JPH10113880A - Manufacuring method of diamond drill bit and diamond grindstone used for it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To highly speedily and continuously carry out drilling without using water and a processing solution at the time of drilling a small hole on a hard and fragile material such as concrete and a stone material by burying a filling material in a slit provided on a diamond grindstone. SOLUTION: A filling material 5 buried in a slit 1 of a diamond grindstone 2 is gradually and properly abrased by cutting dust produced at the time of drilling, and with progree of drilling work, abrasion of a filling material buried part progresses with abrasion of a drindstone part while the filling material buried part maintains a shape to be slightly depressed lower than a grindstone head end surface 3. In the meantime, a material to be cut in the neighbourhood of a central part of a cutting surface which is not cut by the grindstone 2 makes contact with the filling material 5 buried on the grindstone part and slightly abrases it, but as an absolute size is small, it does not grow as a core but soon collapses and becomes fine, and it is also discharged out of a rear system through a dent formed on the filling material 5.

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 (Japanese Patent Application Laid-Open No. Hei 8-238617).

[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 the 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. If the whetstone part breaks greatly, the life of the bit will be there, and even if a small chip occurs, the whetstone part will be severely worn by the drilling immediately after that, and as a result, it is difficult to exhibit stable life performance Met.

On the other hand, in a method of manufacturing a bit as disclosed in Japanese Patent Application No. 8-174537, the diamond grindstone portion is sintered as an integral body and then provided with necessary slits by post-processing or on both sides of the slits. There are two methods of separately sintering in a divided form and then welding them to the body to form an integral body. For example, in the former method, the post-processing is performed by electric discharge machining or the like. However, this method uses a large amount of heat energy, and requires a very long time. 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]

A diamond drill bit according to the present invention for achieving the above object is a diamond drill bit having a structure in which a metal body and a diamond grindstone are integrally joined to the tip of the metal body. ,
The main structural feature is that a filler is buried in at least one slit provided in the diamond grindstone. 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 a plate-shaped filler that has been processed to dimensions and setting it in a sintering mold and sintering it under pressure, an integrated structure of diamond wheels with slits can be obtained without post-processing. Is a structural feature.

In the present invention, more preferably, the width of the slit in which the filler is buried is preferably widened in accordance with the outer diameter of the diamond grindstone within a range of 0.5 mm or more. When it is 20 mm or less, it should be within a range not exceeding 5 mm.
７０70: 30, and the outer diameter of the diamond whetstone is 5
It is preferable that the outer diameter of the metal body is 98% or less, and the concentration of the abrasive grains of the diamond whetstone is 2.0 to 7.0 cts / cm ³ .

In a further preferred aspect of the present invention, the filler buried in the slit is made of a material which is more easily worn than a diamond grindstone and has a low coefficient of thermal expansion,
Moreover, it is desired to have a certain mechanical strength.
Specifically, it is appropriately selected from carbon-based materials such as carbon, graphite, and carbon fibers, mica, molybdenum disulfide, porous ceramics, and sintered metal powder.

[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, the tip area is reduced and
Increasing the diamond outlet means that the proportion of the metal bond in the grindstone decreases at the same time, and as a result, the strength itself as the grindstone portion decreases.

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. The slit preferably has at least one line, particularly preferably two to six lines.

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 It becomes fine and is also discharged out of the rear system through the hollow formed in the filler.

These effects are achieved by the fact that the filler having brittleness and moderately high wear properties is embedded in the slit of the grindstone portion, so that both improvement of the grindstone strength and good dischargeability of cutting chips can be achieved. It is brought by things.
Therefore, when the substance to be filled into the slit is a substance other than the filler of the present invention, for example, a metal having a high bending strength and a low abrasion property, an effective discharge path of the cutting chips can be obtained although it serves as reinforcement of the grindstone. Not only that, but the work material directly hits this metal surface, which becomes cutting resistance and cannot achieve a high drilling speed.

[0020] The method for producing a diamond grindstone for a diamond drill bit according to the present invention is characterized in that a metal bond as a raw material for a diamond grindstone portion and diamond abrasive grains are mixed at a predetermined ratio between a plurality of diamond layer primary compacts. A plate-shaped filler that has been processed to a predetermined size is set in a mold for sintering while being sandwiched, and this is pressed and sintered to obtain an integrated structure of a diamond grindstone having a slit without further processing. It is in. On this occasion,
It is also a preferable embodiment to set the base layer primary molded body adjacent to the sandwich structure of the diamond layer primary molded body 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.

The filler used in the present invention is usually a commercially available carbon-based material such as carbon, graphite, carbon fiber, mica, molybdenum disulfide, porous ceramics,
Easier wear than diamond grinding stone, such as sintered metal powder,
A compact having a low coefficient of thermal expansion can be appropriately selected and used, and the width of the filler, that is, the filler spacer, is set to be wider than 0.5 mm according to the outer diameter of the diamond grindstone. Is preferred. When the maximum outer diameter is set to 20 mm or less, it is preferable to set the maximum outer diameter to a range not exceeding 5 mm. If the width of the filler spacer is less than 0.5 mm, a portion having an extremely low peripheral speed is formed near the center of the diamond grindstone, and the drilling speed is significantly reduced. On the other hand, if it exceeds 5 mm, the core strength of the work material generated at the center of the cutting edge increases, and the work material comes into contact with the filler spacer, which becomes cutting resistance and significantly reduces the drilling speed.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The slit 2 provided so as to include the rotation axis of the diamond grindstone 1 eliminates from the grindstone surface the rotation axis 4 at which the peripheral speed of the tip surface of the grindstone portion becomes zero and the portion where the peripheral speed is extremely low in the vicinity thereof. It plays a role in obtaining high drilling performance of the bit. On the other hand, the filler 5 buried in the slit 2 serves to reinforce the thinned portion of the grindstone, thereby maintaining the necessary strength of the whole grindstone portion and preventing chipping or cracking of the grindstone portion. can do. 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.

EXAMPLE 1 A 1.7 mm thick diamond layer was formed between a diamond layer primary compact and a tungsten bond and a diamond grindstone mixed and molded at a diamond outlet of 5.0 cts / cm ^3.
Graphite plate (MC-5 manufactured by Mechanical Carbon Co., Ltd.)
The primary molded body for the diamond layer was obtained by truing the primary molded body for the diamond layer obtained by charging the sintering mold so that the primary molded body for the underlayer was set adjacent thereto and sintering under pressure. A diamond wheel having a truncated cone shape having an outer diameter of 6.0 mm, a height of 8.0 mm, and a tilt angle of 60 degrees was brazed to the tip of a twist drill type steel body having an outer diameter of 5.0 mm and a total length of 140 mm, and FIG. And FIG.
A diamond drill bit for dry drilling having the structure shown in FIG. Next, the above-mentioned diamond drill bit for dry drilling was mounted on an electric rotary drill, and the number of rotations was 160.
At 0 rpm, a concrete board (age: 1 year, aggregate particle size: 2
(0 mm, plate thickness: 60 mm) with a load of 10 kg and drilling. When drilling concrete with bits while removing cutting chips vigorously, drill continuously without using cooling water or cutting water. Was completed. Average drilling speed is 8
It was 0 mm / min, and it was confirmed that a drilling operation of 80 holes (4800 mm in total) was possible before the grinding wheel portion of this bit reached the worn state.

Example 2 FIG. 3 was obtained in the same manner as in Example 1 except that a graphite plate having a thickness of 1.4 mm (MC-5 manufactured by Mechanical Carbon Co.) was used.
A diamond drill bit for dry drilling having a structure as shown in FIG. 4 was prepared. Then, the above-mentioned diamond drill bit for dry drilling was mounted on an electric rotary drill and pressed against a concrete plate (age: 1 year, aggregate particle size: 20 mm, plate thickness: 60 mm) at a rotation speed of 1600 rpm with a load of 10 kg.
When the drilling work was performed, the bit dug concrete while discharging cutting chips vigorously, and the drill was able to continuously drill in a dry manner without using cooling water or cutting water. The average drilling speed was 100 mm / min, and it was confirmed that drilling of 53 holes (3180 mm in total) was possible by the life of the bit.

Example 3 A diamond drill bit for dry drilling having a structure as shown in FIGS. 1 and 2 in the same manner as in Example 1 except that a mica ceramics plate having a thickness of 1.7 mm was used instead of graphite. It was created. Next, when a drilling operation was performed on the same concrete plate as in Example 1 in the same manner as in Example 1, the bit digged the concrete while vigorously discharging cutting chips, and used cooling water or cutting water. , And could be continuously drilled dry. The average drilling speed was 7
It was 0 mm / min, and it was confirmed that drilling of 95 holes (a total of 5,700 mm) was possible before the complete grinding of the whetstone portion of the bit.

Example 4 In the same manner as in Example 1 except that a tungsten-based metal powder compact having a thickness of 1.8 mm and a bending strength of 10 MPa or less prepared by sintering under pressure was used instead of graphite. Thus, a diamond drill bit for dry drilling having a structure as shown in FIGS. 1 and 2 was prepared. In addition, as a result of the abrasion test, the tungsten-based metal powder compact showed almost the same abrasion resistance as graphite. Next, when a drilling operation was performed on the same concrete plate as in Example 1 in the same manner as in Example 1, the bit digged the concrete plate while vigorously discharging the cutting waste, and cooled water or cutting water. Without using it, it was possible to perform continuous drilling in a dry manner. The average drilling speed at this time was 65 mm / min, and 105 holes (total 6,300 m) were required until the grinding wheel portion of the bit was completely worn.
m) was confirmed to be possible.

Comparative Example 1 An outer diameter of 6.0 mm and a height of 8 mm (not including a graphite plate) formed of a tungsten-based bond and diamond abrasive grains.
A diamond grindstone having a truncated cone shape of 0 mm and an inclination angle of 60 degrees is brazed to the tip of a twist drill type steel plate body having an outer diameter of 5.0 mm and a total length of 140 mm, and has no slit as shown in FIGS. 5 and 6. A diamond drill bit with a structure was created. Then, as in the first embodiment,
At 600 rpm, it is pressed against a concrete plate (age: 1 year, aggregate particle size: 25 mm, plate thickness: 60 mm) with a load of 10 kg.
When dry drilling was performed, the rotational axis of the grinding wheel tip surface and the peripheral speed in the vicinity were zero or extremely low, so this part only pressed against the work material, which resulted in large cutting resistance Could not be satisfactorily perforated.

COMPARATIVE EXAMPLE 2 A diamond grindstone having a truncated cone shape having an outer diameter of 6.0 mm, a height of 8.0 mm, and a tilt angle of 60 degrees formed of a tungsten-based bond and diamond abrasive grains was 5.0 mm in outer diameter and 140 in total length.
mm of twist drill type steel body and brazed to the tip of the diamond grindstone.
A 7 mm slit was formed by electric discharge machining, and FIGS.
As shown in (1), a diamond drill bit for dry drilling having a structure in which a slit portion becomes a void was prepared. Then, in the same manner as in Example 1, at a rotation speed of 1600 rpm, a concrete plate (material age: 1 year, aggregate particle size: 25 mm, plate thickness: 60 mm)
When the drilling work was performed with a dry process, the bit digged concrete while vigorously discharging cutting chips, but a part of the diamond whetstone was broken during the drilling of the first hole, making it impossible to drill. Became.

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

[0031]

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

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

FIG. 3 is a partially cutaway view illustrating a diamond drill bit according to the present invention.

FIG. 4 is a plan view of a distal end portion of FIG. 3;

FIG. 5 is a partially cutaway view showing an example of a conventional diamond drill bit.

FIG. 6 is a plan view of the distal end portion of FIG.

FIG. 7 is a partially cutaway view showing an example of a conventional diamond drill bit.

FIG. 8 is a plan view of the distal end portion of FIG. 7;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Diamond whetstone 2 Slit 3 Grinding stone tip surface 4 Rotation axis 5 Filler 6 Filler embedded part tip 7 Metal body

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Norio Sumida 1770 Hongo, Ebina City, Kanagawa Prefecture Sankyo Diamond Industry Co., Ltd.

Claims (8)

[Claims] 1. A diamond drill bit having a structure in which a diamond grindstone is integrally connected to a tip of the metal body, and a filler is embedded in at least one slit provided in the diamond grindstone. A diamond drill bit characterized in that: 2. The slit provided in the diamond grinding stone has two slits.
The diamond drill bit according to claim 1, wherein the number is from 1 to 6. 3. The diamond drill bit according to claim 1, wherein the filler buried in the slit is made of a material which is more easily worn than the diamond grindstone and has a low coefficient of thermal expansion. 4. The diamond drill bit according to claim 1, wherein said filler is a carbon-based material such as carbon, graphite, carbon fiber, mica, molybdenum disulfide, porous ceramics, or sintered metal powder. 5. The diamond drill bit according to claim 1, wherein the relative area ratio of the grinding wheel surface to the slit of the diamond grinding wheel is 30:70 to 70:30. 6. The diamond drill bit according to claim 1, wherein the diamond grindstone has an outer diameter of 5 to 20 mm, and the metal body has an outer diameter of 98% or less. 7. The diamond drill bit according to claim 1, wherein the metal body has a hollow cylindrical shape provided with a spiral groove along an outer circumference in an axial direction or an inner hole in an axial direction. 8. A plate-shaped filler previously processed to predetermined dimensions is sandwiched between a plurality of diamond layer primary compacts in which metal bonds and diamond abrasive grains are mixed at a predetermined ratio. After setting in the sintering mold,
A method for producing a diamond grindstone for a diamond drill bit, comprising obtaining an integrated structure of a diamond grindstone having a slit without post-processing by sintering under pressure.