Reversible square cutting insert and rotary cutting tool

Abstract

In a cutting tool rotatable about a tool axis, a reversible cutting insert is removably fixed to a tool body. The cutting insert has opposing upper and lower end faces interconnected by a peripheral surface and a median plane disposed between the upper and lower end faces. The peripheral surface includes four side faces alternated with four corner faces, and the side faces and corner faces intersect with the upper surface to form upper major cutting edges and upper corner cutting edges, respectively. Each side face has a median face and an upper major flank face. Each upper major flank face forms an acute internal upper major flank angle with the median plane, and the median plane intersects with the four median faces to define an imaginary median square. When viewed from the top of the cutting insert, the four upper major cutting edges define an imaginary upper major square that is rotationally offset from the imaginary median square.

Description

[Technical Field]

[0001] The present invention relates generally to cutting inserts and cutting tools for use in metal cutting processes, and more particularly to rotatable cutting tools having reversible cutting inserts for milling operations. [Background technology]

[0002] In the field of rotatable cutting tools used in milling processes, there are many examples of reversible cutting inserts removably secured to a cutting body. In one example, the cutting insert is a square insert.

[0003] U.S. Patent No. 7,604,441 discloses a fully indexable square cutting insert having four side faces connecting two end faces. At the intersection of each side face with one end face is a main cutting edge extending downward from the insert corner and along the first side face toward the median face. A wiper extends upward from the same insert corner along an adjacent side face, away from the median face, and rises above the abutment surface of the associated end face. The cutting insert and the insert pocket in which it sits are shaped such that the main cutting edge has a positive axial angle (helical), while the insert has an overall negative axial angle to provide axial clearance and an overall negative radial angle to provide radial clearance.

[0004] U.S. Patent No. 8,491,234 discloses a double-sided cutting insert having multiple indexable convex cutting edges. The cutting insert has an upper surface, a lower surface, at least three convex cutting edges on each surface connected by at least three nose corners, at least three peripheral side surfaces extending from each surface toward an imaginary midplane, and a lateral bearing surface common to each peripheral side surface. Each convex cutting edge has at least a curved cutting edge region and further has a substantially straight primary cutting edge region intermediate the curved cutting edge region and the nose corner. Each peripheral side surface further has a flat primary facet associated with the substantially straight primary cutting edge, and each surface is singularly oriented in the same direction. Furthermore, in various embodiments, the upper and lower surfaces of the cutting insert can be formed to be twisted or rotated relative to each other.

[0005] U.S. Patent No. 8,641,331 discloses a milling insert having a square or triangular rake face delimited in plan view by straight cutting edges and peripheral cutting edges with curved cutting corners. Each cutting edge has an inclined region inclined toward the cutting corner, extending beyond the tangent point determined by the point where the straight cutting edge transitions into the curved cutting corner, adjacent to which the cutting edge rises before the point determined by the cutting corner angle bisector, said raised region extending maximally to a cutting edge on the other side of the cutting corner of an adjacent cutting edge, which is straight in plan view, from which the cutting edge continues, again inclined, and inclined downward, resulting in a rotationally symmetrical configuration with cutting edges of the same shape.

[0006] U.S. Patent No. 9,724,770 discloses a double-sided milling insert having eight major cutting edges and eight wiper edges. The cutting insert includes an upper surface, a lower surface, and four side surfaces. Each side surface includes a first sub-surface and a second sub-surface inclined relative to each other. The first sub-surface has a major cutting edge adjacent to the upper surface and a wiper edge adjacent to the lower surface. The second sub-surface has a wiper edge adjacent to the upper surface and a major cutting edge adjacent to the lower surface. The wiper edges of the second sub-surface are inclined inward relative to the cutting insert with respect to the major cutting edges of the first sub-surface. The wiper edges of the first sub-surface are inclined inward relative to the cutting insert with respect to the major cutting edges of the second sub-surface.

[0007] SUMMARY OF THE INVENTION It is an object of the present invention to provide an improved reversible cutting insert having four major cutting edges per end face.

[0008] It is also an object of the present invention to provide an improved reversible cutting insert with a robust cutting edge.

[0009] It is a further object of the present invention to provide an improved rotatable cutting tool in which the cutting insert is removably secured to the tool body with a high level of stability.

[0010] It is yet another object of the present invention to provide an improved rotatable cutting tool having a greater number of cutting inserts circumferentially spaced about the tool body.

[0011] It is yet another object of the present invention to provide an improved rotatable cutting tool capable of performing square shoulder milling cuts. Summary of the Invention

[0012] According to one aspect of the present invention, there is provided a reversible cutting insert, the cutting insert comprising: having opposed upper and lower end surfaces interconnected by a continuous peripheral surface, a median plane disposed between the upper and lower end surfaces and intersecting the peripheral surfaces to form an insert boundary line and an insert axis perpendicular to the median plane about which the cutting insert is indexable; the peripheral surface includes four corner surfaces and four side surfaces alternately arranged in the circumferential direction; the side and corner surfaces intersect the upper end surface at upper side edges and upper corner edges, respectively, each upper side edge having an upper major cutting edge, and each upper corner edge having an upper corner cutting edge; each side surface including a median surface and an upper major clearance surface adjacent a respective upper major cutting edge; when viewed in a cross section along one of the upper major cutting edges, each upper major relief surface forms an acute internal upper major relief angle with respect to the median plane; the median plane intersects the four median planes to define an imaginary median square having an imaginary inscribed median circle with a median diameter and a center coincident with the insert axis; When viewed from the top end of the cutting insert, the four upper major cutting edges define an imaginary upper major square having an imaginary inscribed upper outer circle with a center coincident with the upper outer diameter and the insert axis; The imaginary upper main square is rotationally offset from the imaginary mid-square about the insert axis.

[0013] According to another aspect of the present invention, there is provided a cutting tool rotationally rotatable about a tool axis, the cutting tool comprising: a tool body extending in the front-rear direction along a tool axis; at least one reversible cutting insert of the type described above removably secured in an insert-receiving pocket of the tool body; One of the upper corner cutting edges of each cutting insert is active, One of the upper main cutting edges of each cutting insert adjacent to the active upper corner cutting edge is the active upper main cutting edge.

[0014] 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 for partial views of elements. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a perspective view of a cutting insert according to an embodiment of the present invention; [Figure 2] FIG. 2 is an end view of the cutting insert shown in FIG. [Figure 3] FIG. 2 is a side view of the cutting insert shown in FIG. [Figure 4] 4 is a cross-sectional view of the cutting insert shown in FIG. 2 taken along line IV-IV. [Figure 5] 3 is a partial cross-sectional view of the cutting insert shown in FIG. 2 taken along line VV. [Figure 6] 6 is a partial cross-sectional view of the cutting insert shown in FIG. 2 taken along line VI-VI. [Figure 7] 1 is a perspective view of a cutting tool according to an embodiment of the present invention; [Figure 8] FIG. 8 is a side view of the cutting tool shown in FIG. 7. [Figure 9] FIG. 9 is a first detailed view of the cutting tool shown in FIG. 8. [Figure 10] FIG. 9 is a second detailed view of the cutting tool shown in FIG. 8. [Figure 11] FIG. 8 is an end view of the cutting tool shown in FIG. 7. [Figure 12] FIG. 12 is a detailed view of the cutting tool shown in FIG. [Figure 13] FIG. 8 is a first detailed view of the cutting tool shown in FIG. 7 with the cutting insert and clamping screw removed. [Figure 14] FIG. 9 is a third detailed view of the cutting tool shown in FIG. 8 with the cutting insert and clamping screw removed. [Figure 15] 9 is a cross-sectional view taken along line XV-XV of the cutting tool shown in FIG. 8. [Figure 16] FIG. 16 is a detailed view of the cutting tool shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0016] One aspect of the present invention, as shown in Figures 1-3, relates to a reversible cutting insert 20 having opposing upper and lower end faces 22 and 122 interconnected by a continuous peripheral surface 24, the peripheral surface 24 including four corner faces 28 and four circumferentially alternating side faces 26.

[0017] In one embodiment of the present invention, the cutting insert 20 may be preferably manufactured by molding, pressing and sintering a cemented carbide such as tungsten carbide, and may be coated or uncoated.

[0018] As shown in FIG. 3, the cutting insert 20 has a median plane M disposed between the upper end surface 22 and the lower end surface 122 and intersecting the peripheral surface 24 to form an insert boundary line LB.

[0019] In some embodiments of the present invention, the median plane M may be located midway between the upper end surface 22 and the lower end surface 122 .

[0020] Additionally, in some embodiments of the present invention, the cutting insert 20 may be configured such that, in end view, no portion of the cutting insert 20 extends outside the insert boundary line LB, as shown in FIG.

[0021] As shown in FIGS. 1 to 3, the cutting insert 20 has an insert axis AI that is perpendicular to a median plane M about which the cutting insert 20 is indexable.

[0022] In some embodiments of the present invention, a through hole 30 coaxial with the insert axis AI may intersect the upper end surface 22 and the lower end surface 122 .

[0023] In addition, in some embodiments of the present invention, the cutting insert 20 may be manufactured by directly pressing along the direction of the insert axis AI.

[0024] Additionally, in some embodiments of the present invention, the cutting insert 20 may be pressed into its final shape and the peripheral surface 24 may be unpolished.

[0025] As shown in Figures 1 to 3, the side surfaces 26 and corner surfaces 28 intersect the upper end surface 22 at upper side edges 32 and upper corner edges 34, respectively, and each upper side edge 32 has an upper major cutting edge 36, and each upper corner edge 34 has an upper corner cutting edge 38.

[0026] In some embodiments of the present invention, each upper corner cutting edge 38 may be curved.

[0027] Additionally, in some embodiments of the present invention, each upper major cutting edge 36 may be tangentially adjacent to one of the upper corner cutting edges 38 .

[0028] As shown in FIG. 3, the four upper main cutting edges 36 may be completely contained within an upper horizontal plane PH perpendicular to the insert axis AI.

[0029] In some embodiments of the present invention, the four upper corner cutting edges 38 may be completely contained within the upper horizontal plane PH.

[0030] As shown in FIGS. 1 to 4, the upper end surface 22 may have an upper central plane 40, and the upper central plane 40 may be disposed between the median plane M and the upper horizontal plane PH.

[0031] In some embodiments of the present invention, the upper central surface 40 may be perpendicular to the insert axis AI.

[0032] Additionally, in some embodiments of the present invention, the through-holes 30 may intersect the upper central plane 40 .

[0033] As shown in FIGS. 1 and 2, the top surface 22 may include an upper rake surface 42 that extends adjacent the upper side edges 32 and the upper corner edges 34 .

[0034] In some embodiments of the present invention, the upper rake surface 42 may surround the upper central surface 40 .

[0035] As shown in FIGS. 1-3, each upper side edge 32 may include an upper minor cutting edge 44 .

[0036] In some embodiments of the present invention, the four upper minor cutting edges 44 may be completely contained within the upper horizontal plane PH.

[0037] Additionally, in some embodiments of the present invention, the upper side edges 32 and upper corner edges 34 may be completely contained within the upper horizontal plane PH.

[0038] As shown in FIGS. 1 and 3, each side surface 26 includes a median surface 46, and each side surface 26 also includes an upper major clearance surface 48 adjacent the respective upper major cutting edge 36.

[0039] In some embodiments of the present invention, each median surface 46 may be perpendicular to the median plane M.

[0040] Additionally, in some embodiments of the present invention, each upper major clearance surface 48 may intersect with top surface 22 to form a respective upper major cutting edge 36 .

[0041] Furthermore, in some embodiments of the present invention, each upper major clearance surface 48 may not be intersected by median plane M.

[0042] As shown in FIG. 4, in a cross-sectional view taken along one of the upper major cutting edges 36, each upper major relief surface 48 forms an acute internal upper major relief angle β1 with respect to the median plane M.

[0043] Also, as shown in FIG. 4, the cross-sectional view along one of the upper major cutting edges 36 may include the insert axis AI.

[0044] It should be understood that the use of the terms "interior angle" and "exterior angle" throughout this description and claims refers to the angle between two linear features as measured on the interior and exterior, respectively, of the member on which at least one of the linear features is formed.

[0045] It should be appreciated that each upper major flank surface 48, also known as an "inverted" flank surface, extends generally outward (i.e., away from the insert axis AI) from the respective upper major cutting edge 36 toward the median plane M, thereby providing beneficial support and rigidity to each upper major cutting edge 36.

[0046] In some embodiments of the present invention, each upper major clearance surface 48 may be flat.

[0047] Also, in some embodiments of the present invention, the upper major relief angle β1 may have a minimum value of 75 degrees and a maximum value of 85 degrees, ie, 75°≦β1≦85°.

[0048] It should be appreciated that in embodiments of the present invention where the upper major clearance angle β1 associated with each upper major clearance face 48 has a minimum value of 75 degrees and a maximum value of 85 degrees, each upper major cutting edge 36 is beneficially supported and advantageously rigid.

[0049] As shown in FIG. 4, in a cross-sectional view taken along one of the upper major cutting edges 36, each upper major flank surface 48 may form an acute internal upper major rake angle σ1 with respect to the upper rake face 42.

[0050] In certain embodiments of the present invention, the upper major rake angle σ1 may have a minimum value of 65 degrees and a maximum value of 75 degrees, i.e., 65°≦σ1≦75°.

[0051] As shown in FIG. 3, in a side view of the cutting insert 20, the upper major relief surface 48 (visible in this view) may have a variable upper major relief width WJ parallel to the insert axis AI, and the upper major relief width WJ may increase in a transverse direction SD parallel to the median plane M.

[0052] In one embodiment of the present invention, the upper main clearance width WJ may increase continuously in the lateral direction SD along the entire length of each upper main cutting edge 36.

[0053] As shown in FIG. 3 , in a side view of the cutting insert 20 , the lateral direction SD may extend from the upper major cutting edge 36 to the upper minor cutting edge 44 of the same upper side edge 32 .

[0054] As shown in FIG. 3, each side surface 26 may also include an upper minor clearance surface 50 adjacent the respective upper minor cutting edge 44 .

[0055] In some embodiments of the present invention, each upper minor clearance surface 50 may intersect with the top end surface 22 to form a respective upper minor cutting edge 44 .

[0056] As shown in FIG. 5, in a cross-sectional view along one of the upper minor cutting edges 44, each upper minor clearance surface 50 may be perpendicular to the median plane M.

[0057] In some embodiments of the present invention, each upper minor relief surface 50 may be coplanar with its associated median surface 46 .

[0058] As shown in FIG. 2, the median plane M intersects the four median surfaces 46 to define an imaginary median square SM having an imaginary inscribed median circle CM with a median diameter DM.

[0059] It should also be understood that, as shown in FIG. 2, the imaginary inscribed median circle CM has a center that coincides with the insert axis AI.

[0060] Furthermore, as shown in FIG. 2, the imaginary median square SM may be divided into four identical quadrants Q1, Q2, Q3, and Q4 by mutually perpendicular first and second vertical planes PV1 and PV2 that contain the insert axis AI and intersect the four side surfaces 26.

[0061] In some embodiments of the present invention, each upper major cutting edge 36 may be located in or straddle two of the four quadrants Q1, Q2, Q3, Q4.

[0062] Also, in some embodiments of the present invention, each upper major clearance surface 48 may be located in or straddle two of the four quadrants Q1, Q2, Q3, Q4.

[0063] Furthermore, in some embodiments of the present invention, each upper corner cutting edge 38 may be located in only one of the four quadrants Q1, Q2, Q3, Q4.

[0064] Furthermore, in some embodiments of the present invention, each upper minor cutting edge 44 may be located in only one of the four quadrants Q1, Q2, Q3, Q4.

[0065] As shown in FIG. 2, in a top view of the cutting insert 20, the four upper major cutting edges 36 define an imaginary upper major square SJ having an imaginary inscribed upper outer circle CJ with an upper outer diameter DJ.

[0066] It should also be understood that, as shown in FIG. 2, the imaginary inscribed upper outer circle CJ has a center that coincides with the insert axis AI.

[0067] 2, in a top view of the cutting insert 20, the imaginary upper main square SJ is rotationally offset from the imaginary midline square SM about the insert axis AI. In this application, "rotationally offset" means that both the square SJ and the square SM are centered on the index axis AI, but one side of one square is not parallel to the other side of the other square.

[0068] In some embodiments of the present invention, the median diameter DM may be greater than the superior outer diameter DJ.

[0069] In one embodiment of the present invention, the maximum upper main relief width WJ of each upper main relief surface 48 MAX may be greater than 20 percent of the upper outer diameter DJ, i.e., WJ MAX>0.20×DJ.

[0070] Furthermore, in one embodiment of the present invention, the maximum upper main relief width WJ MAX may be greater than 20 percent of the median diameter DM, i.e., WJ MAX >0.20×DM.

[0071] Maximum upper main relief width WJ of each upper main relief surface 48 MAX It should be appreciated that in embodiments of the present invention where is greater than 20 percent of the upper outer diameter DJ, each upper major cutting edge 36 is advantageously robust.

[0072] As shown in FIGS. 1, 2, and 4, the through-hole 30 has a hole axis range EA from the upper end surface 22 to the lower end surface 122.

[0073] In some embodiments of the present invention, the bore axis extent EA may be greater than 40 percent of the upper outer diameter DJ, i.e., EA>0.40×DJ.

[0074] Also, in some embodiments of the present invention, the foramen axial extent EA may be greater than 40 percent of the median diameter DM, i.e., EA>0.40×DM.

[0075] As shown in FIG. 2, the four upper minor cutting edges 44 may define an imaginary upper minor square SN having an imaginary inscribed upper minor circle CN having an upper inner diameter DN.

[0076] As shown in FIG. 2, in a top view of the cutting insert 20, the imaginary upper secondary square SN may coincide with the imaginary median square SM.

[0077] It should be understood that in embodiments of the present invention where the imaginary upper minor square SN coincides with the imaginary median square SM, the median diameter DM may be equal to the upper internal diameter DN.

[0078] 2, imaginary upper major square SJ is nested within imaginary upper minor square SN. Thus, in an end view of the insert 20, the upper major cutting edge 36 of a given upper side edge 32 is recessed relative to the upper minor cutting edge 44 of the same upper side edge 32. Furthermore, in some embodiments, the upper major cutting edge 36 is longer than the upper minor cutting edge 44 in a top view.

[0079] As shown in FIGS. 1 to 3, each upper corner cutting edge 36 has a first corner end point NC1 and a second corner end point NC2.

[0080] In one embodiment of the present invention, each first corner end point NC1 may coincide with a first minor end point NN1 of one of the upper minor cutting edges 44, and each second corner end point NC2 may coincide with a first major end point NJ1 of one of the upper major cutting edges 36.

[0081] As shown in FIG. 2, in a top view of the cutting insert 20, the upper major cutting edge 36 and the upper minor cutting edge 44 associated with each upper corner cutting edge 38 may form an acute internal upper corner angle α1.

[0082] In some embodiments of the present invention, the upper corner angle α1 may have a value greater than 80 degrees, ie, α1>80°.

[0083] As shown in FIGS. 1-3, each side surface 26 may have an upper undercut 52 formed with an undercut direction DU parallel to the associated side of the imaginary median square SM.

[0084] It should be understood that use of the term "undercut" throughout this description and claims refers to a recess where a line extending from a given sub-surface of the recess in a particular undercut direction intersects another sub-surface of the same recess.

[0085] In some embodiments of the present invention, each upper undercut 52 may be recessed relative to the associated upper minor relief surface 50 .

[0086] Additionally, in some embodiments of the present invention, each upper primary clearance surface 48 may be located in an upper undercut 52 of a respective side surface 26 .

[0087] 1-3, each upper undercut 52 may include an upper interface 54. Upper interface 54 may connect upper major relief surface 48 to upper minor relief surface 50.

[0088] In some embodiments of the present invention, each upper joining surface 54 may intersect top surface 22 at an upper joining edge 56 .

[0089] Also, in some embodiments of the present invention, each upper joining edge 56 may extend between the upper major cutting edge 36 and the upper minor cutting edge 44 associated with the same upper side edge 32 .

[0090] Additionally, in some embodiments of the present invention, each upper joining edge 56 may not be a cutting edge.

[0091] As shown in Figures 5 and 6, the first virtual straight line L1 and the second virtual straight line L2 extend perpendicular to the median plane M and intersect with one of the first corner end point NC1 and the second corner end point NC2 of the upper corner cutting edge, respectively.

[0092] In one embodiment of the present invention, the first imaginary straight line L1 may intersect with the insert boundary line LB.

[0093] In addition, in one embodiment of the present invention, the second imaginary straight line L2 may pass through the median plane M inside the insert boundary line LB.

[0094] As shown in FIGS. 1-3, each corner face 28 may include an upper corner relief surface 58 adjacent the respective upper corner cutting edge 38.

[0095] It will be appreciated that in embodiments of the present invention in which the second imaginary straight line L2 passes through the median plane M inside the insert boundary line LB, each upper corner relief surface 58 may be partially conical and tapered away from the median plane M, so that each upper minor cutting edge 44 is beneficially supported and advantageously rigid.

[0096] In one embodiment of the present invention, a third imaginary straight line L3 extending perpendicular to the median plane M and intersecting one of the upper main cutting edges 36 at any point along its length may pass through the median plane M inside the insert boundary line LB.

[0097] In some embodiments of the present invention, the upper surface 22 and the lower surface 122 may be the same.

[0098] In embodiments of the present invention in which the upper end surface 22 and the lower end surface 122 are identical, it will be understood that throughout the drawings, this description and claims, all features relating to the lower end surface 122 are assigned the same reference numerals as the corresponding features relating to the upper end surface 22, except that the digit "100" is added before those features.

[0099] In an embodiment of the present invention, the cutting insert 20 may exhibit two-fold rotational symmetry about a first axis A1 formed at the intersection of the first vertical plane PV1 and the median plane M.

[0100] In addition, in an embodiment of the present invention, the cutting insert 20 may exhibit two-fold rotational symmetry about a second axis A2 formed at the intersection line between the second vertical plane PV2 and the median plane M.

[0101] Furthermore, in some embodiments of the present invention, the cutting insert 20 may exhibit four-fold rotational symmetry about the insert axis AI.

[0102] Another aspect of the present invention relates to a cutting tool 60 rotatable about a tool axis AT in a rotational direction RD, as shown in Figures 7 to 12. The cutting tool 60 has a tool body 62 extending in a forward direction DF and a rearward direction DR along the tool axis AT, and at least one reversible cutting insert 20 removably secured in an insert-receiving pocket 64 of the tool body 62.

[0103] In one embodiment of the present invention, the cutting tool 60 may have N cutting inserts 20 removably secured in N insert-receiving pockets 64 circumferentially spaced about the tool body 62, where N is a positive integer greater than 1.

[0104] It should be understood throughout this specification and claims that the number of cutting inserts 20 is equal to the number of insert-receiving pockets 64, where N is a specified integer greater than one.

[0105] As shown in Figures 7 and 8, the tool body 62 may have axially opposed front and rear body ends 66 and 68.

[0106] In some embodiments of the present invention, each insert-receiving pocket 64 may be open toward the front body end 66 .

[0107] Additionally, in some embodiments of the present invention, cutting tool 60 may exhibit N-fold rotational symmetry about tool axis AT.

[0108] As shown in FIGS. 13 and 14, each insert-receiving pocket 64 may have a seating surface 70 intersected by an axial support wall 72 and a radial support wall 74 .

[0109] In some embodiments of the present invention, the bearing surface 70 may face the direction of rotation RD.

[0110] Additionally, in some embodiments of the present invention, the seating surface 70 may be flat.

[0111] Additionally, in some embodiments of the present invention, axial support wall 72 may face axially forward and radial support wall 74 may face radially outward.

[0112] With at least one reversible cutting insert 20 secured in its respective insert-receiving pocket 64: The lower end surface 122 may be in clamping contact with the seating surface 70; a first side surface 26a of the four sides may be in clamping contact with the axial support wall 72; A second of the four sides 26 b may be in clamping contact with the radial support wall 74 .

[0113] In embodiments of the present invention in which the upper end surface 22 and the lower end surface 122 are identical, the lower end surface 122 may have a lower central surface 140 , and the lower central surface 140 may make clamping contact with the seating surface 70 .

[0114] As shown in FIGS. 7 and 13, a clamping screw 76 may extend through the through hole 30 and threadingly engage a threaded hole 78 in the seating surface 70 having a hole axis AB.

[0115] In some embodiments of the present invention, the insert axis AI may be offset from the bore axis AB.

[0116] It should be appreciated that in embodiments of the present invention in which the insert axis AI is offset from the bore axis AB, tightening the clamping screw 76 ensures clamping contact between the first and second sides 26a, 26b of the cutting insert and the axial and radial support walls 72, 74 of the insert receiving pocket, respectively.

[0117] As shown in Figures 15 and 16, in a cross-sectional view taken at a first tool plane PT1 that is perpendicular to the tool axis AT and intersects at least one seating surface 70, a second tool plane PT2 encompasses the tool axis AT and the radially outermost seating point NO of one of the seating surfaces 70.

[0118] In one embodiment of the present invention, the seating surface 70 may form an acute internal radial pocket angle τ1 with the second tool plane PT2.

[0119] Furthermore, in one embodiment of the present invention, the radially outermost seating point NO may not only be the radially outermost point of the seating surface 70 in a cross-sectional view taken at the first tool plane PT1, but may also be the absolute radially outermost point of the seating surface 70 relative to the tool axis line AT.

[0120] It will be appreciated that in embodiments of the present invention in which each seating surface 70 faces the direction of rotation RD and the radial pocket angle τ1 is an internal angle as opposed to an external angle, a reduction in the circumferential spacing between adjacent insert receiving pockets 64 may be achieved without interference from the adjacent, rotationally preceding portion of the tool body 62 while properly directing and threadingly engaging each clamping screw 76 with the threaded hole 78 of the respective insert receiving pocket through the through hole 30 of the respective cutting insert.

[0121] In certain embodiments of the present invention, the radial pocket angle τ1 may have a value greater than 3 degrees, i.e., τ1>3°.

[0122] As shown in FIG. 15, the N radially outermost seating points NO of the N seating surfaces 70 are spaced apart by a maximum seating diameter DS MAX Define an imaginary center circle CS having the following:

[0123] It should be understood that in some embodiments of the present invention, the imaginary seat circle CS may have a center that coincides with the tool axis AT.

[0124] In one embodiment of the present invention, in the fixed state of the at least one reversible cutting insert 20, the lower end surface 122 of each cutting insert 20 may contact the respective radially outermost seating point NO.

[0125] Also, in some embodiments of the present invention, in the fixed state of the at least one reversible cutting insert 20, the lower central surface 140 of each cutting insert 20 may contact the respective radially outermost seating point NO.

[0126] As shown in Figures 9 and 16, the upper major relief surface 48 of the first side surface 26a may be in clamping contact with the axial support wall 72, and the median surface 46 of the second side surface 26b may be in clamping contact with the axial support wall 74.

[0127] As shown in FIG. 14, the axial support wall 72 may form an acute external axial support angle Φ 1 with the bearing surface 70 .

[0128] It should be appreciated that in embodiments of the present invention in which axial support wall 72 forms an acute external axial support angle Φ1 with bearing surface 70, axial support wall 72 is configured to provide a “dovetail” clamp.

[0129] In certain embodiments of the present invention, the acute axial support angle Φ1 may have a value less than or equal to 85 degrees, i.e., Φ1≦85°.

[0130] Additionally, in some embodiments of the present invention, the acute axial support angle Φ1 may correspond to an upper major relief angle β1.

[0131] It should be understood that in embodiments of the present invention in which the acute external axial support angle Φ1 corresponds to the upper major relief angle β1, a dovetail clamping contact may occur between the axial support wall 72 and the upper major relief surface 48 of the first side 26a.

[0132] It should also be appreciated that in embodiments of the present invention in which dovetail clamping contact occurs between the axial support wall 72 and the upper major clearance surface 48 of the first side surface 26a, the cutting insert 20 can be removably secured in its respective insert receiving pocket 64 with a high level of stability.

[0133] As shown in FIG. 16, the radial support wall 74 may be perpendicular to the seating surface 70 .

[0134] In one embodiment of the present invention, the radial support wall 74 may include two radial support sub-walls 74a, 74b spaced axially relative to the tool axis AT.

[0135] As shown in Figures 7 to 12, one of the upper corner cutting edges 38 of each cutting insert 20 is active, and one of the upper main cutting edges 36 of each cutting insert 20 adjacent to the active upper corner cutting edge 38 is active.

[0136] It should be understood throughout this description and claims that the cutting insert 20 may have four index positions on the upper end surface 22, and that in each index position a different one of the upper corner cutting edges 38 is active and a different one of the upper main cutting edges 36 is active.

[0137] The cutting insert 20 may also be described as being reversible and "double-sided" or "double-ended" such that the upper end surface 22 may contact the seating surface 70 when secured in its respective insert receiving pocket 64, and in embodiments where the upper end surface 22 and the lower end surface 122 are identical, the lower end surface 122 may have four lower main cutting edges 136, one of which is active, and four lower main cutting edges 136, one of which is active.

[0138] As shown in Figures 9 and 10, the upper main clearance width WJ of the upper main clearance surface 48 associated with the active upper main cutting edge 36 may increase in the lateral direction SD away from the active upper corner cutting edge 38.

[0139] As shown in FIG. 9, the active upper major cutting edge 36 of each cutting insert 20 may have a negative axial rake angle λ1.

[0140] In certain embodiments of the present invention, the negative axial rake angle λ1 may have a magnitude greater than 3 degrees.

[0141] Additionally, in some embodiments of the present invention, one of the upper minor cutting edges 44 of each cutting insert 20 adjacent to the active upper corner cutting edge 38 may be active.

[0142] As shown in FIGS. 11 and 12, the active upper minor cutting edge 44 of each cutting insert 20 may have a negative radial rake angle δ1.

[0143] It should be understood that in some embodiments of the present invention, the negative radial rake angle δ1 may be greater than the radial pocket angle τ1, and that increasing the radial pocket angle τ1 increases the negative radial rake angle δ1.

[0144] Also, in some embodiments of the present invention, the negative radial rake angle δ1 may have a magnitude greater than 10 degrees.

[0145] In embodiments of the present invention in which the radial rake angle δ1 is a negative value, particularly in embodiments in which the negative radial rake angle δ1 has a magnitude greater than 10 degrees, the cutting load acting on the upper minor cutting edge 44 may be distributed evenly along the upper minor cutting edge 44, thus reducing the risk of cutting edge breakage.

[0146] In some embodiments of the present invention, the radial clearance angle (not shown) between the active upper primary flank face 48 of each cutting insert 20 and the workpiece 80 may have a value between 5 degrees and 10 degrees.

[0147] From Figures 15 and 16, it can be seen that with the upper primary flank 48 configured as an "inverted" flank, it can generally be seen that increasing the radial pocket angle τ1 increases the radial clearance angle, while larger values ​​of radial pocket angle τ1 can be achieved while maintaining an optimum value of the radial clearance angle, e.g., 5 to 10 degrees.

[0148] As shown in FIG. 16, the cutting force FC acting on the active upper main cutting edge 36 of each cutting insert 36 may be directed in a tangential force direction FD, and an acute radial inclination angle ε1 may be formed between the tangential force direction FD and the seat surface 70.

[0149] In an embodiment of the present invention, the radial tilt angle ε1 may have a value between 70 degrees and 80 degrees, ie, 70°<ε1<80°.

[0150] 15 and 16, it can be generally seen that increasing the radial pocket angle τ1 reduces the radial tilt angle ε1, which is typically associated with reduced clamping stability. However, due to the dovetail clamping contact between the axial support wall 72 and the upper major flank surface 48 of the first side surface 26a of each cutting insert 20, larger values ​​of the radial pocket angle τ1 are achievable while maintaining a high level of clamping stability.

[0151] As shown in FIGS. 11 and 15, the active upper major cutting edge 36 of each cutting insert 20 may define a tool cutting diameter DTC.

[0152] It is known in the art that the number N of cutting inserts 20 and the number N of insert receiving pockets 64 circumferentially spaced about the tool body 62 can be approximately proportional to the tool cutting diameter DTC. In embodiments of the present invention configured with a radial pocket angle τ1 that is an internal angle rather than an external angle, reduced circumferential spacing between adjacent insert receiving pockets 64 can be achieved while each clamping screw 76 is well oriented and threadedly engaged through the through hole 30 of the respective cutting insert and into the threaded bore 78 of the respective insert receiving pocket without interference from the adjacent rotational leading portion of the tool body 62 so that the number N of insert receiving pockets 64 and the number N of cutting inserts 20 can be increased for a given tool cutting diameter DTC.

[0153] In one embodiment of the present invention, N multiplied by the pocket spacing factor FP is equal to the tool cutting diameter DTC, i.e., N×FP=DTC, and the pocket spacing factor FP may be less than or equal to 8.5, i.e., FP<8.5.

[0154] Also, in some embodiments of the present invention, the pocket spacing factor FP may be less than or equal to 8, i.e., FP<8.

[0155] It is understood that throughout this specification and claims, the pocket spacing factor FP has units of millimeters and the ratio of N to the tool cutting diameter DTC applies when the tool cutting diameter DTC is measured in millimeters.

[0156] As shown in FIG. 11, in an embodiment of the present invention where N multiplied by the pocket spacing factor FP is equal to the tool cutting diameter DTC, i.e., N×FP=DTC, the angular spacing range ES (degrees) between circumferentially adjacent insert receiving pockets 64 is equal to 360° / (DTC / FP), i.e., ES=360° / (DTC / FP).

[0157] As shown in Figs. 15 and 16, the tool cutting diameter DTC and the maximum seat diameter DS MAX Half the difference between these defines a first diameter range ER1.

[0158] In some embodiments of the present invention, the first diameter range ER1 may be less than 25 percent of the upper outer diameter DJ, i.e., ER1<0.25×DJ.

[0159] It should be appreciated that in embodiments of the present invention in which the first radial range ER1 is less than 25 percent of the upper outer diameter DJ, the radial tilting moment (not shown) of the cutting force FC about each radially outermost seating point NO is advantageously reduced.

[0160] As shown in FIG. 16, the imaginary seating circle CS intersects with the upper end surface 22 of each cutting insert 20 at an upper intersection point NI.

[0161] In one embodiment of the present invention, the upper intersection point NI and the active upper corner cutting edge 38 of the same cutting insert 20 may be located in the same quadrant of the four quadrants Q1, Q2, Q3, Q4 of the insert, and therefore the active upper corner cutting edge 38 can be fully supported by the seat surface 70.

[0162] As shown in Figures 8 and 10, cutting tool 60 has a depth of cut DC measured parallel to tool axis AT.

[0163] In one embodiment of the present invention, the maximum cutting depth DC of the cutting tool 60 in the forward direction DF along the tool axis AT MAX may be greater than half the upper outer diameter DJ of each insert, i.e., DC MAX >DJ / 2.

[0164] In one embodiment of the present invention, the maximum cutting depth DC MAX may be greater than half the median diameter DM of each insert, i.e., DC MAX >DM / 2.

[0165] In embodiments of the invention in which the upper major cutting edge 36 and the upper minor cutting edge 44 associated with each upper corner cutting edge 38 form an acute internal upper corner angle α1, and / or each flank 26 includes an upper undercut 52 relative to the undercut direction DU, a portion of the cutting insert 20 located axially rearward of the active upper major cutting edge 36 relative to the tool axis AT extends radially beyond the tool cutting diameter DTC and therefore the maximum depth of cut DC MAX be limited to a value smaller than the upper outer diameter DJ of the insert.

[0166] Maximum cutting depth DC MAX Although the upper outer diameter DJ of the insert may be limited to a value less than the upper outer diameter DJ of the insert, as shown in FIGS. 8 and 10, the cutting tool 60 may be used in a milling process whereby each cutting insert 20 is oriented within its respective insert-receiving pocket 64 to cut a precise 90-degree or right-angle shoulder of the workpiece 80.

[0167] As shown in FIGS. 10 to 12, each cutting insert 20 has an axially forward-most insert point NF, and the N axially forward-most insert points NF of the N cutting inserts 20 define an imaginary surface circle CF having a front cutting diameter DFC.

[0168] It should be understood that in some embodiments of the present invention, the imaginary surface circle CF may have a center that coincides with the tool axis AT.

[0169] As shown in FIG. 12, half the difference between the tool cutting diameter DTC and the face cutting diameter DFC defines a second diameter range ER2.

[0170] In some embodiments of the present invention, the second diameter range ER2 may be less than 20 percent of the upper outer diameter DJ, i.e., ER2<0.20×DJ.

[0171] In an embodiment of the present invention in which the cutting tool 60 has N cutting inserts 20 and N insert receiving pockets 64, multiple axially forward insert points NF may be contained within a third tool plane PT3 (also referred to as the "face milling plane PT3") perpendicular to the tool axis AT.

[0172] In one embodiment of the present invention, each axially forward most insert point NF may be contained within the associated active upper corner cutting edge 38 .

[0173] Also, in one embodiment of the present invention, each axially forward most insert point NF may coincide with the first corner end point NC1 of its associated active upper corner cutting edge 38, and the active upper minor cutting edge 44 may be substantially parallel to the third tool plane PT3.

[0174] It should be appreciated that in embodiments of the present invention where the face cutting diameter DFC is relatively large and the second diameter range ER2 is less than 20 percent of the upper outer diameter DJ, the cutting tool 60 may be advantageously used in a face milling process to maximize the horizontal machining range of the workpiece 80.

[0175] Also, in embodiments of the present invention in which the cutting tool 60 is used in a milling process, such as a face milling process, the cutting path length of each cutting insert 20 within the workpiece 80 may be proportional to the tool cutting diameter DTC per revolution of the cutting tool 60, and the thermal load generated by the cutting action of each cutting insert 20 may increase with increasing tool cutting diameter DTC.

[0176] Although it is known in the art that increasing the size and mass of a cutting insert can help dissipate the thermal load generated by its cutting action, and that the median diameter DM of each cutting insert 20 can be related to the tool cutting diameter DTC, in embodiments of the present invention in which the cutting insert 20 is rigidly configured to have an “inverted” flank surface adjacent the upper major cutting edge 36, the size of the cutting insert 20 relative to the tool cutting diameter DTC can be reduced.

[0177] In one embodiment of the present invention, the median diameter DM multiplied by the insert size factor FI may be equal to the tool cutting diameter DTC, i.e., DM x FI = DTC, and the insert size factor FI may be greater than 12, i.e., FI > 12.

[0178] It should be appreciated that in embodiments of the present invention where the insert size factor FI is greater than 12, reducing the amount of cemented carbide required to produce the smaller sized cutting inserts 20 reduces manufacturing costs. The smaller sized cutting inserts 20 also contribute to a reduction in the circumferential spacing between adjacent insert receiving pockets 64.

[0179] The present invention contemplates rotary cutting tools having tool cutting diameters DTC less than 100 mm and insert size factors FI greater than 12. While the above-described insert size factors FI greater than 12 may theoretically be applied to cutting tools 60 having tool cutting diameters DTC less than 100 mm, it is recognized that practical factors associated with using an excessively small diameter clamping screw 76 to removably secure a smaller-sized cutting insert 20 within a correspondingly sized insert-receiving pocket 64 may present challenges in such configurations.

[0180] It is understood that throughout this specification and claims, the insert size factor FI is unitless and that when both the median diameter DM and the tool cutting diameter DTC are measured in the same units, e.g., millimeters, the ratio of the median diameter DM to the tool cutting diameter DTC applies.

[0181] Although the present invention has been described in some detail, it should be understood that various changes and modifications can be made without departing from the spirit or scope of the invention as hereinafter claimed.

Claims

1. A reversible cutting insert (20), comprising: the cutting insert (20) comprises opposing upper and lower end faces (22) and (122) interconnected by a continuous peripheral surface (24), a median plane (M) is disposed between the upper and lower end faces (22) and intersects the peripheral surface (24) to form an insert boundary line (LB), an insert axis (AI) is perpendicular to the median plane (M), and the cutting insert (20) is indexable about the insert axis (AI); The peripheral surface (24) includes four side surfaces (26) arranged alternately with four corner surfaces (28) in the circumferential direction; the side surfaces (26) and the corner surfaces (28) intersect the upper end surface (22) at upper side edges (32) and upper corner edges (34), respectively, each upper side edge (32) having an upper major cutting edge (36), and each upper corner edge (34) having an upper corner cutting edge (38); Each side surface (26) includes a median surface (46) and an upper major clearance surface (48) adjacent to the respective upper major cutting edge (36); when viewed in cross section along one of the upper major cutting edges (36), each of the upper major relief surfaces (48) forms an acute internal upper major relief angle (β1) with respect to the median plane (M); said median plane (M) intersects the four median surfaces (46) to define an imaginary median square (SM) having an imaginary inscribed median circle (CM) with a median diameter (DM) and a center coincident with said insert axis (AI); When viewed from the top end of the cutting insert (20), the four upper major cutting edges (36) define an imaginary upper major square (SJ) that defines an imaginary inscribed upper outer circle (CJ) having an upper outer diameter (DJ) and a center that coincides with the insert axis (AI); A cutting insert (20) wherein the imaginary upper main square (SJ) is rotationally offset from the imaginary median square (SM) about the insert axis (AI).

2. The cutting insert (20) according to claim 1, wherein the upper major relief angle (β1) has a minimum value of 75 degrees and a maximum value of 85 degrees.

3. The cutting insert (20) according to claim 1, wherein the four upper major cutting edges (36) are completely contained within an upper horizontal plane (PH) perpendicular to the insert axis (AI).

4. The cutting insert (20) according to claim 3, wherein the four upper corner cutting edges (38) are completely contained within the upper horizontal plane (PH).

5. The cutting insert (20) of claim 1, wherein each median surface (46) is perpendicular to said median plane (M).

6. The imaginary median square (SM) is divided into four identical quadrants (Q1, Q2, Q3, Q4) by a first vertical plane (PV1) and a second vertical plane (PV2) that are perpendicular to each other and contain the insert axis (AI) and intersect the four side surfaces (26); The cutting insert (20) according to claim 1, wherein each upper major cutting edge (36) is located in two of the four quadrants (Q1, Q2, Q3, Q4).

7. The cutting insert (20) of claim 1, wherein, in an end view of the cutting insert (20), no portion of the cutting insert (20) extends outside the insert boundary line (LB).

8. The cutting insert (20) of claim 1, wherein the median diameter (DM) is greater than the top outer diameter (DJ).

9. In a side view of the cutting insert (20), the upper main relief surface (48) has a variable upper main relief width (WJ) parallel to the insert axis (AI); The upper main relief width (WJ) increases in a transverse direction (SD) parallel to the median plane (M), Each upper side edge (32) includes an upper minor cutting edge (44); 2. The cutting insert (20) according to claim 1, wherein, in a side view of the cutting insert (20), the lateral direction (SD) is a direction from the upper major cutting edge (36) toward the upper minor cutting edge (44) of the same upper side edge (32).

10. The four upper minor cutting edges (44) define an imaginary upper minor square (SN) having an imaginary inscribed upper minor circle (CN) having an upper inner diameter (DN); The cutting insert (20) according to claim 9, wherein, in a top view of the cutting insert (20), the imaginary upper minor square (SN) coincides with the imaginary median square (SM).

11. When viewed from the top end of the cutting insert (20), 10. The cutting insert (20) according to claim 9, wherein the upper major cutting edge (36) and the upper minor cutting edge (44) associated with each upper corner cutting edge (38) form an acute internal upper corner angle (α1).

12. 2. The cutting insert (20) according to claim 1, wherein a third imaginary straight line (L3) extending perpendicular to the median plane (M) passes through the median plane (M) inside the insert boundary line (LB), and the third imaginary straight line (L3) intersects one of the upper major cutting edges (36) at any point along the length of the third imaginary straight line (L3).

13. When viewed from the top end of the cutting insert (20), The four upper minor cutting edges (44) define an imaginary upper minor square (SN), The imaginary upper major square (SJ) is nested within the imaginary upper minor square (SN), 10. The cutting insert (20) according to claim 9, wherein at each upper side edge (32), the upper major cutting edge (36) is recessed relative to the upper minor cutting edge (44), and the upper major cutting edge (36) is longer than the upper minor cutting edge (44).

14. A cutting tool (60) rotatable about a tool axis (AT) in a rotational direction (RD), said cutting tool (60) comprising: a tool body (62) extending in a forward direction (DF) and a rearward direction (DR) along the tool axis (AT); at least one reversible cutting insert (20) according to claim 1 removably secured within an insert-receiving pocket (64) of the tool body (62); one of the upper corner cutting edges (38) of each cutting insert (20) is active; A cutting tool (60) wherein one of the upper main cutting edges (36) of each cutting insert (20) adjacent to the active upper corner cutting edge (38) is the active upper main cutting edge (36).

15. Each insert-receiving pocket (64) has a seating surface (70) intersected by an axial support wall (72) and a radial support wall (74), the axial support wall (72) facing axially forward and the radial support wall (74) facing radially outward; the lower end surface (122) of each cutting insert (20) is in clamping contact with its respective seating surface (70); a first side surface (26a) of the four side surfaces of each cutting insert (20) is in clamping contact with the axial support wall (72); 15. The cutting tool (60) of claim 14, wherein a second side (26b) of the four side surfaces of each cutting insert (20) is in clamping contact with the radial support wall (74).

16. the upper major relief surface (48) of the first side surface (26a) is in clamping contact with the axial support wall (72); 16. The cutting tool (60) of claim 15, wherein the median surface (46) of the second side (26b) is in clamping contact with the radial support wall (74).

17. 17. The cutting tool (60) of claim 16, wherein the axial support wall (72) forms an acute external axial support angle (Φ1) with the bearing surface (70).

18. In a cross-sectional view on a first tool plane (PT1) perpendicular to the tool axis (AT) and intersecting the at least one bearing surface (70), 16. The cutting tool (60) of claim 15, wherein a second tool plane (PT2) containing the tool axis (AT) and a radially outermost point (NO) of one of the seating surfaces (70) form an acute internal radial pocket angle (τ1) with respect to the seating surface (70).

19. The maximum cutting width (DC) of the cutting tool (60) in the forward direction (DF) along the tool axis (AT) ＭＡＸ 15. The cutting tool (60) of claim 14, wherein the upper outer diameter (DJ) is greater than half of the upper outer diameter (DJ) of each insert.

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