JPH04315510A - Drill - Google Patents

Abstract

PURPOSE:To provide the shape of the cutting edge of a drill which prevents the occurrence of choking with chips generated during drilling. CONSTITUTION:A drill has a pair of cutting edge parts arranged rotationally symmetrically about a rotary shaft. The cutting edge part has first and second linear cutting edge regions 4a and 4b, which are aligned in one and the same straight line, and a curve cutting edge region 4c located between the first and second cutting edge regions. the curve cutting edge region 4c has third linear cutting edge regions 4e and 4f extending in a direction crossing at a given angle with the second linear cutting edge region.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in the shape of a drill cutting edge that can improve the cutting performance 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. 20 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. 21 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. 22 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 20 or Figure 2
2, conventional twist drills and spade drills have a cutting edge region 23 that directly contributes to cutting the workpiece,
44 is formed on a straight line. When drilling is performed using such a drill, chips are continuously generated with a width corresponding to the width of the straight cutting edge. As a result, wide chips are continuously generated, which frequently causes problems such as the chips clogging the inside of the hole being machined or the chips wrapping around the drill.

Therefore, as shown in FIG. 22, a structure was devised in which a groove-like nick 45 is formed in the straight part of the cutting edge to reduce the width of the chips. Due to the formation of the nick, the chip is divided at the nick portion, so the width of the chip is reduced. However, since the width of the chips was reduced by the nicks, the chips were no longer constrained by the inner wall of the hole being machined or the groove of the drill, and long chips were more likely to be generated. Then, a problem arose in that the chips generated over a long period of time became entangled with the drill, resulting in very poor chip disposal.

[0007] As described above, conventional drills with straight cutting edges have problems such as clogging of the machining hole with chips and deterioration of chip control due to entanglement of chips, especially when drilling deep holes. A problem arose in which clogging caused by this caused damage to the drill.

[0008] Therefore, the present invention has been made to solve the above-mentioned problems, and provides a drill having a cutting edge shape with excellent chip disposal characteristics that does not cause chips to clog or become entangled with the drill. The purpose is to provide

[0009]

[Means for Solving the Problems] A drill according to the present invention has two parts at its tip extending from approximately the center of the rotational axis toward the outside diameter of the drill and arranged at rotationally symmetrical positions with respect to the rotational axis. It has a pair of first and second cutting edges. Each of the first and second cutting edges is arranged between a first linear cutting edge area and a second linear cutting edge area that are aligned on the same straight line, and a space between the first linear cutting edge area and the second linear cutting edge area. It is characterized by having a curved cutting edge region formed in a curved cutting edge region.

0010

[Operation] The drill according to the present invention has a curved region formed in a part of the cutting edge. By forming such a region, the shape of the chips changes from an elongated flat plate shape to a wavy shape in a cross section perpendicular to the axis in the longitudinal direction of the chips. Such chips have increased resistance to deformation, but also become brittle and more likely to break. Therefore, the chips are finely broken into chips, and it is possible to prevent the machining holes from being clogged and from getting entangled with the drill.

[0011]

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

The structure of an 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. 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 is composed of a first straight cutting edge region 4a, a curved cutting edge region 4c, and a second straight cutting edge region 4b from the center of the chisel edge toward the outer diameter region of the drill. 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. A pair of first straight cutting edge regions 4a, 4a and second straight cutting edge regions 4b, 4 are provided.
b are formed parallel to each other. curved cutting edge region 4c,
4c has 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 L2 of the pair of curved cutting edge regions 4c, 4c
, L3 are formed with different sizes. Preferred dimensions of each area of the shape of the cutting edges 4, 4 obtained from various experimental results will be described later.

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, with reference 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. Referring to FIG. 4, a thinning surface 10 is formed on the rake surface side of the pair of cutting blade central regions 4d, 4d centered on the center point 3 of the chisel. The thinning surface 10 is formed to have a side surface shape of a cone with its tip oriented in three directions toward the center of the chisel. Such a thinning shape that utilizes a part of the side surface of the cone improves the sharpness of the drill by reducing the curvature of the central region 4d of the cutting edge on the chisel side and reducing the chisel width. Furthermore, the strength of the tip is increased by increasing the curvature on the rear side of the cutting edge.

Furthermore, the characteristics of the outer diameter shape of the cutting blade tip 1 will be explained. Referring to FIGS. 3 and 4, in the cutting edge 1, the clamped part 16 is held by the clamping parts 21 and 2 of the shank part 20.
1 by the wedge effect, and is fixed to the shank portion 20. In a state where it is fixed to the shank portion 20, the upper and lower surfaces 13, 13 of the cutting blade tip 1 are supported by the support surfaces 21a, 21a of the clamping portion of the shank portion 20. The thrust force applied from the tip of the cutting edge tip 1 to the center of the rotating shaft during cutting is supported by the support surfaces 21a, 21a of the shank portion. That is, a thrust force is applied to the cutting tip 1 in the vicinity of the center of the rotating shaft passing approximately through the center 3 of the chisel, and a support reaction force is applied to the upper and lower surfaces 13, 13 as a reaction force to the thrust force. In such a loaded state, the throat portion 1 between the cutting edge portion 15 and the clamped portion 16
There is a concern that cracks may occur due to stress concentration in 1. Therefore, this throat portion 11 is provided with a curvature of radius R1. Further, the clamping portion 21 of the shank portion 20 is also provided with a curvature portion at a position corresponding to the throat portion 11.

Next, using the drills shown in FIGS. 4 and 9, drilling was performed with various dimensions of the cutting edge 4, and the performance of the drill was tested. The results are shown in Figure 1.
2 and FIG. 13. FIG. 12 shows the cutting edge 4 shown in FIG.
Various parameters L1 to L3, θ that define the shape of
FIG. As shown in FIG. 12, it was found that the shape of the cutting edge portion exhibiting good chip disposal characteristics was region I in FIG. That is, in FIG. 9, the ratio L2 /L1 of the first linear cutting edge area to the second linear cutting edge area,
L3 /L1 is in the range of 1/3 to 2, and the angle θ formed by the third straight cutting edge regions 4e, 4f and the second straight cutting edge region 4b
is preferably in the range of 5 to 40°. This area I
The shape of the chips produced by the drill is shown in FIG. 13(a). Further, the shapes of chips formed by drilling in regions II to IV shown in FIG. 12 are shown in FIGS. 13(b) to 13(d). It turns out that the drills in region I break up the chips into chips more than the drills in other regions.

Next, a comparative test was conducted between the drill according to the embodiment of the present invention and a conventional drill. Table 1 shows the shape of the drill used in the test, and Table 2 shows the test conditions.

[0023]

[Table 1]

[0024]

[Table 2]

Tests were conducted on the product A of the present invention, a conventional drill B with a straight cutting edge and a nick, and a conventional drill C with a straight cutting edge without a nick. is being carried out. The shapes of chips produced as a result of the drilling process are shown in FIGS. 14, 15, and 16, respectively. From these figures, it is clear that in the case of product A of the present invention, the chips are broken into shorter pieces than in the other products, and the width of the chips is also narrower. It can be seen that such chips do not clog during drilling or get tangled with the drill. This means that
This becomes clear when comparing the cutting power of drills. Figure 17
And FIG. 18 is a cutting power diagram showing temporal changes in cutting power during cutting for the product A of the present invention and the conventional drill C. FIG. 17 shows the product of the present invention, and FIG. 18 shows the conventional drill. Figure 17(a), Figure 18(a), Figure 17(b)
) and FIG. 18(b), it can be seen that the cutting power increases with the passage of time in the case of the conventional drill. This proves that as the drilling progresses, the cutting power increases as the chips clog or become entangled with the drill. In contrast, the product of the present invention exhibits a substantially constant cutting power over time during the drilling process. This makes it clear that there is almost no influence from clogging of chips.

[0026]

[Effects of the Invention] As described above, the drill according to the present invention has 1
By forming a straight cutting edge area and a curved cutting edge area on the paired cutting edge parts, the chips are crushed, preventing damage to the drill due to clogging and entanglement of the chips, and a decrease in drilling processing capacity. Chip handling characteristics can be improved.

[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 another cutting edge portion 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 correlation diagram between parameters showing the dimensions of the cutting edge shown in FIG. 9;

FIG. 13: Regions I, II, shown in the correlation diagram of FIG. 12;
It is a photograph showing the shape of chips generated by drilling using drills III and IV, and (a) to (d) correspond to regions I to IV, respectively.

FIG. 14 is a photograph of chips generated in a comparative cutting test between a drill according to the present invention and a conventional drill.

FIG. 15 is a photograph showing the chips as a result of the test, similar to FIG. 14.

FIG. 16, like FIGS. 14 and 15, is a photograph showing the shape of chips based on test results.

FIG. 17 is a cutting power diagram showing the cutting power of the drill according to the present invention measured in a comparative test between the present invention product and the conventional product, and (a) and (b) show that the feed rate of the drill is The cases of 0.1 and 0.15 mm/rev are shown.

FIG. 18 is a cutting power diagram showing the cutting power of a conventional drill in a comparative test similar to FIG. 17;
In b), the feed speed of the drill is 0.1 and 0.15 mm, respectively.
/rev is shown.

FIG. 19 is a plan view of a conventional twist drill.

20 is a diagram showing the shape of the cutting edge of the twist drill shown in FIG. 19. FIG.

FIG. 21 is a plan view of a conventional spade drill.

22 is a diagram showing the shape of the cutting edge of the spade drill shown in FIG. 21. FIG.

[Explanation of symbols]

1 Cutting blade tip 4 Cutting blade part 4a First straight cutting edge area 4b Second straight cutting edge area 4c Curved cutting edge area 4d Cutting blade center area 4e, 4f　Third straight cutting edge area 4g, 4h Arc area 5 of curved cutting edge area Nick 6 Relief surface 7 Rake face

Claims (5)

[Claims] 1. A pair of first and second cutting edges, which extend from approximately the center of the rotational axis toward the outside diameter of the drill, and are disposed at rotationally symmetrical positions with respect to the rotational axis, at the tip thereof. In the drill having the first and second
Each of the cutting edges includes a first linear cutting edge area and a second linear cutting edge area that are aligned on the same straight line, and a curve formed between the first linear cutting edge area and the second linear cutting edge area. A drill, characterized in that it has a cutting edge region. 2. The curved cutting edge region formed on the first cutting edge and the curved cutting edge region formed on the second cutting edge have mutually different shapes. 1
Drill as described. 3. The curved cutting edge region has a third straight cutting edge region extending in a direction intersecting the cutting edge of the second straight cutting edge region, and the third straight cutting edge region and the third straight cutting edge region The angle of intersection with the two straight cutting edge regions is 5° or more and 40° or less,
and the ratio of the width of the curved cutting edge region to the width of the second straight cutting edge region along the radial direction from the center of the rotation axis is 1/
The drill according to claim 1 or 2, characterized in that the number is 4 or more and 3 or less. 4. The drill according to claim 1, wherein a groove is formed from the curved cutting edge region toward the flank surface of the drill. 5. The drill according to claim 1, wherein the curved cutting edge region has an arcuate region that is concave with respect to the rotational direction of the drill.