What is the name of the groove where the lockbolt pin and pintail separate during installation?

The groove where the lockbolt pin and pintail separate during installation is known as the breakneck. This term specifically refers to the point in the assembly process where the tension in the lockbolt assembly causes the pintail to fracture or separate from the pin, resulting in a secure connection. Understanding this term is crucial for aerospace assembly mechanics because it is integral to the proper installation and functionality of lockbolt fasteners, which provide high-strength, reliable connections in various aerospace applications. Recognizing components like the breakneck helps mechanics ensure accurate assembly practices and maintain the integrity of aircraft structures.