JP2003039218A - Drill for deep hole - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a drill made of high speed steel or hard metal for deep hole where an improvement of scraps dischargeability and an improvement of rigidity are reconciled, the flow of scraps is not interfered with, further, a flexural rigidity and a torsional stiffness are enhanced. SOLUTION: In a drill for deep hole with helical flute which is made of high speed steel or hard metal, front edge core thickness part T1 which has 30-70% of length of an effective groove part of drill which deducted the length of an upvalued part of drill flute from the length of a drill groove and with the almost same web thickness is prepared, and at least one web taper part T2 along which web thickness becomes large smoothly and continuously and without level difference towards an upvalued part CS of the drill flute from the front edge core thickness part T1 is prepared.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a deep hole drill which is a twist drill made of high speed steel or cemented carbide and having a spiral groove.

[0002]

2. Description of the Related Art Conventionally, the groove length of a high-speed steel or cemented carbide deep hole drill is longer than that of a normal drill, so that the bending stiffness representing the rigidity of the drill is proportional to the length. Drills that have a reduced groove length and long groove length
Deflection and twisting easily occur. In addition, deep hole drills use a cross-sectional shape with a wider groove area to prevent chips from stagnating in the groove, so the drill becomes more susceptible to deformation, and machining due to chipping or buckling due to vibration of the cutting edge. Bending of holes is likely to occur. In order to avoid these situations, the cutting conditions were lowered during processing, resulting in reduced production efficiency and a neck process.

As shown in FIG. 6, for example, the shape of a conventional deep hole drill made of high-speed steel or cemented carbide emphasizes good chip evacuation, and the helix angle of the drill groove is usually a drill. The core thickness of the effective drill groove is calculated by subtracting the length of the drill groove cut-up portion from the drill groove length to make it stronger and increase the groove width ratio to increase the groove area and prevent the flow of chips. It was constant, that is, the web taper was 0/100. In FIG. 6, W is the core thickness, C is the web, CS is the drill groove cut-up portion, S is the length of the drill groove cut-up portion, F is the effective drill groove length, and L is the drill groove length. Therefore, the rigidity of the deep hole drill is low, and problems such as chipping of the cutting edge, increased wear, and hole bending are likely to occur. As a countermeasure against this, a guide bush is used to suppress the deflection in the bending direction together with the positioning of the drill, or the cutting condition is lowered to reduce the cutting load, so that the bending and twisting deformation is used in a small range. In addition, in order to increase the drill rigidity and the hole position accuracy,
Japanese Patent Laid-Open Publication No. 2004-242242 discloses a small drill for punching a printed circuit board, which has a first core thickness portion having substantially the same core thickness from the distal end to the base end side and a drill diameter larger than the first core thickness portion on the base end side. It has been proposed to have a second core portion having a similar core thickness and a tapered intermediate core portion having a large taper angle connecting the first core portion and the second core portion. However, since the deep hole drill has a poor chip discharge property, it is not possible to provide the second core thickness portion close to the drill diameter or the tapered core thickness portion having a large taper angle.

[0004]

In designing a drill for deep holes, it is necessary to have a shape that allows good chip evacuation, and the necessary range must be determined to ensure that the other parts are sufficient. It is necessary to improve the production efficiency and the life of the drill by improving the rigidity. The object of the present invention is to improve the chip discharge property and the rigidity at the same time, do not hinder the flow of chips, and improve bending stiffness and torsion stiffness. To provide a drill for use.

[0005]

Therefore, in the present invention, in a deep hole drill which is a twist drill made of high speed steel or cemented carbide and having a twist groove, the length of the drill groove cut-up portion is changed from the drill groove length. 30 ~ 7 of the effective groove part of the drill
At least a tip core thick portion having a length of 0% and a core thickness that is substantially the same, and a web taper portion that is smoothly continuous to the tip core thick portion without a step and has a large core thickness toward the drill groove cut-up portion. The problem of the present invention described above has been solved by providing a deep hole drill characterized by being provided with one.

In order for chips to be ejected smoothly, it is necessary that the groove shape or groove area of the drill entering the machined hole is uniform. The groove length of the drill is the processing depth,
The length of the air cut after penetration, the re-grinding allowance, the length of the drill groove cut-up portion, the length to enter the guide bush, the clearance for preventing the machine and the workpiece from contacting are added.
Of these, from the viewpoint of chip evacuation, the groove shape or groove area of the drill is required to be equal to the machining depth +
The groove shape or groove area of the portion of the drill, which has a length corresponding to the re-polishing allowance and is not directly related to the chip discharging property, may not be uniform.

[0007]

As described above, according to the present invention, it is possible to improve the chip discharge property and the rigidity at the same time, prevent the flow of chips, and improve bending stiffness and torsion stiffness. Alternatively, a deep hole drill made of cemented carbide is provided. The tip core thickness portion has a length of 30% to 70% of the effective drill groove portion, but if it is less than 30%, the chip discharge performance will deteriorate, and if it exceeds 70, the bending stiffness and torsion stiffness will be less improved. The thickness of the tip core was 30% to 70% of the effective drill groove.

When at least one web taper portion is provided at the base of the drill groove portion, the effect of improving bending / torsional stiffness is great. This can be approximated to a cantilever beam with a fixed end on the shank side and a bending load on the tip side of the cutting edge when viewed from the material mechanics of a deep hole drill during cutting. Since the moment applied to each part of the beam increases in proportion to the distance from the bending load point, increasing the core thickness of the base part of the drill groove part away from the tip has a great effect.
By improving bending stiffness and torsional stiffness,
It has become possible to increase the cutting load by increasing the processing conditions (feed per rotation). For example, an increase in bending stiffness of 1.5 times increases the feed amount per revolution from the cutting thrust by 1.65 times, and an improvement of torsional stiffness of 1.2 times increases the cutting torque per revolution. It shows that the feed amount can be increased by 1.25 times. By improving the rigidity of the deep hole drill, it is possible to improve the neck process, which has reduced the production efficiency.

Preferably, the taper degree of the web taper portion is 0.5 to 3.0 / 100, and the taper degree is preferably from 0.
If it is less than 5/100, there is no effect, and if it exceeds 3.0 / 100, the chip discharge property deteriorates. The blade portion of the deep hole drill of the present invention includes TiN, TiCN, TiC, and TiA.
The effect of the present invention can be further enhanced by coating a ceramic coating containing one of IN or a combination thereof. Further, the deep hole drill of the present invention can be used as a drill with oil holes.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a virtual view along the axis of rotation for showing the shape of the core thickness portion of a deep hole drill made of high-speed steel or cemented carbide according to the first embodiment of the present invention. Shows a cross-sectional view,
2A is a sectional view taken along the line AA near the drill tip in FIG. 1, and FIG. 2B is a sectional view taken along the line BB near the drill groove cut-up portion in FIG. 1. . W is the core thickness, C is the web, CS is the drill groove cut-up portion, S is the length of the drill groove cut-up portion, F is the drill effective groove length, and L is the drill groove length, and the drill effective groove length is F1 + F2. = Drill groove length L-drill groove cut-up portion length S. According to the present invention, the tip core thickness portion T1 having a core thickness of 30 to 70% of the effective drill groove length and having substantially the same core thickness, and the tip core thickness portion T1 are smoothly continuous without steps and the drill groove cut-up portion is formed. C
One web taper portion T2 whose core thickness increases toward S is provided. The length of the tip thick core portion T1 is F1, and the length of the web taper portion T2 is F2. As compared with the core thickness W1 near the drill tip shown in FIG. 2A, the thickness W2 near the drill groove cut-up portion shown in FIG. 2B is increased by the taper amount of the web taper, and the land width near the drill groove cut-up portion is increased. Since U2 has a groove that is gradually shallower, it becomes larger than the land width U1 near the tip of the drill, and the drill rigidity is increased. Figure 3
Shows a virtual cross-sectional view along the rotation axis for showing the shape of the core thickness portion of the deep hole drill made of high-speed steel or cemented carbide according to the second embodiment of the present invention, the web taper portion T2, T3
Two pieces are provided and the lengths of the two pieces are F2 and F3, respectively.

Example 1: As shown in FIG. 4 (e), a long hole for a deep hole made of cemented carbide with a drill effective groove length L of 191 mm manufactured for deep hole machining with a diameter of 6 mm and a depth of 90 mm. It is an example of a drill. Tip core thickness portion length F1 having almost the same core thickness
When the taper angle is 0/100 up to 100 mm and the size of the taper angle of the remaining web taper portion T2 is changed, the bending stiffness N / mm for each taper angle (relative to 100),
And (c) and (d) show the measured values, and (a) and (b) are graphs showing the effects of the torsional stiffness N cm / deg, respectively.

The entire conventional effective groove has a web taper angle of 0 /
When the drill stiffness of 100 is 1 and the taper angle of the web is 1/100 with the drill of the present invention, the bending stiffness is 1.5 times and the twist stiffness is 1.2 times that of the conventional product having almost the same core thickness. Improved. The web taper angle is 2
When set to / 100, the bending stiffness was improved 1.8 times and the twist stiffness was improved 1.3 times as compared with the conventional product having almost the same core thickness.

Example 2: As shown in FIG. 5 (e), a long hole for a deep hole made of cemented carbide with a drill effective groove length L of 191 mm, which was produced for deep hole machining with a diameter of 6 mm and a depth of 90 mm. In the example of a drill, when the ratio of the length F1 of the tip core thickness part with a web taper angle of 0/100 and the web taper part T2 with a web taper angle of 1/100 is changed in the effective groove length L of 191 mm Showed a change in stiffness (c),
(D) is each measured value, (a), (b) is a graph.

For the effective groove length L, the web taper portion T
When the length F2 of 2 is less than 30%, the improvement of the rigidity of the drill is small and the effect of the present invention is small. Also, the web taper portion T
If the length F2 of 2 exceeds 70%, the effect of improving the rigidity is great, but since there is a hindrance to chip discharge during deep hole drilling, the length F2 of the web taper portion T2 is also seen from FIG.
Is appropriate to be 30% to 70% of the effective groove length L.

[Brief description of drawings]

FIG. 1 is an imaginary cross-sectional view along a rotation axis for showing a shape of a core thickness portion of a high-speed steel or cemented carbide deep hole drill according to a first embodiment of the present invention.

2A is a cross-sectional view taken along the line AA near the drill tip in FIG. 1, and FIG. 2B is a cross-sectional view taken along the line BB near the drill groove cut-up portion in FIG. .

FIG. 3 is an imaginary cross-sectional view taken along the rotation axis for showing the shape of the core thickness portion of the deep hole drill made of high-speed steel or cemented carbide according to the second embodiment of the present invention.

FIG. 4 (a) and (b) are graphs showing the effects of bending stiffness and torsion stiffness on each web taper angle of the cemented carbide deep hole drill of Example 1 of the present invention, respectively.
(C), (d) is a measured value, (e) is an imaginary sectional view.

FIG. 5 (a) and (b) are graphs showing the effects of bending stiffness and torsion stiffness on each web taper angle of a cemented carbide deep hole drill of Example 2 of the present invention, respectively.
(C), (d) is a measured value, (e) is an imaginary sectional view.

FIG. 6 is a virtual cross-sectional view taken along the axis of rotation for showing the shape of the core thickness portion of a conventional deep hole drill made of high speed steel or cemented carbide.

[Explanation of symbols]

C ・ ・ Web CS ・ ・ Drill groove cut-up portion F1 ・ ・ Tip core thickness length F2 ・ ・ Web taper length L ・ ・ Drill groove length S ・ ・ Drill groove cut-up portion length T1 ・ ・ Tip Core thickness part T2 ... Web taper part W ... Core thickness

Claims (4)

[Claims] 1. A deep hole drill, which is a twist drill made of high speed steel or cemented carbide and having a helical groove, having a depth of 30 to 30 that is the effective drill groove portion obtained by subtracting the length of the drill groove cut-up portion from the drill groove length. At least a tip core thickness portion having a core thickness of about 70% and a web taper portion which is smoothly continuous to the tip core thickness portion without a step and has a large core thickness toward the drill groove cut-up portion. A deep hole drill characterized by having one. 2. The taper degree of the web taper portion is 0.5.
The drill for deep holes according to claim 1, wherein the drill is 3.0 to 100. 3. TiN, TiC on the blade portion of the deep hole drill
The deep hole drill according to claim 1, further comprising a ceramic coating containing one of N, TiC, and TiAlN or a combination thereof. 4. The deep hole drill according to claim 1, wherein the deep hole drill is a drill with an oil hole.