Abstract:
The present disclosure is directed to a dual technology relief tap, and more specifically, to a relief tap where a segment on the threaded portion has a first type of relief and the remainder of the threads have a second type of relief or a concentric thread to limit tilt and loosening and ultimately to prevent overfeed or underfeed. In some embodiments, a neutral, negative, positive, convex, or other type of relief is applied generally to most of the threaded portion with or without concentric threads, and a second type of relief of any type, such as a neutral, a negative, a positive, a convex, or other relief, is applied to some selected threads. In another embodiment, the second type of relief is applied to the first threads after the chamfer or are spaced regularly over the threaded surface.

Description:
FIELD OF THE DISCLOSURE 
       [0001]    The present disclosure is directed to a dual relief tap, and more specifically, to a relief tap where a segment on the threaded body, likely next to the chamfer of the tap, has a first relief technology, and at least a second segment of the threaded body has a second relief technology to limit overfeed and underfeed effects during tapping. 
       BACKGROUND OF THE INVENTION 
       [0002]    Threads are used to mate pieces and convert torque into axial force between two objects. The first object, such as a bolt anchored to a piece to be secured, has male threads on its outer surface and is screwed into a second object with mating female threads on the inner surface of an opening. The use of threads as a fastening means is well known. To form threads on the inner surface of the opening, a hole is drilled using a drill bit where female threads are created in a subsequent step. The drill bit, because of its rapid rotational speed, removes chips of matter but leaves the surface of the hole relatively flat. Threads must be added to the surface in a second step using a manual tap as shown in  FIG. 1  or any other type of tap. 
         [0003]    Taps are cutting tools used to create threads in solid substances, including but not limited to metal, wood, or plastic, by shaving away thread-like areas on the inner surface of a cylindrical hole. To ease threading forces on the tap, threads are cut during a process that includes screwing in the tap over a handful rotations to remove small layers as shown in the right end of  FIG. 7 . Male taps  100  in  FIG. 1  (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 equipped with an end portion for positioning the tap in a torque-creating support. 
         [0004]    A user attaches the tap  100  inside a torque support  36 , places the tap on the hole of a piece, and screws the tap  100  into the hole to create threads. The first rotations of the tap inside the hole are critical. Misalignment, uneven driving forces, or incorrect tap technology may result in the creation of undesired, uneven mating threads. 
         [0005]    Taps often include fluted openings made longitudinally along the thread length. These flutes define land portions between two flutes where chips removed from the surface being threaded are evacuated upwards and out of the hole.  FIG. 1  shows a tap  100  placed inside a torque-creating support  36  operated by a user  40  and stabilized in a grip  38 . While a manual support  36  is shown, nonmanual supports are also used interchangeably with the disclosed technology. 
         [0006]    Three types of fluted taps are shown in  FIGS. 2-4 , respectively.  FIG. 2  is a spiral flute tap where the fluted openings spiral along the length of the threaded body creating lands between the fluted openings of fixed lengths but where the cutting edge at the intersection of each land with the flute is a cutting surface at an attack angle.  FIG. 3  illustrates a straight flute tap where the fluted openings are longitudinally aligned with the tap axis. In this type of tap, each thread has a similar cutting edge on the edge of the opening and there is no forward cutting attack angle.  FIG. 4  illustrates a gunpoint tap where, in the chamfer area of each land, the width of each thread decreases to create an intermediary configuration between the tap of  FIG. 2  and the tap of  FIG. 3 . This type of tap benefits from a greater attack angle in the chamfer area for each thread edge and a linear threaded portion past the chamfer. 
         [0007]      FIG. 5  is a close-up view of the cutting edge a variable angle at a cutting edge of a land of a spiral flute tap of  FIG. 2 , or a variable angle at a cutting edge of a land in the chamfer area of the gunpoint tap of  FIG. 4 . As shown, each thread has a leading flank and a trailing flank where both flanks attack at different angles a surface into which they cut.  FIG. 6  shows the opposite configuration of the straight fluted tap of  FIG. 3  or the threaded portion of the gunpoint tap of  FIG. 4  where the cutting edge is aligned with the fluted openings, resulting in a symmetrical cutting angle. 
         [0008]    When taps enter a drilled hole, the surface where material is intended to be cut is removed in incremental layers as the chamfered threads are rotated in. Without a chamfer, the first thread would need to remove the totality of the material to be cut, would require great torque to operate, and would be subject to dulling of the cutting edge. On the right of  FIG. 7  is an animation view of the tip of a tap where a chamfer area enters a drilled hole over six consecutive rotations and creates perfect threads. On the left of  FIG. 7 , a normal tapping process creates a normal thread (i.e., a V-shaped thread in the metal). On the right, an overfed thread (i.e., a staircase-shaped thread in the metal) is created when overfeeding of the tap occurs. At each rotation, the tap advances a fraction of a thread forward and cuts into the thread in a step-forward manner.  FIG. 8  is a close-up view of an overfed tooth where the overfeed is shown while each subsequent thread in the chamfer area is entered. The tap  100  is illustrated along with the cutting layers of the thread as shown in lines within the thread.  FIG. 9  is the same close-up view but of an underfed tooth. Lines  150  show the shape of the teeth produced during the overfeed and underfeed. 
         [0009]    Overfeeding can be caused by a plurality of effects. The main effect stems from the need to reduce frictional forces between the external surface of the threads on the tap as the tap enters the internal surface of the object being threaded. To reduce the friction, flutes are cut into the threads. Also, these flutes serve to evacuate from the chamfer chips of material cut from the surface. To further reduce friction, a portion of each thread in the back of the cutting edge is tapered away from the material surface in what is called a “relief.” A relieved thread is distanced at some point from the inner surface of the hole in which it burrows. The gap created between the thread and the object&#39;s inner surface, while beneficial to the tap, loosens the tap to some extent. A loosened tap may move, tilt, change position, and cause overfeed or underfeed. 
         [0010]    To illustrate the relief,  FIGS. 10-11 ,  13 - 16 , and  18 - 24  use a segment made of a tap with several adjacent threads over a portion of a land between two adjacent flutes. The tap is shown as a solid. The gap created by the relief of each thread, i.e., the distance between the internal surface of the drilled hole and the external surface of the tap, is illustrated using lines over the solid to show the distance from a threaded object&#39;s inner surface as it would be if an x-ray were taken of the tap inside the hole. One of ordinary skill in this art will recognize on these figures how reliefs, thread designs, and chamber designs are made without undue experimentation. 
         [0011]      FIG. 10  illustrates a regular eccentric relief  151  where the distance increases regularly from the front to the back of the land along each thread. Another possible form of relief is illustrated in  FIG. 11  where some threads are removed altogether  152  from the threaded region on the tap.  FIG. 12  shows how the top portion of each thread can be recessed  153  (i.e., a flattened thread) to reduce the contact area between the tap and the material in which the tap is inserted and provide additional relief. As shown in  FIG. 12 , threads distant from the chamfer are shown as recessed, but the use of recessed relief in any portion of the threaded area on a tap is contemplated.  FIG. 13  shows a land concentric threads  154 ,  FIG. 14  illustrates an eccentric  155  thread relief,  FIG. 15  a con-eccentric thread relief  156 , and  FIG. 16  a specially shaped thread relief where portions of the middle thread are shifted away from the contact surface (not illustrated by dashed lined but simply on the solid thread). One of ordinary skill in the art of tap design will understand that while a handful of different types of relief are shown in  FIGS. 10-16 , other single relief types are also contemplated. 
         [0012]    Different technologies of relief exist to help reduce frictional forces on the tap, and each technology results directly or indirectly in overfeed or underfeed of the tap. What is needed is a tap with a new type of relief designed to keep the structure of the tap centered and aligned and to prevent any overfeed or underfeed during the creation of threads by the tap. 
       SUMMARY 
       [0013]    The present disclosure is directed to a dual technology relief tap, and more specifically, to a relief tap where a segment on the threaded portion has a first type of relief and the remainder of the threads have a second type of relief or a concentric thread to limit tilt and loosening and ultimately to prevent overfeed or underfeed. In some embodiments, a neutral, negative, positive, convex, or other type of relief is applied generally to most of the threaded portion with or without concentric threads, and a second type of relief of any type, such as a neutral, a negative, a positive, a convex, or other relief, is applied to some selected threads. In another embodiment, the second type of relief is applied to the first threads after the chamfer or are spaced regularly over the threaded surface. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    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. 
           [0015]      FIG. 1  is an illustration of a fluted tap with a torque-creating support in a piece secured to a vice grip. 
           [0016]      FIG. 2  is a side view of a spiral fluted tap. 
           [0017]      FIG. 3  is a side view of a straight fluted tap. 
           [0018]      FIG. 4  is a side view of a gunpoint tap. 
           [0019]      FIG. 5  is an illustration of the cutting edge on a curved land of a fluted tap. 
           [0020]      FIG. 6  is an illustration of the cutting edge on a straight land of a fluted tap. 
           [0021]      FIG. 7  is a dual animated view of the tapping process of a tap without overfeed and with overfeed. 
           [0022]      FIG. 8  is a close-up view of an overfeed thread created in a material along with traces of the different cutting edges. 
           [0023]      FIG. 9  is a close-up view of an underfeed thread created in a material along with traces of the different cutting edges. 
           [0024]      FIG. 10  is an illustration of a regular thread relief on a fluted tap from the prior art. 
           [0025]      FIG. 11  is an illustration of an interrupted thread relief on a fluted tap from the prior art. 
           [0026]      FIG. 12  is an illustration of a spiral fluted tap, a straight fluted tap, and a gunpoint flute tap with recessed threads from the prior art. 
           [0027]      FIG. 13  is an illustration of concentric threads on a fluted tap from the prior art. 
           [0028]      FIG. 14  is an illustration of an eccentric thread relief on a fluted tap from the prior art. 
           [0029]      FIG. 15  is an illustration of a con-eccentric thread relief on a fluted tap from the prior art. 
           [0030]      FIG. 16  is an illustration of a specially shaped thread relief on a fluted tap from the prior art. 
           [0031]      FIG. 17A  is a side view used to illustrate schematically the nomenclature of tap cutting tools. 
           [0032]      FIG. 17B  is a detailed view of one of the lands located between two flutes of the tap cutting tool of  FIG. 17A . 
           [0033]      FIG. 17C  is a top view of the tap cutting tool of  FIG. 17A  as seen from the cut line  17 C- 17 C as shown in  FIG. 17A . 
           [0034]      FIG. 17D  is a sectional view without shading of the tap cutting tool of  FIG. 17A  as seen from the cut line  17 D- 17 D as shown in  FIG. 17A . 
           [0035]      FIG. 18  is a dual relief tap with an eccentric relief as a first type of relief and a convex relief as a second type of relief according to an embodiment of the present disclosure. 
           [0036]      FIG. 19  is a dual relief tap with an eccentric relief as a first type of relief and concentric threads as a second type of threads according to another embodiment of the present disclosure. 
           [0037]      FIG. 20  is a dual relief tap with an eccentric relief as a first type of relief and a negative relief as a second type of relief according to another embodiment of the present disclosure. 
           [0038]      FIG. 21  is a dual relief tap with an eccentric relief as a first type of relief and a convex relief as a second type of relief according to another embodiment of the present disclosure. 
           [0039]      FIG. 22  is a dual relief tap with an eccentric relief as a first type of relief and a combined negative and concentric relief set as a second type of relief or second type of threads according to another embodiment of the present disclosure. 
           [0040]      FIG. 23  is a dual relief tap with an eccentric relief as a first type of relief and a combined eccentric, negative, and positive relief, and concentric threads at the second type of relief according to another embodiment of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0041]    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. 
         [0042]      FIG. 1  illustrates how a 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, thus activating the cutting edges. 
         [0043]    Describing a tap in general,  FIG. 17A  illustrates a tap  100  with an overall length  6  that may be separated into a thread length  8  and a shank length  10  having a fixed shank diameter  2 . The ratio of these two lengths is purely illustrative, and it is understood that these lengths may 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. The driving length  28  is also of a geometry as shown in  FIG. 17C  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. 
         [0044]    Flutes  18  as shown in  FIG. 17D  separate lands  22  created in the threaded length  8  between two consecutive flutes  18 . In one embodiment as shown in  FIG. 17D , four flutes  18  are positioned at 90 degrees circumferentially around the thread length  8 . Other taps may have flutes  18  of smaller radii and variable curvature as shown in  FIG. 3  and may be placed around a cylindrical tool body or minor diameter  12  of different sizes to create a tap  100  with five or more flutes  18  or three or fewer flutes  18 . Also shown in  FIG. 17A  is a tap  100  with straight flutes  18 . The use of a helical angle, a spiral, or any other type of flute  18  that is not aligned with the longitudinal axis  4  of the tap  100  is also contemplated. 
         [0045]    Returning to  FIG. 17A , the threaded length  8  comprises a series of V-shaped threads, each thread 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. 17D  is a sectional view without shading of the tap cutting tool of  FIG. 17A  as seen from cut line  17 D- 17 D as shown in  FIG. 17A . This section shows the land width  14  and a section with threads having a minor diameter  156  and a major diameter  155 .  FIGS. 17A-17D  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 and a heel as shown in  FIG. 17B . 
         [0046]      FIGS. 18-25  shows a dual relief tap  200  for cutting a thread into a workpiece. The tap  200  as numbered in  FIGS. 2-4  includes a cylindrical tool body  201  having a longitudinal axis  202  rotatable about the longitudinal axis  202  and having successively along the cylindrical tool body a shank  203 , a neck  204  (in some embodiments), a threaded length  205  with a plurality of threads (as shown in  FIGS. 18-25 ) with at least a flute  206  for creating at least a land  207  with a front cutting face  208  with a cutting edge  209 , and a chamfer area  210 . These different parts of the tap  200  are shown in the general illustration of a tap in  FIG. 2 . A tap without a neck  204  is shown in  FIG. 17A , while a tap with a neck  204  is shown in  FIGS. 2-4 . Further, the tap  200  shown in  FIG. 17A  does not include a chamfer  210 , while the taps shown in  FIGS. 2-4  include a chamfer  210 . This disclosure is directed to all different tap configurations, with or without a chamfer, a neck, or other secondary features. 
         [0047]    What is disclosed is a tap  200  where each of the plurality of threads has either similar or different geometries, such as, for example, the pitch as shown in  FIGS. 18-24 , but where each of the plurality of threads has a compound relief  310  made of least two different reliefs where one portion of the threads  311  has a first type of relief resulting either from a new type of relief or from a different geometry of tooth, and a second portion of the threads  312  has a second type of relief. In turn, the first and second portions  311 ,  312  can include only identical threads with identical reliefs, but the first portion  311  can include a first segment of the threaded length  321  with a first portion of the plurality of threads  311  where each of the plurality of threads in the first portion  311  has a first type of relief  331 , and wherein a second segment  322  of the threaded length  205  includes a second portion  312  of the plurality of threads where each of the plurality of threads in the second portion  312  has a second type of relief  332 . 
         [0048]    As illustrative examples of a tap  200  with different portions  311 ,  312 , each with different threaded lengths  321 ,  322  and different types of relief  331 ,  332 ,  FIG. 18  shows a tap  200  with an eccentric relief as a first type of relief  331  and a convex relief as a second type of relief  332 .  FIG. 19  shows a tap  200  with a first eccentric relief  331  and a second relief such as simple concentric threads  332 .  FIG. 20  shows a tap  200  a first eccentric relief  331  and a second negative relief  332 .  FIG. 21  shows a tap  200  with a first eccentric relief  331  and a second convex relief  332 .  FIG. 22  shows a tap  200  with first eccentric relief  331  and a second relief made of combined negative relief threads and concentric threads  332  according to another embodiment of the present disclosure.  FIG. 23  is a dual relief technology tap with a first relief as concentric threads  331  and a second relief made of concentric threads and specially shaped relief  332 .  FIG. 23  shows a gunpoint tap  200 , and  FIG. 24  is a close-up view of the gunpoint tap  200  as shown in  FIG. 23  with a dual relief technology with a first eccentric relief  331  and a second combined eccentric, negative, and positive relief, and concentric threads  332 . 
         [0049]    While  FIGS. 18-22  and  24  illustrate some of the possible configurations of the first and second reliefs  331 ,  332  on the different portions of the threaded length  205  of the tap  200 , taps  200  where the first relief  331  is a an eccentric relief, a flattened thread relief, a removed thread relief, a concentric thread, a con-eccentric relief, a special shape relief, a convex relief, a positive relief, a negative relief, or any combination thereof are contemplated. Also, the second relief  332  may also be any of the eccentric relief, the flattened thread relief, the removed thread relief, concentric threads, the con-eccentric relief, the special shape relief, the convex relief, the positive relief, the negative relief, or any variation thereof. One of ordinary skill in the art will recognize that while a list of known relief types is given, any type of relief is also contemplated. 
         [0050]    In another embodiment, the first segment  331  and second segment  332  are of the length of the threaded length  205 . In another embodiment, the first segment  331  is substantially longer than the second segment  332 . For example, the second segment  332  as shown in most of  FIGS. 18-22  and  24  is one or two threads in length. In one embodiment, the second segment  332  is one to five threads in length, in a further embodiment, the second segment  332  is made of one to three threads, and in yet another embodiment, the second segment  332  is made of two threads in length. 
         [0051]    Further, the second segment  332  may be either in or adjacent to the chamfer area as part of several threads immediately between the first segment  331  and second segment  332 . While configurations of threads are described where two different segments and thread reliefs are shown, the use of other segments, thread reliefs, and portions are contemplated, such as, for example, a third segment of the threaded length with a third portion of the plurality of threads, and wherein the threads from the third portion have a second type of relief, a third type of relief, etc. The principle of this disclosure centers around, at a minimum, the use of selected threads having different relief technologies to alter the side effects resulting from the use of threads with a first technology in a threaded area of a tap. These teachings are consistent with the use of more than one corrective thread; the use of two or more corrective threads along the threaded area is also contemplated. Further, the second portion  312  may be located between the first portion  311  and the third portion on the threaded length or any other area along the threaded length  205 . 
         [0052]    In another embodiment, a method for reducing the overfeed and/or underfeed of a dual relief tap  200  in a workpiece is also contemplated, the method comprising the steps of placing a shank of a dual relief tap  200  in a support  36  and turning the tap  200  into a workpiece along the longitudinal axis  202 . In another embodiment, the method may include a further step of inserting a second segment  322  into the workpiece and inserting at least a portion of the first segment  321  into the workpiece. 
         [0053]    It is understood that the preceding is merely a detailed description of some examples and embodiments of the present invention and that numerous alterations 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.