Method for forming a socket on a pipe of biaxially oriented polyvinyl chloride

A method for forming a socket on a pipe of biaxially oriented polyvinyl chloride having an open end section comprising the steps of:

• inserting a support into the open end section of said pipe;
• initially heating said end section while internally supported by said support until said end section has been substantially homogeneously heated to the glass transition temperature of polyvinylchloride, the internal support preventing shrinkage of said end section in a radial direction and some shrinkage of said end section occurring in an axial direction;
• further heating said initially heated end section while internally supported by said support until said end section has been substantially homogeneously heated to a temperature near the orientation temperature of polyvinyl chloride;
• deforming said further heated end section to form said socket in said further heated end section of said pipe;
• cooling said deformed end section, said deformed end section being internally supported during cooling;
• and
• removing said support from said cooled end section;
• whereby the inception of undesirable stresses which lead to cracking in said socket is avoided.