Device for establishing desired minimum preload condition obtained in a fastener shank

A device for establishing that a desired minimum preload condition has been attained in a fastener shank used in maintaining two bodies together when the device is located and clamped between the bodies, said device comprising:

• an annular portion including a longitudinally extending central bore adapted to receive the fastener shank, said central bore having a first end at one longitudinal end and a second end at its opposite longitudinal end;
• said annular portion including a disk shaped bottoming surface at said first end of said bore and a top area at said second end of said bore;
• said bottoming surface being transverse to said central bore;
• an annular portion thickness being defined between said disk shaped bottoming surface and said top area;
• a frusto-conical portion circumscribing and integrally formed with said annular portion, said frusto-conical portion including a frusto-conical bottoming surface having an inner smaller diameter abutting said disk shaped bottoming surface and an outer larger diameter being in a plane transverse to said central bore and longitudinally spaced from said disk shaped bottoming surface;
• said frusto-conical portion including a top frusto-conical area adjacent said annular portion top area;
• a frusto-conical thickness being defined between said frosto-conical bottoming surface and said top frusto-conical area;
• wherein said annular portion thickness and said frusto-conical thickness are both 0.25 to 0.7 times the sum of the frusto-conical portion smaller diameter less the central bore diameter, and said device is formed of a material whereby, upon placement of a fastener shank through said central bore and use of the fastener shank in drawing the two bodies together, clamping said device therebetween and reaching a desired minimum preload condition in the fastener shank, said frusto-conical portion plastically deforms longitudinally allowing said disk shaped bottoming surface to be drawn to and abut one of the bodies.

A device for establishing that a desired minimum preload condition has been attained in a fastener shank used in maintaining two bodies together when the device is located and clamped between the bodies, said device comprising:

• an annular portion including a longitudinally extending central bore adapted to receive the fastener shank, said central bore having a first end at one longitudinal end and a second end at its opposite longitudinal end;
• said annular portion including a disk shaped bottoming surface at said first end of said bore and a top area at said second end of said bore;
• said bottoming surface being transverse to said central bore;
• an annular portion thickness being defined between said disk shaped bottoming surface and said top area;
• a frusto-conical portion circumscribing and integrally formed with said annular portion, said frusto-conical portion including a frusto-conical bottoming surface having an inner smaller diameter abutting said disk shaped bottoming surface and an outer larger diameter being in a plane transverse to said central bore and longitudinally spaced from said disk shaped bottoming surface;
• said frusto-conical portion including a top frusto-conical area adjacent said annular portion top area;
• a frusto-conical thickness being defined between said frosto-conical bottoming surface and said top frusto-conical area;
• wherein said frusto-conical bottoming surface forms an angle with a plane transverse to said longitudinally extending central bore of between 10 and 30 degrees, and said device is formed of a material whereby, upon placement of a fastener shank through said central bore and use of the fastener shank in drawing the two bodies together, clamping said device therebetween and reaching a desired minimum preload condition in the fastener shank, said frusto-conical portion plastically deforms longitudinally allowing said disk shaped bottoming surface to be drawn to and abut one of the bodies.