Self-attaching female fasteners, method of forming same and strip of interconnected fasteners

A method of forming self-attaching female fasteners, comprising the following steps:

• rolling a metal section and forming a desired cross-section of a self-attaching female fastener, including a continuous central pilot portion and integral flange portions on opposed sides of said central pilot portion, each of said flange portions having a top face and parallel grooves in said top face adjacent said continuous central pilot portion, said central pilot portion and said flange portions extending along a longitudinal axis of said section;
• punching generally cylindrical bores through said central pilot portion equally spaced along said longitudinal axis;
• punching pairs of configured openings through said section, said openings of each of said pairs opposing each other about said longitudinal axis and equally spaced from said bores along said longitudinal axis, each of said opening extending into said central pilot portion and one of said flange portions, each of said openings having arcuate side surfaces defining arcuate side faces of said central pilot portion;
• and
• chopping said strip through said pairs of openings and forming individual self-attaching female fasteners, each of said fasteners including a central pilot portion having arcuate side surfaces, integral flange portions on opposed ends of said central pilot portion and parallel grooves adjacent said central pilot portion.