Milling tool and method for chamfering side edges of teeth on a cylindrical toothed workpiece

Abstract

A milling tool for chamfering the side edges of teeth on a cylindrical toothed workpiece includes an elongated tool body (2) having a rear portion (6) configured for mounting on a machine, a cutting portion (10), and an elongated shank portion (40) carrying the cutting portion and extending from the cutting portion toward the rear portion. The cutting portion (10) has a first cutting edge (11) facing away from the rear portion (6) and a second cutting edge (12) facing the rear portion and located rearward of the first cutting edge. The distance between the second cutting edge and the axis of rotation (3) of the tool body gradually increases from the rear end (12b) of the cutting edge to the front end (12a), with the rear end (12b) located at a greater distance from the axis of rotation (3) than the radially outermost portion of the shank portion's peripheral surface (41).

Description

[Technical Field]

[0001] The present invention relates to a milling tool for chamfering the side edges of internal or external teeth on a cylindrical toothed workpiece at opposite end faces of the workpiece according to the preamble of claim 1. The present invention also relates to a method for chamfering such side edges.

[0002] External or internal teeth or splined teeth may be machined on a cylindrical workpiece by cutting techniques using different types of cutting tools. In such cases, the resulting teeth on the workpiece have burrs and sharp edges at the intersections of the tooth flanks with the respective end faces of the workpiece following the initial machining operation, i.e., at the side edges of the teeth on the opposite end faces of the workpiece. Therefore, a subsequent finishing operation may be required to chamfer the side edges of the teeth on the opposite end faces of the workpiece, thereby removing the burrs and sharp edges.

[0003] WO 2022 / 013068 discloses a method for chamfering side edges of teeth on a cylindrical toothed workpiece at an end surface of the workpiece using a milling tool, where the workpiece and milling tool are rotated at a predetermined relationship between the rotational speed of the milling tool and the rotational speed of the workpiece while maintaining the rotational axis of the milling tool parallel to the central axis of the workpiece. In the method according to WO 2022 / 013068, the side edges are chamfered such that a first side edge of the tooth is chamfered in a direction from the tip to the root of the tooth, and as a result, a second opposite side edge of the adjacent tooth is chamfered in a direction from the root to the tip of the tooth. The milling tool disclosed in WO 2022 / 013068 is configured to move into contact with the forward-facing end surface of the workpiece. If the side edge of the first, forward-facing end face of the workpiece is being chamfered, the workpiece must be repositioned in the workpiece holder so that the opposite, second end face of the workpiece faces forward toward the milling tool before proceeding with the chamfering of the side edge of this second end face of the workpiece.

[0004] Problem to be solved by the invention The object of the present invention is to provide a milling tool of the above mentioned type which has a new and preferred design. Summary of the Invention

[0005] According to a first aspect of the invention, the object is achieved by a milling tool having the features defined in claim 1.

[0006] A milling tool according to a first aspect of the present invention includes an elongated tool body having a rear portion at a rear end thereof configured for attachment to a machine and having a cutting portion with a cutting edge spaced a distance from the rear portion, the tool body including an elongated shank portion carrying the cutting portion and extending from the cutting portion toward the rear portion, the shank portion having a front end facing the cutting portion, an opposite rear end, and a circumferential surface extending around the shank portion between the rear end and the front end, the shank portion having a central longitudinal axis coinciding with an axis of rotation of the tool body.

[0007] The cutting portion is provided with at least a pair of cutting edges including a first cutting edge facing away from the rear portion and a second cutting edge facing the rear portion and positioned rearward of the first cutting edge, the first cutting edge has a rear end and an opposite front end, the rear end of the first cutting edge is located closer to the rear of the tool body than the front end of the first cutting edge, the front end of the first cutting edge is located closer to the rotation axis than the rear end of the first cutting edge, and a distance between the first cutting edge and the rotation axis gradually increases from the front end to the rear end of the first cutting edge as viewed in a direction along the first cutting edge; The second cutting edge has a front end and an opposite rear end, the rear end of the second cutting edge being located closer to the rear of the tool body than the front end of the second cutting edge, the rear end of the second cutting edge being located at a greater distance from the rotation axis than the radially outermost part of the circumferential surface of the shank portion, the rear end of the second cutting edge being located closer to the rotation axis than the front end of the second cutting edge, and the distance between the second cutting edge and the rotation axis gradually increasing from the rear end of the second cutting edge to the front end of the second cutting edge when viewed in a direction along the second cutting edge.

[0008] Furthermore, the cutting portion has an axial extension of the tool body limited to a region between a first plane extending perpendicular to the rotation axis and intersecting the rear end of the second cutting edge, and a second plane extending perpendicular to the rotation axis and intersecting the front end of the first cutting edge. According to a first alternative, the cutting portion constitutes the axially frontmost part of the tool body, i.e., the part of the tool body furthest from the rear part of the tool body. According to a second alternative, the tool body includes a front part protruding from the cutting portion on the side opposite the rear part, and the front end of the first cutting edge is located at a greater distance from the rotation axis than the radially outermost part of this front part.

[0009] The design of the tool body with an elongated shank portion between the cutting portion and the rear portion, the arrangement of the first and second cutting edges on the cutting portion as defined above, and the position of the second cutting edge relative to the circumferential surface of the shank portion as defined above mean that the milling tool can be used to chamfer the side edges of internal or external teeth on a cylindrical toothed workpiece at both end faces of the workpiece without the need to reposition the workpiece. The first cutting edge mentioned above may be used to chamfer the side edges of the teeth of the toothed workpiece at the end face of the workpiece opposite the workpiece holder carrying the workpiece, and the second cutting edge mentioned above may be used to chamfer the side edges of the teeth of the workpiece at the opposite end face of the workpiece.

[0010] The above-mentioned internal or external teeth on the workpiece are preferably gear teeth or spline teeth with modules 2-12.

[0011] The radial distance between the rear end of the second cutting edge and the radially outermost part of the circumferential surface of the shank portion must be appropriately adapted to the tooth depth of the teeth on the toothed workpiece to be machined, and is preferably 2 to 40 mm, more preferably 6 to 30 mm. Advantageously, the radial distance is greater than the tooth depth, but alternatively, it may be somewhat smaller than the tooth depth, taking into account the radial extension of the second cutting edge. If the tool body includes a forward portion protruding from the cutting portion opposite the rear portion, the radial distance between the front end of the first cutting edge and the radially outermost part of the circumferential surface of this forward portion is preferably 2 to 40 mm, more preferably 6 to 30 mm, and preferably, but not necessarily, equal to the radial distance between the rear end of the second cutting edge and the radially outermost part of the circumferential surface of the shank portion.

[0012] According to one embodiment of the present invention, the first cutting edge extends substantially linearly in a third plane containing the rotation axis, and the second cutting edge extends substantially linearly in a fourth plane containing the rotation axis. The fourth plane may be angularly offset from the third plane with respect to the rotation axis. However, the fourth plane preferably coincides with the third plane. The first cutting edge and the second cutting edge are inclined in the third and fourth planes, respectively, such that the extension of the first cutting edge forms a first angle with the rotation axis, and the extension of the second cutting edge forms a second angle with the rotation axis. The first cutting edge and the second cutting edge may be inclined such that the first angle and the second angle are different from each other. However, it is preferred that the first cutting edge and the second cutting edge are inclined such that the first angle and the second angle are substantially equal. The first angle and the second angle are advantageously greater than or equal to 20° and less than 90°, preferably between 30 and 80°.

[0013] Another embodiment of the present invention is a first cutting edge is formed at an intersection of a first surface on the cutting portion and a second surface on the cutting portion, the first surface and the second surface being mirror images of each other with respect to the third plane; The second cutting edge is formed at the intersection of a third surface on the cutting portion and a fourth surface on the cutting portion, and the third surface and the fourth surface are mirror images of each other with respect to the fourth plane.

[0014] This ensures that the cutting performance of each cutting edge is the same in both rotational directions of the milling tool. When chamfering with the first cutting edge, the first surface functions as a rake face and the second surface functions as a flank face when the milling tool is rotated in one rotational direction, while the first surface functions as a flank face and the second surface functions as a rake face when the rotational direction is changed. When chamfering with the second cutting edge, the third surface functions as a rake face and the fourth surface functions as a flank face when the milling tool is rotated in one rotational direction, while the third surface functions as a flank face and the fourth surface functions as a rake face when the rotational direction is changed.

[0015] The first cutting edge and the second cutting edge are preferably mirror images of each other with respect to a plane of symmetry that extends midway between the first cutting edge and the second cutting edge perpendicular to the axis of rotation.

[0016] According to another embodiment of the present invention, the cutting portion includes a holder arm that projects radially relative to the axis of rotation beyond the radially outermost portion of the shank portion's peripheral surface, the holder arm having an inner end facing the axis of rotation, i.e., a radially inner end, and an opposite outer end, i.e., a radially outer end, and the first and second cutting edges are located at the outer ends of the holder arm. Alternatively, the cutting portion may include a disk-shaped holder that projects radially relative to the axis of rotation beyond the radially outermost portion of the shank portion's peripheral surface, and the first and second cutting edges are located on the outer periphery of the disk-shaped holder.

[0017] According to another embodiment of the invention, the first and second cutting edges form part of a cutting insert that is removably mounted in an insert seat provided at the outer end of the holder arm or alternatively on the outer periphery of the disk-shaped holder, thereby allowing the cutting insert to be easily replaced with a new one when either the first or second cutting edge is worn.

[0018] According to another embodiment of the present invention, the cutting portion includes a base that supports the holder arm and is slidably attached to the front end of the shank portion so as to be slidable linearly relative to the shank portion perpendicular to the rotation axis and in the longitudinal direction of the holder arm, the base being lockable to the shank portion in different sliding positions relative to the shank portion, thereby allowing adjustment of the radial distance between the first cutting edge and the rotation axis and the radial distance between the second cutting edge and the rotation axis.

[0019] The shank is preferably rod-shaped and is longer than the length of the workpiece, i.e., longer than the axial distance between two opposing end faces of the workpiece. The shank may have a length of, for example, 25 to 500 mm, preferably 50 to 200 mm, and more preferably 100 to 150 mm.

[0020] According to another embodiment of the invention, the cutting part is removably attached to the front end of the shank part, in which case it is possible, for example, to provide several cutting parts with holder arms of different lengths, so that the milling tool can be easily adapted to the tooth depth of the toothed workpiece to be machined by attaching a cutting part with a holder arm of the appropriate length to the shank part.

[0021] Further advantages of the milling tool according to the invention will become apparent from the following description.

[0022] According to a second aspect of the invention, the object is achieved by a method having the features defined in claim 13.

[0023] A second aspect of the present invention provides a method for chamfering side edges of internal or external teeth on a cylindrical toothed workpiece at a first end face of the workpiece and at an opposite second end face of the workpiece, wherein each tooth on the workpiece has a tip, a root, a first tooth flank extending between the tip and the root on the first side of the tooth, a second tooth flank extending between the tip and the root on the opposite second side of the tooth, a first side edge formed at the intersection of the first tooth flank and the first end face of the workpiece, a second side edge formed at the intersection of the second tooth flank and the first end face of the workpiece, and a second side edge formed at the intersection of the first tooth flank and the second end face of the workpiece. a third side edge formed at an intersection of the second tooth flank and the second end face of the workpiece, and a fourth side edge formed at an intersection of the second tooth flank and the second end face of the workpiece, wherein the workpiece is mounted on a machine and rotatable by the machine about a central axis of the workpiece, and the chamfering is performed by the milling tool according to the present invention, and the milling tool is mounted on a machine and rotatable by the machine about a rotation axis of the tool body and movable by the machine relative to the workpiece in the axial direction of the workpiece and in different directions in a plane perpendicular to the central axis of the workpiece, such that the rotation axis of the tool body is parallel to the central axis of the workpiece, and the method comprises: a) positioning the milling tool at a first predetermined position relative to the workpiece, with a rotational axis of the tool body parallel to a central axis of the workpiece, a cutting portion of the tool body adjacent to a first end surface of the workpiece, and one of first and second cutting edges of at least one pair of cutting edges facing the first end surface; b) rotating the milling tool about the rotation axis of the tool body and simultaneously rotating the workpiece about its central axis with a predetermined relationship between the rotation speed of the milling tool and the rotation speed of the workpiece, while keeping the rotation axis of the tool body parallel to the central axis of the workpiece and moving the milling tool along a predetermined path relative to the workpiece such that one or more cutting edges facing a first end face of the workpiece chamfer first and second side edges of teeth on the workpiece; c) moving the milling tool relative to the workpiece to move one or more cutting edges facing the first end surface of the workpiece out of contact with the workpiece; d) moving the milling tool to a second predetermined position relative to the workpiece, wherein the rotation axis of the tool body is parallel to the central axis of the workpiece, the cutting portion of the tool body is adjacent to a second end face on the opposite side of the workpiece, and the other of the first and second cutting edges of the at least one pair of cutting edges faces the second end face; e) rotating the milling tool about the rotation axis of the tool body and simultaneously rotating the workpiece about its central axis with a predetermined relationship between the rotation speed of the milling tool and the rotation speed of the workpiece, while keeping the rotation axis of the tool body parallel to the central axis of the workpiece and moving the milling tool along a predetermined path relative to the workpiece such that one or more cutting edges facing the second end face of the workpiece chamfer third and fourth side edges of the teeth on the workpiece.

[0024] In this method, the milling tool chamfers the side edges of the internal or external teeth on a cylindrical toothed workpiece at both end faces of the workpiece without requiring repositioning of the workpiece. Thus, the workpiece remains clamped in the appropriate workpiece holder of the machine in one and the same orientation during the entire chamfering process, saving time. A first cutting edge on the milling tool is used to chamfer the side edges of the teeth on the workpiece at the end face of the workpiece facing away from the workpiece holder that rotatably holds the workpiece, and a second cutting edge on the milling tool is used to chamfer the side edges of the teeth on the opposite end face of the workpiece. The chamfering process can begin by chamfering the side edges on the end face of the workpiece facing away from the workpiece holder, and then proceed to chamfering the side edges on the end face of the workpiece facing the workpiece holder. Alternatively, the chamfering process can begin with chamfering the side edges on the end face of the workpiece facing the workpiece holder, and then proceed to chamfering the side edges on the end face of the workpiece facing away from the workpiece holder.

[0025] According to one embodiment of the present invention, the predetermined path for the movement of the milling tool relative to the workpiece in step b includes at least one portion in which the milling tool moves in its axial direction, thereby moving one or more cutting edges facing a first end face of the workpiece in a direction towards this first end face, and / or the predetermined path for the movement of the milling tool relative to the workpiece in step e includes at least one portion in which the milling tool moves in its axial direction, thereby moving one or more cutting edges facing a second end face of the workpiece in a direction towards this second end face.

[0026] According to another embodiment of the present invention, the predetermined path for movement of the milling tool relative to the workpiece in step b includes at least one portion where the distance between the rotation axis of the tool body and the central axis of the workpiece is changed, and / or the predetermined path for movement of the milling tool relative to the workpiece in step e includes at least one portion where the distance between the rotation axis of the tool body and the central axis of the workpiece is changed. The change in the distance between the rotation axis of the tool body and the central axis of the workpiece can be achieved by moving the milling tool in a direction perpendicular to the rotation axis of the tool body and / or by moving the workpiece in a direction perpendicular to the central axis of the workpiece.

[0027] The predetermined path for movement of the milling tool relative to the workpiece in step b and / or step e may of course also include one or more parts in which the milling tool is moved in its axial direction while the distance between the rotation axis of the tool body and the central axis of the workpiece is changed.

[0028] According to another embodiment of the present invention, The first and second side edges of the teeth on the workpiece are respectively chamfered in the machining direction from the root to the tip of the associated teeth in step b; The third and fourth side edges of the teeth on the workpiece are each chamfered in the root-to-tip machining direction of the associated tooth in step e.

[0029] Therefore, the chamfering of each side edge begins at the deepest part of the gap between the two teeth, i.e., the so-called bottom land or root surface, and ends at the tip of the associated tooth. It has been found that chamfering the side edges in the machining direction from the tooth tip to the root can result in burrs in the root area, especially on cutting edges that have begun to wear after extended use. It has also been found that chamfering the side edges in the opposite machining direction from the root to the tip avoids this burr. Therefore, chamfering each side edge of a tooth on a workpiece in the machining direction from the root to the tip improves the quality of the chamfer produced on the side edges.

[0030] According to yet another embodiment, in order to achieve a chamfering of each of the first and second side edges of the tooth on the workpiece in the machining direction from the root to the tip, step b. b1) chamfering a first side edge of a tooth on a workpiece while rotating the workpiece about its central axis in a first rotational direction, with the second tooth flank as the leading tooth flank and the first tooth flank as the trailing tooth flank, and while rotating the milling tool about the rotational axis of the tool body in the same rotational direction as the workpiece if the first side edge being chamfered is a side edge of an internal tooth on the workpiece, or in the opposite rotational direction if the first side edge being chamfered is a side edge of an external tooth on the workpiece; b2) chamfering a second side edge of a tooth on the workpiece while rotating the workpiece about its central axis in a second rotational direction opposite to the first rotational direction and while rotating the milling tool about the rotational axis of the tool body in the same rotational direction as the workpiece if the second side edge being chamfered is a side edge of an internal tooth on the workpiece, or in the opposite rotational direction if the second side edge being chamfered is a side edge of an external tooth on the workpiece.

[0031] In this specification and in the claims that follow, the expression "leading tooth flank" refers to the tooth flank that faces in the direction of rotation, i.e., forward, as the toothed workpiece rotates about its central axis, and the expression "trailing tooth flank" refers to the tooth flank that faces in the opposite direction, i.e., backward, as the toothed workpiece rotates about its central axis.

[0032] According to a further embodiment, in order to achieve a chamfering of each of the third and fourth side edges of the teeth on the workpiece in the machining direction from the root to the tip, step e. e1) chamfering a third side edge of a tooth on the workpiece while rotating the workpiece about its central axis in a first rotational direction and while rotating the milling tool about a rotational axis in the rotational direction of the tool body in the same rotational direction as the workpiece if the third side edge being chamfered is a side edge of an internal tooth on the workpiece, or in the opposite rotational direction if the third side edge being chamfered is a side edge of an external tooth on the workpiece; e2) chamfering a fourth side edge of a tooth on the workpiece while rotating the workpiece about its central axis in a second rotational direction and while rotating the milling tool about the rotational axis of the tool body in the same rotational direction as the workpiece if the fourth side edge being chamfered is a side edge of an internal tooth on the workpiece, or in the opposite rotational direction if the fourth side edge being chamfered is a side edge of an external tooth on the workpiece.

[0033] The above-mentioned substeps are preferably performed in the order b1-b2-e1-e2, where the rotational direction of the milling tool and workpiece is reversed between substeps b1 and b2 and between substeps e1 and e2. However, these substeps may alternatively be performed in the order b1-e1-e2-b2, where the rotational direction of the milling tool and workpiece is reversed only between substeps e1 and e2.

[0034] According to a third aspect, the present invention relates to a computer-based program having instructions which, when executed by a CNC machine, cause the CNC machine to perform the steps of any of the methods described above. The computer program or computer program product may be included in a CAM software product, i.e., software for computer-aided manufacturing. The computer program may be in the form of a computer-readable medium, such as a USB stick, a CD-ROM, or a data stream.

[0035] Further advantages of the method of the present invention will become apparent from the following description.

[0036] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. [Brief explanation of the drawings]

[0037] [Figure 1] FIG. 1 is a perspective view of a milling tool according to one embodiment of the present invention. [Figure 2] FIG. 2 is a side view of the milling tool of FIG. 1. [Figure 3] FIG. 2 is a front view of the milling tool of FIG. 1. [Figure 4a] 2 is an exploded perspective view of a portion of the milling tool of FIG. 1 from a different direction. [Figure 4b] 2 is an exploded perspective view of a portion of the milling tool of FIG. 1 from a different direction. [Figure 5] FIG. 2 is a rear view of a cutting component included in the milling tool of FIG. 1. [Figure 6] FIG. 6 is a side view of the cutting component of FIG. 5. [Figure 7] FIG. 6 is a perspective view of the cutting component of FIG. 5. [Figure 8] FIG. 6 is a plan view of the cutting part of FIG. 5. [Figure 9a] 2 is a perspective view of the milling tool and internally toothed workpiece of FIG. 1 when the milling tool is in position to chamfer a side edge at a first end face of the workpiece. FIG. [Figure 9b]FIG. 9b is a front view of the milling tool and workpiece of FIG. 9a. [Figure 10a] 9b is a perspective view of the milling tool and workpiece of FIG. 9a when the milling tool is in position to chamfer the side edge at the opposite second end face of the workpiece. [Figure 10b] 9b is another perspective view of the milling tool and workpiece of FIG. 9a when the milling tool is in position to chamfer the side edge at the opposite second end face of the workpiece. [Figure 10c] FIG. 10C is a front view of the milling tool and workpiece of FIGS. 10a and 10b. [Figure 11] FIG. 9b is an enlarged perspective view of a portion of the internally toothed workpiece of FIG. 9a. [Figure 12] FIG. 9b is an enlarged front view of a portion of the internally toothed workpiece of FIG. 9a. [Figure 13] 9b is a partial cutaway side view of a portion of the milling tool and workpiece of FIG. 9a. FIG. [Figure 14a] 2A-2C are diagrams of stages in the process of chamfering side edges on an internally toothed workpiece using the milling tool of FIG. 1; [Figure 14b] 2A-2C are diagrams of stages in the process of chamfering side edges on an internally toothed workpiece using the milling tool of FIG. 1; [Figure 14c] 2A-2C are diagrams of stages in the process of chamfering side edges on an internally toothed workpiece using the milling tool of FIG. 1; [Figure 14d] 2A-2C are diagrams of stages in the process of chamfering side edges on an internally toothed workpiece using the milling tool of FIG. 1; [Figure 14e] 2A-2C are diagrams of different stages in the process of chamfering a side edge on an internally toothed workpiece using the milling tool of FIG. 1; [Figure 15a] 2 is a perspective view of the milling tool and externally toothed workpiece of FIG. 1 when the milling tool is in position to chamfer a side edge at a first end face of the workpiece. FIG. [Figure 15b]FIG. 15b is a front view of the milling tool and workpiece of FIG. 15a. [Figure 16a] 15b is a perspective view of the milling tool and workpiece of FIG. 15a when the milling tool is in position to chamfer the side edge on the opposite second end face of the workpiece. [Figure 16b] 15b is another perspective view of the milling tool and workpiece of FIG. 15a when the milling tool is in position to chamfer the side edge at the opposite second end face of the workpiece. FIG. [Figure 16c] FIG. 16c is a front view of the milling tool and workpiece of FIGS. 16a and 16b. [Figure 17] FIG. 10 is a side view of a milling tool according to an alternative embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0038] An embodiment of a milling tool 1 according to the present invention is shown in FIGS. 1-8. The milling tool 1 is used to chamfer the lateral edges of internal or external teeth on cylindrical toothed workpieces at both end faces of the workpiece. The milling tool 1 includes an elongated tool body 2 configured to rotate about a rotation axis 3. The tool body 2 has a front end 2a and an opposite rear end 2b. In the illustrated embodiment, the tool body 2 is provided with a collar 5. A rear portion 6 of the tool body 2, located between the collar 5 and the rear end 2b, forms a connecting member through which the tool body 2 can be attached, either directly or via an intermediate tool holder, to a rotating spindle or the like of a machine, such as a milling machine. In the illustrated embodiment, the rear portion 6 is Coromant Capto®, size C8. Other Coromant Capto® sizes that can be used are sizes C3-C10. The rear portion 6 may also be any other connecting member suitable for such purposes, such as an HSK.

[0039] The tool body 2 includes a cutting portion 10 located away from the rear portion 6 and provided with cutting edges 11, 12. The tool body 2 further includes an elongated shank portion 40 supporting the cutting portion 10 and extending from the cutting portion 10 toward the rear portion 6. The shank portion 40 has a front end 40a facing the cutting portion 10 and an opposite rear end 40b facing the collar 5 and the rear portion 6. The cutting portion 10 is attached to the front end 40a of the shank portion 40. The shank portion 40 has a peripheral surface 41 extending around the shank portion 40 between the rear end 40b and the front end 40a. The shank portion 40 has a longitudinal center axis that coincides with the rotation axis 3 of the tool body 2.

[0040] The cutting portion 10 is provided with a pair of cutting edges, including a first cutting edge 11 facing away from the rear portion 6 of the tool body and a second cutting edge 12 facing the rear portion 6 of the tool body and positioned closer to the rear portion 6 than the first cutting edge 11. Therefore, the first cutting edge 11 is farther from the rear portion 6 of the tool body than the second cutting edge 12. The first and second cutting edges 11, 12 each have a front end 11a, 12a and an opposite rear end 11b, 12b. The rear end 11b of the first cutting edge 11 is positioned closer to the rear portion 6 of the tool body than the front end 11a of the first cutting edge, and the rear end 12b of the second cutting edge 12 is positioned closer to the rear portion 6 of the tool body than the front end 12a of the second cutting edge. As shown in FIGS. 2 and 6 , the leading end 11a of the first cutting edge 11 is located closer to the rotation axis 3 than the trailing end 11b of the first cutting edge 11, and the distance between the first cutting edge 11 and the rotation axis 3 gradually increases from the leading end 11a to the trailing end 11b of the first cutting edge 11, as viewed in a direction along the first cutting edge 11. The trailing end 12b of the second cutting edge 12 is located closer to the rotation axis 3 than the leading end 12a of the second cutting edge 12, and the distance between the second cutting edge 12 and the rotation axis 3 gradually increases from the trailing end 12b to the leading end 12a of the second cutting edge 12, as viewed in a direction along the second cutting edge 12. Furthermore, the trailing end 12b of the second cutting edge 12 is located at a greater distance from the rotation axis 3 than the radially outermost portion of the circumferential surface 41 of the shank portion 40.

[0041] The cutting portion 10 may also include two or more pairs of cutting edges 11, 12 of the type described above.

[0042] The cutting portion 10 has an axial extension of the tool body 2 limited to the region between a first plane P1 (see FIG. 2 ), which extends perpendicular to the rotation axis 3 and intersects the rear end 12b of the second cutting edge 12, and a second plane P2, which extends perpendicular to the rotation axis 3 and intersects the front end 11a of the first cutting edge 11. In the embodiment shown in FIGS. 1 to 8 , the tool body 2 does not have a portion extending axially beyond the cutting portion 10. Therefore, in this case, the cutting portion 10 constitutes the axially frontmost portion of the tool body 2, i.e., the portion furthest from the rear portion 6 of the tool body 2. Alternatively, the tool body 2 may also include a front portion 7, as shown in FIG. 17 , connected to the cutting portion 10 and protruding from the cutting portion on the side opposite the rear portion 6. In this case, the front end 11a of the first cutting edge 11 is located at a greater distance from the rotation axis 3 than the radially outermost portion of the circumferential surface of the front portion 7.

[0043] The radial distance r between the rear end 12b of the second cutting edge 12 and the radially outermost portion of the circumferential surface 41 of the shank portion 40 is preferably 2 to 40 mm, and more preferably 6 to 30 mm. In the embodiment shown in Fig. 17, the radial distance r2 between the front end 11a of the first cutting edge 11 and the radially outermost portion of the circumferential surface of the front portion 7 is preferably 2 to 40 mm, and more preferably 6 to 30 mm.

[0044] In the illustrated embodiment, the shank portion 40 is rod-shaped and has the form of a right circular cylinder. However, the shank portion 40 may also have any other suitable shape. The shank portion 40 has a length L of 25 to 500 mm, preferably 50 to 200 mm, and more preferably 100 to 150 mm.

[0045] The cutting part 10 may be permanently fixed to the shank part 40. However, in the embodiment shown in Figures 1-8, the cutting part 10 is removably attached to the front end 40a of the shank part 40 by fastening elements 42 in the form of two screws that extend through respective through holes 13 in the cutting part 10 and engage with respective threaded holes 43 (see Figure 4a) provided in the front end face 44 of the shank part 40.

[0046] In the illustrated embodiment, the cutting part 10 includes a base 14 to which the cutting part 10 is attached to the shank part 40, and a holder arm 15 fixed to the base 14 and projecting from the base 14 in a radial direction relative to the rotation axis 3 beyond the radially outermost portion of the peripheral surface 41 of the shank part 40. The holder arm 15 has an inner end 15a facing the rotation axis 3 and an opposite outer end 15b. The holder arm 15 is fixed to the base 14 at its inner end 15a, and the first and second cutting edges 11, 12 are disposed on the holder arm 15 at its outer end 15b. In the illustrated embodiment, the first and second cutting edges 11, 12 form part of a cutting insert 16 that is removably attached to an insert seat 17 provided on the outer end 15b of the holder arm 15. The illustrated cutting insert 16 is releasably secured to the insert seat 17 by a fastening element 18 in the form of a screw that extends through a through hole 19 in the cutting insert 16 and engages with a threaded hole 20 (see FIG. 4 a) in a support surface 21 of the insert seat 17. The support surface 21 is advantageously provided with splines 22 or the like that are configured to securely mechanically engage corresponding splines 23 on the underside of the cutting insert 16 to ensure accurate positioning of the cutting insert 16 in the insert seat 17 and to prevent movement of the cutting insert 16 relative to the support surface 21 when properly mounted in the insert seat 17.

[0047] Advantageously, the base 14 and the shank 40 are formed as separate components, and the base 14 may be removably attached to the shank 40. However, the base 14 and the shank 40 may alternatively be formed integrally. In a corresponding manner, the front portion 7 and the base 14 included in the milling tool 1 shown in FIG. 17 may be formed integrally or as separate components attached to each other.

[0048] 1 to 8 , the base 14 is slidably attached to the front end 40a of the shank 40 and is slidable relative to the shank 40 perpendicular to the rotation axis 3 and linearly in the longitudinal direction of the holder arm 15. The base 14 can be locked to the shank 40 at different sliding positions, thereby enabling adjustment of the radial distance between the first cutting edge 11 and the rotation axis 3 and the radial distance between the second cutting edge 12 and the rotation axis 3. Therefore, by adjusting the position of the base 14 relative to the shank 40, it is possible to adjust the above-mentioned radial distance r between the rear end 12b of the second cutting edge 12 and the radially outermost portion of the circumferential surface 41 of the shank 40. In the illustrated example, the rear surface 14a of the base 14 is provided with mutually parallel splines 25 that extend parallel to the longitudinal axis of the holder arm 15 and slidably engage with corresponding splines 45 provided on the front end surface 44 of the shank portion 40 so that the base 14 can be slid in a desired direction relative to the shank portion 40 during adjustment of the sliding position of the base 14 relative to the shank portion 40.

[0049] The milling tool 1 shown in FIGS. 1-8 includes an adjustment mechanism 50 that allows the sliding position of the base 14 relative to the shank 40 to be adjusted. Thus, the precise positioning of the base 14 along the splines 45 on the front end surface 44 of the shank 40 can be adjusted by the adjustment mechanism 50. In the illustrated embodiment, the adjustment mechanism 50 includes an adjustment element 51 configured to act between the base 14 and the shank 40. The adjustment element 51 includes a pin 52 rotatably received in a hole 46 on the front end surface 44 of the shank 40 and a head 53 secured to the pin 52 and rotatably received in a recess 26 on the rear surface 14a of the base 14. The axis of rotation of the pin 52 is parallel to but offset from the axis of rotation of the head 53 such that rotation of the head 53 within the recess 26 results in sliding movement of the base 14 in the longitudinal direction of the splines 25, 45. A socket 54 designed for releasable engagement with a torque tool (not shown) is provided on the front surface of the head 53, allowing the torque tool to be connected to the head 53 when the head 53 is rotated, thereby moving the base 14 in the longitudinal direction of the splines 25, 45. The socket 54 is accessible through a hole 27 in the base 14. The base 14 is provided with through-holes 13 for the fastening elements 42 described above. Each of these through-holes 13 has an elongated cross-sectional shape with a major axis extending substantially in the longitudinal direction of the splines 25, thereby allowing the base 14 to move perpendicular to the shaft 42a of the fastening element 42 in the longitudinal direction of the splines 45 on the front end surface 44 of the shank 40. The base 14 can be locked to the shank 40 in a desired sliding position relative to the shank 40 by tightening the fastening element 42. Of course, the adjustment mechanism 50 may be designed in any other suitable manner.

[0050] In the embodiment shown in FIGS. 1-8 , the first cutting edge 11 extends substantially linearly in a third plane P3 (see FIG. 8 ) that includes the rotation axis 3, and the second cutting edge 12 extends substantially linearly in a fourth plane P4 that also includes the rotation axis 3. The fourth plane P4 preferably coincides with the third plane P3 as shown in FIG. 8 , but the third plane P3 and the fourth plane P4 may alternatively be angularly offset from each other relative to the rotation axis 3 of the tool body 2. The first cutting edge 11 is inclined in the third plane P3 such that an extension of the first cutting edge 11 forms a first angle α1 (see FIG. 2 ) with the rotation axis 3, and the second cutting edge 12 is inclined in the fourth plane P4 such that an extension of the second cutting edge 12 forms a second angle α2 with the rotation axis 3. The first angle α1 and the second angle α2 are preferably equal, or at least substantially equal. The first angle α1 and the second angle α2 are equal to or greater than 20° and less than 90°, preferably 30 to 80°. In the illustrated embodiment, the first angle α1 and the second angle α2 are both approximately 45°.

[0051] 1 to 8, the first cutting edge 11 is formed at the intersection of the first surface 31 and the second surface 32 on the cutting insert 16, and the second cutting edge 12 is formed at the intersection of the third surface 33 and the fourth surface 34 on the cutting insert 16, the first surface 31 and the second surface 32 being mirror-symmetrical to each other with respect to a third plane P3, and the third surface 33 and the fourth surface 34 being mirror-symmetrical to each other with respect to a fourth plane P4. Furthermore, the first cutting edge 11 and the second cutting edge 12 are here mirror-symmetrical to each other with respect to a symmetry plane PS (see FIG. 8), which extends midway between the first cutting edge 11 and the second cutting edge 12 perpendicular to the rotation axis 3 of the tool body 2. The first surface 31 and the second surface 32 are inclined relative to each other and diverge from each other in a direction from the first cutting edge 11 toward the rotation axis 3, so that the first surface 31 and the second surface 32 form a first nose-shaped protrusion 35a on the cutting insert 16. In a corresponding manner, the third surface 33 and the fourth surface 34 are inclined relative to each other and diverge from each other in a direction from the second cutting edge 12 toward the rotation axis 3, so that the third and fourth surfaces 33, 34 form a second nose-shaped protrusion 35b on the cutting insert 16. The first protrusion 35a is provided on a first side of the holder arm 15 at its outer end 15b to form a support for the first nose-shaped protrusion 36a on the cutting insert 16, and the second protrusion 35b is provided on a second opposite side of the holder arm 15 at its outer end 15b to form a support for the second nose-shaped protrusion 36b on the cutting insert 16.

[0052] As described above, the milling tool 1 is to be used to chamfer the side edges 61-64 (see FIGS. 11 and 12) of internal or external teeth 60 on a cylindrical toothed workpiece 8 at a first end face 9a of the workpiece and an opposite second end face 9b of the workpiece. Each tooth 60 on the workpiece 8 has a tip 65, a root 66, a first tooth flank 67a extending between the tip 65 and the root 66 on a first side of the tooth, and a second tooth flank 67b extending between the tip 65 and the root 66 on an opposite second side of the tooth. A first side edge 61 is formed where the first tooth flank 67a intersects with the first end face 9a of the workpiece 8, a second side edge 62 is formed where the second tooth flank 67b intersects with the first end face 9a of the workpiece 8, a third side edge 63 is formed where the first tooth flank 67a intersects with the second end face 9b of the workpiece 8, and a fourth side edge 64 is formed where the second tooth flank 67b intersects with the second end face 9b of the workpiece 8. A bottom land 68 is provided between the roots 66 of adjacent teeth 60, and a top land 69 is provided at the tip 65 of each tooth 60.

[0053] The edges 70 at the contact surfaces between the top land 69 of each tooth 60 on the workpiece 8 and the respective end faces 9a, 9b of the workpiece are typically chamfered in a separate machining operation before the chamfering of the side edges 61-64 is performed by the milling tool 1.

[0054] During the execution of a chamfering operation using the milling tool 1, the workpiece 8 is mounted in a rotatable workpiece holder (not shown) of the machine and is rotatable by the machine about the central axis 4 of the workpiece 8, and the milling tool 1 is mounted in a rotatable tool holder (not shown) of the machine and is rotatable by the machine about the rotation axis 3 of the tool body 2 and is movable by the machine relative to the workpiece 8 in different directions in the axial direction z of the workpiece 8 and in planes x, y perpendicular to the central axis 4 of the workpiece 8, with the rotation axis 3 of the tool body 2 parallel to the central axis 4 of the workpiece 8. The rotational speed of the workpiece 8, the rotational speed of the milling tool 1, and the movement of the milling tool 1 relative to the workpiece 8 are controlled in a programmable manner by an electronic control device (not shown).

[0055] The workpiece holder and tool holder of the machine are typically positioned opposite each other with the tool holder facing the workpiece holder. In the examples shown in Figures 9-10 and 15-16, an end face of the workpiece 8, referred to as the first end face 9a, faces the workpiece holder of the machine, and an opposite second end face 9b of the workpiece 8 faces the tool holder of the machine.

[0056] The workpiece 8 is rotatable about its central axis 4 in a first rotational direction R1, with the second tooth flank 67b of the tooth 60 on the workpiece being the leading tooth flank and the first tooth flank 67a of the tooth 60 on the workpiece being the trailing tooth flank, and in an opposite second rotational direction R2, with the first tooth flank 67a of the tooth 60 on the workpiece being the leading tooth flank and the second tooth flank 67b of the tooth 60 on the workpiece being the trailing tooth flank.

[0057] To perform chamfering of all side edges 61-64 of teeth 60 on workpiece 8 with milling tool 1, the following steps are performed. a) the milling tool 1 is positioned at a first predetermined position relative to the workpiece 8, with the rotation axis 3 of the tool body 2 parallel to the central axis 4 of the workpiece 8, the cutting part 10 of the tool body 2 adjacent to the first end face 9a of the workpiece 8, and the second cutting edge 12 facing this first end face 9a, as shown in Figures 9a and 15a; b) thereafter, the milling tool 1 is rotated about the rotation axis 3 of the tool body 2, and the workpiece 8 is simultaneously rotated about its central axis 4 with a predetermined relationship between the rotation speed of the milling tool 1 and the rotation speed of the workpiece 8, while keeping the rotation axis 3 of the tool body 2 parallel to the central axis 4 of the workpiece 8 and moving the milling tool 1 along a predetermined path relative to the workpiece 8 so that the second cutting edge 12 chamfers the first and second side edges 61, 62 of the teeth 60 on the workpiece; c) the milling tool 1 is then moved relative to the workpiece 8 to move the second cutting edge 12 out of contact with the workpiece 8; d) thereafter, the milling tool 1 is moved relative to the workpiece 8 and positioned at a second predetermined position relative to the workpiece 8, with the rotation axis 3 of the tool body 2 parallel to the central axis 4 of the workpiece 8, with the cutting part 10 of the tool body 2 adjacent to a second end face 9b opposite the workpiece 8 and with the first cutting edge 11 facing this second end face 9b, as shown in Figures 10a and 16a; e) Thereafter, the milling tool 1 is rotated about the rotation axis 3 of the tool body 2, and the workpiece 8 is simultaneously rotated about its central axis 4 with a predetermined relationship between the rotation speed of the milling tool 1 and the rotation speed of the workpiece 8, while keeping the rotation axis 3 of the tool body 2 parallel to the central axis 4 of the workpiece 8 and moving the milling tool 1 along a predetermined path relative to the workpiece 8 so that the first cutting edge 11 chamfers the third and fourth side edges 63, 64 of the teeth 60 on the workpiece.

[0058] During the chamfering in steps b and e above, a portion of one of the active first and second cutting edges 11, 12 is rotated into a gap between two adjacent teeth 60 and then moved with this gap in the direction of rotation of the workpiece 8 during part of the rotation of the workpiece 8, while cuttingly engaging at least a portion of one of the side edges located on either side of the gap before being rotated out of the gap, as shown in Figures 14a-14e. As the milling tool 1 continues to rotate, a portion of the active one of the first and second cutting edges 11, 12 rotates into a new gap between two other adjacent teeth 60 on the workpiece 8, and so on. By gradually moving the milling tool 1 relative to the workpiece 8 during continuous rotation of the milling tool 1 and workpiece 8 so that the distance between the rotation axis 3 of the tool body 2 and the central axis 4 of the workpiece 8 changes, the active cutting edges 11, 12 can be brought into cutting engagement with different portions of each side edge being chamfered at different stages of the chamfering process until these side edges are chamfered along their entire extension.

[0059] The movement of the milling tool 1 relative to the workpiece 8 in step b can begin by first moving the milling tool 1 axially, thereby moving the second cutting edge 12 in a direction toward the first end face 9a of the workpiece 8, so that the second cutting edge 12 contacts the workpiece 8 as the milling tool 1 rotates. The milling tool 1 then remains in this axial position relative to the workpiece 8 during the remaining stages of step b, thereby achieving a chamfer of approximately constant width along each side edge being chamfered. However, the milling tool 1 can also be moved axially relative to the workpiece 8 during at least part of the remaining stages of step b, thereby achieving a chamfer of varying width along each side edge being chamfered.

[0060] In a corresponding manner, movement of the milling tool 1 relative to the workpiece 8 in step e can begin by first moving the milling tool 1 axially, thereby moving the first cutting edge 11 in a direction toward the second end face 9b of the workpiece 8, so that the first cutting edge 11 contacts the workpiece 8 as the milling tool 1 rotates. The milling tool 1 then remains in this axial position relative to the workpiece 8 during the remaining stages of step e, thereby achieving a chamfer of approximately constant width along each side edge being chamfered. However, the milling tool 1 can also be moved axially relative to the workpiece 8 during at least part of the remaining stages of step e, thereby achieving a chamfer of varying width along each side edge being chamfered.

[0061] The relationship between the rotational speed of the milling tool 1 and the rotational speed of the workpiece 8 should be adapted so that a portion of the active cutting edges 11, 12 enters the gaps between all of the teeth 60 on the workpiece 8 after a certain number of revolutions of the workpiece 8. To enable the active cutting edges to move in the same direction as the gaps between two adjacent teeth 60 on the workpiece 8, with the portion of the cutting edge accepted in the gap in question, the milling tool 1 must be rotated about the rotation axis 3 of the tool body 2 in the same rotational direction as the workpiece 8 when the side edges 61-64 of the internal teeth 60 on the workpiece are being chamfered, and in the opposite rotational direction to the workpiece 8 when the side edges 61-64 of the external teeth 60 on the workpiece are being chamfered.

[0062] All side edges 61 - 64 are preferably chamfered in the machining direction from root 66 to tip 65 of the associated tooth 60 .

[0063] To achieve a chamfer of each of the first and second side edges 61, 62 of the tooth 60 on the workpiece 8 in the machining direction from the root 66 to the tip 65, the above-mentioned step b. b1) chamfering a first side edge 61 of a tooth 60 on the workpiece 8 while rotating the workpiece about its central axis 4 in a first direction of rotation R1 and while rotating the milling tool 1 about the rotation axis 3 of the tool body 2 in the same direction of rotation R1 as the workpiece 8 if the first side edge 61 being chamfered is a side edge of an internal tooth 60 on the workpiece 8, or in the opposite direction of rotation R2 if the first side edge 61 being chamfered is a side edge of an external tooth 60 on the workpiece 8; b2) chamfering the second side edges 62 of the teeth 60 on the workpiece 8 while rotating the workpiece about its central axis 4 in the above-mentioned second rotation direction R2 opposite to the first rotation direction R1 and while rotating the milling tool 1 about the rotation axis 3 of the tool body 2 in the same rotation direction R2 as the workpiece 8 if the second side edges 62 being chamfered are side edges of internal teeth 60 on the workpiece 8, or in the opposite direction to the rotation direction R1 if the second side edges 62 being chamfered are side edges of external teeth 60 on the workpiece 8.

[0064] To achieve a chamfer on the workpiece 8 of each of the third and fourth side edges 63, 64 of the tooth 60 in the machining direction from the root 66 to the tip 65, the above-mentioned step e. e1) chamfering the third side edge 63 of the tooth 60 on the workpiece 8 while rotating the workpiece about its central axis 3 in a first rotation direction R1 and while rotating the milling tool 1 about the rotation axis 3 of the tool body 2 in the same rotation direction R1 as the workpiece 8 if the third side edge 63 being chamfered is a side edge of an internal tooth 60 on the workpiece 8, or in the opposite rotation direction R2 if the third side edge 63 being chamfered is a side edge of an external tooth 60 on the workpiece 8; e2) chamfering the fourth side edge 64 of the tooth 8 on the workpiece 8 while rotating the workpiece in a second rotation direction R2 about its central axis 4 and while rotating the milling tool 1 about the rotation axis 3 of the tool body 2 in the same rotation direction R2 as the workpiece 8 if the fourth side edge 64 being chamfered is a side edge of an internal tooth 60 on the workpiece 8, or in the opposite rotation direction R1 if the fourth side edge 64 being chamfered is a side edge of an external tooth 60 on the workpiece 8.

[0065] Of course, the present invention is in no way limited to the above-described embodiments, but on the contrary, many possibilities for modification thereof will be apparent to those skilled in the art without departing from the basic concept of the invention as defined in the appended claims.

Claims

1. A milling tool for chamfering side edges (61-64) of internal or external teeth (60) on a cylindrical toothed workpiece (8) at opposite end faces (9a, 9b) of the workpiece (8), the milling tool (1) comprising an elongated tool body (2) having at its rear end (2b) a rear part (6) adapted for attachment to a machine, and a cutting part (10) provided with cutting edges (11, 12) at a distance from the rear part (6), the tool body (2) comprises an elongated shank portion (40), the elongated shank portion (40) carrying the cutting portion (10), extending from the cutting portion (10) towards the rear portion (6), and comprising a front end (40a) facing the cutting portion (10), an opposite rear end (40b), and a peripheral surface (41) extending around the shank portion (40) between the rear end (40b) and the front end (40a), the shank portion (40) having a longitudinal central axis coinciding with the rotation axis (3) of the tool body (2); The cutting portion (10) is provided with at least a pair of cutting edges, including a first cutting edge (11) facing away from the rear portion (6) and a second cutting edge (12) facing the rear portion (6) and positioned closer to the rear portion (6) than the first cutting edge (11); the first cutting edge (11) has a rear end (11b) and an opposite front end (11a), the rear end (11b) of the first cutting edge (11) is located closer to the rear end (6) of the tool body than the front end (11a) of the first cutting edge (11), the front end (11a) of the first cutting edge (11) is located closer to the rotation axis (3) than the rear end (11b) of the first cutting edge (11), and the distance between the first cutting edge (11) and the rotation axis (3) gradually increases from the front end (11a) to the rear end (11b) of the first cutting edge (11), as viewed in a direction along the first cutting edge (11); the second cutting edge (12) has a front end (12a) and an opposite rear end (12b), the rear end (12b) of the second cutting edge (12) is located closer to the rear portion (6) of the tool body than the front end (12a) of the second cutting edge (12), the rear end (12b) of the second cutting edge (12) is located at a greater distance from the rotation axis (3) than the radially outermost portion of the circumferential surface (41) of the shank portion (40), the rear end (12b) of the second cutting edge (12) is located closer to the rotation axis (3) than the front end (12a) of the second cutting edge (12), and the distance between the second cutting edge (12) and the rotation axis (3) gradually increases as viewed in a direction along the second cutting edge (12) from its rear end (12b) to its front end (12a); The cutting portion (10) has an axial extension of the tool body (2) limited to a region between a first plane (P1) extending perpendicular to the rotation axis (3) and intersecting the rear end (12b) of the second cutting edge (12), and a second plane (P2) extending perpendicular to the rotation axis (3) and intersecting the front end (11a) of the first cutting edge (11), 1. A milling tool, characterized in that the cutting portion (10) constitutes the axially frontmost part of the tool body (2) or the tool body (2) comprises a front portion (7) protruding from the cutting portion (10) on the side opposite the rear portion (6), and the front end (11a) of the first cutting edge (11) is located at a distance from the rotation axis (3) that is greater than the radially outermost part of this front portion (7).

2. the first cutting edge (11) extends substantially linearly in a third plane (P3) that includes the rotation axis; the second cutting edge (12) extends substantially linearly in a fourth plane (P4) containing the rotation axis (3), the fourth plane (P4) preferably coinciding with the third plane (P3); 2. The milling tool according to claim 1, wherein:

3. The first cutting edge (11) is arranged such that an extension of the first cutting edge (11) forms a first angle (α １ ), and the first angle (α １ ) is 20° or more and less than 90°, preferably 30 to 80°; The second cutting edge (12) is arranged such that an extension of the second cutting edge (12) forms a second angle (α ２ ), and the second angle (α ２ ) is 20° or more and less than 90°, preferably 30 to 80°, and the first and second angles (α １ , α ２ ) are preferably substantially equal; 3. The milling tool according to claim 2, wherein:

4. the first cutting edge (11) is formed at an intersection of a first surface (31) on the cutting portion (10) and a second surface (32) on the cutting portion (10), and the first surface (31) and the second surface (32) are mirror images of each other with respect to a third plane (P3); the second cutting edge (12) is formed at an intersection of a third surface (33) on the cutting portion (10) and a fourth surface (34) on the cutting portion (10), and the third surface (33) and the fourth surface (34) are mirror images of each other with respect to a fourth plane (P4); 4. A milling tool according to claim 1, wherein:

5. 5. A milling tool according to claim 1, wherein the first cutting edge (11) and the second cutting edge (12) are mirror images of each other with respect to a plane of symmetry (PS) extending perpendicular to the axis of rotation (3) and midway between the first and second cutting edges (11, 12).

6. 6. The milling tool according to claim 1, wherein the radial distance (r) between the rear end (12b) of the second cutting edge (12) and the radially outermost part of the circumferential surface (41) of the shank portion (40) is 2 to 40 mm, preferably 6 to 30 mm.

7. 7. The milling tool according to claim 1, wherein the cutting portion (10) comprises a holder arm (15) that projects radially relative to the rotation axis (3) beyond the radially outermost portion of the circumferential surface (41) of the shank portion (40), the holder arm (15) having an inner end (15a) facing the rotation axis (3) and an opposite outer end (15b), and the first and second cutting edges (11, 12) are arranged at the outer end (15b) of the holder arm (15).

8. 8. A milling tool according to claim 7, characterized in that the first and second cutting edges (11, 12) form part of a cutting insert (16) removably mounted in an insert seat (17) provided at the outer end (15b) of the holder arm (15).

9. 9. The milling tool according to claim 7 or 8, wherein the cutting part (10) comprises a base (14) that supports the holder arm (15) and is slidably attached to a front end (40a) of the shank part (40) so as to be slidable relative to the shank part (40) perpendicularly to the rotation axis (3) and linearly in the longitudinal direction of the holder arm (15), the base (14) being lockable with respect to the shank part (40) in different sliding positions relative to the shank part (40), thereby enabling adjustment of the radial distance between the first cutting edge (11) and the rotation axis (3) and the radial distance between the second cutting edge (12) and the rotation axis (3).

10. A milling tool according to any one of claims 1 to 9, characterized in that the shank portion (40) is rod-shaped.

11. A milling tool according to any one of claims 1 to 10, characterized in that the shank portion (40) has a length (L) of 25 to 500 mm, preferably 50 to 200 mm, more preferably 100 to 150 mm.

12. 12. A milling tool according to any one of claims 1 to 11, characterized in that the cutting part (10) is detachably attached to the front end (40a) of the shank part (40).

13. A method for chamfering side edges (61-64) of internal or external teeth (60) on a cylindrical toothed workpiece (8) at a first end face (9a) of the workpiece (8) and at an opposite second end face (9b) of the workpiece (8), wherein each tooth (60) on the workpiece (8) has a tip (65), a root (66), a first tooth flank (67a) extending between the tip (65) and the root (66) on a first side of the tooth, and a second tooth flank (67b) on an opposite side of the tooth. a second tooth flank (67b) extending between the tooth tip (65) and the tooth root (66) on the side of the tooth tip (65); a first side edge (61) formed at the intersection of the first tooth flank (67a) and the first end face (9a) of the workpiece (8); a second side edge (62) formed at the intersection of the second tooth flank (67b) and the first end face (9a) of the workpiece (8); a third side edge (63) formed at the difference portion and a fourth side edge (64) formed at the intersection of the second tooth flank (67b) and the second end face (9b) of the workpiece (8), wherein the workpiece (8) is mounted on a machine and is rotatable by the machine about a central axis (4) of the workpiece (8), and the chamfering is performed by the milling tool (1) according to any one of claims 1 to 12, and the milling tool (1) is mounted on the machine and is rotatable by the machine about the rotation axis (3) of the tool body (2) and is movable by the machine relative to the workpiece (8) in different directions in an axial direction (z) of the workpiece (8) and in a plane (x, y) perpendicular to the central axis (4) of the workpiece (8) so that the rotation axis (3) of the tool body (2) is parallel to the central axis (4) of the workpiece (8), and the method comprises: a) positioning the milling tool (1) at a first predetermined position relative to the workpiece (8) with the rotation axis (3) of the tool body (2) parallel to the central axis (4) of the workpiece (8), the cutting portion (10) of the tool body (2) adjacent to a first end face (9a) of the workpiece (8), and one of the first and second cutting edges (11, 12) of at least one pair of cutting edges facing the first end face (9a); b) rotating the milling tool (1) about the rotation axis (3) of the tool body (2) and simultaneously rotating the workpiece (8) about its central axis (4) with a predetermined relationship between the rotation speed of the milling tool (1) and the rotation speed of the workpiece (8), while keeping the rotation axis (3) of the tool body (2) parallel to the central axis (4) of the workpiece (8) and moving the milling tool (1) along a predetermined path relative to the workpiece (8) such that one or more cutting edges facing the first end face (9a) of the workpiece (8) chamfer the first and second side edges (61, 62) of the teeth (60) on the workpiece (8); c) moving the milling tool (1) relative to the workpiece (8) so that one or more cutting edges facing the first end face (9a) of the workpiece (8) are not in contact with the workpiece (8); d) moving the milling tool (1) to a second predetermined position relative to the workpiece (8), wherein the rotation axis (3) of the tool body (2) is parallel to the central axis (4) of the workpiece (8), the cutting portion (10) of the tool body (2) is adjacent to the opposite second end face (9b) of the workpiece (8), and the other of the first and second cutting edges (11, 12) of the at least one pair of cutting edges faces the second end face (9b); e) rotating the milling tool (1) about the rotation axis (3) of the tool body (2) and simultaneously rotating the workpiece (8) about its central axis (4) with a predetermined relationship between the rotation speed of the milling tool (1) and the rotation speed of the workpiece (8), wherein the rotation axis (3) of the tool body (2) is kept parallel to the central axis (4) of the workpiece (8) and the milling tool (1) is moved along a predetermined path relative to the workpiece (8) such that one or more cutting edges facing the second end face (9b) of the workpiece (8) chamfer the third and fourth side edges (63, 64) of the teeth (60) on the workpiece (8).

14. 14. The method according to claim 13, wherein the predetermined path for the movement of the milling tool (1) relative to the workpiece (8) in step b includes at least one portion during which the milling tool (1) moves in its axial direction, thereby moving the one or more cutting edges facing the first end face (9 a) of the workpiece (8) in a direction towards this first end face (9 a), and / or the predetermined path for the movement of the milling tool (1) relative to the workpiece (8) in step e includes at least one portion during which the milling tool (1) moves in its axial direction, thereby moving the one or more cutting edges facing the second end face (9 b) of the workpiece (8) in a direction towards this second end face (9 b).

15. 15. The method according to claim 13 or 14, wherein the predetermined path for the movement of the milling tool (1) relative to the workpiece (8) in step b comprises at least one portion where the distance between the rotation axis (3) of the tool body (2) and the central axis (4) of the workpiece (8) is changed, and / or the predetermined path for the movement of the milling tool (1) relative to the workpiece (8) in step e comprises at least one portion where the distance between the rotation axis (3) of the tool body (2) and the central axis (4) of the workpiece (8) is changed.

16. the first side edge (61) and the second side edge (62) of the tooth (60) on the workpiece (8) are each chamfered in step b in a machining direction from the root (66) to the tip (65) of the associated tooth (60); the third side edge (63) and the fourth side edge (64) of the tooth (60) on the workpiece (8) are each chamfered in a machining direction from the root (66) to the tip (65) of the associated tooth (60) in step e.; 16. The method according to any one of claims 13 to 15.

17. Step b is b1) chamfering the first side edge (61) of the tooth (60) on the workpiece (8) while rotating the workpiece (8) around its central axis (4) in a first rotation direction (R1) with the second tooth flank (67b) as the leading tooth flank and the first tooth flank (67a) as the trailing tooth flank, and while rotating the milling tool (1) around the rotation axis (3) of the tool body (2) in the same rotation direction (R1) as the workpiece (8) if the first side edge (61) being chamfered is the side edge of an internal tooth (60) on the workpiece (8), or in the opposite rotation direction (R2) if the first side edge (61) being chamfered is the side edge of an external tooth (60) on the workpiece (8); b2) chamfering the second side edge (62) of the tooth (60) on the workpiece (8) while rotating the workpiece (8) about its central axis (4) in a second rotational direction (R2) opposite to the first rotational direction (R1) and while rotating the milling tool (1) about the rotational axis (3) of the tool body (2) in the same rotational direction (R2) as the workpiece (8) if the second side edge (62) being chamfered is a side edge of an internal tooth (60) on the workpiece (8) or in the opposite rotational direction (R1) if the second side edge (62) being chamfered is a side edge of an external tooth (60) on the workpiece (8).

18. Step e is e1) chamfering the third side edge (63) of the tooth (60) on the workpiece (8) while rotating the workpiece (8) about its central axis (4) in the first rotation direction (R1) and while rotating the milling tool (1) about the rotation axis (3) of the tool body (2) in the same rotation direction (R1) as the workpiece (8) if the third side edge (63) being chamfered is a side edge of an internal tooth (60) on the workpiece (8) or in the opposite rotation direction (R2) if the third side edge (63) being chamfered is a side edge of an external tooth (60) on the workpiece (8); e2) chamfering the fourth side edge (64) of the tooth (60) on the workpiece (8) while rotating the workpiece (8) about its central axis (4) in the second direction of rotation (R2) and while rotating the milling tool (1) about the rotation axis (3) of the tool body (2) in the same direction of rotation (R2) as the workpiece (8) if the fourth side edge (64) being chamfered is a side edge of an internal tooth (60) on the workpiece (8) or in the opposite direction of rotation (R1) if the fourth side edge (64) being chamfered is a side edge of an external tooth (60) on the workpiece (8).

19. A computer program having instructions which, when executed by a CNC machine, cause the CNC machine to perform the steps of any one of claims 13 to 18.

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