JP7192535B2 - rotary tool - Google Patents

Description

The present invention relates to rotary tools.

Conventionally, rotary tools such as drills, end mills, and reamers are known. The drill described in Patent Document 1 includes a drill body in which a tip cutting edge and a peripheral cutting edge are formed, a shank with an outer diameter larger than the outer diameter of the drill body, and a transition disposed between the drill body and the shank. and A helical groove is formed in the drill body, and another helical groove continuous with the helical groove is formed in the shank, and the bottom of the other helical groove has the same shape and size as the helical groove.

JP 2006-346832 A

Conventional rotary tools have room for improvement in terms of enhancing chip discharge performance while ensuring tool rigidity.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a rotary tool capable of enhancing chip discharging performance while ensuring rigidity of the tool.

One aspect of the present invention is a rotary tool that extends along a central axis and is rotated in a tool rotation direction in a circumferential direction around the central axis, comprising: a blade portion having a cutting edge; A shank portion disposed on the rear end side in the axial direction and having an outer diameter larger than the outer diameter of the blade portion; An outer diameter transition portion whose outer diameter increases toward the side, and a chip discharge groove arranged at least in the blade portion and the outer diameter transition portion and extending in the axial direction, wherein the cutting edge includes the blade portion, Of the outer diameter transition portion and the shank portion, the chip discharge groove is formed only in the blade portion, and the minimum value of the core thickness of the outer diameter transition portion is smaller than the maximum value of the core thickness of the blade portion. has a blade groove portion located in the blade portion and a transition groove portion connected to the blade groove portion and positioned in the outer diameter transition portion, and the width of the transition groove portion in the circumferential direction is the width of the blade groove portion in the circumferential direction. The area of the cross section perpendicular to the central axis of the outer diameter transition portion at the axial position where the thickness of the outer diameter transition portion is the minimum is the axis where the thickness of the cutting portion is the maximum. It is larger than the area of the cross section perpendicular to the central axis of the blade at the directional position .

The rotary tool of the present invention has a cutting edge formed only on the blade portion, and is different from, for example, a stepped drill having a chamfered edge (cutting edge) formed on the outer diameter transition portion.
In the rotary tool of the present invention, the chip discharge groove extends over at least the cutting portion and the outer diameter transition portion, and the minimum core thickness of the outer diameter transition portion is smaller than the maximum core thickness of the cutting portion. That is, in the chip discharge groove, the radial position of the groove bottom of the transition groove portion located in the outer diameter transition portion is radially inner than the radial position of the groove bottom of the blade groove portion located in the blade portion, The groove depth of the transition groove is deep. Therefore, chips generated during cutting work stably flow in the chip discharge groove toward the rear end side in the axial direction, and the chip discharge performance is enhanced.

Further, in the chip discharging groove, the width of the transition groove portion in the circumferential direction is larger than the width (groove width) of the blade groove portion in the circumferential direction. Therefore, the flow of chips toward the rear end side in the axial direction in the chip discharge groove becomes more stable, and the chip discharge performance is improved.
Since the outer diameter of the outer diameter transition portion is larger than the outer diameter of the blade portion, as described above, even if the core thickness of the outer diameter transition portion is smaller than the core thickness of the blade portion, the width of the transition groove portion in the circumferential direction is Even if it is larger than the circumferential width of the blade groove, the rigidity of the outer diameter transition portion is ensured.
Therefore, according to the present invention, it is possible to improve the chip discharging performance while ensuring the rigidity of the tool.
Further, the area of the cross section perpendicular to the central axis of the outer diameter transition portion at the axial position where the thickness of the outer diameter transition portion is the smallest is the above-mentioned It is larger than the area of the cross section perpendicular to the central axis of the blade.
In this case, the rigidity of the outer diameter transition portion can be stably ensured.

In the rotary tool described above, it is preferable that the core thickness of the blade portion decreases from the tip portion toward the rear end side in the axial direction.

In this case, the groove bottom of the blade groove portion is located radially inward from the tip portion in the axial direction toward the rear end side. That is, the groove depth of the blade groove portion becomes deeper toward the rear end side in the axial direction. Therefore, the flow of chips toward the rear end side in the axial direction is well maintained in the blade groove portion, and the chip discharging performance is further enhanced.

In the above rotary tool, it is preferable that the chip discharge groove is also arranged in the shank portion, and that the chip discharge groove has a shank groove portion connected to the blade groove portion and the transition groove portion and located in the shank portion.

In this case, the chips can flow into the shank groove, and the chip discharging performance is further enhanced.

In the above rotary tool, it is preferable that the sum of the axial length of the transition groove portion and the axial length of the shank groove portion is equal to or greater than the outer diameter of the blade portion.

In this case, a large axial length can be secured for the transition groove and the shank groove, and the chip discharging performance can be improved more stably.

In the above rotary tool, it is preferable that the shape of the groove bottom of the blade groove and the shape of the groove bottom of the transition groove are different from each other.

In this case, the shape of the groove bottom of the blade groove and the shape of the groove bottom of the transition groove can be set individually according to the properties and discharge amount of chips, and the degree of freedom in the shape of the chip discharge groove according to the cutting application. increases.

ADVANTAGE OF THE INVENTION According to the rotary tool of one aspect of this invention, chip discharge property is improved, ensuring the rigidity of a tool.

It is a perspective view showing a rotating tool of one embodiment of the present invention. It is a side view showing a rotary tool of one embodiment of the present invention. It is a front view showing a rotary tool of one embodiment of the present invention. FIG. 3 is a sectional view showing the IV-IV section of FIG. 2; FIG. 3 is a cross-sectional view showing a V-V cross section of FIG. 2; It is a figure which shows each sectional drawing of FIG. 4 and FIG. 5 superimposed. FIG. 3 is a diagram for explaining by visualizing the web thickness of the rotary tool in FIG. 2 ;

A rotary tool 10 according to one embodiment of the present invention will be described below with reference to the drawings.
The rotary tool 10 of this embodiment is a drill.

As shown in FIGS. 1 to 3, the rotary tool 10 of this embodiment has a substantially columnar shape with a central axis O. As shown in FIGS. The rotary tool 10 extends along the central axis O. A rotary tool 10 includes a blade portion 1 having a cutting edge 11, a shank portion 2 having an outer diameter larger than the outer diameter of the blade portion 1, and an outer diameter disposed between the blade portion 1 and the shank portion 2. It comprises a transition section 3 and a chip evacuation groove 4 arranged at least in the cutting section 1 and in the outer diameter transition section 3 .
The shank portion 2 is detachably attached to, for example, a spindle of a machine tool, a chuck of a drill press, or the like (hereinafter abbreviated as a spindle of a machine tool, etc.).

[Definition of direction]
In this embodiment, the direction in which the central axis O of the rotary tool 10 extends (the direction along the central axis O) is called the axial direction. The blade portion 1 and the shank portion 2 are arranged at different positions in the axial direction. Of the axial directions, the direction from the shank portion 2 to the blade portion 1 is called the front end side, and the direction from the blade portion 1 to the shank portion 2 is called the rear end side.
A direction orthogonal to the central axis O is called a radial direction. Of the radial directions, the direction closer to the central axis O is called the radial inner side, and the direction away from the central axis O is called the radial outer side.
The direction of rotation around the central axis O is called the circumferential direction. Among the circumferential directions, the direction in which the rotary tool 10 is rotated by the main shaft of the machine tool or the like during cutting is called the tool rotation direction T, and the opposite rotation direction is called the opposite direction to the tool rotation direction T (opposite to the tool rotation direction T). direction of rotation).
The rotary tool 10 of the present embodiment is rotated in the tool rotation direction T and sent to the tip end side in the axial direction to perform cutting (drilling) on the work material.

[Chip discharge groove]
The chip discharge groove 4 is recessed radially inward from the outer peripheral surface of the rotary tool 10 and extends in the axial direction. In this embodiment, the chip discharge groove 4 spirally extends in the direction opposite to the tool rotation direction T as it goes from the tip in the axial direction toward the rear end.

At least one chip discharge groove 4 is provided in the rotary tool 10 . In this embodiment, the rotary tool 10 is a twist drill, and two chip discharge grooves 4 are provided. Three or more chip discharge grooves 4 may be provided in the rotary tool 10 . The plurality of chip discharge grooves 4 are arranged at intervals in the circumferential direction. In this embodiment, a plurality of chip discharge grooves 4 are arranged at equal intervals (at equal pitches) in the circumferential direction on the outer periphery of the rotary tool 10 so as to be rotationally symmetrical with respect to the central axis O. The plurality of chip discharging grooves 4 may be arranged at uneven intervals (at uneven pitches) in the circumferential direction on the outer periphery of the rotary tool 10 .

In this embodiment, chip flutes 4 are arranged in the cutting edge 1 , the outer diameter transition 3 and the shank 2 . The chip discharge groove 4 extends from the tip in the axial direction of the rotary tool 10 toward the rear end in the entire axial direction of the blade portion 1, the entire axial direction of the outer diameter transition portion 3, and the axial direction of the shank portion 2. Extends over the distal portion.

The chip discharge groove 4 has a blade groove portion 4a, a transition groove portion 4b, and a shank groove portion 4c. The blade groove portion 4a, the transition groove portion 4b, and the shank groove portion 4c are arranged in this order from the front end toward the rear end side in the axial direction. The blade groove portion 4a, the transition groove portion 4b, and the shank groove portion 4c are connected and communicate with each other. The blade groove portion 4a and the transition groove portion 4b are smoothly connected without forming a step at the mutual connection portion. The transition groove portion 4b and the shank groove portion 4c are smoothly connected with each other without forming a step at the connection portion.

The blade groove portion 4a is a portion of the chip discharge groove 4 that is positioned at the blade portion 1. As shown in FIG. The blade groove portion 4a opens at an end surface (tip surface) facing the tip side in the axial direction of the rotary tool 10 . As shown in FIG. 4 , the blade groove portion 4 a has a concave curved surface that is recessed radially inward from the outer peripheral surface of the blade portion 1 . In a cross-sectional view perpendicular to the central axis O of the blade portion 1 shown in FIG. 4, the groove bottom of the blade groove portion 4a has a concave curved shape. In FIG. 4, the groove bottom of the blade groove portion 4a is formed, for example, by connecting a plurality of concave curves having mutually different curvature radii.

The transition groove portion 4b is a portion of the chip discharge groove 4 located at the outer diameter transition portion 3. As shown in FIG. A portion (front end portion) of the transition groove portion 4b on the front end side in the axial direction is connected to a portion (rear end portion) of the blade groove portion 4a on the rear end side in the axial direction. As shown in FIG. 5 , the transition groove portion 4 b has a concave curved surface that is recessed radially inward from the outer peripheral surface of the outer diameter transition portion 3 . In a cross-sectional view perpendicular to the central axis O of the outer diameter transition portion 3 shown in FIG. 5, the groove bottom of the transition groove portion 4b has a concave curved shape. In FIG. 5, the groove bottom of the transition groove portion 4b is formed, for example, by connecting a plurality of concave curves having mutually different curvature radii.

FIG. 6 is a diagram showing the cross section (cross section perpendicular to the central axis O) of the blade portion 1 shown in FIG. 4 and the cross section (cross section) of the outer diameter transition portion 3 shown in FIG. As shown in FIG. 6, the circumferential width (groove width) of the transition groove portion 4b is larger than the circumferential width of the blade groove portion 4a. The radial length (groove depth) of the transition groove portion 4b is greater than the radial length of the blade groove portion 4a. The radially innermost innermost end of the transition groove portion 4b is arranged radially inward of the radially innermost innermost end of the blade groove portion 4a.
In this embodiment, the shape of the groove bottom of the blade groove portion 4a and the shape of the groove bottom of the transition groove portion 4b are different from each other.

As shown in FIGS. 1 and 2, the shank groove portion 4c is a portion of the chip discharge groove 4 located in the shank portion 2. As shown in FIG. The tip of the shank groove portion 4c is connected to the rear end of the transition groove portion 4b. In this embodiment, the shank groove portion 4c is arranged only at the tip portion of the shank portion 2. As shown in FIG. The shank groove portion 4 c has a concave surface shape that is depressed radially inward from the outer peripheral surface of the shank portion 2 . The groove depth of the shank groove portion 4c becomes smaller toward the rear end side in the axial direction. The groove width of the shank groove portion 4c in the circumferential direction becomes smaller toward the rear end side in the axial direction.

The sum of the axial length of the transition groove portion 4b and the axial length of the shank groove portion 4c is equal to or greater than the outer diameter of the blade portion 1. As shown in FIG. That is, the sum of the axial length of the transition groove portion 4b and the axial length of the shank groove portion 4c is equal to or greater than the blade diameter. In this embodiment, the sum of the axial length of the transition groove portion 4b and the axial length of the shank groove portion 4c is at least twice the outer diameter of the blade portion 1. As shown in FIG. Further, the axial length of the transition groove portion 4b is equal to or greater than the outer diameter of the blade portion 1. As shown in FIG.

[Blade part]
As shown in FIGS. 1-3, the blade portion 1 has at least one cutting edge 11 . In this embodiment, the rotary tool 10 is a twist drill, and the cutting edge 1 has two cutting edges 11 . Note that the blade portion 1 may have three or more cutting edges 11 .
The cutting edge 11 is formed only on the blade portion 1 out of the blade portion 1 , the outer diameter transition portion 3 and the shank portion 2 .

The cutting edge 11 has a tip edge 11a and a peripheral edge 11b.
The tip cutting edge 11a is formed on a crossing ridgeline between the tip of the wall surface facing the tool rotation direction T of the blade groove portion 4a and the tip surface of the blade portion 1. As shown in FIG. The tip cutting edge 11a extends obliquely toward the rear end side in the axial direction as it extends radially outward.

The outer peripheral cutting edge 11b is formed at the crossing ridge line between the outer peripheral portion of the wall surface facing the tool rotation direction T of the blade groove portion 4a and the outer peripheral surface of the blade portion 1 . The axial tip of the peripheral cutting edge 11b is connected to the radial outer end of the tip cutting edge 11a. The peripheral cutting edge 11b spirally extends in the direction opposite to the tool rotation direction T as it goes axially toward the rear end side from the connecting portion with the tip cutting edge 11a.

The blade portion 1 has a land portion 5 . The land portion 5 is arranged on the outer circumference of the blade portion 1 between the blade groove portions 4a (chip discharge grooves 4) adjacent in the circumferential direction. In this embodiment, the rotary tool 10 is a twist drill, and the cutting portion 1 has two lands 5 . The number of land portions 5 may be one or three or more.

As shown in FIGS. 3 and 4, the land portion 5 has a first margin portion 5a, a second margin portion 5b, and a chamfered surface 5c. That is, in this embodiment, the rotary tool 10 is a double margin type drill, and the land portion 5 has two margin portions 5a and 5b. The land portion 5 may have one or three or more margin portions.

The first margin portion 5a is arranged adjacent to the peripheral cutting edge 11b in the direction opposite to the tool rotation direction T, and is connected to the peripheral cutting edge 11b in the circumferential direction. The first margin portion 5a extends along the peripheral cutting edge 11b. The first margin portion 5a spirally extends in the direction opposite to the tool rotation direction T toward the rear end side in the axial direction. The first margin portion 5a is arranged on a cylindrical rotational locus obtained by rotating the peripheral cutting edge 11b about the central axis O. As shown in FIG.

The second margin portion 5b is arranged in a direction opposite to the tool rotation direction T relative to the first margin portion 5a and spaced apart from the first margin portion 5a in the circumferential direction. The second margin portion 5b extends along the blade groove portion 4a. The second margin portion 5b spirally extends in the direction opposite to the tool rotation direction T as it goes toward the rear end side in the axial direction. The second margin portion 5b is arranged on a cylindrical rotational locus obtained by rotating the peripheral cutting edge 11b about the central axis O. As shown in FIG.

The center chamfered surface 5c is arranged between the first margin portion 5a and the second margin portion 5b in the circumferential direction. The center chamfer 5c is recessed radially inward from the first margin portion 5a and the second margin portion 5b.

FIG. 7 is a diagram for explaining the visualization of the core thickness (web core thickness) of the rotary tool 10. As shown in FIG. As shown in FIG. 7, the web thickness WT1 of the blade portion 1 decreases from the distal end toward the rear end in the axial direction. In other words, the groove depth of the blade groove portion 4a of the blade portion 1 becomes deeper as it goes from the front end portion toward the rear end side in the axial direction.

[Outer diameter transition part]
As shown in FIGS. 1 and 2, the outer diameter transition portion 3 is arranged between the blade portion 1 and the shank portion 2 in the axial direction, and the outer diameter increases toward the rear end side in the axial direction. In the present embodiment, the outer diameter transition portion 3 (the outer peripheral surface thereof) has a displacement amount in the radial direction per unit length in the axial direction (that is, inclination with respect to the central axis O). is substantially constant over the entire length of . That is, although not particularly shown, in a vertical cross-sectional view of the rotary tool 10 including the central axis O, the outer peripheral surface of the outer diameter transition portion 3 has a linear shape extending obliquely with respect to the central axis O. However, not limited to this, for example, the amount of displacement in the radial direction per unit length in the axial direction of the outer diameter transition portion 3 gradually increases from the front end in the axial direction toward the rear end side of the outer diameter transition portion 3. It can grow. In this case, in a vertical cross-sectional view of the rotary tool 10, the outer peripheral surface of the outer diameter transition portion 3 has a concave curved shape.
The outer diameter of the outer diameter transition portion 3 is larger than the outer diameter of the blade portion 1 . The axial length of the outer diameter transition portion 3 is smaller than the axial length of the blade portion 1 .

As shown in FIGS. 2 and 7, the web thickness WT2 of the outer diameter transition portion 3 decreases from the connecting portion of the outer diameter transition portion 3 to the blade portion 1 toward the rear end side in the axial direction. Further, the web thickness WT2 of the outer diameter transition portion 3 decreases from the connection portion of the outer diameter transition portion 3 with the shank portion 2 toward the distal end side in the axial direction. Therefore, the web thickness WT2 of the outer diameter transition portion 3 is the minimum value at the intermediate portion of the outer diameter transition portion 3 located between the axial ends.

Here, FIG. 4 shows a cross section near the tip portion in the axial direction of the blade portion 1 where the core thickness WT1 of the blade portion 1 is the maximum value, and FIG. shows a cross-section of the axially intermediate portion of the outer diameter transition portion 3 where is the minimum value. In FIG. 6, which shows the cross sections of FIGS. 4 and 5 superimposed, the minimum value of the core thickness WT2 of the outer diameter transition portion 3 is smaller than the maximum value of the core thickness WT1 of the blade portion 1. In FIG. Further, the area (first cross-sectional area) of the cross section perpendicular to the central axis O of the outer diameter transition portion 3 at the axial position where the thickness WT2 of the outer diameter transition portion 3 is the minimum is the thickness WT1 of the blade portion 1 is greater than the area of the cross section perpendicular to the central axis O of the blade portion 1 (second cross-sectional area) at the axial position where is the maximum.

[Shank part]
As shown in FIGS. 1 to 3, the shank portion 2 is arranged on the rear end side of the blade portion 1 in the axial direction. In this embodiment, the outer diameter of the shank portion 2 is approximately twice the outer diameter of the blade portion 1 . The axial length of the shank portion 2 is greater than the axial length of the blade portion 1 . In this embodiment, the axial length of the shank portion 2 is greater than the sum of the axial length of the cutting portion 1 and the axial length of the outer diameter transition portion 3 .

[Effects of this embodiment]
The rotary tool 10 of this embodiment described above has the cutting edge 11 formed only on the cutting edge 1, and is different from, for example, a stepped drill in which a chamfered edge (cutting edge) is formed on the outer diameter transition portion.
In the rotary tool 10 of this embodiment, the chip discharge groove 4 extends over at least the blade portion 1 and the outer diameter transition portion 3, and the minimum value of the core thickness WT2 of the outer diameter transition portion 3 is equal to the core thickness of the blade portion 1 Less than the maximum value of WT1. That is, in the chip discharge groove 4, the radial position of the groove bottom of the transition groove portion 4b positioned in the outer diameter transition portion 3 is greater than the radial position of the groove bottom of the blade groove portion 4a positioned in the blade portion 1. The groove depth of the transition groove portion 4b is deep. Therefore, chips generated during cutting work stably flow in the chip discharge groove 4 toward the rear end side in the axial direction, thereby improving the chip discharge performance.

Further, in the chip discharge groove 4, the width of the transition groove portion 4b in the circumferential direction is larger than the width (groove width) of the blade groove portion 4a in the circumferential direction. Therefore, the flow of chips toward the rear end side in the axial direction in the chip discharge groove 4 becomes more stable, and the chip discharge performance is improved.
Since the outer diameter of the outer diameter transition portion 3 is larger than the outer diameter of the blade portion 1, as described above, even if the thickness WT2 of the outer diameter transition portion 3 is smaller than the thickness WT1 of the blade portion 1, the transition groove portion The rigidity of the outer diameter transition portion 3 is ensured even if the circumferential width of the blade groove portion 4b is larger than the circumferential width of the blade groove portion 4a.
Therefore, according to the present embodiment, it is possible to improve the chip dischargeability while ensuring the rigidity of the tool.

Further, in the present embodiment, the web thickness WT1 of the blade portion 1 becomes smaller from the tip portion toward the rear end side in the axial direction.
In this case, the groove bottom of the blade groove portion 4a is located radially inward from the tip portion in the axial direction toward the rear end side. That is, the groove depth of the blade groove portion 4a becomes deeper toward the rear end side in the axial direction. Therefore, the flow of chips toward the rear end side in the axial direction in the blade groove portion 4a is well maintained, and the chip discharging performance is further enhanced.

Further, in this embodiment, the chip discharge groove 4 has a shank groove portion 4c positioned in the shank portion 2 and connected to the blade groove portion 4a and the transition groove portion 4b.
In this case, the chips can flow into the shank groove portion 4c, and the chip discharging performance is further enhanced.

Further, in this embodiment, the sum of the axial length of the transition groove portion 4b and the axial length of the shank groove portion 4c is equal to or greater than the outer diameter (cutting diameter) of the blade portion 1 .
In this case, the axial length of the transition groove portion 4b and the shank groove portion 4c can be kept large, and the chip discharging performance can be improved more stably.

Further, in the present embodiment, the cross-sectional area (first cross-sectional area) of the outer diameter transition portion 3 perpendicular to the central axis O at the axial position where the web thickness WT2 of the outer diameter transition portion 3 is the smallest is the blade portion 1 is larger than the area (second cross-sectional area) of the cross section perpendicular to the central axis O of the blade portion 1 at the axial position where the core thickness WT1 of the blade portion 1 is maximized.
In this case, the rigidity of the outer diameter transition portion 3 can be stably ensured.

Further, in this embodiment, the shape of the groove bottom of the blade groove portion 4a and the shape of the groove bottom of the transition groove portion 4b are different from each other.
In this case, the shape of the groove bottom of the blade groove portion 4a and the shape of the groove bottom of the transition groove portion 4b can be set individually according to the properties and discharge amount of chips, etc., and the shape of the chip discharge groove 4 according to the cutting application etc. degree of freedom increases.

[Other configurations included in the present invention]
It should be noted that the present invention is not limited to the above-described embodiments, and, for example, as described below, changes in configuration can be made without departing from the gist of the present invention.

In the above-described embodiment, the rotary tool 10 is a two-flute twist drill, but is not limited to this. The rotary tool 10 may be a drill with one blade or three or more blades.
Moreover, the rotary tool 10 is not limited to a drill. The rotary tool 10 may be, for example, a rotary tool (rolling tool) such as an end mill or a reamer.

Moreover, in the above-described embodiment, an example in which the chip discharge groove 4 is a twisted groove was given, but the present invention is not limited to this. The chip discharge groove 4 may be a straight groove extending parallel to the central axis O, for example.

Also, the rotary tool 10 may have a coolant hole (not shown). The coolant holes extend axially inside the rotary tool 10 . The coolant hole extends, for example, along the chip discharge groove 4 inside the rotary tool 10 . The coolant hole opens in the blade groove portion 4a or at the tip surface of the blade portion 1. As shown in FIG. A coolant such as an oil-based or water-based cutting fluid or compressed air is supplied into the coolant hole through the spindle of the machine tool or the like. The coolant flows out through the coolant holes to the cutting portion 1 and the machined portion of the work material.

In addition, within the scope that does not deviate from the spirit of the present invention, each configuration (component) described in the above-described embodiments, modifications, notes, etc. may be combined, and addition, omission, replacement, and other Change is possible. Moreover, the present invention is not limited by the embodiments described above, but only by the claims.

According to the rotary tool of the present invention, it is possible to improve the chip discharging performance while ensuring the rigidity of the tool. Therefore, it has industrial applicability.

DESCRIPTION OF SYMBOLS 1... Blade part 2... Shank part 3... Outer diameter transition part 4... Chip discharge groove 4a... Blade groove part 4b... Transition groove part 4c... Shank groove part 10... Rotary tool 11... Cutting edge O... Central axis T... Tool rotation direction WT1... Core thickness of the cutting edge WT2: Core thickness of the outer diameter transition part

Claims (5)

A rotary tool that extends along a central axis and is rotated in a tool rotation direction in a circumferential direction around the central axis,
a blade portion having a cutting edge;
a shank portion disposed on the rear end side of the blade portion in the axial direction and having an outer diameter larger than the outer diameter of the blade portion;
an outer diameter transition portion disposed between the blade portion and the shank portion in the axial direction and having an outer diameter that increases toward the rear end side in the axial direction;
axially extending chip discharge grooves disposed in at least the blade portion and the outer diameter transition portion;
The cutting edge is formed only on the blade portion among the blade portion, the outer diameter transition portion, and the shank portion,
the minimum value of the core thickness of the outer diameter transition portion is smaller than the maximum value of the core thickness of the blade portion;
The chip discharge groove is
a blade groove portion located in the blade portion;
a transition groove portion connected to the blade groove portion and positioned at the outer diameter transition portion,
the width of the transition groove in the circumferential direction is greater than the width of the blade groove in the circumferential direction ,
The area of the cross section of the outer diameter transition portion perpendicular to the central axis at the axial position where the core thickness of the outer diameter transition portion is the minimum is the blade portion at the axial position where the core thickness of the blade portion is the maximum. larger than the area of the cross section perpendicular to the central axis of
rotary tool. The core thickness of the blade portion becomes smaller as it goes from the tip portion in the axial direction toward the rear end side,
The rotary tool according to claim 1. The chip discharge groove is also arranged in the shank portion,
The chip discharge groove has a shank groove portion connected to the blade groove portion and the transition groove portion and located in the shank portion,
A rotary tool according to claim 1 or 2. The sum of the axial length of the transition groove portion and the axial length of the shank groove portion is equal to or greater than the outer diameter of the blade portion.
A rotary tool according to claim 3. The shape of the groove bottom of the blade groove and the shape of the groove bottom of the transition groove are different from each other,
A rotary tool according to any one of claims 1 to 4 .

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