MILLING CUTTER

Abstract: A milling cutter for clamped cutting inserts (12) which are held in position by means of a clamping means (14), which rests against the cutting insert (12) at a first contact surface (17) and against the cutter body (10) at a second contact surface (24) In order to obtain a large chip pocket by means of a clamping means (14) having short radial extent the clamping means is designed such that the distance between the first contact surface (17) and a supporting surface (21) for supporting the cutting insert is larger than the distance between the supporting surface (21) and the second contact surface (24).

Description: MILLING CUTTER This invention relates to a milling cutter for clamped cutting inserts (as distinguished from inserts secured " by brazing), in which a cutting insert is held in position relative to a cutter body by means of a clamping means. The clamping means is adapted to rest against the cutting insert at a first con¬ tact surface on a preferably flat first side face on the cutt¬ ing insert and against the cutter body at a second contact surface. The cutting insert is adapted to rest directly or indirectly against a first supporting surface on the cutter body by means of a second side face, which is opposite to the first side face on the cutting insert. The clamping means is adapted to bridge an edge portion on the cutting insert by means of a side portion which interconnects the first and second contact surfaces without contacting the edge portion; said edge portion being provided on an edge surface which interconnects the first and second side fa¬ ces of the cutting insert. An object of the present invention is to provide a clamping means which does not disturb the chip flow without requiring a large extent radially inwards. Another object of the invention is to positively fix the axial position of the cutting insert. A further object of the invention is to provide the milling OMPI cutter with detachable clamping and supporting means such that Cutting with positive as well as negative axial rake angles is possible. The above and other objects of the invention are attained by giving the invention the characterizing features stated in the claims following hereinafter. The invention is described in detail in the following de¬ scription with reference to the accompanying drawings. It is to be understood that the illustrated embodiments are only shown by way of example and that various modifica¬ tions may be made within the scope of the claims. In the drawings, Pig. 1 is a perspective view of a milling cutter according to the invention showing one cutting in¬ sert mounted and one cutting insert detached. Pig. 2 is a section taken on the line II-II in Pig. 1. Pig. 3 shows a section corresponding to that in Pig. 2, wherein cutting insert, supporting plate and wedge block are detached. Pig. 4 shows a side view of a portion of the milling cutter in Pig. 1. Pig. 5 shows a fragmentary top view of the milling cutter in Pig. 1 having a modified supporting plate. Pig. 6 shows a fragmentary top viev/ of the milling cutter in Pig. 1 having the supporting plate and the wedge block de¬ signed such that a negative axial rake angle is obtained. Corresponding details have been given the same reference nu¬ meral in the various figures. In the drawings, the cutter body of the milling cutter is de¬ noted by 10. The cutter body has recesses 11 in the peri¬ phery thereof for tungsten carbide cutting inserts 12 and their clamping and supporting means. The supporting means of the cutting inserts 12 consist of detachable supporting shim plates or supporting seats 13. The clamping means con¬ sist of detachable wedge blocks 14. The wedge blocks 14 are clamped against the cutting insert 12 by means of screws 15. The screw 15 is provided with a left hand thread portion and a right hand thread portion; the one portion being screwed into the wedge block 14 and the other portion into the cutter body 10. The cutting insert 12 is provided with opposite flat side faces 16, 18. The wedge block 14 rests against the side face 16 at a contact surface 17. By means of its side face 18 the cutting insert 12 rests against the supporting plate 13. The supporting plate 13 is attached to a supporting surface 19 on the cutter body by means of a screw, not shown. By means of a ra ially inner edge surface 20 the cutting in¬ sert 12 rests against a stepped portion 26 on the supporting plate 13 which in its turn rests against a supporting surface 21 on the cutter body 10. The edge surface 20 interconnects the side faces 16, 18 of the cutting insert. The wedge block 14 comprises a base portion which is provided with a side face 22, which faces the cutting insert 12, and a side face 23 which is opposite to and parallel with the side face 22. By means of its side face 22 the wedge block 14 rests against the cutter body at a contact surface 24. By means of its side portion interconnecting the contact surfaces 17, 24 the wedge block 14, then, is adapted to bridge the edge portion 25 of the edge surface 20 being closest to the wedge block without contacting said edge portion. An object of the invention is to design the wedge block 14 such "BUREAU OMPI that it does not disturb the chip flow. This is attained by giving the top side of the wedge block 14 a steep slope from the contact surface 17, thereby providing a large chip pocket. This design is possible by arranging the contact surface 24 under the cutting insert 12, i.e. in such a way that a straight line interconnecting the contact surfaces 17, 24 intersects the edge surface 20 on the cutting insert 12. At the same time as providing a large chip pocket the invention seeks to design the wedge block 14 such that it requires an extent radially inwards as small as possible. An object of the invention, thus, is also to limit the depth of a groove or slot 27 in the cutter body 10 at the bottom of the recess 11 because a large depth thereof weakens the cutter body 10. According to the invention these objects are attained by a wedge block design such that the distance between the con¬ tact surface 17 and ϊhe supporting surface 21 is larger than the distance between the supporting surface 21 and the con¬ tact surface 24. Suitably, the ratio between these distances should be larger than 1,5:1, preferably larger than 2:1. The side faces 22, 23 of the base portion of the wedge block 14 are directed radially inwards and rearwards in such a way that a plane which is transversal to the side faces 22, 23 and to the side face 16 of the cutting insert intersects the side faces 16, 22 along two lines, which form the sides of a triangle wherein the line interconnecting the contact sur¬ faces 17, 24 forms the base; said triangle having an obtuse angle between its sides. The side walls of the groove 17 in the cutter body, 10 are substantially parallel with its respective side face 22, 23 of the base portion of the wedge block 14. In the illustrated embodiments the cutting insert 12 is supported by the shim plate 13. The fact that the shim plate and the wedge block 14 are detachable increases the flexibi¬ lity of the milling cutter, i.e. different types of cutting -BUREA OMPI inserts can be used. However, it is possible to apply the invention in a milling cutter having no shim plates; in this case the cutting insert 12 rests directly against the support¬ ing surface 21. In the cutter body 10 there is a peripheral groove 30 the side walls 28, 29 of which are adapted to positively secure the axial position of the cutting insert 12 by providing supporting surfaces for the shim plate 13; these supporting surfaces being transversal to the supporting surface 19. In the embodiment according to Pigs. 1-4 the supporting surface 28 projects in front of the supporting surface 29 seen in the rotational direction of the milling cutter, and the supporting surface 19 extends radially inwardly of the supporting surfaces 28, 29. The bounding walls of the re¬ cess 11, i.e. the supporting surface 19 and the side face 23, make an angle with the longitudinal direction of the cutter body 10 such that the axially outer ends of the sur¬ faces 19 23 are in front of the axially inner ends thereof seen in the rotational direction of the milling cutter. Due to the fact that the side faces 16, 18 of the cutting insert are parallel with the supporting surface 19 a positive axial rake angle, thus, is obtained. During assembling of the cutting insert 12 and the supporting plate 13 the latter is forced against the supporting surface 28, thereby fixing the axial position of the cutting insert 12. In Fig. 5 a modified embodiment of the supporting plate 13 is shown which is particularly suitable in connection with large positive axial rake angles, i.e. where the side faces 16, 18 of the cutting insert 12 make a larger angle with the longitudinal axis of the cutter body than the supporting sur¬ face 19. The supporting plate 13 is provided with a flange 31 which projects into the groove 30. During assembling the flange 31 is forced against the supporting surface 29 which fixes the axial position of the cutting insert 12 due to the axially outwardly directed force which is applied on the - υ EAcT OMPI ' ^KNATIO '' supporting plate 13 during attachment of the wedge block 14. The embodiment of the supporting plate 13 shown in Pig. 5 can, of course, also be used in connection with the axial rake angle shown in Pigs. 1-4, in whic case it is not required that the supporting surface 28 projects in front of the supporting surface 29. Pig. 6 shows an embodiment where the supporting shim plate 13 and the wedge block 14 are designed such that a negative axial rake angle is obtained. According to the invention, then, the two surfaces of the wedge block 14 at the contact surface 17 and the side face 23 are directed in such a way that they diverge axially outwards. The supporting surface 19 in the cutter body 10 and the side face 16 of the cutting insert 12 converge axially outwards, thereby causing the supporting plate 13 to be forced against the supporting sur¬ face 28 during clamping of the cutting insert 12 by means of the wedge block 14. The invention is applicable in connection with all types of cutting inserts, such as square, rectangular, triangular and round inserts, positive and negative ones, as well as in connection with milling cutters of the type called "Shear- Clear".

Claims: Claims * 1. A milling cutter or clamped cutting inserts comprising a cutter body (10), a clamping means (14) for holding a cutting insert (12) in position relative to said cutter body, said clamping means being adapted to rest against the cutting insert (12) at a first contact surface (17) on a preferably flat first side face (16) on the cutting insert and against said cutter body at a second contact surface (24), said cutting insert being adapted to rest directly or indirectly against a first supporting surface (19) on the cutter body (10) by means of a second side face (18), said second side face being opposite to said first side face, and said clamping means (14) being adapted to bridge an edge portion (25) on the cutting insert (12) by means of a side portion inter¬ connecting said first (17) and second (24) contact surfaces without contacting said edge portion, said edge portion (25) being provided on an edge surface (20) which interconnects said first (16) and second (18) side faces of the cutting insert (12), c h a r a c t e r i z e d in that the distance between said first contact surface (17) and a second support¬ ing surface (21) on the cutter body (10) is larger than the distance between said second supporting surface (21) and said second contact surface (24), said second supporting sur¬ face (21) supporting directly or indirectly said edge sur¬ face (20) on the cutting insert (12) and being positioned bet¬ ween said first (17) and second (24) contact surfaces in radial direction. 2. A milling cutter according to claim 1, c h a r a c t e ¬ r i z e d in that the ratio between said distances is larger than 1,5:1. 3. A milling cutter according to claim 2, c h a r a c t e ¬ i z e in that said ratio is larger than 2:1. 4. A milling cutter according to any of claims 1 - 3, c h a r a c t e r i z e d in that a straight line interconnect¬ ing said first (17) and second (24) contact surfaces inter¬ sects said edge surface (20) on the cutting insert (12) 5. A milling cutter according to claim 4, c h a r a c t e ¬ r i z e d in that the cutting insert (12) in a manner known per se is adapted to rest against a detachable supporting plate (13) by means of said second side face (18) and said edge surface (20), said supporting plate (13) in its turn being adapted to rest against said first (19) and second (21) supporting surfaces on the cutter body. 6. A milling cutter according to any of the preceding claims, c h a r a c t e r i z e d in that the clamping means (14) comprises an one-piece wedge means having a base portion adapted for insertion into a groove (27) in the cutter body (10) during clamping of the cutting insert (12), said base portion having a rear side face (22) which faces the cutting insert and which is directed in such a way that a plane which is transversal to the first side face (16) of the cutting insert and to the rear side face (22) of the base portion intersects said side faces (16, 22) along two lines, said two lines and a line interconnecting said first (17) and second (24) contact surfaces forming a triangle wherein the angle between said two lines is obtuse. 7. A milling cutter according to claim 6, c h a r a c t e ¬ r i z e d in that the base portion of the wedge means com¬ prises a front side face (23) which is opposite and substan¬ tially parallel to said rear side face (22) of said base portion, and that the side walls of the groove (27) in the cutter body (10) are substantially parallel to its respec¬ tive side face (22, 23) on the base portion. 8. A milling cutter according to claim 7, c h a r a c t e ¬ r i z e d in that the two surfaces of the clamping means (14) at respectively the first contact surface (17) and the front side face (23) of the base portion diverge axially outwards such that a negative axial rake angle is obtained. 9. A milling cutter according to claim 8, c h a r a c t e ¬ ri z e d ' in that the first supporting surface (19) of the cutter body (10) and the first side face (16) of the cutting insert (12) converge axially outwards, and that the supporting plate (13) is adapted to be forced against a third supporting surface (28) on the cutter body (10) during clamping of the cutting insert by means of the clamping means (14) > said third supporting surface (28) being transversal to said first supporting surface (19) and providing an axial stop against movement axially inwards of the supporting plate (13). 10. A milling cutter for clamped cutting inserts comprising a cutter body (10), a clamping means (14) for holding a cutting insert (12) in position relative to said cutter body, said clamping means being adapted to rest against a preferably flat first side face (16) on the cutting insert (12), a supporting plate (13) > & second side face (18) on the cutting insert opposite to said first side face (16) which is adap¬ ted to rest against said supporting plate, said supporting plate being adapted to rest against a first supporting sur¬ face (19) on the cutter body (10) and against one of a second supporting surface (28) on the cutter body and a third supporting surface (29) on the cutter body, said second and third supporting surfaces (28,29) being transversal to said first supporting surface (19) . whereby said second supporting surface (28) provides a stop for movement axially inwards of the supporting plate (13) and said third supporting surface (29) provides a stop for movement axially outwards of the supporting plate (13), c h a r a c t e r i z e d by one or several combinations of the ollowing steps: a) the second supporting surface (28) projects in front of the third supporting surface (29) seen in the rotational di¬ rection of the milling cutter, b) the first supporting surface (19) extends radially in¬ wardly of the second (28) and third (29) supporting sur¬ faces, and c) the second (28) and third (29) supporting surfaces are formed by the walls of a peripheral groove (30) in the cutter body (10) .

Inventors: OKADA M
Applicants: OKADA M, SANDVIK AB
Application year: 1979
Main classification: B23C5
IPC codes: B23C5