JPH04343608A - Vanishing drill - Google Patents

Abstract

PURPOSE:To provide a vanishing drill which has excellent chamfer property and high centripetal property and cutting stability, reduces expansion allowance of hole diameter and surface roughness of inner peripheral face of hole, and can cut material which contains carbon such as cast iron. CONSTITUTION:A vanishing drill consists of a cylindrical shank and a small diameter section which is connected with this shank and whose maximum outside diameter is smaller than that of the shank. A pair of first cutting blades 16a and 16b which are formed at the tip of the small diameter section tilt backward with first cutting blade angle from the center of the tip toward the direction of outside of diameter. Second cutting blades 30a and 30b which are formed at the tip of the small diameter section are provided on the plane which includes drill axial line and in the plane which crosses the plane which includes the first cutting blades. The second cutting blades 30a and 30b consist of boron nitride chip 30, have larger maximum outside diameter than that of the first cutting blades 16a and 16b, and tilt backward with second cutting blade angle toward the direction of outside of diameter.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a burnishing drill that combines the functions of a drill and a reamer.

0002

[Prior Art] As shown in Japanese Utility Model Application Publication No. 62-65107, a drill with a reamer is known which has a cutting blade for drilling and a cutting blade for reaming in one tool. . Further, a burnishing drill disclosed in Japanese Utility Model Application Publication No. 2-97510 uses a diamond tip as a cutting blade for reaming provided at the tip of the main body. In this device, the inner circumferential surface of the hole drilled by the first cutting edge for drilling is finished into an even smoother inner circumferential surface by the second cutting edge made of a highly hard diamond tip.

0003

[Problems to be Solved by the Invention] However, although the burnishing drill disclosed in Japanese Utility Model Application Publication No. 2-97510 can be applied to materials such as aluminum alloys, the carbon content is relatively low. With regard to workpiece materials containing high carbon content, such as gray cast iron and spheroidal graphite cast iron, which are commonly used, there is a problem in that the diamond tip wears out significantly, making it difficult to cut the workpiece material. The present invention has been made to solve these problems, and has good sticking properties, high centripetal properties, and high cutting stability, and has a wide range of hole diameter expansion and surface roughness of the inner circumferential surface of the hole. The purpose of the present invention is to provide a burnishing drill that can cut carbon-containing work materials such as cast iron.

0004

[Means for Solving the Problems] A burnishing drill according to the present invention for achieving the above object includes a cylindrical shank, a small diameter portion connected to the shank and having a maximum outer diameter smaller than the maximum outer diameter of the shank, and It is formed at the tip of the small diameter part, and as you go radially outward from the center of the tip, there is a first
a pair of first cutting blades that are inclined with a cutting edge angle of a pair of second cutting blades made of cubic boron nitride thin plates having a maximum outside diameter larger than the maximum outside diameter of the cutting blades, and slanting toward the rear with a second cutting edge angle in the radially outward direction; It is characterized by having the following.

[0005]

[Operation] According to the burnishing drill of the present invention, the inner peripheral surface of the hole drilled by the first cutting edge is covered with the second cutting edge made of highly hard cubic boron nitride (hereinafter referred to as "CBN"). This creates an even smoother inner surface. With this single drill, the first cutting edge and the second cutting edge perform drilling in the same phase, and it is possible to drill a hole with a small hole diameter expansion margin and surface roughness equivalent to or less than that of a reamer blade. Additionally, since drilling and reaming are performed in one process, highly accurate holes can be drilled in a short time. Furthermore, since the axial distance between the radial outer end of the first cutting blade and the radial outer end of the second cutting blade is fixed at a short distance, it is possible to reduce A hole can be drilled on the same axis with a minimum level difference from the finished hole by the second cutting blade.

[0006]

Embodiments Hereinafter, embodiments of the present invention will be explained based on the drawings. 1 to 4 show a first embodiment of a burnishing drill to which the present invention is applied. At the tip 13 of the cylindrical drill body 12 connected to the shank 11, there is a small diameter portion 14 having an outer diameter smaller than the maximum outer diameter of the drill body 12.
They are provided on the distal side from 5a and 15b. Shank 1
From the tip of the small diameter portion 14 that is farthest from the first cutting edge 16a, a first cutting edge 16a slopes on a straight line as it goes radially outward;
16b is formed with a predetermined first cutting edge angle α. The outer peripheral ends of the first cutting edges 16a, 16b are continuous with the guide surface 14a of the small diameter portion 14. First cutting edge 16a, 16b
On the rear side (rotation direction) opposite to the direction of rotation (direction of arrow A shown in FIG.
A slope 18b is formed.

From the outer peripheral end of the first slope 18a to the shank 11
A relief surface 22 extends in the axial direction on the side, and the shank 11
It is connected to A relief portion 21 is formed at the base of the first cutting edge 16a, 16b that escapes from the center of the tip toward the shank 11 side, and a first relief groove 19 is formed in the direction of this relief portion 21 extending toward the shank 11 side. has been done. A CBN tip 30 made of flat cubic boron nitride (CBN) is provided at the outermost tip of the small diameter portion in the direction that intersects the first cutting edges 16a, 16b in FIG.

The CBN chip 30 is shown in FIGS. 3(A) and 3(B).
It has a shape shown in , and is bonded to the concave groove 31 on the rear side in the rotational direction of the relief surface 22 and on the back side of the relief groove 19 through a blade 35 by brazing. The groove 31 supporting the blade 35 to be brazed to the CBN chip 30 is connected to the shank 11.
This support part 32 has a predetermined wall thickness for reinforcement, and a second relief surface 33 is formed on the rear side in the direction of rotation in the shank axis direction. has been done.

As shown in FIG. 3, a second cutting edge 30a (30b) is formed on the CBN tip 30 with a predetermined second cutting edge angle β (for example, β=90°). In this case, the second cutting edge 30a has a cutting edge that extends radially outward by a further distance δ from a circle including the radially outermost end of the first cutting edge 16a. As a result, the first cutting edge 1
The hole made by 6a and 16b is the second cutting edge 30a.
, 30b provides an even smoother finish. Further, the initial engagement by the second cutting edges 30a and 30b is improved.

When the burnishing drill configured as described above is rotated in the direction of arrow A shown in FIG.
, 16b scrape the workpiece and drill holes. In this case, the drill hole drilled by the first cutting blades 16a, 16b is finished into a reamed hole with a smoother inner peripheral surface by the second cutting blades 30a, 30b. At this time, the first cutting blades 16a, 16b and the second cutting blade 30a
, 30b coincide with each other, so that the centripetal property during drilling is improved and cutting stability is greatly improved.

5 to 7 show a second embodiment of the burnishing drill of the present invention. In the second embodiment, the small diameter portion 1
By increasing the wall thickness near the center of 4, high rigidity is ensured. Correspondingly, the width L2 of the CBN chip 30 is changed from the width L1 of the chip of the first embodiment, as shown in FIG.
It is narrower than. Since the other components are substantially the same as those in the first embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the explanation thereof will be omitted.

0012

As explained above, according to the high-speed, high-feed burnishing drill of the present invention, the first cutting edge and the second cutting edge are provided in the small diameter portion provided at the tip of the drill body. The inner circumferential surface of the hole drilled by the first cutting edge is finished to an even smoother inner circumferential surface by the second cutting edge of the highly hard cubic boron nitride chip. High precision hole drilling is possible in materials. In addition, the first cutting edge and the second cutting edge can be drilled in the same phase with one drill, making it possible to drill a hole with a hole diameter enlargement allowance and surface roughness that is equal to or smaller than that of a reamer. .

Furthermore, since drilling and reaming are performed in one step using the first cutting blade and the second cutting blade, highly accurate holes can be drilled in a short time. Furthermore, since the axial distance between the radial outer end of the first cutting blade and the radial outer end of the second cutting blade is fixed at a short distance, the second cutting edge after drilling the pilot hole with the first cutting blade during drilling. It is said that holes can be drilled on the same axis with a minimum level difference from the finished hole using the cutting edge 2, and that the hole diameter expansion and surface roughness can be kept small even if the feed speed is increased within a specified range. effective.

[Brief explanation of the drawing]

FIG. 1 is a front view showing a burnishing drill according to a first embodiment of the present invention.

FIG. 2 is a side view of a burnishing drill according to a first embodiment of the present invention.

FIG. 3(A) is a side view showing a cubic boron nitride chip used in the first embodiment of the present invention. (B) is its plan view.

FIG. 4 is a diagram showing the relationship between the maximum outer diameter of the first cutting edge and the maximum outer diameter of the second cutting edge according to the first embodiment of the present invention.

FIG. 5 is a front view showing a burnishing drill according to a second embodiment of the present invention.

FIG. 6 is a side view showing a burnishing drill according to a second embodiment of the present invention.

FIG. 7(A) is a side view showing a cubic boron nitride chip used in a second embodiment of the present invention. (B) is its plan view.

[Explanation of symbols]

11 Shank 12
Drill body 13
Tip part 14
Small diameter portions 16a, 16b First cutting edge 30 Boron nitride tip 3
0a, 30b Second cutting edge

Claims (1)

[Claims] Claim 1: A cylindrical shank, a small diameter part connected to the shank and having a maximum outer diameter smaller than the maximum outer diameter of the shank, and a small diameter part formed at the tip of the small diameter part, which extends radially outward from the center of the tip. a pair of first cutting edges that are inclined toward the rear side with a first cutting edge angle, and formed at the tip of the small diameter portion;
the first
a pair of second cutting blades made of cubic boron nitride thin plates having a maximum outside diameter larger than the maximum outside diameter of the cutting blades, and slanting toward the rear with a second cutting edge angle in the radially outward direction; A burnishing drill characterized by being equipped with.