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

1. A method of cold-forming a ball plunger blank comprising the steps of:

providing a slug having a generally cylindrical surface extending between a first end and a second end;

transferring the slug to a first forming station;

at the first forming station, forming an indentation in at least one of the first and second ends;

rotating the slug and transferring the slug to a second forming station;

extruding a first bore through the first end while simultaneously forming a hemispherical surface at the second end;

backward extruding a second bore at the first end; and

forming a counterbore in the second end.

2. The method of claim 1 , wherein the step of forming an indentation includes forming a slight indentation in the second end.

3. The method of claim 1 , wherein the step of forming an indentation includes forming an indentation in the first end.

4. The method of claim 1 , further comprising, at the first forming station, forming at least one chamfer at the first end.

5. The method of claim 4 , wherein the step of forming at least one chamfer includes forming a chamfer between the first end and the cylindrical surface simultaneously with the step of forming the at least one indentation.

6. The method of claim 4 , wherein the step of forming at least one chamfer includes forming a chamfer between the at least one indentation and the first end.

7. The method of claim 1 , wherein the step of rotating the slug comprises rotating the slug approximately 180° , wherein the first and second ends switch positions.

8. The method of claim 1 , further comprising rotating the slug and transferring the slug to the third forming station.

9. The method of claim 8 , further comprising:

at a third forming station, further forming the hemispherical surface while simultaneously backward extruding the second bore.

10. The method of claim 9 , further comprising rotating the slug and transferring the slug to a fourth forming station.

11. The method of claim 1 , further comprising further forming the hemispherical surface while simultaneously extruding the second bore.

12. The method of claim 10 , further comprising at the fourth forming station, further forming the hemispherical surface to near final dimensions while simultaneously forming the counterbore.

13. The method of claim 1 , further comprising further forming the hemispherical surface to near final dimensions while simultaneously forming the counterbore.

14. The method of claim 13 , further comprising rotating the slug and transferring the slug to a fifth forming station.

15. The method of claim 14 , further comprising at the fifth forming station, forming the hemispherical surface to final dimensions.

16. The method of claim 15 , further comprising at the fifth forming station, forming a ball seat surface and a retainer receiving surface at the first end.

17. A method of cold-forming a ball plunger blank using a cold-forming machine having a cutoff station and five forming stations each with a die section and a punch section, the method comprising:

at the cutoff station, shearing wire to a desired length to form a slug having a generally cylindrical surface extending between a first end and a second end;

transferring the slug to the first forming station such that the first end faces the die section and the second end faces the punch section;

rotating the slug and transferring the slug to the second forming station such that the first end faces the punch section and the second end faces the die section;

at the second forming station, simultaneously extruding a first bore through the first end and forming a hemispherical surface at the second end;

at the third forming station, backward extruding a second bore at the first end;

at the fourth forming station, forming a counterbore in the second end; and

at the fifth forming station, further forming the hemispherical surface to near final dimensions.

18. The method of claim 17 , further comprising:

at the third forming station, further forming the hemispherical surface while simultaneously backward extruding the second bore; and

at the fourth forming station, further forming the hemispherical surface to near final dimensions while simultaneously forming the counterbore.

19. The method of claim 17 , further comprising:

transferring the slug to the third forming station such that the first end faces the punch section and the second end faces the die section;

rotating the slug and transferring the slug to the fourth forming station such that the first end faces the die section and the second end faces the punch section; and

rotating the slug and transferring the slug to the fifth forming station such that the first end faces the punch section and the second end faces the die section.