Cutting tool and cutting insert for chip removing tools

Abstract

The invention relates to a cutting tool and to a cutting insert for a chip removing tool. The cutting tool has a tool body with at least one recess (3), at least one cutting insert which is releasably secured to the recess, and a fastening device for securing the insert in the recess. The recess has a raised portion (20) with a flat upper support surface (22) to be received in a recess of the insert and supporting the insert by receiving a bottom surface of the recess bearing on the support surface (22). A protruding member (25) of the raised portion (20) has a limiting wall (29) designed to bear against a boundary wall of the recess of the insert to establish mutual contact with the boundary wall and to prevent rotation of the insert in the recess by receiving a rotational moment acting on the insert in an active chip removing state of the tool.

Description

[0001] This application is a divisional application of Chinese application No. 201580047212.8, filed on September 3, 2015, entitled "Cutting inserts for cutting tools and chip removal tools". Invention Field

[0002] The present invention relates to a cutting tool configured for chip removal and a cutting insert, the cutting tool comprising a tool body and at least one such cutting insert.

[0003] This invention relates particularly to cutting tools and indexable cutting inserts used in such tools for milling, and for this purpose, the specific application will be discussed and described below, but the invention is not entirely limited thereto. The tools and inserts can also be used for other types of chip removal processes, such as turning. Examples of conceivable milling processes are face milling, ramping, and interpolation milling.

[0004] Such end mills typically have multiple (e.g., six) recesses to which the cutting insert is releasably secured, allowing the insert to be indexed and thus altering the cutting edge portion for chip removal. Crucially for the machining outcome and the lifespan of the cutting insert, the insert, received in the recess or holder of the cutter body, is properly supported in a fixed position therein. This support is provided by means of a device that supports portions of the insert's side surfaces and a flat support surface that supports the insert's lower surface, with a fastening device pressing the lower surface against the flat support surface while securing the insert in the recess. Equally important is that the insert remains stationary when rotational torque acts on it during the active chip removal state of the cutter, and this is ensured by the interaction of the insert's engagement member with the recess's engagement member. Background Technology

[0005] EP 2764939 A1 discloses a cutting tool and cutting insert of the type defined in the preamble. In this tool, the support surface of the recess is provided by a flat recess bottom surface, and a portion of the lower surface of the insert surrounding the central recess is applied to the flat recess bottom surface to receive support. An engagement member is arranged on the support surface to be received in the recess and forms a protruding member for engaging with a particular recess extension and preventing the insert from rotating in the tool's active chip-removing state. Summary of the Invention

[0006] The object of the present invention is to provide a cutting tool and cutting insert of the type defined in the introduction, which is improved in at least one respect relative to such cutting tools and cutting inserts known.

[0007] Regarding cutting tools, this objective is achieved by providing such cutting tools with certain characteristics.

[0008] By providing the support surface with the aid of a raised section, adequate support can be obtained by using the bottom surface of a groove that provides for indexing and to prevent rotation of the insert received in the recess. This not only means that sufficient support can be provided for the insert from below, but also provides the possibility of using reversible inserts (i.e., double-sided inserts) in the cutting tool, which is not possible in known cutting tools with the support surface as described above.

[0009] According to an embodiment of the invention, the at least one protruding member carries the support surface to support the cutting tool on the bottom surface within the groove extension. This means that the support surface will be close to the outer boundary of the groove receiving the protruding member, thereby improving the protection and support of the cutting tool portion subjected to cutting forces in the chip-removing state of the tool.

[0010] According to another embodiment of the invention, the second engaging member includes a first protruding member positioned to support the insert thereon via a portion of the support surface in a region configured to be loaded during the active chip-removing state of the cutting tool. In a further development of this embodiment, viewed from the central axis of the insert receiving the member, the first protruding member protrudes in a direction deviating by 0-45° from a corresponding direction pointing to the point on the cutting edge to which the maximum load is applied during the active chip-removing state of the cutting tool. With this configuration, the insert will be received and supported by the support surface where the cutting force is highest, thereby reducing any risk of the insert cracking during the cutting operation.

[0011] According to another embodiment of the invention, when the first protruding member is received in the recessed extension, the first protruding member is configured to extend a distance from the central axis, which is at least 70%, 75%-95%, or 80%-90% of the distance from the central axis to the side surface of the blade. The support surface will thus provide support to the blade close to its periphery, thereby reducing the risk of blade breakage, which is typically highest during the cutting operation.

[0012] According to another embodiment of the invention, the blade is provided with at least three of the said groove extensions, and the second engaging member includes two of the said protruding members. The arrangement of two said protruding members improves the stability and support of the blade in the recess compared to the presence of one said protruding member. Thus, preferably, the second of the two protruding members is configured to protrude into a groove extension that follows the groove extension into which the first protruding member protrudes, as seen from the direction of the rotational torque acting on the blade in the chip-removing state of the cutting tool.

[0013] According to another embodiment of the invention, each of the protruding members is designed to protrude into the groove extension, wherein a gap exists between the limiting wall of the protruding member and the groove boundary wall in the groove extension of the groove. The gap can be very small, but is sized such that the groove of the blade can be easily mounted or placed onto the protruding member of the raised portion. However, the protruding member and the groove boundary wall can be pressed against each other by a fastening device arranged to press them together in the fixed position of the blade. This also means that the two protruding members can be formed on the raised portion without making the blade holder formed in the recess statically indeterminate. Therefore, the second protruding member can thus be provided with a slightly larger gap than the first protruding member to further facilitate mounting the groove of the blade onto the support surface and the protruding member.

[0014] According to another embodiment of the invention, the groove is provided with a plurality of valley-shaped or finger-shaped groove extensions evenly distributed around the central axis of the blade, and according to another embodiment of the invention, the number of the extensions may be 2-8, 5-8, 6-8 or 6, thereby generating a corresponding number of blade indexing positions when the cutting edge is used for chip removal.

[0015] According to another embodiment of the invention, the top surface of the blade is circular, and the cutting edge is circular.

[0016] According to another embodiment of the invention, the bottom and top surfaces of the insert are identical and the cutting edge is formed between each of these surfaces and the side surface of the insert. In this sense, the insert is reversible, which results in a doubling of the possible indexing number, which extends the service life of the cutting insert and thus provides better tool economy compared to cutting tools, for example, according to the above-described documents.

[0017] According to another embodiment of the invention, the device for providing support to a portion of the side surface of the cutting tool includes at least one support surface comprising at least three ridges with grooves between them, the grooves being manufactured by a ball-end end mill that imparts a concave arch shape, and the grooves having a depth of 0.015 to 0.025 mm. This support surface and its manufacture are disclosed in EP 1629917 B1, and result in the possibility of manufacturing the support surface in a recessed area of ​​the cutting tool body that is difficult to access. The grooves having this limited depth result in a surface capable of providing good support.

[0018] According to another embodiment of the invention, the cutting tool is a milling cutter having the tool body including a front end and a rear end, a central axis of rotation extending between the front end and the rear end, the tool being rotatable about the central axis of rotation in a rotational direction, and the recess being formed in a transition between the front end and an envelope surface extending between the front end and the rear end of the tool body. The cutting tool according to the invention is particularly suitable for milling operations, especially face milling and ramp milling.

[0019] According to another embodiment of the invention, which constitutes a further development of the last mentioned embodiment, the device configured to provide support to a portion of the side surface of the insert includes two separate support surfaces that provide axial and radial support to the insert, respectively, relative to the central axis of rotation of the tool. These two separate support surfaces, together with the support facets, ensure that the cutting insert will receive precise support and be securely held in the recess in the milling cutter according to the invention. Thus, as described in another embodiment of the invention, this facilitates the first protruding member projecting in a direction deviating from the central axis of rotation of the tool by 0-45°, 0-25°, or 0-5°. This means that the support facets will provide adequate support in the region of the insert where the cutting force is highest. In other words, the support facets extend outward to provide support to the lower surface of the insert, which is located below and along the region of the active cutting edge, during milling.

[0020] The object of the present invention is to provide an indexable cutting insert for a chip removal tool. The advantages of this insert and its embodiments are clearly apparent from the above discussion of the cutting tool and its embodiments according to the invention. A key advantage is that the flat bottom surface of the central groove provides sufficient support for the insert, enabling the use of a reversible insert (i.e., a double-sided insert) in the cutting tool. Therefore, the flat bottom surface of the central groove is configured to form a single portion of the lower surface, which is supported by the support surface located on a raised portion within the recess. The flat bottom surface of the groove thus provides a sufficient surface area for supporting the lower surface of the insert. In other words, the lower surface of the double-sided insert, including the cutting edge (and rake face), does not rest against any surrounding recess portion.

[0021] Other advantageous features and benefits of the present invention will become apparent from the following description. Attached Figure Description

[0022] Referring to the accompanying drawings, the following is a detailed description of embodiments of the present invention as illustrated by examples.

[0023] In the attached diagram:

[0024] Figure 1 A perspective view of a milling cutter according to the present invention is shown.

[0025] Figure 2 Show Figure 1 The perspective view of the tool recess shown in the figure.

[0026] Figure 3 A perspective view of a cutting blade according to an embodiment of the present invention is shown, and

[0027] Figure 4 The acceptance was made transparently based on Figure 2 According to the recess in the seat Figure 3 Cutting inserts. Detailed Implementation

[0028] According to an embodiment of the present invention, the end mill 1 is used in... Figure 1 As shown in the diagram. The cutting tool includes a tool body 2, which has six tool holders or recesses 3, each tool holder or recess 3 receiving a double-sided cutting insert 4 releasably fixed to the recess. To illustrate the structure of the recesses, in... Figure 1In this process, the cutting insert is removed from one of a plurality of recesses. The tool body 2 includes a front end 5 and a rear end 6, with a central rotation axis C1 extending between the front end 5 and the rear end 6, allowing the cutting tool to rotate about the central rotation axis C1 in the rotational direction R. A recess 3 is formed in the transition between the front end and an envelope surface 7 extending between the front and rear ends of the tool body. The double-sided insert 4 has a negative type, is fixed in the recess, and is inclined at an axial angle of -7° to -12° and a radial angle of -8° to -15° relative to the central rotation axis C1 to provide clearance between the cutting insert and the workpiece. Other axial and radial angles are, of course, conceivable.

[0029] Now refer to Figures 1 to 4 To explain Figure 1 The milling cutter shown has a structure and cutting inserts. Figure 3 A cutting insert 4 according to an embodiment of the present invention is shown. The cutting insert is double-sided or reversible, meaning that its top and bottom have the same design, but the side shown as the upper side in the orientation of the cutting insert in the figure will be referred to as the top below, although it may be exactly the bottom or lower side of the cutting insert. Thus, the cutting insert has a concealed lower surface 8, a top surface 9, and a surrounding side surface 10 connecting the lower surface and the top surface, as seen in the figure. The lower surface and the top surface are circular and each has a circular cutting edge 11, 12 formed between these surfaces and the side surface 10. The top surface 9 and the lower surface 8 are provided with a central groove 13, which has a flat bottom surface 14. The groove 13 has six central groove extensions 15 of a valley-like or finger-like design evenly distributed around the blade central axis C2 of the cutting insert. These central groove extensions 15 are defined by the boundary walls 16 of the central groove and extend radially further than the adjacent portions 17 of the central groove relative to the blade central axis C2. The cutting insert is provided with a central axial through hole 18 for fixing the cutting insert in the recess 3 of the cutting tool by screws 19. Each recess 3 has a raised portion 20 that is raised relative to the surrounding recess portion 21 and is provided with a flat support surface 22 as its upper surface. The raised portion 20 is configured to be received in the central groove 13 of the cutting insert fixed in the recess and to be supported to the bottom surface 14 of the central groove by the support surface 22.

[0030] The recess also has means for providing support to a portion of the side surface 10 of the cutting insert received in the recess in the form of two separate support surfaces, one support surface 23 for providing axial support and the other support surface 24 for providing radial support. These two support surfaces are formed by ridges with grooves between them, wherein the grooves are made by a ball-end end mill that imparts a concave arch shape, and the grooves have a depth of 0.015 to 0.025 mm.

[0031] The raised portion 20 of the recess has a first protruding member 25, which is configured to protrude into and be received in a central recess extension 15 of the cutting insert, and engages a portion 26 of the boundary wall of the central recess to establish mutual engagement between the cutting insert and the recess, thereby preventing the cutting insert from rotating about the insert's central axis C2 by receiving the rotational torque acting on the cutting insert in the chip-removing state of the cutting tool. The protruding member 25 carries the support surface 22 to support the cutting insert on the bottom surface 14 within the central recess extension 15. The first protruding member 25 here points to "six o'clock" relative to the central axis of rotation C1 of the cutting tool, which means that it will provide support through the support surface portion 27 thereon in the region of the cutting insert configured to be subjected to maximum load in the chip-removing state of the cutting tool, and thereby effectively counteract any tendency of the cutting insert to crack or break. The central recess extension 15 is designed to allow the first protruding member to extend from the blade's central axis C2, received in the recess, to a distance approximately 90% of the distance from the blade's central axis to the side surface of the blade. The riser 20 provides two of the protruding members, and a second protruding member 28 is configured to protrude into the central recess extension 15, following the central recess extension into which the first protruding member 25 protrudes, as seen in the direction of the rotational torque. Both protruding members are designed to protrude into the central recess extensions, wherein a gap exists between the limiting wall 29 of the protruding member and the boundary wall 26 of the central recess in the corresponding central recess extension of the blade, to simplify blade mounting and prevent static indeterminacy of the recess.

[0032] The raised portion 20 of the recess has a threaded hole 30 for receiving a screw 19 configured to secure the cutting insert within the recess. The hole 30 is positioned slightly offset relative to the through-hole 18 of the cutting insert, meaning that when the screw is tightened, the screw 19 will press against a portion of the side surface 10 of the cutting insert to support it against the support surfaces 23 and 24 under pre-tension, and then press the bottom surface 14 of the central recess 13 of the cutting insert against the support surface 22 of the recess. When operation of the cutting tool begins, a rotational torque about the insert's central axis C2 is applied to each cutting insert to attempt to rotate it and ensures that the cutting insert is stably and reproducibly positioned in the recess by engaging the limiting wall 29 of the first protruding member 25 with a portion 26 of the boundary wall of the central recess of the cutting insert, thereby preventing further rotation of the cutting insert.

[0033] The cutting blade can be rotated six times to receive the first protruding member 25 in each central groove extension 15, and then flipped so that the cutting blade can be rotated 12 times.

[0034] This invention is certainly not limited to the embodiments described above, but many possibilities for modifications to the invention will be apparent to those skilled in the art without departing from the scope of the invention as defined in the appended claims.

[0035] The number of indexings provided by each central groove of the blade may not be six. The blade may have a polygonal cross-section with multiple different straight cutting edges along its upper and lower boundaries. The fastening device for securing the blade in the recess may be, for example, a clamp instead of a screw, and therefore the blade does not need to have a central through-hole, nor does the raised portion of the recess need to have a hole. The blade may be single-sided. Although in the embodiment shown in the figures the groove extensions of the lower and upper surfaces are aligned with each other, they may also be displaced relative to each other at any desired angle. These are merely some possible modifications within the scope of the invention described herein.

Claims

1. A cutting tool comprising: • a tool body (2) having at least one pocket (3), • at least one cutting insert (4) releasably secured to the pocket, the cutting insert having a lower surface (8), a top surface (9), a surrounding side surface (10) connecting the lower surface and the top surface, and at least one cutting edge (11, 12) formed between the top surface and the side surface, the pocket having means configured to provide support to a portion of the side surface and a flat support face (22) configured to provide support to at least a portion of the lower surface of the cutting insert, and • a securing device (19) configured to secure the cutting insert (4) in the pocket (3) while pressing the portion of the lower surface against the support face (22), the cutting insert having a first engagement member and the pocket having a second engagement member configured to establish mutual engagement of the cutting insert and the pocket to prevent rotation of the cutting insert about an insert central axis (C2) extending through the top and lower surfaces of the cutting insert by receiving a rotational moment acting on the cutting insert in an active chip-removing state of the tool, the lower surface of the cutting insert having a central recess (13) with a flat bottom surface (14), the first engagement member comprising at least three central recess extensions (15) of the central recess defined by a boundary wall (16) of the central recess, the at least three central recess extensions extending radially further out than adjacent portions (17) of the central recess and the flat bottom surface (14) with respect to the insert central axis (C2), wherein the second engagement member comprises at least two securing protruding members (25, 28) of the pocket (3), each configured to protrude into and alternatively be received in one of the central recess extensions (15) and to engage portions of the boundary wall (16) of the central recess to establish the mutual engagement and enable indexing of the cutting insert, characterized in that the pocket of the tool body has a raised portion (20) raised with respect to a surrounding pocket portion (21) and has the support face (22) as an upper surface, the raised portion being designed to be received in the central recess (13) of the cutting insert (4) and to support the cutting insert by receiving the flat bottom surface (14) of the central recess (13) supported on the support face (22). and said at least two fixing protruding members (25, 28) of said second engaging member are formed by said elevations (20) having a limiting wall (29) designed to bear against the boundary wall (16) of said central recess of said central recess extension (15) so as to establish said mutual engagement to prevent rotation, wherein said at least two fixing protruding members (25, 28) carry said support face (22) to support said cutting insert on said flat bottom surface (14) also located within said central recess extension (15), wherein a first one of said fixing protruding members (25) is configured to extend from said insert central axis (C2) a distance of 80-90% of the distance from said insert central axis to said side surface (10) of said cutting insert when said first fixing protruding member (25) is received in said central recess extension (15), and wherein each of said fixing protruding members (25, 28) is designed to protrude into said central recess extension (15) with a clearance between said limiting wall (29) of said fixing protruding member and the boundary wall (16) of said central recess in said central recess extension of said cutting insert, a second one of said at least two fixing protruding members being provided with a larger clearance than said first fixing protruding member.

2. The cutting tool according to claim 1, characterized in that, said first fixing protruding member (25) is positioned to support said cutting insert thereon by a portion (27) of said support face in a region configured to be loaded in an active chip-removing state of said cutting tool.

3. The cutting tool according to claim 2, characterized in that, said first fixing protruding member (25) protrudes in a direction deviating 0-45° from the respective direction pointing to the point of said cutting edge (11, 12) to which the maximum load is applied in an active chip-removing state of said cutting tool, seen from said insert central axis (C2) of the cutting insert receiving the member.

4. The cutting tool according to any one of claims 2-3, characterized in that, a second one of said fixing protruding members (28) is configured to protrude into another central recess extension following said central recess extension into which said first fixing protruding member (25) protrudes, seen in the direction of said rotational moment acting on said cutting insert in an active chip-removing state of said cutting tool.

5. A cutting tool according to any one of claims 1-3, characterised in that said central recess (13) is provided with a plurality of recess-like or finger-like central recess extensions (15) uniformly distributed around said insert central axis (C2) of said cutting insert.

6. The cutting tool according to claim 5, characterized in that said cutting insert has 2-8 of said central recess extensions (15) in said central recess (13) in the center.

7. A cutting tool according to any one of claims 1-3, characterized in that said top surface (9) of said cutting insert is circular and said cutting edge (12) is circular.

8. A cutting tool according to any one of claims 1-3, characterized in that The lower surface (8) and the top surface (9) of the cutting insert are identical and the cutting edges (11, 12) are formed between each of these surfaces and the side surface (10) of the cutting insert, such that the cutting insert (4) is reversible.

9. A cutting tool according to any one of claims 1-3, characterized in that The means providing support to the portion of the side surface (10) of the cutting insert comprises at least one support surface (23, 24) comprising at least three ridges with grooves between the ridges, the grooves being manufactured by a ball nose end mill imparting a concave shape to it, and the grooves having a depth of 0.015 to 0.025 mm.

10. The cutting tool according to claim 2, wherein, The cutting tool is a milling cutter having the tool body (2) comprising a front end (5) and a rear end (6), a central rotation axis (C1) extending between the front end and the rear end, the tool being rotatable in a rotation direction about the central rotation axis (C1), and the pocket (3) being formed in a transition between the front end and an envelope surface (7) extending between the front end and the rear end of the tool body.

11. The cutting tool according to claim 10, characterized in that The means configured to provide support to the portion of the side surface (10) of the cutting insert comprises two separate support surfaces (23, 24) providing axial and radial support to the cutting insert with respect to the central rotation axis (C1) of the tool, respectively.

12. A cutting tool according to claim 10 or 11, characterised in that The first fixed protruding member (25) protrudes in a direction deviating 0 to 45° from the extension of the central rotation axis (C1) of the tool.

13. The cutting tool according to claim 6, wherein, The cutting insert has 5 to 8 of the central groove extensions (15) in the central one of the central grooves (13).

14. The cutting tool according to claim 6, wherein, The cutting insert has 6 to 8 of the central groove extensions (15) in the central one of the central grooves (13).

15. The cutting tool according to claim 6, wherein, The cutting insert has 6 of the central groove extensions (15) in the central one of the central grooves (13).

16. The cutting tool according to claim 12, wherein, The first fixed protruding member (25) protrudes in a direction deviating 0 to 25° from the extension of the central rotation axis (C1) of the tool.

17. The cutting tool according to claim 12, wherein, The first fixed protruding member (25) protrudes in a direction deviating 0 to 5° from the extension of the central rotation axis (C1) of the tool.

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