drill bit

Abstract

A drill bit is formed with a chip flute (7) at a front end outer peripheral portion of a drill bit main body (1) that rotates in a drill bit rotation direction (T) about an axis (O), a cutting edge (5) is formed at an intersection ridge line portion of a wall surface of the chip flute (7) that faces the drill bit rotation direction (T) and a front end relief surface (6), the cutting edge (5) has a main cutting edge portion (5B) that extends from an inner peripheral side of the drill bit main body (1) toward an outer peripheral side, and a cutting edge shoulder portion (5C) that reaches the outer periphery of the drill bit main body (1) from an outer peripheral end (P) of the main cutting edge portion (5B), and is honed, an actual rake angle increases on the negative angle side at an outer peripheral end (Q) of the cutting edge shoulder portion (5C) relative to the outer peripheral end (P) of the main cutting edge portion (5B), and a size of the honing is reduced.

Description

Technical Field

[0001] The present invention relates to a drill bit in which a chip removal groove is formed on the outer periphery of the front end of the drill bit body, which rotates about an axis along the rotation direction of the drill bit. The chip removal groove opens on the front end flank face of the drill bit body and extends to the rear end side in the direction of the axis. A cutting edge with the front end flank face as the rake face is formed at the intersection of the wall surface of the chip removal groove facing the rotation direction of the drill bit and the front end flank face.

[0002] This application claims priority to patent application No. 2020-126514 filed in Japan on July 27, 2020 and patent application No. 2021-121845 filed in Japan on July 26, 2021, the contents of which are incorporated herein by reference. Background Technology

[0003] As such a drill bit, Patent Document 1 describes a drill bit as follows: a chip removal groove extending toward the rear end is formed on the outer periphery of the front end side portion, i.e., the tip portion, of the drill bit body that rotates about an axis; and a cutting edge is formed at the intersection of the front face of the chip removal groove in the front end side region of the inner wall surface in the direction of drill rotation and the front rear face of the tip portion.

[0004] The drill bit described in Patent Document 1 has: a cutting edge portion that intersects with the front face and faces outward; a shoulder portion that is the intersection line of the cutting edge portion and the front rear face of the tip portion, and extends from the outer peripheral end of the cutting edge toward the rear side in the direction of drill rotation; and a chisel edge grinding portion that extends toward the front end side of the inner wall surface of the chip removal groove.

[0005] Furthermore, the cutting edge has, sequentially from the center of rotation, a first cutting edge portion formed in the chisel edge grinding portion, a second cutting edge portion further formed on the outer peripheral side from the first cutting edge portion, a shoulder cutting edge portion formed in the shoulder portion, and a cutting edge band cutting edge portion formed in the cutting edge band portion, and the second cutting edge portion, the cutting edge band cutting edge portion, and the shoulder cutting edge portion are honed.

[0006] Furthermore, in the drill bit described in Patent Document 1, the honing width of these parts satisfies the relationship expressed by the following formula (1).

[0007] The honing width of the shoulder cutting edge > the honing width of the cutting edge band > the honing width of the second cutting edge…(1)

[0008] Patent Document 1: Japanese Patent Application Publication No. 2019-209439

[0009] Thus, in the drill bit described in Patent Document 1, the honing width of the shoulder cutting edge is set to be the maximum relative to the honing width of the cutting edge band and the second cutting edge. However, in a drill bit where the honing width of the shoulder of the cutting edge is set to be the maximum, damage in the honing area of ​​the shoulder of the cutting edge is easily aggravated, thus making it prone to weld penetration. Furthermore, when such weld penetration occurs, it may suddenly cause defects on the shoulder of the cutting edge, shortening the drill bit's life.

[0010] Furthermore, in drills where the honing width of the cutting edge shoulder is set to be large, the cutting resistance in the cutting edge shoulder will increase, which may result in large burrs when drilling through holes, for example, when making opening holes. Summary of the Invention

[0011] The present invention was made in this context, and its object is to provide a drill bit that can prevent welding to prevent defects in the cutting edge shoulder while ensuring the cutting edge strength in the cutting edge shoulder on the outer periphery of the cutting edge, and can suppress burrs when drilling through holes.

[0012] To address the aforementioned issues and achieve this objective, the drill bit of the present invention has a chip removal groove formed on the outer periphery of the front end of the drill bit body, which rotates about an axis in the direction of drill bit rotation. This groove opens on the front flank face of the drill bit body and extends toward the rear end of the axis. A cutting edge with the rake face as the rake face is formed at the intersection of the wall surface of the chip removal groove facing the direction of drill bit rotation and the front flank face. The drill bit is characterized in that the cutting edge has a main cutting edge extending from the inner periphery of the drill bit body toward the outer periphery, and a cutting edge shoulder extending from the outer periphery end of the main cutting edge to the outer periphery of the drill bit body. The cutting edge is honed, and at the outer periphery end of the cutting edge shoulder, the angle of inclination of the rake face relative to the straight line connecting the cutting edge and the axis, i.e., the actual rake angle, increases on the negative angle side in a cross section orthogonal to the cutting edge. This is achieved by honing the cutting edge at the outer periphery end of the main cutting edge and at the outer periphery end of the cutting edge shoulder.

[0013] In this drill bit configuration, at the outer peripheral end of the cutting edge shoulder on the outer periphery of the cutting edge, the actual rake angle—the angle of inclination of the rake face relative to the straight line connecting the cutting edge and the drill body axis—in a section orthogonal to the cutting edge, increases on the negative angle side relative to the outer peripheral end of the main cutting edge. This increases the tool angle of the cutting edge within the cutting edge shoulder, thereby ensuring cutting edge strength. Consequently, damage to the cutting edge shoulder is prevented, thus preventing weld penetration, and sudden defects in the cutting edge shoulder caused by weld penetration, which would shorten drill bit life, can be suppressed.

[0014] Furthermore, regarding the size of the honing applied to the cutting edge, since the outer peripheral end of the cutting edge shoulder is smaller than the outer peripheral end of the main cutting edge, it is possible to further reliably prevent welding at the cutting edge shoulder. Moreover, by reducing the honing in this way, the sharpness of the cutting edge at the cutting edge shoulder can be improved, thus suppressing the generation of burrs during drilling when opening through holes.

[0015] Furthermore, in the case of chamfered honing (angle honing) or compound honing in the case of honing having a straight section in a cross-section orthogonal to the cutting edge, the size of the honing refers to the width of the honing surface in the cross-section orthogonal to the cutting edge along the direction of the aforementioned straight line connecting the cutting edge and the axis. And, in the case of circular honing in the case of honing with a convex curve shape such as a convex arc in a cross-section orthogonal to the cutting edge, it is the radius (radius of curvature) of the honing surface in the cross-section orthogonal to the cutting edge.

[0016] Here, in order to increase the actual rake angle at the outer peripheral end of the cutting edge shoulder on the negative angle side compared to the actual rake angle at the outer peripheral end of the main cutting edge, firstly, a front flank face and a chamfer portion disposed on the wall surface are formed at the outer peripheral end of the cutting edge. The chamfer portion is inclined towards the side opposite to the drill rotation direction along the intersection line of the outer peripheral surface extending from the front flank face of the drill body. The cutting edge shoulder is formed at the intersection line of this chamfer portion and the front flank face. In this case, for example, by forming a small-area chamfer portion in a polygonal shape (triangular or quadrilateral shape, etc.), the actual rake angle of the cutting edge shoulder can be increased on the negative angle side compared to the actual rake angle of the main cutting edge.

[0017] Furthermore, secondly, a chamfered strip can be formed along the outer periphery of the wall surface of the chip removal groove facing the direction of drill rotation, intersecting the wall surface at an obtuse angle relative to the inner periphery of the chip removal groove. The cutting edge shoulder is formed at the intersection of this chamfered strip and the front flank face. In this case, even when grinding a new cutting edge after the cutting edge has become dull due to wear, the actual rake angle of the cutting edge shoulder can be increased on the negative angle side by grinding only the front flank face.

[0018] Furthermore, thirdly, a planar chamfer may be formed on the outer periphery of the aforementioned front flank face. This planar chamfer intersects at an obtuse angle with the aforementioned front flank face, which is located further inward than the outer periphery, and with the outer periphery of the drill body extending from the rake face to the side opposite to the drill rotation direction. The cutting shoulder is formed at the intersection of the planar chamfer and the rake face. Fourthly, a convex curved chamfer may also be formed on the outer periphery of the aforementioned front flank face. This convex curved chamfer connects with the aforementioned front flank face, which is located further inward than the outer periphery, and with the outer periphery of the drill body extending from the rake face to the side opposite to the drill rotation direction. The cutting shoulder is formed at the intersection of the convex curved chamfer and the rake face.

[0019] In these cases, without chamfering the rake face, the actual rake angle of the cutting edge shoulder can be increased on the negative angle side compared to the actual rake angle of the main cutting edge, thus preventing the impact of chamfering the rake face on chip removal.

[0020] Furthermore, when viewed from the front end side along the aforementioned axial direction, the width of the cutting edge shoulder, in the direction extending from the straight line connecting the axial direction and the outer peripheral end of the cutting edge shoulder, is preferably 0.2 × D or less relative to the diameter D of the cutting edge. If the width of the cutting edge shoulder is greater than 0.2 × D of the diameter D of the cutting edge, the portion of the actual rake angle that increases on the negative angle side will become excessively long, potentially leading to an increase in cutting resistance.

[0021] Furthermore, the honing size H of the main cutting edge portion is preferably 0.8 × H or less compared to the honing size H of the main cutting edge portion. If the honing size of the cutting edge shoulder portion is greater than 0.8 × H compared to the honing size H of the main cutting edge portion, the sharpness of the cutting edge shoulder portion is impaired, which may fail to suppress burrs generated when drilling through holes. Additionally, the honing size of the cutting edge shoulder portion can be 0.5 × H or less, or 0.3 × H or less, compared to the honing size H of the main cutting edge portion.

[0022] Furthermore, the honing performed on the main cutting edge portion and the cutting edge shoulder can be any of the chamfering honing, combined honing, or circular honing described above, but it is preferred that the honing performed on the main cutting edge portion be chamfering honing and the honing performed on the cutting edge shoulder be circular honing. This ensures sufficient cutting edge strength in the main cutting edge portion, primarily used for hole drilling, while maintaining cutting edge strength and achieving a sharper edge in the cutting edge shoulder.

[0023] As explained above, according to the present invention, the tool angle in the cutting edge shoulder can be increased to ensure the cutting edge strength, and welding can be prevented in the cutting edge shoulder, thereby preventing defects caused by the detachment of the weld. Furthermore, according to the present invention, by increasing the sharpness of the cutting edge shoulder, burrs generated during drilling when opening through holes can be suppressed. Attached Figure Description

[0024] Figure 1 This is a side view showing the first embodiment of the present invention.

[0025] Figure 2 yes Figure 1 An enlarged front view of the cutting edge portion of the embodiment shown.

[0026] Figure 3 From Figure 2 The side view is viewed from the direction of the arrow X (perpendicular to the direction perpendicular to line N1).

[0027] Figure 4 From Figure 2 The side view is viewed from the direction of the arrow Y (perpendicular to the direction of line N2).

[0028] Figure 5 yes Figure 3 Enlarged cross-sectional view of XX in the image.

[0029] Figure 6 yes Figure 4 The enlarged cross-sectional view of YY in the image.

[0030] Figure 7 yes Figure 3 ZZ cross-section diagram.

[0031] Figure 8 It means Figure 1 An enlarged front view of the cutting edge of a modified embodiment shown.

[0032] Figure 9 From Figure 8 The side view is viewed from the direction of the arrow X (perpendicular to the direction perpendicular to line N1).

[0033] Figure 10 This is an enlarged front view showing the cutting edge portion of the second embodiment of the present invention.

[0034] Figure 11 From Figure 10 The side view is viewed from the direction of the arrow X (perpendicular to the direction perpendicular to line N1).

[0035] Figure 12 yes Figure 11 ZZ cross-section diagram.

[0036] Figure 13 It means Figure 10 An enlarged front view of the cutting edge of a modified embodiment shown.

[0037] Figure 14 From Figure 13 The side view is viewed from the direction of the arrow X (perpendicular to the direction perpendicular to line N1).

[0038] Figure 15 This is an enlarged front view showing the cutting edge portion of the third embodiment of the present invention.

[0039] Figure 16 From Figure 15 The side view is viewed from the direction of the arrow X (perpendicular to the direction perpendicular to line N1).

[0040] Figure 17 This is an enlarged front view showing the cutting edge portion according to the fourth embodiment of the present invention.

[0041] Figure 18 From Figure 17 The side view is viewed from the direction of the arrow X (perpendicular to the direction perpendicular to line N1).

[0042] Figure 19 This is a side view showing the fifth embodiment of the present invention.

[0043] Figure 20 yes Figure 19 An enlarged front view of the cutting edge portion of the embodiment shown.

[0044] Figure 21 From Figure 20 The side view is viewed from the direction of the arrow X (perpendicular to the direction perpendicular to line N1).

[0045] Figure 22 This is an enlarged front view showing the cutting edge portion according to the sixth embodiment of the present invention.

[0046] Figure 23 From Figure 22 The side view is viewed from the direction of the arrow X (perpendicular to the direction perpendicular to line N1).

[0047] Figure 24 This is an enlarged front view showing the cutting edge portion according to the seventh embodiment of the present invention.

[0048] Figure 25 It means Figure 24 A side view of the cutting edge of the drill bit, specifically, viewed from a direction perpendicular to line N1. Figure 24 A side view of the cutting edge.

[0049] Figure 26 It means Figure 24 A cross-sectional view (transverse section) of the cutting edge of a drill bit.

[0050] Figure 27 This is an enlarged front view showing a modified example of the seventh embodiment, of the cutting edge.

[0051] Figure 28 It means Figure 27 A cross-sectional view (transverse section) of the cutting edge of a drill bit. Detailed Implementation

[0052] Figures 1 to 7 This illustrates the first embodiment of the present invention. In this embodiment, the drill bit body 1 is integrally formed from a hard material such as cemented carbide into a multi-stage cylindrical shape centered on axis O. The rear end of the large diameter of this drill bit body 1 (at...) Figure 1 The right side portion (in the middle) is designated as handle 2, and the front end portion (with a smaller diameter than handle 2) is designated as handle 2. Figure 1 The middle part (left side) is designated as the cutting edge 3. Furthermore, between the shank 2 and the cutting edge 3 of the drill body 1, a cone neck 4 is formed in the shape of a frustum of a cone that gradually narrows towards the front end and is centered on the axis O.

[0053] In this type of drill bit, the shank 2 of the drill bit body 1 is held on the spindle of the machine tool and rotates around axis O in the drill bit rotation direction T while being fed towards the front end in the direction of axis O. Thus, the drill bit uses the cutting edge 5 formed at the front end of the cutting edge 3 to perform hole opening operations such as through holes on the workpiece.

[0054] A chip removal groove 7 is formed on the outer periphery of the cutting edge portion 3, opening at the front end face 6 of the drill body 1 and extending towards the rear end in the direction of axis O. A cutting edge 5 is formed at the intersection of the wall surface of the chip removal groove 7 facing the drill rotation direction T and the aforementioned front end face 6, with the front end of this wall surface serving as the rake face 8. The cutting edge 5 is given a front end angle as it extends towards the rear end towards the outer periphery of the drill body 1, i.e., radially outward. Furthermore, a first cutting edge 3A is formed on the outer peripheral surface of the cutting edge portion 3 connected to the side of the chip removal groove 7 opposite to the drill rotation direction T. A second cutting edge 3B is formed on the outer peripheral surface of the cutting edge portion 3 connected to the side of the chip removal groove 7 facing the drill rotation direction T.

[0055] In this embodiment, two chip removal grooves 7 are formed symmetrically with respect to the axis O on the cutting edge 3. They twist towards the rear end side in the direction of axis O, opposite to the rotation direction T of the drill bit, to reach the front end of the tapered neck 4. Cutting edges 5 are formed at the intersection of the rake face 8 and the front clearance face 6 of these chip removal grooves 7. That is, the drill bit of this embodiment is a double-edged twist drill.

[0056] Furthermore, on the drill body 1, two coolant holes 9 are formed symmetrically with respect to the axis O, extending from the rear end face of the shank 2 towards the front end, and twisted with a pitch equal to that of the chip flute 7. These coolant holes 9 pass through the chip flute 7 in the cutting edge 3 and open on the front flank face 6. During drilling, coolant such as cutting oil or compressed air is ejected from these coolant holes 9. The front flank face 6 is formed by two stages of flank faces, with the clearance angle increasing towards the side opposite to the drill rotation direction T. The coolant holes 9 open on the flank face opposite to the drill rotation direction T of these two stages of flank faces.

[0057] Furthermore, a chisel edge grinding portion 10 is formed on the inner periphery of the front end of the chip groove 7, such that it cuts through the front end of the wall facing the side opposite to the drill rotation direction T from the inner periphery of the rake face 8. Also, on the cutting edge 5, from the inner periphery of the drill body 1 (near the axis O) towards the outer periphery, there are sequentially: a chisel edge grinding cutting edge portion 5A; a main cutting edge portion 5B, which is formed at the intersection of the rake face 8 and the front flank face 6, connected to the outer periphery of the chisel edge grinding cutting edge portion 5A; and a cutting edge shoulder portion 5C, which extends from the outer periphery end P of the main cutting edge portion 5B to the outer periphery of the drill body 1 and has an outer periphery end Q. In this embodiment, the chisel edge grinding cutting edge portion 5A is formed at the intersection of the chisel edge grinding portion 10 and the front flank face 6, which is connected to the side opposite to the drill rotation direction T of the chisel edge grinding portion 10.

[0058] Furthermore, the chisel edge grinding cutting edge 5A, main cutting edge 5B, and cutting edge shoulder 5C are honed to form honed surfaces 5a, 5b, and 5c, respectively. This honing can be any of the following: chamfering honing (angle honing) with a straight section in a cross-section orthogonal to the cutting edge 5; composite honing where both ends of the straight section are bent into convex curves; or circular honing with a convex arc or other convex curve in a cross-section orthogonal to the cutting edge 5. In this embodiment, the chisel edge grinding cutting edge 5A and main cutting edge 5B are chamfered and honed, and the cutting edge shoulder 5C is circularly honed.

[0059] And, as Figure 6 As shown, in the cross section orthogonal to the cutting edge 5 at the outer peripheral end P of the main cutting edge 5B, the actual rake angle θB is the inclination angle of the rake face 8 relative to the straight line L connecting the cutting edge 5 (main cutting edge 5B) and the axis O. Figure 5 As shown, in the cross section orthogonal to the cutting edge 5 at the outer peripheral end Q of the cutting edge shoulder 5C, the actual rake angle θC is the angle of inclination of the rake face relative to the straight line M connecting the cutting edge 5 (cutting edge shoulder 5C) and the axis O. The actual rake angle θC increases on the negative angle side relative to the actual rake angle θB. Furthermore, in this embodiment, as... Figure 6 As shown, the actual rake angle θB at the outer peripheral end P of the main cutting edge 5B is set as a positive angle, and as... Figure 5As shown, the actual rake angle θC at the outer peripheral end Q of the cutting edge shoulder 5C is set as a negative angle.

[0060] In addition, as in Figure 6 As shown, the size of the honing surface 5b relative to the outer peripheral end P of the main cutting edge 5B is as follows: Figure 5 As shown, the size of the honing surface 5c at the outer peripheral end Q of the cutting edge shoulder 5C becomes smaller.

[0061] Here, in this first embodiment, as Figure 3 and Figure 4 As shown, a front relief face 6 and a triangular chamfered portion (chamfered portion) 11 are formed at the outer peripheral end of the cutting edge 5. The triangular chamfered portion 11 is disposed on the outer peripheral front end of the wall surface of the chip flute 7 facing the drill rotation direction T. The width dimension (radial dimension orthogonal to the axis O) of the triangular chamfered portion 11 narrows as it moves away from the intersection ridge (cutting edge shoulder 5C) with the front relief face 6 toward the rear end side in the direction of axis O. The triangular chamfered portion 11 is inclined toward the side opposite to the drill rotation direction T as it moves toward the intersection ridge (leading edge) with the outer peripheral surface (first cutting edge 3A) of the drill body 1 extending from the front face 8 toward the side opposite to the drill rotation direction T. That is, the triangular chamfered portion 11 is inclined toward the side opposite to the drill rotation direction T as it moves radially outward. Furthermore, in this embodiment, the triangular chamfered portion 11 is inclined toward the side opposite to the drill rotation direction T as it moves toward the front end side in the direction of axis O. By forming a cutting edge shoulder 5C at the intersection of the chamfered triangular portion 11 and the front flank face 6, the actual rake angle θC of the cutting edge shoulder 5C is increased on the negative angle side compared to the actual rake angle θB of the main cutting edge portion 5B.

[0062] Furthermore, in this embodiment, the size of the honing surface 5b, which serves as the main cutting edge 5B for chamfering honing, is located at the outer peripheral end P of the main cutting edge 5B, such as... Figure 6 As shown, the width H of the honing surface 5b in the straight line L direction in the section orthogonal to the cutting edge 5 is set as described. In contrast, in this embodiment, the honing size of the cutting edge shoulder 5C, which is circularly honed, is at the outer peripheral end Q of the cutting edge shoulder 5C, as shown... Figure 5 As shown, the radius (radius of curvature) R of the honing surface 5c in the section orthogonal to the cutting edge 5 is set.

[0063] Furthermore, relative to the honing size of the main cutting edge 5B (width H of the honing surface 5b), the honing size of the cutting edge shoulder 5C (radius R of the honing surface 5c) is set to 0.8 × H or less.

[0064] In addition, such as Figure 2As shown, when viewing the drill body 1 from the front end side along axis O, the width W of the cutting edge shoulder 5C in the direction extending from the straight line N1 connecting axis O and the outer peripheral end Q of the cutting edge shoulder 5C is relative to... Figure 3 The diameter of the cutting edge 5 shown (the diameter of the circle of the rotation trajectory formed by the outer peripheral end Q of the cutting edge shoulder 5C around the axis O) D is set to 0.2 × D or less.

[0065] In addition, in this embodiment, such as Figure 2 As shown, when viewed from the front end along axis O, the chisel edge grinding cutting edge 5A extends in a straight line from near axis O to the outer periphery, then curves in a convex curve to connect with the main cutting edge 5B. Furthermore, similarly... Figure 2 As shown, when viewed from the front end side in the direction of axis O, the main cutting edge 5B extends in a straight line.

[0066] Furthermore, the cutting edge shoulder 5C is formed in the triangular chamfered portion 11 as described above, thereby achieving... Figure 2 As shown, when viewed from the front end side in the direction of axis O, the cutting edge shoulder 5C is formed such that it bends relative to the main cutting edge 5B at the outer peripheral end P of the main cutting edge 5B in the opposite direction to the rotation direction T of the drill bit and extends in a straight line to the outer peripheral end Q.

[0067] In a drill bit constructed in this way, the actual rake angle θC at the outer peripheral end Q of the cutting edge shoulder 5C on the outer peripheral side of the cutting edge 5 is increased on the negative angle side relative to the actual rake angle θB at the outer peripheral end P of the main cutting edge 5B. Therefore, as Figure 5 and Figure 6 As shown, this can increase the tool angle of the cutting edge 5 at the cutting edge shoulder 5C.

[0068] Therefore, the cutting edge strength in the cutting edge shoulder 5C can be ensured, thereby preventing damage to the cutting edge shoulder 5C. Furthermore, it can prevent the occurrence of weld deposits caused by such damage, thus preventing defects in the cutting edge shoulder 5C when the weld deposits fall off, and extending drill bit life.

[0069] Furthermore, regarding the size of the honing applied to the cutting edge 5, the size of the outer peripheral end Q of the cutting edge shoulder 5C (radius R of the honing surface 5c) is smaller than the size at the outer peripheral end P of the main cutting edge portion 5B (width H of the honing surface 5b), thus further reliably preventing the melting of the cutting edge shoulder 5C.

[0070] Furthermore, by reducing the size of the honing, the sharpness of the cutting edge 5 in the cutting edge shoulder 5C can be improved. Therefore, it is also possible to suppress the generation of burrs when drilling through holes during the hole-making process. In addition, regarding the size of the honing, it can continuously decrease from the inner circumference (radial inner side) of the drill body 1 toward the outer circumference end of the cutting edge 5 (outer circumference end Q of the cutting edge shoulder 5C), or it can be constant in the main cutting edge 5B and continuously decrease from the outer circumference end P toward the outer circumference end Q, or it can continuously decrease from the outer circumference end P toward the outer circumference end Q and then become constant until it reaches the outer circumference end Q.

[0071] Furthermore, in this embodiment, as described above, in order to increase the actual rake angle θC at the outer peripheral end Q of the cutting edge shoulder 5C on the negative angle side compared to the actual rake angle θB at the outer peripheral end P of the main cutting edge 5B, a front flank face 6 and a triangular chamfer 11 are formed at the outer peripheral end of the cutting edge 5, and the cutting edge shoulder 5C is formed at the intersection of the triangular chamfer 11 and the front flank face 6.

[0072] Therefore, by forming a small triangular chamfer 11 on the drill body of a general drill bit, the actual rake angle θC of the cutting edge shoulder 5C can be increased on the negative angle side compared to the actual rake angle θB of the main cutting edge 5B, thereby making the manufacture of the drill body 1 easier, more efficient and more affordable.

[0073] Furthermore, in this embodiment, when viewed from the front end side along the axis O, the width W of the cutting edge shoulder 5C in the direction extending from the straight line N1 connecting the axis O and the outer peripheral end Q of the cutting edge shoulder 5C is set to be 0.2 × D or less relative to the diameter D of the cutting edge 5. Therefore, unnecessary increases in cutting resistance can be avoided. That is, if the width of the cutting edge shoulder 5C is greater than 0.2 × D of the diameter D of the cutting edge 5, the portion of the actual rake angle θC that increases on the negative angle side will become too long, which may lead to an increase in cutting resistance.

[0074] Furthermore, in this embodiment, the honing size R of the cutting edge shoulder 5C is set to be 0.8 × H or less relative to the honing size H of the main cutting edge 5B, which can more reliably improve the sharpness of the cutting edge shoulder 5C. That is, if the honing size R of the cutting edge shoulder 5C is greater than 0.8 × H relative to the honing size H of the main cutting edge 5B, the sharpness of the cutting edge shoulder 5C is impaired, which may make it impossible to suppress burrs generated when drilling through holes. In addition, the honing size R of the cutting edge shoulder 5C relative to the honing size H of the main cutting edge 5B can be 0.5 × H or less, or it can be 0.3 × H or less.

[0075] Furthermore, in this embodiment, the honing performed on the main cutting edge portion 5B is chamfering honing, and the honing performed on the cutting edge shoulder portion 5C is round honing. Therefore, it is possible to ensure sufficient cutting edge strength in the main cutting edge portion 5B, which is mainly used for hole drilling, while maintaining cutting edge strength and obtaining a sharper edge in the cutting edge shoulder portion 5C.

[0076] However, conversely, the honing performed on the cutting edge shoulder 5C can be a straight-section honing, such as chamfering honing or combined honing, and the main cutting edge 5B can be a circular honing with a convex curved cross-section. Furthermore, both the main cutting edge 5B and the cutting edge shoulder 5C can be chamfered or combined honing, or both the main cutting edge 5B and the cutting edge shoulder 5C can be circular honing.

[0077] Furthermore, in this first embodiment, when viewed from the front end side along the axis O, the main cutting edge 5B is formed in a straight line shape, but as... Figure 8 and Figure 9 In the modified example shown, the main cutting edge 5B can also be formed as follows: starting from the portion of the chisel edge grinding cutting edge 5A that is formed into a convex curve, it extends in a concave curve shape that is recessed toward the outer periphery of the drill body 1 toward the side opposite to the drill rotation direction T, and then extends toward the drill rotation direction T and connects to the cutting edge shoulder 5C. Furthermore, in this modified example and the second to sixth embodiments and their modifications described later, the... Figures 1 to 7 The common parts of the first embodiment shown are marked with the same symbols.

[0078] then, Figures 10-12 This describes a second embodiment of the invention. The second embodiment is characterized in that, along the outer periphery of the wall surface of the chip groove 7 facing the drill bit rotation direction T, a strip-shaped chamfered portion 12 is formed that intersects the aforementioned wall surface at an obtuse angle with the inner periphery of the chip groove 7. The aforementioned cutting shoulder portion 5C is formed at the intersection line of the strip-shaped chamfered portion 12 and the front flank face 6.

[0079] In this second embodiment, with Figure 5 and Figure 6 Similarly, as shown, the actual rake angle θB at the outer peripheral end P of the main cutting edge 5B of the cutting edge 5 increases on the negative angle side, and the honing size (width H of the honing surface 5b) at the outer peripheral end Q of the cutting edge shoulder 5C decreases relative to the honing size (radius R of the honing surface 5c) at the outer peripheral end P of the main cutting edge 5B. Therefore, the same effect as the first embodiment can be obtained.

[0080] Furthermore, in this second embodiment, as described above, a strip-shaped chamfer 12 is formed along the outer periphery of the wall surface of the chip removal groove 7 facing the drill rotation direction T, intersecting the aforementioned wall surface at an obtuse angle relative to the inner periphery of the chip removal groove 7. The aforementioned cutting edge shoulder 5C is formed at the intersection line of the strip-shaped chamfer 12 and the front flank face 6.

[0081] Therefore, when grinding a new cutting edge 5 when the cutting edge 5 becomes dull due to wear, etc., the actual rake angle θC of the cutting edge shoulder 5C can be increased on the negative angle side by grinding only the front flank face 6. Therefore, it is not necessary to re-form the triangular chamfer 11 to form the cutting edge shoulder 5C after grinding the front flank face 6, as in the first embodiment.

[0082] In addition, in this second embodiment, such as Figure 13 and Figure 14 In the modified example shown, similar to the modified example of the first embodiment, the main cutting edge 5B can also be formed as follows: starting from the portion of the chisel edge grinding cutting edge 5A that is formed into a convex curve shape, it extends in a concave curve shape that is recessed toward the outer periphery of the drill body 1 toward the side opposite to the drill rotation direction T, and then extends toward the drill rotation direction T side and connects to the cutting edge shoulder 5C.

[0083] Furthermore, in these first and second embodiments and their variations, by forming a triangular chamfer 11 or a strip chamfer 12 on the rake face 8 side of the cutting edge 5, the actual rake angle θC at the outer peripheral end Q of the cutting edge shoulder 5C is increased on the negative angle side relative to the actual rake angle θB at the outer peripheral end P of the main cutting edge 5B, and the honing size at the outer peripheral end Q of the cutting edge shoulder 5C is reduced relative to the honing size at the outer peripheral end P of the main cutting edge 5B. Figure 15 and Figure 16 The third embodiment shown or Figure 17 and Figure 18 In the fourth embodiment shown, a chamfer may also be formed on the front end of the cutting edge 5 on the back face 6 side.

[0084] Among them, Figure 15 and Figure 16 In the third embodiment shown, a planar chamfer 13 is formed on the outer periphery of the front flank face 6. The planar chamfer 13 intersects the front flank face 6, which is closer to the inner periphery than the outer periphery, and the outer periphery of the cutting edge 3 of the drill body 1, which extends from the front face 8 to the side opposite to the rotation direction T of the drill, namely the first cutting edge 3A, at an obtuse angle. A straight cutting edge shoulder 5C is formed at the intersection of the planar chamfer 13 and the front face 8.

[0085] Furthermore, in Figure 17 and Figure 18 In the fourth embodiment shown, a convex curved chamfer 14 is formed on the outer periphery of the front flank face 6. The convex curved chamfer 14 is connected to the front flank face 6, which is closer to the inner periphery than the outer periphery, and the outer periphery surface of the cutting edge 3 of the drill body 1, which extends from the front face 8 to the side opposite to the rotation direction T of the drill, namely the first cutting edge 3A. At the intersection of the convex curved chamfer 14 and the front face 8, a cutting edge shoulder 5C that is convex curved when viewed from the direction opposite to the front face 8 is formed.

[0086] In these third and fourth embodiments, without performing chamfering operations such as a triangular chamfer 11 or a strip chamfer 12 on the rake face 8 side, the actual rake angle θC of the cutting edge shoulder 5C can be increased on the negative angle side compared to the actual rake angle of the main cutting edge 5B. Therefore, it is possible to prevent situations where chamfering operations on the rake face 8 side would affect chip removal performance.

[0087] also, Figures 19-21 This represents the fifth embodiment of the present invention. Figure 22 and Figure 23 This represents the sixth embodiment of the present invention. These fifth and sixth embodiments describe the application of the present invention to a countersinking drill bit. That is, in the first to fourth embodiments and their variations, the cutting edge 5 extends toward the rear end along the outer periphery of the drill bit body 1, thereby giving the cutting edge 5 a front end angle. In contrast, in these fifth and sixth embodiments, the cutting edge 5 extends approximately along a plane perpendicular to the axis O, thereby setting the front end angle to 180°.

[0088] Furthermore, in the fifth embodiment, a front flank face 6 and a triangular chamfer 11 are formed on the outer peripheral end of the cutting edge 5 and disposed on the wall surface of the chip removal groove 7 facing the drill rotation direction T. The triangular chamfer 11 is inclined to the side opposite to the drill rotation direction T as it is directed toward the intersection line (leading edge) of the outer peripheral surface (first cutting edge 3A) of the drill body 1 extending from the front flank face 8 to the side opposite to the drill rotation direction T. A cutting edge shoulder 5C is formed at the intersection line of the triangular chamfer 11 and the front flank face 6.

[0089] Furthermore, in the sixth embodiment, a strip-shaped chamfer 12 is formed along the outer periphery of the wall surface of the chip removal groove 7 facing the drill rotation direction T, intersecting the wall surface at an obtuse angle relative to the inner periphery of the chip removal groove 7. A cutting edge shoulder 5C is formed at the intersection line of the strip-shaped chamfer 12 and the front relief face 6. In addition, in these fifth and sixth embodiments, the second cutting edge 3B and the coolant hole 9 are not formed.

[0090] In such a countersinking drill, since the tip angle of the cutting edge 5 is 180°, the cutting edge 5 will bite into the workpiece in one go, and the impact load is easily applied to the cutting edge 5. In contrast, in the fifth and sixth embodiments described above, relative to the outer peripheral end P of the main cutting edge portion 5B, at the outer peripheral end Q of the cutting edge shoulder portion 5C, the actual rake angle θC increases on the negative angle side, and the honing size decreases. As described above, the tool angle of the cutting edge shoulder portion 5C can be increased to ensure the cutting edge strength, thus preventing damage to the cutting edge shoulder portion 5C due to impact load.

[0091] Figures 24-26 This describes a seventh embodiment of the present invention. In this seventh embodiment, a strip-shaped chamfered portion 12 is formed along the outer periphery of the wall surface of the chip groove 7 facing the drill rotation direction T, intersecting the aforementioned wall surface at an obtuse angle relative to the inner periphery of the chip groove 7. Furthermore, a chamfered portion 11 is formed on the outer periphery of the front end of the aforementioned wall surface of the chip groove 7. That is, the drill bit of this embodiment has a structure combining the strip-shaped chamfered portion 12 and the chamfered portion 11. Moreover, by forming a cutting edge shoulder 5C at the intersection of the chamfered portion 11 and the front flank face 6, the actual rake angle θC of the cutting edge shoulder 5C is increased on the negative angle side compared to the actual rake angle θB of the main cutting edge portion 5B.

[0092] More specifically, such as Figure 25 As shown, in this embodiment, the chamfered portion 11 is formed on the wall surface by cutting the front end of the strip-shaped chamfered portion 12, thus appearing as a quadrilateral when viewed from the drill bit rotation direction T. Specifically, the chamfered portion 11 is a trapezoidal shape in which the length of the lower base is longer than the length of the upper base.

[0093] Thus, the chamfered portion 11 is not limited to the triangular chamfered portion 11 described in the first embodiment, but may also be a quadrilateral chamfered portion 11. Furthermore, the chamfered portion 11 may also be a polygonal shape other than a triangular or quadrilateral shape.

[0094] Furthermore, in the seventh embodiment, similarly to the first embodiment described above, as... Figure 24 As shown, when the drill bit is viewed from the front end side in the direction of axis O, the main cutting edge 5B extends in a straight line, but is not limited to this.

[0095] Here, Figure 27 and Figure 28 This represents a variation of the seventh embodiment. For example... Figure 27 As shown, when the drill bit is viewed from the front end side in the direction of axis O, the main cutting edge 5B can be a concave curve that is recessed toward the side opposite to the rotation direction T of the drill bit.

[0096] The present invention can combine the various structures described in the foregoing embodiments and modifications without departing from the spirit of the invention, and can make additions, omissions, substitutions, and other changes to the structures. Furthermore, the present invention is not limited to the foregoing embodiments, but is defined only by the claims.

[0097] Industrial availability

[0098] The drill bit according to the present invention can increase the tool angle in the cutting edge shoulder to ensure cutting edge strength and prevent welding at the cutting edge shoulder, thereby preventing defects caused by the detachment of the weld. Furthermore, by improving the sharpness of the cutting edge shoulder, burrs generated during drilling when opening through holes can be suppressed. Therefore, it has industrial applicability.

[0099] Symbol Explanation

[0100] 1 Drill bit body

[0101] 2 handles

[0102] 3 Cutting edge

[0103] 3A First Blade

[0104] 3B Second Blade

[0105] 4-cone neck

[0106] 5 cutting edges

[0107] 5A Chisel edge grinding of cutting edge

[0108] 5B Main cutting edge

[0109] 5C Cutting edge shoulder

[0110] 5a~5c honing surface

[0111] 6 Front Rake Face

[0112] 7 chip removal slots

[0113] 8 rake faces

[0114] 9 Coolant holes

[0115] 10 Chisel edge grinding department

[0116] 11. Chamfered sections (triangular chamfered sections, quadrilateral chamfered sections)

[0117] 12-strip chamfered section

[0118] 13. Flat chamfered section

[0119] 14. Convex curved chamfered part

[0120] Axis of drill bit body 1

[0121] T-bit rotation direction

[0122] The outer peripheral end of P main cutting edge 5B

[0123] Q cutting edge shoulder 5C outer peripheral end

[0124] The actual rake angle of the main cutting edge 5B at the outer peripheral end P.

[0125] The actual rake angle of the cutting edge shoulder 5C at the outer peripheral end Q.

[0126] Diameter of D cutting edge 5

[0127] In the section L at the outer peripheral end P, which is orthogonal to the cutting edge 5, a straight line connects the cutting edge 5 and the axis O.

[0128] In the section M at the outer peripheral end Q, orthogonal to the cutting edge 5, the straight line N1 connecting the cutting edge 5 and the axis O is viewed from the front end side in the direction of axis O. This straight line connects the axis O and the outer peripheral end Q of the cutting edge shoulder 5C.

[0129] When N2 is viewed from the front end along axis O, the straight line connecting axis O and the outer peripheral end P of the main cutting edge 5B is...

[0130] The honing size of the main cutting edge 5B (width of the honing surface 5b in the straight line L direction).

[0131] The honing size of the shoulder 5C of the R cutting edge (the radius of the honing surface 5c in the section orthogonal to the cutting edge 5).

[0132] The width of the shoulder 5C of the W cutting edge in the straight line N1 direction

Claims

1. A drill bit in which a flute is formed in an outer peripheral portion of a front end of a drill bit body rotating in a drill bit rotation direction about an axis, the flute being opened in a front end flank surface of the drill bit body and extending toward a rear end side in the direction of the axis, and a cutting edge in which a wall surface of the flute facing the drill bit rotation direction and an intersection ridge line portion of the front end flank surface are provided with the wall surface as a rake surface, the drill bit being characterized in that the cutting edge is provided with a main cutting edge portion extending from an inner peripheral side of the drill bit body toward an outer peripheral side, and a cutting edge shoulder portion reaching an outer periphery of the drill bit body from an outer peripheral end of the main cutting edge portion, and is subjected to honing, an inclination angle of the rake surface with respect to a straight line connecting the cutting edge and the axis in a cross section orthogonal to the cutting edge at an outer peripheral end of the cutting edge shoulder portion at the outer peripheral end of the main cutting edge portion is increased on a negative angle side, and a size of the honing is reduced, and a band-shaped chamfer portion intersecting the wall surface at an obtuse angle with respect to the wall surface on an inner peripheral side than the outer peripheral edge portion of the wall surface facing the drill bit rotation direction is formed along the flute in an outer peripheral edge portion of the wall surface, and the cutting edge shoulder portion is formed in an intersection ridge line portion of the band-shaped chamfer portion and the front end flank surface.

2. A drill bit in which a flute is formed in an outer peripheral portion of a front end of a drill bit body rotating in a drill bit rotation direction about an axis, the flute being opened in a front end flank surface of the drill bit body and extending toward a rear end side in the direction of the axis, and a cutting edge in which a wall surface of the flute facing the drill bit rotation direction and an intersection ridge line portion of the front end flank surface are provided with the wall surface as a rake surface, the drill bit being characterized in that the cutting edge is provided with a main cutting edge portion extending from an inner peripheral side of the drill bit body toward an outer peripheral side, and a cutting edge shoulder portion reaching an outer periphery of the drill bit body from an outer peripheral end of the main cutting edge portion, and is subjected to honing, an inclination angle of the rake surface with respect to a straight line connecting the cutting edge and the axis in a cross section orthogonal to the cutting edge at an outer peripheral end of the cutting edge shoulder portion at the outer peripheral end of the main cutting edge portion is increased on a negative angle side, and a size of the honing is reduced, and a convex curved surface-shaped chamfer portion is formed in an outer peripheral portion of the front end flank surface, the convex curved surface-shaped chamfer portion being continuous with the front end flank surface on an inner peripheral side than the outer peripheral portion and an outer peripheral surface of the drill bit body extending from the rake surface toward a side opposite to the drill bit rotation direction, and the cutting edge shoulder portion is formed in an intersection ridge line portion of the convex curved surface-shaped chamfer portion and the rake surface.

3. The drill bit according to claim 1 or 2, characterized in that a width of the cutting edge shoulder portion in a direction in which a straight line connecting the axis and an outer peripheral end of the cutting edge shoulder portion extends is 0.2 x D or less with respect to a diameter D of the cutting edge when viewed from a front end side in the direction of the axis.

4. The drill bit according to claim 1 or 2, characterized in that a size of the honing of the cutting edge shoulder portion is set to be 0.8 x H or less with respect to a size H of the honing of the main cutting edge portion.

5. The drill bit according to claim 1 or 2, characterized in that ​ ​ ​ ​ ​ ​ ​ ​ The honing performed on the main cutting edge portion is chamfer honing, and the honing performed on the cutting edge shoulder portion is round honing.

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