JPH0659566B2 - Drill - Google Patents

Description

Detailed Description of the Invention [Industrial applications]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drill, and more particularly to a blade shape of a drill having a sub-groove for discharging chips in the vicinity of a chisel portion.

[Prior art and its problems]

Generally, the shape and discharge state of the chips discharged during drilling with a drill are different at the three stages shown in FIG. Stage I: The stage where the conical end face with a tip angle is cutting in. Stage II: From the state where all of the above end faces are cut into the work until the tip of the drill penetrates the work and goes outside. Stage III: Stage where the above-mentioned end face penetrates the work and goes out to the outside. In the stage I, as shown in FIG. 5, the chips, which are wound in a spiral shape and are continuous for a relatively long time, are continuously connected for a long time after the chips are discharged from the chip discharge groove on the outer side of the work, and the connection is continued. As the drilled part receives a strong centrifugal force as the drill rotates, it is ejected so that it scatters vigorously to the surrounding area. Also,
In the stage III, as shown in FIG. 7, chips that have a shape in which only the first end is spirally wound and the other parts are elongated and continuous are formed on the outside of the work as in the first stage. Even after coming out from the chip discharge groove, it continues for a long time, and since the continuous part receives a strong centrifugal force as the drill rotates,
It is discharged so as to scatter vigorously to the surrounding area. On the other hand, the second
At the stage, as shown in FIG. 6, although it is wound in a state close to a spiral shape, it is discharged in a short cut state, so that it is not further subjected to centrifugal force after it has come out of the work, It doesn't scatter so vigorously. On the other hand, in order to achieve high efficiency in drilling with a drill, it is necessary to enable a high cutting speed (the number of rotations of the drill). Recently, it has become popular to manufacture a drill with a material having a high hardness such as an alloy. However, as the number of rotations of the drill increases, a large centrifugal force acts on the chips that go out of the work and scatter, and it is very difficult for those working around the machine tool to discharge the above-mentioned chips. It creates a dangerous environment. Therefore, in the case of a drill used at a high cutting speed, such as a cemented carbide drill, it is desirable to break the chips as finely as possible and discharge the chips. By the way, in a drill that has increased rigidity by increasing the core thickness or decreasing the groove width ratio, as a method to reduce the cutting resistance as much as possible, a secondary groove for chip discharge is provided near the chisel part. There is a method of forming. Japanese Patent Publication Sho 62-5727
Japanese Patent Publication discloses a drill having such a sub groove. With this drill, even when drilling a sticky material such as steel, two types of finely divided chips are produced. It is considered that this is because the chips produced by the main cutting edge and the chips produced by the chisel edge are generated separately, and their flow directions are slightly different from each other, so that they interfere with each other to cause crushing.

[Problems to be Solved by the Invention]

However, in order to generate chips that are finely divided as described above, it is necessary that two types of chips interfere with each other.
When only the main cutting edge is performing cutting after the sub cutting edge has penetrated the work piece in stage I, the chips coming out of the sub cutting edge are gone, so the chips coming out of the main cutting edge are still long chips. Will be discharged. Therefore, when the drill penetrates the work, that is, just before the end of the drilling, chips that continue for a long time to the outside of the work are generated, especially when the cutting speed is high like a carbide drill. It is extremely dangerous. The present invention has been made in view of the above problems and to solve these problems effectively. Therefore, the purpose thereof is, in a drill having a sub-groove, a drill having a cutting edge shape that can discharge all chips discharged from the start of cutting to the end of cutting in a finely divided state. To provide.

[Means for solving problems]

The drill according to the present invention has the following configurations in order to solve the problems of the conventional techniques and achieve the object. That is, a chip discharge groove including a main groove forming a main cutting edge located on the outer peripheral side of the cutting edge of the drill and a sub groove forming a sub cutting edge located on the inner peripheral side of the cutting edge is provided. In a drill, the main cutting edge is curved in a concave shape with respect to the rotation direction, the angle between the main cutting edge and the sub cutting edge is 100 degrees or more, The distance to the intersection of the main cutting edge and the sub cutting edge is set to 0.2 times the drill diameter or less.

[Operation of the invention]

In developing the drill according to the present invention, the inventors first analyzed the mechanism of chip discharge during drilling with the drill. That is, when one roll of the chips discharged in the stage I is cut along the line X-X shown in FIG. 5, one that has been narrowed and wound as shown in FIG. The cutting piece 8a is deformed so as to further reduce the winding diameter, while the cutting piece 8b that has been spread and wound.
Was found to deform from the rolled state to a further expanded state, and from this fact the following mechanism of chip formation was considered. The cutting piece 8a of the chip is a portion cut on the center side of the cutting edge of the drill,
Since b is a portion cut on the outer peripheral side of the cutting blade, chips cut out from the center side of the cutting blade are wound small toward the center side, and chips cut off from the outer peripheral side of the cutting blade are It extends long in an attempt to flow along the circumferential direction.
Therefore, in the case of a drill with a sub-groove formed near the chisel part, normally two types of chips are produced, one of which is from the sub-cutting edge located on the center side (formed in the sub-groove part). It is a chip that comes out and is ejected in a small roll toward the center. The other one is the chips generated from the main cutting edge located on the outer peripheral side (formed in the main groove portion),
This does not try to go to the center side but tries to extend long,
The chips produced in this way are difficult to break. Therefore, as the basic idea of the present invention, by utilizing the property of small chips that are emitted from the auxiliary cutting edge on the center side and try to go toward the center side, the chips emitted from the cutting edge on the outer peripheral side together with the chips on the center side are utilized. It was concluded that it should be pulled toward the center and collided with the inner peripheral wall surface of the auxiliary groove. That is, it is sufficient to generate the chips generated from the main cutting edge and the chips generated from the sub cutting edge in a continuous state without dividing them.
And as a constitutional requirement for that, the angle between the main cutting edge and the sub cutting edge is increased to a certain degree or more, and if the angle is approximately 100 degrees or more from the experimental results, the chips and the sub cutting edge that come out from the main cutting edge The fact that the chips coming out of the blade are continuously generated without being divided, and the chips coming out of the auxiliary cutting edge toward the center side are due to the fact that the auxiliary cutting edge is drilled from the axis of the drill. It has been found that it suffices if it is within a radius of 0.2 times the diameter.
Further, in order to surely make the chips drawn toward the center side collide with the inner peripheral wall surface of the auxiliary groove to break, the shape of the main cutting edge is recessed in a concave curved shape with respect to the cutting rotation direction. Improves the rigidity of the chips by curving the cross-sectional shape of the chips coming out of the main cutting edge, and the chips immediately after being cut out from the main cutting edge do not leave the rake face over a relatively long distance. The chips that collide with the inner peripheral wall surface of the auxiliary groove are bent and finely broken without being elastically deformed so much. That is, the chips can be broken finely without depending on the interference between the chips produced from the main cutting edge and the chips produced from the auxiliary cutting edge.
The chips that have been finely broken are discharged in all stages from the above-mentioned stage I to stage III, and even if the cutting speed of the drill is high, the chips are prevented from vigorously scattering out of the work.

【The invention's effect】

As is clear from the above description, according to the present invention, the following excellent effects are exhibited. That is, in a drill having sub-grooves, the cutting edge shape that can discharge all the chips discharged from the start of cutting of the drilling process to the end of cutting in a finely divided state A large centrifugal force does not act on the chips coming out from the outside, and especially in the case of a cemented carbide drill used with a high cutting speed, scattering of the chips can be suppressed and a very safe working environment can be provided.

【Example】

A preferred embodiment of the present invention will be described below with reference to FIGS.
It will be described with reference to the drawings. FIG. 1 is an end view showing a cutting edge shape of a drill according to the present invention,
FIG. 2 is a side view of the drill according to the present invention. As shown in FIG. 1 and FIG. 2, a chip discharge groove formed in a normal drill is defined as a main groove 1 m, and further cutting is performed from around the innermost part of the main groove toward the chisel portion 2. The chip discharge groove 1 of the drill according to the present invention is configured with the groove 1s formed. Therefore, the cutting edge 3 has a main groove of 1 m.
The main cutting edge 3m formed by the above and the sub cutting edge 3s formed by the sub groove 1s. Further, as shown in FIG. 1, the main cutting edge 3m is formed so as to be curved in a substantially concave shape with respect to the rotation direction, and strictly speaking, a negative edge is provided at the outer peripheral side end thereof to prevent chipping of the cutting edge. Since the land 4 is formed, it is formed so as to slightly project in the rotational direction at this portion. As described above, since the main cutting edge 3m is curved, the cross-sectional shape of the chips coming out of the main cutting edge 3m is also curved, and the rigidity of the chip itself is increased, making it difficult to bend. Immediately after being carved out from the main cutting edge 3 m, it does not wind like a vine and flows along a long rake face. On the other hand, in the present embodiment, the sub cutting edge 3s itself is also formed to be slightly concavely curved, but the main cutting edge 3m and the sub cutting edge 3s are formed.
The angle (angle between the respective tangents) θ and is set to be 100 degrees or more. If this θ is greater than 100 degrees, the chips generated from the main cutting edge 3m and the auxiliary cutting edge 3s
The chips generated from the main cutting edge 3m are drawn to the side of the sub groove 1s by the force of winding toward the center side of the chips generated from the sub cutting edge 3s. It is possible to collide with the inner peripheral wall surface of the sub groove 1s together with the chips generated from the cutting blade 3s. In that case, the chips generated from the main cutting edge 3m flow long while not far from the rake face and collide with the inner peripheral wall surface of the sub-groove 1s, so that the chips are elastically collided like in the case of a coil. It does not absorb force, and when it collides, it bends in a state close to buckling and breaks perfectly finely. If this angle θ becomes smaller than 100 degrees, the chips generated from the main cutting edge 3m and the chips generated from the sub cutting edge 3s are separated from each other, and the chips generated from the sub cutting edge 3s move toward the center side. The force to wind it cannot be applied to the chips generated from the main cutting edge 3m, and only the chips generated from the sub cutting edge 3s collide with the inner peripheral wall surface of the sub groove 1s, and the main cutting edge 3m The chips coming out will flow along the main groove 1m as it is, and will not be broken finely. It should be noted that if the main cutting edge 3m and the sub cutting edge 3s are directly intersected with each other, the shape of the cutting edge at the intersection P ₁ becomes extremely sharp, which obviously causes chipping. The shape of the cutting edge in the part is rounded in a very common sense. Assuming that the drill diameter is D, the core thickness dimension of the main groove forming portion (diameter dimension W of the core thickness indicated by the broken circle in contact with the bottom of the main groove 1m in FIG. 1) is 0.25D to 0. It is set to the range of 4D. This core thickness dimension must be 0.25D or more in order to maintain the drill rigidity to the minimum level, and in order to obtain a sufficient cross-sectional opening area of the main groove 1m to maintain good chip discharge performance. Is preferably 0.4 D or less. By the way, the main cutting edge 3m and the sub cutting edge 3 from the axis O
Since the point P ₁ is located on the inner wall surface of the main groove 1 m, the distance to the intersection point P ₁ with s, that is, the distance from the axis O to the outermost peripheral end of the sub cutting edge 3 s is at least the minimum core thickness dimension. Greater than half (0.125D). Of course, from the same idea, it can be larger than half the maximum core thickness dimension (0.2D). By the way, regarding the maximum core thickness of 0.4D, as described in the explanation of the operation of the invention, the chips generated from the main cutting edge 3m are moved toward the center side of the drill by the chips generated from the auxiliary cutting edge 3s. It is necessary to form the auxiliary cutting edge 3s in a portion sufficiently on the axial center side of the drill in order to make it flow in such a way that it can be rolled up. Is weaker in the direction toward the center of the drill), the core thickness dimension that is limitedly involved in shortening the distance from the axis O to the outermost peripheral edge of the sub cutting edge 3s is 0. It is preferably 4D or less. However, geometrically, the position of the point P ₁ can be brought to any position on the inner wall surface of the main groove 1 m, so theoretically, when the drill takes the maximum core thickness dimension of 0.4 D, It is also possible to shorten the distance from the axis O to the point P ₁ to 0.2D, and the point P ₁ can be approached to this position endlessly. Therefore, within the range where the core thickness dimension is smaller than 0.4D, the axis O to the point P
The distance to ₁ can be 0.2D or less. In the example shown in FIG. 1, the actual size is about 10 times, but the core diameter is 3.3 mm for a drill diameter of 10 mm.
And the distance from the axis O to the point P ₁ is 1.75 mm. The core thickness of the sub-groove forming portion is set in the range of 0.04D to 0.17D. This dimension corresponds to the set value range of the core thickness dimension of the main groove forming portion, but is the set value range of the dimension that can sufficiently reduce the cutting resistance (thrust) without performing thinning in the chisel portion, and It is a set value range of dimensions that can secure a sufficient depth as the sub groove 1s and a sufficient length as the sub cutting edge 3s. The length dimension of the sub groove 1s is set in the range of 0.5D to 1.1D. This dimension ensures a minimum repolishing area,
In addition, especially, the chips generated from the main cutting edge 3m are not bent so much in the direction of the vine shape and are generally along the rake face, and are drawn into the chips generated from the sub-cutting edge 3s to be the center of the drill. It is set to 0.5D or more to form the sub-groove 1s to the position where it collides while flowing toward the side, and is set to 1.1D or less as a limit value required to secure the drill rigidity. Regarding this upper limit value, the dimension is such that a sufficient life can be obtained in relation to the drill rigidity and the life. FIG. 3 is a graph showing the result of an experiment on the relationship between various length dimensions of the sub groove 1s and the number of drilled holes. The drill according to the present invention has a groove width ratio of 0.8: 1 to 1.7:
It can be set over a wide range from 1 to 1, and is effective in almost all of the groove width ratios that can be realistically set. Further, as shown in FIG. 1, it is also possible to scrape off the heel portion as shown by the hatching in broken lines to increase the space of the main groove to enhance the chip discharge performance and improve the penetration of cutting oil. . Since the sub-groove 1s is formed in order to make the chisel portion 2 sufficiently small instead of performing the thinning, it is not necessary to perform the thinning at the time of re-polishing. Since the sufficient groove space can be secured by forming the sub groove 1s, it is particularly suitable for deep hole processing.

[Brief description of drawings]

FIG. 1 is an end view showing a cutting edge shape of a drill according to the present invention,
FIG. 2 is a side view of the drill according to the present invention, and FIG. 3 is a graph showing the relationship between various length dimensions of the auxiliary groove and the number of drilled holes,
FIG. 4 is an explanatory view showing three steps in drilling with a drill, FIG. 5 is a view showing the shape of the chips discharged in the stage I, and FIG. 6 is a chip discharged in the stage II. Fig. 7 shows the shape of the chips discharged in the stage III, and Fig. 8 shows one chip of the chip shown in Fig. 5 cut along the line XX. It is a figure which shows the state of two cut pieces of. 1 ... Chip discharging groove, 1 m ... Main groove, 1 s ... Sub groove, 2 ... Chisel part, 3 ... Cutting edge, 3 m ... Main cutting edge, 3 s ... Sub cutting edge, 4 ... Negative land, θ ... Main cutting edge Angle between secondary cutting edge, P
₁ ... Intersection of main cutting edge and sub cutting edge

Claims (3)

[Claims] 1. A main groove (1 m) forming a main cutting edge (3 m) located on the outer peripheral side of the cutting edge (3) of the drill, and a sub cutting located on the inner peripheral side of the cutting edge (3). A drill having a chip discharge groove (1) including a sub-groove (1s) forming a blade (3s), wherein the main cutting edge ( 3m ) is formed to be curved in a concave shape with respect to a rotation direction, An angle (θ) between the main cutting edge ( 3 m ) and the sub cutting edge ( 3 s ) is 100 degrees or more, and the main cutting edge ( 3 m ) and the sub cutting edge ( 3
The distance to the intersection (P ₁ ) with s ) is set to 0.2 times or less of the drill diameter (D). 2. The core thickness dimension of the main groove forming portion is 0.25 times or more and 0.4 times or less the drill diameter (D), and the core thickness dimension of the sub groove forming portion is the drill diameter (D). The range of 0.04 times or more and 0.17 times or less, and the length dimension of the sub-groove (1s) is 0.5 times or more and 1.1 times or less of the drill diameter (D). The listed drill. 3. The drill according to claim 1, further comprising a negative land portion (4) on an outer peripheral side end portion of the main cutting edge (3 m).