JP2000190323A - Drill bit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a drill bit adapted to a rotary hammer drill easy to position with a good drilling efficiency in the case of drilling a concrete, a stone material or the like. SOLUTION: The drill bit comprises three cutting edges 4a, 4b, 4c equidistantly distributed in a circumferential direction at a cutting blade tip 4 made of a cemented carbides for constituting the cutting edges of the bit, and main cutting edges 8 and auxiliary cutting edges 9 formed at the edges 4a, 4b and 4c and crossed at a cutting edge top 10. The top is formed in a sharpened end shape having no chisel point.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drill bit in which a cutting edge tip made of a cemented carbide is fixed to the tip of a bit body by brazing, welding, or the like. The present invention relates to a drill bit suitable for the above.

[0002]

2. Description of the Related Art A special drill bit is attached to a rotary hammer drill for drilling a concrete or stone material, and simultaneously exerts both an axial vibrational impact force and a rotational torque on the drill bit. Perforations have been made. And, in order to meet the demand for higher efficiency of drilling work, as a cutting edge of a drill bit used for this kind of drilling, a cutting edge tip made of cemented carbide having excellent wear resistance is brazed to the tip of the bit body. What is fixed by welding or welding is often used. For example, in Japanese Patent Application Laid-Open No. Hei 7-180463, a cutting blade tip is provided at the tip of a bit body, the cutting blade tip has a rectangular cross section, and a main cutter is formed along one diagonal of the cutting diagonal. A configuration is disclosed in which two auxiliary cutters are formed in such a manner that a chisel edge is formed at their apexes and connected to each other.

[0003]

By the way, generally,
Drilling (cutting) has the following problems.

[0004] That is, in the drilling operation by a drill, the drill has a fatal limit on the bending and torsional rigidity, and thus the accuracy of the completed drill hole is limited. In addition, since the drill has a chisel edge at the center of the cutting edge, when cutting resistance is applied to the tip of the drill during drilling, the drill is relatively easily bent, and both ends of the chisel edge are alternately drilled. In this case, since the length of the chisel edge is constant, a regular polygon including an isosceles triangle between diagonals, that is, a regular triangle, a regular pentagon, etc. This results in a rifle on the wall of the drill hole. That is, rifling occurs, and the properties as a drill hole deteriorate.

[0005] For example, when drilling a hole for anchor bolts used for fixing a structure or the like to solidified concrete later using a special drill bit with a rotary hammer drill, a cutting edge is required. When drilling with a drill bit with a chisel edge at the center, rifling occurs and the roundness of the drill hole decreases, and a fixed diameter hole suitable for anchor bolt planting is not obtained, and the anchor bolt is pulled out after planting There is a surface whose strength is considerably affected. In addition, with a drill bit having a chisel edge, positioning becomes difficult, and the drilling accuracy also decreases from this surface.

[0006]

Therefore, in order to solve the above-mentioned problems, a drill bit according to the present invention comprises:
Three cutting blades are equally distributed in the circumferential direction on a cutting edge chip made of a cemented carbide block body, and the main cutting line between the cutting surface and flank formed on each cutting edge is cut. An edge, a joining line between the connecting surface and the flank is an auxiliary cutting edge, and the main cutting edge and the auxiliary cutting edge intersect at a cutting edge apex, and the cutting edge apex has a pointed shape without chisel points. .

According to the drill bit configured as described above, the conventional drill bit eliminates the chisel edge which is indispensable from the structural point of view. The roundness can be improved. In particular, when drilling holes for anchor bolts used for fixing structures and the like to solidified concrete later using a rotary hammer drill, as in the present invention, the chisel edge is Without forming a main cutting edge and an auxiliary cutting edge on each of the three cutting edge portions and intersecting them at the apex of the cutting edge to form a pointed shape, a rifling does not occur in the drill hole at the time of drilling, and The rotation balance is good and the roundness of the drill hole can be improved. In addition, since the tip of the cutting edge of the pointed structure always corresponds to the center of the drill hole cutting surface, the cutting edge is instantaneously levitated from the drill hole cutting surface and immediately hits with an impact (cutting cutting). Even in the case of drilling, positioning can be easily performed, and a highly accurate fixed-diameter hole with a hole diameter error within an allowable value can be easily drilled, and workability is excellent.

[0008] When drilling in concrete, stone, etc., the drilled hole cutting surface in the middle of drilling forms an uneven rough surface, on which chips are also left. Therefore, if massive chips are caught between the drilled hole cutting surface and the cutting edge of the drill bit during impact cutting, the cutting edge of the drill bit receives biased resistance, disrupts rotational balance, and may cause runout. There is.

Therefore, if a configuration is adopted in which the auxiliary cutting edge is set on an extension of the main cutting edge of the cutting edge portion facing the cutting edge apex, substantially three cutting edges are used as the cutting edge of the drill bit. Since the main cutting edge and the auxiliary cutting edge formed respectively on the part are alternately arranged at equal intervals of 60 degrees and are arranged radially from the apex of the cutting edge, in the case of impact cutting, the drilling hole cutting surface and the cutting edge The massive chips interposed between the adjacent cutting edges and auxiliary cutting edges cooperate to effectively and finely crush them, reducing the biased resistance applied to the cutting edge, so that there is no bit deviation, Higher drilling accuracy from the surface.

A main cutting edge and an auxiliary cutting edge;
In addition, by setting the joining line between the joining surface and the cutting surface that intersect at the cutting edge apex to be straight, the finishing accuracy of the entire cutting edge is improved from the drill bit manufacturing surface, and a high-quality drill bit (product)
Can be provided.

The recess formed between the cutting blades is made continuous with the corresponding chip discharge groove of the drill body. This recessed surface is formed into one continuous surface having a flat surface at both ends of the arc surface. Formed, the concave surface corresponding to the connecting surface is an arc surface,
On the cutting surface side, the radius of curvature of the concave arc surface is such that the joining line end of the joining surface and the cutting surface intersects at the midpoint of the concave arc surface edge, and on the flank side, the auxiliary cutting edge end intersects the concave arc edge. Is preferably set. With this configuration, the chips used for drilling concrete, stone, etc., are smoothly guided through the recessed portions to the chip discharge grooves of the bit body, so that the chips are not stagnated at the cutting edge portion. Increase efficiency.

[0012] Further, as a drill bit used for drilling in concrete or stone, etc., the circumferential thickness at the edge of the cutting edge of the cutting edge is set to about 0.2 to 0.5 times the cutting edge diameter, In addition, it is preferable that the apparent width in the circumferential direction of the cutting surface at each cutting edge is set to be about 0.2 to 0.5 times the circumferential thickness of the cutting edge at the edge of the cutting edge. With such a configuration, the strength of the cutting edge tip can be sufficiently maintained at the time of drilling with impact cutting, and stable drilling is realized.

Further, as a drill bit used for drilling in concrete or stone material, the core diameter of the bit body 1 is practically set to about 0.3 to 0.7 times the cutting edge diameter. The tip height at the edge of the blade is preferably set to about 0.2 to 0.5 times the edge diameter. With this configuration, in drilling with impact cutting, the sliding contact resistance between the outer peripheral surface of the cutting edge portion and the drill hole wall is reduced, the drilling efficiency is increased, and the drilling accuracy can be improved.

Further, a concave portion for confirming the wear of the cutting edge diameter can be provided on the outer peripheral surface of each cutting blade portion. With this configuration, the wear progress of the cutting edge tip can be checked at a glance by seeing the wear of the concave portion for checking the cutting edge diameter wear, and the operator can use the measuring tool without using any special measuring tools. In addition, it is possible to easily form a fixed diameter hole having a hole diameter error within an allowable value. The drill hole thus drilled in concrete, stone, or the like is used for anchor bolt planting or the like, and does not affect the pull-out strength of the anchor bolt after planting.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

In the drawings, FIG. 1 is a front view in which a part of a drill bit according to an embodiment of the present invention is omitted, FIG. 2 is an enlarged front view of a cutting edge portion of the drill bit, and FIG. 3 is a lower end view of the drill bit. It is.

In FIG. 1, reference numeral 1 denotes a steel bit body.
A shank 2 connected to a drive shaft (not shown) is extended on the upper part thereof, a chip discharge groove 3 is provided on the outer periphery of the bit body, and a cemented carbide cutting tip 4 made of a block body is provided at the tip of the bit body. It is fixed by brazing or welding.

2 and 3, the cutting edge tip 4 of the embodiment is described in more detail. As shown in FIG. 3, the cutting edge tip 4 has a circumferential angle of 120 degrees. Three cutting blades 4a, 4b, 4c are formed equally in the direction,
A cutting surface 5 and a flank 6 are formed on each of the cutting blades 4a, 4b and 4c, and a connecting surface between the flank 6 and the cutting surface 5 between the adjacent cutting blades 4a, 4b and 4c. 7 are formed. In each of the cutting edges 4a, 4b, and 4c, the joining line between the cutting surface 5 and the flank 6 is defined as the main cutting edge 8, and the joining line between the flank 6 and the joining surface 7 is defined as the auxiliary cutting edge 9.
Further, the main cutting edge 8 and the auxiliary cutting edge 9 of each of the cutting edge portions 4a, 4b, 4c are crossed at the cutting edge vertex 10, so that the cutting edge vertex 10 has a pointed shape without chisel points.

The joining line 11 between the main cutting edge 8 and the auxiliary cutting edge 9 and the joining surface 7 and the cutting surface 5 that intersect at the cutting edge vertex 10 is set to be a straight line, and the auxiliary cutting edge 9 sandwiches the cutting edge vertex 10. Are set on the extension line of the main cutting edge 8 of the cutting edge portion facing the above.

In this way, the three main cutting edges 8 and the three auxiliary cutting edges 9 forming the cutting edge of the drill bit are alternately arranged at equal intervals of 60 degrees in the radial direction from the cutting edge apex 10.

The recess 12 formed between each of the cutting blades 4a, 4b, 4c is continuous with the corresponding chip discharge groove 3, and the recesses have two flat surfaces 12 on both sides of the arc surface 12a.
b and 12c are formed on one continuous surface.
Then, the flat surface 12b is made parallel to the main cutting edge 8 on the cutting surface 5 side, and the concave surface corresponding to the connecting surface 7 is formed into an arc surface 12a.
The radius of curvature R of the concave arc surface 12a is determined by setting the end of the joining line 11 between the joining surface 7 and the cutting surface 5 at the cutting surface 5 side at the midpoint of the concave arc surface edge, and assisting on the flank 6 side. The edge of the cutting edge 9 is set to intersect at the arc edge of the concave portion.

In addition, the dimensional ratio of each part of the cutting edge is
The settings are as follows.

The circumferential thickness W of each of the cutting edges 4a, 4b, 4c at the end of the cutting edge is defined as 0.2 to 0.
Make it about 5 times. (Refer to FIG. 3) The apparent width W ′ of the cutting surface 5 in each of the cutting edges 4a, 4b, 4c in the circumferential direction is set to 0.2 to 0. Make it about 5 times. (See FIG. 3) The core diameter ΦB of the bit body 1 is set to 0.3 to
Make it about 0.7 times. (See FIG. 3) The tip height H at the end of the cutting edge is set to about 0.2 to 0.5 times the cutting edge diameter ΦA. (See FIG. 2) Further, a recess 13 for confirming the wear of the cutting edge diameter is provided on the outer peripheral surface of each of the cutting blade portions 4a, 4b, 4c.

[0024]

The present invention is embodied in the form as described above. According to the present invention, the basic configuration of the bit body of the drill bit is the same as that of the well-known type of drill bit. Can be used as it is by replacing it with a known drill bit.

However, in the drill bit of the present invention, three cutting edge portions are formed on the cutting edge tip at equal intervals in the circumferential direction, and the conventional drill bit is indispensable from the structural point of view. Since the chisel edge is eliminated, rifling does not occur in the drill hole at the time of drilling, the rotation balance is good, and the roundness of the drill hole can be improved.

Further, since the tip of the cutting edge of the pointed structure always corresponds to the center of the cutting surface of the drill hole, the cutting edge instantaneously floats from the cutting surface of the drill hole and immediately hits it with impact (impact cutting). ), It is possible to easily form a fixed-diameter hole with high positioning accuracy and a hole diameter error within an allowable value.

In addition, even if massive chips are caught between the drill hole cutting surface and the cutting edge during impact cutting, the adjacent main cutting edge and auxiliary cutting edge cooperate to finely crush the chip, thereby cutting the cutting edge. Since the biased resistance applied to the hole is reduced, the bit is not shaken and the drilling accuracy is increased.

Furthermore, since the degree of wear of the cutting edge tip can be checked at a glance from the degree of wear of the concave portion for confirming the wear of the cutting edge diameter, the operator can use the measuring tool without using special measuring tools.
It is possible to easily drill a fixed diameter hole having a hole diameter error within an allowable value.

Therefore, it is suitable as a drill bit for drilling an anchor bolt planting hole used for fixing a structure or the like later to concrete solidified by using a rotary hammer drill. It does not affect the pull-out strength of the anchor bolt after planting by using it for planting bolts.

[Brief description of the drawings]

FIG. 1 is a front view in which a part of a drill bit according to an embodiment of the present invention is omitted.

FIG. 2 is an enlarged front view of a cutting edge of a drill bit.

FIG. 3 is a bottom view of a cutting edge of a drill bit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Bit body 2 Shank 3 Chip discharge groove 4 Cutting edge tip 4a Cutting edge 4b Cutting edge 4c Cutting edge 5 Cutting surface 6 Relief surface 7 Joining surface 8 Main cutting edge 9 Auxiliary cutting edge 10 Tip vertex 11 Joint line 12 Concave Insertion part 12a Arc surface 12b Plane 12c Plane 13 Recess for confirming wear of cutting edge diameter

[Procedure amendment]

[Submission date] November 15, 1999 (1999.11.
15)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Full text

[Correction method] Change

[Correction contents]

[Document Name] Statement

[Title of the Invention] Drill bit

[Claims]

2. A concave surface formed between each cutting edge portion is formed as one continuous surface in which a flat surface is continuous at both ends of an arc surface, and a concave surface corresponding to a connecting surface is formed into an arc surface, and cutting is performed. On the surface side, the radius of curvature of the concave arc surface is adjusted so that the joining line end of the joining surface and the cutting surface intersect at the midpoint of the concave arc surface edge, and on the flank side, the auxiliary cutting edge end intersects the concave arc edge. The drill bit according to claim 1, wherein the drill bit is set.

3. The thickness W of each cutting edge 4a, 4b, 4c in the circumferential direction at the end of the cutting edge is set to about 0.2 to 0.5 times the cutting edge diameter ΦA. The drill bit according to 1 or 2 .

4. The apparent width W 'of the cutting surface 5 in each of the cutting edges 4a, 4b, 4c in the circumferential direction is set to 0.2 to 0.0 of the circumferential thickness W of the cutting edge at the cutting edge. The drill bit according to any one of claims 1 to 3 , wherein the drill bit is set to about five times.

5. A core diameter ΦB of the bit body 1, a drill bit according to claim 1-4 any one of claims, characterized in that set to 0.3 to 0.7 times the blade diameter .PHI.A.

6. tip height H at the cutting edge end, the drill bit of claim 1 to 5 any one of claims, characterized in that set to 0.2 to 0.5 times the blade diameter ΦA .

7. The outer peripheral surface of each cutting edge, the drill bit according to claim 1, characterized in that a cutting edge diameter wear confirmation recess.

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drill bit in which a cutting edge tip made of a cemented carbide is fixed to the tip of a bit body by brazing, welding, or the like. The present invention relates to a drill bit suitable for the above.

[0002]

2. Description of the Related Art A special drill bit is attached to a rotary hammer drill for drilling a concrete or stone material, and simultaneously exerts both an axial vibrational impact force and a rotational torque on the drill bit. Perforations have been made. And, in order to meet the demand for higher efficiency of drilling work, as a cutting edge of a drill bit used for this kind of drilling, a cutting edge tip made of cemented carbide having excellent wear resistance is brazed to the tip of the bit body. What is fixed by welding or welding is often used. For example, in Japanese Patent Application Laid-Open No. Hei 7-180463, a cutting blade tip is provided at the tip of a bit body, the cutting blade tip has a rectangular cross section, and a main cutter is formed along one diagonal of the cutting diagonal. A configuration is disclosed in which two auxiliary cutters are formed in such a manner that a chisel edge is formed at their apexes and connected to each other.

[0003]

By the way, generally,
Drilling (cutting) has the following problems.

[0004] That is, in the drilling operation by a drill, the drill has a fatal limit on the bending and torsional rigidity, and thus the accuracy of the completed drill hole is limited. In addition, since the drill has a chisel edge at the center of the cutting edge, when cutting resistance is applied to the tip of the drill during drilling, the drill is relatively easily bent, and both ends of the chisel edge are alternately drilled. In this case, since the length of the chisel edge is constant, a regular polygon including an isosceles triangle between diagonals, that is, a regular triangle, a regular pentagon, etc. This results in a rifle on the wall of the drill hole. That is, rifling occurs, and the properties as a drill hole deteriorate.

[0005] For example, when drilling a hole for anchor bolts used for fixing a structure or the like to solidified concrete later using a special drill bit with a rotary hammer drill, a cutting edge is required. When drilling with a drill bit with a chisel edge at the center, rifling occurs and the roundness of the drill hole decreases, and a fixed diameter hole suitable for anchor bolt planting is not obtained, and the anchor bolt is pulled out after planting There is a surface whose strength is considerably affected. In addition, with a drill bit having a chisel edge, positioning becomes difficult, and the drilling accuracy also decreases from this surface.

[0006]

Therefore, in order to solve the above-mentioned problems, a drill bit according to the present invention comprises:
Three cutting blades are equally distributed in the circumferential direction on a cutting edge chip made of a cemented carbide block body, and the main cutting line between the cutting surface and flank formed on each cutting edge is cut. and edge, the joining line between the connection surface and the flank and the auxiliary cutting edge, these main cutting edges and the auxiliary cutting edge is crossed by the cutting edge vertices, the cutting edge destination vertices without apex shape of the chisel point, the auxiliary switching
The main cutting of the cutting edge that faces the cutting edge with the cutting edge vertex in between
Main cutting edge and auxiliary cutting set on the extension of the edge
Between the cutting surface and the connecting surface that intersects the edge
The joint line is set to be a straight line .

According to the drill bit configured as described above, the conventional drill bit eliminates the chisel edge which is indispensable from the structural point of view. The roundness can be improved. In particular, when drilling holes for anchor bolts used for fixing structures and the like to solidified concrete later using a rotary hammer drill, as in the present invention, the chisel edge is Without forming a main cutting edge and an auxiliary cutting edge on each of the three cutting edge portions and intersecting them at the apex of the cutting edge to form a pointed shape, a rifling does not occur in the drill hole at the time of drilling, and The rotation balance is good and the roundness of the drill hole can be improved. In addition, since the tip of the cutting edge of the pointed structure always corresponds to the center of the drill hole cutting surface, the cutting edge is instantaneously levitated from the drill hole cutting surface and immediately hits with an impact (cutting cutting). Even in the case of drilling, positioning can be easily performed, and a highly accurate fixed-diameter hole with a hole diameter error within an allowable value can be easily drilled, and workability is excellent.

[0008] Further , when drilling in concrete, stone, or the like, the drilled hole cutting surface during drilling forms an uneven rough surface, on which chips are also left. Therefore, at the time of impact cutting,
When massive chips are sandwiched between the drill hole cutting surface and the drill bit tip, the cutting edge of the drill bit destroys the rotational balance by receiving a biased resistance, although it may cause blurring, the auxiliary cutting edges , By setting on the extension of the main cutting edge of the cutting edge part facing the cutting edge apex ,
As the cutting edge of the drill bit, the main cutting edge and the auxiliary cutting edge formed on each of the three cutting edges are substantially alternately arranged at equal intervals of 60 degrees in the radial direction from the cutting edge apex. Therefore, at the time of impact cutting, the massive chips interposed between the drill hole cutting surface and the cutting edge, the adjacent main cutting edge and auxiliary cutting edge cooperate to effectively crush it, and the cutting edge is Since the biased resistance received is reduced, there is no bit wobble, and the drilling accuracy is also increased from this surface.

A main cutting edge and an auxiliary cutting edge;
Further, by setting the joining line between the joint surface and the cutting surface that intersect at the cutting edge vertex to be a straight line, it is possible to provide a high quality drill bit (product) by increasing the finishing accuracy of the entire cutting edge from the drill bit manufacturing surface.

The recess formed between the cutting blades is continuous with the corresponding chip discharge groove of the drill body. This recess is formed into one continuous surface having a flat surface at both ends of the arc surface. Formed, the concave surface corresponding to the connecting surface is an arc surface,
On the cutting surface side, the radius of curvature of the concave arc surface is such that the joining line end of the joining surface and the cutting surface intersects at the midpoint of the concave arc surface edge, and on the flank side, the auxiliary cutting edge end intersects the concave arc edge. Is preferably set. With this configuration, the chips used for drilling concrete, stone, etc., are smoothly guided through the recessed portions to the chip discharge grooves of the bit body, so that the chips are not stagnated at the cutting edge portion. Increase efficiency.

[0011] Further, as a drill bit used for drilling in concrete or stone, etc., the circumferential thickness at the edge of the cutting edge of the cutting edge is set to about 0.2 to 0.5 times the diameter of the cutting edge. In addition, it is preferable that the apparent width in the circumferential direction of the cutting surface at each cutting edge is set to be about 0.2 to 0.5 times the circumferential thickness of the cutting edge at the edge of the cutting edge. With such a configuration, the strength of the cutting edge tip can be sufficiently maintained at the time of drilling with impact cutting, and stable drilling is realized.

Further, as a drill bit used for drilling in concrete, stone, or the like, the core diameter of the bit body 1 is practically set to about 0.3 to 0.7 times the cutting edge diameter. The tip height at the edge of the blade is preferably set to about 0.2 to 0.5 times the edge diameter. With this configuration, in drilling with impact cutting, the sliding contact resistance between the outer peripheral surface of the cutting edge portion and the drill hole wall is reduced, the drilling efficiency is increased, and the drilling accuracy can be improved.

Further, a recess for confirming the wear of the cutting edge diameter can be provided on the outer peripheral surface of each cutting edge. With this configuration, the wear progress of the cutting edge tip can be checked at a glance by seeing the wear of the concave portion for checking the cutting edge diameter wear, and the operator can use the measuring tool without using any special measuring tools. In addition, it is possible to easily form a fixed diameter hole having a hole diameter error within an allowable value. The drill hole thus drilled in concrete, stone, or the like is used for anchor bolt planting or the like, and does not affect the pull-out strength of the anchor bolt after planting.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

1 is a front view of a drill bit according to an embodiment of the present invention with a part of the drill bit omitted, FIG. 2 is an enlarged front view of a cutting edge of the drill bit, and FIG. 3 is a bottom view of the drill bit. It is.

In FIG. 1, 1 is a steel bit body,
A shank 2 connected to a drive shaft (not shown) is extended on the upper part thereof, a chip discharge groove 3 is provided on the outer periphery of the bit body, and a cemented carbide cutting tip 4 made of a block body is provided at the tip of the bit body. It is fixed by brazing or welding.

2 and 3, the cutting edge tip 4 according to the embodiment will be described in more detail. As shown in FIG. 3, the cutting edge tip 4 has a circumferential angle of 120 degrees as shown in FIG. Three cutting blades 4a, 4b, 4c are formed equally in the direction,
A cutting surface 5 and a flank 6 are formed on each of the cutting blades 4a, 4b and 4c, and a connecting surface between the flank 6 and the cutting surface 5 between the adjacent cutting blades 4a, 4b and 4c. 7 are formed. In each of the cutting edges 4a, 4b, and 4c, the joining line between the cutting surface 5 and the flank 6 is defined as the main cutting edge 8, and the joining line between the flank 6 and the joining surface 7 is defined as the auxiliary cutting edge 9.
Further, the main cutting edge 8 and the auxiliary cutting edge 9 of each of the cutting edge portions 4a, 4b, 4c are crossed at the cutting edge vertex 10, so that the cutting edge vertex 10 has a pointed shape without chisel points.

The joining line 11 between the main cutting edge 8 and the auxiliary cutting edge 9 and the joining surface 7 and the cutting surface 5 intersecting at the cutting edge apex 10 is set to be a straight line, and the auxiliary cutting edge 9 sandwiches the cutting edge apex 10. Are set on the extension line of the main cutting edge 8 of the cutting edge portion facing the above.

In this way, the three main cutting edges 8 and the three auxiliary cutting edges 9 forming the cutting edge of the drill bit are alternately arranged at equal intervals of 60 degrees in the radial direction from the cutting edge vertex 10.

The recess 12 formed between the cutting blades 4a, 4b, 4c is continuous with the corresponding chip discharge groove 3, and the recesses have two flat surfaces 12 on both sides of the arc surface 12a.
b and 12c are formed on one continuous surface.
Then, the flat surface 12b is made parallel to the main cutting edge 8 on the cutting surface 5 side, and the concave surface corresponding to the connecting surface 7 is formed into an arc surface 12a.
The radius of curvature R of the concave arc surface 12a is determined by setting the end of the joining line 11 between the joining surface 7 and the cutting surface 5 at the cutting surface 5 side at the midpoint of the concave arc surface edge, and assisting on the flank 6 side. The edge of the cutting edge 9 is set to intersect at the arc edge of the concave portion.

In addition, the dimensional ratio of each part of the blade is
The settings are as follows. The thickness W in the circumferential direction at the edge of the cutting edge of each cutting edge 4a, 4b, 4c is set to be about 0.2 to 0.5 times the cutting edge diameter ΦA. (Refer to FIG. 3) The apparent width W ′ of the cutting surface 5 in each of the cutting edges 4a, 4b, 4c in the circumferential direction is set to 0.2 to 0. Make it about 5 times. (See FIG. 3) The core diameter ΦB of the bit body 1 is set to 0.3 to
Make it about 0.7 times. (See FIG. 3) The tip height H at the end of the cutting edge is set to about 0.2 to 0.5 times the cutting edge diameter ΦA. (See FIG. 2) Further, a recess 13 for confirming the wear of the cutting edge diameter is provided on the outer peripheral surface of each of the cutting blade portions 4a, 4b, 4c.

[0022]

The present invention is embodied in the form as described above. According to the present invention, the basic configuration of the bit body of the drill bit is the same as that of the well-known type of drill bit. Can be used as it is by replacing it with a known drill bit.

However, in the drill bit of the present invention, three cutting edge portions are formed in the cutting edge tip at equal intervals in the circumferential direction, and the conventional drill bit is indispensable from the structural aspect. Since the chisel edge is eliminated, rifling does not occur in the drill hole at the time of drilling, the rotation balance is good, and the roundness of the drill hole can be improved.

Further, since the tip of the cutting edge of the pointed structure always corresponds to the center of the cutting surface of the drill hole, the cutting edge instantaneously floats up from the cutting surface of the drill hole and immediately hits it with impact (impact cutting). ), It is possible to easily form a fixed-diameter hole with high positioning accuracy and a hole diameter error within an allowable value.

Further, even if massive chips are interposed between the cutting surface of the drill hole and the cutting edge during the impact cutting, the adjacent main cutting edge and auxiliary cutting edge cooperate to finely crush the chip. Since the biased resistance applied to the hole is reduced, the bit is not shaken and the drilling accuracy is increased.

Furthermore, since the degree of wear of the cutting edge tip can be checked at a glance from the degree of wear of the concave portion for confirming the wear of the cutting edge diameter, the operator can use the measuring tool without using special measuring tools.
It is possible to easily drill a fixed diameter hole having a hole diameter error within an allowable value.

Therefore, it is suitable as a drill bit for drilling an anchor bolt planting hole used for fixing a structure or the like later to concrete solidified using a rotary hammer drill. It does not affect the pull-out strength of the anchor bolt after planting by using it for planting bolts.

[Brief description of the drawings]

FIG. 1 is a front view in which a part of a drill bit according to an embodiment of the present invention is omitted.

FIG. 2 is an enlarged front view of a cutting edge of a drill bit.

FIG. 3 is a bottom view of a cutting edge of a drill bit.

[Description of Signs] 1 Bit body 2 Shank 3 Chip discharge groove 4 Cutting edge tip 4a Cutting edge 4b Cutting edge 4c Cutting edge 5 Cutting surface 6 Relief surface 7 Joining surface 8 Main cutting edge 9 Auxiliary cutting edge 10 Cutting edge apex DESCRIPTION OF SYMBOLS 11 Joining line 12 Concave part 12a Circular surface 12b Plane 12c Plane 13 Concave part for confirming wear of cutting edge diameter

Claims (9)

[Claims] 1. A cutting edge chip made of a cemented carbide block body is provided with three cutting edge portions equally distributed in a circumferential direction, and a cutting surface and a flank formed on each cutting edge portion are formed. The joining line was used as the main cutting edge, the joining line between the joining surface and the flank was used as the auxiliary cutting edge, and these main cutting edge and auxiliary cutting edge were crossed at the cutting edge apex, and the cutting edge apex was formed into a pointed shape without a chisel point. A drill bit characterized in that: 2. The drill bit according to claim 1, wherein the auxiliary cutting edge is set on an extension of the main cutting edge of the cutting edge portion facing the cutting edge apex. 3. A main cutting edge and an auxiliary cutting edge;
The drill bit according to claim 1 or 2, wherein the joining line between the joint surface and the cutting surface that intersect at the apex of the cutting edge is set to be a straight line. 4. A concave surface formed between each cutting edge portion is formed as one continuous surface in which a flat surface is continuous at both ends of an arc surface, and a concave surface corresponding to a connecting surface is formed into an arc surface, and cutting is performed. On the surface side, the radius of curvature of the concave arc surface is adjusted so that the joining line end of the joining surface and the cutting surface intersect at the midpoint of the concave arc surface edge, and on the flank side, the auxiliary cutting edge end intersects the concave arc edge. The drill bit according to any one of claims 1 to 3, wherein the drill bit is set. 5. A thickness W of each of the cutting edges 4a, 4b, 4c in a circumferential direction at an end of the cutting edge is set to be about 0.2 to 0.5 times the cutting edge diameter ΦA. The drill bit according to any one of claims 1 to 4. 6. The circumferential apparent width W 'of the cutting surface 5 at each of the cutting edges 4a, 4b, 4c is set to be 0.2 to 0 .0 of the circumferential thickness W of the cutting edge at the cutting edge. The drill bit according to any one of claims 1 to 5, wherein the drill bit is set to about five times. 7. The drill bit according to claim 1, wherein the core diameter φB of the bit body 1 is set to about 0.3 to 0.7 times the cutting edge diameter φA. 8. The drill bit according to claim 1, wherein the tip height H at the end of the cutting edge is set to about 0.2 to 0.5 times the cutting edge diameter ΦA. . 9. The drill bit according to claim 1, wherein a concave portion for confirming wear of the cutting edge diameter is provided on an outer peripheral surface of each cutting edge portion.