Drive head and ECM method and tool for making same

Abstract

A drive head for a bolt, fastener, coupling, nut or other driveable head made from a less malleable metal such as a powder metal nickel alloy. The drive head has an upper drive portion having at least six convex corners spaced around the outer periphery thereof, each corner terminating in an edge. The drive head also has a lower flange portion adjacent to the drive portion and having an edge extending radially outwardly to at least the edge of each corner. The drive portion and the flange portion of the drive head is formed by subjecting a blank having a generally circular head to electrochemical machining (ECM). A tool is also provided for the ECM method to form the drive portion and flange portion of the drive head.

1 . A drive head made from a powder metal nickel alloy comprising at least about 40% nickel, the drive head comprising: 
 (a) an upper drive portion having at least twelve convex corners spaced around the outer periphery thereof, each corner terminating in an edge; and    (b) a lower flange portion adjacent to the drive portion and having an edge extending radially outwardly to at least the edge of each corner of the drive portion;    (c) the drive portion and flange portion being formed by electrochemical machining.    
     
     
         2 . The drive head of  claim 1  wherein the nickel alloy comprises from about 40 to about 75% nickel.  
     
     
         3 . The drive head of  claim 2  wherein the nickel alloy comprises from about 45 to about 60% nickel.  
     
     
         4 . The drive head of  claim 2  wherein the nickel alloy further comprises from about 5 to about 21% cobalt and from about 10 to about 22% chromium.  
     
     
         5 . The drive head of  claim 4  wherein the nickel alloy comprises from about 12 to about 14% cobalt and from about 15 to about 17% chromium.  
     
     
         6 . The drive head of  claim 1  wherein each corner is generally V-shaped.  
     
     
         7 . The drive head of  claim 6  wherein the flange portion comprises an upper generally sloping section and a lower generally circular section that intersect at the edge of the flange portion.  
     
     
         8 . The drive head of  claim 7  wherein the edge of the flange portion extends beyond the edge of each corner.  
     
     
         9 . A bolt made from a powder metal nickel alloy comprising at least about 40% nickel, the bolt comprising: 
 (1) a drive head having: 
 (a) an upper drive portion having at least twelve generally V-shaped convex corners spaced around the outer periphery thereof, each corner terminating in an edge; and  
 (b) a lower flange portion adjacent to the drive portion and having an edge extending radially outwardly to at least the edge of each corner;  
 (c) the drive portion and flange portion being formed by electrochemical machining; and  
   (2) a shank having one end adjacent to the flange portion.    
     
     
         10 . The bolt of  claim 9  wherein the shank has a threaded exterior surface.  
     
     
         11 . The bolt of  claim 9  wherein the nickel alloy comprises from about 45 to about 60% nickel, from about 5 to about 21% cobalt and from about 10 to about 22% chromium.  
     
     
         12 . The bolt of  claim 9  wherein the flange portion comprises an upper generally sloping section and a lower generally circular section that intersect at the edge of the flange portion.  
     
     
         13 . The bolt of  claim 12  wherein the edge of the flange portion extends beyond the edge of each corner.  
     
     
         14 . A tool for forming a drive head from a metal or metal alloy by electrochemical machining, the drive head having an upper drive portion having at least six convex corners spaced along the outer periphery thereof, each corner terminating in an edge, and a lower flange portion adjacent to the drive portion and having an edge extending radially outwardly to at least the edge of each corner, the tool comprising: 
 (1) a shaping end having a cutting face;    (2) a chamber for the passage of electrolyte fluid that opens at the cutting face;    (3) the cutting face having an inner portion adjacent to the chamber, the inner portion of the cutting face having at least six circumferentially spaced concave recesses; and    (4) each recess having a concave relief.    
     
     
         15 . (canceled)  
     
     
         16 . The tool of  claim 14  wherein the concave relief has a generally semicircular shape.  
     
     
         17 . The tool of  claim 14  wherein the inner portion of the cutting face has twelve circumferentially spaced recesses.  
     
     
         18 . The tool of  claim 17  wherein the inner portion of the cutting face is tapered.  
     
     
         19 . A method for forming a drive head from a metal or metal alloy, the drive head having an upper drive portion having at least six convex corners spaced along the outer periphery thereof, each corner terminating in an edge, and a lower flange portion adjacent to the drive portion and having an edge extending radially outwardly to at least the edge of each corner, the method comprising the steps of: 
 (a) providing a blank made from a metal or metal alloy and having a circular head; and    (b) subjecting the head to electrochemical machining to form the drive portion and the flange portion of the drive head.    
     
     
         20 . The method of  claim 19  wherein the metal or metal alloy is a powder metal nickel alloy comprising at least about 40% nickel, at least about 5% cobalt and at least about 10% chromium.  
     
     
         21 . The method of  claim 20  wherein the blank is a bolt blank that further comprises a cylindrical shaft connected to the head.  
     
     
         22 - 29 . (canceled)  
     
     
         30 . A method for forming a drive head in a bolt blank, the drive head having an upper drive portion having at least six generally V-shaped convex corners spaced along the outer periphery thereof, each corner terminating in an edge, and a lower flange portion adjacent to the drive portion and having an edge extending radially outwardly to at least the edge of each corner, the method comprising the steps of: 
 (a) providing a bolt blank made from a powder metal nickel alloy comprising at least about 40% nickel, the bolt blank comprising a circular head and a cylindrical shaft;    (b) providing a shaping tool comprising: 
 (1) a shaping end with a cutting face;  
 (2) a chamber for the passage of electrolyte fluid that opens at the cutting face;  
 (3) the cutting face having an inner portion adjacent to the chamber, the inner portion having at least six circumferentially spaced generally V-shaped concave recesses, each recess having a first segment and a second segment; and  
 (4) a semicircular relief connecting the first and second segments; and  
   (c) moving the cutting face concentrically along the exterior length of the head while applying an electrical current to the bolt blank and the shaping tool and passing an electrolyte fluid through the chamber to conduct current across the gap between the cutting face and the head until the drive portion and flange portion of the drive head are formed.    
     
     
         31 . The method of  claim 30  wherein an electrical potential of from about 12 to about 18 volts is applied across the electrolyte fluid.  
     
     
         32 - 34 . (canceled)  
     
     
         35 . The method of  claim 30  wherein the inner portion of the cutting face has twelve circumferentially spaced recesses and wherein twelve corners are formed in the drive portion of the drive head.