Drilling tools

Abstract

To provide a drilling tool capable of discharging chips well even when machining a work material such as stainless steel, which tends to produce elongated chips. [Solution] This drilling tool has two or more cutting edges 12 and a thinning 20, in which a thinning heel surface 20H facing rearward in the rotation direction of the tool is formed as a convex curved surface, and the thinning through angle τ gradually decreases from the front end of the tool to the rear end. The thinning rake face 20R of the thinning 20 may have a straight shape extending radially or parallel to the tool center 1c from the vicinity of the tool center 1c in a front view of the tool. The thinning rake face 20R may have a spiral shape extending radially in the opposite direction to the tool rotation direction from the vicinity of the tool center 1c in a front view of the tool.

Description

[Technical Field]

[0001] The present invention relates to a drilling tool. [Background technology]

[0002] The shape and length of the thinning heel surface of a drill, which is an example of a drilling tool, are important factors in determining the size of chips (see, for example, Patent Document 1). In this regard, many conventional drills have a large thinning angle to strongly restrain chips and break them into small pieces to improve dischargeability (see, for example, Patent Documents 2 and 3). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2019 / 176452 [Patent Document 2] Japanese Patent Publication No. 2023-68305 [Patent Document 3] International Publication No. 2019 / 031737 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when using conventional drills like those mentioned above to cut workpieces that tend to produce elongated chips, such as stainless steel, the chip breaking effect is often insufficient, and the large thinning angle actually hinders chip evacuation, which results in chips staying near the cutting edge for longer periods of time, potentially causing welding.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a drilling tool that can effectively discharge chips even when machining a workpiece that tends to produce elongated chips, particularly stainless steel. [Means for solving the problem]

[0006] One aspect of the present invention is a tool for drilling having two or more cutting edges and a thinning, The thinning heel surface facing rearward in the rotation direction of the tool is formed as a convex curved surface, A drilling tool in which the thinning angle gradually decreases from the tip to the rear end of the tool.

[0007] A drilling tool having a thinning heel surface configured as a convex curved surface in which the thinning through angle becomes acute toward the rear end of the tool is more likely to perform the function of curling the chips appropriately near the thinning cutting edge at the front end of the tool and smoothly guiding the chips with the curved surface that becomes acute toward the rear end of the tool to promote their discharge, rather than performing the function of shredding chips. Such a drilling tool shortens the chip residence time near the cutting edge, making it easier to suppress the propagation of cutting heat from the chips to the cutting edge, and also makes it easier to suppress welding of the chips to the cutting edge and, consequently, damage when the welding peels off.

[0008] In the drilling tool as described above, the thinning rake face of the thinning may have a straight shape extending from the vicinity of the center of the tool in a radial direction or a direction parallel thereto when viewed from the front of the tool.

[0009] In the drilling tool as described above, the thinning rake face of the thinning may have a shape that extends spirally from the vicinity of the center of the tool toward the radial direction in the opposite direction to the rotation direction of the tool when viewed from the front of the tool.

[0010] In the drilling tool as described above, the radius of curvature of the spiral of the thinning rake face may be constant.

[0011] In the drilling tool as described above, the radius of curvature of the spiral of the thinning rake face does not have to be constant.

[0012] In the drilling tool as described above, the thinning heel surface may be formed along an arc having a predetermined point as its center when viewed from a side perpendicular to the central axis of the tool in a certain direction.

[0013] In the drilling tool as described above, the radius of curvature y of the thinning heel surface may be a value calculated by y=ax+b where x is the tool diameter.

[0014] In the drilling tool as described above, the number of thinnings may be the same as the number of cutting edges.

[0015] In the drilling tool as described above, the plurality of thinnings may be uniformly arranged at equal intervals in the circumferential direction.

[0016] In the drilling tool as described above, the drilling tool may be a head-exchangeable drill having a body and a head that is detachable from the body, and the head may be formed with a cutting edge.

[0017] In the drilling tool as described above, the thinning heel surface of the head may protrude rearward in the tool rotation direction beyond the back metal of the body. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a perspective view showing an example of a drill in an embodiment of a drilling tool according to the present invention, as viewed from the tip side. FIG. [Figure 2] FIG. 2 is a front view of the drill shown in FIG. 1 (viewed from the tip along the central axis). [Figure 3] 3 is a side view of the drill shown in FIG. 2 as viewed in a direction perpendicular to the central axis. [Figure 4] 3 is a front view of the tool when the drill shown in FIG. 2 is rotated clockwise by a predetermined amount. FIG. [Figure 5] 5 is a side view of the drill shown in FIG. 4 as viewed in a direction perpendicular to the central axis. [Figure 6] FIG. 10 is a perspective view showing an example of a drill according to a second embodiment of the present invention, as viewed from the tip side. [Figure 7] FIG. 7 is a front view of the drill shown in FIG. 6. [Figure 8]FIG. 8 is a side view of the drill shown in FIG. 7, viewed from a direction perpendicular to the central axis. [Figure 9] 8 is a front view of the tool when the drill shown in FIG. 7 is rotated clockwise by a predetermined amount. FIG. [Figure 10] FIG. 10 is a side view of the drill shown in FIG. 9 as viewed from a direction perpendicular to the central axis. [Figure 11] 10 is a graph illustrating the relationship between the radius of curvature y of the thinning heel surface and the tool diameter x. [Figure 12] 10A and 10B show examples of drill shapes in which the thinning heel surface is formed along an arc centered at a predetermined point. [Figure 13] The images (A) to (D) show the chip discharge during drilling in chronological order. [Figure 14] These are reference images (A) to (D) showing the chip evacuation process in chronological order when using a conventional drill. DETAILED DESCRIPTION OF THE INVENTION

[0019] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the drilling tool according to the present invention will be described in detail below with reference to the drawings. The following describes a head-exchangeable drill to which the present invention is applied (see FIG. 1, etc.).

[0020] The exchangeable-head drill 1 is a drill having a body 30 and a head 10 that is detachable from the body 30 along a central axis 1x, and configured so that the cutting edge can be changed by replacing the head 10. The head 10 of the exchangeable-head drill 1 is provided with two or more cutting edges 12 and thinnings 20 (see FIG. 1, etc.). The number of thinnings 20 may be the same as the number of cutting edges 12. The multiple thinnings 20 are preferably uniformly arranged at equal intervals around the circumferential direction of the head 10.

[0021] The head 10 of the replaceable head drill 1 has a thinning 20 provided at its drill tip 1t, and is formed with a thinning heel surface 20H and a thinning rake surface 20R (see FIGS. 1 to 5). The thinning heel surface 20H is a heel-side surface (facing rearward in the rotational direction of the replaceable head drill 1) formed by providing the thinning 20. A thinning cutting edge 20C is formed at the intersection of the thinning rake surface 20R and the flank. The thinning rake surface 20R is formed so as to continue from this thinning cutting edge 20C. The angle formed by the thinning heel surface 20H and the central axis 1x is the thinning through angle τ.

[0022] [First embodiment] The thinning heel surface 20H of the head 10 of the exchangeable head drill 1 of this embodiment is formed as a convex curved surface (see FIGS. 2 to 5). This convex curved surface is formed so that the thinning through angle τ gradually decreases from the drill tip end 1t toward the drill rear end 1b (see FIG. 5). Generally, in the exchangeable head drill 1, if the thinning through angle τ of the drill head 10 is too acute at a constant angle from the tool tip side to the rear end side, the back metal 32 on the body 30 side of the exchangeable head drill 1 (referring to the portion of the body 30 that receives the cutting force acting on the drill head 10 through the cutting edge 12 at the rear side in the rotation direction of the body 30; hereinafter, a portion of the back metal is designated by the reference numeral 32) protrudes beyond the thinning heel surface 20H of the thinning 20, which may hinder chip evacuation. In this regard, in the head-exchangeable drill 1 of this embodiment, in which the thinning heel surface 20H is configured as a convex curved surface in which the thinning through angle τ gradually decreases, the thinning heel surface 20H is configured to protrude rearward in the direction of drill rotation beyond the back metal 32 of the main body 30, thereby preventing the back metal 32 from protruding beyond the thinning heel surface 20H and making it possible to prevent obstruction to the discharge of chips.

[0023] In addition, the exchangeable head drill 1, in which the thinning heel surface 20H is configured as a convex curved surface in which the thinning angle τ becomes acute toward the drill rear end 1b, as in this embodiment, is more likely to perform the function of smoothly guiding and discharging chips by appropriately curling the chips near the thinning cutting edge 20C on the drill tip 1t side and using the curved surface (i.e., the thinning heel surface 20H) that becomes acute toward the drill rear end 1b, rather than shredding chips. This exchangeable head drill 1 shortens the chip residence time near the cutting edge 12, thereby reducing the propagation of cutting heat from the chips to the cutting edge. It also reduces chip welding to the cutting edge 12 and chip breakage due to the welding and peeling. This exchangeable head drill 1 is particularly suitable for cutting soft, difficult-to-cut materials such as stainless steel.

[0024] In the head 10 of the replaceable head drill 1 of this embodiment, the thinning rake face 20R has a straight shape extending radially or parallel to the center of the tool when viewed from the drill tip 1t along the center axis 1x in a front view of the tool (see Figures 2 and 4).

[0025] [Second embodiment] In the head 10 of the exchangeable-head drill 1 of this embodiment, similarly to the above, the thinning heel surface 20H is formed so that the thinning angle τ gradually decreases from the drill tip 1t toward the drill rear end 1b, and the thinning rake face 20R has a shape that extends spirally from near the drill center 1c toward the radial direction in the opposite direction to the drill rotation direction when viewed from the front of the tool (see FIGS. 6 to 10). This thinning allows chips to be appropriately curled near the thinning cutting edge 20C on the drill tip 1t side, and the curved surface (i.e., the thinning heel surface 20H) that becomes increasingly acute toward the drill rear end 1b facilitates the function of smoothly guiding and facilitating the discharge of chips. The replaceable-head drill 1 reduces the time chips remain near the cutting edge 12 and effectively suppresses the propagation of cutting heat from the chips to the cutting edge. Furthermore, the replaceable-head drill 1 has a curved thinning rake face 20R that connects more smoothly to the chip flutes 31 than a flat surface. This prevents the back metal 32 of the main body 30 from protruding beyond the thinning heel face 20H (see FIG. 6 ), further improving chip evacuation. In this case, the radius of curvature of the spiral of the thinning rake face 20R may or may not be constant (see FIGS. 7 and 9 ). Even if the radius of curvature is constant, the thinning rake face 20R can smoothly connect to the chip flutes 31. However, if the radius of curvature is not constant, for example, if the radius of curvature of the thinning rake face 20R changes midway, chips can be guided more smoothly into the chip flutes 31.

[0026] [Third embodiment] In the above-described exchangeable head drill 1, the thinning heel surface 20H may be formed along an arc centered at a predetermined location in a side view seen from a certain direction perpendicular to the central axis 1x of the exchangeable head drill 1. A specific example of the exchangeable head drill 1 formed in this manner will be described below as a third embodiment (see FIGS. 11 and 12).

[0027] Although the drill heads 10 of the exchangeable head drill 1 in this embodiment are different in size, in each case the thinning heel surface 20H is formed along an arc centered at a predetermined point in side view (see FIGS. 12(A) and 12(B)). The tool diameter x and the curvature radius y of the thinning heel surface 20H of each of these drill heads 10 are as shown in Table 1. Furthermore, when the tool diameter x and the curvature radius y of the thinning heel surface 20H of each of these two drill heads 10 are plotted on a graph as shown in FIG. 11, it can be seen that the curvature radius y of the thinning heel surface 20H is calculated as y = ax + b (specifically, y = 1.9x - 5.9 in this embodiment) relative to the tool diameter x. [Table 1]

[0028] The above-described embodiment is one example of a preferred embodiment of the present invention, but the present invention is not limited to this embodiment and various modifications are possible within the scope of the present invention. For example, in the above-described embodiment, the present invention is described as being applied to the exchangeable head drill 1, but this is merely one example. It goes without saying that the present invention can also be applied to various other drilling tools, including one-piece drills such as solid drills. [Example]

[0029] The state of chip discharge during drilling using the exchangeable head drill 1 of this embodiment was photographed with a high-speed camera and compared with that of a conventional drill 1′ (see FIGS. 13 and 14). With the conventional drill 1′, the chips remained near the thinning cutting edge 20C and continued to wrap around until they had wrapped around two or more times (see FIG. 14). However, when drilling using the exchangeable head drill 1 of this embodiment, the chips did not remain near the thinning cutting edge 20C after wrapping around one time, but were guided into the chip flute 31 and curled into a spiral shape (see FIG. 13). These results confirm that the exchangeable head drill 1 of this embodiment reduces the constraint on chips between the thinning 20C and the cutting edge 12 compared to the conventional drill, thereby reducing the load on the cutting edge 12 and ultimately contributing to the prevention of weld separation. [Industrial Applicability]

[0030] The present invention is suitable for application to drilling tools such as replaceable head drills. [Explanation of symbols]

[0031] 1,1'...Replaceable head drill (drilling tool) 1b...Drill rear end (tool rear end) 1c...Drill center (tool center) 1t...Drill tip (tool tip) 1x…center axis 10...Drill head 12...Cutting edge 20...Thinning 20C...Thinning cutting edge 20H...Thinning heel surface 20R...Thinning rake face 30...Main body 31...Chip discharge groove 32...Back Metal τ...Thinning through angle x…Tool diameter y... Radius of curvature of thinning heel surface

Claims

1. A tool for drilling having two or more cutting edges and a thinning, The thinning heel surface facing rearward in the rotation direction of the tool is formed as a convex curved surface as a whole, A drilling tool in which the thinning angle gradually decreases from the tip to the rear end of the tool.

2. A tool for drilling having two or more cutting edges and a thinning, The thinning heel surface facing rearward in the rotation direction of the tool is formed as a convex curved surface, The thinning angle gradually decreases from the tip to the rear end of the tool. A drilling tool, wherein the thinning rake face of the thinning has a shape that extends spirally from the vicinity of the center of the tool toward the radial direction in the opposite direction to the rotation direction of the tool when viewed from the front of the tool.

3. 3. The drilling tool according to claim 1, wherein the thinning rake face of the thinning has a straight shape extending from the vicinity of the center of the tool in a radial direction or a direction parallel thereto when viewed from the front of the tool.

4. 2. The drilling tool according to claim 1, wherein the thinning rake face of the thinning has a shape that extends spirally from the vicinity of the center of the tool toward the radial direction in a direction opposite to the rotation direction of the tool when viewed from the front of the tool.

5. 5. The drilling tool according to claim 2 or 4, wherein the radius of curvature of the spiral of the thinning rake face is constant.

6. 5. The drilling tool according to claim 2 or 4, wherein the radius of curvature of the spiral of the thinning rake face is not constant.

7. 3. The drilling tool according to claim 1, wherein the thinning heel surface is formed along an arc centered at a predetermined point when viewed from a side perpendicular to a central axis of the tool in a certain direction.

8. The drilling tool according to claim 7 , wherein the radius of curvature y of the thinning heel surface is a value determined by y=ax+b where x is the tool diameter.

9. The drilling tool according to claim 1 or 2, wherein the number of the thinnings is the same as the number of the cutting edges.

10. The drilling tool according to claim 1 or 2, wherein the plurality of thinnings are uniformly arranged at equal intervals in the circumferential direction.

11. The drilling tool according to claim 1 or 2, wherein the drilling tool is a head-exchangeable drill having a body and a head detachable from the body, and the cutting edge is formed on the head.

12. The drilling tool according to claim 11 , wherein the thinning heel surface of the head protrudes rearward in the tool rotation direction beyond a back metal of the body.

Images