Method of seperating fastener shanks from heads or frames

Abstract

A device and method for removal of fasteners by Electro-discharge Machining (EDM) such that portions of the fastener, such as a flange, may be separated from other portions of the fastener, such as a shank.

1 . A method of separating fastener shanks from heads, the method, comprising:
 Advancing, via electrical discharge machining, a tubular erosion electrode longitudinally through a head and shank of a fastener which is held to a frame via a collar attached to the fastener below the frame;   the fastener having a the shank fixed within a hole in the frame; and, forming an eroded space in the shank, below the frame, equal to or less than the diameter of the hole.   
     
     
         2 . The method of  claim 1 , wherein the erosion electrode rotates as it is advanced longitudinally. 
     
     
         3 . The method of  claim 1 , the method further comprising applying a voltage difference between the erosion electrode and at least one of the fastener and the frame. 
     
     
         4 . The method of  claim 1 , further comprising attaching a ground electrode configured to contact at least one of the fastener and the frame. 
     
     
         5 . The method of  claim 1 , further comprising: forming a ligament in the shank between the head and a portion of the shank within the frame. 
     
     
         6 . The method of  claim 5 , wherein ligament is a thickness configured to sever under an external force applied to the fastener, said force being within an acceptable tolerance of the frame. 
     
     
         7 . The method of  claim 5 , wherein the ligament is a thickness configured to sever under the intrinsic stress from the collar applied to the fastener. 
     
     
         8 . The method of  claim 1 , the method further comprising providing a dielectric fluid between the tubular erosion electrode and at least one of the head and shank of the fastener. 
     
     
         9 . A method of separating a fastener from two or more frames, comprising:
 providing a hollow erosion electrode to a to a fastener fixed through and holding two or more frames together;   placing the electrode aligned with the shank of the fastener within the frame;
 fastener having a head coaxially with the shank and extending beyond at least a portion of the frames; and, 
   the electrode, via electrical discharge matching, eroding a space within the fastener within the frames, the eroded space having an outer radius less than the outer radius of the shank, whereby a substantially concentric ligament of the shank is formed within the frame, the thickness of the ligament being defined by an offset between the outer radius of the eroded space and the outer radius of the shank.   
     
     
         10 . The method of  claim 9 , creating an eroded space comprises:
 providing a voltage difference between the erosion electrode and the fastener.   
     
     
         11 . The method of  claim 9 , wherein creating an eroded space comprises:
 advancing the erosion electrode longitudinally along the axis of the fastener.   
     
     
         12 . The method of  claim 9 , wherein creating an eroded space comprises:
 rotating the erosion electrode as it is advanced longitudinally.   
     
     
         13 . The method of  claim 9 , further comprising:
 forming a thin ligament whereby applying an external force to the head will sever the fastener.   
     
     
         14 . The method of  claim 3 , wherein the external force required to sever the ligament is within an acceptable tolerance of the frame. 
     
     
         15 . The method of  claim 9 , wherein the alignment is concentric. 
     
     
         16 . The method of  claim 9 , the method further comprising providing a dielectric fluid between the tubular erosion electrode and at least one of the head and shank of the fastener.