SEMIHOLLOW RIVET MANUFACTURE METHOD Russian patent published in 1999 - IPC

FIELD: plastic working of metals, in particular, manufacture of semihollow rivets and like parts on automatic cold heading machine. SUBSTANCE: method involves cutting off rodlike bar of measured length; deforming bar in set of passes so as to form head portion on one end of bar and dead axial cavity on other end of bar; determining outer diameter of blank obtained by direct extrusion from expression , where D(bar) is outer diameter of semihollow bar of ready part; d(part) is inner diameter of semihollow bar of ready part; ε is relative deformation extent during cavity extrusion process, which may be within the range of 0.36-0.51. In the process of reduction of semihollow bar, inner diameter is reduced and cavity depth is increased and may reach the value exceeding its diameter by 2.5 times. Inner diameter d(bar) of bar obtained by direct extrusion is determined from expression: d(bar) = , where d(bar) is outer bar diameter; ε is relative deformation extent. Method is used for manufacture of semihollow rivets having relative wall thickness exceeding 0.2 and parts having relative cavity depth h(part)/d(part) > 2.5. EFFECT: wider operational capabilities and improved quality of rodlike parts.