JP2012143866A - Drill body for drill tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a drill tool and a drill body preventing such a phenomenon that an inside insert and an outside insert alternately project in an overlapped region, even if the distance between the inside insert and the outside insert is short.SOLUTION: A drill includes: the inside insert which is mounted to be close to a rotary shaft at a distal end part of the drill body and has an axis-symmetrical contour line composed of four cutting blades and four round corner parts; and the outside insert which is the same as the inside insert and is mounted to be farther from the rotary shaft than the inside insert. The inside insert and the outside insert have the rotary loci partially overlapped with each other. In the region where the rotary loci are overlapped with each other, a cutting blade of the inside insert and a cutting blade of the outside insert extend toward the rotary shaft in a direction of a material to be cut. The locus of the cutting blade of the inside insert projects in the direction of the material to be cut along the rotary shaft of the drill body as compared with the locus of the cutting blade of the outside insert.

Description

The present invention relates to a drill body for a drill tool.

  In the conventional insert type drill tool, two square cutting inserts as shown in FIG. 1A are arranged one by one on the inside and outside of the drill body. The inner insert and the outer insert are arranged on the opposite sides with respect to the rotation axis of the drill body. FIGS. 1B and 1C are each shown by rotating the inner insert by 180 ° with respect to the rotation axis of the drill body. It is shown together with the cutting blade of the insert, and shows the relative positional relationship between the inner insert cutting blade and the outer insert cutting blade during drilling.

  The diameter of the insert type drill tool varies depending on the distance between the inner insert and the outer insert. When the inner insert and the outer insert are arranged as shown in FIG. 1C, only the cutting blade of the inner insert protrudes in a region where the rotation trajectory overlaps between the inner insert and the outer insert cutting blade. Sometimes only cutting with the inner insert occurs. However, as shown in FIG. 1B, when the inner insert and the outer insert are arranged closer to each other, the cutting blade of the inner insert and the cutting of the outer insert are performed in the region where the rotation trajectories of the inner insert and the outer insert overlap. Both blades protrude and a phenomenon occurs in which the work material is alternately cut by both cutting blades during drilling. As a result, a long and thin tip is generated at this portion during drilling, and the side of the drill body is surrounded without being segmented, and is sandwiched between the drill body and the hole being machined to obstruct the drilling work. There was a problem of damaging the cutting material. Such a phenomenon is particularly problematic when the work material is a relatively thin material such as mild steel. In addition, cutting resistance concentrates on the ends of the inner and outer inserts that protrude alternately in the direction of the rotation axis of the drill body in the region where the rotation traces of the inner and outer inserts overlap, reducing the service life of the cutting inserts Therefore, stable cutting performance cannot be guaranteed.

  Korean Patent Application Publication No. 2005-7569 discloses an insert type drill tool different from this. As shown in FIG. 2A, the drill tool uses, as an inner insert, an insert having first and second partial blades 4 and 6 each of which is connected to each other via a transition partial blade 2, and a normal square insert is used as an outer insert. Used as an insert. FIG. 2B shows the arrangement relationship of the two cutting inserts. FIG. 2C shows the relative positional relationship of the cutting blade between the inner insert and the outer insert by rotating the inner insert of FIG. 2B by 180 ° with respect to the rotation axis.

  Korean Patent Application Publication No. 2005-7568 discloses another insert type drill tool. In this drill tool, as shown in FIG. 3, an insert provided with first and second partial blades 4 'and 6', each cutting blade being connected to each other via a transition partial blade 2 ', is used as an inner insert. An insert that is shaped is used as the outer insert.

  In the drill tool, the inner insert and the cutting blade of the outer insert are arranged substantially in parallel in the region where the rotation trajectories of the inner insert and the outer insert overlap, so the distance between the inner insert and the outer insert is close. Even if it becomes, the inner insert and the outer insert do not protrude alternately in the rotation axis direction of the drill main body, and the state in which only the inner insert protrudes can be maintained. As a result, as shown in FIG. 1B, the inner and outer inserts are compared with the structure in which the cutting blades of the inner insert and the outer insert are arranged in opposite directions in the region where the rotation trajectories of the inner insert and the outer insert overlap. Even when the distance between the inserts is short, the inner and outer inserts protrude alternately, and the phenomenon that small and thin chips are generated from that part and the phenomenon that the cutting resistance is locally concentrated on that part can be prevented. .

  However, the inner insert and the outer insert are different from each other, and a separate powder metallurgy mold must be provided in order to manufacture each insert, resulting in inconvenience that the production process must be managed separately. In addition, the insert stock must be managed in two types, and there is an inconvenience that the inserts on the inside and outside must be carefully selected and installed when the insert is installed or replaced.

The object of the present invention is to solve such problems of the prior art, and even when the distance between the inner insert and the outer insert is close, the inner insert and the outer insert alternate in the region where the inner insert and the outer insert overlap. Drill tool with cutting insert that prevents insert phenomenon and improves insert productivity by making the inner insert and outer insert the same shape, and facilitates customer insert inventory management and installation or replacement And a drill body .

In order to solve the above problems, the present invention provides a drill body for a drill tool having a rotating shaft, an inner pocket formed at the tip of the drill body in the vicinity of the rotating shaft, An outer pocket formed at a position farther from the rotation axis than the inner pocket at the distal end, each pocket being a first wall facing the work material, and perpendicular to the first wall and perpendicular to the first wall. A second wall portion disposed in proximity to the rotation axis; and a bottom surface, each of the first wall portion and the second wall portion being adjacent to the bottom surface from a flat lower side surface and the lower side surface. A first wall portion of the inner pocket and a first wall portion of the outer pocket having the same surface shape, and a second wall portion of the inner pocket and a second wall portion of the outer pocket. On the first wall of the inner pocket with the same surface shape Each of the side surface and the upper side surface of the first wall portion of the outer pocket includes a first partial surface, a transition partial surface, and a second partial surface in a direction away from the rotation axis of the drill body, and the first wall portion of the inner pocket A drill for a drill tool, characterized in that the first partial surface of the upper side surface of the first wall and the second partial surface of the upper side surface of the first wall portion of the outer pocket are inclined toward the work material toward the rotation axis of the drill body. Provide the body.

According to the drill tool having a cutting insert described later , the inner insert and the outer insert protrude alternately in the region where the inner insert and the outer insert overlap even when the distance between the inner insert and the outer insert is reduced. At the same time, the shape of the inner insert and the outer insert can be made the same to improve the productivity of the insert, and the customer can manage insert stock and install or replace it.

It is the figure which showed the cutting insert of the conventional insert type drill tool. It is the figure which showed the cutting insert of the conventional insert type drill tool. It is the figure which showed the cutting insert of the conventional insert type drill tool. It is a top view of the cutting insert in one example of the present invention. It is a schematic diagram for demonstrating the shape of the cutting insert in one Example of this invention. It is the partial side view which showed the part with which the cutting insert of the drill tool in one Example of this invention was mounted | worn. It is the fragmentary perspective view which showed the cutting insert mounting part of the drill tool of FIG. It is drawing which showed the positional relationship of the cutting insert of the drill tool of FIG. It is a perspective view of the cutting insert of FIG. FIG. 7 is a rear perspective view of the cutting insert of FIG. 6. It is a perspective view of the pocket by which the inner insert of FIG. 6 is mounted | worn. FIG. 7 is a perspective view of a pocket in which the outer insert of FIG. 6 is mounted. It is an enlarged view of the pocket shown in FIG. It is an enlarged view of the pocket shown in FIG.

  Hereinafter, the present invention will be described with reference to embodiments shown in the accompanying drawings.

  FIG. 4 is a plan view of the cutting insert 10 according to one embodiment of the present invention. The cutting insert 10 is substantially square and has an axis of symmetry and has an axisymmetric contour consisting of four cutting blades 11, 11 ', 11 ", 11"' and four rounded corners. That is, the cutting blades 11, 11 ′, 11 ″, 11 ″ are rotationally symmetric with respect to the rotation axis of the insert. Each cutting blade 11, 11 ′, 11 ″, 11 ″ includes first and second partial blades 14, 16 connected via a transitional partial blade 12. The transition partial blade 12 and the first and second partial blades 14 and 16 are partially straight. The coupling portion between the first partial blade 14 and the transition partial blade 12 forms a convex portion, and the coupling portion between the transition partial blade 12 and the second partial blade 16 bends so as to form a concave portion. Each of the cutting blades 11, 11 ', 11 ", 11"' contacts the virtual inscribed circle (c) at the contact points T1, T2, T3, T4. A line connecting the contact points T2 and T4 or T1 and T3 facing each other becomes a reference line (L or L ′) passing through the center (O) of the cutting insert. Preferably, the transition partial blade 12 extends from the second partial blade 16 in a direction far from the reference line (L) facing the transition partial blade 12, and the second partial blade 16 extends from the transition partial blade 12 to the second It extends in a direction far from the partial reference line (L) facing the partial blade 16. Further, preferably, the first partial blade 14 extends from the transition partial blade 12 in a direction closer to the reference line (L) facing the first partial blade 14.

  Preferably, the angle θ1 with respect to the reference line (L) of the transition partial blade 12 is the same as the angle θ3 with respect to the reference line (L) of the second partial blade 16. In such a case, the shape of the cutting insert 10 is vertically and horizontally symmetrical with respect to the reference line (L) as shown in FIG. 5 which is a schematic diagram for explaining the shape of the cutting insert according to one embodiment of the present invention. It is similar to the shape in which each corner of the butterfly-shaped insert is chamfered along the dotted line.

Preferably, the angle θ1 with respect to the reference line (L) of the transition partial blade 12 and the angle θ3 with respect to the reference line (L) of the second partial blade 16 are about 5 to 7 degrees, and the reference line (L ) Is about 14 to 16 degrees. The angle range is an advantageous angle range when the cutting insert is mounted in the drill body of the present invention and cutting is performed. If the angle θ1, the angle θ3, and the angle θ2 are too large, the cutting blade may partially protrude and the cutting resistance may be concentrated. If the angle θ1 is too small, the cutting force may be close to a linear cutting blade. Problems occur with square cutting inserts.

6 and 7 show the drill tool 1 on which the cutting inserts 10, 10 'are mounted. The inner cutting insert 10 and the outer cutting insert 10 'are mounted in the pockets of the drill body head portion at the tip of the drill body by fixing screws 18, 18'. The inner insert 10 is mounted close to the rotation axis of the drill body, and the outer insert 10 ′ is mounted at a position farther from the rotation axis than the inner insert 10. The inner insert 10 and the outer insert 10 'have the same shape, size, material, and the like. The inserts 10, 10 'are arranged such that the second partial blades 16, 16' are located closer to the axis of rotation of the drill body than the first partial blades 14, 14 '. The inner insert 10 is arranged such that the first partial blade 14 protrudes in the direction of the work material from the second partial blade 16, and the outer insert 10 ′ has the second partial blade 16 ′ from the first partial blade 14 ′. It is arranged so as to protrude in the direction. FIG. 6A shows the inner insert 10 disposed near the rotation axis of the drill body of the present invention , and FIG. 6B shows the outer insert 10 ′ disposed near the outer surface of the drill body of the present invention. .

As described above, the drill tool that is preferably used in the present invention has the same insert insert for the inner insert and the outer insert, which simplifies the insert production process and inventory management, and inserts and replaces the drill tool. Work is also simplified.

  FIG. 8 shows the relative positional relationship of the cutting blades between the inner insert 10 and the outer insert 10 ′ mounted on the drill body head. As shown in FIGS. 6 and 7, the inner insert 10 and the outer insert 10 ′ are actually arranged on opposite sides with respect to the rotation axis of the drill body. FIG. 8 shows the relative positions of the two cutting inserts during drilling. In order to clearly show a typical cutting blade positional relationship, the inner insert 10 is shown rotated 180 degrees with respect to the rotation axis of the drill body. Although the front surfaces of both inserts appear to be located on the same virtual surface in FIG. 8, in fact the front surfaces of both inserts are slightly inclined with respect to the virtual surface to provide a more preferred cutting edge angle. It can be slightly offset from the virtual plane. In such a case, as described above, the angle by which the inner insert 10 is rotationally moved with respect to the rotation axis of the drill body is not strictly limited to 180 °.

  The rotation trajectories of the cutting blades of the inner insert 10 and the outer insert 10 'facing the work material overlap in a partial area. In the overlap region, the first partial blade 14 of the inner insert 10 and the second partial blade 16 'of the outer insert 10' are inclined at a predetermined angle in the direction of the work material toward the rotation axis of the drill body. The first partial blade 14 of the inner insert 10 protrudes from the second partial blade 16 'of the outer insert 10') in the direction toward the work material along the rotation axis of the drill body.

  With such a technical configuration, even when the center of the inner insert 10 and the center of the outer insert 10 ′ are close to each other, the cutting blades of both inserts protrude alternately in the region where the inner insert and the outer insert overlap during drilling. Without doing so, only the cutting blade of the inner insert 10 can be kept protruding. That is, in the region where the inner insert 10 and the outer insert 10 'overlap, both inserts are maintained while the foremost corner of the outer insert 10' is not in contact with the work material by the effective front cutting blade of the inner insert 10. It becomes easy to adjust the radial distance between them. Therefore, it is possible to prevent a long and narrow chip from being generated in the overlapping region of both inserts. Moreover, the phenomenon that cutting resistance concentrates only on the edge part of a cutting blade in the area | region where an inner insert and an outer insert overlap like the prior art can be prevented.

  On the other hand, as compared with the case where the first partial blade 14 of the inner insert 10 is parallel to a plane perpendicular to the rotation axis of the drill body or tilted in the opposite direction of the work material toward the rotation axis of the drill body, It is advantageous for the first partial blade 14 to incline toward the work material toward the rotation axis of the drill body so that the first partial blade 14 first enters the work material and is fixed in the work material. This is because if the first partial blade 14 is inclined in the above-described direction, the first partial blade 14 and the transition partial blade 12 form a V shape and can easily enter and fix the work material.

  Of the first partial blade 14 of the inner insert 10, the portion adjacent to the transition partial blade 12 is a distance d from the portion of the second partial blade 16 ′ of the outer insert 10 ′ on the opposite side of the transition partial blade 12 ′. Protruding. The distance (d) is desirably about 0.12 to 0.15 mm. This is an appropriate numerical range selected in consideration of the drill transfer amount (mm / number of rotations) during cutting.

  The first partial blade 14 of the inner insert is inclined by an angle θ4 with respect to a plane perpendicular to the rotation axis of the drill body. The angle θ4 is 5 degrees or less, more preferably 3 to 5 degrees. If the angle θ4 is too large, the cutting force is reduced, but stable drilling is difficult, and if it is too small, the drilling is stable, but the cutting force can be increased.

  In this way, the first partial blade 14 of the inner insert 10 extends at a relatively small angle with respect to the plane perpendicular to the rotation axis of the drill body, so that the first partial blade 14 of the inner insert 10 is the work material. The cutting force can be uniformly dispersed when entering the steel.

  On the other hand, the first partial blade 14 ′ of the outer insert 10 ′ is inclined in the direction of the work material toward the rotation axis. Specifically, the first partial blade 14 'of the outer insert 10' is inclined at an angle θ5 with respect to a plane perpendicular to the rotation axis of the drill body. The angle θ5 is desirably 18 to 19 degrees. The numerical range is an angle that is advantageous for the first partial blade 14 'of the outer insert 10' to enter the work material. If the angle θ5 is too large, stable drilling work is difficult.

  The transition partial blade 12 ′ of the outer insert 10 ′ is inclined in the opposite direction of the workpiece toward the rotation axis, opposite to the first partial blade 14 ′. This makes it easy for the first partial blade 14 ′ and the transition partial blade 12 ′ of the outer insert 10 ′ to form a V shape and enter and stabilize the work material. Further, the cutting resistance acting on the first partial blade 14 ′ and the transition partial blade 12 ′ is partially offset, and the cutting resistance is reduced.

  The transition partial blade 12 ′ of the outer insert 10 ′ is positioned forward in the work material direction from the second partial blade 16 of the inner insert 10. As a result, the transition partial blade 12 ′ of the outer insert 10 ′ and the second partial blade 16 of the inner insert 10 sequentially enter the work material, and the cutting resistance can be reduced compared to the simultaneous entry. .

  FIG. 9 is a perspective view illustrating an upper surface of a cutting insert according to an embodiment of the present invention, and FIG. 10 is a perspective view illustrating a bottom surface of the cutting insert according to an embodiment of the present invention. The cutting insert comprises four side walls that are rotationally symmetric with respect to each other. Each side wall has an upper side surface 21, 21 ', 21 ", 21"' extending from the upper surface of the cutting insert along the geometry of the four cutting blades 11, 11 ', 11 ", 11"'; Flat lower side surfaces 31, 31 ', 31 ", 31"' extending from the bottom surface of the cutting insert are provided. Corner portions between adjacent lower side surfaces 31, 31 ', 31 ", 31"' are chamfered to form chamfered surfaces 41, 41 ', 41 ", 41"'. The bottom surface 30 of the cutting insert is flat as shown in FIG.

  11 and 12 are perspective views of pockets of a drill body head portion to which cutting inserts 10 and 10 'according to an embodiment of the present invention are mounted. FIG. 11 shows the inner pocket 20 in which the inner insert 10 is mounted, and FIG. 12 shows the outer pocket 20 ′ in which the outer insert 10 ′ is mounted. The inner pocket 20 is formed at the tip of the drill body in the vicinity of the rotation axis, and the outer pocket 20 ′ is formed at the tip of the drill body at a position farther from the rotation axis than the inner pocket 20. Each of the pockets 20 and 20 'has a first wall 51, 61, 51 "", 61 "" facing the work material, and a first wall arranged perpendicular to the first wall and close to the rotation axis of the drill body. Two wall portions 51 ', 61', 51 "', 61"', second wall portions 51, 61, 51 "", 61 "" facing the work material, and bottom surfaces 71, 71 'are provided. The inner pocket 20 may further include third wall portions 51 ″ and 61 ″ facing the second wall portions 51 ′ and 61 ′. The first wall portion, the second wall portion, and the third wall portion are bent to correspond to the upper side surfaces 21, 21 ′, 21 ″, 21 ″ ′ of the cutting inserts 10, 10 ′. , 51 ″, 51 ″ ′, 51 ″ ″ and flat lower side surfaces 61, 61 ′, 61 ″, 61 ″ corresponding to the lower side surfaces 31, 31 ′, 31 ″, 31 ″ ′ of the cutting insert 10, 10 ′. ', 61 "" and flat bottom surfaces 71, 71' corresponding to the bottom surfaces 30 of the cutting inserts 10, 10 '.

  Since the inner pocket 20 and the outer pocket 20 'are fitted with cutting inserts 10, 10' having the same shape and size, the first wall portions 51, 61 of the inner pocket and the first wall portion 51 "" of the outer pocket, 61 "" includes at least partially the same surface shape, and the second wall portions 51 ', 61' of the inner pocket and the second wall portions 51 "', 61"' of the outer pocket are at least partially the same surface. It has a shape.

  Preferably, when the cutting insert 10, 10 ′ is installed in the pocket 20, 20 ′, the cutting insert 10, 10 ′ has a flat bottom surface 71, 71 ′ of the pocket 20, 20 ′ and a flat lower portion of the first wall. Contact is supported only on the side surfaces 61, 61 "" and the flat lower side surface 61 ', 61 "' of the second wall, i.e. extending along the cutting blade geometry of the cutting insert 10, 10 '. The upper side surfaces 21, 21 ′, 21 ″, 21 ″ ′ and the corresponding upper side surfaces 51, 51 ′, 51 ″, 51 ″ ′, 51 ″ ″ of the pockets 20, 20 ′ are not in contact with each other and are separated from each other.

  For example, when the inner insert 10 is mounted in the inner pocket 20, the flat lower side surfaces 31, 31 ′ of the inner insert 10 are supported in contact with the flat lower side surfaces 61, 61 ′ of the inner pocket 20, respectively. The flat bottom surface 30 is supported in contact with the flat bottom surface 71 of the inner pocket 20. Also, for example, when the outer insert 10 'is installed in the outer pocket 20', the flat lower side surfaces 31, 31 'of the outer insert 10' are respectively the flat lower side surfaces 61 "', 61" "of the outer pocket 20'. The flat bottom surface 30 of the outer insert is supported in contact with the flat bottom surface 71 'of the outer pocket 20'.

  Through such a technical configuration, the upper side surface 51 of the pocket corresponding to the upper side surface 61, 61 ′, 61 ″, 61 ′ ″, 61 ″ ″ of the cutting insert 10, 10 ′ having a bent and complicated shape. , 51 ', 51 ", 51'", 51 "" are machined with relatively wide tolerances and are flat and simple shapes that support the cutting insert in contact with the cutting insert 10, 10 '. There is an advantage that only the bottom surfaces 71, 71 ′ and the lower side surfaces 61, 61 ′, 61 ″, 61 ′ ″, 61 ″ ″ of the pockets 20, 20 ′ need to be machined with precise tolerances. Thereby, the pockets 20 and 20 ′ can be efficiently manufactured in terms of time and cost. However, the upper side surfaces 61, 61 ′, 61 ″, 61 ′ ″, 61 ″ ″ of the cutting inserts 10, 10 ′ having a bent shape and the upper side surfaces 51, 51 ′, 51 of the corresponding pockets. The space | interval with '', 51 '' ', 51' '' 'must be so small that a chip piece does not narrow in the meantime.

  13 and 14 are enlarged views of the inner pocket 20 and the outer pocket 20 'shown in FIGS. As shown in FIGS. 13 and 14, the upper side surface 51 of the first wall portion of the inner pocket 20 and the upper side surface 51 ″ ″ of the first wall portion of the outer pocket 20 ′ are far from the rotation axis of the drill body. A first partial surface 82, 82 "", a transition partial surface 84, 84 "" and a second partial surface 86, 86 "" are provided in the direction. Further, the upper side surface 51 ′ of the second wall portion of the inner pocket 20 and the upper side surface 51 ′ ″ of the second wall portion of the outer pocket 20 ′ are each in the direction away from the work material, the first partial surface 82 ′. , 82 ′ ″, transition partial surfaces 84 ′, 84 ′ ″, and second partial surfaces 86 ′, 86 ′ ″. The first partial surface 82 of the upper side surface 51 of the first wall portion of the inner pocket 20 and the second partial surface 86 '' '' of the upper side surface 51 '' '' of the first wall portion of the outer pocket 20 'are formed on the drill body. Inclined in the direction of the work material toward the rotation axis. The first partial surface 82 ′ of the upper side surface 51 ′ of the second wall portion of the inner pocket 20 is inclined in the direction of the rotation axis of the drill body toward the work material, and the upper side surface of the second wall portion of the outer pocket 20 ′. The second partial surface 86 '' 'of 51' '' is inclined in the direction opposite to the rotation axis of the drill body toward the work material. As shown in FIG. 8, the first partial blade 14 of the inner insert 10 and the second partial blade 16 ′ of the outer insert 10 ′ are in a region where the inner insert 10 mounted in the inner pocket 20 overlaps the outer insert 10 ′. Are all inclined at a predetermined angle in the direction of the work material toward the rotation axis of the drill body, and the four cutting blades of the inner insert 10 and the outer insert 10 ′ are rotationally symmetrical with each other. That is, the first partial surface 82 of the upper surface 51 of the first wall portion of the inner pocket 20 and the second partial surface 86 '' '' of the upper surface 51 '' '' of the first wall portion of the outer pocket 20 'are respectively In FIG. 8, the cutting blade portions of the inner insert 10 and the outer insert 10 ′, whose rotation trajectories are superimposed on each other, have a shape suitable for accommodating the cutting blade portion having a 180 ° rotational symmetry, so that the above-described directionality is achieved. To have. The first partial surface 82 ′ of the upper surface 51 ′ of the second wall portion of the inner pocket 20 and the second partial surface 86 ′ ″ of the upper surface 51 ′ ″ of the second wall portion of the outer pocket 20 ′ are respectively In FIG. 8, the cutting blade portions of the inner insert 10 and the outer insert 10 ′ whose rotation trajectories are superimposed on each other have a shape suitable for accommodating the cutting blade portion having a 90 ° rotationally symmetrical relationship. To have.

  While the invention has been described and illustrated through preferred embodiments, those skilled in the art will recognize that various modifications and changes can be made without departing from the scope and scope of the appended claims.

The above-described drill tool with the cutting insert prevents the inner insert and the outer insert from protruding alternately in the region where the inner insert and the outer insert overlap even when the distance between the inner insert and the outer insert is reduced. At the same time, the inner insert and the outer insert can have the same shape to improve the productivity of the insert, and the customer can manage the insert stock and install or replace it.

Claims (2)

A drill body for a drill tool having a rotating shaft,
An inner pocket formed at the tip of the drill body close to the rotating shaft;
An outer pocket formed at a position farther from the rotation axis than the inner pocket at the tip of the drill body,
Each pocket includes a first wall portion facing the work material, a second wall portion perpendicular to the first wall portion and disposed close to the rotation axis of the drill body, and a bottom surface.
Each of the first wall portion and the second wall portion includes a flat lower side surface adjacent to the bottom surface, and an upper side surface bent from the lower side surface,
The first wall portion of the inner pocket and the first wall portion of the outer pocket have the same surface shape, and the second wall portion of the inner pocket and the second wall portion of the outer pocket have the same surface shape,
The upper side surface of the first wall portion of the inner pocket and the upper side surface of the first wall portion of the outer pocket respectively have a first partial surface, a transition partial surface, and a second partial surface in a direction away from the rotation axis of the drill body. Prepared,
The first partial surface of the upper side surface of the first wall portion of the inner pocket and the second partial surface of the upper side surface of the first wall portion of the outer pocket are inclined toward the work material toward the rotation axis of the drill body. Features a drill body for a drill tool. The upper side surface of the second wall portion of the inner pocket and the upper side surface of the second wall portion of the outer pocket each include a first partial surface, a transition partial surface, and a second partial surface in a direction away from the work material,
The first partial surface of the upper side surface of the second wall portion of the inner pocket is inclined in the direction of the axis of rotation of the drill body toward the work material, and the second partial surface of the upper side surface of the second wall portion of the outer pocket is cut. The drill body for a drill tool according to claim 1, wherein the drill body is inclined in a direction opposite to a rotation axis of the drill body toward the material.

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