WO2024014008A1

WO2024014008A1 - Router bit

Info

Publication number: WO2024014008A1
Application number: PCT/JP2022/033001
Authority: WO
Inventors: 史晶高橋; 真二丹羽; 剣華張
Original assignee: 高橋刃物工業株式会社
Priority date: 2022-07-13
Filing date: 2022-09-01
Publication date: 2024-01-18

Abstract

Provided is a router bit (10) which machines a material (20) to be cut and comprises a main body portion which is made of cemented carbide and a body (12) which is formed by cutting one end side of the main body portion and is provided with a blade portion (14). The body (12) is provided with a main flute (18) and a sub flute (19) which discharge chips of the material (20) to be cut. Porosity R in an overall effective blade length (L) of the body (12) is set to 52%≤R≤75%.

Description

router bits

The present invention relates to a router bit for cutting a material to be cut.

A router bit is known as a tool for cutting materials such as wood-based or resin-based organic materials, their composite materials, and ceramic-based inorganic materials (i.e., non-metallic materials) (Patent Document 1) reference). Conventional router bits have a main body made of carbon steel, tool steel, or the like, and a blade made of an ultra-hard sintered body. Then, the router bit is attached to a cutting machine such as an NC router and used for drilling (in the Z direction) and pulling (in the X and Y directions) of the material to be cut.

Japanese Patent Application Publication No. 10-146713

Such router bits generally have a groove-like chip path called a flute formed in the body. For example, when cutting a wooden board as a material to be cut, chips generated during cutting (particularly during drilling) are guided by a flute and discharged upward in the Z direction. However, in machining with a router bit, the material to be cut is usually subjected to tension processing after drilling, so the router bit always performs cutting in a closed or semi-closed state. Therefore, the chips tend to stagnate within the flute, and the flute may become clogged with chips. In particular, when using wood-based or resin-based materials, the chips tend to expand to a large extent (approximately three times the volume) and tend to clog the flute.

As a result, there is a problem in that the discharge of chips by the flute is inhibited, and the power required for cutting, or more precisely, the power required for discharge of chips, increases. Further, when the discharge of chips is inhibited, the cutting surface becomes hot due to friction, and so-called "scorching" may occur. When such burns occur, cutting quality deteriorates, and in the worst case scenario, the cutting surface becomes so hot that chips and dust may ignite, resulting in a fire. In addition, there is also the problem that if the discharge of chips becomes poor, the noise during cutting increases.
The problem to be solved by the present disclosure is to provide a router bit that has significantly improved ability to discharge chips generated during cutting.

In view of the above problems, according to one aspect of the present disclosure, there is provided a router bit (10) for processing a material to be cut (20), comprising:
A main body made of cemented carbide,
a body (12) formed by grinding one end side of the main body portion and provided with a blade portion (14);
The body (12) includes a main flute (18) and a secondary flute (19) for discharging chips of the material to be cut (20),
The porosity R in the overall effective blade length (L) of the body (12) is set to 52%≦R≦75%.

FIG. 1 is a perspective view showing a router bit according to a first embodiment. FIG. 2 is a side view showing the router bit according to the first embodiment. FIG. 2 is an explanatory diagram conceptually showing the functions of the bottom blade and the outer peripheral blade of the router bit. FIG. 2 is an explanatory diagram conceptually showing how a wooden board is drilled and stretched, and shows that up-cutting and down-cutting are performed simultaneously during stretching. (a) is an explanatory diagram conceptually showing how a wooden board is up-cut, and (b) is an explanatory diagram conceptually showing how a wooden board is down-cut. 2 is a graph showing the experimental results of Experimental Example 1, showing the relationship between chip evacuation power and porosity. It is a side view which expands and shows the body of a router bit. FIG. 3 is a developed view schematically showing the body. 7A is a sectional view of the body, (a) is a sectional view taken along the line IX(a)-IV(a) in FIG. 7; FIG. (c) is a sectional view taken along line IX(c)-IV(c) in FIG. 7. FIG. 7 is a cross-sectional view of the third region of the body. FIG. 2 is a cross-sectional view showing a router bit according to a first embodiment and a router bit according to a comparative example, in which (a) shows the router bit according to the first embodiment, and (b) shows a router bit according to a comparative example. Shows router bits. FIG. 7 is an exploded view schematically showing the body of a router bit according to a second embodiment. FIG. 7 is an exploded view schematically showing the body of a router bit according to a third embodiment. FIG. 7 is a developed view schematically showing the body of a router bit according to a fourth embodiment.

(First embodiment)
Next, the router bit 10 according to the first embodiment will be explained below with reference to the drawings. FIG. 1 is an overall perspective view showing a router bit 10 of the first embodiment, and FIG. 2 is a side view of the router bit 10. This router bit 10 is formed by sintering a columnar (round bar) main body made of cemented carbide and grinding the surface of one end of the main body with a grindstone. More specifically, a body 12 is formed by grinding one end side of the main body, and a plurality of blade parts 14 (more specifically, three peripheral blades 14a and a bottom blade 14b) are attached to the body 12. ing. In the following description, the peripheral blades 14a that are closest to the bottom blade 14b may be referred to as first to third peripheral blades 14a in order. Further, in the main body, the portion other than the body 12 is a shank 16, and the shank 16 is attached to a cutting machine (not shown) such as an NC router.

As shown in FIG. 7, the effective blade length L of the router bit 10 is defined as the distance in the axial direction from the bottom blade 14b to the peripheral blade 14a (i.e., the third peripheral blade 14a) closest to the shank 16. In the following description, the effective blade length from the bottom blade 14b to the third outer peripheral blade 14a of this router bit 10 will be referred to as the overall effective blade length L. Further, among the overall effective blade length L, the effective blade length formed by the three peripheral blades 14a is defined as the peripheral blade effective blade length l. In this embodiment, the total effective blade length L is increased by providing three peripheral blades 14a. More specifically, the overall effective blade length L of the router bit 10 is approximately twice the blade diameter (the length in the radial direction from the rotation center of the router bit 10 to the cutting edge of the blade portion 14). However, by forming the router bit 10 from cemented carbide, the overall effective blade length L can be increased to about three times the blade diameter.

As shown in FIG. 7, the body 12 is conceptually divided into a plurality of regions along the axial direction at a portion corresponding to the overall effective blade length L of the router bit 10. In this embodiment, the body 12 is divided into first to third regions A1 to A3 from the distal end toward the shank 16. The body 12 is formed with

flutes

18 and 19 for discharging chips generated during machining. As shown in FIGS. 1 and 2, in this embodiment, a single main flute 18 and a plurality of sub-flutes 19 are each formed by grinding using a grindstone. The main flute 18 is formed from the tip end side (blade bottom side) of the body 12 to the shank 16 over the entire axial direction of the body 12. That is, the main flute 18 extends in the form of one groove over the first to third regions A1 to A3 of the body 12. The main flute 18 is formed so as to hollow out the body 12 to the vicinity of the rotation center (see FIG. 9), and extends spirally from the tip of the body 12 toward the shank 16 in a clockwise direction. As will be described later, the main flute 18 has a chip discharge function that sends out chips generated from the material to be cut during machining from the tip side of the body 12 to the shank 16 side.

The main flute 18 of this embodiment is set such that the lead angle θ on the tip side of the body 12 is larger on the shank 16 side of the body 12 than on the tip side (blade edge side) of the body 12. More specifically, as shown in the developed view of FIG. 8, the lead angle θ3 in the third region A3 of the main flute 18 is larger than the lead angle θ2 in the second region A2, and the lead angle θ2 in the second region A2 is The lead angle θ1 is larger than the lead angle θ1 in the first region A1. For example, the lead angles θ1, θ2, and θ3 are set to 25°, 35°, and 53°, respectively, but the lead angles are not limited to these values.

As mentioned above, the lead angle θ1 of the main flute 18 in the first region A1 has the smallest value. This is because it is necessary to reduce the lead angle θ of the main flute 18 on the cutting edge side (that is, the first region A1) in order to make the rake angle of the bottom blade 14b 20° or less. This is because if the rake angle of the bottom blade 14b is made larger than 20°, chipping of the cutting edge is likely to occur. The rake angle of the bottom blade 14b is defined by the lead angle θ1 on the cutting edge side of the main flute 18. Therefore, in order to make the rake angle of the bottom blade 14b 20 degrees or less, it is necessary to suppress the lead angle θ1 of the main flute 18 to about 25 degrees at the maximum. Therefore, in this embodiment, the lead angle θ1 of the main flute 18 is set to about 25°, and the values of the lead angles θ2 and θ3 are gradually increased toward the shank 16 side.

9A to 9C are cross-sectional views of the router bit 10 in areas A1 to A3, respectively, and are cross-sectional views taken along lines IX(a)-IX(a) and IX(b)- This corresponds to a cross-sectional view taken along the line IX(b) and a cross-sectional view taken along the line IX(c)-IX(c). Note that the line IX(a)-IX(a) in FIG. 9(a) is located in the first region A1 and within the effective length l of the outer peripheral blade. In this embodiment, the circumferential width W of the main flute 18 is set to be larger on the shank 16 side (see FIG. 9(c)) than on the distal end side of the body 12 (see FIG. 9(a)). ing. More specifically, the circumferential width W of the main flute 18 is larger on the shank 16 side than on the distal end side of the body 12 within the effective cutting length l of the outer peripheral edge of the body 12. Further, the width W in the circumferential direction of the main flute 18 gradually increases from the first to third regions A1 to A3 within the effective length l of the outer peripheral blade of the body 12. That is, when the circumferential widths of the main flute 18 in the first to third areas A1 to A3 are defined as W1 to W3, W1<W2<W3. Note that within the effective length l of the outer peripheral blade, the widths W1 to W3 of the main flute 18 in each region A1 to A3 are constant. Further, as shown in FIG. 9, the groove depth D of the main flute 18 in this embodiment is constant in all areas A1 to A3.

As shown in FIG. 8, among the edges defining the main flute 18, the front edge in the rotation direction of the router bit 10 is defined as the front edge 18a, and the rear edge in the rotation direction of the router bit 10 is defined as the rear edge 18b. In this embodiment, the main flute 18 extends rearward in the rotational direction after the front edge 18a of the second region A2 once swells forward in the rotational direction with respect to the front edge 18a of the first region A1. Furthermore, with respect to the front edge 18a of the second area A2, the front edge 18a of the third area A3 once swells forward in the rotational direction and then extends rearward in the rotational direction. The front edge 18a of the first area A1 and the front edge 18a of the second area A2 are connected by a stepped connecting portion 22. Similarly, the front edge 18a of the second area A2 and the front edge 18a of the third area A3 are connected by a stepped connecting portion 22. In this way, by expanding the front edge 18a in the first to third areas A1 to A3 in stages and increasing the lead angles θ1 to θ3 of the main flute 18 in stages, the circumferential direction of the main flute 18 can be increased. The widths W1 to W3 are increased in stages.

Here, the front edge 18a and the rear edge 18b in the first region A1 extend linearly parallel to each other. Similarly, the front edge 18a and the rear edge 18b in the second area A2 and the front edge 18a and the rear edge 18b in the third area A3 extend linearly parallel to each other. Furthermore, in the router bit 10 of this embodiment, as shown in the cross-sectional view of FIG. 10, the front edge 18a of the main flute 18 is shaped to extend in the circumferential direction and has a clearance angle. Therefore, chips generated during cutting can be smoothly accommodated in the main flute 18 from the front edge 18a. On the other hand, the rear edge 18b of the main flute 18 is formed into a sharp acute angle shape and has a rake angle. As a result, the chips stored in the main flute 18 are firmly captured by the rear edge 18b, making it difficult for them to escape from the main flute 18.

As mentioned above, by multiplying the lead angle θ of the main flute 18 on the shank 16 side and increasing it in stages, and by multiplying the circumferential width W of the main flute 18 on the shank 16 side and increasing it in stages, The main flute 18 can be largely expanded (extended) in the circumferential direction. As a result, as shown in FIG. 10, when the main flute 18 is viewed from the axial direction, it is possible to increase the torsional expansion angle α indicating the range in which the main flute 18 extends in the circumferential direction of the body 12. As shown in FIG. 8, this twist development angle α is calculated from a starting point P1 closest to the tip of the body 12 on the main flute 18 to an ending point P2 on the main flute 18 closest to the shank 16, with the center of rotation of the router bit 10 as the center. defined as the angle up to It is desirable that this twist development angle α is set to 150° or more. More preferably, the twist development angle α is set to 180° or more. In this embodiment, the twist development angle α is set to approximately 270°.

FIG. 11 is a diagram comparing the twist development angle α in the router bit 10 of this embodiment and a router bit as a comparative example. FIG. 11(a) is a cross-sectional view of the router bit 10 of the present embodiment in areas A1 to A3, and FIG. 11(b) is a cross-sectional view of the router bit according to the comparative example in areas A1 to A3. . The router bit according to the comparative example is made of a steel material commonly used in conventional products, and is formed by cutting the main flute with a ball end mill. In the router bit according to the comparative example, the lead angle of the main flute is constant at 15°. As described above, when the lead angle is kept constant at 15 degrees, the twist development angle α of the main flute is about 120 degrees, which is smaller than the twist development angle α of the router bit 10 of this embodiment. As will be described later, by making the twist development angle α of the main flute 18 larger than 180°, the overall weight balance of the router bit 10 can be improved.

Further, as shown in FIG. 11(b), in the router bit of the comparative example, the cross section of the main flute has the same arc shape in all regions. Therefore, in the router bit of the comparative example, the width of the main flute is also constant (W). Furthermore, in the router bit of the comparative example, both the front edge and the rear edge of the main flute have an acute-angled shape. Therefore, in the router bit of the comparative example, the front edge of the main flute does not have a shape extending in the circumferential direction (a shape having a clearance angle) as in the present embodiment.

Each sub-flute 19 is provided in a portion of the body 12 where the main flute 18 is not formed, corresponding to each peripheral blade 14a described later. The auxiliary flute 19, like the main flute 18, is ground into a groove shape using a grindstone. The groove depth of the sub-flutes 19 is shallower than that of the main flute 18, and each sub-flute 19 communicates with the main flute 18. The auxiliary flute 19 is configured to guide chips generated by the outer peripheral blade 18a to the main flute 18. In this way, the body 12 of the router bit 10 (more specifically, the portion of the body 12 corresponding to the effective cutting length L) is largely ground away by forming the main flute 18 and the plurality of sub-flutes 19 through the grinding process. It has a solid structure. In other words, by forming the deep and long main flute 18 and the plurality of sub-flutes 19 in the body 12, a large void is formed in the router bit 10, and as a result, it has a large void ratio R. Note that the main flute 18 and the plurality of sub-flutes 19, which are present in a portion of the body 12 corresponding to the overall effective blade length L, greatly contribute to the porosity R. However, what defines the porosity R is not limited to the main flute 18 and the sub flute 19, but includes the portion removed to form the body 12. In other words, the porosity R of the body 12 is defined by all the recesses formed by removing the portions other than the blade portion 14. A detailed definition of the porosity R will be described later.

As shown in FIG. 2, the blade portion 14 consists of a plurality of peripheral blades 14a (three in this embodiment) and a single bottom blade 14b. Each blade part 14 is a chip formed from an ultra-high pressure sintered body such as sintered diamond, and is joined to the side surface (more specifically, the blade body) of each sub-flute 19 in the body 12 by brazing or the like. . The bottom blade (core blade) 14b is joined to the tip of the body 12 and is used for drilling holes in the material to be cut. The bottom blade 14b is also used for side surface machining of the material to be cut. As shown in FIG. 3, the bottom blade 14b is provided on the body 12 so as to have a positive twist angle. The peripheral blade 14a is used for side surface machining of the material to be cut, and as shown in FIG. 3, is provided on the body 12 so as to have a negative twist angle.

Here, the reason why the bottom blade 14b and the peripheral blade 14a are provided to have a positive twist angle and a negative twist angle, respectively, will be explained. For example, the wood-based board 20, which is a wood-based material, is generally covered on both sides with a decorative sheet such as printed paper or resin film. When processing such a wooden board 20 with a router, as shown in FIG. The board 20 is in a state of being attracted to the suction plate 32. During drilling, the router bit 10 penetrates the wooden board 20 and is pushed down until its tip bites into the suction plate 32. In this state, tension processing is performed, and the router bit 10 cuts the wooden board 20 while scraping the suction plate 32 with its tip.

In this way, during drilling and tensioning, although the upper and

lower surfaces

20a and 20b of the wooden board 20 are penetrated by the router bit 10, the lower surface 20b of the wooden board 20 is always closed by the suction plate 32. be. Therefore, the chips generated during machining are not discharged from the bottom of the wooden board 20, but are discharged from the top of the wooden board 20 during drilling, and from the top of the wooden board 20 and the router during tensioning. Chips are discharged from the opposite side of the bit 10 in the feeding direction. Therefore, a dust collector (not shown) is installed in the NC router, and when the wooden board 20 is processed, a strong upward suction pressure is applied from the dust collector to the wooden board 20, and the chips are sucked upward. It is now possible to

Here, paying attention to the functions of the outer peripheral blade 14a and the bottom blade 14b during tension processing, the bottom blade 14b cuts the lower surface 20b of the wooden board 20, and one of the plurality of peripheral blades 14a cuts the upper surface of the wooden board 20. 20a will be cut. By giving the bottom blade 14b a positive twist angle, the bottom blade 14b performs cutting while applying a diagonally upward force (see arrow B in FIG. 3) to the lower surface 20b of the wooden board 20. For this reason, the decorative sheet covering the lower surface 20b of the wooden board 20 is prevented from turning up or fuzzing. On the other hand, the decorative sheet covering the upper surface 20a of the wooden board 20 is cut while being subjected to an oblique downward force by the peripheral blade 14a having a negative twist angle (see arrow A in FIG. 3). For this reason, the decorative sheet on the upper surface 20a of the wooden board 20 is also prevented from turning up or fuzzing during cutting.

In this way, by giving a positive helix angle to the bottom blade 14b and giving a negative helix angle to the peripheral blade 14a, it is possible to improve the finish quality, while also reducing the discharge of chips as described below. It can also be a cause of inhibition. As mentioned above, the lower surface 20b of the wooden board 20 is closed by the suction plate 32 during processing, so only the upper side of the wooden board 20 is closed during drilling, and the upper side of the wooden board 20 and the router are closed during tension processing. Only the opposite side of the bit 10 in the feeding direction is in an open state. Therefore, especially during drilling, there is almost no gap between the router bit 10 and the hole formed in the wooden board 20, and chips escape into the main flute 18. Therefore, the chips are sent upward along the main flute 18 and are discharged upward by the suction force of the dust collector.

As described above, since the bottom blade 14b provided at the tip of the router bit 10 has a positive twist angle, the bottom blade 14b acts in the direction of pushing the chips upward. On the other hand, since the peripheral blade 14a has a negative twist angle, it acts to suppress chips downward. Therefore, downward pressure is applied from the outer circumferential cutter 14a to the chips trying to move upward along the main flute 18. As a result, the discharge of chips is obstructed by the plurality of peripheral blades 14a, making it easier for chips to stagnate and accumulate within the main flute 18, which becomes a factor in increasing cutting resistance. Particularly, in the router bit 10 having a long overall effective blade length L by being provided with a plurality of peripheral blades 14a as in the present embodiment, stagnation and accumulation of chips becomes remarkable. Such an increase in cutting resistance results in an increase in the power required for cutting, which in turn leads to an increase in power consumption required for cutting. Further, an increase in cutting resistance causes an increase in noise generated during machining, and also causes burns on the material to be cut due to chips stuck in the main flute 18. In the worst case scenario, the increased frictional resistance could ignite chips and dust, leading to a dust explosion.

In order to overcome such problems, the inventors of the present application maximized the space (gap) in the overall effective flute length L of the body 12 between the main flute 18 and the sub flute 19, thereby reducing the amount of chips during cutting. I tried to make sure there was enough space for them to escape. In order to ensure sufficient rigidity even with such a large porosity R, the inventors of the present application used steel, which has been used in router bits for non-metallic materials, as the base material of the router bit 10. We decided to use cemented carbide, which is difficult to mold, instead of solid wood.

Here, in this embodiment, the porosity R is defined as follows. In the overall effective cutting length L of the body 12 of the router bit 10, the space created by forming the main flute 18 and the sub-flutes 19 is the same as the space created by the main flute 18 and the sub-flutes 19, etc. The ratio to the volume (see the broken line in FIG. 2) is defined as the porosity R. As a specific method for measuring the porosity R, for example, the body 12 of the router bit 10 is immersed in a measurement container filled with water for the total effective blade length L, and the weight of the water overflowing from the container is measured. Measure. The amount of water that overflows is the weight of a portion corresponding to the entire effective blade length L of the body 12 in a state where the main flute 18, the sub flute 19, etc. are formed by polishing. By removing the weight of the overflowing water from the volume of the body 12 before the main flute 18 and the sub-flutes 19 are formed (hereinafter referred to as the total body volume), the removed parts such as the main flute 18 and the sub-flutes 19 are removed. The weight of the body 12 removed (hereinafter referred to as the void volume of the body 12) is determined as follows. Then, the void ratio R is determined by dividing the calculated void amount of the body 12 by the entire body amount.

The porosity R of the router bit 10 according to this embodiment is set to 69%. However, the porosity R may be set to 52% to 75%. More preferably, the porosity R of the router bit 10 is set to 55% to 72%. As shown in Experimental Examples 1 and 2, which will be described later, by setting the porosity R to 55% or more, it becomes possible to efficiently discharge chips during cutting, and the power consumption during cutting (more details will be explained later). This makes it possible to significantly reduce the amount of power required for ejecting chips. On the other hand, if the porosity R of the body 12 is set too large, the rigidity and strength of the router bit 10 will be affected even if it is made of cemented carbide. Therefore, in order to ensure practical rigidity as the router bit 10, it is desirable that the porosity R be 72% or less. Note that the porosity R of the common steel-based router bits 10 that are currently in circulation is about 45%, and about 50% at most. This is because if the porosity R is greater than 50% in the router bit 10 made of a steel base material, the rigidity will be reduced and the cutting performance will be reduced due to deformation of the body and chips will easily occur.

Here, the main flute 18 that is present throughout the entire axial direction of the body 12 greatly contributes to the porosity R of the router bit 10. Among the porosity R of the router bit 10, the porosity due to the main flute 18 is defined as the flute porosity r. This flute porosity r can be calculated from the design model of the router bit 10. For example, the flute porosity r is calculated by determining the ratio of the area of the main flute 18 to the area of the entire router bit 10 (area of a circle) in the cross-sectional view of the router bit 10 shown in FIG. be done. As described above, the lead angle α of the main flute 18 gradually increases from the distal end side of the body 12 to the shank 16 side. Furthermore, the width W in the circumferential direction of the main flute 18 gradually increases from the tip side of the body 12 to the shank 16 side within the effective length l of the outer peripheral edge of the body 12. As a result, the flute porosity r of the main flute 18 is larger on the shank 16 side than on the distal end side of the body 12 in the effective edge length l of the outer peripheral edge of the body 12. Note that the main flute 18 is formed large at the tip of the router bit 10. That is, as shown in FIG. 7, the flute porosity r of the main flute 18 is maximum on the outside (tip side) of the effective edge length l of the outer peripheral edge in the first region A1 including the bottom edge 14b. However, the flute porosity r of the main flute 18 is larger on the shank 16 side of the body 12 than on the tip side of the body 12 within the effective edge length l of the outer peripheral blade.

More specifically, as shown in FIG. 9, the flute porosity r of the main flute 18 gradually increases from the first to third regions A1 to A3 within the effective length l of the outer peripheral blade ( As described above, FIG. 9(a) is a cross-sectional view taken along line IX(a)-IX(a) in the first region A1 and within the effective cutting length l of the outer peripheral blade). That is, assuming that the flute porosity in the first to third regions A1 to A3 is r1 to r3, r1<r2<r3 within the effective length l of the outer peripheral blade. More specifically, in this embodiment, the flute porosity r1, r2, and r3 are 18.2%, 20.4%, and 23.7%, respectively.

As mentioned above, the chips generated during cutting are sent upward in the main flute 18 by the suction pressure from the dust collector. Therefore, the chips are likely to become clogged at a portion of the main flute 18 near the shank 16. Therefore, by increasing the flute porosity r on the shank 16 side, smooth discharge of chips can be realized even in the vicinity of the shank 16 of the main flute 18. As a result, clogging of chips and occurrence of "scorch" can be suitably avoided.

When comparing this flute porosity r with the router bit according to the comparative example shown in FIG. 11, as shown in FIG. 11(b), in the router bit according to the comparative example, the cross-sectional shape of the main flute is always the same. It has become. Therefore, the flute porosity r of the router bit according to the comparative example is the same in any of the regions A1 to A3. Therefore, in the router bit according to the comparative example, the flute porosity r does not increase on the shank side, and the porosity R of the router bit as a whole does not increase on the shank side.

(Experiment example 1)
In order to consider the influence of increasing the porosity R on the chip evacuation ability, the inventors of the present application verified the relationship between the porosity R and the power during cutting as Experimental Example 1. As shown in Table 1, a plurality of router bits 10 (experimental examples 1 to 7) with a porosity R in the range of 52% to 72% are formed from cemented carbide, and a plurality of sintered diamond tips are bonded to the body as blade parts. did. Then, the power of each router bit 10 during cutting was measured. In addition, a conventional steel router bit with a standard porosity R of 45.4% was manufactured from cemented carbide, and an experiment was conducted as Comparative Example 1. The porosity R of each router bit 10 was adjusted by changing the groove depth and twist angle of the main flute 18, the number and size of the sub-flutes 19, etc. In addition, the power consumption was calculated when the wooden board 20 was used as the material to be cut, and after drilling with each router bit 10, the board was pulled for a predetermined distance.

Here, in order to more accurately measure the influence of the porosity R on the chip evacuation ability, we calculated the amount of power required for ejecting chips (hereinafter referred to as the chip evacuation power) out of the total power required during cutting (hereinafter referred to as the required cutting power). ) was calculated and compared with the porosity R. The power required for cutting with the router bit 10 can be divided as follows.
Required power for cutting = Idle power + Chip generation power + Chip discharge power Idle power is the power required to rotate the router bit 10, and chip generation power is the power necessary for the router bit 10 to drill and process the material to be cut. This is the power required for stretching. Moreover, the chip discharge power is the power required to discharge chips during drilling and pulling processing. Since the idling power and the chip generation power do not depend on the porosity R, they do not reflect the chip evacuation effect due to the porosity R. Therefore, in this experimental example, the chip discharge power was calculated by excluding the idling power and the chip generation power from the required cutting power. In this experimental example, MDF (medium density fiberboard) with a density of 0.6, which is specified by the JIS standard as an industrial material, was used as the material to be cut.

Here, while the idling power can be easily obtained for each of the router bits 10, it is difficult to distinguish between the chip generation power and the chip discharge power. Therefore, the inventors of the present application have found a method to obtain the chip discharge power by first estimating the chip generation power and excluding the estimated chip generation power and idling power from the chip required power using the following method. As mentioned above, when cutting with a normal router bit 10, the router bit 10 and the wooden board 20 are in close contact with each other, as shown in FIG. 4, and energy is required to discharge the chips. (equivalent to emitted power). In particular, during drilling (360° cutting), the wooden board 20 is in an airtight state in which all areas except the upper part are closed, and a large amount of energy is required to discharge the chips.

When the router bit 10 is stretched, two cutting

surfaces

20A and 20B parallel to the feed direction of the router bit 10 are formed on the wooden board 20. Therefore, when tensile machining is performed after 360° drilling (that is, machining in the state shown in FIG. 4), in addition to the chip ejection power, chip generation power is generated for each of the two cutting

surfaces

20A and 20B. . One cutting surface 20A (the upper cutting surface in FIG. 4) is aligned with the feeding direction and the rotation direction during cutting (in FIG. 4, the router bit 10 rotates from left to right with respect to one cutting surface 20A). (so-called up cut). On the other hand, regarding the other cutting surface 20B (the lower cutting surface in FIG. 4), the feed direction and the rotation direction during cutting (in FIG. 4, the rotation direction of the router bit 10 with respect to the other cutting surface 20B is from right to left. (rotated to) are facing each other (so-called down cut). The chip generation power is the sum of the chip generation power due to the upcut and the chip generation power due to the downcut.

On the other hand, as shown in FIGS. 5(a) and 5(b), when the open side of the wooden board 20 is subjected to tension processing after drilling (180° cutting), compared to the case of FIG. As a result, the blockage between the router bit 10 and the wooden board 20 is alleviated. Therefore, the chips are discharged with almost no resistance, and the chip discharge power when drilling and pulling the open side surface as shown in FIG. 5 can be considered to be zero. Therefore, by measuring the power when cutting the side surface of the wooden board 20, only the power generated by the chips can be determined. In other words, the difference between the power required for machining in a closed state as shown in FIG. 4 and the power required for machining in an open state as shown in FIG. 5 is the chip discharge power.

However, in order to accurately estimate the chip generation power, the power when the side surface 20A of the wooden board is up-cut as shown in Figure 5(a), and the power when the side surface 20A of the wooden board is up-cut as shown in Figure 5(b), The power required to cut down the side surface 20B of 24 was measured, and the total value was taken as the chip generation power. Then, the chip evacuation power is determined by subtracting the idling power from the required cutting power, and further excluding the total value of the chip generation power in up-cutting and down-cutting.

Next, the experimental results will be shown. Table 2 shows the chip evacuation power calculated for each router bit 10. Moreover, FIG. 6 is a graph showing the relationship between the porosity R and the chip discharge power.

Thus, it can be seen that as the porosity R increases, the chip evacuation power decreases. In particular, it can be seen that when the porosity R is 54.8% or more, the reduction rate of the chip discharge power becomes large. That is, through this experimental example, the inventors of the present invention have found that by setting the porosity R of the router bit 10 to 55% or more, the chip evacuation ability is significantly improved and the power required for chip evacuation can be reduced. I found out what I can do. In this way, the router bit 10 has excellent chip evacuation ability by having a high porosity R of 55% or more, which is difficult to achieve with conventional router bits 10 made of steel or the like. can be provided. Further, when the porosity R is set to 69.3% as in the embodiment, the chip evacuation power can be reduced by 50% or more compared to Comparative Example 1.

(Experiment example 2)
As described above, from the results of Experimental Example 1, it can be said that the larger the porosity R is, the more the chip discharge efficiency is improved and the power consumption can be suppressed. However, if the porosity R is too large, even if it is a cemented carbide, the rigidity will be insufficient, which may cause deflection and vibration during cutting, and damage to the router bit 10. Therefore, the inventors of the present application measured the amount of deflection of the router bit 10 in order to search for an upper limit value of the porosity R that can withstand practical use. Specifically, a constant load (weight 10.24 [kgf]) was applied to the router bit 10 according to Examples 1 to 7 used in Experimental Example 1, and the amount of deflection of the router bit 10 was measured. It is known that when the same load is applied to currently available steel router bits, the amount of deflection is within the range of 85 to 90 μm. The experimental results are shown in Table 3.

In this way, it can be seen that as the porosity R increases, the amount of deflection gradually increases. However, even if the porosity R is 72%, the amount of deflection is suppressed to 90 μm, which is within the range of the amount of deflection of the conventional steel router bit 10. In other words, if the porosity R is made larger than 72%, the amount of deflection increases to more than 90%, so it can be said that 72% is desirable as the upper limit of the porosity R.

(Experiment example 3)
Next, the relationship between the twist development angle α of the main flute 18 and the weight balance of the router bit 10 was verified. In this experimental example, as experimental example 8, as shown in the first embodiment, the lead angle θ of the main flute 18 is increased stepwise from the tip side of the body 12 to the shank 16 side, thereby developing twisting. A router bit 10 with an angle α of 270° was used. Further, as Comparative Example 2, a conventional steel router bit was used, the lead angle θ of the main flute 18 was kept constant (XX°), and the twist development angle α was about 110°. Further, as Comparative Example 3, a conventional steel router bit was used, the lead angle θ of the main flute 18 was kept constant (YY°), and the twist development angle α was about 130°. The router bits of Experimental Example 8 and Comparative Examples 2 and 3 were attached to a Haimer balancer measuring device to measure the amount of unbalance. Then, a grade of balance (G: JIS standard B0905) was determined from the measured imbalance amount. The experimental results are shown in Table 4.

In this way, in Experimental Example 8 where the torsional development angle α is larger than 180°, the unbalance amount is 8.0, whereas in the router bits of Comparative Examples 2 and 3 where the twisting development angle α is less than 180°. In this case, the amount of imbalance is extremely large. Thus, it can be seen that by increasing the twist development angle α to 180° or more, the balance of the router bit 10 is improved.

As described above, in the router bit 10 according to the embodiment, the body 12 is formed of cemented carbide and includes the main flute 18 and a plurality of sub-flutes 19 by grinding, so that the porosity R of the body 12 is 52. It is set as %≦R≦75%. In particular, the lead angle θ of the main flute 18 is gradually increased from the tip side of the body 12 to the shank 16 side. That is, in the conventional router bit, the lead angle of the main flute is constant, but in the router bit 10 of this embodiment, the lead angle θ of the main flute is multiplied by the shank 16 side to increase it stepwise. The extension length of the main flute 18 in the second and third regions A2 and A3 can be increased. Moreover, by increasing the circumferential width W of the main flute 18 in steps from the tip end of the body 12 to the shank 16 side within the effective length l of the outer peripheral blade, a high flute porosity r can be achieved. ing. As a result, the overall porosity R of the router bit 10 could be set to an unprecedentedly large value of 52% or more. Moreover, by using cemented carbide as the base material, the router bit 10 maintains sufficient rigidity even with a large porosity R of 52% or more, which was not possible with conventional router bits made of steel. There is. As a result, it was possible to provide a router bit 10 with high chip evacuation ability, and it became possible to suppress power consumption during cutting.

Since the chips are sucked up by the dust collector and sent above the main flute 18, they tend to become clogged in the main flute 18 near the shank 16. Therefore, in this embodiment, the lead angle θ and the width W of the main flute 18 are increased in stages from the distal end side of the body 12 to the shank 16 side. As a result, the flute porosity r of the main flute 18 gradually increases from the tip end side of the body 12 to the shank 16 side within the effective edge length l of the outer peripheral blade. Therefore, chips can be smoothly sent upward (towards the shank 16) along the main flute 18, and clogging of chips near the shank 16 can be suitably prevented. Note that in conventional router bits made of steel, the flute porosity r of the main flute is usually constant in the axial direction, or rather becomes smaller toward the shank side. This is because in steel materials, which have lower rigidity than cemented carbide, the main flute is formed shallower on the shank side in order to increase the strength of the shank held by the NC router. On the other hand, in this embodiment, the structure is based on an idea opposite to the previous one, in which the flute porosity r of the main flute 18 is increased on the shank 16 side. In this way, even if the flute porosity r is increased on the shank 16 side, the router bit 10 made of cemented carbide maintains its rigidity and enables stable cutting.

The router bit 10 of the embodiment has a long overall effective blade length L with three peripheral blades 14a, and has a structure in which the discharge of chips is easily obstructed. Therefore, by providing the body 12 with a large porosity R, even if the router bit 10 has a long overall effective blade length L, the chip discharge efficiency can be suitably increased, and power consumption can be suppressed. In particular, in recent years, with SDG management attracting attention, many companies are focusing on keeping power consumption low in the manufacturing process. In such a trend, the router bit as shown in the embodiment can contribute as one of the cutting tools that effectively suppresses power consumption during cutting. Moreover, by increasing the overall effective flute length L, even thick workpiece materials that conventionally required multiple machining can be processed in one process, improving machining efficiency. It is possible. Note that even if the router bit 10 has such a large overall effective cutting length L, stable machining can be ensured by forming it from a highly rigid cemented carbide.

Furthermore, in the embodiment, we focused on the energy required to discharge chips during cutting, accurately measured the chip discharge power, and then verified the relationship between the porosity R and the chip discharge power. As a result, it was discovered that when the porosity R became 55% or more, the chip evacuation power decreased significantly. We also searched for the upper limit of the porosity R by comparing it with the amount of deflection allowed in existing steel router bits. As a result, it was confirmed that if the porosity R is 72% or less, the same level of rigidity as existing steel router bits can be secured. Therefore, by setting the porosity R of the router bit 10 made of cemented carbide to 55%≦R≦72%, it is possible to provide an excellent router bit 10 that significantly reduces power consumption during cutting. .

In this embodiment, the lead angle θ of the main flute 18 is increased stepwise from the tip side of the body 12 to the shank 16 side, thereby ensuring the above-mentioned large porosity R (flute porosity r). In addition to this, it is possible to have a large twisting angle α of 180° or more. It was also confirmed that by increasing the twisting angle α to 180° or more, the advantage of improving the weight balance of the router bit 10 can be obtained. This is because the main flute 18 is present over more than 180° in the circumferential direction of the router bit 10, so compared to the conventional case where the main flute is present unevenly in a part of the circumferential direction, the router bit This is thought to be because the center of gravity of 10 is prevented from shifting from the center of rotation. By improving the weight balance in this way, the router bit 10 can rotate stably, improving machining quality and suppressing noise generation during machining.

In the router bit 10 according to the present embodiment, the front edge 18a of the main flute 18 is formed to gradually expand from the tip side of the body 12 to the shank 16 side. Further, the front edge 18a of the first area A1, the front edge 18a of the second area A2, the front edge 18a of the second area A2, and the front edge 18a of the third area A3 are connected by step-shaped connecting portions 22, respectively. There is. In the cross section of the main flute 18, the front edge 18a is formed to extend in the circumferential direction, so as to have a clearance angle. Therefore, chips generated during cutting can be smoothly introduced into the main flute 18 from the front edge 18a. On the other hand, the rear edge 18b of the main flute 18 is provided with a rake angle by forming an acute angle. Therefore, the chips once accommodated in the main flute 18 can be captured by the rear edge 18b and can be prevented from escaping to the outside of the main flute 18.

(Second embodiment)
Next, the router bit 100 according to the second embodiment will be described below. In the following explanation, only the parts that are different from the first embodiment will be explained, and the same reference numerals will be given to the overlapping parts, and the explanation thereof will be omitted. FIG. 12 is a diagram schematically showing a developed view of the router bit 100 according to the second embodiment. In the router bit 10 according to the first embodiment, the main flute 18 is configured such that the lead angle θ gradually increases from the distal end side of the body 12 to the shank 16 side. In the router bit 100 according to the second embodiment, the lead angle θ of the main flute 18 is configured to continuously increase from the distal end side of the body 12 to the shank 16 side. That is, the main flute 18 has a curved shape extending from the distal end side of the body 12 to the shank 16 side in a developed view, and extends so that the curvature thereof gradually decreases.

As shown in FIG. 12, lead angles θ1 to θ3 formed by tangents at arbitrary points of the main flute 18 in each region A1 to A3 are θ1<θ2<θ3, as in the first embodiment. Further, in the second embodiment, the circumferential width W of the main flute 18 increases continuously from the distal end side of the body 12 to the shank 16 side within the outer peripheral blade effective cutting length l. More specifically, the front edge 18a of the main flute 18 is gently curved (with a large radius of curvature) toward the rear in the rotational direction of the router bit 10 from the distal end side of the body 12 to the shank 16 side. On the other hand, the rear edge 18b of the main flute 18 is curved rearward in the rotational direction of the router bit 10 with a relatively small radius of curvature from the distal end side of the body 12 to the shank 16 side. In this way, by continuously increasing the lead angle θ and the circumferential width W of the main flute 18 toward the shank 16 side, the flute porosity r of the main flute 18 can be increased as in the first embodiment. Within the effective cutting length l of the outer peripheral blade, it gradually increases from the tip side of the body 12 to the shank 16 side. Therefore, the router bit 100 can ensure a high porosity R, and can achieve the same effects as the first embodiment.

Moreover, in the router bit 100 according to the second embodiment, the lead angle θ and the circumferential width W of the main flute 18 are continuously increased toward the shank 16 side, so that the main flute 18 can be The twist development angle α of the flute 18 can be set large (for example, 270°). Therefore, the router bit 100 according to the second embodiment can have the same effect as the first embodiment because the twist development angle α is large.

(Third embodiment)
Next, a router bit 200 according to a third embodiment will be described below. In the following explanation, only the parts that are different from the first embodiment will be explained, and the same reference numerals will be given to the overlapping parts, and the explanation thereof will be omitted. FIG. 13 is a diagram schematically showing a developed view of a router bit 200 according to the third embodiment. In the router bit 10 according to the first embodiment, the main flute 18 is configured such that the lead angle θ gradually increases from the distal end side of the body 12 to the shank 16 side. On the other hand, in the router bit 200 according to the third embodiment, the lead angle θ of the main flute 18 is constant at, for example, 25° in all areas A1 to A3.

On the other hand, the circumferential width W of the main flute 18 gradually increases from the tip side of the body 12 to the shank 16 side. More specifically, the front edge 18a of the main flute 18 is formed to gradually expand forward in the rotational direction from the distal end side of the body 12 to the shank 16 side. The front edge 18a of the first area A1 and the front edge 18a of the second area A2 are connected by a stepped connecting portion 22. Similarly, the front edge 18a of the second area A2 and the front edge 18a of the third area A3 are connected by a stepped connecting portion 22. On the other hand, the rear edge 18b of the main flute 18 extends linearly across the first to third areas A1 to A3. In this way, by increasing the circumferential width W of the main flute 18 in stages toward the shank 16 side, the flute porosity r due to the main flute 18 can be adjusted to Within the length l, the length increases stepwise from the tip side of the body 12 to the shank 16 side. As a result, the overall porosity R of the router bit 11 can be increased, and the same effects as in the first embodiment can be achieved.

(Fourth embodiment)
Next, a router bit 300 according to a fourth embodiment will be explained below. A router bit 300 according to the fourth embodiment is a combination of the structure of the router bit 10 according to the first embodiment and the structure of the router bit 100 according to the second embodiment. That is, in the first region A1 of the main flute 18 of the router bit 300, the lead angle θ1 is constant (for example, about 25°) within the effective edge length l of the outer peripheral blade. In the second region A2 and the third region A3, the lead angles θ2 and θ3 of the main flute 18 continuously increase from the distal end side of the body 12 to the shank 16 side.

The lead angle θ2 of the main flute 18 is larger than the lead angle θ1 of the main flute 18, and the lead angle θ3 of the main flute 18 is larger than the lead angle θ2 of the main flute 18. Furthermore, the front edge 18a in the first area A1 and the front edge 18a in the second area A2 are smoothly connected. Similarly, the front edge 18a in the second area A2 and the front edge 18a in the third area A3 are smoothly connected. The front edge 18a and the rear edge 18b in the first region A1 extend linearly rearward in the rotational direction from the distal end side of the body 12 toward the shank 16 side. On the other hand, the front edge 18a in the second region A2 and the third region A3 is largely and gently curved backward in the rotational direction from the distal end side of the body 12 toward the shank 16 side. Further, the rear edge 18b in the second region A2 and the third region A3 is curved rearward in the rotational direction from the distal end side of the body 12 toward the shank 16 side.

As described above, in the router bit 300 according to the fourth embodiment, the lead angle θ1 of the main flute 18 is kept constant while the lead angles θ2 and θ3 of the main flute 18 are continuously greatly changed. The flute porosity r is increased on the shank 16 side. As a result, the porosity R of the router bit 300 can be increased, and the same effects as in the first embodiment can be achieved. Note that the manner in which the lead angle θ changes is not limited to the fourth embodiment. For example, the lead angles θ1 and θ3 of the first region A1 and the third region A3 may be continuously increased, and the lead angle θ2 of the second region A2 may be constant.

(Example of change)
In the first embodiment, the body 12 is conceptually divided into three regions A1 to A3, and the lead angle θ of the main flute 18 is changed in stages in the three regions, but the configuration is limited to this. It's not a thing. For example, the body 12 may be divided into two regions and the lead angle θ of the main flute 18 may be changed in two stages. Further, the body 12 may be divided into four or more regions, and the lead angle θ of the main flute 18 may be changed in four or more steps.

In the first and second embodiments, a high porosity R was ensured by increasing the lead angle θ and circumferential width W of the main flute 18 from the tip side of the body 12 to the shank 16 side. However, only the lead angle θ of the main flute 18 may be increased toward the shank 16 side, and the width W in the circumferential direction may be constant. In the first and third embodiments, the front edge 18a of the main flute 18 is expanded in stages. However, if the rear edge 18b of the main flute 18 is expanded in stages or continuously, or if both the front edge 18a and the rear edge 18b of the main flute 18 are expanded in stages or continuously, Good too.

In the first to third embodiments described above, by increasing the lead angle θ and/or the circumferential width W of the main flute 18 from the tip side of the body 12 to the shank 16 side, a high air gap of the router bit can be achieved. The structure was designed to ensure a high rate. On the other hand, by setting the groove depth D of the main flute 18 to be larger on the shank 16 side of the body 12 than on the cutting edge side of the body 12, the flute porosity r, and by extension the porosity of the entire body 12. It also becomes possible to increase R. That is, for any one or a combination of (1) lead angle θ, (2) circumferential width W, and (3) groove depth D of the main flute 18, from the tip side of the body 12 to the shank 16 side. A high porosity R of the router bit can be achieved by increasing the porosity R by multiplying by .

In the first to third embodiments, the flutes were removed from the blade portion by grinding, but the flutes may be formed by electrical discharge machining. Further, in the first to third embodiments, a main flute and a plurality of sub-flutes are provided, but a structure having only a single main flute (a structure not including a sub-flute) may also be used. . In the first to third embodiments, the blade portion is constructed by attaching a tip made of a hard sintered body to the body. However, it is also possible to use a so-called solid blade in which the blade portion is integrally formed by grinding a body made of cemented carbide.

In the first to third embodiments, a blade portion was formed by grinding a removed portion such as a flute on the surface of one end side of a round bar material made of sintered cemented carbide. However, the removed portion may be formed by machining the cemented carbide in a semi-sintered state. Then, after forming the removed portion, main sintering is performed and the blade portion is joined to form the body.

In the first to third embodiments, the case where a wood-based board is cut as the material to be cut is shown, but the material to be cut is not limited to such wood-based materials. For example, the router bit of the present invention can be suitably used when cutting resin-based materials such as plastics as the material to be cut. This is because it has been pointed out that resin-based materials, like wood-based materials, have problems such as increased power consumption due to inhibition of chip discharge.

In the first to third embodiments, the bottom cutting edge had a positive rake angle, while the outer peripheral cutting edge had a negative rake angle. On the other hand, both the bottom cutter and the outer peripheral cutter may have a positive rake angle.

10...Router bit 12...Body 14...Blade portion 14a...Peripheral blade 14b...Bottom blade 16...Shank 18...Main flute 18a...Front edge 18b...Rear edge 19...Sub-flute 20...Material to be cut 22...Connection part A1... First area A2...Second area A3...Third area L...Overall effective blade length l...Peripheral edge effective blade length

Claims

A router bit (10) for processing a material to be cut (20),
A main body made of cemented carbide,
a body (12) formed by grinding one end side of the main body portion and provided with a blade portion (14);
The body (12) includes a main flute (18) and a secondary flute (19) for discharging chips of the material to be cut (20),
A router bit characterized in that a porosity R in the overall effective blade length (L) of the body (12) is set to 52%≦R≦75%.
The router bit according to claim 1, wherein the porosity R is set to 55%≦R≦72%.
The router bit according to claim 1, wherein the blade portion (14) is formed from an ultra-high pressure sintered body and joined to the body (12).
The router bit according to claim 1, wherein the blade portion (14) is a solid blade formed by cutting the main body portion.
The router bit according to claim 1, wherein the blade portion includes a bottom blade (14b) having a positive twist angle and a peripheral blade (14a) having a negative twist angle.
Any one of claims 1 to 5, wherein the lead angle θ of the main flute (18) is set to be larger on the shank (16) side of the body (12) than on the cutting edge side of the body (12). The router bit described in item 1.
A portion of the body (12) corresponding to the overall effective blade length (L) is divided into a plurality of regions (A1 to A3) along the axial direction,
6. The lead angle θ increases stepwise from a region (A1) on the cutting edge side of the body (12) to a region (A3) on the shank (16) side of the body (12). Router bits listed.
The main flute (18) is defined by a front edge (18a) at the front in the direction of rotation of the router bit and a rear edge (18b) at the rear in the direction of rotation of the router bit;
The plurality of regions (A1 to A3) include a first region (A1) and a second region (A2) adjacent to the first region (A1) on the shank (16) side of the body (12). Equipped with
Router bit according to claim 7, characterized in that the front edge (18a) in the second area (A2) is widened with respect to the front edge (18a) in the first area (A1).
A stepped connecting portion (22) is formed to connect the front edge (18a) in the first region (A1) and the front edge (18a) in the second region (A2). Router bit described in 8.
The router bit according to claim 6, wherein the lead angle θ continuously increases from the cutting edge side of the body (12) to the shank (16) side of the body (12).
The blade portion includes a bottom blade (14b) and a peripheral blade (14a),
The body (12) has a first region (A1) including the bottom blade (14b) in a portion corresponding to the overall effective blade length (L), and a portion of the body (12) that corresponds to the first region (A1). a second region (A2) adjacent to the shank (16) side of 12);
The lead angle θ1 of the main flute (18) in the first region (A1) is constant;
The lead angle θ2 of the main flute (18) in the second region (A1) is larger than the lead angle θ1 of the main flute (18) in the first region (A1), and 7. The router bit according to claim 6, wherein the router bit becomes larger continuously from the ) side toward the shank (16) of the body (12).
The router bit according to claim 6, wherein the twist development angle α of the main flute (18) is set to 180° or more.
The blade portion includes a bottom blade (14b) and a peripheral blade (14a),
A portion of the body (12) corresponding to the overall effective blade length (L) is divided into a plurality of regions (A1 to A3) along the axial direction,
The width W in the circumferential direction of the main flute (18) is within the effective cutting length (l) of the outer circumferential cutting edge (14a) of the body (12), in the area (A1) on the cutting edge side of the main flute (12). The router bit according to any one of claims 1 to 5, wherein the areas (A2, A3) of the body (12) on the shank (16) side are larger.
The main flute (18) is defined by a front edge (18a) at the front in the direction of rotation of the router bit and a rear edge (18b) at the rear in the direction of rotation of the router bit;
The plurality of regions (A1 to A3) include a first region (A1) and a second region (A2) adjacent to the first region (A1) on the shank (16) side of the body (12). Equipped with
Router bit according to claim 13, characterized in that the front edge (18a) in the second area (A2) is widened with respect to the front edge (18a) in the first area (A1).
A stepped connecting portion (22) is formed to connect the front edge (18a) in the first region (A1) and the front edge (18a) in the second region (A2). Router bit described in 14.
The blade portion includes a bottom blade (14b) and a peripheral blade (14a),
Within the effective flute length (l) of the peripheral cutting edge (14a) of the body (12), the flute porosity r of the main flute (18) is larger than that of the body (12) on the cutting edge side of the body (12). 6. The router bit according to claim 1, wherein the shank (16) side of the router bit is set to be larger.
Any one of claims 1 to 5, wherein the groove depth D of the main flute (18) is set to be larger on the shank (16) side of the body (12) than on the cutting edge side of the body (12). The router bit described in item 1.