Apparatus and method for the installation of a thermoformable fastener assembly at a predetermined preload torque value

An apparatus for torqueing a nut and bolt fastener assembly to a preload and then deforming the fastener assembly to hold the preload, the apparatus comprising:

• a wrench device having a socket with a plurality of engagement surfaces inside the socket, the socket engagement surfaces being dimensioned to engage around the nut of the nut and bolt fastener assembly, the wrench device being operable to rotate the socket around the bolt whereby the socket engaging around the nut rotates the nut on the bolt and torques the nut to a preload;
• and,
• a piercing tip adjacent the socket, the piercing tip being moveable between first and second positions of the piercing tip relative to the socket where in the first position the piercing tip is displaced from the socket and in the second position the piercing tip extends into the socket and into the fastener assembly inside the socket and deforms the fastener assembly.

A method of torqueing a threaded nut and bolt fastener assembly to a preload and then deforming the fastener assembly to hold the preload, the method comprising:

• rotating the nut on the bolt until a torque of rotating the nut on the bolt reaches a preload torque;
• and,
• piercing the fastener assembly and deforming the fastener assembly and thereby holding the preload on the fastener assembly.