JP2001328016A - Twist drill - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a drill with excellent finishing roughness of a work surface and hardly generating a burr by reducing the burr generated on the upper and lower surfaces of a workpiece. SOLUTION: This twist drill composed of covered cemented carbide is constituted such that a tip angle of the drill is set to two stages, a first tip angle is set to 80 to 140 degrees, a second tip angle is set to 1 to 40 degrees and a connecting part of a first stage and a second stage is set to a position of 70 to 95% of a drill outer diameter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drill used for drilling, and more particularly, to a drill which suppresses generation of burrs during drilling.

[0002]

2. Description of the Related Art In drilling, burrs are easily generated on the upper and lower surfaces of a workpiece.
Since it takes too much time, various drills have been proposed in which burrs are reduced as little as possible. When a drill enters or exits a workpiece, a burr is formed at the outer peripheral end of the tip cutting edge, and the burr is deformed by an axial feed force to become a burr. . Among the commonly used twist drills, drills for which countermeasures against burrs are taken are roughly classified into two types. The first is that the outer peripheral edge of the tip cutting edge, called a candle-type drill or fishtail-type drill, is cut before the inside to prevent burrs. Applied to materials using fibers. The second is a double angle drill in which the tip angle of the drill is two steps, and the uncut part is reduced by setting the tip angle to two steps.

For example, JP-A-9-277109 discloses that
A drill having a tip angle of two steps, a tip angle α of 118 to 135 degrees, and a tip angle β of 60 to 90 degrees is described, which has a high twisting function and a high function of suppressing the occurrence of burrs. In Japanese Patent Application Laid-Open No. 9-239610, burrs are taken by performing chamfering simultaneously with drilling.

[0004]

However, candle-type and fishtail-type drills have good sharpness at the beginning of use and less burrs because the outer peripheral end has a sharp pointed shape. As the number increases, the occurrence of burrs gradually becomes a problem. Further, in the above-described double angle drill, if the angle of the second step is not properly set, there is no point in providing the second step, and the problem of burr is similar to that of a drill having a single step angle. appear. In particular, since the angle of the second stage at the tip is large, burr generation does not last long.

[0005] Therefore, in order to solve the above problems, in the present invention, in order to reduce burrs generated on the upper and lower surfaces of the workpiece, the finished roughness of the processed surface is good and the burrs are almost completely eliminated. The purpose is to provide a drill that rarely occurs.

[0006]

According to the present invention, in a twist drill made of a coated super-hard alloy, the tip angle of the drill is two steps, and the first tip angle is 80 to 140.
Degrees, the second tip angle is 1 to 40 degrees, and the first step and the second
A twist drill characterized in that the connecting portion of the step is located at a position of 70 to 95% of the outer diameter of the drill, wherein the length of the cutting edge formed by the second tip angle is 9% to 200% of the drill diameter, Further, the coating is a drill made of TiN, TiAlN or the like, and the super-hard alloy is a drill made of powdered high-speed tool steel, a cemented carbide or the like.

[0007]

The second stage of the drill of the present invention performs the same cutting action as the reamer. By making the tip angle of the second step 1 ° to 40 ° and / or the length of the cutting edge formed by the second tip angle to 9% to 200% of the drill diameter, the same cutting as the reamer at the time of drilling is performed. Is performed to reduce the occurrence of burrs and the like. Therefore, if the angle of the second step is less than 1 degree or the cutting edge length formed by the second tip angle is less than 9% of the drill diameter, the effect of providing the second step is not obtained, and the angle of the second step is not obtained. If the angle exceeds 40 degrees or the cutting edge length formed by the second tip angle exceeds 200% of the drill diameter, it becomes too long to be practically used and reduces the generation of burrs over a long period of time. Therefore, the angle of the second step was in the range of 1 ° to 30 °, and the length of the cutting edge formed by the second tip angle was in the range of 9% to 200% of the drill diameter. In addition, if the position of the second end of the tip is provided with a long cutting edge of the second stage, the end cutting edge of the twist drill itself becomes long, and adverse effects such as an increase in cutting resistance and a decrease in the strength of the end portion are likely to occur. And the range of 70 to 95% of the outer diameter of the drill.

Next, the types of the coatings are TiN film and TiOA which are applied to commercial tools in order to improve the welding resistance in particular.
An 1N film or the like is effective, but especially in the case of aluminum alloys, when boron is added to those films, the welding resistance during aluminum cutting can be improved, and the hardness of the coating itself can be improved. . Hereinafter, a specific description will be given based on examples.

[0009]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows a drill according to the present invention, which has a drill blade diameter of 8 m.
m, the tip blade of the drill body 1 is formed in two steps, the first tip angle is 90 degrees, the second tip angle is 18 degrees, and the first tip portion and the second tip angle
The joint at the tip was at a 75% D position. The coating was a 3 μm coating of a TiAlN film.

Next, cutting speed: 60 m / min, feed speed: 0.1 mm / rev, work material: aluminum alloy, plate thickness 2
The through hole was machined using mm, and the hole machining was continued while observing the state of the burr on the upper surface side and the burr on the lower surface side of the work material.
For comparison, the candle type drill described in the conventional example shown in FIG. 2 and having the same blade diameter and the same coated product was used for the test. In the example of the present invention, burrs did not occur on the upper surface and the lower surface even when processing up to 500 holes, as well as the first hole, and it was possible to use without performing post-processing after hole processing. Although the eyes were good, burrs gradually began to be generated, and burrs were generated to the extent necessary to remove burrs from the 400 hole processing. Further, the test was continued, and processing was performed up to 2,000 holes in the present invention example. However, since cutting was performed by cutting with the cutting edge of the second front end portion, the generation of burrs was small, and the burrs could be used without deburring.

[0011]

By applying the present invention, not only aluminum alloy but also burrs at the time of drilling can be reduced, and at the same time as reamer finishing at the time of drilling, dimensional accuracy and processing surface accuracy can be reduced. Is improved.

[Brief description of the drawings]

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

FIG. 2 shows a front view of a conventional example.

[Explanation of symbols]

 1 Drill body 2 1st tip angle 3 2nd tip angle 4 Connecting part D drill blade diameter d Diameter of 2nd tip corner L Cutting edge length formed by L2 tip angle

Claims (5)

[Claims] 1. A twist drill made of a coated super-hard alloy, wherein the tip angle of the drill is two steps, the first tip angle is 80 to 140 degrees, the second tip angle is 1 to 40 degrees,
Also, the connecting portion between the first stage and the second stage has a drill diameter of 70-95.
Twist drill characterized by being arranged in%. 2. The twist drill according to claim 1, wherein
The length of the cutting edge formed by the second tip angle is 9% to 200% of the drill diameter. 3. The twist drill according to claim 1, wherein said coating is made of a hard coating such as TiN or TiAlN. 4. The twist drill according to claim 1, wherein said super-hard alloy is made of powdered high-speed tool steel. 5. The twist drill according to claim 1,
A twist drill, wherein the coating is formed of a hard coating made of TiN, TiAlN or the like containing boron.