Circular saw blade

Abstract

Provided is a circular saw blade capable of improving chipping resistance of a cutting edge and improving discharging performance of cutting chips.　It has been found that the chipping resistance of the cutting edge is improved by providing a rake face 31 having a negative rake angle, forming the rake face into multiple stages (31a, 31b), and recessing both end parts in the blade thickness direction of the rake face 31b rearward in the rotating direction. Furthermore, by providing a breaker 34 having a positive rake angle in the vicinity of the rake face 31, discharge of generated chips is promoted, and damage to the cut surface caused by the chips can be suppressed while ensuring the chipping resistance of the cutting edge.

Description

Circular saw blade

[0001] The present invention relates to a circular saw blade.

[0002] In cutting a metal material or the like with a circular saw blade, in order to improve productivity, the feed rate of the circular saw blade may be increased. In this case, processing conditions are changed, such as increasing the rotational speed of the main shaft or increasing the depth of cut per tooth.

[0003] Patent No. 7202758, Japanese Utility Model Publication No. 6-74228, Japanese Utility Model Publication No. 62-195414, Japanese Utility Model Publication No. 58-70826, Japanese Patent Application Laid-Open No. 59-7518, WO2021 / 171945A1

[0004] When the depth of cut per tooth is increased (high feed), the impact force applied to the cutting edge increases, so the cutting edge is likely to be damaged, reducing the life of the circular saw blade. To improve the durability of the cutting edge against impact, there are methods such as setting the rake angle to a more obtuse angle, but this can also be a factor in reducing the life because wear progresses more easily due to the increase in cutting temperature. Also, when a groove is provided in the main cutting edge to divide the chips, the cutting width in the blade thickness direction is asymmetric left and right, so when cutting at high feed, the twist in the blade thickness direction per tooth becomes large and damage is likely to occur. In addition, in high-feed cutting, thick chips are generated, so scratches on the cut surface due to the chips are also likely to occur.

[0005] The present invention has been completed in view of the above circumstances, and an object thereof is to provide a circular saw blade that can improve the chip discharge performance while improving the defect resistance of the cutting edge.

[0006] As a result of intensive studies by the inventors to solve the above problems, a rake face having a negative rake angle is provided, the rake face is made multi-stage, and both ends of the rake face in the blade thickness direction are retracted rearward in the rotational direction to set the side rake angle negative, thereby finding that the defect resistance of the cutting edge is improved. Furthermore, by providing a breaker having a positive rake angle near the rake face, the discharge of the generated chips is promoted, and damage to the cut surface due to the chips can be suppressed while ensuring the defect resistance of the cutting edge.

[0007] (1) The circular saw blade of the present invention was completed based on the above findings, and has a disc-shaped base plate and a plurality of tips joined to the outer circumference of the base plate, the tips have a relief surface located on the outer circumference of the saw blade, a front surface formed with a rake face having a negative rake angle, and a main cutting edge formed on the ridge line between the relief surface and the rake face, the front surface has a breaker having a positive rake angle provided adjacent to or near the radially inward direction of the rake face, the rake face consists of a plurality of rake faces including at least a first rake face adjacent to the main cutting edge and a second rake face adjacent radially inward of the first rake face, the rake angle of the plurality of rake faces increases radially inward from the main cutting edge, and at least the second rake face of the plurality of rake faces has a central part located in the center in the blade thickness direction and two receding parts located at both ends in the blade thickness direction that recede backward in the rotational direction as they move toward the sides.

[0008] (2) In particular, the rake face may have a first rake face and a second rake face, and the breaker may be configured to be adjacent to the second rake face.

[0009] (3) Furthermore, in a plan view parallel to the rotational direction and the axis of rotation of the second rake face, the center in the blade thickness direction has a smooth convex shape that protrudes forward in the direction of rotation, which further suppresses stress concentration and further improves the durability of the cutting edge.

[0010] (4) The main cutting edge is divided into multiple sections in the blade thickness direction of the base metal by grooves extending from the main cutting edge toward the rear in the direction of rotation to the relief surface, and it is preferable that the bottom of the groove in the radial direction intersects with the rake face. The formed grooves can divide the chips, and by ensuring that the bottom of the groove intersects with the rake face, which has a negative rake angle, the angle between the groove and the rake face becomes larger in the cross section perpendicular to the axis of rotation, thereby preventing chipping of the bottom of the groove.

[0011] (5) In particular, in order to divide the chips, the groove portion is biased to one side in the blade thickness direction. When this is done, the position of the grooves is alternated in multiple chips, and the chips are divided by the grooves. When the position of the groove portion is biased, the cutting resistance at the cutting edge in the direction opposite to the bias of the groove portion increases, so that a twisting stress is applied to the front surface of the chip.

[0012] (5a) To this end, the central portion of the second rake face is given a shape that is substantially symmetrical in the blade thickness direction, and of the two recessed portions, the recessed portion on the side where the groove is biased has a larger projected area on a plane perpendicular to the rotation direction than the recessed portion that is not biased, thereby increasing the cutting resistance on the side with the larger projected area, and making it possible to offset some or all of the stress caused by the bias of the groove.

[0013] (5b) Of the two recessed portions, the recessed portion on the side where the groove is biased recedes more in the rotational direction towards the side in the blade thickness direction than the recessed portion that is not biased, thereby increasing the cutting resistance on the side with the greater recession, and making it possible to offset some or all of the stress caused by the bias of the groove. Note that if the recessed portion is flat, "less receding in the rotational direction towards the side as you move toward the side" is synonymous with "smaller rake angle".

[0014] (5c) By appropriately combining (5a) and (5b) above, it is possible to offset some or all of the twisting of the tip caused by the bias in the position of the grooves. For example, both configurations of (5a) and (5b) can be adopted. Furthermore, with respect to the two recessed portions, even if the recessed portion on the side where the grooves are biased has a smaller projected area in the direction perpendicular to the rotational direction than the recessed portion that is not biased, it may be possible to set it up so that some or all of the twisting of the tip caused by the bias in the position of the grooves can be offset by adopting configuration (5b). Conversely, even if the opposite configuration to configuration (5b) is adopted, it may be possible to set it up so that some or all of the twisting of the tip caused by the bias in the position of the grooves can be offset by adopting configuration (5a).

[0015] (a) a front view and (b) a view A of the circular saw blade in the embodiment. A perspective view of the tip in Embodiment 1. A plan view of the tip in Embodiment 1. A schematic diagram showing an example of a method for defining the second rake face in Embodiment 1. A perspective view of the tip in Embodiment 2. A perspective view of the tip in Embodiment 2, seen from diagonally above the front. (a) a right side view and (b) a left side view in Embodiment 2. (a) a cross-sectional view showing the cross-sectional shape including the recessed portion in Embodiment 2, and (b) a cross-sectional view showing the cross-sectional shape including the recessed portion in Modified Embodiment 2, respectively.

[0016] The circular saw blade of the present invention will be described in detail below based on embodiments. Note that the drawings used in this specification are schematic diagrams, and their shape, relative positions, and size are not limited; the shape can be modified, or parts of the form can be omitted or added as needed.

[0017] The uses of the circular saw blade of this embodiment are no different from those of a normal circular saw blade and are not particularly limited. For example, it can be used for cutting metal materials. It is especially preferable to use the circular saw blade of this embodiment with a large cutting depth per tooth.

[0018] (Embodiment 1) As shown in Figure 1, the circular saw blade of this embodiment has a disc-shaped base plate 10 and a plurality of tips 20, 30 that protrude radially outward from the outer circumference of the base plate 10 (Figure 1(a)). There are two types of tips, tips 20 and tips 30, and they are joined alternately in the circumferential direction of the base plate 10 (Figure 1(b)). In this specification, "radial direction" is defined with respect to the radial direction of the circular saw blade, "outward" is the direction in which the diameter expands, and "inward" is the direction in which the diameter contracts. Also, "rotational direction" is the direction in which the circular saw blade of this embodiment rotates when used, "forward in the rotational direction" is the direction in which the circular saw blade moves when rotated, and "rearward in the rotational direction" is the direction in which the circular saw blade moves when reversed.

[0019] The base metal 10 has a disc-shaped base metal body 11 with a central axis hole 12 formed in the center. Numerous tooth bases are formed on the outer circumference of the base metal 10 at locations corresponding to where the tips 20 and 30 are formed. The tips 20 and 30 are fixed to the tooth bases. The tips 20 and 30 have a shape that is symmetrical in the direction of the blade thickness, as will be described in more detail later. The tips 20 and 30 are thicker than the base metal 10 and are fixed to the tooth bases of the base metal 10 by welding or other means.

[0020] As shown in Figure 2, the tip 30 has an overall shape that is roughly a rectangular parallelepiped. When fixed to the base metal 10, the tip face 31 faces forward in the direction of rotation, and the tip face 32 faces radially outward. The main cutting edge 33 is formed on the ridge line between the rake face 31 and the relief face 32. A breaker 34 is formed adjacent to the radially inward side of the rake face 31.

[0021] The rake face 31 has a negative rake angle and consists of a first rake face 31a adjacent to the main cutting edge 33 and a second rake face 31b adjacent to the first rake face 31a in the radial direction inward. The ridges of the first rake face 31a and the second rake face 31b (rake face ridge 31c) and the ridge of the second rake face 31b and the breaker 34 (breaker ridge 31d) have a smooth convex shape with the center in the blade thickness direction protruding forward.

[0022] The rake angle of the second rake face 31b is larger than that of the first rake face 31a (because the rake face 31 has a negative rake angle, the second rake face 31b, which has a larger rake angle, is closer to perpendicular to the direction of rotation in a side view than the first rake face 31a).

[0023] The first rake face 31a is flat, and as shown in Figure 3, the second rake face 31b has a smooth convex shape in which the center in the blade thickness direction protrudes forward in a plan view parallel to the rotation direction and parallel to the axis of rotation. There are no particular limitations on the form of the second rake face 31b to be a smooth convex shape, but in the circular saw blade of this embodiment, a smooth convex shape is formed by smoothly increasing the rake angle from the center in the blade thickness direction toward the side. The second rake face 31b has a central part located in the center in the blade thickness direction and two receding parts located at both ends in the blade thickness direction that recede toward the rear in the rotation direction toward the side. In the circular saw blade of this embodiment shown in Figure 2, the central part and the receding parts are smoothly connected and indistinguishable. However, as the second rake face 31b moves toward the side, the normal of the rake face is oriented so that it spreads outward in the blade thickness direction from the front in the rotation direction. Therefore, the stress applied to the second rake face 31b during cutting can be reduced.

[0024] In this embodiment, a method for defining the shape of the second rake face 31b will be described. First, as shown in Figure 4, a virtual line V is defined as a ridge line that intersects the second rake face 31b on the extension surface of the relief face 32 with respect to the main cutting edge 33 (extending in the front-back direction of the drawing). The virtual line may be provided in a part unrelated to the relief face 32. For example, it may be provided radially outward (upper part of the drawing) or forward in the rotational direction (right side of the drawing).

[0025] A line segment is set so that one end is connected to the set virtual line V so as to be freely rotatable with the virtual line V as the center of rotation, and is perpendicular to the virtual line. In Figure 4, this is the line segment β provided at an angle θ from the relief surface 32. The trajectory of this line segment β, which is moved parallel to the virtual line V in the direction of the blade thickness (front and back directions of the paper) while rotating the line segment such that the angle θ between the relief surface and the second rake face becomes smaller as it moves from the center in the blade thickness direction toward the side, is defined as the second rake face 31b.

[0026] Then, the first rake face 31a of the surface passing through the main cutting edge 33 (first rake face 31a) is formed from the second rake face 31b that has been formed. By changing the distance between the main cutting edge and the imaginary line V in the blade thickness direction, the second rake face can be made into a shape such as a part of the side surface of a cylinder or cone.

[0027] Here, the distance between the main cutting edge 33 and the imaginary line V is made small, but not identical (for example, about the length of the radial direction of the first rake face 31a), so that the first rake face 31a can be formed over the entire thickness direction of the tip 30.

[0028] Furthermore, setting the position of the virtual line V at a location away from the first rake face 31a is preferable because it allows the rake face ridge 31c to have a smooth convex shape, thereby suppressing stress concentration. If the virtual line V is set on the first rake face 31a, the rake face ridge 31c coincides with the virtual line and becomes a straight line.

[0029] A breaker 34 is formed at a position adjacent to the second rake face 31b in the radial direction inward. The breaker 34 has a positive rake angle, in contrast to the rake face 31 which has a negative rake angle. Having a positive rake angle for the breaker 34 means that the rake angle of the breaker 34 in the radial direction outward (upward in the drawing) is positive. The shape of the breaker 34 is a smooth concave surface adjacent to the rake face 31 in the radial direction inward (downward in the drawing), and there is a region in the radial direction inward of the breaker 34 where the rake angle is negative.

[0030] The relief surface 32 has a positive relief angle. Chamfered portions 36 (361, 362) are formed at both ends of the relief surface 32 in the direction of the blade thickness. A groove 35 is formed on the relief surface 32, extending from the main cutting edge 33 towards the rear in the direction of rotation.

[0031] At both ends (recessed portion) of the second rake face, the cutting edge that intersects with the chamfered portion of the relief face is connected to the main cutting edge of the first rake face. In addition, the lateral rake angle of the second rake face is inclined toward the rear in the rotational direction toward both sides (negative lateral rake angle), which suppresses damage to the corners of the cutting edge.

[0032] As shown in Figures 2 and 3, the main cutting edge 33 is divided into multiple sections in the thickness direction by the groove 35. As a result, the chip is divided into two in the thickness direction during cutting. The groove 35 divides the first rake face 31a into first rake faces 31a1 and 31a2, and the bottom extends to the second rake face 31b. A radial gap h is provided between the bottom of the groove 35 and the breaker ridge 31d, so that the stress applied to the groove 35 during cutting does not concentrate near the bottom. In other words, since the bottom of the groove 35 intersects with a rake face 31 (the second rake face 31b in this embodiment) which has a negative rake angle rather than a breaker 34 which has a positive rake angle, the bottom can also exhibit effects similar to those of a cutting edge with a negative rake angle, similar to the main cutting edge 33, and the durability of the groove 55 including the bottom can be improved.

[0033] The groove 35 is formed with a bias to the right in Figure 2. In the tip 20, it is plane-symmetrical with the tip 30 in the cutting edge thickness direction, and the groove corresponding to the groove 35 is biased to the left. Therefore, by arranging the tips 20 and 30 alternately, the chips are divided.

[0034] (Modification 1) In Embodiment 1, the rake face 31 was divided into two parts, a first rake face 31a and a second rake face 31b, but it may be divided into three or more parts. Also, in Embodiment 1, the boundary line between the first rake face 31a and the second rake face 31b was clearly defined as the rake face ridge line 31c, but it may be smoothly connected. As for the breaker 34, in addition to being adjacent to the rake face 31, it may also be close to the rake face 31 with a gap between them.

[0035] (Embodiment 2) In this embodiment, the circular saw blade uses tips 40 and 50 instead of tips 20 and 30 in Embodiment 1.

[0036] As shown in Figures 5 to 7, in Embodiment 1, the tip 50 has a second rake face 51 instead of the smooth convex shape of the second rake face 31b. The second rake face 51 has a central portion 51b that is a plane that is generally symmetrical in the direction of the blade thickness, and recessed portions 51e and 51f are provided at both ends.

[0037] Because the groove 55 is biased in the blade thickness direction, the cutting resistance generated at the cutting edge is uneven. Specifically, the cutting edge on the left side of the drawing, where the groove 55 is not formed, experiences greater resistance during cutting than the cutting edge on the right side of the drawing where the groove 55 is formed. As a result, the rake face 51 of the chip 50 twists to face left in the drawing. Therefore, by making the area projected onto a plane perpendicular to the rotational direction of the receding portion 51f larger than that of the receding portion 51e, the unevenness in cutting resistance generated at the cutting edge due to the groove 55 can be corrected, and twisting of the chip 50 can be prevented. The rake face ridge 51c and the breaker ridge 51d are both horizontal.

[0038] (Modification Mode 2) Figure 8(a) shows a cross-section in the vicinity of the cutting edge in Embodiment 2, with planes parallel to the rotational direction and the blade thickness direction, respectively. Figure 8(b) shows a cross-section in the first rake face in Modification Mode 2, with planes parallel to the rotational direction and the blade thickness direction, respectively.

[0039] In Embodiment 2, as shown in Figure 8(a), the area a projected onto a plane perpendicular to the rotational direction of the recessed portion 51f on the side where the groove portion 55 is offset in the blade thickness direction is larger than the area b of the recessed portion 51e on the opposite side. This difference in projected area can offset some or all of the torsional stress on the chip caused by the offsetting of the groove portion 55. Note that in Figure 8, the area projected onto a plane perpendicular to the rotational direction is conveniently shown as being proportional to the width of the drawing, and it is assumed that the projected area is the same when the lengths in Figure 8 are the same.

[0040] In this modified embodiment 2, as shown in Figure 8(b), the area c projected onto a plane perpendicular to the rotational direction of the recessed portion 51g on the side where the groove portion 55 is biased in the blade thickness direction, and the area d of the recessed portion 51h on the opposite side, are the same as in embodiment 2. However, the recessed portion 51g on the side where the groove portion 55 is biased in the blade thickness direction recedes more significantly towards the side in the rotational direction than the recessed portion 51h on the opposite side (i.e., the magnitude of the negative transverse rake angle is larger). This difference in transverse rake angle can offset some or all of the torsional stress on the chip caused by the bias in the position of the groove portion 55. It should be noted that changing the projected area onto a plane perpendicular to the rotational direction, as in embodiment 2, and changing the transverse rake angle, as in this modified embodiment 2, may be combined.

[0041] (Modification 3) The central portion 51b of the second rake face in Embodiment 2 can be made into a smooth convex shape, similar to the second rake face 31b in Embodiment 1. In other words, Embodiment 1 and Embodiment 2 can be combined.

[0042] 10...Base plate 11...Base plate body 12...Center shaft hole 20, 30, 40, 50...Chip 31...Rake face 31a (31a1, 31a2)...First rake face 31b...Second rake face (center, recessed) 31c...Rake face ridge 31d...Breaker ridge 32...Relief face 33 (331, 332)...Main cutting edge 34...Breaker 35...Groove 36 (361, 362)...Chamfered section 51...Rake face 51a (51a1, 51a2)...First rake face 51b, 51e, 51f...Second rake face (center, recessed) 51b...Center 51e, 51f...Recessed 51c...Rake face ridge 51d...Breaker ridge 52...Flap surface 53 (531, 532)...Main cutting edge 54...Breaker 55...Groove 56 (561, 562)...Chamfered section

Claims

1. A circular saw blade having a disc-shaped base and a plurality of tips joined to the outer circumference of the base, wherein each tip has a relief surface located on the outer circumference of the saw blade, a rake face having a negative rake angle, a main cutting edge formed on the ridge line between the relief surface and the rake face, and a breaker having a positive rake angle provided adjacent to or near the radially inward direction of the rake face, wherein the rake face consists of a plurality of rake faces, including at least a first rake face adjacent to the main cutting edge and a second rake face adjacent radially inward of the first rake face, wherein the rake angle of the plurality of rake faces increases radially inward from the main cutting edge, and at least the second rake face of the plurality of rake faces has a central portion located in the center in the blade thickness direction and two receding portions located at both ends in the blade thickness direction that recede backward in the rotational direction as they move toward the sides.

2. The rake face has a first rake face and a second rake face, and the breaker is adjacent to the second rake face, the circular saw blade according to claim 1.

3. The circular saw blade according to claim 1 or 2, wherein, in a plan view parallel to the rotational direction and parallel to the axis of rotation, the center of the blade thickness direction has a smooth convex shape that protrudes forward in the direction of rotation.

4. The circular saw blade according to claim 1 or 2, wherein the main cutting edge is divided in the blade thickness direction by grooves extending from the main cutting edge toward the rear in the rotational direction to the relief surface, and the bottom of the grooves intersects with the rake surface.

5. The circular saw blade according to claim 3, wherein the main cutting edge is divided in the blade thickness direction by grooves extending from the main cutting edge toward the rear in the rotational direction to the relief surface, and the bottom of the grooves intersects with the rake surface.

6. The circular saw blade according to claim 4, wherein the groove portion is biased to one side in the blade thickness direction, the central portion is substantially symmetrical in the blade thickness direction, and of the two recessed portions, the recessed portion on the side where the groove portion is biased has a larger area projected onto a plane perpendicular to the rotation direction than the recessed portion that is not biased, or the amount of recession toward the rear in the rotation direction is greater as it approaches the side surface in the blade thickness direction.

7. The circular saw blade according to claim 5, wherein the groove portion is biased to one side in the blade thickness direction, the central portion is substantially symmetrical in the blade thickness direction, and of the two recessed portions, the recessed portion on the side where the groove portion is biased has a larger area projected onto a plane perpendicular to the rotation direction than the recessed portion that is not biased, or the amount of recession toward the rear in the rotation direction is greater as it approaches the side surface in the blade thickness direction.

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