JPH09277109A - Twist drill - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a twist drill for cutting work having a strong suppressing function of burr occurrence, reducing the height of a burr even if the burr occurs, and capable of easily removing the burr. SOLUTION: This twist drill 1 is provided with a cutting edge 2 at the tip and a helical flute 4 for discharging chips. A chamfer 3 is provided continuously to the cutting edge 2, the tip angle α of the cutting edge 2 is set to 118-135 deg., the bevel angle β of the chamfer 3 is set to 60-90 deg., the spiral angle γ of the helical flute 4 is set to 30-45 deg., and the web thickness W at the tip is set to 14-20%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a twist drill for cutting which has a cutting edge at the tip and a twist groove for discharging chips, and more particularly, a twist drill for cutting which has a strong burr suppressing function. It's about drills.

[0002]

A conventional general twist drill for drilling a steel material, which has a cutting edge at its tip and a twist groove for discharging chips, has a strong tendency to generate a strong burr. When a strong burr is generated, it is difficult to remove this burr, so manual deburring work is required, and in some cases expensive deburring equipment is required. There was a problem that the development of a twist drill for strong cutting was desired.

Therefore, the present invention has a strong function of suppressing the generation of burrs, and even if burrs are generated, the height of the burrs can be made small, and the burrs can be easily removed. The purpose is to provide a twist drill.

[0004]

A twist drill according to the present invention is a twist drill having a cutting edge at its tip and a twist groove for discharging chips as described in claim 1. A chamfer is continuously provided on the cutting edge, the tip angle α of the cutting edge is 118 ° to 135 °, the chamfering angle β of the chamfer is 60 ° to 90 °, and the helix angle γ of the spiral groove is 30 ° to 45 °. It is characterized by having.

Further, in the embodiment of the twist drill according to the present invention, as described in claim 2, the core thickness of the tip is set to 14% to 20%, or as described in claim 3. , The tip shape may be S thinning.

[0006]

1 shows an embodiment of a twist drill according to the present invention. This twist drill 1 has an appropriate outer diameter dimension D and has a cutting edge 2 at its tip. The cutting edge 2 is provided with a chamfer 3 continuously, and further, a cutting groove 4 for discharging chips is provided, and the tip angle α of the cutting edge 2 is 118 ° to 135 °.
The chamfer angle 3 of the chamfer 3 is 60 ° to 90 °, the helix angle γ of the helical groove 4 is 30 ° to 45 °, and the core thickness W of the tip is 14% to 20%. The tip shape is S thinning.

Here, the tip angle α of the cutting edge 2 is 118 ° to
If the tip angle α is smaller than 118 °, the adhesion strength of the burr becomes large and the burr becomes hard to be removed, the cutting resistance becomes large, and the chip discharging property also deteriorates. Because the tip angle α is 135 °
If it is larger than the above range, the adhesion strength of the burr is reduced and the burr is easily removed, but the cutting resistance is increased and the tool life is shortened.

Further, the chamfering angle β of the chamfer 3 is 60 ° to 9
When the chamfering angle β is smaller than 60 °, the adhesive strength of burrs becomes small and the function of suppressing burrs becomes stronger, but the cutting resistance (thrust force) becomes large and the tool life becomes 0 °. If the chamfer angle β is larger than 90 °, the cutting resistance (thrust force) will be small and the tool life will be improved, but the burr adhesion strength will be large. This is because the function of suppressing generation is weakened, and burrs that are difficult to remove are formed.

Furthermore, the twist angle γ of the twist groove 4 is set to 3
When the twist angle γ is smaller than 30 °, the cutting resistance is increased and the sharpness is reduced, and the chip discharge property is reduced, and the burr adhesion strength is set to be 0 ° to 45 °. And a burr that is difficult to remove will be formed,
This is because when the twist angle γ is larger than 45 °, the cutting resistance is small and the adhesion strength of burrs is reduced, but the cutting edge strength is reduced.

Furthermore, the core thickness W of the tip is 14 to 20%.
If the core thickness W is less than 14%, the adhesion strength of the burr becomes low and the burr can be easily removed. However, the rigidity is hindered, and the core thickness is more than 20%. This is because if it is large, the cutting resistance increases, the chip discharge property decreases, and the burr adhesion strength increases, making the burr difficult to remove.

Further, the shape of the tip is preferably S thinning.

[0012]

Example 1 Outer diameter D is 7.5 mmφ, tip angle α is 135 °, chamfering angle β is three types of 60 °, 90 °, 118 °, and twist angle γ
Is 34 ° and the core thickness W is 1.27 mm (17%) using a high speed tool steel high speed drill (made by SKH56),
A chrome steel material (SCr420H) was used as the work material.

Then, as shown in FIG. 2, the work material M has a notch Md having a substantially right-angled shape, and the notch Md.
A test of cutting a round hole Mh having an angle of 63 ° and 117 ° toward the side was performed.

In this test, an NC milling machine was used as a processing machine, water-soluble cutting oil was externally supplied, and cutting was performed by feeding once (without step feeding).

The evaluation of the results of this test is carried out in the state in which the burr Mb as shown in FIG. 2 is formed, the height of each burr Mb at the portion A and the portion B, the adhesion strength of the burr Mb, and the cutting resistance. Judgment was made based on (thrust force) and chip discharge status, and a good one was evaluated as ◯, a good one was evaluated as Δ, and a bad one was evaluated as x.

Here, when measuring the adhesion strength of the burr Mb, as shown in FIG. 3, the hook portion 6 of the force gauge G _F is hooked on the burr Mb, and the force gauge G _F is indicated by the arrow A.
Load Fk when burr Mb is removed when moving in the direction
This was done by measuring gf.

The results are shown in Table 1. The adhesion strength and cutting resistance (thrust force) of the burr Mb are also shown in FIGS. 4 and 5, respectively.

[0018]

[Table 1]

As shown in Table 1, even if the chamfer angle β is changed, the height of the burr hardly changes. However, as the chamfer angle β is smaller, the cutting resistance (thrust force) increases as shown in FIG. Therefore, the tool life is adversely affected. Further, the smaller the chamfer angle β, the less likely the work material M is to undergo plastic deformation,
Since the thickness of the burr becomes thin, the adhesion strength of the burr becomes small as shown in FIG. 4, and the burr can be easily removed.

However, as described above, the smaller the chamfering angle β is, the more the cutting resistance increases as shown in FIG. 5, which shortens the tool life and impairs the rigidity. Needs to be 60 ° or more.

When the chamfering angle β becomes large, as shown in FIG.
As shown in Fig. 6, the adhesion strength of the burr becomes large and it becomes difficult to remove it. Therefore, when the work material M is steel, 90 °
It is better to do the following.

Example 2 Two kinds of outer diameter D 7.5 mmφ, tip angle α 135 °, chamfer angle β 90 °, twist angle γ 30 °, 34 °,
A high-speed tool steel high-speed drill (SKH56) having a core thickness W of 1.27 mm (17%) is used, and the cutout Md of the work material M is formed in the same manner as in Example 1 as shown in FIG. A test of cutting a round hole Mh having angles of 63 ° and 117 ° toward the side was conducted.

In this test, the processing machine and the cutting conditions were the same as in Example 1, and the evaluation of the results in this test was also the same as in Example 1. The results are shown in Table 2. The adhesion strength of the burr Mb is shown in FIG.
Also shown.

[0024]

[Table 2]

As shown in Table 2, when the helix angle γ is small, the chip discharging property is improved, but as shown in FIG. 5, the adhesion strength of the burr becomes large and the burr becomes hard to be removed. The angle γ is preferably 30 ° or more, and
If the helix angle γ is large, the adhesion strength of the burr becomes small and the burr can be easily removed. However, since the chip discharging property and the cutting edge strength decrease, the helix angle γ should be 45 ° or less. Is good.

Example 3 Outer diameter D is 7.5 mmφ, tip angle α is 135 °, chamfer angle β is 90 °, twist angle γ is 34 °, and core thickness W is 1.2.
7 mm (17%) and 2.25 mm (30%), which are two types of high speed tool steel high speed drills (SKH56), are used, and as shown in FIG. A test for cutting a round hole Mh having angles of 63 ° and 117 ° toward the cutout portion Md was conducted.

In this test, the processing machine and the cutting conditions were the same as in Example 1, and the evaluation of the results in this test was also the same as in Example 1. Table 3 shows the results. Also, regarding the adhesion strength of the burr Mb, see FIG.
Also shown.

[0028]

[Table 3]

As shown in Table 3, when the core thickness W of the tip is small, the cutting resistance is small, and as shown in FIG. 7, the adhesion strength of the burr is small and the burr can be easily removed. However, since the rigidity of the drill decreases, the core thickness W is 1
7% or more, and when the core thickness W of the tip is large, the sharpness is reduced (the cutting resistance is increased), and the burr becomes strong, so that the burr adhesion strength as shown in FIG. The core thickness W is 2 because it becomes large and it is difficult to remove burr.
It is better to be 0% or less.

Example 4 Outer diameter D is 7.5 mmφ and tip angle α is 118 °, 13
2 types of 5 °, chamfer angle β is 90 °, twist angle γ is 34
°, a high-speed tool steel high speed drill (SKH56) having a core thickness W of 1.27 mm (17%) is used, and as shown in FIG. A test of cutting a round hole Mh having an angle of 63 ° and 117 ° toward the side was performed.

In this test, the processing machine and the cutting conditions were the same as in Example 1, and the evaluation of the results in this test was carried out at the time of new drilling and at the time of drilling 300 holes and evaluated in the same manner as in Example. Table 4 shows the results. The adhesion strength of the burr Mb is also shown in FIG.

[0032]

[Table 4]

As shown in Table 4, when the tip angle α is small, the adhesion strength of burrs is increased and the cutting resistance is also increased as shown in FIG. Is preferably 118 ° or more. However, when the tip angle α is increased, as shown in FIG. 8, the adhesion strength of burrs is reduced but the cutting resistance is increased.
It has been found that it is better to set it to 35 ° or less.

Then, as shown in FIG. 8, the tip angle α is set to 1
By setting the angle to about 35 °, it is possible to reduce the adhesion strength of burrs, and the adhesion strength of burrs does not increase even when the number of processed holes increases to 300 or more and the drill wears. It was found that the burr suppression function was maintained sufficiently good.

[0035]

According to the twist drill of the present invention, as described in claim 1, in the twist drill having the cutting edge at the tip and the twist groove for discharging chips, the cutting edge is continuously provided. A chamfer is provided, the tip angle α of the cutting edge is 118 ° to 135 °, and the chamfer angle β of the chamfer
Is 60 ° to 90 °, and the twist angle γ of the twist groove is 30 °
Since it has a structure of ~ 45 °, it has a strong function of suppressing the generation of burrs, and even if burrs are generated, the thickness of the burrs can be made thin, and the burrs can be easily removed. As a result, it is possible to eliminate the need for deburring work, which is a remarkable advantage.

Then, as described in claim 2,
By setting the core thickness of the tip to 14% to 20%, it is possible to obtain a burr that can be easily removed without lowering the rigidity of the drill, and as described in claim 3, the shape of the tip is S. The thinning brings about an excellent effect that a twist drill suitable for cutting of steel material can be obtained.

[Brief description of drawings]

FIG. 1 is a front explanatory view (FIG. 1A) and a side explanatory view (FIG. 1) showing an embodiment of a twist drill according to the present invention.
(B)).

FIG. 2 is an explanatory view showing a shape in which a work material is subjected to round hole processing in an example of the present invention.

FIG. 3 is an explanatory diagram showing a method for measuring the adhesion strength of burrs.

FIG. 4 is a graph exemplifying the result of examining the relationship between the chamfer angle β and the burr adhesion strength.

FIG. 5 is a graph exemplifying a result of examining a relationship between a chamfer angle β and a thrust force.

FIG. 6 is a graph exemplifying the result of examining the relationship between the twist angle γ and the adhesion strength of burrs.

FIG. 7 is a graph exemplifying a result of examining a relationship between a core thickness and a burr adhesion strength.

FIG. 8 is a graph exemplifying the result of examining the relationship between the number of processed holes and the adhesion strength of burrs when the tip angle α is 118 ° and 135 °.

[Explanation of symbols]

 1 Twist drill 2 Cutting edge 3 Chamfering 4 Helical groove α Cutting edge tip angle β Chamfering chamfer angle γ Helical groove helix angle W Core thickness

Claims (3)

[Claims] 1. In a twist drill having a cutting edge at its tip and a twist groove for discharging chips, a chamfer is continuously provided on the cutting edge, and a tip angle α of the cutting edge is 11
8 ° to 135 °, chamfering angle β of 60 ° to 9
The twist drill has a twist angle of 0 ° and a twist angle γ of the twist groove of 30 ° to 45 °. 2. The twist drill according to claim 1, wherein the core thickness of the tip is 14% to 20%. 3. The twist drill according to claim 1, wherein the tip has an S-thinning shape.