Abstract:
Erosion electrodes and associated devices, systems, and methods for providing improved performance during a process driven by FEED and facilitated by fluid flushing of a worksite is disclosed. Use of erosion electrodes having varying cross-sectional geometries result in customizable channels, within which the FEED process may proceed, improving efficiency and efficacy of the process as the erosion electrode is advanced longitudinally into a workpiece.

Description:
RELATED APPLICATION 
     This application claims the full Paris Convention benefit of and priority to U.S. Provisional Application Ser. No. 61/461,116, filed Jan. 13, 2011, the contents of which is incorporated herein by reference, as if fully set forth herein. 
    
    
     BACKGROUND 
     1. Field 
     This disclosure relates to electrodes for forceless electrical emission disintegration of a workpiece. 
     2. General 
     Single-use fasteners, such as a rivet or aerospace fastener where the fastener is formed during the assembly process, is common in many industries. In aerospace, the maintenance of air frames frequently requires removal of hundreds of fasteners in order to replace or repair structural members such as longerons, bulkheads, center barrels, and the like. Fasteners commonly include rivets or threaded fasteners which have been malleably distorted so they cannot be directly removed. Many of these fasteners are manufactured in titanium or other difficult to machine materials. 
     For example, during assembly, an extended portion often referred to as a “shank” of a fastener extends through one or more frames and may be pulled with respect to a collar on the opposite side. When the appropriate tension in the fastener shank is achieved, the collar may be malleably crushed against the shank of the fastener to form a permanent structure. Removal of the fastener and collar from the frame(s) may be challenged due to the fixation of the fastener and the collar, the toughness of the materials used for fasteners and collar, and the delicate condition of surrounding frames to which they are applied. 
     Traditional methods which have been utilized for many years to remove such fasteners have been to machine away the head of the fastener with a drill which is manually positioned. The drill adds pressure to the region being drilled as well as heat. Additionally, when the fastener is of titanium or other difficult to machine materials, such drilling results in a significant consumption of drill bits. Traditional drilling of fasteners operation has a known risk of damage to the structure in which the fastener is engaged. Damage to surrounding structures may result from vibration, drill bit slips, or drilling too deep. If drill bit slippage damage occurs to the surrounding material, or if the hole should be cut too deep, an oversized fastener might be used during reassembly, or the entire component may need to be replaced. Measures to correct such undesirable damage may result in additional expense associated with the operation. 
     In some cases, safety regulations and guidelines indicate a maximum number of errors that can be diagnosed and treated before an entire portion of a workpiece must be abandoned and replaced. Some regulations and guidelines may also require inspections of areas which appear to have had drill damage to assess the proper corrective action, if any. Such diagnostics require time, may cause delay, and may result in costs. 
     Electric discharge machining, or EDM, is an established method and apparatus utilized for machining metal. It operates through the utilization of an electrical discharge to remove metal from the workpiece. In the EDM process, an electrode is brought into close proximity to the workpiece. High voltage is applied in pulses at high frequency. The process occurs in the presence of a dielectric fluid. This creates sparking at generally the closest position between the workpiece and the electrode. Particles are removed from the workpiece when sparking is quenched. The duration of the spark (on-time) and the recovery time (off-time) are controlled so that the workpiece and electrode temperatures are not raised to the temperature of bulk melting. Therefore, erosion is essentially limited to a vaporization process. 
     DESCRIPTION 
     In one or more exemplary implementations an erosion electrode with an axial length including a distal segment and a proximal segment is provided, with at least a portion of the distal segment having a cross-sectional geometry that is distinct from a cross-sectional geometry of at least a portion of the proximal segment. 
     In one or more exemplary implementations an erosion electrode with an axial length including a distal segment and a proximal segment is provided with at least a portion of the distal segment having a cross-sectional geometry that is at least one of larger or smaller from a cross-sectional geometry of at least a portion of the proximal segment. 
     In one or more exemplary implementations an erosion electrode with an axial length including a distal segment and a proximal segment is provided with at least a portion of the distal segment having a cross-sectional geometry that is at least one of a different geometric configuration (including but not limited to circle, oval, polygon, and curves) distinct from a cross-sectional geometry configuration of at least a portion of the proximal segment. 
     In some exemplary implementations there is disclosed a FEED method or procedure of providing an erosion electrode of varying cross-sectional geometry to a conductive work piece and flowing a dielectric fluid between the erosion electrode and the workpiece. Thereafter providing an electrical potential between the erosion electrode and the workpiece and advancing the erosion electrode into the workpiece, whereby a channel of varying cross-sectional geometry is formed in the workpiece. 
    
    
     
       DRAWINGS 
       The above-mentioned features of the present disclosure will become more apparent with reference to the following description taken in conjunction with the accompanying drawings wherein like reference numerals denote like elements and in which: 
         FIG. 1A  shows some aspects of a cross-sectional view of an erosion electrode approaching a workpiece; 
         FIG. 1B  shows some aspects of a cross-sectional view of an erosion electrode within a workpiece; 
         FIG. 1C  shows some aspects of a magnified cross-sectional view of an erosion electrode within a workpiece; 
         FIG. 1D  shows some aspects of a magnified cross-sectional view of an erosion electrode within a workpiece; 
         FIG. 2A  shows some aspects of a cross-sectional view of an erosion electrode within a workpiece; 
         FIG. 2B  shows some aspects of a cross-sectional view of an erosion electrode within a workpiece; 
         FIGS. 2C and 2D  show some aspects of a magnified cross-sectional view of an erosion electrode within a workpiece; 
         FIG. 3A  shows some aspects of a cross-sectional view of an erosion electrode approaching a workpiece; 
         FIG. 3B  shows some aspects of a cross-sectional view of an erosion electrode within a workpiece; 
         FIG. 4  shows some aspects of a cross-sectional view of an erosion electrode; 
         FIG. 5  shows some aspects of a cross-sectional view of an erosion electrode within a workpiece; 
         FIG. 6A  shows some aspects of a cross-sectional view of an erosion electrode; 
         FIG. 6B  shows some aspects of a cross-sectional view of an erosion electrode within a workpiece; 
         FIG. 6C  shows some aspects of a cross-sectional view of a workpiece with eroded portions; 
         FIG. 7A  shows some aspects of a cross-sectional view of an erosion electrode; 
         FIG. 7B  shows some aspects of a cross-sectional view of a workpiece; 
         FIG. 7C  shows some aspects of a cross-sectional view of a second electrode within a workpiece; 
         FIG. 8A  shows some aspects of a cross-sectional view of an erosion electrode; and 
         FIG. 8B  shows some aspects of a cross-sectional view of a workpiece with eroded portions. 
         FIG. 9A  shows a sectional view of a hand-held EDM device, shown in association with a fastener receiving a pilot hole; 
         FIG. 9B  shows a sectional view of a hand-held EDM device, shown in association with a fastener having a pilot hole; 
         FIG. 10A  shows a sectional view of a hand-held EDM device, shown during an erosion process and in association with a fastener to be removed; 
         FIG. 10B  shows a sectional view of a hand-held EDM device, shown after an erosion process in association with a fastener to be removed; 
     
    
    
     FURTHER DESCRIPTION 
     As used herein, “cross-sectional geometry” is defined as attributes of an object determinable from a cross-sectional view of the object. The attributes include—but are not limited to—shape, size, outer radius, and inner radius. 
     According to one or more exemplary implementations, a forceless electrical erosion and disintegration or “FEED” (which is a type of electric discharge machining, or EDM) process includes the advancement of an electrode into a workpiece to erode, shape, define, or otherwise modify the workpiece as a product of one or more dielectric breakdown events between the electrode and the workpiece. Such a process may have a variety of applications and uses, some examples of which being disclosed in U.S. application Ser. No. 12/603,507, filed Oct. 21, 2009 which is incorporated by this reference as if fully set forth herein. 
     According to one or more exemplary implementations, as shown in  FIG. 1A , erosion electrode  100  (depicted here as tubular) is provided to a workpiece. Erosion electrode  100  may have a substantially consistent, non-varying, or homogeneous cross-sectional geometry. For example, proximal section  160  and distal section  180  may have substantially similar or equivalent cross-sectional geometries, as shown in  FIG. 1A . 
     According to one or more exemplary implementations, as shown in  FIG. 1B , erosion electrode  100  is advanced within workpiece  10  as the FEED process causes erosion of workpiece  10 , forming eroded space  50 . According to one or more exemplary implementations, a dielectric fluid may be provided in quality, quantity, and flow rate to facilitate FEED spark events, regulate temperature of the workpiece, or transport debris created during the process. High voltage is applied in pulses at high frequency. The process occurs in the presence of a dielectric fluid. This creates sparking at generally the closest position between the workpiece and the electrode. Particles are transported from the workpiece with fluid flow. As shown in the figures, dielectric fluid “DF” may be provided to or from lumen  190  of erosion electrode  100 . Lumen  190  may be in fluid communication with a dielectric inlet (not shown, but described in applicants&#39; co-pending U.S. application Ser. No. 12/603,507, filed Oct. 21, 2009) and/or dielectric outlet to deliver the dielectric fluid to a workspace between erosion electrode  100  and workpiece  10 . As shown in  FIGS. 1C and 1D , debris  15  created (from workpiece  10  or erosion electrode  100 ) during the FEED process is cleared from the space “DG” (also referred to as the dielectric gap or an overcut gap) between erosion electrode  100  and workpiece  10  by the flow of the dielectric fluid “DF”. In some cases, where debris  15  is not properly evacuated, its presence may alter operation of the FEED process by altering the characteristics of the dielectric gap between erosion electrode  100  and workpiece  10 . For example, debris  15  lodged between electrode  100  and workpiece  10  may prevent a desired spark event, cause a short or reduce efficiency of the process by electrically bridging the dielectric gap “DG” due to conductivity of debris  15 . 
     According to one or more exemplary implementations, in addition to erosion of workpiece  10 , erosion electrode  100  experiences its own erosion. Distal end  150  of erosion electrode  100  may recede during a FEED processes. Generally speaking, erosion electrode  100  and eroded space  50  achieve complementary mirror-image geometries, with a gap between erosion electrode  100  and workpiece  10  where spark events occur. 
     As erosion electrode  100  of homogenous cross-section (e.g., straight tube) cuts deeper into workpiece  10 , various issues may arise. The flushing path into eroded space  50 , around distal end  150 , and out of eroded space  50  becomes longer. Resistance to flow of the flushing fluid (which may also be the dielectric fluid DF) increases, causing slower flushing fluid flow. Consequently, the rate at which debris  15  is removed is reduced, increasing debris accumulation within eroded space  150 . By drawing spark events away from distal end  150  of erosion electrode  100 , energy provided for spark events may be wasted on erosion which does not contribute to deepening the eroded space. 
     Furthermore, any tipping of erosion electrode  100  (i.e., a central axis of erosion electrode  100 ) relative to a prior alignment with respect to workpiece  10  causes the gap between erosion electrode  100  and workpiece  10  to vary. In some cases, this may bridge the gap between erosion electrode  100  and workpiece  10  or otherwise change the characteristics contributing to spark events across the dielectric. For example, tipping of erosion electrode  100  may cause a side of the electrode to touch the top edge of the hole, resulting in a short. As eroded space  50  becomes deeper, these issues are magnified in that less tipping is required to produce undesirable results. 
     According to one or more exemplary implementations, erosion electrode  100  has a varying cross-sectional geometry across at least a portion of its axial length. According to one or more exemplary implementations, an outer diameter of erosion electrode  100  may be greater at one portion than at another. As shown in  FIG. 2A , the outer diameter at distal section  180  at or near distal end  150  is greater than an outer diameter at proximal section  160 . The transition from one outer diameter to another may be tapered, curved, gradual, stepped, etc. As shown in  FIGS. 2B and 2C , a distal portion of erosion electrode  100  erodes, including distal section  180 , whereby distal end  150  recedes until it reaches a proximal portion of erosion electrode  100 , including  160 , for example. 
     As the distal portion erodes, erosion electrode  100  defines eroded space  50  of complementary mirror-image geometry within workpiece  10 . The result is that eroded space  50  presents a wider channel at the surface of workpiece  10 . When the narrower proximal portion of erosion electrode  100  remains within the widened channel, an improved flow path for dielectric fluid is provided. Accordingly, debris  15  is more efficiently and effectively evacuated from between erosion electrode  100  and workpiece  10 . Likewise, tipping of erosion electrode  100  is less likely to cause contact with workpiece  10  at the top edge of the hole. 
     According to one or more exemplary implementations, an inner diameter of erosion electrode  100  may be greater at one portion than at another. As shown in  FIG. 3A , an inner diameter at distal section  180  at or near distal end  150  is less than an outer diameter at proximal section  160 . As shown in  FIG. 3B , erosion electrode  100  defines eroded space  50  of complementary mirror-image geometry within workpiece  10 . 
     According to one or more exemplary implementations, both an inner diameter and an outer diameter of erosion electrode  100  may be varied across the axial length. For example, an outer diameter at distal section  180  at or near distal end  150  is greater than an outer diameter at proximal section  160 , and an inner diameter at distal section  180  at or near distal end  150  is less than an outer diameter at proximal section  160 . By further example, the desired cross-section of eroded space  50  could be a “wedge” with the widest part of the wedge at the beginning of eroded space  50 , and the narrowest at the bottom. The cross-section of the wall of erosion electrode  100  that provides this shape would itself begin as a flask-shaped distal portion that erodes to present a smaller and smaller cutting surface as eroded space  50  gets deeper. 
     According to one or more exemplary implementations, cross-sectional geometries of erosion electrode  100  may increase and decrease along an axial length thereof. As shown in  FIG. 4 , an outer diameter at distal section  180  at or near distal end  150  is less than an outer diameter at medial section  170 . The outer diameter at medial section  170  may, in turn, be greater than an outer diameter at proximal section  160 . According to one or more exemplary implementations, a resulting workpiece  10  is shown in  FIG. 5 . 
     According to one or more exemplary implementations, a tapered distal section  180  may assist during alignment of erosion electrode  100  relative to workpiece  10 . For example, where workpiece  10  has a cavity or other opening on a surface thereof, tapered distal section  180  of erosion electrode  100  may provide a corresponding mating feature that facilitates relative alignment by a “fit” within the cavity. Such operation may be performed prior to or during an erosion event. 
     According to one or more exemplary implementations, other cross-sectional geometries vary along the axial length of erosion electrode  100 . For example, cross-sectional shape may vary. Cross-sectional profiles at proximal section  160 , medial section  170 , and distal section  180 , inter alia, may present at least two distinct shapes. For example, as shown in  FIG. 5A , medial section  170  presents an ovoid shape and proximal section  160  presents a circular shape. By further example, as shown in  FIG. 6A , distal section  180  may present a square shape and proximal section  160  presents a circular shape. Other shapes shall be appreciated by those having ordinary skill, such as polygonal, star, pointed, curved, scalloped, etc. The shape may define the inner diameter of a section, the outer diameter of a section, or both. Non-circular eroded space  50  may provide a mating feature for receiving a device for action therein. For example, a torque-imparting device (e.g., breaker bar, etc.), may be provided within eroded space  50  for effecting rotation of workpiece  10 . 
     According to one or more exemplary implementations, as shown in  FIGS. 6B and 6C , a portion of erosion electrode  100  (proximal, medial, distal, or other) having shape and size with greatest outer diameter or least inner diameter defines the upper portion of eroded space  50 , including the opening thereof. For example, as shown in  FIGS. 6A, 6B, and 6C , erosion electrode  100  may have a square portion  180  that extends radially outward at least as far as any other portion of erosion electrode  100 . Accordingly the square portion  180  defines the widest outer boundary of the resultant eroded space  50 , as shown in  FIG. 6C . Accordingly, cross-sectional geometries are selected according to a desired outcome with respect to eroded space  50 . 
     According to one or more exemplary implementations, any given portion of erosion electrode  100  may be of any length, according to desired outcome and suitable purposes. For example, a distal portion having a greater diameter than a proximal portion may be configured to be depleted before an erosion process is complete, such that distal end  150  reaches the proximal portion and at least a portion of the proximal portion contributes to the erosion. Accordingly, only a portion of eroded space  50  may be defined by the greater diameter of the distal portion. By further example, a distal portion having a greater diameter than a proximal portion may be configured to remain throughout an erosion process, such that distal end  150  never reaches the proximal portion. Accordingly, the entire length of eroded space  50  may be defined by the greater diameter of the distal portion. 
     According to one or more exemplary implementations, portions of erosion electrode  100  may each fulfill a given purpose corresponding to workpiece  10 . According to one or more exemplary implementations, as shown in  FIG. 7A , erosion electrode  100  has distal section  180  having first cross-sectional geometry, medial section  170  having second cross-sectional geometry, and proximal section  160  having third cross-sectional geometry. Each of the first, second, and third cross-sectional geometries may be distinct. As shown in  FIG. 7B , the workpiece  10  may have a non-homogenous composition. For example, workpiece may include fastener  20 , first frame  30 , second frame  40 , inter alia. According to one or more exemplary implementations, as shown in  FIG. 7B , distal section  180  may be configured to be exhausted within first frame  30  and before distal end  150  of erosion electrode  100  reaches second frame  40 . Accordingly, only distal section  180  operates on first frame  30 . As shown in  FIG. 7B , where fastener  20  is present, medial section  170  may be configured to taper inward to avoid operation thereof upon second frame  40 . 
     According to one or more exemplary implementations, one or more erosion electrodes  100  may be provided equidistant from a central axis and rotated about the central axis, providing a result analogous to a solid or hollow tubular electrode. 
     According to some exemplary implementations, as shown in  FIG. 7C , second electrode  200  of a distinct profile compared to said first electrode may be provided to an eroded space  50  to continue operation. Accordingly, said first erosion electrode  100  may be configured and operated to provide an operating space in which said second electrode  200  is configured to be used. Those of ordinary skill in the art will also understand that erosion electrode  100  may be configured to have a second portion substantially the same as second electrode  200  rather than requiring electrode switching. 
     According to one or more exemplary implementations, as shown in  FIGS. 8A and 8B , a portion of erosion electrode  100  (proximal, medial, distal, or other) having shape and size with greatest outer diameter or least inner diameter defines the upper portion of eroded space  50 , including the opening thereof. For example, as shown in  FIGS. 8A and 8B , erosion electrode  100  may have square portions  160  and  170  that extend radially outward at least as far as any other portion of erosion electrode  100 . Further, erosion electrode  100  may have a round or circular portion  180  toward distal end  150  thereof. Accordingly, the square portions  160  and  170  define the widest outer boundary of the resultant eroded space  50 , as shown in  FIG. 8B . 
     According to one or more exemplary implementations, other variations on shapes, outer diameters, and inner diameters are contemplated by the present disclosure. For example, portions of any embodiment disclosed herein may be combined with portions of other embodiments to yield combinations with unique and programmable capabilities. 
     According to some exemplary implementations, with varying-cross-section geometries, a part of erosion electrode  100  that does not ever erode (i.e. the “shaft” or a proximal portion of the electrode) is designed with a smaller straight wall cross-section whose diameter is smaller than the more distal portions. Thus, when erosion electrode  100  is well within eroded space  50 , the flushing liquid flow clearances are much larger than in the simple straight wall cutting case. Further, the type of material for such a portion may be varied to provide customized results. 
     According to one or more exemplary implementations, for each new workpiece  10 , a new erosion electrode is used, so each hole cut has the same character. According to one or more exemplary implementations, portions of erosion electrode  100  repeat, where the end-point at a portion of erosion electrode  100  from a previous hole cut becomes the starting point of the repeated cross-section of the next cut. 
     The rate at which distal end  150  of erosion electrode  100  recedes may be known, determinable, controllable, or programmable. Factors such as voltage applied, pulse interval, pulse duration, inter alia contribute to such results. According to one or more exemplary implementations, selection or determination of materials for erosion electrode  100  and workpiece  50 , inter alia, contribute to the rate of erosion of each. Polarity of an electrical potential during a spark event (i.e., dielectric breakdown) may contribute to the rate of erosion of each material. Selection, quality, and flow rate of a dielectric fluid may contribute to the rate of erosion. Accordingly, operation of erosion electrode  100  to create eroded spaces  50  is dependent on a variety of factors, each of which may be varied to produce different outcomes. Likewise, aspects and features of the present disclosure may be modified, rearranged, adjusted, scaled, separated and combined to provide selectable outcomes. Any number of sections or portions of erosion electrode  100  presenting distinct geometries may be provided. 
       FIGS. 9A, 9B, 10A and 10B  show a longitudinal section through a hand-held device  210  according to exemplary implementations. The principle structural reference part of the hand-held device  210  is the base  226 . The base may be maneuvered by handle  228 , which is secured thereto. The handle  228  may be configured to be held in the hand of the workman. Various configurations may be provided to provide hand-held operation of the device  210 . According to some exemplary implementations, the handle  228  may carry a switch  30  to activate components of the hand-held device  210 , as disclosed herein. 
     According to some exemplary implementations, mounted on a distal end of the base  226  is a hood  232 . The hood  232  defines a workspace, within which erosion activity may occur. The hood  232  may be configured to seal against a portion of a workpiece, such as a frame, thereby enclosing the workspace such that the workspace includes access to at least a portion of a fastener  218 , a collar  224 , or another workpiece. The portion enclosed may be at least one of the shank of fastener  218 , the head of fastener  218 , and the collar  224 . According to some exemplary implementations, as the hood  232  engages the workpiece, the hood  232  may be configured to enclose the workspace so as to substantially isolate it from the environment outside the workspace. Accordingly, substances within the workspace may be contained except through controlled inlets and outlets, as disclosed herein. For example, at least a portion of the hood  232  may be of a flexible or deformable material that adaptably interfaces with the surface  220  of the workpiece to create a seal at the interface. There may be provided a rigid structure for stabilizing the hand-held device  210  against a workpiece, such as at the surface  220 , as shown in the figures. Channels may be provided for passage of dielectric fluid there through. 
     According to some exemplary implementations, hand-held device  210  may include a ground electrode  238  and erosion electrode  266 . The erosion electrode  266  may be configured to controllably approach a portion of a workpiece to be eroded, such as a fastener  218  or a collar. 
     According to other exemplary implementations, aspects of which are shown in  FIGS. 10A and 10B  the erosion electrode  266  may be a hollow tubular structure. In some instances aspects of one exemplary implementation may fit properly into another exemplary implementation. The hollow tubular structure of an erosion electrode  66  may be symmetrical about an axis and configured to travel longitudinally along the axis, thereby eroding a ring-shaped portion of the workpiece. This shape is useful for separating the head flange of a fastener  218  from the shank of the fastener  218 . Where erosion of the frame is not desired, such erosion may be minimized or avoided by providing a hollow tubular erosion electrode  266  having an outer diameter that is about equal to or less than the outer diameter of the shank of the fastener  18  or the inner diameter of the hole of the frame. A ground electrode  238  may be disposed central to and concentric with a tubular erosion electrode  266 . The ground electrode  238  may be configured to contact at least a portion of the workpiece that is electrically conductive with another portion of the workpiece that is eroded by the erosion electrode  266 . For example, where portions of the head, flange, or shank of fastener  218  are to be eroded, the ground electrode  38  may be configured to contact a portion of the fastener  218 , such that a dielectric breakdown between the erosion electrode  266  and the fastener  218  may be achieved. 
     According to some exemplary implementations, an erosion electrode  266  having a hollow tubular structure may be further configured to rotate about its axis of symmetry as it advances longitudinally along the axis. The rotation of the hollow tubular structure helps reduce issues associated with uneven wear of the erosion electrode  266  at its distal end. An uneven electrode results in correspondingly uneven workpiece erosion. This corresponding erosion causes the uneven portions of the erosion electrode  266  to remain uneven, because the gap distance between the erosion electrode  266  and the workpiece (the spark gap) at each point is equal. When the device is applied to the next fastener, the uneven erosion electrode  66  will be attenuated since the “high” portions of the erosion electrode  266  will contact first, but will not be completely eliminated for multiple cycles. A rotating electrode will recover sooner than a non-rotating electrode. As the hollow tubular structure is rotated as it advances, the orientation of the uneven surface of the erosion electrode  266  is altered with respect to the correspondingly uneven workpiece. The changing relative orientation causes portions of the erosion electrode  266  that may have disproportionately greater extension to be moved into other locations of which may result in increased erosion activity, whereby the continued wear of the erosion electrode  266  is in some circumstances at least partially self-correcting in terms of providing an even erosion electrode  266  and an evenly eroded workpiece. 
     According to some exemplary implementations, the erosion electrode  266  may be moved by translational motion and rotational motion. According to some exemplary implementations, the translational motion of the erosion electrode  266  may simultaneously create rotational motion. For example, a lead screw may be rotated to advance the erosion electrode  66  and simultaneously rotate it about an axis. According to some exemplary implementations, translational and rotational motion of the erosion electrode  266  may be applied independently, such that rotation and translation may be simultaneously or separately provided. 
     According to some exemplary implementations, an erosion electrode  266  may be a solid pin configured to penetrate a fastener  218  as shown in  FIGS. 9A and 9B . This shape is useful for providing a pilot hole in the fastener  218  for subsequent mechanical drilling. Such pilot holes help control operation of a mechanical drill by providing a non-slip location. This shape electrode is also useful for eroding a central portion of a head of the fastener  218  to allow removal of the flange from the shank (not shown). 
     While the method and agent have been described in terms of what are presently considered to be the most practical and preferred implementations, it is to be understood that the disclosure need not be limited to the disclosed implementations. It is intended to cover various modifications and similar arrangements included within the spirit and scope of the claims, the scope of which should be accorded the broadest interpretation so as to encompass all such modifications and similar structures. The present disclosure includes any and all implementations of the following claims. 
     It should also be understood that a variety of changes may be made without departing from the essence of the disclosure. Such changes are also implicitly included in the description. They still fall within the scope of this disclosure. It should be understood that this disclosure is intended to yield a patent covering numerous aspects of the disclosure both independently and as an overall system and in both method and apparatus modes. 
     Further, each of the various elements of the disclosure and claims may also be achieved in a variety of manners. This disclosure should be understood to encompass each such variation, be it a variation of an implementation of any apparatus implementation, a method or process implementation, or even merely a variation of any element of these. 
     Particularly, it should be understood that as the disclosure relates to elements of the disclosure, the words for each element may be expressed by equivalent apparatus terms or method terms—even if only the function or result is the same. 
     Such equivalent, broader, or even more generic terms should be considered to be encompassed in the description of each element or action. Such terms can be substituted where desired to make explicit the implicitly broad coverage to which this disclosure is entitled. 
     It should be understood that all actions may be expressed as a means for taking that action or as an element which causes that action. 
     Similarly, each physical element disclosed should be understood to encompass a disclosure of the action which that physical element facilitates. 
     Any patents, publications, or other references mentioned in this application for patent are hereby incorporated by reference. In addition, as to each term used it should be understood that unless its utilization in this application is inconsistent with such interpretation, common dictionary definitions should be understood as incorporated for each term and all definitions, alternative terms, and synonyms such as contained in at least one of a standard technical dictionary recognized by artisans and the Random House Webster&#39;s Unabridged Dictionary, latest edition are hereby incorporated by reference. 
     Finally, all referenced listed in the Information Disclosure Statement or other information statement filed with the application are hereby appended and hereby incorporated by reference; however, as to each of the above, to the extent that such information or statements incorporated by reference might be considered inconsistent with the patenting of this/these disclosure(s), such statements are expressly not to be considered as made by the applicant(s). 
     In this regard it should be understood that for practical reasons and so as to avoid adding potentially hundreds of claims, the applicant has presented claims with initial dependencies only. 
     Support should be understood to exist to the degree required under new matter laws—including but not limited to United States Patent Law 35 USC 132 or other such laws—to permit the addition of any of the various dependencies or other elements presented under one independent claim or concept as dependencies or elements under any other independent claim or concept. 
     To the extent that insubstantial substitutes are made, to the extent that the applicant did not in fact draft any claim so as to literally encompass any particular implementation, and to the extent otherwise applicable, the applicant should not be understood to have in any way intended to or actually relinquished such coverage as the applicant simply may not have been able to anticipate all eventualities; one skilled in the art, should not be reasonably expected to have drafted a claim that would have literally encompassed such alternative implementations. 
     Further, the use of the transitional phrase “comprising” is used to maintain the “open-end” claims herein, according to traditional claim interpretation. Thus, unless the context requires otherwise, it should be understood that the term “compromise” or variations such as “comprises” or “comprising”, are intended to imply the inclusion of a stated element or step or group of elements or steps but not the exclusion of any other element or step or group of elements or steps. 
     Such terms should be interpreted in their most expansive forms so as to afford the applicant the broadest coverage legally permissible.