drill

Abstract

To provide a drill having a long service life.SOLUTION: A drill includes: a main blade which has center rising amount f; a thinning blade; a thinning back section; and an oil hole. A thinning bottom section is formed along a first radius R1. The thinning back section is formed along a second radius R2. A pair of thinning bottom sections has thinning separation amount c. The drill has a thinning range g from a thinning first end up to a thinning second end. (1) The first radius R1 is in the range of 0.5×f to 1.2×f with respect to the center rising amount f. (2) The second radius R2 is in the range of 5.5 mm to 7.5 mm. (3) The thinning separation amount c is in the range of 0.5 mm to 1.2 mm. (4) A distance e between thinning and the oil hole is in the range of 0.1 mm to 0.8 mm. (5) The thinning range g is in the range of (D / 2-1.5 mm) to (D / 2-0.2 mm) with respect to a diameter D.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The technology disclosed herein relates to a drill. [Background technology]

[0002] Patent Document 1 discloses a drill equipped with a thinning portion. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-11013 Summary of the Invention [Problem to be solved by the invention]

[0004] The chips generated by the thinning edge are curled and broken up at the thinning section before being discharged. However, if the chips are not broken up and discharged properly, thrust resistance increases, causing abnormal wear and chipping of the drill. [Means for solving the problem]

[0005] According to the configuration of claim 1, by satisfying the numerical ranges (1) to (4), chips can be broken and discharged smoothly, thereby suppressing thrust resistance. Furthermore, by satisfying the numerical range (5), the rigidity of the chisel center can be ensured. This suppresses abnormal wear, chipping, breakage, etc. of the drill, thereby extending the life of the drill. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 2 is a view of the tip end surface of the drill 1. [Figure 2] FIG. 2 is an enlarged view of the vicinity of the axis AX in FIG. [Figure 3]1A and 1B are views of the tip end faces of a conventional drill 101 and a drill 1 of the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0007] (Drill 1 structure) FIG. 1 shows a tip end view of the drill 1. FIG. 1 shows the tip end of the drill 1 as viewed from the direction of the axis AX. FIG. 2 shows an enlarged view of the vicinity of the axis AX in FIG. 1. The drill 1 is primarily used to drill holes in steel materials. One example of such steel materials is crankshaft material.

[0008] The body of the drill 1 has an outer peripheral surface 11. The outer peripheral surface 11 is a surface along a circumscribed circle of diameter D centered on the axis AX. A spiral groove portion GR is formed on the outer peripheral surface 11. The drill 1 mainly includes a pair of main cutting edges 12, a pair of thinning cutting edges 13, a pair of thinning back portions 14, a pair of oil holes 15, a pair of thinning surfaces 16, a pair of first flank surfaces 17, and a pair of second flank surfaces 18. Each of these pairs of components is arranged rotationally symmetrically with respect to the axis AX. Therefore, in this specification, only one of the pair of components may be described.

[0009] The main cutting edge 12 is formed at the tip of the body of the drill 1. The main cutting edge 12 extends from the outer peripheral surface 11 toward the axis AX. As shown in Fig. 2, the main cutting edge 12 is in an off-center position with an amount of off-center f relative to a diameter D passing through the axis AX.

[0010] The thinning edge 13 is a cutting edge formed from a first thinning end S1 to a thinning bottom Sb. The first thinning end S1 is located at the end of the main cutting edge 12 on the axis AX side. The thinning bottom Sb is located closer to the axis AX than the first thinning end S1 and at a position where the center rise amount f is smaller than that of the main cutting edge 12. The thinning bottom Sb is formed along a first inscribed circle C1 having a first radius R1.

[0011] The thinning back portion 14 extends from the thinning bottom portion Sb to the thinning second end portion S2. The thinning back portion 14 is formed along a second inscribed circle C2 having a second radius R2. The second radius R2 is greater than the first radius R1.

[0012] The thinning surface 16 is a surface connected to the thinning edge 13 and the thinning back portion 14. The thinning surface 16 is a surface for discharging chips generated by cutting with the thinning edge 13 into the groove portion GR. The thinning surface 16 can improve chip discharge performance.

[0013] The first flank 17 is a surface connected to the rear of the main cutting edge 12 in the rotation direction RD. The second flank 18 is a surface connected to the first flank 17. The first flank 17 and the second flank 18 are surfaces that are lowered (relieved) to reduce friction during cutting. The oil hole 15 is formed in the second flank 18. Cutting oil can be discharged from the oil hole 15 via an oil tube (not shown).

[0014] The thinning separation amount c, thinning-to-oil hole distance e, thinning range g, chisel remaining width a, and thinning misalignment amount b will be explained using Figure 2. A pair of parallel imaginary lines VL1 are defined that pass through each of the pair of thinning bottoms Sb. The thinning separation amount c is the distance between the pair of imaginary lines VL1. The thinning-to-oil hole distance e is the shortest distance between the oil hole 15 and the thinning back portion 14. The thinning range g is the range from the thinning first end S1 to the thinning second end S2.

[0015] The remaining chisel width a is the shortest distance between the pair of thinning edges 13. The thinning offset b is the amount of offset of the thinning edge 13 from the axis AX. Specifically, a pair of parallel imaginary lines VL2 that pass through each of the pair of thinning first end portions S1 are defined. The thinning offset b is the distance between the pair of imaginary lines VL2.

[0016] The drill 1 in the technology of this specification has the following five numerical ranges (1) to (5). (1) With respect to the center rise amount f, the first radius R1 is in the range of "0.5 x f to 1.2 x f". (2) The second radius R2 is in the range of 5.5 mm to 7.5 mm. (3) The thinning clearance amount c is in the range of 0.5 mm to 1.2 mm. (4) The thinning-to-oil hole distance e is in the range of 0.1 mm to 0.8 mm. (5) The thinning range g is in the range of "(D / 2 - 1.5 mm) to (D / 2 - 0.2 mm)" with respect to the diameter D.

[0017] In the drill 1 according to the technology of the present specification, the remaining chisel width a was set to a range of 0.15 mm to 0.35 mm, and the thinning misalignment b was set to a range of 0.02 mm to 0.12 mm.

[0018] (effect) The effects of the numerical ranges (1) to (5) will be explained using FIG. 3. FIG. 3(A) is a diagram of the tip end surface of a conventional drill 101. FIG. 3(B) is a diagram of the tip end surface of the drill 1 of this embodiment, which is the same as FIG. 1. The conventional drill 101 of FIG. 3(A) is a drill that does not satisfy at least part of the numerical ranges (1) to (5) described above. Specifically, the first radius R101 of the first inscribed circle C101 of the conventional drill 101 is smaller than the lower limit of the numerical range (1). Furthermore, the second radius R102 of the second inscribed circle C102 of the conventional drill 101 is smaller than the second radius R2 of the second inscribed circle C2 of the drill 1 of this embodiment. In FIGS. 3(A) and 3(B), the chip discharge paths are indicated by arrows Y101 and Y1. Furthermore, the ranges where rubbing (wear) occurs on the first flank 17 and the second flank 18 are shown by hatching as rubbing ranges RA101 and RA1. The rubbing ranges RA101 and RA1 can be determined by experiment.

[0019] The effects of the numerical ranges (1) to (3) will be explained. As indicated by arrows Y101 and Y1, chips generated by the thinning edge 13 are curled into a cone shape at the thinning bottom Sb along the curvature of the first radii R101 and R1, and are then broken up and discharged. However, as shown in FIG. 3(A) of a conventional drill 101, if the first radius R101 of the thinning bottom Sb is small, it becomes difficult to curl the chips. Furthermore, the space for chip discharge becomes small. Furthermore, if the second radius R102 of the thinning back portion 14 is small, chip discharge does not occur smoothly, and chip discharge performance deteriorates. This results in increased thrust resistance. Furthermore, the rubbing range RA101 becomes larger.

[0020] Therefore, in the drill 1 of this embodiment shown in Figure 3(B), by using the numerical range (1) for the first radius R1, it is possible to appropriately increase the first radius R1. This makes it easier to curl chips and ensures sufficient evacuation space. Furthermore, by using the numerical range (2) for the second radius R2, it is possible to smoothly evacuate chips. Furthermore, by using the numerical range (3) for the thinning clearance c, it is possible to reduce the flank friction range. Therefore, it is possible to reduce the friction range from RA101 (Figure 3(A)) to RA1 (Figure 3(B)). This reduces thrust resistance.

[0021] The effect of the numerical range of (4) will be explained. If the thinning-back portion 14 overlaps the oil hole 15, a protrusion will be formed on the edge of the oil hole 15 at the boundary between the oil hole and the thinning-back portion 14. This can cause stress to concentrate on the protrusion of the oil hole 15 during cutting with the drill 1, resulting in chipping. Therefore, with the drill 1 of this embodiment, by using the numerical range of (4) for the thinning-to-oil hole distance e, it is possible to prevent the thinning-back portion 14 from overlapping the oil hole 15. Stress concentration on the oil hole 15 can be suppressed, making it possible to prevent chipping.

[0022] The effect of the numerical range of (5) will now be explained. As can be seen from FIG. 2, the larger the thinning clearance c, the smaller the chisel width a. As the chisel width a decreases, the rigidity of the chisel center decreases, making chipping more likely to occur and shortening the tool life. Therefore, in the drill 1 of this embodiment, by using the numerical range of (5) for the thinning range g, the chisel width a can be appropriately set. Since the rigidity of the chisel center can be ensured, it is possible to prevent chipping.

[0023] As a result, the drill 1 of this embodiment can prevent abnormal wear, chipping, breakage, and the like of the drill. [Explanation of symbols]

[0024] 1: Drill 11: Outer surface 12: Main cutting edge 13: Thinning cutting edge 14: Thinning back part 15: Oil hole AX: Shaft center c: Thinning clearance C1: First inscribed circle C2: Second inscribed circle D: Diameter e: Distance between thinning and oil hole f: Center rise amount g: Thinning range R1: First radius R2: Second radius S1: First end of thinning S2: Second end of thinning Sb: Bottom of thinning

Claims

[Claim 1] a drill body having an outer peripheral surface along a circumscribing circle of diameter D centered on an axis; A pair of main cutting edges are formed at the tip portion of the drill body and extend from the outer circumferential surface toward the axis center, a pair of the main cutting edges that are positioned at a center-up position with a center-up amount f relative to a diameter passing through an axis; A pair of thinning blades formed from the thinning first end to the thinning bottom, the thinning first end is located at an end of the main cutting edge on the axial center side, a pair of thinning blades, the thinning bottom portion being located closer to the axis than the thinning first end portion and located at a position where the center rise amount f is smaller than that of the main blades; a pair of thinning back portions extending from the thinning bottom portion to the thinning second end portion; a pair of oil holes formed at the tip of the drill body; A drill comprising: the pair of main cutting edges, the pair of thinning cutting edges, the pair of thinning back portions, and the pair of oil holes are arranged rotationally symmetrically with respect to the axis, The pair of thinning bottoms are formed along a first inscribed circle having a first radius R1, The pair of thinning-back portions are formed along a second inscribed circle having a second radius R2 larger than the first radius R1, a pair of parallel imaginary lines passing through each of the pair of thinning bottoms, the pair of imaginary lines being a distance between the pair of imaginary lines; a thinning-to-oil hole distance e, which is the shortest distance between the oil hole and the thinning back portion; A thinning range g is provided, which is a range from the thinning first end to the thinning second end, (1) With respect to the amount of center rise f, the first radius R1 is in the range of 0.5×f to 1.2×f, (2) the second radius R2 is in the range of 5.5 mm to 7.5 mm; (3) The thinning clearance c is in the range of 0.5 mm to 1.2 mm, (4) The distance e between the thinning and the oil hole is in the range of 0.1 mm to 0.8 mm, (5) The thinning range g is in the range of (D / 2-1.5 mm) to (D / 2-0.2 mm) with respect to the diameter D. drill.

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