Connecting rod with ball joint and manufacturing method thereof

A manufacturing method of a connecting rod for connecting first and second ball-shanks swingably and rotatably on both ends of a rod main body such that shanks thereof are perpendicular to each other, said manufacturing method comprising:

• first step for closing first and second die half bodies, inserting a first ball into a cavity formed in the die half bodies and fixing a first ball in said cavity with a first supporting portion projecting from the die half bodies;
• second step for closing a third die half body with respect to the closed first and second die half bodies in a direction perpendicular to the closing direction of said first and second die half bodies, inserting a second ball into a cavity formed by the three die half bodies, and fixing the second ball in said cavity with the second supporting portion projecting from said first and second die half bodies and third supporting portion projecting from said third die half body;
• third step for casting the rod main body holding said first and second balls and in which opening portions communicating with each of the balls are formed corresponding to said first-third supporting portions by pouring molten metal into cavities in casting dies formed by closing the respective die half bodies;
• fourth step for forming said first and second ball-shanks by joining the shank to each of the balls in said rod main body via an opening portion formed in said rod main body by said first-third supporting portions;
• and
• fifth step for forming a gap between each ball and rod main body by providing said rod main body and each ball-shank with an external force.