If the top of the collar reaches the minimum step when inspecting with a pin protrusion gauge, what does it indicate?

When the top of the collar reaches the minimum step during an inspection with a pin protrusion gauge, it indicates that the collar is under-driven. This means that the collar has not been pushed down adequately during installation, and as a result, it does not meet the specified depth as required for proper function. This condition can lead to issues such as insufficient engagement with the assembly, compromised structural integrity, and potential failure during operational conditions.

In aerospace applications, maintaining precise tolerances is critical for safety and performance. An under-driven collar may increase wear over time or lead to loosening, which could compromise the assembly. Therefore, understanding that the position of the collar in relation to the minimum step is crucial for ensuring that it is adequately secured and aligned within the assembly.