Milling head and tool with milling head

Abstract

Milling head (200), comprising: an elongated body portion (201) having a cutting end (210) and an elongated coupling portion (220) spaced from the cutting end (210); and the coupling section (220) comprising: a nucleus (221); and a plurality of generally helical starting threads (222) arranged circumferentially around the core (221), wherein each starting thread (222) determines a starting index and all starting indices are spaced from each other by substantially equal distances or radial positions / circumferential positions around the core (221), characterized in that each starting thread (222) determines a pitch, wherein the pitch of one starting thread (222) differs from the pitch of another starting thread (222).

Description

[0001] The present invention relates to milling heads and tools comprising milling heads.

[0002] Modular milling heads are often used in cutting operations with reusable toolholders. However, cutting operations often generate a high degree of stress on the milling heads and tools, which can lead to reduced tool performance and / or reduced tool life. In many cases, coupling mechanisms between milling heads and toolholders are unreliable.

[0003] Milling or cutting heads and tools with a milling or cutting head are shown in US 2007 / 0 116 539 A1, US 2012 / 0 009 027 A1, US 7 802 692 B2, US 5 971 670 A, US 5 624 213 A, US 2013 / 0 028 669 A1, DE 202 02 053 U1 and DE 601 16 746 T2.

[0004] The object of the invention is to provide improved milling heads and / or tools that provide reliable coupling mechanisms.

[0005] The object is achieved by a milling head according to claim 1 and a tool according to claim 12.

[0006] In one aspect, milling heads are described herein that may offer one or more advantages over known milling heads. For example, a milling head described herein may provide a balanced distribution of the loads introduced during cutting operations, thereby enabling higher torque performance and increased productivity. Furthermore, a milling head described herein may have a structure that allows interchangeability between cutting operations. Furthermore, milling heads described herein may be used with a variety of tools and / or tool holders of different sizes and / or shapes.

[0007] A milling head described herein includes an elongated body portion having a cutting end and an elongated coupling portion spaced from the cutting end. The coupling portion includes a core and a plurality of generally helical starting threads circumferentially disposed about the core. Starting threads of coupling portions may include square, triangular, or trapezoidal thread profile shapes. In some embodiments, coupling portions include at least two starting threads. Further, coupling portions may include at least three starting threads, including four or five starting threads. Furthermore, the starting threads may include or define starting indices, threads, pitches, core diameters, outside diameters, thread pitch diameters, or combinations thereof.

[0008] Milling heads described herein may have various cross-sectional shapes. For example, a cross-section of the coupling portion may be substantially circular. Alternatively, a cross-section of the coupling portion may be non-circular. Similarly, the core of the coupling portion may have various cross-sectional shapes. In some embodiments, a cross-section of the core is substantially circular. In other embodiments, a cross-section of the core is non-circular.

[0009] In another aspect, tools are described herein that can provide balanced loads introduced into a tool holder and / or a tool head during cutting operations. Therefore, in some embodiments, a tool described herein provides improved load distribution during tool operation, enabling higher torque outputs and increased productivity. Furthermore, a tool described herein can have a structure that enables cutter head interchangeability between cutting operations.

[0010] A tool described herein includes a holder defining a threaded receptacle and a modular milling head threadably engageable within the threaded receptacle. The modular milling head includes an elongated body portion having a cutting end and an elongated coupling portion spaced from the cutting end, the coupling portion including a core and a plurality of generally helical starting threads circumferentially around the core. Additionally, the modular milling head may further include a cutting end including a flute and at least one of a cutting edge and a pocket. In some cases, each starting thread of the modular milling head defines a thread pitch, a lead, an outside diameter, a minor diameter, and a thread pitch diameter.Furthermore, in some cases the threaded receptacle includes an inner thread surface that determines a thread pitch, a pitch height, an outer diameter, a core diameter and a thread pitch diameter.

[0011] These and other embodiments are described in more detail in the following detailed description. Fig. 1 illustrates a cross-sectional view of a tool according to an embodiment described herein. Fig. Figure 2A illustrates a perspective view of a milling head according to an embodiment described herein. Fig. Figure 2B illustrates a perspective view of a milling head according to an embodiment described herein. Fig. 3 illustrates a thread configuration described herein. Fig. Figure 4A illustrates a portion of a thread configuration of a milling head described herein. Fig. Figure 4B illustrates a portion of a thread configuration of a milling head described herein. Fig. Figure 4C illustrates a portion of a thread configuration of a milling head described herein. Fig. Figure 5 illustrates a schematic representation of a known thread configuration described herein. Fig. 6 illustrates a schematic diagram of a thread configuration according to an embodiment of a milling head described herein. Fig. 7 illustrates a perspective view of a milling head according to an embodiment described herein. Fig. Figure 8A illustrates a cross-sectional view of a known milling head described herein. Fig. Figure 8B illustrates a cross-sectional view of a milling head according to an embodiment described herein. Fig. Figure 9 illustrates a cross-sectional view of a portion of a milling head according to an embodiment described herein.

[0012] Embodiments described herein will be more readily understood from the following detailed description and drawings. However, elements, devices, and methods described herein are not limited to the specific embodiments presented in the detailed description and drawings. It should be understood that these embodiments merely illustrate the principles of the present invention. Numerous modifications and adaptations will be readily apparent to those skilled in the art without departing from the spirit and scope of the invention.

[0013] In one aspect, milling heads are described herein that, in some embodiments, demonstrate improved durability, modularity, and torque performance. Further, milling heads described herein may offer configurations that enable a higher thread core diameter to head diameter ratio. Some known milling head coupling sections that include only a single starting thread require a relatively small core diameter to head diameter ratio. Larger thread core to head diameter ratios typically result in improved tool strength and performance. As an increasing number of starting threads are used, larger thread core diameters relative to the head diameter may be used, resulting in a higher thread core to head diameter ratio, thereby achieving increased strength and performance in a milling head, particularly with respect to the coupling section.In some embodiments, milling heads described herein include an elongated body portion having a cutting end and an elongated coupling portion spaced from the cutting end. Coupling portions of the milling heads described herein include a core and a plurality of generally helical starting threads circumferentially disposed about the core. Starting threads of coupling portions may include square, triangular, or trapezoidal thread profile shapes. The coupling portions include at least two starting threads or at least three starting threads. In one embodiment, coupling portions include four or five starting threads.

[0014] Turning now to specific components, milling heads described herein include an elongated body portion. Elongated body portions of milling heads may comprise or be formed from any materials that do not conflict with the objectives of the present invention. For example, an elongated body portion may comprise, consist of, or consist essentially of cemented carbide, high speed steel, ceramic, cermet, cemented carbide, or combinations thereof. An elongated body portion may include a cutting end of any shape, configuration, or design that does not conflict with the objectives of the present disclosure. For example, the cutting end may include a chip flute and at least one of a cutting edge and a pocket, and in certain embodiments, a cutting edge may be used when a uniform cutting end configuration is desirable for certain cutting operations.In some embodiments, at least one insert pocket may be employed when the use of replaceable inserts is desirable. A "insert pocket" is an area on a cutting end of a tool configured to receive and / or secure a removable cutting tip. Any insert pocket configuration may be used that does not conflict with the objectives of the present disclosure. Insert pockets of the milling heads described herein may be configured to receive any cutting, milling, or turning inserts. For example, insert pockets may be configured to receive and / or secure indexable inserts or milling inserts. In some embodiments, a plurality of insert pockets arranged in a single groove may form a cutting edge comprising a plurality of cutting, milling, or turning inserts.In other embodiments, a single insert pocket may be disposed in each of a plurality of grooves in a milling head. Furthermore, in some embodiments, a combination of at least one cutting edge and at least one insert pocket may be used. Insert pockets may be configured to be coupled to inserts via permanent or removable mechanical configurations.

[0015] Elongated body portions of milling heads further include a coupling portion spaced from the cutting end. The coupling portion includes a core and a plurality of generally helical starting threads circumferentially disposed about the core. A core of a coupling portion of the milling head is a central component or region of a coupling portion on which threads may be disposed. The core extends axially away from the cutting end of the elongated body portion of the milling head along the axis of rotation. At least two helical starting threads are circumferentially disposed about the core. Further, in some embodiments, coupling portions of milling heads described herein include at least three starting threads, including four or five starting threads.Cores of coupling portions of the milling heads described herein may have any cross-sectional shape that does not conflict with the objectives of the present invention. For example, in some embodiments, a cross-section of the core taken along a plane perpendicular to the core's axis of rotation is substantially circular. In some embodiments, a cross-section of the core is non-circular. For example, a cross-section of the core may be elliptical or include an irregular rounded shape.

[0016] Coupling sections of milling heads with multiple starting threads may have any starting indices that do not conflict with the objectives of the present invention. "Starting index" refers to the initial position for the individual starting threads on a tool. In some embodiments, the starting indices are spaced from each other by substantially equal distances or radial / circumferential positions around the core. For example, in embodiments with three starting threads, each starting thread may be indexed 120° from each other circumferentially around the coupling section. Alternatively, the starting indices are spaced from each other at unequal distances or radial positions.

[0017] Each starting thread of a coupling section can determine a pitch, a lead, an outside diameter, a minor diameter, and a thread pitch diameter. The "pitch" of a starting thread is the distance from one thread crest to the next crest in an axial direction parallel to the axis of rotation. In the case of a threading tool comprising a thread with a single starting thread, both crests correspond to the same thread. In the case of a threading tool comprising more than one starting thread, the two crests forming a pitch correspond to different threads. The "pitch" of a starting thread is the axial distance along the threaded section of a tool covered by one complete revolution of the starting thread around the tool's circumference. In the case of a threading tool comprising a thread with a single starting thread, the pitch and the pitch are identical.In the case of a threading tool comprising a thread with two or more starting threads, the pitch is greater than the thread. An "outside diameter" of a starting thread is the larger of the two extreme diameters that delimit the height of a thread profile in cross-sectional view. In contrast, a "minor diameter" of a starting thread is the smallest extreme diameter of the thread. In other words, the minor diameter of a starting thread corresponds to the circumferential surface of the core of a coupling portion of a cutting tool described herein. The "thread pitch diameter" of a particular thread is the diameter that intersects the height of a thread profile where the width of the thread ridge equals the width of the thread groove.

[0018] The dimensions, orientations, and configurations of the thread, pitch, outer diameter, minor diameter, and thread pitch diameter of coupling portions of cutting tools described herein may take any form that does not conflict with the objectives of the present disclosure. For example, in some embodiments, the minor diameter of at least one starting thread may remain constant in an axial direction away from the cutting end. In some embodiments, the minor diameter of at least one starting thread decreases in an axial direction away from the cutting end. Similarly, in some embodiments, the outer diameter of at least one starting thread may remain constant in an axial direction away from the cutting end. In certain embodiments, the outer diameter of at least one starting thread decreases in an axial direction away from the cutting end.Furthermore, in some embodiments, the thread pitch diameter of at least one starting thread may remain constant in an axial direction away from the cutting end. In some embodiments, the thread pitch diameter of at least one starting thread decreases in an axial direction away from the cutting end. In some cases, two or more of the outer diameter, minor diameter, and thread pitch diameter decrease in the axial direction away from the cutting portion, forming a taper, and such a tapered coupling portion may form a conical or frustoconical shape.

[0019] Cross-sections of coupling portions of the milling heads described herein may take any shape that does not conflict with the objectives of the present invention. For example, a cross-section along a plane perpendicular to the axis of rotation of the coupling portion may be substantially circular. In certain other embodiments, a cross-section of the coupling portion is not circular, but rather, for example, elliptical or has an irregularly rounded shape. Furthermore, the pitch may be a multiple of the pitch, where the multiple is equal to the number of starting threads arranged circumferentially around the core. For example, in some embodiments, a coupling portion described herein with two starting threads includes a pitch that is twice the pitch.

[0020] Furthermore, starting threads described herein may have any cross-sectional shape or configuration that does not conflict with the objectives of the present invention. For example, starting threads may have thread profiles with square, triangular, or trapezoidal shapes. Square thread cross-sectional shapes include a flattened portion that is substantially parallel at a radially outer portion of the core. Square thread cross-sectional shapes further include sides that are substantially perpendicular to the flattened portion. Rectangular thread cross-sectional shapes may include isosceles, equilateral, and / or scalene triangular shapes. In some embodiments, trapezoidal thread shapes are formed having a base shape that corresponds to a triangular thread profile shape, but that is truncated.Where a triangular thread profile extends in a sharp "V" shape, trapezoidal thread profiles include a flattened portion that is substantially parallel to a radially outer surface of the core. In embodiments with trapezoidal thread profiles, the flattened portion forms the outer diameter of the thread profile. In some cases, the outer diameter of the thread is equal to the thread pitch diameter. In other cases, the outer diameter of the thread is larger than the thread pitch diameter.

[0021] Any combination of the above materials, shapes, and thread profiles may be used that does not conflict with the objectives of the present invention. For example, in some embodiments, a coupling portion of a milling head includes an outer diameter, core diameter, and thread pitch diameter that decreases in an axial direction away from the cutting portion, wherein the coupling portion forms a frustoconical shape. Such embodiments may further include a trapezoidal thread profile shape, wherein the flattened or truncated portion of the thread profile provides an outer diameter that is larger than the thread pitch diameter, and wherein the flattened portion is substantially parallel to an outer surface of the core.

[0022] In another aspect, tools are described herein that not only provide cutting, milling, or grinding functions, but also provide a balanced distribution of the loads exerted on a tool holder and / or tool head during cutting operations, thereby improving the serviceability and durability of the tool during high-torque operations and providing desirable modularity. A tool described herein includes a holder defining a threaded receptacle and a modular milling head that can be screwed into the threaded receptacle to directly couple them together. The modular milling head includes an elongated body portion having a cutting end and an elongated coupling portion spaced from the cutting end.The coupling portion of the elongated body portion includes a core and a plurality of generally helical starting threads arranged circumferentially around the core.

[0023] Turning now to specific components, tools described herein include a threaded receptacle. A threaded receptacle includes an internal thread surface that defines a thread pitch, a pitch, an outer diameter, a minor diameter, and a thread pitch diameter. Since threaded receptacles are internally threaded, a minor diameter corresponds to a crest on a starting thread, and an outer diameter corresponds to a thread root. Any dimensions, orientations, or configurations that do not conflict with the objectives of the present disclosure may be used. For example, one or more of an outer diameter, minor diameter, and thread pitch diameter may remain constant in an axial direction away from an opening in the holder, the opening configured to receive the milling head.In some cases, one or more of an outer diameter, minor diameter, and thread pitch diameter may decrease in an axial direction away from the opening. Furthermore, one or more of an outer diameter, minor diameter, and thread pitch diameter may decrease in an axial direction away from the opening, forming a taper in the threaded receptacle.

[0024] Tools described herein further comprise a modular milling head that can be threaded into the threaded receptacle. The modular milling head comprises an elongated body portion having a cutting end and an elongated coupling portion spaced from the cutting end. The coupling portion comprises a core and a plurality of generally helical starting threads circumferentially disposed about the core. Any milling head consistent with the foregoing may be used. For example, in some embodiments, coupling portions of milling heads described herein comprise at least two starting threads circumferentially disposed about the core. In some embodiments, coupling portions of milling heads described herein comprise at least three starting threads circumferentially disposed about the core.Thread profiles of coupling sections can form any cross-sectional shape that does not conflict with the objectives of the present invention. For example, thread profiles can include square, triangular, or trapezoidal shapes.

[0025] Holders and milling heads may be configured or formed with dimensions, parameters, or orientations that correspond to one another. Additionally, holders and milling heads may be configured to be directly coupled together without additional components or structures. For example, the inner thread surface may include a number of starting threads that corresponds to the number of starting threads arranged on the coupling portion of the modular milling cutter. In some cases, the inner thread surface includes at least two starting threads. In some cases, the inner thread surface includes at least three starting threads. Further, in some embodiments, the pitch of the thread receptacle is equal to the pitch of the coupling portion of a tool described herein. Alternatively, the pitch of the thread receptacle is different from the pitch of the coupling portion.One or more dimensions of the thread profiles of milling head coupling sections and holder coupling sections can be configured to match each other. In some cases, the milling head start threads and the receiving start threads can have threads with matching outer diameters, minor diameters, and / or thread pitch diameters. Depending on the thread profile shapes and matching outer, minor, and / or thread pitch diameters, various contact surfaces are possible in the interaction of a milling head start thread and a threaded receiver. For example, if trapezoidal thread profiles are used in both a milling head coupling section and a holder coupling section with matching minor diameters, then a contact surface is formed along the outer diameters of each thread at a coupling section that is in contact with the outer diameter of the start threads in the threaded receiver.In designs with matching thread pitch diameters, a contact surface is formed along the thread sides instead of at the outer and minor diameters of the starting threads. In some cases, contact surfaces are formed along the outer diameter, minor diameter, and sides of the starting threads.

[0026] Furthermore, configurations of holders and milling heads can be configured to provide desirable mating characteristics. For example, coupling portions of milling heads can provide an outer diameter, minor diameter, and thread pitch diameter that is larger than an outer diameter, minor diameter, and thread pitch diameter of a corresponding holder. In such embodiments, a direct coupling of the milling head and holder achieves elastic deformation of the holder, thereby providing an interference fit. Furthermore, in some embodiments, a milling head coupling portion can have a taper that is larger than the taper of the holder coupling portion.

[0027] Some embodiments will now be described in more detail with reference to the drawings. As will be understood by one skilled in the art, the various elements and / or components shown in the drawings are representative only and are not necessarily drawn to scale. Fig. 1 illustrates a cross-sectional view of a tool according to an embodiment described herein. The tool 100 in Fig. 1 includes a holder 300 defining a threaded receptacle 310 and a modular milling head 200 that can be screwed into the threaded receptacle 310. The modular milling head 200 includes an elongated body portion 201 having a cutting end 210 and an elongated coupling portion 220 spaced from the cutting end 210. The coupling portion 220 includes a core 221 and a plurality of generally helically extending starting threads 222 circumferentially disposed around the core 221.

[0028] Fig. 2A illustrates a perspective view of a milling head according to an embodiment described herein. The embodiment of Fig. Figure 2A illustrates a milling head 200 having an elongated body portion 201 with a cutting end 210 and an elongated coupling portion 220 spaced from the cutting end 210. The cutting end 210 has at least one groove 211 and at least one cutting edge 212. The coupling portion 220 includes a core 221 and a plurality of generally helical starting threads 222 circumferentially disposed around the core.

[0029] Fig. 2B illustrates a perspective view of a milling head according to an embodiment described herein. The embodiment of Fig. Figure 2B illustrates a milling head 200 having an elongated body portion 201 with a cutting end 210 and an elongated coupling portion 220 spaced from the cutting end 210. The cutting end 210 has at least one groove 213 and at least one insert seat 214. The coupling portion 220 includes a core 221 and a plurality of generally helical starting threads 222 circumferentially disposed about the core.

[0030] Fig. 3 illustrates a thread configuration described herein. Fig. 3 illustrates a core diameter (d1), an outer diameter (d) and a thread pitch diameter (d2) of a thread configuration.

[0031] Fig. Figure 4A illustrates a thread configuration of a milling head described herein that includes a single starting thread. Fig. Figure 4B illustrates a thread configuration of a milling head described herein that includes two starting threads. Fig. Figure 4C illustrates a thread configuration of a milling head described herein that includes three starting threads. Taken together, Fig. 4A, Fig. 4B and Fig. 4C illustrates various stages of a coupling portion of an embodiment of a milling head described herein in a non-limiting example of a method for forming multiple starting threads. While other methods or processes may be used to form the milling head described herein, the method in Fig. 4A, Fig. 4B and Fig. 4C shows the positioning of several starting threads relative to each other in an embodiment of a milling head described herein.

[0032] Fig. Figure 5 illustrates a schematic representation of a known thread configuration described herein. As in Fig. As illustrated in Figure 5, during a cutting operation, force is applied along a plane, the direction of the applied force being indicated by the arrow F a is displayed. As in Fig. As illustrated in Figure 5, the force is not applied symmetrically within the coupling section, resulting in an asymmetric load distribution along the rotation axis of the milling head as well as in cross-sections over 90 degrees.

[0033] Fig. Figure 6 illustrates a schematic diagram of a thread configuration according to an embodiment of a milling head described herein. The embodiment of Fig. 6 comprises two starting threads forming a pitch and a pitch. In the embodiment of the Fig. 6 the aisle height is twice the length of the aisle. In Fig. Figure 6 also illustrates the force applied during a cutting operation, indicated by arrows F1 and F2. F1 and F2 demonstrate force applied along a cross-sectional plane that is symmetrical, resulting in a balanced load distribution along the milling head's rotational axis.

[0034] Fig. Figure 7 illustrates a perspective view of a milling head according to an embodiment described herein. The embodiment of Fig. 7 comprises three starting threads with identical starting indices around the circumference of the coupling section.

[0035] Fig. Figure 8A illustrates a cross-sectional view of a known milling head described herein. Fig. 8B illustrates a cross-sectional view of a milling head according to an embodiment described herein. As shown in Fig. 8A and Fig. As shown in Figure 8B, increasing the number of starting threads arranged circumferentially around the coupling portion results in an increasingly symmetrical cross-sectional shape in some embodiments. In some embodiments, the cross-sectional shape becomes more circular with an increasing number of starting threads. Fig. Figure 8B illustrates a cross-section of an embodiment of a milling head described herein that includes three starting threads.

[0036] Fig. Figure 9 illustrates a cross-sectional view of a portion of a milling head according to an embodiment described herein. Fig. 9 illustrates the relationship between a core diameter and a head diameter. Example 1 Milling head

[0037] Two milling heads were electronically modeled, and a compensation analysis was performed for both milling heads. Both milling head models were modeled with a head diameter of 16 mm, which included no cutting geometry. Model A was prepared as a comparative example of known coupling section configurations and included a coupling configuration with one starting thread. Model B was prepared according to an embodiment of milling heads described herein and included two starting threads in the coupling section. Both models were tested under operating conditions of 30,000 rpm in a blank material with a density of 14.5 g / cm 3simulated. Model A included a total tool weight of 98.112 g, exhibited an angular displacement during analysis of -115.112°, a radial displacement of 0.005 mm, and resulted in an unbalanced force of 127.13 N (12.964 g). Model B included a total tool weight of 103.612 g, exhibited an angular displacement during analysis of -108.234°, a radial displacement of 0.0 mm, and resulted in an unbalanced force of 2.0E-5 N (0.002 g).

[0038] Model B demonstrates that multiple starting threads in milling head couplings can provide improved force and load distribution characteristics. Furthermore, the results of the balancing analysis show that coupling sections comprising a large number of starting threads can be suitable for high-speed applications.

[0039] Many modifications and other examples of the disclosure set forth herein, which take advantage of the teachings presented in the foregoing descriptions and the accompanying drawings, will be apparent to one skilled in the art to which the disclosure relates. Therefore, it is to be understood that the disclosure is not limited to the particular embodiments disclosed, and that modifications and other embodiments are intended to be included within the scope of the appended claims. Moreover, although the foregoing descriptions and the accompanying drawings describe example embodiments in the context of certain illustrative combinations of elements and / or functions, it is to be understood that various combinations of elements and / or functions of alternative embodiments may be provided without departing from the scope of the appended claims.

Claims

[1] Milling head (200), comprising: an elongated body portion (201) having a cutting end (210) and an elongated coupling portion (220) spaced from the cutting end (210); and the coupling section (220) comprising: a nucleus (221); and a plurality of generally helical starting threads (222) arranged circumferentially around the core (221), wherein each starting thread (222) determines a starting index and all starting indices are spaced from each other by substantially equal distances or radial positions / circumferential positions around the core (221), characterized by that each starting thread (222) determines a pitch, wherein the pitch of one starting thread (222) differs from the pitch of another starting thread (222). [2] Milling head (200) according to claim 1, wherein the coupling portion (220) comprises at least two starting threads (222). [3] Milling head (200) according to claim 1, wherein the coupling portion (220) comprises at least three starting threads (222). [4] The milling head (200) of claim 1, wherein the cutting end (210) comprises a flute (211) and at least one of a cutting edge (212) and a insert seat (214); and wherein each starting thread (222) defines a pitch, an outer diameter (d), a root diameter (d1), and a thread pitch diameter (d2). [5] Milling head (200) according to claim 4, wherein the outer diameter (d), core diameter (d1) and thread pitch diameter (d2) of at least one starting thread (222) remain constant in an axial direction away from the cutting end (210). [6] Milling head (200) according to claim 4, wherein at least one of the outer diameters (d), core diameters (d1) and thread pitch diameters (d2) of at least one starting thread (222) decreases in an axial direction away from the cutting end (210). [7] Milling head (200) according to claim 4, wherein at least two of the outer diameters (d), core diameters (d1) and thread pitch diameters (d2) of at least one starting thread (222) decrease in an axial direction away from the cutting end (210) and form a taper. [8] Milling head (200) according to claim 1, wherein a cross section of the coupling portion (220) along a plane perpendicular to a rotation axis is substantially circular. [9] Milling head (200) according to claim 1, wherein a cross section of the coupling portion (220) along a plane perpendicular to a rotation axis is non-circular. [10] The milling head (200) of claim 1, wherein a cross-section of the core (221) along a plane perpendicular to a rotation axis is non-circular. [11] Milling head (200) according to claim 1, wherein a cross-section of the core (221) along a plane perpendicular to a rotation axis is substantially circular. [12] Tool (100), comprising: a holder (300) defining a threaded receptacle (310) and an opening configured to receive a modular milling head (200), the threaded receptacle (310) having an inner thread surface with a pitch; and a modular milling head (200) which can be screwed into the threaded receptacle (310), the modular milling head (200) comprising: an elongated body portion (201) having a cutting end (210) and an elongated coupling portion (220) spaced from the cutting end (210); and the coupling section (220) comprising: a nucleus (221); and a plurality of generally helical starting threads (222) arranged circumferentially around the core (221), each starting thread (222) defining a starting index and all starting indices being spaced from each other by substantially equal distances or radial / circumferential positions around the core (221), wherein the holder (300) and the milling head (200) are configured to be directly coupled to each other, characterized by that the pitch of the threaded receptacle (310) is not equal to the pitch of the coupling section (220). [13] The tool (100) of claim 12, wherein the modular milling head (200) further comprises a cutting end (210) including a flute (211) and at least one of a cutting edge (212) and a insert seat (214); and wherein each starting thread (222) defines a first pitch, a first pitch, a first outer diameter (d), a first core diameter (d1), and a first thread pitch diameter (d2); and wherein the threaded receptacle (310) includes an inner thread surface defining a second thread, a second pitch, a second outer diameter, a second core diameter, and a second thread pitch diameter. [14] The tool (100) of claim 13, wherein the inner thread surface comprises a number of starting threads (222) corresponding to the number of starting threads arranged on the coupling portion (220) of the modular milling cutter. [15] Tool (100) according to claim 13, wherein the first outer diameter (d), the first core diameter (d1) and the first thread pitch diameter (d2) of at least one starting thread (222) remain constant in an axial direction away from the cutting end (210) and wherein the second outer diameter, the second core diameter and the second thread pitch diameter of the thread receptacle (310) remain constant in an axial direction away from the opening. [16] The tool (100) of claim 13, wherein at least two of the first outer diameters (d), the first core diameters (d1) and the first thread pitch diameters (d2) of at least one starting thread (222) decrease in an axial direction away from the cutting end (210) and form a first taper. [17] The tool (100) of claim 16, wherein at least two of the second outer diameters, the second core diameters, and the second thread pitch diameters of the threaded receptacle (310) decrease in an axial direction away from the opening and form a second taper. [18] The tool (100) of claim 17, wherein the first taper is larger than the second taper, thereby providing an interference fit when the coupling portion (220) and the threaded receptacle (310) are coupled. [19] Tool (100) according to claim 14, wherein at least one starting thread (222) on the milling head (200) and at least one starting thread (222) on the tool (100) have a trapezoidal cross-sectional shape. [20] Tool (100) according to claim 19, wherein the first outer diameter (d) and the second outer diameter are in contact with each other when the milling head (200) and the holder (300) are coupled.

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