Patent ID: 7334337

Claim:
A method of manufacturing a bushing of a given length for a chain, said bushing having oil-retaining blind grooves, comprising the steps of: extruding a cylindrical column-shaped metallic member having said given length to form a primary intermediate article having a hollow cylindrical body portion and a bottom wall, press-fitting said primary intermediate article into a die having one end flared by a flared punch to form a secondary intermediate article having a flared end portion open at one end of the cylindrical member in a flared manner, and an inner cylindrical portion beyond said flared end portion, pushing down a grooved punch from said one open end into said inner cylindrical portion of said secondary intermediate article to form a tertiary intermediate article having a plurality of grooves formed only in said inner cylindrical portion of the article, press-fitting said tertiary intermediate article into a die whose inner circumferential surface is circular to form a fourth intermediate forged article entirely processed in a round shape with said flared portion narrowed in cylindrical form, said fourth intermediate forged article being closed beyond the bottom ends of said grooves by said bottom wall, and punching out the bottom wall of said fourth intermediate forged article, said fourth intermediate forged article forming a bushing having a plurality of blind grooves, each having blocked ends spaced from the top and bottom ends of the article in the longitudinal direction, parallel to the axial direction of the cylindrical body portion.