JPH10278036A - Dry drilling diamond drill bit and manufacture of diamond whetstone used for the bit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method for a diamond drill bit and a diamond whetstone used for the drill bit whose lines are remarkably improved, and with which high speed drilling is possible without using water or processing liquid just by fitting on a simple rotating tool such as a regular drill when a hard and fragile material such as concrete or stone is to be drilled. SOLUTION: A diamond drill bit is of the structure of jointing integrally a metal body 7 with a diamond whetstone 1 set on the metal body 7, and the channel intervals of a slit 2 formed on the diamond whetstone 1 are formed narrow on the site corresponding to a rotating shaft of the diamond whetstone 1 and wide on a site away from the rotating shaft in the outer peripheral direction, and the diamond drill bit formed by filling a filler in the slit 2 and the diamond whetstone 1 used for the bit are set in an incineration mold in the form of clamping the filler 5 processed into the given dimension set between a plurality of diamond layers primary molded bodies, and then pressure incinerated to manufacture a diamond whetstone integrated with the slit without the necessity of after-processing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for drilling a hard and brittle material represented by concrete, stone or the like, which is mounted on a normal drill without using cooling water or other working fluid. The present invention relates to a diamond drill bit for dry drilling, which can be easily operated only by itself and capable of high-speed drilling, and a method of manufacturing a diamond grindstone used therefor.

[0002]

2. Description of the Related Art Diamond drill bits have been widely used as drilling tools for drilling holes in hard and brittle materials such as stone and concrete structures. These diamond core bits are perforated by a mechanism in which a diamond grindstone formed of diamond abrasive grains and a bond is attached to the tip of a hollow cylindrical body, and a hard and brittle material is cut through rotation of the bit.

[0003] In general, when a diamond grindstone is weak to heat, when it is used, water is mainly supplied to cool the cutting edge. Especially when used as a drill bit, the diamond abrasive grains on the cutting edge are always pressed against the work material,
It is much more thermally severe than that used as a blade or the like. In addition, the smaller the bit diameter, the smaller the heat capacity and heat dissipation area of the bit itself, and the more heat storage at the cutting edge increases, so even if the highest grade diamond is used as abrasive grains, concrete, etc. can be used without using cooling water. In the initial drilling (several tens of seconds), most of the abrasive grains on the cutting edge are thermally worn, and furthermore, seizure of the metal bond occurs, and the drilling becomes impossible immediately.

As a solution to the above-mentioned problems, a wet drilling type diamond core bit for forcing the cooling of the cutting edge and the discharge of cutting chips by supplying water or an appropriate machining liquid from the hollow hole of the body to the cutting edge is also available. Although this method has been proposed, this method requires equipment for supplying water or machining fluid and a dedicated rotating tool, and also requires measures such as contamination of the work environment due to drainage or drainage and measures against electric shock accidents. It requires cumbersome work for setup and cleaning up after work, and is not appropriate for small-diameter drilling work that requires a high working speed.

In order to solve the above-mentioned problems, the present inventors have provided a hollow cylindrical body having an inner hole in the axial direction, and a hollow hole communicating with the inner hole of the body at a tip end thereof. A diamond core bit having a structure in which a diamond grindstone is integrally joined, wherein the shape of the cutting edge of the diamond grindstone is designed to be a truncated cone having a diameter decreasing from a joint surface with a body toward a tip end thereof, and a hollow hole of the diamond grindstone is provided. Of the inner diameter of 10 to 6 with respect to the maximum outer diameter
A diamond core bit for dry drilling, which is set to a range of 0% and provided with at least one chip discharge port at an appropriate position on the side of the body, has been proposed (Japanese Patent Laid-Open No. 8-174).
No. 537).

The present inventors further provide a diamond drill bit having a structure in which a diamond grindstone is integrally connected to a tip end of a body provided with a spiral groove along the outer periphery in the axial direction, wherein the diamond grindstone has a cutting edge shape. Is formed in the shape of a truncated cone having a diameter reduced from the coupling surface with the body toward the distal end portion, and at least one of the grooves reaching the body rotation axis from the tip end surface including the rotation axis of the diamond grindstone and communicating with the spiral groove. A diamond drill bit for dry drilling with a slit has been proposed (JP-A-8-238617).
issue).

[0007]

According to the above-mentioned invention, when drilling stone or concrete, cutting chips are efficiently discharged, and the heat generated at the cutting edge is also efficiently discharged to the outside at the same time. It has good sharpness and generates little frictional heat at the cutting edge, and high-speed drilling increases the heat radiation effect on the work material due to the appearance of new work surfaces one after another. Drilling at an excellent drilling speed is possible without using water, water or other working fluids.

[0008] In order to improve the sharpness of the diamond drill bit, it is necessary to reduce the area of the tip of the grinding stone as much as possible and to make the tip abrasive grains bite into the work material. That is, in the relative area ratio occupied by the grindstone surface and the slit of the diamond grindstone, when the slit area is a denominator and the grindstone area is a numerator, it is preferable to reduce this area ratio. In order to secure the number, the diamond outlet for the bond needs to be high.

As described above, when the tip area ratio is reduced and the diamond outlet is increased in order to improve sharpness, the absolute volume of the bond portion is reduced, and the strength of the whole grindstone is reduced. The problem of chipping and cracking of the whetstone inside was left. Also, if the whetstone part is severely broken, the life of the bit will be there, and even if the chip is small, wear of the whetstone part will be severe in the drilling immediately after that, resulting in stable life performance. Was difficult.

On the other hand, in a method of manufacturing a bit as disclosed in Japanese Patent Application Laid-Open No. H8-174537, the diamond grindstone portion is sintered as an integral body and then provided with necessary slits by post-processing or divided into both sides of the slits. After sintering separately in the form, each is welded to the body to form an integral body,
For example, in the former method, the post-machining uses thermal energy such as electric discharge machining, and requires a very long time, so that mass productivity is extremely low. There's a problem. Further, according to the latter method, the number of parts to be sintered and welded increases because the parts are divided and produced, so that there remains a problem that mass productivity is deteriorated and the cost is increased.

[0011] Accordingly, an object of the present invention is to solve the problems left in the above prior art, and to easily form small holes in hard brittle materials such as concrete and stone materials without using water or a working liquid. A diamond drill bit for dry drilling and a diamond grindstone for the drill bit that can be mounted on a general-purpose tool and that can perform high-speed and continuous drilling, exhibit stable life performance, can be mass-produced, and can be manufactured at low cost It is to provide a manufacturing method of.

[0012]

According to the present invention, there is provided a diamond drill bit for dry drilling according to the present invention, wherein the diamond drill bit has a structure in which a diamond grindstone is integrally joined to a tip of the metal body. The groove interval of the slit provided in the diamond grinding stone is narrow at a portion corresponding to the rotation axis of the diamond grinding stone, and wide at a portion distant from the rotation axis in the outer peripheral direction, and a filler is embedded in the slit. The main configurational feature is to do the following. Further, as a method of manufacturing a diamond grindstone used for the diamond drill bit, a predetermined number of diamond layer primary compacts in which a metal bond and a diamond abrasive grain as a raw material of a diamond grindstone portion are mixed in a predetermined ratio are prepared in advance. By setting the filler processed to the dimensions into a sintering mold in the form of sandwiching it and sintering it under pressure, it is possible to obtain a diamond whetstone integrated structure with slits without post-processing. It is a feature of.

The filler used in the present invention is selected from a heat-resistant material which is easily worn and has a small coefficient of thermal expansion as compared with the composition of the sintered body of the diamond abrasive grains constituting the diamond grinding stone and the bond. You. Although the basis will be described later, examples of the heat-resistant material satisfying the above conditions include carbon-based materials such as carbon, graphite, and carbon fiber, ceramic materials such as silica, alumina, titania, and boron nitride, and tungsten-based compounds. Sintered metal powder,
Examples thereof include mica, molybdenum disulfide, and a Pb-Cu solid lubricant.

In the present invention, a more preferable configuration is that the gap between the slits in which the filler is embedded is in the range of 0.5 to 3.0 mm within a radius of 1 mm from the rotation axis of the diamond grindstone, and more preferably 0 to 3.0. It is in the range of 0.5 to 2.0 mm. On the other hand, the groove interval at a portion that is at a radius of 1 mm or more in the outer peripheral direction from the rotation axis of the diamond grindstone is provided to be wider than the above-mentioned groove interval, and specifically, is preferably 1.0 mm or more, and particularly preferably 2. 5 mm or more. The shape of the groove of the slit is not particularly limited as long as it satisfies the above-mentioned requirements for the groove interval. For example, the shape as viewed from the tip of the diamond drill bit is a dumbbell shape as shown in FIGS. 3 and 8. As shown in FIG. 9, a part slightly distant from the rotation axis in the outer peripheral direction and having a substantially fan-shaped shape may be used. Further, the relative area ratio occupied by the slit and the grinding wheel surface of the diamond grinding stone is 30: 70-7.
0:30, the outer diameter of the diamond grindstone is 3 to 2
0 mm, and the outer diameter of the metal body is desirably 98% or less thereof.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to obtain a high drilling speed (good sharpness) by a diamond drill bit for dry drilling, as described above, the tip area ratio of the diamond grindstone portion is reduced and the diamond outlet is increased. It is necessary. In other words, reducing the tip area makes it easier for the tip diamond to bite into the work material.On the other hand, when the area ratio is reduced, in order to secure the required number of tip abrasive grains, It is necessary to increase the outlet.

However, reducing the tip area and increasing the diameter of the diamond outlet means that the proportion of the metal bond in the grindstone is reduced at the same time, and as a result, the strength of the grindstone portion itself is reduced. Will decrease.

However, according to the structure of the present invention in which the filler is buried in the slit provided in the diamond grindstone by the above means, the filler serves as a reinforcing material for the thin portion of the grindstone, and the required strength of the whole grindstone portion is reduced. The whetstone part can be maintained and chipping and cracking can be prevented. That is, with this structure, it is possible to obtain both a high drilling speed and a stable grinding wheel life.

By the way, the cutting chips generated at the time of drilling are smoothly discharged out of the rear system from the gap between the drilling wall and the body and the spiral groove of the body via the centrifugal force due to the rotational motion and the driving force generated by the inclination angle. Thus, the phenomenon of stagnation on the cutting edge surface is effectively prevented. At the same time, the filler buried in the slit of the diamond grindstone is gradually and appropriately worn by the cutting chips generated at the time of drilling, and as the drilling work progresses, the filler buried part is always slightly depressed from the tip of the grindstone. While maintaining, the wear of the filler buried portion progresses along with the wear of the grindstone portion. On the other hand, the work material near the center of the cutting surface that is not cut by the grindstone contacts the filler buried in the grindstone part and wears it a little, but because of its small absolute size, it quickly collapses without growing as a core And is discharged out of the rear system through the depression formed in the filler.

In order for the work material in the vicinity of the center of the cut surface to quickly break down without growing as a core and become fine, it is necessary to make the non-cut area generated at the slit at the tip of the grinding wheel sufficiently small. This can be achieved by reducing the slit width (groove interval) in the vicinity of the rotation axis of the tip of the grinding wheel to a certain value or less. However, if the slit width is made small over the entire area of the grindstone, the tip area of the grindstone becomes larger by that amount, so that good sharpness cannot be obtained as described above. Therefore, as the structure of the diamond grindstone portion, the slit width is set to be 0 .0 near the rotation axis of the diamond grindstone.
5 to 3.0 mm, and at a portion apart in the outer peripheral direction, the width of the slit is equal to or more than the width of the slit. Brought.

[0020] These effects are achieved by embedding a brittle filler material having moderately high abrasion characteristics in the slits of the grindstone portion, thereby achieving both improvement in grindstone strength and excellent dischargeability of cutting chips. Is brought about by Therefore, when the filling material for the slit is a material other than the filling material of the present invention, for example, a metal having a high bending strength and a low abrasion property, it can reinforce the grindstone but provide an effective discharge path of the cutting chips. In addition to this, the work material directly hits the metal surface, which becomes cutting resistance, and cannot exhibit a high drilling speed.

The method for producing a diamond grindstone for a diamond drill bit for dry drilling according to the present invention is a method for producing a plurality of diamond layer primary compacts in which a metal bond as a raw material of a diamond grindstone portion and diamond abrasive grains are mixed at a predetermined ratio. In the meantime, it is set in a mold for sintering in the form of sandwiching the filler material that has been processed to a predetermined size in advance, and by sintering it under pressure, an integrated structure of diamond whetstone with slits is obtained without further processing It is in. At this time, it is also a preferable embodiment to set the primary molded body of the underlayer adjacent to the sandwich structure of the primary molded body of the diamond layer and the filler and to perform pressure sintering. According to the above method, there is no need to perform machining such as electric discharge machining after sintering as in the conventional example in which a slit space is provided in the grindstone portion, and an integrated structure is obtained as the grindstone portion after sintering. In the above, the production method of the present invention is a method excellent in mass productivity.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 2 is a partially cutaway view illustrating the diamond drill bit of the present invention. In FIG. 2, a slit 2 provided so as to include the rotation axis of the diamond grinding stone 1 has a rotation axis 4 at which the peripheral speed of the tip end surface of the grinding stone portion becomes zero and a portion where the peripheral speed is extremely low in the vicinity of the rotation axis 4. And plays a role in obtaining high drilling performance of the bit. On the other hand, the filler 5 buried in the slit 2
It serves to reinforce the thinned part of the grindstone, thereby maintaining the required strength of the whole grindstone part and preventing chipping or cracking of the grindstone part. That is, according to this structure, it is possible to obtain both a high drilling speed and a stable grinding wheel life.

The cutting chips generated at the time of drilling are smoothly removed from the clearance between the drilling wall and the body 7 and the spiral groove 8 of the body 7 through the centrifugal force due to the rotational motion and the driving force generated by the inclination angle. The phenomenon of being discharged to the outside and staying on the cutting edge surface is effectively prevented. At the same time, the filler 5 buried in the slit 2 of the diamond grindstone is gradually and appropriately worn by cutting chips generated at the time of drilling, and with the progress of the drilling operation, the tip 6 of the filler buried portion is always higher than the grinding wheel tip surface. While maintaining the slightly depressed shape, abrasion of the filler buried portion proceeds prior to abrasion of the grindstone portion. On the other hand, the work material near the center of the cut surface that is not cut comes into contact with the filler 5 and slightly wears it. However, since the absolute size is small, the work material does not grow as a core and immediately collapses and becomes fine. 5 is also discharged to the outside of the rear system through the depression formed in FIG. The tip 6 of the embedded portion of the filler in FIG. 2 has a slightly concave shape, but this is an example at the time of drilling or after drilling. The shape without a dent may be sufficient.

[0024]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

Example 1 A graphite plate having the shape shown in FIG. 1 is sandwiched between a diamond layer primary compact formed by mixing and forming a tungsten-based bond and diamond abrasive grains at a diamond outlet of 5.0 cts / cm ³ . At the same time, an outer diameter 6 formed by truing a diamond grindstone sintered body obtained by charging a sintering mold by setting the primary molded body for the underlayer adjacent to the sintering mold and performing pressure sintering. 0.0mm, height 8.0mm, tilt angle 6 with respect to the rotation axis
A diamond grindstone having a 0-degree frustoconical shape has an outer diameter of 5.0
2 mm and a total length of 140 mm was welded to the tip of a twist drill type steel body to produce a diamond drill bit for dry drilling having a structure as shown in FIGS. 2 and 3. The dimension numbers in FIG. 1 indicate mm.

Next, the above-mentioned diamond drill bit for dry drilling was mounted on an electric rotary drill, and the rotation speed was 1600.
When pressed against a high-strength concrete plate (aggregate particle size: 25 mm, plate thickness: 60 mm) with a load of 10 kg at a rpm and drilling work, the bit dug concrete while discharging cutting chips vigorously. And continuous drilling in dry mode without using cutting water. Average drilling speed is 100mm / m
It was confirmed that it was possible to drill 55 holes (total of 3300 mm) before the grinding wheel portion of this bit was completely worn.

Example 2 A dry drilling diamond having a structure as shown in FIGS. 2 and 3 was prepared in the same manner as in Example 1 except that a mica ceramics plate having the shape shown in FIG. 1 was used instead of the graphite plate. A drill bit was made.

Next, when a drilling operation was performed on the same concrete plate as in the first embodiment in the same manner as in the first embodiment, the bit dug the concrete while vigorously discharging the cutting chips, and the cooling water and Continuous drilling could be performed in a dry manner without using cutting water. The average drilling speed is 80mm / min
In addition, it was confirmed that it was possible to drill 50 holes (total 3000 mm) before the grinding wheel portion of the bit was completely worn.

Example 3 In place of a graphite plate, a tungsten-based metal powder compact having the shape shown in FIG. 1 and having a bending strength of 10 MPa or less prepared by sintering under pressure was used. In the same manner as in Example 1, a diamond drill bit for dry drilling having a structure as shown in FIGS. 2 and 3 was produced.

Next, when a drilling operation was performed on the same concrete plate as in the first embodiment in the same manner as in the first embodiment, the bit dug the concrete while vigorously discharging cutting chips, and the cooling water and Continuous drilling could be performed in a dry manner without using cutting water. The average drilling speed is 70mm / min
It was also confirmed that a drilling operation of 80 holes (4800 mm in total) was possible before the grinding wheel portion of the bit was completely worn.

Comparative Example 1 An outer diameter of 6.0 mm and a height of 8.0 mm (not including a graphite plate) formed of a tungsten-based bond and diamond abrasive grains.
0mm, a diamond wheel having a truncated cone shape with a tilt angle of 60 degrees to the rotation axis is welded to the tip of a twist drill type steel plate body with an outer diameter of 5.0mm and a total length of 140mm, and as shown in Figs. A diamond drill bit with no structure was made.

Next, as in the first embodiment, the number of rotations is 160
At 0rpm, high strength concrete board (aggregate particle size: 25mm,
(Dry thickness: 60 mm) with a load of 10 kg and drilling by dry method. The peripheral speed of the rotation axis at the tip of the grinding wheel and its peripheral speed are zero or extremely low, so this part only needs to be pressed against the work material. This resulted in a large cutting resistance, and the drilling could not be performed satisfactorily.

Comparative Example 2 An outer diameter of 6.0 mm, a height of 8.0 mm, and an inclination angle of 6 with respect to the rotating shaft formed of a tungsten-based bond and diamond abrasive grains.
A diamond grindstone having a 0-degree frustoconical shape has an outer diameter of 5.0
6 mm and a total length of 140 mm of a twist drill type steel body. Weld the diamond grindstone with a slit of 1.7 mm width centered on the rotation axis by electric discharge machining. A diamond drill bit for dry drilling having a structure in which a portion becomes a void was prepared.

Next, as in the first embodiment, the number of rotations was 1600.
At a rpm of 10 kg, a high-strength concrete plate (aggregate particle size: 25 mm, plate thickness: 60 mm) was pressed with a load of 10 kg, and drilling was performed in a dry manner. In the middle of drilling the first hole, a part of the diamond grindstone was broken and came off, making drilling impossible.

In the present invention, the metal body may have a hollow cylindrical shape having an inner hole in the axial direction.

[0036]

As is clear from the examples and comparative examples,
The diamond drill bit according to the present invention can be used for drilling hard and brittle materials such as concrete and stone, especially in relatively small diameter drilling, without using water or machining fluid.
It can be mounted on a simple general-purpose tool to perform high-speed and continuous drilling, and stable life performance is guaranteed. On the other hand, the method for producing a diamond grindstone of the present invention can provide an excellent diamond grindstone at an extremely low cost as compared with a conventionally known method, because a desired slit can be formed by a simple means, so that mass productivity is secured. be able to.

[Brief description of the drawings]

FIG. 1 is a view showing a shape of a filling material buried in a slit of a diamond drill bit grindstone portion according to the present invention.

FIG. 2 is a partially cutaway view illustrating a diamond drill bit according to the present invention.

FIG. 3 is a plan view of a distal end portion of FIG. 2;

FIG. 4 is a partially cutaway view showing an example of a conventional diamond drill bit.

FIG. 5 is a plan view of the distal end portion of FIG.

FIG. 6 is a partially cutaway view showing an example of a conventional diamond drill bit.

FIG. 7 is a plan view of the distal end of FIG. 6;

FIG. 8 is a plan view illustrating a tip portion of the diamond grindstone of the present invention.

FIG. 9 is a plan view illustrating the tip portion of the diamond grindstone of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Diamond grindstone 2 Slit 3 Grindstone tip surface 4 Rotation axis 5 Filling material 6 Tip of filling material embedded part 7 Metal body

Continued on the front page (72) Inventor Norio Sumita 1770 Hongo, Ebina-shi, Kanagawa Prefecture Sankyo Diamond Industry Co., Ltd.

Claims (8)

[Claims] 1. A diamond drill bit having a metal body and a diamond grindstone integrally joined to a tip of the metal body, wherein a groove interval of a slit provided in the diamond grindstone is set to a rotation axis of the diamond grindstone. A diamond drill bit for dry drilling, characterized in that it is narrow at a corresponding portion and wide at a portion distant from the rotation axis in an outer peripheral direction, and has a filler embedded in the slit. 2. The diamond drill bit for dry drilling according to claim 1, wherein the filler is made of a heat-resistant material which is more easily worn than the diamond grindstone and has a low coefficient of thermal expansion. 3. The method according to claim 1, wherein the filler is a carbon-based material, ceramics, sintered metal powder, mica, molybdenum disulfide and P
The diamond drill bit for dry drilling according to claim 1, wherein the diamond drill bit is at least one member selected from b-Cu-based solid lubricants. 4. The diamond grindstone has a groove interval of 0.5 to 3.0 mm at a portion corresponding to the rotating shaft of the diamond grindstone, and a portion apart from the rotating shaft in the outer peripheral direction is more than 0.5 mm. 4. A diamond drill bit for dry drilling according to any one of 1 to 3. 5. The diamond drill bit for dry drilling according to claim 1, wherein a relative area ratio of the grindstone surface of the diamond grindstone to the slit is 30:70 to 70:30. 6. The diamond drill bit for dry drilling according to claim 1, wherein the outer diameter of the diamond grindstone is 3 to 20 mm, and the outer diameter of the metal body is 98% or less thereof. 7. The diamond drill for dry drilling according to claim 1, wherein the metal body has a hollow cylindrical shape provided with a spiral groove along an outer periphery in an axial direction or an inner hole in an axial direction. bit. 8. A sintering method in which a filler previously processed to a predetermined size is sandwiched between a plurality of diamond layer primary compacts obtained by mixing metal bonds and diamond abrasive grains at a predetermined ratio. A method for producing a diamond grindstone for a diamond drill bit for dry drilling, wherein an integrated structure of a diamond grindstone having a slit is obtained without setting any post-processing by sintering under pressure after setting in a mold.