Method of extruding shank portions with 50% or less cross-sectional area than that of the original blanks

Claim 1

THE METHOD OF COLD FORMING A HEADED ARTICLE FROM A CYLINDRICAL WORKPIECE OF METAL IN WHICH THE SHANK OF THE ARTICLE IS OF SMALL DIAMETER AS COMPARED WITH THE HEAD PORTION AND OF MATERIALLY ENHANCED STRENGTH AS COMPARED WITH THE STRENGTH OF THE WORKPIECE, SAID METHOD COMPRISING: (A) PROVIDING A CYLINDRICAL WORKPIECE OF METAL HAVING A CROSS-SECTIONAL AREA AT LEAST TWICE THAT OF THE SHANK PORTION OF THE ARTICLE TO BE FORMED, (B) APPLYING TO THE ENTIRE SURFACE OF ONE END OF SAID WORKPIECE A PRESSURE WHICH DEVELOPS FLOW OF METAL THROUGH A DIE ORIFICE SO AS TO EXTRUDE THERETHROUGH SAID SHANK PORTION HAVING A CROSS-SECTIONAL AREA AT LEAST LESS THAN ONE-HALF THAT OF SAID WORKPIECE, (C) SUPPORTING THE CYLINDRICAL SIDE WALL OF SAID WORKPIECE THROUGHOUT THE ENTIRE LENGTH AND CIRCUMFERENCE THEREOF AGAINST ALL SUBSTANTIAL LATERAL DEFORMATION THROUGHOUT THE PERIOD OF APPLICATION OF SAID PRESSURE BY PLACING THE SAME IN A CIRCULAR CAVITY AS A GUIDE, (D) IN THE TRANSITION REGION BETWEEN A CIRCULAR PORTION OF SAID CAVITY AND THE ORIFICE, CONTROLLING THE MAGNITUDE OF SAID PRESSURE TO BE PROPORTIONAL TO THE REDUCTION IN AREA BETWEEN THE WORKPIECE AND SAID SHANK PORTION BY INDUCING A SMOOTH, UNIFORM AND PROGRESSIVE INWARD FLOW OF METAL FROM THE OUTER PORTION OF SAID WORKPIECE TOWARD SAID ORIFICE AND ALONG A SURFACE OF REVOLUTION DEFINED BY A GENERATRIX REVOLVED ABOUT THE LONGITUDINAL AXIS OF SAID CAVITY, SAID GENERATRIX HAVING A CURVATURE WHICH AT ONE END PORTION IS TANGENTIAL WITH THE CIRCULAR WALL OF SAID CAVITY AND AT THE OPPOSITE END PORTION TERMINATES AT SAID ORIFICE, THE INTERMEDIATE PORTION OF SAID GENERATRIX HAVING A CURVATURE NO GREATER THAN THE DIFFERENCE BETWEEN THE DIAMETER OF SAID CAVITY AND THE DIAMETER OF THE ORIFICE AND NOT LESS THAN ONE-HALF THAT DIFFERENCE, (E) PRODUCING A STRENGTH OF A HIGHER ORDER THAN THAT OF THE METAL OF SAID WORKPIECE BY PARTIAL WORKING OF THE METAL WITHIN SAID TRANSITION REGION, THEREBY IMPROVING THE GRAIN STRUCTURE WITHIN THAT TRANSITION REGION AND BY THROUGHLY WORKING SAID METAL BY ITS INWARD FLOW TOWARD SAID ORIFICE AND THENCE THROUGH SAID ORIFICE FOR PRODUCTION OF SAID SHANK PORTION, (F) TERMINATING THE APPLICATION OF SAID PRESSURE WHEN THE VOLUME OF THE UNWORKED PORTION OF SAID WORKPIECE IS EQUAL TO THAT OF THE HEAD PORTION TO BE FORMED IN PRODUCTION OF A SHAPED BLANK WITH A TRANSITION REGION CONFORMING WITH SAID SURFACE OF REVOLUTION AND OF METAL WHICH HAS BEEN WORKED DURING FORMATION OF SAID SHANK PORTION, (G) ENCLOSING AND SUPPORTING SAID SHANK PORTION ON ALL SIDES THEREOF, (H) WHILE SAID SHANK PORTION IS SO ENCLOSED AND SUPPORTED, FORMING SAID HEAD PORTION LARGELY FROM THE UNWORKED METAL SPACED FROM SAID TRANSITION REGION AND RESHAPING SAID TRANSITION REGION TO ESTABLISH A THROUGHLY AND UNIFORMLY COLD-WORKED METAL PORTION IN THE CRITICAL JUNCTURE BETWEEN SAID HEAD PORTION AND SAID SHANK PORTION.

Claim 2

THE METHOD OF COLD FORMING A HEADED ARTICLE FROM A CYLINDRICAL WORKPIECE OF METAL IN WHICH THE SHANK OF THE ARTICLE IS OF SMALL DIAMETER AS COMPARED WITH THE HEAD PORTION AND OF MATERIALLY ENHANCED STRENGTH AS COMPARED WITH THE STRENGTH OF THE WORKPIECE, SAID METHOD COMPRISING: (A) PROVIDING A CYLINDRICAL WORKPIECE OF METAL HAVING A CROSS-SECTIONAL AREA AT LEAST TWICE THAT OF THE SHANK PORTION OF THE ARTICLE TO BE FORMED, (B) APPLYING TO THE ENTIRE SURFACE OF ONE END OF SAID WORKPIECE A PRESSURE WHICH DEVELOPS FLOW OF METAL THROUGH A DIE ORIFICE SO AS TO EXTRUDE THERETHROUGH SAID SHANK PORTION HAVING A CROSS-SECTIONAL AREA AT LEAST LESS THAN ONE-HALF THAT OF SAID WORKPIECE, (C) SUPPORTING THE CYLINDRICAL SIDE WALL OF SAID WORKPIECE THROUGHOUT THE ENTIRE LENGTH AND CIRCUMFERENCE THEREOF AGAINST ALL SUBSTANTIAL LATERAL DEFORMATION THROUGHOUT THE PERIOD OF APPLICATION OF SAID PRESSURE BY PLACING THE SAME IN A CIRCULAR CAVITY AS A GUIDE, (D) IN THE TRANSITION REGION BETWEEN A CIRCULAR PORTION OF SAID CAVITY AND THE ORIFICE, CONTROLLING THE MAGNITUDE OF SAID PRESSURE TO BE PROPORTIONAL TO THE REDUCTION IN AREA BETWEEN THE WORKPIECE AND SAID SHANK PORTION BY INDUCING A SMOOTH, UNIFORM AND PROGRESSIVE INWARD FLOW OF METAL FROM THE OUTER PORTION OF SAID WORKPIECE TOWARD SAID ORIFICE AND ALONG A SURFACE OF REVOLUTION DEFINED BY A GENERATRIX REVOLVED ABOUT THE LONGITUDINAL AXIS OF SAID CAVITY, SAID GENERATRIX HAVING A CURVATURE WHICH AT ONE END PORTION IS TANGENTIAL WITH THE CIRCULAR WALL OF SAID CAVITY AND AT THE OPPOSITE END PORTION TERMINATES AT SAID ORIFICE, THE INTERMEDIATE PORTION OF SAID GENERATRIX HAVING A CURVATURE NO GREATER THAN THE DIFFERENCE BETWEEN THE DIAMETER OF SAID CAVITY AND THE DIAMETER OF THE ORIFICE AND NOT LESS THAN ONE-HALF THAT DIFFERENCE, (E) PRODUCING A STRENGTH OF A HIGHER ORDER THAN THAT OF THE METAL OF SAID WORKPIECE BY PARTIAL WORKING OF THE METAL WITHIN SAID TRANSITION REGION, THEREBY IMPROVING THE GRAIN STRUCTURE WITHIN THAT TRANSITION REGION AND BY THROUGHLY WORKING SAID METAL BY ITS INWARD FLOW TOWARD SAID ORIFICE AND THENCE THROUGH SAID ORIFICE FOR PRODUCTION OF SAID SHANK PORTION, (F) TERMINATING THE APPLICATION OF SAID PRESSURE WHEN THE VOLUME OF THE UNWORKED PORTION OF SAID WORKPIECE IS EQUAL TO THAT OF THE HEAD PORTION TO BE FORMED IN PRODUCTION OF A SHAPED BLANK WITH A TRANSITION REGION CONFORMING WITH SAID SURFACE OF REVOLUTION AND OF METAL WHICH HAS BEEN WORKED DURING FORMATION OF SAID SHANK PORTION, (G) ENCLOSING AND SUPPORTING SAID SHANK PORTION ON ALL SIDES THEREOF, (H) WHILE SAID SHANK PORTION IS SO ENCLOSED AND SUPPORTED, FORMING SAID HEAD PORTION LARGELY FROM THE UNWORKED METAL SPACED FROM SAID TRANSITION REGION AND RESHAPING SAID TRANSITION REGION TO ESTABLISH A THROUGHLY AND UNIFORMLY COLD-WORKED METAL PORTION IN THE CRITICAL JUNCTURE BETWEEN SAID HEAD PORTION AND SAID SHANK PORTION.