Die structure

Claim 1

THE PROCESS OF EFFECTING A COLD PRESSURE WELD WITH A PAIR OF COLD PRESSURE WELDABLE METAL WORKPIECES AND FIRST AND SECOND SPLIT DIES EACH HAVING SECTIONS EQUIPPED WITH MATING FACES, SAID MATING FACES OF EACH DIE, WHEN IN ABUTTING RELATIONSHIP, DEFINING A WORKPIECE GRIPPING HOLE THEREIN OF A CROSS SECTIONAL CONTOUR DIFFERENT THAN THE CONTOUR OF THE WORKPIECES, THE CROSS SECTIONAL AREA OF THE HOLES BEING GREATER THAN THE CROSS SECTIONAL AREA OF THE WORKPIECES, COMPRISING THE STEPS OF: (A) SEPARATING THE SECTIONS OF EACH DIE; (B) POSITIONING FIRST AND SECOND WORKPIECES IN THE FIRST AND SECOND DIES RESPECTIVELY WITH PORTIONS OF THE PIECES PROJECTING PAST THE DIE FACES; (C) CLOSING THE DIE SECTIONS ON THE WORKPIECES THEREBY BRINGING THE WORKPIECES INTO LINE CONTACT WITH SAID HOLE PORTIONS; (D) COMPLETING THE CLOSING OF THE DIE SECTIONS THEREBY DEFORMING THE WORKPIECES PARTIALLY INTO THE CROSS SECTION OF THE HOLES AND ESTABLISH WORK GRIPPING SURFACE AREA CONTACT BETWEEN THE DIES AND THE WORKPIECES; AND, (E) MUTUALLY UPSETTING THE PROJECTING WORKPIECES PORTIONS TO WELD THE WORKPIECES BY FORCING SAID DIES TOGETHER, AND SIMULTANEOUSLY DISPLACING METAL FROM THE WORKPIECE PORTIONS INTO THE HOLES TO INCREASE THE AREAS OF WORKPIECE GRIPPING CONTACT AND CAUSE SECTIONS OF THE WORKPIECES IN THE HOLES TO ASSUME SUBSTANTIALLY THE CROSS-SECTIONAL CONTOUR OF THE HOLES, THEREBY PREVENTING SLIPPAGE OF THE WORKPIECES RELATIVE TO THE DIES TO PERMIT COMPLETION OF THE WELD.