JP7280636B2 - Cutting tools - Google Patents

Description

The present invention relates to cutting tools. 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 device, and is rotated electrically or manually by the cutting device to cut an object to be cut. Conventional cutting tools are disclosed, for example, in Patent Documents 1 and 2 listed below.

Patent Document 1 below discloses an indexable twist drill in which the torsion angle of the cutting head is 20 degrees to 40 degrees, and the torsion angle of the tool body to which the cutting head is detachably attached is smaller than the torsion angle of the cutting head. It is As a result, sharpness of the cutting edge on the center side of the drill is improved, and reduction in rigidity is prevented. The cutting edge at the tip of the cutting head is provided with a rake face that provides a constant rake angle in the range of 20 degrees to 40 degrees, and a chip breaker is formed at the edge of the rake face that rises to the helical groove. It is

Patent Document 2 listed below discloses a throw-away insert for a spade drill in which chip breakers are 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 indexable insert, a concave portion is provided continuously from the chip breaker on the outer peripheral portion of each rake face, and a concave portion is provided on the outer peripheral portion of the rake face continuously from the chip breaker along the cutting edge. is provided.

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

Generally, in a cutting tool that is driven to rotate, a cutting edge that contacts an object to be cut is formed in a groove on the outer peripheral surface of the cutting tool. The rake face of the cutting edge portion includes a cutting edge provided at the outer diameter side end portion when viewed in a cross section cut along a plane including the rotation axis. Since the cutting edge is the part where the greatest torque is applied to the object to be cut, it is subject to a large load from the object to be cut and is prone to chipping.

Conventionally, for the purpose of suppressing chipping of the cutting edge of a cutting tool and improving the life of the cutting tool, the cutting edge has been chamfered so that a cross section cut along a plane containing the rotation axis has a straight surface. As a result, when viewed in a cross section orthogonal to the rotation axis, the portion of the rake face located on the inner diameter side of the cutting edge protruded downstream of the cutting tool in the rotational direction of the cutting tool. For this reason, when the cutting tool is used for cutting, the cutting edge does not hit the object to be cut at a sharp angle, resulting in a decrease in sharpness.

SUMMARY OF THE INVENTION An object of the present invention is to provide a cutting tool capable of improving sharpness while suppressing a decrease in service life.

A cutting tool according to one aspect of the present invention includes a cutting edge that contacts an object to be cut and that is spirally formed around a rotation axis, and rotates in a predetermined rotation direction around the rotation axis. A cutting tool that is rotated, wherein the cutting edge includes a rotationally downstream facing surface within a groove helically formed about an axis of rotation, the downstream facing surface When viewed in a cross section perpendicular to the rotation axis, the cutting edge surface provided on the outer diameter side end of the surface facing and the body cutting surface provided on the inner diameter side of the cutting edge surface, the cutting edge surface and Each of the blade faces of the main body is a curved surface that is concave toward the downstream side in the rotation direction, and when viewed in a cross section orthogonal to the rotation axis, the inner diameter side end of the blade tip surface and the outer diameter side end of the main blade face is located on the upstream side in the rotational direction of the cutting edge center line connecting the rotation axis and the outer diameter side end of the surface facing downstream, and the length T of the cutting edge surface along the cutting edge center line is , 0.2 mm or more and 1.0 mm or less. The curvature radius R2 of the blade surface has a relationship of 0.9R2≤R1≤1.1R2.

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

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

Preferably, in the above cutting tool, the surface facing the downstream side is covered with a coating layer.

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

BRIEF DESCRIPTION OF THE DRAWINGS 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. 1 is a front view showing the configuration of a cutting tool according to one embodiment of the present invention when viewed from the direction indicated by an arrow W in FIG. 1 (when viewed from the tip side of the cutting tool 1). FIG. FIG. 2 is a cross-sectional view taken along line III-III in FIG. 1 and taken along a plane perpendicular to the rotation axis AX; 4 is an enlarged view of part A in FIG. 3; FIG. FIG. 11 is a cross-sectional view showing one configuration of a rake face 112 in a conventional cutting tool; FIG. 11 is a cross-sectional view showing another configuration of the rake face 112 in the conventional cutting tool; Fig. 2 is a cross-sectional view schematically showing how a cutting edge surface 41 of the cutting tool 1 according to one embodiment of the present invention abuts against a workpiece. FIG. 4 is a diagram showing temporal changes in torque and thrust load required for cutting in one example of the present invention.

An embodiment of the present invention will be described below with reference to the drawings.

[Configuration of cutting tool]

FIG. 1 is a perspective view schematically showing the external configuration of a cutting tool 1 according to one 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 rotated electrically or manually by the cutting device to cut an object to be cut. It is for cutting. The cutting tool 1 is rotationally driven in the rotational direction D around the rotational axis AX when cutting.

The cutting tool 1 has a cutting edge 10 and a shank 50 . The blade portion 10 is provided on the tip end side of the cutting tool 1, and is a portion that performs cutting on an object to be cut. The shank 50 is provided on the rear end side of the cutting tool 1 and is a portion that is attached to the chuck when the cutting tool 1 is used.

Blade 10 includes cutting edges 11 and 21 . The cutting edge portions 11 and 21 are portions that come into contact with an object to be cut, and are spirally formed around the rotation axis AX. The cutting edge portions 11 and 21 are point symmetrical with respect to the rotation axis AX. Cutting edges 11 and 21 are separated by grooves 31 and 32, respectively. Each of the cutting edges 11 and 21 is defined by grooves 31 and 32 .

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

The cutting edge portions 11 and 21 have the same shape and are spirally formed along the rotation axis AX. Each of the cutting edge portions 11 and 21 is symmetrical with respect to the rotation axis AX.

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

1 to 3, the cutting edge portion 11 includes a rake face 12, a margin portion 13a, a flank face 13b, a margin portion 13c, a wall surface 14, and axial end faces 15 to 17. there is The rake face 12 is a face within the groove 31 and faces the downstream side in the rotational direction D. As shown in FIG. The rake face 12 is a face that acts on the workpiece, and has a cutting edge 12a on the outer diameter side end. The margin portion 13 a is adjacent to the rake face 12 . Each of the margin portion 13a, the flank 13b, and the margin portion 13c is provided in this order toward the upstream side in the rotational direction D, and constitutes the cylindrical outer peripheral surface of the cutting tool 1. As shown in FIG. Each of margin portions 13a and 13c protrudes radially outward beyond flank 13b. The wall surface 14 is a surface within the groove 32 and faces the upstream side in the rotational direction D. As shown in FIG. The wall surface 14 is adjacent to the margin portion 13 c and continues to the rake surface 22 of the cutting edge portion 21 within the groove 32 .

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

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

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

Axial end faces 15 to 17 and 25 to 27 form a pyramidal shape centering on apex TP, which is the tip of cutting tool 1 .

An oil hole may be formed in each of axial end faces 16 and 26 (or axial end faces 17 and 27). Each of the boundary line between the axial end face 15 and the margin portion 13a and the boundary line between the axial end face 25 and the margin portion 23a may be chamfered in a flat or curved shape. 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. In addition to the rake faces 12 and 22, the axial end faces 15 and 25 and the margin portions 13a and 23a may also be covered with this coating layer, or the entire blade portion 10 may be covered with this coating layer. good too.

Hereinafter, the configuration of the cutting edge portion 11 will be described in detail. Since the configuration of the cutting edge portion 21 is the same as the configuration of the cutting edge portion 11, the description thereof will not be repeated.

FIG. 4 is an enlarged view of part A in FIG.

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

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

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

Hereinafter, with reference to the cutting edge center line LN, the downstream side in the rotation direction D (the right side in FIG. 4 at the cutting edge center line LN near the rake face 12) is the negative side, and the upstream side in the rotation direction D (near the rake face 12) The left side of the cutting edge centerline LN in FIG. 4) is sometimes referred to as the positive side.

The innermost portion of the rake face 12 (the portion adjacent to the wall surface 24) is 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 of the rake face 12 from the position PO2 to the cutting edge 12a (a portion including the position PO1 and the entire cutting edge surface 41) is on the positive side.

The ratio (rake ratio) of the length (width) H of the portion of the rake face 12 from the position PO2 to the cutting edge 12a along the cutting edge center line LN to the radius RA of the cutting tool 1 is 55% or more and 65% or less (0 .55RA≤H≤0.65RA). When the length H is within the above range, the degree of curvature of the body blade surface 42 becomes steeper (the radius of curvature R2 of the body blade surface 42 becomes smaller), so that the cutting edge 12a further protrudes downstream in the rotational direction R. configuration. In the present embodiment, chipping of the cutting 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).

[Effects of Embodiment]

Next, the effect of the cutting tool 1 in this embodiment will be described.

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

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

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

Referring to FIG. 6, on the other hand, on the rake face 112 of this cutting tool, the cutting edge 112a is chamfered at right angles to the outer peripheral face 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, since the rake angle α is a right angle, when cutting an object to be cut, force is more likely to be applied to the object to be cut than in the case of the cutting tool shown in FIG. On the other hand, since the cutting edge surface 141 extends along the cutting edge centerline LN, the entire cutting edge surface 141 receives a uniform load from the workpiece when cutting the workpiece. As a result, the load applied to the cutting edge 112a increases, and the cutting edge 112a tends to chip.

FIG. 7 is a cross-sectional view schematically showing how the cutting edge surface 41 of the cutting tool 1 according to one embodiment of the present invention comes into contact with the object to be cut.

Referring to FIG. 7, on the other hand, in cutting tool 1 of the present embodiment, cutting edge surface 41 is a curved surface when viewed in a cross section perpendicular to rotation axis AX, 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 an acute angle when cutting the workpiece. As a result, it becomes easier to apply force to the object to be cut, and sharpness can be improved.

In addition, in conventional cutting tools, the cutting edge is treated to prevent chipping at the ridgeline of the cutting edge, so the sharpness is reduced, and the thrust required when cutting the workpiece using the cutting tool is reduced. Directional force was increasing. Therefore, when a through-hole is formed in an object to be cut using a cutting tool, burrs are generated on the through-hole side of the cutting tool. According to the cutting tool of the present embodiment, sharpness is improved, so that when a through-hole is formed in an object to be cut, it is possible to suppress the occurrence of burrs in the through-hole on the cutting tool exit side.

Further, since the blade tip surface 41 is a curved surface, when cutting the object to be cut, the blade tip surface 41 gradually contacts the object to be cut from the blade tip 12a toward the position PO1 as indicated by the 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]

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

The inventors of the present application used the cutting tools of the present invention example and the comparative example to perform cutting (drilling) on a work to be cut, and measured the force required for the cutting. A 6 mm-thick 64 titanium (an alloy composed of 6% by mass of aluminum, 4% by mass of vanadium, and the balance of titanium) was used as the material to be cut.

FIG. 8 is a diagram showing temporal changes in torque and thrust load required for cutting in one embodiment of the present invention. FIG. 8(a) shows the result when the conventional cutting tool shown in FIG. 5 is used. FIG. 8(b) shows the results when the cutting tool 1 according to the present embodiment shown in FIGS. 1 to 4 is used.

Referring to FIG. 8, when cutting is performed using the conventional cutting tool shown in FIG. A thrust load of 853 N on average (a load that presses the cutting tool against the workpiece) was required. On the other hand, when cutting was performed using the cutting tool 1 in the present embodiment (FIG. 8(b)), a maximum torque of 159.8 Ncm was required, and an average thrust load of 189 N was required. .

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

[others]

The cutting tool of the present invention may be an end mill, tap, reamer, milling cutter, or the like.

The number of cutting edges and grooves is arbitrary. When there are a plurality of cutting edge portions, each of the plurality of cutting edge portions may be arranged at equal intervals relative to the rotation axis when viewed in a cross section orthogonal to the rotation axis, or may be arranged at uneven intervals. may have been

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

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 .

The above-described embodiments and examples should be considered illustrative in all respects and not restrictive. The scope of the present invention is indicated by the scope of the claims rather than the above description, and is intended to include all modifications within the scope and meaning of equivalents of the scope of the claims.

1 cutting tool 10 blade portion 11, 21 cutting edge portion 12, 22, 112 rake face 12a, 22a, 112a cutting edge 13a, 13c, 23a, 23c margin portion 13b, 23b flank face 14, 24 wall surface 15-17, 25-27 Axial end face 31, 32 Groove 41, 141 Cutting edge surface 42, 142 Body cutting surface 50 Shank AX Rotational axis D Cutting tool rotation direction LN Cutting edge center line PO1, PO101 Boundary point between cutting edge surface and main cutting surface PO2 Rake surface Intersection with the cutting edge center line TP Vertex at the tip of the cutting tool α Rake angle

Claims (4)

A cutting tool that is rotated in a predetermined rotational direction about the rotation axis, and that includes a cutting edge that contacts an object to be cut and is spirally formed around a rotation axis,
The cutting edge portion includes a surface facing the downstream side in the rotational direction in a groove spirally formed around the rotation axis,
The surface facing the downstream side is
a cutting edge surface provided at an outer diameter side end portion of the surface facing the downstream side;
and a body blade surface provided on the inner diameter side of the blade tip surface,
When viewed in a cross section orthogonal to the rotation axis, each of the cutting edge surface and the main cutting surface is a concave curved surface toward the downstream side in the rotation direction,
When viewed in a cross section orthogonal to the rotation axis, the boundary point between the inner diameter side end portion of the cutting edge surface and the outer diameter side end portion of the main blade surface is the surface facing the downstream side of the rotation shaft. positioned upstream in the rotational direction from the cutting edge center line connecting the outer diameter side end,
The length T of the cutting edge surface along the cutting edge center line is 0.2 mm or more and 1.0 mm or less,
When viewed in a cross section orthogonal to the rotating shaft, each of the cutting edge surface and the main cutting surface has an arc shape,
A cutting tool, wherein the curvature radius R1 of the cutting edge surface and the curvature radius R2 of the main body cutting surface have a relationship of 0.9R2≦R1≦1.1R2. The cutting edge portion is plural,
2. The cutting tool according to claim 1 , wherein each of the plurality of cutting edge portions is arranged at equal intervals with respect to the rotating shaft when viewed in a cross section orthogonal to the rotating shaft. The cutting edge portion is plural,
2. The cutting tool according to claim 1 , wherein each of the plurality of cutting edge portions is arranged at uneven intervals on the rotating shaft when viewed in a cross section orthogonal to the rotating shaft. Cutting tool according to any of the preceding claims, wherein the downstream facing surface is coated with a coating layer.

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