JPH05301108A - Drill - Google Patents

Abstract

PURPOSE:To perform boring processing of highly tough and soft materials such as aluminum with high accuracy by setting the torsion angle, that is the axial direction face angle of tip cutting blade to, 30 deg.-40 deg.. CONSTITUTION:Tip cutting blades 1 are provided at every 120 deg. of the central angle and the web thickness W in relation to the outer diameter D is set within the range of 0.25D-0.5D. Groove width rate (alpha1:alpha2) is set within the range of 1.3:1.7-1.7:1 and the torsion angle gamma is set within 30 deg.-40 deg.. And the radial face angle at a random point on the tip cutting blades 1 is varied along the tip cutting blades 1. Thus highly tough and soft materials such as aluminum member can be bored with high accuracy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drill, and more particularly to a drill suitable for drilling a soft material having high toughness such as an aluminum material.

[0002]

2. Description of the Related Art For example, aluminum materials frequently used in various manufacturing industries such as the automobile industry have higher toughness and are softer than iron-based materials such as steel. When drilling is performed with the drill, "peeling" occurs on the inner peripheral surface of the drilling, or the opening cross section does not become a perfect circle but becomes a shape close to a polygon.

The occurrence of "peeling" on the inner peripheral surface of the drill hole is caused by, for example, increasing the rotational speed of the drill in order to perform high-speed machining, or the peripheral diameter of the outermost peripheral cutting edge of the drill due to the relatively large inner diameter of the drill hole. This can happen at higher speeds.

Further, the inventor of the present application examined the reason why the cross section is not a perfect circle as described above but is a shape close to a polygon. As a result, the drill is generally composed of two blades, and if there are cutting blades at 180 ° opposite positions in the radial direction, there is a strong tendency that the opening cross section does not become a perfect circle but approaches a polygon as described above. It seems that Then, it was investigated whether or not the three-blade drill was conventionally known, but two examples of the three-blade drill could be known as the prior art. The two-blade three-blade drills are used for expanding holes that have already been drilled as pilot holes (for hole expansion) and those that perform drilling from a state without a pilot hole (for drilling). is there.

In the hole expanding drill, the length is 0.1D when the outer diameter is D, as shown in FIG.
It has a tip cutting edge 10 of about 0.2D on the outer peripheral portion.
Further, in the drill for drilling, as shown in its tip surface shape in FIG. 5, a tip cutting blade 11 is formed up to a position close to the axis of the drill. However, each of these tip cutting edges is a linear cutting edge having a radial rake angle of approximately 0 degrees, and the rake angle does not change over the entire area of the cutting edge. Therefore,
Chips are broken only by the difference in peripheral speed between the inner and outer circumferences of the cutting edge, and there is a problem in the chip breakability especially when cutting a soft work material with high toughness such as aluminum. Good perforation was difficult.

The present invention has been devised in order to effectively solve the above-mentioned conventional technical problems.
Therefore, an object of the present invention is to provide a drill capable of drilling a highly tough soft material such as aluminum with high precision.

[0007]

A drill according to the present invention comprises:
In order to solve the problems of the prior art as described above and achieve the object, the following structure is provided. That is, it has a tip cutting edge at every 120 ° center angle, the core thickness is within the range of 0.25D to 0.5D with respect to the outer diameter D, and the groove width ratio is 1.3: 1 to 1 It is within the range of 0.7: 1 and the twist angle is 30 °.
Within the range of -40 °, the radial rake angle at each arbitrary point on the tip cutting edge changes along the cutting edge.

[0008]

In the drill according to the present invention, the three tip cutting edges are evenly arranged in the circumferential direction, and the other tip is positioned 180 ° in the radial direction opposite to the other tip cutting edge. Since there is no blade, the cross section of the opening becomes a perfect circle with good accuracy. The rigidity tends to decrease with a three-blade drill, but the rigidity required for cutting aluminum materials is secured by taking a sufficient core thickness dimension.
In addition, if the core thickness is increased, the chip space in the chip discharge groove is affected, and chip discharge performance is generally poor, but the groove width ratio is at least 1.3: 1 to 1.7: 1. By increasing the size, sufficient chip discharging property can be obtained. further,
The twist angle, that is, the axial rake angle of the tip cutting edge is 30 ° to 40
The cutting performance suitable for cutting aluminum materials is demonstrated by making it larger than the ordinary drill. Further, since the rake angle in the radial direction changes along the cutting edge, the chips scraped off from the cutting edge are curled due to the compressing action and the pulling action and are well broken, and the inner peripheral surface of the hole It does not occur. Therefore, a highly tough soft material such as an aluminum material can be punched with high precision.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A three-blade drill according to an embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a side view showing only the blade portion of the three-blade drill of this embodiment,
FIG. 2 shows the enlarged front view. Further, FIG. 3 shows a detailed shape of the tip cutting edge. The drill of this embodiment is made of cemented carbide and has an outer diameter D of 10 mm, a total length of 105 mm, and a blade length of 60 m.
m, the core thickness W is 0.39 mm, and the core thickness W is 0.3 of the outer diameter D.
It has been multiplied by 39. This value gives the drill sufficient rigidity to cut aluminum. Also, the tip angle θ
Is 140 °, the margin width t is 1 mm, and the second outer peripheral depth c is 0.2 mm. The material may of course be high speed tool steel.

The tip cutting edge 1 is formed at a position where the central angle is 120 ° and is configured as a three-blade drill. The twist angle γ of the drill is set in the range of 30 ° to 40 °, which is set to be 30 ° in this embodiment, which is larger than the general twist angle of the steel drill. The axial rake angle of the tip cutting edge 1 is equal to this twist angle γ, and an axial rake angle larger than that of a steel drill is suitable for cutting aluminum materials. Groove width ratio α
₁ : α ₂ is set to fall within the range of 1.3: 1 to 1.7: 1. In the present embodiment, α ₁ is 70 ° and α ₂ is 50.
In °, it is set to 1.4: 1.

The tip cutting edge 1 is composed of a primary cutting edge 1 ₁ formed on the outer peripheral side by the chip discharge groove 2 and a secondary cutting edge 1 ₂ formed on the chisel portion 3 by thinning. The primary cutting edge 1 ₁ is concavely curved so as to be recessed toward the land portion 4, and a straight line connecting the point P ₁ at the outermost peripheral edge and the point P ₂ at the innermost peripheral edge is separated from the axis O. Thus, the radial rake angle β at any point on the primary cutting edge 1 _1, is set to change in each point along the concave curve of the cutting edge 1 _1.
The secondary cutting edge 1 ₂ is formed by a linear cutting edge extending from the axis O to the point P ₂ , and the radial rake angle does not change in this portion. The length ratio between the primary cutting edge 1 ₁ and the secondary cutting edge 1 ₂ may be about 2: 1. In this embodiment, the primary cutting edge 1 ₁
Is formed as a concave curved line cutting edge, but it may be formed as a straight cutting edge that does not face the axis O, and even in that case, the radial rake angle changes along the cutting edge.

[0012] Thus the primary cutting edge 1 ₁ of the radial rake angle is changed, chips generated from the cutting edge is likely to be finely divided so subjected to a compressive and tensile action, as aluminum material Even in the perforating process of a highly tough soft material, it can be processed without causing "peeling" on the inner peripheral surface of the process. Therefore, the finishing accuracy of the inner peripheral surface of the hole is good.
Further, since the cutting edge does not overlap with the position of 180 ° in the radial direction by the three-blade drill, the roundness of the processed hole is high.

In the above-described embodiment, the chisel portion has a secondary cutting edge formed by thinning as a drill for drilling. However, a secondary cutting edge is formed in the case of a hole expanding drill for enlarging the hole diameter with respect to the prepared hole. However, in this case, the tip surface may be a flat surface instead of a conical surface.

[Brief description of drawings]

FIG. 1 is a side view showing only a blade portion of a three-blade drill according to an embodiment of the present invention.

FIG. 2 is an enlarged front view of the drill shown in FIG.

FIG. 3 is a detailed view showing a tip cutting edge of the drill of FIG.

FIG. 4 is a view showing a tip cutting edge shape of a three-blade drill for hole enlargement according to a conventional technique.

FIG. 5 is a view showing a tip cutting edge shape of a conventional three-blade drill for drilling.

[Explanation of symbols]

1 tip cutting edge 1 ₁ 1 primary cutting edge 1 ₂ secondary cutting edge 2 cutting chip discharging groove 3 chisel portion 4 land portion

Claims (1)

[Claims] 1. A tip cutting edge (1) is provided at each position of a central angle of 120 °, and a core thickness (W) is within a range of 0.25D to 0.5D with respect to an outer diameter (D), The groove width ratio (α ₁ : α ₂ ) is in the range of 1.3: 1 to 1.7: 1, the twist angle (γ) is in the range of 30 ° to 40 °, and the tip cutting edge ( A drill characterized in that the radial rake angle at any point in 1) changes along the cutting edge (1).