blind

A blind fastener, rivet, or bolt is one you can install when you have access to only one side of the work. The fastener is set from the front face, and its tail or mandrel either breaks away, deforms, or collapses inside the material to form a grip on the reverse side, even though you cannot see or touch that side. This is essential in aircraft skin assembly, sheet metal enclosures, and composite layups where drilling through both sides is impossible or where the back surface must remain unbroken.

Blind rivets (pop rivets) are the most common type. A hollow aluminum or steel rivet sits on a mandrel; as you pull the trigger on a rivet gun, the mandrel is drawn up through the rivet's center, expanding the rivet body and fracturing the mandrel, which then drops away. The expanded rivet tail creates a permanent joint. Pull-through blind bolts work similarly but leave the bolt in place with a captive nut or deformed tail on the hidden side. Blind studs with internal threads allow subsequent assembly.

The term "blind" signals to the shop that you cannot measure or work the reverse side. This affects tool choice, design tolerance, and joint strength assumptions. A blind joint will always be weaker in shear and pull-through than a through-rivet because the back-side grip depends entirely on plastic deformation, not full mechanical interlock. Load capacity varies sharply with material thickness, fastener diameter, and the quality of the mandrel pull.

Blind fasteners are measured by their grip range (the material thickness they can join) and their tensile and shear strength. A 3/16-inch aluminum blind rivet might grip 0.062 to 0.125 inches of sheet; oversized or undersized material will either fail to set or break the mandrel prematurely. Corrosion and fatigue are also concerns, especially in aerospace and marine work, because the mandrel remnants and the sealed cavity can trap moisture.

In structural repair and production, blind fasteners trade strength and inspectability for speed and one-sided access. They are not suitable for high-cycle fatigue or tensile-critical joints; they appear instead in cabin trim, non-structural panels, and temporary assemblies. Inspection is difficult: you can pull-test a sample, but you cannot visually confirm that a set fastener on a closed-back assembly is sound. This is why blind fastening is often combined with redundancy, overlap, or adhesive in load-bearing designs.