A wave-shaped variable core thickness drill bit

Abstract

This invention provides a wave-shaped variable core thickness drill bit, relating to the field of micro drill bit technology. This wave-shaped variable core thickness drill bit includes a drill body and a cutting end; the cutting end includes a main cutting edge, a secondary cutting edge, two first flank faces, and two second flank faces; the drill body has a main chip removal groove corresponding to the main cutting edge and a secondary chip removal groove corresponding to the secondary cutting edge; the axial length of the secondary chip removal groove is shorter than that of the main chip removal groove; the core thickness formed by the chip removal grooves gradually increases in a wave-like pattern along the axial direction from the drill tip to the tail of the main chip removal groove; wherein, the core thickness refers to the minimum cross-sectional width of the solid portion remaining after being weakened by the chip removal grooves along the axis on the cross-section of the drill bit. This invention, without significantly altering the chip removal conditions, improves the stability of the pressure bar compared to ordinary single-edge micro drill bits with a core cone, further reducing fracture damage caused by bending in micro drill bits, thereby extending the service life of micro drill bits.

Description

Technical Field

[0001] This invention relates to the field of micro drill bit technology, and more specifically, to a wave-shaped variable core thickness drill bit. Background Technology

[0002] Printed circuit boards (PCBs), as essential basic electronic components in electronic products, have a complex manufacturing process. Before packaging the PCB, tiny holes need to be drilled in the substrate to enable circuit conduction and fixation of the electronic components on the PCB. Therefore, micro-drilling is one of the key steps in the PCB substrate manufacturing process. The drilling quality directly affects the subsequent copper plating process of the substrate and has a crucial impact on the final signal transmission quality and transmission capability of the PCB.

[0003] Currently, the industry typically uses micro drills to perform mechanical micro-drilling on printed circuit board substrates to complete the aforementioned micro-drilling process. Core thickness is one of the most critical geometric parameters affecting the rigidity and strength of micro drills. The greater the core thickness, the better the drill's rigidity and the less likely it is to break due to bending deformation. Therefore, existing micro drill designs often adjust the core thickness to adapt to processing requirements, attempting to find a balance between rigidity, strength, and other performance characteristics.

[0004] With the miniaturization and high integration of electronic products and the increasing demand for multi-layer PCB processing, the length-to-diameter ratio of micro drill bits used for drilling printed circuit boards is constantly increasing. This change directly leads to relatively low tool rigidity and strength. This problem makes micro drill bits prone to slippage and deflection during drilling due to bending deformation, thus reducing drilling quality and, in severe cases, even causing drill bit breakage. After a drill bit breaks, the broken head often becomes stuck in the hole and is difficult to remove, ultimately leading to the scrapping of the entire printed circuit board substrate and adversely affecting production economics. Summary of the Invention

[0005] The present invention provides a wave-shaped variable core thickness drill bit, which aims to improve at least one of the above-mentioned technical problems.

[0006] To address the aforementioned technical problems, this invention provides a wavy variable core thickness drill bit, comprising a drill body and a cutting end. The cutting end includes a main cutting edge, a secondary cutting edge, two first flank faces, and two second flank faces. The drill body has a main chip removal groove corresponding to the main cutting edge and a secondary chip removal groove corresponding to the secondary cutting edge. The axial length of the secondary chip removal groove is shorter than that of the main chip removal groove. The core thickness formed by the chip removal grooves gradually increases axially from the drill tip to the tail of the main chip removal groove in a wavy pattern. The core thickness refers to the minimum cross-sectional width of the solid portion remaining after being weakened by the chip removal grooves along the axis on the cross-section of the drill bit. The axially wavy core thickness has multiple peaks.

[0007] As a further optimization, the main chip removal flute extends from the drill tip to the end of the drill body. The secondary chip removal flute extends from the drill tip to a distance of 0.6–0.8 mm from the drill tip axis and then stops.

[0008] As a further optimization, the multiple peaks from the axial position at the end of the secondary chip removal groove to the tail of the main chip removal groove are constructed such that the maximum core thickness of the subsequent peak is 0.0045 mm to 0.009 mm greater than that of the previous peak.

[0009] As a further optimization, the outer diameter of the drill bit is 0.21 mm.

[0010] As a further optimization, the length of the drill body is 4.3 mm.

[0011] As a further optimization, the axial distance from the end point of the secondary chip removal groove to the drill tip is 0.6 to 0.8 mm.

[0012] As a further optimization, the maximum core thickness difference between the last peak before the secondary chip removal groove stops and the first peak after the secondary chip removal groove stops is 0.0190 mm to 0.0210 mm.

[0013] As a further optimization, the overall taper after fitting the wavy core thickness is 0.17 to 0.20.

[0014] As a further optimization, the thickness from the drill body to each point to the drill tip is as follows:

[0015] The core thickness at a distance of 0 mm from the drill tip is 0.0810 mm.

[0016] The core thickness at a distance of 0.05 mm from the drill tip is 0.0834 mm.

[0017] The core thickness at a distance of 0.10 mm from the drill tip is 0.0866 mm.

[0018] The core thickness at a distance of 0.15 mm from the drill tip is 0.0897 mm.

[0019] The core thickness at a distance of 0.20 mm from the drill tip is 0.0925 mm.

[0020] The core thickness at a distance of 0.25 mm from the drill tip is 0.0954 mm.

[0021] The core thickness at a distance of 0.30 mm from the drill tip is 0.1008 mm.

[0022] The core thickness at a distance of 0.35 mm from the drill tip is 0.0955 mm.

[0023] The core thickness at a distance of 0.40 mm from the drill tip is 0.0937 mm.

[0024] The core thickness at a distance of 0.45 mm from the drill tip is 0.0935 mm.

[0025] The core thickness at a distance of 0.50 mm from the drill tip is 0.0931 mm.

[0026] The core thickness at a distance of 0.55 mm from the drill tip is 0.0938 mm.

[0027] The core thickness at a distance of 0.60 mm from the drill tip is 0.0963 mm.

[0028] The core thickness at a distance of 0.65 mm from the drill tip is 0.0995 mm.

[0029] The core thickness at a distance of 0.70 mm from the drill tip is 0.1033 mm.

[0030] The core thickness at a distance of 0.75 mm from the drill tip is 0.1088 mm.

[0031] The core thickness at a distance of 0.80 mm from the drill tip is 0.1127 mm.

[0032] The core thickness at a distance of 0.85 mm from the drill tip is 0.1161 mm.

[0033] The core thickness at a distance of 0.90 mm from the drill tip is 0.1198 mm.

[0034] The core thickness at a distance of 0.95 mm from the drill tip is 0.1211 mm.

[0035] The core thickness at a distance of 1.00 mm from the drill tip is 0.1188 mm.

[0036] The core thickness at a distance of 1.05 mm from the drill tip is 0.1137 mm.

[0037] The core thickness at a distance of 1.10 mm from the drill tip is 0.1101 mm.

[0038] The core thickness at a distance of 1.15 mm from the drill tip is 0.1086 mm.

[0039] The core thickness at a distance of 1.20 mm from the drill tip is 0.1104 mm.

[0040] The core thickness at a distance of 1.25 mm from the drill tip is 0.1137 mm.

[0041] The core thickness at a distance of 1.30 mm from the drill tip is 0.1174 mm.

[0042] The core thickness at a distance of 1.35 mm from the drill tip is 0.1228 mm.

[0043] The core thickness at a distance of 1.40 mm from the drill tip is 0.1256 mm.

[0044] The core thickness at a distance of 1.45 mm from the drill tip is 0.1218 mm.

[0045] The core thickness at a distance of 1.50 mm from the drill tip is 0.1166 mm.

[0046] The core thickness at a distance of 1.55 mm from the drill tip is 0.1139 mm.

[0047] The core thickness at a distance of 1.60 mm from the drill tip is 0.1146 mm.

[0048] The core thickness at a distance of 1.65 mm from the drill tip is 0.1170 mm.

[0049] The core thickness at a distance of 1.70 mm from the drill tip is 0.1241 mm.

[0050] The core thickness at a distance of 1.75 mm from the drill tip is 0.1289 mm.

[0051] The core thickness at a distance of 1.80 mm from the drill tip is 0.1314 mm.

[0052] The core thickness at a distance of 1.85 mm from the drill tip is 0.1324 mm.

[0053] The core thickness at a distance of 1.90 mm from the drill tip is 0.1299 mm.

[0054] The core thickness at a distance of 1.95 mm from the drill tip is 0.1258 mm.

[0055] The core thickness at a distance of 2.00 mm from the drill tip is 0.1239 mm.

[0056] The core thickness at a distance of 2.05 mm from the drill tip is 0.1248 mm.

[0057] The core thickness at a distance of 2.10 mm from the drill tip is 0.1272 mm.

[0058] The core thickness at a distance of 2.15 mm from the drill tip is 0.1307 mm.

[0059] The core thickness at a distance of 2.20 mm from the drill tip is 0.1364 mm.

[0060] The core thickness at a distance of 2.25 mm from the drill tip is 0.1394 mm.

[0061] The core thickness at a distance of 2.30 mm from the drill tip is 0.1404 mm.

[0062] The core thickness at a distance of 2.35 mm from the drill tip is 0.1409 mm.

[0063] The core thickness at a distance of 2.40 mm from the drill tip is 0.1388 mm.

[0064] The core thickness at a distance of 2.45 mm from the drill tip is 0.1357 mm.

[0065] As a further optimization, the number of peaks is five.

[0066] As a further optimization, the helix angles of the main chip removal groove and the secondary chip removal groove are fixed values, ranging from 40° to 55°.

[0067] As a further optimization, the projection of the flank face along the axial direction is constructed as a triangle. The flank face includes two first flank faces and two second flank faces, namely the area enclosed by the main cutting edge, the secondary cutting edge, and the outer ring of the drill bit.

[0068] By adopting the above technical solution, the present invention can achieve the following technical effects:

[0069] This invention employs a single-blade structure to improve hole position accuracy. At the same time, by designing a wave-shaped core cone, the structure improves the stability of the pressure bar compared to ordinary single-blade micro drill bits with core cones without significantly changing the chip removal conditions. This further reduces the fracture damage of micro drill bits due to bending, thereby extending the service life of micro drill bits. Attached Figure Description

[0070] To more clearly illustrate the technical solutions of the specific embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0071] Figure 1 This is a schematic diagram of the appearance of a wavy variable core thickness drill bit.

[0072] Figure 2This is a schematic diagram of the cutting edge of a wavy variable core thickness drill bit.

[0073] Figure 3 This is a graph showing the local core thickness variation trend of a wavy variable core thickness drill bit.

[0074] Figure 4 This is a comparison diagram of the line connecting the bottom points of the flutes on the same side of the wavy variable core thickness drill bit and the line connecting the bottom points of the flutes on the same side of the existing drill bit.

[0075] The markings in the diagram are: 10-cutting end, 11-main cutting edge, 12-secondary cutting edge, 13-first flank face, 14-secondary flank face, 15-drill tip, 20-drill body, 21-main chip removal groove, 22-secondary chip removal groove. Detailed Implementation

[0076] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0077] Depend on Figures 1 to 4 As shown, this embodiment provides a wave-shaped variable core thickness drill bit, which includes a drill body 20 and a cutting end 10. The cutting end 10 includes a main cutting edge 11, a secondary cutting edge 12, two first flank faces 13, and two second flank faces 14. The drill body 20 is provided with a main chip removal groove 21 corresponding to the main cutting edge 11 and a secondary chip removal groove 22 corresponding to the secondary cutting edge 12. The projection of the flank faces along the axial direction is triangular to form a stable cutting edge angle. The flank faces include two first flank faces 13 and two second flank faces 14, namely the area enclosed by the main cutting edge 11, the secondary cutting edge 12, and the outer ring of the drill bit.

[0078] The axial length of the secondary chip removal groove 22 is shorter than that of the main chip removal groove 21. The core thickness formed by the chip removal grooves gradually increases in a wavy pattern along the axial direction from the drill tip 15 to the tail of the main chip removal groove 21. The core thickness refers to the minimum cross-sectional width of the solid portion remaining after the chip removal grooves weaken the core along the axis on the cross-section of the drill bit. The axially wavy core thickness has multiple peaks. Preferably, the number of peaks is five.

[0079] The main chip removal groove 21 refers to a spiral groove extending along the entire length of the drill body 20, which continuously guides chips out of the machining area. Specifically, the chip removal efficiency and structural strength can be balanced by controlling the helix angle. The secondary chip removal groove 22 refers to an auxiliary chip removal structure terminating at a specific axial position. Its shortened design can increase the cross-sectional area of ​​the drill body. Specifically, a gradually tapering groove shape can be used to avoid sudden stress changes.

[0080] Wavy core thickness refers to the core thickness that varies periodically along the drill bit axis. For example... Figure 3As shown, the core thickness formed by the main chip removal groove 21 and the auxiliary chip removal groove 22 exhibits a wave-like periodic variation along the drill bit axis. This core thickness curve consists of several "peaks" and "troughs," with the overall trend gradually increasing from the drill tip 15 towards the tail of the groove. Each peak corresponds to a local area of ​​maximum core thickness. The number of peaks can be set to other values, and this invention does not impose a specific limitation on this.

[0081] This structure maintains basic chip removal capacity through the main chip removal groove 21, while the shortened design of the secondary chip removal groove 22 provides reinforced support in the area near the drill tip 15. The wavy core thickness distribution of the five peaks creates a differentiated stiffness distribution of the drill bit at different axial depths: the first peak enhances drilling stability, the middle peak resists bending moments, and the final peak prevents chatter during deep hole machining. This non-uniform stiffness distribution ensures both overall rigidity improvement and maintains necessary chip removal space through the trough areas, making the cutting force distribution more uniform.

[0082] Traditional single-tapered core thickness designs exhibit linear stiffness variations along the axial direction, making them ill-suited to the stress characteristics of different machining depths. This solution utilizes a wavy core thickness variation to create multiple stiffness-enhancing zones. During the drilling phase, smaller peaks prevent stress concentration caused by abrupt changes in stiffness, while larger peaks provide ample support during deep hole machining. Compared to a three-peak design, the five-peak structure more precisely matches the varying cutting resistance of multi-layered PCB materials, and compared to a seven-peak structure, it offers better machining economy.

[0083] This embodiment effectively solves the contradiction between increasing the rigidity of the micro drill bit and occupying the chip removal space. While maintaining the original chip removal efficiency, it greatly improves the bending strength and drilling positioning accuracy of the drill bit, and at the same time greatly reduces the breakage rate.

[0084] Based on the above embodiments, in an optional embodiment of the present invention, the main chip removal groove 21 extends from the drill tip 15 to the end of the drill body 20. The secondary chip removal groove 22 extends from the drill tip 15 and stops at a distance of 0.6 to 0.8 mm from the axis of the drill tip 15. Multiple peaks from the axial position of the termination point of the secondary chip removal groove 22 to the tail of the main chip removal groove 21 are configured such that the maximum core thickness of each subsequent peak is 0.0045 mm to 0.009 mm greater than that of the previous peak, to achieve a stepped reinforcement of rigidity.

[0085] The main chip removal groove 21 extends to the end of the drill body 20, meaning the chip removal channel runs through the entire axial length of the drill body 20. This can be achieved using a continuous spiral groove structure. Its function is to ensure that the chips generated by the main cutting edge 11 are discharged along the entire length of the drill body 20. The secondary chip removal groove 22 stops at a distance of 0.6 to 0.8 mm from the axis of the drill tip 15, meaning the axial length of the groove is limited to a specific range. This can be achieved using a gradually narrowing groove tail structure. Its function is to balance the chip removal requirements at the drill tip with the core thickness rigidity distribution.

[0086] The extended length of the main chip removal groove 21 ensures that the chips generated by the main cutting edge 11 can be completely discharged, while the shortened design of the secondary chip removal groove 22 provides structural space for the wave-like variation of the core thickness while maintaining the chip removal efficiency at the front end. The peaks after the termination of the secondary chip removal groove 22 adopt an incremental core thickness design, for example, each peak increases by 0.006 mm compared to the previous one, forming a progressively rigid reinforcement structure, thereby successively improving the bending resistance at different axial positions.

[0087] This embodiment, while maintaining the function of the chip removal channel, controls the termination position and peak parameters of the secondary chip removal groove 22 to create a differentiated rigidity distribution in different axial sections of the drill bit. This design avoids the overall rigidity reduction caused by excessively long chip removal grooves, and achieves directional reinforcement of local rigidity through wavy core thickness variations, thereby effectively suppressing the bending deformation tendency of the drill bit during deep hole machining.

[0088] In this embodiment, the overall taper after fitting the wavy core thickness is 0.17–0.20. The taper fitting was performed using the least squares method. Figure 3 Performing a linear regression on the scatter points yields a straight line whose slope represents the "overall taper." This taper range allows the drill bit to achieve differentiated core thickness support strength at different axial positions.

[0089] Based on the above embodiments, in an optional embodiment of the present invention, the outer diameter of the drill body 20 is 0.21 mm. The length of the drill body 20 is 4.3 mm. The helix angle of the main chip removal groove 21 and the auxiliary chip removal groove 22 is a fixed value, ranging from 40° to 55°, to ensure smooth chip removal while maintaining the overall strength of the drill body 20.

[0090] The fixed helix angle of the main chip removal groove 21 and the auxiliary chip removal groove 22 means that the helix of the two chip removal grooves maintains a constant inclination angle relative to the drill bit axis. This can be achieved using a constant lead helix machining process. This angle range is set to ensure chip removal efficiency while avoiding a decrease in the strength of the groove structure due to an excessively large helix angle. The design of a fixed helix angle of 40 to 55 degrees ensures that the chips maintain a continuous and stable flow path during the removal process, avoiding chip retention caused by abrupt changes in the helix angle.

[0091] The axial distance from the end point of the secondary chip removal groove 22 to the drill tip 15 is 0.7 mm. The maximum core thickness difference between the last peak before the secondary chip removal groove 22 stops and the first peak after the secondary chip removal groove 22 stops is 0.0190 mm to 0.0210 mm, which can effectively reduce the risk of abrupt changes in the stress concentration area. The peak difference before and after the termination position of the secondary chip removal groove 22 is controlled on the order of 0.02 mm, so that the core thickness change in this area can both alleviate stress concentration and avoid local brittle fracture caused by abrupt changes in rigidity.

[0092] Based on the above embodiments, in an optional embodiment of the present invention, the thickness of the drill body 20 from each point to the drill tip 15 is as follows:

[0093] The core thickness at a distance of 0 mm from the drill tip is 0.0810 mm.

[0094] The core thickness at a distance of 0.05 mm from the drill tip is 0.0834 mm.

[0095] The core thickness at a distance of 0.10 mm from the drill tip is 0.0866 mm.

[0096] The core thickness at a distance of 0.15 mm from the drill tip is 0.0897 mm.

[0097] The core thickness at a distance of 0.20 mm from the drill tip is 0.0925 mm.

[0098] The core thickness at a distance of 15 mm from the drill tip and 0.25 mm is 0.0954 mm.

[0099] The core thickness at a distance of 0.30 mm from the drill tip is 0.1008 mm.

[0100] The core thickness at a distance of 15 mm from the drill tip and 0.35 mm is 0.0955 mm.

[0101] The core thickness at a distance of 0.40 mm from the drill tip is 0.0937 mm.

[0102] The core thickness at a distance of 15 mm from the drill tip and 0.45 mm is 0.0935 mm.

[0103] The core thickness at a distance of 0.50 mm from the drill tip is 0.0931 mm.

[0104] The core thickness at a distance of 15 mm from the drill tip and 0.55 mm is 0.0938 mm.

[0105] The core thickness at a distance of 0.60 mm from the drill tip is 0.0963 mm.

[0106] The core thickness at a distance of 15 mm from the drill tip and 0.65 mm is 0.0995 mm.

[0107] The core thickness at a distance of 15 mm from the drill tip and 0.70 mm is 0.1033 mm.

[0108] The core thickness at a distance of 15 mm from the drill tip and 0.75 mm is 0.1088 mm.

[0109] The core thickness at a distance of 0.80 mm from the drill tip is 0.1127 mm.

[0110] The core thickness at a distance of 0.85 mm from the drill tip is 0.1161 mm.

[0111] The core thickness at a distance of 0.90 mm from the drill tip is 0.1198 mm.

[0112] The core thickness at a distance of 0.95 mm from the drill tip is 0.1211 mm.

[0113] The core thickness at a distance of 1.00 mm from the drill tip is 0.1188 mm.

[0114] The core thickness at a distance of 1.05 mm from the drill tip is 0.1137 mm.

[0115] The core thickness at a distance of 1.10 mm from the drill tip is 0.1101 mm.

[0116] The core thickness at a distance of 1.15 mm from the drill tip is 0.1086 mm.

[0117] The core thickness at a distance of 1.20 mm from the drill tip is 0.1104 mm.

[0118] The core thickness at a distance of 1.25 mm from the drill tip is 0.1137 mm.

[0119] The core thickness at a distance of 1.30 mm from the drill tip is 0.1174 mm.

[0120] The core thickness at a distance of 1.35 mm from the drill tip is 0.1228 mm.

[0121] The core thickness at a distance of 1.40 mm from the drill tip is 0.1256 mm.

[0122] The core thickness at a distance of 1.45 mm from the drill tip is 0.1218 mm.

[0123] The core thickness at a distance of 1.50 mm from the drill tip is 0.1166 mm.

[0124] The core thickness at a distance of 1.55 mm from the drill tip is 0.1139 mm.

[0125] The core thickness at a distance of 1.60 mm from the drill tip is 0.1146 mm.

[0126] The core thickness at a distance of 1.65 mm from the drill tip is 0.1170 mm.

[0127] The core thickness at a distance of 1.70 mm from the drill tip is 0.1241 mm.

[0128] The core thickness at a distance of 1.75 mm from the drill tip is 0.1289 mm.

[0129] The core thickness at a distance of 1.80 mm from the drill tip is 0.1314 mm.

[0130] The core thickness at a distance of 1.85 mm from the drill tip is 0.1324 mm.

[0131] The core thickness at a distance of 1.90 mm from the drill tip is 0.1299 mm.

[0132] The core thickness at a distance of 1.95 mm from the drill tip is 0.1258 mm.

[0133] The core thickness at a distance of 2.00 mm from the drill tip is 0.1239 mm.

[0134] The core thickness at a distance of 2.05 mm from the drill tip is 0.1248 mm.

[0135] The core thickness at a distance of 2.10 mm from the drill tip is 0.1272 mm.

[0136] The core thickness at a distance of 2.15 mm from the drill tip is 0.1307 mm.

[0137] The core thickness at a distance of 2.20 mm from the drill tip is 0.1364 mm.

[0138] The core thickness at a distance of 15 mm from the drill tip and 2.25 mm is 0.1394 mm.

[0139] The core thickness at a distance of 2.30 mm from the drill tip is 0.1404 mm.

[0140] The core thickness at a distance of 2.35 mm from the drill tip is 0.1409 mm.

[0141] The core thickness at a distance of 15 mm from the drill tip and 2.40 mm is 0.1388 mm.

[0142] The core thickness at a distance of 15 mm from the drill tip is 0.1357 mm.

[0143] In this embodiment, several peaks exist at positions of 150.30 mm, 0.90 mm, 1.35 mm, 1.85 mm and 2.35 mm from the drill tip, respectively. The core thickness of each peak increases sequentially, showing a wave-like gradient characteristic.

[0144] The wavy variation in core thickness is formed through the synergistic effect of the chip flute spiral structure and the flank geometry. As the drill bit rotates and cuts, the periodically changing core thickness structure creates differentiated support strength at different axial positions: the increased core thickness at the crest enhances bending resistance, while the decreased core thickness at the trough maintains the effective volume of the chip removal channel. This dynamic adjustment mechanism ensures that when the drill bit is subjected to axial loads, the core thickness in high-stress areas is correspondingly increased to resist the common bending stress concentration phenomenon in these areas.

[0145] This embodiment achieves targeted optimization of the mechanical properties of the micro drill bit. In the region of concentrated axial load, the wavy core thickness peak provides targeted support, effectively suppressing fracture failure caused by drill bit bending deformation. At the same time, the reduced core thickness in the trough region maintains the unobstructed chip removal channel, enabling the micro drill bit to maintain stable machining performance even at high length-to-diameter ratios.

[0146] In this invention, the wavy core thickness design significantly improves the axial rigidity and bending stability of the drill body 20 while maintaining stable chip removal performance. Compared with traditional single-flute micro drills with uniform core cone structures, the wavy variable core thickness design of this invention can effectively disperse stress concentration during high-speed micro-drilling, reduce drill rod fracture failure caused by bending, and thus improve hole position accuracy and service life.

[0147] Preferably, the drill bit of the present invention can be made of integral cemented carbide material, or the drill tip 15 and the chip removal groove can be coated and strengthened according to the usage requirements to further improve wear resistance and thermal shock resistance.

[0148] Obviously, the above detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to describe preferred embodiments, not all embodiments, and is not intended to limit the invention. Various modifications and variations can be made to the invention by those skilled in the art. Based on the embodiments of the invention, any modifications, equivalent substitutions, improvements, etc., made by those skilled in the art to all other embodiments obtained without inventive effort are within the scope of protection of the invention.

Claims

1. A wave-shaped variable core bit, comprising a drill body (20) and a cutting end (10); the cutting end (10) comprises a main cutting edge (11), a secondary cutting edge (12), two first flanks (13) and two second flanks (14); the drill body (20) is provided with a main flute (21) corresponding to the main cutting edge (11) and a secondary flute (22) corresponding to the secondary cutting edge (12); characterized in that the axis length of the secondary flute (22) is shorter than that of the main flute (21); the core value formed by the flutes gradually increases in a wave shape from the drill tip (15) to the tail of the main flute (21) in the axial direction; wherein the core value refers to the minimum cross-sectional width of the remaining solid part after the weakening by the flute in the cross section of the drill bit; the core value arranged in a wave shape in the axial direction has multiple wave crests.

2. A wave-shaped variable-cake-thickness bit according to claim 1, wherein, the main flute (21) extends from the drill tip (15) to the end of the drill body (20); the secondary flute (22) extends from the drill tip (15) to a position 0.6-0.8 mm away from the drill tip (15) in the axial direction.

3. A wave-shaped variable-cake-thickness bit according to claim 2, wherein, the multiple wave crests between the axial position where the secondary flute (22) terminates and the tail of the main flute (21) are configured such that the maximum core value of the latter wave crest is greater than that of the former wave crest by 0.0045 mm to 0.009 mm.

4. A wave-shaped variable-cake-thickness bit according to claim 2, wherein, the outer diameter of the drill body (20) is 0.21 mm; the length of the drill body (20) is 4.3 mm; the axial distance from the end of the secondary flute (22) to the drill tip (15) is 0.7 mm.

5. A wave-shaped variable bit thickness drill bit as defined in claim 3 wherein, the maximum core value difference between the last wave crest before the secondary flute (22) stops and the first wave crest after the secondary flute (22) stops is 0.0190-0.0210 mm.

6. A wave-shaped variable bit thickness drill bit as defined in claim 3 wherein, the overall taper of the wave-shaped core value after fitting is 0.17-0.

20.

7. A wave-shaped variable-cake-thickness bit according to claim 6 wherein, the core value at a distance of 0 mm from the drill tip (15) is 0.0810 mm; the core value at a distance of 0.05 mm from the drill tip (15) is 0.0834 mm; the core value at a distance of 0.10 mm from the drill tip (15) is 0.0866 mm; the core value at a distance of 0.15 mm from the drill tip (15) is 0.0897 mm; the core value at a distance of 0.20 mm from the drill tip (15) is 0.0925 mm; the core value at a distance of 0.25 mm from the drill tip (15) is 0.0954 mm; the core value at a distance of 0.30 mm from the drill tip (15) is 0.1008 mm; the core value at a distance of 0.35 mm from the drill tip (15) is 0.0955 mm; the core value at a distance of 0.40 mm from the drill tip (15) is 0.0937 mm; the core value at a distance of 0.45 mm from the drill tip (15) is 0.0935 mm; the core value at a distance of 0.50 mm from the drill tip (15) is 0.0931 mm; the core value at a distance of 0.55 mm from the drill tip (15) is 0.0938 mm; 0.60 mm from the drill tip (15) is 0.0963 mm; 0.65 mm from the drill tip (15) is 0.0995 mm; 0.70 mm from the drill tip (15) is 0.1033 mm; 0.75 mm from the drill tip (15) is 0.1088 mm; 0.80 mm from the drill tip (15) is 0.1127 mm; 0.85 mm from the drill tip (15) is 0.1161 mm; 0.90 mm from the drill tip (15) is 0.1198 mm; 0.95 mm from the drill tip (15) is 0.1211 mm; 1.00 mm from the drill tip (15) is 0.1188 mm; 1.05 mm from the drill tip (15) is 0.1137 mm; 1.10 mm from the drill tip (15) is 0.1101 mm; 1.15 mm from the drill tip (15) is 0.1086 mm; 1.20 mm from the drill tip (15) is 0.1104 mm; 1.25 mm from the drill tip (15) is 0.1137 mm; 1.30 mm from the drill tip (15) is 0.1174 mm; 1.35 mm from the drill tip (15) is 0.1228 mm; 1.40 mm from the drill tip (15) is 0.1256 mm; 1.45 mm from the drill tip (15) is 0.1218 mm; 1.50 mm from the drill tip (15) is 0.1166 mm; 1.55 mm from the drill tip (15) is 0.1139 mm; 1.60 mm from the drill tip (15) is 0.1146 mm; 1.65 mm from the drill tip (15) is 0.1170 mm; 1.70 mm from the drill tip (15) is 0.1241 mm; 1.75 mm from the drill tip (15) is 0.1289 mm; 1.80 mm from the drill tip (15) is 0.1314 mm; 1.85 mm from the drill tip (15) is 0.1324 mm; 1.90 mm from the drill tip (15) is 0.1299 mm; 1.95 mm from the drill tip (15) is 0.1258 mm; 2.00 mm from the drill tip (15) is 0.1239 mm; The core thickness value at a distance of 2.05 mm from the drill tip (15) is 0.1248 mm; The core thickness value at a distance of 2.10 mm from the drill tip (15) is 0.1272 mm; The core thickness value at a distance of 2.15 mm from the drill tip (15) is 0.1307 mm; The core thickness value at a distance of 2.20 mm from the drill tip (15) is 0.1364 mm; The core thickness value at a distance of 2.25 mm from the drill tip (15) is 0.1394 mm; The core thickness value at a distance of 2.30 mm from the drill tip (15) is 0.1404 mm; The core thickness value at a distance of 2.35 mm from the drill tip (15) is 0.1409 mm; The core thickness value at a distance of 2.40 mm from the drill tip (15) is 0.1388 mm; The core thickness value at a distance of 2.45 mm from the drill tip (15) is 0.1357 mm.

8. A wave-shaped variable-cake-thickness bit according to any one of claims 1 to 7, characterized in that The number of the wave crests is five.

9. A wave-shaped variable-cake-thickness bit according to any one of claims 1 to 7, characterized in that The spiral angles of the main and secondary chip flutes (21, 22) are fixed values and range from 40° to 55°.

10. A wave-shaped variable-cake-thickness bit according to any one of claims 1 to 7, characterized in that The projection of the relief surface along the axial direction is triangular; the relief surface comprises two first relief surfaces (13) and two second relief surfaces (14), i.e. the region surrounded by the main cutting edge (11), the secondary cutting edge (12) and the outer circle of the drill bit.

Images