JPH0893377A - Drill bit - Google Patents

Abstract

PURPOSE: To obtain a drilling bit which eliminates crack accidents at the shank and prolongs the durability. CONSTITUTION: A drilling bit is fixed to the recess opened to the front end of a columnar shank body by pressing-in of a circular cylindrical carbide tip or brazing thereof. The sectional area in which the area of the inner diameter of the recess 3 is subtracted from the area of the outer diameter D1 of the columnar shank body, is regarded as X and the sectional area of the outer diameter of the carbide tip inserted and fixed in the recess opened to the front face of the columnar shank body is regarded as Y. The relation between X and Y is regarded as Y/X=Z. In this case, Z is set within the range of 0.20-0.45 to greatly reduce the crack accidents of the shank.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drill bit mounted on the front end of a drill head of an excavator and used as a drill bit.

[0002]

2. Description of the Related Art As an example of an excavating blade attached to the front end of an excavating head of an excavator, the one shown in FIG. 2 is conventionally known. The drill bit 1 shown in this figure is used by being attached to the front end of the excavator. However, the drill bit 1 has a cemented carbide tip 4 that is stuck and stuck to the shank body 2'during use. However, since it became unusable at an early stage, exchanging excavation bits was often troublesome.

[0003]

Therefore, as a result of an investigation on the cause of cracking of the shank body 2 during use of the conventional drilling bit, it is found that the shank outer diameter D1 and the outer diameter D2 of the cemented carbide tip to be inserted. It was found that many of them have a small difference in cross-sectional area and that the rate of crack generation is high in the one having a small corner R on the bottom surface of the recess 3 into which the cemented carbide tip 4 is inserted.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and a columnar cemented carbide tip 4 is press-fitted or brazed into a recess 3 which is open at the tip of a columnar shank body 2. In the case of the fixed drill bit 1, the relationship between the cross-sectional area X obtained by removing the area of the recess inner diameter D2 from the area of the outer diameter D1 of the shank body 2 and the cross-sectional area Y of the outer diameter D3 of the cemented carbide tip 4 is expressed as Y / When X = Z, the value of Z is 0.20
The value of the corner R on the bottom surface of the concave portion 3 formed in the shank body 2 while being formed in the range of 0.45 is R = D × 0.075 to 0.22
It is 5 mm.

[0005]

In the drill bit 1 of the present invention, the shank body 2 for holding the carbide tip 4 has a strong wall thickness and an economical thickness, so that the shank body 2 does not crack. The purpose is to provide.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a side view of a drill bit 1 according to the present invention, in which a columnar shank body 2 is provided with a recessed portion 3 opened at the tip thereof and a cylindrical cemented carbide tip 4 is fixed thereto by press fitting or brazing. It is a drill bit 1. In this excavating bit 1, there are many accidents in which a crack enters the vicinity of the bottom surface of the concave portion 3 during excavation and is cut off and falls off. The removed cross-sectional area (A-A cross section) is defined as X, and the cross-sectional area (BB) of the outer diameter D3 of the cylindrical cemented carbide tip 4 inserted and fixed in the concave portion 3 opening in the front surface of the columnar shank main body 2.
When the cross section) is Y and the relation between X and Y is Y / X = Z, when the value of Z is in the range of 0.20 to 0.345, cracks are generated in the drill bit 1. The cutting accident will be resolved, so X, Y, Z should be within this value.
Are specified respectively. The value of Z is 0.2
If it is less than 0, it is highly probable that cracks will be generated from the shank portion, so it is better not to use it as much as possible. Further, when the value of Z is larger than 0.45, the strength becomes high and there is no problem. However, since the material may be wastefully wasted, it is preferable to mold within the numerical value as much as possible. Also, the corner of the bottom of the recess 3
It is better that R is as large as possible, but preferably a corner
R may be molded in the range of R = D2 × 0.075 to 0.225. Further, the length L of the cylindrical carbide tip 4 is L = (D1
× 1.25) ± 20% is preferable in terms of strength and life.

[0007]

As described above, according to the present invention, a drill bit 1 having a columnar cemented carbide tip 4 fixed by press fitting or brazing to a recess 3 opened at the tip of a columnar shank body 2.
The cross-sectional area of the columnar shank body 2 excluding the area of the outer diameter D1 of the inner diameter D2 of the recess 3 is defined as X, and the columnar shank body 2 is inserted and fixed in the recess 3 opened at the front end. When the cross-sectional area of the outer diameter D3 of the cylindrical carbide tip 4 is Y and the relationship between X and Y is Y / X = Z, the value of Z is in the range of 0.20 to 0.45. And forming the corner R of the bottom surface of the recess 3 in the range of R = D2 × 0.075 to 0.225, and the relationship between the length L of the cemented carbide tip 4 and the outer diameter D1 of the shank body 2. L = (D1 × 1.25) ±
Since it is set in the range of 20%, there is an advantage that the falling accident due to the crack of the drill bit 1 is eliminated, and the tool life is significantly extended.

[Brief description of drawings]

FIG. 1 is a side sectional view of a drill bit according to the present invention.

FIG. 2 is a side view of a conventional drill bit.

FIG. 3 is the outer diameter D1 of the shank body of the drill bit of the present invention.
A-A view for showing the cross-sectional area of FIG.

FIG. 4 is a BB view for showing the cross-sectional area of the outer diameter D3 of the cemented carbide tip mounted on the drill bit of the present invention.

[Explanation of symbols]

 1 drill bit 2 pillar-shaped shank body 3 recess 4 carbide tip

Claims (3)

[Claims] 1. In a drill bit having a columnar cemented carbide tip fixed by press fitting or brazing to a recess opening at the tip of a columnar shank body, a recess is formed from the area of the outer diameter D1 of the columnar shank body. Let X be the cross-sectional area excluding the area of the inner diameter D2, and let Y be the cross-sectional area of the outer diameter D3 of the cemented carbide tip inserted and fixed in the concave portion opened in the columnar shank body.
And when Y / X = Z, the value of Z is 0.20 to 0.
Drilling bit characterized by a range of 45. 2. The length L of a cemented carbide tip inserted and fixed in a recess opening at the tip of a columnar shank body is L =
The drill bit according to claim 1, wherein the range is (D1 x 1.25) ± 20%. 3. A corner R on the bottom surface of a cemented carbide tip that is inserted and fixed in a recess opening at the tip of a columnar shank body.
Is R = D2 * 0.075-0.225 mm, The drill bit according to claim 1 or 2, characterized in that