JP5055869B2 - Throw-away rotary tool - Google Patents

Description

  The present invention relates to a throw-away rotary tool having a throw-away tip, and more particularly to a throw-away rotary tool for repairing a cast hole opened on the surface of a workpiece made of a casting.

As a repair device for repairing a cast hole formed on a flat surface of a casting, there is a repair device described in Japanese Patent Application Laid-Open No. 2004-202562. This repair device is a repair device for repairing a cast hole formed on a flat surface of a casting with a repair tool attached to a milling cutter 30, and is a cylindrical milling cutter 30 that rotates around an axis and moves in a direction perpendicular to the axis. The rake face 13 is 45 to 80 degrees with respect to a plane perpendicular to the side face 12 in the end view and 5 to 10 with respect to the side face 12 in the plan view. At least one repair tool 10 attached to the milling cutter 30 such that a transverse cut surface 17 forming a degree is formed on the side face 12, the rake face 13 is forward in the rotational direction, and the lateral cut face 17 is forward in the moving direction. Become. In this repair device, when the milling cutter 30 is rotated and moved, the rotating rake face 13 and the moving cross-cut face 17 plastically flow the material around the cast hole (see, for example, Patent Document 1). ).
Japanese Patent Laying-Open No. 2004-202562 (FIG. 1)

  However, in the repair device described in Patent Document 1, the rake face 13 of the repair tool 10 functions as a constraining surface that plastically flows the material in the rotation direction of the repair tool, and is 45 ° to 10 ° with respect to the side surface. Therefore, an excessive frictional force acts on the rake face and the casting plane during plastic flow, and the undulation and peeling of the casting plane appear greatly, which may deteriorate the surface roughness.

The present invention has been made in order to solve the above-mentioned problems, repairs a cast hole opened on the surface of a workpiece made of a casting, prevents undulations and swells on the surface of the workpiece, and provides a rough surface. An object of the present invention is to provide a throw-away rotary tool that prevents the deterioration of the length.

  In order to solve the above-described problem, the invention described in claim 1 is a throw-away rotary tool in which at least one throw-away tip is detachably mounted on the outer peripheral portion of the tip of a tool body rotated around a central axis. The throw-away tip includes a secondary cutting edge extending in a direction substantially orthogonal to the central axis, and a chamfered corner continuous to the tool outer peripheral side of the secondary cutting edge, and a cutting angle of the chamfered corner is more than 0 °. Set to a range of 45 ° or less, and the rake face connected to the chamfered corner of the rake face that is connected to the ridge line of the chamfered corner is inclined to the rear side in the tool rotation direction from the rake face toward the cutting edge and A chamfering portion is provided in which an angle formed with a normal line in the rotation direction is set in a range of −20 ° to −75 °, and a ridgeline of the sub cutting edge is disposed in the central axis direction in the chamfering core. Wherein the of was slightly protruding cutting edge equal to or distally.

The invention according to claim 2 is a throw-away rotary tool in which at least one throw-away tip is detachably mounted on the outer peripheral portion of the tip of a tool body rotated around a central axis, wherein the throw-away tip is: A sub-cutting edge extending in a direction substantially perpendicular to the central axis, and a chamfering corner connected to the outer peripheral side of the tool of the sub-cutting edge, wherein a cutting angle of the chamfering corner is greater than 0 ° and not more than 45 °. The range of the rake face connected to the chamfered corner of the rake face connected to the ridge line of the chamfered corner is inclined to the rear side in the tool rotation direction from the rake face toward the cutting edge, and the front side in the tool rotation direction. A chamfered portion formed with a convexly curved surface is provided, and the ridgeline of the auxiliary cutting edge is equal to the leading edge of the chamfered corner in the central axis direction or slightly on the tip side. It is characterized by protruding.

According to the throw-away rotary tool according to claim 1 or 2, an angle formed between a chamfered portion in a chamfered corner and a normal line in a rotation direction of the throw-away rotary tool is −20 ° to −75 °. Or by forming the chamfered portion in the chamfered corner with a convex curved surface toward the front side in the tool rotation direction, the chamfered corner to which a large negative rake angle is given and the workpiece At the contact portion, the generation of cutting resistance including a large frictional force results in a high temperature and high pressure, and a plastic fluidized layer is formed over a certain depth from the surface of the workpiece. Close and repair the casting hole opening on the surface. When the angle formed by the chamfered portion in the chamfered corner and the normal line in the rotation direction is set to a positive side from −20 °, a cutting force including a sufficiently large frictional force is not generated, so that a plastic fluidized bed cannot be formed. If the angle is set to a negative side from −75 °, excessive cutting resistance may act, and the contact portion may become excessively high temperature and high pressure, leading to accelerated cutting edge wear on the chamfered corner and shortening the tool life. There is.
In the contact area between the chamfered corner and the workpiece, the cutting resistance including a large frictional force as described above and chip adhesion occur at high temperature and high pressure due to the cutting resistance. However, the surface roughness of the chamfered corner is deteriorated, but the ridgeline of the secondary cutting edge connected to the inner peripheral side of the chamfered corner is equal to the tip of the chamfered corner in the central axis direction or slightly on the front end side. Since the secondary cutting edge comes into contact with the plastic fluidized bed following the chamfered corner, the swell and flaking are removed to smooth the surface of the workpiece and prevent deterioration of the surface roughness. To do. Therefore, it is possible to repair the casting hole opened on the surface of the work piece, to prevent the surface of the work piece from waviness and flaking, and to prevent the surface roughness from deteriorating.

The cut angle of the chamfered corner affects the depth of the plastic fluidized bed, and if it exceeds 45 °, the plastic fluidized bed cannot be formed over a sufficient depth. For this reason, the plastic fluidized bed is removed by the auxiliary cutting edge, and there is a possibility that the once closed clogging hole opens again on the surface of the workpiece. By setting the cut angle of the chamfered corner to 45 ° or less, the plastic fluidized bed can be formed over a sufficient depth, and the cast hole can be repaired reliably.

Furthermore, the chips generated from the chamfered corner flow to the rake face side that continues from the chamfered portion, and then are discharged to a large space secured on the front side in the tool rotation direction of the rake face. Chip processing performance is realized.

The throw-away rotary tool according to claim 3 is the throw-away rotary tool according to claim 1 or 2, wherein the ridge line is a straight line or a tip substantially perpendicular to the central axis along the ridge line of the sub cutting edge. The arcuate shape is convex to the side, and the length along the ridgeline is set to be larger than the feed per tooth of the throw-away rotary tool.
According to the throw-away rotary tool according to claim 3, along the ridge line of the sub cutting edge, the ridge line is a straight line substantially orthogonal to the central axis line or a circular arc convex to the tip side, and a chamfered corner. Since the secondary cutting edge connected to the inner peripheral side of the blade is longer than the feed per blade of the throw-away rotary tool along the ridgeline of the secondary cutting edge, the surface of the plastic fluidized bed formed by the chamfered corner Make the surface roughness very good. Further, since one throwaway tip is provided with a chamfered corner and a sub-cutting blade positioned slightly on the front end side or slightly at the front end side of the chamfered corner in the central axis direction of the throwaway rotary tool, 1 Two throwaway inserts can repair the cast hole, swell the work surface, improve the surface roughness, and improve the surface roughness.

According to the throw-away rotary tool of the present invention, the casting hole opened on the surface of the work piece is repaired, and the surface of the work piece is prevented from waviness and peeling and the surface roughness is prevented from deteriorating. There is an effect.

Hereinafter, a throw-away cutter according to an embodiment of the throw-away rotary tool of the present invention will be described with reference to FIGS. 1 and 2.
FIG. 1 is a view showing a throw-away cutter according to an embodiment of the present invention. FIG. 1 (a) is a top view and FIG. 1 (b) is a front view. FIG. 2 is an enlarged view of the chamfered portion in FIG. 3 is a view showing a throw-away tip mounted on the throw-away cutter shown in FIG. 1, FIG. 3 (a) is a top view, and FIG. 3 (b) is a view in FIG. 3 (a). It is S1-S1 sectional view taken on the line.

As shown in FIGS. 1 (a) and 1 (b), the present throw-away cutter 1 is provided along the circumferential direction on the outer periphery of the tip of a substantially disk-shaped tool body 2 that is rotated around a central axis CL. It has a configuration in which five throwaway tips 100 are detachably mounted at substantially equal intervals.
Although partially omitted in FIG. 1, five chip pockets are formed along the circumferential direction at the tip outer peripheral portion of the tool body 2, and chip mounting grooves are formed in the tool rotation direction K rear side of the chip pocket. On the opposite end surface of the base end portion side, a mounting surface 3 is formed which is attached to a main shaft of a machine tool (not shown) directly or via an arbor or the like.

As shown in FIG. 3, the throw-away tip 100 mounted in the tip mounting groove is formed on a tip body 10 having a substantially polygonal flat plate shape and one side portion of a polygonal surface which is the upper surface of the tip body 10. And a cutting blade member 20 fixed to the notch step portion 11 by a joining means such as brazing. In the present embodiment, a cutting blade member 20 made of an ultra-high pressure sintered body containing diamond is fixed to a chip body 10 made of a hard material such as cemented carbide or cermet, and a rake face is formed on the upper surface of the cutting blade member 20. 21 and a flank 22 are formed on the side surface, and a cutting edge 23 is formed at a side ridge where the rake face 21 and the flank 22 intersect.

  Each throw-away tip is inserted so that the side surface of the tip body abuts against the bottom surface of the tip mounting groove 5 and the wall surface on the front side in the tool rotation direction K. Further, each tip mounting groove is provided with a wedge member that is screwed into the tool body and movable in the radial direction so as to be adjacent to the rear side in the tool rotation direction K of the throw-away tip 100. By moving the wedge member toward the center in the radial direction, the lower surface of the throw-away tip is fixed by being pressed toward the upper surface. Each throw-away tip 100 is arranged such that the cutting edge 23 protrudes from the outer peripheral surface 2 a and the tip end surface 2 b of the tool body 2. Further, a fine adjustment member 40 that is screwed into the tool main body 2 and can be moved back and forth in the direction of the central axis CL is adjacent to the base end side of the throw-away tip on the wall surface on the base end side of each tip mounting groove 5. It is provided to do. By advancing this fine adjustment member toward the distal end side, each throw-away tip is pushed out toward the distal end side, and the amount of protrusion with respect to the distal end surface 2a of each tool body 2 is adjusted.

The cutting edge 23 includes a sub cutting edge 23a extending in a direction substantially orthogonal to the central axis CL of the tool body 2, a chamfering corner 23b connected to the tool outer peripheral side of the sub cutting edge 23a, and a tool outer peripheral side of the chamfering corner 23b. The main cutting edge 23c is continuous.
In the chamfered corner 23b, an angle between the ridge line and a plane perpendicular to the central axis CL of the tool body 2, that is, a so-called cutting angle β is set in a range exceeding 0 ° and not more than 45 °. Further, a chamfered portion 24 is provided in a region of the rake face 21 continuous with the chamfered corner 23b which is continuous with the ridge line of the chamfered corner 23b. The chamfer 24 is inclined rearward in the tool rotation direction K with respect to the rake face 21 as it goes toward the cutting edge, and when viewed from a direction parallel to the ridge line of the chamfer corner as shown in FIG. The rake angle α1 defined by the angle formed with the normal line P is set in the range of −20 ° to −75 °. The rake angle α1 is defined as negative when the rake face of the chamfer 24 is inclined toward the rear side in the tool rotation direction K toward the cutting edge.
The auxiliary cutting edge 23a has a ridge line that is straight and is formed so as to be equal to the tip of the chamfered corner in the direction of the central axis CL or slightly protrude toward the tip side.
The main cutting edge 23c is formed so that its ridge line is straight and the cutting angle is larger than that of the chamfered corner 23b.
Adapted to the material and cutting conditions of the workpiece in consideration of preventing chipping and chipping and obtaining the desired surface roughness on the ridgelines of the secondary cutting edge 23a and the main cutting edge 23c. The shape of the honing may be provided.

The throw-away cutter 1 having the above-described configuration is face milled on the surface of a workpiece made of a casting by being rotated around the central axis CL and fed in a direction perpendicular to the central axis CL. At this time, in the chamfered corner 23b, the rake angle α1 of the chamfered portion 24 connected to the chamfered corner 23b is set to a large negative value in the range of −20 ° to −75 °. At the contact part, a plastic fluidized layer is formed at a certain depth from the surface of the work piece due to high temperature and pressure due to the generation of cutting resistance including a large frictional force. Close and repair the casting hole opening. The chamfered portion 24 may be provided on a part of the ridgeline of the chamfered corner 23b, but is preferably formed over the entire ridgeline.
At the contact portion between the chamfered corner 23b and the workpiece, cutting resistance including a large frictional force as described above and chip adhesion occur at high temperature and high pressure due to the cutting resistance. The surface of the layer undulates and flutters and the surface roughness is deteriorated, but the ridgeline of the secondary cutting edge 23a connected to the inner peripheral side of the chamfered corner 23b is equal to the forefront of the chamfered corner 23b in the central axis CL direction or Since the secondary cutting edge 23a is in contact with the plastic fluidized bed following the chamfered corner 23b, the surface of the work piece is smoothed to remove the swell and flaking by making the secondary cutting edge 23a come into contact with the plastic fluidized bed. Prevents deterioration of roughness. Therefore, it is possible to repair the casting hole opened on the surface of the workpiece, to prevent the surface of the workpiece from waviness and peeling, and to prevent the surface roughness from deteriorating.

The test results when the cast aluminum alloy AC2C-T6 (JIS H5202) is processed using the present throwaway cutter 1 will be described below. Cutting conditions were cutting speed Vc = 1500 m / min, cutting ap = 0.4 mm, feed 0.2 mm / t, and dry cutting. Table 1 shows the repair status of the cast hole when the rake angle α1 and the cut angle β of the chamfered portion of the chamfered corner 23b of the throwaway tip 100 mounted on the throwaway cutter 1 are varied. FIG. 5 shows the actual surface condition and cross-sectional curve of the workpiece in the test results indicated by * 1 and * 2 in Table 1.
As can be seen from Table 1 and FIG. 5, when the rake angle α1 is set in the range of −20 ° to −75 ° and the cutting angle β is set in the range of 1 ° to 45 °, the surface of the workpiece is The surface roughness was very good without opening the casting cavity. On the other hand, the comparative tool without the chamfered part and the tool with the rake angle and the cutting angle of the chamfered part outside the present invention resulted in the opening of the cast hole. This is because, according to the throw-away cutter according to the present embodiment, the plastic fluidized layer is formed to a sufficient depth so that the cast hole does not open to the surface even if the surface of the plastic fluidized layer is cut and removed by the auxiliary cutting edge 23a. It is to be done.
When the rake angle α1 of the chamfered portion is set to be more positive than −20 °, a cutting resistance including a sufficiently large frictional force is not generated, so that the plastic fluidized layer is not formed and the cast hole cannot be repaired, or After the surface of the plastic fluidized layer is cut and removed by the secondary cutting edge 23a without forming the plastic fluidized layer to a sufficient depth, the casthole opens to the surface, so that the casthole is formed on the surface of the workpiece. Opened and could not be repaired. In addition, when the rake angle α1 of the chamfered portion is set to be more negative than −75 °, excessive cutting resistance acts and the contact portion between the chamfered corner 23b and the workpiece becomes excessively high temperature and high pressure. There was a problem that the cutting edge wear of the chamfered corner 23b was accelerated and the tool life was shortened.
When the cutting angle β of the chamfered corner is larger than 45 °, the plastic fluidized bed is not formed and the cast hole cannot be repaired, or the plastic fluidized layer is not formed over a sufficient depth. After the surface of the plastic fluidized bed was cut off, the cast hole opened to the surface. Further, if the cut angle β of the chamfered corner is not larger than 0 °, the cut in the chamfered corner 23b becomes 0, so that the plastic fluidized layer is not formed and the cast hole cannot be repaired.
As shown in FIG. 2B, the chamfered portion 24 in the chamfered corner 23 b has a width W of 0.03 mm in a direction perpendicular to the ridgeline of the chamfered corner 23 b when viewed from the direction perpendicular to the chamfered portion 24. If it carries out above, the area of the contact part of this chamfering part 24 and a workpiece will be ensured enough, and repair of a cast hole will become reliable. However, if the width W is increased, cutting resistance may increase and chip discharge performance may be deteriorated. Therefore, it is desirable that the thickness is 30% or less, particularly 20% or less of the thickness of the throw-away tip 100.

  When the work piece is made of cast iron or cast steel, the cutting blade member 20 is made of a super high pressure sintered body containing cemented carbide, cermet, ceramics or cubic boron nitride from the viewpoint of the cutting edge life. Either is desirable. When the cutting blade member 20 is any one of cemented carbide, cermet, and ceramics, it is preferable from the viewpoint of ease of manufacture and economy that the chip body 10 and the cutting blade member 20 are integrally formed.

Furthermore, since the rake face 21 that continues from the chamfered portion 24 is inclined rearward with respect to the chamfered portion 24 in the tool rotation direction K, a large space is secured on the front side of the rake face 21 in the tool rotation direction K. Therefore, the chips that come into contact with the chamfered portion 24 flow from the chamfered portion 24 to the rake face 21 side, and then are discharged into the space. Therefore, excellent chip disposal performance without chip clogging is achieved. Realize. When the angle between the rake face 21 and a plane parallel to the center axis CL of the tool body, the so-called rake angle α2 is smaller than −15 °, a sufficient space for discharging chips on the front side in the tool rotation direction K of the rake face 21 is secured. Therefore, chip clogging is likely to occur, and if the rake angle α2 is greater than 45 °, the angle formed by the rake face and the flank face becomes small, so that the strength of the edge of the chamfered corner 23b may be reduced, and chipping or chipping may occur. Therefore, the rake angle α2 of the rake face is preferably set in the range of −15 ° to + 45 °.

  By operating each fine adjustment member 40, the amount of protrusion from the tip end surface 2a of the tool main body of the auxiliary cutting edge 23a in each throw-away tip 100 is almost constant, so that the machining surface is further smoothed and the surface roughness is extremely high. In addition to being improved, the load applied to the cutting edge of each throw-away tip 100 at the time of machining is made uniform, so that the cutting edge life is prolonged and stabilized.

In the present throw-away cutter 1, the ridgeline of the secondary cutting edge 23b is formed in a straight line shape that is substantially perpendicular to the center axis CL of the tool body along the ridgeline or an arc shape that is convex on the tip side, and in the direction along the ridgeline. It is desirable to set the length larger than the feed per blade of the throw-away cutter 1. In that case, the surface of the workpiece becomes good because the secondary cutting edge 23a cuts and smoothes the surface of the plastic fluidized bed formed by the chamfered corner 23b. In a throw-away type cutter to which a plurality of throw-away tips are mounted, the direction length along the secondary cutting edge 23a of the throw-away tip 100 located at the most advanced position is larger than the feed per rotation of the throw-away type cutter. If set, the secondary cutting edge 23a forms a final processed surface, and extremely excellent surface roughness can be obtained.
Since one throwaway tip 100 is provided with a chamfered corner 23b and a sub-cutting edge 23a, the cast hole can be repaired by one throwaway tip 100, and swell and peeling of the processed surface can be prevented. Since it is possible to prevent the surface roughness from being deteriorated, it is very economical, and when a plurality of throw-away tips 100 are provided in the throw-away cutter 1 as in this embodiment, the feed can be increased. This enables extremely efficient processing.

Another embodiment of the chamfer 24 will be described below with reference to FIG. In FIG. 3, the same components as those of the previous embodiment are denoted by the same reference numerals and description thereof is omitted.
4A to 4C are views corresponding to FIG. 2 and showing a chamfered portion according to another embodiment of the present invention. As shown in these drawings, in this embodiment, the chamfered portion 24 is formed as a curved surface that is convex toward the tip side and the front side in the tool rotation direction K. The chamfer 24 shown in FIG. 4A has a circular arc shape that smoothly connects to both the rake face 21 and the flank face 22 in a tangential manner. The chamfered portion 24 illustrated in FIG. 4B has a chord having a rake angle α1 set in a range of −20 ° to −75 °, and has a circular arc shape cut into the rake face 21 and the flank face 22. It is what makes. The chamfered portion 24 shown in FIG. 4C continuously connects a cross-sectional arc that is smoothly connected to the flank 22 in a tangential manner and a cross-sectional arc that has a larger radius of curvature than this arc and is cut out by the rake face 21. It forms a cross-sectional curve shape that is combined. In this curve, the angle formed between the straight line connecting the connection ends of the rake face 21 and the flank face 22 and the normal line P in the tool rotation direction K is set in the range of −20 ° to −75 °. . As described above, the chamfered portion 24 may have a cross-sectional shape of a single arc, a plurality of arcs, or a curved surface including one or more arcs and one or more straight lines. Further, in FIGS. 4A to 4C, the radius of curvature of the cross-section arc constituting the chamfered portion is set to 0.05 mm or more, and the chamfered portion 24 of the chamfered portion 24 is viewed from the direction perpendicular to the chord of the arc. If the width W from the end portion on the rake face 21 side to the end portion on the flank face 22 side is 0.03 mm or more, the area of the contact portion between the chamfered portion 24 and the workpiece is sufficiently secured, and repair of the cast hole is performed. Is certain. However, if the width W is increased, cutting resistance may increase and chip discharge performance may be deteriorated. Therefore, it is desirable that the thickness is 30% or less, particularly 20% or less of the thickness of the throw-away tip 100.

The throw-away cutter described above may be a throw-away tip for finishing without the main cutting edge of the throw-away tip. In that case, since the vibration of the throw-away tip for finishing is suppressed by reducing the load applied to the main cutting edge during processing, the processing accuracy and surface roughness of the processed surface are improved.
When only the above-mentioned throw-away tip for finishing is mounted on the throw-away cutter, the cutting application shared by the main cutting edge cannot be secured, but the machining application is limited to finishing, but at least the rough cutting edge with the main cutting edge is provided. When mounted together with the throw-away tip for processing, it becomes possible to perform roughing and finishing simultaneously. Here, considering that the finishing throw-away tip repairs the cast hole by forming the final machining surface, the finishing throw-away tip slightly protrudes from the roughing throw-away tip toward the tip side. It is desirable to be arranged so as to. At this time, the fine adjustment member 40 is extremely effective for projecting the finishing throw-away tip toward the tip side.

The throw-away rotary tool of the present invention is not limited to the throw-away cutter described above. For example, the throw-away boring cutter used for drilling a hole and the throw-away used for finishing a hole. It can also be applied to a formula reamer.
Further, the throw-away rotary tool of the present invention is not limited to the above-described embodiment, and a plurality of disclosed constituent elements can be appropriately deleted and changed without departing from the gist of the present invention. Moreover, you may combine the component disclosed by each embodiment suitably.

It is a figure which shows the throwaway type cutter which concerns on embodiment of this invention, (a) of FIG. 1 is a top view, (b) of FIG. 1 is a front view. It is A arrow enlarged view of the chamfering part in (a) of FIG. FIG. 4 is a view showing a throw-away tip attached to the throw-away cutter shown in FIG. 1, (a) of FIG. 3 is a top view, and (b) of FIG. 3 is S1-S1 in (a) of FIG. It is line sectional drawing It is a figure corresponding to FIG. 2, and is a figure which shows the chamfering part in other embodiment of this invention. The repair condition and cross-sectional curve of the cast hole in the processing surface of the workpiece processed using the throw-away cutter and the comparative cutter according to the embodiment of the present invention are shown.

Explanation of symbols

1 Throw-away cutter (slow-away rotary tool)
2 Tool body 100 Throw away insert 10 Insert body 20 Cutting edge member 21 Rake face 22 Relief face 23a Sub cutting edge 23b Chamfering corner 23c Main cutting edge 24 Chamfer 30 Wedge member 40 Fine adjustment member α1 Rake angle α2 of chamfer Rake angle β at chamfered corners Cutting angle K at chamfered corners Tool rotation direction

Claims (6)

In a throw-away rotary tool in which at least one throw-away tip is detachably attached to the outer periphery of the tip of a tool body rotated about a central axis, the throw-away tip has a secondary cutting edge and the secondary cutting edge. A chamfered corner continuous with the blade, and a main cutting edge continuous with the chamfered corner, wherein the chamfered corner and the rake face of the throw-away tip are connected via a chamfered portion, and the secondary cutting edge is connected to the central axis. The chamfered corner has a cutting angle greater than 0 ° and not greater than 45 °, and the chamfered portion is a curved surface convex forward in the rotational direction of the tool body. A throwaway rotary tool. The throw-away rotary tool according to claim 1, wherein a cutting angle of the main cutting edge is larger than a cutting angle of the chamfered corner. When the chamfered portion is viewed in a cross section perpendicular to the direction in which the boundary between the chamfered portion and the rake face extends, the cross-sectional shape of the chamfered portion is a curved shape smoothly connected to the rake face and the flank face. The throw-away rotary tool according to claim 1 or 2. When the chamfered portion is viewed in a cross section perpendicular to the direction in which the boundary between the chamfered portion and the rake face extends, the cross-sectional shape of the chamfered portion is an arc shape, and the arc chord and the tool The throw-away rotary tool according to claim 1 or 2, wherein an angle formed by a normal line of the rotation direction of the main body is in a range of -75 ° or more and -20 ° or less. A first curve in which a cross-sectional shape of the chamfered portion smoothly connects to the flank when the chamfered portion is viewed in a cross section perpendicular to a direction in which a boundary between the chamfered portion and the rake face extends; 3. The throwaway rotary tool according to claim 1, wherein the throwaway rotary tool has a shape including a curved line and a second curved line connected to the rake face and having a larger curvature than the first curved line. An imaginary line connecting the first connection portion between the first curve and the flank and the second connection portion between the second curve and the rake face is a normal line in the rotation direction of the tool body. The throw-away rotary tool according to claim 5, wherein an angle formed is in a range of not less than -75 ° and not more than -20.

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