What is the general rule for finding the proper rivet diameter?

The general rule for determining the proper rivet diameter is based on the thickness of the materials being joined. The correct choice states that the diameter should be three times the thickness of the thickest sheet. This guideline is crucial because it helps ensure that the rivet can provide sufficient strength and structural integrity to the joint.

By having a rivet diameter that is three times the thickness of the thickest sheet, it allows for adequate contact area between the rivet and the materials. This increased contact area is essential for distributing the load effectively and preventing failure during operation. The larger diameter also helps accommodate any potential issues related to the rivet during installation and provides better resistance to shear forces.

The other options suggest different relationships between rivet diameter and sheet thickness, which may not provide sufficient strength or structural support in practice. For example, a diameter equal to the thickness of the thicker sheet would likely not be adequate to handle the stresses involved, and the suggestion of a diameter based on the thinner sheet does not consider the strength requirements of the thicker material being riveted. Therefore, using a diameter that is three times the thickest sheet represents a balance between strength, efficiency, and practicality in rivet design.