Which action occurs last during the installation of self-plugging rivets?

The correct choice highlights that flush trimming of the remaining part occurs last during the installation of self-plugging rivets. Here’s why this is the case:

When installing self-plugging rivets, the process begins with the insertion of the rivet through the materials being joined. Once positioned, the stem of the rivet is then pulled, which causes the rivet to expand. This expansion happens as the internal mechanism of the rivet engages, securing it in place by filling the hole and creating a strong bond.

After the rivet has expanded and fully secured the materials, the final step involves trimming off the excess stem that is left protruding. This flush trimming ensures that the surface is smooth and even, which is essential for aerodynamics and preventing snagging on surfaces. Therefore, flush trimming of the remaining part is logically the last action in the sequence of installing self-plugging rivets, affirming why it is the correct answer in this context.