Bar

Abstract

The present invention relates to a burr (1) for cutting metal surfaces, which has a shaft portion (2) and a milling portion (4) made of a hard alloy. A milling section (4) having a milling length (f) has a plurality of cutting tools (10), the plurality of cutting tools (10) having a main flute depth (h) and separated by spaced apart main flutes (14) extending helically along the milling length (f) in a first twist direction (16) having a first twist angle (α), each of the cutting tools (10) having a rake face (20), a flank face (24), and a cutting edge (12) defining a rake angle (γ) and a clearance angle (δ) at a transition between the rake face (20) and the flank face (24), each of the flank faces (24) being provided with a plurality of chip breakers (30) having a chip breaker depth (s), the chip breakers (30) being arranged helically along the milling section (4) in a second twist direction (32) having a second twist angle (β). The bur (1) according to the present invention is characterized in that in the region of the maximum diameter of the milling section (4), the chip breaker depth (s) is in the range of 5 to 25% of the main groove depth (h), the rake angle (γ) is in the range of -3° to +14°, the clearance angle (δ) is in the range of 10° to 20°, the first twist angle (α) is greater than 25°, and the number of main grooves (14) is less than 15 and equal to or less than 12.

Description

Technical Field

[0001] The present invention relates to the bar described in the first half of claim 1.

Background Art

[0002] Such bars are also known as rotary files (the spelling "Bur" is also used in English). According to German Industrial Standard 8032 / 8033 and ANSI (American National Standards Institute) standards, they are used in portable tools or power tools driven by either an electric motor or pneumatic pressure. They are used for manual and automatic (including robot-guided) grinding of metal surfaces by fine material removal.

[0003] Well-known bars for the above purposes have a shaft portion and a milling portion adjacent to the shaft portion and terminating in unconstrained milling chips. At least the milling portion is made of a hard alloy such as tungsten carbide. The shaft portion and the milling portion are rotationally symmetric with respect to the axis of rotation. The milling portion has a milling length and a number of cutting edges separated by spaced main grooves. For example, the typical number of main grooves in a well-known bar is 24 for a 12.7 mm (1 / 2 inch) bar. The main grooves have a groove depth hereinafter referred to as the main groove depth and extend in a first helical direction having a first helical angle along the milling portion. Each of the cutting edges has a rake face, a flank face, and a cutting edge forming a rake angle and a flank angle at the transition between the rake face and the flank face. The first helical angle is measured between the tangent to the cutting edge and a line parallel to the axis of rotation. Each flank face is provided with a plurality of chip breakers. The chip breakers have a depth hereinafter referred to as the chip breaker depth and are helically arranged along the milling portion in a second helical direction having a second helical angle. The second helical angle is measured between the tangent to the line connecting adjacent chip breakers provided on adjacent flank faces and offset sufficiently obliquely from each other and a line parallel to the axis of rotation. The first helical direction extends in the rotational direction of the bar, while the second helical direction may extend in the opposite direction to the first helical direction and thus also in the opposite direction to the rotational direction of the bar, and the second helical angle is negative. Alternatively, the second helical direction may extend in the rotational direction of the bar, in which case the second helical angle is positive.

[0004] The function of the chip breaker is, on the one hand, to control the formation of chips and, on the other hand, to reduce the cutting resistance. If the chips can be broken into a good length, they will not wrap around the workpiece, suppressing vibration, so the probability of damaging the bar is reduced. The low cutting resistance prevents premature breakage of the cutting edge due to vibration. Also, the low cutting resistance helps to relieve the load and heat generation and can delay wear.

[0005] Well-known bars of the type described above have the drawback that it is not possible to improve the cutting performance without considerably shortening their lifespan. So far, no bar has yet appeared that would optimally meet the requirements of long lifespan and high cutting performance.

Summary of the Invention

Problems to be Solved by the Invention

[0006] The problem of the present invention is to provide a bar having both high cutting performance and a long service life, that is, low wear resistance.

Means for Solving the Problems

[0007] This problem is solved by a bar having the features described in claim 1.

[0008] The bar according to the present invention is generally designed in accordance with German Industrial Standard 8032 / 8033 and ANSI standards.

[0009] Furthermore, the bar of the present invention having a milling part made of cemented carbide is particularly suitable for machining the steel surface.

[0010] In the characterizing part of claim 1, by using the expression "in the region having the maximum diameter of the milling part", a certain reference point is given even when the shape of the bar according to the present invention is different. Therefore, for example, the features according to the present invention can be the same whether the milling part is cylindrical or spherical. Although not exact, the designation "the body of the milling part", which can be understood by those skilled in the art, can be chosen especially for distinguishing from the region of the milling chip.

[0011] According to the present invention, the chip breaker depth of the bar of the present invention within the region having the maximum diameter of the milling part is in the range of 5% to 25% of the main groove depth. Such a chip breaker depth is considerably smaller than that known in the prior art. Due to the manufacturing process, when the chip breaker depth is small, the chip breaker width (measured along the cutting edge) becomes relatively small. The technical effect achieved by these features is to make the linear length of the main groove larger compared to the well-known deeper and wider chip breaker depth. In the prior art, a chip breaker depth up to 80% of the main groove depth is known.

[0012] Furthermore, according to the present invention, the relief angle in the region having the maximum diameter of the milling part is in the range of 10° to 20°. Such a relief angle, when combined with other features according to the present invention, has been found to enhance the resistance of the cutting edge and make it less prone to wear.

[0013] Furthermore, according to the present invention, in the region having the maximum diameter of the milling part, the rake angle is in the range of -3° to +14°. This rake angle, which is relatively smaller than that of well-known bars, has been found to contribute to achieving good cutting performance and low wear.

[0014] Furthermore, the first helix angle according to the present invention is greater than 25°. In combination with reducing the number of main grooves, this increases the strength of the main grooves, so that the life of the bar can be made longer. Also, due to the relatively large first helix angle, the cutting edge comes into more contact with the workpiece. Therefore, the load on the cutting edge is reduced and the quality of the surface finish of the workpiece is improved.

[0015] As a further measure according to the present invention, the number of main grooves is made less than 15, preferably 12 or less. As a result, the cutting performance is improved, and the wear of the milling part is surprisingly reduced by the interaction of all the features of claim 1, which should be at least partly due to the high-strength main grooves.

[0016] In the context of the present disclosure, when the expression "value a to value b" is commonly used, it shall be understood as including the two end values a and b.

[0017] The technical effect as a whole of all the features mentioned is that the bar according to the present invention exhibits excellent performance when the grinding process is started. Tests have shown that a performance improvement of more than 80% can be achieved compared to well-known bars. Even after a 40-minute cutting process, the cutting performance of the bars of the present invention tested is approximately 30% higher than that of conventional bars. Surprisingly, this performance improvement does not sacrifice the service life of the bars according to the present invention. The inventor assumes that this unexpected effect is due to the fact that the chip breaker depth is small compared to the main groove depth (and accordingly, the width of the chip breaker along the cutting edge is also small), and the relief angle is also small.

[0018] According to the above, an important feature of the bar of the present invention is that the chip breaker depth is very small (and thus the width is also narrow) compared to well-known milling bars, but the purpose of the chip breaker, i.e., breaking the chips during the cutting process, is maintained. Since the chip breaker depth is small and the chip breaker width related to manufacturing is accordingly small, the resulting straight length of the cutting edge is minimized.

[0019] It has been found that it is particularly advantageous for the chip breaker depth to be in the range of 10% to 20% of the main groove depth in the region having the maximum diameter of the milling part.

[0020] Alternatively, in addition, or supplementarily, the chip breaker depth in the region having the maximum diameter of the milling part is preferably in the range of 0.1 to 0.25 mm, and preferably 0.2 mm or less. Based on the above preferred feature, i.e., the chip breaker depth in the range of 10% to 20% of the main groove depth as a reference value, the main groove depth is 0.5 to 2.5 mm. In an exemplary design, the chip breaker depth for a main groove depth of 1 mm can be 0.1 mm. In another exemplary design, the chip breaker depth for a main groove depth of 2 mm is 0.2 mm.

[0021] In the region having the maximum diameter of the milling part, the chip breaker depth is preferably not more than the maximum width (chip breaker width) of the chip breaker measured along the cutting edge. Preferably, for example, the chip breaker width is twice the size of the chip breaker depth. Such a ratio of the chip breaker depth to the chip breaker width is achieved, for example, when a chip breaker wheel with an angle of 90° is used.

[0022] The chip breakers are particularly preferably completely included in the flank face, that is, they do not protrude into the main groove or the next chip space that does not face the rotation direction.

[0023] Preferably, all the chip breakers have a distance from the transition part between the shaft part and the milling part and / or from the milling chip. This distance is, for example, preferably at least 1 mm. Thereby, the weak point of the cutting edge can be surely eliminated. The cutting edge may break if the intervals between the chip breaker and the shaft part or the milling chip are too small respectively.

[0024] It has been found to be very advantageous if the flank angle in the region having the maximum diameter of the milling part is in the range of 12° to 18°, particularly preferably in the range of 13° to 15°. By combining with other features of the bar of the present invention, the best results regarding cutting performance and durability have been obtained.

[0025] By having the rake angle of the cutting edge in the range of 0° to +12°, very good cutting performance can be achieved with slight wear, and it has been found that the range of +5° to +10° is particularly good.

[0026] According to an advantageous design, the flank face in the region having the maximum diameter of the milling part, measured in the rotation direction of the bar, has a width of 0.2 mm to 1 mm, preferably 0.4 to 0.8 mm.

[0027] The above-mentioned relief surfaces each start directly from the respective cutting edges in the direction opposite to the rotation direction of the bar, and the only relief surface formed during the manufacture of the main groove is particularly preferred. This relief surface is also referred to as the "first relief surface". The second relief surface is in the direction opposite to the rotation direction of the bar but is not adjacent to the relief surface. Instead, the main groove with the corresponding chip space starts immediately after the (first) relief surface. This design has been shown to facilitate the manufacture of the cutting edges or the main groove, while it has not been shown that it is beneficial to provide additional relief surfaces.

[0028] As initially stated, the first helix angle of a well-known bar is typically 25°. According to the present invention, the first helix angle is selected to be larger than that, preferably greater than 27.5°. The first helix angle is particularly preferably in the range of 29° to 32°, and particularly preferably 30°. The second helix angle, i.e., the pitch angle formed by the chip breaker, is preferably smaller than the pitch of the first helix angle. It has been found to be advantageous that this is in the range of -75° to -88°, preferably -78° to -85°, and particularly preferably -80° to -82°. Alternatively, the second helix angle may be positive, preferably +75° to +88°, preferably +78° to +85°, and particularly preferably +80° to +82°.

[0029] In the bar according to the present invention, the first helix angle of all the cutting edges and the main groove is preferably the same. However, a design in which at least two consecutive cutting tools (and main grooves) have slightly different first helix angles may also be within the scope of the present invention. Furthermore, the first helix angle is preferably constant along the milling length. It is also preferred if the second helix angle is constant.

[0030] Generally, the first and / or second torsional angle may be variable. The first variable torsional angle can be achieved for one or more individual main grooves and / or between different main grooves. Regarding the second variable torsional angle, one embodiment may have, for example, an increasing pitch from the shaft to the milling tip. Other embodiments regarding the second variable torsional angle are possible and not limited.

[0031] In the case of a bar according to the invention having a radius on the milling tip (thus, for example, not including a bar having a cylindrical milling part), advantageously, two cutting edges of at least a pair of cutting edges extending on both sides of the milling part become one at the milling tip. Different from a well-known bar where individual cutting edges freely terminate at the milling tip of the bar, in the above advantageous design, at least two cutting edges form a common cutting edge at the milling tip of the bar. The two cutting edges of the at least a pair of cutting edges form an S shape in a top view of the milling tip. In this way, the stability of the milling tip can be improved. The cutting and excavation operations by the milling tip are also possible, although to a small extent. For example, it is also possible that six cutting edges become one at the tip in the center of the tool.

[0032] It is particularly preferred that the number of main grooves is not more than the maximum diameter of the milling part measured in millimeters. Thus, regarding low-wear cutting results: when the maximum diameter of the milling part is 6 mm, the number of main grooves is 5 - 7, preferably 6; when the maximum diameter of the milling part is 8 mm, the number of main grooves is 7 - 9, preferably 8; when the maximum diameter of the milling part is 10 mm, the number of main grooves is 8 ~11, preferably 8; when the maximum diameter of the milling part is 12 or 12.7 mm, the number of main grooves is 9 - 11, preferably 10; and / or when the maximum diameter of the milling part is 15 or 16 mm, the number of main grooves is 11 - 13, preferably 12, and it has been found to be undoubtedly the case.

[0033] The above-specified upper and lower limits of the parameter values should not be regarded as a fixed pair. For example, the preferred range of values may have upper and lower limits different from the above range. For example, a suitable chip breaker depth may be 5% (Claim 1) to 20% (Claim 2) of the main groove depth.

[0034] The milling part of the bar according to the present invention can be coated with various coatings that contribute to reducing wear and extending the life. Such special coatings may be, for example, TiN, TiAlN, AlTiN, DLC, CH-NFE, and CH-FEP coatings.

[0035] Needless to say, within the scope of the claims, different shapes of the milling part and different numerical values regarding the above physical parameters (helix angle, relief angle, rake angle, chip breaker depth, number of main grooves) can also achieve optimal results in each situation regarding the cutting performance and service life of the bar.

[0036] Further advantageous embodiments are characterized by the matters described in the dependent claims.

Brief Description of the Drawings

[0037] Hereinafter, the present invention will be described in more detail with reference to the drawings.

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Modes for Carrying Out the Invention

[0038] Figures 1 to 6 show a first design example of the bar 1 according to the present invention. According to the side view of Figure 1, the bar 1 has a cylindrical shaft portion 2 and a milling portion 4 that is basically conical and slightly curved outward. The milling portion 4 has a milling length f and terminates at the milling tip 6. The shaft portion 2 serves to be fixed within a manually operated or automatically machine-operated tool, and the tool fixes the shaft portion 2. Thus, the entire bar 1 rotates in the rotational direction 9 for grinding a metal workpiece. For this purpose, the shaft portion 2 and the milling portion 4 are rotationally symmetric with respect to the rotation axis 8.

[0039] At least the milling portion 4 is made of cemented carbide. The shaft portion 2 may also be made of cemented carbide (which is preferred), and preferably, it is integrally formed with the milling portion 4. Alternatively, the shaft portion 2 is made of steel and is, for example, brazed to the milling portion 4. The milling portion 4 may have different shapes. Instead of having a basically conical or tapered cross-section, the milling portion 4 may be designed with a constant or spherical cross-section. Many other shapes are possible, and a mixed shape may also be used, and all of them are shapes well-known to those skilled in the art.

[0040] In the milling portion 4, the cutting edges 10 and the main grooves 14 alternate in the rotational direction 9 of the bar 1. These cutting edges 10 and main grooves 14 are formed along the milling portion 4 in a first helical direction 16 having a first constant helix angle α, here 30°, as viewed from the direction of the milling tip 6 (see Figure 1). The first helix angle α is measured in the region having the maximum diameter of the milling portion 4. In this case, it is measured near the transition portion from the milling portion 4 to the shaft portion 2 between the tangent to the cutting edge 12 of the cutting edge 10 (hereinafter referred to) and the line parallel to the rotation axis 8. The first helical direction 16 is along the rotational direction 9. The number of the main grooves 14 is selected to be small and is less than 15. In the shown design example, there are 10 main grooves 14, and thus, there are also 10 cutting edges 10 (see Figure 2).

[0041] According to the present invention, the first torsional angle α is greater than 25°, preferably greater than 27.5°, and preferably within the range of 29° to 32°. This drawing shows a particularly preferred design with a constant first torsional angle α of 30°. It is also possible to design at least two consecutive cutting tools 10 with different first torsional angles α. For example, the first torsional angles α can be different from each other by 0.5°, 1°, or 2°.

[0042] In particular, as can be seen in FIG. 2, each of the cutting tools 10 has a cutting edge 12. On the side facing the rotational direction 9 of each cutting edge 12, there is a well-known rake face 20 that passes through the rotational axis 8 of the bar 1 and forms a rake angle γ with a straight line perpendicular to the rotational axis 8 (see FIG. 3). On the side opposite to the rotational direction 9 of each cutting edge 12, there is a flank face 24 (also referred to as the "first flank face") that forms a clearance angle δ with the tangent line of the cutting edge 12. The tangent line of the cutting edge 12 is with respect to an imaginary circle that contacts the cutting edge 12 (see FIG. 3). There is no further flank face (the "second flank face") following the first flank face 24 on the opposite side of the rotational direction 9, which is generally not preferred.

[0043] In the embodiment shown in the figure, the rake angle γ is approximately 7°, and optionally within the range of -3° to +14°, preferably within the range of 0° to +12°, and particularly preferably within the range of +5° to +10°.

[0044] A variable rake angle is also possible. Such a variable rake angle can be realized for one or more individual cutting tools and / or between different cutting tools.

[0045] In the embodiment shown in the figure, the clearance angle δ is approximately 15°, and according to the present invention, it is generally within the range of 10° to 20°, preferably within the range of 12° to 18°, and particularly preferably within the range of 13° to 15°. The flank face 24 preferably has a width l of 0.2 mm to 1 mm, preferably 0.4 to 0.8 mm, measured in the rotational direction 9 of the bar 1.

[0046] For a bar having a defined forward radius that applies to bar 1 shown in FIGS. 1 to 6, the rake angle γ at the milling tip of each cutting tool 10 is preferably -3° to 0°. A bar without a defined rear radius has, for example, a cylindrical or conical milling portion.

[0047] On each flank 24 along the extending direction of the cutting tool 10, several chip breakers 30 are provided in the first torsion direction 16. Each of the chip breakers 30 has a chip breaker depth s, which, according to the present invention, is smaller than the main groove depth h (see FIG. 4). The chip breakers 30 of adjacent cutting tools 10 are successively formed in a helix in the second torsion direction 32, which is opposite to the first torsion direction 16 and thus also opposite to the rotation direction 9. The second torsion angle is measured between the tangent of the line connecting the adjacent and obliquely offset chip breakers 30 provided on the successive flanks 24 and a line parallel to the rotation axis 8. The second torsion angle β is preferably constant as shown in the embodiment.

[0048] According to the present invention, the above-mentioned chip breaker depth s is in the range of 5% to 25% of the main groove depth h, preferably in the range of 10% to 20% of the main groove depth h. Such a chip breaker depth s smaller than the main groove depth h has great advantages with respect to the effective cutting length of the cutting tool 10, extends the life of the cutting tool 10, reduces wear, and furthermore, it has been found that it effectively achieves the main problem of the chip breaker 30, that is, improving the control of chips while reducing the cutting resistance. In the design example shown in the figure, the chip breaker depth s is approximately 17% of the main groove depth h.

[0049] Considering the exemplary absolute values, the chip breaker depth s is preferably in the range of 0.1 to 0.25 mm. In one example, the chip breaker depth s for a main groove depth h of 1 mm is 0.1 mm. In another example, the chip breaker depth s for a main groove depth h of 2 mm is 0.2 mm. In these two examples, the chip breaker depth is 10% of the main groove depth h. According to the given percentage range, it is also possible when the chip breaker depth s for a main groove depth h of 1 mm is 0.2 mm, that is, the ratio of the two depths is 20%.

[0050] The chip breaker width b (see FIG. 5) is related to the chip breaker height h since the chip breaker 30 is manufactured using a cutting wheel which is well-known per se, and is preferably larger than the chip breaker depth s, for example, twice as large. For example, in the milling part 4 with a diameter of 12 mm, the chip breaker depth s can be 0.2 mm and the chip breaker width can be 0.4 mm.

[0051] The number of chip breakers 30 along the cutting edge 12 depends on the milling length f, the diameter of the milling part 4, and / or the number of cutting tools 10. For example, the number of chip breakers 30 along the cutting tool 10 is between 4 and 8, for example, 5 or 6. In the shown design example, each cutting tool 10 is provided with 5 chip breakers 30.

[0052] As can be seen from the perspective cross-sectional view of FIG. 5, it is particularly advantageous if the chip breaker 30 is completely within or embedded in the flank face 24.

[0053] The chip breaker 30 preferably has a distance from the boundary region between the milling part 4 and the shaft part 2 (see FIG. 1). In that case, the distance a is preferably at least 1 mm. Further, it is preferable that there is also a corresponding distance (not shown but recognizable in FIG. 6) between the chip breaker 30 and the milling chip 6. Both measured values serve to ensure that the effective length of the cutting edge 12 does not become too short between the chip breaker 30 and the free end of the cutting edge 12, so there is little risk that this part of the cutting edge will be damaged when machining the workpiece by grinding or milling.

[0054] The second helix angle β is formed by a chip breaker 30 that runs in a spiral shape along the milling part 4 and is provided on the cutting tool 10 that is continuous in the direction opposite to the rotation direction 9. In the illustrated embodiment, it is 81°, and generally, preferably, it is within the range of -75° to -88°, preferably within the range of -78° to -85°, and particularly preferably within the range of -80° to -82°.

[0055] In the design example shown in the figure, the second helix angle β is negative, but it may also be positive. Advantageously, it is within the range of +75° to +88°, preferably within the range of +78° to +85°, and particularly preferably within the range of +80° to +82°. In this case, both the first helix direction 16 and the second helix direction 32 extend in the rotation direction 9.

[0056] As can be particularly seen from the plan view of FIG. 6, at least a pair of cutting tools 10 on both sides of the milling part 4 are combined into one by the milling chip 6 and form an S shape 18 in the plan view. The other preferably opposing cutting tools 10 of the milling part 4 may also be combined into one, and as a result, for example, these four cutting tools 10 form a cross shape (having curved arms) in the plan view.

[0057] As already described, according to the present invention, the number of main grooves 14 is selected to be relatively small. In the design example shown in the figure, as described above, there are 10 main grooves 14 and 10 cutting tools 10. It has been found to be advantageous if the number of main grooves 14 is equal to or less than the maximum diameter of the milling part 4 measured in millimeters.

[0058] The values given in the design example shown in the figure (particularly the chip breaker depth s, the main groove depth h, the rake angle γ, the clearance angle δ, the value of the clearance surface 24) are related to the region having the maximum diameter of the milling part 4, that is, the region of the transition part between the milling part 4 and the shaft part 2. In this way, a certain reference point is given, which also applies to the milling part 4 having different shapes (for example, spherical). Although not exact, the designation "body of the milling part 4", which can be understood by those skilled in the art, may be selected particularly to distinguish the region of the milling chip 6.

Explanation of reference numerals

[0059] 1 bar 2 shaft part 3 transition part 4 milling part 6 milling chip 8 rotation axis 9 rotation direction 10 cutting tool 12 cutting edge 14 main groove 16 first torsion direction 18 S shape 20 rake surface 24 clearance surface 30 chip breaker 32 second torsion direction f milling length h main groove depth s chip breaker depth b chip breaker width l clearance surface width a distance α first torsion angle β second torsion angle γ rake angle δ clearance angle

Claims

1. a shaft portion (2), a milling portion (4) made of cemented carbide, adjacent to the shaft portion (2) and terminated by a milling tip (6), the milling portion (4) having a milling length (f) has a plurality of cutting edges (10), the plurality of cutting edges (10) have a main groove depth (h), and along the milling length (f), are separated by spaced main grooves (14) that extend helically in a first helical direction (16) having a first helix angle (α), each of the cutting edges (10) has a rake face (20), a flank face (24), and a cutting edge (12) that forms a rake angle (γ) and a flank angle (δ) at a transition between the rake face (20) and the flank face (24), each of the flank faces (24) is provided with a plurality of chip breakers (30) having a chip breaker depth (s), the chip breaker (30) is a bar (1) for an electric or pneumatically actuated portable or automatic tool for face milling a metal surface, arranged helically in a second helical direction (32) having a second helix angle (β) along the milling portion (4), in a region having the maximum diameter of the milling portion (4), the chip breaker depth (s) is within the range of 5% to 25% of the main groove depth (h), the rake angle (γ) is within the range of -3° to +14°, the flank angle (δ) is within the range of 10° to 20°, and the first helix angle (α) is greater than 25°, the bar (1), characterized in that the number of the main grooves (14) is less than 15.

2. The bar (1) according to claim 1, characterized in that in the region having the maximum diameter of the milling portion (4), the chip breaker depth (s) is within the range of 10% to 20% of the main groove depth (h).

3. The bar (1) according to claim 1 or 2, characterized in that in the region having the maximum diameter of the milling portion (4), when the main groove depth (h) is 0.5 mm to 2.5 mm, the chip breaker depth (s) is within the range of 0.1 to 0.25 mm.

4. The bar (1) according to any one of claims 1 to 3, characterized in that the chip breaker depth (s) is at most the same size as the chip breaker width (b) measured along the cutting edge (12).

5. The bar (1) according to any one of claims 1 to 4, wherein the chip breaker (30) is completely within the flank (24).

6. The bar (1) according to any one of claims 1 to 5, wherein all of the chip breaker (30) has a distance (a) with respect to the transition portion between the shaft portion (2) and the milling portion and / or with respect to the milling tip (6).

7. The bar (1) according to any one of claims 1 to 6, wherein in the region having the maximum diameter of the milling portion (4), the flank angle (δ) is in the range of 12° to 18°.

8. The bar (1) according to any one of claims 1 to 7, wherein in the region having the maximum diameter of the milling portion (4), the rake angle (γ) is in the range of 0° to +12°.

9. The bar (1) according to any one of claims 1 to 8, wherein in the region having the maximum diameter of the milling portion (4), the flank (24) has a width (l) of 0.2 to 1 mm measured in the rotational direction (9) of the bar (1).

10. The bar (1) according to any one of claims 1 to 9, wherein since the flank (24) is the only flank formed during the manufacture of the main groove (14), there is no other rake face adjacent to the flank (24) in the rotational direction (9) of the bar (1).

11. The bar (1) according to any one of claims 1 to 10, wherein the first twist angle (α) is greater than 27.5°.

12. The second twist angle (β) is in the range of -75° to -88°, or The bar (1) according to any one of claims 1 to 11, wherein the second twist angle (β) is in the range of +75° to +88°.

13. The bar (1) has a radius at the milling tip (6), At least one pair of the cutting edges (12) on both sides of the milling portion (4) is combined into one at the milling tip (6), which is characterized in that The bar (1) according to any one of claims 1 to 12.

14. The bar (1) according to any one of claims 1 to 13, wherein the two of the at least one pair of cutting edges (12) form an S shape in the plan view of the milling tip (6).

15. The number of the main grooves (14) is equal to or less than the maximum diameter of the milling part (4) measured in millimeters. The bar (1) according to any one of claims 1 to 14.

16. When the maximum diameter of the milling part (4) is 6 mm, the number of the main grooves (14) is 5 to 7. When the maximum diameter of the milling part (4) is 8 mm, the number of the main grooves (14) is 7 to 9. When the maximum diameter of the milling part (4) is 10 mm, the number of the main grooves (14) is 8 to 11. When the maximum diameter of the milling part (4) is 12 or 12.7 mm, the number of the main grooves (14) is 9 to 11. And / or when the maximum diameter of the milling part (4) is 15 or 16 mm, the number of the main grooves (14) is 11 to 13. The bar (1) according to any one of claims 1 to 14. The bar (1) according to any one of claims 1 to 14.

17. The number of the main grooves (14) is 12 or less. The bar (1) according to claim 1. The bar (1) according to claim 1.

Images