JP2001341015A - Twist drill for cutting stainless steel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a twist drill for cutting stainless steel with excellent durability by applying a tool profile of a sharper edge when drilling a comparatively ductile material to be cut such as stainless steel and adopting a shape without applying load to a drill main body in a high speed cutting of 25 m or more. SOLUTION: This coated cemented carbide stainless steel twist drill is constituted of a helix angle: 30 to 45 deg. and a curvature of an edge groove bottom part continuous to a cutting face: 0.2 to 0.4 of a drill diameter and a groove width ratio: 45 to 70% in a cross section diagram perpendicular to the axis.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a ductile work material,
For example, the present invention relates to a drilling tool made of difficult-to-cut materials such as mild steel and stainless steel, and particularly to a stainless steel drilling tool using high-speed tool steel.

[0002]

2. Description of the Related Art Conventionally, various kinds of drills have been proposed for a drilling tool made of a ductile work material, particularly a stainless steel. In the drilling of stainless steel, as shown in Fig. 1, a general twist drill having a twist angle of about 30 degrees can be cut, but it has the property that it is hard to cut due to work hardening, and it is difficult to cut chips. In addition, there is a disadvantage that the chip discharging property (cutting power) and the hole accuracy (enlargement allowance, particularly enlargement allowance at the entrance of the work material) are deteriorated. In addition, the torsion angle of the chip discharge groove is set to be as large as about 30 degrees in order to lower the temperature of the cutting point, prolong the tool life, and lower the cutting resistance. An improved version of this is disclosed in JP-A-9-11.
No. 015 discloses a drilling tool. JP-A-9-1
Japanese Patent Publication No. 1015 is an example in which only the tip blade has a large torsion angle and good sharpness.

[0003] Further, for the same reason as above, a sharp shape of X-type thinning is used for the shape of the chisel portion when cutting stainless steel, but X-type thinning is used for the purpose of reducing cutting resistance and improving centripetality. Japanese Patent Application Laid-Open No. H11-267912 discloses an example in which the mold thinning is improved to eliminate the step, thereby enabling smooth chip discharge. In addition, the tip blade is also concave so as to enhance chip disposal. In drilling stainless steel, the form of chips is also an important issue. Regarding the chip form, a chip called a transition folding step type is the easiest to handle and has good dischargeability, but there is hardly any example focusing on the chip form in stainless steel cutting.

[0004]

As cutting chips in stainless steel cutting, transition step-shaped chips can be obtained as in the case of ordinary steel, but since the shape of the chips is broken by damage to the tip cutting edge, damage is caused. There are many studies to prevent this, and it has not been studied whether the shape is appropriate. Therefore, when the drilling of stainless steel is advanced, the chips are also separated in the initial stage of cutting, but as the number of holes increases, the chips become continuous, and if they continue for a while, the life is extended.
In this process, damage on the tool side is concentrated on the outer peripheral end of the leading edge. In order to extend the form before the chips continue, attention was paid particularly to the shape of the blade groove from the rake face.

[0005] In order to solve the above-mentioned problems, the present invention employs a sharper edge cutter for drilling a relatively ductile work material such as stainless steel, and has a high speed of 25 m or more. An object of the present invention is to provide a stainless steel twist drill having excellent durability by adopting a shape in which a load is not applied to a drill body in cutting.

[0006]

The twist drill according to the present invention is a stainless steel twist drill made of a coated super-hard alloy and having a twist angle of 30 to 45 degrees.
A twist drill for stainless steel cutting, characterized in that the curvature of the bottom of the blade groove connected to the rake face is 0.2 to 0.4 of the drill blade diameter and the groove width ratio is 45 to 70% in a cross section perpendicular to the axis. is there.

First, the radius of curvature at the bottom of the blade groove is generally about 0.15 to 0.35 of the outer diameter of the drill. The smaller the radius of curvature is, the more the chips are curled, and the larger the radius of curvature is, the larger the curl diameter is, and it is difficult to separate the chips as chips. For this reason, if the radius of curvature is set to 0.2 to 0.4 by a synergistic effect with strong torsion and the chips are separated, transition step type chips are obtained even at 0.2 to 0.40. In addition, since the curl is performed with a large curvature, the load applied to the drill is reduced, and the cut chips continue for a long time. Therefore, if the twist angle, which is the rake angle in the axial direction of the twist drill, is large, the sharpness can be improved, but the strength is reduced. If the torsion angle is less than 30 degrees, the cutting resistance is large and the margin for enlargement is large, the hole accuracy is reduced, and if the torsion angle exceeds 45 degrees, the chip discharge is hindered, so the range was 30 to 45 degrees. .

Next, the reason why the radius of curvature is set in the range of 0.2 to 0.4 of the drill blade diameter is not to use the inner wall of the drill to curl, but to use Is to be used in the same way as the inner wall for chip processing.
Therefore, a large blade groove can be provided. If it is less than 0.2, the load applied to chip processing is large, and a load is applied to the drill body, so that the life is shortened.

The groove width ratio is 45 to 7 (in the sectional view, the groove width of the chip discharge groove is divided by the outer peripheral length of the tool and expressed as a percentage).
0%. Here, if the groove width ratio is less than 45%, the groove width becomes narrow in combination with strong torsion, causing chip clogging. Therefore, the groove width ratio is 45 to 70%
Range. Furthermore, a large groove width ratio can be adjusted by the shape of the heel portion of the groove. By forming the tip of the heel portion in an arc shape, the groove width ratio can be increased and the contact of the chip with the inner wall as described above can be reduced. The core thickness of the drill was in the range of 0.10D to 0.30D. If it is less than 0.10D, the rigidity of the tool is insufficient, and the precision of the enlargement allowance of the work material entrance at the time of drilling becomes poor.
Exceeding the limit causes the space of the groove itself to be too narrow, increasing the contact with the wall, increasing the cutting resistance, deteriorating the chip discharge property, and easily causing chip clogging.

Although the twist drill of the present invention has been described using high-speed steel, powdered high-speed steel is more preferred. Since the carbide has a finer grain size as compared with the ordinary ingot high-speed steel, it is advantageous for the drill of the present invention having a large torsion angle. In addition, it can be applied to the size of the honing by making use of the torsion even in the melted high speed steel. Further, a coating is essential for a highly ductile material such as stainless steel, and a coating known in the present invention, for example, TiN or TiAlN
A film formed using a physical vapor deposition method such as described above is suitable. In particular, a film of molybdenum disulfide, a solid lubricant, or the like, which improves lubricity, is effective in the vicinity of the chisel of the tip blade where chip welding and pressure bonding are likely to occur.

By using a twist angle of 30 to 45 degrees, sharpness and high hole accuracy can be obtained. Further, in order to further improve the hole accuracy, it is preferable to make the thinning shape a shape with higher centripetality. For example, as shown in FIG. 5, a large thinning angle is used, and as shown in FIG. 4, the rake angle in the axial direction is set to a negative angle of -5 degrees or more, and a sufficient distance to the blade groove is provided so as to be smoothly connected. This can prevent chips from being clogged. Hereinafter, based on the examples,
The present invention will be specifically described.

[0012]

FIG. 3 is a front view of a drill according to an embodiment of the present invention, FIG. 4 is a top view of the drill shown in FIG. 3 rotated by 90 degrees, and FIG. 5 is a front view of FIG. The twist drill 1 according to the present embodiment is made of high-speed steel (powder high-speed steel) and has a blade diameter of 6 m.
m, two blades, helix angle 2 was 40 degrees, and TiAlN was coated. As shown in FIG. 5, the tip cutting edge 3 around the axis O
Is provided. Further, the radius of curvature R in the cross-section perpendicular to the axis shown in FIG. 6 is connected at a curvature of 30% of the outer diameter of the drill. The thinning of the tip cutting edge 3 was X-shaped.

Next, a drill according to the present invention, a conventional drill 1 having a twist angle of 30 degrees shown in FIG. 1, and a conventional drill 2 shown in FIG.
With respect to and, tests regarding the cutting performance of various work materials were performed. The conventional drill was coated with TiAlN at the same diameter. In the cutting test, SUS30
4, the drilling depth is 3D, the cutting fluid is a water-soluble emulsion type, the cutting speed is 30 m / min, the feed rate is 0.15 mm / rev, and the chipping state, wear amount and wear state of the cutting edge are determined. Checking was performed at a fixed number of times, and drilling was continued. In addition, the allowance for enlargement was measured in the processing of the first hole, and further, it was measured in the steady wear region. First, when 100 holes are drilled, the drill of the present invention can obtain curled chips with good processing properties as shown in FIG.
The enlargement allowance was as good as 0.02 mm at the entrance and at the center, showing normal wear without chipping.
In this case, the cutting speed was too high, so that one hole could not be machined, and the life was shortened. The drill of Conventional Example 2 also had chipping on the outer peripheral side. Therefore, the enlargement allowance was as large as 0.09 mm.

Further, the test was continued, and 200 holes, 400 holes
Although the number of holes and the number of holes continued to be 600, the cutting test was stopped because welding gradually began to be observed on the cutting edge, and the maximum wear amount of the flank became about 0.2 mm due to falling off. 60
The enlargement allowance in the 0-hole processing was as good as 0.03 mm. In addition, the form of the chip has almost no change, and the chip at the time of machining 600 holes is shown in FIG. 8, but not much different from the chip in FIG. 7.
There was no problem with the chips wrapping around the drill body, and the divided chips were obtained.

Next, samples having a radius of curvature R of 15%, 20%, 30%, and 40% of the outer diameter of the drill were manufactured, and a cutting test was performed in the same manner. As a result, up to the 50th hole, only 15% of the radius of curvature led to continuous cutting chips, and the others were good and showed normal wear. Further testing,
When the test was continued up to 200 holes, the chip morphology changed at 20% and continuous chips began to be discharged. Other samples showed normal wear.

Although the above embodiment has been described using high-speed steel, the present invention is not limited to this, and the present invention is similarly applicable to a solid carbide type or a throw-away type drill. Applicable.

[0017]

As described above, by using the drilling tool according to the present invention, it is possible to perform machining with small cutting resistance and high hole accuracy (enlargement allowance), and also to reduce the efficiency with which chips are entangled and reduce efficiency. Demonstrate excellent tool life without any trouble.

[Brief description of the drawings]

FIG. 1 is a front view of a conventional twist drill.

FIG. 2 is a front view of another conventional twist drill.

FIG. 3 shows a front view of a drill according to an embodiment of the present invention.

FIG. 4 is an enlarged view of a main part of FIG. 3;

FIG. 5 shows a front view of FIG. 3;

FIG. 6 is a sectional view taken along the line AA of FIG. 3 at right angles to the axis;

FIG. 7 shows chips when machining 50 holes according to the example of the present invention.

FIG. 8 shows cuttings at the time of machining 600 holes according to the present invention.

[Description of Signs] 1 Twist drill 2 Helix angle 3 Tip cutting edge R Curvature radius

Claims (3)

[Claims] In a coated stainless steel twist drill made of a super-hard alloy, the torsion angle is set to 30 to 45 degrees, and the curvature of the bottom of the blade groove connected to the rake face is defined as 0. 2 to 0.4, groove width ratio 45 to 70
%, A twist drill for stainless steel cutting. 2. The twist drill for stainless steel cutting according to claim 1, wherein said coating is made of a hard film such as TiN or TiAlN. 3. The twist drill for stainless steel cutting according to claim 1, wherein said super-hard alloy is made of high-speed steel.