A self-centering insert and self-centering drill bit

Abstract

The utility model relates to a kind of self-centering blade and self-centering drill bit.The self-centering blade includes flat blade main body, left blade edge and right blade edge located at the top of the blade main body.The middle part of the blade main body is triangularly protruding positioning protrusion, the left blade edge includes left one blade edge and left two blade edges, the left one blade edge and left two blade edges have height difference, the right blade edge includes right one blade edge and right two blade edges, the right one blade edge and right two blade edges have height difference.The left one blade edge and right one blade edge intersect at the top of the positioning protrusion, the included angle is 120 degrees-140 degrees.Left one blade edge and right one blade edge contact material first, carry out preliminary cutting and centering;Left two blade edges and right two blade edges follow up subsequently, carry out secondary cutting and hole wall finishing, both avoid the cutting load of single blade edge too large, and also improve hole wall smoothness, constitute ladder type cutting structure.

Description

Technical Field

[0001] This utility model relates to the field of drilling technology, and in particular to a self-centering insert and a self-centering drill bit. Background Technology

[0002] Once installed on a drilling tool, a drill bit can be used to drill holes in materials. The centering capability of the drill bit has a significant impact on the positional accuracy and coaxiality of the hole. Especially in high-precision drilling operations, particularly for difficult-to-machine materials such as stainless steel and high-strength steel, the material properties and structural design of the cutting inserts directly determine the work efficiency and hole machining quality.

[0003] During drilling, the drill bit relies on the tip of its head for centering, with a locating punch used to mark the material surface for positioning. However, the small contact area between the tip and the material makes it prone to slippage, causing the drill hole to deviate from its intended position. To improve centering performance, existing technologies have introduced drill bits with locating structures, such as locating tips or grooves at the drill head. However, these designs have drawbacks. For instance, some locating structures occupy the cutting space at the drill head, shortening the effective cutting edge length and requiring multiple feeds to complete the drilling, thus extending processing time. Furthermore, the single-plane cutting edge design concentrates the cutting force locally, especially during the centering stage, where the cutting edge bears significant impact loads, making it prone to chipping or wear and severely shortening the drill bit's lifespan. Therefore, improvements are needed. Utility Model Content

[0004] To overcome the problems existing in the related technologies, this utility model provides a self-centering cutting tool and a self-centering drill bit to solve the technical problems of large space occupied by the drill bit head positioning and easy wear and breakage of the cutting edge.

[0005] According to a first aspect of the present invention, a self-centering blade is provided, comprising a flat blade body, a left cutting edge and a right cutting edge located at the top of the blade body, a triangularly protruding positioning protrusion in the middle of the blade body, the left cutting edge comprising a left first cutting edge and a left second cutting edge having a height difference, and the right cutting edge comprising a right first cutting edge and a right second cutting edge having a height difference. The left and right cutting edges intersect at the top of the positioning protrusion, with an included angle of 120-140 degrees.

[0006] In one embodiment, the ratio of the width of the positioning protrusion to the width of the blade body is B, where 1 / 3 ≤ B ≤ 1 / 2.

[0007] In one embodiment, the left first cutting edge and the left second cutting edge are arranged in parallel, and the height difference between the left first cutting edge and the left second cutting edge is h, where 0.15mm≤h≤0.3mm.

[0008] In one embodiment, the left cutting edge includes an intersecting front cutting surface and a rear cutting surface, the angle between the front cutting surface and the cutting surface is greater than the angle between the rear cutting surface and the cutting surface, and the cutting surface is a plane perpendicular to the blade body and coincides with the intersection line of the front cutting surface and the rear cutting surface.

[0009] In one embodiment, the included angle between the front cutting edge and the cutting surface is A, where 65 degrees ≤ A ≤ 70 degrees.

[0010] In one embodiment, the ratio of the width of the rake face to the thickness of the blade body is D, where 0.2 ≤ D ≤ 0.3, and the width of the rake face is the projected width of the rake face on the cutting surface.

[0011] In one embodiment, the blade body further includes a side blade and a rear side angle, the width of the side blade is equal to the width of the front blade, and the angle of the rear side angle is 8 degrees to 10 degrees.

[0012] This utility model also discloses a self-centering drill bit, including a drill rod and a self-centering cutting tool as described above. The end of the drill rod is provided with a fitting groove, and the cutting tool body is embedded in the fitting groove and welded and fixed to the drill rod.

[0013] In one embodiment, the end of the drill rod is provided with an inclined chamfered surface, the chamfered surface being inclined toward the self-centering cutting tool, and at least one chip removal groove of the drill rod is connected to the chamfered surface.

[0014] In one embodiment, four chip removal grooves are provided, with each chamfered surface intersecting two of the chip removal grooves.

[0015] The technical solution provided by the embodiments of this utility model can include the following beneficial effects: A positioning protrusion is disposed at the end of the blade body. The triangular protrusion shape can quickly embed into the material surface in the early stage of drilling, forming a stable position and preventing the blade from slipping or shifting. The apex of the triangular protrusion has a smaller contact area and a larger pressure per unit area, which can quickly penetrate the oxide layer or uneven areas on the material surface, shortening the centering response time. During drilling, the left and right cutting edges first contact the material for initial cutting and centering; the second left and second right cutting edges then follow, performing secondary cutting and hole wall finishing. This avoids excessive cutting load on a single cutting edge and improves the hole wall smoothness, forming a stepped cutting structure. Attached Figure Description

[0016] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the present invention and, together with the description, serve to explain the principles of the present invention.

[0017] Figure 1This is a front view schematic diagram of a self-centering blade according to an embodiment.

[0018] Figure 2 This is a top view schematic diagram illustrating a self-centering blade according to one embodiment.

[0019] Figure 3 This is a schematic cross-sectional view of a self-centering blade according to one embodiment.

[0020] Figure 4 This is a perspective view of a self-centering drill bit according to one embodiment.

[0021] Figure 5 This is a front view schematic diagram of a self-centering drill bit according to one embodiment.

[0022] Figure 6 This is a schematic diagram of the end face of a self-centering drill bit according to one embodiment.

[0023] In the figure, the blade body is 10; the positioning protrusion is 11; the left cutting edge is 20; the left first cutting edge is 21; the left second cutting edge is 22; the front cutting surface is 23; the rear cutting surface is 24; the right cutting edge is 30; the right first cutting edge is 31; the right second cutting edge is 32; the side cutting edge is 40; the side back angle is 41; the drill rod is 50; the chip removal groove is 51; the fitting groove is 52; the chamfered surface is 53; and the cutting surface is 60. Detailed Implementation

[0024] In the accompanying drawings of this utility model, the same or similar reference numerals correspond to the same or similar components. In the description of this utility model, it should be understood that if terms such as "upper," "lower," "left," "right," "inner," and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting this utility model. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0025] like Figures 1 to 3 As shown, this utility model discloses a self-centering cutting tool, which employs a thin-blade cutting head structure made of cemented carbide. The self-centering cutting tool includes a flat cutting body 10, a left cutting edge 20, and a right cutting edge 30 located at the top of the cutting body 10. Optionally, the cutting body 10 is made of cemented carbide and formed by powder metallurgy sintering. For example, the cutting body 10 is made of WC-Co cemented carbide, which ensures both high hardness and toughness, preventing the cutting tool from breaking under impact loads.

[0026] The blade body 10 has a triangular protrusion 11 in the middle. The left blade 20 includes a left first edge 21 and a left second edge 22, which have a height difference. The right blade 30 includes a right first edge 31 and a right second edge 32, which have a height difference.

[0027] The left cutting edge 21 and the right cutting edge 31 intersect at the top of the positioning protrusion 11, with an included angle k of 120-140 degrees. The positioning protrusion 11 is triangular in shape, and the intersection of the left cutting edge 21 and the right cutting edge 31 is located at the tip. Preferably, there is a tip line in the intersection area of ​​the left cutting edge 21 and the right cutting edge 31, and the tip line connects the left cutting edge 21 and the right cutting edge 31.

[0028] The angle k between the left cutting edge 21 and the right cutting edge 31 is designed to be 120-140 degrees. This design allows for rapid determination of the drill hole center through the stability of the triangular structure, while also distributing the cutting load to both sides of the positioning protrusion 11, reducing local stress at the centering tip. The positioning protrusion 11 is located at the end of the insert body 10. Its triangular shape allows for rapid embedding into the material surface during the initial drilling stage, forming a stable position and preventing the insert from slipping or shifting. The smaller contact area at the apex of the triangular positioning protrusion 11 results in greater pressure per unit area, enabling rapid penetration of the oxide layer or uneven areas on the material surface and shortening the centering response time.

[0029] The left first cutting edge 21 and the left second cutting edge 22 have a height difference, and the right first cutting edge 31 and the right second cutting edge 32 have a height difference. The height difference between the left first cutting edge 21 and the left second cutting edge 22, and between the right first cutting edge 31 and the right second cutting edge 32 is controlled to be 0.15mm-0.3mm, preferably, the height difference is controlled to be 0.2mm, forming a stepped cutting function.

[0030] During drilling, the left cutting edge 21 and the right cutting edge 31 first contact the material for initial cutting and centering. The higher cutting edge performs shallow cutting to quickly break the hardened layer on the material surface. For example, the cutting depth is 0.15mm-0.3mm. Then, the lower left and right cutting edges 22 and 32 follow with deeper cutting, distributing the cutting resistance across both edges for secondary cutting and hole wall finishing. This avoids excessive cutting load on a single cutting edge and improves the hole wall finish, forming a stepped cutting structure. This stepped cutting structure avoids chipping of carbide cutting edges due to concentrated stress, and is especially suitable for materials prone to work hardening, such as stainless steel.

[0031] In one embodiment, the width ratio of the positioning protrusion 11 to the width of the blade body 10 is B, where 1 / 3 ≤ B ≤ 1 / 2. When B = 1 / 3, the positioning protrusion 11 is narrower, suitable for drilling small diameter holes of 3mm-8mm, reducing the occupation of the cutting area; when B = 1 / 2, the positioning protrusion 11 is wider, suitable for drilling large diameter holes of 8mm-15mm, improving centering stability. Different proportions of the positioning protrusion 11 allow the drill bit corresponding to the self-centering blade to be suitable for different drilling scenarios, achieving precise centering through the positioning protrusion 11 while ensuring sufficient cutting area for the left cutting edge 20 and the right cutting edge 30.

[0032] Furthermore, the first cutting edge 21 and the second cutting edge 22 on the left are set in parallel, and the height difference between the first cutting edge 21 and the second cutting edge 22 on the left is h, where 0.15mm≤h≤0.3mm. The first cutting edge 21 and the second cutting edge 22 on the left are parallel to each other, which can improve the ease of machining and realize a stepped cutting structure while ensuring structural strength.

[0033] like Figures 1 to 3 As shown, in one embodiment, the left cutting edge 20 includes an intersecting front cutting surface 23 and a rear cutting surface 24. The angle between the front cutting surface 23 and the cutting surface 60 is greater than the angle between the rear cutting surface 24 and the cutting surface 60. The cutting surface 60 is a plane perpendicular to the blade body 10 and coincides with the intersection line of the front cutting surface 23 and the rear cutting surface 24.

[0034] The front cutting edge 23 directly contacts and cuts the critical surface of the material. The larger included angle can ensure the strength of the cutting edge and avoid cracking. The rear cutting edge 24 contacts the wall of the machined hole. The smaller included angle can reduce friction and wear.

[0035] The angle A between the rake face 23 and the cutting face 60 is controlled to be 65 degrees, 66 degrees, 67 degrees, 68 degrees, 69 degrees, and 70 degrees. Within this angle range, the cutting edge has sufficient sharpness and can withstand the impact load during the cutting process. For example, when A=68 degrees, the wear of the cutting edge after continuous cutting is much lower than that of traditional cutting edges.

[0036] The angle between the back cutting face 24 and the cutting face 60 is usually 30-40 degrees, which can reduce the contact area between the back cutting face 24 and the hole wall, reduce the coefficient of friction, and avoid softening of the cutting edge due to excessive friction and heat.

[0037] Furthermore, the ratio of the width of the rake face 23 to the thickness of the insert body 10 is D, where 0.2 ≤ D ≤ 0.3. The width of the rake face 23 is the projected width of the rake face 23 onto the cutting surface 60. The width of the rake face 23 determines the bearing area of ​​the cutting load: if B is less than 0.2, the rake face 23 is too narrow, and the load is concentrated locally on the cutting edge, which can easily lead to edge chipping; if B is greater than 0.3, the rake face 23 is too wide, which increases the cutting flexibility of the cutting edge. For example, when the insert thickness is 1.6 mm, the width of the rake face 23 is 0.4 mm. This ratio can evenly transfer the cutting load to the insert body 10, avoid local stress concentration, and extend the service life of the insert.

[0038] Furthermore, the blade body 10 also includes a side cutting edge 40 and a side clearance angle 41. The width of the side cutting edge 40 is equal to the width of the front cutting face 23, and the side clearance angle 41 is 8-10 degrees. The side cutting edge 40 is used to cut the hole wall to ensure a smooth hole wall: the width of the side cutting edge 40 is consistent with the width of the front cutting face 23, which can avoid steps in the hole wall caused by width differences. The side clearance angle 41 is designed to be 8-10 degrees, which can reduce the friction between the side cutting edge 40 and the hole wall, avoid burrs or scratches on the hole wall, improve the hole wall quality, and reduce the wear rate.

[0039] like Figures 4 to 6 As shown, the self-centering insert disclosed in the above embodiments is applied to a drill bit to form a self-centering drill bit. The self-centering drill bit includes a drill rod 50 and a self-centering insert. The end of the drill rod 50 is provided with a fitting groove 52, and the insert body 10 is embedded in the fitting groove 52 and welded and fixed to the drill rod 50.

[0040] The drill rod 50 is made of high-strength alloy steel to ensure its resistance to bending during drilling. A recessed fitting groove 52 is provided at the end of the drill rod 50. The size of the fitting groove 52 is precisely matched with the insert body 10, which extends beyond a predetermined distance from the end of the drill rod 50 to maintain drilling accuracy. After the insert body 10 is embedded into the fitting groove 52, it is fixed by welding. The weld joint forms a full weld seam to ensure that the insert will not fall off due to impact loads during drilling.

[0041] Furthermore, the end of the drill rod 50 is provided with an inclined chamfered surface 53, which is inclined towards the self-centering insert. At least one chip removal groove 51 of the drill rod 50 extends to the chamfered surface 53. The chamfered surface 53 is an inclined surface oriented towards the self-centering insert; optionally, the inclination angle of the chamfered surface 53 is 20-30 degrees. The chamfered surface 53 can reduce the end area of ​​the drill rod 50, thereby increasing the space of the cutting area of ​​the self-centering insert. Since at least one chip removal groove 51 of the drill rod 50 extends to the chamfered surface 53, the chips generated by the self-centering insert during drilling quickly slide towards the chip removal groove 51, preventing chips from accumulating around the insert.

[0042] Furthermore, four chip removal grooves 51 are provided, which are evenly distributed along the outer peripheral wall of the drill rod 50 to form a balanced chip removal. Each chamfered surface 53 intersects with two chip removal grooves 51. The chip removal area of ​​the four chip removal grooves 51 is large, which can quickly remove chips. In particular, the four chip removal grooves 51 can prevent metal chips from getting entangled in the drill rod 50.

[0043] Preferably, the four chip removal grooves 51 are evenly distributed along the circumference, which can balance the centrifugal force when the drill rod 50 rotates. When drilling at high speed, the vibration amplitude of the drill rod 50 is reduced, improving drilling stability and avoiding hole position displacement caused by vibration.

[0044] It should be understood that this application is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. This application is intended to cover any variations, uses, or adaptations of the present invention that follow the general principles of this application and include common knowledge or customary technical means in the art that are not disclosed in this invention.

Claims

1. A self-centering blade, comprising a flat blade body, a left cutting edge and a right cutting edge located at the top of the blade body, characterized in that, The blade body has a triangular protruding positioning protrusion in the middle. The left blade includes a left first edge and a left second edge, which have a height difference. The right blade includes a right first edge and a right second edge, which have a height difference. The left and right cutting edges intersect at the top of the positioning protrusion, with an included angle of 120-140 degrees.

2. The self-centering blade according to claim 1, characterized in that, The width of the positioning protrusion is B in ratio to the width of the blade body, where 1 / 3 ≤ B ≤ 1 / 2.

3. The self-centering blade according to claim 1, characterized in that, The first and second left cutting edges are arranged in parallel, and the height difference between the first and second left cutting edges is h, where 0.15mm ≤ h ≤ 0.3mm.

4. The self-centering blade according to claim 1, characterized in that, The left cutting edge includes an intersecting front cutting edge and a rear cutting edge. The angle between the front cutting edge and the cutting surface is greater than the angle between the rear cutting edge and the cutting surface. The cutting surface is a plane perpendicular to the blade body and coincides with the intersection line of the front cutting edge and the rear cutting edge.

5. The self-centering blade according to claim 4, characterized in that, The included angle between the front cutting edge and the cutting surface is A, where 65 degrees ≤ A ≤ 70 degrees.

6. The self-centering blade according to claim 4, characterized in that, The ratio of the width of the rake face to the thickness of the blade body is D, where 0.2 ≤ D ≤ 0.

3. The width of the rake face is the projected width of the rake face on the cutting surface.

7. The self-centering blade according to claim 4, characterized in that, The blade body also includes a side blade and a side rear angle. The width of the side blade is equal to the width of the front blade, and the angle of the side rear angle is 8-10 degrees.

8. A self-centering drill bit, characterized in that, The invention includes a drill pipe and a self-centering cutting tool as described in any one of claims 1-7, wherein the end of the drill pipe is provided with a fitting groove, and the cutting tool body is embedded in the fitting groove and welded and fixed to the drill pipe.

9. The self-centering drill bit according to claim 8, characterized in that, The drill rod has an inclined chamfered surface at its end, which is inclined toward the self-centering cutting tool, and at least one chip removal groove of the drill rod extends to the chamfered surface.

10. The self-centering drill bit according to claim 9, characterized in that, The chip removal groove is provided with four grooves, and each chamfered surface intersects with two of the chip removal grooves.

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