If you lose the key to your pin-tumbler cylinder lock and cannot afford a locksmith, your last resort for opening the lock (without damaging the door) is to destroy the pins by drilling through the cylinder. With the pins destroyed, the lock can be opened by inserting a flathead screwdriver into the key hole and rotating it. However, the drilling process will render the lock useless, requiring you to purchase and install an entirely new cylinder lock.
Load the 1/8-inch drill bit into the electric drill's chuck and tighten it into place.
Line up the tip of the drill bit with the lock's key hole.
Drill a 1-inch-deep hole between the top of the key hole and the edge of the cylinder. Be sure to make this hole (known as a "pilot hole") perpendicular to the surface of the lock.
Remove the 1/8-inch bit and replace it with the 1/4-inch HSS bit.
Place the tip of the 1/4-inch bit over the opening of the pilot hole you drilled in Step 3. Drill a 2-inch-deep hole, using the pilot hole as a guide. Again, make sure that the hole is as close to perpendicular to the lock's surface as possible.
To open the lock, remove the drill and insert the tip of a flat head screwdriver into the lock's key hole. Turn the screwdriver to rotate the main cylinder, opening the lock.
Drilling locks creates tiny, almost-invisible metal shavings that can cause serious injury if inhaled or accidentally put in the eye. Wear safety goggles, a dust mask and disposable gloves for the entire process. The gloves are especially important, as unseen shavings can hide on your fingers for hours. If you rub your eyes, these shavings can get inside.