Drill bit body and method of manufacturing the same

Abstract

The present application provides a drill bit main body which, while ensuring rigidity of a front end portion, is provided with a fluid through-hole capable of appropriately supplying cutting fluid to a cutting region. The drill bit main body includes a main body portion, a chip flute, a fluid through-hole, and a mounting portion. The main body portion extends in a rod shape from a base end portion to a front end portion. The chip flute is provided around a central axis of the main body portion and is used to discharge chips. At least a portion of the fluid through-hole passes through an inside of a flute wall of the chip flute in the main body portion and is used to flow fluid from the base end portion to the front end portion. The mounting portion is provided at the front end portion and is used to mount a detachable cutting edge member. The mounting portion has a recess portion provided along the central axis of the main body portion from an end surface of the front end portion. A hole cross section of the fluid through-hole changes from a circular shape to a non-circular shape halfway along a path of the fluid through-hole from the base end portion toward the front end portion. A length of the non-circular hole cross section in a circumferential direction of a cross section of the main body portion is longer than a length in a radial direction of the cross section of the main body portion. A hole cross section of a portion of the fluid through-hole that passes through a side of the recess portion is non-circular.

Description

Technical Field

[0001] This invention relates to the drill bit body and its manufacturing method. Background Technology

[0002] A technique is known in which cutting fluid is supplied to the cutting area through a fluid passage located inside the drill bit body. In such a drill bit, to ensure the rigidity of the drill bit, methods commonly used include setting the cross-sectional shape of the fluid passage to a fan shape according to the shape of the chip removal groove (e.g., Patent Document 1).

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent No. 5926877

[0006] Technical issues

[0007] A drill bit is currently available in which a detachable cutting edge component is mounted on the front end of its body. With the cutting edge component mounted on the front end, the cutting area is located further forward than the front end of the drill bit body. Therefore, even with a fluid passage for cutting fluid inside the drill bit body, it is difficult to properly supply cutting fluid to the cutting area. In particular, even with a mounting portion for the cutting edge component at the front end of the drill bit body, the rigidity of the front end must be ensured.

[0008] To address the aforementioned problems, the present invention provides a drill bit body and a method for manufacturing the same, wherein the drill bit body, while ensuring the rigidity of the front end, has a fluid through-hole capable of supplying cutting fluid to the cutting area appropriately. Summary of the Invention

[0009] The drill bit body according to the first aspect of the present invention includes a main body portion, a chip removal groove, a fluid passage, and a mounting portion. The main body portion extends in a rod shape from a base end portion to a forward end portion. The chip removal groove is arranged around the central axis of the main body portion for discharging waste chips. At least a portion of the fluid passage passes through the interior of the groove wall of the chip removal groove in the main body portion for allowing fluid to flow from the base end portion to the forward end portion. The mounting portion is provided at the forward end portion for mounting a detachable cutting edge component. The mounting portion has a recess provided along the central axis of the main body portion from the end face of the forward end portion. The cross-section of the fluid passage changes from circular to non-circular midway along the path of the fluid passage from the base end portion to the forward end portion. The length of the non-circular cross-section in the circumferential direction of the cross-section of the main body portion is longer than its length in the radial direction of the cross-section of the main body portion. The cross-section of the portion of the fluid passage passing through the side of the recess is non-circular.

[0010] The second aspect of the present invention discloses a method for manufacturing a drill bit body, the drill bit body comprising a main body portion, a chip removal groove, a fluid passage, and a mounting portion. The main body portion extends in a rod shape from a base end to a front end end. The chip removal groove is arranged around the central axis of the main body portion for discharging waste chips. At least a portion of the fluid passage passes through the interior of the groove wall of the chip removal groove in the main body portion, allowing fluid to flow from the base end to the front end end. The mounting portion is located at the front end end and is used to mount a detachable cutting edge component. Steel is laminated and cured along the central axis to form the mounting portion, such that the mounting portion has a recess arranged from the end face of the front end portion along the central axis of the main body portion; and the cross-section of the fluid passage changes from circular to non-circular midway along the path from the base end portion to the front end portion, the non-circular cross-section having a length in the circumferential direction of the main body portion cross-section longer than its radial length in the cross-section of the main body portion, and the portion of the fluid passage passing through the side of the recess has a non-circular cross-section.

[0011] The present invention provides a drill bit body and a method for manufacturing the same, wherein the drill bit body, while ensuring the rigidity of the front end, has a fluid through-hole capable of supplying cutting fluid to the cutting area. Attached Figure Description

[0012] Figure 1 An overall perspective view of the drill bit provided in this embodiment.

[0013] Figure 2 A perspective view of the installation of the cutting edge components onto the drill bit body.

[0014] Figure 3 This is a schematic diagram of the fluid through-hole formed inside the drill bit body.

[0015] Figure 4 This is a side view of the drill bit.

[0016] Figure 5 This is a sectional view of a section orthogonal to the central axis.

[0017] Figure 6 This is a magnified 3D view of the area near the front end.

[0018] Figure 7 An enlarged perspective view of the front end portion provided for another embodiment.

[0019] Figure 8 This is a schematic diagram of manufacturing the drill bit body using a 3D printer.

[0020] Explanation of main component symbols

[0021] Drill bit 10

[0022] Drill bit body 100

[0023] Main body 110

[0024] Base end 111

[0025] Front end 112, 112'

[0026] Chip removal groove 113

[0027] Central shaft 114

[0028] 115 between tank walls

[0029] Installation recess 120

[0030] First end face 120a

[0031] Second end face 120b

[0032] First fluid passage 130, 130'

[0033] Emission outlet 131, 131'

[0034] Supply port 132

[0035] Straight-in Unit 133

[0036] Spiral part 134

[0037] Bending part 135

[0038] Second fluid through-hole 140

[0039] Emission outlet 141

[0040] Supply port 142

[0041] Straight-in section 143

[0042] Spiral part 144

[0043] Bending section 145

[0044] Handle 150

[0045] Cutting edge components 200, 200'

[0046] Mounting protrusion 210

[0047] Cutting edge 220

[0048] Main cutting edge 221

[0049] Thinning of cutting edge 222 Detailed Implementation

[0050] Embodiments of the present invention will now be described with reference to the accompanying drawings. It should be noted that in the figures, elements with the same reference numeral indicate those having the same or identical structure. Furthermore, when multiple structures with the same or identical structure exist in each figure, to avoid complexity, only some structures are labeled, omitting the need to assign the same reference numerals to other parts. Additionally, the structures described in the embodiments are not all necessary means to solve the problem.

[0051] Figure 1 This is an overall perspective view of the drill bit 10 provided in this embodiment. The drill bit 10 is a replaceable cutting edge drill bit with a detachable cutting edge component 200 mounted on the front end of the drill bit body 100. For example, the cutting edge component 200 for cutting the workpiece is made of cemented carbide, while the drill bit body is made of steel instead of cemented carbide. Thus, by making the easily worn and damaged cutting edge component 200 replaceable, the required hardness of the cutting tip and the overall operating cost of the drill bit can be balanced.

[0052] The drill bit body 100 is formed by a straight connection between a main body portion 110 and a shank portion 150. The main body portion 110 is provided with a spiral chip removal groove 113, and the shank portion 150 is fixed to a machine tool such as a drilling machine. It should be noted that, in this embodiment, when the drill bit 10 is fixed to the machine tool, the fixed side is called the base end side, and the side facing the workpiece is called the front end side.

[0053] The main body 110 extends in a rod shape from the base end 111 connected to the shank 150 to the front end 112 on which the cutting edge member 200 is mounted. In the main body 110 provided in this embodiment, the base end 111 connected to the shank 150 expands radially in a serrated shape, but the base end 111 to the front end 112 can be cylindrical with the same diameter.

[0054] Chip removal grooves 113 are spirally arranged around the central axis of the main body 110 to discharge workpiece chips. In this embodiment, two chip removal grooves 113 are provided. For example, chips cut from the workpiece rise along the main body 110 via the chip removal grooves 113 and are discharged from the edge-shaped protruding base end 111 towards the periphery of the drill bit 10. That is, the edge-shaped protruding base end 111 serves to prevent chips from colliding with or adhering to the machine tool supporting the shank 150. This prevents chips from getting stuck when fixing the shank 150, thereby improving the installation accuracy of the drill bit 10 and potentially improving the machining accuracy of the workpiece.

[0055] The drill bit body 100 has a fluid passage formed inside, which allows cutting fluid supplied from the base side of the shank 150 to flow through and discharge from the outlets 131 and 141 located at the front end 112 of the body 110, as described in detail below. Cutting fluid is a medium called coolant, used to eliminate heat generated in the cutting area and reduce friction between the cutting tip and the workpiece. In this embodiment, it is assumed that a liquid such as a water-oil emulsion or cutting oil is used, but a gas such as compressed air can also be used instead of a coolant.

[0056] Figure 2 This is a perspective view showing the mounting of the cutting edge component 200 onto the drill bit body 100. The front end portion 112 of the drill bit body 100 has a mounting recess 120, which is a mounting portion for mounting the cutting edge component 200. Specifically, the mounting recess 120 is a concave structure provided along the central axis P of the body portion 110 from the end face of the front end portion 112. In this embodiment, since the chip removal groove 113 is provided from the front end portion 112, the portion of the concave structure that does not actually coincide with the chip removal groove 113 protrudes towards the front end. Discharge ports 131 and 141 are provided at this protruding portion, the details of which will be described below.

[0057] The cutting edge component 200 has a mounting protrusion 210, which is a mounting portion for inserting the cutting edge component 200 into the mounting recess 120 of the drill body 100. Specifically, the mounting protrusion 210 is approximately cylindrical and can be inserted into the mounting recess 120. Furthermore, the cutting edge component 200 has a plurality of cutting edges 220, which are radially arranged on the side opposite to the workpiece, opposite to the mounting protrusion 210. While confirming the relative positions of the discharge ports 131, 141 and the cutting edges 220, the operator can fix the cutting edge component 200 to the drill body 100 by inserting the mounting protrusion 210 into the mounting recess 120.

[0058] Figure 3 This is a schematic diagram of the fluid through-hole formed within the drill bit body 100. In this embodiment, two chip removal grooves 113 are provided, and correspondingly, two fluid through-holes, a first fluid through-hole 130 and a second fluid through-hole 140, are also provided. Figure 3 The general outline of the drill bit body 100 is shown in dashed lines. The first fluid through hole 130 and the second fluid through hole 140 provided inside the drill bit body 100 are shown in perspective view so that their arrangement is clear at a glance. At the same time, the fluid through holes are extracted and shown separately so that the shape of each fluid through hole is clearly visible.

[0059] The first fluid through-hole 130 guides the cutting fluid supplied from the supply port 132 to the discharge port 131. The first fluid through-hole 130 has a straight section 133 parallel to the central axis P in the portion located within the shank 150, a spiral section 134 parallel to the chip removal groove 113 in most of the portion located within the main body 110, and a bent section 135 in the portion located within the front end 112 of the main body 110. The discharge port 131 is located immediately after the bent section 135.

[0060] The second fluid through-hole 140 guides the cutting fluid supplied from the supply port 142 to the discharge port 141. The second fluid through-hole 140 has a straight section 143 parallel to the central axis P in the portion located within the shank 150, a spiral section 144 parallel to the chip removal groove 113 in most of the portion located within the main body 110, and a bent section 145 in the portion located within the front end 112 of the main body 110. The discharge port 141 is located immediately following the bent section 145.

[0061] Therefore, the straight sections 133 and 143 are parallel to each other, and the spiral sections 134 and 144 are arranged to be intertwined around the central axis P. Furthermore, the bent sections 135 and 145 bend in different directions, thus, as described later, the cutting fluid is discharged in different specific directions.

[0062] Figure 4 This is a side view of drill bit 10. As shown, an AA section orthogonal to the central axis P is defined approximately at the midpoint between the base end side and the front end side of the main body 110. A CC section orthogonal to the central axis P is defined near the front end, traversing the mounting recess 120. A BB section orthogonal to the central axis P is defined between the AA and CC sections.

[0063] Figure 5 These are sectional views of sections orthogonal to the central axis P. Specifically, Figure 5 (a) shows Figure 4 AA section in the middle, Figure 5 (b) shows Figure 4 BB section in Figure 5 (c) shows Figure 4 CC section in the image.

[0064] like Figure 5 As shown in (a), in section AA, the cross-sections of both the first fluid through-hole 130 and the second fluid through-hole 140 are circular. However, if combined with... Figure 3As described, at approximately the center of the main body 110 in section AA, the first fluid through-hole 130 and the second fluid through-hole 140 are intertwined around the central axis P, so each hole cross-section appears at a position symmetrical with respect to the central axis P. Furthermore, relative to the outer circle of the main body 110, in the radial direction of this outer circle, each hole cross-section is located on the outer periphery of the central axis portion 114 sandwiched by two chip removal grooves 113, and in the circumferential direction of this outer circle, each hole cross-section is located within the groove wall 115 between these chip removal grooves 113. In other words, the groove wall 115 is the wall between the two chip removal grooves 113 arranged spirally around the central axis P, therefore both groove walls 115 are also formed spirally around the central axis portion 114.

[0065] The first fluid through-hole 130 and the second fluid through-hole 140 each pass through the interior of the slot wall 115. It should be noted that a portion of the cross-section of each hole may coincide with the central axis portion 114. This arrangement of the first fluid through-hole 130 and the second fluid through-hole 140 ensures both a large hole cross-sectional area and high rigidity of the main body 110. Furthermore, even when a single spiral chip removal groove 113 is provided within the main body 110, identical slot walls 115 are formed between grooves that are in a front-to-back relationship in the direction of the central axis P. Additionally, even when three spiral chip removal grooves 113 are provided, identical slot walls 115 are still formed between adjacent grooves in the direction of the central axis P. The number and size of the fluid through-holes can be determined based on the structure of each slot wall and the specifications of the drill bit 10.

[0066] Furthermore, if the cross-sections of the first fluid through-hole 130 and the second fluid through-hole 140 orthogonal to their respective flow paths are circular, then strictly speaking, the cross-section orthogonal to the central axis P is slightly elliptical due to the influence of flow path torsion. However, considering the normal helix angle of the chip removal groove in the drill bit, even under these circumstances, it is still possible to simultaneously ensure a large hole cross-sectional area and high rigidity of the main body 110. Therefore, the hole cross-section can be considered circular in practice.

[0067] like Figure 5 As shown in (b), in section BB, the cross-section of the first fluid through-hole 130 and the cross-section of the second fluid through-hole 140 are both non-circular and approximately circular, more specifically, elongated ovals. Compared to the circular cross-section AA, the radial length of the outer circle of the main body 110 is shorter.

[0068] like Figure 5 As shown in (c), in the CC section, the cross-sections of both the first fluid through-hole 130 and the second fluid through-hole 140 are non-circular. More specifically, they are elongated ovals, longer in the circumferential direction of the outer circle of the main body 110. Furthermore, in the CC section, a mounting recess 120 is formed in the region corresponding to the central axis portion 114, and the cross-section of the mounting protrusion 210 is shown in the figure.

[0069] like Figure 5 (a) Figure 5 (b) and Figure 5 As shown in (c), the cross-sections of the first fluid through-hole 130 and the second fluid through-hole 140 change from circular to non-circular midway along the path of the fluid through-hole from the base end 111 of the main body 110 to the front end 112. The length of the non-circular cross-section in the circumferential direction of the cross-section of the main body 110 is longer than its length in the radial direction of the cross-section of the main body 110. The cross-section of the portion of the fluid through-hole passing through the side of the mounting recess 120 is non-circular. When the cross-section of the portion of the fluid through-hole passing through the side of the mounting recess 120 is non-circular, the length of the non-circular cross-section in the circumferential direction of the cross-section of the main body 110 is longer than its length in the radial direction of the cross-section of the main body 110. Even if this side is a shape protruding towards the front end, a larger cross-section can be achieved while ensuring high rigidity. Furthermore, although an oblong shape is used for the non-circular shape in this embodiment, an ellipse, a sector, a rectangle, etc., can also be used.

[0070] By changing the cross-sectional shape of the fluid through-hole, even if a mounting portion is provided at the front end of the drill body and a cutting edge component is installed, the overall rigidity of the drill body, including the front end, can be ensured, while the cutting fluid is supplied to a position closer to the cutting area. Furthermore, regarding the position where the circular shape changes to a non-circular shape, it is preferable to be closer to the base end side than the position passing through the side of the mounting recess 120 in this embodiment, but it can also be located on the side of the mounting recess 120. The position where the circular shape changes to a non-circular shape can be determined based on the size of the hole cross-section and the wall thickness on the side of the mounting recess.

[0071] Furthermore, preferably, the cross-sectional area of ​​the non-circular hole is less than or equal to the cross-sectional area of ​​the circular hole. That is, in the case of... Figure 5 (a) shows a circular state towards Figure 5 (c) shows the transition phase of the non-circular state change. Figure 5 (b) As shown in the diagram, preferably, the cross-sectional area of ​​the hole decreases. If this relationship is satisfied, it is possible to obtain a squeezing effect near the front end to increase the discharge pressure while supplying a large amount of cutting fluid.

[0072] Furthermore, in this embodiment, the first fluid through-hole 130 and the second fluid through-hole 140 also penetrate the interior of the handle 150, but the cross-sectional area of ​​the portions penetrating the interior of the handle 150 (straight-in portion 133 and straight-in portion 143) does not need to be circular. Moreover, preferably, the cross-sectional area of ​​this hole is greater than... Figure 5 (a) shows the cross-sectional area of ​​the circle.

[0073] Figure 6 This is a magnified stereoscopic view of the area near the front end 112. More specifically, Figure 6The structure near the front end 112 where the cutting edge component 200 is mounted is shown to illustrate the flow of cutting fluid discharged from the outlet 131 of the first fluid through-hole 130. (As in conjunction with...) Figure 3 The first fluid through-hole 130 is bent to the side of the mounting recess 120, and the discharge port 131 is provided immediately after the bend.

[0074] As shown in the figure, in this embodiment, the discharge port 131 spans the two end faces (first end face 120a and second end face 120b) of the mounting recess 120. The cutting fluid discharged from the opening portion of the discharge port 131 located on the first end face 120a primarily reaches the main cutting edge 221 of the cutting edge component 220. On the other hand, the cutting fluid discharged from the opening portion of the discharge port 131 located on the second end face 120b primarily reaches the thinned cutting edge 222 of the cutting edge component 200. The cutting fluid can be directly supplied to the cutting edge 220 by bending at the front end 112 through the first fluid passage 130.

[0075] In particular, in this embodiment, the opening portion located on the first end face 120a is formed as a non-circular shape. The length of this non-circular opening portion in the extension direction of the main cutting edge 221 is longer than its length in the orthogonal direction. Therefore, even a small amount of cutting fluid can significantly cool the main cutting edge 221. Furthermore, in this embodiment, the cutting edge 220 simultaneously has two regions: the main cutting edge 221 and the thinning cutting edge 222. Therefore, the discharge port 131 spans both the first end face 120a and the second end face 120b. However, the shape and arrangement of the discharge port 131 can be determined according to the structure of the cutting edge 220. In this case, it is sufficient to form a non-circular shape, where the length of the non-circular shape in the extension direction of the cutting edge is longer than its length in the orthogonal direction.

[0076] Figure 6 Although not shown, the discharge port 141 of the second fluid passage 140 also forms the same opening shape as the discharge port 131. Unlike the cutting edge 220 facing the discharge port 131, the discharge port 141 faces other cutting edges 220, directly supplying cutting fluid to their main cutting edge 221 and thinning cutting edge 222. In other words, when the cutting edge component 200 is correctly installed on the drill body 100, the discharge ports 131 and 141 are positioned facing different cutting edges 220. Therefore, if the operator confirms the relative positions of the discharge ports 131, 141, and the cutting edges 220 while simultaneously engaging the mounting protrusion 210 into the mounting recess 120 in conjunction with the rotation phase, the cutting edge component 200 can be correctly fixed to the drill body 100. That is, bending the fluid passage at the front end to adjust the orientation of the discharge port helps to install the cutting edge component 200 onto the drill body 100 as specified.

[0077] On the other hand, depending on factors such as the structure of the cutting edge component 200 and the workpiece material, in some cases, it is more appropriate to discharge the cutting fluid towards the workpiece than directly towards the cutting edge 220. Another implementation method corresponding to this situation will be described below. Figure 7 An enlarged perspective view of the front end portion 112' provided for another embodiment. Unless otherwise specified, in this embodiment, it has the same structure as the drill bit 10, and will not be described again.

[0078] The cutting edge structure of the installed cutting edge component 200' differs from that of the aforementioned cutting edge component 200. As shown in the figure, the first fluid hole 130' is not bent at the front end 112', and the discharge port 131' is positioned towards the workpiece. However, similar to the drill body 100, in the body portion 110, the cross-section of the first fluid hole 130' changes from circular to non-circular midway along the path from the base end 111 to the fluid through hole at the front end 112. The length of the non-circular cross-section in the circumferential direction of the cross-section of the body portion 110 is longer than its radial length in the cross-section of the body portion 110. The cross-section of the portion of the fluid through hole passing through the side of the mounting recess 120 is non-circular. The second fluid through hole, not shown in the figure, also has the same structure. Therefore, the cutting fluid discharged from each discharge port can be directly discharged to and reach the workpiece surface. The drill body 100 with this type of discharge port can also achieve a large hole cross-section while ensuring the rigidity of the portion on the side of the mounting recess.

[0079] The following describes an example of a method for manufacturing the drill body 100. When the drill body 100 is formed of steel rather than cemented carbide, a 3D printer can be used. Figure 8 This is a schematic diagram illustrating the manufacture of the drill body 100 using a 3D printer. There are several well-known methods for 3D printing using metal as a material; here, we will use the FDM method as an example.

[0080] The 3D printer 400 includes a base 410 and a print head 420, as shown in the figure. A control unit (not shown) controls the print head 420 to form a drill body 100 on the base 410. As indicated by the hollow arrow, the print head 420 is movable relative to the base 410 in both planar and height directions. The print head 420 has a nozzle 421 facing the base 410. The laminating material can be a thermoplastic resin material containing steel powder. The laminating material supplied to the print head 420 is heated, melted, and discharged from the nozzle 421. The discharge position and amount of the laminating material discharged from the nozzle 421 are controlled by the control unit.

[0081] The 3D printer 400 ejects material upwards to a specified height from the surface of the base 410, allowing it to solidify. By repeating this operation, the laminated material forms the drill body 100. Subsequently, the resin material is removed through degreasing, and the drill body 100 is manufactured through a sintering process.

[0082] Using this manufacturing method, the first fluid through-hole 130 and the second fluid through-hole 140 can be formed relatively easily inside the drill bit body 100. Furthermore, although this embodiment describes the drill bit body 100 having two fluid through-holes, the first fluid through-hole 130 and the second fluid through-hole 140, the number of fluid through-holes is not limited to this; there can be one or more than three. It should be noted that when three or more chip removal grooves 113 are provided, the number of fluid through-holes can also be adjusted accordingly.

[0083] Furthermore, although the chip removal groove 113 is described as spiral in the above embodiment, the drill body 100 may also have a chip removal groove in a straight line.

Claims

1. A drill bit body comprising: a body portion extending in a bar shape from a base end portion to a front end portion; a chip flute provided around a center axis of the body portion for discharging a waste chip; a fluid passage at least partially passing through an interflute wall inside the chip flute in the body portion for flowing a fluid from the base end portion to the front end portion; a mounting portion provided at the front end portion for mounting a detachable cutting edge member, the mounting portion has a recess provided along the center axis of the body portion from an end surface of the front end portion, a hole cross section of the fluid passage is changed from a circular shape to a non-circular shape halfway along a path of the fluid passage from the base end portion toward the front end portion, the non-circular hole cross section has a length in a cross-sectional circumferential direction of the body portion longer than a length in a cross-sectional radial direction of the body portion, and a hole cross section of a portion of the fluid passage passing by a side of the recess is non-circular.

2. The drill bit body of claim 1, wherein, the non-circular hole cross section has a cross-sectional area equal to or smaller than a cross-sectional area of the circular hole cross section.

3. The drill bit body of claim 1 or 2, wherein, a discharge port of the fluid passage at the front end portion is provided toward a cutting edge of the cutting edge member mounted to the mounting portion.

4. The drill bit body of claim 3, wherein, the discharge port is formed after bending the fluid passage.

5. The drill bit body of claim 4, wherein, an opening portion of the discharge port discharging the fluid toward a main cutting edge constituting the cutting edge is non-circular, and the non-circular opening portion has a length in a first direction along the main cutting edge longer than a length in a second direction orthogonal to the first direction.

6. The drill bit body of claims 1 or 2, wherein, the body portion is made of a steel material.

7. A manufacturing method of a drill bit body comprising: a body portion extending in a bar shape from a base end portion to a front end portion; a chip flute provided around a center axis of the body portion for discharging a waste chip; a fluid passage at least partially passing through an interflute wall inside the chip flute in the body portion for flowing a fluid from the base end portion to the front end portion; a mounting portion provided at the front end portion for mounting a detachable cutting edge member, a steel material is laminated and solidified along the center axis to be shaped such that the mounting portion has a recess provided along the center axis of the body portion from an end surface of the front end portion, and such that a hole cross section of the fluid passage is changed from a circular shape to a non-circular shape halfway along a path of the fluid passage from the base end portion toward the front end portion, the non-circular hole cross section has a length in a cross-sectional circumferential direction of the body portion longer than a length in a cross-sectional radial direction of the body portion, and a hole cross section of a portion of the fluid passage passing by a side of the recess is non-circular.

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