JPH08215914A - Gun drill - Google Patents

Abstract

PURPOSE: To provide a two-edge gun drill capable of drilling a steel material with high efficiency. CONSTITUTION: A cemented carbide tool material accompanied by a twist having a fixed angle of torsion is jointed with the tip of a pipe provided along the long shaft with a straight flute groove 5. A cutting edge body 4 is provided respectively with a pair of cutting edges 7, an opening 9 of a coolant hole 8 and the twisted flute groove 10 to form a two-edge gun drill 1. On the rake surface of the cutting edge body 4 is arranged at least one strip-like projection 11 extending from the inner edge of the cutting edge along the twist. The projection 11 is within a range from the inner edge to the outer edge of the cutting edge 7 and a land 13 is allowed to remain even when the projection is in the outermost edge. Also, the section of the projection 11 is preferably of an arcuate smooth curved shape.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-blade gun drill, which enables highly efficient drilling of steel materials.

[0002]

2. Description of the Related Art A gun drill used to make a deep hole in a work piece is usually a single-edged tool made by brazing a cemented carbide tip with a straight blade to the tip of a pipe having an irregular cross section. It is a shape-shaped gun drill. This gun drill must be used with care to prevent problems such as chip clogging and chip wrapping around the pipe when drilling work materials that are particularly prone to chip debris such as steel. There is. In order to solve this problem, for example, a device disclosed in Japanese Utility Model Publication No. 61-10887 discloses that a curved cutting edge that is convex in the rotational direction is formed as an inner blade, so that the chips can have an appropriate length. It is designed to be divided into two parts.

On the other hand, a two-flute gundrill was developed to obtain a higher cutting efficiency than the one-flute gundrill. This gun drill is also usually a brazed carbide tip with a straight blade brazed to the tip of a pipe having an 8-shaped cross section, which is high for workpieces such as cast iron and light alloys. Although it was possible to machine by feeding, it is not suitable for drilling steel materials due to its large cutting resistance. Therefore, in Japanese Utility Model Application Laid-Open No. 64-12715, a twist is given in the pipe so that the twist angle (lead angle) gradually decreases from the cutting edge of the carbide tip to the pipe on the rear end side. A two-flute gun drill with zero corners is disclosed. As described above, by using a gun drill having a tip cutting edge portion similar to a twist drill, chip discharge and cutting resistance are improved, and it can be applied to drilling of steel materials.

[0004]

The gun drill pipes for both the single-flute type and the double-flute type are generally formed by subjecting a drawn pipe to additional machining. However,
Since the above-mentioned two-blade gun drill has a twist even in a part of the pipe portion, the pipe member by drawing cannot be used and is formed by a laborious cutting process. This is a factor that increases the production cost. Also,
The gradual decrease in the twist angle causes a change in the rake angle due to a change in the twist angle when the cutting edge wears and regrinds from the tip, and a shift in the opening position of the coolant injection hole,
There is a problem that the same cutting performance as the original is not maintained.

The present invention solves the above problems and, by applying the technology of the single-edged gun drill, as a result, realizes a high-efficiency gun drill suitable for drilling a steel material. is there.

[0006]

In order to achieve the above-mentioned object, the present invention uses a pipe provided with a flute groove linearly along the major axis, and has a twist with a constant helix angle at its tip. A cutting tool is formed by joining ultra-hard tool materials accompanied by. And at the tip of this cutting blade,
A cutting blade, a coolant hole opening, and a twisted flute groove are formed symmetrically about the axis to form a 2-flute gun drill. At least one row of extending strip-shaped protrusions is arranged.

The protrusion is located within the range from the inner edge to the outer edge of the cutting edge, and the land is left even when it is located at the outermost edge. Further, the cross-sectional shape of the protrusion may be formed by a smooth arc-shaped curve.

[0008]

[Operation] A pipe member with a straight flute groove
It is relatively easy and inexpensive to obtain because it requires only some additional work on the drawn pipe. On the other hand, since the cutting blade body is formed by the flute groove having a constant helix angle from the tip cutting edge to the base end portion, the cutting resistance at the time of drilling, particularly the thrust force, is formed by the rake effect of the conformal angle. A 2-flute gun drill that can be reduced and applied to steel materials is realized. Moreover, by making the coolant hole spiral along a certain twist, the opening position of the coolant injection can always be kept constant even if the worn cutting edge is reground.

Due to the effect of twisting, in terms of chip discharge, improvement is achieved in comparison with the one without twisting, but the property in which the chips try to connect and extend does not change. Chips in a gun drill are produced when the cutting fluid supplied to the coolant hole communicating from the rear end of the drill is jetted from the tip and returns to the outside of the hole through the flute groove formed between the pipe and the hole wall. Then, it is forcibly pushed back and discharged together with the cutting fluid. There is no problem if the chips are naturally divided by hydraulic pressure or self-weight, but they will remain connected for a long time depending on the work material and cutting conditions. The deeper the processed hole, the more likely it is that trouble will occur. The strip-shaped projection in the present invention is for avoiding such a trouble, and is intended to divide the chip by utilizing the chip contracting action of the projection.

[0010]

Next, an embodiment of the present invention will be described with reference to the drawings.

1 to 3, the gun drill 1 is composed of a driver 2, a pipe 3, and a cutting blade body 4 brazed to the pipe 3. Pipe 3
Originally has a circular cross section, but is plastically processed from the middle to the tip to be formed into an 8-shaped cross section as shown in FIG. The recess formed on the outer side is the flute groove 5, which is linearly formed along the major axis. Also, the internal space becomes the coolant hole 6.

The cutting blade body 4 is provided with a pair of cutting edges 7, a pair of coolant holes 8 and their openings 9, and a pair of flute grooves 10. The coolant holes 8 and the flute grooves 10 are It is twisted with a certain twist angle. Cutting body 4
And the pipe 3 are joined so that the flute grooves 5 and 10 and the coolant holes 6 and 8 are connected to each other. If the length of the flute groove is longer than the depth of the hole to be machined, the cutting fluid sprayed from the opening 9 will push the chips back together when flowing out to the base end side of the gun drill 1 along the flute groove. Discharge to outside.

The cutting edge body 4 made of a super hard tool material provided with the twisted coolant hole 8 and the flute groove 10 can be easily obtained by extrusion molding. Further, since the pipe 3 provided with the coolant groove 5 can be easily obtained, a two-blade gun drill having a twisted blade can be obtained at a low manufacturing cost.

On the rake face of the cutting blade body 4, a projection 11 extends in a strip shape from the cutting edge 7 along the twist. The protrusion 11 may be located anywhere on the rake face, but it is arranged so that the land 13 remains narrow even at the outermost edge so as not to reduce the sharpness of the outer peripheral cutting edge 12. Is preferred. Further, the projections 11 do not necessarily have to form a pair, and are provided only on one side of the pair of cutting edges 7 or one row at an asymmetric position with respect to the axial center, depending on the chip ejection state. Alternatively, for a large diameter gun drill, for example, two rows to one row may be provided.

The cross-sectional shape of the projection 11 is preferably formed by a smooth arc-shaped curve. Since the projection 11 is provided, the rake angle of the rake face is not uniform, and changes at the projection 11. Specifically, since the rake angle at the protrusion is small, the shear angle of the chip is small, and the chip tends to be thick at this part. The surrounding thin chips are pulled and the width becomes narrower overall, and they try to deform into round chips. The rounded chips interfere with the inner wall of the hole and the flute groove 10 at a certain point to bend, and are cut into a shape that is easily discharged. Further, the chips that are intended to be rounded have a short rubbing length with the rake face, so that cutting resistance is also reduced.

[0016]

As described above, according to the present invention, a two-blade gun drill having a low cutting resistance and a good chip discharge can be obtained by the effect of the twisting blade and the effect of the projection.
As a result, it becomes possible to provide a gun drill capable of highly efficient drilling even for deep hole drilling of steel materials. Moreover, this gun drill is obtained according to the invention at a relatively low manufacturing cost.

[Brief description of drawings]

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

FIG. 2 is an enlarged view of a tip portion of FIG.

FIG. 3 is a side view of FIG.

FIG. 4 is a cross-sectional view taken along the line AA of FIG.

[Explanation of symbols]

 1 Gun drill 3 Pipe 4 Cutting edge body 5,10 Flute groove 6,8 Coolant hole 11 Protrusion

Claims (3)

[Claims] 1. A cutting tool body 4 is formed by joining a super-hard tool material with a constant twist angle to the tip of a pipe 3 having a flute groove 5 linearly along the major axis, A two-blade gun drill 1 in which a cutting edge 7, an opening 9 of a coolant hole 8 and a twisted flute groove 10 are formed symmetrically about an axis at the tip of the cutting edge body 4, At least one row of strip-shaped projections 11 extending from the cutting edge 7 along the twist is arranged on the rake face of the cutting edge body 4. 2. The projection 11 is arranged so that the land 13 is formed even within the range from the inner edge to the outer edge of the cutting edge 7 and at the outermost edge. The gun drill according to claim 1. 3. The gun drill according to claim 1, wherein the projection 11 has a cross-sectional shape formed by a smooth curve having an arc shape.