If a rivet head does not fall off after being drilled out, what should you insert into the hole?

Inserting a punch into the hole after the rivet head has not fallen off is a standard practice in aerospace assembly and maintenance. The punch is used to help drive out the remaining rivet shank from the hole, ensuring that the hole is clear for the installation of a new rivet. This is crucial because the integrity of a riveted joint relies on the proper removal of old rivets before new ones can be installed.

Using a punch facilitates the removal process by providing a pointed tool that can effectively apply force to the shank of the rivet. The punch can forcibly push through the remaining material, effectively extracting it without damaging the surrounding structure or creating additional complications.

Other options might not be suitable for this task: a chisel could damage the surrounding material, a screw would not effectively address the rivet's remaining shank, and a drill bit could potentially create further complications, such as enlarging the hole unnecessarily or causing misalignment. Therefore, a punch is the correct tool to ensure the efficient and safe removal of the rivet's remaining parts.