Drill bit and method of manufacturing a perforated article

Abstract

The present invention relates to a drill bit and a method of manufacturing a perforated article. In the case where the rigidity of the main shaft of a perforating machine is sufficient, it goes without saying, but even in the case where perforation is performed using a hand-held tool rotation device or the rigidity of the main shaft of the perforating machine is low, a workpiece composed of a composite material or a metal or the like can be perforated with high accuracy. The drill bit of the embodiment has a first cutting edge formed on the leading end side in such a manner that the leading end angle is continuously or discontinuously reduced from the leading end side to the trailing end side, and on the other hand, the clearance angle is continuously or discontinuously reduced from the leading end side to the trailing end side, and is used to perforate a workpiece to form a pilot hole; a second cutting edge formed by being positioned away from the first cutting edge toward the trailing end side, and used to perform finishing of the pilot hole, and having a clearance angle at the maximum diameter position; and a vibration-damping portion formed between the first cutting edge and the second cutting edge, and reducing vibration of the second cutting edge by being inserted into the pilot hole processed by the first cutting edge.

Description

Technical Field

[0001] The embodiments of the present invention relate to a method for manufacturing a drill bit and a drilled object. Background Technology

[0002] Currently, drill bits used for high-quality drilling of fiber-reinforced plastics (FRP), which are composite materials including not only metals but also glass fiber reinforced plastics (GFRP) or carbon fiber reinforced plastics (CFRP), are known to have a cutting edge with a continuously varying front and rear angles towards the maximum diameter of the cutting edge, and a rear angle at the maximum diameter position of the cutting edge (see, for example, Patent Documents 1, 2, and 3). Compared to existing composite material drilling bits, this drill bit can significantly produce high-quality holes and significantly extends tool life through improved wear resistance; therefore, it is commonly known as the "R drill bit" (registered trademark).

[0003] Furthermore, the projection shape of the cutting edge in the radial direction, which continuously reduces the front angle, is set to a curve shape such as a parabola or a circular arc. Therefore, from the viewpoint of facilitating manufacturing, a polygonal drill bit that intermittently reduces the front angle has also been proposed (see, for example, Patent Document 4).

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2008-36759

[0007] Patent Document 2: Japanese Patent Application Publication No. 2012-135873

[0008] Patent Document 3: Japanese Patent Application Publication No. 2010-214478

[0009] Patent Document 4: Japanese Patent Application Publication No. 2015-221467 Summary of the Invention

[0010] The problem that the invention aims to solve

[0011] When the aforementioned R drill bit (registered trademark) is installed on a machine tool with high spindle rigidity, such as a drilling machine, milling machine, or machining center, and used for drilling, it can produce high-quality holes and significantly reduce the replacement frequency caused by drill bit wear.

[0012] However, when an R-drill bit (registered trademark) is mounted on a handheld tool rotating device such as a manual tool or a simple drilling machine with a low spindle rigidity or precision and piercing is performed, the quality of the hole sometimes deteriorates. As a specific example, a piercing test was conducted using a handheld tool rotating device to hold an R-drill bit (registered trademark). The results confirmed that when the number of cutting edges is three or more, the vibration of the R-drill bit (registered trademark) increases during piercing, and sometimes the cross-sectional shape of the hole becomes polygonal instead of circular. This quality deterioration was observed regardless of whether the workpiece (material being machined) is a composite material or a metal.

[0013] Therefore, the object of the present invention is to enable high-precision drilling of workpieces made of composite materials or metals, not only when the spindle rigidity of the drilling machine is sufficient, but also when drilling is performed using a handheld tool rotating device or when the spindle rigidity and precision of the drilling machine are low.

[0014] Technical solutions for solving the problem

[0015] The drill bit of the present invention includes: a first cutting edge at the front end, which is formed on the front end side with a front end angle greater than 0° and less than 180° that decreases continuously or intermittently from the front end side to the rear end side and a clearance angle that decreases continuously or intermittently from the front end side to the rear end side, and is used to drill a pre-drilled hole in the workpiece; a second cutting edge having a clearance angle at the position of maximum diameter, which is formed at a position away from the first cutting edge toward the rear end side for finishing the pre-drilled hole; and a vibration damping part formed between the first cutting edge and the second cutting edge, which reduces the vibration of the second cutting edge by being inserted into the pre-drilled hole processed by the first cutting edge.

[0016] Furthermore, the method for manufacturing a perforated article according to an embodiment of the present invention manufactures the perforated article by using the above-described drill bit to pierce a workpiece. Attached Figure Description

[0017] Figure 1 This is a front view of the drill bit according to the first embodiment of the present invention, showing a partial change in the direction of the arrow.

[0018] Figure 2 yes Figure 1 The enlarged left side view of the drill bit shown.

[0019] Figure 3 yes Figure 1 The image shows a magnified top view of the front end of the drill bit.

[0020] Figure 4 yes Figure 1 An enlarged cross-sectional view of the drill bit position AA shown.

[0021] Figure 5 is for explaining Figure 1 an enlarged projected view of the cutting edge portion shown onto a projection plane parallel to the tool axis, of the shape of the cutting edge portion.

[0022] Figure 6 is showing Figure 1 a partial front view showing an example of the front angle and the back angle of the front cutting edge shown.

[0023] Figure 7 is showing an example of forming a margin only within a partial range of the hold portion shown in Figure 1 a projected view.

[0024] Figure 8 is a view showing an example of a method of attaching a drill bit to a hand-held tool rotating device and drilling a workpiece.

[0025] Figure 9 is a partial front view of the drill bit of the second embodiment of the present invention.

[0026] Figure 10 is a partial front view of the drill bit of the third embodiment of the present invention, with the arrow direction locally changed.

[0027] Figure 11 is Figure 10 an enlarged left side view of the front end portion of the drill bit shown.

[0028] Figure 12 is Figure 10 an enlarged partial top view of the front end portion of the drill bit shown.

[0029] Figure 13 is Figure 10 an enlarged cross-sectional view taken along line B - B of the drill bit shown.

[0030] Figure 14 is Figure 10 an enlarged projected view of the front end portion of the drill bit shown.

[0031] Figure 15 is a partial front view of the drill bit of the fourth embodiment of the present invention, with the arrow direction locally changed.

[0032] Figure 16 is Figure 15 an enlarged left side view of the front end portion of the drill bit shown.

[0033] Figure 17 is Figure 15 an enlarged partial top view of the front end portion of the drill bit shown.

[0034] Figure 18 is Figure 15An enlarged cross-sectional view of the drill bit position CC shown.

[0035] Figure 19 This is an enlarged partial front view showing a first shape example of the cutting edge portion of the drill bit formed in the fifth embodiment of the present invention.

[0036] Figure 20 This is an enlarged partial front view showing a first shape example of the cutting edge portion of the drill bit formed in the fifth embodiment of the present invention.

[0037] Figure 21 This is a magnified projection view of the reamer cutting edge of the drill bit formed in the sixth embodiment of the present invention.

[0038] Figure 22 This is a magnified projection of an example where the front angle of the reamer is set to 0° without reducing it.

[0039] Figure 23 This is a projection view showing a first shape example of the front cutting edge of the drill bit formed in the seventh embodiment of the present invention.

[0040] Figure 24 This is a projection view showing a second shape example of the front cutting edge of the drill bit formed in the seventh embodiment of the present invention.

[0041] Figure 25 This is a projection view showing a third shape example of the front cutting edge of the drill bit formed in the seventh embodiment of the present invention.

[0042] Figure 26 This is a projection view showing a fourth shape example of the front cutting edge of the drill bit formed in the seventh embodiment of the present invention. Detailed Implementation

[0043] The following describes a method for manufacturing a drill bit and a drilled object according to embodiments of the present invention, with reference to the accompanying drawings.

[0044] (First Implementation)

[0045] (Structure and function of drill bits)

[0046] Figure 1 This is a front view of the drill bit according to the first embodiment of the present invention, showing a partial change in the direction of the arrow. Figure 2 yes Figure 1 The enlarged left side view of the drill bit shown. Figure 3 yes Figure 1 The image shows a magnified top view of the front end of the drill bit. Figure 4 yes Figure 1 An enlarged cross-sectional view of the drill bit's position AA is shown. Furthermore, Figure 1The diagram below the tool axis AX shows the outline of the cutting edge of the drill bit when it is unfolded in a manner parallel to the attached diagram. The multiple cutting edges formed on the drill bit are symmetrical about the tool axis AX, that is, the multiple cutting edges formed on the drill bit have the same shape. Therefore, the detailed outline of the interior is omitted.

[0047] Drill bit 1 is a drilling tool that can perform high-quality drilling even when the workpiece (the part to be cut) is either FRP or metal. That is, drill bit 1 has a shape that can drill with high precision not only metals such as aluminum and titanium, but also FRP or FRP-metal composite materials such as CFRP and GFRP.

[0048] The drill bit 1 is constructed using a body 2 on the front end side of the tool axis AX direction and a shank 3 on the rear end side of the tool axis AX direction. The body 2 and shank 3 can be made from typical raw materials such as hard alloys, tool steel, or polycrystalline diamond (PCD). When the body 2 and shank 3 are made of tool steel, using high-speed tool steel is practical. Furthermore, regardless of the material of the body 2 and shank 3, desired coatings such as diamond coating or DLC (diamond-like carbon) coating can be applied to improve wear resistance, thermal shock resistance, or weld resistance.

[0049] The shank 3 is a part used to hold the drill bit 1 by means of a retainer such as a handheld tool rotating drive or machine tool. Figure 1 In the example shown, the shank 3 has a special shape that facilitates the installation and removal of the retainer, but it can be a shank with a desired shape, such as a straight shank or a tapered shank. If the shape of the shank 3 is as simple as a straight shank or a tapered shank, the body 2 and the shank 3 can be constructed from a single piece of material, and the drill bit 1 can be a solid drill bit. Conversely, if the shape of the shank 3 is complex, the drill bit 1 can be... Figure 1 A cutting-edge drill bit in which the body 2 is inserted into the shank 3 for engagement, as shown in the example.

[0050] A cutting edge 4 for piercing a workpiece is formed at the front end of the main body 2. The cutting edge 4 has a front cutting edge 5 as a first cutting edge, a reaming edge 6 as a second cutting edge, and a stabilizing part 7. The front cutting edge 5 is formed on the front end side of the cutting edge 4 in the tool axis AX direction. On the other hand, the reaming edge 6 is formed on the rear end side of the cutting edge 4 in the tool axis AX direction. In addition, the reaming edge 6 is formed at a position away from the front cutting edge 5 towards the rear end side. Moreover, the stabilizing part 7 is formed between the front cutting edge 5 and the reaming edge 6.

[0051] The front cutting edge 5 has a front face 5A and a rear face 5B. The edge formed by the intersection of the front face 5A and the rear face 5B is the front end of the front cutting edge 5. Similarly, the reamer edge 6 also has a front face 6A and a rear face 6B. The edge formed by the intersection of the front face 6A and the rear face 6B is the front end of the reamer edge 6. In addition, the rear face is also called the second face, and the angle between the rear face and the machined face, i.e., the clearance angle, is also called the second angle.

[0052] Figures 1 to 4 In the example shown, three front cutting edges 5 and reaming edges 6 are provided in the cutting section 4, but the number of front cutting edges 5 and reaming edges 6 is arbitrary. That is, Figures 1 to 4 The drill bit 1 in the example is a drill bit in which the front cutting edge 5 and the reamer edge 6 are respectively arranged adjacent to the planar discharge surface 9A on the three cutting edges of the three cutting strips 9 formed between the three slots 8. However, it can also be a drill bit with two, four, or five cutting edges. The front cutting edge 5 and the reamer edge 6 are arranged on the cutting strips 9, therefore, the number of front cutting edges 5 is the same as the number of reamer edges 6. That is, the number of front cutting edges 5 and the reamer edge 6 is equal to the number of cutting strips 9.

[0053] in addition, Figures 1 to 4 The drill bit 1 in the example is a straight-edged drill bit with untwisted groove 8, but it can also be a twist drill bit with twisted groove 8. When groove 8 is set as a V-groove and it is a straight-edged drill bit, the rigidity of drill bit 1 can be increased. Conversely, when groove 8 is set as a twisted groove, the cutting resistance can be reduced.

[0054] Figure 5 It is used for explanation Figure 1 The enlarged projection view of the cutting edge 4 shown, projected onto a projection plane parallel to the tool axis AX. Figure 6 It means Figure 1 A partial front view of an example of the front angle α and rear angle γ1 of the front cutting edge 5 shown.

[0055] Figure 5 This illustrates an example of the shape obtained by projecting the area through which the cutting edge 4 passes onto a projection plane parallel to the tool axis AX when the cutting edge 4 is rotated around the tool axis AX. That is, Figure 5 This represents an example of the shape obtained by projecting the cutting edge 4, which rotates around the tool axis AX, along a direction perpendicular to the tool axis AX.

[0056] The front angle α of the cutting edge 5 is greater than 0° but less than 180° at the front end. That is, the front angle α of the cutting edge 5 at the front end of the drill bit 1 in the tool axis AX direction has a relationship of 0° < α < 180°. In other words, the drill bit 1 is not a flat drill or a candle-shaped drill (candle-shaped grinding drill) with a front angle of 180°.

[0057] A typical drill bit has a tip angle of 118° or 120°. The tip angle α at the tool center position of the tip of drill bit 1 can also be determined to an appropriate angle based on the cutting conditions such as the material of the workpiece or the tool diameter D. If the workpiece is metal or FRP, from the viewpoint of optimizing cutting conditions such as cutting resistance, it is preferable to set the tip angle α at the tool center position of the tip of the cutting edge 5 to 90° < α < 150°.

[0058] Furthermore, the front cutting edge 5 has a shape in which the front angle α continuously decreases from the tool axis AX direction and from the front end of the drill bit 1 towards the rear end. Therefore, the front angle α at the front end of the front cutting edge 5 becomes the maximum value of the front angle α. In addition, the diameter of the front cutting edge 5 continuously increases from the front end to the rear end. On the other hand, the clearance angle γ1 of the front cutting edge 5 is also formed in a manner that continuously decreases from the front end to the rear end of the drill bit 1 in the tool axis AX direction. Therefore, the clearance angle γ1 of the front cutting edge 5 also becomes the maximum value at the front end.

[0059] Figure 6 This is an example of the front angle α and back angle γ1 of the positions P1, P2 and P3 of the front cutting edge 5. Figure 6 In the example shown, the front angle α of the front cutting edge 5 decreases continuously and gradually in a manner that is 60°, 30° and 20° between the front and rear sides, while the rear angle γ1 of the front cutting edge 5 decreases continuously and gradually in a manner that is 37°, 33° and 31° between the front and rear sides.

[0060] The condition that the clearance angle γ1 of the front end of the cutting edge 5 is determined in such a way that the relationship between γ1 and the front end angle α is γ1 > (180 - α) / 2 is the preferred condition from the point of view of optimizing the cutting conditions. Therefore, if the front end angle α of the front end of the cutting edge 5 is set to 120°, the clearance angle γ1 of the front end of the cutting edge 5 can be determined to be, for example, about 45°.

[0061] When the tip angle α of the front cutting edge 5 is continuously reduced, no corner prone to damage is generated at the edge of the front cutting edge 5, thus reducing the risk of damage. As a result, the tool life of the drill bit 1 can be extended. Furthermore, when the tip angle α of the front cutting edge 5 is gradually reduced, in the case of perforating FRP, the occurrence of delamination (interlayer peeling) is reduced. This is because, even if temporary delamination occurs during perforation of FRP by the front cutting edge 5 with a relatively large tip angle α on the front side of the drill bit 1, the cutting resistance decreases and delamination is eliminated in the subsequent perforation by the front cutting edge 5 with a relatively small tip angle α.

[0062] Furthermore, the closer the shape of the edge of the front cutting edge 5 on the projection plane parallel to the tool axis AX is to a parabola, the more uniform the volume of workpiece cut per unit length of edge in the tool axis AX direction. Therefore, a uniform cutting resistance is achieved throughout the entire front cutting edge 5. If the cutting resistance can be made uniform throughout the entire front cutting edge 5, not only can delamination and burr formation during FRP piercing be reduced, but wear on the front cutting edge 5 can also be reduced.

[0063] On the other hand, when the shape of the edge of the front cutting edge 5 on the projection plane parallel to the tool axis AX is made close to an ellipse, the volume of the workpiece cut per unit length of edge in the tool axis AX direction can be reduced proportionally towards the rear of the front cutting edge 5. Therefore, by avoiding the situation where wear behind the relatively faster cutting edge 5 occurs before wear in front of the relatively slower cutting edge 5 due to different rotation radii, a uniform degree of wear across the entire front cutting edge 5 can be achieved. If the degree of wear across the entire front cutting edge 5 can be uniform, the life of the front cutting edge 5 can be improved.

[0064] Therefore, the shape of the edge of the front cutting edge 5 on the projection surface can be made to approximate a parabola or an ellipse, depending on the desired effect. Of course, the shape of the edge of the front cutting edge 5 can also be determined such that one part of it is close to an ellipse and the other part is close to a parabola on the projection surface.

[0065] However, when the shape of the edge of the front cutting edge 5 on the projection plane parallel to the tool axis AX is set as a parabola or an ellipse, the front angle α of the front end of the front cutting edge 5 becomes 180°. Therefore, the shape of the edge of the front cutting edge 5 needs to be determined in a way that the front angle α of the front end of the front cutting edge 5 is formed in a way that is suitable for the workpiece to be pierced.

[0066] Therefore, for example, such as Figure 5 and Figure 6 As in the example above, we can use only the area near the front end of the edge of the cutting edge 5 as a specific example. Figure 5 The shape of the edge of the front cutting edge 5 is determined by the fact that the front end side of the position PT0 shown is a straight line on the projection plane. Moreover, the shape of the edge of the front cutting edge 5 can be determined by the fact that the edge line connected to the straight edge line of the front end of the front cutting edge 5, and which is located behind the position PT0, is a quadratic curve such as a parabola or an ellipse on the projection plane.

[0067] Alternatively, the shape of the edge of the front cutting edge 5 can be determined by the intersection of two parabolas symmetrical to the projection line of the tool axis AX on the projection plane at the same distance from the axis of symmetry and offset in opposite directions, or two ellipses symmetrical to the major axis at the same distance from the major axis and offset in opposite directions, which become the projection point of the front cutting edge 5. A portion of the two parabolas or ellipses symmetrical to the side of the projection line of the tool axis AX becomes the projection line of the edge of the front cutting edge 5.

[0068] Furthermore, the fabrication of the front cutting edge 5, whose contour on the projection plane is an ellipse or parabola, is complex. Therefore, an ellipse or parabola can also be simulated by connecting arcs using an ellipse or parabola as a baseline RL. For example, if it is Figure 5 In the example shown, positions PT0 and PT1 can be connected on the projection plane using a single arc with the same radius, positions PT1 and PT2 can be connected using another single arc with a larger radius, and positions PT2 and PT3 can be connected using yet another single arc with an even larger radius. That is, if the shape of the edge of the front cutting edge 5 is determined in such a way that the projection line of the edge is a curve without a smooth angle connecting the straight line and the arc, it is possible to obtain the advantages of reducing manufacturing costs and making the projection line of the edge approximate an ellipse or parabola.

[0069] In addition to gradually reducing the front angle α of the front cutting edge 5, as described above, gradually reducing the rear angle γ1 of the front cutting edge 5 can improve the wear resistance of the front cutting edge 5. This is because when the rear angle γ1 of the front cutting edge 5 is reduced smoothly and continuously, the angle that is prone to wear will not be generated at the rear 5B of the front cutting edge 5.

[0070] The rake angle of the front cutting edge 5 can be determined according to the material of the workpiece. When the rake angle of the front cutting edge 5 is set to 0°, that is, when the front face 5A of the front cutting edge 5 is perpendicular to the cutting surface of the workpiece, it is difficult to produce delamination when drilling FRP. This is because if no rake angle is set on the front cutting edge 5, the FRP can be cut finely, which can reduce the open lines of the fibers contained in the FRP. Therefore, when it is important to ensure good quality of the holes machined in FRP, the rake angle of the front cutting edge 5 can be set to zero.

[0071] Conversely, setting the rake angle of the front cutting edge 5 optimizes the piercing conditions when drilling metal. Therefore, when high quality of the hole machined in metal is important, a rake angle can be set on the front cutting edge 5. Furthermore, in the illustrated example, the rake angle of the front cutting edge 5 is 0°. That is, no rake angle is set on the front cutting edge 5.

[0072] On the other hand, the reamer edge 6 can also be configured such that the front angle β and the clearance angle γ2 continuously decrease from the tool axis AX direction and from the front end to the rear end of the drill bit 1 to a shape that becomes 0°. Therefore, the diameter of the reamer edge 6 also continuously increases from the front end to the rear end. Moreover, at the maximum diameter position of the reamer edge 6, the front angle β becomes 0°. That is, the reamer edge 6 has a clearance angle γ2 at the maximum diameter position where the front angle β is 0°.

[0073] The maximum diameter of the rear end of the reamer edge 6 is larger than the maximum diameter D1 of the front cutting edge 5. Therefore, the maximum diameter of the reamer edge 6 becomes the tool diameter D of the drill bit 1. Furthermore, the maximum diameter of the stabilizing part 7 is formed such that it is less than or equal to the maximum diameter D1 of the front cutting edge 5. Therefore, when machining a workpiece using the front cutting edge 5, whose maximum diameter D1 is smaller than the tool diameter D, a pre-drilled hole with a diameter smaller than the finishing hole intended for machining is machined on the workpiece. Thus, the front cutting edge 5 serves as a pre-drilled hole for piercing the workpiece.

[0074] The maximum diameter of the stabilizing part 7, which connects to the front cutting edge 5, is less than or equal to the maximum diameter D1 of the front cutting edge 5. Therefore, when the drill bit 1 is fed out along the tool axis AX while piercing the workpiece, the stabilizing part 7 is inserted into the pre-drilled hole processed by the front cutting edge 5. Thus, the outer surface of the stabilizing part 7 with the maximum diameter contacts the inner surface of the pre-drilled hole, and the stabilizing part 7 is guided by the pre-drilled hole.

[0075] As a result, the vibration of the stabilizing part 7 and the reamer blade 6 connected to the stabilizing part 7 can be reduced during the piercing process. That is, the stabilizing part 7 functions as a vibration damping part to reduce the vibration of the reamer blade 6 by inserting a pre-drilled hole processed by the front cutting edge 5 into the piercing of the workpiece.

[0076] From the viewpoint of enabling the stabilizing part 7 to function as a vibration damping part of the reamer blade 6, and avoiding excessive temperature rise caused by friction between the workpiece and the stabilizing part 7, it is practical to not provide a cutting edge in the stabilizing part 7 and to form the stabilizing part 7 using an edge 7A of appropriate width. When the stabilizing part 7 is formed using an edge 7A without a cutting edge, the edge 7A can be formed by connecting the front cutting edge 5 to the reamer blade 6.

[0077] The width of the edge 7A constituting the stabilizing part 7 can be determined appropriately based on the maximum diameter D1 of the front cutting edge 5, which is equivalent to the diameter of the pre-drilled hole. As a specific example, if the maximum diameter D1 of the front cutting edge 5 is about 3mm to 10mm, the width of the edge 7A can be determined to be in the range of 0.1mm to 1.5mm, for example, about 0.3mm.

[0078] While drilling the workpiece, the drill bit 1 is further fed along the tool axis AX, and a reaming process is performed using a reamer blade 6 formed at a position away from the front cutting edge 5 towards the rear end. That is, hole finishing can be performed to expand the inner diameter of the pre-drilled hole in the workpiece to a tool diameter D that is equivalent to the maximum diameter of the reamer blade 6. Thus, a hole with a diameter corresponding to the tool diameter D can be machined into the workpiece.

[0079] Furthermore, while "reamer edge" sometimes refers narrowly to a cutting edge with a specific shape formed on the side of a tool for hole finishing, here "reamer edge" is used in a broad sense, regardless of its shape, referring to any cutting edge used for hole finishing as a "reamer edge." Therefore, "hole reaming" is also used broadly, referring to hole finishing regardless of the shape of the cutting edge used for hole finishing.

[0080] like Figure 5 In the example, if the ridge line of the reamer blade 6 and the ridge line of the front cutting edge 5 on the projection plane parallel to the tool axis AX are determined in such a way that they lie on the reference line RL formed by a common ellipse or parabola, the drill bit 1 can be manufactured by the following method: after manufacturing a semi-finished drill bit 1 that connects the ridge line of the reamer blade 6 and the ridge line of the front cutting edge 5, a stabilizing part 7 is provided by cutting or grinding.

[0081] In this case, if the stabilizing part 7 is provided only on the semi-finished drill bit 1 with a cutting edge along the baseline RL formed by a quadratic curve, a height difference is generated at the front end of the reamer edge 6. That is, the tool diameter of the drill bit 1 increases in a stepped manner at the front end of the reamer edge 6. However, the test results show that when a height difference exists at the front end of the reamer edge 6, reaming of FRP can be performed under good conditions, but reaming of metal is difficult to perform under good conditions.

[0082] Therefore, in the case where good quality holes can be machined not only for FRP but also for metals, as shown in the figure, it is appropriate to have a cutting edge with a maximum and certain front angle β at the front end of the reamer blade 6, and to connect a cutting edge behind the cutting edge with a certain front angle β where the front angle β and the clearance angle γ2 continuously decrease. Experimental results confirm that, in the case where good quality holes can be machined not only for FRP but also for metals, it is preferable to set the maximum front angle β on the front end side of the reamer blade 6 to be between 80° and 100°.

[0083] Furthermore, in the reaming of FRP, a front angle β of 80° to 100° is not always required. Therefore, when the drill bit 1 is used for piercing FRP, a cutting edge with a certain front angle β can be omitted on the front side of the reamer blade 6, thus creating a height difference. In this case, the maximum front angle β on the front side of the reamer blade 6 becomes the maximum value of a continuously decreasing front angle β.

[0084] However, regardless of whether a cutting edge with a certain front angle β is provided on the front end side of the reamer edge 6, as mentioned above, the front angle β on the rear end side of the reamer edge 6 is always set to 0°. Since there is no line parallel to the axis of symmetry in a parabola, in order to set the front angle β on the rear end side of the reamer edge 6 to 0°, it is appropriate to determine the shape of the edge of the reamer edge 6 in such a way that the projection line of the entire edge of the reamer edge 6, or at least the projection line of a portion of the edge of the rear end side of the reamer edge 6, intersects the minor axis of the ellipse.

[0085] Therefore, if the shapes of the edges of the front cutting edge 5 and the reamer edge 6 are determined by placing the edges of the portion of the projection plane parallel to the tool axis AX, excluding the front end of the front cutting edge 5, and the edges of the reamer edge 6 on multiple arcs simulating the reference line RL formed by a shared ellipse, then by adopting a manufacturing method of setting the stabilizing part 7 by cutting or grinding after manufacturing a semi-finished drill bit 1 that connects the edges of the front cutting edge 5 and the edges of the reamer edge 6, the labor and manufacturing cost of manufacturing a drill bit 1 with the front end angle β of the rear end side of the reamer edge 6 being 0° can be reduced.

[0086] When the clearance angle γ2 is set at the maximum diameter position where the tip angle β of the reamer edge 6 is 0°, the reamer edge 6 at the maximum diameter position contacts the inner surface of the pre-drilled hole machined by the tip cutting edge 5 parallel to it. Therefore, reaming can be performed without burrs. As a result, the hole can be machined with good quality.

[0087] Furthermore, from the viewpoint of notch and wear prevention of the reamer blade 6, the clearance angle γ2 at the maximum diameter position of the reamer blade 6 is preferably set to less than 15°. Therefore, for example, the maximum clearance angle of the cutting edge having a certain front angle β on the front end side of the reamer blade 6 can be set to approximately 11° to 12°, and the minimum clearance angle γ2 at the maximum diameter position of the reamer blade 6 can be set to approximately 10°. On the other hand, the front angle of the reamer blade 6 can be set to 0° like the front cutting edge 5, or set at an appropriate angle.

[0088] On the further rear end side of the reamer blade 6, as Figure 1 , Figure 3 and Figure 4In the example, the edge 10 can be set continuously with the reamer blade 6. This allows the drill bit 1 body 2 to be guided using the hole finished by the reamer blade 6, reducing vibration of the drill bit 1. The width of the edge 10 can be determined appropriately based on the tool diameter D. Specifically, if the tool diameter D is approximately 3mm to 10mm, the width of the edge 10 can be determined to be in the range of 0.1mm to 1.5mm, for example, approximately 0.3mm.

[0089] If an edge 7A is formed in the stabilizing portion 7, and an edge 10 is also provided behind the cutting edge 4, then the edge 10, which is further behind the reamer blade 6, can be guided by the finished hole, and the edge 7A of the stabilizing portion 7 can be guided by the pre-drilled hole. That is, the vibration of the reamer blade 6 can be suppressed at two locations in the tool axis AX direction that clamp the reamer blade 6. As a result, the core of the drill bit 1 in the portion of the reamer blade 6 can be prevented from deviating, and the finished hole can be machined with good quality.

[0090] The diameter of the edge 7A formed in the stabilizing part 7 can be set to a certain value, or an inverted taper can be provided on the edge 7A. When no inverted taper is provided on the stabilizing part 7 and the diameter is set to a certain value, the edge 7A of the stabilizing part 7 is in contact with the inner surface of the pre-drilled hole as a whole, so that the vibration reduction effect of the stabilizing part 7 can be maximized.

[0091] However, when the edge 7A of the stabilizing portion 7 comes into contact with the inner surface of the pre-drilled hole, the temperature of the workpiece is likely to rise due to frictional heat between the edge 7A and the workpiece. Therefore, if the workpiece is made of a material with a low melting point, such as aluminum, the workpiece may weld together. Therefore, when drilling a workpiece made of a material with a low melting point, such as aluminum, an inverted cone can be provided at the edge 7A of the stabilizing portion 7 to prevent the workpiece from welding together.

[0092] Conversely, when piercing difficult-to-machine materials such as titanium or FRP with low thermal conductivity, the cutting resistance increases and welding becomes difficult. Therefore, the vibration reduction effect of the stabilizing part 7 can be improved by not providing an inverted cone or providing a smaller inverted cone at the edge 7A of the stabilizing part 7.

[0093] The test results showed that when a tapered section 7 is provided, it is appropriate to provide a tapered section with a thickness of 0.02 / 100 or more and 0.06 / 100 or less in order to achieve both workpiece welding prevention and vibration prevention of the stabilizing section 7. For the same reason, when a tapered section is not provided on the rear edge 10 of the cutting edge 4, or when a tapered section is provided, it is appropriate to provide a tapered section with a thickness of 0.02 / 100 or more and 0.06 / 100 or less.

[0094] When the maximum diameter of the stabilizing part 7 is excessively reduced, the maximum diameter D1 of the front cutting edge 5 also decreases, reducing the rigidity of the front cutting edge 5 and the stabilizing part 7, and potentially causing excessive cutting depth during finishing with the reamer edge 6. Furthermore, as the maximum diameter D1 of the front cutting edge 5 decreases, the depth of the groove 8 becomes shallower, increasing the risk of chip clogging. Therefore, to ensure stable machining of high-quality holes, it is crucial to maintain the rigidity and dimensions of the front cutting edge 5 and the stabilizing part 7, and to set the cutting depth of the finishing with the reamer edge 6 to an appropriate value. Experimental results indicate that setting the maximum diameter of the stabilizing part 7 to be at least 0.5 times and less than 0.9 times the tool diameter D, which is equivalent to the maximum diameter of the reamer edge 6, is preferable.

[0095] The length Lh of the stabilizing part 7 in the tool axis AX direction can be determined based on the overall cutting length L of the drill bit 1 and the appropriate length L2 of the reamer cutting edge 6. The cutting length L is expressed as the sum of the length L1 of the front cutting edge 5 in the tool axis AX direction, the length Lh of the stabilizing part 7 in the tool axis AX direction, and the length L2 of the reamer cutting edge 6 from the position of minimum diameter to the position of first becoming the maximum diameter in the tool axis AX direction.

[0096] Specifically, setting the blade length L to be more than 1 and less than 2 times (1D≤L≤2D) the maximum diameter of the reamer blade 6, which is equivalent to the tool diameter D, becomes a condition for determining the front angle α of the front cutting edge 5 to an appropriate angle and determining the actual edge shape of the front cutting edge 5 and the reamer blade 6 along an appropriate quadratic curve. The blade length L is expressed as the sum of the length L1 of the front cutting edge 5 in the tool axis AX direction, the length Lh of the stabilizing part 7 in the tool axis AX direction, and the length L2 of the reamer blade 6 in the tool axis AX direction from the minimum diameter position to the position where it first becomes the maximum diameter.

[0097] This is because when the blade length L is too short compared to the tool diameter D, it is necessary to increase the front angle α geometrically, or to make the projection lines of the front cutting edge 5 and the reamer edge 6 close to an arc or an ellipse with the minor axis parallel to the tool axis AX, etc.

[0098] On the other hand, when the cutting length L of drill bit 1 is too long compared to the tool diameter D of drill bit 1, when machining through holes in workpieces such as plates, the cutting edge 4 of the cutting length L protrudes from the back side of the workpiece. As a result, the following problem occurs: the hole cannot be drilled when interference occurs with the fixture or other parts of the workpiece.

[0099] Furthermore, when the cutting length L of drill bit 1 is excessively long compared to the tool diameter D of drill bit 1, problems may arise, such as the inability to machine a finishing hole with good accuracy, unless it is a deep hole. This is because, unless the workpiece is thicker than the cutting length L of drill bit 1 and a through hole with the tool diameter D set to the diameter is being machined, the effect of the front cutting edge 5 penetrating the workpiece before the finishing pre-drilling at the maximum diameter position of the reamer edge 6 reduces the vibration suppression effect of the reamer edge 6 on both the stabilizing part 7 and the edge 10. In other words, as the cutting length L of drill bit 1 increases, the accuracy of the finishing hole may decrease if a longer through hole is not machined.

[0100] Due to the constraints described above, the overall cutting length L of the drill bit 1 depends on the tool diameter D. Therefore, if the maximum diameter D1 of the front cutting edge 5 and the maximum diameter of the stabilizing part 7 are determined by the tool diameter D, then the radius of rotation of the front cutting edge 5 is determined by a reference line RL formed by a quadratic curve such as a parabola or ellipse, thus necessarily determining the length L1 of the front cutting edge 5. Therefore, the length obtained by subtracting the length L1 of the front cutting edge 5 from the overall cutting length L of the drill bit 1 becomes the sum of the length Lh of the stabilizing part 7 and the length L2 of the reamer edge 6. Therefore, the length Lh of the stabilizing part 7 can be determined by subtracting the appropriate length L2 of the reamer edge 6.

[0101] As a specific example, the length L2 of the reamer blade 6 can be set to 0.1 times the tool diameter D (L2 = 0.1D), and the total length L1 of the front cutting edge 5 and the length Lh of the stabilizing part 7 can be set to 1.5 times the tool diameter D (L1 + Lh = 1.5D).

[0102] However, the length of the edge 7A required to perform the vibration damping function of the stabilizing part 7 is sometimes shorter than the length Lh of the stabilizing part 7. In addition, when the contact area between the edge 7A and the pre-drilled hole processed by the front cutting edge 5 is too large, the temperature may rise excessively.

[0103] Therefore, the inverted cone may not be provided throughout the entire stabilizing part 7, but rather locally, or locally with a diameter within a certain range. Empirically, it is believed that if the diameter or inverted cone of the stabilizing part 7, covering at least 1 / 5 or more of its length Lh in the tool axis AX direction (≥Lh / 5), is fixed, the vibration damping effect of the reamer edge 6 can be sufficiently achieved. That is, it is believed that if an edge 7A with a certain maximum diameter or a certain inverted cone is provided within at least 1 / 5 or more of the length of the stabilizing part 7 on the side with the front cutting edge 5, the vibration damping effect of the reamer edge 6 can be obtained.

[0104] Figure 7 It means only when Figure 1 The projection diagram shows an example of a portion R of the stabilizing part 7 having an edge 7A.

[0105] like Figure 7 In the projection diagram shown, it is preferable to form the edge 7A within a range R of the length Lh of the stabilizing portion 7, which is more than 20% and less than 100%. In other words, the edge 7A can also be formed only within a portion R of the stabilizing portion 7, and the rotation radius can be reduced for other portions. Therefore, if the edge 7A is formed by grinding, it is also possible to perform high-precision grinding only within a certain range R to form the edge 7A, and to form the retreat portion by rough grinding for other parts.

[0106] (Manufacturing method of perforated material)

[0107] Figure 8 This is a diagram illustrating an example of a method for mounting a drill bit 1 onto a handheld tool rotating device 20 and piercing a workpiece W.

[0108] like Figure 8 As shown, the drill bit 1, held by a handheld tool rotating device 20, pierces the workpiece W, thereby enabling the manufacture of the pierced item as a finished product or a semi-finished product. When piercing the workpiece W using the handheld tool rotating device 20, a nose piece 22 with a bushing tip 21 is installed on the tool rotating device 20, and a piercing plate 23 is placed on the workpiece W, thereby enabling the positioning of the drill bit 1 relative to the workpiece W.

[0109] That is, by fixing the sleeve head 21 to the perforation plate 23, the position and direction of the drill bit 1 can be positioned. Moreover, for example, not only can a workpiece W made of a single raw material such as FRP or metal be used, but it is also possible to use the drill bit 1 to pierce a workpiece W made of multiple raw materials such as composite materials of FRP and metal.

[0110] also, Figure 8 In the example shown, the tool rotating device 20 has an automatic feeding function for the drill bit 1, but it is also possible to use a simple tool rotating device 20 that only has the function of rotating the drill bit 1 to pierce the workpiece W. Of course, it is also possible to install the drill bit 1 on a machine tool such as a drilling machine or machining center or a non-handheld piercing machine and manufacture the pierced product.

[0111] (Effect)

[0112] The drill bit 1 described above has a stabilizing part 7, consisting of an edge 7A for damping the reamer edge 6, between a front cutting edge 5 where the front angle α and the clearance angle γ1 continuously decrease, and a reamer edge 6 where the front angle β and the clearance angle γ2 continuously decrease, and the clearance angle γ2 is present at the maximum diameter position where the front angle β is 0°. Furthermore, a method for manufacturing a drilled item uses the drill bit 1 described above to manufacture the drilled item.

[0113] Therefore, according to the manufacturing method of drill bit 1 and the workpiece to be drilled, a pre-drilled hole formed by the piercing through the front cutting edge 5 can be used for reaming and finishing by the reamer edge 6 while being guided by the stabilizing part 7. That is, the vibration of the reamer edge 6 can be suppressed by the stabilizing part 7. Therefore, a high-quality hole with a circular cross-section can be machined.

[0114] In particular, in existing R-type drill bits (registered trademark) with three or more cutting edges, where the tip angle and clearance angle of the cutting edge continuously change towards the position of the maximum diameter of the cutting edge, and where the clearance angle is present at the position of the maximum diameter of the cutting edge, there is a problem that the hole becomes polygonal when the rigidity or precision of the spindle of the piercing device is low. This existing problem is believed to be due to the inability to maintain the coaxiality of the tool shaft of the R-type drill bit (registered trademark) when the rigidity or precision of the spindle of the piercing device is low, resulting in vibration of the R-type drill bit (registered trademark). Specifically, it is believed that the cutting edge on the side of the R-type drill bit (registered trademark) vibrates while contacting the inner surface of the hole, thus causing the hole to become polygonal.

[0115] In contrast, if the aforementioned drill bit 1, which is an improved R drill bit (registered trademark), is used, even if the cross-sectional shape of the pre-drilled hole formed by the piercing of the front cutting edge 5 becomes polygonal due to the vibration of the front cutting edge 5, the pre-drilled hole can be finished using the reamer edge 6, whose vibration is suppressed by the stabilizing part 7. Thus, a hole with a circular cross-sectional shape can be machined. Therefore, even if the number of front cutting edges 5 is set to three or more, the hole can be machined with good quality.

[0116] That is, even when drilling conditions require a polygonal cross-sectional shape using existing R-bites with three or more cutting edges (registered trademark), it is possible to machine a hole with a circular cross-sectional shape using the aforementioned drill bit 1. As a specific example, such as... Figure 8 As in the example, even when drilling a workpiece W using a drill bit 1 with three or more cutting edges held by a handheld tool rotating device 20, it is possible to machine a hole with a circular cross-section. That is, manual drilling can be performed using a drill bit 1 with three or more cutting edges.

[0117] When the number of cutting edges 5 and reamer edge 6 of the drill bit 1 is increased, the cutting amount of each cutting edge 5 and reamer edge 6 decreases. Therefore, when the number of cutting edges 5 and reamer edge 6 of the drill bit 1 is set to 3 or more, compared with the existing R drill bit (registered trademark) with 2 cutting edges, it is possible to increase the number of holes that can be drilled while maintaining tool life, i.e. quality.

[0118] Furthermore, even when the number of cutting edges 5 and reamer edges 6 is two, compared to existing two-edge R-drills (registered trademark), vibration in the tool diameter D direction can be suppressed, thus improving hole quality. In particular, the restriction of drill bit 1's vibration in the tool axis AX direction results in finer cutting of metal chips, thus preventing chip clogging. That is, the vibrational energy of drill bit 1 in the tool diameter D direction can be converted into vibrational energy in the thrust direction at the stabilizing section 7, which is beneficial for preventing metal chip clogging.

[0119] (Second Implementation)

[0120] Figure 9 This is a partial front view of the drill bit according to the second embodiment of the present invention. Furthermore, Figure 9 The diagram below the tool axis AX shows the outline of the cutting edge of the drill bit when the front of the cutting edge is unfolded in a manner parallel to the attached figure. The multiple cutting edges formed on the drill bit are symmetrical about the tool axis AX, that is, the multiple cutting edges formed on the drill bit have the same shape. Therefore, the detailed internal outline is omitted.

[0121] Figure 9 In the drill bit 1A of the second embodiment shown, the point where the portion 6C with a fixed diameter and maintained at the maximum diameter extends from the rear end side of the reamer edge 6 differs from that of the drill bit 1 of the first embodiment. The other structures and functions of the drill bit 1A of the second embodiment are not substantially different from those of the drill bit 1 of the first embodiment; therefore, only partial front views are shown, and identical or corresponding structures are labeled with the same symbols and their descriptions are omitted.

[0122] As described in the first embodiment, the vibration of the reamer blade 6 is suppressed by the edge 7A of the stabilizing portion 7. Therefore, the rear edge 10 of the reamer blade 6 is omitted, and instead, a portion 6C with a fixed maximum diameter can be formed. Alternatively, a portion 6C with a fixed maximum diameter can be formed, and the rear edge 10 can be further formed. In short, it is possible to extend the portion 6C with a front end angle β of 0° and a rear end angle γ2.

[0123] Therefore, even if the reamer edge 6 wears and its rotation radius decreases, the maximum diameter position only moves backward from the reamer edge 6. Thus, the hole can be finished using the reamer edge 6 at its new maximum diameter position. As a result, the tool life of the drill bit 1A can be extended. Furthermore, deep hole machining can also be performed by extending the portion 6C with a fixed maximum diameter. In particular, when machining deep holes on workpieces with a thickness of 2.6 times or more than the tool diameter D, the quality of the deep hole is improved.

[0124] (Third Implementation)

[0125] Figure 10 This is a partial front view of the drill bit according to the third embodiment of the present invention, showing a partial change in the direction of the arrow. Figure 11 yes Figure 10 An enlarged left side view of the drill bit's front end, as shown. Figure 12 yes Figure 10 The image shows a magnified top view of the front end of the drill bit. Figure 13 yes Figure 10 The enlarged cross-sectional view of the drill bit position BB shown. Figure 14 yes Figure 10 An enlarged projection of the front end of the drill bit shown.

[0126] exist Figures 10 to 14 In the drill bit 1B of the third embodiment shown, the point at which the tip angle of the reamer edge 6 changes continuously without creating a height difference on the tip side of the reamer edge 6 differs from that of the drill bit 1 of the first embodiment and the drill bit 1A of the second embodiment. The other structures and functions of the drill bit 1B of the third embodiment are not substantially different from those of the drill bit 1 of the first embodiment and the drill bit 1A of the second embodiment; therefore, identical or corresponding structures are labeled with the same symbols and descriptions are omitted.

[0127] like Figures 10 to 14 As shown, the tip angle β of the reamer blade 6 can be smoothly and continuously reduced to 0° from the tool axis AX direction and the front end side of the drill bit 1 towards the rear end side, so as to avoid the portion where the tip angle β of the reamer blade 6 changes discontinuously in the tool axis AX direction. Furthermore, as in the first embodiment, as... Figure 14 As in the example, a non-zero clearance angle γ2 can be formed at the position of the maximum diameter of the reamer blade 6, where the front angle β of the reamer blade 6 is 0°. In this case, the clearance angle γ2 of the reamer blade 6, like the front angle β, is realistically reduced smoothly and continuously from the tool axis AX direction and from the front end to the rear end of the drill bit 1 without producing a discontinuous change.

[0128] At the rear end of the reamer blade 6, where the front angle β decreases and becomes 0° at its maximum diameter position, the diameter can be fixed and extended to the maximum diameter portion 6C as described in the second embodiment. At the rear end of the reamer blade 6 itself, regardless of whether the diameter is fixed and extended to the maximum diameter portion 6C, the edge 10 can be extended as described in the first embodiment.

[0129] The number of cutting edges 5 and reamer edge 6 is arbitrary and not limited to any other type. Figure 11 and Figure 13In the example shown, there are three cutting edges. However, when the number of cutting edges of the front cutting edge 5 and the reamer edge 6 is increased, as explained in the first embodiment, the cutting amount of each of the front cutting edge 5 and the reamer edge 6 is reduced. Therefore, it is possible to increase the tool life of the drill bit 1B and the number of holes that can be drilled. In addition, as in the first embodiment, the drill bit 1B is not limited to a straight-edged drill bit with non-twisting groove 8, but can also be a twist drill bit with twisting groove 8.

[0130] like Figure 10 and Figure 14 As shown, when the front angle β of the reamer blade 6 is smoothly reduced in such a way that no two front angles β are generated at any position on the edge of the reamer blade 6, the same effect can be obtained in the reaming of the pre-drilled hole performed by the reamer blade 6 as when the front angle α of the front cutting edge 5 is smoothly and continuously reduced.

[0131] Specifically, when the tip angle β of the reamer edge 6 is continuously reduced, no angle prone to defects is generated on the edge of the reamer edge 6, thus reducing the risk of defects. As a result, the tool life of the drill bit 1B can be extended. Furthermore, when the tip angle β of the reamer edge 6 is gradually reduced, delamination is reduced when piercing FRP. This is because even if delamination temporarily occurs during reaming of FRP using a reamer edge 6 with a relatively large tip angle β on the front side of the drill bit 1, the cutting resistance decreases and delamination is eliminated during reaming with a reamer edge 6 with a relatively small tip angle β that follows.

[0132] Furthermore, the closer the shape of the reamer edge 6 on the projection plane parallel to the tool axis AX is to a single parabola, the more uniform the volume of workpiece cut per unit length of the reamer edge in the tool axis AX direction. Therefore, an effect such as uniform cutting resistance is achieved throughout the reamer edge 6. If the cutting resistance can be uniform throughout the reamer edge 6, not only can delamination and burr formation during FRP reaming be reduced, but wear on the reamer edge 6 can also be reduced.

[0133] On the other hand, when the shape of the reamer edge 6 on the projection plane parallel to the tool axis AX is made close to a single ellipse, the volume of the workpiece cut per unit length of the reamer edge in the tool axis AX direction can be reduced proportionally towards the rear of the reamer edge 6. Therefore, due to the different radii of rotation, the wear at the rear of the reamer edge 6 (where the cutting speed is relatively fast) is prevented from occurring before the wear at the front of the reamer edge 6 (where the cutting speed is relatively slow), resulting in a more uniform degree of wear across the entire reamer edge 6. If the degree of wear across the entire reamer edge 6 can be made uniform, the life of the reamer edge 6 can be improved.

[0134] Therefore, the shape of the reamer edge 6 on the projection plane can be made to approximate a parabola or an ellipse, depending on the desired effect. Of course, the shape of the reamer edge 6 can also be determined such that one part is approximately elliptical in shape on the projection plane, and another part is approximately parabolic. Furthermore, manufacturing a reamer edge 6 whose profile is at least partly elliptical or parabolic on the projection plane is complex; therefore, an ellipse or parabola can also be simulated by smoothly connecting line segments or arcs without creating angles.

[0135] When the tip angle β of the reamer blade 6 is continuously reduced without creating an angle, and the shape of the reamer blade 6 on the projection plane parallel to the tool axis AX is determined as described above, simulating an ellipse or parabola with line segments or circular arcs, such as... Figure 14 As in the example, the edges of the front cutting edge 5 and the reamer edge 6 respectively become the edges that simulate different baselines RL1 and RL2.

[0136] Specifically, the shape of the projection line 5C obtained by projecting the area through which the front cutting edge 5 passes, when rotated around the tool axis AX, onto a projection plane parallel to the tool axis AX, is a shape that is linearly symmetrical about the straight line obtained by projecting the tool axis AX onto the projection plane and connects multiple first arcs or line segments. As a specific example, for instance, such as... Figure 14 As shown, the first plurality of arcs and line segments can be determined by at least six positions PT10, PT11, PT12 on the projection line 5C formed by connecting the first plurality of arcs and line segments on the first reference line RL1 formed by the first quadratic curve.

[0137] Furthermore, the first quadratic curve used as the first baseline RL1, as described in the first embodiment, can be determined as any one of a single parabola, two parabolas, a single ellipse, or two ellipses that are line-symmetric about the straight line obtained by projecting the tool axis AX onto the projection plane. Figure 14 This represents an example of setting the first baseline RL1 as a single ellipse.

[0138] On the other hand, when the reamer blade 6 is rotated around the tool axis AX, the shape of the projection line 6D obtained by projecting the area through which the reamer blade 6 passes onto a projection plane parallel to the tool axis AX becomes a shape that is linearly symmetrical about the straight line obtained by projecting the tool axis AX onto the projection plane, and connects multiple second arcs or line segments. As a specific example, for instance, such as... Figure 14 As shown, the second plurality of arcs and line segments can be determined by at least six positions PT20, PT21, PT22 on two projection lines 6D that connect the plurality of second arcs and line segments on a second reference line RL2 formed by the second quadratic curve.

[0139] Furthermore, the second quadratic curve used as the second baseline RL2 can be defined as any one of the following: a single parabola, two parabolas, a single ellipse, and two ellipses that are line-symmetric about the straight line obtained by the projection tool axis AX, and is a second quadratic curve that is different from the first quadratic curve used as the first baseline RL1. Figure 14 This represents an example of setting the second baseline RL2 as a single ellipse.

[0140] Of course, instead of simulating a single or two quadratic curves on the projection plane, the shape of at least a portion of at least one of the front cutting edge 5 and the reamer edge 6 can be set as a quadratic curve itself composed of a single or two ellipses or parabolas that serve as references. That is, the shape of at least a portion of the front cutting edge 5 and the reamer edge 6 can also coincide with the reference lines RL1 and RL2.

[0141] However, when using a single ellipse or parabola as the first reference line RL1 to determine the shape of the projection line 5C of the front cutting edge 5, it is necessary to ensure that the maximum front angle α is not 180°. Therefore, near the front end where the front angle α is maximum, the projection line 5C of the front cutting edge 5 should not overlap with the single ellipse or parabola. Therefore, from the viewpoint of ease of manufacturing, it is practical to set the shape of the projection line 5C of the front cutting edge 5 near the front end where the front angle α is maximum as two line segments connected in a line symmetrical manner around the tool axis AX. Furthermore, even... Figure 14 In the case of connecting arcs to simulate the first reference line RL1 as in the example, and in the case of setting two quadratic curves that are symmetrical about the tool axis AX as the first reference line RL1, from the point of view of ease of manufacturing, it is practical to set the shape of the projection line 5C of the front cutting edge 5 near the front end with the largest front end angle α as two line segments connected in a symmetrical manner about the tool axis AX.

[0142] In contrast, with reamer blade 6, unlike the front cutting edge 5, the reamer blades 6 separate at the position where the front angle β is at its maximum. Therefore, regardless of whether the second reference line RL2 is a single quadratic curve or two quadratic curves symmetrical about the tool axis AX, it can include the portion of the projection line 6D where the front angle β is at its maximum and simulate the shape of the portion of the projection line 6D where the front angle β decreases with an arc, or make the second reference lines RL2 overlap. However, in cases such as Figure 14 As in the example, when a portion 6C with a fixed front angle β of 0° is formed, the shape of the projection line 6D in the portion 6C with a front angle β of 0° becomes a line segment.

[0143] Regarding the portion of the reamer blade 6 from the position where its diameter is at its minimum to the position where it first becomes its maximum, and the length L2 of the change in the tip angle β of the reamer blade 6, that is, the projection line 6D in the portion of the reamer blade 6 from the position where the tip angle β of the reamer blade 6 is at its maximum to the position where it first becomes 0°, if it is not simulated as a line segment, then its consistency with the second reference line RL2, which is composed of a single or two second quadratic curves, becomes higher. Therefore, as... Figure 14 In the example, when simulating the second baseline RL2, it is preferable not to use line segments, but only to connect the arcs for simulation.

[0144] Therefore, regarding the shape of the projection line 6D obtained by projecting the portion of the reamer blade 6 through the area of ​​the portion that causes the front end angle β of the reamer blade 6 to change onto a projection plane parallel to the tool axis AX, the arc is equivalent to a part of a circle of a quadratic curve. Therefore, regardless of whether it is set as multiple arcs simulating a second quadratic curve or as part of the second quadratic curve itself, from the viewpoint of improving piercing quality and tool life, it is appropriate to set it as part of a single or multiple quadratic curves.

[0145] Furthermore, in the first embodiment, which allows the tip angle β of the reamer blade 6 to change discontinuously, such as Figure 5 In the example, the quadratic curve of the reference line RL, which becomes the projection line of the reamer blade 6, can be common to the quadratic curve of the reference line RL, which becomes the projection line of the front cutting edge 5. In contrast, in the third embodiment, where the front angle β of the reamer blade 6 is not allowed to change discontinuously, such as... Figure 14 In the example, the projection line 5C obtained by projecting the area through which the front cutting edge 5 passes onto the projection plane when the front cutting edge 5 is rotated about the tool axis AX, and the single or multiple quadratic curves that form part of the projection line 6D of the reamer edge 6, i.e. multiple circles used to simulate a single or two second reference lines RL, or the single or two second reference lines RL themselves, have no common points even if the single or multiple quadratic curves are extended infinitely along the length direction.

[0146] However, the front end of each reamer blade 6, where the front angle β is the largest, is adjacent to the rear end of the edge 7A of the stabilizing portion 7. Therefore, when machining the front end of each reamer blade 6, interference may occur at the rear end of the edge 7A, making manufacturing difficult or forcing the tolerances near the front end of each reamer blade 6 to be rough. Therefore, as shown in the figure, a recessed portion 30 can be provided between the reamer blade 6 and the stabilizing portion 7, so that the minimum diameter of the reamer blade 6 is set below the maximum diameter of the stabilizing portion 7.

[0147] As a result, manufacturing the reamer blade 6 with a smoothly reduced tip angle β becomes easier. Furthermore, the portion of the reamer blade 6 with a smoothly reduced tip angle β reliably contacts the edge of the pre-drilled hole, which is machined by the tip cutting edge 5 and held by the stabilizing portion 7.

[0148] In the third embodiment described above, from the viewpoint of maintaining the piercing quality of FRP and improving tool life, the shape of the reamer blade 6 is set to a more ideal shape. Therefore, according to the third embodiment, especially when FRP is the piercing target, even if the number of cutting edges of the front cutting edge 5 and the reamer blade 6 is increased, the piercing quality can be maintained, and the tool life of the drill bit 1B can be improved.

[0149] (Fourth Implementation)

[0150] Figure 15 This is a partial front view of the drill bit according to the fourth embodiment of the present invention, showing a partial change in the direction of the arrow. Figure 16 yes Figure 15 An enlarged left side view of the drill bit's front end, as shown. Figure 17 yes Figure 15 The image shows a magnified top view of the front end of the drill bit. Figure 18 yes Figure 15 An enlarged cross-sectional view of the drill bit position CC shown.

[0151] exist Figure 15 In the drill bit 1C of the fourth embodiment shown, the difference between the number of cutting edges 5 and the number of cutting edges 6 is different from that of the drill bit 1B of the third embodiment. The other structures and functions of the drill bit 1C of the fourth embodiment are not substantially different from those of the drill bit 1B of the third embodiment; therefore, identical or corresponding structures are labeled with the same symbols and descriptions are omitted.

[0152] When the number of cutting edges of the front cutting edge 5 and the reamer edge 6 is increased, the cutting amount per edge decreases, thus improving tool life. On the other hand, the number of grooves 8 increases, thus reducing the core thickness of the cutting edge 4. When the core thickness of the cutting edge 4 decreases, the rigidity of the cutting edge 4 decreases, leading to a deterioration in piercing quality. Therefore, the number of cutting edges of the front cutting edge 5, which has a relatively small radius of rotation and relatively low wear and tear due to wear and defects, is less than the number of cutting edges of the reamer edge 6, which has a relatively large radius of rotation and relatively high wear and tear.

[0153] Therefore, regarding the front cutting edge 5, which has relatively low wear but relatively high cutting resistance, limiting the number of cutting edges ensures core thickness and rigidity. On the other hand, regarding the reamer edge 6, which has relatively high wear, increasing the number of cutting edges slows down wear. As a result, the overall tool life of drill bit 1C can be increased.

[0154] The cutting test results showed that, from the viewpoint of ensuring core thickness and rigidity, the front cutting edge 5 preferably has 2 or 3 cutting edges. On the other hand, from the viewpoint of slowing down wear, the reamer edge 6 preferably has 3 or more cutting edges. Therefore, considering ease of manufacturing and setting the number of cutting edges of the front cutting edge 5 and the reamer edge 6 to be the same, as in the examples of the first to third embodiments, it is suitable to set the front cutting edge 5 and the reamer edge 6 to have 3 cutting edges. If the number of cutting edges of the reamer edge 6 is increased compared to the number of cutting edges of the front cutting edge 5, it is appropriate to set the front cutting edge 5 to have 2 cutting edges. On the other hand, it is appropriate to set the reamer edge 6 to have 4 or more cutting edges.

[0155] Figure 18 In the example shown, considering ease of manufacturing, the reamer blade 6 has four blades, but it is also possible to set the reamer blade 6 to have five or more blades to improve consumability. Regarding the number of edges 7A of the stabilizing part 7, it is realistic to insert the edges 7A into the pre-drilled holes processed by the front cutting edge 5, so that the number is the same as that of the front cutting edge 5, and that the edges 7A extend from the rear end side of the front cutting edge 5.

[0156] In this way, the number of cutting edges 5 and reamer edge 6 can be determined independently. Therefore, in the first and second embodiments, the number of cutting edges 6 can be greater than the number of cutting edges 5. However, if the number of cutting edges 5 and reamer edge 6 are set to be the same in the first and second embodiments, then as explained in the first embodiment, the drill bits 1 and 1A can be manufactured by a simple method of machining the stabilizing part 7 by cutting or grinding after manufacturing a semi-finished drill bit 1 or 1A that connects the ridge line of reamer edge 6 and the ridge line of front cutting edge 5. Therefore, it is possible to determine whether the number of cutting edges 5 and reamer edge 6 are the same or different, depending on the manufacturing method of the drill bits 1 and 1A and the shape of reamer edge 6.

[0157] Furthermore, since the front cutting edge 5 and the reamer edge 6 rotate around the tool axis AX, the projection of the profile of the cutting edge 4 on the projection plane parallel to the tool axis AX is the same regardless of whether the number of blades of the reamer edge 6 is the same as the number of blades of the front cutting edge 5.

[0158] In the fourth embodiment above, the number of cutting edges of the front cutting edge 5 is limited to ensure the rigidity of the front cutting edge 5. On the other hand, the number of cutting edges of the reamer edge 6 is increased to increase the overall tool life of the drill bit 1C.

[0159] Therefore, according to the fourth embodiment, even when either FRP or metal is used as the drilling object, the drilling quality can be maintained and the tool life can be improved. That is, multiple high-quality holes can be drilled with a single drill bit 1C.

[0160] A drill bit 1C with two front cutting edges 5 and four reaming edges 6 was actually manufactured, and a cutting test was conducted on CFRP with a thickness of 10mm. The results confirmed that compared with the existing R drill bit with two cutting edges, it can process about twice the number of holes, and the drilling speed is increased to about 1.2 times.

[0161] (Fifth Implementation)

[0162] Figure 19 This is an enlarged partial front view showing a first shape example of the cutting edge portion of the drill bit formed in the fifth embodiment of the present invention. Figure 20 This is an enlarged partial front view showing a first shape example of the cutting edge portion of the drill bit formed in the fifth embodiment of the present invention.

[0163] exist Figure 19 or Figure 20 In the drill bit 1D of the fifth embodiment shown, the dimensions such as the lengths L1 and L2 of the front cutting edge 5 and the reamer edge 6 constituting the cutting edge 4, and the maximum diameter D1 of the front cutting edge 5, are optimized according to the method of using the drill bit 1D, which differs from the drill bits 1, 1A, 1B, and 1C of the first to fourth embodiments. The other structures and functions of the drill bit 1D of the fifth embodiment are not substantially different from those of the drill bits 1, 1A, 1B, and 1C of the first to fourth embodiments. Therefore, only an enlarged partial front view showing an example of the shape of the cutting edge 4 is illustrated, and the same symbols are used to label the same or corresponding structures, and descriptions are omitted.

[0164] exist Figure 19 and Figure 20 In the diagram, the outline of the cutting edge 4 is shown above the tool axis AX, and the shape of the projection line obtained by projecting the area through which the cutting edge 4 passes onto a projection plane parallel to the tool axis AX when the cutting edge 4 is rotated around the tool axis AX is shown below the tool axis AX.

[0165] As explained in the first embodiment, from the viewpoint of improving the quality of the finished hole as much as possible without being constrained by the shape of the workpiece, the cutting length L of the cutting edge 4 is preferably set to be more than 1 times and less than 2 times the tool diameter D (1D≤L≤2D). On the other hand, the larger the maximum diameter D1 of the front cutting edge 5, the deeper the groove 8 becomes, thus improving chip removal and also increasing the rigidity of the front cutting edge 5.

[0166] When the maximum diameter D1 of the front cutting edge 5 is increased, the length L1 of the front cutting edge 5 becomes longer, and therefore, the length L2 of the reamer edge 6 becomes shorter. In the drill bits 1, 1A, 1B, and 1C exemplified in the first to fourth embodiments, the length L2 of the reamer edge 6 is shortened in order to increase the maximum diameter D1 of the front cutting edge 5.

[0167] With the cutting edge length L of the cutting edge 4 fixed, the shorter the length L2 of the reamer edge 6, the less cutting material the reamer edge 6 cuts. Conversely, the larger the maximum diameter D1 and length L1 of the front cutting edge 5, the more cutting material the front cutting edge 5 cuts. Furthermore, when the difference between the cutting material of the front cutting edge 5 and the cutting material of the reamer edge 6 increases, the difference in cutting resistance between the pre-drilling process performed by the front cutting edge 5 and the finishing process performed by the reamer edge 6 also increases. That is, after the pre-drilling process performed by the front cutting edge 5 is completed, the reamer edge 6 performs the finishing of the hole under a state of extremely reduced cutting resistance.

[0168] The drill bits 1, 1A, 1B, and 1C of the first to fourth embodiments are mounted on machining centers and drilling machines with automatically controlled spindle movement speeds, or on other working machines equipped with... Figure 8 When using a handheld tool rotating device 20 with an automatic feed function that controls the feed speed to the tool axis AX, as shown in the example, even after pre-drilling by the front cutting edge 5 and when finishing pre-drilling by the reamer edge 6 with extremely reduced cutting resistance, drill bits 1, 1A, 1B, and 1C can be fed towards the tool axis AX at an appropriate feed speed during both pre-drilling and finishing. In other words, when using a drilling machine that controls the feed speed of drill bits 1, 1A, 1B, and 1C towards the tool axis AX, the feed speed of drill bits 1, 1A, 1B, and 1C can be set to a fixed or appropriate speed regardless of changes in cutting resistance.

[0169] In contrast, when the operator installs drill bits 1, 1A, 1B, and 1C of the first to fourth embodiments onto a handheld tool rotating device without an automatic feed function for piercing, the speed at which the operator pushes the tool rotating device out of the workpiece becomes the feed speed of drill bits 1, 1A, 1B, and 1C. Therefore, it is required that even after the pre-drilling process performed by the front cutting edge 5, the cutting resistance is drastically reduced, and during the finishing process of the pre-drilling by the reamer edge 6, the feed speed of the tool rotating device with drill bits 1, 1A, 1B, and 1C installed remains appropriate, adjusting the force of pushing out the tool rotating device as the cutting resistance decreases.

[0170] As a result, with skilled operators, by adjusting the force of the ejector tool's rotating mechanism, drill bits 1, 1A, 1B, and 1C can be fed at appropriate feed speeds during both pre-drilling and pre-drilling finishing. However, with unskilled operators, the following problem arises: after pre-drilling, even with an extreme reduction in cutting resistance, the force of the ejector tool's rotating mechanism is maintained. During pre-drilling finishing with the reamer edge 6, the feed speed of drill bits 1, 1A, 1B, and 1C may be excessive. If the feed speed of drill bits 1, 1A, 1B, and 1C is excessive during pre-drilling finishing with the reamer edge 6, delamination may occur during FRP piercing. In other words, if the cutting resistance during hole finishing is extremely reduced compared to pre-drilling, delamination may occur during FRP piercing if the operator is not skilled.

[0171] Therefore, when using a handheld tool rotating device without an automatic feed function, it is intended to increase the cutting resistance during the finishing of pre-drilled holes by the reamer edge 6 in a way that allows for the machining of high-precision finishing holes without requiring skilled operators. To increase the cutting resistance during the finishing of pre-drilled holes, it is only necessary to increase the length L2 of the reamer edge 6 to a certain extent, and to increase the difference between the maximum diameter D1 of the front cutting edge 5 and the tool diameter D, which is equivalent to the maximum diameter of the reamer edge 6, to a certain extent.

[0172] exist Figure 19 In the drill bit 1D of the first example of the fifth embodiment, the length L2 of the reamer edge 6 is longer than that of the first to fourth embodiments in order to prevent the cutting resistance from decreasing drastically during the finishing of the pre-drilled hole. Furthermore, the maximum diameter D1 of the front cutting edge 5 is smaller than that of the first to fourth embodiments in order to ensure the depth of cut of the reamer edge 6.

[0173] Furthermore, when the length along the tool axis AX from the front end of the cutting edge 5 to the position where the reamer edge 6 first becomes the maximum diameter of the reamer edge 6, i.e., the tool diameter D, is defined as the cutting length L of the drill bit 1D, and on the other hand, when the length along the tool axis AX from the position where the reamer edge 6 becomes the maximum diameter D1 of the cutting edge 5 to the position where it first becomes the maximum diameter of the reamer edge 6, is defined as the length L2 of the reamer edge 6, in Figure 19 In the example shown, the cutting length L of drill bit 1D is 1.6 times the tool diameter D (L = 1.6D), the length L1 of the front cutting edge 5 is 0.3 times the tool diameter D (L1 = 0.3D), the maximum diameter D1 of the front cutting edge 5 is 0.6 times the tool diameter D (D1 = 0.6D), and the length L2 of the reamer cutting edge 6 is 0.96 times the tool diameter D (L2 = 0.96D).

[0174] The results of repeated piercing tests confirmed that, from the viewpoint of avoiding extreme reduction of cutting resistance in finishing after pre-drilling, and that even when using a handheld tool rotary device without automatic feed function, it is easy to feed the drill bit 1D at an appropriate feed speed along with the tool rotary device without requiring skilled personnel, it is appropriate to set the length L2 of the reamer edge 6 to be more than 0.7 times and less than 1.2 times the tool diameter D (0.7D≤L2≤1.2D), and to set the maximum diameter D1 of the front cutting edge 5 to be more than 0.5 times and less than 0.7 times the tool diameter D (0.5D≤D1≤0.7D).

[0175] When the cutting edge length L of the cutting edge 4 and the length Lh of the stabilizing part 7 are not changed, but the length L2 of the reamer edge 6 is extended, the maximum diameter D1 of the front cutting edge 5 will inevitably become smaller. Therefore, as mentioned above, in the drill bit 1D with the extended length L2 of the reamer edge 6, the chip removal performance is reduced.

[0176] However, when using a handheld tool rotary device without an automatic feed function, it is easy to perform stepped drilling by alternating and repeatedly moving the drill bit 1D and the tool rotary device forward and backward, and to reduce the feed speed when cutting resistance is high. Therefore, in pre-drilling with high cutting resistance, by performing stepped drilling or reducing the feed speed, the undesirable situation of chips clogging the drill bit 1D can be avoided.

[0177] On the other hand, even when using a drilling machine with an automatic feed function, if the drilling machine is configured for stepped machining, chip clogging can be avoided even when using a drill bit 1D with a maximum diameter D1 of the front cutting edge 5. Specifically, if a machine tool is used, the stepped machining operation can be performed through a numerical control program. Furthermore, if a handheld tool rotating device with an automatic feed function is used, stepped machining can be performed by mounting an air signal circuit, such as that disclosed in Japanese Patent Application Publication No. 2014-50943, on the tool rotating device.

[0178] As another method, even with either a handheld tool rotating device without automatic feeding or a drilling machine with automatic feeding, it is possible to ensure both the maximum diameter D1 and length L1 of the front cutting edge 5 and the length L2 of the reamer edge 6 are equal without performing stepped processing. That is, the ratio of the length L1 of the front cutting edge 5 to the length L2 of the reamer edge 6 can be set to an appropriate proportion.

[0179] Furthermore, in the third and fourth embodiments where the shapes of the edges of the front cutting edge 5 and the reamer edge 6 are determined along two different reference lines RL1 and RL2, respectively, the length Lh of the stabilizing part 7 is arbitrary. Therefore, experiments were conducted, and the results showed that if the length Lh of the stabilizing part 7 is 0.25 times or more of the tool diameter D (Lh ≥ 0.25D), it is sufficient when all of the stabilizing part 7 is set as edge 7A. Therefore, the length obtained by subtracting the required length Lh of the stabilizing part 7 from the cutting length L of the drill bit 1D can be allocated to the length L1 of the front cutting edge 5 and the length L2 of the reamer edge 6.

[0180] exist Figure 20 In the drill bit 1D of the second example of the fifth embodiment, the maximum diameter D1 of the front cutting edge 5 and the length L2 of the reamer edge 6 are determined from the viewpoint of ensuring chip removal performance and reducing the sharp change in cutting resistance between pre-drilling and pre-drilling finishing. That is, in Figure 20 In the drill bit 1D shown, the maximum diameter D1 of the front cutting edge 5 is such that chip clogging can be avoided even without step machining, and the length L2 of the reamer edge 6 is such that the cutting resistance between pre-drilling and finishing is reduced.

[0181] In addition, Figure 20 In the example shown, the cutting length L of drill bit 1D is 1.6 times the tool diameter D (L = 1.6D), the length L1 of the front cutting edge 5 is 0.5 times the tool diameter D (L1 = 0.5D), the maximum diameter D1 of the front cutting edge 5 is 0.675 times the tool diameter D (D1 = 0.675D), and the length L2 of the reamer cutting edge 6 is 0.74 times the tool diameter D (L2 = 0.74D).

[0182] Repeated piercing tests confirmed that if the maximum diameter D1 of the front cutting edge 5 is set to be more than 0.6 times and less than 0.7 times the tool diameter D (0.6D≤D1≤0.7D), the chip removal performance can be ensured even without special processing such as step processing.

[0183] Conversely, in the absence of a handheld tool rotating device without an automatic feed function, as illustrated in the first to fourth embodiments, from the viewpoint of improving chip removal performance and the rigidity of the front cutting edge 5, it is appropriate to shorten the length L2 of the reamer blade 6, and on the other hand, to increase the maximum diameter D1 of the front cutting edge 5. However, in the case of a reamer blade 6 with a varying front angle β, the longer the length L2 of the reamer blade 6, the longer the portion of the reamer blade 6 in contact with the workpiece, thus having the advantage of delaying the wear of the reamer blade 6. Therefore, while prioritizing the delay of wear on the reamer blade 6, in order to ensure chip removal performance, the maximum diameter D1 of the front cutting edge 5 is set to be at least 0.6 times and less than 1 times the tool diameter D (0.6D≤D1<1.0D). On the other hand, in order to ensure the vibration damping function of the stabilizing part 7, the length Lh of the stabilizing part 7 formed by the edge 7A can also be set to be at least 0.25 times the tool diameter D (Lh≥0.25D), and the length L2 of the reamer blade 6 is extended within the range where the cutting length L of the drill bit 1D is at least 1 times and less than 2 times the tool diameter D (1D≤L≤2D).

[0184] In addition, Figure 10 and Figure 15 In the example shown, the cutting edge length L of drill bits 1B and 1C is 1.6 times the tool diameter D (L = 1.6D), the length L1 of the front cutting edge 5 is 0.6 times the tool diameter D (L1 = 0.6D), the maximum diameter D1 of the front cutting edge 5 is 0.75 times the tool diameter D (D1 = 0.75D), and the length L2 of the reamer cutting edge 6 is 0.56 times the tool diameter D (L2 = 0.56D).

[0185] In the drill bit 1D of the fifth embodiment, the number of the front cutting edge 5 and the reamer edge 6 can be set to three, as described in the first to third embodiments, or the number of the front cutting edge 5 can be set to two, as described in the fourth embodiment, and the number of the reamer edge 6 can be set to four, or different numbers. Furthermore, the front angle β of the reamer edge 6 can be fixed, as described in the first and second embodiments, or the front angle β of the reamer edge 6 can be smoothly varied, as described in the third and fourth embodiments.

[0186] According to the fifth embodiment described above, even when using a handheld tool rotary device without automatic feed function, high-precision finishing holes can be machined without requiring a high level of operator skill. Specifically, in the case of perforated FRP, by preventing excessive feed speed during pre-drilling finishing, the risk of delamination can be reduced.

[0187] (Sixth Implementation Method)

[0188] Figure 21 This is a magnified projection view of the reamer cutting edge of the drill bit formed in the sixth embodiment of the present invention.

[0189] exist Figure 21 In the drill bit 1E of the sixth embodiment shown, the point where the projection line of the reamer edge 6 is a straight line instead of a curve is different from that of the drill bits 1, 1A, 1B, 1C, and 1D of the first to fifth embodiments. The other structures and functions of the drill bit 1E of the sixth embodiment are not substantially different from those of the drill bits 1, 1A, 1B, 1C, and 1D of the first to fifth embodiments. Therefore, only a magnified projection view of the reamer edge 6 is shown, and identical or corresponding structures are labeled with the same symbols and their descriptions are omitted.

[0190] like Figure 21 In the example, the shape of the reamer blade 6 can also be determined by the shape of the edge of the reamer blade 6 on the projection plane parallel to the tool axis AX, which is a shape that connects multiple line segments. In other words, the shape of the reamer blade 6 can be set such that the front angle β decreases intermittently from the front end to the rear end to 0°, and has a rear angle γ2 at the maximum diameter position where the front angle β is 0°.

[0191] Therefore, compared with the case where the tip angle β of the reamer blade 6 is continuously reduced as in the first to fifth embodiments, the shape of the reamer blade 6 can be simplified, thereby reducing the labor and manufacturing cost of the drill bit 1E.

[0192] Figure 22 This is a magnified projection of an example where the tip angle β of the reamer blade 6 is set to 0° without decreasing.

[0193] When FRP is the primary drilling material, the tip angle β of the reamer blade 6 can be fixed at 0° without continuously decreasing. That is, if the clearance angle γ2 is set at the position of the reamer blade 6 at its maximum diameter where the tip angle β is 0°, other shapes can be omitted or changed. This simplifies the shape of the reamer blade 6 and reduces the labor and manufacturing cost of the drill bit 1E.

[0194] Furthermore, in the sixth embodiment, an edge 10 may be formed behind the reamer blade 6, or a portion 6C with a fixed diameter, maintained at the maximum diameter, may be provided, as in the second embodiment. Additionally, by intermittently reducing or fixing the rear angle γ2 of the reamer blade 6 according to the change in the front angle β, the shape of the reamer blade 6 can be simplified. Of course, the number of blades in the reamer blade 6 may be increased compared to the number of blades in the front cutting edge 5, as in the fourth embodiment. Furthermore, as in the fifth embodiment, the dimensions such as the lengths L1 and L2 of the front cutting edge 5 and the reamer blade 6, and the maximum diameter D1 of the front cutting edge 5, may be optimized according to the method of using the drill bit 1D.

[0195] (Seventh Implementation)

[0196] Figure 23 This is a projection view showing a first shape example of the front cutting edge of the drill bit formed in the seventh embodiment of the present invention. Figure 24 This is a projection view showing a second shape example of the front cutting edge of the drill bit formed in the seventh embodiment of the present invention. Figure 25 This is a projection view showing a third shape example of the front cutting edge of the drill bit formed in the seventh embodiment of the present invention. Figure 26 This is a projection view showing a fourth shape example of the front cutting edge of the drill bit formed in the seventh embodiment of the present invention.

[0197] exist Figures 23 to 26 In the drill bit 1F of the seventh embodiment shown, the points where the projection lines of the cutting edge 5 and the reamer edge 6 are connected by line segments instead of curves are different from those of drill bits 1, 1A, 1B, 1C, 1D, and 1E in other embodiments. The other structures and functions of the drill bit 1F of the seventh embodiment are not substantially different from those of drill bits 1, 1A, 1B, 1C, 1D, and 1E in other embodiments. Therefore, only the projection view of the cutting edge 4 is shown, and the same symbols are used to label the same or corresponding structures, and descriptions are omitted.

[0198] In the sixth embodiment, an example was described where the projection of the edge of the reamer blade 6 is a line segment. However, the projection of the edge of the front cutting edge 5 can also be a connected line segment. That is, the shape of each edge of the front cutting edge 5 and the reamer blade 6 can be determined by making the projection lines of each edge of the front cutting edge 5 and the reamer blade 6 into broken lines that simulate quadratic curves such as parabolas or ellipses. In this case, the drill bit 1F can also be classified as a polygonal drill bit that includes a front cutting edge 5 with multiple front angles α and a reamer blade 6 with only 0° or multiple front angles β.

[0199] As a specific example, such as Figure 23 In the example, on a projection plane parallel to the tool axis AX, a single parabola symmetrical about the projection line of the tool axis AX can be used as the reference line RL. The shape of the front cutting edge 5 is determined by the projection line of a broken line symmetrical about the projection line of the tool axis AX, connecting multiple segments with their ends on the single parabola. In this case, the front cutting edge 5 becomes a multi-segment cutting edge with at least three front angles α1, α2, and α3. Alternatively, the reference line RL can be replaced from a parabola to an ellipse.

[0200] Or, such as Figure 24As in the example, on a projection plane parallel to the tool axis AX, a single parabola symmetrical about the projection line of the tool axis AX can be set as the reference line RL. The shape of the front cutting edge 5 can be determined by projecting a broken line symmetrical about the projection line of the tool axis AX, connecting eight or more line segments tangent to the single parabola, into the edge line of the front cutting edge 5. In this case, the front cutting edge 5 becomes a multi-segment cutting edge with at least four front angles α1, α2, α3, and α4. Alternatively, the reference line RL can be replaced with an ellipse instead of a parabola.

[0201] As another example, such as Figure 25 In the example, on a projection plane parallel to the tool axis AX, two ellipses symmetrical about the projection line of the tool axis AX are set as reference lines RL. The shape of the front cutting edge 5 is determined by connecting six or more line segments on the two ellipses, each with its ends positioned close to the projection line of the tool axis AX, to form a symmetrical broken line symmetrical about the projection line of the tool axis AX, thus becoming the projection line of the edge of the front cutting edge 5. In this case, the front cutting edge 5 becomes a multi-segment cutting edge with at least three front angles α1, α2, and α3. Figure 25 In the example shown, four leading angles α1, α2, α3, and α4 are formed. Alternatively, the baseline RL can be replaced by two parabolas instead of two ellipses.

[0202] As yet another example, such as Figure 26 In the example, on a projection plane parallel to the tool axis AX, a portion of the multiple segments of the polygonal line constituting (the projection line of the edge that becomes the front cutting edge 5) can be set as a segment tangent to the reference line RL of a parabola or ellipse, etc., and another portion can be set as a segment with both ends on the reference line RL. Figure 26 In the example shown, the projection line of the edge forming the largest front angle α1 of the front cutting edge 5 becomes a line segment symmetrical to two lines tangent to the baseline RL, which is a single parabola or ellipse that is line-symmetrical about the projection line of the tool axis AX. The projection lines of the edges forming the other front angles α2, α3, and α4 become line segments symmetrical about the baseline RL at both ends.

[0203] Alternatively, on a projection plane parallel to the tool axis AX, a portion of the line segment of the projection line constituting the edge of the front cutting edge 5 can be replaced with a curve such as an arc. For example, if the line segments are connected by arcs, the shape of the front cutting edge 5 can be set to a smooth shape without corners. In this case, the risk of nicks forming in the front cutting edge 5 can be reduced, and the tool life can be extended. Or, refer to... Figure 5 and Figure 6As described in the first embodiment, the shape of the edge of the front cutting edge 5 is determined by making the projection line of the edge of the front cutting edge 5 that forms only the maximum front angle α of the front end a line segment, and the projection lines of the other edge segments a curve that smoothly connects arcs with different radii.

[0204] When the front angle α of the front cutting edge 5 is decreased intermittently, the rear angle γ1 also decreases intermittently according to the decrease of the front angle α, which simplifies the shape of the front cutting edge 5. Therefore, both the front angle α and the rear angle γ1 of the front cutting edge 5 can be decreased continuously or intermittently from the front side to the rear side. Moreover, by setting the shape obtained by projecting the area through which the front cutting edge 5 passes on a projection plane parallel to the tool axis AX when the front cutting edge 5 is rotated around the tool axis AX as the center, and setting the shape to a curve or line segment that is linearly symmetrical about the straight line obtained by projecting the tool axis AX onto the projection plane and connecting multiple arcs, the shape of the front cutting edge 5 can be simplified.

[0205] As a specific example, the shape of the front cutting edge 5 can be determined by placing at least 7 points on the projection lines of the projection lines forming the edge of the front cutting edge 5 on a quadratic curve formed by any one of the following: a single parabola, two parabolas, a single ellipse, or two ellipses, which are linearly symmetrical about the straight line obtained by projecting the tool axis AX onto the projection plane. Therefore, as explained in the first embodiment, it is possible to achieve an effect where the cutting resistance to the front cutting edge 5 and the degree of wear on the front cutting edge 5 are as uniform as possible along the length Lh direction of the front cutting edge 5.

[0206] Furthermore, for the reamer blade 6, when the tip angle β is continuously or intermittently reduced, it is also possible to refer to the third embodiment. Figure 14 As explained above, the shape on the projection plane is set to be a curve or arc that connects multiple line segments or arcs. That is, the shape of the reamer blade 6 can be determined in such a way that the shape obtained by projecting the area through which the reamer blade 6 passes onto a projection plane parallel to the tool axis AX when the reamer blade 6 is rotated about the tool axis AX becomes a curve or line segment that is linearly symmetrical about the straight line obtained by projecting the tool axis AX onto the projection plane and connects multiple arcs or arcs.

[0207] As in the first embodiment, refer to Figure 5 As explained above, regarding the shape of the reamer blade 6, if the same quadratic curve as the quadratic curve used to determine the shape of the front cutting edge 5 on the projection plane is used as the reference line to determine the shape of the projection line, then advantages such as being able to use a manufacturing method that forms a stabilizing part 7 in a semi-finished product formed by connecting the edges of the front cutting edge 5 and the reamer blade 6 can be obtained. Alternatively, as referred to in the third embodiment... Figure 14As explained above, the shape of the projection line of the reamer blade 6 can also be determined based on a quadratic curve that is different from the quadratic curve used to determine the shape of the projection line of the front cutting edge 5, thereby reducing the change in the front angle β of the reamer blade 6.

[0208] According to the seventh embodiment described above, the shape of each edge of the front cutting edge 5 and the reamer edge 6 can be further simplified, and manufacturing labor and manufacturing costs can be further reduced.

[0209] Furthermore, the shape of the ridge line of the reamer blade 6 can also be set as a curve shape in which the front end angle β decreases continuously and smoothly, as described in the third embodiment, so that only the front end angle α of the front cutting edge 5 is as... Figures 23 to 26 The process is simplified intermittently, as in the example below. In this case, the small radius of rotation means that the relatively slow-moving cutting edge 5 is reduced in manufacturing cost by simplifying its shape. On the other hand, the large radius of rotation means that the relatively fast-moving reamer edge 6 is effectively slowed down in terms of wear by optimizing its shape.

[0210] (Another implementation method)

[0211] The above describes specific embodiments, but these embodiments are merely examples and do not limit the scope of the invention. The new methods and apparatus described herein can be embodied in a variety of other ways. Furthermore, various omissions, substitutions, and modifications can be made to the methods and apparatus described herein without departing from the spirit of the invention. The appended claims and their equivalents are included in the scope and spirit of the invention, and include such various ways and variations.

[0212] Symbol Explanation

[0213] Drill bits 1, 1A, 1B, 1C, 1D, 1E, 1F

[0214] 2. Main Body

[0215] 3. Handle

[0216] 4 cutting edge

[0217] 5. Front cutting edge (first cutting edge)

[0218] 5A in front

[0219] 5B after

[0220] 5C projection line

[0221] 6. Reamer blade (second cutting edge)

[0222] 6A in front

[0223] 6B after

[0224] 6C section

[0225] 6D projection lines

[0226] 7. Stabilizing section (vibration damping section)

[0227] 7A Edge

[0228] 8 slots

[0229] 9. Blade band

[0230] 9A Planar Discharge Surface

[0231] 10 Edges

[0232] 20 Tool Rotating Device

[0233] 21. Casing head

[0234] 22 Protruding nose piece

[0235] 23 Perforated Plate

[0236] 30 retreat

[0237] AX tool axis

[0238] D tool diameter

[0239] D1 Maximum diameter of the front cutting edge

[0240] L-shaped drill bit cutting length

[0241] L1 length of the front cutting edge

[0242] L2 Length of the reamer blade

[0243] Length of the stable part Lh

[0244] The range of R's edge

[0245] RL, RL1, RL2 baselines

[0246] W workpiece

[0247] α, α1, α2, α3, α4: Front angles of the cutting edge

[0248] β is the tip angle of the reamer.

[0249] γ1 Back angle of the front cutting edge

[0250] γ2 is the back angle of the reamer blade.

Claims

1. A drill bit, comprising: The first cutting edge at the front end is formed on the front end side with a front end angle greater than 0° and less than 180° that decreases continuously or intermittently from the front end side to the rear end side and a rear end angle that decreases continuously or intermittently from the front end side to the rear end side, and is used to drill a pre-drilled hole through the workpiece being cut. The second cutting edge, which is formed at a position away from the first cutting edge toward the rear end side, is used for finishing the pre-drilled hole and has a back angle at the maximum diameter position; as well as A vibration damping portion, formed between the first and second cutting edges, reduces the vibration of the second cutting edge by being inserted into the pre-drilled hole machined by the first cutting edge. The length along the tool axis from the position where the second cutting edge becomes the maximum diameter of the first cutting edge to the position where it first becomes the maximum diameter of the second cutting edge is more than 0.7 times and less than 1.2 times the maximum diameter of the second cutting edge, and The maximum diameter of the first cutting edge is more than 0.5 times and less than 0.7 times the maximum diameter of the second cutting edge.

2. The drill bit according to claim 1, wherein, The maximum diameter of the first cutting edge is more than 0.6 times the maximum diameter of the second cutting edge.

3. The drill bit according to claim 1, wherein, The length along the tool axis from the tip of the first cutting edge to the position where the second cutting edge first becomes the maximum diameter of the second cutting edge is more than 1 and less than 2 times the maximum diameter of the second cutting edge.

4. The drill bit according to claim 1, wherein, Set the number of blades of the first cutting edge to 2 or 3, and set the number of blades of the second cutting edge to 3 or more.

5. The drill bit according to claim 1, wherein, The number of blades in the first cutting edge is less than the number of blades in the second cutting edge.

6. A method for manufacturing a perforated article, wherein the perforated article is manufactured by perforating a workpiece using a drill bit according to any one of claims 1 to 5.

Images