| 摘要 |
A method and apparatus for making annular metallic blanks for metallic rings having a desired inner diameter wherein an elongated metallic material having a predetermined cross-section is formed into a spiral shape having an inner diameter smaller than that of said rings and such formed material is loosely and coaxially disposed around a cylindrical member the outer diameter of which is usually smaller than the inner diameter of said spiral material but can be made larger than said inner diameter of said inner diameter of said ring. Next, said cylindrical member is enlarged to thereby make said inner diameter of said spiral material larger than said inner diameter of said desired ring, then said enlarged spiral material disposed around said cylindrical member is cut along a straight line parallel to the axis of the cylindrical means to provide a plurality of bends of the spiral material; thereafter, said enlarged cylindrical member is reduced to its original diameter, and the bends are removed from said cylindrical member to be used as annular metallic blanks for said metallic rings. |
