JPH11156617A - Diamond core drill - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress vibration during machining and cutting so as to prevent chipping or cracking by forming the annular end surface of a grinding wheel tip to be a concave and convex curved surface displaced in the rotary shaft direction in a core drill having a cylindrical grinding wheel part having diamond abrasive grains provided in the tip of a shank for constituting a rotary shaft. SOLUTION: A diamond core drill 1 is composed of a cylindrical shank 2 with a step as a rotary shaft and a grinding wheel part 3 having diamond abrasive grains provided in the tip thereof. The diamond core drill 1 is provided with a through-hole 4 formed in the center to supply cooling water or slurry liquid for grinding or cutting along the rotary shaft direction. In this core drill 1, the annular cylindrical end surface (lower end surface) of the grinding wheel part 3 is formed to be a smooth and continuous concave and convex curved surface displaced in the rotary shaft direction (vertical direction). Thus, the cooling water or the liked is sufficiently supplied to a cutting part, vibration during machining and cutting is suppressed and the chipping, cracking or the like of a machined surface is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diamond core drill for boring a brittle material such as a sheet glass or a ceramic.

[0002]

2. Description of the Related Art The structure of a conventional diamond core drill is shown in FIG. (A) is a sectional view, and (B) is a side view.
The diamond core drill 20 includes a steel shank 21 constituting a rotating shaft, and a grindstone portion 22 having diamond abrasive grains provided at the tip thereof. A through-hole 23 for supplying cooling water or a slurry liquid for polishing or grinding is formed at the center of the diamond core drill 20 along the rotation axis direction, and the grindstone portion 22 has a substantially cylindrical shape. In this case, the cylindrical end surface 22a of the grindstone portion 22 is an annular flat surface.

However, in this conventional diamond core drill, since the cylindrical end face 22a of the grinding wheel portion 22 is a flat surface, the supply of cooling water or the like to the grinding point at the tip of the grinding wheel portion during drilling is insufficient, so that the grinding wheel is insufficient. Abnormal wear and seizure of the tip of the part are likely to occur.

In order to deal with this point, as shown in FIG. 5, a slit 24 for passing cooling water or slurry liquid may be formed on the cylindrical tip surface of the grinding wheel portion 22 of the diamond core drill 20 in some cases. In this case, the slit 24 was formed in a rectangular shape having a bent corner as shown in a developed view of FIG.

[0005]

However, when the rectangular slit 24 shown in FIG. 5 is provided, it is possible to supply sufficient cooling water or the like to the tip of the grindstone during drilling, and to cause abnormal wear of the tip of the grindstone. Although the seizure is improved, the tip surface of the grindstone becomes a rectangular uneven surface having a bent corner, and a discontinuous step is formed between the flat surface of the convex portion and the slit concave portion.
For this reason, the angular discontinuous bent corners come into contact with the workpiece while rotating, causing unnecessary vibration during drilling,
Chipping, cracking, chipping and cracking occur on the workpiece when the hole penetrates, and the grinding wheel on the machining side also has chipping or cracking at the discontinuously bent corner of its tip. There was a problem of causing damage to the device.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and provides a sufficient supply of cooling water or the like to the tip of a grindstone during grinding, and a work piece side when a hole is penetrated. It is an object of the present invention to provide a diamond core drill that suppresses the occurrence of cracks, chips, cracks, and the like and damage to the tip of a grinding wheel.

[0007]

According to the present invention, there is provided a diamond core drill having a cylindrical grindstone having diamond abrasive grains at a tip of a shank constituting a rotating shaft. Wherein the annular end face is formed of a smoothly continuous concave and convex curved surface that is displaced in the direction of the rotation axis.

[0008] According to this structure, the tip of the grindstone portion having the diamond abrasive grains is formed so as to change in a continuous state without any discontinuous step in the vertical direction (rotation axis direction). A space is created between the machining cutting point at the tip of the diamond core drill and the continuously changing tip shape. Through this space, the cooling water or the like supplied through the through hole at the center of the diamond core drill easily and sufficiently reaches the cutting portion. In addition, since the contact point between the tip of the grindstone and the workpiece comes into contact with a smoothly continuous curved surface, vibration during machining is suppressed, and cracks, chips, cracks, cracks, Damage such as chipping or cracking on the side is suppressed.

[0009]

1A and 1B are a sectional view and a side view of a diamond core drill according to an embodiment of the present invention. The diamond core drill 1 is composed of a steel shank 2 constituting a rotating shaft, and a grindstone portion 3 having diamond abrasive grains provided at the tip thereof. A through hole 4 for supplying cooling water or a slurry for polishing or grinding is formed in the center of the diamond core drill 1 along the rotation axis direction, the shank 2 has a stepped cylindrical shape, and the grinding stone portion 3 is substantially formed. It has an upper ring or sleeve-like cylindrical shape. The tip of the grindstone portion 3 is formed so as to change in the vertical direction (rotational axis direction) in a continuous state without a step. In other words, the annular cylindrical end surface (lower end surface) of the grinding stone portion 3 is formed by a smoothly continuous uneven surface 5 that is displaced in the rotation axis direction (vertical direction).

As shown in the development of FIG. 2A, the concave / convex curved surface 5 may be a curved surface in which a concave portion (valley) 5a and a convex portion (peak) 5b change in a continuous wave shape. As shown in FIG. (B), the concave portion 5a may have a shape in which both ends are arc-shaped curved surfaces and have a flat surface continuous with the curved surface between them, or as shown in FIG. The convex portion 5b may be a curved surface having a flat surface that is continuous with the curved surface. Cooling water or the like is sufficiently supplied to the cutting contact point of the workpiece through the space of the concave portion 5a surrounded by the smooth curved surface, and the workpiece is bent with respect to the rotating grindstone. Grinding while contacting on a smooth continuous curved surface without any.

FIGS. 3A and 3B are a cross-sectional view and a side view showing another embodiment of the present invention. In this embodiment, the grindstone portion 3 has a tapered portion 3a whose diameter increases conically toward the shank direction (upward) at the end (upper end) of the shank 2 side. The tapered portion 3a performs chamfering of the periphery of the opening of the hole when drilling. The other configurations, functions and effects are the same as those of the embodiment of FIG.

[0012]

EXAMPLE A diamond core drill having a diameter of 16.9 mm was formed with a continuous curve so that the shape of the tip portion of the grinding stone portion had six peaks and six valleys, and a glass plate having a thickness of 5 mm was perforated. As a result, a state is obtained in which the cooling water supplied from the center of the diamond core drill is sufficiently supplied to the glass cutting point at the tip of the grindstone through the trough which is vertically concave at the tip of the grindstone of the diamond core drill. In addition, a smooth contact between the glass cutting surface and the grindstone portion was obtained. When this diamond core drill was used to make a hole in 200 pieces of glass, a good hole was obtained without chipping or cracking in the glass being cut.
No chipping or damage was found at the tip of the grindstone.

[0013]

As described above, according to the present invention, the tip of the grindstone portion having diamond abrasive grains has smooth irregularities in a continuous state without any discontinuous steps in the vertical direction (rotation axis direction). Since it is formed so as to change with a curved surface shape, a space is generated in a concave portion between the machining cutting point of the diamond core drill tip and the continuously changed tip shape. Through this space, the cooling water or the like supplied through the through hole at the center of the diamond core drill easily and sufficiently reaches the cutting portion. In addition, since the contact point between the tip of the grindstone and the workpiece comes into contact with a smoothly continuous curved surface, vibration during machining is suppressed, and cracks, chips, cracks, cracks, Damage such as chipping or cracking on the side is suppressed. Thereby, a high quality perforated product is obtained.

[Brief description of the drawings]

FIGS. 1A and 1B are a cross-sectional view and a side view, respectively, of a diamond core drill according to an embodiment of the present invention.

FIGS. 2A, 2B, and 2C are development views of a grindstone unit according to different embodiments of the present invention, respectively.

FIGS. 3A and 3B are a cross-sectional view and a side view, respectively, of a diamond core drill according to another embodiment of the present invention.

FIGS. 4A and 4B are a cross-sectional view and a side view of a conventional diamond core drill, respectively.

5A, 5B, and 5C are a cross-sectional view, a side view, and a development view of a grindstone portion of another conventional diamond core drill, respectively.

[Explanation of symbols]

 1: Diamond core drill 2: Shank 3: Grinding stone part 3a: Tapered part 4: Through hole 5: Concavo-convex curved surface 5a: Concave part 5b: Convex part

Claims (3)

[Claims] 1. A diamond core drill provided with a cylindrical grindstone portion having diamond abrasive grains at the tip of a shank constituting a rotating shaft, wherein an annular end face at the tip of the grinding stone portion is smoothly and continuously displaced in a rotating shaft direction. A diamond core drill characterized by having a curved surface with irregularities. 2. The diamond core drill according to claim 1, wherein the concave or convex portion of the concave and convex surface has a curved surface and a flat surface continuous with the curved surface. 3. The diamond core drill according to claim 1, wherein the grinding stone portion has a tapered portion at the end on the shank side, the diameter of which increases conically in the shank direction.