Abstract:
The present disclosure is directed toward a compound relief tap, and more specifically, to a compound relief tap with domains made of a plurality of consecutive threads where each domain has different properties associated with variable thread parameters and variable geometrical arrangements such a variation of a taper angle and relief angles for different portions of domain threads or between domains. In a first embodiment, all of the threads in a domain have a given geometrical arrangement. In a second embodiment, several of the threads of the domain possess the geometrical arrangement. In a third embodiment, only the thread of the domain possesses the geometrical arrangement. And in a fourth embodiment, alternative threads in the domain possess the geometrical arrangement. What is also contemplated is a variation in geometrical arrangement between successive domains for any of these threaded domains.

Description:
RELATED APPLICATION 
       [0001]    This application is a divisional application that claims priority to and the benefit of co-pending U.S. patent application Ser. No. 11/857,256, entitled “Compound Relief Tap,” which was filed on Sep. 18, 2007, the disclosure of which is incorporated herein by reference. 
     
    
     FIELD OF THE DISCLOSURE 
       [0002]    The present disclosure is directed toward a compound relief tap, and more specifically, to a compound relief tap with domains made of a plurality of consecutive threads where each domain has different properties associated with variable thread parameters and variable geometrical arrangements such a variation of a taper angle and relief angles for a different portions of domain threads or between domains. 
       BACKGROUND OF THE INVENTION 
       [0003]    Threads are used to convert torque into linear force between two elements. The first element has male threads on its outer surface and it is screwed into a second element with female threads on the inner surface of an opening, or vice versa. To form threads on the inner surface of an opening, a hole is generally drilled using a drill bit. The drill bit, because of its rapid speed of rotation, leaves the surface of the hole flat. Threads must be added to the surface in a second step using a tap. 
         [0004]    Taps are cutting tools used to create screw threads in solid substances including but not limited to metal, wood, or plastic by shaving away thread shapes on the inner surface of a cylindrical hole. Male taps (i.e., taps capable of forming female threads inside of holes) are generally sold in the form of a long cylindrical tool body tool with a threaded length and a shank often equipped with an end portion for positioning the tap in a torque creating support. A user attaches the tap inside the torque support, places the tap on the hole, and screws the tap into the hole to create threads. Taps often include flute openings made longitudinally along the thread length and define lands with threaded surfaces where chips of removed material from the surface of the hole are pushed for removal.  FIG. 4  shows a tap  100  placed inside a torque creating support  36  operated by a user  40  and stabilized in a grip  38 . 
         [0005]    In one device from the prior art shown in  FIG. 1 , the tap has a series of regularly spaced and identically shaped threads along the entire thread length. As a result, the user must place a very high level of torque in the first couple of threads where all of the metal is shaved away from the hole. Over time, the high torque placed upon the first few threads dulls the tap&#39;s cutting edges and results in a tap where the torque needed to operate the tool increases substantially. Other taps have tried with some level of success to correct this inherent problem. 
         [0006]      FIG. 2  shows a tap where, while the pitch and the minor diameter of each thread remains constant over the thread length, the major diameter (or outside diameter) is progressively increased until the desired thread geometry is reached. Consequently, each thread removes a thinner layer of material and less torque is required to operate the first few threads of the tap. This type of tap creates more problems than it resolves. For example, the user is no longer capable of creating completely formed threads over the entire length of a hole to be threaded. To produce the threads, the tap must be inserted throughout the threaded length. These taps are not capable of threading holes with closed bottoms where threads are needed over the entire length of the hole. In addition, as the tap is inserted, more threads are needed to cut the surface of the material, each cutting at a lesser thickness. As a consequence, a higher torque may be expected based on a greater frictional surface and cutting surface between the tap and the hole. 
         [0007]      FIG. 3  illustrated another unsuccessful attempt at alleviating these problems, where a chamfer angle is created in the first threads to cut threads with the right pitch but where less material is removed by increasing the chamfer angle, the major diameter of the crest of each thread. Efforts to soften chamfer torque and associated heat and wear by modifying threads only results in a greater instability of operations and an inability to operate the tap at different depths. 
         [0008]    What is needed is a tap designed for longer tool life by limiting flank wear and reducing operating heat and torque by selectively placing effective cutting surfaces at the adequate positions while relieving some of the inoperative sections of threads to limit friction associated with torque and heat. 
       BRIEF SUMMARY OF THE INVENTION 
       [0009]    The present disclosure is directed toward a compound relief tap, and more specifically, to a compound relief tap with domains made of a plurality of consecutive threads where each domain has different properties associated with variable thread parameters and variable geometrical arrangements such a variation of a taper angle and relief angles for a different portions of domain threads or between domains. In a first embodiment, all of the threads in a domain have a given geometrical arrangement. In a second embodiment, several of the threads of the domain possess the geometrical arrangement. In a third embodiment, only the thread of the domain possesses the geometrical arrangement. And in a fourth embodiment, alternative threads in the domain possess the geometrical arrangement. What is also contemplated is a variation in geometrical arrangement between successive domains for any of these threaded domains. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    The features of the present disclosure are believed to be novel and are set forth with particularity in the appended claims. The disclosure may best be understood by reference to the following description taken in conjunction with the accompanying drawings, where the figures that employ like reference numerals identify like elements. 
           [0011]      FIG. 1  is side view of a first tap from the prior art. 
           [0012]      FIG. 2  is a side view of a chamfered tap from the prior art with a constant chamfer. 
           [0013]      FIG. 3  is a side view of second chamfered tap from the prior art with variable thread height. 
           [0014]      FIG. 4  is an illustration of a fluted tap with a torque-creating support in a piece secured to a vice grip according to a first embodiment of the present disclosure. 
           [0015]      FIG. 5A  is a side view used to illustrate schematically the nomenclature of tap cutting tools. 
           [0016]      FIG. 5B  is a detail of one of the lands located between two flutes of the tap cutting tool of  FIG. 5A . 
           [0017]      FIG. 5C  is a top view of the tap cutting tool of  FIG. 5A  as seen from the cut line  5 C- 5 C as shown in  FIG. 5A . 
           [0018]      FIG. 5D  is a sectional view without shading of the tap cutting tool of  FIG. 5A  as seen from the cut line  5 D- 5 D as shown in  FIG. 5A . 
           [0019]      FIG. 6  is a segmented view of a tapered threaded region with domains of a compound relief tap according to a first embodiment of the present disclosure. 
           [0020]      FIG. 7  is a segmented view of a tapered threaded region with domains of a compound relief tap according to another embodiment of the present disclosure. 
           [0021]      FIG. 8  is a volumetric partial section view of a domain of a compound relief tap with major diameter relief according to another embodiment of the present disclosure. 
           [0022]      FIG. 9  is a volumetric partial section view of a domain of a compound relief tap with pitch relief according to another embodiment of the present disclosure. 
           [0023]      FIG. 10  is a volumetric partial section view of a domain of a compound relief tap with negative pitch flank relief according to another embodiment of the present disclosure. 
           [0024]      FIG. 11  is a volumetric partial section view of a domain of a compound relief tap with heel relief according to another embodiment of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0025]    The present invention is not limited to the particular details of the device depicted and other modifications and applications may be contemplated. Further changes may be made in the above-described device without departing from the true spirit of the scope of the invention herein involved. It is intended, therefore, that the subject matter in the above depiction should be interpreted as illustrative, not in a limiting sense. 
         [0026]    This disclosure relates to an improvement to a tap  100  designed to improve tool life. Tools are made of metal, and while a hard substance, they present some level of ductility when cutting other, softer metals. A cutting edge pushing into metal may be dulled if abrasion occurs locally and heats up due to local friction associated with cutting speeds, torque, and surface polish of the tool. Tool life depends on a plurality of factors including flank wear, hardness, cutting speed, surface temperature, torque, relief of threads, depth of cut, and feed rate. The relief of surfaces on threads that do not serve to enhance the mechanical operability of the tap  100  only increase friction between the tap  100  and the hole surface to be tapped. 
         [0027]      FIG. 4  illustrates how the tap  100  is operated by a user  40  to cut threads into a hole made in a block of material. The block is held in a vice grip  38  vertically using a torque-creating support  36 , such as a small block with lateral support, movable by rotating two horizontal handles placed on each side of the torque-creating support  36 . A user  40  then applies torque by rotating the handles in the horizontal plane. While a manual torque-creating support  36  is shown, what is contemplated within this disclosure is the use of any type of tap  100 , using any engaging mechanism to rotate the tap and thus activate the cutting edges  150  shown in  FIG. 5B  about a longitudinal axis  4  as shown in  FIG. 5A . 
         [0028]      FIG. 5A  illustrates a tap  100  with an overall length  6  that may be separated into a thread length  8  and a shank length  10  of a fixed shank diameter  2 . The ratio of these two lengths is purely illustrative, and it is understood that these lengths vary according to the model and type of tap  100 . The shank length  10  can also include a driving length  28  where the tap  100  is secured to a torque-creating support. This driving length  28  is also of a geometry as shown in  FIG. 5C  to allow for the coupling of the tap  100  to any needed torque-creating support. While a square attachment  30  is shown, any attachment is contemplated. 
         [0029]    Flutes  18  as shown in  FIG. 5D  separate lands  22  created in the threaded length  8  between two consecutive flutes  18 . In one embodiment as shown in  FIG. 5D , four flutes  18  are positioned at 90 degrees circumferentially around the thread length  8 . Other taps may have flutes  18  of smaller radii, variable curvature, placed around a cylindrical tool body or minor diameter  12  of different size to create a tap  100  with five or more flutes  18  or three or less flutes  18 . What is also shown is a tap  100  with straight flutes  18  as shown in  FIG. 5A . What is also contemplated is the use of helical angle, a spiral, or any other type of flute  18  that is not aligned with the longitudinal axis  4  of the tap  100 . 
         [0030]    Returning to  FIG. 5A , the threaded length  8  comprises a series of threads shown in V shape having a thread lead angle  26  corresponding to a pitch or average median thread distance between two consecutive threads. In some embodiments, as shown by dashed lines, the tap  100  includes a point  20 .  FIG. 5D  is a sectional view without shading of the tap cutting tool of  FIG. 5A  as seen from the cut line  5 D- 5 D as shown in  FIG. 5A . This section shows the land width  14 , a section with threads having a minor diameter  156  and a major diameter  155 .  FIGS. 5A-5D  show that the cylindrical tool body of the tap  100  includes a longitudinal axis  4  rotatable about the longitudinal axis  4  and having successively, a shank of shank length  10  and a threaded length  8  with at least a flute  18  for creating at least a land  22  with a front cutting surface  150  with a cutting edge  140  and a heel  130  as shown in  FIG. 8 . Each thread in the threaded length  22  is defined by a minor diameter  156  as the base  96  of a thread a major diameter  155  as the crest  94  of the thread with a leading flank  92  and a trailing flank  131  intersecting at a crest  94  separated by an adjacent thread by a pitch  132  measured at a pitch diameter  133 . 
         [0031]    The threaded length  8  is also divided into a series of successive domains  8 A,  8 B,  8 C,  8 D, etc. as shown in  FIG. 6 , each domain having a fixed number of successive threads  70  along the threaded length  8  and each having a geometrical arrangement. While four successive domains  8 A to  8 D are shown, what is contemplated is the use of any number of domains, based on the total length of the threaded length  8 . In one contemplated embodiment, a tap  100  has between 30 and 90 threads and can be divided into any number of domains consisting of at least 2 threads.  FIG. 6  also shows a proposed angle of rotation  44  for the threaded length  8 . 
         [0032]    In one embodiment as shown in  FIGS. 6 and 7 , the geometrical arrangement is a taper angle Phi (Φ) shown as Φ 1 , Φ 2 , Φ 3 , and Φ 4 .  FIG. 6  shows tapered consecutive domains with the same taper angle measured either at the major diameter  50  or the pitch diameter  52 .  FIG. 7  shows a tap  100  where each domain has a different taper angle Φ 1 , Φ 2 , Φ 3 , and Φ 4  measured either from the major diameter  54 ,  56 ,  58 , and  60 , or measured from the pitch diameter  62 ,  64 ,  66 , and  68 . The taper angle Φ may be a front taper Φ 3  and Φ 4 , a back taper Φ 1 , or no taper Φ 2  for each successive domain. In another embodiment, the taper angle Φ is defined in relation to the minor diameter. 
         [0033]    In another embodiment, shown in  FIGS. 5B , and  8  to  11 , the geometrical arrangement is a thread cutting edge relief  32  as shown on  FIG. 5B   98  for each of the fixed number of successive threads in each successive domain.  FIGS. 5B and 8  show a thread cutting edge relief  32  that may be an eccentric relief  86 , a con-eccentric relief  84  (with concentric margin  88 ), or a concentric relief  82  for each successive domain. As shown in  FIG. 8 , the thread cutting edge relief  32  is defined in relation to the major diameter  155 . Dashed lines show the removed relief material from normative threads or threads with concentric relief  82 . In yet another embodiment, the thread cutting edge relief  34  of  FIG. 5B  is defined in relation to the minor diameter  156 . 
         [0034]      FIGS. 5B and 9  show the thread cutting edge relief  33  as part of leading flank  92  and trailing flank  112  defined as a relief of the pitch diameter  133 . Similarly, the angular value of the taper angle for each successive domain differs and an angular value of the thread cutting edge relief for each successive domain differs. What is shown by dashed lines is the section envelope of the normative thread with a concentric relief on the pitch relief. The figure illustrates a coneccentric relief  104  (with concentric margin  110 ), an eccentric relief  108 , and a concentric relief  106  for the pitch relief at the pitch diameter  133 , respectively. 
         [0035]    In one alternate embodiment, at least a portion of thread for each of the series of successive domains having a geometrical arrangement. In yet another embodiment shown in  FIG. 10 , the pitch relief (or the major diameter relief, not shown) is a high negative relief  120  of the leading flank  92  and the trailing flank  112  at the cutting edge for each of the fixed number of successive threads in each successive domain. In yet another embodiment as shown in  FIG. 11 , the geometrical arrangement is a double or high positive relief  122  of the leading flank and the trailing flank at the heel of the land for each of the fixed number of successive threads in each successive domain. 
         [0036]    In one contemplated embodiment, the geometrical arrangement of each successive domain is an alternating sequence within each successive domain of a thread of a single land on of the pitch with a variable parameter and the remaining threads of the other land of the pitch without the variable parameter; and yet in another embodiment, a single thread for each of the series of successive domains has a geometrical arrangement as defined herebefore. 
         [0037]    What is also contemplated is any variation, using the principle of domains within a threaded length  8 , of different threads using the above-defined reliefs of threads or any other relief based on another geometrical parameter associated with the art of taps. The above nomenclature, definitions, and associated illustrations correspond to the United States Cutting Tool Institute standards for TAPS GROUND THREAD, which are hereby fully incorporated herein by reference. This standard is also published as the American National Standard for Taps-Cut and Ground Thread, ANSI B94.9 also hereby fully incorporated herein by reference. In the case of conflict between theses definitions, nomenclatures, and associated illustrations, the terms defined within the body of this specification prevail upon the Cutting Tool Institute standard, which in turn prevails upon the ANSI standard. 
         [0038]    It is understood that the preceding is merely a detailed description of some examples and embodiments of the present invention and that numerous changes to the disclosed embodiments can be made in accordance with the disclosure herein without departing from the spirit or scope of the invention. The preceding description, therefore, is not meant to limit the scope of the invention but to provide sufficient disclosure to one of ordinary skill in the art to practice the invention without undue burden.