Double-sided cutting insert

Abstract: The invention relates to a double-sided insert for chip­ forming machining, preferably for a lathe tool. The insert (10) is a body of regular polygonal shape comprising combined support and chip faces (24) in each corner. These faces (24) are connected to adjacent cutting edges via a bevelled face (26) which extends all around the insert. The combined support and chip faces (24) are arranged close to the cutting edges in order to avoid insert breakage failure.

Description: The present invention relates to a double-sided cutting insert according to the preamble of claim 1, see US-A-3 875 663. A double-sided cutting insert for chipforming machining is disclosed in US-Patent 4,312,250 in which each upper and lower face of the insert has a centrally raised portion for the purpose of giving the insert an adequate support surface when located against a bottom support. The cutting edge provided at the lower face and its adjacent chip face are arranged at some distance from the bottom support and the insert is therefore susceptible to failure when subjected to large tensile forces. It is an object of the present invention to provide a double-sided cutting insert with as good strength as possible during machining. It is another object of the present invention to provide a cutting insert equipped with a plurality of cutting edges. These and other objects are achieved by the characterizing features outlined in the following patent claims. The invention will now be described more in detail with reference to the accompanying drawings showing: Fig. 1, a plan view of a cutting insert according to the invention; Fig. 2, a side view of the insert of Fig. 1; Fig. 3, a partial sectional enlarged view along the line III-III in Fig. 1, in which a portion of a bottom support is shown adjacent the insert; Fig. 4, a partial sectional enlarged view along the line IV-IV in Fig. 1, in which a portion of a bottom support is shown adjacent the insert; Fig. 5, a perspective view of the insert in Fig. 1; Figs. 6 and 7, an alternative embodiment of an insert of the invention as shown in plan view and in a side view, respectively. Figs. 1 - 5 show a cutting insert 10 according to this invention, preferably for a lathe cutting tool. The insert 10 is manufactured of a ceramic material or cemented carbide or a similar material. The insert is in the form of a body of generally polygonal shape; in this case it has rhombic basic shape and has a central aperture for clamping purpose. The insert includes an upper face 11 and an opposite bottom face 12 which are mainly identical. The faces 11 and 12 intersect with continuously extending side surfaces 13 to 16 to define cutting edges 17 to 20 along the periphery of said upper face 11 and said bottom face 12. The side surfaces 13-16 meet at rounded cutting corners 21. The cutting corner 21 defines a bisector B. Each side has a central depression 22 which slopes downwards and inwards at an angle α from chip faces 23 and from their corner portions 24. The angle α is selected in the range 0.5° - 8°. Each face 23 is mainly perpendicular towards the side surfaces 13-16 and is intended for chip upsetting during machining. The corner portions 24 are arranged in a plane P. Each corner portion 24 is oriented perpendicular in relation to the adjacent side surfaces 13-16 and is intended, in an active position, to upset chips in similarity with the face 23. The face 23 is provided with a certain play 28 from the plane P or the bottom support 25. This play 28 is in the order of 0.05 - 0.5 mm. The face 23 and corner portion 24, via a surrounding negative bevelled face 26, are directly or indirectly connected with the cutting edges 17. The corner portions 24 are symmetrically arranged in relation to the bisector B of the adjacent cutting corner 21. The largest width of the cutting corner in a direction parallel with said bisector B is larger than the largest width of the face 23 as seen perpendicular to adjacent cutting edge. Each of the cutting corners 21 is provided with a depression 27 which is arranged symmetrically in relation to the bisector B of said corner. This depression intersects with the bevelled face 26 and extends inwardly from said bevelled face and occupies about half of the length of the corner portion 24 as seen in the length direction of the bisector. The largest width of the depression perpendicularly from said bisector is less than the largest width of said corner portion in the same direction. Figs. 6 and 7 illustrate an alternative embodiment of an insert 10' of this invention. The insert has a shape identical with insert 10 with the exception, however, that the corner portions 24' and the faces 23 are located in the same plane P. The insert 10' is intended to abut against a support along the entire periphery of the insert whereby the support surfaces of the insert are arragend in the most favourable position. The inserts 10 and 10' can also be provided with projections in the chip face 23, 24 and 23', 24' of the type being described in SE-A-8803354-3 which is herein incorporated in terms of its description. The present invention thus relates to a double-sided insert for chipforming machining of the type wherein the insert has combined support and chip faces which are so designed that the risk for cracking failure is minimized.

Claims: Double-sided cutting insert, in particular of ceramic material, for chip cutting machining comprising a body of generally polygonal shape having an upper face (11), an opposite lower face (12) and clearance faces (13-16) intersecting said upper and lower faces to define cutting edges (17-20, 17'-20'), which extend to the cutting corners (21) of the polygonal body, each said upper and lower face having a centrally recessed portion (22), which adjoins a combined chip and support face, characterized in that a bevelled face (26, 26') adjoins each cutting edge and the combined support and chip face (24; 23', 24'), which extends partially on both sides of the bisector (B) of the cutting corners (21), and is oriented substantially perpendicularly to the clearance faces (13-16), whereby the bevelled face is bevelled such that an inner obtuse angle is formed between said bevelled face and the adjacent support and chip face. Cutting insert as defined in claim 1, characterized in that the combined support and chip face (24) has an extension that is confined to an area around each cutting corner (21). Cutting insert as defined in claim 1, characterized in that the combined support and chip face has an extension alon the periphery of the insert. Cutting insert as defined in claim 1, characterized in that the bevelled face (26, 26') is thinner in the cutting corners (21) than at a location at some distance from said corners. Cutting insert as defined in any of the preceding claims, characterized in that the recess (22) adjoins a central aperture. Cutting insert as defined in claim 1 or 2, characterized in that the cutting edge (17-20) is mainly concave in shape between two adjacent cutting corners (21). Cutting insert as defined in any of the preceding claims, characterized in that the insert (10, 10') has a rhombic basic shape. Cutting insert as defined in claim 1, characterized in that the combined chip and support faces (23) are continuous along respective ones of the cutting edges and are coplanar with said corner chip and support faces (24). Cutting insert as defined in any of the preceding claims, characterized in that it is made of a ceramic material.

Inventors: PETTERSSON LARS TURE, WIMAN JOERGEN VIGGO, PETTERSSON, LARS TURE, WIMAN, JOERGEN VIGGO, Wiman, Jörgen Viggo
Applicants: SANDVIK AB, SANDVIK AKTIEBOLAG
Application year: 1989
Main classification: B23B27
IPC codes: B23B27