When using an H-gauge to measure clinch, what indicates that the clinch is acceptable?

The correct answer is when the rivet head touches the top of the slot while the gauge legs do not touch the assembly. This indicates that the clinch is acceptable because it demonstrates that the rivet has been properly set in the clinch joint. The rivet head's contact with the gauge's slot shows that it is sufficiently embedded into the material and provides a stable connection, achieving the desired compression and security of the joint.

In this context, the H-gauge is a critical tool for assessing the quality of the clinch, ensuring that not only the rivet head is properly seated, but also that there is no excessive penetration into the assembly surface, which could compromise the integrity of the rivet joint. The lack of contact between the gauge legs and the assembly surface further confirms that the clinch is neither too tight nor improperly seated, both of which could lead to structural issues in aerospace applications.

The other options would not indicate an acceptable clinch as they either suggest improper contact or measurement issues that may lead to an unreliable joint. Understanding the nuances of how to properly assess clinching with the H-gauge is vital for maintaining safety and performance standards in aerospace assembly.