drill

Abstract

A drill body of a drill (1) is to rotate around an axis. A plurality of discharge grooves (4) are spirally provided in an outer circumferential surface (31) of the drill body from a tip end part toward a base end part. Cutting edges (5) are formed at ridge portions between inner surfaces of the discharge grooves (4) that face the rotational direction side of the drill body and flank surfaces of the tip end part of the drill body. Thinning edges (7) extend at the tip end part of the drill body from inner ends of the cutting edges (5) toward a chisel (9) that is a tip end portion of the drill body. Thinning surfaces (71) that are rake surfaces of the thinning edges (7) connect the thinning edges (7) and the discharge grooves (4). Gash parts (8) are connected to the thinning surfaces (71), extend in an arc from inner ends of the thinning edges (7) at ridges with the flank surfaces, and are connected to the discharge grooves (4). The gash parts (8) are connected to the discharge grooves (4) so as to twist along the angle of twist of the discharge grooves (4).

Description

[Technical Field]

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

[0002] Conventionally, drills have been known in which a thinning edge and an R-gash are formed at the tip of the drill body (see, for example, Patent Document 1). The thinning edge is formed on the inner end of the cutting edge by thinning the tip of the drill. The R-gash has a ridgeline with the flank that extends in an arc shape from the inner end of the thinning edge toward the outer peripheral surface of the drill. An exhaust flute is provided on the outer peripheral surface of the drill body. The exhaust flute is provided in a spiral shape from the tip to the base end of the drill body. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-59999 Summary of the Invention

[0004] In the above-mentioned drill, a corner is formed at the connection between the R-gasher and the discharge flute. For example, when machining aluminum alloys, which are light and soft, small, short chips tend to be produced when the drill is used. In this case, the chips may get caught in the corner, resulting in a decrease in the drill's chip discharge performance.

[0005] An object of the present invention is to provide a drill that can improve chip discharge performance. [Problem to be solved by the invention]

[0006] A drill according to one aspect of the present invention comprises: a drill body that rotates around an axis; a plurality of discharge flutes that are spirally formed on the outer peripheral surface of the drill body from the tip end to the base end; a cutting edge formed on a ridge between an inner surface of the discharge flute that faces the rotation direction of the drill body and a flank of the drill body at the tip end; a thinning blade that is formed on the tip end of the drill body and extends from an inner end of the cutting edge toward a chisel that is the tip end of the drill body; a thinning surface that is a rake face of the thinning blade and connects between the thinning blade and the discharge flute; and a gash portion that is connected to the thinning surface, and whose ridge with the flank extends in an arc from the inner end of the thinning blade and connects to the discharge flute. The outer circumferential surface is provided with a back opening, The gash portion is connected to the discharge groove while twisting along the twist angle of the discharge groove. When the drill body is viewed from the side, the boundary line between the unreamt section and the gash section extends from the tip end side toward the base end side, and bulges in an arc shape toward the unreamt section at the tip end side, and bulges in an arc shape toward the gash section at the base end side. It is characterized by:

[0007] In the drill of this aspect, the gash portion connects to the discharge flute while twisting to match the helix angle of the discharge flute, thereby enabling a smooth connection between the gash portion and the discharge flute, thereby improving the chip discharge performance of the drill.

[0008] In the drill of this aspect, the gash portion may be connected to the discharge groove while twisting in a direction opposite to the rotation direction from the tip end side to the base end side. In the drill, the portion where the gash portion and the discharge groove connect can be smooth, allowing chips to be discharged smoothly without clogging.

[0009] In the drill of this aspect, the helix angle of the gash portion may be in the range of 0° to −6° with respect to the helix angle of the discharge flute. In the drill, the portion where the gash portion and the discharge flute connect can be made smooth, allowing chips to be discharged smoothly without clogging.

[0010] In the drill of this aspect, the length of the gash portion in the axial direction of the drill may be in the range of 0.5D to 1.4D, where D is the drill diameter. The drill can improve chip discharge performance while maintaining rigidity.

[0011]

[0012] In this drill ,before The gash portion extends from the inner end of the thinning cutting edge toward the radially outer side of the drill body. The aforementioned The drill may extend in an arc shape and be connected to the unrecessed portion. The drill reduces frictional resistance with the workpiece by unrecessing, and the gash portion can be enlarged by connecting the gash portion to the unrecessed portion of the drill body.

[0013] In the drill of this aspect, the drill may have three cutting edges. A three-edge drill can achieve the same effects as the drill of the above aspect.

[0014] In the drill of this aspect, at least the surface of the tip portion of the drill body may be coated with DLC, thereby improving the adhesion resistance of the tip portion of the drill body.

[0015] In the drill of this aspect, the drill may be a drill for cutting aluminum alloys. Aluminum alloys are light and soft, so they tend to produce small, short chips when cut with a drill. The drill can prevent chips from clogging the area where the gash portion and the discharge flute connect, allowing it to cut aluminum alloys well. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 2 is a side view of the drill 1. [Figure 2] FIG. [Figure 3] FIG. [Figure 4] 1 is a table showing the results of Test 1. [Figure 5] 1 is a table showing the results of Test 2. [Figure 6] 10 is a graph showing the results of Test 3. [Figure 7] 10 is a graph showing the results of Test 4. DETAILED DESCRIPTION OF THE INVENTION

[0017] An embodiment of the present invention will be described. The present invention is not limited to the following examples, and appropriate design modifications are possible. For clarity of explanation, some parts in the drawings are shown with dimensional ratios different from the actual dimensional ratios. The present invention should not be interpreted as being limited to the shape.

[0018] The structure of the drill 1 will be described with reference to Figures 1 to 3. As shown in Figures 1 and 2, the drill 1 has three blades and is used to cut, for example, aluminum alloys. The drill 1 is made of a hard material such as cemented carbide or high-speed tool steel (HSS). The drill 1 comprises a shank 2 and a body 3. The shank 2 and body 3 are an example of the "drill body" of the present invention. The shank 2 is a part that is attached to the spindle of a machine tool and is located at the rear end of the drill 1. The body 3 extends from the front end of the shank 2 along the axis AX.

[0019] Three discharge flutes 4 having a predetermined helix angle θ are formed in a spiral on the outer peripheral surface 31 of the body 3. The helix angle θ may be changed as appropriate. The discharge flutes 4 discharge chips. The discharge flutes 4 open at the tip of the body 3, and cutting edges 5 are formed at the opening. The drill 1 cuts the workpiece (not shown) with the cutting edges 5 by rotating around the axis AX, and forms a machined hole while discharging the chips through the discharge flutes 4. The rotation direction T of the drill 1 during machining is counterclockwise when viewed from the front (see Figure 3). The machine tool (not shown) cuts the workpiece by rotating the spindle to which the drill 1 is attached clockwise.

[0020] The discharge groove 4 has an inner surface 41. The cutting edge 5 is formed on a ridge portion where the inner surface 41 facing the rotation direction T intersects with the flank 6. The cutting edge 5 is roughly S-shaped in front view. The inner surface 41 on the cutting edge 5 side of the inner surface 41 is a rake surface, and the cutting edge 5 scoops up the chips cut and sends them into the discharge groove 4.

[0021] The portion of the inner surface 41 where the inner surface 41 on the cutting edge 5 side intersects with the outer peripheral surface 31 of the body 3 is the leading edge 33. A duplex 32 is provided on the outer peripheral surface 31 between circumferentially adjacent leading edges 33. The duplex 32 is formed radially inward of the outer peripheral surface 31 and has a diameter smaller than the drill diameter D. The drill diameter D may be changed as appropriate. The duplex 32 enables the drill 1 to reduce frictional resistance caused by contact between the inner surface of the drilled hole and the outer peripheral surface 31 of the body 3 when forming the drilled hole, thereby suppressing heat generation and drilling torque. The portion of the inner surface 41 opposite the cutting edge 5 where the duplex 32 intersects with the inner surface 41 on the side opposite the cutting edge 5 is the heel 34.

[0022] A chisel 9 is provided at the center of the tip of the drill 1. The tip of the drill 1 is subjected to a thinning process. The thinning process is a process for reducing the core thickness near the chisel 9. The thinning process is performed, for example, by rotating a grinding wheel and cutting the opening of the discharge groove 4 from the inner end 51 of the cutting edge 5 toward the chisel 9, thereby forming a thinning edge 7. The inner end 51 of the cutting edge 5 is the inner end on the axis AX side. The thinning edge 7 extends in an arc shape from the inner end 51 toward the chisel 9 in a front view. By forming the thinning edge 7, a thinning surface 71 is formed at the tip of the drill 1. The thinning surface 71 is a rake face facing the rotation direction T of the thinning edge 7.

[0023] In the thinning process, after forming the thinning edge 7, the grinding wheel is moved toward the heel 34 relative to the drill 1 to further cut away the thinning edge, forming a gash portion 8. The gash portion 8 has a gash surface 81. The gash surface 81 is a curved surface concave inward. The length of the gash portion 8 in the direction of the axial center AX of the drill 1 is L (see FIG. 1). As an example, the length L of the gash portion 8 is machined within a range of 0.5D to 1.4D in relation to the drill diameter D. The ridge where the gash surface 81 intersects with the flank 6 extends in an arc shape from the inner end 72 of the thinning edge 7 toward the outer peripheral surface 31 and connects to the back recess 32. The inner end 72 of the thinning edge 7 is the inner end on the axial center AX side. Because the gash portion 8 connects to the back recess 32 of the body 3, a larger chip pocket capacity can be secured. The chip pocket is a space that accommodates chips cut by the thinning edge 7. Therefore, the drill 1 can be smoothly fed without clogging the discharge flute 4 with chips.

[0024] An arc-shaped groove 10 is formed at the portion where the gash surface 81 and the thinning surface 71 connect. The arc-shaped groove 10 extends straight from near the chisel 9 toward the discharge groove 4, and the cross section in the extension direction presents an arc-shaped groove. The arc-shaped groove 10 can smoothly push out chips cut by the thinning edge 7 and scooped up by the thinning surface 71 into the gash portion 8. Therefore, the drill 1 can reduce cutting resistance and obtain stable chip shapes.

[0025] The gash portion 8 is connected to the discharge groove 4 while twisting in the opposite direction to the rotation direction T from the tip end side to the base end side. As an example, the gash portion 8 is processed so as to be twisted in the range of 0° to -6° with respect to the twist angle θ of the discharge groove 4. Therefore, the gash portion 8 is connected to the discharge groove 4 smoothly.

[0026] When machining a workpiece, the thinning edge 7 near the chisel 9 bites into the workpiece, generating chips. The chips are scooped up by the thinning surface 71 and pushed out into the gash portion 8 through the arc groove 10. The chips are rounded and curled by the gash surface 81, cut off by the leading edge 33, and sent into the discharge groove 4. The gash portion 8 of the present application smoothly connects to the discharge groove 4. This enables the gash portion 8 to smoothly discharge the chips into the discharge groove 4.

[0027] Three coolant passages 11 run spirally through the drill 1 along the discharge grooves 4 from the rear end of the shank 2 to the front end of the body 3 (see Figure 3). Each coolant passage 11 opens in the gash portion 8, forming an oil hole 12. During machining, cutting oil is supplied into the coolant passages 11 and discharged from the oil holes 12 toward the machining position of the workpiece. This reduces the cutting resistance of the drill 1 and suppresses heat generation and machining torque. Chips flow along the discharge grooves 4 with the cutting oil and are smoothly discharged.

[0028] The flank 6 is a surface that avoids contact with the machined surface of the workpiece. The flank 6 includes, in order opposite to the rotation direction T, a second flank 42, a third flank 43, and a fourth flank 44. The second flank 42 is located at the forefront in the rotation direction T and extends from the chisel 9 to the outer peripheral surface 31. The third flank 43 bends from approximately the radial center of the ridge of the second flank 42 opposite the cutting edge 5 toward the rear end. The third flank 43 extends opposite to the rotation direction T and tapers toward the tip end. The fourth flank 44 bends from the ridge of the third flank 43 opposite to the second flank 42 toward the rear end. The fourth flank 44 extends opposite to the rotation direction T and tapers toward the tip end. The tip of the fourth flank 44 is the heel 34.

[0029] In the drill 1 having the above configuration, it is preferable that at least the surface of the tip of the body 3 is coated with DLC (Diamond-Like Carbon). DLC is a general term for a thin film made of a substance whose main component is carbon that has both the carbon-carbon bonds of diamond and graphite. This can improve the adhesion resistance of the tip of the body 3 of the drill 1.

[0030] Test 1 for evaluating chip discharge performance will be described with reference to FIG. 4 . In Test 1, the chip discharge performance of drill 1 was examined when the helix angle of the gash portion 8 was changed. The helix angle of the gash portion 8 was adjusted within a range of 3° to −8°, with the helix angle θ of the discharge flute 4 as the reference, and nine helix angles were examined. The helix angle of drill No. 1 was 3°, the helix angle of drill No. 2 was 2°, the helix angle of drill No. 3 was 1°, the helix angle of drill No. 4 was 0°, the helix angle of drill No. 5 was −2°, the helix angle of drill No. 6 was −4°, the helix angle of drill No. 7 was −5°, the helix angle of drill No. 8 was −6°, and the helix angle of drill No. 9 was −8°. The drill diameter D of drill 1 was φ12.0. In the drills 1 of Nos. 1 to 3, when the gash portion 8 was formed, the gash portion 8 interfered with the flute bottom of the drill 1, and the desired shape of the drill 1 could not be realized.

[0031] In the machining conditions of Test 1, the cutting speed was 377 m / min and the spindle rotation speed was 10,000 rpm. ‐1 The feed rate was set to 10,000 mm / min. The feed rate per revolution of Drill 1 was set to 1 mm / rev. The machining method was set to non-step. The machining depth of the workpiece was set to 90 mm. The workpiece was made of AC4C, an aluminum alloy casting.

[0032] Drills 1 No. 1 to No. 3 were not able to achieve the desired drilling performance, so their chip removal performance was not verified. Therefore, drills 1 No. 4 to No. 9 were used to cut the workpiece and verify their chip removal performance. The results of the chip removal performance verification were rated on a three-point scale: good, fair, or bad. If there was no chip clogging, it was rated good. If there was chip clogging but cutting was possible, it was rated fair. If there was a lot of chip clogging and cutting was impossible, it was rated bad.

[0033] Drills 1 No. 1 to No. 3 were not verified and therefore could not be judged. Drills 1 No. 4 to No. 7 were able to cut without chip clogging. Therefore, the judgement result is ◯. Drill 1 No. 8 had some chip clogging but was able to cut without any problems. Therefore, the judgement result is △. Drill 1 No. 9 had chip clogging and could not cut. Therefore, the judgement result is ×.

[0034] The above test results demonstrate that it is preferable that the twist angle of the gash portion 8 be in the range of 0° to −6° with the twist angle θ of the discharge groove 4 as the reference.

[0035] Test 2 for evaluating chip discharge performance will be described with reference to FIG. 5 . In Test 2, the chip discharge performance was examined when the length L of the gash region 8 was changed. To conduct Test 2, eight drills 1, No. 1 to No. 8, with different lengths L of the gash region 8, were prepared. The length L of the gash region 8 was changed between 0.4D and 1.5D in relation to the drill diameter D. The length L of the gash region 8 of No. 1 was 0.4D, the length L of the gash region 8 of No. 2 was 0.5D, the length L of the gash region 8 of No. 3 was 0.6D, the length L of the gash region 8 of No. 4 was 0.8D, the length L of the gash region 8 of No. 5 was 1D, the length L of the gash region 8 of No. 6 was 1.2D, the length L of the gash region 8 of No. 7 was 1.4D, and the length L of the gash region 8 of No. 8 was 1.5D. The eight drills 1 had a common helix angle of the gash portion 8 of, for example, −2° with respect to the helix angle θ of the discharge groove 4. Other machining conditions were the same as those in Test 1.

[0036] Drills No. 1 to No. 8 were used to cut the workpiece and verify the chip discharge performance. The verification results of the discharge performance were judged on a three-point scale: good, fair, or bad. If there was no chip clogging, it was judged good. If there was little chip clogging and cutting was possible, it was judged bad. If there was a lot of chip clogging and cutting was impossible, it was judged bad.

[0037] Drill 1 No. 1 experienced a lot of chip clogging and was unable to cut. Therefore, the evaluation result was ×. Drills 1 No. 2 and No. 3 experienced some chip clogging but were able to cut without any problems. Therefore, the evaluation result was △. Drills 1 No. 4 to No. 6 were able to cut without chip clogging. Therefore, the evaluation result was ○. Drill 1 No. 7 experienced chatter vibration but was able to cut without clogging the workpiece. Therefore, the evaluation result was △. Drill 1 No. 8 broke. Therefore, the evaluation result was ×.

[0038] The above test results demonstrate that when the drill diameter is D, it is preferable that the length L of the gash portion 8 in the direction of the axis AX of the drill 1 be in the range of 0.5D to 1.4D.

[0039] Tests 3 and 4 for evaluating the durability of the drill 1 will be described with reference to Figures 6 and 7. In Test 3, the maximum thrust resistance (N) when the drill 1 of the present invention was used to machine a workpiece was measured, and the results were compared with those of a conventional drill. Thrust resistance refers to the cutting resistance applied in the direction opposite to the direction of travel of the drill 1. Cutting resistance occurs perpendicular to the cutting edge 5 of the drill 1, and the thrust resistance is what receives this cutting resistance in the axial direction. In Test 4, the maximum cutting torque (N) when the drill 1 of the present invention was used to machine a workpiece was measured, and the results were compared with those of a conventional drill. The conventional drill is a drill that has a corner between the gash surface and the discharge flute.

[0040] In tests 3 and 4, the drill diameter D of drill 1 was set to φ9.8. The helix angle of the gash portion 8 of drill 1 was set to -2° based on the helix angle θ of the discharge flute 4. The length L of the gash portion 8 was set to 1D. The machining depth of the workpiece was set to 50 mm. The cutting speed was set to 298 m / min. The spindle rotation speed was 9700 / min. ‐1 The feed rate was set to 8730 mm / min. The feed rate per revolution of Drill 1 was set to 0.9 mm / rev. The workpiece material used was aluminum die-cast ADC12.

[0041] As shown in Figure 6, the maximum thrust resistance of the conventional drill was 1079 (N), whereas the maximum thrust resistance of the drill 1 of the present invention was 985 (N). This demonstrates that the drill 1 of the present invention can reduce the maximum thrust resistance applied during machining compared to the conventional drill.

[0042] As shown in Figure 7, the maximum torque of the conventional drill was 695 (N m), while the maximum torque of the drill 1 of the present invention was 664 (N m). This demonstrates that the drill 1 of the present invention can reduce the maximum torque applied during machining compared to the conventional drill.

[0043] As described above, the drill 1 of this embodiment includes a body 3, multiple discharge flutes 4, cutting edges 5, thinning edges 7, and a gash portion 8. The body 3 rotates around the axis AX. The multiple discharge flutes 4 are spirally formed on the outer peripheral surface 31 of the body 3 from the tip end to the base end. The cutting edges 5 are formed at the ridge between the inner surface of the discharge flute 4 facing the rotation direction T of the body 3 and the flank 6 of the body 3 at the tip end. The thinning edges 7 are formed at the tip end of the body 3 and extend from the inner end of the cutting edges 5 toward the chisel 9, which is the tip end of the body 3. The thinning surfaces 71 are the rake faces of the thinning edges 7 and connect the thinning edges 7 and the discharge flutes 4. The gash portion 8 is connected to the thinning surfaces 71, and the ridge between the flank 6 and the thinning edges 71 extends in an arc from the inner end of the thinning edges 7 and connects to the discharge flutes 4. The gash portion 8 is connected to the discharge groove 4 while twisting along the twist angle θ of the discharge groove 4.

[0044] The drill 1 connects to the discharge flute 4 while the gash portion 8 twists along the helix angle θ of the discharge flute 4, thereby enabling a smooth connection between the gash portion 8 and the discharge flute 4. Therefore, the drill 1 can improve the chip discharge performance.

[0045] As the gash portion 8 moves from the tip end side to the base end side, it is connected to the discharge groove 4 while twisting in the opposite direction to the rotation direction T. In the drill 1, the portion where the gash portion 8 and the discharge groove 4 connect can be made smooth, allowing chips to be discharged smoothly without clogging.

[0046] The twist angle of the gash portion 8 is in the range of 0° to -6° with respect to the twist angle θ of the discharge groove 4. In the drill 1, the portion where the gash portion 8 and the discharge groove 4 connect can be made smooth, allowing chips to be discharged smoothly without clogging.

[0047] When the drill diameter is D, the length L of the gash portion 8 in the axial direction of the drill 1 is in the range of 0.5D to 1.4D. The drill 1 can improve the chip discharge performance while maintaining rigidity.

[0048] The gash portion 8 extends in an arc shape from the inner end of the thinning cutting edge 7 and connects to a recess 32 that is radially inward of the outer peripheral surface 31 of the body 3. By connecting the gash portion 8 to the recess 32 of the body 3, the drill 1 can increase the size of the gash portion 8 while reducing frictional resistance with the workpiece due to the recess 32.

[0049] The drill 1 has three cutting edges 5. The drill 1 can improve chip discharge performance among three-flute drills.

[0050] The surface of at least the tip of the body 3 is coated with DLC, which allows the tip of the body 3 of the drill 1 to have improved resistance to welding.

[0051] Drill 1 is a drill for cutting aluminum alloys. Because aluminum alloys are light and soft, they tend to produce small, short chips when cut with drill 1. Drill 1 can prevent chips from clogging the area where gash portion 8 and discharge groove 4 connect, allowing it to cut aluminum alloys well.

[0052] The present invention is not limited to the above embodiment, and various modifications are possible. The drill 1 is designed to cut soft work materials such as aluminum alloys, but may also be used to cut hard work materials.

[0053] There are no limitations on the material of the drill 1. At least the surface of the tip of the body 3 is coated with DLC, but the outer peripheral surface 31 may also be coated. The body 3 does not have to be coated with DLC.

[0054] The drill 1 has three flutes, but may have two flutes or four or more flutes. The drill 1 may also be used as a so-called long drill.

[0055] The gash portion 8 may be formed by a method other than thinning. The gash portion 8 is arc-shaped, but may also be linear. The thinning edge 7 does not necessarily have to be formed.

[0056] The coolant passage 11 extends spirally from the rear end of the shank 2 toward the tip of the body 3, but it does not have to be spiral and may be, for example, linear. Three arc grooves 10 are provided at the tip of the body 3, but the arc grooves 10 may be omitted.

[0057] The flank 6 is configured by the second flank 42, the third flank 43, and the fourth flank 44, but is not limited to this, and the third flank 43 and the fourth flank 44 may be omitted.

[0058] The unrecessed portion 32 provided on the outer peripheral surface 31 of the drill 1 may be omitted. In this case, the gash portion 8 may be connected to the outer peripheral surface 31 of the body 3.

Claims

1. a drill body that rotates around an axis; a plurality of discharge grooves spirally formed on the outer peripheral surface of the drill body from the tip end to the base end; a cutting edge formed on a ridge between an inner surface of the discharge flute facing the rotation direction of the drill body and a flank surface of the drill body at the tip portion; a thinning edge provided at the tip portion of the drill body and extending from an inner end of the cutting edge toward a chisel, which is a tip portion of the drill body; a thinning surface that is a rake surface of the thinning edge and connects the thinning edge and the discharge groove; a gash portion connected to the thinning surface, the ridgeline of which with the flank surface extends in an arc shape from the inner end of the thinning blade, and which is connected to the discharge groove; Equipped with The outer circumferential surface is provided with a back opening, The gash portion is connected to the discharge groove while twisting along the twist angle of the discharge groove, When the drill body is viewed from the side, the boundary line between the unreamt section and the gash section extends from the tip end side toward the base end side, and bulges in an arc shape toward the unreamt section side at the tip end side, and bulges in an arc shape toward the gash section side at the base end side.

2. The drill according to claim 1 , wherein the gash portion is connected to the discharge groove while twisting in a direction opposite to the rotation direction from the tip end side to the base end side.

3. The drill according to claim 1 or 2, wherein the helix angle of the gash portion is in the range of 0° to −6° with respect to the helix angle of the discharge flute.

4. The drill according to any one of claims 1 to 3, characterized in that, when the drill diameter is D, the length of the gash portion in the axial direction of the drill is in the range of 0.5D to 1.4D.

5. A drill as described in claim 1, characterized in that the gash portion extends in the arc shape from the inner end of the thinning blade radially outward from the drill body and connects to the backing.

6. The drill according to any one of claims 1 to 5, characterized in that the drill has three cutting edges.

7. 7. The drill according to claim 1, wherein at least the surface of the tip portion of the drill body is coated with DLC.

8. The drill according to any one of claims 1 to 7, wherein the drill is a drill for cutting an aluminum alloy.

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