TOOL AND CUTTING INSERT FOR MILLING

Abstract: The present invention relates to a tool and a cutting insert for milling. The cutting insert is intended to be mounted in a milling body to be rotated in a milling machine. The milling body comprises at least one pocket in order to receive a parallelepipedical cutting insert. The cutting insert comprises two major sides (11) and them uniting minor sides (14) and upper and lower sides (15, 16), and comprises at least one pair of cutting edges (17, 19; 18, 20) which is formed at the transition of the upper side (15) and a major side and a minor side of the cutting insert. The upper side constitutes a chip surface and the major side and the minor side constitute clearance surfaces. Each pair of cutting edges consists of a major cutting edge (17, 18) at the major side and a minor cutting edge (19, 20) at the minor side, which intersect in the area of a cutting corner. The corner is provided inside an imaginary extension line of a major part of the minor side. The minor cutting edge is provided to generate a surface of a work piece. The major cutting edge slopes such that it forms an acute angle with the lower side (16). Each pair of cutting edges (17, 19; 18, 20) connects in direction towards the lower side to a first clearance surface (22A, 22B) protruding relative to the plane containing the major part of the minor and major sides (11). Recesses (30) are formed in surfaces (24) provided in the major sides (11).

Description: TOOL AND CUTTING INSERT FOR MILLING The field of the invention The present invention relates to a tool and a cutting insert for milling according to the preambles of the independent claims. Prior art The U.S. Patent Specifications Serial Nos. 5,145,295, 5,207,538 and 5,078,550 show milling inserts of the above-captioned type. Each known cutting insert comprises planar major sides that during localization in a milling body or a grinding fixture can make the positioning unstable due to dust collections. The instability brings drawbacks for the results from the milling operation and from the grinding of the cutting edges. In addition the known cutting insert demands a lot of grinding when producing the cutting edges. The U.S. Patent Specification Serial No. 5,803,674 discloses a milling insert that has a ledge extending circumferentially and in the plane of the associated support surface. Objects of the invention One object of the present invention is to provide a tool and a cutting insert for milling, which enables rigid localization of the cutting insert in both the milling body and the grinding fixture. Another object of the present invention is to provide a cutting insert for milling, which reduces the amount of material to grind. Still another object of the present invention is to provide a cutting insert for milling, which increases the geometrical freedom during grinding. Still another object of the present invention is to provide a cutting insert for milling, which reduces th§ environmental pollution at grinding. Still another object of the present invention is to provide a tool and a cutting insert for milling, at which the extension of flank wear is predetermined. These and other objects have been achieved by a tool and a cutting insert for milling according to the subsequent claims with reference to the enclosed drawings. Brief description of the drawings Figs. 1A and 1 B show a cutting insert according to the present invention in a top view and a bottom view, respectively. Fig. 2 shows the cutting insert in a side view. Fig. 3 shows the cutting insert in a cross section according to line Ill-Ill in Fig. 1A. Fig. 4 shows the cutting insert in a perspective view. Fig. 5 shows an enlarged cross section of a cutting corner according to the line V in Fig. 1A. Fig. 6 shows an enlarged cross section of a cutting corner according to the line VI in Fig. 1A. Fig. 7 shows cutting inserts according to the present invention mounted to a milling cutter body. Detailed description of the invention With reference to Figs. 1A-4 a one-sided cutting insert 10 for milling according to the present invention is shown, which has a parallelepipedical basic shape and is manufactured from directly pressed cemented carbide. With "cemented carbide" is here meant WC, TiC, TaC, NbC, etc in sintered combination with a binder metal such as for example Co or Ni. The cutting insert is to be mounted in a milling body, not shown, intended to be rotated in a milling machine. The milling body comprises at least one pocket to receive the parallelepipedical cutting insert. The cutting insert 10 comprises two, in a top view substantially parallel, major sides 11 , 12 and them uniting minor sides 13, 14 as well as upper and lower sides 15 and 16. The upper side 14 forms major cutting edges 17, 18 at lines of intersection with the major sides 11 , 12. The major cutting edges slope in opposite directions such that each edge forms an acute angle with the lower side 16. Thereby they give the opposite sides of the cutting insert increased, but oppositely directed axial angles. Each major cutting edge increases the tool's operative, positive axial angle when mounted in the cutting insert pocket in the milling body. Furthermore the upper side 15 forms minor cutting edges or wiper edges 19, 20 at lines of intersection with a smaller portion of each minor side 13, 14. The major cutting edge 17, 18 and the respective associated minor cutting edge 19, 20 form a pair of cutting edges which is active during the milling while the other pair is passive. Two connected edges intersect in the area of a cutting corner 28. The cutting corner defines a bisector B which divides the corner into two equal angles. The bisector B does not intersect the radius center of the corner 28, 29. When one pair of cutting edges is worn out the cutting insert is indexed such that the other pair of cutting edges gets into an active position. The upper side constitutes a chip surface in the area of the cutting edges and forms an edge angle with the major and the minor sides which is smaller than 90°, i.e. the cutting insert has a positive basic shape. Furthermore, the chip surface 15 forms a, preferably incrementally varying, positive rake angle in order to cut easy in the work piece. The lower side 16 forms an obtuse inner angle with the associated parts 24-27 of the minor and major sides in order to obtain clearance in relation to the work piece. A centrally placed hole 21 is provided to receive a fastening device such as a screw at mounting in the milling body 40, Fig. 7. The milling cutter is preferably provided for shoulder milling of 90° corners. So far the described cutting insert according to the present invention substantially adheres to prior art. Each pair of cutting edges 17, 19 and 18, 20 connects in direction towards the lower side 16 to a ledge or protruding first clearance surface 22 and 23, respectively. The ledge 22, 23 projects substantially outside the planes P1 , P2 containing the major parts of the minor and major sides, i.e. parts 24-27. The ledge has a greatest height in the magnitude of 0.4 to 2 mm or about 10-20 % of the height of the cutting insert 10. The ledge 22B, 23B is higher at the minor cutting edge, see H1 in Fig. 5, than at 22A, 22B at the major cutting edge, see H2 in Fig. 6. The ledge 23, Fig. 2, extends from the associated minor side 14 plane P2 along the entire major side 12 past the cutting comer and finishes at a distance L into the other minor side 13. Thus, the ledge 23B is shorter than the length of the minor side 13 for reducing grinding work. The remaining part of the minor side edge is not intended to cut. The ledge projects in the interval from about 0.02 to 0.1 mm at line Ill-Ill in Fig. 1A. The distance L is measured perpendicularly from an imaginary extension line of the major cutting edge 18 to about a quarter of the length of the minor side 13, 14. The ledge thus projects relative to the remaining clearance surfaces, such that advanced grinding of the cutting edges 17-20 can done by conventional grinding methods by grinding the ledge simultaneously as a minimum of material need be machined, which in addition reduces the environmental pollution during grinding. Furthermore, the ledge acts as protection for the milling body at a cutting edge breakage. The lower side 16 forms, as stated above, obtuse inner angles with the parts 24- 27 of associated minor and major sides, which parts will constitute positioning surfaces in a grinding fixture and a milling body. Said parts are directly pressed and consequently shall not be ground. The recesses 30, 31 are formed in the parts 24, 25 contained by the major sides. The recesses 30, 31 are substantially rectangular and are placed longitudinally centrally to reduce the surface on the parts 24, 25 in such a way that the available surface in the plane P1 is displaced in direction towards the corners of the cutting insert. Each recess 30 and 31 is of the same size as or most preferably somewhat greater than each abutment surface 24A, 24B and 25A, 25B, respectively, which are formed at each side of each recess. Thereby side abutment surfaces together with the surfaces 26 and 27 are defined for the cutting insert in an advantageous manner. Furthermore, the cutting insert becomes less sensitive for irregularities in the cooperating surfaces in the grinding fixture and in the milling body. Each recess 30, 31 has an essentially concave shape and extends in the height direction from close to the lower side 16 to close to the ledge 23, 24 such that neither the size of the lower side nor the strength of the ledge is influenced. The cutting edges 17-20 connect to a reinforcing chamfer 32, Figs. 5 and 6, which have a width W along the major cutting edges 17, 18 and the minor cutting edges 19, 20 and a greater width at the cutting corners 28 substantially symmetrically about the bisector B. Thereby the strength at the cutting corners is increased. Further a bevel 32 forms an acute angle with a plane P3 parallel with the lower side 16. At the minor cutting edge, according to Fig. 5, the angle α1 is about 13° and at the major cutting edge, according to Fig. 6, the angle α2 is about 9°. The present invention thus relates to a tool and a cutting insert for milling, which enables rigid localization of the cutting insert in both the milling body and the grinding fixture, whereby the amount of material to grind is reduced and the grinding possibilities are increased. The surface on which flank wear occurs is predetermined by the height of the ledge. The invention is in no way limited to the above-described embodiment and can be varied freely within the limits of the subsequent claims.

Claims: Claims 1. Cutting insert for milling, wherein the cutting insert is intended to be mounted in a milling body to be rotated in a milling machine, said milling body comprising at least one pocket in order to receive a parallelepipedical cutting insert, said cutting insert comprising two major sides (11 ,12) and them uniting minor sides (13,14) as well as upper (15) and lower sides (16), and comprising at least one pair of cutting edges (17, 19; 18,20) which is formed at a transition of the upper side and a major side and a minor side of the cutting insert, said upper side (15) constituting a chip surface and the major side and the minor side constituting clearance surfaces, wherein each pair of cutting edges consisting of a major cutting edge (17, 18) at the major side and a minor cutting edge (19,20) at the minor side, which intersect in the area of a cutting corner (28,29), said corner being provided inside an imaginary line of extension of a major part of the minor side, said minor cutting edge being provided to generate a surface of a work piece, said major cutting edge sloping to form an acute angle with the lower side (16), c h a r a c t e r i z e d i n that each pair of cutting edges (17, 19; 18,20) connects in direction towards the lower side (16) to a first clearance surface (22,23) projecting relative to the planes (P1 ,P2) containing the major parts of the minor and major sides (11 -14), and in that recesses (30,31) are formed in surfaces (24,25) provided in the major surfaces (11 ,12). 2. The cutting insert according to claim 1 , wherein the recesses (30,31) are longitudinally centrally placed to reduce the area of the surfaces (24,25) thereby forming abutment surfaces (24A,24B;25A,25B) at each side of each recess and wherein said recesses are spaced outwardly relative to the abutment surfaces. 3. The cutting insert according to claim 2, wherein each recess (30,31) is substantially rectangular. 4. The cutting insert according to claim 1 , wherein the first clearance surface (22,23) extends from the plane (P2) of the minor side (14) along the entire major side (12) and past the cutting corner (29) and ends at a distance (L) into the other minor side (13). 5. The cutting insert according to claim 4, wherein the distance (L) is measured perpendicularly from an imaginary extension line of the major cutting edge (18) to about a quarter of the length of the minor side (13,14). 6. The cutting insert according to claim 1 , wherein the first clearance surface (22,23) is wider at the minor cutting edge (19,20) than at the major cutting edge (12,18). 7. The cutting insert according to claim 6, wherein the first clearance surface (22,23) has a largest width (H1.H2) in the magnitude of 0.4 to 2 mm or about 10- 20 % of the width of the cutting insert 10. 8. The cutting insert according to claim 2, wherein each recess (30,31) has an essentially concave shape and extends in height direction from close to the lower side (16) to close to the ledge (22A,23A), and that each recess (30,31) is of the same size as or most preferably somewhat bigger than each abutment surface (24A,24B,25A,25B). 9. The cutting insert according to claim 1 , wherein the major and minor cutting edges (17-20) connect to a reinforcing bevel (32), which has one width along the major cutting edges (17,18) and the minor cutting edges (19,20) and a larger width at the cutting comers (28,29) substantially symmetrically about the bisector (B). 10. A milling tool comprising a milling body intended to be mounted in a milling machine, said milling body comprising at least one pocket having an axial inclination in order to receive a parallelepipedical cutting insert of cemented carbide, said cutting insert comprising two major sides (11 ,12) and them uniting minor sides (13,14) as well as upper (15) and lower sides (16), and comprising at least one pair of cutting edges (17,19;18,20) which is formed at a transition of the upper side and a major side and a minor side of the cutting insert, said upper side (15) constituting a chip surface and the major side and the minor side constituting clearance surfaces, wherein each pair of cutting edges consisting of a major cutting edge (17,18) at the major side and a minor cutting edge (19,20) at the minor side, which intersect in the area of a cutting corner (28,29), said corner being provided inside an imaginary line of extension of a major part of the minor side, said minor cutting edge being provided to generate a surface of a work piece, said major cutting edge sloping to form an acute angle with the lower side (16), c h a r a c t e r i z e d i n that each pair of cutting edges (17, 19; 18,20) connects in direction towards the lower side (16) to a first clearance surface (22,23) protruding relative to the planes (P1 ,P2) containing the major parts of the minor and major sides (11-14), and in that recesses (30,31) are formed in surfaces (24,25) provided in the major surfaces (11 ,12), whereof one surface is intended to abut against the pocket of the milling body. AMENDED CLAIMS [received by the International Bureau on 08 February 2000 (08.02.00) ; original claims 1-10 replaced by new claims 1-9 (3 pages)] 1. Cutting insert for milling, wherein the cutting insert is intended to be mounted in a milling body to be rotated in a milling machine, said milling body comprising 5 at least one pocket in order to receive a parallelepipedical cutting insert, said cutting insert comprising two major sides (11 ,12) and them uniting minor sides (13,14) as well as upper (15) and lower sides (16), and comprising at least one pair of cutting edges (17,19;18,20) which is formed at a transition of the upper side and a major side and a minor side of the cutting insert, said upper side (15) 10 constituting a chip surface and the major side and the minor side constituting clearance surfaces, wherein each pair of cutting edges consisting of a major cutting edge (17,18) at the major side and a minor cutting edge (19,20) at the minor side, which intersect in the area of a cutting corner (28,29), said corner being provided inside an imaginary line of extension of a major part of the minor 15 side, said minor cutting edge being provided to generate a surface of a work piece, said major cutting edge sloping to form an acute angle with the lower side (16), c h a r a c t e r i z e d i n that each pair of cutting edges (17,19;18,20) connects in direction towards the lower side (16) to a first clearance surface (22,23) 20 projecting relative to the planes (P1 ,P2) containing the major parts of the minor and major sides (11-14), and in that recesses (30,31 ) are formed in surfaces (24,25) provided in the major sides (11 ,12) and in that the first clearance surface (22,23) extends from the plane (P2) of the minor side (14,13) along the entire major side (11 ,12) and past the cutting corner (29,28) and ends at a distance (L) 25 into the other minor side (13,14). 2. The cutting insert according to claim 1 , wherein the recesses (30,31 ) are longitudinally centrally placed to reduce the area of the surfaces (24,25) thereby forming abutment surfaces (24A,24B;25A,25B) at each side of each recess and 30 wherein said recesses are spaced outwardly relative to the abutment surfaces. 3. The cutting insert according to claim 2, wherein each recess (30,31 ) is substantially rectangular. 4. The cutting insert according to claim 1 , wherein the distance (L) is measured perpendicularly from an imaginary extension line of the major cutting edge (18) to about a quarter of the length of the minor side (13,14). 5. The cutting insert according to claim 1 , wherein the first clearance surface (22,23) is wider at the minor cutting edge (19,20) than at the major cutting edge (12,18). 6. The cutting insert according to claim 5, wherein the first clearance surface (22,23) has a largest width (H1 ,H2) in the magnitude of 0.4 to 2 mm or about 10- 20 % of the width of the cutting insert 10. 7. The cutting insert according to claim 2, wherein each recess (30,31 ) has an essentially concave shape and extends in height direction from close to the lower side (16) to close to the first clearance surface (22A.23A), and that each recess (30,31) is of the same size as or most preferably somewhat bigger than each abutment surface (24A,24B,25A,25B). 8. The cutting insert according to claim 1 , wherein the major and minor cutting edges (17-20) connect to a reinforcing bevel (32), which has one width along the major cutting edges (17,18) and the minor cutting edges (19,20) and a larger width at the cutting corners (28,29) substantially symmetrically about the bisector (B). 9. A milling tool comprising a milling body intended to be mounted in a milling machine, said milling body comprising at least one pocket having an axial inclination in order to receive a parallelepipedical cutting insert of cemented carbide, said cutting insert comprising two major sides (11 ,12) and them uniting minor sides (13,14) as well as upper (15) and lower sides (16), and comprising at least one pair of cutting edges (17,19;18,20) which is formed at a transition of the upper side and a major side and a minor side of the cutting insert, said upper side (15) constituting a chip surface and the major side and the minor side constituting clearance surfaces, wherein each pair of cutting edges consisting of a major cutting edge (17,18) at the major side and a minor cutting edge (19,20) at the minor side, which intersect in the area of a cutting corner (28,29), said corner being provided inside an imaginary line of extension of a major part of the minor side, said minor cutting edge being provided to generate a surface of a work piece, said major cutting edge sloping to form an acute angle with the lower side (16), c h a r a c t e r i z e d i n that each pair of cutting edges (17,19; 18,20) connects in direction towards the lower side (16) to a first clearance surface (22,23) protruding relative to the planes (P1 ,P2) containing the major parts of the minor and major sides (11-14), and in that recesses (30,31) are formed in surfaces (24,25) provided in the major sides (11 ,12), whereof one surface is intended to abut against the pocket of the milling body and in that the first clearance surface (22,23) extends from the plane (P2) of the minor side (14,13) along the entire major side (11 ,12) and past the cutting corner (29,28) and ends at a distance (L) into the other minor side (13,14). AMENDED SHEET (ARTICLE

Inventors: HEDBERG STEFAN, JORDBERG JONAS, HEDBERG, STEFAN, JORDBERG, JONAS
Applicants: SECO TOOLS AB
Application year: 1999
Main classification: B23C5
IPC codes: B23C5