Oil-hole drill

Abstract

Provided is a drill 1 with an oil hole, which at least has two or more oil holes H1, H2 in a tip part thereof and in which a groove length is 10 times or more of the diameter D, wherein the drill 1 with an oil hole has two or more cutting edges 11, 12 extending outward from the center axis O, and the cutting edges 11, 12 are constituted from first cutting edges 11A, 12A linearly extending from a chisel edge 2 and curved second cutting edges 11B, 12B formed continuously with the first cutting edges 11A, 12A and having a predetermined curvature radius r. The size (d) of a chamfer in the first cutting edges 11A, 12A is in the range of 0.015 × D to 0.024 × D with respect to the diameter D of the drill 1 with an oil hole, and the angle alpha of the chamfer is in the range of 18-28°. Through this configuration, wear of a rake face adjacent to the cutting edge is greatly suppressed, and at the same time, the life of the drill is dramatically improved.

Description

[Technical Field]

[0001] The present invention relates to a drill with oil holes having a plurality of oil holes. [Background Art]

[0002] Conventionally, in order to cool a workpiece when performing drilling with a drill, drilling by a so-called external oil supply method has been performed, in which a machine tool applies a coolant to the drill and the workpiece. Further, as disclosed in Patent Document 1, by providing a passage (oil hole) through which coolant can pass inside the drill, the coolant can reach the tip of the drill that performs cutting, and drilling can be performed while injecting the coolant to the cutting site. [Prior Art Literature] [Patent Literature]

[0003] [Patent Document 1] Japanese Unexamined Patent Application Publication No. 2021-88007 [Summary of the Invention] [Problem to be Solved by the Invention]

[0004] However, in the case of a drill whose processed hole depth is 10 times or more the tool diameter (diameter) (a so-called long drill), if the chamfering of the cutting edge is not appropriate, chips generated by cutting will rub against the rake face of the drill, causing localized crater-shaped wear on the rake face. When crater wear progresses, it extends to the cutting edge, and eventually leads to chipping of the cutting edge, which may result in the end of the tool life.

[0005] Therefore, an object of the present invention is to provide a drill with oil holes that can suppress crater-shaped wear on the rake face adjacent to the cutting edge, and at the same time dramatically improve the service life of the drill. [Means for Solving the Problem]

[0006] To solve the aforementioned problems, the oil-hole drill of the present invention has two or more oil holes at its tip and a groove length of 10 times or more the diameter, wherein the oil-hole drill has two or more cutting edges extending outward from the central axis, and these cutting edges consist of a first cutting edge extending linearly from the chisel edge and a second curved cutting edge formed continuously with the first cutting edge and having a predetermined radius of curvature. The size of the chamfer of the first cutting edge is in the range of 0.015 × D to 0.024 × D with respect to the diameter D of the oil-hole drill, and the angle of the chamfer is in the range of 18° to 28°.

[0007] The maximum distance from the tangent line L of the circle S (diameter: 0.33 × D) representing the core thickness of the oil-hole drill, which passes through the outer corner of the oil-hole drill, to the second cutting edge can be in the range of 0.010 × D to 0.055 × D, preferably 0.010 × D to 0.034 × D. A thinning angle can be applied to the first cutting edge in the range of 32° to 42°, and chamfering can also be applied to the outer corner in the range of 8° to 16.5°, preferably 8° to 15°. [Effects of the Invention]

[0008] The oil-hole drill of the present invention significantly reduces wear on the rake face adjacent to the cutting edge, and at the same time dramatically improves the life of the drill. [Brief explanation of the drawing]

[0009] [Figure 1] This is a front view of the oil-hole drill 1 of the present invention. [Figure 2] Figure 1 is a partially enlarged front view of the oil-hole drill 1 shown. [Figure 3] Figure 2 is a cross-sectional view of the oil-hole drill 1 shown along line XX. [Figure 4] Figure 2 is a cross-sectional view of the oil-hole drill 1 along the YY line. [Figure 5] This is a partially enlarged bottom view of the oil-hole drill 1 of the present invention. [Figure 6]This is an enlarged front view of the cutting edge 11 in the oil-hole drill 1 of the present invention. [Figure 7] This is an enlarged front view of the vicinity of the outer corner 14 of the oil-hole drill 1 of the present invention. [Modes for carrying out the invention]

[0010] An embodiment of the oil-hole drill of the present invention will be described with reference to the drawings. Figure 1 is a front view of the oil-hole drill 1, which is one embodiment of the present invention, and Figure 2 is a partially enlarged front view of the oil-hole drill 1 shown in Figure 1. As shown in Figures 1 and 2, the oil-hole drill 1 (diameter D) of the present invention has two cutting edges 11 and 12 at its tip, relief surfaces 3 and 4 on the rear side of each cutting edge 11 and 12 (oil-hole drill 1) in the rotational direction R, and two oil holes H1 and H2 are formed on the rear side of these relief surfaces 3 and 4 in the rotational direction R.

[0011] As shown in Figure 2, these two cutting edges 11 and 12 are formed from the end of the chisel edge 2 toward the outer corner 13, with straight first cutting edges 11A and 12A extending outward from the end of the first cutting edges 11A and 12A toward the outer corner 13.

[0012] Figure 3 shows a cross-sectional view of the oil-hole drill 1 shown in Figure 2 along line XX, and Figure 4 shows a cross-sectional view of the oil-hole drill 1 shown in Figure 2 along line YY. The first cutting edge 11A, as described above, is formed at the intersection of the flank face 3 and the rake face 5, as shown in Figure 3, and is chamfered with a width (size) d1 and an angle α. Similarly, the second cutting edge 11B is formed at the intersection of the razor face 3 and the rake face 5, as shown in Figure 4, and is chamfered with a width (size) d2 and an angle α. The size d1 of the chamfer on the first cutting edge 11A can be in the range of 0.015 × D to 0.024 × D with respect to the diameter D of the oil-hole drill 1.

[0013] Figure 5 shows a partially enlarged bottom view of the oil-hole drill 1 of the present invention, and Figure 6 shows a partially enlarged front view. As shown in Figure 5, the oil-hole drill 1 of the present invention is subjected to thinning, and the through angle θ of the thinning can be in the range of 32° to 42°. Also, as shown in Figure 6, the maximum distance e from the virtual straight line L, which is the tangent to the circle S (diameter: 0.33 × D) representing the core thickness of the oil-hole drill 1 and passes through the outer corner 13 of the oil-hole drill 1, to the second cutting edge 11B can be in the range of 0.010 × D to 0.055 × D, preferably 0.010 × D to 0.034 × D, with respect to the diameter D of the oil-hole drill 1.

[0014] Furthermore, the outer corners of the oil-hole drill 1 of the present invention can be chamfered. For example, Figure 7 shows an enlarged front view of the vicinity of the outer corner 14 of the oil-hole drill 1 of the present invention. The outer corner 14 of the oil-hole drill 1 may be chamfered with an angle β and a width c, as shown in Figure 7. The angle β is preferably in the range of 8° to 15°, and the width c is preferably in the range of 0.02 × D to 0.08 × D relative to the diameter D of the oil-hole drill 1. The angle β of the chamfering of the outer corner 14 can be in the range of 8° to 16.5°, preferably in the range of 8° to 15°.

[0015] The angle β at which the outer corner 14 is chamfered is the angle formed by two imaginary lines: a virtual line extending outward from the chamfered surface towards the oil-hole drill 1, and a virtual line connecting the outer corner to the central axis. The width c is the distance (spacing) between two virtual lines extending tangentially from each chamfered end towards the oil-hole drill 1. [Examples]

[0016] (Example 1) A cutting test was conducted using the drill of the present invention (hereinafter referred to as the invented product) and a conventional drill (hereinafter referred to as the conventional product) to confirm the tool life of the drills. The test results are described below. First, both the invented product and the conventional product adopt the drill configuration shown in Figures 1 to 7, and share the following common specifications: a drill diameter of 6 mm, a flute length of 139 mm, an overall drill length of 190 mm, a shank diameter of 6 mm, and 2 cutting edges.

[0017] Furthermore, for the invented product, the point angle is 140°, the web thickness is 1.98 mm (33% of the drill diameter), the relief angle of the cutting edge is 10°, the size of the chamfer on the first cutting edge is 0.10 mm (0.0166×D), the rake angle of the thinning portion is 3°, and the maximum distance e is 0.198 mm (0.033×D). In contrast, for the conventional product, the point angle is 138°, the web thickness is 1.81 mm (30% of the drill diameter), the relief angle of the cutting edge is 7°, the sizes of the chamfers on the first cutting edge are 0.047 mm (0.0078×D) and 0.055 mm (0.0092×D), the rake angle of the thinning portion is 0°, and the maximum distance e is 0.261 mm (0.044×D).

[0018] In the present example, carbon steel (S50C) was used as the workpiece, and the cutting conditions were set as follows. · Cutting speed: 120m / min · Drill rotation speed: 6400min-1 · Drill feed rate: 1535mm / min · Feed per revolution: 0.24mm / rev · Machined hole depth: 120mm blind hole · Cutting fluid used: water-soluble cutting fluid (internal oil supply) · Processing machine: horizontal machining center (HCN-4000)

[0019] In this embodiment, the results showed that with the conventional product, cutting edge wear progressed as the number of machined holes increased, and chipping occurred on the cutting edge when the cumulative number of machined holes from the start of cutting reached 1066 and 1160, at which point the cutting test was terminated. In contrast, although the cutting edge wear progressed with increasing numbers of machined holes in the inventive product, similar to the conventional product, the rate of increase was smaller than that of the conventional product, and the cutting test was terminated when the cumulative number of machined holes from the start of cutting reached 1740 and 1690. From these test results, it was found that the number of machined holes with the inventive product increased to more than 1.5 times that of the conventional product, and the drill life was improved compared to the conventional product.

[0020] (Example 2) Next, similar to the case of Example 1 described above, cutting tests were conducted using two types of drills: the drill of the present invention (inventive product) and a conventional drill (conventional product). The effect of the chamfer size at the first cutting edge and the change in the maximum distance e shown in Figure 6 on the machining life was confirmed, and the test results will now be explained.

[0021] The invention used a drill (invention) with the following specifications: the size of the chamfer on the first cutting edge was 0.140 mm (0.0233 × D), the size of the chamfer on the second cutting edge was 0.120 mm (0.0200 × D), and the maximum distance e was 0.197 mm (0.0328 × D). On the other hand, conventional products used a total of three levels of drills: a drill with a chamfer size of 0.063 mm (0.0105 × D) for the first cutting edge, a chamfer size of 0.050 mm (0.0083 × D) for the second cutting edge, and a maximum distance e of 0.261 mm (0.0435 × D) (Conventional Product 1); a drill with a chamfer size of 0.082 mm (0.0137 × D) for the first cutting edge, a chamfer size of 0.071 mm (0.0118 × D) for the second cutting edge, and a maximum distance e of 0.197 mm (0.0328 × D) (Conventional Product 2); and a drill with a chamfer size of 0.084 mm (0.0140 × D) for the first cutting edge, and a maximum distance e of 0.227 mm (0.0378 × D) (Conventional Product 3). Both the invented product and the conventional product share the drill configuration shown in Figures 1 to 7, with a common specification of a drill diameter of 6 mm, a groove length of 139 mm, a drill length of 190 mm, a shank diameter of 6 mm, and 2 cutting edges.

[0022] In this example, the same workpiece material as in Example 1 was used as carbon steel (S50C), and the following cutting conditions were applied. ·Cutting speed: 120m / min • Drill rotation speed: 6400 min-1 • Drill feed rate: 1535 mm / min Feed rate: 0.24 mm / rev • Depth of machined hole: 120 mm (blind hole) • Cutting fluid used: Water-soluble cutting fluid (internal lubrication) • Processing machine: Horizontal M / C (HCN-4000)

[0023] In this embodiment, the chisel of the drill chipped when the total number of holes drilled in the cutting test using Conventional Product 1 reached 1160. The drill broke when the total number of holes drilled in the cutting test using Conventional Product 2 reached 1437. The drill broke when the total number of holes drilled in the cutting test using Conventional Product 3 reached 1008.

[0024] In contrast, when the total number of holes machined in the cutting test using the invention reached 3190, the cutting test was terminated at that point due to significant wear on the chisel.

[0025] Based on the results above, the total number of holes machined using conventional products 1 to 3 ranged from 1008 to 1437, and in many cases, the test was terminated due to chisel breakage or the drill itself breaking during the test. In contrast, the invention resulted in more than double the total number of holes machined using conventional products 1 to 3, and no instances of drill breakage during the test were observed.

[0026] (Example 3) Next, cutting tests were conducted using two types of drills, the inventive drill and a conventional drill, but with stainless steel (SUS304) as the workpiece. The inventive drill was the same as the one used in Example 1, while the conventional drill had a maximum distance e of 0.294 mm (0.049 × D) and a chamfer size of 0.05 mm (0.008 × D) at the first cutting edge. The cutting conditions in this example were set as follows. ·Cutting speed: 70m / min • Drill rotation speed: 3715 min-1 • Drill feed rate: 445 mm / min • Feed rate: 0.12mm / rev • Depth of machined hole: 120 mm (blind hole) • Cutting fluid used: Water-soluble cutting fluid (internal lubrication) • Processing machine: Horizontal M / C (HCN-4000)

[0027] In this embodiment, the conventional product showed progressive wear of the cutting edge as the number of machined holes increased, similar to Example 1. When the cumulative number of machined holes reached 543 from the start of cutting, chipping occurred on the cutting edge, and the cutting test was terminated at that point. In contrast, although the inventive product also showed progressive wear of the cutting edge as the number of machined holes increased, similar to the conventional product, the rate of increase was smaller than that of the conventional product. The cutting test was terminated when the cumulative number of machined holes reached 2320 from the start of cutting. Based on these test results, the number of machined holes in the inventive product increased to more than four times that of the conventional product, and the drill life was improved compared to the conventional product.

[0028] (Example 4) Next, similar to Example 3, a cutting test was conducted using two types of drills, the invented product and a conventional product, with stainless steel (SUS304) as the workpiece material, to confirm the effect of the chamfer amount of the first cutting edge on the total number of holes drilled (drill life).

[0029] The inventive product and conventional products 1 to 3 used in this embodiment had a maximum distance e of 0.196 mm (0.033 × D) as shown in Figure 6. Furthermore, the inventive product used a drill with a chamfer size of 0.13 mm (0.0217 × D) at the first cutting edge (inventive product). In contrast, the conventional products used a total of three levels of drills with chamfer sizes of 0.04 mm (0.0067 × D) (conventional product 1), 0.05 mm (0.0083 × D) (conventional product 2), and 0.08 mm (0.0133 × D) (conventional product 3) at the first cutting edge.

[0030] The cutting conditions in this embodiment were set as follows. ·Cutting speed: 70m / min • Drill rotation speed: 3715 min-1 • Drill feed rate: 445 mm / min • Feed rate: 0.12mm / rev • Depth of machined hole: 120 mm (blind hole) • Cutting fluid used: Water-soluble cutting fluid (internal lubrication) • Processing machine: Horizontal M / C (HCN-4000)

[0031] In this embodiment, the results showed that when the total number of holes drilled in the cutting test using Conventional Product 1 reached 1305, the chisel of the drill chipped. When the total number of holes drilled in the cutting test using Conventional Product 2 reached 543, the drill broke. When the total number of holes drilled in the cutting test using Conventional Product 3 reached 1608, the drill broke and a series of spiral-shaped chips were generated.

[0032] In contrast, when the total number of holes machined in the cutting test using the invention reached 2320, the cutting test was terminated at that point due to significant wear on the outer corners of the drill.

[0033] Based on the results above, the total number of holes machined using conventional products 1 to 3 ranged from 543 to 1608, and in many cases, the test was terminated due to drill breakage during the test. In contrast, the number of holes machined using the invented product was approximately 1.5 times or more than that of conventional products 1 to 3, and no instances of drill breakage during the test were observed.

[0034] Therefore, based on the cutting test results of Examples 1 to 4, the oil-hole drill of the present invention, compared to conventional oil-hole drills, has a larger chamfering amount (size of the chamfer) of the first cutting edge and a smaller maximum distance e (distance e shown in Figure 6) from the virtual straight line L, which is the tangent to the circle S representing the core thickness of the oil-hole drill and passes through the outer corner of the oil-hole drill, to the second cutting edge. This reduces stress concentration on the cutting edge during cutting and simultaneously maintains the rigidity of the cutting edge.

[0035] This revealed that the oil-hole drill of the present invention improves chip breaking performance and tool life compared to conventional oil-hole drills. In addition, the oil-hole drill of the present invention has become the optimal oil-hole drill for deep hole drilling in all types of steel materials, from general-purpose steels such as carbon steel to difficult-to-cut materials such as stainless steel. [Explanation of Symbols]

[0036] 1. Drill with oil holes 2 Chisel Edges 3,4 Escape 5 Scoop surface 11,12 Cutting edge 11A, 12A First cutting edge 11B, 12B Second cutting edge 13,14 Outer corner c. Chamfer width of the outer corner d1 Size of the chamfer of the first cutting edge d2 Size of the chamfer on the second cutting edge e Maximum distance from the virtual straight line L to the second cutting edge r Radius of curvature of the second cutting edge D Diameter of oil-hole drill H1,H2 oil hole L virtual line O center axis R Rotation direction of oil-hole drill S Core thickness of oil-hole drill α chamfer angle β Chamfer angle of the outer corner θ Thinning angle

Claims

1. An oil-hole drill having at least two or more oil holes at its tip and a groove length of 10 times or more the diameter D, wherein the oil-hole drill has two or more cutting edges extending outward from the central axis, the cutting edges comprising a first cutting edge extending linearly from the chisel edge and a second curved cutting edge formed continuously with the first cutting edge and having a predetermined radius of curvature, wherein the size d of the chamfer of the first cutting edge is in the range of 0.015 × D to 0.024 × D with respect to the diameter D of the oil-hole drill, and the angle α of the chamfer is in the range of 18° to 28°.

2. The oil-hole drill according to claim 1, characterized in that the maximum distance e from the tangent to the circle S representing the core thickness of the oil-hole drill, which is a virtual straight line L passing through the outer corner of the oil-hole drill, to the second cutting edge is in the range of 0.010 × D or more and 0.055 × D or less with respect to the diameter D of the oil-hole drill.

3. An oil-hole drill according to claim 2, characterized in that the maximum distance e is in the range of 0.010 × D or more and 0.034 × D or less with respect to the diameter D of the oil-hole drill.

4. The oil-hole drill according to claim 2 or 3, characterized in that the first cutting edge is provided with a thinning through angle θ in the range of 32° to 42°.

5. The oil-hole drill according to claim 4, characterized in that the outer corner is chamfered with an angle β of 8° to 15° and a width c of 0.02 × D to 0.08 × D with respect to the diameter D of the oil-hole drill.

6. The oil-hole drill according to claim 4, characterized in that the outer corner is chamfered with an angle β in the range of greater than 15° and less than or equal to 16.5°, and with a width c in the range of 0.02 × D to 0.08 × D with respect to the diameter D of the oil-hole drill.

7. The oil-hole drill according to claim 1, characterized in that the first cutting edge is provided with a thinning through angle θ in the range of 32° to 42°.

Images