Circular saw blade with carbide tip

Abstract

A circular saw blade (1) comprises: a disc-shaped base metal (2) having an outer diameter of 200 to 500 mm; and first tips (11) and second tips (13) that are disposed alternately along the outer periphery of the base metal (2). The circular saw blade (1) has a blade thickness (1a) of 0.8 mm to 2.0 mm. Each of the first tips (11) and the second tips (13) has a cutting edge (11c, 13c) and a pair of chamfers (11f) at both ends of the cutting edge (11c, 13c). A first groove (12) and a second groove (14) are formed in a flank extending in the peripheral direction from the cutting edge (11c, 13c). The first groove (12) has a first groove bottom (12e) that is deepest in the radial direction at a position of a first distance (15a) from a thickness center (7c) in a first thickness direction. The second groove (14) has a second groove bottom (14e) that is deepest in the radial direction at a position of a second distance (15b) from the thickness center (7c) in a second thickness direction opposite the first thickness direction. Th sum of the first distance (15a) and the second distance (15b) is no more than 0.35 mm.

Description

Technical Field

[0001] One aspect of the present disclosure relates to a circular saw blade with tips, which is disc-shaped and has a plurality of tips mounted on its outer circumference, for example, for cutting various metal workpieces at high speed.

Background Art

[0002] Conventionally, as a device for cutting various metal workpieces at high speed, for example, a circular sawing machine that performs cutting using a circular saw blade with a blade thickness of 2 mm is known. The circular saw blade cuts the workpiece by forming grooves in the workpiece made of a steel material or a non-ferrous steel material such as aluminum. The circular saw blade has a disc-shaped base metal and a plurality of tips mounted on the outer circumference of the base metal at predetermined intervals. The tips are, for example, hard tips made of cemented carbide or cermet.

[0003] The tip has a cutting edge that extends linearly in the thickness direction of the base metal and a relief surface facing outward in the radial direction of the base metal. The relief surface extends with a relief angle from the cutting edge to the rear in the rotational direction of the circular saw blade. A groove for dividing the cutting edge is formed in the relief surface. The circular saw blade has a plurality of types of tips with misaligned groove positions. The plurality of types of tips are arranged in the circumferential direction of the base metal in a predetermined order. For example, a first tip having a groove on the left side when viewed from the rake face and a second tip having a groove on the right side are alternately arranged. The cutting edges of the plurality of types of tips cut the workpiece in a predetermined order. Therefore, the chips cut from the workpiece are divided by the cutting edges divided by the grooves of each tip. Therefore, the net cutting power of each tip can be reduced. As a result, the power required to cut the workpiece can be reduced.

[0004] In some cases, circular saw blades with a blade thickness of less than 2 mm are used. International Publication No. 2018 / 074038 describes a circular saw blade with a blade thickness of 1 mm or less and equipped with a tip having grooves formed on the relief surface. By using a circular saw blade with a thin blade thickness, the amount of chips generated during cutting can be reduced. Moreover, grooves, which were previously difficult to create, can be provided on the tip of a circular saw blade with a blade thickness of 1 mm or less. As a result, both the amount of chips and the cutting resistance can be reduced. This further reduces the power required to cut the workpiece.

[0005] Asymmetrical chips with grooves repeatedly receive lateral forces from the workpiece by dividing the chips laterally (in the direction of the thickness of the base metal). These lateral forces can cause the chip to displace (vibrate) laterally. For example, in the case of thin circular saw blades with a blade thickness of 2 mm or less, the ratio of lateral displacement to blade thickness tends to be large. As a result, friction occurs between the side of the chip and the workpiece. In the areas where frictional heat is generated, the chip repeatedly expands and contracts due to heat. This can cause chipping (heat cracks) in the chip.

[0006] In some cases, the workpiece is cut at a feed rate several times higher than normal. The feed rate can be increased by increasing the rotational speed of the circular saw blade or the depth of cut per tooth of the saw chip. However, increasing the feed rate further increases the frictional heat generated between the chip and the workpiece. Therefore, when using a thin circular saw blade and cutting the workpiece at a high feed rate, chipping due to frictional heat is likely to occur on the chip. For this reason, further improvement in the durability of the chips was desired for thin circular saw blades with a blade thickness of 2 mm or less. [Overview of the project] [Problems that the invention aims to solve]

[0007] Therefore, in circular saw blades with carbide tips that are thin and capable of cutting workpieces at high speeds, there has been a conventional need for a configuration that increases the durability of the tips. For example, chipping caused by frictional heat can increase the durability of the tips. [Means for solving the problem]

[0008] According to one feature of this disclosure, a tipped circular saw blade has a disc-shaped base plate with an outer diameter of 200 mm to 500 mm, and first and second tips arranged alternately along the outer circumference of the base plate, projecting radially from the outer circumference of the base plate. The circular saw blade has a blade thickness of 0.8 mm to 2.0 mm. The first and second tips have a rake face facing forward in the rotational direction of the circular saw blade, a relief face facing radially outward from the base plate, and a cutting edge formed between the rake face and the relief face. A pair of chamfers are provided at both ends of the cutting edge, and a groove is formed on the relief face so as to extend circumferentially from the cutting edge. The groove of the first tip has a first groove bottom that is deepest radially at a position of a first distance in the first thickness direction from the thickness center of the cutting edge of the first tip. The groove of the second tip has a second groove bottom that is deepest radially at a position of a second distance in the second thickness direction opposite to the first thickness direction from the thickness center of the cutting edge of the second tip. The sum of the first distance and the second distance is 0.35 mm or less.

[0009] Therefore, the distance between the bottom of the first groove and the bottom of the second groove can be reduced. When cutting the workpiece, the first tip receives a lateral force from the center of the cutting edge thickness toward the first thickness direction where the first groove is located. When cutting the workpiece, the second tip receives a lateral force toward the second thickness direction where the second groove is located. By reducing the sum of the first distance and the second distance, the lateral force received by the first and second tips can be suppressed. As a result, the lateral displacement of the first and second tips can be reduced.

[0010] Furthermore, the sum of the first and second distances is made smaller than conventional methods, to 0.35 mm or less. This suppresses lateral displacement of the first and second chips when cutting workpieces at high feed rates using thin circular saw blades with a blade thickness of 2.0 mm or less. As a result, for example, the generation of frictional heat on the sides of the first and second chips can be suppressed, and chipping due to frictional heat can be suppressed. This increases the durability of the first and second chips.

[0011] Other features indicate that the groove has a pair of groove ends that intersect with the cutting edge, and a pair of inclined surfaces provided between one of the groove ends and the groove bottom, which are inclined relative to the cutting edge. The groove end angle between the cutting edge and the inclined surface at the groove end is 60° to 85°. Therefore, by setting the groove end angle to 85° or less, the corner shape of the groove end can be made obtuse. As a result, chipping of the groove end can be suppressed compared to, for example, when the corner shape of the groove end is right angle. Moreover, by setting the groove end angle to 60° or more, the sum of the first distance and the second distance can be reduced. As a result, lateral displacement of the first and second tips can be suppressed. This suppresses chipping of the first and second tips due to frictional heat.

[0012] Therefore, chipping at both ends of the chip is eliminated. As a result, the ability to maintain a good cutting surface on the workpiece can be sustained for a longer period. Moreover, the increase in cutting resistance of the first and second chips against the workpiece can be suppressed. Therefore, for example, the generation of frictional heat on both sides of the first and second chips can be suppressed. This extends the lifespan of the first and second chips.

[0013] According to other features, the groove has a pair of groove ends that intersect with the cutting edge, and a pair of inclined surfaces provided between either of the groove ends and the groove bottom, and inclined with respect to the cutting edge. At the groove ends, the groove end angle between the cutting edge and the inclined surface is larger than the angle of the pair of chamfers with respect to the cutting edge.

[0014] Other characteristics indicate that the inner edge of the first groove (the groove of the first tip) and the thickness center of the cutting edge of the first tip are separated by a first inner distance. The inner edge of the second groove (the groove of the second tip) and the thickness center of the cutting edge of the second tip are separated by a second inner distance. The sum of the first inner distance and the second inner distance is smaller than the opening width of the first groove at the cutting edge and also smaller than the opening width of the second groove at the cutting edge. Alternatively, the sum of the first inner distance and the second inner distance is smaller than half the opening width of the first groove at the cutting edge and also smaller than half the opening width of the second groove at the cutting edge.

[0015] According to other features, the groove of the first chip has a first depth in the radial direction from the cutting edge. The groove of the second chip has a second depth in the radial direction from the cutting edge. Both the first depth and the second depth are each more than twice and less than five times the radial depth of a pair of chamfers from the cutting edge.

Brief Description of the Drawings

[0016] [Figure 1] It is a side view of a circular saw blade. [Figure 2] It is an enlarged side view of part II in FIG. 1. [Figure 3] It is an enlarged top view of a part of the circular saw blade. [Figure 4] It is an enlarged top view of a part of the circular saw blade. [Figure 5] It is an enlarged front view of the upper part of the circular saw blade. [Figure 6] It is a front view schematically showing the relationship between the chip and the feed when cutting a workpiece with a circular saw blade. [Figure 7] It is an enlarged front view of a part of the chip according to the first embodiment. [Figure 8] It is an enlarged front view of a part of the chip according to the second embodiment. [Figure 9] It is an enlarged front view of a part of the chip according to the third embodiment. [Figure 10] It is an enlarged front view of a part of the chip according to the fourth embodiment. [Figure 11] It is an enlarged front view of a part of the chip according to the fifth embodiment. [Figure 12] It is an enlarged front view of a part of the chip according to the sixth embodiment. [Figure 13] It is an enlarged front view of a part of the chip according to the seventh embodiment. [Figure 14] It is an enlarged front view of a part of the chip according to the eighth embodiment. [Figure 15] It is an enlarged front view of a part of the chip according to the ninth embodiment. [Figure 16] It is an enlarged front view of a part of the chip according to the tenth embodiment. [Figure 17]It is a table showing the relationship between the shape of the groove formed in the chip and the lateral displacement of the chip. [Figure 18] It is a graph showing the relationship between the distance between the groove bottoms and the lateral displacement of the chip. [Figure 19] It is a front view schematically showing the chip and the workpiece to be cut on the chip. [Figure 20] It is a diagram showing the equivalent stress in the cross-section along the line XX-XX in FIG. 19. [Figure 21] It is a diagram showing the equivalent stress in the cross-section along the line XX-XX in FIG. 19. [Figure 22] It is a diagram showing the equivalent stress in the cross-section along the line XX-XX in FIG. 19. [Figure 23] It is a diagram showing the equivalent stress in the cross-section along the line XX-XX in FIG. 19. [Figure 24] It is a diagram showing the equivalent stress in the cross-section along the line XX-XX in FIG. 19. [Figure 25] It is a table showing the relationship between the shape of the groove formed in the chip and the number of heat cracks generated. [Figure 26] It is a table showing the relationship between the number of workpieces cut by the circular saw blade and the chipping of the chip. [Figure 27] It is a partially enlarged top view of the chip after cutting according to the first embodiment. [Figure 28] It is a partially enlarged left side view of the chip shown in FIG. 27. [Figure 29] It is a partially enlarged right side view of the chip shown in FIG. 27. [Figure 30] It is a partially enlarged front view of the chip after cutting according to the first embodiment. [Figure 31] It is a partially enlarged top view of the chip after cutting according to the first embodiment. [Figure 32] It is a partially enlarged left side view of the chip shown in FIG. 31. [Figure 33] It is a partially enlarged top view of the chip after cutting according to the first embodiment. [Figure 34] It is a partially enlarged left side view of the chip shown in FIG. 33. [Figure 35] It is a partially enlarged front view of the chip shown in FIG. 33. [Figure 36] This is a partially enlarged top view of the chip after cutting according to the third embodiment. [Figure 37] This is a magnified left side view of a portion of the chip shown in 36. [Modes for carrying out the invention]

[0017] Preferred embodiments of the present disclosure will be described with reference to Figures 1-7. The same reference numerals in the description refer to the same elements having the same function, without redundant explanation. As shown in Figure 1, the circular saw blade 1 has a disc-shaped base plate 2 and a plurality of tips 7 mounted on the outer circumference of the base plate 2. By rotating the base plate 2, each tip 7 forms a groove in the workpiece, ultimately cutting the workpiece. The workpiece is a steel material such as carbon steel, general structural rolled steel, chromium-molybdenum steel, stainless steel, cast iron, etc., or a non-ferrous metal such as aluminum and aluminum alloys, copper and copper alloys, etc. The workpiece is a material such as a rod, columnar, tubular, or plate, which is cut to a predetermined length by the circular saw blade 1.

[0018] As shown in Figure 1, a roughly circular mounting hole 3 is provided in the center of the base plate 2, penetrating in the direction of the plate thickness of the base plate 2. The rotating shaft of the circular saw cutting machine is inserted into the mounting hole 3. The circular saw cutting machine is used, for example, to cut various metal workpieces at room temperature. When cutting the workpiece, the circular saw blade 1 rotates in direction A and moves in direction B relative to the workpiece. As a result, multiple chips 7 arranged on the outer circumference of the base plate 2 reach the workpiece in sequence.

[0019] As shown in Figure 1, the outer diameter of the circular saw blade 1 is, for example, 200 mm to 500 mm. Preferably, it is 200 mm to 400 mm, more preferably 200 mm to 300 mm, for example, 285 mm. The base plate 2 is made of, for example, steel. The blade thickness 1a of the circular saw blade 1 (see Figure 7) is, for example, 0.8 mm to 2.0 mm. Preferably, the blade thickness 1a is 0.8 mm to 1.0 mm. The base plate 2 has a disc-shaped main body portion 2a and a plurality of protrusions 4 that project radially outward from the outer circumference of the main body portion 2a. The plurality of protrusions 4 are formed at predetermined intervals in the circumferential direction on the outer circumference of the main body portion 2a. The thickness 2c of the base plate 2 is slightly smaller than the blade thickness 1a, for example, 0.6 to 1.8 mm (see Figure 5).

[0020] As shown in Figures 1 and 2, a tooth cavity 5 is formed between adjacent protrusions 4. A tip sheet 6 is formed on the protrusion 4, opening circumferentially and radially outward in the forward direction of rotation. A tip 7 is attached to each tip sheet 6. For example, 40 to 200 tips 7 are attached to the base metal 2 by brazing or the like.

[0021] As shown in Figures 2 and 3, the tip 7 includes a first tip 11 and a second tip 13 with different configurations. The first tip 11 and the second tip 13 are mounted alternately and at predetermined intervals in the circumferential direction of the base metal 2. Therefore, the first tip 11 and the second tip 13 alternately reach the workpiece and cut the workpiece. The tip 7 is a hard tip formed from, for example, cemented carbide or cermet. Cemented carbide can be obtained, for example, by mixing tungsten carbide with a binder such as cobalt and sintering it. Cermet can be obtained by mixing TiN, TiC, TiCN, etc. with a binder such as cobalt and sintering it. The surface of the tip 7 may be coated to improve wear resistance.

[0022] As shown in Figures 2 and 3, the tip 7 is approximately a rectangular parallelepiped and has flank surfaces 11b and 13b facing radially outward. Cutting edges 11c and 13c are formed at one end of the flank surfaces 11b and 13b. The cutting edges 11c and 13c have a thickness 7d (see Figure 5) that is slightly greater than the thickness 2c of the base metal 2. The thickness 7d is, for example, 0.8 mm to 1.1 mm. The tip 7 is mounted on the base metal 2 such that the thickness center 7c of the tip 7 is positioned on the thickness center 2b, which is the center of the base metal 2 in the thickness direction. The cutting edges 11c and 13c are located at the rotational leading end of the flank surfaces 11b and 13b and extend in the thickness direction of the base metal 2. The relief angle 7b between the circumferential tangent of the base metal 2 at the cutting edges 11c and 13c and the flank surfaces 11b and 13b is, for example, 5° to 15°.

[0023] As shown in Figure 2, the tip 7 has rake faces 11a and 13a that extend from the cutting edges 11c and 13c toward the center of the base metal 2. In other words, the cutting edges 11c and 13c are formed at the intersection of the relief faces 11b and 13b and the rake faces 11a and 13a. The rake angle 7a of the rake faces 11a and 13a, which are inclined with respect to the radial direction of the base metal 2, is -30° to 10°. The tip 7 has a recess 7e that is forward in the rotational direction and radially inward from the rake faces 11a and 13a. In a side view, the recess 7e is recessed toward the center of the tip 7 from the rake faces 11a and 13a.

[0024] As shown in Figures 4 and 5, the first tip 11 has a left side 11d and a right side 11e at both ends in the thickness direction of the flank surface 11b. The left side 11d and the right side 11e have an inward inclination angle (lateral centripetal angle) of 0° to 2° with respect to the radial direction of the base metal 2, for example, 30′. This slight inclination reduces the contact area between the left side 11d and the right side 11e and the workpiece. As a result, cutting resistance is reduced. Moreover, because the left side 11d and the right side 11e do not protrude too much from the cut surface of the workpiece, the finish of the cut surface can be made smooth.

[0025] As shown in Figures 4 and 5, a chamfer 11f is formed between the relief surface 11b and the left side surface 11d or the right side surface 11e. The chamfer 11f is inclined with respect to the relief surface 11b and has a chamfer angle 11g of, for example, 45° (see Figure 7). The pair of left and right chamfers 11f have approximately the same chamfer angle with respect to the relief surface 11b. The pair of left and right chamfers 11f are provided symmetrically with respect to the thickness center 7c. The chamfer 11f is formed in a planar shape along the entire length of the edge of the relief surface 11b. The width of the chamfer 11f in the thickness direction is, for example, 0.05 mm to 0.1 mm and has approximately the same width along its entire length.

[0026] As shown in Figures 4 and 5, a first groove 12 extending in the circumferential direction is formed on the relief surface 11b of the first tip 11. The first groove 12 extends from the cutting edge 11c, which is one end of the relief surface 11b, to the rear end of the relief surface 11b in the rotational direction. The first groove 12 is located to the left of the thickness center 7c (in the first thickness direction). The first groove 12 is substantially V-shaped when viewed from the front in the rotational direction of the circular saw blade 1. The first groove 12 has a substantially planar inner inclined surface 12c and an outer inclined surface 12d that are inclined with respect to the cutting edge 11c. The inner inclined surface 12c is located closer to the thickness center 7c than the outer inclined surface 12d. The inner inclined surface 12c and the outer inclined surface 12d are connected by a first groove bottom 12e, which has a substantially arc-shaped curved surface when viewed from the front in the rotational direction of the circular saw blade 1. The first groove bottom 12e is located to the left of the thickness center 7c.

[0027] As shown in Figure 7, the first groove 12 has an inner groove end 12a and an outer groove end 12b located at the cutting edge 11c. The inner groove end 12a is located at the intersection of the cutting edge 11c and the inner inclined surface 12c. The outer groove end 12b is located at the intersection of the cutting edge 11c and the outer inclined surface 12d. The inner groove end 12a is located to the left of the thickness center 7c. The outer groove end 12b is located further from the thickness center 7c than the inner groove end 12a. The inner inclined surface 12c has an inner groove end angle 12f between it and the cutting edge 11c at the inner groove end 12a. The outer inclined surface 12d has an outer groove end angle 12g between it and the cutting edge 11c at the outer groove end 12b. The inner groove end angle 12f and the outer groove end angle 12g are both 65°. The first groove 12 has a symmetrical shape in the thickness direction with respect to the first groove bottom 12e. The groove bottom angle 12h between the inner inclined surface 12c and the outer inclined surface 12d is 50°.

[0028] As shown in Figures 3 and 7, a second groove 14 is formed on the relief surface 13b of the second tip 13, extending circumferentially from the cutting edge 13c to the rear end of the relief surface 13b in the rotational direction. The second groove 14 is symmetrical in shape and position to the first groove 12 with respect to the thickness center 7c. The second groove 14 is located to the right of the thickness center 7c (in the second thickness direction). The second groove 14 has a substantially planar inner inclined surface 14c and an outer inclined surface 14d that are inclined with respect to the cutting edge 13c. The inner inclined surface 14c is located closer to the thickness center 7c than the outer inclined surface 14d. The inner inclined surface 14c and the outer inclined surface 14d are connected by the second groove bottom 14e to form a substantially V shape. The second groove bottom 14e is a substantially arc-shaped curved surface when viewed from the front in the rotational direction of the circular saw blade 1. The second groove bottom 14e is located to the right of the thickness center 7c.

[0029] As shown in Figure 7, the second groove 14 has an inner groove end 14a at the intersection of the cutting edge 13c and the inner inclined surface 14c. The second groove 14 has an outer groove end 14b at the intersection of the cutting edge 13c and the outer inclined surface 14d. The inner groove end 14a is located to the right of the thickness center 7c. The outer groove end 14b is located further from the thickness center 7c than the inner groove end 14a. The inner groove end angle between the inner inclined surface 14c and the cutting edge 13c is 65°, the same as the inner groove end angle 12f. The outer groove end angle between the outer inclined surface 14d and the cutting edge 13c is 65°, the same as the outer groove end angle 12g. The groove bottom angle between the inner inclined surface 14c and the outer inclined surface 14d is 50°, the same as the groove bottom angle 12h.

[0030] As shown in Figure 7, the groove end distance 16 between the inner groove end 12a and the inner groove end 14a is greater than 0 mm, for example, 0.04 mm. The first groove bottom 12e has a first distance 15a between it and the thickness center 7c. The second groove bottom 14e has a second distance 15b between it and the thickness center 7c. The first distance 15a and the second distance 15b are the same size. The groove bottom distance 15, which is the sum of the first distance 15a and the second distance 15b, is 0.35 mm or less. Preferably it is 0.30 mm or less, for example, 0.28 mm. The first distance 15a and the second distance 15b are based on the lower end position shown, which is the deepest radially in the base metal 2 (see Figure 5) among the first groove bottom 12e and the second groove bottom 14e. The groove width of the first groove 12 and the second groove 14 is, for example, 0.26 mm.

[0031] As shown in Figure 6, the chip 9 cut from the workpiece by the first tip 11 is divided into chips 9a and 9b by the first groove 12. The first groove 12 is located to the left of the thickness center 7c. Therefore, the chip 9a on the left is narrower than the chip 9b on the right. The cutting edge 11c to the right of the first groove 12, which cuts the wider chip 9b, receives greater cutting resistance from the workpiece than the cutting edge 11c to the left of the first groove 12, which cuts the narrower chip 9a. The first tip 11 can be displaced laterally due to the cutting resistance. The lateral displacement of the first tip 11 generates friction between the left side surface 11d or the right side surface 11e and the workpiece. Because there is a difference in the magnitude of the cutting resistance between the left and right cutting edges 11c, the frictional heat generated on the right side surface 11e tends to be greater than on the left side surface 11d. Therefore, frictional heat generation is large at the intersection of the right side surface 11e and the chamfer 11f, followed by the intersection of the left side surface 11d and the chamfer 11f.

[0032] As shown in Figure 6, the intersections of the left and right ends of the cutting edge 11c and the pair of chamfers 11f are formed in an obtuse angular shape. Therefore, friction with the workpiece due to lateral displacement is relatively suppressed at the intersections of the left and right ends of the cutting edge 11c and the chamfers 11f. The chips cut from the workpiece by the second tip 13 are reversed left and right around the thickness center 7c compared to the case of the first tip 11. Therefore, frictional heat tends to be generated at the intersection of the left side surface 13d and the chamfer 13f, and then at the intersection of the right side surface 13e and the chamfer 13f.

[0033] As shown in Figure 7, the sum of the first distance 15a and the second distance 15b is 0.35 mm or less, for example, 0.28 mm. Therefore, the difference in width between the narrow chip 9a (see Figure 6) and the wide chip 9b becomes small. As a result, the difference in cutting resistance in the left-right direction (width direction) of the cutting edges 11c and 13c becomes small, and the lateral displacement of the chip 7 can be suppressed. This suppresses the frictional heat generated between the left side surface 11d or the right side surface 11e and the workpiece. Thus, chipping due to frictional heat can be suppressed on the left side surface 11d or the right side surface 11e. The inner groove end angle 12f and the outer groove end angle 12g are 60° or more, for example, 65°. Therefore, the distance between the first groove bottom 12e and the second groove bottom 14e can be brought closer. This makes it easier to provide the first groove 12 and the second groove 14 so that the sum of the first distance 15a and the second distance 15b is 0.35 mm or less.

[0034] As described above, the circular saw blade 1 has a disc-shaped base plate 2 with an outer diameter of 200 mm to 500 mm, as shown in Figures 1 and 5, and first tips 11 and second tips 13 that protrude radially from the outer circumference of the base plate 2 and are alternately arranged along the outer circumference of the base plate 2. The circular saw blade 1 has a blade thickness 1a of 0.8 mm to 2.0 mm. The first tips 11 and second tips 13 have rake faces 11a and 13a facing forward in the rotational direction of the circular saw blade 1, relief faces 11b and 13b facing radially outward from the base plate 2, and cutting edges 11c and 13c formed between the rake faces 11a and 13a and the relief faces 11b and 13b. A pair of chamfers 11f, 13f are provided at both ends of the cutting edges 11c, 13c, and a first groove 12 and a second groove 14 are formed on the relief surfaces 11b, 13b so as to extend circumferentially from the cutting edges 11c, 13c.

[0035] As shown in Figure 7, the first groove 12 of the first tip 11 has its deepest first groove bottom 12e in the radial direction at a position of a first distance 15a from the thickness center 7c of the cutting edge 11c of the first tip 11 in the first thickness direction. The second groove 14 of the second tip 13 has its deepest second groove bottom 14e in the radial direction at a position of a second distance 15b from the thickness center 7c of the cutting edge 13c of the second tip 13 in the second thickness direction opposite to the first thickness direction. The groove bottom distance 15, which is the sum of the first distance 15a and the second distance 15b, is 0.35 mm or less.

[0036] Therefore, the distance between the first groove bottom 12e and the second groove bottom 14e can be reduced. The first tip 11 receives a lateral force in the first thickness direction where the first groove 12 is located when cutting the workpiece. The second tip 13 receives a lateral force in the second thickness direction where the second groove 14 is located when cutting the workpiece. By reducing the sum of the first distance 15a and the second distance 15b, the lateral force received by the first tip 11 and the second tip 13 can be suppressed. As a result, the lateral displacement of the first tip 11 and the second tip 13 is suppressed.

[0037] Furthermore, the sum of the first distance 15a and the second distance 15b is made smaller than conventional methods, to 0.35 mm or less. This makes it possible to suppress the lateral displacement of the first tip 11 and the second tip 13 when cutting a workpiece at a feed rate 2.5 times or more than that of normal cutting, using a thin circular saw blade 1 with a blade thickness 1a of 2.0 mm or less. As a result, the generation of frictional heat can be suppressed on the left side surfaces 11d, 13d and the right side surfaces 11e, 13e of the first tip 11 and the second tip 13, and the occurrence of chipping due to frictional heat is suppressed. This makes it possible to increase the durability of the first tip 11 and the second tip 13.

[0038] As shown in Figure 7, the first groove 12 and the second groove 14 have a pair of inner groove ends 12a, 14a and outer groove ends 12b, 14b that intersect with the cutting edges 11c, 13c. A pair of inner inclined surfaces 12c, 14c and outer inclined surfaces 12d, 14d are provided between either one of the pair of inner groove ends 12a, 14a or the outer groove ends 12b, 14b and the groove bottoms 12e, 14e, and are inclined with respect to the cutting edges 11c, 13c. At the inner groove end 12a, the inner groove end angle 12f between the cutting edge 11c and the inner inclined surface 12c is 60° to 85°. At the outer groove end 12b, the outer groove end angle 12g between the cutting edge 11c and the outer inclined surface 12d is 60° to 85°.

[0039] Therefore, by setting the inner groove end angle 12f and the outer groove end angle 12g to 85° or less, the corner shape of the inner groove end 12a and the outer groove end 12b can be made obtuse. As a result, chipping of the inner groove end 12a and the outer groove end 12b can be suppressed compared to, for example, the case where the corner shape of the groove end is right angle. Moreover, by setting the inner groove end angle 12f and the outer groove end angle 12g to 60° or more, the sum of the first distance 15a and the second distance 15b can be reduced. As a result, lateral displacement of the first tip 11 and the second tip 13 can be suppressed. This suppresses chipping of the first tip 11 and the second tip 13 due to frictional heat.

[0040] Therefore, the occurrence of chipping at both ends of the first tip 11 and the second tip 13 is eliminated. As a result, the ability to machine the cut surface of the workpiece well can be maintained for a longer period of time. Moreover, the increase in the cutting resistance of the first tip 11 and the second tip 13 to the workpiece can be suppressed. As a result, for example, the generation of frictional heat can be suppressed on the left side surfaces 11d, 13d and the right side surfaces 11e, 13e of the first tip 11 and the second tip 13. This extends the lifespan of the first tip 11 and the second tip 13.

[0041] Next, a second embodiment of the present disclosure will be described with reference to Figure 8. The circular saw blade 20 has a first tip 21 and a second tip 23 instead of the first tip 11 and second tip 13 shown in Figure 7. The first tip 21 has a first groove 22 extending circumferentially from the cutting edge 21a instead of the first groove 12 shown in Figure 7. The second tip 23 has a second groove 24 extending circumferentially from the cutting edge 23a instead of the second groove 14 shown in Figure 7.

[0042] As shown in Figure 8, the first groove 22 is provided in the first thickness direction to the left of the thickness center 7c. The first groove 22 has a roughly V-shape that is symmetrical when viewed from the front in the rotational direction of the circular saw blade 20. The first groove 22 has a roughly planar inner inclined surface 22c and an outer inclined surface 22d that are inclined with respect to the cutting edge 21a. The inner inclined surface 22c is provided closer to the thickness center 7c than the outer inclined surface 22d. The inner inclined surface 22c and the outer inclined surface 22d are connected by the first groove bottom 22e, which has a roughly arc-shaped curved surface when viewed from the front in the rotational direction of the circular saw blade 20.

[0043] As shown in Figure 8, an inner groove end 22a is provided at the intersection of the cutting edge 21a and the inner inclined surface 22c. An outer groove end 22b is provided at the intersection of the cutting edge 21a and the outer inclined surface 22d. The inner inclined surface 22c has an inner groove end angle 22f between it and the cutting edge 21a at the inner groove end 22a. The outer inclined surface 22d has an outer groove end angle 22g between it and the cutting edge 21a at the outer groove end 22b. The inner groove end angle 22f and the outer groove end angle 22g are the same, both at 75°. The groove bottom angle 22h between the inner inclined surface 22c and the outer inclined surface 22d is 30°.

[0044] As shown in Figure 8, the second groove 24 is provided in a shape and position symmetrical to the first groove 22 with respect to the thickness center 7c. The second groove 24 is provided in the second thickness direction to the right of the thickness center 7c. The second groove 24 has a substantially planar inner inclined surface 24c and an outer inclined surface 24d that are inclined with respect to the cutting edge 23a. The inner inclined surface 24c is provided in a position closer to the thickness center 7c than the outer inclined surface 24d. The inner inclined surface 24c and the outer inclined surface 24d are connected by a second groove bottom 24e which has a substantially arc-shaped curved surface when viewed from the front in the rotational direction of the circular saw blade 20.

[0045] As shown in Figure 8, an inner groove end 24a is provided at the intersection of the cutting edge 23a and the inner inclined surface 24c. An outer groove end 24b is provided at the intersection of the cutting edge 23a and the outer inclined surface 24d. The inner groove end angle between the inner inclined surface 24c and the cutting edge 23a is 75°, the same as the inner groove end angle 22f. The outer groove end angle between the outer inclined surface 24d and the cutting edge 23a is 75°, the same as the outer groove end angle 22g.

[0046] As shown in Figure 8, the groove end distance 16 between the inner groove end 22a and the inner groove end 24a is, for example, 0.04 mm. The first distance 25a between the first groove bottom 22e and the thickness center 7c is the same size as the second distance 25b between the second groove bottom 24e and the thickness center 7c. The groove bottom distance 25, which is the sum of the first distance 25a and the second distance 25b, is 0.35 mm or less. Preferably it is 0.30 mm or less, for example, 0.26 mm. The groove width of the first groove 22 and the second groove 24 is 0.22 mm.

[0047] Next, a third embodiment of the present disclosure will be described with reference to Figure 9. The circular saw blade 30 has a first tip 31 and a second tip 33 instead of the first tip 11 and second tip 13 shown in Figure 7. The first tip 31 has a first groove 32 extending circumferentially from the cutting edge 31a instead of the first groove 12 shown in Figure 7. The second tip 33 has a second groove 34 extending circumferentially from the cutting edge 33a instead of the second groove 14 shown in Figure 7.

[0048] As shown in Figure 9, the first groove 32 is provided in the first thickness direction to the left of the thickness center 7c. The first groove 32 has a roughly V-shape that is symmetrical when viewed from the front in the rotational direction of the circular saw blade 30. The first groove 32 has a roughly planar inner inclined surface 32c and an outer inclined surface 32d that are inclined with respect to the cutting edge 31a. The inner inclined surface 32c is provided closer to the thickness center 7c than the outer inclined surface 32d. The inner inclined surface 32c and the outer inclined surface 32d are connected by the first groove bottom 32e, which has a roughly arc-shaped curved surface when viewed from the front in the rotational direction of the circular saw blade 30.

[0049] As shown in Figure 9, an inner groove end 32a is provided at the intersection of the cutting edge 31a and the inner inclined surface 32c. An outer groove end 32b is provided at the intersection of the cutting edge 31a and the outer inclined surface 32d. The inner inclined surface 32c has an inner groove end angle 32f between it and the cutting edge 31a at the inner groove end 32a. The outer inclined surface 32d has an outer groove end angle 32g between it and the cutting edge 31a at the outer groove end 32b. The inner groove end angle 32f and the outer groove end angle 32g are both 55°. The groove bottom angle 32h between the inner inclined surface 32c and the outer inclined surface 32d is 70°.

[0050] As shown in Figure 9, the second groove 34 is provided in a shape and position symmetrical to the first groove 32 with respect to the thickness center 7c. The second groove 34 is provided in the second thickness direction to the right of the thickness center 7c. The second groove 34 has a substantially planar inner inclined surface 34c and an outer inclined surface 34d that are inclined with respect to the cutting edge 33a. The inner inclined surface 34c is provided in a position closer to the thickness center 7c than the outer inclined surface 34d. The inner inclined surface 34c and the outer inclined surface 34d are connected by a second groove bottom 34e which has a substantially arc-shaped curved surface when viewed from the front in the rotational direction of the circular saw blade 30.

[0051] As shown in Figure 9, an inner groove end 34a is provided at the intersection of the cutting edge 33a and the inner inclined surface 34c. An outer groove end 34b is provided at the intersection of the cutting edge 33a and the outer inclined surface 34d. The inner groove end angle between the inner inclined surface 34c and the cutting edge 33a is 55°, the same as the inner groove end angle 32f. The outer groove end angle between the outer inclined surface 34d and the cutting edge 33a is 55°, the same as the outer groove end angle 32g. The groove end distance 16 between the inner groove end 32a and the inner groove end 34a is, for example, 0.04 mm. The first distance 35a between the first groove bottom 32e and the thickness center 7c is the same as the second distance 35b between the second groove bottom 34e and the thickness center 7c. The groove bottom distance 35, which is the sum of the first distance 35a and the second distance 35b, is 0.35 mm or less, for example, 0.34 mm. The groove width of the first groove 32 and the second groove 34 is 0.32 mm.

[0052] Next, a fourth embodiment of the present disclosure will be described with reference to Figure 10. The circular saw blade 40 has a first tip 41 and a second tip 43 instead of the first tip 11 and second tip 13 shown in Figure 7. The first tip 41 has a first groove 42 extending circumferentially from the cutting edge 41a instead of the first groove 12 shown in Figure 7. The second tip 43 has a second groove 44 extending circumferentially from the cutting edge 43a instead of the second groove 14 shown in Figure 7.

[0053] As shown in Figure 10, the first groove 42 is provided in the first thickness direction to the left of the thickness center 7c. The first groove 42 has a roughly U-shape that is symmetrical when viewed from the front in the rotational direction of the circular saw blade 40. The first groove 42 has a roughly planar inner upright surface 42c and an outer upright surface 42e that are perpendicular to the cutting edge 41a. The inner upright surface 42c is provided closer to the thickness center 7c than the outer upright surface 42e. The inner upright surface 42c and the outer upright surface 42e are smoothly connected to an inner inclined surface 42d and an outer inclined surface 42f on the side closer to the center of the base plate 2 (downward in the figure). The inner inclined surface 42d and the outer inclined surface 42f are roughly arc-shaped curved surfaces when viewed from the front in the rotational direction of the circular saw blade 40. In other words, the inner inclined surface 42d and the outer inclined surface 42f include surfaces that are inclined with respect to the cutting edge 41a. The inner inclined surface 42d and the outer inclined surface 42f are connected by the first groove bottom 42g at the center of the first groove 42.

[0054] As shown in Figure 10, an inner groove end 42a is provided at the intersection of the cutting edge 41a and the inner upright surface 42c. An outer groove end 42b is provided at the intersection of the cutting edge 41a and the outer upright surface 42e. The inner groove end angle between the inner upright surface 42c and the cutting edge 41a, and the outer groove end angle between the outer upright surface 42e and the cutting edge 41a are 90°. The groove width 42h of the first groove 42 is less than 0.30 mm. The first groove 42 is formed with approximately the same groove depth as the first groove 12 shown in Figure 7.

[0055] As shown in Figure 10, the second groove 44 is provided in a shape and position symmetrical to the first groove 42 with respect to the thickness center 7c. The second groove 44 is provided in the second thickness direction to the right of the thickness center 7c. The second groove 44 has an inner upright surface 44c and an outer upright surface 44e that are substantially planar and perpendicular to the cutting edge 43a. The inner upright surface 44c is provided in a position closer to the thickness center 7c than the outer upright surface 44e. The inner upright surface 44c and the outer upright surface 44e are smoothly connected to an inner inclined surface 44d and an outer inclined surface 44f on the side closer to the center of the base metal 2. The inner inclined surface 44d and the outer inclined surface 44f are curved surfaces that are substantially arc-shaped when viewed from the front in the rotation direction of the circular saw blade 40. The inner inclined surface 44d and the outer inclined surface 44f are connected at the second groove bottom 44g in the center of the second groove 44.

[0056] As shown in Figure 10, an inner groove end 44a is provided at the intersection of the cutting edge 43a and the inner upright surface 44c. An outer groove end 44b is provided at the intersection of the cutting edge 43a and the outer upright surface 44e. The inner groove end 44a is located to the right of the thickness center 7c. The groove end distance 16 between the inner groove end 42a and the inner groove end 44a is, for example, 0.04 mm. The first distance 45a between the first groove bottom 42g and the thickness center 7c is the same size as the second distance 45b between the second groove bottom 44g and the thickness center 7c. The groove bottom distance 45, which is the sum of the first distance 45a and the second distance 45b, is 0.35 mm or less. Preferably it is 0.30 mm or less, for example, 0.20 mm.

[0057] Next, a fifth embodiment of the present disclosure will be described with reference to Figure 11. The circular saw blade 50 has a first tip 51 and a second tip 53 instead of the first tip 11 and second tip 13 shown in Figure 7. The first tip 51 has a first groove 52 extending circumferentially from the cutting edge 51a instead of the first groove 12 shown in Figure 7. The second tip 53 has a second groove 54 extending circumferentially from the cutting edge 53a instead of the second groove 14 shown in Figure 7.

[0058] As shown in Figure 11, the first groove 52 is provided in the first thickness direction to the left of the thickness center 7c. The first groove 52 has a shape in which a roughly V-shape and a roughly U-shape, which are symmetrical when viewed from the front in the rotational direction of the circular saw blade 50, are arranged and connected in the radial direction of the base metal 2. The first groove 52 has a roughly planar inner inclined surface 52c and an outer inclined surface 52f that are inclined with respect to the cutting edge 51a. The inner inclined surface 52c is provided closer to the thickness center 7c than the outer inclined surface 52f. The inner inclined surface 52c is connected to the inner U-shaped surface 52e at the inner U-shaped end 52d on the side closer to the center of the base metal 2 (bottom of the figure). The outer inclined surface 52f is connected to the outer U-shaped surface 52h at the outer U-shaped end 52g on the side closer to the center of the base metal 2.

[0059] As shown in Figure 11, the inner U-shaped surface 52e and the outer U-shaped surface 52h have a substantially flat surface perpendicular to the cutting edge 51a in the upper part shown, which is close to the cutting edge 51a. In addition, the inner U-shaped surface 52e and the outer U-shaped surface 52h have a substantially arc-shaped curved surface in the lower part shown, which is farther from the cutting edge 51a. The inner U-shaped surface 52e and the outer U-shaped surface 52h are connected at the first groove bottom 52i in the center of the first groove 52. The inner U-shaped surface 52e and the outer U-shaped surface 52h are symmetrical with respect to the first groove bottom 52i. The U-shaped groove width 52n of the substantially U-shaped groove formed by the inner U-shaped surface 52e and the outer U-shaped surface 52h is 0.12 mm.

[0060] As shown in Figure 11, an inner groove end 52a is provided at the intersection of the cutting edge 51a and the inner inclined surface 52c. An outer groove end 52b is provided at the intersection of the cutting edge 51a and the outer inclined surface 52f. The inner inclined surface 52c has an inner groove end angle 52j between it and the cutting edge 51a at the inner groove end 52a. The outer inclined surface 52f has an outer groove end angle 52k between it and the cutting edge 51a at the outer groove end 52b. The inner groove end angle 52j and the outer groove end angle 52k are both 55°. The groove bottom angle 52m between the inner inclined surface 52c and the outer inclined surface 52f is 70°.

[0061] As shown in Figure 11, the second groove 54 is provided in a shape and position symmetrical to the first groove 52 with respect to the thickness center 7c. The second groove 54 is provided in the second thickness direction to the right of the thickness center 7c. The second groove 54 has a substantially planar inner inclined surface 54c and an outer inclined surface 54f that are inclined with respect to the cutting edge 53a. The inner inclined surface 54c is provided in a position closer to the thickness center 7c than the outer inclined surface 54f. The inner inclined surface 54c is connected to the inner U-shaped surface 54e at the inner U-shaped end 54d on the side closer to the center of the base metal 2. The outer inclined surface 54f is connected to the outer U-shaped surface 54h at the outer U-shaped end 54g on the side closer to the center of the base metal 2. The inner U-shaped surface 54e and the outer U-shaped surface 54h are connected at the second groove bottom 54i in the center of the second groove 54.

[0062] As shown in Figure 11, an inner groove end 54a is provided at the intersection of the cutting edge 53a and the inner inclined surface 54c. An outer groove end 54b is provided at the intersection of the cutting edge 53a and the outer inclined surface 54f. The inner groove end angle between the inner inclined surface 54c and the cutting edge 53a is 55°, the same as the inner groove end angle 52j. The outer groove end angle between the outer inclined surface 54f and the cutting edge 53a is 55°, the same as the outer groove end angle 52k. The groove end distance 16 between the inner groove end 52a and the inner groove end 54a is, for example, 0.04 mm. The first distance 55a between the first groove bottom 52i and the thickness center 7c is the same as the second distance 55b between the second groove bottom 54i and the thickness center 7c. The groove bottom distance 55, which is the sum of the first distance 55a and the second distance 55b, is 0.35 mm or less, for example, 0.30 mm. The groove widths of the first groove 52 and the second groove 54 are set smaller than the groove widths of the first groove 32 and the second groove 34, for example, when the groove depth of the circular saw blade 30 shown in Figure 9 is the same.

[0063] Next, a sixth embodiment of the present disclosure will be described with reference to Figure 12. The circular saw blade 60 has a first tip 61 and a second tip 63 instead of the first tip 11 and second tip 13 shown in Figure 7. The first tip 61 has a first groove 62 extending circumferentially from the cutting edge 61a instead of the first groove 12 shown in Figure 7. The second tip 63 has a second groove 64 extending circumferentially from the cutting edge 63a instead of the second groove 14 shown in Figure 7.

[0064] As shown in Figure 12, the first groove 62 is provided in the first thickness direction to the left of the thickness center 7c. The first groove 62 has a symmetrical elliptical shape when viewed from the front in the rotational direction of the circular saw blade 60, more specifically, it has the shape of half or part of an ellipse. The first groove 62 has a curved inner inclined surface 62c and an outer inclined surface 62d that form an elliptical surface. The inner inclined surface 62c is provided closer to the thickness center 7c than the outer inclined surface 62d. The inner inclined surface 62c and the outer inclined surface 62d are connected at the first groove bottom 62e in the center of the first groove 62. The inner inclined surface 62c and the outer inclined surface 62d have a symmetrical shape with respect to the first groove bottom 62e. The groove width 62f of the first groove 62 is 0.16 mm, the same as the first groove 42 shown in Figure 10. The first groove 62 is formed with approximately the same groove depth as the first groove 12 shown in Figure 7.

[0065] As shown in Figure 12, an inner groove end 62a is provided at the intersection of the cutting edge 61a and the inner inclined surface 62c. An outer groove end 62b is provided at the intersection of the cutting edge 61a and the outer inclined surface 62d. The inner inclined surface 62c is approximately perpendicular to the cutting edge 61a at the inner groove end 62a. The outer inclined surface 62d is approximately perpendicular to the cutting edge 61a at the outer groove end 62b. The tangents of the inner inclined surface 62c and the outer inclined surface 62d are approximately parallel to the cutting edge 61a at the first groove bottom 62e. In other words, the inner inclined surface 62c and the outer inclined surface 62d include surfaces that are inclined with respect to the cutting edge 61a between the inner groove end 62a or the outer groove end 62b and the first groove bottom 62e.

[0066] As shown in Figure 12, the second groove 64 is provided in a shape and position symmetrical to the first groove 62 with respect to the thickness center 7c. The second groove 64 is provided in the second thickness direction to the right of the thickness center 7c. The second groove 64 has a curved inner inclined surface 64c and an outer inclined surface 64d. The inner inclined surface 64c is provided closer to the thickness center 7c than the outer inclined surface 64d. The inner inclined surface 64c and the outer inclined surface 64d are connected at the bottom of the second groove 64e in the center of the second groove 64.

[0067] As shown in Figure 12, an inner groove end 64a is provided at the intersection of the cutting edge 63a and the inner inclined surface 64c. An outer groove end 64b is provided at the intersection of the cutting edge 63a and the outer inclined surface 64d. The inner groove end 64a is located to the right of the thickness center 7c. The inner inclined surface 64c is approximately perpendicular to the cutting edge 63a at the inner groove end 64a. The outer inclined surface 64d is approximately perpendicular to the cutting edge 63a at the outer groove end 64b. The groove end distance 16 between the inner groove end 62a and the inner groove end 64a is, for example, 0.04 mm. The first distance 65a between the first groove bottom 62e and the thickness center 7c is the same size as the second distance 65b between the second groove bottom 64e and the thickness center 7c. The sum of the first distance 65a and the second distance 65b, which is the groove bottom distance 65, is 0.35 mm or less, for example, 0.20 mm.

[0068] Next, a seventh embodiment of the present disclosure will be described with reference to Figure 13. The circular saw blade 70 has a first tip 71 and a second tip 73 instead of the first tip 11 and second tip 13 shown in Figure 7. The first tip 71 has a first groove 72 extending circumferentially from the cutting edge 71a instead of the first groove 12 shown in Figure 7. The second tip 73 has a second groove 74 extending circumferentially from the cutting edge 73a instead of the second groove 14 shown in Figure 7.

[0069] As shown in Figure 13, the first groove 72 is provided in the first thickness direction to the left of the thickness center 7c. The first groove 72 has a roughly V-shape that is symmetrical when viewed from the front in the rotational direction of the circular saw blade 70. The first groove 72 has a roughly planar inner inclined surface 72c and an outer inclined surface 72d that are inclined with respect to the cutting edge 71a. The inner inclined surface 72c and the outer inclined surface 72d are connected by the first groove bottom 72e. The inner inclined surface 72c, the outer inclined surface 72d, and the first groove bottom 72e have the same shape as the inner inclined surface 12c, the outer inclined surface 12d, and the first groove bottom 12e shown in Figure 7.

[0070] As shown in Figure 13, an inner groove end 72a is provided at the intersection of the cutting edge 71a and the inner inclined surface 72c. An outer groove end 72b is provided at the intersection of the cutting edge 71a and the outer inclined surface 72d. The inner groove end 72a and the outer groove end 72b are provided with a roughly arc-shaped R chamfer when viewed from the front in the rotational direction of the circular saw blade 70. The radius of the R chamfer is, for example, 0.01 to 0.05 mm.

[0071] As shown in Figure 13, the inner inclined surface 72c has an inner groove end angle 72f with respect to the cutting edge 71a. The outer inclined surface 72d has an outer groove end angle 72g with respect to the cutting edge 71a. The inner groove end angle 72f and the outer groove end angle 72g correspond to the angle between the tangent at the lower end of the inner groove end 72a and the outer groove end 72b shown in the figure and the cutting edge 71a. The inner groove end angle 72f and the outer groove end angle 72g are both 65°. The groove bottom angle 72h between the inner inclined surface 72c and the outer inclined surface 72d is 50°.

[0072] As shown in Figure 13, the second groove 74 is provided in a shape and position symmetrical to the first groove 72 with respect to the thickness center 7c. The second groove 74 is provided in the second thickness direction to the right of the thickness center 7c. The second groove 74 has an inner inclined surface 74c and an outer inclined surface 74d that are substantially planar and inclined with respect to the cutting edge 73a. The inner inclined surface 74c and the outer inclined surface 74d are connected by a second groove bottom 74e which has a substantially arc-shaped curved surface.

[0073] As shown in Figure 13, an inner groove end 74a with a roughly arc-shaped R-chamfer is provided at the intersection of the cutting edge 73a and the inner inclined surface 74c. An outer groove end 74b with a roughly arc-shaped R-chamfer is provided at the intersection of the cutting edge 73a and the outer inclined surface 74d. The inner groove end angle between the inner inclined surface 74c and the cutting edge 73a is 65°, the same as the inner groove end angle 72f. The outer groove end angle between the outer inclined surface 74d and the cutting edge 73a is 65°, the same as the outer groove end angle 72g. The groove end distance 16 between the inner groove end 72a and the inner groove end 74a is, for example, 0.04 mm. The first distance 75a between the first groove bottom 72e and the thickness center 7c is the same as the second distance 75b between the second groove bottom 74e and the thickness center 7c. The sum of the first distance 75a and the second distance 75b, which is the groove bottom distance 75, is 0.35 mm or less, for example, 0.30 mm.

[0074] Next, an eighth embodiment of the present disclosure will be described with reference to Figure 14. The circular saw blade 80 has a first tip 81 and a second tip 83 instead of the first tip 11 and second tip 13 shown in Figure 7. The first tip 81 has a first groove 82 extending circumferentially from the cutting edge 81a instead of the first groove 12 shown in Figure 7. The second tip 83 has a second groove 84 extending circumferentially from the cutting edge 83a instead of the second groove 14 shown in Figure 7.

[0075] As shown in Figure 14, the first groove 82 is provided in the first thickness direction to the left of the thickness center 7c. The first groove 82 is a trapezoidal shape, for example, an isosceles trapezoid, which is symmetrical when viewed from the front in the rotational direction of the circular saw blade 80. The first groove 82 has an inner inclined surface 82c and an outer inclined surface 82d that are substantially planar and inclined with respect to the cutting edge 81a. The inner inclined surface 82c and the outer inclined surface 82d are connected by a substantially planar first groove bottom 82e that extends substantially parallel to the cutting edge 81a. The inner inclined surface 82c is connected to the first groove bottom 82e at the inner groove bottom end 82f, which is the right end of the first groove bottom 82e. The outer inclined surface 82d is connected to the first groove bottom 82e at the outer groove bottom end 82g, which is the left end of the first groove bottom 82e. The groove bottom width 82k between the inner groove bottom end 82f and the outer groove bottom end 82g is, for example, 0.10 mm.

[0076] As shown in Figure 14, an inner groove end 82a is provided at the intersection of the cutting edge 81a and the inner inclined surface 82c. An outer groove end 82b is provided at the intersection of the cutting edge 81a and the outer inclined surface 82d. The inner inclined surface 82c has an inner groove end angle 82h between it and the cutting edge 81a at the inner groove end 82a. The outer inclined surface 82d has an outer groove end angle 82i between it and the cutting edge 81a at the outer groove end 82b. The inner groove end angle 82h and the outer groove end angle 82i are both 65°. The groove bottom angle 82j between the inner inclined surface 82c and the outer inclined surface 82d is 50°.

[0077] As shown in Figure 14, the second groove 84 is provided in a shape and position symmetrical to the first groove 82 with respect to the thickness center 7c. The second groove 84 is provided in the second thickness direction to the right of the thickness center 7c. The second groove 84 has a substantially planar inner inclined surface 84c and an outer inclined surface 84d that are inclined with respect to the cutting edge 83a. The inner inclined surface 84c and the outer inclined surface 84d are connected to the second groove bottom 84e, which extends substantially parallel to the cutting edge 83a, at the inner groove bottom end 84f and the outer groove bottom end 84g, respectively.

[0078] As shown in Figure 14, an inner groove end 84a is provided at the intersection of the cutting edge 83a and the inner inclined surface 84c. An outer groove end 84b is provided at the intersection of the cutting edge 83a and the outer inclined surface 84d. The inner groove end angle between the inner inclined surface 84c and the cutting edge 83a is 65°, the same as the inner groove end angle 82h. The outer groove end angle between the outer inclined surface 84d and the cutting edge 83a is 65°, the same as the outer groove end angle 82i. The groove end distance 16 between the inner groove end 82a and the inner groove end 84a is, for example, 0.04 mm. The first distance 85a between the center of the first groove bottom 82e and the thickness center 7c is the same as the second distance 85b between the center of the second groove bottom 84e and the thickness center 7c. The groove bottom distance 85, which is the sum of the first distance 85a and the second distance 85b, is 0.35 mm or less, for example, 0.30 mm.

[0079] Next, a ninth embodiment of the present disclosure will be described with reference to Figure 15. The circular saw blade 90 has a first tip 91 and a second tip 93 instead of the first tip 11 and second tip 13 shown in Figure 7. The first tip 91 has a first groove 92 extending circumferentially from the cutting edge 91a instead of the first groove 12 shown in Figure 7. The second tip 93 has a second groove 94 extending circumferentially from the cutting edge 93a instead of the second groove 14 shown in Figure 7.

[0080] As shown in Figure 15, the first groove 92 is provided in the first thickness direction to the left of the thickness center 7c. The first groove 92 is substantially V-shaped when viewed from the front in the rotational direction of the circular saw blade 90. The first groove 92 has a substantially planar inner inclined surface 92c and an outer inclined surface 92d that are inclined with respect to the cutting edge 91a. The inner inclined surface 92c and the outer inclined surface 92d are connected by the first groove bottom 92e, which has an arc-shaped curved surface when viewed from the front in the rotational direction of the circular saw blade 90.

[0081] As shown in Figure 15, an inner groove end 92a is provided at the intersection of the cutting edge 91a and the inner inclined surface 92c. An outer groove end 92b is provided at the intersection of the cutting edge 91a and the outer inclined surface 92d. The inner inclined surface 92c has an inner groove end angle 92f with respect to the cutting edge 91a. The outer inclined surface 92d has an outer groove end angle 92g with respect to the cutting edge 91a. The inner groove end angle 92f is greater than the outer groove end angle 92g and is 85° or less. For example, the inner groove end angle 92f is 75°. For example, the outer groove end angle 92g is 55°. The groove bottom angle 92h between the inner inclined surface 92c and the outer inclined surface 92d is 50°.

[0082] As shown in Figure 15, the second groove 94 is provided in a shape and position symmetrical to the first groove 92 with respect to the thickness center 7c. The second groove 94 is provided in the second thickness direction to the right of the thickness center 7c. The second groove 94 has a substantially planar inner inclined surface 94c and an outer inclined surface 94d that are inclined with respect to the cutting edge 93a. The inner inclined surface 94c and the outer inclined surface 94d are connected at the bottom of the second groove 94e. An inner groove end 94a is provided at the intersection of the cutting edge 93a and the inner inclined surface 94c. An outer groove end 94b is provided at the intersection of the cutting edge 93a and the outer inclined surface 94d. The inner groove end angle between the inner inclined surface 94c and the cutting edge 93a is the same as the inner groove end angle 92f, for example, 75°. The outer groove end angle between the outer inclined surface 94d and the cutting edge 93a is the same as the outer groove end angle 92g, for example, 55°.

[0083] As shown in Figure 15, the groove end distance 16 between the inner groove end 92a and the inner groove end 94a is, for example, 0.04 mm. The first distance 95a between the first groove bottom 92e and the thickness center 7c is the same size as the second distance 95b between the second groove bottom 94e and the thickness center 7c. The first distance 95a and the second distance 95b are based on the position closest to the center of the base metal 2 (see Figure 5) among the first groove bottom 92e and the second groove bottom 94e. The groove bottom distance 95, which is the sum of the first distance 95a and the second distance 95b, is 0.35 mm or less and is smaller than the groove bottom distance 15 shown in Figure 7. The groove bottom distance 95 is, for example, 0.22 mm.

[0084] Next, a tenth embodiment of the present disclosure will be described with reference to Figure 16. The circular saw blade 100 has a first tip 101 and a second tip 103 instead of the first tip 11 and second tip 13 shown in Figure 7. The first tip 101 has a first groove 102 extending circumferentially from the cutting edge 101a instead of the first groove 12 shown in Figure 7. The second tip 103 has a second groove 104 extending circumferentially from the cutting edge 103a instead of the second groove 14 shown in Figure 7.

[0085] As shown in Figure 16, the first groove 102 is provided in the first thickness direction to the left of the thickness center 7c. The first groove 102 is substantially V-shaped when viewed from the front in the rotational direction of the circular saw blade 100. The first groove 102 has a substantially planar inner inclined surface 102c and an outer inclined surface 102d that are inclined with respect to the cutting edge 101a. The inner inclined surface 102c and the outer inclined surface 102d are connected by the first groove bottom 102e, which has an arc-shaped curved surface when viewed from the front in the rotational direction of the circular saw blade 100.

[0086] As shown in Figure 16, an inner groove end 102a is provided at the intersection of the cutting edge 101a and the inner inclined surface 102c. An outer groove end 102b is provided at the intersection of the cutting edge 101a and the outer inclined surface 102d. The inner inclined surface 102c has an inner groove end angle 102f with respect to the cutting edge 101a. The outer inclined surface 102d has an outer groove end angle 102g with respect to the cutting edge 101a. The outer groove end angle 102g is greater than the inner groove end angle 102f and is 85° or less. The inner groove end angle 102f is, for example, 55°. The outer groove end angle 102g is, for example, 75°. The groove bottom angle 102h between the inner inclined surface 102c and the outer inclined surface 102d is 50°.

[0087] As shown in Figure 16, the second groove 104 is provided in a shape and position symmetrical to the first groove 102 with respect to the thickness center 7c. The second groove 104 is provided in the second thickness direction to the right of the thickness center 7c. The second groove 104 has a substantially planar inner inclined surface 104c and an outer inclined surface 104d that are inclined with respect to the cutting edge 103a. The inner inclined surface 104c and the outer inclined surface 104d are connected at the bottom 104e of the second groove. An inner groove end 104a is provided at the intersection of the cutting edge 103a and the inner inclined surface 104c. An outer groove end 104b is provided at the intersection of the cutting edge 103a and the outer inclined surface 104d. The inner groove end angle between the inner inclined surface 104c and the cutting edge 103a is the same as the inner groove end angle 102f, for example, 55°. The outer groove end angle between the outer inclined surface 104d and the cutting edge 103a is the same as the outer groove end angle 102g, for example, 75°.

[0088] As shown in Figure 16, the groove end distance 16 between the inner groove end 102a and the inner groove end 104a is, for example, 0.04 mm. The first distance 105a between the first groove bottom 102e and the thickness center 7c is the same size as the second distance 105b between the second groove bottom 104e and the thickness center 7c. The groove bottom distance 105, which is the sum of the first distance 105a and the second distance 105b, is 0.35 mm or less and is greater than the groove bottom distance 15 shown in Figure 7. The groove bottom distance 105 is, for example, 0.35 mm. Although the groove bottom distance 105 is relatively large, the angular shape of the inner groove ends 102a and 104a can be formed with a large obtuse angle. Therefore, chipping at the inner groove ends 102a and 104a can be suppressed.

[0089] As shown in Figures 17 and 18, comparative experiments were conducted on the relationship between groove shape and lateral displacement for the circular saw blades of each embodiment described above. All test specimens were circular saw blades with an outer diameter of 285 mm, a blade thickness of 1.0 mm, a base plate thickness of 0.8 mm, a mounting hole diameter of 40 mm, and 80 teeth. Hard tips made of cermet were used for the tips. The workpiece was a non-heat-treated steel bar with an outer diameter of 37 mm. Cutting was performed under cutting conditions of a rotational speed of 150 rpm, a cutting depth of 0.105 mm per tooth, and a feed rate of 1260 mm / min. The feed rate is approximately 2.5 times that of normal cutting. Test specimen 70V corresponds to circular saw blade 30 shown in Figure 9. Test specimen 60V is a circular saw blade in which the inner groove end angle 12f and outer groove end angle 12g of circular saw blade 1 shown in Figure 7 are changed to 60°, and the groove bottom angle 12h is changed to 60°. Test sample 50V corresponds to circular saw blade 1 shown in Figure 7. Test sample 30V corresponds to circular saw blade 20 shown in Figure 8. Test sample 0.2U is a circular saw blade in which the groove width 42h of circular saw blade 40 shown in Figure 10 has been changed to 0.20.

[0090] As shown in Figures 17 and 18, a larger groove end angle allows for a smaller distance between groove bottoms. It was found that a smaller distance between groove bottoms reduces the lateral displacement of the chip. In particular, the lateral displacement was reduced by more than 0.001 mm between test specimen 60V with a groove end angle of 60° and test specimen 50V with a groove end angle of 65°. Furthermore, the lateral displacement of test specimen 0.2U with a groove end angle of 90° was reduced to less than half compared to test specimen 70V with a groove end angle of 55°.

[0091] As shown in Figures 19-24, simulations were performed to analyze the equivalent stress during cutting for each of the above-described embodiments of the chip. The test specimens and cutting conditions were set to be the same as those for the tests shown in Figures 17 and 18. The simulation examined the equivalent stress experienced by the chip at a cross-section at a depth d of 0.10 mm from the bottom of the groove formed in the workpiece when the chip cuts the workpiece.

[0092] Simulation results showed that high equivalent stress occurs near the cutting edge on both sides of each chip, as shown in Figures 20-24. Comparing the narrow cutting edge on the left and the wide cutting edge on the right, the maximum value of the equivalent stress is approximately the same. Regarding the distribution of equivalent stress, the narrow cutting edge shows a wider distribution of high equivalent stress values ​​than the wide cutting edge on the right. Furthermore, the larger the groove end angle of the groove formed on the chip, the more likely it is that a high equivalent stress distribution will spread widely from the side of the chip to the groove. In particular, for test specimen 30V with a groove end angle of 75° and test specimen 0.2U with a groove end angle of 90°, equivalent stress of approximately the same magnitude as on the left side 11d occurs at the positions corresponding to the outer inclined surface 22d shown in Figure 8 and the outer upright surface 42e shown in Figure 10. When a test was conducted to cut a workpiece with test specimen 0.2U, a defect occurred at the position corresponding to the outer upright surface 42e.

[0093] Based on the above-mentioned test and simulation results, a tip with grooves having a groove end angle of 60° to 85° is considered one preferred configuration in this disclosure. This configuration can suppress lateral displacement of the tip and prevent the generation of large equivalent stresses around the groove ends. This can improve the durability of the tip.

[0094] As shown in Figure 25, the number of heat cracks was measured for the circular saw blades 1 and 30 described above. The test specimens and cutting conditions were set to be the same as those for the tests shown in Figures 17 and 18. Cutting was performed until the number of cuts was equivalent to 18,000, and the number of chips with heat cracks was measured for each state of heat cracking. In Figure 25, θ1 represents the inner groove end angles 12f, 32f (see Figures 7 and 9), and θ2 represents the outer groove end angles 12g, 32g. The cutting edges 11c and 31a on the wider side of the blade length represent the region from the inner groove ends 12a and 32a to the intersection with the right chamfer 11f. The cutting edges 11c and 31a on the narrower side of the blade length represent the region from the outer groove ends 12b and 32b to the intersection with the left chamfer 11f.

[0095] As shown in Figure 25, no heat cracks occurred on the cutting edge 11c on the narrower side of the circular saw blade 1. In Figure 25, the chips in parentheses indicate chips in which defects originated in areas other than the boundary wear region where friction with the workpiece occurs. No other defects were found on this chip. Therefore, it was considered not to be a defect caused by a heat crack and was excluded from the number of heat crack occurrences. In 16 chips 7 (see Figure 7), small heat cracks with 1 to 2 lines occurred on the cutting edge 11c on the wider side of the blade (see Figure 7). No large heat cracks with 3 or more lines, or defects due to heat cracks, occurred on the cutting edge 11c on the wider side of the blade.

[0096] As shown in Figure 25, in 13 of the 13 chips 7 (see Figure 9) of the circular saw blade 30, small heat cracks occurred on the cutting edge 31a on the side with the narrower blade length. No large heat cracks or damage due to heat cracks occurred on the cutting edge 31a on the side with the narrower blade length. In all of the chips 7 of the circular saw blade 30, heat cracks occurred on the cutting edge 31a on the side with the wider blade length. Large heat cracks occurred in 65 of the chips 7, and damage due to heat cracks occurred in 3 of the chips 7.

[0097] As shown in Figures 26-37, the chipping condition of the chip 7 generated during cutting was compared for the circular saw blades 1 and 30 described above. The test specimens and cutting conditions were set to be the same as in the tests shown in Figures 17 and 18. For the first circular saw blade 1 shown in Figures 27-30 and the circular saw blade 30 shown in Figures 36 and 37, cutting was performed until the number of cuts was equivalent to 20,000. For the second circular saw blade 1 shown in Figures 31 and 32, the number of teeth was set to 4 and cutting was performed until the number of cuts was equivalent to 20,000. For the third circular saw blade 1 shown in Figures 33-35, the number of teeth was set to 4 and cutting was performed until the number of cuts was equivalent to 25,000.

[0098] As shown in Figures 26 and 30, a large chip occurred on one of the chips 7 of the first circular saw blade 1, on the left side near the bottom of the first groove. This chip originated in a location that was not part of the boundary wear region where friction with the workpiece occurred, as described above. Therefore, it is not considered to be a chip caused by a heat crack. This chip caused streaks to appear on the cut surface of the workpiece. As shown in Figures 26 to 29, no heat cracks occurred on the right side 13e, which is connected to the narrower cutting edge 13c. On the left side 13d, which is connected to the wider cutting edge 13c, small heat cracks with one or two linear streaks occurred.

[0099] As shown in Figures 26, 31, and 32, no heat cracks occurred on the right side 13e of the tip 7 of the second circular saw blade 1, which is connected to the narrower cutting edge 13c. Small heat cracks with one or two linear lines occurred on the left side 13d, which is connected to the wider cutting edge 13c. The cut surface of the workpiece was good.

[0100] As shown in Figures 26, 33-35, no heat crack occurred on the right side 13e of the tip 7 of the third circular saw blade 1, which is connected to the narrower cutting edge 13c. Small heat cracks with one or two linear lines occurred on the left side 13d, which is connected to the wider cutting edge 13c. A crack extended to the right from the left side 13d where the heat crack occurred. The cut surface of the workpiece was good. In summary, in the tip 7 of the circular saw blade 1, a crack occurred near the second groove 14 before cracks occurred on the left side 13d and the right side 13e.

[0101] As shown in Figures 36 and 37, on the tip 7 of the circular saw blade 30, large heat cracks with three or more lines and defects due to heat cracks occurred on the left side surface 13d, which is connected to the wider cutting edge 33a. On the right side surface 13e, which is connected to the narrower cutting edge 13c, the occurrence of heat cracks was suppressed.

[0102] Based on the test results described above, a configuration having a first tip and a second tip in which the sum of the first distance from the bottom of the first groove to the center of the cutting edge thickness and the second distance from the bottom of the second groove to the center of the cutting edge thickness is 0.35 mm or less, and particularly 0.28 mm or less, is considered one preferred configuration in this disclosure. With this configuration, heat cracks that may occur on the side surface of the tip can be suppressed. In particular, the occurrence of heat cracks can be effectively suppressed on the side surface connected to the wider cutting edge. Heat cracks can also be suppressed on the side surface connected to the narrower cutting edge without affecting the cut surface of the workpiece.

[0103] Various modifications can be made to the circular saw blades of each embodiment described above. An example was given in which the thickness centers 7c of the first tip 11 and the second tip 13 are aligned with the thickness center 2b of the base metal 2 and the first tip 11 and the second tip 13 are mounted on the base metal 2. Alternatively, for example, the thickness center 7c of the first tip 11 may be positioned to the right of the thickness center 2b of the base metal 2 and the thickness center 7c of the second tip 13 may be positioned to the left of the thickness center 2b of the base metal 2. An example was given in which the first groove 12 and the second groove 14 do not overlap when viewed from the front in the rotational direction of the circular saw blade 1. Alternatively, the first groove 12 and the second groove 14 may overlap when viewed from the front in the rotational direction of the circular saw blade 1. Or, a part of the first groove 12 or the second groove 14 may straddle the thickness center 2b of the base metal 2.

[0104] An example is shown of a first groove 12 and a second groove 14 provided in a shape and position symmetrically with respect to the thickness center 7c of the tip 7. Alternatively, the first groove 12 and the second groove 14 may be provided in a shape asymmetrically with respect to the thickness center 7c of the tip 7. Or, the first groove 12 and the second groove 14 may be positioned asymmetrically with respect to the thickness center 7c.

[0105] The thickness 7d of the tip 7 is not limited to the exemplified range of 0.8 to 1.1 mm, but may also be, for example, 1.1 to 2.0 mm. The groove end angle is not limited to the exemplified angle, but may be set to, for example, 70°, 80°, or 85°. The groove end angles of a pair of groove ends may both fall within the range of 60° to 85°, or one of them may fall within the range of 60° to 85°. The distance 16 between groove ends may be smaller or larger than the exemplified 0.04 mm.

[0106] For example, the first groove 52 may be provided such that the inner groove end angle 52j and the outer groove end angle 52k are of different sizes. For example, the inner U-shaped end 52d and the outer U-shaped end 52g may have R chamfers. For example, the first groove 62 may be provided such that the groove end angles at the inner groove end 62a and the outer groove end 62b are 60° to 85°. For example, the groove bottom angles 92h and 102h may be set to be smaller or larger than the exemplified 50°. The groove extends in the circumferential direction but may be slightly inclined below the relief angle. Also, the groove width may widen towards the rear in the rotational direction.

Claims

1. It is a circular saw blade with a carbide tip, A disc-shaped base metal with an outer diameter of 200 mm to 500 mm, The base metal has first and second tips that protrude radially from the outer circumference of the base metal and are arranged alternately along the outer circumference of the base metal, The circular saw blade has a blade thickness of 0.8 mm to 2.0 mm. The first tip and the second tip have a rake face facing forward in the rotational direction of the circular saw blade, The flank surface of the base metal facing radially outward, A cutting edge formed between the rake face and the relief face, A pair of chamfers provided at both ends of the cutting edge, The relief surface has grooves formed so as to extend circumferentially from the cutting edge, The groove of the first tip has a first groove bottom that is deepest in the radial direction at a position at a first distance in the first thickness direction in the thickness direction of the base metal from the thickness center of the cutting edge of the first tip, The groove of the second tip has a second groove bottom that is deepest in the radial direction at a second distance from the thickness center of the cutting edge of the second tip in the second thickness direction opposite to the first thickness direction in the thickness direction of the base metal, and the sum of the first distance and the second distance is 0.35 mm or less.

2. A circular saw blade with a tip according to claim 1, The groove has a pair of groove ends that intersect with the cutting edge, and a pair of inclined surfaces provided between either of the pair of groove ends and the groove bottom, which are inclined with respect to the cutting edge. A circular saw blade with a carbide tip, wherein the groove end angle between the cutting edge and the inclined surface at the groove end is 60° to 85°.

3. A circular saw blade with a tip according to claim 1 or 2, The groove has a pair of groove ends that intersect with the cutting edge, and a pair of inclined surfaces provided between either of the pair of groove ends and the groove bottom, which are inclined with respect to the cutting edge. A circular saw blade with a carbide tip, wherein the groove end angle between the cutting edge and the inclined surface at the groove end is larger than the angle of the pair of chamfers relative to the cutting edge.

4. A circular saw blade with a tip according to any one of claims 1 to 3, A circular saw blade with a tipped blade wherein the sum of the first inner distance between the inner groove end of the first groove of the first tip and the thickness center of the cutting edge of the first tip, and the second inner distance between the inner groove end of the second groove of the second tip and the thickness center of the cutting edge of the second tip, is smaller than the opening width of the first groove in the cutting edge and smaller than the opening width of the second groove in the cutting edge.

5. A circular saw blade with a tip according to claim 4, A circular saw blade with a carbide tip, wherein the sum of the first inner distance and the second inner distance is less than half the opening width of the first groove in the cutting edge and less than half the opening width of the second groove in the cutting edge.

6. A circular saw blade with a tip according to any one of claims 1 to 5, A circular saw blade with a tip, wherein the first radial depth of the groove of the first tip from the cutting edge and the second radial depth of the groove of the second tip from the cutting edge are both at least twice and at least five times the radial depth of the pair of chamfers from the cutting edge.

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