JP2019030916A - Step type milling cutter - Google Patents

Abstract

To prevent occurrence of oscillation during high speed rotation of a cutter body in a step type milling cutter.SOLUTION: A step type milling cutter has a cutter body 1 which is rotated in a cutter rotation direction T around an axis O, and plural cutting blades 5 which are provided on an outer periphery of a tip of the cutter body 1. The cutting blade 5 comprises a peripheral cutting edge 5a which extends in the axis O direction, and a bottom edge 5b which extends to a radial direction inner peripheral side with respect to the axis O, and the cutting blades are so provided that positions thereof are gradually shifted along a circumferential direction of the cutter body 1. When the cutter body 1 is configured from an aggregate of plural segments S1 to S8 which sandwich individual cutting blades 5 therebetween in a circumferential direction, and which are mutually partitioned by two flat surfaces including the axis O, these segments S1 to S8 are respectively provided with a pre-balance part 3 which adjusts a position of a center of gravity of each segment S1 to S8 so that a center of gravity of the cutter body 1, in which all segments S1 to S8 are aggregated, is positioned on the axis O.SELECTED DRAWING: Figure 1

Description

  The present invention is a step-type milling cutter in which a plurality of cutting blades are disposed on the outer periphery of the front end portion of the cutter body that is rotated about the axis in the cutter rotating direction while being gradually shifted in position along the circumferential direction of the cutter body. It is about.

  As such a step type milling cutter, for example, in Patent Documents 1 to 3, a plurality of cutting blades are provided on the outer periphery of the cutter body, and the positions of these cutting blades in the axial direction of the cutter body are sequentially arranged along the cutter rotation direction. In addition to the retreat, the position in the radial direction is sequentially reduced. Among these, Patent Document 1 describes that, in such a step milling cutter, when the feed amount is constant, a small and thick chip is generated, so that the specific cutting resistance is low and the sharpness is good. Therefore, chatter vibration can be suppressed, and the chip pocket of the cutter body can be small.

JP 58-051011 A Japanese Patent Laid-Open No. 11-320235 JP 2014-113686 A

  However, in such a stepped milling cutter, the position of the center of gravity of the cutter body including the cutting edge is also displaced from the axial line because the positions of the cutting blades in the axial direction and the radial direction are shifted. If the cutter body is rotated at a high speed, there is a risk of vibration. When such runout occurs, the cutting process becomes unstable, and it may not be possible to obtain good machining accuracy and surface roughness, or in some cases, chipping or chipping may be caused to the cutting edge. is there.

  The present invention has been made under such a background, and even in a step type milling cutter in which the axial and radial positions of a plurality of cutting blades are shifted, the cutter body is rotated at high speed. It is an object of the present invention to provide a step type milling cutter capable of performing stable cutting while preventing the occurrence of vibration.

  In order to solve the above problems and achieve such an object, the present invention provides a cutter main body that is rotated in the cutter rotating direction around an axis, and a plurality of members disposed on the outer periphery of the distal end portion of the cutter main body. A cutting blade, and the cutting blade includes an outer peripheral blade extending in the axial direction, and a bottom blade extending radially inward from the tip of the outer peripheral blade with respect to the axial line. Are stepped milling cutters that are gradually shifted in position along the two sides, wherein the cutter body is sandwiched between two cutting planes in the circumferential direction and includes two planes including the axis. When an aggregate of a plurality of segmented segments is formed, these segments include a program for adjusting the position of the center of gravity of each segment so that the center of gravity of the cutter body that aggregates all the segments is positioned on the axis. It is characterized in that the balance unit is formed respectively.

  In the step type milling cutter configured as described above, when the cutter body is an aggregate of a plurality of segments as described above, the center of gravity of the cutter body in which all the segments are aggregated in these segments is the cutter body. Pre-balance parts that adjust the position of the center of gravity of each segment are formed so as to be positioned on the axis, so even if the cutting blade position is shifted, vibration will occur when the cutter body is rotated at high speed In addition, it is possible to improve the processing accuracy and surface roughness by enabling stable cutting, and also prevent chipping and chipping of the cutting edge.

  The position of the center of gravity of each segment is, for example, as long as the positions of the centers of gravity of a pair of segments located on opposite sides in the circumferential direction across the axis are on the diameter line with respect to the axis and are equidistant from the axis. Even if the distance between the center of gravity and the other pair of segments differs from the axis of gravity center, the center of gravity of the cutter body, which is a collection of all segments, can be positioned on the axis of the cutter body. The center of gravity of the cutter body is positioned on one cylindrical surface with the axis as the center, so that the center of gravity of the cutter body can be reliably positioned on the axis of the cutter body.

  Also, the position of the center of gravity of each segment is the same if the position of the center of gravity of a pair of segments located on opposite sides in the circumferential direction across the axis is on the diameter line with respect to the axis and is equidistant from the axis. Even if the segment of the center and the other pair of segments are different in the circumferential distance of the center of gravity, the center of gravity of the cutter body, which is a collection of all segments, can be positioned on the axis of the cutter body. By positioning the center of gravity of the cutter body at equal intervals in the circumferential direction of the cutter body, the center of gravity of the cutter body can be more reliably positioned on the axis of the cutter body.

  Furthermore, in order to adjust the position of the center of gravity of each segment so that the center of gravity of the cutter main body in which all the segments are assembled as described above is positioned on the axis in the prebalance section, the outer surface of the prebalance section is adjusted. The position of the center of gravity of each segment may be adjusted so that the center of the center of gravity of the cutter body is located on the axis by forming a prebalance surface and adjusting the distance of the prebalance surface from the axis. .

  In this case, the pre-balance surface is a plane perpendicular to a straight line connecting the axis and the corner portion where the outer peripheral edge and the bottom edge of the cutting blade intersect when viewed in the axial direction. By adjusting the interval, the position of the center of gravity of each segment is adjusted so that the center of gravity of the cutter body, which is a collection of all the segments, is positioned on the axis. Desirable for positioning on the axis.

  Further, in the distal end portion of the cutter body, the outer peripheral surface of the segment is formed into a cylindrical surface shape having a radius smaller than the radius from the axis of the outer peripheral blade of the cutting blade sandwiched between the two planes. By setting the difference between the radius of the outer peripheral blade and the radius of the outer peripheral surface of the segment to a small size within an appropriate range between the segments, the outer peripheral blade protrudes more than necessary from the outer peripheral surface of the cutter body tip and the cutting blade It is possible to prevent the rigidity from being lost, or the high cutting depth cannot be achieved because the outer peripheral surface of the tip of the cutter body is positioned on the outer peripheral side of the outer peripheral blade. In such a case, the prebalance portion may be formed at the rear end portion of the cutter body.

  On the other hand, in such a stepped milling cutter, the final accuracy and roughness of the machined surface (finished surface) are determined on the innermost tip side of the cutter body among the plurality of cutting blades. It becomes the bottom blade of the cutting blade. Therefore, the cutting surface arranged on the innermost tip side of this cutter body is a wiper blade whose bottom blade is longer than the bottom blade of other cutting blades, so that the machining surface is finished smoothly. Therefore, it is possible to obtain better processing accuracy and processing surface roughness.

  Then, when the cutting blade disposed on the innermost tip end side of the cutter body is a wiper blade in this way, the other cutting blades other than the cutting blade that is the wiper blade have an effect on the machining surface roughness and the like. Therefore, by forming a nick on the bottom edge of this other cutting edge, it becomes possible to generate chips that have been divided in advance and further reduce the cutting resistance.

  Similarly, when the cutting blade disposed on the innermost distal end side of the cutter body is a wiper blade whose bottom blade is longer than the other cutting blades, the cutter body includes the wiper blade and the wiper blade. By forming the coolant hole for supplying the coolant only to the cut blade, the coolant can be concentrated and supplied to the wiper blade, and it is possible to promote the efficient discharge of the long extending chips.

  As described above, according to the present invention, even if the cutter body is rotated at a high speed, it is possible to prevent occurrence of vibration, and to promote stable cutting and obtain excellent machining accuracy and machined surface roughness. In addition, it is possible to prevent chipping and chipping from occurring on the cutting edge and perform smooth cutting.

It is a perspective view from the upper surface side of the cutter main body which shows one Embodiment of this invention. It is a perspective view from the bottom face side of embodiment shown in FIG. It is a top view of embodiment shown in FIG. It is a bottom view of embodiment shown in FIG. It is a side view of the arrow W direction view in FIG. 3 and FIG. It is a side view of the arrow X direction view in FIG. 3 and FIG. It is a side view of the arrow Y direction view in FIG. 3 and FIG. It is a side view of the arrow line Z direction view in FIG. 3 and FIG. It is a perspective view from the upper surface side of a cutter main body which shows the segment by which a cutting blade is arrange | positioned in the front end inner peripheral side of the cutter main body in embodiment shown in FIG. It is a perspective view from the bottom face side of the segment shown in FIG. It is a top view of the segment shown in FIG. It is a bottom view of the segment shown in FIG. It is a side view of the arrow W direction view in FIG. 9 and FIG. It is a side view of the arrow X direction view in FIG. 9 and FIG. It is a side view of the arrow Y direction view in FIG. 9 and FIG. It is a side view of the arrow line Z direction view in FIG. 9 and FIG. It is the (a) side view seen from the cutter rotation direction T side of the 1st cutting insert attached to the embodiment shown in Drawing 1, and (b) the bottom view seen from the bottom side of the cutter main part. It is the side view seen from the cutter rotation direction T side which shows an example of the 2nd-8th cutting insert attached to embodiment shown in FIG. It is the side view seen from the cutter rotation direction T side which shows the other example of the 2nd-8th cutting insert attached to embodiment shown in FIG.

  FIGS. 1 to 8 show an embodiment of the step type milling cutter of the present invention, and FIGS. 9 to 16 show the cutting edge on the innermost end of the cutter body 1 in the step type milling cutter of this embodiment. It shows the segment in which is disposed. In this embodiment, the cutter body 1 is integrally formed in a substantially disc shape with a metal material such as a steel material, and the tip portion (the lower portion in FIGS. 5 to 8) has a large diameter and a substantially disc shape. The cutting edge part 2 is used, and the rear end part (the upper part in FIGS. 5 to 8) is a polygonal plate-like prebalance part 3 having a smaller diameter than the cutting edge part 2.

  Further, the cutter body 1 is formed so as to pass through a mounting hole 4 having a circular cross section centered on the axis O. The mounting hole 4 has a small diameter in the prebalance portion 3 and a cutting blade portion 2. Is a stepped hole with a large diameter. The cutter body 1 is gripped by the spindle of the machine tool through an arbor attached to the attachment hole 4 and is rotated about the axis O in the cutter rotation direction indicated by a symbol T in the drawing, and is perpendicular to the axis O. The workpiece is fed in the direction, and a flat working surface is formed on the work material by the cutting blade 5 provided on the cutting blade portion 2.

  Here, in this embodiment, the said cutting blade 5 is formed in the cutting insert 6 attached to the cutter main body 1 so that attachment or detachment is possible. That is, the step type milling cutter of the present embodiment is a blade tip exchange type milling cutter, and a plurality of (eight in the present embodiment) chip pockets 7 are provided on the outer periphery of the distal end portion of the cutting blade portion 2 at intervals in the circumferential direction. The insert mounting seats 8 to which the cutting inserts 6 are attached are formed on the wall surfaces of the chip pockets 7 facing the cutter rotation direction T.

  The cutting blade 5 in the cutting insert 6 of this embodiment is directed to the outer peripheral side of the cutter body 1 and extends in the direction of the axis O, and extends from the tip of the outer peripheral blade 5a to the inner side in the radial direction with respect to the axis O. And a bottom blade 5b directed to the distal end side of the cutter body 1. Such cutting blades 5 of a plurality (eight in this embodiment) of the cutting inserts 6 attached to each insert mounting seat 8 have a cutter rotation direction T from the cutter rotation direction T side in the circumferential direction of the cutter body 1. While facing the opposite side, the rotation trajectories around the axis O are overlapped, and the positions are gradually shifted in steps with a step in the axis O direction and the radial direction of the cutter body 1.

  That is, in the present embodiment, the first cutting edge 5A of the first cutting insert 6A shown on the right side in FIG. 4 is such that the outer peripheral blade 5a is located closest to the inner peripheral side of the cutter body 1 and the bottom blade 5b is the most. The second to eighth cutting inserts 6B to 6B are located on the distal end side in the direction of the axis O and from the first cutting insert 6A along the circumferential direction of the cutter body 1 toward the opposite side of the cutter rotation direction T. In the order of 6H, the outer peripheral blades 5a of the second to eighth cutting blades 5B to 5H shift substantially parallel to the outer peripheral side, and the bottom blade 5b shifts substantially parallel to the rear end side in the axis O direction. And these 1st-8th cutting blades 5A-5H have overlapped as mentioned above so that the rotation locus | trajectory around the axis line O of each outer peripheral blade 5a and the bottom blade 5b may cross | intersect.

  Here, in this embodiment, as shown in FIG. 17, the first cutting insert 6A is a polygonal plate-shaped (for example, rectangular plate-shaped) insert body (base metal) made of a hard material such as cemented carbide. Positive in which a rectangular plate-like cutting blade member 6b made of a high hardness sintered body such as a diamond sintered body having a hardness higher than that of the insert body 6a is joined to one side ridge portion on the bottom surface which is a polygonal surface of 6a. A bottom cutting edge 5b is formed at a portion corresponding to the one side ridge portion of the cutting blade member 6b, and from the end of the bottom cutting edge 5b in the thickness direction of the insert body 6a. An outer peripheral edge 5a is formed on the extending side ridge. A through hole 6c that penetrates the insert body 6a is opened at the center of the bottom surface.

  Such a first cutting insert 6A has an insert screw 9 inserted through the through hole 6c with the bottom surface of the insert body 6a facing the front end side of the cutter body 1 and the cutting blade member 6b facing the cutter rotation direction T. It is detachably attached to the cutter body 1 by being screwed into a screw hole formed on the surface facing the front end side of the mounting seat 8. That is, the first cutting insert 6A is attached to the cutter body 1 in a so-called vertical blade type in which the length direction or the width direction having a dimension larger than the thickness direction is directed to the cutter rotation direction T. At this time, a positive axial rake angle is given to the outer peripheral blade 5a directed to the outer peripheral side of the cutter body 1, and the bottom blade 5b directed to the cutter rotation direction T is positioned on a plane perpendicular to the axis O. A negative radial rake angle is provided as shown in FIG.

  On the other hand, the second to eighth cutting inserts 6B to 6H other than the first cutting insert 6A are, for example, as shown in FIG. 18, integrally formed with a hard material such as cemented carbide. A plurality (four in FIG. 18) having a large polygonal plate-like (for example, rectangular plate-like) insert body 6 a and positioned on diagonal lines of a polygonal surface directed in the cutter rotation direction T of the insert body 6 a The outer peripheral edge 5a and the bottom edge 5b of the cutting edge 5 are formed at two side ridges intersecting the corner C of the outer edge. In the present embodiment, a plurality of concave nicks 6d intersecting the bottom blade 5b are formed on the corner portion C side of the bottom blade 5b. A through hole 6c that penetrates the insert body 6a is opened at the center of the polygonal surface.

  Such second to eighth cutting inserts 6B to 6H have the mounting screw 9 inserted through the through hole 6c with the polygonal surface on which the cutting edge 5 is formed oriented in the cutter rotation direction T as described above. It is detachably attached to the cutter body 1 by being screwed into a screw hole formed on the surface of the mounting seat 8 facing the cutter rotation direction T. At this time, the outer peripheral blade 5a is directed to the outer peripheral side of the cutter body 1 and extends from the corner portion C to the rear end side in the axis O direction, and the bottom blade 5b is directed to the distal end side of the cutter main body 1 and the distal end of the outer peripheral blade 5a. The outer peripheral blade 5a is given a positive axial rake angle while the bottom blade 5b is more than the bottom blade 5b of the first cutting insert 6A as shown in FIG. Is also given a large radial rake angle of approximately 0 ° on the positive angle side.

  In the first to eighth cutting blades 5A to 5H in the first to eighth cutting inserts 6A to 6H, the length of the bottom blade 5b is longer than the length of the outer peripheral blade 5a. . Moreover, the length of the bottom blade 5b in the first cutting blade 5A of the first cutting insert 6A is the bottom blade in the second to eighth cutting blades 5B to 5H of the second to eighth cutting inserts 6B to 6H. The bottom blade 5b of the first cutting blade 5A of the first cutting insert 6A is a wiper blade.

  Furthermore, in the first to eighth cutting blades 5A to 5H whose rotational trajectories are shifted in the order from the first cutting insert 6A to the second to eighth cutting inserts 6B to 6H, to the outer peripheral side of the individual outer peripheral blades 5a. Are set to be equal to each other, and the shift amounts to the rear end side of the individual bottom blades 5b are also set to be equal to each other. Furthermore, the corner portion C where the outer peripheral blade 5a and the bottom blade 5b of the first to eighth cutting blades 5A to 5H intersect in the first to eighth cutting inserts 6A to 6H is circumferential in the present embodiment. It arrange | positions so that it may become equal intervals.

  Further, the cutter body 1 is formed with a coolant supply hole (not shown) through which the coolant supplied from the main spindle of the machine tool attached via the arbor or the like is ejected toward the cutting blade 5 as described above. Here, the coolant supply hole opens only in the chip pocket 7 adjacent to the cutter rotation direction T of the insert mounting seat 8 to which the first cutting insert 6A is attached, and the cutting edge of the first cutting insert 6A is formed. It is supposed that coolant is supplied only to 5. The coolant is supplied from the outside of the cutter body 1 to the second to eighth cutting edges 5B to 5H in the other second to eighth cutting inserts 6B to 6H.

  Then, the cutter body 1 including the cutting insert 6 on which the cutting blade 5 as described above is formed and the mounting screw 9 is interposed between the individual cutting blades 5 in the circumferential direction as shown in FIGS. 4 and 9 to 16. And the center of gravity of the segments S1 to S8 is the above-described prebalance when the segment S1 to S8 is an aggregate of a plurality of segments S1 to S8 that are partitioned from each other by two planes P1 to P8 including the axis O. The section 3 is adjusted so that the center of gravity of the cutter body 1, which is an aggregate of all the segments S <b> 1 to S <b> 8, is positioned on the axis O.

  Here, in this embodiment, prebalance surfaces 10A to 10H are respectively formed on the outer peripheral surface of the prebalance portion 3, and the distances from the axis O of the prebalance surfaces 10A to 10H are adjusted. Thus, the positions of the centers of gravity of the segments S1 to S8 are adjusted so that the center of gravity of the cutter body 1 that is a collection of all the segments S1 to S8 is positioned on the axis O. Furthermore, in the present embodiment, the positions of the centers of gravity of these segments S1 to S8 are arranged at equal distances from the axis O and at equal intervals in the circumferential direction.

  More specifically, in the present embodiment, the planes P1 to P8 are arranged at substantially equal intervals in the circumferential direction, and each of the segments S1 to S1 divided by two adjacent planes of the planes P1 to P8 in the circumferential direction. S8 is set to include one cutting edge 5 (one of cutting edges 5A to 5H). Here, the prebalance surfaces 10A to 10H of the respective segments S1 to S8 are, when viewed in the direction of the axis O, the cutting edges 5A to 5H included in the segments S1 to S8 in which the prebalance surfaces 10A to 10H are formed. The outer peripheral blade 5a and the bottom blade 5b are formed into a plane perpendicular to the straight lines L1 to L8 connecting the corner portion C and the axis O.

  Therefore, in the step type milling cutter of this embodiment provided with the eight cutting edges 5A-5H, the prebalance part 3 in which the prebalance surfaces 10A-10H are formed is formed in a substantially octagonal flat plate shape. These prebalance surfaces 10A to 10H are formed with screw holes having a center line parallel to the straight lines L1 to L8 when viewed in the direction of the axis O, that is, perpendicular to the prebalance surfaces 10A to 10H. Balance fine adjustment screws 11 are screwed into these screw holes.

  Moreover, in the cutting blade part 2 of the front-end | tip part of the cutter main body 1, the outer peripheral blade 5a of the cutting blade 5 by which the outer peripheral surface of the said segments S1-S8 is pinched | interposed into said two planes P1-P8 which divide this segment S1-S8. The cylindrical surface has a radius smaller than the radius from the axis O. However, in the peripheral portions of the planes P1 to P8 where these outer peripheral surfaces are in contact, the radius of the cylindrical surface formed by the outer peripheral surface is adjusted, and the outer peripheral surface of the cutting edge portion 2 has a smooth convex curved surface as a whole. To be made. In addition, the protrusion amount of the outer peripheral blade 5a from the outer peripheral surface of each segment S1-S8 in the periphery of the outer peripheral blade 5a is large, and the protrusion amount of the outer peripheral blade 5a of the eighth cutting blade 5H that protrudes to the outermost peripheral side is large. The protruding amount of the outer peripheral blades 5a of the first to seventh cutting blades 5A to 5G is a substantially constant protruding amount smaller than this.

  Further, the distal end surface of the first segment S1 including the bottom blade 5b of the first cutting blade 5A that protrudes most toward the distal end side of the cutter body 1 protrudes most distally from the distal end surface of the cutting blade portion 2. The front end surface of each segment S2 to S8 is also retracted to the rear end side in the direction of the axis O in the order of the second to eighth segments S2 to S8 in which the bottom blade 5b included from the bottom blade 5b of the first cutting blade 5A sequentially retreats. It is formed in a staircase shape. In addition, the protrusion amount of the bottom blade 5b from the front end surface of each segment S1-S8 is substantially constant.

  In the step-type milling cutter configured in this way, when the cutter body 1 including the cutting blade 5 is an aggregate of a plurality of segments S1 to S8 partitioned from each other as described above, all the segments S1 to S1 Since the pre-balance portions 3 for adjusting the positions of the centers of gravity of the segments S1 to S8 are formed in the segments S1 to S8 so that the center of gravity of the cutter body 1 assembled with S8 is positioned on the axis O, the cutting is performed. Even if the cutter body 1 is rotated at a high speed during processing, the cutter body 1 can be prevented from shaking in the radial direction, and stable cutting can be performed.

  Therefore, even if the position of the cutting blade 5 is displaced in the radial direction, the cutter blade 5 can be prevented from being cut into the work material more than necessary due to the shake of the cutter body 1, and the cutting blade 5 As a result, chipping and chipping can be prevented, and machining accuracy and surface roughness of the work material can be improved. The balance of the cutter body 1 can be finely adjusted by adjusting the screwing amount of the balance fine adjustment screw 11.

  Furthermore, in the present embodiment, the positions of the centers of gravity of these segments S1 to S8 are arranged so as to be equally spaced in the circumferential direction on one cylindrical surface at an equal distance from the axis O. Position setting is easy, and it is possible to adjust the center of gravity of the cutter body 1 that is a set of all the segments S1 to S8 more reliably so as to be positioned on the axis O. Furthermore, the center of gravity of the segments S1 to S8 in the prebalance unit 3 is adjusted by adjusting the distance from the axis O of the prebalance surfaces 10A to 10H formed on the outer peripheral surface of the prebalance unit 3 in this embodiment. Since this is done, it is easier to set the position of the center of gravity.

  Further, the prebalance surfaces 10A to 10H in the present embodiment are relative to the straight lines L1 to L8 that connect the corner line C and the axis O where the outer peripheral edge 5a and the bottom edge 5b of the cutting edge 5 intersect in the direction of the axis O. It is a vertical plane. For this reason, the prebalance surfaces 10A to 10H can be formed on the basis of the straight lines L1 to L8, so that the center of gravity of the cutter body 1 can be more reliably arranged on the axis O. Particularly in the present embodiment, the corner portions C of the first to eighth cutting edges 5A to 5H in the first to eighth cutting inserts 6A to 6H are arranged at equal intervals in the circumferential direction. L1 to L8 are also equally spaced, and the prebalance surfaces 10A to 10H can be easily formed accurately, so that the position of the center of gravity of the cutter body 1 can be accurately placed at the axis O.

  Moreover, in this embodiment, in the cutting edge part 2 of the front-end | tip part of the cutter main body 1, the outer peripheral surface of each segment S1-S8 is the radius from the axis line O of the outer peripheral edge 5a of this cutting edge 5 in the periphery of the cutting edge 5. The pre-balance surfaces 10 </ b> A to 10 </ b> H are formed in the pre-balance portion 3 on the rear end side with respect to the cutting edge portion 2. Therefore, the rigidity of the outer peripheral blade 5a of the cutting blade 5 is reduced by setting the difference between the radius of the outer peripheral blade 5a and the radius of the outer peripheral surface of the segments S1 to S8, that is, the protrusion amount of the outer peripheral blade 5a within a proper range. In addition, while ensuring the mounting strength of the cutting insert 6, it becomes possible to perform high cutting with the outer peripheral blades 5 a of the first to eighth cutting inserts 6 </ b> A to 6 </ b> H shifted in the direction of the axis O.

  Moreover, in the present embodiment, the front end surface of the cutting blade portion 2 that is the front end surface of the cutter body 1 also includes the bottom blade 5b of the first cutting blade 5A that protrudes most toward the front end side of the cutter body 1. Each of the segments S2 to S8 is in the order of the second to eighth segments S2 to S8 in which the distal end surface of the segment S1 protrudes to the most distal end, and the bottom blade 5b included in the first cutting blade 5A is sequentially retracted. Are also formed in a stepped shape so as to sequentially retreat toward the rear end side in the axis O direction, and the protruding amount of the bottom blade 5b from the front end surface of each segment S1 to S8 is substantially constant. For this reason, it becomes possible to ensure the rigidity of the bottom blade 5b of the cutting blade 5 and the mounting strength of the cutting insert 6 on the bottom blade 5b side.

  On the other hand, in the step type milling cutter as in this embodiment, among the plurality of cutting blades 5A to 5H, the bottom blade 5b of the first cutting blade 5A disposed on the innermost distal end side of the cutter body 1 is The accuracy and roughness of the final machined surface will be determined. Therefore, if the bottom blade 5b of the first cutting blade 5A is positioned on a plane perpendicular to the axis O, the front runout adjustment in the thickness direction of the first cutting insert 6A is not necessary. In the present embodiment, the bottom blade 5b of the first cutting blade 5A is a wiper blade longer than the other second to eighth cutting blades 5B to 5H, and is on a plane perpendicular to the axis O. Since it is arranged, it becomes possible to finish the machined surface more smoothly and obtain high machining accuracy and machined surface roughness.

  On the other hand, the bottom blade 5b of the other second to eighth cutting blades 5B to 5H is formed with a groove-shaped nick 6d in the present embodiment, and is generated while cutting chips. Since the cutting resistance can be reduced, the step milling cutter of this embodiment can be used from roughing to finishing in combination with the fact that high cutting can be performed as described above. It becomes possible. In addition, when the nick 6d is formed on the bottom blade 5b in this way, the processed surface roughness by the other second to eighth cutting blades 5B to 5H is impaired, but these other second to eighth materials. Since the machining surface by the bottom blade 5b of the cutting blades 5B to 5H is scraped off by the bottom blade 5b of the first cutting blade 5A, the final machining accuracy and the machining surface roughness are not affected.

  Furthermore, in the present embodiment, the first cutting edge 5A disposed on the innermost distal end side of the cutter body 1 in this way has the length of the bottom edge 5b of the other second to eighth cutting edges. While the wiper blade is longer than the bottom blade 5b of 5B to 5H, the cutter body 1 supplies the coolant only to the first cutting blade 5A having the bottom blade 5b serving as the wiper blade. A hole is formed. For this reason, it is possible to concentrate coolant on the bottom blade 5b, which is a wiper blade, and to efficiently discharge chips that are long without being divided because there is no nick.

  In the present embodiment, the second to eighth cutting inserts 6B to 6H having the other second to eighth cutting edges 5B to 5H are integrally formed of a hard material such as cemented carbide. Although the cost is lower than that of the first cutting insert 6A to which the cutting blade member 6b made of a high-hardness sintered body such as a diamond sintered body is joined, these second to eighth cutting inserts 6B to 6B Also in 6H, what joined the cutting blade member 6b which consists of a high-hardness sintered body like the other example shown in FIG. 19 may be used. Here, in FIG. 19, the same code | symbol is distribute | arranged to the part which is common in the cutting insert 6 shown in FIG.

  In other words, the cutting inserts 6B to 6H of the other examples have a cutter rotation direction of a polygonal plate-like (for example, rectangular plate-like) insert body (base metal) 6a integrally formed of a hard material such as cemented carbide. A triangular plate made of a high hardness sintered body such as a diamond sintered body having a hardness higher than that of the insert body 6a at a plurality of (four in FIG. 18) corner portions C located on the diagonal line of the polygonal surface directed to T This is a positive type isomorphous cutting insert of which the cutting blade member 6b is joined. And the outer peripheral blade 5a is formed in the side ridge part toward the cutter body 1 outer peripheral side of these cutting blade members 6b, and the nick 6d is formed in the side ridge part toward the front end side longer than the outer peripheral blade 5a. A bottom blade 5b that is not formed is formed.

  In such other examples of the cutting inserts 6B to 6H, when the chips are originally easily generated as in the case of cutting of cast iron or the like, for example, the cutting resistance can be reduced even if the nick 6d is not formed. Reduction can be achieved. Moreover, since the cutting blade 5 is formed on the cutting blade member 6b made of a high hardness sintered body such as a diamond sintered body having a hardness higher than that of the cemented carbide, the cutting inserts 6B to 6H have a long life. be able to.

  Further, in the first cutting insert 6A, as shown by a broken line in FIG. 17A, the bottom blade 5b is formed on the side surface in which the cutting blade member 6b is joined to the bottom surface side and directed in the cutter rotation direction T. Alternatively, it may be formed in a trapezoidal shape that becomes narrower as it goes from the bottom surface side to the opposite side, and the outer peripheral blade 5a may be inclined toward the inner peripheral side of the cutter body 1 as it goes toward the rear end side in the axis O direction. By tilting the outer peripheral blade 5a in this way, the outer peripheral blade 5a of the first cutting blade 5A that finally determines the processing accuracy and the surface roughness can be given a deburring function, and a better finish can be achieved. A surface can be formed.

  Further, in the first cutting insert 6A, the cutting edge member 6b made of an ultra-high hardness sintered body is shown in FIG. 17B as one side on the polygonal surface (bottom surface) of the insert body (base metal) 6a. It is joined only to the ridge part, and the other one side ridge part on the opposite side of this polygonal surface remains the cemented carbide forming the insert body 6a. Therefore, for example, in the case of cutting a casting spout, the first cutting insert 6A is rotated by 180 ° around the through hole 6c and reattached to the insert mounting seat 8, and the other one side ridge is attached. You may make it use for cutting as a bottom blade.

DESCRIPTION OF SYMBOLS 1 Cutter body 2 Cutting edge part 3 Prebalance part 4 Mounting hole 5 (5A-5H) Cutting blade 5a Outer peripheral blade 5b Bottom blade 6 (6A-6H) Cutting insert 10A-10H Prebalance surface 11 Balance fine adjustment screw O Cutter body 1 axis T cutter rotating direction C corner part P1 to P8 where outer peripheral edge 5a and bottom edge 5b of cutting edge 5 intersect plane S1 to S8 segment L1 to L8 axis line including two axis O sandwiching cutting edge 5 A straight line connecting the corner C and the axis O when viewed in the O direction

Claims (8)

A cutter body that is rotated about the axis in the cutter rotation direction;
A plurality of cutting blades disposed on the outer periphery of the tip of the cutter body,
The cutting blade includes an outer peripheral blade extending in the axial direction and a bottom blade extending from the tip of the outer peripheral blade to the radially inner peripheral side with respect to the axis, and is gradually positioned along the circumferential direction of the cutter body. A step-type milling cutter arranged in a shifted manner,
When the cutter body is an aggregate of a plurality of segments that are separated from each other by two planes that sandwich the individual cutting blades in the circumferential direction and include the axis,
These segments are each formed with a pre-balance portion that adjusts the position of the center of gravity of each segment so that the center of gravity of the cutter body, which is a collection of all segments, is positioned on the axis. Type milling cutter.   2. The step milling cutter according to claim 1, wherein the center of gravity of each segment is located on one cylindrical surface centered on the axis. 3.   3. The step milling cutter according to claim 1, wherein the centers of gravity of the segments are located at equal intervals in a circumferential direction of the cutter body.   A pre-balance surface is formed on the outer peripheral surface of the pre-balance portion, and the center of gravity of the cutter body that collects all the segments is adjusted to the axis by adjusting the distance of the pre-balance surface from the axis. The step milling cutter according to any one of claims 1 to 3, wherein the position of the center of gravity of each segment is adjusted so as to be positioned on a line.   The said prebalance surface is a plane perpendicular | vertical with respect to the straight line which connects the corner | angular part which the outer peripheral blade and bottom blade of the said cutting blade cross | intersect in the said axial direction view, and this axis line. Step milling cutter as described. At the tip of the cutter body, the outer peripheral surface of the segment is a cylindrical surface with a radius smaller than the radius from the axis of the outer peripheral blade of the cutting blade sandwiched between the two planes.
The step type milling cutter according to any one of claims 1 to 5, wherein the prebalance portion is formed at a rear end portion of the cutter body. Among the cutting blades, the cutting blade disposed on the innermost distal end side of the cutter body is a wiper blade in which the length of the bottom blade is longer than the bottom blades of the other cutting blades,
The step type milling cutter according to any one of claims 1 to 6, wherein a nick is formed on a bottom blade of the other cutting blade. Among the cutting blades, the cutting blade disposed on the innermost distal end side of the cutter body is a wiper blade in which the length of the bottom blade is longer than the bottom blades of the other cutting blades,
The step type milling machine according to any one of claims 1 to 7, wherein a coolant hole for supplying coolant only to a cutting blade having the wiper blade is formed in the cutter body. Cutter.

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