Die for installing sealing fastener

An apparatus for forming a low pressure fluid sealed nut and panel assembly, comprising:

• a self piercing nut having an insertion face including a generally rectangular pilot having a top face, said top face bounded by at least two opposing end walls, said fastener further including a flange portion on opposed sides of said pilot, each said flange portion having bearing surfaces lying in a plane spaced apart from said pilot top face, each said flange portion further including a groove in said bearing surface, each said groove having an inner side wall, an outer side wall, and a bottom wall extending between said inner and outer side walls, said inner side walls being disposed proximate said pilot and said outer side walls being disposed distal said pilot,
• a die body having a generally rectangular opening adapted to intimately engage said pilot portion of said fastener, said opening defined by at least two opposing end walls and two opposing side walls, said generally rectangular opening having generally arcuate corners, said opposed end walls being spaced apart such that the distance between said spaced apart end walls is less than the width of said fastener pilot between said two opposing end walls of said pilot, said die body opening being surrounded by a generally planer surface having a generally rectangular outer perimeter having generally arcuate corners, said die body further including
• clinching lips located along opposing sides of said generally rectangular opening, said clinching lips having a flat top portion and inner and outer side walls, said inner side walls adapted to engage a portion of said panel proximate a panel opening and deform said portion of said panel proximate said opening against said inner side walls of said grooves,
• whereby, said panel is adapted to be disposed between said fastener and said die body, and said fastener insertion face is adapted to be passed through a panel opening and brought into operative engagement with said generally planer surface surrounding said generally rectangular opening of said die body, said opposing end walls and said arcuate corners being operative for deforming, parallel to the plane of said flange bearing surfaces, an edge portion of said pilot near said pilot end walls thereby forming a panel bearing surface on said pilot, said panel bearing surface generally extending across the width of the fastener end walls and into said grooves, said panel being supported upon said pilot bearing surface in a sealed relationship thereto in conjunction with said panel being deformed into said groves, thereby providing a continuous low pressure seal between said fastener and said panel and whereby said arcuate corners of said outer perimeter of said die body planer surface are adapted to engage said panel thereby forming arcuate depressions in said panel, said arcuate depressions being effective for resisting panel cracking due to fatigue.