CUTTING INSERT FOR PARTING OFF A METAL WORK PIECE

Abstract

A cutting insert for parting off a metal work piece includes an elongated body having a top surface, a bottom surface, a first lateral surface, a second lateral surface connecting the top surface and the bottom surface at one lateral side each, a front surface connecting the first and second lateral surfaces, the top surface and the bottom surface, a longitudinal axis extending axially rearward from the front surface in a central plane, and a cutting head having a cutting edge. The cutting edge is formed at an intersection between the front surface and the top surface. The cutting edge includes a leading cutting corner at the first lateral side surface and a trailing cutting corner at the second lateral side surface. The trailing cutting corner is located axially rearward of the leading cutting corner. The cutting edge has a rearmost point located axially rearward from the trailing cutting corner.

Claims

1. A cutting insert for parting off a metal work piece, the cutting insert comprising; an elongated body, the elongated body having a top surface, a bottom surface, a first lateral surface and a second lateral surface connecting the top surface and the bottom surface at one lateral side each, a front surface connecting the first and second lateral surfaces, the top surface and the bottom surface, a longitudinal axis extending axially rearward from the front surface in a central plane, and a cutting head including a cutting edge, wherein the cutting edge is formed at an intersection between the front surface and the top surface, and wherein the cutting edge includes a leading cutting corner at the first lateral side surface (8), a trailing cutting corner at the second lateral side surface, wherein the trailing cutting corner is located axially rearward of the leading cutting corner, and a rearmost point, wherein the rearmost point is located axially rearward from the trailing cutting corner.

2. The cutting insert according to claim 1, wherein the cutting insert has a width, the width, as measured in a transverse direction, being a distance between the leading cutting corner and the trailing cutting corner, and wherein, as measured in an axial direction, a distance between the leading cutting corner and the trailing cutting corner is in a range from 5% to 15% of the width.

3. The cutting insert according to claim 1, wherein a primary section of the cutting edge adjacent to the leading cutting corner includes a primary angle, wherein the primary angle is an average angle between a line perpendicular to the longitudinal axis and the primary section of the cutting edge, and wherein the primary angle is in a range from 15° to 25°.

4. The cutting insert according to claim 1, wherein the cutting edge has a shape between the leading cutting corner, the rearmost point and the trailing cutting corner such that, when the cutting insert is fed along the longitudinal axis towards the work piece and when the entire cutting edge is in engagement with the work piece, a resulting force forms an angle with the longitudinal axis, wherein the angle is equal to or smaller than 20°.

5. The cutting insert according to claim 1, wherein, as measured in a transverse direction, the rearmost point is located closer to the longitudinal axis than to the leading cutting corner and to the trailing cutting corner.

6. The cutting insert according to claim 1, wherein the cutting edge includes a first cutting edge section, wherein the first cutting edge section extends from the leading cutting corner to the rearmost point, and a second cutting edge section, wherein the second cutting edge section extends from the rearmost point (16) to the trailing cutting corner, and wherein the first cutting edge section and the second cutting edge section each have a monotonic shape in a coordinate system, the coordinate system having the longitudinal axis as a y-axis.

7. The cutting insert according to claim 1, wherein the cutting edge includes a first cutting edge section and a second cutting edge section, wherein the first cutting edge section is located between the leading cutting corner and the rearmost point, has a length of at least ⅔ of an entire length of the cutting edge from the leading cutting corner to the rearmost point, and is straight, or, wherein the second cutting edge section is located between the rearmost point and the trailing cutting corner, has a length of at least ⅔ of an entire length of the cutting edge from the rearmost point to the trailing cutting corner, and is straight.

8. The cutting insert according to claim 7, wherein the first section and the second section meet at the rearmost point.

9. The cutting insert according to claim 1, wherein, as measured in a transverse direction, the leading cutting corner and the trailing cutting corner have different distances from the longitudinal axis.

10. The cutting insert according to claim 1, wherein at least one of the leading cutting corner and the trailing cutting corner is convexly curved having a radius of curvature in a range from 0.05 mm to 0.5 mm.

11. The cutting insert according to claim 1, wherein the cutting edge has a concavely curved section, wherein the curved section includes the rearmost point, and wherein the curved section has a radius of curvature in a range from 1 mm to 5 mm.

12. The cutting insert according to claim 1, wherein the cutting insert has a width, wherein the width is a transverse distance perpendicular to the longitudinal axis between the leading cutting corner and the trailing cutting corner, and wherein the width is 5 mm or less.

13. A parting tool for parting off a metal work piece, the parting tool comprising: a tool body and the cutting insert according to claim 1, wherein the tool body has an insert seat, and wherein the cutting insert is mounted in the insert seat.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0042] Further advantages, features and applications of the present invention will become apparent from the following description of embodiments and the attached figures. The foregoing as well as the following detailed description of embodiments of the present invention will be better understood when read in conjunction with the attached figures. It should be understood that the depicted embodiments are not limited to the precise arrangements and instrumentalities shown. Unless other-wise indicated, like reference numerals in different figures refer to alike or corresponding parts.

[0043] FIG. 1 is an isometric view from above of a cutting insert according to a first embodiment of the present invention.

[0044] FIG. 2 is a top view onto the cutting insert of FIG. 1.

[0045] FIG. 3 is a side view of the cutting insert of FIGS. 1 and 2.

[0046] FIG. 4 is an enlarged broken away top view of a cutting head of the cutting insert of FIGS. 1 to 3.

[0047] FIG. 5 is an enlarged broken away top view of a cutting head of a cutting insert according to a second embodiment of the present invention.

[0048] FIG. 6 is an enlarged broken away top view of a cutting head of a cutting insert according to a third embodiment of the present invention.

[0049] FIG. 7 is an enlarged broken away top view of a cutting head according to a fourth embodiment of the present invention.

[0050] FIG. 8 is an enlarged broken away top view of a cutting head of a cutting insert according to a fifth embodiment of the present invention.

[0051] FIG. 9 is an enlarged broken away top view of a cutting head of a cutting insert according to a sixth embodiment of the present invention.

[0052] FIG. 10 is an enlarged broken away top view of a cutting head of a cutting insert according to a seventh embodiment of the present invention.

[0053] FIG. 11 is an enlarged broken away top view of a cutting head of a cutting insert according to an eighth embodiment of the present invention.

DETAILED DESCRIPTION

[0054] With reference to FIGS. 1 to 4, a first embodiment of a cutting insert 1 according to the present invention is described.

[0055] The cutting insert 1 is an indexable cutting insert having an elongated body 18, wherein two cutting heads 2 are provided at each end of a mounting portion 3. When in use, the mounting portion 3 is clamped in an insert seat of a tool holder. To increase the overall tool life of the cutting insert 1, the two cutting heads 2 are used one after the other. The cutting insert 1 has a top surface 4 and a bottom surface 5. Along the mounting portion 3, the top surface 4 is delimited by two top lateral edges 6, 7. The top lateral edges 6, 7 are each formed at an intersection between a lateral surface 8, 9 and the top surface 4. Along the mounting portion 3, the top lateral edges extend parallel to each other. Furthermore, the lateral surfaces 8, 9 in the mounting portion 3 are parallel to each other. The cutting insert 1 comprises a longitudinal axis 10 which longitudinal axis 10 in the mounting portion 3 is parallel to the two top lateral edges 6, 7 and thus is located in a central plane of the cutting insert 1. When in use, the cutting insert 1 is fed towards a work piece along a direction coinciding the longitudinal axis 10 of the cutting insert 1.

[0056] The width w of the cutting insert 1 is a transverse distance measured in a direction perpendicular to the longitudinal axis 10 between the leading cutting corner 13 and the trailing cutting corner 14.

[0057] For all embodiments according to FIGS. 1 to 11, the width w of the cutting insert is 3 mm. The axial distance as measured parallel to the longitudinal axis 10 between the leading cutting corner 13 and the trailing cutting corner 15 in each of the embodiments amounts to 0.3 mm.

[0058] The design of each of the two identical cutting heads 2 is now described in particular with reference to FIG. 4.

[0059] Each of the two cutting heads 2 comprises a cutting edge 11, which cutting edge 11 is formed at an intersection between a front surface 12 and the top surface 4 of the cutting insert. Furthermore, the cutting edge 11 includes two cutting corners 13, 14. The cutting corners 13, 14 are formed at an intersection between the front surface 12, the top surface 4 as well as one of the lateral surfaces 8, 9 each. The cutting edge 11 is located in a plane spanned by the first and second top lateral edges 6, 7 at the respective cutting head 2.

[0060] The top lateral edges 6, 7 and the lateral surfaces 8, 9 at the cutting head 2 taper rearwardly from the cutting edge 11 towards the mounting section 3 Thus, a clearance is provided in the axial direction rearwardly from the two cutting corners 13, 14.

[0061] The upper cutting corner 13 of FIG. 4 is denoted as the leading cutting corner 13 and the lower cutting corner 14 of FIG. 4 is denoted the trailing cutting corner 14. The trailing cutting corner 14 is located axially rearward of the leading cutting corner 13. Expressed in other words, the trailing cutting corner 14 in the axial direction is located closer to the mounting portion 3 than the leading cutting corner 13.

[0062] Due to the top lateral edges 6, 7 and the lateral surfaces 8, 9 at the cutting head 2 converging rearwards from the cutting edge 11 towards the mounting section 3, as measured in the transverse direction, the leading cutting corner 13 has a larger distance from the longitudinal axis 10 than the trailing cutting corner 14.

[0063] The cutting edge 11 along a first cutting edge section 15 extends axially rearward until the cutting corner 11 reaches a rearmost point 16. Equally, a second cutting edge section 17 extends axially rearward from the trailing cutting corner 14 to the rearmost point 16. Consequently, the rearmost point 16 is located axially rearward of the trailing cutting corner and axially rearward of the leading cutting corner 13.

[0064] In the first embodiment of FIGS. 1 to 4 each of the two cutting edge sections 15, 17 are straight cutting edge sections meeting and intersecting each other at the rearmost point 16. In the first embodiment, the first cutting edge section 15 including the leading cutting corner 13 and a line 19 perpendicular to the longitudinal axis 10 form a primary angle α1 of 15°, wherein the second cutting edge section 17 and the line 19 perpendicular to the longitudinal axis 10 form a secondary angle α2 of 8°.

[0065] As the first and second cutting edge sections 15, 17 are straight lines, the first and second cutting edge sections 15, 17 form of the primary section and the secondary section, respectively in the sense of the present application.

[0066] A straight line 20 connecting the leading cutting corner 13 and the trailing cutting corner 14 forms an angle β with the line 19 perpendicular to the longitudinal axis 10 of 2°.

[0067] In the embodiment of FIGS. 1 to 4, the rearmost point 16 with respect to the longitudinal axis 10 is located at the side towards the leading cutting corner 13. As the slope of the first cutting edge section 15 is steeper than the slope of the second cutting edge section 17, the first cutting edge section 15 is shorter than the second cutting edge section 17.

[0068] The cutting edge 11 comprises a leading cutting corner 13, a trailing cutting corner 14 as well as a rearmost point 16. Due to this design the primary angle α1 at the leading cutting corner is much larger than the angle β of a straight line connecting the leading cutting corner 13 and the trailing cutting corner 14. Thus, the cutting insert 1 of FIGS. 1 to 4 provides a parting off of a work piece which is more precise and causes a reduced slug formation at the work piece when compared to a prior art cutting insert comprising a leading cutting corner and a trailing cutting corner having the same axial offset ad as the insert 1 of FIGS. 1 to 4, but which leading and trailing cutting corners are part of a straight cutting edge, which straight cutting edge spans from the leading cutting corner to the trailing cutting corner.

[0069] Still, the overall off-axis forces acting on the cutting insert 1 when parting off a workpiece are in the order of the off-axis forces acting on the prior cutting insert with a straight cutting edged connecting the leading cutting corner and the trailing cutting corner.

[0070] For the further embodiments described below with reference to FIGS. 5 to 11, only broken away top surfaces of the cutting heads 2 are shown as the cutting heads 2 implement the essential vari-ations between the individual embodiments.

[0071] In the second embodiment of FIG. 5, the pointed leading cutting corner 13 of the first embodiment according to FIGS. 1 to 4 has been replaced by a rounded leading cutting corner 13, wherein the leading cutting corner is convexly curved having a radius of curvature of 0.4 mm. This well strengthens the leading cutting corner 13 and thus enhances the service life of the cutting insert 1.

[0072] When compared to the first embodiment of FIGS. 1 to 4, the third embodiment according to FIG. 6 has first and second cutting edge sections 15, 17 which are no longer straight lines along their entire extension from the leading cutting corner 13 to the rearmost point 16 and from the trailing cutting corner 14 to the rearmost point 16, respectively. Instead, the cutting edge 11 has a concavely curved section 21, which concavely curved section includes the rearmost point 16 of the cutting edge 11. Consequently, there are no straight first and second cutting edge sections meeting at the rearmost point 16, but the rearmost point 16 is formed by a curved cutting edge section having a considerably large radius of curvature of 3 mm. Consequently, crack formation at the rearmost point 16 the cutting edge 11 is reduced.

[0073] In those embodiments, wherein the cutting edge 11 comprises at least a curved section 21 like in the embodiment of FIG. 6, the primary angle α1 is the average angle between the primary section 22 of the cutting edge 11, which primary section is adjacent to the leading cutting corner and extends over 10% of the width of the cutting insert 1.

[0074] The fourth embodiment of the cutting insert 1 of FIG. 7 combines the designs of the cutting inserts according to the first to third embodiments. The cutting head 2 has a leading cutting corner 13 with a radius of curvature of 0.4 mm like the second embodiment of FIG. 5 and the cutting edge 11 around the rearmost point 16 comprises a concavely curved section 21 having a radius of curvature of 3 mm like the third embodiment of FIG. 6. Due to the overall strengthening of the cutting edge 11, the cutting insert 1 of the fourth embodiment of FIG. 7 has an increased tool life.

[0075] The embodiments depicted in FIGS. 8 to 11 differ from those of FIGS. 1 to 7 in that the rearmost point 16 is no longer located at the side of the longitudinal axis 10 towards the leading cutting corner 13. Instead, the rearmost point 16 is shifted towards the side of the longitudinal axis 10 towards the trailing cutting corner 14.

[0076] Other than that, the fifth embodiment of FIG. 8 well corresponds to the first embodiment of FIGS. 1 to 4. The first and second cutting edge sections 15, 17 are straight. Consequently, when compared to the first embodiment of FIGS. 1 to 4, in the fifth embodiment of FIG. 8 the first cutting edge section 15 has a slightly smaller primary angle α1 while still maintaining the desired functionality.

[0077] The embodiment of FIG. 9 well corresponds to the second embodiment of FIG. 5. I.e. the leading cutting corner 13 has an enlarged radius of curvature strengthening the cutting edge 11.

[0078] The embodiment of FIG. 10 well corresponds to the third embodiment of FIG. 6. The cutting edge 11 has a curved section 21 around the rearmost point 16 with a radius of curvature of 4 mm strengthening the cutting edge 11.

[0079] Like the embodiment of FIG. 7, the eighth embodiment of FIG. 11 combines the designs of the fifth, sixth and seventh embodiments of FIGS. 8 to 10 and thus except for the position of the rearmost point 16 with respect to the longitudinal axis corresponds to the fourth embodiment of FIG. 7.

[0080] It is noted that features described in connection with one embodiment also can be used in other embodiments as is readily understandable by a person skilled in the art.

[0081] While the invention has been described in detail and with reference to the Figures, this description is only an example and is not considered to restrict the scope of protection as it is defined by the claims.

[0082] In the claims the word “comprising” does not exclude other elements or steps and the undefined article “a” does not exclude a plurality. The mere fact that some features have been claimed in different claims does not exclude their combination. Reference numbers in the claims are not considered to restrict the scope of protection.

REFERENCE NUMERALS

[0083] 1 cutting insert [0084] 2 cutting head [0085] 3 mounting portion [0086] 4 top surface [0087] 5 bottom surface [0088] 6, 7 top lateral edge [0089] 8, 9 lateral surface [0090] 10 longitudinal axis [0091] 11 cutting edge [0092] 12 front surface [0093] 13 leading cutting corner [0094] 14 trailing cutting corner [0095] 15 first cutting edge section [0096] 16 rearmost point [0097] 17 second cutting edge section [0098] 18 body [0099] 19 line perpendicular to the longitudinal axis 10 [0100] 20 line connecting the leading cutting corner 13 and the trailing cutting corner 14 [0101] 21 concavely curved section of the cutting edge 11 [0102] 22 primary section of the cutting edge 11 [0103] w width [0104] ad axial offset between the leading cutting corner 13 and the trailing cutting corner 14 [0105] α1 primary angle [0106] α2 secondary angle [0107] β angle between line 19 and line 20