To determine the correct chuck key for your tool, first identify the chuck type and size. Most chucks have a size stamped on them, typically in inches or millimeters. Match this size to the corresponding chuck key. For example, a 1/2-inch chuck requires a 1/2-inch key. Additionally, ensure the key’s teeth align with the chuck’s grooves. Always refer to the tool’s manual for specific requirements. Using the wrong key can damage both the chuck and the tool. Proper selection ensures efficient and safe operation.