A spiral flute drill bit with chip breaker flutes

Abstract

The application provides a drill bit with a spiral groove, which comprises a cutting part, an optional guide part and an optional shank, the cutting part has a cutting edge, the cutting edge has a rake face, a relief face and an edge, the rake face forms a first rake angle at each position of the edge, a chip breaker groove is arranged on the rake face, the chip breaker groove extends in the direction of the edge in the length direction, the chip breaker groove has a groove face close to the edge, so that the groove face close to the edge of the chip breaker groove forms a second rake angle, the second rake angle is greater than the corresponding first rake angle. The application controls the shape and size of the chip by the unique chip breaker groove extending in the direction of the edge, reduces the size of the chip, improves the uniformity of the chip, is beneficial to the discharge of the chip, forms the second rake angle greater than the corresponding first rake angle through the groove face of the chip breaker groove, improves the sharpness of the drill bit, reduces the cutting resistance and improves the machining efficiency.

Description

Technical Field

[0001] This invention relates to the field of drill bit technology, and more particularly to a drill bit including a chip breaker groove. Background Technology

[0002] A drill bit is a hole-making tool used to create holes in solid materials or enlarge existing holes. Because hole-making tools operate within the workpiece, their structural dimensions are limited, leading to defects in chip removal, strength and rigidity, and guidance. Twist drills are the most widely used hole-making tools. Their main cutting edge is relatively long, resulting in wide chips and difficulties in chip removal, especially in deep hole machining. To facilitate chip removal, the chip flutes of twist drills are usually helical. Generally, the smaller the helix angle and the shorter the helix length of a helical flute drill, the better the chip removal. However, the helix angle of a helical flute drill not only directly affects chip removal performance but is also closely related to the sharpness and strength of the cutting edge, as well as the overall rigidity and strength of the tool. While a smaller helix angle facilitates chip removal, it also results in a smaller rake angle, increasing cutting resistance and affecting the tool's cutting performance and lifespan. A larger helix angle results in a larger rake angle of the cutting edge, reducing cutting resistance. However, an excessively large helix angle not only makes chip removal difficult but also makes the cutting edge corners very sharp, reducing its strength and making it prone to chipping and breakage. This significantly reduces the drill bit's lifespan and the quality of the machined surface. Existing drill bits cannot meet the demands of high-precision, high-efficiency machining of parts in advanced manufacturing industries. Therefore, a drill bit with a sharp cutting edge, good chip removal, and high overall strength is needed to improve its cutting performance and service life. Summary of the Invention

[0003] The present invention provides a drill bit including a chip breaker groove, which includes the following embodiments:

[0004] Embodiment 1. A drill bit with a helical groove, comprising a cutting portion, an optional guide portion, and an optional tool holder, wherein the cutting portion has a cutting edge and a helical groove corresponding to the cutting edge, the cutting edge having a rake face, a flank face, and a cutting edge formed by the intersection of the rake face and the flank face, the rake face forming a first rake angle at each point of the cutting edge, characterized in that a chip breaker groove is provided on the rake face, the chip breaker groove extending along the direction of the cutting edge in the length direction, the chip breaker groove having a groove surface close to the cutting edge, such that the groove surface of the chip breaker groove close to the cutting edge forms a second rake angle, the second rake angle being greater than the corresponding first rake angle, and the chip breaker groove having a groove surface away from the cutting edge for curling the chips in the cutting direction.

[0005] Implementation Method 2. The drill bit according to Implementation Method 1, characterized in that the spiral groove extends into the guide portion, and the length-to-diameter ratio of the guide portion is greater than or equal to 5 and less than or equal to 50, greater than or equal to 8 and less than or equal to 45, greater than or equal to 10 and less than or equal to 40, and greater than or equal to 15 and less than or equal to 35.

[0006] Implementation Method 3. The drill bit according to Implementation Method 1 or 2, characterized in that the angle of the spiral groove is 0 to 30 degrees, 5 to 10 degrees, 10 to 20 degrees, or 7 to 25 degrees.

[0007] Embodiment 4. The drill bit according to Embodiment 3, characterized in that the core thickness of the drill bit is 30% to 50%, 32% to 45%, 33% to 42%, 35% to 40%, or 36% to 38% of the drill bit diameter.

[0008] Embodiment 5. The drill bit according to Embodiment 1 or 2, characterized in that the drill bit with spiral grooves is made of integral cemented carbide.

[0009] Embodiment 6. The drill bit according to Embodiment 1, characterized in that the groove surface near the cutting edge and / or the groove surface away from the cutting edge is a wavy, undulating surface.

[0010] Implementation Method 7. The drill bit according to Implementation Method 1 is characterized in that the cutting edge has a cutting edge undulation, and the bottom of the chip breaking groove has a groove bottom undulation corresponding to the cutting edge undulation, so that the chips are subjected to a curling force in the cutting edge extension direction.

[0011] Implementation Method 8. The drill bit according to Implementation Method 7, characterized in that the cutting edge undulation is a wave-shaped undulation.

[0012] Embodiment 9. The drill bit according to Embodiment 1 or 4, characterized in that the drill bit with helical grooves has two or three cutting edges.

[0013] Embodiment 10. The drill bit according to Embodiment 1, characterized in that the drill bit further has a chisel edge, and the chip breaking groove extends to the chisel edge.

[0014] Implementation Method 11. The drill bit according to Implementation Method 1, characterized in that the chip breaker groove is prepared by a processing method that does not produce thermal damage.

[0015] Implementation Method 12. The drill bit according to Implementation Method 1, characterized in that the chip breaking groove is prepared by a femtosecond pulsed laser processing method.

[0016] Embodiment 13. A method for preparing a drill bit with helical grooves according to any one of Embodiments 1 to 10, wherein the drill bit with helical grooves comprises a cutting portion, an optional guiding portion, and an optional tool holder, the cutting portion having a cutting edge and a helical groove corresponding to the cutting edge, the cutting edge having a rake face, a flank face, and a cutting edge formed by the intersection of the rake face and the flank face, the rake face forming a first rake angle at each point of the cutting edge, characterized in that the method comprises:

[0017] A chip breaker groove is formed on the rake face. The chip breaker groove extends along the direction of the cutting edge in the length direction. The chip breaker groove has a groove surface close to the cutting edge, so that the groove surface of the chip breaker groove close to the cutting edge forms a second rake angle, which is greater than the corresponding first rake angle.

[0018] Implementation Method 14. The method according to Implementation Method 13, wherein the chip breaker groove is prepared by a processing method that does not produce thermal damage.

[0019] Implementation Method 15. The method according to Implementation Method 13, wherein the chip breaking groove is prepared by a femtosecond pulsed laser processing method.

[0020] This application utilizes a unique chip breaker groove extending along the cutting edge to control the shape and size of chips, reducing chip size, improving chip uniformity, and facilitating chip removal. The groove surface near the cutting edge forms a second rake angle greater than the corresponding first rake angle, increasing drill bit sharpness, reducing cutting resistance, and improving machining efficiency. This application employs a chip breaker groove to achieve a high sharpness value, solving the problem of insufficient sharpness at small helix angles. A small helix angle reduces friction between the chip and the workpiece and shortens the chip removal distance, thus facilitating chip removal, preventing heat accumulation in the chips, and improving drill bit machining accuracy and service life. Furthermore, the chip breaker groove design of this application allows for smooth chip removal with a smaller chip removal space and shorter chip removal distance. In deep hole machining with a large length-to-diameter ratio, it effectively solves the problem of difficult chip removal while ensuring drill bit strength and rigidity, significantly improving the drill bit's cutting performance and service life. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the embodiments of this disclosure, the accompanying drawings of the embodiments will be briefly described below. Obviously, the drawings described below only relate to some embodiments of this disclosure and are not intended to limit this disclosure.

[0022] Figure 1 This is a perspective view of the drill bit described in Embodiment 1 of this application;

[0023] Figure 2 This is a schematic diagram of the cutting part of the drill bit;

[0024] Figure 3 This is a schematic diagram of the ends of the drill bit's cutting edge and chisel edge;

[0025] Figure 4 This is a partial schematic diagram of the cutting edge of a cutting edge;

[0026] Figure 5 This is a schematic diagram of the first and second rake angles on the cutting edge;

[0027] Figure 6 This is a schematic diagram of the wavy cutting edge undulation in Example 6.

[0028] 100-Cutting part, 110-Cutting edge, 111-Rake face, 112-Flag face, 113-Cutting edge, 10-Chip breaker groove, 11-Groove surface near the cutting edge, 12-Groove surface away from the cutting edge, 13-Bottom of chip breaker groove, 120-Helical groove, 130-Chisel edge, 200-Guide part, 300-Tool holder. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this disclosure. All other embodiments obtained by those skilled in the art based on the described embodiments of this disclosure without creative effort are within the scope of protection of this disclosure.

[0030] This application discloses a drill bit with helical grooves, comprising a cutting portion, an optional guide portion, and an optional tool holder. The cutting portion has a cutting edge and a helical groove corresponding to the cutting edge. The cutting edge has a rake face, a flank face, and a cutting edge formed by the intersection of the rake face and the flank face. The rake face forms a first rake angle at each point of the cutting edge. The drill bit is characterized by having a chip breaker groove on the rake face, extending along the direction of the cutting edge in the length direction. The chip breaker groove has a groove surface near the cutting edge, such that the groove surface near the cutting edge forms a second rake angle, which is greater than the corresponding first rake angle. The chip breaker groove has a groove surface away from the cutting edge for curling the chips in the cutting direction. In some embodiments, the drill bit of this application does not include a guide portion and a tool holder; the cutting portion has a connecting portion that connects to an external guide portion and an external tool holder to form a complete working drill bit. In some embodiments, the drill bit of this application does not include a shank, but includes a cutting portion and a guiding portion. The guiding portion has a connecting portion that engages with an external shank to form a complete working drill bit.

[0031] The rake angle is a crucial geometric parameter of a cutting tool, determining its sharpness and strength. It significantly impacts the cutting process. Increasing the rake angle reduces chip deformation and improves edge sharpness, thereby reducing cutting force and power, decreasing heat generation, and improving tool durability. However, increasing the rake angle decreases the wedge angle, which weakens the cutting edge, making it more prone to chipping, and reduces the heat dissipation volume of the tool tip, leading to higher cutting temperatures. Therefore, excessively large rake angles decrease tool durability. For tools made of various materials, both excessively large and small rake angles result in low tool durability. Under certain machining conditions, there exists a rake angle that maximizes tool durability. For twist drills with helical flutes, the cutting edge is located at the drill tip, and the helical flute corresponding to the cutting edge has a helix angle ω. The helix angle ω is the angle between the tangent at any point on the intersection line (helix) of the drill's outer cylinder and the surface of the helical flute and the drill axis. Let the lead of the helical groove be P, and the outer diameter of the drill bit be d0. Then tanω = πd0 / P. Since the radii are different at different points on the cutting edge, while the lead is the same at all points on the same helix, the helix angle is different at any point on the cutting edge. For any point m on the cutting edge, because it is located at a diameter of d... m On the cylinder, the helix angle ω of the spiral passing through point m is... m It can be represented as: tanω m =d m As can be seen from the equation / d0·tanω, the helix angle is largest at the outer diameter of the drill bit and decreases as it approaches the center. The helix angle is actually the rake angle of the drill bit within the assumed working plane.

[0032] The rake angle γ at any point on the cutting edge is measured in the orthogonal plane at that point. It is the angle between the rake face and the base plane in the orthogonal plane. The rake angle γ at any point m on the cutting edge... m The spiral angle ω at that point m Principal deflection angle k rm and the blade inclination angle λ stm The relationship is: tanγ m =(tanω) m +tanλ stm ·cosk rm ) / sink rm The rake angle is also large where the helix angle is large. Therefore, the rake angle is largest at the outer edge of the drill bit. The closer to the center of the drill bit, the smaller the rake angle becomes, and it is a negative value. The rake angle at the drill core cannot be increased by increasing the helix angle.

[0033] It is evident that for twist drills with helical flutes, a larger helix angle and a larger rake angle result in a sharper cutting edge. However, an excessively large helix angle weakens the strength of the cutting edge, worsens heat dissipation, and for drills at the same machining depth, a larger helix angle leads to a longer chip removal distance. An excessively large helix angle can cause chip removal difficulties, thus affecting the tool's machining efficiency, accuracy, and lifespan. Therefore, for twist drills machining holes of a specific depth, achieving smooth chip removal with a smaller helix angle while maintaining the drill's strength, toughness, and sharpness can significantly improve its cutting performance and lifespan.

[0034] This application effectively resolves the contradiction between chip removal, cutting edge sharpness, and cutting edge strength in drill bits with helical grooves by setting chip breaker grooves extending along the cutting edge direction, forming a second rake angle greater than the corresponding first rake angle. This achieves a large rake angle with a constant or small change in the helix angle, while also improving drill bit sharpness, reducing cutting resistance, increasing sharpness, stabilizing centering, reducing torque, making the drill bit less prone to breakage, and extending its lifespan. A smaller helix angle also reduces the chip removal distance. Furthermore, compared to relying solely on the helical surface for chip breaker, the chip breaker groove plays a more effective role in chip breaker. Although existing technologies can create chip breaker grooves on the rake face to facilitate chip removal, these grooves cannot improve drill bit cutting edge sharpness with a smaller helix angle and suffer from difficulties in machining and damage to the cutting edge, failing to fundamentally solve the chip removal problem. This application controls the shape and size of chips by using chip breaker grooves extending along the cutting edge. The chip breaker grooves reduce the size of chips and improve chip uniformity through chip breaker action. Furthermore, by reducing the chip removal distance, it facilitates chip removal. The strength and heat dissipation volume of the cutting edge with a large rake angle are not significantly reduced, which makes it less likely to cause chipping and thermal damage to the workpiece surface. This greatly improves cutting efficiency and cutting accuracy, thereby improving machining accuracy and enabling the tool to maintain machining accuracy even after long-term use. Therefore, the life of the drill bit is also greatly improved.

[0035] In this application, the "first rake angle" is defined the same as the aforementioned "rake angle γ," which is the angle between the rake face and the base plane in an orthogonal plane. The "second rake angle" refers to the angle between the groove surface near the cutting edge and the base plane in an orthogonal plane. The base plane of any point on the cutting edge is a plane passing through that point and perpendicular to the cutting velocity direction at that point. For a twist drill with helical flutes, its cutting edge includes a primary cutting edge and a secondary cutting edge. The primary cutting edge is the intersection of the rake face and the flank face, and the secondary cutting edge is the intersection of the rake face and the secondary flank face, i.e., the edge. The secondary flank face is a narrow edge on the outer cylindrical surface of the drill bit opposite to the machined surface (hole wall). Unless otherwise specified, the cutting edge in this application refers to the primary cutting edge.

[0036] In this application, the second rake angle at the cutting edge is formed by a groove surface near the cutting edge. The second rake angle is larger than the corresponding first rake angle. That is, this application uses a chip breaker groove to obtain a large sharpness value, making cutting easier and centering more stable. The specific shape and size of the chip breaker groove can directly affect the shape and size of the chips. The groove surface away from the cutting edge can further curl the chips in the cutting direction, allowing the chip breaker groove to play the role of curling and breaking chips. There is no limitation on the width and depth range of the chip breaker groove, and it can usually be selected without significantly damaging the rigidity of the cutting edge. The typical width of the chip breaker groove can be 1 / 20 to 1 / 3 of the drill bit diameter, for example, 1 / 10 to 1 / 3, 1 / 20 to 1 / 10, 1 / 15 to 1 / 10, for example, 1 / 6 to 1 / 4. The depth of the chip breaker groove can be 1 / 10 to 1 / 2, 1 / 8 to 1 / 3, 1 / 3 to 1 / 2, or 1 / 6 to 1 / 3 of the width of the chip breaker groove. In this application, the width and depth of the chip breaker groove vary at each location. The term "depth of the chip breaker groove" refers to the deepest point of the entire chip breaker groove relative to the rake face, and the term "width of the chip breaker groove" refers to the widest point of the entire chip breaker groove in the direction perpendicular to the cutting edge.

[0037] In some embodiments, the spiral groove extends into the guide portion, the guide portion having a length-to-diameter ratio of 5 to 50, 8 to 45, 10 to 40, or 15 to 35. Holes with a depth-to-diameter ratio greater than 5 are generally called deep holes, and the drill bits used to machine deep holes are called deep hole drills. The drill bit parameter corresponding to the depth-to-diameter ratio is the length-to-diameter ratio. The drill bit with chip breaker grooves in this application is particularly suitable for deep hole drilling. Deep hole machining differs from ordinary hole machining, with some problems being more prominent. In deep hole machining, due to the slender drill bit, its strength and rigidity are relatively poor, making it prone to vibration and causing borehole skew, affecting machining accuracy and productivity. Simultaneously, due to the large hole depth, the chip removal space is small, the chip flow path is longer, making chip removal more difficult, increasing friction, and facilitating the accumulation of cutting heat, further increasing the difficulty of deep hole machining. This application presents a deep hole drill bit with a chip breaker groove. Not only does the chip breaker groove's chip-breaking effect result in smaller chips and a shorter chip removal distance, facilitating chip evacuation, but more importantly, a smaller helix angle means less cutting and guiding portion of the drill bit is removed by the helical groove, thus improving the drill bit's strength and rigidity. The second rake angle of this application depends on the chip breaker groove's design and is independent of the helix angle of the helical groove. This allows for a smaller helix angle in deep hole drills with a larger length-to-diameter ratio, ensuring higher drill bit strength and rigidity while simultaneously meeting chip removal and strength / rigidity requirements, thereby improving both the quality and efficiency of deep hole machining.

[0038] In some embodiments, the angle of the helical groove is 0 to 30 degrees, 5 to 10 degrees, 10 to 20 degrees, or 7 to 25 degrees. The smaller the helical angle, the less friction between the chip and the workpiece, facilitating chip removal; conversely, the larger the helical groove angle, the less conducive it is to chip removal. This application provides a chip-breaking groove extending along the cutting edge direction. By using a chip-breaking groove, a large sharpness value is obtained, solving the problem of insufficient sharpness when the helical angle is small. Simultaneously, it facilitates chip removal, further meeting the chip removal needs of deep hole drilling.

[0039] In some embodiments, the core thickness of the drill bit is 30% to 50%, 32% to 45%, 33% to 42%, 35% to 40%, or 36% to 38% of the drill bit diameter. Core thickness is closely related to the drill bit's rigidity and chip removal capability. A larger core thickness results in better drill bit rigidity, but reduces the flute area, decreasing the chip removal space and making chip removal more difficult. For high-speed steel drill bits used on drilling machines, the core thickness is typically 10% to 20% of the drill bit diameter; this proportion is larger for smaller diameter drill bits and decreases as the diameter increases. High-speed steel drill bits have high toughness, thus chip removal is a priority. However, for high-speed, high-efficiency carbide drill bits used on high-rigidity, high-power machining centers, the core thickness is typically 20% to 30% of the diameter to improve drill bit rigidity. This application features a chip-breaking groove extending along the cutting edge. The chip-breaking groove curls and breaks the chips, resulting in smaller and more uniform chips. It can adapt to a smaller groove area. Even with an increased core thickness, the spiral groove with a smaller chip-discharge space can still discharge chips, ensuring smooth chip removal even when the drill bit rigidity is enhanced.

[0040] In some embodiments, the drill bit with helical flutes is made of solid carbide. This application specifies that the drill bit with helical flutes is made of solid carbide. With solid carbide drill bits, the rake face of the cutting edge cannot be ground to create chip-breaking grooves, and existing processing methods cannot create chip-breaking grooves extending along the cutting edge direction. Therefore, it is impossible to control the shape and size of the chips, making chip removal difficult, and it cannot effectively solve the problem of insufficient sharpness when the helical angle is small. This results in poor drill bit machining accuracy, efficiency, and lifespan.

[0041] In this application, cemented carbide has the common meaning understood by those skilled in the art. In this field, cemented carbide is a powder metallurgy product sintered in a vacuum furnace or hydrogen reduction furnace, with micron-sized powders of high-hardness refractory metal carbides (WC, TiC) as the main component and cobalt (Co) or nickel (Ni), molybdenum (Mo) as binders. Its toughness is much higher than high-speed steel, with a cutting speed permissible at approximately 4 to 10 times that of high-speed steel at around 800–1000°C. Its hardness is very high, reaching (89–91) HRA, and some even reaching 93 HRA; however, its bending strength is only 1.1–1.5 GPa, half that of high-speed steel; its impact toughness is 0.04 MJ / m. 2It is approximately 1 / 25 to 1 / 10 the size of high-speed steel. Due to its good heat resistance and wear resistance, its application in cutting tools with less complex cutting edges is increasing. The cemented carbide described in this application includes one of the following: for example, tungsten-cobalt (WC-Co) cemented carbide, tungsten-titanium-cobalt (WC-Ti-Co) cemented carbide, tungsten-titanium-tantalum (niobium) cemented carbide (WC-TaC(NbC)-Co) cemented carbide, tungsten-titanium-cobalt-tantalum (niobium) cemented carbide (WC-TiC-TaC(NbC)-Co) cemented carbide, etc., cemented carbide with WC as the matrix, or TiC-based cemented carbide, fine-grained and ultra-fine-grained cemented carbide, steel-bonded cemented carbide, coated cemented carbide, etc.

[0042] In some embodiments, the groove surface near the cutting edge and / or the groove surface away from the cutting edge is a wavy, undulating surface. The wavy, undulating surface can further enhance the chip-breaking effect of the chip breaker groove, resulting in uniformly fine chips that are easy to remove.

[0043] In some embodiments, the cutting edge has undulations, and the bottom of the chip breaker groove has undulations corresponding to the undulations of the cutting edge, thereby subjecting the chip to a curling force in the direction of the cutting edge extension. The undulations of the cutting edge increase the cutting edge length, reduce the cutting force, and extend the cutting edge life. By controlling the shape of the chip through the undulations of the bottom of the chip breaker groove corresponding to the undulations of the cutting edge, the shape of the chip can be controlled by the shape of the chip breaker groove. Each undulation forms a type of chip, further reducing the size of the chip and facilitating chip removal.

[0044] In some embodiments, the cutting edge undulation is wavy. When the cutting edge has a wavy undulation, it has the best rigidity, the least stress, and the longest service life.

[0045] In some embodiments, the drill bit with spiral grooves has two or three cutting edges. This application achieves better chip removal even with a smaller chip clearance space by using chip breaker grooves to reduce chip size. It can also employ a design with a large core thickness, which increases drill bit rigidity and overcomes the problems of easy breakage and weakened rigidity in three-flute drills, while also leveraging the long lifespan advantage of three-flute drills.

[0046] In some embodiments, the drill bit also has a chisel edge, and the chip breaker extends to the chisel edge, such that the groove surface of the chip breaker near the cutting edge forms a second rake angle on the cutting edge of the chisel edge that is greater than the corresponding first rake angle. This increases the sharpness of the chisel edge, which is more conducive to centering and stability, and is particularly advantageous when applied to difficult-to-machine materials.

[0047] In some embodiments, the chip breaker groove is prepared using a machining method that does not cause thermal damage. This ensures that there is no thermal damage layer at the chip breaker groove location, and the tool strength will not deteriorate due to thermal damage after the chip breaker groove is installed.

[0048] In some embodiments, the chip breaker groove is prepared using a femtosecond pulsed laser processing method. The chip breaker groove described in this application can be prepared using femtosecond pulsed laser processing, for example, using a precision CNC laser machine purchased from DMG MORI (trade name LASERTEC 50Shape). It is generally believed that laser processing degrades the properties of cemented carbide; for example, picosecond and nanosecond processing can cause thermal damage, forming a thermal damage layer at the chip breaker groove location, damaging the tool, resulting in very poor surface finish, failing to meet finishing requirements, and drastically reducing tool life. Without theoretical limitations, it is believed that the formation of this thermal damage layer is due to the high temperatures generated during processing causing oxidation of the cemented carbide, altering the microstructure of the alloy, and reducing hardness and wear resistance. This can be clearly seen by comparing the tool life with that of tools without a thermal damage layer; the life of a tool with a thermal damage layer is often less than half that of a tool without a thermal damage layer, and some even deteriorate to one-fifth or less of their normal life. Femtosecond pulsed laser processing, due to its extremely high speed, does not cause thermal damage. The surface finish can reach 0.1-0.2nm, and even a mirror finish can be achieved. It is suitable for precision machining. Moreover, the chip breaker groove is small in size, which has almost no impact on the mechanical properties of the tool. It not only effectively solves the chip breaking problem, but also significantly improves the tool life, achieving high-precision, high-flexibility, and high-efficiency machining, and reducing machine tool downtime on automated production lines.

[0049] This application also discloses a method for preparing the aforementioned drill bit with helical grooves, wherein the drill bit with helical grooves comprises a cutting portion, an optional guiding portion, and an optional tool holder, the cutting portion having a cutting edge and a helical groove corresponding to the cutting edge, the cutting edge having a rake face, a flank face, and a cutting edge formed by the intersection of the rake face and the flank face, the rake face forming a first rake angle at each point of the cutting edge, characterized in that the method comprises: forming a chip breaker groove on the rake face, the chip breaker groove extending along the direction of the cutting edge in the length direction, the chip breaker groove having a groove surface close to the cutting edge, such that the groove surface of the chip breaker groove close to the cutting edge forms a second rake angle, the second rake angle being greater than the corresponding first rake angle.

[0050] The existing method for manufacturing drill bits with helical grooves is known to those skilled in the art and includes the following steps: 1. Calculate the shape of the drill bit with helical grooves according to actual needs and select a suitable carbide bar; 2. Starting from the carbide bar, grind the carbide bar to form a blank of the drill bit with helical grooves; 3. Grind the blank to form a semi-finished product of the drill bit with helical grooves; 4. Apply a PVD coating to the semi-finished product to form the finished drill bit with helical grooves.

[0051] One method for preparing a drill bit with helical grooves in this application mainly involves machining chip breaker grooves on the semi-finished product, and then applying a PVD coating to the semi-finished product with chip breaker grooves. Additionally, this application also provides a method for processing a drill bit with helical grooves (which may be a used or non-used drill bit), including optionally grinding the flank face of the drill bit with helical grooves, then setting chip breaker grooves on the rake face of the drill bit with helical grooves, and finally applying a PVD coating to the drill bit with helical grooves and chip breaker grooves.

[0052] In some embodiments, the chip breaker groove is prepared using a processing method that does not produce thermal damage.

[0053] In some embodiments, the chip breaker groove is fabricated using a femtosecond pulsed laser processing method.

[0054] The scope described above can be used alone or in combination. The following examples will make this application easier to understand.

[0055] Example

[0056] Example 1

[0057] like Figures 1 to 5 As shown, this embodiment provides a solid carbide drill bit with helical grooves, comprising a cutting portion 100, a guiding portion 200, and a tool holder 300. The cutting portion 100 has two cutting edges 110 and two helical grooves 120 corresponding to the cutting edges, as shown... Figure 2 As shown, the cutting edge has a rake face 111, a flank face 112, and a cutting edge 113 formed by the intersection of the rake face and the flank face. The rake face forms a first rake angle at each point of the cutting edge. A chip breaker groove 10 is provided on the rake face. The chip breaker groove extends along the direction of the cutting edge in the length direction. The drill bit also has a chisel edge 130, and the chip breaker groove extends to the chisel edge.

[0058] Figure 4 This is a partial schematic diagram of one of the cutting edges. The chip breaker groove 10 has a groove surface 11 close to the cutting edge, a groove surface 12 away from the cutting edge, and a bottom 13 of the chip breaker groove, so that the groove surface 11 close to the cutting edge forms a second rake angle, which is greater than the corresponding first rake angle. The groove surface 12 away from the cutting edge is used to curl the chip in the cutting direction.

[0059] The spiral groove extends into the guide portion, the guide portion has a length-to-diameter ratio of 5, the drill bit diameter is 10mm, the angle of the spiral groove is 30 degrees, and the groove surface 11 near the cutting edge and the groove surface 12 away from the cutting edge are wavy undulating surfaces.

[0060] Figure 5 The figure shows the first and second rake angles formed at point 1 near the outer edge of the drill bit cutting edge and point 2 near the center of the drill bit's chisel edge. For point 1, the angle 'a' between the rake face and the base surface in the orthogonal plane (O1-O1 plane) is the first rake angle, and the angle 'b' between the groove surface near the cutting edge and the base surface is the second rake angle. Both the first and second rake angles are positive angles, with the second rake angle being greater than the first. For point 2, on the chisel edge, the angle 'c' between the rake face and the base surface in the orthogonal plane (O2-O2 plane) is the first rake angle, and the angle 'd' between the groove surface near the cutting edge and the base surface is the second rake angle. The first rake angle is negative, and the second rake angle is positive.

[0061] The second rake angle is formed by the chip breaker groove set on the rake face and extending to the chisel edge, which increases the sharpness of the cutting edge, reduces cutting resistance, and makes cutting easier. The chip breaking effect of the chip breaker groove reduces the chip size and improves the uniformity of the chips, which is conducive to chip removal, avoids chip heat accumulation, and improves the machining accuracy, machining efficiency and service life of the drill bit.

[0062] Example 2

[0063] This embodiment provides a solid carbide drill bit with spiral grooves, the drill bit diameter is 0.25mm, and other features are basically the same as those in Embodiment 1.

[0064] Example 3

[0065] This embodiment provides a drill bit made of integral cemented carbide with spiral grooves. The drill bit has a diameter of 36 mm, and other features are basically the same as those in Embodiment 1.

[0066] Cutting test

[0067] Using solid carbide drill bits from Examples 1 to 3, hole machining tests were conducted on 316 stainless steel. Drill bits of the same model without chip breakers were used as corresponding controls (Comparison 1 to Comparison 3). The chip shape, size, and chip removal were observed. The drill bit's machining life was determined by the number of holes machined. The results are shown in Table 1 below:

[0068] Table 1

[0069]

[0070]

[0071] As can be seen from the table above, the chip breaker has a significant impact on the shape and size of the chips. Compared with the control, the chip breaker generates finer chips that are easier to remove. Furthermore, the chip breaker improves the drill bit's sharpness, making cutting smoother, centering more stable, reducing cutting resistance and torque, making the drill bit less prone to breakage, and extending its lifespan.

[0072] Example 4

[0073] This embodiment provides a drill bit made of integral cemented carbide with helical grooves, which is largely the same as that in Embodiment 1, except that the angle of the helical grooves is 20 degrees, and the cutting part has three cutting edges and three helical grooves corresponding to the cutting edges.

[0074] Example 5

[0075] This embodiment provides a drill bit made of integral cemented carbide with spiral grooves, which is largely the same as that in Embodiment 1. The difference is that the angle of the spiral groove is 20 degrees, the drill bit diameter is 0.25 mm, and the groove surface near the cutting edge and the groove surface away from the cutting edge are not provided with wavy undulations, but are flat curved surfaces that extend along the direction of the cutting edge and extend to the transverse cutting edge.

[0076] Example 6

[0077] This embodiment provides a solid carbide drill bit with spiral grooves, which is largely the same as that in Embodiment 1, except that the spiral groove angle is 20 degrees and the drill bit diameter is 36mm. Figure 6 As shown, the cutting edge has a wavy undulation, and the bottom of the chip breaker groove has a groove bottom undulation corresponding to the cutting edge undulation, so that the chip is subjected to a curling force in the direction of the cutting edge extension. Each undulation forms a chip, further reducing the size of the chip and facilitating chip removal.

[0078] Cutting test

[0079] Using solid carbide drill bits from Examples 4 to 6, hole machining tests were conducted on 316 stainless steel. Drill bits of the same model without chip breakers and with a helix angle of 30 degrees were used as corresponding controls (Comparisons 4 to 6, where Comparison 6 has no cutting edge undulation). The chip shape, size, and chip removal were observed. The drill bit's machining life was determined by the number of holes machined. The results are shown in Table 2 below.

[0080] Table 2

[0081]

[0082] As shown in the table above, the chip breaker has a significant impact on the shape and size of the chips. Compared to the control, the chip breaker controls the shape and size of the chips, improves sharpness, forms fine chips that are easy to remove, and shortens the chip removal distance at a smaller helix angle, reducing friction between the chips and the workpiece. The chip removal distance in the table is the length of the helix of the helix groove. By using a chip breaker, the drill bit's sharpness is ensured at a small helix angle, resulting in smoother cutting, more stable centering, lower cutting resistance and torque, reduced drill bit breakage, and increased lifespan.

[0083] In Example 4, the three-flute drill core is 50% thick, resulting in better drill bit rigidity. This overcomes the problem of three-flute drills being prone to breakage, significantly improving processing efficiency and extending the processing life to over 2600 drills. In contrast, the three-flute drill in Comparison 4 has a core thickness of only 20%, poor drill bit rigidity, and is prone to breakage.

[0084] In Example 6, the wavy undulations of the cutting edge and the bottom of the groove are set, which further reduces the chip size. Moreover, the wavy undulations provide the best rigidity, the lowest stress, and further improve the life of the drill bit.

[0085] Example 7

[0086] This embodiment provides a solid carbide drill bit with spiral grooves, which is a deep hole drill. It is largely the same as that in Embodiment 1, except that the length-to-diameter ratio of the guide portion is 10, the angle of the spiral groove is 10 degrees, and the core thickness is 30% of the drill bit diameter.

[0087] Example 8

[0088] This embodiment provides a solid carbide drill bit with spiral grooves, which is a deep hole drill. It is largely the same as that in Embodiment 1, except that the length-to-diameter ratio of the guide portion is 30, the angle of the spiral groove is 10 degrees, and the core thickness is 30% of the drill bit diameter.

[0089] Example 9

[0090] This embodiment provides a solid carbide drill bit with spiral grooves, which is a deep hole drill. It is largely the same as that in Embodiment 1, except that the length-to-diameter ratio of the guide portion is 50, the angle of the spiral groove is 10 degrees, and the core thickness is 30% of the drill bit diameter.

[0091] Cutting test

[0092] Hole machining tests were conducted on 42GrMo steel using solid carbide deep hole drills as described in Examples 7 to 9. Drills of the same model without chip breakers and with a helix angle of 30 degrees were used as corresponding controls (Comparisons 7 to 9). The chip shape, size, and chip removal were observed, and the drill bit life was determined by the number of holes machined. The results are shown in Table 3 below.

[0093] Table 3

[0094]

[0095] As shown in the table above, for deep hole drills with a large length-to-diameter ratio, a smaller helix angle can be set using a chip breaker to ensure higher strength and rigidity of the drill bit. The chip breaker ensures the sharpness of the drill bit at a small helix angle, resulting in more stable centering and smoother cutting. The chip breaker's chip-breaking action forms fine chips, and with a smaller helix angle, the chip removal distance is shortened, reducing friction between the chips and the workpiece, making them easier to remove. The chip breaker simultaneously meets the chip removal requirements and the strength and rigidity requirements of deep hole drills. By using a chip breaker, cutting resistance and torque are reduced, significantly improving drill bit life. When the length-to-diameter ratio reaches 50, the machining life is more than doubled compared to drills without a chip breaker.

[0096] Example 10

[0097] This embodiment provides a deep hole drill that is the same as that in Embodiment 7, wherein the length-to-diameter ratio of the guide portion is 10, the drill bit diameter is 10mm, the angle of the spiral groove is 10 degrees, and the core thickness is 30% of the drill bit diameter.

[0098] Example 11

[0099] This embodiment provides a deep hole drill, which differs from Embodiment 10 in that the guide portion has a length-to-diameter ratio of 30 and a core thickness of 40% of the drill bit diameter.

[0100] Example 12

[0101] This embodiment provides a deep hole drill, which differs from Embodiment 10 in that the guide portion has a length-to-diameter ratio of 50 and a core thickness of 50% of the drill bit diameter.

[0102] Cutting test

[0103] Hole machining tests were conducted on 42GrMo steel using solid carbide deep hole drill bits from Examples 10 to 12. Drill bits of the same model without chip breakers, with a helix angle of 30 degrees and core thicknesses of 30%, 20%, and 20% were used as controls (Comparison 10 to Comparison 12). The chip shape, size, and chip removal were observed, and the breakage rate of the drill bits (based on breakage rate per 100 bits) was measured. The results are shown in Table 4 below.

[0104] Table 4

[0105]

[0106]

[0107] As can be seen from the table above, for deep hole drills with a large length-to-diameter ratio, the chip breaking action of the chip breaker groove forms fine chips, improving chip uniformity and making chips easier to remove. This allows the deep hole drill to be set with a smaller helix angle and a larger core thickness. The smaller helix angle shortens the chip removal distance, reduces friction between the chips and the workpiece, and makes chip removal smoother. The larger core thickness enhances the rigidity and strength of the deep hole drill bit. In addition, the increased sharpness reduces cutting resistance and torque, stabilizes centering, and makes the drill bit less prone to breakage. As the length-to-diameter ratio of drill bits increases, the difference in breakage rate per 100 bits becomes more pronounced. When the length-to-diameter ratio reaches 50, drill bits without chip breakers have a thin core and an extremely high breakage rate of 50-60 bits per 100 bits. However, the technical solution of this application improves the cutting performance of drill bits from multiple perspectives, resulting in an extremely low breakage rate of only 12-15 bits per 100 bits. This effectively resolves the contradiction between chip removal, cutting edge sharpness, and drill bit strength in drill bits with spiral flutes, thus meeting the chip removal requirements, strength, and rigidity requirements of deep hole drilling.

[0108] The above description is merely an exemplary embodiment of this disclosure and is not intended to limit the scope of protection of this disclosure, which is determined by the appended claims.

Claims

1. A drill bit with helical flutes, comprising a cutting portion, an optional guiding portion, and an optional tool holder, the cutting portion having a cutting edge and a helical flute corresponding to the cutting edge, the cutting edge having a rake face, a flank face, and a cutting edge formed by the intersection of the rake face and the flank face, the rake face forming a first rake angle at each point of the cutting edge, characterized in that, A chip breaker groove is provided on the rake face, extending along the cutting edge in the longitudinal direction. The chip breaker groove has a groove surface close to the cutting edge, thereby forming a second rake angle. This second rake angle is larger than the corresponding first rake angle, thus improving the sharpness of the drill bit. The chip breaker groove has a groove surface away from the cutting edge to cause the chip to curl in the cutting direction. The groove surface near the cutting edge and the groove surface away from the cutting edge are wavy surfaces. The core thickness of the drill bit is 30% to 50% of the drill bit diameter. The angle of the helical groove is 5 to 20 degrees. The helical groove extends into the guide portion. The length-to-diameter ratio of the guide portion is greater than or equal to 10 and less than or equal to 50. The cutting edge has a cutting edge undulation. The bottom of the chip breaker groove has a groove bottom undulation corresponding to the cutting edge undulation, thereby causing the chip to be subjected to a curling force in the cutting edge extension direction.

2. The drill bit according to claim 1, characterized in that, The spiral groove extends into the guide portion, the guide portion having a length-to-diameter ratio greater than or equal to 15 and less than or equal to 40.

3. The drill bit according to claim 1 or 2, characterized in that, The angle of the spiral groove is 10 to 20 degrees.

4. The drill bit according to claim 3, characterized in that, The core thickness of the drill bit is 33% to 45% of the drill bit diameter.

5. The drill bit according to claim 1 or 2, characterized in that, The drill bit with spiral grooves is made of solid cemented carbide.

6. The drill bit according to claim 1, characterized in that, The undulation of the cutting edge is wave-shaped.

7. The drill bit according to claim 1 or 4, characterized in that, The drill bit with spiral grooves has two or three cutting edges.

8. The drill bit according to claim 1, characterized in that, The drill bit also has a chisel edge, and the chip breaker extends to the chisel edge.

9. The drill bit according to claim 1, characterized in that, The chip breaking groove is prepared using a processing method that does not produce thermal damage.

10. The drill bit according to claim 1, characterized in that, The chip breaking groove is prepared using a femtosecond pulsed laser processing method.

11. A method for manufacturing a drill bit with helical grooves according to any one of claims 1 to 10, wherein the drill bit with helical grooves comprises a cutting portion, an optional guiding portion, and an optional tool holder, the cutting portion having a cutting edge and a helical groove corresponding to the cutting edge, the cutting edge having a rake face, a flank face, and a cutting edge formed by the intersection of the rake face and the flank face, the rake face forming a first rake angle at each point of the cutting edge, characterized in that, The method includes: A chip breaker groove is formed on the rake face, the chip breaker groove extending along the cutting edge in the length direction, the chip breaker groove having a groove surface close to the cutting edge, such that the groove surface of the chip breaker groove close to the cutting edge forms a second rake angle, the second rake angle being greater than the corresponding first rake angle, thereby improving the sharpness of the drill bit, the chip breaker groove having a groove surface away from the cutting edge for curling the chips in the cutting direction, the groove surface close to the cutting edge and / or the groove surface away from the cutting edge being a wavy undulating surface, the core thickness of the drill bit being 32% to 50% of the drill bit diameter, the angle of the helical groove being 5 to 20 degrees, the helical groove extending into the guide portion, the length-to-diameter ratio of the guide portion being greater than or equal to 10 and less than or equal to 50.

12. The method according to claim 11, characterized in that, The chip breaking groove is prepared using a processing method that does not produce thermal damage.

13. The method according to claim 11, characterized in that, The chip breaking groove is prepared using a femtosecond pulsed laser processing method.

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