JPH09290311A - Throwaway type drilling tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a chip disposal performance in drilling by prompting the division in the width direction of a chip, of cause, and the efficient division in its longitudinal direction. SOLUTION: Inner/outer circumferential side cutting edge tips 16A, 16B mounted on the tip of a tool main body 11 are crossed each other in a projection shape respectively and formed in a flat hexagonal plate having a pair of mutually parallel short side for combining the long side which is mutually facing two pairs of cutting edges with these ends 18a, 18b and an inner circumferential side cutting edge tip 16A is arranged so that the inner circumferential end 18a of the cutting edge is made in an over center beyond a tool axis O. Further, an outer periphery side cutting edge tip 16B is arranged so that the outer periphery end 18b of the cutting edge is projected to a tool outer periphery side and the outer periphery side cutting edge 18B of the inner circumferential side cutting edge tip 16A and the inner circumferential side cutting edge 18A of the outer periphery side cutting edge tip 16B are arranged so as to be crossed each other in the rotation locus around the axis O.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has cutting edge chips removably attached to the inner peripheral side and the outer peripheral side of the tip of a tool body, and the cutting edges formed on these cutting edge chips are used to cut a work material. The present invention relates to a throw-away type drilling tool for making holes.

[0002]

2. Description of the Related Art Generally, it is well known that chips are generated when cutting metal or non-ferrous metal. In order to efficiently obtain the required shape, size, accuracy, etc. by processing the work material as the first purpose, how to generate and control these chips that are ultimately unnecessary Stable, safe, and reliable processing is often the key to achieving this goal. In response to the demands of the times such as high speed, high efficiency, unmanned operation, continuous operation, safety and health accompanying the progress of cutting technology, such chip disposal has become an indispensable technology. ing.

However, various factors are involved in the chip formation process and cannot be dealt with by a uniform solution. For example, factors such as the material of the work material, hardness,
Strictly considering the material of the cutting tool, the shape of the cutting tool, the shape of the cutting edge of the cutting tool, the friction coefficient, the cutting conditions, the presence and composition of cutting fluid, the pressure and capacity, the structure and rigidity of the machine, etc. There is no. Further, particularly in the case of a drilling tool for making a hole in a work material, severer conditions are added as compared with the processing forms by other cutting tools. This means that the chip discharge space is limited, and that chips must be discharged quickly and smoothly from the inside of the machined hole. If these conditions are not fully satisfied, immediate Machining becomes impossible and tool damage is caused.

[0004]

FIG. 12 shows an example of a twist drill generally used for drilling of this kind. The twist drill is a tool body 1 having a substantially cylindrical shape. A pair of spiral chip discharge grooves 2 and 2 are formed at the tip of the chip, and these chip discharge grooves 2 and 2 are formed.
2 has cutting edges 3 and 3 formed at the tip thereof, and while the tool body 1 is rotated around its central axis O and is fed in the direction of the axis O, a machined hole H is formed in the workpiece W.
To form. However, the chips C generated by such a twist drill are, as shown in the figure, continuous and relatively long ones in a spiral shape or a spiral shape, and are swung along with the rotation of the tool body 1 to be slewed by the tool body 1 or a work material. May get entangled in the and may interfere with smooth processing. Further, in order to divide the chip C in the lengthwise direction, it is necessary to stop the feeding of the tool body 1 in the direction of the axis O or perform operations such as step feed and inching to retract the tool body 1 once. It is unavoidable that it becomes complicated.

On the other hand, FIGS. 13 and 14 show the tool body 4
A pair of diamond-shaped throw-away inserts 5 at the tip of the
5 shows the tip end of a throw-away type drilling tool which is attached as a cutting blade tip. Here, in this throw-away type drilling tool, the pair of throw-away tips 5 and 5 are arranged so as to be offset from each other on the inner peripheral side (central axis O side) and the outer peripheral side of the tip portion of the tool body 4. The cutting edge chip 5A on the inner peripheral side and the cutting edge chip 5B on the outer peripheral side divide the inner peripheral side and the outer peripheral side of the processing hole H so as to cut the chips C as shown in FIG.
Can be generated in the state of being divided into two in the width direction.

However, even in such a throw-away type drilling tool, it is not possible to effectively divide the length of the chip C, and it is necessary to rely on the above-mentioned operations such as step feed and inching, or throwing. A chip breaker must be formed along the cutting edge of the away chips 5 and 5 so that the chips can be bent and divided. However, in the case of the former, the work is complicated as described above, while in the case of the latter, the cutting performance of the chips is influenced by the performance of the chip breaker, and the applicable range of cutting conditions is limited. The problem arises.

In view of the above background, the present invention promotes efficient cutting not only in the width direction of chips but also in the longitudinal direction thereof to improve the chip processing performance in drilling. The first purpose is to further improve the precision of the cut surface and expand its adaptability.

[0008]

SUMMARY OF THE INVENTION In order to solve the above problems and achieve the above object, the present invention has a pair of chip discharge grooves formed on the outer periphery of the tip of a substantially cylindrical tool body. In a throw-away type drilling tool in which an inner peripheral side cutting edge tip and an outer peripheral side cutting edge tip are detachably attached to the tip mounting seat formed at the tip of the chip discharge groove, respectively, A flat hexagon that has two pairs of long sides that intersect each other in a convex shape and that face each other, and that have a pair of short sides that are parallel to each other and that connect the ends of these two pairs of long sides. And a cutting blade is formed on each of the two pairs of long side portions, and a pair of cutting blades of these two pairs of cutting blades are formed so that their intersections protrude toward the tip side of the tool body. The inner cutting edge tip above the The inner peripheral ends of the pair of cutting blades are arranged so as to be over-centered beyond the central axis of the tool body, and the outer peripheral side cutting blade tip is such that the outer peripheral ends of the pair of cutting blades are the tip of the tool body. Arranged so as to project to the outer peripheral side of the part, and the outer peripheral side cutting edge of the pair of cutting blades of the inner peripheral side cutting blade tip, and the pair of cutting blades of the outer peripheral side cutting blade tip The cutting edge on the inner peripheral side is arranged so as to intersect with each other in the rotation locus around the central axis.

However, according to the drilling tool thus constructed, the chips are divided in the width direction between the inner peripheral side and the outer peripheral side of the machined hole by the inner peripheral side cutting edge tip and the outer peripheral side cutting edge tip. Of course, the pair of cutting edges used for cutting each cutting edge tip intersect in a convex shape, and the intersection point is projected toward the tool tip side, and further the inner circumference side cutting edge tip Since the rotation loci around the central axis of the cutting edge on the outer peripheral side and the cutting edge on the inner peripheral side of the outer peripheral side cutting edge tip intersect, chips that are divided in the width direction between the inner peripheral side and the outer peripheral side are Further, the pair of cutting blades further divides in the width direction. Moreover, the pair of cutting blades intersect each other in a convex shape, so that chips at each cutting blade tip out in a direction in which they collide with each other and interfere with each other, whereby the chips are bent in the longitudinal direction and divided into smaller pieces. Will be done. Further, by forming the cutting blade tip into a flattened hexagonal shape as described above, the cutting blade tip can be made smaller than when using, for example, a regular hexagonal throw-away tip, and effective use of the chip material. Can be achieved.

Here, in order to surely bring out the effect of dividing the above-mentioned chips in the longitudinal direction and to promote stable cutting, in order to promote stable cutting, the cutting edge tip on the inner peripheral side from the central axis in the radial direction of the tool main body. The ratio of the distance to the intersection of the pair of cutting edges and the distance from the central axis to the intersection of the pair of cutting edges of the outer peripheral side cutting edge tip is 1: 1.2-1:
It is desirable to set it in the range of 1.8. This is, as the position of the rotation locus of both intersections approaches such that the ratio of the distance from the central axis to the intersection of the cutting edges of the inner and outer cutting edges falls below the above range, the inner peripheral side of the outer cutting edge tip The width of the chips generated by the cutting edge and the cutting edge on the outer peripheral side of the inner cutting edge tip becomes too small, and the cutting effect due to the interference with the chips generated by the cutting edge on the opposite side is fully achieved. On the other hand, if the above ratio exceeds the above range, the outer peripheral cutting edge tip is too biased toward the outer peripheral side, the balance of the cutting load between the inner peripheral cutting edge tip is lost, and the cutting stability is improved. This is because there is a risk of damage.

Further, in order to further ensure the division of the chips in the longitudinal direction, it is desirable to form a chip breaker on the cutting edge chip along the pair of cutting edges used for cutting, and a tool. Considering the generation rate of chips on the inner and outer circumferences of the main body, it is desirable that the chip breaker exerts a progressively larger cutting force on the chips from the inner circumference side to the outer circumference side of the tool body. Further, in order to prevent the cutting edge tip from being damaged, it is desirable to form a nose round blade at the inner peripheral side end and the outer peripheral side end of the pair of cutting blades of the cutting blade tip. In this case, if the amount of overcenter at which the inner peripheral edge of the cutting edge of the inner peripheral side cutting edge exceeds the central axis is set to be equal to or less than the radius of the nose radius blade, the cutting speed becomes 0, which is the largest. On the central axis of the tool body where the cutting load acts, the nose-Rear part of the inner cutting edge tip will be located, and it is possible to prevent the cutting edge tip from being damaged due to such a large cutting load. it can.

On the other hand, a nose round blade is formed at the outer peripheral side end portions of the pair of cutting blades, and the outer peripheral side cutting blade tip is formed such that the short side connecting to the nose round blades goes toward the rear side in the axial direction. By arranging the nozzle so as to be inclined toward the inner peripheral side, the short side of the nose round blade or the tip continuous with this acts as a sub-cutting edge, and the precision of the finished surface of the inner periphery of the machined hole can be improved. Here, the inclination angle formed by the short side with respect to the axial direction is preferably set in the range of 0 ° 10 ′ to 5 °, and when the inclination angle exceeds this range, the auxiliary cutting edge is used. On the other hand, when the inclination angle is less than this range, the short side is strongly pressed against the inner circumference of the machined hole when the tool body is twisted, bent, or tilted due to the load during cutting. On the contrary, the cutting resistance may increase.

Further, in order to effectively cool and lubricate the pair of cutting blades of each cutting blade tip used for cutting,
Forming a pair of cutting oil supply paths in the tool body, the tip of each of these supply paths, at least on the wall surface of the pair of chip discharge groove, the inner cutting edge chip and the outer cutting edge chip It is desirable that the cutting oil be formed so as to open toward the pair of cutting blades, whereby the cutting fluid can be efficiently supplied by being concentrated on the pair of cutting blades.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1 to 7 show an embodiment of the present invention. In this embodiment, the tool body 11 has a substantially columnar shape as shown in FIGS. 1 and 2, and a shank 12 for attaching the tool body 11 to a spindle of a machine tool is formed at a rear end of the tool body 11. On the outer periphery of the tip portion, a pair of chip discharge grooves 13, 13 having a substantially V-shaped cross section are provided on opposite sides of the center axis O of the tool body 11 from the tip of the tool body 1 to the axis O.
Is formed so as to extend in parallel with. Further, on the rear end side of the tip end portion of the tool main body 11, in front of the shank 12, a disc-shaped flange portion 14 is formed so as to be expanded in diameter by one step.
The front end surface of the flange portion 14 is formed in a conical surface shape whose diameter gradually increases toward the rear end side, and the rear end portion of the chip discharge grooves 13, 13 is formed in the flange portion 14 Is formed so as to cut up toward the outer peripheral side along the cone formed by the tip surface of the.

Furthermore, chip mounting seats 15A and 15B are formed at the tip of the wall surfaces 13A and 13A facing the tool rotation direction T side of the chip discharge grooves 13 and 13 so as to be recessed from the wall surfaces 13A and 13A by one step. As the cutting edge tips, the throw-away tips 16 and 16 are detachably attached to the tip attachment seats 15A and 15B by the clamp screws 17, respectively. Here, these tip mounting seats 15A and 15B are formed at positions asymmetric to each other in the radial direction with respect to the axis O of the tool body 11, that is, one tip mounting seat 15A is the tool body 1
1 is formed so as to deviate to the inner peripheral side of the tool 1 so as to cross the axis O, and the other tip mounting seat 15B is deviated to the outer peripheral side of the tool body 11 and open to the outer periphery of the tip end portion of the tool body 11. Has been formed.

On the other hand, these chip mounting seats 15A, 15
The throw-away tip 16, 16 attached to B
Is a positive throw-away tip of the same shape and size, which is made of a hard material such as cemented carbide and has a flattened hexagonal flat plate shape as shown in FIGS. 4 and 5. That is, this flat throw-away tip 16
The upper surface 16a, which is a rake face, connects two pairs of long sides of equal length that intersect each other at an intersection point P at an obtuse angle α in a convex shape and the ends of these two pairs of long sides. A virtual line A having a pair of parallel short sides and having equal lengths and connecting the intersection points P and P of the two pairs of long sides to each other, and a virtual line connecting the midpoints of the pair of short sides. It is formed so as to be symmetrical with respect to B as well. In other words, the upper surface 16a has a hexagonal shape crushed in the direction of the imaginary line A, or a barrel shape centered on the imaginary line B.

The cutting edges 18 are formed on the two pairs of long sides of the upper surface 16a of the throw-away tip 16, respectively.
Are formed. Further, nose-round blades are provided at the corners of the upper surface 16a, that is, at the intersections P and P and at the intersections of the long sides and the short sides (ends 18a and 18b of the cutting edge 18), respectively. 19 are formed so as to be in contact with each side smoothly, and the radius R thereof is 0.2 m in this embodiment.
It is set in the range of m to 2.0 mm. In addition, in the present embodiment, these short sides and the long sides (cutting edge 18) that are continuous with these short sides.
The angle of intersection with and is also set to the angle α, so this angle α is 120 °.

The lower surface 16b, which is a seating surface on the side opposite to the upper surface 16a, has a flat hexagonal shape that is a little smaller than the upper surface 16a, and is between the upper and lower surfaces 16a, 16b. The side surfaces 16c, which are arranged and serve as flanks, are formed to incline inward with a clearance angle β as shown in FIG. 5 from the upper surface 16a side toward the lower surface 16b side. Furthermore, the virtual line A,
From the intersection of B, that is, the central portion of the upper surface 16a, the mounting hole 16d into which the clamp screw 17 is inserted is inserted.
However, it is formed so as to penetrate the throw-away tip 16 in the thickness direction thereof toward the central portion of the lower surface 16b.

Furthermore, this throw-away tip 1
A grooved chip breaker 20 is formed on the upper surface 16a of No. 6 along the cutting edges 18 formed on the two pairs of long sides. Here, this chip breaker 2
0 is formed to be curved in an arc shape with respect to the upper surface 16a in a cross section orthogonal to the cutting edge 18, and the width in the direction orthogonal to the cutting edge 18 is set to a pair of long sides intersecting with each other. Regarding the pair of formed cutting edges 18, 18, as shown in FIG. 3, from the one end portion 18a side to the other end portion 18b side through the intersection point P (in the counterclockwise direction around the mounting hole 16d in FIG. 3). The throw-away tip 16 is formed so as to gradually widen toward the tip.
With the tool body 11 mounted with the tool body 16, the sliding contact length with the chip C becomes longer from the inner circumference side to the outer circumference side of the tool body 11, and a large chip breaking force is applied.

However, in the present embodiment, such throw-away tips 16 and 16 face the upper surface 16a, which is a rake surface, toward the tool rotating direction T, and the lower surface 16b, which is a seating surface, on the chip mounting seat 15A. , 15B are brought into close contact with each other, and further, a pair of long-side cutting edges 18, 18 among the two pairs of long-side cutting edges 18 are directed toward the tip end side of the tool main body 11, and the intersection point P is A pair of cutting blades 18 that project toward the tip of the tool and that face these tips,
The side surfaces 16c, 16c connected to the other pair of cutting blades 18, 18 on the opposite side to 18 are brought into contact with the wall surfaces of the tip mounting seats 15A, 15B, and the clamp screws 17 are used to attach these to the tip mounting seats 15A, 15B. Each is installed.

In the present embodiment, the throw-away tips 16 and 16 are arranged so that their upper surfaces 16a and 16a are located on one plane including the axis O as shown in FIG. As shown, the respective imaginary lines A, A are substantially parallel to the axis O of the tool body 11,
That attitude is set. Further, the distance S in the direction of the axis O between the intersections P, P of the pair of cutting edges 18, 18 of both throw-away tips 16, 16 protruding toward the tool tip side is
In this embodiment, the positions of these intersections P, P in the direction of the axis O are set to 0 so that they are equal to each other. However,
If the distance S is within a range of about ± 0.2 mm, the intersection point P of the one throw-away tip 16 is arranged at a position displaced from the intersection point P of the other throw-away tip 16 in the direction of the axis O. May be.

Then, as described above, the chip mounting seat 15
As A and 15B are formed at positions asymmetric to each other with respect to the axis O of the tool main body 11, the throw-away tip 1 mounted on these tip mounting seats 15A and 15B.
A pair of cutting blades 18, 18 facing the tip side of 6, 16 also have an axis O
Are asymmetrical to each other.
That is, in the present embodiment, the inner peripheral side chip mounting seat 15A
The throw-away tip (inner peripheral side cutting edge tip) 16A mounted on the inner peripheral edge of the pair of cutting blades 18, 18, that is, the one end portion 18a, is overcentered beyond the axis O. The throw-away tip (outer peripheral side cutting edge tip) 16B that is arranged and mounted on the outer peripheral side tip mounting seat 15B has a tool having the outer peripheral ends of the pair of cutting blades 18, 18, that is, the other end portion 18b. It is arranged so as to project to the outer peripheral side of the tip portion of the main body 11. Further, the outer peripheral side cutting blade 18B of the pair of cutting blades 18, 18 of the inner peripheral side cutting blade tip 16A and the inner peripheral side of the pair of cutting blades 18, 18 of the outer peripheral side cutting blade tip 16B. The cutting edge 18A is arranged so as to intersect with each other in the rotation locus around the axis O as shown in FIGS. 6 and 7.

Further, in the present embodiment, the distance L from the axis O in the radial direction of the tool body 11 to the intersection P of the pair of cutting blades 18, 18 of the inner cutting edge tip 16A and the outer circumference from the axis O. The pair of cutting blades 1 of the side cutting blade tip 16B
The ratio L: M with the distance M to the intersection P of 8 and 18 is 1:
It is set in the range of 1.2 to 1: 1.8. Further, the position of the intersection Q where the cutting edge 18B on the outer peripheral side of the inner cutting edge tip 16A and the cutting edge 16A on the inner peripheral side of the outer cutting edge tip 16B intersect in the rotation locus around the axis O is: The rotation diameter N about the axis O and the diameter of the hole processed by the perforating tool, that is, the cutting edge 18 of the outer peripheral side cutting edge tip 16B,
The ratio N: D of the outer peripheral end (the other end) 18b of 18 to the rotation diameter D around the axis O is set to be in the range of 0.25: 1 to 0.75: 1. Furthermore, a distance at which the inner peripheral end (one end) 18a, which is the overcenter of the cutting blades 18, 18 of the inner peripheral side cutting blade tip 16A, exceeds the axis O,
That is, the overcenter amount E is set to be equal to or less than the radius R of the nose round blade 19 formed at the inner peripheral end 18a.

Further, the tool main body 11 is formed with a pair of cutting oil supply paths 21 and 21 from the rear end surface 12A of the shank 12 toward the front end side of the tool main body 11. These supply paths 21 and 21 are respectively provided from the shank 12 to the chip discharge grooves 13 and 1 at the tip of the drill body 11.
3 is formed so as to extend in parallel to the axis O, and the tip end portion is formed so as to be reduced in diameter by one step, and the tip end portions are each branched into two paths, one of which extends straightly. So as to open to the tip surface (tip flank) of the tool body 11, and the other extends to the rear side in the tool rotation direction T and to the inner peripheral side of the tool.
Wall surfaces 13B, 13B facing the tool rotation direction T rear side of 13
Further, it is formed so as to open toward a pair of cutting blades 18 facing the tip side of the inner peripheral side cutting blade tip 16A and the outer peripheral side cutting blade tip 16B.

In the throw-away type drilling tool constructed as described above, the shank 12 is attached to the spindle of a machine tool such as a machining center as described above.
While being rotated around the axis O in the tool rotation direction T, it is fed to the tip side in the direction of the axis O, and the inner / outer peripheral cutting edge tip 1 is provided.
Machining holes H are formed in the workpiece W by the pair of cutting blades 18 on the tip side of 6A and 16B. However, in the drilling tool of the present embodiment, the pair of cutting blades 18, 18 used for cutting the cutting blade tips 16A, 16B are formed so as to intersect in a convex shape through the intersection P, and Peripheral cutting edge tip 16A
Since the cutting edge 18B on the outer peripheral side and the cutting edge 18A on the inner peripheral side of the outer peripheral side cutting edge tip 16B are arranged so as to intersect each other in the rotation locus around the axis O, these cutting blades 18 ... As shown in FIGS. 6 and 7, the rotation locus due to has a shape in which two peaks overlap in the radial direction with respect to the axis O, and as a result, the chips C scraped off by these cutting edges 18 ... It will be generated in a state of being divided into four.

Moreover, the pair of cutting blades 18, 18 that intersect the cutting blade tips 16A, 16B in a convex shape project the intersection point P toward the tip side, and form the bisector of the cutting blades 18, 18. Since the virtual line A is substantially parallel to the axis O, the cutting edges 18A, 1 on the inner and outer circumferences of these cutting tips 16A, 16B are formed.
The chips C, C generated by 8B respectively flow out so as to extend toward the virtual line A side as shown in FIGS. 6 and 7, and collide with each other to interfere with each other. It will be bent and will receive stress and will be divided. Therefore, according to the present embodiment, the chips C can be efficiently divided into small pieces not only in the width direction but also in the longitudinal direction, and thereby the machining work can be performed without complication. It is possible to promote smooth drilling in response to a wide range of cutting conditions.

Further, in the present embodiment, the throw-away tip 16 which is the inner and outer peripheral cutting edge tips 16A and 16B.
Is formed into a flat hexagonal flat plate shape having two pairs of long sides and a pair of short sides, and a pair of the cutting edges 18, 18 is formed on each of these two pairs of long sides, By making the throw-away tip 16 symmetrical with respect to the imaginary line B connecting the midpoints of the short sides, one throw-away tip 16 can use the cutting blades 18, 18 twice. it can. On the other hand, by forming the throw-away tip 16 in the flattened hexagonal shape in this way, in the present embodiment, for example, compared to the case where the throw-away tip is formed in the regular hexagonal shape,
The volume can be reduced without reducing the number of times the cutting blade 18 can be reused. In other words, according to the present embodiment, the cutting edge 18 for the chip material per unit volume is
Since it is possible to increase the number of times of use, it is possible to obtain an advantage that a relatively expensive chip material such as cemented carbide can be effectively used.

Further, in the present embodiment, in the radial direction of the tool body 11, the distance from the central axis O to the intersection P of the pair of cutting blades 18, 18 used for cutting the inner cutting edge tip 16A. L and cutting edge tip 1 on the outer peripheral side from the axis O
The ratio L: M with the distance M to the intersection point P of the pair of cutting blades 18 of 6B, 18 is set in the range of 1: 1.2 to 1: 1.8, whereby the above-mentioned chips C It is possible to promote stable cutting while surely exerting the effect of dividing into the longitudinal direction. That is, when the ratio L: M of these distances L and M is less than the above range, the positions of the intersections P and P on the rotation locus are too close to each other, and the inner peripheral cutting edge 18A of the outer peripheral cutting edge tip 16B. And the length of the portion used for cutting the outer peripheral side cutting edge 18B of the inner peripheral side cutting edge tip 16A becomes shorter. Then, the width of the chips C, C generated by the cutting blades 18A, 18B is also reduced accordingly, so that the chips C, C are on the opposite side of the cutting blade tips 16A, 16B ( Even if the chips C, C generated by the outer peripheral side cutting edge 18B of the outer peripheral side cutting edge tip 16B and the inner peripheral side cutting edge 18A of the inner peripheral side cutting edge tip 16A are hit, these chips C,
The chip cutting effect due to the interference of C may not be sufficiently exerted, and it may be difficult to reliably cut the chip C in the longitudinal direction.

On the other hand, as the ratio L: M exceeds the above range, the distance between the two intersections P, P in the rotation locus widens, and accordingly the outer peripheral cutting edge tip 16A moves toward the outer peripheral side of the tool body 11. As a result, the positions where the cutting load acts on the entire tool body 11 during cutting largely deviate from the central axis O of the tool body 11 during cutting, and the tool body 11 is being drilled during drilling. There is a risk that the cutting stability will be impaired due to, for example, runout in the surface. For the same reason, the outer peripheral side cutting edge 18B of the inner peripheral side cutting edge tip 16A and the inner peripheral side cutting edge 1 of the outer peripheral side cutting edge tip 16B intersect in the rotation locus around the axis O.
The ratio N: D between the rotation diameter N formed by the intersection Q with 6A and the machining hole diameter (the rotation diameter of the outer peripheral end 18b of the cutting edge 18B of the outer peripheral side cutting edge tip 16B) D by the perforating tool is described above. Therefore, it is desirable to set it in the range of 0.25: 1 to 0.75: 1.

Further, in this embodiment, the cutting edge 1 is provided on the upper surface 16a which is the rake surface of the throw-away tip 16.
A groove-shaped chip breaker 20 is formed along the lines 8 and 18, which also makes it possible to bend the chip C in the longitudinal direction to a small extent to promote efficient division thereof. Moreover, in the present embodiment, the chip breaker 20
Is from the one end 18a side of the cutting blades 18, 18 used for cutting to the other end 18b side via the intersection point P, that is, from the inner peripheral side to the outer peripheral side of the tool body 11 in the chip mounted state, The chips C are formed so as to gradually widen. Therefore, the chips C generated by the cutting blades 18, 18 are longer as they are generated on the other end 18b side (outer peripheral side of the tool body 11). It will come into sliding contact with the bottom surface of the breaker 20 and receive a large chip breaking force.
However, in the drilling tool of this type, due to the difference in the rotational speed of the rotating tool body 11 in the radial direction, the generation rate of the chips C is higher toward the outer peripheral side, and the chips C tend to be elongated.
According to the present embodiment, it is possible to apply a great dividing force to the chips C that are generated in such a stretched manner and to reliably divide them.

However, in the present embodiment, the width of the chip breaker 20 is increased from the inner peripheral side to the outer peripheral side (from the one end portion 18a side to the other end portion 18b side) in this way, so that the tool body Although the cutting force C is gradually increased from the inner peripheral side to the outer peripheral side of the chip 11, the groove depth of this chip breaker is formed so as to become deeper from the inner peripheral side of the tool toward the outer peripheral side. Alternatively, the groove width may be gradually widened accordingly. In addition, such a groove-shaped chip breaker 20
In addition to this, for example, a projecting tip breaker may be formed inside the upper surface 16a of the throw-away tip 16 rather than the tip breaker 20, especially along the inner cutting edge 18A. Furthermore, in order to prevent an increase in cutting resistance due to the sliding contact between the chip breaker and the chips C, the bottom surface of the grooved chip breaker 20 is provided with
A rib-shaped portion extending along the sliding contact direction of the chip C may be formed, or the protruding chip breakers may be scattered along the cutting edge 18A.

On the other hand, as described above, due to the difference in the rotational speed of the tool body 11 in the radial direction, the cutting speed by the cutting edges 18, 18 decreases toward the inner peripheral side. Becomes 0 and the cutting edge 18 takes a form of crushing the work W rather than cutting the work W. Therefore, the load acting on the cutting edge 18 during cutting is It becomes the maximum on the axis O. However, in the present embodiment, on the other hand, the corners of the throw-away tip 16 (both ends 1 of the cutting blades 18, 18).
8a, 18b and the intersection point P) is formed with a nose round blade 19, and the overcenter amount E at which the inner peripheral side cutting edge 18A of the inner peripheral side cutting edge tip 16A crosses the axis O and becomes overcenter, Since the radius R of the nose round blade 19 is set to be equal to or less than the radius R, the nose round blade 19 formed at the one end portion 18a of the inner peripheral side cutting blade 18A is always located on the axis O. Therefore, according to the present embodiment, it is possible to provide the cutting edge 18 with high strength at the position of the axis O where a large cutting load acts, thereby causing a situation such as a breakage of the throw-away tip 16. Can be prevented.

In addition, the throw-away tip 1
As the nose round blade 19 is formed at each corner of 6, the nose round blade 19 is formed at the other end (outer peripheral end) 16b of the outer peripheral side cutting blade 18B in the outer peripheral side cutting blade tip 16B as well. Since it is formed, it becomes possible to sufficiently secure the strength of the cutting edge 18 at the outer peripheral end 16b. Moreover, in the present embodiment, the imaginary line A of each of the inner and outer peripheral side cutting edge chips 16A and 16B is the axis O.
Are arranged so as to be substantially parallel to the outer peripheral edge 16b of the outer peripheral side cutting edge tip 16B.
Since the short side continuing to is also arranged parallel to the axis O as shown in FIG. 1, FIG. 6 and FIG. 7, this short side portion acts as a sub-cutting edge during drilling, The inner periphery of the machined hole formed by the blades 18 can be exposed to improve the accuracy of the finished surface.

By the way, when the throw-away tip 16 is arranged such that the imaginary line A is parallel to the axis O as described above, if the tool body 11 is twisted, bent or collapsed due to a load during cutting or the like. The short side portion located on the outer peripheral side of the outer peripheral cutting edge tip 16B is the other end of the cutting blade 18 (outer peripheral end).
There is a risk that it will protrude to the outer peripheral side of 18b and will be strongly pressed against the inner peripheral surface of the machined hole, leading to an increase in cutting resistance and the like. Therefore, it is desirable that the outer peripheral side cutting edge tip 16B is arranged such that the short side portion inclines toward the inner peripheral side of the tool as it goes toward the rear side in the direction of the axis O, as shown in FIG. However, if the inclination angle γ formed by the short side with respect to the direction of the axis O is too large, there is a possibility that the above-described action of the short side portion as the sub-cutting edge may not be sufficiently achieved. Therefore, the inclination angle γ formed by the short side of the upper surface 16a of the outer peripheral side cutting edge tip 16B with respect to the axis O direction is preferably set in the range of 0 ° 10 ′ to 5 °.

Furthermore, in the present embodiment, the tool body 11
A pair of cutting oil supply passages 21 and 21 are formed in the inner surface of the tool body 11. The supply passages 21 and 21 are opened at the tip end surface of the tool body 11, and the tip end portions are branched to form the chip discharge groove 13, The wall surfaces 13B and 13B of the tool 13 that face the rear side in the tool rotation direction T are formed so as to open toward the cutting edge 18 used for cutting the cutting edge tips 18A and 18B. Therefore, according to the present embodiment, the wall surface 13B,
The cutting fluid is intensively supplied from the supply paths 21 and 21 opening to 13B toward the cutting blades 18 used for cutting, thereby promoting efficient cooling and lubrication of the cutting blades 18. be able to. Moreover, in the present embodiment, since the tip portions of these supply paths 21 and 21 are reduced in diameter by one step, while cutting the supply paths 21 and 21 at the tip portions thereof as described above, It is possible to secure a sufficient supply pressure of the oil agent.

In this embodiment, as shown in FIG. 2, the inner and outer circumference side cutting edge tips 16A and 16B are arranged so that their upper surfaces 16a and 16a are located on one plane including the axis O, respectively. However, for example, one throw-away tip 16 is arranged such that its upper surface 16a is located on one plane including the axis O, and the other throw-away tip 16 is arranged as shown in FIG. The upper surface 16a may be arranged so as to be parallel to the one plane and to be receded rearward in the tool rotation direction T, or as shown in FIG. 10, the upper surface 16a may be an outer periphery with respect to the one plane. You may arrange | position so that it may be located in the direction diagonally crossed toward the back side of the tool rotation direction T as it goes to the side.

However, as shown in FIG. 9, when the upper surfaces 16a, 16a of the two throw-away tips 16, 16 are arranged parallel to each other and in a staggered manner, the deviation amount F is 0.2 m.
m or less, and as shown in FIG.
When the a and 16a are arranged in a diagonal direction, it is desirable that the inclination angle θ be set to 15 ° or less. This is because if the deviation amount F or the inclination angle θ becomes larger than the above range, the balance of the cutting load acting on the inner and outer peripheral side cutting edge chips 16A and 16B is impaired, and stable machining may be hindered. Is caused.

Further, in the present embodiment, as described above, the tool body 11 is rotated around its axis O and is fed in the direction of the axis O to form the machined hole H in the workpiece W. Alternatively, as shown in FIG. 11, it is also possible to fix the tool body 11 and rotate the work material W to make the both approach in the direction of the axis O to form the machining hole H. However, in this case, the center axis O of the tool body 11 and the center of rotation X of the work material W are displaced in the radial direction so that the machining hole diameter (the outer peripheral end of the outer peripheral side cutting edge tip 16B) by the perforating tool is shifted. It is possible to form a machined hole H in the work material W having a diameter larger than the diameter D of rotation about the axis O of 18b). Further, in the present embodiment, the chip discharge grooves 13 and 13 are formed so as to extend parallel to the axis O of the tool body 11, but they may be formed in the shape of a twist groove twisted around the axis O.

[0039]

As described above, according to the present invention,
The chips can be generated by dividing them in the width direction, of course, the chips generated by the cutting edge on the inner peripheral side and the outer peripheral side of the cutting blade tip interfere with each other by hitting each other, It becomes possible to divide also in the longitudinal direction. And, by doing so, it is possible to improve the chip discharge capacity in machining where the degree of freedom of hole machining is low and the tool rigidity can not be increased endlessly, and it is possible to prevent situations such as tool breakage and stabilize it. In addition, it becomes possible to promote smooth drilling. In addition, it is possible to effectively use the chip material by forming the throw-away chip into a flat hexagonal plate shape while exhibiting such excellent chip disposal performance.

[Brief description of drawings]

FIG. 1 is a side view showing an embodiment of the present invention.

FIG. 2 is a front view of the embodiment shown in FIG.

FIG. 3 is a side view of the tip portion of the embodiment shown in FIG. 1 viewed from the opposite side.

FIG. 4 is a plan view of the throw-away tip 16 according to the embodiment shown in FIG.

5 is a cross-sectional view of the throw-away tip 16 shown in FIG.

FIG. 6 is a diagram showing drilling according to the embodiment shown in FIG. 1.

FIG. 7 is a diagram showing a drilling process according to the embodiment shown in FIG. 1 (a state in which the tool body 11 is half-turned from the state shown in FIG. 6).
It is.

FIG. 8 is a diagram showing a modification of the embodiment shown in FIG.

FIG. 9 is a diagram showing a modification of the embodiment shown in FIG.

FIG. 10 is a diagram showing a modification of the embodiment shown in FIG.

FIG. 11 is a diagram showing another example of the boring process according to the embodiment shown in FIG. 1.

FIG. 12 is a view showing a drilling process using a conventional twist drill.

FIG. 13 is a diagram showing processing by a conventional throw-away type drilling tool.

FIG. 14 is a view showing a rotation trajectory of throw-away inserts 5A and 5B of the drilling tool shown in FIG.

[Explanation of symbols]

11 Tool Body 13 Chip Discharge Groove 16 Throwaway Tip 16A Inner Circumferential Side Cutting Edge Tip 16B Outer Side Cutting Edge Tip 18 Cutting Edge 18A Inner Circumferential Side Cutting Edge 18B Outer Side Cutting Edge 18a One End (Inner Circumferential End) of Cutting Edge 18 18b Other end of cutting edge 18 (outer peripheral edge) 19 Nose round blade 20 Chip breaker 21 Cutting fluid supply path O Center axis of tool body 11 Tool rotation direction P Crossing point of cutting edges 18, 18 R Nose round blade 19 Radius A A virtual line connecting the intersection points P and P of the throw-away tip 16 L A distance between the axis O and the intersection point P of the inner cutting edge tip 16A M A distance between the axis O and the intersection point P of the outer cutting edge tip 16B Q Axis Inner peripheral cutting edge tip 1 in the rotation trajectory around O
6A Outer peripheral side cutting edge 18B and outer peripheral side cutting edge tip 16B inner peripheral side cutting edge 18A intersection point N Rotating diameter of intersection Q around axis O O D of outer peripheral side cutting edge tip 16 around axis O Rotation diameter of the other end (outer peripheral end of the cutting edge 18) 18b (diameter of a hole processed by a drilling tool) E Inner-side cutting edge Tip 16 overcenter amount of one end 18a of the cutting edge 18 C Chip W Work material H processing hole

Claims (6)

[Claims] 1. A pair of chip discharge grooves are formed on the outer periphery of the tip of a substantially cylindrical tool body, and a chip mounting seat formed at the tip of these chip discharge grooves has an inner cutting edge chip and an outer periphery, respectively. In a throw-away type drilling tool in which a side cutting edge tip is detachably mounted, the above cutting edge tips have the same shape and the same size as each other, and each of which has a pair of lengths that intersect each other in a convex shape and face each other. Forming a flat hexagonal flat plate having a side and a pair of short sides parallel to each other that connect the ends of these two pairs of long sides, and a cutting edge is formed on each of the two pairs of long sides. And, a pair of cutting blades of these two pairs of cutting blades, the intersections are arranged such that they are arranged to project toward the tip side of the tool body, the inner peripheral side cutting blade tip, the The inner peripheral ends of the pair of cutting blades cross over the central axis of the tool body. While being arranged so as to be a bar center, the outer peripheral cutting edge tip is arranged such that the outer peripheral ends of the pair of cutting blades protrude toward the outer peripheral side of the tool body tip portion, and the inner peripheral side. A cutting edge on the outer peripheral side of the pair of cutting blades of the cutting blade tip, and an inner peripheral cutting edge of the pair of cutting blades of the outer peripheral side cutting blade tip, the rotation trajectory around the central axis A throw-away drilling tool characterized in that they are arranged so as to intersect with each other. 2. The distance from the central axis in the radial direction of the tool body to the intersection of the pair of cutting edges of the inner cutting edge tip, and the pair of the outer cutting edge tips from the central axis. The ratio to the distance to the intersection of the cutting edges is 1: 1.
The throw-away drilling tool according to claim 1, wherein the throw-away drilling tool is set in a range of 2-1 to 1.8. 3. The cutting edge chip is formed with a chip breaker along the pair of cutting edges, and the chip breaker is configured to gradually increase the cutting force from the inner peripheral side to the outer peripheral side of the tool body. The throw-away drilling tool according to claim 1 or 2, wherein the throw-away drilling tool is provided. 4. A nose radius blade is formed at least on the inner peripheral side ends of the pair of cutting blades of the cutting blade tip, and the inner periphery of the pair of cutting blades of the inner peripheral side cutting blade tip is formed. The throw-away type drilling tool according to any one of claims 1 to 3, wherein the amount of overcenter at which the end exceeds the central axis line is equal to or less than the radius of the nose radius blade. 5. A nose round blade is formed on at least outer peripheral side end portions of the pair of cutting blades of the cutting blade tip, and the outer peripheral side cutting blade tip has a short side continuous with the nose round blade. Are arranged so as to be inclined toward the inner peripheral side toward the rear side in the axial direction, and the inclination angle formed by the short side with respect to the axial direction is 0 ° 10 ′ to 5 ′.
The throw-away type drilling tool according to any one of claims 1 to 4, wherein the throw-away drilling tool is set in a range of °. 6. The tool main body is formed with a pair of supply paths for cutting fluid, and the tips of these supply paths are formed on at least the wall surfaces of the pair of chip discharge grooves, respectively, on the inner peripheral side cutting blade. The throw-away drilling tool according to any one of claims 1 to 5, wherein the insert and the outer peripheral cutting edge tip are formed so as to open toward the pair of cutting edges.