Coupling mechanism for cutting tools

Abstract

Rotating cutting tool (10), comprising: a generally cylindrically shaped cutter (14) disposed about a central longitudinal axis (A), the cutter (14) having a first end with an active serrated portion (16), and an opposite second end, the second end having an externally threaded portion (22) disposed thereon; and a generally cylindrically shaped shaft (12) disposed about the central longitudinal axis (A), the shaft (12) having a recessed internally threaded portion (32) formed at a first end, wherein the external thread portion (22) comprises a series of threads (22a) which extend over a first pitch (P 1 ), and the internal thread portion (32) comprises a series of threads (32a) having a second pitch (P 2 ), wherein the cutter (14) and the shaft (12) are selectively coupled via the threaded connection of the externally threaded portion (22) and the internally threaded portion (32), and wherein the cutter (14) has an axial stop shoulder (30) and the shank (12) has an axial stop surface (34), characterized in that the difference between the first gradient (P 1 ) and the second slope (P 2 ) is in the range of about 0.002 to about 0.010 mm, wherein in an assembled state the axial stop shoulder (30) of the cutter (14) bears against the axial stop surface (34) of the shaft (12) and a load concentration on a thread (22a) closest to the axial stop shoulder (30) is avoided.

Description

CROSS-REFERENCES TO RELATED APPLICATIONS

[0001] This application claims priority to and the benefit of U.S. Patent Application Serial No. 14 / 273,456, filed May 8, 2014, which is a continuation-in-part (CIP) application claiming priority benefit over U.S. Patent Application Serial No. 13 / 950,407, filed July 25, 2013, "Coupling Mechanism for Cutting Tool," both of which are incorporated herein by reference. BACKGROUNDField of the invention

[0002] The present invention relates to coupling mechanisms for use with rotating cutting tools and, more specifically, to rotating cutting tools having such coupling mechanisms. Background information

[0003] In the past, end mills for metal cutting machines were produced as a single unit, with a serrated cutting section and a cylindrical or tapered shank section suitable for attachment to a machine spindle. The increasingly global pricing of modern tool alloys, as well as the recently developed complex surface treatments, have made such single units less economical, as the expensive shank material is often not utilized. Therefore, it has become common practice to produce a separate cutter from high-quality alloy or cemented carbide, which is then concentrically bonded to the end of a reusable steel shank.

[0004] It is highly desirable that the cutter can be easily replaced when worn, while the shank remains in the machine spindle, so no further adjustments are necessary after cutter replacement. A particular requirement associated with such precise milling applications is that each replacement cutter is precisely aligned to the exact spindle rotation axis and axially correctly positioned multiple times.

[0005] A basic method currently used for the cutter-to-shank connection is disclosed, for example, in U.S. Patent No. 5,114,286, which describes an interchangeable system for aligning and positioning cutting tools comprising a first tool segment with a male coupling segment and a second tool segment with a female coupling segment. The male coupling segment includes a pilot in the form of a first cylindrical mating surface, a concentric aligner in the form of a second cylindrical mating surface separate from the pilot, an external thread extending between the pilot and the concentric aligner, and an axial stop in the form of a flat surface.The female coupling segment includes a pilot bore in the form of a complementary cylindrical mating surface corresponding to the cylindrical mating surface of the pilot, a concentric bore in the form of a complementary cylindrical mating surface corresponding to the cylindrical mating surface of the concentric aligner, an internal thread extending between the pilot bore and the concentric bore, and an axial stop in the form of a complementary flat surface.

[0006] The described pilot, concentric aligner, pilot hole and concentric hole are necessary because the threaded coupling alone is not sufficiently precise for such repeated cutter replacement.

[0007] Further improvements to the basic concept described above are also known. For example, U.S. Patent No. 6,485,220 discloses a frusto-conical radial alignment instead of a cylindrical alignment, as well as a reinforced lead screw, and U.S. Patent No. 7,329,073 describes adjacent axial and radial stop surfaces.

[0008] Furthermore, coupling mechanisms for cutting tools are known from DE 10 2012 107 546 A1, US 2006 / 0 073 744 A1, US 2007 / 0 248 421 A1, DE 601 16 746 T2, US 2006 / 0 072 977 A1 and DE 39 12 503 A1.

[0009] DE 38 27 711 A1 shows a pipe coupling.

[0010] A screw set with external and internal threads is known from US 5 672 037 A.

[0011] DE 870 344 B shows a stud bolt connection for securing stud bolts in a threaded hole.

[0012] However, all of the solutions described above suffer from restrictive production requirements. Typical production tolerances of the cylindrical mating surfaces on the cutter and shank, sufficient to meet the need for replaceable cutters that repeatedly fall within the desired concentricity and axis position range, are less than 5 micrometers. Such tight tolerances require an additional grinding process.

[0013] Furthermore, cemented carbide cutters are inherently very hard, yet also very brittle. The direct coupling of the hard cutter to the steel shank results in stress on the coupling where the two dissimilar materials come into contact. Specifically, in cases where a carbide cutter is threaded into a steel shank, the connection is likely to break at or near the base of the carbide cutter's threaded portion, typically damaging the steel shank as well, rendering it unfit for further use.

[0014] Therefore, there is a need to improve the coupling mechanisms for use with rotating cutting tools and also for rotating cutting tools that have such coupling mechanisms. SUMMARY OF THE INVENTION

[0015] According to one aspect of the invention, a rotary cutting tool is provided. The rotary cutting tool includes a generally cylindrically shaped cutter disposed about a central longitudinal axis. The cutter has a first end with an active serrated portion and an opposite second end, the second end having a portion with external threads disposed thereon. The rotary cutting tool also includes a generally cylindrically shaped shank disposed about the central longitudinal axis, the shank having a recessed internally threaded portion formed at a first end. The externally threaded portion includes a series of threads having a first pitch, and the internally threaded portion includes a series of threads having a second pitch different from the first.The cutter and the shank are selectively coupled via the threaded connection of the external thread section and the internal thread section. The cutter has an axial stop shoulder, and the shank has an axial stop surface. The difference between the first pitch and the second pitch ranges from approximately 0.002 to approximately 0.010 mm. In the assembled state, the axial stop shoulder of the cutter rests against the axial stop surface of the shank. This prevents stress concentration on a thread closest to the axial stop shoulder.

[0016] The first slope can be smaller than the second slope.

[0017] The first pitch can be about 0.005 mm less than the second pitch.

[0018] The cutter can be made of a carbide material and the shank of a tool steel.

[0019] The cutter may include an outwardly facing circumferential surface extending a distance along the central longitudinal axis between the active serrated portion and the externally threaded portion, the shank may include an inwardly facing circumferential surface extending a distance along the central longitudinal axis between the internally threaded portion and the first end of the shank, and the outwardly facing circumferential surface may be disposed adjacent to, and opposite, the inwardly facing circumferential surface when the externally threaded portion and the internally threaded portion are threadably connected.

[0020] The outwardly facing peripheral surface may generally have the shape of a portion of a truncated cone arranged at a first angle relative to the central longitudinal axis, and the inwardly facing peripheral surface generally has the shape of a portion of a truncated cone arranged at a second angle relative to the central longitudinal axis.

[0021] The first angle can be in the range of about 1° to about 7°.

[0022] The second angle can be in the range of about 1° to about 7°.

[0023] The outwardly facing peripheral surface may be generally a cylindrical surface arranged parallel to the central longitudinal axis, and the inwardly facing peripheral surface may be generally a cylindrical surface arranged parallel to the central longitudinal axis.

[0024] The cutter may include an outwardly facing circumferential surface extending a distance along the central longitudinal axis adjacent to the externally threaded portion and opposite the active serrated portion, the shank may include an inwardly facing circumferential surface extending a distance along the central longitudinal axis between the internally threaded portion opposite the first end of the shank, and the outwardly facing circumferential surface may be disposed adjacent to, and opposite the inwardly facing circumferential surface when the externally threaded portion and the internally threaded portion are threadably connected.

[0025] The outwardly facing peripheral surface may be arranged at an angle of approximately 0° to approximately 6° with respect to the central longitudinal axis.

[0026] The inwardly facing circumferential surface may be arranged in a range of 0° to 2° of the angle of the outwardly facing circumferential surface.

[0027] The cutter may include a first outwardly facing circumferential surface extending a distance along the central longitudinal axis located between the active serrated portion and the externally threaded portion, and a second outwardly facing circumferential surface extending a distance along the central longitudinal axis adjacent to the externally threaded portion and opposite the active serrated portion. The shank may have a first inwardly facing circumferential surface extending a distance along the central longitudinal axis between the internally threaded portion and the first end of the shank, and a second inwardly facing circumferential surface extending a distance along the central longitudinal axis adjacent to the internally threaded portion at the opposite first end of the shank. The first outwardly facing circumferential surface may be located adjacent to and opposite the first inwardly facing circumferential surface.when the external and internal threaded portions are connected by the thread, and the second outwardly facing circumferential surface may be arranged adjacent to and opposite the second inwardly facing circumferential surface when the external and internal threaded portions are connected by the thread.

[0028] According to another aspect of the invention, a rotary cutting tool is provided. The rotary cutting tool comprises: a cutter of generally cylindrical shape disposed about a central longitudinal axis, the cutter having a first end with an active serrated portion and an opposite second end, the second end having an externally threaded portion disposed thereon; and a shank of generally cylindrical shape disposed at the central longitudinal axis, the shank having a recessed internally threaded portion at a first end.The external thread section comprises a series of threads having a first pitch and a first taper angle, the internal thread section comprises a series of threads having a second pitch and a second taper angle that is different from the first taper angle, and the cutter and the shank are selectively coupled via the threaded connection of the external and internal thread sections. The cutter has an axial stop shoulder and the shank has an axial stop surface. Furthermore, the first pitch and the second pitch differ. The difference between the first pitch and the second pitch is in the range of approximately 0.002 to approximately 0.010 mm. In an assembled state, the axial stop shoulder of the cutter rests against the axial stop surface of the shank. This avoids stress concentration on a thread closest to the axial stop shoulder.

[0029] The first cone angle can be smaller than the second cone angle.

[0030] The first slope may be less steep than the second slope. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The concepts of the present invention will now be described in connection with specific, non-limiting embodiments with reference to the following illustrations in order that they may be better understood.

[0032] With specific reference now to the detailed drawings, it is emphasized that the details shown are to be understood as examples only, as well as for the purpose of illustrating the preferred embodiments of the present invention, and are presented for the purpose of providing what the authors believe to be a particularly useful and readily understandable description of the principles and conceptual aspects of the invention. In this regard, no attempt is made to set forth structural details of the invention in more detail than is necessary for a basic understanding of the invention, since the description, taken in conjunction with the drawings, will make it clear to those skilled in the art how the various forms of the invention may be put into practice. Fig. 1 shows an isometric view of an example embodiment of a modular rotary cutting tool according to the present invention. Fig. 1B shows a side view of the modular rotating cutting tool of Fig. 1, where the shaft section is shown in cross section. Fig. 2 shows an isometric exploded view of the rotating cutting tool of Fig. 1. Fig. 3 shows an exploded side view of the modular rotating cutting tool of Fig. 1, where the shaft section is shown in cross-section to show internal details. Fig. 4 shows a detailed side view of the cutting section of the rotating cutting tool of Fig. 1. Fig. Figure 5 shows a detailed side view of a portion of the shank portion of the rotating cutting tool of Fig. 1. Fig. Figure 6 shows a side view of another example embodiment of a coupling mechanism according to the present invention, shown partially in cross-section to show internal details. Fig. Figure 7 shows an exploded side view of another example embodiment of a modular cutting tool according to the present invention, with the shank portion shown in cross-section to show internal details.

[0033] In the illustrations, identical parts are provided with the same reference symbols. DESCRIPTION OF THE EMBODIMENTS

[0034] The term “number” as used herein shall refer to a quantity that is not zero (i.e., one or a quantity greater than one).

[0035] The term "selectively coupled" as used herein shall refer to two or more components that are coupled or connected in a manner that can be selectively uncoupled (i.e., decoupled) without damaging either component.

[0036] The term "pitch" as used herein shall refer to a distance parallel to a central axis of a threaded part between corresponding points on adjacent thread forms on the same axial plane and on the same side of the axis.

[0037] The Fig. 1-5 show a modular rotary cutting tool 10 according to a first exemplary embodiment of the invention, arranged on a central longitudinal axis A. The cutting tool 10 includes a reusable shaft 12 and a replaceable cutter 14, which are selectively coupled via a coupling mechanism (not numbered) formed from cooperating portions of the shaft 12 and the cutter 14, respectively, which are discussed in detail below. In the Fig. In the exemplary embodiment illustrated in Figures 1-5, the cutter 14 is in the form of an end mill formed from a carbide material; however, it should be understood that any other rotary cutting tool, such as, without limitation, an end mill, a round-tip mill, a slot mill, a drill, a reamer, or any other interchangeable bit for milling, drilling, reaming, or other metalcutting applications made from carbide or other suitable material or materials, may be used without departing from the scope of the present invention. The shank 12 may be made of steel, carbide, or other suitable material formed in a generally cylindrical shape with a slightly reinforced section; however, it should be understood that other cross-sections, shapes, and materials may also be used without departing from the scope of the present invention.It should also be noted that the shaft 12 may be formed as a generally solid piece, as in the example embodiment of FIG. Fig. 1-5, or may also comprise one or more internal passages through which a coolant or lubricant supply to the cutter 14 can take place.

[0038] Furthermore, with reference to Fig. 1, the exposed portion of the cutter 14 (when inserted into the shaft 12) may have an active serrated portion 16 structured to perform cutting operations on a workpiece (not shown), followed by a short cylindrical portion 18. The cylindrical portion 18 is preferably provided with at least two opposing parallel planes 20 (only in Fig. 1) formed therein / on which a standard spanner (not shown) can engage for inserting or removing the cutter 14 from the shaft 12, as further described below.

[0039] The exploded drawings of the Fig. 2 and Fig. 3 and the detailed views in Fig. 4 and Fig. 5 show details of the portions of the shank 12 and cutter 14 that form the coupling mechanism between the cutter 14 and the shank 12. More specifically, the coupling mechanism as part of the cutter 14 includes: an outwardly projecting externally threaded portion 22 extending opposite the actively serrated portion 16; a radial aligning portion 28 disposed concentrically with the longitudinal axis A and extending between the short cylindrical portion 18 and the threaded portion 22; and a flat axial stop shoulder 30 bridging the radial gap between the smaller diameter, radial aligner 28, and the larger diameter, short cylindrical portion 18. As shown in the illustrated example embodiment, the shoulder 30 may be disposed perpendicular to the longitudinal axis A.In other embodiments, the shoulder 30 may be slightly inclined with respect to a reference perpendicular to the longitudinal axis A (up to + / -3°).

[0040] The coupling mechanism further includes as part of the shaft 12: a generally smooth alignment bore 24 disposed concentrically with the longitudinal axis A, an internally threaded bore 32 extending from the alignment bore 24, and an axial stop surface 34 disposed perpendicular to the longitudinal axis A at one end of the shaft 12 adjacent the alignment bore 24.

[0041] With reference to the detailed view of the cutter 14 as in Fig. 4, the radial alignment portion 28 is generally shaped as a portion of a frustoconical shape and includes an outwardly facing circumferential surface 29 disposed at an angle δ1 relative to the longitudinal axis A. In example embodiments of the present invention, the angle δ1 is typically in the range of about 1° to about 7°. Alternatively, the radial alignment portion 28 may be generally cylindrically shaped (i.e., δ1 = 0 degrees). In general, the frustoconical shape has been found to be preferred when the cutter 14 is coupled to steel shanks, while the cylindrical shape is preferred when the cutter 14 is coupled to carbide shanks.

[0042] With respect to the cross-sectional detail view of an end portion of a shaft 12 as shown in Fig. 5, the alignment bore 24 is generally formed with a shape corresponding to the alignment portion 28. In general, the diameter of the alignment portion 28 may be slightly larger (preferably for steel shafts) or equal (preferably for carbide shafts) to the diameter of the alignment bore 24.

[0043] Since the alignment bore 24 is formed in a shape generally corresponding to the alignment portion 28, the alignment bore 24 in the illustrated embodiment is also generally formed as a portion of a truncated cone and includes an inwardly facing circumferential surface 25 disposed at an angle δ2 relative to the longitudinal axis A. Since the inwardly facing circumferential surface 25 of the shank 12 generally cooperates with the outwardly facing circumferential surface 29 of the cutter 14, the angle δ2 in the example embodiments of the present invention is generally in the range between about 0° to about 7°, depending on the angle δ1 of the outwardly facing circumferential surface 29.

[0044] With reference to the Fig. 4 and Fig. 5, the threaded portion 22 of the cutter 14 comprises a number of threads 22a, preferably at least 4 (although a different number may be used), aligned with a first pitch P1 along the longitudinal axis A, and the threaded bore 32 comprises at least a corresponding number of internal threads 32a aligned with the longitudinal axis A with a second pitch P2 that is not the same as P1. In the Fig. 1-5, the second pitch P2 is approximately 0.005 mm greater than the first pitch P1. By using a larger pitch P2 in the threaded bore 34 of the shank 12 and therefore a smaller pitch P1 in the cutter 14, the corresponding load on the threaded portion 22 of the cutter 14 when coupled to the shank 12 is more evenly distributed among the threads 22a than in an embodiment using cooperating threads of generally the same size. In the example embodiments of the present invention, varying thread pitches of approximately 0.002 - 0.010 mm were used between the respective threads of the shank 12 and the cutter 14.In contrast to embodiments of the present invention, in cases where cooperating threads of generally equal pitch are used, the load is generally concentrated on the thread closest to the axial stop shoulder 30 due to the overall rigidity of the carbide or steel cutter 14. By more evenly distributing the load among the threads 22a of the threaded portion 22, embodiments of the present invention allow for greater loads to be applied to the joint prior to failure.

[0045] Assembly of the modular cutting tool assembly 10 is performed by connecting the threaded portion 22 of the cutter 14 to the threaded bore 32 of the shank 12, and then rotating the cutter 14 and / or the shank 12 until the radial alignment portion 28 of the cutter 14 is located within the alignment bore 24 of the shank 12 and the axial stop shoulder 30 of the cutter 14 is adjacent the axial stop surface 34 of the shank 12. The axial position of the cutter 14 with respect to the shank 12 is determined by the first direct contact of the stop shoulder 30 of the cutter 14 with the axial stop surface 34 of the shank 12. Once stop shoulder 30 and stop surface 34 are connected, the coupling is preferably further tightened to a specific torque using a torque limiter to avoid excessive tension on cutter 14.

[0046] Fig. 6 shows a detailed view of another embodiment of a coupling mechanism between a shank 12' (shown in cross-section) and a cutter 14' of a modular cutting tool 10'. The cutting tool 10' may externally resemble the cutting tool 10 as described above, and the cutter 14' and shank 12' interact in a similar manner to the cutter 14 and shank 12, except for the inclusion of a second radial alignment portion 40 disposed adjacent the threaded portion 22 opposite the radial alignment portion 28. When the cutter 14' is coupled to the shank 12', as in Fig. 6, the outwardly facing circumferential surface (unnumbered) of the second radial alignment portion 40 engages the inwardly facing circumferential surface (unnumbered) of a second alignment bore 42 formed in the shank 12' adjacent the threaded bore 32 opposite the first alignment bore 24. In example embodiments of the present invention, the radial alignment portion 40 has a generally similar or slightly smaller diameter than the diameter of the second alignment bore 42. The surface (unnumbered) of the second radial alignment portion 40 may also be disposed at angles between 0° and about 6° with respect to the central longitudinal axis A, while the surface (unnumbered) of the second alignment bore 42 is disposed at the same angle or within a range of 1°-2° of the angle of the surface of the second radial alignment portion 40.Although the second radial alignment portion 40 is shown in addition to the radial alignment portion 28, it should be noted that embodiments of the present invention may include only the second radial alignment portion 40 without the radial alignment portion 28.

[0047] Fig. 7 shows an exploded view of another exemplary embodiment of a modular cutting tool 50 according to the present invention, which includes a shank 52 and a cutter 54 coupled via another coupling mechanism according to the present invention. Shank 52 and cutter 54 may be constructed generally similarly to the shanks 12, 12' and cutters 14, 14' described above and each include an internally threaded bore 58 (including internal threads 58a, 58b) and an externally threaded portion 60 (including external threads 60a, 60b). Nevertheless, the Fig. 7 achieves a similar result by orienting the male and female threaded portions at different angles with respect to each other, in contrast to the embodiments discussed above, in which different thread pitches were used for the male and female threaded portions in order to distribute the load more evenly across the threads when the two components are firmly in a threaded coupling. In the embodiment shown in Fig.For example, in the embodiment illustrated in Figure 7, the threads 60a, 60b of the externally threaded portion 60 are arranged at a first taper angle ac (measured with respect to a reference value arranged parallel to the central longitudinal axis A), while the threads 58a, 58b of the internally threaded bore 58 are arranged at a second taper angle αs (measured with respect to a reference value arranged parallel to the central longitudinal axis A). More specifically, by arranging the internal threads 58a, 58b with a second taper angle αs that is greater than the first taper angle ac of the external threads 60a, 60b, a spatial relationship is created between the external and internal threaded portions 58, 60 that is similar to that created by using different thread pitches, as discussed above, even when the thread pitches Ps and Pc are the same.It should be noted that such an embodiment could also be used with different thread pitches Ps and Pc as an alternative to use with sections having the same pitch.

[0048] Although in the particular embodiments described here the shaft is provided with a threaded bore to receive a corresponding external thread on the cutter, the reverse case is also possible, in which the shaft is provided with a protruding external thread portion and the cutter has an internal threaded bore.

[0049] It will be apparent to those skilled in the art that the invention is not limited to the details of the embodiments set forth above, and that the present invention may be embodied in other specific forms without departing from the spirit and essential characteristics of the invention. Therefore, the present embodiments are to be considered in all respects as illustrative and not restrictive, with the scope of the invention being defined by the following claims rather than by the foregoing description, and all changes which come within the spirit and scope of equivalent claims should therefore be considered as embraced therein.

Claims

[1] Rotating cutting tool (10), comprising: a generally cylindrically shaped cutter (14) disposed about a central longitudinal axis (A), the cutter (14) having a first end with an active serrated portion (16), and an opposite second end, the second end having an externally threaded portion (22) disposed thereon; and a generally cylindrically shaped shaft (12) disposed about the central longitudinal axis (A), the shaft (12) having a recessed internally threaded portion (32) formed at a first end, wherein the external thread portion (22) comprises a series of threads (22a) which extend over a first pitch (P 1 ), and the internal thread portion (32) comprises a series of threads (32a) having a second pitch (P 2 ), wherein the cutter (14) and the shaft (12) are selectively coupled via the threaded connection of the externally threaded portion (22) and the internally threaded portion (32), and wherein the cutter (14) has an axial stop shoulder (30) and the shank (12) has an axial stop surface (34), characterized by that the difference between the first slope (P 1 ) and the second slope (P 2 ) is in the range of about 0.002 to about 0.010 mm, wherein in an assembled state the axial stop shoulder (30) of the cutter (14) bears against the axial stop surface (34) of the shaft (12) and a load concentration on a thread (22a) closest to the axial stop shoulder (30) is avoided. [2] A rotating cutting tool (10) according to claim 1, wherein the first pitch (P 1 ) is less than the second slope (P 2 ). [3] A rotating cutting tool (10) according to claim 2, wherein the first pitch (P 1 ) is about 0.005 mm less than the second pitch (P 2 ). [4] A rotary cutting tool (10) according to claim 1, wherein the cutter (14) is made of a carbide material and wherein the shank (12) is made of a tool steel. [5] Rotating cutting tool (10) according to claim 1, wherein: the cutter (14) has an outwardly facing circumferential surface (29) extending a distance along the central longitudinal axis (A) disposed between the active serrated portion (16) and the externally threaded portion (22); the shaft (12) has an inwardly facing circumferential surface (25) extending a distance along the central longitudinal axis (A) between the internally threaded portion (32) and the first end of the shaft (12); and the outwardly facing circumferential surface (29) is arranged adjacent to and opposite the inwardly facing circumferential surface (25) when the externally threaded portion (22) and the internally threaded portion (32) are connected by threads (22a, 32a). [6] A rotary cutting tool (10) according to claim 5, wherein the outwardly facing peripheral surface (29) is generally in the shape of a portion of a truncated cone inclined at a first angle (δ 1 ) relative to the central longitudinal axis (A), and wherein the inwardly facing peripheral surface (25) is generally in the shape of part of a truncated cone which is inclined at a second angle (δ 2 ) in relation to the central longitudinal axis (A). [7] Rotating cutting tool (10) according to claim 6, wherein the first angle (δ 1 ) is between about 1° and about 7°. [8] Rotating cutting tool (10) according to claim 7, wherein the second angle (δ 2) is between about 1° and about 7°. [9] The rotary cutting tool (10) of claim 5, wherein the outwardly facing circumferential surface (29) is a generally cylindrical surface arranged parallel to the central longitudinal axis (A), and wherein the inwardly facing circumferential surface (25) is a generally cylindrical surface arranged parallel to the central longitudinal axis (A). [10] Rotating cutting tool (10) according to claim 1, wherein: the cutter (14) has an outwardly facing peripheral surface (29) extending a distance along the central longitudinal axis (A) adjacent to the externally threaded portion (22) and opposite the active serrated portion (16), the shaft (12) has an inwardly facing circumferential surface (25) extending a distance along the central longitudinal axis (A) adjacent the internally threaded portion (32) opposite the first end of the shaft (12); and the outwardly facing circumferential surface (29) is arranged adjacent to and opposite the inwardly facing circumferential surface (25) when the externally threaded portion (22) and the internally threaded portion (32) are connected by threads (22a, 32a). [11] Rotating cutting tool (10) according to claim 10, wherein the outwardly facing peripheral surface (29) is at an angle (δ 1 ) of approximately 0° to approximately 6° with respect to the central longitudinal axis (A). [12] Rotating cutting tool (10) according to claim 11, wherein the inwardly facing peripheral surface (25) is in a range of 0° to 2° of the angle (δ 1 ) of the outwardly facing peripheral surface (29). [13] Rotating cutting tool (10') according to claim 1, wherein: the cutter (14') has a first outwardly facing circumferential surface (29) extending a distance along the central longitudinal axis (A) located between the active serrated portion (16) and the externally threaded portion (22), and a second outwardly facing circumferential surface extending a distance along the central longitudinal axis (A) adjacent to the externally threaded portion (22) and opposite the active serrated portion (16). the cutter (14') has a first inwardly facing circumferential surface (25) extending a distance along the central longitudinal axis (A) located between the internally threaded portion (32) and the first shank end, and a second inwardly facing circumferential surface extending a distance along the central longitudinal axis (A) adjacent the internally threaded portion (32) opposite the first end of the shank (12'); the first outwardly facing circumferential surface (29) is arranged adjacent to and opposite the first inwardly facing circumferential surface (25) when the externally threaded portion (22) and the internally threaded portion (32) are connected by threads (22a, 32a); and the second outwardly facing circumferential surface is arranged adjacent to and opposite the second inwardly facing circumferential surface when the externally threaded portion (22) and the internally threaded portion (32) are connected by threads (22a, 32a). [14] Rotating cutting tool (10), comprising: a generally cylindrically shaped cutter (14) disposed about a central longitudinal axis (A), the cutter (14) having a first end with an active serrated portion (16) and an opposite second end, the second end having an externally threaded portion (22) disposed thereon; and a generally cylindrically shaped shaft (12) disposed about the central longitudinal axis (A), the shaft (12) having a recessed internally threaded portion (32) formed at a first end, wherein the external thread portion (22) has a number of threads (22a) with a first pitch (P 1 ) and a first cone angle (a C ), wherein the internal thread portion (32) has a number of threads (32a) with a second pitch (P 2) and a second cone angle (a S ) which is determined by the first cone angle (a C ) deviates, wherein the cutter (14) and the shaft (12) are selectively coupled via the threaded connection of the externally threaded portion (22) and the internally threaded portion (32), wherein the cutter (14) has an axial stop shoulder (30) and the shank (12) has an axial stop surface (34), and where the first gradient (P 1 ) and the second slope (P 2 ) differentiate, characterized by that the difference between the first slope (P 1 ) and the second slope (P 2 ) is in the range of about 0.002 to about 0.010 mm, wherein in an assembled state the axial stop shoulder (30) of the cutter (14) bears against the axial stop surface (34) of the shaft (12) and a load concentration on a thread (22a) closest to the axial stop shoulder (30) is avoided. [15] Rotating cutting tool (10) according to claim 14, wherein the first cone angle (a C ) is less than the second cone angle (a S ). [16] A rotating cutting tool (10) according to claim 14, wherein the first pitch (P 1 ) is less than the second slope (P 2 ).

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