drill

Abstract

To provide a drill capable of hole boring processing of high precision of a highly hard material of rigidity 50HRC or more, for example.SOLUTION: A drill 10 includes: a first cutting edge 1 adjacent to a thinning surface 3 in the center; and a second cutting edge 2 formed outward in continuation to the first cutting edge 1. A first point angle formed by the first cutting edge 1 is within 80° and 100° and a second point angle formed by the second cutting edge 2 is within 130° and 150°. Also, in a tip view of the drill 10, a diameter of a virtual circle encircling an area up to a connection point S of the first cutting edge 1 and the second cutting edge 2 around a rotation axis of the drill 10 is within 30% and 40% of diameter D0 of the drill 10.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a drill for drilling holes in high-hardness metal materials such as die steel. [Background technology]

[0002] Conventionally, when drilling holes using a two-blade (two cutting edges) drill, particularly when drilling holes in high-hardness materials such as mold steel, the tip of the drill has multiple cutting edges with different point angles and a thinning process in the center of the drill, as disclosed in Patent Document 1, for example. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-0719 Summary of the Invention [Problem to be solved by the invention]

[0004] However, depending on the size of the drill point angle and thinning shape, when drilling holes in high-hardness materials, for example, those with a hardness of 50 HRC or higher, chipping or abnormal wear can occur at the tip of the drill, making it impossible to ensure the surface precision of the drilled hole.

[0005] Therefore, an object of the present invention is to provide a drill that can achieve high-precision drilling of high-hardness materials (for example, die steel with a hardness of 50 HRC or more). [Means for solving the problem]

[0006] To solve the above-mentioned problems, the drill of the present invention has a thinning surface in the center, a first cutting edge adjacent to the thinning surface, and a second cutting edge formed continuously outward from the first cutting edge, with a first flank surface formed rearward in the direction of rotation of the drill from the first cutting edge as the starting point, and a second flank surface formed forward in the direction of rotation of the drill from the first flank as the starting point and adjacent to the thinning surface. The first point angle formed by the first cutting edge can be in the range of 80° to 100°, and the second point angle formed by the second cutting edge can be in the range of 130° to 150°.

[0007] In addition, the diameter D1 of an imaginary circle C1 that surrounds the connection point of the first cutting edge and the second cutting edge and is centered on the rotation axis when viewed from the tip of the drill is set to be in the range of 30% to 40% of the drill diameter D0. Furthermore, the diameter D2 of an imaginary circle C2 of the tip core thickness that is centered on the rotation axis of the drill when viewed from the tip of the drill can also be set to be in the range of 8% to 10% of the drill diameter D0. [Effects of the Invention]

[0008] The drill of the present invention has the effect of ensuring the accuracy of the drilled hole (minimizing the amount of enlargement of the hole diameter) even when drilling high-hardness materials (for example, die steel with a hardness of 50 HRC or more). [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a plan view of a drill 10 of the present invention. [Figure 2] FIG. 1 is a front view of a drill 10 according to the present invention. [Figure 3] 2 is a view of the drill 10 shown in FIG. 1 as viewed from the arrow A. FIG. [Figure 4] FIG. 2 is an enlarged view of the center portion of the drill 10 shown in FIG. [Figure 5] FIG. 1 is a front view of a conventional drill 100 used in a cutting test of an example. [Figure 6] 1 is a left side view of a conventional drill 100 used in a cutting test of an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] An embodiment of a drill 10 of the present invention will be described with reference to the drawings. Fig. 1 shows a plan view of the drill 10 according to one embodiment of the present invention, Fig. 2 shows a front view, Fig. 3 shows a view of the drill 10 shown in Fig. 1 as viewed from the arrow A, and Fig. 4 shows an enlarged view of the center portion of the drill 10 shown in Fig. 1. As shown in Figs. 1 to 4, the drill 10 of this embodiment is a drill with two cutting edges (so-called two-blade) and has thinning surfaces 3, 3 in the center of the drill 10. Each cutting edge has a first cutting edge 1 adjacent to the thinning surface 3 and a second cutting edge 2 formed outward and continuous with the first cutting edge 1, as shown in Figs. 1 and 2.

[0011] First flanks 21, 21 are formed adjacent to the first cutting edges 1, 1 on the rear side of the two first cutting edges 1, 1 in the rotational direction (counterclockwise in Fig. 1) as shown in Fig. 1. Furthermore, second flanks 22, 22 are formed on the front side of the first flanks 21, 21 in the rotational direction via the chisel edge 4 as shown in Fig. 4. These second flanks 22, 22 are formed on the tip side of the drill 10 so as to be adjacent to the thinning surfaces 3, 3.

[0012] 1 and 4, the first flanks 21, 21 and the second flanks 22, 22 are arranged rotationally symmetrically around the rotation axis O of the drill 10, and at the same time, the first flank 21 and the second flank 22 are arranged adjacent to each other along the rotation direction of the drill 10, with the chisel edge 4 as the boundary. Therefore, the tip of the drill 10 has two first flanks 21, 21 and two second flanks 22, 22, and thus has an overall quadrangular pyramid shape, and the vicinity of the rotation axis O of the drill 10 can maintain high rigidity, making it possible to drill high-hardness materials.

[0013] 2 and 3, the drill 10 of this embodiment is a so-called candle-sharpened drill in which the point angles formed by the first and second cutting edges 1, 2 are different. Regarding the point angles, the first point angle θ1 formed by the first cutting edge 1 can be in the range of 80° to 100°, and the second point angle θ2 formed by the second cutting edge 2 can be in the range of 130° to 150°.

[0014] 4, the diameter D1 of an imaginary circle C1 that surrounds the connection point S of the first cutting edge 1 and the second cutting edge 2 around the rotation axis O of the drill 10 is set to be in the range of 30% to 40% of the diameter D0 of the drill 10. Similarly, the tip core thickness D2 of the drill 10 (the imaginary circle C2 that surrounds the connection point S of the first cutting edge 1 and the second cutting edge 2 around the rotation axis O shown in FIG. 4) is set to be in the range of 8% to 10% of the diameter D0 of the drill 10.

[0015] 1 and 3, the drill 10 of this embodiment has a diameter D1 of an imaginary circle C1 that surrounds the connection point S of the first cutting edge 1 and the second cutting edge 2 from the rotation axis O, and is set to a range of 30% to 40% of the diameter D0 of the drill 10, thereby enabling a small point angle and achieving high-precision hole drilling. Also, by setting the tip core thickness D2 at the center of the drill 10 to a range of 8% to 10% of the diameter D0 of the drill 10, chipping and abnormal wear can be significantly suppressed when drilling high-hardness materials. [Example]

[0016] A cutting test was conducted to confirm the cutting characteristics of the drill of the present invention, particularly the accuracy of holes drilled in high-hardness materials (e.g., die steel with a hardness of 50 HRC or more). The test was conducted using the drill of the present invention (hereinafter referred to as the invention) and a conventional drill 100 (hereinafter referred to as the conventional drill) shown in Figures 5 and 6, under the following cutting conditions. The drill diameter for both the invention and the conventional drill was 6 mm. ·Workpiece material: Mold die steel (SKD61) - Hole type: 12mm deep blind hole ·Cutting speed: 30m / min Feed rate: 0.06mm / rev Cooling condition: External oil supply Cutting process: Non-step cutting

[0017] After cutting a specified number of holes (n=3) using both the inventive and conventional products, the horizontal diameter (x-axis) and vertical diameter (y-axis) were measured at two locations, the entrance and bottom of each hole, to determine the dimensional error from the target hole diameter of 6.00 mm. When measuring the dimensions of the holes after cutting using the conventional product, changes in the machined holes were confirmed within a range of -25 to -40 μm at the entrance of the hole and within a range of -7 to +7 μm at the bottom of the 12 mm deep hole. In contrast, when using the inventive product, changes in the machined holes were confirmed within a range of -4 to +10 μm at the entrance of the hole and within a range of -1 to +13 μm at the bottom of the 12 mm deep hole.

[0018] The above test results confirmed that the drill of the present invention is effective in minimizing the amount of hole diameter expansion even when drilling high-hardness materials (for example, die steel with a hardness of 50 HRC or more). [Explanation of symbols]

[0019] 1 First cutting edge 2 Second cutting edge 3 Thinning surface 4 Chisel Edge 10 Drill 21 First flank 22 Second flank 100 Drill θ1 1st tip angle θ2 Second point angle C1 Virtual circle C2 Virtual circle D0 Drill diameter D1 Diameter of imaginary circle C1 D2 Diameter of virtual circle C2 (drill tip core thickness) O Rotation axis S Connection point between the first and second cutting edges

Claims

1. A drill having a thinning surface in the center, a first cutting edge adjacent to the thinning surface, and a second cutting edge formed continuously outward from the first cutting edge, characterized in that a first flank surface is formed rearward in the rotation direction of the drill from the first cutting edge as a starting point, and a second flank surface is formed forward in the rotation direction of the drill from the first flank surface and at a position adjacent to the thinning surface.

2. The drill according to claim 1, characterized in that a first point angle (θ1) formed by the first cutting edge is in the range of 80° or more and 100° or less, a second point angle (θ2) formed by the second cutting edge is in the range of 130° or more and 150° or less, and a diameter (D1) of an imaginary circle (C1) centered on the rotation axis of the drill and surrounding a connection point between the first cutting edge and the second cutting edge, when viewed from the tip of the drill, is in the range of 30% or more and 40% or less of the diameter of the drill.

3. The drill according to claim 2, characterized in that, when viewed from the tip of the drill, a diameter (D2) of an imaginary circle (C2) centered on the rotation axis of the drill and surrounding the end of the chisel edge is in a range of 8% to 10% of the diameter of the drill.

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