Method of manufacturing valve seat

Claim 1

THE METHOD OF FORMING A VALVE SEAT HAVING AN INSERT OF PLASTIC MATERIAL, SAID METHOD COMPRISING: MACHINING A GROOVE IN THE FACE OF THE VALVE SEAT TO RECEIVE THE PLASTIC INSERT; PROVIDING THE GROOVE WITH AN INSERT HOLDING PORTION OF THREAD SERRATIONS HAVING A DEPTH OF APPROXIMATELY .008" BETWEEN THE ROOT AND CREST OF SUCH SERRATIONS; PLACING THE INSERT ABOUT A MANDREL LOCATED ON THE VALVE SEAT; THE CROSS SECTIONAL AREA OF SAID INSERT BEING LARGER THAN THE CROSS SECTIONAL AREA OF THE GROOVE, THE INSERT HAVING AN INNER DIAMETER APPROXIMATELY .002" SMALLER THAN THE INNER DIAMETER OF THE GROOVE AND AN OUTER DIAMETER APPROXIMATELY .002" LARGER THAN THE OUTER DIAMETER OF THE GROOVE AND A HEIGHT APPROXIMATELY 1/16" LONGER THAN THE DEPTH OF THE GROOVE, APPLYING A GRADUAL PRESSURE TO THE INSERT UNTIL IT IS BOTTOMED, THE GRADUAL ENTRY OF THE INSERT ALLOWING ENTRAPPED AIR IN THE GROOVE TO ESCAPE; INCREASING THE PRESSURE ON THE INSERT TO INDUCE COLD FLOW CHARACTERISTICS IN THE PLASTIC MATERIAL CAUSING THE RESILIENT MATERIAL TO FLOW INTO THE INSERT HOLDING PORTION OF THE GROOVE; RETAINING THE PRESSURE A SUFFICIENT LENGTH OF TIME TO CAUSE THE PLASTIC MATERIAL TO BECOME INTIMATELY INTERENGAGED WITH THE INSERT HOLDING PORTION OF THE GROOVE, AND MACHINING THE PROTRUDING PORTION OF THE INSERT TO THE DESIRED HEIGHT ABOVE THE FACE OF THE SEAT.