Should the inside radius of a rivet set be larger or smaller than the radius of the rivet head?

The inside radius of a rivet set should be larger than the radius of the rivet head to ensure that the rivet can be properly formed without restricting the flow of material during the riveting process. A larger radius allows for the rivet head to fit into the set without creating stress concentrations or potential deformation of the head itself. This design consideration helps to achieve a uniform and effective upset of the rivet material, thereby creating a strong bond that meets structural integrity requirements.

If the inside radius of the set were smaller than that of the rivet head, it could lead to improper rivet formation, including incomplete or uneven deformation, compromising the joint's strength and reliability. Having the same radius might seem sufficient, but it doesn’t account for the flexibility required during the riveting process. Therefore, ensuring that the inside radius of the rivet set is larger is fundamental for creating solid, secure riveted joints in aircraft structures.