JPH0839319A - Three-blade drill - Google Patents

Abstract

PURPOSE:To provide a drill in which not only a deep hole machining having no prepared hole but also a high speed drilling work having a casted hole can be stably performed. CONSTITUTION:In a three-blade drill, an oil hole for blowing out cutting oil agent from the drill top end is provided within a land 3 along a helical angle, the helical angle is set to 30 deg.-45 deg., the point angle alpha is set to 140 deg.-160 deg., the sinning angle gamma is set to 25 deg.-35 deg., the core thickness omega is set to 1/3D-3/5D to the outer diameter D of the drill top end, and the groove width ratio represented by the ratio of the angle theta2 of a groove part 1 to the angle theta1 of the land part 3 is set to theta2/theta1=1.5/1-2.5/1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drill for drilling a soft material such as an aluminum alloy.

[0002]

2. Description of the Related Art In drilling a soft material such as an aluminum alloy, a three-flute drill is known for highly accurate drilling (Japanese Patent Laid-Open No. 5-301108).

[0003]

However, in the conventional three-blade drill, for example, deep hole drilling with a hole depth L of 3 to 5 times or more of the outer diameter D of the drill tip is performed at high speed (cutting speed of 300 to 50).
Attempting to machine at 0 m / min or more) has the following problems.

Because of the high speed, the cutting edge temperature rises too much.

Due to the chips that are discharged, cutting oil does not reach the cutting edge.

Since the chip discharge speed is high because of the high speed, if the chip discharge is delayed even for a moment, chip jamming is likely to occur, and the drill life is extremely shortened due to chatter, and eventually drill breakage, etc. Can not stand.

Therefore, an object of the present invention is to solve the problems of the above-mentioned conventional techniques, and in drilling an aluminum alloy or the like, not only deep hole drilling without a pilot hole but also high speed drilling with a cast hole. However, we provide a drill that can perform stable drilling.

[0008]

In order to achieve the above object, the first invention is a three-blade drill, and an oil hole for ejecting a cutting fluid from the drill tip is formed in the land portion along the helix angle. The twist angle β is 30 ° to 45 °, the tip angle α is 140 ° to 160 °, and the thinning angle γ is 25.
° ~ 35 °, core thickness ω 1 / 3D of the outer diameter D of the drill tip ~
The groove width ratio represented by 3 / 5D and the ratio of the groove angle θ2 and the land angle θ1 is θ2 / θ1 = 1.5 / 1 to
It is set to 2.5 / 1.

A second aspect of the present invention is one in which a hard material made of TiN, TiCN, diamond or the like is formed in a single layer or multiple layers in at least a portion including the tip of the cutting edge of the groove.

[0010]

Since the three-blade drill of the present invention is a three-blade drill, even in the processing where there is a prepared hole such as a cast hole, the guideability is increased by the margin portion as compared with the ordinary two-blade, and the hole expansion hole bending is accompanied. Stable cutting is possible without chattering. Further, even in deep hole machining without a prepared hole, the cutting oil can be reliably supplied to the tip of the cutting edge, so that it has the following excellent features.

B) The progress of wear can be delayed by cooling the cutting edge.

(B) It is possible to reduce welding that occurs on the cutting edge.

C) The supply of hydraulic pressure also facilitates chip discharge.

The helix angle corresponds to the rake angle of the cutting tool and is required to be 30 ° or more in terms of sharpness and chip discharge, but it is set to 45 ° or less in terms of the strength of the cutting edge.

Next, if the thinning angle γ is smaller than 25 °, the chip discharging property is good, but the tip chisel portion is liable to be chipped and chipped easily. If the angle is larger than 35 °, the chip discharging property is deteriorated, which causes chip jamming and welding of the cutting edge near the center. Therefore, the thinning angle γ
Was 25 ° to 35 °.

The tip angle α is α = 140 ° to 16 ° in consideration of the improvement in torsional rigidity and the chip outflow direction in the three-blade.
It was set to 0 °.

The larger the core thickness ω, the more the torsional rigidity increases, but the flute becomes shallower, so that the chip discharging property deteriorates. Higher-speed cutting requires more consideration in torsional rigidity and chip evacuation than in normal work in terms of stability and reliability. Therefore, the core thickness ω is set to 1 / 3D to 3/5 of the outer diameter D of the drill tip.
D was set to a larger value to secure rigidity, and by combining the groove width ratio θ2 / θ1, the helix angle β, the tip angle α, and the thinning angle γ, the chip discharging property was improved.

By forming a coating layer or layers of TiN, TiCN, diamond or the like on at least a portion of the groove portion including the tip of the cutting edge, the coating improves the wear resistance and reduces the cutting speed of the central shaft. Adhesion in the vicinity can be reduced. Particularly when drilling a hole in an aluminum alloy, it is preferable to provide a diamond film or an amorphous diamond-like carbon film that is less welded and has a higher hardness.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, reference numeral 100 denotes a drill tip portion of a three-blade drill, and needless to say, the drill tip portion 100 is provided with three blade portions 100a. The land portion 3 of the three-blade drill is provided with an oil hole 4 for ejecting cutting fluid from the tip of the drill, and the oil hole 4 has a helix angle β.
Extending along.

Further, according to this embodiment, various dimensions of the drill tip 100 are determined as follows according to the result of the experiment described later.

Referring to FIGS. 1 and 2, the twist angle β is 3
0 ° to 45 °, tip angle α is 140 ° to 160 °, thinning angle γ is 25 ° to 35 °, core thickness ω is 1 / 3D to 3 / 5D of outer diameter D of the drill tip, and angle θ2 of groove 1 is And the groove width ratio represented by the ratio of the angle θ1 of the land portion 3 is θ2 / θ
1 = 1.5 / 1 to 2.5 / 1.

Next, an experimental example will be shown.

First, with respect to the twist angle α and the groove width ratio θ2 / θ1, a cutting test was carried out at a vertical machining center using a cemented carbide 3-flute drill with oil holes having an outer diameter D of 8 mm. The dimensions other than the twist angle and the groove width ratio are the outer diameter D = 8 mm, the tip angle α = 150 °, the thinning angle γ = 30 °, and the contact width b = 0.4 of the margin 2 (t = 0.8 mm).
mm Core thickness ω = 3.6 mm (= 0.45 D) Oil hole diameter d = 1.0 mm Back taper = 0.15 / 100 The carbide round bar material of the drill has a drill outer diameter D at the time of extrusion molding. Three holes were formed at equal intervals of 120 ° according to the twist so that a predetermined helix angle was obtained, and it was manufactured by sintering similarly to general cemented carbide.

The cutting test conditions are as follows: Work material ADC12 rotation speed (cutting speed) 1000 min ^-1 (380 m / min) Feed amount per rotation 0.12 mm / rev Hole depth 40 mm Cutting oil Water-soluble cutting oil The evaluation of the results at this time is shown in Table 1.

The evaluation criteria are judged by chip evacuation, chatter vibration and hole drilling accuracy (hole surface roughness, expansion allowance, amount of tilt), and sequentially from good to bad overall evaluation ◎ ( It is shown in the table by symbols of excellent, good (good), fair (fair), and bad (x).

[0027]

[Table 1] In Table 1, when the helix angle was 55 °, there was severe chattering, and some chips had chipping defects, so normal cutting could not be performed. This is because a) the effective cross-sectional area of the groove is small when viewed at right angles to the twist, even if the groove width ratio is θ2 / θ1 and the twist is weak, so chip clogging is likely to occur, b) At a helix angle of 55 °, this is probably because the wedge angle becomes too small and the strength of the cutting edge deteriorates even though it is aluminum cutting.

Regarding the groove width ratio θ2 / θ1, θ
It is considered that 2 / θ1 = 1.5 / 1 to 2.5 / 1 is a good range.

Next, with a drill having an outer diameter D of 6.8 mm, a test with an eccentric prepared hole was performed under the following cutting conditions, assuming casting hole processing.

The drill used is a 3-flute oil hole drill (made of cemented carbide, equivalent to K10) outer diameter D = 6.8 mm tip angle α = 150 ° helix angle β = 35 ° thinning angle γ = 30 ° groove width ratio θ2 / θ1 = 1.8 / 1 Core thickness ω = 3.5 mm (= 0.51 D) Margin width t = 0.4 mm Oil hole diameter d = 0.8 mm Back taper = 0.15 / 100 Cutting conditions Work material ADC12 Rotational speed 12000, 15000 min ^-1 Cutting speed 256 320 m / min Feed per rotation 0.1 mm / rev Hole depth 16 mm, but with prepared hole (φ4 mm, depth 20 mm, misalignment 0.8 mm) Cutting oil Water-soluble cutting oil For comparison, a comparative product having two blades (the shape is basically the same as the product of the present invention except for the number of blades) was also tested.

The two-flute drill of the comparative product exhibited a great amount of chattering from the early stage of cutting, but the product of the present invention showed no chattering even in the machining of the eccentric prepared hole, and the cutting sound was quiet. The difference between these states is that the cutting load (axial component force <thrust force>, radial component force <bending force>) shown in FIG. This can be seen from the fact that the average value of the radial component force and its fluctuation are extremely small and stable under any condition of / min.

Further, under the same conditions, drilling was performed without a pilot hole. The hole depth to be machined at this time is 30 mm.

According to this, the outer diameter D of the drill tip of the present invention
Although the 6.8 mm 3-flute drill had welding in the vicinity of the center of the cutting edge, it was possible to perform stable drilling without chipping due to the effect of internal lubrication.

By using a drill coated with a diamond-like carbon film, the welding generated on the cutting edge could be significantly reduced, and the drilling accuracy and the service life could be improved.

[0035]

As is apparent from the above description, according to the first aspect of the invention, the three-blade drill is provided with the oil hole,
In addition, by specifying the helix angle, groove width ratio, thinning angle, core thickness, and groove width ratio, it is possible to perform deep hole machining without a pilot hole as well as high-speed and stable cutting with a cast hole. Can be improved.

According to the second aspect of the invention, by coating the groove portion including the tip of the cutting edge with a diamond-like film having a low affinity for aluminum, the reliability is improved and the processing accuracy is further improved. You can

[Brief description of drawings]

FIG. 1 shows a front view of an embodiment of the present invention.

2 shows a bottom view of FIG.

FIG. 3 shows measurement results of axial component force (thrust force) of cutting resistance and spindle power.

[Explanation of symbols]

 1 Groove 2 Margin 3 Land 4 Oil hole b Margin contact width D Outer diameter γ Thinning angle α Tip angle β Twist angle ω Core thickness θ1 Land angle θ2 Groove width angle

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kiyoshi Hasegawa 2 Takaracho, Kanagawa-ku, Yokohama, Kanagawa Nissan Motor Co., Ltd. (72) Inventor Nobuyasu Nonaka 2100, Kamiimaizumi, Ebina, Kanagawa Hitachi Seiko Co., Ltd. (72) Inventor Etsuomi Sugano 4-13 Toyo, Koto-ku, Tokyo Inside Hitachi Tool Co., Ltd.

Claims (2)

[Claims] 1. A three-flute drill has an oil hole for ejecting a cutting fluid from the tip of the drill along a helix angle in a land portion, and has a helix angle β of 30 ° to 45 ° and a tip angle α of 140. ° ~ 160 °, thinning angle γ 25 ° ~
35 °, core thickness ω is 1 / 3D to 3 / of the outer diameter D of the drill tip
5D, and the groove width ratio represented by the ratio of the groove angle θ2 and the land angle θ1 is θ2 / θ1 = 1.5 / 1 to 2.
A 3-flute drill characterized by being 5/1. 2. The three-blade drill according to claim 1,
TiN, T
One or two layers of hard material such as iCN and diamond
A 3-flute drill characterized by being layered.