After drilling and enlarging the holes in the assembly, which step is necessary for fillet relief?

Chamfering the holes is a critical step in the assembly process to ensure proper fillet relief. When holes are drilled and subsequently enlarged, the edges can become sharp or create stress concentration points that may lead to premature failure or cracking in the assembly. By chamfering the holes, you create a beveled edge that not only aids in reducing the stress concentration but also enhances the overall fit and finish of the assembly components.

Additionally, chamfering improves the access for fasteners or inserts, ensuring that they seat correctly and evenly. It also facilitates assembly by preventing any interference with other components and allows for smoother transitions in areas where different materials or parts meet. This is key in aerospace applications where structural integrity and durability are paramount.

The other options, while they have their respective uses in different contexts, do not address the specific need for alleviating stress around the edges of drilled and enlarged holes that chamfering effectively resolves.