To check the depth of the countersink tool, what should be done first?

The first step in checking the depth of the countersink tool involves drilling and chamfering holes in a scrap assembly. This practice is essential because it allows the mechanic to physically assess how the tool interacts with the material being used. By performing these actions on a scrap piece, the mechanic can directly observe the resulting countersink depth, ensuring that it meets the required specifications.

This hands-on approach is vital, as it provides clear feedback on how the countersink tool behaves in practical scenarios. It enables adjustments and calibrations to be made on the tool before working on actual parts, ultimately ensuring quality assembly processes in aerospace applications.

The other choices, while important for overall maintenance and preparation, do not directly contribute to assessing the countersink depth. Inspecting tools can ensure that all equipment is in working order, checking drill speed is related to the efficiency of the drilling process, and reviewing engineering drawings is crucial for understanding design specifications, but these steps do not provide the immediate, experiential feedback needed to check countersink depth.