METHOD OF MAKING HOLES Russian patent published in 1995 - IPC

FIELD: sheet material forming. SUBSTANCE: method comprises steps of making a preliminary hole in a sheet material; placing a rod with an oblique end surface in the prepared hole at one side and resting the rod; at other side acting upon an annular portion of the material around the hole by a punch; providing formation of a hardened layer with non-symmetricaly arranged shear surface in the result of plastic yielding of the material; removing the rod; going on to shear the hardened layer up to making the hole with necessary dimensions. EFFECT: high-quality of holes parts from low ductile materials. 1 cl, 4 dwg