Losing the chuck key to your drill can stop your DIY project in its tracks because you won't be able to change your drill bit. If you lost the chuck, buy a replacement. Ensuring you get the correct-sized chuck avoids a second trip to the shops. There are more then 12 variations of drill chucks, so have the right information when making your selection.
Look closely at the chuck on the drill for the engraved numbers. The chuck size is typically displayed in millimetres (mm) and ranges from 2 mm to 25 mm on most power drills.
Measure the diameter of the hole on the side of the chuck in millimetres with a ruler. This measurement is called the pilot shank.
Take these two dimensions to your local DIY centre or home improvement shop to make your selection.
Many chuck key manufacturers have lists of common drills the key will fit. Look on the back of the package before buying.