JP2001341024A - Drill for cutting stainless steel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a twist drill with superior durability adopting a sharper- edged tool profile and preventing welding and crimping of an outer circumference part in high speed cutting of 25 m or more when perforating a material relatively having ductility such as stainless steel. SOLUTION: This drill for cutting stainless steel made of coated cemented carbide is composed by providing a helix angle as a high helix angle of 35 to 45 deg., linearly forming a tip cutting edge, and chamfering a connecting part of the tip cutting edge and an outer circumference.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drilling tool for a difficult-to-cut material such as stainless steel, which is a ductile work material, and more particularly to a shape of a cutting edge at a tip.

[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 hardened due to work hardening,
There is a characteristic that chips are hard to be divided, and there is a disadvantage that chip dischargeability (cutting power) and hole accuracy (enlargement allowance, particularly enlargement allowance at an entrance of a 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-9-110.
No. 15 discloses a drilling tool. JP-A-9-11
No. 015 is an example in which only the tip cutting edge has a large torsion angle to improve 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 cutting edge is also concave so as to enhance chip disposal.

[0004]

However, in the drilling of stainless steel, if the cutting speed is increased, the life tends to be extremely short if the cutting speed is increased. For example, in the drill shown in FIG. ~ 15
Although machining of about 0 holes can be performed, even at a cutting speed of about 30 m, even a single hole cannot be machined, resulting in breakage. Similarly, JP-A-9-11
No. 015, Japanese Patent Application Laid-Open No. 11-267912, the outer peripheral side affected by the cutting speed has a shorter life,
In particular, in Japanese Patent Application Laid-Open No. H11-267912, the sharpness of the connecting portion with the outer peripheral side lowers the strength, so that chipping or the like is likely to occur and it is difficult to increase the efficiency.

[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 20 m or more. In cutting, welding of the outer periphery,
An object of the present invention is to provide a twist drill which prevents crimping and has excellent durability.

[0006]

A drilling tool according to the present invention is a stainless steel drill made of a coated super-hard alloy, which has a strong torsion angle of 35 to 45 degrees and a substantially straight cutting edge. A drill for cutting stainless steel, characterized in that the connecting portion between the cutting edge and the outer periphery is chamfered.

A description will be given with reference to FIGS. First, the torsion angle, which is the rake angle in the axial direction, can be sharpened by taking a large value, but on the other hand, the strength decreases. If the helix angle is less than 35 degrees, the cutting force is large and the allowance for expansion is large,
If the hole accuracy is reduced and the torsion angle exceeds 45 degrees, the discharge of chips is hindered, so the range was 35 degrees to 45 degrees. In addition, as shown in FIG. 4, the lowering of the strength is compensated for smoothly by connecting the lowering of the cutting edge to the cutting edge of the cutting edge, which is a rake angle in the radial direction. In order to obtain the strength and further secure the strength, a honing treatment such as that performed by a twist drill made of cemented carbide may be performed. The honing process is used for a twist drill made of a brittle material such as a cemented carbide, but has not been applied to a high speed tool steel drill. High-speed tool steel tools have high strength and hardly cause chipping even if a sharp blade is adopted. However, when a high twist of 35 to 45 degrees occurs, honing processing is performed on a part of the cutting edge. And the plus side is larger.

The core thickness of the drill is 0.10D to 0.25D
In the range of less than 0.10D, the tool rigidity is insufficient, and the precision of the enlargement allowance of the work material inlet at the time of drilling becomes poor.
If it exceeds 5D, the space of the groove itself becomes too narrow, so that the contact with the inner wall increases, the cutting resistance increases, and the chip discharge property deteriorates, so that chip clogging is likely to occur. Further, the groove width ratio is 55 to 7 (in the sectional view, the groove width of the chip discharge groove is divided by the tool outer peripheral length and expressed as a percentage).
0%. Here, if the groove width ratio is less than 55%, the groove width is narrowed due to strong twisting, causing chip clogging. If the groove width ratio is more than 70%, chip processing becomes unstable due to the wide groove width, and especially chip Becomes difficult to control and the cutting power becomes unstable, so that the groove width ratio is 55 to 7
The range was 0%. 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 part in an arc shape, a large groove width ratio is taken,
The contact of the chips with the inner wall as described above can be reduced.

Although the stainless steel cutting drill of the present invention has been described using high speed steel, powdered high speed steel is more preferable. 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 particular, high-hardness powdered high-speed steel with an added amount of vanadium of about 3 to 10% is suitable. In addition, it is also possible to apply a molten high-speed steel by adjusting the honing or the like by utilizing the twist. Furthermore, coating is indispensable for a material having a high ductility such as stainless steel, and a known coating in the present invention, for example, a film formed by using a physical vapor deposition method such as TiN or TiAlN is suitable. In particular, a coating of a solid lubricant such as Cr nitride, DLC, molybdenum disulfide, etc., which is rich in lubricity, is effective near the chisel at the tip cutting edge where chip welding and pressure bonding are likely to occur.

By adopting a twist angle of 35 to 45 degrees, sharpness and high hole accuracy can be obtained. Furthermore, in order to further improve the hole accuracy, the thinning shape is made a shape with higher centripetality. As shown in FIG. 5, the thinning angle is large, and as shown in FIG.
By providing a negative angle of 5 degrees or more and providing a sufficient distance to the blade groove so as to smoothly tie, the clogging of chips is prevented, and in combination with the convex action of the above-mentioned cutting edge, it is discharged axially rearward. Is done. Hereinafter, the present invention will be specifically described based on examples.

[0011]

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
Are provided substantially linearly. Further, the outer peripheral end 4 of the leading edge cutting edge 3 is smoothly connected in a chamfered shape with a chamfered surface 5, and a chip discharge groove 6 is formed. The thinning of the tip cutting edge is X
Type.

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 20 m / min, the feed rate is 0.12 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. After drilling 100 holes, the drill of the example of the present invention has a maximum flank wear of 0.07 m in VBmax.
m, the wear was normal, but with the drills of Conventional Examples 1 and 2, the chipping at the outer peripheral edge became large, and the test was stopped.
The enlargement allowance in 100-hole machining is 0.015 m according to the present invention.
Conventional Example 2 was 0.12 mm with respect to m.

The test was continued for only the example of the present invention, and 200 holes, 4 holes
Welding was gradually observed at the 00 and 600 holes, and a part of the 800 holes was dropped during the drilling. The maximum flank wear exceeded 0.3 mm, so the cutting test was stopped. The enlargement allowance in 800 hole processing was as good as 0.02 mm.

Next, a cutting test was performed in the same manner as in the above embodiment, except that the torsion angle, the chamfer, and the like of the present invention were changed. Twist angles of 35 degrees, 38 degrees, 40 degrees, and 45 degrees, and 50 degrees as comparative examples were manufactured. As a result of cutting test,
At the first hole, the normal wear was only at a helix angle of 35 degrees, and the other 38-50 degrees drills had chipping at the outer end of the leading edge.

Therefore, chamfered surfaces were applied to the inventive examples and comparative examples at 38 to 50 degrees. The chamfered surface was C-chamfered and had a length of 0.1 mm to 0.5 mm and 10 to 60 degrees. They were similarly subjected to a cutting test.
Prevention of chipping or the like in the first hole could be prevented by chamfering the present invention examples to comparative examples having a twist angle of 38 degrees. As the test was continued and further increased to 100 and 200 holes, a good cutting state could be continued.

[0016]

As described above, by using the drilling tool according to the present invention, machining with small cutting resistance and good hole precision (enlargement allowance) can be performed, and wear is stabilized by combination with honing processing. And exhibits excellent tool life.

[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;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Twist drill 2 Helix angle 3 Tip cutting edge 4 Peripheral end of tip cutting edge 3 5 Chamfer 6 Chip discharge groove

Claims (4)

[Claims] 1. A coated stainless steel drill made of a super-hard alloy and having a torsion angle of 35 to 45 degrees with a strong torsion angle, a substantially straight tip cutting edge, and a chamfered joint between the tip cutting edge and the outer periphery. Drill for stainless steel cutting, characterized in that it is shaped like a stainless steel. 2. The stainless steel cutting drill according to claim 1, wherein said coating comprises a hard film and / or a lubricating film such as TiN or TiAlN. 3. A drill for stainless steel cutting according to claim 1, wherein said super-hard alloy is made of high-speed steel made of molten high-speed steel or high-speed steel made of powdered high-speed steel. 4. The twist drill according to claim 1,
A drill for cutting stainless steel, wherein the super-hard alloy is made of a super-hard alloy.