Indexable insert for shoulder milling cutter and shoulder milling cutter with mounting cutouts for indexable inserts

Abstract

Indexable insert has a non-rectangular parallelogram shape with nearly rhombic basic shape and an imaginary intermediate plane spanned by four corners of an imaginary rhombus with sides running at a distance away from the upper side and the underside along the peripheral lateral surface in a plane such that each equivalent cutting edge has the same variation of distance and angle from the intermediate plane. Two diagonally opposing corners of both the upper side and the underside each have a greater distance from the intermediate plane than do the respective diagonally opposing corners of the upper side and the underside lying therebetween, and the diagonally opposing corners of the upper side and of the underside are shifted parallel to the intermediate plane and, as viewed in a plan view onto the intermediate plane, in mutually opposite directions away from the associated diagonals of the rhombus spanning the intermediate plane.

Claims

1. An indexable insert having a top side and an underside which are connected together by a peripherally extending side surface comprising a plurality of surface portions, wherein at least some intersection lines between the surface portions and the top side and the underside respectively form equivalent cutting edges, wherein the indexable insert in a plan view on to the top side and the underside is respectively in the shape of a non-rectangular parallelogram with an almost rhombic basic shape and has a notional intermediate plane which is spanned by four corners of a notional rhombus, whose sides extend at a spacing relative to the top side and the underside along the peripherally extending side surface in a plane in such a way that each of the equivalent cutting edges of the top side and the underside has the same variation in spacing and angle relative to the intermediate plane, wherein two mutually diagonally opposite corners of the top side and two diagonally opposite corners of the underside are respectively at a greater spacing from the intermediate plane than the respectively interposed mutually diagonally opposite corners of the top side and the underside, wherein the mutually diagonally opposite corners of the top side as well as the mutually diagonally opposite corners of the underside are displaced in parallel relationship with the intermediate plane and in the plan view on to the intermediate plane respectively in mutually opposite directions away from an associated diagonal of the rhombus spanning the intermediate plane, wherein the rhombus which defines the intermediate plane and which is spanned by sides extending along the peripherally extending side surface is non-rectangular, wherein the top side and the underside are respectively formed by two substantially triangular surfaces of which a tip respectively coincides with acute-angled corner of the parallelogram-shaped top side and underside respectively, wherein the sides of the triangular surfaces, that are opposite said tip, extend parallel and extend approximately between obtuse-angled corners of the parallelogram shape, wherein said triangular surfaces forming the topside are oriented relative to each other at an angle of between about 110° and 165° and said triangular surfaces forming the underside are oriented relative to each other at an angle of between about 110° and 165°, and wherein, in the plan view on to the top side and the underside, respectively, two diagonally opposite corners are displaced in the clockwise direction with respect to the associated diagonal of the rhombus and the corners therebetween are displaced in the anti-clockwise direction with respect to the associated diagonal, whereby the rhombic basic shape of the top side and the rhombic basic shape of the underside are shifted relative to each other and each have a parallelogram shape with sides having different lengths.

2. An indexable insert according to claim 1, wherein the corners of the top side and the underside, that are arranged in relation to the same corner of the rhombus of the intermediate plane, are displaced in opposite directions with respect to the associated diagonal.

3. An indexable insert according to claim 1, wherein the cutting edges are respectively provided along long sides of the parallelogram shape.

4. An indexable insert according to claim 1, wherein cutting corners of the indexable insert are at a greater spacing from the intermediate plane at the acute-angled corners of the parallelogram as compared to the obtuse-angled corners of the parallelogram.

5. An indexable insert according to claim 1, wherein the thickness of the insert as measured perpendicularly to the intermediate plane between the top side and the underside in the region of the obtuse-angled corners is between 40 and 70% the thickness at the acute-angled corners.

6. An indexable insert according to claim 1, wherein extending on the top side and on the underside is a respective narrow planar surface oriented parallel to the intermediate plane between the parallel sides of the triangular surfaces.

7. An indexable insert according to claim 1, wherein the side surface substantially comprises four surface portions and that each of the surface portions along a cutting edge has a relief surface which extends only over a portion, near the cutting edge, of the surface portion, the relief surface including a smaller wedge angle with the top side and the underside respectively than the remaining portion of the surface portion.

8. An indexable insert according to claim 1, wherein the triangular surfaces of the top side and the underside as well as the surface portions of the side surfaces, that define cutting edges, as well as relief surfaces are all non-parallel surfaces.

9. An indexable insert according to claim 1, wherein the acute-angled corners and/or the obtuse-angled corners of the indexable insert are flattened or rounded, and the top side and the underside each have two cutting edges of which a first extends between one of the obtuse-angled corners and one of the acute-angled corners and the second extends between the corners disposed in diagonally opposite relationship therewith.

10. An indexable insert according to claim 1, wherein the indexable insert is point-symmetrical.

11. An indexable insert according to claim 1, wherein it is symmetrical in relation to 180° rotations about both diagonals of the rhombus of the intermediate plane and about a central axis through the rhombus perpendicularly to the intermediate plane.

12. An indexable insert according to claim 1, wherein the indexable insert has no mirror symmetry in relation to any plane and no symmetry in relation to any rotation which is not an integer multiple of 180°.

13. An indexable insert according to claim 1, wherein the rhombus has an angle of between 60° and 88° at its acute-angled corners.

14. An indexable insert according to claim 5, wherein the thickness of the insert as measured perpendicularly to the intermediate plane between the top side and the underside in the region of the obtuse-angled corners is approximately half the thickness at the acute-angled corners.

15. An indexable insert according to claim 1, wherein said triangular surfaces are oriented relative to each other at an angle of between 135° and 155°.

16. An indexable insert according to claim 4, wherein the thickness of the insert as measured perpendicularly to the intermediate plane between the top side and the underside in the region of the obtuse-angled corners is approximately half the thickness at the acute-angled corners.

17. A shoulder milling cutter including: a plurality of mounting cutouts for indexable inserts which respectively have at least three seat surfaces of which a first seat surface provides a support predominantly in a radial direction, a second seat surface provides a support predominantly in an axial direction and a third seat surface provides a support predominantly in the tangential direction, wherein the third seat surface comprises at least two mutually angled surface portions of which one includes a positive axial angle with the axis of the shoulder milling cutter and the other includes a negative axial angle, and a plurality of indexable inserts according to claim 1 positioned in the mounting cutouts.

Description

(1) Further advantages, features and possible uses of the present invention will be apparent from the description hereinafter of preferred embodiments and the accompanying Figures in which:

(2) FIG. 1 diagrammatically shows the geometrical basic structure of an indexable insert according to the invention as a plan view on to the top side or the underside,

(3) FIG. 2 shows an embodiment of an indexable insert according to the invention in a plan view from above or below,

(4) FIG. 3 shows a side view of the indexable insert of FIG. 2,

(5) FIG. 4 shows a superimposition of top side and underside of an indexable insert according to the invention in a position of being turned through 90° relative to FIG. 1,

(6) FIG. 5 shows a section through the indexable insert of FIG. 4 corresponding to section line V-V,

(7) FIG. 6 shows a perspective view of a shoulder milling cutter equipped with indexable inserts as shown in FIG. 2,

(8) FIGS. 6a-6c show various views of a shoulder milling cutter equipped with indexable inserts as shown in FIG. 2,

(9) FIG. 7 shows a perspective view of a shoulder milling cutter according to the invention without indexable inserts, and

(10) FIG. 8 shows a detail from FIG. 7.

(11) FIG. 1 diagrammatically shows the basic shape of an indexable insert according to the invention as a transparent view, specifically as a plan view on to the top side (which is identical to a plan view on to the underside). All visible edges of the geometrical basic shape are reproduced by solid lines while the lines which are concealed but which are rendered visible here by virtue of the transparent view are shown as dash-dotted lines. Finally a broken line shows the contours of a rhombus R.sub.Z which is inscribed into the indexable insert and which defines an intermediate plane Z which here can be imagined as being coincident with the plane of the paper.

(12) The rhombus is spanned by its corners z.sub.a to z.sub.d or by four equal-length sides z.sub.1, z.sub.2, z.sub.3 and z.sub.4 which extend along the side surfaces 2a, 1b, 1c and 1d of the indexable insert and which lie in a common plane which here is referred to as the intermediate plane Z.

(13) The top side 1 of this basic geometry of the indexable insert is formed by two triangular surfaces 1a and 1b which are spanned by the corners 4a, 4b and 4d, and 4c, 4b and 4d respectively. Those triangular surfaces of the top side 1 including the edges 3a, 3b, 3c, 3d delimiting them lie above the plane of the paper. The junction (not shown) of the corners 4b and 4d forms a common side of the triangular surfaces 1a and 1b.

(14) The underside is similarly spanned by two identical triangular surfaces delimited by the corners 4a′, 4b′ and 4d′, and by 4c′, 4b′ and 4d′ respectively. The underside and the delimiting edges 3a′, 3b′, 3c′ and 3d′ are disposed below the plane of the paper.

(15) Starting from a body which is rhombic in plan view and in which the corners (4a, b, c, d and 4a′, b′, c′, d′) of the top side and the underside in plan view are respectively brought into alignment with the corners of the rhombus R.sub.Z so that all corners and edges of the top side and the underside fall in the plan view on to the corners and broken lines of the intermediate plane, production of the specific geometrical shape can be imagined for example in such a way that the body is twisted helically both about the diagonal d.sub.1 and also about the diagonal d.sub.2 of the rhombus z, as indicated by arrows at the ends of the diagonals d.sub.1 and d.sub.2. In other words, the edge joining the corners 4a of the top side and 4a′ of the underside is turned about the axis or diagonal d.sub.1 in a first direction and the diagonally opposite edge joining the corner 4c of the top side and the corner 4c′ of the underside is turned about the axis d.sub.1 in the opposite direction. Similarly the body is also twisted about the axis d.sub.2, more specifically so that the direction of rotation of the helical twisting is opposite to the direction of rotation in relation to the axis d.sub.1. In other words the corner 4a, starting from the associated corner of the rhombus z, is displaced towards the right, and the corner 4c is displaced by the same amount from the corner of the rhombus or the diagonal d.sub.1 towards the left, while the displacements on the underside are precisely in the opposite direction. The specific indexable insert shown in the following Figures differs from that geometrical basic shape only in respect of minor modifications, namely by rounding of the edges joining the corners 4a, 4a′ and 4c, 4c′ and by flattening or beveling of the edge joining the corners 4b, 4b′ and 4d, 4d′ and by virtue of the fact that in addition the two triangular surfaces 1a, 1b of the top side and the corresponding surfaces of the underside are also separated from each other by a narrow flat strip 5, 5′ disposed in a plane parallel to the intermediate plane Z of the rhombus R.sub.Z.

(16) A plan view of such an actual indexable insert is shown in FIG. 2.

(17) In FIG. 2 only the corners, edges and surfaces of the top side are provided with references.

(18) As will be seen the corners 4a and 4c are rounded and the corners 4b and 4d are flattened. In addition extending transversely over the top side there is also a narrow strip-shaped flat surface 5 which is parallel to the above-mentioned intermediate plane Z but which is also angled somewhat in relation to a line centrally joining the flattened corners. The parallel sides 7a, 7b of the triangular surfaces 1a, 1b, which moreover are also interrupted by a central bore 6, form the two edges of the flat surface 5. Accordingly, adjoining that strip-shaped flat surface 5 are the two triangular surfaces 1a, 1b which, as already mentioned, are angled out of the plane of the paper and relative to each other through an angle of about 40°, that is to say they include approximately an angle of 140° therebetween, as can also be seen from FIG. 3.

(19) At the centre of the indexable insert the surfaces 1a, 1b and 5 are interrupted by a central fixing bore 6 whose axis C extends perpendicularly to the notional intermediate plane Z, wherein the plane Z is in turn defined by the pairs of cutting corners 4a, 4a′ and 4c, 4c′ respectively being at the same spacing relative to the intermediate plane and the corners 4b and 4b′ as well as 4d and 4d′ being at a spacing (which is smaller in specific terms) relative to the intermediate plane Z, which spacings are equal to each other but different in relation to the spacing of the corner 4a.

(20) As can already be seen on the basis of the fundamental structure of the geometry of the indexable insert shown in FIG. 1 two respective opposite edges which connect the corners 4a, 4d and 4c, 4b respectively together are relatively long edges (3a and 3c respectively) while the other edges of the top side, namely those which connect the corners 4a and 4b, and 4c and 4d respectively, are shorter. Conversely at the underside the edges 3a′ and 3c′ opposite to the long edges 3a, 3c are short edges while the edges 3b′ and 3d′ arranged therebetween are long edges and thus form main cutting edges.

(21) That also applies to the specific indexable insert shown in FIGS. 2 to 5, even if the rounded configurations and bevels of the corners additionally also somewhat shorten the remaining edges. The angle between the main and the secondary cutting edges, which blend into each other by way of a rounded cutting corner 4a, 4c and 4a′, 4c′ respectively, is about 82° in the plan view in the illustrated embodiment. The radius of the cutting corner is between 1 and 2 mm. The flattened corners 4b, b′ and 4d, d′ are not provided for engagement with a workpiece. The flattened corners provide that the surfaces 1a and 1b are not exactly triangular but have a cut-off corner. Nonetheless the surfaces 1a and 1b remain substantially triangular and are here still identified as triangular surfaces, even with such small deviations.

(22) FIG. 3 shows a side view of the indexable insert corresponding to a view in a direction on to the indexable insert of FIG. 2 from the right.

(23) As will be seen the side surfaces 2a, 2b, 2c and 2d in respectively adjoining relationship with a cutting edge have a clearance surface 8 which is slightly angled relative to the remaining part of the respective side surface and which is additionally also set off from the other part of the surface portion 2a, b, c, d by a flat rounded groove 9. Due to the greater inclination of the clearance surface 8 relative to the other part of the side surface the positive wedge angle (wedge angle <90°) is still increased somewhat than it would in any case already be without that angled configuration.

(24) FIG. 4 again shows a plan view on to the top side of the indexable insert in a position of being turned through 90° relative to FIG. 2, in which case also the indexable insert is again shown as being transparent and the edges which are concealed in themselves are shown in broken line. It will be seen from this view that the longitudinal direction of the flat surface 5 is additionally inclined somewhat in relation to a diagonal between the corresponding corners in the longitudinal orientation thereof. The two surfaces 5, 5′ however extend parallel to the intermediate plane Z which is shown in FIG. 3 by a horizontal dash-dotted line and which corresponds in FIGS. 2 and 4 to the plane of the paper.

(25) Finally FIG. 5 also shows a section through the indexable insert according to the invention along line A-A in FIG. 4. In this case also the position of the intermediate plane Z is shown by a dash-dotted line. In the region of the cutting corners (measured perpendicularly to the intermediate plane) the thickness of the indexable insert is between about 6 and 12 mm and the thickness in the region of the flattened corners is about 40 to 70% of the thickness in the region of the cutting corners 4a, 4a′, 4c, 4c′.

(26) As will be seen a central bore 6 extends perpendicularly to the intermediate plane Z and from the top side of the indexable insert to the underside thereof. The bore 6 is symmetrical in relation to a rotation through 180° about one of the diagonals d1 and d2, as were defined in relation to FIG. 1.

(27) FIG. 6 shows a perspective view of a milling cutter equipped with corresponding indexable inserts and FIGS. 6a to c show the same milling cutter as an end plan view and two side views displaced through 90° relative to each other.

(28) In accordance with the arrangement of the indexable inserts 10 on this milling cutter this involves a shoulder milling cutter 20 which has five seats and indexable inserts 10 correspondingly arranged therein. In this case the indexable inserts are so oriented that a respective one of the main cutting edges 3a, 3c and 3b′ or 3d′ respectively is arranged approximately in axis-parallel relationship at the periphery of the shoulder milling cutter and secondary cutting edges (3b, 3d, 3a′ and 3c′) respectively adjoining the cutting corners 4a, 4c and 4a′ and 4c′ respectively extend inclinedly at a slight clearance angle with respect to a plane E perpendicular to the axis of rotation 15.

(29) It will be seen in particular from the end view in FIG. 6a that this arrangement involves a positive cutting geometry for the main cutting edges with a positive rake angle y as the rake surface respectively follows behind the main cutting edge in the direction of rotation.

(30) FIG. 7 once again shows a corresponding milling cutter but without indexable inserts, as a perspective view, while FIG. 8 shows a portion from FIG. 7 on an enlarged scale.

(31) As will be seen a seat 28 for a corresponding indexable insert has a radial contact and support surface 21, an axial contact surface 22, and three seat surfaces 23, 24 and 25 which predominantly support in the peripheral direction, wherein in each case at least one of the surfaces 23 and 24 serves as a support surface for at least a respective one of the triangular surface portions 1a, 1b (or 1′a, 1′b). The surfaces 21 and 22 respectively come into contact with the side surfaces 2c and 2d when the active main cutting edge is the edge 3a.

(32) At the transition between the contact surfaces 21 and 22 and towards the surface 23 it is possible to see respective relief grooves 26, 27 which contact-lessly receive the edges of an indexable insert 10. A threaded bore 16 is arranged centrally in the surface 25 and also involves the surfaces 23 and 24.

(33) As can be seen from FIGS. 6 to 8 a corresponding seat 28 of a shoulder milling cutter 20 affords large, mutually angled contact surfaces for the complementary surfaces of the indexable insert 10 and in particular the surface 24 opposite the main cutting edges supports the indexable insert and its respectively active cutting edge securely and over a large area.

(34) The indexable insert according to the invention has four equivalent cutting edges to be oriented as main cutting edges and disposed in mutually opposite paired relationship on the same side (top side and underside respectively) so that the cutting edges do not have any jointly used corners so that a main cutting edge is respectively unused after turning or indexing, including the corners thereof. In that respect the main cutting edges of the top side are opposite the secondary cutting edges of the underside and vice-versa. In other words, each of the surface portions 2a, 2b, 2c and 2d either forms a main cutting edge with the top side or with the underside and a secondary cutting edge with the respective other side. At the same time main and secondary cutting edges are respectively of a positive cutting geometry and are supported on the opposite side securely and over a large area. Non-active cutting edges are respectively received in well-protected fashion in the seat of the miffing cutter.

(35) The indexable insert according to the invention is thus particularly well suited to high-output shoulder milling cutters.