True or false: The bucking bar must be perpendicular to the rivet centerline when in use.

The assertion that the bucking bar must be perpendicular to the rivet centerline when in use is indeed true. This is essential for ensuring that the force applied to the rivet is distributed evenly, allowing it to form properly and securely. When the bucking bar is positioned at a perpendicular angle, it provides optimal contact with the rivet, ensuring that the tail of the rivet deforms evenly and creates a strong mechanical bond. If the bucking bar is not perpendicular, it can result in an improper rivet formation, leading to weak joints and potential structural failure. Proper alignment in riveting practices is crucial for maintaining the integrity of aerospace components.