JP5750741B2 - Replaceable radius end mill - Google Patents

Description

  The present invention relates to a blade end replaceable radius end mill in which an insert provided with a cutting edge can be detachably mounted on a mounting seat provided at a tip portion of a tool body, particularly, in the finishing and finishing of a work material. The present invention relates to a blade end replaceable radius end mill which has been improved so as to ensure the accuracy of mounting an insert on a seat and which enables high-speed, high-precision cutting.

  When manufacturing various types of dies, it is necessary to perform three-dimensional cutting on a work material that is a material of the dies. Conventionally, a radius end mill or a ball end mill is used as a tool for cutting a mold. The ball end mill has a hemispherical shape when viewed from the side, so it is suitable as a cutting tool for finishing a curved surface at high speed, but the blade near the tip axis (tool rotation axis) of the tool body Since the rotation speed of the part is slow, there is a disadvantage that the cutting of the blade tends to be lost when cutting is performed using the blade near the tool tip axis.

  On the other hand, the radius end mill includes a bottom blade, an outer peripheral blade, and an R-shaped corner R blade formed between the bottom blade and the outer peripheral blade. it can. For this reason, in recent years, a radius end mill has been frequently used in place of a ball end mill as a cutting tool used for finishing and intermediate finishing of a mold having a complicated curved surface.

  In recent years, the dimensions of various molds tend to increase in size. Along with this, cutting tools for cutting molds perform high-speed, high-efficiency, high-precision cutting, and have a long service life. Is required. Under such circumstances, a radius end mill is used as a cutting tool for processing various dies. Also, in order to perform cutting work with high efficiency and high accuracy, a method in which an insert with a cutting edge is detachably attached to a mounting seat formed on the tool body with a clamp screw, etc., rather than a solid type cutting tool. A blade end replaceable radius end mill (blade end replaceable radius end mill) is suitable. The reason for this is that when the cutting edge formed on the insert is worn out and the sharpness is lowered, it can be immediately replaced with a new insert, so that high efficiency and high accuracy of cutting can be maintained and cutting can be performed. This is because the cost for the tool can be reduced.

  Regarding the technology of the blade end replaceable radius end mill, for example, the inventions described in the following Patent Documents 1 to 3 have been proposed.

  Patent Document 1 (Japanese Patent Laid-Open No. 10-156616) proposes an invention for the purpose of providing a throw-away type radius end mill that enables thrusting, drilling, and shouldering. This throw-away type radius end mill is a system in which a plurality of throw-away tips are mounted on a tool body, a round tip is used as a first tip, an arc side surface as a second tip, and a linear side surface connected thereto. This straight side surface is extended to the vicinity of the center axis of the tool body and a chamfering blade is provided at a corner portion located near the center axis.

  Patent Document 2 (Japanese Patent Application Laid-Open No. 2005-319558) proposes an invention relating to a radius end mill for finishing with a blade edge replacement for the purpose of improving the surface roughness of a work material during copying. . This blade end replaceable radius end mill has a structure in which an insert having a cutting edge is mounted on a slit-like insert mounting seat provided at the tip of the tool body, and the shape of the cutting edge of the insert is an arc shape on the outer peripheral side. When the radius of the cutting edge is r1 and the tool diameter is D, 0.31D ≦ r1 ≦ 0.45D and D ≧ 8 mm are set, and the bottom edge is an arcuate inner peripheral edge of radius r2 and the arcuate inner periphery. It is composed of a linear inner peripheral blade connected to the blade and formed up to the tool axis, and r1> r2.

  Patent Document 3 (Japanese Unexamined Patent Application Publication No. 2009-107046) describes that the tool body is shaken even if the insert body itself is attached to the cutting tool and rotated at a high speed while ensuring the strength of the insert body itself and the attachment strength to the insert mounting seat. There has been proposed an invention relating to a cutting insert and an insert detachable cutting tool for the purpose of further improving the processing efficiency without impairing the processing accuracy.

  As shown in FIGS. 8 and 11 of the drawings as a radius end mill, the insert detachable cutting tool described in Patent Document 3 has a cutting edge formed at the tip edge and a mounting hole in the thickness direction. A flat plate-like insert main body is provided, and the insert is inserted into a slit-like insert mounting seat of an insert detachable cutting tool and fixed with a clamp screw. Further, in the insert, a plurality of through portions penetrating the insert body in the thickness direction are provided on the inner side of the sandwiched surface sandwiched by the mounting seat wall surface around the mounting hole provided in the insert body. It is improved by reducing the weight of the insert by forming it open and preventing the tool body from wobbling even when rotated at high speed.

  In addition, in blade-replaceable radius end mills and blade-replaceable ball end mills, inserts that are mounted on the mounting seat and fixed with clamp screws, etc., are prevented from shifting their fixing positions due to cutting loads generated during cutting. In addition, improving the structure of the tip of the tool body so that chips can be discharged well, and the cutting edge formed on the insert in particular when the new insert is mounted on the mounting seat. It is also important to improve the method and means for fixing the insert to the mounting seat so that the length (position) protruding from the tip portion of the insert is always fixed and maintained accurately at a predetermined position.

  As techniques for improving the mechanism for fixing the above-described insert to the mounting seat of the tool body, inventions described in Patent Documents 4 to 6 below have been proposed.

  Patent Document 4 (Japanese Utility Model Laid-Open No. 54-29490) proposes a drilling tool in which the cutting edge can be exchanged by eliminating chippings, preventing damage to the tool, and improving work efficiency. Yes. In the invention described in Patent Document 4, in a drilling tool in which a cutting edge tip is inserted between a pair of opposing holding portions of a holder and is fixed by a fastening bolt penetrating the cutting edge tip, an edge portion of one holding portion Is cut away so as to form an obtuse angle with respect to one side surface of the cutting edge tip in the rotation direction of the holder to form one cutting waste discharging groove, and the edge of the other clamping portion at a symmetrical position is cut. The other side surface of the blade tip is notched so as to form an obtuse angle in the rotation direction of the holder to form the other cutting waste discharging groove, and the clamping bolt is connected to the notched surface of one clamping portion and the other clamping portion. It is disclosed that the structure is inclined so as to be substantially parallel to the notched surface.

  Patent Document 5 (Japanese Patent Laid-Open No. 2001-121339) proposes an invention related to a throwaway end mill having a configuration substantially similar to that of Patent Document 4. In this throwaway end mill, the clamp bolt inserts the chip from a direction inclined by a required angle in the circumferential direction with respect to a position perpendicular to the mounting seat of the chip fitted in the chip fitting groove formed in the holder body. This is an end mill that allows a large chip pocket to be obtained by inserting a hole and screwing it over both chip holding halves.

  Patent Document 6 (Japanese Patent No. 4531981) relates to a boring tool provided with a mechanism for securely clamping a cutting insert inserted into a groove formed in a tip (groove leg) of a holder with a clamp screw. An invention has been proposed. In this clamp mechanism (see FIG. 3 of Patent Document 6), the center axis of the hole for the clamp screw provided in the groove leg portion is inclined with respect to the X direction, and the center axis of the receiving hole provided in the cutting insert is also X The clamp screw has a tapered configuration in which the outer peripheral surface of the shaft part between the head and the screw part at the tip is tapered from the head toward the screw part. Is described. By adopting such a configuration, the cutting insert cooperates in a form like a wedge surface transmission device of a clamp screw and is pressed against the stopper surface, so that there is no vibration generated in the cutting insert during the cutting process, It is described that an excellent clamping action can be achieved.

  In order to extend the life of the cutting edge of the radius end mill, a radius end mill having a hard sintered cutting edge made of cubic boron nitride (CBN) having wear resistance has been proposed. For example, Patent Literature 7 and Patent Literature 8 have been proposed for a radius end mill whose cutting edge is made of a hard sintered body made of cubic boron nitride (CBN).

  Patent Document 7 (Japanese Patent Laid-Open No. 2008-279520) proposes an invention related to a radius end mill for the purpose of preventing the corner R blade from being broken and extending its life. This radius end mill is a radius end mill in which a corner R blade is provided on the outer periphery of the tip end of the end mill main body 2 and is composed of a tip portion of the corner R blade and a bottom blade 4 disposed on the tip side of the corner R blade. The tip blade portion is formed of a cubic boron nitride sintered body, and the length L in the axis O direction of the tip blade portion is configured to be smaller than the radius R of the corner R blade.

  Patent Document 8 (Japanese Patent Application Laid-Open No. 2009-241190) proposes an invention related to a radius end mill whose life is improved by strengthening the boundary between the bottom edge and the radius edge of the CBN radius end mill. This CBN radius end mill has a structure in which a CBN sintered body is joined to the tip of a tool body, and the CBN sintered body is provided with two cutting edges. The cutting blade is composed of a bottom blade, a connecting blade, a 1 / 4-radius blade, and an outer peripheral blade, the rake angle is set to -30 ° to -50 °, and the wedge angle is each part of the cutting blade. A negative land that is constant at the same time is formed on the rake face along the entire area of the cutting edge, and the clearance angle γ0 is smaller than the clearance angle γ1 of the bottom edge between the bottom edge and the radius edge, and 0 The connecting blade 3b that satisfies the condition of 5 ° ≦ γ0 ≦ 2 ° is formed.

Japanese Patent Laid-Open No. 10-156616 JP 2005-319558 A JP 2009-107046 A JP 54-29490 A JP 2001-121339 A Japanese Patent No. 4531981 JP 2008-279520 A JP 2009-241190 A

  The throwaway type radius end mill described in Patent Document 1 is a blade end exchange type radius end mill, but in order to enable thrusting, drilling, or shoulder cutting, a round tip is used as the first tip. Using a tip composed of an arc side surface and a linear side surface connected to this as the second tip, this linear side surface is extended to the vicinity of the central axis of the tool body, and a chamfering blade is provided at a corner portion located near the central axis. It has been configured. However, there is no disclosure of a mechanism for preventing the displacement of the tip with respect to a load acting on these tips during processing.

  The radius end mill for exchangeable cutting edge described in Patent Document 2 is the relationship between the shape of the cutting edge formed on the insert and the tool diameter in order to improve the surface roughness of the work material in the finishing work of the work material. About the improvement of the mechanism for mounting and fixing the insert to the mounting seat in order to prevent the displacement of the insert more reliably due to the processing load acting on the insert during machining Is not disclosed.

  8 and 11 of Patent Document 3, the blade end exchange type radius end mill is provided with a plurality of through portions that penetrate in the thickness direction of the insert around the mounting hole provided in the insert body. By reducing the weight of the tool, the tool body does not wobble even when high-speed cutting is performed. No measures to prevent it are disclosed.

  The drilling tool described in Patent Document 4 is a tool dedicated to drilling that secures a large chip discharge groove by tightening a clamping bolt from the inclined direction to the tool tip to fix the cutting edge tip. It is. Therefore, this drilling tool cannot be used as a tool for performing three-dimensional cutting such as a mold cavity at high speed. Further, Patent Document 4 does not disclose details of the engagement relationship between the insertion hole formed in the cutting edge tip and the outer peripheral surface of the tightening bolt.

  The throwaway end mill described in Patent Document 5 is clamped from a direction inclined by a required angle in the circumferential direction with respect to a position orthogonal to a chip mounting seat fitted in a chip fitting groove formed in the holder body. It is a blade-end-changing type end mill that has a structure that allows bolts to be inserted over both insert-clamping halves by inserting bolts through the insert-insertion hole of the insert, thereby enabling a large chip pocket and improving chip dischargeability. . However, since this throwaway end mill has two cutting edges, it is difficult to apply as a ball end mill for cutting a die at high speed. In order to cut a mold or the like at a high speed, it is desirable that the cutting edge is composed of at least four blades. Further, Patent Document 5 does not disclose details of the engagement relationship between the insertion hole formed in the chip and the outer peripheral surface of the clamp bolt.

  The drilling tool provided with the cutting insert described in Patent Document 6 is a tool dedicated to drilling, and cannot be used as a tool for cutting a mold cavity or the like at high speed. Further, there is no description about a specific engagement relationship between the tapered outer peripheral surface of the clamp screw and the insertion hole provided in the cutting insert in order to prevent the displacement of the cutting insert during processing.

  The radius end mills described in Patent Document 7 and Patent Document 8 are solid type end mills in which the corner R blade formed at the tip portion of the end mill body and the tip blade portion of the bottom blade are composed of a cubic boron nitride sintered body. This is not a blade end replaceable radius end mill. In order to cut a work material such as a mold with high efficiency and high speed, it is apparent that the end mill with an exchangeable blade edge is superior to the solid type.

  On the other hand, in a blade end type radius end mill, etc., the insert is mounted and fixed on the tool body by inserting the insert mounted on the mounting seat into the screw insertion hole formed in the insert and inserting the fixing screw. A means for screwing with the mounting seat is employed. In general, in a blade-tip-exchangeable tool used for finishing a work material such as a die, every time a worn insert is replaced with a new insert, the newly installed insert is mounted / fixed. The position of the cutting edge with respect to the tip of the tool body, the shape of the cutting edge, etc. may be confirmed, and the fixing position of the insert may be finely adjusted as necessary. Therefore, every time a new insert is mounted and fixed when the insert is mounted on the tool body, an improvement to obtain high accuracy for this fixed position leads to a reduction in the position adjustment time of the insert. One of the challenges.

  The inventor of the present application is various about the configuration of the blade end replaceable radius end mill for performing high-speed and high-precision mold cutting, particularly finishing, and further improving the configuration of the insert and the fixing method to the mounting seat. As a result of examining and experimenting, the direction of the screw insertion hole for fixing the insert, the surface roughness of the inner peripheral surface of this screw insertion hole, and the surface roughness of the outer peripheral surface of the cylindrical portion of the fixing screw are appropriately set. Thus, it was found that it is important to closely engage the inner peripheral surface of the screw insertion hole of the insert and the outer peripheral surface of the cylindrical portion of the fixing screw.

  Accordingly, an object of the present invention is to improve a fixing mechanism for mounting and fixing the first insert, the second insert, and the third insert to the respective mounting seats at the tip of the tool body in a blade end replaceable radius end mill. This makes it possible to process workpieces such as dies at high speed, high efficiency, and high precision, and also provides a blade-replaceable radius that extends the life of the tool per insert. It is to provide an end mill.

The blade end replaceable type radius end mill according to claim 1 of the present invention is provided with a mounting seat at the tip of a tool body that rotates around an axis, and an insert having a cutting edge can be detachably mounted on the mounting seat. An exchangeable radius end mill,
The mounting seat is
A first insert inserted into the insert fitting groove is formed of a slit-like insert fitting groove formed in a radial direction of the tool body including the axis at the tip of the tool body. A first mounting seat for fixing by screw fastening in which a first fixing screw having an outer peripheral surface portion having a finished outer peripheral surface is inserted into an inclined screw insertion hole formed through the insert;
A mounting seat provided on one and the other half of the tip half formed on the tip of the tool body by the insert fitting groove, and the second insert is detachably fixed by a fixing screw. A second mounting seat, and a third mounting seat for detachably fixing the third insert with a fixing screw,
The first insert, which is flat and has a substantially square shape in plan view, has a cutting edge as a bottom blade formed from the center portion of the tip surface portion toward each side portion, and each of the side portions. The outer peripheral blade formed and a corner R blade connecting the bottom blade and the outer peripheral blade are provided, and the center line of the inclined screw insertion hole is on the rear side in the rotational direction with respect to the direction orthogonal to the flat plate-like plane. as well as the angle θ inclined to, the inner peripheral wall has an inner peripheral surface subjected to finishing,
The second and third inserts having a flat plate shape include a bottom blade formed on the front end surface portion, an outer peripheral blade formed on one side surface portion, the bottom blade and the outer peripheral blade as cutting blades. It has a corner R blade that connects,
The tip half part is a screw hole formed so as to reach the inside of the other tip half part from the outer surface of one tip half part through the axis in the insert fitting groove. A first insert fixing formed in a direction inclined by the angle θ in a direction opposite to a rotation direction of the tool body with respect to a direction orthogonal to a direction in which the insert fitting groove extends in a radial direction of the tool body. With screw holes for
When the first insert is fixed to the first mounting seat by screw fastening with the first fixing screw,
The outer peripheral surface portion of the first fixing screw and the inner peripheral surface portion of the inclined screw insertion hole are closely engaged with each other.

The blade edge replaceable radius end mill according to claim 2 is related to the blade edge replaceable radius end mill according to claim 1, wherein the first insert is mounted and fixed to the first mounting seat, and the second mounting seat is fixed. When the second insert is further attached to the third mounting seat and the third insert is fixed,
The lowest point of the insert mounted on the tool main body with respect to the axial direction is on the same plane perpendicular to the axial line, and the cutting edge of the first insert has two locations, the second and third It is characterized in that there is one each on the cutting edge of the insert.

The blade tip replaceable radius end mill according to claim 3 is related to the blade tip replaceable radius end mill according to claim 1 or 2, wherein the first insert is made of cemented carbide,
The bases of the second and third inserts are made of cemented carbide, and the cutting edges of the second and third inserts are hard sintered bodies including a cubic boron nitride sintered body in the bases. It is characterized by comprising a structure in which cutting edges formed from are joined.

  The tip exchange type radius end mill according to claim 4 relates to the blade tip exchange type radius end mill according to claim 1 or 2, wherein the first insert and the second and third inserts have a base that is super The cutting blades of the first, second, and third inserts are made of hard alloys, and the cutting blades are formed of a hard sintered body including a cubic boron nitride sintered body on each of the substrates. It is characterized by having a joined structure.

  The tip-replaceable radius end mill according to claim 5 relates to the blade-tip replaceable radius end mill according to claim 1, wherein the surface roughness of the outer peripheral surface portion of the first fixing screw subjected to the finishing process is The inclined screw insertion hole of the first insert is made rougher than the surface roughness of the inner peripheral surface portion subjected to the finishing process.

  The tip exchange type radius end mill according to claim 6 relates to the blade tip exchange type radius end mill according to claim 1, wherein the angle θ is set in a range of 20 ° ≦ θ ≦ 40 °. Yes.

The pre-exchangeable radius end mill of the present invention can achieve the following effects.
(1) By tilting the screw insertion hole for fixing the first insert and the screw hole for fixing the first insert of the tool body in the direction opposite to the normal rotation direction of the tool body, the second and third inserts are Since a space that can be mounted by screws can be provided sufficiently, the blade end replaceable radius end mill can have four blades. As a result, the present invention reduces the load per blade by half compared to the conventional two-blade type radius end mill, and the feed speed Vf can be doubled, and the tool life is also reduced. The cutting performance per cutting tool can be improved, such as doubled, and the blade end replaceable radius end mill has high efficiency, high accuracy, and excellent tool life in flat cutting and high-speed cutting of standing walls. Can be provided.

  (2) Further, when the first insert is fixed to the first mounting seat using the first fixing screw, the finishing process formed on the inner peripheral surface of the inclined screw insertion hole of the first insert is performed. Since the inner peripheral surface portion that has been applied and the outer peripheral surface portion that has been subjected to finishing processing on the outer peripheral surface of the first fixing screw are closely engaged, the first insert is removed from the first mounting seat during the cutting process. Misalignment can be prevented. Accordingly, it is possible to provide a blade end replaceable radius end mill that is highly efficient, highly accurate, and has an excellent tool life in high-speed cutting such as a mold.

  (3) The blade-tip-exchangeable radius end mill of the present invention has the tool body when the first, second, and third inserts are mounted and fixed from the first mounting seat to the third mounting seat of the tool body, respectively. The lowest point with respect to the direction of the axis O is on the same plane perpendicular to the axis O, so that there are two places on the cutting edge of the first insert and one place on each of the cutting edges of the second and third inserts. I have to. Thereby, when control of the cutting process of the flat surface portion mainly including the bottom blade is performed, the occurrence of vibration accompanying the cutting process load is suppressed. Therefore, in addition to the effect described in the above (2), the first It is possible to further prevent displacement of the insert with respect to the first mounting seat.

  (4) The blade end replaceable type radius end mill of the present invention has the tool body when the first, second, and third inserts are mounted and fixed from the first mounting seat to the third mounting seat of the tool body, respectively. The rotation locus of the outermost peripheral point of the outer peripheral cutting edge of the first insert with the axis O as the rotation center forms a circle whose diameter is the tool diameter (Dc), and the cutting edges of the second and third inserts on this circumference. The outermost peripheral point of is present. Thereby, when controlling the cutting of the standing wall mainly using the outer peripheral blade, the cutting load per blade is equalized, thereby suppressing the occurrence of vibration. Therefore, in addition to the effects described in (2) and (3) above, it is possible to further suppress the occurrence of vibration, which is preferable.

It is a top view which shows the state of a tool main body when not mounting | wearing with embodiment of the blade-tip-exchange-type radius end mill which concerns on this invention. It is a side view which shows the structure of the front-end | tip part when it sees from a rotation center axis direction about the blade-tip-exchange-type radius end mill shown in FIG. It is a partial front view for demonstrating the structure of a front-end | tip part about the blade-tip-exchange-type radius end mill shown in FIG. It is a top view which shows a state when an insert is mounted | worn about the blade-tip-exchange-type radius end mill shown in FIG. It is a side view which shows the structure of the front-end | tip part when it sees from a rotation center axis direction about the blade-tip-exchange-type radius end mill shown in FIG. It is a partial front view for demonstrating the structure of a front-end | tip part about the blade-tip-exchange-type radius end mill shown in FIG. It is a top view which shows the structure of the 1st insert shown in FIG. It is a side view which shows a structure when the 1st insert shown in FIG. 7 is seen from the left side direction of a paper surface. It is sectional drawing which shows the shape of the cross section along the AA line about the 1st insert shown in FIG. It is a figure for demonstrating the procedure for giving the finishing process to the internal peripheral surface about the inclination screw penetration hole of the 1st insert shown in FIG. 9, Comprising: (a) is shape | molding the 1st insert by powder molding. The cross-sectional view of the sintered material shape, (b) is a cross-sectional view for explaining the state when finishing the inner peripheral surface portion shown in (a). It is a front view which shows the structure of the 1st fixing screw shown in FIG. It is a top view which shows the structure of the 2nd insert shown in FIG. It is a side view which shows a structure when the 2nd insert shown in FIG. 12 is seen from the left side direction of a paper surface. It is a front view which shows a structure when it sees from the cutting-edge direction about the 2nd insert shown in FIG. It is a front view which shows the structure of the 2nd (or 3rd) fixing screw shown in FIG. It is a figure which shows the specification about the blade edge | tip-exchange-type radius end mill of the example of this invention and the prior art example which were made as an experiment in order to implement Experimental example 2. FIG.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of a blade end replaceable radius end mill according to the present invention will be described in detail with reference to the drawings.

(Tool body configuration)
FIGS. 1-3 is a figure which shows the structure of the tool main body 2 when not installing the insert used as a cutting edge about the blade-tip-exchange-type radius end mill 1 which shows one Embodiment of this invention. 1 is a plan view of the tool body 2, and FIG. 2 is a configuration of the tip portion of the tool body 2 when the tool body 2 is viewed from the tip portion in the direction of the rotation center axis O (hereinafter referred to as "axis O"). FIG. 3 is a front view showing the configuration of the tip when the tool body 2 shown in FIG. 1 is viewed from a direction different from the axis O by 90 °.

  A mounting seat for detachably fixing the insert with a fixing screw as a fastening member after mounting the insert serving as a cutting blade is formed on the tip 3 serving as one end of the tool body 2. . The other end of the tool body 2 serves as a shank portion for attaching the blade-tip-exchangeable radius end mill 1 to the processing apparatus. The tool body 2 is manufactured from, for example, an alloy tool steel such as SKD61.

  Next, the structure of the mounting seat for mounting and fixing the insert with the cutting edge will be described. A first mounting seat 4, a second mounting seat 5, and a third mounting seat 6 are formed at the tip 3 of the tool body 2. As shown in FIGS. 2 and 3, the first mounting seat 4 has a predetermined depth in the direction of the axis O including the axis O from the front surface portion of the tip 3, and the diameter of the tool body 2. It is comprised from the slit-like insert fitting groove | channel 7 formed so that the front-end | tip part 3 might be penetrated in the direction.

As shown in FIG. 3, the insert fitting groove 7 serving as the first mounting seat 4 includes side walls 7a and 7b formed so as to face each other with a predetermined interval, and a bottom portion 7c. 7a and 7b are formed by machining so as to be parallel across the axis O. The center line of the groove in which the insert fitting groove 7 is formed in the direction of the axis O is aligned with the axis O. The first mounting seat 4 is a mounting for mounting the first insert 12 (see FIGS. 5 and 7) having a cutting edge in the insert fitting groove 7 and fixing it in the insert fitting groove 7. Become a seat.
The tip 3 of the tool body 2 is divided into two parts by the formation of the insert fitting groove 7, and in the following description, one of the two divided tip parts 3 is the tip half part 3a and the other part. Is described as the tip half 3b.

  As shown in FIGS. 1-3, the 2nd mounting seat 5 is formed in the outer surface part of the front-end | tip half-body part 3a, and the 3rd mounting seat 6 is formed in the outer-surface part of the front-end | tip half body 3b. The second mounting seat 5 is a mounting seat for mounting and fixing the second insert 13 (see FIGS. 5 and 12) having a cutting edge. The third mounting seat 6 is a mounting seat for mounting and fixing the third insert 14 (see FIG. 5) having a cutting edge. The second mounting seat 5 and the third mounting seat 6 are provided with seating surfaces formed in the direction of the axis O for mounting the second and third inserts 13 and 14 respectively. It should be noted that the second and third inserts 13 and 14 are fixed to these seating surfaces by screw fastening with second and third fixing screws 15 and 16 (see FIG. 15) that serve as fastening members, respectively. A screw hole 10 is formed.

  Further, as shown in FIG. 2, a first insert fixing screw hole 8 is formed from the surface portion of one tip half body portion 3a through the insert fitting groove 7 into the other tip half body portion 3b. Has been. The first insert fixing screw hole 8 is used to fix the first insert 12 mounted in the first mounting seat 4 (insert fitting groove 7) with the first fixing screw 9 (see FIG. 11). It becomes a screw hole. The first insert fixing screw hole 8 penetrates the one end half half 3a and is formed to a predetermined depth inside the other end half half 3b via the insert fitting groove 7, A thread groove is formed in the first insert fixing screw hole 8 provided in the body portion 3b. This screw groove is provided for screw fitting with the screw portion 9e (see FIG. 11) of the first fixing screw 9.

Furthermore, as shown in FIG. 2, the direction of the center line of the first insert fixing screw hole 8 (straight line O ₃ ) is a straight line in which the insert fitting groove 7 is directed in the radial direction of the tool body 2 ( Center line) It is formed in a direction inclined by an angle θ with respect to a straight line O ₂ orthogonal to O ₁ . Further, this angle θ, that is, the direction O ₃ of the first insert fixing screw hole 8 is, as shown in FIG. 2, when the rotation direction of the tool body 2 (radius end mill) at the time of cutting is R, The angle θ is inclined in the direction opposite to the rotation direction R with respect to the straight line O ₂ .
In the present invention, the inclination angle θ at which the direction of the first insert fixing screw hole 8 is inclined with respect to the straight line O ₂ is desirably set in a range of 20 ° ≦ θ ≦ 40 °. In addition, 11 shown in FIG. 2 is a chip discharge groove formed in the tip portion 3.

(Configuration of radius end mill)
4-6 is a figure for demonstrating the structure of the blade end | tip-exchange-type radius end mill 1 used as embodiment of this invention, Comprising: A 1st insert is inserted in the 1st mounting seat 4 of the tool main body 2 shown in FIG. 12 is a view showing a state when the second insert 13 is fixed to the second mounting seat 5 and the third insert 14 is fixed to the third mounting seat 6.

  As shown in FIG. 4 (FIG. 6), the first insert 12 mounted in the insert fitting groove 7 constituting the first mounting seat 4 is fixed by screw tightening using the first fixing screw 9. The Further, the second insert 13 mounted on the second mounting seat 5 is fixed by screw tightening using the second fixing screw 15, and the third insert 14 mounted on the third mounting seat 6 is The third fixing screw 16 is used to fix the screw. Note that the second fixing screw 15 and the third fixing screw 16 are preferably the same screw.

  In the example shown in FIG. 5, the second insert 13 and the third insert 14 are fixed to mounting seats 5 and 6 provided on the respective tip half bodies 3 a and 3 b that are symmetrical with respect to the axis O. Although an example is shown, it is not always necessary to fix the second and third inserts 13 and 14 at positions symmetrical with respect to the axis O. In this case, the positions and shapes of the second mounting seat 5 and the third mounting seat 6 formed on the tip half portions 3a and 3b are appropriately set.

(Configuration of the first insert)
Then, the structure of the 1st insert 12 is demonstrated with reference to FIGS. FIG. 7 is a diagram showing the configuration of the upper surface portion of the first insert 12, and FIG. 8 is a side view showing the configuration of the first insert 12 shown in FIG. 7 when viewed from the left side (the cutting edge direction) of the drawing. FIG. 9 is a diagram showing a cross-sectional shape along line AA shown in FIG.

  The shape of the first insert 12 is a flat plate having a predetermined thickness, and has a substantially rectangular shape with a horizontal length X and a vertical length Y in plan view. Made of hard alloy. Bottom blades 12c and 12d serving as cutting edges are formed on the front surface portion surrounded by the upper surface portion 12a and the lower surface portion 12b of the first insert 12, and a corner R blade having a radius of curvature r1 is formed in the peripheral portion of the front surface portion. 12e and 12f are formed, and outer peripheral blades 12g and 12h are formed on the two side surfaces. The bottom blades 12c and 12d are formed from the end portions of the corner R blades 12e and 12f toward the axis O direction, respectively, and are further angled α with respect to the surface perpendicular to the axis O in the rear surface portion 12i direction. It is formed to be inclined at. This inclination angle α is set in the range of 10 ° to 20 °.

  In the first insert 12, the outer peripheral blade 12 g formed from the front surface side of the side surface portion toward the rear surface portion side and the bottom blade 12 c formed on the front surface portion of the first insert 12 have a curvature radius. The corner R blade 12e forming r1 is connected, and the bottom blade 12c, the corner R blade 12e, and the outer peripheral blade 12g constitute one cutting edge in the first insert 12. The cutting edge is configured such that one end of the corner R blade 12e is connected to the end of the bottom blade 12c, and the other end of the corner R blade 12e is connected to the end of the outer peripheral blade 12g. . Similarly, with respect to the outer peripheral blade 12h, the bottom blade 12d, and the corner R blade 12f, one end of the corner R blade 12f is connected to the end of the bottom blade 12d, and the other end of the corner R blade 12f is the outer peripheral blade 12h. It is comprised so that it may connect with the edge part of, and the one cutting edge is comprised.

  Thus, the first insert 12 has two (two) cutting edges. Then, the first insert 12 is mounted on the first mounting seat 4 (insert fitting groove 7), and the upper surface portion 12a and the lower surface portion 12b are brought into contact with the side walls 7a and 7b of the corresponding insert fitting groove 7. When fixed in contact, the bottom blades 12c and 12d, the corner R blades 12e and 12f, and the outer peripheral blades 12g and 12h of the first insert 12 protrude from the tip 3 and the outer portion of the tool body 2 by a predetermined length. I will let you. The outer peripheral blade 12g and the outer peripheral blade 12h are formed so as to be parallel to the axis O shown in FIG. 7, or have a tapered shape inclined at a predetermined angle in the direction of the axis O (the direction of the bottom blade 12c (12d)). You may make it provide the cutting blade which was made.

  The rear end portion 12i of the first insert 12 shown in FIG. 7 is, for example, a surface that forms a linear plane (linear plane portion), and the first insert 12 is attached to the first mounting seat 4. When it does, it becomes a part made to contact | abut to the bottom part 7c of the insert fitting groove | channel 7. For this reason, it is desirable to finish the linear plane part 12i. Further, as another embodiment of the linear flat surface portion 12i, in order to align the first insert 12 with the bottom portion 7c of the insert fitting groove 7, for example, a convex shape such as a V shape is formed in a plan view. The bottom portion 7c of the insert fitting groove 7 may have a concave shape.

As shown in FIG. 7, the first insert 12 includes an inclined screw insertion hole 12 j that is inclined and penetrates from the upper surface portion 12 a toward the lower surface portion 12 b. Further, an inner peripheral surface portion 12k that is finished is formed on the inner peripheral surface of the inclined screw insertion hole 12j.
In addition, 12p shown in FIG. 7 is a rake face, and has a planar shape with a slightly lower height than the upper surface portion 12a (lower surface portion 12b). A straight line O ₄ shown in FIG. 7 is a straight line that bisects the height Y of the first insert 12 in a plan view, and the first insert 12 is attached to the first mounting seat 4 and fixed. Sometimes the straight line coincides with the axis O. One end of each of the two bottom blades 12c and 12d is formed up to the straight line O ₄ or the vicinity of the straight line O ₄ , and the two bottom blades 12c and 12d have an angle α toward the straight line O ₄ . It is formed to have a medium to low gradient.

Note that S1 and S2 shown in FIG. 7 indicate positions that become the lowest point of the tool body 2 when the first insert 12 is mounted and fixed to the first mounting seat 4 of the tool body 2. The position of the lowest point S1 is on the connecting portion (connecting portion) between the corner R blade 12e and the bottom blade 12c, or on the cutting edge ridge line of the corner R blade 12e so as to be close to the connecting portion. The shape of one insert 12 and the structure of the seating surface of the first mounting seat 4 are appropriately designed. Similarly, the position of the lowest point S2 is on the connecting portion (connecting portion) between the corner R blade 12f and the bottom blade 12d, or on the cutting edge ridge line of the corner R blade 12f, and in the vicinity of this connecting portion. Like that. The lowest points S1 and S2 are positioned on a plane orthogonal to the axis O (O ₄ ) when the first insert 12 is mounted and fixed to the first mounting seat 4.

  G1 shown in FIG. 7 indicates the outermost peripheral point G1 located at the connecting portion between the corner R blade 12e and the outer peripheral blade 12g. G2 indicates the outermost peripheral point G2 located at the connecting portion between the corner R blade 12f and the outer peripheral blade 12h. As described above, when the first insert 12 is mounted and fixed to the first mounting seat 4 of the tool body 2, the two lowest points S1 and S2 and the two outermost peripheral points G1 and G2 in the tool body 2 are the first. Will occur on the cutting edge of one insert 12.

Then, the structure of the inclination screw insertion hole 12j with which the 1st insert 12 with which the radius end mill of this invention is mounted | worn is provided is demonstrated.
9 showing a state of a cross section of the first insert 12 of the A-A line shown in FIG. 7 (inclined screw insertion holes 12j center line as the straight line O ₄ perpendicular to the plane of), the orientation of the inclined screw insertion holes 12j That is, the direction of the straight line O ₈ passing through the center line of the inclined screw insertion hole 12 j is inclined by an angle δ with respect to the center line O ₇ of the cross section of the first insert 12. A straight line O ₇ shown in FIG. 9 indicates a straight line orthogonal to the upper surface portion 12 a (or the lower surface portion 12 b) of the first insert 12. The direction in which the inner circumferential surface of the inclined screw insertion hole 12j is along a straight line O ₈ is also provided with a direction which is inclined as the angle [delta], the inclined screw insertion hole inner peripheral surface to the inner circumferential surface subjected to finishing 12j 12k Is forming. The angle [delta], the angular theta, i.e. the same angle as the inclination angle of the orientation O ₃ of the first insert fixing screw holes 8, i.e., set to an appropriate angle of 20 ° ≦ δ ≦ 40 in °.

  Details of the configuration of the inclined screw insertion hole 12j provided in the first insert 12 will be described as follows with reference to FIGS. 10 (a) and 10 (b).

As will be described later, the first insert 12 made of cemented carbide is press-molded (or mold-molded) using mixed granulated powder prepared by adding tungsten carbide particles, cobalt particles and additives as necessary. Thus, a molded body of the first insert 12 having the inclined screw insertion hole 12j can be manufactured.
FIG. 10A shows the cross-sectional shape after sintering the material of the molded body of the first insert 12 formed by the above-described powder press molding. This sintered compact has a thickness t. In powder press molding, by appropriately designing the shape of the cavity of the mold, it is provided with an inclined screw insertion hole 12j that is inclined by the angle δ described above and has a length L (length after sintering). The first insert 12 can be molded.

In this press molding, as shown in FIG. 10 (a), as an inclined screw insertion hole 12j, an inner peripheral surface portion 12m having an inner diameter D0 over the length L1 is formed at the center thereof, and both end portions of the inner peripheral surface portion 12m. The molded body having an inner diameter D1 larger than the inner diameter D0 and having an inner peripheral surface portion 12n of a predetermined length in the direction of the inclined screw insertion hole 12j (straight line O ₈ ), the length of each portion after sintering is Preliminarily molded with a larger size in anticipation of shrinkage by 20-30%. For convenience, L, L1, D0, D1, D2 and thickness t shown in FIGS. 10 (a) and 10 (b) are materials of the molded body of the first insert 12 formed by powder press molding. The dimensions after sintering are shown.

  And after sintering this molded object, finishing process is given to the whole inner peripheral surface part 12m of length L1, and the inner peripheral surface part 12k which gave the finishing process as shown in FIG.10 (b) is formed. In addition, D2 shown in FIG.10 (b) has shown the internal diameter of the finishing internal peripheral surface part 12k after performing the above-mentioned finishing process. In the following description, the finished inner peripheral surface portion 12k obtained by finishing the inner peripheral surface portion 12m may be simply referred to as “inner peripheral surface portion 19k”.

As described above, the radius end mill 1 of the present invention has the first insert 12 mounted on the first mounting seat 4 (insert fitting groove 7) and fixed by the first fixing screw 9. Both the inclined screw insertion hole 19 of the insert 12 and the direction of the first insert fixing screw hole 8 provided in the tool body 2 are orthogonal to the straight line O _{1 in} which the insert fitting groove 7 is directed in the radial direction of the tool body 2. with respect to the straight line O _2, the rotation direction R of the tool body 2 (the angle θ, 20 ° ~40 °) angle theta ([delta]) in the opposite direction is configured such that the direction is inclined. This configuration is one of the features of the present invention (hereinafter referred to as “first feature”).

  With this first feature, the second and third inserts 13 and 14 are mounted on the second and third mounting seats 5 and 6, respectively, and are stabilized by the second and third fixing screws 15 and 16. Space for fixing in a state, that is, for screwing the second and third mounting seats 5 and 6 and the second and third fixing screws 15 and 16 into the tip half portions 3a and 3b of the tool body 2. A sufficient space for providing the screw holes can be secured, and the second and third inserts 13 and 14 can be firmly and firmly fixed to the second and third mounting seats 5 and 6, respectively. It becomes possible.

  Further, according to the first feature, the blade end replaceable radius end mill 1 includes a first insert 12 having two (two) cutting edges, and second and third inserts each having one cutting edge. Since it can be set as a so-called four-blade replaceable radius end mill with 13 and 14, it is possible to perform cutting at a higher speed compared to a two-blade replaceable radius end mill. An effect is produced.

  As described above, there is sufficient space for mounting and fixing the second and third inserts 13 and 14 to the second and third mounting seats by the second and third fixing screws 15 and 16, respectively. In order to ensure and make a configuration of a blade end replaceable radius end mill having four blades, it is desirable to set the angle θ (δ) in a range of 20 ° ≦ θ (δ) ≦ 40 °. This is because, in a tool body having a tool diameter (Dc) of about 20 mm to 30 mm, when θ (δ) is set in a range of 20 ° ≦ θ (δ) ≦ 40 °, the second and third inserts 13 and 14 are inserted. This is because it is possible to secure a sufficient space for fixing them to the second and third mounting seats by the second and third fixing screws 15 and 16 in a stable state.

(First insert manufacturing method)
Then, the manufacturing method of the 1st insert 12 is demonstrated. The 1st insert 12 made from a cemented carbide can be manufactured by the following procedures (1)-(5), for example.

  (1) Using the mixed granulated powder prepared by adding tungsten carbide particles, cobalt particles and additives as necessary, the molded body of the first insert 12 is molded by mold molding using a mold. . As described above, at the time of molding the mold, as shown in FIG. 10A, the inner peripheral surface portion 12m having a length L1 having an inner diameter D0 at the center portion and the inner diameter D1 and a predetermined length at both ends. The inclined screw insertion hole 12j provided with the inner peripheral surface portion 12n having a diameter is increased in consideration of shrinkage from 20% to 30% after sintering by the powder metallurgy method, and further, 0.05 mm as a grinding allowance for the inner peripheral surface portion 12m. Add ~ 0.3mm to form.

  (2) Subsequently, the molded body of the first insert 12 molded in the above (1) is charged into a heating furnace heated to a predetermined temperature (about 1300 ° C. to 1400 ° C.) and sintered.

  (3) Subsequently, as shown in FIGS. 10 (a) and 10 (b), a grinding allowance of 0.05 mm to 0.3 mm is applied to the inner peripheral surface portion 12m having a length L1 at the center of the inclined screw insertion hole 12j. An inner peripheral surface portion having an inner diameter D2 is applied to a whole surface of the inner peripheral surface by a finishing process using any one or a combination of grinding using a grindstone having diamond (or CBN) abrasive grains, buffing, or honing. 12k is formed. In this finishing process, the surface roughness Rza value (ten-point average roughness) of the finished inner peripheral surface portion 12k is 1.0 μm or less by appropriately setting the material, grain size, and processing time of the abrasive grains. To be.

  (4) Further, diamond (or CBN) abrasive grains are applied to the cutting edges (bottom edges 12c and 12d, corner R edges 12e and 12f, outer peripheral edges 12g and 12h) formed on the sintered first insert 12. Finishing is performed by using the grinding wheel. Further, finishing is also applied to the linear flat surface portion 12i.

  (5) Subsequently, the first insert 12 is coated on the surface excluding the inclined screw insertion hole 12j with a coating for imparting wear resistance and heat resistance. As the material of this coating, for example, a coating such as Ti—Al-based nitride, Ti—Si-based nitride, Ti—B-based nitride is formed by the PVD method. The inner diameter D2 of the inner peripheral surface portion 12k of the first insert 12 that has been finished is, for example, 3.5 mm when the radius end mill tool diameter (Dc) is 20 mm, and the tool diameter (Dc) is 30 mm. In this case, the target is set to 5.0 mm.

(Configuration of first fixing screw)
Next, the configuration of the first fixing screw 9 will be described. The first fixing screw 9 is a fastening member for fixing the first insert 12 mounted in the insert fitting groove 7 serving as the first mounting seat 4 to the first mounting seat 4 by screw fastening. When the first insert 12 is fixed to the first mounting seat 4, a portion where the first fixing screw 9 is inserted into the inclined screw insertion hole 12 j provided in the first insert 12 (the outer peripheral surface portion shown in FIG. 11) 9c) closely engages with the inner peripheral surface portion 12k in the inclined screw insertion hole 12j. As described above, in the blade end replaceable radius end mill 1 of the present invention, when the first insert 12 is fixed to the first mounting seat 4, the inner peripheral surface portion 12k of the inclined screw insertion hole 12j and the first fixing screw. There is also a feature (hereinafter referred to as “second feature”) in which the entire outer peripheral surface portion 9c of FIG.

  According to the second feature, when a high-speed cutting is performed, the first fixed to the first mounting seat 4 even if a large cutting load acts on the first insert 12 serving as the main cutting edge. This makes it possible to prevent displacement of the insert 12 from the first mounting seat 4 and to cut the work material at high speed and with high accuracy.

  FIG. 11 shows a front view of the first fixing screw 9. The first fixing screw 9 has a screw head portion 9a formed at the upper end portion thereof. The first cylindrical portion 9b, an outer peripheral surface portion 9c subjected to finishing, and a second cylindrical portion are directed downward from the screw head portion 9a. 9d, the lower end portion is provided with a screw portion 9e having a predetermined length in which screw grooves (threads) are formed on the outer peripheral surface.

  In the radius end mill 1 of the present invention, when the first insert 12 is mounted on the first mounting seat 4 and fixed by the first fixing screw 9, as described above, The finished outer peripheral surface portion 9c is closely engaged with the inner peripheral surface portion 12k formed in the inclined screw insertion hole 12j of the first insert 12.

Therefore, the length of the first cylindrical portion 9b, the second cylindrical portion 9d, and the screw portion 9e provided in the axial direction of the first fixing screw 9 is such that the first insert 12 is fixed by the first fixing screw 9. Sometimes, the outer peripheral surface portion 9c is appropriately set so as to be engaged with the inner peripheral surface portion 12k of the first insert 12, and the length of the outer peripheral surface portion 9c subjected to finishing is the length of the inner peripheral surface portion 12k. When the length is slightly longer than L1 and both are closely engaged, the entire inner peripheral surface portion 12k is closely engaged with the outer peripheral surface portion 9c. As described above, the entire inner peripheral surface portion 12k is intimately engaged with the outer peripheral surface portion 9c, so that the first insert 12 is attached to the first mounting seat 4 by the cutting load applied to the first insert 12 during the cutting. It is possible to further prevent displacement from the position.
In the following description, the outer peripheral surface portion 9c of the first fixing screw 9 subjected to the finishing process may be simply described as “the outer peripheral surface portion 9c”.

  The finishing process of the outer peripheral surface part 9c of the first fixing screw 9 is performed using a technique similar to the method of finishing the inner peripheral surface part 12k of the first insert 12, for example, diamond (or CBN) abrasive grains. Finishing can be performed using a cylindrical grinding wheel. And when finishing, when the surface roughness of the outer peripheral surface portion 9c is (Rzb), this surface roughness is a 10-point average roughness (Rz) of about 1.5 μm to 3.5 μm. It has a processed surface so that it becomes rougher than Rz = 1.0 μm or less, which is the surface roughness (Rza) of the inner peripheral surface portion 12k formed in the inclined screw insertion hole 12j of the first insert 12 described above.

  In the radius end mill 1 of the present invention, the reason why the surface roughness of the outer peripheral surface portion 9c of the first fixing screw 9 is made rougher than the surface roughness of the inner peripheral surface portion 12k formed in the inclined screw insertion hole 12j of the first insert 12 Is as follows.

  The first reason is that when the first insert 12 is fixed to the first mounting seat 4 with the first fixing screw 9 by making the surface roughness of the two different, the inclined screw insertion hole 12j The frictional force between the first fixing screw 9 and the contact between the first fixing screw 9 and the screw tightening can be reduced. However, when the outer surface 9c of the first fixing screw 9 made of steel is subjected to high-quality grinding or lapping to reduce its surface roughness, there is a problem that the cost increases.

For this reason, the second reason is that the outer peripheral surface portion 9c of the first fixing screw 9 is a finished surface that has been ground so as to have an appropriate surface roughness. The inner peripheral surface portion 12k of the insert 12 is subjected to high-quality grinding or lapping so that the first insert 12 made of cemented carbide, which is hard to wear, has a surface roughness accuracy standard for daily processing. This is because it becomes easier to manage accuracy.
In addition, the first insert 12 with the worn cutting edge can be reused by re-polishing the worn cutting edge, so that the inner peripheral surface portion 12k of the first insert 12 is finished with high quality. This is because the processing can contribute to the cost reduction of the first insert 12.

(Method for manufacturing first fixing screw)
For example, the first fixing screw 9 can be manufactured by the following method. After forming the outer peripheral surface portion 9c, screw portion 9e, etc. by pressing or lathe processing from a rod (wire) made of alloy tool steel such as SKD61, mechanical polishing using a grindstone having diamond (or CBN) abrasive grains The finishing process is performed on the entire outer peripheral surface of the outer peripheral surface portion 9c. The outer diameter (d2) of the outer peripheral surface portion 9c is slightly smaller than the inner diameter of the inner peripheral surface portion 12k of the first insert 12 by about 3 μm to 10 μm. As a result, when the outer peripheral surface portion 9c of the first fixing screw 9 is inserted into the inner peripheral surface portion 12k of the first insert 12, both are closely engaged.

(Configuration of the second insert)
Next, the configuration of the second insert 13 that is detachably attached to the second mounting seat 5 will be described. 12 is a plan view showing the configuration of the upper surface portion of the second insert 13, FIG. 13 is a view when the second insert 13 shown in FIG. 12 is viewed from the left side (bottom blade side), and FIG. It is a figure when the 2nd insert 13 shown in 12 is seen from the peripheral blade direction.

As shown in FIGS. 12 to 14, the shape of the second insert 13 is a flat plate having a predetermined thickness, a substantially square shape or a polygonal shape in plan view, and the base is made of cemented carbide. It has become. A straight bottom blade 13c serving as a cutting edge is formed on the side surface portion between the upper surface portion 13a and the lower surface portion 13b of the second insert 13, and an R shape is formed on the outer end portion of the front surface portion. The corner R blade 13e is formed with an outer peripheral blade 13g on the outer surface. The corner R blade 13e has a cutting edge having an R shape with a radius of curvature r1 in plan view.
The value of the radius of curvature r1 is the same radius of curvature r1 as that of the corner R blade 12e (12f) of the first insert 12. The outer peripheral blade 13g and the bottom blade 13c are connected to respective end portions of the corner R blade 13e. Therefore, the second insert 13 is configured as an insert having one (one) cutting edge including a bottom blade 13c, a corner R blade 13e, and an outer peripheral blade 13g.

  As shown in FIG. 12, the bottom blade 13c is formed so as to be inclined from the end of the corner R blade 13e in the direction of the second screw insertion hole 13j in the plan view. This inclination angle α is set in a range of about 10 ° to 20 °.

  Furthermore, the 2nd insert 13 is provided with the 2nd screw penetration hole 13j formed by penetrating from the upper surface part 13a to the lower surface part 13b. The second screw insertion hole 13 j is an insertion hole through which the second fixing screw 15 is inserted when the second insert 13 is mounted and fixed to the second mounting seat 5. The direction of the center line of the second screw insertion hole 13j is formed in a direction orthogonal to the lower surface portion 13b, and the lower surface portion 13b is a portion fixed to the seating surface of the second mounting seat 5.

Furthermore, as a desirable example when the tool diameter (Dc) is smaller than 40 mm, the direction of the center line of the second screw insertion hole 13j is desirably inclined with respect to the lower surface portion 13b. The tilt at this time is preferably tilted at an angle of 10 degrees or less in the direction opposite to the rotation direction R of the tool body 2. This is because the number of effective threads to be screwed between the screw portion 15c of the fixing screw 15 and the female screw portion provided on the second mounting seat 5 when fixed to the tool body can be increased.
Moreover, 13p shown in FIG. 12 is a rake face of the second insert 13, and has a planar shape with a slightly lower height than the upper surface portion 13a.

  As described above, the base body of the second insert 13 is composed of a cemented carbide member, and the bottom blade 13c, the corner R blade 13e, and the outer peripheral blade 13g, which are cutting edges, are also integrated with the cemented carbide base body. It can be molded by mold molding or the like.

  In the present invention, the second insert 13 is made of a cemented carbide whose base is made by molding or the like, and a hard sintered body is formed on the side surface formed by the upper surface portion 13a and the lower surface portion 13b of the base body. It is desirable to attach the second insert 13 having the configuration shown in FIG. 12 by joining the bottom blade 13c, the corner R blade 13e, and the outer peripheral blade 13g, which are made of a cutting blade, by brazing. As the hard sintered body, it is preferable to use a member containing about 95% of a cubic boron nitride sintered body (CBN) by mass.

  As described above, in the present invention, when the bottom blade 13c serving as the cutting edge of the second insert 13, the corner R blade 13e, and the outer peripheral blade 13g are composed of a hard sintered body including a cubic boron nitride sintered body, Compared with an insert made entirely of cemented carbide, it is possible to exhibit more wear resistance and heat resistance as an insert for performing high-speed cutting.

In the blade end replaceable type radius end mill of the present invention, the third insert 14 to be mounted on the third mounting seat 6 can have the same configuration as the second insert 13 described above, so the configuration of the third insert 14 A description of the process will be omitted.
The outer peripheral blades 13g and 14g (see FIG. 6) formed on the second and third inserts 13 and 14 are parallel to the axis O when mounted on the second mounting seat 5 and the third mounting seat 6. Alternatively, a cutting blade having a tapered shape inclined at a predetermined angle in the direction of the axis O (the direction of the bottom blade 13c (14c)) may be provided.

When the second insert 13 is mounted on the second mounting seat 5 and fixed, the corner R blade 13e of the second insert 13 is disposed on the outer peripheral side of the tip 3 of the tool body 2, and the second insert 13 is fixed. The bottom blade 13c of the second insert 13 protrudes from the distal end portion 3 of the tool body 2 by a predetermined length in the direction of the axis O, and the outer peripheral blade 13g extends from the end portion of the distal end portion 3 to the outer peripheral direction of the tool body 2 by a predetermined length. Make it protrude.
Further, when the second insert 13 is mounted and fixed to the second mounting seat 5, as shown in FIG. 5 or FIG. 6, the bottom blade 13c of the second insert 13 (the third insert 14 in FIG. 6). The bottom blade 14c of the third insert 14 in FIG. 6 is not positioned on the axis O. Even when the third insert 14 is mounted and fixed to the third mounting seat 6, the arrangement is the same as that of the second insert 13.

  S3 shown in FIG. 6 shows the position which becomes the lowest point of the tool body 2 when the second insert 13 is mounted and fixed to the second mounting seat 5, and G3 shows the outermost peripheral point. The position of the lowest point S3 is on the connecting portion (connecting portion) between the corner R blade 13e and the bottom blade 13c, or on the cutting edge ridge line of the corner R blade 13e and in the vicinity of this connecting portion. The shape of the second insert 13 and the structure of the seating surface of the second mounting seat 5 are appropriately designed so that the outer peripheral point G3 is located at the connecting portion between the corner R blade 13e and the outer peripheral blade 13g.

  Similarly, when the third insert 14 is mounted and fixed on the third mounting seat 6, S4 which is the lowest point of the tool body 2 and G4 which is the outermost peripheral point are the cutting edges of the third insert 14. To occur above. The position of the lowest point S4 is on the connecting portion (connecting portion) between the corner R blade 14e and the bottom blade 14c of the third insert 14 or on the cutting edge ridge line of the corner R blade 14e and in the vicinity of this connecting portion. The outermost peripheral point G4 is located at the connecting portion between the corner R blade 14e and the outer peripheral blade 14g.

  In the present invention, the first insert 12 is mounted on the first mounting seat 4 of the tool body 2, the second insert 13 is mounted on the second mounting seat 5, and the third insert 14 is mounted on the third mounting seat 6. When fixed in this manner, the four lowest points S1, S2, S3 and S4 described above are planes orthogonal to the axis O and located on the same plane.

  Further, when the first, second, and third inserts 12, 13, and 14 are respectively attached and fixed from the first mounting seat 4 to the third mounting seat 6 of the tool body 2, the axis O of the tool body 2 is fixed. The rotation locus of the outermost peripheral points G1 and G2 on the outer peripheral blades 12g and 12h of the first insert 12 with the rotation center as the rotation center forms a circle with the tool diameter (Dc) as the diameter, and on the circumference of this rotation locus, The outermost peripheral points G3 and G4 on the outer peripheral blades 13g and 14g of the second and third inserts 13 and 14 are made to exist. However, the outermost peripheral points G3 and G4 may have a positional deviation of ± 20 μm in the rotation axis direction. When the outer peripheral blades 12g, 12h and the outer peripheral blades 13g, 14g are formed to have a tapered shape as described above, when the inserts 12, 13, 14 of the tool body 2 are mounted, their outermost peripheral points G1. , G2, G3, and G4 are located at the outermost peripheral point of the tool body 2.

  In the present invention, as described above, when the first insert 12, the second insert 13, and the third insert 14 are attached and fixed to the tool body 2, the four lowest points S1, S2, S3, and By adopting a configuration in which S4 is positioned on the same plane orthogonal to the axis O, the following effects can be exhibited.

(1) When performing planar machining on the work material, it becomes possible to start cutting while simultaneously contacting the surface of the work material, thus preventing chatter vibrations that occur with the work. Thus, it is possible to improve the accuracy of the finished surface.
(2) In the cutting process of the first insert 12, the second insert 13 and the third insert 14, particularly in the cutting of the bottom blade and the corner R blade, the present invention is 1 By reducing the load per blade by half, the feed rate Vf can be doubled and the tool life can be improved by a factor of about two. Will be able to maintain. As a result, the present invention can provide a blade end replaceable radius end mill capable of extending the service life.

  The manufacturing method of the substrate made of the cemented carbide constituting the second insert 13 is substantially the same as the manufacturing method of the first insert 12 made of the cemented carbide described above, but on the inner peripheral surface of the screw insertion hole 13j. It is not always necessary to provide a finished inner peripheral surface portion subjected to finishing.

  In addition, the 2nd insert 13 which brazed the cutting blade (the bottom blade 13c, the corner R blade 13e, the outer peripheral blade 13g) which consists of a hard sintered compact containing a cubic boron nitride sintered compact to the base | substrate which consists of cemented carbides. The method of manufacturing can be manufactured by the following 1st to 4th processes, for example. The third insert 14 can be manufactured by the same manufacturing process as described below.

(First step)
A notch portion is prepared in advance at a location corresponding to the blade portion of the second insert 13 made of a cemented carbide substrate (a side surface portion formed by the upper surface portion 13a and the lower surface portion 13b of the substrate). This notch can also be created when a cemented carbide substrate is molded. In addition, after sintering the molded body formed by the mold forming, a cutting edge made of a cubic boron nitride sintered body is fixed to the notch portion, so that a diamond ( Alternatively, it is preferable to form the finished surface with a grindstone having CBN) abrasive grains.

(Second step)
From a cubic boron nitride sintered body formed in a predetermined shape so that the bottom blade 13c, the corner R blade 13e, and the outer peripheral blade 13g form a continuous cutting blade, the bottom blade 13c and the corner R blade 13e are cut by wire cutting. The blade part in which the outer peripheral blade 13g is continuous is cut out one by one.

(Third step)
A blade portion made of a cubic boron nitride sintered body prepared in the second step is bonded to the notch portion of the cemented carbide substrate prepared in the first step using a brazing material, and heat treatment is performed. Go and firmly fix both.

(Fourth process)
Subsequently, as a final step, a finish grinding process or the like is performed on the blade portion bonded to the cemented carbide substrate with a diamond grindstone.
With such a manufacturing process, the second insert 13 including the bottom blade 13c, the corner R blade 13e, and the outer peripheral blade 13g can be manufactured as one cutting blade.

  Note that the first insert 12 described above in the present invention also includes bottom blades 12c and 12d, corner R blades 12e and 12f, and outer peripheral blades 12g and 12h that constitute the cutting edge, and a cubic boron nitride sintered body (CBN). As a cutting edge made of a hard sintered body including a solid sintered body, a brazing material may be fixed to a cemented carbide substrate by heat treatment. Thus, by using the cutting edge of the first insert 12 as an insert having a cutting edge made of CBN, the tool life of the radius-end-exchangeable end mill equipped with the first insert 12 serving as the main cutting edge is further increased. It becomes possible to make it.

(Configuration of second fixing screw)
The configuration of the second fixing screw 15 is shown in FIG. The second fixing screw 15 includes a screw head 15a, a cylindrical portion 15b, and a screw portion 15c. When the second insert 13 is mounted on the second mounting seat 5 and fixed by tightening the second fixing screw 15, the second fixing screw 15 passes through the second screw insertion hole 13j. The screw portion 15c is screwed into a screw hole provided in the second mounting seat 5. Thereby, the second insert 13 is firmly fixed to the second mounting seat 5. The mechanism for fixing the third insert 14 to the third mounting seat 6 is the same as that of the second insert 13 described above.

  In addition, since the 2nd and 3rd fixing screws 15 can be made the same, the manufacturing method is the same as the above-mentioned 1st fixing screw 9, but the bar material made from alloy tool steel, such as SKD61 ( From a wire) using a machining process such as press working or screw machining.

(Attaching and fixing the insert to the tool body)
Next, an outline of an operation procedure for mounting the first, second, and third inserts on the tool body 2 will be described. This operation procedure can be performed by the following procedure, for example.

(Operation procedure 1)
The first insert 12 is inserted into the first mounting seat 4 (insert fitting groove 7) provided at the tip 3 of the tool body 2, and temporarily fixed using the first fixing screw 9 (predetermined tightening torque). 70% of the value).

(Operation procedure 2)
The second insert 13 is temporarily fixed using the second fixing screw 15 in accordance with the second mounting seat 5 provided at the tip 3 of the tool body 2 (a value of 70% of the predetermined tightening torque).

(Operation procedure 3)
The third insert 14 is temporarily fixed using the third fixing screw 16 in accordance with the third mounting seat 6 provided at the tip 3 of the tool body 2 (a value of 70% of the predetermined tightening torque).

(Operation procedure 4)
With respect to the first, second, and third inserts 12, 13, and 14 temporarily fixed in advance, the positioning accuracy, that is, the length that these cutting edges protrude from the tip 3 is set to a predetermined value. After confirming whether or not, the fixing screws 9, 15, 16 are tightened to a predetermined torque value and fixed to the mounting seats. Thereby, as shown in FIGS. 4 to 6, the first, second, and third inserts 12, 13, and 14 can be attached and fixed to the mounting seats 4, 5, and 6 of the tool body 2, respectively. it can.

  Then, the experiment example and the result which tested the performance are demonstrated about the blade-tip-exchange-type radius end mill of this invention provided with the above-mentioned structure.

(Experimental example 1)
[Accuracy of fixing the first insert to the mounting seat]
The insert mounted on the blade end replaceable radius end mill wears the cutting edge as the cutting time increases, and the cutting accuracy decreases. For this reason, for example, when the cumulative value of the cutting time reaches a predetermined time, a new insert is mounted on the mounting seat of the tool body before the predetermined cutting accuracy can be obtained before the predetermined cutting accuracy can be obtained. Then, the cutting process is resumed.

In the operation of re-attaching the insert to the mounting seat of the tool body (including the initial mounting), the cutting edge of each insert including the new insert is at a predetermined position, that is, the axis line, at the tip 3 of the tool body 2. It is necessary to fix the insert to the mounting seat so that it can be accurately positioned at a preset position in both the direction (A direction) and the radial direction (R direction). In particular, the first to third inserts 12, 13, 14 are related to the positional accuracy in the axial direction so that the four lowest points S 1, S 2, S 3, S 4 are located on the same plane orthogonal to the axial line O. Must be mounted and fixed on the first mounting seat 4, the second mounting seat 5, and the third mounting seat 6, respectively.
Further, the outermost peripheral point of the cutting edge related to the positional accuracy in the radial direction is also required to have high accuracy in the inclined surface processing such as the standing wall.
This is because, when an error occurs in the positioning position of the cutting edge of the insert, every time the insert is remounted, the machining accuracy of the cutting process is lowered and a step or the like is generated. In particular, in finishing cutting such as a mold, particularly high accuracy is required for positioning of the cutting edge.

  In this Experimental Example 1, when the blade edge replaceable radius end mill according to the present invention was prototyped and the first insert 12 was repeatedly fixed to the first mounting seat 4 of the tool body 2, the first insert 12 A test was conducted to confirm the accuracy of the fixed position of the cutting edge.

  In order to perform a confirmation test of the fixing accuracy of the first insert, the tool body 2 having a tool diameter (Dc) shown in FIG. 1 (FIG. 2) of 30 mm and the first mounting seat 4 of the tool body 2 are mounted. Four types of first inserts 12 to be manufactured and three types of first fixing screws 9 for fixing the first inserts 12 attached to the first mounting seats 4 were produced. And the test which confirms the fixing precision when the 1st insert was mounted | worn with respect to the 1st attachment seat 4 was done about the manufactured 12 samples.

  The test for confirming the fixing accuracy of the first insert was performed based on the following procedure. That is, when the manufactured first insert 12 is mounted on the first mounting seat 4 and fixed with the first fixing screw 9, the fixing position of the first insert 12 with respect to the first mounting seat 4 is changed five times. Repeatedly measured. In addition, this “repeat” means that “attachment and removal (detachment)” to the first mounting seat 4 was repeated five times for the same first insert 12 and first fixing screw 9. Indicates.

In addition, about the cutting edge of the above-mentioned 1st insert 12, the confirmation method of the precision of the fixing position is set to the exclusive sleeve jig | tool which has a conical surface, and the tool main body 2 is set with respect to the reference | standard horizontal stage. Then, a method of measuring the coordinates of the cutting edge position using an image processing apparatus mounted vertically and equipped with a CCD camera was adopted. As the measured data, the coordinates of the lowest point of the cutting edge and the coordinates of the outermost peripheral point were measured. As a measuring apparatus, it can carry out with the tool blade edge | tip inspection apparatus etc. by Osaka Koki Co., Ltd., for example.
Moreover, about the surface roughness (Rza) of the inner peripheral surface part 12k of the produced first insert 12, and the surface roughness (Rzb) of the outer peripheral surface part 9c of the first fixing screw 9, a surface roughness measuring device is previously provided. Measured by.

  The test for confirming the accuracy of the fixed position of the first insert 12 was performed as follows. The evaluation of the accuracy of the fixed position is the same when the position of the two lowest points S1 and S2 in the tool body is orthogonal to the axis O when the first insert 12 is mounted on the first mounting seat 4 for the first time. The position of the lowest points S1 and S2 at the first time is set to a reference value “0” for evaluating the accuracy of the fixed position of the first insert 12, and the lowest point S1 is adjusted. , S2 position was measured.

Here, the reference value “0” for performing the accuracy evaluation means that the coordinates at the lowest points S1 and S2 of the cutting edge of the insert are set to the reference zero points, respectively. The coordinates of S1 are (S1 _A0 , S1 _R0 ), and the coordinates of the lowest point S2 are (S2 _A0 , S2 _R0 ). In the above-described coordinates (S1 _A0 , S1 _R0 ), etc., the subscript “A” indicates the axial direction, and the subscript “R” indicates the radial direction. By adjusting so that the positions of the lowest points S1 and S2 are on the same plane orthogonal to the axis, S1 _A0 and S2 _A0 are set to the same or substantially the same value.

Subsequently, the insert 12 is removed once, and the coordinates of the positions of the lowest points S1 and S2 when the insert 12 is fixed to the first mounting seat 4 by using the first fixing screw 9 are measured again. A difference (fixed position accuracy Fp _A ) from the position of each of the lowest points S1 and S2 measured was obtained. The Fp _A related to the positional accuracy in the axial direction is the difference between the axial components when the remeasured lowest point S1 is (S1 _A1 , S1 _R1 ) and the lowest point S2 is (S2 _A1 , S2 _R1 ). (S1 _A0 -S1 _A1), obtained by _{(S2 A0 -S2 A1), ···} . This operation was repeated 4 times. At the same time, Fp _R related to the positional accuracy in the radial direction was also measured in the same manner as described above. The Fp _R is measured by calculating the coordinates of the outermost peripheral points G1 and G2 of the cutting edge of the insert as ( _G1A0 , _G1RO ), ( _G2A0 , _G2R0 ),... Was obtained by (G1 _R0 -G1 _R1 ), (G2 _R0 -G2 _R1 ),..., And used as the Fp _R value at each measurement.

The above-mentioned “positions of the lowest points S1 and S2” are the positions where the two lowest points S1 and S2 are the tips of the cutting edges of the inserts mounted on the tool body 2 and project in the rotational axis direction. Show. The positions of the lowest points S1 and S2 and the outermost peripheral points G1 and G2 were detected using an image processing apparatus equipped with a CCD camera, and the accuracy Fp _A and Fp _R were obtained based on the detected data.

  In addition, the diameter D2 of the finished inner peripheral surface portion 12k formed in the inclined screw insertion hole 19 of the first insert 12 used in the accuracy check test of the fixed position is the same as that of the first insert 12 within the range of “(5 mm + 5 μm) to 5 mm + 15 μm)”. On the other hand, the diameter d2 of the finished outer peripheral surface portion 9c formed on the first fixing screw 9 is selected as the first fixing screw 9 within the range of “(5 mm + 2 μm) to (5 mm−5 μm)” and the diameter d2 The first insert 12 and the first fixing screw 9 in which the difference between D2 and the diameter d2 falls within 3 μm to 20 μm are mounted in combination. Then, the insert 12 was fixed to the first mounting seat 4 so that the finished inner peripheral surface portion 12k of the first insert 12 and the finished outer peripheral surface portion 9c of the first fixing screw 9 were closely engaged.

Table 1 shows the specifications of the tool body, the specifications of the first insert attached to the tool body, for each tool body (sample numbers 1 to 12) used in the accuracy confirmation test of the fixed position of the first insert 12. The accuracy (Fp _A , Fp _R ) and the evaluation of the first fixing screw and the fixing position of the cutting edge are described.

In the “fixed position accuracy and evaluation” column shown in Table 1, Fp _A (axial direction) and Fp _R (radial direction) are the results of the above five repeated tests for each sample number. Show.
The Fp _A value is determined when the coordinate values in the axial direction of the lowest points S1 and S2 measured in the second to fifth tests are compared with the respective coordinate values of the first lowest points S1 and S2. The range of the maximum value of the difference is shown. Similarly, the Fp _R value indicates the range of the maximum value of the difference when compared with the initial coordinate values of the lowest points G1 and G2.
In the “Evaluation” column shown in Table 1, “◎” indicates the case where the fixed position accuracy (Fp _A ) values are Fp _A <5.0 μm and Fp _R <5.0 μm for all four times. “○” indicates the case where the accuracy (Fp _A ) is included even once, and the value of (Fp _R ) is within 5.0 μm ≦ Fp _A <10.0 μm, and “△” indicates the accuracy (Fp _A ) even once. , (Fp _R ) is 10.0 μm or more.

As apparent from the description in the column “Accuracy and Evaluation of Fixed Position” shown in Table 1, the surface roughness (Rza) value of the inner peripheral surface portion 12k of the first insert is 0.8 μm or less, and The combination of the first insert and the first fixing screw 9 in which the surface roughness (Rzb) value of the outer peripheral surface portion 9c of the one fixing screw 9c is 6.3 μm or less, that is, sample numbers 1, 2, 4 and 5, the error (accuracy Fp _A, Fp _R ) of the fixed position of the first insert 12 is smaller than 5.0 μm, and the accuracy (Fp _A, Fp _R ) of the fixed position is extremely high, which is satisfactory. Results were obtained.
On the other hand, in the sample numbers 10 to 12, the first insert and the first fixing for which the error (accuracy Fp _A, Fp _R ) exceeds 10.0 μmm (accuracy Fp _A, Fp _R ) is inferior. In the combination with the screw 9c, the variation in the dimensional accuracy of the fixing position increases accordingly, and an operation and adjustment time for fine adjustment of the fixing position of the first insert are required.

  From the result of the accuracy check test of the fixed position of the first insert 12 according to the above-described experimental example 1, the surface roughness of the inner peripheral surface portion 12k of the first insert 12 to be mounted on the blade edge replaceable radius end mill of the present invention. A combination of the first insert 12 and the first fixing screw 9 in which Rza is 0.8 μm or less, and the surface roughness Rzb of the outer peripheral surface portion 9c of the first fixing screw 9 is 6.3 μm or less, And it can be said that it is desirable to closely engage the inner peripheral surface portion 12k and the outer peripheral surface portion 9c.

(Experimental example 2)
[Cutting test of work material]
Trial manufacture of a blade end replaceable radius end mill as an example of the present invention and a conventional example, and using a triaxial NC machine tool, cutting is performed on a standing wall of a work material having an inclined surface (planar surface) having an inclination angle of 5 °. A cutting test was conducted to evaluate the high-efficiency workability. In the cutting test of the planar standing wall, cutting was performed using the bottom blades and the corner R blades of the first, second, and third inserts of the prototyped edge replacement type radius end mill.
Below, the content of the cutting test which concerns on this experiment example 2, and its result are demonstrated.

  In this cutting trial processing experiment, the material of the work material was S50C (220HB), and a cutting test by contour processing was performed on an inclined surface having an inclination angle of 5 °. And in order to implement a cutting test, four types of blade end exchange type radius end mills (sample numbers A1 to A4 shown in FIG. 16) were produced. FIG. 16 shows the specifications of the tool body and the first, second, and third inserts mounted on the tool body and the four types of blade end replaceable radius end mills.

  As shown in FIG. 16, sample numbers A1 and A2 are composed of four pieces with the first, second and third inserts attached thereto, and the blade end replaceable radius end mill according to the present invention having a tool diameter (Dc) of 30 mm. It is. Sample No. A1 is that the first, second and third inserts mounted on the tool body are all made of cemented carbide, including the cutting edges, and the surfaces of all these inserts are coated with a coating film. It was an alloy insert. Sample No. A2 is that all of the first, second and third inserts mounted on the tool body are made of cemented carbide, and the base is made of a hard sintered body (CBN) with a bottom blade and a corner. An insert provided with a CBN-made cutting blade brazed with a cutting blade composed of an R blade and an outer peripheral blade. The inserts attached to the sample number A2 were CBN, and the coating film was not covered.

  For sample number A1 and sample number A2, the fixed positions of the four cutting edges are measured, and the maximum runout at the lowest point and the outermost peripheral point is 10 μm or less at the lowest point, respectively. In this case, the cutting test was performed in a state adjusted to 20 μm or less. Inserts were inserted into the tool body in the order of inserts 1 to 3. The mounting at this time was temporarily fixed at a value of 70% of the predetermined tightening torque. Next, after fixing the insert with a predetermined tightening screw torque in the order of the inserts 1 to 3, the fixing position was measured.

Sample numbers A3 and A4 are composed of two pieces having only the first mounting seat, and only the first insert is mounted on the first mounting seat, and according to the conventional example in which the tool diameter (Dc) is 30 mm. It is a blade end exchangeable radius end mill. The inserts mounted on the tool body of sample number A3 were all made of cemented carbide, including the cutting edge, and further, the insert was made of cemented carbide with the surface coated with a coating film. In addition, the insert mounted on the tool body of sample number A4 is made of a cemented carbide alloy, and a base blade made of a hard sintered body (CBN), a corner R blade and an outer peripheral blade are brazed to the base. It was set as the insert provided with the attached cutting edge made from CBN.
In both the present invention example and the conventional example, the material of the coating film coated on the surface of the insert was Ti—Al—Si—N, and the thickness of the film was 3 μm.

  Moreover, as shown in FIG. 16, the blade-tip-exchangeable radius end mills of sample numbers A1 and A2 according to the example of the present invention were configured as follows. That is, the inclination angle θ of the center line of the first insert fixing screw hole 8 formed in the distal end portion 3 of the tool body 2 is 25 °, and the inclination angle δ of the inclined screw insertion hole 12j of the first insert 12 described above. Also, the angle was set to 25 °, which is the same as the angle θ.

  Further, although not shown in FIG. 16, in order to fix the first insert 12 to the first mounting seat 4, the inner diameter D2 of the inner peripheral surface portion 12k after finishing the inclined screw insertion hole 12j is 5.007 mm. With respect to the first fixing screw 9, the diameter d2 of the outer peripheral surface portion 9c subjected to finishing was set to 4.997 mm.

  Sample numbers A3 and A4, which are conventional examples, are composed of two blades with only the first insert, and the angles θ and δ are set to 0 °.

In Experimental Example 2, the evaluation of the test result by cutting was performed as follows.
For sample numbers A1 and A3, when the cutting speed Vc was set to Vc = 200 m / min (cutting condition 1) and Vc = 565 m / min (cutting condition 2), the first cutting was performed. When the dimensional change of the cutting edge of the insert reaches 0.02 mm and the flank wear width (VBmax) reaches 0.10 mm, it is determined that the insert has reached the end of life, and the life until this end of life (insert tool life) is reached. The cutting length (insert tool life L) of the work material was measured.

  Also, for sample numbers A2 and A4, that is, a blade end replaceable radius end mill of sample numbers A2 and A4, in which a CBN cutting blade is brazed with a hard sintered body (CBN) cutting blade on the base of the insert Only cutting with a cutting speed Vc as high as Vc = 565 m / min was carried out, the insert life was determined in the same procedure as the above-mentioned sample numbers A1 and A3, and the cutting length (insert tool life L ) Was measured.

  The cutting conditions (cutting conditions 1 and 2 described above) set for performing the cutting test according to Experimental Example 2 are collectively described as follows.

<Cutting condition 1>
Cutting speed Vc: 200 m / min
Processing method: Contour cutting (finishing) of standing wall (5 ° inclined surface)
Dry cutting Rotational speed n: 2120 min ⁻¹
Feeding speed Vf: 1060, 2120 mm / min
Feed amount per blade fz: 0.25 mm / blade Axial cut amount ap: 0.1 mm
Radial cutting depth ae: 0.3 mm
Tool protrusion: 110mm

<Cutting condition 2>
Cutting speed Vc: 565 m / min
Processing method: Contour cutting (finishing) of standing wall (5 ° inclined surface)
Dry cutting Rotational speed n: 6000 min ⁻¹
Feed speed Vf: 3000, 6000 mm / min
Feed amount per blade fz: 0.25 mm / blade Axial cut amount ap: 0.1 mm
Radial cutting depth ae: 0.3 mm
Tool protrusion: 110mm

  Table 2 shows the results of the cutting test according to Experimental Example 2 for each of sample numbers A1 to A4. “Insert tool life L (m)” in the evaluation result column of Table 2 indicates the tool life of the above-described insert as the cutting length of the work material by cutting speed (Vc).

From the results of the cutting test shown in Table 2, the following became clear.
In a cutting test with a cutting speed Vc = 200 m / min, the sample life A (cutting length) of the sample No. A3, which is a conventional example consisting of two blades equipped with a cemented carbide insert coated with a coating film, is It was 400 m. In the cutting test with the cutting speed Vc as high as 565 m / min, the tool life L (cutting length) of the insert was 250 m.

  On the other hand, in the sample number A1, which is an example of the present invention consisting of four blades with the first to third inserts made of cemented carbide, the insert tool life L (when the cutting speed Vc = 200 m / min) Cutting length) was 800 m, and in the cutting test with the cutting speed Vc as high as 565 m / min, the insert tool life L (cutting length) was 500 m. As described above, the inventive example A1 showed twice the tool life as compared with the sample number A3 of the conventional example.

The reason is considered as follows.
(1) By using a blade end replaceable radius end mill with two cutting edges for the first insert 12, one cutting edge for each of the second and third inserts 13 and 14, and a total of four blades, The cutting load on the blade was dispersed, and the wear resistance of the insert was improved even when high-speed cutting was performed.

  (2) The inner peripheral surface portion of the inclined screw insertion hole of the first insert 12 is closely engaged with the outer peripheral surface portion of the first fixing screw, so that the first insert 12 is in the first mounting seat. No misalignment occurred.

  (3) When the first to third inserts 12, 13, and 14 are mounted and fixed to the first to third mounting seats 4, 5, and 6 of the tool body 2, respectively, the tool body 2 with respect to the axis O direction The lowest point is on the same plane perpendicular to the axis O, and the cutting edge of the first insert has two locations (the lowest points S1 and S2), and the cutting edges of the second and third inserts have one each. There are two locations (the lowest point S3 and the lowest point S4). As a result, when flat machining is performed with the bottom blade as the main component, the occurrence of vibrations associated with the cutting is suppressed, and in particular, displacement of the first insert 12 with respect to the first mounting seat 4 occurs. Probably not.

  On the other hand, Vc = 565 m / min and a high speed of Sample No. A2 which is an example of the present invention in which an insert in which a CBN cutting edge is brazed to a cemented carbide substrate is mounted and Sample No. A4 which is a conventional example The tool life L when cutting is performed is 8000 m for sample number A2 and 4000 m for sample number A4. Sample number A2 according to the present invention has a tool life L twice that of sample number A4 as the conventional example. It was. Furthermore, even when compared with the tool life (Vc = 565 m / min) of A1, which is an example of the present invention in which all of the first to third inserts are made of cemented carbide, a tool life 16 times longer was obtained.

  The reason why the tool life of Sample No. A2, which is an example of the present invention, is remarkably improved as described above is that it has a four-blade equipped with the first to third inserts, and all of the first to third inserts. It can be inferred that the cutting edge is made of CBN excellent in heat resistance and wear resistance, and that, as described above, the four lowest points S1 to S4 are on the same plane. .

  From the experimental results of Experimental Example 2 described above, all of the first to third inserts to be attached to the blade end replaceable radius end mill of the present invention are made of cemented carbide including the cutting edge, or the tool life is further increased. In order to improve, the base body of the first to third inserts is made of cemented carbide, and a CBN bottom blade, a corner R blade, and a cutting edge that becomes an outer peripheral blade are brazed to the cemented carbide base body. It can be said that it is more desirable to make the insert more firmly coupled.

  In the present invention, the first insert is a cemented carbide base having a CBN cutting edge, and the second and third inserts are cemented carbide having a cutting edge made of cemented carbide. Of course, it is possible to improve the tool life even if a high-speed cutting process is carried out even if an insert made of steel is mounted.

DESCRIPTION OF SYMBOLS 1 ... Radius end mill, 2 ... Tool main body, 3 ... Tip part, 3a, 3b ... Tip half body part,
4 ... 1st mounting seat, 5 ... 2nd mounting seat, 6 ... 3rd mounting seat,
7: Insert fitting groove,
7a, 7b ... side wall, 7b ... bottom,
8 ... 1st insert fixing screw hole,
9: First fixing screw,
9c ... Outer peripheral surface part, 9e ... Screw part,
10 ... Screw hole, 11 ... Chip discharge groove,
12 ... first insert,
12a ... Upper surface portion, 12b ... Lower surface portion, 12c, 12d ... Bottom blade,
12e, 12f ... Corner R blade, 12g, 12h ... outer peripheral blade,
12j ... inclined screw insertion hole, 12k ... inner peripheral surface portion subjected to finishing,
12m ... inner peripheral surface part, 12n ... inner peripheral surface part, 12p ... rake face,
13 ... second insert,
13a ... Upper surface portion, 13b ... Lower surface portion, 13c ... Bottom blade, 13e ... Corner R blade,
13g ... outer peripheral blade, 13j ... second screw insertion hole 13j, 13p ... rake face,
14 ... Third insert,
15 ... Second fixing screw, 16 ... Third fixing screw,
O ... axis (rotation center axis),
O ₁ ... the center line in which the insert fitting groove faces in the radial direction of the tool body,
O ₂ ... a center line orthogonal to the straight line O ₁ ,
O ₃ ... direction of the first insert fixing screw hole,
O ₄ ... rotation center axis of the first insert (same as the axis O),
O ₅ ... center line of the first insert,
O ₆ ... a center line orthogonal to the straight line O ₅ of the first insert,
O ₇ ... the center line of the sectional view of the first insert,
O ₈ ... Center line of the screw insertion hole inclined with respect to the straight line O ₇ ,
O ₉ ... a straight line orthogonal to O ₇ ,
R: Direction of rotation of the tool body,
S1, S2, S3, S4 ... bottom point,
G1, G2, G3, G4 ... outermost peripheral point,
r1, r3: radius of curvature of the corner R blade,
θ: angle formed by the straight line O ₂ and the straight line O ₃ ,
δ: The inclination angle of the inclined screw insertion hole of the first insert.

Claims (6)

A blade end replaceable radius end mill that is provided with a mounting seat at the tip of a tool body that rotates about an axis, and that can be detachably mounted with an insert having a cutting blade on the mounting seat,
The mounting seat is
A first insert inserted into the insert fitting groove is formed of a slit-like insert fitting groove formed in a radial direction of the tool body including the axis at the tip of the tool body. A first mounting seat for fixing by screw fastening in which a first fixing screw having an outer peripheral surface portion having a finished outer peripheral surface is inserted into an inclined screw insertion hole formed through the insert;
A mounting seat provided on one and the other half of the tip half formed on the tip of the tool body by the insert fitting groove, and the second insert is detachably fixed by a fixing screw. A second mounting seat, and a third mounting seat for detachably fixing the third insert with a fixing screw,
The first insert, which is flat and has a substantially square shape in plan view, has a cutting edge as a bottom blade formed from the center portion of the tip surface portion toward each side portion, and each of the side portions. The outer peripheral blade formed and a corner R blade connecting the bottom blade and the outer peripheral blade are provided, and the center line of the inclined screw insertion hole is on the rear side in the rotational direction with respect to the direction orthogonal to the flat plate-like plane. as well as the angle θ inclined to, the inner peripheral wall has an inner peripheral surface subjected to finishing,
The second and third inserts having a flat plate shape include a bottom blade formed on the front end surface portion, an outer peripheral blade formed on one side surface portion, the bottom blade and the outer peripheral blade as cutting blades. It has a corner R blade that connects,
The tip half part is a screw hole formed so as to reach the inside of the other tip half part from the outer surface of one tip half part through the axis in the insert fitting groove. A first insert fixing formed in a direction inclined by the angle θ in a direction opposite to a rotation direction of the tool body with respect to a direction orthogonal to a direction in which the insert fitting groove extends in a radial direction of the tool body. With screw holes for
When the first insert is fixed to the first mounting seat by screw fastening with the first fixing screw,
The blade end replaceable radius end mill, wherein the outer peripheral surface portion of the first fixing screw and the inner peripheral surface portion of the inclined screw insertion hole are closely engaged. When the first insert is mounted on the first mounting seat, the second insert is mounted on the second mounting seat, and the third insert is mounted and fixed on the third mounting seat,
The lowest point of the insert mounted on the tool main body with respect to the axial direction is on the same plane perpendicular to the axial line, and the cutting edge of the first insert has two locations, the second and third 2. The blade end replaceable radius end mill according to claim 1, wherein each of the cutting edges of the insert is provided in one place. The first insert is made of cemented carbide;
The bases of the second and third inserts are made of cemented carbide, and the cutting edges of the second and third inserts are made of a hard sintered body including a cubic boron nitride sintered body on the base. The blade end replaceable radius end mill according to claim 1 or 2, wherein the formed cutting blade is joined.   The first insert and the bases of the second and third inserts are made of cemented carbide, and the cutting edges of the first, second and third inserts are cubic on each base. The blade end replaceable type radius end mill according to claim 1 or 2, wherein a cutting edge formed of a hard sintered body including a crystal boron nitride sintered body is joined.   The surface roughness of the outer peripheral surface portion subjected to the finishing process of the first fixing screw is made rougher than the surface roughness of the inner peripheral surface portion subjected to the finishing process of the inclined screw insertion hole of the first insert. The blade end replaceable radius end mill according to claim 1, wherein 2. The blade end replaceable radius end mill according to claim 1, wherein the angle θ is set in a range of 20 ° ≦ θ ≦ 40 °.

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