True or False: Drilled bolt heads and screws need to be safety wired if self-locking nuts are installed on them.

The statement is true because drilled bolt heads and screws are typically required to be safety wired, even when self-locking nuts are used. This is a precautionary measure designed to provide additional security against the loosening that can occur due to vibrations or dynamic forces during operation.

Self-locking nuts do have mechanisms that are meant to prevent them from backing off under normal circumstances. However, relying solely on self-locking features may not suffice in high-stress environments or applications where safety is critical. Therefore, to ensure the utmost integrity of the assembly, especially in applications such as aircraft or critical machinery where failure could have severe consequences, safety wiring is a recommended practice.

This requirement is established in many engineering and safety standards to provide a fail-safe mechanism that works in conjunction with the locking properties of the nut. Safety wired components offer extra assurance that any unintentional loosening will be mitigated, maintaining the overall safety and reliability of the assembly.