Variable clamp fastener and method

In a fastening system including a fastener for securing workpieces together with a selectively variable clamp with said fastener adapted to be finally installed via a relative axial force applied by an installation tool, said fastener comprising:

• a pin member having an elongated shank terminating at one end in an enlarged pin head,
• a lock groove portion on said shank including a plurality of helically extending lock grooves defining a thread form,
• a tubular collar adapted to be located on said pin shank and to be swaged into said lock grooves in response to a first preselected magnitude of said relative axial force applicable by the installation tool,
• said collar having a through bore of a diameter to generally receive said lock grooves in clearance relationship,
• said collar having a limited female thread formed on said through bore and adapted to threadably engage said thread form defined by said lock grooves, whereby said collar can be torqued onto said lock groove portion to selectively clamp or locate the workpieces relative to each other more or less under a selectively variable torque whereby the workpieces can be selectively adjusted or aligned,
• said limited collar thread having a preselected strength selected to deform out of said lock grooves in response to a second preselected magnitude of said relative axial force applied between said pin member and said collar by the installation tool with said second preselected magnitude being less than said first preselected magnitude whereby said collar can be moved axially over said pin member after deformation of said limited collar thread and prior to initiation of swaging of said collar into said lock grooves.

In a fastening system including a fastener for securing workpieces together with a selectively variable clamp with said fastener adapted to be finally installed via a relative axial force applied by an installation tool, said fastener comprising:

• a pin member having an elongated shank terminating at one end in an enlarged pin head,
• a lock groove portion on said shank including a plurality of helically extending lock grooves defining a thread form,
• a tubular collar adapted to be located on said pin shank and to be swaged into said lock grooves in response to a first preselected magnitude of said relative axial force applicable by the installation tool,
• said collar having a through bore of a diameter to generally receive said lock grooves in clearance relationship,
• said collar having a limited female thread formed on said through bore and adapted to threadably engage said thread form defined by said lock grooves,
• wrenching means comprising a plurality of discontinuities on said collar and said pin member for facilitating torquing of said collar onto said lock groove portion to selectively clamp or locate the workpieces relative to each other more or less under a selectively variable torque whereby the workpiece can be selectively adjusted or aligned,
• said limited collar thread having a preselected strength selected to deform out of said lock grooves in response to a second preselected magnitude of said relative axial force applied between said pin member and said collar by the installation tool with said second preselected magnitude being less than said first preselected magnitude whereby said collar can be moved axially over said pin member after deformation of said limited collar thread and prior to initiation of swaging of said collar into said lock grooves.