Replaceable cutting head and rotary cutting tool with external thread featuring concave curved tooth root

Abstract

A rotary cutting tool includes a replaceable cutting head and a tool holder. The replaceable cutting head includes a front cutting portion and a rear mounting portion. The mounting portion includes a male coupling member comprising an external thread defined by an outer inner cylinder and an outer outer cylinder. The external thread has a concave, curved external thread root, both of which merge with a corresponding straight external load surface at a first external thread root point. The first external thread root point is spaced from the outer inner cylinder by a first external radial distance. The first external 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 comprising an internal thread. When the rotary cutting tool is in a locked position, the external thread engages with the internal thread.

Description

Technical Field

[0001] The subject matter of this application relates to a type of rotary cutting tool in which a replaceable cutting head having a male coupling is removably held in a female coupling of a tool holder by means of a threaded coupling mechanism. Background Technology

[0002] Rotary cutting tools may be equipped with a threaded connection mechanism or "tool connector" for securely holding the replaceable cutting head within the tool holder.

[0003] The replaceable cutting head may include a male coupling component, and the tool holder may include a female coupling component. The male coupling component may include external threads. The female coupling component may include internal threads corresponding to the external threads on the male coupling component.

[0004] External threads have an external load-bearing surface that abuts the corresponding surface on the internal thread. The external load-bearing surface is typically straight. External threads have an external root that merges with the corresponding external load-bearing surface.

[0005] In some of these rotary cutting tools, the outer threads are generally straight and have a small radius where they meet the corresponding external load surface. Examples of such rotary cutting tools are disclosed, for example, in US 6,485,220. A disadvantage of such external threads is that they are prone to stress fracture in the region where the outer threads adjoin the corresponding external load surface (i.e., at the small radius).

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

[0007] In some other rotary cutting tools, the external thread has a tooth root defined by one or more radii. Examples of such rotary cutting tools are disclosed in US 4,549,754, US 6,196,598B1, US 7,997,842 B2 and US 9,874,058 B2.

[0008] The purpose of this application is to provide a replaceable cutting head with external threads that has improved stress reduction.

[0009] The purpose of this application is to provide a replaceable cutting head with external threads that has an improved stress concentration distribution. Summary of the Invention

[0010] According to a first aspect of the subject matter of this application, a replaceable cutting head is provided, having a head longitudinal axis extending in a forward to rearward direction, including...

[0011] The front portion, which is formed by a cut portion including at least one cut edge; and

[0012] The rear portion forms a mounting portion, which includes a male connecting member with external threads projecting rearward from the head base surface, the head base surface extending laterally relative to the longitudinal axis of the head, and defining the boundary between the cutting portion and the mounting portion, wherein:

[0013] The external thread includes an external thread ridge that extends helically about the external thread axis, and includes a front outer side surface and a rear outer side surface and an outer top surface extending therebetween.

[0014] The front outer side surface and the rear outer side surface generally face and define a helical external thread groove, including the outer bottom surface, along opposite axial directions.

[0015] External threads have a constant external thread pitch;

[0016] External threads have a constant external thread height;

[0017] The external thread of the male connector is a straight thread, defined by an inner cylinder and an outer cylinder. The inner cylinder has a smaller thread diameter, and the outer cylinder has a larger thread diameter.

[0018] In a cross-sectional view taken along an axial plane containing the axis of the external thread:

[0019] The front outer side surface and the rear outer side surface respectively form multiple straight external load surfaces and multiple external non-load surfaces;

[0020] The outer bottom surface forms multiple concave, curved external thread roots, each external thread root extending between a first external thread root point and a second external thread root point, and merging with a corresponding outer load surface at the first external thread root point. The first external thread root point is spaced from the outer inner cylinder by a first outer radial distance; and

[0021] The first external radial distance is greater than the external thread height H. E One-third of the total length, and less than the external thread height H. E Two-thirds.

[0022] According to a second aspect of the subject matter of this application, a rotary cutting tool is provided, having a longitudinal axis and extending in a forward to rearward direction, comprising:

[0023] A tool retainer having a longitudinal axis and a replaceable cutting head of the type described above, the replaceable cutting head being threaded into the tool retainer.

[0024] It is understood that the above is a summary, and the features described below may be applied to the subject matter of this application in any combination; for example, any of the following features may be applied to a replaceable cutting head or a rotary cutting tool:

[0025] The first external radial distance can be greater than the external thread height H. E Five-twelfths of the total length, and less than the external thread height H. E Seven-twelfths.

[0026] Each external load surface may have an external load surface length measured along its profile. Each external thread root may have an external thread root length measured along its profile between a first external thread root point and a second external thread root point. The external thread root length may be between three and six times the length of the external load surface.

[0027] The diameter of a small thread can be at least 75% of the diameter of a large thread.

[0028] External threads can have between three and four turns in the axial direction.

[0029] External threads can be single-start threads.

[0030] The height of the external thread can be greater than one-third of the external thread pitch and less than half of the external thread pitch.

[0031] Each external thread root can be defined by a single external thread root radius.

[0032] The external tooth base radius R can be greater than or equal to 0.3 mm and less than or equal to 0.5 mm.

[0033] The first and second external root points can be located at the center of an imaginary circle defined by the radius of the external root, facing each other at an opposing angle to the external root. The opposing angle θ of the external root can be greater than or equal to 90° and less than or equal to 160°.

[0034] The external unloaded surface may be straight. Each external thread root may merge tangentially with the corresponding external unloaded surface at the second external thread root point. The external thread root angle θ may be greater than or equal to 120° and less than or equal to 140°.

[0035] The radius of the external thread root can be greater than one-third of the external thread pitch and less than half of the external thread pitch.

[0036] Each external thread root can be tangentially joined to the corresponding external load surface.

[0037] Each external thread root can merge with the corresponding external unloaded surface at the second external root point.

[0038] The external unloaded surface can be straight.

[0039] Each external thread root can be tangentially joined to the corresponding external unloaded surface.

[0040] The first external thread root point and the second external thread root point can be spaced apart in the axial direction. The distance between the two points can be greater than one-third of the external thread pitch PE and less than half of the external thread pitch.

[0041] The external load surface may be inclined at an outer surface angle relative to the head radial plane perpendicular to the external thread axis. The outer surface angle is in the range of 28° < α < 34°.

[0042] In the cross-sectional view taken along an axial plane containing the external thread axis, the outer top surface may form a plurality of external thread crests, each including a radially outermost external crest surface, which may be parallel to the external thread axis and collinear with each other.

[0043] In the cross-sectional view taken along an axial plane containing the external thread axis, each straight external load surface may have an external load surface height measured perpendicular to the external thread axis. The external load surface height may be greater than the external thread height H. E One-third of the height, and less than three-fifths of the external thread height.

[0044] The replaceable cutting head can be made of a first material. The tool holder can be made of a second material. The first material can be harder than the second material.

[0045] The tool retainer may have a female coupling member with an internal thread extending rearward from the front surface of the retainer, the front surface of the retainer extending laterally relative to the longitudinal axis of the retainer. The rotary cutting tool may be adjustable between a released position and a locked position, in which the internal and external threads may not thread-engage with each other, and in which the male coupling member may be removably secured in the female coupling member, wherein the internal and external threads are thread-engaged with each other.

[0046] The internal thread of the female connector can be a straight thread, which is defined by an inner cylinder and an outer cylinder.

[0047] Internal threads can have a constant internal thread pitch, which can be the same as the external thread pitch.

[0048] The internal thread may include an internal thread ridge extending helically about the internal thread axis, and includes a front inner side surface and a rear inner side surface, and an inner top surface extending therebetween. The front and rear inner side surface surfaces may face generally in opposite axial directions and define a helical internal thread groove including an inner bottom surface. The front outer side surface and the front inner side surface surfaces may face in a forward direction. The rear outer side surface and the rear inner side surface surfaces may face in a rearward direction. In the locked position, the rear inner side surface surface may abut the front outer side surface surface.

[0049] In the locked position, the front inner side surface may be spaced apart from the rear outer side surface. The inner top surface may be spaced apart from the outer bottom surface. The inner bottom surface may be spaced apart from the outer top surface.

[0050] In a cross-sectional view taken along an axial plane containing the internal thread axis, the front inner side surface and the rear inner side surface can respectively form multiple internal non-loaded surfaces and multiple internal loaded surfaces, and the internal loaded surfaces can be straight.

[0051] The inner top surface may form multiple internal thread crests, each of which includes a radially innermost inner crest surface that may be parallel to the internal thread axis and may be collinear with each other.

[0052] Each of the plurality of internal thread crests may include an unloading internal crest surface extending between a corresponding radially innermost internal crest surface and a corresponding internal load surface. Each unloading internal crest surface may be laterally oriented relative to the corresponding radially innermost internal crest surface and the corresponding internal load surface. Attached Figure Description

[0053] To better understand this application and to show how it can be implemented in practice, reference will now be made to the accompanying drawings, in which:

[0054] Figure 1 A perspective longitudinal section view of the rotary cutting tool;

[0055] Figure 2 for Figure 1 The exploded perspective longitudinal section view of the rotary cutting tool is shown in the figure;

[0056] Figure 3 for Figure 1 and Figure 2 The side view of the replaceable cutting head is shown in the image.

[0057] Figure 4 for Figure 3 Details;

[0058] Figure 5 for Figure 4A partial longitudinal cross-sectional view of the male connector component is shown in the figure;

[0059] Figure 6 for Figure 1 and Figure 2 The tool holder shown in the figure has a perspective view;

[0060] Figure 7 for Figure 6 The longitudinal cross-sectional view of the female connector shown in the figure;

[0061] Figure 8 for Figure 7 Details; and

[0062] Figure 9 For when the rotary cutting tool is in the locked position, Figure 1 Details of the longitudinal section view of the rotary cutting tool shown in the image.

[0063] It will be recognized that, for the sake of simplicity and clarity, the elements shown in the figures are not necessarily drawn to scale. For example, for clarity, the dimensions of some elements may be enlarged relative to other elements, or several physical components may be included in a single functional block or element. Where deemed appropriate, reference numerals may be repeated in the figures to indicate corresponding or similar elements. Detailed Implementation

[0064] In the following description, various aspects of the subject matter of this application will be described. For purposes of explanation, specific constructions and details are elaborated sufficiently to provide a thorough understanding of the subject matter of this application. However, it will also be apparent to those skilled in the art that the subject matter of this application can be practiced without the specific constructions and details set forth herein.

[0065] First, pay attention Figure 1 and Figure 2 , Figure 1 and Figure 2 A rotary cutting tool 20 of the type for milling operations (specifically, end milling) is shown as an embodiment of the subject matter of this application. The rotary cutting tool 20 has a tool longitudinal axis L, and when performing a metal cutting operation, the tool rotates about the tool longitudinal axis L in the rotational direction R.

[0066] The rotary cutting tool 20 includes a replaceable cutting head 22 with a head longitudinal axis A, which rotates about the head longitudinal axis A in the rotation direction R. The head longitudinal axis A moves forward D... F Towards D R Directional extension. The replaceable cutting head 22 is made of a first material. The first material may be cemented carbide.

[0067] The rotary cutting tool 20 also includes a tool holder 24 having a longitudinal axis C. The tool holder 24 is made of a second material. The second material may be harder than the first material. The second material may be steel. A replaceable cutting head 22 may be removably held in the tool holder 24 by means of a threaded connection mechanism. Such a threaded connection mechanism may be advantageous for other types of rotary cutting operations besides those described above, such as, for example, reaming or drilling.

[0068] It should be recognized that the terms "forward" and "backward" throughout the specification and claims refer to the relative position of the replaceable cutting head 22 with respect to the tool holder 24 of the assembled rotary cutting tool 20, such as... Figure 1 The terms "forward" and "backward" can also be found in [the context of the text]. Figure 3 and Figure 4 The longitudinal axis A of the head points to the left and right, and respectively in... Figure 6 and Figure 7 The retainer's longitudinal axis C is applied in a direction oriented to the left and right. It is understood that the tool retainer 24 also extends along its own forward to backward direction along the retainer's longitudinal axis C.

[0069] Now refer to Figures 3 to 5 The replaceable cutting head 22 has a front portion forming the cutting portion 26 and a rear portion forming the mounting portion 28. According to some embodiments of the subject matter of this application, the replaceable cutting head 22 can be formed as a single, integrated monolithic structure. This provides the advantage that the replaceable cutting head 22 does not have a removable cutting blade (not shown).

[0070] Reference Figure 3 The cutting portion 26 includes at least one cutting edge 30, 30b. In this non-limiting example shown in the figures, the at least one cutting edge 30, 30b may specifically include four peripheral cutting edges. Each peripheral cutting edge 30 is formed at the intersection of the peripheral front cutting surface 32 and the peripheral rear cutting surface 34. Relative to the rotation direction R, the peripheral front cutting surface 32 is rotatably located behind the peripheral cutting edge 30, and the peripheral rear cutting surface 34 is rotatably located in front of the peripheral cutting edge 30. The orientation of the peripheral cutting edges 30 allows the metal cutting operation to be performed.

[0071] According to some embodiments of the subject matter of this application, the cutting portion 26 may include at least one groove 36 for draining chips (not shown) generated during the cutting operation. One groove 36 is associated with each outer peripheral cutting edge 30. At least one cutting edge 30, 30b may include one or more end cutting edges 30b at the end face 37 of the cutting portion 26. In this non-limiting example shown in the drawings, at least one cutting edge 30, 30b may specifically include four end cutting edges 30b.

[0072] Now refer to Figure 3 and Figure 4 The mounting portion 28 includes a male connecting member 38 projecting rearward from the head base surface 40. The head base surface 40 extends laterally relative to the longitudinal axis A of the head and defines the boundary between the cutting portion 26 and the mounting portion 28. That is, the cutting portion 26 is formed in front of the head base surface 40, and the mounting portion 28 is formed behind the head base surface 40. According to some embodiments of the subject matter of this application, the male connecting member 38 may be rigid. The head base surface 40 may be perpendicular to the longitudinal axis A of the head. The head base surface 40 is intended to abut a corresponding surface 70 on the tool holder 24 (described further below) when the rotary cutting tool 20 is in the locked position, as will be described below.

[0073] The male connector 38 includes an external (male) thread 42. (See reference...) Figure 3 The external thread 42 includes an external thread ridge 44 that extends helically about the external thread axis B. The external thread axis B coincides with the longitudinal axis A of the head. Therefore, the external thread portion 42 and the replaceable cutting head 22 are coaxial. (Refer to...) Figure 4 The external thread ridge 44 includes a front outer side surface 46 and a rear outer side surface 48, and an outer top surface 50 extending therebetween. The front outer side surface 46 and the rear outer side surface 48 are along opposite axial directions D. F D R Facing, wherein the front outer side surface 46 is along the forward direction D F Facing, and the rear outer side surface 48 along the rearward direction D R Facing the viewer, the front outer side surface 46 and the rear outer side surface 48 define the external thread groove 52. The external thread groove 52 extends helically about the external thread axis B and includes an outer bottom surface 54. The external thread 42 has an external thread pitch PE. The external thread pitch PE is constant.

[0074] like Figure 4 As shown in the cross-sectional view taken along the axial plane (i.e., the plane containing the external thread axis B), the outer top surface 50 forms a plurality of external thread crests 56, and the outer bottom surface 54 forms a plurality of external thread roots 58.

[0075] In the same cross-sectional view, the front outer side surface 46 and the rear outer side surface 48 respectively form a plurality of external load surfaces 59a and a plurality of external non-load surfaces 59b. The external load surfaces 59a are for contacting the corresponding surfaces on the internal (female) threads. The external load surfaces 59a are straight. Each external load surface 59a has an external load surface length L1, which is measured along the contour of the external load surface 59a. Each external load surface 59a has an external load surface height H. S The external load surface 59a is measured perpendicular to the external thread axis B. According to some embodiments of the subject matter of this application, the external load surface 59a may be inclined with respect to the head radial plane RP1 at an external lateral angle α, which is perpendicular to the external thread axis B. Preferably, the external lateral angle α may be between 28° and 34°, and more preferably 31°. The external non-load surface 59b may be straight. The external non-load surface 59b may be inclined with respect to the head radial plane RP1 at the same lateral angle α as the external load surface 59a (but reflected with respect to the head radial plane RP1). The external thread 42 defines the external thread form 60.

[0076] According to some embodiments of the subject matter of this 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 thread ridge and thread groove extend about a corresponding cylinder, and therefore, like all thread roots 58, 90, all thread crests 56, 88 are equidistant from the thread axis. Thus, in a straight thread, the two thread diameters (the major thread diameter d1 of the external thread ridge 44 and the minor thread diameter d2 of the external thread groove 52) are in the rearward direction D of the cutting head 22. F The upper part is constant. Such straight threads can be formed by threading the hollow front end of a cylindrical steel rod to an external turning tool. As the steel rod rotates and moves axially to form the external thread, the external thread does not move radially away from the "static" cutting tool, thus giving the thread a cylindrical structure. Specifically, the thread groove extends around an outer inner cylinder EC1, which is defined by the point on its outer bottom surface 54 closest to the external thread axis B. The external thread ridge extends around an outer outer cylinder EC2, which is defined by the point on its outer top surface 50 furthest from the external thread axis B. The outer inner cylinder EC1 and outer outer cylinder EC2 have the external thread axis B as their respective axis.

[0077] Specifically, multiple external thread crests 56 define the major thread diameter of the external thread 42 (which corresponds to the outer outer cylinder EC2), and multiple external thread roots 58 define the minor thread diameter of the external thread 42 (which is associated with the outer inner cylinder EC1). The difference between the major and minor diameters, divided by two, equals the external thread height H of the external thread 42. E External thread height HE The diameter d2 of the small thread in the external thread groove 52 can be at least 75% of the diameter d1 of the large thread in the external thread ridge 44. Therefore, the overall strength and stiffness of the external thread 42 are not adversely affected. External thread height H E It can be greater than one-third of the external thread pitch PE. External thread height H E It can be less than half of the external thread pitch PE. External load surface height H S It can be greater than the external thread height H E One-third. External load surface height H S It can be less than the external thread height H E Three-fifths of it.

[0078] According to some embodiments of the subject matter of this application, the external thread 42 may have between three and four turns in the axial direction. Advantageously, this allows the cutting head 22 to be manufactured using less material than other cutting heads (not shown) with more turns. The external thread 42 may be a single-start thread.

[0079] In a cross-sectional view taken along an axial plane containing the external thread axis B, each external thread root 58 is concavely curved. That is, each external thread root 58 curves inward. Advantageously, this configuration reduces stress at the external thread root 58. Each external thread root 58 extends between a first external thread root point P1 and a second external thread root point P2. The first external thread root point P1 and the second external thread root point P2 are points on the external thread form 60 where the opposite ends of each concavely curved external thread root 58 terminate and transition into adjacent non-concave curved external load surfaces 59a and external unload surfaces 59b, respectively. The first external thread root point P1 and the second external thread root point P2 are farther from the external thread axis B than the middle portion of the external thread root 58. Each external thread root 58 has an external thread root length L2, which is measured along the profile of the external thread root 58 between the first external thread root point P1 and the second external thread root point P2. According to some embodiments of the subject matter of this application, the external thread root length L2 may be greater than the external load surface length L1. In particular, the external thread root length L2 may be between three and six times the external load surface length L1.

[0080] Special reference Figure 5 Each external thread root 58 merges with the corresponding external load surface 59a at the first external root point P1. The first external root point P1 is spaced from the outer inner cylinder EC1 by a first external radial distance ERD1. The first external root point P1 is spaced from the outer outer cylinder EC2 by a second external radial distance ERD2. The sum of the first external radial distance ERD1 and the second external radial distance ERD2 is equal to the external thread height H. EThe first external radial distance ERD1 is greater than the external thread height H. E One-third of the total length, and less than the external thread height H. E Two-thirds. Advantageously, in combination with the concave curved tooth root, this provides a reduction in stress at the root of the external thread, thereby increasing tool life, while simultaneously providing sufficient contact area between the outer load surface 59a and the inner load surface 91a for a secure threaded connection. More advantageously, this configuration provides an enlarged clearance to allow thread engagement with an internal thread having an increased height. Preferably, according to some embodiments of the subject matter of this application, the first external radial distance ERD1 may be greater than the external thread height H. E Five-twelfths of the total length, and less than the external thread height H. E Seven-twelfths.

[0081] According to some embodiments of the subject matter of this application, in a cross-sectional view taken along an axial plane containing the external thread axis B, the first external thread root point P1 and the second external thread root point P2 may be spaced apart by a point distance d in the axial direction. The point distance d may be greater than one-third of the external thread pitch PE. The point distance d may be less than half of the external thread pitch PE.

[0082] According to some embodiments of the subject matter of this application, the first external radial distance ERD1 may be less than the second external radial distance ERD2. In other words, the first external thread root point P1 is farther from the outer outer cylinder EC2 than from the outer inner cylinder EC1. Each external thread root 58 may merge tangentially with a corresponding external load surface 59a. Each external thread root 58 may merge with a corresponding external non-load surface 59b at a second external thread root point P2. In such a configuration, each external thread root 58 extends between one of the external load surfaces 59a and one of the external non-load surfaces 59b. In a configuration where the external non-load surface (59b) is straight, each external thread root 58 may merge tangentially with a corresponding external non-load surface 59b.

[0083] According to some embodiments of the subject matter of this application, each external thread root 58 may be defined by a single external thread root radius R. Advantageously, this provides improved stress distribution at the external thread root 58. More advantageously, such a cut head 22 is easier to manufacture. The external thread root radius R may be greater than or equal to 0.3 mm. The external thread root radius R may be less than or equal to 0.5 mm. The first external thread root point P1 and the second external thread root point P2 may be opposite to the external thread root at the center O of an imaginary circle defined by the external thread root radius R with an opposing angle θ. The external thread root opposing angle θ may be greater than or equal to 90° and less than or equal to 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 half of the external thread pitch PE. In a configuration in which the outer unloaded surface (59b) is straight and each external thread root 58 is tangentially merged with the corresponding outer unloaded surface 59b at the second outer thread root point P2, the external thread root opposing angle θ may be greater than or equal to 120° and less than or equal to 140°.

[0084] According to some embodiments of the subject matter of this application, a plurality of external thread crests 56 each include a radially outermost external crest surface 61a. The radially outermost external crest surface 61a may be parallel to the external thread axis B and collinear with each other. Therefore, the radially outermost portion of the outer crest surface 50 may be located on the outer outer cylinder EC2.

[0085] like Figure 3 and Figure 4 As shown, the male coupling member 38 includes a front bearing portion 62. The front bearing portion 50 is positioned on the front side of the external thread 42. The front bearing portion 62 includes a front head abutment surface 64, which in the rearward direction D R The head tapers radially inward toward the longitudinal axis A. That is, the front head abutment surface 64 has a conical shape that extends radially outward. Note that when the rotary cutting tool 20 is in the locked position, the front head abutment surface 64 is intended to abut the corresponding surface 94 on the tool holder 24 (described further below), as will be described below.

[0086] It should be recognized that the terms "radially inward / inward" and "radially outward / outward" are used throughout the specification and claims to refer to relative positions toward and away from the respective axes in a direction perpendicular to the longitudinal axis A of the head and / or the longitudinal axis C of the retainer (in... Figures 3 to 4 and Figure 7 middle).

[0087] Now refer to Figures 6 to 8 The tool holder 24 has a holder longitudinal axis C, which extends forward along D. F Towards D RThe tool holder 24 includes a retainer outer peripheral surface 71 that extends about the retainer longitudinal axis C. The tool holder 24 includes a female coupling member 68 that extends rearward from the retainer front surface 70. The retainer front surface 70 extends laterally relative to the retainer longitudinal axis C. According to some embodiments of the subject matter of this application, the retainer front surface 70 may be perpendicular to the retainer longitudinal axis C.

[0088] The female connector 68 includes an internal (female) thread 72. As shown in a longitudinal cross-sectional view of the female connector 68 including the internal thread axis D (i.e., Figure 7 As shown in the diagram, the internal thread 72 includes an internal thread ridge 74 that extends helically about the internal thread axis D. The internal thread axis D coincides with the longitudinal axis C of the retainer. Therefore, the internal thread 72 is coaxial with the tool retainer 24. The internal thread ridge 74 includes a front inner side surface 76 and a rear inner side surface 78, and an inner top surface 80 extending between them. The front inner side surface 76 and the rear inner side surface 78 are in opposite axial directions D. F D R Facing, where the front inner side surface 76 is along the forward direction D F Facing, and the rear inner side surface 78 along the rearward direction D R Facing inwards, the front inner side surface 76 and the rear inner side surface 78 define an internal thread groove 82. The internal thread 72 has an internal thread pitch P1. According to some embodiments of the subject matter of this application, the internal thread pitch P1 may be constant. The internal thread pitch P1 may be the same as the external thread pitch PE.

[0089] The internal thread groove 82 extends helically about the internal thread axis D and includes an inner bottom surface 84. In a cross-sectional view taken along an axial plane (i.e., the plane containing the internal thread axis D), the inner top surface 80 forms a plurality of internal thread crests 88, and the inner bottom surface 84 forms a plurality of internal thread roots 90. The tool holder 24 has a holder thickness T, which is measured radially between the outer peripheral surface 71 and the inner top surface 80 of the holder.

[0090] Special reference Figure 7 and Figure 8 A cross-sectional view taken along an axial plane containing the internal thread axis D (i.e., Figure 7In this embodiment, the front inner side surface 76 and the rear inner side surface 78 form a plurality of internal load surfaces 91a and a plurality of internal non-load surfaces 91b, respectively. According to some embodiments of the subject matter of this application, the internal load surfaces 91a may be straight. The internal load surfaces 91a may be inclined with an inner side angle β relative to the retainer radial plane RP2, which is perpendicular to the internal thread axis D. Preferably, the inner side angle β may be 31°. The inner side angle β may have the same value as the outer side angle α, so that continuous surface-to-surface abutment can be achieved between the internal load surfaces 91a and the outer load surfaces 59a. The internal non-load surfaces 91b may be straight. The internal non-load surfaces 91b may be inclined in the same manner as the internal load surfaces 91a (but reflected with respect to the retainer radial plane RP2). The internal thread 72 defines an internal thread form 86.

[0091] According to some embodiments of the subject matter of this application, the internal thread 72 may be a straight thread. Specifically, the internal thread ridge 74 extends about an inner inner cylinder IC1, which is defined by the point on its inner top surface 80 closest to the internal thread axis D. The internal thread groove 82 extends about an inner outer cylinder IC2, which is defined by the point on its inner bottom surface 84 furthest from the internal thread axis D. The inner inner cylinder IC1 and the inner outer cylinder IC2 have the internal thread axis D as their respective axes.

[0092] Specifically, multiple internal thread crests 88 define the minor diameter of the internal thread 72 (which corresponds to the inner cylinder IC1), and multiple internal thread roots 90 define the major diameter of the internal thread 72 (which is associated with the inner outer cylinder IC2). The difference between the major and minor diameters, divided by two, equals the internal thread height H of the internal thread 72. I Internal thread height H I It can be constant. Internal thread height H I It can be greater than one-third of the internal thread pitch PI. Internal thread height H I It can be less than half of the internal thread pitch PI.

[0093] According to some embodiments of the subject matter of this application, the internal thread 72 may have between three and four turns in the axial direction. The internal thread 72 may be a single-start thread.

[0094] According to some embodiments of the subject matter of this application, a plurality of internal thread crests 88 may each include a radially innermost inner crest surface 96a. The radially innermost inner crest surface 96a may be parallel to the internal thread axis D and collinear with each other. Therefore, the radially innermost portion of the inner top surface 80 may be located on the inner inner cylinder IC1. A plurality of internal thread roots 90 may each include a radially outermost inner root surface 96b. The radially outermost inner root surface 96b may be parallel to the internal thread axis D and collinear with each other. Therefore, the radially outermost portion of the inner bottom surface 84 may be located on the inner outer cylinder IC2.

[0095] According to some embodiments of the subject matter of this application, each of a plurality of internal thread crests 88 may include an unloading internal crest surface 98 extending between a corresponding radially innermost internal crest surface 96a and a corresponding internal load surface 91a. In a longitudinal sectional view of the female coupling member 68 including the internal thread axis D (i.e., Figure 8 In this design, each unloading internal crest surface 98 can be laterally oriented relative to the corresponding radially outermost internal root surface 96b and the corresponding internal load surface 91a. The unloading internal crest surface 98 can merge with the corresponding internal load surface 91a at the internal crest point P'. The internal crest point P' is spaced apart from the internal inner cylinder IC1 by a first internal radial distance IRD1. The internal crest point P' is spaced apart from the internal outer cylinder IC2 by a second internal radial distance IRD2. The sum of the first internal radial distance IRD1 and the second internal radial distance IRD2 is equal to the internal thread height H. I The first internal radial distance IRD1 is greater than the internal thread height H. I One-quarter of the length, and less than the internal thread height H. I Half of it. By increasing the internal thread height H I The retainer thickness T was also increased. It was found that the increased retainer thickness reduced the stress at 90° of the internal thread root.

[0096] like Figure 6 and Figure 7 As shown, the female connector 68 includes a front support portion 92. The front support portion 92 is positioned on the front side of the internal thread 72. The front support portion 92 includes a front retainer abutment surface 94, which in the rearward direction D R The upper retainer longitudinal axis C tapers radially inward. That is, the front retainer abutment surface 94 has a conical shape facing radially inward. The front retainer abutment surface 94 is constructed and sized to complement the front head abutment surface 64 discussed above.

[0097] The assembly of the rotary cutting tool 20 is known, for example, from US 6,485,220 B2, which is hereby incorporated herein by reference in its entirety. Note that the rotary cutting tool 20 is adjustable between a released position and a locked (or assembled) position.

[0098] In order to adjust the rotary cutting tool 20 to the locked position, the external thread 42 is screwed (i.e., rotated) into the internal thread 72.

[0099] In the locked position, the male coupling member 38 is removably held in the female coupling member 68. Furthermore, the external thread 42 and the internal thread 72 engage with each other. Now refer to... Figure 9 The front head abutment surface 64 abuts the front retainer abutment surface 94. According to some embodiments of the subject matter of this application, the rearward-facing head base surface 40 may abut the front-facing retainer front surface 70. The rear inner side surface 78 may abut the front outer side surface 46. The front inner side surface 76 may be spaced apart from the rear outer side surface 48. The inner top surface 80 may be spaced apart from the outer bottom surface 54. The inner bottom surface 84 may be spaced apart from the outer top surface 50. According to the foregoing, in a cross-sectional view taken along an axial plane including the longitudinal axis L, each of the inner load surfaces 91a abuts the corresponding outer load surface 59a. Each of the inner non-load surfaces 91b is spaced apart from the corresponding outer non-load surface 59b. Each internal thread crest 88 is spaced apart from the corresponding external thread root 58. Each internal thread root 90 is spaced apart from the corresponding external thread crest 56.

[0100] Although the subject matter of this application is described with a certain degree of specificity, it should be understood that various changes and modifications may be made without departing from the spirit or scope of the invention as claimed below.

Claims

1. A replaceable cutting head (22) having a forward (D) F ) to the rear (D) R The longitudinal axis (A) of the head extending in the direction of ) includes The front portion, which is formed by a cut portion (26) including at least one cut edge (30); and The rear portion forms a mounting portion (28), which includes a male connecting member (38) having external threads (42) and projecting rearward from a head base surface (40), the head base surface (40) extending laterally relative to the longitudinal axis (A) of the head and defining the boundary between the cut portion (26) and the mounting portion (28), wherein: The external thread (42) includes an external thread ridge (44) that extends helically about the external thread axis (B) and includes a front outer side surface (46) and a rear outer side surface (48) and an outer top surface (50) extending therebetween. The front outer side surface (46) and the rear outer side surface (48) are generally along opposite axial directions (D). F D R )Facing and defining a helical external thread groove (52) including the outer bottom 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 ; The external thread (42) of the male connecting component (38) is a straight thread, defined by an outer inner cylinder (EC1) and an outer outer cylinder (EC2), the outer inner cylinder (EC1) having a small thread diameter d2, and the outer outer cylinder (EC2) having a large thread diameter d1; and In a cross-sectional view taken along an axial plane containing the external thread axis (B): The front outer side surface (46) and the rear outer side surface (48) respectively form a plurality of straight external load surfaces (59a) and a plurality of external non-load surfaces (59b); The outer bottom surface (54) forms a plurality of concave curved external thread roots (58), each external thread root (58) extending between a first external thread root point (P1) and a second external thread root point (P2), and merging with a corresponding outer load surface (59a) at the first external thread root point (P1), the first external thread root point (P1) being spaced from the outer inner cylinder (EC1) by a first external radial distance ERD1; and The first external radial distance ERD1 is greater than the external thread height H. E One-third of, and less than the external thread height H E Two-thirds.

2. The replaceable cutting head (22) according to claim 1, wherein, The first external radial distance ERD1 is greater than the external thread height H. E Five-twelfths of that, and less than the external thread height H E Seven-twelfths.

3. The replaceable cutting head (22) according to claim 1, wherein: Each external load surface (59a) has an external load surface length L1 measured along its contour; as well as Each external thread root (58) has an external thread root length L2 measured along its profile between the first external thread root point (P1) and the second external thread root point (P2); and The length L2 of the external thread root is between three and six times the length L1 of the external load surface.

4. The replaceable cutting head (22) according to claim 1, wherein, The smaller thread diameter d2 is at least 75% of the larger thread diameter d1.

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

6. The replaceable cutting head (22) according to claim 1, wherein, Each external thread root (58) is defined by a single external thread root radius R.

7. The replaceable cutting head (22) according to claim 6, wherein: The first external tooth base point (P1) and the second external tooth base point (P2) are located at the center (O) of an imaginary circle defined by the radius R of the external tooth base, facing each other at an angle θ toward the external tooth base; and The external tooth root facing angle θ is greater than or equal to 90° and less than or equal to 160°.

8. The replaceable cutting head (22) according to claim 7, wherein: The external unloaded surface (59b) is straight; Each external thread root (58) merges tangentially with the corresponding external unloaded surface (59b) at the second external root point (P2); and The external tooth root facing angle θ is greater than or equal to 120° and less than or equal to 140°.

9. The replaceable cutting head (22) according to claim 6, 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.

10. The replaceable cutting head (22) according to claim 1, wherein, Each external thread root (58) is tangentially joined to the corresponding external load surface (59a).

11. The replaceable cutting head (22) according to claim 1, wherein, Each external thread root (58) merges with the corresponding external unloaded surface (59b) at the second external root point (P2).

12. The replaceable cutting head (22) according to claim 11, wherein, The external unloaded surface (59b) is straight.

13. The replaceable cutting head (22) according to claim 12, wherein, Each external thread root (58) is tangentially joined to the corresponding external unloaded surface (59b).

14. The replaceable cutting head (22) according to claim 1, wherein, The first external thread root point (P1) and the second external thread root point (P2) are spaced apart by a point distance d in the axial direction. 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.

15. The replaceable cutting head (22) according to claim 1, wherein, In the cross-sectional view taken along the axial plane containing the external thread axis (B): The outer top surface (50) forms a plurality of external thread crests (56), each of which includes a radially outermost external crest surface (61a), which is parallel to the external thread axis (B) and collinear with each other.

16. A rotary cutting tool (20) having a longitudinal axis (L) and moving forward (D) F ) to the rear (D) R Extending in the direction, including: A tool holder (24) having a longitudinal axis (C) of the holder and a replaceable cutting head (22) according to claim 1, the replaceable cutting head (22) being threadedly engaged with the tool holder (24).

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

18. The rotary cutting tool (20) according to claim 16, wherein: The tool holder (24) has a female connection member (68) having an internal thread (72) extending rearward from the front surface (70) of the holder, the front surface (70) of the holder extending laterally relative to the longitudinal axis (C) of the holder; and The rotary cutting tool (20) can be adjusted between the following positions: In the release position, the internal thread (72) and the external thread (42) are not threadedly engaged with each other, and In the locked position, the male connector (38) is removably held in the female connector (68), wherein the internal thread (72) and the external thread (42) are threadedly engaged with each other.

19. The rotary cutting tool (20) according to claim 18, wherein, The internal thread (72) of the female connector (68) is a straight thread, which is defined by an inner cylinder (IC1) and an outer cylinder (IC2).

20. The rotary cutting tool (20) according to claim 18, wherein: The internal thread (72) includes an internal thread ridge (74) that extends helically about the internal thread axis (D) and includes a front inner side surface (76) and a rear inner side surface (78) and an inner top surface (80) extending therebetween. The front inner side surface (76) and the rear inner side surface (78) are generally along opposite axial directions (D). F D R ) facing, and defining a helical internal thread groove (82) including the inner bottom surface (84); and The front outer side surface (46) and the front inner side surface (76) are along the forward (D) F ) Direction facing; The rear outer side surface (48) and the rear inner side surface (78) are along the rearward (D) R ) Direction; and In the locked position, the rear inner side surface (78) is adjacent to the front outer side surface (46).

21. The rotary cutting tool (20) according to claim 20, wherein, At the locked position: The front inner side surface (76) is spaced apart from the rear outer side surface (48); The inner top surface (80) is spaced apart from the outer bottom surface (54); and The inner bottom surface (84) is spaced apart from the outer top surface (50).

22. The rotary cutting tool (20) according to claim 20, wherein, In a cross-sectional view taken along an axial plane containing the axis (D) of the internal thread: The front inner side surface (76) and the rear inner side surface (78) respectively form a plurality of internal non-loaded surfaces (91b) and a plurality of internal loaded surfaces (91a), wherein the internal loaded surfaces (91a) are straight.

23. The rotary cutting tool (20) according to claim 20, wherein: The inner top surface (80) forms a plurality of internal thread crests (88), each of the plurality of internal thread crests (88) including a radially innermost inner crest surface (96a) parallel to the internal thread axis (D), the radially innermost inner crest surfaces (96a) being collinear with each other.

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