JP2000061931A - Core bit having clearance in base metal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable enhancement of the effect of discharge of cut powder, while avoiding an increase in the thickness of a base metal as far as possible, in a core bit having abrasive grains fixed directly on the surface of the base metal. SOLUTION: This core bit 10 has a constitution wherein abrasive grains 16 and 18 are fixed respectively on an end face and inner and outer faces of the fore end part of a cylindrical base metal 12 by a brazing method. In this case, a matrix forming the base metal 12 is constituted of a base part 12a and a bulging part 12c positioned in the end of the base part 12 and having a larger thickness than this part, and the distance between the surface of the base part and that of the bulging part is made to be in the range of being 1/2-1 time as large as the sizes of the abrasive grains.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a core bit used for core removal of asphalt or concrete, geological survey, drilling and the like.

[0002]

2. Description of the Related Art A core bit is provided with a base metal having abrasive grains, which are made of diamond or the like, for boring asphalt, concrete, rock, etc., fixed to its tip.

The type of base metal of the core bit differs depending on the purpose of processing, and it is a surface set type in which a small amount of diamond is mounted on the surface by using a matrix, or a powder metallurgy method by mixing diamond abrasive grains and a metal binder. Known types include an impregnated type that is sintered and an electrodeposition type in which diamond abrasive grains are fixed by an electrodeposition method using a metal such as nickel.

FIG. 6 shows a conventional implementation type core bit. Reference numeral 30 is a cylindrical base metal, 31 is a diamond tip which is annularly arranged on the tip end surface of the base metal 30 with a gap, and 32 is a rotation of a machine. It is a boss for attaching to the shaft.

In use, when cooling water is supplied from the shaft center of the mechanical rotation shaft and rotated at high speed, an object such as concrete is cut into a circular shape by the diamond tip 31, and a cylindrical core is formed by this. The perforation work is performed while storing the inside of the base metal 30.

In recent years, in addition to the one in which the segment tip is fixed to the tip of the cylindrical base metal as described above, a core bit in which abrasive grains are directly fixed to the surface of the base metal tip has been considered. With such a structure, there is no need to mold segment chips or fix segment chips to the base metal, and the base metal can be molded relatively freely according to the purpose of use. is there.

As described above, as a method for directly fixing the abrasive grains to the surface of the base metal tip, there are an electrodeposition method using so-called electroplating and a brazing method using silver solder or the like. Here, the tool by the electrodeposition method has a larger amount of protrusion of abrasive grains than other bond type tools, so it has excellent sharpness and enables high-efficiency grinding.High abrasive grain density results in less wear deformation The accuracy is stable, and when the abrasive layer is a single layer, it has a shorter life than other bond type tools.

[0008]

In addition to the above matters, the core bit has an important performance such as how to efficiently discharge chips. When drilling concrete or the like, if the chips generated at the tip of the core bit are not properly discharged to the outside, not only will the cutting ability drop extremely, but in the worst case, it may even cause burns. In particular, unlike the segment type described above, in the case where the abrasive grains are directly fixed to the base metal, the space (clearance) for discharging the chips is small, and such a phenomenon is remarkable.

As a measure against this, in a structure in which abrasive grains are directly adhered to the surface of a base metal, similar to a segment type, the tip end to which the abrasive grains are adhered is swelled out from the base,
It is conceivable to provide a clearance between the surface of the abrasive grain forming portion and the surface of the base portion on which the abrasive grains are not formed.

On the other hand, in a core bit that requires precision processing, the base metal of the core bit tends to be thinner year by year. For example, a core bit used for anchor bolt drilling has a thickness of about 1.0 mm. Things are required. Therefore, in such a case, if the bulging portion is made too thick as compared with the thickness of the base portion, it is against the demand for precision processing.

The problem to be solved in the present invention is an effective means for enhancing the chip discharging effect in a core bit in which abrasive grains are directly fixed to the surface of a base metal without increasing the base metal thickness as much as possible. To provide.

[0012]

In order to solve the above problems, the present invention provides a core bit in which abrasive grains are fixed to the end surface and inner and outer surfaces of a cylindrical base metal by a brazing method. The base material to be formed is composed of a base portion and a bulge portion located ahead of the base portion and having a thickness larger than that of the base portion, and the distance between the base surface and the bulge portion surface is 1/2 to 1 of the abrasive grain size. It is characterized in that the range is set to 1 time.

The size of the chips generated by perforation is determined by various factors, but the large chips particularly have a great influence on clogging. According to the test by the present inventor, the generation of large chips is found to depend mainly on the particle size of the diamond abrasive grains fixed to the surface of the core bit, and therefore, the large chips are successfully discharged. By doing so, it was found that clogging can be effectively prevented.

When various experiments were repeated based on such knowledge, firstly, the abrasive grains were fixed to the end surface and the inner and outer surfaces of the tip of the base metal by the brazing method, and secondly, the surface of the base portion. It was found that this can be solved by setting the distance between the surface of the bulging portion and the surface of the bulging portion to be in the range of 1/2 to 1 times the grain size of the abrasive grains.

First, the point that the brazing method is adopted will be described. Both the electrodeposition method and the brazing method are known techniques for fixing the abrasive grains to the base metal, but in the case of electrodeposition,
As shown in FIG. 5B, the bonding metal M has the thinnest portion in contact with the abrasive grains D, and is in a state of swelling between the abrasive grains. On the other hand, in the case of brazing, as shown in FIG.
As shown in FIG. 5, the bonded metal M has the thickest portion in contact with the abrasive grains D, and is in a state of being depressed between the abrasive grains. Therefore, the depression serves as a passage for discharging the chips, and the chip discharging effect is superior to that of the electrodeposition.

Further, the chips discharged from the surface to which the abrasive grains are fixed in this manner are discharged to the outside from the space (clearance) formed between the surface of the workpiece and the surface of the base metal. However, as shown in the graph of FIG. 3, as the clearance between the base surface and the bulging surface becomes 1/2 of the abrasive grain diameter D, the chip discharging capacity, that is, the drilling capacity, increases as the clearance increases. When the distance between the surface of the base portion and the surface of the bulging portion exceeds 1 times the grain size of the abrasive grains, the piercing ability is maintained in substantially the same state. Therefore, even if a clearance exceeding 1 time of the abrasive grain size is taken, the thickness of the bulging portion only becomes thicker, and the chip discharging capacity is not so affected. It can be said that the range of 2 to 1 times is an appropriate range for keeping the thickness of the base metal as thin as possible and improving the drilling ability.

The base metal is preferably an iron-based material having a carbon content of 0.8% or less, the base thickness is 1.0 to 3.0 mm, and the bulge thickness is 1.2 to 4.2 mm. It is desirable to set the range.

Diamond or CBN can be used as the abrasive grains, and its grain size is preferably in the range of 0.2 to 0.6 mm, which is suitable for drilling concrete.

Further, there is an angle of 2 between the base and the bulge.
It is desirable to provide a taper of 0 to 60 degrees from the viewpoint that chips are discharged to the outside without staying.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION The core bit of the present invention will be described below in detail with reference to the embodiments shown in the drawings. 1 is an overall perspective view of a core bit according to an embodiment of the present invention, and FIG. 2 is a partial vertical cross-sectional view of the core bit shown in FIG.

In the figure, 10 is a core bit, 12 is a cylindrical base metal forming the main body of the core bit, and this base metal 12 is
A base portion 12a located on the machine side, a bulging portion 12c located at the tip of the base portion 12a and having a larger thickness than the base portion 12a, and a taper portion 12b linearly connecting the base portion 12a and the bulging portion 12c.
It is composed by.

14 attached to the bottom of the base 12a
Is a boss for attaching the core bit 10 to the rotating shaft of the machine, and the inside thereof is hollow so that the grinding fluid can be supplied. 16 and 18 are diamond abrasive grains fixed to the end surface and the inner and outer surfaces of the tip portion of the base metal 12 by a brazing method, and are fixed substantially uniformly to each surface.

In the present embodiment, the abrasive grain size is set to 0.
The above product was manufactured by the following procedure, with the distance between the abrasive grains being 4 mm and the abrasive grain spacing being 0.8 mm. 1. An abrasive is put into a synthetic rubber adhesive (Bond G17: manufactured by Konishi Co., Ltd.) and stirred to apply the adhesive to the surface of the abrasive. 2. A felt-tip pen (φ0.2 mm) on a metal pipe (base metal)
Mark with. 3. Marking is performed at predetermined positions and intervals while looking through with a microscope. 4. Take a grain of adhesive with the needle tip. 5. Place an abrasive with an adhesive on the marked area. 6. Make fine adjustments with the needle tip. 7. It is placed in a drying oven (120 ° C.) for 3 hours to dry the adhesive and fix the abrasive. 8. Silver wax (TB-604A: manufactured by Tokyo Blaze Co., Ltd.) is uniformly applied. 9. It is heated by gas combustion and the silver wax is welded to the base metal.

Next, with reference to FIG. 4 showing the condition of core removal of concrete, the action of the core bit when drilling will be described. In the figure, 20 is a silver wax applied by the brazing method, C is a chip, and arrows show the flows of the grinding liquid.

When the boss 14 of the core bit 10 is attached to a device (not shown) and rotated, concrete is ground into a cylindrical shape by the diamond abrasive grains 16 on the end face of the tip of the base metal 12, and the core is stored in the internal space of the base metal 12. While piercing progresses. At that time, the side surface of the hole is shaved by the diamond abrasive grains 18 on the inner and outer surfaces of the tip of the base metal, and the peripheral friction with the concrete is reduced.

As shown in the partially enlarged view of FIG. 4, the chips C generated by the perforation form an upward flow on the outer peripheral surface of the base metal 12 due to the cooling water injected from the boss 14, which causes the chips to flow to the outside. Although the chips are discharged, the chips are discharged without causing clogging by using the hollow portion in the center of the silver solder 20 fixed by brazing as a passage.

Further, when it passes through the portion provided with the inner and outer surface abrasive grains 18, it passes through the space formed between the base portion 12a of the base metal 12 and the concrete surface. Between the surface of the base portion 12a and 1/2 of the abrasive grain size
Since it has 1 times the clearance, it can be discharged to the outside together with the cooling water without causing clogging.

[Test Example] The core bit (invention) of the present invention shown in FIG. 1 and the basic shape shown in FIG. 1 have a distance (clearance) between the base surface and the bulging surface of the base metal of the present invention. A drilling test of concrete was conducted under the following conditions for a comparative product smaller than the range and a conventional product having no bulging portion. Table 1 shows the specifications of the core bits used in the test, and Table 2 shows the test results.

[0029]   Test condition     Core bit: outer diameter 25 mm     Machine: Electric motor 100V, 10.5A, rotation speed 1000rpm     Drilling method: Wet (cooling water amount 1.5 liters / min)                 Drilling depth 250 mm, manual feed     Work Material: Reinforced Concrete, Thickness 200mm

[0030]

[Table 1]

[0031]

[Table 2]

As can be seen from Table 2, in the invention product, the chips are sufficiently discharged to the outside of the base metal, and the drilling work can be completed efficiently, while the clearance product is smaller than the range of the present invention. , The discharge of chips was good, but the drilling efficiency decreased. Further, in the conventional product, the chips were not discharged during the drilling, clogging occurred and the drilling was impossible, and the excellent drilling ability of the core bit of the present invention was confirmed.

Further, a punching test was conducted on a core bit having a structure similar to that of the invention product by electrodeposition.
The chips could not be sufficiently discharged from the outer surface, and the perforation ability decreased significantly with the passage of time. Furthermore, the abrasive grain holding power was weak, and it was confirmed that some of the abrasive grains had fallen off.

As described above, the abrasive grains are fixed to the end surface and the inner and outer surfaces of the base metal tip portion by the brazing method, respectively, and the distance between the base surface and the bulging portion surface is set to 1 /
According to the core bit of the present embodiment having a range of 2 to 1 times, the chip discharging effect can be enhanced without making the base metal thickness so thick.

[0035]

According to the present invention, the following effects can be obtained.

(1) The base material forming the base metal is composed of a base portion and a bulging portion located ahead of this and having a thickness larger than that of the base portion, and the distance between the base surface and the bulging portion surface is defined by the abrasive grains. By setting the particle size in the range of 1/2 to 1 time, the effect of discharging chips can be enhanced without increasing the thickness of the base metal so much.

(2) The base metal is an iron-based material having a carbon content of 0.8% or less, the base thickness is in the range of 1.0 to 3.0 mm, and the bulging thickness is 1.2 to 4. By setting the range to 2 mm, the chips can be efficiently discharged, and it becomes possible to stably perform highly efficient and highly accurate machining.

(3) If the abrasive grains are diamond or CBN and the grain size is in the range of 0.2 to 0.6 mm, the abrasive grains are suitable for drilling concrete.

[Brief description of drawings]

FIG. 1 is an overall perspective view of a core bit that is an embodiment of the present invention.

FIG. 2 is a partial vertical cross-sectional view of the core bit shown in FIG.

FIG. 3 is a graph showing the relationship between the distance between the surface of the base portion and the surface of the bulging portion and the drilling ability.

FIG. 4 is a cross-sectional view showing a usage state of the core bit shown in FIG.

FIG. 5A is a cross-sectional view showing the fixing state of abrasive grains by the brazing method, and FIG. 5B is a cross-sectional view showing the fixing state of abrasive grains by the electrodeposition method.

FIG. 6 is a partially cutaway front view of a conventional segment type core bit.

[Explanation of symbols]

10 core bits 12 units 12a base 12b taper part 12c bulge 14 Boss 16 Abrasive grain on the end face 18 Abrasive grains on inner and outer surfaces 20 silver wax C chips

Continued front page    (72) Inventor Naoki Toge             210 Takeno, Odaiba, Ukiha-gun, Fukuoka             Noritake Diamond Co., Ltd. (72) Inventor Tetsuya Nonoshita             210 Takeno, Odaiba, Ukiha-gun, Fukuoka             Noritake Diamond Co., Ltd. F-term (reference) 3C069 AA04 BA09 BB01 BB02 BC01                       CA07 DA07 EA01

Claims (3)

[Claims] 1. A core bit in which abrasive grains are fixed to the end surface and inner and outer surfaces of a tip end portion of a cylindrical base metal by a brazing method, respectively, wherein a base material forming the base metal is located at a base and ahead of the base. It consists of a thick bulge,
The core bit is characterized in that the distance between the surface of the base portion and the surface of the bulging portion is in the range of 1/2 to 1 times the grain size of the abrasive grains. 2. The base metal is an iron-based material having a carbon content of 0.8% or less, the base thickness is in the range of 1.0 to 3.0 mm, and the bulging portion has a thickness of 1. The core bit according to claim 1, having a range of 2 to 4.2 mm. 3. The core bit according to claim 1, wherein the abrasive grains are diamond or CBN and the grain size is in the range of 0.2 to 0.6 mm.