JP2009184036A - Cutting tool - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cutting tool improving the inner wall surface roughness of a hole to be machined, and performing excellent cutting by preventing the occurrence of chattering vibration or chipping. <P>SOLUTION: A boring bar 1, in which an insert 20 is detachably mounted to a tool body 10 rotating around an axis O, is inserted into a pre-bored hole previously formed in a workpiece material, and forms the hole having a predetermined inner diameter by cutting the inner wall surface of the pre-bored hole. A straight blade 23a is installed by forming a flat part in the insert 20, and the insert 20 is mounted to the tool body 10 so that the straight blade 23a faces the tool radially outwardly and becomes parallel to the axis O. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a cutting tool such as a boring bar that is used when an inner wall surface of a prepared hole previously formed in a workpiece is cut into a predetermined inner diameter.

  In recent years, as a cutting tool used for processing a cylinder bore of an engine, for example, a boring bar or the like as shown in Patent Document 1 in which an insert having a cutting edge is detachably attached to the outer periphery of a tip end portion of a tool body is known. It has been.

  Such a boring bar has a cylindrical tool body rotated about an axis, and an insert having a cutting edge is fixed to the outer periphery of the tool body tip side by a clamp screw or the like. This insert has a rectangular flat plate shape, and is attached to the tool main body with the cutting edge formed at the side ridge portion of the corner portion of the square surface facing outward in the tool radial direction.

The boring bar has a tool body attached to the main end shaft of the machine tool, is rotated at high speed around the axis of the tool body, is fed in the axial direction of the tool body, and is provided in advance on the workpiece. The inner wall surface of the prepared hole is cut by a cutting blade that is inserted into the prepared hole and protrudes toward the outer side in the tool radial direction at the tip end portion of the tool body to form a processed hole having a predetermined inner diameter.
JP 2005-246527 A

  By the way, in the conventional cutting tool as described above, since the cutting edge is formed at the side ridge portion of the corner portion of the insert, it has a sharp and sharp shape. Therefore, when the tool body is fed in the axial direction, this sharp cutting edge cuts while cutting against the inner wall surface of the workpiece's pilot hole. Depending on the shape of the tip, it will be sharpened. Therefore, the inner surface of the machined hole has a shape in which the locus of the cutting edge is shifted and overlapped by the feed amount per rotation, and the surface roughness becomes rough when the feed amount per revolution of the boring bar is increased. There was a problem that processing accuracy was lowered. Furthermore, there is a problem that chatter vibrations and defects are likely to occur because cutting resistance concentrates on the tip of the cutting edge.

  The present invention has been made in view of such a problem, and can improve the surface roughness of the inner wall surface of the processing hole and perform good cutting processing by preventing chatter vibrations and defects. It aims at providing the cutting tool which can be performed.

In order to solve the above problems, the present invention proposes the following means.
That is, in the cutting tool according to the present invention, an insert is detachably attached to a tool body rotated about an axis, and is inserted into a prepared hole formed in a workpiece, and an inner wall surface of the prepared hole is cut. A cutting tool for forming a machining hole having a predetermined inner diameter, wherein the insert has a rectangular flat plate shape, has two rectangular surfaces and four side surfaces, and is cut at a corner of one of the side surfaces. A blade is formed, a flat portion forming a flat shape is formed at a boundary portion between the square surface and the other side surface adjacent to the one side surface, and an intersecting ridge line portion with the flat portion in the cutting blade is formed The groove is a straight blade, and a groove is formed in the outer periphery of the tool body at the tip of the tool and toward the outer side in the tool radial direction, and a mounting seat is provided on the surface of the groove on the tool tip side. And the insert is attached to the mounting seat. Toward the tool radially outward, and the straight line edge is characterized in that it is mounted so as to be parallel to said axis.

  According to the cutting tool having such a feature, the straight blades formed on the intersecting ridge line portion with the flat portion of the cutting blades are directed outward in the radial direction of the tool body and arranged so as to be parallel to the axis. Therefore, the straight blade comes into sliding contact along the prepared hole of the workpiece. Therefore, it is possible to cut so that the prepared hole of the workpiece is exposed by this straight blade, and the cutting is performed along the surface shape of the prepared hole while increasing the contact length between the cutting blade and the prepared hole. Therefore, it is possible to prevent the surface roughness of the inner wall surface of the processed hole from deteriorating. Furthermore, since cutting resistance can be disperse | distributed, it can suppress that chatter vibration and a defect | deletion generate | occur | produce.

  In the cutting tool according to the present invention, a corner R portion having a predetermined radius of curvature is provided at a boundary portion between the flat portion and the quadrangular surface, and a cross ridge line portion with the corner R portion in the cutting blade is a nose. It is characterized by the R blade.

  When the tool body is sent in the direction of the tool tip on the axis during machining, the nose R blade first contacts the pilot hole of the workpiece, so that concentration of stress during machining is suppressed, and chatter vibrations at the cutting edge Defects can be further suppressed.

  According to the cutting tool of the present invention, it is possible to improve the surface roughness of the inner wall surface of the processed hole by processing the prepared hole with a straight blade, and to prevent the occurrence of chatter vibration and defects. Cutting can be performed.

  Hereinafter, a boring bar of an embodiment of a cutting tool according to the present invention will be described in detail with reference to the drawings. 1 is a side view of a boring bar according to an embodiment of the present invention, FIG. 2 is a partially enlarged view of FIG. 1, FIG. 3 is a front view of the boring bar according to an embodiment of the present invention, and FIGS. FIG. The boring bar 1 of the present embodiment is configured by mounting a plurality of inserts 20 on the tip of a tool body 10.

  As shown in FIG. 1, the tool body 10 has a long cylindrical shape formed around an axis O made of, for example, steel, and the tool rear end side (upper side in FIG. 1) An attachment portion 11 for attaching the tool body 10 to a machine tool or the like (not shown) is formed.

  In addition, a coolant supply hole 12 extending along the axis O is formed in the tool body 10, and one end of the coolant supply hole 12 is opened in the attachment hole 11. Further, a coolant supply path 13 is formed from the tip of the coolant supply hole 12 toward each of a plurality of recessed grooves 15 described later.

  Further, a groove 15 formed on the outer periphery of the tip of the tool body 10 so as to open toward the tool front end side and the tool radial direction outer side and extend a certain distance toward the tool rear end side is shown in FIG. As shown in FIG. 5, a plurality (seven in this embodiment) are formed at intervals in the circumferential direction.

  A coolant supply path 13 is opened in the concave groove 15, and a mounting seat 16 for mounting the insert 20 is provided behind the concave groove 15 in the tool rotation direction T. The end-side wall surface 16a is an inclined surface that approaches the tool tip side as it goes inward in the tool radial direction, and an insert mounting screw hole (not shown) is formed in the wall surface 16a.

  The insert 20 to be mounted on the outer periphery of the tip end of the tool body 10 is made of a hard material such as cemented carbide, and as shown in FIGS. 4 and 5, two rectangular surfaces 21 (21a, 21b) on the front and back sides, It has a substantially hexahedron shape having four side surfaces 22 (22a, 22b, 22c, 22d) in contact with these rectangular surfaces 21a, 21b.

  The two rectangular surfaces 21 have a substantially rectangular shape and are arranged in parallel so as to be rotationally symmetrical with each other by 90 ° around the central axis when the front and back are reversed. An insert screw insertion hole 26 for inserting the attachment screw 30 is formed.

  In FIG. 5, when the insert 20 is viewed from the direction A, as shown in FIG. 6, the side surface 22a has an isosceles trapezoidal shape with the back side longer than the front side, and from the short side of the square surface 21a on the front side to the back side. The side surface 22c opposite to the side surface 22a is also disposed in the same manner. In addition, when the insert 20 is viewed from the B direction in FIG. 5, the side surface 22b is formed in an isosceles trapezoidal shape with a short rear surface with respect to the front side as shown in FIG. The rectangular surface 21a is inclined so as to gradually recede toward the long side, and the side surface 22d facing the side surface 22b is also disposed in the same manner. That is, the insert 20 is formed so as to be symmetric with respect to a plane passing through the midpoints of two side ridges facing each other when viewed from the front.

  Moreover, as shown in FIG.4 and FIG.6, the cutting edge 23 which makes the side surface 22a a rake face is formed in the intersection ridgeline part with the square surface 21a and side surface 22b, 22d in the corner | angular part of the short side both ends of the side surface 22a. Is provided. Further, the boundary portion between the quadrangular surface 21a and the side surface 22b and the boundary portion between the quadrangular surface 21a and the side surface 22d are formed so as to be cut out in a flat shape from the side surface 22a toward the side surface 22c opposite to the side surface 22a. Two flat portions 24 are provided, and an intersecting ridge line portion between the flat portion 24 and the side surface 22a in the cutting blade 23 described above is a straight blade 23a.

  Further, a corner R portion 25 having a predetermined radius of curvature and extending from the side surface 22a toward the side surface 22c is provided at the boundary between the two flat portions 24 and the square surface 21a. The crossing ridge line part of 25 and the side surface 22a is made into the nose R blade 23b. Therefore, the cutting edge 23 is configured such that a curved nose R edge 23b and a linear straight edge 23a are continuous from the short side to the oblique side of the side surface 21a. Moreover, the intersection ridgeline of the side surface 22a and the square surface 21a is also used as a cutting edge as needed.

  Further, such a cutting edge 23 is similarly provided at the corners of both ends of the short side of the side surface 22c facing the side surface 22a, and the side surfaces 22b and 22d adjacent to the side surface 22a are similarly short-sided. Cutting edges 23 are formed at the corners of both ends, and a flat portion 24 and a corner R portion 25 are formed between the square surface 21b on the back side and the side surfaces 22a, 22b, thereby forming a straight blade 23a and a nose R blade 23b. Is formed on each cutting edge 23.

  In such an insert 20, either one of the two rectangular surfaces 21 a and 21 b is brought into contact with the wall surface 16 a on the tool rear end side of the mounting seat 16, and the insert mounting screw 30 is inserted into the insert screw insertion hole 26. The tool body 10 is mounted by being screwed into an insert mounting screw hole (not shown) of the wall surface 16a.

  In the present embodiment, for example, the back side square surface 21b shown in FIG. 4 is mounted in a state of being in contact with the wall surface 16a, and at this time, the boundary between the square surface 21a facing the tool tip side and the side surface 22d The flat part 24 formed in the part is directed outward in the tool radial direction. Along with this, the cutting edges 23 at the corners of the side surfaces 22a and 22c are also directed outward in the tool radial direction, and as shown in FIGS. 1 and 2, the linear blade 23a in the cutting edge 23 faces outward in the tool radial direction, And it arrange | positions so that it may become parallel with respect to the axis line O. In the present embodiment, the cutting blades 23 directed to the outer side in the tool radial direction of the inserts 20 attached to the plurality of mounting seats 16 are arranged so that the intervals in the circumferential direction are illegally divided.

  The boring bar 1 configured as described above is attached to the main spindle end of the machine tool via the attachment portion of the tool body 10 and is rotated at high speed around the axis O and feed is directed toward the tool tip of the axis O. And inserted into a pilot hole formed in advance in the workpiece. Then, the inner wall surface of the prepared hole is cut by the cutting blade 23 on the front side in the tool rotation direction T among the cutting blades 23 directed to the outer side in the tool radial direction of the insert 20 to form a processing hole having a predetermined inner diameter. . Further, during the cutting process, the coolant is supplied to the cutting blade 23 through the coolant supply hole 12 and the coolant supply path 13 to reduce friction and to remove the processing heat and perform smooth cutting.

    According to the boring bar 1 of the present embodiment, at the time of cutting, the straight blade 23a arranged parallel to the axis O comes into sliding contact along the prepared hole of the work material. Therefore, since it is possible to cut the prepared material so that the prepared hole is exposed by the straight blade 23a, the surface roughness of the inner wall surface of the processed hole can be made smooth. Further, since it is possible to perform cutting while increasing the contact length between the cutting edge 23 and the pilot hole, even if the feed amount of the boring bar 1 is increased, the surface of the inner wall surface of the processed hole It is possible to prevent the roughness from being deteriorated. Moreover, since cutting resistance can be disperse | distributed compared with the case where the front-end | tip of the cutting blade 23 is sharp, it becomes possible to prevent chatter vibration and a defect | deletion. In addition, in the present embodiment, the cutting blades 23 are arranged so that the circumferential intervals are unduly divided, so that chatter vibrations are prevented even when the action of the cutting resistance becomes non-uniform and cancel each other out. Can do.

  Further, when the tool body 10 is sent in the tool tip direction of the axis O during machining, the nose R blade 23b having a predetermined radius of curvature first comes into contact with the prepared hole of the material to be cut. Concentration is suppressed, and it is possible to further prevent the cutting edge 23 from being damaged.

  The boring bar 10 as an embodiment of the cutting tool of the present invention has been described above, but the present invention is not limited to this and can be appropriately changed without departing from the technical idea of the present invention. For example, in this embodiment, the square surface 21b on the back side is in contact with the wall surface 16a facing the tool tip side of the mounting seat 16, but the square surface 21a on the front side is in contact with the wall surface 16a. It may be attached to. That is, since the insert 20 has the rectangular surfaces 21a and 21b on the front and back sides to be rotated by 90 °, both the front and back surfaces of the insert 20 can be used.

  Moreover, since the insert 20 is formed so as to be a target with respect to the surface passing through the midpoint of the two side ridges when viewed from the front, the insert 20 may be used after being rotated by 180 °. . Furthermore, since the cutting blades 23 are provided at both ends of the short side of each side surface 22, the cutting blades 23 may be attached to the tool body 10 whose tool rotation direction T is opposite.

It is a side view of the boring bar which is an embodiment of the present invention. It is the elements on larger scale of FIG. It is a front view of the boring bar which is an embodiment of the present invention. It is a perspective view of an insert. It is a front view of an insert. It is an A direction arrow directional view in FIG. It is a B direction arrow directional view in FIG.

Explanation of symbols

1 Boring bar (cutting tool)
DESCRIPTION OF SYMBOLS 10 Tool main body 15 Concave groove 16 Mounting seat 20 Insert 21 Square surface 22 Side surface 23 Cutting blade 23a Straight blade 23b Nose R blade 24 Flat part 25 Corner R part

Claims (2)

An insert is detachably mounted on a tool body that rotates about an axis, and is inserted into a prepared hole formed in the workpiece, and the inner wall surface of the prepared hole is cut to form a processed hole with a predetermined inner diameter. A cutting tool that
The insert has two rectangular surfaces and four side surfaces, a cutting edge is formed at a corner portion of the one side surface, and a boundary portion between the square surface and the other side surface adjacent to the one side surface A flat portion that forms a flat shape is formed, and an intersecting ridge line portion with the flat portion in the cutting blade is a straight blade,
A groove is formed in the outer peripheral portion of the tip of the tool body so as to open toward the tool tip side and the tool radial direction outer side, and a mounting seat is provided on the tool tip side of the groove,
The cutting tool, wherein the insert is mounted on the mounting seat so that the straight blade faces the outside in the tool radial direction and the straight blade is parallel to the axis.   A corner R portion having a predetermined radius of curvature is provided at a boundary portion between the flat portion and the quadrangular surface, and an intersecting ridge line portion of the cutting edge with the corner R portion is a nose R blade. The cutting tool according to claim 1.

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