Ball plunger for use in a hydraulic lash adjuster and method of making same

A method of cold-forming a ball plunger blank using a cold-forming machine having a cutoff station and five forming stations, the method comprising the steps of:

• at the cutoff station, shearing wire to a desired length to form a slug having first and second ends;
• at the first forming station, squaring the first and second ends of the slug and forming an indentation in the first end of the slug;
• at the second forming station, backward extruding the slug at its first end to form a first bore that is defined by a tubular wall and forming a generally ball-shaped surface to near final dimensions;
• at the third forming station, backward extruding the slug through its first end to form a second bore in the slug having a smaller diameter than the first bore;
• at the fourth forming station, upsetting at least a portion of the tubular wall to form a shoulder that at least partially closes the first bore and defines a ball seat surface to near final dimensions;
• and
• at the fifth forming station, coining the shoulder to form the ball seat surface to final dimensions.

A method of manufacturing a ball plunger for use in a lash adjuster assembly, the method comprising the steps of:

• cold-forming a ball plunger blank having a longitudinal axis to near net shape including the steps of:
• providing a slug having first and second ends;
• backward extruding the slug at its first end to form a body portion having a cavity disposed therein that is defined by a wall,
• forming a ball portion adjacent the second end of the slug, the ball portion including a generally ball-shaped surface sized to its final dimensions, and
• upsetting at least a portion of the wall to form a shoulder that at least partially closes the cavity and defines a ball seat surface sized to its final dimensions;
• and
• machining the ball plunger blank to complete the finished ball plunger.