JP2001252809A - Drill insert - Google Patents

Abstract

[PROBLEMS] To use a single drill insert having an inner peripheral side cutting edge and an outer peripheral side cutting edge, and to secure chip dischargeability even when drilling a particularly sticky work material. It is an object to provide a drill insert that can be used. A land portion is provided only at a portion corresponding to an outer peripheral side cutting edge on an upper surface to be a rake surface, and a breaker of an inner peripheral side cutting edge is made to be an upper surface without a rising surface, or an inner peripheral side and an outer peripheral side cutting edge When a land portion having a rising surface of the breaker groove of the blade is formed, the land portion corresponding to the inner peripheral cutting edge is made lower than the outer peripheral cutting edge.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drill insert mounted on a turning tool or a turning tool for drilling holes.

[0002]

2. Description of the Related Art In a drilling tool as a milling tool or a turning tool for drilling a hole, an inner peripheral side insert and an outer peripheral side insert are detachably attached so that a rotation locus crosses a tip end of a tool body mutually. You are using the one that will be attached.
The inner and outer inserts having the same shape and commonized so as to be used as one type of drill insert are also widely used.

[0003] This kind of drill insert mainly has an inner peripheral cutting edge for cutting a bottom surface of an inner peripheral side hole when used as an inner peripheral side insert and an outer peripheral cutting edge mainly when used as an outer peripheral side insert. One drill insert is provided with an outer peripheral side cutting blade for cutting the side hole bottom surface.

[0004] Normally, when drilling, the outer peripheral side cutting edge has a higher peripheral speed than the inner peripheral side cutting edge between the chips generated by the inner peripheral side cutting edge and the chips generated by the outer peripheral side cutting edge. Due to the rotation, the amount and shape of the chips will be different. As a result, the inner cutting edge and the outer cutting edge have completely different designs, and in order to realize stable drilling,
Improvements have been made to achieve dedicated chip handling.

[0005] For example, in Japanese Patent Application Laid-Open No. Hei 6-134611, an inner peripheral chip breaker formed on an inner peripheral cutting edge and an outer peripheral chip breaker groove formed on an outer peripheral cutting edge are formed in different shapes. Good chip disposability is realized on both the inner and outer peripheral sides. Specifically, the inner peripheral side chip breaker forms the breaker wall surface directly from the rake face, while the outer peripheral side chip breaker groove forms the breaker wall surface via a concave groove on the rake surface. By changing the degree of bending of both breakers, long chips produced by the outer peripheral cutting edge having a higher peripheral speed can be curled into small pieces and separated, so that both can be discharged well.

[0006]

As described above, by forming the inner peripheral side chip breaker and the outer peripheral side chip breaker groove in different shapes, as a work material, a steel material such as carbon steel or chromium molybdenum steel (normal steel material) is used. Despite good chip evacuation for workpieces), it is still improved for more sticky workpieces (difficult to cut) such as stainless steel and low carbon steel. The fact is that there is room left.

More specifically, in the case of a normal work material, the chips on the inner peripheral side are umbrella-shaped chips in a single spiral shape and are continuously discharged neatly. In the case of cutting materials, it becomes a dumpling-shaped chip in which an irregular umbrella shape is intertwined,
Emission tends to be extremely poor. As a result, the chips on the inner peripheral side are clogged, causing problems such as increased cutting resistance during machining and the machining surface of the work material being scratched by the chips. Cannot be maintained.

As a countermeasure, there is a possibility that the breaker width of the inner chip breaker may be increased or the distance to the wall of the breaker may be increased, but the shape of the adjacent outer chip breaker can be freely designed. And the shape of the outer chip breaker groove itself may be affected, which may adversely affect the processing of the outer chip. The present invention has been made in view of such circumstances, and an object of the present invention is to use a single drill insert having an inner peripheral side cutting edge and an outer peripheral side cutting edge, and in particular, a work material having stickiness. An object of the present invention is to provide a drill insert that can ensure good chip dischargeability even when drilling a hole.

[0009]

In order to achieve the above object, a drill insert according to the first aspect of the present invention is provided with an inner peripheral cutting edge and an outer peripheral cutting edge at an upper edge of a polygonal plate. In the drill insert formed adjacent to the upper surface, the upper surface is provided with an outer peripheral breaker groove along the outer peripheral cutting edge, and a land portion along the outer peripheral breaker groove, and the top surface of the land portion has an inner peripheral surface. It is characterized by being higher than the upper surface of the side cutting blade.

[0010] The drill insert according to the second aspect of the present invention is a drill insert in which an inner peripheral side cutting edge and an outer peripheral side cutting edge are formed adjacent to an upper edge of a polygonal plate-like body. The upper surface includes an inner peripheral side breaker groove along the inner peripheral side cutting edge and an inner peripheral side land portion along the inner peripheral side breaker groove, and an outer peripheral side breaker groove and the outer peripheral side breaker groove along the outer peripheral side cutting blade. And an outer land portion along the outer periphery. The top surface of the inner land portion is formed lower than the top surface of the outer land portion.

According to these drill inserts, only the portion corresponding to the outer peripheral cutting edge is provided on the upper surface serving as the rake surface, and the breaker of the inner peripheral cutting edge is formed as the upper surface without the rising surface. When a land part having a rising surface of the breaker groove of the peripheral side and the outer peripheral side cutting edge is formed,
By making the land portion corresponding to the inner peripheral side cutting edge lower than the outer peripheral side cutting edge, it is possible to increase the chip processing capacity on the inner peripheral side.

Particularly, according to the drill insert of the first aspect, it is preferable when the processing diameter is large, and according to the drill insert of the second aspect, it is preferable when the processing diameter is small. It is possible to achieve both generation and dischargeability of the helical chips.

The present invention will be specifically described below with reference to the drawings.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a drill using the drill insert of the present invention will be described.

FIG. 1 is a view showing a drill D using a replaceable drill insert as a cutting edge. This drill D has a substantially cylindrical shape, and has a shank portion S fixed to a machine tool and a drill body. T. In the drill body T, flute grooves F and F ′ for discharging chips from the tip to the shank side are formed in a spiral shape in the longitudinal direction. At the tips of the flute grooves F and F ′, tip pockets 3 and 5 for mounting the drill insert 1 are provided on the surface of the drill body on the rotation direction side, respectively. The front end pocket 3 of the flute groove F is for detachably mounting the outer peripheral side insert 2 for mainly cutting the outer diameter side, and the outer peripheral surface side is open. The distal end pocket 5 of the flute groove F ′ is for detachably mounting the inner peripheral side insert 4 for cutting the inner diameter side similarly to the outer peripheral side insert 2, and the rotation axis direction of the drill body T is open. Have been. In addition, this pocket 3,5
Are formed such that the respective outer inserts 2 and inner inserts 4 to be mounted are rotated by about 90 degrees about the clamp screw L as a rotation center so that the respective inserts can be mounted.

A drill insert 1 having the same size and shape, which will be described later, is fixed to the pockets 3 and 5 with a clamp screw L.

Next, the drill insert of the present invention will be described.

FIG. 2 is a front view showing the external shape of the drill insert of the present invention, and FIG. 3 is a side view thereof.
The drill insert indicated by 1 as a whole has a polygonal shape, and a cutting edge is formed over the entire periphery of the insert at a ridge portion between a side surface 7 serving as a flank and an upper surface 8 serving as a rake face. These cutting blades have a pair of facing cutting blades having the same function. As a whole, the cutting blade is formed at the center O1 of a through hole 9 formed in the thickness direction of the insert main body for inserting a clamp screw. On the other hand, it has a point-symmetrical shape.

Of these cutting edges, 12 and 12 'are inner cutting edges, and 14 and 14' are outer cutting edges.

Between the inner peripheral side cutting edges 12 and 12 ', there is provided a biting cutting edge portion 30 which first comes into contact with the work material during drilling as the inner peripheral side cutting edge. On the other hand, the outer peripheral cutting edge 14, 1
4 ′ has two corner R portions 15 at both ends of the cutting blade 14,
16 to form a projecting portion 18 projecting from the drill insert 1 as a whole. Further, the corner R portion 16 between the outer peripheral side cutting edges 14 and 14 'functions as a biting cutting edge portion which comes into contact with the work material at the time of drilling.

Here, the corners R, 15 and 16 are formed such that the angles α, α ′ formed by straight lines continuing to the curved portions are close to right angles, and are approximately in the range of 60 ° to 105 °.

The cutting edge is formed into a sharp edge with both the inner cutting edge 12, 12 'and the outer cutting edge 14, 14' so as to be suitable for difficult-to-cut materials or deep-drilling, so as to reduce the cutting resistance during the processing. I have to.

This will be described with reference to a sectional view.

FIG. 4 is a cross-sectional view taken along the line AA in FIG. 2, and is a cross-sectional view showing the shape of the cutting edge of the protruding portion 18 provided with the outer peripheral cutting edge 14. As shown in FIG. The side surface 7 including the outer cutting edge 14 functions as a clearance surface, and the upper surface 8 functions as a rake surface. The upper surface 8 is provided with a land 31 and a breaker groove 32 inside the cutting blade 14, and a land portion 3 is formed from a rising surface 33 of the breaker groove.
4 are formed.

The breaker groove 32 has a curved shape larger than that of the land 31, and forms a rising surface 33 so that the land 34 is higher than the land 31 when viewed in the height direction of the drill insert 1. are doing. By forming the land portion 34 at such a large curved and high standing position, the chips cut by the outer peripheral side cutting edge 14 curl and can be divided into small pieces.

FIG. 5 is a sectional view taken along the line BB in FIG. 2, and is a sectional view showing the shape of the cutting edge of the outer peripheral cutting edge 14 '. The outer peripheral side cutting edge 14 ′ is located inside the cutting edge 14 during drilling, and the corner R portion 1 during drilling.
Due to the presence of 6, the chips generated by the cutting blade 14 are separated from the chips.

This cutting edge shape has a narrower and shallower breaker groove 32 'and a land portion 34' higher than the land portion 34 described above with respect to the cutting edge 14 described above. Except for this, the shape is substantially similar.

Next, the cutting edge shape of the inner peripheral side cutting edges 12, 12 'will be described.

As shown in FIG. 2, the inner cutting edge 12 forms the cutting edges 12, 12 'from the corner R portion 15 located near the center axis of the drill, and the two cutting edges are convex. It is formed in the shape of a letter. Further, a cutting edge portion 30 is provided at a corner located between the two cutting edges 12, 12 '.

The cutting blades have substantially the same shape as the two cutting blades 12 and 12 ', and have the shape shown in FIG. 6, which is a cross-sectional view taken along the line CC in FIG. Specifically, cutting blade 1
A flat breaker surface 36 having no land portion on the upper surface is formed from the lands 2 and 12 'via the land 31.

The outer cutting edges 14, 14 'and the inner cutting edges 12, 12' both have a larger rake angle β1 (corresponding to the outer cutting edges 14, 14 ') and β2 (to reduce the cutting resistance). (Corresponding to the inner peripheral side cutting edges 12, 12 ').

In particular, when the rake angle β1 is small, the outer peripheral cutting edge 14 has the following problem. That is, the protruding shape portion 18 of the outer peripheral side cutting edge 14 is a portion that first bites into the work material at the time of cutting, but if the rake angle β1 is small and receives a large resistance, it is slightly Although the amount is small, the protruding portion is twisted in the opposite direction to the rotation direction and on the inner peripheral side, so that the processing diameter is reduced. And since the processing is continued with the processing diameter small, the hole surface and the holder may contact during processing, or
When the holder is removed after processing, the insert may come into contact with the hole surface, and the finished state of the hole surface may be poor. In addition, in order to secure a balance between the cutting resistance of the outer cutting edge having a large cutting amount and the inner cutting edge having a small cutting amount, the rake angle β1 of the outer cutting edge is set to be smaller than the rake angle β2 of the inner cutting edge. Largely formed.

On the other hand, the inner peripheral cutting edge 12 'preferably has a large rake angle β2, but the cutting resistance is balanced so that the projecting portion 18 of the outer peripheral cutting edge 14 is not twisted. As described above, it is preferable to receive a somewhat larger cutting resistance than the protruding shape portion 18. Therefore, the rake angle β1 of the outer peripheral side cutting edge is formed larger than the rake angle β2 of the inner peripheral side cutting edge.

The rake angles in the drill insert of the present invention are appropriately determined according to the strength of the base material of the insert and the cutting conditions, and β1 is 23 to 33 degrees and β2 is 12 to 22 degrees, respectively. In this embodiment, β1 is formed at 27 degrees and β2 is formed at 18 degrees. When the rake angle is increased, the cutting force decreases, but the cutting edge strength decreases. Conversely, when the rake angle decreases, the cutting force increases, but the cutting edge strength increases. In the present invention, in order to realize a large rake angle, a land 31 is formed on the inner peripheral side of the cutting edge, and a high cutting edge strength and a small cutting resistance are provided in a well-balanced manner. The width of this land depends on the size of the insert, but is generally in the range of 0.02-0.
It is desirable to form a width of 07 mm.

Further, it is desirable that the breaker depth is formed deeper on the outer peripheral side than on the inner peripheral side. It is desirable that the breaker corresponding to the cutting edge 14) of the shape portion 18 be formed deeper from the viewpoint of cutting off chips and discharging. Specifically, the outer peripheral breaker groove h1 (corresponding to the cutting edge 14) is 0.15 to 0.35 m.
m and h2 (corresponding to the cutting edge 14 ') are 0.05 to 0.20 m
m is preferable.

Further, the width of the breaker grooves 32, 32 'formed along the outer peripheral side cutting blades 14, 14' is such that the breaker groove 32 along the cutting blade 14 for cutting the outermost peripheral portion is formed wider. I have. In this embodiment, the cutting blade 1 of the protruding shape portion 18 is used.
The breaker groove 32 along 4 is a large breaker groove including the entire protruding shape portion 18. Further, the breaker groove 32 of the cutting edge 14 of the protruding shape portion 18 is made deep and the rising surface 33 is made low, while the breaker groove 32 'of the other cutting edge 14' of the outer peripheral cutting edge is made shallow, and , The rising surface 33 'is raised.

Next, the reason why the shape of the breaker groove along the outer peripheral cutting edge is different depending on the portion will be described.

First, the chips of the cutting blade 14 along the protruding portion 18 are wide and have high rigidity (width d4 in FIG. 12).
), And easily bends. If such a chip is made shallow at the breaker groove so that the chip strongly hits the groove surface, the chip is quickly curled. When the curled chips hit the rising surface 33, the chips are likely to be clogged, and a large cutting resistance is generated. Therefore, in the present embodiment, the breaker groove 32 is formed so that the chip does not strongly hit the surface of the breaker groove, and the chip breaker groove 32 is formed so that the chip is smoothly discharged without forcibly curling.
And the rising surface 33 is formed low.

On the other hand, the chips of the other portion (cutting edge 14 ') of the outer peripheral cutting edge have a short effective blade length (see width d5 in FIG. 12) and the width of the chip is narrow. This narrow chip has a low rigidity and therefore has a property that it is difficult to bend. Therefore,
In this embodiment, the breaker groove 32 'is made shallow, narrow, and the rising surface 33' is raised so that the chips bounce against the surface of the breaker groove and furthermore bend securely at the rising surface.

By adjusting the width and the like of the breaker groove in this manner, the chip controllability is improved.

The width of the breaker grooves 32, 32 'differs depending on the size of the drill insert, but W1 is 1.6 to
It is good to form 3.5 mm and W2 in the range of 0.9 to 2.0 mm, respectively. Also, the land portions 34, 3 with respect to the cutting blade
The height of 4 'is 0.05 for h3 (corresponding to the cutting blade 14).
0.13mm, h4 (corresponding to cutting edge 14 ') is 0.13 ~
It is preferable to form each in the range of 0.2 mm.

Returning to FIG. 2, the shape of the land portion corresponding to the outer peripheral cutting edge will be described.

The land portions 34, 34 'used in the present invention are portions formed in an island shape on the rake face.

The land portions 34, 34 ′ have outer peripheral cutting edges 1.
Rising surface 3 of breaker groove 32, 32 'of 4, 14'
It is formed to secure the width and height of 3, 33 ', and has a rising surface corresponding to the length of the cutting blade 14, 14'.

On the other hand, the rake face where the inner peripheral side cutting edge exists is as follows:
In this example, in order to ensure sufficient chip evacuation,
A flat breaker surface 36 without a land portion is formed to ensure a sufficiently large surface.

Therefore, the boundary of the land portions 34 and 34 ′ with the rake face along the inner peripheral cutting edge connects a pair of corners located substantially diagonally with respect to the center O 1 of the drill insert 1. It is formed along a diagonal line. And, of these land portions 34, 34 ', the land portion 34 corresponding to the outer peripheral side cutting edge 14 adjacent to the corner R15 has the corner R
The side end part is slightly protruded from the diagonal line to the upper surface of the inner cutting edge. By adopting such a configuration,
A large breaker groove for finely cutting chips along the outer peripheral cutting edge 14 can be provided. In this case, since the inner peripheral side cutting edge 12 adjacent to the corner R15 has a relation including the rotation center axis O3 of the drill (see FIG. 12), a wide flat breaker surface for efficiently discharging umbrella-shaped chips is provided. However, the rotation center axis O3 has a corner R
The inclined portion 40 between the land portion 34 and the inner peripheral cutting edge groove surface of the land portion 34 may protrude more inward than the diagonal line described above, since the inclined portion 40 is located slightly in the inner peripheral cutting edge direction. it can.

With this configuration, a wide and deeply curved large groove for the outer peripheral cutting edge can be secured, and a flat and large breaker groove surface 36 can be formed on the inner peripheral side.

In the present embodiment, the breaker surface 36 is a flat surface without a land portion. However, the breaker surface 36 has a shape other than a flat surface such as a curved surface shape without a land portion, for example, without a land portion. No problem.

Next, the relationship between the land formed on the outer periphery and the upper surface along the inner cutting edge will be described.

FIG. 7 showing this relationship is shown in FIG.
FIG. This sectional view shows the outer peripheral side cutting edge 14 ′.
From the land → the outer peripheral side cutting edge groove → the land portion → the upper surface portion of the inner peripheral side cutting edge → the land portion → the outer peripheral side cutting edge breaker groove → the land → the outer peripheral side cutting edge 14. From FIG. 7, the depth relationship of the breaker groove, the height relationship between the land and the land portion, and the height relationship between the land portion corresponding to the outer peripheral cutting edge and the upper surface corresponding to the inner peripheral cutting edge can be understood. .

That is, the depth h1 of the breaker groove 32 of the cutting edge 14 for cutting the outermost peripheral portion of the outer peripheral side cutting edge is larger than the depth h2 of the breaker groove 32 'of the other portion 14' and the land portion. 34, 34 'are outer peripheral cutting edges 14, 1
The breaker surface 36 provided on the upper surface of the inner peripheral cutting edge is formed lower than the land 31, which is higher than the land 31 of 4 ′. By forming in this way, the outer peripheral side cutting blades 14, 1
While satisfying the chip processing property of 4 ′, the inner peripheral side cutting edge 12,
This improves the chip controllability of 12 '.

Next, the relationship between the top surface of the outer land portion will be described with reference to FIG. FIG. 8 is a cross-sectional view taken along the line JJ in FIG. 2 and shows a land from the inner peripheral cutting edge 12 ′ → the upper surface portion of the inner peripheral cutting blade → the outer peripheral land portion 34 ′ → the step portion → the outer peripheral land portion 34 → The surface extends from the upper surface portion of the inner peripheral cutting blade to the land to the inner peripheral cutting blade 12. From FIG. 8, the outer peripheral land portion 34 along the cutting edge 14 ′ of the other portion with respect to the top surface of the outer peripheral land portion 34 along the cutting edge 14 for cutting the outermost peripheral portion of the outer peripheral cutting edge. '
It can be understood that the top surface of the is raised.

As described above, for the outer land portions 34 and 34 ', the top surface of the land portion 34 corresponding to the cutting edge 14 for cutting the outermost periphery is made somewhat lower than 34' as described above. In addition, since the chips of the cutting edge 14 are wide and easily curved, the rising surface 33 is formed low in order to bend the chip without difficulty. This is because the chips at the portion 34 '(cutting edge 14') are narrow and difficult to curve, so that the rising surface 33 'is raised so as to be surely curved at the rising surface.

In the case of a drill insert having a small machining diameter, the width of the chips on the outer peripheral side cutting edges 14 and 14 'is almost the same between the cutting edge 14 of the projection-shaped portion 18 and the other cutting edge 14'. There is no problem even if the top surfaces of both land parts are the same height.

In the above-mentioned example, the breaker surface corresponding to the inner peripheral side cutting blade was flat, and the breaker rising surface was not formed. However, an inner land portion that is lower than the land portion corresponding to the outer cutting edge can be provided as long as the discharge performance of the inner chip is not impaired. At this time, it is desirable that the height of the top surface of the inner peripheral land portion is lower than the height at which the cutting edge is located in the height direction of the drill insert. FIG. 9 is a front view of the drill insert provided with such a low inner peripheral side land portion 70, and FIG. 10 is a cross-sectional view taken along line G-G showing the relationship between the cutting edge and the land portion.

Referring to FIGS. 9 and 11, the drill insert 1 'has an outer circumferential land portion and an inner circumferential land portion 70, and a gentle slope 40 at the boundary between both ends and a sharp slope. A step portion 50 with a sharp rise is formed. Of these,
The inclined portion 40 formed between the land portion 34 and the inner peripheral side breaker groove 71 has a gentle inclination with respect to the step portion 50 formed between the land portion 34 'and the inner peripheral side breaker groove 71. Forming a surface. Further, as is apparent from FIG. 9, the inclined surface 40 has a substantially triangular shape with the vertex at the corner R15. This is because, particularly when the processing diameter is small, by forming such an inclined portion 40, the inner peripheral side chips formed in an umbrella shape around the corner R side are more effectively cleaned in a clean umbrella shape. The function of the flat inner peripheral side breaker 36 also works, and the discharge efficiency can be increased.

FIG. 11 is a sectional view taken along the line II for explaining the height relationship between the land portions.

In this modified example, since the inner peripheral side breaker groove 71 has a low rising surface 72, the umbrella-shaped chips formed by the inner peripheral side cutting edge 12 'can be formed with a smaller turning radius. It becomes possible. Particularly when a small insert is used, the flute of the drill body also becomes smaller, so it is desirable to make the chip itself smaller, and a land portion having such a low rising surface is effective.

In the case of such a small drill, it is difficult to form a sufficient space as a guide for discharging chips from the insert to the flute. Therefore, it is particularly desirable that the inclined portion 40 between the outer peripheral land portion and the inner peripheral land portion adjacent to the corner R located near the rotation center of the drill has a surface having a particularly gentle inclination angle. By doing so, the flow of the chips is not hindered by the inclined portion 40, so that the chip transportability to the flute that discharges the inner peripheral side chips is improved. This is particularly effective for smaller drill inserts as compared to the previous embodiment.

Another reason for making the inclination of the inclined portion 40 gentle is as follows.

That is, in the case where the inner peripheral land portion 70 is not provided in the insert, when the processing diameter is small, the chips of the inner peripheral cutting blade tend to be discharged without being curled.
Therefore, a chip is applied to the land 70, and the corner R
On the 15th side, an inclined portion 40 is formed as a rising surface where the chip hits in the depth of the land portion 70, so that the chip hits the two-step rising surface and forms a clean umbrella. However, when the inclined surface 40 rises up abruptly, the chips tend to be irregular umbrella-shaped rather than clean umbrella-shaped, so in the present embodiment, the inclined portion 40 is formed on a gentle slope, In addition, by making the inclination more gently deeper than the inclined portion 40, the chips can be discharged in a clean umbrella shape.

Next, the relationship between the two drill inserts 1 (the outer insert 2 and the inner insert 4) during drilling will be described with reference to FIG.

FIG. 12 is a perspective layout view of the drill body T viewed from the outer periphery of the side surface.
Reference numeral 2 denotes an outer peripheral line of the drill body T, and T3 denotes an inner surface on which drill processing is performed. And FIG.
The middle and outer peripheral side inserts 2 and the inner peripheral side insert 4 are shown by solid lines, and the outer peripheral side insert 2 is viewed from the rake face side, and the inner peripheral side insert 4 is viewed from the mounting face side to the pocket. Are respectively shown. The outer insert 2 indicated by the dotted line overlaps with the inner insert 4 in which the outer insert 2 is rotated by 180 degrees with respect to the rotation trajectory of the outer insert 2 around the axis T1 of the drill body T. Explains the state.

The outer peripheral side insert 2 has a corner R portion 15
Is attached to the pocket portion 3 so as to be located outside the outer peripheral surface of the drill body T, and the inner peripheral side insert 4 is attached with the corner R15 located outside the rotation center line O3. In these two drill inserts, the outer peripheral side cutting edge 14 'and the inner peripheral side cutting edge 12' intersect at a point P on the rotation locus.

As a result, the width d1 from the center of rotation O3 to the intersection point P is the cutting area of the inner cutting edge, and the width from the point P to the inner working surface T3 is the outer cutting edge. This is the cutting area for the cutting edge. “D1 + d2” indicates the processing radius, and d3 indicates the processing diameter. Further, d4 indicates the blade length of the cutting edge 14 of the protruding portion 18 of the outer peripheral side cutting blade, and d5 indicates the effective blade length of another portion of the outer peripheral side cutting blade.

At this time, according to the present invention, the cutting area widths d1 and d2 of the inner peripheral side cutting edge 2 and the outer peripheral side cutting edge 4 are set to be substantially the same, and the characteristic breaker as described above is used as a drill insert. By providing the shape and the land portion, it is possible to secure the balance between the cutting areas d1 and d2 and to improve the dischargeability of chips in the inner peripheral cutting area d1.
As a result, the chip on the outer peripheral side is divided into two in the width direction at the corner R portion 16, and the action of the breaker groove and the land portion causes
It is further finely divided in the length direction and discharged to the flute groove F (outer peripheral side). On the other hand, the inner peripheral side chips can be efficiently discharged to the flute groove F '(inner peripheral side) even when processing a sticky work material due to the presence of the wide breaker surface. The present invention can take any form as long as the relationship between the top surface of the land portion formed on the outer peripheral side cutting edge and the shape of the rake face of the inner peripheral side cutting blade is satisfied.
For example, the general shape of the drill insert 1 may be a polygonal shape other than a quadrangle, and the drill insert 1 may not be provided with the protruding portion 7.

[0067]

According to the present invention described above, when a land portion is formed in which the rising surface of the breaker groove of the inner and outer peripheral cutting edges is greatly raised on the upper surface serving as the rake surface, the inner peripheral side cutting edge is formed. The upper surface where the land portion corresponding to the blade is lower than the outer cutting edge, or the land portion is provided only at the portion corresponding to the outer cutting edge, and the breaker surface of the inner cutting edge has no rising surface By doing so, it is possible to prevent the chip processing capacity on the inner peripheral side from being reduced.

This is particularly effective when machining a sticky work material.

[Brief description of the drawings]

FIG. 1 shows a drill D using a replaceable drill insert as a cutting edge.

FIG. 2 is a front view showing an external shape of the drill insert according to the first embodiment of the present invention.

FIG. 3 is a side view of the drill insert of FIG. 2;

FIG. 4 is a sectional view taken along line AA in FIG. 2;

FIG. 5 is a sectional view taken along line BB in FIG. 2;

FIG. 6 is a sectional view taken along line CC in FIG. 2;

FIG. 7 is a sectional view taken along the line EE in FIG. 2;

8 is a sectional view taken along the line JJ in FIG.

FIG. 9 is a front view showing an external shape of a drill insert according to a second embodiment of the present invention.

FIG. 10 is a sectional view taken along the line GG in FIG. 9;

11 is a sectional view taken along the line II in FIG. 9;

FIG. 12 is a perspective layout view of the drill body T as viewed from the outer periphery of the side surface.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Drill insert 12, 12 'Inner peripheral side cutting edge 14, 14' Outer peripheral side cutting edge 15, 16 Corner R part 18 Projection shape part 32, 32 'Outer peripheral side breaker groove 34, 34' Outer peripheral side land part 36 No breaker surface 40 Inclined part 70 Inner peripheral land part 71 Inner peripheral breaker groove

Claims (7)

[Claims] 1. A drill insert in which an inner peripheral side cutting edge and an outer peripheral side cutting edge are formed adjacent to a ridge of an upper surface of a polygonal plate-like body, the upper surface has an outer periphery along the outer peripheral side cutting blade. A side breaker groove, and a land portion along the outer peripheral side breaker groove,
A top surface of the land portion is higher than an upper surface along an inner peripheral cutting edge. 2. A drill insert in which an inner peripheral side cutting edge and an outer peripheral side cutting edge are formed adjacent to a ridge of an upper surface of a polygonal plate-like body, the upper surface extends along the inner peripheral cutting edge. An inner peripheral side land portion along the inner peripheral side breaker groove and the inner peripheral side breaker groove, and an outer peripheral side breaker groove along the outer peripheral side cutting edge and an outer peripheral side land portion along the outer peripheral side breaker groove are provided, respectively. ,
A drill insert, wherein the top surface of the inner land portion is formed lower than the top surface of the outer land portion. 3. The drill insert according to claim 2, wherein the top surface of the inner peripheral land portion is formed to be lower than the height at which the cutting edge is located when viewed in the height direction of the drill insert. 4. The drill insert according to claim 3, wherein an inclined portion is formed at a boundary between the outer land portion and the inner land portion having different heights. 5. The drill insert according to claim 1, wherein in the drill insert, at least one outer peripheral side cutting edge is formed at a ridge of a protruding portion having two corners R. 6. The drill insert according to claim 1, wherein the outer land portion forms top surfaces having different heights. 7. The outer peripheral side breaker has a wide breaker groove corresponding to the cutting edge formed in the protruding shape portion, and a narrow breaker groove corresponding to the cutting edge adjacent to the protruding shape portion. 6. The drill insert according to 6.