Abstract:
A split re-threading die includes two halves pivotally attached to each other and defining a through-bore and a hexagonal external surface when closed. Each half has inward facing teeth at the free end. The through-bore is configured to receive an externally threaded fastener to be re-threaded and the hexagonal external surface is configured to be received within a mechanical socket. The teeth rethread the fastener as the die is turned and the teeth traverse the threads of the fastener.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims the benefit of co-pending U.S. provisional patent application Ser. No. 62/096,591, filed on 24 Dec. 2014. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    It has happened to everyone. A nut is cross-threaded on a bolt and ruins the threads or the threads are damaged in some other way, for example, by exposure to the elements. In order for the bolt to be once again usable, the bolt must be rethreaded with a rethreader die. 
         [0003]    Rethreader dies are well known in the art. Many rethreader operations require starting the die at the end of the bolt and threading in a direction towards the head of the bolt. This works well when there are good threads at the end on which to start the rethreader die, but may not work well when the damaged threads are located at the end of the bolt. When this is the case, a split rethreader die is a preferred device to be used as it is able to start at a point where there are good threads. 
         [0004]    Split rethreader dies, however, may come in multiple pieces that are easy to lose or assemblies that are cumbersome to place about the bolt accurately. Accordingly, the art of split rethreader dies could benefit from a single assembly device capable of accurate placement on any part of a bolt. 
       SUMMARY OF THE INVENTION 
       [0005]    The present invention relates to a rethreader die, and more particularly to a single assembly split rethreader die capable of accurate placement on a bolt at any location having good threads. 
         [0006]    One aspect of the present invention provides a rethreader die having a first half pivotally connected to a second half at a joint; the first half and the second half combining to define a through-bore, a socket engagement portion, and a thread engagement portion; the joint located opposite the thread engagement portion; the socket engagement portion having a socket engagement portion outer surface configured to be received within a mechanical socket; and the thread engagement portion having at least one set of teeth extending inward from the through-bore and configured to engage the threads of a threaded fastener. 
         [0007]    The socket engagement portion outer surface may taper at a taper angle from the thread engagement portion through the socket engagement portion, and the taper angle may be in the range from about 0 degrees to about 15 degrees or in the range from about 0 degrees to about 10 degrees or in the range from about 0 degrees to about 5 degrees. 
         [0008]    The joint may have a first half knuckle overlapping a second half knuckle and a pin securing the first half knuckle and the second half knuckle together. 
         [0009]    Additionally or alternatively, the joint may have a cross-member attached to each of the first half and the second half with a pin and may provide that the cross-member and pins are set within a recess in the first and second halves. A relief may be provided in the first half and the second half near the joint, the relief has a relief angle provided between the first half and the second half when the rethreader die is in a rethreading position. The relief angle may be in the range from about 15 degrees to about 45 degrees or in the range from about 25 degrees to about 35 degrees or about 30 degrees. 
         [0010]    Another aspect of the present invention provides a method for repairing a threaded fastener with damaged threads and undamaged threads, including the steps of: providing a rethreader die having a first half pivotally connected to a second half at a joint; the first half and the second half combining to define a through-bore, a socket engagement portion, and a thread engagement portion; the joint located opposite the thread engagement portion; the socket engagement portion having a socket engagement portion outer surface configured to be received within a mechanical socket; and the thread engagement portion having at least one set of teeth extending inward from the through-bore and configured to engage the threads of a threaded fastener; opening the rethreader die by pivoting the first half and the second half away from each other about the pivot; receiving the fastener within the through-bore; closing the rethreader die around the fastener and engaging the at least one set of teeth with the undamaged threads; and rotating the rethreader die in a direction towards and through the damaged threads. 
         [0011]    Additionally or alternatively, the socket engagement portion outer surface of the rethreader die may taper at a taper angle from the thread engagement portion through the socket engagement portion. If this is the case the method may also include the steps of providing a mechanical socket sized to impart a circumferential force on the rethreader die when the socket engagement portion is substantially received within the mechanical socket; placing the mechanical socket around the rethreader die; and imparting a circumferential force from the mechanical socket through the at least one set of teeth of the rethreader die to the threaded fastener. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  is a perspective view of a first embodiment of a split rethreader die according to the present invention. 
           [0013]      FIG. 2  is an exploded view of the die shown in  FIG. 1 . 
           [0014]      FIG. 3  is a top view of the die shown in  FIG. 1 . 
           [0015]      FIG. 4  is a side view of the die shown in  FIG. 1 . 
           [0016]      FIG. 5  is a cross-sectional view of the die along line  5 - 5  of  FIG. 3 . 
           [0017]      FIG. 6  is a bottom view of the die shown in  FIG. 1 . 
           [0018]      FIG. 7  is a perspective view of the die shown in  FIG. 1  received within a mechanical socket. 
           [0019]      FIG. 8  is a perspective view of a second embodiment of a split rethreader die according to the present invention received within a mechanical socket. 
           [0020]      FIG. 9  is a side view of the die shown in  FIG. 8  received within a mechanical socket. 
           [0021]      FIG. 10  is a top view of a third embodiment of a split rethreader die according to the present invention. 
           [0022]      FIG. 11  is a side view of the die shown in  FIG. 10 . 
           [0023]      FIGS. 12-14  illustrate a method of using the first embodiment of the split rethreader die to rethread an external threaded fastener according to the present invention. 
           [0024]      FIG. 15  is a side view of a rethreaded fastener. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0025]    Although the disclosure hereof is detailed and exact to enable those skilled in the art to practice the invention, the physical embodiments herein disclosed merely exemplify the invention which may be embodied in other specific structures. While the preferred embodiment has been described, the details may be changed without departing from the invention, which is defined by the claims. 
         [0026]      FIG. 1  illustrates a first embodiment  100  of the split rethreader die. The split rethreader die  100  comprises a first half  110 A and a second half  110 B. 
         [0027]    Preferably the first half  110 A and the second half  110 B are substantially identical. 
         [0028]    The first and second halves  110 A,  110 B preferably have a substantially semi-circular profile and each comprise a socket engagement portion  112 A,  112 B and a thread engagement portion  118 A,  118 B. When combined, the first and second halves  110 A,  110 B have a substantially circular through-bore  130  extending from the socket engagement portions  112 A,  112 B through the thread engagement portions  118 A,  118 B. 
         [0029]    The socket engagement portions  112 A,  112 B each have an inside surface  114 A,  114 B along the through-bore  130  and an outside surface  116 A,  116 B. The joined combination of the outside surfaces  116 A,  116 B is configured to emulate the inside of a the operating end of a wrench-type hand tool (i.e., a box end wrench, an open end wrench, a crescent wrench, a mechanical socket  10  as shown in  FIG. 7 , and other similar tools as are known in the art). As shown here, for example, the socket engagement portion outside surfaces  116 A,  116 B combine to define a hexagonal socket engagement portion outer surface  116  (see  FIG. 7 ). 
         [0030]    The portion of the through-bore  130  in the combined socket engagement portions  112 A,  112 B provides a pocket  140 , whereby the pocket  140  has a first diameter D 1 . The first diameter D 1  is at least as wide as the diameter D 2  of the peaks  28  of external threads  26  of an external threaded fastener  20  (see  FIG. 14 ) to be re-threaded. 
         [0031]    The thread engagement portions  118 A,  118 B each preferably have at least one set of teeth  120 A,  120 B extending inward from the through-bore  130 . The at least one set of teeth  120 A,  120 B are configured to align with the valleys  30  of the external threads  26  of the external threaded fastener  20  (see  FIG. 14 ) to be rethreaded. 
         [0032]    As shown in  FIG. 2 , the first and second half thread engagement portion at least partially overlap with the first and second half socket engagement portion. 
         [0033]    The first and second halves  110 A,  110 B are pivotally attached to one another at joints  150  on the socket engagement portions  112 A,  112 B. The joints  150  preferably comprise interfacing knuckles  152 A,  152 B of the first and second halves  110 A,  110 B, respectively, secured together by pins or rivets  154 ; however, any means of pivotally connecting the first and second halves  110 A,  110 B which does not interfere with insertion of the die  100  into a mechanical socket  10  (see  FIG. 15 ) or the through-bore&#39;s  130  reception of an external threaded fastener  20  (see  FIG. 15 ), are contemplated herein. 
         [0034]    For example, a third embodiment  300  of a split rethreader die according to the present invention, wherein similar numbers represent similar elements, is provided in  FIGS. 10 and 11 . The split rethreader die  300  has a first half  310 A connected to a second half  310 B wherein the joint  350  comprises a pair of cross-members  324 . Each cross-member  324  is attached to the first half  310 A and the second half  310 B by a pair of pins  354 . 
         [0035]    A recess  322  is preferably provided in the first and second halves  310 A, 310 B to house the cross-members  324  and pins  354  so as limit interference with a mechanical socket  10 . As the first and second halves  310 A, 310 B do not rotate about the same axis, reliefs  326  are provided near the joints  350  to allow for rotation of the first and second halves  310 A, 310 B about the respective pins  354 . The reliefs  354  are configured between the first half and the second half at an angle α when the first and second halves  310 A, 310 B are in a rethreading position (as depicted in  FIG. 11 ). Preferably angle α is in the range from about 15 degrees to about 45 degrees, more preferably from about 25 degrees to about 35 degrees, more preferably angle α is about 30 degrees. 
         [0036]      FIGS. 8 and 9  illustrate a second embodiment  200  of a split rethreader die according to the present invention, wherein similar numbers represent similar elements. The split rethreader die  200  comprises tapered outside surfaces  216 A,  216 B on the socket engagement portions  212 A,  212 B. The first and second half socket engagement sections  212 A,  212 B have a combined exterior dimension ED at or near the first and second half threaded engagement portions  218 A,  218 B (hidden) from which the first and second half socket engagement section outside surfaces  216 A,  216 B taper inward at a taper angle θ in the direction of the joints  250 . 
         [0037]    The exterior dimension ED is preferably larger in dimension than the socket size of the mechanical socket  10  to be used in conjunction with the rethreader die  200 . The taper angle θ is preferably in the range of about 0 degrees to about 15 degrees, more preferably in the range of about 0 degrees to about 10 degrees, more preferably in the range of about 0 degrees to about 5 degrees. When in use, the mechanical socket  10  preferably imparts a circumferential force on the rethreader die  200  when the socket engagement portions  212 A, 212 B are substantially received within the mechanical socket  10  and the circumferential force is transferred through the teeth  220 A, 220 B (hidden) to the threaded fastener  20 . 
         [0038]    A method for rethreader an external threaded fastener  20  with undamaged threads  26 , damaged threads  32 , a proximal end  22 , and a distal end  24  is shown in  FIGS. 12-14 .  FIG. 12  shows the two halves  110 A,  110 B of the die  100  pivoted away from each other about pivot  154 . Looking to  FIG. 15 , the fastener  20  is shown placed within the die  100  with the two halves  110 A,  110 B brought together around the fastener  20  with the teeth  120 A,  120 B positioned within the fastener valleys  30  of undamaged threads  26  between the damaged threads  32  and the proximal end  22 . The socket engagement portions  212 A,  212 B are received within a mechanical socket  10 , then the mechanical socket  10 , along with the die  100 , are turned to move along the undamaged threads  26  of the fastener  20  in the direction of the damaged threads  32  (here the die  100  is turned counter-clockwise as the fastener  20  has right-hand threads and the teeth  120 A,  120 B are placed on the proximal side of the damaged threads  32 ). 
         [0039]      FIG. 14  illustrates the teeth  120 A,  120 B repairing the damaged threads  32  as the die  100  continues to rotate about the fastener  20  until the teeth  120 A,  120 B reach undamaged threads  26  on the distal side of the damaged threads  32  (not depicted here) or the distal end  24  of the fastener  20 . 
         [0040]    The die  100  is removed from the mechanical socket  10  and the fastener  20  to leave a re-threaded fastener  20  as shown in  FIG. 15 . 
         [0041]    The foregoing is considered as illustrative only of the principles of the invention. Furthermore, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described. While the preferred embodiment has been described, the details may be changed without departing from the invention, which is defined by the claims.