drill

Abstract

We offer a highly durable drill with enhanced core strength. [Solution] A drill 100A that rotates around a central axis AX to drill holes in a workpiece, comprising a rod-shaped drill body 10, a pair of cutting edges 12 extending radially from the tip of the drill body 10, a pair of first relief surfaces 13 and second relief surfaces 14 provided on the rear side of the cutting edges 12 in the rotation direction R, a pair of thinning surfaces 21 provided on the rear side of the second relief surface 14 in the rotation direction R, and a chisel edge 25 provided between the thinning surfaces 21 at the center of the drill body 10, wherein the thinning surfaces 21 are formed in a curved concave shape and have edges 21e with a curvature that increases toward the center of the drill body 10.

Description

[Technical Field]

[0001] The present invention relates to a drill. [Background Art]

[0002] Patent Document 1 discloses that a drill is subjected to thinning processing, and a honing processing is performed on a thinning cutting edge formed by thinning such that the maximum width is located radially inward. It is described that in this drill, a sufficient honing width is ensured at the radially inner end of the thinning cutting edge, which tends to have high cutting load and insufficient cutting edge strength among the cutting edges, and the tip rigidity of the drill is improved. [Prior Art Document] [Patent Document]

[0003] [Patent Document 1] Japanese Unexamined Patent Application Publication No. 2019-5882 [Summary of the Invention] [Problem to be Solved by the Invention]

[0004] By the way, depending on cutting conditions, rotational direction stress applied to the central portion of a drill becomes large, which may lead to breakage.

[0005] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a drill with improved central portion strength and excellent durability. [Means for Solving the Problem]

[0006] In order to achieve the above object, the drill of the present invention is: A drill that is rotated around a central axis to perform drilling on a workpiece, comprising: a rod-shaped drill body, a pair of cutting edges provided at a tip end of the drill body and extending in a radial direction, and a pair of flank faces provided on a rear side in the rotational direction with respect to the cutting edges, A pair of thinning surfaces provided on the rear side in the rotational direction relative to the relief surface, A chisel edge provided between the thinning surfaces in the center of the drill body, It has, The thinning surface is formed in a curved concave shape and has an edge with a curvature that increases toward the center of the drill body.

[0007] With this drill configuration, a thinning surface with an edge that has a greater curvature towards the center of the drill body can be provided, allowing the thickness of the chisel edge to be increased to a sufficient degree of durability, thereby improving the durability of the central part. This reduces damage to the central part that occurs when cutting by rotating in the rotational direction.

[0008] In the drill of the present invention, a honed portion is formed on the chisel edge.

[0009] With this drill configuration, honing the chisel edge to form a honed section ensures sufficient thickness at the base of the chisel edge, suppressing a decrease in strength in the center, while also reducing axial stress on the center during cutting. Therefore, damage to the center of the tip of the drill body during cutting can be further reduced.

[0010] In the drill of the present invention, the chisel edge on which the honing portion is formed is shaped to be pointed toward the tip.

[0011] In this drill configuration, the chisel edge is honed to form a honed section, resulting in a pointed shape at the tip. This reduces axial stress on the center during cutting while improving grip on the workpiece, enabling smooth cutting.

[0012] In the drill of the present invention, the drill body has a pair of flutes formed helically in the axial direction, and the thinning surface has a discharge pocket that is recessed in a curved shape and communicates with the flutes.

[0013] According to the drill with this configuration, chips generated during cutting can be smoothly delivered to the discharge pocket, and then discharged to the outside through the flutes. This can suppress chip clogging and achieve high cutting efficiency. Effects of the Invention

[0014] According to the present invention, a drill with increased strength at the center portion and excellent durability can be provided. Brief Description of the Drawings

[0015] [Figure 1] FIG. 1 is a front view of the drill illustrating the drill according to the first embodiment. [Figure 2] FIG. 2 is a front view of the drill illustrating the drill according to a reference example. [Figure 3] FIG. 3 is a front view of the drill illustrating the drill according to the second embodiment. [Figure 4] FIG. 4 is a side view of the tip end of the drill illustrating the drill according to the second embodiment. Mode for Carrying Out the Invention

[0016] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. (First Embodiment) First, the drill according to the first embodiment will be described. FIG. 1 is a front view of a drill 100A illustrating the drill 100A according to the first embodiment.

[0017] As shown in FIG. 1, the drill 100A according to the present embodiment includes a drill body 10 that is circular in front view. The drill body 10 is formed in a rod shape.

[0018] A drill 100A is a cutting tool used when drilling a workpiece. The rear end side of the drill 100A is gripped by a chuck of a machine tool or a drilling machine, rotated in the rotation direction R about the central axis AX, and the tip end is pressed against the workpiece. Thereby, drilling is performed on the workpiece.

[0019] A drill body 10 has a pair of flute grooves 11. These flute grooves 11 are formed on the outer peripheral surface of the drill body 10, and are helically formed along the axial direction.

[0020] The drill body 10 having a pair of flute grooves 11 has, at a tip end portion thereof, a cutting edge 12, a first flank 13, a second flank 14, and an oil hole 15. The cutting edge 12, the first flank 13, the second flank 14, and the oil hole 15 are each provided in a pair, and are arranged rotationally symmetrically with respect to the central axis AX.

[0021] The cutting edge 12 is formed at a tip end portion of the drill body 10. The first flank 13 and the second flank 14 are sequentially provided consecutively rearward in the rotation direction R with respect to the cutting edge 12. The oil holes 15 are formed in the second flank 14, and a lubricant such as coolant can be discharged from these oil holes 15.

[0022] In the drill 100A according to the present embodiment, thinning is performed on the tip end portion of the drill body 10. As a result, a thinning surface 21 and a thinning cutting edge 22 are formed at the tip end portion of the drill body 10. The thinning surface 21 and the thinning cutting edge 22 are each provided in a pair, and are arranged rotationally symmetrically with respect to the central axis AX.

[0023] The thinning surface 21 is formed in a portion of the flute groove 11 at the tip end portion of the drill body 10. The thinning cutting edge 22 is formed at the tip end portion of the drill body 10 by forming the thinning surface 21. These thinning cutting edges 22 are formed continuously with the cutting edge 12 on the center side of the drill body 10.

[0024] In a front view, the thinning surface 21 is formed in a curved, concave shape. At the center of the tip of the drill body 10, the space between these thinning surfaces 21 forms a chisel edge 25. The edges 21e of the curved, concave thinning surface 21 have a greater curvature toward the center of the drill body 10. As a result, the space between the edges 21e of the thinning surface 21 is widened, and the thickness W1 of the chisel edge 25 at the center of the tip of the drill body 10 is increased.

[0025] Furthermore, by forming a thinning surface 21 at the tip of the drill body 10, this thinning surface 21 is made into a curved recessed discharge pocket 23, and this discharge pocket 23 is in communication with the flute groove 11.

[0026] Here, we will describe the drill as an example. Note that components identical to those in the first embodiment described above are denoted by the same reference numerals and their descriptions are omitted. Figure 2 is a front view of the drill 200 illustrating a reference example.

[0027] As shown in Figure 2, the reference example drill 200 has undergone general thinning, and the edge 31e of the thinned surface 31 has a straight shape that follows the radial direction. In this drill 200, the thickness W2 of the chisel edge 25 is smaller than that of the drill 100A according to this embodiment.

[0028] In this drill 200, when performing cutting by rotating it in the rotational direction R, a large stress is generated on the thinning cutting edge 32 located in the center, which may cause the center to break. Furthermore, in this reference example, the drill 200 lacks a chip discharge pocket 23 on the thinning surface 31, which may cause chip clogging and reduce cutting efficiency.

[0029] In contrast, according to the drill 100A of the first embodiment, which has a thinning surface 21 with a curved edge 21e whose curvature increases toward the center, the thickness W1 of the chisel edge 25 in the center can be increased, thereby improving the durability of the center. This makes it possible to suppress damage to the center that occurs when cutting by rotating in the rotational direction R.

[0030] Furthermore, in the drill 100A according to the first embodiment, since a discharge pocket 23 is formed in the thinning surface 21, chips generated during cutting can be smoothly sent to the discharge pocket 23 and then discharged to the outside through the flute groove 11. This suppresses chip clogging and allows for high cutting efficiency.

[0031] (Second Embodiment) Next, we will describe the drill according to the second embodiment. Note that components identical to those in the first embodiment described above are denoted by the same reference numerals and their descriptions are omitted. Figure 3 is a front view of the drill 100B illustrating the drill 100B according to the second embodiment. Figure 4 is a side view of the tip of the drill 100B illustrating the drill 100B according to the second embodiment.

[0032] As shown in Figures 3 and 4, the drill 100B according to the second embodiment has a honed portion 27 at the tip of the drill body 10. Compared to the drill 100A according to the first embodiment, the drill 100B has a honed portion 27 formed in the center of the tip of the drill body 10 by honing the chisel edge 25. This ensures that the thickness of the chisel edge 25 of the drill body 10 is maintained at the base while creating a pointed shape towards the tip.

[0033] In the first embodiment, the drill 100A, which has a chisel edge 25 with a thickness W1, has improved durability of the central part against stress applied during cutting. However, because the thickness of the chisel edge 25 is large, the thrust resistance, which is the stress in the axial direction, becomes large. For this reason, in the second embodiment, the drill 100B has a honed portion 27 provided by honing only the chisel edge 25. With this drill 100B, it is possible to sufficiently secure the thickness at the base of the chisel edge 25 to suppress the reduction in strength in the central part, while suppressing the thrust resistance, which is the axial stress applied to the central part during cutting. Therefore, damage to the central part of the tip of the drill body 10 during cutting can be further suppressed.

[0034] Furthermore, by honing the chisel edge 25 to create a honed section 27, the tip becomes pointed, which reduces thrust resistance, the axial stress applied to the center during cutting, while improving grip on the workpiece, enabling smooth cutting. [Explanation of Symbols]

[0035] 10 Drill body 11 flute grooves 12 cutting edges 13. First escape route (escape route) 14. Second escape route (escape route) 21 Thinning surface 21e Edge 23 Discharge pockets 25 Chisel Edge 27 Honing section 100A, 100B Drill AX center axis R rotation direction

Claims

1. A drill that rotates around a central axis to drill holes in a workpiece, A rod-shaped drill body, A pair of cutting edges extending radially are provided at the tip of the drill body, A pair of relief surfaces provided on the rear side in the rotational direction relative to the cutting edge, A pair of thinning surfaces provided on the rear side in the rotational direction relative to the relief surface, A chisel edge provided between the thinning surfaces in the center of the drill body, It has, The thinning surface is formed in a curved concave shape and has an edge with a curvature that increases toward the center of the drill body. drill.

2. A honed portion is formed on the chisel edge. The drill according to claim 1.

3. The chisel edge on which the honing portion is formed is shaped to be pointed towards the tip. The drill according to claim 2.

4. The drill body has a pair of flute grooves formed spirally in the axial direction, The thinning surface has a curved recess and a discharge pocket that communicates with the flute groove. A drill according to any one of claims 1 to 3.

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