JP2007136891A - Drill bit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a drill bit allowing continuation of operation even when a chip is abraded or broken. <P>SOLUTION: A first and second cutting edges 4 and 5 are inclined backward toward an outside diameter, with the second cutting edge 5 inclined more backward than the first cutting edge 4. A recessed part 6b is formed at the back of the first cutting edge 4 and in the outer periphery of the chip 3, and a third cutting edge 6 extending from the recessed part 6b to the outermost part of the chip 3 is provided. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a drill bit having a shank connected to the tip of a power drill or the like and a tip attached to the tip of the shank by brazing or welding.

  In recent years, concrete construction has increased. In concrete construction, it is necessary to drill holes to install anchor bolts. An electric drill equipped with a drill bit is used for this work.

  FIG. 3 shows an example of a conventional drill bit. The drill bit 11 includes a shank portion 12 that is connected to a power drill (not shown) and is driven to rotate, and a tip 13 that is attached to the tip of the shank portion 12 by brazing. The chip 13 is formed with two cutting blades 14 that extend while tilting backward from the tip to the outer periphery, and these cutting blades 14 cut into the work material during the drilling operation.

  In such a drill bit 11, the maximum diameter portion 14a, which is the portion on the outermost diameter side of the cutting blade 14, has the highest rotational speed and performs a large work. In addition, gravel is mixed in the concrete, and the cutting edge 14 may hit the gravel to break the chip 13 and the drilling speed may be significantly reduced. Since the maximum diameter portion 14a of the tip 13 has the highest rotational speed, it is a portion that performs the largest work and is also a portion that is most easily worn or broken.

  Inventions for improving the life of the chip are described in, for example, Patent Document 1 and Patent Document 2.

JP 2001-179518 A Japanese Patent No. 2984446

  However, in these inventions, when the tip is worn or broken, the drilling speed is remarkably reduced and it cannot be used. In this case, the operator determines that the life of the drill bit has been reached, and is forced to replace the drill bit with a new one, resulting in high costs.

  An object of the present invention is to provide a drill bit that solves the above-described problems and can continue work even if the tip is worn or broken.

  The present invention provides a shank portion that is attached to a power drill and is driven to rotate, and a plate-like tip that is attached to the tip of the shank portion. In the drill bit having a tip having two cutting edges, the first and second cutting edges are inclined rearwardly toward the outer diameter direction, and the second cutting edge is the first cutting edge. One feature is that it is configured to be inclined more backward than the first cutting blade.

  A shank portion attached to a power drill and driven to rotate, and a plate-like tip attached to the tip of the shank portion, the first and second extending from the tip of the tip in the outer diameter direction of the tip A drill bit having a cutting edge, and a third cutting edge extending from the concave portion to the maximum outer shape of the tip, provided at the outer periphery of the tip behind the first cutting blade. One feature is to provide a blade.

  According to the first aspect of the present invention, only the first cutting blade cuts into the work material during the drilling operation. Even if the drill bit is inclined with respect to the work material, rubbing does not occur between the second cutting blade and the work material, and the drilling speed does not decrease. Further, the second cutting blade does not wear. If the first cutting edge hits a hard part of the work material and breaks, or if the first cutting edge wears significantly due to prolonged work, the second cutting edge is replaced by the first cutting edge. The cutting material can be cut and the drilling operation can be continued. Therefore, it is possible to provide a drill bit that can continue work even if the tip is worn or broken.

  According to the invention described in claim 2, even when the first cutting blade and the second cutting blade are worn or broken, the third cutting blade cuts into the work material, so that the drilling operation can be continued. it can. Therefore, it is possible to provide a drill bit that can continue work even if the tip is worn or broken.

  A drill bit according to an embodiment of the present invention will be described with reference to FIGS. Since the shank portion of the drill bit is the same as the conventional one, it will be omitted and only the tip 3 that is a characteristic portion of the present invention will be illustrated and described.

  As shown in FIG. 1, the tip 3 includes a first cutting edge 4 extending backward from the tip 3a to the maximum outer diameter 4a at an inclination angle α, and from the tip 3a to the maximum outer diameter 5a. A second cutting blade 5 is formed that extends while tilting backward at an inclination angle β.

  The first cutting edge 4 is inclined rearward at a gentler inclination angle α than the inclination angle β of the second cutting edge 5. That is, the second cutting blade 5 is inclined more backward than the first cutting blade 4. If the two cutting edges 4 and 5 are inclined backward at the same inclination angle, the first cutting edge 4 cuts into the work material due to the inclination of the drill bit with respect to the drill hole, etc. The second cutting blade 5 has an insufficient amount of cut into the work material and only rubs the surface of the work material. Such rubbing between the second cutting edge 5 and the work material not only prevents perforation, but also causes the wear of the second cutting edge 5 to be accelerated.

  On the other hand, in the present invention, as described above, the second cutting blade 5 is inclined more rearward than the first cutting blade 4, so that only the first cutting blade 4 is cut. The material is cut into the material, and the second cutting blade 5 and the work material are not rubbed. As a result, even if the drill bit is tilted with respect to the drilling hole during the operation, the drilling speed does not decrease and the wear of the second cutting edge 5 is not promoted. If the first cutting edge 4 is worn or broken during the drilling operation, the second cutting edge 5 cuts into the work material instead of the first cutting edge 4, and the drill bit is not changed. Drilling can continue.

  A recess 6b is formed behind the first cutting edge 4 (lower side in FIG. 1), and the third cutting edge 6 is formed so as to extend while tilting backward from the recess 6b to the maximum outer diameter part 6a. ing. That is, two cutting edges 4 and 6 are formed on one side surface of the chip 3 so as to be aligned in the front-rear direction. Note that the distances La and Lb from the maximum outer diameter portions 4a, 5a, and 6a to the central axis of the chip 3 are the same so that the drill bit is not shaken during the drilling operation. With this configuration, when the first cutting blade 4 breaks during the drilling operation and the second cutting blade 5 also breaks, the third cutting blade 6 formed on the rear side becomes the second cutting blade. Instead of 5, cut into the work material. Therefore, even if the first cutting blade 4 and the second cutting blade 5 break, the drilling operation can be continued without exchanging the drill bit.

  FIG. 2 also shows a recess 7b and a fourth cutting edge 7 extending rearwardly from the recess 7b to the maximum outer diameter portion 7a while inclining backward from the second cutting edge 5. FIG. The distance Lb from the maximum outer diameter portion 7a to the central axis is the same as the distance La from the other maximum outer diameter portions to the central axis so that the drill bit does not break during the drilling operation. In this manner, the drilling operation can be continued for a longer time by connecting the cutting blades rearward.

The external view of the chip | tip with which the drill bit concerning embodiment of this invention was equipped. The external view of the chip | tip with which the drill bit concerning another embodiment of this invention was equipped. The front view which shows the conventional drill bit.

Explanation of symbols

3 Tip 3a Tip
4 First cutting edge 4a Maximum outer diameter part 5 Second cutting edge 5a Maximum outer diameter part 6 Third cutting edge 6a Maximum outer diameter part 6b Recess 7 Fourth cutting edge 7a Maximum outer diameter part 7b Recess

Claims (2)

A shank attached to a power drill and driven to rotate;
A chip-like chip attached to the tip of the shank part, the chip having first and second cutting edges extending from the tip of the chip in the outer diameter direction of the chip;
Drill bit with
The first and second cutting blades are inclined rearward toward the outer diameter direction, and the second cutting blade is inclined more rearward than the first cutting blade. A featured drill bit. A shank attached to a power drill and driven to rotate;
A chip-like chip attached to the tip of the shank part, the chip having first and second cutting edges extending from the tip of the chip in the outer diameter direction of the chip;
Drill bit with
A drill bit, wherein a recess is provided in an outer peripheral portion of the tip behind the first cutting blade, and a third cutting blade extending from the recess to a maximum outer shape portion of the tip is provided.

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