Rotary cutting tool having a central coolant passage of non-circular cross section

Abstract

The rotary cutting tool (20) is rotatable in a rotational direction about a tool axis and has a front cutting portion (24) and a rear connecting portion (26). The front cutting portion (24) has a front outer peripheral surface (28) with a plurality of N circumferentially spaced notches, each notch having an associated active cutting edge. A central coolant passage (34, 48) extends along the tool axis from the rear end of the rear connecting portion (26) to the front cutting portion (24). A first plane (P1) perpendicular to the tool axis intersects the central coolant passage (34, 48) and the N active cutting edges. In a cross section along the first plane (P1), the central coolant passage (34, 48) has a non-circular shape with N radially outer coolant regions (52). At least one coolant duct (58) extends laterally from each radially outer coolant region (52) and intersects and opens at a corresponding one of the N notches in the coolant outlet ports (60).

Description

[Technical Field]

[0001] The present invention relates generally to rotary cutting tools used in metal cutting processes, and more particularly in milling operations, having a central coolant passage of a non-circular cross-sectional shape. [Background technology]

[0002]

[0002] In the field of rotary cutting tools used in milling operations, there are many examples of cutting tools having central coolant passages, and in some cases the central coolant passages have non-circular cross-sectional shapes.

[0003]

[0003] U.S. Patent No. 7,207,755 discloses a cutting tool arrangement and a tool for chip removal machining, the cutting tool arrangement including a tool, a fixture arrangement, and a shank. The tool is an integral unit having an axial channel. The axial channel has a non-circular cross section to provide a key grip, and an end of the axial channel includes a material that at least partially closes the axial channel.

[0004]

[0004] U.S. Patent Application Publication No. 2012 / 163931 discloses a tool having a shank with a central continuous internal channel and an insert protruding into the internal channel and securely connected to the shank by friction and / or mechanical means, the internal channel having one or more extensions that function as cooling channels during the working process of the tool.

[0005]

[0005] Japanese Patent No. 7057550 (US Patent Application Publication No. 2023 / 0063846) discloses a rotary cutting tool configured to supply coolant fluid toward its cutting edge. The cutting tool includes a holding portion, a cutting portion, and a flow passage that guides the cooling fluid to an outlet port in the cutting portion. The flow passage includes a plurality of first flow passages that extend at least partially parallel to a central axis of rotation of the tool and a plurality of second flow passages that extend from the first flow passages toward the cutting edge.

[0006]

[0006] It is an object of the present invention to provide an improved rotary cutting tool having a central coolant passage having a non-circular cross-sectional shape.

[0007]

[0007] It is also an object of the present invention to provide an improved rotary cutting tool having coolant ducts that extend laterally away from a central coolant passage so as to provide design flexibility with respect to the direction and extent of each coolant duct.

[0008]

[0008] A further object of the present invention is to provide an improved rotary cutting tool which promotes uniform and axisymmetric flow of cooling fluid along each coolant duct. Summary of the Invention

[0009]

[0009] According to the present invention, there is provided a rotary cutting tool that is rotatable around a tool axis in a rotational direction, the tool axis defining a forward direction and a rearward direction, and the rotary cutting tool comprises a tool body having a front cutting portion and a rear connecting portion; the leading cutting portion having a leading outer peripheral surface with a plurality of N circumferentially spaced notches, N being a specified integer greater than 1, each notch opening at a leading end of the leading cutting portion and having an active cutting edge associated with the leading end; a central coolant passage extending along the tool axis from a rear end of the rear connecting portion to the front cutting portion, and a first plane perpendicular to the tool axis intersects the central coolant passage and the N active cutting edges; In a cross section along the first plane, the central coolant passage has a non-circular shape having N radially outer coolant regions, each radially outer coolant region having a first radially outermost coolant point, and the central coolant passage is circumscribed by an imaginary first circle having a first diameter and a center coincident with the tool axis; At least one coolant duct extends laterally from each radially outer coolant region to intersect and open in one of the N notches at a coolant outlet port.

[0010]

[0010] In order that the invention may be better understood, it will now be described, by way of example only, with reference to the accompanying drawings in which dashed lines represent cutting boundaries of partial views of elements. [Brief explanation of the drawings]

[0011] [Figure 1]

[0011] FIG. 1 is a first perspective view of a rotary cutting tool according to an embodiment of the present invention. [Figure 2]

[0012] FIG. 2 is a second exploded perspective view of the cutting tool shown in FIG. [Figure 3]

[0013] FIG. 2 is a side view of the cutting tool shown in FIG. [Figure 4]

[0014] FIG. 2 is an end view of the cutting tool shown in FIG. [Figure 5]

[0015] FIG. 4 is a cross-sectional view taken along line VV of the cutting tool shown in FIG. [Figure 6]

[0016] FIG. 6 is a detailed view of the cutting tool shown in FIG. 5. [Figure 7]

[0017] FIG. 7 is a cross-sectional view of the cutting tool shown in FIG. 5 taken along line VII-VII. [Figure 8]

[0018] FIG. 8 is a detailed view of the cutting tool shown in FIG. 7. [Figure 9]

[0019] 9 is a cross-sectional view of the cutting tool taken along line IX-IX in FIG. 8. [Figure 10]

[0020] 4 is a cross-sectional view of the cutting tool shown in FIG. 3 taken along line XX. [Figure 11]

[0021] FIG. 11 is a detailed view of the cutting tool shown in FIG. [Figure 12]

[0022] 12 is a cross-sectional view of the cutting tool shown in FIG. 3 taken along line XII-XII. DETAILED DESCRIPTION OF THE INVENTION

[0012]

[0023] First, attention is directed to FIGS. 1 to 4, which show a rotary cutting tool 20 according to the present invention.

[0013]

[0024] The rotary cutting tool 20 is rotatable in a rotational direction RD about a tool axis AT, which defines a forward direction DF and a rearward direction DR, and the rotary cutting tool 20 comprises a tool body 22 having a front cutting portion 24 and a rear connecting portion 26, the rear connecting portion 26 being positioned axially rearward of the front cutting portion 24.

[0014]

[0025] As shown in Figures 1-4, the front cutting portion 24 has a front outer peripheral surface 28 having a plurality of N circumferentially spaced notches 30, where N is a specified integer greater than 1, i.e., N>1.

[0015]

[0026] In some embodiments of the present invention, the front outer periphery 28 may be cylindrical.

[0016]

[0027] Also, in some embodiments of the present invention, N may preferably be 8 or less, i.e., 1 <N≦8であってもよい。

[0017]

[0028] Each notch 30 opens at a forward end 32 of the front cutting portion 24 and has an active cutting edge 34' associated with the forward end 32.

[0018]

[0029] In one embodiment of the present invention, as shown in Figures 1-4, each notch 30 may have an insert-receiving pocket 36 in which a cutting insert 38 is removably secured, and an active cutting edge 34' may be formed on the cutting insert 38.

[0019]

[0030] In other embodiments of the present invention (not shown), the N working cutting edges 34' may be integrally formed on the tool body 22 such that the cutting tool 20 has a unitary, one-piece (i.e., "monolithic") construction.

[0020]

[0031] As shown in Figures 1-4, each cutting insert 38 may be indexable and may have multiple cutting edges 34, and each cutting insert 38 may be positioned within its associated insert-receiving pocket 36 such that only one of the cutting insert's multiple cutting edges 34 is the active cutting edge 34', i.e., positioned to engage a workpiece (not shown).

[0021]

[0032] In one embodiment of the present invention, the cutting insert 38 may include a through hole 40, and the cutting insert 38 may be removably secured to the tool body 22 by a clamping screw 42 that occupies the through hole 40 and threadably engages a threaded hole 44 in a seating surface 46 of the insert receiving pocket 36.

[0022]

[0033] Also, in some embodiments of the present invention, the cutting insert 38 may be made from a moderately hard material, such as, for example, a cemented carbide, and the tool body 22 may be made from a less hard material, such as, for example, a tool steel.

[0023]

[0034] Furthermore, in some embodiments of the present invention, as shown in FIGS. 1-4, the cutting insert 38 may be a "radial" type cutting insert.

[0024]

[0035] In other embodiments of the present invention (not shown), the cutting insert 38 may be a "tangential" type cutting insert.

[0025]

[0036] As shown in Figures 5 and 7, a single central coolant passage 48 extends along the tool axis AT from the rear end 50 of the rear connecting portion 26 to the front cutting portion 24, and a first plane P1 perpendicular to the tool axis AT intersects the central coolant passage 48 and the N active cutting edges 34' as shown in Figures 3 and 7. In embodiments in which each notch 30 has an insert-receiving pocket 36, the first plane P1 may intersect each of the insert-receiving pockets 36 and each of the associated seating surfaces 46.

[0026]

[0037] As shown in Figures 5 and 6, in a cross section along the first plane P1, the central coolant passage 48 is non-circular having N radially outer coolant regions 52, each having a first radially outermost coolant point NCO1, and the central coolant passage 48 has a first diameter D1 and is circumscribed by an imaginary first circle C1 whose center coincides with the tool axis AT.

[0027]

[0038] In one embodiment of the present invention, as shown in FIGS. 5 and 6, in a cross section along the first plane P1, each of the first radially outermost coolant points NCO1 may be located on an imaginary first circle C1.

[0028]

[0039] Also, in one embodiment of the present invention, as shown in Figures 5 and 6, in a cross section along the first plane P1, each first radially outermost coolant point NCO1 may define one of N vertices of a first regular polygon RP1 with N sides.

[0029]

[0040] It should be noted that in this embodiment of the present invention, the N radially outer coolant regions 52 of the central coolant passage 48 define, in a cross section along the first plane P1, a first regular polygon RP1 having N sides, where N is a particular integer greater than 2, i.e., N>2.

[0030]

[0041] 1 to 6 show an embodiment of the present invention in which N is equal to 3, ie, N=3, and the N-sided first regular polygon RP1 is an equilateral triangle.

[0031]

[0042] As shown in Figures 1 and 4, the leading end 32 of the leading cutting portion may have a first end surface 54 facing forward.

[0032]

[0043] In some embodiments of the present invention, the central coolant passage 48 may terminate axially rearward of the first end surface 54. It should be noted that in such embodiments of the present invention, the tool axis AT may intersect the first end surface 54.

[0033]

[0044] As shown in Figures 5 and 6, in a cross section along the first plane P1, the central coolant passage 48 may include N radially outer coolant regions 52 and N radially recessed coolant regions 56 arranged alternately in the circumferential direction.

[0034]

[0045] In one embodiment of the present invention, each radially recessed coolant region 56 may have a first radially innermost coolant point NCI1 located inside the first regular polygon RP1.

[0035]

[0046] It should be noted that in such an embodiment of the present invention, the N radially recessed coolant regions 56 contribute to maintaining the core strength of the tool body 22 .

[0036]

[0047] According to the present invention, as shown in Figures 5-8, at least one coolant duct 58 extends laterally from each radially outer coolant region 52 and intersects and opens at one of the N notches 30 at one or more coolant outlet ports 60.

[0037]

[0048] It should be noted that by configuring each coolant duct 58 to extend from one of the radially outer coolant regions 52 of the non-circular central coolant passage 48 to one of the N notches 30, as shown in Figures 5 and 7, greater design flexibility is provided with regard to the direction and extent of each coolant duct 58.

[0038]

[0049] 7 and 8, each coolant duct 58 may merge into an associated radially outer coolant region 52 via a convexly curved interface 61 that promotes smooth, undisturbed flow of coolant fluid from the central coolant passage 48 to each coolant duct 58. In such an embodiment of the invention, it will be appreciated that the cutting tool body 22 may be manufactured by additive manufacturing, resulting in an additively manufactured tool body. One skilled in the art can determine whether a given tool body has been manufactured by an additive manufacturing process by examining the microstructure of the material comprising the tool body.

[0039]

[0050] Additionally, in some embodiments of the present invention, each notch 30 may intersect the first end surface 54 and each coolant outlet port 60 may be located axially rearward of the first end surface 54 .

[0040]

[0051] Additionally, in some embodiments of the present invention, as shown in FIGS. 5 and 7, each coolant duct 58 may direct coolant fluid towards the active cutting edge 34' of the associated notch 30.

[0041]

[0052] It has been found that directing coolant to the working cutting edge 34' significantly reduces wear and extends its useful life.

[0042]

[0053] As shown in Figures 5 and 6, in a cross section along the first plane P1, each first radially outermost coolant point NCO1 may be located on a concavely curved first inner wall 62 of the associated radially outer coolant region 52, and the first inner wall 62 may have a first radius R1.

[0043]

[0054] In some embodiments of the present invention, as shown in FIG. 6, each coolant duct 58 may extend away from a first inner wall 62 of an associated radially outer coolant region 52 .

[0044]

[0055] It should be noted that in embodiments of the present invention where N is equal to 2, i.e., N=2 (not shown), and the central coolant passage 48 has two radially outer coolant regions 52 having two concavely curved first inner walls 62, in a cross section of the central coolant passage 48 perpendicular to the tool axis AT, the central coolant passage 48 may have the shape of the number "8".

[0045]

[0056] In some embodiments of the present invention, the first radius R1 may be greater than 10 percent of the first diameter D1, ie, R1>0.10×D1.

[0046]

[0057] Also, in some embodiments of the present invention, each first inner wall 62 may have a first angular range EA1 that is greater than 90 degrees, i.e., EA1 > 90°. In some embodiments, the first angular range EA1 may be greater than 180°.

[0047]

[0058] It should be noted that in embodiments of the present invention in which the concavely curved first inner wall 62 has a relatively large first radius R1, i.e., R1 > 0.10 × D1, and / or a relatively large first angular range EA1, i.e., EA1 > 90°, a smooth and undisturbed flow of coolant fluid from the central coolant passage 48 to each coolant duct 58 is promoted.

[0048]

[0059] As shown in FIG. 6, in a cross section along the first plane P1, each first radially innermost coolant point NCI1 may be located on the convexly curved second inner wall 64 of the associated radially concave coolant region 56.

[0049]

[0060] In some embodiments of the present invention, each convexly curved second inner wall 64 may merge tangentially with a circumferentially adjacent concavely curved first inner wall 62 .

[0050]

[0061] It is noted that embodiments of the present invention in which the convexly curved second inner wall 64 tangentially merges with the circumferentially adjacent concavely curved first inner wall 62 promote a smooth, undisturbed flow of coolant fluid from the central coolant passage 48 to each coolant duct 58. It is noted that in such embodiments of the present invention, the cutting tool body 22 may be manufactured by additive manufacturing methods.

[0051]

[0062] As shown in FIG. 6, in a cross section along the first plane P1, the plurality of N cutouts 30 may be inscribed by an imaginary second circle C2 at N first radially innermost cutout points NGI1.

[0052]

[0063] In some embodiments of the present invention, at least N coolant ducts 58 may intersect the imaginary second circle C2 or its axial projection.

[0053]

[0064] Also, in some embodiments of the invention, each of the at least N coolant ducts 58 may intersect the imaginary second circle C2 or its axial projection rotationally forward of an associated first radially innermost cutout point NGI1. In such embodiments of the invention, it can be seen that the associated first radially innermost cutout point NGI1 of each of the at least N coolant ducts 58 is the first radially innermost cutout point NGI1 of the notch 30 through which the coolant duct 58 extends and intersects.

[0054]

[0065] As shown in FIG. 6, the imaginary second circle C2 has a second diameter D2, and its center coincides with the tool axis line AT.

[0055]

[0066] In some embodiments of the present invention, the first diameter D1 may be greater than 50% of the second diameter D2, ie, D1>0.50×D2.

[0056]

[0067] It should be noted that in embodiments of the present invention where the first diameter D1 is relatively large, i.e., D1 > 0.50 x D2, configuring the central coolant passage 48 to have N radially recessed coolant regions 56 may be even more important in maintaining the core strength of the tool body 22.

[0057]

[0068] As shown in Figures 1-4, each active cutting edge 34' has an axially forward-most cutting point NFC and an active main cutting edge portion 66' extending radially outward and axially rearward from the axially forward-most cutting point NFC.

[0058]

[0069] In some embodiments of the present invention, the first plane P1 may intersect N active primary cutting edge portions 66'.

[0059]

[0070] As shown in Figures 3 and 4, each active cutting edge 34' may have an active secondary cutting edge portion 70' extending radially inward from an associated axially forward most point NFC.

[0060]

[0071] In some embodiments of the present invention, each active secondary cutting edge portion 70' may be described as a wiper edge.

[0061]

[0072] As shown in FIG. 4, the N axially forward-most points NFC may define an imaginary third circle C3 having a third diameter D3 and a center coincident with the tool axis AT.

[0062]

[0073] In some embodiments of the present invention, the third diameter D3 may be greater than the second diameter D2, ie, D3>D2.

[0063]

[0074] As shown in FIG. 3, the N axially forward-most points NFC may be contained within a second plane P2 perpendicular to the tool axis AT, and no part of the cutting tool 20 may be located axially forward of the second plane P2.

[0064]

[0075] In one embodiment of the present invention, the cutting tool 20 may be used in a milling operation, wherein the major working edge portion 66' of each working edge 34' may bear the majority of the cutting forces associated therewith, and the minor working edge portion 70' may bear a minor portion of the cutting forces associated therewith.

[0065]

[0076] Additionally, in some embodiments of the present invention, each coolant duct 58 may direct coolant fluid toward the active main cutting edge portion 66' of the associated active cutting edge 34'.

[0066]

[0077] It should be noted that directing coolant toward the active main cutting edge portion 66' of the associated active cutting edge 34' significantly reduces wear and extends its useful life.

[0067]

[0078] As shown in Figures 5-8, each coolant duct 58 may have a circumferentially closed inner duct surface 68, and each coolant duct 58 may extend along a duct axis AD from the central coolant passage 34 to an associated coolant outlet port 60.

[0068]

[0079] In some embodiments of the present invention, each duct axis AD may be straight, and each coolant duct 58 may extend from the central coolant passage 48 to an associated coolant outlet port 60 without its duct axis AD intersecting an associated inner duct surface 68.

[0069]

[0080] In such an embodiment of the invention, as shown in FIGS. 5-8, each coolant duct 58 may extend linearly along its duct axis AD from the central coolant passage 48 to an associated coolant outlet port 60.

[0070]

[0081] In other embodiments of the invention (not shown), each coolant duct 58 may have some longitudinal curvature, but each coolant duct 58 may extend from the central coolant passage 48 to the associated coolant outlet port 60 without its straight duct axis AD intersecting the associated inner duct surface 68.

[0071]

[0082] It should be noted that in embodiments of the present invention in which each coolant duct 58 extends linearly along its duct axis AD, uniform and axisymmetric flow of coolant fluid along each coolant duct 58 is promoted.

[0072]

[0083] It should also be noted that for embodiments of the present invention in which each coolant duct 58 is advantageously constrained to extend linearly along its associated duct axis AD, configuring each coolant duct 58 to extend from one of the radially outer coolant regions 52 of the non-circular central coolant passage 48 to one of the N notches 30 provides even greater design flexibility regarding the direction and extent of each coolant duct 58.

[0073]

[0084] As shown in FIG. 8, each coolant duct 58 has a duct length DL measured along its linear duct axis AD.

[0074]

[0085] In certain embodiments of the present invention, the duct length DL may be greater than 40 percent of the second diameter D2, i.e., DL > 0.40×D2.

[0075]

[0086] Also, in certain embodiments of the present invention, as shown in FIG. 8, each coolant duct 58 may extend in the forward direction DF as it extends from the central coolant passage 48 toward one of the N notches 30.

[0076]

[0087] As shown in FIG. 6, in a cross-section along the first plane P1, each coolant duct 58 has a duct length DLP projected in the axial direction.

[0077]

[0088] Note that in embodiments of the present invention where each coolant duct 58 extends in the forward direction DF as it extends from the central coolant passage 48 toward one of the N notches 30, the duct length DLP projected in the axial direction is smaller than the duct length DL, i.e., DLP < DL.

[0078]

[0089] In certain embodiments of the present invention, the duct length DLP projected in the axial direction may be greater than half the difference between the first diameter D1 and the second diameter D2, i.e., DLP > 0.5×(D2 - D1).

[0079]

[0090] By configuring the central coolant passage 48 to be non-circular and have N radially outer coolant regions 52, it is advantageously possible for each coolant duct 58 to have a sufficiently long duct length DLP and duct length DL projected in the axial direction. As a result, each coolant duct 58 can extend linearly along its duct axis AD and direct a uniform and axially symmetric flow of coolant fluid toward the working cutting edge 34'.

[0080]

[0091] In certain embodiments of the present invention, each coolant duct 58 may have a non-circular cross-sectional shape.

[0081]

[0092] Also, in some embodiments of the present invention, each coolant duct 58 may have a different cross-sectional area along its length from the central coolant passage 48 to the associated coolant outlet port 60 .

[0082]

[0093] As shown in FIG. 9, in a cross section along a third plane P3 that is perpendicular to one of the duct axes AD and intersects the associated coolant duct 58, the coolant duct 58 may have an elliptical shape.

[0083]

[0094] Also, as shown in FIG. 9, in a cross section along the third plane P3, an imaginary fourth circle C4 having a fourth diameter D4 and a center coinciding with the duct axis AD circumscribes the associated coolant duct 58.

[0084]

[0095] In some embodiments of the present invention, the fourth diameter D4 may be less than 30% of the first diameter D1, ie, D4<0.30×D1.

[0085]

[0096] 6, in a cross section along the first plane P1, a fourth plane P4 contains the tool axis AT and a first radially outermost coolant point NCO1 of one of the radially outer coolant zones 52. A duct axis AD associated with the radially outer coolant zone 52 forms a first angle α1 with the fourth plane P4.

[0086]

[0097] In some embodiments of the present invention, the first angle α1 may be greater than 60 degrees and less than 120 degrees, ie, 60°<α1<120°.

[0087]

[0098] As shown in FIG. 6, in a cross section along the first plane P1, each duct axis AD intersects the fourth plane P4 of the associated radially outer coolant region 52 at an intersection point NI.

[0088]

[0099] In an embodiment of the present invention, the intersection point NI may be located closer to the associated first radially outermost coolant point NC01 than to the tool axis AT.

[0089]

[0100] As shown in FIG. 6, in the cross section along the first plane P1, an imaginary fifth circle C5 is inscribed in the first regular polygon RP1.

[0090]

[0101] In one embodiment of the present invention, the axial projection of each duct axis AD may intersect the first regular polygon RP1 outside the imaginary fifth circle C5.

[0091]

[0102] As shown in FIG. 5, in a cross section along the first plane P1, the first radially outermost coolant point NCO1 of each radially outer coolant region 52 is a minimum first distance DS1 from the coolant outlet port 60 of one of the associated coolant ducts 58. MIN and the first radially outermost coolant point NCO1 of each radially outer coolant region 52 is at a minimum second distance DS2 from the coolant outlet port 60 of one of the unassociated coolant ducts 58. MIN are located at.

[0092]

[0103] In one embodiment of the present invention, the minimum first distance DS1 MIN is the minimum second distance DS2 MIN may be larger than DS1 MIN >DS2 MIN may be.

[0093]

[0104] Also, in one embodiment of the present invention, the coolant outlet port 60 of the non-associated coolant duct 58 may be rotationally adjacent to and forward of the coolant outlet port 60 of the associated coolant duct 58.

[0094]

[0105] As shown in FIGS. 5 and 6, the first plane P1 may intersect at least N coolant ducts 58.

[0095]

[0106] In some embodiments of the invention, the first plane P1 may intersect exactly N coolant ducts 58 along its entire length. In such an embodiment of the invention, the communication between the central coolant passage 48 and the plurality of N cutouts 30 via said exactly N coolant ducts 58 is clearly visible in a cross section along the first plane P1, as shown in Figures 5 and 6.

[0096]

[0107] As shown in FIGS. 5 and 6, in a cross section along the first plane P1, the tool body 22 may exhibit N-fold rotational symmetry about the tool axis AT.

[0097]

[0108] As shown in FIGS. 7 and 8, two coolant ducts 58 may extend laterally from each radially outer coolant region 52 to intersect and open at the same cutout 30 .

[0098]

[0109] In one embodiment of the present invention, the two duct axes AD associated with the two coolant ducts 58 may be parallel.

[0099]

[0110] As shown in FIG. 3, each active main cutting edge 34′ has an axially rearmost cutting point NRC, and a fifth plane P5 that is perpendicular to the tool axis AT and intersects the central coolant passage 48 axially rearward of the first plane P1 may encompass a plurality N of the axially rearmost cutting points NRC.

[0100]

[0111] In some embodiments of the present invention, each active main cutting edge portion 66' may extend between an axially forward-most cutting point NFC and an axially rearward-most cutting point NRC of the associated active main cutting edge 34'.

[0101]

[0112] As shown in Figures 10 and 11, in a cross section along the fifth plane P5, the central coolant passage 48 may have a non-circular shape defined by N radially outer coolant regions 52, which have a sixth diameter D6 and are circumscribed by an imaginary sixth circle C6 whose center coincides with the tool axis AT.

[0102]

[0113] Also, as shown in Figures 10 and 11, in a cross section along the fifth plane P5, each radially outer coolant region 52 has a second radially outermost coolant point NCO2, and each second radially outermost coolant point NCO2 is located on the imaginary sixth circle C6.

[0103]

[0114] In one embodiment of the present invention, as shown in Figures 10 and 11, in a cross section along the fifth plane P5, each second radially outermost coolant point NCO2 may define one of N vertices of a second regular polygon RP2 with N sides.

[0104]

[0115] It should be noted that in an embodiment of the present invention in which the N radially outer coolant regions 52 of the central coolant passage 48 define a second regular polygon RP2 of N sides in a cross section along the fifth plane P5, N is a particular integer greater than 2, i.e., N>2.

[0105]

[0116] In some embodiments of the present invention, the second N-sided regular polygon RP2 may be rotationally congruent with the first N-sided regular polygon RP1. In this context, two axially spaced triangles are considered to be "rotationally congruent" if they share the same center and the same angular orientation when projected onto a common plane. Thus, the central coolant passage 48 does not "twist" as it extends axially between the fifth plane P5 and the first plane P1. In other embodiments (not shown), the central coolant passage 48 may experience such a "twist," in which case the second N-sided regular polygon RP2 may be rotationally offset from the first N-sided regular polygon RP1.

[0106]

[0117] Additionally, in one embodiment of the present invention, in any cross section along a plane perpendicular to the tool axis AT and disposed between the first plane P1 and the fifth plane P5, the radially outermost coolant point of the central coolant passage 48 may define a regular polygon with N sides that is rotationally aligned with the first regular polygon RP1 and the second regular polygon RP2.

[0107]

[0118] It should be noted that the term "any cross section" above can also be interpreted as "any cross section."

[0108]

[0119] In some embodiments of the present invention, the sixth diameter D6 may be equal to or greater than the first diameter D1 and may be less than 120% of the first diameter D1, i.e., D1≦D6 <D1×1.20であってもよい。

[0109]

[0120] As shown in Figure 11, in a cross section along the fifth plane P5, the plurality of N notches 30 are inscribed by an imaginary seventh circle C7 at the N second radially innermost notch points NGI2, and the imaginary seventh circle C7 may have a seventh diameter D7, and its center coincides with the tool axis line AT.

[0110]

[0121] In one embodiment of the present invention, the seventh diameter D7 may be equal to or greater than 90% of the second diameter D2 and less than 110%, i.e., D2 x 0.90. <D7<D2×1.10であってもよい。

[0111]

[0122] Additionally, in some embodiments of the present invention, the rear end 50 of the rear connecting portion may have a rearward-facing second end surface 72, and the central coolant passage 48 may intersect with and open at the second end surface 72.

[0112]

[0123] As shown in FIG. 12, in a cross section along a sixth plane P6 that is perpendicular to the tool axis AT and intersects the rear connecting portion 26 and the central coolant passage 48, the central coolant passage 48 may have a circular shape with an eighth diameter D8.

[0113]

[0124] In some embodiments of the present invention, the eighth diameter D8 may be greater than the first diameter D1, ie, D8>D1.

[0114]

[0125] Also, in some embodiments of the present invention, the eighth diameter D8 may be greater than the sixth diameter D6, ie, D8>D6.

[0115]

[0126] As shown in FIG. 2, the rear connecting portion 26 may have an annular shoulder surface 74 facing in the rearward direction DR.

[0116]

[0127] In some embodiments of the present invention, shoulder surface 74 may intersect front outer peripheral surface 28 .

[0117]

[0128] As shown in FIGS. 1 to 3, the rear connecting portion 26 may have an externally threaded portion 76 that extends helically along the tool axis AT.

[0118]

[0129] In some embodiments of the present invention, the externally threaded portion 76 may be located axially rearward of the shoulder surface 74 .

[0119]

[0130] Although the present invention has been described in some detail, it should be noted that various changes and modifications may be made without departing from the scope of the invention as claimed below.

Claims

1. A rotary cutting tool (20) rotatable in a rotational direction (RD) about a tool axis (AT), the tool axis (AT) defining a forward direction (DF) and a rearward direction (DR), the rotary cutting tool (20) comprising a tool body (22) having a front cutting portion (24) and a rear connecting portion (26); the leading cutting portion (24) has a leading outer peripheral surface (28) with a plurality of N circumferentially spaced notches (30), N being a specified integer greater than 1, each notch (30) opening at a leading end (32) of the leading cutting portion (24) and having an active cutting edge (34') associated with the leading cutting portion (24); a central coolant passage (48) extending along the tool axis (AT) from a rear end (50) of the rear connecting portion (26) to the front cutting portion (24), and a first plane (P1) perpendicular to the tool axis (AT) intersects the central coolant passage (48) and the N working cutting edges (34'); In a cross section taken along the first plane (P1), the central coolant passage (48) has a non-circular shape having N radially outer coolant regions (52), each having a first radially outermost coolant point (NCO1), and the central coolant passage (48) is circumscribed by an imaginary first circle (C1) having a first diameter (D1) and a center coincident with the tool axis (AT); At least one coolant duct (58) extends laterally from each radially outer coolant region (52) and intersects and opens in one of the N notches (30) at a coolant outlet port (60).

2. In a cross section along the first plane (P1), 2. The cutting tool (20) according to claim 1, wherein each first radially outermost coolant point (NCO1) is located on the imaginary first circle (C1).

3. Each coolant duct (58) has a circumferentially closed inner duct surface (68); 3. The cutting tool (20) of claim 1 or 2, wherein each coolant duct (58) extends along a straight duct axis (AD) from the central coolant passage (48) to the associated coolant outlet port (60) without the duct axis (AD) intersecting the associated inner duct surface (68).

4. In a cross section along the first plane (P1), a fourth plane (P4) containing the tool axis (AT) and the first radially outermost coolant point (NCO1) of one of the radially outer coolant regions (52); the duct axis (AD) associated with the radially outer coolant region (52) forms a first angle (α1) with the fourth plane (P4); The cutting tool (20) of claim 3, wherein the first angle (α1) is greater than 60 degrees and less than 120 degrees.

5. In a cross section along the first plane (P1), each duct axis (AD) intersects the fourth plane (P4) of the associated radially outer coolant region (52) at an intersection point (NI); 5. The cutting tool (20) of claim 4, wherein the intersection point (NI) is located closer to the associated first radially outermost coolant point (NC01) than the tool axis (AT).

6. In a cross section along the first plane (P1), 6. The cutting tool (20) according to any one of claims 1 to 5, wherein each first radially outermost coolant point (NCO1) defines one of N vertices of a first regular polygon (RP1) with N sides.

7. In a cross section along the first plane (P1), The central coolant passage (48) includes N radially recessed coolant regions (56) circumferentially alternately arranged with the N radially outer coolant regions (52), 7. The cutting tool (20) of claim 6, wherein each radially recessed coolant region (56) has a first radially innermost coolant point (NCI1) located inside the first regular polygon (RP1).

8. 8. The cutting tool (20) of claim 7, wherein each first radially innermost coolant point (NCI1) is located on the convexly curved second inner wall (64) of an associated radially concave coolant region (56).

9. Each active major cutting edge (34') has an axially most rearward cutting point (NRC), a fifth plane (P5) perpendicular to the tool axis (AT) intersects the central coolant passage (48) axially rearward of the first plane (P1) and includes N of the plurality of axially rearward cutting points (NRC); In a cross section along the fifth plane (P5), the central coolant passage (48) has a non-circular shape defined by the N radially outer coolant regions (52); Each radially outer coolant zone (52) has a second radially outermost coolant point (NCO2); 9. The cutting tool (20) according to any one of claims 6 to 8, wherein each second radially outermost coolant point (NCO2) defines one of N vertices of a second regular polygon (RP2) with N sides.

10. 10. The cutting tool (20) of claim 9, wherein the second regular polygon (RP2) with N sides is rotationally coincident with the first regular polygon (RP1) with N sides.

11. In any cross section along a plane perpendicular to the tool axis (AT) and disposed between the first plane (P1) and the fifth plane (P5), 11. The cutting tool (20) of claim 10, wherein the radially outermost point of the central coolant passage (48) defines a regular polygon with N sides that is rotationally aligned with the first regular polygon (RP1) and the second regular polygon (RP1).

12. the front end (32) of the front cutting portion has a first end surface (54) facing forward; The cutting tool (20) of any one of claims 1 to 11, wherein the central coolant passage (48) terminates axially rearward of the first end face (54).

13. Each notch (30) intersects the first end surface (54); 13. The cutting tool (20) of claim 12, wherein each coolant outlet port (60) is located axially rearward of the first end face (54).

14. The cutting tool (20) according to any one of claims 1 to 13, wherein the first plane (P1) intersects at least N coolant ducts (58).

15. In a cross section along the first plane (P1), 15. The cutting tool (20) of claim 14, wherein the tool body (22) exhibits N-fold rotational symmetry about the tool axis (AT).

16. In a cross section along the first plane (P1), The plurality of N notches (30) are inscribed by a virtual second circle (C2) at N first radially innermost notch points (NGI1), The cutting tool (20) according to any one of the preceding claims, wherein at least N coolant ducts (58) intersect the imaginary second circle (C2) or an axial projection of the imaginary second circle (C2).

17. the imaginary second circle (C2) has a second diameter (D2) and its center coincides with the tool axis (AT); 17. The cutting tool (20) of claim 16, wherein the first diameter (D1) is greater than 50% of the second diameter (D2).

18. In a cross section along the first plane (P1), each first radially outermost coolant point (NCO1) is located on a concavely curved first inner wall (62) of an associated said radially outer cooling zone (52) having a first radius (R1); The cutting tool (20) according to any one of the preceding claims, wherein the first radius (R1) is greater than 10% of the first diameter (D1).

19. 20. The cutting tool (20) of claim 18, wherein each first inner wall (62) has a first angular extent (EA1) greater than 90 degrees.

20. 20. A cutting tool (20) according to any one of claims 1 to 19, wherein each active cutting edge (34') has an axially forward most cutting point (NFC) and an active main cutting edge portion (66') extending radially outward and axially rearward from the axially forward most cutting point (NFC).

21. 21. The cutting tool (20) of claim 20, wherein each coolant duct (58) directs coolant fluid towards the active main cutting edge portion (66') of an associated active cutting edge (34').

22. The N axially forward most points (NFC) are contained in a second plane (P2) perpendicular to the tool axis (AT), 22. A cutting tool (20) according to claim 20 or 21, wherein no part of the cutting tool (20) is located axially forward of the second plane (P2).

23. Each notch (30) has an insert-receiving pocket (36) in which a cutting insert (38) is removably secured; The cutting tool (20) of any one of claims 1 to 22, wherein the active cutting edge (34') is formed on the cutting insert (38).

24. In a cross section along the first plane (P1), The first radially outermost coolant point (NCO1) of each radially outer coolant region (52) is at a minimum first distance (DS1) from the coolant outlet port (60) of one of the associated coolant ducts (58) or from the axial projection of the coolant outlet port (60). ＭＩＮ ) and The first radially outermost coolant point (NC01) of each radially outer coolant region (52) is at a minimum second distance (DS2) from the coolant outlet port (60) of one of the non-associated coolant ducts (58) or from an axial projection of the coolant outlet port (60). ＭＩＮ ) and The minimum first distance (DS1 ＭＩＮ ) is the minimum second distance (DS2 ＭＩＮ 24. The cutting tool (20) of any one of claims 1 to 23, wherein the cutting tool (20) has a diameter greater than 1 / 2 mm.

25. a rotary cutting tool body (22) rotatable in a rotational direction (RD) about a tool axis (AT), said tool axis (AT) defining a forward direction (DF) and a rearward direction (DR), said rotary cutting tool body (22) comprising a front cutting portion (24) and a rear connecting portion (26); the front cutting portion (24) has a front outer peripheral surface (28) with a plurality of N circumferentially spaced notches (30), N being a specified integer greater than 1, each notch (30) opening at a front end (32) of the front cutting portion (24) and having an insert-receiving pocket (36) associated with the notch (30), the insert-receiving pocket (36) having a seat (46) with a threaded hole (44) formed therein; a central coolant passage (48) extending along the tool axis (AT) from a rear end (50) of the rear connecting portion (26) to the front cutting portion (24), and a first plane (P1) perpendicular to the tool axis (AT) intersects the central coolant passage (48) and the N seating surfaces (46); In a cross section taken along the first plane (P1), the central coolant passage (48) has a non-circular shape having an integer number N of radially outer coolant regions (52), each of which has a first radially outermost coolant point (NCO1), and the central coolant passage (48) is circumscribed by an imaginary first circle (C1) having a first diameter (D1) and a center coincident with the tool axis (AT); At least one coolant duct (58) extends laterally from each radially outer coolant region (52) and intersects and opens at one of the N notches (30) of the coolant outlet port (60).

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