What is the recommended drill bit size for a #5 rivet?

The recommended drill bit size for a #5 rivet is indeed a #21 drill bit. This specification is important because it ensures that the hole for the rivet is neither too large nor too small.

Using a #21 drill bit creates a hole that is suitable for forming a proper fit for the #5 rivet, allowing it to be installed securely while ensuring that the surrounding material retains its integrity. If the hole is too large, the rivet may not hold effectively, leading to a weak joint, while a hole that is too small could make it impossible to insert the rivet.

In aircraft structural repairs, achieving the correct hole size is crucial for maintaining the strength and reliability of the structure, as rivets play a vital role in joining metal components. This precision helps to ensure that the aircraft meets safety standards and performs as intended.