JP2001341019A - Twist drill - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a twist drill with hardly generating a burr and with excellent durability by adopting a tool profile of a sharper edge when drilling a comparatively ductile material to be cut such as stainless steel and preventing welding and press adhesion of an outer peripheral part in a high speed cutting of 25 m or more. SOLUTION: This coated cemented carbide twist drill is constituted by making a helix angle as a high helix angle of 35 deg. to 450 deg., forming a tip cutting edge into a protrusion shape in a tip view of the drill, providing the tip cutting edge on a 1 to 10% rotating direction rear side of an edge diameter for a virtual line for joining an uppermost protrusion part of the protrusion shape part to a thinning edge and providing a chamfer on a connecting part of the tip edge and an outer periphery.

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 mild steel, stainless steel, etc., 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] Furthermore, for the same reason as described above, a sharp X-type thinning is used as the shape of the chisel when cutting stainless steel. However, X-type thinning is used for the purpose of reducing cutting resistance and improving centripetality. Japanese Patent Application Laid-Open No. 11-267912 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 the case of a high-strength work material such as stainless steel, burrs are generated during drilling, particularly on the lower surface side of the work. The drill must be removed, and the removal operation takes a great deal of time. Therefore, the development of a drill that does not generate burrs is desired.

[0004]

However, in the drilling of stainless steel or the like, when the cutting speed is increased, the life tends to be extremely short when the cutting speed is increased. For example, in a drill as shown in FIG. 100-1
Processing of about 50 holes can be performed, but at a cutting speed of about 30 m, even one hole cannot be processed and breaks. Similarly, Japanese Patent Laid-Open No. 9-1
In the examples of JP-A No. 1015 and JP-A-11-267912, the life is shortened on the outer peripheral side which is affected by the cutting speed. At present, chipping and the like are apt to occur due to a decrease in strength, and it is difficult to increase 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 25 m or more. In cutting, welding of the outer periphery,
An object of the present invention is to provide a twist drill excellent in durability, which prevents pressure bonding and hardly generates burrs.

[0006]

According to the present invention, there is provided a drilling tool comprising: a twisted drill made of a coated super-hard alloy; a torsion angle of 35 to 45 degrees; The tip cutting edge is convex, and, with respect to an imaginary line connecting the most convex portion of the convex portion and the thinning blade,
The tip cutting edge is provided on the rear side in the rotation direction of 1 to 10% of the blade diameter,
This twist drill is characterized in that a chamfer is provided at the connecting portion between the tip blade and the outer periphery, and the tip blade is made convex, dispersing and reducing the load applied to the connecting portion between the tip blade and the outer periphery, and discharging chips. The burrs are reduced and burrs are reduced by providing the chamfer.

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. Further, by making the tip blade convex, the cutting resistance received by the tip blade is forcibly divided into the outer peripheral side and the inner peripheral side, and further, the chamfer with the outer peripheral side can be provided at a large angle. The strength of the blade and chamfer can be increased.
Next, since the tip cutting edge from the convex portion to the thinning cutting edge affects the dispersion and reduction of the cutting resistance and the restraint of the chip, the tip cutting edge corresponds to an imaginary line connecting the most convex portion of the convex portion and the thinning blade. The tip cutting edge is provided on the rear side in the rotation direction by 1 to 10% of the blade diameter. The reason why the tip cutting edge is set at 1 to 10% of the blade diameter on the rear side in the rotation direction is that when the cutting edge is less than 1% of the blade diameter, like the straight cutting edge,
No effect on chip generation and 10% of blade diameter
If it exceeds the thickness, the thickness of the land width becomes relatively thin and the strength is inferior. Also,
The generated chips are constrained by the convex portions and are forcibly moved in the axial direction of the chip discharge grooves and discharged. In particular, the convex part can be controlled by the radial position of the most convex part and the convex part difference in the front view shown in FIG. In addition, by connecting the lowering of the strength with the tip blade which is a rake angle in the radial direction, a chamfer is provided as shown in FIG. did. Further, in order to further ensure the strength, a cutting edge treatment as performed by a twist drill made of cemented carbide may be performed. By providing the chamfer, the strength of the connecting portion between the tip blade and the outer periphery can be increased even when strong torsion is adopted, and it is also a measure against burrs. The chamfer is set at an angle of 25 ° to 45 ° with respect to the perpendicular to the rotation center line, because the drill tip angle is generally 118 ° to 13 °.
About 5 degrees are used, and in the expression of the present application, 3 degrees are used.
When the angle is less than 25 degrees, the chamfer itself cannot be provided because it substantially overlaps the tip angle, and when it exceeds 60 degrees, the length becomes longer in the axial direction, which affects the effective blade length and the like. The chamfer angle is 25 degrees
The range was 60 degrees. Preferably it is 25 degrees to 45 degrees.

Next, the reason that the length of the chamfer is set to 0.1 mm or more is substantially ineffective when it is less than 0.1 mm.
Since the strength cannot be improved, the thickness is set to 0.1 mm or more. Further, when the length is long, the same effect as that of the taper can be obtained, and the effect of the burr countermeasure can be obtained. Further, the same effect can be obtained even if the chamfer has an arc shape or a substantially straight shape between the tip blade and the outer periphery. In particular, when the angle is around 30 degrees, the length of the chamfer is short, so that the shape of the arc is good. However, when the angle is large, the chamfer is long, so that the shape may be substantially linear. It is desirable that the connecting portion to be R-connected. The position of the most convex portion may be any position between 80% of the diameter and the end of the thinning blade, or preferably 30 to 70% of the diameter. If it exceeds 70%, there is not enough room at the connecting portion with the outer peripheral end, and it is difficult to connect in a curved shape. On the other hand, if it is less than 30%, the connection with the thinning blade cannot be performed smoothly. Further, the shape of the most convex portion is preferably provided in a gentle curved shape. Since the difference in the convex portions affects the dispersion and reduction of the cutting resistance and the restraint of the chips, the difference is set to 0.5 to 5% of the diameter. At this time, it is defined as shown in FIG. When the diameter is less than 0.5%, the substantial effect is small. When the diameter exceeds 5%, the convex portion is excessively formed.
5 to 5%. The direction in which the chips move can be restricted in the axial direction depending on the position and size of the projection.
Further, as shown in FIG. 5, the outer peripheral end of the tip blade is connected to the most convex portion of the above-described convex portion in a curved shape and provided at a larger angle. By increasing the angle, the chipping resistance of the cutting edge is increased.

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 width of the blade groove is narrowed in combination with strong torsion, causing chip clogging. If it is more than 70%, the chip processing becomes unstable due to the wide groove width, particularly Since the chips are easy to grow and difficult to control and the cutting power becomes unstable, the groove width ratio is 55%.
-70%. Furthermore, a large groove width ratio can be adjusted by the shape of the heel portion of the groove. By forming the heel end in an arc shape, take a large groove width ratio,
The contact of the chips with the inner wall as described above can be reduced.

Although the twist 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 addition, it is possible to apply the shape of the cutting edge treatment by utilizing the torsion even in the case of 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, a film formed by using a physical vapor deposition method such as TiN or TiAlN is suitable. In particular,
In the vicinity of the chisel at the tip cutting edge where chips are easily welded or pressed, a coating of a solid lubricant such as Cr nitride, DLC and molybdenum disulfide for lubricity is also effective.

By employing 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, chips are prevented from being clogged, and in combination with the convex action of the tip blade, the chips are discharged rearward in the axial direction. You. Hereinafter, the present invention will be specifically described based on examples.

[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 blade 3 around the axis O is provided with a convex portion 4, and the difference 6 from the most convex portion 5 is 3% of the diameter. In addition, a chamfer 7 is attached to the outer peripheral end of the tip blade 3 at an angle of 3 degrees.
It was provided at 0 degree and 0.25 mm in length. The thinning of the tip blade 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, in the first hole, the drill of the example of the present invention obtains curled chips with good processing properties as the chip form, and the enlargement margin of the first hole is as good as 0.02 mm at both the entrance and the center. There was normal wear without chipping, but in Conventional Example 1, since the cutting speed was too high, one hole could not be machined and the life was extended. The drill of Conventional Example 2 also had chipping on the outer peripheral side. Therefore, the enlargement allowance was as large as 0.08 mm. Further, as a result of continuing the drilling test, the drill of the present invention was found to
The state of the holes continued, and the maximum flank wear was 0.08 mm in VBmax, which was normal wear. However, with the drill of Conventional Example 2, chipping at the outer peripheral end became large, and the test was stopped. The enlargement allowance in 100 hole machining is 0.02 in the present invention.
Conventional Example 2 was 0.08 mm in mm.

Further, the test was continued, and 200 holes, 400 holes
Welding gradually began to appear at the holes and 600 holes.
The cutting test was stopped because a part of the flank fell off during the 00 hole drilling and the maximum flank wear exceeded 0.3 mm. 80
The enlargement allowance in the 0-hole processing was as good as 0.02 mm.

Next, cutting tests were performed in the same manner by changing the torsion angle, chamfer, etc. of the examples of the present invention used in the previous embodiment. First, the torsion angles were 35, 38, 40, and 4 degrees.
Five degrees and 50 degrees as Comparative Example 1 were produced. As a result of the cutting test, in the first hole, normal wear was only at a twist angle of 35 degrees, and the other drills at 38 to 50 degrees caused chipping. Therefore, a chamfer was provided in the present invention example and the comparative example of 38 to 50 degrees. The chamfer is 0.1 to 0.3 mm at 38 degrees corresponding to the torsion angle, and 0.1 to 0.3 at 40 degrees.
After 0.5 to 1 mm at 45 ° and 0.1 to 1 mm at chamfer angles of 25 °, 35 °, 45 ° and 60 °, each joint was additionally processed into an R shape. In addition, a chamfer having a similar angle and length formed in a circular arc shape was similarly manufactured and subjected to a cutting test. Prevention of chipping or the like at the first hole can be prevented by providing a chamfer in all of the examples of the present invention having a twist angle of 38 degrees, and a sufficient effect was confirmed with a chamfer of about 0.1 mm in processing amount. As the test is continued and the holes are further increased to 100 and 200 holes, by providing the chamfer, the larger the angle of the chamfer is, the less the burr is generated and the better the cutting is.

Using a sample having a position of 50% of the most convex portion, the difference 6
Were prepared with 0.5%, 2%, 3%, 4%, 5%, and 10% of the diameter, and the cutting test was performed in the same manner. As a result, only the sample having a 10% difference 6 caused a defect in the first hole, and the others showed normal wear. The protrusion was lost because the protrusion was too protruding. Further testing is continued, and in 100 hole processing,
In the sample having a difference 6 of 5%, abrasion of the projections was increased, and welding was observed. Other samples showed normal wear. In addition, 50
If the test is continued up to 0 holes, the difference 6 is a 0.5% sample,
The swarf morphology changed and continuous swarf began to be ejected. Other samples showed normal wear.

After coating with 5 μm TiAlN using the twist drill used in the above embodiment, the coated blade edge was treated by magnetic polishing. Since the unevenness of the coating surface after coating intersects with the cutting edge after coating by the edge processing, the unevenness can be smoothed and the edge line of the cutting edge can be smoothed. In addition, in addition to the effect similar to the chisel,
Droplets and large particles existing on the surface of the coating can be smoothed out, and the surface of the coating can be smoothed. In particular, in the case of a ductile material such as mild steel, the projections such as the droplets of the film cause pressure bonding and the like, so that the effect is large.

[0018]

As described above, by using the drilling tool according to the present invention, machining with small cutting resistance and good hole accuracy (enlargement allowance) can be performed, and cutting is stabilized by providing a chamfer. Demonstrates excellent tool life with less burrs. Burr countermeasures can be taken by the difference in the outer diameter of the chamfer, and dimensional accuracy and machining surface accuracy are improved.

[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 Twist angle 3 Tip blade 4 Convex part 5 Most convex part 6 Difference from the most convex part 7 Chamfer 8 Chip discharge groove 9 Chamfer angle 10 Chamfer length

Claims (5)

[Claims] 1. A twist drill made of a coated super-hard alloy and having a torsion angle of 35 to 45 degrees with a strong torsion angle. A tip cutting edge is provided on the rear side in the rotation direction of 1 to 10% of the blade diameter with respect to an imaginary line connecting the most convex portion of the shape portion and the thinning blade, and a chamfer is provided at a connecting portion between the tip blade and the outer periphery. Characteristic twist drill. 2. The twist drill according to claim 1, wherein
Set the chamfer at 25 degrees to 60 degrees with respect to the perpendicular to the rotation center line.
A twist drill characterized by being provided at a degree angle. 3. The twist drill according to claim 1, wherein the length of the chamfer is 0.1 mm or more. 4. A twist drill according to claim 1, wherein said chamfer is substantially arc-shaped. 5. The twist drill according to claim 1, wherein said chamfer is substantially straight.