Long drill for hard brittle materials

Abstract

[Problem] To provide a long drill for hard brittle materials, which has a new configuration that is suitable for drilling a small-diameter deep hole in a product of a hard brittle material. [Solution] A long drill 1 is configured to comprise: a drill part 3; a straight part 5 that is formed continuously to the rear end of the drill part 3; and a shaft part 7 attached to the straight part 5. The straight part 5 is formed integrally from a guide part 17 provided contiguously to a base end portion 13 of the drill part 3 and a connecting extension part 19 extending from the rear end of the guide part 17, and a cylindrical shaft part 7 is attached to the straight part 5 by being fitted to the outer circumference of the connecting extension part 19.　

Description

Long drill for hard and brittle materials

[0001] The present invention relates to a long drill or drill for drilling small diameter deep holes in articles made of hard and brittle materials such as silicon, glass or ceramics.

[0002] Drills for drilling small, deep holes in hard, brittle materials such as silicon have a long, thin drill shaft, which is rotated while being forced into the hole, causing the drill tip to rotate as the drill shaft rotates. Because the material being drilled is hard and brittle, cuttings turn into powder. To remove these powdery cuttings from the bottom of a deep hole, it is effective to form a coolant hole in the drill shaft along the axial direction and eject coolant from the tip or drill of the drill shaft.

[0003] When using a twist drill with a spiral discharge flute along the entire length of the drill shank as such a long drill, the discharge flutes are formed on the outside of the small-diameter drill shank and the coolant holes are formed on the inside, which can significantly weaken the strength of the drill shank, making it more likely to break when drilling deeper holes.

[0004] Therefore, as described in Patent Document 1, a drill shank is formed into a prismatic shape with a square cross section. With such a drill, cutting chips or powder can be discharged from between each flat surface of the drill shank and the drilled hole, so there is no need to provide a long spiral discharge groove on the outer periphery of the drill shank. Therefore, even if a coolant hole is formed in the drill shank in the axial direction, the drill shank does not become extremely thin and prone to breakage.

[0005] Japanese Patent Application Laid-Open No. 2001-179517

[0006] However, as described in Patent Document 1, drill shanks are made of hard materials such as cemented carbide, making it difficult to machine thin, long, high-aspect-ratio drills. Furthermore, since the wall thickness of the drill shank needs to be as thick as possible when drilling coolant holes, the coolant holes inevitably become thin, which can make it difficult to ensure the required coolant flow rate. Furthermore, if the drill shank is made of a hard material along its entire length, it may easily break even if the drill portion is thickened.

[0007] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a long drill or drill for drilling small-diameter deep holes in products made of hard and brittle materials, which can solve at least one of the above problems.

[0008] To achieve this objective, the present invention provides a long drill or drill for drilling small-diameter (thin) deep holes in hard and brittle materials. The drill or drill includes a drill portion having a cutting edge or cutting blade, a front guide portion or self-guiding portion, and a connecting protrusion or connecting extension portion as a rear connecting portion. The drill portion also includes a straight portion provided rearward of the drill portion to ensure the straightness of the drilled hole, a shank portion extending rearward from the straight portion, and a coolant discharge hole formed in the drill portion or the straight portion. The shank portion is formed in a pipe shape and is fitted and fixed to the outer periphery of the connecting protrusion or connecting extension portion of the straight portion. Here, the shank portion is a separate member from the straight portion. The straight portion, guide portion, or self-guiding portion can be harder than the shank portion, and the shank portion can be formed to be tougher than the straight portion, guide portion, or self-guiding portion. The highly resilient shank absorbs the vibrations and vibrations of the drill, and even if the shank is about to buckle, it contacts the wall of the small-diameter drilled hole, preventing buckling and preventing the shank from easily breaking. The shank is formed with a diameter smaller than the drill diameter (e.g., the maximum diameter) of the drill portion so that cutting chips or powder can be discharged through the gap between the outer periphery and the drilled hole, eliminating the need for a drainage groove or spiral groove on the outer periphery. The shank is, for example, rotated while being pressed into the drilled hole. The shank is formed in a pipe shape, but the inner hole or inner bore extending axially of the shank can form a coolant hole or part of a coolant hole. By providing a sufficient length for the connecting protrusion or connecting extension, the attachment strength between the shank and the straight portion can be increased or the joint area can be widened. For example, the straight portion may be integrally formed with a guide portion or self-guiding portion and a connecting protrusion or connecting extension.

[0009] The guide portion or self-guiding portion of the straight portion can be made of a hard material (for example, cemented carbide, cemented carbide coated with diamond or DLC), and the shaft portion can be formed to have high toughness.

[0010] The guide portion or self-guide portion of the straight portion can be formed with a square cross section. The corners can also be formed with an R-shape (e.g., a chamfered R-shape or an arc-shaped cross section). If the diagonal dimension of the guide portion or self-guide portion of the straight portion is equal to the drill diameter (e.g., the maximum diameter) of the drill portion (this includes cases where the diagonal dimension is smaller than the drill diameter and the dimensional difference is up to 0.02 mm or approximately equal, i.e., the dimensional difference is up to approximately 0.02 mm), the corners of the guide portion, e.g., the R-shaped corners, function as guides, and the flat portions of the guide portion or self-guide portion function as discharge portions for cutting chips or powder. Therefore, there is no need to form a discharge groove or spiral groove on the outer periphery of the straight portion, guide portion, or self-guide portion.

[0011] A diamond electrodeposited layer can be formed on the rear or rear outer periphery of the straight guide or self-guide portion, with the diagonal dimension of this diamond electrodeposited layer being larger than the drill diameter. The diamond electrodeposited layer is formed, for example, with a square cross section, and the corners are formed, for example, with an R-shape (for example, an R-chamfered shape or a circular cross section). Here, the diagonal dimension of the guide or self-guide portion other than where the diamond electrodeposited layer is formed can be equal to or smaller than the drill diameter of the drill portion.

[0012] The drill portion can be formed, for example, in a twisted shape with an ejection groove or a spiral ejection groove, but can also be formed, for example, in a pyramidal shape made of single crystal diamond without an ejection groove or a pyramidal base combined with a square prism (for example, a short square prism).

[0013] The long drill or drill of the present invention to achieve this object is also a long drill or drill for hard and brittle materials for drilling small-diameter (thin-diameter) deep holes in hard and brittle materials, and has a drill portion with a cutting edge or cutting blade, a front guide portion or self-guide portion, and a rear connecting portion, and is equipped with a straight portion provided at the rear of the drill portion to ensure the straightness of the drilled hole, a shank portion connected to the connecting portion of this straight portion and extending rearward from this straight portion, and a coolant discharge hole formed in the drill portion or the straight portion, and the guide portion or self-guide portion of the straight portion is made of a hard material, and the shank portion is formed to have high toughness.

[0014] The long drill for hard and brittle materials of the present invention is suitable for drilling small-diameter, deep holes in hard and brittle materials.

[0015] 3 is a perspective view of a long drill for hard and brittle materials according to the present invention; FIG. 4 is an exploded perspective view of the long drill; FIG. 5 is a side view of the long drill; FIG. 6 is an enlarged cross-sectional view taken along line A-A in FIG. 3; FIG. 7 is an enlarged cross-sectional view of line B-B in FIG. 3; FIG. 8 is a diagram illustrating a case where a deep hole is drilled using a long drill; FIG. 9 is a diagram illustrating a case where the long drill is bent; FIG. 10 is a perspective view of a modified long drill; FIG. 11 is a diagram illustrating a case where a deep hole is drilled using a modified long drill;

[0016] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0017] First, the configuration of a long drill for hard and brittle materials according to the present invention will be described with reference to FIGS. 1 to 5. FIG.

[0018] The long drill or drill 1 includes a drill portion 3, a straight portion 5 formed continuously with the rear end of the drill portion 3, and a shaft portion 7 attached to the straight portion 5. The shaft portion 7 is formed as an elongated body that also serves as a shank. In this example, the straight portion 5 and the shaft portion 7 form a drill shaft.

[0019] The drill portion 3 has a tip portion 11 having a cutting edge 9 and a base portion 13 to which the tip portion 11 is bonded by sintering or integrally molded with the tip portion 11 (the figure shows the PCD diamond tip portion 11 and the cemented carbide base portion 13 bonded by sintering). The tip portion 11 can be made of ultrafine cemented carbide, ultra-superfine cemented carbide, or high-speed steel with a diamond coating, or single-crystal diamond or PCD diamond, ultra-fine cemented carbide, ultra-superfine cemented carbide, or high-speed steel with diamond electrodeposition. The base portion 13 can be made of ultra-fine cemented carbide or ultra-superfine cemented carbide. A spiral discharge flute 15 is formed from the tip portion 11 to the base portion 13. The drill diameter L1 (see FIG. 6) of the tip portion 11 of the drill portion 3 can be 0.2 to 1.2 mm or 0.3 to 0.8 mm, but is 0.45 mm or approximately 0.45 mm in this example.

[0020] The straight portion 5 is integrally formed with a guide portion 17 provided continuously with the base end 13 of the drill portion 3 and a connecting extension portion 19 extending from the rear end of this guide portion 17. Since the guide portion 17 is integrally formed with the base end 13 of the drill portion 3, the base end 13 and the straight portion 5 are integrally formed using an ultrafine particle cemented carbide alloy or an ultra-super fine particle cemented carbide alloy. The discharge groove 15 of the base end 13 may be formed to terminate at the tip of the guide portion 17 or to enter and terminate at the tip of the guide portion 17.

[0021] The length of the guide portion 17 can be 1.0 mm to 3.0 mm, but in this example it is 2.0 mm or approximately 2.0 mm. The guide portion 17 has a square cross section, but each of the four corners is rounded (see reference numeral 21), and the diagonal length or diagonal dimension L2 is the same as or approximately the same as the drill diameter L1.

[0022] The connecting extension 19 is formed to have a circular cross section and a length which can be set to 1.0 mm to 5.0 mm, but here is set to 3.0 mm or approximately 3.0 mm.

[0023] The shank 7 is formed in a cylindrical or thin-walled cylindrical shape, with an outer diameter smaller than the drill diameter L1 of the drill portion 3 and the diagonal length L2 of the guide portion 17, and a length of 10 to 60 mm, but can also be made longer. The shank 7 is attached to the straight portion 5 by, for example, using or applying adhesive 23 to the outer periphery of the connecting extension portion 19 of the straight portion 5 and fitting it until it abuts against the rear end of the guide portion 17. The material of the shank 7 can be a material (e.g., metal) that is tougher than the material of the straight portion 5 or the guide portion 17; here, stainless steel is used, for example. The Young's modulus of the shank 7 or the material or materials of the shank 7 is 250 GPa or less, and the density is 9.0 g / cm. ３ It can be as follows:

[0024] A coolant hole 25 is formed in the straight portion 5 in the axial direction, opening at the rear end of the connecting extension 19 and extending to the tip of the guide portion 17. This coolant hole 25, together with an inner hole 27 extending in the axial direction of the shaft portion 7, forms a coolant hole 29 for supplying coolant, and the coolant supplied from the coolant hole 29 is discharged from coolant discharge holes 31 formed on both side surfaces of the tip of the guide portion 17. Because the straight portion 5 is short, even if the coolant hole 25 is formed with a large diameter, the straight portion 5 will not become easily broken, and conversely, even if the coolant hole 25 is formed with a small diameter, the coolant flow rate will not be significantly reduced.

[0025] Next, with reference to FIG. 6, drilling of a deep hole using the long drill 1 will be described.

[0026] First, a pilot hole 35 is drilled in the silicon product 33 using a short, highly rigid drill (not shown) ( FIG. 6 a). Then, a long drill 1 is inserted into the pilot hole 35 ( FIG. 6 b). The shank 7 is rotated and driven into the silicon product 33, forming a small-diameter, deep drilled hole 37 with the rotating drill portion 3 ( FIG. 6 c). The drill portion 3 is guided by the cutting edge 9 and the rounded corner 21 of the guide portion 17 to form a highly straight drilled hole 37. Cutting chips generated by the cutting action of the rotating cutting edge 9 travel, for example, along the discharge groove 15 of the drill portion 3, along with the coolant discharged from the coolant discharge hole 31, passing outside the flat or side surface of the guide portion 17, and then being discharged through the outer periphery of the shank 7. Even if the shank 7 vibrates slightly, its toughness absorbs the vibrations and prevents them from being transmitted to the drill portion 3. Furthermore, although the shaft 7 is not easily broken, as the depth of the machined hole 37 increases, a large thrust load is applied, causing bending. However, this bending does not become large because it abuts against the inner surface of the small-diameter machined hole 37 (see Figure 7), so it does not buckle.

[0027] FIG. 8 shows a modified example of the long drill 1. In FIG.

[0028] In the long drill variation 39, for example, the square cross section of the guide portion 17 is slightly reduced, and diamond electrodeposition is performed on the outer periphery of the rear end of the guide portion 17 (e.g., within a length range of 1.0 mm) to form an enlarged portion 45 (e.g., a square cross section with rounded corners 47 (e.g., chamfered or arc-shaped cross section)) in which diamond abrasive grains 43 are embedded in nickel plating 41. The diagonal length L3 of the corners 47 of the enlarged portion 45 (the diagonal length L3 is longer than the diagonal length L2 by the height of the diamond abrasive grains 43) is configured to be longer than the drill diameter L1. However, since the rest of the configuration is the same as the long drill 1, for example, identical parts are denoted by the same reference numerals and a description thereof is omitted. The diagonal length L3 can be 0.01 to 0.03 mm longer than the drill diameter L1, but here it is made 0.02 mm or approximately 0.02 mm larger. Furthermore, here, for example, the diagonal length L2 of the guide portion 17 is smaller than the drill diameter L1 and is smaller or slightly smaller than the diagonal length L2 in FIG. 5 .

[0029] When formed in this manner, the enlarged portion 45 further cuts and enlarges the hole 49 drilled by the drill portion 3 to form a machined hole 51 (see Figure 9), thereby improving the straightness guide function provided by the cutting edge 9 and the corner 47 of the enlarged portion 45.

[0030] 1, 39 Long drill 3 Drill portion 5 Straight portion 7 Shank portion 9 Cutting edge 17 Guide portion 19 Connecting extension portion 31 Coolant discharge hole

Claims

1. A long drill for hard and brittle materials, for drilling small-diameter, deep holes in hard and brittle materials, comprising: a drill portion having a cutting edge or cutting blade; a front guide portion or self-guiding portion; and a rear connecting protrusion or connecting extension portion, a straight portion provided at the rear of the drill portion to ensure the straightness of the drilled hole; a shank portion extending rearward from this straight portion; and a coolant discharge hole formed in the drill portion or the straight portion, wherein the shank portion is formed in a pipe shape and is fitted and fixed onto the outer periphery of the connecting protrusion or connecting extension portion of the straight portion.

2. A long drill for hard and brittle materials as described in claim 1, characterized in that the guide portion or self-guiding portion of the straight portion is made of a hard material, and the shank portion is formed to have high toughness.

3. A long drill for hard and brittle materials according to claim 1, characterized in that the guide portion or self-guiding portion of the straight portion is configured to have a square cross section, and the corners are formed in an R-shape.

4. A long drill for hard and brittle materials according to claim 3, wherein the diagonal dimension of the guide portion or self-guiding portion of the straight portion is equal to the drill diameter of the drill portion.

5. A long drill for hard and brittle materials as set forth in claims 3 or 4, characterized in that a diamond electroplated layer is provided on the outer periphery of the straight portion behind the guide portion or self-guiding portion, and the diagonal dimension of this diamond electroplated layer is larger than the drill diameter of the drill portion.

6. A long drill for hard and brittle materials for drilling small-diameter, deep holes in hard and brittle materials, comprising: a drill portion having a cutting edge or cutting blade; a front guide portion or self-guiding portion; and a rear connecting portion, a straight portion provided at the rear of the drill portion to ensure the straightness of the drilled hole; a shank portion connected to the connecting portion and extending rearward from this straight portion; and a coolant discharge hole formed in the drill portion or the straight portion, wherein the guide portion or self-guiding portion of the straight portion is made of a hard material, and the shank portion is formed to have high toughness.

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