JPH0192019A - Drill - Google Patents

Abstract

PURPOSE:To prevent chipping and to improve stability of biting by forming the inner circumferential section of drill body of a honing cutter such that the width thereof is decreased gradually from the outer circumferential side toward the center of rotation. CONSTITUTION:The width of a land on a chamfer face 15a at a linear section of a honing cutter 15 is constant from the outer circumferential side toward the inner circumferential side, and the width of land on a chamfer face 15b at a curved section is decreased such that it will be zero at the center of rotation. Axial angle of the chamfer face 15b increases gradually toward the center of rotation. Consequently, it can withstand against a large impact on the outer circumferential face having a high cutting speed. Since the width of the chamfer face 15b is zero in the center of rotation, biting stability is improved and chipping of edge is prevented.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a drill having a honed blade, such as a carbide drill, and particularly to a drill that improves biting stability and significantly reduces thrust load. It's about technology.

[Conventional technology] In general, in drills whose cutting edges are made of materials such as cemented carbide, the edges of the cutting edges are honed to remove sharp edges and prevent chipping, while reducing the width of the chisel. A thinning process is applied to reduce thrust load and improve bite stability.

For example, the drills shown in FIGS. 9 and 10 have been subjected to a process called X-thinning, and have a chisel width that is almost zero. The drill shown in these figures has two twists N (chip discharge grooves) 2 and 2 formed on the outer periphery of the drill body l made of a sintered body such as cemented carbide, and the tip surface of the drill body l. 3
A flank surface 4 is formed in approximately half of the rotation direction side,
A thinning portion 5 cut down with a downward slope is formed on the opposite side.

Here, a honing blade 6 extending from the outer periphery to the rotation center of the drill body l is formed at the intersection of the flank surface 4 and the wall surface facing the rotation direction of the helical groove 2.

The honing blade 6 is configured to form a chamfered surface at the intersection of the flank 4 and the wall surface of the helical groove 2, and the width of the chamfered surface 71 is approximately constant over the entire length of the honing blade 6. It is said that

[Problems to be Solved by the Invention] However, in the above-mentioned drill, as a result of using the honing blade 6 as the cutting edge, a chisel 7 is formed near the center of rotation, and a so-called scraping motion occurs when biting. There was a problem that the thinning process became almost meaningless due to the occurrence of thinning and an increase in the thrust load.

[Purpose of the Invention] This invention was made in view of the above circumstances, and can not only prevent the occurrence of chipping of the cutting edge, but also improve the biting stability and reduce the thrust load. The purpose is to provide a drill that can.

[Means for Solving the Problems] The drill of the present invention has at least a portion of the honing blade on the inner circumferential side of the drill body so that the width thereof gradually becomes narrower from the outer circumferential side of the drill body toward the rotation center side. It was formed.

[Effect] When drilling holes with a drill, the cutting speed is faster on the outer periphery than on the rotation center side, so a larger impact force acts on the outer periphery of the cutting edge than on the inner periphery, resulting in chipping. etc. are likely to occur. For drills with the above configuration,
Since the width of at least the inner circumferential side of the drill body of the honing blade gradually narrows from the outer circumferential side toward the rotation center, the width is wide on the outer circumferential side of the honing blade, so a large impact force is generated. On the other hand, since the width is narrow near the center of rotation, the width of the formed chisel is also small, thus making it possible to improve the biting stability and reduce the thrust load.

Furthermore, if the width of the honing blade is made approximately zero at the center of rotation, the width of the chisel will also be approximately zero, so that the biting stability can be further improved and the thrust load can be further reduced.

Furthermore, if the honing blade is configured by chamfer honing, and the chamfer surface of the honing blade is formed so that its axial angle gradually becomes positive as it goes from the outer circumference side of the drill body toward the rotation center side, the honing on the inner circumference side The rake angle of the blade is in the positive direction, reducing cutting resistance.

[Embodiment] Hereinafter, an embodiment of the present invention will be described with reference to FIGS. 1 to 8. FIG. 1 is a bottom view showing the drill of the embodiment. The drill shown in Fig. 1 has two twisted grooves (chip discharge grooves) 1 on the outer periphery of the drill body lO made of cemented carbide.
1 and 11 are formed, a flank 13 is formed in approximately half of the tip face 12 of the drill body 10 on the rotation direction side, and a thinning part 14 cut down with a downward slope is formed in the opposite part. Cage, flank 13 and twist WItl
A honing blade 15 extending from the outer periphery to the rotation center of the drill body l is formed at the intersection with the wall surface facing the rotational direction of the drill body l. The chamfer surfaces 15a, 1
5b. The above points are similar to the conventional drill.

However, in this drill, the land width of the chamfer surface 15a in the straight portion of the honing blade 15 in FIG. 1 is constant from the outer peripheral side to the inner peripheral side, but the land width of the chamfer surface 15b in the curved portion is gradually narrowed from the outer circumferential side toward the center of rotation of the drill body 10, and becomes zero at the center of rotation.

As a result, the width of the chamfer surface 15b gradually becomes narrower from the outer circumferential side toward the rotation center, and becomes zero at the rotation center. Furthermore, the axial angle of the chamfer surface 15b gradually becomes positive as it goes from the outer circumferential side toward the center of rotation.

Here, when the drill radius is R, 0.
In the portion separated by 25R, the land width W of the chamfer surface 15b is 0.01R, and the axial angle θ is 10°. On the other hand, the land width W at the outer periphery of the chamfer surface 15a is 0.02R1, and the axial angle θ is 30°.
It is said that

The entire surface of the drill is coated with a hard layer of TiN, T1CN, etc., which prevents the built-up cutting edge from adhering and improves wear resistance.

In such a drill, the width of the chamfer surfaces 15a and 15b is wide on the outer peripheral side where the cutting speed is high, so that the drill can sufficiently withstand a large impact force. Moreover, since the width of the chamfer surface 15b is zero at the center of rotation, the chisel width is zero.

Therefore, the biting stability can be improved and the thrust load can be reduced.

Furthermore, in the above drill, the axial angle of the chamfer surface 15b gradually becomes positive as it goes from the outer circumferential side toward the center of rotation, so that cutting resistance can also be significantly reduced.

That is, in general, when the cutting allowance is, for example, less than half the width of the chamfer surface, the axial angle of the chamfer surface becomes an effective rake angle. Therefore, the effective rake angle is negative in a considerable portion on the inner peripheral side of the honing blade, and the cutting resistance is quite large.

However, by configuring as described above, the effective rake angle on the low depth of cut side can be set in the positive direction, making it possible to significantly reduce cutting resistance.

Next, such effects will be clarified based on specific experimental examples. In this experimental example, the drills shown in FIG. 9 and FIG. The drill diameter was 12 mm. The cutting conditions were as follows: work material S 0M440, hardness HRC 30-35, hole depth 30 mm, cutting speed 3.
5m/min, feed speed 0.15~0,
The speed was varied within a range of 55 mm/rev. and,
The experimental results for the drill of the embodiment are shown in FIG. 5, and the experimental results for the conventional drill are shown in FIG. 6.

In Figures 5 and 6, the upper row shows the thrust load for drilling, the middle row shows the cutting torque, the solid line in the lower row shows the cutting power (power consumption), and the dashed line shows the main axis of the processing equipment for drilling. Indicates the amplitude of vibration′. Note that the horizontal axis indicates time. As is clear from these figures, in the drill of the example, the thrust load could be significantly reduced. The difference is particularly noticeable on the high depth of cut side, and it can be seen that the drill of the example is extremely effective for heavy cutting. In addition, not only the thrust load but also the cutting torque and cutting power were able to be reduced. Furthermore, the amplitude of the vibration of the main shaft can be set to a much smaller value than in the conventional example, and it can be seen that the vibration of the drill can be significantly reduced.

In the above embodiment, the axial angle of the chamfer surface 15b is made to gradually become positive as it goes from the outer circumferential side toward the rotation center, but as shown in FIGS. 7 and 8, the axial angle of the chamfer surface 15b The axial angle θ may be kept constant (for example, 30°), and the land width of the chamfer surface 15b may be gradually narrowed from the outer circumferential side toward the center of rotation. Further, the land width of the chamfer surface 15a may also be made to gradually become narrower from the outer circumferential side toward the rotation center side. Furthermore, chamfer surface 15
The width b does not necessarily have to be zero at the center of rotation, but may be one that becomes gradually narrower toward the center of rotation.

By the way, the present invention is not limited to the above-mentioned chamfer honing cutting blade, and it goes without saying that similar effects can be obtained by using a cutting blade shape such as chamfer honing. It may also be applied to a drill with an oil hole. Further, it may be applied to a straight-edged drill. Furthermore, as the material of the drill body, an ultra-high hardness sintered body or the like may be used in addition to cemented carbide.

[Effects of the Invention] As explained above, in the drill of the present invention, the width of at least the inner peripheral side of the drill body of the honing blade is gradually narrowed from the outer peripheral side of the drill body toward the rotation center side. This not only prevents chipping of the cutting edge, but also reduces the vibration of the drill and improves biting stability, and also significantly reduces the thrust load. This provides an excellent effect of reducing the amount of water used.

[Brief explanation of the drawing]

1 to 8 are diagrams showing one embodiment of the present invention, in which FIG. 1 is a bottom view showing a drill, and FIG. 2 is a bottom view of the drill shown in FIG.
Direction arrow view, Figure 3 is a cross-sectional view along the ■-■ line in Figure 1 4
The figure is a cross-sectional view of the TV-TV line in Figure 1. Figure 5 is a line diagram showing the results of an experiment in which hole drilling was performed using the drill of the example. Figure 6 is a diagram showing the same experiment conducted using a conventional drill. Diagrams showing the results, FIGS. 7 and 8 are diagrams showing modifications of the drill of the example, and FIG.
Figure 8, a cross-sectional view along the line ■-■ in Figure 1, and Figure 1θ show an example of a conventional drill. 9 is a view taken in the X direction of FIG. 9; FIG. l...Drill body, 2...Twisted groove (chip discharge groove), 4...
・Running surface, 6... Honing blade, lO...
...Drill body, 11... Twisted groove (chip discharge groove), 13...
... Flank surface, 15 ... Honing blade, 15a
...Changfa side.

Claims (2)

[Claims] (1) A chip discharge groove is formed on the outer circumference of the drill body made of a sintered body, and extends from the outer circumference to the rotation center of the drill body at the intersection of the wall surface facing the rotation direction of the chip discharge groove and the tip flank. A drill formed with a honed blade, characterized in that at least a portion of the honed blade on the inner peripheral side of the drill body is formed so that the width thereof gradually becomes narrower from the outer peripheral side of the drill body toward the rotation center side. drill. (2) The honing blade is formed by chamfer honing, and the chamfer surface of the honing blade is formed such that its axial angle gradually becomes positive as it goes from the outer circumferential side of the drill body toward the rotation center side. A drill according to claim 1. (3) The drill according to claim 1 or 2, wherein the width of the honing blade is approximately zero at the center of rotation of the drill body.