HIGH FEED PARTING-OFF INSERT FOR NARROW-WIDTH PARTING OPERATIONS

Abstract

A parting-off insert for relatively high feed includes a rake surface including a reinforced front sub-edge extending between two convex corner sub-edges. A cutting width W.sub.C is defined between distal points of the first and second convex corner sub-edges. The cutting width W.sub.C fulfills the condition: W.sub.C6 mm. The front sub-edge including a minimum front sub-edge thickness T.sub.F fulfilling the condition: T.sub.F>0.20 mm.

Claims

1. A narrow-width parting-off insert comprising: a shank portion; and a cutting portion connected to the shank portion and defining a cutting direction from the shank portion towards the cutting portion, and a rearward direction opposite to the cutting direction. the cutting portion comprising: a rake surface; a support surface comprising at least a support surface seat portion located underneath the rake surface, a downward direction being defined as directed from the rake surface towards the support surface seat portion; a front relief surface connected to the rake surface and support surface and being the forwardmost surface of the cutting portion, the front relief surface extending downwardly from the rake surface; a first side relief surface connected to the front relief surface and the rake surface, the first side relief surface extending rearwardly from the front relief surface and extending downwardly from the rake surface; a second side relief surface connected to the front relief surface and the rake surface, the second side relief surface extending rearwardly from the front relief surface and extending downwardly from the rake surface; and a cutting edge comprising: a reinforced front sub-edge formed at an intersection of the rake surface and the front relief surface; a first side sub-edge formed at an intersection of the rake surface and the first side relief surface; a second side sub-edge formed at an intersection of the rake surface and the second side relief surface; a first convex corner sub-edge connecting the front sub-edge and the first side sub-edge and having a first radius R1; and a second convex corner sub-edge connecting the front sub-edge and the second side sub-edge and having a second radius R2; wherein: the rake surface comprises a chip-former arrangement located rearward of the front sub-edge and extending downwardly or downwardly and rearwardly from the front sub-edge; a cutting width WC is defined from a first point of the first convex corner sub-edge which is distal to the second convex corner sub-edge, to a second point of the second convex corner sub-edge which is distal to the first convex corner sub-edge; a minimum front sub-edge thickness TF is defined from a forwardmost point of the front sub-edge to a closest point of an intersection of the front sub-edge and the chip-former arrangement; a top aspect ratio of the front sub-edge, RT=WC/TF, is less than 30; the cutting width WC fulfills the condition WC6 mm; and the minimum front sub-edge thickness TF fulfills the condition: TF>0.20 mm.

2. The parting-off insert according to claim 1, wherein the cutting width WC fulfills the condition: 2.5 mmWC4 mm.

3. The parting-off insert according to claim 1, wherein the minimum front sub-edge thickness TF fulfills the condition: TF>0.25 mm.

4. The parting-off insert according to claim 1, wherein the support surface seat portion extends parallel to the rake surface.

5. The parting-off insert according to claim 1, wherein the front relief surface extends downwardly and rearwardly from the rake surface; the first side relief surface extends rearwardly and inwardly from the front relief surface; and the second side relief surface extends rearwardly and inwardly from the front relief surface.

6. The parting-off insert according to claim 1, wherein the front sub-edge is straight in a plan view of the rake surface.

7. The parting-off insert according to claim 1, wherein the front sub-edge has a uniform thickness.

8. The parting-off insert according to claim 1, wherein the first radius R1 fulfills the condition: R1>0.20 mm; and the second radius R2 fulfills the condition: R2>0.20 mm.

9. The parting-off insert according to claim 8, wherein the first radius R1 fulfills the condition: R1>0.30 mm; and the second radius R2 fulfills the condition: R2>0.30 mm.

10. The parting-off insert according to claim 8, wherein the first radius R1 fulfills the condition: R1<0.60 mm; and the second radius R2 fulfills the condition: R2<0.60 mm.

11. The parting-off insert according to claim 10, wherein the first radius R1 fulfills the condition: R1<0.45 mm; and the second radius R2 fulfills the condition: R2<0.45 mm.

12. The parting-off insert according to claim 1, wherein the insert only comprises a single cutting edge.

13. The parting-off insert according to claim 1, wherein, in a plan view of the rake surface, the cutting width WC at the cutting edge is the largest dimension of the insert perpendicular to the cutting direction.

14. The parting-off insert according to claim 1, wherein the chip-former arrangement comprises only a single recess.

15. The parting-off insert according to claim 1, wherein, in a plan view of the rake surface, at an upper surface of the shank portion a coolant groove is formed and extends towards the rake surface.

16. The parting-off insert according to claim 1, wherein the support surface is formed with a support lateral securing arrangement.

17. The parting-off insert according to claim 16, wherein the support lateral securing arrangement is located on the support surface seat portion.

18. The parting-off insert according to claim 1, wherein a rear surface of the insert comprises a rear lateral securing arrangement.

19. The parting-off insert according to claim 1, wherein the support surface comprises a support surface abutment portion extending downward from the support surface seat portion.

20. The parting-off insert according to claim 19, wherein the support surface abutment portion extends downward and rearward.

21. The parting-off insert according to claim 19, wherein the support surface abutment portion is devoid of a lateral securing arrangement.

22. The parting-off insert according to claim 19, wherein the support surface comprises a bottom surface portion extending rearward from a support surface abutment portion to a rear surface of the insert.

23. The parting-off insert according to claim 1, wherein the only surfaces of the insert which have a lateral securing arrangement are the support surface seat portion and a rear surface.

24. The parting-off insert according to claim 1, wherein the insert has a solid construction.

25. The parting-off insert according to claim 1, wherein rearward of a connection area of the shank and cutting portion, the shank portion further extends downwardly or downwardly and rearwardly.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0062] For a better understanding of the subject matter of the present application, and to show how the same may be carried out in practice, reference will now be made to the accompanying drawings, in which:

[0063] FIG. 1A is a side view of a tool assembly schematically machining a workpiece;

[0064] FIG. 1B is a plan view of the tool assembly and workpiece in FIG. 1A;

[0065] FIG. 1C is a front view (also called a front view in the rearward direction) of the tool assembly in FIG. 1A without the workpiece;

[0066] FIG. 2A is a first side perspective view of the cutting insert of the tool assembly in FIG. 1A;

[0067] FIG. 2B is a second side perspective view of the cutting insert in FIG. 2A;

[0068] FIG. 2C is a top view (also called a plan view of the rake surface or a view in the downward direction towards the rake surface) of the cutting insert in FIG. 2A;

[0069] FIG. 2D is a front view of the cutting insert in FIG. 2A (also called a view of the front surface in the rearward direction);

[0070] FIG. 2E is a top view of the cutting insert corresponding to the view in FIG. 2C;

[0071] FIG. 2F is a side view of the cutting insert in FIG. 2A;

[0072] FIG. 2G is a bottom view of the cutting insert in FIG. 2A; and

[0073] FIG. 2H is a rear view of the cutting insert in FIG. 2A.

DETAILED DESCRIPTION

[0074] Referring to FIGS. 1A to 1C, illustrated is an exemplary tool assembly 10 comprising a tool holder 12, a tool 14, a solid parting-off insert 16, and a steel workpiece 18 being machined in FIG. 1A with a chip 20 being schematically shown.

[0075] From FIGS. 1A and 1B, it will be understood, as is known in the art, that a cutting direction D.sub.C is defined as the direction in which the insert 16 is moved into the workpiece 18. This could be alternatively defined as a direction parallel to a rake surface 22 and towards a front relief surface 24 (FIG. 1C) of the insert 16. A rearward direction D.sub.R is defined opposite to the cutting direction (or forward direction) D.sub.C.

[0076] A downward direction D.sub.D is defined as directed from the rake surface 22 towards the support surface seat portion 26. An upward direction D.sub.R is defined opposite to the downward direction D.sub.D.

[0077] For the sake of good order, first and second side directions D.sub.S1, D.sub.S2 are defined orthogonal to the cutting direction D.sub.C, rearward direction D.sub.R, downward direction D.sub.D and upward direction D.sub.R. Although, as will be understood from the following drawings, inward or outward directions to the insert relative to the other features thereof, is more relevant to understand the geometry, and such specific names upward, downward side are for convenience only. As is known, such tool assembly 10 can also operate upside down.

[0078] The exemplary tool assembly 10 shown, has a tool 14 which is a parting blade configured for particularly long overhangs. Accordingly, the tool 14 has a tool thickness T.sub.B which is smaller than a cutting width We of the insert. Accordingly, the tool 14 can enter the workpiece 18 until, for example, the workpiece reaches the tool holder 12 (or stability cannot be maintained).

[0079] The tool 14 comprises a resilient pocket 28 which only contacts a support surface 30 and a rear surface 32 of the insert 16.

[0080] Referring now to FIGS. 2A to 2H, the invention will be described with reference to a preferred but non-limiting insert geometry.

[0081] The insert 16 comprises an exemplary, but not limiting, shank portion 34 and a cutting portion 36. As shown, spaced apart from the cutting portion 36, the shank portion extends downwardly, in this example only downwardly.

[0082] The insert 16 can be defined as comprising the following surfaces: a front relief surface 24, a rear surface 32 located opposite the front relief surface 24, an upper surface 38, a support surface 30 located opposite to the upper surface 38, and first and second side surfaces 40, 42 connecting the front relief surface 24, rear surface 32 upper surface 38 and support surfaces 30.

[0083] As shown best in FIG. 2F, the front relief surface 24 extends downwardly and rearwardly from the rake surface 22.

[0084] The rear surface 32 comprises a rear lateral securing arrangement 44. More precisely, the rear lateral securing arrangement 44 comprises a rear groove 46 having opposing rear side groove surfaces 48, 50 extending inwardly and forwardly (see, e.g., FIG. 2C).

[0085] The upper surface 38 can be theoretically divided into the rake surface 22 at the cutting portion 36, and into a shank upper surface 52.

[0086] The rake surface 22 comprises a cutting edge 54, and a chip-former arrangement 56 having a single recess 58.

[0087] The cutting edge 54 comprises a front sub-edge 60, a first side sub-edge 62, a second side sub-edge 64, a first convex corner sub-edge 66 having a first radius R.sub.1 and a second convex corner sub-edge 68 having a second radius R.sub.2.

[0088] As exemplified in this non-limiting example, the front sub-edge 60 is straight in a plan view of the rake surface 22 (see FIG. 2C), extends perpendicular to the cutting direction (see FIG. 2C), is straight in a view of the front relief surface along the rearward direction (see FIG. 2D), and has a uniform thickness T.sub.F (see FIG. 2C). The thickness T.sub.F reinforces, and thereby strengthens, the front sub-edge 60, extending the life of the insert, even while cutting at higher-than-normal feed rates in the cutting direction D.sub.C. Thus, the front sub-edge 60 may be considered in one sense to have a reinforced land provided with an enlarged thickness in a direction parallel to the cutting direction D.sub.C.

[0089] For clarity only, arcuate extensions of each of the first and second convex corner sub-edges 66, 68 can form an imaginary circle C.sub.1 (only one being shown in FIG. 2C) and the radius of the circle C.sub.1 provides the values of the radii R.sub.1, R.sub.2.

[0090] As shown in more detail in FIG. 2C, the cutting width W.sub.C is defined from a first point 82 of the first convex corner sub-edge 66, to a second point 84 of the second convex corner sub-edge 68. Inserts in accordance with the subject matter of the present application have narrow-width front sub-edges 60. For present purposes, a narrow-width front sub-edge 60 is defined to be one that has a cutting width that is less than or equal to 6 mm. However, in some embodiments and for some applications, the cutting width of the front sub-edge 60 can be smaller, such as no greater than 4 mm or preferably 3 mm. While it is unknown what the lower limit of such narrow parting off insert could be in future, currently it is theorized that a smallest value cutting width that is practical is 2 mm or greater. The currently preferred range of values is 2.5 mm to 4.5 mm. Such optimal range being a compromise between a minimum insert size that can handle a substantial cutting force load and a desire for a cutting width to be as small as possible to reduce wasted material.

[0091] A top aspect ratio R.sub.T for the front sub-edge 60 is defined as the ratio of the cutting width W.sub.C to the thickness T.sub.F, as seen in a top view of the insert (FIG. 2C); i.e., R.sub.T=W.sub.C/T.sub.F. An insert in accordance with the subject matter of the present application has a top aspect ratio less than 30; i.e., R.sub.T<30.

[0092] The shank upper surface 52 can comprise a coolant configuration 70. The coolant configuration 70 can comprise a coolant groove 72. The coolant groove 72 can open out to the rake surface 22 at a coolant rake opening 74. The coolant groove 72 can open out to the rear surface 32 at a coolant rear opening 76.

[0093] The first side surface 40 can comprise a first side relief surface 78 (FIG. 2A). The first side relief surface 78 can extend rearwardly and inwardly from the front relief surface 24 (FIG. 2G) and can extend downwardly and inwardly from the rake surface 22 (FIG. 2D).

[0094] The second side surface 42 can comprise a second side relief surface 80 (FIG. 2A). The second side relief surface 80 can extend rearwardly and inwardly from the front relief surface 24 (FIG. 2G) and can extend downwardly and inwardly from the rake surface 22 (FIG. 2D).

[0095] Referring to FIG. 2F, the support surface 30 can comprise a support surface seat portion 26, a support surface abutment portion 86 and a bottom surface portion 88.

[0096] The support surface seat portion 26 can be formed with a support lateral securing arrangement 90 (FIG. 2A). The support lateral securing arrangement 90 can comprise a support groove 92 and opposing support side groove surfaces extending inwardly and upwardly 94, 96.

[0097] The support surface abutment portion 86 provides a counter abutment surface to the rear surface 32. Preferably, the support surface abutment portion 86 is devoid of a lateral securing arrangement. It will be understood, however, that alternate locations for lateral securing arrangements are possibilities, albeit less preferred. As are the options to have projections instead of grooves.

[0098] Example parting-off test results of a parting-off insert according to the invention and a comparative insert only differing with respect to the minimum front sub-edge thickness T.sub.F and radii R.sub.1, R.sub.2 is detailed below.

[0099] In the parting-off test, both inserts were made of the same grade material, both had W.sub.C=4 mm, and cutting speed V.sub.C was set to 100 m/min. Maximum wear was defined as 0.25 mm.

[0100] The feed rate F1 was set to normal conditions for the comparative insert (F1=0.18 mm/rev, which was slightly larger than the minimum front sub-edge thickness thereof, i.e. 0.115 mm, and so R.sub.T=4 mm/0.115 mm=34.78). The feed rate F2 was set to what is expected to be normal conditions for the insert according to the invention (F2=0.4 mm/rev, which was slightly larger than the minimum front sub-edge thickness T.sub.F thereof, i.e. 0.3 mm, and so R.sub.T=4 mm/0.3 mm=13.33).

[0101] The radii R.sub.1, R.sub.2 for the comparative insert was 0.24 mm. The radii R.sub.1, R.sub.2 for the insert according to the invention was 0.50 mm.

[0102] In the test, the two comparative inserts tested reached maximum wear after 20 and 25 minutes, respectively. The two inserts according to the present invention reached maximum wear after 100 and 110 minutes, respectively.

[0103] Accordingly, there was a tremendous unexpected improvement in tool life for the inserts according to the present invention, even though both inserts were tested under normal operating conditions.

[0104] In a grooving test of the same types of inserts described above, the cutting speed V.sub.C was set to 200 m/min and the feed for both was set at 0.4 mm/rev. In this test the insert according to the present invention performed three times as many grooves as the comparative insert.