Patent Abstract:
A method in which a cutting tip is ground to form an intermediate cutting tool; a first predetermined portion of the intermediate cutting tool is masked; a wear-resistant material is deposited onto the exposed portion of the intermediate cutting tool to form a sharpened cutting tool; and a workpiece is cut with the sharpened cutting tool.

Full Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 11/580,184 filed on Oct. 12, 2006, now U.S. Pat. No. 8,703,240 which claims the benefit of U.S. Provisional Application No. 60/727,755 filed on Oct. 18, 2005. The entire disclosure of each of the above applications is incorporated herein by reference as if fully set forth in detail herein. 
    
    
     FIELD 
     The present disclosure relates to a method for forming workpieces using tool blades that are coated in a process that uses masking to partly cover the tool blades. 
     BACKGROUND 
     This section provides background information related to the present disclosure which is not necessarily prior art. 
     Many vehicle drivelines include power transmission devices having a number of gears in meshing engagement with one another. Each gear typically includes a plurality of teeth spaced apart from one another to properly mesh with the teeth of another gear. Each gear tooth must be precisely formed to provide reliable power transmission over an extended period of time. 
     The gears are constructed using gear cutting tools operable to remove material from a gear blank to define the gear teeth. In high volume manufacturing, it is desirable to quickly and accurately cut the gear teeth into a desired finished shape. It is also desirable to minimize the costs associated with constructing such gears. Accordingly, tooling design engineers strive to define manufacturing processes where not only the finished gear is constructed according to specification but where the cutting tools remain sharp for extended periods of time. A number of cutting tool manufacturers have constructed cutting tools from high speed steel, tungsten carbide and other cutting materials. In one instance, tool life has been extended by coating a tungsten carbide tool with a wear resistant material such as titanium aluminum nitride. Titanium nitride may be used as a coating for high speed steel applications. The coating is typically applied by immersing the tool in an environment containing a mixture of gas including titanium aluminum nitride or titanium nitride for six to eight hours. During exposure to the gas mixture, a coating is deposited on all surfaces exposed to this environment. Cutting tools exposed to this process have exhibited up to double the cutting life of similar tools not coated with the wear resistant material. 
     Once a cutting tool has become dull, it is common practice to grind the tip of the cutting tool to sharpen and/or redefine the cutting edge or edges. Unfortunately, the grinding process removes the coating previously applied to the cutting surfaces. Typically, the entire tool is exposed to the coating process once again to assure that the recently ground surfaces are coated. Because not all of the cutting tool is ground during the sharpening process, most of the cutting tool receives an additional coating thickness of the wear resistant material. It has been found that this grinding and recoating process may be repeated approximately five times until an undesirable result occurs. Specifically, once five or more layers of the coating are accumulated on the non-ground surfaces, the coating no longer properly adheres and causes the tool to fail. 
     It has been contemplated to remove the coating from the entire cutting tool prior to recoating using a chemical process. The chemical process negatively affects the cutting tool by removing the Cobalt from the cutting tool surface. The carbide microstructure is adversely altered and no longer exhibits the excellent cutting properties for which the tool is designed. 
     Alternately, it has been contemplated to machine more surfaces of the cutting tool to remove the previous coatings prior to reapplying another coating to the reground cutter. Unfortunately, the additional machining processes are very costly and may negatively interfere with the geometry of the cutting tool and repeatability of the machining operation. Accordingly, a need exists for a method of sharpening and recoating a cutting tool to extend the interval between cutting tool sharpening operations and to increase the number of times a given tool may be sharpened. 
     SUMMARY 
     This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features. 
     In one form, the present teachings provide a method for forming a sharpened cutting tool. The method includes: grinding a cutting tip to form an intermediate cutting tool, the cutting tip of the intermediate cutting tool comprising a planar face and a sharpened cutting edge at a distal end of the planar face, the cutting tip being relieved on a side and an end that cooperate with the planar face to define the sharpened cutting edge; masking the intermediate cutting tool such that a first predetermined portion of the planar face is exposed and a second predetermined portion of the planar face is not exposed, the exposed portion of the planar face including the sharpened cutting edge and including at least portions of the end and the side that cooperate to define the cutting edge; and depositing a wear-resistant material onto the exposed portion of the planar face of the intermediate cutting tool to form the sharpened cutting tool. 
     In another form, the present teachings provide a method for forming a sharpened cutting tool. The method includes: grinding a cutting tip to form an intermediate cutting tool, the cutting tip of the intermediate cutting tool comprising a planar face and a sharpened cutting edge at a distal end of the planar face, the cutting tip being relieved on a side and an end that cooperate with the planar face to define the sharpened cutting edge; masking the intermediate cutting tool such that a first predetermined portion of the planar face is exposed and a second predetermined portion of the planar face is not exposed, the second predetermined portion being spaced apart from the sharpened cutting edge; and depositing a wear-resistant material onto the first predetermined portion of the cutting tip of the intermediate cutting tool to form the sharpened cutting tool, the wear-resistant material not being deposited on the second predetermined portion of the cutting tip of the intermediate cutting tool. 
     In yet another form, the present teachings provide a method that includes: grinding a cutting tip to form an intermediate cutting tool, the cutting tip of the intermediate cutting tool comprising a planar face and a sharpened cutting edge at a distal end of the planar face, the cutting tip being relieved on a side and an end that cooperate with the planar face to define the sharpened cutting edge; masking the intermediate cutting tool such that a first predetermined portion of the planar face is exposed and a second predetermined portion of the planar face is not exposed, the exposed portion of the planar face including the sharpened cutting edge and including at least portions of the end and the side that cooperate to define the cutting edge; depositing a wear-resistant material onto the exposed portion of the planar face of the intermediate cutting tool to form a sharpened cutting tool; and forming a workpiece, the workpiece being cut with the sharpened cutting tool. 
     In still another form, the present teachings provide a method that includes: grinding a cutting tip to form an intermediate cutting tool, the cutting tip of the intermediate cutting tool comprising a planar face and a sharpened cutting edge at a distal end of the planar face, the cutting tip being relieved on a side and an end that cooperate with the planar face to define the sharpened cutting edge; masking the intermediate cutting tool such that a first predetermined portion of the planar face is exposed and a second predetermined portion of the planar face is not exposed, the second predetermined portion being spaced apart from the sharpened cutting edge; depositing a wear-resistant material onto the first predetermined portion of the cutting tip of the intermediate cutting tool to form the sharpened cutting tool, the wear-resistant material not being deposited on the second predetermined portion of the cutting tip of the intermediate cutting tool; and cutting a workpiece with the sharpened cutting tool. 
     Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
    
    
     
       DRAWINGS 
       The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure. 
         FIG. 1  is perspective view of an exemplary cutting tool; 
         FIG. 2  is an exploded perspective view of a fixture operable to hold and mask cutting tools during a coating process; 
         FIG. 3  is a top view of a portion of the fixture illustrated in  FIG. 2  having a plurality of cutting tools positioned therein; 
         FIG. 4  is an end view of the fixture illustrated in  FIG. 2  having a plurality of cutting tools positioned therein; 
         FIG. 5  is a partial fragmentary plan view of a portion of a cutting tool and a portion of a mask positioned on the cutting tool; and 
         FIG. 6  is an exploded perspective fragmentary view illustrating alternate embodiment masks. 
     
    
    
     Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings. 
     DETAILED DESCRIPTION 
     Example embodiments will now be described more fully with reference to the accompanying drawings. 
       FIG. 1  depicts an exemplary cutting tool  10  operable to remove material from a gear blank and form a portion of the gear teeth. Typically, cutting tools are arranged in pairs where the first tool of the pair removes material from one side of the “V-shaped” groove and the other tool having an opposite hand removes material from the opposite side of the same “V-shaped” groove. Depending on the gear to be manufactured, many pairs of cutting tools may be mounted to a cutting head (not shown) to form a gear. 
     Cutting tool  10  is formed from an elongated bar of tungsten carbide having a rectangular cross-section. Cutting tool  10  includes a gripping portion  12  having a width  14  and height  16 . Gripping portion  12  maintains a substantially rectangular cross-section. Gripping portion  12  includes a top face  18 . A cutting tip  20  is formed at an opposite end of cutting tool  10  from gripping portion  12 . Cutting tip  20  is formed by machining a cutting face  22  at a 12° angle to top face  18 . Cutting tip  20  includes a first side  24  and a second side  26 . The first and second sides terminate at a rounded root cutting portion  28 . The intersection of cutting face  22  and first side  24  forms a cutting edge  30  operable to remove material from the gear blank. Second side  26  is shaped to provide clearance for the opposite hand cutting element (not shown) paired with cutting tool  10 . An edge  32  formed at the intersection of cutting face  22  and second side  26  does not typically remove any material from the gear blank. 
     As previously described, after a number of gears have been cut, cutting edge  30  dulls. At this time, cutting tool  10  is removed from the gear cutting apparatus and sharpened. During sharpening, the cutting tool is ground along first side  24 , second side  26  and rounded root cutting portion  28 . The grinding forms a sharpened cutting edge  30 . After cutting tool  10  has been sharpened, first side  24 , second side  26  and rounded root cutting portion  28  will no longer be coated by the previously deposited wear resistant coating. Accordingly, sharpened cutting tools are prepared to be exposed to an environment within an enclosed chamber (not shown) to coat cutting edge  30 , first side  24 , second side  26  and rounded root cutting portion  28  with the wear resistant material. 
     After sharpening, cutting tool  10  is thoroughly cleaned to remove any dirt, oil or metal shavings from the surfaces of the cutting tool  10 . A single sharpened cutting tool  10  or a number of sharpened cutting tools similar to cutting tool  10  are next placed in a fixture  100  illustrated in  FIGS. 2-4 . Fixture  100  is operable to accurately align a number of cutting tools relative to one another and mask a majority of the external surfaces of the cutting tools from exposure to an environment containing a wear resistant coating. Fixture  100  is sized to support the cutting tools  10  in the enclosed chamber having a mixture of gases and titanium aluminum nitride and/or titanium nitride coating circulating throughout the chamber. The surfaces exposed to the environment within the chamber are coated with a predetermined thickness of wear resistant material based on the time of exposure to the environment in the chamber. 
     To assure that less than five thicknesses of wear resistant coating are present on cutting tip  20  at any one time, fixture  100  is sized and shaped to expose only a very limited portion of each cutting tool  10  to the environment within the chamber. Specifically, the surface of the portion of cutting tool  10  that is exposed to the environment approximately corresponds to the portion of cutting tool  10  that would be removed when cutting tool  10  is resharpened.  FIG. 5  depicts the amount of cutting face  22  exposed after mounting and masking the cutting tools  10  within fixture  100 . In this manner, only one or two thicknesses of wear resistant coating are on cutting edge  30  at any one time. By maintaining a proper thickness of wear resistant coating, tool life is greatly extended. 
     Fixture  100  includes a shell  110 , a cover  112  and a mask  114 . Shell  110  is a substantially “U” shaped member having a first side wall  116 , a second side wall  118  and an end wall  120  interconnecting the side walls. End wall  120  includes a substantially planar top surface  122  extending between first side wall  116  and second side wall  118 . First side wall  116  includes a substantially planar upper surface  124 . Second side wall  118  includes a substantially planar upper surface  126 . Upper surface  124  and upper surface  126  are substantially co-planar with one another. Threaded apertures  128  extend transversely through first side wall  116 . Threaded bores  130  are positioned in first side wall  116  and extend through upper surface  124 . Threaded bores  132  are positioned within second side wall  118 . Bores  132  extend through upper surface  126  of second side wall  118 . 
     Cover  112  is substantially shaped as a plate having a hat-shaped cross-section. Cover  112  includes a body portion  134  and laterally extending flanges  136 . Flanges  136  include lower surfaces  138 . Body portion  134  includes a lower surface  140 . Apertures  142  extend through the thickness of cover  112 . Apertures  142  are sized and positioned to receive threaded fasteners  144 . Threaded fasteners  144  threadingly engage bores  130  and bores  132  formed in shell  110 . Fasteners  144  are operable to clamp cutting tools  10  and mask  114  between top surface  122  of end wall  120  and bottom surface  140  of cover  112 . 
     Mask  114  is a plate-like structure having a plurality of teeth  150  formed at one end. Each tooth  150  includes a first face  152  and a second face  154  interconnected by a rounded end  156 . First face  152 , second face  154  and rounded end  156  are shaped substantially similarly to first side  24 , second side  26  and rounded root cutting portion  28  of cutting tip  20 . Furthermore, each tooth  150  is spaced apart a distance equivalent to the spacing between adjacent cutting tips  20  of cutting tools  10  when positioned adjacent to one another. As best illustrated in  FIG. 4 , each tooth  150  includes an angled back face  158  positioned to engage one of the cutting faces  22  formed on each cutting tool  10 . 
     After the individual cutting tools  10  have been sharpened, a number of cutting tools are positioned within shell  110 . Cutting tips  20  are aligned along a common plane and then cutting tools  10  are mounted to shell  110  using a pair of threaded fasteners  160 . Threaded fasteners  160  are threadingly engaged with apertures  128  and protrude through first side wall  116  to engage one of the cutting tools positioned within shell  110 . A compressive load is placed on each of the cutting tools via threaded fasteners  160  to secure the cutting tools within the shell. 
     One skilled in the art will appreciate that any number of manufacturing techniques may be used to align cutting tips  20  along the common plane. For example, a cap  200  may be temporarily coupled to shell  110  to provide a datum surface  202  on which each of the cutting tools are abutted prior to clamping cutting tools  10  to shell  110 . Specifically, cap  200  is a substantially “C” shaped member having a wall  204  interconnecting a first leg  206  and a second leg  208 . First leg  206  includes an aperture  210  extending therethrough for receipt of a fastener  212 . Fastener  212  is threadingly engageable with an aperture  214  formed in first side wall  116 . Similarly, second leg  208  includes an aperture  216  for receipt of another fastener  212  threadingly engaged with an aperture  218  formed in second side wall  118 . Datum surface  202  is formed on wall  204  and spaced apart a predetermined distance “B” from an end surface  230  of shell  110 . 
     Cap  200  may also be used to properly position mask  114  relative to the cutting tools  10 . Alternatively, mask  114  may include a key or a pin (not shown) to align mask  114  relative to shell  110  at a predetermined location. Because teeth  150  of mask  114  are similarly shaped to cutting tips  20  of cutting tool  10 , mask  114  is axially offset from the plurality of cutting tools  10  such that teeth  150  formed on mask  114  do not completely cover the entire cutting face  22  of each cutting tool  10 . As illustrated in  FIG. 5 , rounded end  156  is offset from rounded root cutting portion  28  by a predetermined distance. In the example shown, the predetermined distance is 1 mm. It should be appreciated that this distance may vary depending on the amount of cutting tool that must be removed during each grinding or sharpening process. Furthermore, because rounded end  156  is offset from rounded root cutting portion  28 , a portion of cutting face  22  adjacent cutting edge  30  and edge  32  is exposed to atmosphere. Based on the orientation of the components previously described, each cutting tool  10  will receive a coating of wear resistant material on first side  24 , second side  26 , rounded root cutting portion  28 , cutting edge  30 , edge  32  and a relatively small portion of cutting face  22 . 
     Once the positioning of cutting tool  10  and mask  114  is completed, fasteners  144  interconnect cover  112  and shell  110  to clamp cutting tools  10  and mask  114  therebetween. The subassembly of cutting tools and fixture  100  are placed within an enclosed vessel and the portions of each of the cutting tools  10  exposed to atmosphere are coated with a predetermined thickness of wear resistant material. 
     Upon completion of the sharpening and coating processes, the cutting tools are mounted to a cutting head and used to manufacture gears once again. Once the cutting tools  10  are dull, the tools are removed and the sharpening and coating processes are repeated. It should be appreciated that the external surfaces of cutting tools  10  that were previously coated are now removed during the sharpening process. Therefore, an undesirable amount of wear resistant coating is not accumulated at any time through tool life. 
     An alternate embodiment mask assembly  300  is depicted at  FIG. 6 . A plurality of masks  302  are used in conjunction with shell  110 . Each mask  302  is shaped substantially similar to the cutting end of a cutting tool  10 . Each mask  302  is positioned substantially similarly as teeth  150  were positioned relative to cutting tips  20  in the previous embodiment. It is contemplated that masks  302  may be used in place of mask  114  and vice versa. 
     The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.

Technology Classification (CPC): 2