End Mills

Abstract

A metal-cutting end mill comprising a body (1) having a cutting portion (6) extending axially rearward from a forward end (2) with the cutting portion (6) having a plurality of radially projecting and axially extending teeth (7). Each tooth (7) of the plurality of teeth (7) has a leading cutting edge (13) extending axially rearward and radially outward from an axially forward-most point (14, 14a) of a corresponding cutting edge (12). When the body (1) rotates, the cutting edges (12) of each tooth (7) form a line of intersection in a central plane that includes the central longitudinal axis (4). Each leading cutting edge (13) is separated by at least two chip-splitting grooves (17) such that the intersection line between the leading cutting edge (13) and the separating chip-splitting grooves (17) comprises an outer crest (22) lying on an imaginary convex curve (24), at least two inner valleys (23) and a curved portion (25) extending from a corresponding one of the at least two valleys (23) to the axially nearest one of the corresponding two crests (22). Each curved portion (25) comprises a convexly curved outer portion (26) extending inwardly from the crest (22) and having a radius of curvature (27) always greater than 0.1 mm.

Description

[Technical field]

[0001] The present invention relates to an end mill for cutting metal. [Background technology]

[0002] A wide variety of components are machined from many different types of materials, such as metals, composites, or combinations thereof. In response, a variety of different cutting tools, specifically milling tools such as end mills, have been developed. Traditionally, end mills include multiple cutting blades that extend axially along the tool. Some end mills, such as ball nose end mills, have cutting blades that begin at a radially inward position at the front end and extend radially outward and axially rearward therefrom. Such cutting blades typically include a portion at the front end that cuts primarily forward and a portion that cuts primarily radially along the axial portion of the tool. Thus, the cutting blade includes a curved portion at the front end and / or at the transition between the forward cutting front portion and the radial cutting portion.

[0003] A problem associated with such known end mills is that in some applications, the curved portion of the cutting edge makes it difficult for the cut chips to escape, causing jams between the tool and the workpiece being machined, which can cause vibrations in the tool and / or damage to the workpiece and / or the end mill. Summary of the Invention

[0004] The object of the present invention is to at least partially solve the above-mentioned problems. This object is achieved according to the invention by an end mill as claimed in claim 1.

[0005] The present invention relates to an end mill having a body, the body comprising: a front end, a rear end, and a central longitudinal axis extending from the front end to the rear end, the body being configured such that the body is rotationally rotatable about the central longitudinal axis; a cutting portion extending axially rearward from the forward end, the cutting portion including a plurality of radially projecting and axially extending teeth; In the cutting portion, each tooth of the plurality of teeth includes a rake face, a flank face, and a cutting edge at an intersection of the rake face and the flank face; each cutting edge of the plurality of teeth comprises a leading cutting edge extending axially rearward and radially outward from an axially forward-most point of a corresponding cutting edge; As the body rotates, the cutting edges of each tooth form a line of intersection in a central plane that includes the central longitudinal axis. Each front cutting edge is such that the intersection line between the front cutting edge and the chip-splitting groove is: at least three outer peaks each lying on a virtual curve, the virtual curve extending in the central plane and being convex; at least two inner valleys each located between two axially closest corresponding peaks of the at least three peaks; and and a curved portion extending from a corresponding one of at least two valley portions to a corresponding one of two peak portions closest in an axial direction, It is separated by at least two chip-separating grooves, Each curved portion is a convexly curved outer portion, Extending inward from the mountain, The end mill includes a convexly curved outer portion having a radius of curvature greater than 0.1 mm at all locations.

[0006] To this end, the subject end mill comprises leading cutting blades, each of which exhibits a shape defined by its image in a central longitudinal plane containing the central longitudinal axis. The corresponding image of the cutting blade is obtained by rotating the end mill about the central longitudinal axis such that the cutting blade forms a line of intersection in the central plane. In this image, the radially outer peaks of the leading cutting blades are visible as peaks of the line of intersection and the bottoms of the chip-splitting grooves are visible as valleys of the line of intersection. An imaginary curve connects the peaks of the line of intersection. The curvature of the imaginary curve represents the curvature of the leading cutting blade. The portion of the cutting blade extending from the outer peak to the bottom of the chip-splitting groove is visible in the image as a curved portion extending from the peak to the valley of the line of intersection.

[0007] According to the subject end mill, each curvature of the intersecting line has a radius of curvature greater than 0.1 mm at all positions of the curvature. This represents that the cutting blade with the chip-splitting groove lacks sharp corners that may adversely affect strength. Strength is particularly important for the curved leading cutting blade of the end mill, since the cutting conditions at the curved leading cutting blade are more difficult than those along an axially extending cutting blade, for example. This is due, for example, to the variation in speed and cutting force at the radially inner and radially outer positions of the curved leading cutting blade that extends in the radial direction. Due to the special design of the chip-splitting groove described herein, the leading cutting blade having a curvature represented by a virtual curve can be provided with a chip-splitting groove, even though strength is particularly important for the curved leading cutting blade. In this way, it is possible to obtain an improved end mill having better chip evacuation properties and a stronger leading cutting blade, which leads to reduced vibration during operation.

[0008] The subject end mills have a body with a leading end, a trailing end, and a central longitudinal axis extending from the leading end to the trailing end. Preferably, the body is elongated in the direction of the central longitudinal axis. The body is configured to be rotationally rotatable about the central longitudinal axis. The center of the body lies on the central longitudinal axis.

[0009] The body of the end mill has a cutting part at its front end. Preferably, the cutting part is an axial length of the body, which part is the most forward part of the body. According to one embodiment, the body comprises a further part such as a coupling part at its rear end to provide a mounting contact surface. Optionally, the mounting contact surface is designed to be coupled to a rotatable machine spindle or to an adapter for a rotatable machine spindle. Preferably, the coupling part is a rod, and both the rod and the cutting part are integral parts that are integral with the body.

[0010] The cutting portion includes a plurality of radially projecting teeth, each tooth of the plurality of teeth including a rake face, a clearance face, and a cutting edge at an intersection of the rake face and the clearance face, each tooth extending radially and axially along the body, with the cutting edge following an extension of a corresponding tooth.

[0011] According to one embodiment, the cutting part comprises axially extending chip flutes arranged on the radially outward peripheral surface of the cutting part of the body. Each of the teeth is associated with one corresponding chip flute, preferably each tooth and chip flute extending parallel to each other. Optionally, the chip flutes / teeth are arranged parallel to the central longitudinal axis, inclined to the central rotation axis or along a curve, for example a spiral. Chip flutes parallel to the central longitudinal axis, also referred to as axially straight chip flutes, are favorable for breaking the chips into smaller pieces. Inclined or spiral chip flutes are favorable for conveying the chips backwards along the tool, resulting in an easier cutting tool.

[0012] The flank surface extends rotationally rearward from the corresponding cutting blade. In one embodiment including chip flutes, the end mill body includes an envelope surface extending between the rotationally advancing cutting blade and the trailing chip flute closest to the rotational rear, the flank surface being the rotationally advancing portion of the envelope surface. The rake surface is the radially outer portion of the chip flute closest to the rotational front of that cutting blade.

[0013] The cutting edge of each tooth extends along the extension of the corresponding tooth. Each cutting edge comprises a forward cutting edge extending from a forward-most point. Optionally, the forward-most point of the forward cutting edge is on the central longitudinal axis, i.e., in or near the central longitudinal axis.

[0014] According to one embodiment, two of the leading cutting blades include a central cutting edge, e.g., a chisel edge, extending across the central longitudinal direction and interconnecting the two leading cutting blades at the central longitudinal axis. In this embodiment or other embodiments, the other leading cutting blade optionally has a forward-most point radially outward from the central longitudinal axis, with a non-cutting recess between the forward-most point and the central longitudinal axis. Such a design is advantageous since only a few of the leading cutting blades have a central edge, which is more susceptible to damage due to high cutting forces resulting from slow cutting speeds in the center.

[0015] Preferably, the subject end mill is suitable for cutting metallic workpieces. Preferably, the end mill is designed with a maximum cutting diameter of 1-32 mm on the front cutting edge.

[0016] The front cutting edge of each tooth is separated by at least two chip-splitting grooves. A range of 2 to 8, more preferably 3 to 6, and most preferably 4 to 5 chip-splitting grooves has been found to be suitable for the preferred diameter of the end mill. In some applications, more grooves may adversely affect the strength of the corresponding front cutting edge and may leave uneven surfaces. Front cutting edges with fewer grooves may not be able to cut chips small enough for proper chip evacuation in some applications.

[0017] According to one embodiment, each of the at least one leading cutting edge has an axially forward cutting leading portion, the leading portion having: It extends from an axially forward most point in the form of a point at the central longitudinal axis, forms an angle of at least 75° with respect to the central longitudinal axis at every location along its length, and is devoid of at least two chip-splitting grooves. Because the front portion cutting axially forward is devoid of chip-splitting grooves, the strength of the front cutting edge is increased when subjected to high cutting forces resulting from slow rotational speeds at the center.

[0018] According to one embodiment, the chip-splitting groove extends rotationally rearward from the leading cutting edge at the flank, optionally over a portion of the flank or over the entire flank, terminating in a subsequent chip flute.

[0019] Preferably, at least one leading cutting edge has at least one chip-splitting groove at a different axial position than the corresponding chip-splitting groove of another leading cutting edge. According to one embodiment, at least two of the leading cutting edges have corresponding chip-splitting grooves at different axial positions. Preferably, the chip-splitting grooves of leading cutting edges of the plurality of cutting edges are arranged in a staggered manner. Preferably, the chip-splitting groove of a first leading cutting edge is arranged such that the radially outer apex of the other leading cutting edge is located at the same axial position as the chip-splitting groove so that the end mill cuts along the entire extension of the cutting section as the tool rotates. Preferably, the outer apex of each leading cutting edge has a curvature and axial extension to overlap with the chip-splitting groove of the leading cutting edge, the design of which may be optimized according to the desired surface finish.

[0020] In this application, a line is an elongated graphic element, optionally straight and / or curved. The curvature of a line can be measured at each point of the line as the radius of curvature at the corresponding point. "Convex" and "concave" are viewed in a direction outward from the center of the body, e.g., radially outward or axially forward.

[0021] Terms such as "outward", "outer", "inward", "inner" and the like are viewed relative to the center of the body, e.g., the central region of the body. Radial outward is viewed relative to the central longitudinal axis at the tool or central plane. Axial is in the direction of the central longitudinal axis.

[0022] At least the leading cutting edge of each cutting edge has extensions in both the radial and axial directions such that the leading cutting edge exhibits an overall curvature defined by an imaginary curve. Preferably, the leading cutting edge cuts primarily axially forward at its axially most forward point and cuts primarily radially as well as axially aft.

[0023] Optionally, the leading cutting blade is designed to be curved in other directions, such as, for example, curved circumferentially around the body at a certain radial distance. For example, in an embodiment including helical teeth and chip flutes, the associated leading cutting blade also exhibits a helical curvature in the circumferential direction in addition to the overall curvature represented by the curvature of the virtual curve. However, the helical curvature in the circumferential direction is not visible at the center plane in the image.

[0024] According to one embodiment, the imaginary curve is a circular arc. Preferably, the circular arc has a radius of curvature between 0.5 and 16 mm, more preferably between 2 and 12.5 mm, and most preferably between 5 and 12.5 mm. In some applications, chip evacuation is particularly difficult with a cutting blade having a curvature defined by the arc of the imaginary curve. A smaller radius of curvature represents a leading cutting blade that often produces inherently thin chips, while a larger radius of curvature represents a leading cutting blade where chip evacuation and strength are less of an issue.

[0025] According to one embodiment, the body has a ballnose front end, with each of the leading cutting edges being located on the ballnose front end. In end mills that constitute ballnose end mills, the leading cutting edges create a virtual curve in the central plane with a circular arc, and chip evacuation and strength at the leading cutting edges are particularly problematic. Therefore, the leading cutting edges in question are particularly advantageous in ballnose end mills.

[0026] Preferably, the ball nose end of the ball nose end mill has a ball radius that forms an angle with the central longitudinal axis at each location of the imaginary curve in a central plane that includes the central longitudinal axis. According to one embodiment, the forward cutting front portion of the leading cutting blade is devoid of a chip splitting groove at an angle of 0-15°. In an embodiment in which at least one of the leading cutting blades has a forward-most point at a distance from the central longitudinal axis and a non-cutting recess exists between the forward-most point and the central longitudinal axis, preferably the forward cutting front portion of another leading cutting blade extends the same length as the non-cutting recess.

[0027] According to one embodiment, at least one of the cutting blades comprises a rear cutting blade extending axially rearward from the axial rear end of the front cutting blade, and at least a radially outer portion of the intersection line of the at least one rear cutting blade lies on an imaginary straight line. In an exemplary embodiment in the form of a ball nose end mill, each cutting blade comprises a front cutting blade located on a ball and a rear cutting blade extending along a shaft portion of the cutting part. The shaft portion of the cutting part is, for example, cylindrical or conical such that the intersection line of each rear cutting blade is a straight line parallel to the central axis of rotation or a straight line diverging toward or converging from the central axis of rotation in the axial rearward direction. Preferably, each rear cutting blade cuts mainly in the radial direction.

[0028] Optionally, at least one of the rear cutting edges is provided with a chip-splitting groove similar to the associated front cutting edge.

[0029] In the central plane, the leading cutting edge is represented by a line of intersection, which includes a peak, a valley, a curved portion, and optionally a straight portion. Preferably, the peak is located radially outward and the valley is located radially inward. The curved portion includes a curved portion, each preferably including a convexly curved outer portion extending radially inward from the peak. Preferably, each convexly curved outer portion has a curvature with a minimum value along the length of the corresponding curved outer portion, the minimum value of the curvature being smaller than 0.3 mm. Thus, preferably, the minimum value of the curvature is smaller than 0.3 mm and larger than 0.1 mm. Thereby, advantageously at the same time, a sufficiently strong radially outer corner of the chip-splitting groove and a sufficient break in the connection along which the cut chips are broken up are achieved.

[0030] According to one embodiment, the convexly curved outer portions of the curved portions connect at their radially inner ends to respective concavely curved radially inner portions, from which each of the concavely curved inner portions extends radially inwardly to a corresponding one of the valleys, where each of the concavely curved inner portions abuts another of the axially nearest convexly curved inner portions.

[0031] According to one embodiment, the two axially closest convexly curved outer portions abut the axially central peak of the at least three peaks. Alternatively, the intersection line includes peaks in the form of straight line segments connecting the two axially closest convexly curved outer portions on either side.

[0032] The image of each such leading cutting edge defines wavy intersecting lines at the center plane.

[0033] Preferably, the end mill is configured for a maximum feed per tooth and the inward extension of each curvature on each leading cutting edge is at least the maximum feed per tooth. Preferably, the maximum inward extension is at least 0.1 mm. This allows the chip-splitting groove to be deep enough for the cutting edge to produce split chips.

[0034] Preferably, the bottoms of the chip-splitting grooves are non-cutting such that each of the leading cutting edges has a cutting radially outer apex and a non-cutting radially inner bottom.

[0035] The intersection line includes at least one arc length, i.e., a period arc length, extending from a first crest to a second crest of two axially closest corresponding crests. In embodiments including more than two chip-splitting grooves, the intersection line includes several period arc lengths. Optionally, all period arc lengths are the same or different along the axial extension of one or all of the leading cutting edges. In embodiments where the intersection line is wavy, the arc length corresponds to a period of the wave.

[0036] According to one embodiment, the inward extension, e.g. the radially inward extension, of each curved portion is at most 20% of the periodic arc length of the virtual curve. Thereby, a suitable relationship has been found between the distance between the two axially closest valleys on the one hand and a depth sufficient to achieve chip splitting in the desired application on the other hand. Preferably, the inward extension, e.g. the radially inward extension, of each curved portion is at most 10% of the periodic arc length of the virtual curve. This is suitable for creating a uniform surface in the embodiment in which the ball nose end mill is subjected to a finishing treatment.

[0037] The flank of each tooth has a first clearance angle closest to the cutting edge. The flank may have a second or further clearance angle at its rear in the direction of rotation. To measure the clearance angle at a point on the flank where the flank follows one of the leading cutting edges, a central plane is identified that includes the intersection line and an imaginary curve. The imaginary curve has a radius that passes through the intersection line at a point that corresponds to the location of the point in the flank. A tangent to the imaginary curve on this radius is perpendicular to the plane to measure the clearance angle of the corresponding point on the flank in the end mill.

[0038] Preferably, at every axial position along the axial extension of each of the leading cutting edges, the flanks all have the same first clearance angle. In other words, the clearance angle of the rear flank of the first cutting edge at the first axial position is the same for all other flanks following other corresponding leading cutting edges. The leading cutting edge with the chip-splitting groove at the first axial position has the same clearance angle in the chip-splitting groove as the leading cutting edge with the crest. This creates a section where the desired clearance angle is present in both chip-splitting grooves, allowing for more predictable cutting performance of the end mill. This can increase stability.

[0039] Preferably, the first clearance angle is a minimum of 0.5° and a maximum of 5°. This achieves a strong leading cutting edge with good support to avoid vibrations. Furthermore, there is sufficient clearance to avoid the end mill jamming. According to one embodiment, the clearance face of each tooth is provided with a reinforcing bevel closest to the cutting edge, preferably with a first clearance angle within the preferred range. Preferably, embodiments with a small first clearance angle or reinforcing bevel have a second clearance face at the rear in the direction of rotation. The second clearance angle of the second clearance face is preferably a minimum of 6° and a maximum of 14°.

[0040] Optionally, from a respective axially forward-most point of the leading cutting edge axially rearward along the axial extension of the leading cutting edge, the first clearance angle is constant, continuously increases or continuously decreases, such that the cutting characteristics of the leading cutting edges of the end mill may be optimized with different cutting characteristics along the axial extension of the leading cutting edge. [Brief description of the drawings]

[0041] Exemplary embodiments will now be described in more detail with reference to the accompanying drawings. [Figure 1] FIG. 1 is a side view of a first embodiment of the subject end mill in the form of a finishing ball nose end mill. [Diagram 2] FIG. 2 is an enlarged view of FIG. 1 showing the cutting portion. [Diagram 3] FIG. 3 is an enlarged view of FIG. [Figure 4] FIG. 2 is a diagram of a plane for measuring the clearance angle of the flank of the embodiment of FIG. 1. [Diagram 5] FIG. 2 is a perspective view of the front end of the embodiment of FIG. 1. [Figure 6] FIG. 2 is a front end view of the embodiment of FIG. 1. [Figure 7] FIG. 2 is a graphical representation of the leading cutting edge of the embodiment of FIG. 1. [Figure 8] FIG. 8 is an enlarged view of the graphical representation of one of the front cutting edges according to FIG. 7. [Figure 9] FIG. 2 is a side view of a second embodiment of the subject end mill in the form of a ball nose end mill for rough cutting. [Figure 10] FIG. 9 is a graphical representation corresponding to FIG. 7 for the second embodiment of FIG. All figures are schematic and not necessarily to scale, generally showing only parts necessary to clarify the respective embodiment, while other parts may be omitted or merely suggested. Unless otherwise indicated, like reference signs refer to like parts in the different figures. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0042] With reference to Figures 1 to 8, a first embodiment of the subject end mill in the form of a finishing ball nose end mill is shown. The end mill comprises a body 1 having a front end 2, a rear end 3 and a central longitudinal axis 4. The end mill is configured to be rotatable in a rotational direction 5 about the central longitudinal axis 4. A cutting part 6 extends axially rearward from the front end 2. A coupling part 8 extends axially rearward from the rear end of the cutting part 6 to the rear end 3 of the body 1. The coupling part 8 is configured to be mountable on a machine spindle. The cutting part 6 comprises a front end in the form of a hemispherical ball nose with a radius of 7.8 mm.

[0043] The cutting portion 6 comprises a plurality of four radially projecting and axially extending teeth 7. The cutting portion 6 comprises axially extending chip flutes 9 having recesses in the radially outward peripheral surface of the cutting portion 6. Each tooth 7 is associated with one corresponding chip flute 9, and each tooth 7 and chip flute 9 extend helically parallel to one another. The helix angle is 30°.

[0044] Each tooth 7 comprises a flank 10, a rake face 11 and a cutting edge 12 at the intersection of the flank 10 and the rake face 11. The flank 10 extends backwards in the direction of rotation from the corresponding cutting edge 12 to the next chip flute 9 following the direction of rotation.

[0045] Each cutting blade 12 comprises a leading cutting edge 13 extending axially rearward and radially outward from an axially forward most point 14, 14a. Each leading cutting edge 13 follows a corresponding helical line radially outward and axially rearward along the hemispherical shape of the ballnose. Two of the leading cutting edges 13 comprise a front portion in the form of a portion of a central edge 16. At the center, the central edge 16 extends across the central longitudinal axis 4, and the corresponding two leading cutting edges 13 have a central forward most point 14 and extend in opposite directions therefrom. The remaining two of the four leading cutting edges 13 have a forward most point 14a at a radially outward distance from the central longitudinal axis 4. The end mill has a non-cutting recess 15 forward of the forward most point 14a of these leading cutting edges 13. The maximum cutting diameter of the leading cutting edges 13 is 15.6 mm (diameter of the ballnose end).

[0046] The central cutting edge 16 has an angle α of at least 75° with respect to the central longitudinal axis 4 everywhere along its length. In an exemplary embodiment, the central cutting edge 16 extends through an angular arc of an angle β of 10°.

[0047] Each leading cutting edge 13 is separated by at least two chip-splitting grooves 17, and in the exemplary embodiment, four chip-splitting grooves 17. The two leading cutting edges 13 having a centrally located forward-most point 14 further have a chip-splitting groove 17. The central cutting edge 16 is devoid of a chip-splitting groove 17. The chip-splitting grooves 17 extend rotationally rearward from each leading cutting edge 13 on the clearance face.

[0048] Each leading cutting edge 13, and the clearance face 10 extending therefrom, has a radially outer apex 20 that is between the two axially nearest chip-splitting grooves 17, and a bottom 21 that is within each corresponding chip-splitting groove 17.

[0049] All four leading cutting edges 13 have corresponding chip-splitting grooves 17 at different axial positions.

[0050] At each location along each cutting edge 12, the flank 10 includes a first portion 18 closest to the cutting edge 12. The flank 10 at the first portion 18 has a first clearance angle ε closest to the cutting edge 12, see FIG. 4. In an exemplary embodiment, the first clearance angle ε varies continuously along the leading cutting edge 13, with the first clearance angle ε being 8° at the central longitudinal axis 4 and 12° at the axially aft end of the hemispherical ball nose end. At the axially aft end of the hemispherical ball nose end, the radius of the ball nose end forms an angle of 90° with the central longitudinal axis. Rotationally aft of the first portion 18 of the flank 10, the clearance angle ε of the flank 10 increases.

[0051] At every axial position along the axial extension of the ball nose end of the end mill, each of the leading cutting edges 13 has the same first clearance angle ε.

[0052] The leading cutting edges 13 of the cutting blades 12 of an exemplary end mill are graphically represented in Figures 7 and 8. An image or graphical representation of the corresponding cutting edges 12 is obtained by rotating the end mill about the central longitudinal axis 4 such that each leading cutting edge 13 forms a line of intersection 19 in the central plane. In this view, the radially outer peaks 20 (see Figure 3) of the leading cutting edges 13 are visible as peaks 22 of the line of intersection 19, and the bottoms 21 of the chip-splitting grooves (see Figure 3) are visible as valleys 23 of the line of intersection 19. Each curved portion 25 extends from a corresponding valley 23 to a corresponding peak 22. Each curved portion 25 includes a convexly curved outer portion 26 extending inwardly from one corresponding peak 22 and having a radius of curvature 27 greater than 0.1 mm at all locations. In the exemplary ballnose end mill, the radius of curvature 27 is 0.2 mm.

[0053] An imaginary curve 24 connects the peaks 22 of the intersection lines 19. The imaginary curve 24 is convex radially outward. The radius of curvature of the imaginary curve 24 corresponds to the radius of the ball nose end, i.e., 7.8 mm, in the exemplary embodiment.

[0054] The peaks 22, valleys 23, and curves 25 create the wavy intersecting lines 19. The arc length between the two axially closest peaks 22 constitutes a periodic arc length 28. The periodic arc lengths 28 of each leading cutting edge 13 all have the same length. The inward extension of each curve 25, i.e., the radial distance from the corresponding peak 22 to the corresponding groove 23, is a maximum of 10% of the periodic arc length 28, which in the exemplary embodiment is 0.2 mm.

[0055] All four leading cutting edges 13 have corresponding chip-splitting grooves 17 at different axial positions and are therefore visible as four intersecting lines in FIG. 7. As can be seen, the peaks 22 and valleys of each intersecting line 19 are at different axial positions. This represents a leading cutting edge 13 whose crest 22 overlaps with its bottom 21, thereby achieving a desired surface finish on the workpiece being cut. Thus, when looking at all four leading cutting edges 13 at the same axial position, all four leading cutting edges 13 have various points of one corresponding curvature 25 at that axial position. Furthermore, as mentioned above, all leading cutting edges have the same first clearance angle ε at the same axial position.

[0056] As can be seen in Figure 3, the first clearance angle ε at a selected location along the leading cutting edge 13 is measured in the plane of Figure 4. The selected location of the leading cutting edge 13 is found in a central plane that includes the intersection line 19 and the imaginary curve 24. A tangent to the imaginary curve 24 at the selected location is perpendicular to the plane of Figure 4. When measuring the clearance angle ε at the center 4, the relevant plane is the longitudinal plane, and when measuring the clearance angle ε at the axial trailing end of the ballnose, the relevant plane is the axial plane.

[0057] FIG. 9 shows a second embodiment of the subject end mill in the form of a ball nose end mill for rough cutting, which differs from the first embodiment in that the cutting part 6 comprises a shaft portion 30 and in the shape of the cutting blade 12.

[0058] The cutting edges 12 each include a rear cutting edge 29. The rear cutting edges 29 each extend axially rearward from a corresponding one of the front cutting edges 13 and spirally along the shaft portion 30. Each rear cutting edge 29 is separated by a chip-splitting groove 17, just like the front cutting edges 13. Here, each rear cutting edge 29 has at least two chip splitting grooves 17 such that the intersection line 19 of the rear cutting edge 29 has at least three radially outer peaks 22 each located on an imaginary straight line 31, at least two radially inner valleys 23 each located between two axially closest corresponding peaks 22 among the at least three peaks 22, and a curved portion 25 each extending from one corresponding valley 23 among the at least two valleys 23 to one of the two axially closest corresponding peaks 22, and each curved portion has a convexly curved outer portion 26 extending radially inward from the peak and having a radius of curvature 27 greater than 0.1 mm at all positions.

[0059] The periodic length 32 of the imaginary straight line extends from the first to the second of the two axially closest corresponding peaks, and for each cutting blade 12 comprising one of the front cutting blades 13 and one of the rear cutting blades 29, the periodic length 32 is equal to the periodic arc length 28.

[0060] The tips 22 of the cutting blades 12 each have a greater curvature than the tips of the cutting blades 12 of the first embodiment. This results in more wavy intersection lines 19, as can be seen in Figure 10, which represents a rough cutting tool with a less good surface finish.

Claims

1. An end mill for cutting metals, comprising a body (1), the body (1) comprising: a front end (2), a rear end (3), and a central longitudinal axis (4) extending from the front end to the rear end, wherein the body (1) is configured to be rotatable in a rotational direction (5) about the central longitudinal axis (4); a cutting portion (6) extending axially rearward from the front end (2), the cutting portion (6) having a plurality of radially projecting and axially extending teeth (7); In the cutting portion, each tooth of the plurality of teeth comprises a rake face (11), a flank face (10), and a cutting edge (12) at the intersection of the rake face (11) and the flank face (10); Each cutting edge of the plurality of teeth includes a leading cutting edge (13) extending axially rearward and radially outward from an axially forward-most point (14, 14a) of the corresponding cutting edge (12); When the body (1) rotates, the cutting edges (12) of each tooth (7) form a line of intersection in a central plane containing the central longitudinal axis (4), Each of the front cutting edges (13) has an intersection line between the front cutting edge (13) and the chip-separating groove (17) that separates the chips. at least three outer ridges (22) each located on an imaginary curve (24), said imaginary curve (24) extending in said central plane and being convex; At least two inner valley portions (23) located between two corresponding peak portions (22) that are closest in the axial direction among the at least three peak portions (22); and and a curved portion (25) extending from one corresponding valley portion (23) of the at least two valley portions (23) to one of the two corresponding peak portions (22) closest in the axial direction, It is separated by at least two chip-splitting grooves (17), Each of said curved portions (25) has a convexly curved outer portion (26), Extending inward from the peak portion (22), An end mill characterized in that it comprises a convexly curved outer portion (26) having a radius of curvature (27) greater than 0.1 mm at all locations.

2. 2. The end mill of claim 1, wherein the radius of curvature of the convexly curved outer portion has a minimum value, and wherein the radius of curvature at the minimum value is less than 0.3 mm.

3. the clearance face (10) of each tooth has a first clearance angle ε closest to the cutting edge (12); 2. The end mill according to claim 1, wherein at any axial position along the axial extension of each of the leading cutting edges (13), all of the flank faces (10) have the same first clearance angle ε.

4. the flank (10) of each tooth (7) has a reinforcing bevel closest to the cutting edge (12); 4. The end mill of claim 3, wherein at any axial position along the axial extension of each of the leading cutting edges (13), the first clearance angle (10) is the clearance angle of the reinforcing bevel, and the first clearance angle is a minimum of 0.5° and a maximum of 5°.

5. 4. The end mill of claim 3, wherein the first clearance angle ε is constant, continuously increases, or continuously decreases axially rearward from the axially most forward point (14, 14a) of each of the leading cutting edges (13) along the axial extension of the leading cutting edges.

6. 2. The end mill of claim 1, wherein the end mill is configured for a maximum feed per tooth (7), and the inward extension of each of the curved portions (25) of each of the leading cutting edges (13) is at least the maximum feed per tooth (7).

7. 7. The end mill of claim 6, wherein the inward extension of each curved portion (25) is a maximum of 20% of a periodic arc length (28) of the imaginary curve (24), and the periodic arc length (28) extends from a first peak to a second peak of two corresponding peaks (22) that are closest in the axial direction.

8. A first one of the leading cutting edges (13) has a leading portion (16) that cuts axially forward, and at least a second one of the leading cutting edges (13) has the forward-most point (14a) axially rearward of the non-cutting recess (15), and the leading portion (16) extending axially rearward from the axially forward-most point (14) of the central longitudinal axis (4) at least an axial distance corresponding to the axial length of the non-cut recess (15); 2. The end mill of claim 1, wherein the end mill does not include any of the at least two chip-splitting grooves (17).

9. The end mill according to claim 1, wherein the imaginary curve (28) is arc-shaped and has a radius of curvature of 2 to 12.5 mm.

10. 2. The end mill of claim 1, wherein the body (1) comprises a ball nose front end, and each of the forward cutting edges (13) is located on the ball nose front end.

11. 2. The end mill of claim 1, wherein each of said leading cutting edges (13) has 3 to 6 chip-splitting grooves (17).

12. 2. The end mill of claim 1, wherein at least one of the cutting edges (12) comprises a rear cutting edge (29) extending axially rearward from the axial rear end of the front cutting edge (13), and at least a radially outer portion (22) of the intersection line (19) of the at least one rear cutting edge (29) is located on an imaginary straight line (31).

13. Each of the rear cutting edges (29) is such that the intersection line (19) of the rear cutting edge (29) is: At least three radially outer peaks (22) each located on the imaginary straight line; At least two radially inner valleys (23) each located between two axially closest corresponding peaks (22) among the at least three peaks (22); a curved portion (25) extending from one corresponding valley portion (23) of the at least two valley portions (23) to one of the two corresponding peak portions (22) closest in the axial direction; To be equipped with separated by at least two chip-separating grooves (17); Each of said curved portions (25) has a convexly curved outer portion (26), Extending radially inward from the peak (22), 13. An end mill according to claim 12, comprising a convexly curved outer portion (26) having a radius of curvature (27) greater than 0.1 mm at all locations.

14. 14. An end mill according to claim 7 and 13, wherein the periodic length (32) of the imaginary straight line (31) extends from the first to the second of the two corresponding peaks (22) that are closest in the axial direction, and wherein the periodic length (32) is equal to the periodic arc length (28) for each of the cutting edges (12) comprising one of the front cutting edges (13) and one of the rear cutting edges (29).

15. 2. The end mill of claim 1, wherein at least two of the leading cutting edges (13) have corresponding chip-splitting grooves (17) at different axial positions.

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