JP7516771B2 - Indexable drill - Google Patents

Description

The present invention relates to an indexable drill in which an insert mounting seat is formed at the tip of a drill body that rotates around an axis and a cutting insert is removably attached to the insert mounting seat, a cutting insert that is removably attached to the insert mounting seat of such an indexable drill, and a drill body of such an indexable drill.

For example, Patent Document 1 describes such an indexable drill in which the insert mounting seat of the drill body has a dividing surface extending perpendicular to the axis and a torque transmission surface adjacent to this dividing surface, and the cutting insert has a dividing surface extending perpendicular to the axis and a torque receiving surface extending from this dividing surface toward the tip flank and adjacent to the tip flank, and the cutting insert is removably attached to the insert mounting seat by a fastening screw.

European Patent No. 2408581

However, in the indexable drill described in Patent Document 1, the torque receiving surface of the cutting insert is adjacent to and intersects with the tip flank, and the contact area between this torque receiving surface and the torque transmission surface of the drill body is exposed at the tip of the indexable drill. For this reason, particularly in wet cutting where drilling is performed while supplying coolant, fine chips generated by cutting turn into sludge together with the coolant and tend to enter the contact area between the torque receiving surface and the torque transmission surface from the tip side of the drill body, and this sludge may wear down the torque receiving surface and torque transmission surface, shortening the life of the drill.

The present invention was made against this background, and aims to provide an indexable drill that can prevent such sludge from entering the contact area between the cutting insert and the insert mounting seat from the tip side of the drill body, thereby preventing the drill life from being shortened, a cutting insert that can be removably attached to the insert mounting seat of such an indexable drill, and a drill body of such an indexable drill.

In order to solve the above problems and achieve the above object, the present invention provides an indexable drill in which an insert mounting seat is formed at the tip of a drill body that rotates around an axis, and a cutting insert is removably attached to the insert mounting seat, and a body chip discharge groove is formed on the outer periphery of the tip of the drill body, the body chip discharge groove opening at the tip surface of the drill body and extending toward the rear end, and an insert chip discharge groove is formed in the cutting insert, the insert chip discharge groove opening at the tip flank of the cutting insert and communicating with the body chip discharge groove, a cutting edge is formed at the intersection ridge between the wall surface of the insert chip discharge groove facing the drill rotation direction and the tip flank, and the insert mounting seat is provided with a cutting edge formed in the insert chip discharge groove. The cutting insert has a bottom surface facing the tip of the drill body, a wall surface extending from the bottom surface toward the tip of the drill body and facing the drill rotation direction, and a screw hole opening into the bottom surface, and the cutting insert has a seating surface facing the rear end of the drill body and seated on the bottom surface, a contact surface facing the opposite side to the drill rotation direction and contacting the wall surface from the drill rotation direction, a convex portion protruding from the contact surface on the tip side of the contact surface toward the opposite side to the drill rotation direction, and a mounting hole penetrating from the tip relief surface to the seating surface, and the cutting insert is attached to the insert mounting seat by screwing a clamp screw inserted into the mounting hole into the screw hole.

That is, the indexable drill of the present invention is an indexable drill in which an insert mounting seat is formed at the tip of a drill body that rotates around an axis, and a cutting insert is removably attached to this insert mounting seat, and a body chip discharge groove is formed on the outer periphery of the tip of the drill body, opening on the tip surface of the drill body and extending toward the rear end, and an insert chip discharge groove is formed in the cutting insert, opening on the tip flank of the cutting insert and communicating with the body chip discharge groove, a cutting edge is formed at the intersection ridge between the wall surface of the insert chip discharge groove facing the drill rotation direction and the tip flank, and the insert mounting seat has a bottom surface facing the tip side of the drill body and a drill chip discharge groove extending toward the tip side of the drill body from the bottom surface. A wall surface facing the rotation direction and a screw hole opening to the bottom surface are formed, and the cutting insert has a seating surface facing the rear end side of the drill body and seated on the bottom surface, an abutment surface facing the opposite side to the drill rotation direction and abutting against the wall surface from the drill rotation direction, a convex portion protruding from the tip of the abutment surface to the opposite side to the drill rotation direction, and a mounting hole penetrating the seating surface from the tip relief surface, and the cutting insert is attached to the insert mounting seat by screwing a clamp screw inserted into the mounting hole into the screw hole, and when the cutting insert is attached to the insert mounting seat in this manner, the tip of the abutment portion between the abutment surface and the wall surface is covered by the convex portion.

The cutting insert of the present invention is a cutting insert that is detachably attached to the insert mounting seat of the drill body of the drill body of the replaceable cutting edge drill as described above, and is characterized in that an insert chip discharge groove is formed that opens on the tip flank of the insert body and communicates with the body chip discharge groove, a cutting edge is formed at the intersection ridge between the wall surface of the insert chip discharge groove facing the drill rotation direction and the tip flank, a seating surface facing the rear end side of the drill body and seated on the bottom surface of the insert mounting seat, an abutment surface facing the opposite side to the drill rotation direction and abutting against the wall surface of the insert mounting seat from the drill rotation direction, a convex portion that protrudes from the abutment surface on the tip side of the abutment surface in the opposite direction to the drill rotation direction, and an attachment hole that penetrates from the tip flank to the seating surface.

The drill body of the present invention is a drill body for an indexable drill as described above, characterized in that an insert mounting seat is formed at the tip, and a body chip discharge groove is formed on the outer periphery of the tip, opening at the tip surface and extending toward the rear end, and the insert mounting seat has a bottom surface facing the tip, a wall surface extending toward the tip from the bottom surface and facing the direction of drill rotation, and a screw hole opening at the bottom surface and into which the clamp screw is screwed.

In the replaceable drill, cutting insert, and drill body configured as described above, a convex portion is formed on the tip side of the abutment surface (torque receiving surface) of the cutting insert that faces the opposite direction to the drill rotation direction and abuts against the wall surface (torque transmission surface) of the insert mounting seat from the drill rotation direction, and the abutment surface of the cutting insert is discontinuous without being adjacent to the tip relief surface. Then, when the cutting insert is attached to the insert mounting seat, the convex portion is disposed on the tip side of the abutment portion between the abutment surface and the wall surface, and this abutment portion is covered by the convex portion, so that the abutment portion between the abutment surface of the cutting insert and the wall surface of the insert mounting seat is not exposed at the tip of the replaceable drill.

Therefore, even in the case of wet cutting, in which drilling is performed while supplying coolant, the fine chips generated by cutting can be prevented from turning into sludge together with the coolant and entering the contact area between the contact surface of the cutting insert and the wall surface of the insert mounting seat from the tip side of the drill body, and wear on the contact surface and wall surface caused by such sludge can be prevented. Therefore, with the replaceable tip drill, cutting insert, and drill body configured as described above, it is possible to prevent the shortening of the drill life due to such wear, and it becomes possible to perform stable drilling over a long period of time.

However, with such replaceable-tip drills, if the cutting edge wears and becomes dull over a long period of drilling, the tip flank of the cutting insert can be reground and a new cutting edge can be sharpened at the intersection ridge between the reground tip flank and the wall surface of the insert chip discharge groove facing the drill rotation direction. In such cases, the convex portion can be formed with a side surface that faces the opposite direction of the drill rotation and is adjacent to the tip flank, and the axial width of this side surface can be checked to visually check whether or not the cutting edge needs to be reground.

In addition, in the replaceable-tip drill described in Patent Document 1, a shaft portion is formed on the dividing surface of the cutting insert, and a hole portion is formed on the dividing surface of the insert mounting seat, and the shaft portion is inserted into this hole. However, this hole portion is a circular hole with a continuous inner circumferential surface, and if this hole portion is a blind hole that does not penetrate the drill body and the difference between the inner diameter of the hole and the outer diameter of the shaft portion of the cutting insert is small, the air inside the hole portion is compressed when the shaft portion is inserted, and the resulting pressure creates a force that pushes out the cutting insert.

Therefore, in the replaceable drill with the above configuration, a shaft portion is formed centered on the axis on one of the seating surface of the cutting insert and the bottom surface of the insert mounting seat, and a hole portion into which the shaft portion can be fitted is formed centered on the axis on the other, with the hole portion desirably opening into the main body chip discharge groove or the insert chip discharge groove.

As a result, when the hole is a blind hole having a bottom surface, even if the difference between the inner diameter of the hole and the outer diameter of the shank is reduced, the air in the hole is discharged from the opening to the main body chip discharge groove or the insert chip discharge groove, so no force is exerted to push out the cutting insert. And by reducing the difference between the inner diameter of the hole and the outer diameter of the shank in this way, the runout accuracy of the cutting edge of the cutting insert can be ensured.

Furthermore, by forming the wall surface and the abutment surface so that the outer periphery of the drill body is wider in the axial direction than the inner periphery, it is possible to ensure a large abutment area of the abutment surface with the wall surface on the outer periphery of the drill body, where the greatest cutting load acts during drilling. This makes it possible to reduce the stress acting on the outermost periphery of the drill body at the insert mounting seat.

In addition, the insert mounting seat has a recess that is recessed into the bottom surface and the wall surface at the corner where the bottom surface and the wall surface intersect, extending from the body chip discharge groove to the outer circumferential surface of the drill body. This prevents the intersection ridge between the seating surface and the abutment surface of the cutting insert from interfering with the corner where the bottom surface and the wall surface of the insert mounting seat intersect, thereby preventing the mounting stability of the cutting insert from being impaired.

When such a recess is formed, the cross-sectional area of the recess is made larger at the opening on the outer peripheral surface side of the drill body than at the opening on the main body chip discharge groove side, thereby reducing stress concentration on the recess on the outer peripheral surface side of the drill body where the greatest cutting load acts during drilling as described above. On the other hand, since the cross-sectional area of the opening on the main body chip discharge groove side is small, the rigidity of the convex wall portion of the drill body where the wall surface is formed is not impaired.

Furthermore, by chamfering the intersecting ridge between the wall surface and the inner peripheral surface of the main body chip discharge groove, it is possible to prevent this intersecting ridge from being scratched compared to when the edge is left sharp.

As explained above, according to the present invention, even in wet cutting where drilling is performed while supplying coolant, it is possible to prevent chips from turning into sludge together with the coolant and entering the contact area between the contact surface of the cutting insert and the wall surface of the insert mounting seat from the tip side of the drill body, thereby preventing wear on these contact surfaces and walls and enabling stable drilling over a long period of time.

1 is a first perspective view showing a first embodiment of an indexable drill according to the present invention; FIG. FIG. 2 is a second perspective view of the embodiment shown in FIG. 1 from another direction. FIG. 2 is a front view of the embodiment shown in FIG. 1; 4 is a side view of the embodiment shown in FIG. 1 as viewed in the direction of the arrow A in FIG. 3 . 4 is a side view of the embodiment shown in FIG. 1 as viewed in the direction of the arrow B in FIG. 3 . 4 is a side view of the embodiment shown in FIG. 1 as seen in the direction of the arrow C in FIG. 3 . FIG. 2 is an exploded view of the embodiment shown in FIG. 1. 1 is a front view showing a first embodiment of a drill body according to the present invention. FIG. FIG. 9 is a side view of the embodiment shown in FIG. 8 as viewed in the direction of the arrow A. 1 is a first perspective view showing a first embodiment of a cutting insert according to the present invention; FIG. FIG. 11 is a second perspective view of the embodiment shown in FIG. 10 from another direction. FIG. 11 is a front view of the embodiment shown in FIG. 13 is a side view of the embodiment shown in FIG. 10 as viewed in the direction of the arrow A in FIG. 12 . 13 is a side view of the embodiment shown in FIG. 10 as viewed in the direction of the arrow B in FIG. 12 . FIG. 2 is a first perspective view showing a second embodiment of an indexable drill according to the present invention. FIG. 16 is a second perspective view of the embodiment shown in FIG. 15 from another direction. FIG. 16 is a front view of the embodiment shown in FIG. 17 is a side view of the embodiment shown in FIG. 15 as viewed in the direction of the arrow A in FIG. 16 . 17 is a side view of the embodiment shown in FIG. 15 as viewed in the direction of the arrow B in FIG. 16 . 17 is a side view of the embodiment shown in FIG. 15 as viewed in the direction of the arrow C in FIG. 16 . FIG. 16 is an exploded view of the embodiment shown in FIG. FIG. 4 is a front view showing a second embodiment of a drill body according to the present invention. 23 is a side view of the embodiment shown in FIG. 22 as viewed in the direction of arrow A. 23 is a side view of the embodiment shown in FIG. 22 as viewed in the direction of arrow B. FIG. 2 is a first perspective view showing a second embodiment of a cutting insert according to the present invention. FIG. 26 is a second perspective view of the embodiment shown in FIG. 25 from another direction. FIG. 26 is a front view of the embodiment shown in FIG. 27 in the direction of the arrow A of FIG. 27. FIG. 27 in the direction of the arrow B in FIG. 27 of the embodiment shown in FIG. 25. 27 in the direction of the arrow C in FIG. 27 of the embodiment shown in FIG. 25. 16 is an exploded cross-sectional view taken along an axial line of the cutting insert and the drill body of the embodiment shown in FIG. 15.

Figures 1 to 6 show a first embodiment of the indexable drill of the present invention, and Figure 7 shows an exploded view of the indexable drill of this first embodiment. Also, Figures 8 and 9 show a first embodiment of the drill body of the first embodiment of the present invention of the indexable drill of this first embodiment, and Figures 10 to 14 show a first embodiment of the cutting insert of the first embodiment of the present invention of the indexable drill of this first embodiment that is detachably attached to the drill body.

The drill body 1 is made of a metal material such as steel and is formed into a multi-stage cylindrical shape centered on the axis O. The rear end of the drill body 1 (the right side in Figs. 1, 2, 4-7, and 9) is a large-diameter shank portion 2, and the tip end (the left side in Figs. 1, 2, 4-7, and 9) is a cutting blade portion 3 to which an insert body 11 of a cutting insert is removably attached. The cutting blade portion 3 has a smaller diameter than the shank portion 2, and a flange portion 4 is formed between the shank portion 2 and the cutting blade portion 3, which is expanded in diameter by one step toward the tip side and then contracts in diameter to the same diameter as the cutting blade portion 3.

In such an indexable drill, the shank portion 2 of the drill body 1 is gripped by the spindle of a machine tool and rotated around the axis O in the drill rotation direction T while being fed toward the tip side in the direction of the axis O, so that the cutting edge of the cutting insert drills a hole in the workpiece. The outer peripheral surface of the shank portion 2 is formed with a flat surface 2a that extends parallel to the axis O with a gap between the front and rear ends of the shank portion 2, and the flange portion 4, which is expanded in diameter relative to the shank portion 2, is also formed with a flat surface 4a that is parallel to the flat surface 2a.

On the outer periphery of the drill body 1, from the tip of the cutting edge portion 3 to just before the rear end of the flange portion 4, multiple body chip discharge grooves 5 are formed at intervals in the circumferential direction. In this embodiment, two body chip discharge grooves 5 are formed at equal intervals in the circumferential direction, and these body chip discharge grooves 5 are spiral-shaped, gently twisting around the axis O in the opposite direction to the drill rotation direction T as they move toward the rear end of the drill body 1.

An insert mounting seat 6 is formed at the tip of the cutting edge portion 3. This insert mounting seat 6 is formed by cutting out the tip of the cutting edge portion 3 in a rectangular cross section that is flattened in the radial direction of the axis O from the wall surface facing the drill rotation direction T of the two main body chip discharge grooves 5 to the wall surface facing the opposite side from the drill rotation direction T.

The insert mounting seat 6 has a bottom surface 6a that extends perpendicular to the axis O and faces the tip of the drill body 1, and wall surfaces 6b that extend perpendicular to the bottom surface 6a and parallel to the axis O from both sides of the bottom surface 6a and face two opposing parallel drill rotation directions T. In this embodiment, the wall surfaces 6b are rectangular with their longitudinal direction in the radial direction relative to the axis O.

In this embodiment, a circular hole 6c with a constant inner diameter and centered on the axis O is formed so as to open in the center of the bottom surface 6a and extend toward the rear end of the drill body 1. However, the inner diameter of the hole 6c is larger than the diameter of a circle inscribed in the bottom surface of the body chip discharge groove 5 facing the outer periphery of the drill body 1 in a cross section perpendicular to the axis O. Therefore, the hole 6c opens to the bottom surface of the body chip discharge groove 5, and the bottom surface 6a of the insert mounting seat 6 is divided into two parts by the hole 6c. The hole 6c is a blind hole with a bottom surface facing the tip side of the drill body 1.

Furthermore, the bottom surface 6a thus divided into two by the hole portion 6c has a screw hole 6d formed therein, the screw hole 6d being spaced apart from the hole portion 6c and having its center at an equal distance from the axis O. Furthermore, the drill body 1 has a coolant hole 1a formed from the rear end surface of the shank portion 2 toward the tip side along the axis O, and this coolant hole 1a branches into two just before the insert mounting seat 6 and opens into the wall surface of the body chip discharge groove 5 facing away from the drill rotation direction T.

In addition, on the side opposite to the drill rotation direction T of the wall surface 6b of the insert mounting seat 6, a convex wall portion 7 is left surrounded by this wall surface 6b, the outer peripheral surface of the cutting edge portion 3, and the wall surface of the main body chip discharge groove 5 facing the opposite side to the drill rotation direction T, and the tip surface 7a of this convex wall portion 7 is a plane perpendicular to the axis O. Furthermore, in the corner portion where the bottom surface 6a and the wall surface 6b intersect, a recess 6e with a constant inner diameter and a circular cross section that is recessed into the bottom surface 6a and the wall surface 6b is formed as a relief portion in this embodiment. This recess 6e is for avoiding interference between the bottom surface 6a and the wall surface 6b of the insert mounting seat 6 and the cutting insert. Furthermore, the insert mounting seat 6 and the two main body chip discharge grooves 5 are 180° rotationally symmetrical with respect to the axis O.

The cutting insert that is removably attached to such an insert mounting seat 6 has an insert body 11 formed of a hard material, such as cemented carbide, that is harder than the drill body 1. When attached to the insert mounting seat 6, this insert body 11 is also formed so as to have a 180° rotationally symmetric shape with respect to the axis O of the drill body 1.

When the insert body 11 is attached to the insert mounting seat 6 in this manner, it is formed with a tip flank 12 that faces the tip side of the drill body 1, and an insert chip discharge groove 13 that opens into the tip flank 12 and communicates with each of the two body chip discharge grooves 5, and a cutting edge 14 is formed at the intersection ridge between the wall surface of the insert chip discharge groove 13 that faces the drill rotation direction T and the tip flank 12. The tip flank 12 is inclined toward the rear end of the drill body 1 as it moves toward the opposite side to the drill rotation direction T and the outer periphery of the drill body 1, thereby providing the cutting edge 14 with a clearance angle and a tip angle.

Similarly, when attached to the insert mounting seat 6, the rear end surface of the insert body 11 is a plane perpendicular to the axis O, facing the rear end side of the drill body 1 and serving as a seating surface 15 that seats on the bottom surface 6a of the insert mounting seat 6. Furthermore, a multi-stage cylindrical shaft portion 15a with a large diameter at the tip and a slightly smaller diameter at the rear end is formed in the center of this seating surface 15 so as to protrude toward the rear end side, centered on the axis O, and the outer diameter of the tip portion of this shaft portion 15a is large enough to be fitted into the hole portion 6c of the insert mounting seat 6.

Furthermore, from the wall surfaces of the two insert chip discharge grooves 13 facing away from the drill rotation direction T to the outer peripheral surface of the insert body 11, abutment surfaces 16 are formed facing away from the drill rotation direction T and abutting against the wall surface 6b of the insert mounting seat 6 from the drill rotation direction T. These abutment surfaces 16 are formed to intersect perpendicularly with the seating surface 15, extend parallel to the axis O, and extend parallel to each other, and in this embodiment, are rectangular with a longitudinal direction in the radial direction relative to the axis O.

In addition, two mounting holes 11a are formed in the insert body 11 at a distance from the shaft portion 15a, penetrating from the tip flank 12 to the seating surface 15. These mounting holes 11a are arranged so as to be coaxial with the two screw holes 6d of the insert mounting seat 6 when the abutment surface 16 is abutted against the wall surface 6b of the insert mounting seat 6, and the inner diameter gradually decreases from the opening on the tip flank 12 side toward the seating surface 15 side, and is constant on the seating surface 15 side.

The insert body 11 of the cutting insert is formed with a protrusion 17 that protrudes from the abutment surface 16 on the tip side toward the opposite side of the drill rotation direction T. Therefore, when the shaft portion 15a of the insert body 11 is fitted into the hole portion 6c of the insert mounting seat 6 to bring the seating surface 15 into close contact with the bottom surface 6a and bring the abutment surface 16 into contact with the wall surface 6b, the protrusion 17 is disposed on the tip side of the abutment portion P between the abutment surface 16 and the wall surface 6b, and is disposed so as to cover the tip of the abutment portion P.

That is, the rear end surface 17a of the protrusion 17 facing the rear end side of the drill body 1 is a plane perpendicular to the axis O that can slide against the tip surface 7a of the convex wall portion 7, which is a plane perpendicular to the axis O, when the seating surface 15 of the insert body 11 is in close contact with the bottom surface 6a of the insert mounting seat 6 as described above. In this way, by sliding the rear end surface 17a of the protrusion 17 against the tip surface 7a of the convex wall portion 7, the tip of the contact area P between the contact surface 16 and the wall surface 6b is covered by the protrusion 17.

The side surface 17b of the protrusion 17 facing the opposite side to the drill rotation direction T extends parallel to the abutment surface 16 and is adjacent to the tip flank 12, i.e., extends parallel to the axis O and perpendicular to the rear end surface 17a, and intersects with the tip flank 12 of the insert body 11 at an angle at the intersection ridge Q. Note that the protrusion 17 does not cover the entire tip surface 7a of the protruding wall portion 7 of the drill body 1, and the tip surface 7a is exposed on the side of the side surface 17b opposite to the drill rotation direction T.

The insert body 11 of such a cutting insert is removably attached to the insert mounting seat 6 by fitting the shaft portion 15a into the hole portion 6c of the insert mounting seat 6 as described above, bringing the seating surface 15 into close contact with the bottom surface 6a and bringing the abutment surface 16 into contact with the wall surface 6b, and then screwing the clamp screw 18 inserted into the mounting hole 11a from the tip side of the drill body 1 into the screw hole 6d as shown in Figure 7.

In the replaceable drill and cutting insert configured in this manner, a coolant such as cutting oil is sprayed from the coolant hole 1a formed in the drill body 1, while the cutting edge 14 of the insert body 11 of the cutting insert cuts the workpiece to drill a hole in the workpiece. At this time, a convex portion 17 is formed on the tip side of the contact surface 16 that contacts the wall surface 6b of the insert mounting seat 6 in the insert body 11, protruding from the contact surface 16 toward the opposite side of the drill rotation direction T. This convex portion 17 is disposed on the tip side of the contact portion P between the contact surface 16 and the wall surface 6b and covers the tip of the contact portion P, so that the contact portion P is not exposed at the tip of the replaceable drill.

As a result, even if fine chips produced by cutting turn into sludge together with the cutting oil in wet cutting as described above, this can be prevented from entering the contact area P between the contact surface 16 of the cutting insert and the wall surface 6b of the insert mounting seat 6 from the tip side of the drill body 1. This prevents the contact surface 16 and wall surface 6b from being worn down by such sludge, suppresses the shortening of the life of the replaceable drill due to such wear, and enables stable drilling over a long period of time.

In this embodiment, the side surface 17b of the protrusion 17, which faces the opposite side of the drill rotation direction T and is adjacent to the tip flank 12, is formed so as to intersect the tip flank 12 at an angle at the intersecting ridge Q. Therefore, when the cutting edge 14 is worn down and becomes dull, when the tip flank 12 is re-ground and a new cutting edge 14 is sharpened at the intersecting ridge with the wall surface of the insert chip discharge groove 13 facing the drill rotation direction T, the width of the side surface 17b between the intersecting ridge Q and the seating surface 15 in the axial O direction can be visually confirmed as to whether or not re-grinding is necessary. This makes it possible to avoid a situation in which the protrusion 17 becomes too thin and wear occurs in the protruding wall portion 7 of the drill body 1.

Furthermore, in this embodiment, a shaft portion 15a is formed on the seating surface 15 of the insert body 11 of the cutting insert, centered on the axis O, and a hole portion 6c into which the shaft portion 15a can be fitted is formed on the bottom surface 6a of the insert mounting seat 6, centered on the axis O. Therefore, the cutting insert can be attached with high precision, centered on the axis O of the drill body 1, and the runout accuracy of the cutting edge 14 can be ensured.

And because this hole 6c opens into the body chip discharge groove 5 of the drill body 1, the air in the hole 6c can be discharged when the shank 15a is fitted into the hole 6c, and the air in the hole 6c can be prevented from being compressed. Therefore, there is no force exerted by the compressed air to push the insert body 11 toward the tip side of the drill body 1, and according to this embodiment, the cutting insert can be firmly and stably attached to the insert mounting seat 6.

In this embodiment, as described above, the seating surface 15 of the insert body 11 is formed with a shaft portion 15a centered on the axis O, and the bottom surface 6a of the insert mounting seat 6 is formed with a hole portion 6c centered on the axis O into which the shaft portion 15a can be fitted. However, conversely, the seating surface 15 of the insert body 11 may be formed with a hole portion centered on the axis O, and the bottom surface 6a of the insert mounting seat 6 may be formed with a shaft portion centered on the axis O into which the hole portion can be fitted, and the hole portion may be opened to the insert chip discharge groove 13.

In addition, in this embodiment, a coolant hole 1a is formed in the drill body 1 from the rear end surface of the shank portion 2 toward the tip side along the axis O, and this coolant hole 1a is branched into two just before the insert mounting seat 6 and opens into the wall surface of the body chip discharge groove 5 facing away from the drill rotation direction T. However, instead, two coolant holes may be formed from the rear end surface of the shank portion 2 toward the tip side of the drill body 1 through the two body chip discharge grooves 5, and these coolant holes may be opened into the wall surface just before the insert mounting seat 6 facing away from the drill rotation direction T of the body chip discharge groove 5.

In addition, in this embodiment, the two mounting holes 11a that penetrate from the tip clearance surface 12 to the seating surface 15 of the insert body 11 are arranged so as to be coaxial with the two screw holes 6d of the insert mounting seat 6 when the abutment surface 16 is abutted against the wall surface 6b of the insert mounting seat 6. Alternatively, the two screw holes 6d of the insert mounting seat 6 may be arranged slightly off-center on the opposite side of the abutment surface 16 relative to the two screw holes 6d of the insert mounting seat 6.

Next, Figs. 15 to 20 show a second embodiment of the indexable drill of the present invention, and Figs. 21 and 31 show exploded views of the indexable drill of this second embodiment. Also, Figs. 22 to 24 show a second embodiment of the drill body of the second embodiment of the indexable drill of this invention, and Figs. 25 to 30 show a second embodiment of the cutting insert of the second embodiment of the indexable drill of this invention that is detachably attached to the drill body. In the indexable drill, drill body, and cutting insert of these second embodiments, parts that are common to the first embodiment shown in Figs. 1 to 14 are assigned the same reference numerals.

In the first embodiment, the wall surface 6b of the insert mounting seat 6 facing the drill rotation direction T and the abutment surface 16 of the insert body 11 of the cutting insert that abuts against this wall surface 6b are rectangular, and the width of the wall surface 6b and the abutment surface 16 in the direction of the axis O is constant in the radial direction relative to the axis O. In contrast, in this second embodiment, the wall surface 6b and the abutment surface 16 are wider in the direction of the axis O on the outer periphery side of the drill body 1 than on the inner periphery side.

In the second embodiment, as shown in Figures 21, 24, 29, and 30, the wall surface 6b and the abutment surface 16 are formed so that the width in the axis O direction gradually increases from the inner periphery side to the outer periphery side of the drill body 1, and the wall surface 6b and the abutment surface 16 are formed in a substantially trapezoidal shape.

In addition, in the first embodiment, the recess 6e formed as a relief at the corner where the bottom surface 6a and wall surface 6b of the insert mounting seat 6 intersect is a circular cross section with a constant inner diameter, and therefore has a constant cross-sectional area, whereas in this second embodiment, the cross-sectional area of the recess 6e is formed so that the opening on the outer peripheral surface side of the drill body 1 is larger than the opening on the main body chip discharge groove 5 side.

Here, in this second embodiment, the recess 6e is formed, in order from the opening on the main body chip discharge groove 5 side to the opening on the outer peripheral surface side of the drill body 1, by a portion with a circular cross section and a portion with a concave curved cross section whose cross-sectional area is two stages larger than that of the circular portion, and the length of the portion with a circular cross section that opens to the main body chip discharge groove 5 side of the recess 6e is the longest. Furthermore, in this second embodiment, the intersection ridge portion between the wall surface 6b of the insert mounting seat 6 and the inner peripheral surface of the main body chip discharge groove 5 is chamfered to form a chamfered portion 6f that intersects with the wall surface 6b and the inner peripheral surface of the main body chip discharge groove 5.

The replaceable-tip drill, cutting insert, and drill body 1 of the second embodiment configured in this manner can of course achieve the same effects as the first embodiment, but first, the wall surface 6b of the insert mounting seat 6 and the abutment surface 16 of the cutting insert are wider in the axial O direction on the outer periphery side of the drill body 1 than on the inner periphery side, so that a large abutment area can be secured for the abutment surface 16 with the wall surface 6b on the outer periphery side of the drill body 1, where the greatest cutting load acts during drilling.

This reduces the stress acting on the outermost circumference of the drill body 1 on the insert mounting seat 6, making it possible to stably hold the cutting insert even against the cutting load during drilling, and enabling high-precision drilling. In particular, in this embodiment, the width of the wall surface 6b and the abutment surface 16 in the axial O direction is formed to gradually increase from the inner circumference side to the outer circumference side of the drill body 1, making it possible to ensure a larger abutment area of the abutment surface 16 with the wall surface 6b.

In addition, in this second embodiment, the cross-sectional area of the recess 6e formed as a relief at the corner where the bottom surface 6a and wall surface 6b of the insert mounting seat 6 intersect is recessed from the bottom surface 6a and wall surface 6b, and is formed so that the opening on the outer peripheral surface side of the drill body 1 is larger than the opening on the main body chip discharge groove 5 side. Therefore, as described above, stress concentration on the recess 6e can be alleviated on the outer peripheral surface side of the drill body 1 where the largest cutting load acts during drilling.

On the other hand, since the cross-sectional area of the opening on the side of the main body chip discharge groove 5 is small, the rigidity of the convex wall portion 7 of the drill body 1 on which the wall surface 6b is formed is not impaired, and stable holding of the cutting insert is not hindered. In particular, in this embodiment, the cross-sectional area of this recess 6e is formed to increase in stages, and the length of the step of the part whose cross section is circular on the side of the main body chip discharge groove 5 is the longest, so that the rigidity of the convex wall portion 7 can be maintained more reliably. Note that the cross-sectional shape of this recess 6e may be circular in any step, or may be a non-circular concave curve.

Furthermore, as in this second embodiment, by chamfering the intersecting ridge between the wall surface 6b of the insert mounting seat 6 and the inner peripheral surface of the main body chip discharge groove 5 to form a chamfered portion 6f that intersects the wall surface 6b and the inner peripheral surface of the main body chip discharge groove 5, it is possible to prevent scratches and chipping compared to when the intersecting ridge is left with a sharp edge. Note that this chamfered portion 6f does not come into contact with the insert body 11, and most of it is formed as a concave curved surface inclined toward the axis O.

Now, the shaft portion 15a and the hole portion 6c in this second embodiment will be described in detail with reference to FIG. 31. In this embodiment, the hole portion 6c opening into the bottom surface 6a of the insert mounting seat 6 of the drill body 1 has a large diameter portion 6c1 at the tip end, which has a circular cross section centered on the axis O with a constant inner diameter and a long length in the direction of the axis O, and a small diameter portion 6c2 at the rear end, which has a circular cross section centered on the axis O with a constant inner diameter slightly smaller than that of the large diameter portion 6c1 and a shorter length in the direction of the axis O than the large diameter portion. However, the portions where these large diameter portion 6c1 and small diameter portion 6c2 open into the bottom surface of the body chip discharge groove 5 facing the outer periphery of the drill body 1 are cut out by this bottom surface.

On the other hand, the shaft portion 15a protruding from the seating surface 15 of the insert body 11 of the cutting insert is formed in a multi-stage cylindrical shape centered on the axis O, with the tip portion being a large diameter portion 15a1 as in the first embodiment, and the rear end portion being a small diameter portion 15a2 that is slightly smaller in diameter than the large diameter portion 15a1, and the length of the large diameter portion 15a1 in the direction of the axis O is longer than that of the small diameter portion 15a2. However, even in this shaft portion 15a, the portion where the insert chip discharge groove 13 is formed is cut out along the bottom surface facing the outer periphery of the insert chip discharge groove 13.

In this embodiment, the outer diameter of the large diameter portion 15a1 of the shank 15a is sized to fit into the large diameter portion 6c1 of the hole 6c, which allows the insert body 11 of the cutting insert to be attached coaxially with high precision around the axis O of the drill body 1, ensuring high runout accuracy of the cutting edge 14. To ensure such high runout accuracy, it is desirable that the fit class in JIS B 0401-1:1998 (ISO 286-1:1988) be within the range of h6 to h7 for the shank 15a and within the range of H6 to H7 for the hole 6c.

The length of the entire shaft 15a in the axial direction O is slightly smaller than the length (depth) of the hole 6c in the axial direction O, and the length of the large diameter portion 15a1 of the shaft 15a in the axial direction O is also slightly smaller than the length (depth) of the large diameter portion 6c1 of the hole 6c in the axial direction O, so that when the shaft 15a is fitted into the hole 6c, no gap is formed between the bottom surface 6a of the insert mounting seat 6 of the drill body 1 and the seating surface 15 of the insert body 11 of the cutting insert. Note that these configurations are also the same as in the first embodiment, except that the hole 6c has a constant inner diameter.

According to the present invention, even in wet cutting, in which drilling is performed while supplying coolant, cutting chips can be prevented from turning into sludge together with the coolant and entering the contact area between the contact surface of the cutting insert and the wall surface of the insert mounting seat from the tip side of the drill body, preventing wear on these contact surfaces and walls and enabling stable drilling over a long period of time.

1 Drill body 1a Coolant hole 5 Body chip discharge groove 6 Insert mounting seat 6a Bottom surface of insert mounting seat 6 6b Wall surface of insert mounting seat 6 6c Hole 6c1 Large diameter portion of hole 6c 6c2 Small diameter portion of hole 6c 6d Screw hole 6e Concave 6f Chamfered portion 7 Convex wall portion 7a Tip surface of convex wall portion 7 11 Insert body 11a Mounting hole 12 Tip relief surface 13 Insert chip discharge groove 14 Cutting edge 15 Seating surface 15a Shank 15a1 Large diameter portion of shaft 15a 15a2 Small diameter portion of shaft 15a 16 Contact surface 17 Convex portion 17a Rear end surface of convex portion 17 17b Side surface of convex portion 17 facing opposite to drill rotation direction T 18 Clamp screw O Axis of the drill body 1 T Drill rotation direction P Contact portion between the wall surface 6b and the contact surface 16 Q Intersecting ridge line between the tip flank surface 12 and the side surface 17b of the protrusion 17

Claims (6)

A replaceable drill having an insert mounting seat formed at a tip of a drill body that is rotated about an axis, and a cutting insert removably attached to the insert mounting seat,
A body chip discharge groove is formed on the outer periphery of the tip portion of the drill body, the groove opening on the tip surface of the drill body and extending toward the rear end side,
The cutting insert has an insert chip discharge groove formed therein, the insert chip discharge groove opening on a tip flank of the cutting insert and communicating with the main body chip discharge groove;
A cutting edge is formed at an intersection ridge between a wall surface of the insert chip discharge groove facing the drill rotation direction and the tip flank,
The insert mounting seat is formed with a bottom surface facing the tip side of the drill body, a wall surface extending from the bottom surface toward the tip side of the drill body and facing the drill rotation direction, and a screw hole opening to the bottom surface,
The cutting insert is provided with a seating surface facing the rear end side of the drill body and seated on the bottom surface, a contact surface facing the opposite side to the drill rotation direction and contacting the wall surface from the drill rotation direction, a convex portion protruding from the contact surface on the tip side of the contact surface toward the opposite side to the drill rotation direction, and a mounting hole penetrating from the tip flank to the seating surface,
The cutting insert is attached to the insert mounting seat by screwing a clamp screw inserted into the mounting hole into the screw hole,
a protruding wall portion is provided on a side of the wall surface of the insert mounting seat opposite to the direction of rotation of the drill, the protruding wall portion being surrounded by the wall surface, an outer peripheral surface of the drill body, and a wall surface of the body chip discharge groove facing in a direction opposite to the direction of rotation of the drill,
a tip surface of the convex wall portion is partially covered by the convex portion of the cutting insert and partially exposed on a side opposite to a drill rotation direction of the convex portion when viewed from a tip side of the indexable drill . The replaceable drill according to claim 1, characterized in that the convex portion has a side surface that faces the opposite direction to the drill rotation direction and is adjacent to the tip relief surface. a shaft portion centered on the axis line is formed on one of the seating surface of the cutting insert and the bottom surface of the insert mounting seat, and a hole portion into which the shaft portion can be fitted is formed on the other of the seating surface of the cutting insert and centered on the axis line,
3. The indexable drill according to claim 1, wherein the hole opens into the body chip discharge groove or the insert chip discharge groove. The replaceable drill according to any one of claims 1 to 3, characterized in that the wall surface and the abutment surface are wider in the axial direction on the outer periphery side of the drill body than on the inner periphery side. The insert mounting seat has a recess formed at a corner where the bottom surface and the wall surface intersect, the recess being recessed relative to the bottom surface and the wall surface from the body chip discharge groove to an outer peripheral surface of the drill body,
5. The replaceable drill according to claim 1, wherein a cross-sectional area of the recess is larger at an opening on an outer peripheral surface side of the drill body than at an opening on a chip discharge groove side of the drill body. The replaceable drill according to any one of claims 1 to 5, characterized in that the intersecting ridge between the wall surface and the inner peripheral surface of the body chip discharge groove is chamfered.

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