CHIP FORMING INSERT, ESPECIALLY FOR TURNING AND SLOTTING

Abstract: The invention relates to a cutting insert for machining tools wherein the insert adjacent its cutting edge (5) has a chip forming device. The novelty lies in that there is close to the cutting edge and essentially centrally of a surface adjoining said cutting edge a recess (8), said recess having on either side surface portions (10) for engaging the edge strakes of the chip and that there are close to the cutting edge (5) further surface portions having obliquely upwardly directed abutment surfaces (11) adapted to engage the edge strakes of the chip and bend the chip upwardly for breaking the chip into pieces.

Description: Ch i p form i ng i nsert , espec ia l l y for tu rn i ng and s l ott i ng Technical field of the invention This invention relates to cutting bits or inserts for cutting work especially turning wherein the insert is detachably attachable at a tool holder. Background of the invention Within the technical field is known a cutting bit insert which adjacent to the cutting edge presents a recess, down into which the middle portion of the chip is pressed during the machining operation whereas the side portions are kept in a somewhat higher plane in order to give the chip a lateral bending so that it will have less width than it has just upon leaving the cutting edge and thereby becomes narrower than the groove cut. The laterally bent chip can then roll itself and form a roll, which is narrower than the turned groove and because of that causes no damage to the machined surfaces or the like. Within this field of the technique it is also known to arrange, remote from the cutting edge of any tool, a so called chip breaker, that is a protruding portion which will be engaged by the cut chip in order to be guided away abruptly which results in a breaking of the chip preventing it from forming continuous rolls, spirals or spools which in turn might cause tool damages or damage the work piece and machined surfaces. One problem arising here is that the chip, because of the deformation, is subjected to by the breaking off increases its lateral width and because of that might cause congestion of chips and bad surface finish at the side surfaces of the groove. One essential aspect with this invention is to bring about a new cutting insert so arranged that it besides lateral bending of the chip also causes it to break which results in short chips having less width than the groove cut and which chips are easily removed from the groove without tendency to adhere to the sides of the groove, the tool or the like. Summary of the invention Characterizing the cutting inserts according to the new invention is that projections are arranged beyond the cutting edge seen in the direction of movement of the chip such projections arranged to guide the chip away from the surface adjacent the cutting edge and act as chip breaker and said projections being arranged laterally remote from each other seen in the direction of movement and that there is between such projections commencing adjacent the cutting edge, a concave recess having along its sides defined by the facing surfaces of said projections obliquely arranged and concave surfaces. A chip cut from the work piece slides inwardly over the middle recess arranged adjacent the edge and is thereupon subjected to an initial lateral bending as the portion of the chip still attached to the work pieces presses the free portion of the chip against the surface portion adjacent the edge. Simultaneously the edge strakes or flanks are guided by the surface portions on either side of the recess and after a short further movement along these, meet the protruding projections, which force the chip still attached to the work piece by an intermediate portion and pushed forwardly thereby, to bend off upwardly, wherein the chip portion between the projections eventually leaves the bottom of the middle recess and floats freely between the end surfaces of the projections. The chip then heavily deformed both in its length and lateral directions will break beyond the top portions of the projections and form laterally bent or arched and lengthwise curved short chip pieces having smaller width than the groove cut by the cutter edge. Brief description of the drawings The above as well as other features and advantages of the invention will be apparent through consideration of the detailed description in connection with the several drawing in which: Figure 1 is a side view showing one as an example selected cutting insert according to the invention. Figure 2 shows the same insert seen from the edge end. Figure 3 is a top view of the cutting insert, and Figure 4 is a sectional view taken along the line C-C in Figure 3. The cutting insert 1, the main features of which essentiall correspond to those of a known insert, has a V-shaped botto ridge 2 intended to cooperate with a V-groove at the insert holder and an upper abutment surface 3 intended to be engaged by an abutment portion at the holder in order to, b pressing the shaft portion 4 of the insert, hold it in position at the insert holder. The insert 1 presents one edge 5 and a planar surface 6 and to this is connected the middle portion 7 of said surface 6 having being narrow in the direction of movement of the chips and passes over in a recess 8 having a concave bottom and defined by convex outwardly inclined side portions 9 whereas the side portions 10 of the planar surface are wide seen in the same direction. As already indicated the recess 8 adjoining to the narrow central portion 7 of the surface 6 adjacent the edge 5, has as main task to allow the middle portion of the cut chip to be displaced downwardly beyond the level of the edge strake of the chip guided by the outer portions 10 of the surface 6 and thereby give the chip a bending or arching laterally. The end end edges 11 of the side walls or portions 9 adjoining to the said side portions 10 of the surface 6 form chip breaking abutments to be engaged by the edge strakes of the chip guided by the outer portions abruptly upwardly away from the plane even with the edge. In a preferred embodiment the angle between the surface adjacent the edge 5 and formed by a narrow middle portion 7 and wider side portions 10 and the end surfaces 11 serving o as chip breaker is about 55 . Further, the angle between same surface and the surfaces of the projections 9 defining o the recess 8 is about 30 The lateral bending results in a reduction of width at the chip so it becomes considerably narrower than the groove 5 cut by the insert. The chip thereby cannot seize up at the groove sides and be pulled along and cause damages on work piece or tools. The guiding or bending upwardly of the chip already bent laterally results in the breaking off in rather short pieces of the chip because of the heavy material stress brought about by the deformation which pieces fall away from the working area without collecting or causing damages. The cutting fluid added during the turning contributes in removing the broken off pieces of chip.

Claims: C L I M S 1. Cutting insert for cutting operations preferably insert intended to be mounted at an insert holder for the use in a lathe or similar machining apparatus, wherein the insert adjacent its cutting edge presents portions deforming the cut chip so as to facilitate the removal thereof, characterized in that there is adjacent the cutting edge (5) and beyond same, seen in the movement direction of the chips, in a middle portion (7) of a surface adjoining the edge, a recess over the one end of which the middle portion of a just cut chip is intended to project whereas the side strakes of the chip are carried by the side portions (10) of the said surface and that at said side portions there are protruding abutment surfaces (11) to be engaged by the side strakes of the chip in order to be continually bent away from the plane of the surface adjoining the cutting edge and causing an abrupt bending of the chip resulting in breaking thereof. 2. Cutting insert according to claim 1, characterized by that the end surfaces (11) of the recess (8) side portions (9) facing the cutting edge form the real chip breaking means. 3. Cutting insert according to claim 1 or 2, characterized in that the angle between the plane of the surface adjacent the cutting edge (5) and the end surfaces (11) for engaging the chip side strakes is in the range of 45 - 65 , whereas the angle between the same plane and the recess (8) side portions (9) is in the range of 20*- 40° . 4. Cutting insert according to claim 3, characterized in that the angle between the plane adjoining to the cutting edge and the chips engaging end surfaces preferably is 55* and that the angle between the same plane and recess side portions preferably is 30 AMENDED CLAIMS [received by the International Bureau on 1 October 1992 (01.10.92); original claims 1-4 replaced by amended claims 1-3 (1 page)].' 1. Cutting insert for cutting operations preferably insert intended to be mounted at an insert holder for the use in a lathe or similar machining apparatus, wherein the insert adjacent its cutting edge presents portions deforming the cut chip so as to facilitate the removal thereof, and wherein there is, adjacent the cutting edge (5) and beyond same, seen in the movement direction of the chips, in a middle portion (7) of a surface adjoining the edge, a recess over the one end of which the middle portion of a just cut chip is intended to project whereas the side strakes of the chip are carried by the side portions (10) of the said surface, characterized in that at said side portions there are protruding abutment end surfaces (11) to be engaged by the side strakes of the chip in order to continually bend said side strakes away from the plane of the surface adjoining the cutting edge and cause an abrupt bending of the chip resulting in breaking thereof, and in. 2. Cutting insert according to claim 1, characterized in that the angle between the plane of the surface adjacent the cutting edge (5) and the protruding abutment end surfaces (11) for engaging and breaking the chip side strakes is in the range of 45 - 65 , whereas the angle between the same plane and the recess (8) side portions (9) is in the range of 20 - 40°. 3. Cutting insert according to claim 2, characterized in that the angle between the plane adjoining to the cutting edge and the chips engaging protruding end surfaces preferably is 55 and that the angle between the same plane and recess side portions preferably is 30°

Inventors: MIHIC WLAJKO, MIHIC, WLAJKO
Applicants: MIRCONA AB
Application year: 1992
Main classification: B23B27
IPC codes: B23B27