Milling burr and use thereof

Abstract

The invention relates to a milling burr (1) for an electrically or pneumatically operated hand-held tool for deburring, shaping, grinding and finishing iron-free surfaces, comprising: - a shank portion (2) and - a milling portion (4) made of a hard metal, in particular tungsten carbide, which adjoins the shank portion (2) and ends in a milling tip (6), wherein the milling portion (4) has a milling length (f) and a plurality of cutting edges (10) which are separated by mutually spaced main flutes (14) which have a main flute depth (h) and extend helically in a first twist direction (16) with a first twist angle (α) along the milling length (f), wherein each of the cutting edges (10) has a rake face (20) and a relief face (24) and a cutting edge (12) at the transition of rake face (20) and relief face (24), forming a rake angle (γ) and a relief angle (δ). The milling burr (1) according to the invention is characterized in that said relief face (24) is a first relief face (24) and said relief angle (δ) is a first relief angle (δ), wherein the first relief face (24) is adjoined in the circumferential direction of the milling portion (4) by a second relief face (26) which extends at a second relief angle (ε), and, in the region of the milling portion (4) with the largest diameter, the first relief angle (δ) is in the range from 6° to 20° and the second relief angle (ε) is in the range from 8° to 30°, and the second relief angle (ε) is greater than the first relief angle (δ). The invention also relates to the use of such a milling burr (1).

Description

[0001] Milling cutter and its use

[0002] The invention relates to a milling cutter according to the preamble of claim 1.

[0003] The invention also relates to the use of such a milling cutter.

[0004] Such milling cutters are also known as rotary files (in English: bur or burr). For the purposes of this invention and in accordance with the definition in DIN 8032 / 8033 and ANSI, they are used primarily in hand-held tools powered by an electric motor or pneumatically, and for the manual processing of metal surfaces in particular by fine material removal. Milling cutters are generally used for deburring, shaping, grinding, and finishing metal, but also other materials such as wood, plastic, and composites. They are frequently used in applications where precision and intricate details are required, e.g., in metalworking, but also in jewelry making and dentistry.

[0005] Burrs differ from end mills primarily in their use in other tools and in the way they machine their respective surfaces. End mills are used in stationary machines, especially CNC or foot-operated machines, and are primarily used for cutting and shaping materials, especially by milling. They are commonly used in metalworking, woodworking, and other machining processes to remove material from a workpiece and create specific shapes, slots, or features.

[0006] Common milling cutters for hand-operated tools have a shaft portion and a milling portion that adjoins the shaft portion and terminates in a free milling tip. At least the milling portion is made of hard metal, such as tungsten carbide. The shaft portion and the milling portion are rotationally symmetrical about a rotational axis. The milling portion has a milling length and a plurality of cutters separated by spaced-apart main flutes. A typical number of main grooves for known milling cutters with a head diameter (largest or maximum diameter of the milling section, ie at its thickest point) of 12 mm or 12.7 mm (ie 1 / 2 inch or 1 / 2”) for machining ferrous surfaces is, for example, 24. The main grooves have a groove depth (English:flute depth), hereinafter referred to as the main flute depth, and extend helically in a first twist direction with a first twist angle along the milling section. Each of the cutting edges has a rake face and a relief face as well as a cutting edge at the transition between the rake face and the relief face, forming a rake angle and a relief angle. The first twist angle is measured between a tangent to the cutting edge and a line parallel to the axis of rotation.

[0007] Commercially available milling cutters of the aforementioned type have the disadvantage that they do not offer optimal cutting performance, particularly when machining aluminum and other non-ferrous materials, but also when machining ferrous materials.

[0008] The object of the present invention is to provide a milling cutter with improved overall performance, particularly when machining aluminum and other non-ferrous materials, but also ferrous materials. This object is achieved by a milling cutter having the features of claim 1. This object is also achieved by corresponding uses of such a milling cutter.

[0009] The invention proposes, for the first time, the design of milling cutters with a second flank, which adjoins a milling surface, which can then be referred to as the first milling surface. Such second flanks have previously only been known in end mills. The advantages of a second flank have not yet been recognized for milling cutters. With milling cutters, the focus has so far been on the cutting characteristics of the milling cutters and their stock removal performance.

[0010] According to the invention, the first clearance angle in the region of the milling section with the largest diameter (in other words: in the region of the largest diameter of the milling section) is in the range of 6° to 20° and the second clearance angle is in the range of 8° to 30°, wherein the second clearance angle is greater than the first clearance angle in order to create a clearance behind the first clearance surface.

[0011] According to the invention, the use of second flank faces in milling cutters significantly improves chip evacuation during the machining process due to the chip space created behind the first flank face. The second flank face thus assists in the efficient removal of chips and prevents them from accumulating, which could lead to tool damage or poor surface finish of the workpiece. The second flank face also reduces friction between the milling cutter and the machined surface, as the creation of clearance reduces the contact area between the tool and the workpiece, thereby significantly reducing heat generation and tool wear. This also results in an improved surface quality, i.e. a smoother surface. Finally, the effective chip evacuation and reduced friction can extend the service life of the milling cutter.The first clearance surface may also be referred to as the primary clearance surface, and the second clearance surface as the secondary clearance surface. Accordingly, the first clearance angle may also be referred to as the primary clearance angle, and the second clearance angle as the secondary clearance angle.

[0012] The term "in the area of ​​the milling section with the largest diameter" is used to provide a consistent reference point, even for different geometries of the burrs according to the invention. Thus, for example, the features according to the invention can be identified for both a cylindrical and a spherical milling section. Somewhat less precise, but still understandable to the person skilled in the art, the term "main body of the milling section" could be chosen, particularly to distinguish it from the area of ​​the milling tip.

[0013] It should be emphasized that these flanks are distinct from the heel, which is located downstream of the cutter against the direction of rotation of the burr and leads to the root of a subsequent main groove (the chip space formed by the groove is referred to as the gullet). For the purposes of this invention and application, this heel is referred to as the "transition region." Generally speaking, the transition region lies between the successive flanks and the root of the next main groove, opposite the direction of rotation of the burr.

[0014] More precisely, the said transition area or heel is the rear area of ​​the cutting edge that extends from the rear edge of the last clearance surface (opposite the direction of rotation of the burr) to the groove bottom or groove base of the associated main groove of the burr. In other words, the transition area adjoins the last clearance surface opposite the direction of rotation of the burr and leads to the groove bottom or groove base of the respective main groove. The angle or curvature of this transition area generally varies in its course relative to the groove bottom or groove base of the respective main groove. Thus, in the context of the present invention and in accordance with general technical knowledge, a clearance surface is to be distinguished from the transition area (heel, shoulder, "heel"), and a clearance angle is to be distinguished from any angle of the transition area that leads to the groove bottom or groove base of the associated main groove.The transition area typically has a much greater extent in the circumferential direction of the milling cutter than any of the flanks. This preferably also applies to the milling cutter according to the invention.

[0015] It has proven to be advantageous for chip removal if the first clearance angle in the area of ​​the milling section with the largest diameter is in the range of 5° to 18° and preferably in the range of 12° to 15°.

[0016] The same applies if the second clearance angle in the area of ​​the milling section with the largest diameter is in the range of 13° to 27°, preferably in the range of 20° to 23° - again under the condition that the second clearance angle is larger than the first clearance angle.

[0017] Tests have also shown that improved chip removal also benefits if the width of the first flank in the area of ​​the milling section with the largest diameter is in the range of 0.2 mm to 2 mm, preferably in the range of 1 mm to 1.6 mm.

[0018] In this context, it has also proven advantageous that the width of the second flank in the region of the milling section with the largest diameter is in the range of 0.3 mm to 2 mm, preferably in the range of 0.4 to 1.6 mm.

[0019] The above-mentioned size selection regarding angle and width of the first and second

[0020] Open surfaces have proven to be particularly advantageous for achieving excellent machining performance on the one hand and excellent chip removal on the other, particularly when machining aluminum surfaces and surfaces of other non-ferrous materials.

[0021] But the milling cutter according to the invention has also generally proven to be very advantageous in terms of cutting performance and chip removal when machining ferrous surfaces.

[0022] The invention is not limited to providing two clearance surfaces. It is equally possible for the second clearance surface to be followed in the circumferential direction of the milling section by a third clearance surface and optionally by a fourth clearance surface and further optionally by one or more further clearance surfaces. In the region of the milling section with the largest diameter, the third clearance surface runs at a third clearance angle and the optional fourth clearance surface at a fourth clearance angle. This can provide further improved clearance for chip removal. Advantageously, the third clearance angle is in the range from 10° to 40°, preferably in the range from 20° to 30°, and is greater than the second clearance angle. The optional fourth clearance angle is in the range between more than 10° and 60°, preferably in the range from 22° to 42° and particularly preferably in the range from 30° to 35°, and is greater than the third clearance angle.Furthermore, it is advantageous if the width of the third free surface is in the range of 0.3 mm to 2 mm, preferably in the range of 0.4 to 1.6 mm. The width of the optional fourth free surface is preferably in the range of 0.3 mm to 2 mm, preferably in the range of 0.4 to 1.6 mm.

[0023] Good cutting performance with minimal wear has been achieved with cutting edge rake angles in the range between -10° and +25°, preferably in the range of -5° to 20°, and particularly preferably in the range of 0° to 15°, most preferably in the range of 5° to 15°. The aforementioned positive rake angles have proven particularly advantageous when machining softer materials such as aluminum. A negative rake angle can be advantageous when machining ferrous materials such as steel.

[0024] The rake angle can be constant or, within the aforementioned ranges, vary over the milling length. Accordingly, it can be advantageous if the rake angle varies along the length of the main flutes. For example, the rake angle could be 5° near the tip of the burr, 10° in the middle of its milling section, and 7° or even decrease to 5° on the side facing the shank. Variable rake angles and pitches can help reduce vibration during material processing.

[0025] According to an advantageous embodiment, the first helix angle is positive and, in the region of the milling section with the largest diameter, lies in the range of 15° to 50°, preferably in the range of 30° to 35°. The first helix angle can be constant or vary. In the latter case, the first helix angle preferably varies in the range of 15° to 40°.

[0026] According to an alternative, the first helix angle is negative and lies in the area of ​​the milling section with the largest diameter in the range of

[0027] -10° to -50°, preferably in the range of -30° to -35°. Here, too, the first helix angle can be constant or vary, preferably in the range of -15° to -40°.

[0028] The number of main grooves is preferably no more than 12 and preferably no more than 10, in particular with a maximum diameter of the milling section (head diameter) of 12 mm or 12.7 mm or less. The milling cutter particularly preferably has no more than 8 main grooves and, for example, no more than 6. One design which has proven advantageous in certain cases, particularly for aluminum, has 5 main grooves. Compared to conventional milling cutters, this is a small number, but has proven advantageous in many cases. In particular when machining non-ferrous materials or surfaces, the choice of a relatively small number of main grooves, namely up to 12, for example 10 or 8 or 6 or 5, has proven advantageous, in particular with a maximum diameter of the milling section of up to 12 mm or 12.7 mm.

[0029] With a larger maximum diameter of the milling section, for example, 16 mm or 20 mm, it may be advantageous to select a larger number of main grooves compared to a maximum diameter of 12 mm or 12.7 mm. In such embodiments, it may be advantageous to provide at least 10 and preferably at least 14 main grooves, for example, 18 or 20 main grooves or even more.

[0030] The main groove depth in the area of ​​the milling section with the largest diameter is preferably in the range of 0.5 mm to 3 mm, preferably in the range of 0.9 to 1.35 mm.

[0031] According to advantageous embodiments, in addition to the main flutes, secondary flutes run through the cutting edges, wherein the secondary flutes extend helically along the milling length in a second helix direction with a second helix angle of opposite sign to the first helix angle, wherein the depth of the secondary flutes is 1% to 100% of the depth of the main flutes, preferably 5% to 50%. Such designs are also known under the term "cross-cut" and can also be translated as "double cut". The overlapping flute paths create more cutting edges along the length and circumference of the burr, which increases its cutting and stock removal efficiency in multiple directions and thus its performance compared to burrs with only cutting edges in one direction.The milling cutters according to the invention can generally have the shape of a right-handed spiral (cutting edges run spirally upwards to the right, viewed from the cutter tip to the shank section) and a right-handed cut (material removal by the cutting edges with clockwise rotation, viewed from the cutter tip to the shank section). It is also possible to produce milling cutters according to the invention with a left-handed spiral and a right-handed cut. Another option is a left-handed spiral with a left-handed cut.

[0032] According to an advantageous embodiment, the burr has a plurality of chip breakers in each cutting edge. The chip breakers have a depth, which is referred to below as the chip breaker depth, and preferably extend helically in a third helix direction with a third helix angle along the milling section. The third helix angle is measured between a tangent to the connecting line between adjacent chip breakers provided in successive flanks, but offset obliquely to one another, and the aforementioned parallel to the rotation axis. The first helix direction runs in the direction of rotation of the burr, while the third helix direction can run opposite to the first helix direction and thus also opposite to the direction of rotation of the burr; the third helix angle is then negative. Alternatively, the third helix direction can also run in the direction of rotation of the burr, in which case the third helix angle is positive.

[0033] The function of chip breakers is, on the one hand, to control chip formation and, on the other hand, to reduce cutting resistance. If the chips can be broken to a suitable length, they do not wrap around the workpiece, vibrations are suppressed, and the likelihood of damage to the burr is reduced. Low cutting resistance prevents premature breakage of the cutting edge due to vibration. Low cutting resistance also contributes to reducing load and heat generation and can delay wear. If chip breakers are present in the cutting surfaces, they should preferably have a chip breaking depth in the range of 0.05 mm to 0.5 mm in the area of ​​the milling section with the largest diameter.Alternatively or additionally, the chip breaker depth in the region of the milling section with the largest diameter is advantageously up to 80% of the main groove depth, particularly preferably in the range of 5% to 25% and most preferably in the range of 10% to 20% of the main groove depth.

[0034] The clamping breakers preferably extend in the circumferential direction of the milling section not only over the first flank, but also over the second flank (and if present, also over the third and if present, also over further flanks).

[0035] The distance (the so-called pitch) of adjacent chip breakers along each cutting edge is advantageously in the range of 0.5 mm to 7 mm, preferably in the range of 3 mm to 6 mm.

[0036] Particularly preferably, the first flank surface is produced using a tangential grind. The first flank surface is ground at a 90° angle to the grinding wheel, which is usually diamond-coated. This results in a first flank surface that is arranged tangentially to the cutting edge of the drill. The purpose of the tangential flank surface is to create an increased clearance between the cutting edge and the material being machined. This distance improves chip evacuation and reduces friction and heat generation, thereby preventing premature wear and extending the service life of the cutting edge. Alternatively or additionally, the second flank surface is also ground tangentially.

[0037] Alternatively, other grinding geometries are also possible. According to one example, the first flank is produced with a radial grind; the resulting radial flank forms a fixed angle with the rotational axis of the burr.

[0038] The second and any additional flanks can also have a tangential grind. Alternative grinds are also possible here, particularly radial or straight grinds. It is also possible for the grinds to be different for different flanks, for example, the first flank has a tangential grind and the second flank has a radial grind.

[0039] All of the aforementioned lower and upper limits for parameter values ​​should not be considered closed or fixed pairs. For example, the preferred lower limit of one specified pair of values ​​can be combined with the upper limit of another specified pair of values ​​to form a further advantageous range.

[0040] The milling sections of the burrs according to the invention can be provided with various coatings that contribute to reducing wear and increasing service life. Such special coatings can consist of TiN, TiAIN, AITiN, DLC, CH-NFE, and CH-FEP, for example.

[0041] The invention further relates to the use of a milling cutter as described above in an electrically or pneumatically operated, hand-held tool, in particular to deburr, shape, grind and / or finish a non-ferrous surface.

[0042] According to a particularly preferred use, the surface to be machined consists of aluminum or titanium or an alloy containing these materials, or of reinforced plastic. In particular, the milling cutter according to the invention has proven to be excellent for machining non-ferrous materials. However, the use of the milling cutter according to the invention is not limited to machining non-ferrous surfaces. By changing the geometry of the milling cutter, machining ferrous surfaces is also possible and advantageous.

[0043] It is understood that different geometries of the milling sections with different numerical values ​​in relation to the aforementioned physical parameters (helix angle, clearance angle, rake angle, chip breaker depth, number of main flutes) within the specified ranges lead to optimal results in terms of cutting performance and service life of the burrs. Based on the above, the geometries of burrs according to the invention, for example, should be selected accordingly for machining non-ferrous surfaces or accordingly for machining ferrous surfaces.

[0044] Advantageous further developments are characterized by the features of the subclaims.

[0045] The invention is explained in more detail below with reference to the figures. They show:

[0046] Fig. 1 is a side view of a milling pin according to the invention;

[0047] Fig. 2 is a front view of the milling cutter of Fig. 1;

[0048] Fig. 3 cross-sectional view along AA in Fig. 1 ;

[0049] Fig. 4 is an enlarged detail B of Fig. 3;

[0050] Fig. 5 shows a second embodiment of a milling cutter with a so-called cross-cut; Fig. 6 shows a third embodiment of a milling cutter with clamping breakers, and

[0051] Fig. 7 shows a fourth embodiment with a third free surface.

[0052] When numerical values ​​and ranges of numerical values ​​are mentioned below with regard to the milling cutter shown in the figures, these generally refer - unless expressly stated otherwise or it is obvious - to the area of ​​the milling section of the milling cutter with the largest diameter.

[0053] 1-4 show an embodiment of a milling cutter 1 according to the invention, which has proven particularly advantageous for machining softer materials such as aluminum. According to the side view of FIG. 1, the milling cutter 1 has a cylindrical shaft section 2 and, in this case, a substantially conical milling section 4, the latter having a milling length f and ending in a milling tip 6. The shaft section 2 is used for fastening in a tool, in particular a hand-operated tool, which rotates the shaft section 2 and thus the entire milling cutter 1 in a direction of rotation 9 in order to grind a workpiece, in particular a metallic, iron-free workpiece. For this purpose, the shaft section 2 and the milling section 4 are designed to be rotationally symmetrical to a rotation axis 8.

[0054] At least the milling section 4 is made of hard metal, preferably a carbide material, in particular tungsten carbide. The shaft section 2 can also—which is also preferred—be made of hard metal and is then preferably formed integrally with the milling section 4; alternatively, the shaft section 2 is made of steel, in which case the shaft section 2 is connected to the milling section 4, for example, by brazing. The milling section 4 can have different geometries. Instead of a substantially conical or tapered cross-section, the milling section 4 can be formed with a constant or spherical cross-section. Many other shapes are possible, as are mixed shapes, all of which are known to those skilled in the art.

[0055] At the milling section 4, cutting edges 10 and main grooves 14 alternate in the direction of rotation 9 of the burr 1, with these cutting edges 10 and main grooves 14 running helically along the milling section 4, viewed in the direction of the milling tip 6, in a helix direction 16 with a first, here constant, helix angle a of approximately 32° (see Fig. 1). The helix angle a is measured - in the area of ​​the milling section 4 with the largest diameter, i.e. here in the area of ​​the transition from the milling section 4 to the shank section 2 - between a tangent applied to the cutting edge 12 (see below) of a cutting edge 10 and a line parallel to the rotation axis 8. The first twist direction 16 runs - looking towards the milling tip 6 - in the direction of rotation 9. The number of main grooves 14 is selected to be low and not greater than 12. In the illustrated embodiment, which uses a milling cutter 1 with a maximum diameter of 12 mm or 12.7 mm (1 / 2 inch or1 / 2”), there are only five main grooves 14 and thus only five cutting edges 10, see also the top view of Fig. 2.

[0056] The helix angle α, in the region of the milling section 4 with the largest diameter, is preferably in the range of 15° to 50°, preferably in the range of 22° to 42°, and particularly preferably in the range of 30° to 35°. Embodiments are also possible in which at least two consecutive cutting edges 10 have a different helix angle α from one another, for example, with a helix angle α that differs by 0.5°, 1°, or 2°.

[0057] As shown particularly in the sectional view of Fig. 3 and in the detailed enlargement B of Fig. 4, each of the cutting edges 10 has a cutting edge 12. On the side of each cutting edge 12 facing the direction of rotation 9 of the milling cutter 1, there is, as is known, a rake face 20 which forms a rake angle y with a straight line G running perpendicular to and through the axis of rotation 8 of the milling cutter 1 (cf. Fig. 3).

[0058] On the side of each cutting edge 12 facing away from the direction of rotation 9, there is a first relief surface 24 (primary relief), which forms a first clearance angle θ with a tangent T adjacent to the cutting edge 12, this tangent T being applied to an imaginary circle touching the cutting edges 12 and running perpendicular to the straight line G (cf. Fig. 3). According to the invention, the first relief surface 24 is adjoined, opposite to the direction of rotation 9, by a second relief surface 26 (secondary relief), which forms a second clearance angle θ with the said tangent T adjacent to the cutting edge 12.

[0059] The first clearance angle 6 is approximately 15° in the exemplary embodiment depicted in the figures and, according to the invention, generally in the range of 6° to 20°, preferably in the range of 5° to 18°, and particularly preferably in the range of 12° to 15°. The clearance surface 24 preferably has a width a, measured in the direction of rotation 9 of the milling cutter 1, in the range of 0.2 mm to 2 mm, preferably in the range of 1 to 1.6 mm (see Fig. 4).

[0060] The second clearance angle s in the embodiment shown in the figures is approximately 21° and according to the invention is generally in the range from 8° to 30°, preferably in the range from 13° to 27° and particularly preferably in the range from 20° to 23°. The second clearance angle s is always greater than the first clearance angle 6. The second clearance surface 26 preferably has a width b, measured in the direction of rotation 9 of the milling cutter 1, in the range from 0.3 mm to 2 mm, preferably in the range from 0.4 to 1.6 mm.

[0061] The first free surface 24 is advantageously formed by means of a tangential

[0062] Alternatively or additionally, the second flank surface 26 (and any further flank surfaces that may follow it, see below) can also be produced with a tangential grind. Alternatively, one or more of the flank surfaces 24, 26, 28 (see below) can also have a radial or straight grind.

[0063] It should be emphasized that the flanks 24, 26 differ from the back of the cutting edge or the heel 40 (referred to as "heel" in English), which leads to the groove bottom 42 (also called the groove root; English "root") of a subsequent main groove 14. The heel 40 is also referred to as the transition region 40 in the context of this application and is arranged between the adjoining flanks 24, 26 and the groove bottom 42 of the next main groove 14, opposite the direction of rotation 9 of the milling cutter 1. In the embodiment of Fig. 1-4, the transition area 40 extends from the rear edge of the last flank (in the embodiment according to Fig. 1 to 4 this is the flank 26) against the direction of rotation 9 of the milling cutter 1 to the groove bottom 42 of the next main groove 14. In Fig. 3, the groove bottoms 42 of the main grooves 14 lie on the circumference of the core R of the milling cutter 1 (in Engi, also referred to as “core”), which is shown in dash-dotted lines in Fig. 3. The angle orThe curvature of the transition region 40 generally varies from the rear edge of the last flank (here: flank 26) to the groove bottom 42 of the respective main groove 14. Thus, in the context of the present invention and in accordance with general technical knowledge, the flanks 24, 26 and any further adjoining flanks (see below) are to be distinguished from the transition region 40, and the corresponding clearance angles θ, θ, ... are to be distinguished from each angle or each curvature of the transition region 40 that leads to the groove bottom 42 of the respective main groove 14. In the present case, the transition region 40 has a greater extent in the circumferential direction of the milling cutter 1 than each of the flanks 24, 26 (wherein the extent of the flanks 24, 26 here corresponds to their width a, b). The rake angle y in the exemplary embodiment shown in the figures is approximately+7° and is advantageously in the range between -10° and +25°, preferably in the range from -5° to +20°, and particularly preferably in the range from 0° to +15°. The range from +5° to +15° has proven particularly suitable. Variable rake angles over the length of individual or all cutting edges 10 are also possible.

[0064] The main groove depths, ie the depths of the main grooves 14, are in the region of the milling section (4) with the largest diameter preferably in the range from 0.5 mm to 3 mm, preferably in the range from 0.9 to 1.35 mm.

[0065] In the following description of the alternative embodiments illustrated in Figs. 5 and 6, the same reference numerals are used for features that are identical in their design and / or mode of operation compared to the first embodiment illustrated in Figs. 1-4. Unless otherwise stated, their design and / or mode of operation corresponds to the design and / or mode of operation of the features already described above.

[0066] Fig. 5 shows a second embodiment of a milling cutter 1 according to the invention, in which a plurality of secondary grooves 30 are provided in each cutting edge 10, spaced apart along the course of the respective cutting edge 10. These secondary grooves 30 run helically in a second helix direction 32 with a second helix angle β - measured between a tangent to a connecting line of secondary grooves 30 provided in adjacent cutting edges 10, but offset obliquely from one another, and a line parallel to the axis of rotation 8 - with a different sign compared to the first helix angle α of the main grooves 14. The depth of the secondary grooves 30 is 1% to 100% of the depth of the main grooves 14 and is preferably in the range of 5% to 50%. The design with the secondary grooves 30 is also referred to as a cross-cut or two-cutting edge design.The overlapping courses of the main grooves 14 and the secondary grooves 30 create more cutting edges on the milling section 4 compared to the design of Fig. 1-4, which can increase cutting and material removal efficiency. The second helix angle ß, in the area of ​​the milling section 4 with the largest diameter, is preferably in the range of -15° to -50°, preferably in the range of -22° to -42°, and particularly preferably in the range of -30° to -35°.

[0067] Fig. 6 shows a further alternative embodiment of a milling cutter 1 according to the invention, in which a plurality of chip breakers 34 are provided along the length of each cutting edge 10 in each cutting edge 10 - and in this case in both the first flank 24 and the second flank 26 of the cutting edges 10. The chip breakers 34 each have a chip breaker depth that is small compared to the main groove depth h. For example, the depth of the chip breakers 34 is in the range between 5% and 25% of the main groove depth h and is preferably in the range between 10% and 20% of the main groove depth h. The chip breakers 34 of adjacent cutting edges 10 follow one another in the form of a helix, which extends in a third helix direction 36, which is opposite to the first helix direction 16 and thus also to the direction of rotation 9.The third helix angle α is also measured here between a tangent to a connecting line between adjacent chip breakers 34 provided in successive cutting edges 10, but offset from one another, and a line parallel to the rotation axis 8. The third helix angle α formed in this way is preferably constant, as shown in the embodiment shown in Fig. 6. It is advantageously in the range between -65° and -88°; however, the third helix angle α can also be positive and advantageously lie between +65° and +88°.

[0068] The number of chip breakers 34 along a cutting edge 12 depends on the

[0069] Milling length f, the diameter of the milling section 4, and / or the number of cutting edges 10. The number of chip breakers 34 along a cutting edge 10 is, for example, between four and eight, for example, five or six. The spacing between adjacent chip breakers 34 along the cutting edges 10 is preferably in the range of 0.5 mm to 7 mm, for example, in the range of 3 mm to 6 mm.

[0070] Fig. 7 shows a section of a further exemplary embodiment in which, by way of example, a third clearance surface 28 adjoins the second clearance surface 26 counter to the direction of rotation 9 of the burr 1. The other features of the burr 1 according to this embodiment correspond to those of the other embodiments. The third clearance surface 28 forms, with the tangent T to the cutting edge 12, a third clearance angle which is greater than the second clearance angle s (which in turn is greater than the first clearance angle θ, see above). As already shown in the embodiment shown in Figs. 1 to 4, the transition region 40 leading to the groove base 42 adjoins the last - here third - clearance surface 28 (seen counter to the direction of rotation). The third clearance surface 28 preferably has a width c, measured in the direction of rotation 9 of the burr 1, in the range from 0.3 mm to 2 mm, preferably in the range from 0.4 to 1.6 mm.In this embodiment, too, the transition region 40 has a greater extension in the circumferential direction of the milling cutter 1 than each of the flanks 24, 26, 28; the extension of the flanks 24, 26, and 28 corresponds in this case to their widths a, b, and c, respectively.

[0071] Mixed forms of the embodiments in Fig. 1-7 are also possible.

[0072] The values ​​given for the embodiments shown in the figures (in particular for the clearance angles 6, s, The dimensions of the flanks 24, 26, 28 and the rake angle y) refer to the area of ​​the milling section 4 with the largest diameter, i.e., in this case, to the area just before the transition between the milling section 4 and the shank section 2. In this way, a uniform reference point is specified, which also applies to milling sections 4 with a different geometry (e.g., spherical head-shaped). Somewhat less precise, but still understandable for the expert, the term "basic body of the milling section 4" could be chosen, particularly to distinguish it from the area of ​​the milling tip 6.

[0073] Figs. 1-7 show an example of a milling cutter 1 with a conical milling section 4. Other geometries of the milling section 4 are also possible, e.g. cylindrical, spherical, conical, conical with a rounded milling tip, cone-shaped, etc.

[0074] The milling cutter 1 according to the invention is particularly suitable for deburring, shaping, grinding, and finishing non-ferrous surfaces such as aluminum. However, by adjusting certain parameters, ferrous materials, such as steel, can also be machined, for example, by using a larger number of main grooves 14 (i.e., more or even significantly more than the five main grooves 14 shown in Figs. 1-7) and selecting a negative rake angle y.

[0075] List of reference symbols

[0076] 1 burr

[0077] 2 shaft section

[0078] 4 Milling section

[0079] 6 milling tips

[0080] 8 Rotation axis

[0081] 9 Direction of rotation

[0082] 10 cutting edges

[0083] 12 cutting edge

[0084] 14 main grooves

[0085] 16 first twist direction

[0086] 20 chip surface

[0087] 24 First open space

[0088] 26 Second open space

[0089] 28 Third open space

[0090] 30 secondary grooves

[0091] 32 second twist direction

[0092] 34 chip breakers

[0093] 36 third twist direction

[0094] 40 transition area (heel)

[0095] 42 Groove bottom (groove base) f Milling length h Main groove depth a Width of the first flank b Width of the second flank c Width of the third flank

[0096] R core

[0097] G Straight line through rotation axis

[0098] T Tangent

[0099] B Detail enlargement a first helix angle ß second helix angle o third helix angle y rake angle

[0100] 6 First clearance angle s Second clearance angle Third clearance angle

Claims

Patent claims 1 . Milling cutter (1 ) for an electrically or pneumatically operated, hand-held tool for deburring, shaping, grinding and finishing non-ferrous surfaces, comprising: - a shaft section (2) and - a milling section (4) made of a hard metal, in particular tungsten carbide, which adjoins the shank section (2) and ends in a milling tip (6), wherein the milling section (4) has a milling length (f) and a plurality of cutting edges (10) which are separated by spaced-apart main grooves (14) which have a main groove depth (h) and extend helically in a first helix direction (16) with a first helix angle (α) along the milling length (f), wherein each of the cutting edges (10) has a rake face (20) and a flank face (24) as well as a cutting edge (12) at the transition between the rake face (20) and the flank face (24) forming a rake angle (γ) and a clearance angle (α), characterized in that the said flank face (24) is a first flank face (24) and the said clearance angle (6) is a first clearance angle (α), wherein the first flank face (24) in the circumferential direction of the milling section (4) a second free surface (26) adjoins,which extends at a second clearance angle (s), wherein in the region of the milling section (4) with the largest diameter, the first clearance angle (6) is in the range from 6° to 20° and the second clearance angle (s) is in the range from 8° to 30°, and wherein the second clearance angle (s) is greater than the first clearance angle (6)., 2. Milling pin (1 ) according to claim 1 , characterized in that the first Clearance angle (6) in the area of ​​the milling section (4) with the largest Diameter is in the range of 5° to 18°, preferably in the range of 12° to 15°.

3. Milling pin (1) according to claim 1 or 2, characterized in that the second clearance angle (s) in the region of the milling section (4) with the largest diameter is in the range from 13° to 27°, preferably in the range from 20° to 23°.

4. Milling pin (1) according to at least one of the preceding claims, characterized in that the width (a) of the first flank (24) in the region of the milling section (4) with the largest diameter is in the range from 0.2 mm to 2 mm, preferably in the range from 1 mm to 1.6 mm.

5. Milling pin (1) according to at least one of the preceding claims, characterized in that the width (b) of the second free surface (26) in the region of the milling section (4) with the largest diameter is in the range from 0.3 mm to 2 mm, preferably in the range from 0.4 mm to 1.6 mm.

6. Milling pin (1) according to at least one of the preceding claims, characterized in that a third clearance surface (28) and optionally a fourth clearance surface and further optionally one or more further clearance surfaces adjoin the second clearance surface (26) in the circumferential direction of the milling section (4), wherein in the region of the milling section (4) with the largest diameter, the third clearance surface (28) runs in a third clearance angle (Q) and the optional fourth clearance surface in a fourth clearance angle, the third clearance angle (Q) is in the range from 10° to 40°, preferably in the range from 20° to 30°, and is greater than the second clearance angle (s), the optional fourth clearance angle is in the range of more than 10° and 60°, preferably in the range of 30° to 35°, and is greater than the third clearance angle (Q, wherein furthermore the width (c) of the third clearance surface (28) is in the range of 0.3 mm to 2 mm, preferably in the range of 0.4 mm to 1.6 mm, and wherein the width of the optional fourth clearance surface is in the range of 0.3 mm to 2 mm, preferably in the range of 0.4 mm to 1.6 mm.

7. Milling pin (1) according to at least one of the preceding claims, characterized in that the rake angle (y) is in the range from -10° to +25°, preferably in the range from -5° to 20° and particularly preferably in the range from 0° to 15°, most preferably in the range from 5° to 15°, and wherein the rake angle (y) is constant or variable over the milling length (f).

8. Milling pin (1) according to at least one of the preceding claims, characterized in that the first helix angle (a) is positive and in the region of the milling section (4) with the largest diameter is in the range from 15° to 50°, preferably in the range from 22° to 42°, and particularly preferably in the range from 30° to 35°, and wherein the first helix angle (a) is constant or variable, wherein a variable helix angle (a) is in the range from 15° to 40°.

9. Milling pin (1) according to at least one of the preceding claims, characterized in that the first helix angle (a) is negative and in the region of the milling section (4) with the largest diameter lies in the range of -10° to -50°, preferably in the range of -30° to -35°, and wherein the first helix angle (a) is constant or variable.

10. Milling pin (1) according to at least one of the preceding claims, characterized in that the number of main grooves (14), in particular with a maximum diameter of the milling section (4) of 12 mm or 12.7 mm or less, is not greater than 12, preferably not greater than 10, particularly preferably not greater than 8, most particularly preferably not greater than 6, and according to an advantageous embodiment is 5.

11. Milling pin (1) according to at least one of the preceding claims except for the preceding one, characterized in that the number of main grooves (14), in particular with a maximum diameter of the milling section (4) of more than 12.7 mm, is at least 10, preferably at least 14, for example at least 18 or 20.

12. Milling pin (1) according to at least one of the preceding claims, characterized in that the depth of the main grooves (14) in the region of the milling section (4) with the largest diameter is in the range from 0.5 mm to 3 mm, preferably in the range from 0.9 mm to 1.35 mm.

13. Milling cutter (1) according to at least one of the preceding claims, characterized in that secondary grooves (30) run through the cutting edges (10), wherein the secondary grooves (30) extend helically along the milling length (f) in a second helix direction (32) with a second helix angle (ß) with a changed sign compared to the first helix angle (α), wherein the depth of the secondary grooves (30) is 1% to 100% of the depth of the main grooves (14), preferably 5% to 50%.

14. Milling pin (1) according to at least one of the preceding claims, characterized in that a plurality of chip breakers (34) is provided in each cutting edge (10), wherein the chip breakers (34) in the region of the milling section (4) with the largest diameter have a chip breaker depth which is in the range from 0.05 mm to 0.5 mm and / or up to 80% of the depth of the main grooves (14), preferably in the range from 5% to 25% of the depth of the main grooves (14), particularly preferably in the range from 10% to 20%.

15. Milling pin (1) according to at least one of the two preceding claims, characterized in that the distance between adjacent chip breakers (34) along the cutting edges (10) is in the range from 0.5 mm to 7 mm, preferably in the range from 3 mm to 6 mm.

16. Milling pin (1) according to at least one of the preceding claims, characterized in that the first flank (24) and / or the second flank (26) has a tangential grind, alternatively a radial or a straight grind.

17. Use of a milling cutter (1) according to one or more of the preceding claims in an electrically or pneumatically operated, hand-held tool for deburring, shaping, grinding and finishing a particularly iron-free surface, preferably a surface made of aluminum or titanium or an alloy with these materials or of reinforced plastic.

18. Use of a milling cutter (1) according to one or more of the preceding device claims in an electrically or pneumatically operated, hand-held tool for deburring, shaping, grinding and finishing a ferrous surface.

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