to the second cutting insert (120); the third cutting insert (220) has at least one third cutting edge (230a, 230b, 230c, 230d); one of the third cutting edges (230a, 230b, 230c, 230d) of the third cutting insert (220) is active and extends radially outward of the first cutting diameter (DC1) relative to the tool axis (AT); 20. The rotary cutting tool (44) of claim 18, wherein effective cutting edges of the drilling insert (20), the second cutting insert (120), and the third cutting insert (220) together establish the tool cutting diameter (DCT).

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