Title of Invention

AN IMPROVED TANGENTIAL CUTTING INSERT FOR MOUNTING ON CUTTING TOOLS

Abstract

An improved tangential cutting insert for mounting on cutting tools having a body with an operative front surface (2) and at least three side surfaces intersecting said front surface at insert edges (10, 12) which merge with each other via corner edge (14), at least one of said insert edges being a main cutting edges (10); characterized in that said operative front surface comprising a peripheral surface (18) which extends from said insert edges and said corner edges, along the entire length thereof, in an inward direction of the cutting insert (1, 1',1 ")

Full Text

1 FIELD OF THE INVENTION The present invention refers to an improved tangential (on-edge) cutting insert for mounting thereof on cutting tools for different cutting operations. BACKGROUND OF THE INVENTION Tangential cutting inserts are often used with rotary milling cutters such as slotting cutters or extended-flute cutters, with turning cutting tools or the like. Examples of such use may be found in US 3,416,209, US 3,490,117, US 3,701,187 and US 4,790,693. A conventional tangential cutting insert of the kind to which the present invention refers has a prismatic body with a clamping screw bore and with an operative front surface which is generally parallel to the clamping screw bore's axis and which is associated with upper and lower cutting edges and side edges extending therebetween and merging therewith via insert corners. Usually, for the provision of the upper and lower cutting edges with an appropriate positive chip rake angle, the operative front surface of the cutting insert is ground adjacent the cutting edges so as to extend therefrom in an inward direction of the cutting insert. Such grinding of the operative front surface of the insert adjacent its cutting edges makes impossible the use of side edges extending therebetween and of corner edges adjacent thereto in cutting operations, since these side and corner edges cannot be provided with appropriate cutting geometry. Moreover, the insert corners are relatively weak and are therefore subject to breakage. It is the object of the present invention to provide a new cutting insert which inter alia has advantages in the above respect. 3 SUMMARY OF THE INVENTION In accordance with the present invention, there is provided a tangential cutting insert having a body with an operative front surface and at least three side surfaces intersecting said front surface at insert edges which merge with each other via corner edges, at least one of said insert edges being a main cutting edge; said operative front surface comprising a peripheral surface which extends from said insert edges and said corner edges, along the entire length thereof, in an inward direction of the cutting insert. Preferably, the body of the cutting insert is formed with a clamping screw bore having a longitudinal axis which is substantially parallel to the operative front surface and substantially transverse to the main cutting edge. Preferably, the insert is indexable and has a prismatic body with a pair of identical front and rear surfaces at two ends thereof and two pairs of opposite side surfaces extending between said front and rear operative surfaces and intersecting each of them at a pair of identical upper and lower main cutting edges, a pair of identical auxiliary cutting edges extending between the main cutting edges and four cutting corner edges therebetween. Preferably, the auxiliary cutting edges are formed, adjacent each corner edge, with a portion which is capable of functioning as a wiper. Alternatively, a wiper portion may be formed on each main cutting edge adjacent the corner edges associated therewith. Preferably, the corner edges are rounded and merge continuously with adjacent main and auxiliary cutting edges. Preferably, the cutting insert has an imaginary reference plane passing through extremities of the corner edges thereof, and said peripheral surface of each of said front and rear surfaces is oriented so that an acute angle formed thereby with a normal to said imaginary plane is of 4 predetermined values along each of said main, auxiliary and corner cutting edges. The value of this angle may vary along these cutting edges. Preferably, each main cutting edge of the insert has two lateral component cutting edges extending from adjacent corner edges away from said reference plane in an inward direction of the insert, and merging with a central component cutting edge. By virtue of the design according to the present invention, the cutting insert may be provided with eight indexable effective cutting corners, each associated with main and auxiliary cutting edges, all having appropriate shapes and cutting geometries and, particularly, positive chip rake surfaces associated therewith. In addition, in the cutting insert according to the present invention the corners may be essentially strengthened. The cutting insert geometry of the present invention is particularly suitable for the manufacturing of cutting inserts by net-shape processes, where no grinding operations are required, by virtue of which any desired design, in particular, non-planar, of the chip rake and relief surfaces may be obtained. BRIEFDESCRIPTION OF THE ACCOMPANYING DRAWINGS For a better understanding of the present invention and to show how the same may be carried out in practice, reference will now be made to the accompanying_drawings, in which Fig. 1 is perspective view of a cutting insert according to the present invention; Fig. 2 is a front view of the cutting insert shown in Fig. 1; Fig. 3 is a top view of the cutting insert shown in Fig. 1; Fig. 4 is a side view of the cutting insert shown in Fig. 1; Figs. 5A, 5B, 5C and 5D are cross-sectional views of the cutting insert shown in Fig. 2, taken along the respective lines A-A, B-B, C-C and D-D; 5 Fig. 6A is a perspective view of a slotting disk cutter with cutting inserts according to the present invention mounted therein in a right-hand and left-hand manner; Fig. 6B is a top view of the cutting insert shown in Fig. 1, in an enlarged scale, when mounted in the slotting disk cutter shown in Fig. 6A; Fig. 7 is a partial side view of a face milling cutter with cutting inserts according to the present invention mounted therein; Figs. 8A and 8B are plan views of two different turning tools with a cutting insert according to the present invention mounted therein; and Figs. 9Aand 9B show a prior art cutting insert of the kind to which the present invention relates. DETAILED DESCRIPTION OF THE DRAWINGS Figs, 9A and 9B show a conventional tangential cutting insert 101 of the kind to which the present invention refers. As seen, the cutting insert 101 has a prismatic body with front and rear operative surfaces 102, two pairs of opposite side surfaces 106 and 108 extending therebetween and forming with each of said front and rear surfaces 102, respectively, a pair of opposite upper and lower cutting edges 110 and a pair of the opposite side edges 112 extending between the upper and lower cutting edges 110 and meeting therewith via corners 114. The operative front and rear surfaces 102 are each formed with ground positive chip rake surfaces 118 extending, along the entire length of the cutting edges 110, away from these edges in an inward direction of the cutting insert. With the insert 101 having such a geometry, the insert side edges 112 extending between the cutting edges 110 and also the insert corners 114 therebetween clearly cannot function, if desired, as effective cutting edges. Moreover, the insert corners are relatively weak and are therefore, subject to breakage. Figs. 1, 2, 3 and 4 illustrate an indexable tangential cutting insert 1 according to the present invention. The cutting insert 1 has eight 6 effective cutting edges and eight effective cutting corners and is capable of being used in a wide range of different cutting operations. As seen in Fig. 1, the cutting insert 1 has a prismatic body with front and rear operative surfaces 2 and two pairs of opposite side surfaces 6 and 8 extending therebetween. The insert 1 has a clamping screw bore 9 having a longitudinal axis A and extending between the side surfaces 6, for mounting the insert on a cutting tool. The front and rear operative surfaces 2 are parallel to the axis A of the clamping screw bore 9 and have identical design. Therefore, only one of these surfaces, namely the operative front surface 2, will further be described. As seen in Figs.l and 2, the front operative surface 2 is bound by identical upper and lower main cutting edges 10 associated with the side surfaces 6, identical auxiliary cutting edges 12 associated with the side surfaces 8, and four identical corner cutting edges 14 which are rounded and extend between adjacent main cutting edges 10 and auxiliary cutting edges 12, merging continuously therewith. The cutting insert 1 has an imaginary reference plane designated as P in Fig. 3, which passes through extreme points of the corner cutting edges 14. As seen in Fig. 3, the operative front surface 2 is generally depressed relative to the reference plane P along its entire circumference. More particularly, as seen in Fig. 1, the operative front surface 2 has a peripheral surface, generally designated as 18, having portions 20, 22 and 24 which extend, respectively, along the main cutting edges 10, the auxiliary cutting edges 12 and the corner cutting edges 14. As seen in Figs. 5a to 5d, these portions extend inwardly away from their corresponding main, auxiliary and corner cutting edges 10, 12 and 14 and constitute their respective chip rake surfaces 20. 22, 24. As shown in Figs. 5a to 5d, the chip rake surfaces 20, 22 and 24 form respective angles ?10, ?12 and ?14 with a normal to the reference plane P, which angles may be of different values and may vary along the length of the respective cutting edges 10, 12 and 14. 7 As seen in Figs. 1, 2 and 5A to 5D, the main cutting edges 10, the auxiliary cutting edges 12 and the corner cutting edges 14 are provided with a land 26 extending therefrom towards respective chip rake surfaces 20, 22 and 24 associated therewith. As seen in Figs. 1, 3, 4 and 5A to 5D, side surfaces 6 and 8 of the cutting insert and insert corner portions 27 therebetween are each formed with relief flank surfaces 28a, 28b and 28c disposed, respectively, adjacent the main cutting edges 10, the auxiliary cutting edges 12 and corner cutting edges 14, and provide these cutting edges with appropriate relief angles, when the insert is mounted on a cutting tool. The relief flank surface 28a is, preferably, substantially normal to the reference plane P. Each side surface 6 is also formed with a projecting central base portion 29 for the support of the insert in the cutting tool. As seen in Fig. 3, each main cutting edge 10 extends generally inwardly relative to the reference plane P and has two identical lateral component cutting edges 30 extending away from the adjacent corner edges 14 and away from the reference plane P towards a central component cutting edge 32. The lateral component cutting edges 30 merge with the central component cutting edge 32 via intermediate component cutting edges 34 oriented substantially transversely to the reference plane P. Preferably, the intermediate component cutting edges 34 are oriented so that their associated extremities overlap in the direction perpendicular to the reference plane P, whereby effective chip splitting may be provided during a cutting operation. As clearly seen in Figs. 1 and 5a, the front operative surface 2 generally repeats the geometry of the main cutting edges 10, i.e. it has lateral portions 40 which extend inwardly away from the auxiliary cutting edges 12 towards a central portion 42 and merge therewith via intermediate portions 44. -8- Figs. 6A and 7 show, by way of example only, the use of a cutting insert of the present invention in milling cutters, where the main cutting edge of the insert or at least one lateral component cutting edge thereof functions as a peripheral cutting edge and the auxiliary edge functions as a front cutting edge. Figs. 8a and 8b show examples of the use of the cutting insert 1 of the present invention in turning cutting tools. Fig. 6A shows a slotting cutter 46 with cutting inserts 1' and 1", according to the present invention, tangentially mounted therein by means of clamping screws 48, respectively, in a left-hand and right-hand manner. As shown in Fig. 6B, by virtue of the fact that the lateral component cutting edges 30 of the main cutting edge 10 of the cutting inserts are oriented as described above, it is ensured that an operative lateral cutting edge 30 associated with a free side surface 8 of the cutting insert 1" has a required positive axial rake angle (A. In addition, with the lateral component cutting edges 30 being inclined in opposite senses, the axial cutting forces acting on the cutting edge 10 during a cutting operation are counterbalanced. Fig. 7 shows a face milling cutter 52 with cutting inserts 1' and 1" according to the present invention mounted therein for machining a workpiece W. As seen, in cutting insert 1' the lateral component cutting edge 30 of the main cutting edge 10 functions as a peripheral cutting edge and a portion 12' of the auxiliary cutting edge 12 disposed adjacent the operative comer cutting edge 14 functions as a wiper. Fig. 8a shows a turning cutting tool 50 machining a workpiece W, in which the cutting insert 1 is mounted so as to present an operative cutting edge 10 and an operative corner cutting edge 14. Fig. 8b shows a turning tool 51 machining a workpiece W, in which the cutting edge 12 functions as an operative cutting edge and the cutting edge 10 does not participate in cutting. 9 Cutting inserts according to the present invention may be used for any other appropriate applications and also may have alternative designs comprising features not described above. For example, the main cutting edges of the cutting inserts may be straight or continuously concave. Their geometry may be asymmetric relative to their central points. They may have no central component cutting edge, or rather their central component cutting edge may protrude relative to adjacent lateral portions in the outward direction of the insert. The lateral component cutting edges may also extend outwardly. The auxiliary cutting edges may have any required configuration rather than being substantially straight as shown in the drawings. The corner cutting edges may be chamfered. All cutting edges may have any other appropriate shapes and cutting geometries. Also, the central and lateral portions of the operative front surface may be planar and non-planar, e.g. they may be specifically shaped to provide chip control means of any appropriate geometry. Furthermore, the central and lateral portions of the operative front surface do not necessarily need to be fully depressed relative to the reference plane P but rather they may have areas protruding outwardly therefrom. 10 LIST OF REFERENCE NUMERALS: 1, 1', 1" cutting insert 2 front and rear operative surfaces 6 one pair of opposite side surfaces 8 another pair of opposite side surfaces 9 clamping screw bore 10 main cutting edges 12 auxiliary cutting edges 12' a portion of the side edge 12 functioning as a wiper 14 corner cutting edges 18 peripheral surface of the front operative surface 2 20, 22, 24 portions of the peripheral surface 18 extending along respective cutting edges 10, 12 and 14 26 land 27 insert corner portions 28a, 28b, 28c relief flank surfaces of respective cutting edges 10, 12, 14 29 projecting central base portion 30 lateral component cutting edges 32 central component cutting edge 11 34 intermediate component cutting edges 40 lateral portions of the front operative surface 2 42 central portion of the front operative surface 44 intermediate portions of the front operative surface 46 slotting cutter 48 clamping screw turning cutting tools 52 face milling cutter 101 prior art tangential cutting insert 102 front and rear operative surfaces of the insert 101 106 one pair of opposite side surfaces of the insert 101 108 another pair of opposite side surfaces of the insert 101 110 upper and lower cutting edges of the insert 101 112 side edges of the insert 101 114 corners of the insert 101 118 chip rake surfaces of the cutting edges 110 A longitudinal axis of the clamping screw bore 9 12 p imaginary reference plane w workpiece (A axial rake angle of the component cutting edge 30 in the cutting tool 46 ?10, ?12, ?14 angles defined between the chip rake surfaces 20, 22 and 24 and a normal to the reference plane P 13 WE CLAIM: 1. An improved tangential cutting insert for mounting on cutting tools having a body with an operative front surface (2) and at least three side surfaces intersecting said front surface at insert edges (10, 12) which merge with each other via corner edges (14), at least one of said insert edges being a main cutting edge (10); characterized in that said operative front surface comprising a peripheral surface (18) which extends from said insert edges and said comer edges, along the entire length thereof, in an inward direction of the cutting insert (1,1', 1"). 2. An improved tangential cutting insert as claimed in claim 1, wherein the body of the cutting insert is formed with a clamping screw bore (9) having a longitudinal axis (A), said longitudinal axis being substantially parallel to said operative front surface and substantially transverse to said main cutting edge. An improved tangential cutting insert as claimed in claim 1, wherein at least one of said insert edges associated with the main cutting edge (10) constitutes an auxiliary cutting edge (12) of the insert and the comer edge therebetween constitutes a corner cutting edge (14). 4. An improved tangential cutting insert as claimed in claim 3, wherein a portion of said auxiliary cutting edge of the insert disposed adjacent the corner edge and merging therewith is capable of functioning as a wiper. 5. An improved tangential cutting insert as claimed in claim 4, wherein the insert is an indexable cutting insert and has a prismatic body with a pair of identical front and rear surfaces (2) at two ends thereof. 6. An improved tangential cutting insert as claimed in claim 5, wherein the body of the insert has two pairs of opposite side surfaces (6, 8) extending between said front and rear operative surfaces and intersecting each of them at a pair of identical upper and lower main cutting edges (10), a pair of 4. 14 identical auxiliary cutting edges (12) extending between the main cutting edges and four identical corner cutting edges therebetween. 7. An improved tangential cutting insert as claimed in claim 3, wherein said peripheral surface of the operative front surface is oriented so that an acute angle (?10,?12, ?14) formed thereby with a normal to an imaginary reference plane (P) passing through extremities of the corner edges of the cutting insert, is of predetermined values along each of said main, auxiliary and corner cutting edges. 8. An improved tangential cutting insert as claimed in claim 7, wherein the value of said angle varies at least along the main cutting edge of the insert. 9. An improved tangential cutting insert as claimed in claim 1, wherein said main cutting edge has two lateral component cutting edges (30) extending from adjacent comer edges (14) towards a central component cutting edge (32). 10. An improved tangential cutting insert as claimed in claim 9, wherein said lateral component cutting edges extend away from an imaginary' reference plane (P) passing through extremities of the corner edges of the cutting insert, in an inward direction of the insert. 11. An improved tangential cutting insert as claimed in claim 9, wherein the lateral component cutting edges merge with the central component cutting edge via intermediate component cutting edges (34) which are oriented so that their associated extremities overlap in the direction perpendicular to the reference plane (P). 12. An improved tangential cutting insert as claimed in any one of the preceding claims, wherein the said insert is manufactured by a net-shape process. An improved tangential cutting insert for mounting on cutting tools having a body with an operative front surface (2) and at least three side surfaces intersecting said front surface at insert edges (10, 12) which merge with each other via corner edge (14), at least one of said insert edges being a main cutting edges (10); characterized in that said operative front surface comprising a peripheral surface (18) which extends from said insert edges and said corner edges, along the entire length thereof, in an inward direction of the cutting insert (1, 1',1 ")

Documents:

01354-cal-1998 abstract.pdf

01354-cal-1998 claims.pdf

01354-cal-1998 correspondence.pdf

01354-cal-1998 description(complete).pdf

01354-cal-1998 drawing.pdf

01354-cal-1998 form-1.pdf

01354-cal-1998 form-2.pdf

01354-cal-1998 form-3.pdf

01354-cal-1998 gpa.pdf

1354-CAL-1998-CORRESPONDENCE 1.1.pdf

1354-CAL-1998-FORM-27-1.pdf

1354-CAL-1998-FORM-27.pdf

1354-cal-1998-granted-abstract.pdf

1354-cal-1998-granted-claims.pdf

1354-cal-1998-granted-correspondence.pdf

1354-cal-1998-granted-description (complete).pdf

1354-cal-1998-granted-drawings.pdf

1354-cal-1998-granted-examination report.pdf

1354-cal-1998-granted-form 1.pdf

1354-cal-1998-granted-form 2.pdf

1354-cal-1998-granted-form 3.pdf

1354-cal-1998-granted-letter patent.pdf

1354-cal-1998-granted-pa.pdf

1354-cal-1998-granted-reply to examination report.pdf

1354-cal-1998-granted-specification.pdf

1354-CAL-1998-OTHERS.pdf

1354-CAL-1998-PA.pdf