Abstract:
An insert retention screw having a head with a radius that is sufficient size to fit within a mounting hole of a cutting insert and seat within a seating plane within the mounting hole that is generally perpendicular to the axis of the insert when the screw is at an angle of about 0-15 degrees is disclosed. The retention screw provided for holding a cutting insert in the pocket of a tool body. The pocket is partially defined by a floor and a seating surface. A threaded hole is at an angle that is taken with reference to the pocket floor. The insert has a mounting hole passing therethrough. The retention screw passed through the mounting hole and threads into the threaded hole so as to draw the insert against the seating surface.

Description:
FIELD OF THE INVENTION 
   The present invention relates to an insert retention screw for holding a cutting insert in the pocket of a tool body and that resists binding with the insert during a cutting operation. The screw can be oriented to match the lubricity coefficient of the insert and the tool body and thus allow the insert to slide into the apex of seating surfaces in a pocket of the tool body. 
   BACKGROUND OF THE INVENTION 
   Cutting tools are well known. A conventional cutting tool typically comprises a tool body that is adapted to mate with a cutting machine. The tool body has a working end and one or more pockets in the working end. A conventional pocket ordinarily includes floor and two seating surfaces, which intersect one another at an apex. The pockets are provided for receiving cutting inserts. A retention screw passes through a mounting hole in each insert and is threaded into a threaded hole in the floor of a corresponding pocket. 
   A conventional threaded hole is generally perpendicular to the floor of the pocket. As a result, the retention screw is vulnerable to a shear force, which renders the retention screw prone to breaking. The perpendicular orientation of the retention screw is also not the most suitable orientation for the screw because the screw, in this orientation, does not direct the insert toward the seating surfaces effectively. It is desirable to provide a seating arrangement that overcomes these deficiencies. 
   A conventional cutting insert typically has a top rake face, flank faces, and a cutting edge between the rake and flank faces. An inboard rake face extends radially inward from the flank face of the cutting insert  30 . A ramp edge is provided between an inboard flank face and the rake face. The cutting edge is generally parallel to the bottom of the insert. The ramp edge has a negative geometry. The parallel orientation of the cutting edge and the negative geometry of the ramp edge are not the most suitable characteristics for a cutting insert. These characteristics typically require greater force to cut the workpiece, affecting the ramping angle that can be achieved by the cutting insert, and producing an inferior finish. Consequently, greater efforts and extended cutting operations are required. Moreover, additional independent cutting operations are required to achieve a desired finish. To this end, it is desirable to provide an insert that would achieve greater ramping angles, require less force, and achieve a desired finish in fewer cutting operations. 
   A conventional tool body has radial and axial surfaces adjacent the pockets. These surfaces may engage the workpiece during cutting operations, especially when performing ramping (i.e., the cutting tool moves axially and radially) or helical interpolation (i.e., the cutting tool moves axially and radially in a helical direction) operations. This surface engagement adversely affects the finish produced by the conventional cutting tool. It is desirable to provide a tool body that has sufficient clearance between the radial and axial surfaces and the workpiece during cutting operations to produce a desirable finish and thus reduce or eliminate the need for additional cutting operations. 
   During a cutting operation, the temperature of the cutting tool is elevated due to the frictional engagement of the cutting tool and the workpiece. A conventional retention screw can bind with the cutting insert due to the elevated temperature of the cutting tool. As a consequence, the retention screw and thus the cutting insert cannot be readily removed. This is a deficiency with a conventional retention screw. What is needed is a retention screw that is less likely to bind with an insert than a conventional retention screw. 
   Some conventional tool bodies have flutes for evacuating chips from the workpiece during a cutting operation. The flutes are defined by sidewalls, which are cut into the tool body. The flutes typically originate from the cutting insert and extend in an axial direction away from the working end of the tool body. The transition between the cutting insert and the flute is generally discontinuous and thus obstructs the flow of chips through the flute. What is needed is a cutting tool that has a continuous or smooth transition between the insert and the flute and thus effectively discharges chips from the working end of the cutting tool. 
   SUMMARY OF THE INVENTION 
   Generally speaking, the invention is directed to an insert retention screw comprising a head with a radius. The radius is a sufficient size to fit within a mounting hole of a cutting insert and seat within a seating plane within the mounting hole, wherein the seating plane is generally perpendicular to the axis of the mounting hole when the screw is at an angle in a range of about 0-15 relative to the axis of the mounting hole. 
   The invention is further directed to a cutting tool comprising a tool body having a pocket, an insert, and a retention screw holding the insert in the pocket. The pocket is partially defined by a floor and a seating surface. A threaded hole is in the pocket. The threaded hole is at an angle that is taken with reference to the pocket floor. The insert has an upper rake face, at least one side defining a flank face, a cutting edge provided between the rake face and the flank face, and a mounting hole passing therethrough. The retention screw passes through the mounting hole and threads into the threaded hole in the floor of the pocket so as to draw the insert against the seating surface. 
   The invention is still further directed to a method for orienting an insert retention screw at an angle. The method comprises the steps of selecting a tool body and a cutting insert, determining the frictional force between the tool body and cutting insert, and determining the angle for the retention screw, wherein a force component of the retention screw is greater than or equal to the frictional force between the tool body and the cutting insert. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further features of the present invention, as well as the advantages derived therefrom, will become clear from the following detailed description made with reference to the drawings in which: 
       FIG. 1  is a partial side elevational view of a cutting tool according to a preferred embodiment of the invention; 
       FIG. 2  is a side elevational view of the working end of the cutting tool illustrated in  FIG. 1  rotated approximately 90 degrees; 
       FIG. 3  is a side elevational view of the cutting tool shown in  FIG. 1  with a cutting insert removed from the tool body pocket; 
       FIG. 4  is an enlarged-scale perspective view of a cutting insert according to a preferred embodiment of the invention; 
       FIG. 5  is a front elevational view thereof with the rear being a mirror image thereof; 
       FIG. 6  is a right side elevational view thereof with the left side being a mirror image thereof; 
       FIG. 7  is a top plan view thereof; 
       FIG. 8  is a bottom plan view thereof; 
       FIG. 9  is a plan view of the cutting insert and angled retention screw according to a preferred embodiment of the invention; 
       FIG. 10  is a cross-sectional view of the cutting insert and angled retention screw taken along the line  10 - 10  in  FIG. 9 ; 
       FIG. 11  is a cross-sectional view of the cutting insert and angled retention screw taken along the line  11 - 11  in  FIG. 9 ; 
       FIG. 12  is a cross-sectional view of the cutting insert and angled retention screw taken along the line  12 - 12  in  FIG. 9 ; 
       FIG. 13  is a front elevational view of a axial clearance face and a radial clearance face according to the present invention; 
       FIG. 14  is a front elevational view of the radial clearance face illustrated in  FIG. 13 ; 
       FIG. 15  is an enlarged-scale side elevational view of the axial clearance face illustrated in  FIG. 13 ; 
       FIG. 16  is a partial side elevational view of an alternative cutting tool; 
       FIG. 17  is a cross-sectional view taken along the line  17 - 17  in  FIG. 16 ; 
       FIG. 18  is a cross-sectional view taken along the line  18 - 18  in  FIG. 16 ; 
       FIG. 19  is a cross-sectional view taken along the line  19 - 19  in  FIG. 16 ; 
       FIG. 20  is a cross-sectional view taken along the line  20 - 20  in  FIG. 16 ; 
       FIG. 21  is an enlarged partial schematic representation of the cutting tool illustrated in  FIG. 16 ; and 
       FIG. 22  is a side elevational view of the retention screw of the cutting tool illustrated in  FIG. 16 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   With reference now to the drawings, wherein like numerals designate like components throughout all of the several figures, there is illustrated in  FIG. 1  a cutting tool  10  according to a preferred embodiment of the invention. The cutting tool  10  is adapted for use in face milling (i.e., the cutting edge is on the face of the tool), peripheral milling (i.e., the cutting edge is on the periphery of the tool), ramp milling, and/or helical interpolation operations. Multiple cutting tools typically perform these machining operations. Since the cutting tool  10  according to the instant invention is capable of performing any one or all these machining operations, it requires less machining time. 
   The cutting tool  10  comprises a holder, such as the tool body  12  shown. The tool body  12  preferably has a generally cylindrical outer peripheral surface  14 , a portion of which defines a shank (not shown) that is adapted to mate with an adaptor of a type well known in the art to adapt the tool to a machining center or cutting machine (not shown). 
   The cutting tool  10  according to the present invention comprises a tool body  12  that has a cutting or working end, generally indicated at  25  (i.e., to the left when viewing  FIG. 1 ), with one or more pockets  26  therein, as clearly shown in  FIG. 3 . The pockets  26  are adapted to receive cutting inserts  30 . The cutting inserts  30  can be in any suitable form and are preferably indexable to aid in positioning and repositioning the cutting inserts  30  in the pockets  26 . The cutting inserts  30  are held within the pockets  26  by hold-down or retention screws  32  (shown in  FIG. 2 ). The retention screws  32  are adapted to be inserted through the cutting inserts  30  and threaded into holes  34  that extend transversely relative to the longitudinal axis  36  (shown in  FIG. 1 ) of the tool body  12 . The tool body  12  and the inserts  30  cooperatively define flutes  37  for evacuating chips from a workpiece (not shown). 
   As illustrated in  FIG. 3 , the pockets  26  are preferably defined, at least in part, by a radially extending floor  27  and at least two sidewalls or seating surfaces (i.e., the radial and axial walls  28 ,  28 ′). These surfaces  28 ,  28 ′ extend from the pocket floor  27  and intersect one another at an apex, which is clearly illustrated at  29  in  FIG. 3 . In the illustrated embodiment, three pockets  26  are provided for supporting three cutting inserts  30  that cooperatively form three corresponding flutes  37  in the tool body  12 . However, those of ordinary skill in the art should appreciate that one or more pockets, inserts, and flutes can be used to carry out the invention. 
   A cutting insert  30  according to the preferred embodiment of the invention is illustrated in  FIGS. 4-8 . As shown in the drawings, an elliptical cutting edge  38  with a wiper facet  39  is designed into a front edge of the cutting insert  30 . The elliptical cutting edge  38  has a radius that graduates or diminishes, instead of being constant, from the nose  40  of the cutting insert  30  to the trailing end (i.e., opposite the nose  40 ) of the cutting edge  38 . The specific radius of the cutting edge  38  is measured from an imaginary focal point and can be, for example, in a range of about 0.500-25 inches. The radius obviously depends on the size of the cutting tool. The cutting edge  38  is preferably tangential to the radius of the nose  40  and the inboard ramping cutting edge  41  of the cutting insert  30 . This produces an exceptional surface finish on both the face and sidewall of the workpiece (not shown) when operated under certain parameters. For example, the wiper facet  39  may be about 0.08 inches wide and the radius of the cutting edge  38  may be about two inches. When the cutting tool  10  is operated at a feed rate per revolution (i.e., about 0.08 inches per revolution) that is within the width of the wiper facet  39 , an exceptional surface finish can be produced. The radius of the cutting edge  38  is based on the orientation of the cutting insert  30  in the tool body  12  and the aggregate diameter of the cutting tool  10  with the cutting inserts  30  therein (as depicted in the end view in  FIG. 13 ). A radius is determined between various compensation requirements (i.e., the orientation of the pocket to the face of the workpiece) that will allow the cutting insert  30  to produce a shoulder that is about 90 degrees and manufacturing tolerances that can be held to do so. 
   The elliptical cutting edge  38  of the insert  30  is preferably elliptical to contribute to a positive cutting geometry (i.e., raised geometry) on the rake face  42  of the insert  30  (i.e., the top surface when viewing  FIGS. 4 and 5 ). The positive cutting geometry of the rake face  42  requires less cutting force than conventional cutting inserts. Moreover, the elliptical cutting edge  38  produces a truer 90 degree shoulder on the workpiece (not shown), much like that produced by a conventional solid carbide end mill. The elliptical cutting edge  38  produces a final finish, thus reducing or eliminating the need for additional finishing operations by additional cutting tools. 
   The cutting insert  30  further has three-dimensional capabilities. That is to say, the inboard ramping cutting edge  41 , which increases ramping capabilities (i.e., due to a positive geometry of the ramping edge  41 ) when compared to conventional inserts. The term “ramping” refers to a cutting operation wherein the insert is moved both axially and radially relative to the workpiece (not shown). The ramping edge  41  is normally parallel to the flat bottom of a conventional insert, resulting in a negative geometry, which requires greater cutting forces. Unlike a conventional ramping edge, the ramping edge  41  of the present invention has a positive geometry (i.e., the ramping edge  41  is raised relative to the rake face  42 ), which reduces cutting forces, as compared to the cutting forces required by the negative geometry of conventional inserts. The inboard ramping edge  41  additionally allows the cutting tool  10  to perform true ramping operations and helical interpolating operations at a much higher rate with machines, such as routers and shell mill cutters (not shown), which are not normally capable of performing ramping and helical interpolating operations. A “helical interpolating operation” is a cutting operation wherein the insert  30  moves axially and radially relative to the workpiece. The insert  30  begins by first cutting the periphery of a hole in the workpiece (not shown). Then, the insert  30  is moved in a helical pattern to the center of the hole while continuing in a direction of the axis of the hole until a required depth is achieved. This operation is generally performed without interruption. 
   As clearly illustrated in  FIGS. 9-12 , the attitude of the retention screws  32  and the holes  34  in the tool body  12  are at a non-perpendicular axial angle to an insert mounting hole  48 , which will be described in greater detail hereinbelow, or the pocket floor  27 . This permits proper seating of the cutting insert  30  without placing added stresses on the retention screw  32 . That is to say, the attitude of the screw  32  allows the screw  32  to be in a tension orientation rather than a shear orientation. Consequently, the screw  32  is utilized in its strongest orientation. 
   The attitude of the retention screws  32  can be at a compound angle to the bottom  46  of the cutting insert  30  or the pocket floor  27 . This angle can be calculated to match the lubricity coefficient (i.e., coefficient of friction) of the insert  30  and the tool body  12 . This allows the insert  30  to slide into the apex  29  (shown in  FIG. 12 ) of the seating surfaces  28 ,  28 ′ (shown in  FIG. 12 ) and thus prevents  15  any additional stresses to the screw  32 . For example, for a given screw force F SCREW , the following are known:
 
F z =F SCREW  cos Θ,
 
F f =C f F SCREW  cos Θ, and
 
F x =F SCREW  sin Θ,
 
   wherein F z  is the force component in a direction perpendicular to the pocket floor  27 , F f  is the frictional force, and F x  is the force component in a direction parallel to the pocket floor  27 . These forces F z , F f , and F x  are all depicted in  FIG. 12 . The force component F x  must be sufficient to overcome the frictional force F f . At what angle Θ is the force component F x  greater than or equal to the frictional force F f  or at what angle Θ does F f =F x  @ C f ?
 
F f =F x  or C f F SCREW  cos Θ=F SCREW  sin Θ
 
C f =tan Θ
 
Θ=tan −1 C f 
 
   If the coefficient of friction C f  is 0.5, which is the coefficient of friction of uncoated carbide on uncoated steel, then angle Θ is 26.56 degrees. If the coefficient of friction C f  is 0.2, which is the coefficient of friction of uncoated carbide on uncoated carbide, the angle Θ is 11.3 degrees. If the coefficient of friction C f  is 0.27, which is the coefficient of friction of oxide film applied steel on steel, the angle Θ is 15.1 degrees. 
   Hence, the foregoing may be summarized by selecting material compositions of the tool body  12  and the cutting insert  30 , determining the coefficient of friction of the materials, and determining an angle for the retention screw  32 , wherein the force component F x  parallel to the pocket floor  27  is greater than or equal to the frictional force F f  between the materials. The force component F x  parallel to the pocket floor  27  may be oriented toward either seating surface  28 ,  28 ′ or the apex  29  therebetween to draw the insert  30  toward a seating surface  28 ,  28 ′ or the apex  29 . 
   The coefficient of friction for materials may be affected by the environment (i.e., temperature) or foreign substances (i.e., lubricants). These factors may be considered when determining a desired angle. Also, external forces (i.e., dynamic forces) encountered during a cutting operation may be considered. It may be desirable to angle the retention screw  32  to compensate for the effects of such forces. 
   The angled orientation of the screw  32  also permits an increase in steel under the bottom  46  of the insert  30  for added support and permits the retention screw  32  to have increased thread engagement on smaller diameter tool bodies. Insufficient thread engagement is a known flaw of retention screws that are oriented perpendicularly to the bottom of the insert. 
   It should be noted upon viewing  FIGS. 10 and 11  that the retention screw  32  is angled relative to both the radial and axial walls  28 ,  28 ′. This angular orientation slides the insert  30  toward the radial seating surface  28  (i.e., to the right when viewing  FIG. 10 ) and toward the axial seating surface  28 ′ (i.e., upward when viewing  FIG. 11 ). It should be appreciated by one of ordinary skill in the art that this effectively slides the insert  30  into the apex  29  (i.e., to the right when viewing  FIG. 12 ) between the seating surfaces  28 ,  28 ′. 
   Referring back to  FIG. 6 , there is illustrated an angular mounting hole  48  for the retention screw  32  (shown in  FIGS. 9-12 ). The mounting hole  48  passes through the center of the cutting insert  30 . It should be noted that the mounting hole  48  is oblong and oriented with the greater length of the mounting hole  48  extending between the opposing noses  40  of the insert  30 . The mounting hole  48  is arranged and configured to guide the retention screw  32  into the threaded hole  34  (clearly illustrated in  FIGS. 10-12 ) in the tool body  12 . The mounting hole  48  is oblong because the illustrated embodiment is indexable. That is to say, the insert can be removed from the pocket  26  (also shown in  FIGS. 10-12 ), rotated 180 degrees (i.e., clockwise or counter-clockwise when viewing  FIG. 6 ), and reinserted into the pocket  26 . 
   It should be further noted that the retention screw  32  according to a preferred embodiment of the invention has a spherical or radius head  50 , as clearly illustrated in  FIGS. 10-12 . The mounting hole  48  through the insert  30  is preferably conical. It should be appreciated that the head  50  and the mounting hole  48  may be cooperatively sized and configured so that the head  50  has limited contact with the mounting hole  48 . This limited contact reduces the risk of the retention screw  32  becoming bound to the insert  30 . The contact could be limited to approximately 180-degree contact, which, in the drawings, occurs on the side of the mounting hole  48  closest to the apex  29  of the pocket  26  (i.e., between the seating surfaces  28 ,  28 ′) as shown in  FIG. 12 . The limited contact may occur when force is applied to the retention screw  32  since the retention screw  32  contacts the side of the mounting hole  48  closest to the apex  29  of the pocket  26  and forces the cutting insert  30  toward the apex  29 . 
   In operation, the tool body  12  is supported in an adapter of a type well known in the art to adapt the tool to the machining center or cutting machine (not shown). The insert  30  is secured in the pocket  26  with the angled retention screw  32 , as set forth above. As the spindle turns, the insert  30  engages a workpiece (not shown) to remove material from the workpiece. As material is removed from the workpiece, chips are discharged through the flutes  37 . 
   According to a preferred embodiment of the invention, the cutting insert  30  and the tool body  12  cooperatively form the flutes  37 . As clearly  FIGS. 1-3 , the flutes  37  are defined by sidewalls, which are, for the most part, cut into the tool body  12 . However, a small portion of the sidewalls is represented by the rake face  42  of the insert  30 . It should be appreciated that there is a smooth transition between the portion of the sidewalls that is represented by the rake face  42  and the portion cut into the tool body  12 . This smooth transition results in a continuous, or uninterrupted, and unobstructed gullet or flute for efficient and effective evacuation of chips from the workpiece. 
   The flutes  37  are also designed so that the elliptical, helical shape of the cutting edge  38  forms a continuous, level surface with the helical flute of the tool body  12 . The flutes  37  provide helical-shaped chip gullets that encourage a natural chip flow from the working end  25  of the tool body  12 . This further results in an unobstructed flow of chips from the cutting edge  38  of the insert  30  through the flutes  37 . 
   According to a preferred embodiment of the invention, the bottom  54  of each flute  37  moves further away from the longitudinal axis  36  of the tool body  12  in a radial direction as the flute  37  extends toward the shank from the working end  25  of the tool body  12 . This adds rigidity to the tool body  12  because the cross-sectional area of the tool body  12  between the flutes  37  becomes greater toward the shank. 
   Conventional tool bodies have axial and radial surfaces that may engage the workpiece during cutting operations. The present invention has a face clearance or axial clearance face  60 , as illustrated in  FIG. 13  and a graduated radial clearance face  62 , as illustrated in  FIG. 14 . The axial clearance face  60  is best described with reference to  FIG. 15 , wherein a conventional axial surface is illustrated in broken line. The conventional axial surface does not provide sufficient clearance for higher ramping angles during ramping or helical interpolating operations. The axial clearance face  60  of the present invention, by comparison, is preferably at an angle Φ in a range of about 5-25 degrees relative to that of a conventional axial clearance face or relative to a plane that is perpendicular to the longitudinal axis  36  (shown in  FIG. 13 ) of the tool body  12 . According to a preferred embodiment of the invention, the axial clearance face  60  is at an angle Φ in a range of about 8-10 degrees. Consequently, the cutting tool  10  according to the present invention has an increased ability to achieve higher ramp angles than a conventional tool body. It should be noted that the axial clearance face  60  coincides with the clearance face (i.e., to the left when viewing  FIG. 15 ) of the insert  30 . Alternatively, the axial clearance face  60  may be offset and generally parallel or at some angle greater than parallel to the clearance face of the insert  30 . 
   Similarly, a conventional radial surface is illustrated in broken line in  FIG. 14 . The conventional radial surface does not provide sufficient clearance for higher feed rates during face milling or helical interpolating operations. This is a typical failure or deficiency of conventional cutting tools. Unlike conventional cutting tools, the radial clearance face  62  of the present invention allows the cutting tool  10  to achieve higher feed rates and thus overcomes this deficiency. The increased clearance is achieved by tapering the diameter of the radial clearance face  62 . For example, a first radial clearance face diameter is indicated at  70  in  FIG. 14  and a second radial clearance face diameter is indicated at  72 . This results in an additional clearance, indicated, for example, at  74 . The additional clearance  74  is with reference to the peripheral or cylindrical surface  14  of the tool body  12  (shown in  FIG. 1 ). The radial clearance face  62  has a diminishing radius that begins at the pocket floor  27 . The beginning of the radial clearance face  62  generally coincides with the flank face on the front end of the insert  30 . The clearance of the radial clearance face  62  is based on a lateral feed rate in a range of about 0.030-0.050 inches per tooth (0.762-1.27 mm per tooth). A nominal clearance is based on a feed rate of about 0.040 inches per tooth (1.016 mm per tooth), which provides the most clearance without losing support of the tool body  12  and safety of the cutting tool  10  itself. 
   An alternative insert  80  and retention screw  94  are illustrated in  FIGS. 16-21 . Note that the insert  80  has an upper rake face  82  and four sides, each of which may define a flank face  84  (shown in  FIGS. 17 and 18 ). A cutting edge  86  (also shown in  FIGS. 17 and 18 ) may be provided between the rake face  82  and each flank face  84  of the insert  80 . Consequently, the insert  80  may be indexable. 
   The insert  80  is adapted to be mounted in the pocket  92  of a tool body  90  by a retention screw  94 . The retention screw  94  is threaded into a threaded hole  98  in the floor  100  of the pocket  92 . The threaded hole  98  is preferably at a compound angle Ω (illustrated in  FIG. 19 ), which is taken with reference to a plane that is perpendicular to the pocket floor  100  and two seating surfaces  102 ,  102 ′, or the apex  104  between the seating surfaces  102 ,  102 ′. In the illustrated embodiment, the compound angle Ω is about 5 degrees. This is a nominal angle. However, an angle in a range of about 0-15 degrees may be suitable for carrying out the present invention. The specific angle depends upon the insert geometry, the size and shape of the retention screw  94 , and the coefficient of friction between the tool body  90  and the cutting insert  80 . It should be appreciated that the angle Ω need not be a compound angle but instead may be an angle relative to either one of the seating surfaces  102 ,  102 ′. 
   As clearly shown in  FIGS. 17-20 , the bottom  114  of the mounting hole  112  through the cutting insert  80  may be tapered or conical to provide clearance for the angled retention screw  94 . Alternatively, the bottom  114  of the mounting hole  112  may have another form of relief or otherwise have an increased diameter portion, which is neither tapered or conical, to provide clearance for the angled retention screw  94 . As yet another alternative, the mounting hole  112 , or the bottom  114  thereof, may be sufficiently large, without the provision of a relief, to provide the requisite clearance to receive the angled retention screw  94  regardless of the indexed orientation of the insert  80 . The clearance permits the insert  80  to be indexed while the screw  94  is angled without regard to the indexed orientation of the insert  80 . 
   It should be noted that the benefit of providing the angle Ω of the screw  94  increases the distance D 1  between the bottom of the screw  94  and the cylindrical surface  106  of the tool body  90 . This is clearly illustrated in  FIG. 21 . Compare this with the distance D 2  between the bottom of a conventional screw and the cylindrical surface of the tool body, as indicated between the lines  108 ,  110 . The distance D 3  between the top of the screw  94  and the cylindrical surface  106  of the tool body  90  is also increased slightly. The increased distances provide more tool body material between the screw  94  and the cylindrical surface  106  and thus increases the strength of the tool body  90  to better hold the screw  94  and the insert  80 . The increased distance further precludes or eliminates the risk of the screw  94  protruding from the tool body  90  and/or allows a longer screw to be used. Longer screws have added strength. 
   As illustrated in  FIG. 22 , the screw  94  has a spherical or radius head  116 , similar to that of the screw  30  described above. The radius head  116  permits the screw  94  to properly seat in the mounting hole  112  (shown in  FIG. 21 ), especially conventional mounting holes that are sized to comport with ISO or other industry standards. This is advantageous because a conventional retention screw (i.e., one that has a tapered or conical screw head), if oriented at an angle other than zero degrees, could contact a conventional mounting hole only on one side of the screw head, close to the top of screw  94 . An opposing side would then protrude from the mounting hole  112 . The radius head  116  is a sufficient size that still fits within the mounting hole  112  and seats within the proper seating plane within the hole  112 . The proper seating plane is in a plane that is generally perpendicular to the axis of the insert  80 , the mounting hole  112 , or the floor  100  of the pocket  92  (shown in  FIG. 21 ) and not necessarily perpendicular to the axis of screw  94 . The screw  94  does not protrude from the mounting hole  112 . Locating the radius of the head  116  depends on where lock-up (i.e., locking engagement of the screw  94  and mounting hole  112 ) is desired. If the screw  94  is too far out of the mounting hole  112  or too far in the mounting hole  112 , then the insert  80  may not seat properly in the pocket  92 . 
   It should be appreciated that various features of the invention are adapted for use together or independent of one another. For example, the threaded holes  34  and the clearance faces  60 ,  62  of the tool body  12  are believed to be novel and adapted for use independent of one another. Moreover, the tool body  12  is adapted for use with either insert  30 ,  80  describe herein as well as other inserts, which are not described herein. The elliptical cutting edge  38 , the inboard ramping cutting edge  41 , and the angular mounting hole  48 , among other features, of the insert  30 , described herein, are believed to be independently novel features that are not intended to be limited to the particular insert  30  shown and described herein. Further, the retention screws  32 ,  94  are interchangeable with the various embodiments described herein and are adapted for use with other cutting tools. The orientation of the screw and the method of determining the orientation are not intended to be limited to the tool bodies  12 ,  90 , the inserts  30 ,  80 , and the screws  32 ,  94  shown or described herein but may be practiced with other tool bodies, insert, and screws. 
   The cutting tool according to the present invention has several advantages. The tool has improved performance in providing surface finish. The tool has improved three-dimensional capabilities. The tool produces true perpendicular wall surfaces when making single or multiple passes on peripheral cuts. The tool provides improved insert retention. Moreover, the tool body provides increased support and clearances. 
   While the invention has been described with respect to several preferred embodiments, various modifications and additions will become apparent to persons of ordinary skill in the art. All such modifications and additions are intended to be encompassed within the scope of this patent, which is limited only by the claims appended hereto.