Drill

Abstract

In a drill 10 having two or more cutting edges 2, 3, 4 provided extending outward from a central axis O, the cutting edges 2, 3, 4 are formed from: first cutting edges 2A, 2B having linear portions that extend from chisel edges 1A, 1B outward of the drill 10; second cutting edges 3A, 3B extending from end parts of the first cutting edges 2A, 2B outward of the drill 10, and to a circumferential direction and rearward; and linear third cutting edges 4A, 4B extending from end parts of the second cutting edges 3A, 3B rearward of the drill 10 and connected to a leading edge 5. A hard film of either diamond or diamond-like carbon is coated on the surface of the drill.

Description

drill

[0001] The present invention relates to a drill that can suppress burrs that occur on the surface of a workpiece after drilling.

[0002] In drilling using a drill, burrs are generated around the hole after drilling, so a deburring process is added after drilling to remove the burrs. For this reason, Patent Documents 1 to 3 disclose drills that can reduce the burrs generated after drilling.

[0003] However, these drills have the problem that burrs remain after drilling depending on the type of work material. To address this problem, Patent Document 4 discloses multiple types of drills with different shapes, classified according to the type of work material.

[0004] Utility Model Registration No. 3199122 JP 2021-65967 A JP 2005-279848 A JP 2021-151681 A

[0005] However, the drill disclosed in Patent Document 4 has an inflection point at the connection between the cutting edge at the tip of the drill and the margin at the rear of the drill, which causes the problem of burrs and burrs forming on the surface of the workpiece depending on the hole drilling conditions, such as high speed rotation and high feed.

[0006] Therefore, an object of the present invention is to provide a drill that suppresses the generation of burrs around a drilled hole, regardless of drilling conditions such as high rotation speed and high feed rate. The applicant previously filed International Patent Application No. PCT / JP2023 / 016092, which discloses an invention relating to the basic shape of a drill bit, and confirmed that the shape of the invention in this prior application reduces the generation of burrs. However, subsequent continuous development activities have revealed that there is room for further improvement, particularly when cutting relatively soft metal materials such as aluminum alloys.

[0007] To solve the above-mentioned problems, the drill eliminates the step portion seen in conventional drills by providing a smooth transition between the cutting edge at the leading end of the drill and the margin at the rear end (shank side). Specifically, the drill of the present invention has at least two cutting edges extending outward from the central axis. These cutting edges are formed of a first cutting edge having a linear portion extending outward from the chisel edge, a second cutting edge that is a curved cutting edge extending outward, circumferentially, and rearward from the end of the first cutting edge, and a linear third cutting edge that extends rearward from the end of the second cutting edge and connects to the leading edge. The drill surface is also coated with a hard coating of either diamond or diamond-like carbon (DLC).

[0008] Alternatively, in a drill having two or more cutting edges extending outward from the central axis, these cutting edges are formed from a first cutting edge having a straight portion extending outward from the chisel edge of the drill, a second cutting edge extending outward, circumferentially, and rearward from the end of the first cutting edge, and a curved third cutting edge extending rearward from the end of the second cutting edge to connect to the leading edge. Furthermore, if the second cutting edge is a curved cutting edge, the radius of curvature of the third cutting edge may be larger than the radius of curvature of the second cutting edge. Furthermore, the surface of the drill is coated with a hard coating of either diamond or diamond-like carbon (DLC).

[0009] The third cutting edge may be connected to the leading edge of the drill, and the flank adjacent to the third cutting edge may be formed continuously with the margin of the drill, and the angle (θ1, θ2) formed by the ridgeline that forms the boundary between the flank adjacent to the third cutting edge and the margin may be set to a range of 4° to 25°. The clearance angles of the second and third cutting edges of the drill may be set to a range of 5° to 18°.

[0010] The drill of the present invention is effective in suppressing the generation of burrs around the drilled hole regardless of the type of workpiece or drilling conditions such as high speed rotation, high feed, etc. In particular, when the workpiece is a non-ferrous metal material such as an aluminum alloy or a copper alloy, by setting the rake angles of the second and third cutting edges in the range of 8° to 23°, it is possible to suppress the generation of burrs around the edge of the drilled hole and also suppress the adhesion of the aluminum alloy to the cutting edges.

[0011] FIG. 1 is a front view of the drill 10 of the present invention. FIG. 2 is a right side view of the drill 10 shown in FIG. 1. FIG. 3 is a view taken along arrow A of the drill 10 shown in FIG. 1. FIG. 4 is a schematic projection view of the drill 10 of the present invention in the longitudinal direction. FIG. 5 is a schematic enlarged view (first embodiment) of the vicinity of the second cutting edge 3 and the third cutting edge 4 of the drill 10 of the present invention. FIG. 6 is a schematic enlarged view (second embodiment) of the vicinity of the second cutting edge 3 and the third cutting edge 4 of the drill 10 of the present invention. FIG. 7 is a photograph showing the state of the periphery of a machined hole on the machined surface in a cutting test using the drill 10 of the present invention. FIG. 8 is a photograph showing the state of the periphery of a machined hole on the machined surface in a cutting test using a comparative drill.

[0012] An embodiment of the drill of the present invention will be described with reference to the drawings. An embodiment of the drill of the present invention will be described with reference to the drawings. FIG. 1 shows a front view of a drill 10 according to one embodiment of the present invention, FIG. 2 shows a right side view, and FIG. 3 shows a view of the drill 10 as viewed from the arrow A in FIG. 1. As shown in FIGS. 1 and 2, the drill 10 of the present invention includes first to third cutting edges 2, 3, and 4 extending radially (outwardly) from chisel edges 1 (1A, 1B) located at the tip portion of the drill 10, and flanks 6 (6A, 6B), 11 (11A, 11B), and 51 (51A, 51B) formed adjacent to the first to third cutting edges 2, 3, and 4.

[0013] In particular, the flank (first flank) 51 (51A, 51B) adjacent to the first cutting edge 2 (2A, 2B) and the flank (second flank) 11 (11A, 11B) adjacent to the second cutting edge 3 (3A, 3B) are formed as flanks that are separate and independent of each other, as shown in Figures 1 to 3. In addition, the flank (first flank) 51 (51A, 51B) adjacent to the first cutting edge 2 (2A, 2B) is further provided with a separate flank (third flank) 6 (6A, 6B) on the rear side in the rotation direction of the drill.

[0014] The first cutting edges 2 (2A, 2B) of the drill 10, each having a straight portion extending outward, are generally referred to as "main cutting edges." In this embodiment, the first cutting edges 2 (2A, 2B) are in the form of cutting edges that extend outward in a straight line as shown in FIGS. 1 to 3 , but the first cutting edges 2 (2A, 2B) are not limited to this form. For example, when the workpiece is a light metal such as an aluminum alloy or a difficult-to-cut material such as stainless steel, the drill may be configured with multiple cutting edges of different shapes, such as a short, straight or curved cutting edge (thinning cutting edge) on the side of the central axis O shown in FIG. 1 or a curved cutting edge (R cutting edge) in the central portion.

[0015] As shown in Figures 2 and 3, the first cutting edges 2 (2A, 2B) are formed adjacent to the rake face 7 (7A, 7B) and the continuous flutes (helical flutes) 8 (8A, 8B). The first cutting edges 2 (2A, 2B) have a linear portion, which breaks up and discharges chips generated during drilling without continuously generating them. Furthermore, the point angle α of the first cutting edges 2 (2A, 2B) shown in Figure 2 is set to a range of 90° to 140°, which improves the centripetal movement of the drill (preventing runout) and the biting ability (initial workability on flat workpieces) at the start of drilling. Furthermore, by setting the point angle α to a range of 170° to 200°, the drill is not affected by the inclined surface when drilling begins, and drilling can be performed without bending.

[0016] Here, the "point angle" is defined as "the angle when the cutting edges are projected parallel to a plane parallel to the axis of the drill" as defined in Japanese Industrial Standards (JIS) B0171. In other words, the point angle α formed by the first cutting edges 2A, 2B is the angle when the two first cutting edges 2A, 2B are projected parallel to a plane parallel to the axis (center axis O) of the drill 10 as shown in Figure 2.

[0017] Next, a schematic projection view of the drill 10 of this embodiment in the longitudinal direction (axial direction) is shown in Figure 4, and schematic enlarged views of the vicinity of the second cutting edge 3 and the third cutting edge 4 of the drill 10 are shown in Figures 5 (first embodiment) and 6 (second embodiment), respectively. As shown in Figures 2 and 3, the drill 10 of this embodiment has second cutting edges 3 (3A, 3B) extending from the end of the first cutting edge 2 (2A, 2B) outward and circumferentially of the drill 10 and toward the rear side of the drill 10, and third cutting edges 4 (4A, 4B) extending from the end of the second cutting edge 3 (3A, 3B) toward the rear side of the drill 10 and connected to the leading edge 5. By forming the second cutting edges 3 (3A, 3B) and the third cutting edges 4 (4A, 4B), burrs are suppressed around the through hole when drilling a through hole (through hole). In particular, by coating the surface of the drill (10), specifically the cutting edges such as the first cutting edge 2 (2A, 2B), the second cutting edge 3 (3A, 3B), and the third cutting edge 4 (4A, 4B) and the adjacent flank and scoop surfaces with a hard coating of either diamond or diamond-like carbon (DLC), adhesion to the cutting edge is suppressed when drilling non-ferrous metal materials such as aluminum alloys and copper alloys, thereby significantly reducing burrs that occur on the edge of the drilled hole.

[0018] Since the second cutting edges 3 (3A, 3B) are curved as shown in Figures 1 to 4, two or more cutting edges with different radii of curvature may be combined. In this case, the radius of curvature of the cutting edge connected to the end of the first cutting edge 2 (2A, 2B) may be smaller than the radius of curvature of the cutting edge connected to the end of the third cutting edge 4 (4A, 4B). In other words, the radius of curvature of the curved second cutting edges 3 (3A, 3B) may be gradually increased from the tip end to the rear end of the drill 10.

[0019] Furthermore, by setting the rake angles of the second cutting edges 3 (3A, 3B) and the third cutting edges 4 (4A, 4B) in the range of 8° to 23°, it is possible to suppress the generation of burrs around the drilled hole when the workpiece is a non-ferrous metal material such as an aluminum alloy or copper alloy. Here, the "rake angle" refers to the angle between the line (T0) connecting the cutting edge of the cutting edge to the rotation axis of the drill and the tangent line (T1) to the rake face on a cross section perpendicular to the axis of the drill of the present invention.

[0020] The third cutting edge 4 is either curved or linear (not shown), and is connected to the leading edge 5 via an outer corner toward the rear side (right side of the drawing) of the drill 10 as shown in Fig. 5. That is, the connection between the third cutting edge 4 and the leading edge 5 corresponds to the outer corner of the drill 10 of this embodiment, and is the outermost position of the drill 10. Furthermore, when the second cutting edge 3 and the third cutting edge 4 are curved as shown in Fig. 4, the radius of curvature r4 of the third cutting edge 4 may be larger than the radius of curvature r3 of the second cutting edge 3.

[0021] 5, the flank 11 adjacent to the third cutting edge 4 is formed continuously with the margin 12 of the drill 10 of this embodiment, and the connection (joining) from the flank 11 of the third cutting edge 4 to the margin 12 gradually changes in slope from the front end to the rear end of the drill 10. The linear ridge 20 (first embodiment) that is the boundary between the flank 11 adjacent to the third cutting edge 4 and the margin 12 can have an angle θ (θ1) with the leading edge 5 in the range of 4° to 25°.

[0022] Furthermore, as a different embodiment regarding the boundary between the flank 11 and the margin 12, a ridge 21 (second embodiment) which is the boundary between the flank 11 and the margin 12 may be configured to include a straight portion and a curved portion as shown in Fig. 6. It is preferable that the angle θ (θ2) formed by the ridge 21 with the leading edge 5 is in the range of 4° to 25°.

[0023] Furthermore, the angle θ (θ1, θ2) can be optimized according to various parameters, such as the diameter (drill diameter) φD0 of the drill 10, the angle (rake angle) of the rake face 7 (7A, 7B), the angle (twist angle) of the groove (twist groove) 8 (8A, 8B), the axial length L1 of the second cutting edge 3 (3A, 3B) and the third cutting edge 4 (4A, 4B), and the magnitudes of the radii of curvature r3, r4.

[0024] In addition, the axial length L1 of the second cutting edge 3 (3A, 3B) and the third cutting edge 4 (4A, 4B) in the drill 10 of the present invention is preferably in the range of 0.10 to 0.40 x D0, where D0 is the diameter of the drill 10 as shown in Figure 4.

[0025] Furthermore, in the drill 10 of the present invention, the radial distance (shortest distance) E1 from the end of the first cutting edge 2 (2A, 2B) to the outermost periphery of the drill 10 (a virtual straight line parallel to the axial direction of the drill 10 and passing through the outer corner) is preferably in the range of 0.01 to 0.20 x D0, where D0 is the diameter of the drill 10 as shown in Figure 4.

[0026] Furthermore, the "diamond-like carbon (DLC: amorphous diamond)" in the present invention can be appropriately selected from types of hard coatings such as a-C (amorphous carbon), ta-C (tetrahedral amorphous carbon), a-C:H (hydrogen-containing amorphous carbon), and ta-C:H (hydrogen-containing tetrahedral amorphous carbon) depending on conditions such as the machining speed during cutting using a drill, the size of the drilled hole, and the type of workpiece.

[0027] Example 1 The results of a cutting test comparing the height of burrs generated around holes after cutting (drilling) between a drill according to the present invention (hereinafter referred to as the invention product) and a comparative drill (hereinafter referred to as the comparative product) are described below. In this test, an aluminum alloy (A5052), which is prone to burrs during drilling, was used as the workpiece. After drilling (10 holes) under the following conditions, the height of burrs generated around the periphery (edge) of the through holes was measured. The burr height was measured by measuring the shape of the exit side (through side) of the workpiece using a non-contact three-dimensional measuring device, and then measuring the height of the burrs on the periphery of the through hole relative to the plane of the exit side.

[0028] The cutting conditions were as follows: Cutting speed: 100 m / min, Rotational speed: 5305 rpm, Feed rate: 1432 mm / min, Feed rate: 0.27 mm / rev, Machining hole depth: 24 mm blind hole, Oil supply method: Water-soluble cutting oil externally supplied

[0029] The drill shapes of the invention and comparative drills used in this test were as shown in Figures 1 and 2: diameter: 6 mm, flute length: 42 mm, total length: 82 mm, shank diameter: 6 mm, point angle: 135°, r3 of the second cutting edge = 3.8 mm, and the third cutting edge was linear. The invention drill had a helix angle of 38°, a rake angle of the second and third cutting edges of 20°, and a DLC (diamond-like carbon) coating, while the comparative drill had a helix angle of 30°, a rake angle of the second and third cutting edges of 5°, and an AlCrN and AlTiN coating.

[0030] The results of this test showed that the burr height (protrusion height) of holes drilled using the comparative product was measured in the range of 3.19 mm to 3.25 mm, while the burr height of holes drilled using the inventive product was 0.02 mm (20 μm). This indicates that the inventive product has the ability to more effectively suppress burrs on aluminum alloys than the comparative product. Furthermore, when comparing photographs of the exits of the drilled holes, no burrs were observed on the edge of the drilled hole on the surface drilled using the inventive product (Figure 7), while the drilled surface drilled using the comparative product (Figure 8) showed a protrusion due to the hole not penetrating through and a portion of the workpiece being stretched.

[0031] From the above, when the workpiece is a soft metal such as an aluminum alloy, the inventive product has excellent machining performance, being able to reduce burr height more effectively than the comparative product. The reason for this is that the inventive product has a larger helix angle (38°) and peripheral rake angle (20°) than the comparative product, which reduces the resistance generated during cutting.

[0032] Furthermore, the DLC coating applied to the inventive product suppressed wear and welding on the drill cutting edge, maintaining stable cutting performance, which is thought to have been a factor in suppressing the occurrence of burrs. Furthermore, the tip shape with a point angle of 135° and corner chamfering (R = 3.8 mm) minimized deformation of the material (aluminum alloy) during hole drilling, reducing the occurrence of burrs. These factors interacted with each other, and it is thought that the inventive product performed better than the comparative product in many applications requiring high-precision cutting work.

[0033] Example 2 Next, similarly to Example 1, a comparison was made of cutting (drilling) performance with different peripheral rake angles using an aluminum alloy (A5052) as the workpiece. The drill used in this example was the same DLC-coated drill (flute length: 42 mm, total length: 82 mm, shank diameter: 6 mm) with a drill diameter (diameter) of 6 mm as in Example 1. The cutting conditions were a cutting speed of 100 m / min, rotation speed of 5305 rpm, feed rate of 1432 mm / min, feed rate of 0.15 mm / rev, and hole depth of 24 mm, and a water-soluble cutting fluid was supplied externally.

[0034] First, when the peripheral rake angle was 5°, the burr height was 0.227 mm, but when drills with 8°, 12°, 15°, and 20° were used, burrs were observed under all conditions, but the burr height was significantly reduced when the peripheral rake angle was between 8° and 20° (burr height: 0.018 to 0.035 mm).Next, when a drill with a peripheral rake angle of 25° was used, chipping occurred on the peripheral cutting edge, making it impossible to measure the burr height.

[0035] The above test results confirmed that a peripheral rake angle of 8° or more can more effectively suppress burrs, but that if the peripheral rake angle is too large, chipping is more likely to occur. In other words, in the present invention, it is important to select an optimal peripheral rake angle that takes into account the balance between the quality of the drilled hole and the tool life, and it was found that the angle range is 8° or more and less than 25°. Considering the risk of chipping of the cutting edge after repeated use, the preferred angle range is 8° or more and 23° or less, and more preferably 8° or more and 20° or less.

[0036] 1 Chisel edge 2 First cutting edge 3 Second cutting edge 4 Third cutting edge 5 Leading edge 6 Flank (third flank) 7 Rake face 8 Flute (helical flute) 10 Drill 11 Flank (second flank) 12 Margin 20, 21 Ridge line that is the boundary between the flank and the margin 51 Flank (first flank) D0 Drill diameter (drill diameter) O Central axis r3 Radius of curvature of the second cutting edge r4 Radius of curvature of the third cutting edge α Point angle θ (θ1, θ2) Angle between the ridge line and the leading edge

Claims

1. A drill having at least two or more cutting edges extending outward from the central axis, wherein the cutting edges are formed from a first cutting edge having a straight portion extending outward from the chisel edge to the drill, a curved second cutting edge extending outward, circumferentially and rearward from the end of the first cutting edge to the drill, and a straight third cutting edge extending rearward from the end of the second cutting edge and connected to the leading edge, wherein the surface of the drill is coated with a hard coating of either diamond or diamond-like carbon. The drill is characterized in that the third cutting edge is connected to the leading edge via an outer corner, and the relief surface adjacent to the third cutting edge is formed continuously with the margin of the drill.

2. A drill having at least two or more cutting edges extending outward from a central axis, wherein the cutting edges are formed from a first cutting edge having a straight portion extending outward from the chisel edge to the drill, a curved second cutting edge extending outward, circumferentially and rearward from the end of the first cutting edge to the drill, and a curved third cutting edge extending rearward from the end of the second cutting edge and connected to the leading edge, wherein the radius of curvature of the third cutting edge is greater than the radius of curvature of the second cutting edge, and the surface of the drill is coated with a hard coating of either diamond or diamond-like carbon. The drill is characterized in that the third cutting edge is connected to the leading edge via an outer corner, and the relief surface adjacent to the third cutting edge is formed continuously with the margin of the drill.

3. The drill according to claim 1 or 2, characterized in that the rake angles of the second and third cutting edges are in the range of 8° to 23°.

4. The drill according to claim 1 or 2, characterized in that the ridge line forming the boundary between the relief surface adjacent to the third cutting edge and the margin has an angle with the leading edge in the range of 4° to 25°.

5. The drill according to claim 1 or 2, characterized in that the relief angles of the second and third cutting edges are in the range of 5° to 18°.