Explanation:
In riveting, the minimum pitch refers to the minimum distance between the centers of two adjacent rivets in a row or a staggered pattern. The pitch is important because it determines the strength and stability of the joint.

The gross diameter of the rivet is the total diameter of the rivet, including the shank and the head. It is important to ensure an adequate pitch to avoid compromising the integrity of the joint and prevent the rivets from being too close together.

Reasoning:
To determine the minimum pitch of rivets, we need to consider the gross diameter of the rivet. The pitch should be sufficient to maintain the structural integrity of the joint.

If the pitch is too small, it can lead to overcrowding of rivets, causing them to interfere with each other and weaken the joint. On the other hand, a larger pitch allows for better distribution of the load and ensures a stronger connection.

Minimum pitch calculation:
The minimum pitch of rivets should not be less than 2.5 times the gross diameter of the rivet.

This means that the distance between the centers of two adjacent rivets should be at least 2.5 times the total diameter of the rivet.

For example, if the gross diameter of the rivet is 10 mm, the minimum pitch should be 2.5 times 10 mm, which is 25 mm.

Conclusion:
To ensure the structural integrity and strength of a joint, the minimum pitch of rivets should not be less than 2.5 times the gross diameter of the rivet. This allows for proper spacing and distribution of load, preventing the overcrowding of rivets and maintaining a strong connection.