Interchangeable cutting head and rotary cutting tool having a concavely curved male thread

Abstract

The rotary cutting tool includes an exchangeable cutting head and a tool holder. The exchangeable cutting head includes a front cutting portion and a rear assembly portion. The assembly portion includes a male coupling member including an external thread, the external thread being defined by an externally threaded inner cylindrical body and an externally threaded outer cylindrical body. The external thread has concavely curved external thread roots, each of which meets with a respective straight external thread load application surface at a first external thread root point. The first external thread root point is spaced from the externally threaded inner cylindrical body by a first external thread radial distance. The first external thread radial distance is greater than one-third and less than two-thirds of the external thread height. The tool holder includes a female coupling member including a female thread. When the rotary cutting tool is in a locked position, the external thread threads threadably mate with the female threads.

Description

[Technical Field]

[0001] The subject matter of this application relates to rotary cutting tools of the type in which an interchangeable cutting head having a male coupling member is removably retained within a female coupling member of a tool holder by a threaded engagement mechanism. [Background technology]

[0002] Rotary cutting tools may include a threaded mechanism or "tool interface" to securely hold interchangeable cutting heads within the tool holder.

[0003] The interchangeable cutting head may include a male coupling member and the tool holder may include a female coupling member. The male coupling member may include external threads. The female coupling member may include internal threads that correspond to the external threads on the male coupling member.

[0004] The external threads have external load application flanks that abut corresponding flanks on the internal threads. The external load application flanks are typically straight. The external threads have external roots that merge with each external load application flank.

[0005] In some such rotary cutting tools, the male thread roots are substantially straight and have a small radius where they meet the respective male thread load application flanks. An example of such a rotary cutting tool is disclosed, for example, in U.S. Pat. No. 6,485,220. A disadvantage of such male threads is that they are prone to fracture due to stress in the region where the male thread roots are adjacent to the respective male thread load application flanks (i.e., at the small radius).

[0006] In other such rotary cutting tools, the valleys are elliptical to overcome such problems. Examples of such rotary cutting tools are disclosed, for example, in US 4,799,844 and US 5,060,740.

[0007] In yet other such rotary cutting tools, the external thread has a root defined by one or more radii. Examples of such rotary cutting tools are disclosed, for example, in US 4,549,754, US 6,196,598 B1, US 7,997,842 B2 and US 9,874,058 B2. Summary of the Invention [Problem to be solved by the invention]

[0008] It is an object of the subject matter of the present application to provide an interchangeable cutting head having external threads with improved stress reduction.

[0009] It is an object of the subject matter of the present application to provide an interchangeable cutting head having external threads with improved distribution of stress concentrations. [Means for solving the problem]

[0010] According to a first aspect of the subject matter of the present application, there is provided an interchangeable cutting head having a head longitudinal axis extending in a front-to-rear direction, the interchangeable cutting head comprising: a front portion forming a cutting portion with at least one cutting edge; a rear portion forming an assembly portion, the assembly portion has a male coupling member; the male coupling member has an external thread and projects rearward from the head base surface; the head base surface extends transversely to the head longitudinal axis and defines a boundary between the cutting portion and the assembly portion; The male screw has an external thread, The male thread extends spirally around the male thread axis and includes a leading male thread flank surface and a trailing male thread flank surface, and a male thread upper surface extending between the leading male thread flank surface and the trailing male thread flank surface, the leading and trailing external thread flank surfaces generally face in opposite axial directions and define a helical external thread groove having an external thread root surface; The external thread has a constant external thread pitch, The external thread has a constant external thread height, the male threads of the male coupling member are straight threads defined by an externally threaded inner cylindrical body and an externally threaded outer cylindrical body; The externally threaded inner cylindrical body has an inner diameter; The externally threaded outer cylindrical body has an outer diameter; In a cross-sectional view taken on an axial plane including the male screw shaft, the leading and trailing male thread flank surfaces respectively define a plurality of straight male thread load application surfaces and a plurality of male thread non-load application surfaces; The male thread bottom surface forms a plurality of concavely curved male thread roots; each external thread root extends between a first external thread root point and a second external thread root point and merges with a respective external thread load application surface at the first external thread root point; the first external thread root point is spaced from the externally threaded inner cylindrical body by a first external thread radial distance; The first radial distance of the male thread is the male thread height H E and the male thread height H E is less than two-thirds of the

[0011] According to a second aspect of the subject matter of the present application, there is provided a rotary cutting tool having a longitudinal axis and extending in a fore-aft direction, the rotary cutting tool comprising: It comprises a tool holder having a holder longitudinal axis and an interchangeable cutting head of the type described above threadedly engaged with the tool holder.

[0012] It should be understood that the above is a summary and that the features described below may be applicable to the subject matter of the present application in any combination, for example, any of the following features may be applicable to an interchangeable cutting head or a rotary cutting tool.

[0013] The first radial distance of the male thread is the male thread height H E and may be less than 7 / 12 of the male thread height.

[0014] Each male thread load application flank can have a male thread load application flank length measured along the outer contour of the male thread load application flank. Each male thread root can have a male thread root length measured along the outer contour of the male thread root between a first male thread root point and a second male thread root point. The male thread root length can be between 3 and 6 times greater than the male thread load application flank length.

[0015] The inner diameter may be at least 75% of the outer diameter.

[0016] The external thread may have between 3 and 4 turns in the axial direction.

[0017] The external thread may be a single-start thread.

[0018] The external thread height may be greater than one-third of the external thread pitch and less than one-half of the external thread pitch.

[0019] Each external thread root may be defined by a single external thread root radius.

[0020] The male thread root radius may be 0.3 mm or more and 0.5 mm or less.

[0021] The first and second thread root points may define a thread root angle θ with respect to a center of an imaginary circle defined by the thread root radius, and the thread root angle θ may be greater than or equal to 90° and less than or equal to 160°.

[0022] The male thread non-load-applying flanks may be straight. Each male thread root may meet its respective male thread non-load-applying flank tangentially at a second male thread root point. The male thread root subtending angle θ may be greater than or equal to 120° and less than or equal to 140°.

[0023] The male thread root radius may be greater than one-third the male thread pitch and less than half the male thread pitch.

[0024] Each male thread root may meet a respective male thread load application flank tangentially.

[0025] Each external thread root may meet the respective external thread non-load-applying flank at a second external thread root point.

[0026] The non-load-bearing surface of the male thread may be straight.

[0027] Each male thread root may meet tangentially with a respective male thread non-load-applying surface.

[0028] The first external thread root point and the second external thread root point are axially separated by a point distance, which may be greater than one-third of the external thread pitch PE and less than half the external thread pitch.

[0029] The male thread load application surface may be inclined at a male thread flank angle relative to a head radial plane perpendicular to the male thread axis, the male thread flank angle being in the range 28°<α<34°.

[0030] In the cross-sectional view taken in an axial plane including the male screw axis, the upper surface of the male thread can form a plurality of male thread crests, each of which has a radially outermost male thread crest surface, and the radially outermost male thread crest surfaces can be parallel to the male screw axis and collinear with one another.

[0031] In said cross-sectional view taken in an axial plane containing the male thread axis, each straight male thread load application surface may have a male thread load application surface height measured perpendicular to the male thread axis. E may be greater than one-third of the external thread height and less than three-fifths of the external thread height.

[0032] The replaceable cutting head may be made from a first material, the tool holder may be made from a second material, and the first material may be harder than the second material.

[0033] The tool holder has a female coupling member with internal threads extending rearwardly from a front face of the holder, the front face extending transversely to the longitudinal axis of the holder. The rotary cutting tool can be adjustable between a released position in which the internal and external threads do not threadably engage with one another and a locked position in which the male coupling member is removably retained within the female coupling member with the internal and external threads threadably engaging with one another.

[0034] The female threads of the female coupling member may be straight threads defined by a female threaded inner cylinder and a female threaded outer cylinder.

[0035] The female threads may have a constant female thread pitch which may be the same as the male thread pitch.

[0036] The female thread may have an internal thread that extends helically around the female thread axis and may have leading and trailing female thread flank surfaces and an internal thread top surface extending between the leading and trailing female thread flank surfaces. The leading and trailing female thread flank surfaces may generally face in opposite axial directions and define a helical internal thread groove that includes an internal thread root surface. The leading and trailing male thread flank surfaces may face in a leading direction. The trailing male thread flank surfaces may face in a trailing direction. In the locked position, the trailing female thread flank surface may abut the leading male thread flank surface.

[0037] In the locked position, the leading female thread flank surface can be spaced apart from the trailing male thread flank surface, the female thread top surface can be spaced apart from the male thread root surface, and the female thread root surface can be spaced apart from the male thread top surface.

[0038] In a cross-sectional view taken in an axial plane containing the female thread axis, the leading female thread flank surface and the trailing female thread flank surface form a plurality of female thread non-load application surfaces and a plurality of female thread load application surfaces, respectively, and the female thread load application surfaces may be straight.

[0039] The upper surface of the female thread forms a plurality of female thread crests, each of which has a radially innermost female thread crest surface that may be parallel to the female thread axis, and the innermost female thread crest surfaces may be collinear with one another.

[0040] Each of the plurality of internal thread crests may include a relief internal thread crest surface extending between a respective radially innermost internal thread crest surface and a respective internal thread load application surface, and each relief internal thread crest surface may be oriented transversely relative to the respective radially innermost internal thread crest surface and the respective internal thread load application surface.

[0041] For a better understanding of the present application, and to show how the subject matter may be carried out in practice, reference will now be made to the accompanying drawings, in which: [Brief explanation of the drawings]

[0042] [Figure 1] FIG. 1 is a perspective longitudinal cross-sectional view of a rotary cutting tool. [Figure 2] FIG. 2 is an exploded perspective longitudinal cross-sectional view of the rotary cutting tool shown in FIG. 1. [Figure 3] FIG. 3 is a side view of the replaceable cutting head shown in FIGS. 1 and 2. [Figure 4] FIG. 4 is a detailed view of FIG. 3. [Figure 5] 5 is a partial longitudinal cross-sectional view of the male coupling member shown in FIG. 4. [Figure 6] FIG. 3 is a perspective view of the tool holder shown in FIGS. 1 and 2. [Figure 7] FIG. 7 is a longitudinal cross-sectional view of the female coupling member shown in FIG. 6. [Figure 8] FIG. 8 is a detailed view of FIG. [Figure 9] 2 is a detailed view of the longitudinal cross section of the rotary cutting tool shown in FIG. 1 when the rotary cutting tool is in a locked position. DETAILED DESCRIPTION OF THE INVENTION

[0043] It will be understood that for simplicity and clarity of illustration, elements shown in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity, or several physical components may be contained within a single functional block or element. Where considered appropriate, reference numerals may be repeated among the figures to indicate corresponding or analogous elements.

[0044] In the following description, various aspects of the subject matter of the present application are described. For purposes of explanation, specific configurations and details are shown in sufficient detail to provide a thorough understanding of the subject matter of the present application. However, it will be apparent to one skilled in the art that the subject matter of the present application may be practiced without the specific details presented herein.

[0045] 1 and 2, which illustrate a rotary cutting tool 20 of the type used in milling operations, particularly facing operations, in accordance with some embodiments of the subject matter of the present application. The rotary cutting tool 20 has a tool longitudinal axis L about which the tool rotates in a rotational direction R when performing a metal cutting operation.

[0046] The rotary cutting tool 20 includes an exchangeable cutting head 22 having a head longitudinal axis A about which the exchangeable cutting head 22 rotates in a rotational direction R. The head longitudinal axis A is oriented in a forward direction D. F From rear direction D R The replaceable cutting head 22 is made from a first material, which may be a cemented carbide alloy.

[0047] The rotary cutting tool 20 also includes a tool holder 24 having a holder longitudinal axis C. The tool holder 24 is made from a second material. The second material may be harder than the first material. The second material may be steel. The interchangeable cutting head 22 may be removably retained within the tool holder 24 by a threaded engagement mechanism. Such a threaded engagement mechanism may potentially be advantageous in other types of rotary cutting operations besides those described above, such as boring or drilling.

[0048] It should be understood that the use of the terms "front" and "rear" throughout the specification and claims refers to the relative position of the interchangeable cutting head 22 of the rotary cutting tool 20 with respect to the assembled tool holder 24 shown in Figure 1. The terms "front" and "rear" may also apply to the direction of the head longitudinal axis A, which runs from side to side in Figures 3 and 4, and the direction of the holder longitudinal axis C, which runs from side to side in Figures 6 and 7, respectively. It should be understood that the tool holder 24 extends along the holder longitudinal axis C, which also runs along the front-to-back direction of the tool holder 24 itself.

[0049] 3-5, the interchangeable cutting head 22 has a front portion forming a cutting portion 26 and a rear portion forming an assembly portion 28. According to some embodiments of the subject matter of the present application, the interchangeable cutting head 22 may be formed to have a single, integral, monolithic structure, which provides the advantage that the interchangeable cutting head 22 does not have a removable cutting insert (not shown).

[0050] 3, the cutting portion 26 includes at least one cutting edge 30, 30b. In this illustrated, non-limiting example, the at least one cutting edge 30, 30b may include exactly four peripheral cutting edges. Each peripheral cutting edge 30 is formed at the intersection of a peripheral flank 32 and a peripheral rake face 34. The peripheral flank 32 is rotationally rearward of the peripheral cutting edge 30, and the peripheral rake face 34 is rotationally forward of the peripheral cutting edge 30, both relative to the direction of rotation R. The orientation of the peripheral cutting edges 30 enables the performance of a metal cutting operation.

[0051] According to some embodiments of the subject matter of the present application, the cutting portion 26 may include at least one flute 36 for evacuating chips (not shown) generated during the cutting operation. One flute 36 is associated with each peripheral cutting edge 30. The at least one cutting edge 30, 30b may include one or more leading edges 30b on an end face 37 of the cutting portion 26. In this illustrated, non-limiting example, the at least one cutting edge 30, 30b may include exactly four end edges 30b.

[0052] 3 and 4, the mounting portion 28 includes a male coupling member 38 that projects rearward from a head base surface 40. The head base surface 40 extends transversely to the head longitudinal axis A and defines a boundary between the cutting portion 26 and the mounting portion 28. That is, the cutting portion 26 is formed forward of the head base surface 40, and the mounting portion 28 is formed rearward of the head base surface 40. According to some embodiments of the present subject matter, the male coupling member 38 may be rigid. The head base surface 40 may be perpendicular to the head longitudinal axis A. The head base surface 40 is intended to abut a corresponding surface 70 (described further below) on the tool holder 24 when the rotary cutting tool 20 is in a locked position, as described below.

[0053] The male coupling member 38 includes an external thread 42. Referring to FIG. 3, the external thread 42 includes an external thread 44 that extends helically about an external thread axis B. The external thread axis B is coincident with the head longitudinal axis A. Thus, the externally threaded portion 42 and the interchangeable cutting head 22 are coaxial. Referring to FIG. 4, the external thread 44 includes a leading external thread flank surface 46 and a trailing external thread flank surface 48, and an external thread top surface 50 that extends between the leading external thread flank surface 46 and the trailing external thread flank surface 48. The leading external thread flank surface 46 and the trailing external thread flank surface 48 are oriented in opposite axial directions D. F , D R The front male thread flank surface 46 faces the front direction D F The rear male thread flank surface 48 faces the rear direction D R The leading thread flank surface 46 and the trailing thread flank surface 48 define an external thread groove 52. The external thread groove 52 extends helically about the external thread axis B and includes an external thread root surface 54. The external thread 42 has an external thread pitch PE. The external thread pitch PE is constant.

[0054] As shown in FIG. 4, in a cross-sectional view taken in an axial plane (i.e., a plane containing the male screw axis B), the male screw upper surface 50 forms a plurality of male screw crests 56, and the male screw bottom surface 54 forms a plurality of male screw roots 58.

[0055] In the same cross-sectional view, the leading thread flank surface 46 and the trailing thread flank surface 48 form a plurality of male thread load application surfaces 59a and a plurality of male thread non-load application surfaces 59b, respectively. The male thread load application surfaces 59a serve the purpose of contacting corresponding surfaces on the female thread. The male thread load application surfaces 59b are straight. Each male thread load application surface 59a has a male thread load application surface length L1 measured along the outer contour of the male thread load application surface 59a. Each male thread load application surface 59a has a male thread load application surface height H measured perpendicular to the male thread axis B. S According to some embodiments of the subject matter of the present application, the male thread load application surface 59a may be inclined at a male thread flank angle α relative to a head radial plane RP1 that is perpendicular to the male thread axis B. Preferably, the male thread flank angle α may be between 28° and 34°, and more preferably, 31°. The male thread non-load application surface 59b may be straight. The male thread non-load application surface 59b may be inclined relative to the head radial plane RP1 at the same flank angle α as the male thread load application surface 59a (but mirrored about the head radial plane RP1). The male thread 42 defines an male thread profile 60.

[0056] According to some embodiments of the subject matter of the present application, the external thread 42 is a straight thread. It should be understood that the term "straight thread" throughout the specification and claims refers to a thread in which the threads and grooves extend around the respective barrels, as do all the thread roots 58, 90, and therefore all the thread crests 56, 88 are equidistant from the thread axis. Thus, for a straight thread, the thread diameters (the major thread diameter d1 of the external thread 44 and the minor thread diameter d2 of the external thread groove 52) are equal in distance from the rearward direction D of the cutting head 22. FSuch a straight thread may be formed by threading the hollow front end of a cylindrical steel rod with an externally threaded turning insert. As the steel rod rotates and moves axially to form the external thread, the steel rod does not move radially away from the "stationary" cutting insert so that the thread has a cylindrical configuration. In particular, the thread groove extends around an externally threaded inner cylinder EC1, which is defined by the point where the external thread bottom surface 54 is closest to the external thread axis B. The external thread extends around an externally threaded outer cylinder EC2, which is defined by the point where the external thread top surface 50 is furthest from the external thread axis B. The externally threaded inner cylinder EC1 and the externally threaded outer cylinder EC2 each have the external thread axis B as their respective axes.

[0057] The plurality of external thread crests 56 respectively define the thread outer diameter (corresponding to the external thread outer cylinder EC2) of the external thread 42, and the plurality of external thread roots 58 respectively define the thread inner diameter (associated with the external thread inner cylinder EC1). Subtracting the inner diameter from the outer diameter and dividing by 2 gives the external thread height H of the external thread 42. E Equal to the male thread height H E is constant. According to some embodiments of the subject matter of the present application, the inner diameter d2 of the external thread groove 52 may be at least 75% of the outer diameter d1 of the external thread 44. Thus, the overall strength and stiffness of the external thread 42 is not adversely affected. E can be greater than one-third of the male thread pitch PE. E can be smaller than half of the male thread pitch PE. S is the male thread height H E The height of the male screw load application surface H S is the male thread height H E It can be less than three-fifths of the

[0058] According to some embodiments of the present subject matter, the external threads 42 may have between 3 and 4 axial turns. Advantageously, this allows the cutting head 22 to be manufactured using less material than other cutting heads (not shown) that have a greater number of turns. The external threads 42 may be single-start threads.

[0059] In a cross-sectional view taken on an axial plane containing the male thread axis B, each male thread root 58 is concavely curved. That is, each male thread root 58 is inwardly curved. Advantageously, such a configuration reduces stress in the male thread root 58. Each male thread root 58 extends between a first male thread root point P1 and a second male thread root point P2. The first male thread root point P1 and the second male thread root point P2 are points on the male thread profile 60 where opposite tips of each concavely curved male thread root 58 terminate and transition to adjacent non-concavely curved male thread load application surface 59a and non-load application surface 59b, respectively. The first male thread root point P1 and the second male thread root point P2 are farther from the male thread axis B than the intermediate portion of the male thread root 58. Each external thread root 58 has an external thread root length L2 measured along the external contour of the external thread root 58 between a first external thread root point P1 and a second external thread root point P2. According to some embodiments of the present subject matter, the external thread root length L2 can be greater than the external thread load application flank length L1. In particular, the external thread root length L2 can be between 3 and 6 times greater than the external thread load application flank length L1.

[0060] See particularly Figure 5. Each external thread root 58 meets a respective external thread non-load application surface 59a at a first external thread root point P1. The first external thread root point P1 is spaced apart from the external thread inner cylinder EC1 by a first external thread radial distance ERD1. The first external thread root point P1 is spaced apart from the external thread outer cylinder EC2 by a second external thread radial distance ERD2. The sum of the first external thread radial distance ERD1 and the second external thread radial distance ERD2 is the external thread height H E The first radial distance ERD1 of the male thread is equal to the height H E and the male thread height H E Advantageously, this, in combination with the concavely curved roots, results in reduced stresses in the male thread roots, thereby increasing tool life, while at the same time providing sufficient contact area for a secure threaded engagement between the male thread load application surface 59a and the female thread load application surface 91a. Further advantageously, this configuration provides an increased clearance, allowing for engagement with increased height female threads. Preferably, according to some embodiments of the subject matter of the present application, the first male thread radial distance ERD1 is less than the male thread height H Eand the male thread height H E It can be smaller than 7 / 12 of the original size.

[0061] According to some embodiments of the subject matter of the present application, in a cross-sectional view taken on an axial plane containing the male thread axis B, the first male thread root point P1 and the second male thread root point P2 can be axially separated by a point distance d. The point distance d can be greater than one-third of the male thread pitch PE. The point distance d can be less than one-half of the male thread pitch PE.

[0062] According to some embodiments of the subject matter of the present application, the first external thread radial distance ERD1 can be less than the second external thread radial distance ERD2. In other words, the first external thread root point P1 is farther from the external thread outer cylinder EC2 than from the external thread inner cylinder EC1. Each external thread root 58 meets a respective external thread load application flank 59a tangentially. Each external thread root 58 can meet a respective external thread non-load application flank 59b at a second external thread root point P2. In such a configuration, each external thread root 58 extends between one of the external thread load application flanks 59a and one of the external thread non-load application flanks 59b. In a configuration in which the external thread non-load application flanks 59b are straight, each external thread root 58 can meet a respective external thread non-load application flank 59b tangentially.

[0063] According to some embodiments of the subject matter of the present application, each external thread root 58 may be defined by a single external thread root radius R. Advantageously, this provides improved stress distribution in the external thread roots 58. Further advantageously, such a cutting head 22 is easier to manufacture. The external thread root radius R may be 0.3 mm or greater. The external thread root radius R may be 0.5 mm or less. The first external thread root point P1 and the second external thread root point P2 subtend an external thread root defining angle θ at a circular center O of an imaginary circle defined by the external thread root radius R. The external thread root defining angle θ may be greater than 90° and less than 160°. The external thread root radius R may be greater than one-third of the external thread pitch PE. The external thread root radius R may be less than one-half of the external thread pitch PE. In a configuration in which the male thread non-load application surface (59b) is straight and each male thread valley 58 tangentially meets its respective male thread non-load application surface 59b at a second male thread valley point P2, the male thread valley subtending angle θ can be greater than or equal to 120° and less than or equal to 140°.

[0064] According to some embodiments of the subject matter of the present application, each of the plurality of external thread crests 56 includes a radially outermost external thread crest surface 61 a. The radially outermost external thread crest surfaces 61 a are parallel to the external thread axis B and may be collinear with one another. Thus, the radially outermost portion of the external thread top surface 50 may be on the external thread outer cylinder EC2.

[0065] 3 and 4, the male coupling member 38 includes a front bearing portion 62. The front bearing portion 50 is located in front of the male threads 42. The front bearing portion 62 is oriented in the rearward direction D R 1 includes a front head abutment surface 64 that tapers radially inward toward the head longitudinal axis A. That is, the front head abutment surface 64 has a conical shape that faces radially outward. Note that the front head abutment surface 64 is intended to abut against a corresponding surface 94 (described further below) on the tool holder 24 when the rotary cutting tool 20 is in a locked position, as described below.

[0066] It should be understood that the use of the terms "radially inward / inwardly" and "radially outward / outwardly" throughout the specification and claims refers to relative positions in directions perpendicular to the head longitudinal axis A and / or holder longitudinal axis C, toward and away from the respective axes in Figures 3-4 and 7.

[0067] Next, referring to FIGS. 6 to 8, the tool holder 24 is rotated in the forward direction D F From rear direction D R The tool holder 24 has a holder longitudinal axis C extending to a holder front surface 70. The tool holder 24 includes a holder peripheral surface 71 extending about the holder longitudinal axis C. The tool holder 24 includes a female coupling member 68 extending rearwardly from a holder front surface 70. The holder front surface 70 extends transversely to the holder longitudinal axis C. According to some embodiments of the subject matter of the present application, the holder front surface 70 may be perpendicular to the holder longitudinal axis C.

[0068] The female coupling member 68 includes an internal thread 72. As shown in a longitudinal cross-section of the female coupling member 68 including the internal thread axis D (i.e., FIG. 7), the internal thread 72 includes internal thread ridges 74 that extend helically about the internal thread axis D. The internal thread axis D is coincident with the holder longitudinal axis C. Thus, the internal thread 72 is coaxial with the tool holder 24. The internal thread ridges 74 include a leading internal thread flank surface 76 and a trailing internal thread flank surface 78, and an internal thread top surface 80 that extends between the leading internal thread flank surface 76 and the trailing internal thread flank surface 78. The leading internal thread flank surface 76 and the trailing internal thread flank surface 78 extend in opposite axial directions D. F , D R The front female thread flank surface 76 faces the front direction D F The rear female thread flank surface 78 faces the rear direction D R The leading and trailing female thread flank surfaces 76, 78 define a female thread groove 82. The female thread 72 has a female thread pitch PI. According to some embodiments of the subject matter of the present application, the female thread pitch PI may be constant. The female thread pitch PI may be the same as the male thread pitch PE.

[0069] The female thread groove 82 extends helically around the female thread axis D and includes a female thread root surface 84. In a cross-sectional view taken in an axial plane (i.e., a plane containing the female thread axis D), the female thread top surface 80 defines a plurality of female thread crests 88, and the female thread root surface 84 defines a plurality of female thread roots 90. The tool holder 24 has a holder thickness T measured radially between the holder outer circumferential surface 71 and the female thread top surface 80.

[0070] See particularly Figures 7 and 8. In a cross-sectional view taken in an axial plane including the female thread axis D (i.e., Figure 7), the leading female thread flank surface 76 and the trailing female thread flank surface 78 form a plurality of female thread load application surfaces 91a and a plurality of female thread non-load application surfaces 91b, respectively. According to some embodiments of the subject matter of the present application, the female thread load application surface 91a may be straight. The female thread load application surface 91a may be inclined at a female thread flank angle β with respect to a holder radial plane RP2 that is perpendicular to the female thread axis D. Preferably, the female thread flank angle β may be 31°. The female thread flank angle β may have the same value as the male thread flank angle α so that a continuous surface for facial abutment can be realized between the female thread load application surface 91a and the male thread load application surface 59a. The female thread non-load application surface 91b may be straight. The female thread non-load application surface 91b may be inclined in the same manner as the female thread load application surface 91a (but is mirrored about the holder radial plane RP2).

[0071] According to some embodiments of the subject matter of the present application, the internal thread 72 may be a straight thread. In particular, the internal thread ridge 74 extends around an internally threaded inner cylinder IC1 defined by the point where the internal thread top surface 80 is closest to the internal thread axis D. The internal thread groove 82 extends around an internally threaded outer cylinder IC2 defined by the point where the internal thread bottom surface 84 is furthest from the internal thread axis D. The internally threaded inner cylinder IC1 and the internally threaded outer cylinder IC2 each have the internal thread axis D as their axis.

[0072] The plurality of crests 88 define an inner diameter (corresponding to the inner cylindrical portion IC1) of the female thread 72, and the plurality of roots 90 define an outer diameter (associated with the inner cylindrical portion IC2) of the female thread 72. Subtracting the inner diameter from the outer diameter and dividing by 2 gives the female thread height H of the female thread 72. I Equal to the female thread height H I can be kept constant. Female thread height H I can be greater than one-third of the female thread pitch PI. I may be half the female thread pitch PI.

[0073] According to some embodiments of the subject matter of the present application, the internal thread 72 may have between 3 and 4 axial turns. The internal thread 72 may be a single start thread.

[0074] According to some embodiments of the subject matter of the present application, each of the plurality of female thread crests 88 may include a radially innermost female thread crest surface 96a. The radially innermost female thread crest surfaces 96a may be parallel to the female thread axis D and may be collinear with one another. Thus, the radially innermost portion of the female thread top surface 80 may be located on the female thread inner cylinder IC1. Each of the plurality of female thread roots 90 may include a radially outermost female thread root surface 96b. The radially outermost male thread root surfaces 96b may be parallel to the female thread axis D and may be collinear with one another. Thus, the radially outermost portion of the female thread root surface 84 may be located on the female thread outer cylinder IC2.

[0075] According to some embodiments of the subject matter of the present application, each of the plurality of female thread crests 88 can include a relief female thread crest surface 98, which extends between a respective radially innermost female thread crest surface 96a and a respective female thread load application surface 91a. In a longitudinal cross-sectional view of the female coupling member 68 including the female thread axis D (i.e., FIG. 8), each relief female thread crest surface 98 can be oriented transversely to a respective radially outermost female thread crest surface 96b and a respective female thread load application surface 91a. The relief female thread crest surface 98 can merge with a respective female thread load application surface 91a at a female thread apex P'. The female thread apex P' is spaced from the female thread inner cylinder IC1 by a first female thread radial distance IRD1. The female thread apex P' is spaced from the female thread outer cylinder IC2 by a second female thread radial distance IRD2. The sum of the first female thread radial distance IRD1 and the second female thread radial distance IRD2 is the female thread height H I The first radial distance IRD1 of the female thread is equal to the height H I and the female thread height H I Smaller than half of the female thread height H I By increasing , the holder thickness T also increases. Increasing the holder thickness has been found to reduce stresses in the female thread roots 90.

[0076] 6 and 7, the female coupling member 68 includes a front support portion 92. The front support portion 92 is located in front of the female thread 72. The front support portion 92 extends in the rearward direction D R 1 and 2. The front holder abutment surface 94 includes a front holder abutment surface 94 that tapers radially inward toward the holder longitudinal axis C. That is, the front holder abutment surface 94 has a radially inward facing conical shape. The front holder abutment surface 94 is configured and dimensioned to be complementary to the front head abutment surface 64 described above.

[0077] The assembly of a rotary cutting tool 20 is known, for example, from US 6,485,220 B2, which is incorporated herein by reference in its entirety. It is noted that the rotary cutting tool 20 is adjustable between a released position and a locked (or assembled) position.

[0078] To adjust the rotary cutting tool 20 to the locked position, the external threads 42 are threaded (ie, rotated) into the internal threads 72 .

[0079] In the locked position, the male coupling member 38 is removably retained within the female coupling member 68. Additionally, the male threads 42 and the female threads 72 threadably engage with one another. Referring now to FIG. 9 , the front head abutment surface 64 abuts the front holder abutment surface 94. According to some embodiments of the subject matter of the present application, the rearward-facing head base surface 40 may abut the forward-facing holder front surface 70. The rearward female thread flank surface 78 may abut the frontward male thread flank surface 46. The frontward female thread flank surface 76 may be spaced apart from the rearward male thread flank surface 48. The female thread top surface 80 may be spaced apart from the male thread root surface 54. The female thread root surface 84 may be spaced apart from the male thread top surface 50. To the above, in a cross-sectional view taken in an axial plane containing the longitudinal axis L, each of the female thread load application surfaces 91 a abuts a respective male thread load application surface 59 a. Each of the female thread non-load application surfaces 91b is spaced from a respective male thread non-load application surface 59b. Each of the female thread crests 88 is spaced from a respective male thread root 58. Each of the female thread roots 90 is spaced from a respective male thread crest 56.

[0080] Although the subject matter of the present application has been described in some detail, it should be understood that various substitutions and modifications can be made without departing from the spirit or scope of the invention as hereinafter claimed.

Claims

1. Forward direction (D Ｆ ) to the rear (D Ｒ ), wherein the interchangeable cutting head (22) has a head longitudinal axis (A) extending from a front portion forming a cutting portion (26) with at least one cutting edge (30); a rear portion forming an assembly portion (28), The assembly portion (28) has a male coupling member (38), The male coupling member (38) has external threads (42) and projects rearward from the head base surface (40); the head base surface (40) extends transversely to the head longitudinal axis (A) and defines a boundary between the cutting portion (26) and the assembly portion (28); The external screw (42) has external threads (44); The male thread (44) extends spirally around the male thread axis (B) and includes a leading male thread flank surface (46) and a trailing male thread flank surface (48), and a male thread upper surface (50) extending between the leading male thread flank surface (46) and the trailing male thread flank surface (48), The leading and trailing external thread flank surfaces (46, 48) are generally axially opposed (D Ｆ , D Ｒ ) and bounding an external helical thread groove (52) with an external thread base surface (54); The external thread (42) has a constant external thread pitch PE, The external thread (42) has a constant external thread height H Ｅ and the external thread (42) of the male coupling member (38) is a straight thread defined by an externally threaded inner cylinder (EC1) and an externally threaded outer cylinder (EC2); The male threaded inner cylindrical body (EC1) has an inner diameter d ２ and The male thread outer cylinder (EC2) has an outer diameter d １ and In a cross-sectional view taken on an axial plane including the male screw shaft (B), the leading and trailing external thread flank surfaces (46, 48) respectively define a plurality of straight external thread load application surfaces (59a) and a plurality of straight external thread non-load application surfaces (59b); The external thread root surface (54) defines a plurality of concavely curved external thread roots (58); Each of the male thread roots (58) extends between a first male thread root point (P1) and a second male thread root point (P2) and merges with a respective male thread load application surface (59a) at the first male thread root point (P1); the second male thread root point (P2) is a point where the male thread non-load application surface (59b) meets the respective male thread non-load application surface (59b), the male thread non-load application surface (59b) is a straight surface, and each male thread root (58) meets the respective male thread non-load application surface (59b) in a tangential direction at the second male thread root point (P2); the first external thread root point (P1) is spaced from the externally threaded inner cylindrical body (EC1) by a first external thread radial distance ERD1; The first radial distance ERD1 of the male thread is Ｅ and the male thread height H Ｅ less than two-thirds of The replaceable cutting head (22), wherein the first external thread radial distance ERD1 is greater than 5 / 12 of the external thread height H E and less than 7 / 12 of the external thread height H E .

2. Each of the male thread load application surfaces (59a) has a male thread load application surface length L1 measured along the outer shape of the male thread load application surface (59a), Each of the external thread roots (58) has an external thread root length L2 measured along the external contour of the external thread root (58) between the first external thread root point (P1) and the second external thread root point (P2); 2. The replaceable cutting head (22) of claim 1, wherein the male thread root length L2 is between 3 and 6 times greater than the male thread load application flank length L1.

3. The inner diameter d ２ is the outer diameter d １ 2. The replaceable cutting head (22) of claim 1, wherein the cutting head (22) has a diameter of at least 75%.

4. The male thread height H Ｅ 2. The replaceable cutting head (22) of claim 1, wherein is greater than one-third of the external thread pitch PE and less than half of the external thread pitch PE.

5. The interchangeable cutting head (22) of claim 1, wherein each of the external thread roots (58) is defined by a single external thread root radius R.

6. The first male thread root point (P1) and the second male thread root point (P2) define a male thread root defining angle θ at a circle center (O) of an imaginary circle defined by the male thread root radius R, 6. The cutting head (22) of claim 5, wherein the external thread root defining angle θ is greater than or equal to 90° and less than or equal to 160°.

7. The male thread non-load application surface (59b) is straight, Each of the male thread roots (58) meets a respective male thread non-load application surface (59b) tangentially at the second male thread root point (P2); 7. The cutting head (22) of claim 6, wherein the external thread root defining angle θ is greater than or equal to 120° and less than or equal to 140°.

8. 6. The interchangeable cutting head (22) of claim 5, wherein the external thread root radius R is greater than one-third of the external thread pitch PE and less than half of the external thread pitch PE.

9. 2. The interchangeable cutting head (22) of claim 1, wherein each of the external thread roots (58) meets a respective external thread load application surface (59a) tangentially.

10. 2. The interchangeable cutting head (22) of claim 1, wherein each of the external thread roots (58) meets the respective external thread non-load-applying surface (59b) at the second external thread root point (P2).

11. 11. The interchangeable cutting head (22) of claim 10, wherein the externally threaded non-load-applying surface (59b) is straight.

12. 12. The interchangeable cutting head (22) of claim 11, wherein each said external thread root (58) meets a respective said external thread non-load-applying surface (59b) tangentially.

13. The first external thread root point (P1) and the second external thread root point (P2) are axially spaced apart by a point distance d, 2. The interchangeable cutting head (22) of claim 1, wherein the point distance d is greater than one-third of the external thread pitch PE and less than half of the external thread pitch PE.

14. In the cross-sectional view taken on an axial plane including the male screw shaft (B), The upper surface (50) of the external thread forms a plurality of external thread crests (56); Each of the plurality of male thread crests (56) has a radially outermost male thread crest surface (61a), 2. The replaceable cutting head (22) according to claim 1, wherein the radially outermost external thread crest surfaces (61a) are parallel to the external thread axis (B) and are collinear with one another.

15. Forward direction (D Ｆ ) to the rear (D Ｒ 1. A rotary cutting tool (20) having a longitudinal axis (A) extending from a a tool holder (24) having a holder longitudinal axis (C); An interchangeable cutting head (22) according to claim 1, which is threadedly coupled to a tool holder (24); A rotary cutting tool (20) comprising:

16. The replaceable cutting head (22) is made from a first material; the tool holder (24) is made from a second material; The rotary cutting tool (20) of claim 15, wherein the first material is harder than the second material.

17. The tool holder (24) has a female coupling member (68) having internal threads (72) extending rearward from a holder front face (70); said holder front face (70) extending transversely to said holder longitudinal axis (C); The rotary cutting tool (20) a release position in which the female thread (72) and the male thread (42) are not threaded together; a locked position in which the male coupling member (38) is removably retained within the female coupling member (68) with the female threads (72) and the male threads (42) threadedly engaging one another; The rotary cutting tool (20) of claim 15, wherein the rotary cutting tool (20) is adjustable between

18. 18. The rotary cutting tool (20) of claim 17, wherein the internal threads (72) of the female coupling member (68) are straight threads defined by an internally threaded inner cylinder (IC1) and an internally threaded outer cylinder (IC2).

19. The internal screw (72) has internal threads (74); The female thread (74) extends helically around the female thread axis (D) and includes a leading female thread flank surface (76) and a trailing female thread flank surface (78), and an upper female thread surface (80) extending between the leading female thread flank surface (76) and the trailing female thread flank surface (78), The leading and trailing female thread flank surfaces (76, 78) are generally axially opposed (D Ｆ , D Ｒ ) and bounding an internal helical thread groove (82) with an internal thread root surface (84); The front male thread flank surface (46) and the front female thread flank surface (76) are Ｆ ) facing The rear male thread flank surface (48) and the rear female thread flank surface (78) are Ｒ ) facing 18. The rotary cutting tool (20) of claim 17, wherein in the locked position, the trailing female thread flank surface (78) abuts the leading male thread flank surface (46).

20. In the locked position, the leading female thread flank surface (76) is spaced from the trailing male thread flank surface (48); The female thread top surface (80) is spaced from the male thread bottom surface (54), 20. The rotary cutting tool (20) of claim 19, wherein the female thread bottom surface (84) is spaced from the male thread top surface (50).

21. In a cross-sectional view taken on an axial plane including the female screw shaft (D), The front female thread flank surface (76) and the rear female thread flank surface (78) respectively form a plurality of female thread non-load application surfaces (91b) and a plurality of female thread load application surfaces (91a); 20. The rotary cutting tool (20) of claim 19, wherein the internal thread load application surface (91a) is straight.

22. The upper surface (80) of the internal thread forms a plurality of internal thread crests (88); Each of the plurality of female thread crests (88) has a radially innermost female thread crest surface (96a) that is parallel to the female thread axis (D), 20. The rotary cutting tool (20) of claim 19, wherein the innermost radial thread crest surfaces (96a) are collinear with one another.

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