JP3461538B2 - Super hard drill - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a super hard drill,
Particularly, the present invention relates to an ultra-hard drill suitable for drilling a hardened material having a hardness of around HRC60.

[0002]

2. Description of the Related Art With the demand for higher precision and higher quality of molds, the materials have become difficult to cut, especially the hardness has increased. These materials are hardened to a hardness of around HRC60 by quenching. Hardened steel with an HRC of about 50 could be used for shallow hole drilling with a conventional ultra-hard drill, but with HRC of 60 or more, the conventional ultra-hard drill breaks early or becomes uncut. It is considered very difficult to perform drilling on such a high hardness material with a drill, and in the past, the electrical discharge machining method was mainly used. Therefore, the processing efficiency has been suppressed to be extremely low.

In recent years, super hard drills have been manufactured for the purpose of drilling high hardness materials around HRC60, and those having end face cutting edge shapes as shown in FIG. 4 are known.
These drills use cemented carbide as the material and have a weaker twist angle (or tip mounting angle) than ordinary drills.
The drill rigidity is improved by adopting. In addition, in order to improve the sharpness, a flat two-stage blade is installed and further thinned.

By the way, regarding the above three super hard drills shown in FIG. 4, the die steel (SK) having hardness HRC63 is used.
When the punching processing of D11) was performed, 2 to 7 through holes could be processed. However, it has also been found that such a drill life in which only a few holes can be drilled has no superiority to electrical discharge machining in view of the overall cost and is not practical. It has also been found that in the processing of through-holes, when the drill penetrates the work material, so-called chipping tends to occur around the hole on the side where the drill comes out.

The present invention has been made in view of the above-mentioned conventional technical problems, and was devised to effectively solve the problems.
Therefore, an object of the present invention is to achieve a sufficient life even when drilling a high hardness material around HRC60, and in drilling a through hole, what is called a chipped surface on the side from which the drill comes out. It is to provide an ultra-hard drill that does not cause

[0006]

The ultra-hard drill according to the present invention has the following constitution in order to solve the problems of the prior art as described above and to achieve the object thereof. That is, in a super hard drill made of a super hard material such as cemented carbide, cermet or ceramics, and having a thinned tip surface, with a drill outer diameter D, a core portion having a diameter of 0.3D or more is provided. , The tip angle is set within the range of 135 to 145 °, and the cutting edge outer peripheral portion is chamfered at an angle of 10 to 15 ° with respect to the tip surface with a width of 0.1 to 0.15D, The cutting edge is chamfered so-called blade-killing. The angle of the blade killing with respect to the axial direction is usually 20 to 30 °
However, various dimensions are generally applied to the width, and the width is set in the range of 0.01 to 0.05 mm in the present invention.

In the ultra-hard drill of the present invention, it is preferable that the chip discharge groove has a twist angle of 14 to 16 °. Further, it is more preferable if a super-hard thin film such as a titanium compound is coated.

[0008]

In the ultra-hard drill according to the present invention, the material of the drill and various specifications are set to the work material before and after HRC60 so as to reduce the cutting resistance while increasing the rigidity of the drill and the strength against chipping. However, since the optimum shape that can be cut is achieved, it is possible to achieve a long tool life, which is unparalleled in the prior art, even when cutting these high hardness work materials.

In particular, the chamfered portion formed on the outer peripheral portion of the cutting edge not only contributes to prolonging the service life of the tool, but is also effective for suppressing the occurrence of chipping when cutting the through hole.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a super hard drill according to the present invention will be described below with reference to FIGS. Figure 1
It is a side view of the super hard drill of the present embodiment, FIG. 2 is a diagram showing an end face shape of the super hard drill of the present embodiment, and FIG. 3 is an enlarged side view of an essential part showing an enlarged chamfer of a cutting edge. Is.

The drill of this embodiment is made of cemented carbide, and
The chip discharge groove 1 of the strip has a twist angle θ of 15 ° and is slightly twisted. The outer diameter D of the drill is 10 mm. Tip angle α
Is given at 140 °. At the outer periphery of the tip surface, tip surface 2
Is chamfered at an angle β = 12 °. Figure 2
As shown in, the front end surface 2 is subjected to semi-cross type thinning. The chamfer 3 includes the cutting edge 4 to the heel 5
And is formed until reaching the thinning surface 6 in this embodiment. The width of the chamfer 3 is about 0.125D = 1.25mm at the position of the cutting edge 4,
It extends slightly backward in the direction of rotation. As for the width of the chamfered portion 3, it is necessary to maintain the drill rigidity such that the tip end surface 2 having the prescribed tip angle occupies at least the central portion having a diameter of 0.7D or more, and the chamfered portion 3 is reliable. In order to prevent the chipping of the knuckle, it is preferable to form the width of 0.1D or more. Therefore, the effective range of the width of the chamfered portion 3 is 0.1 to 0.15D. If the outer peripheral chamfer is processed later than the thinning, and the thinning surface 6 is higher than the chamfered portion 3,
This chamfering of the outer periphery also extends to the thinning surface 6.

The diameter of the core thickness portion 7 is 0.363D = 3.63.
It is given in mm and is set to obtain sufficient drill rigidity.

As shown in FIG. 3, the cutting edge 4 is chamfered with a very small width, so-called "blade killing", by honing. The width T of this blade killer 8 is 0.04 to 0.05 mm
The degree is such that chipping is prevented without impairing the sharpness of the cutting edge. The inclination angle γ with respect to the axial direction is approximately 25 °, and is usually given within a range of about ± 5 °.

When a cutting test was conducted using the ultra-hard drill of the present embodiment constructed as described above, excellent results were obtained as compared with the conventional ultra-hard drill. In the test, SKD11 having a hardness of HRC63 was used as a work material. Cutting speed is 10m / min, feed amount is 0.05mm / rev
Met. The processing length of the hole was 20 mm, which was a through hole. These conditions are the same as the tests performed on the prior art ultra-hard drill described above. With the ultra-hard drill of this example, 66 holes could be machined, and no chipping was observed around the through hole. Table 1 below shows the results of the above-mentioned tests conducted on various experimentally manufactured ultra-hard drills including the above-mentioned prior art products. In Table 1, the drill A is the present embodiment,
The drill B is another embodiment of the present invention, the drills C to E are comparative drills, the drill F is the drill of FIG. 4 (I) shown in the prior art, and the drill G is of FIG. 4 (II). 4 and the drill H are the drills of (III) in FIG.

[0015]

[Table 1]

From the above results, the drills A and B have a far longer drill life than the conventional drills F to H, and there is no occurrence of chipping. Comparing the drill A of the present invention with the drill E of the comparative example, the core thickness, the tip angle, the twist angle, and the thinning point are almost the same for both drills, but the point where the blade is killed, the outer peripheral portion The drill A is different from the drill E in that the chamfering is performed, and the difference in the drill life and the presence or absence of a chipped chip greatly differ due to this difference. Further, the drill D of the comparative example is closest to the conventional drill F except that the drill D has the outer peripheral chamfer, but the life is approximately doubled only by the presence or absence of the outer peripheral chamfer. There was no chipping. Comparing these drills, the core thickness is 0.3 with the drill diameter D.
If it is less than twice, the drill life is insufficient and the core thickness is 0.3D.
Even if it is more than the above, the life of the drill which has not been blade-killed is insufficient. Further, it is necessary to increase the tip angle to at least 135 ° or more, and it is effective to extend the life up to about 145 °. Further, even if the blade is killed, if the width becomes 0.06 mm or more, the resistance of the cutting edge becomes large and the life of the drill is shortened. In addition, a twist angle of 14 to 16 ° with a slight twist is also a preferable requirement for drill life. The chamfering of the outer peripheral portion has a great effect on the life of the drill, and is an essential condition for preventing the chipping of the teeth.

Combining each of these conditions, the material is a superhard material such as cemented carbide or equivalent cermet or ceramic, the tip surface is thinned, and the diameter of the core thickness part is 0 of the drill outer diameter. .3 times or more, the tip angle is 135 to 1
It is set within the range of 45 °, and the outer circumference of the cutting edge is
It must be chamfered at an angle of at least 10 ° and up to about 15 ° with respect to the front end face with a width of 0.15D. Further, it is necessary that the cutting edge has a width of 0.01 to 0.05 mm. further,
The twist angle is preferably set in the range of 14 to 16 °. Further, it is naturally effective to coat the surface of the drill with an ultra-hard film such as a titanium compound.

[Brief description of drawings]

FIG. 1 is a side view of an ultra-hard drill according to this embodiment.

FIG. 2 is a view showing an end face shape of a super hard drill according to this embodiment.

FIG. 3 is an enlarged side view of an essential part showing an enlarged chamfer of a cutting edge in the ultra-hard drill of the present embodiment.

FIG. 4 is a view showing end face shapes of various ultra-hard drills in the related art.

[Explanation of symbols]

1 Chip discharge groove 2 Tip surface 3 Chamfer 4 Cutting edge 5 Heel 6 Thinning surface 7 Heart-thick part 8 Blade killing 8 Width of blade killing α Tip angle β Angle of chamfer γ Angle of blade cutting θ twist angle

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-2-36010 (JP, A) Hikichi, Minoru Arai, Makoto Ogawa, Proc. Of the 1992 Precision Engineering Society Autumn Meeting, 1992, 519〜520 (58) Fields surveyed (Int.Cl. ⁷ , DB name) B23B 51/00

Claims (3)

(57) [Claims] 1. A super hard drill made of a super hard material such as cemented carbide, cermet or ceramics, having a thinned tip surface, and a core thickness portion having a diameter of 0.3D or more where D is the outer diameter of the drill. (7), the tip angle (α) is set in the range of 135 to 145 °, the outer peripheral portion of the cutting edge has a width of 0.1 to 0.15D, and 10 to 15 with respect to the tip surface. The chamfer (3) is applied at an angle (β) of °, and the cutting edge (4) has a width (T) of 0.01 to 0.05 mm and an angle (γ of 20 to 30 ° with respect to the axial direction (γ. ) Chamfer (8)
A super hard drill characterized by being subjected to. 2. The twist angle (θ) of the chip discharge groove (1) is 1
The ultra-hard drill according to claim 1, wherein the ultra-hard drill is set within a range of 4 to 16 °. 3. The ultra-hard drill according to claim 1, which is coated with an ultra-hard thin film of a titanium compound or the like.