Which type of rivet requires the head to be flush with the surface of the assembly?

A fluid-tight rivet is specifically designed to create a seal that prevents infiltration of fluids, making it critical for applications where moisture or other substances could compromise the integrity of the assembly. For this type of rivet to function effectively, the head must be flush with the surface of the material. This flush design ensures that there are no gaps or recesses that could allow fluids to enter, thus maintaining the integrity of the seal.

In contrast, solid rivets can have heads that are slightly proud of the surface or flush, depending on the design requirement. Protruding head rivets are characterized by their heads that are distinctly raised above the surface and are not suitable when a flush finish is needed. Blind rivets, while useful in situations where access to the back of the assembly is restricted, can also have heads that do not need to be flush. The focus on ensuring a secure seal is what makes the flush requirement paramount for fluid-tight rivets.