Abstract:
To evaluate a fastener, a cam that is contoured to correspond to a relationship between a first dimension of the fastener and a second dimension of the fastener is utilized. The cam is movable between a first position and a second position and the fastener is evaluated based on whether an electrical connection is completed when contact occurs between the cam and the fastener while the cam is moved from the first position to the second position.

Description:
FIELD OF THE INVENTION 
     The present invention generally relates to an inspection device. More particularly, the present invention pertains to a device and method of inspecting swaged collars. 
     BACKGROUND OF THE INVENTION 
     Mechanical fasteners are utilized to bind a variety of materials. While there are a great variety of mechanical fasteners, a few specific examples includes rivets, lock-bolts, screws, and the like. To facilitate a relatively strong and durable bond, mechanical fasteners are typically installed according to a manufacturer&#39;s recommended procedure. Often, these procedures include the application of a specified force to permanently deform the fastener. For example, rivets, lock-bolts, and various crimped connectors are installed in such a manner. 
     In relatively high technology industries, such as the aerospace industry, it is important that each fastener perform its function with a sufficiently high degree of precision to maintain fastener integrity. In this regard, these fasteners are often manually inspected following installation. Prior art procedures for this inspection involve carefully placing a series of indicator cards upon each fastener and visually inspecting the points of contact to determine fastener compliance. Other prior art procedures include precisely measuring several dimensions of each fasten and manually comparing the measured values to a table of allowable values. Unfortunately, these prior art procedures are tedious, time consuming, prone to human error, expensive, and/or lack the ability to audit. As such, an improperly installed fastener having undesirable material and/or electrical properties may result. 
     Accordingly, it is desirable to provide a method and apparatus capable of overcoming the disadvantages described herein at least to some extent. 
     SUMMARY OF THE INVENTION 
     The foregoing needs are met, at least to a great extent, by the present invention, wherein in one respect an apparatus and method is provided that in some embodiments inspects a swaged collar of a fastener. 
     An embodiment of the present invention pertains to a device to evaluate a fastener. This device includes a cam that is contoured to correspond to a relationship between a first dimension of the fastener and a second dimension of the fastener. The cam is movable between a first position and a second position and the fastener is evaluated based on whether an electrical connection is completed when contact occurs between the cam and the fastener while the cam is moved from the first position to the second position. 
     Another embodiment of the present invention relates to a system to evaluate a fastener. This system includes a device and a processor. The device includes a sensor having a cam contoured to correspond to a relationship between a first dimension of the fastener and a second dimension of the fastener. The cam is movable between a first position and a second position and the fastener is evaluated based on whether an electrical connection is completed when contact occurs between the cam and the fastener while the cam is moved from the first position to the second position. The processor receives signals from the sensor and determines whether the first dimension and the second dimension are between a first value and a second value. 
     Yet another embodiment of the present invention pertains to an apparatus for evaluating a fastener installed in a substrate. The fastener has a height relative to the substrate. This apparatus includes a means for sensing the height, a means for sensing a feature of the fastener, and a means for determining whether the feature is between a first value and a second value in response to the sensed height. 
     Yet another embodiment of the present invention relates to a method of evaluating a fastener installed in a substrate. The fastener has a height relative to the substrate. In this method, the height is sensed, a feature of the fastener is sensed, and it is determined whether the feature is between a first value and a second value in response to the sensed height. 
     Yet another embodiment of the present invention pertains to a method of generating a probe to evaluate a fastener. The fastener includes a plurality of dimensions. In this method a set of relationships is determined for the plurality of dimensions and a table based on the set of relationships is generated. This table includes a plurality of columns and a plurality of rows. Each column corresponds to a dimension of the plurality of dimensions and each row corresponds to the relationship between the plurality of dimensions at a particular value. In addition, a cam is shaped to include a contour that corresponds to a column of the plurality of columns. 
     There has thus been outlined, rather broadly, certain embodiments of the invention in order that the detailed description thereof herein may be better understood, and in order that the present contribution to the art may be better appreciated. There are, of course, additional embodiments of the invention that will be described below and which will form the subject matter of the claims appended hereto. 
     In this respect, before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of embodiments in addition to those described and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein, as well as the abstract, are for the purpose of description and should not be regarded as limiting. 
     As such, those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A and 1B  are perspective views of a device for inspecting a swage collar according to an embodiment of the invention. 
         FIGS. 2A and 2B  are cross sectional views of the inspection device according to  FIGS. 1A and 1B . 
         FIG. 3  is a block diagram of a system for inspecting a swage collar suitable for use with the inspection device according to  FIGS. 1A and 1B . 
         FIG. 4  is a system architecture for a controller suitable for use in the system according to  FIG. 3 . 
         FIG. 5  is a flow diagram according to an embodiment of the invention. 
         FIG. 6  is an example of a graph of pin height (abscissa) as it affects the shoulder height (ordinate) according to an embodiment of the invention. 
         FIGS. 7A and 7B  are examples of cams suitable for use with the inspection device according to  FIGS. 1A and 1B . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     An embodiment of the invention will now be described with reference to the drawing figures, in which like reference numerals refer to like parts throughout. As shown in  FIGS. 1A and 1B , an inspection device  10  is operable to evaluate a fastener  12 . This fastener  12  includes a collar  14  swaged on to a lock-bolt pin  16 . This fastener  12  is installed in a material  18 . The inspection device  10  includes an orifice  20 , a plurality of position sensors  22 A– 22 C, a plurality of indicators  24 A and  24 B, a power connector  26 , and a network connector  28 . 
     The orifice  20  is sized to be slightly larger in diameter than a portion of the collar  14  that has been materially deformed during the swaging process. In this swaging process, a swaging die is forced over a portion of the collar  14 , narrowing that portion of the collar  14 . At the conclusion of the swaging process a shoulder  30  is created on the collar  14  at the limit of the swaging die&#39;s progress. The position along the collar  14  that this shoulder  30  is created is indicative of the degree to which the collar  14  has been swaged. The orifice  20  is sized so that when the inspection device  10  is placed over the collar  14 , it slides over the narrowed portion of the collar  14  and rest upon the shoulder  30 . 
     The position sensors  22 A– 22 C are optionally included to indicate contact with the surface  18 . In various forms, the position sensors  22 A– 22 C may include any suitable device such as, for example: electrical contact pads; pressure sensors; snap-action type switches; and the like. Specific examples of snap-action type switches include series K switches manufactured by The Cherry Corporation of Waukegan, Ill. USA. If present, the inspection device  10  may include one or more position sensors. Therefore, the three position sensors  22 A– 22 C are for illustration purposes only. 
     The indicators  24 A and  24 B emit a signal such as, for example, a visual, auditory, and/or tactile signal. The signal is to inform a user as to whether or not the fastener  12  is within acceptable tolerances. In an embodiment of the invention, there are two indicators: one to indicate the fastener is within tolerance and; one to indicate the fastener is out of tolerance. For example, the indicator  24 A may include a green light emitting diode (LED) that, when lit, indicates that the fastener  12  is within tolerance. In addition, the indicator  24 B may include a red LED that, when lit, indicates that the fastener  12  is outside of acceptable tolerances. In various other embodiments of the invention, the inspection device  10  includes any reasonable number of indicators, such as, for example: 3 to 10 indicators. 
     The power connector  26  is to supply power to the various components of the inspection device  10 . In addition, the network connector  28  is optionally included to provide a two way communication path between the inspection device  10  and any other suitably configured electronic device. 
       FIGS. 2A and 2B  are cross sectional views of the inspection device  10  according to  FIGS. 1A and 1B . The inspection device  10  shown in  FIG. 1A  is depicted in a ready state. As shown in  FIG. 2A , the inspection device  10  includes a housing  34 , shoulder feeler  36 , pin feeler  38 , plurality of cams  40 A– 40 C, camshaft  42 , actuator  44 , plurality of pickups  46 A– 46 C, controller  48 , and power supply  50 . The housing  34  provides a support structure and protective envelope for the various other components of the inspection device  10 . In this regard, the housing  34  is generally formed from a relatively rigid and impermeable material. Examples of suitable materials include metals, resins, plastics, composite materials, and the like. In a preferred form, the housing  34  is formed from an electrically conductive material such as metal. 
     The shoulder feeler  36  is formed to include a number of features. Primary among these features is the orifice  20 . The orifice  20  includes a shoulder land  52  configured to approximately mate with the shoulder  30 . That is, the shoulder  30  is formed at an angle of between 15° and 90° relative to the plane of the material  18 . This angle depends upon the particular application and the fasteners&#39; manufacture&#39;s specifications. For a specific application, the angle is essentially equal to 45° and thus, the shoulder land  52  is formed at a complementary angle. In this manner, positive contact between the two surfaces is facilitated and excessive wear is reduced. Subsequent to the shoulder land  52 , the bore of the orifice  20  is increased somewhat to ease entry of the fastener  12  into the orifice  20 . 
     In addition, the shoulder feeler  36  includes a pair of contacts  54 A and  54 B. The contact  54 A is configured to complete a circuit when touching the cam  40 A. In a similar manner, the contact  54 B is configured to complete a circuit when touching the cam  40 B. The shoulder feeler  36  further includes a bearing surface  56  and  58 . The bearing surface  56  substantially prevents the shoulder feeler  36  from being withdrawn from the housing  34 . In this regard, the housing  34  includes a retaining lip  60  that acts in conjunction with the bearing surface  56  to substantially prevent the shoulder feeler  36  from being withdrawn from the housing  34 . The bearing surface  58  provides a surface onto which a spring  62  may thrust. The spring  62  provides sufficient force so as to urge the shoulder feeler  36  towards the retaining lip  60 . 
     The shoulder feeler  38  further includes an axial bore  64  to guide the operation of the pin feeler  38 . This axial bore  64  includes a stop  66  and bearing surface  68 . The stop  66  substantially prevents the pin feeler  38  from being withdrawn from the axial bore  64 . The bearing surface  68  provides a surface onto which a spring  70  may thrust. In this regard, the pin feeler  38  includes a retainer  72  that acts in conjunction with the stop  66  to retain the pin feeler  38  within the axial bore  64 . The retainer  72  also provides a bearing surface onto which the spring  70  may thrust. In this manner, the retainer  72  is urged towards the stop  66  by the action of the spring  70  thrusting against the bearing surface  68 . 
     As shown in  FIG. 2B , as the inspection device  10  is positioned over the fastener  12 , the pin feeler  38  is displaced towards the cam  40 C in response to contact with the lock-bolt pin  16 . In addition, the shoulder feeler  36  is displaced towards the cams  40 A and  40 B in response to the shoulder land  52  contacting the shoulder  30 . 
     The cams  40 A– 40 C (shown edge-on in  FIGS. 2A and 2B ) are rotatable about the camshaft  42 . The profiles of the cams  40 A– 40 C are based upon a table of offsets. This table is generated in response to extensive testing of fasteners. For example, many hundreds of a particular type of fastener are installed in a variety of materials over a range of conditions. These fasteners are then stressed until failure to determine acceptable values for this type of fastener. An example of such a table of offsets follows: 
     
       
         
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                   
                   
                 Minimum 
                 Maximum 
               
               
                   
                 Entry 
                 Pin Height 
                 Shoulder Height 
                 Shoulder Height 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                  1 
                 0.302 
                 0.085 
                 0.121 
               
               
                   
                  2 
                 0.301 
                 0.084 
                 0.121 
               
               
                   
                  3 
                 0.300 
                 0.084 
                 0.120 
               
               
                   
                 . 
                 . 
                 . 
                 . 
               
               
                   
                 . 
                 . 
                 . 
                 . 
               
               
                   
                 . 
                 . 
                 . 
                 . 
               
               
                   
                 82 
                 0.221 
                 0.036 
                 0.075 
               
               
                   
                 83 
                 0.220 
                 0.036 
                 0.074 
               
               
                   
                 84 
                 0.219 
                 0.036 
                 0.074 
               
               
                   
                   
               
             
          
         
       
     
     As shown in Table 1, the minimum shoulder height (S min ) and the maximum shoulder height (S max ) vary relative to the pin height (P height ). Stated in another manner, the range of acceptable heights for the shoulder  30  varies in accordance to the P height . In addition, it is to be noted that pin heights falling outside those listed in Table 1 are out of tolerance. That is, the P height  listed at entry 1 of the Table 1 represents a maximum P height  (P max ) and the P height  listed at entry  84  represents a minimum P height  (P min ). Thus, a sensed P height  falling outside the P max  and the P min  is outside an acceptable range of tolerance. 
     For the purpose of this disclosure, the term “cam” is used to describe a surface that is contoured to correspond a table of offsets such as those of Table 1. For the purpose of illustration, examples of cams suitable for use in the inspection device  10  are illustrated in  FIGS. 7A and 7B . However, the invention is not limited to these example, but rather, any suitable surface contoured to conform to a table of offsets may be utilized in the inspection device  10  and thus is within the scope of the invention. As the cam  40 C is rotated about the camshaft  42 , the radius of the cam  40 C measured above the pin feeler  38  varies according to the values listed in the pin height column of Table 1. Similarly, as the cams  40 A and  40 B are rotated about the camshaft  42 , the radius of the cams  40 A and  40 B as measured above the contacts  54 A and  54 B vary respectively according to the values listed in the minimum shoulder height and maximum shoulder height columns of Table 1. In addition, as the cams  40 A– 40 C rotate in a substantially unison manner, the ratios found in each row of Table 1 that relates pin height to S min  and S max  is essentially maintained. 
     The cams  40 A– 40 C are electrically isolated from each other. In addition, when not touching the contacts  54 A and  54 B, and the pin feeler  38 , the cams  40 A– 40 C are electrically isolated from these components as well. However, at least a portion of the surface of each of the cams  40 A– 40 C is electrically conductive and, when contacted by the respective contacts  54 A,  54 B, or pin feeler  38 , a respective electrically conductive path is created. 
     According to various embodiments of the invention, the actuator  44  includes any suitable rotating or actuating device configured to rotate the camshaft  42 . Examples of suitable rotating devices include stepper motors, electro servomotors, induction motors, alternating current (AC) brushed and brushless motors, direct current (DC) brushed and brushless motors, and the like. Examples of other suitable actuating devices include linear motors, linear actuators, and the like. In addition, according to another embodiment of the invention, the actuator  44  is a knob or handle that is rotatable by the user. In this manner, the inspection device may be constructed for considerably less expense. 
     Each of the pickups  46 A– 46 C are in electrical contact with a respective one of the cams  40 A– 40 C. For example, the pickup  46 A may include a flexible metal wire or ribbon disposed under tension against the cam  40 A. 
     The controller  48  is optionally included in the inspection device  10  to reduce human error, increase automation and repeatability, and increase traceability of the inspection process. If present, the controller  48  is operable to execute computer readable code, receive signals from the position sensors  22 A– 22 C and the pickups  46 A– 46 C, communicate via the network connector  28 , control the indicators  24 A and  24 B and the actuator  44 , and receive power via the power supply  50 . According to the computer readable code, the controller  48  is configured to interpret the signals received from the pickups  46 A– 46 C and modulate the various components it is configured to control. 
     The power supply  50  provides power for the various components of the inspection device  10 . In various embodiments of the invention, the power supply  50  includes power storage, generating, transforming, and/or conditioning capabilities. For example, the power supply  50  may include a rechargeable battery that is operable to be recharged via the power connector  26 . 
       FIG. 3  is a block diagram of a system  80  suitable for use with the inspecting device  10 . As shown in  FIG. 3 , the controller  48  is operable to execute computer readable code. In this regard, the system  80  includes a set of computer readable instructions or code  82 . According to the code  82 , the controller  48  is configured to generate and store data to a file  84 . This file  84  includes one or more of the following: data gathered while evaluating fasteners; timestamp information; positional information; identification numbers; and the like. The controller  48  is further configured to communicate across a network  86  via the network connector  28 . The network  86  is optionally included to provide additional data storage and/or processing capabilities. In this regard, the network includes a database  88  and a server  90 . The database  88  is configured to store a copy of the file  84 . The server  90  is configured to process the file  84 . In this manner, trends associated with the installation of fasteners may be extrapolated. In addition, the server  90  is operable, via the network  86 , to forward updates for the code  82 . 
     Also shown in  FIG. 3  is an actuator controller  92 . The actuator controller  92  is optionally included in the systems  80  depending upon the requirements of the actuator  44 . That is, if the actuator  44  is operable to be modulated by the controller  48  directly, the system  80  may not include the actuator controller  92 . If present, parameters of the actuator controller  92  are based upon the specification of the actuator  44  and the controller  48 . 
       FIG. 4  is a system architecture for the controller  48  suitable for use in the system  80 . As shown in  FIG. 4 , the controller  48  includes a processor  96 . This processor  96  is operably connected to a power supply  98 , memory  100 , clock  102 , analog to digital converter (A/D)  104 , and an input/output (I/O) port  106 . The I/O port  106  is configured to receive signals from any suitably attached electronic device and forward these signals to the A/D  104  and/or the processor  96 . For example, the I/O port  106  may receive signals associated with pin height sensed by the cam  40 C and forward the signals to the processor  96 . In another example, the I/O port  106  may receive signals via the network connector  28  and forward the signals to the processor  96 . If the signals are in analog format, the signals may proceed via the A/D  104 . In this regard, the A/D  104  is configured to receive analog format signals and convert these signals into corresponding digital format signals. Conversely, the A/D  104  is configured to receive digital format signals from the processor  96 , convert these signals to analog format, and forward the analog signals to the I/O port  106 . In this manner, electronic devices configured to receive analog signals may intercommunicate with the processor  96 . 
     The processor  96  is configured to receive and transmit signals to and from the A/D  104  and/or the I/O port  106 . The processor  96  is further configured to receive time signals from the clock  102 . In addition, the processor  96  is configured to store and retrieve electronic data to and from the memory  100 . Furthermore, the processor  96  is configured to determine signals operable to modulate the actuator controller  92  and thereby control the actuator  44  to exert a particular force and/or rotate to a particular degree. For example, signals associated with rotating the actuator  44 , 1° in the counterclockwise direction may be forwarded to the actuator controller  92  by the processor  96  via the I/O port  106 . 
     According to an embodiment of the invention, the processor  96  is configured to execute the code  82 . Based on this set of instructions and signals from the various components of the inspection device  10 , the processor  96  is configured to: determine the height of the pin  16 ; determine whether the pin height is within a predetermined range of heights and further; whether the shoulder height is between the S min  and S max  for the given pin height. For example, the processor  96  controls the actuator  44  to rotate until the cam  40 C contacts the pin feeler  38 . The processor  96  determines whether the degree of rotation correlates to an acceptable pin height. If the pin height is within an acceptable range, the processor  96  further determines if the shoulder height is acceptable based on whether the cam  40 A and not the cam  40 B are in respective contact with the contacts  54 A and  54 B. In this manner, the fastener  12  is evaluated. 
       FIG. 5  is a flow diagram of a method  110  according to an embodiment of the invention. Prior to the method  110 , one or more fasteners such as the fastener  12  are installed in a material such as the material  18 . In order to determine if these one or fasteners have been installed in a suitable manner, the method  110  is performed by the inspection device  10 . The method  110  is initiated at step  112  in response to turning on the device  10 . For example, in response to signals from the position sensors  22 A– 22 C, the processor  96  is configured to follow the set of instructions set forth in the code  82 . According to this code  82 , the processor  96  creates and/or accesses the file  84  at step  114 . 
     At step  116  the various sensors are monitored. For example, the processor  96  determines if one or more of the plurality of cams  40 A– 40 C is in contact with their respective contact  54 A and  54 B or pin feeler  38 . 
     At step  118  data is written to the file  84 . For example, data associated with signals forwarded to the processor  96  by the various sensors is written to or stored to the file  84 . In addition, time stamp information and other data associated with evaluation of the fastener  12  may be stored to the file  84  at step  118 . 
     At step  120  it is determined whether the inspection is completed. For example, if the processor  96  determines that the cam  40 B and/or  40 C is in contact with its respective contact  54 B and/or pin feeler  38 , then it is determined that the inspection is complete and the fastener is evaluated at step  124 . If it is determined that neither the cam  40 B nor  40 C is in contact with its respective contact  54 B and pin feeler  38 , then it is determined that the inspection is incomplete and the cams  40 A– 40 C modulated at step  122 . 
     At step  122  the cams  40 A– 40 C modulated. For example, the actuator  44  is controlled to rotate the camshaft  42  and thereby rotate the cams  40 A– 40 C. 
     At step  124  a determination is made as to whether fastener  12  is suitably installed in material  18 . In general, if one or more parameter(s) of fastener  12  are outside the respective tolerance range then, a determination is made that fastener has failed the evaluation. For example, if the P height  is determined to be outside of the P max  and P min  then it is determined that the fastener  12  has failed the evaluation. In another example, if the P height  is determined to be within the P max  and P min  and the shoulder height is determined to be greater than S max  then it is determined that the fastener  12  has failed the evaluation. If it is determined that the fastener  12  has failed the evaluation, the user is notified and data associated with the failure is stored to the file  84  at step  126 . Alternatively, if it is determined that the fastener  12  is installed in the material  18  within accepted tolerances then, the user is notified and data associated with the inspection process is written to the file  84  at step  128 . 
     At step  126  the user is notified and data associated with the failure of the fastener  12  is stored to the file  84 . For example, the controller  48  controls the indicator  24 B to emit a visual and/or auditory signal and the various sensed parameters of the fastener  12  such as the P height , shoulder height, and the like may be stored to the file  84 . In addition, a timestamp or other such information may be stored to the file  84 . In general, it is desirous that the visual and/or auditory signal associated with a failure of the fastener  12  be such that it is clearly differentiated from a passing of fastener  12 . For example, a red light signifies an out-of-tolerance condition whereas, a green light signifies an acceptable condition. Following the step  126 , the inspection device  10  may idle or shutdown until the method  110  is initiated again. 
     At step  128  the user is notified and data associated with the fastener  12  is stored to the file  84 . For example, the controller  48  controls the indicator  24 A to emit a visual and/or auditory signal and the various sensed parameters of the fastener  12  such as the P height , shoulder height, and the like may be stored to the file  84 . In addition, a timestamp or other such information may be stored to the file  84 . Following the step  126 , the inspection device  10  may idle or shutdown until the method  110  is initiated again. 
     The method  110  may exist in a variety of forms both active and inactive. For example, it may exist as software program(s) comprised of program instructions in source code, object code, executable code or other formats. Any of the above may be embodied on a computer readable medium, which include storage devices and signals, in compressed or uncompressed form. Examples of computer readable storage devices include conventional computer system RAM (random access memory), ROM (read only memory), EPROM (erasable, programmable ROM), EEPROM (electrically erasable, programmable ROM), flash memory, and magnetic or optical disks or tapes. Examples of computer readable signals, whether modulated using a carrier or not, are signals that a computer system hosting or running the computer program may be configured to access, including signals downloaded through the Internet or other networks. Concrete examples of the foregoing include distribution of the program(s) on a CD ROM or via Internet download. In a sense, the Internet itself, as an abstract entity, is a computer readable medium. The same is true of computer networks in general. 
       FIG. 6  is an example of a graph  132  of pin height, in thousandths of an inch, (abscissa) as it affects the shoulder height, in thousandths of an inch, (ordinate). As shown in  FIG. 6 , the minimum and maximum shoulder height (respectively S min  and S max ) may be plotted in terms of the pin height (P height ). In general, the S min  and S max  are shown to increase as the P height  increases. In this regard, a line  134  includes a plurality of circular data nodes representing the S min  at the respective P height . Similarly, a line  136  includes a plurality of square data nodes representing the S max  at the respective P height . As described herein with reference to Table 1, these data nodes may be determined empirically and/or may be based on computer modeling of fasteners. As shown in  FIG. 6 , the curvature of the lines  134  and  136  differ somewhat. However, the graph  132  is for illustrative purposes only, and thus, the respective curvatures, slopes and y-intercepts may be the same or different depending on the response of the various components. 
     In addition, the graph  132  is subdivided into sections A, B and C. Section A represents pin heights that exceed the maximum acceptable pin height (P max ). Section B represents acceptable pin heights that are between the P max  and P min . Section C represents pin heights that fall below the P min . 
       FIGS. 7A and 7B  are examples of cams suitable for use with the inspection device  10  according to  FIGS. 1A and 1B . In  FIGS. 7A and 7B , the cams  40 A– 40 C are viewed from a direction inline with the camshaft  42 . As shown in  FIG. 7A  the cams  40 A– 40 C include the sections A, B and C that correspond to the sections A, B and C of the graph  132  shown in  FIG. 6 . In particular, as the cam  40 A is utilized to sense the S min , the contour of the perimeter of the cam  40 A is based upon the contour of the line  134 . Similarly, the contour of the perimeter of the cam  40 B is based upon the contour of the line  136 . 
     With regard to cam  40 C, in various embodiments of the invention, the electrical properties of the material in sections A and C differ from that of section B. For example, sections A and C may be formed from or coated with an essentially non-conducting material. In this manner, if the pin feeler  38  contacts these essentially non-conducting regions, an error may be noted and the fastener  12  would fail the inspection. In another example, the electrical properties of the material in section A may differ from section C. In this example, section B is electrically conductive, section A has a first resistive property, and section C has a second resistive property. In this manner, the controller  48  may be configured to determine whether the pin  16  is below the P min , above the P max , or within an acceptable range of pin heights. In another embodiment, sections A, B and C of the cam  40 C are substantially conductive and the controller  48  determines the pin height based upon the rotation of the camshaft  42 . 
     The many features and advantages of the invention are apparent from the detailed specification, and thus, it is intended by the appended claims to cover all such features and advantages of the invention which fall within the true spirit and scope of the invention. Further, since numerous modifications and variations will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation illustrated and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.