JP2000280110A - Twist drill with extra-high pressure sintered body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve flowing-out of chips in a twist drill formed by joining an extra-high pressure sintered body tip to its corner. SOLUTION: In placing an extra-high pressure sintered body tip 9 on a counterfore 8 formed at the corner of a drill body 1, a sub cutting edge 6 is formed which includes a main cutting edge 3 where the extra-high pressure sintered body tip 9 and the drill body are of the same order and higher order gradually toward the rear end of a sub cutting edge 6 from the main cutting edge 3, and is discontinuous to the sub cutting edge 6 of the drill body 1. It is thus possible to prevent generation of obstacles to flowing-out of cutting chips 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a twist drill with an ultra-high pressure sintered body, and more particularly to a shape of a joint of an ultra-high pressure sintered body chip.

[0002]

2. Description of the Related Art A drill in which an ultra-high-pressure sintered compact tip is joined to a corner is a straight-groove-shaped drill using a sintered diamond tip, and is used for drilling light metals such as aluminum alloys. . When this is used as a twist drill, chip processing is improved and thrust is reduced, so that improvement in performance as a drill is expected. However, although there is a track record of small-diameter drills in which the entire tip of the drill is formed of an ultra-high-pressure sintered compact tip and twist drills in which a plate-shaped ultra-high-pressure sintered compact tip is sandwiched, a twist with an ultra-high-pressure sintered compact corner is used. Drills are not widespread.

FIGS. 4 and 5 show a conventional twist drill with an ultra-high pressure sintered body, and the same reference numerals are given to the same portions as those of an embodiment of the present invention described later. The material of the ultra-high-pressure sintered body chip 9 is a flat plate, and the ultra-high-pressure sintered body has poor grinding properties and a small thickness. When this is used by being joined to the corner 7 of the drill body 1, conventionally, the main cutting edge 3 and the sub cutting edge 6 are continuously joined to the main cutting edge 3 and the sub cutting edge 6 of the drill body 1. . That is, the axially inclined angle β of the ultrahigh-pressure sintered body chip 9 is disposed so as to substantially coincide with the twist angle α of the outer edge of the flute groove 2.

[0004]

Such drills are not widely used for the following reasons. That is, as shown in FIG. 6, the twist of the sub-cutting edge 6 is formed continuously, but since the upper surface 10 of the ultrahigh-pressure sintered compact chip 9 is flat, the drill away from the sub-cutting edge 6 The torsion angle of the main body 1 does not match, and a smaller axial inclination angle is obtained. As a result, the upper surface 10 of the ultra-high pressure sintered
Appears, and a step surface 12 rising from the ultrahigh-pressure sintered chip 9 appears. This step surface 1
2 prevents the chips 11 from flowing out and causes chip clogging.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has a flute groove which extends with a twist in the axial direction at one end of a drill body having a round bar shape. A corner is formed by the main cutting edge provided at the tip of the flute groove and the sub-cutting edge provided at the outer peripheral edge of the flute groove. In the twist drill with an ultra-high pressure sintered body that is joined, the ultra-high pressure sintered body tip has a main cutting edge that is at the same level as the drill body, and gradually becomes higher from the main cutting edge to the rear end of the sub cutting edge. With respect to the sub cutting edge, a sub cutting edge discontinuous with the drill body is formed.

[0006] The discontinuous sub-cutting edge is formed by mounting an ultra-high pressure sintered compact chip at an axial inclination angle smaller than the twist angle of the flute groove, and furthermore, The axially inclined angle of the ultrahigh-pressure sintered body tip is formed so as to substantially coincide with the torsion angle of a portion of the undercut portion closest to the axis of the drill body.

[0007] Drilling is performed by the main cutting edge. In the present invention, since the main cutting edge is formed continuously, there is no difference in use from a normal twist drill. And
The generated chips flow out slightly in the axial direction while rubbing the rake face, forming a spiral like a series of shades,
It is discharged from the flute groove to the outside of the machining hole together with the cutting fluid. At this time, since the ultrahigh-pressure sintered body tip is formed at a height equal to or higher than the rake face of the drill body,
The flow of generated chips is not hindered. It is an easy and convenient method to form the ultrahigh-pressure sintered body chip at an axial inclination angle smaller than the twist angle. The reason why the axial inclination angle of the ultrahigh-pressure sintered body chip is substantially matched with the torsion angle of the portion of the dug portion closest to the axis of the drill body is that the twist is weakened in forming the present invention. This is because it is a method of minimizing performance degradation.

[0008]

Next, an embodiment of the present invention will be described with reference to the drawings. FIGS. 1 and 2 show the tip of the twist drill of the present invention. A pair of flute grooves 2 having a twist having a twist angle α is provided in a drill body 1. The tip is the main cutting edge 3, and the center of the main cutting edge 3 is provided with a thinning 4 and is called a thinning cutting edge 5. Further, the outer peripheral edge of the flute groove 2 becomes the sub cutting edge 6, and the portion of the rake face sandwiched between the main cutting edge 3 and the sub cutting edge 6 is the corner 7.

[0009] The corner 7 is dug 8. The digging 8 is generally formed in a fan shape or a substantially rectangular shape as in the present embodiment in a rake face view. Then, the ultra-high pressure sintered compact chip 9 is placed on the counterbore 8 and joined mainly by brazing. At this time, the drill main body 1 and the ultra-high pressure sintered compact chip 9 are positioned at the same position at the tip of the drill so that the continuous main cutting edge 3 is formed. The sub cutting edge 6 that is discontinuous is formed so as to be higher than the cutting edge 6.

By making the axial inclination angle β of the ultrahigh-pressure sintered chip 9 smaller than the torsion angle α, the configuration of the present invention can be easily performed while the upper surface 10 of the ultrahigh-pressure sintered chip 9 is flat. It can be realized. However, if the axial inclination angle β is too small, the effect of the positive rake angle is reduced. 1
Is formed so as to substantially coincide with the torsion angle of the portion closest to the axis of the. The axial inclination angle β is specifically obtained from β = tan ⁻¹ (2H · tan α / D) in FIG.
Here, H is the shortest distance in the diameter direction between the axis and the ultrahigh-pressure sintered compact chip 9, and D is the drill diameter. In this manner, the inclination angle β in the axial direction does not become excessively small.

FIG. 3 is a diagram for explaining the outflow state of the chips 11. Unlike the above-described conventional twist drill, the height relationship of the steps is reversed, so that there is nothing to hinder the outflow of the chips 11, and the drilling is performed smoothly. In an actual cutting example, for example, the drill diameter of the twist drill of the present invention is 8 mm, and the width of the sintered diamond tip is 1.5 m.
m, a drill having a helix angle of 30 ° and a drilling speed of 50 m / min when drilling an aluminum alloy using a drill having an axial inclination angle β of 19.8 ° according to a calculation formula. And feed 0.3mm / r
Although ev cutting was obtained stably, a similar conventional twist drill broke due to chip clogging at a feed rate of 0.2 mm / rev.

[0012]

According to the present invention, it is possible to provide a twist drill in which an ultrahigh-pressure sintered compact tip is joined to a corner of the drill, and which can be used practically. Since chip clogging caused by a step at the joint between the ultra-high pressure sintered body tip and the drill body is eliminated, the excellent performance of the twist drill, such as good chip discharge and low thrust, is utilized, and the ultra-high pressure sintered body tip , The life of the cutting edge can be extended.

[Brief description of the drawings]

FIG. 1 is a plan view (drill tip) showing an embodiment of the present invention.

FIG. 2 is a front view of FIG.

FIG. 3 is a perspective view of a corner portion of the drill shown in FIG.

FIG. 4 is a plan view (drill tip) showing an example of the related art.

FIG. 5 is a front view of FIG. 4;

6 is a perspective view of a corner portion of the drill shown in FIG.

[Explanation of symbols]

 Reference Signs List 3 main cutting edge 6 sub cutting edge 8 counterbore 9 super-high pressure sintered compact chip 12 step surface α helix angle β axial inclination angle

Claims (3)

[Claims] 1. A flute groove extending in an axial direction with twisting is provided at one end of a drill body having a round bar shape, and a main cutting edge provided at an end of the flute groove and an outer peripheral edge of the flute groove. In the twist drill with the ultra-high-pressure sintered body in which the corner formed by the provided sub-cutting edge is provided with a super-high-pressure sintered compact tip joined to the counter-bored portion, The body chip has a main cutting edge that is at the same position as the drill main body, and is disposed so as to be gradually higher from the main cutting edge to the rear end of the sub cutting edge, and the sub cutting edge is discontinuous with the drill main body. A twist drill with an ultra-high pressure sintered body characterized by forming a secondary cutting edge. 2. The discontinuous sub-cutting edge is formed by mounting an ultra-high pressure sintered compact chip with an axial inclination angle smaller than a helix angle of a flute groove. Item 2. A twist drill with an ultra-high pressure sintered body according to item 1. 3. The axially inclined angle of the ultrahigh-pressure sintered compact tip is formed so as to substantially coincide with the torsion angle of a portion of the dug portion closest to the axis of the drill body. The twist drill with an ultra-high pressure sintered body according to claim 1 or 2, wherein the twist drill is provided.