Metal Stamping

Author:  Greenway
Source:  US Patent 5,265,320
Doc ID:  1991100
Year of Publication:  1991
Abstract:  
A method of prgressive die stamping for cutting apertures in a sheet metal strip without producing stress induced distortion of the apertures after cut-off of the strip. The sheet metal strip is peened to form one dent between the aperture and one edge of the strip and to form another dent between the aperture and the other edge of the strip and subsequently cutting the strip with a cut-off punch. The peening operation may be done before, during or after the aperture punching operation.