Method of forming close tolerance tubing

Claim 1

A COLD STRETCHING METHOD OF TRANSFORMING STOCK RESILIENT METALLIC TUBING TO CLOSE TOLERANCE TUBING HAVING IMPROVED PHYSICAL QUALITIES AND OF A WALL THICKNESS LESS THAN THAT OF SAID STOCK TUBING, COMPRISING THE STEPS OF; DISPOSING A LENGTH OF SAID STOCK TUBING IN A LONGITUDINALLY EXTENDING POSITION; PLACING SAID LENGTH OF TUBING UNDER TENSION BY APPLYING A FIRST FORCE LONGITUDINALLY TO THE END PORTIONS THEREOF; INCREASING THE TENSION ON SAID LENGTH OF TUBING BY INCREASING SAID FIRST FORCE TO A VALUE LESS THAN THE YIELD STRENGTH OF THE MATERIAL FORMING SAID STOCK TUBING; EXERTING A SECOND FORCE ON AT LEAST ONE HARD SURFACE TO SINK THE SAME RADIALLY INTO SAID STOCK TUBING TENSIONED BY SAID FIRST FORCE TO THE DEPTH THAT IT IS DESIRED TO REDUCE SAID WALL THICKNESS; CIRCUMFERENTIALLY ROTATING SAID HARD SURFACE AT SAID DESIRED DEPTH ABOUT SAID STOCK TUBING; MOVING SAID HARD SURFACE LONGITUDINALLY RELATIVE TO SAID STOCK TUBING WITH CONCURRENT APPLICATION OF A THIRD LONGITUDINALLY DIRECTED FORCE TO SAID HARD SURFACE WHICH THIRD FORCE IN COMBINATION WITH SAID FIRST FORCE SUBJECTS A TRANSVERSE AREA OF SAID STOCK TUBING WHICH IS IN PRESSURE CONTACT WITH SAID HARD SURFACE TO A STRESS ABOVE THAT AT WHICH SAID MATERIAL PERMANENTLY DEFORMS; AND CONTINUING TO MOVE SAID ROTATING HARD SURFACE LONGITUDINALLY RELATIVE TO SAID STOCK TUBING AT SAID COMBINED FIRST AND THIRD FORCES UNTIL THE LENGTH OF SAID TUBING HAS HAD THE WALL THICKNESS THEREOF REDUCED SUBSTANTIALLY THE AMOUNT WHICH SAID HARD SURFACE WAS SUNK THEREIN.