JP3166607B2 - Indexable drill - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a throw-away type drill (hereinafter, referred to as a drill) in which a substantially triangular plate-shaped throw-away tip (hereinafter, referred to as a tip) is detachably mounted at the tip of a drill body. ) And the most suitable inserts for such drills.

[0002]

2. Description of the Related Art This type of insert and drill includes:
For example, one described in Japanese Patent Application Laid-Open No. 4-269108 is known. The drill described in this publication has a regular triangular plate shape on a tip mounting seat formed at the tip of a drill body that is rotated around an axis, and a ridge portion between one triangular surface and one side surface. A negative tip formed with a cutting edge is detachably attached to the drill rotation direction side with the triangular surface as a rake face and toward the tip side of the drill body with the one side face as a tip flank. Yes,
The cutting edge is provided with a negative rake angle in the radial direction, and an inner peripheral portion thereof is directed toward another triangular surface serving as a seating surface for the tip mounting seat, that is, in a drill rotation direction. It is formed so as to be convexly curved toward the rear side. Note that a breaker groove is formed at an edge of the one triangular surface which is a rake surface. However, according to the drill having such a configuration, since the inner peripheral side of the cutting edge is formed in a convexly curved shape as described above, especially in the vicinity of the rotation center of the drill where a large cutting load is applied, the high cutting edge is used. Strength can be obtained.

[0003]

However, in the above-mentioned drill, since the tip is a negative tip formed in a direction where the triangular surface and the side face are perpendicular to each other, the one side face serving as a flank face is used. Also, on the outer peripheral side of the cutting edge, an intersection ridge portion with another side surface adjacent to the one side surface is also formed in a direction orthogonal to the triangular surface and the cutting edge which are rake faces. It will be. Therefore, in order to make this cross ridge line escape from the inner periphery of the processing hole formed by the cutting edge, the above-mentioned drill gives the cutting edge a negative rake angle in the radial direction. In this case, the tip comes into contact with the inner periphery of the processing hole only at the corner of the triangular surface at the outer peripheral end of the cutting blade. It is inevitable that the finished surface roughness of the peripheral surface is impaired. In addition, since the tip and the drilled hole are in contact only at the corners of the tip, the guideability of the drill against radial runout is likely to be impaired, and it is difficult to drill a hole with high straightness accuracy. Become.

Further, at the outer peripheral end of the cutting edge, since the corner of the triangular surface, which is a rake face, is acute, even if the tip is a negative tip, its strength is insufficient. And there is also a problem that the cutting edge is likely to be damaged. On the other hand, in drilling with such a drill, chips are generated longer on the outer peripheral side of the cutting blade than on the inner peripheral side due to the difference in the rotation diameter of each part of the cutting blade with respect to the axis. However, in the above chip, although a breaker groove for chip processing is formed at an edge of a triangular surface which is a rake surface,
The breaker groove is uniform over the entire length of the cutting edge, and it must be said that it is insufficient for efficiently performing chip processing particularly on the chip generated on the outer peripheral side of the cutting edge. Furthermore, since the tip is a negative tip, the axial rake angle of the cutting edge has to be set to the negative angle side, that is, the rake face moves toward the axial direction of the drill toward the drill rotation direction side. It is arranged to be inclined so as to face. For this reason, the chips generated by the cutting blade are once extruded in the drill rotation direction,
This is fed into the chip discharge groove and discharged to the rear side in the axial direction, resulting in further impeding efficient chip processing.

The present invention has been made in view of such circumstances, and it is possible to improve the finished surface roughness of the inner peripheral surface of a machining hole while maintaining the strength on the inner peripheral side of the cutting blade. ,
It is another object of the present invention to provide a drill capable of sufficiently securing the strength at the outer peripheral end of the cutting blade, and further capable of more efficiently processing chips.

[0006]

In order to solve the above-mentioned problems and to achieve the above object, a drill according to claim 1 of the present invention has its tip formed in a substantially triangular flat plate shape and its one triangular shape. While the surface is directed to the drill rotation direction side as a rake face, one side face is directed to the drill tip side as a tip flank, and the cutting edge formed on the ridge portion of these rake face and flank, one end of which is described above. A positive indexable insert in which the rake face and the flank face intersect at an acute angle with the drill body positioned near the center of rotation of the tip of the drill body and the other end positioned on the outer periphery.
The rake angle of the cutting edge is set to 0 ° or a regular angle side , and a portion at one end side of the cutting edge is formed so as to be convex toward the one end side and toward the rear side in the drill rotation direction. On the other hand, at the other end of the cutting blade, a cylindrical surface centered on the axis is formed at an intersection ridge line of the one side surface and another side surface adjacent to the one side surface so as to extend in the axial direction. The cylindrical surface is in sliding contact with the inner peripheral surface of the drilled hole during drilling
It is characterized by doing so.

[0007]

However, according to the above-described drill, the one end of the cutting blade arranged near the center of rotation of the tip of the drill is formed in a convex shape toward the one end to form another triangle. Since it is formed so as to face the surface side, that is, toward the rear side in the drill rotation direction, the strength of the cutting edge can be reliably maintained. On the other hand, on the other end side of the cutting edge arranged on the outer periphery of the drill, a convex cylindrical surface is formed at the intersection ridge portion between the side surfaces of the chip located on the outer periphery side, and the one end of the tip It is formed so as to extend from the triangular surface toward the other triangular surface side, that is, to extend in the axial direction of the drill, and in the drill, by making this cylindrical surface the center of the drill rotation axis, When the drill drills a processing hole, this cylindrical surface comes into sliding contact with the inner peripheral surface of the processing hole as a margin portion, so that a burnishing effect occurs and the inner peripheral surface of the processing hole can be finished smoothly. .

[0009] Further, since the convex cylindrical surface is formed as described above, the thickness of the tip in the thickness direction of the tip can be increased at the corner on the other end side of the cutting blade. The surface is formed so as to extend from one side surface to the other side surface of the tip, that is, to extend in the axial direction of the drill, so that the cutting edge strength at the other end of the cutting edge is reduced. In addition, it is possible to prevent loss and the like. Furthermore, since the rake face and the flank face are positive tips that intersect at an acute angle, the rake angle of the cutting edge can be set to 0 ° or a regular angle side, and prompt discharge of chips can be promoted. Here, in order to further improve the strength of the cutting edge on the other end side of the cutting edge, it is desirable to form the cylindrical surface in a direction intersecting the cutting edge at an obtuse angle.
In this case, in the drill, a negative rake angle in the radial direction is given to the cutting edge, so that the strength of the cutting edge is further improved.

On the other hand, in order to efficiently treat chips generated long on the outer peripheral side of the cutting edge when drilling, a drill body is provided at the edge of the rake face on the cutting edge side. It is desirable to form a breaker groove that gradually widens from the inner circumferential side to the outer circumferential side or that gradually becomes a deep groove, and when such a configuration is adopted, a larger chip breaker is formed on the outer circumferential side of the cutting blade. Since the action occurs,
The chips generated for a long time can be reliably and efficiently processed. Also, in the chip, a breaker groove that gradually becomes wider or deeper from the above-mentioned one end side to the other end side of the cutting edge is formed at the edge of the rake face on the cutting edge side. Desirably, the tip having such a configuration has the same operation and effect as in the case where the insert is mounted on a throw-away type cutting tool and the work is turned, for example, in addition to the case where the insert is used for the drill.

Further, in the chip, a ridge portion of another triangular surface opposite to the one triangular surface and another one side surface adjacent to the one side surface at the other end side of the cutting blade, The other triangular surface is used as a rake face and another cutting edge is formed as a flank of the other side, and the cutting edge is formed at an intersection ridge line between the one side and the other side. A first cylindrical surface formed in a direction intersecting at a predetermined angle with respect to the second cutting cylinder formed in a direction intersecting the other cutting edge at an angle equal to the predetermined angle. If the surface is formed, one chip can be provided with two cutting edges, the above-mentioned cutting edge and the other cutting edge, and can be used twice, and these cutting edges can be used. When using the same, make the angles of each cylindrical face It is possible to reproduce the use state.

[0012]

1 to 3 show an embodiment of a drill according to the present invention. In these figures, the drill body 1 is formed in a substantially cylindrical shape centered on the axis O, and its outer periphery is open at the tip of the drill body 1 at the rear side in the drill rotation direction T around the axis O. A pair of chip discharge grooves 2, 2 twisting toward the base end side are formed with the axis O interposed therebetween. A shank 1B extends along the axis O from the base end face 1A inside the drill body 1.
, A supply passage 3 for lubricating coolant or the like is formed, which branches off in the vicinity of the distal end and opens in the distal end face 1C of the drill body 1. Further, tip mounting seats 4 and 4 are formed on the inner wall surface facing the drill rotation direction T at one end of each of the chip discharge grooves 2 and 2 so as to be recessed one step backward in the drill rotation direction T. A chip 5 according to an embodiment of the present invention as shown in FIGS. 4 to 9 is mounted on the chip mounting seats 4 and 4, respectively.

The chip 5 is formed of a hard material such as a cemented carbide in a substantially equilateral triangular plate shape (more precisely, an isosceles trapezoidal flat plate shape). A mounting hole 7 is formed at the center of 6 so as to penetrate the chip 5 in the thickness direction. The ridge line between one triangular surface 6A of the triangular surfaces 6 and 6 and one side surface 8A of the three side surfaces 8 of the chip 5 intersecting the triangular surfaces 6 and 6 has a first edge. A cutting edge 9A is formed, and a second cutting edge 9B is formed at a ridge line between the other triangular surface 6B and the other side surface 8B. In addition, chamfers 10, 10 are formed at the ridges of the triangular surfaces 6A, 6B and the remaining one side surface 8C, respectively.

Here, in the one triangular surface 6A, the portion of the corner 11A where the side surface 8A and the side surface 8C intersect is drawn as a convex cylindrical surface toward the corner 11A as a whole, The end 9a of the first cutting edge 9A located on the side of the corner 11A is also formed so as to be curved toward the triangular surface 6B of the end 9A.
It is formed so as to be curved in a convex curve toward the other triangular surface 6B as it goes to the side a. A corner 11B between the side surface 8B and the side surface 8C on the other triangular surface 6B side forms a triangular surface 6A while drawing a convex cylindrical surface.
Side, whereby the one end 9a of the second cutting edge 9B is curved in a convex curve toward the one triangular surface 6A side.

On the other hand, on the other end 9b, 9b side of the first and second cutting blades 9A, 9B, the intersection ridge 12 between the one side surface 8A and the other side surface 8B is formed as one triangle. Face 6
A is cut out from A to the other triangular surface 6B,
As a result, both triangular surfaces 6 at the intersection ridge 12
A, 6B corners 11C, 11D correspond to the remaining one side 8
By being formed to extend in a direction parallel to C,
As described above, the chip 5 is more strictly formed in the shape of a trapezoidal flat plate. The notched intersection ridge 12 has a first triangular surface 6A on the side of the first triangular surface 6A.
13A, and a second cylindrical surface 13B is formed on the other triangular surface 6B side. Here, these cylindrical surfaces 13A and 13B are formed so as to form a convex shape that bulges outside the chip 5 from one of the triangular surfaces 6A and 6B toward the other, that is, in the thickness direction of the chip 5. Each of the first side surfaces 8 is curved and formed.
A is formed between A and the other side surface 8B.

Here, the first and second cylindrical surfaces 13
A and 13B are the other ends 9b and 9B of the cutting edges 9A and 9B, respectively, as viewed from a direction parallel to the side surface 8C of the chip 5 and facing the side surfaces 8A and 8B as shown in FIGS.
At b, the first and second cutting blades 9A and 9B are formed so as to intersect at an equal and obtuse angle θ. Further, in this embodiment, the widths of the first and second cylindrical surfaces 13A and 13B in the chip thickness direction are set so as to be substantially equal from the side surface 8A to the side surface 8B as shown in FIG. As a result, these first
The intersection ridge line S formed by the cylindrical surface 13A and the second cylindrical surface 13B is formed so as to extend in a direction orthogonal to the thickness direction of the chip 5 as shown in FIG.

Further, in this embodiment, the breaker grooves 14, 10 are formed along the edges 9A, 9B of the triangular surfaces 6A, 6B of the tip 5 along the cutting edges 9A, 9B, respectively.
14 are formed. This breaker groove 14 has a bottom surface 14 in a cross section orthogonal to the cutting edge 9 as shown in FIG.
A has an arc shape, and its groove width W is formed so as to gradually increase from one end 9a to the other end 9b along the cutting edge 9, and the groove depth D also increases. The cutting blade 9 is formed so as to gradually become deeper from one end 9a to the other end 9b. Furthermore, in the present embodiment, the triangular surfaces 6A and 6B, which are the rake surfaces,
These triangular surfaces 6A, 6B have cutting edges 9A, 9B, respectively.
And the side surfaces 8A and 8B intersecting each other at an acute angle, that is, the chip 5 of the present embodiment is different from the positive chip in which the side surfaces 8A and 8B, which are flank surfaces, are provided with a clearance angle. Have been.

The chip 5 of the present embodiment having the above-described configuration is configured such that one of the triangular faces 6A and 6B is directed to the drill rotation direction T as a rake face and cut into the triangular face 6 to be the rake face. The side surface 8 adjacent via the blade 9 is directed to the drill tip side as a tip flank, and the cutting edge 9
However, the one end 9a is positioned near the center of rotation of the drill at the tip of the drill body 1, and the other end 9b is positioned so as to protrude toward the outer periphery of the tip of the drill body 1. And is fixed to the drill main body 1 by a clamp screw 15 inserted through the mounting hole 7, thereby constituting the drill of the above embodiment. Here, the wall surface 4a of the tip mounting seat 4 facing the drill tip side.
2 is formed so as to be inclined toward the rear end of the drill as it goes toward the bottom surface 4b of the chip mounting seat 4, while the triangular surfaces 6A and 6B and the side surfaces 8A and 8B of the chip 5 are formed. Respectively, intersect at an acute angle, so that the side surface 8 of the tip 5 facing the rear end of the drill also inclines toward the rear end of the drill toward the triangular surface 6 seated on the bottom surface 4b. The chip 5 is firmly fixed to the chip mounting seat 4 by contacting with the wall surface 4a.

However, in such a state that the tip 5 is mounted on the tip mounting seat 4, the tip 5 of the drill of the present embodiment is arranged so that the remaining one side face 8C is parallel to the axis O, and the tip of the drill is Cutting edge 9 arranged on
2, so as to provide 0 ° or a positive axial rake angle as shown in FIG. 2 and a negative radial rake angle as shown in FIG. The chips 5, 5 mounted on the chip mounting seats 4, 4 are of the same shape and the same shape, and are mounted symmetrically with respect to the axis O. The tip angle formed by the cutting blades 9, 9 is set to approximately 120 °. The two chips 5, 5 are arranged such that the inner peripheral ends of the cutting blades 9, 9 (tips of the one end 9a) are spaced apart in the radial direction with the axis O interposed therebetween. On the axis O, the cutting edge 9 does not exist, and a cutting form in which the generated columnar core is threaded is adopted.

Further, in the drill and the tip 5 of the present embodiment, the cutting edge 9 of the first and second cylindrical surfaces 13A and 13B of the tip 5 which is arranged at the tip of the drill.
So that the cylindrical surface 13 intersects the axis O and the distance from the axis O to the other end 9b of the cutting edge 9, that is, the radius of the cutting edge 9 of the drill. Thus, the cylindrical surface 13 extends in the direction of the axis O on the outer peripheral surface of the drill, and forms a margin portion having no relief angle. Since the cutting edge 9 is given a negative rake angle in the radial direction, the cylindrical surface 13 serving as the margin portion is, as viewed from the front end side in the direction of the axis O, as shown in FIG. The cylindrical surface 13 is arranged so as to be curved toward the outer peripheral side of the drill with respect to the imaginary line L passing through the other end 9b which is the end and orthogonal to the cutting edge 9. Accordingly, in this embodiment, the cylindrical surface 13 is cut as described above. They intersect at an angle θ that forms an obtuse angle with the blade 9.

However, in the drill constructed as described above, first, one end 9a of the cutting blades 9, 9 formed on the chips 5, 5 is connected to the triangular surface 6 opposite to the triangular surface 6 as a rake surface. The cutting edge 9 is formed so as to be convex toward the side 6, and therefore, by mounting the tips 5, 5 with the one end 9 a of the cutting edge 9 positioned near the center of rotation of the drill, the one end 9 a becomes , In the drill rotation direction T rearward. Therefore, a high cutting edge strength can be obtained in the vicinity of the drill rotation center where a particularly large cutting load acts during drilling, and it is possible to prevent the cutting edge 9 from being broken at one end 9a.

On the other hand, on the other end 9b side of the cutting edge 9 (the outer peripheral side of the drill), the cylindrical surface 13 intersecting the cutting edge 9 is formed in the direction of the axis O along the intersection ridge 12 of the tip 5. Since the drill body 1 is formed so as to extend, when the drill body 1 is rotated around the axis line O and is sent in the direction of the axis line O to drill a work material, the inside of the processing hole formed by the cutting blades 9 is formed. Drilling is performed while the cylindrical surface 13 is in sliding contact with the peripheral surface as a margin portion. Therefore, according to the drill having the above-described configuration, the inner peripheral surface of the machined hole is smoothly finished by the burnishing effect of the cylindrical surface 13, and the tip of the drill has the cylindrical surfaces 13, 13 of the tips 5, 5.
As a result, the workpiece can be advanced so as to be guided along the processing hole, so that a processing hole having high finished surface roughness and straightness can be obtained.

In the drill equipped with the tip 5 having the above configuration, the cylindrical surface 13 of the tip 5 is connected to the other end 9 b of the cutting edge 9.
(The outer peripheral end) is formed so as to intersect the cutting edge 9 at an obtuse angle θ, and this cylindrical surface 13 extends in the direction of the axis O. The thickness of the tip 5 in the drill rotation direction T at 9b can be sufficiently ensured to provide high cutting edge strength, and it is possible to prevent a situation where the cutting edge 9 is broken at the other end 9b. it can. Therefore, according to the drill having the above configuration, the strength of the cutting edge is ensured even at one end (inner peripheral end) 9a of the cutting edge 9 as described above. By providing the rake angle in the axial direction, the strength of the entire cutting edge 9 can be improved, so that it is possible to sufficiently cope with a case where high-speed feeding is performed, and to efficiently drill holes. It is possible to encourage.

Further, in the tip 5, the triangular surfaces 6A and 6B, which are rake surfaces, intersect with the triangular surfaces 6A and 6B via cutting edges 9A and 9B, respectively, to form a tip flank. The side surfaces 8A and 8B are formed so as to intersect each other at an acute angle.
Is a positive tip, so that the triangular surface 6 to be a rake face is arranged in a direction parallel to the axis O or in a direction inclined toward the rear in the drill rotation direction T toward the rear end of the drill. A clearance angle can be given to the side surface 8 which is a tip flank, and the cutting edge 9 used for cutting can be given a 0 ° or positive axial rake angle as described above. Accordingly, along with this, chips generated by the cutting blade 9 are not once pushed out to the drill rotation direction T side as in the case where the conventional axial rake angle takes a negative angle, and the rake face is formed. Thus, it flows along the triangular surface 6 and is quickly accommodated in the chip discharge groove 2 and discharged to the rear end side of the drill, whereby it is possible to promote efficient chip processing.

Further, since the triangular surface 6 and the side surface 8 intersect at an acute angle as described above, the side surface 8 facing the rear side of the drill is brought into contact with the wall surface 4a of the tip mounting seat 4 inclined as described above. 5 can be mounted. However,
By adopting such a configuration, when the cutting force (feed component force) generated at the time of cutting causes the tip 5 to be pressed to the rear side of the drill, the side surface 8 of the tip 5 and the triangular surface 6 serving as a seating surface, and the tip 5 The wall surface 4a of the mounting seat 4
A so-called wedge effect is generated between the base and the bottom surface 4b,
The advantage that the chip 5 can be held more firmly can also be obtained.

Further, in the chip 5, a breaker groove 14 is formed along the cutting edge 9 at an edge of the triangular surface 6 which is a rake face on the cutting edge 9 side. Is the other end 9b side of the cutting blade 9 (the outer peripheral side of the drill)
Are formed so as to gradually become wider and deeper. Therefore, in the above-mentioned drill equipped with such a tip 5, a strong chip breaker action can be given to chips generated long on the outer peripheral side of the cutting edge 9 due to a difference in the rotation diameter thereof. Chips can be surely divided, and in combination with the above-described effect of providing the cutting edge 9 with a 0 ° or a positive axial rake angle, more efficient chip processing can be achieved. Becomes

In the chip 5 of this embodiment, the breaker groove 14 is formed to be wide and deep toward the other end 9b of the cutting edge 9 as described above. It is possible to increase the chip breaker action on the outer peripheral side of the drill even if the groove width is gradually increased with a constant depth, or even if the groove depth is gradually increased with a constant groove width. It is. However,
In order to achieve more reliable and efficient chip processing, the breaker groove 14 has a groove width W and a groove depth D as in this embodiment.
However, it is preferable that both are formed so as to increase toward the other end 9b side of the cutting blade 9.

On the other hand, in the chip 5 of the present embodiment, the cutting edges 9A and 9B are formed at the ridges of the pair of triangular surfaces 6A and 6B and the side surfaces 8A and 8B, respectively. It can be used twice, and the side face 8A,
Since the cylindrical surfaces 13A and 13B are formed at the intersection ridge 12 of the 8B so as to intersect the other ends 9b and 9b of the cutting edges 9A and 9B at an equal angle θ to each other, the cutting edges 9A and 9B are formed. Even if one of 9B is used up and then the other is used, the positional relationship between cutting edge 9 and cylindrical surface 13 does not change. For this reason, the same use state can be maintained regardless of which of the cutting blades 9A and 9B is used, that is, the above-described functions and effects can be exerted equally.

In the tip 5 of this embodiment, the cylindrical surfaces 13A and 13B are formed so as to intersect the cutting edges 9A and 9B at an obtuse angle.
13B, the other cylindrical surface 13 is disposed radially inward of the circumferentially extending curved surface of one cylindrical surface 13 with respect to the other. Therefore, in the case where either of the cutting edges 9A and 9B is used as described above, the margin between the one cylindrical surface 13 slidingly contacting the processing hole and the other cylindrical surface 13 and the inner peripheral surface of the processing hole. Since a clearance is defined between the two, the other cylindrical surface 13 does not interfere with the machined hole. In the tip 5 and the drill according to the present embodiment, one end 9a of the cutting edge 9 is directed toward the other triangular surface 6B toward the one end 9a, that is, in the drill rotation direction T.
It is formed so as to be curved in a convex curve toward the rear side of the cutting edge 9. However, if one end 9 a of the cutting blade 9 is formed in a convex shape, it is not limited to such a curved shape. One end 9a may be formed by connecting short straight lines in a convex shape.

In the above description, the case where the tip 5 according to the present embodiment is mounted on a drill has been described. However, the tip 5 according to the above-described embodiment according to the present invention may be replaced with another type such as a throw-away boring bar. Can also be used as a drilling tool of the type described above or as a tip of a throw-away type tool used for turning. When the drilling tool is used as a tip of the above-mentioned drilling tool, the cylindrical surface 1
3 can be obtained in the same manner, and even when used as a turning insert, both ends 9a,
9b can be improved in strength. In the case where the insert 5 is used for turning a deep cut, for example, one end 9a is located on the inner peripheral side (cutting side) of the rotating work material, and the other end 9b is located on the outer peripheral side. Thus, for the chips generated long on the outer peripheral side of the work material due to the difference in the rotation diameter, the above-mentioned breaker groove 14 can promote efficient chip processing as in the case of the drill.

[0031]

As explained above, the drill of the present invention
According to the present invention, the chip has a substantially triangular flat plate shape, with one triangular surface facing the drill rotation direction as a rake face, and one side facing the drill tip side as a tip flank, and flank the rake face. The cutting edge formed on the ridge line portion with the surface is arranged such that one end is located near the rotation center of the tip of the drill body and the other end is located on the outer periphery, and the rake face and the flank are further arranged. Positive throwaway tips that intersect at an acute angle.
The rake angle of the blade is set to 0 ° or a regular angle side , and a portion at one end of the cutting blade is formed so as to be convex toward the one end and toward the drill rotation direction rear side,
At the other end of the cutting blade, at the intersection ridge of the one side surface and another side surface adjacent thereto, a cylindrical surface around the axis is formed so as to extend in the axial direction , hole
At the time of machining, the cylindrical surface should be in sliding contact with the inner peripheral surface of the machining hole.
Since the, by positioning on the outer peripheral side and the other end with placing the one end of the cutting edge on the inner peripheral side of the drill body,
While maintaining the cutting edge strength on the inner peripheral side of the drill, the cylindrical surface is slid in contact with the inner peripheral surface of the drilled hole as a margin extending in the axial direction to improve the finished surface roughness and straightness of the drilled hole. The rake angle of the cutting edge can be set to 0 ° or a regular angle.
Side, once the chips generated by the cutting edge
It is possible to smoothly and promptly feed chips into the chip discharge groove without being pushed out in the rotation direction . Further, by forming the cylindrical surface in a direction that intersects the cutting edge at an obtuse angle, the strength at the other end of the cutting blade can also be reliably ensured. By forming a breaker groove that gradually becomes wider or becomes deeper toward the side, efficient processing of chips can be achieved.

[Brief description of the drawings]

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

FIG. 2 is a side view of a tip portion of the drill shown in FIG.

FIG. 3 is a front view of a tip portion of the drill shown in FIG.

FIG. 4 is a plan view showing an embodiment of the chip of the present invention.

FIG. 5 is a front view of the chip 5 shown in FIG.

FIG. 6 is a rear view of the chip 5 shown in FIG.

FIG. 7 is a side view of the chip 5 shown in FIG.

FIG. 8 is a DD sectional view of the chip shown in FIG. 4;

9 is an EE sectional view of the chip shown in FIG. 4;

[Explanation of symbols]

 Reference Signs List 1 drill body 2 chip discharge groove 4 chip mounting seat 5 chip 6 (6A, 6B) triangular surface of chip 5 8 (8A, 8B, 8C) side surface of chip 5 9 (9A, 9B) cutting blade 9a one end of cutting blade 9 Part 9b The other end of the cutting blade 9 11A, 11B, 11C, 11D Corner of the triangular surface 6 Intersecting ridge line part of the side surfaces 8A, 8B 13 (13A, 13B) Cylindrical surface 14 Breaker groove O Drill rotation axis R Cutting blade 9 Radius of rotation T drill rotation direction θ angle between cylindrical surface 13 and cutting edge 9

Continuation of front page (56) References JP-A-9-262711 (JP, A) JP-A-1-81210 (JP, U) JP-A-58-191913 (JP, U) JP-A-63-124416 (JP) , U) Shokai Sho 58-117308 (JP, U) JP-B Sho 59-43249 (JP, B2) (58) Fields investigated (Int. Cl. ⁷ , DB name) B23B 51/00, 27/14

Claims (4)

(57) [Claims] 1. A chip discharge groove extending from a tip to a base end is formed on an outer periphery of a drill body that is rotated around an axis, and a throw-away chip is mounted on a chip mounting seat formed at a distal end of the chip discharge groove. In the throw-away type drill which is detachably mounted, the above-mentioned throw-away tip has a substantially triangular flat plate shape, and the one triangular surface is directed to the drill rotation direction side as a rake face, and the one side face is escaped at the tip. A cutting edge formed on the ridge of the rake face and flank face as a face, and a cutting edge formed on the ridge portion of the rake face and the flank face, with one end located near the rotation center of the drill body tip and the other end located on the outer circumference. A positive indexable insert in which the rake face and the flank intersect at an acute angle, wherein the rake angle of the cutting edge is 0 ° or
Is set to a regular angle side , and a portion on one end side of the cutting edge is formed so as to be convex toward the one end side and toward the drill rotation direction rear side, while the other end portion of the cutting edge is formed. In, at the intersection ridge portion of the one side surface and another side surface adjacent thereto, a cylindrical surface centered on the axis is formed so as to extend in the axial direction, and the cylindrical surface is formed at the time of drilling. Addition
A throw-away drill characterized in that it comes into sliding contact with the inner peripheral surface of the drill hole . 2. The indexable drill according to claim 1, wherein the cylindrical surface is formed in a direction intersecting the cutting edge at an obtuse angle. 3. An edge on the cutting edge side of the rake face,
The throw-away drill according to claim 1 or 2, wherein a breaker groove that gradually widens from the one end side to the other end side of the cutting blade is formed. 4. An edge on the cutting edge side of the rake face,
The indexable drill according to any one of claims 1 to 3, wherein a breaker groove that becomes a gradually deeper groove is formed from the one end side to the other end side of the cutting blade.