Milling tool and method for chamfering tooth relief edges on cylindrical toothed workpieces

Abstract

A milling tool (1) for chamfering the clearance edges of teeth on a cylindrical toothed workpiece comprises a tool body (2) with a rear part (6) configured for attachment to a machine and a cutting part (10). A cutting insert (20) is mounted in the cutting part and has first and second cutting edges (21, 22) extending in a common extension plane parallel to a longitudinal plane containing the rotation axis (3) of the tool body. The cutting edges (21, 22) are arranged opposite each other on opposite sides of a radial plane containing the rotation axis (3) and perpendicular to the longitudinal plane, and the cutting edges (21, 22) are inclined relative to this radial plane. The cutting insert has a rake face (25) facing radially outward from the rotation axis (3).

Description

[Technical Field]

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

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

[0003] WO 2022 / 013068 A1 discloses a method for chamfering the clearance edges of teeth on a cylindrical toothed workpiece at an end face thereof using a milling tool, in which the workpiece and milling tool are rotated with a predetermined relationship between the rotational speed of the milling tool and the rotational speed of the workpiece, while the rotational axis of the milling tool is kept parallel to the central axis of the workpiece. In the method according to WO 2022 / 013068 A1, the clearance edges are chamfered in such a way that when a first clearance edge of a tooth is chamfered in the direction from the tip to the root of the tooth, a second clearance edge of an adjacent, opposite tooth is chamfered in the direction from the root to the tip of the tooth. During the chamfering of the clearance edge on one of the end faces of the workpiece, the milling tool is moved in different predetermined directions in a plane perpendicular to the central axis of the workpiece, thereby changing the relative position between the rotational axis of the milling tool and the central axis of the workpiece during the chamfering operation. WO 2022 / 013068 A1 discloses a milling tool that is configured to be moved into contact with a forward-facing end face of a workpiece. When a clearance edge on a first forward-facing end face of the workpiece has been chamfered, the workpiece must be repositioned in the workpiece holder so that this second end face of the workpiece faces forward toward the milling tool before proceeding to chamfer the clearance edge on a second, opposite end face of the workpiece. Summary of the Invention

[0004] SUMMARY OF THE INVENTION It is an object of the present invention to provide a milling tool of the above type which has a new and effective design.

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

[0006] A milling tool according to a first aspect of the present invention comprises a tool body having a rear portion at a rear end configured for attachment to a machine so as to enable the tool body to be rotated by the machine about its axis of rotation, the tool body including a cutting portion located in front of the rear portion when viewed in the axial direction of the tool body, and at least one cutting insert mounted on the cutting portion.

[0007] the at least one cutting insert has at least a first cutting edge and a second cutting edge extending in a common extension plane parallel to a longitudinal plane including the rotation axis, the first cutting edge and the second cutting edge being arranged opposite each other on opposite sides of a radial plane including the rotation axis and perpendicular to the longitudinal plane; the first cutting edge has a rear end and an opposite front end, the rear end of the first cutting edge being 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 being located closer to the radial plane than the rear end of the first cutting edge, and a distance between the first cutting edge and the radial plane gradually increasing along the first cutting edge in a direction from its front end to its rear end; The second cutting edge has a rear end and an opposite front end, the rear end of the second cutting edge being positioned closer to the rear of the tool body than the front end of the second cutting edge, the front end of the second cutting edge being positioned closer to the radial plane than the rear end of the second cutting edge, and the distance between the second cutting edge and the radial plane gradually increasing along the second cutting edge in the direction from its front end to its rear end.

[0008] Additionally, the at least one cutting insert has a rake face with one or more rake surfaces for the first and second cutting edges, the rake face facing radially outward from the axis of rotation.

[0009] The arrangement of the first and second cutting edges and rake faces on the cutting portion as defined above implies that the milling tool can be used to chamfer the relief edges of internal or external teeth on a cylindrical toothed workpiece at one end face of the workpiece in a manner that will be described in more detail below. A first clearance edge on a first side of the tooth can be chamfered by a first cutting edge at a first end face of the workpiece during rotation of the milling tool in a first direction of rotation, without any movement of the milling tool in a plane perpendicular to the central axis of the workpiece being required during chamfering of these first clearance edges, and a second clearance edge on a second side of the tooth on the opposite side can be chamfered by a second cutting edge at the same end face of the workpiece during rotation of the milling tool in a second, opposite direction of rotation, without any movement of the milling tool in a plane perpendicular to the central axis of the workpiece being required during chamfering of these second clearance edges, so that the cutting forces on the milling tool during the chamfering operation are directed substantially towards the axis of rotation of the tool body, and this is valid for the duration of the milling tool.

[0010] The aforementioned internal or external teeth on the workpiece are preferably gear teeth or spline teeth.

[0011] According to one embodiment of the present invention, the rake face is planar and extends in the same plane of extension as the first and second cutting edges, which facilitates the manufacture of the cutting insert, however, the rake face may alternatively include rake surfaces below and / or above this plane of extension.

[0012] The first and second cutting edges are preferably straight or at least substantially straight, and extend at a first angle and a second angle, respectively, relative to the radial plane. The first and second cutting edges may be inclined such that the first and second angles are different from each other. However, it is preferred that the first and second cutting edges are inclined such that the first and second angles are substantially equal. Advantageously, the first and second angles are greater than or equal to 15° and less than 85°, preferably between 20 and 80°.

[0013] According to another embodiment of the invention, the first and second cutting edges are mirror images of each other with respect to the radial plane, so that the cutting performance of the first cutting edge when the milling tool is rotated in a first rotational direction and the chamfering is performed by the first cutting edge is the same as the cutting performance of the second cutting edge when the milling tool is rotated in the opposite rotational direction and the chamfering is performed by the second cutting edge.

[0014] Another embodiment of the present invention is the at least one cutting insert also includes a third cutting edge and a fourth cutting edge extending in the same extension plane as the first and second cutting edges, the third cutting edge and the fourth cutting edge being disposed opposite each other on opposite sides of the radial plane; the third cutting edge has a rear end and an opposite front end, the rear end of the third cutting edge being located closer to the rear of the tool body than the front end of the third cutting edge, the rear end of the third cutting edge being located closer to the radial plane than the front end of the third cutting edge, and the distance between the third cutting edge and the radial plane gradually increasing along the third cutting edge in a direction from the rear end to the front end thereof; The fourth cutting edge has a rear end and an opposite front end, the rear end of the fourth cutting edge being located closer to the rear of the tool body than the front end of the fourth cutting edge, the rear end of the fourth cutting edge being located closer to the radial plane than the front end of the fourth cutting edge, and the distance between the fourth cutting edge and the radial plane gradually increasing along the fourth cutting edge in a direction from the rear end to the front end thereof. And, The rake face also includes one or more rake surfaces for the third and fourth cutting edges. It is characterized by:

[0015] This allows the milling tool to be used to chamfer the clearance edges of the internal or external teeth on a cylindrical toothed workpiece on both end faces of the workpiece without the need to reposition the workpiece. In this way, the workpiece can remain clamped in a suitable workpiece holder of the machine in one and the same orientation during the full-surface chamfering process, which saves time. The first and second cutting edges described above can be used to chamfer the clearance edges of the teeth on the workpiece on a first end face of the workpiece facing away from the workpiece holder that rotatably mounts the toothed workpiece, and the third and fourth cutting edges described above can be used to chamfer the clearance edges of the teeth on the workpiece on a second end face on the opposite side of the workpiece. The chamfering process may begin with chamfering the clearance edges on the end face of the workpiece facing away from the workpiece holder, and then proceed to chamfering the clearance edges on the end face of the workpiece facing the workpiece holder. Alternatively, the chamfering process may begin with chamfering the relief edge on the end face of the workpiece facing the workpiece holder, and then proceed to chamfering the relief edge on the end face of the workpiece facing away from the workpiece holder. The third clearance edges on a first side of the tooth can be chamfered by the third cutting edge at said second end face of the workpiece during rotation of the milling tool in a first direction of rotation, without any movement of the milling tool in a plane perpendicular to the central axis of the workpiece being required during chamfering of these third clearance edges, and the clearance edges on a second side of the opposite tooth can be chamfered by the fourth cutting edge at the same end face of the workpiece during rotation of the milling tool in a second, opposite direction of rotation, without any movement of the milling tool in a plane perpendicular to the central axis of the workpiece being required during chamfering of these fourth clearance edges, and the cutting forces on the milling tool during the chamfering operations performed by the third and fourth cutting edges will be directed substantially towards the rotation axis of the tool body, and this is valid for the duration of the milling tool.

[0016] The third and fourth cutting edges are preferably mirror images of each other with respect to said radial plane, so that the cutting performance of the third cutting edge when the milling tool is rotated in a first rotational direction and the chamfering is performed by the third cutting edge is the same as the cutting performance of the fourth cutting edge when the milling tool is rotated in the opposite rotational direction and the chamfering is performed by the fourth cutting edge.

[0017] Another embodiment of the present invention is the first cutting edge and the third cutting edge are mirror images of each other with respect to a plane of symmetry that extends halfway between the first and third cutting edges perpendicular to the radial plane and perpendicular to the extension plane; Similarly, the second cutting edge and the fourth cutting edge are mirror-symmetrical with respect to the symmetry plane. It is characterized by:

[0018] According to another embodiment of the present invention, the at least one cutting insert includes a base and an extension arm fixed to and projecting from the base, the extension arm having an inner end facing the base and an opposite outer end, the cutting edge and the rake face being arranged on the extension arm at the outer end thereof, the base configured to be received in an insert seat of the cutting portion, and the extension arm configured to project radially from the cutting portion relative to the rotation axis when the cutting insert is mounted in the cutting portion. The length of the extension arm should be appropriately adapted to the tooth depth of the teeth of the toothed workpiece to be machined, and is suitably 1 to 20 mm, preferably 1 to 15 mm, more preferably 3 to 9 mm.

[0019] The cutting insert is preferably releasably mounted in the insert seat, so that the cutting insert can be easily replaced with a new one when any of the cutting edges on the cutting insert become worn.

[0020] Another embodiment of the present invention is the tool body including an elongated shank portion carrying the cutting portion and extending rearward from the cutting portion, the shank portion having a forward end facing the cutting portion, an opposite rearward end, and a peripheral surface extending around the shank portion between the rearward end and the forward end, the shank portion having a central longitudinal axis coincident with an axis of rotation of the tool body; The inner end of the extension arm is disposed at a longer distance from the rotation axis than the outermost portion in the radial direction of the peripheral surface of the shank portion when the cutting insert is attached to the cutting portion. It is characterized by:

[0021] The shank is preferably rod-shaped and should be longer than the length of the workpiece, i.e., longer than the axial distance between the two opposite end faces of the workpiece. The shank may have a length of, for example, 50 to 200 mm, preferably 100 to 150 mm.

[0022] According to another embodiment of the invention, the cutting part is slidably mounted on the shank part at its front end so as to be linearly slidable relative to the shank part perpendicular to the axis of rotation and in the longitudinal direction of the extension arm, and the cutting part can be locked on the shank part in different sliding positions relative to the shank part, thereby allowing adjustment of the radial distance between the extension plane and the axis of rotation. Alternatively, however, the cutting part and the shank part may be formed integrally.

[0023] According to another embodiment of the present invention, the cutting part includes a disk-shaped or cylindrical base having a central axis coinciding with the rotation axis, and at least one extension arm fixed to the base and projecting radially from the base relative to the rotation axis, the extension arm having an inner end facing the base and an opposite outer end, and the at least one cutting insert mounted on the extension arm at its outer end. The radial distance between the extension plane and the radially outermost portion of the base is suitably 5 to 40 mm, preferably 7 to 30 mm, and more preferably 9 to 22 mm. The cutting insert is preferably releasably mounted in an insert seat provided at the outer end of the associated extension arm. This allows the cutting insert to be easily replaced with a new one when any cutting edge on the cutting insert becomes worn.

[0024] The cutting portion may include two or more such extension arms distributed evenly or at least substantially evenly about the central axis of the base, the number of cutting inserts on the milling tool corresponding to the number of extension arms, each cutting insert being mounted on a respective one of the extension arms at its outer end, so that the relief edges of two or more teeth on the workpiece can be machined during each revolution of the milling tool.

[0025] Further advantages of the milling tool according to the invention will become apparent from the description that follows.

[0026] According to a second aspect of the invention, the above object is achieved by means of a method having the features presented in claim 19.

[0027] A method according to a second aspect of the present invention is a method for chamfering clearance edges of internal or external teeth on a cylindrical toothed workpiece, on at least one of two opposite end faces of the workpiece, each of said teeth having a tip, a root, a first clearance surface extending between the tip and the root on a first side of the tooth, and a second clearance surface extending between the tip and the root on a second, opposite side of the tooth, the first clearance edge being formed at an intersection between the first clearance surface and a first of the two end faces of the workpiece, and the second clearance edge being formed at an intersection between the second clearance surface and said first of the two end faces of the workpiece, the workpiece being rotatable by a machine about a central axis of the workpiece, and the chamfering being performed with a milling tool according to the present invention, the milling tool being rotatable by the machine about an axis of rotation of the tool body, a) positioning the milling tool at a first predetermined position relative to the workpiece with the rotation axis of the tool body parallel to the central axis of the workpiece, the cutting portion of the tool body adjacent to a first of two end faces of the workpiece, and the first and second cutting edges facing this end face; b) rotating the workpiece about its central axis in a rotational direction with the second tooth relief surface as the leading tooth relief surface and the first tooth relief surface as the trailing tooth relief surface, and simultaneously rotating the milling tool about the rotational axis of the tool body in the same rotational direction as the workpiece if the teeth are internal teeth of the workpiece, or in the opposite rotational direction if the teeth are external teeth of the workpiece, with 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 tool body parallel to the central axis of the workpiece with the first cutting edge as the leading cutting edge and the second cutting edge as the trailing cutting edge, so that the first cutting edge chamfers at least a portion of the first relief edge of each tooth from the tip towards the root of the tooth; c) positioning the milling tool at a second predetermined position relative to the workpiece with the rotation axis of the tool body parallel to the central axis of the workpiece, with the cutting portion of the tool body adjacent to the first of the two end faces of the workpiece, and with the first and second cutting edges facing this end face; d) rotating the workpiece about its central axis in a rotational direction with the first tooth relief surface as the leading tooth relief surface and the second tooth relief surface as the trailing tooth relief surface, and simultaneously rotating the milling tool about the rotational axis of the tool body in the same rotational direction as the workpiece if the teeth are internal teeth of the workpiece, or in the opposite rotational direction if the teeth are external teeth of the workpiece, with 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 tool body parallel to the central axis of the workpiece with the second cutting edge as the leading cutting edge and the first cutting edge as the trailing cutting edge, so that the second cutting edge chamfers at least a portion of the second relief edge of each tooth from the tip towards the root of the tooth; The method includes:

[0028] Thus, each of the first and second clearance edges on the above-mentioned first end face of the workpiece is chamfered along at least a part of its extension in the machining direction from the tip to the root of the associated tooth, and the cutting forces on the milling tool during the chamfering operation are directed substantially towards the rotation axis of the tool body. During the chamfering in step b and the chamfering in step d, the rotation axis of the tool body can remain in a fixed position relative to the central axis of the workpiece when viewed in a plane perpendicular to the central axis of the workpiece.

[0029] In this description and in the claims that follow, the expression "leading tooth relief surface" refers to a tooth relief surface that faces in the direction of rotation, i.e., forward, when the toothed workpiece is rotated about its central axis, while the expression "trailing tooth relief surface" refers to a tooth relief surface that faces in the opposite direction, i.e., backward, when the toothed workpiece is rotated about its central axis. In a corresponding manner, the expression "leading cutting edge" refers to a cutting edge that faces in the direction of rotation, i.e., forward, when the milling tool is rotated about the axis of rotation of the tool body, while the expression "trailing cutting edge" refers to a cutting edge that faces in the opposite direction, i.e., backward, when the milling tool is rotated about the axis of rotation of the tool body.

[0030] According to one embodiment of the present invention, the milling tool is moved axially relative to the workpiece in steps b and d, thereby gradually moving the first cutting edge toward the first of the two end faces of the workpiece during chamfering of the first clearance edge of the tooth in step b, and gradually moving the second cutting edge toward this end face of the workpiece during chamfering of the second clearance edge of the tooth in step d.

[0031] Further advantages of the method according to the invention become apparent from the dependent claims and the description that follows.

[0032] According to a third aspect, the present invention relates to a computer-implemented program having instructions which, when executed by a CNC machine, cause the CNC machine to carry out the steps of any of the methods described above. The computer program, or computer program product, may be comprised 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.

[0033] A specific description of embodiments of the invention follows, given by way of example with reference to the accompanying drawings. [Brief explanation of the drawings]

[0034] [Figure 1a] 1 is a perspective view of a milling tool according to a first embodiment of the present invention; [Figure 1b] FIG. 1b is a side view of the milling tool of FIG. 1a. [Figure 1c] FIG. 1b is a front view of the milling tool of FIG. 1a. [Figure 1d] 1b is a side view of the milling tool of FIG. 1a from another direction. [Figure 1e] 1b is a side view of a cutting part included in the milling tool of FIG. 1a, on a larger scale, taken from the same direction as FIG. 1d. [Figure 1f] FIG. 1b is an exploded perspective view of the milling tool of FIG. 1a; [Figure 2a] 1b is a perspective view of a cutting insert included in the milling tool of FIG. 1a; FIG. [Figure 2b] 1b is a perspective view of a cutting insert included in the milling tool of FIG. 1a from another direction. [Figure 2c] FIG. 2c is a side view of the cutting insert of FIGS. 2a and 2b. [Figure 3a] 1b is a perspective view of the milling tool and internally toothed workpiece of FIG. 1a, with the milling tool shown in position for chamfering a relief edge on a first end face of the workpiece; FIG. [Figure 3b] 1b is another perspective view of the milling tool and internally toothed workpiece of FIG. 1a, with the milling tool shown in position for chamfering a relief edge on a first end face of the workpiece; FIG. [Figure 3c] FIG. 3c is a front view of the milling tool and workpiece of FIGS. 3a and 3b. [Figure 4a] 3a-3c are perspective views of the milling tool and workpiece of FIGS. 3a-3c, with the milling tool shown in position to chamfer a relief edge on an opposite second end face of the workpiece. FIG. [Figure 4b] FIG. 4b is a front view of the milling tool and workpiece of FIG. 4a. [Figure 5] 3b is a perspective view of a portion of the internally toothed workpiece of FIG. 3a on a larger scale. FIG. [Figure 6a] 3b is a larger scale end view of a portion of the internally toothed workpiece of FIG. 3a, showing the chamfered relief edge on the first end face of the workpiece. FIG. [Figure 6b] 3b is another end view, on a larger scale, of a portion of the internally toothed workpiece of FIG. 3a, showing the chamfered relief edge on the second end face of the workpiece. FIG. [Figure 7] 1a-h are schematic diagrams of different stages in the process of chamfering the relief edge of an internally toothed workpiece using the milling tool of FIG. 1a; [Figure 8a] FIG. 10 is a perspective view of a milling tool according to a second embodiment of the present invention. [Figure 8b] FIG. 8b is a side view of the milling tool of FIG. 8a. [Figure 8c] 8b is an exploded perspective view of the milling tool of FIG. 8a. FIG. [Figure 8d] 8b is an exploded perspective view of the milling tool of FIG. 8a from another direction. [Figure 9a] FIG. 10 is a perspective view of a milling tool according to a third embodiment of the present invention. [Figure 9b] FIG. 9b is a front view of the milling tool of FIG. 9a. [Figure 9c] FIG. 9b is a side view of the milling tool of FIG. 9a. [Figure 9d] 9b is a side view of the milling tool of FIG. 9a from another direction. [Figure 9e] 9b is an exploded perspective view of a portion of the milling tool of FIG. 9a. FIG. [Figure 9f] 9b is another exploded perspective view of a portion of the milling tool of FIG. 9a. FIG. [Figure 10a] 9b is a front view of a cutting insert included in the milling tool of FIG. 9a; [Figure 10b] FIG. 10b is a rear view of the cut of FIG. 10a. [Figure 10c] FIG. 10b is a side view of the cutting insert of FIG. [Figure 10d]FIG. 10b is a plan view of the cutting insert of FIG. [Figure 11] FIG. 10 is a perspective view of a milling tool according to a fourth embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0035] Different embodiments of a milling tool 1 according to the invention are shown in FIGS. 1a to 1f, 8a to 8d, 9a to 9f, and 11. The milling tool 1 is intended to be used to chamfer the relief edges of internal or external teeth on cylindrical toothed workpieces at opposite end faces of the workpiece. The milling tool 1 comprises a tool body 2 configured to be rotated 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 part 6 of the tool body 2, located between the collar 5 and the rear end 2b, forms a connection member by which the tool body 2 can be mounted to a rotating spindle or a similar machine, such as a milling machine, either directly or via an intermediate tool holder.

[0036] The tool body 2 comprises a cutting part 10 arranged in front of the rear part 6, seen away from the rear part 6 in the axial direction of the tool body. Cutting inserts 20, 20' with cutting edges 21, 22, 23, 24 are mounted on the cutting part 10.

[0037] The cutting inserts 20, 20′ include a first cutting edge 21 and a second cutting edge 22 extending in a common extension plane EP that is parallel to a longitudinal plane LP that includes the rotation axis 3 and passes through the tool body 2. The first cutting edge 21 and the second cutting edge 22 are disposed opposite each other on opposite sides of a radial plane RP that includes the rotation axis 3 and is perpendicular to the longitudinal plane LP and, consequently, perpendicular to the extension plane EP. The first cutting edge 21 and the second cutting edge 22 each have a leading end 21 a, 22 a and an opposite trailing end 21 b, 22 b. The trailing end 21 b of the first cutting edge 21 is disposed closer to the rear end 6 of the tool body than the leading end 21 a of the first cutting edge, and the trailing end 22 b of the second cutting edge 22 is disposed closer to the rear end 6 of the tool body than the leading end 22 a of the second cutting edge. The leading end 21a of the first cutting edge 21 is disposed closer to the radial plane RP than the trailing end 21b of the first cutting edge 21, and the distance between the first cutting edge 21 and the radial plane RP gradually increases when viewed along the first cutting edge 21 in the direction from its leading end 21a to its trailing end 21b. The leading end 22a of the second cutting edge 22 is disposed closer to the radial plane RP than the trailing end 22b of the second cutting edge 22, and the distance between the second cutting edge 22 and the radial plane RP gradually increases when viewed along the second cutting edge 22 in the direction from its leading end 22a to its trailing end 22b.

[0038] In the illustrated embodiment, the first cutting edge 21 is substantially straight and extends at an angle α1 relative to the radial plane RP, and the second cutting edge 22 is substantially straight and extends at an angle α2 relative to the radial plane RP. The first angle α1 and the second angle α2 may be different from each other, but are preferably equal or at least substantially equal. The first angle α1 and the second angle α2 are greater than or equal to 15° and less than 85°, preferably between 20 and 80°. In the illustrated embodiment, both the first angle α1 and the second angle α2 are approximately 45°.

[0039] In the illustrated embodiment, the cutting insert 20, 20′ also includes a third cutting edge 23 and a fourth cutting edge 24 that extend in the same extension plane EP as the first cutting edge 21 and the second cutting edge 22. The third cutting edge 23 and the fourth cutting edge 24 are arranged opposite each other on opposite sides of the radial plane RP. The third cutting edge 23 and the fourth cutting edge 24 each have a leading end 23a, 24a and an opposite trailing end 23b, 24b. The trailing end 23b of the third cutting edge 23 is located closer to the rear end 6 of the tool body than the leading end 23a of the third cutting edge 23, and the trailing end 24a of the fourth cutting edge 24 is located closer to the rear end 6 of the tool body than the leading end 24a of the fourth cutting edge 24. The rear end 23b of the third cutting edge 23 is located closer to the radial plane RP than the front end 23a of the third cutting edge 23, and the distance between the third cutting edge 23 and the radial plane RP gradually increases when viewed along the third cutting edge 23 in the direction from the rear end 23b to the front end 23a. The rear end 24b of the fourth cutting edge 24 is located closer to the radial plane RP than the front end 24a of the fourth cutting edge 24, and the distance between the fourth cutting edge 24 and the radial plane RP gradually increases when viewed along the fourth cutting edge 24 in the direction from the rear end 24b to the front end 24a.

[0040] The cutting insert 20, 20′ has a rake face 25 with one or more rake surfaces for the cutting insert's cutting edges 21-24. This rake face 25 faces radially outward from the rotation axis 3. In the illustrated embodiment, the rake face 25 is planar and extends in the same or at least substantially the same extension plane EP as the cutting edges 21-24.

[0041] The cutting insert 20, 20' also has clearance faces 26a, 26b, 26c, 26d associated with the cutting edges 21-24, with the first cutting edge 21 formed at the intersection between the cutting face 25 and the first clearance face 26a, the second cutting edge 22 formed at the intersection between the cutting face 25 and the second clearance face 26b, the third cutting edge 23 formed at the intersection between the cutting face 25 and the third clearance face 26c, and the fourth cutting edge 24 formed at the intersection between the cutting face 25 and the fourth clearance face 26d.

[0042] In the illustrated embodiment, the first cutting edge 21 and the second cutting edge 22 are mirror-symmetrical to each other with respect to the radial plane RP, and the third cutting edge 23 and the fourth cutting edge 24 are also mirror-symmetrical to each other with respect to this radial plane RP. Furthermore, the first cutting edge 21 and the third cutting edge 23 are mirror-symmetrical to each other with respect to a plane of symmetry PS (see FIGS. 1e and 9d) that extends through an intermediate portion between the first and third cutting edges 21, 23 perpendicular to the radial plane RP and perpendicular to the extension plane ES, and the second cutting edge 22 and the fourth cutting edge 24 are mirror-symmetrical to each other with respect to this plane of symmetry PS.

[0043] In the embodiment shown in Figures 1a-1f and 8a-8d, the cutting insert 20 includes a base 27 and an extension arm 28 fixed to and projecting from the base 27. The extension arm 28 has an inner end 28a facing the base 27 and an opposite outer end 28b, and the cutting edges 21-24 and the rake face 25 are arranged on the extension arm 28 at the outer end 28b of the extension arm 28. In this case, the clearance surfaces 26a-26d are arranged on the extension arm 28 and are provided on a peripheral surface 26 extending around the extension arm 28 between the inner end 28a and the outer end 28b of the extension arm 28. The extension arm 28 suitably has a length of 1-20 mm, preferably 1-15 mm, and more preferably 3-9 mm.

[0044] The base 27 is configured to be received in the insert seat 11 of the cutting part 10, and the extension arm 28 is configured to protrude radially from the cutting part 10 relative to the rotation axis 3 when the cutting insert 20 is mounted in the cutting part 10. The inner end 28a of the extension arm 28 is preferably positioned at a greater distance from the rotation axis 3 than the radially outermost surface on the cutting part 10 when the cutting insert 20 is mounted in the cutting part 10.

[0045] The illustrated cutting insert 20 is releasably secured to the seat 11 using a fastening element 12 in the form of a screw that extends through a through hole 29 in the cutting insert 20 and engages with a threaded hole 13 (see FIG. 1f) in the tangential support surface 14a of the seat 11. The seat 11 also includes an axial support surface 14b and a radial support surface 14c for supporting the cutting insert 20 when mounted in the seat 11. An axial abutment surface 30b is provided on a base 27 of the cutting insert 20 and is configured to abut against the axial support surface 14b of the seat 11. The base 27 also includes a radial abutment surface 30c configured to abut against the radial support surface 14c of the seat 11 and a tangential abutment surface 30a configured to abut against the tangential support surface 14a of the seat 11.

[0046] In the embodiment shown in FIGS. 1a-1f and 8a-8d, the tool body 2 includes an elongated shank portion 40 carrying the cutting portion 10 and extending from the cutting portion 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 flange 5 and the rear portion 6. The cutting portion 10 is fixed to the shank portion 40 at the front end 40a. 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. The inner end 28a of the extension arm 28 is positioned at a greater distance from the rotation axis 3 than the radially outermost portion of the peripheral surface 41 of the shank portion 40 when the cutting insert 20 is installed in the insert seat 11 of the cutting portion 10.

[0047] In the illustrated embodiment, the shank portion 40 is rod-shaped and in the form of a right circular cylinder. However, the shank portion 40 may also have any other suitable shape. The shank portion 40 may have a length L of 50 to 200 mm, preferably 100 to 150 mm.

[0048] In the embodiment shown in Figures 1a to 1f, the cutting portion 10 and the shank portion 40 are integrally formed.

[0049] In the embodiment shown in Figures 8a to 8d, the cutting part 10 is removably attached to the shank part 40 at its front end 40a by means of fastening elements 42 in the form of two screws, which extend through respective through holes 15 in the cutting part 10 and engage with respective threaded holes 43 provided in the front end face 44 of the shank part 40.

[0050] 8a-8d, the cutting part 10 is slidably mounted to the shank part 40 at a front end 40a thereof so as to be linearly slidable relative to the shank part 40 perpendicular to the rotation axis 3 and in the longitudinal direction of the extension arm 28, and the cutting part 10 can be locked to the shank part 40 in different sliding positions relative to the shank part 40, thereby enabling adjustment of the radial distance between the extension plane EP and the rotation axis 3. In the illustrated example, the rear face 16 of the cutting part 10 is provided with mutually parallel splines 17 which extend parallel to the longitudinal axis of the extension arm 28 and slidably engage with corresponding splines 47 provided on a front end face 44 of the shank part 40 to enable the cutting part 10 to slide relative to the shank part 40 in a desired direction during adjustment of the sliding position of the cutting part 10 relative to the shank part 40.

[0051] The milling tool 1 shown in FIGS. 8a-8d includes an adjustment mechanism 50 that allows the sliding position of the cutting part 10 relative to the shank portion 40 to be adjusted. Thus, the actual positioning of the cutting part 10 along the splines 47 on the front end face 44 of the shank portion 40 can be adjusted using the adjustment mechanism 50. In the illustrated embodiment, the adjustment mechanism 50 includes an adjustment element 51 configured to act between the cutting part 10 and the shank portion 40. The adjustment element 51 includes a pin 52 rotatably received in a hole 46 in the front end face 44 of the shank portion 40, and a head 53 fixed to the pin 52 and rotatably received in a recess 18 in the rear face 16 of the cutting part 10. 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 18 affects the longitudinal sliding movement of the splines 17, 47 of the cutting part 10. 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 to be rotated to move the cutting part 10 longitudinally along the splines 17, 47. The socket 54 is accessible through a hole in the cutting part 10. Each of the through holes 15 has an elongated cross-sectional shape with its longer axis extending substantially in the longitudinal direction of the splines 17, thereby allowing the cutting part 10 to move perpendicular to the shaft 42a of the fastening element 42 in the longitudinal direction of the splines 47 on the front end surface 44 of the shank part 40. The cutting part 10 can be locked on the shank part 40 in a desired sliding position relative to the shank part 40 by tightening the fastening element 42. The adjustment mechanism 50 may, of course, also be designed in any other suitable manner.

[0052] In the embodiment shown in Figures 9a to 9f, the cutting part 10 includes a disk-shaped or cylindrical base 32 having a central axis coinciding with the rotation axis 3. In this case, the cutting part 10 also includes an extension arm 33 fixed to the base 32 and protruding from a peripheral surface 34 of the base 32 in a radial direction relative to the rotation axis 3. The extension arm 33 has an inner end 33a facing the base 32 and an opposite outer end 33b. The extension arm 33 is fixed to the base 32 at its inner end 33a, and the cutting insert 20' is attached to the extension arm 33 at its outer end 33b. The extension arm 33 has a length such that the radial distance between the above-mentioned extension plane EP and the radially outermost part of the base 32, i.e., the peripheral surface 34, is 5 to 40 mm, preferably 7 to 30 mm, and more preferably 9 to 22 mm.

[0053] The cutting part 10 may include two or more such extension arms 33 distributed evenly or at least substantially evenly around the central axis of the base 32 with equal angular distances between every two consecutive extension arms 33, as shown in Figure 11 where the cutting part 10 includes three extension arms 33. In this case, the number of cutting inserts 20' of the milling tool 1 corresponds to the number of extension arms 33, with each cutting insert 20' attached to a respective one of the extension arms 33 at the outer end 33b of the extension arm 33.

[0054] In the embodiment shown in Figures 9a-9f, the cutting insert 20' is releasably mounted in a seat 35 provided on the outer end 33b of the extension arm 33. The illustrated cutting insert 20' is releasably secured to the seat 35 using a fastening element 36 in the form of a screw that extends through the through hole 29 of the cutting insert 20' and engages with a threaded hole 39 in a support surface 37 of the seat 35. The support surface 37 advantageously includes splines 38 or the like configured for positive mechanical engagement with corresponding splines 31 on the underside of the cutting insert 20' to ensure correct positioning of the cutting insert 20' in the seat 35 and to prevent movement of the cutting insert 20' relative to the support surface 37 when properly mounted in the seat 35.

[0055] As mentioned above, the milling tool 1 is intended to be used to chamfer clearance edges 61-64 (see FIGS. 5 and 6) of internal or external teeth 60 on a cylindrical toothed workpiece 8 at a first end face 9a of the workpiece and at 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 clearance surface 67a extending between the tip 65 and the root 66 on a first side of the tooth, and a second clearance surface 67b extending between the tip 65 and the root 66 on an opposite second side of the tooth. A first clearance edge 61 is formed at the intersection between the first tooth clearance surface 67a and the first end face 9a of the workpiece 8, a second clearance edge 62 is formed at the intersection between the second tooth clearance surface 67b and the first end face 9a of the workpiece 8, a third clearance edge 63 is formed at the intersection between the first tooth clearance surface 67a and the second end face 9b of the workpiece 8, and a fourth clearance edge 64 is formed at the intersection between the second tooth clearance surface 67b and the second end face 9b of the workpiece 8. A root surface 68 is provided between the roots 66 of every two adjacent teeth 60, and a tip surface 69 is provided between the tips 65 of each tooth 60.

[0056] The edges 70 at the interface between the tip surface 69 of each tooth 60 on the workpiece 8 and the respective end surfaces 9a, 9b of the workpiece are typically chamfered in a separate machining operation before the chamfering of the relief edges 61-64 is performed using the milling tool 1.

[0057] During the chamfering operation using the milling tool 1, the workpiece 8 is mounted on a rotatable workpiece holder (not shown) of the machine and can be rotated by the machine about the central axis 4 of the workpiece 8, and the milling tool 1 is mounted on a rotatable tool holder (not shown) of the machine and can be rotated by the machine about the rotation axis 3 of the tool body 2 and can be moved by the machine in the axial direction z of the workpiece 8 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 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 program-controlled manner using an electronic control device (not shown).

[0058] The workpiece holder and the tool holder of the machine are typically arranged opposite each other, with the tool holder facing the workpiece holder. In the example shown in Figures 3-4, an end face of the workpiece 8, referred to as the first end face 9a, faces the tool holder of the machine, and a second end face 9b, opposite the workpiece 8, faces the workpiece holder of the machine.

[0059] When mounted on a workpiece holder of the machine, the workpiece 8 can be rotated by the machine about its central axis 4 in a first rotational direction R1 and an opposite second rotational direction R2. When the workpiece 8 is positioned with the second end face 9b of the workpiece 8 facing the workpiece holder (as shown in FIGS. 3-4), the workpiece 8 will be rotated in the first rotational direction R1 with the second tooth relief surface 67b of the tooth 60 on the workpiece as the leading tooth relief surface and the first tooth relief surface 67a of the tooth 60 on the workpiece as the trailing tooth relief surface, and when rotated in the second rotational direction R2 with the first tooth relief surface 67a of the tooth 60 on the workpiece as the leading tooth relief surface and the second tooth relief surface 67b of the tooth 60 on the workpiece as the trailing tooth relief surface.

[0060] To perform the chamfering of the first clearance edge 61 and the second clearance edge 62 of the tooth 60 on the workpiece 8, the following steps are performed. a) The milling tool 1 is positioned in 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, with the cutting part 10 of the tool body 2 adjacent to a first end face 9a of the workpiece 8, and with the first cutting edge 21 and the second cutting edge 22 facing this end face 9a, as shown in Figures 3a and 3b. b) The workpiece 8 is rotated about its central axis 4 in a rotational direction R1 with the second tooth relief surface 67b as the leading tooth relief surface and the first tooth relief surface 67a as the trailing tooth relief surface. At the same time, the milling tool 1 is rotated around the rotation axis 3 of the tool body 2 in the same rotation direction R1 as the workpiece 8 if the teeth 60 are internal teeth of the workpiece 8 (see Figures 3a to 3c), or in the opposite rotation direction R2 if the teeth 60 are external teeth of the workpiece 8, with the rotation axis 3 of the tool body 2 kept parallel to the central axis 4 of the workpiece 8, with the first cutting edge 21 as the leading cutting edge and the second cutting edge 22 as the trailing cutting edge, so that the first cutting edge 21 chamfers a portion of the first clearance edge 61 of each tooth 60 from the tip 65 towards the root 66 of the tooth 60. c) The milling tool 1 is positioned in 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 the first end face 9a of the workpiece 8, and with the first cutting edge 21 and the second cutting edge 22 facing this end face 9a. d) the workpiece 8 is rotated about its central axis 4 in a rotational direction R2 with the first tooth relief surface 67a as the leading tooth relief surface and the second tooth relief surface 67b as the trailing tooth relief surface. Simultaneously, the milling tool 1 is rotated about the rotational axis 3 of the tool body 2 in the same rotational direction R2 as the workpiece 8 if the tooth 60 is an internal tooth of the workpiece 8, or in the opposite rotational direction R1 if the tooth 60 is an external tooth of the workpiece 8, according to a predetermined relationship between the rotational speed of the milling tool 1 and the rotational speed of the workpiece 8, while keeping the rotational axis 3 of the tool body 2 parallel to the central axis 4 of the workpiece 8 with the second cutting edge 22 as the leading cutting edge and the first cutting edge 21 as the trailing cutting edge, so that the second cutting edge 22 chamfers a portion of the second relief edge 62 of each tooth 60 from the tip 65 towards the root 66 of the tooth 60.

[0061] To perform the chamfering of the third clearance edge 63 and the fourth clearance edge 64 of the tooth 60 on the workpiece 8, the following additional steps are performed. e) The milling tool 1 is positioned in a third 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 the second end face 9b of the workpiece 8, and with the third cutting edge 23 and the fourth cutting edge 24 facing this end face 9b, as shown in Figures 4a and 4b. f) The workpiece 8 is rotated about its central axis 4 in a rotational direction R1 with the second tooth relief surface 67b as the leading tooth relief surface and the first tooth relief surface 67a as the trailing tooth relief surface. At the same time, the milling tool 1 is rotated around the rotation axis 3 of the tool body 2 in the same rotation direction R1 as the workpiece 8 if the teeth 60 are internal teeth of the workpiece 8 (see Figures 4a to 4c), or in the opposite rotation direction R2 if the teeth 60 are external teeth of the workpiece 8, in 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, with the third cutting edge 23 as the leading cutting edge and the fourth cutting edge 24 as the trailing cutting edge, so that the third cutting edge 23 chamfers a portion of the third clearance edge 63 of each tooth 60 from the tip 65 towards the root 66 of the tooth 60. g) The milling tool 1 is positioned in a fourth 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 the second end face 9b of the workpiece 8, and with the third cutting edge 23 and the fourth cutting edge 24 facing this end face 9b. h) the workpiece 8 is rotated about its central axis 4 in a rotational direction R2 with the first tooth relief surface 67a as the leading tooth relief surface and the second tooth relief surface 67b as the trailing tooth relief surface. Simultaneously, the milling tool 1 is rotated about the rotational axis 3 of the tool body 2 in the same rotational direction R2 as the workpiece 8 if the tooth 60 is an internal tooth of the workpiece 8, or in the opposite rotational direction R1 if the tooth 60 is an external tooth of the workpiece 8, according to a predetermined relationship between the rotational speed of the milling tool 1 and the rotational speed of the workpiece 8, while keeping the rotational axis 3 of the tool body 2 parallel to the central axis 4 of the workpiece 8 with the fourth cutting edge 24 as the leading cutting edge and the third cutting edge 23 as the trailing cutting edge, so that the fourth cutting edge 24 chamfers a portion of the fourth relief edge 64 of each tooth 60 from the tip 65 towards the root 66 of the tooth 60.

[0062] During the chamfering in each of steps b, d, f, and h described above, a portion of the effective cutting edge of cutting edges 21-24 is rotated into a gap between two adjacent teeth 60, and then during part of one rotation of workpiece 8, is moved together with this gap in the direction of rotation of workpiece 8, and comes into cutting engagement with a portion of one of the relief edges located on the opposite side of the gap, and then is rotated out of the gap, as shown in Figures 7a-7i. As rotation of milling tool 1 continues, the portion of the effective cutting edge of cutting edges 21-24 is rotated into the next gap between two other adjacent teeth 60 on workpiece 8, and so on. The position of the milling tool 1 relative to the workpiece 8 and the rotation of the milling tool 1 relative to the rotation of the workpiece 8 are adapted so that the effective cutting edges of the cutting edges 21 to 24 in each of the above steps b, d, f and h contact the respective clearance edges 61, 62, 63, 64 to be chamfered at the tooth tip 65, and then move in cutting engagement along part of the clearance edges 61, 62, 63, 64 in a direction towards the tooth root 66 and chamfer this part of the clearance edge, as shown in Figures 7c to 7g.

[0063] The relationship between the rotational speed of the milling tool 1 and the rotational speed of the workpiece 8 is adapted in each of the above steps b, d, f, and h so that a portion of the effective cutting edges of the cutting edges 21-24 penetrates into the gaps between all of the teeth 60 on the workpiece 8 after a specific number of revolutions of the workpiece 8. In order to enable the effective cutting edges to move in the same direction as the gaps between two adjacent teeth 60 on the workpiece 8, with a portion of the cutting edge received 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 if the clearance edges 61-64 of the internal teeth 60 on the workpiece are chamfered, or in a rotational direction opposite to the rotational direction of the workpiece 8 if the clearance edges 61-64 of the external teeth 60 on the workpiece are chamfered.

[0064] During the chamfering in each of the above-described steps b, d, f, and h, the rotation axis 3 of the tool body 2 is maintained in a fixed position relative to the central axis 4 of the workpiece 8, as seen in a plane x, y perpendicular to the central axis 4 of the workpiece 8. However, the milling tool 1 is moved relative to the workpiece 8 in the workpiece axial direction z in each of steps b and d, so that the first cutting edge 21 can be gradually moved in a direction toward the first end face 9 a of the workpiece 8 during the chamfering of the first clearance edge 61 in step b, and the second cutting edge 22 can be gradually moved in a direction toward the first end face 9 a of the workpiece 8 during the chamfering of the second clearance edge 62 in step d. Each of the first clearance edges 61 is chamfered by the first cutting edge 21 in multiple consecutive cuts during step b, and each of the second clearance edges 62 is chamfered by the second cutting edge 22 in multiple consecutive cuts during step d. The milling tool 1 is also moved relative to the workpiece 8 in the workpiece axial direction z in each of steps f and h, so that the third cutting edge 23 is gradually moved in a direction toward the second end face 9 b of the workpiece 8 during the chamfering of the third clearance edge 63 in step f, and the fourth cutting edge 24 is gradually moved in a direction toward the second end face 9 b of the workpiece 8 during the chamfering of the fourth clearance edge 64 in step h. Each of the third clearance edges 63 is chamfered by the third cutting edge 23 in multiple consecutive cuts during step b, and each of the second clearance edges 62 is chamfered by the second cutting edge 22 in multiple consecutive cuts during step d. Alternatively, the milling tool 1 may remain in a fixed position relative to the workpiece 8, as seen in the workpiece axial direction z, during the chamfering of steps b, d, f, and h, and each individual clearance edge 61-64 is chamfered by an effective one of the cutting edges 21-24 in one single cut.

[0065] During the chamfering in steps b, d, f, and h, the rotation axis 3 of the tool body 2 must be positioned relative to the workpiece 8 such that the rake face 25 does not collide with the root surface 68 adjacent to the clearance edge being chamfered. Therefore, with the milling tool 1 according to the invention, it is not possible to chamfer the clearance edges 61-64 along their entire length. Instead, the chamfering of the individual clearance edges 61-64 must be terminated away from the adjacent root surface 68, as shown in Figures 6a and 6b.

[0066] The present invention is, of course, not limited in any way to the embodiments described above. On the contrary, many possibilities for modification of the present invention will be apparent to those skilled in the art without departing from the basic concept thereof as defined in the appended claims.

Claims

1. A milling tool (1) for chamfering clearance edges (61-64) of internal or external teeth (60) on a cylindrical toothed workpiece (8) at least on one of two opposite end faces (9a, 9b) of said workpiece, comprising: a tool body (2) having a rear portion (6) at a rear end (2b) configured for attachment to a machine so that the tool body (2) can be rotated by the machine about a rotation axis (3) of the tool body (2), and including a cutting portion (10) arranged in front of the rear portion (6) when viewed in the axial direction of the tool body (2); At least one cutting insert (20, 20') attached to the cutting portion (10); In a milling tool (1) comprising: the at least one cutting insert (20, 20') comprises at least a first cutting edge (21) and a second cutting edge (22) extending in a common extension plane (EP) parallel to a longitudinal plane (LP) containing the axis of rotation (3), the first cutting edge (21) and the second cutting edge (22) being arranged opposite each other on opposite sides of a radial plane (RP) containing the axis of rotation (3) and perpendicular to the longitudinal plane (LP); the first cutting edge (21) has a rear end (21b) and an opposite front end (21a), the rear end (21b) of the first cutting edge (21) is located closer to the rear part (6) of the tool body than the front end (21a) of the first cutting edge (21), the front end (21a) of the first cutting edge (21) is located closer to the radial plane (RP) than the rear end (21b) of the first cutting edge (21), and the distance between the first cutting edge (21) and the radial plane (RP) gradually increases along the first cutting edge (21) in the direction from its front end (21a) to its rear end (21b); The second cutting edge (22) has a rear end (22b) and an opposite front end (22a), the rear end (22b) of the second cutting edge (22) being located closer to the rear portion (6) of the tool body than the front end (22a) of the second cutting edge (22), the front end (22a) of the second cutting edge (22) being located closer to the radial plane (RP) than the rear end (22b) of the second cutting edge (22), and the distance between the second cutting edge (22) and the radial plane (RP) gradually increasing along the second cutting edge (22) in the direction from its front end (22a) to its rear end (22b). And, the at least one cutting insert (20, 20') has a rake face (25) with one or more rake surfaces for the first and second cutting edges (21, 22), the rake face (25) facing radially outward from the rotation axis (3); A milling tool (1) characterized by:

2. 2. A milling tool according to claim 1, characterized in that the rake face (25) is planar and extends in the same extension plane (EP) as the first and second cutting edges (21, 22).

3. The first cutting edge (21) is substantially straight and has an angle (α) with respect to the radial plane (RP) of 15° or more and less than 85°, preferably 20 to 80°. １ ) and extending The second cutting edge (22) is substantially straight and has an angle (α) with respect to the radial plane (RP) of 15° or more and less than 85°, preferably 20 to 80°. ２ ) and extending 3. A milling tool according to claim 1 or 2, characterized in that:

4. 4. A milling tool according to any one of claims 1 to 3, characterized in that the first cutting edge (21) and the second cutting edge (22) are mirror images of each other with respect to the radial plane (RP).

5. the at least one cutting insert (20, 20') also comprises a third cutting edge (23) and a fourth cutting edge (24) extending in the same extension plane (EP) as the first and second cutting edges (21, 22), the third cutting edge (23) and the fourth cutting edge (24) being arranged opposite each other on opposite sides of the radial plane (RP); the third cutting edge (23) has a rear end (23b) and an opposite front end (23a), the rear end (23b) of the third cutting edge (23) being located closer to the rear part (6) of the tool body than the front end (23a) of the third cutting edge (23), the rear end (23b) of the third cutting edge (23) being located closer to the radial plane (RP) than the front end (23a) of the third cutting edge (23), and the distance between the third cutting edge (23) and the radial plane (RP) gradually increasing along the third cutting edge (23) in the direction from its rear end (23b) to its front end (23a); The fourth cutting edge (24) has a rear end (24b) and an opposite front end (24a), the rear end (24b) of the fourth cutting edge (24) being located closer to the rear portion (6) of the tool body than the front end (24a) of the fourth cutting edge (24), the rear end (24b) of the fourth cutting edge (24) being located closer to the radial plane (RP) than the front end (24a) of the fourth cutting edge (24), and the distance between the fourth cutting edge (24) and the radial plane (RP) gradually increasing along the fourth cutting edge (24) in the direction from its rear end (24b) to its front end (24a). And, The rake face (25) also comprises one or more rake surfaces for the third and fourth cutting edges (23, 24); A milling tool (1) according to any one of claims 1 to 4, characterized in that

6. 6. A milling tool according to claim 5, characterized in that the third cutting edge (23) and the fourth cutting edge (24) are mirror images of each other with respect to the radial plane (RP).

7. the first cutting edge (21) and the third cutting edge (23) are mirror images of each other with respect to a plane of symmetry (PS), the plane of symmetry (PS) extending perpendicular to the radial plane (RP) and perpendicular to the extension plane (EP) at an intermediate portion between the first and third cutting edges (21, 23); Similarly, the second cutting edge (22) and the fourth cutting edge (24) are mirror symmetrical to each other with respect to the symmetry plane (PS).

7. A milling tool according to claim 5 or 6, characterized in that:

8. 8. The milling tool according to claim 5, wherein the at least one cutting insert (20) comprises a base (27) and an extension arm (28) fixed to and projecting from the base (27), the extension arm (28) having an inner end (28a) facing the base (27) and an opposite outer end (28b), the cutting edges (21-24) and the rake face (25) are arranged on the extension arm (28) at the outer end (28b) of the extension arm (28), the base (27) is configured to be received in an insert seat (11) of the cutting portion (10), and the extension arm (28) is configured to project from the cutting portion (10) in a radial direction relative to the rotation axis (3) when the cutting insert (20) is mounted in the cutting portion (10).

9. A milling tool according to claim 8, characterized in that the extension arm (28) has a length of 1 to 20 mm, preferably 1 to 15 mm, more preferably 3 to 9 mm.

10. the tool body (2) includes an elongated shank portion (40) carrying the cutting portion (10), extending from the cutting portion (10) toward the rear portion (6), having 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 inner end (28a) of the extension arm (28) is disposed at a longer distance from the rotation axis (3) than the radially outermost portion of the peripheral surface (41) of the shank portion (40) when the cutting insert (20) is mounted on the cutting portion (10).

10. A milling tool according to claim 8 or 9, characterized in that

11. 11. A milling tool according to claim 10, characterized in that the cutting part (10) is slidably mounted on the shank part (40) at the front end (40a) of the shank part (40) so as to be linearly slidable relative to the shank part (40) perpendicular to the axis of rotation (3) and in the longitudinal direction of the extension arm (28), and the cutting part (10) can be locked on the shank part (40) in different sliding positions relative to the shank part (40), thereby allowing adjustment of the radial distance between the extension plane (EP) and the axis of rotation (3).

12. 11. A milling tool according to claim 10, characterized in that the cutting part (10) and the shank part (40) are formed in one piece.

13. A milling tool according to any one of claims 10 to 12, characterized in that the shank part (40) is rod-shaped.

14. Milling tool according to any one of claims 10 to 13, characterized in that the shank part (40) has a length (L) of 50 to 200 mm, preferably 100 to 150 mm.

15. 8. The milling tool according to claim 5, wherein the cutting portion (10) comprises a disk-shaped or cylindrical base (32) having a central axis coinciding with the axis of rotation (3), and at least one extension arm (33) fixed to the base (32) and projecting from the base (32) in a radial direction relative to the axis of rotation (3), the extension arm (33) having an inner end (33a) facing the base (32) and an opposite outer end (33b), and the at least one cutting insert (20') is attached to the extension arm (33) at the outer end (33b) of the extension arm (33).

16. 16. A milling tool according to claim 15, characterized in that the radial distance between the extension plane (EP) and the radially outermost part of the seat (32) is between 5 and 40 mm, preferably between 7 and 30 mm, more preferably between 9 and 22 mm.

17. 17. A milling tool according to claim 15 or 16, characterized in that the at least one cutting insert (20') is releasably mounted in an insert seat (35) provided at the outer end (33b) of the associated extension arm (33).

18. 18. A milling tool according to any one of claims 15 to 17, characterized in that the cutting part (10) comprises two or more extension arms (33) distributed evenly or at least substantially evenly around the central axis of the base (32), the number of cutting inserts (20') of the milling tool (1) corresponds to the number of extension arms (33), and each cutting insert (20') is attached to a respective one of the extension arms (33) at the outer end (33b) of the extension arm (33).

19. 1. A method for chamfering clearance edges of internal or external teeth (60) on a cylindrical toothed workpiece (8) at least on one of two opposite end faces (9a, 9b) of the workpiece (8), wherein each of the teeth (60) has a tip (65), a root (66), a first clearance surface (67a) extending between the tip (65) and the root (66) on a first side of the tooth, and a second clearance surface (67b) extending between the tip (65) and the root (66) on an opposite second side of the tooth, wherein a first clearance edge (61) is formed between the first clearance surface (67a) and 19. A method performed with a milling tool (1) according to any one of claims 1 to 18, wherein a second relief edge (62) is formed at an intersection between the second tooth relief surface (67b) and a first end face (9a) of the two end faces of the workpiece (8), a second relief edge (62) is formed at an intersection between the second tooth relief surface (67b) and the first end face (9a) of the two end faces of the workpiece (8), the workpiece (8) being rotatable about a central axis (4) of the workpiece (8) by a machine, and the chamfering is performed by the machine about a rotation axis (3) of the tool body (2), 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), with the cutting part (10) of the tool body (2) adjacent to the first end face (9 a) of the two end faces of the workpiece (8), and with the first and second cutting edges (21, 22) facing the end face (9 a); b) rotating the workpiece (8) around its central axis (4) in a rotation direction (R1) with the second tooth relief surface (67b) as the leading tooth relief surface and the first tooth relief surface (67a) as the trailing tooth relief surface, and simultaneously 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 tooth (60) is an internal tooth of the workpiece (8) with a predetermined relationship between the rotation speed of the milling tool (1) and the rotation speed of the workpiece (8); or in the opposite rotation direction (R2) if the teeth (60) are external teeth 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) with the first cutting edge (21) as the leading cutting edge and the second cutting edge (22) as the trailing cutting edge, so that the first cutting edges (21) chamfer at least a portion of the first clearance edges (61) of each tooth (60) from the tip (65) towards the root (66) of the tooth (60); c) positioning the milling tool (1) 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 the first end face (9a) of the two end faces of the workpiece (8), and with the first and second cutting edges (21, 22) facing the end face (9a); d) rotating the workpiece (8) about its central axis (4) in a rotation direction (R2) with the first tooth relief surface (67a) as the leading tooth relief surface and the second tooth relief surface (67b) as the trailing tooth relief surface, and simultaneously rotating the milling tool (1) about the rotation axis (3) of the tool body (2) in the same rotation direction (R3) as the workpiece (8) if the tooth (60) is an internal tooth of the workpiece (8) with a predetermined relationship between the rotation speed of the milling tool (1) and the rotation speed of the workpiece (8); 2), or in the opposite rotation direction (R1) if the teeth (60) are external teeth of the workpiece (8), while maintaining the rotation axis (3) of the tool body (2) parallel to the central axis (4) of the workpiece (8) with the second cutting edge (22) as the leading cutting edge and the first cutting edge (21) as the trailing cutting edge, so that the second cutting edge (22) chamfers at least a portion of the second clearance edge (62) of each tooth (60) from the tip (65) towards the root (66) of the tooth (60); A method comprising:

20. In step b, the milling tool (1) is moved in an axial direction (z) relative to the workpiece (8), thereby gradually moving the first cutting edge (21) in a direction toward the first end face (9 a) of the two end faces of the workpiece (8) during the chamfering of the first clearance edge (61) of the tooth (60); In step d, the milling tool (1) is moved in an axial direction (z) relative to the workpiece (8), thereby gradually moving the second cutting edge (22) in a direction toward the first end face (9 a) of the two end faces of the workpiece (8) during the chamfering of the second clearance edge (62) of the tooth (60).

20. The method of claim 19.

21. 19. A method according to any one of claims 5 to 18, wherein a third clearance edge (63) is formed at an intersection between the first clearance surface (67a) of each of the teeth (60) and a second end face (9b) of the two end faces of the workpiece (8), and a fourth clearance edge (64) is formed at an intersection between the second clearance surface (67b) of each of the teeth (60) and the second end face (9b) of the two end faces of the workpiece (8), and wherein the milling tool (1) is a milling tool (1) according to any one of claims 5 to 18, e) positioning the milling tool (1) at a third 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 the second end face (9b) of the two end faces of the workpiece (8), and with the third and fourth cutting edges (23, 24) facing the end face (9b); f) rotating the workpiece (8) around its central axis (4) in a rotation direction (R1) with the second tooth relief surface (67b) as the leading tooth relief surface and the first tooth relief surface (67a) as the trailing tooth relief surface, and simultaneously 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 tooth (60) is an internal tooth of the workpiece (8) with a predetermined relationship between the rotation speed of the milling tool (1) and the rotation speed of the workpiece (8); or in the opposite rotation direction (R2) if the teeth (60) are external teeth of the workpiece (8), while maintaining the rotation axis (3) of the tool body (2) parallel to the central axis (4) of the workpiece (8) with the third cutting edge (23) as the leading cutting edge and the fourth cutting edge (24) as the trailing cutting edge, such that the third cutting edge (23) chamfers at least a portion of the third clearance edge (63) of each tooth (60) from the tip (65) towards the root (66) of the tooth (60); g) positioning the milling tool (1) at a fourth 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 the second end face (9b) of the two end faces of the workpiece (8), and with the third cutting edge (23) and the fourth cutting edge (24) facing the end face (9b); h) rotating the workpiece (8) about its central axis (4) in a rotation direction (R2) with the first tooth relief surface (67a) as the leading tooth relief surface and the second tooth relief surface (67b) as the trailing tooth relief surface, and simultaneously rotating the milling tool (1) about the rotation axis (3) of the tool body (2) in the same rotation direction (R) as the workpiece (8) if the tooth (60) is an internal tooth of the workpiece (8) with a predetermined relationship between the rotation speed of the milling tool (1) and the rotation speed of the workpiece (8); 2), or in the opposite rotation direction (R1) if the teeth (60) are external teeth of the workpiece (8), while maintaining the rotation axis (3) of the tool body (2) parallel to the central axis (4) of the workpiece (8) with the fourth cutting edge (24) as the leading cutting edge and the third cutting edge (23) as the trailing cutting edge, so that the fourth cutting edge (24) chamfers at least a portion of the fourth clearance edge (64) of each tooth (60) from the tip (65) towards the root (66) of the tooth (60); 21. The method of claim 19 or 20, additionally comprising:

22. In step f, the milling tool (1) is moved in an axial direction (z) relative to the workpiece (8) to gradually move the third cutting edge (23) toward the second end face (9b) of the two end faces of the workpiece (8) during the chamfering of the third relief edge (63) of the tooth (60); In step h, the milling tool (1) is moved in an axial direction (z) relative to the workpiece (8), thereby gradually moving the fourth cutting edge (24) in a direction toward the second end face (9b) of the two end faces of the workpiece (8) during the chamfering of the fourth clearance edge (64) of the tooth (60).

22. The method of claim 21.

23. 23. 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 19 to 22.

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