JPH05220611A - Twist drill - Google Patents

Abstract

PURPOSE:To make it unnecessary to draw out and supply the cutting oil thereto during the operation, increase the working efficiency, supply the cutting oil abundantly, prevent the seizure of the drill and increase the life of the drill by providing a small groove to the land in a spiral manner. CONSTITUTION:When the boring operation is achieved by using a drill, the inside of the hole becomes vacuum as the cutting chips are discharged out of the small groove 20 provided to the land 18 in a spiral manner. In this condition, if the cutting oil is supplied to the small groove 22 of the outside part, this vacuum allows the cutting oil to be sucked to reach the end. On the other hand, the cutting oil which has reached the end comes out through this groove 20 together with the cutting chips, resulting in a kind of forced circulation of the cutting oil. Thus, when the cutting oil is supplied abundantly, the drill will not be seized, making it unnecessary to frequently draw out the drill and supply the cutting oil thereto.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a twist drill.

[0002]

2. Description of the Related Art FIG. 3 is a front view of a twist drill, and FIG. 4 is a cross-sectional view.
Two outer diameter cutting edges 14 that are formed radially with a tip angle of slightly less than 0 ° and that are continuous with each tip cutting edge 12 are formed in a spiral shape.

By the way, a portion where the outer diameter cutting edge 14 is present is called a margin 16, and a portion which is continuous with the margin 16 and has a slightly smaller diameter is called a land 18. A double groove 20 is also provided between the adjacent margin 16 and the land 18. It is formed in a spiral shape. The groove 20 serves as a chip discharge passage, and the chips cut by the tip blade edge 12 are discharged from the groove 20, so that continuous cutting can be performed. The groove 20 also serves as a cutting oil injection passage described later.

[0004]

On the other hand, the drill generates heat during cutting, and this heat lowers the machinability and wears the cutting edge. Therefore, it is necessary to cool this heat. Conventionally, this is dealt with by applying cutting oil to the groove 20 of the drill that is exposed to the outside, but the fact that chips are discharged inside the groove 20 and that the spiral direction of the groove 20 is It is difficult to inject the cutting oil to the inside through the groove 20 because it is formed in the discharge direction accompanying the rotation of the cutting material or the drill. Therefore, it is necessary to extract the drill many times during the work and apply the cutting oil, which reduces the efficiency.

Further, if this operation is neglected, the drill will be burnt or damaged, and the cutting edge will be hardened to form a built-up cutting edge to increase the hole diameter or roughen the hole surface roughness. To become. The drill can be used vertically or horizontally, but the horizontal structure is predominantly used due to the structure of the machine. When using the horizontal type, it becomes more difficult to inject the cutting oil, and the above-mentioned phenomena become more remarkable.

As a means for improving this, there is a drill (hole drill) in which a hole is formed in the core of the drill and the cutting oil is forcibly fed from this hole, but such a drill is expensive. In particular, the structure of a rotating boring machine such as a boring machine or drilling machine is difficult and the price is very high. The present invention solves such a problem, and forms a small groove that functions to introduce cutting oil in addition to the groove for discharging chips.

[0007]

In order to solve the above problems, the present invention is characterized in that a small groove is spirally formed on a land, and preferably, the small groove is provided with a margin. It is characterized by being formed along with.

[0008]

By the above measures, the internal pressure becomes negative as the chips are discharged from the groove, but at this time, the cutting oil is applied to the portion exposed to the outside of the drill by the same method as the conventional method. If it is applied, this negative pressure will suck the cutting oil, and it will be forcibly sent to the inside through the small groove.

[0009]

FIG. 1 is a front view of a twist drill according to the present invention, and FIG. 2 is a sectional view. The main structure of the twist drill is the same as that of the conventional one described above, but only in the land 18 part. The difference is that the small groove 22 is formed. Small groove 22
Is continuous with the land 18, the tip thereof extends to the tip edge portion 12 and the rear end thereof extends to the neck portion 24 having a small diameter. It is not necessary to match the spiral angle of. However, considering the ease of manufacture, it is preferable to match the spiral angle of the land 18. Further, the small groove 22 may be formed on any part of the land 18, but due to the problem of the constituent cutting edge and the like described later, the margin 16 is formed as shown in FIG.
It is most suitable to form along. In addition, although FIG. 5 is a cross-sectional view showing another example, the small groove 22 may be formed apart from the margin 16 as described above. Furthermore, a plurality of small grooves 22 may be formed.

The width and depth of the small groove 22 are not particularly limited, and may be set appropriately within a range that does not affect the strength of the drill itself. Although the cross-sectional shape of the small groove 22 may be various, a semi-circular shape is the most common in view of easiness of processing and cost. In addition, if the cross section of the small groove 22 is semicircular, the flowability of the cutting oil is also improved. From these things, it seems that a drill having a diameter of 20 mm is ideally one having a diameter of about 2.5 to 3R.

By the way, in the conventional drill, the width of the margin 16 is widened to some extent in consideration of an increase in cutting resistance due to insufficient supply of cutting oil. The margin 16 contacts the inner circumference of the hole cut by the tip cutting edge 12 and performs the finishing cutting and the guide of the drill itself.
When the width of the margin 16 is wide, the number of constituent cutting edges is increased.

The formation of the constituent cutting edge has various adverse effects such as shortening the life of the drill, lowering the accuracy of the finished surface, increasing cutting resistance, and forming a back line when the drill is pulled out. In the drill formed along the margin 16, the supply of cutting oil is abundant and the cutting resistance does not increase so much, so that the width of the margin 16 can be narrow. Specifically, if it is a drill with a diameter of 20 mm,
The width of the margin 16 may be about 1 to 1.5 mm (about 3 mm in the conventional product). On the contrary, by narrowing the width of the margin 16, an advantage that the machinability is improved can be expected.
There are various drill materials, such as high-speed steel, carbide, and those coated with a hardened film, and the present invention can be applied to any of these.

As described above, when a drilling operation is performed using this drill, the inside of the groove 20 becomes negative pressure as the chips are discharged from the groove 20. In this state, if cutting oil is supplied to the small groove 22 that is exposed to the outside, this negative pressure causes the cutting oil to be sucked and reach deep inside. On the other hand, since the cutting oil that has reached the depths comes out through the groove 20 together with the cutting chips, it can be said that the cutting oil is subjected to a kind of forced circulation.

When the cutting oil is abundantly supplied in this way,
The drill does not burn, so it is not necessary to frequently remove it and apply cutting oil during the work. According to a test conducted by the inventors, it was not necessary to pull out about 50 mm to make a hole having a diameter of 12 mm. Especially SUS,
A material such as SCM is a difficult-to-cut material that easily holds heat, but the drill according to the present invention exerts a great effect on such a difficult-to-cut material. Moreover, this prolongs the life of the drill. Where the inventors confirmed,
It has been found that the life is extended by 7 to 8 times compared with the conventional product.

[0015]

Since the present invention is as described above, the following effects can be expected. a) The work efficiency is improved because it is not necessary to take out a drill and apply cutting oil during the work.
In particular, the effect is more remarkable when deep-hole cutting is performed on a difficult-to-cut material. b) Due to the abundant supply of cutting oil, the drill will not burn,
Longevity. c) This means that it is also difficult to form a cutting edge, so if the finished surface is clean and the accuracy is rough, reamer threading is unnecessary. d) Since the cutting resistance is small, the cutting speed can be increased and the wear of the cutting edge can be reduced. e) Since only a small amount of work is added to an ordinary inexpensive drill, the cost can be reduced. f) Even if an expensive thing such as a hole drill is not used, the same effect is exhibited.

[Brief description of drawings]

FIG. 1 is a front view of a twist drill according to the present invention.

FIG. 2 is a sectional view of a twist drill according to the present invention.

FIG. 3 is a front view of a conventional twist drill.

FIG. 4 is a sectional view of a conventional twist drill.

FIG. 5 is a cross-sectional view of another example of the twist drill according to the present invention.

[Explanation of symbols]

 16 Margin 18 Land 22 Small groove

Claims (5)

[Claims] 1. A twist drill in which a small groove is spirally engraved on a land. 2. The twist drill according to claim 1, wherein the small groove is arranged along a margin. 3. The twist drill according to claim 1, wherein the small groove is separated from the margin. 4. The twist drill according to claim 1, wherein the width of the margin is narrower than that of the conventional one. 5. The cross-sectional shape of the small groove is semicircular.
A twist drill of any one of 4 to 4.