FACE MILLING TOOL AND A TANGENTIAL CUTTING INSERT THEREFORE

Abstract

A face milling tool includes a tool body having an axial front end surface with several seats. Each seat has support surfaces for rotationally locking and supporting a tangential cutting insert in the seat. One of the support surfaces is a flat axial support surface for supporting the tangential cutting insert in an axial direction defined by the central rotation axis. The flat axial support surface extends perpendicular to the central rotation axis and is situated axially foremost in the seat. A side wall of each seat is formed out of round side support surfaces. Each tangential cutting insert includes an axial back side with a flat axial contact surface abutting the flat axial support surface and a projecting member extending axially from the flat axial contact surface and having a circumferential side surface forming out of round side contact surfaces abutting the out of round side support surfaces.

Claims

1. A face milling tool for chip removing machining comprising: a tool body being rotatable around a central rotation axis in a direction of rotation, the tool body including an envelope surface being concentric with the central rotation axis and an axial front end surface extending transverse to the central rotation axis, the axial front end surface having a plurality of seats; and a plurality of tangential cutting inserts mounted in the plurality of seats, each seat including a plurality of support surfaces for rotationally locking and supporting a tangential cutting insert in a respective seat, one of the plurality of support surfaces being a flat axial support surface for supporting the tangential cutting insert in an axial direction defined by the central rotation axis, the flat axial support surface is extending perpendicular to the central rotation axis and situated axially foremost in the seat, wherein each seat is provided with a recess in relation to the flat axial support surface, the recess including a bottom surface and a side wall, the side wall forming out of round side support surfaces for rotationally locking and supporting the tangential cutting insert in directions perpendicular to the axial direction, each tangential cutting insert including an axial back side having a flat axial contact surface abutting the flat axial support surface and a projecting member extending axially from the flat axial contact surface, the projecting member including a circumferential side surface forming out of round side contact surfaces abutting the out of round side support surfaces, wherein a gap is provided between the bottom surface of the recess and the projecting member of the tangential cutting insert.

2. The face milling tool of claim 1, wherein the tool body includes a replaceable ring shaped member provided with the plurality of seats, wherein the replaceable ring shaped member is mounted to the tool body to form an annular portion including the plurality of seats on the axial front end surface of the tool body.

3. The face milling tool of claim 1, wherein the tool body 94 is formed in one piece and the flat axial support surface of each of the plurality of seats is situated axially foremost on the axial front end surface of the one piece tool body.

4. The face milling tool according to claim 1, wherein the side wall of the recess forms clearance spaces between at least two out of round side support surfaces.

5. The face milling tool according to claim 1, wherein the out of round side support surfaces in the side wall of the recess are formed by two side support surfaces, wherein the circumferential side surface of the projecting member forms two out of round side contact surfaces abutting the two side support surfaces.

6. The face milling tool of claim 5, wherein the two out of round side support surfaces are facing each other and mutually converge in a direction opposite to the direction of rotation of the tool body, wherein the two out of round side contact surfaces extend to mutually converge in the same manner.

7. The face milling tool according to claim 1, wherein the tangential cutting insert is being mounted in the seat by means of a screw, which is in engagement with a threaded hole in the bottom surface of the recess, wherein the tangential cutting insert including a screw hole extending axially through the tangential cutting insert inside the projecting member.

8. The face milling tool of claim 7, wherein the screw hole has a centre axis displaced from a geometrical centre of the projecting member to provide a sole mounting orientation of the tangential cutting insert in which the position of the centre axis of the screw hole in relation to the out of round side contact surfaces corresponds to a position of a centre axis of the threaded hole in relation to the out of round side support surfaces.

9. A tangential cutting insert for the face milling tool according to claim 1, the tangential cutting insert having an axial direction coinciding with the axial direction of the face milling tool, wherein the tangential cutting insert comprises: an axial back side having a flat axial contact surface extending perpendicular to the axial direction, of the tangential cutting insert; an axial front side forming an axial clearance surface opposite to the flat axial contact surface; a rake face arranged in a peripheral side surface extending between the flat axial contact surface and the axial clearance surface; a cutting edge formed at the intersection between the rake face and the axial clearance surface; and a positive axial clearance angle being provided by the axial clearance surface sloping toward the flat axial contact surface as it extends from the cutting edge, wherein the axial back side includes a projecting member extending axially from the flat axial contact surface, the projecting member having a circumferential side surface forming out of round side contact surfaces to rotationally lock and support the tangential cutting insert in directions being perpendicular to the axial direction of the tangential cutting insert.

10. The tangential cutting insert of claim 9, wherein the circumferential side surface of the projecting member forms a polygon in a cross section perpendicular to the axial direction of the tangential cutting insert, wherein the out of round side contact surfaces are formed along the sides of the polygon.

11. The tangential cutting insert of claim 10, wherein the polygon being formed by the circumferential side surface is a square or a triangle.

12. The tangential cutting insert according to claim 9, wherein a screw hole extends axially through the tangential cutting insert from the axial front side to the axial back side, wherein the screw hole extends inside the projecting member and mouths in an axial back end surface of the projection member.

13. The tangential cutting insert of claim 12, wherein the screw hole has a centre axis displaced from a geometrical centre of the projecting member to provide a sole mounting orientation of the tangential cutting insert defined by a position of the centre axis of the screw hole in relation to the out of round side contact surfaces.

14. The tangential cutting insert according to claim 9, wherein the cutting edge includes a wiper edge connected to a main cutting edge, the main cutting edge being inclined in relation to the wiper edge and extending at an entering angle of at most 10.

15. The tangential cutting insert of claim 14, wherein the wiper edge and the main cutting edge form a continuously arched cutting edge.

16. The tangential cutting insert of claim 11, wherein the triangle is a circular triangle.

17. The tangential cutting insert of claim 16, wherein the circular triangle is a Reuleaux triangle.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The invention will in the following be described by means of example with reference to the appended drawings, in which:

[0026] FIG. 1 is a perspective view of a face milling tool according to a first embodiment of the present invention;

[0027] FIG. 1a is a front end view of the face milling tool according to the first embodiment;

[0028] FIG. 1b is a side view of the face milling tool according to the first embodiment;

[0029] FIG. 1c is an exploded view of the face milling tool according to the first embodiment;

[0030] FIG. 2 is an enlarged portion of the face milling tool showing a seat and a tangential cutting insert to be mounted in the seat;

[0031] FIG. 2a is an exploded view of the seat with the tangential cutting insert;

[0032] FIG. 2b is a front view of a face milling tool according to a second embodiment of the present invention with two cross sections A-A and B-B of the tangential cutting insert mounted in the seat;

[0033] FIG. 3 is a perspective axial front side view of a tangential cutting insert of the present invention;

[0034] FIG. 3a is a perspective axial back side view of the tangential cutting insert;

[0035] FIG. 3b is another perspective axial back side view of the tangential cutting insert;

[0036] FIG. 3c is an axial back side view of the tangential cutting insert;

[0037] FIG. 3d is a front side view toward a rake face of the tangential cutting insert:

[0038] FIG. 3e is an axial front side view of the tangential cutting insert;

[0039] FIG. 3f is a back side view of the tangential cutting insert;

[0040] FIG. 3g is a longitudinal side view of the tangential cutting insert;

[0041] FIG. 3h is a longitudinal side view of the tangential cutting insert.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

[0042] FIGS. 1-1c discloses a first embodiment of a face milling tool 1 for chip removing machining according to the invention. The face milling tool comprises a tool body 2 being rotatable around a central rotation axis C1 in an intended direction of rotation R. The tool body 2 comprises an envelope surface 3 being concentric with the central rotation axis C1 and an axial front end surface 4 extending transverse the central rotation axis C1. The axial front end surface 4 comprises several seats 5 in which a plurality of tangential cutting inserts 10 are mounted.

[0043] In the first embodiment a replaceable ring shaped member 2a is provided with the seats 5, wherein the replaceable ring shaped member 2a is mounted to the tool body 2 to form an annular portion/track of seats 5 on the axial front end surface 4 of the tool body. The ring shaped member 2a is concentric with the central rotation axis C1 of the milling tool 1 and mounted by means of screws 2b onto the tool body 2 to form the annular portion/track of seats 5 on the axial front end surface 4 of the tool body 2. The ring shaped member 2a is mounted in an annular shoulder of the tool body being formed with axial and radial shoulder surfaces 2c, 2d for supporting the ring shaped member 2a.

[0044] FIGS. 2 and 2a discloses the seat 5 and different views of the tangential cutting insert to be mounted therein. The seat comprises several support surfaces 5a, 5b, 5c for rotationally locking and supporting the tangential cutting insert 10. One of the support surfaces is a flat axial support surface 5a for supporting the tangential cutting insert 10 in an axial direction A1 defined by the central rotation axis C1 of the tool body. The flat axial support surfaces 5a are extending perpendicular to the central rotation axis C1 and are situated axially foremost in the seats 5. The flat axial support surfaces 5a of the seats are arranged flush with the axial front end surface 4, wherein the seat 5 is provided with a recess 6 in relation to the flat axial support surface 5a. The recess 6 comprises a bottom surface 6a and a side wall 6b. The side wall 6b is forming out of round side support surfaces 5b, 5c for rotationally locking the tangential cutting insert 10 and supporting the tangential cutting insert 10 in directions perpendicular to the axial direction A1 (in radial and tangential directions of the face milling tool). More precisely, the out of round side support surfaces 5b, 5c in the side wall are formed by two (planar) side support surfaces 5b, 5c, which face each other and mutually converge in a direction opposite to the direction of rotation R of the tool body 2. The angle between the converging side support surfaces is in this specific embodiment 34.

[0045] The tangential cutting insert 10 comprises an axial back side 11 having a flat axial contact surface 12 abutting the flat axial support surface 5a of the seat. The back side of the tangential cutting insert comprises a projecting member 13 extending axially from the flat axial contact surface 12. The projecting member 13 comprises a circumferential side surface 13a forming out of round side contact surfaces 13b, 13c for abutting the out of round side support surfaces 5b, 5c. More precisely, the out of round side contact surfaces are formed by two planar side contact surfaces 13b, 13c that extend to mutually converge in the direction opposite to intended direction of rotation R of the tool body 2 (i.e. in the same manner as the side support surfaces 5b, 5c). The angle between the converging side contact surfaces is in this specific embodiment 34.

[0046] FIG. 2b discloses a front view of a face milling tool 1 according to a second embodiment of the present invention with two cross sections A-A and B-B of the tangential cutting insert 10 mounted in the seat 5. The second embodiment of the face milling tool 1 differs from the first embodiment only in that the tool body 2 is formed in one piece. Hence, the tool body 2 does not have replaceable the ring shaped member 2a. The flat axial support surfaces 5a of the seats 5 are situated axially foremost on the axial front end surface 4 of the one piece tool body 2.

[0047] In cross sections A-A and B-B it can be seen that a gap 7 is provided between the bottom surface 6a of the recess 6 and an axial back end surface 13d of the projecting member 13. In other words, the axial extension of the projecting member 13 is less than the axial extension (depth of) the recess 6 to ensure that the projecting member 13 is out of contact with the bottom surface 6a of the recess and that only the flat axial support/contact surfaces 5a, 12 are abutting each other for a well-defined axial support of the tangential cutting inserts 10.

[0048] The side wall 6b of the recess 6 is furthermore forming clearance spaces 8 between the two side support surfaces 5b, 5c (see also FIGS. 2 and 2a). Hence, the side support surfaces 5b, 5c are protruding from the side wall 6b of the recess 6, wherein the clearance spaces 8 are housing portions of the circumferential side surface 13a of the projecting member 13 that extend between the two side contact surfaces 13b, 13c to ensure that only the side support/contact surfaces 5b, 5c, 13b, 13c are abutting each other. A well-defined rotational and radial/tangential support for the cutting insert 10 is hereby achieved as the clearance spaces 8 ensure that the rest of the circumferential side surface 13a of the projecting member 13 is out of contact with the remaining portions of the side wall 6b of the recess 6.

[0049] The tangential cutting insert 10 is mounted in the seat 5 by means of a screw 20 being in engagement with a threaded hole 9 in the bottom surface 6a of the recess 6. The tangential cutting insert is provided with a screw hole 19 extending axially through the tangential cutting insert from the axial front side 14 to the axial back side 11. The screw hole 19 is extending inside the projecting member 13 and mouths in the axial back end surface 13d of the projection member 13. The tangential cutting insert 10 is mounted by screwing the screw 20 into the threaded hole 9 in the bottom surface 6a of the recess so that the flat axial contact surface 12 and the side contact surfaces 13b, 13c are pressed against the flat axial support surface 5a and the side support surfaces 5b, 5c respectively. The distances between a centre C2 of the screw hole 19 and the side contact surfaces 13b, 13c may hereby be slightly larger than the distances between the centre C3 of the threaded hole 9 and the side support surfaces 5b, 5c so that the screw 20, being made of steel, provides a spring bias due to its elasticity pressing the side contact surfaces 13b, 13c against the side support surfaces 5b, 5c. In other words, the centre axis C2 of the screw hole 19 and the centre axis C3 of the threaded hole are slightly offset (typically by fractions of a millimetre) to provide the spring bias of the mounting screw 20.

[0050] Furthermore, the centre axis C2 of the screw hole 19 is displaced from a geometrical centre G of the projecting member 13 to provide a sole mounting orientation of the tangential cutting insert 10 in which the position of the centre axis C2 of the screw hole in relation to the two side contact surfaces 13b, 13c correspond to the position of a centre axis C3 of the threaded hole 9 in relation to the two side support surfaces 5b, 5c. More precisely, the sole mounting orientation is such that the tangential cutting insert 10 have a rake surface 16 with cutting edge 18 facing the direction of rotation R. In other words, the tangential cutting insert cannot be mounted to face in the wrong/non-intended direction of rotation of the tool body.

[0051] FIGS. 3 to 3h disclose different views of the tangential cutting insert 10. The tangential cutting insert comprises an axial direction A2 coinciding with both the centre axis C2 of the screw hole 19 and the axial direction A1 of the face milling tool 1. The tangential cutting insert 10 comprises the axial back side 11 having the flat axial contact surface 12 extending perpendicular to the axial direction A2. The projecting member 13 on the axial back side 11 is extending axially in relation to the flat axial contact surface 12. The projecting member 13 comprises the circumferential side surface 13a forming the out of round (in this case planar) side contact surfaces 13b, 13c to rotationally lock and support the tangential cutting insert in directions being perpendicular to the axial direction A2 (i.e. in the radial and tangential direction of the face milling tool). The circumferential side surface 13a of the projecting member 13 is hereby forming a polygon in a cross section perpendicular to the axial direction A2. More precisely, the polygon has the form of a convex circular triangle (a Reuleaux triangle) with the two planar side contact surfaces 13b, 13c being formed along two convex sides of the convex triangular cross section. As can be seen, the back side 11 is hereby provided with a single and centrally located projecting member 13, wherein the flat contact surface 12 extend both in front and behind (as seen in the rotational direction of the milling tool) of the centrally located projecting member 13. The projecting member 13 comprises a tapering shape in the axial extension away from the flat axial contact surface 12 to the axial back end surface 13d of the projecting member 13, wherein the axial back end surface 13d is a planar surface.

[0052] An axial front side 14 of the tangential cutting insert 10 is forming an axial clearance surface 15 opposite to the flat axial contact surface 12. A peripheral side surface 17 is hereby extending between the flat axial contact surface 12 and the axial clearance surface 15, wherein a rake face 16 is arranged in the peripheral side surface 17 and a single cutting edge 18 is formed at the intersection between the rake face 16 and the axial clearance surface 15. A positive axial clearance angle is provided by the axial clearance surface 15 sloping toward the flat axial contact surface 12 as it extends from the cutting edge 18 (see in particular FIGS. 3g and 3h). The sloping axial clearance surface is necessary to provide an axial clearance behind the cutting edge when face milling, since the flat axial support/contact surface 5a, 12 is extending perpendicularly to the axial direction A1, A2. The axial clearance surface 15 is hereby sloping in the entire extension along a longitudinal side view of the tangential cutting insert (see FIGS. 3g and 3h). The most significant clearance angle is however provided directly behind the cutting edge 18 to provide the necessary axial clearance behind the cutting edge 18.

[0053] The cutting edge 18 comprises a wiper edge 18a connected to a main cutting edge 18b (see in particular FIGS. 3d and 3f). The main cutting edge 18b is inclined in relation to the wiper edge 18a and is extending at an entering angle of at most 10. As can be seen, the wiper edge 18a and the main cutting edge 18b is hereby forming a continuously arched cutting edge 18, wherein the radius of curvature of the wiper edge 18a is larger than the radius of curvature of the main cutting edge 18b. Furthermore, the tangential cutting insert of the present embodiment is made of cemented carbide and is provided with a brazed tip of PCD or CBN material, which tip is forming the cutting edge 18 and a portion of the rake surface 16 and the clearance surface 15. Incorporating such a tip of PCD or CBN is a particularly useful when face milling in aluminium.

[0054] As previously mentioned the invention makes it possible to manage any deviations in the axial position between the flat axial support surfaces by subjecting the seats 5 on the axial front end surface 4 to a single flat grinding operation so that the flat axial support surfaces 5a become situated in a common plane extending perpendicular to the central rotation axis C1.

[0055] The final axial run-out of the milling tool also depends on the insert tolerances. As also previously mentioned the axial run-out contribution from the tangential cutting inserts 10 are also easily managed by grinding the flat axial contact surface 12 on the back side 11 and/or the cutting edge 18 with its axial clearance surface 15 on the front side 14 to minimize/eliminate deviations in the axial distance between the cutting edges 18 and the flat axial contact surfaces 12 on the tangential cutting inserts 10. The wiper edge 18a of the embodiment is hereby situated axially foremost (or furthest away from the flat axial contact surface 12) on the axial front side 14 of the tangential cutting insert 10 (the main cutting edge 18b is forming a setting angle in relation to the wiper edge 18a). The axial run-out of the cutting insert is hereby easily managed (i.e. minimized/eliminated) by grinding the cutting insert 10 to minimize/eliminate the variations in distances between the flat axial contact surface 12 and the wiper edge 18a of the tangential cutting insert 10. No other insert tolerances will contribute to the final axial run-out of the face milling tool.

[0056] The embodiment is specifically developed for face milling of so called bi-metal engine blocks (where some parts are of aluminium and other parts are of cast iron). It hereby reduces problems of scratches, burrs of in the machined aluminium parts and flaking/frittering of the cast iron edges in the bi-metal engine block. However, the present invention is applicable in face milling in general, whereby improvements in the surface finish can be achieved by reducing/eliminating the axial run-out on the milling tool.

[0057] The invention is not limited to the embodiments described above and shown in the drawings. Hence, the axial clearance surface 15 does not have to slope in its entire extension along the longitudinal side view of the cutting insert. Instead it may only slope a portion behind the cutting edge, wherein the remaining axial clearance surface is for instance extending in parallel with the flat axial contact surface. The tangential cutting insert of the embodiment is a single sided cutting insert with a single cutting edge arranged on the axial front side. However, the tangential cutting insert may be double-sided with a single cutting edge also on the back side of the tangential cutting insert. In this case a portion of the axial clearance surface is necessarily formed as the flat axial contact surface, so that the tangential cutting insert can be turned over and mounted with the flat axial contact surface on the axial front side against the flat axial support surface in the seat when the cutting edge on the axial front side is worn out. The cutting edge may also be formed on a projecting member forming a projecting cutting head with one side carrying the cutting edge/rake face and opposite sides comprising side contact surfaces for abutting the side support surfaces of the seat. Such projecting member/cutting heads may extend axially on both the front side and axial back side of the tangential cutting insert, wherein the projecting member/cutting head on the axial back side is recessed in the seat in the mounted condition.