Drilling tool and body of the same

Abstract

To provide a drilling tool capable of increasing a coolant supply quantity without damaging rigidity of a drill, by devising a shape of a coolant channel and a position of a channel, and contributing to discharge property of chip and improvement of a service life of a blade edge.SOLUTION: There is provided a body 10 of a drilling tool, which comprises a coolant channel 50 and a chip discharge groove 30, and rotates about a center axis during cutting. The coolant channel 50 is a long circular shaped channel including a pair of straight line parts in a cross section vertical to a center axis. In a cross section vertical to the center axis, a solid part 40 excluding the chip discharge groove 30 is arranged on a position which is separated rearward in a rotation direction from a front groove wall face 41 where receives force applied from chip discharged through the chip discharge groove 30 in cutting, or from coolant, and on a position outside of a radial direction relative to a core 12 of the body 10 in the cross section.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a drilling tool and its body. [Background technology]

[0002] Some drills used as drilling tools have coolant passages in the body to supply coolant for the purpose of cooling the cutting edge and promoting chip evacuation. Conventional coolant passages are sometimes provided near the cutting edge at the tip of the tool, inside the chip evacuation groove (flute), or on the side of the body, with a round cross section that can be machined with a drilling tool. However, when the cross section of the coolant passage is made round, it becomes difficult to ensure rigidity if the coolant hole is made large, which can limit the cooling performance.

[0003] To address these issues, a drill has been proposed in which the cross-sectional shape of the coolant passage is noncircular, for example, elliptical (see, for example, Patent Document 1). In this drill, the outlet of the elliptical coolant passage is opened near the cutting edge on the tip side of the tool, and the coolant is supplied to the entire cutting edge, thereby improving the cooling efficiency.

[0004] Also, a tool has been proposed in which the shape of the coolant flow passage changes from a circular shape to a noncircular shape that is longer in the circumferential direction than in the radial direction in the axial cross section of the main body part midway from the base end to the tip end of the tool (see, for example, Patent Document 2). Other drills and tools have been proposed in which the cross-sectional shape of the coolant flow passage is noncircular as described above (see Patent Documents 3 to 5). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2004-154883 A [Patent Document 2] Patent No. 7205656 [Patent Document 3] JP 2011-020256 A [Patent Document 4] Special Publication No. 2016-514625 [Patent Document 5] International Publication No. 2023 / 058950 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in terms of improving tool rigidity, coolant supply amount, chip removal performance, and cutting edge life, there is still room for improvement in conventional drilling tools, particularly with regard to the shape and position of the coolant flow passages.

[0007] Therefore, the present invention aims to provide a drilling tool and its body in which the shape of the coolant flow passage and the position of the flow passage are devised to increase the amount of coolant supplied without compromising the rigidity of the drill, and further to contribute to improving chip removal performance and cutting edge life. [Means for solving the problem]

[0008] In order to solve such problems, the present inventor has conducted various studies focusing on the coolant flow passage and its surrounding structure while keeping the above problems in mind. An elliptical shape, i.e., a shape in which two sets of parabolas that are linearly symmetrical about the major and minor axes are connected, has four vertices in the parabola, and the external force received during cutting is concentrated on these four points, which become, so to speak, stress concentration areas, and it is considered that the rigidity is inevitably reduced. In addition, if the coolant flow passage is processed with a drilling tool, it is difficult to smoothly bend the coolant flow passage at any position, so the coolant flow passage cannot be made large enough to ensure rigidity, and the amount of coolant supplied is reduced. In addition, if the open end of the coolant flow passage is located near the cutting edge, the tip of the drill becomes hollow, which leads to a decrease in rigidity, which is also a problem. Focusing on these points and proceeding with the study, the present inventor has obtained knowledge that leads to the solution of the problem.

[0009] The present invention has been conceived based on such findings, and one aspect thereof is a body of a drilling tool having a coolant flow path and a chip discharge groove, and rotating around a central axis during cutting, The coolant flow path is In a cross section perpendicular to the central axis, the shape is an ellipse including a pair of straight line portions; The body of a drilling tool is arranged such that, in a cross section perpendicular to the central axis, the solid portion excluding the chip discharge groove is located rearward in the direction of rotation from a front groove wall surface that receives forces from chips or coolant discharged through the chip discharge groove during cutting, and is located radially outward from a core of the body in the cross section.

[0010] In the body of the drilling tool as described above, the coolant passage is disposed radially outward from the core of the body, so that the thickness or width of the core can be secured to obtain the rigidity of the tool. Also, since the coolant passage is disposed at a position away from the front groove wall surface toward the rear side in the rotational direction, the coolant passage can be prevented from being deformed by the influence of an external force acting from the front groove wall surface toward the rear side in the rotational direction during drilling. Furthermore, since the coolant passage is an elliptical shape including a pair of straight portions, the number of places where stress is concentrated can be reduced, so that the coolant passage can be further synergistically prevented from being deformed.

[0011] In the body of the drilling tool as described above, the coolant passage may be arranged at a position rearward in the direction of rotation from the circumferential center of the solid portion when viewed from the front groove wall surface in a cross section perpendicular to the central axis.

[0012] In the body of the drilling tool as described above, the core portion may be a portion of the stem of the body that does not interfere with the chip groove.

[0013] In a cross section perpendicular to the central axis of the body of the drilling tool as described above, the coolant passage may be disposed at a position close enough to be in contact with the core.

[0014] The coolant flow passage having an elliptical shape in a cross section perpendicular to the central axis of the body of the drilling tool as described above may be arranged so as to be inclined rearward in the direction of rotation and outward in the radial direction.

[0015] Another aspect of the present invention is a body of a drilling tool having a coolant passage and a chip discharge groove, the body rotating about a central axis during cutting, In a cross section perpendicular to the central axis, the coolant flow path is formed by a front wall portion on the front side in the rotation direction, an axial wall portion on the central axis side, a rear wall portion on the rear side in the rotation direction, and an outer peripheral wall portion on the radially outer side, The shaft wall portion and the outer peripheral wall portion are a body of the drilling tool that is configured with convex curved surfaces that protrude toward the inside of the coolant flow passage.

[0016] In a cross section perpendicular to the central axis of the body of the above-mentioned drilling tool, in the solid portion excluding the chip discharge groove, a coolant flow passage may be arranged at a position away from the front groove wall surface that receives forces from the chips or coolant discharged through the chip discharge groove during cutting, and at a position radially outward from the core of the body in the cross section.

[0017] In the body of the drilling tool as described above, the curvature of the outer peripheral wall portion may be greater than the curvature of the shaft wall portion.

[0018] In the body of the drilling tool as described above, the coolant flow passage may be shaped such that the distance from the central axis to the outer peripheral wall portion is longer at the rear end on the rear wall portion side than at the front end on the front wall portion side.

[0019] In the body of the drilling tool as described above, at least a part of the shaft wall portion may be in the shape of a circular arc along a circle concentric with the central axis.

[0020] In the body of the drilling tool as described above, the coolant passage may be spaced 0.4 mm or more from a rear groove wall surface located between the solid portion on the rear side of the coolant passage in the rotational direction and the chip discharge groove.

[0021] In the body of the drilling tool as described above, the coolant passage may be spaced 0.4 mm or more from the outer circumferential surface of the body.

[0022] In the body of the drilling tool as described above, the axial wall portion may pass through a point that is 0.35D or more away from the outer circumferential surface, where D is a distance between the outer circumferential surface of the body and the central axis.

[0023] In the body of the drilling tool as described above, the coolant passage may be configured as a pair of passages.

[0024] In the body of the drilling tool as described above, the open end of the coolant passage may be formed on the outer circumferential surface of the body.

[0025] A drilling tool according to one aspect of the present invention includes the body described above.

[0026] A head-exchangeable drilling tool according to one aspect of the present invention is a drilling tool as described above, in which the head attached to the tip of the body is detachable. [Brief description of the drawings]

[0027] [Figure 1] 1 is a perspective view showing an example of a head-exchangeable drill (hole-drilling tool) according to the present invention. [Diagram 2] 1 is a perspective view showing a head-exchangeable drill with the head removed from the tip of the body. FIG. [Diagram 3] 1 is a diagram (side view) showing a head-exchangeable drill as viewed from a direction perpendicular to the central axis of the body. FIG. [Figure 4] 4 is a cross-sectional view of the body taken along line IV-IV in FIG. 3. [Diagram 5] FIG. 4 is a schematic view showing an example of a configuration of a coolant flow passage. [Figure 6] FIG. 2 is a diagram showing the cross-sectional configuration of the body in more detail. [Figure 7]1A and 1B are diagrams illustrating stress concentration portions in a coolant flow passage having an elliptical cross-sectional shape like a track including a pair of straight line portions; [Figure 8] FIG. 4 is a side view of a head-exchangeable drill according to a second embodiment of the present invention. [Figure 9] 9 is a cross-sectional view of the body taken along line IX-IX in FIG. 8. [Figure 10] FIG. 11 is a schematic view showing an example of a configuration of a coolant flow passage in the second embodiment. [Figure 11] 10 is a cross-sectional view of the body illustrating the first elliptical shape C1. FIG. [Figure 12] 13 is a cross-sectional view of the body illustrating the second elliptical shape C2. FIG. [Figure 13] 13 is a diagram illustrating a structure in which, when the front wall portion is arc-shaped, the distance between the center point of an imaginary circle VC that includes the arc and the central axis is a predetermined value. [Figure 14] 13A and 13B are diagrams illustrating another example of a coolant passage structure that prevents a decrease in the rigidity of the body. [Figure 15] FIG. 13 is a diagram showing an elliptical coolant passage for reference. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of a drilling tool and its body according to the present invention will be described in detail with reference to the drawings (see FIG. 1, etc.).

[0029] The drilling tool according to the present invention is a tool having a body 10 which has a coolant passage 50 and a chip discharge groove 30 and rotates around a central axis 10A relative to a workpiece (not shown) during cutting. In the following, the case where the present invention is applied to a head-exchangeable drill 1 as an example of a drilling tool will be described, but this is merely one suitable example, and it goes without saying that the present invention can be applied to drilling tools other than the head-exchangeable drill 1.

[0030] The head-replaceable drill 1 includes a cutting head 20 that can be attached to the tip 10t of the body 10 (see Figs. 1 and 2). The base end 10b of the body 10 of the head-replaceable drill 1 has an outer periphery 16 formed, for example, in a cylindrical shape, and is detachable from a cutting device such as a machining center or a milling machine. A chip discharge groove (also called a flute) 30 for discharging chips is carved in a groove shape and formed in a spiral shape on the outer periphery of the tip 10t side of the body 10 (see Figs. 1, 3, etc.). In this embodiment, two spiral chip discharge grooves 30 are arranged symmetrically about the central axis 10A (see Fig. 5, etc.). The rotation direction of the head-replaceable drill 1 of this embodiment during cutting is counterclockwise in Fig. 6 (a cross-sectional view taken along line IV-IV in Fig. 3), which is a cross-sectional view of the body 10 from the tip 10t side to the rear end 10b side (hereinafter, also referred to as the drill rotation direction).

[0031] Inside the body 10, a coolant flow passage 50 for supplying coolant toward the head 20 is provided (see FIG. 4, etc.). In this embodiment, the coolant flow passage 50 is configured by arranging a pair of two spiral flow passages symmetrically about the central axis 10A (see FIG. 6, etc.). The shape and flow passage position of these coolant flow passages 50 are set so as to increase the amount of coolant supplied without impairing the rigidity of the head-exchangeable drill 1 and to contribute to improving chip removal performance and the cutting edge life of the head 20.

[0032] [First embodiment] The coolant passage 50 in the head-exchangeable drill 1 of this embodiment has an elliptical track-like shape (in other words, a long non-circular shape) in a cross section perpendicular to the central axis 10A (see Figs. 6 and 7) that includes a pair of opposing straight line portions 50S (see Figs. 4, 6, etc.). If the cross-sectional shape of the coolant passage is elliptical, the portions where stress acting during drilling tends to concentrate are the vertices of a parabola in a total of four places (four places indicated by circles in Fig. 15), whereas if the cross-sectional shape is an elliptical track-like shape including a pair of straight line portions 50S as in this embodiment, the portions where stress tends to concentrate can be reduced to two places (see Fig. 7).

[0033] In a cross section perpendicular to the central axis 10A, a front groove wall surface 41 of a portion excluding the chip discharge groove 30 (referred to as a "solid portion" in this specification and indicated by reference numeral 40 in the drawing) becomes a force acting surface F on which a force acts from chips or coolant discharged through the chip discharge groove 30 during drilling by the head-exchangeable drill 1 (see FIG. 6). In this embodiment, the coolant passage 50 is disposed at a position away from the front groove wall surface 41 toward the rear side in the drill rotation direction (clockwise direction in FIG. 6) and at a position radially outward from the core portion 12 of the body 10 in the cross section, so as to be away from the force acting surface F (i.e., the front groove wall surface 41) (see FIG. 6). Furthermore, in this embodiment, the elliptical coolant passage 50 is disposed in a state inclined toward the rear side in the drill rotation direction and toward the radially outward, so that the radially outer portion in particular is away from the force acting surface F (see FIG. 6). In this way, by arranging the coolant passage 50 at a position away from the front groove wall surface 41, which is the force acting surface F, it is possible to suppress the coolant passage from being deformed by the influence of an external force acting from the front groove wall surface 41 toward the rear side in the rotation direction during drilling. In addition, by arranging the coolant passage 50 radially outward from the core portion 12 of the body 10, the thickness or width of the core portion 12 is ensured, and thus the rigidity of the head-exchangeable drill 1 can be obtained. Note that the core portion 12 of the body 10 refers to a solid imaginary cylindrical portion into which the chip discharge groove 30 and the coolant passage 50 do not enter in any cross section at any position, that is, a portion of the mandrel that does not interfere with the chip discharge groove 30 and the coolant passage 50. By arranging the coolant passage 50 radially outward from the core portion 12 and close enough that a part of the coolant passage 50 contacts the core portion 12, it is possible to ensure the thickness or width of the core portion 12 as much as possible (see FIG. 6, etc.).

[0034] As described above, in the body 10 of the replaceable head drill 1 of this embodiment, the coolant passage 50 is disposed outside the core 12 to ensure the core thickness and ensure the rigidity of the replaceable head drill 1. In addition, the coolant passage 50 is disposed at a position farther rearward in the rotation direction than the circumferential center of the solid portion 40 as viewed from the front groove wall surface 41 in a cross section perpendicular to the central axis 10A. This suppresses the deformation of the coolant passage 50 due to the force acting from the front groove wall surface 41, which is the acting surface F of the force in the drill rotation direction, thereby contributing to improving the rigidity of the replaceable head drill 1. Furthermore, by making the coolant passage 50 have an elliptical shape that extends radially and is inclined, it is possible to suppress the deformation of the coolant passage 50 and increase the cross-sectional area of ​​the coolant passage 50 (and thus increase the amount of coolant supplied). The above-mentioned structure is particularly suitable for use with a replaceable head drill 1 having a relatively small outer diameter.

[0035] [Second embodiment] The coolant flow passage 50 in the head-exchangeable drill 1 of this embodiment is formed so that its cross-sectional shape in a cross section perpendicular to the central axis 10A is formed by a front wall portion 51, an axial wall portion 52, a rear wall portion 53, and an outer peripheral wall portion 54 (see Figure 9).

[0036] The front wall 51 is a generally arcuate portion on the front side in the rotation direction of the drill. The shaft wall 52 is a generally arcuate portion along the core 12 of the body 10 near the central axis 10A, and is configured with a convex curved surface that protrudes toward the inside of the coolant passage 50. The rear wall 53 is a portion on the rear side in the rotation direction of the drill. The outer peripheral wall 54 is a gently curved portion on the radially outer side, and is configured with a convex curved surface that protrudes toward the inside of the coolant passage 50. The outer peripheral wall 54 is continuously connected to the front wall 51, the shaft wall 52, and the rear wall 53 such that the boundaries between them are smoothly connected. The rear wall 53 and the outer peripheral wall 54 are smoothly connected via the arcuate wall 55 (see FIG. 9). At least a part of the shaft wall 52 is in an arcuate shape that is concentric with the central axis 10A. Moreover, the curvature of the outer peripheral wall portion 54 is greater than the curvature of the axial wall portion 52 .

[0037] The coolant passage 50 is disposed in the solid portion 40 in a cross section perpendicular to the central axis 10A, at a position away from the front groove wall surface 41 toward the rear side in the rotational direction, and at a position radially outward from the core portion 12 of the body 10 in the cross section (see FIG. 9, etc.). As described above, the front groove wall surface 41 is a portion that becomes the action surface F of the force acting from the chips or coolant discharged through the chip discharge groove 30 during drilling using the head-exchangeable drill 1 (see FIGS. 11 and 12). Furthermore, the coolant passage 50 is shaped such that the distance from the central axis 10A to the outer peripheral wall portion 54 is longer at the rear distance L54r at the end on the rear wall portion 53 side than at the front distance L54f at the end on the front wall portion 51 side (see FIG. 9).

[0038] The cross-sectional shape of the coolant passage 50 in the head-exchangeable drill 1 of this embodiment is formed by these walls, so to speak, in a shape in which two long non-circular shapes are smoothly connected by an arc of large curvature that is convex inward on both the outer periphery side and the rear side in the drill rotation direction. The two long non-circular shapes here are a first elliptical shape C1 like a track including a pair of opposing straight lines 50S as in the first embodiment (see FIG. 11), and a second curved elliptical shape C2 including a pair of opposing curves that curve on a concentric circle (or a curve that approximates this) along the core 12 (see FIG. 12). In the coolant passage 50 in the head-exchangeable drill 1 of this embodiment, the rear wall 53 does not have the straight line 50S (it cannot be visually confirmed) (see FIG. 12). This can be explained as follows. That is, when the coolant passage 50 is formed by sequentially connecting the front wall portion 51, the shaft wall portion 52, the rear wall portion 53, the outer peripheral wall portion 54, and further the arc-shaped wall portion 55, a straight line may not appear at the outer edge of the coolant passage 50, but even in that case, the oval shape C1 having a pair of straight line portions 50S is still included within the area of ​​the coolant passage 50 (see FIG. 11). Incidentally, the larger the drill diameter, the more likely it is that a portion close to a straight line will be formed on the rear wall portion 53 side. In any case, by devising a shape in which the first oval shape C1 including the straight line portion 50S and the second oval shape C2 are smoothly connected by a large arc, it is possible to realize a coolant passage 50 that increases the amount of coolant supplied without impairing the rigidity of the head-exchangeable drill 1 and further contributes to improving chip discharge performance and cutting edge life. From this point of view, the straight line portion 50S does not need to be a completely straight line, and may be a very gently curved line as long as it can reduce stress concentration appropriately.

[0039] The specific configuration of the coolant passage 50 as described above may be various in terms of securing the cross-sectional area of ​​the coolant passage 50 without impairing rigidity. For example, the coolant passage 50 may be formed at a position 0.4 mm or more away from the rear groove wall surface 42 located between the solid portion 40 and the chip discharge groove 30 on the rear side in the drill rotation direction. The coolant passage 50 may also be formed at a position 0.4 mm or more away from the outer peripheral surface 14 of the body 10 (here, this refers to the outer peripheral surface of the portion of the body 10 where the chip discharge groove 30 is formed). Furthermore, the shaft wall portion 52 forming the cross-sectional shape of the coolant passage 50 may be formed to pass through a point 0.35D or more away from the outer peripheral surface 14 of the body 10 with respect to the distance D between the outer peripheral surface 14 and the central axis 10A.

[0040] When the front wall portion 51 is arc-shaped, the center point of an imaginary circle VC that includes the arc may be on a pitch circle of approximately 0.40D (D is the length from the central axis 10A to the outer peripheral surface 14) (see FIG. 13). If the center point of the imaginary circle is on a pitch circle of 0.45D to 0.55D, the rigidity of the body 10 is relatively likely to decrease (see Patent Document 4, for example), but by using such a structure, it is possible to prevent the rigidity from decreasing accordingly.

[0041] In addition, when the cross-sectional shape of the coolant passage is a hole shape that is non-circular in the circumferential direction (rotation direction), the rigidity of the body may decrease depending on the arrangement (see, for example, Patent Document 2). In consideration of this point, the following may be used. That is, the coolant passage 50 has a shape like a long non-circular coolant passage 50, which has an arc part of the core 12 as one side (in this case, the shaft wall part 52) ​​and has an arc part of the center axis 10A as one side, which passes through a point that is 35% or more (for example, 46%) away from the outer peripheral surface 14 when the length D from the center axis 10A to the outer peripheral surface 14 is taken as 100%, and the front wall part 51 located on the front side in the drill rotation direction and the rear wall part 53 located on the rear side in the drill rotation direction are both outwardly convex, and is arranged at a position 0.4 mm or more away from the outer peripheral surface 14 and the chip discharge groove 30 (see FIG. 14).

[0042] Moreover, the coolant passage 50 in the head-exchangeable drill 1 of this embodiment is formed so that its open end 59 on the tip 10t side is located on the outer circumferential surface 14 of the body 10 (see Figs. 8, 10, etc.). Generally, if the open end 59 of the coolant passage 50 is located near the cutting edge of the head 20, the tip 10t of the body 10 becomes hollow, which may result in a decrease in rigidity, but the head-exchangeable drill 1 of this embodiment as described above makes it possible to avoid a decrease in rigidity. Furthermore, the coolant passage 50 is formed so that it starts from a supply port (not shown) on the base end 10b side of the body 10, smoothly curves inside the body 10, and opens on the outer circumferential surface 14, thereby suppressing pressure loss and increasing the amount of coolant supplied.

[0043] As described above, in this embodiment, the coolant flow passage 50 has a shape in which two long non-circular portions (i.e., one is a radially long oval shape C1 located on the rear side in the rotation direction of the drill and outside the core portion 12, and is located at a position more than a predetermined value away from the outer circumferential surface 14 and the central axis 10A, and the other has an arc-shaped portion (shaft wall portion 52) along the core portion 12 and, on the opposite side, an arc-shaped portion (outer circumferential wall portion 54) centered on the central axis 10A and passing through a point more than a predetermined percentage away from the outer circumferential surface 14, and the front wall portion 51 located on the front side in the rotation direction of the drill and the rear wall portion 53 located on the rear side are both outwardly convex), which are connected by a large arc, and the coolant flow passage 50 is shaped to be smoothly curved toward the outer periphery, thereby making it possible to supply a larger amount of coolant (for example, 30% or more) to the cutting edge of the head 20 without compromising rigidity. This makes it possible to achieve excellent cooling and chip removal properties while maintaining the strength of the head-exchangeable drill 1.

[0044] The above can be restated as follows in light of each configuration. That is, by making the shaft wall 52 arc-shaped along the core 12, the thickness of the core 12 is ensured, and the rigidity of the body 10 is easily ensured. Also, by making the outer peripheral wall 54 an arc-shaped portion sufficiently distant from the outer peripheral surface 14, the rigidity of the coolant passage 50 is ensured, and the rigidity of the body 10 is easily ensured. Furthermore, by making the oval shape C2 a characteristic non-circular shape extending in the rotation direction, both the deformation of the coolant passage 50 is suppressed and the cross-sectional area of ​​the coolant passage 50 is increased. Furthermore, by making the coolant passage 50 a shape that is smoothly connected by an arc with a large curvature that is convex inward on both the outer peripheral side and the rear side in the drill rotation direction, the deformation of the coolant passage 50 is further suppressed. The above-mentioned structure is particularly suitable for application to a head-exchangeable drill 1 having a relatively large outer diameter.

[0045] In addition, while it may not be possible to freely design the coolant flow path with conventional tools or the methods for manufacturing them, the head-exchangeable drill 1 or its body 10 of the present invention can be freely designed, for example by employing 3D printing, to realize the flow path shape, position, and configuration that can achieve the above-mentioned features.

[0046] The above-described embodiment is one example of a preferred embodiment of the present invention, but the present invention is not limited to this embodiment and can be modified in various ways without departing from the gist of the present invention. [Industrial Applicability]

[0047] The present invention is suitable for application to a drilling tool having a coolant passage and a chip discharge groove, and to the body of the drilling tool. [Explanation of symbols]

[0048] 1...Replaceable head drill (hole drilling tool) 10. Body 10A…Center axis 10b...Proximal end 10t...Tip 12...core part 14...Outer surface 16...(base end side) outer periphery 20…Head 30…Chip discharge groove 40…Solid section 41…Front ditch wall 42…Rear groove wall 50…Coolant passage (in drill body) 50S: A pair of opposing straight sections 51…Front wall 52...Axial wall 53...Rear wall 54…Outer peripheral wall part 55...Arc-shaped wall 59…Open end C1…First oval shape C2: Second oval shape D: Distance between the outer periphery and the central axis F: Force acting surface L54f: the forward distance from the central axis 10A to the outer peripheral wall 54 at the end on the front wall 51 side L54r: rear distance from the central axis 10A to the outer peripheral wall 54 at the end on the rear wall 53 side VC: Virtual circle

Claims

1. A body of a drilling tool having a coolant flow path and a chip discharge groove, the body rotating around a central axis during cutting, The coolant flow path is In a cross section perpendicular to the central axis, the shape is an ellipse including a pair of straight line portions, A body of a drilling tool, in a cross section perpendicular to the central axis, a solid portion excluding the chip discharge groove is located at a position away from a front groove wall surface that receives forces from chips or coolant discharged through the chip discharge groove during cutting, and is located at a position radially outward from a core of the body in the cross section.

2. 2. The body of a drilling tool according to claim 1, wherein the coolant flow passage is arranged at a position away from the circumferential center of the solid portion toward the rear side in the direction of rotation when viewed from the front groove wall surface in a cross section perpendicular to the central axis.

3. The drilling tool body according to claim 2 , wherein the core portion is a portion of the stem of the body that does not interfere with the chip groove.

4. The body of a drilling tool according to claim 3 , wherein in a cross section perpendicular to the central axis, the coolant passage is disposed at a position close enough to be in contact with the core portion.

5. The body of a drilling tool according to claim 1 , wherein the coolant flow passage, which is elliptical in a cross section perpendicular to the central axis, is arranged so as to be inclined rearward in the direction of rotation and outward in the radial direction.

6. A body of a drilling tool having a coolant flow path and a chip discharge groove, the body rotating around a central axis during cutting, In a cross section perpendicular to the central axis, the coolant flow passage is formed by a front wall portion on a front side in a rotational direction, an axial wall portion on a central axis side, a rear wall portion on a rear side in the rotational direction, and an outer peripheral wall portion on a radially outer side, The body of the drilling tool, wherein the axial wall portion and the outer peripheral wall portion are configured as convex curved surfaces that protrude toward the inside of the coolant flow path.

7. 7. The body of a drilling tool as described in claim 6, wherein in a cross section perpendicular to the central axis, in a solid portion excluding the chip discharge groove, the coolant flow passage is arranged at a position away from a front groove wall surface that receives a force from chips or coolant discharged through the chip discharge groove during cutting, toward the rear side in the rotational direction, and at a position radially outward from a core portion of the body in the cross section.

8. The drilling tool body according to claim 6 , wherein the curvature of the outer peripheral wall portion is greater than the curvature of the axial wall portion.

9. 7. The body of a drilling tool according to claim 6, wherein the coolant flow passage is shaped such that a rearward distance from the central axis to the outer peripheral wall portion at an end portion on the rear wall portion side is longer than a forward distance at an end portion on the front wall portion side.

10. The body of a drilling tool according to claim 6 , wherein at least a portion of the shaft wall portion is in the shape of a circular arc along a circle concentric with the central shaft.

11. 6. The body of a drilling tool according to claim 5, wherein the coolant passage is spaced 0.4 mm or more from a rear groove wall surface located between the solid portion and the chip discharge groove on a rear side of the coolant passage in the rotational direction.

12. 6. A drilling tool body as claimed in claim 5, wherein the coolant passage is spaced from the outer periphery of the body by 0.4 mm or more.

13. The body of a drilling tool according to claim 6 , wherein the axial wall portion passes through a point that is 0.35D or more away from the outer circumferential surface of the body, where D is a distance between the outer circumferential surface of the body and the central axis.

14. The drilling tool body according to claim 1 , wherein the coolant passage comprises a pair of passages.

15. The drilling tool body of claim 14 , wherein the open ends of the coolant passages are formed on an outer periphery of the body.

16. A drilling tool comprising a body according to claim 15.

17. 17. The drilling tool according to claim 16, wherein the head attached to the tip of the body is detachable.

Images