Drilling tool

Abstract

The present invention provides a drilling tool capable of favorably discharging cuttings even when machining a material to be cut, such as stainless steel, in which the cuttings tend to extend. A drilling tool is provided with two or more cutting edges (12) and a grinding part (20), a ground cutting edge surface (20H) facing the rear in the direction of rotation of the drilling tool is formed as a convex curved surface, and a grinding passage angle (tau) gradually decreases from the front end to the rear end of the tool. In a front view of the tool, a grinding rake surface 20R of the grinding part 20 may have a linear shape extending straightly from the vicinity of the tool center 1c in the diametrical direction or in a direction parallel to the diametrical direction. In a front view of the tool, the grinding rake face 20R may have a shape extending helically in a diametrical direction from the vicinity of the tool center 1c and in a direction opposite to the direction of rotation of the tool.

Description

Technical Field

[0001] This invention relates to a drilling tool. Background Technology

[0002] The shape and length of the heel face after webthinning in a drill bit, an example of a drilling tool, are important factors determining the chip size (see, for example, Patent Document 1). In this regard, in conventional drill bits, the thinning angle is often increased in order to strongly control the chips and break them finely, thereby improving the evacuation performance (see, for example, Patent Documents 2 and 3).

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: International Publication No. 2019 / 176452

[0006] Patent Document 2: Japanese Patent Application Publication No. 2023-68305

[0007] Patent Document 3: International Publication No. 2019 / 031737

[0008] Technical issues

[0009] However, as mentioned above, when machining easily elongated chips such as stainless steel using conventional drill bits, insufficient chip breaking is frequently observed, and large over-grinding angles can actually hinder chip removal. Consequently, chips remain near the cutting edge for a longer period, potentially leading to chip adhesion.

[0010] Therefore, the purpose of this invention is to provide a drilling tool that can effectively remove chips, especially when machining materials such as stainless steel where the chips are easily elongated. Summary of the Invention

[0011] One embodiment of the present invention is as follows:

[0012] A drilling tool, wherein the drilling tool includes two or more cutting edges and a thinning or web-thinning section, wherein the back edge of the thinning section facing the direction of rotation of the drilling tool is formed as a convex curved surface, and the thinning pass angle gradually decreases from the front end to the rear end of the tool.

[0013] After sharpening, the cutting edge of the drilling tool is formed into a convex curved surface, and the sharpening pass angle becomes an acute angle, gradually decreasing from the front end to the rear end. For such a drilling tool, it is easier to perform the following function than simply cutting chips: to moderately curl the chips near the sharpened cutting edge on the front end of the tool, while smoothly guiding the chips using the acute angle (gradually decreasing from the front end to the rear end), thereby promoting chip removal. With such a drilling tool, the time the chips remain near the cutting edge is shortened, making it easier to suppress the transfer of cutting heat from the chips to the tool tip. It also makes it easier to prevent chips from adhering to the cutting edge, thus reducing defects caused by chip peeling.

[0014] In the drilling tool described above, in the front view of the tool, the rake face after web thinning of the shaving section can be a straight line shape extending directly from near the center of the tool along the diametrical direction or along a direction parallel to the diametrical direction.

[0015] In the drilling tool described above, in the front view of the tool, the shaving rake face of the shaving part can be a shape that extends spirally from near the center of the tool along the diametrical direction and in the opposite direction to the rotation direction of the tool.

[0016] In the drilling tool described above, the radius of curvature of the helix used for regrinding the rake face can be fixed.

[0017] In the drilling tool described above, the radius of curvature of the helix used for regrinding the rake face may not be fixed.

[0018] In the drilling tool described above, in a side view taken along a direction perpendicular to the central axis of the drilling tool, the post-grinding cutting edge can be formed along an arc centered at a predetermined position.

[0019] In the drilling tool described above, the radius of curvature y of the honed cutting edge relative to the tool diameter x can be obtained by the formula y = ax + b.

[0020] In the drilling tools described above, the number of regrinding sections can be the same as the number of cutting edges.

[0021] In the drilling tool described above, multiple grinding sections can be uniformly arranged at equal intervals along the circumferential direction.

[0022] In the drilling tools described above, the drilling tool can be a replaceable drill bit, which has a body and a cutter head that can be detached from the body, and the cutter head has a cutting edge formed thereon.

[0023] In the drilling tools described above, the post-sharpening cutting edge of the cutting head can protrude further rearward in the direction of tool rotation compared to the back metal of the main body. Attached Figure Description

[0024] Figure 1 This is a perspective view of an example of a drill bit in one embodiment of the drilling tool provided by the present invention, viewed from the front end of the drill bit.

[0025] Figure 2 yes Figure 1 The tool front view of the drill bit shown (viewed from the front end of the drill bit along the central axis).

[0026] Figure 3 From a direction perpendicular to the central axis Figure 2 The side view obtained by observing the drill bit shown.

[0027] Figure 4 Is to make Figure 2 The tool is shown in the front view with the drill bit rotated clockwise to a set position.

[0028] Figure 5 From a direction perpendicular to the central axis Figure 4 The side view obtained by observing the drill bit shown.

[0029] Figure 6 This is a perspective view of an example of a drill bit according to the second embodiment of the present invention, viewed from the front end side of the drill bit.

[0030] Figure 7 yes Figure 6 The tool front view of the drill bit shown.

[0031] Figure 8 From a direction perpendicular to the central axis Figure 7 The side view obtained by observing the drill bit shown.

[0032] Figure 9 Is to make Figure 7 The tool is shown in the front view with the drill bit rotated clockwise to a set position.

[0033] Figure 10 From a direction perpendicular to the central axis Figure 9 The side view obtained by observing the drill bit shown.

[0034] Figure 11 It is a chart illustrating the relationship between the radius of curvature y of the sharpened cutting edge and the tool diameter x.

[0035] Figure 12(A) and (B) in the diagram are schematic examples of drill bit shapes formed by the cutting edge along an arc centered at a predetermined position after grinding.

[0036] Figure 13 Images (A) to (D) in the image show the chip removal process in chronological order when machining with the drill bit of this application.

[0037] Figure 14 (A) to (D) are reference images showing the chip removal process in chronological order when machining with conventional drill bits.

[0038] Explanation of main component symbols

[0039] Replaceable drill bit (drilling tool) 1, 1'

[0040] Drill bit rear end (tool rear end) 1b

[0041] Drill bit center (tool center) 1c

[0042] Drill bit tip (tool tip) 1t

[0043] Central axis 1x

[0044] Drill bit (cutting head) 10

[0045] Cutting edge 12

[0046] Grinding Department 20

[0047] Sharpening the cutting edge 20C

[0048] 20H after grinding

[0049] Sharpening the rake face to 20R

[0050] Main body 30

[0051] Chip discharge groove 31

[0052] Metal back pad 32

[0053] Grinding through angle τ

[0054] tool diameter x

[0055] The radius of curvature y of the cutting edge after grinding Detailed Implementation

[0056] Hereinafter, preferred embodiments of the drilling tool provided by the present invention will be described in detail with reference to the accompanying drawings. The following describes a drill bit with a replaceable cutter head suitable for use with the present invention (see attached drawings). Figure 1 wait).

[0057] The replaceable drill bit 1 has a main body 30 and a cutter head 10 that is detachably mounted to the main body 30 along a central axis 1x. The cutting tip can be replaced by replacing the cutter head 10. The cutter head 10 of the replaceable drill bit 1 is provided with two or more cutting edges 12 and a grinding section 20 (see reference). Figure 1 (etc.). The number of grinding sections 20 can be the same as the number of cutting edges 12. Multiple grinding sections 20 can be evenly arranged at equal intervals along the circumference of the tool head 10.

[0058] On the drill bit 10 of the replaceable drill bit 1, which has a grinding section 20, a grinding rear cutting face 20H and a grinding front cutting face 20R are formed (see reference). Figures 1-5 The regrinding back face 20H is a face on the back edge formed by providing the regrinding section 20 (facing the rear of the rotation direction of the drill bit 1). The regrinding cutting edge 20C is formed on the intersection line of the regrinding rake face 20R and the regrinding back face. Immediately after regrinding the cutting edge 20C, the regrinding rake face 20R is formed. The angle formed by the regrinding back face 20H and the central axis 1x is the regrinding passage angle τ.

[0059] [First Implementation Method]

[0060] In this embodiment, the cutting edge 20H of the replaceable drill bit 10 is formed into a convex curved surface after sharpening (see reference). Figures 2-5 The convex surface is formed such that the angle τ gradually decreases as it is ground from the drill bit front end 1t toward the drill bit rear end 1b (refer to...). Figure 5 Generally, in a replaceable drill bit 1, if the grinding pass angle τ of the drill bit 10 is a certain acute angle and the angle is too small, from the front end to the rear end, the backing metal (referring to the part that bears the cutting force acting on the drill bit 10 by the cutting edge 12 from the rear of the main body 30 in the rotation direction of the main body 30; hereinafter, a part of this backing metal is indicated by reference numeral 32) 32 on the main body 30 side of the replaceable drill bit 1 will protrude more than the grinding post-grinding cutting edge 20H of the grinding part 20, thus hindering the discharge of chips. In this respect, in the replaceable drill bit 1 of this embodiment, the grinding post-grinding cutting edge 20H is formed as a convex curved surface with a gradually decreasing grinding pass angle τ. By making the grinding post-grinding cutting edge 20H protrude more than the backing metal 32 of the main body 30 in the rotation direction of the drill bit, the backing metal 32 will not protrude more than the grinding post-grinding cutting edge 20H, thereby suppressing the obstruction of chip discharge.

[0061] Furthermore, in the replaceable drill bit 1 of this embodiment, the honed cutting edge 20H is formed as a convex curved surface, and the honing angle τ becomes an acute angle, gradually decreasing from the drill tip 1t towards the drill rear end 1b. For such a replaceable drill bit 1, it is easier to perform the following function than simply cutting chips: the chips are moderately curled near the honed cutting edge 20C on the drill tip 1t side, while the honed cutting edge 20H, with its acute angle τ (gradually decreasing from the drill tip 1t towards the drill rear end 1b), smoothly guides the chips, thereby promoting chip removal. With such a replaceable drill bit 1, the time chips remain near the cutting edge 12 is shortened, the transfer of cutting heat from the chips to the tool tip is easily suppressed, and the adhesion of chips to the cutting edge 12 is also easily suppressed, thus also suppressing defects caused by chip peeling. This type of replaceable drill bit is particularly suitable for cutting high-toughness, difficult-to-cut materials, such as stainless steel.

[0062] In the tool head 10 of the tool head replaceable drill 1 of this embodiment, in the front view of the tool head replaceable drill 1 obtained by viewing the tool head replaceable drill 1 from the front end 1t along the central axis 1x, the pre-grinding cutting face 20R is a straight line shape extending directly from near the center of the tool along the diametrical direction or along a direction parallel to the diametrical direction (see reference). Figure 2 , Figure 4 ).

[0063] [Second Implementation]

[0064] Similar to the above, for the cutting head 10 of the replaceable drill bit 1 in this embodiment, the regrinded cutting face 20H is formed such that the regrinding angle τ gradually decreases from the drill tip 1t towards the drill rear end 1b. Furthermore, when viewed from the front of the tool, the regrinded cutting face 20R has a spiral shape extending from near the drill center 1c along the diameter direction in the opposite direction to the tool's rotation direction (see reference). Figures 6-10 With such a grinding section, it becomes easy to achieve the following functions: the chips are moderately curled near the grinding cutting edge 20C on the drill tip 1t side, and the chips are smoothly guided by the curved surface (i.e., the grinding post-grinding cutting edge 20H) with a grinding pass angle τ that becomes an acute angle (the grinding pass angle τ gradually decreases from the drill tip 1t towards the drill tip 1b), thereby promoting chip removal. With such a tool-changeable drill 1, the residence time of chips near the cutting edge 12 is shortened, and the transfer of cutting heat from the chips to the tool tip is easily suppressed. In addition, the grinding rake face 20R of this tool-changeable drill 1 is a curved surface. Compared with the case where the grinding rake face 20R is a flat surface, since the shape of the grinding rake face 20R is more smoothly connected to the chip discharge groove (flute) 31, it is possible to prevent the backing metal 32 of the body 30 from protruding more than the grinding post-grinding cutting edge 20H (see reference). Figure 6 This further enhances chip removal performance. At this point, the radius of curvature of the helix on the 20R rake face can be fixed or not (see [reference]). Figure 7 and Figure 9 When the radius of curvature is fixed, the regrinding rake face 20R can be smoothly connected to the chip discharge groove (chip groove) 31. When the radius of curvature is not fixed, for example, when the shape of the regrinding rake face 20R is a shape in which the radius of curvature changes in the middle, the chips can be guided to the chip discharge groove 31 more smoothly.

[0065] [Third Implementation Method]

[0066] In the aforementioned replaceable drill bit 1, in a side view taken along a direction perpendicular to the central axis 1x of the replaceable drill bit 1, the ground cutting edge 20H can be formed along an arc centered at a predetermined position. Hereinafter, a specific example of a replaceable drill bit 1 formed in this manner will be described as a third embodiment (see reference). Figure 11 , Figure 12 ).

[0067] Although the drill bits 10 of the replaceable drill bit 1 in this embodiment are different in size, in the side view, the sharpened cutting edge 20H of each drill bit 10 is formed along an arc centered at a predetermined position (see reference). Figure 12 (A), (B)). The tool diameter x and the radius of curvature y of the honed cutting edge 20H of these drill bits 10 are shown in Table 1. Furthermore, if the tool diameter x and the radius of curvature y of the honed cutting edge 20H of each of these two drill bits 10 are plotted on a graph, then... Figure 11 As shown, the radius of curvature y of the honed cutting edge 20H relative to the tool diameter x is obtained by the formula y = ax + b (in this embodiment, specifically, y = 1.9x - 5.9).

[0068] Table 1

[0069]

[0070] It should be noted that the above embodiments are examples of preferred embodiments of the present invention, but are not limited thereto. Various variations and implementations are possible without departing from the spirit of the invention. For example, the above embodiments describe the application of the invention to a replaceable drill bit 1, but this is only one example. Furthermore, the present invention can certainly be applied to various drilling tools, such as one-piece drill bits like parallel shank twist drills or solid drills.

[0071] Example

[0072] The chip removal during drilling using the replaceable drill bit 1 described in this embodiment was captured by a high-speed camera and compared with that when using a conventional drill bit 1' (see reference). Figure 13 , Figure 14 In previous drill bits 1', chips would remain near the regrinding cutting edge and continue to coil until they were coiled more than twice (see reference). Figure 14 However, when drilling using the replaceable drill bit 1 described in this embodiment, it was confirmed that after the chips have rolled around once, they do not remain near the regrinding cutting edge 20C, but are guided to the chip discharge groove 31 and curled into a spiral shape (see reference). Figure 13 Based on this result, it can be confirmed that, compared with the prior art, the replaceable drill bit 1 of this embodiment reduces the constraint on the chips between the regrinding section 20 and the cutting edge 12, thereby reducing the load on the cutting edge 12 and thus helping to suppress adhesion peeling.

[0073] Industrial availability

[0074] Preferably, the present invention is applicable to a drilling tool represented by a replaceable drill bit.

Claims

1. A drilling tool, wherein, The drilling tool includes two or more cutting edges and a grinding section. The grinding surface of the cutting edge facing the direction of rotation of the drilling tool is formed into a convex curved surface, and the grinding pass angle gradually decreases from the front end to the rear end of the tool.

2. The drilling tool according to claim 1, wherein, In the front view of the tool, the shaving face of the shaving part is a straight line shape that extends straight from near the center of the tool along the diametrical direction or along a direction parallel to the diametrical direction.

3. The drilling tool according to claim 1, wherein, In the front view of the tool, the shaving face of the shaving part is a shape that extends spirally from near the center of the tool along the diameter direction and in the opposite direction to the rotation direction of the tool.

4. The drilling tool according to claim 3, wherein, The radius of curvature of the helix on the pre-grinding face is fixed.

5. The drilling tool according to claim 3, wherein, The radius of curvature of the helix on the pre-grinding face is not fixed.

6. The drilling tool according to any one of claims 1 to 5, wherein, In a side view taken along a direction perpendicular to the central axis of the drilling tool, the honed cutting edge is formed along an arc centered at a predetermined position.

7. The drilling tool according to claim 6, wherein, The radius of curvature y of the sharpened cutting surface, relative to the tool diameter x, is a value obtained by the formula y = ax + b.

8. The drilling tool according to any one of claims 1 to 5, wherein, The number of grinding sections is the same as the number of cutting edges.

9. The drilling tool according to any one of claims 1 to 5, wherein, The plurality of the grinding sections are evenly spaced along the circumferential direction.

10. The drilling tool according to any one of claims 1 to 5, wherein, The drilling tool is a replaceable drill bit, which has a main body and a cutter head that can be detached from the main body, and the cutting edge is formed on the cutter head.

11. The drilling tool according to claim 10, wherein, Compared to the backing metal of the main body, the sharpened cutting edge of the blade protrudes further rearward in the direction of tool rotation.

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