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 the first end to form a first bore having a first diameter that is defined by a tubular wall, and forming a generally ball-shaped surface at the second end;
• at the third forming station, backward extruding the slug through the first end to form a second bore in the slug having a second diameter that is smaller than the first diameter, wherein the first and second bores extend collectively substantially along a longitudinal length of the slug;
• at the fourth forming station, (i) upsetting only a portion of the tubular wall at the first end to form a counterbore having a third diameter and a shoulder, wherein the third diameter is greater than the first diameter and wherein the shoulder only partially closes the first bore and defines a ball seat surface to near final dimensions, wherein the first and second bores are both open to the counterbore through the shoulder subsequent to the upsetting, and (ii) simultaneously with the upsetting, forming a closed hemispherical surface at the generally ball-shaped outer surface at the second end of the slug to near final dimensions;
• and
• at the fifth forming station, coining the shoulder to form the ball seat surface and forming the closed hemispherical 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 the first end to form a body portion having a cavity disposed therein that has a first diameter and is defined by a wall,
• forming a ball portion at the second end of the slug, the ball portion including a generally ball-shaped surface, and
• upsetting only a portion of the wall to form a counterbore having a second diameter and a shoulder, wherein the second diameter is greater than the first diameter and wherein the shoulder only partially closes the cavity and defines a ball seat surface sized to final dimensions wherein the cavity is defined exclusively by the slug and remains open to the counterbore through the shoulder subsequent to the upsetting, simultaneously with the upsetting, forming a closed hemispherical surface at the generally ball-shaped outer surface at the second end of the slug to near final dimensions;
• and
• subsequent to the upsetting and the forming the closed hemispherical surface, forming the closed hemispherical surface to final dimensions and machining the ball plunger blank to complete the finished ball plunger.

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 the first end to form a first bore having a first diameter that is defined by a tubular wall and forming a generally ball-shaped surface;
• at the third forming station, backward extruding the slug through the first end to form a second bore in the slug having a second diameter that is smaller than the first diameter;
• at the fourth forming station, upsetting the tubular wall at the first end to form a counterbore having a third diameter and a shoulder, wherein the third diameter is greater than the first diameter and wherein the shoulder partially closes the first bore and defines a ball seat surface to near final dimensions, wherein the first and second bores are both open during formation of the counterbore, simultaneously with the upsetting, forming a closed hemispherical surface at the generally ball-shaped outer surface at the second end of the slug to near final dimensions;
• and
• at the fifth forming station, coining the shoulder to form the ball seat surface and forming the generally ball-shaped surface to final dimensions.