Is it necessary for the head and collar of a Hi-Lok fastener to contact the structure?

The head and collar of a Hi-Lok fastener do not necessarily need to make contact with the structure for proper installation. Hi-Lok fasteners are designed to leave a gap between the head and collar and the structure when properly installed. This is due to the fact that the fastener is typically designed for tension applications, and the load is carried by the shank of the fastener itself.

In specific applications or situations, it may be essential for the fastener’s design and the materials being joined to ensure the fastener can effectively perform its function without the head or collar interfering with the geometry of the assembly. This makes it key to understand the specific requirements and tolerances dictated by the engineering specifications for the assembly being worked on. The installation procedures and maintenance manuals will provide guidance on whether contact is necessary for the specific application. Thus, while the head and collar may not often make contact, it is no longer a strict requirement in every application.