Rotatable cutting head and rotary cutting tool having a torque transmission surface on a mounting boss

Abstract

A cutting head rotatable about a head axis has a cap portion and a mounting protrusion connected thereto. The cap portion has N cutting portions circumferentially alternating with N head flutes. The mounting protrusion has N circumferentially spaced engagement portions, each engagement portion including a clamping surface and a torque transfer surface facing radially outward. In a cross-section taken in a head plane perpendicular to the head axis, a first imaginary circle having a first diameter circumscribes the N clamping surfaces, and the N radially outermost torque points of the N torque transfer surfaces define a second imaginary circle having a second diameter. The second diameter is greater than ninety percent of the first diameter. A rotary cutting tool comprises a tool shank extending along the shank axis and a head receiving recess at a front end thereof, and the cutting head is releasably secured in the head receiving recess.

Description

Technical Field

[0001] The present invention relates to a rotatable cutting head having a torque transmission surface on a mounting boss and a rotary cutting tool having such a cutting head, which are generally used in metal cutting processes and in particular for drilling operations. Background Art

[0002] In the field of cutting tools used in drilling operations, there are examples of rotary cutting tools having a cutting head with a torque transmitting surface on a mounting boss.

[0003] US Pat. No. 6,582,164 discloses a removable tip having a front end and a rear end. The front end has two cutting portions circumferentially alternating with two chip flutes, and the rear end is defined by a shaft adapted to be inserted into a connecting internal bore of a drill body and having diametrically opposed external threads extending therefrom. Each external thread has a reduced radius defining a drive surface that mates with a drive surface of a corresponding internal thread of the drill body for transmitting rotational force between the drill body and the removable tip.

[0004] US 10,071,430 discloses a cutting head designed to be inserted into a support in a modular rotary tool. The cutting head comprises a coupling pin having a torque surface and a clamping surface on its outer periphery. The coupling pin is divided into a front pin portion and a rear pin portion. The front pin portion is defined by a circumferential groove. A stop surface for axial pull-out safety is formed in the transition region between the front pin portion and the rear pin portion. The torque surface and the clamping surface are arranged in different pin portions. The clamping surface is preferably formed on the front pin portion, and the torque surface is preferably formed in the rear pin portion.

[0005] It is an object of the present invention to provide an improved rotatable cutting head having a torque transmitting surface on a mounting boss.

[0006] It is another object of the present invention to provide an improved rotatable cutting head configured for high levels of torque transfer between the tool shank and the mounting boss.

[0007] It is yet another object of the present invention to provide an improved rotary cutting tool configured for efficient and optimized torque transfer between the tool shank and the rotatable cutting head. Summary of the Invention

[0008] According to the present invention, there is provided a cutting head capable of rotating in a cutting rotation direction about a head axis, the head axis forming an axial forward direction and an axial rearward direction, the cutting head comprising:

[0009] a cap portion having N cutting portions circumferentially alternating with the N head flutes and a cap bottom surface facing in an axial rearward direction; and

[0010] A mounting protuberance, which is joined to the cap portion, extends axially rearwardly from the cap bottom surface and has:

[0011] a mounting end surface, which is distal to the cap portion, facing in an axial rearward direction, and

[0012] N circumferentially spaced engagement portions,

[0013] Each engagement portion includes a clamping surface facing radially outward and a torque transmission surface facing away from the direction of cutting rotation,

[0014] in:

[0015] N is an integer greater than 1, and

[0016] In a cross section taken in a first head plane perpendicular to the head axis, intersecting the N engagement portions and passing through the N clamping surfaces and the N torque transmission surfaces:

[0017] A first imaginary circle centered on the head axis and having a first diameter circumscribes N clamping surfaces,

[0018] a second imaginary circle centered on the head axis and having a second diameter is defined by the N radially outermost torque points of the N torque transmitting surfaces, and

[0019] The second diameter is greater than ninety percent and less than one hundred percent of the first diameter.

[0020] Furthermore, according to the present invention, there is provided a rotary cutting tool comprising in combination:

[0021] a tool shank extending along a shank axis and having a head-receiving recess at a forward end thereof, and

[0022] A cutting head of the above-described type is releasably secured to the head receiving pocket in the assembled position of the tool. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] For a better understanding, the invention will now be described, by way of example only, with reference to the accompanying drawings in which dot-dash lines indicate cut-off boundaries of partial views of components, and in which:

[0024] Figure 1 is a first perspective view of a cutting head according to some embodiments of the present invention;

[0025] Figure 2 is a second perspective view of a cutting head according to some embodiments of the present invention;

[0026] Figure 3 yes Figure 1 and Figure 2 A front view of the cutting head shown in ;

[0027] Figure 4 yes Figure 1 and Figure 2 A rear view of the cutting head shown in ;

[0028] Figure 5 yes Figure 1 and Figure 2 A side view of the cutting head shown in ;

[0029] Figure 6 It is taken along line VI-VI Figure 5 A cross-sectional view of the cutting head shown in ;

[0030] Figure 7 It is taken along line VII-VII Figure 5 A cross-sectional view of the cutting head shown in ;

[0031] Figure 8 is a first perspective view of a rotary cutting tool according to some embodiments of the present invention;

[0032] Figure 9 yes Figure 8 An exploded perspective view of a rotary cutting tool shown in ;

[0033] Figure 10 yes Figure 8 A side view of a rotary cutting tool shown in;

[0034] Figure 11 It is taken along line XI-XI Figure 10 A cross-sectional view of the rotary cutting tool shown in ; and

[0035] Figure 12 is a front view of a tool handle according to some embodiments of the present invention. DETAILED DESCRIPTION

[0036] A first aspect of the invention relates to a cutting head 20 rotatable about a head axis AH in a cutting direction of rotation RC.

[0037] The head axis AH defines an axial forward direction DF and an axial rearward direction DR.

[0038] In some embodiments of the present invention, the cutting head 20 may preferably be manufactured by form pressing and sintering a cemented carbide such as tungsten carbide, and may be coated or uncoated.

[0039] The cutting head 20 includes a cap portion 22 and a mounting boss 24 coupled to the cap portion 22 .

[0040] like Figures 1 to 5 As shown in FIG, the cap portion 22 has N cutting portions 26 circumferentially alternating with N head flutes 28 and a cap bottom surface 30 facing in the axial rearward direction DR.

[0041] It should be understood that throughout the specification and claims, N is a specific integer greater than 1, and thus the plurality of head flutes 28 is equal in number to the plurality of cutting portions 26 .

[0042] like Figure 3 As shown in , each cutting portion 26 may have a radially extending cutting edge 32 , and the N radially outermost cutting points NCO of the N radially extending cutting edges 32 may define an imaginary cutting circle CC having a cutting diameter DC.

[0043] In some embodiments of the present invention, it will be appreciated that the imaginary cutting circle CC may have a center that coincides with the head axis AH.

[0044] Additionally, in some embodiments of the present invention, the cutting head 20 may be used for drilling operations. Thus, the cutting head 20 may be a drill bit having a radially extending cutting edge 32 that also extends in the axial rearward direction DR.

[0045] Furthermore, in some embodiments of the present invention, the cutting head 20 may exhibit N-fold rotational symmetry about the head axis AH.

[0046] like Figures 1 to 5 As shown in FIG, the mounting projection 24 extends axially rearwardly from the cap bottom surface 30 and includes N circumferentially spaced engagement portions 34.

[0047] It should be understood that the N engaging portions 34 are equal in number to the N cutting portions 26 .

[0048] In some embodiments of the present invention, the cap bottom surface 30 may be perpendicular to the head axis AH.

[0049] Additionally, in some embodiments of the present invention, the cap bottom surface 30 may include N circumferentially spaced coplanar cap bottom sub-surfaces 30a.

[0050] The mounting projection 24 also includes a mounting end surface 36 facing in the axial rearward direction DR away from the cap portion 22 .

[0051] In some embodiments of the present invention, N head flutes 28 may extend axially rearward from the cap portion 22 and intersect the mounting end surface 36 , and a plurality of the N engagement portions 34 may circumferentially alternate with the N head flutes 28 .

[0052] Additionally, in some embodiments of the present invention, the mounting end surface 36 may be planar.

[0053] Furthermore, in some embodiments of the present invention, Figure 5 As shown in , the mounting end surface 36 may be axially spaced apart from the cap bottom surface 30 by a first height H1 , and the first height H1 may be less than thirty percent of the cutting diameter DC, ie, H1<0.30*DC.

[0054] For embodiments of the present invention in which the first height H1 is less than thirty percent of the cutting diameter DC, the mounting boss 24 can be considered axially compact, and the cutting head 20 can advantageously be manufactured from a reduced amount of cemented carbide.

[0055] like Figures 1 to 5 As shown in , each engagement portion 34 has a radially outwardly facing clamping surface 38 and a torque transfer surface 40 facing away from the cutting rotation direction RC. In the mounting boss 24, the clamping surface 38 and the torque transfer surface 40 overlap in the axial direction (ie, along the head axis AH).

[0056] In some embodiments of the present invention, each clamping surface 38 may be rotationally forward of its associated torque transfer surface 40 relative to the cutting rotational direction RC.

[0057] Additionally, in some embodiments of the present invention, the clamping surface 38 and the torque transfer surface 40 of each engagement portion 34 may be circumferentially spaced apart by an angled surface 42 .

[0058] Furthermore, in some embodiments of the present invention, Figure 5 As shown in FIG, the N clamping surfaces 38 may taper in the axial forward direction DF.

[0059] Furthermore, in some embodiments of the present invention, each clamping surface 38 may not intersect the mounting end surface 36 .

[0060] like Figure 2 、 Figure 4 and Figure 5 As shown in FIG, each engagement portion 34 may include an end chamfer 43 , and each clamping surface 38 may be spaced apart from the mounting end surface 36 by its associated end chamfer 43 .

[0061] By configuring the N torque transfer surfaces 40 to be disposed on the mounting protrusion 24 opposite the cap portion 22, the cutting portion 26 is advantageously allowed to be arranged in an optimized manner (e.g., with respect to the generation and flow of cutting chips) without requiring additional space to be provided for torque transfer between the tool shank and the cap portion 22 of the cutting head.

[0062] It will be appreciated that for a cap portion 22 having a smaller cutting diameter and a cutting head 20 having an N value greater than 2 (ie, N>2), it is more significant to arrange the cutting portion 26 in an optimized manner.

[0063] like Figure 6 As shown in , in a cross section taken in a first head plane PH1 perpendicular to the head axis AH, intersecting the N engagement portions 34 and passing through both the clamping surfaces 38 and the torque transfer surfaces 40 , a first imaginary circle C1 having a first diameter D1 circumscribes the N clamping surfaces 38 .

[0064] In some embodiments of the present invention, each clamping surface 38 may be located on a first imaginary circle C1 in a cross-section taken in the first head plane PH1 .

[0065] In addition, in some embodiments of the present invention, the first diameter D1 may be greater than seventy percent of the cutting diameter DC, that is, D1>0.70*DC.

[0066] Furthermore, in some embodiments of the present invention, it should be understood that the first imaginary circle C1 may have a center that coincides with the head axis AH.

[0067] like Figure 6 As shown in FIG, in a cross section taken in the first head plane PH1, the N radially outermost torque points NTO of the N torque transmitting surfaces 40 define a second imaginary circle C2 having a second diameter D2.

[0068] It should be understood that throughout the specification and claims, the N radially outermost torque points NTO may not be the absolute radially outermost torque points of the N torque transfer surfaces 40, but the radially outermost torque points of the N torque transfer surfaces 40 in the first head plane PH1.

[0069] In some embodiments of the present invention, it will be appreciated that the second imaginary circle C2 may have a center that coincides with the head axis AH.

[0070] According to the first aspect of the present invention, the second diameter D2 is greater than 90% and less than 100% of the first diameter D1, that is, 0.90*D1 <D2<1.00*D1。

[0071] In some embodiments of the present invention, the second diameter D2 may be greater than 95% and less than 100% of the first diameter D1, that is, 0.95*D1 <D2<1.00*D1。

[0072] It will be appreciated that configuring the N torque transfer surfaces 40 such that the second diameter D2 is greater than ninety percent of the first diameter D1 advantageously enables a high level of torque transfer between the tool shank and the mounting boss 24 .

[0073] It will also be appreciated that for embodiments of the present invention in which the first diameter D1 is greater than seventy percent of the cutting diameter DC, a high level of torque transmission may be further ensured.

[0074] like Figure 6 As shown in , each corner surface 42 may be convexly curved and tangentially abut its associated clamping surface 38 in a cross-section taken in the first head plane PH1 .

[0075] In addition, if Figure 6 As shown in FIG, in a cross-section taken in the first head plane PH1, each torque transmitting surface 40 may extend linearly from its corresponding radially outermost torque point NTO and define a first imaginary straight line L1.

[0076] In some embodiments of the present invention, Figure 6 As shown in FIG, each first imaginary straight line L1 may pass through another portion of the mounting protrusion 24 .

[0077] Additionally, in some embodiments of the present invention, each torque transmitting surface 40 may be planar.

[0078] like Figure 6 As shown in , each radially outermost torque point NTO can be contained in a second head plane PH2 containing the head axis AH.

[0079] In addition, if Figure 6 As shown in FIG, in a cross section taken in the first head plane PH1, each first imaginary straight line L1 may form a first angle α1 with its associated second head plane PH2.

[0080] In some embodiments of the present invention, the first angle α1 may be smaller than thirty-five degrees, that is, α1<35°.

[0081] It will be appreciated that for embodiments of the present invention in which the first angle α1 is less than thirty-five degrees, the N torque transfer surfaces 40 are advantageously oriented such that torque transfer between the tool shank and the mounting boss 24 can occur efficiently.

[0082] like Figures 1 to 5 As shown in , N can be equal to three, that is, N=3, and as Figure 6 As shown in FIG, in a cross-section taken in the first head plane PH1, a plurality of the N torque transmitting surfaces 40 may define an imaginary torque triangle TT.

[0083] In some embodiments of the present invention, Figure 6 As shown in , the N radially outermost torque points NTO of the N torque transmitting surfaces 40 may be located outside of the imaginary torque triangle TT.

[0084] Furthermore, in some embodiments of the present invention, a third imaginary circle C3 having a third diameter D3 may inscribe the torque triangle TT, and the third diameter D3 may be less than sixty percent of the first diameter D1 , ie, D3<0.60*D1.

[0085] It will be appreciated that for embodiments of the present invention in which the third diameter D3 is less than sixty percent of the first diameter D1 , the N torque transfer surfaces 40 are advantageously oriented such that torque transfer between the tool shank and the mounting boss 24 can occur efficiently.

[0086] In some embodiments of the present invention, the N torque transmitting surfaces 40 may be inclined outwardly in the axial forward direction DF such that Figure 6 As shown in FIG, the portions of the N torque transmitting surfaces 40 axially forward of the first head plane PH1 are located outside the torque triangle TT.

[0087] It will be appreciated that for embodiments of the present invention in which the N torque transmitting surfaces 40 are outwardly inclined in the axial forward direction DF, the N engagement portions 34 may be highly robust.

[0088] like Figures 1 to 5 As shown in , each torque surface 40 may be formed in a torque notch 44 of its corresponding engagement portion 34 .

[0089] In some embodiments of the present invention, each torque transfer surface 40 may intersect with an adjacent joining surface 46 to form a straight torque boundary edge 48 .

[0090] like Figure 5 As shown in , each torque transfer surface 40 may define a third head plane PH3 , and each third head plane PH3 may intersect the mounting boss 24 along its associated torque boundary edge 48 .

[0091] In some embodiments of the present invention, each joining surface 46 may intersect one of the head flutes 28 .

[0092] like Figure 7 As shown in FIG, each torque boundary edge 48 defines a second imaginary straight line L2 that may not intersect with or pass through any other portion of the mounting bump 24.

[0093] In addition, if Figure 7 As shown in FIG, each second imaginary straight line L2 may not intersect or pass through any other portion of the cutting head 20, except that each second imaginary straight line L2 coincides with its corresponding torque boundary edge 48. This can be achieved by Figure 7It is understood that neither portion of the second imaginary straight line L2 extending from the end of the torque boundary edge 48 overlaps with the “cutting” or “hatched” portion of the cutting head 20 .

[0094] In some embodiments of the present invention, Figure 5 As shown in , each second imaginary straight line L2 may intersect the first head plane PH1.

[0095] In addition, in some embodiments of the present invention, Figure 5 As shown in FIG, each torque boundary edge 48 may intersect the first head plane PH1.

[0096] Furthermore, in some embodiments of the present invention, Figure 5 and Figure 7 As shown in , each torque boundary edge 48 may intersect the mounting end surface 36 .

[0097] It will be appreciated that for embodiments of the present invention in which each second imaginary straight line L2 does not intersect or pass through any other portion of the cutting head 20, other than coinciding with its corresponding torque boundary edge 48, the associated torque transfer surface 40 may be formed by means of a grinding operation, thereby providing sufficient clearance for the large diameter grinding wheels typically used to perform such grinding operations.

[0098] It should also be appreciated that after the grinding operation, the N torque transmitting surfaces 40 may be highly precise.

[0099] For such embodiments of the present invention, the mounting boss 24 may be configured such that the first imaginary straight line L1 associated with each torque transmitting surface 40 passes through another portion of the mounting boss 24, such as an embodiment where N=3.

[0100] like Figures 8 to 12 As shown in , a second aspect of the present invention relates to a rotary cutting tool 50, which in combination has: a tool shank 52, which extends along a shank axis AS and has a head receiving pocket 54 at its front end 56; and a cutting head 20, which is releasably fixed to the head receiving pocket 54 in the assembled position of the tool.

[0101] In some embodiments of the present invention, the tool shank 52 may preferably be manufactured from tool steel.

[0102] In addition, in some embodiments of the present invention, the rotary cutting tool 50 can be used for drilling operations. As seen in these figures, the cutting tool 50 is a drill 50 comprising a drill bit 20 and a drill shank 52.

[0103] Furthermore, in some embodiments, the cutting head 20 may be releasably secured to the head receiving pocket 54 without the need for additional fastening members such as clamping screws.

[0104] like Figure 9 and Figure 12 As shown in FIG, the head receiving pocket 54 may include N circumferentially spaced apart securing portions 58, and each securing portion 58 may have an axially forward facing shank support surface 60.

[0105] In some embodiments of the present invention, the N handle support surfaces 60 may be coplanar.

[0106] Additionally, in some embodiments of the present invention, the N handle support surfaces 60 may be perpendicular to the handle axis AS.

[0107] like Figure 9 and Figure 10 As shown in , the head receiving pocket 54 can have a bottom surface 62 that faces axially forward, and the bottom surface 62 can be axially spaced apart from the N shank support surfaces 60 by a second height H2.

[0108] In some embodiments of the present invention, bottom surface 62 may be planar.

[0109] like Figure 8 、 Figure 10 and Figure 11 As shown in FIG, in the assembled position of the rotary cutting tool 50:

[0110] The cap bottom surface 30 may face N handle support surfaces 60 ;

[0111] The head axis AH may coincide with the handle axis AS;

[0112] Each clamping surface 38 may contact a radially inwardly facing abutment surface 64 of one of the securing portions 58; and

[0113] Each torque transfer surface 40 may be in contact with a drive surface 66 of one of the fixed portions 58 , each drive surface 66 facing in the cutting rotation direction RC.

[0114] like Figure 10 and Figure 12 As shown in FIG, each drive surface 66 extends from its associated abutment surface 64 in a generally radially inward direction.

[0115] In some embodiments of the present invention, the cap bottom surface 30 may be in contact with N handle support surfaces 60 .

[0116] like Figure 10 As shown in , the second height H2 may be greater than the first height H1.

[0117] For embodiments of the present invention in which the second height H2 is greater than the first height H1 , the mounting end surface 36 of the cutting head may be axially spaced from the bottom surface 62 of the head receiving pocket.

[0118] It should be understood that in the assembled position of the rotary cutting tool 50, other than the N clamping surfaces 38 contacting the N abutment surfaces 64 and the N torque transfer surfaces 40 contacting the N drive surfaces 66, no other surface of the mounting protrusion 24 may contact the tool shank 52.

[0119] like Figure 11 As shown in , in a cross section taken in a first tool plane PT1 coinciding with the first head plane PH1 , the radially outermost contact point between each torque transfer surface 40 and its intersecting drive surface 66 may occur at the radially outermost torque point NTO of the torque transfer surface.

[0120] For such an embodiment of the present invention, it will be appreciated that torque transfer between the N drive surfaces 66 and the N torque transfer surfaces 40 is optimized because the most efficient torque transfer occurs at the radially outermost contact points.

[0121] In some embodiments of the present invention, each abutment surface 64 may be rotationally forward of its associated drive surface 66 relative to the cutting rotational direction RC.

[0122] Additionally, in some embodiments of the present invention, the N abutment surfaces 64 may extend radially inward in the axial forward direction DF.

[0123] Furthermore, in some embodiments of the present invention, the N abutment surfaces 64 and the N clamping surfaces 38 may be correspondingly inclined in the axial forward direction DF.

[0124] For embodiments of the present invention in which the N abutment surfaces 64 and the N clamping surfaces 38 are correspondingly inclined in the axial forward direction DF, the clamping forces between the N abutment surfaces 64 and the N clamping surfaces 38 may be directed axially rearwardly and radially inwardly.

[0125] The present invention also relates to a method of assembling a rotary cutting tool 50, comprising the following steps:

[0126] a) orienting the cap bottom surface 30 to face the N handle support surfaces 60;

[0127] b) aligning the head axis AH with the handle axis AS;

[0128] c) rotationally aligning the N head flutes 28 with the N fixed portions 58;

[0129] d) inserting the mounting protrusion 24 into the head receiving recess 54; and

[0130] e) Rotate the cutting head 20 about the head axis AH counter to the cutting rotation direction RC until:

[0131] The N clamping surfaces 38 are held against the N abutment surfaces 64, and

[0132] The N torque-transmitting surfaces 40 are in contact with the N drive surfaces 66 .

[0133] In some embodiments of the present invention, in step d) of tool assembly, the mounting protuberance 24 may be inserted into the head receiving recess 54 until the cap bottom surface 30 contacts the N shank support surfaces 60 .

[0134] The embodiment of the present invention having the convexly curved corner surface 42 tangentially adjoining the N clamping surfaces 38 may advantageously enable smooth engagement of the N engaging portions 34 with the N fixing portions 58 in step e) of tool assembly.

[0135] It will be appreciated that in order for the N clamping surfaces 38 to be successfully held against the N abutment surfaces 64 during step e) of tool assembly, the second diameter D2 may need to be less than one hundred percent of the first diameter D1 .

[0136] like Figures 8 to 12 As shown in , the tool shank 50 may have a generally cylindrical shank peripheral surface 68 .

[0137] In some embodiments of the present invention, Figure 11 and Figure 12 As shown in FIG, the shank peripheral surface 68 may have a shank diameter DS, and the shank diameter DS may be smaller than the cutting diameter DC.

[0138] In addition, in some embodiments of the present invention, the second height H2 may be less than 30 percent of the handle diameter DS, that is, H2<0.30*DS.

[0139] like Figures 8 to 12 As shown in FIG, N shank flutes 70 may be formed in the shank peripheral surface 68 and extend along the shank axis AS.

[0140] In some embodiments of the present invention, N shank flutes 70 may extend axially rearward from the front end 56 of the shank, and the N securing portions 58 may circumferentially alternate with the N shank flutes 70 .

[0141] Additionally, in some embodiments of the present invention, the N shank flutes 70 may extend helically along the shank axis AS.

[0142] Furthermore, in some embodiments of the present invention, the N shank flutes 70 may intersect the bottom surface 62 of the head receiving pocket.

[0143] It should be understood that in the assembled position of the rotary cutting tool 50 , the N shank flutes 70 may at least partially correspond to the N head flutes 28 .

[0144] like Figure 11 As shown in FIG, in a cross section taken in a first tool plane PT1 , each fixing portion 58 subtends a first angular extent E1 about the shank axis AS between two circumferentially adjacent shank flutes 70 thereof.

[0145] In some embodiments of the present invention, the first angle range E1 may be smaller than eighty degrees, that is, E1<80°.

[0146] In addition, in some embodiments of the present invention, the first angle range E1 may be smaller than seventy degrees, that is, E1<70°.

[0147] Furthermore, in some embodiments of the present invention, it should be understood that the first angular range E1 is measured around the circumference of the handle peripheral surface 68 .

[0148] For embodiments of the present invention in which the first angular range E1 is less than eighty degrees, it will be appreciated that the N shank flutes 70 may have an increased volume, thereby advantageously providing increased space for chip evacuation.

[0149] like Figure 9 、 Figure 11 and Figure 12 As shown in FIG, each abutment surface 64 may be circumferentially spaced apart from its associated drive surface 66 by a retaining recess 72 having a recess surface 74 .

[0150] like Figure 11 As shown in FIG, each recess surface 74 may be located outside the first imaginary circle C1 in a cross section taken in the first tool plane PT1.

[0151] It should be appreciated that in the assembled position of the rotary cutting tool 50 , each recess surface 74 may be radially spaced from one of the corner surfaces 42 of the cutting head.

[0152] In addition, if Figure 11 As shown in FIG, in a cross section taken in the first tool plane PT1, each recess surface 74 has a radially outermost recess point NRO.

[0153] In some embodiments of the present invention, each radially outermost concave point NRO may be located at least twice farther from the first imaginary circle C1 than each radially outermost torque point NTO.

[0154] like Figure 11 As shown in , each radially outermost recess point NRO is contained in a first shank plane PS1 containing the shank axis AS, and each fixing portion 58 includes a first fixing sub-portion 58a and a second fixing sub-portion 58b located on opposite sides of its associated first shank plane PS1.

[0155] It will be appreciated that in the assembled position of the rotary cutting tool 50 , each first shank plane PS1 may intersect one of the corner surfaces 42 of the cutting head.

[0156] In some embodiments of the present invention, each abutment surface 64 may be provided on one of the first fixed sub-portions 58 a , and each drive surface 66 may be provided on one of the second fixed sub-portions 58 b .

[0157] like Figure 11 As shown in the cross section taken in the first tool plane PT1, for an embodiment of the present invention in which the shank peripheral surface 68 is substantially cylindrical, the first wall thickness T1 of each fixing portion 58 at its corresponding fixing recess 72 can be smaller than the second wall thickness T2 of the fixing portion 58 at its circumferentially adjacent abutment surface 64.

[0158] For such an embodiment of the present invention, it will be appreciated that each first fixation sub-portion 58a and its corresponding abutment surface 64 may be resiliently displaceable independently of the second fixation sub-portion 58b.

[0159] Additionally, with this embodiment of the present invention, it will be appreciated that the second stator portion 58b can maintain a high level of rigidity so that torque transfer between each drive surface 66 and its intersecting torque transfer surface 40 can occur with a high level of efficiency and stability.

[0160] For embodiments of the invention in which the second height H2 is less than thirty percent of the shank diameter DS, the provision of a fixing recess 72 at each fixing portion 58 is very effective in providing a suitably high level of resilience to the associated first fixing sub-portion 58a during the above-mentioned step e) of tool assembly, while at the same time directing a suitably high level of clamping force from its respective abutment surface 64 to the interfacing clamping surface 38.

[0161] like Figures 8 to 12 As shown in FIG, each fixed portion 58 may include an inclined transition surface 76, and each transition surface 76 may be rotationally located behind its associated drive surface 66 relative to the cutting rotational direction RC.

[0162] In some embodiments of the present invention, each transition surface 76 may be inclined in an axial rearward direction DR opposite to the cutting rotation direction RC.

[0163] In addition, in some embodiments of the present invention, Figure 10 As shown in FIG, each transition surface 76 may intersect its adjacent rear shank flute 70 axially rearward of the first head plane PH1.

[0164] Furthermore, in some embodiments of the present invention, Figure 12 As shown in FIG, each transition surface 76 may intersect its associated shank support surface 60 radially outward of its associated drive surface 66 .

[0165] like Figures 8 to 12 As shown in FIG, each transition surface 76 may be circumferentially spaced apart from its associated drive surface 66 by an inclined clearance surface 78 .

[0166] It will be appreciated that for some embodiments of the present invention, the N clearance surfaces 78 may be configured to provide sufficient space for step e) of tool assembly to be performed without inadvertent contact between the N engaging portions 34 and the N securing portions 58, particularly in the region of the N connecting surfaces 46 of the cutting head.

[0167] like Figures 8 to 12 As shown in , the tool shank 52 may include N axially extending coolant passages 80 , and each coolant passage 80 may open to one of the transition surfaces 76 .

[0168] Although the present invention has been described with a certain degree of particularity, it will be understood that various changes and modifications can be made without departing from the spirit or scope of the invention as hereinafter claimed.

Claims

1. A cutting head (20) rotatable in a cutting rotation direction (RC) about a head axis (AH), said head axis (AH) defining an axial forward direction (DF) and an axial rearward direction (DR), comprising: a cap portion (22) having N cutting portions (26) circumferentially alternating with N head flutes (28) and a cap bottom surface (30) facing in the axial rearward direction (DR); and A mounting protuberance (24) is attached to the cap portion (22), extends axially rearwardly from the cap bottom surface (30), and has: a mounting end surface (36) facing away from the cap portion (22) in the axial rearward direction (DR), and N circumferentially spaced engagement portions (34), each engagement portion (34) including a radially outwardly facing clamping surface (38) and a torque transfer surface (40) facing away from said cutting rotation direction (RC), in: N is an integer greater than 1, and In a cross section taken in a first head plane (PH1) perpendicular to the head axis (AH), intersecting the N engagement portions (34) and passing through the N clamping surfaces (38) and the N torque transmission surfaces (40): A first imaginary circle (C1) centered on the head axis (AH) and having a first diameter (D1) circumscribes the N clamping surfaces (38), a second imaginary circle (C2) centered on the head axis (AH) and having a second diameter (D2) defined by the N radially outermost torque points (NTO) of the N torque transmitting surfaces (40), The second diameter (D2) is greater than ninety percent and less than one hundred percent of the first diameter (D1), and Each torque transmitting surface (40) extends linearly from its respective radially outermost torque point (NTO) and defines a first imaginary straight line (L1).

2. The cutting head (20) according to claim 1, wherein Each first imaginary straight line (L1) passes through another portion of the mounting protrusion (24).

3. The cutting head (20) according to claim 1 or 2, wherein: N is equal to 3, and In a cross section taken in the first head plane (PH1), the N torque transfer surfaces (40) define an imaginary torque triangle (TT).

4. The cutting head (20) according to claim 3, wherein: The N torque transfer surfaces (40) are inclined outwardly in the axial forward direction (DF) so that in a cross section taken in the first head plane (PH1), portions of the N torque transfer surfaces (40) axially forward of the first head plane (PH1) are located outside the torque triangle (TT).

5. The cutting head (20) according to claim 1 or 2, wherein: The N head flutes (28) extend axially rearwardly from the cap portion (22) and intersect the mounting end surface (36), and The N engaging portions (34) circumferentially alternate with the N head flutes (28).

6. The cutting head (20) according to claim 1 or 2, wherein: In a cross section taken in the first head plane (PH1), each clamping surface (38) lies on the first imaginary circle (C1).

7. The cutting head (20) according to claim 1 or 2, wherein: Each cutting portion (26) has a radially extending cutting edge (32), N radially outermost cutting points (NCO) of the N radially extending cutting edges (32) define an imaginary cutting circle (CC) centered about the head axis (AH) and having a cutting diameter (DC), and The first diameter (D1) is greater than seventy percent of the cutting diameter (DC).

8. The cutting head (20) according to claim 7, wherein: The mounting end surface (36) is axially spaced apart from the cap bottom surface (30) by a first height (H1), and The first height (H1) is less than thirty percent of the cutting diameter (DC).

9. The cutting head (20) according to claim 1 or 2, wherein: The N clamping surfaces (38) taper in the axial forward direction (DF).

10. The cutting head (20) according to claim 1 or 2, wherein: Each torque transmitting surface (40) is formed in a torque notch (44) of its corresponding engagement portion (34), Each torque transfer surface (40) intersects an adjacent joining surface (46) to form a straight torque boundary edge (48), and Each torque boundary edge (48) defines a second imaginary straight line (L2) that does not intersect or pass through any other portion of the mounting bump (24).

11. The cutting head (20) according to claim 10, wherein In addition to each second imaginary straight line (L2) coinciding with its corresponding torque boundary edge (48), each second imaginary straight line (L2) does not intersect with or pass through any other portion of the cutting head (20).

12. The cutting head (20) according to claim 10, wherein Each torque boundary edge (48) intersects the first head plane (PH1).

13. The cutting head (20) according to claim 10, wherein: Each torque transmitting surface (40) defines a third head plane (PH3), and Each third head plane (PH3) intersects the mounting bump (24) along its associated torque boundary edge (48).

14. A rotary cutting tool (50) comprising, in combination: a tool shank (52) extending along a shank axis (AS) and having a head-receiving recess (54) at a forward end (56) thereof, and a cutting head (20) releasably secured to the head receiving pocket (54) in an assembled position of the tool, A cutting head (20) rotatable in a cutting rotation direction (RC) about a head axis (AH), said head axis (AH) defining an axial forward direction (DF) and an axial rearward direction (DR), and comprising: a cap portion (22) having N cutting portions (26) circumferentially alternating with N head flutes (28) and a cap bottom surface (30) facing in the axial rearward direction (DR); and A mounting protuberance (24) is attached to the cap portion (22), extends axially rearwardly from the cap bottom surface (30), and has: a mounting end surface (36) facing away from the cap portion (22) in the axial rearward direction (DR), and N circumferentially spaced engagement portions (34), each engagement portion (34) including a radially outwardly facing clamping surface (38) and a torque transfer surface (40) facing away from said cutting rotation direction (RC), in: N is an integer greater than 1, and In a cross section taken in a first head plane (PH1) perpendicular to the head axis (AH), intersecting the N engagement portions (34) and passing through the N clamping surfaces (38) and the N torque transmission surfaces (40): A first imaginary circle (C1) centered on the head axis (AH) and having a first diameter (D1) circumscribes the N clamping surfaces (38), a second imaginary circle (C2) centered about the head axis (AH) and having a second diameter (D2) defined by the N radially outermost torque points (NTO) of the N torque transmitting surfaces (40), and The second diameter (D2) is greater than ninety percent and less than one hundred percent of the first diameter (D1), The head receiving pocket (54) includes N circumferentially spaced apart securing portions (58), each securing portion (58) having an axially forwardly facing shank support surface (60), Wherein, in the assembly position of the tool: The cap bottom surface (30) faces the N handle support surfaces (60); The head axis (AH) coincides with the handle axis (AS); Each clamping surface (38) contacts a radially inwardly facing abutment surface (64) of one of the fixing portions (58); and Each torque transmission surface (40) is in contact with a drive surface (66) of one of the fixed parts (58), each drive surface (66) facing the cutting rotation direction (RC), wherein each abutment surface (64) is circumferentially spaced from its associated drive surface (66) by a fixed recess (72) having a recess surface (74), and Wherein, in a cross section taken in a first tool plane (PT1) coinciding with the first head plane (PH1), each recess surface (74) is located outside the first imaginary circle (C1).

15. The rotary cutting tool (50) of claim 14, wherein: The N clamping surfaces (38) and the N abutment surfaces (64) are inclined in the axial forward direction (DF).

16. The rotary cutting tool (50) according to claim 14 or 15, wherein In a cross section taken in a first tool plane (PT1) coinciding with the first head plane (PH1), the radially outermost point of contact between each torque transfer surface (40) and its intersecting drive surface (66) occurs at the radially outermost torque point (NTO) of the torque transfer surface.

17. The rotary cutting tool (50) according to claim 14 or 15, wherein: The tool shank (52) has a generally cylindrical shank peripheral surface (68), and N shank flutes (70) are formed in the shank peripheral surface (68) and extend along the shank axis (AS).

18. The rotary cutting tool (50) of claim 17, wherein: The N shank flutes (70) extend axially rearward from the front end (56) of the shank, and The N fixing portions (58) circumferentially alternate with the N shank flutes (70).

19. The rotary cutting tool (50) according to claim 18, wherein In a cross section taken in a first tool plane (PT1) coinciding with said first head plane (PH1): Each fixing portion (58) subtends a first angular extent (E1) about the shank axis (AS) between two circumferentially adjacent shank flutes (70) thereof, and The first angle range (E1) is smaller than 80 degrees.

20. The rotary cutting tool (50) according to claim 14 or 15, wherein In a cross section taken in the first tool plane (PT1): Each recess surface (74) has a radially outermost recess point (NRO), and Each radially outermost concave point (NRO) is located at least twice further from the first imaginary circle (C1) than each radially outermost torque point (NTO).

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