JPH0141526Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a gun drill, which has been improved to be particularly suitable for drilling deep holes in steel-based materials.

Conventionally, when machining steel-based workpieces that produce long chips during this type of gun drilling, long and thin chips that are separated in the axial direction tend to be generated, resulting in wrapping around the pipe section or the feed rate being too high. In some cases, chips could become clogged.

Therefore, in order to deal with the problem of chip disposal, for example, as in Japanese Utility Model Application Publication No. 55-41276, a V-shaped rake face is used, or the cutting oil pressure is increased. In particular, there were limits to shipping. In other words, for steel materials with H _B 200 or less, the proper feed cannot be achieved with a cutting edge diameter of 10 mmφ.
It was about 0.02 to 0.03 mm/rev.

For this reason, we have developed a gundrill that can improve chip feed by changing the shape of the cutting edge to effectively dispose of chips during gundrill machining of steel-based workpieces that produce long chips. is requested.

The present invention was developed in view of the above-mentioned points, and a cutting tip is attached to the tip of the pipe-shaped main body to form a front cutting edge and an outer cutting edge. To provide a gun drill equipped with a chip breaker having a land and two concave parts connected to each other along the edge of the blade.

In other words, in the cross-sectional direction of the rake face, the chip breaker has two concave portions that are concavely curved and have a predetermined size relationship, and are continuous from the outer peripheral cutting edge side via the land, and furthermore, these concave portions are A crossing ridge is formed at a predetermined depth in the connecting portion. Further, the front cutting edge ridge is formed by forming a linear ridge by a land, two concave curved ridges by the chip breaker, and a straight ridge by the remaining rake surface, respectively, as the chip breaker is formed. By adopting such a cutting blade configuration, high-feed machining becomes possible when machining holes in steel-based materials.

Hereinafter, one embodiment of the gun drill of the present invention will be described with reference to the drawings.

In FIGS. 1 and 2, reference numeral 1 denotes a pipe-shaped main body, which has a cutting tip 2 at its tip and a shank 3 at its rear end.

The cutting tip 2 has a front cutting edge 5a and an outer cutting edge 5b, and is usually made of cemented carbide. Further, a chip breaker 7 is ground into the rake face 4 via a land 6 in a direction along the outer peripheral cutting edge ridge 5b.

As clearly shown in FIG. 2, this chip breaker 7 has lands 6 in the transverse direction of the rake face 4.
A small recessed portion 8 and a larger recessed portion 9 are connected from the sides, and a raised intersecting ridge 7a is formed at the connecting portion. In this case, the size relationship between the recessed portions 8 and 9 is the same in terms of depth and width.
In FIG. 2, arc-shaped concave portions 8 and 9 are connected to each other, and these concave portions 8 and 9 are connected to the rake face 4 through the width W ₃ of the land 6.
It is given by the virtual widths W ₁ and W ₂ seen above and the depths t ₁ and t ₂ from the rake face 4. Regarding the depth, t ₁ > t ₂ , and the depth t ₃ of the intersecting edge 7a is t ₃ ≦0.7t ₂ with respect to the depth t 2 of the recessed portion ₈ .
It is set in relation to This is to apply to gun drilling having a center hole as shown in FIG.

Further, in FIG. 3, a small angular recessed portion 8 and a generally arcuate recessed portion 9, which is somewhat larger than the recessed portion 8 in terms of width and depth, are arranged in series. In this case, the arc-shaped concave portions 8 and 9 include not only a circular arc shape with a radius R based on the cross section but also a circular arc shape line such as a parabola or hyperbola. Further, the angular recessed portion 8 has a shape line that is cut upward in an arc shape from a downwardly inclined straight line with the cross section as a reference.

Regarding the land 6, its width is W ₃
The width is usually 0.1 to 0.8 mm. In addition, the concave portion 9 having an arc shape
is in the relationship R=(0.06 to 0.2)D with the diameter D of the cutting edge, where R is the radius.

Furthermore, the size relationship between the virtual widths W ₁ and W ₂ of the concave portions 8 and 9 as seen on the rake face 4 is 0.2≦W ₂ /W ₁ ≦
It is 0.8. Furthermore, there is a relationship between the imaginary width W ₁ of the concave portion 9 and the depth t ₁ from the rake face 4, t ₁ /W ₁ =0.15 to 0.40.

These relationships were obtained from the results of cutting tests and the like, and are also applied to the angular recessed portion 9 shown in FIG. 3 described above. The continuous width W of the recessed portions 8 and 9 is W = 0.3 based on the size of the flute and the virtual widths W ₁ and W ₂ of the recessed portions 8 and 9 based on the diameter D of the cutting edge. A grade of D is appropriate. Further, as can be seen from FIGS. 2 and 3, the recessed portion 8 is of a circular arc shape or an angular shape as described above, and the recessed portion 9 is only of a circular arc shape. Ru.

Hereinafter, the chip flow situation and cutting performance of the gun drill of the present invention will be explained based on FIGS. 5 to 7.

In other words, FIG. 5 conceptually shows the flow of chips when machining with the gun drill of the present invention, and the chips flow through the so-called raised rim part due to the presence of the concave parts 8 and 9. The accompanying convex shape is transferred and generated. In this case, the rim part is
It refers to something like the wavy protrusion formed on the top end of beer cans, drums, etc. As a result,
A bending moment acts on the raised rim portion relative to the concave portions 8 and 9, and the chips are drawn toward the concave portion 8, especially in the vicinity of the land 6, reducing the width of the chips. receive. The reason why the small concave portion 8 starts from the land 6 side is, firstly, so that it can be applied to gun drilling with a center hole as shown in FIG. 4, and secondly, This is because in normal cutting, as is clear from FIG. 5, the overall curl of chips is controlled by the upward cut portion of the recessed portion 9 on the axial center side. As a result, the chip starting from the small concave portion 8 side has a good balance of chip generation with respect to the unit radius length, the concave portion of the same size is connected in succession, and the large concave portion 9 and the small concave portion start from the land 6 side. This device is more effective in curling and breaking chips than the opposite device in which the portions 8 are provided in series.

FIG. 6 shows the product of the present invention having the bevel-shaped cutting edge shown in FIG. This is a performance evaluation of conventional bevel-shaped products. In this case, the outer angle is 30°, the inner angle is 20°, and the workpiece material is high carbon alloy steel (Prinell hardness H _B
<230). As for the results, the product of the present invention is shown by a solid line, and the conventional product without the recessed portions 8 and 9 is shown by a dotted line. In addition, the cutting speed of this device is
70m/min, conventional product 90m/min. The difference in cutting speed is due to the amount of feed.

As a result, the gun drill of the present invention is capable of a high feed rate approximately twice as high as that of conventional products, although the preferred range is indicated by hatching in terms of per revolution (mm/rev). In addition, in Fig. 6,
The concave portions 8 and 9 in the product of the present invention have the configuration shown in FIG. 2, and the width relationship W ₂ /W ₁
is set to a constant value of 0.5. And W ₂ /
It was confirmed from other tests that the range of W ₁ is 0.2≦W ₂ /W ₁ ≦0.8 based on changes in chip shape, workpiece material, etc. that it is a suitable range. In this test, the continuous width W of the concave portions 8 and 9 was kept constant, and the ratio thereof was varied to evaluate the improvement in feed and the chip disposability.

FIG. 7 is a comparison of the shapes of chips produced by the product of the present invention and a conventional product having a V-shaped rake face as seen in Japanese Utility Model Application No. 55-41276. As a result, the product of this invention is 0.07mm/rev
Under the high feed conditions, the chips were curled into a substantially C-shape and broken to an appropriate length. On the other hand, with the conventional product, chips were crushed under the same feeding conditions, making chip clogging more likely to occur. The reason why high feed was not possible with the conventional product is that the cutting edge on the front side has a V-shaped straight edge, and the center height near the outer periphery makes the cutting difficult. Therefore, it was confirmed from FIG. 7 that the product of the present invention is capable of high feed rates when drilling holes in steel-based materials and has excellent chip disposal properties.

Further improvement in cutting performance can be expected by forming a hard coating layer on the cutting edge tip 2, such as a carbide such as Ti, a nitride, a carbonitride, or an oxide such as alumina.

As explained above, in the present invention, a chip breaker is formed in which a small concave portion 8 and a large concave portion 9 are arranged in series on the cutting edge tip of a gun drill. Because this process can be carried out smoothly, high feed rates are possible, and along with this, improvements in cutting performance, service life, and finishing accuracy can be expected.

[Brief explanation of the drawing]

FIG. 1 is a front view of essential parts showing one embodiment of the gun drill of the present invention, FIG. 2 is a partially enlarged sectional view taken along the - line in FIG. 1, and FIG.
FIG. 4 is a front view showing one form of cutting in the gun drill of the present invention; FIG. 5 is a partially enlarged cross-sectional view showing a modified example corresponding to Fig. 2; and Fig. 5 is a state of outflow of chips in another form. A perspective view of the main parts showing the
FIG. 6 is an explanatory diagram conceptually comparing the cutting performance of the product of the present invention and the conventional product, and FIG. 7 is an explanatory diagram comparing the shapes of chips produced by the product of the present invention and the conventional product. 1... Main body, 2... Cutting blade tip, 5a... Front cutting edge ridge, 5b... Outer cutting edge ridge, 7... Chip breaker, 8, 9... Concave portion.

Claims (1)

[Claims for Utility Model Registration] A cutting tip 2 is attached to the tip of the pipe-shaped main body 1, thereby forming a front cutting edge 5a and a peripheral cutting edge 5b. , a gun drill in which a land 6 and a chip breaker 7 are provided along the outer peripheral cutting edge edge 5b, and a shank 3 is attached to the rear end of the main body 1, the chip breaker 7 comprising: In the transverse cross-sectional direction of the rake face 4, two concave portions 8 and 9 are arranged in series from the outer peripheral cutting edge ridge 5b toward the shaft center line via the land 6, and these concave portions 8,
A raised crossing ridge 7a is formed at the connecting portion of 9, and the recessed portion 8 is formed from a substantially arc-shaped line extending from the land 6 side to the crossing ridge 7a, or from a downwardly inclined straight line cut upward into an arc shape. In addition, the recessed portion 9 has a generally arcuate shape line starting from the intersecting edge 7a in the cross-sectional direction, and the depth t ₂ of the recessed portion 8 is equal to the depth of the recessed portion 9. The depth t ₃ of the intersecting edge 7a due to the continuous arrangement of the recessed portions 8 and 9 is set to be smaller than the depth t 1 of the recessed portion 8 _, and the relationship of t ₃ ≦0.7t ₂ with respect to the depth t ₂ of the recessed portion 8. Furthermore, the virtual widths W ₂ and W ₁ of the concave portions 8 and 9 as seen on the rake face 4 are 0.2≦
The relationship is set such that W ₂ /W ₁ ≦0.8, and the front cutting edge 5a has concave portions 8 and 9.
As the chip breaker 7 is formed, a straight edge formed by the land 6, a concave curved edge formed by two series of shape lines formed by the concave portions 8 and 9, and a straight edge formed by the remaining rake surface 4 are respectively formed. A gun drill featuring.