JPH071218Y2 - Core drill - Google Patents

Description

[Detailed description of the device]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a core drill used for drilling brittle materials such as plate glass and ceramics.

[0002]

2. Description of the Related Art Conventionally, as a tool for punching plate glass such as window glass or ceramics, as shown in FIG. 4, diamond abrasive grains or CBN are attached to the tip of a pipe-shaped base metal 10.
A core drill C in which an annular cutting edge 11 is formed by adhering superabrasive grains such as abrasive grains is often used.

In this core drill C, an annular cutting edge 11 is cut into the glass B while rotating, and a hole is drilled while leaving the core in the center.

[0004]

By the way, as shown in the drawing, the conventional core drill has a cutting blade 11 in which the outer diameter surface and the end surface are formed in a straight shape, and the core drill that comes into surface contact with glass during processing. A large stress acts on the glass B from the end face of. For this reason, when the drilling progresses and the thickness of the remaining glass B becomes thin, the glass B becomes a core drill C.
There is a drawback that it cannot withstand the stress from the inside, and the lower surface side of the glass is damaged at the time of penetration to make a large chip.

Conventionally, in order to prevent such chipping, there have been adopted a method of processing waste glass on the lower side of the glass plate and a method of processing with a core drill from the upper and lower surfaces of the glass plate. The method has a problem that it takes a lot of work time and processing cost.

Further, in the conventional core drill, the entire outer diameter surface of the cutting edge 11 contacts the glass B. Therefore, if the core drill has a runout when it is attached to a machine, a rasping phenomenon of the drill occurs, and the runout directly occurs. There is a problem that affects processing accuracy. Therefore, in order to guarantee the processing accuracy, it is necessary to attach the drill with high accuracy and suppress the runout as much as possible.
The attachment of such a drill has the drawback that the work is extremely laborious.

In view of the above, the present invention has a technical problem to solve the above problems, to provide a core drill capable of suppressing the chipping of a work piece at the time of penetration and making a hole with high machining accuracy.

[0008]

In order to solve the above-mentioned problems, the present invention, as shown in FIG.
An annular cutting edge 2 is formed by adhering superabrasive grains to the tip of the cutting edge 2, the outer diameter surface of the cutting edge 2 is formed in a tapered shape, and the tip portion 2a and the maximum outer diameter portion 2b of the cutting edge are The structure has the arc surfaces 3 and 4.

The cutting edge may be formed by combining the entire outer diameter surface with a plurality of arc surfaces.

[0010]

In the above structure, since the tip of the cutting blade 2 is thin in an arc shape, the area of the workpiece penetrated by the tip is small and the chipping at the time of penetration is small. Further, after the tip portion penetrates, the outer diameter surface of the cutting blade 2 having a gradually increasing diameter is scraped off the through hole, and the maximum outer diameter portion 2 of the blade tip 2 is cut.
When b is completely removed, the chip generated during penetration is removed.

Further, since the outer peripheral surface of the cutting edge 2 tapers the workpiece to advance the drilling, the cutting edge 2 is cut from the workpiece.
The core drill is centered by the cutting force applied to the blade and the rubbing phenomenon of the cutting edge is prevented.

[0012]

FIG. 1 shows a core drill according to the present invention. The base metal 1 is formed of a hard metal such as a thin pipe, and its tip portion 1a is formed in a complex R shape including a plurality of arc surfaces 3 and 4. That is, the tip of the base metal 1 is formed by the circular arc surface 3 having a small radius of curvature R _1, and the rear end side of the circular arc surface 3 is continuous with the circular arc surface 3 and has a large radius of curvature R _2. Is formed, and the outer diameter surface of the tip portion of the base metal 1 is formed in a tapered shape in which the diameter is smoothly reduced from the arc surface 4 to the arc surface 3 as a whole.

Further, an annular cutting edge 2 is formed on the surface of the tip portion 1a of the base metal 1 by adhering diamond abrasive grains by electrodeposition. The maximum outer diameter portion 2b of this cutting edge 2
The (apex portion of the arc surface 4) is dimensioned by truing after forming the abrasive grain layer, and high outer diameter accuracy is ensured.

When glass is drilled using the core drill A of the embodiment having the above structure, the strength T is the weakest in the remaining processed thickness portion T of the glass B as shown in FIG. Since the tip of the cutting blade 2 is thin in an arc shape, the stress applied from the cutting blade 2 to the glass is small. In addition, since the area penetrated by the tip of the cutting blade is small, it is possible to reduce chipping of the glass when the cutting blade penetrates.

After the tip of the cutting blade 2 penetrates, the stress applied from the core drill A to the glass B becomes small, and the outer diameter surface of the cutting blade 2 having a gradually increasing diameter is scraped off to cut the through hole. At the time when the maximum outer diameter portion 2b of the blade 2 is completely removed, most of the chips generated when the tip portion penetrates are removed. Therefore, the chip remaining on the back surface can be significantly reduced.

Further, since the cutting edge 2 of the core drill A progresses the hole while the outer diameter surface taps against the glass B, the core drill is centered by the cutting resistance from the glass and the maximum outer diameter of the cutting edge 2 is reached. At the time when the diameter portion 2b participates in the machining, the influence of the shake at the time of attaching the drill is suppressed as much as possible. Therefore, the machining accuracy of drilling is determined by the maximum outer diameter portion 2b of the cutting edge whose dimensional accuracy is ensured by truing, and high dimensional accuracy can be guaranteed.

FIG. 3 shows another embodiment. In this example,
The tip end of the cutting edge 2'and the maximum outer diameter portion are respectively formed into an arc surface 3,
4 and the two arcuate surfaces 3 and 4 are connected by a straight inclined surface 5. Even if the space between the arcuate surfaces 3 and 4 is formed by the inclined surface 5 as described above, the same effect as described above can be obtained.

<Experimental example> A diamond abrasive having a grain size of 80 mesh is electrodeposited on the tip of a base metal (outer diameter 10 mm, inner diameter 4 mm) having the shape shown in FIG. 1 to form a cutting edge, and the core drill is used. The alumina plate having a thickness of 15 mm was processed with 10 through holes.

As a result of processing, the chippings on the back surface of the 10 through holes were all in the range of 0.2 to 0.8 mm, and the hole diameter tolerance of each through hole had a value within 0.01 mm. Was obtained.

[0020]

[Effects] With the core drill of the present invention having the above-mentioned configuration, the chipping of the back surface of the workpiece can be greatly reduced, and high machining accuracy can be stably assured. Therefore, by using the core drill of the present invention, it is possible to perform drilling and reaming at the same time in through-hole processing, and it is possible to greatly reduce the number of processing steps.

[Brief description of drawings]

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

FIG. 2 is a sectional view showing the processing state of the same.

FIG. 3 is a sectional view showing another embodiment.

FIG. 4 is a sectional view showing a conventional example.

[Explanation of symbols] 1 base metal 2, 2'cutting edge 2a tip part 2b maximum outer diameter part 3, 4 arc surface 5 inclined surface A core drill

Claims (2)

[Scope of utility model registration request] 1. A core drill comprising a pipe-shaped base metal and a super-abrasive grain bonded to the tip thereof to form an annular cutting edge, wherein the outer diameter surface of the cutting edge is formed into a tapered shape. A core drill characterized in that the tip portion and the maximum outer diameter portion are arcuate surfaces. 2. The core drill according to claim 1, wherein the entire outer diameter surface of the cutting edge is formed by combining a plurality of arc surfaces.