Patent Publication Number: US-2006002782-A1

Title: Indicating fastener devices and methods of use therefor

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      This invention relates generally to assembly of material layers, and more particularly to fabrication of items from multiple layers of sheet material.  
      2. Description of the Related Art  
      In the fabrication of aircraft components, multiple layers of sheet material, such as aircraft skin and doubler materials, are typically assembled together using permanent fasteners, such as rivets, that are received through small openings in the sheet material to secure the individual layers together into a common assembly. Until final assembly, conventional spring-loaded or draw-type temporary panel retainers are useful in keeping the various layers of sheet materials temporarily aligned and clamped together at small holes that are defined in the sheet material layers, pending enlargement of the holes for final assembly using permanent fasteners. Differing layer thicknesses and varying stackup configurations at different areas of the assembly mean that differing lengths of permanent fasteners may be required to secure different areas of the assembly.  
      Grip gages have been developed for measuring the thickness of assembled layers of sheet material to determine the length of permanent fastener that should be employed. However, such grip gages are designed to be inserted into the openings in the sheet material, thus requiring removal of a corresponding temporary panel retainer for measurement of material thickness. When the layers do not remain aligned and/or clamped together after removal of the temporary panel retainer, the measured permanent fastener length may be false. There are a variety of reasons why surfaces of multiple layers of materials often do not fit flush together. For example, gaps between multiple layers may exist due to differing part contour(s), excessive sealant existing between layers that has not yet been squeezed out, etc. Existence of such gaps between material layers may lead to false thickness measurements by conventional grip gages and to incorrect fastener length selection. Incorrect permanent fastener length selection translates into time and materials being wasted while installing and removing/destroying the incorrectly-sized fastener. In this regard, some permanent fasteners are relatively expensive. Furthermore, removal of permanent fasteners also risks costly damage to one or more layers of the structure.  
       FIG. 1  illustrates a conventional spring-loaded temporary panel retainer  110  having a main body  116  and nose assembly  160  that includes neck segments  131  and  133  and nose segments  132  and  134 . In  FIG. 1 , neck segments  131  and  133  of nose assembly  160  are shown protruding through opening  140  defined in three sheet materials  120 ,  122 ,  124  of a stackup assembly that are temporarily aligned and clamped together by virtue of pressure exerted on the back surface  121  of sheet  120  by nose segments  132  and  134  of nose assembly  160 , and on the front surface  125  of sheet  124  by shoulder area  118  of main body  116 . As shown, stationary piece  130  is fixedly attached to body  116  that maintains separation of nose segments  132  and  134  so that nose segments  132  and  134  will not fit back through opening  140 . Not shown is an internal spring that acts to retract nose and neck segments of nose assembly  160  toward body  110  so as to clamp sheet materials  120 ,  122  and  125  between main body  116  and nose segments  132  and  134 .  FIG. 1  also shows plunger  114  that internally contacts nose assembly  160 , and is operable to extend nose assembly  160  away from back surface  121  of sheet  120  when depressed in the direction indicated by the arrow. A space is created between nose segments  132  and  134  when they are extended far enough so that they are no longer in a position proximate to stationary piece  130 . This space allows nose segments  132  and  134  to come together so that they may pass though opening  140 , allowing retainer  110  to be withdrawn from engagement with opening  140 . Also shown in  FIG. 1  is shoulder segment  112  that is provided to facilitate grip of retainer  110  for purposes of depressing assembly extension actuator  114 .  
     SUMMARY OF THE INVENTION  
      Disclosed herein are apparatus and methods that allow two or more sheet materials to be aligned and clamped together at a given fastener location while simultaneously being measured for appropriate fastener length at the given fastener location. Advantageously, the disclosed apparatus and methods may be so employed to help prevent incorrect fastener length selection, and thus to avoid costly installation problems that may result from attempted installation of fasteners having incorrect length. At the same time, the disclosed apparatus and methods may be implemented to have a variable or adjustable clamping dimension capability that allows for use with different stackup assemblies having varying overall thicknesses. By providing simultaneous clamping action and measurement capabilities, the disclosed apparatus and methods may be employed in a manner that eliminates the need for separate measurement steps using separate measurement devices, such as grip gages.  
      In one respect, disclosed herein is an indicating fastener device that includes a fastener body, a fastener extension and retention mechanism slidably received within the fastener body, and a thickness indicator configured to indicate a position of the fastener extension and retention mechanism relative to the fastener body. The thickness indicator may include a graduated scale, and the graduated scale may be disposed on at least one of the fastener body or the fastener extension and retention mechanism. In one exemplary embodiment, the fastener extension and retention mechanism may be configured with at least one retention member on an insertion end and with an actuator extension on an actuation end. In such an embodiment, a graduated scale may be disposed on the actuator extension. In another embodiment, the external dimensions of the indicating fastener device may be configured to correspond to the external dimensions of a conventional temporary panel retainer. In yet another embodiment, the thickness indicator may include an electronic indicator.  
      In another respect, disclosed herein is an indicating fastener device that includes: a fastener body having a proximal end and a distal end, the fastener body having an internal opening defined therein between the proximal end and the distal end; a fastener extension and retention mechanism slidably received within the internal opening of the fastener body, the fastener extension and retention mechanism having an insertion end that may be received adjacent the proximal end of the fastener body and an actuation end that may be received adjacent the distal end of the fastener body, and further including at least one retention member provided on the insertion end and an actuator extension provided on the actuation end; and a thickness indicator provided on the fastener extension and retention mechanism. The fastener extension and retention mechanism may further include at least one extension member positioned between the retention member and the actuator extension, and the insertion end of the fastener extension and retention mechanism may be dimensionally configured to be extendable from the proximal end of the fastener body and to be received through an opening defined in at least one sheet of material (e.g., a stack up assembly of two or more sheets of material) having a back surface and a front surface such that the at least one extension member extends through the opening from the front surface to the back surface and such that the retention member may be positioned adjacent the back surface when the proximal end of the fastener body may be positioned adjacent the front surface. The at least one retention member may be configured to selectably engage the back surface of the at least one sheet of material in retaining relationship at the same time that the proximal end of the fastener body contacts the front surface of the at least one sheet of material, and the thickness indicator may be configured to move with the fastener extension and retention mechanism relative to the fastener body so as to indicate the distance between the front surface and the back surface of the at least one sheet of material when the retention member engages the back surface of the at least one sheet of material in retaining relationship at the same time that the proximal end of the fastener body contacts the front surface of the at least one sheet of material.  
      In one embodiment, the indicating fastener device of claim may further include a retraction mechanism configured to bias the fastener extension and retention mechanism in a direction that retracts the insertion end of the fastener extension and retention mechanism toward the proximal end of the fastener body so as to clamp the at least one sheet of material between the retention member and the proximal end of the fastener body when the at least one retention member engages the back surface of the at least one sheet of material in retaining relationship at the same time that the proximal end of the fastener body contacts the front surface of the at least one sheet of material. The actuator extension may extend from the distal end of the fastener body when the insertion end of the fastener extension and retention mechanism is retracted toward the proximal end of the fastener body. The fastener extension and retention mechanism may include at least two retention members provided on the insertion end of the fastener extension and retention mechanism that may include, for example, first and second opposing tang segments. A first extension member may be provided between the first tang segment and the actuator extension and a second extension member may be provided between the second tang segment and the actuator extension, the first and second extension members being biased toward each other and deflectable away from each other to form a space therebetween. The indicating fastener device may further include a separating member received in the space between the first and second extension members, the separating member configured to extend from the proximal end of the fastener body so as to as to be disposed adjacent and between the first and second tang segments when the first and second tang segments engage the back surface of the at least one sheet of material in retaining relationship at the same time that the proximal end of the fastener body contacts the front surface of the at least one sheet of material so that the insertion end of the fastener extension and retention mechanism has an external dimension that may be greater than the diameter of the opening defined in the at least one sheet of material.  
      In another respect, disclosed herein is a method of determining the thickness of at least one sheet of material, the method including providing an indicating fastener device, the indicating fastener device that includes: a fastener body having a proximal end and a distal end, a fastener extension and retention mechanism slidably received within the fastener body and having an insertion end extending from the proximal end of the fastener body and having a retention mechanism provided thereon, and a thickness indicator configured to indicate a position of the fastener extension and retention mechanism relative to the fastener body. The method may include positioning the insertion end of the fastener extension and retention mechanism within an opening defined in the at least one sheet of material and in operative relationship with the fastener body so that the retention mechanism selectably engages a back surface of the at least one sheet of material (e.g., a stack up assembly of at least two sheets of material) at the same time the proximal end of the fastener body contacts a front surface of the at least one sheet of material such that the position of the fastener extension and retention mechanism relative to the fastener body corresponds to the thickness of the at least one sheet of material, and determining the thickness of the at least one sheet of material from the thickness indicator. In one embodiment, the method may further include selectably clamping at least two sheet materials of a stack up assembly together between the retention mechanism of the fastener extension and retention mechanism and the proximal end of the fastener body so that substantially no gap exists between the at least two sheet materials of the stack up assembly. The method may also further include disengaging the retention mechanism of the fastener extension and retention mechanism from the back surface of the at least two sheet materials of the stack up assembly; and removing the insertion end of the fastener extension and retention mechanism from the opening defined in the at least two sheet materials of the stack up assembly. A permanent fastener may be selected based at least in part on the determined thickness of the at least two sheets of material of the stack up assembly; the at least two sheets of material of the stack up assembly assembled together using the selected permanent fastener. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a simplified side view of a conventional panel retainer.  
       FIG. 2A  is a simplified and partial cut-away side view of an indicating fastener device according to one embodiment of the disclosed apparatus and methods.  
       FIG. 2B  is a simplified side view of a fastener extension and retention mechanism according to one embodiment of the disclosed apparatus and methods.  
       FIG. 2C  is a simplified cut-away side view of a fastener extension and retention mechanism according to one embodiment of the disclosed apparatus and methods.  
       FIG. 2D  is a simplified cut away side view of the proximal end of the fastener extension and retention mechanism of  FIG. 2C .  
       FIG. 2E  is a side view of a separating member assembly according to one embodiment of the disclosed apparatus and methods.  
       FIG. 2F  is a top view of the separating member assembly of  FIG. 2E .  
       FIG. 2G  is an end view of a separating member retainer according to one embodiment of the disclosed apparatus and methods.  
       FIG. 2H  is a top view of the separating member retainer of  FIG. 2G .  
       FIG. 2I  is a side view of the separating member retainer of  FIG. 2G .  
       FIG. 3  is a simplified side view of an indicating fastener device according to one embodiment of the disclosed apparatus and methods.  
       FIG. 4  is a simplified side view of an indicating fastener device according to one embodiment of the disclosed apparatus and methods.  
       FIG. 5  is a simplified side view of an indicating fastener device according to one embodiment of the disclosed apparatus and methods.  
       FIG. 6  is a simplified side view of an indicating fastener device according to one embodiment of the disclosed apparatus and methods.  
    
    
     DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS  
       FIG. 2A  illustrates one embodiment of an indicating fastener device  200  shown in operable relation to a plurality of assembled sheet materials  210 ,  212  and  214  that are assembled in  FIG. 2A  to form a stackup assembly  250 . In this exemplary embodiment, indicating fastener device  200  is configured with a fastener body  202  having an internal opening  203  defined therein that is centered along the longitudinal axis of body  202  between proximal end  205  and distal end  201  of body  202  as indicated in the cut-away section of  FIG. 2A . As shown in  FIG. 2A , internal opening  203  is configured to slidably receive a fastener extension and retention mechanism  220  that on an insertion end  291  includes extension members  222  and  224  and two opposed retention members in the form of tang segments  226  and  228 , and that on an opposing actuation end  293  includes an actuator extension  280 . As illustrated, extension members  222  and  224  are separate members that are deflectable away from each other to form a space  223  configured to receive separating member  270  for maintaining separation between extension members  222  and  224  as described further below.  
       FIG. 2B  shows an exemplary fastener extension and retention mechanism  220  of the embodiment of  FIG. 2A . As illustrated in  FIG. 2B , extension members  222  and  224  (with tang segments  226  and  228 ) are biased against each other in the absence of separating member  270  positioned therebetween.  FIGS. 2C-2I  illustrate an exemplary embodiment of internal configuration for an indicating fastener device  200  that employs a multi-piece (e.g., two-piece) fastener extension and retention mechanism.  
      In  FIG. 2A , extension members  222  and  224  of insertion and retention mechanism  220  are shown received in an opening  260  defined by individual aligned openings formed in respective multiple sheet materials  210 ,  212  and  214  of stackup assembly  250 , e.g., for purposes of temporary clamping, alignment, measurement and/or other suitable purpose/s. As illustrated, a retention mechanism may be configured to selectably engage a back surface  209  of stackup assembly  250  in temporary retaining relationship. For example, in the illustrated embodiment, separating member  270  may be fixed to fastener body  202  and is provided to maintain separation of tang segments  226  and  228  so that tang segments  226  and  228  will remain sufficiently separated so that insertion end  291  has an expanded outer dimension that will contact back surface  209  and not fit through opening  260  when tang segments  226  and  228  are positioned proximate to separating member  270  as shown.  
      Although one exemplary embodiment of insertion and retention mechanism  220  is shown illustrated in  FIGS. 2A and 2B , it will be understood that extension members  222  and  224  of insertion and retention mechanism  220  may be integrally formed with, or separately coupled to, actuator extension  280  in any manner suitable so that movement of extension members  222  and  224  relative to body  202  causes corresponding movement of actuator extension  280  relative to body  202 . For example, extension members  222  and  224  and actuator extension  280  may be formed of a single piece of material (e.g., to form a single piece insertion and retention mechanism  220 ), or extension members  222  and  224  may be separate components that terminate against a separate actuator extension  280  component at a point within body  202  (e.g., to form a multi-piece insertion and retention mechanism  220 ). Alternatively, insertion and retention mechanism  220  may be a multi-piece assembly that includes extension members  222  and  224  coupled to actuator extension  280  by one or more other intermediate members that are internally and slidably disposed therebetween within body  202 .  
      Not shown in  FIG. 2A  is a retraction mechanism (e.g., internal spring or other suitable biasing mechanism) that may be provided to retract extension members  222  and  224  (with tang segments  226  and  228 ) of insertion and retention mechanism  220  toward body  202  so as to clamp sheet materials  210 ,  212  and  214  between main body  202  and tang segments  226  and  228 . In the illustrated embodiment, this clamping action is achieved by virtue of contact between tang segments  226 ,  228  and back surface  209  of stack up assembly  250  simultaneously with contact between proximal end  205  of fastener body  202  and front surface  215  of stack up assembly  250  in a manner as will be described further herein. It will be understood that a retraction mechanism may be any external and/or internal component/s suitably configured to retract or otherwise bias one or more retention members of an insertion and retention mechanism toward a fastener body so as to clamp sheet materials between the fastener body and the retention member/s.  
       FIG. 2C  illustrates an exemplary embodiment of an indicating fastener device  200  that employs a two-piece fastener extension and retention mechanism assembly in the form of a proximal portion  269  and distal portion  289 . A proximal spring collar  265  fixedly coupled to proximal portion  269  and a distal spring collar  253  fixedly coupled to distal portion  289  are shown provided between proximal and distal portions  269  and  289  in a manner that couples the spring force of respective springs  269  and  263  to the fastener extension and retention mechanism assembly relative to fastener body  202 . As illustrated, proximal portion  269  includes tang segment  226  and extension member  222 . Not shown in the cutaway view of  FIG. 2C  is corresponding tang segment  228  and extension member  224 .  FIG. 2D  shows proximal end of indicating fastener device  200  of  FIG. 2C  from a cut-away view oriented perpendicular to the view of  FIG. 2C , and thus illustrates both tang segments  226  and  228  and their respective extension members  222  and  224 .  
      Still referring to  FIGS. 2C and 2D , separating member  270  is provided as shown for separating extension members  222  and  224  in a manner as described elsewhere herein. In the illustrated exemplary embodiment, separating member  270  is provided as part of a separating member assembly  251  that includes a separating member base  271  that supports separating member  270 , as further illustrated in  FIGS. 2E and 2F . Separating member assembly  251  is dimensioned (e.g., formed to be relatively flat in profile) so as to allow sufficient room for tang segments  226  and  228 , and extension members  222  and  224 , to pass on opposing sides of separating member assembly  251  in the manner illustrated.  
      As shown in  FIGS. 2C and 2D , separating member assembly  251  is received by a separating member retainer  262  that is positioned between proximal spring  261  and separating member assembly  251 . Separating member retainer  262  is shown in greater detail in  FIGS. 2G through 2I , and includes opening  264  that is suitably dimensioned for receiving tang segments  226  and  228 , extension members  222  and  224 , and separating member  270  that is positioned between segments  226  and  228  and members  222  and  224 . A channel  266  is provided as shown for receiving separating member base  271 .  
      Still referring to the embodiment of  FIGS. 2C-2I , proximal spring  261  may be provided as a relatively stronger spring in relation to distal spring  263  that may be provided as a relatively weaker spring. In such a configuration, proximal spring acts as a retraction mechanism to retract extension members  222  and  224  (with tang segments  226  and  228 ) of proximal portion  269  toward body  202  by virtue of bias force exerted against proximal spring collar  265 . Distal spring  263  may be optionally provided to maintain distal portion  289  (including actuator extension  280 ) in corresponding relation with proximal portion  269  as it moves by virtue of bias force exerted against distal spring collar  253 . It will be understood that distal spring  263  and distal spring collar  253  may be absent, for example, when a single-piece fastener extension and retention mechanism  220  is employed such as illustrated in  FIG. 2B .  
      Referring now to  FIG. 3 , movement of actuation end  293  of insertion and retention mechanism  220  of this exemplary embodiment in the direction indicated by the arrow results in extension of insertion end  291  away from back surface  209  of sheet  210  to disengage tang segments  226  and  228  from back surface  209 , e.g., when actuator extension  280  is depressed in the direction of the arrow. In a manner similar to a conventional panel retainer, tang segments  226  and  228  are allowed to deflect toward each other when they are extended far enough so that they are no longer in a position proximate to stationary separating member  270 . This reduces the external dimensions of insertion end  291  of insertion and retention mechanism  220  so that it will pass though opening  260  as shown by the dashed lines in  FIG. 3 , allowing the entire fastener device  200  to be withdrawn from engagement with opening  260  while insertion end  291  is extended so that tang segments  226  and  228  are not in a position proximate to stationary separating member  270  as shown. A similar movement of actuation end  293  of insertion and retention mechanism  220  in the direction indicated by the arrow relative to fastener body  202  may be used to reduce the external dimensions of insertion end  291  of insertion and retention mechanism  220  so that it may be inserted into opening  260  or another opening of suitable dimension (e.g., an opening in a stack up assembly having a different thickness). In this manner, indicating fastener device  200  may be inserted and removed multiple times.  
      As shown in the figures, an optional shoulder member  204  may be provided to facilitate grip of fastener device  200  for purposes of depressing actuator end  293  of insertion and retention mechanism  220  using conventional temporary panel retainer release tools and/or methods. Thus, in one embodiment, a fastener device  200  may be provided that advantageously may be used interchangeably and/or in the place of conventional spring-loaded temporary panel retainers without requiring new tools and/or operational steps, while at the same providing unique stack up thickness measurement capabilities as described further herein. In such an exemplary embodiment, an indicating fastener device  200  may be provided that is configured with one or more of the thickness indicating features of the disclosed apparatus in combination with the same external dimensions and operating characteristics as a conventional temporary panel retainer, although this is not necessary to realize the benefits of the disclosed apparatus and methods. Furthermore, if desired, an indicating fastener device may additionally or alternatively be configured with one or more of the same or similar internal operating mechanism/s of a conventional panel retainer in combination with the thickness indicating features of the disclosed apparatus. Examples of conventional temporary panel retainers include, but are not limited to, “K” Series Temporary Fasteners (“Clecos”) available from Brown Aviation Tool Supply Company of Oklahoma City, Okla.  
      Referring again to  FIG. 2A , when extension members  222  and  224  of insertion and retention mechanism  220  are received in opening  260 , contact surface  218  of body  202  is positioned to make contact with front surface  215  of front sheet  214  while at the same time contact surfaces  219  and  221  of respective tang segments  226  and  228  are positioned to make contact with back surface  209  of back sheet  210 . Retraction of extension members  222  and  224  toward body  202  (e.g., by suitable retraction mechanism) toward body  202  acts to selectably engage and clamp sheet materials  210 ,  212  and  214  between main body  202  and tang segments  226  and  228  when tang segments  226  and  228  are positioned proximate to separating member  270  while extending through opening  260  as shown. Because actuator extension  280  of insertion and retention mechanism  220  is coupled to move relative to body  202  in a manner corresponding to movement of extension members  222 ,  224  and tang segments  226 ,  228 , the position of actuator extension  280  relative to body  202  is determined by the thickness “T” of stack up assembly  250 . In the illustrated embodiment, this relationship allows determination of thickness “T” for a given stack up assembly  250  by using a thickness indicator that in this case includes a graduated scale  284  that is disposed on a surface  282  of actuator extension  280  so that scale  284  moves relative to body  202  in a corresponding manner with extension members  222 ,  224  and tang segments  226 ,  228 . However, it will be understood that any other location may be employed for a graduated scale or other form of thickness indicator so that it moves in corresponding manner with extension members  222 ,  224  and tang segments  226 ,  228  relative to body  202 , or so that it is otherwise operable to indicate thickness in a manner as will be described further herein.  
      In the illustrated exemplary embodiment of  FIG. 2A , thickness of a stack up assembly (e.g., such as stack up assembly  250 ) may be determined by reading the position of graduated scale  284  relative to body  202 . For example, as shown, graduated scale  284  may be read relative to a reference feature in the form of reference surface  217  of body  200 . In this regard,  FIG. 2A  shows reference surface  217  positioned adjacent a thickness value between “3” and “4” on graduated scale  284 . It will be understood that thickness values of a graduated scale may represent a recognized unit of measurement (e.g., millimeters, centimeters, fractions of an inch, etc.), or may be any other suitable configuration of indicator (e.g., arbitrary unit of measure, relative thickness indication, etc.) that corresponds to the distance between contact surfaces  219  and  221  of tang segments  226 ,  228  and contact surface  218  of body  202 . Furthermore, although a reference surface  217  is illustrated in  FIG. 2A , it will be understood that any other suitable configuration of reference feature may be employed that is provided on, or that is otherwise configured to maintain a constant position relative to fastener body  202  so that graduated scale  284  may be read in a manner that allows thickness of a stack up assembly to be determined.  
       FIG. 4  shows indicator fastener device  200  with fastener extension and retention mechanism  220  in fully retracted position relative to body  202 . As illustrated in  FIG. 4 , indicator fastener device  200  may be configured so that when it is removed from stack up assembly  250 , and extension members  222 ,  224  are fully retracted relative to body  202  so that contact surfaces  219  and  221  of tang segments  226  and  228  make contact with contact surface  218  of body  202 , then indicator surface  217  will be positioned adjacent a value “0” on graduated scale  284 . Also shown in  FIG. 4  are sheet materials  210 ,  212  and  214  having gaps  207  and  209  therebetween. As illustrated, gaps  207  and  209  have formed in the absence of the clamping action provided by indicating fastener device  200 , creating a false stack up assembly thickness of “FT” that may be inadvertently measured, for example, by a conventional grip gage when inserted through opening  260 . In this regard gaps  207  and  209  are shown as they may exist prior to insertion of indicating fastener device  200  into opening  260 , or after removal of indicating fastener device  200  from opening  260 .  
      It will be understood that the illustrated graduated scale and corresponding reference feature embodiment described in relation to  FIGS. 2-4  is exemplary only. In this regard, any other configuration of thickness indicator may be employed that is suitable for indicating an absolute or relative distance between contact surfaces  219  and  221  of tang segments  226 ,  228  and contact surface  218  of body  202 . For example,  FIG. 5  illustrates a thickness indicator that includes a graduated scale  294  disposed on an internal slidable member  296  (e.g., internal portion of fastener extension and retention mechanism  220 , or internal slidable member/s that moves in corresponding manner with fastener extension and retention mechanism  220 ) that is positioned within body  202  of another exemplary embodiment of indicating fastener  200 . As illustrated in  FIG. 5 , a window or cut-out section  297  may be defined within body  202  to allow the position of graduated scale  294  to be read relative to body  202  (e.g., using index marker  298  or other suitable reference feature). An actuator extension  280  is shown provided on actuation end  293  of fastener extension and retention mechanism  220  that is operable (e.g., with or without optional shoulder member  204 ) to extend insertion end  291  of insertion and retention mechanism  220  away from back surface  209  of sheet  210  when depressed in the direction indicated by the arrow in a manner as previously described herein.  
       FIG. 6  illustrates another exemplary embodiment of indicating fastener  200  that includes a thickness indicator in the form of a graduated scale  274  disposed on an external surface  273  of fastener body  202  and indicator feature in the form of indicator pointer  275  that is slidably and cooperatively positioned relative to graduated scale  274 . As shown, indicator pointer  275  is coupled to actuator extension  280  on actuation end  293  of fastener extension and retention mechanism  220  so that that it moves in corresponding manner with fastener extension and retention mechanism  220  when actuator extension  280  is depressed in the direction indicated by the arrow in a manner as previously described herein so as allow the position of indicator pointer  275  to be read relative to body  202  (e.g., using graduated scale  274 ).  
      In yet another embodiment (not illustrated), a thickness indicator may be provided in the form of an electronic indicator (e.g., digital gauge responsive to movement of insertion and retention mechanism  220  relative to body  202 ). Such an electronic indicator may be implemented using any electronic device suitable for indicating position of insertion and retention mechanism  220  relative to body  202 , e.g., proximity sensor, limit switch, etc. Such an electronic thickness indicator may be provided in any form and/or position relative to an indicating fastener body (e.g., as a digital display window on surface of indicator body  202 ) that is suitable for displaying stack up thickness information. As with other embodiments, such an embodiment may be implemented with an optional actuator extension that is operable (e.g., with or without optional shoulder member) to extend an insertion and retention mechanism of the indicating fastener in a manner as previously described herein.  
      It will be understood that the illustrated embodiments are exemplary only, and that other configurations are possible. For example, an indicating fastener device may be provided with any configuration of insertion and retention mechanism having an insertion end that is suitable for being extendably received through openings in one or more sheet materials. In this regard, an insertion and retention mechanism may be configured with a single retention member (e.g., a single tang segment with corresponding single extension member), or more than two retention members (e.g., three or more tang segments with corresponding extension members) may be provided. Furthermore, it will be understood that an insertion and retention mechanism may be configured to operate without the presence of a separating member. For example, an insertion and retention mechanism may be configured with a single tang segment that may be inserted through one or more sheet material opening/s so that it is offset relative to the center of the opening/s in a manner so that a contact surface of the single tang segment may be positioned to make contact with a back surface of the sheet material/s. Furthermore, it will be understood that one or more retraction mechanisms may be provided that are internal and/or external to a fastener body.  
      While the invention may be adaptable to various modifications and alternative forms, specific embodiments have been shown by way of example and described herein. However, it should be understood that the invention is not intended to be limited to the particular forms disclosed. Rather, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims. Moreover, the different aspects of the disclosed apparatus and methods may be utilized in various combinations and/or independently. Thus the invention is not limited to only those combinations shown herein, but rather may include other combinations.