Patent Publication Number: US-2010129167-A1

Title: Roughing cut edge insert with a finishing wiper

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an indexable cutting insert having a roughing cut edge combined with a finishing wiper edge. More particularly, the present invention relates to an indexable cutting insert having a roughing cut edge with a corner radius and a finishing cutting edge spaced from the roughing cut edge. 
     2. Description of Related Art 
     Typical metalworking turning operations are conducted with a lathe or similar tool using a cutting insert. First, machining is undertaken with one or more inserts suitable for rough cutting, which removes large amounts of material from a workpiece but leaves a relatively rough surface finish. Then, the roughly turned surface is machined by another insert configured to give the workpiece a finished cut. Such operations are time consuming and expensive since multiple cutting inserts must be used to machine a single workpiece to a desired shape and operations must be periodically halted in order to replace the inserts for different cutting operations. 
     The prior art includes several instances where the problem of providing an insert with the ability to make rough and finish cuts has been addressed. For example, U.S. Pat. No. 4,990,036 to Eklund et al. discloses a cutting insert having a main cutting edge extending around a corner radius for producing a roughing cut and a secondary cutting edge for producing a finishing cut. However, the secondary cutting edge is disposed very close to the main cutting edge. As a result, feed rates must be kept at a relatively low rate suitable for finishing cutting operations in order to ensure that the secondary cutting edge will properly engage the surface to provide a finishing cut. Thus, inserts such as the one disclosed by Eklund et al. limit the possible feed rate below what is suitable for normal rough cutting operations. 
     SUMMARY OF THE INVENTION 
     Accordingly, there is a general need in the art for a single cutting insert that includes both a primary roughing cutting edge and a secondary finishing cutting edge to sequentially perform with a single insert roughing cutting and finishing cutting operations and that permits this sequential cutting operation to be conducted on a lathe or other machine at a higher feed rate suitable for roughing cutting operations while still achieving good results for both operations. 
     The present invention provides a cutting insert having both roughing cutting edges and finishing cutting edges that together are able to achieve favorable finish at a feed rate suitable for rough cutting operations. The roughing cutting edges and the finishing cutting edges are spaced along the sides of the insert at a distance sufficient to allow for a rough cutting feed rate to be used. 
     According to an embodiment of the present invention, an indexable cutting insert having a body with a central axis extending therethrough is provided. The body includes a first opposing surface and a second opposing surface spaced along the central axis of the body; and at least a first side, a second side, and a third side connecting the first and second opposing surfaces, the first side and the second side intersecting at a first primary corner, the first side and the third side intersecting at a first secondary corner. An intersection between the first opposing surface and the first primary corner forms a first primary cutting edge having a first corner radius, and the first corner radius terminates at an end on the first side and at an end on the second side. The first side intersects with the first opposing surface to form an intermediate portion between the first primary corner and the first secondary corner, the intermediate portion defining a first side secondary cutting edge having a convex shape extending beyond a line connecting the first primary corner and the first secondary corner. The closest distance between the first primary cutting edge and the first side secondary cutting edge is at least approximately one-eighth of the length of a line extending between the end of the first corner radius on the first side and the first secondary corner. 
     According to a further embodiment of the present invention, an assembly of a cutting insert and a workpiece is provided. The assembly includes an indexable cutting insert having a body with a central axis extending therethrough. The body includes a first opposing surface and a second opposing surface spaced along the central axis of the body; and at least a first side, a second side, and a third side connecting the first and second opposing surfaces, the first side and the second side intersecting at a first primary corner, the first side and the third side intersecting at a first secondary corner. An intersection between the first opposing surface and the first primary corner forms a first primary cutting edge having a first corner radius, and the first corner radius terminates at an end on the first side and at an end on the second side. The first side intersects with the first opposing surface to form an intermediate portion between the first primary corner and the first secondary corner, the intermediate portion defining a first side secondary cutting edge having a convex shape extending beyond a line connecting the first primary corner and the first secondary corner. The closest distance between the first primary cutting edge and the first side secondary cutting edge is at least approximately one-eighth of the length of a line extending between the end of the first corner radius on the first side and the first secondary corner. The assembly further includes a workpiece. The insert is positioned relative to the workpiece such that the central axis is generally perpendicular to the longitudinal axis and both the primary cutting edge and the secondary cutting edge engage the workpiece. 
     Further details and advantages of the invention will become clear upon reading the following detailed description in conjunction with the accompanying drawing figures, wherein like parts are designated with like reference numerals throughout. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a top side perspective view of a cutting insert according to an embodiment of the present invention. 
         FIG. 2  is a top plan view of the cutting insert shown in  FIG. 1 . 
         FIG. 3  is a side view of the cutting insert shown in  FIG. 1 . 
         FIG. 4  is a cross-section view taken along line  4 - 4  shown in  FIG. 2 . 
         FIG. 5  is a cross-section view taken along line  5 - 5  shown in  FIG. 2 . 
         FIG. 6  is a cross-section view taken along line  6 - 6  shown in  FIG. 2 . 
         FIG. 7  is a more detailed view of the circled area shown in  FIG. 4 . 
         FIG. 8  is a view of an assembly according to an embodiment of the present invention. 
     
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     For purposes of the description hereinafter, spatial orientation terms, if used, shall relate to the referenced embodiment as it is oriented in the accompanying drawing figures or otherwise described in the following detailed description. However, it is to be understood that the embodiments described hereinafter may assume many alternative variations and embodiments. It is also to be understood that the specific devices illustrated in the accompanying drawing figures and described herein are simply exemplary and should not be considered as limiting. 
     Referring to  FIGS. 1-7 , an indexable cutting insert according to an embodiment of the present invention is shown. A plurality of lines are provided in the drawings across the surfaces and features of the insert in order to connote the continuous curvature of the surfaces, which as a result, will not have distinct lines to highlight discontinuities. It is to be appreciated, though, that any curved surfaces shown and described herein may be replaced by multi-faceted surfaces. As shown in  FIG. 1 , the insert is of a generally polygonal shape and includes a body  10  made of wear-resistant material. The body  10  includes first opposing surface  60   a  and a second opposing surface  60   b  (shown in  FIG. 4 ) spaced along a central axis  14  that extends through the body  10 . The first  60   a  and second  60   b  opposing surfaces are interconnected by a first side  11   a , a second side  11   b , a third side  11   e , and a fourth side  11   d . As shown in  FIGS. 1 and 2 , the sides  11   a ,  11   b ,  11   c , and  11   d  are parallel to the central axis  14  of the body  10 . The first side  11   a  intersects with the second side  11   b  at a first primary corner  12   a  and with the third side at a first secondary corner  13   a . The fourth side  11   d  intersects with the third side  11   c  at a second primary corner  12   b  and with the second side  11   b  at a second secondary corner  13   b . A first primary cutting edge  20   a  is formed at an intersection between the first opposing surface  60   a  and the first primary corner  12   a.    
     For the purposes of this discussion, an insert geometry identified as an 80° diamond, which is a rhombic configuration having two rounded 80° corners (primary corners  12   a ,  12   b ) and two 100° corners (secondary corners  13   a ,  13   b ), will be presented. As shown in  FIGS. 1 and 2 , the first secondary corner  13   a  and the second secondary corner  13   b  are sharp 100° corners. It is to be appreciated that the first secondary corner  13   a  and the second secondary corner  13   b  may be of any suitable configuration, including rounded or beveled corners and could additionally be provided with cutting edges. It is also to be appreciated that the configuration of the body  10  is not limited to an 80° diamond and that other geometric shapes may be substituted. Among the shapes may be other rhombic configurations such as a 55° diamond, a 50° diamond, a 35° diamond, a pentagon, a triangle, or a trigon. 
     The body  10  of the insert should be manufactured of a wear-resistant material. Refractory coated cemented carbide materials, such as KC9140, KC9240, KC8050, P25-40, M25-40, and K25-40 may be used. Ceramic materials may also be used. 
     KC9140 is a trademark of Kennametal Inc., representing a ceramic-coated carbide grade of a TiC/Al 2 O 3 /TiN coating over a substrate. KC9240 is a trademark of Kennametal Inc., representing a ceramic-coated carbide grade of a TiC/Al 2 O 3 /TiN coating over a substrate. KC8050 is a trademark of Kennametal Inc., representing a multilayered coated carbide grade having a TiCN/Al 2 O 3 /TiN coating over a substrate. P25-40 is a trademark of Kennametal Inc., representing a multilayered coated carbide grade having a TiCN/Al 2 O 3 /TiN coating over a substrate. M25-40 is a trademark of Kennametal Inc., representing a multilayered coated carbide grade having a TiCN/Al 2 O 3 /TiN coating over a substrate. K25-40 is a trademark of Kennametal Inc., representing a multilayered coated carbide grade having a TiCN/Al 2 O 3 /TiN coating over a substrate. 
     Returning to  FIGS. 1 and 2 , the first primary cutting edge  20   a  has a first corner radius CR. The first corner radius CR terminates at an end  21   a  on the first side  11   a  and at an end  21   b  on the second side  11   b . Further, a second primary cutting edge  20   b  is formed at an intersection between the first opposing surface  60   a  and the second primary corner  12   b . The second primary cutting edge  20   b  has a second corner radius CR terminating at an end  21   c  on the third side  11   c  and at an end  21   d  on the fourth side  11   d . The first corner radius CR and the second corner radius CR are equal and according to the current embodiment of the invention are approximately 1/16 in. The first primary cutting edge  20   a  and the second primary cutting edge  20   b  are roughing cutting edges according to the current embodiment of the invention suitable for high volume cutting/machining of a workpiece  100  (shown in  FIG. 8 ), though it is to be appreciated that the primary cutting edge  20   a  and the second primary cutting edge  20   b  may be of any type known to those of ordinary skill in the art. 
     An intermediate portion  15   a  is formed at an intersection between the first side  11   a  and the first opposing surface  60   a  between the first primary corner  12   a  and the first secondary corner  13   a . The intermediate portion  15   a  defines a first side secondary cutting edge  30   a . As shown in  FIGS. 1 and 2 , the first side secondary cutting edge  30   a  has an arcuate shape with a radius WR extending in a direction away from the central axis  14  of the body  10  beyond a line  16   a  extending between the end  21   a  of the first corner radius CR on the first side  11   a  and the first secondary corner  13   a . The first side secondary cutting edge  30   a  has a first end  31   a  and a second end  31   b  with the first end  31   a  being disposed between the end  21   a  of the first corner radius CR on the first side  11   a  and the second end  31   b . The first end  31   a  of the first side secondary cutting edge  30   a  is spaced from the end  21   a  of the first corner radius CR on the first side  11   a  by a distance of at least approximately one-eighth (⅛) and less than approximately one-quarter (¼) of the length of the line  16   a  extending between the end  21   a  of the first corner radius CR on the first side  11   a  and the first secondary corner  13   a.    
     According to the current embodiment of the invention, the radius of the first side secondary cutting edge  30   a  is approximately 9/32 in. The first side secondary cutting edge  30   a  is a finishing edge, particularly a wiper edge, according to the current embodiment of the invention suitable for precision cutting of the workpiece  100 , though it is to be appreciated that the first side secondary cutting edge  30   a  may be of any type known to those of ordinary skill in the art. 
     As shown in  FIGS. 1 and 2 , in like manner to the first side secondary cutting edge  30   a , second side, third side, and fourth side secondary cutting edges  30   b ,  30   c ,  30   d  are formed at intersections between the first opposing surface  60   a  and intermediate portions  15   b ,  15   c ,  15   d  of the second  11   b , third  11   c , and fourth  11   d  sides, respectively. Each of these secondary cutting edges  30   b ,  30   c , and  30   d  has an arcuate shape with the radius WR extending in a direction away from the central axis  14  of the body  10 . The radius WR of the second side secondary cutting edge  30   b  extends past a line  16   b  extending between the end  21   b  of the corner radius CR on the second side  11   b  and the second secondary corner  13   b . The radius WR of the third side secondary cutting edge  30   c  extends past a line  16   c  extending between the end  21   c  of the second corner radius CR on the third side  11   c  and the secondary corner  13   a . The radius WR of the fourth side secondary cutting edge  30   d  extends past a line  16   d  extending between the end  21   d  of the second corner radius CR on the fourth side  11   d  and the second secondary corner  13   b . Each of the second side  30   b , third side  30   c  and fourth side  30   d  secondary cutting edges have a first end  31   c ,  31   e ,  31   g  and a second end  31   d ,  31   f ,  31   h  with the first end  31   c ,  31   e ,  31   g  being disposed between the second end  31   d ,  31   f ,  31   h  and the corresponding end  21   b ,  21   c ,  21   d  of the first corner radius CR or the second corner radius CR. The first end  31   c  of the second side secondary cutting edge  30   b  is spaced from the end  21   b  of the first corner radius CR on the second side  11   b  by distance of at least approximately one-eighth (⅛) and less than approximately one-quarter (¼) of the length of the line  16   b  extending between the end  21   b  of the first corner radius CR on the second side  11   b  and the second secondary corner  13   b . The first end  31   e  of the third side secondary cutting edge  30   c  is spaced from the end  21   c  of the second corner radius CR on the third side  11   c  by a distance of at least approximately one-eighth (⅛) and less than approximately one-quarter (¼) of the length of the line  16   c  extending between the end  21   c  of the second corner radius CR on the third side  11   c  and the first secondary corner  13   a . The first end  31   g  of the fourth side secondary cutting edge  30   d  is spaced from the end  21   d  of the second corner radius CR on the fourth side  11   b  by a distance of at least approximately one-eighth (⅛) and less than approximately one-quarter (¼) of the length of the line  16   d  extending between the end  21   d  of the second corner radius CR on the fourth side  11   d  and the second secondary corner  13   b . It is to be appreciated that the second side  30   b , third side  30   c , and fourth side  30   d  secondary cutting edges are also formed as finishing edges, particularly wiper edges, as is the first side secondary cutting edge  30   a , discussed above. It is also to be appreciated that the radiuses WR of each of the first side  30   a , second side  30   b , third side  30   c , and fourth side  30   d  secondary cutting edges are equal. 
     As shown in  FIGS. 1 and 2 , the body  10  further includes a peripheral land  18  extending about the entire periphery or perimeter of the body  10 . It is to be appreciated that the land  18  is not needed to achieve the benefits of the current embodiment of the invention and may be eliminated in favor of a honed radius edge. 
     With reference to  FIGS. 2-5 , the body  10  is symmetric about a plane  19   a  extending between the first primary corner  12   a  and the second primary corner  12   b  as well as about a plane  19   b  extending between the first secondary corner  13   a  and the second secondary corner  13   b . Accordingly, the first side  11   a , second side  11   b , third side  11   c , and fourth side  11   d  have identical dimensions and configurations. Likewise, the primary cutting edges  20   a ,  20   b , and secondary cutting edges  30   a ,  30   b ,  30   c ,  30   d  are identical. As such, the insert may be used either in a left-handed or a right-handed manner. 
     Further, the body  10  is also symmetric about a central plane  17 , which is perpendicular to the central axis  14  and midway through the body  10 . Accordingly, a third primary cutting edge  20   c  and a fourth primary cutting edge  20   d  are formed by intersections of the first side  11   a , the second side  11   b , the third side  11   e , the fourth side  11   d , and the second opposing surface  60   b , which are identical to the primary cutting edge  20   a  and the second primary cutting edge  20   b . Likewise, fifth  30   e  (shown in  FIGS. 1 and 3 ), sixth  30   f  (shown in  FIG. 5 ), seventh  30   g  (shown in  FIGS. 1 and 5 ), and eighth (not shown) secondary cutting edges are formed by intersections between the intermediate portions  15   a ,  15   b ,  15   c ,  15   d  of the sides  11   a ,  11   b ,  11   e ,  11   d , and the second opposing surface  60   b  and are identical to the first side  30   a , second side  30   b , third side  30   c , and fourth side  30   d  secondary cutting edges. As such, the insert is also invertible. 
     Since the size and configuration of each of the sides  11   a ,  11   b ,  11   e ,  11   d  is identical and the size and configuration of the various cutting edges described above are also identical as to each of the sides  11   a ,  11   b ,  11   e ,  11   d , further details of the current embodiment of the invention as to both the primary cutting edges and the secondary cutting edges will be restricted to a discussion regarding the first opposing surface  60   a , first side  11   a , the first primary cutting edge  20   a  and the first side secondary cutting edge  30   a  with the understanding that corresponding features of the current embodiment of the invention will be identical. 
     With reference to  FIGS. 1-3 , the first primary cutting edge  20   a  includes a flat segment  22  extending around the first corner radius CR from the end  21   a  of the first corner radius CR on the first side  11   a  to the end  21   b  of the first corner radius CR on the second side  11   b . As shown in  FIG. 3 , the flat segment  22  of the first primary cutting edge  20   a  is disposed at a height H above the central plane  17  of the body  10 . The first primary cutting edge  20   a  also includes a first side segment  23  extending from the end  21   a  of the first corner radius CR on the first side  11   a  to the first end  31   a  of the first side secondary cutting edge  30   a . The first side segment  23  of the first primary cutting edge  20   a  tapers downward toward the central plane  17  of the body  10  with a linear taper. 
     As shown in  FIG. 3 , the first side secondary cutting edge  30   a  includes a central flat segment  32  that is disposed at height H above the central plane  17  of the body  10 . The height of the central flat segment  32  of the first side secondary cutting edge  30   a  and the height of the flat segment  22  of the first primary cutting edge  20   a  are equal. The first side secondary cutting edge  30   a  also includes a first tapered segment  33 , which tapers upward from the central plane  17  of the body  10  and extends from the first end  31   a  of the first side secondary cutting edge  30   a  to the central flat segment  32  and a second tapered segment  34 , which tapers downward toward the central plane  17  of the body  10  and extends from the central flat segment  32  to the second end  31   b  of the first side secondary cutting edge  30   a . The first  33  and second  34  tapered segments of the first side secondary cutting edge  30   a  have arcuate tapers. The first side segment  23  of the first primary cutting edge  20   a  serves to provide a positive rake. It is to be appreciated that the first side segment  23  of the first primary cutting edge  20   a  and the first tapered segment  33  of the first side secondary cutting edge  30   a  may be replaced with a level segment extending between the end  21   a  of the first corner radius CR on the first side  11   a  and the central flat segment  32  of the first side secondary cutting edge  30   a.    
     As shown in  FIGS. 1 and 2 , the intermediate portion  15   a  of the first side  11   a  has an arcuate shape extending outward from a plane that contains line  16   a  and extends between the end  21   a  of the first corner radius CR on the first side  11   a  and the secondary corner  13   a  so as to conform to the curvature of the first side secondary cutting edge  30   a . All other portions of the first side  11   a  extend along the plane. 
     As shown in  FIGS. 1 and 2 , the body  10  includes a primary cutting rake face  24  extending upwardly from the first opposing surface  60   a  to the first primary cutting edge  20   a . The primary cutting rake face  24  serves to convey chips formed during a cutting process of the workpiece  100  away from the first primary cutting edge  20   a  as it cuts the workpiece  100 . To that end, the primary cutting rake face  24  includes a chip control feature  25  to channel chips away from the first primary cutting edge  20   a . The chip control feature  25  extends from the first opposing surface  60   a  opposite to the corner radius CR and includes a first triangular face  26   a  and a second triangular face  26   b . The first  26   a  and second  26   b  triangular faces are inclined with respect to the primary cutting rake face  24  and have adjoining sides so as to form a central ridge  26   c  such that the chip control feature  25  has a pyramidal shape. 
     More particularly, as shown in  FIGS. 6 and 7 , the first  26   a  and second  26   b  triangular faces are inclined upward from the adjacent portions of the primary cutting rake face  24  and meet at the central ridge  26   c . The primary cutting rake face  24  extends upward from the first opposing surface  60   a  to the primary cutting edge  20   a  with respect to the central plane  17 . Thus the chip control feature  25  forms channels between the first  26   a  and second  26   b  triangular faces and the primary cutting rake face  24  to facilitate the movement of chips away from the primary cutting edge  20   a . The height of the chip control feature  25  is approximately 0.009 in. as measured from the intersection between the primary cutting rake face  24  and the first opposing surface  60   a  to the central ridge  26   c . The length of the chip control feature  25  is approximately 0.055 in. as measured along the length of the central ridge  26   c  from the first opposing surface  60   a  to the primary cutting rake face  24 . It is to be appreciated that the chip control feature  25  may be formed as any configuration known by those of ordinary skill in the art to be suitable for channeling chips away from a cutting edge during a cutting or machining operation, including a curved configuration or a plurality of fingers along the cutting rake face. 
     As shown in  FIGS. 1 ,  2 , and  5 , a first side secondary cutting rake face  35  extends upwardly from the first opposing surface  60   a  to the first side secondary cutting edge  30   a  for conveying chips away from the first side secondary cutting edge  30   a  during a cutting operation. 
     As shown in  FIGS. 1 ,  4  and  5 , the first opposing surface  60   a  has a convex dome shape and the body  10  includes a bore  50  extending from the first opposing surface  60   a  to the second opposing surface  60   b  co-extensive with the central axis  14  of the body  10 . The convex dome shape of the first opposing surface  60   a  includes a flat portion  61  in the central area of the first opposing surface  60   a  that forms the periphery of the bore  50 . The bore  50  accepts a bolt (not shown) for fastening the insert to a toolholder. The insert fits within a standard toolholder that may be modified for clearance customized to the particular insert. The first opposing surface  60   a  is given a dome shape in order to provide sufficient thickness to the insert for fastening. The first opposing surface  60   a  is provided with the flat portion  61  in order to allow for adequate engagement between the insert and head of the bolt. Further, the bore  50  may include beveled segments for receiving the head of the bolt. Alternatively, the insert may be clamped within the toolholder, thereby eliminating need for the bore  50 . 
     With reference to  FIG. 2 , an angle A of approximately 5° is formed between the line  16   a  extending between the end  21   a  of the first corner radius CR on the first side  11   a  and the secondary corner  13   a  and a line  37  extending between the end  21   a  of the first corner radius CR on the first side ha and the first side secondary cutting edge  30   a  at an apex point  36 . The apex point  36  being the point of the first side secondary cutting edge  30   a  disposed the farthest distance beyond the line  16   a . Thus, as is shown in  FIG. 8 , the insert is oriented relative to the surface of the workpiece  100  at an angle of 5° to ensure that both the first primary cutting edge  20   a  and the first side secondary cutting edge  30   a  both engage the workpiece  100 . Further, the insert may also be oriented at a 5° angle to the vertical with respect to the workpiece  100  to provide a positive cutting angle. 
     With reference to  FIG. 8 , an assembly according to an embodiment of the present invention is shown. The assembly includes the insert body  10  and the workpiece  100 , which may be made from a variety of materials. As shown in  FIG. 8 , the insert is used in a lathe operation for cutting the workpiece  100  to a desired shape. The insert body  10  is fastened or clamped to a lathe (not shown) and positioned relative to the workpiece  100  such that the central axis  14  of the insert body  10  is generally perpendicular to the longitudinal axis of the workpiece  100  and both the first primary cutting edge  20   a  and the first side secondary cutting edge  30   a  engage the workpiece  100 . The insert body  10  is moved by the lathe relative to the workpiece  100  in a direction F that is substantially parallel to the longitudinal axis of the workpiece  100 . Further, the lathe is activated to rotate the workpiece  100  with respect to the insert body  10  in a direction feed rotation FR. It is to be appreciated that though the indexable cutting insert has been described as being usable in a lathe operation, the insert according to the current invention may be adapted for use in other cutting applications 
     The distance that the insert body  10  is moved relative to the workpiece  100  in the feed direction F per revolution of the workpiece  100  in the direction of feed rotation FR is defined as the feed rate. A portion of the workpiece  100  is engaged by the first primary cutting edge  20   a  to make a rough or high-volume cut of the portion during a single revolution or pass. This rough cut leaves a scallop  101  in the workpiece  100 . The distance between adjacent scallops  101  created by the first primary cutting edge  20   a  in successive revolutions or passes corresponds to the feed rate of the insert body  10  relative to the workpiece  100 . The height of the scallops  101  corresponds to the length of cut of the primary cutting edge  20   a . According to the current embodiment of the invention, the length of cut of the first primary cutting edge  20   a  is at least one half of an inscribed circumference (IC) of the insert body  10  in order to ensure that the workpiece  100  is engaged by both the first primary cutting edge  20   a  and the first side secondary cutting edge  30   a  during a cutting operation. The inscribed circumference (IC) of the insert body  10  is between approximately ⅜ and ¾ in., according to the current embodiment of the invention. The feed rate of the insert body  10  is kept relatively low during a cutting operation in comparison to typical rough cutting operations in order to account for the higher than normal length of cut and attendant high volume of cut material to be removed from the area of the first primary cutting edge  20   a.    
     During a subsequent revolution or pass of the workpiece  100  with respect to the insert body  10 , the same portion of the workpiece  100  having previously been cut by the first primary cutting edge  20   a , leaving scallop  101 , is engaged by the first side secondary cutting edge  30   a  to make a finishing cut of the portion. This finishing cut removes the scallop  101  left during the rough cut of the portion and creates scallops  102 , spaced further apart. As shown in  FIG. 8 , the height of scallops  102  relative to the scallop  101  is exaggerated for purposes of illustration. In actuality, the height of the scallops  102  is negligible and the presence of such scallops  102  cannot be determined by visual inspection of the workpiece  100 . 
     As shown in  FIG. 8 , the insert  10  is capable of cutting the workpiece  100  at a feed rate such that the portion of the workpiece  100  cut by the first primary cutting edge  20   a  during a revolution or cutting pass of the workpiece  100  will be cut by the first side secondary cutting edge  30   a  during the next revolution or cutting pass of the workpiece  100 . Accordingly, the feed rate of the insert  10  is at least 0.01 in. per revolution of the workpiece  100  but no more than 0.03 in. per revolution of the workpiece  100 . Because the first side secondary cutting edge  30   a  is spaced from the first primary cutting edge  20   a , as discussed above, the workpiece  100  may be cut at a higher feed rate with respect to typical finishing operations since the first side secondary cutting edge  30   a  will not engage a portion of the workpiece during rough cutting. Thus, a machining operation can be performed at a feed rate appropriate for rough cutting operations while still achieving the benefits of performing a rough cutting and a finishing cutting operation in a single operation of the lathe using a single cutting insert  10 . 
     With reference to  FIG. 8 , in operation the indexable cutting insert  10  is provided along with a workpiece  100 . A feed rate of the workpiece  100  with respect to the first primary cutting edge  20   a  of the insert is selected such that a portion of the workpiece  100  cut by the first primary cutting edge  20   a  during a cutting pass will be cut by the first side secondary cutting edge  30   a  of the insert during a subsequent cutting pass. Ideally, the first side secondary cutting edge  30   a  will engage a portion of the workpiece  100  cut by the first primary cutting edge  20   a  on the next revolution or cutting pass of the workpiece  100 , though it is to be appreciated that a number of revolutions or cutting passes of the workpiece  100 , for instance 2-3 revolutions, may occur between the rough cut and the finishing cut. The workpiece  100  is then cut to a desired shape in a plurality of cutting passes with the primary cutting edge  20   a  and the first side secondary cutting edge  30   a  at the selected feed rate. Accordingly, the feed rate of the insert  10  is at least 0.01 in. per revolution of the workpiece  100  but no more than 0.03 in. per revolution of the workpiece  100 . 
     While several embodiments of an indexable cutting insert were described in the foregoing detailed description, those skilled in the art may make modifications and alterations to these embodiments without departing from the scope and spirit of the invention. Accordingly, the foregoing description is intended to be illustrative rather than restrictive. The invention described hereinabove is defined by the appended claims and all changes to the invention that fall within the meaning and the range of equivalency of the claims are embraced within their scope.