Patent Publication Number: US-2021187626-A1

Title: Rotary cutting tool

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to U.S. Provisional Patent Application No. 62/949,889 filed Dec. 18, 2019, and to U.S. Provisional Patent Application No. 62/949,894 filed Dec. 18, 2019, and to U.S. Provisional Patent Application No. 62/949,913 filed Dec. 18, 2019, each of which is hereby incorporated by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The present invention pertains in general to cutting processes and tools for removing a cylinder of material from a substrate, and in particular to rotational cutting tools configured to remove a cylinder of material from a substrate, which tools are configured for use with a cutting fluid. 
     2. Background Information 
     Rotary cutting tools are often used to produce an aperture extending through a substrate. A well-known example of such a rotary cutting tool is a twist drill. Twist drills typically include a shank portion disposed adjacent a first axial end and a cutting portion disposed adjacent a second axial end. The cutting portion terminates at tapered surfaces that form a point angle. Cutting edges helically extend through the cutting portion and helical flutes provide passages along the cutting portion. Axial force is applied to the twist drill as it is rotating, and the drill operates to remove material and create the aperture. In instances where a rotating cutting tool such as a twist drill is used to produce a through aperture within a substrate, surface imperfections (splintering, fracturing, etc.) adjacent the substrate exit of the aperture are commonly produced as the drill breaks through the surface. These exit surface imperfections may be produced in many substrate material types, but can be particularly pronounced in wooden or composite substrates. The surface imperfections are produced, at least in part, by outwardly radial forces applied to the substrate by the tapered point. These surface imperfections can create unacceptable surface irregularities and stress concentration factors. In instances where apertures are produced in composite substrates produced for load bearing structures, stress concentration factors can be a significant concern. Very often it is necessary to add further manufacturing processes (e.g., deburring, chamfering, etc.) to address the surface imperfections and the concomitant stress concentration factors. The additional processes add cost and time to the manufacturing process. 
     Another type of rotary cutting tool used to create an aperture within a substrate is typically referred to as a “core drill”. Many core drills utilize a cylindrical cutter having teeth disposed at an axial end. As the teeth cut into the substrate, a “plug” of the substrate is disposed within the interior of the cylindrical cutter. As the cylindrical cutter breaks through the opposing substrate surface, the plug becomes independent from the substrate and can removed. Many core drills also produce undesirable surface imperfections adjacent the exit of the aperture as described above. 
     Friction between a rotary cutting tool (e.g., a twist drill, a core drill, etc.) and a substrate typically produces thermal energy, thereby causing the rotary cutting tool and the substrate to increase in temperature. The increase in temperature can be particularly problematic for resin-based composite substrates. If the temperature of the substrate and the incorporated resin is excessively increased, the material properties of the composite can be detrimentally altered. For example, in some instances excessive heat can cause thermal decomposition of the resin matrix which in turn can result in a depletion of the structural integrity of the composite. 
     What is needed is a rotary cutting tool that can be used to create a through aperture with minimal or no surface irregularities at the exit of the aperture. 
     SUMMARY 
     According to an aspect of the present disclosure, a rotary cutting tool having a lengthwise extending central axis is provided. The tool includes a shank portion and a cutting portion, both extending along the central axis. The cutting portion is connected to the shank portion, and includes a fluted section and a plurality of teeth extending axially outwardly from the fluted section at a cutting end. The fluted section includes a plurality of flutes disposed within an exterior surface of the fluted section. The cutting portion includes an internal cavity disposed within the fluted section and open to the cutting end. Each tooth includes a front side surface, an exterior side surface, an interior side surface, and an axial end surface. The front side surface intersects with the axial end surface to form an axial end cutting edge that extends radially between an outer radial tip and an inner radial tip, and the outer radial tip is disposed axially outside of the inner radial tip. 
     In any of the aspects or embodiments described above and herein, the front side surface, the exterior side surface, and the axial end surface may intersect at the outer radial tip, and the outer radial tip may be disposed at a first radius from the central axis. The fluted section may include an outer diameter having a second radius from the central axis, and the first radius may be greater than the second radius. 
     In any of the aspects or embodiments described above and herein, the front side surface, the interior side surface, and the axial end surface may intersect at the inner radial tip, and the inner radial tip may be disposed at a third radius from the central axis. The internal cavity may be defined by an interior wall surface disposed at a fourth radius from the central axis. The third radius may be less than the fourth radius. 
     In any of the aspects or embodiments described above and herein, the front side surface may be skewed by an acute axial rake angle, and the axial rake angle may be defined by the front side surface and a line parallel to the central axis that is tangential to the axial end cutting edge. 
     In any of the aspects or embodiments described above and herein, the front side surface may extend axially between the axial end cutting edge and an inner edge, and the axial end cutting edge may be disposed circumferentially forward of the inner edge. 
     In any of the aspects or embodiments described above and herein, the exterior side surface and the front side surface may intersect to form an exterior cutting edge, and the front side surface may be skewed by an acute radial rake angle, the radial rake angle defined by the front side surface and a line perpendicular to the central axis that is tangential to the exterior cutting edge. 
     In any of the aspects or embodiments described above and herein, the interior side surface and the front side surface may intersect to form an interior cutting edge, and the exterior cutting edge may be disposed circumferentially forward of the interior cutting edge. 
     In any of the aspects or embodiments described above and herein, the axial end surface may be skewed by an acute axial end surface relief angle, the axial end surface relief angle defined by the axial end surface and a circumferential line that is perpendicular to the central axis. 
     In any of the aspects or embodiments described above and herein, the axial end surface may extend circumferentially between axial end cutting edge and an aft edge, and the axial end cutting edge may be disposed axially outside of the inner edge. 
     In any of the aspects or embodiments described above and herein, the exterior side surface may be skewed by an acute exterior side surface radial relief angle, the exterior side surface radial relief angle defined by the exterior side surface and a circumferential line that is perpendicular to the central axis. 
     In any of the aspects or embodiments described above and herein, the exterior side surface may extend circumferentially between the exterior cutting edge and an aft edge, and the exterior cutting edge may be disposed radially outside of the aft edge. 
     In any of the aspects or embodiments described above and herein, the interior side surface may be skewed by an acute interior side surface radial relief angle, the interior side surface radial relief angle defined by the interior side surface and a circumferential line that is perpendicular to the central axis. 
     In any of the aspects or embodiments described above and herein, the interior side surface may extend circumferentially between the exterior cutting edge and an aft edge, and the interior cutting edge may be disposed radially inside of the aft edge. 
     In any of the aspects or embodiments described above and herein, the exterior side surface may be skewed by an acute exterior side surface axial relief angle, the exterior side surface axial relief angle defined by the exterior side surface and a line parallel to the central axis. 
     In any of the aspects or embodiments described above and herein, the exterior side surface may extend axially between an outer axial edge and an inner axial edge, and the outer axial edge may be disposed radially outside of the inner axial edge. 
     In any of the aspects or embodiments described above and herein, the interior side surface may be skewed by an acute interior side surface axial relief angle, the interior side surface axial relief angle defined by the interior side surface and a line parallel to the central axis. 
     In any of the aspects or embodiments described above and herein, the interior side surface may extend axially between an outer axial edge and an inner axial edge, and the outer axial edge may be disposed radially inside of the inner axial edge. 
     In any of the aspects or embodiments described above and herein, the fluted section and the plurality of teeth may be a unitary structure. 
     In any of the aspects or embodiments described above and herein, each tooth may include at least one cutting insert, and the at least one cutting insert may form at least a part of the front side surface, the exterior side surface, the interior side surface, and the axial end surface. 
     In any of the aspects or embodiments described above and herein, the at least one cutting insert may comprise a superhard material. 
     In any of the aspects or embodiments described above and herein, the tool may further comprise a fluid passage extending through the shank portion to the internal cavity, providing fluid communication from the shank end to the internal cavity. 
     In any of the aspects or embodiments described above and herein, the internal cavity may be defined by an interior wall surface, and a plurality of channels may be disposed within the interior wall surface, each channel open to the internal cavity. 
     In any of the aspects or embodiments described above and herein, each of the channels may be configured to provide a fluid passage from the internal cavity to the plurality of teeth. 
     In any of the aspects or embodiments described above and herein, the plurality of channels may extend axially, and each channel may include an open end adjacent the teeth. 
     These and other objects, features and advantages of the present invention will become apparent in light of the detailed description of the invention provided below, and as illustrated in the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a present disclosure rotary cutting tool embodiment. 
         FIG. 2  is a planar view of a present disclosure rotary cutting tool embodiment. 
         FIG. 2A  is a planar view of a present disclosure rotary cutting tool embodiment. 
         FIG. 3  is a diagrammatic sectional view of the present disclosure rotary cutting tool embodiment shown in  FIG. 2 . 
         FIG. 4  is an end view of a present disclosure rotary cutting tool embodiment from the cutting end. 
         FIG. 4A  is an expanded view of a portion of the present disclosure rotary cutting tool embodiment shown in  FIG. 4 . 
         FIG. 5  is the end view of a present disclosure rotary cutting tool embodiment shown in  FIG. 4 . 
         FIG. 5A  is an expanded view of a portion of the present disclosure rotary cutting tool embodiment shown in  FIG. 5 . 
         FIG. 6  is a partial planar view of the cutting portion of a present disclosure rotary cutting tool embodiment. 
         FIG. 6A  is an expanded view of a portion of the present disclosure rotary cutting tool embodiment shown in  FIG. 6 . 
         FIG. 6B  is the expanded view of  FIG. 6A , with the inserts removed to show the pocket. 
         FIG. 7  is a partial planar view of the cutting portion of a present disclosure rotary cutting tool embodiment. 
         FIG. 7A  is an expanded view of a portion of the present disclosure rotary cutting tool embodiment shown in  FIG. 7 . 
         FIG. 8  is a perspective view of a present disclosure rotary cutting tool embodiment. 
         FIG. 9  is a perspective view of a present disclosure rotary cutting tool embodiment. 
         FIG. 9A  is an expanded view of a portion of the present disclosure rotary cutting tool embodiment shown in  FIG. 9 . 
         FIG. 9B  is an expanded view of a portion of the present disclosure rotary cutting tool embodiment shown in  FIG. 9 . 
         FIG. 10  is a diagrammatic view of a present disclosure rotary cutting tool embodiment. 
         FIG. 11  is a diagrammatic perspective view of a rotary cutting tool insert. 
         FIG. 11A  is a diagrammatic front side view of the rotary cutting tool insert shown in  FIG. 11 . 
         FIG. 11B  is a diagrammatic top side view of the rotary cutting tool insert shown in  FIG. 11 . 
         FIG. 11C  is a diagrammatic right side view of the rotary cutting tool insert shown in  FIG. 11 . 
         FIG. 11D  is a diagrammatic left side view of the rotary cutting tool insert shown in  FIG. 11 . 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIGS. 1-3 , a rotary cutting tool  20  includes a body  22  that extends lengthwise along a central axis  24  between a shank end  26  and an opposite cutting end  28 . The body  22  includes a shank portion  30  and a cutting portion  32 . The shank portion  30  typically extends from the shank end  26  to the cutting portion  32 , and the cutting portion  32  extends from the cutting end  28  to the shank portion  30 . In some embodiments, the rotary cutting tool  20  may include a relief section (not shown) disposed between the shank portion  30  and the cutting portion  32 . The shank portion  30  is typically configured to facilitate attachment within a rotationally driven clamping device (sometimes referred to as a “chuck”). The rotary cutting tools  20  shown in the FIGURES have a cylindrically shaped shank portion  30 , but the present disclosure rotary cutting tool  20  is not limited to a cylindrically shaped shank portion  30 ; e.g. in some embodiments the shank portion  30  may include one or more planar surfaces that facilitate securing the rotary cutting tool  20  within the clamping device (e.g., a driving tang), or the shank portion  30  may have a multi-planar configuration (e.g., hexagonal), etc.  FIGS. 1 and 2  illustrate a rotary cutting tool  20  embodiment having a shank portion  30  with an outer diameter that is approximately equal to the outer diameter of the cutting portion  32 . The present disclosure is not limited to such rotary cutting tools  20 ; e.g., the outer diameter of the shank portion  30  (or other widthwise dimension for non-circular shanks) may not equal the outer diameter of the cutting portion  32 . The rotary cutting tool  20  shown in  FIG. 2A , for example, has a shank portion  30  with an outer diameter that is smaller than the outer diameter of the cutting portion  32 . 
     The cutting portion  32  includes a fluted section  34  and a cutting teeth section  36 . The fluted section  34  has a plurality of flutes  38  disposed into an exterior surface  40 . The exterior surface  40  may be described as having an outer diameter and therefore a radius that extends perpendicular to the central axis  24 . The outer diameter may be defined by the outermost radial points of the fluted section  34 ; e.g., when the rotary cutting tool  20  is rotated about its central axis  24 , the outer most points of the fluted section  34  define the outer diameter of the fluted section  34 . The cross-section shown in  FIG. 3  diagrammatically shows a plurality of flutes  38 , each having a cross-section with an arcuate shape, but the present disclosure in not limited to any particular flute  38  shape. The flutes  38  are spaced apart from one another around the circumference of the exterior surface  40 ; e.g., equi-spaced from one another. Each flute  38  may be described as having a width  42 , a depth  44 , and a widthwise cross-sectional area. In the embodiment shown in  FIGS. 1-3 , the flutes  38  extend helically along the exterior surface  40 . As will be explained below, each helically extending flute  38  has a tip end that is disposed adjacent a respective tooth  46  and is configured to provide a passage for removal of cutting fluid and cutting debris. As will be described below, the teeth  46  are circumferentially spaced apart from one another, with a void (sometimes referred to as a “gullet  48 ”) disposed between each set of adjacent teeth  46 . The base surface of the gullet  48  may include one or more transitional surfaces  50  that create an entry to the tip end of the respective flute  38 . Hence, each respective flute  38  (at its tip end) is in communication with a respective gullet  48 . The present disclosure is not limited to helically extending flutes  38 , however; e.g., other axially extending flutes  38  may be included alternatively. As will be described below, each flute  38  is configured to provide a fluid passage. 
     The cutting portion  32  further includes an internal cavity  52  disposed within the body  22 , extending inwardly from the cutting end  28 . The internal cavity  52  is defined by an interior wall surface  54  and a base  56 . The interior wall surface  54  extends axially away from the base  56 , towards the cutting end  28 . The rotary cutting tool  20 , including the internal cavity  52 , is configured such that during the cutting process, a “plug  58 ” (e.g., see  FIG. 10 ) of substrate material enters the internal cavity  52 . As will be described below, once the aperture is cut through the entire thickness of the substrate  60 , the substrate plug  58  cut in the process is readily removable from the internal cavity  52 ; e.g., by fluid pressure acting on the plug  58 . 
     A plurality of channels  62  are disposed in the interior wall surface  54 . The channels  62  are open to the internal cavity  52 , and each channel  62  includes an open end  63  disposed adjacent the teeth  46  (see  FIG. 9 ). As will be explained below, during operation of the rotary cutting tool  20  a plug  58  will enter the internal cavity  52 . The portion of each channel  62  open to the internal cavity  52  permits cutting fluid to enter the channel  62  and the open end  63  of the channel  62  permits cutting fluid within the channel to exit the channel  62  adjacent the teeth  46 . The channels  62  are spaced apart from one another around the circumference of the interior wall surface  54 ; e.g., equi-spaced from one another. Each channel  62  may be described as having a width  64 , a depth  66 , and a widthwise cross-sectional area (e.g., see  FIG. 4A ). The end view shown in  FIG. 4  diagrammatically shows a plurality of channels  62 , each having a cross-section with an arcuate shape, but the present disclosure in not limited to any particular channel  62  shape. In the embodiment shown in  FIG. 4 , the channels  62  extend axially along the interior wall surface  54 , each thereby providing a fluid channel from about the base  56  of the internal cavity  52  to the teeth  46 . Also in  FIG. 4  (and expanded view  FIG. 4A ), each channel  62  is disposed adjacent a tooth  46 , but also may be described as being disposed “forward” of the adjacent following tooth  46 . The term “forward” as used herein refers to the relative circumferential positions of the channel  62  and the adjacent tooth  46 ; i.e., during rotation of the rotary cutting tool  20  the channel  62  will pass a given point during rotation of the tool  20  prior to adjacent tooth  46  passing the same point. As indicated by arrow  68 , the rotary cutting tool  20  shown in  FIG. 4  is configured for counter-clockwise rotation. As will be described below, the forward position of a channel  62  relative to a following tooth  46  enables cutting fluid exiting the channel  62  (e.g., via the open end  63  of the channel  62 ) to wash radially outwardly in front of the following tooth  46  (identified as “ 46 FT” in  FIGS. 4, 4A, 8, and 9 ) to facilitate removal of cutting debris into a respective flute  38 . The configuration of each channel  62  (e.g., width, depth, cross-sectional area) and the number of channels  62  can be selected to collectively provide a volumetric fluid flow rate and fluid pressure profile that is adequate for the material being cut and the type of cutting fluid being used during the cutting process. 
     The cutting teeth section  36  includes a plurality of teeth  46  disposed at the cutting end  28  of the tool  20 , extending axially between the fluted section  34  and the cutting end  28 . The teeth  46  are circumferentially spaced apart from one another, with a void (sometimes referred to as a “gullet  48 ”) disposed between each set of adjacent teeth  46 . The exemplary rotary cutting tool  20  shown in the FIGURES includes five (5) teeth  46  disposed within the cutting teeth section  36 . The present disclosure rotary cutting tool  20  is not limited to any particular number of teeth  46 , other than having at least two teeth  46 . 
     Referring to  FIGS. 4-7A, 9A, and 9B , each tooth  46  includes a front side  70 , an aft side  72 , an exterior side  74 , an interior side  76 , and an axial end side  78 . The front side  70  is the forward of the aft side  72 , and is disposed on the opposite side of the tooth  46  relative to the aft side  72 . The exterior side  74  is disposed radially outside of the interior side  76 , and the exterior side  74  is disposed on the opposite side of the tooth  46  relative to the interior side  76 . The axial end side  78  is the axial end of the tooth  46 . Each of the front side  70 , exterior side  74 , interior side  76 , aft side  72 , and axial end side  78  includes at least one surface. 
     A front side surface  80  disposed at the front side  70  may be referred to as a “rake face”. An exterior side surface  82  intersects with the front side surface  80  to form an exterior cutting edge  84 , an interior side surface  86  intersects with the front side surface  80  to form an interior cutting edge  88 , and an axial end surface  90  intersects with the front side surface  80  to form an axial end cutting edge  92 . In some embodiments, the front side surface  80  may include an inner edge  94  disposed at the axial end of the front side surface  80  opposite the axial end cutting edge  92  (see  FIGS. 9A and 9B ). In these embodiments, therefore, the front side surface  80  may be described as extending axially between the axial end cutting edge  92  and the inner edge  94 , and extending radially between the exterior cutting edge  84  and the interior cutting edge  88 . In some embodiments, the exterior side surface  82  includes an aft edge  96 , an inner axial edge  97 , and an outer axial edge  99 . The outer axial edge  99  is defined by the intersection between the exterior side surface  82  and the axial end surface  90 . In these embodiments, therefore, the exterior side surface  82  may be described as extending axially between the inner axial edge  97  and the outer axial edge  99 , and extending in a circumferential direction between the exterior cutting edge  84  and the aft edge  96 . In some embodiments, the interior side surface  86  includes an aft edge  98 , an inner axial edge  101 , and an outer axial edge  103 . The outer axial edge  103  is defined by the intersection between the interior side surface  86  and the axial end surface  90 . In these embodiments, therefore, the interior side surface  86  may be described as extending axially between the inner axial edge  101  and the outer axial edge  103 , and extending in a circumferential direction between the interior cutting edge  88  and the aft edge  98 . In some embodiments, the axial end surface  90  includes an aft edge  100 . In these embodiments, therefore, the axial end surface  90  may be described as extending radially between the outer axial edge  99  of the exterior side surface  82  and the outer axial edge  103  of the interior side surface  86 , and extending in a circumferential direction between the axial end cutting edge  92  and the aft edge  100 . 
     The intersection point of the exterior side surface  82 , the front side surface  80 , and the axial end surface  90  (referred to hereinafter as the “outer radial tip  102 ”) is disposed at a radial position outside of the outer diameter of the fluted section  34 ; i.e., the radius of the aforesaid outer radial tip  102  from the central axis  24  is greater than the radius of the fluted section  34  exterior surface  40  from the central axis  24 . Hence, the outer radial tip  102  may be described as being “proud” of the exterior surface  40  of the fluted section  34 . In some embodiments, the entirety of the exterior cutting edge  84  (i.e., the edge formed by the intersection of the exterior side surface  82  with the front side surface  80 ) may be “proud” of the exterior surface  40  of the fluted section  34 . 
     The intersection point of the interior side surface  86 , the front side surface  80 , and the axial end surface  90  (referred to hereinafter as the “inner radial tip  104 ”) is disposed at a radial position inside of the interior wall surface  54  of the internal cavity  52 ; i.e., the radius of the aforesaid inner radial tip  104  from the central axis  24  is less than the radius of the interior wall surface  54  of the internal cavity  52  from the central axis  24 . Hence, the inner radial tip  104  may be described as being “proud” of the interior wall surface  54  of the internal cavity  52 . In some embodiments, the entirety of the interior cutting edge  88  (i.e., the edge formed by the intersection of the interior side surface  86  with the front side surface  80 ) may be “proud” of the interior wall surface  54  of the internal cavity  52 . 
     Referring to  FIGS. 4A, 5, and 5A , in some embodiments the front side surface  80  of each tooth  46  (i.e., the rake face) is skewed by an acute radial rake angle “RR” relative to a radial line  106  extending out from the central axis  24  that is tangential to the exterior cutting edge  84 . As a result of the angle RR, the exterior cutting edge  84  of the tooth  46  is disposed forward of the interior cutting edge  88  at any given axial position of the exterior cutting edge; i.e., at a given axial position where the radial line  106  is tangential to the exterior cutting edge  84 , the exterior cutting edge is forward of the interior cutting edge  88 . The magnitude of the acute angle RR can be varied to best suit the rotary cutting tool  20  for different applications; e.g., different types of substrate  60  materials, rotational cutting speeds, etc. The present disclosure is not limited to any particular angle RR value. 
     Referring to  FIG. 6 , in some embodiments the front side surface  80  of each tooth  46  (i.e., the rake face) is skewed by an acute axial rake angle “AR” relative to a line  108  extending parallel with the central axis  24  of the rotary cutting tool  20  that is tangential to the axial end cutting edge  92 . As a result of the angle AR, the axial end cutting edge  92  of the tooth  46  is disposed circumferentially forward of the front side surface  80  inner edge  94  at any given radial position of the axial end cutting edge  92 ; i.e., at a given radial position where the line  108  is tangential to the axial end cutting edge  92 , the axial end cutting edge  92  is circumferentially forward of the front side surface inner edge  94  (e.g., see  FIGS. 9A and 9B ). The magnitude of the acute angle AR can be varied to best suit the rotary cutting tool  20  for different applications; e.g., different types of substrate materials, rotational cutting speeds, etc. The present disclosure is not limited to any particular angle AR value. 
     Referring to  FIG. 6A , in some embodiments the axial end surface  90  is skewed by an acute axial end surface relief angle “AESR” relative to a circumferential line  110  that is tangential to the outer radial tip  102 , and that is perpendicular to the central axis  24 . As a result of the angle AESR, the axial end cutting edge  92  is axially displaced from the aft edge  100  of the axial end surface  90 ; i.e., the axial end cutting edge  92  is disposed axially outside of the aft edge  100  of the axial end surface  90  (e.g., see  FIGS. 9A and 9B ). The magnitude of the acute angle AESR can be varied to best suit the rotary cutting tool  20  for different applications; e.g., different types of substrate  60  materials, rotational cutting speeds, etc. The present disclosure is not limited to any particular angle AESR value. 
     Referring to  FIGS. 5 and 5A , in some embodiments the exterior side surface  82  of each tooth  46  is skewed by an acute exterior side surface radial relief angle “ESSRR” relative to a line  112  that is tangential to the exterior cutting edge  84  (e.g., see  FIGS. 9A and 9B ) and perpendicular to a radial line  114  extending out from the central axis  24  (as can be seen in  FIG. 5 , radial line  106  and radial line  114  may be collinear). As a result of the angle ESSRR, the exterior cutting edge  84  of the tooth  46  is disposed radially outside of the aft edge  96  of the exterior side surface  82 . The magnitude of the acute angle ESSRR can be varied to best suit the rotary cutting tool  20  for different applications; e.g., different types of substrate  60  materials, rotational cutting speeds, etc. The present disclosure is not limited to any particular angle ESSRR value. 
     Referring to  FIGS. 5 and 5A , in some embodiments the interior side surface  86  of each tooth  46  is skewed by an acute interior side surface radial relief angle “ISSRR” relative to a line  116  that is tangential to the interior cutting edge  88  and perpendicular to a radial line  114  extending out from the central axis  24 . As a result of the angle ISSRR, the interior cutting edge  88  (e.g., see  FIGS. 9A and 9B ) of the tooth  46  is disposed radially inside of the aft edge  98  of the interior side surface  86 . The magnitude of the acute angle ISSRR can be varied to best suit the rotary cutting tool  20  for different applications; e.g., different types of substrate materials, rotational cutting speeds, etc. The present disclosure is not limited to any particular angle ISSRR value. 
     Referring to  FIGS. 7 and 7A , in some embodiments the exterior side surface  82  of each tooth  46  is skewed by an acute exterior side surface axial relief angle “ESSAR” relative to a line  118  that is tangential to the outer radial tip  102  and parallel to the central axis  24 . As a result of the angle ESSAR, the outer axial edge  99  of the exterior side surface  82  is disposed radially outside of the inner axial edge  97  of the exterior side surface  82 . The magnitude of the acute angle ESSAR can be varied to best suit the rotary cutting tool  20  for different applications; e.g., different types of substrate  60  materials, rotational cutting speeds, etc. The present disclosure is not limited to any particular angle ESSAR value. 
     In some embodiments the interior side surface  86  of each tooth  46  is skewed by an acute interior side surface axial relief angle “ISSAR” relative to a line  120  that is tangential to the inner radial tip  104  and parallel to the central axis  24 . As a result of the angle ISSAR, the outer axial edge  103  of the interior side surface  86  is disposed radially inside of the inner axial edge  101  of the interior side surface  86 . The magnitude of the acute angle ISSAR can be varied to best suit the rotary cutting tool  20  for different applications; e.g., different types of substrate  60  materials, rotational cutting speeds, etc. The present disclosure is not limited to any particular angle ISSAR value. 
     In some embodiments the axial end surface  90  of each tooth  46  is skewed by an acute radial cutting angle “RC” relative to a radial line  122  that is tangential to the outer radial tip  102 , and that is perpendicular to the central axis  24 . As a result of the angle RC, the axial position of the inner radial tip  104  is displaced from the outer radial tip  102 ; i.e., the outer radial tip  102  is disposed axially outside of the inner radial tip  104 . To illustrate further, when the rotary cutting tool  20  is moved in a direction parallel to the central axis  24  into engagement with a planar substrate, the outer radial tip  102  will engage the substrate before the inner radial tip  104  as a result of the radial cutting angle RC. The entirety of the outer axial edge  99  of the exterior side surface  82  may be disposed axially outside of the outer axial edge  103  of the interior side surface  86 . The magnitude of the acute angle RC can be varied to best suit the rotary cutting tool  20  for different applications; e.g., different types of substrate  60  materials, rotational cutting speeds, etc. The present disclosure is not limited to any particular angle RC value. 
     The geometric configuration of the outer radial tip  102  may be varied to best suit the rotary cutting tool  20  for different applications; e.g., different types of substrate materials, rotational cutting speeds, etc. For example, the outer radial tip  102  may be configured with a radius, a multi-radius arcuate shape, a chamfer, or the like. 
     The geometric configuration of the inner radial tip  104  may be varied to best suit the rotary cutting tool  20  for different applications; e.g., different types of substrate materials, rotational cutting speeds, etc. For example, the inner radial tip  104  may be configured with a radius, a multi-radius arcuate shape, a chamfer, or the like. 
     In some embodiments, each tooth  46  may be formed completely from the same material as the body  22  of the rotary cutting tool  20  (e.g., the entirety of the tooth  46  may be formed by removing surrounding tool material via a machining process). In these embodiments, the tool  20  may be described as a unitary structure. In some embodiments, each tooth  46  may be formed to include a pedestal portion  120  formed from the same material as the body  22  of the rotary cutting tool  20 . One or more inserts  122  may be attached to the pedestal portion  120  of the tooth  46  to complete the respective tooth  46 . 
     In the exemplary embodiment shown in FIGURES, for example, the pedestal portion  120  is formed to include a pocket  124  configured to receive one or more inserts  122  (e.g., see  FIG. 6B ). The pedestal pocket  124  may include a seat surface  124 S and a back surface  124 B. The pocket seat surface  124 S is configured to contact a base surface  191  of an insert  122  (see  FIG. 11 ), and the pocket back surface  124 S is configured to contact an aft surface  193  of an insert  122  when the insert  122  is mounted within the pocket  124 . Each pedestal pocket  124  may be configured to receive an insert(s) that is geometrically configured to produce the tooth surface angle characteristics described above. Alternatively, a pedestal pocket  124  may be configured to receive an insert  122  that itself is not configured to provide the one or more of the surface angle characteristics described above, but upon the insert being received and attached to the pedestal  124 , the aforesaid configuration characteristic(s) is achieved; e.g., a pedestal pocket  124  may be oriented relative to radial and axial lines of the tool  20  (e.g., skewed) such that the aforesaid surface angle(s) is present when the insert  122  is installed, but is not present in the insert  122  itself. 
     Non-limiting examples of inserts  122  include carbide inserts, superhard material inserts, carbide inserts with superhard material grown on one or more surfaces of the carbide insert, etc. The present disclosure is not limited to any particular insert material. The term “superhard material” is understood to be an industry term referring to particular types of materials. Non-limiting examples of superhard materials include natural diamond, chemical vapor deposition diamond (CvD), and polycrystalline superhard materials (PSHM) such as polycrystalline diamond (PCD) and polycrystalline cubic boron nitride (PcBN). The embodiment shown in the FIGURES include a carbide support insert  122 A and a superhard material insert  122 B both disposed within the pedestal pocket  124 , and both fixed (e.g., by braze, adhesive, mechanical attachment, etc.) to the pedestal portion  120 . In this example, the carbide support insert  122 A is disposed between an aft surface of the pocket  124  and the superhard material insert  122 B. In the above example, the superhard material insert  122 B forms a portion or all of the front side surface  80 , the exterior side surface  82 , the interior side surface  86 , and axial end surface  90 . As stated above, the exemplary insert  122  that includes a carbide support insert  122 A portion and a superhard material insert  122 B portion is an example, and the present disclosure is not limited thereto. 
     In some embodiments (including those described above), each tooth  46  may include a coating applied to particular surfaces of the tooth  46  (e.g., at least one of the front side surface  80 , the exterior side surface  82 , the interior side surface  86 , or the axial end surface  90 ). Examples of coatings include chemical vapor deposition diamond (CvD) 
     To be clear, although the rotary cutting tool  20  shown in the FIGURES includes inserts attached to a pedestal portion  120  of the tooth  46 , the present disclosure is not limited to a rotary cutting tool  20  having teeth  46  with inserts  122 . As stated above, in some embodiments each tooth  46  may be formed completely from the same material as the body  22  of the rotary cutting tool  20 ; i.e., the rotary cutting tool  20  is a unitary structure comprising the same material throughout, including the teeth  46 . These unitary embodiments of the rotary cutting tool  20  may include a coating applied to particular surfaces of each tooth  46 . 
     The rotary cutting tool body  22  includes at least one fluid passage  126  extending internally within the body  22  from the shank end  26  of the body  22  to the base  56  of the internal cavity  52 . The at least one fluid passage  126  is configured to permit a fluid (e.g., a cutting fluid) entry at the shank end  26  of the rotary cutting tool body  22  and passage through the tool body  22  to the internal cavity  52 . 
     As described herein, the present disclosure rotary cutting tool  20  is configured for use with a rotary machine tool configured for driving the rotary cutting tool  20 , which rotary machine tool includes a pressurized cutting fluid system configured to feed cutting fluid (gas or liquid) to the shank end  26  of the rotary cutting tool  20 . Hence, the present disclosure includes a system that includes a rotary machine tool having a pressurized cutting fluid source and at least one rotary cutting tool  20  as described herein. 
     Referring to  FIGS. 11-11D , according to an aspect of the present disclosure, an insert  122  for a rotary cutting tool is provided. As described above, the insert  122  may be a unitary body or may be formed from a plurality of insert portions; e.g., carbide support insert  122 A portion and superhard material insert  122 B portion. The insert  122  includes a front side surface  180  (i.e., a “rake face”), an exterior side surface  182 , an interior side surface  186 , an axial end surface  190 , a base surface  191 , and an aft surface  193 . The insert may be described as extending heightwise (shown as the “X” axis in the orthogonal legend in  FIG. 11 ) between the axial end surface  190  and the base surface  191 , widthwise (shown as the “Y” axis) between the exterior side surface  182  and the interior side surface  186 , and depthwise (shown as the “Z” axis) between the front side surface  180  and the aft surface  193 . The exterior side surface  182  intersects with the front side surface  180  to form an exterior cutting edge  184 , an interior side surface  186  intersects with the front side surface  180  to form an interior cutting edge  188 , and an axial end surface  190  intersects with the front side surface  180  to form an axial end cutting edge  192 . The front side surface  180  includes an inner edge  194  disposed at an end of the front side surface  180  opposite the axial end cutting edge  192 . The front side surface  180  may be described as extending in a heightwise direction between the axial end cutting edge  192  and the inner edge  194 , and extending in an orthogonal widthwise direction between the exterior cutting edge  184  and the interior cutting edge  188 . The exterior side surface  182  includes an aft edge  196 , an inner axial edge  197 , and an outer axial edge  199 . The outer axial edge  199  is defined by the intersection between the exterior side surface  182  and the axial end surface  190 . The exterior side surface  182  may, therefore be described as extending in a heightwise direction between the inner axial edge  197  and the outer axial edge  199 , and extending in an orthogonal depthwise direction between the exterior cutting edge  184  and the aft edge  196 . The interior side surface  186  includes an aft edge  198 , an inner axial edge  201 , and an outer axial edge  203 . The outer axial edge  203  is defined by the intersection between the interior side surface  186  and the axial end surface  190 . The interior side surface  186  may, therefore, be described as extending in a heightwise direction between the inner axial edge  201  and the outer axial edge  203 , and extending in an orthogonal depthwise direction between the interior cutting edge  188  and the aft edge  198 . The axial end surface  190  includes an aft edge  200 . The axial end surface  190  may be described as extending in a widthwise direction between the outer axial edge  199  of the exterior side surface  182  and the outer axial edge  203  of the interior side surface  186 , and extending in an orthogonal depthwise direction between the axial end cutting edge  192  and the aft edge  200 . In some embodiments, the aft surface  193  may be perpendicular to the base surface  191   
     Referring to  FIG. 11B , in some embodiments the front side surface  180  of an insert  122  (i.e., the rake face) may be skewed by an angle “RR”. As a result of the angle RR, the distance between the front side surface  180  and the aft surface  193  along the interior side surface  186  is less than the distance between the front side surface  180  and the aft surface  193  along the exterior side surface  182  at the same heightwise position. The line  214  defining the angle “RR” is parallel to the widthwise axis Y. In those embodiments wherein the aft surface  193  and the base surface  191  are perpendicular one another, the line  214  is parallel to the aft surface  193 . The angle “RR” is described above in the context of a tooth  46 . 
     Referring to  FIGS. 11C and 11D , in some embodiments the front side surface  180  of an insert  122  may be skewed by an angle “AR”. The line  208  defining the angle “AR” is parallel to the heightwise axis X. In those embodiments wherein the aft surface  193  and the base surface  191  are perpendicular one another, the line  208  is parallel to the aft surface  193 . The angle “AR” is described above in the context of a tooth  46 . 
     Referring to  FIG. 11C , in some embodiments the axial end surface  190  of an insert  122  may be skewed by an angle “AESR”. The line  210  defining the angle “AESR” is parallel to the depthwise axis Z. In those embodiments wherein the aft surface  193  and the base surface  191  are perpendicular one another, the line  210  is parallel to the base surface  191 . The angle “AESR” is described above in the context of a tooth  46 . 
     Referring to  FIG. 11B , in some embodiments the exterior side surface  182  of an insert  122  may be skewed by an angle “ESSRR”. The line  212  defining the angle “ESSRR” is parallel to the depthwise axis Z. In those embodiments wherein the aft surface  193  and the base surface  191  are perpendicular one another, the line  212  is perpendicular to the aft surface  193 . The angle “ESSRR” is described above in the context of a tooth  46 . 
     Referring to  FIG. 11B , in some embodiments the interior side surface  186  of an insert  122  may be skewed by an angle “ISSRR”. The line  216  defining the angle “ISSRR” is parallel to the depthwise axis Z. In those embodiments wherein the aft surface  193  and the base surface  191  are perpendicular one another, the line  216  is perpendicular to the aft surface  193 . The angle “ISSRR” is described above in the context of a tooth  46 . 
     Referring to  FIG. 11A , in some embodiments the exterior side surface  182  of an insert  122  may be skewed by an angle “ESSAR”. The line  218  defining the angle “ESSAR” is parallel to the heightwise axis X. In those embodiments wherein the aft surface  193  and the base surface  191  are perpendicular one another, the line  218  is perpendicular to the base surface  191 . The angle “ESSAR” is described above in the context of a tooth  46 . 
     Referring to  FIG. 11A , in some embodiments the interior side surface  186  of an insert  122  may be skewed by an angle “ISSAR”. The line  220  defining the angle “ISSAR” is parallel to the heightwise axis X. In those embodiments wherein the aft surface  193  and the base surface  191  are perpendicular one another, the line  220  is perpendicular to the base surface  191 . The angle “ISSAR” is described above in the context of a tooth  46 . 
     Referring to  FIG. 11A , in some embodiments the axial end surface  190  of an insert  122  may be skewed by an angle “RC”. The line  222  defining the angle “RC” is parallel to the widthwise axis Y. In those embodiments wherein the aft surface  193  and the base surface  191  are perpendicular one another, the line  222  is parallel to the base surface  191 . The angle “RC” is described above in the context of a tooth  46 . 
     The diagrammatic depictions of an insert embodiment shown in  FIGS. 11-11D  are not intended to be to scale. The angles described above may be very small in magnitude and therefore not easily discernible if shown to scale. Hence, the aforesaid surface angles shown in  FIGS. 11-11D  are exaggerated to facilitate the explanation. In addition, the above description provides that an insert may include surface angles RC, ESSAR, ISSAR, AR, RR, ESSRR, and ISSRR, each greater than zero degrees. The present disclosure contemplates that insert embodiments may include one or more of these angles surfaces or all of these angles surfaces. 
     In the operation of the rotary cutting tool  20 , a length of the shank portion  30  is fixed within a chuck of a rotary machine tool. The rotary machine tool is configured to rotationally drive the rotary cutting tool  20  at one or more selected rotational speeds. The rotary machine tool includes a cutting fluid source that provides cutting fluid to the shank end  26  of the rotary cutting tool  20  and internal fluid passage  126  at a selected pressure (greater than ambient) and volumetric flow rate. The particular cutting fluid used in the cutting process, which may be a gas or a liquid, may depend on several factors such as, but not limited to, the mechanical and material properties of the substrate material being cut, the thickness of the substrate  60 , the feed rate of the cutting device, and the like. The present disclosure rotary cutting tool  20  is not limited to use with any particular type of cutting fluid, or any particular cutting fluid volumetric flow rate and/or supply pressure. However, as described herein, the number of channels  62  disposed in the interior wall surface  54  of the internal cavity  52 , and the geometric configuration of those cavities  52 , is typically selected to provide a cutting fluid flow rate and pressure profile that is acceptable for the substrate  60  being cut, the applied machine operational parameters, and the type of cutting fluid being used during the cutting process. 
     Referring to  FIGS. 8-10 , as the rotary cutting tool  20  engages a first surface  128  of the substrate  60 , the cutting teeth  46  begin to cut an annular void within the substrate  60 . The annular void defines a central core of substrate  60  material (i.e., a “plug  58 ”) that enters the internal cavity  52  of the tool as the cutting proceeds. The portion of the internal cavity  52  devoid of the plug  58  fills with cutting fluid at an elevated pressure “P 2 ” greater than ambient pressure “P 1 ” from the fluid passage  126 . Cutting fluid within the internal cavity  52  exits the internal cavity  52  of the rotary cutting tool  20  via the channels  62  (e.g., the open ends  63  of the channels  62 ; shown diagrammatically in  FIG. 10 ) disposed within the interior wall surface  54  of the internal cavity  52 . As stated above, the channels  62  (e.g., collective number and individual geometric configuration) create a cutting fluid volumetric flow rate to the teeth  46  and a pressure profile between the internal cavity  52  and the ambient surroundings across that is acceptable for the material being cut and the type of cutting fluid being used during the cutting process. For example, the channels  62  are typically configured to provide a cutting fluid flow that is adequate to remove debris created during the cutting process as will be described below. The channels  62  are also typically configured so that the fluid pressure within the internal cavity  52  itself does not cause deformation of the plug  58  during the cutting process (e.g., plug  58  flexure when cutting thin substrates  60 ), or substrate material failure and premature separation of the plug  58 , or substrate surface deformations surrounding the aperture and/or within the substrate itself, but rather the channels  62  are configured to establish a fluid pressure within the internal cavity  52  is sufficient to remove the plug  58  from the internal cavity  52  upon completion of the cutting process without detrimental effect to the substrate  60 . 
     Each channel  62  within the interior wall surface  54  of the internal cavity  52  is positioned forward of a respective tooth  46  (e.g., described above as a “following tooth  46 FT”). A respective flute  38  inlet (shown diagrammatically in  FIG. 10 ) is disposed adjacent the following tooth  46  (e.g., see  FIGS. 8 and 9 ). The relative positions of each respective channel  62 , flute  38  and tooth  46  is such that cutting fluid  132  exiting the channel  62  passes between a pair of adjacent teeth  46  and passes in front of the aft tooth  46  (i.e., the following tooth  46 FT) of the pair of teeth  46 . The cutting fluid  132  exiting the channel  62  may be described as “washing” across the gullet  48  between the pair of adjacent teeth  46 , in front of the following tooth  46 FT where cutting debris is captured by the cutting fluid flow  132 , and enters the flute  38  adjacent the following tooth  46 . The substrate  60  being cut creates one or more surfaces that bound the teeth  46  that effectively enclose the teeth  46 , thereby forming a part of a fluid passage for cutting fluid to pass from a respective channel  62  to a respective flute  38 . The cutting fluid with cutting debris subsequently passes within the flute  38  and exits outside of the substrate  60 . The pressure difference between the cutting fluid residing within the internal cavity  52  (at P 2 ) and the ambient pressure surrounding the substrate  60  (at P 1 ) provides a motive force acting on the cutting fluid propelling it along the aforesaid path. In those rotary cutting tool  20  embodiments having helical flutes  38 , the rotation of the rotary cutting tool  20  may provide additional motive force for the removal of the cutting fluid and captured debris. 
     The angled surfaces of each tooth  46  (e.g., one or more of the ESSRR, ISSRR, ESSAR, ISSAR, and AESR angles) decrease the amount of contact between the tooth  46  and the substrate  60  and thereby reduce friction. As indicated above, thermal energy as a result of friction produced during the cutting process, if excessive, can produce undesirable thermal decomposition of a composite substrate. The decrease in friction associated with the angled surfaces of the present disclosure decreases the potential for excessive temperature. In those instances where the substrate  60  material being cut possesses some amount of elastic recovery, the aforesaid angled surfaces also account for the aforesaid elastic recovery. 
     The radial cutting angle RC (e.g., see  FIG. 7A ) provides significant advantages. For example as a result of the RC angle of each tooth  46 , the forces applied to the substrate  60  by the present disclosure rotary cutting tool  20  are directed predominantly radially inwardly towards the plug  58  being cut and therefore predominantly away from the periphery of the substrate  60  surrounding the aperture being cut. The forces directed radially inward greatly reduce the potential for surface deformations and/or thermally caused degradation being formed within the entry and exit surfaces  128 ,  130  of the substrate  60  surrounding the aperture and/or within the body of the substrate  60 . This characteristic of the present rotary cutting tool  20  is particularly advantageous when the substrate  60  being cut is a composite material having one or more fibrous layers where fibers may otherwise be frayed, or pulled during the cutting process. The ability of the present rotary cutting tool  20  to produce an aperture with significantly reduced deformations within the substrate can in many instances mitigate or eliminate the need to apply secondary machining processes to the substrate; e.g., deburring, chamfering, etc. 
     As stated above, the present disclosure provides rotary cutting tools  20  that provide a significant improvement for cutting apertures within composite substrates. Aspects of the present disclosure include a method for cutting a composite substrate. The cutting tool embodiments described above detail the tool characteristics that mitigate the potential for damage to the composite substrate during the cutting process. The above description also details a methodology wherein cutting fluid may from a fluid source may be provided to the internal cavity of the cutting tool and the fluid pressure within the internal cavity can be controlled (e.g., in view of the channels  62  disposed in the interior wall surface  54  of the internal cavity  52 , to produce an acceptable fluid pressure level within the internal cavity  52  (e.g., sufficient to remove the plug upon completion, while not negatively affecting the composite substrate during the cutting process), and to provide a flow of cutting fluid through each channel that exits the channel  62  and washes across the gullet  48  between adjacent teeth  46  and removes cutting debris, carrying it to a respective flute  38 . 
     It is noted that various connections are set forth between elements in the present description and drawings (the contents of which are included in this disclosure by way of reference). It is noted that these connections are general and, unless specified otherwise, may be direct or indirect and that this specification is not intended to be limiting in this respect. A coupling between two or more entities may refer to a direct connection or an indirect connection. An indirect connection may incorporate one or more intervening entities or a space/gap between the entities that are being coupled to one another. 
     Furthermore, any reference to singular includes plural embodiments, and any reference to more than one component or step may include a singular embodiment or step. Also, any reference to attached, fixed, connected or the like may include permanent, removable, temporary, partial, full and/or any other possible attachment option. 
     Furthermore, no element, component, or method step in the present disclosure is intended to be dedicated to the public regardless of whether the element, component, or method step is explicitly recited in the claims. No claim element herein is to be construed under the provisions of 35 U.S.C. 112(f) unless the element is expressly recited using the phrase “means for.” As used herein, the terms “comprises”, “comprising”, or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.