Router Bit

Abstract

To provide a router bit with reduced manufacturing costs. [Solution] The router bit (10) for machining a non-metallic workpiece (20) includes a main body (12) and peripheral cutting edges (14a, 14b) formed on the main body (12). The peripheral cutting edges (14a, 14b) are joined to a tip seat (36) provided on the body (12). The peripheral cutting edges (14a, 14b) have curved inner edges (44) on the tip seat (36) side when viewed from the rake surface.

Description

[Technical Field]

[0001] The present invention relates to a router bit for cutting a non-metallic workpiece and a method for manufacturing the router bit. [Background technology]

[0002] Router bits are known as tools used to cut wood-based, resin-based, or ceramic-based materials (see Patent Document 1). Because router bits are rotated at high speeds by a router machine, peripheral cutting edges made of cemented carbide alloys wear out quickly. For this reason, peripheral cutting edges made of sintered diamond are now commonly used. Sintered diamond is an expensive material, and its finishing process requires expensive electrical discharge machines, which tends to increase the product price. Furthermore, while peripheral cutting edges worn down with use can be resharpened using electrical discharge machines, such resharpening services using electrical discharge machines are sometimes unavailable in depopulated areas. Due to these circumstances, there is a growing demand for affordable router bits that can be used only once. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 10-146713 Summary of the Invention [Problem to be solved by the invention]

[0004] As shown in the comparative example of Figure 11, the peripheral cutting edge of the cutting section attached to the router bit is formed from a cutting tip 520 cut by wire cutting a diamond sintered body (blank 300). The cut cutting tip 520 is then attached to a tip sheet provided on the body of the router bit. In a typical cutting tip 520, when the rake face is viewed from the front, the edge on the tip sheet side (inner edge 440) is straight, while the edge on the opposite side to the tip sheet (outer edge 460) is curved, forming a so-called semi-cylindrical shape.

[0005] However, when cutting multiple such semi-cylindrical cutting tips 520 from a diamond sintered body (blank 300), as shown in FIG. 11, there is a drawback in that a large amount of wasted diamond sintered body (so-called cut loss W) is produced, resulting in a reduced number of cutting tips 520 being obtained from one blank 300. Furthermore, in conventional peripheral cutting tools, the cutting tips 520 are attached primarily by bonding the surface opposite the rake face of the cutting tip 520 (the back surface in FIG. 11) to the tip sheet. Therefore, in order to ensure the bonding strength (in other words, the contact area), it was necessary to increase the tip height h (see FIG. 10). Increasing the tip height h of the cutting tip 520 correspondingly reduces the number of cutting tips 520 that can be cut from one blank 300, which also contributes to the increased cost of the router bit.

[0006] The present disclosure aims to provide a router bit that reduces the cost of the peripheral cutting edge by reducing cutting loss during chip cutting. It also aims to provide a method for manufacturing a router bit that can efficiently cut chips and reduce manufacturing costs. [Means for solving the problem]

[0007] In view of the above problems, according to one aspect of the present disclosure, there is provided a router bit for processing a non-metallic workpiece, the router bit comprising: a main body; and a body formed on the main body and having a peripheral cutting edge;The peripheral cutting edge is a cutting tip cut out from a diamond sintered body consisting of a cemented carbide layer and a diamond layer, and is formed from a cutting tip having an outer edge portion and an inner edge portion which are a pair of parallel curved surfaces; The peripheral cutting edge is joined to the tip seat provided on the body, and is located on the tip seat side when viewed from the rake face. Concave surface Inner edge and the convex outer edge portion opposite the chip sheet; is curved. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a side view showing a router bit 10 according to an embodiment. [Figure 2] An explanatory diagram conceptually showing the function of the peripheral cutting edge of the router bit 10. [Figure 3] 2 is an enlarged perspective view showing one of the peripheral cutting edges 14a of the router bit 10 according to the embodiment. FIG. [Figure 4] 2 is an explanatory diagram showing the relationship between the outer edge portion 46 and the inner edge portion 44 of the peripheral cutting edge 14a according to the embodiment. FIG. [Figure 5] 1 is a flowchart showing a method for manufacturing a router bit 10 according to an embodiment. [Figure 6] 10 is an explanatory diagram showing how cut chips 52 are cut out from a blank 30. FIG. [Figure 7] FIG. 2 is a perspective view showing a blank 30. [Figure 8] FIG. 2 is a perspective view showing how cut chips 52 are cut out from a blank 30. [Figure 9] 10 is a perspective view showing a state in which a cutting tip 52 (peripheral cutting edge 14a) is joined to a tip sheet 36. FIG. [Figure 10] FIG. 2 is an enlarged perspective view of a peripheral blade 140a according to a comparative example. [Figure 11] 10 is an explanatory diagram showing a state in which a cut chip 520 is cut out from a blank 300 in a comparative example. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0009] Next, a router bit 10 according to this embodiment will be described with reference to the drawings. FIG. 1 is a side view of the router bit 10 of this embodiment. This router bit 10 is formed by sintering a cylindrical (round bar) body made of cemented carbide and then grinding away the surface of one end of the body with a grinding wheel. More specifically, one end of the body is ground to form a body 12, to which multiple cutting edges (more specifically, peripheral cutting edges 14a, 14b and bottom cutting edge 14c) are attached. The portion of the body other than the body 12 forms a shank 16, which is adapted to be attached to a processing device (not shown) such as an NC router.

[0010] The body 12 is formed with flutes 18, 19 for discharging chips generated during machining. The router bit 10 of this embodiment has a single main flute 18 and multiple sub-flutes 19, each formed by grinding. The main flute 18 is formed over the entire axial length of the body 12, from the tip side (bottom side) of the body 12 to the shank 16. The main flute 18 extends counterclockwise in a spiral pattern from the tip of the body 12 toward the shank 16. In this embodiment, the router bit 10 is a high-lead product in which the lead angle of the main flute 18 exceeds 45 degrees. For example, the lead angle of the main flute 18 is approximately 54 degrees.

[0011] Each sub-flute 19 is formed to communicate with the main flutes 18 lined up in the axial direction in the body 12. The peripheral cutting edges 14a, 14b are provided between the multiple sub-flutes 19. The sub-flute 19 is formed in a groove shape like the main flutes 18. The groove depth of the sub-flute 19 is shallower than that of the main flutes 18. The sub-flute 19 guides and discharges chips generated by the peripheral cutting edges 14a, 14b.

[0012] As shown in FIG. 1, the cutting edge is made up of multiple peripheral cutting edges 14a, 14b (six in this embodiment) and a single bottom cutting edge 14c. Each cutting edge is a tip formed from an ultra-high-pressure sintered material such as sintered diamond, and is joined to the side of the main flute 18 (more specifically, to the tip sheet 36 described below) in the body 12 by brazing. The bottom cutting edge 14c is joined to the tip of the body 12 and is used to drill holes in the workpiece. The peripheral cutting edges 14a, 14b are used to process the side surfaces of the workpiece and are made up of one peripheral cutting edge 14b (see FIG. 2) with a positive twist angle and five peripheral cutting edges 14a with negative twist angles.

[0013] The peripheral cutting edge 14b having a positive twist angle is provided at the tip of the body 12. The peripheral cutting edge 14b having a positive twist angle has a lead angle of, for example, approximately 54°. The peripheral cutting edge 14a having a negative twist angle is provided so as to be arranged in a spiral on the circumferential surface of the body 12. The peripheral cutting edges 14a having negative twist angles are each provided in an inclined position so as to have a lead angle along the extension direction of the main flutes 18. The lead angle of the peripheral cutting edge 14a having a negative twist angle is the same as the lead angle of the main flutes 18 described above (for example, approximately 54°).

[0014] Here, the reason why the peripheral cutting edges 14a, 14b are provided with positive and negative twist angles, respectively, will be explained. For example, a wood board 20, which is a wood-based material, is generally covered on both sides with decorative sheets such as printed paper or resin film. When processing such a wood board 20 with a router, as shown in FIG. 2, the wood board 20 is placed on an adhesive plate 31 installed on a surface plate (not shown) of an NC router, and the wood board 20 is attached to the adhesive plate 31. During drilling, the router bit 10 penetrates the wood board 20 and is pressed down until its tip bites into the adhesive plate 31. In this state, a pulling process is performed, and the router bit 10 cuts the wood board 20 while scraping the adhesive plate 31 with its tip.

[0015] Focusing on the function of the peripheral blades 14a, 14b during the pulling process, as described above, in this embodiment, the peripheral blades 14a, 14b are provided with strong positive and negative lead angles. One peripheral blade 14b with a positive twist angle cuts the underside 20b of the wood board 20, while one of the peripheral blades 14a with a negative twist angle cuts the upper side 20a of the wood board 20. By providing the peripheral blade 14b with a positive twist angle, the peripheral blade 14b applies an obliquely upward force (see arrow B in FIG. 2 ) to the underside 20b of the wood board 20 while cutting. This prevents the decorative sheet covering the underside 20b of the wood board 20 from turning up or becoming frayed. Meanwhile, the decorative sheet covering the upper side 20a of the wood board 20 is cut by the peripheral blade 14a with a negative twist angle while receiving an obliquely downward force (see arrow A in FIG. 2 ). This prevents the decorative sheet on the upper surface 20a of the wood board 20 from turning up or becoming frayed during cutting. Moreover, the peripheral cutting edges 14a and 14b have a strong lead angle, which increases the force that holds down the decorative sheet, improving the quality of the finished product.

[0016] (Configuration of the peripheral cutting edges 14a and 14b) Next, the specific configuration of the peripheral cutting edges 14a and 14b will be described in detail below. Figure 3 is a perspective view showing the peripheral cutting edges 14a and 14b (more specifically, one of the peripheral cutting edges 14a with a negative twist angle). The peripheral cutting edges 14a and 14b have substantially the same or similar shapes except for the fact that the twist angles are positive and opposite. Therefore, the following description will focus on the peripheral cutting edge 14a with a negative twist angle. The peripheral cutting edge 14a is made of a diamond sintered body 30 consisting of a cemented carbide layer 30a and a diamond layer 30b. Each peripheral cutting edge 14a is made of six faces. That is, the peripheral cutting edge 14a comprises a rake face 32, a rear face 34 located on the opposite side of the rake face 32, a joint face 38 located on the chip seat 36 side (the inner diameter side of the router bit 10) and abutting against the seating surface 36a of the chip seat 36, an outer peripheral face 40 located on the opposite side of the joint face 38 (chip seat 36), and a pair of side faces 42. The rake face 32 and the rear face 34 are flat and parallel to each other. The pair of side faces 42 are also flat and parallel to each other. On the other hand, the joint face 38 and the outer peripheral face 40 are curved surfaces and are not parallel to each other.

[0017] The rake face 32 is a flat surface formed by the diamond layer 30b. When the rake face 32 is viewed from the front side (hereinafter referred to as "rake face view"), the edge on the tip sheet 36 side (hereinafter referred to as inner edge 44) is curved.

[0018] The edge (hereinafter referred to as outer edge 46) opposite the inner edge 44 of the cutting face 32, which becomes the cutting edge of the peripheral cutting edge 14a, is also curved. Here, the peripheral cutting edge 14a is formed by, for example, laser processing or electrical discharge machining (hereinafter referred to as electrical discharge machining, etc.) of the outer peripheral surface 40 of the peripheral cutting edge 14a after bonding to the tip sheet 36 (sharpening, which will be described later). At this time, the outer edge 46 of the cutting face 32 is processed so as to curve along a predetermined elliptical shape when viewed from the rake face. In other words, the outer edge 46 of the cutting face 32 can be said to be defined by the outer peripheral surface 40 formed by electrical discharge machining.

[0019] 4 is a schematic diagram illustrating the relationship between the inner edge 44 and the outer edge 46 of the rake face 32. As shown in FIG. 4, the inner edge 44 of the rake face 32 is set to follow a predetermined circular shape O1 (a perfect circle). On the other hand, the outer edge 46 of the rake face 32 is set to follow a predetermined elliptical shape O2. Note that on the rake face 32, a pair of side edges connecting the outer edge 46 and the inner edge 44 are straight lines parallel to each other.

[0020] Table 1 shows the range of radii that can be used for the inner edge 44 when the diameter of the router bit 10 (main body) and the lead angle of the peripheral cutting edge 14a are changed. For router bits 10 of various diameters, when the lead angle (θ) is set within a predetermined range, it is desirable to set the radius (R) of the inner edge 44 of the peripheral cutting edge 14a within the following range. [Table 1]

[0021] The joining surface 38 of the peripheral cutting edge 14a is a surface curved in an arc shape. More specifically, the joining surface 38 is a concave surface that forms part of a cylindrical shape. The concave surface of the joining surface 38 follows the circular shape described by the inner edge portion 44 of the rake face 32. This joining surface 38 is mainly composed of a cemented carbide layer 30a. The portion of the joining surface 38 that corresponds to the cemented carbide layer 30a is joined to the seating surface 36a of the tip seat 36 by brazing.

[0022] As described above, the outer peripheral surface 40 of the peripheral cutting edge 14a is formed by electrical discharge machining or the like, and is a curved surface. More specifically, the outer peripheral surface 40 is a convex surface conforming to the elliptical shape O2 along which the outer edge 46 of the rake face 32 follows. This outer peripheral surface 40 is composed of a cemented carbide layer 30a and a diamond layer 30b. The rear surface 34 of the peripheral cutting edge 14a is composed only of the cemented carbide layer 30a and is a plane parallel to the rake face 32. The rear surface 34 is joined to the back surface 36b of the tip sheet 36 by brazing. The edge of the rear surface 34 facing the tip sheet 36 (hereinafter referred to as the inner edge) has the same arc shape as the rake face 32. In other words, the inner edge of the rear surface 34 is also curved to conform to a predetermined circular shape. It can also be said that the inner edge of the rear surface 34 is defined by the joining surface 38. On the other hand, the edge of the rear surface 34 opposite to the inner edge (hereinafter referred to as the outer edge) is curved to follow a predetermined elliptical shape, similar to the outer edge 46 of the rake face 32. It can also be said that the outer edge of the rear surface 34 is defined by the outer peripheral surface 40.

[0023] Each of the pair of side surfaces 42 of the peripheral cutting edge 14a has a trapezoidal shape with opposing sides parallel to each other. Of the sides of each side surface 42, the length of the side (horizontal side) that contacts the seat surface 36a of the tip seat 36 is longer than the side (height side) that defines the side edge of the rake face 32. Furthermore, of the sides of the side surface 42, the side (height side) that defines the side edge of the rear face 34 is shorter than the side that defines the side edge of the rake face 32. Note that the side (height side) that defines the side edge of the rear face 34 may be approximately equal to the side that defines the side edge of the rake face 32 (i.e., the shape of the side surface 42 may be approximately a parallelogram).

[0024] Furthermore, the angle γ of the corner of the side surface 42 of the peripheral cutting edge 14a, formed by the edge that contacts the bearing surface 36a of the tip seat 36 and the edge that contacts the back surface 36b of the tip seat 36, is a predetermined acute angle. This is achieved by cutting the workpiece (blank 30) at a predetermined angle when cutting the cut chips 52 by wire cutting in the cutting process described below. The angle γ of the corner of the side surface 42 is set appropriately taking into account the rake angle and clearance angle of the peripheral cutting edge.

[0025] (About the configuration of chip sheet 36) Six tip seats 36 are formed on the body 12, corresponding to the number of peripheral cutting edges 14a. Each tip seat 36 is composed of a seating surface 36a and a back surface 36b. The seating surface 36a is curved to match the mating surface 38 of the peripheral cutting edge 14a. More specifically, the seating surface 36a, like the mating surface 38, is an arc-shaped, upwardly convex cylindrical surface. This allows the mating surface 38 of the peripheral cutting edge 14a to abut against the seating surface 36a without any gap when the mating surface 38 is set on the seating surface 36a. Meanwhile, the back surface 36b is formed flat to correspond to the rear surface 34 of the peripheral cutting edge 14a. When the rear surface 34 of the peripheral cutting edge 14a is set on the back surface 36b, the rear surface 34 abuts against the back surface 36b without any gap.

[0026] The angle of the corner formed by the bearing surface 36a and the back surface 36b of the tip seat 36 is formed to be an acute angle in accordance with the angle γ formed by the corner of the peripheral cutting edge 14a described above, so that the corner of the peripheral cutting edge 14a fits into the corner formed by the bearing surface 36a and the back surface 36b with almost no gap.

[0027] (About the manufacturing method of router bit 10) Next, a method for manufacturing the router bit 10 will be described. As shown in Fig. 5, the method for manufacturing the router bit 10 according to this embodiment includes a cutting step S1, a tip sheet forming step S2, a joining step S3, and a blade sharpening step S4. Each step will be described below in order.

[0028] (Cutting process S1) As shown in FIG. 6, in the cutting step S1, a plurality of cutting tips 52 that become the peripheral cutting edge 14a of the router bit 10 are cut out from a diamond sintered body 30 (hereinafter also referred to as a blank 30) that is made of a cemented carbide layer 30a and a diamond layer 30b. As shown in FIG. 7, the blank 30 is formed into a disk shape from the cemented carbide layer 30a and the diamond layer 30b. In this case, the blank 30 has a cemented carbide layer 30a with a thickness of, for example, about 2.0 mm. In this manner, the cemented carbide layer 30a used in the embodiment is thicker than the usual cemented carbide layer 30a (about 1.6 mm). On the other hand, the diamond layer 30b has a general thickness (for example, about 0.5 mm).

[0029] As shown in FIG. 8, when wire cutting is performed, the metal wire cuts the blank 30 while inclined at a predetermined angle relative to the normal direction of the blank 30. More specifically, the blank 30 (workpiece) is held at a predetermined angle φ relative to the horizontal plane S, so that the metal wire cuts the blank 30 obliquely. The inclination angle φ is preferably 3°≦φ≦30°, more preferably 5°≦φ≦25°, taking into account the rake angle and clearance angle. By cutting the blank 30 at a predetermined angle relative to the horizontal plane S, the cut chip 52 has a parallelogram shape in side view (see FIG. 9). Furthermore, as described above, the blank 30 has a thicker cemented carbide layer 30a than usual. As a result, when viewed from the side, the side of the cut chip 52 including the cemented carbide layer 30a and the diamond layer 30b (horizontal side) is longer than the side defining the rake face 32 (height side). Furthermore, when the cut tip 52 is viewed from the side, the angle γ of the corner formed by the side corresponding to the seat surface 36a of the tip sheet 36 and the side corresponding to the back surface 36b of the tip sheet 36 is an acute angle (γ<90°).

[0030] Furthermore, as shown in FIG. 6, when wire cutting is performed, when the blank 30 is viewed from the normal direction (i.e., when viewed from the rake surface), arc-shaped cut chips 52 are cut out. The concave-side edge (i.e., inner edge 44) and the convex-side edge (i.e., outer edge 46) of each cut chip 52 have the same arc shape. In other words, the inner edge 44 of one adjacent cut chip 52 coincides with the outer edge 46 of the other cut chip 52. As a result, when the inner edge 44 of one cut chip 52 is cut, the outer edge 46 of the adjacent cut chip 52 is also cut out at the same time. This reduces material waste (cut loss W) when cutting the cut chips 52 and improves the efficiency of the cutting operation.

[0031] (Chip sheet forming process S2) In this process, a plurality of tip sheets 36 for joining cut tips 52 are formed on the main body (body 12) of the router bit 10. This tip sheet forming process S2 is performed independently of the cutting process S1. Therefore, the order in which the cutting process S1 and the tip sheet forming process S2 are performed does not matter. That is, the tip sheet forming process S2 may be performed before the cutting process S1, or the two processes may be performed simultaneously. In this embodiment, the main body of the router bit 10 is made of cemented carbide. Therefore, each tip sheet 36 is formed by processing the body 12 with a grinding wheel. However, in the case of a steel body, the tip sheets 36 may be formed using a milling tool.

[0032] In the tip sheet molding process, the seating surface 36a of the tip sheet 36 is formed to have a curved convex surface (cylindrical surface) that matches the joining surface 38 of the cut tip 52. Meanwhile, the back surface 36b of the tip sheet 36 is formed to have a flat shape. The tip sheet 36 is also formed so that the corners formed by the seating surface 36a and the back surface 36b form an acute angle. In this case, the angle formed by the corners of the seating surface 36a and the back surface 36b approximately matches the angle γ formed by the corners of the cut tip 52 when viewed from the side of the cut tip 52 (see FIG. 9).

[0033] (Joining process S3) In the joining step S3, the cut tip 52 is joined to the tip sheet 36 by brazing. However, the cut tip 52 may be joined to the tip sheet 36 by other methods. For example, the joining step S3 may be performed by laser welding or resistance welding. First, the joining surface 38 of the cut tip 52 is set on the seating surface 36a of the tip sheet 36. As described above, the seating surface 36a of the tip sheet 36 is formed to match the joining surface 38 of the cut tip 52. Therefore, the joining surface 38 of the cut tip 52 is tightly attached to the seating surface 36a of the tip sheet 36. The rear surface 34 of the cut tip 52 is set on the back surface 36b of the tip sheet 36. Then, brazing is performed with the joining surface 38 and rear surface 34 of the cut tip 52 aligned with the seating surface 36a and back surface 36b of the tip sheet 36. This firmly joins the cut tip 52 to the body 12 of the router bit 10.

[0034] By repeating the above steps, a plurality of cutting tips 52 are attached to the outer periphery of the body 12 as the peripheral cutting edge 14a.

[0035] (Blade sharpening process S4) In the sharpening step S4, the joined cutting tip 52 is subjected to finishing (sharpening). That is, the surface of the cutting tip 52 opposite the tip sheet 36 is subjected to electrical discharge machining using an electrical discharge machine. This sharpening may be performed by laser machining instead of electrical discharge machining. In this embodiment, this electrical discharge machining forms the outer edge 46 of the cutting tip 52 to have a predetermined elliptical shape when viewed from the rake face (see FIG. 3).

[0036] Here, the tip height h of the peripheral cutting edge 14a after electrical discharge machining (the height of the rake face 32 when viewed from the rake face) is set, for example, to 0.6 mm≦h≦5.0 mm. More preferably, it is set to 0.8 mm≦h≦3.0 mm. Thus, even when the tip height h is extremely low, such as 0.8 mm, by using a body 12 made of cemented carbide as in this embodiment, the cutting tip 52 can be replaced by re-brazing. Re-brazing is possible approximately 10 times, and the main body of the router bit 10 can be reused, thereby achieving significant cost reductions and a reduced environmental impact.

[0037] (Comparison with comparative examples) Next, the effects of the router bit 10 of this embodiment will be described in comparison with a comparative example. FIG. 10 is an enlarged perspective view of the peripheral cutting edge 140a of the router bit 100 of the comparative example. As described above, the peripheral cutting edge 140a of the comparative example is formed in a semi-cylindrical shape. FIG. 11 is a schematic diagram showing the cutting of cutting tips 520 from the peripheral cutting edge 140a of the comparative example. In the comparative example, a blank 300 is used, which is composed of a cemented carbide layer 300a of a normal thickness (e.g., 1.6 mm) and a diamond layer 300b of a normal thickness (e.g., 0.5 mm). In the comparative example, each cutting tip 520 is cut out in a semi-cylindrical shape when viewed from the rake surface. That is, the outer edge 460 of the cutting tip 520 is cut out in an arc shape, and the inner edge 440 of the cutting tip 520 is cut out in a linear shape. In this way, in the comparative example, the upper edge portion and the inner edge portion 440 of adjacent cut chips 520 are cut out separately, which increases the cut loss W and reduces the efficiency of the cutting process.

[0038] In the comparative example, when cutting out the cut chips 520, the blank 300 is cut while being held in a position parallel to the horizontal plane S. As a result, the cut out cut chips 520 have a rectangular shape in a side view.

[0039] In the peripheral cutting edge 140a of the comparative example, as with the router bit 10 of the embodiment, the outer edge 460 of the rake face 320 is curved to conform to a predetermined elliptical shape by sharpening. On the other hand, the inner edge 440 of the rake face 320 of the peripheral cutting edge 140a of the comparative example extends linearly. That is, the joining surface 380 of the peripheral cutting edge 140a of the comparative example is flat. The seating surface 360a of the tip seat 360 is also formed flat to match the shape of this joining surface 380. The back surface 360b of the tip seat 360 is also formed flat, as in the embodiment.

[0040] The peripheral cutting blade 140a of the comparative example has a trapezoidal shape in side view. However, the angle γ between the joining surface 380 and the rear surface 340 of the peripheral cutting blade 140a is a right angle (γ = 90°). Furthermore, in side view of the peripheral cutting blade 140a, the horizontal length of the trapezoidal side surface 420 is shorter than the vertical length. When attaching the peripheral cutting blade 140a to the body 120, as in the embodiment, the joining surface 380 and the rear surface 340 of the peripheral cutting blade 140a are set on the seat surface 360a and the rear surface 360b of the tip sheet 360, respectively, and then joined by brazing. At this time, since the tip height h of the peripheral cutting blade 140a is set large, a large contact area is ensured between the rear surface 340 of the peripheral cutting blade 140a and the rear surface 360b of the tip sheet 360. Therefore, the peripheral cutting edge 140a is attached to the body 120 mainly by joining the rear surface 340 and the back surface 360b. In other words, in the comparative example, by increasing the height dimension of the rear surface 340 of the peripheral cutting edge 140a, the contact area with the back surface 360b of the tip sheet 360 is secured, and the joining strength between the peripheral cutting edge 140a and the tip sheet 360 is obtained. Therefore, in the comparative example, the tip height h is larger than in the embodiment, and the area of ​​the diamond layer 300b of the peripheral cutting edge 140a is also increased. As a result, the cost per peripheral cutting edge 140a is higher than that of the peripheral cutting edge 140a of the embodiment.

[0041] On the other hand, as shown in FIG. 3, the router bit 10 according to this embodiment has a shape in which the horizontal length is greater than the vertical length in side view. Therefore, the contact area between the joining surface 38 of the peripheral cutting edge 14a and the seating surface 36a of the tip seat 36 significantly contributes to the bonding between the peripheral cutting edge 14a and the body 12. Furthermore, in this embodiment, the joining surface 38 of the peripheral cutting edge 14a is curved in an arc (cylindrical) shape, further ensuring a larger contact area with the seating surface 36a. This increases the bonding strength between the peripheral cutting edge 14a and the tip seat 36, enabling the peripheral cutting edge 14a to be firmly attached to the body 12. Therefore, unlike the comparative example, there is no need to increase the tip height, and the area of ​​the diamond layer 30b used per peripheral cutting edge 14a can be reduced. As a result, the cost of the router bit 10 can be reduced. It is generally known that the price of a sintered diamond blank is proportional only to the area of ​​the diamond layer and is hardly affected by its thickness.

[0042] Moreover, as described above, in this embodiment, the outer edge 46 and the inner edge 44 of the cut chip 52 have the same arc shape. Therefore, as shown in Fig. 6, the cut chip 52 can be efficiently cut out from the blank 30, and the amount of cut loss W can also be reduced.

[0043] (Example of change) The router bit 10 and the manufacturing method thereof according to the above-described embodiment are merely examples of the present disclosure, and various modifications are possible as described below.

[0044] In the router bit 10 according to the embodiment, the inner edge 44 of the rake face 32 of the peripheral cutting edge 14a has an arc shape. However, the inner edge 44 of the rake face 32 of the peripheral cutting edge 14a may be curved along an elliptical shape. In other words, when cutting the cut chips 52 from the blank 30, the outer edge 46 and the inner edge 44 of the rake face 32 of the cut chips 52 may be curved along the same elliptical shape.

[0045] In the router bit 10 according to the embodiment, the peripheral cutting edge 14a has a trapezoidal shape in which the horizontal sides are longer than the vertical sides in a side view. However, the side surface 42 of the peripheral cutting edge 14a may have a trapezoidal shape in which the horizontal sides are shorter than the vertical sides. Furthermore, as in the side surface 42 of the peripheral cutting edge 14a according to the embodiment, the angle of the corner formed by the joining surface 38 and the rear surface 34 does not necessarily have to be an acute angle, and may be a right angle as in the comparative example.

[0046] In the embodiment, the main body of the router bit 10 is made of cemented carbide. However, the material of the router bit 10 is not limited to cemented carbide, and the router bit 10 may be made of, for example, steel or heavy metal.

[0047] In the embodiment, a case where a wood board is cut as the cutting material is shown, but the cutting material is not limited to such wood-based materials. For example, the router bit 10 of the present invention can also be suitably used when cutting resin-based materials such as plastics. [Explanation of symbols]

[0048] 10...Router bit 12...Body 14a...Peripheral blade 14b…Peripheral blade 20...Material to be cut 30...Sintered diamond 30a...Cemented carbide layer 30b...diamond layer 36...Chip sheet 36a...seat 36b…Back 44...Inner edge 46...Outer edge 52...Cut chip S1: Cutting process S2: Chip sheet forming process S3…Joining process O1: Circular O2: Oval shape S…Horizontal surface

Claims

1. A router bit (10) for machining a non-metallic workpiece (20), a main body; a body (12) formed on the main body portion and having peripheral cutting edges (14a, 14b); The peripheral cutting edge is formed from a plurality of cutting tips (52) cut out from a diamond sintered body (30) consisting of a cemented carbide layer (30a) and a diamond layer (30b), the cutting tips (52) having an outer edge portion (46) and an inner edge portion (44) which are a pair of parallel curved surfaces, The peripheral cutting edges (14a, 14b) are joined to a tip seat (36) provided on the body (12), and when viewed from the rake surface, the concave inner edge portion (44) on the tip seat (36) side and the convex outer edge portion (46) on the opposite side to the tip seat are curved. A router bit characterized by:

2. The inner edge (44) of the peripheral cutting edge (14a, 14b) has a circular shape (O １ 2. The router bit of claim 1, wherein the router bit is curved along a curved edge.

3. The router bit according to claim 1, wherein the inner edges (44) of the peripheral cutting edges (14a, 14b) are curved along an elliptical shape.

4. The outer edge portion (46) is finished to have an elliptical shape (O ２ ) and is curved along the The inner edge (44) of the peripheral cutting edge (14a, 14b) has a circular shape (O １ 2. The router bit of claim 1, wherein the router bit is curved along a curved edge.

5. The tip seat (36) has a seat surface (36a) and a back surface (36b), 2. The router bit according to claim 1, wherein the bearing surface (36a) is curved to match the shape of the inner edge (44) of the peripheral cutting edge (14a, 14b).

6. The peripheral cutting edges (14a, 14b) are trapezoidal in side view, 6. The router bit according to claim 5, wherein the bearing surface (36a) and the back surface (36b) form an acute angle in side view corresponding to the trapezoidal shape of the peripheral cutting edge (14a, 14b).

7. The router bit according to claim 1, wherein the peripheral cutting edges (14a, 14b) are trapezoidal in side view with a lateral side longer than a height side.

8. The router bit according to claim 1, wherein the peripheral cutting edges (14a, 14b) are trapezoidal in side view, with lateral sides shorter than vertical sides.

9. The router bit according to claim 1, wherein the peripheral cutting edges (14a, 14b) are parallelogram-shaped in a side view, with the lateral sides longer than the height sides.

10. The router bit of claim 1 , wherein the body portion is formed from a cemented carbide alloy.

11. The router bit of claim 1 , wherein the body is formed from steel.

12. A method for manufacturing a router bit (10) for processing a non-metallic workpiece (20), comprising: A step (S1) of cutting out a plurality of cut chips (52) having a pair of parallel curved surfaces, that is, a convex surface and a concave surface, from a diamond sintered body (30) consisting of a cemented carbide layer (30a) and a diamond layer (30b); a step (S2) of forming a tip seat (36) on the body (12) of the main body portion, the tip seat having a convex bearing surface (36a) curved to match the concave surface of the cut tip (52); and a step (S3) of attaching the cutting tip (52) to the body (12) as a peripheral cutting edge (14a, 14b) by joining the concave surface of the cutting tip (52) to the seat surface (36a). A method for manufacturing a router bit.

13. The method for manufacturing a router bit according to claim 12, wherein the cut tip (52) is cut from the diamond sintered body (30) so that the convex surface and the concave surface are cylindrically curved.

14. 13. A method for manufacturing a router bit as described in claim 12, wherein the diamond sintered body (30) is cut in an attitude inclined at a predetermined angle with respect to a horizontal plane (S), so that the cut chip (52) has a parallelogram shape with its horizontal sides longer than its height sides when viewed from the side when attached to the body (12).

15. A method for manufacturing a router bit as described in claim 12, further comprising a step (S4) of finishing the convex surface of the cutting tip.

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