Drill

Abstract

To provide a drill that can cut chips into pieces and suppress chipping from being caused.SOLUTION: A drill 1 comprises a body 3 extending with a shaft center AX as a center. Two torsional grooves 4 are formed on an outer peripheral surface 31 of the body 3. The torsional grooves 4 are formed on the outer peripheral surface 31 in a spiral shape, from a tip part of the body 3 toward a base end part thereof. Two cutting edges 5 are formed at the tip part of the body 3. The cutting edges 5 are formed at ridge line parts between inner surfaces 41 of the torsional grooves 4 pointing to a rotating direction T and flank faces 6. The cutting edges 5 are provided with thinning edges 9. The thinning edges 9 extend from an inner end part in a radial direction of the body 3 to outside in the radial direction, of the cutting edges 5. Two dented parts 51 and 52 in a circular arc-shape are formed at predetermined portions between outer end parts in the radial direction of the thinning edges 9 of the cutting edges 5 and the outer peripheral surface 31 of the body 3. The dented parts 51 and 52 are formed in a direction crossing a direction of torsion angles of the torsional grooves 4, with respect to the cutting edges 5.SELECTED DRAWING: Figure 3

Description

[Technical field]

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

[0002] A drill is known which has a stepped cutting edge at the tip and a twist groove that discharges chips cut by the cutting edge along the outer peripheral surface as the tip rotates, the cutting edge being adjacent to the end of the twist groove and inclined toward the center of rotation of the tip (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2022-70465 Summary of the Invention [Problem to be solved by the invention]

[0004] Since the cutting edge is stepped, there is a problem in that chipping is easily induced at the corners.

[0005] An object of the present invention is to provide a drill that can break down chips into smaller pieces and suppress the induction of chipping. [Means for solving the problem]

[0006] A drill of one embodiment of the present invention is characterized in that it comprises a body extending around an axis, a plurality of twist grooves spirally arranged on the outer peripheral surface of the body from the tip end to the base end of the body, cutting edges provided on a ridge portion between an inner surface of the twist groove facing the rotation direction of the body and a clearance face of the body at the tip end, thinning edges extending from a radially inner end of the cutting edges to the radially outer side of the body, and an arc-shaped recess provided at a predetermined portion between the radially outer end of the thinning edge and the outer peripheral surface of the body, and formed in a direction of a negative angle with respect to the twist angle of the twist groove.

[0007] According to this aspect, by forming an arc-shaped recess in a predetermined portion of the cutting edge in a direction of a negative angle with respect to the twist angle of the twist flute, the chips can be pushed out in a direction intersecting the flute rake face, not in the flute rake direction. As a result, the chips stop at the flute rake face and are broken up at the recess, so that the chips can be broken down into smaller pieces. In addition, by forming an arc-shaped recess, the direction of the cutting resistance at the cutting edge is dispersed, so that the force acting in the bending direction of the drill is dispersed. This makes it possible to suppress chatter vibrations that occur during machining. In addition, since the recess is arc-shaped, the load is not concentrated compared to a shape with an edge, and chipping is less likely to occur, so that a long life can be expected. In addition, by forming a recess on the cutting edge, the unevenness is transferred to the machining surface of the workpiece, so that the drill is restrained against the workpiece during machining. This suppresses the vibration of the drill in the radial direction, so that the enlargement of the machining hole due to the whirling of the drill is suppressed. In addition, because the recess is arc-shaped, it can be made shallower relative to the cutting edge than an edged shape. For example, by making the arc-shaped recess shallower in the axial direction, the previously machined recess is removed when the tip is re-sharpened after use. This allows a new recess to be formed after re-sharpening without the hassle of having to worry about aligning it with the previously machined recess.

[0008] The cutting edges may be arranged at equal intervals in a circumferential direction around an axis of the body, and the number of recesses provided on each of the cutting edges may be the same. Since the number of recesses on each cutting edge is the same, the balance of the drill during rotation can be well maintained.

[0009] The recesses may be provided in a plurality of the predetermined portions and may be arranged continuously in the radial direction to form a wave shape. By forming a wave shape with a plurality of arc-shaped recesses, the direction of cutting resistance is more dispersed, so that the force acting in the bending direction of the drill can be more dispersed. This makes it possible to effectively suppress chatter vibrations that occur during machining. [Brief description of the drawings]

[0010] [Figure 1] FIG. [Diagram 2] FIG. [Diagram 3] FIG. 2 is a perspective view of the drill 1 with the tip side facing up. [Figure 4] FIG. 2 is a partially enlarged perspective view of the tip side of the drill 1. [Diagram 5] 1 is a diagram showing the positional relationship and distances between recesses 51, 52 provided on a cutting edge 5 on a flank 6. FIG. [Figure 6] 2 is an image diagram of cutting resistance R generated on a cutting edge 5. FIG. [Figure 7] 1 is a table showing the evaluation and details of the chip discharge situation. [Figure 8] 1 is a table showing the results of chip discharge when SS400 material is machined with a standard cutting edge. [Figure 9] 1 is a table showing the results of chip removal when A5052 material is machined with a standard cutting edge. [Figure 10] This is a photo of chips generated when cutting SS400 material with a standard cutting edge. [Figure 11] This is a table evaluating the state of chipping of the cutting edge after machining SS400 material with a standard cutting edge. [Figure 12]1 is a table showing the results of chip discharge when SS400 material is machined with a stepped cutting edge. [Figure 13] 1 is a table showing the results of chip discharge when A5052 material is machined with a stepped cutting edge. [Figure 14] This is a photo of chips generated when machining SS400 material with a stepped cutting edge. [Figure 15] This is a table showing an evaluation of the chipping state of the cutting edge after machining SS400 material with a stepped cutting edge. [Figure 16] 1 is a table showing the results of chip discharge when SS400 material is machined with a wavy cutting edge. [Figure 17] 1 is a table showing the results of chip discharge when A5052 material is machined with a wavy cutting edge. [Figure 18] This is a photo of chips generated when cutting SS400 material with a wavy cutting edge. [Figure 19] This is a table evaluating the state of chipping of the cutting edge after machining SS400 material with a wavy cutting edge. [Figure 20] FIG. [Figure 21] 1 is a graph showing test results of hole accuracy. [Figure 22] 13 is a graph showing test results of hole position accuracy. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] An embodiment of the present invention will be described. The shape of the drill 1 described below is not intended to be limited to that shape, and is merely an illustrative example, unless otherwise specified. The drawings are used to explain technical features that can be adopted by the present invention.

[0012] The shape of the drill 1 will be described with reference to Figs. 1 to 4. The drill 1 shown in Fig. 1 has two blades, but may have three blades. The drill 1 may be formed of a hard material such as cemented carbide or high-speed tool steel (HSS). Furthermore, the surface of the base material may be coated with a hard film or a lubricating film. As shown in Figs. 2 and 3, the drill 1 includes a shank portion 2 and a body 3. The shank portion 2 is formed in a cylindrical shape. The body 3 is fixed coaxially to the tip of the shank portion 2 and extends linearly along the axis of the shank portion 2. The tip of the body 3 is the tip of the drill 1, and the rear end of the shank portion 2 is the rear end of the drill 1. The rear end of the shank portion 2 is attached to the spindle of a machine tool (not shown). The drill 1 rotates integrally with the spindle around the axis AX.

[0013] On the outer peripheral surface 31 of the body 3, two helical flutes 4 for discharging chips are formed in a spiral shape around the axis AX. The helical flute 4 has a helix angle with respect to the axis AX of α (see FIG. 2). The helical flute 4 opens at the tip of the body 3, and two cutting edges 5 are formed at the opening. When the tip of the drill 1 is viewed from the front (see FIG. 1), the two cutting edges 5 are arranged symmetrically with the axis AX in between. The cutting edges 5 are formed at the ridge where the inner surface 41 of the helical flute 4 facing the rotation direction T intersects with the clearance surface 6 provided at the tip of the body 3.

[0014] Each of the two cutting edges 5 has two arc-shaped recesses 51, 52 arranged side by side at a predetermined interval along the cutting edge of the cutting edge 5. Between the recesses 51 and 52, a peak portion 53 is provided that protrudes in a substantially arc shape in the opposite direction to the recessed direction of the recesses 51, 52. By arranging these continuously, the cutting edge 5 is formed in a wave shape (see Figs. 1, 3, and 4). The specific shapes, dimensions, and positional relationship of the recesses 51, 52 will be described later. The inner surface 41 on the cutting edge 5 side among the inner surfaces 41 is a scooping surface, which scoops up the chips cut by the cutting edge 5 and flows them into the twisted groove 4.

[0015] The portion of the inner surface 41 where the inner surface 41 on the cutting edge 5 side intersects with the outer peripheral surface 31 of the body 3 is the leading edge 33. A duplex 32 is provided between adjacent leading edges 33 in the circumferential direction. The duplex 32 has a diameter smaller than the drill diameter. The duplex 32 reduces frictional resistance caused by contact between the inner surface of the machined hole and the outer peripheral surface 31 of the body 3 when the machined hole is formed, and suppresses heat generation and machining torque. The portion of the inner surface 41 on the opposite side to the cutting edge 5 where the duplex 32 intersects with the inner surface 41 on the opposite side to the cutting edge 5 is the heel 34.

[0016] The flanks 6 are surfaces that avoid contact with the machined surface of the workpiece, and are provided corresponding to each of the two cutting edges 5. The flanks 6 include a second flank 62, a third flank 63, and a fourth flank 64, in this order, toward the opposite side to the rotation direction T. The second flank 62 is located at the front end of the rotation direction T and extends from the chisel 10 to the outer peripheral surface 31. The third flank 63 inclines toward the rear end of the drill 1 from the ridgeline of the second flank 62 opposite to the cutting edge 5 and extends toward the opposite side to the rotation direction T. The fourth flank 64 inclines toward the rear end of the drill 1 from the ridgeline of the third flank 62 opposite to the second flank 62 side and extends toward the opposite side to the rotation direction T. The fourth flank 64 becomes thinner toward the tip portion extending toward the opposite side to the rotation direction T, and connects to the twist groove 4. The tip of the fourth relief surface 64 corresponds to the heel 34 and is connected to the unlined part 32 .

[0017] A chisel 10 is provided at the center of the tip of the drill 1. The tip of the drill 1 is subjected to a thinning process. The thinning process is a process for thinning the core thickness near the chisel 10. As a result, a thinning blade 9 is provided on the chisel 10 side of the cutting edge 5. The thinning blade 9 is formed in an arc shape that bulges toward the rotation direction T when viewed from the front. By forming the thinning blade 9, a thinning surface 91 (see Figures 1 and 2) is formed at the tip of the drill 1. The thinning surface 91 is a rake surface that faces the rotation direction T side of the thinning blade 9.

[0018] The drill 1 having the above-mentioned shape cuts the workpiece with the cutting edge 5 by rotating about the axis AX, and forms a machined hole while discharging chips generated by the cutting through the twisted flutes 4. The rotation direction T of the drill 1 during machining is counterclockwise when viewed from the front. In other words, a machine tool holding the drill 1 in its spindle rotates the spindle clockwise to cut the workpiece.

[0019] Next, the recesses 51, 52 provided on the cutting edge 5 will be specifically described. As shown in FIG. 1, the recesses 51, 52 are provided side by side on the cutting edge 5 with a predetermined distance between them, and each recess is formed in an arc shape recessed in the opposite direction to the rotation direction T. As shown in FIG. 2, the recesses 51, 52 are formed on the cutting edge 5 in B1 and B2 directions intersecting with the A1 direction, which is the direction of the twist angle α of the helical groove 4. Both of the intersection angles β1 and β2 of the B1 and B2 directions with respect to the A1 direction are acute angles. The intersection angles β1 and β2 may be the same or different.

[0020] Here, in order to define the size and positional relationship of the recesses 51 and 52 on the cutting edge 5, as shown in FIG. 5, the imaginary circle for forming the arc shape of the recess 51 is C1, the imaginary circle for forming the arc shape of the recess 52 is C2, and the imaginary circle for forming the arc shape of the arch portion 53 is C3. The radius of the imaginary circle C1 is r1, the radius of the imaginary circle C2 is r2, and the radius of the imaginary circle C3 is r3. Note that these radii r1 to r3 may all be the same or may all be different, but it is preferable that one set (two) of the radii r1 to r3 are the same. This can improve the restraint of the drill 1 against the machining surface.

[0021] In this case, the radii r1 to r3 are preferably set to 5 to 7% of the nominal diameter of the drill 1. The distance between the bottom points of the recesses 51 and 52, i.e., the distance L1 between the centers of the virtual circles C1 and C2, is preferably set to 15 to 20% of the nominal diameter of the drill 1. Furthermore, the distance L3 between the recesses 51 and 52 is preferably set to 0.1 mm or less. For example, if the thinning edge 9 occupies 25% of the cutting edge 5, the two virtual circles C1 and C2 are preferably arranged within the remaining 75% so as to fall within the above-mentioned numerical range. The virtual circle C3 is preferably arranged so as to be in contact with the virtual circles C1 and C2 from below. As a result, the two recesses 51 and 52 can be formed side by side with a gap in the part of the cutting edge 5 excluding the thinning edge 9, and one mountain portion 53 can be formed between them. Therefore, a smooth wave shape in which the recesses 51, 52 and the peaks 53 are alternately arranged can be formed on the cutting edge 5.

[0022] In addition, the depth L2 of the recesses 51, 52 formed in the cutting edge 5 is preferably 6% or less of the nominal diameter of the drill 1. As a result, the recesses 51, 52 can be formed shallow in the axial direction relative to the cutting edge 5, so that when the cutting edge 5 is re-ground, the old recesses 51, 52 do not remain in the cutting edge 5. As a result, the recesses 51, 52 can be repeatedly machined and reproduced in the cutting edge 5. In addition, by making the arc-shaped recesses 51, 52 shallow in the axial direction, the recesses 51, 52 previously machined are removed in the re-grounding to fill the tip of the drill 1 after use. As a result, new recesses 51, 52 can be formed after re-ground without the hassle of having to worry about alignment with the previously machined recesses 51, 52. In addition, since the recesses 51, 52 can be formed shallow relative to the cutting edge 5, the rigidity of the cutting edge of the cutting edge 5 can be secured, so that chipping can be prevented and the tool life can be extended. The depths L2 of the recesses 51 and 52 may be the same as or different from each other.

[0023] As shown in FIG. 1, two cutting edges 5 are provided at the tip of the drill 1, and two recesses 51, 52 and one crest 53 are provided on each cutting edge 5. The recesses 51, 52 and crest 53 on each of the two cutting edges 5 are located on concentric circles K1, K2, and K3 centered on the tip of the drill 1. As a result, the phases of the recesses 51, 52 and crest 53 on each cutting edge 5 are the same when the drill 1 rotates. Since the number of recesses 51, 52 on each cutting edge 5 is the same, the balance of the drill 1 can be well maintained when rotating.

[0024] Next, the action and effect of the cutting edge 5 when cutting the workpiece will be described. As described above, as shown in FIG. 2, the recesses 51 and 52 are formed in the cutting edge 5 in the B1 and B2 directions intersecting with the A1 direction, which is the direction of the twist angle α of the twist flute 4. When cutting a workpiece with such a cutting edge 5, the chips generated in the recesses 51 and 52 are pushed out in the B1 and B2 directions, that is, in the direction intersecting with the groove rake face, which is the inner surface 41 of the twist flute 4, rather than in the groove rake direction along the inner surface 41 of the twist flute 4. As a result, the chips stop on the groove rake face and are broken up at the recesses 51 and 52, so that the chips can be broken up into smaller pieces. Therefore, the drill 1 can discharge the broken up chips well along the twist flute 4, so that the chips can be prevented from clogging the twist flute 4.

[0025] As shown in Fig. 6, the cutting edge 5 has a wave shape in which recesses 51, 52 and peaks 53 are alternately arranged. By cutting the workpiece with such a wave-shaped cutting edge 5, the direction of the cutting resistance R applied from the workpiece is dispersed. This also disperses the force acting in the bending direction of the drill 1, suppressing chatter vibrations that occur when cutting the workpiece. In addition, since the recesses 51, 52 are arc-shaped, the load is not concentrated compared to a shape with edges, and chipping is less likely to occur, which can lead to a longer life.

[0026] Furthermore, when cutting the workpiece, the uneven shapes of the recesses 51, 52 and the convex portion 53 are transferred to the machined surface of the workpiece. As a result, the drill 1 is constrained to the machined surface, suppressing radial deviation of the drill 1. Furthermore, suppressing radial deviation improves hole accuracy (cylindricity) and hole position accuracy caused by whirling of the drill 1 during rotation.

[0027] Next, a machining test was conducted to verify the effect of the drill 1 according to the present invention. In this test, a machining test was conducted on three types of drills, namely, the drill 1 with the corrugated cutting edge 5 according to the present invention, a drill with a standard cutting edge, and a drill with a stepped cutting edge. The standard cutting edge is a general cutting edge with a straight cutting edge. The stepped cutting edge is a cutting edge with a stepped cutting edge. The diameter of each drill was φ12 mm, and the discharge state of the chips, the shape of the chips, and the occurrence state of chipping when a hole was formed in the workpiece were confirmed. The hole was a blind hole, and the hole depth was set to 36 mm. A water-soluble cutting oil (emulsion) was used as the cutting oil. Two types of workpiece materials were examined: SS400 material and A5052 material. The drill feed rate (mm / rev) during machining was examined in six patterns: 0.12, 0.18, 0.24, 0.3, 0.36, and 0.42 for SS400 material. Six patterns were examined: 0.1, 0.2, 0.3, 0.4, 0.5, and 0.6 for A5052 material. Three cutting speeds (m / min) were examined: 50, 60, and 70.

[0028] The chip discharge status was evaluated using four levels: ××, ×, △, and ◯. As shown in the table in Fig. 7, XX indicates that long, spiral chips were generated and entangled around the drill, × indicates that chips were generated that were not broken up and wound around the drill several times, △ indicates that continuous chips were discharged, and ◯ indicates that broken chips were generated stably and were discharged well.

[0029] The results of the standard cutting edge will be described with reference to Figs. 8 to 11. Fig. 8 is a table showing the results of chip discharge when SS400 material is machined with the standard cutting edge. When the drill feed rate (mm / rev) was set to 0.12, all results were ×× at any cutting speed. When the drill feed rate (mm / rev) was set to 0.18, the cutting speed (m / min) was × at 50 and △ at 60 and 70. When the drill feed rate (mm / rev) was set to 0.24, the cutting speed (m / min) was △ at 50 and 60 and ◯ at 70. When the drill feed rate (mm / rev) was set to 0.3, the cutting speed (m / min) was △ at 50 and ◯ at 60 and 70. When the drill feed rate (mm / rev) was set to 0.36, the cutting speed (m / min) was ◯ at 50 and 60 and △ at 70. When the drill feed rate (mm / rev) was set to 0.42, the cutting speed (m / min) was rated as ◯ at 50, △ at 60, and △ at 70, but the cutting noise was loud. From this, there were a total of 6 combinations where the chip discharge situation was rated as ◯.

[0030] Figure 9 is a table showing the results of chip discharge when A5052 material was machined with a standard cutting edge. When the drill feed rate (mm / rev) was set to 0.1, the results were ×× at all cutting speeds. When the drill feed rate (mm / rev) was set to 0.2, the results were × at cutting speeds (m / min) of 50 and 60, and ×× at 70. When the drill feed rate (mm / rev) was set to 0.3, the results were × at all cutting speeds. When the drill feed rate (mm / rev) was set to 0.4, the results were ◯ at cutting speeds (m / min) of 50, and △ at 60 and 70. When the drill feed rate (mm / rev) was set to 0.5, the results were ◯ at cutting speeds (m / min) of 50 and 60, and △ at 70. When the drill feed rate (mm / rev) was set to 0.6, the results were ◯ at all cutting speeds. From this, there were a total of six combinations in which the chip discharge results were ◯.

[0031] Figure 10 is a photograph of the chips generated when SS400 material was machined with a standard cutting edge. When the drill feed rate (mm / rev) was set to 0.3 and the cutting speed (m / min) to 50, many of the chips were connected without being broken up, so the evaluation was △ as above. When the drill feed rate (mm / rev) was set to 0.36 and the cutting speed (m / min) to 50, many of the chips were broken up and short, so the evaluation was ◯ as above. When the drill feed rate (mm / rev) was set to 0.42 and the cutting speed (m / min) to 50, the chips were even more broken up and shorter than when the feed rate (mm / rev) was 0.36, so the evaluation was ◯ as above.

[0032] Figure 11 is a table that evaluates the chipping state of the cutting edge after machining SS400 material with a standard cutting edge. The chipping state was evaluated in three stages: O, △, and ×. O was indicated if there was no chipping, △ was indicated if there was small chipping, and × was indicated if there was large chipping. When the drill feed rate (mm / rev) was set to 0.3, the cutting speed (m / min) was 50 and 60 and △ was indicated at 70. When the drill feed rate (mm / rev) was set to 0.36, the cutting speed (m / min) was 50 and 60 and △ was indicated at 70. When the drill feed rate (mm / rev) was set to 0.42, the cutting speed was △ for all cases. From this, there were a total of four combinations in which the chipping state of the cutting edge was ◯.

[0033] The results of the stepped cutting edge will be described with reference to Figs. 12 to 15. Fig. 12 is a table showing the results of the chip discharge state when SS400 material is machined with the stepped cutting edge. When the drill feed rate (mm / rev) was set to 0.12, all were ×× at any cutting speed. When the drill feed rate (mm / rev) was set to 0.18, all were × at any cutting speed. When the drill feed rate (mm / rev) was set to 0.24, the cutting speed (m / min) was × at 50 and 60, and ◯ at 70. When the drill feed rate (mm / rev) was set to 0.3, the cutting speed (m / min) was × at 50, △ at 60, and ◯ at 70. When the drill feed rate (mm / rev) was set to 0.36, the cutting speed (m / min) was △ at 50, ◯ at 60, and ◯ at 70. When the drill feed rate (mm / rev) was set to 0.42, the cutting noise was loud and rated △ at all cutting speeds. From this, the chip discharge status was rated 〇 in only three combinations, which were worse than the standard cutting edge.

[0034] FIG. 13 is a table showing the results of chip discharge when A5052 material is machined with a stepped cutting edge. When the drill feed rate (mm / rev) was set to 0.1, all cutting speeds were ××. When the drill feed rate (mm / rev) was set to 0.2, cutting speeds (m / min) were ×× at 50 and 60, and × at 70. When the drill feed rate (mm / rev) was set to 0.3, all cutting speeds were ×. When the drill feed rate (mm / rev) was set to 0.4, cutting speeds (m / min) were × at 50, and △ at 60 and 70. When the drill feed rate (mm / rev) was set to 0.5, all cutting speeds were △. When the drill feed rate (mm / rev) was set to 0.6, all cutting speeds were △. From this, there was no pattern combination with a good chip discharge, and the results were worse than those of the standard cutting edge.

[0035] Figure 14 is a photograph of the chips generated when SS400 material was machined with a stepped cutting edge. When the drill feed rate (mm / rev) was set to 0.3 and the cutting speed (m / min) was set to 50, the chips were long and spiral, and many of them were entangled in the drill, so the evaluation was × as above. When the drill feed rate (mm / rev) was set to 0.36 and the cutting speed (m / min) was set to 50, the chips were broken up compared to when the feed rate was 0.3, but many of them were long and continuous, so the evaluation was △ as above. When the drill feed rate (mm / rev) was set to 0.42 and the cutting speed (m / min) was set to 50, the chips were broken up compared to when the feed rate was 0.3, but many of them were long and continuous, so the evaluation was △ as above.

[0036] Figure 15 is a table evaluating the chipping condition of the cutting edge after machining SS400 material with a stepped cutting edge. When the drill feed rate (mm / rev) was set to 0.3, the results were rated as good at cutting speeds (m / min) of 50 and 60, and fair at 70. When the drill feed rate (mm / rev) was set to 0.36, the results were bad at all cutting speeds. When the drill feed rate (mm / rev) was set to 0.42, the results were bad at all cutting speeds. From this, it can be seen that only two combinations in total rated the chipping condition of the cutting edge as good, which was worse than the standard cutting edge.

[0037] The results of the wavy cutting edge of the present invention will be described with reference to Figs. 16 to 19. Fig. 16 is a table showing the results of the discharge state of chips when SS400 material is machined with the wavy cutting edge. When the drill feed rate (mm / rev) was set to 0.12, all were × at any cutting speed. When the drill feed rate (mm / rev) was set to 0.18, the cutting speed (m / min) was × at 50 and 60, and ◯ at 70. When the drill feed rate (mm / rev) was set to 0.24, the cutting speed (m / min) was × at 50, and ◯ at 60 and 70. When the drill feed rate (mm / rev) was set to 0.3, all were ◯ at any cutting speed. When the drill feed rate (mm / rev) was set to 0.36, the cutting speed (m / min) was ◯ at 50 and 60, and △ at 70. When the drill feed rate (mm / rev) was set to 0.42, the cutting speed (m / min) was rated as ◯ at 50 and △ at 60 and 70. From this, the chip removal conditions were rated as ◯ in a total of 9 combinations, which were better than the results for the standard cutting edge and stepped cutting edge.

[0038] FIG. 17 is a table showing the results of chip discharge when A5052 material is machined with a wavy cutting edge. When the drill feed rate (mm / rev) was set to 0.1, all results were negative at any cutting speed. When the drill feed rate (mm / rev) was set to 0.2, the results were negative at a cutting speed (m / min) of 50, and positive at 60 and 70. When the drill feed rate (mm / rev) was set to 0.3, 0.4, 0.5, and 0.6, the results were positive at any cutting speed. From this, there were a total of 14 combinations in which the chip discharge was positive, which was a better result than the results for the standard cutting edge and the stepped cutting edge.

[0039] Figure 18 is a photograph of the chips generated when SS400 material was machined with a wavy cutting edge. When the drill feed rate (mm / rev) was set to 0.3 and the cutting speed (m / min) was set to 50, the chips were mostly broken up and short, so the evaluation was rated as ◯ as above. When the drill feed rate (mm / rev) was set to 0.36 and the cutting speed (m / min) was set to 50, the chips were even more broken up and short compared to when the feed rate was 0.3, so the evaluation was ◯ as above. When the drill feed rate (mm / rev) was set to 0.42 and the cutting speed (m / min) was set to 50, the chips were even more broken up and short compared to when the feed rate was 0.36, so the evaluation was ◯ as above.

[0040] Figure 19 is a table evaluating the chipping condition of the cutting edge after machining SS400 material with a wavy cutting edge. When the drill feed rate (mm / rev) was set to 0.3, all cutting speeds were rated as good. When the drill feed rate (mm / rev) was set to 0.36, cutting speeds (m / min) of 50 and 60 were rated as good, and 70 was rated as fair. When the drill feed rate (mm / rev) was set to 0.42, cutting speeds (m / min) of 50 and 60 were rated as good, and 70 was rated as fair. From this, a total of seven combinations were rated as good for chipping of the cutting edge, which was a better result than the results for the standard cutting edge and stepped cutting edge.

[0041] From the above results, it was found that by drilling a workpiece with the drill 1 having a wavy cutting edge of the present invention, it is possible to improve the effect of breaking up the chips generated by the cutting. In addition, the chipping condition of the cutting edge after cutting was better than that of the standard cutting edge and the stepped cutting edge, so it was found that the induction of chipping was suppressed.

[0042] The drill 1 of the present embodiment can be used for any work material, but may be used for cutting metals that tend to produce chips such as mild steel and drawn aluminum. Mild steel includes, for example, SS400, S10C, and S15C. Drawn aluminum includes, for example, A5052, A6061, and A7072.

[0043] Next, the circular accuracy (cylindricity) of the drill 1 according to the present invention was verified. In this verification, a machining test was performed on two types of drills, the drill 1 with the wavy cutting edge 5 according to the present invention and the conventional drill with a standard cutting edge. The phase of the wavy cutting edge 5 of the present invention was the same. The standard cutting edge is a general cutting edge with a straight cutting edge. The diameter of each drill was φ12 mm, and the value (hole diameter at the mouth - hole diameter) was measured when a hole was formed in the workpiece (see FIG. 20). The workpiece was an aluminum alloy (JIS A5052). The cutting speed was 75 to 125 m / min, and the feed rate was 0.3 to 0.9 mm / rev. A water-soluble cutting oil (emulsion diluted 20 times) was used as the cutting oil. A horizontal machining center was used for machining.

[0044] The results of the processing test will be described with reference to FIG. 21. The average value X of the (hole diameter at mouth - hole diameter) value of the conventional type was 0.0287 mm, and the standard deviation σ was 0.0346 mm. The average value X of the (hole diameter at mouth - hole diameter) value of the wave shape of the present invention (same phase) was 0.0213 mm, and the standard deviation σ was 0.0284 mm. Looking at the above results, the average value X and standard deviation σ of the (hole diameter at mouth - hole diameter) value of the wave shape of the present invention were both smaller than those of the conventional type. This shows that the wave shape of the present invention has improved hole precision (cylindricity) compared to the conventional type.

[0045] Next, the hole position accuracy of the drill 1 of the present invention was verified. The test conditions were a cutting speed of 100 m / min and a feed rate of 0.3 mm / rev and 0.9 mm / rev. The other test conditions were the same as above, and the value of (hole diameter at mouth - hole diameter) was measured when a hole was formed in the workpiece.

[0046] The results of the machining test will be explained with reference to Figure 22. (1) and (2) are the test results with a feed rate of 0.3 mm / rev. (1) is the test result for the conventional type, and (2) is the test result for the wavy shape of the product of the present invention. Regarding the value of (hole diameter at mouth - hole diameter), the data for (2) is concentrated at the 0 position in the center of the graph compared to the data for (1). This shows that the wavy shape of the product of the present invention (with phase shift) has improved hole position accuracy compared to the conventional type.

[0047] (3) and (4) are the test results when the feed rate was increased to 0.9 mm / rev. (3) is the test result for the conventional type, and (4) is the test result for the wavy shape of the product of the present invention. The value of (hole diameter at mouth - hole diameter) is concentrated at 0 in the center of the graph for data (4) compared to data (3). This shows that the wavy shape of the product of the present invention has improved hole position accuracy compared to the conventional type.

[0048] As described above, the drill 1 of this embodiment includes a body 3 extending around the axis AX. Two helical flutes 4 are provided on the outer peripheral surface 31 of the body 3. The helical flutes 4 are provided in a spiral shape on the outer peripheral surface 31 from the tip end to the base end of the body 3. A cutting edge 5 is provided on the tip end of the body 3. The cutting edge 5 is provided on the ridge between the inner surface 41 of the helical flute 4 facing the rotation direction T side of the body 3 and the flank surface 6 of the body 3. The cutting edge 5 is provided with a thinning edge 9. The thinning edge 9 extends from the radially inner end of the cutting edge 5 to the radially outer side of the body 3. Two arc-shaped recesses 51, 52 are provided in a predetermined portion between the radially outer end 50 of the thinning edge 9 and the outer peripheral surface 31 of the body 3. The recesses 51 and 52 are formed on the cutting edge 5 in directions B1 and B2 that intersect with the direction A1, which is the direction of the twist angle α of the helical groove 4.

[0049] The present invention is not limited to the above embodiment, and various modifications are possible. The drill 1 has two cutting edges 5, but the number of cutting edges 5 may be two or more. The cutting edge 5 of the above embodiment has two recesses 51, 52, but one recess or two or more recesses may be provided. When a plurality of recesses are provided, the two adjacent recesses may be separated from each other, but as described above, it is preferable to keep the distance within 0.1 mm. The two recesses can be brought close to each other to form a wave shape. The crest portion 53 may be omitted. In other words, the recesses 51, 52 do not have to be in an arc shape. The arc of the recesses 51, 52 does not have to be a perfect circular arc. An oil hole for discharging cutting oil may be provided at the tip of the drill 1. The number of twisted grooves 4 may be two or more. The phases of the recesses 51, 52 and the crest portion 53 in each of the two cutting edges 5 are the same, but may be shifted. In this case, the same performance is also exhibited. [Explanation of symbols]

[0050] 1 Drill 3. Body 4 Twist groove 5 Cutting Edge 6 Flank 9 Thinning blade 31 Outer surface 41 Inside 50 End 51,52 Recess AX axis center A1,B1,B2 direction α Twist angle

Claims

1. A body extending around an axis; a plurality of helical grooves formed in a spiral shape on an outer circumferential surface of the body from a tip end portion to a base end portion of the body; A cutting edge is provided on a ridge between an inner surface of the twist groove facing the rotation direction of the body and a relief surface of the body at the tip portion; A thinning edge of the cutting edge extending from an end portion of the body on the radial inner side to the radial outer side; an arc-shaped recess portion provided at a predetermined portion between the radially outer end portion of the thinning edge of the cutting edge and the outer circumferential surface of the body, the arc-shaped recess portion being formed in a direction intersecting with a direction of a twist angle of the twist groove; A drill comprising:

2. The cutting edges are multiple and are arranged at equal intervals in the circumferential direction around the axis of the body, The number of the recesses provided on each of the plurality of cutting edges is equal to each other. The drill according to claim 1 .

3. The recessed portions are provided in a plurality of portions at the predetermined portion, and are arranged continuously in the radial direction to form a wave shape.

3. The drill according to claim 1 or 2,

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