JP2537134Y2 - Drilling tool - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drilling tool such as a drill, and more particularly to an improvement of a cutting tool suitable for drilling an aluminum casting.

[0002]

2. Description of the Related Art Conventionally, drilling tools as described above have been disclosed in Japanese Utility Model Application No. 60-74885 (FIGS. 8 and 9), Japanese Utility Model Application No. 60-156140 (FIG. 10), and Japanese Patent Application No. 56-23.
No. 571 (FIG. 11). Figure 8
The drill shown in FIG. 9 has a linear chip discharge groove 2 composed of two wall surfaces that are substantially perpendicular to each other at the outer peripheral portion of the drill body 1. The cutting edge 3 is formed at the intersection ridge line, and a thinning portion 4 that is cut off from the center of rotation toward the other of the two wall surfaces is formed at the center of the distal end surface of the drill body 1. is there. In such a drill, the chisel has substantially disappeared due to the presence of the thinning portion 4, and therefore, there is an advantage that the centripetality of the drill is high and the runout of the core at the time of biting can be prevented.

In the drill shown in FIG. 10, a thinning portion 6 similar to the above-mentioned drill is formed on the tip end surface of the drill body 5, and two sub-chip discharge grooves 7, 8 are formed on the land portion of the drill body 5. Formed, and a secondary cutting edge 9,
10 is formed. Such a drill also has the same advantages as the above-mentioned drill because no chisel is present. Further, in the drill shown in FIG. 11, the shape of the cutting
The thinning portion 12 is formed by removing a part of the front end surface including the inner peripheral end portion of No. 1.

[0004]

However, in the above-mentioned drill, thinning cannot be performed by mechanical grinding such as processing of a rake face, and is generally performed manually. However, in such manual processing, the surface roughness of the thinning portion becomes 1.6S or more, and the surface becomes considerably rough as compared with the rake face having a surface roughness of 0.5S. For this reason, particularly when machining a soft material such as aluminum, deposition tends to occur at a thinning portion where the cutting speed is slow and the flow of chips is slow. And, by such attachment of chips to the thinning portion, the chisel width of the drill becomes substantially large, thereby causing a problem that thrust resistance increases and deflection at the time of biting becomes severe. . Furthermore, even during drilling, the drill is likely to vibrate due to repeated formation and dropping of the attachment portion, which not only deteriorates the hole accuracy, but also may cause a drill breakage accident in some cases. In addition, in the drill shown in FIG. 11, since the thinning portion is formed, the cutting edge is bent toward the center from the point where the cutting edge approaches the thinning portion (indicated by a point P in the drawing). For this reason, at the bending point, the chips are separated into two inside and outside strips, and as a result, there is a problem that the chips are not normally discharged such as curling and cutting of the chips, and the chips extend to the shank of the drill. Was.

[0005]

The purpose of the present invention is to solve the above-mentioned drawbacks of the conventional drill, which eliminates the need for thinning, and therefore eliminates the drawbacks caused by the presence of thinning. An object of the present invention is to provide a drilling tool that can perform the drilling.

[0006]

The drilling tool according to the present invention is provided with two chip discharge grooves extending linearly from the front end to the rear end on the side of the tool body that is rotated around the axis. provided first margin land portion in the rotation direction rear side adjacent each chip discharge flute, a second margin on a land portion of the heel side respectively, crossing the wall surface and the distal flank face facing the direction of rotation of the chip discharge flute A straight cutting edge is provided on the ridge line when viewed from the front in the axial direction, and the first and second margins are arranged in substantially equal divisions. The cutting edge passes through the outermost point of the cutting edge and is orthogonal to the cutting edge. The distance from the straight line to the bottom of at least the tip side portion of the chip discharge groove is 55 to 75% of the tool diameter.

[0007]

In the drilling tool having the above construction, the distance from a straight line passing through the outermost point of the cutting edge and perpendicular to the cutting edge to the bottom of at least the tip side of the chip discharge groove is defined as the tool diameter. Since it is 55 to 75% , it is not necessary that the cutting edge extends linearly to the center of the tool body to form thinning. Therefore, it is possible to eliminate various adverse effects caused by the attachment of the chips to the thinning. Further, since the chip discharge groove is deep, the chips can be surely curled at the bottom thereof, and the chip discharge property can be greatly improved. Here, the lower limit of the distance is set to 55%.
The purpose of this is to secure the effective length of the blade.
This eliminates the need for thinning. Also, the upper limit is 75%
The reason is to ensure drill rigidity.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a bottom view showing the drill of the embodiment, and FIG. 2 is a side view thereof. In the figure, reference numeral 20 denotes a tool main body, and a chip discharge groove 21 extending linearly from a front end side to a rear end side is formed on a side portion of the tool main body 20. A straight cutting edge 23 is formed at the intersection ridgeline between the wall surface of the chip discharge groove 21 facing the rotation direction and the flank surface 22 at the tip end. The flank 22 is formed such that its center line substantially passes through the axis of the drill, and the width T is 5 to 20% of the drill diameter. Furthermore, rake face 2
The land portion 24 that continues rearward in the rotation direction 2 is formed in a flat surface, and thereby the drill has a rectangular shape in bottom view.

The flat portion of the land portion 24 and the chip discharge groove 2
1 between the chip discharge groove 21 and the first
The margin 25 has a second margin 26 formed on the front side in the rotation direction. Then, these first and second margins 2
5 and 26 are equally divided around the axis. The arrangement of the first and second margins 25 and 26 does not have to be strictly equal, and it is sufficient that the angle between the margins about the axis of the tool main body is within a range of 90 ° ± 10 °.

Further, a recess 27 is formed near the center of the side wall of the land portion 24 of the chip discharge groove 21 and extends linearly from the front end to the rear end. The recess 27 is provided with the cutting blade 23.
It is formed so that it falls one step in the direction along the rake face,
The bottom is a flat surface parallel to the chip discharge groove 21. Thereby, the cutting blade 23 extends linearly to the center of the drill. Here, the distance W from the straight line L passing through the outermost point of the cutting edge 23 and orthogonal to the cutting edge 23 to the bottom of the recess 27 is set to 55 to 75% of the drill diameter. The reason why the lower limit of the distance W is set to 55% is that the cutting edge 23
This is because the effective length is secured, and the conventional thinning becomes unnecessary. Also, the upper limit is 7
The reason for setting it to 5% is to secure drill rigidity. Further, the length S in the axial direction of the deepest portion of the concave portion 27 is set at least equal to or larger than the diameter of the drill in order to surely curl the chips and secure the re-grinding length of the drill.

As described above, in the drill having the above-described structure, the concave portion 27 extending from the front end side to the rear end side is formed in a portion which is a thinning portion in the conventional drill. Thereby, the above-mentioned drill can provide the following excellent effects. That is, the cutting blade 23 is
Since it extends linearly to the center of the zero, separation of chips can be prevented. Moreover, the chips can be surely curled at the bottom of the concave portion 27 and cut into short pieces,
The chip discharge property can be improved. Also, the recess 27
Since the area for chip discharge is increased only in the portion, the chip discharge property can be further improved in combination with the cutting effect. In addition, processing of relatively deep holes (for example, 5 to 6D) can be performed only by external lubrication in order to improve chip dischargeability. Further, the processing of the recess 27 is performed by the chip discharge groove 2.
1 can be performed simultaneously with the NC controlled machine tool, so that it can be finished to the same surface roughness as the chip discharge groove 21, that is, 0.5S or less, and the frictional resistance with the chip is small and the chip Can be effectively prevented. In addition, since there is no thinning as in a conventional drill, there is no problem of naturally attaching chips to the thinning part. Therefore, defects such as an increase in thrust load and a deterioration in hole accuracy due to vibration of the drill can be eliminated. Regarding the re-polishing of the drill, the flank 22 (the second surface) and the third surface behind the flank 22 only need to be polished, so that the re-polishing process can be greatly simplified.

Although the recess 27 is formed only at the tip of the tool body 20 in the above embodiment, it may be formed up to the shank of the tool body 20. Further, although the bottom surface of the concave portion 27 is formed flat, the concave portion 27 may be formed in a shape capable of more reliably curling chips, for example, a concave curved surface.
Further, the bottom shape of the concave portion 27 may be a step shape in which the depth becomes shallower from the inner circumference side to the outer circumference side, or a step shape in which the depth is gradually increased.

FIG. 3 is a bottom view showing a drill according to a second embodiment of the present invention. In the drill shown in this figure, the land portion is formed in a substantially V shape, so that the sub-groove 28 is formed ahead of the second margin 26 in the rotation direction. In addition,
The same components as those in the above embodiment are denoted by the same reference numerals.
In such a drill, the sub-groove 28 serves as a pocket for accommodating chips generated by burnishing by the first and second margins 25 and 26, so that fine holes are prevented from being caught and the hole is smoothened. Can be finished. The sub-groove 28
A cutting edge may be formed at the intersection ridge line between the first and second margins 26 to provide a reamer function. Furthermore, the rake face may be formed up to the center of the drill, and a portion behind the center of the drill may be a so-called third relief. An example of this case is shown in FIGS. In FIG. 4, the cutting edge 26a is provided at the edge of the margin 26.
Are formed. The cutting blade 26a is protruded from the cutting blade 23 to the outer peripheral side of T (0.02 to 0.10 mm). The inner peripheral wall of the hole machined by the cutting blade 23 is polished. The radial rake angle of the cutting edge is positive, but the axial rake angle may be positive or negative. FIG. 5 shows an example where the axial rake angle θ is positive, and FIG. 6 shows a case where the axial rake angle θ is negative.

FIG. 7 is a bottom view showing a drill according to a third embodiment of the present invention. In the drill shown in this figure, two sub-grooves 30 and 31 are formed in a land portion, and a third margin 32 is formed between the sub-grooves 30 and 31. In such a drill, since the drill is guided by the six margins 25 to 31, the occurrence of vibration is extremely small,
Further, since the burnishing effect is high, the holes can be finished even more smoothly. As in the case of the second embodiment, the sub-grooves 30 and 31 and the second and third margins 2 are provided.
A cutting edge may be formed at each of the intersection ridges 6 and 31 to provide a reamer function. Further, the number of the cutting edges may be odd or even, and may be arranged unequally.

Incidentally, the present invention is not limited to the shape of the land portion as in the above embodiment, but may be formed into a cylindrical curved surface or a concave curved surface. Further, an oil hole may be formed in the tool body.

[0016]

As described above, in the drilling tool of the present invention, as described above, the distance between the straight line passing through the outermost point of the cutting edge and perpendicular to the cutting edge and the bottom of at least the tip end portion of the chip discharge groove is described. Since the distance is set to 55 to 75% of the tool diameter, the separation of the chips can be prevented, the chips can be surely curled at the bottom of the chip discharge groove and cut into short pieces, and the chip discharge performance is improved. be able to. Further, since the area for chip discharge is large, the chip discharge property can be further improved in combination with the cutting effect. In addition, machining of relatively deep holes can be performed only by external lubrication in order to improve chip dischargeability, and furthermore, all can be machined by mechanical grinding. It can be finished as follows, and the frictional resistance with the chips is small and the attachment of the chips can be effectively prevented. In addition, since there is no thinning unlike conventional drills, there is no problem such as the attachment of chips to the thinning part, and therefore, the disadvantages such as an increase in thrust load and deterioration of hole accuracy due to drill vibration are eliminated. And excellent effects such as greatly simplifying the drill re-polishing step can be obtained.

[Brief description of the drawings]

FIG. 1 is a bottom view of a drill according to a first embodiment of the present invention.

FIG. 2 is a side view of the drill shown in FIG.

FIG. 3 is a bottom view of the drill according to the second embodiment of the present invention;

FIG. 4 is a bottom view showing a modification of the drill shown in FIG. 3;

5A is a side view showing details of an outer peripheral cutting edge of the drill shown in FIG. 4, and FIG. 5B is a bottom view of FIG.

6 is a modification of the drill shown in FIG. 5, (a) is a side view showing details of an outer peripheral cutting edge of the drill, and (b) is (a)
FIG.

FIG. 7 is a bottom view of the drill according to the third embodiment of the present invention.

FIG. 8 is a sectional view showing an example of a conventional drill reamer.

FIG. 9 is a bottom view of the conventional drill shown in FIG.

FIG. 10 is a bottom view showing another example of the conventional drill reamer.

FIG. 11 is a bottom view showing still another example of the conventional drill.

[Explanation of symbols]

 Reference Signs List 20 Tool body 21 Chip discharge groove 23 Cutting blade 24 Land 25 First margin 26 Second margin

Claims (1)

(57) [Scope of request for utility model registration] 1. A chip body that is rotated about an axis is provided with two chip discharge grooves linearly extending from a front end side to a rear end side on a side portion of a tool body, and a rear side in a rotation direction adjacent to each chip discharge groove. the on land portion 1 of the margin, the second margin are respectively provided on the land portion of the heel side, further, axially distal view in cross ridge line between the wall and the distal flank face facing the direction of rotation of the chip discharge groove A straight cutting edge is provided,
In the drilling tool in which the first and second margins are arranged in substantially equal divisions, at least a part of the chip discharge groove at a front end side from a straight line passing through the outermost point of the cutting edge and orthogonal to the cutting edge. The distance to the bottom is 55 to 75% of the tool diameter
A drilling tool characterized by the following.