JP7510647B2 - Rotary tools - Google Patents

Description

The present invention relates to a rotary tool in which at least one of the tool and the workpiece rotates to cut the workpiece.

Patent Document 1 discloses a drill as a rotary tool. In this drill, the cutting edge at the tip of the drill is chamfered to prevent damage to the cutting edge at the tip. As a result, the cutting edge is composed of a chamfered portion.

In this drill, the chamfer width, which is the length of the chamfered portion in the axial direction of the drill, is constant throughout a specified range extending from the center of the tip of the drill outward. Throughout the entire range outside the specified range, the chamfer width is constant and smaller than the chamfer width of the specified range.

Japanese Utility Model Application Publication No. 60-175513

However, drills with cutting edges that are chamfered have a lower sharpness than drills with cutting edges that are not chamfered. When sharpness is reduced, various problems occur, such as increased cutting resistance and reduced machining accuracy. For this reason, it is desirable to improve the sharpness of drills with cutting edges that are chamfered. This is not limited to drills, but can also be said for rotating tools other than drills that have cutting edges that are chamfered.

In view of the above, the present invention aims to provide a rotary tool whose cutting edge is configured with a chamfered portion, and which can improve the sharpness of the tool.

In order to achieve the above object, according to the invention described in claim 1,
A rotary tool that rotates about an axis (L1) to cut a workpiece,
A cutting edge forming surface (11, 14) formed on a tip portion (3) of the rotary tool for forming a cutting edge;
a relief surface (12) formed at the tip portion, forming the cutting edge at a portion between the cutting edge forming surface and the relief surface, and forming a relief for the workpiece;
The cutting edge (4) is formed in a portion of the tip portion between the cutting edge forming surface and the flank surface, and extends from an outer side of the tip portion toward a center side of the tip portion,
The cutting edge is configured with a chamfered portion, and at least a part of the chamfered portion is a flat surface,
a chamfer width (W1), which is the length of the chamfer in an axial direction (D1) parallel to the axis, is constant over the entire central range from the end position (P1) of the chamfered portion on the central side of the tip portion to a predetermined position (P2) on the outer side of the tip portion relative to the end position on the central side, and the chamfer width is gradually reduced from the reduction start position to the outer end portion of the tip portion, with the predetermined position being a reduction start position, as it moves toward the outside of the tip portion ,
The cutting edge forming surface includes a rake surface (11) located outside the center of the tip portion and which is a surface for rake the portion to be cut out and removed from the workpiece, and a thinning portion (14) formed to thin a portion of the tip portion located closer to the center of the tip portion than the rake surface,
The cutting edge includes a main cutting edge (13) formed in a region between the rake face and the flank, and a thinning cutting edge (15) formed in a region between the thinning portion and the flank and continuing toward the center of the tip portion with respect to the main cutting edge,
The reduction start position is a midpoint of the main cutting edge between an end of the main cutting edge on the center side of the tip portion and an end of the main cutting edge on the outer side of the tip portion .
In order to achieve the above object, according to the invention described in claim 2,
A rotary tool that rotates about an axis (L1) to cut a workpiece,
A cutting edge forming surface (11, 14) formed on a tip portion (3) of the rotary tool for forming a cutting edge;
a relief surface (12) formed at the tip portion, forming the cutting edge at a portion between the cutting edge forming surface and the relief surface, and forming a relief for the workpiece;
The cutting edge (4) is formed in a portion of the tip portion between the cutting edge forming surface and the flank surface, and extends from an outer side of the tip portion toward a center side of the tip portion,
The cutting edge is configured with a chamfered portion, and at least a part of the chamfered portion is a flat surface,
a chamfer width (W1), which is the length of the chamfer in an axial direction (D1) parallel to the axis, is constant over the entire central range from the end position (P1) of the chamfered portion on the central side of the tip portion to a predetermined position (P2) on the outer side of the tip portion relative to the end position on the central side, and the chamfer width is gradually reduced from the reduction start position to the outer end portion of the tip portion, with the predetermined position being a reduction start position, as it moves toward the outside of the tip portion,
The cutting edge forming surface includes a rake surface (11) located outside the center of the tip portion and which is a surface for rake the portion to be cut out and removed from the workpiece, and a thinning portion (14) formed to thin a portion of the tip portion located closer to the center of the tip portion than the rake surface,
The cutting edge includes a main cutting edge (13) formed in a region between the rake face and the flank, and a thinning cutting edge (15) formed in a region between the thinning portion and the flank and continuing toward the center of the tip portion with respect to the main cutting edge,
The reduction start position is a boundary position between the thinning cutting edge and the main cutting edge.

The inventors have found that by giving the chamfered portion this shape, the sharpness of the drill is improved. By giving the chamfered portion this shape, a portion of the workpiece that is cut out from the workpiece during cutting processing can be allowed to continue to adhere to the chamfered portion as a retained material. This allows the retained material that adheres to the chamfered portion to become the cutting edge, improving the sharpness of the drill whose cutting edge is made up of the chamfered portion.

The reference symbols in parentheses attached to each component indicate an example of the correspondence between the component and the specific components described in the embodiments described below.

FIG. 2 is a view showing a tip surface of the drill according to the first embodiment when viewed from the tip side. FIG. 2 is a perspective view of the drill of FIG. 1 . 3 is a perspective view of the drill of FIG. 1 as viewed from a different direction than FIG. 2; FIG. 4 is a cross-sectional view taken along line IV-IV of FIG. 3. 1 is a graph showing a comparison result of sharpness between the drill of Example 1 and the drill of Comparative Example 1. FIG. 11 is a view showing a tip surface of a drill according to a second embodiment when viewed from the tip side. FIG. 7 is a perspective view of the drill of FIG. FIG. 11 is a view showing a tip surface of a drill according to a third embodiment when viewed from the tip side. FIG. 9 is a perspective view of the drill of FIG. 8 .

The following describes embodiments of the present invention with reference to the drawings. In the following embodiments, parts that are the same or equivalent to each other are denoted by the same reference numerals.

First Embodiment
The drill 1 of this embodiment shown in Figures 1 to 3 is a cutting tool used in drilling, and is a rotary tool that cuts the workpiece by rotating at least one of the drill 1 and the workpiece. When the drill 1 rotates, it rotates about an axis line L1. The axis line L1 is the center line of the drill 1. The drill 1 includes a drill body 2 shown in Figures 2 and 3, and a shank portion (not shown).

The drill body 2 is a part of the drill 1 located on the tip side in the axial direction D1. The axial direction D1 is a direction parallel to the axis L1. The drill body 2 has a cutting edge 4 at the tip 3 of the drill body 2 for cutting the workpiece. The cutting edge 4 extends from the outside of the tip 3 toward the center of the tip 3. The position of the center C1 of the tip 3 coincides with the position of the axis L1 in the tip 3. The drill body 2 has a groove 5 for discharging chips generated when the workpiece is cut by the cutting edge 4. The groove 5 extends from the tip 3 toward the rear end side in the axial direction D1 while twisting around the axis L1. The shank is a handle part of the drill 1 located on the rear end side of the drill 1 relative to the drill body 2. The shank is held by the rotating shaft of the machine tool.

The drill 1 is composed of a material such as high-speed tool steel, cemented carbide, or cermet, and a coating layer that covers the material. The drill 1 does not have to have a coating layer. In addition, the entire drill 1 is not limited to being composed of the above-mentioned material, and only the tip portion 3 of the drill 1 may be composed of the above-mentioned material.

As shown in Figures 1 and 2, the drill body 2 has two sets, each of which includes a rake face 11, a clearance face 12, a main cutting edge 13, a thinning portion 14, and a thinning cutting edge 15. Each set will be described below. The rake face 11, the clearance face 12, the main cutting edge 13, the thinning portion 14, and the thinning cutting edge 15 are formed on the tip portion 3. The main cutting edge 13 and the thinning cutting edge 15 form the cutting edge 4. In Figures 1 and 2, a pattern is applied to the cutting edge 4 for ease of viewing. This is also true in Figures 6 to 9.

The rake face 11 is located outside the center C1 of the tip 3. The rake face 11 is a surface that continues to the main cutting edge 13. The rake face 11 is a surface that rakes the portion to be cut out and removed from the workpiece. The rake face 11 is a surface that faces forward in the drill rotation direction D2 among the inner wall surfaces that form the groove 5 in the tip 3. The rake face 11 forms the main cutting edge 13 in the area between the rake face 11 and the clearance face 12. Therefore, the rake face 11 is a cutting edge forming surface for forming the cutting edge 4.

The relief surface 12 is a surface that forms an escape for the workpiece to avoid unnecessary friction with the workpiece when the tip 3 cuts into the workpiece. The escape is a gap. The relief surface 12 is located on the rear side of the rake face 11 in the drill rotation direction D2.

The flank 12 includes a first flank 121 and a second flank 122. The first flank 121 forms the main cutting edge 13 in the area between the rake face 11. The second flank 122 is connected to the rear side of the first flank 121 in the drill rotation direction D2. The second flank 122 is not parallel to the first flank 121 but intersects it. An oil hole 123 is formed in the flank 12 to spray cutting oil from the tip 3 during drilling. The oil hole 123 does not have to be formed because cutting oil can be supplied even without the oil hole 123.

The main cutting edge 13 is formed in the tip 3 at a location between the rake face 11 and the flank 12. In other words, the main cutting edge 13 is formed at the end of the rake face 11 and at the end of the flank 12. The main cutting edge 13 extends from the outside of the tip 3 toward the center of the tip 3.

The thinning portion 14 is a surface at the tip 3 that continues rearward from the clearance 12 in the drill rotation direction D2 and forward from the inner wall surface that constitutes the groove 5 in the drill rotation direction D2. The thinning portion 14 is formed to thin the portion of the tip 3 that is closer to the center of the tip 3 than the rake face 11. The thinning portion 14 forms a thinning cutting edge 15 at the portion between the first clearance 121 and the center of the tip 3. Therefore, the thinning portion 14 is a cutting edge forming surface for forming the cutting edge 4.

More specifically, the thinning portion 14 includes a first thinning surface 141 and a second thinning surface 142. The first thinning surface 141 forms a thinning cutting edge 15 between the first flank 121 and the first flank 121 at the center side of the tip portion 3. The second thinning surface 142 is connected to the second flank 122 of a different set of flank 12 from the flank 12 including the first flank 121. As shown in FIG. 2, the first thinning surface 141 is connected to the second thinning surface 142 at an obtuse angle. The intersection line 143 between the first thinning surface 141 and the second thinning surface 142 extends from the outside of the tip portion 3 toward the center C1 of the tip portion 3 so as to be located on the tip side of the drill 1 in the axial direction D1.

The thinning portion 14 is a so-called X-type. However, the thinning portion 14 may be a type other than the X-type.

The thinning cutting edge 15 is formed between the thinning portion 14 and the flank 12 on the center side of the tip portion 3. The thinning cutting edge 15 is connected to the main cutting edge 13 on the center side of the tip portion 3. The cutting edge 4, including the main cutting edge 13 and the thinning cutting edge 15, extends from the outer peripheral end of the tip portion 3 to the center C1 of the tip portion 3.

The thinning cutting edge 15 and the main cutting edge 13 are each chamfered. That is, the thinning cutting edge 15 and the main cutting edge 13 are each configured with a chamfered portion. At least a portion of the chamfered portion is a flat surface. In this embodiment, the entire chamfered portion is a flat surface. However, the portion of the chamfered portion excluding the end portion may be a flat surface, and the end portion of the chamfered portion may be a curved surface.

Figure 4 is a cross-sectional view taken along line IV-IV in Figure 3. As shown in Figure 4, the angle that the flat surface of the chamfered portion constituting the cutting edge 4 makes with respect to the axial direction D1 is the chamfer angle θ1. The chamfer angle θ1 is constant over the entire area from the end on the center side of the tip 3 of the chamfered portion to the outer end of the tip 3 of the chamfered portion. The chamfer angle θ1 is set to any angle between 10 degrees and 50 degrees. Note that in this embodiment, the chamfer angle θ1 is constant over the entire area of the chamfered portion, but it does not have to be constant over the entire area of the chamfered portion.

As shown in Figure 4, the length of the chamfered portion in the axial direction D1 is the chamfer width W1. As shown in Figures 1 to 3, the chamfer width is constant over the entire central range of the chamfered portion located toward the center of the tip 3. The central range is the range from position P1 of the end of the chamfered portion toward the center of the tip 3 to a specified position P2 that is further outside the tip 3 than the central end position P1. Then, with that specified position P2 as the reduction start position, the chamfer width W1 gradually decreases from that reduction start position toward the outside of the tip 3.

In this embodiment, the position P1 of the end of the chamfered portion on the center side of the tip portion 3 is the end of the thinning cutting edge 15 on the center side of the tip portion 3, and is the position of the center C1 of the tip portion 3. The specified position P2 of the chamfered portion is the middle position of the main cutting edge 13. The middle position of the main cutting edge 13 is the position between the end of the main cutting edge 13 on the center side of the tip portion 3 and the outer end of the main cutting edge 13 on the tip portion 3. The chamfered width W1 gradually decreases from the middle position of the main cutting edge 13 to the position P3 of the outer end of the tip portion 3 of the main cutting edge 13. In addition, the reduction rate of the chamfered width W1 is constant. Note that the reduction rate of the chamfered width W1 does not have to be constant. The chamfered width W1 may decrease quadratically.

The size of the chamfer width W1 is set based on the depth of cut. The depth of cut is the machining length in the direction of advance of the cutting edge that processes the workpiece per rotation of the drill 1. The depth of cut is calculated based on the feed rate of the drill 1. The feed rate is the distance that the drill 1 advances in the axial direction D1 per rotation of the drill 1.

Specifically, the chamfer width W1 of the chamfered portion in the central range is the size of the cut multiplied by a first constant. The first constant is any one of the values between 1.0 and 3.0. The chamfer width of the chamfered portion at position P3, the outer end of the tip 3, is the size of the cut multiplied by a second constant. The second constant is a number smaller than the first constant and is any one of the values between 0.3 and 1.0.

The drill 1 of this embodiment is used for drilling a workpiece. During drilling, the drill 1 rotates about the axis L1 while being fed toward the tip side in the axial direction D1. As a result, the workpiece is cut by the thinning cutting edge 15 and the main cutting edge 13. The chips generated by the thinning cutting edge 15 and the main cutting edge 13 are discharged through the groove 5 to the rear end side in the axial direction D1. The rotational speed of the drill 1 during drilling is set according to the material of the workpiece.

Next, we will explain why the chamfer width W1 is set as above.

During drilling, if a portion of the workpiece cut by the drill 1 adheres to the chamfer as a retained material, this retained material functions as a cutting edge. This retained material that functions as a cutting edge is called a built-up cutting edge. In addition, the cutting speed at each radial position on the tip 3 while the drill 1 is rotating is 0 at the center C1 of the tip 3 and increases radially outward from the center C1 of the tip 3. In this specification, the cutting speed is the relative circumferential speed between the drill and the workpiece at any radial position on the tip 3.

When the cutting speed exceeds a predetermined speed, the size of the constructed cutting edge becomes smaller. The inventors have discovered that by setting the position of the tip 3 where the cutting speed becomes the predetermined speed as the reduction start position described above, the sharp constructed cutting edge can continue to remain in the chamfered portion. This is believed to improve the sharpness of the cutting edge.

In the drill 1 of this embodiment, when drilling a specific workpiece material at a predetermined rotational speed, the cutting speed at which the constituent cutting edge begins to become sharp is 50 m/min. The position in the tip 3 where the cutting speed becomes 50 m/min is midway along the main cutting edge 13. For this reason, the reduction start position of the chamfer width W1 is set to a midway along the main cutting edge 13.

Figure 5 shows the results of comparing the sharpness of the drill of Example 1 and the drill of Comparative Example 1. Figure 5 shows the results of measuring the number of holes formed when repeatedly drilling a workpiece using each of the drills of Example 1 and Comparative Example 1. The drill of Example 1 is an example of the drill of this embodiment. In the drill of Comparative Example 1, the chamfer width is constant and the same size as the chamfer width of the thinning cutting edge in Example 1 over the entire area between the thinning cutting edge and the main cutting edge. The other configurations are the same as those of the drill of this embodiment.

The diameter of both the drill of Example 1 and the drill of Comparative Example 1 is 4 mm. The cutting speed at the outer periphery of the tip is 80 m/min. The feed rate is 0.17 mm/rev. The drilling process was performed while flowing cutting oil into the oil holes formed in each drill. The chamfer angle of each drill is 25 degrees.

In the drill of Example 1, the chamfer width W1 at the predetermined position P2, which is the reduction start position, is the depth of cut × 1.6. In the drill of Example 1, the chamfer width W1 at the position P3 of the outer end of the tip 3 is the depth of cut × 0.6. In the drill of Comparative Example 1, the chamfer width W1 is the depth of cut × 1.6.

As shown in Figure 5, when the number of holes in the drill of Comparative Example 1 exceeded 1000, the cutting edge was damaged, making it impossible to continue machining. In contrast, when the number of holes in the drill of Example 1 exceeded 3000, the cutting edge was not damaged and machining could be continued. From the results shown in Figure 5, it was confirmed that the cutting performance of the drill of Example 1 was improved compared to that of the drill of Comparative Example 1.

In the drill of Comparative Example 1, the chamfer width is uniform over the entire cutting edge, and the chamfer width is the same as the maximum chamfer width W1 of this embodiment. In the drill of Comparative Example 1, the chamfer width is larger in the outer portion of the tip of the cutting edge compared to the drill of Example 1, so the cutting edge is less sharp and the cutting resistance is large. In addition, since the chamfer width is larger in the outer portion of the tip of the cutting edge, it is presumed that there is an area in the chamfer where no residue adheres.

In contrast, in the drill of Example 1, the width of the chamfer gradually decreases in the outer portion of the tip of the cutting edge as it moves outward from the tip. Therefore, the deterioration of the sharpness of the cutting edge is suppressed compared to the drill of Comparative Example 1. Also, compared to the drill of Comparative Example 1, the retained material adheres to the entire surface of the chamfer. As a result, it is believed that the sharpness of the drill of Example 1 has been improved, as shown in Figure 5.

Incidentally, Japanese Patent Application Laid-Open Publication No. 2004-268230 discloses a drill in which the cutting edge is configured with a chamfered portion. In this drill, the chamfer width is constant over the entire area of the thinning cutting edge. The chamfer width gradually increases from the boundary between the main cutting edge and the thinning cutting edge toward the outside of the tip.

If the chamfer width of the thinning cutting edge of this drill is the same as that of this embodiment, the chamfer width of the main cutting edge is larger than that of this embodiment. Therefore, in this case, the sharpness of the main cutting edge is reduced and the cutting resistance is large compared to this embodiment. Also, in this case, it is presumed that, as with the drill of Comparative Example 1 described above, there will be an area in the chamfer where no residue adheres. As a result, it is presumed that the sharpness will be inferior to that of this embodiment.

Although not shown, the inventors prepared a drill for Comparative Example 2 in which the chamfer width is uniform across the entire cutting edge and the chamfer width is the same as the minimum chamfer width W1 of this embodiment. The other shapes of this drill are the same as those of this embodiment. Experiments conducted by the inventors have confirmed that the cutting performance of the drill for Comparative Example 2 is worse than that of the drill for this embodiment. This is presumably because the chamfer portion of the drill for Comparative Example 2 is narrower than that of this embodiment, resulting in less residue adhering to the chamfer portion.

In addition, in the drill described in Patent Document 1, the chamfer width is constant over the entire area of the thinning cutting edge. The chamfer width of the main cutting edge is constant and smaller than the chamfer width of the thinning cutting edge.

The chamfer width of the thinning cutting edge of the drill described in Patent Document 1 is set to the same size as the thinning cutting edge of this embodiment. The chamfer width of the main cutting edge of this drill is set to the same size as the minimum chamfer width of the main cutting edge of this embodiment. In this case, the chamfered portion of the main cutting edge is narrower than in this embodiment. For this reason, it is presumed that less residue adheres to the chamfered portion of the main cutting edge. Therefore, it is presumed that the sharpness of the drill described in Patent Document 1 is inferior to that of this embodiment.

As explained above, according to this embodiment, the chamfer width W1 is constant throughout the entire central range of the chamfer. Outside the tip 3 of the chamfer, the chamfer width W1 gradually decreases from a predetermined position P2, which is the reduction start position, toward the outside of the tip 3. This shape of the chamfer allows a portion of the workpiece that is cut out of the workpiece during cutting processing to remain attached to the chamfer as a retained material in the chamfer. This allows the retained material that adheres to the chamfer to become the cutting edge, improving the sharpness of the drill in which the cutting edge 4 is composed of the chamfer.

Second Embodiment
6 and 7, in this embodiment, a predetermined position P2, which is a reduction start position of the chamfer width W1 of the chamfered portion constituting the cutting edge 4, is a boundary position between the thinning cutting edge 15 and the main cutting edge 13. The other configurations of the drill 1 are the same as those of the first embodiment.

In this embodiment, the material of the workpiece is different from that in the first embodiment. The rotational speed of the drill 1 is set to a higher rotational speed than in the first embodiment. In this case, the position of the tip 3 where the cutting speed is 50 m/min is the boundary between the thinning cutting edge 15 and the main cutting edge 13. Therefore, in this embodiment, the boundary between the thinning cutting edge 15 and the main cutting edge 13 is set as the reduction start position of the chamfer width W1.

In this embodiment, the chamfer width W1 is constant throughout the entire center range of the chamfered portion. In this embodiment, the center range is the range from the end of the thinning cutting edge 15 on the center side of the tip 3 to the boundary between the thinning cutting edge 15 and the main cutting edge 13. In other words, the center range is the entire area of the thinning cutting edge 15. Then, outside the center range of the chamfered portion on the tip 3, the boundary between the thinning cutting edge 15 and the main cutting edge 13 is the reduction start position, and the chamfer width W1 gradually decreases from the reduction start position toward the outside of the tip 3. This provides the same effect as the first embodiment.

Third Embodiment
8 and 9, in this embodiment, a predetermined position P2, which is the reduction start position of the chamfer width W1 of the chamfered portion constituting the cutting edge 4, is a midway position of the thinning cutting edge 15. The midway position of the thinning cutting edge 15 is a position between the end of the thinning cutting edge 15 on the center side of the tip portion 3 and the outer end of the thinning cutting edge 15 on the tip portion 3. The other configurations of the drill 1 are the same as those of the first embodiment.

In this embodiment, the material of the workpiece is different from that in the first and second embodiments. The rotational speed of the drill 1 is set to a higher rotational speed than in the second embodiment. In this case, the position of the tip 3 where the cutting speed is 50 m/min is the midpoint of the thinning cutting edge 15. Therefore, in this embodiment, the midpoint of the thinning cutting edge 15 is set as the reduction start position of the chamfer width W1.

In this embodiment, too, the chamfer width W1 is constant throughout the central range of the chamfered portion. In this embodiment, the central range is the range from the end of the thinning cutting edge 15 on the central side of the tip 3 to a midpoint of the thinning cutting edge 15. Outside the central range of the chamfered portion on the tip 3, the midpoint of the thinning cutting edge 15 as a predetermined position P2 is set as the reduction start position, and the chamfer width W1 gradually decreases from the reduction start position toward the outside of the tip 3. This provides the same effect as the first embodiment.

Other Embodiments
(1) In each of the above-described embodiments, the reduction start position of the chamfer width W1 is a position of the tip portion 3 where the cutting speed becomes 50 m/min. However, 50 m/min is only an example. This cutting speed may be any speed that sharpens the built-up cutting edge, and may be a speed other than 50 m/min.

(2) In each of the above-described embodiments, the position P1 of the end of the thinning cutting edge 15 on the center side of the tip portion 3 is the position of the center C1 of the tip portion 3. However, the position P1 of the end of the thinning cutting edge 15 on the center side of the tip portion 3 may be a position outside the center C1 of the tip portion 3.

(3) In each of the above-described embodiments, the cutting edge 4 includes the thinning edge 15. However, the cutting edge 4 may not include the thinning edge 15 and may be composed of only the main cutting edge 13 out of the main cutting edge 13 and the thinning cutting edge 15.

(4) In each of the above-described embodiments, the present invention is applied to a drill 1 as a rotating tool. However, the present invention may be applied to a rotating tool other than the drill 1, in which the cutting edge is configured with a chamfered portion. Examples of rotating tools other than the drill 1 include a reamer, an end mill, etc.

(5) The present invention is not limited to the above-described embodiment, and can be modified as appropriate within the scope of the claims, and includes various modified examples and modifications within the equivalent scope. The above-described embodiments are not unrelated to each other, and can be combined as appropriate, except when the combination is clearly impossible. In the above-described embodiments, it goes without saying that the elements constituting the embodiments are not necessarily essential, except when they are specifically stated to be essential or when they are clearly considered to be essential in principle. In the above-described embodiments, when the numbers, values, amounts, ranges, etc. of the components of the embodiments are mentioned, they are not limited to the specific numbers, except when they are specifically stated to be essential or when they are clearly limited to a specific number in principle. In the above-described embodiments, when the material, shape, positional relationship, etc. of the components are mentioned, they are not limited to the material, shape, positional relationship, etc., except when they are specifically stated to be essential or when they are clearly limited to a specific material, shape, positional relationship, etc. in principle.

3 tip portion 4 cutting edge 11 rake face 12 relief face 13 main cutting edge 14 thinning portion 15 thinning cutting edge

Claims (2)

A rotary tool that rotates about an axis (L1) to cut a workpiece,
A cutting edge forming surface (11, 14) formed on a tip portion (3) of the rotary tool for forming a cutting edge;
a relief surface (12) formed at the tip portion, forming the cutting edge at a portion between the cutting edge forming surface and the relief surface, and forming a relief for the workpiece;
The cutting edge (4) is formed in a portion of the tip portion between the cutting edge forming surface and the flank surface, and extends from an outer side of the tip portion toward a center side of the tip portion,
The cutting edge is configured with a chamfered portion, and at least a part of the chamfered portion is a flat surface,
a chamfer width (W1), which is the length of the chamfer in an axial direction (D1) parallel to the axis, is constant over the entire central range from the end position (P1) of the chamfered portion on the central side of the tip portion to a predetermined position (P2) on the outer side of the tip portion relative to the end position on the central side, and the chamfer width is gradually reduced from the reduction start position to the outer end portion of the tip portion, with the predetermined position being a reduction start position, as it moves toward the outside of the tip portion ,
The cutting edge forming surface includes a rake surface (11) located outside the center of the tip portion and which is a surface for rake the portion to be cut out and removed from the workpiece, and a thinning portion (14) formed to thin a portion of the tip portion located closer to the center of the tip portion than the rake surface,
The cutting edge includes a main cutting edge (13) formed in a region between the rake face and the flank, and a thinning cutting edge (15) formed in a region between the thinning portion and the flank and continuing toward the center of the tip portion with respect to the main cutting edge,
A rotating tool , wherein the reduction start position is a midpoint position of the main cutting edge between an end of the main cutting edge on a center side of the tip portion and an end of the main cutting edge on an outer side of the tip portion .
A rotary tool that rotates about an axis (L1) to cut a workpiece,
A cutting edge forming surface (11, 14) formed on a tip portion (3) of the rotary tool for forming a cutting edge;
a relief surface (12) formed at the tip portion, forming the cutting edge at a portion between the cutting edge forming surface and the relief surface, and forming a relief for the workpiece;
The cutting edge (4) is formed in a portion of the tip portion between the cutting edge forming surface and the flank surface, and extends from an outer side of the tip portion toward a center side of the tip portion,
The cutting edge is configured with a chamfered portion, and at least a part of the chamfered portion is a flat surface,
a chamfer width (W1), which is the length of the chamfer in an axial direction (D1) parallel to the axis, is constant over the entire central range from the end position (P1) of the chamfered portion on the central side of the tip portion to a predetermined position (P2) on the outer side of the tip portion relative to the end position on the central side, and the chamfer width is gradually reduced from the reduction start position to the outer end portion of the tip portion, with the predetermined position being a reduction start position, as it moves toward the outside of the tip portion,
The cutting edge forming surface includes a rake surface (11) located outside the center of the tip portion and which is a surface for rake the portion to be cut out and removed from the workpiece, and a thinning portion (14) formed to thin a portion of the tip portion located closer to the center of the tip portion than the rake surface,
The cutting edge includes a main cutting edge (13) formed in a region between the rake face and the flank, and a thinning cutting edge (15) formed in a region between the thinning portion and the flank and continuing toward the center of the tip portion with respect to the main cutting edge,
A rotating tool , wherein the reduction start position is a boundary position between the thinning cutting edge and the main cutting edge .

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