Exchangeable cutting head and cutting tool having the same

An exchangeable cutting head that is inserted into a mounting hole formed on a tool body, screwed on a mounting screw section provided on a bottom portion of the mounting hole, and is attached removably to the tool body, the exchangeable cutting head includes: a cutting head body including: a cutting portion provided at a front-end section; a mounting portion provided at a rear-end section and inserted into the mounting hole; and an engaging hole having an inner-peripheral face on which a recessed portion is formed, the cutting head body being made of a hard material; and a connection member including: a shaft portion that is inserted into the engaging hole, includes an outer periphery attached firmly to the inner-peripheral face of the engaging hole, and is engaged with the inner-peripheral face; a head screw section screwed with the mounting screw section; and a hole section formed inside of the head screw section and the shaft portion and along a center line of the shaft portion, the connection member being made of a metal material having a degree of hardness lower than a degree of hardness of the hard material and the connection member being connected to the cutting head body.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a cutting tool in which an exchangeable cutting head having a cutting portion is attached removably to a tool body.

This application is based on and claims priority from Japanese Patent Application No. 2009-079852, filed on Mar. 27, 2009 and Japanese Patent Application No. 2009-286638, filed on Dec. 17, 2009, the contents of which are incorporated herein by reference.

2. Background Art

Conventionally, a cutting tool in which an exchangeable cutting head is attached removably to a tool body is known.

In the cutting tool having the exchangeable cutting head, the exchangeable cutting head includes a cutting head body having a cutting portion and a connection member that is provided at a rear-end of the cutting head body and has a head screw section.

In addition, the tool body has a mounting hole formed at the tool body and a female screw section formed at the mounting hole.

In the foregoing cutting tool having the exchangeable cutting head, the exchangeable cutting head is inserted into the mounting hole of the tool body, and the head screw section of the connection member is screwed into the female screw section of the mounting hole of the tool body.

As an example, a cutting head body and a connection member are formed so as to be integrated in one body in a powder metallurgy process, and an exchangeable cutting head made of a hard material is disclosed in Japanese Unexamined Patent Application, First Publication No. H07-164234.

In the structure, a head screw section of the above-described connection member is screwed into a female screw section formed at a mounting hole of a tool body, and the cutting head body is thereby detachably attached to the tool body.

In addition, as an example, an exchangeable cutting head in which a cutting head body and a connection member are removably coupled each other is disclosed in Japanese Unexamined Patent Application, First Publication No. 2004-98272.

In the structure, in a state where the cutting head body is connected with the connection member, a head screw section of the connection member and a female screw section formed at a mounting hole of a tool body are screwed together, and the exchangeable cutting head is attached removably to the tool body.

In a method for connecting the cutting head body with the connection member, an end portion of a hook section is formed at one of the cutting head body and the connection member, a hook hole of the hook section is formed at the other of the cutting head body and the connection member, the end portion is inserted into and passed through the hook hole.

Subsequently, the cutting head body is rotated in relative to the connection member in a circumferential direction, the cutting head body is connected with the connection member.

In the above-described cutting tool having the exchangeable cutting head, it is preferable that the cutting head body be made of a hard material in order to improve sharpness or abrasion resistance in a machining process.

On the other hand, when the head screw section of the connection member is screwed in the tool body, since stress is generated at a screw thread, it is preferable that the head screw section of the cutting head be made of a material with a high level of toughness.

However, in the above-described exchangeable cutting head used in the cutting tool having the exchangeable cutting head disclosed in Japanese Unexamined Patent Application, First Publication No. H07-164234, the cutting head body and the connection member are formed of a hard material so as to be integrated in one body, and there is a drawback in that a screw thread thereof is easily fractured when stress occurs at the head screw section.

In addition, due to concentrated stress at a root portion of the screw, there is a drawback in that the screw may break.

In order to avoid the foregoing drawback, it is necessary to machine each screw thread in a particular form to spread stress generated in the screw thread, therefore a manufacturing cost increases.

In addition, in the exchangeable cutting head of the cutting tool having the exchangeable cutting head disclosed in Japanese Unexamined Patent Application, First Publication No. 2004-98272, since the cutting head body can be separated from the connection member, it is possible to form each of the cutting head body and the connection member by use of a different material.

However, a configuration of the hook section or the hook hole is complicated, and a manufacturing cost for molding the hook section or the hook hole increases.

In addition, in a step for attaching the cutting head body to the tool body, it is necessary to initially combine the cutting head body with the connection member, and there is a problem in that an hour of labor is required.

SUMMARY OF THE INVENTION

The present invention was made in order to solve the above problems, and has an object to provide an exchangeable cutting head in which it is possible to easily and reliably connect the cutting head body with the connection member and reduce a cost of manufacturing thereof.

In order to solve the above-described problems, an exchangeable cutting head of a first aspect of the present invention is inserted into a mounting hole formed on a tool body, is screwed on a mounting screw section provided on a bottom portion of the mounting hole, and is attached removably to the tool body. The exchangeable cutting head includes a cutting head body and a connection member. The cutting head body includes: a cutting portion provided at a front-end section; a mounting portion provided at a rear-end section and inserted into the mounting hole; and an engaging hole having an inner-peripheral face on which a recessed portion is formed, the cutting head body being made of a hard material. The connection member includes: a shaft portion that is inserted into the engaging hole, includes an outer periphery (outer-peripheral section) attached firmly to the inner-peripheral face of the engaging hole, and is engaged with the inner-peripheral face; a head screw section screwed with the mounting screw section; and a hole section formed inside of the head screw section and the shaft portion and along a center line of the shaft portion, the connection member being made of a metal material having a degree of hardness lower than the degree of hardness of the hard material and the connection member being connected to the cutting head body.

In the exchangeable cutting head including the foregoing structure, an individual cutting head body and an individual connection member are used, and they are connected to each other. For this reason, it is possible to form the cutting head body including the cutting portion used for cutting a work piece, from, for example, a hard material such as cemented carbide, and to form the connection member from, for example, a plastically-deformable material with a high degree of toughness such as stainless steel. Therefore, it is possible to easily form the connection member including the head screw section on which a screw is formed by a machining process at a low cost while maintaining a high level of sharpness or durability in the cutting portion of the cutting head body. In addition, it is possible to solve a problem in that a screw of the head screw section is easily cracked.

In addition, in the connection structure constituted of the cutting head body and the connection member, the outer periphery of the shaft portion protrudes in a state where the shaft portion of the connection member is inserted into the engaging hole of the cutting head body, the outer periphery is fitted into the recessed portion formed at the inner-peripheral face of the engaging hole, and the cutting head body is engaged with the connection member. Therefore, it is possible to easily connect the cutting head body with the connection member.

In the connection structure constituted of the cutting head body and the connection member as described above, for example, by pressing a rod member into the hole section of the connection member in a state where the shaft portion of the connection member is inserted into the engaging hole of the cutting head body, the connection member is plastically-deformed so that the diameter of the shaft portion of the connection member increases.

In this manner, since the outer periphery of the shaft portion is attached firmly to the inner-peripheral face of the engaging hole, it is possible to reliably connect the cutting head body with the connection member.

In addition, since a simple structure in which the engaging hole is formed in the cutting head body and the shaft portion and the hole section are formed in the connection member is employed, it is possible to easily connect the cutting head body with the connection member.

Consequently, when the exchangeable cutting head is manufactured, it is not necessary to perform a complicated machining process, and it is possible to reduce a cost of manufacturing.

Furthermore, since the connection member can be inexpensively manufactured in a high-volume production by use of a automatic lathe or the like including a barfeeder, it is thereby possible to further reduce the cost of manufacturing the exchangeable cutting head.

In addition, it is preferable that, in the exchangeable cutting head of the first aspect of the present invention, the recessed portion be an uneven face in which the surface roughness in maximum height (maximum height of roughness profile) Rz is 5 μm to 200 μm, the outer periphery of the shaft portion be attached firmly to the inner-peripheral face of the engaging hole, and part of the outer periphery be plastically-deformed along the uneven face.

Also, in the exchangeable cutting head including the foregoing structure, an individual cutting head body and an individual connection member are used, and they are connected to each other. For this reason, it is possible to form the cutting head body including the cutting portion used for cutting a work piece, from, for example, a hard material such as cemented carbide, and to form the connection member from, for example, a plastically-deformable material with a high degree of toughness such as stainless steel. Therefore, it is possible to easily form the connection member including the head screw section on which a screw is formed by a machining process at a low cost while maintaining a high level of sharpness or durability in the cutting portion of the cutting head body. In addition, it is possible to solve a problem in that a screw of the head screw section is easily cracked.

In addition, in the case where the surface roughness in maximum height Rz is less than 5 μm, the condition of the inner-peripheral face is smooth, and the connection member is easily removed from the cutting head body.

In addition, in the case where the surface roughness in maximum height Rz is less than or equal to 200 μm, it is easy to insert the shaft portion into the cutting head body.

Therefore, it is preferable that the surface roughness in maximum height Rz of the uneven face formed on the inner-peripheral face be greater than or equal to 5 μm and be less than or equal to 200 μm.

In addition, in the connection structure constituted of the cutting head body and the connection member, the outer periphery of the shaft portion is plastically-deformed along the uneven face formed on the inner-peripheral face of the engaging hole in a state where the shaft portion of the connection member is inserted into the engaging hole of the cutting head body. Therefore, it is possible to easily and reliably connect the cutting head body with the connection member.

In the connection structure constituted of the cutting head body and the connection member as described above, for example, by pressing a rod member into the hole section of the connection member in a state where the shaft portion of the connection member is inserted into the engaging hole of the cutting head body, the connection member is plastically-deformed so that the diameter of the shaft portion of the connection member increases.

In addition, since a simple structure in which the engaging hole is formed in the cutting head body and the shaft portion and the hole section are formed in the connection member is employed, it is possible to easily connect the cutting head body with the connection member.

Consequently, when the exchangeable cutting head is manufactured, it is not necessary to perform a complicated machining process, and it is possible to reduce the cost of manufacturing.

Furthermore, since the connection member can be inexpensively manufactured in high-volume by use of an automatic lathe or the like which is provided with a barfeeder, it is thereby possible to further reduce the cost of manufacturing the exchangeable cutting head.

In addition, it is preferable that, in the exchangeable cutting head of the first aspect of the present invention, at least one of a wall section that faces the front-end section and a wall section that faces in a circumferential direction around the center line be formed at the recessed portion.

In the foregoing exchangeable cutting head, in the case where the wall section facing the front-end section in a center line direction is formed at the recessed portion, the outer periphery of the shaft portion of the connection member is the fitted into the recessed portion, and the recessed portion is engaged with the outer periphery. As a result, it is possible to prevent the connection member from being separated from the cutting head body in the center line direction toward the rear-end section, and from being moved relative to the cutting head body. That is, it is possible to prevent the connection member from being removed from the cutting head body.

In addition, in the case where the wall section facing in a circumferential direction around the center line is formed at the recessed portion, the outer periphery of the shaft portion of the connection member is fitted into the recessed portion, and the recessed portion is engaged with the outer periphery. As a result, it is possible to prevent the connection member from being rotated relative to the cutting head body around the center line. In the cutting head body, it is possible to prevent the connection member from being rotated.

Therefore, it is possible to reliably connect the cutting head body with the connection member.

In addition, it is preferable that, in the exchangeable cutting head of the first aspect of the present invention, a planar wall face extending in the center line direction be formed at the engaging hole, and the wall face be the wall section that faces in a circumferential direction around the center line in the recessed portion.

In the foregoing exchangeable cutting head, when the outer periphery of the shaft portion of the connection member is fitted into the recessed portion, since the shaft portion is planarly plastically-deformed so as to be in close contact with the wall face, it is possible to prevent the connection member from being rotated relative to the cutting head body around the center line. Therefore, it is possible to further reliably connect the cutting head body with the connection member.

In addition, it is preferable that, in the exchangeable cutting head of the first aspect of the present invention, the mounting portion have an outer-peripheral face, the mounting hole of the tool body be a tapered hole, and the outer-peripheral face be tapered such that an external diameter thereof gradually decreases toward the rear-end section and has a taper surface into which the tapered hole is fitted.

In the foregoing exchangeable cutting head, the outer-peripheral face of the mounting portion which is the taper surface of the cutting head body is evenly and uniformly pressed onto an inner-peripheral face of the tapered hole of the mounting hole, and both thereof are fitted (engaged) with each other so as to form a tapered structure. Because of this, it is possible to further tightly attach the cutting head body to the tool body, perfectly coincide the center line of the cutting head body with the center line of the tool body, and perform a centering thereof.

In addition, high pressure is generated between the outer-peripheral face of the mounting portion and the tapered hole, due to a wedge effect in that the outer-peripheral face of the mounting portion which is the taper surface is fitted onto the tapered hole of the mounting hole so as to form a tapered structure. High friction resistance is generated by the pressure, and it is thereby possible to tightly combine the cutting head body with the tool body in an integrated manner.

In addition, since the friction resistance is generated, all of the tightening torque generated between the cutting head body and the mounting portion is avoided from being applied to the head screw section and the mounting screw section.

For this reason, an excessive axial tension is prevented from being generated between the head screw section and the mounting screw section, it is possible to prevent the head screw section and the mounting screw section from being fractured, and prevent the connection member from being removed from the cutting head body.

Furthermore, in a state where the exchangeable cutting head is attached to the tool body, an axial tension applied to the head screw section and the mounting screw section is relieved. Therefore, even if the cutting head body is not connected with the connection member tighter than necessary, the connection member is not removed from the cutting head body. Thus, in a state where the exchangeable cutting head is removed from the tool body, it is possible to easily separate the connection member from the cutting head body.

In addition, it is preferable that, in the exchangeable cutting head of the first aspect of the present invention, an inclined angle of the taper surface relative to the center line be set in the range of 1° to 20°.

Furthermore, it is preferable that, in this range, the inclined angle be set in the range of 2° to 20°.

By means of this structure, a tapered portion of the cutting head body is tightly and reliably fitted into (engaged with) the tapered hole of the mounting hole. In addition, it is possible to remove the cutting head from the mounting hole.

Specifically, it is further preferable that the above-described inclined angle be set in the range of 3° to 5°.

In addition, it is preferable that, in the exchangeable cutting head of the first aspect of the present invention, the hole section be a through hole penetrating the connection member along the center line, and the cutting head body have a coolant hole that is communicated with the through hole and opens at the cutting portion.

In the foregoing structure, it is possible to cause a coolant supplied from the tool body to be passed through the through hole and the coolant hole, and supply the coolant to the cutting portion.

In addition, it is preferable that, in the exchangeable cutting head of the first aspect of the present invention, the cutting head body include a rotation section having at least a pair of parallel faces that are parallel to each other relative to the center line.

In the foregoing structure, it is possible to engage a tool such as a wrench with the rotation section, and rotate the cutting head body. In this way, it is possible to tightly hold the cutting head body and the connection member onto the tool body.

In addition, it is preferable that, in the exchangeable cutting head of the first aspect of the present invention, the rotation section have a rear-end, and a flange that protrudes a radial-outer direction around the center line be provided at the rear-end of the rotation section.

In the foregoing structure, for example, by attaching a jig onto the flange, it is possible to tightly fix the cutting head body in the center line direction. In addition, at this time, by supporting the rotation section by use of the jig, it is possible to stably fix the cutting head body.

In this way, it is possible to easily connect the cutting head body with the connection member, and easily separate the connection member from the cutting head body. In addition, when the cutting portion is re-polished or coated by use of a PVD method, it is possible to reliably support the cutting head body.

In addition, it is preferable that, in the exchangeable cutting head of the first aspect of the present invention, the mounting portion have a rear-end, and the engaging hole extend from the rear-end of the mounting portion to the inside of the cutting portion.

By means of this structure, since it is possible to reduce the weight of the cutting head body, it is possible to prevent vibration from being generated in the cutting portion during a machining process.

In addition, it is preferable that, in the exchangeable cutting head of the first aspect of the present invention, the cutting head body be molded by use of any material of cemented carbide, cermet, and ceramic.

Since the cutting head body having the cutting portion used for cutting a work piece is formed from cemented carbide as described above, it is possible to maintain a high level of sharpness or durability in the cutting portion of the cutting head body. That is, an amount of abrasion is reduced, and it is possible to maintain a high level of durability.

In order to solve the above-described problems, a cutting tool having an exchangeable cutting head of a second aspect of the present invention includes: a tool body; and the above-described exchangeable cutting head that is attached to the tool body.

According to the foregoing cutting tool having the exchangeable cutting head, since the above-described exchangeable cutting head in which the cutting head body is reliably connected with the connection member is fixed into the cutting tool having the exchangeable cutting head, it is possible to prevent vibration from being generated therein during a machining process and perform a machining process with a high level of precision.

According to the cutting tool having the exchangeable cutting head related to the present invention, in the connection structure constituted of the cutting head body and the connection member, the outer periphery of the shaft portion of the connection member protrudes toward the recessed portion formed on the engaging hole of the cutting head body, the outer periphery fitted into and engaged with the recessed portion.

Consequently, it is possible to easily connect the cutting head body with the connection member.

In addition, since the connection structure constituted of the foregoing cutting head body and the connection member is obtained by providing a simplified structure, it is possible to reduce the cost of manufacturing.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

First Embodiment

In the explanation below, a position which is close to the front-end position is referred to as “a front-end side (front-end section)” in a direction from a rear-end position to toward a front-end position. In this case, a rear-end face15(described below) of a tool body10is formed at the rear-end position, and a cutting edge23B (described below) is formed at the front-end position.

In addition, a position which is close to the rear-end position is referred to as “rear-end side (rear-end, rear-end section)” in a direction from the front-end position toward the rear-end position.

As shown inFIG. 1, a cutting tool1having an exchangeable cutting head of a first embodiment is constituted of a tool body10and an exchangeable cutting head2.

The tool body10rotates around a center line O.

The exchangeable cutting head2is constituted of a cutting head body20and a connection member30. The cutting head body20is fixed to and attached removably to the tool body10. The connection member30is used for attaching the cutting head body20to the tool body10.

The tool body10is formed of, for example, steel or the like. The tool body10is formed substantially as a circular cylinder around the center line O.

In the tool body10, a mounting hole12is formed in a direction from a front-end face11toward the rear-end face15around the center line O.

The mounting hole12has a tapered hole13and a mounting screw section.

The tapered hole13is a hole formed substantially as a circular truncated cone in which the internal diameter of the hole gradually decreases with a constant gradient in a direction from the front-end face11of the tool body10toward the rear-end face15.

The mounting screw section14is provided at a bottom portion of the mounting hole12, aligned with a rear-end of tapered hole13, and has a female screw formed at an inner-peripheral face.

In addition, a coolant supply hole16is formed at a rear-end of the mounting screw section14.

The coolant supply hole16has the diameter that is smaller than the diameter of the mounting screw section14by a step-difference, extends along the center line O, and opens at the rear-end face15of the tool body10.

In addition, in the embodiment, an inclined angle the above-described tapered hole13relative to the center line O is set in the range of 1° to 20°, and it is preferable that, in this range, the angle be set in the range of 2° to 20°. Furthermore, it is preferable that the angle be set in the range of 3° to 5°. In addition, an optimal angle of the inclined angle is approximately 4°.

The cutting head body20is made of a hard material such as cemented carbide, cermet, ceramic. As shown inFIG. 2, the cutting head body20includes a cutting portion21that machines a work material, and a mounting portion28aligned with a rear-end of the cutting portion21. The center of the cutting head body20is coincided with the center line O.

In the cutting head body20, the cutting portion21is provided at a front-end section, and the mounting portion28is provided at a rear-end section.

In addition, an outer-peripheral face of the mounting portion28is a taper surface28bin which the external diameter of the taper surface28bgradually decreases with a constant gradient in a direction from the front-end section toward the rear-end.

Therefore, the mounting portion28is formed substantially as a circular truncated cone.

In addition, in the embodiment, an inclined angle of the taper surface28bof the above-described mounting portion28relative to the center line O is substantially equal to the inclined angle of the above-described tapered hole13relative to the center line O.

That is, the inclined angle is set in the range of 1° to 20°.

Here, the cutting portion21of the cutting head body20will be described in detail.

A plurality of flutes22are formed at the cutting portion21. Each of the flutes22is positioned in a circumferential direction related to the center line O so as to be twisted in the center line O toward a rear-end side and in a backward direction of a tool rotation direction T.

In a plurality of the flutes22, a portion of the front-end side of a wall face that faces in a forward direction of the tool rotation direction T is a rake face24.

An outer-peripheral cutting edge23A is formed at a ridge line portion that is positioned at an outer-peripheral side of the rake face24.

In addition, a cutting edge23B is formed in an intersect ridge line portion in which the rake face24is intersected with and a tip flank face25. The cutting edge23B is a cutting point (tip) of the cutting head body20and extends from an adjacent center line O toward an outer-peripheral side.

In addition, in the cutting portion21, a wrench engagement section26(rotation section) is formed at a position which is closer to the rear-end than the position at which a plurality of outer-peripheral cutting edges23A is formed.

The wrench engagement section26is formed substantially as a circle in a cross section orthogonal to the center line O.

A portion of the wrench engagement section26that is positioned on an outer-peripheral face is machined in a direction parallel to the center line O and in a direction from the outer-peripheral face to the center line O by a predetermined depth.

Consequently, at least a pair of parallel faces26a(notched face) is formed on the outer-peripheral face of the wrench engagement section26and at positions that are opposite to each other. The parallel faces26aare symmetrically positioned relative to the center line O.

In the embodiment, three pair of the foregoing pair of parallel faces26ais formed on the outer-peripheral face of the wrench engagement section26. Therefore, the wrench engagement section26is formed substantially as a hexagon in a cross section orthogonal to the center line O.

In addition, the wrench engagement section26includes a support face26b. The support face26bforms a step-difference between the wrench engagement section26and the mounting portion28. The support face26bfaces the rear-end side and is a flat face orthogonal to the center line O.

An engaging hole29is formed inside of the mounting portion28of the cutting head body20. The engaging hole29opens at a rear-end face28aof the mounting portion28and extends along the center line O.

The rear-end face28ais a flat face orthogonal to the center line O.

The engaging hole29has an inner-peripheral face29athat is formed substantially as a circular cylinder. The engaging hole29has an internal diameter29b.

As shown inFIG. 3, a toroidal groove60(recessed portion) is formed at the inner-peripheral face29a.

The toroidal groove60is a depressed portion in a radial-outer direction with respect to the engaging hole29and formed as a ring around the center line O.

The toroidal groove60includes a wall section60a(first wall section) facing the front-end side toward the center line O, and a wall section60b(second wall section) facing the rear-end toward the center line O.

In addition, the structure in which single toroidal groove60is formed is shown inFIG. 3; however, a plurality of toroidal grooves60may be formed on the engaging hole29.

In addition, the coolant hole (not shown in drawings) that is formed inside of the cutting portion21of the cutting head body20is connected to a portion positioned at the front-end side of the engaging hole29.

The coolant hole is communicated with each flute22.

The connection member30is made of a plastically-deformable metal material having a degree of hardness lower than the degree of hardness of the hard material such as cemented carbide that forms the cutting head body20. The connection member30is made of a material, for example, stainless steel having a high level of toughness.

As shown inFIG. 4, the connection member30is formed substantially as a multiple-stage circular cylinder along the center line O.

A head screw section31is provided at a rear-end section of the connection member30. The head screw section31has an outer-peripheral face on which a male screw is formed.

In addition, in connection member30, a flange section32is provided at a portion of the front-end side of the head screw section31. The flange section32has a diameter that is greater than the external diameter of the shaft portion33by a step-difference.

The flange section32is formed as a circle in a cross section orthogonal to the center line O.

A face of the flange section32facing the front-end side is a flat face orthogonal to the center line O and is a contact face32a.

Furthermore, a shaft portion33is provided at the front-end side of the above-described flange section32, and the shaft portion33extends along the center line O from the contact face32atoward the front-end side.

An outer periphery33aof the shaft portion33has a face formed as a circular cylinder around the center line O.

In a state where before the above-described cutting head body20is connected with the connection member30, an external diameter33cof the outer periphery33ais smaller than the flange section32and is slightly smaller than the internal diameter29bof the inner-peripheral face29aof the engaging hole29in the above-described cutting head body20.

In this state, the external diameter33cof the outer periphery33ais smaller than the internal diameter29bof the inner-peripheral face29aof the engaging hole29, for example, by 0.1 mm to 0.5 mm.

In addition, a through hole34(hole section) is formed in the connection member30. The through hole34opens at the rear-end of the head screw section31, extends along the center line O, opens at a front-end (front-end side) of the shaft portion33and penetrates the connection member30.

In the embodiment, the through hole34includes a small-diameter hole34aand a large-diameter hole34b.

The small-diameter hole34ais formed inside of the flange section32and the shaft portion33and has a constant internal diameter35aalong the length.

The large-diameter hole34bis formed inside of the head screw section31, and has the internal diameter35bgreater than that of the small-diameter hole34a.

The internal diameter29bof the inner-peripheral face29aand the external diameter33cof the outer periphery33aare determined depending on an amount of torque that is applied to the exchangeable cutting head2.

If, for example, the amount of torque applied to the exchangeable cutting head2is large, it is necessary to increase the internal diameter29band the external diameter33cin order to reliably transmit the torque of the cutting tool1to the cutting portion21.

The internal diameter35aof the small-diameter hole34aand the internal diameter35bof the large-diameter hole34bare determined depending on a diameter of a large-diameter portion50aof a press member50as described below.

Specifically, the internal diameter35bof the large-diameter hole34bis greater than the diameter of the large-diameter portion50aof the press member50.

Therefore, when the press member50is inserted into the connection member30, the large-diameter portion50areaches an entrance between the small-diameter hole34aand the large-diameter hole34b.

In addition, the internal diameter35aof the small-diameter hole34ais smaller than the diameter of the large-diameter portion50aof the press member50.

Therefore, as described below, when the press member50is pressed into the small-diameter hole34a, the internal diameter35aof the small-diameter hole34aincreases, the external diameter33cof the outer periphery33aincreases, and the outer periphery33aof the shaft portion33is attached firmly to the inner-peripheral face29aof the engaging hole29.

Next, a method for assembling the exchangeable cutting head2by coupling the above-described cutting head body20with the connection member30will be described.

Firstly, as shown inFIG. 5, the shaft portion33of the connection member30is inserted into the engaging hole29of the cutting head body20.

By means of this structure, the outer periphery33aof the shaft portion33is opposed to the inner-peripheral face29aof the engaging hole29with a slight clearance interposed therebetween.

In this case, since the external diameter33cof the outer periphery33aof the shaft portion33is less than the internal diameter29bof the inner-peripheral face29aof the engaging hole29, the shaft portion33can be easily inserted into the engaging hole29.

In a state where the shaft portion33is inserted into the engaging hole29in the above-described manner, the rear-end face28aof the mounting portion28of the cutting head body20is in contact with the contact face32aof the flange section32.

Due to the contact, an inserted distance by which the shaft portion33of the connection member30is inserted into the engaging hole29of the cutting head body20is determined, and the shaft portion33is thereby prevented from being inserted into the engaging hole29while exceeding the inserted distance.

In addition, since the rear-end face28aand the contact face32aare flat faces orthogonal to the center line O, the center line O of the cutting head body20is parallel to the center line O of the connection member30.

Subsequently, the press member50(rod member) is inserted into the through hole34from the rear-end of the connection member30.

The press member50is made of a material harder than the connection member30and is formed in the shape of a rod.

The press member50includes a front-end52, the above-described large-diameter portion50a, and the above-described small-diameter portion50b.

An external diameter53aof the large-diameter portion50ais greater than an external diameter53bof the small-diameter portion50b.

The difference between the external diameter53aand the external diameter53bis, for example, 20 μm to 200 μm. In addition, the external diameter of the press member50gradually decreases in a direction from the large-diameter portion50ato the small-diameter portion50bbetween the large-diameter portion50aand the small-diameter portion50b.

The external diameter53aof the large-diameter portion50aof the press member50is slightly greater than the internal diameter35aof the small-diameter hole34aformed inside of the shaft portion33.

In addition, the front-end52of the press member50is tapered in which the diameter of the front-end52gradually decreases in a direction from a rear-end side of the large-diameter portion50atoward the front-end52.

By means of this structure, when the press member50is inserted into the through hole34, it is possible to easily coincide a position of the press member50with a position of the through hole34(alignment).

When the press member50is inserted into the through hole34, since the diameter of the press member50is greater than that of the small-diameter hole34aof the through hole34, it is necessary to apply a load F for the press member50toward the front-end side and press the press member50into the through hole34.

The connection member30is made of stainless steel that is a plastically-deformable material. Therefore, when the press member50is pressed into the through hole34in the above-described manner, the connection member30is plastically-deformed such that the internal diameter of the through hole34(the internal diameter35aof the small-diameter hole34a) of the shaft portion33and the external diameter33cof the outer periphery33aincrease.

For this reason, as shown inFIG. 3, a protuberance portion33bis formed so as to protrude and enter into the toroidal groove60formed on the inner-peripheral face29aof the engaging hole29at a portion of the outer periphery33aof the shaft portion33.

In addition, in the entire area between the inner-peripheral face29aand the outer periphery33a, the outer periphery33aof the shaft portion33is in contact with the inner-peripheral face29aof the engaging hole29and the outer periphery33athereby evenly and uniformly presses the inner-peripheral face29a.

Therefore, the protuberance portion33bof the outer periphery33aof the shaft portion33is fitted into the toroidal groove60.

In addition, the outer periphery33ais attached firmly to the inner-peripheral face29aof the engaging hole29.

In this way, the outer periphery33aof the shaft portion33is engaged with the inner-peripheral face29aof the engaging hole29and the cutting head body20is connected with (coupled to) the connection member30.

Specifically, the toroidal groove60has a wall section60afacing the front-end side toward the center line O, and a wall section60bfacing the rear-end toward the center line O.

By means of this structure, as shown inFIG. 3, when the outer periphery33aof the shaft portion33is fitted into the toroidal groove60, the cutting head body20is prevented from being moved relative to the connection member30along the center line O.

That is, the moving the cutting head body20relative to the connection member30toward the center line O is prevented, and both thereof are in an integrated manner.

After the shaft portion33is attached firmly to the engaging hole29in the above-described manner, the press member50is removed from the through hole34.

In addition, the shaft portion33is plastically-deformed while exceeding an elastic region, and a restorative force for returning to a former shape is not generated in the shaft portion33. Therefore, even if the press member50is removed, a state where the shaft portion33is attached firmly to the engaging hole29is maintained.

In addition, when the press member50is pressed into the small-diameter hole34aof the through hole34, the internal diameter35aof the small-diameter hole34aincreases depending on the external diameter53aof the large-diameter portion50a; however, there is a case where a restorative force is generated such that the internal diameter35aof the small-diameter hole34ais restored to an original internal diameter.

In this case, a part of the small-diameter hole34ais attached firmly to only the large-diameter portion50a, and a frictional force is generated at the position at which the small-diameter hole34ais attached to the large-diameter portion50a.

Specifically, as described above, the press member50is constituted of the large-diameter portion50aand the small-diameter portion50b. The small-diameter portion50bhas the external diameter53bthat is less than the diameter of the large-diameter portion50a.

Thus, when the press member50is removed from the through hole34, the small-diameter portion50bis not in contact with the small-diameter hole34a.

Consequently, a frictional force is not generated between the small-diameter hole34aand the small-diameter portion50b.

In addition, even if the small-diameter portion50bis in contact with the small-diameter hole34aand a frictional force is generated between the small-diameter hole34aand the small-diameter portion50b, the frictional force is much smaller than the frictional force generated between the small-diameter hole34aand the large-diameter portion50a.

Therefore, when the press member50is removed from the through hole34, a large amount of force is not necessary. Practically, it is possible to remove the press member50from the through hole34by applying the force greater than the frictional force generated between the small-diameter hole34aand the large-diameter portion50a.

By removing the press member50from the through hole34in the above-described manner, the through hole34serves as a flow passage in which coolant flows, the coolant is used in a machining process.

The external diameter53aof the large-diameter portion50ain the press member50and the internal diameter35aof the small-diameter hole34ain the shaft portion33are adequately determined so that the shaft portion33is attached firmly to the engaging hole29.

If, for example, the external diameter53aof the large-diameter portion50aexceeds a predetermined diameter, the external diameter33cof the shaft portion33increases more than necessary, and there is a concern that the cutting head body20is cracked.

If, for example, the external diameter53aof the large-diameter portion50ais less than a predetermined diameter, it is not possible to adequately attach the inner-peripheral face29aof the engaging hole29to the external diameter33cof the shaft portion33, and there is a concern that the connection member30is removed from the cutting head body20.

For this reason, the external diameter53aof the large-diameter portion50aand the internal diameter35aof the small-diameter hole34aare determined so as to prevent the cutting head body20from being cracked and so that the outer periphery33aof the shaft portion33can be adequately attached to the inner-peripheral face29aof the engaging hole29.

Furthermore, as described above, the internal diameter29bof the inner-peripheral face29aand the external diameter33cof the outer periphery33aare determined depending on an amount of torque that is applied to the exchangeable cutting head2; however, it is necessary to attach the connection member30to the engaging hole29in order to sufficiently transmit a torque from the connection member30to the cutting head body20.

Therefore, in terms of the torque, the external diameter53aof the large-diameter portion50ain the press member50and the internal diameter35aof the small-diameter hole34ain the shaft portion33are adequately determined so that the shaft portion33is attached to the engaging hole29.

Subsequently, a method for attaching the exchangeable cutting head2in which the cutting head body20is connected with the connection member30in the above-described manner, to the tool body10will be described.

Firstly, the mounting portion28of the cutting head body20and the head screw section31of the connection member30are inserted into the mounting hole12of the tool body10.

The head screw section31is screwed into the mounting screw section14formed in the mounting hole12, and the cutting head body20is rotated around the center line O and screwed thereinto by use of a wrench that is engaged with the parallel faces26aof the wrench engagement section26of the cutting head body20.

In this way, substantially all of the taper surface28bof the mounting portion28of the cutting head body20presses substantially all of the inner-peripheral face of the tapered hole13of the mounting hole12, the center line O of the cutting head body20coincides with the center line O of the tool body10, and a centering is thereby performed. Thus, the exchangeable cutting head2is removably attached to and fixed to the tool body10.

In addition, the cutting head body20is further screwed into the mounting hole12in the above-described manner, high pressure is generated between the taper surface28band the tapered hole13caused by a wedge effect in that the taper surface28bof the mounting portion28of the cutting head body20fitted onto the tapered hole13of the mounting hole12so as to form a tapered structure.

A high friction resistance is generated caused by the pressure, and it is thereby possible to tightly combine the cutting head body20with the tool body10in an integrated manner.

In addition, this structure avoids all of the tightening torque that is generated between the cutting head body20and the mounting portion28caused by the friction resistance to be applied to the head screw section31and the mounting screw section14.

For this reason, an excessive axial tension is prevented from being generated between the head screw section31and the mounting screw section14, it is possible to prevent the head screw section31and the mounting screw section14from being fractured, and prevent the connection member30from being removed from the cutting head body20.

In addition, in a state where the exchangeable cutting head2is attached to the tool body10, an axial tension applied to the head screw section31and the mounting screw section14is relieved.

Therefore, even in a case where the cutting head body20is not connected with the connection member30tighter than necessary, the connection member30is not removed from the cutting head body20.

Thus, in a state where the exchangeable cutting head2is removed from the tool body10, it is possible to easily separate the connection member30from the cutting head body20.

Here, in the connection structure constituted of the above-described cutting head body20and connection member30, it is possible to easily separate the connection member30from the cutting head body20by use of a connection release jig70, for example, shown inFIG. 6.

The connection release jig70is provided with a jig body71, a slide member72, a bolt member73, a screw-nut member74, a pair of support sections75and75, and a pair of arm sections76and76.

The jig body71has a cylinder portion extending along the center line O and a bottom portion connected to the cylinder portion.

An opening portion is formed at a front-end face71aof the cylinder portion.

A rear-end of the connection structure constituted of the cutting head body20and the connection member30is inserted into the opening portion.

When the cutting head body20and the connection member30are inserted into the opening portion, the front-end face71aof the jig body71is in contact with the support face26bof the wrench engagement section26(now shown inFIG. 6) of the cutting head body20.

In this way, in a state where the mounting portion28and the head screw section31in the connection structure constituted of the cutting head body20and the connection member30is only inserted into the inside of the jig body71, and the connection structure is supported by the jig body71.

In addition, a pair of notched holes71bis formed at the cylinder portion of the jig body71and is arranged so as to be opposed to each other with the center line O interposed therebetween.

The notched holes71bare formed in parallel to the center line O so as to penetrate an outer-peripheral face of the cylinder portion.

The slide member72is a planer member inserted into the pair of the notched holes71bof the above-described jig body71and can slide along the direction of the center line O relative to the jig body71in a region in which the above-described notched holes71bare formed.

In addition, a female screw mounting hole72ais formed at the center of the slide member72along the direction of the center line O.

In a state where the cutting head body20and the connection member30are supported by the jig body71, the head screw section31of the connection member30is screwed into the female screw mounting hole72aof the slide member72.

Because of this, the slide member72is fixed to the connection member30toward the center line O in an integrated manner.

The bolt member73is formed as a rod shape and extends along the direction of the center line O.

A male screw is formed at an outer-peripheral face of the bolt member73.

A front-end of the bolt member73is in contact with a rear-end of the above-described jig body71.

In addition, the bolt member73can rotate relative to the jig body71.

In addition, a bolt rotation section73ais provided at a rear-end side of the bolt member73. The bolt rotation section73ais engaged with a wrench or the like.

The screw-nut member74is screwed with the above-described bolt member73.

When the screw-nut member74rotates relative to the bolt member73, the screw-nut member74moves relative to the bolt member73toward the center line O.

The pair of support sections75and75extending in a direction orthogonal to the center line O is provided at an outer-peripheral face of the screw-nut member74.

The support sections75and75are symmetrically provided relative to the center line O.

Consequently, the arm sections76and76are provided at the support sections75and75, respectively. The arm sections76and76extend in parallel to the center line O toward the front-end side.

A front-end of the arm sections76and76is curved in a radial-inner direction around the center line O, and is connected with the slide member72so as to be engaged with a face of the slide member72that faces toward the front-end side.

When removing the connection member30from the cutting head body20by use of the foregoing connection release jig70, the bolt rotation section73ais rotated around the center line O by use of a wrench or the like, and the screw-nut member74is moved relative to bolt member73in a direction toward the rear-end side.

In this way, the slide member72that is connected with the screw-nut member74with the support sections75and75and the arm sections76and76interposed therebetween is slid toward the rear-end side relative to the jig body71.

The cutting head body20is supported by the jig body71, and movement of the cutting head body20in the direction of the center line O is limited.

For this reason, the connection member30that is screwed with the slide member72is only pulled in the direction of the center line O toward the rear-end side.

That is, in a state where the cutting head body20is fixed, the connection member30is pulled away from the cutting head body20.

Therefore, contrary to the structure in which the protuberance portion33bis fitted into the toroidal groove60caused by plastic-deformation of the shaft portion33, and contrary to the adhesive force by which the shaft portion33is attached firmly to the engaging hole29, the connection member30is removed from the cutting head body20. Thus, it is possible to easily separate the connection member30from the cutting head body20.

The cutting tool1including the above-described structure rotates around the center line O in the tool rotation direction T in a state where the tool body10is attached to a machine tool.

Consequently, a work material is machined by the outer-peripheral cutting edge23A and the cutting edge23B of the cutting portion21. A chip generated in the machining process is ejected by the flutes22from the tip to the rear-end side of the cutting portion21.

In addition, the coolant is supplied to the coolant supply hole16of the tool body10, and the coolant is ejected via the through hole34formed in the connection member30and the coolant hole (not shown) provided at the cutting head body20in the machining process.

In the cutting tool1of the embodiment, an individual cutting head body20and connection member30are employed, and a structure in which they are detachably connected with each other is adopted.

Therefore, it is possible for a material of the cutting head body20to be different from a material of the connection member30.

That is, the cutting head body20having the cutting portion21used for machining a work material can be formed of a hard material such as cemented carbide, cermet, or ceramic, and the connection member30can be formed of a plastically-deformable material having a high degree of toughness such as stainless steel.

Therefore, it is possible to easily form the head screw section31by a machining process at a low cost while maintaining a high level of sharpness or durability in the cutting portion21of the cutting head body. Furthermore, it is possible to solve a problem in that a screw of the head screw section31is easily cracked. That is, an amount of abrasion in the cutting portion21is reduced, and it is possible to maintain a high level of sharpness or durability in the cutting portion21.

In addition, the connection structure constituted of the cutting head body20and the connection member30is realized by pressing the press member50into the through hole34of the connection member30in a state where the shaft portion33of the connection member30is inserted into the engaging hole29of the cutting head body20.

By means of this structure, it is possible to simply connect the connection member30with the cutting head body20.

Furthermore, when the connection member30is connected with the cutting head body20, the shaft portion33of the connection member30is plastically-deformed so that the diameter of the shaft portion33increases, and the protuberance portion33bis formed on the inner-peripheral face29aof the engaging hole29so as to protrude from the outer periphery33aof the shaft portion33and to fit into the toroidal groove60.

Therefore, it is possible to easily connect the connection member30with the cutting head body20.

At this time, since the outer periphery33aof the shaft portion33is attached firmly to the inner-peripheral face29aof the engaging hole29, it is possible to reliably connect the cutting head body20with the connection member30in an integrated manner.

Furthermore, it is possible to easily and reliably connect the cutting head body20with the connection member30, by a simple structure in which the engaging hole29and the toroidal groove60are formed at the cutting head body20and in which the shaft portion33and the through hole34are formed at the connection member30.

Consequently, when the cutting head body20and the connection member30are manufactured, it is not necessary to perform a complicated machining process, and it is possible to reduce the cost of manufacturing.

In addition, since the wall section60afacing toward the front-end side in the direction of the center line O and the wall section60bfacing toward the rear-end in the direction of the center line O are formed on the toroidal groove60formed on the inner-peripheral face29aof the engaging hole29, it is possible to prevent the cutting head body20from being moved toward the center line O in relative to the connection member30.

Therefore, it is possible to reliably connect the cutting head body20with the connection member30.

Furthermore, when the head screw section31of the connection member30is screwed into the mounting screw section14of the mounting hole12, the taper surface28bof the mounting portion28of the cutting head body20is evenly and uniformly pressed onto the inner-peripheral face of the tapered hole13of the mounting hole12, and they are thereby fitted onto each other so as to form a tapered structure.

Because of this, it is possible to further tightly attach the cutting head body20to the tool body10, perfectly coincide the center line O of the cutting head body20with the center line O of the tool body10, and perform a centering thereof.

In addition, a friction resistance is generated by a wedge effect in that the taper surface28bof the mounting portion28of the cutting head body20is fitted onto the tapered hole13of the mounting hole12so as to form a tapered structure.

By the friction resistance, it is possible to tightly combine the cutting head body20with the tool body10in an integrated manner. Since the friction resistance is generated, all of the tightening torque generated between the cutting head body20and the mounting portion28is avoided from being applied to the head screw section31and the mounting screw section14.

For this reason, it is possible to prevent the head screw section31and the mounting screw section14from being fractured, and prevent the connection member30from being removed from the cutting head body20.

In addition, since a axial tension applied to the head screw section31and the mounting screw section14in the above-described manner is relieved, it is not necessary to connect the cutting head body20with the connection member30tighter than necessary.

Because of this, it is possible to easily separate the cutting head body20from the connection member30.

In addition, the through hole34is formed at the connection member30, and the coolant hole (not shown) is formed at he cutting head body20. The coolant hole is communicated with the through hole34and the flutes22.

Consequently, it is possible to eject the coolant that is supplied to the cutting portion21via the coolant supply hole16of the tool body10from the cutting portion21, lubricity is improved in a machining process, heat caused by a machining process is removed, and it is thereby possible to improve a precision in a machining process. In addition, when the cutting head body20and the connection member30are attached to the tool body10, it is possible to easily and tightly attach the exchangeable cutting head2to the tool body10by screwing and rotating a wrench around the center line O in a state where the wrench is engaged with the parallel faces26aof the wrench engagement section26formed at the cutting head body20.

In addition, it is possible to easily separate the cutting head body20from the connection member30via the above-described connection release jig70.

Therefore, even if, for example, the cutting portion21of the cutting head body20cannot be used due to abrasion, it is possible to retrieve only the cutting head body20made of cemented carbide, cermet, ceramic or the like as a resource in which impurities are not mixed, separately from the other material. Therefore, it is possible to realize recycling such that parts are re-formed.

In addition, in a state where the connection structure constituted of the cutting head body20and the connection member30are attached to the tool body10, the through hole34of the connection member is positioned at the inside of the mounting portion28of the cutting head body20. Therefore, a hollow portion is formed inside of the mounting portion28.

Therefore, when the taper surface28bof the mounting portion28presses onto the tapered hole13of the mounting hole12, since the taper surface28bis attached firmly to the tapered hole13in a state where the diameter of the mounting portion28slightly decreases, it is possible to comfortably and reliably fit the tapered hole13onto the mounting portion28so as to form a tapered structure.

As a result, it is possible to reliably attach the cutting head body20to the tool body10.

Furthermore, for example, even if the support face26bof the wrench engagement section26is in contact with the front-end face11of the tool body10in addition to the structure in which the tapered hole13is in contact with the taper surface28b, that is, even if the cutting head body20is restrained by the two faces, since the taper surface28bis attached firmly to the tapered hole13while the diameter of the mounting portion28slightly decreases in the above-described manner, an adhesion between the taper surface28band the tapered hole13is ensured, and it is possible to improve the attachment strength.

In this case, a frictional force is generated in a first structure in which the taper surface28bis in contact with the tapered hole13, and a frictional force is generated in a second structure in which the support face26bis in contact with the front-end face11. Therefore, it is possible to improve the attachment strength.

Moreover, during a machining process by use of the cutting tool1, even if the diameter of the tapered hole13increases because of a centrifugal force caused by a high speed rotation, the diameter of the taper surface28bof the mounting portion28of the cutting head body20at the same time. Therefore, the strength of the attachment between the mounting portion28and the tapered hole13is not reduced, and it is possible to reliably fit the two taper surfaces together.

Thus, it is possible to perform a machining process in a state where the cutting head body20is reliably attached to the tool body10.

Second Embodiment

Next, a cutting tool80having an exchangeable cutting head of a second embodiment of the present invention will be described with reference toFIGS. 7 and 8.

InFIGS. 7 and 8, identical symbols are used for the elements which are identical to those of the cutting tool1of the first embodiment, and the explanations thereof are omitted or simplified.

In the cutting tool80of the second embodiment, a cutting head body81has a wrench engagement section86(rotation section).

A wrench engagement section86has an outer-peripheral face formed as a center circular cylinder around the center line O.

A portion of the outer-peripheral face is machined in a direction parallel to the center line O and in a direction from the outer-peripheral face to the center line O by a predetermined depth.

Consequently, the outer-peripheral face of the wrench engagement section86has two pairs of parallel faces86a(notched face).

In the circumferential direction, a curved surface that is a part of the outer-peripheral face remains between the parallel faces86aadjacent to each other.

Consequently, the wrench engagement section86is formed as a chamfered regular tetragon. Specifically, in the chamfered regular tetragon, each of angle portions of the regular tetragon in a cross section orthogonal to the center line O is chamfered by a circular arc. The center of the circular arc is the center line O.

In addition, at the rear-end side of the wrench engagement section86, that is, at the rear-end side of the parallel faces86a, an outer-peripheral face formed as a circular cylinder remains so as to be aligned with the wrench engagement section86. Therefore, a flange87is formed so as to protrude in a radial-outer direction from the center line O.

InFIGS. 7 and 8, a configuration of the flange87viewed from a cross-sectional face orthogonal to the center line O is substantially a circular form. The present invention is not limited to being circular. The flange87may be, for example, a polygon or an ellipse.

In addition, as a configuration of the flange87, not only a configuration in which the flange87protrudes in a circumferential direction of the entire area from the center axis O, but also a configuration in which the flange87protrudes from one of a plurality of parallel faces86amay be formed.

Furthermore, in the flange87, a face facing the front-end side in the direction of the center line O is a flat flange face87a(first flange face) that is substantially orthogonal to an axis line O. In addition, a face facing the rear-end side in the direction of the center line O is a flat flange face87b(second flange face) that is substantially orthogonal to an axis line O.

The flange faces87aand87bare perpendicularly intersected with each parallel face86aof the wrench engagement section86.

In the foregoing cutting tool80of the second embodiment, for example, by disposing the flange faces87aand87bof the flange87so as to be in contact with a jig or the like, it is thereby possible to tightly fix the cutting head body81in the direction of the center line O.

In addition, it is possible to further tightly and stably fix the cutting head body81to the head fixing jig90by employing a structure in which the above-described jig is in contact with the flange faces87aand87band the parallel faces86aof the wrench engagement section86is in contact with the above-described jig.

Therefore, it is possible to easily connect the cutting head body81with the connection member30and easily separate the connection member30from the cutting head body81.

In addition, when the cutting portion is re-polished or coated by use of a PVD method, it is possible to reliably support the cutting head body81.

In addition, in the cutting tool80of the second embodiment, by employing the above-described connection release jig70and a head fixing jig90shown inFIG. 9, it is possible to easily separate a connection structure constituted of the cutting head body81and the connection member30into two components.

As specifically shown inFIGS. 10A and 10B, the head fixing jig90includes a circular cylinder portion91and a cap section93that is provided at one end of the circular cylinder portion91and is connected with the circular cylinder portion91in an integrated manner.

An external form of the circular cylinder portion91is substantially a circular cylinder whose center is an axis line L.

A cutting portion insert portion92that is formed as a U-shape a is formed at a part of circular cylinder portion91in a circumferential direction.

The cutting portion insert portion92has a predetermined width in the circumferential direction.

The cutting portion insert portion92is formed by machining from one end of the circular cylinder portion91toward the other end thereof.

The size of the cutting portion insert portion92is determined such that the cutting portion21of the cutting head body81can be inserted into the circular cylinder portion91from the outside toward the inside in a radial direction of the circular cylinder portion91through the cutting portion insert portion92.

A configuration of the cap section93is substantially a circular disk having the same external diameter as that of the circular cylinder portion91.

An insert slit94that is U-shaped from an outer-peripheral side toward the inside thereof in a radial direction is provided at the cap section93.

The insert slit94includes slit side edges94afacing each other in parallel.

The width of the insert slit94, that is, a distance between the slit side edges94ais substantially the same distance between the pair of the parallel faces86aof the wrench engagement section86in the cutting head body81.

In addition, a slit rear-end94bthat is positioned at a rear-end of the insert slit94is orthogonal to each slit side edge94a.

The cap section93is provided at one end of the circular cylinder portion91and formed so as to be integrated with the circular cylinder portion91in one body in a state where a position of the insert slit94in a circumferential direction thereof is coincided with a position of the cutting portion insert portion92of the circular cylinder portion91.

The foregoing head fixing jig90supports the cutting head body81of the exchangeable cutting head2which is attached to the connection release jig70in a manner similar to the first embodiment. In the connection release jig70of the second embodiment shown inFIG. 9, a flange support section71cis provided at the front-end face71aof the jig body71.

That is, the cutting portion21of the cutting head body81is inserted into the inside of the circular cylinder portion91through the cutting portion insert portion92from the radial-outer direction with respect to the head fixing jig90.

In addition, the wrench engagement section86of the cutting head body81is inserted into the insert slit94of the cap section93.

At this time, the center line O of the exchangeable cutting head2is coincided with the axis line L of the head fixing jig90, and the flange face87aof the flange87is in contact with one end of the cap section93. The flange face87bis in contact with the flange support section71c.

Furthermore, each of three parallel faces86aof the wrench engagement section86of the cutting head body81is in contact with the pair of the slit side edge94aand the slit rear-end94b.

In this way, a position of the cutting head body81can be coincided with the direction of the center axis O (alignment), and the cutting head body81can be stably and tightly fixed.

Consequently, in the state described above, when the bolt rotation section73ais rotated around the center line O by use of a tool such as a wrench, the flange face87bis attached firmly to the flange support section71c, a pressure is applied to the flange support section71c, and the connection member30is pulled away from the cutting head body81. Therefore, it is possible to pull the connection member30away from the cutting head body81in the center line O in a state where the cutting head body81is stably fixed.

As a result, it is possible to remove the connection member30from the cutting head body81and easily separate the connection member30from the cutting head body81.

In the above-described manner in the second embodiment, the flange face87aof the flange87of the cutting head body81is in contact with the cap section93of the head fixing jig90, the flange face87bis attached firmly to the flange support section71c; furthermore, the wrench engagement section86is locked inside of the insert slit94of the cap section93.

For this reason, it is possible to stably and easily separate the connection member30from the cutting head body81by use of the connection release jig70.

In addition, since the cutting head body81from which the connection member30has been separated is stabilized to the head fixing jig90, the cutting head body81is prevented from dropping off or the like, and it is thereby possible to safely perform a separation operation.

Next, a method for connecting the connection member30with the cutting head body81by use of the above-described connection release jig70, head fixing jig90, and press member50will be described with referenceFIG. 11.

Firstly, as shown inFIG. 11, the cutting head body81fixed to the above-described head fixing jig90. A structure in which the cutting head body81is fixed to the head fixing jig90is the same structure as shown inFIG. 9.

InFIG. 11, the center line O of the cutting head body81coincides with the axis line L of the head fixing jig90, and the flange face87aof the flange87is in contact with one end of the cap section93.

Next, as shown inFIG. 11, the connection member30is inserted into the cutting head body81. Specifically, as shown inFIG. 5, the shaft portion33of the connection member30is inserted into the engaging hole29of the cutting head body81.

Next, the press member50is inserted into the through hole34from the rear-end of the connection member30, the press member50is pressed into the small-diameter hole34a, and the internal diameter35aof the small-diameter hole34athereby increases. At this time, the center line O of the exchangeable cutting head2is coincided with the axis line L of the head fixing jig90, and the flange face87aof the flange87is in contact with one end of the cap section93.

Furthermore, a pressure is applied to one end of the cap section93while inserting the press member50, and the connection member30is pressed into the cutting head body81.

Consequently, it is possible to press the connection member30into the cutting head body81in a state where the cutting head body81is stably fixed to the head fixing jig90.

As described above, the flange87is in contact with the head fixing jig90by use of the head fixing jig90, and it is possible to fix the cutting head body81to the head fixing jig90.

For this reason, even if the cutting portion21(cutting edge) including the outer-peripheral cutting edge23A and the cutting edge23B has been formed on the cutting head body81, it is possible to connect the connection member30with the cutting head body81without damaging the cutting portion21.

In addition, since the flange87is supported by the head fixing jig90, the cutting head body81is prevented from dropping off, and it is possible to separate the connection member30from the cutting head body81.

Generically, an operation of connecting the connection member with the cutting head body is performed before forming the cutting edge.

That is, in a state where the connection member is connected with the cutting head body, the cutting edge is formed by use of a high temperature process including a coating process.

In this case, the connection structure constituted of the cutting head body and the connection member is subjected to a high temperature atmosphere, the connection member is deformed along with temperature change, and there is a concern that a degree of precision of the head screw section is degraded.

In contrast, in this embodiment, the cutting portion21(cutting edge) including the outer-peripheral cutting edge23A and the cutting edge23B is preliminarily formed on the cutting head body81; thereafter, the cutting head body81is fixed to the head fixing jig90, the cutting head body81is connected with the connection member30. In this case, the connection structure constituted of the cutting head body81and the connection member30is not subjected to a high temperature atmosphere such as a coating process.

That is, it is possible to ensure the degree of precision in the head screw section without deformation of the connection member.

Third Embodiment

Next, a cutting tool100having an exchangeable cutting head of a third embodiment of the present invention will be described with reference toFIGS. 12 and 13.

InFIGS. 12 and 13, identical symbols are used for the elements which are identical to those of the cutting tool1of the first embodiment, and the explanations thereof are omitted or simplified.

In the cutting tool100of the third embodiment, the engaging hole29that opens at the rear-end face28aof the mounting portion28of the cutting head body110is not only formed at the inside of the mounting portion28but also formed so as to further extend toward the front-end side and reach the inside of the cutting portion21.

As a result, since the weight of the cutting head body110can be reduced, vibration is prevented from being generated at the cutting portion21during a machining process, and it is thereby possible to perform a machining process with a high level of precision.

As described above, the cutting tool1,80, and100of the embodiment of the present invention are described in detail. The technical scope of the present invention is not limited to the above embodiments, but various modifications may be made without departing from the scope of the present invention.

In the first embodiment, the structure including the toroidal groove60having the wall section60afacing the front-end side toward the center line O and the wall section60bfacing the rear-end toward the center line O is described; however, at least the wall section60afacing the front-end side toward the center line O may be simply formed.

By means of this structure, in a case in which the protuberance portion33bis formed at the connection member30in a state where the cutting head body20is coupled to the connection member30, movement of the cutting head body20in relative to the connection member30so as to be away from each other in the direction of the center line O is prevented.

In the direction (direction of the center line O) in which the connection member30is inserted into the cutting head body20, since the rear-end face28aof the mounting portion28of the cutting head body20is in contact with the contact face32aof the flange section32of the connection member30, the inserted distance by which the connection member30is inserted into the cutting head body20is determined.

Because of this, even if the wall section60bfacing the rear-end toward the center line O is not formed, a problem does not occur.

In addition, a linear groove extending along the direction of the center line O may be formed at the inner-peripheral face29ainstead of the foregoing toroidal groove60.

In this case, the linear groove has a wall section facing in a circumferential direction around the center line O.

By means of this structure, when a protuberance portion33bthat is fitted into the linear groove is formed at the connection member30in a state where the cutting head body20is coupled to the connection member30, it is possible to reliably prevent the cutting head body20from being rotated around the center line O relative to the connection member30.

In addition, both of the foregoing linear groove and the above-described toroidal groove60may be formed. In addition, the foregoing toroidal groove60or the linear groove may be formed at a plurality of portions.

Furthermore, a groove formed as a spiral (helix) may be formed around an axis line O. In addition, at least two spiral grooves (helix groove) may be formed around an axis line O. In this case, twist directions of the two grooves toward the axis line O are opposite to each other.

In addition, a recessed portion formed at the inner-peripheral face29ais not limited to grooves, and a structure in which a plurality of recessed portions is formed as dots may be employed.

As long as a structure in which the inner-peripheral face29aof the cutting head body20is engaged with the shaft portion33of the connection member30, the present invention is not limited to the above-described structure, and a recessed portion having the other configuration may be formed at the inner-peripheral face29a.

In addition, in the above-described embodiments, a structure in which the recessed portion is formed at the inner-peripheral face29aof the cutting head body20is described; however a protuberance portion may be provided at the shaft portion33of the connection member30, and the shaft portion33may be fixed to the inner-peripheral face29a.

However, in this case, the shaft portion33is made of stainless steel that is a plastically-deformable material, and the cutting head body20is made of a hard material harder than stainless steel. Therefore, when the press member50is pressed into the through hole34in the above-described manner, the protuberance portion provided at the shaft portion33is compressed and plastically-deformed, and the inner-peripheral face29aof the cutting head body20is thereby in contact with the shaft portion33of the connection member30.

In the case in which the protuberance portion is provided at the shaft portion33in the above-described manner, there is a concern that a contact area between the inner-peripheral face29aand the shaft portion33can not sufficiently-obtained.

In addition, a recessed portion may be provided at the shaft portion33of the connection member30, and the shaft portion33may be locked to the inner-peripheral face29a.

However, in this case, since the inner-peripheral face29ais not engaged with the recessed portion of the shaft portion33, there is a concern that the connection member30is easily removed from the cutting head body20.

Therefore, as a structure in which the connection member30is reliably fixed to the cutting head body20, the structure in which the recessed portion is formed at the inner-peripheral face29aof the cutting head body20as described above is preferably employed.

In addition, in the above-described embodiments, in the entire area between the inner-peripheral face29aand the outer periphery33a, the structure in which the outer periphery33aof the shaft portion33is in contact with the inner-peripheral face29aof the engaging hole29is described; however, a structure in which the outer periphery33ais in contact with the inner-peripheral face29ain a part of a region between the inner-peripheral face29aand the outer periphery33amay be employed.

That is, because of the above-described plastic-deformation in the inside of the engaging hole29, a structure including a region in which the diameter of a outer periphery33ais large and a non-plastically-deformed region may be employed.

In this case, an area in which the outer periphery33ais in contact with inner-peripheral face29ais set so as to sufficiently-obtain a connection strength in the connection structure constituted of the cutting head body20and the connection member30.

In the structure, when the connection member30is separated from the cutting head body as shown inFIG. 6orFIG. 9, it is possible to relatively reduce a force for removing the connection member30from the cutting head body, and easily perform a separation step.

In addition, as a position at which the recessed portion is formed, recessed portions may be formed in the inside of the engaging hole29by a constant distance, recessed portion may be partially formed inside of the engaging hole29.

The recessed portion (toroidal groove60) may be formed, for example, at a region indicated by reference numeral85inFIG. 2, that is, at a position adjacent to an opening portion of the engaging hole29(position close to the rear-end face28a).

In this case, it is preferable that the press member50be inserted into the through hole34so as to cause the a region indicated by reference numeral95inFIG. 4, namely, positions adjacent to the flange section32to be plastically-deformed.

In this case, it is not necessary to insert the press member50into the inside of the through hole34so that the press member50is positioned at the entire area of the through hole34.

A depth at which the press member50is inserted into the through hole34is determined so as to correspond to a position at which the recessed portion is formed.

In this manner, the outer periphery33ais intensively plastically-deformed at a region85of the engaging hole29on which the recessed portion is formed, the protuberance portion33bis formed, and it is thereby possible to tightly engage the cutting head body with the connection member30.

That is, since the outer periphery33ais partially plastically-deformed in the vicinity of an inlet port of the engaging hole29in a state where the outer periphery33ais not plastically-deformed in the entire area between the inner-peripheral face29aand the outer periphery33a, a connection strength can be sufficiently obtained.

In addition, since the outer periphery33ais not plastically-deformed in the entire between the inner-peripheral face29aand the outer periphery33a, it is possible to relatively reduce a force for removing the connection member30from the cutting head body when the connection member30is separated from the cutting head body. As a result, it is possible to easily perform a separation step.

In addition, a recessed portion that is provided with at least one of the wall section facing the front-end side toward the center line O and the wall section facing toward the circumferential direction around the center line O may be formed at the inner-peripheral face29aof the engaging hole29in addition to the above-described toroidal groove60or the linear groove.

Also, in the foregoing structure, part of the outer periphery33aof the shaft portion33of the connection member30protrudes toward the recessed portion and is fitted into the recessed portion. It is possible to prevent the connection member30from being separated from the cutting head body20toward the center line O and from being moved relative to the cutting head body20. In addition, it is possible to prevent the connection member30from being rotated relative to the cutting head body20around the center line O.

In addition, instead of the above-described toroidal groove60, an uneven face (recessed portion) in which the surface roughness in maximum height Rz of the uneven face is 5 μm to 200 μm may be formed on the inner-peripheral face29aof the engaging hole29.

A steps for manufacturing the cutting head body20includes molding a molding process and a sinter bonding process.

The molding process includes a first step (first molding step) in which a fine powder material is solidified and the cutting head structure is obtained, a step for machining the cutting head structure, and a second step (second molding step) in which a face having a desired surface roughness is formed on the cutting head structure.

A condition of the uneven face is adjusted by controlling a forming condition in the second step. When the uneven face is formed in the above-described manner, the above-described toroidal groove60, the linear groove, or the recessed portion may be formed on the inner-peripheral face29aof the engaging hole29. In addition, it is not necessary for the above-described grooves or the recessed portion to be formed on the inner-peripheral face29a.

In the case where the uneven face is formed at the inner-peripheral face29aof the engaging hole29in the above-described manner, when the press member50is pressed into the through hole34of the connection member30in a state where the shaft portion33of the connection member30is inserted into the engaging hole29of the cutting head body20, the outer periphery33aof the shaft portion33of the connection member30is plastically-deformed along the uneven face of the above-described the inner-peripheral face29aof the engaging hole29.

In this way, a frictional force generates between the inner-peripheral face29aof the engaging hole29and the outer periphery33aof the shaft portion33, and the cutting head body20is easily and reliably connected with the connection member30.

In addition, a cobalt-rich region is formed on a surface of the inner-peripheral face29a. In the cobalt-rich region, cobalt that is one of constituent materials of the cutting head body20with large amount is included. The cobalt-rich region is appeared on a surface of the inner-peripheral face29aby heating the cutting head structure in the above-described sinter bonding process. The above-described cobalt-rich region may be a thin film having cobalt as main component and a thickness of 0.5 μm to 5 μm.

In addition, it is possible to easily control a value of the surface roughness in maximum height Rz of the inner-peripheral face29aof the engaging hole29by omitting a polishing treatment after the cutting head body20is molded.

Next, a method for adjusting the maximum height of roughness profile Rz of the inner-peripheral face29awill be specifically described.

Firstly, a cutting head structure is formed in the first molding step.

Subsequently, the inner-peripheral face29ais machined in the second molding step in order to obtain a predetermined degree of surface roughness, and the degree of roughness of the inner-peripheral face29ais thereby adjusted.

After the second molding step, the cutting head structure is heated by performing the sinter bonding process, the cutting head structure is sintered, and the cutting head body20is obtained.

As a result, the degree of roughness of the inner-peripheral face29awhich is finally obtained, that is, the surface roughness in maximum height Rz of the inner-peripheral face29ais 5 μm to 200 μm.

As described above, in the method for manufacturing the cutting head body20, in terms of the degree of roughness (second degree of roughness) of the inner-peripheral face29awhich is finally obtained in the sinter bonding process, the degree of roughness (first degree of roughness) of the inner-peripheral face29ais preliminarily adjusted in the second molding step.

That is, in the second molding step, the cutting head structure is machined so that the surface of the inner-peripheral face29ahas a predetermined degree of roughness (first degree of roughness); thereafter, the cutting head structure obtained in the second molding step is sintered, and the cutting head body20in which the inner-peripheral face29ahaving the second degree of roughness is formed is thereby manufactured.

In this case, a final surface roughness of the inner-peripheral face29ais determined depending on molding conditions in the second molding step and sintering conditions in the sinter bonding process.

In addition, the cutting head body20may be manufactured without machining the surface of the inner-peripheral face29ain the second molding step. In this case, in the cutting head structure, the inner-peripheral face29ahaving the first degree of roughness is obtained in the first molding step. The cutting head structure in which the surface of the inner-peripheral face29ais not machined in the second molding step is sintered. In this case, a final surface roughness of the inner-peripheral face29ais determined depending on the molding conditions of the first molding step and the sintering conditions of the sinter bonding process.

Next, a case where the surface roughness in maximum height Rz of the inner-peripheral face of the engaging hole29was adjusted to 7.0 μm and the surface roughness in maximum height Rz of the outer periphery33aof the shaft portion33of the connection member30was adjusted to 2.0 μm will be described.

After the connection member30was connected with the cutting head body20in a above-described manner, the cutting head body20was broken down, and the connection member30was retrieved. Next, a value of the surface roughness in maximum height Rz of the outer periphery33aof the shaft portion33was measured, and it is confirmed that the surface roughness in maximum height Rz thereof is changed to 5.5 μm.

As a result, it is seen that the outer periphery33aof the shaft portion33of the connection member30was plastically-deformed along the inner-peripheral face of the engaging hole29so as to have the above-described surface roughness in maximum height Rz.

The above-described Rz is the surface roughness in maximum height defined under JIS B 0601:2001 (ISO 4287:1997) and is a measurement result under the evaluation condition in which reference length is 0.8 mm, cut-off value λs is 0.0025 mm, and λc is 0.8 mm.

In addition, in the embodiment, the inner-peripheral face29aof the engaging hole29is formed as a circular cylinder whose center is the center line O; however, the present invention is not limited to being a circular cylinder, the engaging hole29may be formed as a cylinder having a planar wall face parallel to the center line O.

Even if the foregoing structure is employed, when the shaft portion33is plastically-deformed so as to increase the diameter thereof, the outer periphery33aof the shaft portion33is attached firmly to the above-described planar wall face, the outer periphery33ais deformed along the wall face, and a recessed portion is formed at the outer periphery33a.

In this way, a wall section facing toward the circumferential direction is formed in the recessed portion, and the connection member30is thereby prevented from being rotated around the center line O relative to the cutting head body20.

Therefore, it is possible to reliably connect the cutting head body20with the connection member30.

Furthermore, in the above-described embodiment, the structure in which a female screw is provided at the mounting screw section14of the tool body10and a male screw is provided at the head screw section31of the cutting head body20is described; however, the present invention is not limited to this structure.

A structure including, for example, a bolt having a male screw which serves as the mounting screw section14, and a connection member30in which a female screw is provided at the large-diameter hole34bof the through hole34may be adopted.

In this case, the bolt is inserted into a through hole formed at the tool body10, and the female screw provided at the large-diameter hole34bis screwed with the male screw provided at the bolt.

However, in the structure, there is a concern that it is difficult for coolant to supply to the flutes22.

As a result, in a manner similar to the structure of the above-described embodiments, it is desirable that the structure in which a female screw is provided at the mounting screw section14of the tool body10and a male screw is provided at the head screw section31of the connection member30be employed.