JPH0615512A - Drill and formation of cutting blade of drill - Google Patents

Abstract

PURPOSE:To drill a hole which is excellent in roundness and needs no reaming after drilling without causing run-out of its center during drilling and without making flaws on the inwall of the drilled hole. CONSTITUTION:On a drill 1 formed with a chip discharge groove 11 and margin parts 33 on a shank 10 and cutting blades 31 on its point part, between the outer peripheral end of the cutting blades 31 and the margin parts 33, inclined surfaces 4 gradually increasing distance from the central axis of the drill 1 are formed, and a rotational locus formed by the margin parts 33 is formed larger in diameter by 5/1000-200/1000mm than a rotational locus formed by the outer peripheral end of the cutting blades 31, and formation of its cutting blades thereby is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drill having a cutting edge formed at its tip and a chip discharging groove formed on a shank, and a method for forming a cutting edge of the drill.

[0002]

2. Description of the Related Art As a drill for drilling a metal material, a drill having a cutting edge formed at its tip and a chip discharge groove and a margin formed on a shank is widely used. Then, in the conventional structure, the cutting edge is configured so that the outer peripheral end of the cutting edge forms the maximum diameter of the drill, and the outer peripheral end of the cutting edge and the margin portion form a rotation trajectory of the same diameter. .

[0003]

With the above-described structure, it is inevitable that center runout will occur during drilling, and the roundness of the machined hole will be destroyed due to this runout, and the inner wall of the machined hole will be cut. It was unavoidable that the edge of the blade was scratched. Therefore, after the conventional drilling process, reaming is necessary for adjusting the roundness and smoothing the inner wall surface.

The present invention has been made in order to eliminate the above-mentioned conventional drawbacks, in which no center runout occurs during processing, and therefore the inner wall of the processed hole is not scratched. It is an object of the present invention to provide a drill and a method for forming a cutting edge of the drill, which are excellent in roundness of a hole and therefore do not require reaming to perform accurate hole processing.

[0005]

A drill of the present invention is a drill having a chip discharge groove and a margin portion formed on a shank and a cutting blade formed at a tip end thereof, and a rotation locus formed by an outer peripheral end of the cutting blade. The rotation locus formed by the margin is 5/1000 to 20 / 1000m
It has a large diameter.

[0006] It is preferable to form an inclined surface between the outer peripheral end of the cutting edge and the margin portion, the distance gradually increasing from the center axis of the drill.

The method for forming a cutting edge of a drill according to the present invention is
In a drill in which a chip discharge groove and a margin portion are formed on a shank, and a cutting edge is formed at the tip to the outer peripheral edge, by forming the outer edge of the cutting edge by grinding the intersection of the cutting edge and the margin portion. The rotation locus formed by the margin part is 5/1000 to 20
An inclined surface whose distance from the center axis of the drill gradually increases is formed between the outer peripheral edge of the cutting edge and the margin portion so that the diameter is 0/1000 mm.

[0008]

In the above construction, the cutting edge is used to form a hole having a predetermined diameter, and the cutting edge is formed to have a diameter slightly smaller than the inner wall of the processing hole so that the margin portion is always in contact with the inner wall surface of the processing hole. Therefore, this acts as a guide and core runout is prevented. Further, the inner wall of the machined hole formed at the outer peripheral edge of the cutting edge is pressed outward by the inclined surface and the margin portion following the outer peripheral edge, whereby the inner wall of the machined hole is finished into a smooth surface. Therefore, the machined hole has excellent roundness, and the inner wall of the machined hole is finished very smooth, so that the machined hole does not need to be finished by a reamer.

[0009]

1 to 3, a drill 1 comprises a shank 10 made of general tool steel, and a pair of cemented carbide tips 3 attached to the tip of the shank 10. Each of the tips 3 has a cutting edge 31. Has been formed. The cutting edge 31 has a center portion formed in a curved line which is convex in the rotational direction in a bottom view, and is formed substantially straight on the outer peripheral side thereof, and the cutting edges 31 are arranged symmetrically with respect to the center point O of the drill. Has been done. Further, a chip discharge groove 11 is formed in a spiral shape on the shank 10, and the tip end portion of the cutting edge discharge groove 11 is the rake face 3 of the cutting blade 31.
5 consecutive times. The tip surface of the tip 3 forms the flank 36 of the cutting edge 31, the outer peripheral surface of the tip 3 forms the outermost peripheral surface of the drill 1, and the marginal portion 33 of the drill 1 is formed by this outer peripheral surface.

An inclined surface 4 is formed between the outer peripheral end 34 of the cutting edge 31 and the margin portion 33 so that the distance from the central axis of the drill 1 gradually increases, and the outer peripheral edge 34 of the cutting edge 31 is formed.
The rotation locus formed by the margin portion 33 is formed to have a larger diameter by a predetermined amount d than the rotation locus formed by. This predetermined amount d is 5/1000 to 200/10
00 mm, preferably 10/1000 to 100/100
0 mm, more preferably 20/1000 to 40/10
Set to 00 mm. If this value is smaller than 5/1000 mm, there will be problems such as runout of the drill core and scratches on the inner wall of the processed hole. If it is larger than 20/1000 mm, the margin will be strongly pressed against the inner wall of the processed hole. The rotation resistance of the drill during drilling is unfavorable.

The diameter of the margin portion 33 is 40/1000 to 300 / than the diameter of the shank 10.
It may be formed to be 1000 mm larger.

In order to form the cutting edge shape, first, the shank 1 is formed in a state where the inclined surface 4 is not formed on the tip 3.
The cutting edge 31 is attached by a means such as brazing to form the cutting edge 31 by a known method, so that the outer peripheral edge of the cutting edge 31 reaches the outer peripheral edge of the tip 3. Then, the corner portion 5 of the triangle shown by the imaginary line in FIG. 1 is ground by a grinder so that the diameter of the cutting edge 31 is reduced by a radius t (5/2000 to 200/2000 mm). The inclined surface 4 may be a flat surface or a curved surface curved in the axial direction or the circumferential direction.

FIG. 4 shows another embodiment of the present invention, in which a pair of cutting blades 31 are integrally formed at the tip of the shank 12 made of high-speed steel, cemented carbide or the like and are arranged point-symmetrically to each other. A margin portion 50 is formed along the edge of the chip discharge groove 11 of the shank 12. Then, between the outer peripheral end 34 of the cutting edge 31 and the margin portion 53, the inclined surface 4 in which the distance from the central axis of the drill 1 gradually increases is formed as in the above embodiment, and the outer periphery of the cutting edge 31 is formed. The rotation locus formed by the margin portion 53 is 5/1000 to 20/1000 mm more than the rotation locus formed by the end 34.
It has a large diameter. In addition, similarly to the above, the diameter of the rotation trajectory formed by the outer peripheral edge 34 of the cutting edge is the shank 11
Is formed to be larger than the diameter of the.

In the above embodiment, the shape of the cutting edge 31 is shown only as an example, but the present invention is characterized by the structure of the outer peripheral edge portion of the cutting edge, and therefore the shape of the cutting edge itself is not limited to this. The thing of can be adopted. Further, in the first embodiment, the margin portion is not formed along the chip discharge groove 11, but is formed only on the outer peripheral surface of the chip 3, but the shank according to the present invention includes the chip discharge groove and the margin portion. Is formed is a concept including such an aspect.

When drilling is performed by the drill 10 having each of the above-described configurations, the cutting blade 31 drills a hole having a predetermined diameter. The machined hole has excellent roundness, and the inner wall of the machined hole is finished very smooth, so that the machined hole does not need to be finished by a reamer. The smoothness of the inner wall of the machined hole is about 3 s when the rotation locus formed by the margin portion 33 is formed to have a diameter of 30/1000 mm larger than the rotation locus formed by the outer peripheral end 34 of the cutting edge 31, which is about 3 s. It can be said that the smoothness is very excellent because it is about 100 s when using a drill.

The processing with such accuracy is performed
This is probably due to the following reasons. That is, in the conventional drill, the outer peripheral end of the cutting blade cuts the inner wall of the processing hole to widen the hole in accordance with the runout during machining, and the inner wall is damaged in the circumferential direction. On the other hand, in the structure of the above-described embodiment, the cutting edge 31 is formed to have a diameter slightly smaller than the inner wall of the processing hole, and the margin portions 33 and 50 are always in contact with the inner wall surface. As a result, runout is prevented. In order for center runout to occur, it is necessary to cut and widen the machining hole at the outer peripheral edge of the cutting edge.If the outer peripheral edge of the cutting edge does not reach the inner wall of the machining hole, the machining hole cannot be widened and the inside of the machining hole cannot be expanded. Since the margin portion is always in contact with the wall surface, core runout is prevented from occurring.

Further, the inner wall of the machining hole formed at the outer peripheral edge 34 of the cutting edge is pressed outward by the inclined surface 4 and the margin portions 33 and 50 following the outer peripheral edge 34, whereby a smooth surface is finished.

[0018]

As described above, according to the present invention, a hole having a predetermined diameter is machined by the cutting blade, the cutting blade is formed to have a diameter slightly smaller than the inner wall of the processing hole, and the inner wall surface is always provided with a margin. Since the parts are in contact with each other, this acts as a guide to prevent runout. Further, the inner wall of the machined hole formed at the outer peripheral edge of the cutting edge is pressed outward by the inclined surface and the margin portion following the outer peripheral edge, whereby the inner wall of the machined hole is finished into a smooth surface. Therefore, the machined hole has excellent roundness, and the inner wall of the machined hole is finished very smooth, so that the machined hole does not need to be finished by a reamer. Further, according to the cutting edge forming method of the present invention, in the drill having the conventional structure, the outer peripheral end of the cutting edge only needs to be grinded by the grinder by a predetermined amount, and the cutting can be performed very easily.

[Brief description of drawings]

FIG. 1 is a front view of a drill tip portion showing an embodiment of the present invention.

FIG. 2 is a side view of FIG.

FIG. 3 is a bottom view of FIG.

FIG. 4 is a side view showing another embodiment of the present invention.

[Explanation of symbols]

 1 drill, 3 tip 4 inclined surface 10,12 shank 11 chip discharge groove 33,50 margin part

Claims (3)

[Claims] 1. In a drill having a chip discharge groove and a margin portion formed on a shank and a cutting blade formed at a tip portion, a rotation locus formed by the margin portion is larger than a rotation locus formed by an outer peripheral end of the cutting blade. 5/1000
A drill having a large diameter of up to 200/1000 mm. 2. The drill according to claim 1, wherein an inclined surface whose distance from the center axis of the drill gradually increases is formed between the outer peripheral end of the cutting edge and the margin portion. 3. In a drill having a chip discharge groove and a margin portion formed on a shank, and a cutting edge formed at the tip to the outer peripheral end, the intersection of the cutting edge and the margin portion is ground to cut the cutting edge of the cutting edge. The rotation locus formed by the margin is 5 /
4. An inclined surface having a gradually increasing distance from the center axis of the drill is formed between the outer peripheral edge of the cutting edge and the margin portion so as to have a large diameter of 1000 to 200/1000 mm. A method for forming a cutting edge of a drill described.