JP2003266225A - Drilling tool - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve accuracy of hole drilling and tool life. <P>SOLUTION: A pair of chip discharging grooves are helically formed in an outer periphery of an end of a nearly column shaped tool body in symmetry with respect to a rotation axis O of the tool body. A cutting edge is formed on an intersection ridge between a wall surface of each chip discharge groove facing in a tool rotating direction and an end flank 4. A thinning surface 4a is formed on the end flank 4 from a trailing side in the tool rotating direction to a side of the rotation axis O. The thinning surface 4a forms a portion on an inner peripheral side of the cutting edge into a thinning edge 6 bent to the rotation axis O side and reaching the other cutting edge side. A chisel 7 is defined between the thinning edges 6, and a Y size of the chisel 7 is set in a range from -0.10 mm to 0 mm. A portion of the thinning surface 4a following the thinning edge 6 and facing in the tool rotating direction is connected with a portion of the end flank 4 extending from the trailing side in the tool rotating direction toward the rotation axis O side via a concave surface 4b. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drilling tool suitable for drilling difficult-to-cut materials.

[0002]

2. Description of the Related Art As shown in a side view of FIG. 3 and a front end view of FIG. 4, a conventional drilling tool 21 has a rotation axis O on the outer periphery of the tip of a tool body 22 rotated about a rotation axis O1.
A pair of chip discharge grooves 23, 23 twisted around once are formed symmetrically with respect to the rotation axis O1, and each chip discharge groove 2 is formed.
The cutting edge 25 is formed at the ridge line intersecting the wall surface 23a of the tool 3 facing the tool rotation direction and the tip flank 24. A thinning surface 24a reaching from the vicinity of the rotation axis O1 to the outer peripheral surface is formed by X thinning behind the tip flank 24 in the tool body 22 in the tool rotation direction, and the thinning surface 24a forms the inner peripheral side of the cutting edge 25. The part is bent toward the rotation axis O1 side and is connected to the tip flank 24 on the front side (outer peripheral side) of the rotation axis O1.
A chisel 27 is formed between the inner peripheral ends of the thinning blades 26. Here, the dimension X1 of the chisel 27 in the direction substantially orthogonal to the thinning blade 26 is defined as X dimension, and the dimension Y1 of the chisel 27 along the thinning blade 26 is defined as Y dimension. Further, the Y dimension when the thinning blades 26 do not face each other is positive, and the Y dimension when at least a part of the thinning blades 26 faces each other is negative. Note that, in FIG. 4, the shape of the portion near the chisel 27 is schematically shown, and in reality, the dimension of the portion near the chisel 7 is extremely small.

[0003]

In the conventional drilling tool 21 described above, the clearance of the tip flank 24 of the thinning blade 26 is smaller than the feed, and this portion (buffer portion) rubs against the work material. As a result, the tool body 22 is liable to run out due to the cutting resistance, and it is difficult to secure the hole machining accuracy. Further, since the tool body 22 thus swings, the load applied to the tool body 22 also increases, resulting in a shorter tool life.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a drilling tool having improved drilling accuracy and tool life.

[0005]

In order to achieve the above object, a drilling tool according to the present invention comprises a pair of chip discharge grooves twisted around a rotation axis on the outer periphery of the tip of a tool body rotated around the rotation axis. Is formed symmetrically with respect to the axis of rotation, and in the drilling tool in which the cutting edges are formed at the ridges intersecting the wall surface of each chip discharge groove facing the tool rotation direction and the flank of the tool, the tool rotation at the flank of the tool A thinning surface is formed from the direction rear side toward the rotation axis side, and the inner peripheral side portion of the cutting edge is bent by the thinning surface toward the rotation axis side and reaches the other cutting edge side with each other. The portion of the thinning surface that is continuous with the thinning blade and faces the tool rotation direction, and the portion of the tip flank that extends from the rear side of the tool rotation direction toward the rotation axis side have a concave curved surface. It is characterized in that it is connected.

In the drilling tool constructed as described above, the thinning surface is formed on the tool inner peripheral side of the tip flank, so that the inner peripheral portion of the cutting edge is bent toward the rotation axis side to be mutually bent. It is a thinning blade that reaches the other cutting edge side. That is, the Y dimension of the chisel is set to 0 or negative. Thereby, the space formed between the thinning surface and the thinning blade becomes wider, and the chips scraped off from the work material by the thinning blade are easily discharged to the space formed between the thinning surface and the thinning blade. Therefore, the chip discharging property is improved. In addition, by setting the Y dimension of the chisel to 0 or negative as described above, the buffer portion rubbed by the work material on the flank of the tip becomes small, and the cutting resistance becomes small. Here, when the Y dimension of the chisel formed between these thinning blades is smaller than -0.1 mm, the thin part in the vicinity of the chisel becomes too large and the strength of the chisel decreases, resulting in a shorter tool life. It gets shorter. On the other hand, when the Y dimension of the chisel has a positive value larger than 0 mm, the space formed between the thinning surface and the thinning blade becomes narrower, and the thinning blade scrapes the work material during drilling. The chip discharge performance will decrease. Furthermore, if the space formed between the thinning surface and the thinning blade becomes narrower in this way, the chips are more likely to be crushed in this space, so that under the influence of this, runout easily occurs in the tool body and hole machining Since the accuracy is lowered and the runout is generated, the load applied to the tool main body is increased and the tool life is shortened. Therefore, the Y of the chisel formed between these thinning blades
The dimensions are preferably within the range of -0.1 mm to 0 mm. Here, the removal of the work material by the chisel is not performed by cutting, but is performed by crushing the work material, resulting in high resistance. For this reason, if the width V of the chisel is larger than 0.1 mm, the biting of the drilling tool with respect to the work material is deteriorated, so that the width V of the chisel is reduced.
Is from 0 mm (in this case, the chisel is dotted) to 0.1 m
It is preferably within the range of m.

Further, on the thinning surface, a portion which is continuous with the thinning blade and faces the tool rotating direction (that is, a portion which forms the rake surface of the thinning blade) and a tip flank extending from the rear side of the tool rotating direction toward the rotation axis side. Since the portion is connected via the concave curved surface, the chips scraped off from the work material by the thinning blade are guided by the concave curved surface from the portion facing the tool rotation direction in the thinning surface, and the tool on the thinning surface The chips are smoothly guided from the rear side in the rotation direction to the portion extending toward the rotation axis side, and stable chips are generated.

By honing the thinning blade of the chisel, the strength of the thinning blade can be secured. The end portion on the rotation axis side of the honing surface formed on the thinning blade can be formed in a curved shape such as a concave curved surface along the concave curved surface of the thinning surface to ensure the strength of this portion. Here, by adjusting the honing amount applied to the thinning blade, the X dimension of the chisel,
The width V of the chisel can be adjusted independently of the Y dimension. If the X dimension of the chisel is 0 mm,
Honing is not applied to the thinning blade.

The concave curved surface may be a cylindrical surface. In this case, the concave curved surface can guide the chips more smoothly. Here, when the radius of curvature R of the concave curved surface that connects the portion facing the tool rotation direction and the portion extending from the tool rotation direction rear side toward the rotation axis side on the thinning surface is smaller than 0.1 mm, the concave curved surface is formed. Since the direction of the chips guided by the abruptly changes, the tool body receives a great resistance. On the other hand, if the radius of curvature R of the concave curved surface is larger than 0.5 mm, the width of the chisel formed between the thinning surfaces becomes large and the cutting resistance increases. For this reason,
The radius of curvature R of the concave curved surface is preferably within the range of 0.1 mm to 0.5 mm.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of a drilling tool according to the present invention will be described below with reference to FIGS. 1 and 2. In the present embodiment, an example in which the present invention is applied to a drill will be described. Here, FIG. 1 is a front end view showing the shape of the drill according to the present embodiment, and FIG. 2 is an enlarged view of FIG.

The drill 1 shown in this embodiment is a two-blade twist drill, and has a substantially cylindrical tool body 2 formed of a hard material such as steel or cemented carbide on the outer periphery of the tip end portion thereof.
A pair of chip discharge grooves 3 and 3 are formed so as to be symmetrical with respect to the rotation axis O of the tool body 2 and to be twisted rearward in the tool rotation direction T at the time of machining toward the rear end side of the tool body 2. Here, the tool body 2 may be provided with an oil hole communicating from the base end side to the tip flank 4. Cutting edges 5 are formed at the ridges of the intersections between the wall surfaces of the chip discharge grooves 3 facing the tool rotation direction T and the tip flanks 4. Here, the core thickness of the tool body 2 is, for example, 0.2 when the outer diameter of the cutting edge is D.
It is set within the range of xDmm to 0.35xDmm. In the present embodiment, the cutting edge outer diameter D is 8.6 mm.
In the present embodiment, the core thickness is 0.25 × Dmm.

A thinning surface 4a is formed from the rear side in the tool rotation direction of the tip flank 4 toward the rotation axis O side. With this thinning surface 4a, the portion on the inner peripheral side of the cutting edge 5 is on the rotation axis O side. The thinning blades 6 are bent so as to reach the other cutting blade 5 side. That is, the drill 1 is X-thinned. In the present embodiment, the thinning blade 6 is formed so as to partially face the other thinning blade 6. A portion of the thinning surface 4a that is continuous with the thinning blade 6 and faces the tool rotation direction, and a portion of the tip flank 4 that extends from the rear side of the tool rotation direction toward the rotation axis O side have a concave curved surface 4a.
It is connected via b. Here, in the present embodiment, the concave curved surface 4b is a cylindrical surface. Further, the cutting blade 5 and the thinning blade 6 are provided with honing 8 to secure their strength. The honing amount H applied to the cutting blade 5 and the thinning blade 6 is set to 0 to 0.025 mm in order to prevent the welding of the chips to the cutting edge. The honing surface F formed by the honing 8 has an end portion on the rotation axis O side formed into a curved surface such as a concave curved surface along the concave curved surface 4b of the thinning surface 4a.
This ensures the strength of this portion.

A chisel 7 is formed between the thinning blades 6, and the dimension Y of the chisel 7 in the direction along the thinning blade 6 is within the range of 0 mm to 0.1 mm. That is, the Y dimension of the chisel 7 is -0.1 mm to 0.
It is set within the range of mm. Further, the size of the chisel 7 in the direction substantially orthogonal to the thinning blade 6 (X size of the chisel 7)
Is within the range of 0 mm to 0.3 m. Here, in FIG. 2, for comparison, the shape of the thinning surface 4a when the Y dimension of the chisel is positive is shown by a chain double-dashed line. Further, the removal of the work material by the chisel 7 is performed not by cutting but by crushing the work material, which results in high resistance. Because of this, chisel 7
If the width V of the drill 1 is larger than 0.1 mm, the biting of the drill 1 with respect to the work material deteriorates. Therefore, in the present embodiment,
The width V of the chisel 7 is in the range of 0 mm (in this case, the chisel 7 has a dot shape) to 0.1 mm.

In the drill 1 thus constructed, the thinning surface 4 is provided on the tool inner peripheral side of the tip flank surface 4.
By forming a, the portion on the inner peripheral side of the cutting blade 5 is bent to the rotation axis O side to form the thinning blades 6 that reach the opposite cutting blade 5 side, and these thinning blades 6 are part of each other. Are facing each other. That is, the Y dimension of the chisel formed between the thinning blades 6 is negative. As a result, the space S formed between the thinning surface 4a and the thinning blade 6 becomes wider, and the chips scraped off from the work material by the thinning blade 6 become thinner.
Will be easily discharged into the space S formed between the thinning blade 6 and the thinning blade 6.

Here, when the Y dimension of the chisel 7 formed between these thinning blades 6 is larger than 0 mm,
The space S formed between the thinning surface 4a and the thinning blade 6 becomes narrow, and the dischargeability of the chips scraped off from the work material by the thinning blade 6 deteriorates. further,
Since the space S formed between the thinning surface 4a and the thinning blade 6 is narrowed in this way, chips are easily crushed in the space S during drilling, and the tool body is affected by this. The runout of the tool 2 is likely to occur, the hole machining accuracy is reduced, and the runout also increases the load applied to the tool body 2 and the tool life is also reduced. Further, when the Y dimension of the chisel 7 is smaller than -0.1 mm, the strength of the chisel 7 is reduced and the tool life is shortened. Therefore, the Y dimension of the chisel 7 formed between the thinning blades 6 is within the range of −0.10 mm to 0 mm.

Further, the X dimension of the chisel 7 is set within the range of 0 mm to 0.3 mm, and a wide space S formed between the thinning surface 4a and the thinning blade 6 is secured, so that the thinning is performed. The chips scraped off from the work material by the blade 6 are easily discharged into the space S formed between the thinning surface 4 a and the thinning blade 6. Here, when the X dimension of the chisel 7 is smaller than 0 mm (that is, when it is negative), the chisel 7 disappears,
The strength of the tool tip is reduced and the tool life is shortened. Further, when this dimension is larger than 0.3 mm, the space S formed between the thinning surface 4a and the thinning blade 6 becomes small, and the chips scraped off from the work material by the thinning blade 6 become smaller. Ejectability is reduced. Furthermore, since the chips are easily crushed in the space S formed between the thinning surface 4a and the thinning blade 6 during drilling, the tool body is susceptible to runout under the influence of this and the drilling accuracy is improved. And the deflection causes a large load to be applied to the tool body 2 and the tool life is also shortened. Because of this, chisel 7
The X dimension of is preferably in the range of 0 mm to 0.3 mm. Also, set the Y dimension of the chisel 7 to 0 as described above.
Alternatively, by setting the X dimension to be in the range of 0 mm to 0.3 mm with a negative value, the cushioning portion rubbed by the work material on the tip flank 4 becomes small, so that the cutting resistance can be made small.

Further, on the thinning surface 4a, a portion which is continuous with the thinning blade 6 and faces the tool rotation direction (that is, a portion which forms the rake surface of the thinning blade 6) and a rotation axis O from the rear side of the tip flank 4 in the tool rotation direction. Since the portion extending toward the side is connected via the concave curved surface 4b,
The chips scraped off from the work material by the thinning blade 6 are guided by the concave curved surface 4b from the portion of the thinning surface 4a facing the tool rotation direction, and from the rear side of the thinning surface 4a in the tool rotation direction to the rotation axis O side. It will be smoothly guided to the part extending toward and stable chips will be generated. Here, in the thinning surface 4a, the radius of curvature R of the concave curved surface 4b that connects the portion facing the tool rotation direction and the portion extending from the tool rotation direction rear side toward the rotation axis O side is smaller than 0.1 mm. When,
Since the direction of the chips guided by the concave curved surface 4b changes abruptly, the tool body 2 receives a large resistance. On the other hand, when the radius of curvature R of the concave curved surface 4b is larger than 0.5 mm, the width V of the chisel 7 formed between the thinning surfaces 4a becomes large and the cutting resistance increases. Therefore, the radius of curvature R of the concave curved surface 4b is
Is preferably in the range of 0.1 mm to 0.5 mm.

According to the drill 1 thus constructed,
The Y dimension of the chisel 7 formed between the thinning blades 6 is −
It is set within the range of 0.10 mm to 0 mm, and
Since the X dimension of the chisel 7 is set within the range of 0 mm to 0.3 mm, the space S formed between the thinning surface 4a and the thinning blade 6 is secured while securing the strength of the chisel 7. The chip discharging property can be improved.
Further, as described above, by setting the Y dimension of the chisel 7 to 0 or negative and setting the X dimension within the range of 0 mm to 0.3 mm, the buffer portion rubbed by the work material on the tip flank 4 becomes small. The cutting resistance can be reduced.
Further, a portion of the thinning surface 4a, which is continuous with the thinning blade 6 and faces the tool rotation direction, and a portion of the tip flank 4 which extends from the tool rotation direction rear side toward the rotation axis O side are connected via a concave curved surface 4b. Therefore, the chips scraped from the work material by the thinning blade 6 are guided from the portion of the thinning surface 4a facing the tool rotation direction to the concave curved surface 4b, and from the tool rotation direction rear side toward the rotation axis O side. It will be smoothly guided to the extended part,
It is possible to generate stable chips. As a result, the influence of chips on the drill 1 during drilling is reduced, and swinging of the drill 1 is less likely to occur. As a result, the drilling accuracy and the biteability of the drill 1 with respect to the work material can be improved. Further, since the swinging of the drill 1 is less likely to occur in this way, the load applied to the drill 1 can be reduced and the tool life can be extended.

[0019]

According to the drilling tool of the present invention, since the Y dimension of the chisel formed between the thinning blades is 0 or negative, the thinning surface and the thinning blade are secured while ensuring the strength of the chisel. It is possible to secure a wide space formed between and to improve the chip discharging property. Also,
By setting the Y dimension of the chisel to 0 or negative as described above, the buffer portion rubbed by the work material on the flank of the tip becomes small, so that the cutting resistance can be made small. Further, since the portion of the thinning surface that is continuous with the thinning blade and faces the tool rotation direction and the portion of the tip flank that extends from the rear side of the tool rotation direction toward the rotation axis side are connected via the concave curved surface, the thinning is performed. The chips scraped off from the work material by the blade will be guided by the concave curved surface from the surface of the thinning surface facing the tool rotation direction, and will be smoothly guided to the portion extending from the tool rotation direction rear side toward the rotation axis side. , Can produce stable chips. This reduces the influence of chips on the drilling tool during drilling, and makes it difficult for the drilling tool to swing. As a result, it is possible to improve the drilling accuracy and the biteability of the drilling tool with respect to the work material. Further, since the boring tool is less likely to swing in this way, the load applied to the boring tool can be reduced and the tool life can be extended.

[Brief description of drawings]

FIG. 1 is a front end view of a drill (drilling tool) according to an embodiment of the present invention.

FIG. 2 is an enlarged view of FIG.

FIG. 3 is a side view showing the shape of a conventional drill (drilling tool).

4 is a front end view of the drill shown in FIG.

[Explanation of symbols]

1 Drill (drilling tool) 2 Tool body 3 Chip discharge groove 4 Tip flank 4a Thinning surface 4b Concave surface 5 cutting edge 6 thinning edge 7 Chisel 8 Honing O Rotation axis Y Chisel Y dimension

Claims (3)

[Claims] 1. A pair of chip discharge grooves twisted about the rotation axis are formed on the outer periphery of a tip end portion of a tool body rotated about the rotation axis symmetrically to the rotation axis, and the tool rotation of each chip discharge groove is performed. In a drilling tool in which cutting edges are respectively formed at the ridges of intersections of a wall surface and a tip flank that face in a direction, a thinning surface is formed from the tool rotation direction rear side of the tip flank toward the rotation axis side. By this thinning surface, the inner peripheral side portion of the cutting edge is bent toward the rotation axis side to be a thinning blade reaching the other cutting edge side, and the tool is connected to the thinning edge on the thinning surface. A portion that faces the rotation direction and a portion that extends from the rear side of the tip flank in the tool rotation direction toward the rotation axis side are connected via a concave curved surface. Drilling tool to be a butterfly. 2. The drilling tool according to claim 1, wherein the thinning blade of the chisel is provided with honing. 3. The drilling tool according to claim 1, wherein the concave curved surface is a cylindrical surface.