Drop-forging process for forming bolt heads - uses blind hole in matrix or punch to centre billet during pressing thus eliminating burrs

摘要

The hot or cold-drop-forging process is used to form a hexagonal bolt head or similar shape on a metal billet, incorporating a matrix hole (3) by which the billet is centered and eliminating burrs. The billet may comprise a cut length of round bar which is subdivided into primary and secondary axial zones, the former being reshaped to form the head. A blind circular hole (3) centres the primary zone at the initiation of deformation, being provided in central position on the punch or in the matrix. The matrix (1) may have a square cavity (2) with a plane base, the centering hole (3) being sited axially in the base. Alternatively the hole may be formed by a circular coaxial rib which rises above the base level.