Drill bit

Abstract

The invention provides a drill bit which has good sharpness and excellent durability. A drill is provided with: a chip groove (6) formed in the outer periphery of a drill body (2) that rotates about an axis line; a first polishing surface (10) formed diagonally upward toward the tip end side from the outer periphery of the drill body across the chip groove; a first flank surface (11) which forms a first cutting edge (14) serving as a main cutting edge on a boundary ridge line with the first grinding surface, and which is formed on the opposite side of the first grinding surface in the direction of rotation of the drill bit in contact with the first grinding surface; a second polishing surface (12) which is located on the tip side of the first polishing surface, is in contact with the first polishing surface, and is formed on the opposite side in the drill rotation direction; and a second cutting edge (15) formed on a boundary ridge line between the second grinding surface and the first flank surface.

Description

Technical Field

[0001] The invention relates to a drill bit as a whole, in particular to a drill bit for medical use. Background Art

[0002] Drill bits for drilling are used in many industrial fields. Drill bits used in surgery are often used to drill holes in bones. Bones are covered with hard cortical bone on the surface and soft spongy bone on the inside. Cortical bone is very hard, with a Shore hardness of more than 90, which is equivalent to 820HV on the Vickers hardness scale and 64.7HRc on the Rockwell hardness scale.

[0003] Fig.10 The drill shown is a surgical drill, and its purpose is to provide a medical drill which is less susceptible to wear and has excellent cutting force by increasing the cutting force and the cutting ability of the cutting edge extending from the inner terminal of the front end to the outer periphery.

[0004] Fig.10 It is equivalent to Patent Document 1 Figure 2 The picture, Fig.10 (a) is a top view from the front end side, Fig.10 (b) is a side view of the front end portion. A honed cutting edge 101 is formed at the front end portion, and the honed cutting edge 101 is formed at the boundary between the rake face 106 formed by grinding and the flank face 103. The main cutting edge 102 is continuous with the honed cutting edge 101 and is formed on the outer peripheral side of the honed cutting edge 101. A rake face 105 formed by the main cutting edge and a grinded face 108 formed by the honed cutting edge 101 are formed. A chisel edge 104 is formed between the two honed cutting edges 101.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2018-108223 Summary of the invention

[0008] Problems to be solved by the invention

[0009] In the medical drill described in Patent Document 1, the grinding surface 108 forming the grinding cutting edge 101 is only provided at two locations on the shaft object. If the grinding concave portion is enlarged to improve the sharpness, the core thickness becomes smaller, the rigidity of the drill bit decreases, and damage to the drill bit is inevitable. Generally, a drill bit is used repeatedly, so durability is required, but the drill bit described in Reference Document 1 has problems in terms of durability.

[0010] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a drill having good sharpness and excellent durability.

[0011] Solutions to Solve Problems

[0012] The present invention (1) is a drill bit, which comprises: a chip groove formed on the outer periphery of a drill bit body rotating around an axis; a first grinding surface formed from the outer periphery of the drill bit body across the chip groove and obliquely upward toward the front end side; a first back cutting edge formed on a boundary ridgeline with the first grinding surface to become a main cutting edge, which is in contact with the first grinding surface and formed on the opposite side of the drill bit rotation direction; a second grinding surface located on the front end side of the first grinding surface, in contact with the first grinding surface, and formed on the opposite side of the drill bit rotation direction; and a second cutting edge formed on a boundary ridgeline between the second grinding surface and the first back cutting surface, the outer peripheral end of the first cutting edge reaching the drill bit outer peripheral surface or near the drill bit outer peripheral surface.

[0013] In the present invention (1), since the first grinding surface and the second grinding surface are provided in the axial direction, the core thickness can be increased. As a result, the sharpness and durability of the drill can be improved. In addition, since the outer peripheral end of the first cutting edge reaches the outer peripheral surface of the drill or the vicinity of the outer peripheral surface of the drill, a certain sharpness can be maintained regardless of the position of the cutting edge.

[0014] The present invention (2) is the drill bit of the present invention (1), characterized in that the second rake angle of the second cutting edge formed by the second grinding surface is a positive angle.

[0015] In the present invention (2), the second cutting edge has a second rake angle formed by the second grinding surface, which is a positive angle, so that when the drill bit is tilted against the object to be drilled to perform drilling, the deviation of the drill bit can be reduced. It is particularly preferred to drill a hard material such as cortical bone.

[0016] The present invention (3) is the drill bit of the present invention (2), wherein the second rake angle is 20° to 60°. If the rake angle is too small, the strength of the blade tip decreases, and if the rake angle is too large, the front end of the drill bit is prone to sliding. When studying various angles, the lower limit is preferably 20°, more preferably 30°, and even more preferably 35°. The upper limit is preferably 60°, more preferably 50°, and even more preferably 45°.

[0017] The present invention (4) is a drill bit according to any one of the present inventions (1) to (3), wherein the length of the chisel edge formed at the front end is zero. Since there is substantially no chisel edge, the front end is sharp, and when the front end of the drill bit is brought into contact with the cortical bone and rotated in the cortical bone, the initial stage of the biting becomes better and the bit becomes less likely to slip.

[0018] Effects of the Invention

[0019] According to the present invention, a drill having good sharpness and excellent durability can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a side view showing the entire drill bit according to the first embodiment of the present invention.

[0021] Figure 2 It is a perspective view showing the entire drill bit according to Embodiment 1 of the present invention.

[0022] Figure 3 It is a perspective view showing the tip portion of the drill according to the first embodiment of the present invention.

[0023] Figure 4 This is a schematic diagram to illustrate the positive and negative rake angles of the drill.

[0024] Figure 5 It is a side view showing the entire drill bit according to Embodiment 2 of the present invention.

[0025] Figure 6 It is a perspective view showing the tip portion of a drill according to a second embodiment of the present invention.

[0026] Figure 7 This is a photograph showing the state of the tip portion after a drilling test was performed using the drill bit according to the first embodiment of the present invention.

[0027] Figure 8 This is a photograph showing the state of the tip portion after a drilling test using the drill described in Patent Document 1.

[0028] Fig. 9 This is a diagram showing the results of drilling tests of the drill bit according to Embodiment 1 of the present invention and the drill bit described in Patent Document 1.

[0029] Fig.10 This is a diagram showing the structure of a drill described in Patent Document 1. DETAILED DESCRIPTION

[0030] Hereinafter, embodiments of the present invention will be described in detail based on the drawings. Note that the following embodiments are merely preferred examples in nature and are not intended to limit the scope of the present invention, its applications, or its uses.

[0031] Figure 1 The drill 1 is a side view showing the entire drill according to the first embodiment of the present invention. The drill 1 includes a shank 3 formed at one end of a drill body 2 and a blade 4. The blade 4 has a chip groove 6 formed from the front end to the shank 3 and connected to the cutting edge 5.

[0032] Figure 21 is a perspective view showing the entire drill bit according to the first embodiment of the present invention. The drill bit 1 includes a shank portion 3 formed at one end of a drill body 2 and a blade portion 4. The present invention is characterized by the shape of a cutting edge portion 5. A first cutting edge 14 is formed at a boundary between a first ground surface 10 and a first relief surface 11. A second relief surface 13 is formed on the side of the first relief surface 11 opposite to the rotation direction.

[0033] A second ground surface 12 is formed at the front end side of the first ground surface 10 and in contact with the first ground surface 10 on the opposite side of the drill rotation direction. A second cutting edge 15 is formed at the boundary ridgeline between the second ground surface 12 and the first relief surface 11.

[0034] A chisel edge 16 is formed between the two opposing first flank surfaces 11 . The second flank surface 13 is connected to the chip flute 6 .

[0035] The first cutting edge 14 is connected to the outer periphery of the drill bit, and the cutting edges are the first cutting edge 14 and the second cutting edge 15, but it is not necessary to be limited to this method. As in the drill bit of patent document 1, the chip groove 6 can be used as the front cutting face, the back cutting face can be formed on the outer peripheral surface of the drill bit, and the main cutting edge can be set on the outer peripheral side of the first cutting edge 14.

[0036] Figure 3 Yes Figure 2 The enlarged perspective view of the tip portion 5 of the front end portion of the drill 1 according to the first embodiment of the present invention is shown. The chip groove 6, the first ground surface 10, the first clearance surface 11, the second ground surface 12, the second clearance surface 13, the first cutting edge 14, the second cutting edge 15, and the chisel edge 16 are shown in the figure, and the description thereof is omitted.

[0037] Figure 4 This is a schematic diagram showing the positive and negative rake angles of the drill bit. Figure 4 (A) indicates the case where the front blade angle is positive. Figure 4 (B) indicates the case where the rake angle is negative. The relationship between the rake face and the flank face is (A) when the rake angle = positive angle, and (B) when the rake angle = negative angle. When the rake angle is positive, the blade tip is sharp and bites into the object to be drilled, so the drill tip is difficult to slide.

[0038] Figure 5 2 is a perspective view showing the entire drill bit according to Embodiment 2 of the present invention. Figure 2 The drill bit of the embodiment 1 shown in the figure has a substantially similar structure, but in the drill bit of the embodiment 1, a chisel edge 16 is provided at the front end of the drill bit, but Figure 5 In the drill of the second embodiment shown, there is no chisel edge, and the front end is point P.

[0039] With the chisel edge, the wall thickness formed by the second grinding surface 12 becomes larger, but without the chisel edge, the wall thickness of the front end becomes smaller, and instead, the front end pierces the drilled body sharply, and the sharpness becomes better. Figure 2 The same, therefore the description is omitted.

[0040] Figure 6 2 is a perspective view showing the front end portion of the drill bit of the second embodiment, except that the chisel edge is not formed at the front end P. Figure 3 The drill bit of the illustrated embodiment 1 is the same and therefore description thereof will be omitted.

[0041] Figure 7 (A) and Figure 7 (B) is a photograph showing the state of the front end portion after a drilling test using the drill bit of Embodiment 1 (Example), Figure 8 (A) and Figure 8 (B) is a photograph showing the state of the tip portion after a drilling test of the drill bit (comparative example) described in Patent Document 1. The drilling test conditions are shown below.

[0042] <Drilling test conditions>

[0043] (1) Drill shape: The drills of the embodiment and the comparative example both have a diameter of 3.2 mm. The core thickness of the embodiment is 1.2 mm, and the core thickness of the comparative example is 0.8 mm.

[0044] (2) Object to be drilled: cortical bone sheet (SAW3401-06) 10 mm thick plate.

[0045] (3) Speed: 760 RPM

[0046] (4) Drill bit pressure: 30N

[0047] Figure 7 (A) is a photograph of the blade tip after the drilling test of Example 1, and no damage was observed. Figure 7 (B) Yes Figure 7 The photograph of the blade tip on the opposite side of (A) also shows no damage.

[0048] Figure 8 (A) is a photograph of the blade tip after the drilling test of the comparative example, and curling damage of the blade is observed in the portion surrounded by a circle. Figure 8 (B) Yes Figure 8 (A) shows a photograph of the blade tip on the opposite side. A large concave damage is generated on the cutting edge. The damage is at a position 0.84 mm from the front end and is 0.5 mm long. Based on these observations, it is believed that the drill bit of the embodiment of the present invention is much more durable than the comparative example.

[0049] Fig. 9(A) is a test result when a drilling test was performed under the above conditions. The drilling time of the drill bit of Embodiment 1 of the present invention was 11 seconds, while it took 20 seconds in the comparative example described in Patent Document 1, which is a large difference.

[0050] The test results of the drilling test at an inclination of 45° are shown. The drilling time of the drill bit of the first embodiment of the present invention is 16 seconds, while it takes 22 seconds in the comparative example described in Patent Document 1, which is a large difference. In addition, regarding the sliding distance of the drill bit at an inclination of 45°, the sliding distance of the drill bit of the first embodiment of the present invention is 4 mm / s, while it is 8 mm in the comparative example described in Patent Document 1, which is a significant difference.

[0051] Fig. 9 (B) is the test result when the drilling test under the above conditions was repeated (3 times). The drilling time of the drill bit of the first embodiment of the present invention hardly changed between 13 seconds and 16 seconds, but in the comparative example described in Patent Document 1, the drilling time changed greatly between 17 seconds and 47 seconds, which shows that the durability of the drill bit of the first embodiment is much better than that of the comparative example.

[0052] The reason why the durability of the drill bit according to the first embodiment of the present invention is considered to be better than that of the comparative example is that Figure 7 In the drill bit of the embodiment 1 of the present invention shown in FIG. 1 , almost no damage to the cutting edge portion is observed. In contrast, in the comparative example, as shown in FIG. Figure 8 As shown, damage was produced during a drilling test.

[0053] Possibility of Industrial Application

[0054] As described above, the drill bit of the present invention can be suitably used as a drill bit having good sharpness and excellent durability in, for example, a surgery for drilling a hole in a bone.

[0055] Explanation of symbols

[0056] 1—drill, 2—drill body, 3—shank, 4—blade, 5—tip, 6—chip groove, 10—first grinding surface, 11—first back surface, 12—second grinding surface, 13—second back surface, 14—first cutting edge, 15—second cutting edge, 16—chisel edge, P—front end point.

Claims

1. A drill bit, characterized in that: have: a chip removal groove formed on the outer periphery of a drill body that rotates about an axis; A first grinding surface is formed from the outer periphery of the drill body across the chip removal groove and obliquely upward toward the front end side; A first flank surface, which forms a first cutting edge serving as a main cutting edge on a boundary ridgeline with the first ground surface, is in contact with the first ground surface and is formed on the opposite side of the drill bit rotation direction; a second grinding surface located at the front end side of the first grinding surface, in contact with the first grinding surface and formed on the opposite side of the drill bit rotation direction; and A second cutting edge is formed at a boundary line between the second grinding surface and the first relief surface, The outer peripheral end of the first cutting edge reaches the outer peripheral surface of the drill or the vicinity of the outer peripheral surface of the drill.

2. The drill bit according to claim 1, characterized in that A second rake angle of the second cutting edge formed by the second grinding surface is a positive angle.

3. The drill bit according to claim 2, characterized in that The second rake angle is 20° to 60°.

4. The drill bit according to any one of claims 1 to 3, characterized in that: The length of the chisel edge formed at the front end is zero.

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