Abstract:
A molding apparatus for making a cutting tool includes a cylindrically shaped elastic bag having an internal cavity for receiving a granulated material, such as a mixture of cobalt and carbide. The profile of the interior cavity substantially corresponds to the shape of the cutting tool being produced. The ends of the bag are open to provide access to the interior cavity of the bag. A substantially rigid tubular-shaped pressure sleeve encloses an outer circumference of the elastic bag. A pair of end caps operate to seal the open ends of the elastic bag and are engageable with the ends of the pressure sleeve. The granulated material can be formed into a solid coherent structure by placing the assembled mold containing the granulated material into a hydrostatic press for applying a substantially uniform compressive load to the outer periphery of the elastic bag.

Description:
RELATED APPLICATIONS  
       [0001]     This application claims the benefit under 35 U.S.C. § 119(e) of U.S. Provisional Application Ser. No. 60/642,635 filed Jan. 10, 2005, which is hereby incorporated in its entirety. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates to cutting tools, and more particularly, to a mold and method for making a sintered carbide cutting tool.  
       BACKGROUND AND SUMMARY OF THE INVENTION  
       [0003]     Machine cutting tools can be produced from a variety of materials, including but not limited to carbon steel, high-speed steel, cobalt high-speed steel, tungsten carbide, and the like. Cutting tools made from cobalt and/or carbide can withstand higher operating temperatures and can thus be run at higher cutting speeds and feeds than tools made from carbon steel or high-speed steel. Cutting tools containing cobalt and/or carbide, however, may be more time consuming and costly to produce than tools made from carbon steel or high-speed steel due to the increased hardness of the materials.  
         [0004]     There exists a variety of known manufacturing methods for producing cutting tools. For example, the process of producing a twist drill from carbon steel may involve rough milling a cylindrically-shaped blank to produce drill flutes in a straight line along the length of the blank. The milled blank can then be heated and twisted to form the flutes into a desired helix. The twist drill can then be semi-finished milled and ground to size. The manufacturing process generally becomes more complex and time consuming when producing cutting tools made from cobalt and/or carbide. For example, manufacturing twist drills from carbide may require more extensive and complex machining operations to produce than tools made from carbon steel of high-speed steel. The time and cost of producing cutting tools from cobalt and/or carbide could be reduced by producing a cutting tool blank that more nearly approximates the finished shape of the cutting tool. Accordingly, there is a need to develop an apparatus and method for manufacturing a cutting tool that more closely approximates the finished shape of the cutting tool being produced.  
         [0005]     In accordance with the present invention, a preferred embodiment of a molding apparatus for making a cutting tool includes a cylindrically shaped elastic bag having an internal cavity for receiving a granulated material, such as a mixture of cobalt and carbide. The profile of the interior cavity substantially corresponds to the shape of the cutting tool being produced. The ends of the bag are open to provide access to the interior cavity of the bag. A further aspect of the invention includes a substantially rigid tubular-shaped pressure sleeve that encloses an outer circumference of the elastic bag. Yet another aspect of the invention includes a pair of end caps that operate to seal the open ends of the elastic bag and are engageable with the ends of the pressure sleeve. The granulated material can be formed into a solid coherent structure by placing the assembled mold containing the granulated material into a hydrostatic press for applying a substantially uniform compressive load to the outer periphery of the elastic bag. After forming, the cutting tool blank can be removed from the mold and may be subjected to further processing. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]     The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:  
         [0007]      FIG. 1  is an exploded perspective view of a preferred embodiment mold of the present invention for manufacturing a cutting tool;  
         [0008]      FIG. 2  is a cross-sectional view of a flexible bag employed in the preferred embodiment mold, taken along line  2 - 2  of  FIG. 1 ;  
         [0009]      FIG. 3  is longitudinal cross-sectional view of the flexible bag employed in the preferred embodiment mold;  
         [0010]      FIG. 4A  is a side elevational view of an end cap incorporating a straight core pin employed in the preferred embodiment mold;  
         [0011]      FIG. 4B  is a top elevational view of the end cap incorporating a straight core pin;  
         [0012]      FIG. 5A  is a side elevational view of a second end cap employed in the preferred embodiment mold:  
         [0013]      FIG. 5B  is a top elevational view of the end cap shown in  FIG. 5A ;  
         [0014]      FIG. 6A  is a side elevational view of an exemplary cutting tool that can be formed using the mold and method of the present invention;  
         [0015]      FIG. 6B  is a side elevational view of the exemplary cutting tool shown in  FIG. 4A , viewed perpendicular to the cutting flutes;  
         [0016]      FIG. 7  is a perspective view of the flexible bag employed in the preferred embodiment mold shown with an end cap attached to one end of the bag;  
         [0017]      FIG. 8  is a side elevational view of certain components of the preferred embodiment mold shown being filled with a carbide mixture while resting on a mechanical vibrating plate, with certain components shown in cross-section;  
         [0018]      FIG. 9  is side perspective view of a pressure sleeve employed with the preferred embodiment mold;  
         [0019]      FIG. 10  is a side perspective view of the mold with certain components shown disassembled from the mold;  
         [0020]      FIG. 11  is a side elevational view of a exemplary installation tool;  
         [0021]      FIG. 12  is a side elevational view of the flexible bag showing the exemplary cutting tool of  FIGS. 6A and 6B  being separated from the bag;  
         [0022]      FIG. 13  is a diagrammatic representation of a method for forming a cutting tool using the preferred embodiment mold; and  
         [0023]      FIG. 14  is a side elevational view of an end cap incorporating a helical core pin employed in the preferred embodiment mold. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0024]     The following description of the preferred embodiment is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.  
         [0025]     Referring to  FIG. 1 , there is shown a mold  20  for producing a cutting tool in accordance with the present invention. The cutting tool may have one or more internal passages. Mold  20  can be used to form a variety of differently configured cutting tools, such as end mills, reamers, twist drills, straight flute drills, and the like. The cutting tools may be formed from materials known to be used in the production of cutting tools, such as powdered carbide mixtures. One such carbide mixture consists of finely ground carbide and cobalt combined with one or more binder materials, such as wax. The binder material operates to hold the particles of material together when forming the carbide mixture into a desired shape. The carbide mixture may include, for example, 90% carbide, 9% cobalt, and 1% other trace elements by volume. A wax binder may also be added to the mixture in an approximate ratio of one (1) part wax binder to forty-nine (49) parts carbide mixture.  
         [0026]     Referring to  FIGS. 6A and 6B , there is shown an exemplary straight flute drill  22  that can be produced using mold  20  and the method of the present invention. Straight flute drill  22  is merely one example of the various types of cutting tools that can be produced using the mold and method of the present invention.  
         [0027]     Straight flute drill  22  is shown to have a generally cylindrical shape. A pair of diameterally opposed recessed channels  24  extend lengthwise over a portion of straight flute drill  22 . Channels  24  define edges of a pair of flutes  26  forming a cutting surface of straight flute drill  22 .  
         [0028]     Straight flute drill  22  includes an elongated internal passage  28  oriented along a central longitudinal axis of straight flute drill  22  for supplying a fluid to an end  36  of straight flute drill  22 . Cooling passage  28  includes an inlet port  30  located in an end  32  of straight flute drill  22  opposite flutes  26 . An end  34  of passage  28  opposite inlet  30  terminates short of end  36  of straight flute drill  22  so as to not penetrate end  36 . A pair of opposing discharge passages  38  extend from passage  28  and have an exit port  40  located within recessed channel  24 . Although passage  28  is shown to have a substantially linear tube-like configuration, it shall be appreciated that differently configured cooling passages may also be produced using mold  20 , including but not limited to, helical shaped passages and passages having multiple inlet and exit ports.  
         [0029]     Referring to  FIGS. 1-3 , mold  20  includes a generally cylindrical-shaped bag  42  having a first end  47  and a second end  49 . Bag  42  has a hollow interior cavity  44 . For purposes of illustration, bag  42  is shown to have an interior profile corresponding to straight flute drill  22 . It shall be appreciated, however, that bag  42  may also include a different interior profile depending on the particular cutting tool being produced. It shall also be understood the dimensions and/or profile of the cutting tool formed using bag  42  may differ from those of interior cavity  44 . The dimension of interior cavity  44  may be larger than the resulting cutting tool due to compacting of the carbide material used to produce the cutting tool during the forming process.  
         [0030]     Bag  42  preferably has a generally cylindrical shape with a circular cross-section. Other cross-sectional shapes, however, may also be used with satisfactory results, such as octagonal, hexagonal, and the like. Inner cavity  44  includes a pair of elongated ribs  46  protruding inward toward a center of cavity  44 . Ribs  46  are positioned opposite one another at 180 degree intervals and correspond to recessed channels  24  of straight flute drill  24 .  
         [0031]     Bag  42  is preferably made from a resilient elastic material having a Durometer hardness of approximately 35-40, such as urethane, silicone, or another material having similar physical characteristics. It is preferable the bag material be capable of withstanding multiple compression cycles involving compressive loads in excess of 30,000 psi without incurring any appreciable degradation of the physical properties of the material. Its also preferable the bag material not incur a permanent set as a result of the compressive loads.  
         [0032]     Referring also to  FIGS. 4A-5B , mold  20  includes a first end cap  48  for sealing end  47  of bag  42 . End cap  48  has a generally circular disk-shaped portion  50  having an end surface  52  engagable with end  47  of bag  42  when end cap  48  is attached to the bag. An L-shaped notch  54  extends around an entire circumference  56  of disk portion  50 . A first surface  58  of notch  52  is oriented substantially parallel to a center axis of disk portion  50  and intersects end surface  52  of disk portion  50 . A second surface  60  of notch  52  is oriented substantially perpendicular to the center axis of disk portion  50  and intersects outer circumference  56  of disk portion  50 . Surface  58  preferably has a diameter larger than the diameter of bag  42 . Although shown as having a generally circular-shaped outer perimeter, disk portion  50  may also be configured to have other shapes, such as hexagonal, octagonal, and the like. For example, if bag  42  has a hexagonal cross-sectional shape, it may be preferable that notch surface  58  also have a hexagonal shape. Similarly, it may also be desirable that outer circumference  56  also have a hexagonal shape.  
         [0033]     Extending from end surface  52  of disk portion  50  is a cylindrically-shaped boss  62  having an outer circumference surface  64 . A center axis of boss  62  substantially coincides with the center axis of disk portion  50 . Boss  62  may be integrally formed with disk portion  50 , or may be fixedly attached using any suitable method, such as brazing, welding, gluing, and the like. With end cap  48  attached to bag  42 , boss  62  extends into cavity  44 , wherein circumference  64  engages the interior periphery of cavity  44 . The outer diameter of circumference  64  is preferably larger than the diameter of cavity  44  adjacent end  47  of bag  42  to produce an interference fit between bag  42  and boss  64  when attaching end cap  48  to bag  42 .  
         [0034]     Attached to an end surface  66  of boss  62  opposite disk portion  50  is a core pin  68  for forming passage  28  of straight flute drill  22 . Although core pin  68  is: shown to have a rod-like shape, it shall be appreciated that core pin  68  may also be configured to produce a passage having a different shape, such as helical core pin  69  shown in  FIG. 14 . Core pin  68  may be permanently attached to boss  62  using any suitable means, such as welding, brazing, adhesives, and the like. Alternatively, core pin  68  may be removably attached to boss  62 , such as by threading, to enable differently configured core pins to be readily interchanged.  
         [0035]     A resilient cylindrically-shaped first transition member  70  having an outer circumference  72  adjoins end surface  66  of boss  62  opposite disk portion  50 . First transition member  70  provides an elastic transition between rigid boss  70  and interior cavity  44  of bag  42  to minimize possible flaring of the end of the cutting tool formed using mold  20 . A center axis of first transition member  70  substantially coincides with the center axis of boss  62  and disk portion  50 . First transition member  70  includes a bore  74  oriented along the longitudinal center axis of first transition member  70 . Bore  74  is engageable with core pin  68 .  
         [0036]     With end cap  48  attached to bag  42 , first transition member  70  extends into cavity  44  enabling circumference  72  of the first transition member to engage the interior periphery of cavity  44 . The outer diameter of circumference  72  preferably is larger than the diameter of cavity  44  adjacent end  47  of bag  42  so as to produce an interference fit between bag  42  and first transition member  70  when attaching end cap  48  to bag  42 . First transition member  70  is preferably made of a resilient material, such as rubber, but may also be made of another material having similar properties.  
         [0037]     End cap  48  can be attached to bag  42  by guiding core pin  68 , first transition member  70 , and boss  62  into cavity  44  of bag  42  until end surface  52  of disk portion  50  contacts end surface  47  of bag  42 . Bag  42  may be secured to end cap  48  using a strap  112   a.  Strap  112   a  is preferably placed around bag  42  and in alignment with boss  62 . Strap  112   a  can then be tightened to secure bag  42  to end cap  48 .  
         [0038]     Mold  20  further includes a second end cap  76  for sealing end  49  of bag  42  to prevent fluid from entering cavity  44  from the exterior of bag  42 . End cap  76  has a generally circular disk-shaped portion  78  having an end surface  80  that is engageable with end  49  of bag  42  when end cap  76  is attached to bag  42 . An L-shaped notch  82  extends around an entire circumference  84  of disk portion  78 . A first surface  86  of notch  82  is oriented substantially parallel to a center axis of disk portion  78  and intersects end surface  80  of disk portion  78 . A second surface  88  of notch  82  is oriented substantially perpendicular to the center axis of disk portion  78  and intersects outer circumference  84  of disk portion  78 . Surface  86  preferably has a diameter larger than the outer diameter of bag  42 .  
         [0039]     Although shown as having a generally circular outer perimeter, disk portion  78  may also be provided with a different shape, such as hexagonal, octagonal, and the like, so as to substantially mirror the shape of the outer periphery of bag  42 . For example, if the outer periphery of bag  42  has a hexagonal shape, it may be desirable that notch surface  86  likewise have a hexagonal shape. Similarly, it may also be desirable that outer circumference  84  of disk portion  78  also have a hexagonal shape.  
         [0040]     Extending from end surface  80  of disk portion  78  is a cylindrically-shaped boss  90  having an outer circumference surface  92 . A center axis of boss  90  substantially coincides with the center axis of disk portion  78 . Boss  90  may be integrally formed with disk portion  78 , or may be fixedly attached using any suitable method, such as brazing, welding, gluing, and the like. With end cap  76  attached to bag  42 , boss  90  extends into cavity  44  so that circumference  92  engages the interior periphery of cavity  44  of bag  42 . The outer diameter of circumference  92  of boss  90  is preferably larger than the interior diameter of cavity  44  of bag  42  to produce an interference fit between bag  42  and boss  90  when engaging end cap  76  with bag  42 .  
         [0041]     Mold  20  further includes a washer-shaped seal  94 . Seal  94  is positionable between end cap  76  and bag  42  when end cap  76  is attached to bag  42 . A first surface  96  of seal  94  is engagable with surface  80  of end cap  76 , while an opposite surface  98  of seal  94  is engageable with end surface  49  of bag  42 . Seal  94  includes a circular-shaped aperture  100  that is engagable with circumference  92  of boss  90 . Aperture  100  preferably has a diameter smaller than the diameter of circumference  92  to produce an interference fit between seal  94  and boss  90  when the two components are assemble together. Seal  94  is preferably made from an resilient elastic material, such as rubber, or another material having similar physical properties.  
         [0042]     A second transition member  102  having an outer circumference  104  is insertable within interior cavity  44  of bag  42 . Second transition member  102  can be engaged with inner cavity  44  of bag  42  and operates to accomplish the same general function as first transition member  70  by providing an elastic transition between rigid boss  90  and interior cavity  44  of bag  42  to minimize possible flaring of the end of the cutting tool formed using mold  20 . A threaded bore  106  is provided in one end of second transition member  102  for engaging a correspondingly threaded insertion tool  108  (see  FIG. 11 ) that can be used for inserting second transition member  102  into cavity  44 . With second transition member  102  inserted in cavity  44  of bag  42 , outer circumference  104  of second transition member  102  engages the inner periphery of cavity  44 . The outer diameter of circumference  104  preferably is larger than the inner diameter of cavity  44  adjacent end  49  of bag  42  to produce an interference fit between bag  42  and second transition member  102 . Second transition member  102  is preferably made of a resilient material, such as rubber, or alternatively, another material having similar properties.  
         [0043]     Second transition member  102  can be installed in cavity  44  of bag  42  by engaging a threaded end  110  of installation tool  108  with threaded bore  106  of second transition member  102 . With second transition member  102  attached to installation tool  108 , second transition member  106  can be inserted into cavity  44  of bag  42 , after which installation tool  108  can be detached from second transition member  102 . Seal  94  can be positioned adjacent end surface  49  of bag  42  with aperture  100  substantially aligned with the opening to cavity  44  in end  49  of bag  42 . End cap  76  can be attached to bag  42  by guiding boss  90  into cavity  44  of bag  42  until end surface  80  of disk portion  78  contacts end surface  49  of bag  42 . Bag  42  may be secured to end cap  76  using a strap  112   b.  Strap  112   b  is preferably positioned around bag  42  and in alignment with boss  90 . Strap  112   b  can then be tightened to secure bag  42  to end cap  48 .  
         [0044]     Mold  20  may also include a fill sleeve  114  and a pressure sleeve  118 . The two sleeves are not used simultaneously, with each serving a separate function. Referring also to  FIG. 8 , with end cap  76  removed from bag  42 , fill sleeve  114  can be positioned over bag  42  prior to filling bag  42  with a powdered carbide mixture  115 , or a like material having properties suitable for producing cutting tools. Filling bag  42  with carbide mixture  115  may cause bag  42  to expand due to the bag&#39;s elastic nature. Fill sleeve  114  operates to limit the amount of expansion that may occur during the filling process. Fill sleeve  114  has a generally hollow tubular shape with an inner diameter sufficiently large to allow fill sleeve  114  to be slid over bag  42 . Fill sleeve  114  and bag  42  preferably are substantially the same length. An end  116  of fill sleeve  114  is engageable with surface  52  of end cap  48  when fill sleeve  114  is placed over bag  42 . Bag  42  can be filled with a predetermined quantity of powdered carbide mixture  115 . Fill sleeve  114  can be removed from bag  42  once cavity  44  is suitably filled with carbide mixture  115 .  
         [0045]     Referring also to  FIGS. 9 and 10 , mold  42  may also include a cylindrically-shaped pressure sleeve  118 . Pressure sleeve  118  can be positioned over bag  42  so as to enclose at least a portion of the exterior periphery  120  of bag  42 . Pressure sleeve  118  provides support for bag  42  and helps maintain proper alignment of the bag during the pressure forming processes. A first end  122  of pressure sleeve  118  is engageable with notch  54  formed in end cap  48  and a second end  124  is engageable with notch  82  formed in end cap  76 . The diameter of an inner circumference  121  of first end  122  of pressure sleeve  118  is larger than the diameter of surface  58  of notch  54  to enable pressure sleeve  118  to slide over surface  58  and engage surface  60  of notch  54 . Similarly, the diameter of inner circumference  121  of end  124  of pressure sleeve  118  is larger than the diameter of surface  86  of notch  82  to enable pressure sleeve  118  to slide over surface  86  and engage surface  88  of notch  82 . The inside diameter of circumference  121  of pressure sleeve  118  is also preferably larger than the diameter of the exterior periphery  120  of bag  24  to produce a circumferential gap  126  between inner circumference  121  of pressure sleeve  118  and exterior periphery  120  of bag  42 .  
         [0046]     Each end  122  and  124  of pressure sleeve  118  includes a notched region  128  and  130 , respectively. Notched regions  128  and  130  provide access to straps  112   a  and  112   b,  and allow fluid to enter gap  126  formed between pressure sleeve  118  and bag  42  during the forming process. One or more apertures  132  extend through a wall  134  of pressure sleeve  118  for fluidly connecting the exterior region of pressure sleeve  118  with the interior region of the pressure sleeve.  
         [0047]     A cutting tool, such as straight flute drill  22 , can be formed using mold  20  by assembling bag  42  to end cap  48 . Strap  112   a  is not used to attach bag  42  to end cap  48  at this time. Fill sleeve  114  can be slid over bag  42  and end  116  of fill sleeve  114  can be engaged with end surface  52  of end cap  48 . Bag  42  can then be filled with a predetermined quantity of powdered carbide mixture  115 . To help compact carbide mixture  115  present in cavity  44  of bag  42 , end cap  48 , fill sleeve  114 , and bag  42  can be placed on a mechanical vibrating plate  134 , or another similar device. Vibrating plate  134  includes a plate  135  that can made to vibrate at a predetermined frequency. Vibrating the end cap/fill sleeve/bag assembly ( 48 , 114 , 42 ) helps to eliminate voids that could form in carbide mixture  115  and prevent cavity  44  from being filled with the desired quantity of carbide mixture  115 . Sleeve  114  can be removed from bag  42  after the bag is filled with the desired quantity of carbide mixture  115 .  
         [0048]     After bag  42  has been filled with carbide mixture  115 , end  47  of bag  42  may be secured to end cap  48  using strap  112   a.  Pressure sleeve  118  is then slid over bag  42  and end  122  of pressure sleeve  118  is engaged with notch  54  of end cap  48 . Second strap  112   b  is initially loosely installed around end  49  of bag  42 . End cap  48  may be secured to pressure sleeve  118  by releasably engaging a pair of clips  131  with a pair of pockets  133  formed in an end surface  135  of end cap  48 . Second transition member  102  can be attached to installation tool  108  and inserted into cavity  44  of bag  42  to the point where end surface  136  of second transition member  102  contacts carbide mixture  115 .  
         [0049]     End  49  of bag  42  is sealed to prevent fluid from entering cavity  44  from the exterior region of bag  42  by positioning seal  94  adjacent end  49  of bag  42 . End cap  76  is then attached to end  49  of bag  42  by guiding boss  92  of end cap  76  into cavity  44  of bag  42  until notch  82  of end cap  76  engages end  124  of pressure sleeve  118 . End cap  76  can be secured to end  49  of bag  42  by tightening second strap  112   b  around bag  42 . End cap  76  may also be secured to pressure sleeve  118  by releasably engaging a pair of clips  137  with a pair of pockets  139  formed in an end surface  139  of end cap  76 .  
         [0050]     Referring to  FIG. 13 , carbide mixture  115  can be pressed into a solid form using a known isostatic press  140 , or a similar device. Mold  20  containing carbide mixture  115  is placed in isostatic press  140 , whereupon the isostatic press is activated (see step  142 ). Isostatic press  140  utilizes a high pressure liquid, preferably operating at a pressure in excess of 20,000 psi, to apply a generally uniform compressive load to at least a portion of the exterior of mold  20 . The high pressure fluid flows through orifice  132  and notched regions  128  and  130  of pressure sleeve  118  into gap  126  formed between bag  42  and pressure sleeve  116 . The high pressure fluid present in gap  126  exerts a substantially uniform pressure along at least a portion of exterior surface  120  of bag  42 . The high pressure fluid causes bag  42  to compress radially, compacting carbide mixture  115  into a cohesive structure. Rigid pressure sleeve  118  prevents carbide mixture  115  from being compressed axially. After compressing carbide mixture  115  for a predetermined period of time, the high pressure fluid surrounding mold  20  is discharged and mold  20  is removed from isostatic press  140 .  
         [0051]     Bag  42  containing the compressed carbide mixture can be separated from mold  20  by first disengaging clips  131  from end cap  48  and clips  137  from end cap  76 . Straps  112   a  and  112   b  can then be released to allow end caps  76  and  48  to be detached from bag  42 . Bag  42  can then be withdraw from pressure sleeve  118 . Transition member  102  can be removed from cavity  44  of bag  42  using installation tool  108 . Referring to  FIG. 12  and step  144  of  FIG. 13 , a “green state” straight flute drill  22   a,  being of substantially the same configuration as straight flute drill  22  (see  FIGS. 6A and 6B ) can be extracted from bag  42  by applying a force  141  to the fluted end  32   a  of straight flute drill  22   a  to force straight flute drill  22   a  out through the access opening to cavity  44  located in end  47  of bag  42 .  
         [0052]     Continuing to refer to  FIG. 10 , in step  146  cooling passages  38  (see  FIGS. 6A and 6B ), are drilled in straight flute drill  22   a  using a drill press  148 , or another suitable tool. To ensure proper orientation of cooling passages  38 , straight flute drill  22   a  may be placed in a suitably configured fixture  149 . To facilitate machining of cooling passages  38 , it is preferable the cooling passages be drilled while straight flute drill  22   a  is in a “green state” prior to undergoing heat treatment. Alternatively, the cooling passages may be formed at any other desired stage of the forming process.  
         [0053]     After machining cooling passages  38 , straight flute drill  22   a  can be placed in a pre-sintering furnace  150  preheated to a predetermined temperature, for example 600° F. Heating straight flute drill  22   a  causes the wax binder to be removed from straight flute drill  22   a.  Straight flute drill  22   a  is maintained at the elevated temperature for a predetermined period of time after which it is removed from pre-sintering furnace  150  and allowed to cool to approximately room temperature. The heat treated straight flute drill is identified by reference number  22   b.    
         [0054]     After straight flute drill  22   b  has sufficiently cooled, an outer circumference  152  of straight flute drill  22   b  may be ground to achieve a desired surface finish and diameter using a conventional centerless grinder  154 , or another suitable apparatus (see step  151 ). Straight flute drill  22   b  can then be heated in a high temperature sintering furnace  156  preheated to a predetermined temperature in step  155 . Sintering furnace  156  is preferably capable of performing a known heating cycle so as to cause the individual particles in carbide mixture  115  to bind together and form a unitary solid straight flute drill  22   c  having certain desirable physical properties that enable straight flute drill  22   c  to function as a cutting tool. If desired, straight flute drill  22   c  may undergo further processing in step  158  after being removed from sintering furnace  156 , such as grinding cutting flutes on an end  36   c  of straight flute drill  22   c  using conventional grinding methods in step.  
         [0055]     While various aspects of the mold have been disclosed, it will be appreciated that many other variations may be incorporated without departing from the scope of the present invention. It is intended by the following claims to cover these and any other departures from the disclosed embodiments that fall within the true spirit of the invention. The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.