JP2017217724A - Cutting edge replaceable drill - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely execute boring without generating disk-like chips even when a through-hole is formed by stacking materials to be cut.SOLUTION: An inner blade insert 5 and an outer blade insert 6 in which a rotation locus around the axis of a cutting edge 12 protruded to the tip of a drill body 1 are set continuous in the radial direction of the drill body 1 are detachably attached to at least two insert attaching seats 9 formed with a gap in a peripheral direction at the tip part of the columnar drill body 1 around an axis O. The cutting edge 12 of at least the outer peripheral part of the inner blade insert 5 and the cutting edge 12 of the outer blade insert 6 incline so as to extend toward a rear end side nearer to the outer peripheral side of the drill body 1. The cutting edge 12 of the outer blade insert 6 is formed into a polygonal line shape so that the inclination angle θ1 of the outer peripheral part of the cutting edge 12 to the axis O can be smaller than the inclination angle θ2 of the inner peripheral part of the cutting edge 12 to the axis O.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a blade-replaceable drill in which a cutting insert is detachably attached to a tip of a drill body to drill a work material.

  As such a blade-tip-replaceable drill, for example, in Patent Document 1, at least two drill inserts having a square plate-like insert body are attached to the tip end of the drill body, on the inner peripheral side and the outer peripheral side. Is described. These drill inserts have the above-mentioned insert body of the same shape and the same size, and one of the square surfaces is a rake face, and one cutting edge formed on a side ridge portion of the rake face is used as the tip of the drill body. The rotation trajectories around the drill body axis of each of the first cutting blades are attached so as to intersect each other.

JP 2009-262319 A

  However, in the cutting edge-exchangeable cutting tool described in Patent Document 1, the cutting edge has a first main cutting edge portion having a convex curve shape, and a linear second main portion in contact with the first main cutting edge portion. The angle formed by the second main cutting edge portion of the first cutting edge in the inner peripheral side insert with respect to the plane perpendicular to the axis of the drill body is 3 ° to 8 °, and the outer periphery. The angle formed by the second main cutting edge portion of the first cutting edge in the side insert with respect to the plane perpendicular to the axis of the drill body is 1 ° to 3 °, both of which are extremely small angles, In other words, the above-mentioned one cutting blade protruding from the tip end of the drill body of both inserts is arranged so as to be substantially positioned on a plane perpendicular to the axis of the drill body.

For this reason, if you try to drill a hole that forms a through-hole in a work piece such as a laminar plate using such a blade-tip replaceable drill, the pressing force by the cutting blade becomes too strong, so the first penetration When the hole is pulled out, a disk-shaped or Jinkasa-shaped chip with the same diameter as the hole diameter of the through hole is generated at the part between the bottom surface of the through hole and the next work material on the through side. Since it is interposed between the next work material while rotating, a phenomenon occurs that the next work material cannot be drilled.
Also, in drilling such as forming a through hole in the end of an automobile engine part, for example, a connecting rod, it is carried to the next process with disc-like chips adhering to the work material after drilling. There is a risk of frequent occurrence of abnormal clamping and the need to remove chips.

  The present invention has been made under such a background, and it is possible to reliably perform drilling without generating disk-shaped chips in a process of forming a through hole by overlapping work materials. The object is to provide a possible exchangeable drill.

  In order to solve the above problems and achieve such an object, according to the present invention, at least two insert mounting seats are formed at intervals in the circumferential direction at the tip of a cylindrical drill body centering on an axis. An inner blade insert and an outer blade insert in which the rotation trajectory around the axis of the cutting blade protruding from the tip of the drill body is made continuous in the radial direction of the drill body are attached to and detached from these insert mounting seats. The cutting blades of at least the outer peripheral portion of the inner blade insert and the cutting blades of the outer blade insert are extended toward the rear end side toward the outer peripheral side of the drill body. Among these, the cutting edge of the outer blade insert has an inclination angle formed by the outer peripheral portion of the cutting blade with respect to the axis, and an inclination formed by the inner peripheral portion of the cutting blade with respect to the axis. Corner Characterized in that it is formed in the remote becomes smaller polygonal line.

  In the blade type replaceable drill configured as described above, the cutting blade of at least the outer peripheral portion of the inner blade insert and the cutting blade of the outer blade insert are inclined so as to extend toward the rear end side toward the outer peripheral side of the drill body. Among them, the cutting edge of the outer blade insert is formed in a polygonal line shape in which the inclination angle formed by the outer peripheral portion with respect to the axis is smaller than the inclination angle formed by the inner peripheral portion with respect to the axis. When the through hole is pulled out, the portion between the bottom surface of the through hole and the side surface of the work material on the through side is cut so as to be gradually expanded from the inner peripheral side, and further the outer periphery of the through hole The part is cut without receiving a strong pressing force by the outer peripheral part whose inclination angle is smaller than the inner peripheral part of the cutting edge of the outer blade insert.

  In addition, the inner blade insert and the outer blade insert attached to at least two insert mounting seats spaced in the circumferential direction indicate the rotation trajectory around the axis of each cutting blade protruding from the tip of the drill body. Since the cutting edge of the outer blade insert is formed in a polygonal line, the outer blade insert is cut between the inner blade insert and the outer blade insert, and between the inner peripheral portion and the outer peripheral portion of the outer blade insert. Chips can be divided. For this reason, even when forming a through hole by stacking work materials, it is possible to prevent the generation of disc-shaped chips and to prevent the drilling from being hindered. Further, even when a through hole is formed at the end of the connecting rod, it is possible to prevent the attachment of disk-shaped chips and to prevent occurrence of abnormal clamping in the next process.

  Here, in order to make the cutting edge of the outer blade insert into a polygonal line in this way, at least the outer blade insert is formed in a rhombus plate shape, and the above-mentioned cutting blade is formed on the side ridge portion of the rhombus surface using the rhombus surface as a rake face. Then, the side ridge portion of the rhombus surface is bent into a convex shape, and the angle between the side ridge portions intersecting the acute angle portion of the rhombus surface is the acute angle of the side ridge portion connected to the obtuse angle portion. Forming the inner peripheral portion of the cutting edge of the outer blade insert at a side ridge portion connected to the obtuse angle portion of the rhombus surface, and forming the side of the acute angle portion of the rhombus surface What is necessary is just to form the said outer peripheral part of the cutting blade of the said outer blade insert in a ridge part. The cutting edge can be formed in a broken line shape on the acute angle side where the included angle of the side ridge portion of the rhomboid surface is increased and on the obtuse angle side where the included angle is smaller than this.

  In particular, when the outer blade insert is in the shape of a rhombus, the inner blade insert has a similar shape to the outer blade insert, except that the inner blade insert is formed larger than the outer blade insert. The life of the inner blade insert and the outer blade insert can be balanced due to the different peripheral speeds and the wear of the cutting blades. Furthermore, similarly, in order to balance the insert life, the inner blade insert may have a higher hardness than the outer blade insert.

  On the other hand, in order to make the rotation trajectories of the inner blade insert protruding from the tip of the drill body and the cutting blade of the outer blade insert continuous, first, the outer peripheral portion of the cutting blade of these inner blade inserts and the cutting of the outer blade insert. What is necessary is just to continue the said internal peripheral part of a blade in the shape of a straight line in the rotation locus | trajectory around the said axis line. Thus, even if the outer peripheral part of the cutting edge of the inner blade insert and the inner peripheral part of the cutting edge of the outer blade insert are made straight in the rotation locus, both inserts are spaced apart in the circumferential direction of the drill body. Chips can be broken into pieces.

  Similarly, in order to continue the rotation trajectories of the cutting blades of the inner blade insert and the outer blade insert, secondly, the inclination angle formed by the inner peripheral portion of the cutting blade of the outer blade insert with respect to the axis line, You may make larger than the inclination-angle which the said outer peripheral part of the cutting blade of the said inner blade insert makes with respect to the said axis line. Thus, even if the inclination angle formed by the inner peripheral portion of the cutting edge of the outer blade insert with respect to the axis is increased, the outer peripheral portion of the cutting blade of the outer blade insert is bent in a polygonal line with respect to the inner peripheral portion. Since the inclination angle formed with respect to the axis can be reduced, it is possible to prevent the occurrence of disk-like chips by preventing a large pressing force from acting when the through hole is pulled out.

  As described above, according to the present invention, it is possible to prevent a large amount of pressing force from acting on the work material when the through-hole is pulled out, and to prevent generation of disk-shaped chips. It is possible to achieve a smooth drilling process even when the work material is stacked, and even when a through hole is formed at the end of the connecting rod, It is possible to prevent a clamp abnormality or the like in the next process due to adhesion.

It is a side view which shows the 1st Embodiment of this invention. It is an enlarged front view of the cutting blade part of embodiment shown in FIG. It is an expanded side view which shows the rotation locus | trajectory of the inner blade insert of the embodiment shown in FIG. 1, and the periphery of an outer blade insert. It is a side view which shows the 2nd Embodiment of this invention. It is an enlarged front view of the cutting blade part of embodiment shown in FIG. It is an enlarged side view which shows the rotation locus | trajectory of the inner blade insert and outer blade insert of embodiment shown in FIG.

  1 to 3 show a first embodiment of the present invention. In the present embodiment, the drill body 1 is formed in a multi-stage columnar shape centering on the axis O with a metal material such as steel, and the rear end side (right side in FIG. 1) is the axis O on the outer peripheral surface of the column. 1 and a tip end side (left side in FIG. 1) is a cutting blade portion 3, and the most between the shank portion 2 and the cutting blade portion 3 is the shank portion 2. A flange 4 having a large truncated cone shape is formed.

  In such a blade-replaceable drill having the drill body 1, the shank portion 2 is usually held by the main spindle of the machine tool and is fed in the direction of the axis O while being rotated in the drill rotation direction indicated by T in the drawing. Then, drilling is performed on the work material by the inner blade insert 5 and the outer blade insert 6 attached to the distal end portion of the cutting blade portion 3. In the drill body 1, a coolant hole 7 having a constant inner diameter is formed along the axis O from the rear end to the front end side of the shank portion 2, and this coolant hole 7 is the front end portion of the cutting edge portion 3. In FIG. 2, the opening is branched into two with a small diameter, and at the time of drilling, the coolant is injected through the coolant hole 7 and supplied toward the inner blade insert 5 and the outer blade insert 6.

  On the outer periphery of the cutting edge portion 3, two chip discharge grooves 8 are provided on opposite sides of the axis O from the front end surface of the cutting edge portion 3 (the front end surface of the drill body 1) toward the rear end side. Is formed. The chip discharge groove 8 in the present embodiment is formed so as to cut out the outer peripheral portion of the cutting blade portion 3 in an L shape in a cross section orthogonal to the axis O, and the axis O except for the tip portion of the cutting blade portion 3. The groove wall surface facing the side opposite to the drill rotation direction T is cut out to the outer peripheral side in front of the flange portion 4.

  Moreover, in the front-end | tip part of the cutting-blade part 3, the groove wall surface which faces the opposite side to the drill rotation direction T of one chip discharge groove 8 (upper chip discharge groove 8 in FIG. 2) is the other as it goes to the front end side. The tip is inclined so as to extend toward the chip discharge groove 8 (the lower chip discharge groove 8 in FIG. 2), and is formed so as to slightly exceed the axis O at the tip surface of the cutting blade portion 3. On the other hand, the groove wall surface of the other chip discharge groove 8 facing away from the drill rotation direction T is concave on the one chip discharge groove 8 side at the tip of the cutting edge 3 as shown in FIG. After forming a concave curved surface, the drill body 1 is formed so as to extend to the outer peripheral side toward the tip side.

  Furthermore, insert mounting seats 9 are respectively formed at the end portions of the groove wall surfaces facing the drill rotation direction T side of the chip discharge grooves 8, and the inner blade insert 5 and the outer blade insert 6 are inserted into these inserts. The mounting seat 9 is detachably attached by a clamp screw 10. Each of these insert mounting seats 9 is a recess that is recessed in one step from the groove wall surface facing the drill rotation direction T side of the chip discharge groove 8 to the opposite side of the drill rotation direction T and opening to the tip surface of the cutting blade portion 3. A bottom surface 9a having a generally rhombus shape that faces the drill rotation direction T side and two wall surfaces 9b extending from the bottom surface 9a to the drill rotation direction T side are provided. The clamp screw 10 is provided on the bottom surface 9a. A screw hole to be screwed is formed.

  The inner blade insert 5 and the outer blade insert 6 attached to such an insert mounting seat 9 are formed in a substantially rhombic plate shape by a hard material such as cemented carbide having a hardness higher than that of the drill body 1. A mounting hole 11 through which the clamp screw 10 is inserted is opened at the center of the surface. Further, the inner blade insert 5 and the outer blade insert 6 of the present embodiment are inclined so that the side surfaces arranged around the both rhombus surfaces are directed toward the inner circumference side from one rhombus surface to the other rhombus surface. This is a positive type insert, and is attached to the insert mounting seat 9 with the one rhombus surface as the rake face in the drill rotation direction T.

  Further, a cutting edge 12 is formed on a side ridge portion of the one rhombus surface which is a rake face of the inner blade insert 5 and the outer blade insert 6. Here, each of the four side ridges of the one rhombus surface is formed in a bent line shape that is bent into a convex shape, and the included angle of the side ridge portion that intersects the acute angle corner of the one rhombus surface is an obtuse angle. The inner edge insert 5 and the outer edge insert 6 in the present embodiment are strictly an octagonal plate shape, and are formed so as to be larger than the included angle on the acute angle portion side of the side ridge portion connected to the corner portion. Is formed.

  The 1st cutting edge part 12a formed in the side ridge part connected to the obtuse angle part of one rhombus surface among the said cutting edges 12 is the 2nd cutting edge part formed in the side ridge part which cross | intersects an acute angle corner part. A corner blade 12c having a convex curve shape such as a convex arc in contact with the two second cutting blade portions 12b is formed at the corner portion of the two second cutting blade portions 12b which is longer than 12b and intersects the acute angle portion. Is formed. Further, the inner blade insert 5 and the outer blade insert 6 have similar shapes, but the size of the inner blade insert 5 is larger than that of the outer blade insert 6 in this embodiment.

  The inner blade insert 5 and the outer blade insert 6 as described above have the other rhombus surface opposite to the one rhombus surface, which is a rake face, in close contact with the bottom surface 9a of the insert mounting seat 9, and one of the rhombus surfaces 1 The side surfaces connected to the two first cutting edge portions 12 a extending in the direction intersecting the two acute angle corner portions are brought into contact with the two wall surfaces of the insert mounting seat 9 and are seated on the insert mounting seat 9. Then, the clamp screw 10 inserted through the mounting hole 11 as described above is screwed into the screw hole of the bottom surface 9a, thereby being pressed against the bottom surface 9a and pressed against the two wall surfaces 9b so as to be detachably attached.

  As shown in FIG. 3, the inner blade insert 5 and the outer blade insert 6 attached to the insert mounting seat 9 project one cutting blade 12 from the tip surface of the cutting blade portion 3 as shown in FIG. The rotation trajectories of the two cutting blades 12 around the axis O are arranged so as to continue in the radial direction until they slightly protrude from the axis O to the outer periphery of the cutting blade portion 3.

  Furthermore, at least the outer peripheral portion of the drill body 1 of the cutting blade 12 of the inner blade insert 5 and the cutting blade 12 of the outer blade insert 6 are inclined so as to extend toward the rear end side toward the outer peripheral side of the drill main body 1. At the same time, the cutting blade 12 of the outer blade insert 6 is formed in the shape of a broken line that is bent into a convex shape as described above, and the cutting edge 12 of the cutting blade 12 at the outer peripheral portion of the drill body 1 is formed. The inclination angle θ1 with respect to the axis O of the two cutting edges 12b is arranged to be smaller than the inclination angle θ2 with respect to the axis O of the first cutting edge 12a in the inner peripheral portion.

  Accordingly, the tip angle of the second cutting edge portion 12b in the outer peripheral portion of the cutting blade 12 of the outer blade insert 6 is also made smaller than the tip angle of the first cutting edge portion in the inner peripheral portion. The tip angle is defined as an angle when the cutting blade 12 is projected in parallel on a plane parallel to the axis O of the drill body 1 and is opposite to each other in the radial direction of the drill body 1 as in the present embodiment. When the inner blade insert 5 and the outer blade insert 6 are respectively disposed on the side, that is, one side, the rotation trajectory around the axis O of each cutting blade 12 of the inner blade insert 5 and the outer blade insert 6 is along the axis O. It is possible to make the included angle in a flat plane.

  Here, in the present embodiment, the inner blade insert 5 has the second cutting blade portion 12b out of the cutting blade 12 protruding from the tip, and the corner blade 12c connected to the second cutting blade portion 12b is positioned on the axis O. The first cutting edge portion 12a, which is disposed on the inner peripheral side of the drill body 1 so as to extend on a plane perpendicular to the axis O, and therefore bends convexly with respect to the second cutting edge portion 12b, As it goes to the outer peripheral side of the drill main body 1, it is inclined so as to go to the rear end side. In addition, one rhombus surface used as the rake face of the inner blade insert 5 is located on a plane including the axis O.

  On the other hand, in the present embodiment, the outer blade insert 6 has a first cutting edge portion 12a disposed on the inner peripheral side of the drill body 1 among the cutting blades 12 protruding from the tip opposite to the inner blade insert 5, The inclination angle θ1 with respect to the axis O of the second cutting edge portion 12b bent in a convex shape with respect to the first cutting edge portion 12a is made smaller than the inclination angle θ2 with respect to the axis O of the first cutting edge portion 12a. The corner blade 12c in contact with the two cutting edge portions 12b is disposed so as to protrude from the outer peripheral surface of the cutting edge portion 3 to the outer peripheral side. In addition, one rhombus surface used as the rake face of this outer blade insert 6 is a flat outer blade insert 6 side where the corner blade 12c of the outer peripheral end contains the axis line O in which the rake surface of the inner blade insert 5 is located. Is located in parallel with the axis O so as to be slightly toward the drill rotation direction T as it goes toward the inner peripheral side of the drill body 1, thereby drilling the outer blade insert 6. The cutting edge 12 used in is provided with a negative radial rake angle.

  Furthermore, in this embodiment, the 1st cutting blade part 12a located in the outer peripheral part of the inner blade insert 5 and the 1st cutting blade part 12a located in the inner peripheral part of the outer blade insert 6 are as shown in FIG. Are arranged so as to be continuous in a straight line in the rotation locus around the axis O. Here, in the first cutting edge portion 12a of the inner blade insert 5 and the outer blade insert 6 that are continuous in this manner, the obtuse angle portion side portion of one rhombus surface partially overlaps in the rotation locus around the axis O in this embodiment. However, the length of the overlapping portion is shorter than the length of the first cutting edge portion 12a of the inner blade insert 5 and the outer blade insert 6 of the non-overlapping portion.

  When drilling a work material using the blade tip replaceable drill configured as described above, the one cutting blade of the inner blade insert 5 and the outer blade insert 6 disposed at intervals in the circumferential direction. Of course, the one cutting blade 12 is formed by the first and second cutting blade portions 12a and 12b that are bent in a convex shape in the present embodiment. Therefore, the chips can be divided also by the individual inner blade insert 5 and the outer blade insert 6. For this reason, improvement in chip disposal can be achieved and smooth drilling can be performed.

  Further, in the blade-tip replaceable drill having the above-described configuration, the rear end of the first cutting edge portion 12a on the outer peripheral portion of the inner blade insert 5 and the cutting blade 12 of the outer blade insert 6 moves toward the outer peripheral side of the drill body 1. Since it inclines so that it may go to the side, when forming a through-hole by overlapping a cut material, it can form so that the opening part of a through-hole may be gradually extended from an inner peripheral side. Therefore, even when the through hole is pulled out, it is possible to avoid a strong pressing force from acting on a portion between the bottom surface of the through hole and the side surface of the work material on the through side.

  Further, among these, the one cutting blade 12 of the outer blade insert 6 is formed by the first and second cutting blade portions 12a and 12b that are bent in a convex shape, and is a second cutting blade that becomes the outer peripheral portion. The inclination angle θ1 with respect to the axis O of the part 12b is made smaller than the inclination angle θ2 with respect to the axis O of the first cutting edge part 12a serving as the inner peripheral part. For this reason, the pressing force which acts on the work material can be further reduced in the final stage when the second cutting edge portion 12b of the outer blade insert 6 passes through the work material.

  Therefore, according to the blade-tip-exchangeable drill having the above-described configuration, it is possible to reliably prevent the disk-shaped chips from coming out of the work material by such pressing force, and to smoothly smooth the stacked work materials without any trouble. A through hole can be formed. Also, for example, in drilling such as forming a through hole at the end of a connecting rod in an engine part of an automobile, it is possible to prevent disc-like chips from adhering to the work material after drilling, It is possible to prevent the manufacturing operation from being interrupted due to the occurrence of a clamp abnormality or the like when a part to which such chips are attached is carried to the next process. In addition, by reducing the inclination angle θ1 with respect to the axis O of the second cutting edge portion 12b in this way, it is possible to prevent burrs from occurring at the periphery of the opening portion of the through hole.

  Further, in this embodiment, at least the outer blade insert 6 is formed in a rhombus plate shape, and the cutting blade 12 is formed on the side ridge portion of the rhombus surface with the rhombus surface as a rake face. 12 is formed so that the included angle at the portion intersecting the acute angle portion of the rhomboid surface of the side ridge portion is larger than the included angle on the acute angle portion side of the portion connected to the obtuse angle portion. Thus, it is formed in a polygonal line shape bent in a convex shape.

  Of these, the portion connected to the obtuse angle portion is arranged as the first cutting edge portion 12a on the inner peripheral portion of the drill body 1 in the outer blade insert 6, and the portion intersecting the acute angle portion is the second cutting edge portion 12b. As shown in FIG. Accordingly, the outer blade insert 6 can also more reliably prevent the generation of disk-like chips as described above by making the inclination angle θ1 with respect to the axis O of the outer peripheral portion of the cutting blade 12 smaller than the inner peripheral portion.

  Furthermore, in this embodiment, the inner blade insert 5 is also formed in a rhombus plate shape, and has a similar shape to the outer blade insert 6, but its size is larger than that of the outer blade insert 6. For this reason, since the length of the cutting blade 12 is longer in the inner blade insert 5 than in the outer blade insert 6, the cutting speed is such that the peripheral speed is slow and the work material is scraped off because the radius from the axis of the drill body 1 is small. Therefore, the insert replacement time can be adjusted by balancing the lifespan between the inner blade insert 5 in which the progress of wear is fast and the outer blade insert 6 in which the progress of wear is slow.

  However, in this embodiment, the inner blade insert 5 is made larger than the outer blade insert 6 as described above. However, if the inner blade insert 5 and the outer blade insert 6 have the same shape and the same size, the inner blade insert 5 The two cutting blades 12 can be used as the outer blade insert 6, and the cutting blade 12 with the entire circumference of the diamond-shaped surface that is raked with one insert can be used. It becomes possible.

  In order to balance the insert life in this way, the inner blade insert 5 with fast wear may be harder than the outer blade insert 6 with slow progress. Here, in order to make the inner blade insert 5 harder than the outer blade insert 6 in this way, for example, the insert material type of the inner blade insert 5 itself is harder than the insert material type of the outer blade insert 6. What should I do?

  In addition to or in place of this, the hard coating of the inner blade insert 5 is applied to the outer blade insert 6 with the hard coating coated on the surfaces of the inner blade insert 5 and the outer blade insert 6 with the same insert material type. It may be made harder than the hard coating. Furthermore, the inner blade insert 5 may be coated with a hard coating while the outer blade insert 6 may not be coated.

  Furthermore, in order to make the rotation locus | trajectory of the cutting blade 12 of the inner blade insert 5 and the cutting blade 12 of the outer blade insert 6 continue as mentioned above, it is an outer peripheral part in the cutting blade 12 of the inner blade insert 5 in this embodiment. It arrange | positions so that the rotation locus | trajectory of the 2nd cutting blade part 12b and the 1st cutting blade part 12a which is the inner peripheral part in the cutting blade 12 of the outer blade insert 6 may extend in a straight line form. And even if the 2nd cutting blade part 12b of the inner blade insert 5 and the 1st cutting blade part 12a of the outer blade insert 6 extend in a straight line in the rotation locus in this way, the inner blade insert 5 and the outer blade insert 6 Are disposed at intervals in the circumferential direction, so that the chips produced by the first and second cutting edge portions 12a and 12b can be divided and processed satisfactorily.

  However, instead of arranging the outer peripheral portion of the cutting blade 12 of the inner blade insert 5 and the inner peripheral portion of the cutting blade 12 of the outer blade insert 6 in a straight line in the rotation locus around the axis O in this way, FIG. Like the blade-exchangeable drill of the second embodiment of the present invention shown in FIG. 6, the inclination angle θ12 of the cutting blade 12 of the outer blade insert 6 with respect to the axis O at the inner periphery of the drill body 1 is set to the inclination angle θ12 of the inner blade insert 5. The rotation trajectory of the cutting blades 12 may be made continuous after the inclination angle θ11 of the cutting blade 12 with respect to the axis O in the outer peripheral portion of the drill body 1 is made larger. In the second embodiment shown in FIGS. 4 to 6, the same reference numerals are assigned to the same parts as those in the first embodiment shown in FIGS.

  That is, in the second embodiment, one cutting edge 12 of the outer blade insert 6 protruding from the tip of the drill body 1 is inclined so as to go to the rear end side as it goes to the outer peripheral side of the drill body 1 as a whole. However, the inclination angle θ12 with respect to the axis O of the first cutting edge portion 12a of the inner peripheral portion of the drill body 1 in the cutting blade 12 of the outer blade insert 6 is the drill main body in the cutting blade 12 of the inner blade insert 5. It is set larger than the inclination angle θ11 with respect to the axis O of the second cutting edge portion 12b of one outer peripheral portion. In this embodiment, the first cutting edge portion 12a of the outer blade insert 6 has an inner blade slightly in front of the obtuse angle portion of the rhombic surface where the first cutting edge portion 12a is connected in the rotation locus around the axis O in this embodiment. It intersects with the second cutting edge portion 12b of the insert 5.

  Further, in the second embodiment, the chip discharge groove 8 is formed in a spiral shape so as to be twisted in the direction opposite to the drill rotation direction T toward the rear end side of the drill body 1, and the rear end thereof is a ridge. The tip end surface of the portion 4 having the shape of a truncated cone is cut off to the outer peripheral side. Further, the bottom surface excluding both ends in the circumferential direction of the chip discharge groove 8 is recessed so as to form a concave curve in a cross section perpendicular to the axis O on the rear end side of the insert mounting seat 9.

  Furthermore, in the present embodiment, the coolant hole 7 has a constant inner diameter having a large diameter in the shank portion 2 and extends along the axis O from the front side of the flange portion 4 to a constant inner diameter having a medium diameter. The tip branches off to a small diameter and opens to the chip discharge groove 8. Also, the diamond-shaped surface that is the rake face of the outer blade insert 6 of the present embodiment is slightly more in the drill rotation direction T than the extended surface of the diamond-shaped surface that is the rake face of the inner blade insert 5 toward the outer blade insert 6 side. It is located on the side and is arranged parallel to the rake face of the inner blade insert 5.

  Also in the blade-tip-exchangeable drill of the second embodiment configured as described above, at least the outer peripheral portion of the inner blade insert 5 among the cutting blades 12 protruding from the tip of the drill body 1 as in the first embodiment. The first cutting edge portion 12a and the cutting edge 12 of the outer cutting edge insert 6 are inclined so as to go to the rear end side toward the outer peripheral side, and the cutting edge 12 protruding from the tip of the drill body 1 of the outer cutting insert 6 is The first cutting edge portion 12a on the inner peripheral portion and the second cutting edge portion 12b on the outer peripheral portion are bent in a polygonal line shape, and the second cutting edge portion 12b has an axis O smaller than the first cutting edge portion 12a. Since the inclination angle θ13 is provided, even when a through-hole is formed, the generation of disc-like chips is prevented, and a smooth hole can be obtained even when a work material is stacked or a drilling process such as an end of a connecting rod is performed. Dawn processing can be performed.

  Further, in the present embodiment, the inclination angle θ12 with respect to the axis O of the first cutting edge 12a of the cutting edge 12 of the outer cutting insert 6 is set to the axis O of the first cutting edge 12a of the cutting edge 12 of the inner cutting insert 5. Since the rotation locus of the first cutting edge portion 12a of the inner blade insert 5 and the outer blade insert 6 is made continuous after the inclination angle θ11 is made larger, conversely, the cutting edge 12 of the outer blade insert 6 As in the case where the inclination angle θ12 with respect to the axis O of the first cutting edge portion 12a is made smaller than the inclination angle θ11 with respect to the axis O of the first cutting edge portion 12a of the cutting edge 12 of the inner blade insert 5, It is possible to avoid the obtuse angle portion of the rhombus surface, which is one of the rake surfaces of the blade insert 5 and the outer blade insert 6, from protruding toward the tip side of the drill body 1.

  Therefore, the work material cut on the inner peripheral side from the projecting obtuse angle portion is not pushed out into a disk shape when the through hole is pulled out, and smoother drilling can be performed more reliably. It becomes possible. Such an effect can be similarly obtained in the first embodiment in which the rotation trajectories of the first cutting edge portion 12a of the outer blade insert 6 and the second cutting edge portion 12b of the inner blade insert 5 are aligned. it can. Here, the inclination angles θ11 to θ13 of the second embodiment and the inclination angles θ1 and θ2 of the first embodiment satisfy θ1 <θ2 and θ13 <θ11 <θ12 in the range of 50 ° to 75 °. desirable.

  Moreover, in this 2nd Embodiment, since the chip discharge groove 8 is formed in the spiral shape, the chip discharge effect by rotation of the drill main body 1 is high, and also the bottom face of the chip discharge groove 8 is a cross-sectional concave curve shape. Therefore, the capacity for accommodating chips can be increased, and good chip disposal can be obtained. Furthermore, since the chip discharge groove 8 extends to the flange part 4, it is possible to discharge the chip even if the entire length of the cutting blade part 3 is made to penetrate the work material. Furthermore, since the coolant hole 7 has a large diameter in the shank portion 2, the coolant can be efficiently supplied with the large diameter portion as an oil reservoir.

  In these first and second embodiments, only one of the two inserts of the inner blade insert 5 and the outer blade insert 6 is attached to the distal end portion of the drill body 1, and one cutting blade protruding from the distal end thereof. The rotation trajectories of the 12 cutting blades of the inner blade insert 5 and the outer blade insert 6 are separated from each other in the radial direction. Alternatively, the cutting blades of a plurality of intermediate inserts may be arranged on the rotation locus so that the cutting blades are continuous.

  Furthermore, chip breakers having different shapes may be formed on the rhombic surfaces that are the rake faces of the inner blade insert 5 and the outer blade insert 6, for example, depending on the peripheral speed thereof. Furthermore, in these 1st, 2nd embodiment, although the inner blade insert 5 and the outer blade insert 6 are formed in the rhombus plate shape, the shape of the one cutting blade 12 which protrudes at the front-end | tip of the drill main body 1 is shown. If these are the same, as these inner blade insert 5 and outer blade insert 6, for example, a square plate-like insert as described in Patent Document 1 may be used.

DESCRIPTION OF SYMBOLS 1 Drill main body 2 Shank part 3 Cutting edge part 4 Gutter part 5 Inner blade insert 6 Outer blade insert 7 Coolant hole 8 Chip discharge groove 9 Insert mounting seat 10 Clamp screw 11 Mounting hole 12 Cutting edge 12a 1st cutting edge part 12b 2nd Cutting edge portion 12c Corner blade O Axis line of drill body 1 Drill rotation direction θ1, θ2, θ11 to θ13 Inclination angle of first and second cutting edge portions 12a and 12b of cutting edge 12 with respect to axis O

Claims (6)

At least two insert mounting seats are formed at the distal end portion of a cylindrical drill body centering on the axis at intervals in the circumferential direction, and these insert mounting seats have cutting edges protruding from the tip of the drill body. An inner blade insert and an outer blade insert in which the rotation trajectory around the axis of the blade is made continuous in the radial direction of the drill body are detachably attached,
The cutting blades of at least the outer peripheral portion of the inner blade insert and the cutting blades of the outer blade insert are inclined so as to extend toward the rear end side toward the outer peripheral side of the drill body, respectively.
Among these, the cutting blade of the outer blade insert is a broken line in which the inclination angle formed by the outer peripheral portion of the cutting blade with respect to the axis is smaller than the inclination angle formed by the inner peripheral portion of the cutting blade with respect to the axis. A blade-type replaceable drill characterized by being formed into a shape. At least the outer blade insert has a rhombus plate shape, the rhombus surface is a rake face, and the cutting edge is formed on the side ridge portion of the rhombus surface,
The side ridge portion of the rhombus surface is bent in a convex shape, and the included angle of the side ridge portion intersecting the acute angle corner portion of the rhombus surface is the acute angle corner side of the side ridge portion continuous with the obtuse angle corner portion Formed larger than the included angle of
The inner peripheral portion of the cutting edge of the outer blade insert is formed on the side ridge portion that is continuous with the obtuse angle portion of the rhombus surface, and the cutting edge of the outer blade insert is formed on the side ridge portion of the acute angle portion of the rhombus surface The cutting edge exchanging type drill according to claim 1, wherein the outer peripheral portion is formed.   3. The blade tip replaceable drill according to claim 1, wherein the inner blade insert and the outer blade insert have a similar shape, and the inner blade insert is larger than the outer blade insert.   4. The blade tip replaceable drill according to claim 1, wherein the inner blade insert has higher hardness than the outer blade insert. 5.   2. The outer peripheral portion of the cutting blade of the inner blade insert and the inner peripheral portion of the cutting blade of the outer blade insert are continuous in a straight line in a rotation locus around the axis. The blade tip replaceable drill according to any one of claims 1 to 4.   The inclination angle formed by the inner peripheral portion of the cutting blade of the outer blade insert with respect to the axis is larger than the inclination angle formed by the outer peripheral portion of the cutting blade of the inner blade insert with respect to the axis. The blade-tip-exchangeable drill according to any one of claims 1 to 4, wherein:

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