Patent Publication Number: US-6986552-B1

Title: Hardened rotary cutting tip

Description:
The applicant claims priority from his provisional application filed Nov. 3, 2003 and assigned Ser. No. 60/516,886. The present invention relates to the cutting tips of rotary mounted tools and, in particular, to an improved tip which will prolong the useful life of the tool. 

   BACKGROUND OF THE INVENTION 
   Machines that remove the upper layer of pavement from a concrete road employ a plurality of cutting tools mounted on a drum, with each of the tools rotatable about its longitudinal axis. When such machines are employed to remove the upper surface of a road, the tools become worn and must be periodically replaced. Depending upon weather conditions, it may be necessary to replace the tools mounted on the drum of such machines daily, and sometimes twice daily. The drums of such machines typically mount more than one hundred of such tools, and therefore, the machines that remove the upper surface from a road must be removed from service for a lengthy period of time while the tools on the drum are replaced. The time loss that occurs while tools are replaced contributes significantly to the cost of resurfacing roads. 
   Similarly configured tools are used in trenching machines and rock saws for cutting grooves in concrete and the replacement of the tools on these machines increases the costs of operating these machines. 
   It is desirable, therefore, to extend as long as possible the useful life of the tools mounted on such machines. In order to extend the useful life of the tools, the manufacturers of such tools are engaged in a heated competition to find a configuration of a tool body with improved endurance to wear. 
   The tools mounted on such machines have an elongate metal body symmetric about a longitudinal axis and consist of a cutting end at the forward end of which is a seat for receiving a hardened tip, and behind the cutting end is an elongate cylindrical shank which is rotationally received in a cylindrical bore of a tool holder. The failure of such tools can be classified into certain clearly defined categories. First, tools may fail as a result of fracture of the hardened tip. Second, the braze that retains the hardened tip in the seat at the forward end of the tool may fail, such that the tip becomes dislodged from the tool. The tool may also fail because of washaway of the metal from which the tool body is made. Finally, a tool may fail because the hardened tip at the forward end of the tool has become dull and the tool can no longer effectively cut the hard surface against which the tools on the drum are directed. The manufacturers of such tools have been seeking a configuration of a cutting tip and tool body that will maximize the useful life of the tool. 
   One way of reducing the washaway of the steel bodies of such tools is to provide an enlarged tungsten carbide tip at the forward end of the tool. The most expensive portion of such tools, however, is the tungsten carbide from which the hardened tip is constructed and therefore providing a tool with an enlarged cutting tip greatly increases the cost of the tool. Furthermore, it has been found that a tool having an enlarged diameter tip will not maintain a sharp configuration for an extended period of time and therefore, although the tool does not suffer from washaway, it must be prematurely discarded when the cutting tip has become dull. 
   One configuration of a cutting tip which has had recognized success is disclosed by Ojanen, U.S. Pat. No. 4,497,520. The Ojanen tip has a tapered forward end, a generally frustoconical midsection that diverges gradually along its length, followed by an enlarged diameter base with a fillet between the frustoconical midsection and the base. 
   The enlarged diameter base of the Ojanen tip provided an enlarged surface area for bonding the tip into the seat at the forward end of the tool. During use, the material that forms the sharpened forward end of the cutting tip is gradually worn away. The elongate mid-portion of the tip gradually becomes shortened, but the outer diameter surrounding the sharpened portion of the tip remained substantially the same because of the gradual incline of the frustoconical mid-portion. As a result, even though material has eroded away from the surface of the tip, the tip generally remained relatively sharp and the tool continued to be useful as the carbide of the mid-portion is not worn away. It is not until the material that comprises the fillet between the midsection and the base begins to wear away that the tip will become dull and no longer useful. 
   In the meantime, however, existing tools employing tips embodying the configuration of the Ojanen tip have generally suffered greatly from washaway. Generally, long before a cutting tip embodying the configuration disclosed by Ojanen has become dull, washaway has so eroded the central body of the tool that the tool has acquired an hourglass configuration, and breakage of the tool body could occur between the base of the cutting tip and the shank. 
   On milling machines used to remove the surface of pavement, the tools are mounted on a rotating drum with the tools positioned on the drum to cut grooves in the surface of the asphalt or concrete with each of the grooves cut by the cutting tip of one of the tools. The tools of a milling machine are mounted on the drum in a spiral configuration and positioned to form grooves having a distance of approximately five-eighths inch between the center lines of adjacent valleys of the grooves with a solid ridge of material between the adjacent valleys of each of the grooves. 
   I have observed that it is the ridges between the valleys of the asphalt or concrete surface that are responsible for causing a great deal of the washaway that leads to the hourglass configuration of the tool body. It has thus been apparent to me that a tool body would be less subject to washaway if the tools could be configured so as to cut grooves in the hardened asphalt or concrete with less pronounced ridges. On the other hand, it would be desirable to provide a tip which would offer certain protection to the tool body behind the tip without greatly increasing the mass of tungsten carbide material from which the tip is made, such that the cost of the tip is not substantially increased. 
   BRIEF DESCRIPTION OF THE INVENTION 
   Since the machines used to cut hard surfaces employ numerous tools, tool manufacturers have continuously strived to minimize the cost of manufacturing the tool while maximizing the useful life thereof. Since the most expensive portion of such cutting tools is the tungsten carbide insert or tip fitted in the seat at the forward end of the tool, it is desirable that the mass of the tip be minimized. On the other hand, if the tool is manufactured with an undersized cutting tip, the tip will become worn away long before the tool body, thereby increasing the frequency with which the tools must be replaced and rendering the tool a less desirable product for such machines. Years of development of such tools have resulted in a standardization of the diameter of the base of the tungsten carbide tips or inserts at the forward end of the tools used in the milling industry of between 0.690 inch to 0.750 inch. The standardization of the base diameter of such tips or inserts occurred as the result of the efforts of manufacturers to reach that perfect balance in which the useful life of the tungsten carbide tip equals the useful life of the metal tool body on which the tungsten carbide tip is mounted. In similar fashion, the tips used at the forward end of the tools of trenching machines, and the tools for rock saws and the like have also become standardized over the years, where the standardization has occurred to maximize the useful life of both the cutting tip and the tool body in which it is mounted. 
   I have discovered, however, that providing a cutting tool having a carbide insert with an abnormally large diameter base will enhance the useful life of the tool because washaway of the tool body is reduced. 
   The advantages of the invention are best seen when studied with respect to the tools mounted on the drums of milling machines. The tools of such machines are mounted so as to engage the surface to be cut at an up angle of approximately 45 degrees and a side angle of about seven degrees. As a result of this orientation, the particles of hardened material loosened by the cutting tip will move along the body of the cutting tool and cause washaway which gradually erodes the tool body. One of the factors which causes the particles of loosened material to erode the tool body is the configuration of the grooves being cut by the tools. Existing tools cut somewhat parallel grooves with relatively high standing ridges between the valleys of the adjacent grooves. The ridges direct the loosened particles of hardened material towards the tool body after the cutting tip has cut the valley of the groove. The standing ridges are also contacted by the tool body of the trailing tool. 
   I have observed, however, that by providing an insert with a base having an enlarged diameter, the diameter being significantly larger than the standard 0.690 diameter for tips currently used in milling machines, the ridges formed between the valleys cut by the tips will be reduced in size. This occurs because a portion of the outer circumference of the base of the carbide insert breaks off peaks extending from the upper portion of the ridge thereby reducing the relative elevation of the ridges between the adjacent valleys. The reduction of the ridges alters the direction of loosened particles and directs them away from the metal body of the tools and reduces washaway of the tool body. 
   The tip or insert of the present invention consists of a tapered forward cutting end configured to cut the hard surface and axially align behind the forward cutting tip a mid-section, which diverges radially outward and rearward. The general configuration of the cutting end and the mid-section of insert or tip in accordance with the present invention are generally consistent with existing standards in the industry. Existing tips, for example, have an overall length from the forward end of the base to the forward end of the cutting end of approximately 0.625 inches and a diameter of the forward cutting end of approximately 0.375 to 0.425 inches. The mid-section of existing inserts normally diverges to a diameter of no more than about 0.480 inches. 
   Positioned axially behind the mid-section of the insert is a base with the outer surface of the base defining a cylinder. Where the insert is to be used at the cutting end of a tool for a milling machine, the base has an enlarged diameter of approximately 0.825 inches as opposed to a diameter of 0.690 to 0.750 inches of the prior art. Between the rearward end of the mid-section and the forward end of the base the insert of the present invention has a substantially planar surface. 
   In a more refined embodiment of the invention, the mid-section of the cutting tip is divided into a first mid-section portion and a second rearward mid-section portion, with the first mid-section portion being generally frustoconical in shape and the second rearward mid-section portion flaring outwardly such that the silhouette of the rearward second portion defines a curve. 
   The advantages of the insert of the present invention are further enhanced by providing a plurality of notches in the circumference of the base, the notches extending from the radially extending planar forward surface of the base to a rearward surface of the base such that the outer portion of the base is divided into a plurality of spaced flanges. The provision of the notches allows particles of hardened material loosened by the cutting tip to erode grooves in the tool body behind the cutting tip corresponding to the notches. The grooves in the tool body serve to channel particles of loosened material along the tool body without causing further washaway of the tool body. The grooves which become worn in the tool body may also facilitate rotation of the tool, thereby insuring that the cutting tip of the tool becomes evenly worn around the circumference thereof so as to maximize its useful life. The flanges that make up the outer portion of the base shield the remaining circumference of the tool body from erosion or washaway. 
   The peripheral portions of the enlarged diameter base provide a better mechanical advantage for supporting the base than has been available with prior art inserts, and as a result, there is a lesser incidence of failure at the braze joints. Also, the breaking strength of the insert can be further improved by providing a thicker base. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A better understanding of the present invention will be had from a reading of the following detailed description taken in conjunction with the drawings, wherein: 
       FIG. 1  is a schematic view of a drum of a milling machine having tool mountings for retaining tools thereon; 
       FIG. 2  is a side elevational view, partially in cross-section, of a tool in accordance with the prior art used on the drum of the milling machine shown in  FIG. 1 ; 
       FIG. 3  is an enlarged side elevational view of the insert in the seat of the tool shown in  FIG. 2 ; 
       FIG. 4  is a cross-sectional view of the grooves cut in a hard surface by prior art tools on the drum shown in  FIG. 1 ; 
       FIG. 5  is a side elevational view of a tool in accordance with the prior art that has suffered washaway of the tool body giving it an hourglass appearance; 
       FIG. 6  is a side elevational view of a tool fitted with an insert in accordance with the present invention; 
       FIG. 7  is a front view of the insert fitted into the seat of the tool shown in  FIG. 6 ; 
       FIG. 8  is a side-elevational view of the insert shown in  FIG. 7 ; 
       FIG. 9  is a cross-sectional view of the grooves cut in a hard surface by tools shown in  FIG. 6  mounted on the drum shown in  FIG. 1 ; 
       FIG. 10  is an isometric view of the forward end of a tool body fitted with the insert shown in  FIG. 7  after the tool body has endured some wear; 
       FIG. 10A  is a side-elevational view of the tool shown in  FIG. 10  prior to incurring wear; 
       FIG. 10B  is a front-end view of the tool shown in  FIG. 10  prior to incurring wear; 
       FIG. 10C  is a side-elevational view of the tool shown in  FIG. 10A  after it has incurred a small amount of wear; 
       FIG. 10D  is a front view of the slightly worn tool shown in  FIG. 10C ; 
       FIG. 10E  is a side-elevational view of the tool shown in  FIG. 10A  after it has incurred more wear than shown in  FIG. 10C ; 
       FIG. 10F  is a front view of the partially worn tool shown in  FIG. 10E ; 
       FIG. 10G  is a side-elevational view of the tool shown in  FIG. 10A  after it has become fully worn and in need of replacement; 
       FIG. 10H  is a side-elevational view of the worn tool shown in  FIG. 10G ; 
       FIG. 11  is an enlarged, fragmentary, partially cross-sectional view of the insert shown in  FIG. 7  taken through line  11 — 11  thereof; 
       FIG. 12  is a front-end view of another insert in accordance with the invention showing a four-flange configuration; 
       FIG. 13  is a front-end view of another insert in accordance with the invention, the insert having three flanges that scribe more than fifty percent of the circumference of the cylinder defined by the outer surface; 
       FIG. 14  is a front-end view of another configuration of flanges in accordance with the invention; 
       FIG. 15  is a front-end view of another configuration of flanges in accordance with the invention; 
       FIG. 16  is a front-end view of a configuration of flanges in accordance with the invention where the flanges scribe less than fifty percent of the circumference of the cylinder defined by the outer surface thereof; 
       FIG. 17  is a front-end view of an insert in accordance with the invention that is without indentation in the base; 
       FIG. 18  is a side-elevational view of the insert shown in  FIG. 17 ; 
       FIG. 19  is a side-elevational view of another insert embodying the present invention; 
       FIG. 20  is a front view of the insert shown in  FIG. 19 ; 
       FIG. 21  is a fragmentary cross-sectional view of the insert shown in  FIG. 19  taken through line  21 — 21  of  FIG. 20 ; 
       FIG. 22  is a front view showing another configuration of flanges on an insert in accordance with the invention; 
       FIG. 23  is a side-elevational view of yet another insert in accordance with the invention; and 
       FIG. 24  is a front view of the insert shown in  FIG. 23 . 
   

   DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT 
   Referring to  FIGS. 1 ,  2 , and  4 , a milling machine employs a rotatable drum  10  on which are a plurality of tool mountings for mounting a plurality of cutting tools  12  with the cutting tools  12  positioned in a spiral around the circumference of the drum  10 . Each of the tools  12  is mounted to the drum  10  such that the forward cutting end of the tool  12  will cut a groove in the hard surface  18  of the material such as concrete or asphalt. By mounting the tools  12  in a spiral around the circumference of the drum  10 , the cutting ends of the various tools  12  are positioned to form a plurality of adjacent grooves  16 A,  16 B,  16 C as the drum  10  rotates adjacent the hard surface  18 . 
   Each of the tools  12  is mounted on the drum  10  to engage the hard surface  18  at an up angle of approximately 45 degrees and a side angle of seven degrees. The tools  12  are also retained in holders  11  on the drum  10  so as to be rotatable about the longitudinal axis  19  of the tool  12  such that the tool  12  wears evenly around the circumference thereof, thereby maximizing the useful life of the tool  12 . 
   Referring to  FIG. 2 , a typical tool  12  for use in such machines includes a tool body  20  having a cylindrical shank  22  which is received in a complementarily shaped cylindrical bore in the holder  11  on the drum  10  for permitting the tool  20  to rotate about its longitudinal axis  19 . The tool body  20  also includes a generally tapered cutting portion  26 , and between the cutting portion  26  and the cylindrical shank  22  a radial flange  28 . At the most forward end of the cutting portion  26  is a seat  30  into which is fitted a hardened cutting insert  32 . 
   Referring to  FIG. 3 , tools  12  of the type used in the milling industry have the seat  30  with a cylindrical inner wall with a diameter of approximately 0.700 inches. The cutting insert  32  that is received in the seat  30  has a forward cutting tip portion  34 , and axially behind the cutting tip portion  34  is a tapered mid-portion  36 . At the rearward end of the tapered mid-portion  36  is an outwardly diverging portion or fillet  38 , and behind the fillet  38  is a cylindrical base  40 . For existing milling machines, the cylindrical base  40  has an outer diameter  42  of approximately 0.700 inches. The fillet  38  of prior art inserts  12  extends to the outer diameter  42  of the base  40 . The mid-portion  36  of the cutting tip  32  has a lower diameter  44 , adjacent the fillet  38 , of about 0.480 inches and the forward cutting tip  34  has a maximum outer diameter  45  of about 0.420 inches. Although the diameters of the mid-portions  36  and the diameter of the tip  34  may vary from one manufacturer to another, the greatest diameter  44  of the mid-portion  36  is about 0.480 inches and the diameter of the base is standardized at about 0.700 inches. 
   Referring further to  FIGS. 1 ,  2  and  4 , the tools  12  are mounted on the drum  10  to cut grooves  16 A– 16 C in the surface  18  with each of the grooves  16 A– 16 C having troughs  46  that are spaced apart a distance of five-eighths inch. Between adjacent troughs  46  are ridges  48  left standing after the successive cutting from the inserts  32  of the tool  12 . I have found that the ridges  48  cause particles of hard material loosened by the tool  12  to be directed around the surface of the tool body  20  causing washaway of the metal of the tool body  20  and thereby causing the tool body  20  to become worn away more rapidly than the cutting tip  32  becomes worn. Often the tool body  20  becomes so worn away as to render the tool  12  unusable before the insert  32  has become fully worn, leaving an hourglass configuration to the tool body  20 ′ shown in  FIG. 5 . 
   Referring to  FIGS. 6 ,  7 , and  8 , the useful life of a tool can be increased by providing a tool  49  having a tool body  50  with an insert  51  in accordance with the present invention. The insert  51  has a tapered forward cutting tip  52  with a maximum diameter  53 , and axially behind the forward cutting tip  52  is a tapered mid-portion  54 . The mid-portion  54  may be divided into two sections, a forward section  55  which is typically frustoconical, tapering gradually from its forwardmost portion adjacent the maximum circumference  53  of the tip  52  to the lower end  57  thereof, and having a maximum diameter  56 , and rearward of the forward section  55  is a rearward mid-section  58  which flares out from the intersection  57  with the forward mid-section to a maximum diameter  59 . The cross-sectional dimensions of the diameters  53 ,  56 ,  59  respectively of the tip  52 , the forward mid-section  55  and the rearward mid-section  58  are within the commonly accepted dimensions of the diameters  45 ,  44 ,  42  designated for the corresponding parts of the prior art inserts  32  described with respect to  FIG. 3 . 
   The inventive element of the insert  51  resides behind the rearward mid-section  58 . Positioned axially behind the rearward mid-section  58  is a cylindrical base  60  having a diameter which is significantly larger than the diameter  42  of the insert  32  of the prior art. Preferably, for milling purposes, the cylindrical base  60  has a diameter  61  of 0.800 to 0.850 inch, but certain advantages of the present invention will be achieved by the provision of a cylindrical base  60  having an outer diameter larger than the 0.750 inch. Between the outer diameter  59  of the rearward mid-section  58  and the diameter  61  of the base  60  is a generally planar forwardly facing surface  62 . 
   Referring to  FIGS. 8 and 11 , to provide strength to the insert, a fillet  63  having a relatively small radius is provided between the rearward midsection  58  and the generally planar forwardly facing surface  62 . 
   By providing a generally planar forward surface  62 , the divergence of the rearward mid-section  58  is not overly accentuated and the outermost diameter  56  of the forward mid-section  54  can be manufactured so as to be within the 0.480 limits which is standard for cutting tips currently in use. An insert  51  in accordance with the present invention, therefore can be used to cut grooves  16 A– 16 C in a hard surface and remain just as sharp during the cutting process as the cutting tips currently in use. 
   The enlarged diameter  61  of the cylindrical base  60  offers four desirable advantages that enhance the life of the tool  12  to which it is affixed. First, referring further to  FIG. 9 , the enlarged diameter  61  of the base  60  causes portions of the outer circumference of the base  60  to engage portions of the ridges  48 ′ between troughs  46 ′ of the grooves  16 A′– 16 C′, which are cut in a hard surface. The contact between the outer circumference of the base  60  and the ridges  48 ′ reduces the elevation of the ridges  48 ′ to a lesser level. By reducing the elevation of the ridges  48 ′ between the troughs  46 ′, the amount of loose particles directed toward the tool body  50  is reduced, thereby reducing the amount of washaway suffered by the tool body  50 . A milling tool insert having a base diameter over 0.800 inch will cause a significant reduction in the elevation of the ridges  48 ′ with respect to the troughs  46 ′ in the groove made by a milling machine. 
   The second advantage of the enlarged diameter  61  of the base  60  is that the lower surface  69  of the base  60 , which is retained by braze to the tool body  50 , has greater surface area thereby improving braze adherence. The incidence of tool failure as a result of the insert becoming dislodged from the tool body is greatly reduced. 
   The third advantage to the enlarged diameter  61  of the base  60  is that the base  60  provides a degree of protection, or shielding, to the tool body  50  and literally protects the tool body  50  from the washaway effects of loosened particles of hard material from the surface  18 , and the tool body  50  does not acquire the hourglass configuration shown in  FIG. 5 . 
   The fourth advantage is that tool rotation is improved. As a tool body suffers washaway, the diameter of the tool body narrows reducing the leverage about the tool body axis of rotation and the tool is not as easily rotated as it is forced against a hard surface. Once a tool stops rotating, the tip of the tool will develop a flat which creates a resistance to rotation. A tool with a flat must be immediately discarded. 
   Referring further to  FIGS. 7 and 8 , although certain advantages are achieved by providing an enlarged diameter  61  for the cylindrical base  60 , the benefits of the large diameter base  60  are maximized when the base  60  is provided with a plurality of notches or indentations  66 ,  67 ,  68  around the circumference thereof, with each of the indentations  66 – 68  extending from the generally planar upper surface  62  to the lower surface  69  of the base  60 , without extending into the rearward mid-section  58 , as shown. As a result of the indentations  66 – 68 , the base  60  is broken into a plurality of flange segments  70 ,  71 ,  72  with each flange segment having an arcuate outer surface that defines a portion of a cylinder having a diameter  61 . 
   It should be appreciated that although the lower surface  69  is depicted in  FIG. 8  as being conical, the lower surface  69  may be planar, or semi-spherical, or a combination of shapes. The present invention relates to diameter  61  of the base  60  and to the intersection between the midsection  58  and the base  60 , and not to the shape of the lower surface  69 . 
     FIG. 11  depicts the upper surface  62  of the outer forward circumference of the base  60  as being blended into the mid-portion  58  by virtue of the fillet  63 . This configuration maximizes the strength of the base  60  of the insert  51 , but the advantages of the invention can still be achieved by an insert having a somewhat different configuration. 
     FIGS. 19 ,  20 , and  21  depict an insert  149  having a tapered cutting tip  152 , a generally more robust, frustoconically shaped midsection  155  behind the cutting tip  152 . Axially behind the midsection  155  is an enlarged diameter base  160 . A shoulder  154  defines an inner circumference and arcuate indentations  165 ,  166 ,  167  in the base  160  have inner, generally vertical, surfaces that follow the curve of the shoulder  154 . Between the indentations  165 – 167  are arcuate flanges  170 ,  171 ,  172 , the outer edges of which define the maximum circumference of the insert  149 . A first fillet  174  extends between the midsection  155  and the shoulder  154  and a second fillet  176  extends between the shoulder  155  and the flanges  170 – 172  of the base  160 . In this embodiment the diameter of the midsection  155  is greater than the diameter of the forward section  55  of insert  51  described above and therefore the insert  149  will be subjected to greater transverse forces than insert  51 . In order to bear the greater transverse forces the cross sectional area of the flanges  170 – 172 , as determined by the thickness of the flanges and the arcuate length thereof, must be greater than the cross sectional area of the flanges  70 – 72  of insert  51 . The flanges  170 – 172  therefore have a greater thickness than the flanges  70 – 72  of insert  51 . 
   Referring to  FIGS. 10 through 10H , when a tool body  50  is fitted with an insert  51  in accordance with the present invention having a plurality of indentations  66 – 68  around the circumference of the base  60  thereof, usage of the tool will cause the metal of the tool body  50  to be washed away behind the indentations  66 – 68  causing a plurality of grooves  74 ,  75 ,  76  therein. This effect is explained in further detail in my U.S. Pat. No. 5,551,760 issued Sep. 3, 1996. The grooves  74 – 76  serve many purposes. First, the grooves assist in causing rotation of the tool body  50  in the cylindrical bore of the tool holder  11 , thereby insuring that the tool body  50  wears evenly around the circumference thereof so as to maximize its useful life. Also, the grooves  74 – 76  provide channels for directing particles of material loosened by the insert  51  thereby enabling these particles of material to flow along the tool body  50  without causing the entire tool body  50  to suffer from significant washaway. The pattern of washaway that occurs during the useful life of the tool is shown in  FIGS. 10A through 10H . As can be seen, the grooves  74 ,  75 ,  76  made into the surface of the tool body  50  as a result of washaway are not deep and as a result, the tool body  50  retains most of its mass and diameter through its useful life. The consequence is that the tool body  50  will not reach the hourglass configuration of prior art tools having inserts  20 ′ as depicted in  FIG. 5 . Another benefit is that the tool  49  will continue to rotate during its useful life because the tool body  50  will maintain most of its diameter throughout its useful life. 
   Referring further to  FIG. 7 , it can be seen that the indentations  66 – 68  in the base  60  leave intact arcuate portions  70 – 72  of the base  60  with the arcuate portions  70 – 72  having arcuate outer edges that constitute approximately 50 percent of the circumference of the base. It should also be appreciated that the indentations  66 – 68  have surfaces  81 ,  82 ,  83 ,  84 ,  85 ,  86  which slope at an angle of about five degrees from the vertical. The sloping surfaces  81 – 86  have radiused corners that reduce the stresses in the arcuate portions  70 – 72  of the base  60 , which would occur if the side wall between the indentations  66 – 68  and the flanges  70 – 72  formed sharp corners. 
   Referring to  FIG. 11 , the insert  51  is formed in a die and the formed insert must be removable from the die without damaging the surfaces of the insert  51 . To remove the insert  51  from the die in which it is formed, vertical surfaces such as the outer surfaces of the arcuate flanges  70 ,  71 ,  72  and the curved surfaces  81 – 86  of the indentations  66 – 68  must have a gentle taper  90  of about five degrees with the perpendicular  91 , such that the side surfaces are gradually reduced toward the forward or tip  52  of the insert  51  and larger towards the base  60 . Also, the upper surface  62  of the flanges  70 – 72  that form the base  60  have been described as “generally planar” but not truly “planar.” In order to remove the formed insert  50  from a die, the upper surfaces  62  cannot be planar and perpendicular to the axis  19  of the tool  49 , but must have an incline  92  of about eight degrees, and therefore the upper surfaces cannot be truly “planar,” but can only be nearly or “generally planar,” as described above. 
   Referring to  FIG. 12 , in the preferred embodiment, the arcuate portions of the base extend around approximately 50 percent of the outer circumference of the base. The insert  94  depicted in  FIG. 12  has four flanges  95 ,  96 ,  97 ,  98  interrupted by indentations  99 ,  100 ,  101 ,  102 , with the arcuate segments of the flanges  95 – 98  representing approximately 50 percent of the circumference of the cylinder defined by the arcs. Many of the benefits of the present invention, however, can be achieved where the arcuate portions comprise significantly less than 50 percent of the outer circumference of the base  60 , or significantly larger than 50 percent of the outer circumference of the base. Referring to  FIGS. 13 ,  14 , and  15 , inserts  103 ,  104 , and  105  depict inserts having all the benefits of the invention with flange configurations in accordance with the invention where the flanges comprise more than fifty percent of the circumference of the cylinder defined by the segments of the base.  FIG. 16 , on the other hand, depicts a insert  106  with a configuration of flanges  111 ,  112 , and  113  in accordance with the invention where the flanges occupy only about thirty percent of the circumference defined by their outer surfaces. 
   Referring to  FIGS. 9 ,  17 , and  18  it should also be appreciated that many of the benefits of the invention, specifically the reduction of the elevation of the ridges  48 ′ between adjacent troughs  46 ′ of the grooves cut in hard material will occur by providing an insert  120  which embodies many of the features of the invention. Specifically, the insert  120  has a conical forward cutting tip  121 , a diverging mid-portion  122 , having cross-sectional dimensions similar to those of the prior art and described with respect to the insert  51  above, and a cylindrical base  123 . The base  123  does not have indentations or flanges, but scribes a full cylinder as shown. The cylindrical base  123  has an enlarged diameter, larger than the 0.690 diameter of the prior art inserts, such that the material of the enlarged diameter base  123  will, during use of a tool bearing the insert  120 , engage the ridges  48 ′ between adjacent troughs  46 ′ breaking the tops of the ridges  48 ′ and causing the ridges to be reduced in size. The enlarged diameter of the base  123  will also protect the tool body to which it is attached from washaway. 
   Referring to  FIG. 22 , it should be appreciated that the outer edges of the flanges  270 ,  271 ,  272  of an insert  249  in accordance with the invention need not form segments of the same cylinder. The flanges  270 ,  271 ,  272  need only define a maximum outer diameter. I have found that an insert with a base having flanges  270 ,  271 ,  272  that define a larger diameter, as shown, achieve the benefit of the invention. Surprisingly, even though the area of the flanges  270 – 272  occupy only a small fraction of the area between the inner circumference  277  of the base and outer circumference  279 , the braze holding the insert  249  into a seat will be nearly as strong as an insert with a solid cylindrical base equal to the maximum circumference  279  defined by base. This is believed to occur because the side surfaces  81 – 86  that define the indentations  66 – 68  provide additional surface area to which the braze attaches. It is also believed that the five degree taper of the nearly vertical side surfaces  81 – 86  to which the braze attaches further assists in retaining the insert  51  within the seat of the tool body  50 . 
   Referring to  FIGS. 23 and 24 , the midsection  355  of an insert  349  may also be cylindrical, as shown, without departing from the invention. 
   The invention has been primarily discussed with respect to milling tools, but the present invention has benefits when used in any cutting machines that employ cutting tools rotatable about their longitudinal axis. 
   Trenching machines use tools having inserts having appearances that are much like the insets used on milling machines; however, the inserts on trenching tools have larger dimensions including larger diameters than the inserts used on milling machines. The insert typically used on a tool for a trenching machine has a tip with a diameter of 0.750 to 1.000 inch, an elongate midsection behind the tip, and a cylindrical base behind the midsection. The inserts of such tools have profiles that look almost identical to the profiles of the inserts of a milling machine, but much larger. The bases of such inserts have an outer diameter of about 1.000 inch to 1.250 inch. The inserts for the cutting tools used in the trenching industry have bases that seldom exceed 1.250 inch in diameter. 
   By providing an insert to a trenching machine embodying the configuration described for  FIGS. 7 and 8 , advantages similar to those described with respect to milling tools will be achieved. A trenching tool having an insert with a base that is over 1.250 inch in diameter, perhaps 1.500 inch in diameter, will protect the tool body behind it against washaway in the same manner that the insert  51  protects the tool body  50  for a milling machine. Providing indentations and dividing the base into arcuate flanges as described with respect to indentations  66 – 68  and flange segments  70 – 72  will improve the rotation of the tool and further protect the tool against washaway. 
   The salt mining industry also employs cutting tools that are rotatable about their longitudinal axis and have tungsten carbide cutting inserts having configurations similar to that describe with respect to insert  51  and depicted in  FIGS. 6 and 7 . Salt is a softer media than asphalt or concrete and therefore the inserts used in the salt mining industry are correspondingly smaller. The rotatable tools employed in the salt mining industry, none-the-less, are subject to the force of erosion and tool failure similar to the erosion suffered by tools employed in the milling and the trenching industries. By providing a tool having an insert with a configuration as shown in  FIGS. 6 and 7 , and having a base with a correspondingly enlarged diameter, the enlarged base will protect the tool body supporting the tool against erosion or washaway. 
   While the present invention has been described with respect to specific embodiments, it will be appreciated that many modifications and variations may be made without departing from the true spirit and scope of the invention. It is therefore the intent of the appended claims to cover all such variations and modifications which fall within the true sprit and scope of the invention.