Rotary tool and method for producing cut workpiece

Abstract

A rotary tool according to one non-limiting aspect of the present disclosure comprises a main body. The main body has a first cutting edge, a second cutting edge, a first gash, a second gash, and a discharge groove. In a cross section passing through the first gash and the second gash, parallel to a rotation axis, and orthogonal to the first cutting edge in a front view of a first end, the second gash has a first portion, and an angle formed by the first portion and a reference line, which is a virtual line parallel to the rotation axis, is larger than an angle formed by a portion of the first gash connected to the first cutting edge and the reference line.

Description

Rotary Tool and Method for Manufacturing a Machined Product Cross-Reference to Related Applications

[0001] This application claims the priority of Japanese Patent Application No. 2024-195777 filed on November 8, 2024, and the entire disclosure of the prior application is incorporated herein by reference.

[0002] The present disclosure relates to a rotary tool and a method for manufacturing a machined product.

[0003] As a rotary tool also used when machining a workpiece such as metal, for example, the rotary tool described in International Publication No. 2022 / 064699 (Patent Document 1) can be mentioned. In the rotary tool described in Patent Document 1, the gullets are formed in two steps.

[0004] In the rotary tool described in Patent Document 1, all the two-step gullets are connected to the cutting edges. In such a case, the chip dischargeability is likely to be enhanced. However, since the chips generated near the tip continue to contact the gullets, the cutting resistance is likely to increase due to friction. Furthermore, chatter is likely to occur as the cutting resistance increases.

[0005] A rotary tool according to a non-limiting aspect of the present disclosure includes a bar-shaped body extending from a first end toward a second end along a rotation axis. The body includes a first cutting edge located on the first end side, a second cutting edge located on an outer periphery of the body and extending toward the second end, a first gullet connected to the first cutting edge, a second gullet extending from the first gullet toward the outer periphery and separated from the first cutting edge and the second cutting edge, and a discharge groove connected to the first gullet and the second gullet and extending toward the second end. In a cross-section parallel to the rotation axis and orthogonal to the first cutting edge in a front view of the first end, passing through the first gullet and the second gullet, the second gullet has a first portion connecting to the first gullet on the first end side. A virtual line parallel to the rotation axis is referred to as a reference line, and an angle formed by the first portion and the reference line is larger than an angle formed by a portion of the first gullet connected to the first cutting edge and the reference line.

[0006] This is a perspective view showing a rotary tool with one facet not limited to the present disclosure. This is an enlarged view of region A1 shown in Figure 1. This is a plan view of the rotary tool shown in Figure 1, viewed from direction B1. This is a side view of the rotary tool shown in Figure 1, viewed from direction B2. This is an enlarged view of region A2 shown in Figure 4. This is a cross-sectional view taken along the line VI-VI shown in Figure 5. This is a cross-sectional view taken along the line VII-VII shown in Figure 6. This is an enlarged view of region A3 shown in Figure 7. This is a cross-sectional view taken along the line IX-IX shown in Figure 6. This is a perspective view showing a rotary tool with one facet not limited to the present disclosure. This is an enlarged view of region A4 shown in Figure 10. This is an enlarged view of region A5 shown in Figure 11. This is a plan view of the rotary tool shown in Figure 10, viewed from direction B3. This is a side view of the enlarged portion shown in Figure 11, viewed from direction B4. This is a cross-sectional view taken along the line XV-XV shown in Figure 14. This is an enlarged view of region A6 shown in Figure 15. This is a schematic diagram showing one step in a method for manufacturing a machined workpiece with one facet not limited to the present disclosure. This is a schematic diagram showing one step in a method for manufacturing a machined workpiece with one facet not limited to the present disclosure. This is a schematic diagram showing one step in a method for manufacturing a one-sided machined workpiece, not limited to the present disclosure.

[0007] <Rotating Tool> A rotating tool 1, which is an example of the present disclosure not limited thereto, will be described in detail below with reference to the drawings. However, for the sake of clarity, the drawings referenced below show only the main components necessary to explain the rotating tool 1 of the embodiment in a simplified manner. Therefore, the rotating tool 1 may include any components not shown in the drawings referenced. Also, the dimensions of the components in each drawing do not faithfully represent the dimensions of the actual components or the dimensional ratios of each component. Note that the present disclosure is not limited to the following embodiments.

[0008] Examples of rotary tools 1 include end mills and milling tools. Examples of end mills include square end mills, radius end mills and flat end mills. In the example shown in Figures 1 to 9, which is not limited to this case, rotary tool 1 is a radius end mill. In the example shown in Figures 10 to 16, which is not limited to this case, rotary tool 1 is a square end mill.

[0009] In the following explanation, parts that are common to both the radius end mill and the square end mill versions of the rotary tool 1 are denoted by the same reference numerals and described together.

[0010] As shown in the embodiments in Figures 1 and 10, the rotary tool 1 may include a body 3 extending along the rotation axis R from a first end 3a to a second end 3b. The first end 3a may be called the "tip 3a," and the second end 3b may be called the "rear end 3b." The body 3 is rotatable around the rotation axis R. In the embodiments shown in Figures 1 and 10, the counterclockwise direction corresponds to the direction of rotation.

[0011] As shown in the embodiments in Figures 1 and 10, the main body 3 may be in the shape of a rod extending from the tip 3a to the rear end 3b. The term "rod shape" here may refer to any elongated shape extending from the tip 3a to the rear end 3b.

[0012] In the embodiments shown in Figures 1 and 10, the main body 3 may be cylindrical in shape, extending from the front end 3a to the rear end 3b. Note that the term "cylindrical shape" here is not limited to a strictly cylindrical shape. For example, a chip discharge groove 15, as described later, may be provided on the outer circumference of the main body 3. When the main body 3 is cylindrical, the rotary tool 1 rotates more stably.

[0013] In the embodiments shown in Figures 1 and 10, the body 3 is a so-called solid tool composed of a single component. However, the body 3 is not limited to this configuration. For example, the body 3 may be composed of a holder and an insert.

[0014] As shown in the embodiments in Figures 2 and 11, the main body 3 may have cutting blades 5. There may be one cutting blade 5, or there may be multiple cutting blades 5. If there are multiple cutting blades 5, the number of cutting blades 5 may be 2 to 8. In the embodiments shown in Figures 2 and 11, the main body 3 has six cutting blades 5.

[0015] As shown in the embodiments in Figures 2 and 11, the cutting edge 5 may have a first cutting edge 7 and a second cutting edge 9. That is, the main body 3 may have a first cutting edge 7 and a second cutting edge 9. The first cutting edge 7 may be located on the side of the tip 3a of the main body 3. Therefore, the first cutting edge 7 may be referred to as the tip edge 7. The second cutting edge 9 may be located on the outer circumference of the main body 3. Therefore, the second cutting edge 9 may be referred to as the outer circumference edge 9.

[0016] As shown in the embodiments in Figures 2 and 11, the tip blade 7 may extend toward the outer circumference of the main body 3. The tip blade 7 may be straight or curved. In the embodiments shown in Figures 2 and 11, the tip blade 7 is straight.

[0017] Note that "straight" here does not necessarily mean a straight line in the strict sense. Specifically, "straight" may mean that the radius of curvature of the tip blade 7 is 10 times or more the length of the tip blade 7.

[0018] The term "curved" may also mean that the radius of curvature of the tip blade 7 is less than 10 times the length of the tip blade 7. In the following explanation, the definitions of "straight" and "curved" may be the same as the definitions above.

[0019] The cutting edge 7 may be connected to the rotation axis R, or it may be separated from it. In the embodiments shown in Figures 2 and 11, the cutting edge 7 is separated from the rotation axis R. In the rotary tool 1, when the cutting edge 7 is separated from the rotation axis R, the cutting resistance tends to be lower.

[0020] The outer periphery blade 9 may be connected to the tip blade 7, or it may be separated from the tip blade 7. In one example not limited to Figure 2, the outer periphery blade 9 is located separately from the tip blade 7 and is connected to the tip blade 7 via a third cutting edge 21 (corner cutting edge 21), which will be described later. In one example not limited to Figure 11, the outer periphery blade 9 is connected to the tip blade 7.

[0021] Furthermore, as shown in the embodiments in Figures 2 and 11, the outer peripheral blade 9 may extend toward the rear end 3b. In the example shown in Figure 2, the outer peripheral blade 9 extends toward the rear end 3b from the third cutting edge 21, which will be described later. In the example shown in Figure 11, the outer peripheral blade 9 extends toward the rear end 3b from the tip blade 7.

[0022] The outer blade 9 may extend straight along the rotation axis R, or it may have a helical shape that curves backward in the direction of rotation of the rotation axis R as it approaches the rear end 3b. If the outer blade 9 has a helical shape, the angle that the outer blade 9 makes with the rotation axis R when viewed from the side may be a so-called helix angle. That is, the angle that the outer blade 9 makes with the rotation axis R may be a helix angle. The helix angle may also be referred to as the helix angle of the outer blade 9. The helix angle of the outer blade 9 is not limited to a specific value. For example, the helix angle of the outer blade 9 may be about 30 to 60°. The helix angle of the outer blade 9 may be constant or it may change. In the embodiments shown in Figures 5 and 14, the helix angle of the outer blade 9 is shown as θ4.

[0023] As shown in the embodiments in Figures 2 and 11, the main body 3 may have a gash located on the side of the tip 3a. A gash is a groove provided in the axial center (web) on the side of the tip 3a to improve chip evacuation. The gash may be connected to the cutting edge 5, in which case the gash can function as a so-called rake face.

[0024] The main body 3 may have a first gash 11 and a second gash 13 as gashes. The first gash 11 may be a groove extending from the rotation axis R toward the outer circumference of the main body 3 along the tip blade 7. The first gash 11 may extend straight toward the outer circumference of the main body 3 from the rotation axis R, or it may extend in a curved manner.

[0025] Furthermore, "the first gash 11 extends straight" may mean that the bottom of the first gash 11, which is a groove, extends straight. "The first gash 11 extends in a curve" may mean that the bottom of the first gash 11, which is a groove, is curved.

[0026] The first gash 11 may or may not extend to the outer circumference of the main body 3. In the embodiments shown in Figures 3 and 13, the first gash 11 does not reach the outer circumference of the main body 3. In other words, the first gash 11 is separated from the outer circumference of the main body 3.

[0027] As shown in the embodiments in Figures 2 and 11, the first gash 11 may extend inclined toward the outer circumference of the main body 3 from the rotation axis R, away from the tip 3a. In other words, the first gash 11 may extend straight toward the outer circumference of the main body 3 from the rotation axis R, while being inclined toward the tip 3a.

[0028] In the embodiments shown in Figures 2 and 11, the first gash 11 may be connected to the tip blade 7. The portion of the first gash 11 connected to the tip blade 7 may function as the rake face of the tip blade 7. The rake angle of the tip blade 7 is not limited to a specific value. For example, the rake angle of the tip blade 7 may be around -10 to 10°.

[0029] As shown in the embodiments in Figures 2 and 11, the second gash 13 may extend from the first gash 11 toward the outer circumference of the main body 3. Alternatively, the second gash 13 may be a groove extending from the first gash 11 toward the outer circumference of the main body 3. In this case, the second gash 13 may be formed so as to be partially scooped out from the first gash 11 toward the outer circumference of the main body 3. Therefore, the second gash 13 may be positioned so as to be inclined toward the rear in the rotational direction of the rotation axis R with respect to the first gash 11.

[0030] Furthermore, the second gash 13 may extend straight toward the outer circumference of the main body 3, or it may extend in a curved manner. In the embodiments shown in Figures 5 and 14, the second gash 13 extends straight from the first gash 11 toward the outer circumference of the main body 3.

[0031] Note that "the second gash 13 extends straight" may also mean that the bottom 19 of the second gash 13, as described later, extends straight. "The second gash 13 extends in a curve" may also mean that the bottom 19 of the second gash 13 is curved.

[0032] As shown in the embodiments in Figures 2 and 11, the second gash 13 may extend inclined away from the tip 3a from the rotation axis R toward the outer circumference of the main body 3. In other words, the second gash 13 may extend straight while being inclined away from the tip 3a from the rotation axis R toward the outer circumference of the main body 3.

[0033] As shown in the embodiments in Figures 2 and 11, the second gash 13 may be located away from the tip blade 7. A part of the first gash 11 may be located between the tip blade 7 and the second gash 13. When the second gash 13 is located away from the tip blade 7, the distance from the tip blade 7 to the second gash 13 may be about 0.05 to 0.5 mm.

[0034] When the second gash 13 is positioned away from the tip blade 7, the tip blade 7 takes on a state where a so-called land surface is formed. As a result, the cutting edge strength of the tip blade 7 tends to increase, making it easier to perform stable machining.

[0035] As shown in the embodiments in Figures 2 and 11, the second gash 13 may be located away from the outer peripheral blade 9. A discharge groove 15, which will be described later, may be located between the second gash 13 and the outer peripheral blade 9. To summarize the position of the second gash 13, the second gash 13 may be sandwiched between the first gash 11 and the discharge groove 15, and its entire circumference may be surrounded by the first gash 11 and the discharge groove 15.

[0036] As shown in the embodiments in Figures 1 and 10, the main body 3 may have a discharge groove 15. The discharge groove 15 may extend toward the rear end 3b. The discharge groove 15 may also extend toward the rear end 3b from the first gash 11 and the second gash 13. The discharge groove 15 may be connected to the first gash 11 and the second gash 13.

[0037] The discharge groove 15 may have the function of directing the chips generated by the cutting edge 5 toward the rear end 3b and discharging the chips to the outside of the rotating tool 1. Furthermore, the region of the discharge groove 15 connected to the outer peripheral blade 9 may function as the rake face of the outer peripheral blade 9 during cutting. In this case, the rake angle of the outer peripheral blade 9 may be about -15 to 15°. Note that the rake angle of the outer peripheral blade 9 may refer to the rake angle of the above-mentioned region in the discharge groove 15. Therefore, the rake angle of the outer peripheral blade 9 may be evaluated as the inclination angle of the above-mentioned region in the discharge groove 15 with respect to a virtual straight line perpendicular to the rotation axis R.

[0038] As shown in the embodiments in Figures 4, 5, and 14, the discharge groove 15 may extend along the outer peripheral blade 9 toward the rear end 3b. In this case, if the outer peripheral blade 9 extends straight along the rotation axis R, the discharge groove 15 may also extend straight along the rotation axis R. If the outer peripheral blade 9 has a spiral shape that points toward the rear in the rotation direction of the rotation axis R, the discharge groove 15 may also have a spiral shape that points toward the rear in the rotation direction of the rotation axis R.

[0039] The discharge groove 15 extends toward the rear end 3b of the main body 3, but does not have to reach the rear end 3b. In other words, the discharge groove 15 may be located away from the rear end 3b. If the discharge groove 15 is located away from the rear end 3b, the portion closer to the rear end 3b than the discharge groove 15 may be the so-called shank.

[0040] The cross section passing through the first gash 11 and the second gash 13, parallel to the axis of rotation R, and perpendicular to the tip blade 7 in a front view of the tip 3a may be defined as the first cross section C1. Specifically, the cross section along the line VII-VII in Figure 6 and the line XV-XV in Figure 14 may be the first cross section C1.

[0041] As shown in the embodiments in Figures 7 and 15, in the first cross-section C1, the second gash 13 may have a first portion 17 and a bottom portion 19. In the first cross-section C1, the first portion 17 may be connected to the first gash 11 on the side of the tip 3a. The first portion 17 may be straight or curved.

[0042] As shown in each aspect of FIGS. 7 and 15, in the first cross-section C1, the bottom 19 may be the part farthest from the first gutter 11. As shown in each aspect of FIGS. 5 and 14, when the second gutter 13 extends straight from the first gutter 11 toward the outer periphery of the main body 3, the bottom 19 may extend straight from the first gutter 11 toward the outer periphery of the main body 3. Here, the "straight" is not limited to strictly straight.

[0043] Also, in each aspect shown in FIGS. 5 and 14, the dashed-dotted line on the second gutter 13 indicates the bottom 19. When the dashed-dotted line on the second gutter 13 is linear from the first gutter 11 toward the outer periphery of the main body 3, it may indicate that the bottom 19 extends straight. In each aspect shown in FIGS. 5 and 14, since the dashed-dotted line on the second gutter 13 is linear from the first gutter 11 toward the outer periphery of the main body 3, it indicates that the bottom 19 extends straight.

[0044] A virtual line parallel to the rotation axis R may be defined as the reference line L1. That is, in the first cross-section C1, a virtual line parallel to the rotation axis R may be referred to as the reference line L1. As shown in each aspect of FIGS. 8 and 16, in the first cross-section C1, the angle formed by the portion of the first gutter 11 connected to the tip blade 7 and the reference line L1 may be defined as the first angle θ1. The first angle θ1 may be a so-called rake angle with respect to the tip blade 7.

[0045] When the reference line L1 passing through the tip blade 7 and the first gutter 11 connected to the tip blade 7 are parallel, the first angle θ1 is 0°. From this state, when the first gutter 11 is inclined forward in the rotation direction of the rotation axis R, it may mean that the first angle θ1 is a negative value. On the other hand, from the state where the first angle θ1 is 0°, when the first gutter 11 is inclined backward in the rotation direction of the rotation axis R, it may mean that the first angle θ1 is a positive value.

[0046] In the first cross-section C1, when the portion of the first gullet 11 connected to the tip edge 7 is indicated by a straight line, the angle formed by this straight line and the reference line L1 is the first angle θ1. In the first cross-section C1, when the portion of the first gullet 11 connected to the tip edge 7 is indicated by a curve, a tangent line at the portion of the first gullet 11 connected to the tip edge 7 may be specified, and the angle formed by this tangent line and the reference line L1 may be defined as the first angle θ1.

[0047] In each aspect shown in FIGS. 8 and 16, the upper side is the front in the rotation direction of the rotation axis R, and the lower side is the rear in the rotation direction of the rotation axis R. The first gullet 11 connected to the tip edge 7 is inclined forward in the rotation direction of the rotation axis R. Therefore, the first angle θ1 is a negative value.

[0048] As in each aspect shown in FIGS. 8 and 16, in the first cross-section C1, the angle formed by the first portion 17 and the reference line L1 may be defined as the second angle θ2. When the first portion 17 is curved, a tangent line of the first portion 17 passing through the intersection of the first portion 17 and the first gullet 11 may be specified, and the angle formed by this tangent line and the reference line L1 may be defined as the second angle θ2.

[0049] The magnitude of the second angle θ2 may be defined in the same definition as the magnitude of the first angle θ1. That is, when the reference line L1 passing through the tip edge 7 and the first portion 17 are parallel, the second angle θ2 is 0°. From this state, when the first portion 17 is inclined forward in the rotation direction of the rotation axis R, it may mean that the second angle θ2 is a negative value. On the other hand, from the state where the second angle θ2 is 0°, when the first portion 17 is inclined rearward in the rotation direction of the rotation axis R, it may mean that the second angle θ2 is a positive value.

[0050] In each aspect shown in FIGS. 8 and 16, the first portion 17 is inclined rearward in the rotation direction of the rotation axis R. Therefore, the second angle θ2 is a positive value.

[0051] When the first portion 17 is curved, the "first portion 17" as defined above may be read as "the tangent line of the first portion 17 passing through the intersection of the first portion 17 and the first gullet 11".

[0052] As shown in the embodiments of Figures 8 and 16, the second angle θ2 may be greater than the first angle θ1. Here, the magnitude of the angles may be compared not only with respect to the absolute value of the angles, but also with respect to the magnitude of the angle values ​​considering whether they are positive or negative. In the embodiments of Figures 8 and 16, the first angle θ1 is a negative value, and the second angle θ2 is a positive value. Therefore, the second angle θ2 is greater than the first angle θ1.

[0053] When the chips generated by the cutting edge 7 continue to contact the first gash 11 and are sent to the discharge groove 15, the friction between the chips and the first gash 11 increases the cutting resistance. Consequently, chatter is more likely to occur during cutting, making stable cutting difficult.

[0054] However, if a second gash 13 is provided and the second angle θ2 is greater than the first angle θ1, the chips generated at the cutting edge 7 are more likely to flow from the first gash 11 to the second gash 13 while flowing through the first gash 11. When the chips flow to the second gash 13, they come into contact with the first gash 11 less frequently. Also, because the second angle θ2 is greater than the first angle θ1, it is easier to flow the chips from the first gash 11 to the second gash 13 with less resistance.

[0055] Therefore, when the rotary tool 1 has the above configuration, the cutting resistance tends to be low. Furthermore, chatter is less likely to occur, making stable cutting easier. In particular, when cutting workpieces that have a higher hardness compared to general metals, such as workpieces manufactured by metal additive manufacturing, the cutting resistance tends to be high and chatter is more likely to occur. The rotary tool 1 having the above configuration makes it easier to reduce cutting resistance and less likely to cause chatter, making it useful when cutting workpieces manufactured by metal additive manufacturing.

[0056] The first angle θ1 and the second angle θ2 are not limited to specific values. For example, the first angle θ1 may be around -10 to 10°, and the second angle θ2 may be around 5 to 60°.

[0057] As shown in the embodiments in Figures 8 and 16, the first angle θ1 may be less than 0°. In other words, the first gash 11 connected to the tip blade 7 may be inclined forward in the direction of rotation of the rotation axis R. Also, since the first angle θ1 is the rake angle with respect to the tip blade 7, a configuration in which the first angle θ1 is less than 0° can be rephrased as a negative rake angle with respect to the tip blade 7.

[0058] When the rotary tool 1 has the above configuration, the cutting edge strength of the tip blade 7 tends to increase. Therefore, the rotary tool 1 is less likely to break and stable machining is easier to achieve.

[0059] Furthermore, chips tend to flow more easily to the second gash 13 than to the first gash 11, which has a negative rake angle. As a result, cutting resistance tends to be lower.

[0060] As shown in the embodiments in Figures 5 and 14, the angle between the second gash 13 and the axis of rotation R may be defined as the third angle θ3. The third angle θ3 may also be the angle between the extension of the base 19 and the axis of rotation R. In the embodiments shown in Figures 5 and 14, the angle between the extension of the base 19 L2 and the axis of rotation R is shown as the third angle θ3. The third angle θ3 may be between 25 and 55°.

[0061] As shown in the embodiments in Figures 5 and 14, the third angle θ3 may be smaller than the helix angle θ4 of the outer blade 9. When comparing the third angle θ3 and the helix angle θ4 of the outer blade 9, the outer blade 9 and the second gash 13 connected via the discharge groove 15 may be compared.

[0062] When the rotary tool 1 has the above configuration, the chips that pass through the second gash 13 flow easily into the discharge groove 15. Therefore, the chips are easily discharged efficiently.

[0063] As shown in the embodiments in Figures 3 and 13, the first gash 11 may have a first outer end P1 in a front view of the tip 3a. The first outer end P1 is the end of the first gash 11 located on the outer circumference side of the main body 3 in a front view of the tip 3a. In other words, the first outer end P1 is the point of the first gash 11 that is closest to the outer circumference of the main body 3 in a front view of the tip 3a.

[0064] As shown in the embodiments in Figures 3 and 13, the second gash 13 may have a second outer end P2 in a front view of the tip 3a. The second outer end P2 is the end of the second gash 13 located on the outer circumference side of the main body 3 in a front view of the tip 3a. In other words, the second outer end P2 is the point of the second gash 13 that is closest to the outer circumference of the main body 3 in a front view of the tip 3a.

[0065] As shown in the embodiments in Figures 3 and 13, in a front view of the tip 3a, the second outer end P2 may be located closer to the axis of rotation R than the first outer end P1. In other words, in a front view of the tip 3a, the first gash 11 may extend further outward than the second gash 13 towards the outer circumference of the main body 3.

[0066] When the rotary tool 1 has the above configuration, the outer circumference of the main body 3 is not cut by the second gash 13, making it easier to maintain the thickness near the outer circumference of the main body 3. Therefore, when cutting is performed using the part of the tip blade 7 that is close to the outer circumference of the main body 3 and the outer blade 9, the rotary tool 1 is less likely to be damaged. Consequently, the rotary tool 1 is more likely to perform stable cutting.

[0067] As shown in the embodiments in Figures 4, 5, and 14, the first gash 11 may extend beyond the second gash 13 to the rear end 3b. When the rotary tool 1 has the above configuration, the area of ​​the first gash 11 and the discharge groove 15 that is cut by the second gash 13 is reduced, and the rigidity of the rotary tool 1 tends to increase. Therefore, the rotary tool 1 is more likely to perform stable cutting.

[0068] As shown in the embodiments in Figures 2 and 11, the second gash 13 may have a second inner end P3. The second inner end P3 is the end of the second gash 13 on the side of the rotation axis R. In other words, the second inner end P3 is the point of the second gash 13 closest to the rotation axis R. Note that the second inner end P3 may also be simply called the inner end P3.

[0069] In a cross-section perpendicular to the axis of rotation R and including the second inner end P3, the distance from the second inner end P3 to the circumscribed circle of the main body 3 may be smaller than the distance from the second inner end P3 to the axis of rotation R. In other words, the second inner end P3 may be located closer to the outer circumference of the main body 3 than the midpoint of the radius of the circumscribed circle of the main body 3.

[0070] When the rotary tool 1 has the above configuration, the second gash 13 is located relatively on the outer circumference side of the main body 3. When the second gash 13 is located on the outer circumference side of the main body 3, the area around the rotation axis R of the rotary tool 1 remains untouched, making it easier to secure the core thickness. As a result, the rigidity of the rotary tool 1 tends to increase.

[0071] Furthermore, the above configuration can also be evaluated in the following way instead of evaluation in cross-section. First, in each embodiment shown in Figures 2 and 11, a virtual straight line may be set that is perpendicular to the rotation axis R and passes through the second inner end P3. Then, the distance from the second inner end P3 to the outer circumference of the main body 3 on this virtual straight line may be evaluated as the distance from the second inner end P3 to the circumscribed circle of the main body 3. Alternatively, the distance from the second inner end P3 to the rotation axis R on the virtual straight line may be evaluated as the distance from the second inner end P3 to the rotation axis R. Therefore, the above configuration can be rephrased as: on a virtual straight line perpendicular to the rotation axis R and passing through the second inner end P3, the distance from the second inner end P3 to the outer circumference of the main body 3 is smaller than the distance from the second inner end P3 to the rotation axis R.

[0072] As shown in the example not limited to Figure 2, the main body 3 may further have a third cutting edge 21 and a corner groove 23. The third cutting edge 21 may be connected to the tip blade 7 and the outer peripheral blade 9. The third cutting edge 21 may be located at the corner between the tip blade 7 and the outer peripheral blade 9. Therefore, the third cutting edge 21 may also be called a corner cutting edge 21.

[0073] As shown in the example not limited to Figure 2, the corner groove 23 may be positioned along the corner cutting edge 21. In particular, the corner groove 23 may be positioned along the corner cutting edge 21, between the corner cutting edge 21 and the second gash 13. That is, the corner groove 23 may be positioned so as to be sandwiched between the corner cutting edge 21 and the second gash 13. The width from the corner cutting edge 21 to the second gash 13 may be about 0.05 to 0.5 mm.

[0074] As shown in the example not limited to Figure 2, the corner groove 23 may be connected to the first gash 11 and the discharge groove 15. In other words, the corner groove 23 may be positioned between the first gash 11 and the discharge groove 15.

[0075] To summarize the corner groove 23, it may be positioned along the corner cutting edge 21 and sandwiched between the corner cutting edge 21, the first gash 11, the second gash 13, and the discharge groove 15.

[0076] When the rotary tool 1 has the above configuration, the corner groove 23 becomes like the so-called land surface of the corner cutting edge 21, and the strength of the corner cutting edge 21 tends to increase. The corner groove 23 may be connected to the corner cutting edge 21. The corner groove 23 may also be connected to the second gash 13.

[0077] The corner groove 23 may function as the rake face of the corner cutting edge 21 during cutting. The rake angle of the corner cutting edge 21 may be approximately -20 to 14°. The rake angle of the corner cutting edge 21 may be smaller than the rake angle of the outer peripheral cutting edge 9. When the rotary tool 1 has the above configuration, the strength of the corner cutting edge 21 tends to be higher. Note that the rake angle of the corner cutting edge 21 may refer to the rake angle of the region of the corner groove 23 that can function as the rake face of the corner cutting edge 21 during cutting. Therefore, the rake angle of the corner cutting edge 21 may be evaluated as the inclination angle of the above region in the corner groove 23 with respect to a virtual straight line perpendicular to the tangent at any point on the corner cutting edge 21.

[0078] As shown in the example below (not limited to Figure 9), the cross section passing through the first gash 11, the second gash 13, and the corner groove 23 may be defined as the second cross section C2. As shown in the example below (not limited to Figure 9), the corner groove 23 may be concave in the second cross section C2.

[0079] In the second cross-section C2, if the corner groove 23 is concave, the connection portion between the corner groove 23 and the second gash 13 becomes convex. The chips generated by the corner cutting edge 21 flow through the corner groove 23 and collide with the convex shape of the connection portion between the corner groove 23 and the second gash 13. As a result, the chips tend to become finely coiled.

[0080] For the reasons stated above, when the rotary tool 1 has the above configuration, the chips become finer and are easily discharged. In addition, in the second cross section C2, the bottom of the corner groove 23 may be located forward of the bottom 19 of the second gash 13 in the direction of rotation of the rotation axis R.

[0081] In the second cross-section C2, the corner groove 23 may be flat. However, "flat" does not mean that the corner groove 23 is flat in the strict sense, and it may be slightly curved. "Slightly curved" may mean that the radius of curvature of the curved corner groove 23 is sufficiently large compared to the width of the corner groove 23. Specifically, in the second cross-section C2, the radius of curvature of the corner groove 23 may be 10 times or more the width of the corner groove 23. The width of the corner groove 23 may mean the length of the line segment connecting the opposite edges at the opening of the corner groove 23 in the second cross-section C2.

[0082] In the second cross-section C2, if the corner groove 23 is flat, the connection from the corner groove 23 to the second gash 13 is smooth. As a result, the chips generated at the corner cutting edge 21 can easily flow into the second gash 13.

[0083] For the reasons stated above, when the rotary tool 1 has the above configuration, chips are more easily discharged into the second gash 13. This configuration can also be described as a smooth connection from the corner groove 23 to the second gash 13 in the second cross-section C2.

[0084] As shown in the example (not limited to) in Figures 12 and 14, the first gash 11 may have a first region 25 and a second region 27. The first region 25 may be a region of the first gash 11 connected to the second gash 13.

[0085] As shown in the example (not limited to) in Figures 12 and 14, the second region 27 may be located on the outer circumference side of the main body 3 than the first region 25. The second region 27 may also be connected to the discharge groove 15. The first region 25 and the second region 27 may be connected to the tip blade 7. The boundary between the first region 25 and the second region 27 may be a line that extends from the connection point between the second gash 13 and the discharge groove 15 to the tip blade 7 and is perpendicular to the tip blade 7.

[0086] As shown in the example not limited to Figures 12 and 14, the area from the boundary line between the first gash 11 and the second gash 13 in the first region 25 to the boundary line between the first gash 11 and the discharge groove 15 in the second region 27 may be defined as area T. In the example not limited to Figures 12 and 14, area T is shown with a thick line for visual clarity.

[0087] As shown in the example (not limited to) in Figures 12 and 14, part T may have a convex shape that protrudes toward the rear end 3b.

[0088] If part T has a convex shape, the chips generated near the outer circumference of the main body 3 are more likely to bend when they pass over part T. Therefore, if the rotary tool 1 has the above configuration, the width of the chips tends to be smaller, and the chips are easier to discharge.

[0089] Examples of materials for the rotary tool 1 include cemented carbide, cermet, and ceramic inorganic materials. Examples of cemented carbide compositions include WC (tungsten carbide)-Co, WC-TiC (titanium carbide)-Co, and WC-TiC-TaC (tantalum carbide)-Co. WC, TiC, and TaC are hard particles, and Co is the bonding phase. Cermet is a sintered composite material in which metal is combined with ceramic components. Specifically, examples of cermets include compounds mainly composed of TiC or TiN (titanium nitride). However, the rotary tool 1 is not limited to these materials.

[0090] Furthermore, the surface of the rotary tool 1 may be coated with a coating layer by chemical vapor deposition (CVD) or physical vapor deposition (PVD). Examples of materials for the coating layer include aluminum oxide (alumina), titanium carbides, nitrides, oxides, carbonites, nitrogen oxides, and carbonitrin oxides. The coating layer may contain only one of the above substances, or it may contain multiple substances. The coating layer may consist of only one layer, or it may consist of multiple layers stacked together. The material of the coating layer is not limited to these.

[0091] <Method for Manufacturing Machined Workpieces> Next, a method for manufacturing machined workpieces according to an embodiment not limited to the present disclosure will be described.

[0092] A machined workpiece can be produced by cutting the workpiece 101. A method for manufacturing a machined workpiece in an embodiment not limited to this disclosure may include the following steps: (1) rotating a rotary tool 1; (2) bringing the rotating rotary tool 1 into contact with the workpiece 101; and (3) moving the rotary tool 1 away from the workpiece 101.

[0093] More specifically, as shown in the example without limitation in Figure 17, the rotary tool 1 may be brought relatively closer to the workpiece 101 while rotating around the rotation axis R. Next, as shown in the example without limitation in Figure 18, the cutting edge 5 of the rotary tool 1 may be brought into contact with the workpiece 101 to cut the workpiece 101. Then, as shown in the example without limitation in Figure 19, the rotary tool 1 may be moved relatively further away from the workpiece 101.

[0094] In the example shown in Figure 17, the workpiece 101 is fixed and the rotary tool 1 is rotated in the X1 direction around the rotation axis R, and the rotary tool 1 is moved in the Y1 direction to bring it closer to the workpiece 101. In the example shown in Figure 19, the workpiece 101 is fixed and the rotary tool 1 is moved away from the workpiece 101. In the cutting process in the manufacturing method of the embodiment, the workpiece 101 is fixed and the rotary tool 1 is moved in each step, but of course, the method is not limited to these configurations.

[0095] For example, in step (1), the workpiece 101 may be brought closer to the rotary tool 1. Similarly, in step (3), the workpiece 101 may be moved away from the rotary tool 1. If cutting is to be continued, the rotary tool 1 may be kept rotating, and the process of bringing the cutting edge 5 of the rotary tool 1 into contact with different parts of the workpiece 101 may be repeated.

[0096] In the example shown in Figures 17-19, which is not limited to this example, cutting is performed using the radius end mill shown in Figures 1-9. However, the tool used for cutting is not limited to a radius end mill. Cutting may also be performed using the square end mill shown in Figures 10-16.

[0097] Examples of materials for the workpiece 101 include aluminum, carbon steel, alloy steel, stainless steel, cast iron, and non-ferrous metals. In addition to common metals, the workpiece 101 may also be a metal manufactured by metal additive manufacturing.

[0098] 1... Rotary tool 3... Main body 3a... First end (tip) 3b... Second end (rear end) 5... Cutting edge 7... First cutting edge (tip edge) 9... Second cutting edge (outer edge) 11... First gash 13... Second gash 15... Discharge groove (flute) 17... First section 19... Bottom 21... Third cutting edge (corner cutting edge) 23... Corner groove 25... First area 27... Second area 101... Workpiece L1... Reference line R... Rotation axis P1... First outer end P2... Second outer end P3... Second inner end

Claims

1. A rotary tool comprising a rod-shaped body extending from a first end to a second end along a rotation axis, wherein the body has: a first cutting edge located on the side of the first end; a second cutting edge located on the outer circumference of the body and extending toward the second end; a first gash connected to the first cutting edge; a second gash extending from the first gash toward the outer circumference and separated from the first and second cutting edges; and a discharge groove connected to the first and second gashs and extending toward the second end, wherein in a cross section passing through the first and second gashs, parallel to the rotation axis, and perpendicular to the first cutting edge in a front view of the first end, the second gash has a first portion connected to the first gash on the side of the first end, and a virtual line parallel to the rotation axis is referred to as a reference line, and the angle between the first portion and the reference line is greater than the angle between the portion of the first gash connected to the first cutting edge and the reference line.

2. The rotary tool according to claim 1, wherein the angle formed by the portion of the first gash connected to the first cutting edge and the reference line is less than 0°.

3. The rotary tool according to claim 1 or 2, wherein the angle between the second gash and the rotation axis is smaller than the helix angle between the second cutting edge and the rotation axis.

4. The rotary tool according to any one of claims 1 to 3, wherein, in a front view of the first end, the first gash has a first outer end which is the end on the outer circumference side, and the second gash has a second outer end which is the end on the outer circumference side, and the second outer end is located closer to the axis of rotation than the first outer end.

5. The rotary tool according to any one of claims 1 to 4, wherein the first gash extends beyond the second gash to the second end.

6. The rotary tool according to any one of claims 1 to 5, wherein the second gash has a second inner end which is the end on the side of the rotation axis, is perpendicular to the rotation axis, and in a cross section including the second inner end, the distance from the second inner end to the circumscribed circle of the main body is smaller than the distance from the second inner end to the rotation axis.

7. The rotary tool according to any one of claims 1 to 6, wherein the main body further comprises a third cutting blade connected to the first cutting blade and the second cutting blade, and a corner groove positioned along the third cutting blade.

8. The rotary tool according to claim 7, wherein the rake angle of the third cutting edge is smaller than the rake angle of the second cutting edge.

9. The rotary tool according to claim 7, wherein in a cross-section passing through the first gash, the second gash, and the corner groove, the corner groove is concave.

10. The rotary tool according to claim 7, wherein in a cross-section passing through the first gash, the second gash, and the corner groove, the corner groove is flat.

11. The rotary tool according to any one of claims 1 to 10, wherein the first gash has a first region connected to the second gash and a second region connected to the discharge groove on the outer circumference side of the first region, and the portion extending from the boundary line between the first gash and the second gash in the first region to the boundary line between the first gash and the discharge groove in the second region has a convex shape that protrudes toward the second end.

12. A method for manufacturing a machined workpiece, comprising the steps of: rotating a rotary tool according to any one of claims 1 to 11; bringing the rotating rotary tool into contact with a workpiece; and separating the rotating tool from the workpiece.

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