Low swage load fastening system and method

A low swage load fastening system for securing a plurality of workpieces together suing a swage-type fastener, said low swage load fastening system comprising:

• a pin member having an elongated pin shank adapted to be located in aligned openings in the workpieces and terminating at a first end in an enlarged head which engages a surface on one side of the workpieces and at a second end in a grooved portion which extends past an opposite surface on the opposite side of the workpieces, aid grooved portion comprising a locking portion having a plurality of lock grooves defined by circumferentially extending pin grooves and associated pin shoulders terminating in pin crests, said locking portion of said pin having an outer diameter;
• a substantially straight pull portion extending from the second end of said pin, and including a plurality of pull grooves, said pull portion having an outer diameter which is smaller than the outer diameter of said locking portion of said pin;
• an installation tool including an anvil member with a swage cavity, and a collet having a pull section with a plurality of teeth structured to complimentarily engage the pull grooves of said pull portion;
• and
• a collar including a generally straight collar shank adapted to be swaged into said lock grooves on said pin member in response to a relative axial pulling force applied to said pull portion of said pin member by said pull section of said installation tool thereby providing a desired magnitude of clamp load on the workpieces, which are fastened together to define a fastened joint by said swage cavity of said installation tool which is structured to apply a swage load by engaging said collar shank and swaging it radially inward, said collar when swaged, having collar grooves and shoulders interlocking said pin grooves and shoulders, said pin member and said collar being of different materials having ultimate shear stresses of different magnitudes in order that yielding of said pin member is substantially avoided upon swaging said collar thereto,
• wherein said pull portion of said pin has a length;
• wherein the length of said pull portion is substantially less than the length of said locking portion of said pin in order that the protrusion length of said pull portion from the second end of said pin is relatively short;
• and
• wherein said pull portion is structured to remain on the second end of said pin after the installation of said fastener.

A low swage load fastening system for securing a plurality of workpieces together using a swage-type fastener, said low swage load fastening system comprising:

• a pin member having an elongated point shank adapted to be located in aligned openings in the workpieces and terminating at a first end in an enlarged head which engages a surface on one side of the workpieces and at a second end in a grooved portion which extends past an opposite surface on the opposite side of the workpieces, said grooved portion comprising a locking portion having a plurality of lock grooves defined by circumferentially extending pin grooves and associated pin shoulders terminating in pin crests, said locking portion of said pin having a outer diameter;
• an installation tool including an anvil member with a swage cavity;
• and
• a collar including a generally straight collar shank adapted to be swaged into said lock grooves on said pin member in response to a relative axial force or swage load applied between said pin member and said collar by said installation tool, thereby providing a desired magnitude of clamp load on the workpieces which are fastened together to define a fastened joint, said swage cavity of said installation tool being structured to engage said collar shank and to swage it radially inward, said collar when swaged, having collar grooves and shoulders interlocking said pin grooves and shoulders, said pin member and said collar being of different materials having ultimate shear stresses of different magnitudes in order that yielding of said pin member is substantially avoided upon waging said collar thereto,
• wherein said lock grooves of said pin comprise a thread form defined by a number of radii for each of said pin grooves, said pin shoulders, and said pin crests of said lock grooves, said radii being blended in order to have a substantially smooth transition between said radii and thereby promote the complimentary interlocking engagement of said collar grooves with said lock grooves when said collar is swaged, and to reduce the swage load required to swage said collar, and
• wherein each of said lock grooves has a pitch length and a depth;
• and wherein the ratio of the pitch length to the depth is between about 2.5 to 4.

A method of installing a swage-type fastener using a low swage load fastening system, said swage-type fastener including a pin member having an elongated pin shank, said pin member terminating at a first end in an enlarged head and at a second end in a grooved portion, said grooved portion comprising a locking portion having a plurality of lock grooves defined by circumferentially extending pin grooves and associated pin shoulders terminating in pin crests, said method comprising:

• inserting said elongated point shank of said pin through aligned openings in a plurality of workpieces;
• applying a collar to said pin, said collar having a generally straight collar shank adapted to be swaged into said lock grooves on said pin in order that, when swaged, said collar has collar grooves and shoulders interlocking said pin grooves and shoulders, wherein the hardness of said as-headed collar is between about 85 Rb to 95 Rb;
• engaging a pull portion of said pin with an installation tool, said pull portion comprising a substantially straight pull portion extending from the second end of the point, said pull portion including a plurality of pull grooves and having an outer diameter which is smaller than the outer diameter of said locking portion of said pin, said installation tool comprising an anvil member with a swage cavity, and a collet having a pull section with a plurality of teeth structured to complimentarily the pull groves of said pull portion;
• actuating said installation tool thereby closing said pull section of said collet in order that said teeth complimentarily engage the pull grooves of said pull portion and drawing said collet into said anvil and, said collet pulling said pin and said collar into said anvil in order to swage said collar into said lock grooves;
• and
• deactivating said installation tool in order to withdraw said collet, releasing said pull portion and ejecting said collar when said fastener has been installed and said workpieces are clamped together.

A low swage load fastening system for a swage-type fastener structured to secure a plurality of workpieces together, said swage-type fastener including a pin member having an elongated pin shank adapted to be located in aligned openings in the workpieces, said pin member terminating at one end in an enlarged head adapted to engage a surface on one side of the workpieces and at its opposite end in a grooved portion adapted to extend past an opposite surface on the opposite side of the workpieces, said grooved portion comprising a locking portion having a plurality of lock grooves defined by circumferentially extending pin grooves and associated pin shoulders terminating in pin crests, said low swage load fastening system comprising:

• an installation tool including an anvil member with a swage cavity;
• and
• an as-headed collar including a generally straight collar shank adapted to be swaged into said lock grooves on said pin member in response to a relative axial force or swage load applied between said pin member and said as-headed collar by said installation tool, thereby providing a desired magnitude of clamp load on the workpieces which are fastened together to define a fastened joint, said swage cavity of said installation tool being structured to engage said collar shank and to swage it radially inward, said as-headed collar when swaged, having collar grooves and shoulders interlocking said pin grooves and shoulders, said pin member and said as-headed collar being of different materials having ultimate shear stresses of different magnitudes in order that yielding of said pin member is substantially avoided upon swaging said collar to said pin member,
• wherein said as-headed collar does not require thermal processing, and the generally straight collar shank of said as-headed collar has a wall thickness which is relatively thin thereby reducing the swage load required to swage said as-headed collar, and
• wherein the hardness of said as-headed collar is between about 85 Rb to 95 Rb.