INDEXABLE DRILL, CUTTING INSERT AND DRILL MAIN BODY

In an indexable drill, a cutting insert having a cutting edge is detachably mounted on an insert mounting seat of a drill main body. The insert mounting seat has a bottom surface facing a tip side of a drill main body, and a wall surface extending to the tip side and facing a drill rotation direction. The cutting insert has a seating surface seated on the bottom surface toward a rear end side of the drill main body, a contact surface coming into contact with the wall surface toward a side opposite to the drill rotation direction, a projection portion projecting to the side opposite to the drill rotation direction on a tip side of the contact surface, and a mounting hole penetrating the seating surface from a tip flank.

TECHNICAL FIELD

The present invention relates to an indexable drill in which an insert mounting seat is formed in a tip portion of a drill main body rotating around an axis, and a cutting insert is detachably mounted on the insert mounting seat, a cutting insert detachably mounted on the insert mounting seat of the indexable drill, and a drill main body of the indexable drill.

Priority is claimed on Japanese Patent Application No. 2019-50081, filed on Mar. 18, 2019 and Japanese Patent Application No. 2020-25571, filed on Feb. 18, 2020, the contents of which are incorporated herein by reference.

BACKGROUND ART

For example, in an indexable drill disclosed in Patent Document 1, an insert mounting seat of a drill main body has a split surface extending perpendicular to an axis and a torque transmitting surface adjacent to the split surface. A cutting insert has a split surface extending perpendicular to an axis and a torque receiving surface extending from the split surface toward a tip flank and adjacent to the tip flank. The cutting insert is detachably mounted on the insert mounting seat by a fastening screw.

CITATION LIST

Patent Document

SUMMARY OF INVENTION

Technical Problem

However, in the indexable drill disclosed in Patent Document 1, the torque receiving surface of the cutting insert intersects with and is adjacent to the tip flank. A contact portion between the torque receiving surface and the torque transmitting surface of the drill main body is exposed in a tip portion of the indexable drill. Therefore, particularly when wet cutting is performed for drilling while a coolant is supplied, fine chips generated by the cutting become sludge together with the coolant, and the sludge is likely to enter the contact portion between the torque receiving surface and the torque transmitting surface from a tip side of the drill main body. Due to the sludge, the torque receiving surface or the torque transmitting surface may be worn, thereby causing a possibility that a drill life may be shortened.

The present invention aims to prevent a drill life from being shortened, by preventing sludge from entering a contact portion between a cutting insert and an insert mounting seat from a tip side of a drill main body.

Solution to Problem

According to one aspect of the present invention, there is provided an indexable drill including a drill main body configured to have an insert mounting seat formed in a tip portion and to be rotated around an axis, and a cutting insert configured to be detachably mounted on the insert mounting seat.

An outer periphery of the tip portion of the drill main body has a main body chip discharge flute open on a tip surface of the drill main body and extending toward a rear end side of the drill main body. The cutting insert has an insert chip discharge groove open on a tip flank of the cutting insert and communicating with the main body chip discharge flute.

A cutting edge is formed in an intersecting ridgeline portion between a wall surface of the insert chip discharge groove facing a drill rotation direction and the tip flank. The insert mounting seat has a bottom surface facing a tip side of the drill main body, a wall surface extending to the tip side of the drill main body with respect to the bottom surface and facing the drill rotation direction, and a screw hole open on the bottom surface.

The cutting insert has a seating surface seated on the bottom surface toward the rear end side of the drill main body, a contact surface coming into contact with the wall surface in the drill rotation direction toward a side opposite to the drill rotation direction, a projection portion projecting to the side opposite to the drill rotation direction with respect to the contact surface on a tip side of the contact surface, and a mounting hole penetrating the seating surface from the tip flank. A clamp screw inserted into the mounting hole is screwed into the screw hole so that the cutting insert is mounted on the insert mounting seat.

In the indexable drill of the above-described aspect, in a state where the cutting insert is mounted on the insert mounting seat, a tip portion of the contact portion between the contact surface and the wall surface is covered by the projection portion projecting to the side opposite to the drill rotation direction on a tip side of the contact surface. That is, a tip of a contact interface between the contact surface and the wall surface is closed by the projection portion projecting to the side opposite to the drill rotation direction with respect to the contact surface. In this manner, it is possible to suppress a possibility that foreign substances such as sludge may enter from the tip of the contact portion between the contact surface and the wall surface.

According to the present invention, there is provided a cutting insert detachably mounted on the insert mounting seat of the drill main body in the drill main body of the above-described indexable drill. The cutting insert includes an insert chip discharge groove open on a tip flank of the insert main body and communicating with the main body chip discharge flute, a cutting edge formed in an intersecting ridgeline portion between a wall surface of the insert chip discharge groove facing a drill rotation direction and the tip flank, a seating surface seated on the bottom surface of the insert mounting seat toward a rear end side of the drill main body, a contact surface coming into contact with the wall surface of the insert mounting seat in a drill rotation direction toward a side opposite to the drill rotation direction, a projection portion projecting to the side opposite to the drill rotation direction with respect to the contact surface on a tip side of the contact surface, and a mounting hole penetrating the seating surface from the tip flank.

According to the present invention, there is provided a drill main body in the above-described indexable drill. In the drill main body, an insert mounting seat is formed in a tip portion of the drill main body. An outer periphery of the tip portion of the drill main body has a main body chip discharge flute open on a tip surface of the drill main body and extending to a rear end side of the drill main body. The insert mounting seat has a bottom surface facing a tip side, a wall surface extending to the tip side with respect to the bottom surface and facing a drill rotation direction, and a screw hole open on the bottom surface and into which the clamp screw is screwed.

The indexable drill, the cutting insert, and the drill main body which are described above have the projection portion projecting to the side opposite to the drill rotation direction with respect to the contact surface on the tip side of the contact surface (torque receiving surface) coming into contact with the wall surface (torque transmitting surface) of the insert mounting seat in the drill rotation direction toward the side opposite to the drill rotation direction of the cutting insert. The contact surface of the cutting insert is not continuous with the tip flank without being adjacent to the tip flank. In a state where the cutting insert is mounted on the insert mounting seat, the projection portion is disposed on the tip side of the contact portion between the contact surface and the wall surface. The contact portion is covered by the projection portion. Therefore, the contact portion between the contact surface of the cutting insert and the wall surface of the insert mounting seat is not exposed in the tip portion of the indexable drill.

Therefore, even when wet cutting is performed for drilling while a coolant is supplied, when fine chips generated by the cutting become sludge together with the coolant, it is possible to prevent the sludge from entering the contact portion between the contact surface of the cutting insert and the wall surface of the insert mounting seat from the tip side of the drill main body. Accordingly, it is possible to prevent the contact surface and the wall surface from being worn due to the sludge. Therefore, according to the indexable drill, the cutting insert, and the drill main body which are configured as described above, it is possible to prevent a drill life from being shortened due to the wear, and it is possible to perform stable drilling over a long period of time.

Incidentally, in the indexable drill configured in this way, when the cutting edge is worn and sharpness is dull while the drilling is performed over a long period of time, the tip flank of the cutting insert is re-polished. In some cases, a new cutting edge may be sharpened in the intersecting ridgeline portion between the re-polished tip flank and the wall surface of the insert chip discharge groove facing the drill rotation direction. In this case, the projection portion has a side surface adjacent to the tip flank toward the side opposite to the drill rotation direction. Accordingly, whether or not to re-polish the tip flank can be visually confirmed by confirming a width of the side surface in a direction of an axis.

In addition, in the indexable drill disclosed in Patent Document1, the shaft portion is formed on the split surface of the cutting insert, and the hole portion is formed on the split surface of the insert mounting seat. The shaft portion is inserted into the hole portion. However, the hole portion is a circular hole having a continuous inner peripheral surface, and the hole portion is a blind hole that does not penetrate the drill main body. Accordingly, if a difference between an inner diameter of the hole portion and an outer diameter of the shaft portion of the cutting insert is small, air inside the hole portion is compressed when the shaft portion is inserted into the hole portion. Consequently, due to a pressure thereof, a force of pushing out the cutting insert acts.

Therefore, in the indexable drill having the above-described configuration, it is desirable to adopt a configuration as follows. One of the seating surface of the cutting insert and the bottom surface of the insert mounting seat has a shaft portion formed around the axis, and the other has a hole portion into which the shaft portion is fitted, and formed around the axis. The hole portion is open in the main body chip discharge flute or the insert chip discharge groove.

In this manner, when the hole portion is a blind hole having the bottom surface, even when a difference between the inner diameter of the hole portion and the outer diameter of the shaft portion is reduced, the air inside the hole portion is discharged from an opening portion to the main body chip discharge flute or the insert chip discharge groove. Therefore, a force of pushing out the cutting insert does not act. Deflection accuracy of the cutting edge of the cutting insert can be secured by reducing the difference between the inner diameter of the hole portion and the outer diameter of the shaft portion in this way.

In addition, the wall surface and the contact surface are formed so that an outer peripheral side of the drill main body has a wider width in a direction of the axis than an inner peripheral side of the drill main body. In this manner, it is possible to secure a large contact area between the contact surface and the wall surface on the outer peripheral side of the drill main body on which a largest cutting load acts during drilling. Therefore, it is possible to reduce stress acting on an outermost periphery of the drill main body of the insert mounting seat.

In the insert mounting seat, a corner portion where the bottom surface and the wall surface intersect with each other has a recess portion recessed with respect to the bottom surface and the wall surface and formed from the main body chip discharge flute to an outer peripheral surface of the drill main body. In this manner, it is possible to prevent the intersecting ridgeline portion between the seating surface and the contact surface of the cutting insert from impairing mounting stability of the cutting insert by interfering with the corner portion where the bottom surface and the wall surface of the insert mounting seat intersect with each other.

When the recess portion is formed, in a cross-sectional area of the recess portion, an opening portion on the outer peripheral surface side of the drill main body is larger than an opening portion on the main body chip discharge flute side. In this manner, it is possible to relax stress concentration on the recess portion on the outer peripheral surface side of the drill main body on which the largest cutting load acts during the drilling as described above. On the other hand, the cross-sectional area of the opening portion on the main body chip discharge flute side is small. Accordingly, rigidity of the projection wall portion of the drill main body in which the wall surface is formed is not impaired.

An intersecting ridgeline portion between the wall surface and the inner peripheral surface of the main body chip discharge flute is chamfered. In this manner, compared to when a sharp edge remains in the intersecting ridgeline portion, it is possible to prevent the intersecting ridgeline portion from being damaged.

Advantageous Effects of Invention

As described above, according to the present invention, even in a case of wet cutting in which drilling is performed while a coolant is supplied, when chips become sludge together with the coolant, it is possible to prevent the sludge from entering the contact portion between the contact surface of the cutting insert and the wall surface of the insert mounting seat from the tip side of the drill main body. Therefore, it is possible to perform stable drilling over a long period of time by preventing the contact surface or the wall surface from being worn.

DESCRIPTION OF EMBODIMENTS

FIGS. 1 to 6show a first embodiment of an indexable drill according to the present invention, andFIG. 7shows an exploded view of the indexable drill of the first embodiment.FIGS. 8 and 9show the first embodiment of a drill main body used for the indexable drill of the first embodiment, andFIGS. 10 to 14show the first embodiment of a cutting insert detachably mounted on the drill main body.

A drill main body1is formed of a metal material such as a steel material in a multi-stage columnar shape formed around an axis O. A rear end portion (right side portion inFIGS. 1, 2, 4 to 7, and 9) of the drill main body1is a large diameter shank portion2, and a tip portion (left side portion inFIGS. 1, 2, 4 to 7, and 9) is a cutting edge portion3on which an insert main body11of a cutting insert10is detachably mounted.

In the present specification, unless otherwise defined, a “tip side” will be referred to as a tip side of the drill main body1, and a “rear end side” will be referred to as a rear end side of the drill main body1. The cutting edge portion3has a smaller diameter than the shank portion2. A flange portion4whose diameter is decreased after being increased one stage toward the tip side than the shank portion2to have the diameter the same as that of the cutting edge portion3is formed between the shank portion2and the cutting edge portion3.

In the indexable drill, the shank portion2of the drill main body1is gripped by a spindle of a machine tool. While being rotated in a drill rotation direction T around the axis O, the shank portion2is fed to the tip side in a direction of the axis O. In this manner, drilling is performed on a workpiece by the cutting edge of the cutting insert10. A flat surface2aextending parallel to the axis O is formed on an outer peripheral surface of the shank portion2with an interval between a tip and a rear end of the shank portion2. A flat surface4aparallel to the flat surface2ais also formed in a portion of the flange portion4whose diameter is increased than the shank portion2.

In an outer peripheral portion of the drill main body1, a plurality of main body chip discharge flutes5are formed at an interval in a circumferential direction from a tip of the cutting edge portion3to a front of a rear end of the flange portion4. In the present embodiment, two main body chip discharge flutes5are formed at an equal interval in the circumferential direction. The main body chip discharge flutes5have a spiral shape that gently twists to a side opposite to the drill rotation direction T around the axis O toward a rear end side of the drill main body1.

An insert mounting seat6is formed in a tip portion of the cutting edge portion3. As shown inFIGS. 5, 7, and 8, the insert mounting seat6is formed by cutting out a central portion of the tip of the cutting edge portion3in a rectangular shape when viewed in a direction perpendicular to the axis O. As shown inFIG. 8, a cutout region extends in a radial direction with respect to the axis O, and spreads from one main body chip discharge flute5to the other main body chip discharge flute5. A width of the cutout rectangular region spreads from a wall surface facing the drill rotation direction T in each of the main body chip discharge flutes5to a wall surface facing a side opposite to the drill rotation direction T. When viewed in a direction perpendicular to the axis O, the cutout region is flat while a depth in the direction of the axis O is smaller than a width in the radial direction.

As shown inFIG. 8, the insert mounting seat6includes a bottom surface6aextending in a direction perpendicular to the axis O and facing the tip side of the drill main body1, and two wall surfaces6bextending perpendicular to the bottom surface6afrom both side portions of the bottom surface6aand parallel to the axis O, and facing the drill rotation direction T. The wall surfaces6bface each other, and are parallel to each other. Each of the wall surfaces6bhas a rectangular shape having a longitudinal direction in the radial direction with respect to the axis O in the present embodiment.

In the present embodiment, a hole portion6chaving a circular cross section with a constant inner diameter around the axis O to be open in a central portion of the bottom surface6ais formed to extend to a rear end side of the drill main body1. The inner diameter of the hole portion6cis larger than a diameter of a virtual circle inscribed in the bottom surface of the main body chip discharge flute5facing an outer peripheral side of the drill main body1in a cross section orthogonal to the axis O. Therefore, both sides of the hole portion6care open in a rectangular shape on the bottom surface of each of the main body chip discharge flutes5, and the bottom surface6aof the insert mounting seat6is divided into two portions by the hole portion6cso that the two portions are rotationally symmetric around the axis O by 180°. The hole portion6cis a blind hole having a bottom surface facing the tip side of the drill main body1.

Each of screw holes6dhaving a center at an equal distance from the axis O is formed at an interval from the hole portion6con the bottom surface6adivided into the two portions by the hole portion6c. In the drill main body1, a coolant hole1ais formed toward the tip side along the axis O from a rear end surface of the shank portion2. The coolant hole1ais branched into two portions in front of the insert mounting seat6. Each tip is open on the wall surface of the main body chip discharge flute5which faces the side opposite to the drill rotation direction T.

On the side opposite to the drill rotation direction T of the wall surface6bof the insert mounting seat6, a projection wall portion7surrounded by the wall surface6b, the outer peripheral surface of the cutting edge portion3, and the wall surface of the main body chip discharge flute5which faces the side opposite to the drill rotation direction T is left. A tip surface7aof the projection wall portion7is a flat surface perpendicular to the axis O. In the present embodiment, as shown inFIGS. 8 and 9, in a corner portion where the bottom surface6aand the wall surface6bintersect with each other, a recess portion6ehaving a circular cross section with a constant inner diameter and recessed from the bottom surface6aand the wall surface6bis formed as a flank portion. The recess portion6eis formed to avoid interference between the bottom surface6aand the wall surface6bof the insert mounting seat6and the cutting insert10. Furthermore, the insert mounting seat6and the two main body chip discharge flutes5each have a shape in which both are rotationally symmetric around the axis O by 180°.

As shown inFIGS. 10 to 14, the cutting insert10detachably mounted on the insert mounting seat6includes an insert main body11formed of a hard material such as a cemented carbide harder than that of the drill main body1. The insert main body11has a shape rotationally symmetric around the axis O of the drill main body1by 180° in a state of being mounted on the insert mounting seat6.

In a state of being mounted on the insert mounting seat6, the insert main body11has a tip flank12facing the tip side of the drill main body1, and an insert chip discharge groove13open in the tip flank12to communicate with each of the two main body chip discharge flutes5. A cutting edge14is formed in an intersecting ridgeline portion between the wall surface of the insert chip discharge groove13facing the drill rotation direction T and the tip flank12. The tip flank12is inclined toward the rear end side of the drill main body1as the tip flank12faces toward the side opposite to the drill rotation direction T and the outer peripheral side of the drill main body1. In this manner, the cutting edge14is provided with a flank angle and a tip angle.

In a state of being mounted on the insert mounting seat6, a rear end surface of the insert main body11is a flat surface perpendicular to the axis O as shown inFIGS. 13 and 14, and serves as a seating surface15seated on the bottom surface6aof the insert mounting seat6toward a rear end side of the drill main body1. In a central portion of the seating surface15, a multi-stage columnar shaft portion15ahaving a large diameter in the tip portion and a slightly small diameter in the rear end portion around the axis O is formed to project to the rear end side. The outer diameter of the tip portion of the shaft portion15ais set to have a size that can be fitted into the hole portion6cof the insert mounting seat6.

In addition, each of contact surfaces16coming into contact with the wall surface6bof the insert mounting seat6in the drill rotation direction T toward the side opposite to the drill rotation direction T is formed to the outer peripheral surface of the insert main body11from the wall surface of the two insert chip discharge grooves13facing the side opposite to the drill rotation direction T. The contact surfaces16are formed to perpendicularly intersect with the seating surface15, to be parallel to the axis O, and to extend parallel to each other. The contact surface16of the present embodiment has a rectangular shape having a longitudinal direction in the radial direction with respect to the axis O.

In the insert main body11, two mounting holes11a penetrating the seating surface15from the tip flank12are formed at an interval from the shaft portion15a. In a state where the contact surface16comes into contact with the wall surface6bof the insert mounting seat6, the mounting holes11aare disposed to be coaxial with each of the two screw holes6dof the insert mounting seat6. As shown inFIG. 12, the inner diameter of the mounting hole11a gradually decreases toward the seating surface15side from the opening portion on the tip flank12side, and is constant on the seating surface15side.

As shown inFIGS. 10 and 11, the insert main body11of the cutting insert10has projection portions17projecting to the side opposite to the drill rotation direction T from the contact surface16on the tip side of the contact surface16. Therefore, in the projection portions17, the shaft portion15aof the insert main body11is fitted into the hole portion6cof the insert mounting seat6. The seating surface15is brought into close contact with the bottom surface6a. In a state where the contact surface16is brought into contact with the wall surface6b, the projection portions17are disposed without any substantial gap on the tip side of the contact portion P between the contact surface16and the wall surface6b, and cover the tip portion of the contact portion P. In this manner, the contact portion P between the contact surface16and the wall surface6bis closed by the projection portion17without any substantial gap, and foreign substances are prevented from entering from the tip.

That is, in a state where the seating surface15of the insert main body11is brought into close contact with the bottom surface6aof the insert mounting seat6as described above, a rear end surface17aof the projection portion17facing the rear end side of the drill main body1is a flat surface that can be in slidable contact with the tip surface7aof the projection wall portion7which is a flat surface perpendicular to the axis O, and is perpendicular to the axis O. In this way, the rear end surface17aof the projection portion17is brought into contact with the tip surface7aof the projection wall portion7. Accordingly, the tip portion of the contact portion P between the contact surface16and the wall surface6bis covered by the projection portion17.

A side surface17bof the projection portion17facing the side opposite to the drill rotation direction T extends parallel to the contact surface16, and is adjacent to the tip flank12. That is, the side surface17bof the projection portion17extends parallel to the axis O and perpendicular to the rear end surface17a, and intersects with the tip flank12of the insert main body11at an angle in an intersecting ridgeline Q. The projection portion17of the present embodiment does not cover the whole tip surface7aof the projection wall portion7of the drill main body1, and the tip surface7ais exposed on the side of the side surface17bopposite to the drill rotation direction T. When the tip of the contact portion P between the contact surface16and the wall surface6bis covered by the rear end surface17aof the projection portion17, an advantageous effect of suppressing sludge entrance can be obtained. However, the projection portion17may cover the whole tip surface7aof the projection wall portion7of the drill main body1.

In the insert main body11of the cutting insert10configured in this way, as described above, the shaft portion15ais fitted into the hole portion6cof the insert mounting seat6. The seating surface15is brought into close contact with the bottom surface6a, and the contact surface16is brought into contact with the wall surface6b. Thereafter, as shown inFIG. 7, the clamp screw18inserted into the mounting hole11afrom the tip side of the drill main body1is screwed into the screw hole6d. In this manner, the insert main body11of the cutting insert10is detachably mounted on the insert mounting seat6.

In the indexable drill and the cutting insert10which are configured in this way, while a coolant such as a cutting fluid is ejected from the coolant hole1aformed in the drill main body1, the cutting edge14of the insert main body11in the cutting insert10performs drilling on a workpiece by cutting the workpiece. In this case, the projection portion17projecting to the side opposite to the drill rotation direction T from the contact surface16is formed on the tip side of the contact surface16coming into contact with the wall surface6bof the insert mounting seat6in the insert main body11. The projection portion17is disposed on the tip side of the contact portion P between the contact surface16and the wall surface6bto cover the tip portion of the contact portion P. Accordingly, the tip portion of the contact portion P is closed by the projection portion17, and the contact portion P is not exposed in the tip portion of the indexable drill.

Therefore, in wet cutting in which the cutting fluid is ejected as described above, even when fine chips generated by the cutting become sludge together with the cutting fluid, it is possible to prevent the sludge from entering the contact portion P between the contact surface16of the cutting insert10and the wall surface6bthe insert mounting seat6from the tip side of the drill main body1. Therefore, it is possible to prevent the contact surface16or the wall surface6bfrom being worn due to the sludge. It is possible to prevent a life of the indexable drill from being shortened due to the wear, and thus, it is possible to perform stable drilling over a long period of time.

In the present embodiment, in the projection portion17, the side surface17badjacent to the tip flank12toward the side opposite to the drill rotation direction T is formed to intersect with the tip flank12at an angle in the intersecting ridgeline Q. Therefore, when the cutting edge14is worn and sharpness becomes dull, the tip flank12is re-polished. When a new cutting edge14is sharpened in the intersecting ridgeline portion between the insert chip discharge groove13and the wall surface facing the drill rotation direction T, the width of the side surface17bbetween the intersecting ridgeline Q and the seating surface15in the direction of the axis O is confirmed. In this manner, it is possible to visually confirm whether or not to re-polish the cutting edge14. Therefore, it is possible to avoid a situation in which the projection portion17is excessively thinned and the projection wall portion7of the drill main body1is worn.

In the present embodiment, the shaft portion15aaround the axis O is formed on the seating surface15of the insert main body11of the cutting insert10, and the hole portion6cinto which the shaft portion15acan be fitted is formed around the axis O on the bottom surface6aof the insert mounting seat6. Therefore, the cutting insert10can be accurately mounted around the axis O of the drill main body1, and deflection accuracy of the cutting edge14can be secured.

The hole portion6cis open in the main body chip discharge flute5of the drill main body1. Accordingly, air inside the hole portion6ccan be discharged when the shaft portion15ais fitted into the hole portion6c, and the air inside the hole portion6ccan avoid being compressed. Therefore, a force of pushing out the insert main body11to the tip side of the drill main body1does not act due to a pressure of the compressed air. Therefore, according to the present embodiment, the cutting insert10can be firmly and stably mounted on the insert mounting seat6.

In the present embodiment, as described above, the shaft portion15aaround the axis O is formed on the seating surface15of the insert main body11, and the hole portion6cinto which the shaft portion15acan be fitted is formed around the axis O on the bottom surface6aof the insert mounting seat6. However, conversely, the hole portion around the axis O may be formed on the seating surface15of the insert main body11, and the shaft portion that can be fitted into the hole portion may be formed around the axis O on the bottom surface6aof the insert mounting seat6. In this manner, the hole portion may be open in the insert chip discharge groove13.

In addition, in the present embodiment, the coolant hole1ais formed in the drill main body1from the rear end surface of the shank portion2toward the tip side along the axis O. The coolant hole1ais branched into the two portions in front of the insert mounting seat6, and is open on the wall surface of the main body chip discharge flute5facing the side opposite to the drill rotation direction T. However, alternatively, two coolant holes may be formed from the rear end surface of the shank portion2toward the tip side of the drill main body1after passing between the two main body chip discharge flutes5. The coolant holes may be open on the wall surface facing the side opposite to the drill rotation direction T of the main body chip discharge flute5in front of the insert mounting seat6.

Furthermore, in the present embodiment, in a state where the contact surface16is brought into contact with the wall surface6bof the insert mounting seat6, each of the two mounting holes11apenetrating the seating surface15from the tip flank12are disposed in the insert main body11to be coaxial with each of the two screw holes6dof the insert mounting seat6. However, alternatively, the two mounting holes11amay be disposed to be slightly eccentric to the side opposite to the contact surface16with respect to the two screw holes6dof the insert mounting seat6.

Next,FIGS. 15 to 20show a second embodiment of the indexable drill according to the present invention, andFIGS. 21 and 31show an exploded view of the indexable drill according to the second embodiment.FIGS. 22 to 24show the second embodiment of the drill main body according to the present invention of the indexable drill of the second embodiment, andFIGS. 25 to 30show the second embodiment of the cutting insert10detachably mounted on the drill main body. In the indexable drill, the drill main body, and the cutting insert10of the second embodiment, the same reference numerals will be assigned to elements common to those of the first embodiment shown inFIGS. 1 to 14. Contents which are not described later are incorporated with reference to the description in the first embodiment.

In the first embodiment, the wall surface6bof the insert mounting seat6facing the drill rotation direction T and the contact surface16of the insert main body11of the cutting insert10which is brought into contact with the wall surface6bhave the rectangular shape. The width of the wall surface6band the contact surface16in the direction of the axis O is constant in the radial direction with respect to the axis O. In contrast, in the second embodiment, on the wall surface6band the contact surface16, the width on the outer peripheral side of the drill main body1in the direction of the axis O is larger than that on the inner peripheral side.

In the second embodiment, as shown inFIGS. 21, 24, 29, and 30, the wall surface6band the contact surface16are formed so that the width in the direction of the axis O is gradually widened to the outer peripheral side from the inner peripheral side of the drill main body1. The wall surface6band the contact surface16are formed in a substantially trapezoidal shape.

In addition, in the first embodiment, the recess portion6eserving as the flank portion formed in the corner portion where the bottom surface6aand the wall surface6bof the insert mounting seat6intersect with each other has the circular cross section with the constant inner diameter. Therefore, the recess portion6ehas a constant cross-sectional area. In contrast, in the second embodiment, a cross-sectional area of the recess portion6eis formed so that the opening portion on the outer peripheral surface side of the drill main body1is larger than the opening portion on the main body chip discharge flute5side.

In the second embodiment, as shown inFIG. 22, in order from the opening portion on the main body chip discharge flute5side toward the opening portion on the outer peripheral surface side of the drill main body1, the recess portion6eis formed by a circular cross-sectional portion and a portion whose cross section having a cross-sectional area larger by two stages than that of the circular cross-sectional portion has a recess curve shape. In the recess portion6e, the length of the circular cross-sectional portion open to the main body chip discharge flute5side is longest. In addition, as shown inFIGS. 22 and 23, in the second embodiment, the intersecting ridgeline portion between the wall surface6bof the insert mounting seat6and the inner peripheral surface of the main body chip discharge flute5is chamfered, thereby forming a chamfered portion6fthat intersects with the wall surface6band the inner peripheral surface of the main body chip discharge flute5.

In the indexable drill, the cutting insert10, and the drill main body1of the second embodiment, an advantageous effect the same as that of the first embodiment can be obtained as a matter of course. First, the wall surface6bof the insert mounting seat6and the contact surface16of the cutting insert10are formed so that the width in the direction of the axis O on the outer peripheral side of the drill main body1is wider than the inner peripheral side. Accordingly, it is possible to secure a large contact area between the wall surface6band the contact surface16on the outer peripheral side of the drill main body1on which the largest cutting load acts during the drilling.

Therefore, stress acting on the outermost periphery of the drill main body1of the insert mounting seat6can be reduced. The cutting insert10can be stably held against the cutting load during the drilling, and the drilling can be accurately performed. In particular, in the present embodiment, the wall surface6band the contact surface16are formed so that the width in the direction of the axis O is gradually widened from the inner peripheral side toward the outer peripheral side of the drill main body1. Accordingly, it is possible to secure the large contact area between the wall surface6band the contact surface16.

In the second embodiment, the cross-sectional area of the recess portion6eformed to be recessed from the bottom surface6aand the wall surface6bwhich serves as the flank portion in the corner portion where the bottom surface6aand the wall surface6bof the insert mounting seat6intersect with each other is formed so that the opening portion on the outer peripheral surface side of the drill main body1is larger than the opening portion on the main body chip discharge flute5side. Therefore, as described above, stress concentration on the recess portion6ecan be relaxed on the outer peripheral surface side of the drill main body1on which the largest cutting load acts during the drilling.

On the other hand, the opening portion on the main body chip discharge flute5side has a small cross-sectional area. Accordingly, rigidity of the projection wall portion7of the drill main body1in which the wall surface6bis formed is not impaired, and stable holding of the cutting insert10is not disturbed. In particular, in the present embodiment, the recess portion6eis formed so that the cross-sectional area gradually increases, and the stage length of the circular cross-sectional portion on the main body chip discharge flute5side is the longest. Accordingly, the rigidity of the projection wall portion7can be more reliably maintained. A cross-sectional shape of the recess portion6emay be a circular shape in any stage, or may be a non-circular recess curve.

As in the second embodiment, the intersecting ridgeline portion between the wall surface6bof the insert mounting seat6and the inner peripheral surface of the main body chip discharge flute5is chamfered to form the chamfered portion6fin which the wall surface6band the inner peripheral surface of the main body chip discharge flute5intersect with each other. In this manner, compared to when a sharp edge remains in the intersecting ridgeline portion, it is possible to prevent the intersecting ridgeline portion from being damaged or broken. The chamfered portion6fdoes not come into contact with the insert main body11, and most of the chamfered portion6fis formed in a concave curved surface shape inclined in the direction of the axis O.

The shaft portion15aand the hole portion6cin the second embodiment will be described in detail with reference toFIG. 31. In the present embodiment, in the hole portion6copen on the bottom surface6aof the insert mounting seat6of the drill main body1, a portion on the tip side is a large diameter portion6c1having a constant inner diameter, having a circular cross-sectional shape around the axis O, and having the long length in the direction of the axis O. A portion on the rear end side is a small diameter portion6c2having a constant inner diameter slightly smaller than that of the large diameter portion6c1, having a circular cross-sectional shape around the axis O, and having the shorter length in the direction of the axis O than that of the large diameter portion. However, a portion where the large diameter portion6c1and the small diameter portion6c2open on the bottom surface of the main body chip discharge flute5facing the outer peripheral side of the drill main body1is cut out by the bottom surface.

On the other hand, as in the first embodiment, in the shaft portion15aprojecting from the seating surface15of the insert main body11of the cutting insert10, the tip portion serves as a large diameter portion15a1. The rear end portion is formed in a multi-stage columnar shape around the axis O which serves as a small diameter portion15a2having the diameter slightly smaller than that of the large diameter portion15a1. The length of the large diameter portion15a1in the direction of the axis O is longer than that of the small diameter portion15a2. However, in the shaft portion15a, the portion where the insert chip discharge groove13is formed is also cut out along the bottom surface facing the outer peripheral side of the insert chip discharge groove13.

In the present embodiment, the outer diameter of the large diameter portion15a1of the shaft portion15ais set to have a size that can be fitted into the large diameter portion6c1of the hole portion6c. In this manner, the insert main body11of the cutting insert10can be accurately and coaxially mounted around the axis O of the drill main body1. Accordingly, high deflection accuracy of the cutting edge14can be secured. In order to secure the high deflection accuracy in this way, it is desirable that the shaft portion15afalls within a range of h6to h7, and it is desirable that the hole portion6cfalls within a range of H6to H7in the fitting class in JIS B 0401-1: 1998 (ISO 286-1: 1988).

The length of the whole shaft portion15ain the direction of the axis O is slightly smaller than the length (depth) of the hole portion6cin the direction of the axis O. The length of the large diameter portion15a1of the shaft portion15ain the direction of the axis O is slightly smaller than the length (depth) of the large diameter portion6c1of the hole portion6cin the direction of the axis O. When the shaft portion15ais fitted into the hole portion6c, no gap is formed between the bottom surface6aof the insert mounting seat6of the drill main body1and the seating surface15of the insert main body11of the cutting insert10. The configurations are common to those of the first embodiment except that the hole portion6chas the constant inner diameter.

INDUSTRIAL APPLICABILITY

According to the present invention, even in a case of wet cutting in which drilling is performed while a coolant is supplied, when chips become sludge together with the coolant, it is possible to prevent the sludge from entering a contact portion between a contact surface of a cutting insert and a wall surface of an insert mounting seat from a tip side of a drill main body. Therefore, it is possible to perform stable drilling over a long period of time by preventing the contact surface or the wall surface from being worn. Therefore, the present invention is industrially applicable.

REFERENCE SIGNS LIST

1: Drill main body

5: Main body chip discharge flute

6: Insert mounting seat

6a: Bottom surface of insert mounting seat6

6b: Wall surface of insert mounting seat6

6c: Hole portion

6c1: Large diameter portion of hole portion6c

6c2: Small diameter portion of hole portion6c

7: Projection wall portion

7a: Tip surface of projection wall portion7

10: Cutting insert

11: Insert main body

13: Insert chip discharge groove

14: Cutting edge

15: Seating surface

15a1: Large diameter portion of shaft portion15a

15a2: Small diameter portion of shaft portion15a

16: Contact surface

17a: Rear end surface of projection portion17

17b: Side surface of the projection portion17facing side opposite to drill rotation direction T

O: Axis of drill main body1

T: drill rotation direction

P: Contact portion between wall surface6band contact surface16