JP2007001011A - Drilling tool - Google Patents

Abstract

To improve hole machining accuracy and tool life.
A pair of chip discharge grooves are formed on the outer periphery of the tip of a substantially cylindrical tool body so as to be twisted symmetrically with the rotation axis O of the tool body, and a wall surface of each chip discharge groove facing the tool rotation direction is provided. A cutting edge is formed at each of the intersecting ridge lines with the tip flank 4. A thinning surface 4a is formed from the rear side of the tip flank 4 in the tool rotation direction toward the rotation axis O, and the thinning surface 4a causes the inner peripheral portion of the cutting edge to be bent toward the rotation axis O. The thinning blade 6 reaches the other cutting blade side. A chisel 7 is formed between the thinning blades 6 so that the Y dimension of the chisel 7 is in the range of −0.10 mm to 0 mm. A portion of the thinning surface 4a that is continuous with the thinning blade 6 and faces the tool rotation direction is connected to a portion of the tip flank 4 that extends from the rear side in the tool rotation direction toward the rotation axis O via the concave curved surface 4b.
[Selection] Figure 2

Description

  The present invention relates to a drilling tool such as a drill suitable for drilling difficult-to-cut materials.

As shown in the side view of FIG. 3 and the front end view of FIG. 4, the conventional drilling tool 21 has a pair of twists around the rotation axis O1 around the outer periphery of the tip of the tool body 22 rotated about the rotation axis O1. The chip discharge grooves 23, 23 are formed symmetrically with respect to the rotation axis O 1, and the cutting edge 25 is formed at the crossing ridge line portion of the wall surface 23 a facing the tool rotation direction of each chip discharge groove 23 and the tip flank 24. It is. In the tool body 22, 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 rotation direction, and the thinning surface 24a forms the inner peripheral side of the cutting blade 25. The portion is bent to the rotation axis O1 side and is a thinning blade 26 connected to the tip flank 24 on the front side (outer peripheral side) of the rotation axis O1, and a chisel is formed between the inner peripheral ends of these thinning blades 26. 27 is formed. Here, the dimension X1 of the chisel 27 in the direction substantially orthogonal to the thinning blade 26 is defined as the X dimension, and the dimension Y1 of the chisel 27 along the thinning blade 26 is defined as the Y dimension. Further, the Y dimension when the thinning blades 26 are not facing each other is positive, and the Y dimension when at least a part of the thinning blades 26 is facing is negative.
In FIG. 4, the shape of the portion in the vicinity of the chisel 27 is schematically shown, and the size of the portion in the vicinity of the chisel 7 is actually very small.

In the conventional drilling tool 21 described above, the thinning blade 26 has a flank amount of the tip flank 24 smaller than the feed amount, and this portion (buffer portion) is rubbed against the work material, resulting in cutting resistance. As a result, the tool body 22 is likely to be shaken, and it has been difficult to ensure the hole machining accuracy.
In addition, since the load applied to the tool main body 22 is increased due to the vibration of the tool main body 22 as described above, the tool life is shortened.

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

  In order to achieve the above object, the drilling tool according to the present invention forms a pair of chip discharge grooves twisted around the rotation axis on the outer periphery of the tip of the tool body that is rotated around the rotation axis so as to be symmetric with respect to the rotation axis. In addition, in a drilling tool in which a cutting edge is formed at each of the intersecting ridge lines between the wall facing the tool rotation direction and the tip flank of each chip discharge groove, the tool flank on the tip flank faces from the rear side to the rotation axis side. A thinning surface is formed, and by this thinning surface, the inner peripheral side portion of the cutting blade is bent to the rotation axis side to reach the other cutting blade side, and the thinning surface is connected to the thinning blade. The portion that faces the tool rotation direction and the portion of the tip flank extending from the rear side in the tool rotation direction toward the rotation axis are connected via a concave curved surface. To have.

In the drilling tool configured as described above, the inner peripheral side portion of the cutting blade is bent toward the rotation axis side by forming a thinning surface on the inner peripheral side of the tip flank, and the other cutting edge is mutually cut. Thinning blade reaching the blade side. That is, the Y dimension of the chisel is 0 or negative.
As a result, a space formed between the thinning surface and the thinning blade is widened, and chips scraped from the work material by the thinning blade are easily discharged into the space formed between the thinning surface and the thinning blade. Therefore, chip discharge property is improved.
In addition, by setting the Y dimension of the chisel to 0 or negative as described above, the buffer portion that is rubbed against the work material on the tip flank is reduced, and the cutting resistance is reduced.
Here, when the Y dimension of the chisel formed between these thinning blades is smaller than -0.1 mm, the thickness of the chisel is reduced in the vicinity of the chisel, so that the strength of the chisel is reduced and the tool life is shortened. It will be shorter.
On the other hand, when the Y dimension of the chisel is a positive value larger than 0 mm, the space formed between the thinning surface and the thinning blade is narrowed and is cut off from the work material by the thinning blade during drilling. This will reduce the discharge of chips. In addition, if the space formed between the thinning surface and the thinning blade becomes narrow in this way, chips are easily crushed in this space, so that the tool body is likely to sway under the influence, and drilling is performed. When the accuracy is lowered and the vibration is generated, the load applied to the tool main body is increased and the tool life is also reduced.
For this reason, it is preferable that the Y dimension of the chisel formed between these thinning blades is in 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 drilling tool bites against the work material, and the width V of the chisel becomes 0 mm (in this case, the chisel becomes dot-like). It is preferable to be within a range of 1 mm.

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

Moreover, the intensity | strength of a thinning blade is securable by giving honing to the thinning blade of a chisel.
In the honing surface formed on the thinning blade, the end on the rotation axis side is formed in a curved surface shape such as a concave curved surface along the concave curved surface of the thinning surface, whereby the strength of this portion can be ensured.
Here, by adjusting the honing amount applied to the thinning blade, the width V of the chisel can be adjusted independently of the X and Y dimensions of the chisel. In addition, when the X dimension of the chisel is set to 0 mm, the thinning blade is not honed.

The concave curved surface may be a cylindrical surface.
In this case, chips can be guided more smoothly by the concave curved surface.
Here, when the curvature radius R of the concave curved surface connecting the portion facing the tool rotation direction on the thinning surface and the portion extending from the rear side in the tool rotational direction toward the rotation axis is smaller than 0.1 mm, the concave curved surface Therefore, the direction of the chips guided by the abruptly changes, and thus the tool body is subjected to a large resistance. On the other hand, if the curvature radius 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 in the range of 0.1 mm to 0.5 mm.

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 chisel is formed between the thinning surface and the thinning blade while ensuring the strength of the chisel. It is possible to secure a wide space to improve the chip discharge performance.
Further, by setting the Y dimension of the chisel to 0 or negative as described above, the buffer portion that is rubbed against the work material on the tip flank is reduced, so that the cutting resistance can be reduced.
Further, the thinning surface is connected to the thinning blade in the direction of the tool rotation direction and the portion of the tip flank extending from the rear side of the tool rotation direction toward the rotation axis is connected via a concave curved surface. Chips scraped from the work material by the blade are guided smoothly by the concave curved surface from the surface of the thinning surface facing the tool rotation direction and smoothly guided to the portion extending from the rear side of the tool rotation direction toward the rotation axis side. Stable chips can be generated.
This reduces the influence of the chips on the drilling tool during drilling and makes it difficult for the drilling tool to shake.
Thereby, the biting property of the drilling tool with respect to the drilling accuracy and the work material can be improved.
In addition, since it is difficult for the drilling tool to be shaken in this way, the load applied to the drilling tool can be reduced, and the tool life can be extended.

  Hereinafter, an embodiment of a drilling tool according to the present invention will be described with reference to FIGS. 1 and 2. In this 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 the present embodiment is a two-blade twist drill, and a pair of chip discharge grooves on the outer periphery of the distal end portion of a substantially cylindrical tool body 2 formed of a hard material such as steel or cemented carbide. 3, 3 and 3 are formed so as to be symmetric with respect to the rotation axis O of the tool body 2 and twist toward the rear in the tool rotation direction T at the time of machining as it goes toward the rear end side of the tool body 2. Here, the tool body 2 may be provided with an oil hole that leads from the base end side to the tip flank 4.
Cutting edges 5 are respectively formed on the intersecting ridges of the wall surfaces of the chip discharge grooves 3 facing the tool rotation direction T and the tip flank 4.
Here, the core thickness of the tool body 2 is, for example, in the range of 0.2 × Dmm to 0.35 × Dmm, where D is the outer diameter of the cutting edge. 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 of the tip flank 4 in the tool rotation direction toward the rotation axis O, and the inner peripheral side portion of the cutting blade 5 is bent toward the rotation axis O by the thinning surface 4a. Thus, the thinning blade 6 reaches the other cutting blade 5 side. That is, the drill 1 is subjected to X thinning.
In the present embodiment, the thinning blade 6 is formed so as to partially face the other thinning blade 6.
Then, the portion of the thinning surface 4a that faces the thinning blade 6 and faces the tool rotation direction is connected to the portion of the tip flank 4 that extends from the rear side in the tool rotation direction toward the rotation axis O via the concave curved surface 4b. Has been.
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 ensure the strength thereof. And in order to prevent the welding of the chip to a blade edge | tip, the honing amount H given to the cutting blade 5 and the thinning blade 6 shall be 0-0.025 mm. The honing surface F formed by the honing 8 is formed with a curved surface such as a concave curved surface along the concave curved surface 4b of the thinning surface 4a at the end on the rotation axis O side. Strength is secured.

A chisel 7 is formed between the thinning blades 6, and the dimension Y of the chisel 7 along the thinning blade 6 is in the range of 0 mm to 0.1 mm. That is, the Y dimension of the chisel 7 is in the range of −0.1 mm to 0 mm.
In addition, the size of the chisel 7 in the direction substantially orthogonal to the thinning blade 6 (X size of the chisel 7) is in the range of 0 mm to 0.3 m.
Here, in FIG. 2, the shape of the thinning surface 4a when the Y dimension of the chisel is positive is indicated by a two-dot chain line for comparison.
Further, the removal of the work material by the chisel 7 is not performed by cutting, but is performed by crushing the work material, resulting in high resistance. For this reason, when the width V of the chisel 7 is larger than 0.1 mm, the bite of the drill 1 with respect to the work material is deteriorated. Therefore, in this embodiment, the width V of the chisel 7 is 0 mm (in this case, the chisel 7 is It is within the range of 0.1 mm from the point).

In the drill 1 configured as described above, the thinning surface 4a is formed on the inner peripheral side of the tool on the tip flank 4 so that the inner peripheral side portion of the cutting blade 5 is bent toward the rotation axis O side to each other. The thinning blade 6 reaches the opposite cutting blade 5 side, and the thinning blades 6 are partially opposed to each other. That is, the Y dimension of the chisel formed between the thinning blades 6 is negative.
Thereby, the space S formed between the thinning surface 4a and the thinning blade 6 is widened, and chips scraped from the work material by the thinning blade 6 are formed between the thinning surface 4a and the thinning blade 6. It will be easily discharged into the space S.

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 thinning blade 6 The discharge | emission property of the chip | piece scraped off from the workpiece will fall. Furthermore, 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 therefore affected by the influence. The tool body 2 is likely to be shaken, the hole machining accuracy is lowered, and the shake is caused to increase the load applied to the tool body 2 and reduce the tool life.
Moreover, when the Y dimension of the chisel 7 is smaller than −0.1 mm, the strength of the chisel 7 is lowered and the tool life is shortened. For this reason, the Y dimension of the chisel 7 formed between the thinning blades 6 is set in the range of −0.10 mm to 0 mm.

Further, the X dimension of the chisel 7 is in the range of 0 mm to 0.3 mm, and the space S formed between the thinning surface 4a and the thinning blade 6 is secured widely. Chips cut off from the work material 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), since the chisel 7 is eliminated, the strength of the tool tip is lowered and the tool life is shortened.
In addition, 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 from the work material by the thinning blade 6 are reduced. Emission 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 likely to shake due to the influence, and the hole machining accuracy is increased. As a result, the load applied to the tool body 2 is increased and the tool life is reduced.
For this reason, the X dimension of the chisel 7 is preferably in the range of 0 mm to 0.3 mm.
Further, by setting the Y dimension of the chisel 7 to 0 or negative and the X dimension to be in the range of 0 mm to 0.3 mm as described above, the buffer portion rubbed against the work material on the tip flank 4 is reduced. , Cutting resistance can be reduced.

Further, a portion of the thinning surface 4a that faces the thinning blade 6 and faces the tool rotation direction (that is, a portion that forms the rake face of the thinning blade 6), and the tip flank 4 faces from the rear side of the tool rotation direction to the rotation axis O side. Therefore, the chip scraped off from the work material by the thinning blade 6 is guided by the concave curved surface 4b from the portion facing the tool rotation direction on the thinning surface 4a. Thus, a stable chip is generated by being smoothly guided to a portion extending from the rear side in the tool rotation direction of the thinning surface 4a toward the rotation axis O side.
Here, in the thinning surface 4a, the radius of curvature R of the concave curved surface 4b connecting the portion facing the tool rotation direction and the portion extending from the rear side in the tool rotation direction toward the rotation axis O side is smaller than 0.1 mm. Then, 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 increases, and the cutting resistance increases. For this reason, it is preferable that the curvature radius R of the concave curved surface 4b be in the range of 0.1 mm to 0.5 mm.

According to the drill 1 configured as described above, the Y dimension of the chisel 7 formed between the thinning blades 6 is in the range of −0.10 mm to 0 mm, and the X dimension of the chisel 7 is Since it is in 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 widely while ensuring the strength of the chisel 7 and the chip discharging property is improved. be able to.
Further, by setting the Y dimension of the chisel 7 to 0 or negative and the X dimension to be in the range of 0 mm to 0.3 mm as described above, the buffer portion rubbed against the work material on the tip flank 4 is reduced. , Cutting resistance can be reduced.
Further, a portion of the thinning surface 4a that is continuous with the thinning blade 6 and faces the tool rotation direction is connected to a portion of the tip flank 4 that extends from the rear side in the tool rotation direction toward the rotation axis O via the 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 directed from the rear side in the tool rotation direction toward the rotation axis O side. It will be smoothly guided to the extending part, and stable chips can be generated.
Thereby, the influence on the drill 1 by a chip at the time of a drilling process decreases, and it becomes difficult to produce a vibration in the drill 1. FIG.
Thereby, the drilling precision of the drill 1 with respect to a drilling precision and a workpiece can be improved.
Moreover, since it becomes difficult to produce the vibration in the drill 1 in this way, the load added to the drill 1 can be reduced and the tool life can be extended.

It is a tip end view of a drill (drilling tool) concerning one embodiment of the present invention. It is an enlarged view of FIG. It is a side view which shows the shape of the conventional drill (drilling tool). FIG. 4 is a front end view of the drill shown in FIG. 3.

Explanation of symbols

1 Drill (drilling tool)
2 Tool body 3 Chip discharge groove 4 Tip clearance surface 4a Thinning surface 4b Concave surface 5 Cutting blade 6 Thinning blade 7 Chisel 8 Honing O Rotating axis Y Dimension of chisel

Claims (3)

A pair of chip discharge grooves twisted around the rotation axis are formed on the outer periphery of the tip of the tool main body rotated about the rotation axis so as to be symmetric with respect to the rotation axis, and a wall surface facing the tool rotation direction of each chip discharge groove; In the drilling tool in which the cutting edge is formed at each cross ridge line part with the tip flank,
A thinning surface is formed from the rear side in the tool rotation direction toward the rotation axis side on the tip flank surface, and the inner peripheral side portion of the cutting blade is bent toward the rotation axis side by this thinning surface, and is mutually connected. It is a thinning blade that reaches the other cutting edge,
A portion of the thinning surface that is continuous with the thinning blade and faces the tool rotation direction and a portion of the tip flank extending from the rear side in the tool rotation direction toward the rotation axis are connected via a concave curved surface. A drilling tool characterized by   The drilling tool according to claim 1, wherein the thinning blade of the chisel is subjected to honing.   The drilling tool according to claim 1 or 2, wherein the concave curved surface forms a cylindrical surface.

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