JP2018126842A - Cutting tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cutting tool of which sharpness can be improved while suppressing shortening of a service life thereof.SOLUTION: A cutting tool comprises a cutting blade which contacts a cut object, and is rotated in a prescribed rotation direction D around a rotation axis. The cutting blade includes a rake face 12 which is a face directed to a downstream side in the rotation direction D. The rake face 12 includes a tip face 41 which is provided at a tip 12a of an outer diameter side end part of the rake face 12, and a body blade face 42 which is provided on an inner diameter side with respect to the tip face 41. When viewing with a cross section orthogonal to the rotation axis, each of the tip face 41 and the body blade face 42 is a curve surface. A position PO1, which is a boundary point of the tip face 41 and the body blade face 42, is positioned on an upstream side of the rotation direction D with respect to a tip center line LN which connects the rotation axis and the tip 12a to each other.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a cutting tool. More specifically, the present invention relates to a cutting tool capable of improving sharpness while suppressing a decrease in life.

  A cutting tool such as a drill bit, an end mill, a tap, a reamer, or a milling cutter is attached to a chuck of a cutting apparatus, and cuts a workpiece by being driven by an electric or manual operation by the cutting apparatus. Conventional cutting tools are disclosed, for example, in Patent Documents 1 and 2 below.

  Patent Document 1 listed below discloses a blade-tip-replaceable twist drill in which the cutting head has a twist angle of 20 to 40 degrees, and the tool body to which the cutting head is detachably attached has a smaller twist angle than the cutting head. Has been. Thereby, the sharpness of the cutting edge on the drill center side is improved, and a reduction in rigidity is prevented. The cutting edge at the tip of the cutting head is provided with a rake face that gives a constant rake angle in the range of 20 degrees to 40 degrees, and a chip breaker is formed at the end of the rake face to the twisted groove. Has been.

  Patent Document 2 below discloses a throw-away tip for a spade drill in which a chip breaker is recessed along the left and right tip cutting edges, and an appropriate number of nicks are provided on the left and right tip cutting edges. In this throw-away tip, a concave portion is continuously provided from the chip breaker to the outer peripheral portion of each rake face, and the concave portion is continuously provided from the chip breaker along the cutting edge to the outer peripheral portion of the rake face. Is provided.

JP 2003-136319 A JP-A-10-109210

  Usually, in a cutting tool that is rotationally driven, a cutting edge portion that comes into contact with a workpiece is formed in a groove on the outer peripheral surface of the cutting tool. When viewed in a cross section cut by a plane including the rotation axis, the rake face of the cutting edge portion includes a cutting edge provided at the outer diameter side end portion. Since the cutting edge is the portion where the torque applied to the workpiece is the largest, the load received from the workpiece is large and has a property of being easily chipped.

  Conventionally, for the purpose of suppressing chipping of the cutting edge of the cutting tool and improving the life, the cutting edge has been chamfered so as to be a straight surface when viewed in a cross section cut by a plane including a rotation axis. As a result, when viewed in a cross section orthogonal to the rotation axis, the portion of the rake face that is on the inner diameter side of the cutting edge protrudes downstream of the cutting edge in the rotation direction of the cutting tool. For this reason, when cutting using a cutting tool, the cutting edge does not hit at a sharp angle with respect to the workpiece, resulting in a decrease in sharpness.

  This invention is for solving the said subject, The objective is to provide the cutting tool which can improve a sharpness, suppressing the fall of a lifetime.

  A cutting tool according to one aspect of the present invention is a cutting tool that includes a cutting edge portion that comes into contact with an object to be cut and is rotated in a predetermined rotation direction about a rotation axis. Including a rake face that is a surface facing the downstream side, the rake face includes a blade edge surface provided at an outer diameter side end portion of the rake face, and a main body blade face provided on an inner diameter side of the blade edge surface, When viewed in a cross section orthogonal to the rotation axis, each of the blade edge surface and the main body blade surface is a curved surface, and when viewed in a cross section orthogonal to the rotation axis, the boundary point between the blade edge surface and the main body blade surface is rotated. It is located upstream of the cutting edge center line connecting the shaft and the outer diameter side end of the rake face in the rotational direction.

In the above cutting tool, preferably, the length H along the edge center line from the intersection position of the rake face and the edge center line to the outer diameter side end of the rake face and the radius RA of the cutting tool are 0.55. RA ≦ H ≦ 0.65RA.

  In the cutting tool, preferably, the length T of the cutting edge surface along the cutting edge center line is greater than 0 and 1.0 mm or less.

  Preferably, in the above cutting tool, each of the blade edge surface and the main body blade surface has an arc shape when viewed in a cross section orthogonal to the rotation axis, and the curvature radius R1 of the blade edge surface and the curvature radius R2 of the main body blade surface. And 0.9R2 ≦ R1 ≦ 1.1R2.

  In the cutting tool, preferably, the cutting edge portion is formed in a spiral shape around the rotation axis.

  Preferably, the cutting tool includes a plurality of cutting blade portions, and each of the plurality of cutting blade portions is disposed at equal intervals with respect to the rotation axis when viewed in a cross section orthogonal to the rotation axis.

  Preferably, the cutting tool includes a plurality of cutting blade portions, and each of the plurality of cutting blade portions is arranged at unequal intervals with respect to the rotation axis when viewed in a cross section orthogonal to the rotation axis.

  In the above cutting tool, the rake face is preferably covered with a coating layer.

  ADVANTAGE OF THE INVENTION According to this invention, the cutting tool which can improve a sharpness can be provided, suppressing the fall of a lifetime.

It is a perspective view which shows typically the structure of the external appearance of the cutting tool 1 in one embodiment of this invention. It is a front view which shows the structure of the cutting tool in one Embodiment of this invention when it sees from the direction shown by the arrow W in FIG. 1 (when it sees from the front end side of the cutting tool 1). FIG. 3 is a cross-sectional view taken along the line III-III in FIG. 1 and is a cross-sectional view taken along a plane orthogonal to the rotation axis AX. It is an enlarged view of the A section in FIG. It is sectional drawing which shows one structure of the rake face 112 in the conventional cutting tool. It is sectional drawing which shows the other structure of the rake face 112 in the conventional cutting tool. In cutting tool 1 in one embodiment of the present invention, it is a sectional view showing typically signs that blade edge surface 41 contacts a work piece. In one Example of this invention, it is a figure which shows the time change of the torque required for cutting, and a thrust load.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  [Composition of cutting tool]

  FIG. 1 is a perspective view schematically showing an external configuration of a cutting tool 1 according to an embodiment of the present invention.

  Referring to FIG. 1, a cutting tool 1 according to the present embodiment is attached to a chuck of a cutting device (not shown), and is rotated by an electric or manual operation by a cutting device. It is to cut. The cutting tool 1 is rotationally driven in the rotation direction D around the rotation axis AX when performing the cutting process.

  The cutting tool 1 is a drill bit, for example, and includes a blade portion 10 and a shank 50. The blade portion 10 is provided on the distal end side of the cutting tool 1 and is a portion that performs cutting on a workpiece. The shank 50 is provided on the rear end side of the cutting tool 1 and is a part attached to the chuck when the cutting tool 1 is used.

  The blade portion 10 includes cutting blade portions 11 and 21. The cutting edge portions 11 and 21 are portions that come into contact with the workpiece, and are formed in a spiral shape around the rotation axis AX. The cutting edge portions 11 and 21 are point symmetric with respect to the rotation axis AX. The cutting edges 11 and 21 are separated by grooves 31 and 32, respectively. Each of the cutting edge portions 11 and 21 is defined by grooves 31 and 32.

  The grooves 31 and 32 have the same shape and are formed in a spiral shape along the rotation axis AX. Each of the grooves 31 and 32 is point-symmetric with respect to the rotation axis AX.

  The cutting blade portions 11 and 21 have the same shape and are formed in a spiral shape along the rotation axis AX. Each of the cutting blade portions 11 and 21 is point-symmetric with respect to the rotation axis AX.

  2 is a front view showing the configuration of the cutting tool according to the embodiment of the present invention when viewed from the direction indicated by the arrow W in FIG. 1 (when viewed from the front end side of the cutting tool 1). FIG. 3 is a cross-sectional view taken along line III-III in FIG. 1 and is a cross-sectional view taken along a plane orthogonal to the rotation axis AX.

  1 to 3, the cutting edge portion 11 includes a rake surface 12, a margin portion 13 a, a clearance surface 13 b, a margin portion 13 c, a wall surface 14, and axial end surfaces 15 to 17. Yes. The rake face 12 is a face in the groove 31 and faces the downstream side in the rotation direction D. The rake face 12 is a face that acts on the workpiece, and has a cutting edge 12a at an outer diameter side end. The margin portion 13a is adjacent to the rake face 12. Each of the margin part 13a, the flank 13b, and the margin part 13c is provided in this order toward the upstream side in the rotation direction D, and constitutes a cylindrical outer peripheral surface of the cutting tool 1. Each of the margin portions 13a and 13c protrudes in the outer diameter direction from the flank 13b. The wall surface 14 is a surface in the groove 32 and faces the upstream side in the rotation direction D. The wall surface 14 is adjacent to the margin portion 13 c and continues to the rake face 22 of the cutting edge portion 21 in the groove 32.

  The axial end surfaces 15 to 17 are surfaces on the tip side of the cutting tool 1. The axial end face 15 is located on the downstream side in the rotational direction D and is adjacent to the rake face 12. The axial end surface 17 is located on the upstream side in the rotation direction D and is adjacent to the wall surface 14. The axial end face 16 is located between the axial end face 15 and the axial end face 17. The area of the axial end face 16 is larger than the area of each of the axial end faces 15 and 17.

  The cutting edge portion 21 includes a rake surface 22, a margin portion 23a, a clearance surface 23b, a margin portion 23c, a wall surface 24, and axial end surfaces 25 to 27. The rake face 22 is a face in the groove 32 and faces the downstream side in the rotation direction D. The rake face 22 is a face that acts on the workpiece, and has a cutting edge 22a at the outer diameter side end. The margin part 23 a is adjacent to the rake face 22. Each of the margin part 23a, the flank 23b, and the margin part 23c is provided in this order toward the upstream side in the rotation direction D, and constitutes a cylindrical outer peripheral surface of the cutting tool 1. Each of the margin portions 23a and 23c protrudes in the outer diameter direction from the flank 23b. The wall surface 24 is a surface in the groove 31 and faces the upstream side in the rotation direction D. The wall surface 24 is adjacent to the margin portion 23 c and continues to the rake face 12 of the cutting edge portion 11 in the groove 31.

  The axial end surfaces 25 to 27 are surfaces on the distal end side of the cutting tool 1. The axial end face 25 is located on the downstream side in the rotational direction D and is adjacent to the rake face 22. The axial end surface 27 is located on the upstream side in the rotation direction D and is adjacent to the wall surface 24. The axial end face 26 is located between the axial end face 25 and the axial end face 27. The area of the axial end face 26 is larger than the area of each of the axial end faces 25 and 27.

  The axial end faces 15 to 17 and 25 to 27 form a cone shape centering on the vertex TP which is the cutting edge of the cutting tool 1.

  An oil hole may be formed in each of the axial end faces 16 and 26 (or the axial end faces 17 and 27). Each of the boundary line between the axial end surface 15 and the margin portion 13a and the boundary line between the axial end surface 25 and the margin portion 23a may be chamfered in a planar shape or a curved surface shape. The margin portions 13c and 23c may not be provided.

  The rake faces 12 and 22 may be coated with a coating layer. This coating layer is made of, for example, TiN or TiCN, and may be formed using a PVD (Physical Vapor Deposition) method, a CVD (Chemical Vapor Deposition) method, or the like. Further, in addition to the rake faces 12 and 22, the axial end faces 15 and 25 and the margin portions 13a and 23a may be covered with this coating layer, or the entire blade portion 10 is covered with this coating layer. Also good.

  Hereinafter, the configuration of the cutting edge portion 11 will be described in detail. About the structure of the cutting blade part 21, since it is the same as the structure of the cutting blade part 11, the description is not repeated.

  FIG. 4 is an enlarged view of a portion A in FIG.

  Referring to FIGS. 3 and 4, rake surface 12 includes a blade edge surface 41 and a main body blade surface 42. The cutting edge surface 41 is provided on the cutting edge 12a of the rake face 12, and is adjacent to the margin portion 13a (the outer peripheral surface of the cutting tool 1). The main body blade surface 42 is adjacent to the blade edge surface 41 and is provided on the inner diameter side of the blade edge surface 41. The position PO1 is a boundary point between the blade edge surface 41 and the main body blade surface. The cutting edge surface 41 has an arcuate curved surface when viewed in the cross section of FIG. 4, and has a radius of curvature R1. The main body blade surface 42 has an arcuate curved surface when viewed in the cross section of FIG. 4 and has a curvature radius R2. The curvature radius R1 of the cutting edge surface 41 is 0.9 times or more as large as the curvature radius R2 of the main body cutting surface 42, and 1.1 times or less than the curvature radius R2 of the main body cutting surface 42 (0). .9R2 ≦ R1 ≦ 1.1R2) is preferable. Each of curvature radii R1 and R2 is 2.1 mm or more and 2.5 mm or less, for example.

  In particular, when the relationship between the curvature radius R1 and the curvature radius R2 is set as described above, the cutting edge surface 41 and the main body cutting surface 42 can be formed using the same grindstone, which simplifies the manufacturing process. Can be planned.

  A straight line connecting the rotation axis AX and the blade edge 12a (the outer diameter side end of the rake face 12) is defined as a blade edge center line LN. The cutting edge center line LN also passes through the cutting edge 22a (the outer diameter side end of the rake face 22). The cutting edge center line LN is a center line that exerts a force on the workpiece when the cutting tool 1 cuts the workpiece.

  Thereafter, the downstream side in the rotation direction D with respect to the cutting edge center line LN (the right side in FIG. 4 in the cutting edge center line LN in the vicinity of the rake face 12) is the negative (negative) side, and the upstream side in the rotation direction D (in the vicinity of the rake face 12). The blade edge center line LN on the left side in FIG. 4 may be referred to as a positive (positive) side.

  A portion of the rake face 12 on the innermost diameter side (a portion adjacent to the wall surface 24) exists on the negative side. Since the rake face 12 is recessed toward the upstream side in the rotational direction D, the rake face 12 and the cutting edge center line LN intersect at the position PO2. A portion from the position PO2 to the blade edge 12a (a portion including the position PO1 and the entire blade edge surface 41) on the rake face 12 exists on the positive side.

The ratio (rake ratio) of the length (width) H of the portion from the position PO2 to the cutting edge 12a on the rake face 12 along the cutting edge center line LN to the radius RA of the cutting tool 1 is not less than 55% and not more than 65% ( 0 .55 RA ≦ H ≦ 0.65 RA). When the length H is in the above range, the curvature of the main body blade surface 42 becomes steep (the radius of curvature R2 of the main body blade surface 42 becomes smaller), so that the blade edge 12a further protrudes downstream in the rotational direction R. It becomes the composition which did. In the present embodiment, chipping of the blade edge 12a can be prevented even with such a configuration.

  The length (width) T of the cutting edge surface 41 along the cutting edge center line LN is greater than 0 and 1.0 mm or less (0 <T ≦ 1.0 mm), preferably 0.2 mm, regardless of the radius RA of the cutting tool 1. It may be set within a certain range of 0.3 mm or less (0.2 mm ≦ T ≦ 0.3 mm).

  [Effect of the embodiment]

  Next, the effect of the cutting tool 1 in this Embodiment is demonstrated.

  5 and 6 are cross-sectional views showing the configuration of the rake face 112 in the conventional cutting tool. 5 and 6 are cross-sectional views of a portion corresponding to FIG. 4 on the rake face 112.

  Referring to FIG. 5, the rake face 112 in the conventional cutting tool includes a cutting edge surface 141 provided on the cutting edge 112 a at the outer diameter side end, and a main body cutting edge surface 142 provided on the inner diameter side of the cutting edge surface 141. Is included. The blade edge 112a is chamfered for the purpose of suppressing chipping of the blade edge 112a and improving the life. The blade edge surface 141 has a linear cross-sectional shape, and is recessed from the position PO101, which is a boundary point between the blade edge surface 141 and the main body blade surface 142, toward the blade edge 112a on the positive side. As a result, the portion near the position PO101 on the rake face 112 protrudes to the negative side.

  In the configuration of the cutting tool shown in FIG. 5, the rake angle α is an obtuse angle, so that the cutting edge 112a does not hit the workpiece at a sharp angle when cutting the workpiece. For this reason, it is difficult to apply force to the workpiece, and the sharpness is poor.

  Referring to FIG. 6, on the other hand, at the rake face 112 of this cutting tool, the cutting edge 112a is chamfered at right angles to the outer peripheral surface of the cutting tool. The cutting edge surface 141 has a linear cross-sectional shape and extends along the cutting edge center line LN.

  In the configuration of the cutting tool shown in FIG. 6, the rake angle α is a right angle. Therefore, when cutting the workpiece, a force is more easily applied to the workpiece than in the cutting tool shown in FIG. 5. On the other hand, since the cutting edge surface 141 extends along the cutting edge center line LN, when the workpiece is cut, the entire cutting edge surface 141 receives a load uniformly from the workpiece. As a result, the load received by the cutting edge 112a is increased, and the cutting edge 112a is easily chipped.

  FIG. 7 is a cross-sectional view schematically showing how the cutting edge surface 41 abuts on the workpiece in the cutting tool 1 according to the embodiment of the present invention.

  Referring to FIG. 7, on the other hand, in cutting tool 1 of the present embodiment, when viewed in a cross section orthogonal to rotation axis AX, cutting edge surface 41 is a curved surface and position PO1 is located on the positive side. . As a result, the rake angle α becomes an acute angle, and the cutting edge 12a hits the workpiece at a sharp angle when the workpiece is cut. As a result, it becomes easy to apply force to the workpiece, and the sharpness can be improved.

In addition, in conventional cutting tools, the cutting edge ridge line is subjected to cutting edge processing to prevent chipping, so that the sharpness is reduced, and the thrust required when cutting the workpiece using the cutting tool is reduced. The direction force was increasing. For this reason, when a through-hole was formed in the workpiece using a cutting tool, burrs were generated on the through-hole side of the cutting tool in the through-hole. According to the cutting tool of the present embodiment, the sharpness is improved, so that when a through hole is formed in the workpiece, burrs generated on the through side of the cutting tool in the through hole can be suppressed.

  Further, since the cutting edge surface 41 is a curved surface, when cutting the workpiece, the cutting edge surface 41 gradually comes into contact with the workpiece from the cutting edge 12a toward the position PO1, as indicated by an arrow AR. The load that the cutting edge 12a receives from the workpiece is distributed over the entire cutting edge surface 41 along the direction indicated by the arrow AR. As a result, the cutting edge 12a is less likely to be chipped, and a reduction in the life of the cutting tool 1 can be suppressed.

  [Example]

  Subsequently, an embodiment of the present invention will be described.

  The inventor of the present application performed cutting (drilling) on the workpiece using the cutting tools of the present invention and the comparative examples, and measured the force required for the cutting. As the workpiece, 64 titanium having a thickness of 6 mm (an alloy made of 6% by mass of aluminum, 4% by mass of vanadium, and the remaining titanium) was used.

  FIG. 8 is a diagram showing temporal changes in torque and thrust load required for cutting in one embodiment of the present invention. FIG. 8A shows the result when the conventional cutting tool shown in FIG. 5 is used. FIG.8 (b) is a result at the time of using the cutting tool 1 in this Embodiment shown in FIGS. 1-4.

  Referring to FIG. 8, when cutting is performed using the conventional cutting tool shown in FIG. 5 (FIG. 8 (a)), a maximum torque of 182.2 Ncm (force for rotating the cutting tool) is applied. A thrust load of 853 N on average (load for pressing the cutting tool against the workpiece) was required. On the other hand, when cutting is performed using the cutting tool 1 according to the present embodiment (FIG. 8B), a maximum torque of 159.8 Ncm is required, and an average thrust load of 189 N is required. .

  From these results, it was found that according to the present embodiment, the force required for the cutting process can be reduced, and the sharpness of the cutting tool is improved.

  [Others]

  In the above-described embodiment, the case where the cutting tool is a drill bit has been described. However, the cutting tool of the present invention may be an end mill, a tap, a reamer, or a milling cutter in addition to the drill bit.

  The number of cutting edge portions and grooves is arbitrary. When there are a plurality of cutting blade portions, each of the plurality of cutting blade portions may be arranged at equal intervals with respect to the rotation axis or arranged at unequal intervals when viewed in a cross section orthogonal to the rotation axis. May be.

  The cutting blade portion 21 may have a configuration different from that of the cutting blade portion 11. The cutting blade portion 21 and the cutting blade portion 11 may be asymmetric.

  The cutting edge surface 41 may be provided on the entire rake face 12 along the rotation axis AX as described above, or may be provided only on a part of the rake face 12. The cutting edge surface 41 may be provided, for example, only on the rake face 12 in the vicinity of the axial end face 15, and is not provided on the cutting edge part on the tip side in the two-stage drill, but on the rear end side (shank part side). It may be provided only in the cutting blade part.

  The above-described embodiments and examples are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

DESCRIPTION OF SYMBOLS 1 Cutting tool 10 Blade part 11,21 Cutting edge part 12,22,112 Rake face 12a, 22a, 112a Cutting edge 13a, 13c, 23a, 23c Margin part 13b, 23b Flank 14,24 Wall 15 ~ 17,25-27 Axial direction end face 31, 32 Groove 41, 141 Cutting edge face 42, 142 Body cutting edge 50 Shank AX Rotating axis D Cutting tool rotation direction LN Cutting edge center line PO1, PO101 Boundary point between cutting edge and main cutting edge PO2 Rake face Intersection with cutting edge center line TP Vertex that is the cutting edge of cutting tool α Rake angle

In the above cutting tool, preferably, the length H along the cutting edge center line from the intersection position of the rake face and the cutting edge center line to the outer diameter side end of the rake face and the radius RA of the cutting tool are 0.55 RA. ≦ H ≦ 0.65RA.

The ratio (rake ratio) of the length (width) H of the portion from the position PO2 to the cutting edge 12a on the rake face 12 along the cutting edge center line LN to the radius RA of the cutting tool 1 is from 55% to 65% (0 .55RA ≦ H ≦ 0.65RA). When the length H is in the above range, the curvature of the main body blade surface 42 becomes steep (the radius of curvature R2 of the main body blade surface 42 becomes smaller), so that the blade edge 12a further protrudes downstream in the rotational direction R. It becomes the composition which did. In the present embodiment, chipping of the blade edge 12a can be prevented even with such a configuration.

In addition, in conventional cutting tools, the cutting edge ridge line is subjected to cutting edge processing to prevent chipping, so that the sharpness is reduced, and the thrust required when cutting the workpiece using the cutting tool is reduced. The direction force was increasing. For this reason, when a through-hole was formed in the workpiece using a cutting tool, burrs were generated on the through-hole side of the cutting tool in the through-hole. According to the cutting tool of the present embodiment, the sharpness is improved, so that when a through hole is formed in the workpiece, burrs generated on the through side of the cutting tool in the through hole can be suppressed.

Claims (8)

A cutting tool that includes a cutting edge portion that comes into contact with a workpiece and is rotated in a predetermined rotation direction about a rotation axis,
The cutting edge portion includes a rake face that is a face facing the downstream side in the rotation direction,
The rake face is
A cutting edge surface provided at an outer diameter side end of the rake face;
A main body blade surface provided on the inner diameter side of the blade edge surface,
When viewed in a cross section orthogonal to the rotation axis, each of the blade edge surface and the main body blade surface is a curved surface,
When viewed in a cross section orthogonal to the rotation axis, the boundary point between the blade edge surface and the main body blade surface is more than the blade edge center line connecting the rotation axis and the outer diameter side end of the rake face. A cutting tool located upstream in the direction. The length H along the cutting edge center line from the crossing position of the rake face and the cutting edge center line to the outer diameter side end of the rake face and the radius RA of the cutting tool are 0.55 RA ≦ The cutting tool according to claim 1, having a relationship of H ≦ 0.65 RA.   The cutting tool according to claim 1 or 2, wherein a length T of the cutting edge surface along the cutting edge center line is greater than 0 and 1.0 mm or less. When viewed in a cross section orthogonal to the rotation axis, each of the blade edge surface and the main body blade surface has an arc shape,
The cutting tool according to any one of claims 1 to 3, wherein a curvature radius R1 of the blade edge surface and a curvature radius R2 of the main body blade surface have a relationship of 0.9R2 ≦ R1 ≦ 1.1R2.   The cutting tool according to claim 1, wherein the cutting edge portion is formed in a spiral shape with the rotation axis as a center. The cutting blade part is plural,
The cutting tool according to any one of claims 1 to 5, wherein each of the plurality of cutting blade portions is disposed at equal intervals with respect to the rotation axis when viewed in a cross section orthogonal to the rotation axis. The cutting blade part is plural,
The cutting tool according to any one of claims 1 to 5, wherein each of the plurality of cutting blade portions is disposed at unequal intervals with respect to the rotation axis when viewed in a cross section orthogonal to the rotation axis. .   The cutting tool according to claim 1, wherein the rake face is covered with a coating layer.

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