Methods and assemblies for forming an annular object

The method of claim 5, wherein

• the external die assembly includes an inner clamp member and an outer clamp member;
• the frustoconical preform is clamped between an outer surface of the inner clamp member and an inner surface of the outer clamp member;
• and
• the outer surface of the inner clamp member is angularly offset from the axis by an external die angle that is different that the die clamp angle. The method of claim 6, wherein the external die angle is equal to the preform angle.

A method for forming an annular object, comprising:

• clamping a frustoconical preform with an external die assembly, wherein a surface of the external die assembly abutted against the frustoconical preform is angularly offset from an axis by an external die angle;
• translating the external die assembly axially along the axis to externally draw the frustoconical preform over an outer surface of a punch and an outer surface of an internal die clamp to provide an externally drawn body, wherein the outer surface of the internal die clamp is angularly offset from the axis by a die clamp angle that is different than the external die angle;
• mating an internal die with the internal die clamp to provide an internal die assembly, wherein the externally drawn body is clamped radially between the internal die and the internal die clamp;
• and
• translating the internal die assembly axially along the axis and into a bore of the punch to at least partially internally draw the externally drawn body against an inner surface of the punch.

An assembly for forming an annular object, comprising:

• a punch, an external die assembly and an internal die assembly that comprises an internal die clamp and an internal die;
• the external die assembly configured to clamp onto a frustoconical preform, and the external die assembly further configured to translate axially along an axis to externally draw the frustoconical preform over an outer surface of the punch and an outer surface of the internal die clamp to provide an externally drawn body, wherein a surface of the external die assembly configured to contact the frustoconical preform is angularly offset from the axis by an external die angle, and the outer surface of the internal die clamp is angularly offset from the axis by a die clamp angle that is different than the external die angle;
• the internal die configured to mate with the internal die clamp such that the externally drawn body is clamped radially between the internal die and the internal die clamp;
• and
• the internal die assembly configured to translate axially along the axis and into a bore of the punch to at least partially internally draw the externally drawn body against an inner surface of the punch.