Abstract:
Bits configured for drilling rock that are of the type that includes a plurality of teeth supported in pockets that are on a cutting face that is driven to rotate. The pockets are configured to allow the teeth to passively rotate while in the pockets. The present disclosure provides a bit having hardfacing around the pockets and related methods.

Description:
[0001]    This application is being filed on 30 Nov. 2011, as a PCT International Patent application in the name of Vermeer Manufacturing Company, a U.S. national corporation, applicant for the designation of all countries except the US, and Randy R. Runquist, Keith Hoelting and Chris Fontana, citizens of the U.S., applicants for the designation of the US only, and claims priority to U.S. Provisional Patent Application Ser. No. 61/418,772, filed Dec. 1, 2010, which is incorporated herein by reference. 
     
    
     TECHNICAL FIELD 
       [0002]    The present disclosure provides a drill bit with hardfacing in the vicinity of a rotary tooth located on a cutting face and a method of manufacturing the same. 
       SUMMARY 
       [0003]    Bits configured for drilling rock that are of the type that includes a plurality of teeth supported in pockets that are on a cutting face that is driven to rotate. The pockets are configured to allow the teeth to passively rotate while the teeth are secure in the pockets. The present disclosure provides a bit having hardfacing in the vicinity of the pockets and related methods. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0004]      FIG. 1  is a perspective view of a drill bit according to the principles of the present disclosure; 
           [0005]      FIG. 2  is a perspective view of the drill bit of  FIG. 1  with the rotatable teeth removed; 
           [0006]      FIG. 3  is an end view of the drill bit of  FIG. 1 ; 
           [0007]      FIG. 4  is a partial cross-sectional view of the drill bit of  FIG. 1  showing a plug within a tooth pocket; 
           [0008]      FIG. 5  is a partial cross-sectional view of the drill bit of  FIG. 1  showing the plug removed from the tooth pocket; 
           [0009]      FIG. 6  is a partial cross-sectional view of the drill bit of  FIG. 1  showing a tooth within the tooth pocket; 
           [0010]      FIG. 7  is a perspective view of an alternative embodiment to the drill bit shown in  FIG. 1 ; 
           [0011]      FIG. 8  is a side view of the drill bit of  FIG. 1 ; 
           [0012]      FIG. 9  is a side view of the drill bit of  FIG. 1  at a different orientation than is shown in  FIG. 8 ; and 
           [0013]      FIG. 10  is an end view of the drill bit of  FIG. 1  oriented parallel to the angled surface on the drill bit. 
       
    
    
     DETAILED DESCRIPTION 
       [0014]    The present disclosure is directed to bits configured for drilling rock. The bit  10  includes a distal cutting end  12  and a proximal mounting end  14 . The mounting end  14  is configured to mount to a component that drives rotation of the bit  10  (e.g., sonde housing, pilot/starter drill rod, drill rod, etc.) about its central axis AA. 
         [0015]    In the depicted embodiment, the distal cutting  12  end includes a plurality of pockets  16 ,  18 ,  20 , each pocket configured to support a cutting tooth  22 ,  24 ,  26  such that the tooth is free to rotate passively about a longitudinal axis BB of the tooth (see  FIG. 6 ). In other words, the teeth rotate about axis AA with the cutting end and are also free to rotate passively about axis BB relative to the cutting end. In the depicted embodiment, the distal cutting end  12  includes three pockets and three teeth. However, it should be appreciated that many other configurations are possible. 
         [0016]    In the depicted embodiment the distal cutting end  12  defines a cutting face  28  having hardfacing thereon (hexagon shapes illustrate hardfacing in  FIGS. 1 and 2 ). In the depicted embodiment the cutting face  28  is a generally domed shaped partial ring having a periphery defined by straight lines  30 ,  32  and curved lines  34  and  36 . However, it should be appreciated than many other cutting face configurations are also possible. 
         [0017]    In the depicted embodiment the bit  10  includes angled surface  38  that defines a leading edge  40  at a junction between the angled surface  38  and the distal cutting end  12 . In the depicted embodiment the angled surface  38  extends radially outwardly towards the mounting end. In the depicted embodiment, the pocket  16  is a lead pocket when the drill string is rotated in a clockwise direction. The lead pocket  16  is configured to support a cutting tooth such that the tooth  22  extends past a plane defined by the angled surface  38  ( FIGS. 9 and 10 ). In other words, the lead pocket  16  is arranged and configured such that a portion of the tooth  22  engages the drilling medium (e.g., rock) before other portions of the bit engage the drill medium. The depicted configuration provides a drill bit that drills effectively and is relatively easy to steer. 
         [0018]    In a depicted embodiment the minimum distance between the leading edge  40  and a periphery edge of the lead pocket  16  is less than 0.5 inches (e.g., 0.33 of an inch). In a depicted embodiment the hardfacing is provided in the narrowest portion between the lead pocket  16  and the leading edge  40 . It should be appreciated that many other configurations are also possible. 
         [0019]    In the depicted embodiment, hardfacing is provided on substantially the entire cutting face  28  (e.g., at least seventy-five percent of the face, at least ninety percent of the cutting face, etc.). The hardfacing on the cutting face  28  avoids the need to also provide carbide buttons  42  thereon. In the depicted embodiment the carbide buttons  42  are provided around the side surface  44  of bit  10 . However, it should be appreciated that in alternative embodiments, less of the cutting face  28  may be covered by hardfacing and/or carbide buttons  42  may also be provided on the cutting face  28 . 
         [0020]    In the depicted embodiment the hardfacing is provided near the edge of the pockets  16 ,  18 ,  20 . In a depicted embodiment at least some of the hardfacing is provided within one-thirty second of an inch from a periphery edge of the pocket. For example, right up to the edge of the pocket (zero offset as shown in  FIGS. 3 ,  4 ,  5  and  6 ; less than 1/32, less than 1/64 offset, etc.). 
         [0021]    The present disclosure also provides a method of manufacturing a drill bit. The method includes the step of inserting plugs  46  into the plurality of pockets  16 ,  18 ,  20 . The plugs facilitate the hardfacing process by preventing hardfacing material from entering the pockets, which could otherwise cause interference between the teeth  22 ,  24 ,  26  and the pockets  16 ,  18 ,  20  and hinder the passive rotation of the teeth while in the pocket. 
         [0022]    In the depicted embodiment, the use of the plugs allows for hardfacing right up to and around the periphery edge of the pockets  16 ,  18 ,  20 , which is also the edge of the plugs. In some embodiments hardfacing is provided around the entire periphery edge of the pocket by hardfacing right up to and around the entire periphery edge of the plug. In a depicted embodiment the plugs are snuggly fit into the pockets. For example, the plugs include a maximum cross-sectional dimension that is within one-sixteenth of an inch (1.59 millimeters) of a maximum cross-sectional dimension of the pockets. In a depicted embodiment the plugs includes a first cylindrical portion  48  and a second cylindrical portion  50 , the first cylindrical portion  48  including a larger diameter than the second cylindrical portion  50 . In the depicted embodiment the plugs include a brass exterior portion, which facilitates their removal from the pockets after the hardfacing. 
         [0023]    In the depicted embodiment, the plugs are removed from the bit after the hardfacing process, and teeth are inserted into the plurality of pockets. The teeth include a larger cylindrical portion  52  and a smaller cylindrical portion  54 . The diameter of the larger cylindrical portion of the plug is between one-sixteenth of an inch to one-thirty second of an inch greater than the diameter of the larger cylindrical portion of the teeth. In the depicted embodiment the diameter of the second cylindrical portion of the plug is between one-sixteenth to one sixty-fourth greater than the diameter of the smaller cylindrical portion of the teeth. This configuration provides more clearance between the pocket and the teeth at its distal end which is adjacent to the hardfacing, and less clearance between the pocket and the teeth at its proximal end. This configuration allows the teeth to rotate during operation relative to the cutting face. The rotation results in more effective drilling and more even wear of the teeth. 
         [0024]    The above specification, examples and data provide a complete description of the manufacture and use of the composition of the invention. Since many embodiments of the invention can be made without departing from the spirit and scope of the invention, the invention resides in the claims hereinafter appended.