A tool holder having a coupling hole and a locking through hole, and a rotary cutting tool equipped with the tool holder.

Abstract

The cutting head (22) has a driven surface and includes a head coupling pin that protrudes rearward from the rear surface of the head. The head coupling pin includes a pin recess that is recessed into the outer surface of the pin. The tool holder (24), which is elongated along the holder longitudinal axis (D), has a drive member and a holder coupling hole (96) that is recessed into the base surface of the holder. The fastening member (26) is disposed in a holder through hole (102) that extends from the base surface of the holder to the outer surface of the holder. The holder through hole (102) is located entirely on one side of the longitudinal plane containing the holder longitudinal axis (D). When the cutting tool (20), including the cutting head (22) and the tool holder (24), is in the fastening position, the head coupling pin engages with the fastening member (26) and is removably held in the holder coupling hole (96).

Description

[Technical Field]

[0001] The subject of this application relates to a type of rotary cutting tool in which the cutting head is held in a tool holder in a releasable manner by a coupling mechanism. [Background technology]

[0002] A rotary cutting tool may include a coupling mechanism that securely holds the cutting head within a tool holder. The cutting head may include a male coupling member, and the tool holder may include a female coupling member. At least one fastening member in the form of a screw may be used to releasably secure the male coupling member within the female coupling member by engaging with notches formed within the male coupling member.

[0003] Examples of such rotary cutting tools are disclosed, for example, in US2005 / 098359AA, US2011 / 110739AA, US5,649,794, KR200171644Y1, and Japanese Patent No. 3436110. [Overview of the project] [Means for solving the problem]

[0004] According to a first aspect of the subject matter of this application, a tool holder is provided having a holder longitudinal axis extending from the front to the rear. The tool holder is rotatable around its longitudinal axis in the rotational direction. The tool holder is The outer circumferential surface of the holder extends circumferentially around the longitudinal axis of the holder and forms the boundary of the holder base surface at the front end of the tool holder, Two drive members spaced apart in the circumferential direction and extending forward from the holder base surface, A holder coupling hole recessed within the base surface of the holder, comprising a coupling hole outer surface extending circumferentially around the longitudinal axis of the holder, A holder through-hole, the holder through-hole having an outer surface extending circumferentially along the holder through-hole axis, and opening to the outer surface of the connecting hole that forms an inner opening of the through-hole, and to the outer surface of the holder that forms an outer opening of the through-hole, It comprises a first holder longitudinal plane that extends parallel to the holder through-hole axis and includes the holder longitudinal axis, The holder through-hole is located entirely on one side of the longitudinal plane of the first holder.

[0005] According to a second aspect of the subject matter of the present application, a rotary cutting tool is provided, Rotary cutting tools are, The above-mentioned types of tool holders, A cutting head having a head central axis, It comprises a fastening member that is releasably engaged with the tool holder through a holder through-hole, The cutting head has a front end that forms the cutting portion of the head and a rear end that forms the head connecting portion. The cutting part of the head is The rear surface of the head defines the boundary between the cutting portion of the head and the head joint portion, The rear contact surface of the head, located on the rear of the head, The head comprises two cutting arms extending radially with respect to the central axis, each having a drive surface, The head coupling portion has a head coupling pin that protrudes rearward from the rear surface of the head along the head's central axis. The head coupling pin is, The pin rear surface is separated from the rear surface of the head, The outer circumferential surface of the pin extends between the rear surface of the head and the rear surface of the pin, A pin recess having a pin recess that is recessed within the outer surface of the pin, the pin recess having a pin contact surface that is inclined radially outward with respect to the head central axis in the rear direction of the cutting head, The rotary cutting tool is adjustable between a free position and a fastened position. At the fastening location, The cutting head is releasably attached to the tool holder by a fastening member. The head coupling pin is located inside the holder coupling hole. Each cutting arm contacts its respective drive member, The fastening member protrudes into the holder coupling hole and contacts the pin contact surface.

[0006] According to another aspect of the subject matter of this application, a tool holder is provided having a holder longitudinal axis extending from the front to the rear. The tool holder is rotatable around its longitudinal axis in the rotational direction. The tool holder is The outer circumferential surface of the holder extends circumferentially around the longitudinal axis of the holder and forms the boundary of the holder base surface at the front end of the tool holder, Two drive members spaced apart in the circumferential direction and extending forward from the holder base surface, A holder coupling hole recessed within the base surface of the holder, comprising a coupling hole outer surface extending circumferentially around the longitudinal axis of the holder, A holder through hole is provided, The holder through-hole has an outer surface of the hole that extends circumferentially along the holder through-hole axis, and opens to the outer surface of the coupling hole that forms the inner opening of the through-hole, and to the outer surface of the holder that forms the outer opening of the through-hole. In the diagram along the through-hole axis, the longitudinal axis of the holder is not visible from the outer surface of the holder through the through-hole.

[0007] The above is a summary, and it should be understood that the features described below can be applied to the subject matter of this application in any combination, for example, any of the following features can be applied to a tool holder or a rotary cutting tool.

[0008] The holder through-hole may have a non-threaded engagement portion, and the inner opening of the through-hole is formed on the non-threaded engagement portion. The outer circumferential surface of the hole in the non-threaded engagement portion may be on a virtual hole cylinder having the holder through-hole axis as the axis of the outer circumferential surface of the hole. In a cross-sectional view taken in the holder radial plane extending perpendicular to the holder longitudinal axis and tolerance to the inner opening of the through-hole, the virtual hole cylinder may define parallel inner and outer hole lines, the inner hole line being closer to the first holder longitudinal plane than the outer hole line. Both the inner and outer hole lines may be located on the same side of the first holder longitudinal plane. At least the inner hole line of the inner and outer hole lines may intersect the outer circumferential surface of the connecting hole.

[0009] The holder through-hole axis does not necessarily intersect the holder coupling hole.

[0010] Only the inner hole line of the inner hole line and the outer hole line can intersect the outer peripheral surface of the coupling hole.

[0011] The first holder longitudinal plane and the tangent line can be separated by a certain tangent distance. The tangent line is directed parallel to the holder hole axis and contacts the outer peripheral surface of the coupling hole in the tangent direction. The first holder longitudinal plane and the inner hole line can be separated by a certain inner line distance. The inner line distance can exceed 75% of the tangent distance.

[0012] The inner hole line can intersect the outer peripheral surface of the coupling hole twice so as to define the first intersection point and the second intersection point. The first intersection point is in front of the second intersection point in the rotational direction. The first intersection point and the second intersection point can define the range of the intersection angle on the holder longitudinal axis. The intersection angle can be 45° or more and 75° or less.

[0013] The tool holder can have a second holder longitudinal plane. The second holder longitudinal plane extends orthogonally to the first holder longitudinal plane and includes the holder longitudinal axis. The first intersection point and the second intersection point can be on both sides of the second holder longitudinal plane.

[0014] The tool holder can be provided with exactly one holder through-hole.

[0015] The tool holder can be provided with a holder base contact surface located on the holder base surface. The holder base contact surface is flat and can be directed orthogonally to the holder longitudinal axis.

[0016] The tool holder can be provided with two holder grooves. The two holder grooves are recessed within the outer peripheral surface of the holder and extend helically around the holder longitudinal axis. The holder coupling hole can open into the two holder grooves.

[0017] The tool holder can further include a fastening member that extends along the fastening member axis. The fastening member can include a fastening engagement portion and a fastening fixing portion that is axially offset from the fastening engagement portion.

[0018] The fastening and fixing portion may include a fastening male thread portion. The fastening and engaging portion may be non-threaded. The non-threaded fastening and engaging portion may be longer than the fastening male thread portion in the direction along the fastening member axis.

[0019] The holder through-hole may include a hole fixing portion for releasably attaching a fastening member to the holder through-hole. The hole fixing portion may include a female threaded portion.

[0020] The holder through-hole may include a non-threaded hole engagement portion, and the inner opening of the through-hole is formed on the non-threaded hole engagement portion. The non-threaded hole engagement portion may be located axially opposite to the female threaded portion of the hole. The non-threaded hole engagement portion may include a through-hole support surface located diametrically opposite to the inner opening of the through-hole around the through-hole axis.

[0021] The holder through-hole axis can be located within the radial plane of the holder.

[0022] At the fastening position of the rotary cutting tool, the fastening male thread portion can be screwed into the hole female thread portion.

[0023] At the fastening position of the rotary cutting tool, the fastening engagement portion can simultaneously contact the pin contact surface and the through-hole support surface.

[0024] The fastening engagement portion may comprise a fastening engagement end face and a fastening engagement outer circumferential surface, the fastening engagement outer circumferential surface extending circumferentially along the fastening member axis and indicating the circumferential boundary of the fastening engagement end face. The fastening engagement portion may comprise a fastening contact surface and a fastening outer circumferential support surface, the fastening outer circumferential support surface located diametrically opposite the fastening contact surface around the fastening member axis. At the fastening position of the rotary cutting tool, the fastening contact surface may contact the pin contact surface, and the fastening outer circumferential support surface may contact the through-hole support surface.

[0025] At the fastening position of the rotary cutting tool, the holder radial plane may intersect the pin contact surface. In a cross-sectional view taken from the holder radial plane, the pin contact surface may form an acute angle with respect to the through-hole axis, and the fastening surface angle may be between 5° and 15°.

[0026] The pin recess may be located on a virtual recessed cylinder that extends circumferentially along a recessed cylindrical axis oriented perpendicular to the head central axis, such that the pin contact surface is curved in a concave shape.

[0027] The tool holder may have a holder base contact surface located on the holder base surface. In the fastening position of the rotary cutting tool, the rear contact surface of the head may contact the holder base contact surface.

[0028] The head coupling pin may have exactly one pin recess. The tool holder may have exactly one holder through hole and exactly one fastening member that releasably engages with the tool holder.

[0029] At the fastening position of the rotary cutting tool, the fastening member may contact the pin contact surface in a contact area located on the same side as the first intersection on the longitudinal plane of the second holder.

[0030] The outer surface of the pin may have a cylindrical shape with a certain pin diameter. The cutting head may have a certain cutting outer diameter. The pin diameter may exceed one-third of the cutting outer diameter.

[0031] To better understand this application and to show how it can be actually implemented, please refer to the attached drawings. [Brief explanation of the drawing]

[0032] [Figure 1] This is a perspective view of the rotary cutting tool according to the present invention. [Figure 2] Figure 1 is an exploded perspective view of the front end of the rotary cutting tool shown. [Figure 3] Figures 1 and 2 are perspective views of the cutting head. [Figure 4] This is a side view of the cutting head shown in Figure 3, along the axis of the concave cylindrical body. [Figure 5] Figure 3 is a rear view of the cutting head. [Figure 6] Figures 1 and 2 are perspective views of the tool holder. [Figure 7]This is a cross-sectional view of the tool holder in Figure 6, taken in the radial plane passing through the inner opening of the through-hole along line VII-VII. [Figure 7A] This is a detailed view of Figure 7. [Figure 8] This is a cross-sectional view of the tool holder in Figure 6, taken in a plane parallel to the longitudinal axis of the holder and including the axis of the through hole, along the line VIII-VIII in Figure 7. [Figure 9] This is a cross-sectional view of the tool holder in Figure 6, taken in a plane parallel to the longitudinal axis of the holder and perpendicular to the axis of the through hole, along the line IX-IX in Figure 7. [Figure 10] Figure 1 is a side view of the front end of the rotary cutting tool at the fastening position shown. [Figure 11] Figure 10 shows a cross-sectional view of a rotary cutting tool taken along line XI-XI. [Figure 11A] This is a detailed view of Figure 11. [Figure 12] This is a cross-sectional view of a rotary cutting tool taken along line XII-XII in Figure 11. [Modes for carrying out the invention]

[0033] For simplicity and clarity, it should be understood that the elements shown in the drawings are not necessarily drawn to a consistent scale. For example, the dimensions of some elements may be emphasized relative to others for clarity, or several physical components may be included within a single functional block or element. Furthermore, reference numbers may be repeated in the drawings to indicate corresponding or similar elements, where deemed appropriate.

[0034] In the following description, various aspects of the subject matter of the present application will be explained. For illustrative purposes, certain configurations and details will be described in sufficient detail to provide a complete understanding of the subject matter of the present application. However, it will be apparent to those skilled in the art that the subject matter of the present application can be carried out without the specific configurations and details presented herein.

[0035] First, please look at Figures 1 and 2, which show a type of rotary cutting tool 20 used for drilling operations according to an embodiment of the subject matter of the present application. The rotary cutting tool 20 has a cutting head 22, which can typically be made from cemented carbide. The rotary cutting tool 20 also has a tool holder 24 complementary to the cutting head 22, which can typically be made from steel. The rotary cutting tool 20 is adjustable between at least a released position and a locked position. In the locked position of the rotary cutting tool 20, the cutting head 22 is releasedly mounted within the tool holder 24 by a locking member 26.

[0036] Next, please refer to Figures 3 to 5, which show the cutting head 22 according to the subject matter of this application. The cutting head 22 is manufactured from a single, integrated, one-piece structure ("monolithic structure"). The cutting head 22 has a head central axis A, and the cutting head 22 is rotatable about the head central axis A in the rotational direction R. The rotational direction R is the cutting direction. According to some embodiments of the subject matter of this application, the head central axis A may be the longitudinal axis. The head central axis A is in the forward direction D F D in the rear direction R It extends to the front. As best shown in Figure 4, the cutting head 22 includes a front end that forms the head cutting portion 28 and a rear end that forms the head coupling portion 30. The use of the terms “front” and “rear” throughout the specification and claims should be understood to refer to relative positions in the direction of the head central axis A, which is upward and downward in Figure 4, respectively.

[0037] The head cutting portion 28 includes opposing head front surfaces 32 and rear surfaces 34, and a head outer peripheral surface 36 extending between the head front surfaces 32 and the rear surfaces 34. The head outer peripheral surface 36 extends circumferentially around the head central axis A. The head central axis A extends through the head front surfaces 32 and the rear surfaces 34. The head rear surface 34 defines the boundary between the head cutting portion 28 and the head coupling portion 30. The head cutting portion 28 includes a head contact rear surface 38, which extends approximately in the rearward direction D. RIt faces in a direction and contacts a complementary surface on the tool holder 24. The head contact rear surface 38 is located on the head rear surface 34. According to some embodiments of the subject matter of the present application, the head rear surface 34 may be flat and perpendicular to the head central axis A.

[0038] The head cutting portion 28 includes a head radial center portion 40. The head cutting portion 28 includes two cutting arms 42, which extend radially outward from the head radial center portion 40 with respect to the head longitudinal axis A. In this non-limiting example shown, the head cutting portion 28 includes exactly two cutting arms 42 that are radially opposite to each other. Each cutting arm 42 includes opposing arm rotation leading surface 44 and arm rotation trailing surface 46, and an arm circumferential surface 48 extending circumferentially between the arm rotation leading surface 44 and the arm rotation trailing surface 46. The arm rotation leading surface 44, the arm rotation trailing surface 46, and the arm circumferential surface 48 are all located on the head circumferential surface 36. The use of the terms “rotation leading” and “rotation trailing” should be understood throughout the specification and claims as referring to positions with respect to the head rotation direction R. Each cutting arm 42 includes a driven surface 50 that is driven and engaged by a complementary surface on the tool holder 24. As shown in Figure 5, in this non-limiting example, each driven surface 50 may be flat. Furthermore, each driven surface 50 may be parallel to the head central axis A. According to some embodiments of the subject matter of the present application, the driven surface 50 may be located on the arm rotation trailing surface 46. Advantageously, this allows for effective torque transmission to the cutting head via the driven surface 50. The driven surface 50 may be spaced apart from the head rear surface 34. Preferably, the driven surface 50 may be located axially forward from the head rear surface 34.

[0039] Each cutting arm 42 includes its own main cutting edge 54. The main cutting edge 54 is formed along at least a portion of the intersection line between the arm rotation leading surface 44 and the head front surface 32. The head front surface 32 includes a plurality of main relief surfaces 56. Each main relief surface 56 extends from its own main cutting edge 54, which is associated toward the opposite arm rotation trailing surface 46 on the same cutting arm 42. Each arm rotation leading surface 44 includes its own main rake surface 58. Each main rake surface 58 extends from its own main cutting edge 54, which is associated toward the head rear surface 34. As is well known in the field of rotary cutting tools, each cutting arm 42 may include a cutting arm groove 59 associated with its own main cutting edge 54 for chip evacuation.

[0040] The head coupling portion 30 includes a head coupling pin 60 that protrudes rearward from the head rear surface 34 along the head central axis A. The purpose of the head coupling pin 60 is to coupling with the tool holder 24 and to provide a means for centering the tool holder 24. The head coupling pin 60 includes a pin rear surface 62 spaced apart from the head rear surface 34 and a pin outer peripheral surface 64 extending between the pin rear surface 62 and the head rear surface 34. According to some embodiments of the subject matter of this application, the pin outer peripheral surface 64 may have a cylindrical shape having a pin diameter PD. As shown in Figure 5, the pin diameter PD may exceed one-third of the cutting outer diameter OD of the cutting head 22. The head rear surface 34 may form the outer peripheral boundary of the pin outer peripheral surface 64 in the region where the head coupling pin 60 protrudes from the head rear surface 34.

[0041] For example, as shown in US7,625,161, according to some embodiments of the subject matter of this application, a portion of the head coupling pin 60 may form part of a groove section (configured for chip ejection) of the assembled rotary cutting tool 20. Thus, the head coupling pin 60 may be grooved.

[0042] The head coupling pin 60 includes a pin recess 70 that receives a portion of the fastening member 26. The pin recess 70 is recessed into the outer surface 64 of the pin. The pin recess 70 includes a pin concave surface 72. Referring to Figure 4, according to some embodiments of the subject matter of the present application, as seen in the side view of the cutting head 22, the pin concave surface 72 may lie on a virtual recess cylinder IC that extends circumferentially along the recess cylinder axis CA. The recess cylinder axis CA may be oriented perpendicular to the head central axis A (rather than intersecting the head central axis A). The pin recess 70 may be spaced apart from the pin rear surface 62. The pin recess 70 may be spaced apart from the head rear surface 34.

[0043] The pin recess 72 includes a pin contact surface 74 that engages with the fastening member 26. The pin contact surface 74 is located in the rear direction D of the cutting head 22 with respect to the head central axis A. R It is inclined radially outward. According to some embodiments of the subject matter of the present application, the pin contact surface 74 may be curved in a concave shape. In particular, the pin contact surface 74 may be formed on the lower half of the cylindrical pin concave surface 72.

[0044] Next, please refer to Figures 6 to 9, which show a tool holder 24 according to a first embodiment of the subject matter of this application. The tool holder 24 has a holder longitudinal axis D. At the fastening position of the rotary cutting tool 20, the tool holder 24 is coaxial with the cutting head 22 (i.e., the head central axis A and the holder longitudinal axis D coincide), and therefore the holder longitudinal axis D is in the forward direction D F D in the rear direction R It may extend in the direction of rotation R. Furthermore, the tool holder 24 is rotatable about the longitudinal axis D of the holder in the rotational direction R. The tool holder 24 includes a holder outer circumferential surface 78 that extends circumferentially about the longitudinal axis D of the holder. The holder outer circumferential surface 78 forms the boundary of the holder base surface 80 at the front end of the tool holder 24. The tool holder 24 includes a holder base contact surface 82, which extends approximately in the forward direction D. F It faces in a direction and contacts a complementary surface on the cutting head 22. The holder base contact surface 82 is located on the holder base surface 80. According to some embodiments of the subject matter of the present application, the holder base surface 80 may be flat and perpendicular to the holder longitudinal axis D.

[0045] The tool holder 24 includes two drive members 84 that are circumferentially spaced apart and extend forward from the holder base surface 80. The drive members 84 function to apply a driving torque T to the cutting head 22 when the tool holder 24 rotates. In this non-limiting example shown, the tool holder 24 includes exactly two drive members 84 that are diametrically opposed to each other. Each drive member 84 includes an opposing drive member leading rotating surface 86 and a drive member trailing rotating surface 88, and a drive member outer peripheral surface 90 that extends on the outer periphery between the drive member leading rotating surface 86 and the drive member trailing rotating surface 88. According to some embodiments of the subject matter of the present application, each drive member 84 may include a respective drive member front surface 91 that axially defines the boundary of the drive member in the forward direction D D whereby the driving torque T is transmitted to the cutting head 22. F Each drive member leading rotating surface 86 includes a drive surface 92 that drivingly engages with a respective complementary surface on the cutting head 22. According to some embodiments of the subject matter of the present application, the drive surface 92 may be located axially forward of the holder base surface 80.

[0046] According to some embodiments of the subject matter of the present application, the tool holder 24 may include two holder grooves 94 that are recessed within the holder outer peripheral surface 78. The two holder grooves 94 may extend helically around the holder longitudinal axis D. Each holder groove 94 extends to the holder base surface 80 between the two respective drive members 84 in the forward direction D

[0047] The tool holder 24 includes a holder coupling hole 96 that receives the head coupling pin 60 of the cutting head 22. The holder coupling hole 96 is recessed within the holder base surface 80 and extends in the rearward direction D F and is axially aligned with the drive members 84.

[0048] and is axially aligned with the drive members 84. RThe holder coupling hole 96 extends along the longitudinal axis D of the holder. The holder coupling hole 96 includes a coupling hole rear surface 98 spaced apart from the holder base surface 80 and a coupling hole outer surface 100 extending between the coupling hole rear surface 98 and the holder base surface 80 around the longitudinal axis D of the holder. According to some embodiments of the subject matter of the present application, the coupling hole outer surface 100 may have a cylindrical shape. The intersection line of the coupling hole outer surface 100 and the holder base surface 80 may be inclined to allow for the initial easy insertion of the head coupling pin 60 when assembled to the rotary cutting tool 20.

[0049] According to some embodiments of the subject matter of the present application, the holder coupling hole 96 may open into two holder grooves 94 such that a portion of the head coupling pin 60 can form part of a grooved section (configured for chip ejection) of the assembled rotary cutting tool 20 (as described above).

[0050] The tool holder 24 includes a holder through-hole 102 extending along the holder through-hole axis B from the holder coupling hole 96 to the holder outer circumferential surface 78. The holder through-hole 102 includes a hole outer circumferential surface 104 extending circumferentially along the holder through-hole axis B. The hole outer circumferential surface 104 intersects with the coupling hole outer circumferential surface 100 to form an inner through-hole opening 107A (i.e., opens into the coupling hole outer circumferential surface 100). The inner through-hole opening 107A extends over a circumferential range of the coupling hole outer circumferential surface 100. The hole outer circumferential surface 104 also intersects with the holder outer circumferential surface 78 to form an outer through-hole opening 107B. Note that the holder through-hole 102 is located behind the holder base surface 80 and therefore is not formed in any part of the two drive members 84.

[0051] The tool holder 24 has a holder radial plane RP oriented perpendicular to the holder longitudinal axis D. The holder radial plane RP intersects the through-hole inner opening 107A (and thus the holder coupling hole 96 and the holder through-hole 102). Referring to Figure 7, the tool holder 24 also includes a first holder longitudinal plane LP1, which extends parallel to the holder through-hole axis B and includes the holder longitudinal axis D. Finally, the tool holder 24 has a second holder longitudinal plane LP2, which extends perpendicular to the first holder longitudinal plane LP1 and also includes the holder longitudinal axis D. It should be understood that a radial plane is a plane perpendicular to the central axis of the member, and a longitudinal plane is a plane that includes the central axis of the member.

[0052] According to some embodiments of the subject matter of the present application, as shown in Figures 8 and 9, the holder through-hole axis B may be in the holder radial plane RP. The holder through-hole 102 may include a hole fixing portion 105 for releasably mounting a fastening member 26 into the holder through-hole 102. In this non-limiting example, the hole fixing portion 105 is adjacent to the outer circumferential surface 78 of the holder. The hole fixing portion 105 may include a hole female thread portion 121.

[0053] The holder through-hole 102 may include a non-threaded hole engaging portion 106, which is located axially opposite to the hole female thread portion 121. The non-threaded hole engaging portion 106 is located along the through-hole axis B from the through-hole outer opening 107B to the inside of the hole female thread portion 121. The non-threaded hole engaging portion 106 may include a through-hole support surface 108 that supports the fastening engaging portion 112 described below in this specification. The through-hole inner opening 107A is formed on the non-threaded hole engaging portion 106 and may be located diametrically opposite to the through-hole support surface 108 around the through-hole axis B.

[0054] According to some embodiments of the subject matter of this application, the outer circumferential surface 104 of the hole in the non-threaded hole engagement portion 106 may lie on a virtual hole cylindrical body IB having the holder through-hole axis B as the axis of the outer circumferential surface 104. Referring to Figure 7A, in a cross-sectional view taken in the holder radial plane RP, the virtual hole cylindrical body IB may define parallel inner hole line LI and outer hole line LO. The inner hole line LI is closer to the first holder longitudinal plane LP1 than the outer hole line LO. Note that the inner hole line LI and the outer hole line LO are parallel to the through-hole axis B (and therefore also parallel to the first holder longitudinal plane LP1).

[0055] The holder through-hole 102 is located entirely on one side of the first holder longitudinal plane LP1. Therefore, in the cross-sectional view taken along the holder radial plane RP, as best shown in Figure 7A, both the inner hole line LI and the outer hole line LO are located on the same side of the first holder longitudinal plane LP1. Consequently, the holder axis D does not pass through the virtual extension of the hole cylinder IB. Furthermore, the holder axis D is not visible from the holder outer surface 78 through the holder through-hole 102 in the view along the hole axis B.

[0056] At least the inner hole line LI of the inner hole line LI and the outer hole line LO intersect the outer circumferential surface 100 of the coupling hole. According to some embodiments of the subject matter of this application, only the inner hole line LI of the inner hole line LI and the outer hole line LO intersect the outer circumferential surface 100 of the coupling hole line LI. That is, the outer hole line LO does not intersect the outer circumferential surface 100 of the coupling hole. Preferably, the holder through-hole axis B does not have to intersect the holder coupling hole 96.

[0057] According to some embodiments of the subject matter of this application, in a cross-sectional view taken in the holder radial plane RP, the inner hole line LI penetrates the outer surface 100 of the coupling hole by 2 degrees so as to define a first intersection I1 and a second intersection I2, with the first intersection I1 being in front of the second intersection I2 in the rotational direction. The first intersection I1 and the second intersection I2 can define a range of intersection angle β in the holder longitudinal axis D. The intersection angle β can be 45° or more and 75° or less. The first intersection I1 and the second intersection I2 can be on opposite sides of the second holder longitudinal plane LP2.

[0058] As shown in Figure 7A, according to some embodiments of the subject matter of the present application, in a cross-sectional view taken in the holder radial plane RP, the first holder longitudinal plane LP1 and the tangent T may be separated by a tangent distance TD, the tangent T is oriented parallel to the holder hole axis B and contacts the outer circumferential surface 100 of the coupling hole in the tangential direction. The first holder longitudinal plane LP1 and the inner hole line LI may be separated by an inner line distance ID. The inner line distance ID may exceed 75% of the tangent distance TD. Preferably, the inner line distance ID may exceed 85% of the tangent distance TD.

[0059] Returning to Figures 1 and 2, the tool holder 24 includes a fastening member 26, which may be a screw that engages with the pin contact surface 74 of the head coupling pin 60. The fastening member 26 is releasably engaged with the tool holder 24 in the holder through hole 102. The fastening member 26 extends along the fastening member axis C, which is coaxial with the holder through hole axis B, at the fastening position of the cutting tool 20. According to some embodiments of the subject matter of the present application, the fastening member 26 may include a fastening fixed portion 110 near its proximal end and a fastening engaging portion 112 that is axially offset from the fastening fixed portion 110 near its distal end (tip) along the fastening member axis C. The fastening member 26 may be a headless fastening member (e.g., of the grub screw type).

[0060] According to some embodiments of the subject matter of this application, the fastening portion 110 may include a fastening threaded portion 120. The fastening engagement portion 112 may be non-threaded. The non-threaded fastening engagement portion 112 may be at least half the length of the fastening threaded portion 120 in the direction along the fastening member axis C, as shown in Figure 11. The non-threaded fastening engagement portion 112 may even be longer than the fastening threaded portion 120 in the direction along the fastening member axis C (as shown in Figure 11). The fastening engagement portion 112 comprises a fastening engagement end face 114 oriented perpendicular to the fastening member axis C and a fastening engagement outer circumferential surface 116, the fastening engagement outer circumferential surface 116 extending circumferentially along the fastening member axis C and indicating the circumferential boundary of the fastening engagement end face 114. The fastening engagement outer circumferential surface 116 faces radially outward. The fastening engagement outer circumferential surface 116 may have a cylindrical shape. The end face 114 and the outer peripheral face 116 may intersect to form a fastening engagement tapered surface 117 that intersects the fastening engagement end face 114. The fastening engagement tapered surface 117 may extend 360° around the fastening member axis C. The fastening engagement tapered surface 117 may have a tapered angle that decreases in the direction toward the fastening fixing portion 110, so as to curve convexly (in the side view of the fastening member 26). The fastening member axis C does not intersect the fastening engagement tapered surface 117.

[0061] The fastening engagement portion 112 may include a fastening contact surface 118 that contacts the pin contact surface 74. In particular, the fastening contact surface 118 may be located on the fastening engagement tapered surface 117. The fastening engagement outer peripheral surface 116 may include a fastening outer peripheral support surface 119 that contacts the through-hole support surface 108 (described below in this specification). The fastening outer peripheral support surface 119 may be located on the diametrically opposite side of the fastening contact surface 118 around the fastening member axis C. Therefore, the fastening outer peripheral support surface 119 may also be located on the fastening engagement tapered surface 117. Thus, it should be understood that the fastening contact surface 118 and the fastening outer peripheral support surface 119 are established only when the rotary cutting tool 20 is in the fastening position.

[0062] The fastening member 26 is releasably engaged with the tool holder 24 by the fastening fixing portion 110 engaging with the hole fixing portion 105. In this non-limiting example, the fastening fixing portion 110 may include a fastening male thread portion 120, the hole fixing region 105 may include a hole female thread portion 121, and the fastening male thread portion 120 screws into the hole female thread portion 121.

[0063] A further aspect of the subject matter of the present application includes a rotary cutting tool 20, which comprises a tool holder 24 and a cutting head 22 that is releasably attached to the tool holder 24 by a fastening member 26. Referring next to Figures 1-2 and 10-12, the rotary cutting tool 20 is adjustable between a released position and a fastened position.

[0064] In the released position of the rotary cutting tool 20, the head coupling pin 60 is not located within the holder coupling hole 96. The cutting head 22 is not removably mounted within the tool holder 24.

[0065] Next, referring to Figures 10 to 12, in the fastening position of the rotary cutting tool 20, the cutting head 22 is releasably attached within the tool holder 24 by a fastening member 26. The head coupling pin 60 is located within the holder coupling hole 96. The head central axis A and the holder longitudinal axis D are coaxial. Each cutting arm 42 is in contact with its respective drive member 84. In particular, each driven surface 50 abuts against its respective drive surface 92. The fastening member 26 protrudes into the holder coupling hole 96 and abuts against the pin contact surface 74 (i.e., tightens and engages). The head rearward contact surface 38 abuts against the holder base contact surface 82.

[0066] According to some embodiments of the subject matter of the present application, the head coupling pin 60 may include exactly one pin recess 70 (in such a configuration, the head coupling pin 30 does not have to be rotationally symmetric about the head central axis A, i.e., it has rotational symmetry only 360°).

[0067] Alternatively, the head coupling pin 60 may include two pin recesses 70 that are strictly opposite each other in the diametrical direction around the head central axis A. Thus, engagement of the fastening member 26 with one of the two pin recesses 70 is ensured regardless of the rotational position in which the head coupling pin 60 is first inserted into the holder coupling hole 96.

[0068] The tool holder 24 may include strictly one holder through-hole 102 and strictly one fastening member 26 that releasably engages with the tool holder 24. Therefore, advantageously, only one fastening member is required to securely mount the cutting head 22 to the tool holder 24. This eliminates the need for additional individual retaining screws to securely fasten the cutting head 22 to the tool holder 24, as disclosed in, for example, US2011 / 110739. In this configuration, a portion of the outer circumferential surface 64 of the pin, located diametrically opposite the pin contact surface 74, contacts a portion of the outer circumferential surface 100 of the coupling hole, located diametrically opposite the inner opening 107A of the through-hole.

[0069] The assembly of the rotary cutting tool 20 is achieved by performing the following steps: Position the head coupling pin 60 axially forward of the holder coupling hole 96, facing the holder coupling hole 96. Note that in this position, each cutting arm 42 is circumferentially positioned axially forward between adjacent pairs of drive members 84 (as best shown in Figure 2). Next, displace the cutting head backward so that the head coupling pin 60 is first inserted into the holder coupling hole 96. Next, displace the cutting head 22 further backward so that the rear surface 34 of the head first contacts the base surface 80 of the holder.

[0070] Next, the cutting head 22 is rotated relative to the tool holder 24 in a direction relative to the rotational direction R until each driven surface 50 first contacts its respective drive surface 92. Then, the fastening member 26 is inserted into the holder through hole 102 (first into the fastening engagement portion 112) until the fastening member 26 protrudes into the holder coupling hole 96 and first contacts the pin recess 70, in particular the pin contact surface 74. The fastening member 26 exerts a fastening force F along the line of force L on the pin contact surface 74. The line of force L is parallel to the fastening member axis C and the holder through hole axis B (but offset from the holder longitudinal axis D).

[0071] Referring to Figure 11, the fastening engagement portion 112 of the fastening member 26 abuts against the pin contact surface 74 in a contact area located on one side of the first holder longitudinal plane LP1. Thus, the fastening force F prompts the cutting head 22 to rotate relative to the tool holder 24 in a direction relative to the rotational direction R until a firm contact is achieved between the driven surface 50 and the driving surface 92. Advantageously, the holder through-hole 102 is positioned entirely on one side of the first holder longitudinal plane LP1, ensuring that the contact area is sufficiently far from the first holder longitudinal plane LP1 (and therefore from the holder longitudinal axis D), thereby reducing the fastening force F required to fasten the cutting head 22 to the tool holder 24. According to some embodiments of the subject matter of this application, the contact area may be located on the same side of the second holder longitudinal plane LP2 as where the fastening fixing portion 110 engages with the hole fixing portion 105.

[0072] According to some embodiments of the subject matter of this application, in a cross-sectional view taken in the holder radial plane RP (e.g., Figures 11 and 11A), the pin contact surface 74 can form a chord of a circle defined by the outer circumferential surface 60 of the pin. At the fastening position, the holder radial plane RP intersects the fastening contact surface 74, and the pin contact surface 74 forms an acute angle α with the through-hole axis B. The acute angle α can be shallow, i.e., 5° or more and 15° or less.

[0073] As best illustrated in Figure 12, the pin contact surface 74 is inclined radially outward with respect to the head central axis A, thereby allowing the cutting head 22 to move in the rearward direction D. RWhen the fastening member 26 is further inserted, the fastening force F causes the cutting head to be displaced in the rearward direction so that the rear surface 34 of the head firmly contacts the base surface 80 of the holder.

[0074] In the above configuration, the fastening position for the rotary cutting tool 20 is formed. At the fastening position for the rotary cutting tool 20, the fastening member 26 tightens and engages with the head coupling pin 60. More specifically, the fastening engagement portion 112 tightens and engages with the pin contact surface 74 of the head coupling pin. More specifically, the fastening contact surface 118 located on the fastening engagement tapered surface 117 tightens and engages with the pin contact surface 74.

[0075] Returning to Figure 11A, note that, along with the aforementioned contact between the fastening member 26 and the head coupling pin 60, the fastening engagement portion 112, particularly the fastening outer peripheral bearing surface 119, also contacts the through-hole support surface 108. The pin contact surface 74 exerts an engagement force G opposite to the fastening force F. The engagement force G is directed perpendicular to the pin contact surface 74 on the fastening member 26 (i.e., radially outward). Due to the shallow fastening surface angle α, the engagement force G is advantageously directed towards the through-hole support surface 108, providing a firm support (this is the opposite of the engagement force G being directed towards the screw connection, as shown, for example, in US9,162,295, which may damage the screw(s)). Furthermore, the fastening member 26 is effectively pressed between the head coupling pin 60 and a portion of the tool holder 24.

[0076] Advantageously, a firm clamping engagement of the cutting head 22 is achieved in this fastening position of the rotary cutting tool 20. Such an engagement has been found to be particularly effective for intermittent drilling. Furthermore, the fastening engagement prevents the cutting head 22 from being pulled axially out of the tool holder 24 when the rotary cutting tool 20 is removed from the workpiece.

[0077] While the subject matter of this application has been described in some detail, please understand that various modifications and alterations can be made without departing from the spirit or scope of the invention as claimed below.

Claims

1. Forward direction (D Ｆ ) from the rear direction (D Ｒ A tool holder (24) having a holder longitudinal axis (D) extending to the ), The tool holder (24) is rotatable in the rotational direction (R) around the longitudinal axis (D) of the holder, The tool holder (24) is The holder outer circumferential surface (78) extends circumferentially around the longitudinal axis (D) of the holder and forms the boundary of the holder base surface (80) at the front end of the tool holder (24), Two drive members (84) are spaced apart in the circumferential direction and extend forward from the holder base surface (80), A holder coupling hole (96) recessed within the holder base surface (80), comprising a coupling hole outer surface (100) extending circumferentially around the holder longitudinal axis (D), A holder through-hole (102), the holder through-hole (102) comprises an outer circumferential surface (104) of the hole extending circumferentially along the holder through-hole axis (B), and opens to the outer circumferential surface (100) of the connecting hole that forms the inner opening (107A) of the through-hole, and the outer circumferential surface (78) of the holder that forms the outer opening (107B) of the through-hole, It comprises a first holder longitudinal plane (LP1) that extends parallel to the holder through-hole axis (B) and includes the holder longitudinal axis (D), The holder through hole (102) is located entirely on one side of the first holder longitudinal plane (LP1) of the tool holder (24).

2. The holder through hole (102) is provided with a non-threaded hole engagement portion (106), The inner opening of the through hole (107A) is formed on the non-threaded hole engagement portion (106), The outer circumferential surface (104) of the hole in the non-threaded hole engagement portion (106) is located on a virtual hole cylindrical body (IB) having the holder through-hole axis (B) as the axis of the outer circumferential surface (104) of the hole, In a cross-sectional view taken from a holder radial plane (RP) that extends perpendicular to the holder longitudinal axis (D) and is tolerant to the through-hole inner opening (107A), The virtual hole cylinder (IB) defines parallel inner hole lines (LI) and outer hole lines (LO), The inner hole line (LI) is closer to the longitudinal plane of the first holder (LP1) than the outer hole line (LO). Both the inner hole line (LI) and the outer hole line (LO) are located on the same side of the longitudinal plane (LP1) of the first holder. The tool holder (24) according to claim 1, wherein at least the inner hole line (LI) of the inner hole line (LI) and the outer hole line (LO) intersects the outer circumferential surface (100) of the connecting hole.

3. The tool holder (24) according to claim 1 or 2, wherein the holder through-hole axis (B) does not intersect the holder coupling hole (96).

4. The tool holder (24) according to claim 2 or 3, wherein only the inner hole line (LI) of the inner hole line (LI) and the outer hole line (LO) intersects the outer circumferential surface (100) of the connecting hole.

5. The longitudinal plane (LP1) and tangent (T) of the first holder are separated by a tangential distance (TD). The tangent (T) is oriented parallel to the holder hole axis (B) and contacts the outer circumferential surface (100) of the coupling hole in the tangential direction. The longitudinal plane of the first holder (LP1) and the inner hole line (LI) are spaced apart by an inner line distance (ID), The tool holder (24) according to any one of claims 2 to 4, wherein the inner line distance (ID) exceeds 75% of the tangential distance (TD).

6. The inner hole line (LI) is inserted twice into the outer surface (100) of the connecting hole so as to define the first intersection (I1) and the second intersection (I2). The first intersection (I1) is in front of the second intersection (I2) in the direction of rotation. The first intersection (I1) and the second intersection (I2) define the range of the intersection angle (β) in the longitudinal axis (D) of the holder, The tool holder (24) according to any one of claims 2 to 5, wherein the intersection angle (β) satisfies the condition: 45° ≤ θ ≤ 75°.

7. The tool holder (24) has a second holder longitudinal plane (LP2), The second holder longitudinal plane (LP2) extends perpendicular to the first holder longitudinal plane (LP1) and includes the holder longitudinal axis (D). The tool holder (24) according to claim 6, wherein the first intersection (I1) and the second intersection (I2) are located on opposite sides of the second holder longitudinal plane (LP2).

8. A tool holder (24) according to any one of claims 1 to 7, comprising exactly one holder through hole (102).

9. The tool holder (24) is provided with a holder base contact surface (82) located on the holder base surface (80), The tool holder (24) according to any one of claims 1 to 8, wherein the holder base contact surface (82) is flat and oriented perpendicular to the holder longitudinal axis (D).

10. The tool holder (24) is provided with two holder grooves (94), The two holder grooves (94) are recessed into the outer circumferential surface (78) of the holder and extend spirally around the longitudinal axis (D) of the holder. The tool holder (24) according to any one of claims 1 to 9, wherein the holder coupling hole (96) opens into the two holder grooves (94).

11. The fastening member (26) further extends along the fastening member axis (C), The fastening member (26) comprises a fastening engagement portion (112) and a fastening fixing portion (110) positioned axially offset from the fastening engagement portion (112), the tool holder (24) according to any one of claims 1 to 10.

12. The fastening and fixing portion (110) includes a fastening male screw portion (120), The fastening engagement portion (112) is non-threaded. The tool holder (24) according to claim 11, wherein the non-threaded fastening engagement portion (112) is longer than the fastening male threaded portion (120) in the direction along the fastening member axis (C).

13. The holder through hole (102) is provided with a hole fixing portion (105) for removably attaching the fastening member (26) to the holder through hole (102), The tool holder (24) according to any one of claims 1 to 12, wherein the hole fixing portion (105) is provided with a female screw portion (121).

14. The holder through hole (102) is provided with a non-threaded hole engagement portion (106), The inner opening of the through hole (107A) is formed on the non-threaded hole engagement portion (106), The non-threaded hole engaging portion (106) is located opposite the axial direction of the female threaded hole portion (121), The tool holder (24) according to claim 13, wherein the non-threaded hole engaging portion (106) includes a through-hole support surface (108) located diametrically opposite to the through-hole inner opening (107A) around the through-hole axis (B).

15. The tool holder (24) according to any one of claims 1 to 14, wherein the holder through-hole axis (B) is located in the radial plane (RP) of the holder.

16. A rotary cutting tool (20), The rotary cutting tool (20) is A tool holder (24) according to any one of claims 1 to 15, A cutting head (22) having a head central axis (A), The fastening member (26) is releasably engaged with the tool holder (24) through the holder through hole (102), The cutting head (22) has a front end that forms the head cutting portion (28) and a rear end that forms the head connecting portion (30), The head cutting portion (28) is A rear surface of the head (34) defines a boundary between the head cutting portion (28) and the head joining portion (30), The head contact rear surface (38) located on the head rear surface (34), The head comprises two cutting arms (42) extending radially with respect to the head central axis (A), each of which has a driven surface (50), The head coupling portion (30) has a head coupling pin (60) that protrudes rearward from the rear surface (34) of the head along the head central axis (A), The head coupling pin (60) is The pin rear surface (62) is spaced apart from the head rear surface (34), The pin outer circumferential surface (64) extends between the head rear surface (34) and the pin rear surface (62), A pin recess (70) is recessed within the outer circumferential surface (64) of the pin and has a pin recess (72), wherein the pin recess (72) is located in the rearward direction (D) of the cutting head (22). Ｒ ) has a pin contact surface (74) that is inclined radially outward with respect to the head central axis (A), and a pin recess (70) The rotary cutting tool (20) is adjustable between a free position and a fastening position. At the fastening position, The cutting head (22) is releasably attached to the tool holder (24) by the fastening member (26). The head coupling pin (60) is located within the holder coupling hole (96), Each of the cutting arms (42) is in contact with its respective drive member (84), The fastening member (26) is a rotary cutting tool (20) that protrudes into the holder coupling hole (96) and contacts the pin contact surface (74).

17. The fastening member (26) extends along the fastening member axis (C), The fastening member (26) comprises a fastening engagement portion (112) and a fastening fixing portion (110) positioned axially offset from the fastening engagement portion (112), The fastening and fixing portion (110) includes a fastening male screw portion (120), The holder through hole (102) is provided with a hole fixing portion (105) for removably attaching the fastening member (26) to the holder through hole (102), The hole fixing portion (105) includes a hole female thread portion (121), The rotary cutting tool (20) according to claim 16, wherein at the fastening position of the rotary cutting tool (20), the fastening male thread portion (120) is screwed with the hole female thread portion (121).

18. The holder through hole (102) is provided with a non-threaded hole engagement portion (106), The non-threaded hole engaging portion (106) is located opposite the axial direction of the female threaded hole portion (121), The inner opening of the through hole (107A) is formed on the non-threaded hole engagement portion (106), The non-threaded hole engaging portion (106) includes a through-hole support surface (108) located on the diametrically opposite side of the through-hole inner opening (107A) around the through-hole axis (B), At the fastening position of the rotary cutting tool (20), The rotary cutting tool (20) according to claim 17, wherein the fastening engagement portion (112) simultaneously contacts the pin contact surface (74) and the through-hole support surface (108).

19. The fastening engagement portion (112) comprises a fastening engagement end face (114) and a fastening engagement outer peripheral surface (116), The fastening engagement outer peripheral surface (116) extends circumferentially along the fastening member axis (C) and indicates the circumferential boundary of the fastening engagement end surface (114). The fastening engagement portion (112) comprises a fastening contact surface (118) and a fastening outer peripheral support surface (119), The fastening outer peripheral bearing surface (119) is located diametrically opposite to the fastening contact surface (118) around the fastening member axis (C), At the fastening position of the rotary cutting tool (20), The fastening contact surface (118) contacts the pin contact surface (74), The rotary cutting tool (20) according to claim 18, wherein the fastening outer peripheral support surface (119) abuts against the through-hole support surface (108).

20. At the fastening position of the rotary cutting tool (20), the holder radial plane (RP) intersects the pin contact surface (74), In the cross-sectional view taken in the radial plane (RP) of the holder, the pin contact surface (74) forms an acute angle (α) with the through hole axis (B) of the fastening surface. The aforementioned fastening surface angle (α) satisfies the condition: 5° ≤ α ≤ 15°, and is a rotary cutting tool (20) according to any one of claims 16 to 19.

21. The rotary cutting tool (20) according to any one of claims 16 to 20, wherein the pin recess (72) is located on a virtual recessed cylindrical body (IC) that extends circumferentially along a recessed cylindrical body axis (CA) oriented perpendicular to the head central axis (A) such that the pin contact surface (74) is curved in a concave shape.

22. The tool holder (24) is provided with a holder base contact surface (82) located on the holder base surface (80), The rotary cutting tool (20) according to any one of claims 16 to 21, wherein, at the fastening position of the rotary cutting tool (20), the rear surface of the head contact (38) contacts the holder base contact surface (82).

23. The head coupling pin (60) is provided with exactly one pin recess (70), The rotary cutting tool (20) according to any one of claims 16 to 22, wherein the tool holder (24) comprises strictly one holder through hole (102) and strictly one fastening member (26) that releasably engages with the tool holder (24).

24. In a cross-sectional view taken from a holder radial plane (RP) that extends perpendicular to the holder longitudinal axis (D) and is tolerant to the through-hole inner opening (107A), The outer surface of the hole (104) defines an inner hole line (LI) and an outer hole line (LO), and the inner hole line (LI) is closer to the longitudinal plane of the first holder (LP1) than the outer hole line (LO). Both the inner hole line (LI) and the outer hole line (LO) are located on the same side of the longitudinal plane (LP1) of the first holder. The inner hole line (LI) is inserted twice into the outer surface (100) of the connecting hole so as to define the first intersection (I1) and the second intersection (I2). The first intersection (I1) is in front of the second intersection (I2) in the direction of rotation. The tool holder (24) has a second holder longitudinal plane (LP2), The second holder longitudinal plane (LP2) extends perpendicular to the first holder longitudinal plane (LP1) and includes the holder longitudinal axis (D). The rotary cutting tool (20) according to any one of claims 16 to 23, wherein at the fastening position of the rotary cutting tool (20), the fastening member (26) abuts against the pin contact surface (74) in a contact area located on the same side as the first intersection (I1) of the second holder longitudinal plane (LP2).

25. The outer surface of the pin (64) has a cylindrical shape with a pin diameter (PD), The cutting head (22) has a cutting outer diameter (OD), The rotary cutting tool (20) according to any one of claims 16 to 24, wherein the pin diameter (PD) is greater than one-third of the cutting outer diameter (OD).

26. Forward direction (D Ｆ ) from the rear direction (D Ｒ A tool holder (24) having a holder longitudinal axis (D) extending to the ), The tool holder (24) is rotatable in the rotational direction (R) around the longitudinal axis (D) of the holder, The tool holder (24) is The holder outer circumferential surface (78) extends circumferentially around the longitudinal axis (D) of the holder and forms the boundary of the holder base surface (80) at the front end of the tool holder (24), Two drive members (84) are spaced apart in the circumferential direction and extend forward from the holder base surface (80), A holder coupling hole (96) recessed within the holder base surface (80), having an outer circumferential surface (100) of the coupling hole that extends circumferentially around the holder longitudinal axis (D), It comprises a holder through hole (102), The holder through-hole (102) has an outer circumferential surface (104) of the hole that extends circumferentially along the holder through-hole axis (B), and opens to the outer circumferential surface (100) of the coupling hole to form an inner through-hole opening (107A), and opens to the outer circumferential surface (78) of the holder to form an outer through-hole opening (107B). The longitudinal axis (D) of the holder is a tool holder (24) that is not visible from the outer circumferential surface (78) of the holder through the holder through hole (102) in the diagram along the through hole axis (B).

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