Abstract:
An indexable insert has one or more recesses formed in a frontside or backside surface which receives a surface of the head of a locking screw. When mounted, the insert is forced against respective support surfaces of an insert pocket. The locking screw is threaded into a counterbored tap hole to engage the insert and provide side locating forces and clamping forces to secure the indexable insert in the insert pocket. More particularly, the indexable insert has a shaped surface recess that mates to a complimentarily-shaped surface on the head of a locking screw and secures the indexable insert in multiple dimensions to a seating surface. A material removal tool and a method of mounting the indexable insert are also disclosed.

Description:
FIELD 
     The present disclosure relates to an indexable insert and associated material removal tools. More particularly, the present disclosure relates to an indexable insert, such as a milling insert, a turning insert, a boring insert, a grooving insert or a parting insert, of any shape and either positive or negative, that can be secured to a tool and a method of securing the insert to the tool. 
     BACKGROUND 
     In the discussion of the background that follows, reference is made to certain structures and/or methods. However, the following references should not be construed as an admission that these structures and/or methods constitute prior art. Applicant expressly reserves the right to demonstrate that such structures and/or methods do not qualify as prior art. 
     Known tools comprising replaceable inserts use various means for mounting the inserts to the tool body. Some known inserts are mounted with a locking screw passed through the center of the insert and secured in a taped hole in the insert seating surface. The axis of the taped hole may be perpendicular to the insert and the insert seating surface or the axis of the taped hole may be skewed. However, the density of inserts on the milling tool is limited because of the clearance required when taping the lock screw hole in the insert seating surface, and by the use of wedges and or clamps. In addition, the hole in the insert itself reduces the cross section of the insert, which can reduce insert performance such as strength, in particular for ceramic inserts such as silicon nitride (SiNi) inserts. Some known inserts are mounted with a set screw descending from a side of the insert seating surface. The point of the set screw inserts into and/or contacts, e.g., a depression in the surface of the insert to place the set screw in compression and press the insert against the insert seating surface. However, the chip room for this insert and tool may not be adequate and may foul the tool during operation. 
     Examples of milling cutters wherein inserts are mounted to the tool body using screws are illustrated in U.S. Pat. No. 4,934,880. Examples of milling cutters wherein inserts are held to the tool body by releasable clamps are illustrated in U.S. Pat. No. 3,588,977. GB 1,209,181 discloses a cutter with an insert secured in a slot by one or more screws. 
     Inserts for tooling and manufacturing perform under rigorous conditions during operations on iron components. Typically, different irons have different operating conditions and, therefore, different inserts are typically used. Some irons of interest include gray irons, nodular irons, high tensile irons and compacted graphite iron (CGI irons). An insert that may be operationally functional across more than one type iron would be advantageous. Other considerations for inserts include the type of surface provided (rough and finish), ease of indexing of inserts and change-out time of used inserts, secure seating to minimize “fling” of inserts under centrifugal forces, tool life, simple and commonly available accessories, compatibility with existing milling equipment and hardware and securing means that reliably and repeatably place inserts in secure seats. 
     SUMMARY OF THE INVENTION 
     An exemplary embodiment of an indexable insert has one or more recesses in a front and/or back surface which receives a surface of the head of a locking screw. When mounted, the indexable insert is forced tangentially, axially and radially against respective support surfaces of the insert pocket. The locking screw is placed in tension and deflected slightly so that the forces secure the indexable insert in the insert pocket. More particularly, the indexable insert has, in one example, a concave-shaped surface recess that mates to a corresponding convex surface on the head of a locking screw and secures the indexable insert in multiple directions to a seating surface. 
     An exemplary embodiment of an indexable insert comprises a body including a front polygonal surface, a back polygonal surface and a plurality of side edge surfaces joining the front polygonal surface and the back polygonal surface, the intersections of the side edge surfaces and the polygonal surfaces defining line edges of the insert and intersections of sequential side edge surfaces defining corner edges of the insert, and a receiver for a region of a head of a locking screw in the front polygonal surface, wherein the receiver includes a plurality of recesses, each recess having a surface that is complimentary to the region of the head of the locking screw. 
     An exemplary embodiment of a material removal tool comprises a tool body including a head with a plurality of insert pockets at a first end and an axially extending portion at a second end, the head having a diameter, and a plurality of indexable inserts, each of the plurality of indexable inserts seated in one of the plurality of insert pockets, wherein the plurality of indexable inserts are arranged on the head at a density of about 4 inserts per inch diameter of head. 
     Another exemplary embodiment of a material removal tool comprises a body with a plurality of insert pockets at a first axial end, each of the plurality of insert pockets including a wall supporting surface, a floor supporting surface and a threaded tap hole with a counterbore, the threaded tap hole having a centerline oriented at an angle to the floor supporting surface, an indexable insert including a front polygonal surface, a back polygonal surface and a plurality of side edge surfaces joining the front polygonal surface and the back polygonal surface, the intersections of the side edge surfaces and the polygonal surfaces defining line edges of the insert and intersections of sequential side edge surfaces defining corner edges of the insert, and including a receiver for a region of a head of a locking screw in the front polygonal surface, wherein the receiver includes a plurality of recesses, and wherein the indexable insert is seated in the insert pocket with the back polygonal surface contacting the floor supporting surface, with a first one of the plurality of side edge surfaces contacting the wall supporting surface, and with a second one of the plurality of side edge surfaces protruding radially past an outer peripheral surface of the body, and a locking screw for the threaded tap hole, the locking screw including a threaded portion, a concentric shoulder and an angular shoulder, the angular shoulder between the threaded portion and the concentric shoulder, wherein the locking screw inserted into the threaded tap hole engages a first region of the concentric shoulder and a first region of the angular shoulder against one of the plurality of recesses. 
     An exemplary method to mount an indexable insert on a material removal tool, the indexable insert including a body having a front polygonal surface, a back polygonal surface and a plurality of side edge surfaces joining the front polygonal surface and the back polygonal surface, the intersections of the side edge surfaces and the polygonal surfaces defining line edges of the insert and intersections of sequential side edge surfaces defining corner edges of the insert, and including a receiver in the front polygonal surface, wherein the receiver includes a plurality of recesses, the method comprising placing the indexable insert on a seating surface of an insert pocket of the material removal tool, and threading a lock screw including an angular shoulder and a concentric shoulder into a tap hole to engage a region of a head of the locking screw with one of the plurality of recesses. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       The following detailed description can be read in connection with the accompanying drawings in which like numerals designate like elements and in which: 
         FIGS. 1-6  show representative examples of embodiments of indexable inserts.  FIGS. 1-3  illustrate inserts that are solid bodies and  FIGS. 4-6  illustrate inserts with a bore through the body. 
         FIG. 7  illustrates the interaction between an exemplary embodiment of an indexable insert and a locking screw. 
         FIG. 8  illustrates the interaction between another exemplary embodiment of an indexable insert and a locking screw 
         FIG. 9  shows an exemplary embodiment of a material removal tool. 
         FIG. 10  illustrates an exploded view of an indexable insert, a locking screw and an insert pocket. 
         FIGS. 11-13  illustrate an exemplary insert pocket in a material removal tool showing both an indexable insert and a locking screw. In the  FIG. 11  view, two side edge surfaces are shown view-on; in the  FIG. 12  view, an angled view from above is shown; and in the  FIG. 13  view, a cut away view of the indexable insert and the fully inserted locking screw is shown. 
         FIGS. 14 and 15  illustrate exemplary embodiments of material removal tools and methods of mounting indexable inserts that relate to these additional polygonal shaped indexable inserts. 
     
    
    
     DETAILED DESCRIPTION 
     Indexable inserts of interest herein have front and back surfaces of polygonal shape joined by side edges. At least portions of the intersections of the side edge surfaces with the polygonal surfaces define line edges of the insert and at least portions of the intersections of sequential side edge surfaces define corner edges of the insert. Line edges may be linear or non-linear, as known in the art; corner edges may be round, truncated or other geometries, as known in the art. In general, machining operations are performed so that cutting occurs at an insert corner formed by intersections of corner edges at corners of the polygonal surface, or are performed so that cutting, e.g., milling, occurs at line edges of the insert. In each case, the insert can be traversed along a workpiece surface as the workpiece rotates or the insert can be stationary as the workpiece is rotated and translated. Other combinations of relative motion between the indexable insert and the workpiece can also be used. 
     Exemplary embodiments of an indexable insert comprises a body and a receiver for a region of a head of a locking screw.  FIGS. 1-6  show representative examples of embodiments of indexable inserts. 
     In the exemplary embodiments of  FIGS. 1-6 , the indexable insert  10  comprises a body  12  including a front polygonal surface  14 , a back polygonal surface  16  and a plurality of side edge surfaces  18  joining the front polygonal surface  14  and the back polygonal surface  16 . The intersections of the side edge surfaces  18  and the polygonal surfaces define line edges  20  of the insert  10  and the intersections of sequential side edge surfaces  18  define corner edges  22  of the insert  10 . A receiver  24  for a region of a head of a locking screw is located in the front polygonal surface  14 . The receiver includes a plurality of recesses  26 . The recesses can be of any form. For example, the recess can be convex, concave or have one or more planar surfaces. Generally, the number of the plurality of recesses  26  is the same as a number of sides of the front polygonal surface  14 . However, some indexable inserts have different numbers of recesses than numbers of cutting edges. In addition, a single recess may be used to secure the indexable insert in the insert pocket when one more than one cutting feature of the indexable insert is positioned, e.g., a wiper edge and a rough edge. 
     In some exemplary embodiments, an optional second receiver can be positioned on the back polygonal surface  16  of the body  12 . In such an instance, the receiver can be as described and illustrated herein with respect to the receiver on the front polygonal surface  14 . The optional second receiver allows mounting of the indexable insert for utilization of the line edges and corner edges associated with the back polygonal surface  16 , thereby increasing the number of indexable positions for any one indexable insert. 
     The receiver  24  is located generally in a radial center of the indexable insert  10 . In  FIGS. 1-2  and  4 - 5 , the receiver  24  has recesses  26  that are not adjacent to each other, but rather are separated from each other by a portion of the front polygonal surface  14 . Nevertheless, the recesses  26  are positioned in the general area of the radial center, and when a bore is present, are positioned about the periphery of the bore. In  FIGS. 3 and 6 , the recesses are collocated in a contiguous structure in a radial center of the indexable insert  10 . At least two adjacent recesses are separated by a ridgeline  28  or other transition area. In some embodiments, the ridgeline  28  is oriented such that a projection of the ridgeline  28  intersects at least one of the corner edges  22  of the indexable insert  10  or the long edges  20  of the indexable insert  10 . In addition and in some embodiments, a number of ridgelines  28  or transition areas is the same as a number of corner edges  22  of the indexable insert  10 . When a bore  30 , used in aid of manufacturing the insert body, is present, the recesses  26  are positioned about the periphery of the bore  30 . 
       FIGS. 1-6  show non-limiting variations of the indexable insert  10 . For example, the geometric shape of  FIGS. 1-6  include squares, rectangles and hexagons, but other polygonal shapes can be utilized, including triangles, pentagons and trigons. In another example,  FIGS. 1-3  illustrate indexable inserts  10  that are solid bodies  12 , while  FIGS. 4-6  illustrate indexable inserts  10  with a bore  30  through the body  12 . Generally, the bore  30  is oriented axially in the radial center of the indexable insert  10 . The plurality of recesses  26  of the receiver  24  can be arranged around a periphery  32  of the bore  30 . In some embodiments, e.g., see  FIG. 5 , the bore is positioned off-center from the radial center of the indexable insert  10 . 
     Other optional features shown in one or more exemplary embodiments in  FIGS. 1-6  include one or more chip splitters  40 , angling of surfaces to obtain desired material removing function and coatings (discussed further herein below). 
     In exemplary embodiments, the surfaces of the recesses of the receiver corresponds to a surface of the region of the head of the locking screw.  FIGS. 7 and 8  illustrate the interaction between exemplary embodiments of indexable inserts and a locking screw. Although illustrated by concavely formed recesses and corresponding convexly formed regions of the head of the locking screw, it should be understood that the recesses can be of any form including concave, convex and planar and the corresponding regions of the head of the locking screw can be of any form that conforms to the recess when the region of the head of the locking screw engages the recess. 
     In the  FIG. 7  example, an indexable insert  100  has a receiver  102  in a front polygonal surface  104 . The receiver has two recesses  106 , each having a concavity into the body of the indexable insert  100 . The locking screw  110  includes a threaded portion  112 , a concentric shoulder  114  and an angular shoulder  116 . The angular shoulder  116  is between the threaded portion  112  and the concentric shoulder  114 . In some instances, the angular shoulder  116  serves as a transition for the different diameters of the threaded portion and the concentric shoulder  114 . The concentric shoulder  114  and the angular shoulder  116  are each shown with a surface that is convex, but can be planar, concave or convex or of any other form. 
     In some embodiments, the surface is conformal to the surface of the recess. For example, a convexity of the concentric shoulder  114  and the angular shoulder  116  corresponds to the concavity of the recesses  106  in the receiver  102 . When the locking screw  110  is fully engaged, the convex concentric shoulder  114  and the angular shoulder  116  mate with the concave recess  106  across an increased surface area, and in some cases up to an entire surface area of the concave recess  106 . 
     In other embodiments, the surface is not conformal of the surface is partially conformal to the surface of the recess. For example, the concavity, convexity, angularity or planarity of the centric shoulder and the angular shoulder can be different from the concavity, convexity, angularity or planarity of the surface of the recess. Also for example, the surfaces that meet can be 25%, 35%, 40%, 50%, 60%, 66%, 75% or more conformal, with higher degrees of conformity reducing stresses on the insert. 
     As shown in the  FIG. 7  example, the locking screw  110  engages one of the plurality of recesses  106 . In this example, the recess  106  is a recess closest to a material-removing feature of the indexable insert  100 , such as line edge  120  for a milling insert. The receiver could be reoriented such that the recess  106  is closest to a different material-removing feature of the indexable insert  100 , such as an insert corner  122  formed by intersections of corner edges at corners of the polygonal surface. 
     As shown in the  FIG. 8  example, an indexable insert  140  has a receiver  142  in a front polygonal surface  144 . The receiver has six recesses  146 , each having a concavity into the body of the indexable insert  140 . The locking screw  150  includes a threaded portion  152 , a concentric shoulder  154  and an angular shoulder  156 . The angular shoulder  156  is between the threaded portion  152  and the concentric shoulder  154 . In some instances, the angular shoulder  156  serves as a transition for the different diameters of the threaded portion  152  and the concentric shoulder  154 . The concentric shoulder  154  and the angular shoulder  156  are each convex. A convexity of the concentric shoulder  154  and the angular shoulder  156  corresponds to the concavity of the recesses  146  in the receiver  142 . When the locking screw  150  is fully engaged, the convex concentric shoulder  154  and the angular shoulder  156  mate with the concave recess  146  across an increased surface area, and in some cases up to an entire surface area of the concave recess  146  between two sequential ridgelines  148  separating adjacent recesses  146 . 
     As shown in the  FIG. 8  example, the locking screw  150  engages one of the plurality of recesses  146 . In this example, the recess  146  is a recess farthest from a material-removing feature of the indexable insert  140 , such as line edge  160  for a milling insert. The receiver could be reoriented such that the recess  146  is farthest from a different material-removing feature of the indexable insert  140 , such as an insert corner  162  formed by intersections of corner edges at corners of the polygonal surface. 
     The body of the indexable insert can be formed from any suitable material. For example, the body can be formed from cemented carbide or from a ceramic. Representative cemented carbides comprise tungsten carbide and a matrix binder comprising cobalt, can comprise approximately 70-97 percent by weight metal carbide and approximately 3-30 percent by weight of a matrix binder material. Metal carbides selected from the group consisting of Cr, Mo, V, Nb, Ta, Ti, Zr, Hf and mixtures thereof can also be included. Representative ceramics include alumina-based or silicon-based ceramics, such as silicon nitride (SiNi). 
     The indexable insert can have an optional coating on an outer surface of the body. Representative coatings include at least one layer of a Ti-based layer or at least one layer of an Al 2 O 3 -layer. An example of a Ti-based layer is TiC x N y O z , where x+y+z=1. An example of an Al 2 O 3 -layer is α-Al 2 O 3 , κ-Al 2 O 3 , or a mixture thereof. The coating can optionally include an outermost TiN layer. 
     As described herein, features of the indexable insert can be incorporated into milling inserts for milling tools or into turning inserts, boring inserts, grooving inserts and parting inserts for a turning tool, a grooving tool and a parting tool. 
     On milling tools, for a fixed speed, an increase in density can result in an increased feed rate, decreased cycle and, ultimately increase production. It is desirable to have as high a density as possible provided that machine power is sufficient to turn the tool. Typically, a tool having inserts mounted by a set screw or by a screw passing through the insert has a density of one to three insert pockets per inch diameter of tool head. Higher densities tend to have a negative impact on performance due to a negative compromise with tool geometry to accommodate the mounting mechanism as well as the chip receiving space. In general, however, the locking screw and receiver on the indexable insert disclosed herein allows for a higher density of inserts to be mounted on a material removal tool due to, at least in part, the reduced size of the mounting mechanism contained in the open chip pocket. In some embodiments, a density of greater than 3 to about 4.5, alternatively greater than about 4 (e.g., ±0.25) can be achieved. Contributing to the increase in density is the fact that no extra hardware is associated with the mounting of the exemplary indexable inserts. Items such as wedges and clamps are not necessary for mounting. 
     Therefore, in exemplary embodiments as shown in  FIG. 9 , a material removal tool. The material removal tool  200  comprises a tool body  202  including a head  204  with a plurality of insert pockets  206  at a first end and an axially extending portion  208  at a second end The head  204  has a diameter D, and a plurality of indexable inserts  210 . Each of the plurality of indexable inserts  210  is seated in one of the plurality of insert pockets  206 . The plurality of indexable inserts  210  are arranged on the head  204  at a density of about 4.5 insert pockets per inch diameter of head. 
     As used herein density can be determined by the following:
 
Density=(number of insert pockets)/(diameter of tool head (in inches))
 
     The indexable insert  210  is retained in the insert pocket  206  by a locking screw  212 .  FIG. 10  illustrates an exploded view of an indexable insert  210 , a locking screw  212  and an insert pocket  206 . The indexable insert  210  is placed into the insert pocket  206  and the locking screw  212  is threaded into the tap hole  214 . As the locking screw is tightened, a region of the head  216  of the locking screw  212  contacts a region of a receiver  218  on a surface of the indexable insert  210 . For example, the region of the head of the locking screw can be an angular shoulder and a concentric shoulder of the locking screw and the region of the receiver can be a recess. In an exemplary embodiment, the region of the head  216  of the locking screw  212  has a convexity that corresponds to a concavity of the region of the receiver  218 . In other exemplary embodiments, the region of the head of the locking screw has a concavity that corresponds to a convexity of the region of the receiver. In a still further exemplary embodiment, the region of the head of the locking screw has a planarity (e.g., one or more planar surfaces) that corresponds to a planarity (e.g., one or more planar surfaces) of the region of the receiver. The receiver  218  and associated recesses can be as illustrated and described herein with respect to any of the embodiments in  FIGS. 1-8 . 
     In exemplary embodiments, the diameter of the head of the material removal tool is two to twenty inches, alternatively four to ten inches, and the number of inserts arranged on the too head is between about 9 and about 90, at a density of about 4.5 inserts per inch diameter. 
     In another exemplary embodiment, a material removal tool comprises a body with a plurality of insert pockets at a first axial end, an indexable insert, and a lock screw for a threaded tap hole. The lock screw, when inserted into the threaded tap hole, engages a region of the concentric shoulder of the lock screw and a region of the angular shoulder of the lock screw against one of the recesses of a receiver of an indexable insert and engages a second region of the concentric shoulder against a surface of the counterbore of the threaded tap hole. 
       FIGS. 11 to 13  illustrate an exemplary insert pocket  300  in a material removal tool showing both an indexable insert  302  and a locking screw  304 . In the  FIG. 11  view, two side edge surfaces of the insert and the side of the locking screw are shown view-on; in the  FIG. 12  view, an angled view from above is shown; and in the  FIG. 13  view, a cut away view of the indexable insert and the fully inserted locking screw is shown. 
     The insert pocket  300  includes a wall supporting surface  306 , a floor supporting surface  308  and a threaded tap hole  310  with a counterbore  311 . The threaded tap hole  310  has a centerline  312  oriented at an angle, θ, to the floor supporting surface  308 . The indexable insert  302  can be as illustrated and described herein with respect to any of the embodiments in  FIGS. 1-8  including having a receiver  320  (shown in  FIGS. 12 and 13 ) for a region of a head of the locking screw in the front polygonal surface or back polygonal surface, the receiver including a plurality of recesses, the recesses being concavely formed, convexly formed or planar or a combination thereof. 
     In the  FIG. 11  view, the back polygonal surface is shown contacting the floor supporting surface  308  and a first one of the plurality of side edge surfaces is shown contacting the wall supporting surface  306 . A second one  314  of the plurality of side edge surfaces protrudes radially past an outer peripheral surface  316  of the body. Also seen in  FIG. 11  is a clearance  318  between the locking screw  304  and the indexable insert  302  while maintaining at least a portion of the locking screw  304  threaded in the tap hole  310 . This clearance  318  results in the ability to insert and remove an indexable insert from an insert pocket while maintaining at least a portion of the locking screw threaded in the tap hole. This facilitates efficient indexing and/or replacement of the indexable insert. 
     In the  FIG. 12  view, the locking screw  304  is further inserted in the tap hole  310 . Such partial insertion of the locking screw  304  begins to place the head of the locking screw  304  into the receiver  320 , e.g., a portion of the head breaks the plane of the front polygonal surface, such that the indexable insert  302 , while not fully seated in the insert pocket  300 , also cannot be removed from the insert pocket  300 , thereby reducing the risk of falling out or being lost during indexing or change out. 
     In the  FIG. 13  view, the locking screw  304  is fully inserted into the tap hole  310  with the region of the head of the locking screw contacting a recess  322  of the receiver  320 . For example, the locking screw  304  includes a threaded portion  324 , a concentric shoulder  326  and an angular shoulder  328 , the angular shoulder  328  between the threaded portion  324  and the concentric shoulder  326 . When inserted into the tap hole  310 , the angular shoulder  328  first engages against one of the plurality of recesses  322 , causing the protruding portion of the locking screw  304  to flex in a direction F. When further threaded, the flexing of the locking screw  304  is limited by the second region  330  of the concentric shoulder  326  engaging against a surface  332  of the counterbore  311  of the tap hole  310 , which also brings the first region  334  of the concentric shoulder  326  into engagement against one of the plurality of recesses  322 . Overall, when seated, the lock screw  304  stretches axially along axis S. Also, when seated, the lock screw  304  engaging with one of the plurality of recesses and the surface of the counterbore produces a side locking force against side walls of the insert pocket, e.g., side wall  306  and other side walls of the insert pocket, and produces a clamping force against floor supporting surface  308  of the insert pocket. The locking screw  304  inserted into the threaded tap hole to engage the first region of the concentric shoulder and the region of the angular shoulder against one of the plurality of recesses and to engage the second region of the concentric shoulder against a surface of the counterbore asserts a force against the indexable insert in a tangential direction, an axial direction and a radial direction. The forces generated by the locking screw  304  is shown in  FIG. 13  as vectors {right arrow over (k)}, {right arrow over (l)} and {right arrow over (m)}, respectively. As shown in  FIG. 13 , vector {right arrow over (R)} is the resultant of {right arrow over (l)} and {right arrow over (m)}. 
     The indexable insert can be mounted in a material removal tool. The type of insert and the type of material removal tool are not limited. Exemplary embodiments of the disclosed material removal tool can be a milling tool and the indexable insert is a milling insert or can be one of a turning tool, a grooving tool and a parting tool and the indexable insert is one of a turning insert, a boring insert, a grooving insert and a parting insert. 
     An exemplary method to mount an indexable insert on a material removal tool is disclosed. The indexable insert includes a body having a front polygonal surface, a back polygonal surface and a plurality of side edge surfaces joining the front polygonal surface and the back polygonal surface, the intersections of the side edge surfaces and the polygonal surfaces defining line edges of the insert and intersections of sequential side edge surfaces defining corner edges of the insert, and includes a receiver for a region of a head of a locking screw in the front polygonal surface, wherein the receiver includes a plurality of recesses. Examples of indexable inserts are shown and described in connection with  FIGS. 1-8  herein. The exemplary method comprises placing the indexable insert on a seating surface of an insert pocket of the material removal tool and threading a locking screw including an angular shoulder and a concentric shoulder into a tap hole to engage a portion of the angular shoulder and a portion of the concentric shoulder with one of the plurality of recesses. 
     Engaging the portion of the angular shoulder and the portion of the concentric shoulder with one of the plurality of recesses seats the indexable insert in the insert pocket. For example, engaging the portion of the angular shoulder with one of the plurality of recesses flexes the locking screw and engaging the portion of the angular shoulder and the first portion of the concentric shoulder with one of the plurality of recesses and engaging the second portion of the concentric shoulder with a surface of the counterbore stretches the locking screw. In another example, engaging the portion of the angular shoulder and the first portion of the concentric shoulder with one of the plurality of recesses and engaging the second portion of the concentric shoulder with a surface of the counterbore asserts a force against the indexable insert in a tangential direction, an axial direction and a radial direction. 
     The compressive clamping forces on the insert produced by the disclosed method takes advantage of the inherent compressive properties of the commonly used tool materials. Examples of inserts disclosed herein have been tested by repetitive mounting, indexing and unmounting operations. The indexable inserts have maintained performance for cycles exceeding 10,000 in number. In addition, the interaction of the regions of the head of the locking screw and the recess of the receiver contribute, with the shape of the insert pocket, e.g., the wall surfaces and floor supporting surface, and the counterbore, to properly orient the indexable insert in the insert pocket. 
     Although shown and described in connection with  FIGS. 9-13 , which show a polygonal indexable insert as a hexagon, similar figures, discussions and principles can apply to indexable inserts of other polygonal shapes, including but not limited to the polygonal shapes illustrated in  FIGS. 1-2  and  4 - 5 .  FIGS. 14 and 15  illustrate exemplary embodiments of material removal tools  400 ,  500  and methods of mounting indexable inserts  402 ,  502  that relate to these additional polygonal shaped indexable inserts. 
     Although described in connection with preferred embodiments thereof, it will be appreciated by those skilled in the art that additions, deletions, modifications, and substitutions not specifically described may be made without department from the spirit and scope of the invention as defined in the appended claims.