This application claims priority under 35 U.S.C. §119 to Swedish Patent Application No. 1050557-6, filed on Jun. 2, 2010, which is incorporated by reference herein in its entirety.
The present invention relates generally to a cemented carbide insert of the type that includes an upper side, an under side, and a number of side surfaces extending between the same as well as at least one cutting edge, which includes a nose edge and two main edges converging toward the same and is included in an inset, which includes a material that is harder than the cemented carbide, and which is countersunk in the surrounding cemented carbide and co-ground with the same. In a second aspect, the invention also relates to a cemented carbide blank for the manufacture of cutting inserts of the kind in question.
By U.S. Pat. No. 7,387,474, an indexable turning insert is previously known, which has a rhombic basic shape and includes two diametrically opposed cutting edges, which individually comprise two main edges, which converge toward a common secondary or nose edge, which forms a rounded transition between the two main edges, and which always generates the exposed surface in the workpiece irrespective of which one of the two main edges that is active and provides for the active chip removal. In order to enable good machining results in respect of dimensional accuracy and surface smoothness irrespective of the index position of the cutting insert, it is important that the nose edges of the cutting insert are situated at exactly equally large distances not only from the center of the cutting insert (which in this case is represented by a through hole for a fixing screw), but also from the under side of the cutting insert. Only in such a way it is ensured that the active nose edge always assumes one and the same spatial position in relation to the basic body of the tool in which the cutting insert is mounted. For this reason, it is necessary to precision grind not only the upper side of the cutting insert but also the clearance surfaces that delimit the cutting edges together with the upper side. In this connection, the requirements of dimensional accuracy are often within the range of ±0.025 mm.
The same stiff requirements of dimensional accuracy are also made on cutting inserts having only one cutting edge. Thus, it is required that the single cutting edge is located in an accurately defined spatial position in relation to the support points of the cutting insert (e.g. rear side support surfaces or a groove in a lower connecting surface) for the nose edge to assume an exact predetermined position in relation to the basic body of the tool in which the cutting insert is mounted.
All forms of grinding of cemented carbide inserts are costly. The rule is that the cost increases with increasing grinding surface and increasing grinding depth. Another factor than the cost factor of great importance to the user is the quality of the grinding. A user responsible for machining an expensive workpiece needs of course to have reliance in not only the basic body of the tool but above all the replaceable cutting inserts, which gradually are consumed. Therefore, if a cutting insert would be impaired by even the slightest defective grinding, e.g. in transitions between different surfaces on the cutting insert, the ability of the cutting insert to machine the workpiece in a dimensionally accurate way would diminish. In this connection, it should be pointed out that also utmost small grinding defects will be visible to the naked eye by the reflection of the light from the ground surfaces. If the user would suspect that a cutting insert is defect, there is a risk that he directly discards the same.
Already grinding of genuine cemented carbide inserts, i.e., cutting inserts exclusively made from cemented carbide, is accordingly a delicate task, in particular if the pressing/sintering and the grinding, respectively, of the cutting inserts are carried out by different actors in different works. The task becomes even more delicate if the cemented carbide inserts in addition are to be provided with particularly hard insets precisely in the area of the cutting edges. When turning materials particularly difficult to machine, such as hardened steel, cast iron and the like, it is accordingly desirable to supplement the cemented carbide with a particular inset of a material, e.g. cubic boron nitride (CBN), and to form the individual cutting edge in the inset, more precisely by grinding a chip surface as well as a connecting clearance surface. Although such insets usually are only of millimeter size, they make the grinding significantly more difficult, not only in respect of time-consumption and cost, but also in respect of the quality of the finish-ground surfaces, in particular in transitions between the individual inset and the surrounding cemented carbide.
An example of a cutting insert that makes use of a superhard inset, in which the cutting edge is shaped, is disclosed in U.S. Patent Application Publication No. 2004/0258944 A1. A disadvantage of this cutting insert is, however, that the manufacture requires grinding of large cemented carbide surfaces in addition to the relatively small surfaces on the inset that are required to delimit the cutting edge. Thus, not only the chip surface of the hard inset but also the adjacent cemented carbide surface included in the upper side of the cutting insert has to be ground. In an analogous way, the cemented carbide surfaces surrounding the clearance surfaces of the inset have to be ground all the way from the inset to the center of the cutting insert. This means that unnecessary energy and time are consumed to grind in the inset while ensuring neat transitions between the inset and the surrounding cemented carbide.
The present invention aims at obviating the above-mentioned problems and at providing an improved cemented carbide insert of the type that requires simultaneous precision grinding of surfaces on an extremely hard inset as well as surrounding surfaces of cemented carbide. Therefore, an object of the invention is to provide a cemented carbide insert, in particular a turning insert, e.g. of the type that is disclosed in U.S. Pat. No. 7,387,474, which can be made with an inset difficult to grind of an extraordinary hard nature, and which in spite of said inset can be precision ground in a simple and cost-effective way.
In an embodiment, the invention provides a cemented carbide insert, including an upper side, an under side, a plurality of side surfaces extending between the upper side and the underside, and an inset including a cutting edge. The cutting edge includes a nose edge and two main edges converging toward the nose edge. The inset is formed of a material that is harder than the cemented carbide, and is countersunk in the surrounding cemented carbide and co-ground with the surrounding cemented carbide. The inset is arranged in a front, wedge-shaped head delimited by one chip surface and two clearance surfaces running along the main edges. The inset transforms into an adjacent body part via limiting surfaces situated inside imaginary planes in the extension of the chip surface and the clearance surfaces.
In another embodiment, the invention provides a cemented carbide blank for the manufacture of the cemented carbide insert.
The accompanying drawings, which are incorporated herein and constitute part of this specification, illustrate the presently preferred embodiments of the invention, and together with the general description given above and the detailed description given below, serve to explain features of the invention.
A ready for use, ground cutting insert according to an embodiment of the invention is shown in
In the exemplified embodiment, the under side of the cutting insert 2 has the shape of a connecting surface, which includes two female-like recesses or grooves 2a, 2b intended to alternately co-operate with a ridge-shaped male member of a complementary connecting surface in the basic body of the tool (not shown) in which the cutting insert is mounted. The distance between the cutting edge 3a and the groove 2a should be as great as the distance between the cutting edge 3b and the groove 2b to ensure that the individual nose edge 5 always assumes one and the same spatial position in relation to the basic body of the tool irrespective of which cutting edge that has been indexed up to an active position.
Reference is now made to
The geometrical structural difference between the conventional cutting insert according to
Reference is now made to
In
As is clearly seen in
Beside the cemented carbide blank shown in
In order to house the individual inset 14, in each head 7, there is formed a pocket 19 that is delimited by a plane bottom surface 20 and a rear end wall 21, which forms essentially the same angle (e.g. 90°) with the bottom surface 20 as the end surface 18 of the inset 14 forms with the surfaces 15. The pocket may advantageously be provided by grinding, although also milling is possible.
The next step of the manufacture is shown in
The final step of the manufacture is illustrated in
In the preferred embodiment, the tip angle or angle of convergence of the individual head 7 is as great as the angle of convergence of the body part 8.
In order to additionally clarify the structure of the cutting insert, reference is now made to
In
For the sake of clarity, it should be pointed out that the described cutting insert is intended for a maximum cutting depth that does not exceed the length L2 of the inset 14. In other words, the chip removal should solely take place along the individual main edge 4 that is formed in the hard inset, but not along the adjacent edge that is obtained by the grinding of the surrounding cemented carbide of the chip and clearance surfaces 71, 72 of the head.
Reference is now made to
A fundamental advantage of the cutting insert according to the embodiment is that the same can be provided with an extraordinary hard nose inset, the cutting edge of which for certain can be located in an exact, desired position in the cutting insert in respect of the distance of the nose edge from the support points of the cutting insert as well as of the vertical position thereof in relation to the under side of the cutting insert. Another advantage is that the need of grinding is reduced to an absolute minimum, since the requisite grinding is limited to the comparatively short head in which the individual inset is countersunk.
The invention is not limited only to the embodiment described above and shown in the drawings. Thus, the invention may also be applied to other cutting inserts than turning inserts, e.g. milling inserts. Furthermore, the tip angle or angle of convergence of the wedge-shaped head may vary most considerably, e.g. within the range of 30-90°. Also, the shape of the nose edge may deviate from the round or circular shape that has been exemplified in the drawings. The concept “grinding” should be interpreted in wide sense so far that comparable machining methods that provide the same final result as grinding also can be employed without deviating from the general idea of the invention. An example of such a method is sparking. It is also possible to combine grinding and sparking, for instance by sparking the chip surface while providing chip breakers of most varying topography, at the same time as plane clearance surfaces are provided by grinding. Furthermore, it should be pointed out that indexable cutting inserts, of the type that includes two or more cutting edges, may be manufactured with only one superhard inset such as CBN, diamond or ceramics, while other cutting edges are formed of cemented carbide. It should also be pointed out that the blank according to the embodiment (as shipped) may have either the shape shown in
While the invention has been disclosed with reference to certain preferred embodiments, numerous modifications, alterations, and changes to the described embodiments are possible without departing from the sphere and scope of the invention, as defined in the appended claims and their equivalents thereof. Accordingly, it is intended that the invention not be limited to the described embodiments, but that it have the full scope defined by the language of the following claims.
Number | Date | Country | Kind |
---|---|---|---|
1050557 | Jun 2010 | SE | national |
Number | Name | Date | Kind |
---|---|---|---|
4159885 | Schott | Jul 1979 | A |
5193948 | Noggle | Mar 1993 | A |
5246315 | Hansson et al. | Sep 1993 | A |
5569000 | Littecke et al. | Oct 1996 | A |
5921721 | Hintze et al. | Jul 1999 | A |
6155755 | Kanada et al. | Dec 2000 | A |
6612786 | Kanada et al. | Sep 2003 | B1 |
6742970 | Oles et al. | Jun 2004 | B2 |
7387474 | Edler et al. | Jun 2008 | B2 |
7520701 | Kukino | Apr 2009 | B2 |
7687156 | Fang et al. | Mar 2010 | B2 |
7765902 | Kuroda et al. | Aug 2010 | B2 |
7946792 | Oles et al. | May 2011 | B2 |
20040258944 | Oles et al. | Dec 2004 | A1 |
Number | Date | Country |
---|---|---|
102008042493 | Apr 2009 | DE |
GB 1093055 | Nov 1967 | EP |
0 940 215 | Sep 1999 | EP |
1 702 703 | Sep 2006 | EP |
902193 | Jul 1962 | GB |
63221906 | Sep 1988 | JP |
08192305 | Jul 1996 | JP |
10180507 | Jul 1998 | JP |
2004042157 | Feb 2004 | JP |
2008260090 | Oct 2008 | JP |
Number | Date | Country | |
---|---|---|---|
20110299948 A1 | Dec 2011 | US |