How is the stem of a self-plugging (friction lock) rivet handled during installation?

During the installation of a self-plugging (friction lock) rivet, the correct procedure involves pulling the stem until it snaps off. This method is essential because it ensures that the rivet has adequately formed a secure and strong joint by allowing the plug inside the rivet to reach its designed locking mechanism.

As the stem is pulled, it creates the necessary tension required to drive the rivet into the material, forming the flush head. Once the required tension is achieved, the stem will break, leaving the rivet properly installed with the internal plug securely locked in place. This mechanism plays a crucial role in the rivet's effectiveness, as it differs from traditional rivet installation methods that may not use a self-locking feature.

The other options do not align with the intended installation process for a self-plugging rivet, as twisting or leaving the stem untrimmed would not allow for the proper locking action and could compromise the rivet's performance. Pushing the stem through the head is also incorrect as it does not pertain to how the rivet is designed to work; instead, it relies on pulling to achieve the necessary snap-off action for effective installation.