JPH04315512A - Drill - Google Patents

Abstract

PURPOSE:To provide a drill on which a web thinning work is applied to improve a cutting quality and ensure a desired cutting edge strength. CONSTITUTION:A web thinning work is applied on the face, located in the vicinity of a chisel edge 3, of a drill. A web-thinned surface 10 is machined in a manner to form a curved surface having a relatively low curvature so that the curvature of a cutting edge in the vicinity of the chisel edge 3 is decreased and the width of the chisel edge 3 is decreased. Further, the rear of the cutting edge is formed in the shape of a curved surface having a relatively high curvature to ensure the strength of the cutting edge part. The web-thinned surface 10 is formed in the shape of a curved surface, extending along the shape of the side of a truncated cone, on the whole.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to thinning of the cutting edge of a drill used primarily for drilling steel materials.

0002

2. Description of the Related Art A drill is one of the cutting tools used for drilling holes in steel materials. As an example, the structure of a twist drill is shown in FIG. twist drill 3
0 is composed of a cutting blade part 31 used for drilling, and a shank part 32 that does not participate in cutting and is mainly used for ejecting chips and for attaching to a chuck part of a cutting machine such as a ball plate. .

FIG. 15 shows the tip shape of the cutting edge of a twist drill. The pair of cutting edges 33, 33 are arranged at rotationally symmetrical positions with respect to the rotation axis of the drill. Further, the cutting edge portion 33 is formed to extend linearly from the end of the chisel edge 34 toward the outer diameter direction of the drill.

FIG. 16 shows another example of a conventional drill.
It shows the structure of a spade drill. spade drill 4
0 is composed of a shank portion 41 and a cutting edge portion 42 fixed to the shank portion by a mounting pin 43. FIG. 17 shows the shape of the cutting edge of the cutting edge portion 42. The cutting edge portion 42 of the spade drill 40 is formed into a flat plate shape. A pair of symmetrically arranged cutting edges 44, 44 are formed at the tip of the cutting edge portion 42, extending linearly from the center toward both ends. In addition, there is a cutting edge 4 on the side that becomes the flank of the drill.
An elongated groove-like nick portion 45 is formed in a direction substantially perpendicular to 4.

[0005]

[Problem to be solved by the invention] Figure 15 or Figure 1
As shown in FIG. 7, regions 34 and 46, commonly referred to as chisel edges, are formed on the cutting edge of the drill. This chisel edge increases cutting resistance and receives a large thrust during cutting, so thinning is sometimes performed to sharpen this part and reduce the edge width.

On the other hand, the present inventor has developed a self-grip type drill as described below. Then, we tried thinning the cutting edge of the drill tip in a manner similar to conventional thinning. FIG. 18 is a plan structural view showing a conventional thinning process applied to the cutting tip of a drill developed by the inventor, and FIG. 19 is a front structural view thereof. The thinning surface 10 formed by conventional thinning processing is formed into a curved surface along the side surface of the cylinder from the chisel edge portion 3 toward the rear of the cutting edge. The width of the chisel edge 3 is defined by a radius R1 formed at the upper end of this thinning surface 10. If this radius R1 is made large, the roundness of the central portion of the cutting edge 4 will become large, and the width of the chisel edge will also become large, resulting in poor cutting ability of the drill. Furthermore, if the radius R1 is made smaller, the cutting quality of the drill will improve, but the radius R2 of the thinning surface 13 at the rear part of the cutting edge will also become smaller, and a relatively steep curved surface will be formed in the shape of a groove on the rake face of the drill. become. Therefore, a problem arose in that stress concentration occurred near the thinning surface 10 and the strength of the drill decreased.

[0007] Therefore, the present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a drill that has been subjected to a thinning process that improves the sharpness of the cutting edge and maintains the strength of the drill. With the goal.

[0008]

[Means for Solving the Problems] The drill according to the present invention has a pair of lenses extending from the center of the rotational axis toward the outside diameter of the drill at the tip thereof and arranged at rotationally symmetrical positions with respect to the rotational axis. It has a cutting edge and a thinning surface formed on the rake face near the chisel edge. and,
This thinning surface is characterized by having a curved surface area along the side surface shape of a truncated cone, which is assumed to have a smaller diameter toward the cutting edge of the drill.

[0009]

[Operation] The shape of the curved surface formed by thinning requires different conditions at the cutting edge and at the rear of the cutting edge. It is desirable to have a shape that improves cutting quality by reducing the roundness of the cutting edge and reducing the width of the chisel edge. Further, the rear part of the cutting edge is required to have a relatively large curvature so that the thinned surface has a gentle shape change. therefore,
In this invention, the above conditions are satisfied by forming the thinning surface in a shape that follows the side surface of the truncated cone, and by forming the radius of curvature of the cutting edge portion to be smaller than the radius of curvature of the rear portion of the cutting edge.

0010

Embodiments Hereinafter, embodiments of the present invention will be explained in detail with reference to the drawings.

The structure of the indexable drill according to the present invention is shown in FIGS. 1 to 3. FIG. 1 is a plan view of the indexable drill according to the present invention, and FIG.
is its left side view. The indexable drill includes a cutting tip 1 for cutting a workpiece such as steel, and a shank portion 20 for holding the cutting tip 1 and attaching the drill to a cutting tool. FIG. 3 is an exploded perspective view showing a method of joining the cutting blade tip 1 and the shank portion 20. Referring to FIG. 3, the cutting blade tip 1 is moved to the shank portion 3 due to the frictional force generated when the clamped surface 2 of the tip contacts the inner end surfaces of the clamping portions 21, 21 of the shank portion 20.
Fixed to 0. Such a method of joining the cutting blade tip 1 and the shank portion 20 is referred to as a self-grip method.

Next, the structure of the cutting blade tip 1 will be explained using FIGS. 4 to 8(a) to 8(d). FIG. 4 is a front structural view of the cutting tip 1, FIG. 5 is a plan view thereof, FIG. 6 is a bottom view, and FIG. 7 is a left side view thereof. Furthermore, Fig. 8 (a
), (b), (c), and (d) are respectively cut along the cutting line A- in FIG.
It is a cross-sectional structure diagram taken from directions along A, BB, CC, and DD. Referring to these figures, the cutting blade tip 1 is
It consists of a cutting edge part 15 where a cutting edge is formed and a held part 16 which is held by a holding part 21 of a shank part 20, and is formed into a substantially T-shaped flat plate shape. Drill flank surfaces 6, 6 are formed on the tip surface of the cutting edge portion 15. Moreover, rake faces 7, 7 of the drill are formed on the side surfaces. Cutting edges 4, 4 of the drill are formed along the line of intersection between the flank face 6 and the rake face 7. The pair of cutting edges 4, 4 are arranged at rotationally symmetrical positions with respect to the rotation axis of the drill passing through the center of the chisel edge 3. The shape of the cutting edge 4 is shown in FIG. FIG. 9 is a plan structural diagram showing the shape of the cutting edge portion 4. As shown in FIG. The cutting edge portion 4 has a first straight cutting edge region 4a, a curved cutting edge region 4c, and a second curved cutting edge region 4c toward the outer diameter region of the drill from the chisel edge 3.
It is composed of a straight cutting edge region 4b. Furthermore, the cutting edge central region 4d is formed between the first straight cutting edge region 4a and the chisel edge 3 by thinning. The first linear cutting edge region 4a and the second linear cutting edge region 4b are formed aligned on the same straight line. and the first of the pair
Straight cutting edge regions 4a, 4a and second straight cutting edge region 4b,
4b are formed parallel to each other. Curved cutting edge area 4c
, 4c have third straight cutting edge regions 4e and 4f, respectively. The third linear cutting edge regions 4e and 4f are formed to intersect with the second linear cutting edge region 4b at an intersection angle θ. Both ends of the third straight cutting edge regions 4e, 4f are connected to the first and second straight cutting edge regions 4a, 4b by smooth curved regions. Further, the curved cutting edge regions 4c, 4c of the pair of cutting edge portions 4, 4 are formed in mutually different shapes, for example, different widths. That is, in FIG. 9, the width L of the pair of curved cutting edge regions 4c, 4c
2 and L3 are formed with different sizes.

As shown in FIG. 9, by providing the pair of cutting edges 4 with curved cutting edge regions 4c, 4c, chips are formed in a shape that follows the shape of the cutting edges 4. Such chips are easily broken when they come into contact with the drill or the inner wall of the hole being machined. Therefore, the chips are crushed into chips, and the processing characteristics of the chips are improved.

FIG. 10 is a plan structural view showing a modification of the cutting blade portion 4. As shown in FIG. Curved cutting edge region 4c of the cutting edge portion 4 shown in FIG.
, instead of the third straight cutting edge regions 4e and 4f shown in FIG. 9, curved regions 4g and 4h consisting of a part of a circular arc with radius
is formed.

Furthermore, FIG. 11 is a plan structural view showing another modification of the cutting blade portion 4. As shown in FIG. The cutting edge portion 4 shown in FIG. 11 has two curved cutting edge regions and three straight cutting edge regions. The shapes shown in FIGS. 9 and 10 above can be applied to the shapes of each of the plurality of curved cutting edge regions.

Next, the nick portion will be explained. Figure 4,
With reference to FIG. 5 and FIGS. 9 to 11, the cutting blade tip 1
A nick 5 in the form of an elongated groove extending from the curved cutting edge region 4c to the surface of the rake face 6 is formed on the flank 6. For example, referring to FIG. 9, by providing a nick 5 in the curved cutting edge region 4c, chips generated by the first straight cutting edge portion 4a and the second straight cutting edge portion 4b are directed in the generation direction with the nick 5 as a boundary. It is divided into parts and discharged. This allows the width of the chips to be reduced.

Next, the chip breaker of the cutting tip 1 of the drill shown in FIG. 4 will be explained. A chip break surface 8 is formed on the side surface of the cutting edge chip 1 so as to be continuous with the rake face 7. As shown in FIG. 8(d), the chip break surface 8 is formed with a constant inclination with respect to the rake surface 7. Furthermore, first chip breakers 9a, 9a each having two spherical protrusions are formed on the rake face 7, and a second chip breaker 9b having a spherical protrusion larger than the first chip breaker 9a is formed on the chip breaking surface 8. There is.

Furthermore, the thinning shape of the cutting blade tip 1 will be explained. FIG. 12 is a cutting edge shape diagram showing the shape of the cutting edge. Further, FIG. 13 is a partial front view of the cutting edge for explaining the shape of the thinning surface. Referring to FIGS. 12 and 13, a thinning surface 10 is formed on the rake surface side of a pair of cutting edge central regions 4d, 4d centered on the chisel edge 3. The thinning surface 10 is formed so as to follow the shape of the side surface of the truncated cone 17, which is placed so that its tip is in the direction of the chisel edge 3. Such a thinning shape that utilizes a part of the side surface of the truncated cone 17 can be
The curvature on the chisel edge side of d is reduced, and the chisel width W
Improve the sharpness of the drill by making it smaller. Furthermore, the strength of the tip is increased by increasing the curvature on the rear side of the cutting edge.

A preferable range of the curvature of the thinning surface 10 is that the radius R1 of the tip of the cutting edge is 0.1 mm<R.
1 <3 mm, and the curvature R2 at the rear of the cutting edge is 0.5 mm<R2 <10 mm.

[0020]

[Effects of the Invention] As described above, the drill according to the present invention has a truncated conical side surface thinning surface with a small curvature at the tip of the cutting edge and a large curvature at the rear portion of the cutting edge, so that the cutting quality of the cutting edge is improved. At the same time, the strength of the cutting edge portion can be ensured at the same time.

[Brief explanation of drawings]

FIG. 1 is a plan structural view of an indexable drill according to the present invention.

FIG. 2 is a left side view of the indexable drill shown in FIG. 1.

3 is an exploded perspective view showing a joining structure between a cutting tip and a shank portion of the drill shown in FIG. 1. FIG.

FIG. 4 is a front structural view of the cutting tip of the indexable drill of the present invention.

FIG. 5 is a plan view of the structure of the cutting tip shown in FIG. 4;

FIG. 6 is a bottom view of the cutting tip shown in FIG. 4;

7 is a left side view of the cutting tip shown in FIG. 4. FIG.

FIG. 8 is a cross-sectional structural diagram of the cutting edge tip shown in FIG.
a) is cut line A-A in Figure 4, (b) is also cut line B
-B, (c) is the same cutting line C-C, (d) is the same D
It is a sectional view from the direction along -D.

9 is a plan view showing the shape of the cutting edge portion of the cutting tip shown in FIG. 4. FIG.

FIG. 10 is a plan view showing the shape of the cutting edge portion according to another embodiment of the cutting edge tip.

FIG. 11 is a plan view showing the shape of the cutting edge portion according to still another embodiment of the cutting edge tip.

FIG. 12 is a cutting edge shape diagram showing the shape of the cutting edge.

FIG. 13 is a partial front view for explaining the shape of a thinning surface formed on the side surface of the cutting blade tip.

FIG. 14 is a plan view of a conventional twist drill.

15 is a diagram showing the shape of the cutting edge of the twist drill shown in FIG. 14. FIG.

FIG. 16 is a plan view of a conventional spade drill.

17 is a diagram showing the shape of the cutting edge of the spade drill shown in FIG. 16. FIG.

FIG. 18 is a plan structural view of a drill developed by the inventor, showing a conventional thinning process applied to the cutting tip of the drill.

19 is a front structural view of the drill shown in FIG. 18. FIG.

[Explanation of symbols]

1 Cutting blade tip 3 Chisel edge 4 Cutting blade part 10 Thinning surface 17 truncated cone

Claims (2)

[Claims] 1. A pair of cutting blades are provided at the distal end thereof, which extend from approximately the center of the rotation axis toward the outside diameter of the drill and are arranged at rotationally symmetrical positions with respect to the rotation axis, and a pair of cutting blades located near the chisel edge. A drill having a thinning surface formed on the rake face, characterized in that the thinning surface has a curved surface area that follows the side shape of a truncated cone that is assumed to have a smaller diameter toward the cutting edge of the drill. Do, drill. 2. In the curved surface area of the thinning surface, the radius of curvature of the cutting edge portion is 0.1 mm or more and 3 mm or less, and the radius of curvature of the curved surface formed behind the cutting edge is 0.5 mm or more and 10 mm or less. Drill according to claim 1, characterized in that: