What is an essential step to ensure safety when using a pneumatic hand drill?

To ensure safety when using a pneumatic hand drill, disconnecting the air supply when making adjustments is a crucial step. This practice prevents accidental activation of the tool, which could lead to serious injuries to the operator or nearby personnel. By ensuring that the tool is completely de-energized, users can safely make the necessary changes or repairs without the risk of the drill starting unexpectedly.

Safety goggles are important for protecting the eyes from flying debris, and using a chuck key correctly prevents the drill bit from coming loose during operation. However, these steps do not directly prevent the risk associated with adjusting or servicing the tool while it is still connected to the air supply. Securing the workpiece with hands is hazardous as it exposes the operator to the risk of injury from the drill if the tool is inadvertently activated. Thus, disconnecting the air supply is the most effective safety measure in this context.