METHOD OF TRIMMING HOLES IN RIGID MATERIAL Russian patent published in 1996 - IPC

FIELD: metal pressure forming. SUBSTANCE: method comprises steps of successive stepped trimming of holes, namely step of punching a preliminary hole in a part of a thickness of a material of a blank, a step of initial trimming of the preliminary hole in a part of the thickness of a material of a blank and a step of final trimming of the preliminary hole in a remaining part the thickness of the material; performing the final trimming with less allowance in comparison with an allowance of the initial trimming step. EFFECT: simplified process of trimming holes in rigid materials. 4 cl, 10 dwg