twist drill

Abstract

The application belongs to the technical field of drilling tools, and discloses a twist drill, which comprises a cutting part, the cutting part comprises two blade petals, the two blade petals are arranged at intervals, and a main helical groove is formed between the two blade petals; the blade petal comprises a blade bottom surface, an inverted edge surface, a first blade band surface and a second blade band surface; the blade bottom surface intersects with a groove bottom surface of the main helical groove and forms a bottom cutting edge; the inverted edge surface intersects with the groove bottom surface of the main helical groove and forms an outward convex circular-arc edge; the first blade band surface intersects with the groove bottom surface of the main helical groove and forms a first circumferential edge; the bottom cutting edge and the first circumferential edge are connected through the outward convex circular-arc edge; the second blade band surface is arranged at intervals with the first blade band surface, and a secondary helical groove is formed between the first blade band surface and the second blade band surface; the helical direction of the secondary helical groove is the same as that of the main helical groove; the second blade band surface intersects with a groove bottom surface of the secondary helical groove and forms a second circumferential edge. The twist drill provided by the application has high machining quality and can prolong the service life.

Description

Technical Field

[0001] This invention relates to the field of drilling tool technology, and more particularly to a twist drill. Background Technology

[0002] As the most basic and widely used hole-making tool in the field of machining, the twist drill's cutting performance directly determines the quality and efficiency of the machined hole. Currently, standard twist drills generally adopt a two-flute symmetrical structure, meaning that the drill tip has two centrally symmetrically distributed cutting edges (bottom cutting edges), and material removal is achieved through the coordinated rotation of the two cutting edges.

[0003] However, existing two-flute twist drills have a series of inherent defects caused by their structural characteristics during actual machining. Specifically, because they rely solely on two cutting edges for cutting, it is difficult to maintain a strict dynamic balance of radial cutting forces on the two cutting edges during drilling. When factors such as uneven local hardness of the workpiece material, fluctuations in cutting parameters, or manufacturing deviations of the tool itself are combined, the force imbalance between the two cutting edges will cause the drill bit to deviate irregularly radially around the center of the hole (i.e., "yaw"). This deviation is not a stable periodic motion, but rather manifests as unpredictable random oscillation, causing the drill bit to continuously deviate from the ideal axis during the feed process. The irregular deviation of the drill bit will further increase the surface roughness of the hole wall, often accompanied by axially extending scratches, leaving room for further improvement in machining quality. At the same time, due to the uneven force on the two cutting edges, the wear of the two cutting edges at the tool tip exhibits asymmetrical characteristics, which in turn shortens the overall service life of the tool. Summary of the Invention

[0004] This application provides a twist drill to solve the technical problem of not being able to simultaneously achieve processing quality and service life.

[0005] Based on the above concept, the technical solution adopted in this application is: A twist drill includes a cutting section comprising two cutting edges spaced apart, with a main helical groove formed between the two cutting edges. Each cutting edge includes a bottom surface, a chamfered surface, a first cutting edge surface, and a second cutting edge surface. The chamfered surface, the first cutting edge surface, and the second cutting edge surface are all connected to the bottom surface. The bottom surface intersects with the bottom surface of the main helical groove to form a bottom cutting edge. The chamfered surface intersects with the bottom surface of the main helical groove to form a convex arc cutting edge. The first cutting edge surface intersects with the bottom surface of the main helical groove to form a first circumferential cutting edge. The bottom cutting edge and the first circumferential cutting edge are connected by the convex arc cutting edge. The second cutting edge surface is spaced apart from the first cutting edge surface, and a secondary spiral groove is formed between the first cutting edge surface and the second cutting edge surface. The spiral direction of the secondary spiral groove is the same as that of the main spiral groove. The second cutting edge surface intersects with the bottom surface of the secondary spiral groove to form a second circumferential cutting edge.

[0006] In one or more embodiments of this application, the diameter of the cutting part is D, and the radius of curvature of the convex circular arc blade is R, wherein the value of R / D ranges from 0.005 to 0.2.

[0007] In one or more embodiments of this application, the connecting line between the second circumferential cutting edge and the axis of the cutting part is the first connecting line, and the connecting line between the first circumferential cutting edge and the axis of the cutting part is the second connecting line. The angle α between the first connecting line and the second connecting line in the circumferential direction of the cutting part satisfies: 30°≤a≤70°.

[0008] In one or more embodiments of this application, the radial rake angle b of the second circumferential cutting edge satisfies: -25°≤b≤25°.

[0009] In one or more embodiments of this application, each of the blades has a secondary helical groove, and the imaginary tangent circle diameter of the bottom of the two secondary helical grooves is the characteristic core diameter d, 50%D≤d≤80%D, where D is the diameter of the cutting part.

[0010] In one or more embodiments of this application, the blade also includes a back surface of a shovel connected between the first blade surface and the secondary spiral groove, the back surface of the shovel being a surface recessed relative to the first blade surface.

[0011] In one or more embodiments of this application, the blade bottom surface includes a first bottom surface and a second bottom surface connected together. The first bottom surface is connected to the main spiral groove and the chamfered surface, and the second bottom surface is connected to the back of the shovel, the first blade surface, the secondary spiral groove and the chamfered surface.

[0012] In one or more embodiments of this application, the bottom surfaces of the two blades intersect to form a transverse blade, and the two ends of the transverse blade are correspondingly connected to the two bottom cutting edges.

[0013] In one or more embodiments of this application, the bottom cutting edge includes a first transition section, a main cutting section, and a second transition section connected in sequence. The first transition section is connected between the main cutting section and the transverse cutting edge, and the second transition section is connected between the main cutting section and the outwardly convex arc cutting edge. The main cutting section is an inwardly concave curve.

[0014] In one or more embodiments of this application, the main helical groove has a characteristic groove bottom surface, which intersects with the downstream edge bottom surface of the main helical groove in the helical direction to form a first transition section; the characteristic groove bottom surface intersects with the upstream edge bottom surface of the main helical groove in the helical direction to form a connected first arc junction segment and a second arc junction segment, the first arc junction segment and the second arc junction segment have opposite convex directions, and one end of the first arc junction segment away from the second arc junction segment is connected to the transverse edge; the second edge band surface intersects with the edge bottom surface to form a connecting segment, one end of the connecting segment is connected to the second circumferential edge, and one end of the second arc junction segment away from the first arc junction segment is connected to the other end of the connecting segment.

[0015] The beneficial effects of this application are: This application provides a twist drill where the bottom cutting edge on each cutting edge transitions to the first circumferential cutting edge via a convex arc cutting edge. This allows the convex arc cutting edge to gradually remove material from the hole wall according to the thickness of the cutting layer, thereby significantly eliminating scratches on the hole wall surface. Furthermore, after machining with the convex arc cutting edge, the springback height of the cut material surface on the hole wall can be controlled, thus reducing the cutting amount of the subsequent second circumferential cutting edge. The second circumferential cutting edge can further improve the surface finish of the hole wall, reduce roughness, and correct the diameter and roundness of the hole, ensuring... Based on the effect of precision machining of the hole wall, the wear of the second circumferential cutting edge is reduced, thereby extending the service life of the entire twist drill. Each cutting edge includes a first circumferential cutting edge and a second circumferential cutting edge, so that the twist drill has four circumferential cutting edges. The four circumferential cutting edges form four support points in the circumferential direction, which can effectively increase the guidance and machining stability of the twist drill during machining, reduce the risk of random vibration and irregular radial offset during machining, make the cutting process smooth, and significantly improve the machining quality of the hole, achieving dual optimization of machining life and machining quality. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments of this application will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the content of the embodiments of this application and these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the structure of a twist drill provided in one embodiment of this application from one perspective; Figure 2 This is a partially enlarged view of a twist drill provided in an embodiment of this application; Figure 3 This is a bottom view of a twist drill provided in an embodiment of this application; Figure 4 This is a cross-sectional view of a twist drill provided in an embodiment of this application; Figure 5 This is a schematic diagram of the structure of a twist drill provided in one embodiment of this application from another perspective.

[0018] Explanation of reference numerals in the attached figures: 10. Cutting section; 101. Drill tip; 1. Blade edge; 11. Blade bottom surface; 111. First bottom surface; 112. Second bottom surface; 12. Chamfered surface; 13. First cutting edge surface; 14. Second cutting edge surface; 15. Back of the shovel; 21. Main spiral groove; 211. Bottom surface of the characteristic groove; 22. Secondary spiral groove; 31. Bottom cutting edge; 311. First transition section; 312. Main cutting section; 313. Second transition section; 32. Outwardly convex arc cutting edge; 33. First circumferential cutting edge; 34. Second circumferential cutting edge; 35. Chisel cutting edge; 41. First connecting line; 42. Second connecting line; 51. First arc intersection segment; 52. Second arc intersection segment; 6. Connecting section; 20. Handle. Detailed Implementation

[0019] To make the technical problems solved by this application, the technical solutions adopted, and the technical effects achieved clearer, the technical solutions of this application will be further described below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely for explaining this application and not for limiting it. Furthermore, it should be noted that, for ease of description, only the parts relevant to this application are shown in the accompanying drawings, not all of them.

[0020] It should be understood that the phrase "an embodiment" or "one embodiment" throughout the specification means that a specific feature, structure, or characteristic related to the embodiment is included in at least one embodiment of this application. Therefore, "in one embodiment" or "in one embodiment" appearing throughout the specification does not necessarily refer to the same embodiment. Furthermore, these specific features, structures, or characteristics can be combined in any suitable manner in one or more embodiments.

[0021] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0022] In the description of this application, unless otherwise expressly specified and limited, the terms "connected," "linked," and "fixed" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0023] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature. In the description of this embodiment, unless otherwise specified, "multiple" specifically refers to two or more.

[0024] In the description of this embodiment, the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential," etc., are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of description and simplification of operation. They 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, and therefore should not be construed as a limitation of this application. In addition, the terms "first" and "second" are only used for distinction in description and have no special meaning.

[0025] It should be noted that when a component is referred to as "fixed to" or "set on" another component, it can be directly on the other component or it can be located in between the component.

[0026] The technical solution of this application will be further described below with reference to the accompanying drawings and specific embodiments.

[0027] This embodiment provides a twist drill for machining holes and grooves, which has high machining quality and can extend service life.

[0028] In this embodiment, twist drills can be used for machining structures such as holes and slots.

[0029] For example, such as Figures 1 to 5 As shown, the twist drill includes a cutting section 10. The cutting section 10 includes two cutting edges 1, which are spaced apart, and a main helical groove 21 is formed between the two cutting edges 1. Thus, there are two main helical grooves 21, and the two main helical grooves 21 and the two cutting edges 1 are alternately arranged along the circumference of the cutting section 10. The cutting edges 1 are used to cut the material, and the main helical groove 21 is used for chip removal during the cutting process.

[0030] like Figure 2 or Figure 3 As shown, each cutting edge 1 includes a bottom surface 11, a chamfered surface 12, a first cutting edge surface 13, and a second cutting edge surface 14. The chamfered surface 12, the first cutting edge surface 13, and the second cutting edge surface 14 are all connected to the bottom surface 11. The bottom surface 11 is located on the end face of the cutting section 10, while the chamfered surface, the first cutting edge surface 13, and the second cutting edge surface 14 are located on the side face of the cutting section 10. The bottom surface 11 intersects with the bottom surface of the main helical groove 21 to form a bottom cutting edge 31, which is used to directly contact the material and thus serves as the main cutting edge. The chamfered surface 12 intersects with the bottom surface of the main spiral groove 21 to form a convex arc-shaped cutting edge 32. The first cutting edge surface 13 intersects with the bottom surface of the main spiral groove 21 to form a first circumferential cutting edge 33. The bottom cutting edge 31 and the first circumferential cutting edge 33 are connected by the convex arc-shaped cutting edge 32, allowing a smooth transition between the bottom cutting edge 31 and the first circumferential cutting edge 33. This enables the removal of hole wall material according to the thickness of the cutting layer, from large to small, significantly eliminating scratches on the hole wall surface, improving machining quality, and controlling the springback height of the cut material surface. It should be noted that the convex arc-shaped cutting edge 32 is equivalent to a shoulder set on the bottom cutting edge 31.

[0031] For example, such as Figure 2 As shown, the second cutting edge surface 14 and the first cutting edge surface 13 are spaced apart, for example, the second cutting edge surface 14 and the first cutting edge surface 13 are spaced apart circumferentially in the cutting section 10. Furthermore, a secondary helical groove 22 is formed between the first cutting edge surface 13 and the second cutting edge surface 14. The helical direction of the secondary helical groove 22 is the same as the helical direction of the main helical groove 21, and the bottom surface of the secondary helical groove 22 intersects with the bottom surface of the cutting edge 11. The second cutting edge surface 14 intersects with the bottom surface of the secondary helical groove 22 to form a second circumferential cutting edge 34. The second circumferential cutting edge 34 is used for finishing the hole wall, reducing the roughness of the hole wall, and thus improving the smoothness of the hole wall.

[0032] It should be noted that both the first circumferential cutting edge 33 and the second circumferential cutting edge 34 are spiral-shaped and in the same direction. The first circumferential cutting edge 33 works in conjunction with the bottom cutting edge 31 to perform the main cutting of the material. The second circumferential cutting edge 34 then contacts the material after the first circumferential cutting edge 33, the bottom cutting edge 31, and the convex arc cutting edge 32, and is used for further finishing of the hole wall.

[0033] During the hole-making process of a twist drill, the bottom cutting edge 31 first contacts the workpiece to remove material and initially form a hole. Then, the convex arc-shaped cutting edge 32 contacts the hole wall and further processes it. Subsequently, the first circumferential cutting edge 33 further processes the hole wall to improve the accuracy of the hole. Finally, the second circumferential cutting edge 34 performs a finishing process on the hole wall, thereby improving the quality of the machined hole.

[0034] This embodiment provides a twist drill. The bottom cutting edge 31 on each cutting edge 1 transitions to the first circumferential cutting edge 33 via a convex arc cutting edge 32. This allows the convex arc cutting edge 32 to gradually remove material from the hole wall according to the thickness of the cutting layer, thus significantly eliminating scratches on the hole wall surface. Furthermore, after processing by the convex arc cutting edge 32, the springback height of the cut material surface on the hole wall can be controlled, thereby reducing the cutting amount of the subsequent second circumferential cutting edge 34. The second circumferential cutting edge 34 can further improve the surface finish of the hole wall, reduce roughness, and correct the hole diameter. While ensuring the roundness and finish of the hole wall, the wear on the second circumferential cutting edge 34 is reduced, thereby extending the service life of the entire twist drill. Each cutting edge 1 includes a first circumferential cutting edge 33 and a second circumferential cutting edge 34, giving the twist drill four circumferential cutting edges. These four cutting edges form four support points in the circumferential direction, which effectively increases the guidance and processing stability of the twist drill during processing, reduces the risk of random vibration and irregular radial offset during processing, makes the cutting process smooth, and significantly improves the processing quality of the hole, achieving a dual optimization of processing life and processing quality.

[0035] It should be noted that the hardness of the cutting part 10 is usually greater than the hardness of the workpiece to be machined. Therefore, during hole machining, the bottom cutting edge 31 contacts the workpiece and removes material to form the initial hole wall. At the same time, due to the contact of the cutting edge, the flank face, and the radial cutting force, the hole wall material will be subjected to a certain degree of compression, causing the hole wall to undergo a certain degree of elastic deformation. Furthermore, when the external force on the hole wall decreases, the hole wall will spring back to a certain extent. The convex arc-shaped cutting edge 32 is arc-shaped, allowing it to cut the hole wall material during the material springback process. This allows it to contact the hole wall after springback and perform micro-cutting or trimming on the springback portion, thereby reducing the impact of hole wall springback on hole diameter accuracy and surface quality. In some embodiments, after the convex arc-shaped cutting edge 32 is machined, the cutting allowance of the machined surface can usually be controlled within the range of 0.005mm-0.050mm to effectively reduce the cutting amount of the subsequent second circumferential cutting edge 34, thus ensuring the finishing effect of the hole wall. Normally, the second circumferential cutting edge 34 is sharper and more pointed, and its service life is the shortest link in the entire twist drill's service life. Excessive cutting amount of the second circumferential cutting edge 34 will shorten its service life. Therefore, reducing the cutting amount of the second circumferential cutting edge 34 can also reduce its wear and thus extend its service life.

[0036] In some alternative embodiments, the twist drill also includes a shank 20, which is coaxially connected to the cutting portion 10 and is used for fixing to other devices.

[0037] Optionally, the bottom surface 11 and the bottom cutting edge 31 constitute the drill tip 101 of the twist drill. The drill tip 101 is convex outward to achieve higher machining efficiency. It should be noted that the bottom cutting edge 31, the convex arc edge 32, and the first circumferential edge 33 work together to form the main cutting edge of the twist drill.

[0038] In one or more embodiments, the diameter of the cutting part 10 is D, and the radius of curvature of the convex arc-shaped cutting edge 32 is R, wherein the value of R / D ranges from 0.005 to 0.2. When the value of R / D is within the range, the convex arc-shaped cutting edge 32 can better realize the transition between the bottom cutting edge 31 and the first circumferential cutting edge 33, and can ensure that the convex arc-shaped cutting edge 32 removes material from the hole wall according to the thickness of the cutting layer from large to small, so as to effectively control the springback height of the material.

[0039] The R / D value cannot be too large. If it is too large, the length of the convex arc cutting edge 32 will be too large, which will in turn reduce the length of the bottom cutting edge 31 and the first circumferential cutting edge 33, thus affecting the machining efficiency. The R / D value cannot be too small. If it is too small, the convex arc cutting edge 32 will form a sharp point, which will prevent the material from being removed from the hole wall in a way that is from large to small according to the cutting layer thickness. The control over the material springback height will be limited, and the service life of the second circumferential cutting edge 34 cannot be effectively improved.

[0040] For example, the value of R / D can be any value or a range between any two values, such as 0.005, 0.008, 0.01, 0.012, 0.015, 0.018, 0.02, 0.05, 0.08, 0.1, 0.12, 0.15, 0.18, 0.2, etc., without any limitation.

[0041] In some alternative embodiments, such as Figure 4 As shown, the connecting line between the second circumferential cutting edge 34 and the axis of the cutting part 10 is the first connecting line 41, and the connecting line between the first circumferential cutting edge 33 and the axis of the cutting part 10 is the second connecting line 42. The included angle α between the first connecting line 41 and the second connecting line 42 in the circumferential direction of the cutting part 10 satisfies: 30°≤a≤70°. The included angle between the first connecting line 41 and the second connecting line 42 in the circumferential direction of the cutting part 10 reflects the distance between the first circumferential cutting edge 33 and the second circumferential cutting edge 34 in the circumferential direction of the cutting part 10. The larger α is, the greater the distance between the first circumferential cutting edge 33 and the second circumferential cutting edge 34 in the circumferential direction of the cutting part 10; the smaller α is, the smaller the distance between the first circumferential cutting edge 33 and the second circumferential cutting edge 34 in the circumferential direction of the cutting part 10.

[0042] The angle α between the first connecting line 41 and the second connecting line 42 in the circumferential direction of the cutting portion 10 cannot be too large. If it is too large, the second circumferential cutting edge 34 will be closer to the main helical groove 21, resulting in a narrower second cutting edge surface 14. This, in turn, will lead to lower structural strength of the second circumferential cutting edge 34 and a greater risk of breakage. The angle α between the first connecting line 41 and the second connecting line 42 in the circumferential direction of the cutting portion 10 cannot be too small. If it is too small, the secondary helical groove 22 will be too narrow, making it impossible to quickly remove the chips cut by the second circumferential cutting edge 34. This will result in a higher risk of the chips scratching the machined surface and compromise the machining quality of the machined surface.

[0043] For example, the angle α between the first connecting line 41 and the second connecting line 42 in the circumferential direction of the cutting part 10 can be any value such as 30°, 40°, 50°, 60°, 70°, or any range between any two values.

[0044] It should be noted that the first connecting line 41 and the second connecting line 42 are both imaginary lines and are not actual lines on the twist drill.

[0045] In some alternative embodiments, such as Figure 4 As shown, the radial rake angle b of the second circumferential cutting edge 34 satisfies: -25°≤b≤25°. When the radial rake angle b of the second circumferential cutting edge 34 is within the specified range, the second circumferential cutting edge 34 can possess both high structural strength and strong sharpness, resulting in a smoother machined surface.

[0046] It should be noted that the radial rake angle b of the second circumferential cutting edge 34 is the angle between the rake face of the second circumferential cutting edge 34 and the base surface in a radial plane that simultaneously includes the axis of the cutting part 10 and the radius of that point on the second circumferential cutting edge 34. The base surface is the surface passing through that point and the axis of the cutting part 10, and perpendicular to the axis of the cutting part 10. A negative radial rake angle b of the second circumferential cutting edge 34 indicates that the rake face is below the base surface. In this case, the squeezing effect during cutting is significant, increasing cutting deformation and cutting force, but the wedge angle of the cutting edge increases, resulting in higher strength. A positive radial rake angle b of the second circumferential cutting edge 34 indicates that the rake face is above the base surface. In this case, the cutting is sharper, and the surface finish is higher.

[0047] In this embodiment, the radial rake angle b of the second circumferential cutting edge 34 cannot be too large, otherwise there is a risk of insufficient strength and breakage. The radial rake angle b of the second circumferential cutting edge 34 cannot be too small, otherwise it will result in insufficient sharpness, which will affect the smoothness of the machined surface.

[0048] For example, the radial rake angle b of the second circumferential blade 34 can be any value or a range between any two values, such as -25°, -15°, -10°, 0°, 10°, 15°, 20°, 25°.

[0049] In some embodiments, both the main spiral groove 21 and the secondary spiral groove 22 are arc-shaped grooves. This configuration reduces the risk of chip clogging and improves chip removal smoothness.

[0050] In some alternative embodiments, such as Figure 2 or Figure 3 As shown, each cutting edge 1 has a secondary helical groove 22, resulting in the twist drill having two secondary helical grooves 22. The diameter of the imaginary tangent circle at the bottom of the two secondary helical grooves 22 is the characteristic core diameter d, where 50%D≤d≤80%D, and D is the diameter of the cutting part 10. It should be noted that D is the outer diameter of the cutting part 10.

[0051] In this embodiment, when the characteristic core diameter d is within the specified range, the setting of the secondary helical groove 22 has a relatively small impact on the overall structural strength of the cutting part 10, ensuring that the cutting part 10 still has high structural strength. At the same time, the secondary helical groove 22 can efficiently remove the chips cut by the second circumferential cutting edge 34 from the cutting part 10, reducing the risk of chip blockage, thus balancing high structural strength and high chip removal efficiency. The value of the characteristic core diameter d cannot be too large, otherwise the secondary helical groove 22 will be too shallow, resulting in poor chip removal and the possibility of chips in the secondary helical groove 22 scratching the machined surface, affecting the machining quality. The value of the characteristic core diameter d cannot be too small, otherwise the secondary helical groove 22 will be too deep, resulting in an excessively large area for the groove in the cutting part 10, which will affect the structural strength of the cutting part 10, making it prone to breakage during machining, with low stability and a higher likelihood of radial displacement.

[0052] For example, the value of the characteristic core diameter d can be any value or a range between any two values, such as 50%D, 55%D, 60%D, 70%D, 75%D, 80%D, etc.

[0053] In some alternative embodiments, such as Figure 2 or Figure 3 As shown, the cutting edge 1 also includes a back face 15 connected between the first cutting edge surface 13 and the secondary spiral groove 22. The back face 15 is a surface recessed relative to the first cutting edge surface 13. The back face 15 reduces friction and heat generation. Specifically, without the back face 15, the contact area with the hole wall during drilling is large, resulting in excessive friction, severe heat generation, and rapid wear. The back face 15 prevents contact with the hole wall, significantly reducing the frictional resistance between the cutting part 10 and the hole wall during drilling, thus reducing the heat generation of the twist drill. In addition, the back face 15 leaves a gap behind the first cutting edge surface 13, preventing chips from being squeezed into the gap between the drill bit's outer edge and the hole wall, which facilitates the flow of coolant and the smooth discharge of chips.

[0054] In some alternative embodiments, the width of the back face 15 of the shovel is smaller than the width of the first cutting edge 13, so that the arrangement of the back face 15 of the shovel does not affect the support effect of the twist drill, thereby reducing the risk of radial displacement.

[0055] In one or more embodiments, such as Figure 2As shown, each blade bottom surface 11 includes a first bottom surface 111 and a second bottom surface 112 connected to each other. The first bottom surface 111 is connected to the main spiral groove 21 and the chamfered surface 12; that is, the first bottom surface 111 intersects the bottom surface of the main spiral groove 21 and the chamfered surface 12. The second bottom surface 112 is connected to the back surface of the shovel 15, the first cutting edge surface 13, the secondary spiral groove 22, and the chamfered surface 12; that is, the second bottom surface 112 intersects the bottom surface of the secondary spiral groove 22, the back surface of the shovel 15, the first cutting edge surface 13, and the chamfered surface 12.

[0056] By setting the first bottom surface 111 and the second bottom surface 112 to form an obtuse angle, the drill tip 101 can protrude outward, which improves cutting efficiency and structural strength of the drill tip 101, thereby extending the service life of the twist drill.

[0057] In some alternative embodiments, please continue to refer to Figure 2 and Figure 3 The bottom surfaces 11 of the two cutting edges 1 intersect to form a chisel edge 35, and the two ends of the chisel edge 35 are connected to the two bottom cutting edges 31. By setting the chisel edge 35, the machining efficiency of the twist drill can be further improved.

[0058] In this embodiment, the first bottom surfaces 111 of the two blade bottom surfaces 11 intersect to form a transverse blade 35.

[0059] In some embodiments, the bottom cutting edge 31 can be a segmented structure. For example, as... Figure 2 and Figure 3 As shown, each bottom cutting edge 31 includes a first transition section 311, a main cutting section 312, and a second transition section 313 connected in sequence. The first transition section 311 connects the main cutting section 312 and the chisel edge 35, and the second transition section 313 connects the main cutting section 312 and the outwardly convex arc cutting edge 32. It should be noted that the first transition section 311 of one bottom cutting edge 31 connects to one end of the corresponding main cutting section 312 and the chisel edge 35, while the first transition section 311 of another bottom cutting edge 31 connects to the other end of the corresponding main cutting section 312 and the chisel edge 35. The second transition section 313 connects the main cutting section 312 and the corresponding outwardly convex arc cutting edge 32. By setting the first transition section 311, the transition between the chisel edge 35 and the main cutting section 312 can be achieved, thereby improving the machining quality and the structural strength of the drill tip 101. By setting a second transition section 313, the transition between the main cutting section 312 and the convex arc blade 32 can be realized, avoiding the reduction in machining quality and the shortening of service life caused by the abrupt change at the connection.

[0060] In some alternative embodiments, such as Figure 3As shown, the main cutting section 312 is a concave curve, specifically recessed towards the interior of the cutting edge 1. This design allows for a larger length of the main cutting section 312 and a larger contact area with the material, thereby improving machining efficiency. Furthermore, the concave main cutting section 312 also possesses high structural strength.

[0061] It is understandable that the bottom cutting edge 31 can also have a smooth structure, and this is not limited here.

[0062] In at least one possible implementation, such as Figure 2 As shown, the main helical groove 21 has a characteristic groove bottom surface 211. The characteristic groove bottom surface 211 intersects with the downstream cutting edge bottom surface 11 in the helical direction of the main helical groove 21 to form the aforementioned first transition section 311. The remaining area of ​​the main helical groove 21 intersects with the cutting edge bottom surface 11 to form the main cutting section 312 and the second transition section 313. Figure 3 As shown, in a blade 1, the bottom surface 211 of the feature groove intersects with the upstream blade bottom surface 11 in the helical direction of the main helical groove 21 to form a connected first arc junction segment 51 and a second arc junction segment 52. The protrusion directions of the first arc junction segment 51 and the second arc junction segment 52 are opposite. The end of the first arc junction segment 51 facing away from the second arc junction segment 52 is connected to the transverse blade 35. Please refer to... Figure 2 and Figure 3 The second cutting edge 14 intersects with the bottom cutting edge 11 to form a connecting segment 6. One end of the connecting segment 6 is connected to the second circumferential cutting edge 34. The end of the second arc junction segment 52 that is away from the first arc junction segment 51 is connected to the other end of the connecting segment 6.

[0063] By setting the first arc junction section 51 and the second arc junction section 52, a multi-segment arc junction transition spiral groove is realized, thereby solving the problem that the bottom cutting edge 31 of the cutting part 10 has the largest circumferential diameter and therefore wears quickly due to the maximum linear velocity. It also solves the problem that the degree of curvature between the bottom cutting edge 31 and the tail of the main spiral groove 21 is not suitable, resulting in insufficient chip curling and poor chip space when machining soft steel materials. Furthermore, it solves the problem that the tail of the main spiral groove 21 extends in the opposite direction to the bottom cutting edge 31, causing the chips to easily scrape the hole wall and resulting in poor hole wall quality. It can simultaneously achieve high cutting edge strength and good chip breaking ability, and has good versatility and economy.

[0064] The twist drill provided in this embodiment, by setting an outwardly convex arc-shaped cutting edge 32, is equivalent to forming an R-angle structure at the end of the bottom cutting edge 31. The outwardly convex arc-shaped cutting edge 32 can remove the hole wall material in descending order of cutting layer thickness, thereby significantly eliminating scratches on the hole wall surface and controlling the springback height of the cut material surface. Typically, the cutting allowance of the machined surface can be controlled within the range of 0.005mm-0.050mm, reducing the cutting amount of the subsequent second circumferential cutting edge 34, ensuring the finishing effect of the hole wall while extending the service life of the second circumferential cutting edge 34. The second circumferential cutting edge 34 can perform secondary finishing cutting on the machined surface of the hole wall (i.e., after cutting by the outwardly convex arc-shaped cutting edge 32), which can further improve the surface finish and roughness of the hole wall, and correct the diameter and roundness of the hole, resulting in a high-quality hole. Furthermore, the twist drill provided in this embodiment, with the synergistic effect of the convex arc cutting edge 32 and the second circumferential cutting edge 34, achieves a four-flute structure with step-by-step cutting, making the cutting process more stable and significantly improving the hole machining quality, thus achieving dual optimization of machining life and machining quality.

[0065] Obviously, the above embodiments of this application are merely examples for clear illustration and are not intended to limit the implementation of this application. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the scope of protection of the claims of this application.

Claims

1. A twist drill, characterized in that, The device includes a cutting section (10), which includes two cutting edges (1) spaced apart and forming a main helical groove (21) between the two cutting edges (1). Each cutting edge (1) includes a bottom surface (11), a chamfered surface (12), a first cutting edge surface (13), and a second cutting edge surface (14). The chamfered surface (12), the first cutting edge surface (13), and the second cutting edge surface (14) are all connected to the bottom surface (11). Next, the bottom surface (11) of the cutting edge intersects with the bottom surface of the main spiral groove (21) to form a bottom cutting edge (31), the chamfered surface (12) intersects with the bottom surface of the main spiral groove (21) to form a convex arc cutting edge (32), and the first cutting edge surface (13) intersects with the bottom surface of the main spiral groove (21) to form a first circumferential cutting edge (33); the bottom cutting edge (31) and the first circumferential cutting edge (33) are connected by the convex arc cutting edge (32); The second cutting edge surface (14) is spaced apart from the first cutting edge surface (13), and a secondary spiral groove (22) is formed between the first cutting edge surface (13) and the second cutting edge surface (14). The spiral direction of the secondary spiral groove (22) is the same as the spiral direction of the main spiral groove (21). The second cutting edge surface (14) intersects with the bottom surface of the secondary spiral groove (22) to form a second circumferential cutting edge (34).

2. The twist drill according to claim 1, characterized in that, The diameter of the cutting part (10) is D, and the radius of curvature of the convex circular arc blade (32) is R, wherein the value of R / D ranges from 0.005 to 0.

2.

3. The twist drill according to claim 1, characterized in that, The connecting line between the second circumferential cutting edge (34) and the axis of the cutting part (10) is the first connecting line (41), and the connecting line between the first circumferential cutting edge (33) and the axis of the cutting part (10) is the second connecting line (42). The included angle α between the first connecting line (41) and the second connecting line (42) in the circumferential direction of the cutting part (10) satisfies: 30°≤a≤70°.

4. The twist drill according to claim 1, characterized in that, The radial front angle b of the second circumferential cutting edge (34) satisfies: -25°≤b≤25°.

5. The twist drill according to claim 1, characterized in that, Each of the blades (1) has a secondary helical groove (22), and the imaginary tangent circle diameter of the bottom of the two secondary helical grooves (22) is the characteristic core diameter d, 50%D≤d≤80%D, where D is the diameter of the cutting part (10).

6. The twist drill according to claim 1, characterized in that, The blade (1) also includes a back surface (15) of the shovel connected between the first blade surface (13) and the secondary spiral groove (22), the back surface (15) of the shovel being a surface recessed relative to the first blade surface (13).

7. The twist drill according to claim 6, characterized in that, The blade bottom surface (11) includes a first bottom surface (111) and a second bottom surface (112) connected to each other. The first bottom surface (111) is connected to the main spiral groove (21) and the chamfered surface (12). The second bottom surface (112) is connected to the back surface of the shovel (15), the first blade surface (13), the secondary spiral groove (22) and the chamfered surface (12).

8. The twist drill according to claim 1, characterized in that, The bottom surfaces (11) of the two blades (1) intersect to form a transverse blade (35), and the two ends of the transverse blade (35) are connected to the two bottom cutting edges (31).

9. The twist drill according to claim 8, characterized in that, The bottom cutting edge (31) includes a first transition section (311), a main cutting section (312) and a second transition section (313) connected in sequence. The first transition section (311) is connected between the main cutting section (312) and the transverse cutting edge (35), and the second transition section (313) is connected between the main cutting section (312) and the convex circular arc cutting edge (32). The main cutting section (312) is a concave curve.

10. The twist drill according to claim 9, characterized in that, The main spiral groove (21) has a characteristic groove bottom surface (211), which intersects with the downstream cutting edge bottom surface (11) of the main spiral groove (21) in the spiral direction to form the first transition section (311); the characteristic groove bottom surface (211) intersects with the upstream cutting edge bottom surface (11) of the main spiral groove (21) in the spiral direction to form a connected first arc junction section (51) and a second arc junction section (52), the first arc junction section (51) and The second arc junction segment (52) has a convex direction opposite to that of the first arc junction segment (51), and the end of the first arc junction segment (51) opposite to the second arc junction segment (52) is connected to the transverse blade (35); the second blade surface (14) intersects with the blade bottom surface (11) to form a connecting segment (6), one end of the connecting segment (6) is connected to the second circumferential blade (34), and the end of the second arc junction segment (52) opposite to the first arc junction segment (51) is connected to the other end of the connecting segment (6).

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